Long Life and Quiet Pavement: Research and Issues : Research and Issues [1 ed.] 9781617282478, 9781607418887

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TRANSPORTATION INFRASTRUCTURE – ROADS, HIGHWAYS, BRIDGES, AIRPORTS AND MASS TRANSIT

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LONG LIFE AND QUIET PAVEMENT: RESEARCH AND ISSUES

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TRANSPORTATION INFRASTRUCTURE – ROADS, HIGHWAYS, BRIDGES, AIRPORTS AND MASS TRANSIT

LONG LIFE AND QUIET PAVEMENT: RESEARCH AND ISSUES

GORDON E. DANIELS Copyright © 2010. Nova Science Publishers, Incorporated. All rights reserved.

EDITOR

Nova Science Publishers, Inc. New York

Long Life and Quiet Pavement: Research and Issues : Research and Issues, Nova Science Publishers, Incorporated, 2010. ProQuest Ebook

Copyright © 2010 by Nova Science Publishers, Inc. All rights reserved. No part of this book may be reproduced, stored in a retrieval system or transmitted in any form or by any means: electronic, electrostatic, magnetic, tape, mechanical photocopying, recording or otherwise without the written permission of the Publisher. For permission to use material from this book please contact us: Telephone 631-231-7269; Fax 631-231-8175 Web Site: http://www.novapublishers.com

NOTICE TO THE READER The Publisher has taken reasonable care in the preparation of this book, but makes no expressed or implied warranty of any kind and assumes no responsibility for any errors or omissions. No liability is assumed for incidental or consequential damages in connection with or arising out of information contained in this book. The Publisher shall not be liable for any special, consequential, or exemplary damages resulting, in whole or in part, from the readers’ use of, or reliance upon, this material. Any parts of this book based on government reports are so indicated and copyright is claimed for those parts to the extent applicable to compilations of such works.

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Independent verification should be sought for any data, advice or recommendations contained in this book. In addition, no responsibility is assumed by the publisher for any injury and/or damage to persons or property arising from any methods, products, instructions, ideas or otherwise contained in this publication. This publication is designed to provide accurate and authoritative information with regard to the subject matter covered herein. It is sold with the clear understanding that the Publisher is not engaged in rendering legal or any other professional services. If legal or any other expert assistance is required, the services of a competent person should be sought. FROM A DECLARATION OF PARTICIPANTS JOINTLY ADOPTED BY A COMMITTEE OF THE AMERICAN BAR ASSOCIATION AND A COMMITTEE OF PUBLISHERS. LIBRARY OF CONGRESS CATALOGING-IN-PUBLICATION DATA Long life and quiet pavement : research and issues / editors, Gordon E. Daniels. p. cm. Includes bibliographical references and index. ISBN:  (eBook)

1. Pavements--Performance. 2. Roads--Government policy--United States. I. Daniels, Gordon E. TE251.5.L66 2010 625.8--dc22 2010014079

Published by Nova Science Publishers, Inc.

New York

Long Life and Quiet Pavement: Research and Issues : Research and Issues, Nova Science Publishers, Incorporated, 2010. ProQuest Ebook

CONTENTS Preface Chapter 1

The Little Book of Quieter Pavements United States Department of Transportation 

Chapter 2

Long-Life Concrete Pavements in Europe and Canada United States Department of Transportation 

Chapter 3

Long Term Pavement Performance Computed Parameter: Moisture Content United States Department of Transportation 

147 

Long Term Pavement Performance Computed Parameter: Frost Penetration United States Department of Transportation 

229 

Chapter 4

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vii 

Chapter 5

LTPP beyond FY 2009: What Needs to be Done? United States Department of Transportation 

1  31 

301 

Chapter Sources

319 

Index

321 

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Copyright © 2010. Nova Science Publishers, Incorporated. All rights reserved. Long Life and Quiet Pavement: Research and Issues : Research and Issues, Nova Science Publishers, Incorporated, 2010. ProQuest Ebook

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PREFACE The idea of designing and building quieter pavements is not new, but in recent years there has been a groundswell of interest in making this a higher priority. Various State Highway Agencies and the Federal Highway Administration have responded accordingly with both research and implementation activities that both educate on the state-of-the-practice, and advance the state-of-the-art. This book aims to educate the transportation industry, and in some cases the general public, about the numerous principles behind quieter pavements, as well as summarizing the Long-Term Pavement Performance programs and its major activities. Chapter 1 - Why was this Book Written? The idea of designing and building quieter pavements is not new, but in recent years there has been a groundswell of interest in making this a higher priority. Various State Highway Agencies and the Federal Highway Administration have responded accordingly with both research and implementation activities that both educate on the state-of-the-practice, and advance the state- of-the-art. The Little Book of Quieter Pavements was developed with this purpose in mind... to help educate the transportation industry, and in some cases the general public, about the numerous principles behind quieter pavements, and how they connect together. Who is this Book Written for? This book is not a synthesis. It is not a textbook. And it is not a policy guide. Instead, it is intended to briefly touch on the numerous aspects of tire-pavement noise and quieter pavements that may be of interest to anyone. In other words, this book is intended to appeal to a wide audience. So while some of the content of this book is technical in nature, the depth of these discussions is minimal. Instead, resources are identified herein for further study. How Can I Listen along? In addition to the Little Book of Quieter Pavements, a listening experience has been developed, built off of the Soundscape DesignTM concept pioneered by Mr. Nicholas P. Miller, Senior Vice President of Harris Miller Miller & Hanson Inc. This listening experience is in the form of a collection of MP3 files. To experience it properly, this collection should be loaded onto an MP3 player and played in a setting free from other noise sources or distractions. Throughout the Little Book, notations of corresponding track numbers are given as a small blue speaker with a track number. While the listening experience can be useful as a stand-alone tool, the tracks played at the appropriate times will allow the reader to enjoy a

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Gordon E. Daniels

more fulfilling educational experience. A reference to each of the tracks can also be found at the end of the Little Book. Chapter 2 - THE INTERNATIONAL Technology Scanning Program, sponsored by the Federal Highway Administration (FHWA), the American Association of State Highway and Transportation Officials (AASHTO), and the National Cooperative Highway Research Program (NCHRP), accesses and evaluates innovative foreign technologies and practices that could significantly benefit U.S. highway transportation systems. This approach allows advanced technology to be adapted and put into practice much more efficiently without spending scarce research funds to re-create advances already developed by other countries. FHWA and AASHTO, with recommendations from NCHRP, jointly determine priority topics for teams of U.S. experts to study. Teams in the specific areas being investigated are formed and sent to countries where significant advances and innovations have been made in technology, management practices, organizational structure, program delivery, and financing. Scan teams usually include representatives from FHWA, State departments of transportation, local governments, transportation trade and research groups, the private sector, and academia. After a scan is completed, team members evaluate findings and develop comprehensive reports, including recommendations for further research and pilot projects to verify the value of adapting innovations for U.S. use. Scan reports, as well as the results of pilot programs and research, are circulated throughout the country to State and local transportation officials and the private sector. Since 1990, about 70 international scans have been organized on topics such as pavements, bridge construction and maintenance, contracting, intermodal transport, organizational management, winter road maintenance, safety, intelligent transportation systems, planning, and policy. The International Technology Scanning Program has resulted in significant improvements and savings in road program technologies and practices throughout the United States. In some cases, scan studies have facilitated joint research and technology-sharing projects with international counterparts, further conserving resources and advancing the state of the art. Scan studies have also exposed transportation professionals to remarkable advancements and inspired implementation of hundreds of innovations. The result: large savings of research dollars and time, as well as significant improvements in the Nation’s transportation system. Scan reports can be obtained through FHWA free of charge by e-mailing international@ fhwa.dot.gov. Scan reports are also available electronically and can be accessed on the FHWA Office of International Programs Web Site at www.international.fhwa.dot.gov. Chapter 3 - Time domain reflectometry (TDR) information has been collected as a key component of the Long Term Pavement Performance (LTPP) program’s seasonal monitoring program (SMP) to monitor subsurface moisture conditions in pavement structures. The TDR waveform data do not provide in situ moisture contents directly. Rather, the data must be analyzed to determine parameters—such as volumetric moisture content (VMC)—that are of use in pavement design and performance prediction. Interpretation that included the development of empirical-based methodologies to convert waveform characteristics and in situ soil properties to moisture parameters was performed on a portion of these TDR data under previous analysis.[1] The computed parameter data from this effort are currently available in the LTPP Pavement Performance database. Since then, approximately 175,000 more automated TDR measurements have been added to the database but have not been interpreted. The current study was performed to not only compute the

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Preface

ix

moisture parameters for these additional TDR measurements but also to assess other feasible computational procedures. The objectives of the current study were to: • • •

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•

Investigate the differences between the automated and manual TDR trace interpretation methods. Investigate the adequacy of the models used to estimate VMC from the TDR interpreted dielectric constant. Investigate the adequacy of data used to compute gravimetric moisture content from VMC. Determine adequacy of data to support computation of other moisture-related indices such as degree of saturation.

A significant portion of the analysis was focused on alternative computational processes, wherein previously uninterpretable traces could be utilized. Based on this investigation, a new approach was recommended that computed the soil dielectric constant using a solution of the transmission line equation (TLE) for each TDR trace and the computation of the dry density and the moisture content using a micromechanics model. The new approach eliminated many of the issues related to the trace interpretations and provided a relatively accurate assessment of the in situ moisture content. In phase 1 of this project, the basic procedures of the new approach were developed and evaluated using measured moisture contents from the SMP Installation Reports and other sources.[2] The new approach was shown to work and to produce reasonable estimates of the in situ moisture contents compared with ground truth measurements in both field and laboratory settings. Phase 2 of the project entailed the development of a new computer program to automate the computation process, the computation of the moisture content for 274,000 TDR traces, and the uploading of this data into the LTPP database. Quality control (QC) checks were developed and performed on all of the computed data. This chapter presents the development of the new computational procedures, evaluation of results from the new approach, development of the computer program automating the process, and the QC initiatives implemented to ensure data reported in the LTPP database are of research quality. Chapter 4 - Importance of Frost Penetration Information Knowledge of frost penetration beneath the pavement structure is critical for many pavement design, analysis, and management applications. Problems caused by frost include the seasonal change in the bearing capacity of soils brought by freezing and thawing. As subsurface temperatures decrease, the moisture in the unbound pavement layers freezes into ice that binds the aggregate particles together. Frost penetration leads to an increase in the strength and stiffness of the unbound pavement layers and subgrade soil. The process of ice formation also draws moisture into the freezing zone. When the frost thaws in the spring, the moisture increase in the soil can lead to weakened support for the pavement structure. Another mechanical process associated with frost is the volumetric change in frostsusceptible soils, referred to as frost heave, which can lead to vertical differential movements of the road and subsequent poor performance. This heaving of roadbeds out of vertical alignment and breaking of the pavement surface often complicates highway maintenance.

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Over the years, the National Oceanic and Atmospheric Administration (NOAA)[1] and Environment Canada[2] have developed and published the climatic maps containing historical frost penetration values, as well as the number of freeze-thaw cycles in the form of contour maps. These maps provide frost depth estimates for natural (uncovered) land in the United States and Canada. The frost penetration conditions under pavements may be different from that of exposed land surfaces. In addition, deicing salts may have an effect on frost penetration as they eventually dissipate into the soil. Seasonal Monitoring Program To provide the transportation community with the data needed to understand the magnitude and impact of diurnal, seasonal, and annual variations in pavement properties and responses, including the effects of frost penetration beneath pavement section, the Federal Highway Administration (FHWA) Long Term Pavement Performance (LTPP) program selected a number of test sites throughout the United States and Canada for the Seasonal Monitoring Program (SMP). The original SMP (hereto referred as SMP I) included a total of 65 test sections and lasted from 1992 to 1999. As a part of the SMP I experiment, 37 pavement test sections were instrumented with electrical resistivity (ER) probes to monitor the frost penetration in unbound pavement layers. In addition, these sections were instrumented with time domain reflectometry (TDR) and temperature probes. At the conclusion of SMP I, the LTPP team realized the need for additional monitoring of these sites and initiated the SMP II program. The objective of the SMP II monitoring was to continue providing the data needed to attain a fundamental understanding of the magnitude and impact of variations in pavement response and properties due to the separate and combined effects of temperature, moisture, and frost penetration. The SMP II included a total of 22 test sections and lasted from 2000 to October 2004. LTPP continued monitoring the ER trend as a part of the SMP II experiment at 12 test sites. To aid in the interpretation of the ER data, an interactive computer program called FROST was developed in the late 1990s, and the available data were analyzed (see FHWARD-99-088 for more information on FROST).[3] FROST used ER data (voltage, contact resistance, and resistivity) in conjunction with soil temperature data to determine the depth of frost penetration in unbound layers for the SMP sections. The results of frost penetration analysis are stored in two computed parameter tables in the LTPP database as follows: • •

SMP_FREEZE_STATE. SMP FROST PENETRATION.

The SMP_FREEZE_STATE table characterizes the freeze state as frozen or nonfrozen at each ER measurement depth. This information is useful for understanding or reevaluating the process by which the results presented in table SMP_FRO ST_PENETRATION were derived. The data in table SMP_FRO ST_PENETRATION translate the freeze state at each measurement depth into starting and ending depths of frozen layer(s). The SMP_FRO ST_PENETRATION table is the end product of the data analysis to determine the boundaries of frozen layers within the pavement cross section. These computed parameters tables contain information necessary analyzing the changes in pavement structural responses due to the seasonal changes in pavement layer properties.

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These tables were updated twice with the new batches of the processed data: the first upload was based on the July 1999 version of the LTPP data for SMP I sections, and the second upload included SMP II sections based on the July 2001 version of the LTPP data. With the completion of monitoring measurements on the SMP sections in October 2004, there was a need to complete the interpretation of measurements not previously interpreted and to add the results to the database. In addition, through previous interpretation of SMP ER and soil temperature data, it became evident that the accuracy of the LTPP frost predictions could be improved by adding thermodynamic analysis capability to estimate missing temperature readings and by cross- referencing ER trends with moisture and temperature changes. Chapter 5 - This chapter summarizes the current status of the Long-Term Pavement Performance (LTPP) program and its major activities—data collection, data storage, data analysis, and product development. It describes the work that will be needed beyond 2009 to realize the full potential of the world’s most comprehensive pavement performance database and the benefits that will be accrued by capitalizing on the investment that has been made. The work that remains is as follows:

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1. Provide ongoing security and maintenance of the LTPP database and manage the Materials Reference Library (MRL). 2. Continue to support LTPP database users. 3. Further develop the LTPP database including additional data collection and database refinements. 4. Continue data analysis and product development. Addressing these needs is included in the Federal Highway Administration’s (FHWA) planning for future infrastructure research and development as documented in Highways of the Future—A Strategic Plan for Highway Infrastructure Research and Development (FHWA-HRT-08-068). The LTPP program is an ongoing and active program. To obtain more information, LTPP data users should visit the LTPP Web site at http://www.fhwa.dot.gov/ pavement/ltpp. LTPP data requests, technical questions, and data user feedback can be submitted to LTPP customer service via e-mail at [email protected].

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In: Long Life and Quiet Pavement: Research and Issues ISBN: 978-1-60741-888-7 Editor: Gordon E. Daniels © 2010 Nova Science Publishers, Inc.

Chapter 1

THE LITTLE BOOK OF QUIETER PAVEMENTS United States Department of Transportation INTRODUCTION

Copyright © 2010. Nova Science Publishers, Incorporated. All rights reserved.

Why was this Book Written? The idea of designing and building quieter pavements is not new, but in recent years there has been a groundswell of interest in making this a higher priority. Various State Highway Agencies and the Federal Highway Administration have responded accordingly with both research and implementation activities that both educate on the state-of-the-practice, and advance the state- of-the-art. The Little Book of Quieter Pavements was developed with this purpose in mind... to help educate the transportation industry, and in some cases the general public, about the numerous principles behind quieter pavements, and how they connect together.

Who is this Book Written for? This book is not a synthesis. It is not a textbook. And it is not a policy guide. Instead, it is intended to briefly touch on the numerous aspects of tire-pavement noise and quieter pavements that may be of interest to anyone. In other words, this book is intended to appeal to a wide audience. So while some of the content of this book is technical in nature, the depth of these discussions is minimal. Instead, resources are identified herein for further study.

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2

United States Department of Transportation

How Can I Listen along? In addition to the Little Book of Quieter Pavements, a listening experience has been developed, built off of the Soundscape DesignTM concept pioneered by Mr. Nicholas P. Miller, Senior Vice President of Harris Miller Miller & Hanson Inc. This listening experience is in the form of a collection of MP3 files. To experience it properly, this collection should be loaded onto an MP3 player and played in a setting free from other noise sources or distractions. Throughout the Little Book, notations of corresponding track numbers are given as a small blue speaker with a track number. While the listening experience can be useful as a stand-alone tool, the tracks played at the appropriate times will allow the reader to enjoy a more fulfilling educational experience. A reference to each of the tracks can also be found at the end of the Little Book.

THE BIG PICTURE

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Why is Noise so Important? Traffic noise pollution has become a growing problem, particularly in urban areas where the population density near major thoroughfares is much higher and there is a greater volume of commuter and commercial traffic. To mitigate the noise – at least for those living and working near these roads – engineers are currently resorting to noise barriers at a cost of two million dollars or more per mile. But while effective in many instances, noise barriers aren’t always the best solution for noise pollution. For one thing, they must break the line of sight to be effective. Barriers are also of questionable effectiveness in rolling terrain or on arterial streets where gaps are required for side streets and driveways, as sound tends to “bend” over the top and around the ends of walls. In recent years, alternative solutions to noise barriers have been advanced – ones that can mitigate noise for both the drivers and for those living and working alongside the highway. Motivated in large part by public outcry leading to policy, engineers worldwide have developed alternative pavement types and surfaces that reduce the noise generated at the tirepavement interface. While the noise produced from tire-pavement interaction is just one of several sources, for almost all roads and for most vehicles, it becomes the primary source of traffic noise for vehicular speeds over about 30 mph.

Where did All this Talk of Noise Begin? Until recently, the demand for quieter pavement surfaces has not existed in the United States, therefore little expertise, much less experience, can be found here. However, this demand is significant throughout Europe, Japan, and elsewhere in the world. In some cases, dedicated research programs have been underway for many years on this topic. Noise has likely taken a more pronounced role in other countries due to the proximity of their residents with respect to major transportation corridors including rail and highways. With the exception

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The Little Book of Quieter Pavements

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of the older areas of the United States, development along transportation corridors here has been reasonably managed through large right of ways and zoning restrictions. Over the years, numerous researchers, particularly in Europe, have advanced innovative tire-pavement noise solutions. Novel solutions for quieter pavements can be found in both asphalt and concrete. In the early 1990s, the FHWA and AASHTO began to take note of these paving technologies, and conducted international scanning trips to investigate the details of these techniques first-hand. However, with some exceptions, little was subsequently implemented in the US. While some obstacles were technological and economic, the resistance to adopt the techniques was likely due to political and institutional reasons. Today, this climate has changed. A renewed demand for quieter pavements now exists, and the solutions to fill this demand are more readily available and proven. In this book, some of these solutions are described, along with a rationale behind their selection in light of the numerous other decision-making criteria.

THE BASICS OF SOUND AND NOISE

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What is Sound and What is Noise? Sound is all around us. It comes from the baby crying next to you on the plane, the radio playing your favorite song, the lawn mower that startles you out of your slumber on Saturday morning, and from waves crashing on the beach. Sound is all of these things and more. From a technical perspective, sound is small but fast changes in air pressure that cycle higher and then lower than the air pressure that is all around us. It includes everything we can hear, and even some things we can’t. Noise is sound. However, not all sounds are noise. The difference is that noise is sound that we find objectionable. As such, what is noise to one person may not be to another. What is your favorite song? Would everyone you know enjoy it as much as you do? To everyone, that song will be sound. However, to someone who doesn’t enjoy it, the song is noise. In terms of quieter pavements, we often interchange the terms Sound and Noise, but we must be careful to understand the difference.

How do We Hear? As we learned, sound is simply small air pressure changes. The human hearing system is a marvel in converting these air pressure changes into a human response. It begins with a vibration of the eardrum as a result of the pressure changes. If you hold a piece of paper flat in front of a speaker, you will feel vibrations in the same way that your eardrum vibrates. These vibrations then move some small bones that transfer the vibration to the inner ear. Full of fluid, the inner ear transfers the vibrations to the basilar membrane which has small, sensitive nerve endings that convert this information to what your brain interprets as sound.

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United States Department of Transportation

What is a Decibel? Our hearing system is capable of sensing a very wide range of pressure changes. Pressure is often given in either units of Pascals (Pa) or pounds per square inch (psi). We know that most people can sense sounds as little as 0.00002 Pa. Furthermore, at some point in our lives, we may experience something that is 100 Pa or more. Our hearing is what is called non-linear. Hearing something change from 0.1 to 1 Pa (an increase of 0.9 Pa) sounds about the same as a change from 1 Pa to 10 Pa (an increase of 9 Pa). In addition, something heard at 2 Pa does not sound twice as loud as 1 Pa. As a result of this, we often convert measures of sound to sound level. More specifically, we convert pressure changes in Pa to something that crudely relates to the human experience – units of decibels (dB). Mathematically, this conversion is made as follows:

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Figure 1 also shows this conversion, along with pictures that help to identify what kinds of sounds produce the various levels. Rules of thumb regarding sound level are sometimes helpful. To begin, most would consider a 1 to 3 dB change as “just noticeable”, and it takes a 5 dB change to be considered definite. This is especially true if there is any gap in time between listening to the sounds being compared. Most also consider 10 dB change a “doubling” (or “halving”) of sound. There is one very important thing to note about these rules of thumb... they are only true for the same sound. If the type of sound changes, these changes in perception may no longer be valid.

Figure 1. Comparison of sound pressure, sound levels, and common examples Long Life and Quiet Pavement: Research and Issues : Research and Issues, Nova Science Publishers, Incorporated, 2010. ProQuest Ebook

The Little Book of Quieter Pavements

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Figure 2. Definition of various sound

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What is the Difference between Lmax and Leq and L10 and...? In most situations, the sound levels around us will not stay the same from moment to moment. As someone talks, for example, we will experience higher levels as they speak, and lower levels when they stop. There are a number of ways to convert these types of non-uniform sounds into a single measurement (number). To illustrate how this can be done, Figure 2 shows what a sound level meter might produce if placed next to a road. It shows the rise and fall of the sound level over time. The sound from individual vehicles can be noted as they pass by the meter alongside the road. The levels of each vehicle vary depending on the type (e.g., car vs. a truck) and the distance between passing vehicles. The first thing to note when reporting this type of information is the length of time that such a measurement is made. In the case of traffic noise measurements, this is typically on the order of 5 to 90 minutes, and sometimes up to 24 hours. Next is the selection of the single level that represents the data. This will depend on what is important to you. The following are the most common options used in traffic noise: •

Lmax – This level is the maximum sound level during the measurement period. In Figure 2, this is 85 dB. It may be this single event that is most significant to you (e.g., a loud motorcycle going by at 3AM).

•

LXX – The “XX” is instead actually a number (e.g., 10). It represents the sound level that is exceeded only XX% of the time. Like Lmax, this type of measurement is relevant in those instances where isolated and infrequent sounds may be dominating the perception of the road. In reporting aircraft noise, this type of measurement is often used. In Figure 2, this is 81 dB.

•

Leq – This level is the equivalent sound level during the measurement time. In Figure 2, this is 78 dB. It is calculated by adding up all the sound energy during the measurement period, and then dividing it by the measurement time. Leq is probably the most common way of reporting traffic noise, as not only is it required to interpret FHWA policy, but it also is representative of the actual traffic noise that is present, and thus a function of both the vehicle type and speed, as well as the pavement.

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United States Department of Transportation

There are numerous other ways to report sound levels. Ldn, for example, is a type of weighted average of the sound level to account for what time of day it is heard – (d)ay or (n)ight. Sound heard at night is effectively “penalized” since it is more likely to affect sleep. Another metric, Sound Exposure Level (LE), is also used sometimes to describe a single event – giving what the level would be if all of the sound energy occurred in 1 second.

What is a Hertz? The frequency or pitch of a sound describes how fast the small air pressure changes are occurring. This is often reported in cycles per second or Hertz (Hz). Like sound levels, the perception of frequency is also non-linear. A change from 1000 Hz to 2000 Hz (an increase of 1000 Hz) is perceived in a similar way as a change from 2000 Hz to 4000 Hz (an increase of 2000 Hz). These doubling of frequencies are called octaves, and will be discussed in more detail later.

What Frequencies Matter?

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In addition to hearing over a wide range of sound levels, humans can also hear over a wide range of frequencies. Assuming you have no hearing loss, you may be able to hear sounds from 20 cycles per second (Hz) to 20,000 Hz. Human hearing is less sensitive near these extremes, and is often most sensitive in the range from 1000 to 4000 Hz. As we get older, or if our hearing has been damaged, we tend to lose our sensitivity to some frequencies, particularly those on the higher end of this range.

Figure 3. Time and frequency domains of simple sounds (source: Brüel & Kjær)

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How do We View and Understand Frequencies? In order to interpret highway noise, we must understand how frequency content is often reported. To begin, Figure 3 illustrates two simple sounds – a tone of 1000 Hz and one at 4000 Hz. When shown as pressure vs. time, both tones have very simple sinusoidal patterns. When converting from the time domain to the frequency domain, each signal is shown as a single bar at its characteristic frequency. The length of the bar is representative of the size (“height”) of the waves. Figure 3 shows the addition of these two simple sounds into more complex-looking sounds. The frequency domain of this sound is still very simple, however. More complex sounds are given in Figure 4. The first is the sounds of gears meshing. On a time domain plot, this is very complex looking, and it is difficult to understand from this plot alone what kind of sound this is. On the frequency domain plot, however, characteristic tonal peaks can be seen at various frequencies (likely corresponding to the number of teeth and speed of the gears). These peaks are sometimes an indication that a sound might be unpleasant. The second example looks similar to the first in the time domain, but very different in the frequency domain. As rain on the umbrella, this sound is more random (or broadband), and thus often more pleasant. The third sound is that of an anvil being hit. While very similar to the umbrella example in the frequency domain, it is much different in the time domain. This type of sound is transient, meaning that it changes significantly with time. This underscores the importance of looking at both the time and frequency domains when interpreting sounds. Figure 5 shows various ways that frequencies can be plotted for a sound. The first is called a narrow-band plot, and while very complicated looking, allows for subtle components of a sound to be identified. The second is a one-third-octave band plot that adds up the sound energy into various standardized bands. These bands simplify the reporting, but compromise some of the ability to interpret the sound. Octave bands can also be reported which sum the energy in groups of three consecutive third-octave bands. Each octave represents a doubling of frequency. Finally, a total level can be reported by summing all of sound energy in the octave bands together.

Figure 4. Time and frequency domains of real sounds (source: Brüel & Kjær) Long Life and Quiet Pavement: Research and Issues : Research and Issues, Nova Science Publishers, Incorporated, 2010. ProQuest Ebook

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Figure 5. Frequency spectra forms of the same sound

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How does Sound Travel? Sounds can often be analyzed by breaking them down into a source, propagation path, and receiver. If the position and intensity of a source is known, along with the path, a good prediction can often be made of the sound level at the receiver. This calculation becomes increasingly complex, however, as things that may block or reflect sound are introduced. Furthermore, the way that sound travels through the air is dependent on climatic variables including temperature, humidity, and barometric pressure. While predictions at shorter distances (less than 100 m) can often ignore these, longer distances may require more sophisticated models.

How is Sound Perceived? Ideally, the way that a person will respond to a sound is the way the measurement should be reported. However, there are numerous reasons why this is easier said than done. Human response will vary as a function of the transient and frequency characteristics of a sound, not to mention the individual’s definition of noise. To simplify this, measurements are often reported after being filtered using a weighting scheme. Weighting means that the levels at the various frequencies are modified according to how a person might hear them. As Figure 6 illustrates, there are four commonly used weighting schemes to do this, with the A-weighting scheme the most commonly used in traffic noise measurements. In this case, the most importance is placed on frequencies between 1000 and 4000 Hz, as people are most sensitive in this range. Levels outside of this range are attenuated (reduced).

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Figure 6. Weighting schemes for sound level calculation

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When reporting sound levels, it is important to include the designation of the weighting scheme. One way is to add the letter (e.g., “A”) to the index. For example, LAeq should be used instead of just Leq. The units of the calculated sound levels could also include the weighting scheme that was applied. For example, dB(A) or dBA should be used instead of just dB when the A-weighting scheme is used. Ideally, the term “A-weighted decibels” should be used to minimize any chance of confusion. Furthermore, if no weighting is used, it is better to use linear weighting (or LIN) instead of simply leaving the designation off.

Figure 7. Speed effects on vehicle noise sources and crossover speed Long Life and Quiet Pavement: Research and Issues : Research and Issues, Nova Science Publishers, Incorporated, 2010. ProQuest Ebook

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TRAFFIC NOISE What is Traffic Noise? While a clear distinction between sound and noise was given previously, the sound generated by traffic is usually termed traffic noise. It is all of the sound that is heard as a result of vehicles traveling down a road, and includes the combination of all possible sources of noise on a vehicle. These sources are commonly divided into propulsion, tire-pavement, and aerodynamic noise. Propulsion noise includes sounds generated by the engine, exhaust, intake, and other powertrain components. The tire-pavement noise is that which is generated as the tire rolls along the pavement. Aerodynamic noise is caused by turbulence around a vehicle as it passes through the air.

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What Effect does Vehicle Type and Speed Have? Figure 7 illustrates the relative importance of the three primary sources of traffic noise – propulsion, tire-pavement, and aerodynamic. Propulsion noise will dominate the total noise at very low speeds. As speed increases, a crossover speed is reached at which the tire-pavement noise becomes the dominant source. Only at very high speeds will aerodynamic sources begin to dominate. The crossover speed is an important concept. One way to view it is as a practical threshold, above which quieter pavements will be most helpful. It is a function of vehicle type and operating condition. As car engines become quieter, the crossover speed becomes lower, and quieter pavements become more practical. Vehicle type is an important variable in the noise that is generated. Heavy trucks with their large propulsion systems and numerous tires are among the noisiest vehicles on the road. A “typical” heavy truck is on the order of 10 dBA louder than a “typical” passenger car at highway speeds. This means that one truck generates the same sound energy as ten cars, and thus if trucks make up more than 10% of the traffic stream, they will likely dominate the overall sound level. As Figure 7 illustrates, speed is also a variable in traffic noise. On many highways, an increase in speed of 10 mph will result in an increase in sound level of approximately 2 to 3 dBA.

What other Things Affect Traffic Noise? The amount of traffic on a highway will also affect the sound level, but not as significantly as some would think. Assuming speeds and traffic mix stay the same, doubling the traffic volume will result in only a 3 dBA increase. Vehicle operating characteristics including braking (especially engine braking), accelerating, climbing, and cornering will all increase noise to varying degrees.

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How Can We Control Traffic Noise? Within the FHWA policy found in 23 CFR 772, there are six possible methods to reduce traffic noise. If noise mitigation is found to be feasible and reasonable, noise barriers of some type are the most commonly used option. These often take the form of sound walls and/or earthen berms. The height of the barrier is a factor since if the line of sight between the source and the receiver is not broken, the barrier will not reduce the noise. Fortunately, most of the sound is generated close to the ground, which is the reason why most barriers can be effective to some degree. The effectiveness of a barrier is a function of how far away you are. For example, if you are directly behind a barrier, you may experience a decrease in sound level of typically 5 to 10 dBA. Once you are 100 to 150 m from the barrier, however, its effectiveness is different. A “shadow effect” will often occur, meaning that some of the traffic noise will “bend” around the top of the barrier. At this distance, however, background noise in the neighborhood may begin to dominate as spreading of the sound generated by the highway will decrease its level. It should be similarly noted that the effectiveness of a barrier can also be partially lost if there are any breaks in it – driveway access, for example. Spreading is a natural decrease in sound level, and varies depending on the type of traffic. As Figure 8 illustrates, sparse traffic can be viewed as individual point sources, and the sound level will decrease by approximately 6 dB per doubling of distance. Heavy traffic can viewed as a line source, which often has only a 3 dB decrease in sound level per doubling of distance.

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When is a Noise Barrier Used? For projects in the US that qualify for federal cost sharing, federal policy governs when funding for noise mitigation will be provided. Within the policy, a systematic method of data collection and analysis is outlined, along with specific thresholds that must be met before funding will be allowed. The State Highway Agencies, in turn, weave these guidelines into their policies and practices in order to conduct noise studies.

Figure 8. Spreading of traffic noise from various source types. Long Life and Quiet Pavement: Research and Issues : Research and Issues, Nova Science Publishers, Incorporated, 2010. ProQuest Ebook

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While the specifics of this can be sought from the FHWA Noise webpage and elsewhere, some highlights are as follows:

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1. Federal cost share for noise abatement is only considered on some types of projects. This includes the addition of lanes or significant changes to vertical or horizontal alignment; a renewal of the pavement surface is not a candidate project. 2. Highway traffic noise impacts are determined by analyzing exterior (outdoor) areas with frequent human use. If there are no usable exterior areas, then an interior analysis may be done. In addition, the area must already be developed, or have building development approved or underway. 3. As part of the data collection and subsequent modeling, it must be determined that the potentially impacted parties meet specific Noise Abatement Criteria (NAC). The NAG is an absolute A-weighted sound level that must be approached before the party is considered impacted. The definition of “approach” is set by the State; however, most select an approach level that is 1 dBA lower than the NAG. 4. The NAG is not intended to be a level that will be achieved after noise abatement is in place. Furthermore, the NAG varies depending on the land use, and includes different criteria for different categories. Residential land falls under Gategory B, for example. In this case, an impact occurs when approaching 67 dBA. This level is about where conversational speech can be adversely affected. It is also far below a level that can lead to hearing damage, as Figure 1 illustrates. 5. The potential noise mitigation methods are then evaluated for being feasible and reasonable in their ability to control noise. Only if these tests are passed can mitigation be approved for federal funding.

TIRE-PAVEMENT NOISE What Things about A Tire Affect Noise? Tires in use today are the result of a high level of engineering. Heavy competition and overcapacity of production also make them a commodity item. As a result, cost is a principal consideration, but many other aspects of a tire still govern its design and construction. Safety, for example, is paramount and cannot be compromised. Durability and handling are also important, as buyers will often include these in their decision-making process. Noise is an additional consideration, although the emphasis is on noise inside the vehicle, and not alongside the road. Tires are often engineered for a specific application; from summer tires that are optimized for handling and noise, to mud and snow tires that move water and improve friction. The tire tread pattern and rubber compounds are what typically affect most of the properties of interest to the tire companies as well as tire-pavement noise. The more aggressive a tire tread pattern is (with clearly defined blocks and gaps), the louder it will typically be. Harder tires (rubber compounds) will also typically be louder compared to softer compounds.

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Figure 9. Typical features of a tire (source: Yokohama Tires).

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As illustrated in Figure 9, there are other more subtle but important tire and tread characteristics. One important characteristic for noise is the degree of randomness of the tread block size, which will minimize tonal frequencies that most would find objectionable. Skewed (angled) blocks are also used since they allow for a more gradual roll in and out of each block. This prevents sudden impacts that can lead to a noisier tire. Air gaps in the tread pattern (including grooves and sipes) help to minimize some sounds from being generated, but also amplify other sounds. More on this later.

What Things about a Pavement Affect Noise? The influence of a pavement on tire-pavement noise is as equally important as the tire. Quieter pavements are typically smooth, but still provide adequate “ventilation”. To a lesser degree, pavements that are “softer” will also typically be quieter. Pavements, like tires, must not be built just for noise, however. Of paramount concern is safety, with additional considerations for cost and durability. Fortunately, we know that quieter pavements do not have to compromise these other characteristics of interest.

Figure 10. “The Hammer” generation mechanism Long Life and Quiet Pavement: Research and Issues : Research and Issues, Nova Science Publishers, Incorporated, 2010. ProQuest Ebook

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What Makes Tire-Pavement Noise? When the tire and pavement get together, they sure get noisy! And they do so in a very complex way. The sound often begins with various types of generation mechanisms. Making it complex is the fact that numerous mechanisms happen simultaneously, and to varying degrees, depending on the specific tire-pavement combination. Generation mechanisms are those that make sound. In the next section, we will discuss things that can amplify these sounds. To better understand the complexity of the various tire-pavement noise generation mechanisms, they are often described using physical analogies. The more prominent of these mechanisms are described as follows: Tread impact (a.k.a. “The Hammer”) – As the tire rolls along the pavement, the tread on the tire and the texture on the pavement will come together as individual impacts. The resulting interaction can be seen as hundreds or even thousands of small hammer strokes occurring each second, each generating sound. See Figure 10.

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Air pumping (a.k.a. “The Clapper”) – In between the tread on a tire and the texture on a pavement are gaps filled with air. As the tire and the pavement roll together, some of that air is squeezed out, and some is trapped and compressed. Moments later, as the tire loses contact with the pavement, what air was trapped is now forced out. And in some cases, air is sucked back in. All of this happens hundreds or thousands of times a second. This process is similar to clapping your hands, where much of the sound that is heard is air being pushed away quickly. Whistling is another example, where air is forced out of a small opening, generating sound as a result. See Figure 11. Stick-slip (a.k.a. “The Sneaker”) – As one watches a basketball game, the distinctive sound of sneakers squeaking on the court can be heard. This same type of sound is produced as a tire rolls along the pavement. As the rubber is continually deformed and distorted underneath the tire, it will mostly stick, but also periodically slip once a critical limit is reached. These “corrections” under each tread block happen thousands of times a second, thus generating high frequency sound. See Figure 12.

Figure 11. “The Clapper” generation mechanism

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Figure 12. “The Sneaker” generation mechanism.

Figure 13. “The Suction Cup” generation mechanism.

Stick-snap (a.k.a. “The Suction Cup”) – A suction cup can stick to a smooth surface because of both adhesion and a vacuum that is created when the air in the cup is pushed out. As tread blocks interact with some pavements, a similar effect can occur, generating sound. See Figure 13.

What Makes Tire-Pavement Noise Even Louder? The sound that is created by the various generation mechanisms is simply not enough to explain all of the noise that is heard. It is well accepted that a number of amplification mechanisms are also at play which increase the sound level. Amplification of tire-pavement noise is also complex. Like many musical instruments, the sound at some frequencies will be amplified more than others. As a result, if one seeks to reduce overall noise, they should target those frequencies that are amplified the most. To better understand specific amplification mechanisms that affect tire-pavement noise, physical analogies are again used. These include:

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United States Department of Transportation Acoustical Horn (a.k.a. “The Horn”) – The geometry of a tire and a pavement in contact includes a wedge-shaped segment of open air. Within this wedge, multiple reflections of sound generated near the throat can occur, much like the reflections that occur within a musical horn or megaphone. In the case of tire-pavement though, the horn is poor as it is open on two sides. The result is a significant amplification in the forward and aft directions, along with a distortion of some frequencies. See Figure 14.

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Figure 14. “The Horn” amplification mechanism.

Figure 15. “The Pop Bottle” amplification mechanism.

Helmholtz Resonance (a.k.a. “The Pop Bottle”) – When you blow across the top of a pop bottle, a distinct tone can be heard. This occurs as the air in the neck of the bottle (acting as a mass) vibrates up and down on the pillow of air inside the bottle (acting as a spring). By itself, blowing creates very little sound. However, blowing across the bottle significantly amplifies the frequency that is distinct to that bottle. A similar geometry can be found close into the wedge where the tire and pavement meet. In this case, the mass and spring are sideby-side. The result is an amplification of some frequencies unique to the geometry of the tire and the pavement. See Figure 15. Pipe Resonance (a.k.a. “The Organ Pipe”) – When air is blown across an organ pipe, a sound will be amplified that is unique to the length of the pipe and how many openings are in the pipe. On a tire, similar “pipe” geometries can be found as the various grooves and sipes on a tire are pinched off and opened up at various places underneath the contact patch. Sound that is generated elsewhere can be amplified within these pipes. See Figure 16.

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Figure 16. “The Organ Pipe” amplification mechanism.

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Sidewall Vibrations (a.k.a. “The Pie Plate”) – An electric shaver or vibrating cell phone do not make much sound by themselves. However, if one is placed on top of an upsidedown pie plate, the small vibrations are amplified significantly. Many of the small vibrations described as generating mechanisms will be similarly amplified as vibrations of the tire sidewall. See Figure 17.

Figure 17. “The Pie Plate” amplification mechanism

Figure 18. “The Balloon” amplification mechanism

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Cavity Resonance (a.k.a. “The Balloon”) – When a balloon is thumped, a distinctive ringing sound can be heard. The same is true as a tire is kicked. This sound can actually be better heard inside the vehicle. In fact, this mechanism is less important for noise heard outside the vehicle as it is inside the vehicle, as the vehicle itself tends to further amplify this frequency. See Figure 18.

MEASUREMENTS

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What are Wayside Noise Measurements? The most common way of measuring noise is “at the side of the road”. Technically, these are termed wayside measurements, and can be done either at a fixed distance from the road (commonly 7.5 or 15 m), or else at the location of receivers such as a residential backyard or playground. Ideally, wayside measurements include the measurement of sound levels using microphones, as well as traffic speeds and classifications. This is illustrated in Figure 19. There are three common types of wayside testing. In instances where there is little traffic, statistical pass-by (SPB) testing can be done. In this case, a microphone at a fixed position is used to measure the maximum sound levels (Lmax) of hundreds of individual vehicles. From these, a calculation is made of the sound level from an “average” car, medium truck, and heavy truck traveling at a standardized speed. A similar test is sometimes done with one or more known test vehicle/tire combinations. In this case, it is called a controlled pass-by (CPB) test. Using SPB and CPB, pavements at different locations can be compared to one another. Some caution must be exercised, however, as there can always be differences in the “average” vehicle from site to site (for SPB) or unique interactions between a specific tire and pavement combination (for CPB). A third type of wayside testing that is commonly conducted is termed time-averaged. This is sometimes referred to as continuous flow traffic time-integrated model (CTIM). In this case, the microphone is set to record all of the traffic noise over a fixed time (commonly 5 to 30 minutes) and traffic levels and speeds are simultaneously recorded. An average equivalent sound level (Leq) over this period is calculated, and is often reported as an average of repeat measurements.

Figure 19. Components of a wayside measurement Long Life and Quiet Pavement: Research and Issues : Research and Issues, Nova Science Publishers, Incorporated, 2010. ProQuest Ebook

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Figure 20. CPX and OBSI test equipment

All wayside testing is subject to some degree of human interpretation. For example, consideration must be given to the presence of objects that might reflect or block sound. Weather conditions must also be monitored, especially the wind which can affect the sound level. Finally, “contaminating sources” must also be identified including aircraft and roadside noise (lawn mowers, trains, etc.). If significant enough, measurements must be discarded.

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What are Source Noise Measurements? A measure of tire-pavement noise as opposed to traffic noise is of increasing interest, particularly for those that wish to design and build quieter pavements. Source measurements measure sound “near the tire”. There are currently two principal techniques for measuring tire-pavement noise: closeproximity (CPX) and on-board sound intensity (OBSI). CPX is currently documented as a draft international (ISO) standard 11819-2. OBSI was initially developed by General Motors for use in tire evaluation at their test facilities. The technology was developed further by Dr. Paul Donavan of Illingworth & Rodkin as part of quiet pavement research for the Departments of Transportation in both California and Arizona. The OBSI measurement technique is now in the process of being standardized. As Figure 20 illustrates, both techniques are similar in that they include microphones positioned close to the tire-pavement contact patch. Both collect measurements as the vehicle is in motion. However, there are also some important differences: •

•

The CPX method uses single microphones that measure sound pressure. OBSI uses dual-microphone probes that measure sound intensity. The latter is directive, meaning that the measurements from each of the two microphones can be used to sort out the direction of the various sources. Currently, the CPX and OBSI methods specify different positions for the microphone including the height (from the ground), spacing between the front and rear positions, and distance from the tire sidewall. These differences mean that the generation and amplifying mechanisms will play different roles in the sound measured by the two tests.

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•

While not required, CPX testing is often run in an enclosed trailer that is intended to isolate the microphones from other sources of sound. Because of the ability of OBSI to identify the direction of a sound source, this is not required. There is more experience with the OBSI method in the US, while the CPX technique has been the preferred method elsewhere in the world.

The measurements from any source measurement will be highly dependent on the tire that is used during testing. Specifications for both CPX and OBSI remain under development, with the identification of suitable test tires being a significant issue. Until recently, the vast majority of OBSI testing has been conducted using a Goodyear Aquatred III tire (P205/70R15). Recently, a newer Standard Reference Test Tire (SRTT) (P225/60R16) has been introduced and adopted for noise testing (ASTM F 2493). CPX testing in the US has also used the Aquatred, as well as a Uniroyal Tiger Paw AWP which differs only slightly from the new SRTT. According to the draft ISO CPX standard from 2000, the two most commonly used tires to date are an Avon/Cooper ZV1 (P185/65R15) and a Dunlop SP Arctic (P185/R14).

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What other Kind of Noise Measurements are There? In addition to measuring noise wayside or at the source, there are measurements that can be conducted in-vehicle, using microphones placed inside the passenger compartment. Data is collected as the vehicle is in motion, but without other potential sources such as the air conditioning or radio. In-vehicle noise is commonly much lower frequency than noise outside. Not only does the vehicle attenuate (decrease) the high frequency sound, but it also amplifies it at low frequencies. Any measurements collected and reported as in-vehicle should be interpreted with caution, as the effect of the vehicle type and condition is significant.

What Kind of Pavement Properties Relate to Noise? Three pavement properties that affect tire-pavement noise (in decreasing order of importance) are texture, porosity, and stiffness. Texture can be thought of as the “bumps and dips” on the pavement surface. There are long bumps and dips that might give your car a rough ride. There are also very short bumps and dips that cannot be seen by the naked eye – things that result from the type and amount of sand in the pavement, for example. Noise heard outside the vehicle is affected most by texture that repeats itself every 10 to 150 mm. All else being equal, this type of texture should be minimized (“flattened”). Smaller texture – that less than 10 mm in size – may actually prove beneficial, as it provides “escape paths” for air that lessen the effect of some of the mechanisms previously described. There is also evidence that so-called negative texture is a benefit. Negative texture means that the pavement surface is largely flat on top, but does have occasional dips that can create escape paths. Being flat on top also means that there are not as many bumps that would otherwise punch into the tire, generating noise.

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Figure 21. CTM and RoboTex test equipment (source: CP Tech Center)

Texture can be measured using a volumetric technique such as the “sand patch” test (ASTM E 965), or using laser-based height sensors such as that on various pavement profilers (ISO 13473). Specialized laser-based techniques for measuring texture include the Circular Texture Meter and RoboTex (see Figure 21). The porosity of a material is the ratio of the volume of air to the total volume. Materials used in most pavement surfaces have a porosity less than 5%. However, when the porosity increases to 20% or more and/or when air can flow through the material, the result can be a benefit in noise reduction. Porosity increases acoustical absorption, which is the ability of a material to absorb sound, and thus prevent it from reflecting back into the air. Porous materials also have less contact area between the tire and the pavement, and thus provide additional escape paths for air that can reduce noise. This effect may also be possible when inclusions are used in the pavement surface layer. Inclusions can be materials such as rubber, polymers, or fibers that partially replace air voids. Porosity can be calculated from a simple evaluation of the weight and volume of a pavement specimen and its components. Acoustic absorption can also be evaluated directly using a number of techniques; both in the laboratory and in-place (see Figure 22). The most well known uses a core sample inserted into an impedance tube (ASTM C 384/E 1050). Another technique that has been used with both lab samples and in-place involves impulse response measurements using the extended surface method (ISO 13472-1). A third technique uses effective flow resistivity (ANSI S1.18). This is believed to be a more relevant measure of absorption since it is measured at a shallow angle rather than perpendicular to the pavement surface. The stiffness of the pavement surface also contributes to tire-pavement noise, but to a lesser degree. To minimize the influence of many of the mechanisms previously described, a pavement stiffness that approaches that of the tire is ideal. In fact, significant noise reductions have been noted on experimental pavements containing epoxy-bound shredded rubber termed poroelastic. These pavements are similar to the surface of a running track on many sports arenas. It will absorb impacts from tires much in the same way that the sports tracks absorb impacts from running shoes. While not as extreme, inclusions of rubber and other materials are sometimes used in pavement surfaces. Depending on what material is used and to what extent, the stiffness of the pavement surface can be affected. Stiffness is not a simple parameter to measure as it is often significantly affected by temperature, and the type, rate, and amount of force that is applied to the material being tested. Most techniques used to date (that are relevant to noise) involve small impact loads such as those used by the impact echo technique (ASTM C 1383).

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Figure 22. Acoustical absorption test equipment (source: NCAT, Zircon, Caltrans)

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Figure 23. TPTA test equipment and sample surface (source: Purdue SQDH)

Can Noise be Measured in the Laboratory? If quieter pavements become a goal, it is imperative that fast, accurate, and relevant test procedures be developed for measuring tire-pavement noise in the laboratory. One technique that is in use today is the laboratory drum. While several drums are in use around the world, the only known device of its kind in the US is operated at the Institute for Safe, Quiet, and Durable Highways at Purdue University. Shown in Figure 23, the Tire-Pavement Test Apparatus (TPTA) consists of a rotating arm with a tire assembly which is in contact with individual test panels that allow real pavement materials to be tested for tire-pavement noise at up to 30 mph. Microphones and probes can be positioned to collect CPX or OBSI style measurements. While large in size and used primarily for screening potential quieter pavement types in a research environment, the TPTA serves as a model for potential lab tests of the future to measure tire-pavement noise more directly prior to full-scale implementation.

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Figure 24. Conceptual schematics of “bad” and “good” texture

QUIETER PAVEMENTS What Things Make a Quieter Pavement?

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A quieter pavement can be designed and built in virtually any location subject to any environment and any amount and type of traffic. Furthermore, quieter pavements of both asphalt and concrete can achieve the same level of cost effectiveness, durability, and safety expected of our highways today. While much is still to be learned about quieter pavements, there is guidance that can be provided today to help us achieve this goal. To begin, we should recognize that quieter pavements are generally quieter for three reasons, in decreasing order of importance: 1. Texture – Goal: Keep it Small and Negative – Texture that will stab and poke at a tire will lead to undesired noise. As such, an objective common to all quieter pavements is to reduce the dimensions of any texture that is 10 mm or larger (“peak to peak”). However, some texture must remain to allow for “escape paths” for air. This remaining texture should be small (less than 5 mm) and negative (see Figure 24). 2. Porosity – Goal: Make it High – Porosity can help absorb noise and reduce contact area, especially when in excess of 20%. However, since additional air voids can affect durability of any paving material, this tradeoff must be balanced. Inclusions (e.g., rubber, polymers, and fibers) in lieu of air voids continue to be looked at as a viable alternative. 3. Stiffness – Goal: Keep it Low – While the most difficult to control for practical purposes, it is known that pavements that have stiffness characteristics approaching that of a tire can be quieter than those that are more typical of asphalt and concrete in use today. The target of a very low stiffness will be the most difficult one to meet, as durability of such soft pavements will likely be highly compromised.

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Figure 25. Porous asphalt schematic and photo

When optimizing a pavement material and/or surface for noise, however, one should recognize that focusing on controlling just one noise mechanism may lead to disappointing results. Quite often, there is more than one mechanism that contributes significantly to the overall sound level. As a result, reducing just one will lead to an overall reduction in noise that is less than expected. For example, one might think that a very smooth pavement would be the quietest. However, this is not the case, due in part to the air pumping, stick-slip, and possibly stick-snap mechanisms that will remain as significant noise generating mechanisms.

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What Asphalt Alternatives for Quieter Pavement are There? Under sponsorship of the FHWA, the National Center for Asphalt Technology (NCAT), located at Auburn University, has been evaluating a number of US and European materials and techniques for quiet asphalt pavements. Utilizing a 2-mile test track, dozens of asphalt mixtures have been placed and evaluated at various stages of accelerated truck loading. Quiet asphalt pavements can be constructed of virtually any nominal mix type: densegraded, gap-graded (SMA), and open-graded (porous). Mixtures containing rubber or other polymer modifiers have also been demonstrated to be quiet. In following the principles of quieter pavements described previously, one of the common elements to a quiet asphalt pavement is small texture. This can be engineered using a small maximum aggregate size (“top size”). Pavements in Europe that are among the quietest include double-layer porous asphalt, where the surface course consists of a top size of 6 to 8 mm. This compares to mixtures in the US that typically range from 9.5 to 12.5 mm. To achieve a smaller top size while maintaining reasonable durability demands, both porous asphalt and gap-graded stone-matrix asphalt (SMA) mixtures are commonly used. Figure 25 illustrates porous asphalt pavements, where the size and combination of aggregates is selected to result in a high porosity (15 to 25%). The aggregates are opengraded, and sometimes almost uniformly graded, giving the pavement surface the appearance of a “puffed rice cereal square”. Because the mixture contains so many voids, “drain down” of the binder during placement can be a concern. Polymers and/or fibers are therefore used in the mixture to minimize this. Furthermore, while the additional porosity is beneficial in producing a quieter pavement, it is also the source of potential durability issues due to freezethaw effects, rapid oxidation, raveling, and/or fatigue cracking.

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Figure 26. Gap-graded SMA schematic and photo

Stone matrix asphalt (SMA) is a gap-graded mixture that “leaves out” intermediate sized material (see Figure 26). The mixture therefore consists of the larger aggregates and mastic (a blend of the binder and the smallest aggregate fraction). During construction, the larger stones are aligned so that they are in contact with one another, forming a “skeleton”. By doing so, SMA mixtures can be constructed with smaller aggregates without significantly affecting durability.

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Dense-graded asphalt mixtures (Figure 27) can also be built quiet, but more work is needed to identify specific mixtures and/or construction techniques that result in consistently quieter pavements. The work at NCAT on these and other mixtures will result in more guidance in the near future.

Figure 27. Dense-graded asphalt schematic and photo

Figure 28. Drag and diamond ground concrete pavements (source: CP Tech Center) Long Life and Quiet Pavement: Research and Issues : Research and Issues, Nova Science Publishers, Incorporated, 2010. ProQuest Ebook

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United States Department of Transportation

The asphalt rubber friction course (ARFC) used in Arizona has received a lot of attention due to the large overlay initiative in the Phoenix metropolitan area. It is an open-graded material, but contains additional binder due to the addition of the rubber. Helping make ARFC a quieter surface is the smaller aggregate (9.5 mm), along with a possible change in stiffness that makes it a closer match to the tire.

What Concrete Alternatives for Quieter Pavement are There?

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The National Concrete Pavement Technology Center (CP Tech Center), located at Iowa State University, currently has a joint research effort underway in cooperation with the FHWA, American Concrete Pavement Association (ACPA), and a consortium of State Highway Agencies. The primary objective of the Concrete Pavement Surface Characteristics Program is to identify the quieter concrete pavement options that do not compromise safety. As part of this effort, over one thousand pavement test sections throughout the US and Canada have been tested for noise, texture, friction, and smoothness. The resulting database has allowed for the characteristics of quieter vs. louder concrete pavements to be identified. The project is now seeking to connect tire-pavement noise characteristics back to specific design and construction elements. Among the concrete pavement textures in use today, both drag surfaces (burlap and artificial turf) and diamond ground surfaces are among the quietest. These can be seen in Figure 28. If an appropriate concrete mix design is used (containing hard, durable aggregates), both of these textures can be used to produce a quiet, safe concrete pavement. Longitudinal tining (Figure 29, left) can also be used to produce quieter pavements. However, some longitudinal tining has also been found to be loud. To ensure a quieter surface, a higher degree of quality control is required, especially when texturing. There must also be a compatibility between the mix, speed of placement/texturing, and the texturing technique, which must be identified in advance. While specifics of this process are under development as part of the ongoing study at the CP Tech Center, simple guidance includes techniques to minimize periodic deposits of concrete displaced by the tining process. Minimizing vibrations of the paver and texture cart may also help.

Figure 29. Longitudinal and transverse tined concrete pavements (source: CP Tech Center) Long Life and Quiet Pavement: Research and Issues : Research and Issues, Nova Science Publishers, Incorporated, 2010. ProQuest Ebook

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Transverse tining (Figure 29, right) is responsible for many objectionable concrete pavements. Not only are they among the loudest, but when tined with a uniform spacing, they can contain “whine” that increases the annoyance even further. Quieter transverse tined pavements are possible, but are often found to have a short spacing between the tines – nominally 12 mm or less. Furthermore, randomizing this short spacing can minimize the potential for “whine”. Even with this nominal spacing, however, the potential remains for constructing an objectionable pavement in terms of noise. Both material compatibility and quality control issues must be addressed to help overcome this. In Europe, a technique for concrete pavement surfacing termed exposed aggregate (Figure 30, left) is sometimes touted as a quiet concrete pavement. Measurements on similar surfaces placed in North America have not been favorable. Furthermore, noise measurements found in the literature show these pavements to be at a similar level to those constructed with more conventional concrete pavement textures that are typical in the US. Finally, porous concrete pavements (Figure 30, right) have been built in trial sections. While many have measured quieter than any dense concrete, their durability remains an unresolved issue.

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How do I Choose a Quieter Pavement? Before any quieter pavement is selected, it is in the best interest of all stakeholders to evaluate a number of other criteria. These include the durability of the pavement; not only in resisting the effects of both traffic loads and climate, but also the ability of the pavement to remain quiet over time (acoustical durability). The cost of the pavement – both initially and over the life cycle – should also be evaluated and considered. Finally, safety must never be compromised. Any quieter pavement that is constructed should face the same scrutiny as any pavement for its ability to provide a safe stopping distance as well as other issues including vehicle handling and splash and spray. Tools for decision-making based on such different criteria are readily available. Some are based on the conversion of many of these factors to equivalent dollars, with further consideration to the time phasing of these costs by way of life-cycle costs. Other tools include multi-criteria analysis methods, which have historically been used in other industries where complex decisions must be made.

Figure 30. Exposed aggregate and porous concrete Long Life and Quiet Pavement: Research and Issues : Research and Issues, Nova Science Publishers, Incorporated, 2010. ProQuest Ebook

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FOR MORE INFORMATION Where can I read to learn more? • • • •

Tyre/Road Noise Reference Book by Ulf Sandberg and Jerzy Ejsmont • www.informex.info Traffic Noise Model Technical Manual (FHWA-PD-96-010) An Introduction to Tire/Pavement Noise by Robert Bernhard, et al. (SQD 2005-1) Advanced References • Fundamentals of Acoustics by Lawrence E. Kinsler • Signal, Sound, and Sensation by William M. Hartmann • Noise and Vibration Control Engineering by Leo Beranek and István Vér

What are Some Good Web Sites? •

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•

•

•

•

Federal Highway Administration • Noise – www.fhwa.dot.gov/environment/noise • Pavements – www.fhwa.dot.gov/pavement • International Technology Scan on Quiet Pavement Systems in Europe – international.fhwa.dot.gov/quiet_pav State Department of Transportation Arizona – • Arizona – www.quietroads.com • California www.dot.ca.gov/hq/env/noise • Washington – www.wsdot.wa.gov/Projects/QuieterPavement Transportation Research Board Committees • Noise and Vibration (ADC40) – www.adc40.org • Surface Properties – Vehicle Interaction (AFD90) – www.trb.org/directory/comm_detail.asp?c=AFD90 Paving Industry Research • Asphalt (NCAT) – www.ncat.us • Concrete (National CP Tech Center) – www.cptechcenter.org Institutes of Noise Control Engineering • International – www.i-ince.org • USA – www.inceusa.org

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European Union Noise Policy • ec.europa.eu/environment/noise Institute for Safe, Quiet, and Durable Highways (SQDH) • tools.ecn.purdue.edu/~sqdh Center for Pavement Surface Characteristics • www.tcpsc.com

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Who are We? •

Robert Otto Rasmussen, Ph.D., P.E. (TX) Robert Otto Rasmussen is an internationally recognized expert in pavement engineering and construction, including the analysis and modeling of pavement smoothness, texture, and noise. He holds a B.S. in Civil Engineering from the University of Arizona, and a M.S.E. and Ph.D. from the University of Texas at Austin. He currently serves as Vice President and Chief Engineer of The Transtec Group, Inc., a pavement and materials engineering firm headquartered in Austin, Texas and is a registered professional engineer in the State of Texas. Dr. Rasmussen has authored dozens of peer-reviewed papers, and is an active member on numerous editorial boards, expert task groups, and industry groups including TRB, AAPT, ASCE, ACPA, RILEM, INCE, and ASA.

•

Robert J. Bernhard, Ph.D., P.E. (IN) Robert J. Bernhard received a B.S. in Mechanical Engineering from Iowa State University in 1973, an M.S. in Mechanical Engineering from the University of Maryland at College Park in 1976, and his Ph.D. in Engineering Mechanics from Iowa State University in 1982. He joined Purdue University in 1982. He was the Director of the Ray W. Herrick Laboratories from 1994 through 2004, and has been the Director of the Institute for Safe, Quiet, and Durable Highways since 1998. He became the Associate Vice President for Research at Purdue University in December 2004. In 2007, Dr. Bernhard became Vice President for Research of Notre Dame University.

•

Ulf Sandberg, Sc.D. Ulf Sandberg is a Senior Research Scientist at the Swedish National Road and Transport Research Institute in Linköping. He is also an Adjunct Professor at Chalmers University of Technology in Göteborg. He is known worldwide as one of the leading experts in tire-pavement noise, and is maybe most well known in the US as a co-author of the “Tyre/Road Noise Reference Book”. Dr. Sandberg’s accomplishments in this field are vast, and include service as chairperson and member on numerous ISO, TRB, and CEN committees related to highway noise.

•

Eric P. Mun Eric P. Mun received his B.S. in Mechanical Engineering from The University of Texas at Austin in 2002. He joined The Transtec Group, Inc. in 2005 and is currently

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United States Department of Transportation a Project Manager specializing in pavement surface characteristics. He has extensive experience in designing and building equipment systems for evaluating pavement surface characteristic and has collected and analyzed pavement noise, texture, and friction data on hundreds of pavement surfaces throughout North America. •

Nicholas P. Miller, M.S.M.E. (Developer of Accompanying Listening Experience) Nicholas P. Miller is Senior Vice President of Harris Miller Miller & Hanson Inc. He started his work in environmental acoustics in 1970 at the University of North Dakota. In 1973, he began working at Bolt Beranek and Newman in highway noise and regulatory acoustics. He then helped to found Harris Miller Miller & Hanson in 1981. His recent innovations include revisions to sleep disturbance analysis and development of Virtual SoundscapesTM - a technique that permits listeners to hear how a place will sound.

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What Can I Find in the Listening Experience? • • • • • • • • • • • • • •

Introduction Is it Sound or Noise? Decibels Frequencies Complex Sounds The Perception of Sound Introduction to Traffic Noise Controlling Traffic Noise Controlled Pass-By Testing Comparing Noise Measurement Types Comparing Pavements at Wayside Comparing Pavements at the Source Pavement Variability Who are We?

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In: Long Life and Quiet Pavement: Research and Issues ISBN: 978-1-60741-888-7 Editor: Gordon E. Daniels © 2010 Nova Science Publishers, Inc.

Chapter 2

LONG-LIFE CONCRETE PAVEMENTS IN EUROPE AND CANADA United States Department of Transportation

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ACKNOWLEDGMENTS This scanning study would not have been successful without the assistance of many individuals. The team is particularly appreciative of the contributions of the officials, engineers, technical personnel, and their staffs in the places we visited (Appendix B). These individuals and their organizations spent many hours responding to the team’s questions, preparing and presenting technical information, arranging and guiding site visits, and giving generously of their time and expertise. Sponsors of the trip were the Federal Highway Administration (FHWA), the American Association of State Highway and Transportation Officials, and the National Cooperative Highway Research Program. American Trade Initiatives, Inc., under contract to FHWA, oversaw the execution of this international scan and coordinated the group’s travel.

INTERNATIONAL TECHNOLOGY Scanning Program THE INTERNATIONAL Technology Scanning Program, sponsored by the Federal Highway Administration (FHWA), the American Association of State Highway and Transportation Officials (AASHTO), and the National Cooperative Highway Research Program (NCHRP), accesses and evaluates innovative foreign technologies and practices that could significantly benefit U.S. highway transportation systems. This approach allows advanced technology to be adapted and put into practice much more efficiently without spending scarce research funds to re-create advances already developed by other countries.

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United States Department of Transportation

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FHWA and AASHTO, with recommendations from NCHRP, jointly determine priority topics for teams of U.S. experts to study. Teams in the specific areas being investigated are formed and sent to countries where significant advances and innovations have been made in technology, management practices, organizational structure, program delivery, and financing. Scan teams usually include representatives from FHWA, State departments of transportation, local governments, transportation trade and research groups, the private sector, and academia. After a scan is completed, team members evaluate findings and develop comprehensive reports, including recommendations for further research and pilot projects to verify the value of adapting innovations for U.S. use. Scan reports, as well as the results of pilot programs and research, are circulated throughout the country to State and local transportation officials and the private sector. Since 1990, about 70 international scans have been organized on topics such as pavements, bridge construction and maintenance, contracting, intermodal transport, organizational management, winter road maintenance, safety, intelligent transportation systems, planning, and policy. The International Technology Scanning Program has resulted in significant improvements and savings in road program technologies and practices throughout the United States. In some cases, scan studies have facilitated joint research and technology-sharing projects with international counterparts, further conserving resources and advancing the state of the art. Scan studies have also exposed transportation professionals to remarkable advancements and inspired implementation of hundreds of innovations. The result: large savings of research dollars and time, as well as significant improvements in the Nation’s transportation system. Scan reports can be obtained through FHWA free of charge by e-mailing [email protected]. Scan reports are also available electronically and can be accessed on the FHWA Office of International Programs Web Site at www.international .fhwa.dot.gov.

Scan Reports International Technology Scanning Program: Bringing Global Innovations to U.S. Highways

Safety Safety Applications of Intelligent Transportation Systems in Europe and Japan (2006) Traffic Incident Response Practices in Europe (2006) Underground Transportation Systems in Europe: Safety, Operations, and Emergency Response (2006) Roadway Human Factors and Behavioral Safety in Europe (2005) Traffic Safety Information Systems in Europe and Australia (2004) Signalized Intersection Safety in Europe (2003) Managing and Organizing Comprehensive Highway Safety in Europe (2003) European Road Lighting Technologies (2001)

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Commercial Vehicle Safety, Technology, and Practice in Europe (2000) Methods and Procedures to Reduce Motorist Delays in European Work Zones (2000) Innovative Traffic Control Technology and Practice in Europe (1999) Road Safety Audits—Final Report and Case Studies (1997) Speed Management and Enforcement Technology: Europe and Australia (1996) Safety Management Practices in Japan, Australia, and New Zealand (1995) Pedestrian and Bicycle Safety in England, Germany, and the Netherlands (1994)

Planning and Environment

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Active Travel Management: The Next Step in Congestion Management (2007) Managing Travel Demand: Applying European Perspectives to U.S. Practice (2006) Transportation Asset Management in Australia, Canada, England, and New Zealand (2005) Transportation Performance Measures in Australia, Canada, Japan, and New Zealand (2004) European Right-of-Way and Utilities Best Practices (2002) Geometric Design Practices for European Roads (2002) Wildlife Habitat Connectivity Across European Highways (2002) Sustainable Transportation Practices in Europe (2001) Recycled Materials In European Highway Environments (1999) European Intermodal Programs: Planning, Policy, and Technology (1999) National Travel Surveys (1994)

Policy and Information European Practices in Transportation Workforce Development (2003) Intelligent Transportation Systems and Winter Operations in Japan (2003) Emerging Models for Delivering Transportation Programs and Services (1999) National Travel Surveys (1994) Acquiring Highway Transportation Information from Abroad (1994) International Guide to Highway Transportation Information (1994) International Contract Administration Techniques for Quality Enhancement (1994) European Intermodal Programs: Planning, Policy, and Technology (1994)

Operations Commercial Motor Vehicle Size and Weight Enforcement in Europe (2007) Active Travel Management: The Next Step in Congestion Management (2007) Managing Travel Demand: Applying European Perspectives to U.S. Practice (2006) Traffic Incident Response Practices in Europe (2006)

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Underground Transportation Systems in Europe: Safety, Operations, and Emergency Response (2006) Superior Materials, Advanced Test Methods, and Specifications in Europe (2004) Freight Transportation: The Latin American Market (2003) Meeting 21st Century Challenges of System Performance Through Better Operations (2003) Traveler Information Systems in Europe (2003) Freight Transportation: The European Market (2002) European Road Lighting Technologies (2001) Methods and Procedures to Reduce Motorist Delays in European Work Zones (2000) Innovative Traffic Control Technology and Practice in Europe (1999) European Winter Service Technology (1998) Traffic Management and Traveler Information Systems (1997) European Traffic Monitoring (1997) Highway/Commercial Vehicle Interaction (1996) Winter Maintenance Technology and Practices— Learning from Abroad (1995) Advanced Transportation Technology (1994) Snowbreak Forest Book—Highway Snowstorm Countermeasure Manual (1990)

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Infrastructure—General Audit Stewardship and Oversight of Large and Innovatively Funded Projects in Europe (2006) Construction Management Practices in Canada and Europe (2005) European Practices in Transportation Workforce Development (2003) Contract Administration: Technology and Practice in Europe (2002) European Road Lighting Technologies (2001) Geometric Design Practices for European Roads (2001) Geotechnical Engineering Practices in Canada and Europe (1999) Geotechnology—Soil Nailing (1993)

Infrastructure—Pavements Long-Life Concrete Pavements in Europe and Canada (2007) Quiet Pavement Systems in Europe (2005) Pavement Preservation Technology in France, South Africa, and Australia (2003) Recycled Materials In European Highway Environments (1999) South African Pavement and Other Highway Technologies and Practices (1997) Highway/Commercial Vehicle Interaction (1996) European Concrete Highways (1992) European Asphalt Technology (1990)

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Infrastructure—Bridges Prefabricated Bridge Elements and Systems in Japan and Europe (2005) Bridge Preservation and Maintenance in Europe and South Africa (2005) Performance of Concrete Segmental and Cable-Stayed Bridges in Europe (2001) Steel Bridge Fabrication Technologies in Europe and Japan (2001) European Practices for Bridge Scour and Stream Instability Countermeasures (1999) Advanced Composites in Bridges in Europe and Japan (1997) Asian Bridge Structures (1997) Bridge Maintenance Coatings (1997) Northumberland Strait Crossing Project (1996) European Bridge Structures (1995) All publications are available on the Internet at www.international.fhwa.dot.gov.

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ABBREVIATIONS AADT average annual daily traffic AASHTO American Association of State Highway and Transportation Officials ASFiNAG Autobahnen und Schnellstraßen Finanzierungs Aktiengesellschaft ASR alkali-silica reaction BASt Bundesanstalt für Straßenwesen (German Federal Highway Research Institute) CBR California bearing ratio CRIC Centre National de Recherche Scientifique et Technique pour L’industrie Cimentière (Research Center of the Belgian Cement Industry) CRCP continuously reinforced concrete pavement CROW The Netherlands’ national information and technology platform for infrastructure, traffic, transport, and public space CSH or C-S-H calcium silicate hydrate DBFO design-build-finance-operate DOT department of transportation ELLPAG European Long-Life Pavement Group ESAL equivalent single-axle load ETR electronic toll road EU European Union FEBELCEM Fédération de l’Industrie Cimentière Belge (Belgian Cement Industry Federation) FEHRL Forum of European National Highway Research Laboratories FHWA Federal Highway Administration FSV Österreichische Forschungsgesellschaft Straße— Schiene—Verkehr (Austrian Association for Research on Road, Rail, and Transport) GNP gross national product HMA hot-mix asphalt IRI International Roughness Index JPCP jointed plain concrete pavement

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MET Ministere de l’Equipemente et des Transports (Walloon Ministry of Equipment and Transport) MTO Ontario Ministry of Transportation MTQ Ministère des Transports du Quèbec (Québec Ministry of Transport) NCHRP National Cooperative Highway Research Program PCA Portland Cement Association PCC portland cement concrete PMS pavement management system PPP public-private partnership RFP request for proposal RVS Richtlinien und Vorschriften für den Strassenbau (Austrian Guideline Code for the Planning, Construction, and Maintenance of Roads) STIP scan technology implementation plan TRB Transportation Research Board TRL Transport Research Laboratory TRDI Texas Research and Development Institute VDZ Verein Deutscher Zementwerke (German Cement Works Association) VÖZ Vereinigung der Österreichischen Zementindustrie (Austrian Cement Industry Association)

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EXECUTIVE SUMMARY IN May 2006, A TEAM of concrete pavement and materials specialists from the United States visited Canada and five countries in Europe to identify design philosophies, materials requirements, construction practices, and maintenance strategies used to construct and manage portland cement concrete pavements with long life expectancies. They met with representatives of federal and provincial government roadway authorities, public-private partnerships for roadway construction and management, the cement and concrete pavement industries, and transportation research laboratories. The team members visited several longlived concrete pavements and discussed with their hosts the design, construction, materials, and maintenance factors chiefly responsible for the longevity of these pavements. The team also toured a major urban freeway operated as a public-private partnership (PPP) and talked with their hosts in each country about their policies on and experience with PPPs. This roadway construction and management approach has special relevance to long-life concrete pavements because the long time commitment typically involved favors the use of materials, design features, and construction techniques that result in long life and low maintenance. The Technology Exchange Program of the Federal Highway Administration (FHWA) accesses and evaluates innovative foreign technologies and practices that could significantly benefit highway transportation systems in the United States. This approach allows advanced technology to be adapted and put into practice much more efficiently without spending scarce research funds to recreate advances already achieved in other countries. The main channel for accessing foreign innovations is the International Technology Scanning Program. The program is undertaken jointly with the American Association of State Highway and Transportation Officials (AASHTO) and its Special Committee on International Activity

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Coordination and the Transportation Research Board’s National Cooperative Highway Research Program (NCHRP), with the cooperation of the private sector and academia.

Team Members

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The long-life concrete pavement scan team was made up of representatives of State departments of transportation (DOTs), FHWA, NCHRP, academia, and the consulting, cement, and concrete pavement industries. The team members were Tom Cackler (Concrete Pavement Technology Center at Iowa State University), Angel Correa (FHWA), Dan Dawood (cochair, Pennsylvania DOT), Peter Deem (Holcim (US) Inc.), Jim Duit (Duit Construction Co., Inc.), Georgene Geary (Georgia DOT), Andrew Giwsi (Kansas DOT), Amir Hanna (NCHRP), Steve Kosmatka (Portland Cement Association), Robert Rasmussen (The Transtec Group, Inc., representing the Concrete Reinforcing Steel Institute), Shiraz Tayabji (CTL Group, representing the International Society for Concrete Pavements), Suneel Vanikar (cochair, FHWA), and Gerald Voigt (American Concrete Pavement Association). They were joined for a portion of the trip by Robert Tally (cochair, FHWA). The trip reporter was Kathleen Hall (consultant). The long-life concrete pavement (LLCP) scan effort began in November 2005 with the completion of a review that identified Australia, Austria, Belgium, Canada, France, Germany, the Netherlands, Sweden, and the United Kingdom as the countries most likely to provide useful insights into how to achieve long-lasting concrete pavements. At the scan team’s initial planning meeting in Washington, DC, in December 2005, the team selected six countries to visit: Austria, Belgium, Canada, Germany, the Netherlands, and the United Kingdom. The scan trip to these countries took place May 11–27, 2006.

Objectives The following overview statement describes the motivation for an international scan of long-life concrete pavement technology: Safety and mitigation of congestion are two of the most important strategic goals of the U.S. highway community. Long-life concrete pavements require less frequent repair, rehabilitation, and reconstruction, and therefore contribute to improving highway safety and mitigating congestion. Experience with long-life concrete pavements, including examples of concrete pavements that have remained in service for more than 40 years, has been noted in previous scans of European countries. Information about these long-lasting pavements and the design and construction practices that produced them will be valuable to those involved in the design, construction, and maintenance of concrete pavements in the United Sates. In the United States, the typical design life for pavements in the past was 20 years, although a number of States use longer design lives. Major rehabilitation and reconstruction of pavements are difficult and expensive to accomplish, especially in urban areas. The next generation of portland cement concrete (PCC) pavements in the United States must be designed and constructed to achieve longer service life.

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United States Department of Transportation

The purpose of this scan is to identify design philosophies, materials requirements, construction practices, and maintenance strategies (including winter maintenance strategies), used by selected European and other countries to construct and operate portland cement concrete pavements with life expectancies of 40 years or more, that differ from U.S. practices and would be applicable in the United States. The scope of the scan is to include the following: • • • •

Materials evaluation and specification procedures for both virgin and recycled materials Methods used to design long-life concrete pavements Construction practices Maintenance practices

The ultimate benefit of the scan will be achieved by implementing technologies that will result in increased service life and reliability and decreased life-cycle costs of concrete pavements built in the United States in the future.

Issues of Interest The scan panel has also identified the following specific topics of interest pertaining to long-life concrete pavement technology in Canada and Europe:

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• • • • • • • • •

Materials (cement, coarse and fine aggregates, admixtures, and supplementary cementitious materials) Concrete mixture design Pavement thickness design (including geometrics, spacing, and location of joints) Specifications Construction procedures Maintenance procedures Rapid construction and rehabilitation techniques Performance of jointed plain, jointed reinforced, and continuously reinforced concrete pavements (JPCP, JRCP, and CRCP, respectively) Life-cycle costs

Key Findings The team’s key findings and recommendations from the long-life concrete pavement scanning study are summarized below.

Pavement Selection Strategies Long-life concrete pavements: In every country visited, “concrete pavement” is considered synonymous with “long life.” These countries expect concrete pavements to be strong and durable, provide service lives of 25, 30, or more years before rehabilitation or replacement, and require little if any maintenance intervention over the service life.

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The public and the environment: The public is expressing concerns about environmental issues such as noise, congestion, and safety. Environmental issues, especially noise, are becoming major concerns to the driving public. In all the countries visited, there is a heavy emphasis on traffic safety, noise mitigation, congestion relief, and the use of recycled materials. In some countries, a multicriteria analysis process is used to address these factors in pavement type selection. In the United Kingdom, political forces have driven the decision that, to reduce noise, all highway pavements must have asphaltic surfaces. Public-private partnerships and innovative contracting: To maintain and improve their roadway infrastructures, most European Union (EU) countries and Canadian provinces have adopted nontraditional financing methodologies such as public-private partnerships (PPP) and alternative bids. Politicians recognize the advantages of these financing mechanisms and of sharing risk with private entities. Most of the EU nations visited embraced PPP efforts to reduce the national debt and comply with EU financial requirements. As a result, contractors are accepting more responsibility for design, construction, and longterm maintenance of roadways. Under such systems, contractors are more likely to choose concrete pavement because its longer life and lower maintenance requirements reduce future risks. Another aspect of contracting practice observed was the awarding of contracts based on best value rather than low bid.

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Pavement management: Use of pavement management systems is inconsistent among the EU countries visited and generally not a driving force in pavement type selection. Pavement type selection factors: Although most countries visited state that they consider life-cycle costs, in practice, other factors such as functional class, truck traffic levels, initial cost, and environmental issues drive pavement type selection. In the province of Québec, a policy decision has been made that certain segments of the network will be concrete pavement, others will be asphalt, and others may be either. In Austria, it is policy that concrete pavement is used above a certain traffic level. The Netherlands has a similar policy.

Design Catalog design: Germany and Austria routinely use a design catalog to select pavement thickness and some other pavement features. The design features and thicknesses in the countries’ catalogs reflect their long-term experience with their materials, climate, and traffic levels. Mechanistic modeling, laboratory testing, and field observations are used to validate the cross-sections in the design catalogs. In the Netherlands and the United Kingdom, mechanistic-empirical design software is used for project-level design work. However, these two countries construct only a few miles of concrete pavement per year. Maximum concrete slab thicknesses are a common feature of the German and Austrian design catalogs. The maximum slab thicknesses appear to be thinner than those designed in the United States for similar traffic levels and in many cases heavier trucks. Fatigue cracking does not appear to be a performance issue with these thinner concrete slabs.

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Design lives: The design lives being used for concrete pavements in the countries visited are typically at least 30 years. In the Netherlands, a design life of 40 years is typical, for both provincial roads and motorways. The agencies are satisfied with the design and construction practices they use to achieve service lives of up to 40 or 50 years. Traffic management and future expansion: With an eye toward safety and the mitigation of congestion, widened lanes and full-depth concrete shoulders (emergency lanes that are wider than U.S. shoulders) are used in design. These emergency lanes are constructed with the same thickness and cross slope as the pavement lanes. Widened slabs: Widened slabs are used routinely in the outer traffic lane to keep truck tires away from the pavement edge, thereby reducing slab stresses and deflections and extending pavement life. The traffic lane cross-section is carried out to the edge of the pavement, including the emergency lane. Some subsurface layers are daylighted beyond the edge of the concrete slab for drainage and constructability.

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Tie bars: Most of the European countries visited place fewer tie bars across longitudinal joints to tie lanes together (about half the number used in the United States). No problems were reported with lane separation, longitudinal joint load transfer deficiency, or compromised pavement performance because of this. Doweled jointed concrete pavements (JCP): In the European countries that build JCP (Germany, Austria, Belgium, and Netherlands), doweled joints with 1-inch (in) (25millimeter (mm)) diameter bars are typically used and appear to be performing well, without joint faulting. This may be because of the large proportion and high quality of the aggregates used in the concrete mixes, which lead to good aggregate interlock and load transfer. The 1-in (25-mm) bars are used on sections that are typically 8 to 12 in (200 to 300 mm) thick and built on thick, usually stabilized, foundations. Continuously reinforced concrete pavement (CRCP): This pavement type is recognized in the countries visited as a heavy- duty, long-life pavement. Some countries, such as Belgium and the United Kingdom, have a long history with CRCP. Belgium’s CRCP design and construction technology was in fact adapted from U.S. practice years ago. The United Kingdom reported unique and undesirable crack patterns with skewed transverse steel. The techniques for longitudinal steel design (percent steel) varied from country to country, although crack width control appeared to be a common denominator. None of the countries visited used epoxy-coated steel, but the Québec Ministry of Transport (MTQ) in Québec, Canada, uses galvanized steel. In the Netherlands, as a rule of thumb, the thickness required for CRC is 90 percent of the thickness required for JCP. This can be confirmed with the VENCON 2.0 software; for example, for a motorway with a JCP thickness of 11 in (280 mm), the software calculates a CRCP thickness of 10 in (250 mm). In Belgium, CRCP is constructed about an inch (2 to 3 cm) thinner than JCP. Germany has just a few CRCP test sections, but on the 0.9-mile (1.5-kilometer) stretch of experimental CRCP test sections on the A-5 Autobahn near Darmstadt, the slab thickness is 9.5 in (24 cm), which is about an inch (2 to 3 cm) less than German design practice would dictate for JPCP for similar conditions.

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The thickness reduction was based on analyses conducted by the Technical University at Munich. Pavement bases: Open-graded permeable base layers, using high-quality aggregates, are used in Canada but not in the European countries visited. Dense-graded hot-mix asphalt and cement-treated base layers were used in several countries. In Germany, where in the past cement-treated bases were constructed to bond with concrete slabs, an interlayer of either 0.2in-thick (5-mm-thick) unwoven geotextile or dense-graded hot-mix asphalt is used now to separate a cement-treated base from the concrete layer. Unstabilized bases are used in Germany, based on the success of this base type in test sections built since 1986. Old concrete pavements in the former East Germany affected by alkali-silica reaction have also been successfully recycled for use in unstabilized bases.

Construction

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Joint sealing: Based on observations during site visits, sealed and unsealed joints appeared to have performed equally well on older projects. Belgium, however, reports that the long-term performance of unsealed joints is not the same as that of sealed joints, especially on heavily trafficked roads. Both hot-poured and compression seals are used in Austria and Germany. In Austria, strip drains (a few inches (5 to 10 cm) wide and at most 0.5 in (1.25 cm) thick) under about 3 feet (ft) (1 meter (m)) of the transverse joint in the emergency lane have recently been added as a design feature. Longitudinal contraction joints in some regions of Germany used to be left unsealed, but this practice was discontinued because it allowed water that entered unsealed longitudinal joints to flow beneath the sealant in transverse joints. Foundations: Thick foundations are used for frost protection. These systems were drainable and stable, but not open graded. Recycled materials, including asphalt, concrete, and in one case, masonry from building demolition, were used in the foundations. Interlayers: The use of a 0.2-in-thick (5-mm-thick) geotextile interlayer as a bond breaker between concrete pavement and cement-treated base is a recent requirement in Germany. German engineers indicated that the mortar is presumed to saturate the geotextile during construction, adding just enough stiffness to provide support while still acting as a bond breaker. The required concrete thickness for the cement-treated base alternative was increased from 10.2 to 10.6 in (26 to 27 cm) when the design was changed from one with a bonded base to one with a base separated by from the slab by a geotextile. In the other countries visited, the typical interlayer between a concrete slab and a cement-treated base is a layer of hot-mix asphalt concrete. Jointless bridge joints: A “jointless joint” bridge approach was described in the Netherlands, and although it was a trial section, the Dutch appear interested in what may be a lowmaintenance solution to bridge approach joints. They made clear, however, that this technique is costly.

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Materials Cementitious materials: Normal and blended cements, containing either slag or fly ash, are used. Limestone is allowed in all portland cements, at a dosage of up to 5 percent. Cements with varying sodium-equivalent contents (generally below 0.9 percent) or blended cements are used to mitigate alkali-silica reaction (ASR) if test results show ASR potential. Most countries have minimum cement content requirements by mixture type. Supplementary cementitious materials are not considered in the water/cement ratio, nor as part of the cementitious materials content. In countries applying an exposed aggregate surface, mixtures and consolidation processes that produce low paste thickness at the surface are used.

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Aggregate requirements: Great attention is given to aggregate selection, quality, and gradation, especially for the top layer, in countries using two-course construction. Goodquality aggregates are generally available (although there are cases of aggregate being imported). All of the countries use well-graded aggregates, with several separate aggregate sizes (three to four, depending on the layer). The maximum aggregate size typically used in Europe is 0.8 in (20 mm). The top layer of concrete in two-lift construction usually has a 0.3- to 0.4-in (8- to 11-mm) maximum aggregate size. In the Netherlands, where primarily single-lift construction is done, 1.25 in (32 mm) is the maximum aggregate size. In some countries, the concrete mixtures are considered proprietary. The agency controls quality by specifying the end-product requirements. Recycling: Recycled materials (including concrete and masonry from demolition) have been used in the base layers in various countries. Austria requires the use of recycled concrete and recycled asphalt pavement (RAP) in the lower layer of two- course concrete (and for base). Recycled asphalt is allowed up to a maximum of 30 percent of the coarse aggregate in these mixtures. The polished stone value test is routinely applied by EU countries for aggregate durability assessment. In Austria, a Los Angeles abrasion test value of no more than 20 is required for the top layer in two-layer construction. Corrosion protection: Québec now requires the use of galvanized rebar. Germany and Austria use tie bars coated in the middle third only and coated dowel bars. Compaction control: Intelligent compaction control equipment (automated feedback on rollers, etc.) is used in Austria. The European countries visited are strict about control of compaction of all layers, and in some countries load testing of granular layers to check compaction is conducted with a small plate. Cement and concrete testing: Construction process control is typically the responsibility of the contractor in the countries visited. Workability is evaluated using a compaction test, similar to the ASTM Vebe test. Ontario and Austria check the air content in hardened concrete, although in Austria this is done only if a problem is encountered or suspected. In the European countries visited, alkali-silica reaction (ASR) is controlled, if detected by

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preconstruction testing, using blended cements or cements with low alkali content. No country reported difficulty with controlling ASR. Pavement testing: The countries visited do not perform quality control testing for noise, and no one method is used consistently from country to country to measure noise. Texture measurements are made, both for end-product and pavement management system-based data collection. The MIT-SCAN equipment developed in Germany for detecting dowel bar misalignment is specified in Canada (Ontario) for both quality control and quality assurance purposes, but not in the other countries visited. A 4-m straightedge is typically used to measure roughness in the EU countries visited. Belgium also uses the APL (Analyseur de Profil en Long, or length profile analyzer) to measure pavement profile. The smoothness of pavements on which the scan team traveled was excellent in all countries visited.

Maintenance

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Maintenance techniques: In general, most of the countries visited have had little or no need to do maintenance of concrete pavements. Joint resealing is conducted in a sporadic manner, if at all. One widely used maintenance technique is a thin asphalt overlay to correct rutting caused by studded tires or to mitigate tire-pavement noise. Only in Canada is diamond grinding used to improve smoothness on bare concrete pavements. In the United Kingdom, concrete pavement is overlaid with asphalt to reduce noise. Precast slabs for rapid repair: Canada is evaluating the use of U.S.-developed precast concrete technology for rapid repair. In a field experiment the scan team visited, the team observed that panels were used for individual slab and multislab replacement. The Michigan and Fort Miller methods of placing precast slabs were examined in the Canadian experiment. Canada is also examining modification of the Michigan method. While both applications exhibited some premature distresses in the Canadian tests, primarily because of issues related to installation, the Ontario Ministry of Transportation believes that this will become a practical specialty method of construction and repair.

Research Concrete pavement research: In Europe, most research related to cement and concrete materials and concrete pavements is conducted by academic and trade institutions. For example, the German Cement Works Association (VDZ) in Germany is conducting research on the behavior of synthetic air entraining agents and alkali-silica reaction. Nanotechnology: A cooperative venture for research in nano-technology for cementitious materials (Nanoscience of Cementitious Materials, Nanocem) has been organized in Europe. The consortium consists of academia and industry members, with financial support from the cement industry and the European Community. This effort should lead to improvements in the durability and mechanical properties of concrete. The current focus of Nanocem’s research activities is cement behavior; research into concrete mixture properties is some years away.

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Industry Relations Contractor training: In most of the countries visited, no formal training of construction contractor personnel is routinely conducted through preconstruction meetings or other required education. Most construction training seems to occur on the job. However, most countries seemed to have well-educated and qualified field personnel. Some training is provided by the cement industry groups. Certification: There are no certification standards for inspectors and contractors’ employees in the European countries visited. Training is the contractor’s responsibility and not a requirement. Concern was expressed that less-experienced paving construction workers come from eastern European countries, which may necessitate more training programs in the future.

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Communications: In general, the European countries visited have good communications between contractors and highway agencies. Academic and industry input is highly valued. For example, committees of agency, industry, and academic experts are formed to develop design catalogs. Standards: European standards are in the long, slow process of harmonization. Meanwhile, individual European countries continue to use their own standards. The Comité Européen de Normalisation (CEN) is mandated by the European Commission to develop standards for a variety of European Community products. The EC Construction Products Directive (CPD) requires that construction products be fit for their intended use. Works in which these products will be used must satisfy CPD requirements over an economically reasonable service life. Such products are placed on the market with a “CE” stamp. In the case of cement, even if the producer declares that a product conforms to the CEN standard, independent testing must be done to ensure this conformity. The CE “seal of approval” is useful, for example, if a paving contractor runs out of cement from one source in the middle of a paving job and must use cement from a different source (although tests have to be repeated with the new cement). CEN standards have not yet been developed, however, for many concrete paving materials (dowels, rebar, joint sealants, etc.). European (EN) or national standards continue to be used for these materials.

Recommendations The long-life concrete pavement scan team identified the following technologies as having the greatest potential for implementation in the United States: Two-lift construction: Austria, Belgium, the Netherlands, and Germany use two-lift construction to build concrete pavements with good friction and noise characteristics, economize on the use of aggregates, and use reclaimed paving materials. In two-lift construction, a relatively exposed aggregate surface lift containing high-quality aggregates is

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placed atop a lift containing virgin aggregates of lesser quality or reclaimed aggregate from concrete or asphalt pavements, resulting in materials cost savings. Two-lift construction is not new to the U.S. concrete paving industry. Two-lift paving was specified by many State DOTs in the past when wire-mesh-reinforced pavements were constructed and mesh depressors were not allowed. In recent decades, a number of States have experimented with two-lift construction to promote recycling and enhance surface characteristics. Catalog design: Pavement design catalogs have been used successfully in Europe for many years. In the United States, the design of concrete pavement traditionally has been done on a project-by-project basis. This approach has served the U.S. pavement engineering community fairly well for many years. However, with the increasing difficulty of predicting traffic loads, volumes, and axle configurations, designing on a project-by- project basis may not always be required. In addition, changes and new developments in materials have created a need for a design procedure with the flexibility to consider the effects of material properties on the responses of the pavement structure. This need is being addressed with the development of the Mechanistic-Empirical Pavement Design Guide (MEPDG). The catalog design method is a simple procedure for selecting an initial pavement structure. Most of the European countries visited have routinely used design catalogs to select pavement thicknesses and some other pavement features. The countries using design catalogs recognize that simply extrapolating empirical trends is not reliable and often leads to overdesign of concrete pavements. The design features and thicknesses in the catalogs reflect long-term experience with the local climate, materials, and traffic levels. These experiences are validated through analysis by expert teams using mechanistic principles. The expert teams employ laboratory testing and field observations to validate the cross-sections in the design catalogs. The designs are defined and refined about every 5 years. The use of a catalog for selection of pavement thicknesses and other pavement design features offers advantages of consistency and simplicity. Catalog design is not itself a design procedure, but rather a medium for identifying appropriate pavement design features for use in pavement analysis. The quickest form of developing a catalog design is simply to incorporate the standard designs that have shown good, consistent, long-term performance. A design features matrix is another part of the catalog concept that identifies alternatives for features (e.g., base types) and provides information on such items as the cost, performance, and feasibility of constructing the feature to allow an agency to make an informed decision on whether to include it in a design. Nevertheless, the information recommended in the catalog needs to be validated by laboratory and field investigations. Deep, high-quality foundations: The unbound granular materials used for concrete pavement subbases in Europe are generally better quality materials (better graded, better draining although not open-graded, and with lower fines content) than the materials typically used as select fill and granular subbase in the United States. Aggregate standards were mentioned in all the countries visited. A closer look at the aggregate standards in place in the United States and a comparison to the European standard may provide some insights into improving foundations in this country.

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Recycled concrete not reused in the pavement itself is commonly used in the base material of pavements in Europe. It appeared that it was also fractionated and part of the grading. Cement-treated bases were also in wide use in several countries, with an asphalt or geotextile interlayer as a separator. In addition, it was noted that intelligent compaction is used in Austria. Germany uses a plate load test for quality assurance of layer compaction equipment. Attention to mix design components: One key to long-lasting concrete pavements in Europe appears to be the great attention to cement and concrete mixture properties. The mixtures produce strong, dense, and durable concrete, despite the apparent widespread presence of reactive aggregates in western Europe. The flexural strength noted in the top lift was about 1,000 pounds per square inch (7 megapascals), much higher than the typical flexural strength target in the United States. The careful consideration of cementitious materials used in the mix is one area that could yield benefits for the United States.

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Geotextile interlayer: A key detail recently introduced in Germany for cement-treated bases is the use of a thick geotextile interlayer to prevent the concrete slab from bonding to the cement-treated base. This geotextile material is thicker than the materials commonly used for layer separation purposes in the United States. It is sufficiently porous that mortar from the fresh concrete permeates the geotextile, which provides a good mechanical bond of the geotextile to the concrete layer while achieving separation from the base layer. This geotextile may provide a suitable alternate to the asphalt interlayer used in many States. Low-noise exposed aggregate surfacing: The public’s concern about environmental issues is evident in densely populated, traffic-congested Europe. The solution to concrete pavement noise popular in some European countries is exposed aggregate surfacing, in which exceptionally high-quality, durable aggregates are used in the top course of the concrete slab, and a process of set retardation and abrasion is used to produce an exposed aggregate surface with good low-noise properties. Exposed aggregate is also touted as yielding other benefits, including good friction and durability. However, favorable noise levels may also be achieved by specific pavement texturing techniques.

1. INTRODUCTION Purpose of Scan SAFETY AND MITIGATION OF CONGESTION are two of the most important strategic goals of the U.S. highway community. Long-life concrete pavements require less frequent repair, rehabilitation, and reconstruction and therefore contribute to improving highway safety and mitigating congestion. Experience with long-life concrete pavements, including examples of concrete pavements that have remained in service for more than 40 years, has been noted in previous scans of European countries. Information about these longlasting pavements and the design and construction practices that produced them will be valuable to pavement designers in the United States.

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In the United States, the typical design life for pavements is about 20 years, although a number of States use longer design lives. Major rehabilitation and reconstruction of pavements are difficult and expensive to accomplish, especially in urban areas. Portland cement concrete (PCC) pavements built in the United States in the future must be designed and constructed for longer service life. The purpose of this scan was to identify design philosophies, materials requirements, construction procedures, and maintenance strategies (including winter maintenance strategies), used by selected European and other countries to construct and operate portland cement concrete pavements with life expectancies of 40 years or more, that would be applicable in the United States. The ultimate benefit of the scan will be achieved by implementing technologies that will result in increased service life and reliability and decreased life-cycle costs of concrete pavements built in the United States in the future.

Background

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While the U.S. highway community embraces the concept of long-life concrete pavements, it lacks a clear definition of what a long-life concrete pavement should be. The Federal Highway Administration’s (FHWA) Concrete Pavement Road Map, formally known as the Long-Term Plan for Concrete Pavement Research and Technology,[1] identifies longlife concrete pavements as one of the 12 major tracks along which concrete pavement research over the next 7 to 10 years should be directed. The road map team discovered that the concept of long-life pavements was difficult to define. Among the proposed definitions were the following: • • •

“A ‘no-fix-required’ pavement that would last 50 to 60 years with relatively heavy loads throughout its life” “Planned maintenance between 10 and 30 years, followed by heavy joint repair and possibly an overlay to take the total pavement life to 60 years” “A mandatory strong foundation with a thinner slab designed for 20 years of service, followed by the construction of a wraparound slab that would provide service for an additional 30 to 40 years”

Among the features mentioned as necessary to a long-life concrete pavement were the following: • • • •

“Long-term foundation and drainage at initial construction with service life of 50 to 60 years or beyond” “Improvements to the functional requirements only (surface improvements)” “Predetermined staged construction for the slab” “Some major rehabilitation, but only if it can be done at very high speed and be limited to the slab only”

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Yet another set of requirements for long-life concrete pavements, sharing some features with those already mentioned and identifying some not mentioned, is outlined in a paper presented at the 8th International Conference on Concrete Pavements.[2] Given the prevailing lack of clarity and agreement on what a long-life concrete pavement should be, the concrete pavement road map identified the very first objective for this research track as “develop clear and detailed definitions of long-life concrete pavements, including information about warrants, required maintenance, a range of low- to high-traffic roadways, and other information.” The road map team specifically mentioned two topics it believed must be considered to effectively confront the issue of how to build longer-life concrete pavements: use of CRCP and costs. About the use of CRCP, the road map states the following: “Continuously reinforced concrete pavements (CRCP) should be considered in long-life solutions for heavy-duty pavements, but few States use the technology routinely. It would take considerable effort to reenergize CRCP, but it should be considered because it has a solid performance record in many locations.”

About costs, the road map states the following:

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“The cost issue should be addressed in any final application of long-life principles. The challenge is not simply to add more ‘bells and whistles,’ but to add value and performance without increasing the cost significantly. Increasing life and holding the cost are inherent if long-life pavements are to have a role in pavement selection.”

The challenge is not to build more conservative designs without improving existing design and construction practices, nor even to add value and performance without increasing the cost significantly. Indeed, the challenge is to increase the cost- effectiveness of concrete pavements by improving performance without increasing costs.

Countries Building Long-Life Concrete Pavements The variety of design, construction, and maintenance practices employed in the countries that have successful experience with long-life concrete pavements is expected to lend useful perspective on the ways long concrete pavement service lives can practically and costeffectively be achieved. While many countries build concrete pavements, not all have insights to offer the U.S. highway community on how to design and build long-life concrete pavements. It makes sense that the world’s richer countries have the means to make investments in strategic infrastructure improvements such as long-life concrete pavements a high priority. Less economically developed countries must put strategic infrastructure improvement behind more pressing concerns, such as poverty, unemployment, violent crime, and civil unrest. There are a variety of ways to quantify the wealth and economic development of countries.[3] Perhaps the most familiar measure is per capita (per person) gross national product (GNP). The countries with the highest per capita GNP are the United States, Canada, most of the countries in western Europe, Australia, New Zealand, Japan, and a few countries

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in the Middle East (although these latter ones, i.e., Israel and some of the petroleumproducing Arab states, rank among less developed economies by other measures). A better measure of a country’s relative wealth than per capita GNP is per capita purchasing power because it includes the relative prices of products. For example, Switzerland, Sweden, and Japan have higher per capita GNPs than the United States, but the United States has the world’s highest per capita purchasing power because of relatively lower prices for food, housing, fuel, merchandise, and services. The countries with the highest per capita purchasing power are the United States, Canada, most western European countries, Australia, and Japan. By any of a variety of other specific and widely used economic measures, more or less the same group of countries is consistently identifiable as the world’s richest and most highly developed. In general, the most economically robust and densely populated countries have the greatest need for strategic infrastructure investments such as long-life concrete pavements. Important exceptions exist, however. For example, parts of southeastern Europe (e.g., Romania, Bulgaria, Turkey) and parts of the Indian subcontinent (India, Pakistan, and Bangladesh) are densely populated and have dense road networks, yet are economically far behind the most highly developed countries. India, for example, has an extensive road network, but the roads are overcrowded (traffic on the network has increased thirtyfold since independence in 1948), and 80 percent of villages lack all-weather roads. Other countries, most notably Canada and Australia, are sparsely populated overall, with most of the population concentrated in one or more small regions of the country. These are countries where strategic infrastructure investments such as long-life concrete pavements make sense only for those densely populated zones. The United States is rather unusual in that it is almost completely blanketed by a dense roadway network, while at the same time it is relatively sparsely and unevenly populated. Figures 1 and 2 illustrate where the U.S. population is concentrated. These figures provide insight into the regions of the United States for which long-life concrete pavements offer the greatest potential benefit in reducing passenger traffic congestion. Another important place for long-life concrete pavements in the United States is on the most heavily truck-trafficked Interstate and U.S. routes, including but not limited to the eastwest routes I-10, I-20, I-40, I-70, I-80, and I-90, the north-south routes I-5, I-15, I-25, I-35, I55, I-65, and I-95, and the routes near the major ports (Miami, FL; New Orleans, LA; Houston, TX; Los Angeles, CA; Chicago, IL; and New York/New Jersey) where goods move in and out of the country. Another factor to consider in assessing where long-life concrete pavements would be of greatest benefit in the United States is the effect that major airports have in spurring business and residential growth. Where there is a very busy airport—even in what once seemed the middle of nowhere—eventually there will be a buildup of commercial activity and housing construction. According to an article about this “aerotropolis” phenomenon in the The Economist, “when Washington Dulles National Airport opened in 1962 in rural Virginia, it was considered a white elephant, but it has spawned a high-tech corridor and now sits in the fastest-growing county in the United States. Denver’s ten-year-old international airport, about 40 miles (64 kilometers) out of town, is expected to be the center of a community of 500,000 people by 2025—almost as many people as live in Denver itself.”(4) The Economist article further points out that development near an airport is constrained by height restrictions on buildings, which forces growth outward rather than upward.

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An additional factor to consider is the unusually rapid growth occurring in other specific regions of the country. Two examples often cited are Phoenix, AZ; and Las Vegas, NV; the fastest and fourth-fastest growing metropolitan areas in the United States. While California and Florida remain popular and populous, people are also moving to Arizona and Nevada in droves, attracted by lower housing prices. In 2005 alone, according to The Economist, 120,000 Californians were expected to move to Arizona, a group equivalent to about 2.5 percent of Arizona’s existing population. In Las Vegas, driver’s license records suggest that as many as 35 percent of newcomers are from California.[4] In general, while the most densely populated areas of the United States remain the eastern seaboard and the Great Lakes region, shifts in the population are predominantly toward the southwest, west, and south. According to a recent report on urban sprawl, the top 20 fastest growing counties in the United States are in Arizona, California, Nevada, Texas, Florida, and Washington.[5] How these and other metropolitan regions in the United States grow in coming years will be influenced by whether sprawl is controlled or uncontrolled, but in either case there is little doubt that these fast-growing regions will continue to experience rapidly increasing levels of traffic congestion. There is also no doubt that traffic congestion levels will be high even in more stably growing major metropolitan regions.

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Countries and Agencies Visited Austria, Belgium, Canada, Germany, the Netherlands, and the United Kingdom were selected for inclusion in this international scan. They were chosen from among the countries that have the means to invest in strategic infrastructure improvements such as long-life concrete pavements, and that have population densities and passenger car and truck levels warranting consideration of long pavement service lives. Canada—The scan team met in Toronto with representatives of the Ontario and Québec ministries of transport (MTO and MTQ), the Cement Association of Canada (CAC), and the consortium operating the 407 ETR, the world’s first all- electronic, open-access toll highway. Germany—The scan team visited the office of the German Cement Works Association (Verein Deutscher Zementwerke, VDZ) in Düsseldorf and met with personnel from the concrete technology department of the German cement industry’s research institute. The team next visited the offices of the German Federal Research Institute (Bundesanstalt für Straßenwesen, BASt) in Bergisch-Gladbach, and then traveled to Munich, visiting concrete pavement sites along the way on the A-5 Autobahn. The team’s final meetings in Germany were with faculty and researchers at the Technical University of Munich. Austria—The scan team toured several concrete pavement sites between Vienna and Salzburg, accomanied by the head of the research institute of the Austrian Cement Industry Association (Vereinigung der Österreichischen Zementindustrie, VÖZ). The team also visited the offices of VÖZ for a meeting with representatives of the Austrian cement industry association and its research institute, as well as representatives of the Austrian Ministry of

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Transport, the University of Vienna, the Austrian Ministry of Finance, and Austrian concrete pavement consultants and builders. Some team members also visited a concrete paving job site in Austria to see its concrete plant and paving equipment.

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Figure 1. United States population density map based on 2000 census data (1 square mi = 2.59 square km)

Figure 2. Primary and secondary metropolitan areas of the United States

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Nanocem Consortium. The director of the construction materials laboratory at the Federal Polytechnical School of Lausanne (École Polytechnique Fédérale de Lausanne, EPFL) in Switzerland gave the presentation. Belgium—In Namur, the team met with personnel from the Walloon Ministry of Equipment and Transport (MET) and the Federation of the Belgian Cement Industry (FEBELCEM). The director-general of the Roads and Traffic Administration of the Flemish Community made a presentation to the scan team on concrete pavements in the Flemish region of Belgium. The team visited several long-lasting concrete pavements in Belgium with representatives of FEBELCEM. The Netherlands—The team visited the office of the CROW (Foundation Center for Research and Contract Standardization in Civil and Traffic Engineering) Technology Center in Ede for presentations by CROW personnel and representatives of the Dutch cement industry, the provincial and state road authority in the Netherlands, and Dutch concrete paving contractors. The United Kingdom—In England, the team met with representatives of the concrete pavement association, Britpave, and the Transport Research Laboratory (TRL).

Comparison of Countries Visited with United States

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Because the purpose of this scan is to study the performance of long-life concrete pavements in other countries for insights into how long-life concrete pavement performance and cost- effectiveness in the United States can be improved, it is relevant to make some comparisons between the United States and the countries visited. Geography, climate, and soils[5]—The continental United States lies between the 25th and 49th parallels. The populous southeastern portions of the Canadian provinces of Ontario and Québec also lie below this latitude and share the climate of the Great Lakes region. In Québec, temperatures range from -22°F (-30°C) in the winter to 86°F (30°C) in the summer, and total precipitation is typically between 31.5 and 55 inches (in) (800 and 1,400 millimeters (mm)) per year. The depth of frost penetration is typically 4 to 10 feet (ft) (1.2 to 3.0 meters (m)). The predominant soils in the Toronto area are high-nutrient soils (alfisols), which are also found in the United States in large areas of Ohio, Indiana, Michigan, Wisconsin, Minnesota, Pennsylvania, and New York.* Further north in the Ontario and Québec provinces, conifer forest soils (spodosols) predominate, as they do in large areas of Maine, New Hampshire, Vermont, upper New York, and northern Michigan and its Upper Peninsula. The vicinity of Ottawa and Montréal, along the Ottawa River, is an area of soils with little profile development (inceptisols); such soils are also found (although do not prevail) in southern New York, central and western Pennsylvania, West Virginia, eastern Ohio, and the Pacific Northwest.

* All soils information in this section is taken from reference 5. Long Life and Quiet Pavement: Research and Issues : Research and Issues, Nova Science Publishers, Incorporated, 2010. ProQuest Ebook

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The European countries visited are almost entirely located farther north than the northern border of the continental United States. Munich (in southern Germany) and Vienna (in central Austria) are at about the 48th parallel, further north than both Duluth, MN, and Seattle, WA. Central and northern Germany, Belgium, the Netherlands, and the United Kingdom all lie further north than the northern border of the United States. Belgium, the Netherlands, and northern Germany all lie along the North Sea and have a temperate maritime climate, with cool, mild winters, fairly cool summers, and rain throughout the year. The Netherlands in particular is known (and indeed, named) for its low elevation: about half of the country’s area is less than one meter above sea level, and large portions of it are actually below sea level, protected from flooding by an extensive network of dykes and dunes. The climate in central (e.g., Frankfurt) and southern (e.g., Munich) Germany is cool and temperate, with mild, occasionally very cold winters and warm but rarely hot summers. The climate is similarly temperate, ranging to continental (with humid westerly winds) in upper Austria along the Danube River Valley, where both Salzburg and Vienna are located. The Alps, however, dominate the area and climate of southern Austria. The climate of England, which makes up the central and southern portions of Great Britain, is temperate, with rainfall throughout the year and temperatures ranging typically from about 23°F (-5°C) in the winter to about 86°F (30°C) in the summer. It is driest in the east, near the Atlantic Ocean, and warmest in the southwest, near the European continent. The terrain is predominantly rolling hillside, with some low mountains in the north and low-lying marshland in the east. Snowfall is fairly uncommon except at higher elevations. The same types of soils described as common in southeastern Canada and northeastern and north central United States— high-nutrient alfisols, conifer forest spodosols, and inceptisols without much profile development—are also common throughout much of northern Europe and the British Isles. Overall, the geography, climate, and soils of the countries visited most resemble those of the upper Great Lakes and northeastern regions of the United States. Concrete pavements in other areas of the United States are subjected to colder winter temperatures and/or higher summer temperatures, as well as lower precipitation levels, than these regions. Roadway networks**—The United States has by far the most extensive road network of any country in the world: some 3.9 million miles (mi) (6.3 million kilometers (km)), nearly twice the mileage of second-place India, with 2.0 million mi (3.3 million km).[6] The mileage of roads in some of the other countries visited for this scan range from some 0.9 million mi (1.4 million km) in Canada to some 72,000 mi (116,000 km) in the Netherlands. However, the countries visited have denser roadway networks than the United States. Belgium, with 7.9 mi of road per square mi (4.9 km of road per square km) of land area, has the fourth-highest roadway density in the world, followed by the Netherlands at eighth with 4.7 mi/mi2 (2.9 km/km2), Austria at 10th with 3.9 mi/mi2 (2.4 km/km2), and the United Kingdom at 21st with 2.4 mi/mi2 (1.5 km/km2). The density of the roadway network in Germany is not among the top 40 in the world and, not surprisingly, neither is that of Canada or the United States. Germany, however, has one of the most crowded roadway networks in the world, ranking fourth at 312.9 vehicles per mi (194.5 vehicles per km). Among the countries visited, the ** All statistics in this section are taken from reference 6.

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United Kingdom and the Netherlands are next, ranking 23rd and 24th at 100.2 and 93.2 vehicles per mi (62.3 and 57.9 vehicles per km), respectively. The traffic density of the United States and Belgium are similar, at 58.1 and 57.8 vehicles per mi (36.1 and 35.9 vehicles per km). Neither Austria nor Canada is in the top 50 countries in roadway traffic density. Similar statistics emerge for annual roadway use, in vehicle- miles per year per mile of road network (or equivalently, vehicle-kilometers per year per km of road network). Germany ranks fourth in the world at 2.55 5 million vehicle-miles per mile, the United Kingdom ranks 10th at 1.243 million vehicle-miles per mile, Belgium ranks 11th at 1.062 million vehiclemiles per mile, and the Netherlands ranks 13th at 944,000 vehicle-miles per mile. The United States, meanwhile, ranks 17th at 700,000 vehicle-miles per mile. Neither Austria nor Canada is among the top 30 countries in terms of annual roadway use. Roadway crowding and annual roadway use in the TorontoMontréal corridor in southeastern Canada are comparable to those in the northeastern United States in general, while in both countries, traffic density is lower in other regions. While traffic density in Austria is lower than in European countries farther to the west, the reductions in trade barriers associated with the development of the European Union, along with the collapse of the Soviet Union, are contributing to increasing truck traffic between eastern and western Europe, and one of the principal routes for this traffic is through Austria.

2. PAVEMENT SELECTION STRATEGIES

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Canada ABOUT 75 PERCENT OF THE population of Canada is concentrated within 100 mi (160 km) of the nation’s southern border with the United States, with more than 60 percent living along the Great Lakes and St. Lawrence Seaway in the provinces of Ontario and Québec. Nearly 80 percent of Canadians live in urban areas. As in the United States and other highly developed nations, the economy is dominated by the service sector, which employs about 75 percent of all Canadians, about the same percentage as in the United States.[7] At the same time, the primary goods sector is an important part of the Canadian economy, especially the logging and oil industries. Possessing vast deposits of oil and natural gas as well as abundant hydroelectric power, Canada is one of the few developed countries that are net exporters of energy. Canada has no federal equivalent of the U.S. Federal Highway Administration (FHWA) or American Association of State Highway and Transportation Officials (AASHTO). The provincial governments function largely independently. No federal funding goes to highways; the provinces are responsible for financing all highway work. Capital construction funds come from general revenue, not fuel taxes. Ontario is the most populous of Canada’s provinces, home to nearly 13 million people, about 38 percent of the total population of Canada. Most of Ontario’s population and economic activity are concentrated in the southeastern portion along the Great Lakes and the St. Lawrence Seaway.

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The key high-volume highways in Ontario are the 400-series highways in the southern part of the province. The most important of these is the 401, the busiest highway in North America, with average annual daily traffic (AADT) of more than 425,000 vehicles in 2004, and daily traffic sometimes exceeding 500,000 vehicles. In much of the Toronto area, the 401 has six lanes in each direction, but some segments have seven, eight, and even nine lanes in each direction. The next most heavily trafficked freeways in the 400 system are the 427, with an AADT of about 312,000 vehicles, and the Queen Elizabeth Way, with an AADT of about 175,000 vehicles. Ontario is a cement-rich province, and as a result, Canada is able to satisfy all of its domestic cement demand and export its surplus. In 2004, Canada exported about 7 million tons (6.4 million metric tons) of cement, of which about 6.3 million tons (5.7 million metric tons) went to the United States.[8] The United States, in contrast, despite being the world’s third-largest producer of cement, can meet only about 75 percent of its domestic cement demand and must import the other 25 percent. In the 1980s, the Ontario Ministry of Transportation (MTO) began using life-cycle cost analysis in its pavement type selection process. Pavement design alternatives are compared based on present worth over a 50-year analysis period. Concrete pavements are assumed to have an initial service life of 28 years to the first rehabilitation; asphalt pavements are assumed to have an initial service life of 19 years. MTO uses a social discount rate, set by the Ministry of Finance, in life-cycle cost analysis. A social discount rate, also called a social or societal rate of time preference, “reflects the government’s judgment about the relative value which the community as a whole assigns, or which the government feels it ought to assign, to present versus future consumption.”[9] The societal time preference rate “need bear no relation to the rates of return in the private sector, interest rates, or any other measurable market phenomena.”(10] In MTO’s life-cycle cost procedure, the salvage value of a pavement is defined as the prorated remaining life at the end of the analysis period. User costs are not currently incorporated in the life-cycle cost procedure; MTO is studying what user cost model would be most appropriate. MTO implemented alternate bid contracts on major freeway projects in 2001. Alternate bid contracts allow both the asphalt and concrete industries to bid on the same contract. Since then, concrete has been selected for all six of the alternate bid contracts awarded. MTO sets bid adjustment factors in advance based on life-cycle cost analysis results. Alternate bid contracting procedures result in higher upfront engineering costs for MTO because two separate sets of bid documents must be prepared. However, allowing the two industries to compete on the work has resulted in US$23 million (Can$26 million) in savings in initial construction costs. (Note: all currency conversions to U.S. dollars in this chapter are based on late April 2007 exchange rates.) Ontario’s most prominent experience with public-private partnerships to date is the 407 (shown in figure 3 on next page), originally planned as a bypass for the 401 and leased to a private consortium in 1999 for about US$2.8 billion (Can$3.1 billion). This purchase price covered the existing 43-mi (69-km) central section (built as concrete pavement) and the right to build extensions on the east and west ends (these extensions were built as asphalt pavement) to increase the full length of the highway to 67 mi (108 km). Work is already underway to widen 30 mi (50 km) in the central section from six to eight lanes, and another

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30 mi (50 km) of widening is planned. By the end of 2020, nearly the entire 67-mi (108-km) length will have 10 lanes, with one short section having eight lanes. The 99-year lease agreement allows for the private operation of the 407 ETR (electronic toll road), but requires adherence to the provincial government’s highway safety and design standards and auditing on a regular basis. MTO conducts about 10 audits of the 407 ETR and its subcontractors and subconsultants per year. In addition, an independent auditor, hired by and reporting to both parties, conducts frequent auditing. The 407 ETR is the world’s first all-electronic, open-access tollway. Electronic sensors mounted on overhead gantries at on- and off-ramps detect transponders mounted on vehicle windshields and log toll transactions (see figure 4). Trips on the 407 by vehicles not equipped with transponders are logged using a state-of-the-art license plate recognition system (by law, transponders are mandatory for vehicles with gross weights of 5 metric tons or more). Users receive monthly statements by mail and can check their account balance and sign up for automatic credit card billing on the 407 ETR Web site. Traffic on the 407 ETR averages about 300,000 trips per day. Tolls on the 407 ETR are about five times higher than on the New York State Thruway. A trip from one end of the 407 ETR to the other costs about US$18 (Can$20). The leaseholder sets tolls for trucks much higher than for cars, with the intent of shifting truck traffic to the public highway system. Ontario anticipates that major new roadway construction will be done by public-private partnerships (PPP). The ministry is exploring PPP contracts or area-term contracts, in which a private contractor will be responsible for design, rehabilitation, and maintenance of all provincial roads within a certain geographic area. PPP contracts are viewed as a growing trend throughout Canada, consistent with a trend of government downsizing out of operations and into a management role.

Figure 3. Highway 401 at 407 ETR.

In the province of Québec, concrete pavements make up 767 two-lane mi (1,239 two-lane km) of the 18,000-mi (29,000-km) road network, only about 4 percent, but carry about 75 percent of Québec’s traffic. Most of this concrete pavement is in and around the city of Montréal. Québec builds both jointed plain concrete pavements and continuously reinforced concrete pavements. The appeal of the CRCP option is the “get in, get out, stay out!” aspect that is important because of the limited funds available for pavement maintenance. Life-cycle

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cost calculations conducted by the Québec Ministry of Transport (MTQ) indicate that for one case, CRCP is about 5 percent lower in cost than JPCP in terms of net present value over a 50-year analysis period. The actual life-cycle cost differential for a specific route depends on the traffic level.

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Figure 4. Vehicle passes under electronic sensors on gantry at on-ramp to 407 ETR

MTQ has used life-cycle cost analysis since the mid 1990s. Projects over about US$900,000 (Can$1 million) are subjected to life-cycle cost analysis to help in the selection of the best construction or rehabilitation alternative. A 50-year analysis period is used, and discount rates between 4 and 6 percent are considered. Both residual value and work zone user costs are considered in the life-cycle cost analysis. MTQ uses two computer programs to conduct life-cycle cost analysis: one (RealCost) developed by the U.S. FHWA and one (Visual LCCA) developed by the Transportation Research and Development Institute (TRDI). In 2001, Québec adopted a departmental policy on pavement type selection that dictates which routes in the Montréal and Québec city areas—a total of 484 mi (779 km)—will be concrete pavement. The choice of JPCP or CRCP for pavements in the “white zone” is a regional decision, which can be based on life- cycle cost analysis but does not necessarily need to be. Another 226 mi (364 km) of nearby routes are classified by the policy as being in the “gray zone,” and for these routes, life-cycle cost analysis and other factors (environmental concerns, technical criteria, and economic consequences) are to be used in pavement type selection. The policy dictates that all other routes in the province will be asphalt pavement. Figure 5 illustrates the assignment of routes to the concrete and gray zone groups. This assignment of concrete pavement to specific routes largely corresponded to the location of existing concrete pavements in the province, and was well received by government authorities and industry.

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MTQ uses pavement management software called Visual/PMS, developed by TRDI, to store pavement construction, inventory, and condition data; project future pavement conditions; and assist in developing long-term maintenance plans.

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Figure 5. Concrete and “gray zone” routes for which a multiple criteria analysis is used in pavement type selection, according to Québec Ministry of Transport policy

Québec embraced the concept of public-private partnerships as part of its 2004–2007 Modernization Plan. MTQ considers three types of PPP contracts as options for large projects: (1) design and construction, (2) delegation of exploitation and maintenance, and (3) conception-design-maintenanceexploitation and funding. Planned PPP projects are the completion of Highways 25 and 30 around Montréal, and construction and maintenance of several rest areas. The Highway 30 project, which will have a cost of about US$900,000 (Can$1 billion), involves a 22-mi (35-km) stretch of highway and 4 mi (7 km) of other roads to complete a link between Châteaugauy and Highway 20 in Ontario. Plans are for this work to be done under a conception-design-maintenanceexploitation and funding arrangement, but whether this will be a concrete pavement has not been determined.

Germany GERMANY CONSIDERS CONCRETE PAVEMENTS to be long-life pavements, and jointed plain concrete pavements make up some 25 percent of the German high-volume motorway network. Germany has no long-term experience with continuously reinforced

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concrete pavement on motorways. The scan team visited a 0.9-mi (1.5-km) stretch of CRCP test sections built in 2005 on the A-5 Autobahn near Darmstadt. When a new motorway or reconstruction is planned, the government issues a request for proposals, specifying the construction class (e.g., motorway). Bidders use the catalog to select the type of construction (asphalt or concrete pavement and base type). Alternative offers with different construction types are permitted. The bidders’ offers include only the initial construction cost, not life-cycle costs, and while the concrete pavement alternatives tend to have a slightly higher initial cost than the corresponding asphalt pavement alternatives, concrete pavements are given a credit of US$0.22 per square foot (€1.80 per square meter) because their maintenance costs are presumed to be lower. The selection of this value was arbitrary and the German cement industry believes it is too low, although it has not yet proposed another specific value. On government-funded projects (as opposed to public-private partnerships), contractors must provide a 4-year warranty for concrete and asphalt paving. Regulations are being developed to stipulate the functional requirements of the pavement at the end of the 4-year warranty period. In addition to the mix design, the contractor is responsible for construction testing of concrete strength, air content, thickness, smoothness, and skid resistance. For PPP projects, the construction company is responsible for constructing the road and maintaining it for up to 30 years. Some PPP projects have maintenance periods of 20 or fewer years. The contractual provision related to maintenance becomes void at an earlier age if the actual accumulated traffic loadings reach the traffic loadings forecasted for the contractspecified maintenance period. The construction company derives its revenue from tolls. Lifecycle costs play a role in the construction method selected because alternatives with lower life-cycle costs yield higher profits for the construction company. Public-private partnerships are less common than conventional construction contracting arrangements. Three types of alternative contracting models have been employed in Germany for public-private partnership contracts for road construction projects of 6 to 9 mi (10 to 15 km). Under the “functional building contract” (or “C”) model, a 30-year contract is let to build and maintain the road, with financing from the Federal budget. Four pilot projects, two in asphalt and two in concrete, totaling about 25 mi (40 km), have been built under this model. Under the “F” model, a maximum of 20 percent of the startup financing comes from the Federal budget; the remainder of the construction and maintenance costs is paid by tolls. Several concrete and asphalt pavement projects have been built using this model. The “A” model is similar to the “F” model except that 50 percent of the startup financing, rather than 20 percent, comes from the Federal budget. About 148 mi (238 km) of roadways have been built under five contracts using “A” model financing. A pavement management system maintained by the Federal Highway Research Institute (Bundesanstalt für Straßenwesen, BASt) is used to store construction information, monitoring data (friction and high-speed profile measurements), traffic data, and accident data. Noise data are not collected. Most monitoring data are collected by contractors, with government oversight in each German state. Monitoring data are collected on a 4-year cycle; during the first 2 years the expressways are measured and during the second 2 years the other federal trunk roads are measured. The pavement management system is used primarily to generate short-term maintenance plans.

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Austria MOTORWAYS MAKE UP ABOUT ONE fourth of Austria’s Federal road network (8,700 mi (14,000 km)).[11] About two thirds of high-volume motorways (about 2,485 onedirectional mi (4,000 one-directional km)) are concrete pavements. Austria built its first concrete pavement in 1925 and its first motorway just before World War II. Austria’s high-volume roadways constructed after World War II were built in concrete, following the model of the German Autobahns. At the time, bituminous pavement designs for heavy traffic had not been developed, and there was no competition for concrete for high- traffic applications. In the 1970s, the Ministry of Transport adopted a pavement plan dictating which pavement type would be used for which roadways, as a function of truck traffic volume, soils and geologic conditions, and local government preferences. The ministry’s pavement type selection plan was abandoned in the 1980s, and the lifecycle costs began to be considered in pavement type selection. Asphalt pavement technology developed rapidly in Austria in the 1980s. Concrete pavements were also viewed during this era to be too expensive, noisy, and difficult to repair. Budget constraints in the 1980s required financing of motorway construction by loans, and cost-cutting measures such as reductions in layer thicknesses and lane and shoulder widths were instituted. Something of a renaissance in concrete pavement technology in Austria began in the early 1990s, when a program of reconstruction, widening, and geometric improvements of some of the older roads in the network began in 1990. Figure 6, for example, shows a section of the A1 motorway between Vienna and Salzburg, originally constructed in concrete between 1959 and 1961 and reconstructed in concrete in 2003. Among the technological improvements that contributed to increased use of concrete pavements in Austria beginning in the 1990s were the development of techniques for exposed aggregate surfacing, recycling of old concrete pavements, and rapid repair methods. Increasing traffic volumes and a decrease in the price difference between asphalt and concrete pavement also contributed to resurgence in concrete pavement construction. With the collapse of the Soviet Union and the opening of previously closed borders to the east, truck volumes on Austrian roads have increased and are expected to continue increasing greatly.

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Not all of Austria’s concrete pavements built in the 1950s and 1960s have been reconstructed. One such road is the Mölltalroad, in the Carinthia region in southern Austria, which opened to traffic in 1956. About half of its original length (some 30 mi (50 km)) is still in use and in good condition. The remaining half was redesigned to improve the alignment and intersections. The road is located in a mountainous area. Along its length, its average annual daily traffic ranges from 3,325 vehicles (5.7 percent trucks) to 6,136 vehicles (4.5 percent trucks). The Mölltalroad’s concrete surface is only 8 inches (in) (20 centimeters (cm)) thick, and was constructed on grade without any base layer. Despite the inadequacy of its design by modern Austrian standards, it still has good smoothness and friction and little distress after 50 years in service.[12] In the late 1990s, the Austrian Association for Research on Road, Rail, and Transport (FSV) developed the guide document RVS 2.21, Economic Evaluation of Different Pavement Alternatives, which became mandatory for use in pavement type selection for all Federal roads in 2001. Today, pavement type selection is done using life-cycle cost analysis as outlined in RVS 2.21. In general, concrete is preferred for heavy-duty roads (over 8,000 heavy vehicles per day) and for roadway sections with slow-moving, heavy traffic. Figure 7 illustrates conceptually the roles that average annual daily heavy truck traffic and proportion of slow-moving heavy vehicles in the traffic stream tend to play in the choice between asphalt and concrete. In Austria, concrete pavements are viewed as the economical pavement choice for heavily loaded roads in the following cases:

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• • •

Their life cycle is at least 40 to 50 years. No major maintenance is required for the first 15 to 20 years. Only one or two maintenance interventions (e.g., joint sealing, sporadic slab replacement, thin overlay) are required in the second 20 years or more of the life cycle.

Figure 7. Influence of traffic volume and proportion of slow-moving heavy vehicles on pavement type selection in Austria

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Figure 8. Austrian motorway network

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Proper design (thickness, joint spacing, dowels, etc.) and uniformly high construction quality along the length of the project are believed to be crucial to attaining the life-cycle benefits of concrete pavements. Austria has a sophisticated pavement management system used to store pavement data, forecast pavement conditions, and conduct life-cycle cost analysis of pavement maintenance strategies. Austria uses pavement management software called VIAPMS (a commercial pavement management program developed by a Canadian company) to manage its road network. A key component of this network is the motorway network, shown in figure 8. The structure of the Austrian pavement management system is shown in figure 9.

Figure 9. Structure of Austrian pavement management system

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Network-wide pavement condition monitoring includes collection of data on rutting, friction, roughness, cracking in concrete pavements, and surface defects. To keep the number of pavement sections in the database manageable, a dynamic segmentation algorithm is used to combine similar sections based on condition as well as inventory data.

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Figure 10. Calculation of benefit for each pavement treatment strategy considered in the incremental benefit-cost algorithm in Austria’s pavement management system

Friction, rutting, and longitudinal profile data are used to compute a Comfort and Safety Index (CSI) for each pavement section, while surface defects, slab cracking, and (for concrete pavements) age are used to compute a Structure Index (SI). These indexes are used to compute a Total Condition Index (TCI) for each pavement section, which is the parameter used in network-level optimization algorithms. Linear and logarithmic regression models are used to project future pavement conditions. Simplified models and a limited number of regression variables (age, equivalent single-axle loads (ESALs), a design index, and a frost index) are used for various pavement types. A recent research project in conjunction with the Technical University of Vienna focuses on improving the existing pavement condition prediction models and developing new ones. The cost-benefit analysis routine of Austria’s VIPMS system uses incremental benefitcost analysis to select from among multiple treatment options for each of the many pavement sections in the network. Benefit is quantified as the area between the forecasted condition curves of the treatment option and the do-nothing alternative, weighted for traffic. Figure 10 (see next page) illustrates this benefit definition. Work is underway to develop a user cost model for the Austrian pavement management system that takes into account travel time, fuel consumption, and accidents. The model is expected to be ready to implement in 2007. Among the outputs of the VIAPMS software are color-coded maps illustrating road condition by pavement section, as shown in figure 11. The portion of roadway highlighted in figure 11 is on the A1 motorway between Vienna and St. Pölten. Pavement surface friction is a significant safety consideration in Austria, especially in mountainous areas with heavy snowfall, steep gradients, and numerous tunnels. Friction testing is mandated in Austria for construction acceptance and at the end of the warranty period. Periodic friction testing of in-service pavements is also conducted for network-level

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pavement management purposes. Three cycles of friction testing of the entire motorway network have been conducted (1991–1994, 1994, and 2004–2005), as well as two cycles of friction testing of the trunk roads network (1991–1996 and 2001–2002).

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Figure 11. Pavement section condition mapping by Austrian pavement management software

Friction testing in Austria is done with a vehicle called a RoadSTAR (Road Surface Tester of Arsenal Research), developed by Austrian arsenal research experts in cooperation with the Stuttgart Research Institute of Automotive Engineering and Vehicle Engines. RoadSTAR’s measuring equipment is mounted on a two-axle truck with a 1,585-gallon (6,000-liter) water tank. RoadSTAR is capable of measuring surface friction at driving speeds of 25 to 75 miles per hour (mi/h) (40 to 120 kilometers per hour (km/h)), and at a speed of 50 mi/h (80 km/h) can measure friction on pavements with gradients of up to 8 percent. Recently, examination of friction acceptance testing data has revealed that new pavements in tunnels tend to have noticeably lower friction levels than other new pavements on the road network, and a national research study has been launched to investigate the reasons for this difference.[13] Today, management of the Austrian motorway network is the responsibility of a rather unusual form of public-private partnership: a private company owned by the Austrian Federal government. The Austrian motorway company ASFiNAG (Autobahnen und Schnellstrassen Finanzierungs Aktiengesellschaft) plans, finances, maintains, and operates the entire Austrian motorway and expressway network. ASFiNAG was formed as a financing company in 1982 as a step toward achieving a balanced national budget, a requirement for entry into the European Union. In 1997, its scope of responsibilities was increased through the Austrian government’s passage of the ASFiNAG Authorization Act. ASFiNAG is authorized to charge tolls and receive any income generated from property or other installations on the Federal road network. It is not authorized to set the tolls; that authority remains with the Austrian government. ASFiNAG is a public limited company and its shares are held entirely by the Republic of Austria.

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At the beginning of 2004, a fully electronic distance-related toll system for vehicles with a total weight over 3.5 tons (3.1 metric tons) was introduced on the primary road network. From this design-build-finance-operate public-private partnership (DBFO PPP) with EUROPASS, a subsidiary of the Italian firm AUTOSTRADE, ASFiNAG expects revenues of about US$816 million (€600 million) per year and another US$816 million (€600 million) per year from tolls charged on lighter vehicles. ASFiNAG has planned four packages of motorway improvement contracts to be let as public-private partnerships. These packages make up a program for building 70 mi (113 km) of roads in eastern Austria around Vienna to reduce traffic congestion in the Vienna area, improve traffic movement between Vienna and areas to the north, and provide an efficient north-south connection with the Czech Republic.[14]

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Belgium LINGUISTICALLY AND CULTURALLY, Belgium is composed of two regions: the Dutch-speaking Flanders region to the north, where Brussels, the capital of Belgium, is located and the predominantly French-speaking Walloon region to the south. Legally, Belgium is composed of three regions: the two aforementioned and the capital region of Brussels, where both French and Dutch are spoken. Three separate road administration authorities oversee matters relating to road construction and maintenance in these three regions. Belgium does not have dedicated funds for highways; general revenue funds are used. Belgium is densely populated—10 million people in an area of 11,600 square miles (30,000 square kilometers), less than the size of Maryland. About 10 percent of the population resides in Brussels, another 60 percent lives in Flanders, and the remaining 30 percent lives in Wallonia. The economy of Belgium is highly service oriented, and the Flanders region has one of the highest per capita GNPs in the European Union. The Walloon economy lags about one quarter behind in terms of personal income. A large portion of the Belgian motorway network has been constructed in continuously reinforced concrete pavement. Belgium and France are the only two European countries to have employed CRCP on a large scale; Belgium in particular has embraced it enthusiastically. Even more interesting for the purposes of this scan is the fact that Belgium’s CRCP design and construction technology was adapted from the United States. With the Belgian motorway network largely complete, much of the current investment in roads is allocated to renovation of the oldest concrete pavements in the network. Some old asphalt roads are also being replaced with concrete, sometimes by complete reconstruction and sometimes by a concrete inlay of the outer traffic lane. Environmental awareness is a significant public and political influence in Belgium. Tirepavement noise and recycling of construction materials are factors in pavement design, materials, and construction choices made in Belgium. As one recent Belgian research paper[15] puts it: “While most people are now convinced that concrete can be a preferred solution in economical terms, when taking into account the whole-life cost including maintenance and if Long Life and Quiet Pavement: Research and Issues : Research and Issues, Nova Science Publishers, Incorporated, 2010. ProQuest Ebook

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possible costs to the user, it has certainly become just as important to show that concrete roads are environmentally friendly and sustainable.”

The Belgian concrete industry produces about 30 million tons (27.2 million metric tons) of concrete and concrete products every year. Concrete has a good reputation in Belgium for being recyclable at the end of its life. In addition, in the Flanders region, about 85 percent of all rock-like building rubble is recycled. Two-lift construction, wherein lower quality materials are used in the thicker lower lift and higher quality, more wear- resistant, more durable aggregates are used in the thinner upper lift, has been used for a few special projects in Belgium. Good- quality aggregates are readily available in Belgium, so recycling of crushed concrete in the bottom layer has not been done in Belgium. A first trial of this type of construction, however, is planned. The exposed aggregate surface finishing technique popular in Austria is also used in Belgium. Both Belgium and Austria have found that one of the lownoise surface alternatives, a porous concrete surface, tends not to remain very porous or quiet for very long. The Walloon and Flanders regions are responsible for nearly equal amounts of the Belgian motorway network (both between 530 and 560 mi (850 and 900 km)), and the Brussels region is responsible for a smaller amount (7 mi (11 km)). Overall, Belgium has the highest roadway density (length of roads per unit land area) of any country in Europe, followed closely by the Netherlands. The Belgian road network consists of about 83,000 mi (134,000 km) of motorways and regional, provincial, local, and rural roads. Motorways make up about 1,100 mi (1,700 km), just over 1 percent, of this total. Concrete pavements make up 40 percent of these motorways. Concrete pavements are used more on lower-volume roads in Belgium than in most of the other countries visited on this scan, even rural roads, 60 percent of which are concrete. Overall, concrete pavements make up 17 percent of all roads in Belgium. Belgium has many examples of concrete pavements that have provided several decades of service. Belgium’s first concrete pavement, Lorraine Avenue, shown in figure 12, was constructed in 1925 and remained in service until 2003, when it received a concrete overlay.(16] In the Flanders region, management of the roadway network (shown in figure 13 on next page) is the responsibility of the Infrastructure Agency (IAA) in the Flemish Ministry for Mobility and Public Works. With a staff of about 1,600, the agency manages a network of some 3,900 mi (6,300 km) of roads and 4,200 mi (6,700 km) of bicycle paths. Highways make up 531 mi (855 km) of the Flemish road network. The annual budget of IAA is about US$426 million (€313 million), of which US$303 million (€223 million) is earmarked for investments in the road network and US$121 million (€89 million) for road maintenance.

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Figure 12. Belgium’s first concrete pavement, built in 1925, remained in service for 78 years

Figure 13. Major roads in the Flemish region of Belgium.

In the Walloon region, management of the roadway network (figure 14) is the responsibility of the Directorate-General of Highways and Roads in the Walloon Ministry of Equipment and Transport. With a staff of about 1,600, the Directorate-General manages a network of some 540 mi (870 km) of motorways and some 4,200 mi (6800 km) of other roads. The annual budget of the Directorate-General of Highways and Roads is about US$265 million (€195 million). About US$83 million (€61 million) of this goes to motorway and road investments, about US$91 million (€67 million) goes to routine maintenance (which includes winter maintenance), and about US$66 million (€49 million) goes to special maintenance projects. Life-cycle cost analysis is not used for pavement type selection at the project level in Belgium, except for large projects. A recent report by the Walloon Ministry of Equipment and Transport (MET) demonstrates why CRCP is the predominant pavement type used on motorways. In an economic comparison of asphalt pavement and CRC pavement for motorways, asphalt pavement was found to have lower initial construction costs, but CRC was judged more cost- effective over any analysis period greater than about 14 years.[17]

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Figure 14. Major roads in the Walloon region of Belgium

Primarily for non-motorway roads, the MET is developing a multicriteria analysis method for pavement type selection. The quantitative factors considered include cost, rutting resistance, skid resistance, cracking rate, and noise. The qualitative factors considered include surface and subsurface drainability, disruption to traffic, inconvenience for the public, ease of access to utilities for future repairs, compatibility with other pavement types nearby on the route, suitability of the surfacing for local conditions, ease of maintenance, ease of construction, susceptibility to frost damage, and ease of winter maintenance.[18] No roadway projects have been constructed in Belgium by a public-private partnership, though PPPs are being used for other types of public projects (e.g., school construction). However, six large roadway improvement projects now in the planning stages will be done as public-private partnerships. For these projects, the contractor will contribute to the initial construction cost and will be responsible for maintaining the roadway for 30 years. Functional requirements (friction and ride) will be defined for these projects and will not necessarily be the same functional requirements used for publicly managed roads. Lane rental fees will be charged every time during the 30-year period that the contractor closes a portion of the road for repairs.

The Netherlands THE NETHERLANDS, WITH A POPULATION of 16 million, is the most densely populated country in Europe. Despite its relatively small size and the fact that 18 percent of the country’s area is water, food processing is an important industry in the Netherlands. It is the world’s third-largest exporter of agricultural products, after the United States and France. The energy sector is another important part of the Dutch economy. The world’s secondlargest oil company, Royal Dutch Shell, is based in the Netherlands, and one of the world’s largest natural gas fields is located in the northeast part of the country. Nonetheless, gasoline consumption is heavily taxed; gasoline prices are higher in the Netherlands than in any other country in Europe and two to three times higher than in the United States. Funding for

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highway projects comes from fuel taxes and vehicle registration fees. Of the 24 percent of the annual public works budget of nearly US$11 billion (€8,000 million) that goes to highways, about 60 percent goes to construction and about 40 percent to operations and maintenance. The roadway network of the Netherlands consists of some 70,000 mi (113,000 km) of roads. Some 1,400 mi (2,300 km) are motorways, only 2 percent of the total by length, but these motorways carry 38 percent of all traffic by volume. Five percent of the motorway mileage in the Netherlands is concrete pavement. About half is CRCP and the other half is JPCP. The country also has 87 mi (140 km) of JPCP on the regional roadway network. Overall, concrete pavements make up about 4 percent of the roads in the Netherlands. In addition to roadways for motorized traffic, the Netherlands also has 12,000 mi (20,000 km) of bicycle paths, 10 percent of which are concrete. The Noise Abatement Act of 1985 stirred discussion in the Netherlands about traffic noise associated with different types of pavement surfaces. Concrete pavements with the traditional brushed finish were found to produce about 3 dBA (decibels adjusted) more noise than that of the reference pavement surface (dense asphalt concrete) defined in the Prescribed Standards for the Calculation and Measurement of Traffic Noise. In the late 1980s, the Motorways Department decided to address this issue by using porous asphalt concrete surfacing on concrete pavements. In general, concrete pavement is favored over asphalt pavement for Dutch roads with average annual daily traffic levels of about 50,000 vehicles per direction or more. Concrete is also preferred for roundabout construction. In the late 1980s and early 1990s, the prevailing practice to reduce surface noise with concrete pavements was to apply a porous asphalt surface course. In the mid 1990s, however, the Netherlands began to experiment with exposed aggregate finishes for concrete pavement, in either one-lift or two-lift construction. In recent years, interest in concrete pavements has revived because of their lower lifecycle costs and maintenance needs— heavy traffic congestion being an obstacle to lane closures for pavements, especially around the four big cities of Amsterdam, Rotterdam, The Hague, and Utrecht. While concrete pavements have higher initial construction costs and are not considered in the Netherlands as environmentally friendly as asphalt pavements, the drawback of asphalt pavements is seen to be their higher maintenance costs, with intervention required more frequently to remove ruts and extend service life. This renewed interest in longer-life concrete pavements coincides with a trend toward government downsizing in the Netherlands, with public-private partnerships expected to play an increasingly important role in roadway investment and maintenance. In the past 5 years, design-build contracts for road construction with a 7-year warranty period have become increasingly common in the Netherlands. Contractors’ bids for designbuild contracts will be rated according to the following weighting scheme: • • • • •

Price—60 percent Past performance—15 percent Technical quality—10 percent Durability—10 percent Aesthetics—5 percent

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In contracts awarded after 2007, the government will make the decision on pavement type, but the contractor will be allowed to select the design details, using the government’s pavement design software. A CROW working group of representatives of government, industry, consultants, and contractors has been formed to develop a decision support model to select pavement type and design details as a function of economic, environmental, and other factors.[19] Up to six design options can be compared in a single analysis. For each option, the user must enter or select data on the composition of the pavement, subbase, and sand bed for the road type in question. The program includes default pavement cross-sections for different pavement types and road classes. The three major factors used in the Dutch decision support model are costs, environmental impact, and other factors. Costs include those for construction, reconstruction, maintenance, and demolition. All costs are calculated based on net present value. Environmental impact is assessed using a model that considers both quantitative (e.g., emissions) and qualitative (e.g., nuisance) components. The “other factors” category gives the user the latitude to consider a range of other items of potential interest. In 1995, the Dutch government decided that the economic assessment of national projects must take into account a 4 percent discount rate. For this reason, the multicriteria decision support program uses a default discount rate of 4 percent. According to the developers of the Dutch decision support model, other European countries use different government-set discount rates (e.g., Germany uses 3 percent, the United Kingdom 6 percent, Denmark 7 percent, and France 8 percent), while the European Union considers 5 percent an appropriate discount rate. The decision support model uses a criteria weighting system, perhaps the most debated aspect of the model, because the subjective assignment of weights influences the outcome of the analysis. The counterargument is that not applying weights to the decision criteria would in fact be a form of weighting too, but one that would not allow the flexibility to consider priorities that might be different in the future than they are today. For the three major decision criteria used in the program (costs, environmental impact, and other factors), a weighting triangle, shown in figure 15 (see next page), can be used to compare different sets of weights and indicate the degree to which the weighting set influences the final result. The sides of the triangle represent the weighting factors for the “cost,” “environmental impact,” and “other factors” criteria on scales of 0 to 100 percent. The pavement alternatives evaluated in the analysis are numbered (up to a maximum of six; only two alternatives are compared in the example shown in figure 15). Each cell in the triangle represents a possible combination of the three factors’ weights, and the number in each cell is the design alternative favored for that combination. The box around the cell represents the actual combination of factor weights used in the present analysis. The box’s proximity to any boundary where the preferred option changes is a graphical illustration of the sensitivity of the result to the combination of weighting factors selected.

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Figure 15. Triangle illustrating sensitivity of multicriteria analysis results to weighting factors

While concrete pavements traditionally have not been as popular in the Netherlands as in some other European countries, they have long been popular in parts of the country, especially in the southern province of Noord-Brabant. Here, concrete pavements have been constructed steadily since the 1950s, and about 35 percent of the roadway network now consists of concrete pavements. In a recent survey of the pavement construction and maintenance practices in Noord- Brabant and other Dutch provinces, a key finding was that “the analysis data confirm the generally held, but not yet substantiated, notion that a concrete pavement is practically maintenance-free during its lifespan.”[20] The same study arrived at a summary, shown in table 1, of typical design lives and actual expected lifespans for four types of concrete pavements on Dutch roads of different functional classes. These actual lifespans are based on more than 50 years of experience in the Netherlands. Type 1 roads are on the primary roadway network and on motorways managed by the Motorways Department and the provinces. Type 2 roads are heavily used roads and county roads managed by the provinces. Type 3 roads are moderately used roads, access roads, and bus lanes managed by the provinces, municipalities, and water boards. Type 4 roads are lightly used roads and farm tracks managed by municipalities and water boards.

United Kingdom THE UNITED KINGDOM IS A political union made up of four countries: England, Scotland, Wales, and Northern Ireland. The United Kingdom also has several overseas territories, including Gibraltar and the Falkland Islands. The United Kingdom is a constitutional monarchy with close relationships with—but not direct administrative control

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over—15 other Commonwealth countries that share the same monarch, Queen Elizabeth II, as head of state. With more than 58 million people, the United Kingdom is the third most populous state in the European Union, after Germany and France. About 83 percent of the population of the United Kingdom lives in England; a quarter lives in southeast England, with some 7.5 million in London. Table 1. Expected lifespans for different classes of Dutch concrete roads.

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Road Type 1 1 1 2 3 4 4

Design Life, years 30 30 30 30 30 20 to 30 20 to 30

Expected Lifespan, years 45 to 50 30 to 40 25 to 30 40 to 50 40 to 50 40 to 50 25 to 30

Comment Provincial concrete roads Concrete motorways Motorways subject to overloading (not representative) Provincial concrete roads Water board roads Municipal concrete roads Water board farm tracks (not representative)

The United Kingdom is a highly developed country with the fifth-largest economy in the world and the second largest in Europe after Germany. Manufacturing and agriculture are far smaller segments of the British economy than they used to be, but a perennially important industry that places a significant demand on the road network is tourism. The United Kingdom is the sixth most popular tourist destination in the world. The energy sector is another important part of the economy. The United Kingdom has large coal, natural gas, and oil reserves. Nonetheless, gasoline taxes are among the highest in Europe, partly to control congestion on the motorways. Recently, London’s municipal government took the controversial step of imposing a stiff tax on all vehicles entering the city during the workweek in an effort to reduce traffic congestion in the city center. There are some 177,000 mi (285,000 km) of roads in the United Kingdom’s roadway network, about 900 lane-mi (1,500 lane-km) of which are concrete pavements. The English portion of this roadway network is shown in figure 16; the road networks of Wales, Scotland, and Northern Ireland are not shown in this figure. Until the early 1980s, JPCP and JRCP were the most common concrete pavement types built. From the mid 1980s to the mid 1990s, the typical concrete pavement construction was CRCP with a brushed surface. In the late 1990s, as a matter of public policy, thin hot-mix asphalt surfacing (see figure 17) came to be required on concrete pavements. This occurred because of public pressure on lawmakers to compel the Highways Agency to find a way to reduce noise from road surfaces. This Highways Agency prohibition on bare concrete road surfaces applies only in England, not elsewhere in the United Kingdom. In the case of a public-private partnership project, the contractor may request a “departure from standards” and select any pavement type. The Highways Agency generally approves such requests because the contractor bears the risk. The typical requirement for PPP projects is that the roadway must be returned after 30 years with 10 years of remaining life. The

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Highways Agency does not have a protocol for how the remaining life in the 30th year is to be established. An asphalt overlay, for example, placed during that last year would very likely be considered to meet the requirement for furnishing 10 years of remaining life.

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Figure 16. Network of motorways and all-purpose roads in England

Figure 17. Thin asphalt surfacing mandated on concrete roads in England

One of the first roadway improvement projects in the United Kingdom conducted as a public-private partnership was the widening of the A1(M) motorway between Alconbury and Peterborough. This DBFO contract, awarded in 1996, required the consortium of partners to finance the widening, operation, and maintenance of a 13-mi (21-km) section of the A1 motorway between London and Newcastle until 2026. The estimated construction cost was US$255 million (€128 million). In exchange, the consortium receives payments from the Highways Agency in the form of a “shadow toll” (roadway users do not pay tolls) computed as a function of the road’s usage. The Highways Agency retains ownership of the road and

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has hired an independent consultant to act as the agency’s representative in monitoring the construction, operation, and maintenance of the roadway. The Highways Agency maintains a pavement management system for the United Kingdom’s roadway network. Traffic data stored in the pavement management system is now limited to information on heavy commercial vehicles because the original focus of the pavement management system was pavement deterioration. Now, as operational issues gain importance, work is underway to improve the information on passenger car volumes in the pavement management system’s database. The Highways Agency operates the TRAC equipment for measuring longitudinal profile, the SCRIM device for measuring skid resistance, and a deflectograph for testing nondestructive deflection. Visual surveys of pavement condition are also conducted. A computer program called SWEEP (software for the whole- life economic evaluation of pavements) is used for project-level maintenance treatment selection. A network-level analysis program has been under development for 7 years and for the last 4 years has been used to help generate the annual program of pavement investment and maintenance activities. This stand-alone, network-level analysis program was developed by the private-sector Transport Research Laboratory. It does not interact with the other modules in the Highway Agency’s pavement management system software.

3. CONCRETE PAVEMENT DESIGN

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Canada ONTARIO HAS BUILT CONCRETE PAVEMENTS since the 1930s, with the 1960s and early 1970s a period of major expansion of the freeway network. Many of Ontario’s major freeways were originally constructed in concrete. This era of expansion was followed by one of reduced highway construction activity and a loss of experience and expertise because of the retirement of many older engineers. A highway technology program launched in the 1980s formed the basis for the pavement design and construction practices used in Ontario today. The standard concrete pavement in Ontario is a dowelled, jointed plain concrete pavement with a 14-ft (4.25-m) widened outside lane. Perpendicular transverse joints are randomly spaced at an average 14 ft (4.25 m). Concrete pavement thicknesses range from 8 to 11 in (200 to 280 mm). The thickness design is based on both the 1993 AASHTO Guide for the Design of Pavement Structures and the Canadian Portland Cement Association’s mechanistic-empirical rigid design method. Since 1992, a 4-in-thick (100-mm-thick), asphalttreated, open-graded drainage layer (0.75-in (19 mm) top size crushed stone, 1.8 percent asphalt cement) has been used for pavements on the highest-volume routes. Untreated opengraded layers, 6 in (150 mm) thick, are allowed on lower-volume routes. The design standards allow open-graded cement-treated base as an option, and a project to be built in 2007 on Highway 410 will be the first with this type of base. Full-length perforated plastic pipe subdrains are placed in a filter-wrapped trench in the shoulder area, backfilled with open-graded aggregate.

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After trying various concrete pavement designs over the past 50 years, the province of Québec now builds both jointed plain and continuously reinforced concrete pavements. In the 1950s and ‘60s, Québec built 9-in (230-mm) jointed reinforced concrete pavements, but had problems with joint deterioration. In the 1970s, Québec switched to an undowelled jointed plain concrete pavement design, also with 9-in (230-mm) slabs, but these pavements experienced problems with joint faulting and frost heave. In the 1980s, Québec built 8-in (200-mm) jointed plain concrete pavements, which experienced construction, structural, and frost heave problems. By the early 1990s, nearly all of Québec’s concrete highway pavements were in need of reconstruction. In 1994, two standard concrete pavement designs were adopted by the Québec Ministry of Transportation (MTQ). The first is JPCP, with the slab thickness designed for truck traffic over a 30-year design period according to the 1993 AASHTO Guide for the Design of Pavement Structures[21] method (using 50 percent reliability), and a total pavement thickness adequate for protection against frost heave. Truck factors (ESALs/truck) have been developed to characterize expected truck traffic for pavement design purposes. Typical JPCP slab thicknesses built according to the current standard are between 10 and 13 in (250 and 325 mm). Jointed concrete pavements are dowelled, with sealed joints, and rest on 6 in (150 mm) of granular base and a variable thickness of granular subbase for frost protection. Since making these changes to the standard JPCP design in 1994, fewer than 1 percent of the JPCP slabs constructed have exhibited cracking. The main distress type in these pavements is joint and corner spalling, usually addressed by partial-depth repair. The second standard concrete pavement design used in Québec is CRCP. The first experiment in CRCP, a 1.2-mi (2-km) section, was built on Highway 13 in 2000. This pavement was a 10.6-in (270-mm) slab on granular subbase with 0.70 percent black steel. The right shoulder was paved as JPCP, and the left shoulder was paved as CRCP. Six other CRCP projects have been built in Québec since 2003. The 5.6-mi (9.1-km) section on Highway 40 is typical of these. It has an 11-in (285-mm) slab on an open-graded cement-stabilized layer, 0.76 percent galvanized steel, and JPCP shoulders. A 30-year design period is also used for CRCP. Uncertainty about the potential for steel corrosion in CRCP is a concern because Québec applies 44 to 66 tons (40 to 60 metric tons) of deicing salt per two-lane km to its roadways every winter (about two to three times as much salt as Illinois uses, for example).

Germany GERMANY BEGAN BUILDING concrete roads in the late 1880s and in 1934 started using concrete pavement extensively in the construction of its motorway (expressway) system. Between 1935 and 1939, some 2,200 mi (3,500 km) of motorways were built in Germany with a pavement cross-section of about 9 in (220 mm) of wire-mesh reinforced concrete on 4 in (100 mm) of sand base course, and expansion joints every 33 to 66 ft (10 to 20 m). Until the early 1960s, Germany built primarily jointed reinforced concrete pavements on unbound base courses, using expansion joints and transverse contraction joints spaced 25 to 33 ft (7.5 to 10 m) apart. The standard jointed plain concrete pavement design for motorways

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in Germany was changed in 1972 to one without expansion joints and with transverse contraction joints spaced 16 ft (5 m) apart on cement-treated or asphalt-treated base. The first slipform paving on German motorways was done in 1982.[22] Today, about 25 percent of Germany’s 7,500 mi (12,050 km) of motorways are concrete pavements. Motorways make up about 2 percent of Germany’s total road network (389,500 mi (626,800 km)), but their investment value is estimated at about 26 percent of the total value of Germany’s roadway network, about US$342 billion (€250 billion) in 2003. The average traffic load on German expressways is about 8,000 trucks per day, although some routes carry three to four times that. The axle load limit is 11.5 tons (10.4 metric tons) for German trucks and 13 tons (11.7 metric tons) for trucks from neighboring countries. These heavy traffic volumes and loads are a major reason for using concrete for many of the expressway resurfacing and new construction projects in the former German Democratic Republic. Germany uses a catalog for selecting concrete pavement slab thickness and other details as a function of traffic level and other factors. This catalog[23] is updated about every 10 years (most recently in 2001). The standard designs are based on the forecasted traffic loads over a period of 30 years. The number of standard axle loads through the 30th year is termed the load value, B, and this value determines the construction class, which in turn determines the pavement layer thicknesses required. Of the seven construction classes defined in the German catalog, the highest class, labeled SV, corresponds to 32 million or more standard axle loads over 30 years. Motorways are assumed to fall into the SV construction class. The total pavement thickness to be constructed, according to the requirements of the German catalog, is the sum of the thicknesses of the concrete surface, base course (cementtreated, asphalt-treated, or untreated), and frost protection layer. The thickness of the frost protection layer depends on the climate of the region and the frost sensitivity of the subsoil. The typical total pavement thickness is 22 to 35 in (55 to 90 cm). Figure 18 illustrates the motorway (construction class SV) cross-section designs indicated in the German design catalog for three base types (cement-treated, asphalt-treated, and untreated) for a location requiring a total pavement depth of 35 in (90 cm) for frost protection. Figure 19 shows a portion of Germany’s design catalog page for concrete pavement design alternatives.

Figure 18. Concrete pavement design alternatives in German catalog for motorway traffic (construction class SV, >32 million axle loads over 30 years) and 35 in (90 cm) total depth (1 in = 2.54 cm)

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Figure 19. Portion of Germany’s design catalog page for concrete pavement design alternatives

Germany’s pavement design catalog now requires the use of a geotextile to separate a concrete slab from a cement-treated base. In the past, Germany’s standard design for cementtreated base depended on these two layers being bonded and the cement-treated base being notched at locations matching the joints in the concrete slab to facilitate controlled cracking in the base. The required concrete slab thickness for the new cement-treated base alternative is 10.6 in (27 cm); it was 10.2 in (26 cm) for the old design with a bonded base. The design compressive strength of the cement-treated base is 2,100 pounds per square inch (psi) (15 megapascals (MPa)) under a concrete slab and 1,000 psi (7 MPa) under asphalt layers. The geotextile used with the cement-treated base design alternative is a nonwoven polyethylene or polypropylene, 0.2 in (5 mm) thick. This fabric is attached to the cementtreated base before the concrete slab is placed, and care is taken to prevent construction traffic from damaging the geotextile once it has been laid. Figure 20 shows a core through a concrete pavement with cement-treated base and geotextile interlayer. The unbound base used with the third design alternative is crushed aggregate with a minimum thickness of 12 in (300 mm), and a gradation sufficiently open to prevent water that enters the pavement structure from accumulating near joints and cracks and pumping out under traffic loads.[24]

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Figure 20. Concrete, cement-treated base, and geotextile interlayer used in Germany

Figure 21. Joint layout details for standard German concrete pavement design

For all three JPCP design alternatives, the joint spacing is 16 ft (5 m). Dowel bars at the transverse joints are spaced every 10 in (250 mm) in the wheel paths and every 20 in (500 mm) outside of the wheel paths. The dowels are plastic-coated steel, with a diameter of 1 in (25 mm) and length of 20 in (500 mm). Deformed, plastic-coated tie bars, 0.8 in (20 mm) in diameter and 31.5 in (800 mm long), are used at the longitudinal joints. Five tie bars per slab are used in longitudinal construction joints, and three tie bars per slab are used in longitudinal contraction joints. Concrete slabs for the driving lanes are paved wider than the painted traffic lane to reduce stresses and deflections at the slab edges. The joint layout details are illustrated in figure 21.

Austria AUSTRIA’S CONCRETE PAVEMENT DESIGN and construction standard, RVS 8S.06.32, was developed and is kept up to date by the Concrete Pavements Working Group of the Austrian Association for Research on Road, Rail, and Transport (Österreichische

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Forschungsgesellschaft Strasse– Schiene–Verkehr, FSV).[25] This standard dictates the thicknesses of concrete surfacing and underlying layers to be used for each of six different traffic load classes, as illustrated in figure 22. The highest traffic loading class, the “S” class (18 to 40 million design axle loads), is used for motorways. The standard concrete pavement design constructed in Austria for motorways and other roadways in the S traffic loading class is a jointed plain concrete pavement, 10 in (25 cm) thick, on 2 in (5 cm) of bituminous interlayer and either 18 in (45 cm) of unbound base or 8 in (20 cm) of cement-stabilized base. The joints are spaced at 18 to 20 ft (5.5 to 6 m).[26] All concrete pavement surfaces in Austria are built in two lifts, with virgin or recycled concrete aggregate used in the lower 8 in (21 cm) and more wear-resistant aggregate used in the upper 1.5 in (4 cm). The surface is given an exposed aggregate texture. Details of the twolift construction process and exposed aggregate surface texturing process are described in Chapter 4.

Figure 22. Portion of Austria’s design catalog page showing concrete pavement layer thicknesses for different traffic loading levels. Motorways are in the S class.

Figure 23. Standard Austrian jointed plain concrete pavement design (1 in = 2.54 cm) Long Life and Quiet Pavement: Research and Issues : Research and Issues, Nova Science Publishers, Incorporated, 2010. ProQuest Ebook

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Dowels in the transverse joints are 1 in (26 mm) in diameter and 20 in (500 mm) long. Dowels are spaced more closely in the traffic lane wheelpaths and farther apart between the wheelpaths. Tie bars in the longitudinal joints are 0.55 in (14 mm) in diameter and 27.5 in (700 mm) long, and spaced 6.5 ft (2 m) apart (three tie bars per slab). Sealant reservoirs are sawed 0.3 in (8 mm) wide in both transverse and longitudinal joints; preformed seals are used in transverse joints and liquid sealant is used in longitudinal joints. Figure 23 shows details of the standard Austrian concrete pavement design.

Belgium

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BELGIUM HAS A LONG HISTORY of concrete road construction. The Avenue de Lorraine in Brussels, constructed in 1925, remained in service until 2003, when it received a concrete overlay. This pavement, on an old forestry road connecting southern Brussels to the highway, was just 6 in (15 cm) thick.

Figure 24. Thickened-edge concrete pavement design used in Belgium in the 1930s

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Examination of Belgian design details from the 1930s reveal a recognition of the influence of edge loadings on concrete pavement cracking, as shown in figure 24. The design alternatives at the time were a minimum thickness of 5 in (12 cm) for slabs constructed on a gravel base and a minimum thickness of 6 in (15 cm) for slabs on grade, with the slab 2 in (5 cm) thicker at the edges for either case. The Avenue de Lorraine is not unique; Brussels has many examples of concrete roads that have served traffic for 50 years or more. Figure 25 shows a photo of a concrete pavement built in 1950 on the road between Leopoldsburg and Hechtel that is still in service today. Problems over the years with slab cracking because of excessive length, as well as joint spalling and faulting, led to incremental changes in the standard Belgian concrete pavement design. Today, jointed plain concrete pavements in Belgium are constructed with a joint spacing between 13 and 16 ft (4 and 5 m), dowels in the transverse joints, and a rigid base layer. Belgium built its first continuously reinforced concrete pavement in 1960. The steel content in this pavement was between 0.3 and 0.5 percent. The second CRC pavement in Belgium was built in 1964, and the first CRC overlay was built in 1968. In the late 1960s, a team of Belgian engineers of the Road Authorities and the Belgium Cement Research Centre made a field trip to the United States, where by that time more than 2,400 mi (3,800 km) of CRCP had been constructed. American CRCP design and construction technologies were adapted to Belgium and used to construct a large portion of the Belgian motorway network in the 1970s. Between 1970 and 1977, CRC pavements were built 8 in (20 cm) thick, with 0.85 percent steel placed at a depth of 30 percent of the slab thickness. A 2.4-in (6-cm) bituminous separation layer was used between the concrete slab and the lean concrete base, which was built over a drainable granular layer. In 1977, the steel content in the standard Belgian CRCP design was reduced to 0.67 percent, and this was the design used until 1991. The depth of steel placement was changed from 2.4 in (6 cm) to 3.5 in (9 cm). The concrete slab and lean concrete base thicknesses remained 8 in (20 cm), but the bituminous separation layer was eliminated. The layer thickness reductions, steel reduction, and elimination of the bituminous separation layer were all done to reduce costs.

Figure 26. Pumping of fines from lean concrete base under Belgian CRCP built between 1977 and 1991. Long Life and Quiet Pavement: Research and Issues : Research and Issues, Nova Science Publishers, Incorporated, 2010. ProQuest Ebook

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A typical problem of the CRC pavements built with these design details was erosion of the lean concrete base, pumping of water and fines from the longitudinal joint (see figure 26), and the formation of punchouts. A large research study in 1992 identified several deficiencies in the then-current design practices for CRCP. As a result, the 2.4-in (6-cm) bituminous separation layer was reintroduced to the standard CRCP design, the standard CRCP slab thickness was increased to 9 in (23 cm), and the steel content was increased to 0.72 percent. In 1995, the steel content was changed to 0.76 percent. This change in the reinforcement design was made not for engineering reasons but because of the disappearance of 0.7-in (18-mm) bars from the market. The 0.76 percent steel content, as well as the 9-in (23-cm) slab thickness, 2.4-in (6-cm) separation layer, and 8-in (20-cm) lean concrete base, remain Belgium’s standard CRCP design today for the construction class corresponding to the heaviest traffic loads and a design life of 30 years. The standard JPCP design for the same construction class and 30-year design life is 10 in (25 cm) of concrete on a 2.4-in (6-cm) bituminous separation layer and 8 in (20 cm) of lean concrete. For both JPCP and CRCP, these standard designs produce pavements that easily meet the 30-year design life and survive 40 years or more without requiring major intervention.

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The Netherlands IN THE 1950S, CONCRETE PAVEMENTS built on the Netherlands’ motorway system were undowelled JPCP. Dowelling of transverse joints in JPCP became the practice in the Netherlands in the 1960s. While about half of the existing concrete pavements on Dutch motorways are JPCP, in recent years, almost all new concrete pavements on the motorways have been built as CRCP. Before 2005, concrete pavement construction in the Netherlands used materials and methods specifications. A change to end-result specifications occurred in 2005 and, as discussed earlier, the current trend in concrete pavement construction contracting is the use of design-build contracts with a 7-year post-construction warranty period. The Netherlands uses a mechanistic-design software package called VENCON for concrete pavement design.[27,28] The Netherlands also has a pavement design catalog. Typical cross sections and other details for pavements for different roadway functional classes and traffic levels are available in the Dutch Cement Concrete Pavement Manual— Basic Structures.[29] Based on field measurements, a preset distribution of axle types is used in the pavement design software. The total number of axles applied is assumed to be 39 percent dual-wheel front axles, 38 percent dual-wheel rear axles, and 23 percent wide- based single-wheel axles. There are plans to introduce super wide-base single-wheel axles in the near future. Default axle load spectra (distribution of axle loads by weight) are also assumed in the program, depending on the road class. Jointed concrete pavements are designed according to a slab-on-dense-liquid model (springs with stiffness represented by a k value). Stresses in the concrete slab are calculated using Westergaard’s 1948 equations, modified by van Cauwelaert’s multilayer slab model to include consideration of a treated base. Thermal stresses in the concrete slab are recalculated

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using Eisenmann’s equations. A table of typical degrees of deflection load transfer for different types of joints and bases is used to calculate an effective reduction in applied load. A fatigue damage accumulation model is used to determine the life of a candidate slab thickness.

Figure 27. Longitudinal joint layout details for concrete pavement in the Netherlands

A tensile stress model developed at Delft University is used to determine the required steel content for CRCP. Design lives of 30 to 40 years are typically used for CRC pavements. A typical design would be 10 in (25 cm) of CRC with a 2-in (5-cm) porous asphalt surface, 2.4 in (6 cm) of bituminous material below the CRC slab to separate it from the base, and 10 in (25 cm) of base composed of a mix of crushed concrete, crushed masonry, and a hydraulic binder. These treated layers would be constructed on a roadbed of at least 16 in (40 cm) of sand. (Frost penetration depth is not so much the issue in the Netherlands as the minimum height of the roadway above the water table. The bottom of the subbase must be at least 31.5 in (80 cm) above the highest recorded level of the water table.)[30] The longitudinal steel content in a 10-in (25-cm) CRC slab would be 0.70 percent. Figure 27 shows longitudinal joint details.

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United Kingdom AN EMPIRICAL DESIGN APPROACH was used for CRC pavements built in the United Kingdom before 1975. According to this approach, a minimum thickness was used up to a certain level of traffic, and above this level, the required thickness was a function of the traffic level. The required thickness was based on an assumed concrete strength of 5,800 psi (40 MPa), and no credit was given for higher concrete strength. New design curves for CRCP have recently been developed, based on the design flexural strength of the concrete rather than a fixed strength value.[31] The longitudinal steel content used is 0.6 percent.

4. CONCRETE PAVEMENT CONSTRUCTION

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Canada AROUND 1995, ONTARIO SWITCHED from using predominantly method specifications to end-result specifications. This was envisioned as a transition to long-term (e.g., 20-year) warranties, but this vision did not have the support of the financial industry. MTO is experimenting with performance-based warranty contracts in which the ministry asks contractors to warrant a specific condition level (e.g., greater than or equal to 79 on MTO’s 0–100 Pavement Condition Index scale) 7 years after construction. So far, this type of construction warranty has been obtained only for lower-volume asphalt pavements, not concrete freeways. MTO’s acceptance for concrete freeways is based on the mean and standard deviation of the lot measurements for core compressive strength, slab thickness, and surface roughness. The contractor may receive a combined bonus of up to 5 percent of the item or a penalty of up to 20 percent. Notwithstanding the overall percent within limits, the contractor is required to repair a sublot if any individual compressive strength or thickness is less than 60 percent of the specified value or if any individual sublot for surface roughness is greater than a specified value. Scallops greater than 0.4 in (10 mm) for concrete pavements and 0.6 in (15 mm) for concrete bases must be repaired by diamond grinding. The contractor uses a computerized California profilograph, which is approved by the owner on an annual basis. Ontario is moving away from the use of epoxy-coated dowels in favor of stainless steel and black steel. Joints in concrete pavements are sealed with rubberized hot-poured sealant in 0.4-in-wide (10-mm-wide) reservoirs. Tining is done transversely, at a 0.75-in (19-mm) uniform spacing. A longitudinal tining trial was constructed on Highway 401 in 2006. Ontario has allowed the use of dowel bar inserters since the 1990s, and still allows both baskets and inserters, though the latter are more often used. In 2006, MTO implemented the use of MIT-SCAN equipment during construction to assess dowel bar alignment on a few trial contracts. Random scanning is done daily during construction, usually within 24 hours after paving. Concrete paving contractors in Ontario also have MIT-SCAN equipment and do their own testing for quality control. MTO’s acceptance for concrete pavement on these trial contracts also includes the alignment and position of dowel bars. Data from the MIT-SCAN during production is used to assess bonus or penalty.

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Québec paves full-width concrete shoulders with concrete pavements and uses preformed sealants in transverse joints in JPCP. Joint reservoirs are not sawn for longitudinal joints. The standard JPCP joint spacing used is 16 ft (5 m). Tie bars and dowels are placed before paving. Québec uses random transverse tining to texture concrete pavement surfaces, but has experimented with exposed aggregate and shotpeened surfaces as possible low-noise solutions. MTQ has used smoothness specifications for all concrete pavement projects since the early 1990s.[32] The Profile Ride Index (PRI) was replaced by the International Roughness Index (IRI) in 1998 so that the same smoothness specification would apply to both asphalt and concrete pavements. Some contractors still use a profilograph for control purposes. Based on a 2000 study comparing different kinds of roughness measuring equipment, the rolling profiler was selected as best suited for construction control. MTQ’s smoothness specifications include penalties for inadequate smoothness. MTQ enters into contracts with warranty, or “performance guarantee,” requirements with paving contractors. The contractor must guarantee the performance of the roadway for a period of time (5 to 10 years for several contracts let between 1995 and 2005). Annual performance monitoring, including measurement of profile, skid resistance, rutting, and distress, is conducted on 328-ft (100-m) control lots in the traffic lane.

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Germany SLIPFORM PAVERS ARE USED TO place concrete pavements in Germany, normally in two courses. Old concrete pavements are reclaimed and crushed into aggregate for use in the lower course of two-course concrete pavement slabs and in crushed aggregate base courses. Concrete recycled from old pavements with concrete durability problems (alkaliaggregate reaction or damage caused by freezing or deicing agents) cannot be used in new concrete slabs. Concrete resurfacing work on existing expressways typically must be carried out within short timeframes, and thus severe penalties are imposed on contractors if deadlines are not met. Either batch mixers, with capacities of 130 to 390 cubic yards (yd3) (100 to 300 cubic meters (m3)) per hour, or continuous mixers, with capacities of up to 390 yd3 (300 m3) per hour, are used to produce the volume of concrete (up to 3,900 yd3 (3,000 m3) per day) typically needed for such projects. For single-course concrete paving, dowels and tie bars are placed in baskets. For twocourse paving, dowels and tie bars are vibrated into the slab after the first course has been placed, and then the second concrete course is placed. The two concrete layers must be placed wet on wet to achieve full bond between them. Two-course construction may be done using two slipform pavers or with a large single paver. To achieve concrete pavement surfaces with good skid resistance, smoothness, and low noise, the concrete surface is finished and smoothed, and then textured using a longitudinal heavy burlap drag. Since May 2006, the standard surfacing method for concrete roads on motorways in Germany has been the exposed aggregate technique, which has been used for many years in Austria and Belgium.[33] The top lift in two-lift construction is 1.6 in (4 cm) thick, and the

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maximum aggregate size in the top lift is 0.3 in (8 mm). The mix for the top lift has a cement content of at least 26 pounds per cubic foot (420 kilograms per cubic meter), a water-cement ratio of about 0.40, and a gap-graded aggregate composed of 30 percent sand and 70 percent crushed stone. Two surface preparation techniques have been used in Germany for two-lift construction: application of a set retarder combined with a liquid curing compound, and application of a set retarder followed by covering with a plastic sheet. With both techniques, the goal is to be able to brush the surface of the concrete while it is still green to remove the mortar at the surface and expose the coarse aggregates.

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Figure 28. Two-lift paving in Austria

Figure 29. Dowel and tie bar inserters on back of front paver for two-lift paving in Austria

Transverse and longitudinal joints are cut 0.12 in (3 mm) wide as soon as possible to prevent uncontrolled slab cracking. Transverse joints are cut to 25 to 30 percent of the slab thickness, and longitudinal joints are cut to 40 to 45 percent of the slab thickness. Joint sealant reservoirs are cut 0.24 to 0.6 in (6 to 15 mm) wide and 0.6 to 1.4 in (15 to 35 mm) deep. Transverse joints are sealed with preformed elastomeric joint seals, and longitudinal joints are sealed with bituminous sealant compounds. Cores taken every 10,800 square feet (1,000 square meters) from the finished pavement are tested for strength and thickness, and the smoothness and skid resistance of the finished pavement are also measured. A 13-ft (4-m) straightedge is used for initial smoothness acceptance testing.

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Austria

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CONCRETE PAVEMENT SLABS in Austria are paved in two lifts, wet on wet, above the base layer and bituminous interlayer. The lower concrete course is 8.3 in (21 cm) thick, made with virgin or recycled concrete aggregates (1.25-in (32-mm) maximum aggregate size) that do not need to be highly wear resistant. The upper concrete course is 1.5 in (4 cm) thick and contains smaller (0.3- to 0.43-in (8- to 11-mm) maximum aggregate size) aggregates with high wear resistance. Figure 28 shows the upper course being placed on top of the lower course. Figure 29 shows the dowel and tie bar inserters on the back of the front paver. The exposed aggregate surface texture is created by a set retarder on the concrete after texturing, followed within 20 minutes by curing compound or plastic sheeting. The mortar is later brushed off the surface with a brushing machine, exposing the aggregate. Figure 30 shows an exposed aggregate surface constructed using a 0.3-in (8-mm) maximum aggregate size. Transverse joints are cut before the longitudinal joints, between 8 and 24 hours after concrete placement, depending on the weather conditions. For concrete motorways with concrete slab thicknesses of 10 in (25 cm), transverse joints are sawed 3 in (75 mm) deep and longitudinal joints are sawed 4 in (100 mm) deep.

Figure 30. Exposed aggregate surface on Austrian concrete pavement.

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To facilitate drainage of water that infiltrates the joints, flat drainage tapes are placed below the concrete slab at locations corresponding to the transverse joint locations and running from the middle of the outer traffic lane to the outside edge of the emergency lane, as shown in figure 31. Figure 32 shows these drainage tapes placed before paving. Since 1996, Austria has been constructing roundabouts using concrete pavement, especially in the eastern part of the country. About 40 percent of these concrete roundabouts have been designed for the highest traffic loading class in the Austrian pavement catalog (class S, the same traffic loading level used for designing motorways). The key differences between motorway construction and roundabout construction are in the details of the joints. Because heavy loads frequently cross the lanes in a roundabout, dowels are used in the longitudinal joints instead of tie bars. Slabs with free edges must have a 1:1 ratio of length to width, and the free edges are thickened by 1.2 in (3 cm). Concrete for roundabouts is placed primarily by hand, but recently some roundabout paving has been done using small slipform pavers. Careful attention to joint design and layout, both in plan preparation and at the job site, are considered crucial to good long-term performance of concrete roundabouts.[34,35]

Figure 32. Flat drain tapes placed before paving

Belgium CRCP IS THE CONCRETE PAVEMENT of choice in Belgium for motorways, but JPCP is also built. Dowels are 1 in (25 mm) in diameter, 24 in (60 cm) long, and spaced every 12 in (30 cm) across transverse joints. Dowels are coated with epoxy or bitumen. Tie bars are deformed steel, uncoated, 0.6 in (16 mm) in diameter, 31.5 in (80 cm) long, and spaced every 30 in (75 cm) along longitudinal joints. Black (iron-oxide-coated) steel is used for CRCP. Transverse steel in CRCP is skewed 60 degrees. For JPCP, the contractor can choose what type of joint sealants to use. Typically, hot- poured sealants are used in transverse joints and preformed elastomeric seals are used in longitudinal joints. The government typically does all testing during construction, but for some large projects, quality assurance/quality control (QA/QC) approaches are being used. Recent con-

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tracts have included pay factors for thickness, compressive strength, smoothness, and friction. The warranty practice in Belgium is to require a 3-year guarantee from the contractor. Slipform pavers were first used in Belgium around 1970. Figure 33 (see next page) shows the paving of the E34 road between vosselaar and Turnhout, one of the first slipform paving projects in Belgium. This pavement is still in service 35 years later, carrying more than 40,000 vehicles per day with 12 percent trucks. One of the most prominent concrete pavement projects undertaken in Belgium to date is the reconstruction of the Antwerp Ring Road, one of the most heavily trafficked freeways in Europe.[36] The Ring Road is about 9 mi (14 km) long, with four to seven lanes in each direction. Six radial freeways tie into it, and on its busiest sections it carries nearly 200,000 vehicles per day, with 25 percent heavy trucks.

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Figure 33. Slipform paving in Belgium began around 1970

Figure 34. CRCP roundabout construction in Belgium

The new pavement is a 9-in (23-cm) CRC slab over 2 in (5 cm) of bituminous interlayer, 10 in (25 cm) of cement-treated granulated asphalt rubble, and 6 in (15 cm) of granulated lean concrete rubble. The CRC slab has an exposed aggregate surface. CRCP was selected based on multicriteria analysis that included consideration of life-cycle costs, noise, recycling opportunities, comfort, safety, and other factors. The reconstruction of the Antwerp Ring Road was notable for its cost, about US$136 million (€100 million), and tight construction schedule. the outer ring was reconstructed in a 5-month period beginning in November 2004, and the inner ring was reconstructed in a 5month period beginning in April 2005. An A+B contract was used, and the contractor worked around the clock to meet the construction schedule.

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Belgium has constructed more than 50 intersection roundabouts (see figure 34) with CRCP since 1995. they are built with a slipform paver or with sideforms and a vibrating beam. Belgium’s first experiences with exposed aggregate surfaces were in the 1970s. major improvements to the technique, especially in mix design, were made in 1996 after a field study of low-noise surfaces (see figure 35). Six different surfaces were built on a layer of CRCP. the top layers were asphalt, porous asphalt, porous concrete, and fine exposed aggregate concrete. Noise measurements were done on the sections immediately after construction and 3 years later. initially the porous surfaces had the lowest noise levels, but after 3 years the exposed- aggregate concrete surface appeared to have a lower noise level. In another field test, conducted in 2003, four test sections were constructed within a larger two-lift CRC paving job to compare four combinations of lower lift thickness, upper lift thickness, and upper lift maximum aggregate size. the influence of maximum aggregate size on measured noise levels is illustrated in figure 36.

Figure 35. Field test of low-noise surfacings in Belgium in 1996

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Exposed aggregate surfaces are now used on all high-speed roads in Belgium. on motorways, after the set retarder is applied to the surface, plastic sheeting is used for the first 24 hours and then removed for brushing of the surface. For JPCP, the transverse joints are sawcut through the plastic. For non-motorway construction, the liquid curing compound, rather than plastic, is applied after the set retarder. In Belgium, contractors have been pleased with the results obtained with laser guidance of the slipform paver on some round-the-clock paving jobs and others done at night to avoid daytime traffic congestion. employees sometimes trip over the stringline during nighttime paving, and this problem is eliminated using a laser system.

Figure 37. Jointed concrete motorway pavement in the Netherlands with full-width outer shoulder as emergency lane

The Netherlands THE NETHERLANDS’ PRACTiCES in CRCP construction are based largely on the Belgian model and by experience gained with successive projects. Sections of CRCP were constructed on the A76 motorway in 1991, the A73 motorway in 1993, the A12 motorway in 1998, and the A5 and A50 motorways in 2004 and 2005. Construction of a 12-mi (20-km) segment on the A73/74 motorway began in 2006. Minor maintenance work is commonly done at night in the Netherlands because of daytime traffic congestion. New construction and major maintenance work are done in the daytime, with full closure of the motorway and alternate routes provided for traffic. The outer shoulder is paved full width to serve as an emergency lane (see figure 37). Tie bars across longitudinal joints in JPCP are 0.8 in (20 mm) in diameter, 31.5 in (800 mm) long, and spaced every 5.5 ft (1.67 m). The steel used for CRCP is uncoated. Standard procedure in the Netherlands is to place the steel at the mid- depth of the concrete slab, although in theory and according to the vENCoN 2.0 design program, the steel can be placed

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at a depth of 35 to 50 percent of the slab thickness. The required 0.7 percent steel for a 10-in (25-cm) slab is obtained using 0.6-in-diameter (16-mm-diameter) bars spaced at 4.7 in (120 mm). Transverse steel (0.5-in-diameter (12-mm-diameter) bars, spaced at 27.5 in (700 mm)) is skewed 60 degrees. Tie bars are used in CRCP only in longitudinal construction joints, not in longitudinal contraction joints. When used, tie bars have the same 0.5-in (12-mm) diameter as the transverse steel, are 31.5 in (800 mm) long, and are spaced every 3 ft (1 m). The tie bars are placed in the fresh concrete if it is paved in two lifts, or drilled in and grouted later. The tie bars for both JPCP and CRCP are covered by a synthetic coating in the middle third to inhibit corrosion. Sealing of joints is not standard procedure in the Netherlands. The typical end treatment for a CRC slab is four anchor beams 5 ft (1.5 m) deep (from the top of the pavement), spaced 23 ft (7 m) apart. At the transition to a bridge structure, the end of the CRC slab is typically separated by the head joint of the structure by a 49-ft (15-m) transitional section of asphalt pavement. A novel “jointless joint” (see figure 38) has been used in conjunction with CRCP at bridge approaches on the A50 motorway in the Netherlands. it is recognized, however, that this is an expensive solution to the CRCP/bridge junction problem.

Figure 38. “Jointless joint” bridge approach used in CRCP construction of A50 motorway in the Netherlands

The Dutch standards do not provide definitive requirements for opening to traffic. in general, no traffic or pedestrians are allowed on a concrete slab for the first 24 hours, pedestrians and cyclists may be granted access after 24 hours, cars and other light two-axle vehicles (maximum weight 3,300 pounds (1,500 kg)) are permitted after 48 hours, and opening to other traffic is allowed after 7 days or attainment of 70 percent of the design 28day compressive strength, whichever comes first. In the past 10 years or so, some regions of the Netherlands have used exposed aggregate surfaces on concrete pavements as an alternative to a porous asphalt concrete surface course. Noise levels with the exposed aggregate surfaces appear to be comparable to those for asphalt pavements. Full-scale field tests (see figure 39 on next page) have been conducted to examine the effects of different aggregate types and gradations, texture depths, set retarding methods, and paving methods (one-lift versus two-lift construction, and use of a super smoother to correct localized surface unevenness).[37,38,39] The different set retarding methods, construction methods, and mix designs used were not found to produce significant differences in smoothness. The initial friction level achieved was

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found to be related to the type of curing compound used. The different aggregate types examined yielded similar initial friction results. A 0.3-in (8-mm) top size quartzite was found to provide the most durable friction properties. Small gradations were found to produce more desirable noise characteristics for both cars and trucks. Although the use of a super smoother reduces texture depth, its contribution to the evenness of the surface was found to be beneficial in terms of noise. Concrete roundabouts are becoming more popular in the Netherlands. Technical guidance has been developed for the construction of both JPC and CRC roundabouts. The thickness designs are standardized for simplicity. The construction guidelines emphasize the details of joint and reinforcement layouts.[40]

Figure 39. Location of exposed aggregate test sections in the Netherlands

United Kingdom ARECENT REVIEW oF the U.K.’s CRC design procedure found, among other things, that the cement- treated base used under CRCP is significantly higher in strength than the cement-treated base used in other countries. This high strength is considered a contributor to the formation of wide cracks in the base and increased crack spacings in the CRCP, bringing with them an increased risk for localized slab failures. The new design guidelines for CRCP would allow a wider range of lower-strength, cement-bound bases than previously specified.(41)

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5. CEMENT AND CONCRETE Canada ONTARIO REQUIRES THAT the contractor be responsible for the concrete mix design. A minimum concrete compressive strength of 4,350 psi (30 mPa) is required. The coarse aggregate has a combined gradation of nominal maximum size 1.5-in (37.5-mm) and 0.75-in (19-mm) aggregates. The air content is specified as 6.0 percent, plus or minus 1.5 percent. Portland cement is required, but a portion of it may be replaced by supplementary cementitious material. The supplementary cementitious material can be a ground granulated blast furnace slag (up to 25 percent) or fly ash (up to 10 percent) or a combination of the two materials (a mixture of slag and fly ash up to 25 percent except that the amount of fly ash shall not exceed 10 percent by mass of the total cementitious materials). Québec allows the use of ternary mixes (portland cement, blast furnace slag, and fly ash) in mix designs for CRCP, but not for JPCP. Blended cements are also allowed. For both CRCP and JPCP, a compressive strength of 5,100 psi (35 mPa) is required.

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Germany GERMANY ADOPTED THE EUROPEAN concrete standard EN 206-1 in 2000. This standard, together with German standard DiN 1045-2, now constitutes the new German concrete standard. in some areas, the European standard provides only framework definitions, making supplementation by national standards possible and indeed necessary because EN 206 does not yet have the legal status of a harmonized standard in the European Union.(42) one feature of the new standard is an increased emphasis on durability through the use of exposure classes. Roads and bridge decks are in the most extreme exposure class, XF4, characterized by a high degree of water saturation and exposure to freezing and deicing agents. The German concrete standard sets the maximum water-cement ratio (0.50), minimum strength class (C30/37*), minimum cement content (20 lb/ft3 (320 kg/m3)), and minimum air content (4.0 percent) for concrete used in road construction. Beyond the requirements of this standard, the German guideline ZTv Beton-StB 2001, Additional Guidelines for the Construction of Concrete Pavements, sets an upper limit of 0.45 on the water-cement ratio and a minimum cement content of 22 lb/ft3 (350 kg/m3) for paving concrete, as well as a minimum cement content of 26 lb/ft3 (420 kg/m3) for concrete used in an exposed aggregate layer. The European cement standard EN 197 was adopted at about the same time as the European concrete standard. it defines 27 types of cement. The types of cement to be used for different concrete construction applications are identified in the German standard DiN 10452. Among the European standards for cement, aggregate, admixtures, mixing water, etc., so far only the cement standard EN 197 has been adopted as a harmonized standard. Aggregates must meet the requirements of the European standard EN 12620. higher standards apply to aggregates for road construction than for aggregates used in buildings and * Minimum cylinder compressive strength of 4350 psi (30 MPa) at 60 days and minimum cube compressive strength of 5,400 psi (37 MPa) at 28 days. Long Life and Quiet Pavement: Research and Issues : Research and Issues, Nova Science Publishers, Incorporated, 2010. ProQuest Ebook

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other structures. These include a limit on loss of mass in freeze- thaw resistance testing, limits on the content of lightweight organic contaminants, shape and flakiness index requirements, polished stone value requirements (50 for conventional road surfacing, 53 for exposed aggregate surfacing), and guidelines for mitigating alkali-silica reaction. Portland cement grade CEm i 32.5 R (equivalent to ASTm Type i), which also has to satisfy additional requirements, is used for concrete paving in Germany.[22,43] With the client’s agreement, portland slag cement CEm ii/A-2 or CEm ii/B-S, portland burnt shale cement CEm ii/A-T or B-T, portland limestone cement CEm ii/A-LL, or blast furnace cement CEm iii/A (at least 42.5 strength class) may also be used. The cement may not be too finely ground (maximum fineness 3,500 square centimeters per gram (cm2/g)), and must not set for at least 2 hours after placement. in the 1980s, cracking resembling that caused by alkali-aggregate reaction was observed in several pavements between 5 and 10 years old, all built with cements having alkali contents (Na2o equivalent) between 1.0 and 1.4 percent. Since then, only cements with alkali contents less than 1.0 percent have been used for road construction, and these pavements have not exhibited the kind of cracking observed in pavements built earlier. The current German standard limits the alkali content of the CEm I cement to 0.80 percent Na2o equivalent by mass. Germany has 25 cement-producing groups and plants and 10 concrete pavement contractors. Contractors have responsibility for mix design in Germany and in general the mixes are not proprietary. (Cement products, however, are proprietary.) Fly ash or fillers may be added to the concrete, but fly ash and silica fume may not be used together. Supplementary cementitious materials are not taken into account in the calculation of the cementitious content or the water-cement ratio. In two-course construction, recycled materials or inexpensive gravels may be used in the lower course, and different strength requirements exist for the upper and lower courses. At least 35 percent of all aggregates must be crushed. high freezing resistance and high resistance to polishing are also required. Germany imports some aggregate from Norway to meet its concrete pavement construction needs. Concrete in the C30/37 strength class required for road construction must have compressive strength of 4,350 psi (30 MPa) in 6-in-diameter (150-mm-diameter) cores at 60 days, and a compressive strength of 5,400 psi (37 MPa) in 6-in (150-mm) cubes at 28 days. Bending tensile strength is tested only in qualification tests before paving begins. it must be at least 650 psi (4.5 MPa) at 28 days in four-point testing in accordance with EN 12 390-5 (which is nearly identical to a required bending strength of 800 psi (5.5 MPa) tested in accordance with the former DiN 1048 under three-point loading and different test conditions).

Austria Austria’s Specification for cement and concrete for concrete paving (RvS 8S.06) requires the European standard type CEM ii cement, with an initial set time of no less than 2 hours at 68°F (20°C), Blaine fineness no greater than 3,500 cm2/g, and 28-day cube strength no less than 1,000 psi (7 MPa). Austria’s concrete paving specification (RvS 8S.06.32) requires the concrete mix used in the lower course of two-lift construction to have a 28-day flexural strength of at least 800 psi

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(5.5 MPa) and a 28-day compressive strength of at least 5,000 psi (35 MPa). The material used in the upper course is required to have a 28-day flexural strength of at least 1,000 psi (7 MPa) and a 28-day compressive strength of at least 5,800 psi (40 MPa). Concrete mix design is the contractor’s responsibility, and the laboratory that the contractor hires can use any method its wants to develop the mix. The contractor’s mixture is not considered a proprietary product. Aggregates used in an exposed aggregate concrete surface layer must have, among other properties, a polished stone value of at least 50. The aggregate used in the lower concrete course may be recycled from old concrete pavement as well as from old asphalt pavement, although the recycled asphalt pavement content is restricted to no more than 10 percent of the total aggregate amount. When an old concrete pavement is recycled, 100 percent of the old pavement is reclaimed, crushed, graded, and reused on site in the new concrete pavement and the cement-treated base, if any. Portland cement with 20 to 25 percent slag is used in Austria. The minimum cement content for concrete in the lower course is 20 lb/ft3 (320 kg/m3) for fixed-form paving and 22 lb/ft3 (350 kg/m3) for slipform paving. The minimum cement content for concrete in the upper course is 23 lb/ft3 (370 kg/m3) for fixed-form paving, 25 lb/ft3 (400 kg/m3) for slipform paving, and 28 lb/ft3 (450 kg/m3) for an exposed aggregate layer. An air content of 3.5 to 5.5 percent is required for fixed-form paving and 4.0 to 6.0 percent for slipform paving.

Figure 40. Aggregate gradations for concrete paving mixes in Belgium

Belgium Three Types of Concrete Mixes are used for concrete pavements in Belgium. The cements used are either portland cement (CEM i) or a blast furnace slag cement (CEM iii/A) of strength class 42.5, with a limited alkali content to prevent alkali-aggregate reaction. high cement contents, low water-cement ratios, and the use of air entraining agents lead to a very durable, high-strength concrete.

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Belgium has not had a problem with alkali-aggregate reaction with its local aggregates, so cements with alkali contents up to 0.9 percent are allowed. Air entraining agents were not used in concrete pavements in Belgium until about 10 years ago. Figure 40 shows gradation curves for aggregates used in concrete pavement mixes in Belgium for maximum aggregate sizes of 20 mm and 32 mm.

The Netherlands Although not stipulated as a requirement, the use of portland fly ash cement (CEM ii/B-v 32.5 R, containing 30 to 35 percent fly ash) or portland cement is preferred for concrete pavement construction in the Netherlands. Blended cements containing up to 60 percent slag are also used. Concrete in the 3 5/45 strength class is used for concrete paving in the Netherlands. An air-entrained concrete mix with a minimum cement content of 20 lb/ft3 (320 kg/m3) and a water- cement ratio no greater than 0.55 is used. The Netherlands has had no problems with alkali-silica reaction with its local aggregates.

6. MAINTENANCE PRACTICES

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Canada IN ONTARIO, MAINTENANCE and rehabilitation schedules for concrete pavements are included in the life-cycle costing procedure. For doweled JPc pavement, the initial joint resealing operation occurs in year 12, with resealing operations in years 18 and 28. Diamond grinding to improve friction is scheduled for years 18 and 28. Major rehabilitation of JPc in the form of concrete pavement restoration (cPR) occurs in year 28. cPR includes full- and partial-depth repairs, including some slab replacements, diamond grinding, and joint resealing. Ontario has conducted field tests of different types of precast slab installations for rapid repair. Two methods for individual slab replacement and one for multiple slab replacement have been tested. These techniques are applicable in situations where the only possible time for a lane closure for slab repair is between 11 a.m. and 5 p.m. MTO believes that slab repairs can be accomplished using precast slabs at production rates comparable to fast-track cast-inplace slab repair, with less dependence on weather conditions. Québec developed manuals for rigid pavement distress identification[44] and rigid pavement maintenance and rehabilitation.[45] However, no budget for pavement maintenance is provided.

Germany Germany uses high-early-strength concrete to repair individual slabs in existing concrete pavements, opening the road to traffic during the evening of the same day the repairs are cast.

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A cement content of 22 to 25 lb/ft3 (360 to 400 kg/m3) is required to achieve a compressive strength of 1,740 psi (12 MPa) at 6 hours. superplasticizers are used to achieve sufficient workability in these mixes.

Austria

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ON MOTORWAYS IN THE VIENNA area, pavement repairs are started on Friday evening or early saturday afternoon, and pavement must be reopened to traffic by sunday afternoon. To open repairs in 3 days, a concrete mix with a water-cement ratio of 0.42 is used; for one-day opening, a mix with a water-cement ratio of no more than 0.40 is used; and for opening in 12 hours or less, a mix with a water-cement ratio of no more than 0.36 is used.

Figure 41. CRC inlay construction in Belgium

Figure 42. Belgium’s first concrete overlay after 45 years in service

Austria has recently been studying the use of whitetopping (thin bonded concrete overlay of asphalt) to correct rutting in asphalt pavements. Testing conducted by the Research Long Life and Quiet Pavement: Research and Issues : Research and Issues, Nova Science Publishers, Incorporated, 2010. ProQuest Ebook

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Institute of the Austrian cement Industry Association indicates that a wedge-splitting test is a better way to measure the bond between the asphalt and concrete than the more commonly used tensile test. Other tests showed that the asphalt-concrete bond achieved by thoroughly cleaning the milled asphalt surface was not improved by the application of bonding agents.[46]

Belgium

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Concrete overlays and inlays are important techniques for rehabilitating old asphalt and concrete pavements in Belgium. An overlay raises the pavement grade and the old pavement structure becomes the base for the new pavement structure. with an inlay, the existing asphalt (often just in the outer traffic lane) is milled out to a depth equal to the new concrete pavement thickness required. Belgium was the only country visited to mention a concrete inlay as an often-used rehabilitation technique. Belgium constructed its first concrete inlay in 1933. concrete inlays in Belgium may be either JPCP or CRCP. In either case, a bituminous layer is required below the concrete slab. Figure 41 shows a CRC inlay being placed. The first concrete overlay in Belgium was constructed in 1960 over a concrete pavement originally constructed in 1934. The jointed concrete overlay was constructed of 7-in-thick (18-cm-thick) reinforced concrete slabs. Figure 42 shows the overlay still in service nearly 45 years later. Belgium’s first concrete pavement, the avenue de lorraine in Brussels, was overlaid with concrete in 2003 after 78 years in service. the overlay, shown in figure 43, is 7.8 in (20 cm) thick and 1.8 miles (2.95 km) long and was constructed in 11 days.

Figure 43. Concrete overlay constructed in 2003 on Avenue de Lorraine in Brussels

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Figure 44. CRC overlay construction on E40/A10 in Belgium

Figure 44 shows construction of a concrete overlay on the e40/a10 road from Brussels to Ostende. two mobile concrete plants were used to produce the 2,600 yd3 (2,000 m3) of concrete a day required for this project. the average paving rate was 3,900 ft (1,200 m) per day, 24 ft (7.25 m) wide. Figure 45 shows a closer view of the paver. Because of the tight schedule for this project, concrete was placed without interruption, 24 hours a day, 7 days a week. as a result, the CRC overlay has no construction joints. a slipform paver was also used to construct the safety barriers on this job, as shown in figure 46. Fast-track concrete paving mixes are used for rapid repair and reopening to traffic in Belgium. typically, the base layer is also replaced. these fast-track mixes contain either 28 lb/ft3 (450 kg/m3) of type cem I, strength class 42.5 cement with a water-cement ratio of 0.33, or 28 lb/ft3 (450 kg/m3) of type CEM I, strength class 52.5 cement with a water-cement ratio of 0.38. The mixes used are designed to achieve a compressive strength of 5,800 psi (40 MPa) after 30 to 36 hours, the maximum allowable lane closure time according to Belgian standard specifications. The concrete mixture contained no fly ash or silica fume. Belgium experimented with using precast slabs for rapid repair, but abandoned the technique because of problems with joint faulting.

Figure 45. CRC overlay paving on E40/A10 in Belgium.

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Figure 46. Slipform paving of the safety barriers on the E40/A10 CRC overlay project.

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The Netherlands The frequency of pavement maintenance in the Netherlands depends on the type of surface. single-layer porous asphalt surfaces are assumed to need replacement in the right lane after 10 years and across all lanes after 14 years. Double-layer porous asphalt surfaces are assumed to need replacement of the top layer in the right lane after 6 years and replacement of both layers across all lanes after 10 years. Bare cRc pavements are assumed to need no maintenance in the first 15 years of service. Sealing joints in JPcP was tried in the Netherlands in the 1980s, but no beneficial effect of sealing on pavement performance or life was observed. Joints in JPcP now are typically left unsealed.[20]

7. RESEARCH, TRAINING, AND COOPERATION Canada The ONTARIO MINISTRY OF TRANSPORTATION works closely with the Ontario Road Builders Association (ORBA), cement Association of canada (CAC), and Ready Mix concrete Association of Ontario (RMCAO), and participates in various Transportation Association of canada (TAC), FHWA, TRB, ASTM, AND AASHTO committees. Research partnerships also exist between the ministry and various universities, including carleton, Queens, McMaster, the university of Toronto, and the university of waterloo. These partnerships provide input in developing specifications and carrying out trials for using the MIT-SCAN, precast concrete pavement repairs, noise studies, etc. The Québec Ministry of Transport interacts on a regular basis with members of the Road Builders Association, the canadian cement Association, and Bitume Québec (the asphalt

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industry’s organization in Québec). Industry representatives participate with MTQ personnel on technical committees that discuss contracts, standards, and specifications. For example, MTQ’s 2001 policy on pavement type selection was based on 2 years of discussion between government authorities and representatives of the asphalt and concrete industries. MTQ sponsors some research activities by the concrete and asphalt industries in Québec. MTQ is conducting research on the use of glass fiber- reinforced polymer bars in cRcP, based on a similar study done in Illinois. At the end of a 2006 CRCP project, a set of test sections was constructed with 12 combinations of steel content, slab thickness, and singleversus-double layering of the steel. MTQ is also researching the potential use of glass fiberreinforced polymer dowel bars in jointed plain concrete pavements. Other areas of research for MTQ include skid resistance and noise mitigation with different concrete pavement surface preparations (exposed aggregate, longitudinal tining, shotpeening, and microgrinding), and development of a device called the ADR (audiomètre routier dynamique) for measuring tire- pavement noise. Thirty field sites are being monitored with the ADR device to assess the progression of tire-pavement noise over time.

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Germany The GERMAN CEMENT WORKS ASSOCIATION (Verein Deutscher Zementwerke, VDZ), located in Düsseldorf, is the technical and scientific association of the German cement industry. The organizational structure of VDZ is similar to that of the Portland cement Association (PcA) in the united states. Nearly all of Germany’s cement producers are members of VDZ, which has 29 international members as well. VDZ’s Research Institute conducts research in environment and plant technology, cement chemistry, concrete technology, environmental measuring, and quality assurance. VDZ’s laboratories are equipped with state-of-the-art equipment for cement and concrete testing. VDZ maintains a library and an electronic database of literature in cement and concrete research. This electronic database is accessible on the Internet as well as at the Research Institute. About 38 percent of VDZ’s budget goes to research (some of which is done at universities), and another 37 percent goes to consulting services, including kiln emissions testing, cement sampling, frost testing, and measurement of air content in hardened concrete. The German government’s research arm within the Federal Ministry of Transport is the Federal Highway Research Institute (Bundesanstalt für straßenwesen, BASt), located in BergischGladbach. BAst’s research activities encompass highway construction, highway capacity, safety, accidents, and winter maintenance. BAst also provides technical guidance to the state highway authorities, which administer the federal interstate highways and autobahns on behalf of the German government. BAst has a staff of 400 and an annual budget of about us$40 million (€32 million). The Technical university of Munich (TuM) plays a leading role in developing German pavement design standards and researching many aspects of concrete pavement behavior and performance. The scan team was impressed with both the quality of concrete pavement research in Germany and the cooperation among the industry, government, and academia. The three entities also work together to set standards (such as the design catalog). VDZ, BASt, and

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TuM conveyed an image of cooperation and a shared desire to provide the driving public with good, safe, long-lasting pavements. VDZ does a considerable amount of training for kiln and plant operations. Paving contractors, however, do not have access to as much training. The Federal government in Germany does not work closely with contractors in training and implementation.

Austria The AUSTRIAN CEMENT INDUSTRY Association (VÖZ) represents Austria’s 13 cement producers. VÖZ’s technical branch is its Research Institute (Forschungsinstitut), which has a staff of 18. It is an accredited inspection body and testing laboratory for cement and concrete. The Research Institute does work in testing, inspection, consulting, product development, and technology transfer. Past and current studies on concrete pavement topics include the following:

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• • • • • • • • • • •

Recycling of concrete for new concrete pavements and the influence of asphalt particles Noise-reducing concrete surfaces for roads Retarders and curing compounds for the exposed aggregate technique Early trafficking of concrete pavements High-performance concrete: heat of hydration, shrinkage, and modulus of elasticity Recycling of building concrete Thin bonded concrete overlays for existing asphalt pavements Alkali-aggregate reaction Minimization of reflection cracking from cement-bound bases Adaptation of concrete pavement strength requirements to European standards New cements for concrete pavements with alkali-aggregate reaction

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The Austrian Association for Research on Road, Rail, and Transport (Österreichische Forschungsgesellschaft strasse– schiene–Verkehr, FsV) serves as a forum for the nine Austrian regional governments, the Ministry of Transport, AsFiNAG, consultants, academics, and construction industry representatives to set uniform technical standards for constructing roads and railways. A managing committee and advisory boards provide oversight of FsV’s activities. A full-time secretary-general manages the FsV headquarters in Vienna. some 70 working groups and committees develop technical guidelines, instruction sheets, and working papers on a broad range of road and rail topics. The flowchart in figure 47 illustrates how ideas for new standards or revision of existing standards proceed through FsV’s standards development process. FSV publishes a series of guidelines for planning, construction, and maintenance. One publication in this series is the concrete pavement standard RVs 8s.06.32, developed and kept up to date by FsV’s concrete Pavements working Group.

Belgium

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The BELGIAN GOVERNMENT created the National center for scientific and Technical Research for the cement Industry (centre National de Recherche scientifique et Technique pour L’industrie cimentière, cRIc) in 1960 to oversee research on cement and concrete materials. Representatives of the Belgian cement industry, academia, business, the unions, and the government ministries overseeing research all participate in cRIc’s managing boards. The following are some of the cRIc research topics related to concrete pavements: • • • • • • •

Environmental compatibility of concrete Durability of concrete exposed to chemical environments Prevention of alkali-silica reaction Interaction of air-entraining admixtures with type cEM III cement Effects of air-entraining admixtures on concrete strength and durability Optimal use of concrete admixtures Effects of fillers and admixtures on early-age concrete strength

Some of cRIc’s research is sponsored by the Belgian cement Industry Federation (Fédération de l’Industrie cimentière Belge, FEBELcEM), which is composed of Belgium’s three cement producers. FEBELcEM also conducts its own cement and concrete research through its department for promotion, research, and development. Belgium has about a dozen large concrete pavement contractors, all but one or two of whom also do asphalt paving. contractors train their own personnel; the government and industry do not provide any construction training.

The Netherlands In 1972, the dutch ministry of Transport and the Dutch Road Builders Association established the RAw Foundation to develop standard specifications for road building. As the

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group’s activities grew beyond specifications development to research, it became necessary to restructure the organization in 1987 as the Foundation center for Research and contract standardization in civil and Traffic Engineering, better known as CROW. CROW is the Netherlands’ national information and technology platform for infrastructure, traffic, transport, and public space. It is a not-for-profit organization with a mission to develop, disseminate, and manage practically applicable knowledge on policy development, planning, design, construction, management, and maintenance. The national, regional, and local governments, water boards, private consultants, construction companies, materials suppliers, transport organizations, public transit companies, and research and education institutes are all cROw partners. cROw is financed by member subsidies, research sponsorship, and profits from the sale of RAw system standard specifications. CROW’s activities are clustered in seven areas: infrastructure, contract standardization, alternative contract forms, building process management, public space, mobility/transport, and traffic engineering. In each area, steering committees oversee working groups that develop guidelines and recommendations on specific topics and disseminate information to the concrete paving community in the Netherlands. In addition to its technical publications, cROw publishes the monthly Wegen (Roads) magazine, organizes the annual Roads conference, and conducts workshops and training courses for thousands of participants every year. CROW also maintains a library of technical publications, journals, reports, and conference papers, and this library is open to the public. some of CROW’s publications are available on the CROW web site. The Netherlands’ seven cement companies plan to form a cement association in 2007 and dedicate a budget of us$3 million (€2.2 million) to promoting concrete and government affairs. The cost to each cement association member will be based on its market share in cement tonnage. The cement association will be small, with only seven full-time employees, and will outsource much of its promotion work. The cement association itself will probably not operate a laboratory, since the member cement companies have their own laboratories. The Netherlands has about a half dozen concrete pavement contractors, most of whom do asphalt paving as well. The contractors share their concrete paving equipment but have their own asphalt plants. Practical construction training is done on the job, but several training courses on concrete paving technology are provided for contractor and government personnel by consultants and education institutes.

United Kingdom The LEADING TRANSPORTATION RESEARCH organization in the united kingdom is the Transport Research laboratory (TRl). Established in 1936 as a government laboratory, TRl was made independent and self-supporting in 1990. It has four major divisions, the largest of which is the infrastructure and environment division, which employs about 140 people. Other divisions do a great deal of research on a wide variety of topics related to vehicle safety, public transportation, resource management, and sustainable development. TRl also has one of the oldest and largest pavement testing facilities in Europe. TRL participates in the Forum of European National Highway Research laboratories (FEHRl), along with highway research laboratories in 11 other European countries. FEHRl

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has initiated a collaboration called the European long-life Pavement Group (ELLPAG). The aim of ELLPAG is to provide a forum for initiating and stimulating new ideas in the field of long-life pavement design, assessment, and maintenance in an economic and sustainable manner. ELLPAG also aims to encourage the exchange of information on long-life pavements, coordinate research efforts in this area, and promote the wider use of long- life pavements. The first specific objective of ELLPAG was to review the state of the art of design and maintenance of fully flexible long-life pavements in Europe.[47] work is underway to develop a similar review of the state of the art of design and maintenance of concrete pavements. ELLPAG’s long-term objective is to produce user-friendly best practices guidelines on long-life pavement design and maintenance for all common types of pavement construction in Europe. The concrete paving industry in the united kingdom is represented by Britpave, the British In-situ concrete Paving Association, formed in 1991. Its members include contractors, consulting engineers, materials suppliers, and academics. Britpave’s task groups focus on roads, airfields, rail, soil stabilization, sustainable construction, and specialist applications. Concrete pavements have a poor image in the united kingdom with the public and engineers. As a consequence, few researchers and consultants work in the area of concrete pavements, and contractors involved in concrete paving projects are hard-pressed to find and retain skilled personnel. An independent pavement consultant that briefed the scan team on the status of concrete pavement research in the united kingdom identified the following areas of research needed to improve the image, economic viability, and technical excellence of concrete pavements in that country:

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• • • • •

• •

Publication and dissemination of up-to-date, definitive guidance on concrete pavement maintenance needs and treatment options Development of training programs on concrete pavement maintenance Development of the concept of indeterminate-life pavements for concrete roads, with the aim of capping concrete pavement thickness at the appropriate traffic level Development and integration of whole-life costing models for concrete pavements into the Highways agency’s procedures and models Development of concrete pavement condition assessment technology for use in network-level and project-level monitoring monitoring of selected CRCP projects to build up a knowledge base on CRCP performance and maintenance needs Development of new design approaches, incorporating mechanistic models as appropriate, for concrete pavements and asphalt-overlaid concrete pavements Pursuit of the objective of maintaining concrete pavements as concrete

European Union The scan team was briefed on nanocem, a European union-wide initiative in nanotechnology research in cementitious materials. The briefing was given by Professor karen scrivener of the Ecole Polytechnique Fédérale (Federal Institute of Technology) in lausanne, switzerland. nanocem is a consortium of more than 30 academic and cement industry partners (see figure 48), with a mission to manage an integrated research and

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education organization to generate basic knowledge of phenomena on the nanoscopic and microscopic scales that influence the macroscopic performance of cementitious materials. Nanotechnology is research and development at the atomic, molecular, or macromolecular level of 1 to 100 nanometers (a nanometer is one billionth of a meter, about 100,000 times less than the thickness of a human hair). nanotechnology is being pursued in many countries in a wide variety of fields. To date, nanotechnology applications have been predominantly in the field of medicine. The nanocem consortium has four core research projects in cementitious materials underway: •

•

•

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•

Assemblages of calcium silicate hydrate (c-s-H) and other hydrates: determination of thermodynamic data to predict phase assemblages occurring in (portland) cementitious systems magnetic resonance analysis of nanoscale water interactions in cement paste and relationship to microtransport: use of proton resonance as a nondestructive method to probe the state of water in pores over a range of length scales Organo-aluminate interactions: synthesis and characterization of compounds formed between superplasticizers and aluminate phases during early hydration Hydration of blended cements: development of a methodology for measuring the reactivity of clinker phases and supplementary cementitious materials independently in blended cements

Nanotechnology research in cementitious materials is expected to produce better understanding and more quantitative measures of such things as cement mortar durability, alkali-silica reaction, the effects of temperature on cement hydration and compressive strength, the phases present in anhydrous cement, the structure of c-s-H, and the microstructure of cement.

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In the united states, the potential benefits of nanotechnology research and development are being explored through the national nanotechnology Initiative (www.nano.gov). The u.s. Department of Transportation is one of 21 Federal agencies participating in this initiative.

8. KEY FINDINGS AND RECOMMENDATIONS Key Findings The TEAM’S KEY FINDINGS and recommendations from the long-life concrete pavement scanning study are summarized below.

Pavement Selection Strategies Long-life concrete pavements: In every country visited, “concrete pavement” is considered synonymous with “long life.” these countries expect concrete pavements to be strong and durable, provide service lives of 25, 30, or more years before rehabilitation or replacement, and require little if any maintenance intervention over the service life.

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The public and the environment: the public is expressing concerns about environmental issues such as noise, congestion, and safety. Environmental issues, especially noise, are becoming major concerns to the public. In all the countries visited, there is a heavy emphasis on traffic safety, mitigation of noise, congestion relief, and the use of recycled materials. In some of the countries, a multicriteria analysis process is used to address these factors in pavement type selection. In the united kingdom, political forces have driven the decision that, to reduce noise, all highway pavements must have asphaltic surfaces. Public-private partnerships and innovative contracting: To maintain and improve their roadway infrastructures, most Eu countries and canadian provinces have adopted nontraditional financing methodologies such as public-private partnerships and alternative bids. Politicians recognize the advantages of these financing mechanisms and of sharing risk with private entities. most of the Eu nations visited embraced PPP efforts to reduce the national debt and comply with Eu financial requirements. As a result, contractors are accepting more responsibility for design, construction, and long-term maintenance of roadways. under such systems, contractors are more likely to choose concrete pavement because its longer life and lower maintenance requirements reduce future risks. Another aspect of contracting practice observed was the awarding of contracts based on best value rather than low bid. Pavement management: use of pavement management systems is inconsistent among the Eu countries visited and generally is not a driving force in pavement type selection. Pavement type selection factors: Although most countries visited state that they consider life-cycle costs, in practice, other factors such as functional class, truck traffic levels, initial cost, and environmental issues drive pavement type selection. In the province of Long Life and Quiet Pavement: Research and Issues : Research and Issues, Nova Science Publishers, Incorporated, 2010. ProQuest Ebook

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Québec, a policy decision has been made that certain segments of the network will be concrete pavement, others will be asphalt, and others may be either. In Austria, it is policy that concrete pavement is used above a certain traffic level. A similar policy is exists in the Netherlands.

Design Catalog design: Germany and Austria routinely use a design catalog to select pavement thickness and some other pavement features. the design features and thicknesses in the countries’ catalogs reflect their long-term experience with their materials, climate, and traffic levels. mechanistic modeling, laboratory testing, and field observations are used to validate the cross- sections in the design catalogs. In the Netherlands and the united kingdom, mechanistic-empirical design software is used for project-level design work. However, these two countries construct only a few miles of concrete pavement per year. maximum concrete slab thicknesses are a common feature of the German and Austrian design catalogs. the maximum slab thicknesses appear to be thinner than those designed in the united states for similar traffic levels and in many cases heavier trucks. Fatigue cracking does not appear to be a performance issue with these thinner concrete slabs.

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Design lives: the design lives used for concrete pavements in the countries visited are typically at least 30 years. In the Netherlands, a design life of 40 years is typical for provincial roads and motorways. the agencies are satisfied with the design and construction practices they use in achieving service lives of up to 40 or 50 years. Traffic management and future expansion: with an eye toward safety and congestion mitigation, widened lanes and full-depth concrete shoulders (emergency lanes wider than u.s. shoulders) are used in design. these emergency lanes are constructed with the same thickness and cross slope as the pavement lanes. Widened slabs: widened slabs are used routinely in the outer traffic lane to keep truck tires away from the pavement edge, thereby reducing slab stresses and deflections and extending pavement life. the traffic lane cross-section is carried out to the edge of the pavement, including the emergency lane. Some subsurface layers are daylighted beyond the edge of the concrete slab for drainage and constructability. Tie bars: Most of the European countries visited place fewer tie bars across longitudinal joints to tie lanes together (about half the number used in the united states). No problems were reported with lane separation, longitudinal joint load transfer deficiency, or compromised pavement performance because of this. Doweled jointed concrete pavements (JCP): In the European countries that build JcP (Germany, Austria, Belgium, and the Netherlands), doweled joints with 1-in-diameter (25mmdiameter) bars are typically used and appear to perform well, without joint faulting. this may be because of the large proportion and high quality of the aggregates used in the concrete mixes, which lead to good aggregate interlock and load transfer. the 1-in (25-mm) bars are

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used on sections that are typically 8 to 12 in (200 to 300 mm) thick and built on thick, usually stabilized, foundations. Continuously reinforced concrete pavement (CRCP): this pavement type is recognized in the countries visited as a heavy-duty, long-life pavement. some countries, such as Belgium and the united kingdom, have a long history with CRCP. Belgium’s CRCP design and construction technology was in fact adapted from u.s. practice years ago. the united kingdom reported unique and undesirable crack patterns with skewed transverse steel. the techniques for longitudinal steel design (percent steel) varied from country to country, although crack width control appeared to be a common denominator. None of the countries visited used epoxy-coated steel, but the MtQ in Québec, canada, uses galvanized steel. In the Netherlands, as a rule of thumb, the thickness required for cRc is 90 percent of the thickness required for JcP. this can be confirmed with the VENCON 2.0 software; for example, for a motorway with a JcP thickness of 11 in (280 mm), the software calculates a CRCP thickness of 10 in (250 mm). In Belgium, CRCP is constructed about an inch (2 to 3 cm) thinner than JcP. Germany has just a few CRCP test sections, but on the 0.9-mi (1.5-km) stretch of experimental CRCP test sections on the A-5 Autobahn near Darmstadt, the slab thickness is 9.5 in (24 cm), which is about an inch (2 to 3 cm) less than German design practice would dictate for JPcP for similar conditions. the thickness reduction was based on analyses conducted by the technical university at Munich.

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Pavement bases: Open-graded permeable base layers, using high-quality aggregates, are used in canada but not in the European countries visited. Dense-graded hot-mix asphalt and cement-treated base layers were used in several countries. In Germany, where in the past cement-treated bases were constructed to bond with concrete slabs, an interlayer of 0.2-inthick (5-mm-thick) unwoven geotextile or dense-graded hot-mix asphalt is used now to separate a cement-treated base from the concrete layer. unstabilized bases are used in Germany, based on the success of this base type in test sections built since 1986. Old concrete pavements in the former East Germany affected by alkali-silica reaction have also been successfully recycled for use in unstabilized bases.

Construction Joint sealing: Based on observations during site visits, sealed and unsealed joints appeared to have performed equally well on older projects. Belgium, however, reports that the long-term performance of unsealed joints is not the same as that of sealed joints, especially on heavily trafficked roads. Both hot-poured and compression seals are used in Austria and Germany. In Austria, strip drains (a few inches (5 to 10 cm) wide and at most 0.5 in (1.25 cm) thick) under about 3 ft (1 m) of the transverse joint in the emergency lane have recently been added as a design feature. longitudinal contraction joints in some regions of Germany used to be left unsealed, but this practice was discontinued because it allowed water that entered unsealed longitudinal joints to flow beneath the sealant in transverse joints.

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Foundations: thick foundations are used for frost protection. these systems were drainable and stable, but not open graded. Recycled materials, including asphalt, concrete, and in one case, masonry from building demolition, were used in the foundations. Interlayers: the use of a 0.2-in-thick (5-mm-thick) geotextile interlayer as a bond breaker between concrete pavement and cement-treated base is a recent requirement in Germany. German engineers indicated that the mortar is presumed to saturate the geotextile during construction, adding just enough stiffness to provide support while still acting as a bond breaker. the required concrete thickness for the cement-treated base alternative was increased from 10.2 to 10.6 in (26 to 27 cm) when the design was changed from one with a bonded base to one with a base separated from the slab by a geotextile. In the other countries visited, the typical interlayer between a concrete slab and a cement-treated base is a layer of hot-mix asphalt concrete. Jointless bridge joints: A “jointless joint” bridge approach was described in the Netherlands, and although it was a trial section, the Dutch appear interested in what may be a low-maintenance solution to bridge approach joints. they made clear, however, that this technique is costly.

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Materials Cementitious materials: Normal and blended cements, containing either slag or fly ash, are used. Limestone is allowed in all portland cements, at a dosage of up to 5 percent. cements with varying sodium-equivalent contents (generally below 0.9 percent) or blended cements are used to mitigate alkali-silica reaction (ASR) if test results show ASR potential. Most countries have minimum cement content requirements by mixture type. supplementary cementitious materials are not considered in the water/cement ratio, nor as part of the cementitious materials content. In countries applying an exposed aggregate surface, mixtures and consolidation processes that produce low paste thickness at the surface are used. Aggregate requirements: Great attention is given to aggregate selection, quality, and gradation, especially for the top layer, in countries using two-course construction. Goodquality aggregates are generally available (although aggregate is imported in some cases). All of the countries use well-graded aggregates, with several separate aggregate sizes (three to four, depending on the layer). The maximum aggregate size typically used in Europe is 0.8 in (20 mm). The top layer of concrete in two-lift construction usually has a 0.3- to 0.4-in (8- to 11-mm) maximum aggregate size. In the Netherlands, where primarily single-lift construction is done, 1.25 in (32 mm) is the maximum aggregate size. In some countries, the concrete mixtures are considered proprietary. The agency controls quality by specifying the end-product requirements. Recycling: Recycled materials (including concrete and masonry from demolition) have been used in the base layers in various countries. Austria requires the use of recycled concrete and recycled asphalt pavement (RAP) in the lower layer of two- course concrete (and for

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base). Recycled asphalt is allowed up to a maximum of 30 percent of the coarse aggregate in these mixtures. The polished stone value test is routinely applied by Eu countries for aggregate durability assessment. In Austria, a Los Angeles abrasion test value of no more than 20 is required for the top layer in two-layer construction. Corrosion protection: Québec now requires the use of galvanized rebar. Germany and Austria use tie bars coated only in the middle third and coated dowel bars. Compaction control: Intelligent compaction control equipment (automated feedback on rollers, etc.) is used in Austria. The European countries visited are strict about control of compaction of all layers, and in some countries, load testing of granular layers to check compaction is conducted with a small plate.

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Cement and concrete testing: construction process control is typically the responsibility of the contractor in the countries visited. workability is evaluated using a compaction test, similar to the ASTM Vebe test. Ontario and Austria check the air content in hardened concrete, although in Austria this is done only if a problem is encountered or suspected. In the European countries visited, alkali-silica reaction (ASR) is controlled, if detected by preconstruction testing, using blended cements or cements with low alkali content. No country reported difficulty with controlling ASR. Pavement testing: The countries visited do not perform quality control testing for noise, and no one method is used consistently from country to country to measure noise. Texture measurements are made both for end-product and pavement management system-based data collection. The MIT-SCAN equipment developed in Germany for detecting dowel bar misalignment is specified in canada (Ontario) for both quality control and quality assurance purposes, but not in the other countries visited. A 4-m straightedge is typically used to measure roughness in the Eu countries visited. Belgium also uses the APL (Analyseur de Profil en Long, or length profile analyzer) to measure pavement profile. The smoothness of pavements on which the SCAN team traveled was excellent in all countries visited.

Maintenance Maintenance techniques: In general, most of the countries visited have had little or no need to do maintenance of concrete pavements. Joint resealing is conducted in a sporadic manner, if at all. One widely used maintenance technique is a thin asphalt overlay to correct rutting caused by studded tires or mitigate tire-pavement noise. Only in canada is diamond grinding used to improve smoothness on bare concrete pavements. In the united kingdom, concrete pavement is overlaid with asphalt to reduce noise. Precast slabs for rapid repair: canada is evaluating the use of U.S.-developed precast concrete technology for rapid repair. In a field experiment the SCAN team visited, the team observed that panels were used for individual slab and multislab replacement. The Michigan and Fort Miller methods of placing precast slabs were examined in the canadian experiment. canada is also examining modification of the Michigan method. while both applications

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exhibited some premature distresses in the canadian tests, primarily because of issues related to installation, the Ontario Ministry of Transportation believes this will become a practical specialty method of construction and repair.

Research Concrete pavement research: In Europe, academic and trade institutions conduct most research related to cement and concrete materials and concrete pavements. For example, the VDZ in Germany is conducting research on the behavior of synthetic air entraining agents and alkali-silica reaction. Nanotechnology: A cooperative venture for research in nanotechnology for cementitious materials (Nanoscience of cementitious materials, Nanocem) has been organized in Europe. the consortium consists of academia and industry members, with financial support from the cement industry and the European community. this effort should lead to improvements in the durability and mechanical properties of concrete. the focus of Nanocem’s research activities is cement behavior; research into concrete mixture properties is some years away.

Industry Relations

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Contractor training: In most countries visited, no formal training of construction contractor personnel is routinely conducted through preconstruction meetings or other required education. most construction training appears to occur on the job. However, most countries visited appeared to have well- educated and qualified field personnel. some training is provided by the cement industry groups. Certification: there are no certification standards for inspectors and contractors’ employees in the European countries visited. training is the contractor’s responsibility and not a requirement. concern was expressed that less-experienced paving construction workers come from eastern European countries, which may necessitate more training programs in the future. Communications: In general, the European countries visited have good communications between contractors and the highway agencies. Academic and industry input is highly valued. For example, committees of agency, industry, and academic experts are formed to develop design catalogs. Standards: European standards are in the long, slow process of harmonization. meanwhile, individual European countries continue to use their own standards. the comité Européen de Normalisation (CEN) is mandated by the European commission to develop standards for a variety of European community products. the EC’s construction Products Directive (CPD) requires that construction products be fit for their intended use. works in which these products will be used must satisfy CPD requirements over an economically reasonable service life. such products are placed on the market with a “CE” stamp. In the case of cement, even if the producer declares that a product conforms to the CEN standard,

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independent testing must be done to ensure this conformity. the CE “seal of approval” is useful, for example, if a paving contractor runs out of cement from one source in the middle of a paving job and must use cement from a different source (although tests have to be repeated with the new cement). CEN standards have not yet been developed, however, for many concrete paving materials (dowels, rebar, joint sealants, etc.). European (EN) or national standards continue to be used for these materials.

Recommendations The long-life concrete pavement SCAN team identified the following technologies as having the greatest potential for implementation in the united states.

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Two-lift construction: Austria, Belgium, the Netherlands, and Germany use two-lift construction to build concrete pavements with good friction and noise characteristics, economize on the use of aggregates, and use reclaimed paving materials. In two-lift construction, a relatively exposed aggregate surface lift containing high-quality aggregates is placed atop a lift containing virgin aggregates of lesser quality or reclaimed aggregate from concrete or asphalt pavements, resulting in materials cost savings. Two-lift construction is not new to the u.s. concrete paving industry. two-lift paving was specified by many state DOTS in the past when wire mesh-reinforced pavements were constructed and mesh depressors were not allowed. In recent decades, a couple of states have experimented with two-lift construction to promote recycling and enhance surface characteristics. Catalog design: Pavement design catalogs have been successfully used in Europe for many years. In the united states, the design of concrete pavement has traditionally been done on a project-by-project basis. this approach has served the u.s. pavement engineering community fairly well for many years. However, with the increasing difficulty of predicting traffic loads, volumes, and axle configurations, designing on a project-byproject basis may not always be required. In addition, changes and new developments in materials have created a need for a design procedure with the flexibility to consider the effects of material properties on the responses of the pavement structure. this need is being addressed with the development of the MechanisticEmpirical Pavement Design Guide (MEPDG). The catalog design method is a simple procedure for selecting an initial pavement structure. most European countries visited have routinely used design catalogs to select pavement thicknesses and some other pavement features. the countries using design catalogs recognize that simply extrapolating empirical trends is not reliable and often leads to overdesign of concrete pavements. the design features and thicknesses in the catalogs reflect long-term experience with the local climate, materials, and traffic levels. these experiences are validated through analysis by expert teams using mechanistic principles. the expert teams employ laboratory testing and field observations to validate the cross-sections in the design catalogs. The designs are defined and refined about every 5 years.

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The use of a catalog for selecting pavement thicknesses and other pavement design features offers advantages of consistency and simplicity. catalog design is not itself a design procedure, but rather a medium for identifying appropriate pavement design features for use in pavement analysis. the quickest form of developing a catalog design is simply to incorporate the standard designs that have shown good, consistent, long-term performance. A design features matrix is another part of the catalog concept that identifies alternatives for features (e.g., base types) and provides information on such items as the cost, performance, and feasibility of constructing the feature to allow an agency to make an informed decision on whether to include it in a design. Nevertheless, the information recommended in the catalog needs to be validated by laboratory and field investigations.

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Deep, high-quality foundations: The unbound granular materials used for concrete pavement subbases in Europe are generally better-quality materials (better graded, better draining although not open-graded, and with lower fines content) than the materials typically used as select fill and granular subbase in the United States. Aggregate standards were mentioned in all the countries visited. A closer look at the aggregate standards in place in the United States and a comparison to the European standard may provide some insights into improving foundations in this country. Recycled concrete not reused in the pavement itself is commonly used in the base material of pavements in Europe. It appeared that it was also fractionated and part of the grading. Cement-treated bases were also in wide use in several countries, with an asphalt or geotextile interlayer as a separator. In addition, it was noted that intelligent compaction is used in Austria. Germany uses a plate load test for quality assurance of layer compaction equipment. Attention to mix design components: One key to long-lasting concrete pavements in Europe appears to be the great attention to cement and concrete mixture properties. The mixtures produce strong, dense, and durable concrete, despite the apparent widespread presence of reactive aggregates in western Europe. The flexural strength noted in the top lift was about 1,000 psi (7 MPa), much higher than the typical flexural strength target in the United States. The careful consideration of cementitious materials used in the mix is one area that could yield benefits for the United States. Geotextile interlayer: A key detail recently introduced in Germany for cement-treated bases is the use of a thick geotextile interlayer to prevent the concrete slab from bonding to the cement-treated base. This geotextile material is thicker than the materials commonly used for layer separation purposes in the United States. It is sufficiently porous that mortar from the fresh concrete permeates the geotextile, which provides a good mechanical bond of the geotextile to the concrete layer while achieving separation from the base layer. This geotextile may provide a suitable alternate to the asphalt interlayer used in many States. Low-noise exposed aggregate surfacing: The public’s concern about environmental issues is evident in densely populated, traffic-congested Europe. A concrete pavement noise solution popular in some European countries is exposed aggregate surfacing, in which exceptionally high-quality, durable aggregates are used in the top course of the concrete slab, and a process of set retardation and abrasion is used to produce an exposed aggregate surface

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with good low-noise properties. Exposed aggregate is also touted as yielding other benefits, including good friction and durability. However, favorable noise levels may also be achieved by specific pavement texturing techniques.

APPENDIX A. AMPLIFYING QUESTIONS The following general questions were submitted to the host countries before the SCAN team’s visit. 1. Experience • Please provide a brief history of pavement and pavement types in your country. • Describe the role that concrete pavement has played in this timeframe. • What types of concrete pavements have been used, and how have they performed?

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2. Current Usage • Please describe the current situation with concrete pavement in your country, with respect to pavement type selection, performance expectations, and shortterm and long-term applications. • What role does life-cycle cost analysis play in decisions about pavement type and pavement design? • What are the factors considered in life-cycle cost analysis? 3. Terminology • Do you use a term such as “long-life pavements” or something similar? • How do you distinguish between a “long-life” concrete pavement and concrete pavement designed for a “normal” life? 4. Pavement Management • Do you use long-life pavements as part of your network-level pavement management? • Do you use pavements with longer service lives in some situations and pavements with shorter service lives in other situations to optimize the overall condition and performance of your pavement network? • How is information about pavement performance, specifically concrete pavement performance, used in your pavement management system? 5. Government-Industry Relations • Please describe the relationship between government and the paving industry in your country with respect to pavement research and development, technical services, and training. • How does the industry work with the government? • What role do industry associations play?

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6. Public-Private Partnerships • How do public-private partnerships and concessionaires operate in your country, in terms of investment, pavement type selection, etc.? • What do you see as the probable future trends in public- private interaction in the pavement field in your country? 7. Methods Used to Maximize Concrete Pavement Life • Materials evaluation (coarse and fine aggregate properties, cements, additives, fly ash, etc.) • Concrete mix design • Pavement thickness design • Pavement geometric design (slab dimensions, joint design, etc.) • Specifications • Construction procedures • Maintenance practices (including winter maintenance) • Rapid construction and rehabilitation techniques The following detailed questions were used by the SCAN team members in discussions with their hosts in the countries visited. 1. Experience 1.1. What types of concrete pavements do you build? 1.2. What are the typical failure modes for your concrete pavements?

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2. Current Usage 2.1. How are initial costs and life-cycle costs balanced in the decisionmaking process of pavement selection and design? 3. Terminology 3.1. What design life (in years or accumulated traffic) is used for concrete pavements? 4. Pavement Management 4.1. Are materials and construction data stored and subsequently linked to long-term performance? 4.2. How are functional characteristics (smoothness, friction, noise) controlled during the life cycle of a “long-life” pavement? 5. Government-Industry Relations (No detailed questions) 6. Public-Private Partnerships (No detailed questions) 7. Methods Used To Maximize Concrete Pavement Life 7.1. How much emphasis is placed on concrete materials versus structural design when designing a “long-life” pavement?

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United States Department of Transportation 7.2. What types of aggregates do you use in concrete slabs? 7.3. What quality requirements do you have for aggregates used in concrete slabs? 7.4. What types of aggregates do you use in bases and subbases? 7.5. What quality requirements do you have for aggregates used in bases and subbases? 7.6. Is aggregate availability a concern? If so, how do you address that? 7.7. In the United States, the practice for aggregates is shifting to use of combined aggregate grading (e.g., the Shilstone approach) instead of gap-graded aggregates for slipform paving. What is your agency’s current practice? Is this practice a change from previous practice? 7.8. What types of cements do you use? 7.9. What kinds of supplementary cementitious materials and/or chemical admixtures do you use? What limits, if any, do you place on the use of supplementary cementitious materials for paving concrete? 7.10. For what types of materials will you accept the manufacturer’s certification in lieu of testing upon receipt? Is there a trend toward or away from acceptance of manufacturer’s certification in lieu of testing? 7.11. How willing is the agency to accept substitutions for conventional materials using new and innovative alternatives? How are the costs and risks shared when substitutions are used? 7.12. What has been the result of European Committee for Standardization (CEN) and European Organization for Technical Approvals (EOTA) normalization on concrete pavement material evaluations in your country? Does your country use specifications or procedures not standardized under CEN or EOTA? 7.13. What procedures are used to design your concrete mixtures? What materials properties, performance indicators, or other factors (e.g., cost, air content, strength, workability, cracking resistance) are used to optimize and/or select your concrete mixtures? Which of these factors is most important? 7.14. Is compatibility of concrete materials a concern for your agency? Do you test for compatibility of various concrete materials? 7.15. Are alkali-silica reactivity (ASR) and/or D-cracking concerns for your agency? If so, how do you address these problems? 7.16. Are recycled materials used in concrete pavements? If so, what requirements do you have for recycled materials used as aggregate? 7.17. Is the concrete mixture used by the contractor considered a proprietary product? 7.18. Do you test for concrete drying shrinkage and/or coefficient of thermal expansion? If so, how? 7.19. Do you perform testing for concrete permeability? 7.20. What type(s) of joint sealing materials do you use? 7.21. What are the typical thicknesses and thickness ranges for the base, concrete slab, and asphalt concrete surface (if any) for the type or types of concrete pavements you build? 7.22. Do you use a structural design procedure to design pavements or do you use a design catalog approach? 7.23. What performance measures (smoothness, International Roughness Index (IRI), noise, specific distresses) do you use in concrete pavement design? What condition levels are used to define “failure?” 7.24. What are your practices with respect to the following: Joint spacing Dowels at transverse joints (size, spacing, materials, corrosion prevention, etc.) JRCP steel reinforcement (size, spacing, layers, corrosion prevention, etc.)

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CRCP steel reinforcement (size, spacing, layers, corrosion prevention, etc.) Texturing Curing Joint sawing (one versus two cuts, conventional versus early entry saws) Joint sealing 7.25. Do you use any of the following, and if so, do you have any design or performance issues associated with them? Concrete shoulders Widened slabs Subsurface drainage systems 7.26. What types of stabilized or unstabilized bases and subbases do you use? Do you have any design or performance issues with any particular base types? 7.27. What types of reinforcement (e.g., round steel, flat “ribbon” steel, glass fiber reinforced polymer (GFRP), etc.) have been used in concrete pavements in your country? What, if any, differences in performances have there been in pavements with different types of reinforcement? 7.28. How are pavement terminals designed for your rein- forced pavements? Is terminal anchorage (e.g., anchor lugs, slabs) used? Is pavement reinforcement ever tied into reinforcement of adjacent bridges or structures? 7.29. What concrete strength do you specify? 7.30. What surface texture requirements do you specify? 7.31. How do you specify concrete workability? What testing is conducted to determine concrete workability? 7.32. Do you use end result, quality assurance/quality control, or performance-based specifications for paving concrete? 7.33. Who performs construction testing—the agency or the contractor? 7.34. Is the contractor required to submit a quality management plan? 7.35. Do you use warranties for concrete pavements and, if so, for what duration? 7.36. What materials properties are evaluated by the public agency if the project is constructed under a warranty contract versus another contract type? What pavement performance indicators are monitored in each instance? 7.37. What requirements do you have for the foundation (including embankment)? 7.38. What are your workability requirements for slipformed concrete? Do you conduct any testing to determine concrete workability? 7.39. How do you test freshly placed concrete? Do you test for the following? Consolidation Air content Segregation 7.40. How much hand finishing is allowed behind the paver for slipformed concrete? 7.41. For dowel bars, do you use baskets or inserter machines? If inserters are used, what has been your experience with them? Do you test for dowel alignment? If so, what method is used? 7.42. Are multiple-lift pavers used? 7.43. Are nondestructive test methods (e.g., maturity, pulse velocity, MIT-SCAN) used to check in-place concrete properties? If so, do these supplement or replace traditional test methods? 7.44. What acceptance criteria do you think are most important? 7.45. What are the certification requirements for the contractor’s crew and for testing and inspection personnel?

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United States Department of Transportation 7.46. Do you reseal joints? If so, is it done on a regular predetermined cycle or as needed based on sealant condition? 7.47. What types of maintenance and repair cycles (surface grinding, etc.) do you consider acceptable? 7.48. Do you consider expedited construction a tradeoff with longer life, or can both be achieved for a single project? 7.49. What rapid construction methods are used for long-life concrete pavements? 7.50. What rapid rehabilitation methods are used for long-life concrete pavements? 7.51. Do you use high early strength concrete mixtures for rapid construction and/or rehabilitation? If so, what are the criteria for opening to traffic? 7.52. Do you use precast paving, and if so, in what situations? 7.53. How are repairs performed on CRCP? 7.54. What deicing materials do you use on concrete pavements?

APPENDIX B. HOST CONTACT INFORMATION

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Canada Gerry Chaput, P.Eng. Chief Engineer Director, Engineering Standards Branch Ontario Ministry of Transportation 301 St. Paul Street, 2nd Floor St. Catherines, ON L2R 7R4 Canada Tel: (905) 704-2089 Fax: (905) 704-2055 E-mail: [email protected] Guy Cautillo, P.Eng. Senior Manager, Materials Engineering and Research Office Engineering Standards Branch Ontario Ministry of Transportation Building C, Room 233 1201 Wilson Avenue Downsview, ON M3M 1J8 Canada Tel: (416) 235-3732 Fax: (416) 235-3487 E-mail: [email protected] Thomas J. Kazmierowski, P.Eng. Manager, Pavements and Foundations Section Materials Engineering and Research Office Ontario Ministry of Transportation Building C, Room 232 1201 Wilson Avenue Downsview, ON M3M 1J8 Canada Tel: (416) 235-3512 Fax: (416) 235-3919 E-mail: [email protected]

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Long-Life Concrete Pavements in Europe and Canada Becca Lane, P.Eng. Senior Pavement Design Engineer Pavement and Foundations Section Materials Engineering and Research Office Ontario Ministry of Transportation Building C, Room 232 1201 Wilson Avenue Downsview, ON M3M 1J8 Canada Tel: (416) 235-3513 Fax: (416) 235-3919 E-mail: [email protected]

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Hannah C. Schell, M.Sc., P.Eng. Manager, Concrete Section Materials Engineering and Research Office Ontario Ministry of Transportation Building C, Room 235 1201 Wilson Avenue Downsview, ON M3M 1J8 Canada Tel: (416) 235-3708 Fax: (416) 235-3388 E-mail: [email protected] Denis Thébeau, Ing. Direction du Laboratoire des Chaussés Ministère des Transports du Quèbec (Quebec Ministry of Transport) E-mail: [email protected] Guy Tremblay, ing. Msc. A. Chef du Service des Chaussées Ministère des Transports du Québec (Québec Ministry of Transport) 930, chemin Sainte-Foy, 5e étage Québec (Québec) G1S 4X9 Canada Tel: (418) 664-0890, ext. 4066 Fax: (418) 646-6195 E-mail: [email protected]

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Germany Dr. Rer. Net. Silvan Baetzner Head of Cement Chemistry Department Verein Deutscher Zementwerke e.V. Forschungsinstitut der Zementindustrie Tannenstrasse 2 D-40476 Düsseldorf, Germany Postfach 30 10 63 D-40410 Düsseldorf, Germany Tel: +49-211-4578-290 Fax: +49-211-4578-296 E-mail: [email protected] www.vdz-online.de

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Dr.-Ing. Dieter Birmann Technische Universität München (Technical University of Munich) Lehrstuhl und Prüfamt für Bau von Landverkehrwegen Baumbachstrasse 7 D-81245 München (Munich), Germany Tel: +49-089-289-27036 E-mail: [email protected] Dipl.-Ing. Ingmar Borchers Concrete Technology Department Verein Deutscher Zementwerke e.V. Forschungsinstitut der Zementindustrie Tannenstrasse 2 D-40476 Düsseldorf, Germany Postfach 30 10 63 D-40410 Düsseldorf, Germany Tel: +49-211-4578-368 Fax: +49-211-4578-219 E-mail: [email protected] www.vdz-online.de Dipl.-Ing. Eberhard Eickschen Concrete Technology Department Verein Deutscher Zementwerke e.V. Forschungsinstitut der Zementindustrie Tannenstrasse 2 D-40476 Düsseldorf, Germany Postfach 30 10 63 D-40410 Düsseldorf, Germany Tel: +49-211-4578-228 Fax: +49-211-4578-219 E-mail: [email protected] www.vdz-online.de

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Long-Life Concrete Pavements in Europe and Canada Dr.-Ing. Josef Eisenmann Emeritus Professor Technische Universität München (Technical University of Munich) Arcistrasse 21 80290 München (Munich), Germany Tel: +49-089-289-22431 Dr.-Ing. Walter Fleischer WALTER-HEILIT Verkehrswegebau GmbH Klausenburger Strasse 9 D-81677 München (Munich), Germany E-mail: [email protected]

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Dipl.-Ing. Stefan Höller Bundesanstalt für Strassenwesen (German Federal Highway Research Institute) Brüderstrasse 53 51427 Bergisch Gladbach, Germany Tel: +49-(0)2204-43-734 Fax: +49-(0)2204-43-159 E-mail: [email protected] Dipl.-Ing. Jürgen Huber Technische Universität München (Technical University of Munich) Centrum Baustoffe und Materialprüfung Baumbachstrasse 7 D-81245 München (Munich), Germany Tel: +49-089-289-27127 Fax: +49-089-289-27064 E-mail: [email protected] www.cbm.bv.tum.de Dr.-Ing. Christine Kellermann National and International Research Management and Cooperation Bundesanstalt für Strassenwesen (German Federal Highway Research Institute) Brüderstrasse 53 51427 Bergisch Gladbach, Germany Tel: +49-(0)2204-43-31 1 Fax: +49-(0)2204-43-673 E-mail: [email protected]

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United States Department of Transportation Dipl.-Ing. Eckhard Kempkens Department of Pavement Management Bundesanstalt für Strassenwesen (German Federal Highway Research Institute) Brüderstrasse 53 51427 Bergisch Gladbach, Germany Tel: +49-(0)2204-43-71 5 Fax: +49-(0)2204-43-673 E-mail: [email protected]

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Dipl.-Ing. Martin Langer Proj ektleitungsassistent HEILIT+WEOERNER Bau GmbH Zentrale Technik Klausenburger Strasse 9 81677 München (Munich), Germany Tel: +49-089-9-30-03-507 Fax: +49-089-9-30-03-297 E-mail: [email protected] www.heiwoe.com Dr.-Ing. Bernhard Lechner Technische Universität München (Technical University of Munich) Lehrstuhl und Prüfamt für Bau von Landverkehrwegen Baumbachstrasse 7 D-81245 München (Munich), Germany Tel: +49-089-289-27033 E-mail: bernard. lechner@ bv.tu-muenchen.de Univ.-Prof. Dr.-Ing. Günther Leykauf Technische Universität München (Technical University of Munich) Lehrstuhl und Prüfamt für Bau von Landverkehrwegen Baumbachstrasse 7 D-81245 München (Munich), Germany Tel: +49-089-289-27022 E-mail: [email protected] Dr.-Ing. Peter Reichelt Director and Professor Bundesanstalt für Strassenwesen (German Federal Highway Research Institute) Brüderstrasse 53 51427 Bergisch Gladbach, Germany Tel: +49-(0)2204-43-700 Fax: +49-(0)2204-43-675

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Long-Life Concrete Pavements in Europe and Canada E-mail: [email protected] Dipl.-Ing. Patrick Schäffel Gert Wischers Stiftung Foundation (Science Foundation of the German Cement Industry) Tannenstrasse 2 D-40476 Düsseldorf, Germany Postfach 30 10 63 D-40410 Düsseldorf, Germany Tel: +49-211-4578-233 Fax: +49-211-4578-296 E-mail: [email protected] www.vdz-online.de

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Dr.-Ing. Eberhard Siebel Head of Concrete Technology Department Verein Deutscher Zementwerke e.V. Forschungsinstitut der Zementindustrie Tannenstrasse 2 D-40476 Düsseldorf, Germany Postfach 30 10 63 D-40410 Düsseldorf, Germany Tel: +49-211-4578-222 Fax: +49-211-4578-219 E-mail: [email protected] www.vdz-online.de Dr. Martin Schneider Chief Executive of the German Cement Works Association Head of the Research Institute Verein Deutscher Zementwerke e.V. Forschungsinstitut der Zementindustrie Tannenstrasse 2 D-40476 Düsseldorf, Germany Postfach 30 10 63 D-40410 Düsseldorf, Germany www.vdz-online.de Univ.-Prof. Dr.-Ing. Rupert Springenschmid Technische Universität München (Technical University of Munich) Baustoffinstitut (Prüfamt) Baumbachstrasse 7 D-81245 München (Munich), Germany Tel: +49-089-289-2-7073 Fax: +49-089-289-2-7064 Dr.-Ing. Ulf Zander Bundesanstalt für Strassenwesen Long Life and Quiet Pavement: Research and Issues : Research and Issues, Nova Science Publishers, Incorporated, 2010. ProQuest Ebook

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United States Department of Transportation (German Federal Highway Research Institute) Brüderstrasse 53 51427 Bergisch Gladbach, Germany Tel: +49-(0)2204-43-740 Fax: +49-(0)2204-43-159 E-mail: [email protected]

Austria

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Dipl.-Ing. Peter Beiglböck Amt der NÖ Landesregierung Autobahnen und Schnellstrassen Bau 3109 St. Pölten Landhausplatz 1 Haus 17, Zi, 17.501 Tel: +43-02742-9005-60711 Fax: +43-02742-9005-60701 E-mail: [email protected] Univ. Prof. Dipl.-Ing. Dr. Ronald Blab Institutvorstand Institut für Strassenbau und Strassenerhaltung Technische Universität Wien (Technical University of Vienna) Gusshausstrasse 29 1040 Wien (Vienna), Austria Tel: +43-01-58801-23314 DW 23301 Fax: +43-0158801-23314 DW 23301 E-mail: [email protected] Günter Breyer Deputy Road Director and Head of Technology and Road Safety Division Stubenring 1 A-1010 Vienna, Austria Tel: +43-1-711-00-5419 Fax: +43-1-711-00-2291 E-mail: [email protected] www.bmvit.gv.at Dipl.-Ing. Martin Car General Secretary Österreichische Forschungsgesellschaft Strasse–Schiene–Verkehr, FSV (Austrian Association for Research on Road, Rail, and Transport) Karlsgasse 5

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Long-Life Concrete Pavements in Europe and Canada A-1040 Wien (Vienna), Austria Tel: +43-1-585-55-67 Fax: +43-1-504-15-55 E-mail: [email protected] Dipl.-Ing. Karl Wolfgang Gragger Konzernsteurung Autobahnen und Schnellstrassen Finanzierungs Aktiengesellschaft (ASFiNAG) Rotenturmstrasse 5-9 Postfach 983 A-1011 Wien (Vienna), Austria Tel: +43-(0)5-01-08-10324 Fax: +43-(0)5-01-08-10320 E-mail: [email protected]

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Dipl.-Ing. Rudolf Gruber Amt der NÖ Landesregierung Gruppe Strasse 3109 St. Pölten Landhausplatz 1 Haus 17, Zi, 17.501 Tel: +43-02742-9005-60111 Fax: +43-02742-9005-60101 E-mail: [email protected] Mag. Rainer Kienreich Baulich Erhaltung/Projektcontrolling ASFINAG Autobahn Service Gmbh Süd Wilhelm Raabe Gasse 24, PF 832 A-8010 Graz, Austria Tel: +43 (0) 50108-13422 Fax: +43 (0) 50108-13420 E-mail: [email protected] www.asfinag.at Bmstr. Ing. Peter Schöller Österreichische Betondecken Arge Lagergasse 346 A-8055 Graz, Austria Tel: +43-0316-222-183 Fax: +43-0316-222-188 E-mail: [email protected] Baurat h.c. Prof. Dipl.-Ing. Dr. Hermann Sommer Zeltgasse 3-5/15 Long Life and Quiet Pavement: Research and Issues : Research and Issues, Nova Science Publishers, Incorporated, 2010. ProQuest Ebook

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United States Department of Transportation 1080 Wien (Vienna), Austria Tel: +43-0664-1308876 Fax: +43-01-405-2541 E-mail: [email protected] Dipl.-Ing. Dr. Johannes Steigenberger Head of the Research Institute Vereinigung der Österreichischen Zementindustrie (Austrian Cement Industry Association) Reisnerstrasse 53 A-1030 Vienna, Austria Tel: +43-1-714-66-81-50 Fax: +43-1-714-66-81-66 E-mail: [email protected] www.zement.at

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Dipl.-Wirtsch.-Ing. Gunther Thaler Autobahnen und Schnellstrassen Finanzierungs Aktiengesellschaft (ASFiNAG) Rotenturmstrasse 5-9 Postfach 983 A-1011 Wien (Vienna), Austria Tel: +43-(0)5-01-08-10676 Fax: +43-(0)5-01-08-10672 E-mail: [email protected] Alfred Weninger-Vycudil, M.Sc, Ph.D. Engineering Office for Traffic and Infrastructure PMS Consult Karlsgasse 5 1040 Wien (Vienna), Austria Tel: +43 (0) 699-1947-4422 E-mail: [email protected] www.pms-consult.at

Belgium Chris Caestacker Infrastructure Agency (IAA) of the Flemish Ministry of Mobility and Transport E-mail: christian.caestecker@lin. vlaanderen.be Raymond Debroux Ministere de l’Equipemente et des Transports (MET) (Walloon Ministry of Equipment and Transport)

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Long-Life Concrete Pavements in Europe and Canada André Jasienski Director of Promotion, Research, and Development Federation of the Belgian Cement Industry (FEBELCEM) Voltestraat 8 1050 Brussels, Belgium Tel: +32-2-645-52-45 Fax: +32-2-640-06-70 E-mail: [email protected] www.febelcem.ce Luc Rens Engineering Consultant for Infrastructure Federation of the Belgian Cement Industry (FEBELCEM) Voltestraat 8 B-1050 Brussels, Belgium Tel +32-2-645-52-55 Fax +32-2-640-06-70 E-mail: [email protected] www.febelcem.ce

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The Netherlands Dr.-Ir. J. W. Frénay Technical Marketing and Product Development ENCI B.V. Heidelberg Cement Group Sint Teunislaan 1 P.O. Box 3233 5203 DE s-Hertogenbosch The Netherlands Tel: +31-73-640-1366 Fax: +31-6-290-912-46 E-mail: [email protected] Ir. Jaap Jager Project Manager CROW Technology Platform for Transport, Infrastructure, and Public Space Galvinistraat 1 P.O. Box 37 NL-6710 BA Ede The Netherlands Tel: +31-318-69-53-44 Fax: +31-318-62-11-12 E-mail: [email protected] www.crow.nl

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Dr.-Ir. Iman Koster Director CROW Technology Platform for Transport, Infrastructure, and Public Space Galvinistraat 1 P.O. Box 37 NL-6710 BA Ede The Netherlands Tel: +31-318-69-53-28 Fax: +31-318-62-11-12

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Ing. M. J. A. Stet Senior Advisor Via Aperta Verhardingsadviseurs Mina Kresemanlaan 90 7421 LL Deventer The Netherlands Tel: +32-0570-657-563 Fax: +32-0570-657-783 E-mail: [email protected] www.via-apert.nl Robert Jan van den Berg CROW Technology Platform for Transport, Infrastructure, and Public Space Galvinistraat 1 P.O. Box 37 NL-6710 BA Ede The Netherlands Tel: +31-318-69-53-51 Fax: +31-318-62-11-12 E-mail: [email protected] www.crow.nl Steven van Hartskamp Pavement Maintenance Advisor Province of Noord-Brabant Brabantlaan 1 5216 TV den Bosch The Netherlands E-mail: [email protected] www.brabant.nl Adrian J. van Leest, M.Sc. Project Manager CROW Technology Platform for Transport, Infrastructure, and Public Space Galvinistraat 1 P.O. Box 37

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NL-6710 BA Ede The Netherlands Tel: +31-318-69-53-04 Fax: +31-318-62-11-12 E-mail: [email protected] www.crow.nl A.C. Maagdenberg Road and Hydraulic Engineering Institute Van der Burghweg 1 P.O. Box 5044 2600 GA Delft The Netherlands Tel: +31-15-2-518-377 Fax: +31-15-2-518-555 E-mail: a.c.maagdenberg@dww. rws. minvenw.nl

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Arjan A. M. Venmans GeoDelft—National Institute for Geo-engineering Stieltjesweg 2 P.O. Box 69 2600 AB Delft The Netherlands Tel: +31-15-2-693-563 Fax: +31-15-2-610-821 E-mail: [email protected] www.GeoDelft.nl Caroline de Zoeten Marketing and Communications Advisor CROW Technology Platform for Transport, Infrastructure, and Public Space Galvinistraat 1 P.O. Box 37 NL-6710 BA Ede The Netherlands Tel: +31-318-69-53-91 Fax: +31-318-62-11-12 E-mail: [email protected] www.crow.nl

Switzerland Professor Karen Scrivener Laboratoire de Matériaux de Construction (Laboratory of Construction Materials) Ecole Polytechnique Fédérale de

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United States Department of Transportation Lausanne (Swiss Federal Institute of Technology) EPFL-STI-LMC IMX-G-Ecublens CH-1015 Lausanne, Switzerland Tel +41-21-693-58-43 Fax +41-21-693-58-00 E-mail: [email protected] www.epfl.ch/lmc www.nanocem.net

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United Kingdom Richard Abell, BSc, MSc Chief Research Scientist, Highways Transportation Research Laboratory (TRL) Crowthorne House Nine Mile Ride Wokingham Berkshire RG40 3GA United Kingdom Tel: +44-01344-770355 Fax: +44-01344-770356 E-mail: [email protected] www.trl.co.uk Richard Betteridge Contracts Manager Mowlem Civil Engineering Foundation House Eastern Road Bracknell Berkshire RG12 2UZ United Kingdom Tel: +44-01344-742293 Fax: +44-01344-742129 E-mail: [email protected] www.mowlem.com Peter Brindley, BSc Ceng MICE Laing O’Rourke Civil Engineering Limited Bridge Place Anchor Boulevard, Admirals Park

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Long-Life Concrete Pavements in Europe and Canada Crossways, Dartford, Kent DA2 6SN United Kingdom Tel: +44-01322-296200 Fax: +44-01322-296262 E-mail: [email protected]

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Patrick Brogran, C Eng, MICE, MIHT Head of Highways Transportation Research Laboratory (TRL) Crowthorne House Nine Mile Ride Wokingham Berkshire RG40 3GA United Kingdom Tel: +44-01344-770556 Fax: +44-01344-770356 E-mail: [email protected] www.trl.co.uk Bob Collis, DipGeog, FCIT, FILT, MIHT Director of Infrastructure and Environment Transportation Research Laboratory (TRL) Crowthorne House Nine Mile Ride Wokingham Berkshire RG40 3GA United Kingdom Tel: +44-01344-770474 Fax: +44-01344-770356 E-mail: [email protected] www.trl.co.uk Eur. Ing. John P. Donegan, BA, BAI, C Eng, MIEI, FIHT General Manager Roller Compacted Concrete Company Ltd. Victoria Stables South Road Bourne Lines PE10 9JZ United Kingdom Tel: +44-01778-394400 Fax: +44-01778-394984 E-mail: [email protected] www.rollercompactedconcrete.co.uk Brian Ferne, BSc (Eng) Infrastructure and Environment Division Transportation Research Laboratory (TRL) Crowthorne House Nine Mile Ride Wokingham

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United States Department of Transportation Berkshire RG40 3GA United Kingdom Tel: +44-01344-770668 Fax: +44-01344-770356 E-mail: [email protected] www.trl.co.uk

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John W. E. Chandler, MIHT Project Manager/Senior Researcher Transportation Research Laboratory (TRL) Crowthorne House Nine Mile Ride Wokingham Berkshire RG40 3GA United Kingdom Tel: +44-01344-770327 Fax: +44-01344-770356 E-mail: [email protected] www.trl.co.uk Michael Harding, C Eng, MIEE Project Manager/Senior Researcher Transportation Research Laboratory (TRL) Crowthorne House Nine Mile Ride Wokingham Berkshire RG40 3GA United Kingdom Tel: +44-01344-770507 Fax: +44-01344-770356 E-mail: [email protected] www.trl.co.uk Khaled E. Hassan, B Eng, PhD Team Leader Transportation Research Laboratory (TRL) Crowthorne House Nine Mile Ride Wokingham Berkshire RG40 3GA United Kingdom Tel: +44-01344-770840 Fax: +44-01344-770356 E-mail: [email protected] www.trl.co.uk Don Henry, BSc C Eng, MICE, MIHT Business Manager Long Life and Quiet Pavement: Research and Issues : Research and Issues, Nova Science Publishers, Incorporated, 2010. ProQuest Ebook

Long-Life Concrete Pavements in Europe and Canada Birse Civils Limited Midlands Office 500 Pavilion Drive Northampton Business Park Northampton Northamptonshire NN4 7YJ United Kingdom Tel: +44-01604-664200 Fax: +44-01604-661721 E-mail: [email protected] www.birsecl.co.uk

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David Jones, B.A., F.I.Q., M.I.H.T. Director The British In-situ Concrete Paving Association (Britpave) Riverside House 4 Meadows Business Park Station Approach Blackwater, Camberley Surrey GU17 9AB United Kingdom Tel: +44-01276-33160 E-mail: [email protected] Alex Lake, B Eng, C Eng, MICE, MIHT Director Burks Green Architects and Engineers Sherwood House Sherwood Avenue Newark Nottinghamshire NG24 1QQ United Kingdom Tel: +44 01636-605700 Fax: +44-01636-610696 E-mail: [email protected] www.burksgreen.com David Lee Project Manager Highways Agency Heron House, Room 336 49-52 Goldington Road, Bedford MK40 3LL United Kingdom Tel: +44-01234-796048 Fax: +44-01234-796029 E-mail: [email protected] Mike O’Brien, B Eng, MIAT Engineering Services Department Civil Engineering Long Life and Quiet Pavement: Research and Issues : Research and Issues, Nova Science Publishers, Incorporated, 2010. ProQuest Ebook

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United States Department of Transportation Alfred McAlpine Capital Projects Exchange House Kelburn Court Leacroft Road, Birchwood Warrington WA3 6SY United Kingdom Tel: +44-01925-858000 Fax: +44-01925-858099 E-mail: mike.o’brien@ alfredmcalpineplc.com www.alfredmcalpineplc.com Tony Stock, C Eng, BSc Mphil PhD MICE MIHT Stock Tynana Associates 10 Mapperley Hall Drive Mapperley Park Nottingham NG3 5EP United Kingdom Tel: +44-0115-960-4349 Fax: +44-0115-960-4349

APPENDIX C. TEAM MEMBERS

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Contact information Dan A. Dawood (AASHTO cochair) Chief, Pavement Design & Analysis Pennsylvania Department of Transportation Bureau of Maintenance & Operations Commonwealth Keystone Building, 6th Floor 400 North Street Harrisburg, PA 17120 Tel: (717) 787-4246 Fax: (717) 787-7004 E-mail: [email protected] Robert F. Tally (FHWA cochair) Division Administrator FHWA Indiana Division 575 North Pennsylvania Street, Room 254 Indianapolis, IN 46204 Tel: (317) 226-7476 Fax: (317) 226-7341 E-mail: [email protected]

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Long-Life Concrete Pavements in Europe and Canada Suneel N. Vanikar (FHWA cochair) Concrete Team Leader FHWA Office of Pavement Technology, HIPT-20 Nassif Building, Room 3118 400 Seventh Street, SW. Washington, DC 20590 Tel: (202) 366-0120 Fax: (202) 493-2070 E-mail: [email protected] Tom Cackler Director Center for Portland Cement Concrete Pavement Technology Iowa State University 2901 S. Loop Drive, Suite 3100 Ames, IA 50010 Tel: (515) 294-3230 Fax: (515) 294-0467 E-mail: [email protected]

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Angel L. Correa Pavement Design Engineer FHWA Resource Center 61 Forsyth Street, SW. Suite 17T26 Atlanta, GA 30303 Tel: (404) 562-3907 Fax: (404) 562-3700 E-mail: [email protected] Peter Deem Vice President, National & Regional Promotions Holcim (US) Inc. 400 Centennial Parkway, Suite 190 Louisville, CO 80027 Tel: (303) 926-3711 Fax: (303) 926-3730 E-mail: [email protected] James Duit President Duit Construction Co, Inc. 6250 Industrial Blvd. PO Box 3788 Edmond, OK 73034 Tel: (405) 340-6026 Fax: (405) 348-7627 E-mail: [email protected] Georgene Geary State Materials & Research Engineer Georgia Dept. of Transportation Long Life and Quiet Pavement: Research and Issues : Research and Issues, Nova Science Publishers, Incorporated, 2010. ProQuest Ebook

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United States Department of Transportation 15 Kennedy Dr. Forest Park, GA 30297 Tel: (404) 363-7512 Fax: (404) 362-4251 E-mail: [email protected] Andy Gisi Assistant Geotechnical Engineer Kansas DOT 2300 Van Buren Dr. Topeka, KS 66611 Tel: (785) 296-3008 Fax: (785) 296-2526 E-mail: [email protected]

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Dr. Kathleen T. Hall (report facilitator) 1271 Huntington Drive South Mundelein, IL 60060 Tel: (847) 549-8568 Fax: (847) 589-4284 E-mail: [email protected] Dr. Amir Hanna Senior Program Officer NCHRP 500 5th St., NW Washington, DC 20001 Tel: (202) 334-1892 Fax: (202) 334-2006 E-mail: [email protected] Steven H. Kosmatka Staff Vice President for Research and Technical Services Portland Cement Association 5420 Old Orchard Road Skokie, IL 60077 Tel: (847) 972-9164 Fax: (847) 972-9165 E-mail: [email protected] Dr. Robert Otto Rasmussen Vice President & Chief Engineer The Transtec Group, Inc. 1012 East 38 1/2 Street Austin, TX 78751 Tel: (512) 451-6233, ext.23 Fax: (512) 692-2921

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E-mail: [email protected] Dr. Shiraz Tayabji President International Society for Concrete Pavements CTL Group 5565 Sterrette Place, Suite 312 Columbia, MD 21044 Tel: (410) 997-0400 Fax: (410) 997-8480 E-mail: [email protected] Gerald F. Voigt President & CEO American Concrete Pavement Association 5420 Old Orchard Road, Suite A100 Skokie, IL 60077 Tel: (847) 966-2272 Fax: (847) 966-9970 E-mail: [email protected]

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Biographic Sketches DAN DAWOOD (AASHTO cochair) is chief of the Pavement Design and Analysis Section for the Pennsylvania Department of Transportation in Harrisburg, PA. Dawood is responsible for all policy, specifications, and standards that relate to pavement design and construction statewide. He is also responsible for establishing and managing research projects that enhance pavement design and construction technology. Before becoming chief pavement engineer, Dawood worked in regional district offices as a highway designer and traffic safety engineer. He also spent time as a private sector engineer after beginning his career as a geotechnical engineer. Dawood received a bachelor’s degree in civil engineering from Pennsylvania State University and is a licensed professional engineer in Pennsylvania. He serves on various task forces and committees nationally. He chairs the American Association of State Highway and Transportation Officials (AASHTO) Joint Technical Committee on Pavements. SUNEEL VANIKAR (FHWA cochair) is the Concrete Team leader for the Federal Highway Administration (FHWA) in the Office of Pavement Technology in Washington, DC. Vanikar directs activities related to concrete pavement and concrete materials, including policy, guidance, research, and technology transfer. He is involved in fast-track construction, nondestructive testing of concrete, and high-performance concrete programs. He has written numerous publications on high-performance concrete and is a frequent speaker at national and international meetings. Vanikar earned a master’s degree in civil engineering from Colorado State University and is a licensed professional engineer in New Hampshire. He serves on

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technical committees of the Transportation Research Board (TRB) and the American Concrete Institute (ACI). He is a recipient of the FHWA Administrator’s Award and the Public Official of the Year Award from the American Concrete Pavement Association (ACPA).

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ROBERT F. TALLY, JR. (FHWA cochair) is the division administrator for the FHWA Indiana Division. Tally directs a multidisciplinary staff that administers the Federal-Aid Highway Program throughout Indiana to improve its transportation system. Before his promotion to division administrator, he served as the assistant division administrator in the Texas Division, Program Delivery Team leader in the California Division, and bridge engineer in the Arizona Division, and in other engineering positions in the South Carolina, Michigan, and Louisiana Divisions. During his FHWA career, Tally has worked on a number of noteworthy projects, including the $3.5 billion Central Texas Turnpike project in Austin, TX; the $3.2 billion San Francisco/Oakland Bay Bridge replacement project in San Francisco, CA; the Hoover Dam Bypass Bridge Project in Boulder City, NV; the Navajo Bridge project in Arizona; and the Cooper River Bridge and Wando River Bridge projects in Charleston, SC. Tally received bachelor’s and master’s degrees in civil engineering from the University of Louisville and is a licensed civil engineer in South Carolina. Tally’s expertise and focus are on implementing applied research and technological advances to improve delivery of transportation systems in the United States. TOM CACKLER is the director of the National Concrete Pavement Technology Center at Iowa State University. The CP Tech Center manages more than $8 million in concrete pavement technology research, including four Transportation Pooled Fund Program studies. Cackler was part of the research team that produced the CP Road Map publication and directed the acquisition of the CP Tech Center’s 2,500-square-foot mobile laboratory. Before joining the CP Tech Center, Cackler worked for more than 25 years for the Iowa Department of Transportation, most recently serving as the director of the Highway Division. Cackler earned a bachelor’s degree in civil engineering from Iowa State University and is a licensed professional engineer in Iowa. He serves on the TRB Construction Management Committee (A2F05) and has served on the AASHTO Standing Committee on Highways, AASHTO Subcommittee on Construction, and joint industry quality improvement committees with the Associated General Contractors of Iowa, Asphalt Paving Association of Iowa, and Iowa Concrete Paving Association. ANGEL L. CORREA is a pavement and materials engineer for the FHWA Resource Center in Atlanta, GA. Correa provides technical assistance and training to State departments of transportation in all aspects of portland cement concrete pavement design, construction, materials, and rehabilitation. Correa has been with FHWA for more than 15 years, spending the past 10 years in concrete pavement rehabilitation and preservation. He has held technical positions in the FHWA Resource Center in Atlanta and the Office of Pavement Technology in Washington, DC. Correa received a bachelor’s degree in civil engineering from the University of Puerto Rico and a master’s degree in civil engineering from the University of Illinois at Urbana-Champaign. He is a licensed professional engineer in Maryland and serves on various State and TRB technical committees on concrete pavements.

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PETER DEEM is vice president of national and regional promotion for Holcim (US) Inc. Deem works with the major national associations in the cement industry and represents Holcim (US) on many of their boards and committees. Deem’s position as chairman of the American Concrete Pavement Association (ACPA) involves him in all aspects of the concrete paving industry. Before becoming vice president of national and regional promotion, Deem was vice president for sales for the Holcim West Division. He received a bachelor’s degree in liberal arts from the University of Minnesota. He is on the board of directors and executive committee of ACPA, the board of directors of the American Concrete Pipe Association, and several committees of the Portland Cement Association and the National Ready Mix Concrete Association. He is also involved with the boards of directors of a number of regional promotion groups for the cement industry.

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JIM DUIT is the president of Duit Construction Company, Inc., a concrete paving contractor in Edmond, OK. Duit is now constructing concrete paving projects in Oklahoma, Texas, Arkansas, and Kansas. He started his company in 1969 and has been building concrete pavements ever since. He is a graduate of Iowa State University. He is the past national chair of the American Concrete Paving Association and past president of the Oklahoma Associated General Contractors and Oklahoma/ Arkansas American Concrete Paving Association. Duit is also active on many association committees. GEORGENE M. GEARY is the State materials and research engineer for the Georgia Department of Transportation. Geary oversees the testing, pavement, geotechnical, and administration functions of the Office of Materials and Research, involving more than 380 employees. Her office is responsible for the quality of all materials used in Georgia DOT construction projects and the management of a $6 million-a-year research program. The Georgia DOT is involved in a “Fast Forward” program that includes widening, reconstruction, and rehabilitation of the Interstates, many of which were originally constructed as concrete pavements. Geary earned a bachelor’s degree in civil engineering from the University of Illinois at Urbana-Champaign and a master’s degree in civil engineering from the Georgia Institute of Technology. She is a licensed professional engineer in Georgia. She serves on several TRB technical committees, is on several committees for ASTM and AASHTO, and is on the American Society of Civil Engineers’ (ASCE) Transportation and Development Institute Research Committee. ANDREW GISI is the geotechnical engineer with the Kansas Department of Transportation in Topeka, KS. Gisi directs the activities of the Geotechnical Unit with responsibilities in soil, pavement, geology, and pavement management. He serves as technical expert in design, construction, maintenance, and performance of highway pavements. He has served in his present capacity for 4 years. He has 30 years of experience in pavement evaluation and design and 7 years of experience in the accelerated pavement testing arena. Gisi is a graduate of South Dakota State University and holds a master’s degree in civil engineering from Kansas State University. He is a licensed professional engineer in Kansas and serves on several technical committees of the ASCE, ASTM, AASHTO, and National Cooperative Highway Research Program (NCHRP).

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DR. KATHLEEN T. HALL (report facilitator) is a consultant specializing in design, evaluation, structural analysis, and rehabilitation of concrete and asphalt-overlaid concrete pavements. She has served as the principal investigator for several NCHRP and FHWA research studies on subjects including the cost-effectiveness of sealing joints in concrete pavements; the effectiveness of subsurface drainage systems in asphalt and concrete pavements in the Long-Term Pavement Performance program (LTPP) SPS-1 and SPS-2 experiments; the performance of concrete and asphalt pavement maintenance and rehabilitation techniques in the LTPP SPS-3, SPS-4, SPS-5, and SPS-6 experiments; and the development of guidelines for pavement rehabilitation. She is a codeveloper of the National Highway Institute (NHI) training course “Concrete Pavement Design Details and Construction Practices,” principal investigator for presentation of the NHI course “Pavement Subsurface Drainage Design,” and coprincipal investigator for the development of the NHI course “Analysis of New and Rehabilitated Pavement Performance with MechanisticEmpirical Design Guide Software.” Hall received her bachelor’s, master’s, and Ph.D. degrees in civil engineering from the University of Illinois at Urbana-Champaign and is a licensed professional engineer in Illinois and Indiana. She is a past chair of the TRB Committee on Rigid Pavement Design, as well as a member of TRB’s committees on pavement rehabilitation, and sealants and fillers for joints and cracks. She is vice president of the International Society of Concrete Pavements and a member of ACPA. DR. AMIR N. HANNA is a senior program officer with the National Cooperative Highway Research Program (NCHRP), a division of the National Academy of Sciences’ Transportation Research Board. Hanna joined NCHRP in 1992. He manages research projects in the areas of pavement design, materials, construction, and maintenance. He was responsible for the $7 million project that developed the Mechanistic-Empirical Pavement Design Guide and several projects dealing with concrete pavements and concrete materials used in pavements and bridges. Previously, he worked for 5 years as a project manager for the Strategic Highway Research Program, during which he was part of the Long-Term Pavement Performance (LTPP) studies group and was responsible for the development of the Specific Pavement Studies. He worked for 15 years as a principal engineer for the Construction Technology Laboratories of the Portland Cement Association. He also worked for the Transportation Development Centre of the Canadian Ministry of Transport and the Technical University of Munich, Germany. Hanna holds a Ph.D. degree from the Technical University of Munich and is a registered professional engineer in the Province of Ontario, Canada. He is a fellow and life member of ASCE, a fellow of ACI, and a member of ASCE and ACI technical committees. He was a member of several TRB technical committees for more than 20 years and chaired the TRB committee on strength and deformation characteristics of pavements from 1979 to 1985. Hanna was a member of the 1992 U.S. Tour of European Concrete Highways. STEVEN KOSMATKA is staff vice president of Research and Technical Services for the Portland Cement Association (PCA), in Skokie, IL. Kosmatka oversees PCA’s Research, Construction Technology Center, Product Standards and Technology, and Cement Manufacturing programs. This includes research and standards development aimed at improving durability of concrete pavements. Kosmatka has 25 years of experience addressing

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durability issues, such as alkali-aggregate reactivity, deicer scaling, frost resistance, and sulfate attack. He received his civil engineering degree from the University of North Dakota. He is a licensed professional engineer and serves on technical committees of ACI, TRB, and the American Society for Testing and Materials.

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DR. ROBERT RASMUSSEN is vice president and chief engineer of The Transtec Group, Inc., a pavement, materials, and construction engineering firm headquartered in Austin, TX. On this SCANning tour, he represented the Concrete Reinforcing Steel Institute, with which he has worked on numerous projects. Rasmussen’s accomplishments include the development of design and construction guidelines for concrete overlays, the FHWA HIPERPAV software to predict the early age behavior of concrete pavements, and a concrete materials and mix performance analysis system (COMPASS), as well as the measurement and modeling of concrete pavement unevenness, texture, friction, and tire-pavement noise. He received a bachelor’s degree in civil engineering from the University of Arizona, and master’s and Ph.D. degrees from the University of Texas at Austin. Rasmussen is a registered professional engineer in Texas, has written dozens of peer-reviewed papers, and is the recipient of an international award from the World Road Association (PIARC). He belongs to numerous editorial boards, expert task groups, and industry groups, including TRB, ASCE, ACPA, Association of Asphalt Pavement Technologists, RILEM (International Union of Laboratories and Experts in Construction Materials, Systems, and Structures), and Institute of Noise Control Engineering. DR. SHIRAZ D. TAYABJI is the regional manager for the CTL Group of Columbia, MD. A past president and founding member of the International Society for Concrete Pavements, he is involved in developing, improving, and implementing technologies for highway and airfield concrete pavements. He has been involved in design, construction, testing, and rehabilitation of concrete pavements for many years, and provides consulting services on problems related to airfield and highway concrete pavements. He serves as the project manager for two major multiyear contracts funded by FHWA to improve pavement performance and implement technology transfer activities for concrete pavements. He was recently awarded a project funded by the Federal Aviation Administration (FAA) and overseen by the Innovative Pavement Research Foundation (IPRF) to revise the P-50 1 specification for construction of FAA-funded airfield concrete pavements. Tayabji received a bachelor’s degree in civil engineering from the University of East Africa in Nairobi, Kenya, and master’s and Ph.D. degrees in civil engineering from the University of Illinois at UrbanaChampaign. He is a registered engineer in Illinois, Pennsylvania, Maryland, Delaware, Virginia, and New Jersey. GERALD VOIGT is the president and chief executive officer of the American Concrete Pavement Association, headquartered in Skokie, IL. Voigt leads the association in its full array of services, including technical, market development, research, and government affairs. Under his leadership, the association has formed a National Concrete Pavement Technology Center that will provide research and technology transfer support to the industry. He is the author of many industry technical documents covering a broad range of concrete pavement topics, including design, construction, rehabilitation, and materials. He was appointed ACPA president in 2005, having been with the association since 1988. Voigt earned bachelor’s and

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master’s degrees in civil engineering from the University of Illinois at Urbana-Champaign and is a registered professional engineer in Illinois. He serves on several boards and technical committees, including the National Concrete Pavement Technology Center, Transportation Engineering Road Research Alliance, and TRB.

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REFERENCES [1] Center for Portland Cement Concrete Pavement Technology at Iowa State University, The Concrete Pavement Road Map: Long- Term Plan for Concrete Pavement Research and Technology, 2005. [2] Tayabji, S. D., (2005). mework for Design and Construction of Long-Life Concrete Pavements, Proceedings of the Eighth International Conference on Concrete Pavements, Colorado Springs, CO. [3] Stutz, F. P., and de Souza, A. R., (1998). The World Economy, third edition, PrenticeHall, Inc., Upper Saddle River, NJ. [4] The Economist, (2005). Volume 377, Number 8454, Nov. 26. [5] Brady, N. C., and Weil, R. R., (2002). The Nature and Properties of Soils, 13th edition, Prentice-Hall, Inc., Upper Saddle River, NJ. [6] (2006). The Economist, Pocket World in Figures, The Economist Newspaper, Ltd., edition. [7] Central Intelligence Agency, (2006). The CIA World Factbook, Washington, DC. [8] LaCroy, J., (2005). Keynote Address to the 10th Meeting of the Ontario Cement Caucus, Nov. 16. [9] Henderson, P.D., (1968). “The Investment Criteria for Public Enterprises,” Public Enterprises, editor R. Turvey, Penguin Books. [10] Howe, C.W., (1971). “Benefit-Cost Analysis for Water System Planning,” Water Resources, Monograph 2, American Geophysical Union, Washington, DC. [11] Wistuba, M., Steigenberger, J., and Pichler, R., (2004). Joint Design on Concrete Motorways in Austria, Proceedings of the Ninth International Symposium on Concrete Roads, Istanbul, Turkey. [12] Pichler, R., (2006). Mölltal—Concrete Pavement—50 Years Under Traffic, Proceedings of the Tenth International Symposium on Concrete Roads, Brussels, Belgium,. [13] Maurer, P., Gruber, J., and Steigenberger, J., Skid Resistance in Austrian Tunnels with Special Attention to Concrete Pavements. [14] Nagl, C., and Thaler, G., (2005) Austrian Roads—The DBFO Route, Infra-News, Global PPP/Infrastructure Yearbook. [15] Rens, L., Caestecker, C., and Decramer, H., Sustainable Road Building with Low-Noise CRCP on Belgian Motorways. [16] Reeners, V., and Jasienski, A., (2004). A New Youth for An Old Lady— Rehabilitation of the Lorraine Avenue in Brussels, Belgium, Proceedings of the Ninth International Symposium on Concrete Roads, Istanbul, Turkey. [17] Wansart, L., Kral, Z., and Debroux, R., (2006). Bituminous and Continuously Reinforced Concrete Pavements for Motorways— An Economic Comparison, Technical Document, 19, The MET Collection. [18] Lemlin, M., Pilate, O., Pirlot, M., and Fiordaliso, A., Multicriteria Aid to the Choice of Road Surfacings, Walloon Ministry of Equipment and Transport, Belgium. [19] Van Leest, Aj., van der Loos, R.M.M., Venmans, A.A.M., and van Hartskamp, S.B., (2006). Decision Support Model for Road Pavements Based on Whole Life Costing,

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Life-Cycle Analysis, and Multi-Criteria Analysis, Proceedings of the Tenth International Symposium on Concrete Roads, Brussels, Belgium. [20] Grob, T.S., and van Leest, Aj., (2004) Investigation of Maintenance Needs for In-Service Concrete Pavements, Proceedings of the Ninth International Symposium on Concrete Roads, Istanbul, Turkey. [21] American Association of State Highway and Transportation Officials, (1993) Guide for the Design of Pavement Structures, Washington, DC. [22] Springenschmid, R., and Fleischer, W., (2001). Recent Developments in the Design and Construction of Concrete Pavements for German Expressways (Autobahns), Proceedings of the Seventh International Conference on Concrete Pavements, Orlando, FL. [23] Guidelines for Standardization of Pavement Structures for Traffic Areas, RstO, (2001). [24] Blessman, W., Fleischer, W., and Wippermann, D., (1998). Concrete Pavement on Crushed Aggregate Unbound Roadbase, A New Design for Heavy-Traffic Motorways, Proceedings of the Eighth International Symposium on Concrete Roads, Lisbon, Portugal. [25] Austrian Association for Research on Road, Rail, and Transport, Guidelines and Specifications for Road Construction, RVS 8S.06.32, February 2006 edition, English translation, April 2006. [26] Steigenberger, J., (2003). Concrete Roads in Austria—The Newest Trends and Developments, Proceedings of the International Concrete Roads Conference, Bratislava, Slovak Republic. [27] Stet, M. J. A., van Leest, A. J., and Frénay, J. W., (2006). Dutch Design Tool for Jointed and Continuously Reinforced Concrete Pavements, Proceedings of the Tenth International Symposium on Concrete Roads, Brussels, Belgium. [28] Van Leest, A. J., Stet, M. J. A., and Frénay, J. W., (2005). VENCON 2.0: A Fast and Reliable Design Tool for Concrete Road Pavements (Jointed and Continuously Reinforced Applications), Proceedings of the Eighth International Conference on Concrete Pavements, Colorado Springs, CO. [29] CROW, (2005). Cement Concrete Pavement Manual—Basic Structures, in Dutch, Publication 220, Ede, the Netherlands. [30] Stet, M. J. A., and van Leest, A. J., (2004). CRCP: A Long-Lasting Pavement Solution for Today’s Motorways, The Dutch Practice, Proceedings of the Ninth International Symposium on Concrete Roads, Istanbul, Turkey. [31] Hassan, K. E., Chandler, J. W. E., Harding, H. M., and Dudgeon, R. P., (2005) New Continuously Reinforced Concrete Pavement Designs, Report TRL630, Transport Research Laboratory. [32] Thébeau, D., Delisle, M., and Cormier, B., (2005). Québec’s Experience with Smoothness Specifications on Concrete Pavements, Proceedings of the Eighth International Conference on Concrete Pavements, Colorado Springs, CO. [33] Sommer, H. (1994).Development of the Exposed Aggregate Technique in Austria, Proceedings of the Seventh International Symposium on Concrete Roads, Vienna, Austria. [34] Steigenberger, J., (2005). Concrete Roundabouts in Austria, Proceedings of the International Concrete Roads Conference, Bratislava, Slovak Republic. [35] Blab, R. and Steigenberger, J., (2006). Austrian Experience with Concrete Pavement Design and Construction of Highly Trafficked Roundabouts, Proceedings of the Tenth International Symposium on Concrete Roads, Brussels, Belgium.

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[36] Diependaele, M., and Rens, L., (2005). The Rehabilitation of the Antwerp Ring Road in CRCP, Proceedings of the Eighth International Conference on Concrete Pavements, Colorado Springs, CO. [37] Teuns, K. C. J. G., Stet, M. J. A., and van Keulen, W., (2004). Full-Scale Pavement Tests of Exposed Concrete Aggregates: Acoustical Aspects and Friction Characteristics, Proceedings of the Ninth International Symposium on Concrete Roads, Istanbul, Turkey. [38] Van Keulen, W., and van Leest, A.J., (2004). The Acoustical Properties of Optimized Exposed Aggregate Concrete in the Netherlands, Proceedings of the Ninth International Symposium on Concrete Roads, Istanbul, Turkey. [39] Van Leest, A. J., and van Keulen, W., (2004). The Structural Properties of Optimized Exposed Aggregate Concrete in the Netherlands, Proceedings of the Ninth International Symposium on Concrete Roads, Istanbul, Turkey. [40] Stet, M. J. A., van Leest, A. J., and Jurrians, G., (2004). Guidelines for Concrete Roundabouts: The Dutch Practice, Proceedings of the Ninth International Symposium on Concrete Roads, Istanbul, Turkey. [41] Hassan, K. E., Chandler, J. W. E., Harding, H. M., and Dudgeon, R P., (2005). New Continuously Reinforced Concrete Pavement Designs, Summary of TRL Report TRL 630, Transport Research Laboratory. [42] Grube, H., and Kerkhoff, B, The New German Concrete Standards DIN EN 206-1 and DIN EN 1045-2 as the Basis for the Design of Durable Constructions, Research Institute of the German Cement Industry, German Cement Works, Concrete Technology Reports, Volume 29, 2001–2003. [43] Springenschmid, R., and Fleischer, W., (1994). Influence of Cement on the Durability of Concrete Pavements, Proceedings of the Seventh International Symposium on Concrete Roads, Vienna, Austria. [44] Québec Ministry of Transport, (2003). Rigid Pavement Distress Identification Manual, Direction du Laboratoire des Chaussés, Government of Québec, 1997, English translation. [45] Québec Ministry of Transport, (2003) Rigid Pavement Maintenance and Rehabilitation Guide, Direction du Laboratoire des Chaussés, Government of Québec, 1997, English translation. [46] Macht, J., Tschegg, E.K., Jamek, M., and Steigenberger, J., (2006). Whitetopping— Assessment of Asphalt Concrete Interfaces, Tenth International Symposium on Concrete Roads, Brussels, Belgium. [47] Forum of European National Highway Research Laboratories, (2004). A Guide to the Use of Fully Flexible Long-Life Pavements, FEHRL Report 2004/01.

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Chapter 3

LONG TERM PAVEMENT PERFORMANCE COMPUTED PARAMETER: MOISTURE CONTENT United States Department of Transportation

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FOREWORD The ability to accurately monitor subsurface soil parameters on a continuous basis is extremely beneficial in pavement design, evaluation, and performance prediction. The time domain reflectometry (TDR) data collected as part of the Long Term Pavement Performance seasonal monitoring program (SMP) can be used to estimate moisture content, conductivity, reflectivity, and density. This chapter provides valuable information on calculating these parameters utilizing TDR traces and documents the process of interpreting over 270,000 TDR traces taken at SMP sites across North America. In situ data availability is critical to pavement engineering, particularly as the process moves toward mechanistic-empirical techniques. This study not only provides useful information from in-service pavements, but also provides a method that can be utilized by State highway agencies interested in monitoring subsurface conditions and analyzing their effect on pavement response. Gary Henderson Director, Office of Infrastructure Research and Development

LIST OF ACRONYMS AND ABBREVIATIONS AASHTO AC FHWA IMS LTPP

American Association of State Highway and Transportation Officials asphalt concrete Federal Highway Administration Information Management System Long Term Pavement Performance

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United States Department of Transportation QC SID SMP SPS SWCC TDR TEM TLE VMC

quality control system identification method seasonal monitoring program Specific Pavement Study soil-water characteristic curve time domain reflectometry transverse electromagnetic mode transmission line equation volumetric moisture content

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1. INTRODUCTION Time domain reflectometry (TDR) information has been collected as a key component of the Long Term Pavement Performance (LTPP) program’s seasonal monitoring program (SMP) to monitor subsurface moisture conditions in pavement structures. The TDR waveform data do not provide in situ moisture contents directly. Rather, the data must be analyzed to determine parameters—such as volumetric moisture content (VMC)—that are of use in pavement design and performance prediction. Interpretation that included the development of empirical-based methodologies to convert waveform characteristics and in situ soil properties to moisture parameters was performed on a portion of these TDR data under previous analysis.[1] The computed parameter data from this effort are currently available in the LTPP Pavement Performance database. Since then, approximately 175,000 more automated TDR measurements have been added to the database but have not been interpreted. The current study was performed to not only compute the moisture parameters for these additional TDR measurements but also to assess other feasible computational procedures. The objectives of the current study were to: • • • •

Investigate the differences between the automated and manual TDR trace interpretation methods. Investigate the adequacy of the models used to estimate VMC from the TDR interpreted dielectric constant. Investigate the adequacy of data used to compute gravimetric moisture content from VMC. Determine adequacy of data to support computation of other moisture-related indices such as degree of saturation.

A significant portion of the analysis was focused on alternative computational processes, wherein previously uninterpretable traces could be utilized. Based on this investigation, a new approach was recommended that computed the soil dielectric constant using a solution of the transmission line equation (TLE) for each TDR trace and the computation of the dry density and the moisture content using a micromechanics model. The new approach eliminated many of the issues related to the trace interpretations and provided a relatively accurate assessment of the in situ moisture content.

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In phase 1 of this project, the basic procedures of the new approach were developed and evaluated using measured moisture contents from the SMP Installation Reports and other sources.[2] The new approach was shown to work and to produce reasonable estimates of the in situ moisture contents compared with ground truth measurements in both field and laboratory settings. Phase 2 of the project entailed the development of a new computer program to automate the computation process, the computation of the moisture content for 274,000 TDR traces, and the uploading of this data into the LTPP database. Quality control (QC) checks were developed and performed on all of the computed data. This chapter presents the development of the new computational procedures, evaluation of results from the new approach, development of the computer program automating the process, and the QC initiatives implemented to ensure data reported in the LTPP database are of research quality.

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2. BACKGROUND AND LITERATURE REVIEW Environmental factors such as moisture content, temperature gradient, and depth of frost penetration have a significant effect on pavement performance. Understanding the effect of these factors on performance is crucial to the optimal design of pavement structures and involves consideration of not only seasonal variations but also changes throughout the day. To provide a means for studying the contribution of environmental factors on pavement structures, SMP was initiated within LTPP. This program was designed to provide (1) the means to link pavement response data obtained at random points in time relative to critical design conditions, (2) the means to validate models for relationships between environmental conditions and in situ structural properties of pavement materials, and (3) expanded knowledge of the magnitude and impact of the changes involved. To accomplish this, SMP sites were instrumented with the equipment in table 1. The design of SMP was a two-tiered approach including the core experiment and supplemental studies. The core experiment included 64 LTPP test sections selected by the categories listed in table 2. An additional six test sections were included as supplemental studies to the original SMP experimental design. To capture seasonal and diurnal changes, pavement response data were collected more frequently than routine LTPP monitoring. The supplemental studies were carried out in response to highway agencies’ desire to collect data on LTPP test sections not included in the core sites. Table 1. Instrumentation for SMP[3] Instruments TDR (time domain reflectometry) Thermistor sensors Electrical resistivity probes Piezometer Tipping-bucket rain gauge

Measurement Moisture content of subsurface Pavement temperature gradients and air temperature Depth of frost/thaw Depth of ground water table Precipitation

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United States Department of Transportation Table 2. SMP core experiment sectioning category[3]

Pavement type Subgrade soil Environment

• Flexible-thin asphalt concrete (AC) surface (127 mm (5 inches)) • Rigid-jointed plain concrete • Rigid-jointed reinforced concrete • Fine grained • Coarse grained • Wet-freeze • Wet-no freeze • Dry-freeze • Dry-no freeze

Overview of Time Domain Reflectometry (TDR)

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The collection of TDR waveforms from subsurface materials is of particular interest in this study. Although the importance of in situ moisture content of subsurface layers in pavement structures has been well recognized, moisture measurement has sometimes been difficult because of the limitations of existing measurement and computational methods.

Figure 1. Diagram. TDR probe for SMP [3]

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The TDR method was selected for use in the SMP core experiment. TDR equipment was originally developed for measuring electromagnetic wave travel times to detect breaks or shorts in electrical conductors and subsequently was adapted to collect sufficient data to allow for soil moisture to be estimated. The TDR system records an electromagnetic waveform that can be analyzed as it is transmitted and reflected to characterize the nature of objects that reflect the waves. The waveform pulse is transmitted along a coaxial metallic cable shielded by a waveguide at a velocity that is influenced by the dielectric constant (ε) of material surrounding the conductors. This dielectric constant is a dimensionless ratio of a material’s dielectric permittivity to the permittivity of free space. Changes in the dielectric constant of the surrounding material occur as its moisture content or conductivity (the reciprocal of resistance) changes. Signal reflectivity also varies (from 1 to -1) as a function of the degree of open to short circuitry, respectively, and exists in the wave reflections as evidenced by slope changes in the return wave pulse recorded by the TDR readout unit. A full short circuit eliminates any additional return signals, while varying degrees of an open circuit results in a variety of return signals.[3]

Figure 2. Graph. Typical TDR signal [3] Long Life and Quiet Pavement: Research and Issues : Research and Issues, Nova Science Publishers, Incorporated, 2010. ProQuest Ebook

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Figure 3. Diagram. Illustration of instrumentation installation [3]

The Federal Highway Administration (FHWA) TDR moisture probe is shown in figure 1. The coaxial lead cable (signal lead) is connected to the center of the three stainless steel rods, which are inserted horizontally into the soil at the point of monitoring. The cable’s outer shield is connected to the outer rods, which serve as the waveguide. The recorded TDR signal rises to a peak (initial inflection point), as the electromagnetic wave enters the probe rods, followed by a fall in the return signal to a second inflection point as the wave hits the end of the probes as illustrated in figure 2. The distance between the first inflection point (point Dl) and final inflection point (point D2) is known as the “apparent” length of the probe, La.[3] Ten TDR probes were used to measure in situ moisture content of pavement sublayers at SMP test sections that were placed in one hole located in the outer wheel path.[4] At most sites, the TDR installation hole was located at approximately 0.76 m (2.5 ft) from the outside edge of the white stripe and at least 1.2 m (4 ft) away from joints and/or cracks to avoid unrepresentative surface moisture infiltration. Figure 3 provides a schematic of the instrumentation. The TDR probes were placed at specified depths as the type of sublayer and its thickness varied. If the top granular base (or subbase) layer was greater than 305 mm (12 in), the first TDR probe was placed 152 mm (6 in) below the surface layer and/or bottom of the lowest stabilized layer; otherwise, the probe was placed at mid depth of the top granular base (or subbase) layer. The next seven TDR probes were placed at 152 mm (6 in) intervals and the last two probes were placed at 305 mm (12 in) intervals. [3]

Interpretation of TDR Trace The waveform obtained from the TDR sensor must be analyzed to determine in situ soil parameters. Existing procedures for the interpretation of TDR data have included determining

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the apparent length (La) so as to compute the dielectric constant and the VMC for the material surrounding the TDR probe. The initial inflection point (D1) is located where the signal enters the probe rods while the final inflection point (D2) occurs at the end of the probes. Both are displayed in the TDR readout device. The distance between Point D1 and D2 is the La value used to determine the dielectric constant of surrounding material. The La value can be determined using a variety of methods. Klemunes studied ways to find the most accurate methodology to determine the La value of the TDR signal response.[5] The study investigated and compared five methods: (1) Method of Tangents, (2) Method of Peaks, (3) Method of Diverging Lines, (4) Alternate Method of Tangents, and (5) the Campbell Scientific Method. Differences among the methods are centered on the procedure of locating the initial and final inflection points of the TDR trace. From the study, the method of tangents was found to be the most accurate while the least accurate methods are the alternate method of tangents and the method of diverging lines. The method of tangents employs the tangent lines at the local values of the TDR traces to isolate the inflection points. D1 is located at the intersection of the horizontal and negatively sloped tangents (i.e., local maximum) of the TDR trace, and D2 is located at the intersection of the horizontal and positively sloped tangents (i.e., local minimum) as shown in figure 4(a). However, the method cannot be applied to very dry or partially frozen soils, so the method of peaks is used for those soil type situations.[6] In the Method of Peaks, D1 is determined by locating the intersection of the tangents drawn on both sides of the initial inflection point, and D2 is at the intersection of the tangents drawn of both sides of the final inflection point, as shown in figure 4(b).

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Previous Computation Methodology of Dielectric Constant An electromagnetic signal is transmitted along the TDR probe. When the signal reaches the end of the probe, it is reflected back to the data acquisition unit and the reflected signal is recorded. The velocity of this reflected electromagnetic wave in the probe depends on the dielectric constant and magnetic permeability of the surrounding material (relative to the speed of light in a vacuum) and is given in equation 1 as:[7]

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(1) Where: c = velocity of electromagnetic wave, ε = dielectric constant, (approximately 1.0 for air, 80 for water, and 3–5 for dry soil) μ = relative magnetic permeability of the soil c0 = speed of light in vacuum Assuming the effects of ferromagnetic components in soils are not significant, the magnetic permeability of soil can be set to unity (ì = 1).[8] By substituting the velocity of electromagnetic wave with the travel time and the length of probe (c = 2L/Δt), the dielectric constant is:

(2)

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Where: Δt = the travel time of the TDR signal L = actual length of TDR probe The travel time of the signal is also dependent on the dielectric constant, which includes signal propagation in the soil-moisture mixture; hence, the apparent probe length can be determined by the travel time of the signal if it were propagating at the speed of light:

(3) Therefore, the dielectric constant of soil can be expressed as the ratio of apparent length to actual length of TDR probe from equations 2 and 3:

(4) Where: La = apparent length of probe, m

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The dielectric constant can be determined with the phase velocity considering the propagation as follows:[5]

(5) Where: L = actual length of TDR probe, 0.203 m (8 inches) for FHWA probes Vp = phase velocity setting on TDR cable tester (usually 0.99); this is the ratio of the actual propagation velocity to the speed of light. In short, the dielectric constant is derived from the relationship between the speed of light and the wave velocity (delayed due to wave propagation caused by the dielectric properties of the soil surrounding the TDR probe).

Previous Methodology for Determination of in situ Volumetric Moisture Content

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The methods currently used to determine soil VMC from dielectric constants are mainly based on empirical approaches: (1) Topp’s equation (2) Klemunes’ model (3) Third-order polynomial Ka – soil gradation model Topp’s equation employs empirical regression functions to relate the dielectric constant to the VMC.[8] The third-order polynomial function developed by Topp is widely used for calculating moisture content of soil materials. Topp’s equation can be applied to all types of soils but is inaccurate for certain scenarios: [1,8]

(6) Where: θ = volumetric moisture content (%) Klemunes developed calibrated mixing models for soil samples obtained from 28 LTPP sites.[5, 6] TDR traces were obtained from the soil samples prepared at various combinations of moisture content and compaction levels. The moisture content and dry density of each combination was determined by laboratory testing after the TDR trace was obtained. A total of 415 data points were obtained; however, outliers and TDR traces that were impossible to interpret were removed from the dataset. Consequently, 397 data points were available and

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used to develop Klemunes’ moisture models, which employ a hierarchal methodology (i.e., level 1 to level 4) relative to the level of information available and the desired accuracy. At level 1, the moisture content would be determined without any information about the properties of the soil, such as coarse-/fine-grained or American Association of State Highway and Transportation Officials (AASHTO) classification. Therefore, level 1 has the lowest explained variance and the highest standard error. At level 2, moisture content is determined on the basis of the soil being identified as either coarse- or fine-grained. The accuracy of this level is better than that of level 1. At level 3, the VMC is based on the AASHTO soil classification, accounting for the soil’s gradation and the characteristics of fraction passing No. 40. The most accurate level of Klemunes’ model is level 4 since this involves testing the soil at various moisture and density levels in the laboratory and correlating the results with the TDR recordings. Accordingly, a calibration curve is developed for a range of VMC expected in the field. The following equation is used to predict the VMC for each of the four levels. Table 3 provides the specific regression coefficients for each level.

(7)

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Where: γd, ,γw = unit weight of the soil and water Gs = specific gravity of the soil B0, B1 = regression coefficients As part of the third-order polynomial Ka-soil gradation approach, four models were developed for the VMC computation. The first three models take the third-order polynomial Ka model based on soil type while the fourth model applies to only fine- gradation soils and incorporates the contribution of the gradation into the model.[1] A computer program entitled MOISTER incorporates all four of the third-order polynomial Ka models to determine the VMC of soil, the method of tangents, and the method of peaks to determine the apparent length (and dielectric constant) of the TDR trace. Table 3. Coefficient for mixing model[5, 6] Level Level 1 Level 2 Level 3

Level 4

Soil Type B0 B1 All-type 1.41 7.98 Coarse 1.06 9.30 Fine 1.50 7.56 A-1-b 1.43 7.69 A-2-4 1.00 9.57 A-3 1.11 9.02 A-4 1.77 6.25 A-6 -1.56 12.26 A-7-5 1.04 8.49 A-7-6 1.02 10.31 Determined based on a site-specific calibration

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The third-order polynomial Ka models were developed based on the regression of dielectric constants and VMC from the dataset obtained in Klemunes’ study. The coarsegrained soil has a different trend compared with fine- grained soil, but both of them show a third-order polynomial functional form. Hence, in order to provide a more accurate model, data for coarse-grained soil and fine-grained soil were modeled separately. The models are valid only within the dielectric constant range or the inference space that was used to develop the model.[1] The three empirical regression equations developed using the dielectric constant as the sole independent variable are given below with the regression coefficients shown in table 4.

(8) Where:

ε = dielectric constant a0, a1, a2, a3 = regression coefficients To refine the regression model and to increase the R2 for fine-grained soil, another model was developed using gradation, plastic limit, and liquid limit as independent variables. Equation 9 provides the VMC model for fine-grained soil with variables:[1]

(9)

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Where:

θ ε

= volumetric moisture content = dielectric constant a0, a1,..., a10 = regression coefficients (see table 5) This model was used for computing the VMC for the fine-grained soils where gradation and other parameters were available and within the inference region of the model. Table 5 shows the descriptions, values, and inference ranges of these variables. The four models are selected based on the dielectric constant and properties of soil to calculate moisture content. The flow chart of the model selection scheme is shown in figure 5. Table 4. Third order polynomial Ka-soil model parameters [1] Model type Coarse-Ka model Fine-Ka model All soil-Ka model

a0 -5.7875 0.4756 -0.8 120

a1 3.41763 2.75634 2.3 8682

a2 -0.13 117 -0.061667 -0.04427

a3 0.0023 1 0.000476 0.000292

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United States Department of Transportation Table 5. Refined third order polynomial Ka-soil model parameters[1] Description Dielectric constant

%passing 1½-sieve %passing ½-sieve %passing No.4 sieve %passing No.10 sieve %passing No.200 sieve Plastic limit Liquid limit

Coef. a0 a1 a2 a3 a4 a5 a6 a7 a8 a9 a10

Value 1761.78 2.9145 -0.07674 0.000722 -19.6649 4.3667 -5.1516 2.7737 0.06057 -0.2057 0.1023 1

Inference Range 3 - 58.4

99 - 100 97 - 100 90 - 100 84 - 100 12.6 - 94.6 0 - 45 0 - 69

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Variable Intercept Ka Ka2 Ka3 G11_2 G1_2 No4 No10 No200 PL LL

Figure 5. Flowchart. Volumetric moisture model selection process [9] Long Life and Quiet Pavement: Research and Issues : Research and Issues, Nova Science Publishers, Incorporated, 2010. ProQuest Ebook

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Calculation of Gravimetric Moisture Content VMC can be converted to a gravimetric basis using volume and weight relationships. The volume relationships used for soil solid-moisture-air mixture are degree of saturation, void ratio, and porosity as shown below:[10]

(10)

(11)

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(12) Where: S = degree of saturation e = void ratio n = porosity Vs = volume of soil solids (cm3) Vw = volume of water (cm3) Vv = volume of void (cm3) V = total volume of mixture (cm3) The weight relationship can be represented by moisture content and unit weight:

(13)

(14) Where: w = gravimetric moisture content (%) γ = unit weight (g/cm3) Ww = weight of water (g) Ws = weight of solids (g) W = total weight of mixture (g)

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To calculate gravimetric moisture content, a relationship among moisture content and unit weight can be derived from a volume of soil mixture in which the volume of the soil solids is set to 1 as shown in figure 6. The volume of water can be defined as:

(15) Where: γw = unit weight of water (g/cm3) Gs = specific gravity of solids The dry density of soil can be written as:

(16) Where: γd = dry unit weight of soil (or soil dry density, g/cm3)

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Also, the degree of saturation is changed as follows:

(17) Thus, the gravimetric moisture content can be expressed in terms of the unit weight of water, unit weight of solids, and VMC by combining equations 16 and 17:

(18) Where: θ = volumetric moisture content (%) Equation 18 is used to convert soil moisture from a volume to a weight basis as needed in pavement engineering applications. Reasonably accurate in situ dry density estimates of material surrounding the TDR sensors must be made for moisture conversion. During installation, field moisture measurements were performed on the material placed around TDR probes with additional material samples retained for laboratory analyses.[3]

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Figure 6. Diagram. Soil mixture with volume of soil solids equal to 1

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CHAPTER 3. RESEARCH APPROACH The existing empirical methodology used to determine dielectric constant and VMC were evaluated along with new mechanistic-based techniques to determine to determine the best approach to use in computing TDR traces collected at LTPP SMP sites. This section provides details on the evaluation conducted and details on the methodology selected for use on SMP TDR data. The existing methodology used in the analysis of SMP TDR traces to determine the dielectric constant is shown in equation 5. The dielectric constant for the soil-moistureair mixture has been determined by comparing the “apparent” electrical length (La) of the probe from the TDR signal to its actual length. This method of determination of the dielectric constant is independent of the conducting medium’s other electrical properties besides the dielectric constant, which influences the resultant computed parameters because the soil magnetic permeability is, for instance, assumed to be unity. Saline or alkaline soils can create an effective electrical short with the shielding rods due to the ions in the water, which can increase the effect of conductivity on the value of the dielectric constant. Consequently, trace interpretation difficulties and erroneous determinations result because of the soil’s high electrical conductivity, suggesting that an improved method of determining the dielectric constant would involve the consideration of the effect of the soil conductivity. Furthermore, the difficult-to-interpret wave forms result from “dispersion” and “attenuation,” which are directly related to the level of electrical conductivity in the medium. The dielectric constant—or permittivity—of a soil is really a complex number, composed of a real and an imaginary part. It is assumed in the above method of analyzing TDR data that

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the imaginary part is negligible. The imaginary part is a measure of the ratio of the electrical conductivity of the soil to the dielectric property that is computed from TDR data. Conductivity is important in identifying corrosive soils and in indicating the presence of anions, such as sulfates, which are capable of expanding to produce large buckling movements in lime-stabilized pavement layers. Reduction in the wave form distortion over time indicates that the conductive elements in the soil are leaching out. In short, when the TDR signal is distorted and, consequently, difficult to interpret, it is providing additional information about the soil permittivity. The wave form shown in figure 2 is typical of a soil with low conductivity. The horizontal axis in that graph is labeled as an apparent length, La. However, it is a plot of the voltage measured by the TDR device versus the time of arrival of that voltage. This is a signal of voltage as a function of time exactly as is analyzed when using ground- penetrating radar signals. A distorted wave form can be further analyzed to produce both the real and the imaginary parts of the permittivity of the soil—and what has been previously considered to be a limitation of the equipment is actually a benefit. In terms of the sources of error in TDR measurements, there is a difference between the meaning of “regular” and “distorted” waveforms. Measurement error is inherent in the instrumentation itself. This type of error is normally random and can be reduced by repeating the measurement.[11] The other kind of error is systematic error and arises from the assumptions that are made in the analysis of the data, precisely the type of error referred to in the above discussion. Further discussion in this regard will be presented later relative to the new approach to evaluate the soil dielectric property. The new approach for the calculation of the VMC consists of three steps: 1. Calculate the dielectric constant, conductivity, and reflectivity from the TLE. 2. Given the ground truth moisture content data recorded at the installation of each device and the above parameters, backcalculate the permittivity of the solids for the particular TDR location and calibrate the micromechanics volumetric water model to site specific conditions. [12] 3. Using the calibrated micromechanics volumetric water model (specific to each TDR and location), forward calculate the volumetric water content and the dry density of the soil for other times and seasons based on the TDR traces and the associated dielectric constant. Step (1) involves the use of the TLE for voltage (V): [12] (19) Where: V = applied voltage z = distance along the transmission line (TDR probe), m

=

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c = μ0 =

magnetic permeability of free space

= ε0 =

electric permittivity of free space

t V+ Vk

= = = = =

time of travel relative to the peak relative voltage voltage amplitude in the positive z direction voltage amplitude in the negative z direction dispersion coefficient = kR – jkI (real and imaginary components) = =

for a slightly conducting medium for a highly conducting medium)

ε ω σ L

= = = =

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= a, b = μ C

= =

dielectric constant of the soil waveform frequency (Hz) soil conductivity (S/m) inductance (H/m)

inside and outside coaxial transmission line diameters, respectively (see figure 7) soil magnetic permeability (H/m) capacitance (F/m)

=

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(20) Where:

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Writing the relative voltage (v(z)) in terms of time of travel (t) of the microwave:

(21) The above expression can be used to analyze the voltage trace that is obtained from the TDR device. Notice that the voltage is a function of not only the dielectric constant but also of the conductivity and the reflectivity. Both of these parameters affect the inferred dielectric constant, or, in other words, they influence the value as it would be deducted from the characteristics of the trace. Systematic errors that would result from not accounting for conductivity and reflectivity are corrected by accurately accounting for the actual physics of wave transmission through a dielectric medium in the model. The use of the TLE to analyze the data reduces the systematic error introduced by assuming that conductivity and reflectivity have no influence on the shape of the transmitted voltage with distance down the length of the TDR probe. The dielectric constants produced after correcting for the effects of conductivity and reflectivity more accurately and precisely reflect the actual moisture state of the soil. The concept of the TLE and electromagnetics involved in the new approach is addressed in more detail in appendix A. The constants used to compute the dielectric constant are the voltage and relative distance, the magnetic permeability of free space, and the electric permittivity of free space. While the voltage and relative distance are obtained from the TDR trace, the magnetic permeability and electric permittivity are fixed values, which are 4π x 10-7 H/m and

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1/36π x 10-9 F/m, respectively. The inside and outside diameters of the coaxial cable are not required to compute dielectric constant values using the TLE.

Solution Methodology (Step 1) The method of solving for the dielectric, conductivity, and reflectivity parameters (step 1) is by use of the system identification method (SID).[11] This method is used to fit the equation for relative voltage (v(z)) to the form of the TDR trace (an example of which is shown in figure 2) by iterating ΔXi until it equals zero by satisfying the following expression for each point selected from the trace:

(22) Where: = conductivity (σ), dielectric constant (ε), or reflection coefficient (Γ) m = number of Xi (in this case = 3) that are determined for each voltage recorded from the TDR trace = n = iteration count

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=

= the measured voltage = the current calculated voltage based on the current values of In matrix form, the iteration process is capable of solving a set of simultaneous equations developed for each set of data points taken from the TDR trace:

(23) Where:

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The number of recorded voltage points from the TDR trace determines the number of rows in matrices [F] and [r]; where the number rows in{β} and the number of columns in [F] depends on the number of unknowns. Solving for{β}:

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(24) By minimizing the {β} matrix, solutions for Xin (i.e., conductivity (σ), dielectric constant (ε), and the reflection coefficient (Γ)) are found. The minimization of error contained within the residual matrix [r] is analogous to the minimization or reduction of error employed in least squared error analysis as elaborated in appendix B. Another type of systematic error is reduced by the method of allocation inherent in the use of the SID approach. The squared error between the actual measurement and the predicted measurement (residual matrix[r]) is calculated by using the physically correct model of a mixture dielectric to determine the sensitivity of the weighting coefficients for allocating the squared error. It is possible to adjust the model coefficients until there is no squared error remaining. However, because of the presence of random error (i.e., measurement error in the TDR device), the values of the residual matrix [r] should not be forced to zero. Furthermore, the size of the random errors should be determined by statistical evaluation of repeated TDR measurements that are not presently available. Inherent in this analysis are the minimum number of points (N) from the TDR trace that should be used to provide a reasonably accurate estimate of the dielectric constant. Accordingly, this analysis suggests that using twice as many data points as the number of coefficients to be computed (which would be 6 in this case) would be sufficient in estimated dielectric constant, conductivity, and reflectivity assuming a measurement error of 3 percent in the TDR voltage trace. In this regard, the six points would be selected between the first and second inflection points, where the first and second inflection points are points 1 and 6, respectively, and the other four points were equally distributed between the inflection points. This approach was used only for the calibration process (step 2) to characterize the manual TDR traces obtained from the installation reports. In the computational program, which was developed for the new approach, all data points between the inflection points were used to determine the dielectric constant because the data are readily available in the automated TDR trace format, allowing the program to interpret a large number of points relatively quickly.

Determination and Calibration of Soil Component Dielectric Constants (Step 2) The VMC is currently estimated in the MOISTER program from the measured dielectric constant using regression-type equations 8 or 9. It is suggested from literature that a more fundamental approach would account for the effect of individual constituent soil dielectrics on the moisture content.[12] In this regard, a theory of dielectric properties of composite materials from a micromechanics/self consistent scheme yields a general expression for the composite dielectric constant (ε-for a 2-phase system):[13]

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(25) Where: ε1 = dielectric constant for phase 1 ε 2 = dielectric constant for phase 2 v1 = volume fraction of phase 1 v2 = volume fraction of phase 2 The justification for a self-consistent scheme lies in the volume fractional bounds or limits in which the computed VMC fall. In other words, the computed moisture contents (based on equation 28 below) are consistent with bounded values of dielectric constants of the individual phases and their volume fractions. The upper (+) and lower (-) dielectric expressions, illustrated in figure 8, are as follows:

(26)

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(27)

Figure 8. Graph. Bounding of dielectric constant as a function of the computed volumetric moisture content (θ ) using equation 28

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Using this concept, an expression can be written based on equation 25 for a three-phase system (air, water, and solids—such as in a soil material):

(28)

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Where: γd = dry density of soil, g/cm3 Gs = specific gravity of soil γw = density of water, g/cm3 dielectric ε1 = dielectric constant of solids ε2 = dielectric constant of water ε3 = dielectric constant of air (= 1) ε = dielectric constant of the soil determined from step 1 θ = ratio of soil fraction With a value for ε determined from the SID analysis of a TDR trace, values of ε1, ε2, and Gs of the model are adjusted based on the ground truth data of measured values of γd and θ. The dielectric constants of the water (ε2) and the soil solids (ε1) can be found by applying the SID approach to equation 28. Typical values of ε1 range between 3 and 5 while typical values of Gs range between 2.6 and 2.9. Using this approach, analysis results of selected TDR traces are shown in tables 6 and 7. Computations of the dielectric constant based on the apparent length method are headed by the notation of “La” while the proposed determinations made by the new approach are noted by the heading “new.” The calibration shown in table 7 also includes the Gs parameter. Table 6. Comparison of volumetric moisture contents during TDR installation*

Section/ TDR #

Soil Type

Dry Density (g/cm3)

364018/9

Gravel

091803/4

Soil Dielectric

Volumetric Moisture Contents (%)

La

New

Field Measured

MOISTER Program

2.24

9.83

10.04

26.12

17.33

Sand

2.26

14.02

14.33

33.28

22.71

131031/8

Silt

1.80

12.16

18.40

40.75

20.53

421606/6

Clay

1.94

7.34

5.76

19.01

17.57

CoarseKa CoarseKa CoarseKa Fine-Ka

* All information used was obtained from Installation Reports.

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Micromechanics Method 25.71 32.92 39.86 18.75

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Table 7. Calibrated and calculated values determined by micromechanics method Section 364018 091803 131031 421606

Dielectric Constant Soil (ε1) Water (ε 2) 3.70 79.7 3.65 80.4 3.47 79.9 3.38 80.0

Air (ε 3) 1.0 1.0 1.0 1.0

Specific Gravity (Gs) 2.70 2.74 2.77 2.78

Forward Computation of Water Content and Dry Density (Step 3)

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In the forward calculation of volumetric water content and dry density that is performed in step 3, the self-consistent model in equation 28 is used together with the calibration constants ε1, ε2, and Gs to determine the new values of γd and θ from values of the dielectric constant for the soil mixture derived from subsequent TDR data collection records. These new dielectric values are determined by analysis of the TDR traces obtained at different times throughout the monitoring period. Thus, once particular soil characteristics ε1, ε2, and Gs are “identified” by step 2, all future calculations of γd and θ can be determined from the SID in step 3 using a new soil mixture dielectric constant measured in step 1. Along with the calculation of γd and θ, the volume relationship of degree of saturation (S), porosity (n), and void ratio (e) can be redefined from step 3:

(29)

(30)

(31) It is important to note that two additional sources of systematic error are countered in this approach. First, the three-phase model accounts for the dielectric effect of the air in the soil. Additionally, dry unit weights are obtained from each TDR trace and not assumed to be constant over time.

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Validation The new procedures’ effectiveness was analyzed by comparing the moisture content computed both from the MOISTER program and the micromechanics method to laboratory moisture content tests from representative SMP sites. Ground truth data that are linked to specific TDR traces for SMP soils were identified from three sources.

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1. Calibration validation – Data captured during the equipment installation at the SMP sites. As part of this process, in situ soil samples were matched to the TDR installation location and tested for moisture content. These data were used in the calibration process previously described. 2. Laboratory validation – Data obtained from Klemunes’[5] study of collecting TDR data in a laboratory setting where soil moisture content and density are known. 3. Field validation – Available information from sites in which forensic evaluations were performed. TDR traces were taken in the field just prior to removal of the equipment and soil sampling. All three of these sources provide important reference moisture contents to evaluate the capabilities of the micromechanics model. These sources provided the only data available to conduct validation specific to the LTPP equipment and protocols. The first validation consisted of comparing the moisture content from the laboratory tests in various installation reports to that indicated by the MOISTER program and the micromechanics method. This was presented as part of the calibration process and in table 6. Figure 9 further demonstrates how the calibration of the micromechanics method provides accurate estimates of the ground truth data. While promising, it was necessary to verify the accuracy of the methodology against both laboratory and field data to establish confidence in the micromechanics method. A second verification effort consisted of computing the moisture content and dry density for the test data noted in Klemunes’ thesis work.[5] Data from four of the 28 SMP sections used in the study were selected to provide a range of soil types (i.e., gravel, sand, silt, and clay). For each SMP section, one TDR trace obtained during installation (and corresponding moisture content/dry density) was used to calibrate the micromechanics model. Calibration information relative to the soil and water dielectric constants can be found in table 8. Using this information and the TDR traces obtained at different moisture contents, estimates of moisture content and dry densities were computed and can be found in table 9 along with estimates from the MOISTER program and the laboratory test results. Figure 10 provides the associated difference of each method for all trials. As can be seen, the micromechanics method provides relatively accurate estimates of actual moisture conditions with the majority of estimates falling within 5 percent of the laboratory derived data. Given the circumstances surrounding the collection of the different types of moisture data involved in this analysis, the degree of comparability is remarkable. The evaluation of estimated dry densities was performed through a comparison to measured values obtained from laboratory testing. Figure 11 shows the relatively high capability and accuracy of the micromechanics model in estimating dry density with a maximum resulting difference of less than 6 percent. This verification was considered to be laboratory verification as the soil mixtures and TDR traces

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were obtained in a laboratory setting where the sampling and data collection were more controlled. A third evaluation was performed using the data being developed for the forensic report on LTPP-SMP site 091803. In this case, the micromechanics method was calibrated using the laboratory moisture content obtained during the equipment installation as shown in table 10. The calibrated model was used to estimate moisture content based on the TDR traces obtained during the forensic investigation. These resulting moisture estimates were compared to the laboratory test results for samples taken just after the TDR traces were obtained during the forensic activities. Those test comparisons can be seen in table 11 with the resulting difference quantities in figure 12. In general, error of the micromechanics method is very low and is under 5 percent for all but one scenario. The values of dry density estimated by the new approach were evaluated by comparing them to measured values. As shown in figure 13, the resulting differences on measured values were slightly greater than for the laboratory verification but still highly accurate at less than 7 percent.

Figure 9. Bar Chart. Errors in volumetric moisture content estimates (calibration validation)

Table 8. Calibration of dielectric constants by transmission line equation

Section

Soil Type

271028 231026 091803 081053

Gravel Sand Silt Clay

Spec. Gravity 2.724 2.782 2.864 2.890

Dry Density (g/cm3) 2.017 1.960 2.264 1.634

Dielectric Constant Soil (ε 1)

Water (ε 2)

3.79 3.79 3.89 3.79

80.6 80.0 81.0 80.0

Volumetric Moisture Content (%) 7.06 19.35 20.38 21.57

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United States Department of Transportation Table 9. Comparison of moisture contents

Soil Type

Section

271028

231026

091803

C F K B F M C I P W

Gravel

Sand

Silt

G 081053

K

Clay

U

Dry Density (g/cm3)

Volumetric Moisture Contents (%)

Lab.

M.M.1

1.730 1.712 1.766 1.574 1.635 1.605 0.976 0.965 0.965 0.973

1.810 1.700 1.869 1.558 1.610 1.569 0.989 0.924 0.927 0.923

Ground Truth (Lab Result) 7.09 12.50 18.98 14.88 22.98 7.54 38.45 27.12 29.65 39.30

1.406

1.350

44.07

1.40

1.321

48.83

1.377

1.440

30.72

Moister Program (3rd Polynomial Equation) 9.36 Coarse-Ka 13.92 Coarse-Ka 20.06 Coarse-Ka 15.40 Coarse-Ka 21.78 Coarse-Ka 8.34 Coarse-Ka 29.63 Fine-Ka 21.01 Fine-Ka 20.48 Fine-Ka 32.35 Fine-Ka Fine51.80 Gradation Fine51.80 Gradation Fine29.67 Gradation

M.M.1 7.79 12.17 19.78 14.25 21.95 7.18 38.05 28.07 28.94 38.16 44.81 48.03 31.29

1

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Micromechanics method.

Figure 10. Bar Chart. Errors of volumetric moisture contents on ground truth data (laboratory validation)

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Figure 11. Bar Chart. Errors of laboratory estimated dry density on ground truth data (laboratory validation)

Table 10. Calibration of dielectric constants for Section 091803

Layer Type

Dielectric Constant

Specific Gravity

Dry Density (g/cm3)

Soil (ε 1)

Water (ε 2)

2.44 2.74

2.255 2.260

3.69 3.65

79.8 80.4

Base Subbase

Volumetric Moisture Content (%) 25.71 32.92

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Table 11. Comparison of moisture contents for Section 091803

Layer Type

Base

Subbase

1

Medium brown gravel

Grayish brown silty gravel with large rock

TDR No. 1

Depth (mm) 330

Dry Density (g/cm3)

Volumetric Moisture Content (%)

Field

M.M.2

Ground Truth

2.229

2.297

17.39

20.69

1

1

Moister Program

2

437

2.255

N/A

15.81

N/A

3

584

2.163

2.243

27.94

26.96

4

737

2.163

2.293

26.00

22.54

5

889

2.166

2.021

19.82

22.54

6

1041

2.192

2.343

16.80

20.69

7

1194

2.192

2.196

20.75

21.25

8

1346

2.091

1.988

25.76

25.94

CoarseKa CoarseKa CoarseKa CoarseKa CoarseKa CoarseKa CoarseKa

Impossible to interpret TDR trace. Micromechanics method.

2

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M.M. 2 16.25 N/A1 26.75 26.34 19.19 17.11 21.67 25.57

174

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Figure 12. Bar Chart. Errors of volumetric moisture contents on ground truth data (field validation)

Figure 13. Bar Chart. Errors of estimated dry density on ground truth data (field validation)

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Through these three validation exercises, it was found that the micromechanics method is capable of predicting accurate moisture and density results. The largest variation between estimates from the micromechanics method and the measured values was under 10 percent with the vast majority falling under 5 percent. Based on the results of this evaluation, it was proposed that the micromechanics method be used to compute moisture estimates for all interpretable TDR data in the LTPP database. This approach was approved by FHWA. Developing a computer program and methodologies necessary for computing and reviewing parameters for the LTPP database is described in the next chapter.

4. COMPUTER PROGRAM DEVELOPMENT

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As a part of the study, a computational program was developed to interpret TDR traces and estimate dry density and moisture content using the TLE and micromechanics models. Due to the large differences between the former and current approaches, a new computational program named LTPP MicroMoist was developed to facilitate proper interpretation of the collected traces. However, some of the programming from the MOISTER program was utilized in developing the new program. Much of the appearance and graphical viewing features in the LTPP MicroMoist program were copied from the source code of the MOISTER program.

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Overview of the LTPP Micromoist Program The program was designed to automate the interpretation process with consideration given to certain user input data to ensure the highest quality end product. The program generates output database tables that store data to be uploaded into the LTPP database. The tables can also be used to review data as part of QC processes. Figure 14 shows the main display screen of the new program. A summary of the procedures in the new program can be found in table 12. The user’s manual for the program can be found in appendix C.

Program Algorithm The program logic flow consists of three parts: (1) determination of the TDR trace inflection points, (2) calculation of the soil dielectric constant, and (3) computation of the soil moisture content and dry density. These steps are automatically performed with logical checks and user input incorporated, where applicable.

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Inflection Point Determination A local peak in the TDR trace is created as the electromagnetic wave enters the TDR probe. From this point, the trace falls to a local minimum point and then rebounds upward at a lower rate as the wave hits the end of the probe. Figure 15 depicts the inflection points on TDR traces. The descending portion of the trace represents the waveform at the TDR sensor. This is the portion of the trace that is of interest for soil parameter computation because it represents the characteristics of the in situ soil. Therefore, the inflection points were used to identify the limits for the range of points in the TLE. Table 12. Overview of LTPP MicroMoist program Procedures Determination of inflection points Calculation of dielectric constant Calculation of moisture content Calculation of dry density Input table

Output table

MicroMoist program Local maxima/minima located and used as beginning/ending points for the range of data to be analyzed. Transmission line equation (function of dielectric constant, conductivity, and reflectivity of the soil composite) Micromechanics/self consistent model (calibrated to site-specific conditions using installation data) Micromechanics/self consistent model (calibrated to site-specific conditions using installation data) SMP_TDR_AUTO SMP_TDR_DEPTHS_LENGTH SMP_TDR_CALIBRATE (developed from TDR traces and moisture contents acquired during installation) SMP_TDR_AUTO_DIELECTRIC SMP_TDR_MOISTURES

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Figure 15. Graph. Inflection points in TDR trace

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The inflection points are determined by the program using a step-wise routine. Depending on the distance between wave points, which usually is 0.01 m but can be 0.02 m, the local maxima search routine is limited to the left portion of the trace. A complete TDR trace consists of 245 data points. For traces with a wave point distance of 0.01 m, the maxima search routine is limited to the first 200 data points. For traces with a wave point spacing of 0.02 m, the maxima search routine only involves the first 100 data points. By doing this, the program reduces the number of iterations and accelerates the process without reducing the utility of the program. This step-wise iteration consists of the following steps: 1. Identify the global maximum point (Pi) within the probable range (i.e., first 200 or 100 data points as defined above). 2. Find the local maximum point by starting from Pi and comparing it with the three points before and after Pi. a. If the point is smaller than one of six points, change to the point to the left (pi-1) and compare again. Continue until the condition in b. below is satisfied. b. If the point is larger than all six points, identify the point as the first inflection point. c. As in the TDR trace in figure 15 (b), when a local maximum point is not found even though the changes and comparisons are carried on up to first data point (p1), the global maximum point is identified as the first inflection point. 3. Find the local minimum point (second inflection point) by a routine similar to step 2. a. Run the routine from the point to the right of the established first inflection point, as the second inflection point is on the right side of the first in the TDR trace. 4. Flag the TDR trace if the program cannot find the local maximum or minimum point (i.e., uninterpretable trace). Along with the determination of the inflection points, the above routine helps to locate records without a negative slope. Where both points fall at the same location or the magnitude of the second point is higher than that of first point, the trace is deemed to have a positive Long Life and Quiet Pavement: Research and Issues : Research and Issues, Nova Science Publishers, Incorporated, 2010. ProQuest Ebook

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slope between inflection points. These cases may indicate that the traces were taken in frozen soil and are flagged as suspect records. Additionally, the program allows the user to review each trace and manually adjust the inflection point locations, if necessary. Figure 16 illustrates the flow chart of the inflection point determination.

Figure 16. Flowchart. Determination of inflection points

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Calculation of Dielectric Constant, Reflectivity, and Conductivity Once the inflection points are determined, the program calculates the dielectric constant, conductivity, and reflectivity using the TLE and the SID solution method previously defined. The calculation is conducted based on fitting the measured voltage trace between the inflection points using the iteration process described in chapter 3. While six points from the installation TDR traces were used in the calibration process, all data points between the inflection points were used in the MicroMoist program to determine the dielectric constant. The program calculates the dielectric constant, conductivity, and reflectivity using the automated TDR traces acquired from the LTPP Information Management System (IMS) database. By using all of the data points, the accuracy of the TDR interpretation is improved. The calculation process involves the following steps: 1. Provide initial estimates of dielectric constant, reflectivity, and conductivity as well as the range of acceptable variation. a. Equation 5 is used to determine the initial value of the dielectric constant. It serves as an initial estimate and reduces the number of iterations to convergence. The soil dielectric constant ranges between 1 and 85 and is increased or decreased by a constant factor after each iteration. This factor is determined by the change vector (β-matrix) generated from the SID method. b. Reflectivity is assigned at 0.1 as an initial value but can vary between -1 and 1. Within the SID iteration, the reflectivity varies by a factor similar to the dielectric constant and is dependent on the change vector. c. Conductivity is assigned a value of 0.5 initially, but the range is not fixed. The adjustment factor applied to the conductivity is a function of the change vector. 2. Calculate the parameters based on the SID method. a. The change vector, consisting of a 3 by 1 matrix, is determined based on the algorithm implemented in the program. The SID method calculates the relative voltage based on the assumed parameters and then compares it with the measured relative voltage obtained from the trace. The change vector is the measure of variation between each parameter. b. This calculation process is contained within a loop that terminates when all elements of the change vector are less than 1.0 percent. These steps are implemented for each trace, and the values of dielectric constant, reflectivity, and conductivity are stored in the SMP_TDR_AUTO_DIELECTRIC table. The dielectric constant value is then used to calculate moisture content and dry density. The constants used to compute the dielectric constant are the voltage and relative distance, the magnetic permeability of free space, and the electric permittivity of free space. While the voltage and relative distance are obtained from the TDR trace, the magnetic permeability and electric permittivity values are fixed values, which are 4π x 10-7 H/m and 1/36 π x 10-9 F/m, respectively. Therefore, users do not need to change any constants for the computation of the dielectric constant in the program. Figure 17 illustrates this calculation procedure.

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Figure 17. Flowchart. Calculation of dielectric constant, conductivity, and reflectivity

Calculation of Moisture Content and Dry Density Moisture content and dry density are calculated based on the micromechanics and self consistent models previously described. The ε1, ε2, and Gs parameters in these models are calibrated to site-specific conditions based on TDR traces and moisture content testing performed during installation. The dielectric constant of the soil, determined from the SID

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iteration process, is also an input into the model. The following routine was used for this calculation in the program: 1. Assign initial values to the unknown parameters of dry density and VMC. Each TDR location has dry density and VMC data measured during the installation process, which are stored in the calibration table. These values are used as seed values for the SID method to calculate the dry density and VMC. 2. Calculate the dry density and moisture content based on the SID method. a. The algorithm implemented in the program is a loop system which calculates ec using the inputted parameters and then compares it with εm. The following equation is used to calculate εc:

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(32)

Figure 18. Flowchart. Calculation of moisture content and dry density

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United States Department of Transportation b. The change vector (2x1 matrix) is the measure of variation in dry density and moisture content calculated from εc and the inputted parameters. c. Once the variation is less than 1 percent, the loop terminates and the values of dry density and moisture content are reported.

The VMC and dry density calculated from the above procedure are presented in the output table, MICROMOIST_SMP_TDR_MOISTURES, and are also used to compute the gravimetric moisture contents. In this step, the calibrated dielectric constants of solid and water as well as the specific gravity are used as constants. The density of water and the dielectric constant of air are also needed, but they are fixed as 1.0 g/cm3 and 1.0, respectively. In the micromechanics method, the physical properties of the TDR probe, such as length of TDR, are not considered in the computation process. Therefore, the program can be used to interpret other types of TDR probes as long as calibration data are available. Figure 18 illustrates the procedure for calculating the dry density and moisture content values.

Development of the Calibration Table In order to calculate the moisture content and dry density using the new approach, the program requires the following calibration values for each SMP site and each layer:

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• • • •

Dielectric constant of solids (ε1) Dielectric constant of water (ε 2) Dielectric constant of air (ε 3) Specific gravity (Gs)

These values are calibrated using the ground truth data obtained from the LTPP SMP Site Installation and Initial Data Collection reports for each SMP test section.[2] The ground truth data consisted of measured moisture content and manual TDR traces recorded during the installation process as well as dry density values available in the LTPP database. This calibration data are stored in the MICROMOIST_SMP_TDR_ CALIBRATE table.

Calculation of Dielectric Data from Manual TDR Traces The manual trace taken during installation is used to determine dielectric constant of the soil using the TLE and routine. This dielectric constant is used in the micromechanics equation to determine moisture content and dry density. The micro-mechanics equation is calibrated to each site and layer by adjusting the dielectric constant of solids, dielectric constant of water, and the specific gravity. Adjustments are made to these parameters so that the predicted moisture content and dry density (from manual TDR traces) are equivalent to the measured ground truth moisture content (taken at installation) and the measured ground truth dry density (reported in the LTPP database). The adjusted values for dielectric of solids, dielectric of water, and specific gravity are then used for subsequent moisture and density estimates for the site/layer combination. In

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essence, the micromechanics model is calibrated to every site/layer combination before it is used to generate moisture estimates for subsequent TDR traces. Because the TDR traces obtained during installation were measured manually, they required digitization to obtain actual data points for use in the routine. Data Thief Ш was used to digitize the manual TDR traces into engineering data points.[14] The digitized TDR trace provided easily identifiable data points including the inflection data points in which to calculate the dielectrics. Figure 19 shows an example of a manually measured TDR trace and its corresponding digitized TDR trace. Based on the digitized data points, the dielectric constant, conductivity, and reflectivity were calculated using the TLE and the SID method.

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Sources of Ground Truth Dry Density and Moisture Content To calibrate the dielectric contents of soil components and specific gravity, the measured dry density and VMC were required at each TDR location for all the SMP sites. Moisture content measured during installation was reported in the SMP Installation Reports and was given in terms of gravimetric moisture content. Equation 18 was used to convert the gravimetric values to VMC for use in the calibration process. Because in situ dry density data was not always available from the SMP Installation Reports, information was taken from multiple locations within the LTPP database. The following sources were queried to acquire the information: • • • • • • • •

SMP Installation Report (priority 1) SMP Installation Report – I07 form (priority 2) SMP Installation Report – S04 form (priority 3) SMP Installation Report – I05 form (priority 4) LTPP database table TST_ISD_MOIST (priority 4) LTPP database table TST _SS08 (priority 5) LTPP database table INV_SUBGRADE (priority 6) Appendix C of “Analysis of Time Domain Reflectometry Data From LTPP Seasonal Monitoring Program Test Sections – Final Report” [1] (priority 7)

The dry density of the highest priority source was used if more than one source provided dry density information.[7] Additionally, these dry densities were adjusted based on depth, as described in the following section.

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United States Department of Transportation

Adjustment of Dry Density Although the in situ gravimetric moisture contents were measured for each TDR depth, only a single dry density was reported for each layer type. It is known that dry density is influenced by the depth below the surface. Therefore, adjustments to the reported dry density values were required to reflect conditions at each TDR depth. Additionally, it was observed that dry densities and measured moisture contents resulted in unreasonable phase diagram volumetrics. In these cases, adjustments were made to correct for negative air voids in the soil. The following procedure was followed to adjust the reported dry densities: Step 1. Soil Component Volume and Porosity Calculation Using the measured gravimetric moisture content and reported dry density, the volume of each component and porosity of soil was calculated using equations 32, 34, and 35.

(33) (34)

(35)

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Where: θw = volumetric moisture content (%) θs = volumetric solid content (%) θa = volumetric air content (%) Porosity, defined in figure 20, can be calculated as:

(36) Where: n = porosity of soil

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Step 2. Adjust Porosities, Densities, Volumes of Soil Components Based on Depth Each layer has a single porosity, but due to the assumption that dry density varies as a function of depth, the values of porosity will also vary accordingly within each layer. Therefore, all porosities were adjusted based on vertical location using the following equation.

(37) Where: i = number of TDR placed at each layer n´i = recomputed porosity of ith TDR depth at each layer (%) zi = depth of ith for each layer TDR from surface Z0 = depth of last TDR for each layer from surface (Z0 > zi) Equation 37 is a general rule useful for checking the consistency of 10 densities and moisture contents based on the assumption porosities should decrease with depth. Figure 21 is provided to illustrate Z0 and zi in this adjustment process. Using the recomputed porosity values, the dry density and volumetric contents of solids, water, and air were recalculated for each TDR using the following equations.

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(38)

(39)

Figure 21. Diagram. Profile of TDR and depth at each layer

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(40)

(41) Where: = recalculated dry density using n′i = recalculated volume of water, solids, and air (%)

Step 3. Air volume check and dry density adjustment The air volume in a soil mixture cannot be less than zero but could be equal to zero if the soil is fully saturated. This condition is defined in terms of the porosity, gravimetric moisture content, and specific gravity:

(42) Which can be defined as:

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(43) If the air volume recalculated in step 2 was less than zero, it was assumed that the soil was fully saturated and that the air volume was zero:

(44) Thus, the porosity was adjusted with equation 43 to achieve an air volume of zero:

(45) Where: = adjusted porosity for soil having negative air volume Using the adjusted porosity, the dry density was also adjusted using equation 46. (46)

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Where: = adjusted dry density for soil having negative air volume The volumes of water and solid were also recomputed using the adjusted dry density : value

(47)

(48)

(49) Where:

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=

adjusted volume of water, solids, and air

This adjustment was only performed if the air volume was found to be less than zero. If the air volumes at TDR probes were larger than zero, the porosity and dry density determined from step 2 were utilized in the calibration process. As an example, table 13 shows the adjustment process of sections 331001 and 533813. TDR sensor numbers 4 and 5 for section 331001 and numbers 3, 4, and 5 of section 533813 had negative values of air volume based on step 2 calculations. After applying equation 44 and 45, the dry densities were adjusted and the volumes of air were converted to zero. The dry densities of all other TDR sensors remained at the values calculated in step 2 because their air volumes were larger than zero. The final dry densities and VMC were placed in the fields of DRY_DENSITY and VOLUMETRIC_MOISTURE_CONTENT, respectively, in the MICROMOIST_SMP_TDR_CALIBRATE table.

Calculation of Calibrated Values Using the dielectric constant (determined from the manual TDR trace taken at installation) and the ground truth measured moisture content and dry density, ε1, ε2, and Gs values were calculated. The value of ε3 was defined as 1.0. The calibrated dielectric constants of solids and water ranged between 3 and 4.5 and 78 and 82, respectively.

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Table 13. Dry density adjustment of Sections 331001 and 533813 Section

331001

533813

TDR No 1 2 3 4 5 6 7 8 9 10 1 2 3 4 5 6 7 8 9 10

Layer Type Base Base Base Subbase Subbase Subgrade Subgrade Subgrade Subgrade Subgrade Subbase Subbase Subbase Subbase Subbase Subbase Subgrade Subgrade Subgrade Subgrade

w 2.55 2.16 3.75 10.75 11.00 9.73 6.16 5.85 6.99 7.89 12.20 12.90 16.00 18.90 15.70 13.20 14.90 14.80 13.20 14.90

γd

Gs

2.15 3

2.695

2.10 5

2.647

1.85 8

2.647

1.88 5

2.734

1.82 1

2.717

θw 0.05 0.05 0.08 0.23 0.23 0.18 0.11 0.11 0.13 0.15 0.23 0.24 0.30 0.36 0.30 0.25 0.27 0.27 0.24 0.27

Step 1 θs θa 0.80 0.15 0.80 0.15 0.80 0.12 0.80 -0.02 0.80 -0.03 0.70 0.12 0.70 0.18 0.70 0.19 0.70 0.17 0.70 0.15 0.69 0.08 0.69 0.07 0.69 0.01 0.69 -0.05 0.69 0.01 0.69 0.06 0.67 0.06 0.67 0.06 0.67 0.09 0.67 0.06

n 0.20 0.20 0.20 0.20 0.20 0.30 0.30 0.30 0.30 0.30 0.31 0.31 0.31 0.31 0.31 0.31 0.33 0.33 0.33 0.33

n'' 0.19 0.19 0.18 0.20 0.20 0.28 0.28 0.28 0.27 0.27 0.30 0.30 0.29 0.29 0.28 0.28 0.31 0.31 0.30 0.30

γd ′ 2.18 2.19 2.21 2.13 2.13 1.90 1.91 1.91 1.93 1.94 1.91 1.92 1.94 1.95 1.96 1.97 1.88 1.88 1.90 1.91

Step 2 θw ′ 0.06 0.05 0.08 0.23 0.23 0.19 0.12 0.11 0.13 0.15 0.23 0.25 0.31 0.37 0.31 0.26 0.28 0.28 0.25 0.28

θs ′ 0.81 0.81 0.82 0.80 0.80 0.72 0.72 0.72 0.73 0.73 0.70 0.70 0.71 0.71 0.72 0.72 0.69 0.69 0.70 0.70

θè′ 0.13 0.14 0.10 -0.03 -0.04 0.10 0.16 0.17 0.14 0.12 0.07 0.05 -0.02 -0.08 -0.02 0.02 0.03 0.03 0.05 0.01

n" 0.19 0.19 0.18 0.22 0.23 0.28 0.28 0.28 0.27 0.27 0.30 0.30 0.30 0.34 0.30 0.28 0.31 0.31 0.30 0.30

γd ′ 2.18 2.19 2.21 2.06 2.05 1.90 1.91 1.91 1.93 1.94 1.91 1.92 1.90 1.80 1.91 1.97 1.88 1.88 1.90 1.91

Step 3 θw ′ 0.06 0.05 0.08 0.22 0.23 0.19 0.12 0.11 0.13 0.15 0.23 0.25 0.30 0.34 0.30 0.26 0.28 0.28 0.25 0.28

θs ′ 0.81 0.81 0.82 0.78 0.77 0.72 0.72 0.72 0.73 0.73 0.70 0.70 0.70 0.66 0.70 0.72 0.69 0.69 0.70 0.70

θa′ 0.13 0.14 0.10 0.00 0.00 0.10 0.16 0.17 0.14 0.12 0.07 0.05 0.00 0.00 0.00 0.02 0.03 0.03 0.05 0.01

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Table 14. Calibrated values of Sections 331001 and 533813 Section

331001

533813

TDR No 1 2 3 4 5 6 7 8 9 10 1 2 3 4 5 6 7 8 9 10

TDR Depth 0.362 0.518 0.683 0.819 0.953 1.121 1.276 1.438 1.740 2.045

Layer Type Base Base Base Subbase Subbase Subgrade Subgrade Subgrade Subgrade Subgrade

Soil Type Gravel Gravel Gravel Sand Sand Sand Sand Sand Sand Sand

Measured Values w γd θ 2.55 2.153 5.49 2.16 2.153 4.65 3.75 2.153 8.07 10.75 2.105 22.63 11.00 2.105 23.16 9.73 1.858 18.08 6.16 1.858 11.45 5.85 1.858 10.87 6.99 1.858 12.99 7.89 1.858 14.66

Calibrated Values ε1 ε2 ε3 Gs 3.90 80.06 1.0 2.695 3.89 80.06 1.0 2.694 3.92 80.07 1.0 2.695 4.08 80.02 1.0 2.647 4.07 80.02 1.0 2.647 4.05 80.01 1.0 2.647 4.03 80.00 1.0 2.647 4.03 79.97 1.0 2.646 4.03 79.96 1.0 2.646 4.01 79.96 1.0 2.647

0.357 0.505 0.660 0.810 0.962 1.116 1.255 1.415 1.721 2.020

Subbase Subbase Subbase Subbase Subbase Subbase Subgrade Subgrade Subgrade Subgrade

Sand Sand Sand Sand Sand Sand Sand Sand Sand Sand

12.20 12.90 16.00 18.90 15.70 13.20 14.90 14.80 13.20 14.90

4.03 4.04 4.07 4.06 4.05 4.05 4.07 4.09 4.10 4.06

1.885 1.885 1.885 1.885 1.885 1.885 1.821 1.821 1.821 1.821

23.00 24.32 30.16 35.63 29.59 24.88 27.13 26.95 24.04 27.13

80.12 80.12 80.11 80.14 80.13 80.11 80.12 80.13 80.13 80.13

1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0

2.735 2.734 2.735 2.735 2.732 2.734 2.717 2.717 2.715 2.718

ε1

Average Values ε2 ε3 Gs

3.90

80.06

1.0

2.695

4.08

80.02

1.0

2.647

4.03

79.98

1.0

2.647

4.05

80.12

1.0

2.734

4.08

80.13

1.0

2.717

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The fundamental assumption associated with the micromechanics and self consistent scheme is that each layer is statistically homogeneous. Therefore, one set of ε1, ε2, and Gs values were used for each test section/layer combination. That is, the same ε1, ε2, and Gs values were utilized to calculate moisture content and dry density for all TDR probes placed in the same layer. The ε1, ε2, and Gs values used were averages from all TDR traces in the layer. Table 14 shows the calibrated values and average values at each layer for LTPP sections 331001 and 533813 as an example.

Micromoist Input and Output Data Table

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As with all computational programs, a specific format of input data is required to process the TDR traces and compute the soil dry density and moisture content.

Input Tables The program needs the following three input tables: MICROMOIST_SMP_TDR_AUTO for TDR trace reading, MICROMOIST_SMP_TDR_DEPTHS_LENGTH for TDR depth information, and MICROMOIST_SMP_TDR_CALIBRATE for calibrated soil data. The first two tables are available directly from the LTPP database while the third was developed as part of this study. The program extracts the TDR trace point data from the MICROMOIST _SMP_TDR_AUTO table containing TDR sensor response waveforms. The measured waveform consists of 245 intervals and stored in the WAVP_1 through WAVP_245 fields. The distance interval between data points is recorded in the DIST_WAV_POINTS field and is either 0.01 or 0.02 m. This raw TDR trace data can be acquired from the LTPP database. Table 15 shows the field information included in the table. The table structure is required to match the SMP_TDR_AUTO table in the LTPP IMS database. Table 15. Field names and description of MICROMOIST_SMP_TDR_AUTO table Field Name SHRP_ID STATE_CODE CONSTRUCTION_ NO SMP _DATE TDR _TIME TDR_NO DIST _WAV_ POINTS WAVP_1 ~ 245

Description Test section identification number Numerical code for state or province Event number used to relate changes in pavement structure with other time dependent data elements Measurement date TDR measurement time (HHMM) ID number of TDR probe Distance between waveform points (meters) 245 data points defining TDR waveform

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Table 16. Field names and description of MICROMOIST SMP TDR DEPTHS LENGTH table Field Name SHRP_ID STATE_CODE CONSTRUCTION _NO INS TALL _DATE TDR_NO TDR_DEPTH TDR_PROBE_LENGTH

Description Test section identification number assigned by LTPP Numerical code for state or province Event number used to relate changes in pavement structure with other time dependent data elements Instrumentation installation date ID number of TDR probe Depth from pavement surface to TDR probe Actual length of TDR probe

Table 17. Field names and description of MICROMOIST_SMP_TDR_CALIBRATE table

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Field Name SHRP_ID STATE_CODE INS TALL _DATE TDR_NO TDR_DEPTH LAYER_TYPE SOIL_TYPE DRY_DENSITY VOLUMETRIC_ MOISTURE _CONTENT CONSTRUCTION _NO DIELECTRIC _SOILDS DIELECTRIC _WATER DIELECTRIC _AIR SPECIFIC_GRAVITY

Description Test section identification number assigned by LTPP Numerical code for state or province Instrumentation installation date ID number of TDR probe Depth from pavement surface to TDR probe at installation Type of sublayer at TDR probe installation Soil type of layer at TDR probe installation Measured dry density of soil at installation (g/cm3) Measured volumetric moisture content of soil at installation Event number used to relate changes in pavement structure with other time dependent data elements Calibrated dielectric constant value of solid Dielectric constant value of water (= 1.0) Calibrated dielectric constant value of air Calibrated specific gravity of soil

As shown in table 16, the MICROMOIST_SMP_TDR_DEPTHS_LENGTH table contains the physical characteristics of the TDR probes, including the installed depth below the pavement surface and probe length for each TDR probe at each site. The table links to the SMP_TDR_AUTO table using SHRP_ID, STATE_CODE, TDR_NO and CONSTRUCTION _NO to identify the depth of each TDR. This table is populated in the LTPP database. The table structure is required to match the SMP _TDR _DEPTHS _LENGTH table in the LTPP IMS database. The data contained in the MICROMOIST _SMP _TDR _CALIBRATE table are the calibrated dielectric constants of the soil components and specific gravity. The calibration was accomplished using the micromechanics and self-consistent scheme and the SID approach previously described. The calibrated values are used to calculate moisture content by linking SMP_TDR_CALIBRATE by STATE_CODE, SHRP_ID and TDR_NO fields.

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The installation date, TDR depth, and layer and soil types are obtained from the SMP installation report. Information included in this table is shown in table 17. Table 18. Field names and description of MICROMOIST_ SMP_TDR_AUTO_DIELECTRIC table Field Name SHRP_ID STATE_CODE CONSTRUCTION _NO SMP _DATE TDR _TIME TDR_NO INFLEC_A INFLEC_B SOIL _DIELECTRIC _CONSTANT SOIL _CONDUCTIVITY SOIL _REFLECTIVITY

Description Test section identification number Numerical code for state or province Event number used to relate changes in pavement structure with other time dependent data elements Measurement date TDR measurement time (HHMM) ID number of TDR probe First inflection point in TDR trace (meters) Second inflection point in TDR trace (meters) Computed dielectric constant of soil Computed conductivity of soil Computed reflectivity of soil

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Table 19. Field names and description of MICROMOIST_SMP_TDR_AUTO_MOISTURE table Field Name SHRP_ID STATE_CODE CONSTRUCTION_NO SMP _DATE TDR _TIME TDR_NO TDR_DEPTH LAYER _TYPE SOIL _TYPE SOIL _DIELECTRIC _CONSTANT DRY_DENSITY VOLUMETRIC_ MOISTURE _CONTENT GRAVIMETRIC_ MOISTURE _CONTENT ERROR _COMMENT

Description Test section identification number Numerical code for state or province Event number used to relate changes in pavement structure with other time dependent data elements Measurement date TDR measurement time (HHMM) ID number of TDR probe Depth from pavement surface to TDR probe at installation Type of sublayer at TDR probe installation Soil type of layer at TDR probe installation Computed dielectric constant of soil Computed dry density of soil Computed volumetric moisture content Computed gravimetric moisture content Assigned error code

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Output Tables Two tables are generated upon running the program: MICROMOIST _SMP _TDR _AUTO _DIELECTRIC and MICROMOIST_SMP_TDR_ MOISTURE. The dielectric constant, conductivity, and reflectivity parameters determined from the analysis of automated TDR traces are stored in the MICROMOIST _SMP _TDR _AUTO _DIELECTRIC table. The table structure is summarized in table 18. The dielectric constant values reported in this table are used to compute moisture content and dry density values. The MICROMOIST_SMP_TDR_MOISTURE table contains dry density, VMC, and gravimetric moisture content data computed from TDR traces. The dry density is used to convert moisture content from volumetric to gravimetric using equation 18. Table 19 shows the field name and descriptions in SMP_TDR_MOISTURE. The program was developed to produce quality data for the LTPP database. To this end, features were incorporated into the program to ensure quality. Additional measures were implemented for manual review, including a thorough program testing process during development. This will be described in the following chapter.

5. PARAMETER COMPUTATION AND QUALITY REVIEW

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To ensure the highest quality data were provided to FHWA for inclusion into the LTPP database, various QC measures were incorporated into the MicroMoist program. Manual review procedures were also developed and implemented as part of the data processing activities. This chapter provides details on all of the QC and quality assurance tools used in this process.

Internal Program Quality Control Features Due to the large quantity of data analyzed, MicroMoist was developed to process all TDR traces and compute parameters automatically, but additional consideration was given to unique data requiring user input to ensure the highest quality end product. For example, TDR traces not exhibiting a negative slope could not be analyzed using the proposed method. Also, some computed parameters, especially dry density, could be unreasonable. Therefore, a flagging function was developed to assign comment codes to the TDR traces exhibiting suspect characteristics and/or resulting in questionable computed parameters. The error codes are assigned in the ERROR_COMMENT field of the SMP _TDR _MOISTURE output table. An example of an uninterpretable TDR trace that did not exhibit a negative slope between the inflection points is shown in figure 22. These traces may be caused by abnormal TDR device operation or the environmental effects near TDR probes, such as temperature or very high salinity of the soil. Figure 23 provides an example of a TDR trace in which the first inflection point was not captured. The TLE can still be used to estimate dielectric constant from these traces. While the method can interpret dielectric constant using only a small portion of the TDR trace, the

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prediction error is greatly reduced as the portion of the TDR trace utilized in the computation increases. A check for these types of traces was included in the program. If the program could not capture a negative slope between the inflection points, the traces were flagged as uninterpretable TDR traces in the program. The number of the questionable TDR trace is displayed as “Dubious Trace” in the program display. Also, a comment code of “TDR_ERR” is assigned to the ERROR_COMMENT field in the SMP_TDR_MOISTURE table. The program was also designed with a visual feature to allow user review of all TDR traces. Every trace in the input tables can be visually reviewed by a user. This feature allows users to identify unique traces not detected by the automated checks, while also providing a visual verification of those traces that were flagged. As part of the viewing function, the user has the capability of modifying the ranges used in the TLE for cases where they were improperly identified by the program.

Figure 22. Graph. Uninterpretable TDR trace

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The measured ground truth values of dry density reported in the LTPP database were in the range of 1.3 to 2.5 g/cm3. Most of the dry densities calculated from the program were also within this range as well. However, the dry density values of some TDR traces were calculated to be less than 1.3 g/cm3, most likely due to unreasonably high moisture content or frozen soil material. In these instances, the program assigns a comment of “DD ERR” in the SMP TDR MOISTURE table. One of the key advantages of this computation process over previous methods is the calibration of the micromechanics model to site specific conditions and equipment. In order to calibrate the micromechanics model, ground truth measured moisture content and dry density were required. Without this information, the model could not be calibrated and accurate computations could not be generated. It was discovered that ground truth data were unavailable at five SMP sites installed on the Specific Pavement Study (SPS)-5 and SPS-9 in New Jersey. For these cases, a comment code of “CALI_ERR” is assigned to ERR_ COMMENT field. The error codes used to identify TDR trace inconsistencies are listed in table 20. Table 20. Error codes used in the program Description TDR trace does not have a negative slope. Calculated dry density is less than 1.3 g/cm3. Calibration data from installation activities are unavailable.

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Error Code TDR_ERR DD_ERR CALI _ERR

Figure 24. Graph. Shift zone in LTPP section 091803, TDR sensor No. 7

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Shift Zone in Trend Line between Dielectric Constant And Moisture Content Moisture content is expected to decrease as the dielectric constant is reduced. However, in a few TDR sensors, a shift in the VMC occurs even though the dielectric constant decreases, as illustrated in figure 24. The data trends in this figure are from LTPP section 091803. TDR sensor number 7 exhibits a shift in the relationship for dielectric constant values between 3 and 5. Also, the dry density values of the left side of the shift were a little higher than those of the right side. The shift is associated with the circumstances related to the calibration for the soil moisture content. This shift occurred on other sections as well.

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Soil-Water Characteristic Curve As the water content of the soil is reduced, the matric suction is increased as a result of the change of pore-water pressure in the soil-moisture system. The relationship between the matric suction and the water content of a soil is called the soil-water characteristic curve (SWCC) as shown in figure 25. As seen in figure 25, the SWCC has a transition zone at which the volumetric water content rapidly drops compared to the matric suction variation. This is particularly prevalent in sandy soils. The TDR sensors located in soils associated with a shift zone most likely have been calibrated with moisture data on the wet side of the SWCC. Figure 26 illustrates two densitymoisture conditions in the same soil. The wet condition shown in figure 26 (b) has higher VMC and lower dry density values than the dry condition, but the weight of solids is the same.

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Figure 26. Diagram. Diagrams of soil having different volume

Figure 27. Graph. Comparison of SWCC and VMC-DC trend

Figure 27 also shows the relationship between the SWCC and the VMC trend.

Recalibration for Shift Zone As seen in figure 27, when the calibration of a TDR sensor was carried out on the wet side, the higher dry density soil exhibits a lower dielectric constant but similar VMC because the volume of water was smaller (on a percentage basis) in the higher density material.

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As a consequence, any TDR trace containing a shift in the moisture content-dielectric constant trend indicates that an additional calibration needs to be carried out in order to determine the correct interpretation of the TDR trace over the full range of moisture contents. Because the LTPP database did not have additional ground truth data to perform further calibrations, the values in the transition zone were adjusted (and flagged) accordingly.

Post-Processing Quality Control Review

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Moisture content and dry density estimates generated from the program were plotted to review seasonal trends and variation with depth using pivot tables in Microsoft Excel. An example of moisture content seasonal trends can be found in figure 28. The pivot table configuration allowed large quantities of data to be reviewed relatively quickly, while the graphical nature made questionable or anomalous data readily identifiable. Problematic or frequently occurring trends in the data could also be easily recognized through the process. During the program development phase of the project, the pivot tables served as a critical part of the beta testing. The review provided valuable insight, identified issues with the software, and was an integral part of the debugging process. Multiple programming and testing iterations were conducted in completing the MicroMoist program.

Figure 28. Graph. Sample plot of moisture content seasonal trend

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The pivot tables were also used after MicroMoist was finalized to perform a 100 percent review on all computed moisture content and dry density estimates. Outliers and anomalous data identified were manually flagged in the final data submittal to FHWA. The QC measures incorporated into the program and the post-processing reviews were designed as a supplement to the LTPP database QC checks. Coupling the LTPP checks with the reviews conducted by the analysis team, the data provided to FHWA for inclusion into the LTPP database underwent a very rigorous QC process. Table 21. Description of SMP_TDR_CALIBRATE table for the LTPP IMS Database Field STATE_CODE SHRP_ID TDR_NO CAL _DRY _DENS ITY

SOURCE _DRY _DENSITY _T DR

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CAL_DRY_DENS ITY_ ADJUSTMENT_METHOD CAL _VOLUMETRIC_ MOISTURE _CONTENT CAL _SOIL _DIELECTRIC CAL _DIELECTRIC_ SOLIDS

CAL _DIELECTRIC_ WATER

CAL _DIELECTRIC _AIR

CAL _SPECIFIC _GRAVITY

Comment Numerical code for State or Province. Test section identification number assigned by LTPP. TDR sensor number. Retrieved from other LTPP tables or assumed. Code indicating source of CAL_DRY_DENSITY. 1 -SMP installation report 2-SMP installation report - I07 form 3-SMP installation report - S04 form 4-SMP installation report - I05 form 5-IMS table TST _ISD _MOIST 6-IMS table TST_S S08 7-IMS table INV_SUBGRADE 8-From Appendix C of “Analysis of Time Domain Reflectometry Data From LTPP Seasonal Monitoring Program Test Sections-Final Report” FHWA-RD-99- 115 Code indicating type of adjustment made to CAL_DRY_DENSITY. 1-Adjustment based on vertical variation 2-Adjustment based on vertical variation and air volume Measured VMC from samples taken during installation. Dielectric constant estimated from manual TDR trace taken at installation (from SMP Installation Report). Computed using measured VMC and TDR trace taken during installation. This is used to calibrate the micromechanics equation to the specific TDR sensor for subsequent VMC computations. Computed using measured VMC and TDR trace taken during installation. This is used to calibrate the micromechanics equation to the specific TDR sensor for subsequent VMC computations. Computed using measured VMC and TDR trace taken during installation. This is used to calibrate the micromechanics equation to the specific TDR sensor for subsequent VMC computations. Computed using dry density and TDR trace taken during installation. This is used to calibrate the micromechanics equation to the specific TDR sensor for subsequent density computations.

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Estimate of Error Unlike an empirical approach, which provides an error of estimate based on the fit of the regression equation, the micromechanics approach provides no such comparison. The micromechanics model is solved through an iterative process, which closes on a solution with an error of less than one percent. This, however, does not give a realistic error estimate on the resultant moisture content and dry density because there are multiple steps involved in the computation process (i.e., TLE and micromechanics model). The best estimate of error for this type of approach is achieved by comparing the computed moisture content solutions to those obtained from both the laboratory and field moisture tests. This was described in chapter 3 as part of the validation discussion. Data from Klemunes’ work with TDR data in soils from SMP sites were considered from laboratory tests. The field moisture tests used in this validation were obtained during a forensic analysis of LTPP-SMP test section 091803. The differences between the micromechanics solution and the laboratory tests are shown in figure 10, while those from the field tests are shown in figure 12. For most of the test results, the differences were less than five percent, with one set of test results indicating a difference of 10 percent. Based on this information, a conservative estimate of the possible error in the computations of the micromechanics approach is approximately 10 percent.

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6. LTPP DATABASE DELIVERY This chapter provides details on the data delivered for upload into the LTPP IMS database. Two tables were developed specifically to store data from this study: SMP_TDR_ CALIBRATE and SMP_TDR_MOISTURE. The SMP _TDR _MOISTURE table contains dielectric constant, moisture, conductivity, and reflectivity data estimated from automated TDR traces. A description of each field can be found in table 22. Table 22. Description of SMP_TDR_MOISTURE table for the LTPP IMS Database Field STATE_CODE SHRP_ID SMP _DATE TDR_TIME TDR_NO TLE _BEGIN TLE_END SOIL _DIELECTRIC

Comment Numerical code for State or Province. Test section identification number assigned by LTPP. Date TDR trace was obtained. Time TDR trace was obtained. TDR sensor number. Starting point of interval on TDR trace captured for use in the Transmission Line Equation. Ending point of interval on TDR trace captured for use in the Transmission Line Equation. Dielectric constant estimated from TDR trace (from SMP_TDR_AUTO).

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Table 22. (Continued) Field SOIL _CONDUCTIVITY SOIL _REFLECTIVITY DRY_DENSITY VOLUMETRIC_ MOIS TURE _CONTENT GRAVIMETRIC_ MOIS TURE _CONTENT

TDR_COMPUTATION_ COMMENT_CODE

Comment Conductivity estimated from TDR trace (from SMP_TDR_AUTO). Reflectivity estimated from TDR trace (from SMP_TDR_AUTO). Dry density estimated from SOIL_DIELECTRIC and calibrated micromechanics equation. VMC estimated from SOIL_DIELECTRIC and calibrated micromechanics equation. GMC estimated from VMC and DRY _DENSITY. Codes to describe traces that could not be interpreted. 1 -TDR trace uninterpretable due to lack of negative slope 2-Questionable data due to low dry density value 3-Calibration data from installation activities are unavailable 4-Outlier data based on time series analysis 5-Volumetric moisture content was in transition zone and was adjusted

7. DATA OBSERVATIONS As discussed in previous parts of this chapter, TDR trace data as well as computed parameters developed under this project were thoroughly reviewed. Observations discovered during the project are described in this chapter.

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Comparison between New and Existing Data Limited comparisons were made between data computed using the TLE micromechanics method and the moisture estimates computed previously using the apparent length method. A series of comparisons (discussed in chapter 3 of this book) were performed to validate the new procedure. Additional comparisons were made during the development phase to ensure that the MicroMoist program was working properly. In many cases, the same trends show up for both computational processes and the resultant estimates are very similar. However, in some cases, significant differences are present, typically in higher moisture content settings. In these situations, the TLE/micromechanics method results in a moisture content that is closer to the in situ moisture content (acquired during equipment installation) as compared with the apparent length method. This is expected because the micromechanics model was calibrated to the in situ moisture content at each site/layer. As an example, results for LTPP section 063042 from the apparent length approach and the TLE/micromechanics method can be found in figures 29 and 30, respectively. Also included in the figures are the in situ VMC obtained during equipment installation. As can be seen in figure 29, VMC from the apparent length approach ranged from 35 to 55 percent (with the majority of values falling between 35 and 39 percent). For some of the TDR sensors, the predictions are drastically higher than the measured in situ moisture content. The results from the TLE/micromechanics method shown in figure 30 correlate more closely with the measured in situ moisture content trends.

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Figure 29. Graph. Results from the apparent length approach for LTPP section 063042

Figure 30. Graph. Results from the TLE micromechanics method for LTPP section 063042

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Figure 31. Graph. Results from the apparent length approach for LTPP section 313018

Figure 32. Graph. Results from the TLE micromechanics method for LTPP section 313018

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Figures 31 and 32 provide similar information for LTPP site 313018. The data for both computational processes range from 5 to 22 percent with similar distributions. Differences between the two approaches are generally site specific and largely dependent on the measured in situ data. The TLE/micromechanics method is calibrated to the measured data and, therefore, yields estimates that are closer to the measured data as compared with the apparent length approach. The apparent length approach is a general empirical regression model that can vary significantly from ground truth data under certain circumstances.

Frost Effects Limited frost effects show up in the new data. In general, there is an expectation that the VMC values will decrease as the moisture in the ground freezes in both the wet and dry freeze regions. This can be seen in the values computed for site 274040. Where there is a distinct reduction in the volumetric moisture values during the winter months of 1993- 1994, 1994-1995 and 1996-1997. There were no measurements recorded during the winter of 1996 at that location. It has been documented that frozen ground results in a TDR trace that does not have a negative slope between inflection points (i.e., an “open trace”).[15] These traces cannot be interpreted using the TLE/micromechanics method. Therefore, TDR traces flagged as uninterpretable during the winter months are indicative of frost effects.

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Sources of Error in Calibration Data The ability to calibrate to measured in situ data is one of the key advantages of the TLE/micromechanics method. Computed parameter estimates are directly affected by measurement errors in the ground truth data. The in situ information came from limited soil tests performed during equipment installation. At that time, the apparent length approach was the accepted method for interpreting TDR traces to determine moisture estimates and was independent of the ground truth data. The soil was tested for in situ moisture content for general background information regarding the installation, not for calibration of moisture estimate algorithms. The procedure established for collection of the in situ moisture consisted of heating samples in an open pan over a propane stove in the field. The in situ dry density values were determined for each soil type based on a one point proctor test. Both of these tests have errors associated with them that directly affect soil parameters developed in this study. A very likely source of error associated with moisture content testing in the field is soil loss due to either exploding aggregate (caused by rapid heating) or loss of fines (blown away during heating and stirring). Loss of soil during the drying process will produce moisture content results that can be up to five percent higher than the actual moisture content. The dry density values used to calibrate the MicroMoist program often came from the one point proctor test performed on the soil samples taken during installation (when available). While the results from the one point proctor test provide reasonably accurate estimates of in situ densities, the findings are derived from disturbed samples, which can be another source of error. For some sites, dry density values reported were extremely high and

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not physically possible as they would result in a negative percentage of air voids. These cases were discussed in chapter 4 along with details on an adjustment procedure used to mitigate the problem. However, no correction was made for densities that were relatively low. These results were likely from deeper depths, where standard proctor densities would likely have provided more reasonable density values. Future endeavors utilizing TDR equipment to monitor in situ conditions should focus on obtaining more accurate ground truth moisture and density data for use in the calibration of the TLE/micromechanics method. As such, soil from each layer should be sampled from a second hole and taken to the laboratory for testing. The moisture content could then be determined using a standard moisture test. The density could be estimated for each layer from a standard proctor test based on the moisture content established for each layer. For the deeper layers the density used may be 90 to 95 percent of the standard proctor density, assuming the in situ densities were below the influence area of the normal construction process. The ideal approach would be to dig test pits and perform nuclear density tests on each layer as it is excavated. However, the costs of this approach may be prohibitive and could require placement of the TDR probes in the shoulder next to the traveled lane.

8. RECOMMENDATIONS FOR FUTURE RESEARCH

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This section provides recommendations on future research needed to improve and/or further the TLE/micromechanics approach to estimating soil parameters. These recommendations would provide complete validation of the process and improve the overall accuracy while reducing variability in the estimates.

Investigate the Effects of Soil Suction on the Composite Dielectric Constant As discussed in chapter 5 of this book, a shift was observed in the relationship between composite dielectric constant and VMC. This shift typically occurred at dielectric constant values below five. Upon investigation, the research team believed that this phenomenon was caused by soil suction influences. However, the data needed to fully examine this issue is not currently available. It is recommended that additional research be conducted to more fully investigate the effects of soil suction on the composite dielectric constant as it is used to compute moisture content using the micromechanics models used in this project. This would require laboratory evaluation of TDR traces in soils at different stages of the soil water characteristic curve.

Investigate the Use of Conductivity and Reflectivity As a result of this project, conductivity, reflectivity, and dielectric constant were computed and reported. Only the dielectric constant was used for estimating the VMC and dry density on this project. In some cases this seemed to lead to unrealistic values for the dielectric constant relative to the moisture content. While the resulting moisture content

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values were reasonable as compared to the ground truth calibration moisture content, the composite dielectric constant was very low relative to the moisture content estimate. It is likely that the soil reflectivity and conductivity information obtained from TDR traces would account for these anomalous data. It is recommended that further research in this area be conducted to fully document the relationship of all components of the TDR trace on soil parameters.

Investigate Repeatability of TDR Traces

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This project did not address the relative accuracy, variability, or repeatability of the computation process. Because the project dealt with existing data, there was no option available to obtain better information on the relative accuracy of the procedure other than to provide basic estimates from observations. It is recommended that future research be conducted to investigate the accuracy and repeatability of the micromechanics-based procedure used on this project. The relative accuracy of the procedure was tested against the existing data from the site installations, as well as the data from Klemune’s thesis data. [5] It is also recommended that more in situ information be collected and utilized to quantify the repeatability of the models. One such source of information would be from additional soil samples collected at the end of the TDR data collection sequence. This information could be used to compare estimates from the last TDR trace to ground truth data at a point in time other than during installation. In addition, it is recommended that repeated TDR traces be taken to determine the resultant variation in soil parameter estimates.

Sensitivity of Micromoist Program Output to Variation in Input Values The data needed to fully evaluate and document the sensitivity of the MicroMoist program were not available for this study. This would require a series of laboratory tests where moisture content and/or dry density is changed using a constant soil sample. The TDR traces from multiple conditions over a range of soil types and conditions could be used to fully document sensitivity. This information could also be compared to ground truth values derived from moisture content and dry density laboratory testing.

9. SUMMARY AND CONCLUSIONS TDR traces have been used to estimate the subsurface moisture content for unbound layers in pavement structures. In particular, the moisture content of the various roadway sublayers at SMP test sections were monitored with TDR instrumentation because it is relatively fast and accurate and provides a nondestructive in situ measurement. The TDR waveforms, however, do not provide moisture content estimates directly. In situ conditions of interest must be derived from the TDR waveforms and are largely dependent on the methodology used. However, it is clear that interpretation of electrically induced

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reflectometry depends not only on the material dielectric constant but also the reflectance and conductance attributes. Moisture parameters had been estimated from TDR traces in the LTPP database previously, but significant quantities of TDR data have been collected since the completion of the original study. Therefore, one objective of this current study was to develop soil parameter estimates from TDR waveforms not previously analyzed. An additional objective was to investigate new methodologies or improvements to existing processes for interpreting TDR waveforms. Based on the investigation conducted in phase 1 of the study, a new approach utilizing TLEs to compute dielectric constants from the TDR waveform and micromechanic models to estimate moisture and density parameters was proposed. This approach was approved by FHWA and was used to interpret 274,000 automated TDR traces in the LTPP database. This new approach for calculation of the VMC consists of four steps: Step 1: Calculate the dielectric constant, conductivity, and reflectivity from the TDR trace using the TLE. • •

The TLE uses the shape of the trace to provide a more complete estimate of the dielectric constant. The solution method is the SID, which can minimize the error between the actual measurement and the calculated measurement.

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Step 2: Given the moisture content and density data from the installation reports, along with the parameters calculated at step 1, backcalculate the permittivity of the solids and calibrate the micromechanics volumetric water model. •

This backcalculation is based on a theory of dielectric properties of composite materials from the micromechanics and self consistent scheme as follows:

(50) •

The dielectric constant of soil and water (ε1, ε2) and specific gravity of soil (Gs) are calibrated, based on the in situ information obtained during equipment installation, using the SID approach.

Step 3: Given the calibrated micromechanics volumetric water model, forward calculate the volumetric water content and the dry density of the soil for other times and seasons based on the TDR traces and the associated dielectric constant. • •

The self-consistent model was used together with the calibration constants ε1, ε2, and Gs to calculate soil dry density (γd) and VMC (θ ). Systematic error was removed through consideration of the effect of individual constituent soil dielectrics.

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Step 4: Compute the gravimetric moisture content using the VMC and dry density from step 3. The TLE method used to determine dielectric constant is able to consider the soil conductivity and reflectivity influence on the dielectric value. Additionally, the micromechanics models are calibrated to site-specific conditions and equipment using ground truth measured data. These two processes work together to minimize systematic errors in the resulting moisture and density estimates. An evaluation of the new approach was conducted by comparing moisture estimates to measured values using data from SMP Installation Reports, Klemunes’ thesis, and LTPP forensic studies. The estimates were relatively accurate and were all within 10 percent of the measured values. The previous LTPP interpretation procedures did not have a mechanism for estimating dry density for the soils represented by the TDR trace, but the new method provides the capability of estimating dry density values from TDR measurements. A key advantage to the new micromechanics-based procedure is that it incorporates the engineering properties associated with the TDR measurements, as well as the mechanical properties of the soils being measured. Beyond this, it makes use of the physical and electrical properties of the materials being measured. In order to quickly and efficiently compute soil parameters for the large quantity of records in the LTPP database, a new program, LTPP MicroMoist, was developed. The program utilized many of the same graphical and visual features as the MOISTER program. The new program was designed to calculate all components of the soil parameters automatically. Logic and reasonableness checks were incorporated into the program to ensure anomalous data were manually reviewed and verified. Data not passing established checks were flagged as part of the process. The program was designed so that quality took precedence over the computation efficiency and ensured that the highest quality data were obtained in a practical manner. External to the program, post-processing graphs were developed and used in beta testing and debugging of the program. These graphs were also used to perform a 100 percent review of the final set of computed parameters. Anomalous or outlier data were manually flagged in the dataset delivered to FHWA for inclusion into the database. As a result of this study, approximately 274,000 automated TDR traces were analyzed. Some were not interpreted due to questionable TDR trace characteristics or questionable results. The vast majority of those not interpreted were from the five sites in New Jersey where ground truth moisture content data were unavailable. The analysis team worked with FHWA contractors to deliver the data in the most efficient manner and provided table and field descriptions for their use. It is anticipated that the data will be available in the 2008 LTPP Standard Data Release.

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APPENDIX A. TRANSMISSION LINE EQUATION The new approach for calculating dielectric constant in this project utilizes the transmission line equation (TLE). The following describes the basic theories and concepts of electromagnetics and the TLE.

Maxwell’s Equations In the study of electromagnetics, the four vector quantities called electromagnetic fields, which are functions of space and time, are involved:[12] E D H B

= = = =

electric field strength (volts per meter, V/m) electric flux density (coulombs per square meter, C/m2) magnetic field strengths (amperes per meter, Am/m) magnetic flux density (webers per square meter, wb/m2)

The fundamental theory of electromagnetic fields is based on Maxwell’s equations governing the fields E, D, H, and B:

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(51)

(52) (53)

(54) Where: J = electric current density (Am/m2) Pv = electric charge density (C/m3) J and Pv are the sources generating the electromagnetic field. The equations express the physical laws governing the E, D, H, and B fields and the sources J and Pv at every point in space and at all times. In order to understand concepts of Maxwell’s equations, some definitions and vector identities are described. The symbol ∇ in Maxwell’s equations represents a vector partialdifferentiation operator as following,

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(55) Where xˆ, y ˆ , and zˆ= unit vectors along the x, y, and z axes If A and B are vectors, the operation ∇ × A is called the curl of A, and the operation ∇.B is called the divergence of B. The former is a vector and the latter is a scalar. In addition, if φ (x, y, z) is a scalar function of the coordinates, the operation ∇φ is called the gradient of φ. The operator as a vector is only permissible in rectangular coordinates. Some useful vector identities are as follows:[12] (56) (57) (58) (59)

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(60)

Conservation Law of Electric Charge The Maxwell equation (55) can be presented using the vector identity (57) and multiplying both sides by ∇ as follows:

(61) Being replaced with equation 54, the conservation law for current and charge densities is defined as the following:

(62) The conservation law means that the rate of transfer of electric charge out of any differential volume is equal to the rate of decrease of total electric charge in that volume. This law is also known as the continuity law of electric charge. In fact, to solve electromagnetic

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field problems, it is essential to assume that the sources J and ρv are given and satisfy the continuity equation.[12]

Constitutive Relations Constitutive relations can provide physical information for the environment in which electromagnetic fields occur, such as free space, water, or composite media. Also, they can characterize a simple medium mathematically with a permittivity, ε, and a permeability, μ, as follows: (63) (64) For free space such as air, μ = μ0 = 4π×10-7 H/m and ε = ε 0 = 8.85×10-12 F/m

Maxwell’s Equations for Time-Harmonic Fields

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Time-harmonic data is the large class of physical quantities that vary periodically with time. While physical quantities are usually described mathematically by real variables of space and time and by vector quantities, the time-harmonic real quantities are represented by complex variables.[12] A time-harmonic real physical quantity V(t) that varies sinusoidally with time can be expressed as follows: (65) Where: V0 = amplitude, ω = angular frequency ( = 2πf ) f = frequency of V(t) t = time φ = phase of V(t) Figure 33 illustrates V(t) as a function of time t.

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The V(t) can be expressed by using the symbol of Re { }, which means taking the real part of the quantity in the brace as follows:

(66) Hence, the derivation with respect to time can be expressed as

(67) So,

(68) As shown in equation 67, the time derivative ∂/∂t can be replaced by jω in the complex representation of time-harmonic quantities. Maxwell’s equations can be expressed with respect to the complex representations for the time-harmonic quantities as follows:

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(69)

(70) (71)

(72)

Uniform Plane Waves in Free Space Given that electromagnetic fields are generated in free space by source J and ρv in a localized region, then, for electromagnetic fields outside the region, J and ρv are equal to zero and Maxwell’s equation can be expressed with free space constitutive relations of equations 63 and 64 as the following:[11]

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(73)

(74)

(75) (76) By taking the curl of (73) and substituting (74), the following can be obtained:

(77) The wave equation for E can be obtained with regard to vector identity (56) and equation 74 as follows:

(78) The wave equation (78) is a vector second-order differential equation. The simple solution is expressed as follows;

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(79) From equations 78 and 79, the following is obtained;

(80) The magnetic field H of the wave can be determined from equation 73 or 74:

(81) In equation 81, the factor

is known as the intrinsic impedance of free space,

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Figure 34. Graph. Electric field as a function of z direction at different times[12]

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The wave has the electric field E in the xˆ -direction and the magnetic field H in the yˆ direction and propagates in the zˆ -direction. Figure 34 shows the velocity of propagation with time in a sinusoidal wave. Therefore, the velocity of light in free space becomes:

(83) Where: ω = angular frequency k = propagation constant

Transmission Line Equation of Coaxial Transmission Line In the case that electromagnetic waves propagate in free space, the path of the wave is straight, and the intensity is uniform on the transverse plane. However, if the wave is guided along a curved and limited path, the wave is not uniform on the transverse plane and the intensity is limited to a finite cross-section. The finite structure transmitting electromagnetic waves is called a transmission line or waveguide. The wave can be transmitted along different types of waveguides: parallel-plate waveguides, rectangular waveguides, and coaxial lines. This study considers the coaxial lines, which are involved in TDR.

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Coaxial Lines The most commonly used transmission line to guide the electromagnetic wave is the coaxial line. The coaxial line consists of inner and outer conductors and an inner dielectric insulator. As shown in figure 35, a coaxial line has an inner conductor of radius, a, and an outer conductor of inner radius, b, insulated by a dielectric layer of permittivity, ε. Figure 36 presents the cylindrical coordinate system for the solution inside coaxial lines.

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Figure 35. Diagram. Coaxial line [11]

Figure 36. Cylindrical coordinate system [12]

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In the cylindrical coordinate system, coordinate ñ is the distance from the z-axis or length 0A, φ is the angle between 0A and the x-axis, and z represents the distance from the x-y plane. The three coordinates, ρ, φ, and z represent the point P and are expressed in terms of unit vectors, ρ ˆ, φ^ and zˆ.

Transverse Electric and Magnetic (Tem) Mode in a Coaxial Line In order to explain the fundamental mode on the coaxial line, it is necessary to consider the case where the inner radius, a, is close to the outer radius, b. When the coaxial line is cut along the x-y plane and unfolded into a parallel strip, the line can be illustrated as figure 33: From Figure 37, it is realized that the wave has the electric field E in the ρ ˆ -direction and the magnetic field H in the φ ˆ -direction and propagates in the zˆ -direction. Therefore, E and H can be expressed as follows:

(84)

(85)

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Where:

Since the E and H are transverse to the direction of wave propagation, the set of equations 84 and 85 is called the transverse electromagnetic mode (TEM) of the coaxial line.

Figure 37. Diagram. Coaxial line developed into a parallel-plate waveguide [12]

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Transformation Rules for Transmission Lines The following rules are for transforming the field quantities into network parameters.[12]

(86) Where: α1 = proportional constant Ct = integration path transverse to z

(87) Where:

α2 = proportional constant C0 = closed contour of integration The power relationship must hold:

(88)

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Where A = cross-sectional area of the line or waveguide

Transmission Line Equation The electric and magnetic fields E and H for a coaxial line in the TEM mode are:

(89)

(90) By applying the field equations to the transformation rule, the following equations can be defined as:

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(91)

(92)

Where: α1, α2 = calibration constants = applied voltage V0 a, b = inside and outside coaxial transmission line diameters (figure 13) If the calibration constants are one (α1= α2 = 1), equations 91 and 92 become:

(93)

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(94) Maxwell’s equations for electric and magnetic fields can be cast in the standard form of TLEs in terms of voltage and current, V and I, by using cylindrical coordinates. Maxwell’s two curl equations are defined as the following TLEs:

(95)

(96) By eliminating I from equation 95, a wave equation for the voltage V can be obtained as follows:

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V has two solutions of and . Each solution has an integration constant as a multiplier. V can be expressed by introducing two constants, V+ and V–, as:

(98) Where k = The amplitude of V+ represents a wave traveling in the positive z-direction and the amplitude of V– represents a wave traveling in the negative z-direction.

APPENDIX B. CHARACTERIZATION OF ERROR IN THE SID Relative to the least squares error associated with linear regression, assuming that yi = axi + b, then the error (ri) and the variance (ri2) at a point can be expressed as: (99)

(100)

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The total variance over all points n is:

(101) Setting the derivatives of the variance with respect to the coefficients a and b to zero gives:

(102)

(103) and yields two equations in the two unknown coefficients a and b:

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(104) Which expresses the definition of linear regression. In matrix form, where there are a number (i) independent variables xi associated with observations yj (dependent variable) that form a matrix of independent variables, xi,j can be expressed as: (105) Where: y = vector of j observations X = matrix of xi,j a = vector of unknown coefficients r = vector of regression errors Solving for a :

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(106)

(107)

(108) Where the second part of the above expression represents the residual regression error. Formulating this on the basis of partial derivatives:

(109)

(110) Differentiating with respect to the vector of unknown coefficients a and setting to zero:

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(111)

(112)

(113) Rearranging and solving for a :

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(114)

(115) Where again the second part of the above expression represents the residual regression error. Drawing the analogy to the system identification method (SID):

(116) Where

is the matrix of model predictions. Rearranging:

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[F] =

which is a rectangular sensitivity matrix (k × n); k = number of coefficients a

{β} =

which is the matrix of change in the model coefficient (n × 1)

= the matrix of change in the model prediction or the residual error (k × 1) Therefore:

(118)

(119) This yields a solution for the changes in the model coefficients based on the residual error in the model prediction.

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APPENDIX C. MICROMOIST USER’S MANUAL The user’s manual documents and describes the various features of the MicroMoist program. This will serve as a tool in the installation, navigation, and data processing components of the program. The program was developed to automate, to the extent practical, procedures in interpreting time domain reflectometry (TDR) traces to estimate soil parameters such as moisture content and dry density. MicroMoist was developed specifically for use on data stored in the LTPP database. The program requires input tables to be in a specified format. Other data can be analyzed in with MicroMoist as long as the input data are structured in accordance with this manual. This manual is divided into three main sections: • • •

Introduction to the Program Getting Started in the Program Program Features

Introduction to the Program In 1992, the Seasonal Monitoring Program (SMP) was initiated within the LTPP study in order to understand the environmental factors and the relationship with pavement

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performance. Sixty-four LTPP test sections were selected for the SMP according to pavement type, thickness, environment, and subgrade type. Several instruments were installed at each section to acquire data on in situ moisture content and temperature of sublayers, frost penetration, and depth to ground water. As part of this program, TDR technology was selected to measure in situ moisture content of pavement sublayers. TDR data were collected with 8-inch TDR probes developed by FHWA. Ten TDR probes were installed for each SMP test section at specified depths in the unbound base and subgrade layers below the outer wheel path. This program was developed based on the approach of using transmission line equations (TLE) and micromechanic models to estimate soil parameters from TDR traces. In this approach, the TLE is used to solve for the dielectric constant of the soil. The dielectric value was then employed in a micromechanics model calibrated specifically to each site and layer combination to determine soil parameters. MicroMoist allows users to view and process TDR traces based on this approach. MicroMoist extracts data from three input tables that are in Microsoft Access format and shows the smoothed trace on the screen. The trace shown on the screen is processed automatically using the algorithm implemented by the program, which identifies the inflection points and displays the points on the trace. The soil dielectric constant is determined using the data points on the TDR trace between the inflection points. The program can process TDR traces in the following ways: •

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•

MicroMoist automatically processes all the TDR traces collectively and shows the identified inflection points on the screen for review. For QC purposes, users can view all traces and have the option of adjusting the location of the inflection points. Changed inflection points automatically get recorded as new points on the trace and are hence used for the calculation.

The resultant soil parameters and supporting computations are provided in two Access database tables. The program was designed with features that make it an efficient tool for reviewing TDR traces and computing parameters of interest.

Getting Started in the Program Getting started with the new program is easy, especially if Windows XP operating system is currently installed on the target workstation.

System Requirements To run MicroMoist, the following minimum hardware and software requirements must be met: • • •

IBM-compatible Pentium processor 512 MB of RAM (1 GB recommended) 1 MB of available hard disk space, depending on the size of the TDR trace table

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Super video graphics adapter with at least 800*600 resolution and 256 colors Microsoft mouse or compatible pointing device Microsoft Windows XP operating system.

Installing and Running the Program The MicroMoist program is an executable file which does not need to be installed. The program can be run once the program files are copied to the appropriate drive.

Program Features MicroMoist was developed to allow users to view TDR traces as well as to automate the process of estimating soil parameters from the traces. In light of this, the following functions and features were incorporated into the program. MicroMoist is a powerful tool for the analysis of TDR traces; however, users must be familiar with TDR data collection principles, equipment, and techniques.

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Raw TDR Trace Data The program extracts raw TDR trace data points from an Access database into an Access table. This table should be the same format and structure as the SMP _TDR _AUTO table in the LTPP database. The table contains a flat representation of the TDR waveform sampled at 245 intervals and stored in the WAVEP_1 through WAVP_245 field. The table to be queried by MicroMoist can have any name. A sample table is provided with the program. This table must be provided with the following two tables (SMP_TDR_DEPTHS_LENTH and SMP_TDR_CALIBRATE) together in one Access database prior to running the program. TDR Depth Records The MicroMoist program also requires the SMP_TDR_DEPTHS_LENGTH table in the Access database to extract information on installation depths of TDR sensors. This table needs to be the same structure and format as the SMP _TDR_DEPTHS _LENGTH table in the LTPP database, which contains the physical information of the TDR probes such as the depths at which the probes are installed, their installation date, and the length of TDR probes. This table is used to link to SMP_TDR_AUTO to determine the depth corresponding to a TDR trace, using the STATE_CODE, SHRP_ID, TDR _NO, and CONSTRUCTION _NO. A sample table is provided with the program. This table must be provided with the raw TDR trace table and the following table (i.e., SMP_TDR_CALIBRATE) in one Access database prior to running the program. TDR Calibration Records MicroMoist also utilizes calibration information for each site and TDR sensor. A table named SMP_TDR_CALIBRATE is required in the Access database. The SMP _TDR _CALIBRATE table contains the calibrated dielectric constants of soil components and specific gravity. The calibrated values are required to calculate moisture content and dry density values by linking SMP _TDR _CALIBRATE by STATE_CODE, SHRP_ID, and TDR _NO fields. A sample table is provided with the program. This table must be provided

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with the raw TDR trace table and the SMP_TDR_DEPTHS_LENGTH table in an Access database prior to running the program.

Starting the Program When MicroMoist is started, the main TDR data processing window appears. The user must first open an Access database containing the raw TDR trace table as described in “Raw TDR Trace Data.” TDR Program Menus Menus in MicroMoist are context sensitive; both the available menus and their contexts change according to which part of the program is active. Menu features are briefly discussed in this section. The toolbar buttons provide shortcuts to all the menu items. The menu items and corresponding toolbar buttons are both described below. Menu bar: •

OPEN: Opens dialog box to select the database for processing.

•

EXIT: Ends the program, closing all the connections and the database.

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Toolbar: Contains icons in the order listed below: • •

OPEN: Open dialog box to select the database for processing. CLOSE: Ends the program, closing all the connections and the database.

•

Previous Trace: View previous TDR trace in database.

•

Go To: View a specific TDR trace based on location in the database.

•

Next Trace: View next TDR trace in database.

•

Show Trace: Refresh current TDR trace.

•

Change Inflection Points: Manually select inflection points on TDR trace.

•

Write Dielectric Output: Compute dielectric constant of TDR trace and store in database.

•

Write Moisture Output: Compute moisture content and store in database.

The screen contains a combo box, labeled “Dubious Records,” which lists TDR traces that do not pass criteria checks. Traces with positive slope or wrong inflection points fall into this category. Additional information is also provided on the screen, including SHRP_ID, STATE CODE, CONSTRUCION NUMBER, SMP DATE, TDR TIME, and TDR NUMBER, DIST_WAV of the TDR trace currently displayed.

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Output Table after Running Program Utilizing data from the input database tables described above, the program generates two output tables: SMP_TDR_AUTO_DIELECTRIC and SMP_TDR_ MOISTURE. These tables are automatically generated in the Access database containing the input data tables. The SMP_TDR_AUTO_DIELECTRIC table contains dielectric constant, conductivity, and reflectivity values computed from interpretable TDR records in SMP_TDR_AUTO. This table is generated by running the Write Dielectric Output option on the toolbar. The SMP_TDR_ MOISTURE table contains the dry density, volumetric moisture content, and gravimetric moisture content values computed from interpretable TDR traces in the SMP_TDR_AUTO table and is generated by running the Write Moisture Output option on the toolbar.

REFERENCES

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[1]

Jiang, Y. J. & Tayabji, S. D. (1999). Analysis of Time Domain Reflectometry Data from LTPP Seasonal Monitoring Program Test Sections – Final Report, FHWA-RD-99115, Federal Highway Administration. [2] LTPP SMP (CD-ROM). (2004). Version 1.2, Federal Highway Administration. [3] Rada, G. R., Elkins, G. E., Henderson, B., Sambeek, R. J. & Lopez, A. (1995). LTPP Seasonal Monitoring Program: Instrumentation Installation and Data Collection Guidelines, Report No. FWHA-RD-94-1 10, Federal Highway Administration. [4] FHWA-LTPP Technical Support Services Contractor. (2000). LTPP Manual for Falling Weight Deflectometer Measurements Operational Field Guidelines, Federal Highway Administration. [5] Klemunes, J. A. (1995). Determining Volumetric Moisture Using the Time Domain Reflectometry Response, M.S. Thesis, University of Maryland. [6] Klemunes, J. A. (1998). Determining Soil Volumetric Moisture Content Using Time Domain Reflectometry, FHWA-RD-97- 139, Federal Highway Administration. [7] Roth, K., Schulin, R., Flühler, H. & Attinger, W. (1990). Calibration of Time Domain Reflectometry for Water Content Measurement Using a Composite Dielectric Approach, Water Resource Research, Vol. 26, No. 10. [8] Topp, G. C., Davis, J. L. & Anna, A. P. (1980). Electromagnetic Determination of Soil Water Content: Measurement in Coaxial Transmission Lines, Water Resource Research, Vol. 16, No. 3. [9] LTPP Information Management System. (2002). Database Scheme and QC specification for SMP_TDR_MANUAL_MOISTURE Tables-Draft Final, Federal Highway Administration. [10] Das, B. M. (1985). Principles of Geotechnical Engineering, PWS Engineering: Boston. [11] Lytton, R. L. (1989). Backcalculation of Pavement Layer Properties, Nondestructive Testing of Pavements and Backcalculation of Moduli. ASTM 1026. (A.J. Bush III and G.Y. Baladi, eds.), American Society of Testing Materials: Philadelphia, pp. 7–38. [12] Shen, L. C. & Kong, J. A. (1983). Applied Electromagnetism, Brooks/Cole Engineering Division: Monterey, CA.

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[13] Hashin, Z. (1969). Theory of Composite Materials, in Mechanics of Composite Materials, Pergamon Press: Oxford, UK, pp. 201–242. [14] Tummers, B. (2005). DataThief III manual v.1 β, http://www.datathief.org/,. [15] Interpretation of Manual TDR Traces. (1998). Long Term Pavement Performance Program Directive SM-28, FHWA, August 7.

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In: Long Life and Quiet Pavement: Research and Issues ISBN: 978-1-60741-888-7 Editor: Gordon E. Daniels © 2010 Nova Science Publishers, Inc.

Chapter 4

LONG TERM PAVEMENT PERFORMANCE COMPUTED PARAMETER: FROST PENETRATION United States Department of Transportation

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FOREWORD In-situ data availability is vital to pavement engineering. As the pavement design process moves toward mechanistic-empirical techniques, knowledge of seasonal changes in pavement structural characteristics becomes critical. Specifically, frost penetration information is necessary for determining the effect of freeze and thaw on pavement structural responses. This chapter describes a methodology for determining frost penetration in unbound pavement layers and subgrade soil using electrical resistivity, moisture, and temperature data collected for instrumented Long Term Pavement Performance (LTPP) Seasonal Monitoring Program (SMP) sites. The report also contains a summary of LTPP frost depth estimates and a detailed description of the computed parameter tables containing frost penetration information for LTPP SMP sites. The report will be of interest to highway agency engineers as well as researchers who will use the LTPP frost penetration data to improve pavement design and analysis procedures. In addition to the information from the LTPP in service pavements, a method for monitoring frost depth presented in this chapter can be utilized by State highway agencies interested in monitoring freeze-thaw conditions in unbound pavement layers. Gary L. Henderson Director, Office of Infrastructure Research and Development

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1. INTRODUCTION Background

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Importance of Frost Penetration Information Knowledge of frost penetration beneath the pavement structure is critical for many pavement design, analysis, and management applications. Problems caused by frost include the seasonal change in the bearing capacity of soils brought by freezing and thawing. As subsurface temperatures decrease, the moisture in the unbound pavement layers freezes into ice that binds the aggregate particles together. Frost penetration leads to an increase in the strength and stiffness of the unbound pavement layers and subgrade soil. The process of ice formation also draws moisture into the freezing zone. When the frost thaws in the spring, the moisture increase in the soil can lead to weakened support for the pavement structure. Another mechanical process associated with frost is the volumetric change in frostsusceptible soils, referred to as frost heave, which can lead to vertical differential movements of the road and subsequent poor performance. This heaving of roadbeds out of vertical alignment and breaking of the pavement surface often complicates highway maintenance. Over the years, the National Oceanic and Atmospheric Administration (NOAA)[1] and Environment Canada[2] have developed and published the climatic maps containing historical frost penetration values, as well as the number of freeze-thaw cycles in the form of contour maps. These maps provide frost depth estimates for natural (uncovered) land in the United States and Canada. The frost penetration conditions under pavements may be different from that of exposed land surfaces. In addition, deicing salts may have an effect on frost penetration as they eventually dissipate into the soil. Seasonal Monitoring Program To provide the transportation community with the data needed to understand the magnitude and impact of diurnal, seasonal, and annual variations in pavement properties and responses, including the effects of frost penetration beneath pavement section, the Federal Highway Administration (FHWA) Long Term Pavement Performance (LTPP) program selected a number of test sites throughout the United States and Canada for the Seasonal Monitoring Program (SMP). The original SMP (hereto referred as SMP I) included a total of 65 test sections and lasted from 1992 to 1999. As a part of the SMP I experiment, 37 pavement test sections were instrumented with electrical resistivity (ER) probes to monitor the frost penetration in unbound pavement layers. In addition, these sections were instrumented with time domain reflectometry (TDR) and temperature probes. At the conclusion of SMP I, the LTPP team realized the need for additional monitoring of these sites and initiated the SMP II program. The objective of the SMP II monitoring was to continue providing the data needed to attain a fundamental understanding of the magnitude and impact of variations in pavement response and properties due to the separate and combined effects of temperature, moisture, and frost penetration. The SMP II included a total of 22 test sections and lasted from 2000 to October 2004. LTPP continued monitoring the ER trend as a part of the SMP II experiment at 12 test sites.

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To aid in the interpretation of the ER data, an interactive computer program called FROST was developed in the late 1990s, and the available data were analyzed (see FHWARD-99-088 for more information on FROST).[3] FROST used ER data (voltage, contact resistance, and resistivity) in conjunction with soil temperature data to determine the depth of frost penetration in unbound layers for the SMP sections. The results of frost penetration analysis are stored in two computed parameter tables in the LTPP database as follows:

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• •

SMP_FREEZE_STATE. SMP FROST PENETRATION.

The SMP_FREEZE_STATE table characterizes the freeze state as frozen or nonfrozen at each ER measurement depth. This information is useful for understanding or reevaluating the process by which the results presented in table SMP_FRO ST_PENETRATION were derived. The data in table SMP_FRO ST_PENETRATION translate the freeze state at each measurement depth into starting and ending depths of frozen layer(s). The SMP_FRO ST_PENETRATION table is the end product of the data analysis to determine the boundaries of frozen layers within the pavement cross section. These computed parameters tables contain information necessary analyzing the changes in pavement structural responses due to the seasonal changes in pavement layer properties. These tables were updated twice with the new batches of the processed data: the first upload was based on the July 1999 version of the LTPP data for SMP I sections, and the second upload included SMP II sections based on the July 2001 version of the LTPP data. With the completion of monitoring measurements on the SMP sections in October 2004, there was a need to complete the interpretation of measurements not previously interpreted and to add the results to the database. In addition, through previous interpretation of SMP ER and soil temperature data, it became evident that the accuracy of the LTPP frost predictions could be improved by adding thermodynamic analysis capability to estimate missing temperature readings and by cross- referencing ER trends with moisture and temperature changes.

Project Objective and Scope The objective of the current project was to update and complete the interpretations of frost penetration using measurements collected at the instrumented SMP sites. To achieve this objective, the project team was charged to review and enhance LTPP procedures for frost penetration determination. The enhanced procedures were subsequently used to critically review and flag questionable previous frost estimates and to complete the interpretation of frost depth in the unbound layers for new data and to update previous estimates. The project was divided into two phases. The objectives of Phase I were to assess the existing LTPP frost penetration analysis methodology and frost penetration results, propose enhancements to the LTPP frost penetration analysis process, and develop a detailed research plan that would include the proposed enhancements for the frost penetration determination procedures. The objectives of Phase II were to implement these procedures in a software

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research tool, conduct frost penetration analysis, and develop new LTPP frost predictions using SMP data.

Report Overview This final report documents the investigations performed during the study, describes the enhancements to the frost penetration analysis methodology developed, and summarizes the results of frost penetration estimates for LTPP SMP sections. Activities performed throughout the remainder of this chapter are discussed as follows: • • • • • • •

Chapter 2. Review of LTPP Frost Procedures and Assessment of Previous Estimates. Chapter 3. Review of Advances in the State of Knowledge in Frost Penetration Analysis. Chapter 4. Enhanced Methodology for LTPP Frost Determination. Chapter 5. Implementation of the Enhanced Frost Analysis Methodology. Chapter 6. LTPP Data Used for Frost Determination. Chapter 7. Frost Penetration Analysis Results. Chapter 8. Summary and Recommendations.

In addition, the following two appendices are provided with the report: Appendix A. E-FROST User’s Guide. Appendix B. List of Inputs to the EICM Program.

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• •

Figure 1. Illustration. LTPP SMP instrumentation layout.[4] Long Life and Quiet Pavement: Research and Issues : Research and Issues, Nova Science Publishers, Incorporated, 2010. ProQuest Ebook

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2. REVIEW OF LTPP FROST PROCEDURES AND ASSESSMENT OF PREVIOUS ESTIMATES LTPP SMP Directives and Experiment Design To obtain a better understanding of the early LTPP frost depth determination procedures, the LTPP reports, SMP directives, software, and other literature relating to detection of frost in unbound pavement layers were obtained and reviewed in detail. In addition, a coordination meeting took place between the Data Analysis Technical Support (DATS) team, FHWA/LTPP team and regional service centers, and Technical Support Services Contract (TSSC) representatives. The review included SMP installation/de-installation reports, the procedures and equipment used to collect data needed for the interpretation of LTPP ER and TDR data, and the quality control (QC) procedures used to evaluate the SMP data prior to upload into the database, all of which include the following documents: (See references 3, 4, 5, 6, 7, 8, and 9.) • • • • •

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• •

Determination of Frost Penetration in LTPP Sections, Report No. FHWA-RD-99088. FHWA, LTPP Seasonal Monitoring Program: Instrumentation Installation and Data Collection Guidelines, Report No. FHWA-RD-94-1 10. FHWA, LTPP Guidelines for SMP Phase II Equipment and Instrumentation Installation, SM-35. FHWA, LTPP SMP Phase II Monitoring, SM-31. LTPP Seasonal Monitoring Program SMP II Equipment Installation/De-Installation Reports prepared by LTPP Regional Contractor Offices for individual sites. Computed Parameters: Freeze/Thaw Monograph for LTPP. Publication No. FHWARD-98–1 77. FHWA, LTPP Information Management System, IMS Quality Control Checks.

In the SMP I experiment, 37 test sites were instrumented to measure ER, moisture content, and temperature in the unbound pavement layers (base and subbase) and the upper layers of subgrade. The LTPP SMP instrumentation layout is shown in figure 1. The techniques, equipment, and schemes of data collection under the SMP are described in detail in the LTPP Seasonal Monitoring Program: Instrumentation Installation and Data Collection Guidelines, Report No. FHWA-RD-94-1 10.[4] This section of the report provides a summary of how temperature, moisture, and ER data are collected and their relevance to frost penetration in pavement layers.

Electrical Resistivity Measurements The electrical resistivity probes used in the initial SMP program were developed by the U.S. Army Corps of Engineers’ Cold Regions Research and Engineering Laboratory (CRREL). The probes were installed to monitor the freeze state in the unbound pavement layers and the top subgrade layers. Each resistivity probe consists of 36 metal wire electrodes spaced 51 mm (2 inches) apart on a solid polyvinyl chloride (PVC) rod 1.9 m (73 inches) long. The top of the resistivity probe was installed approximately 50 mm (2 inches) below the

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bottom of the lowest bound pavement layer. The weakness with this multiplexer was that there was no reference to check the voltage outputs recorded. In the SMP II experiment, the CRREL multiplexer was replaced with an ERB20 multiplexer, manufactured by ABF Manufacturing, Inc. This multiplexer provides an input voltage at the start of each cycle and reference voltage through a 100k resistor at the completion of the cycle. The electrical resistivity technique is based on the fact that the bulk resistivity of a soil increases dramatically when the soil freezes. Electricity is conducted exclusively by the pore water contained in the soils because the soil minerals and air voids are nonconductive. The electrical resistivity of frozen water is much higher than that of liquid water, and this difference is used to differentiate between frozen and unfrozen soil. However, if water content is low, or if the water phase is discontinuous, the difference in electrical resistivity between the frozen and unfrozen soil is difficult to detect reliably. For SMP I, the automated and manual resistivity profiles were collected at the time of the Falling Weight Deflectometer (FWD) data collection to evaluate changes in layer stiffness based on the soil properties. As a result, only limited ER measurements were taken at the time of FWD data collection for the majority of LTPP sites: once a month or less every other year for SMP I sites and six months a year for SMP II noncontinuous sites. During the SMP II experiment, more extensive ER data were collected at selected continuous monitoring sites. The challenge working with ER data is that the majority of data were not collected continuously, except at a few SMP II sites that were set up for continuous monitoring. Sparse measurements make it difficult to capture the beginning and ending of freezing and thawing periods. Changes in ER equipment and measuring techniques also created challenges when comparing the values collected during the SMP I and SMP II experiments. For the SMP I experiment, ER data were stored in the following tables: • • •

SMP_ERESIST_AUTO. SMP_ERESIST_MAN_CONTACT. SMP ERESIST MAN 4POINT.

Since the launch of the SMP II program, the collection, processing, and storage of ER data for SMP II sites has been modified. The SMP II ER data are collected using different continuous automatic equipment and are stored in the following tables: • •

SMP_ERESIST_ABF_REF_VA— Applied voltage and resistance voltage values measured on the internal reference resistor used in ABF multiplexer. SMP_ERESIST_AUTO_ABF—Resistance voltage and computed resistance for ABF type resistivity probe.

The sites that were moved from the SMP I experiment to the SMP II experiment have ER data collected prior to 2000 in the old ER data tables and ER data collected after 1999 in the new data tables. In addition, manually collected ER data are stored in the tables used in SMP I.

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Moisture Measurements The volumetric moisture content (VMC) is determined using TDR probes placed at approximately 10 depths in the unbound base, subbase (if present), and subgrade layers. The VMC represents a ratio of the volume of water to the total volume (soil solids + water + voids). The probe closest to the pavement surface was installed at the mid-height of the highest unbound layer unless that layer was more than 300 mm (12 inches) thick, in which case the probe was installed 150 mm (6 inches) below the top of the layer regardless of thickness. The next seven probes were installed at 1 50-mm (6-inch) depth intervals, and the two deepest probes were installed at 300-mm (12-inch) depth intervals, thereby placing the deepest probe approximately 1.8 m (6 ft) below the top of the highest unbound pavement layer. The data collected with the TDR instrumentation are used to determine the dielectric constants for the soil. The volumetric moisture content is then computed using regression equations relating the dielectric constant to moisture content, which are discussed in Report No. FHWARD-99-1 15.[10] The results from the recently completed LTPP data analysis study LTPP Computed Parameter: Moisture Content, Report No. FHWA-HRT-08-030,[22] contain computed volumetric moisture content values estimated based on the dielectric constant and properties of soil using calibrated micromechanics equation. These results are included in the LTPP table MP TDR MOISTURE. Since the dielectric constant for ice is significantly different than that for water, the water contents measured by the TDR probes during the frozen periods may reflect the presence of ice. Like the ER data, the majority of TDR data were not collected continuously, except at a few SMP II sites that were set up for continuous monitoring. Sparse measurements make it difficult to capture the beginning and ending of freezing and thawing periods. Temperature Measurements The temperature profile is measured by thermistors installed at 18 depths through pavement structure. The thermistors are permanently installed in a 0.25-m (10-inch) diameter hole located near the section end. The first three thermistors are embedded in the surface bound layer, and the rest are embedded in the base, subbase, and subgrade layers. The five thermistors closest to the pavement surface are spaced 75 mm (3 inches) apart. The rest are spaced 150 mm (6 inches) apart. Data from the first five thermistors are recorded hourly. Daily temperature statistics, including maximum, minimum, average temperature, and times of maximum and minimum temperature, are recorded for all thermistors in table SMP_MRCTEMP_AUTO_DAY_STATS. Subsurface temperature measurements are taken every day, providing a complete picture of temperature changes in subsurface layers throughout the year. Seasonal temperature trends can be used to correlate temperature, moisture, and ER data. From these correlations, it is possible to establish freezing and thawing temperatures, freezing isotherm, and the freeze state of the soil for a given SMP section.

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Table 1. LTPP Section with Previous Frost Depths Estimates STATE_CODE 4 8 9 16 18 20 23 24 25 27 27 27 27 30 30 31 31 32 32 33 36 36 39 39 42 46 46 48 49 49 50 56 83 83 87 89 90

SHRP_ID 1024 1053 1803 1010 3002 4054 1026 1634 1002 1018 1028 4040 6251 0114 8129 0114 3018 0101 0204 1001 0801 4018 0204 0901 1606 0804 9187 1077 1001 3011 1002 1007 1801 3802 1622 3015 6405

SMP I Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y

SMP II

Y Y Y Y Y

Y

Y Y Y

Y Y

Y

State Arizona Colorado Connecticut Idaho Indiana Kansas Maine Maryland Massachusetts Minnesota Minnesota Minnesota Minnesota Montana Montana Nebraska Nebraska Nevada Nevada New Hampshire New York New York Ohio Ohio Pennsylvania South Dakota South Dakota Texas Utah Utah Vermont Wyoming Manitoba Manitoba Ontario Quebec Saskatchewan

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Initial LTPP Frost Interpretation Methodology Previous LTPP frost penetration methodology is documented in FHWA, Determination of Frost Penetration in LTPP Sections, Report No. FHWA-RD-99-088.[3] This chapter was reviewed in detail to obtain a thorough understanding of the procedures used to generate the existing LTPP computed parameter tables with regard to frost depth in unbound pavement layers. The previous method used to determine SMP FREEZE STATE and SMP FROST PENETRATION is shown in the flowchart in figure 2. Upon review of the SMP I and II experimental designs and LTPP frost analysis methodology, the following shortcomings and potential future improvements were identified: •

•

•

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•

Evaluations of frost penetration were made only for the dates when ER measurements were taken. With the exception of a few SMP II sites, these early measurements were taken once a month or less frequently. Thus, ER data were insufficient to establish the frost penetration profile for the whole freeze season. ER time-series trends were difficult to interpret due to frequent unexplained fluctuations in ER values and sometimes counterintuitive trends (i.e., low ER in winter and high ER in summer). At the same time, temperature trends appeared to be very reliable and correlated well with changes in air temperature and with the Enhanced Integrated Climatic Model (EICM)-based subsurface temperature changes with time. Subsurface temperatures were considered in the frost analysis only when ER data were available. However, these temperatures were available for nearly every day of the year. More extensive use of the temperature data could have improved the accuracy of frost estimates. Moisture content data were not included in the FROST interactive procedure. Use of moisture data could improve the determination of the freeze state, especially at the beginning of the freezing and thawing periods.

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Previous LTPP Frost Estimates Previously estimated frost information stored in the SMP_FREEZE_STATE and SMP_FRO ST_PENETRATION tables was reviewed during the study. The estimates were available for 37 SMP I sections and 12 SMP II sections and are listed in table 1 for the period from 1994 to 2001. The primary method of reviewing the LTPP frost estimates was by examining the ER, moisture, and temperature data collected as part of the SMP study and then comparing the trends observed in these data with freeze estimates obtained from the LTPP database. During the review, the following potential data problems and drawbacks of previous methodology were identified: • • • • •

Limited ER data availability. Unexplained fluctuations in ER values. Questionable noncontinuous frost regions. Noninclusion of moisture data. Underutilization of temperature and moisture data.

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The results of review are discussed in detail in the following subsections.

Limited ER data availability The sparse ER data put limitations on the accuracy and validity of the frost estimates. The example in figure 3 demonstrates the limitation of the frost penetration estimates attributed to limited ER data availability. The example shows a comparison between frost predictions based on ER and temperature data for SMP II section 0114 in Montana for the 2000–200 1 winter season. The frost penetration profile based on ER probe measurements is laid over the freeze state predictions based on subsurface temperature profile, as shown in the graph’s legend. Blue “Freeze” cells indicate temperatures below -1 oC. Grey “No Freeze” cells indicate temperatures above 0 oC. Yellow cells indicate temperatures between 0 o and -1 oC. Burgundy cells indicate a freeze state based on ER data. As can be seen from the plot, ER data were collected almost daily during November 2000. Frost predictions show agreement between temperature-based and ER-based predictions for this period. However, no ER data were collected again until January 8, 2001. As a result, the LTPP database contains no frost penetration predictions for December 2000, while temperature data strongly suggest a freeze state up to 1 m (3.28 ft) in depth, as indicated by the blue region. After data collection on January 8, 2001, no ER measurements are reported until mid March 2001, completely missing the spring thaw period. Figure 4 shows a comparison of ER, temperature, and moisture trends for the same site, as evaluated 0.52 m (1.71 ft) below the pavement surface. ER and moisture data are reported on the left axis. ER data are normalized between 0 and 1 to provide better means for analysis of seasonal fluctuations. Temperature data are reported in degrees (o) Celsius on the right axis. The following can be observed from this figure: •

All three types of measurements show an “as-expected” trend—as temperature falls below 0 oC, ER values increase and moisture values decrease.

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Spring thaw is clearly defined by a sharp increase in moisture values. Temperature and moisture data are more complete compared to ER data, providing a better indication of freezing conditions in this case.

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Figure 3. Chart. Frost predictions for section 0114 in Montana

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Figure 5. Chart. Frost predictions for section 1028 in Minnesota. Fluctuations in ER Value

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Figure 5 shows frost predictions for SMP I site 1028 in Minnesota. While most ER-based frost predictions (marked as “Previous Freeze” on the plot) follow the temperature-based frost predictions, it is evident that ER-based frost estimates are more questionable when temperatures are between 0 oC and -1 oC (see yellow section of the plot). The state of soil may be in transition between frozen and unfrozen for these temperatures.

Fluctuations in ER Values Review of the ER data pointed to the instability in ER trends—ER values may go down during freezing temperatures and up during hot summer months, although the opposite trend is expected. Because the previous methodology relies heavily on the ER data, such ER trends may result in inaccurate frost estimates. Figure 6 illustrates the failure to predict frost penetration at lower depths where soil temperature remained below -1 oC for extended periods of time. The reasons for inaccurate frost predictions include subjectivity when establishing an ER threshold value and unexplained dips in ER values during the cold season. Figure 7 shows changes in ER, moisture, and temperature values with time at a depth of 1.01 m (3.31 ft). Examination of the temperature data in figure 7 indicates that freezing at that depth occurred during mid to late December. The freezing process was accompanied by a constant temperature around 0 oC for several days while heat loss took place. After that period, the soil temperature fell below 0 oC, indicating a freeze state. The soil remained frozen until mid March, when temperatures rose above 0 oC and moisture content increased. Moisture content values decreased sharply between December and April, also indicating a “Freeze” condition. The example in figure 7 shows high fluctuations in resistivity values taken in February and then in early March 2005. The ER values differ by over 80 percent, although temperature and moisture data indicate that the soil remained frozen for both dates.

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Figure 6. Chart. Frost predictions for section 0804 in South Dakota for 1994–1995 winter season

Figure 7. Chart. Comparison of ER, temperature, and moisture trends for section 0804 in South Dakota at 1.01 m (3.31 ft) depth

Further data review indicates that the accuracy of ER predictions had improved once the same sections became part of the SMP II continuous monitoring experiment. However, ERbased determination of frost penetration for temperatures just below the freezing point remained challenging.

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Noncontinuous Frost Regions There were eight sites with noncontinuous frost regions found in the LTPP database during the data review task. Each case with noncontinuous frost regions was reviewed. The following reasons were found that might have affected judgment when assigning noncontinuous frost regions: • • •

Missing subsurface temperature—decisions were based solely on ER measurements. Subsurface temperatures close to 0 oC—soil may be in a transition state. Drop in ER values relative to surrounding dates—sometimes ER values drop even when surrounding temperatures remain below freezing.

In all cases, assignments of freeze or no freeze conditions were highly subjective. Other noncontinuous frost layers could form as a result of thawing and refreezing of the top layers while a deep frozen layer remained in place until the end of the freezing period. Identifying areas of noncontinuous frost regions is difficult using either ER or temperature data. ER measurements can be ambiguous at the freezing isotherm. Temperature data are not adequate to identify noncontinuous frost regions because nonfrozen water between two frozen zones would be very near to 0 °C. To remove some subjectivity in these assignments, moisture content analysis could be added to the frost analysis algorithm.

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LTPP Data Review Conclusions Two conclusions have been drawn from reviewing the existing LTPP frost data. The first conclusion is that the previous values for SMP_FREEZE_STATE and SMP_FRO ST_PENETRATION are not describing the actual freeze conditions in the subsurface layers accurately. This conclusion is primarily derived from examining the previously derived LTPP frost data. The reasons are as follows: •

• • •

•

ER measurements for SMP I and SMP II noncontinuous sites are sparse and do not provide enough data to determine the length of the freeze period or freezing-thawing changes that take place during the winter season. In some cases, ER data are erratic and counterintuitive (high values in summer and low in winter or high/low values in one of three collected ER values). The existing interpretation methodology does not utilize changes in moisture content. Frost predictions were made only for the dates with ER data; dates with subsurface temperatures below freezing were not included in the analysis if ER measurements were not obtained on the same dates. Many difficulties arise in determining freeze conditions around the freezing isotherm when soil transitions between freeze and no-freeze states.

The second conclusion is that a more accurate determination of the freeze state of the soil is possible by using subsurface temperature and moisture data in addition to ER measurements more extensively and by incorporating thermodynamic modeling to fill the Long Life and Quiet Pavement: Research and Issues : Research and Issues, Nova Science Publishers, Incorporated, 2010. ProQuest Ebook

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gaps in measured temperature data. Thermodynamic modeling also could be useful for analyzing heat and moisture transfer processes that take place in subsurface layers, as well as assisting the analyst with frost predictions.

3. REVIEW OF ADVANCES IN THE STATE OF KNOWLEDGE IN FROST PENETRATION ANALYSIS Relevant literature was reviewed during Phase I of the project and is summarized in this chapter. The review included several published documents. (See references 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, and 21.) To improve the accuracy of frost predictions for the instrumented LTPP sections, alternative approaches to detection of frost in unbound pavement layers were investigated, including thermodynamic modeling of time-based changes in subsurface temperatures and changes in TDR traces. The key outcomes of this background review included the following recommendations to improve the accuracy of frost predictions for the instrumented LTPP sections: •

•

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•

Enhance current frost penetration methodology and accompanying FROST interactive program by integrating in-situ moisture content data from TDR measurements in frost penetration prediction and cross-reference changes in temperature, ER, and moisture to determine freeze state. Place more emphasis on analysis subsurface temperatures as these data were found to be most complete and reliable when comparing to ER and moisture data from SMP sections. Use thermodynamic modeling integrated into EICM to fill the gaps in measured subsurface temperatures.

Details are discussed in the following sections.

In-Situ Moisture Content from TDR Measurements Another viable method to identify frost regions is to use TDR data to identify the presence of ice by a decrease in moisture content when the soil is frozen. This method is detailed by Benson and Bosscher.[13] Moisture content in the unbound pavement layers and subgrade soil affects frost severity due to the physical phenomenon of moisture migration in response to freezing. Even when the temperatures fall below the freezing point of the contained water, frozen soil may contain both frozen and unfrozen water in varying proportions depending on temperature depression, specific surface area, and salt content. The presence of unfrozen water provides the opportunity for moisture to migrate vertically, resulting in formation and thickening of ice lenses. Ice lenses represent horizontal layers of solid ice that form below the ground surface, separating the soil above from the soil below to form noncontinuous frost regions. Ice lenses may damage the pavement structure due to the large vertical displacements known as frost

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heaves.[18] As the pore water freezes, the volumetric moisture content drops to a very low level wherever a frost condition exists and therefore serves as a cross-reference for frost depth analysis. (See references 15, 16, 17, 18, and 19.)

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Figure 8. Chart. Frost predictions for section 1026 in Maine

Figure 9. Chart. Comparison of ER, temperature and moisture trends for section 1026 in Maine

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Table 2. Freeze state evaluations using different data sources Date: ER: MC: T:

11/14/94 NF NF NF

12/12/94 NF NF NF

1/17/95 F F TR

2/14/95 F N/A F

3/6/95 NF F F

3/20/95 NF F/TR TR

4/3/95 NF NF NF

5/1/95 NF NF NF

Example Using Moisture Data in Frost Analysis The following example shows how moisture content (MC) data can improve the accuracy of frost predictions. As shown in figure 8, the SMP section 1026 in Maine experienced several periods of freeze-thaw during the 1994–1995 winter season. Light blue indicates that most subsurface temperature readings were taken between 0 oC and -1 oC, making freeze state prediction using ER values very challenging. At this temperature range, pore water may or may not have enough energy loss to freeze. Plus, soil salinity may affect the actual freezing isotherm value and depress it below 0 oC. ER measurements were taken on seven dates during that winter season, as shown in figure 9. On the same dates, TDR measurements were taken and moisture content was computed. Of the seven ER measurement dates, the freeze state of the soil was detected on only two dates (January and February measurements) based on the ER data. Based on the analysis of moisture content fluctuations, an additional measurement on March 6, 1995, indicated that the soil was in a frozen state. This date has corresponding low moisture content and subzero temperature values. A summary of freeze state determination using different data sources is shown in table 2.

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Enhanced Integrated Climatic Model The Integrated Climatic Model (ICM) was developed in the late 1980s to simulate temporal variations in the temperature, moisture, and freeze-thaw conditions internal to the pavement and their impact on key pavement material properties.[14] In FHWA-HRT-04079,[17] this program was recognized as the most comprehensive model addressing the effects of climate on pavements. As its name suggests, the EICM is an enhanced version of the ICM. It was used as the basis for considering seasonal variations in the MechanisticEmpirical Pavement Design Guide (M-E PDG). The EICM consists of three models addressing different aspects of climatic effects on the pavement: • • •

Climatic-Materials-Structures (CMS) model, developed at the University of Illinois.[19] Infiltration and Drainage (ID) model, developed at the Texas Transportation Institute.[20] Frost Heave and Thaw Settlement Model, developed by the CRREL.[21]

The EICM provides the capability to simulate temperature, moisture, and freeze-thaw conditions internal to the pavement structure as a function of time. The accuracy of the Long Life and Quiet Pavement: Research and Issues : Research and Issues, Nova Science Publishers, Incorporated, 2010. ProQuest Ebook

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predictions depends greatly on a proper selection of boundary conditions, climatic parameters, and material properties. The EICM engages a coupled heat moisture finite element/difference model. It models heat flow by considering climatic and solar inputs at the surface along with the deep ground constant heat source. These thermal boundary conditions are used in conjunction with the moisture content of the subpavement soils to model heat flow, the freezing state of the soil, and frost penetration accurately. The model is coupled in the sense that changes in moisture content affect the thermal properties of the unbound layers—an increase in the moisture content increases the heat capacity and thermal conductivity of the material. Moisture content in the unbound layer is affected by the thermal conditions when freezing occurs. The drying process in the unbound layer causes moisture to move to the freezing zone. This tool could be particularly useful for modeling subsurface temperatures when temperature data are not available for some dates or depths.

Example Using EICM model to predict missing temperature The EICM analysis algorithm provides enhanced options to fill in the gaps in partial or incomplete measured subsurface temperature data, including a temperature auto-correction option. The analysis starts with inputting pavement and unbound layer data from the LTPP database and historical climate measurements into the EICM program. After the initial program run, the EICM temperature predictions are compared to the measured temperature data. The detailed examination of the measured and predicted data gives further guidance on how the inputs can be refined. For example, the unbound materials may model as being wetter or drier than the initial inputs suggest. Adjustments to the moisture content present in the profile can be achieved by varying inputs into the soil water characteristic curves (SWCC) of each unbound layer or by adjusting the depth of the water table. These small refinements can bring the predicted and measured values into agreement. The auto-correction option is used to further improve predictions. Using this option, the temperature profile for each SMP site is modeled and calibrated against available partial field measured data on a daily basis, with the initial temperature profile being the previous day’s temperature reading. For each time step where temperature is known, the measured value will supersede and overwrite the predicted temperature, causing the measured and predicted temperatures to track exactly in line with one another. When measured data are missing for a time period, the EICM model will start in perfect agreement with measured data at the beginning of the time period. As the model steps through time increments, it no longer has measured data to correct to, and the predicted output represents the only understanding of what the temperature is. However, because of the agreement that was achieved in the initial modeling and accurate initial profile (corrected by the measured data), the EICM is capable of accurately bridging short gaps in the data. When measured data are once again available, it is possible to observe the error in the prediction and again correct the predicted data with LTPP measured data. Figure 10 illustrates the comparison between the model predictions and the LTPP field data before auto-calibration, and figure 11 illustrates the comparison after auto-correction calibration.

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Figure 10. Chart. Measured and EICM predicted temperatures for section 6251 in Minnesota at 0.8 m (2.6 ft) depth before auto-correction

Figure 11. Chart. Measured and EICM predicted temperatures for section 6251 in Minnesota at 0.8 m (2.6 ft) depth after auto-correction

4. ENHANCED METHODOLOGY FOR LTPP FROST DETERMINATION Overview The following outline the basis of the enhanced LTPP frost penetration methodology:

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United States Department of Transportation • •

• •

•

Include all three subsurface measurements (temperature, moisture, and electrical resistivity) collected by LTPP SMP program in freeze state determination. Place more emphasis on using subsurface temperatures for prediction of frost penetration, as these LTPP data were found to be the most complete, consistent, and reliable. Use the freezing isotherm as a threshold value to determine freeze or no-freeze state of the unbound materials. Use analysis of moisture and electrical resistivity trends for temperatures close to the freezing isotherm value, where available, to evaluate temperature-based frost predictions and make corrections as necessary. Use thermodynamic modeling to predict missing temperatures and to gain insights into the heat exchange processes in the unbound layers to aid in frost penetration determination.

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Determination of Freezing Isotherm In the LTPP frost penetration analysis, the freezing isotherm was used to define a threshold temperature value differentiating between the freeze and no-freeze states of unbound pavement layers. The official definition of frost condition provided by the National Snow and Ice Data Center (NSIDC) is the condition which exists when the temperature of earth-bound objects falls below freezing (0 oC) (http://nsidc.org/cgi-in/words/letter.pl?F). However, based on the soil type and salinity, this temperature could have been depressed below 0 oC, making frost determination based on temperature alone questionable at lowfreezing temperatures (0 oC to -1 oC). In such circumstances, changes in moisture and ER values were used to aid in freeze state determination. As soil temperature crosses over the freezing isotherm value, the following changes in moisture and ER values are expected: •

•

Transition from a no-freeze to freeze state—sharp decrease in moisture at the end of transitional period in wet soils. ER values are low before the beginning of freezing and high once the complete freeze occurs; ER readings can be ambiguous during the transition period. Temperature drops below 0 oC at the end of transition. Transition from freeze to no-freeze state—increase in the moisture and sharp decrease in ER values at the end of the freezing period. Temperature rises above 0oC at the end of transition.

Close examination of the LTPP data showed that no sites had strong or consistent evidence of the freezing isotherm being depressed below -1 oC. Based on these observations and considering the NSIDC frost definition presented at the beginning of this section, 0 oC was chosen as a default freezing isotherm for the analysis. To account for the possibility that the freezing isotherm could be below 0 oC, a step was added to the analysis procedure that required a manual review and assignment of a freeze state based on conclusions from temperature, ER, and moisture trends analyses for the periods of time with temperatures between 0 oC and -1 oC. This provision allowed assignment of nofreeze or transitional conditions even when temperatures were below 0 oC.

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Determination of Freeze State

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Freeze-thaw processes Frost forms in unbound pavement layers and subgrade when moisture is present in the soil and the temperature of the soil matrix falls below the freezing point of the contained water. When soil undergoes freezing or thawing, temperature stays constant at about the freezing/thawing point until the entire body of water is completely frozen or thawed. This physical process is known as the latent heat of fusion. The length of the constant temperature period varies with soil type, the amount of moisture in the soil, and the rate of change in air temperature. More saturated soils take longer to freeze. Granular materials are more likely to have a distinct freezing temperature, while fine-grained soils can have a considerable freezing range over which the soil water freezes. In the spring, sunshine and warm air temperatures result in a top-down thawing of the pavement system. The water released by the melting ice can be trapped by deeper, still frozen material, creating saturated or supersaturated conditions that weaken the pavement structure. The thawing process can take from several weeks to several months, depending on the type of soil and the ease with which the excess water can drain back to the water table. Freeze state assignment Close examination of daily thermistor readings in conjunction with the observation of ER and moisture trends were used to determine the freeze state of the unbound materials. The first-order approximation of the freeze state of the soil was determined by analyzing changes in subsurface temperatures with respect to the 0 °C freezing isotherm. For each site with subsurface temperature measurements, a frozen state of the soil was assigned for dates and depths with temperatures below 0 °C freezing isotherm. A no-freeze state was assigned to the soil for dates and depths with temperatures above 0 °C freezing isotherm. Following this initial freeze state assignment, a more detailed analysis was conducted for the dates and depths with temperatures that fell in the range 0 ° to -1 °C. In this analysis, in addition to temperature readings, changes in ER and moisture values were analyzed over time and through the depths to determine the freeze state of the soil. If analysis of ER and moisture trends did not provide evidence supporting either transitional or no-freeze state, the freeze state previously assigned using the 0 °C freezing isotherm was not changed; otherwise, a new freeze state was assigned. Table 3 provides a summary of expected trends in temperature, moisture, and ER measurements to support assignment of different freeze state conditions. Due to a limited availability of ER and moisture data for the dates of interest and sometimes due to inconclusive or unexplained ER and moisture trends, only a limited number of sites had the results of temperature-based freeze state prediction changed based on ER and moisture trend analysis, resulting in a limited number of transitional and no-freeze state assignments reported for temperatures at or below 0 °C. In addition, for some of the SMP I sites that had ER data available but no measured or predicted temperature and moisture data, freeze states were established based on the analysis of seasonal changes in ER trends. Freeze states were determined for the dates that corresponded to the historical winter months and had high ER values on a scale normalized from 0 to 1.

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United States Department of Transportation Table 3. Freeze state characteristics

Soil freeze state Frozen

ER trend High

TDR trend Low

Unfrozen

Low

High

Transitional

Unstable

Rapid change

Temperature trend Below freezing isotherm

Above freezing isotherm or above 0 °C Around freezing isotherm

Characterized by physical process Pore water is solid frozen. Ice lenses formed in frostheave susceptible soils Pore water is in a liquid state Pore water is transitioning between liquid and solid state or partially frozen

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Thermodynamic Modeling of Subsurface Temperatures Thermodynamic modeling of the pavement structure was included in the LTPP frost penetration analysis for two reasons. First, it provided means for small amounts of missing subsurface temperature data to be accurately interpolated from the measured data. Second, thermodynamic modeling based on measured temperatures was used to aid in understanding the physical processes that took place in the field. Thermodynamic modeling of the pavement structure was accomplished using EICM. The EICM’s temperature auto-correction option was used in the analysis of LTPP data. Using this option, the EICM-predicted temperature values for each day were auto-corrected based on actual measured thermistor readings. The temperature profile for each SMP site was modeled on a daily basis, with the initial temperature profile being the previous day’s temperature reading. If there were measured data for the following day, the EICM prediction were ignored. If measured temperature data were missing for the following day, temperature predictions considering all of the required inputs were made. Prior to this daily auto-correction, the site was modeled and the inputs were calibrated to give an accurate set of predictions using the following procedure: 1. Select model inputs for a specific site from the LTPP construction history, materials, and testing tables, along with the collected climatic data. 2. Run the model. 3. Compare these predictions to the actual measured values. 4. Calibrate the model by varying the initial parameters so that the EICM predicted temperature profile exactly matches the known measured profile. The secondary use of the EICM was to ensure that basic thermodynamic behavior was not violated in the course of determining frozen and thawed zones within the structure. For example, it is practically impossible for a soil to freeze to a depth of 2 m (6.56 ft) over a 24hour period. The amount of heat released from freezing such a large quantity of water could not escape from the pavement or ground.

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Figure 12. Chart. Frost depth and layers interpretation using E-FROST

Cautionary Note The thermodynamic modeling of subsurface pavement and soil layers can be an inexact science. Nonuniformity of materials, variable ground water tables, and other poorly defined inputs can cause considerable divergence between actual and predicted values. Careful modeling and selection of appropriate defaults can appreciably increase the prediction accuracy of thermodynamic programs but still will not yield accurate predictions for all cases.

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The auto- correction process is tedious and is based on the subjective analyst’s judgment in selection of unknown input parameters. Furthermore, the EICM requires an extensive list of site-specific inputs. Not all of the required input parameters were available in the LTPP database, and those that were available were not available for all SMP sites.

LTPP Frost Penetration Analysis Procedure The flowchart in figure 12 shows the step-by-step process used to determine freeze state and layers for unbound pavement layers and subgrade for each LTPP site included in this study.

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Additional Analysis Rules Upon a detailed data review, it became apparent that not all of the data were available for every measurement date and depth, and some of the trends based on the in-situ data were difficult to interpret, leading to subjectivity in assignment of freeze states by the analyst. To minimize the subjectivity of the frost estimates and to provide uniformity of the analysis procedures, a set of guidelines was developed and followed by the data analyst. During the data analysis phase, the following rules were followed when data were sparse or some of the measurements were ambiguous: 1. For each date and measurement depth that had at least subsurface temperature or ER data available, freeze state estimates were conducted using methodology presented earlier in the report. 2. If subsurface temperature measurements and ER data were missing for a portion of the winter season and there were sufficient LTPP data to estimate missing temperatures from EICM analysis, these estimated temperatures were used to evaluate freeze state. The source of the temperature in the SMP_FREEZE_STATE table was specified as estimated from EICM. 3. For measurement depths and/or dates where no in-situ data and no EICM-predicted temperature values were available to predict the freeze state, no freeze state determinations were made, even though frozen depths were reported for surrounding depths and/or dates. 4. For some SMP I sites that had ER data available but no measured or predicted temperature and moisture data, freeze states were determined based on the analysis of seasonal changes in ER trends. Freeze states were determined for the dates that corresponded to the historical winter months and have high ER values on normalized scale from 0 to 1. 5. If, for a particular date and depth, the soil temperature was above 0 oC, the freeze state was reported as N-unfrozen. 6. If, for a particular date and depth, the soil temperature was below -1 oC, the freeze state was reported as F-frozen. 7. If, for a particular date and depth, the soil temperature was below 0 oC, the moisture values were low, and ER values were high, the freeze state was reported as F-frozen.

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8. If, for a particular date and depth, the soil temperature was below 0 oC, the moisture values were low, and no ER values were reported, the freeze state was reported as Ffrozen. 9. If, for a particular date and depth, the soil temperature was below 0 oC, the ER values were high, and no moisture values were reported, the freeze state was reported as Ffrozen. 10. In the absence of moisture and ER data or when ER and moisture trends are inconclusive, the freeze state was reported as F-frozen for temperatures less or equal 0 oC. 11. If, for a particular depth, constant negative temperatures near 0 oC were observed over a few days, the freeze state was reported as T-transition and the following trends arose: • Constant negative temperature near 0 oC over a few days + continuous rapid increase in moisture + low ER at the end of transition (thawing process). • Constant negative temperature near 0 oC over a few days + continuous rapid decrease in moisture + high ER at the end of transition (freezing process). • Constant negative temperature near 0 oC over a few days + continuous rapid increase in moisture, No or ambiguous ER data (thawing process). • Constant negative temperature near 0 oC over a few days + continuous rapid decrease in moisture, No or ambiguous ER data (freezing process).

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Data Normalization and Interpolation To aid in the visual interpretation of the analysis results, electrical resistivity values were normalized on a scale from 0 to 1. Normalization was carried out for each analysis depth and construction event, which was identified by the change in the construction number. The following basic normalization formula was utilized:

Figure 13. Equation. Normalized measurement

Where: Normalized_Measuremen Actual_Measuremen Min_Of_Actual_Measurement Max_Of_Actual_Measurement

= Normalized measurement = Actual measurement = Minimum actual measurement = Maximum actual measurement

Extracted LTPP temperature and moisture content data were interpolated to ER analysis depths established in earlier LTPP frost penetration studies[3] using the following linear interpolation formula:

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Where: Interpolated_Measurement = Interpolated temperature or MC value Upper_Measurement = Temperature at upper thermistor or MC for upper TDR sensor Lower_Measurement = Temperature at lower thermistor or MC for lower TDR sensor = Distance from the ER analysis depth to the upper X thermistor or TDR sensor L = Distance between the two thermistors or TDR sensors

Quality Control/Quality Assurance Process

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The results of data analysis were independently reviewed. During the review process, emphasis was placed on evaluating whether or not the results produced by the analyst followed the basic physical process of latent heat of fusion as described earlier in this chapter. In addition to reviewing the frost penetration profiles, trends in temperature, ER, and moisture changes were reviewed and correlated to evaluate the accuracy of analyst assigned freeze states.

Spatial and Temporal Checks Frost penetration profiles were reviewed to evaluate the progression of frost penetration with time and depth and to check for any potential data gaps or presence of intermediate unfrozen layers. The following two checks were used to QC the initial freeze state assignments for all the cells in frost penetration plot except the boundary cells (boundary cells belong to the first frozen depth layer, the last frozen depth layer, the first and the last date with frost for each depth): Spatial check for a given date is as follows: •

•

If a layer above (= depth i-1) was determined as frozen, a layer below (= depth i+1) was determined as frozen, and the temperature remained < = 0 oC, then the layer in between (= depth i) is likely to be frozen and should be assigned as freeze. If a layer above was determined as no-freeze (= depth i-1), a layer below (= depth i+1) was determined as no-freeze, and the temperature remained near 0 oC, then the layer in between (= depth i) is likely to be no-freeze and should be assigned as nofreeze.

Temporal check for a given depth is as follows •

If the freeze state for a date before was determined as frozen, the freeze state for a date after was determined as frozen, and the temperature remained < = 0 oC for all three dates, then the freeze state for the date in between is likely to be frozen and should be assigned as freeze.

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If the freeze state for a date before was determined as no-freeze, the freeze state for a date after was determined as no-freeze, and the temperature remained near 0 oC for all dates, then the freeze state for the date in between is likely to be no-freeze and should be assigned as no-freeze.

Trend reasonableness check ER, moisture, and temperature time-series plots were reviewed to evaluate reasonableness of ER and moisture changes with respect to temperature changes. The expected trends for ER and moisture changes are described as follows: •

•

Moisture: Expect to see a drop in moisture at the beginning of freeze period, as temperatures drop below 0 oC; low moisture values during frozen period; and rise in moisture during thawing, as temperatures climb above 0 oC. ER: Expect to see rise in ER at the beginning of freeze period, as temperatures drop below 0 oC; high ER values during freeze period; and drop in ER during spring thaw, as temperatures climb above 0 oC.

If and when the moisture and/or ER trends did not follow the expected trends described above, freeze assignment was based on temperature values with 0 oC used as freezing isotherm.

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Analysis results database checks Finally, the results of the analysis compiled in the LTPP computed parameter tables were reviewed to assure data completeness, data integrity, and proper formatting.

5. IMPLEMENTATION OF THE ENHANCED FROST ANALYSIS METHODOLOGY Updates to Frost Program Using the data analysis methodology presented in chapter 4, the existing FROST interactive procedure was updated to enhance the analysis algorithm, to address changes from SMP II experiment, and to assure compatibility with current database technology. The updated supporting research tool was named E-FROST to differentiate with the previous version.

E-Frost Overview The E-FROST research tool was developed to aid the data analyst in reviewing LTPP SMP data (temperature, ER, and moisture) and assigning freeze states based on the observed data trends. The primary functions of E-FROST are (1) to show time-series data from the insitu measurements (ER, temperature, and moisture), (2) to generate and graphically represent

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frost penetration profiles, and (3) to create a frost penetration table containing frost penetration depths for different dates for which in-situ measurements were taken. The EFROST user’s guide with detailed instructions and examples is provided in appendix A.

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Enhancements to LTPP Frost Interactive Procedure Several improvements were made to the existing FROST interactive procedure to help determine the freeze state. To improve accuracy in frost penetration predictions in subsurface layers, the FROST algorithm was modified to include all available temperature, moisture, and ER data in the frost penetration analysis. The E-FROST graphic user interface was updated to provide means for review of daily temperature, moisture, and ER data plotted on the same plot. This feature enables the analyst to conduct comprehensive trend analysis of changes in temperature, ER, and moisture data in order to determine the freeze state of the soil at any date and depth that had in-situ measurements collected by LTPP. The AutoFrost option was added to generate the initial frost penetration profile based on subsurface temperature values. This feature uses an objective measure, such as temperature at water freezing point, as a threshold value to determine the initial frost penetration profile instead of an arbitrary threshold value selected by the analyst, as was used in the previous FROST algorithm. The EICM software was used for thermodynamic modeling of temperature distribution in subsurface layers, as appropriate, to fill the gaps in the field data and to aid the analyst in the examination of heat transfer processes based on the in-situ temperature data for the site. EICMestimated subsurface temperature data was included in the E-FROST database so that it can be displayed on the interactive trend plots for the sites with missing or limited measured temperature data. Changes from SMP II Experiment The original FROST program was developed to process data from the SMP I experiment. Introduction of the SMP II experiment led to the development of the new LTPP database tables to store ER data and resulted in a significant increase in the quantity of data to process for each site. Introduction of the SMP II experiment also resulted in a different ER table structure and a significant increase of data to be processed for each SMP II site. E-FROST accounts for these changes. To cope with massive amounts of data, the program provides the analyst with options to review the data for the selected time intervals instead of displaying data for all dates on a single plot. The program routines and preprocessing database were updated to ensure database compatibility with Microsoft® Access 2000 or later, which is needed to facilitate preprocessing of the new SMP II data.

Enhanced Frost Algorithm The decision tree algorithm for the E-FROST program is presented in figure 15.

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E-FROST Symbol Color Codes and Shapes for the Decision Tree Upon execution, E-FROST creates a temperature-based first order approximation of frost penetration profile for each SMP site using the AutoFrost analysis option. The profile consists of a grid with the horizontal axis displaying different SMP dates on a daily scale and the vertical axis displaying different analysis depth based on ER probe depths. Each cell is colorcoded to provide information about the freeze state at a given date and given depth (see table 4).

Figure 15. Chart. Enhanced FROST algorithm.

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United States Department of Transportation Table 4. Freeze State and Frost Depth Chart Symbol Shape and Color Coding

Color code Blue

Symbol shape Rectangle

Assigned freeze state Freeze

Subsurface temperature T < - 1 oC

White

Rectangle

No freeze

T > 0 oC

Light blue

Triangle

Review

T < 0 oC and T > - 1 oC

Pink

Diamond

Transitional

Near freezing isotherm

Analyst’s action Assigned automatically; however, the analyst has an option to change the state to transitional (pink) or no-freeze (white) upon data review Assigned automatically; however, the analyst has an option to change the state to transitional pink) or freeze (blue) upon data review Assigned automatically; however, the action is required from analyst to manually review the data and change the state to freeze, no-freeze, or transitional This color is assigned upon analyst review of all supporting data when it is not clear whether soil is frozen or not (partially frozen case)

The E-FROST algorithm automatically assigns the state of subsurface freeze condition at each electrode location using the following rules: •

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• •

The 0 oC freezing isotherm value is used as the low boundary to define the no-freeze state. No-freeze is automatically assigned to all points with temperatures above 0 oC (white cells). A value of -1 oC is used as an upper boundary to define the freeze state. Freeze is automatically assigned to all points with temperatures below -1 oC (blue cells). All data that fall between the two boundaries are flagged for manual review by the analyst to determine the appropriate freeze state based on ER, temperature, and moisture trend analysis (light blue triangles).

Based on the assigned freeze state, different actions will be required. No actions are required for blue or white cells. If E-FROST assigns the cell as “Review” (light blue triangle), the analyst must review the data and change the freeze state as appropriate. To aid in this decision, E-FROST creates a time-series plot of ER, temperature, and moisture content changes. The plot appears on the screen once the analyst clicks on the light blue triangle cell. Similar plots can be brought up for review by clicking on any other cell on the frost penetration profile chart.

Frost Penetration Analysis Example The following example demonstrates the frost penetration analysis procedure to determine the freeze state and layers for unbound pavement layers and subgrade for LTPP site 0804 in South Dakota. This site was chosen for the example because it contains the most

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comprehensive temperature, ER, and moisture data and provides means for cross-comparison of changes in all three measurement types. The plots provided in this example were generated using E-FROST.

Step 1. Prepare E-FROST Inputs Database ER, temperature, and moisture content data were obtained from the LTPP tables, which are specified in chapter 6. When measured subsurface temperatures were not available, temperature values were estimated using the EICM thermodynamic model; EICM inputs are listed in appendix B. An example of how temperature gaps could be filled out by EICM predictions using the thermodynamic model was shown in figure 11 (chapter 3). Extracted LTPP data were preprocessed to obtain normalized ER values at calculated analysis depths and to interpolate temperature and moisture content data to those depths. Preprocessed electrical resistivity, temperature, and moisture content data were assembled in the analysis database table required to run E-FROST.

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Step 2. Generate an “AutoFrost” Freeze State Profile An automatic frost penetration profile was generated based on thermistor readings with the 0 oC isotherm used as a threshold value to differentiate freeze states. In the example shown in figure 16, all data points with temperature readings above 0 oC are shown using white squares with grey borders. These data points correspond to no-freeze states. All data points with temperature readings below -1 oC are shown using blue squares. These data points correspond to freeze states. Data points with temperature readings between data 0 oC and -1 o C are shown using light blue triangles. These data points require manual review, as they may represent a(n) frozen, unfrozen, or transitional state of soil.

Figure 16. Chart. Example of temperature-based frost penetration profile for section 0804 in South Dakota Long Life and Quiet Pavement: Research and Issues : Research and Issues, Nova Science Publishers, Incorporated, 2010. ProQuest Ebook

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Step 3. Review ER, Moisture, and Temperature Trends Temperature, ER, and moisture content time-series trends were examined to verify the freeze state of soil assigned by the AutoFrost option, especially when temperatures were close to 0 oC. This was done by reviewing and correlating changes in temperature with changes in ER and moisture trends. E-FROST was used to graph temperature, ER, and moisture changes with time for each winter season and each measurement depth. Upon data review, the state of soil was assigned to every date at every depth using trends described in table 3 as guidance. For the example shown in figure 17, the no-freeze state was assigned to dates prior to December 15 because the temperature readings, although close to 0 o C, never crossed the 0 axis. The state of the soil between December 16 and 24 was assigned as freeze as the data show a rapid drop in temperature values below 0 oC, followed by a decrease in moisture content. A transitional state of soil was assigned to December 25–27 and 30–31. Even though the temperature reading remained below 0 oC for these dates, there was a significant increase in moisture content, indicating thawing. The state of the soil for December 28 and 29 was assigned as no-freeze, as temperature values for these dates were above 0 oC. The state of the soil from January 1, 1999, to February 21, 2000, was assigned as freeze, as the trends in all three types of measurements (temperature, moisture, ER) indicated the possibility of frost—sharp decrease in moisture, sharp increase in ER, and temperature drop below 0 oC. For February 22, 2000, the no-freeze state was assigned based on observed trends in all three measurements: temperature rapidly rising above 0 oC, sharp decrease in ER, and sharp increase in moisture.

Figure 17. Chart. Example of ER, temperature, and moisture trends for section 0804 in South Dakota at 0.55 m (1.8 ft) depth. Long Life and Quiet Pavement: Research and Issues : Research and Issues, Nova Science Publishers, Incorporated, 2010. ProQuest Ebook

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Step 4. Generate and Review Frost Penetration Profile Upon the completion of trend analysis at each of the 35 measurement depths and assignment of freeze states by the analyst, the E-FROST algorithm displays color-coded frost penetration profiles for review and quality assurance, as shown in figure 18. Because of many less-than-ideal scenarios in the field data, the data interpretation process can be subjective. If the freezing condition at a particular point is in disagreement with the surrounding points (e.g., the point shows freezing while the soil above and below shows a nofreeze state), then the freeze state of that point may be changed by the analyst or QA reviewer to agree with that of the surrounding soil. Step 5. Calculate Frost Depth Using Freeze State Information Using freeze state information at each measurement depth, frost depths were computed for each date using E-FROST. Frost depth calculations were based on the interpreted freeze states (F-frozen and T-transitional or partially frozen). For each date, frost depths were computed based on the interpreted freeze states (F-frozen and T-transitional or partially frozen) using the following algorithm: Starting (top) depth of a frozen layer was determined as the first measurement depth from the pavement surface where “F” freeze state was determined on frost penetration plot (shown in figure 18).

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•

Figure 18. Chart. Example of final frost penetration profile for SMP site 46-0804 for the winter of 1999. Long Life and Quiet Pavement: Research and Issues : Research and Issues, Nova Science Publishers, Incorporated, 2010. ProQuest Ebook

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•

•

Ending (bottom) depth of a frozen layer was determined as the last measurement depth from the pavement surface where “F” freeze state was determined on frost penetration plot. If, for a given date, a no-freeze state “N” was found within the vertical array of freeze states “F,” then multiple freeze layers were reported for that date. In these cases, the bottom of the first frozen layer was determined as the last measurement depth with freeze state “F” before the intermediate no-freeze ”N” layer. The top of the second frozen layer was determined as the first measurement depths with freeze states “F” after the intermediate no-freeze ”N” layer. No frozen depths or layers were estimated for depths and dates without measured temperature and ER data.

Freeze state information was added to SMP_FREEZE_STATE, and frost depth information was added to the SMP FROST PENETRATION table.

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Limitations of Transitional Freeze State Estimates During temperature data analysis, there were multiple cases when temperatures were around 0 oC over a period of several days, pointing to a possibility of a transitional freeze state. However, these temperature trends were not consistently observed from one depth to another or for different years. Therefore, without supporting data (ER, moisture, soil salinity) or in cases of inconclusive supporting data trends, it was not possible to make definite conclusions whether or not the soil was in a transitional state.

Figure 19. Chart. Temperature and ER trends at 1.02 m (3.35 ft) for site 50-1002 during winter season 2000–2001. Long Life and Quiet Pavement: Research and Issues : Research and Issues, Nova Science Publishers, Incorporated, 2010. ProQuest Ebook

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Analysis of the sites that had similar temperature trends and had supporting ER and moisture data revealed that, although temperature values may indicate possible transitional state, low moisture and high ER values during the same period may provide evidence that soil may be in a freeze or no-freeze state. The following example demonstrates subjectivity of transitional state assignment based on temperature data alone. The temperature trend shown in figure 19 indicates the possibility of a transitional state of soil during the months of January and February 2001 based on temperatures just below 0 oC over an extended period of time. However, high ER values during the same period indicate that the state of soil is likely to be frozen. No moisture data are available for the same analysis period. As a result of this limitation, the majority of freeze state estimates developed in this analysis study fall in either frozen or unfrozen categories. No transitional states were assigned based on the analysis of the temperature data alone, as that approach was found to be too subjective in absence of other supporting information (moisture, ER, soil salinity). When supporting ER and moisture data were available, a more detailed trend analysis was conducted resulting in a limited number of transitional state assignments.

6. LTPP DATA USED FOR FROST DETERMINATION

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During Phase I of the project, the research team assessed the availability of the LTPP data needed to support the enhanced algorithm for evaluation of frost penetration. This assessment included data utilized by the existing FROST procedure and the LTPP data that will be utilized by the enhanced FROST procedure. The results of the assessment are summarized in this section.

Data Required for E-Frost Analysis The following LTPP database tables containing subsurface temperature, electrical resistivity, and moisture data were used to determine frost penetration under bound pavement layers: • • •

•

SMP_ERESIST_AUTO_ABF—Contains new ER measurements (VOLTAGE and RESISTANCE) for SMP II sections. SMP_ERE SIST_AUTO—Contains automated electrical contact voltage data for each electrode number. SMP_ERESIST_MAN_4POINT—Contains manually collected four point electrical contact resistance measurements: • Voltage reading between voltage electrodes. • Electrical current reading between current electrodes. • Computed electrical resistivity. SMP_ERESIST_MAN_CONTACT—Contains manually collected two point electrical contact resistance measurements: • Voltage reading between electrodes. • Electrical current reading between electrodes.

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• • • •

• •

•

• Computed contact resistance between two electrodes. SMP_ERE SIST_DEPTHS—Contains depth from the pavement surface for each electrode. SMP_MRCTEMP_AUTO_DAY_STAT S—Contains daily pavement subsurface temperature for the thermistors in the MRC thermistor probe closest to the surface. SMP_MRCTEMP_DEPTH S—Contains the installed thermistor depth. SMP _ERESIST _ABF _REF _VA—Contains background information related to ER measurements using ABF equipment for SMP II sections (this table is not be used directly in the ER data processing). SMP_TDR_AUTO_MOISTURE—Contains computed volumetric moisture content in percentile form. SMP _TDR _MANUAL _MOISTURE—Contains volumetric moisture content in percentile form based on most probable value of apparent length interpreted from manual TDR trace. SMP_TDR_DEPTHS_LENGTH TDR_DEPTH— Contains depth from pavement surface to TDR probe in meters.

Data from 1993 to 2001 were used to reinterpret previous frost estimates, and data from 2001 to 2004 were used to develop new frost estimates.

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Data Required for EICM Analysis In applying the EICM, the project team used section-specific data where they were available and pertinent to subsurface temperature prediction. The actual climatic measurements, layer, and material information collected at the site were used as inputs to the EICM. These measurements are included in the following tables: • • • • • • • • • • • • •

INV_ID—Contains longitude, latitude and elevation information. INV_GRADATION—Contains information about particle sizes. TST_L05B— Contains information about number of layers, layer and material type and layer thickness. TST_UG04_SS03—Contains information about plasticity index. TST_SS1 1—Contains hydraulic conductivity and initial water content information. TST_UG09—Contains hydraulic conductivity information. SMP_ATEMP_RAIN_DAY—Contains daily air temperature and rainfall statistics. SMP_ATEMP_RAIN_HOUR—Contains hourly ambient air temperature and rainfall. SMP _DRY _DENSITY—Contains subgrade dry density measurements. SMP_ELEV_AC_DATA—Contains AC surface elevation measurements. SMP_ELEV_PCC_DATA—Contains PCC surface elevation measurements. SMP_GRAV_MOIST—Contains pavement subsurface gravimetric moisture content. SMP_MRCTEMP_AUTO_DAY_STAT S—Contains daily pavement subsurface temperature statistics.

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SMP_WATERTAB_DEPTH_MAN—Contains automated data on the depth to ground water table. CLM_VWS_TEMP_DAILY—Contains daily temperature data. CLM_VWS_WIND_DAILY—Contains daily wind data. AWS_DAILY_DATA—Contains daily temperature and wind data.

Default or assumed values were used for some of the required data elements that were not included in the LTPP database. The climatic data from the National Climatic Data Center for a specified longitude and latitude were used where section-specific weather data were not available. These climatic data are integrated in the EICM program. EICM inputs are provided in appendix B.

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Analysis Database Summary The data from the LTPP tables discussed above were assembled in the analysis database. All records were organized by LTPP site, date, and measurement depth. For each analysis site and date, up to 35 records containing ER, temperature, and moisture data were prepared—one for each analysis depth. One of the issues in processing electrical resistivity, moisture, and soil temperature data was that these data elements are measured at different depths. Therefore, data manipulation was required to correlate various electrical resistivity, soil temperature, and moisture values. To preserve the same interpretation depths as were used in the previous LTPP frost studies,[3] linear interpolation was used to obtain soil temperature and moisture values at the ER interpretation depth. In the previous LTPP frost studies, ER interpretation depth was defined as a middepth between two neighboring electrodes, resulting in 35 analysis depths for 36 electrodes included in the resistivity probe. Only dates that had either ER or temperature data were included in the analysis database. Records for the months with the minimum monthly temperature above +1 oC and with no ER data were not included in the analysis database because no freeze conditions are possible when temperatures are above +1 oC. EICM-predicted temperatures were added to the database to fill in the gaps in measured temperature data. EICM predictions were provided only for the sites that had sufficient sitespecific EICM inputs. Only gaps of less than one month were filled with EICM predicted temperature values. Source of temperature data was specified in the analysis database to differentiate between measured and predicted temperature data. Table 5 summarizes the number of records that were assembled in the analysis database for each of the 41 LTPP SMP sites included in the frost study. As can be seen, measured temperature data were the most complete data element, corresponding to the largest number of records in the analysis database.

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Table 5. Summary of Data Assembled for Frost Penetration Analysis

State code 4 (AZ) 8 (CO) 9 (CT) 16 (ID) 18 (IN) 20 (KS) 23 (ME) 24 (MD) 25 (MA) 27 (MN) 27 (MN) 27 (MN) 27 (MN) 30 (MT) 30 (MT) 31 (NE) 31 (NE) 32 (NV) 32 (NV) 33 (NH) 34 (NJ) 34 (NJ)

SHRP ID

Years with data

Days with data

Minimum date

Maximum date

1024 1053 1803 1010 3002 4054 1026 1634 1002 1018 1028 4040 6251 0114 8129 0114 3018 0101 0204 1001 0504 0505

4 5 5 5 4 4 5 4 2 7 5 5 10 5 6 7 9 6 2 5 3 3

22 285 277 355 250 117 466 142 83 568 835 629 1,486 896 326 441 724 355 67 417 170 186

9/14/1995 7/1/1 993 8/19/1993 10/1/1993 9/8/1 995 8/25/1995 9/16/1993 5/12/1995 9/1/1993 8/24/1993 9/9/1993 9/22/1993 9/15/1993 7/16/2000 8/12/1992 8/8/1995 8/11/1995 11/6/1996 12/1/1996 10/14/1993 2/11/2002 2/11/2002

11/19/1998 9/26/1997 10/16/1997 6/26/1997 9/28/1998 11/19/1998 10/21/1997 4/8/1998 10/26/1994 9/8/1997 9/10/1997 9/9/1 997 10/8/2003 9/22/2004 10/1/1997 7/11/2002 12/31/2003 3/19/2003 9/9/1997 10/22/1997 3/13/2004 4/7/2004

Number of ER data records 770 1,320 1,375 1,235 412 694 1,324 978 490 1,569 1,352 1,420 2,110 7,876 1,728 1,203 1,446 4,267 239 1,219 1,915 2,695

Number of measured temperature records 490 9,286 9,102 10,596 8,273 3,671 15,801 4,445 2,625 19,022 28,844 20,448 50,401 30,038 10,194 13,382 22,852 10,399 2,234 14,078 3,924 3,925

Number of EICMmodeled temperature records 0 0 0 1,157 0 0 0 0 0 0 0 1,088 774 0 0 0 1,922 0 0 0 0 0

Number of volumetric moisture records 561 587 1,042 1,031 280 477 888 823 227 628 691 767 1,128 26,000 498 637 825 4,889 196 652 0 0

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Table 5. (Continued) State code

SHRP ID

34 (NJ) 0506 34 (NJ) 0507 34 (NJ) 0902 36 (NY) 0801 36 (NY) 4018 39 (OH) 0204 39 (OH) 0901 42 (PA) 1606 46 (SD) 0804 46 (SD) 9187 49 (UT) 1001 49 (UT) 3011 50 (VT) 1002 56 (WY) 1007 83 (MB) 1801 83 (MB) 3802 87 (ON) 1622 89 (QC) 3015 90 (SK) 6405 Total Records

Years with data

Days with data

Minimum date

Maximum date

3 3 3 10 5 2 6 8 9 4 5 5 10 5 11 6 5 9 6

179 174 147 913 442 45 720 656 1,113 344 143 281 1,270 393 2,116 458 469 1,605 755

2/1/2002 2/2/2002 3/26/2002 8/23/1995 10/28/1993 3/18/1998 1/1/1998 8/10/1995 7/15/1994 7/19/1994 10/14/1993 8/3/1993 10/7/1993 8/11/1993 10/13/1993 10/15/1993 9/23/1993 9/30/1 993 10/6/1993

4/7/2004 4/7/2004 4/7/2004 3/31/2004 10/14/1997 10/14/1999 10/16/2003 10/15/2003 12/16/2003 9/23/1997 9/24/1997 9/22/1997 11/30/2003 9/30/1997 11/10/2003 11/5/1998 10/30/1997 6/6/2001 5/31/1999

Number of ER data records 1,610 1,295 2,415 15,408 1,252 504 1,218 1,715 22,741 827 1,155 1,338 12,278 1,285 27,051 1,150 1,393 1,635 1,255 135,162

Number of measured temperature records 2,579 3,913 3,363 29,258 14,961 1,290 22,360 21,950 36,826 9,759 3,999 9,367 42,387 13,147 60,475 13,268 15,864 55,570 25,815 680,181

Number of EICMmodeled temperature records 1,285 0 87 1,713 0 0 2,354 0 0 1,928 0 0 941 0 0 0 0 0 0 13,249

Number of volumetric moisture records 0 0 0 11,141 707 282 562 1,410 15,384 629 894 765 11,498 989 20,476 643 947 1,044 1,031 111,229

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7. FROST PENETRATION ANALYSIS RESULTS Data Analysis Summary Using the E-FROST research analysis tool, all previously processed sections with ER data were reprocessed using the enhanced analysis methodology presented in chapter 4, and new frost depths and layer estimates were determined. In addition to the reinterpretation of the previously processed data, all SMP II sections with ER data that had not been previously analyzed were analyzed using E-FROST, and new frost depths and layer estimates were prepared for the LTPP database upload. The analysis results, as well as the LTPP computed parameters developed under this project, were reviewed thoroughly. Frost penetration analysis was conducted for 41 LTPP sites from the SMP I and II experiments. The schematic location of LTPP sites used in the frost penetration analysis study is shown in figure 21. Data from 21,953 dates were analyzed, and frost penetration depths were estimated. There were between 2 and 11 years of data analyzed for the different LTPP sites. Detailed frost penetration results were reported in two LTPP computed parameters tables discussed later in this chapter.

Frost Observations

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Observations discovered during the project are described in this section.

Figure 20. Picture. Locations of LTPP SMP sites analyzed in this study.

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Severity of Frost Penetration Using the results of the frost penetration analysis, average and maximum frost depths were determined, along with the first and the last cold month with freeze conditions for each LTPP site with in-situ measurement data. This information could be used to assess the severity of frost penetration at different LTPP sites. Maximum freeze depth corresponds to the maximum frost depth for the year with the deepest frost penetration detected during the analysis. Maximum frost depth is used in the design to account for the worst case scenario. Average maximum freeze depth corresponds to the average of maximum frost depths based on all years used in the analysis and represents average or typical frost penetration conditions. The first and the last months with freeze conditions are based on the worst case scenario. These months were determined by reviewing frost data for all available years and selecting the earliest month at the beginning of the freeze period and the latest months at the end of the freeze period. A summary of frost determinations is provided in table 6. Frost penetration profiles generated for all Minnesota, Manitoba, and Saskatchewan sites and site 4018 in New York indicate that frost penetration goes beyond the last interpretation depth. For Arizona site 1024 and Nevada site 0101, the first interpretation depth was lower than the expected frost penetration depth. These cases are noted by starred comments in table 6.

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Table 6. Summary of Frost Determinations STATE CODE

SHRP ID

Number of years analyzed

Average max freeze depth, m

Maximum freeze depth, m

4 (AZ) 8 (CO) 9 (CT) 16 (ID) 18 (IN) 20 (KS) 23 (ME) 24 (MD) 25 (MA) 27 (MN) 27 (MN) 27 (MN) 27 (MN) 30 (MT) 30 (MT) 31 (NE) 31 (NE) 32 (NV) 32 (NV)

1024 1053 1803 1010 3002 4054 1026 1634 1002 1018 1028 4040 6251 0114 8129 0114 3018 0101 0204

4 5 5 5 4 4 5 4 2 5 5 5 10 5 6 7 9 6 2

*

*

0.336 0.544 0.763 1.036 1.056 1.107 0.436 1.017 1.791 2.275 1.900 2.126 1.165 0.793 0.844 1.289

0.374 0.794 0.864 1.213 1.056 1.819 0.436 1.017 2.181*** 2.386*** 2.317*** 2.308*** 1.256 1.082 1.173 1.679

**

**

0.612

0.612

First freeze month -DEC JAN NOV DEC JAN NOV FEB JAN NOV NOV NOV NOV NOV NOV DEC DEC — DEC

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Last freeze month -FEB MAR FEB FEB FEB APR FEB MAR APR APR MAY APR MAR MAR MAR MAR — JAN

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STATE CODE

SHRP ID

33 (NH) 34 (NJ) 34 (NJ) 34 (NJ) 34 (NJ) 34 (NJ) 36 (NY) 36 (NY) 39 (OH) 39 (OH) 42 (PA) 46 (SD) 46 (SD) 49 (UT) 49 (UT) 50 (VT) 56 (WY) 83 (MB) 83 (MB) 87 (ON) 89 (QC) 90 (SK)

1001 0504 0505 0506 0507 0902 0801 4018 0204 0901 1606 0804 9187 1001 3011 1002 1007 1801 3802 1622 3015 6405

Table 6. (Continued) Number of Average max Maximum years analyzed freeze depth, m freeze depth, m 5 0.954 1.394 3 0.406 0.406 3 0.458 0.458 3 0.608 0.608 3 0.455 0.455 3 0.643 0.668 10 0.627 0.988 5 1.090 2.102*** 2 0.705 0.705 6 0.704 0.776 8 0.568 0.771 9 1.445 1.998 4 1.243 1.827 5 1.557 2.019 5 0.553 0.692 10 1.020 1.498 5 0.741 0.999 11 2.033 2.13*** 6 1.798 2.424*** 5 1.194 1.743 9 1.316 1.587 6 1.999 2.058***

First freeze month DEC JAN JAN JAN JAN JAN DEC DEC JAN DEC DEC NOV NOV DEC DEC NOV NOV OCT NOV NOV NOV OCT

Last freeze month MAR FEB FEB FEB JAN FEB MAR APR JAN FEB MAR APR APR DEC FEB APR MAR MAY MAY APR MAY MAY

1 m = 3.28 ft — No data available. * First interpreted depth at 0.38 m. ** First interpreted depth at 0.51 m. *** Possibility of frost beyond the last interpreted depth.

Frost Penetration Profile Characteristics Using frost estimates computed based on in-situ data, frost penetration profiles were analyzed for each of the 41 LTPP sites for all available years of data. The changes in frost profiles over the cold seasons (fall, winter, and spring) were examined for each available year. The review indicated that even for similar frost depths, the observed profiles varied from site to site and year to year. Hence, knowledge of the maximum frost depth without an understanding of seasonal changes in frost penetration profile would not be enough for accurate characterization of seasonal changes in pavement structural characteristics. Some of the commonly observed frost penetration profile characteristics were multiple freeze thaw cycles, shallow fall freeze with thaw followed by solid deep freeze with a spring thaw, and solid freeze with spring thaw and refreeze. Figure 21 through figure 23 show examples of each of these commonly observed frost penetration profiles.

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Figure 21. Chart. Frost penetration profile showing multiple freeze-thaw cycles

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271

Table 7. Typical Frost Penetration Profile Characteristics for LTPP SMP Sites

State code

SHRP ID

#of years w/ data

Frost profile description

Arizona Colorado

4 8

1024 1053

3 3

No Freeze* No Freeze

Connecticut

9

1803

4

No Freeze

Idaho

16

1010

3

Indiana

18

3002

2

Kansas

20

4054

3

Possible Medium Freeze-Thaw Re-freeze (up to 0.66 m) Medium FreezeThaw No Freeze

Maine

23

1026

4

Manitoba

83

1801

9

Manitoba

83

3802

4

Maryland

24

1634

4

State or province

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Fall (Sept 21–Dec 21)

Shallow freeze-thaw re-freeze (up to 0.55 m) Deep Freeze, possibly preceded by Shallow Freeze w/ Thaw (up to 1.72 m) Deep Freeze (up to 1.3 1m) No Freeze

Winter (Dec 22–Mar 20)

Spring (Mar 21–June 21)

No Freeze* Multiple Shallow Freeze-Thaw Cycles (up to 0.37 m) Shallow or Medium freeze-thaw (up to 0.79 m) Multiple Shallow or Medium FreezeThaw Cycles (up to 0.86 m)

No Freeze* No Freeze

Multiple Medium to Deep FreezeThaw Cycles (up to 1.21 m) Multiple Medium to Deep FreezeThaw Cycles (up to 1.06 m) Continuous Deep Freeze (up to 1.82 m)

No Freeze

Continuous Deep Freeze (up to 2.13 m)***

Deep Freeze, Shallow Thaw followed by Refreeze, Prolonged Deep Thaw (up to 2.13 m)***

Continuous Deep Freeze (up to 2.42 m)***

Deep Freeze, Shallow Thaw followed by Refreeze, Prolonged Deep Thaw (up to 2.42 m)*** No Freeze

Shallow freeze-thaw (up to 0.44 m)

No Freeze No Freeze

No Freeze Prolonged Deep Thaw (up to 1.77 m)

Table 7. (Continued) State code

SHRP ID

#of years w/ data

Frost profile description

Massachusetts

25

1002

2

No Freeze

Minnesota

27

1018

4

Minnesota

27

1028

3

Minnesota

27

4040

3

Medium to Deep Freeze (up to 1.83 m) Deep Freeze, possibly proceeded by Medium Freeze w/ Thaw. (up to 1.83 m) Deep Freeze (up to 1.20 m)

Minnesota

27

6251

8

Deep Freeze (up to 1.85 m)

Montana

30

0114

4

Montana

30

8129

3

Nebraska

31

0114

6

Multiple Shallow/ Medium Freeze-Thaw Cycles or Deep Freeze (up to 1.05 m) Medium Freeze (up to 0.83 m) Medium Freeze w/ Thaw (up to 0.67 m)

State or province

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Fall (Sept 21–Dec 21)

Winter (Dec 22–Mar 20)

Deep Freeze w/ Thaw, followed by Medium Freeze w/ Thaw (up to 1.02 m) Deep Freeze, Shallow Thaw followed by Re- freeze (up to 2.18 m)

Spring (Mar 21–June 21)

No Freeze

Prolonged Deep Thaw (up to 2.13 m)

Continuous Deep Freeze (up to 2.39 m)***

Deep Freeze, Possible Shallow Thaw followed by Re-freeze, Prolonged Deep Thaw (up to 2.39 m)***

Deep Freeze, Possible Shallow Thaw followed by Re-freeze (up to 2.32 m)*** Deep Freeze, Possible Shallow Thaw followed by Re-freeze (up to 2.31 m)*** Multiple Medium/Deep Freeze-Thaw Cycles or Deep Freeze with Shallow Thaw and Re-freeze (up to 1.26 m)

Prolonged Deep Thaw (up to 2.3 2m)***

Multiple Medium/Deep Freeze-Thaw Cycles (up to 1.08 m) Multiple Medium/Deep Freeze-Thaw Cycles (up to 1.17 m)

No Freeze

Prolonged Deep Thaw (up to 2.31 m)***

Possible Deep Freeze and Thaw (up to 0.95 m)

No Freeze

Table 7. (Continued) State code

SHRP ID

#of years w/ data

Frost profile description

Nebraska

31

3018

8

Nevada Nevada

32 32

0101 0204

5 1

New Hampshire

33

1001

4

New Jersey

34

0504

3

Possible Shallow Freeze w/ Thaw (up to 0.33 m) No Freeze

New Jersey

34

0505

3

No Freeze

New Jersey New Jersey New Jersey

34 34 34

0506 0507 0902

2 3 3

No Freeze No Freeze No Freeze

New York

36

0801

7

Multiple Shallow Freeze-Thaw Cycles (up to 0.48 m)

State or province

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Fall (Sept 21–Dec 21)

Possible Deep Freeze (up to 1.2 2m) No Freeze** No Freeze

Winter (Dec 22–Mar 20)

Spring (Mar 21–June 21)

Deep Freeze (up to 1.68 m)

No Freeze

No Freeze** Multiple Shallow FreezeThaw Cycles (up to 0.61 m) Multiple Medium/Deep Freeze-Thaw Cycles or Single Deep Freeze (up to 1.39 m) Multiple Shallow Freeze-Thaw Cycles (up to 0.41 m) Multiple Shallow Freeze-Thaw Cycles (up to 0.46 m) Medium Freeze-Thaw (up to 0.61m) Shallow Freeze-Thaw (up to 0.46 m) Multiple Shallow/Medium FreezeThaw Cycles (up to 0.67 m) Multiple Shallow to Deep FreezeThaw Cycles or Single Deep Freeze (up to 0.99 m)

No Freeze** No Freeze Possible Thaw (up to 1.19 m) No Freeze No Freeze No Freeze No Freeze No Freeze

Possible Multiple Shallow Freeze-Thaw Cycles (up to 0.28 m)

Table 7. (Continued) State code

SHRP ID

#of years w/ data

Frost profile description

State or province

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New York

36

4018

4

No Freeze

Ohio

39

0204

2

No Freeze

Ohio

39

0901

6

Ontario

87

1622

4

Pennsylvania

42

1606

8

Quebec

89

3015

6

Saskatchewan

90

6405

3

South Dakota

46

0804

7

Possible Medium Freeze (up to 0.57 m) Multiple Shallow Freeze-Thaw Cycles (up to 0.42 m) Multiple Shallow Freeze-Thaw Cycles (up to 0.42 m) Shallow to Medium Freeze-Thaw followed by Deep Freeze (up to 1.03 m) Shallow Freeze-Thaw, followed by Deep Freeze (up to 1.80 m) Medium Freeze-Thaw, followed by Medium to Deep Freeze (up to 1.24 m)

Fall (Sept 21–Dec 21)

Winter (Dec 22–Mar 20)

Spring (Mar 21–June 21)

Multiple Shallow to Deep FreezeThaw Cycles or Single Deep Freeze (up to 2.10 m)*** Medium Freeze-Thaw (up to 0.71 m) Multiple (B) Shallow to Medium Freeze-Thaw Cycles (up to 0.78 m)

Possible Shallow Freeze-thaw or Prolonged Deep Thaw (up to 2.10 m)***

Single Deep Freeze or Multiple Deep Freeze- Thaw Cycles (up to 1.74 m) Multiple Shallow to Medium FreezeThawCycles (up to 0.77 m)

Possible Shallow Freeze-Thaw, Prolonged Deep Thaw (up to 1.69 m)

Deep Freeze, Shallow Thaw followed by Re-freeze (up to 1.54 m)

Prolonged Deep Thaw, Possible Deep Freeze (up to 1.59 m)

Continuous Deep Freeze (up to 2.06m)***

Deep Freeze, Multiple Shallow Thaw & deep Refreeze periods, Prolonged Deep Thaw (up to 2.06 m)*** Deep Freeze, Possible Shallow Thaw followed by Re-freeze, Prolonged Deep Thaw (up to 1.95 m)

Deep Freeze, Possible Shallow Thaw followed by Re-freeze (up to 2.00 m)

No Freeze No Freeze

No Freeze

State code

SHRP ID

#of years w/ data

Table 7. (Continued)

South Dakota

46

9187

2

Utah

49

1001

3

Utah

49

3011

3

Vermont

50

1002

8

Wyoming

56

1007

3

State or province

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Frost profile description Fall (Sept 21–Dec 21)

Multiple shallow Freeze-Thaw Cycles followed by Medium to Deep Freeze (up to 1.02 m) Mid Depth to Deep Freeze (up to 2.02 m) No Freeze Period Multiple Shallow to Medium FreezeThaw Cycles (up to 0.64 m) Multiple Shallow Freeze-Thaw Cycles (up to 0.49 m)

1 m = 3.28 ft * First interpreted depth at 0.38 m. ** First interpreted depth at 0.51 m. *** Possibility of frost beyond the last interpreted depth.

Winter (Dec 22–Mar 20)

Spring (Mar 21–June 21)

Deep Freeze, Multiple Shallow Thaw followed by Re-freeze Cycles up to 1.83 m)

Medium to Deep Freeze, Shallow Thaw & Re-freeze periods, Prolonged Thaw (up to 1.63 m)

No Freeze

No Freeze

Multiple Shallow to Medium FreezeThawCycles (up to 0.69 m) Multiple Shallow to Deep freezethaw cycles,Possible Continuous Deep Freeze (up to1.50 m)

No Freeze

Multiple Shallow to Deep FreezeThaw Cycles (up to 1.00 m)

No Freeze

Possible Deep Thaw (up to 1.40 m)

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Figure 23. Chart. Frost penetration profile showing solid freeze with partial spring thaw and refreeze

Table 7 summarizes typical frost penetration characteristics observed for each SMP site. To describe frost penetration profile characteristics, frost depth was characterized as shallow, medium, or deep. A shallow frost depth was defined between 0 m and 0.6 m (0 ft and 1.97 ft); a medium frost depth was defined between 0.6 m and 0.9 m (1.97 ft and 2.95 ft); and a deep frost depth was defined for frost that penetrated 0.9 m (2.95 ft) or more. Since these definitions are subjective, the seasonal maximum frost depth is also reported in the table for each site. Furthermore, the depth of the top of the first unbound layer was different for each SMP site, which occasionally limited frost determination at shallow and medium depths where the first unbound layer was placed below the expected freeze depth. The information in table 7 could be used to infer the typical frost penetration characteristics for LTPP SMP sites.

Comparison with Historical Non-LTPP Frost Data The computed maximum frost penetration depths were compared to the historical frost penetration values, as published in the climatic maps developed by NOAA[1] and Environment Canada.[2] Data from the historical maps were interpolated to the LTPP site locations. The results of the comparison are shown in figure 24.

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Figure 24. Graph. Comparison of frost penetration depths

The graph in figure 24 shows a good overall agreement between LTPP and historical maximum frost depth predictions. Some of the differences can be attributed to the fact that, while comparisons are provided for the same region, the historical values are not site-specific and that local variations are possible due to factors such as soil type, moisture content, altitude, and land development. In addition, for Canadian sites, some inaccuracies could result from estimation of frost depth from the freezing index data provided on the climatic map. For the three Canadian sites shown in the upper-right corner on the graph, LTPP frost penetration profiles indicate the possibility of frost beyond the last interpreted depth; however, the full frost depth cannot be established as no LTPP measurements are available at these lower depths. The extreme frost predictions for U.S. sites provided on the NOAA map are based on longer monitoring period than the LTPP frost predictions; hence, covering more seasons where extreme conditions could occur. Table 8 contains data used in the analysis.

Comparison with Previous LTPP Frost Estimates When comparing the results of the current frost penetration data analysis to the previous results, the following improvements can be noted: •

The new methodology resulted in the development of the complete frost penetration time histories for LTPP SMP I and II sites instead of previously reported freeze depth snapshots based on ER measurement dates. Frost penetration information for the previously analyzed periods increased over 8 times by the addition of results for the 14,903 dates that previously were not included in the analyses.

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Long Term Pavement Performance Computed Parameter: Frost Penetration Table 8. Comparison of Average Frost Depth for LTPP SMP Sites

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STATE _ CODE 4 (AZ) 8 (CO) 9 (CT) 16 (ID) 18 (IN) 20 (KS) 23 (ME) 24 (MD) 25 (MA) 27 (MN) 27 (MN) 27 (MN) 27 (MN) 30 (MT) 30 (MT) 31 (NE) 31 (NE) 32 (NV) 32 (NV) 33 (NH) 34 (NJ) 34 (NJ) 34 (NJ) 34 (NJ) 34 (NJ) 36 (NY) 36 (NY) 39 (OH) 39 (OH) 42 (PA) 46 (SD) 46 (SD) 49 (UT) 49 (UT) 50 (VT) 56 (WY) 83 (MB) 83 (MB) 87 (ON) 89 (QC) 90 (SK)

SHRP _ ID

Number of years analyzed

LTPP maximum freeze depth, m

1024 1053 1803 1010 3002 4054 1026 1634 1002 1018 1028 4040 6251 0114 8129 0114 3018 0101 0204 1001 0504 0505 0506 0507 0902 0801 4018 0204 0901 1606 0804 9187 1001 3011 1002 1007 1801 3802 1622 3015 6405

4 5 5 5 4 4 5 4 2 5 5 5 10 5 6 7 9 6 2 5 3 3 3 3 3 10 5 2 6 8 9 4 5 5 10 5 11 6 5 9 6

* 0.374 0.794 0.864 1.213 1.056 1.819 0.436 1.017 2.181*** 2.386*** 2.317*** 2.308*** 1.256 1.082 1.173 1.679 ** 0.612 1.394 0.406 0.458 0.608 0.455 0.668 0.988 2.102*** 0.705 0.776 0.771 1.998 1.827 2.019 0.692 1.498 0.999 2.13*** 2.424*** 1.743 1.587 2.058***

Historic maximum freeze depth, m 0.250 0.875 1.167 1.125 0.875 0.750 1.792 0.390 1.240 1.917 2.042 2.245 2.250 1.500 1.500 1.000 1.031 0.600 0.500 1.531 0.750 0.750 0.750 0.750 0.750 1.208 1.208 0.875 0.875 0.938 1.667 1.688 0.625 0.833 1.625 1.475 2.670 2.670 1.710 2.130 2.790

1 m = 3.28 ft * First interpreted depth at 0.38 m. ** First interpreted depth at 0.51 m. *** Possibility of frost beyond the last interpreted depth.

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•

•

Analysis of frost penetration histories led to the discovery of multiple freeze-thaw periods or of freeze-thaw periods during late fall or early spring characteristic for several LTPP sites, as discussed in this chapter. This information was not previously available. This new information is important for understanding and tracking of seasonal changes in pavement structural responses. Analysis based on cross-referenced ER, moisture, and temperature data provided means far more informed and less subjective determinations of frost penetration for the LTPP sites compared to the previous estimates. ER and moisture data used in freeze state analysis are provided in the LTPP SMP_FREEZE_STATE table. Additionally, moisture data used in the analysis can be found in the LTPP SMP_TDR_MOISTURE table. Major differences with the previous LTPP frost information are the availability of frost predictions for longer freeze seasons, the availability of data on fall and spring partial thaw and refreeze and multiple freeze-thaw cycles for some sites, and deeper frost estimates for some sites.

LTPP Frost Data Table Descriptions

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As a result of this data analysis effort, two tables were created for inclusion in the LTPP database. The proposed computed parameter tables (CPT) are based on the existing LTPP frost CPT tables with changes and additions made as a result of the current frost penetration analysis study. These tables have the same names as in the previous LTPP database releases and are defined as follows: •

SMP_FREEZE_STATE—Contains the interpreted soil freeze state (F-frozen, Nnofrozen, and T-transitional or partially frozen) based on the soil temperature and electrical resistivity data and supplemented by the soil moisture data trend analysis. Caution: Only a limited number of transitional states were determined based on the methodology used in LTPP Frost study.

•

SMP_FROST_PENETRATION—Contains the interpreted frozen layers and frost depth information, based on the interpreted freeze states (F-frozen and T-transitional or partially frozen) in table SMP_FREEZE_STATE. Caution: No frozen depths or layers were reported for depths and dates without sensor measurements. Use the SMP_FREEZE_STATE table to identify dates and depths that have no data.

These new tables contain freeze state interpretations for all the available temperature and ER data collected during the SMP I and II experiments. As such, the intent of these tables is to replace the existing SMP_FREEZE_STATE and SMP_FROST_PENETRATION tables. Summaries of the information included in the CPT frost tables are provided in table 9 and table 10.

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Table 9. Summary of Information Included in the Revised Table SMP_FREEZE_STATE Data element or parameter STATE code SHRP ID SMP date Interpretation depth number Interpretation depth

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Interpreted freeze state Interpretation basis

Normalized resistivity Normalized resistance Normalized voltage Soil temperature Temperature source

DESCRIPTION State code SHRP identification code Date corresponding to SMP data collection Depth number where freeze state is interpreted, increasing from top downward. Middepth between electrodes used in the freeze state interpretation, measured for pavement surface; two consecutive electrodes are used in voltage and contact resistance measurements and four in resistivity. Interpreted freeze state at the interpret depth: F-Freeze, N-No-freeze, TTransitional (or partial freeze). Code indicating the basis for freeze state interpretation: 1. Freeze state based on temperature data using 0 oC freezing isotherm, not forced. 2. Freeze state determined by the analyst after reviewing the temperature, electrical resistivity, and moisture data trends. 3. Temperature data is not available. Freeze state determined by the analyst from ER and moisture. Electrical resistivity of the soil at the measurement depth, relative to the extreme values measured at that depth. Electrical resistance of the soil at the measurement depth, relative to the extreme values measured at that depth. Voltage drop of the soil at the measurement depth, relative to the extreme values measured at that depth. Average soil temperature of the day, calculated at the interpretation depth. This could either be based on interpolation of measured values, or derived using EICM. Source of the temperature data used in freeze state interpretation: (1) based on measured, (2) derived using EICM.

Table 10. Summary of Information Included in the Revised Table SMP_FROST_PENETRATION Filed name STATE code SHRP ID SMP date Frozen layer Top depth number Bottom depth number Freeze from Freeze to

DESCRIPTION State code SHRP identification code Date corresponding to SMP data collection Code for interpreted frozen layer number. A value of zero indicates no frozen layers. Serial number for the starting depth (top) of a frozen layer, increasing from pavement surface downward. Serial number for the ending depth (bottom) of a frozen layer, increasing from pavement surface downward. Starting (top) depth (meter) of a frozen layer, measured from the pavement surface. Ending (bottom) depth (meter) of a frozen layer, measured from the pavement surface.

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8. SUMMARY AND RECOMMENDATIONS

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Summary A comprehensive review of the previous LTPP frost penetration analysis methodology and an assessment of frost depth estimates provided in the LTPP database were conducted, followed by recommendations for improvements. As a result of these recommendations, an enhanced methodology and the accompanying E-FROST research analysis tool were developed for determination of frost penetration in unbound pavement layers and subgrade soil for LTPP SMP sections. The enhanced methodology uses electrical resistivity, moisture, and soil temperature data collected for instrumented SMP sections to predict frost depth in unbound pavement layers. In addition, the EICM model was used to fill in the gaps in the measured soil temperature data. Using the enhanced analysis methodology and E-FROST, in-situ data were analyzed to determine freeze conditions and frost depths in the unbound pavement layers. The results of the frost penetration analysis for LTPP SMP sections were assembled in the LTPP computed parameter tables described in this chapter. The results presented in this chapter demonstrate how frost penetration beneath the pavement structure was predicted for LTPP SMP sites using a combined empirical and mechanistic technique. This technique utilizes data from LTPP in-situ measurements and thermodynamic modeling. Study findings stress the importance of using all three different types of in-situ measurements for accurate frost penetrations prediction: temperature, electrical resistivity, and moisture content. The EICM has proven useful for filling in the gaps of measured subsurface temperatures and for understanding the thermodynamic processes that occur in pavement layers. This information could help practitioners and researchers design seasonal monitoring field experiments and analyze field data to determine frost penetration under pavement layers.

Recommendations for Future Research Future E-FROST Development to Support M-E PDG Implementation The E-FROST research tool developed during this study could be very useful for analysis of seasonal changes in unbound pavement layers. In the future, this tool could become particularly useful for implementation of the M-E PDG, which emphasizes estimating seasonal changes in pavement layer moduli. We recommend that LTPP consider further development of this tool into an LTPP software product similar to the LTPP profile viewer software so that the pavement research and practicing community at large can have easy access to ER, temperature, and moisture data, as well as frost penetration profiles for LTPP SMP sites. In addition, data from FWD tests can be added to this software to relate changes in mechanistic properties of pavement layers and in pavement responses and to cross reference this information with frost penetration data.

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Future LTPP Data Analysis Study of Pavement Responses under FWD Loading during Freeze-Thaw Conditions During spring thaw, sunshine and warm air temperatures result in a top-down thawing of the pavement system. The water released by the melting ice can be trapped by deeper, stillfrozen material, creating saturated or supersaturated conditions that weaken the pavement structure. The change in pavement strength could be observed by FWD measurements. The database tables developed under this study provide detailed information about the periods and the depth of freeze-thaw based on continuous temperature, ER, and moisture data analyzed. This information could be utilized to cross reference with and analyze FWD data collected during the thaw periods to capture the conditions of the supporting layers during the weakest period and to correlate these conditions with pavement responses. This task can be accomplished through mechanistic modeling of pavement responses under FWD loading based on the inventory, climatic, testing, and FWD data from the LTPP database. The result of the proposed study could contribute to understanding pavement deterioration, as triggered by seasonal changes in pavement layer moduli and could be utilized in the development of spring load restrictions. Future Development of In-Situ Frost Measurement Devices One of the challenges in LTPP frost penetration analysis was the interpretation of the data from ER measurement devices, as the following describes:

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•

•

ER measurements were expected to be high during cold winter months when temperatures plunge below ground water freezing point. However, a number of ER readings during warm summer months (with temperatures high above 0 oC) were found to be as high as readings during cold winter months. These were unexpected trends. LTPP collected in-situ data to evaluate three types of ER parameters: voltage, resistance, and resistivity. All three parameters are expected to follow a similar trend when soil goes through freeze and thaw cycles. However, it was not uncommon that the data showed opposite trends, or one of the trends would be nearly flat (indicating no changes in the soil freeze state). This inconsistency was unexpected.

We highly recommend that LTPP promote the need for future research and development of in-situ frost measurement devices. Perhaps the next generation of such devices would have multifunctional sensors capable of monitoring temperature and moisture changes in the soil, in addition to electrical resistivity measurements, and use output of all three types of measurements to determining frost penetration.

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APPENDIX A. E-FROST USER’S GUIDE Introduction This guide is designed to familiarize new users with the E-FROST user interface and analysis options. The guide includes screen captures to help the user navigate through the software screens. E-FROST was designed to view time-series data from the in-situ measurements (ER, temperature, and moisture) used in frost penetration analysis, to generate and view frost penetration profiles, and to create frost penetration table documenting frost penetration depths for different dates for which in-situ measurements were taken.

E-Frost Installation and Removal Complete the following steps to install E-FROST: 1. Make sure that all other applications are closed and that the E-FROST installation CD-ROM has been inserted into the CD-ROM drive. 2. From the Windows Start menu, select Run. 3. In the Run dialog box, type “(CD drive):setup.exe,” where (CD drive) is the letter assigned to your CD-ROM drive. 4. Follow the simple instructions in the installation program. When installation is completed, E-FROST program will be available from the Start menu.

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Complete the following steps to remove E-FROST: 1. 2. 3. 4. 5. 6.

Click the Start button and choose the Settings option. Select Control Panel. From the Control Panel, double-click the Add/Remove Programs icon. Once within that dialog box, click the Install/Uninstall tab. Select E-FROST from the list of programs; then click the Add/Remove button. A final warning will ask if the user want to delete E-FROST from your computer. If this is the case, click Yes to remove all E-FROST files.

Starting E-Frost To start the program, click on E-FROST program name available from the Windows Start menu.

Main form When the E-FROST program is opened, a blank form with file menu and inactive tool buttons in the top left corner of the interface appears as shown figure 25.

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Figure 25. Screen capture. Opening screen in E-FROST

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Figure 26. Screen capture. Tool buttons

There are four tool buttons in E-FROST that help navigate between screens and provide different program functions. These tool buttons are located on the left side of the screen and are shown in figure 26. Each button’s function is described below the figure.

Select Sections The Select Sections tool button allows the user to choose a site for analysis from a list that is linked to the database. Frost Graph The Frost Graph tool button shows the frost graph after all missing temperature data and all temperature data between -1 oC and 0 oC have been reviewed. The Frost Graph button will be inactive until all review has taken place and the frost graph has been finalized. Auto Frost The Auto Frost tool button displays the frost graph with the original data set from the database before any review has taken place. Exit The Exit tool button safely closes the E-FROST program.

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Load Database To run E-FROST analyses, the analysis database needs to be loaded first. The analysis database contains preprocessed temperature, ER, and moisture data for the SMP sites. To load a database, click File > Open Database, as shown in figure 27. A dialog box appears, prompting the user to open the database, as shown in figure 28. After locating and selecting the database, click the Open button located in the bottom right portion of the dialog box. Select analysis table Once the analysis database is uploaded, the E-FROST analysis table selection window will appear as shown in figure 29.

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Figure 27. Screen capture. Open database

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Figure 29. Screen capture. Select data table for analysis

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Select SMP Site Select the table with the SMP site data, which is EFrostAll_QC and click OK to complete the database linking process. Once the database is connected to the program, the Select Sections and Exit user buttons will become active (figure 30).

Figure 30. Screen capture. Frost linked to database with some tool buttons activated

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Figure 31. Screen capture. SMP Section window

Figure 32. Screen capture. Blank Frost Penetration Analysis screen

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To select an SMP site for analysis, click the Select Sections tool button. A Section Selection window will appear containing a list of available SMP sections for analysis, as shown in figure 31. Click an SMP section name and then click OK. In the following example SMP site 46-0804-1 was selected for analysis. The last digit in section ID represents LTPP construction number.

E-Frost Analysis Options

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Frost penetration analysis form A blank Frost Penetration Analysis form becomes visible once an SMP site is selected for analysis, as shown in figure 32. If more than 2 years of data (730 days) are available for the site, a warning message will appear to prompt the user to select a shorter time period. The MinDate and MaxDate fields on the form indicate the range of the available data. Above the minimum and maximum dates are the text boxes where the user can enter date ranges for review. The user can move between different years of frost data by using the buttons to the right (to progress forward) or the left (to move backward) of the default user date range. The user can also manually enter the beginning and ending dates of interest by typing over the values in User Date boxes and clicking the Plot New button.

Figure 33. Chart. Automatically generated frost penetration profile at SMP site 46-0804 for the winter of 1999 Long Life and Quiet Pavement: Research and Issues : Research and Issues, Nova Science Publishers, Incorporated, 2010. ProQuest Ebook

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Table 11. Freeze State and Frost Depth Chart Color Coding Color code Blue

Rectangle

Assigned freeze state Freeze

Subsurface temperature T < - 1 oC

White

Rectangle

No freeze

T > 0 oC

Light blue

Triangle

Review

T < 0 oC and T > -1 oC

Pink

Diamond

Transitional

Near FR

Shape

Analyst’s action Assigned automatically; however, the analyst has an option to change the state to transitional (pink) or nofreeze (white) upon data review Assigned automatically; however, the analyst has an option to change the state to transitional (pink) or freeze (blue) upon data review Assigned automatically; however, the action is required from analyst to manually review the data and change the state to freeze, nofreeze, or transitional This color is assigned upon analyst review of all supporting data when it is not clear whether or not soil is frozen (partially frozen case)

Review auto generated frost profile Clicking on the Auto Frost tool button results in a generation of temperature-based frost penetration profile, as shown in figure 33. In this example, the automated frost penetration profile was generated for SMP Site 46-0804 for the winter season of 1999–2000. The profile consists of a grid with the horizontal axis displaying different SMP dates on a daily scale and the vertical axis displaying different analysis depth based on ER probe depths. Each cell is color- coded to provide information about freeze state at a given date and at a given depth, as indicated in table 11. In addition, black “X”s are used to indicate data points missing temperature data. The AutoFrost algorithm automatically assigns the state of subsurface freeze condition at each electrode location using the following rules: •

• •

The 0 oC freezing isotherm is used as the low boundary to define the no-freeze state. No- freeze is automatically assigned to all points with a temperature above 0 oC (white cells). A value of -1 oC is used as an upper boundary to define the freeze state. Freeze is automatically assigned to all points with a temperature below -1 oC (blue cells). All data that fall between two boundaries are flagged for manual review to determine the appropriate freeze state based on ER, temperature, and moisture trend analysis (light blue triangles).

Review time series data The light blue triangles on the AutoFrost profile graph indicate that the analyst must review the data and change the freeze state in the analysis table as appropriate. To aid in this analysis, E-FROST creates a time-series plot of ER, temperature, and moisture content

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changes. The plot is brought up to the screen once the analyst clicks on the light blue triangle cell. Similar plots can be brought up for review by clicking on any other cell on the frost penetration profile chart. To review temperature, ER, and moisture time-series trends for a selected measurement depth, identify measurement depth on left vertical axis in the frost penetration profile plot, then click on any cell in the automated frost penetration graph for a selected depth value depth to bring up the time series graph (see the example shown in figure 34). Use the “” buttons next to the No. label on the form to review the time series at different depths, or select the desired depth from the dropdown menu.

Review revised frost penetration profile Upon completion of the trend analysis and assignment of freezing conditions, an updated frost penetration plot can be reviewed by clicking on the Frost Graph tool button, as shown in figure 35.

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View previously processed data After the analysis of all sites is complete and all frost penetration profiles are finalized, the user can select any previously analyzed SMP site and view the frost penetration profiles at that site. To view previously processed data, click the Select Sections tool button and select an SMP site. Next, click the Frost Graph tool button to see the final frost penetration profile of the selected site. From the Frost Graph screen, the user can click on any cell to view the time series graph at selected depth. To view automatically generated frost penetration profile, click the Auto Frost tool button. To exit the program, click Exit on the tool bar.

Figure 34. Chart. Time series plot for SMP site 46-0804 for the winter of 1999 at analysis depth = 0.55 m (1.8 ft) Long Life and Quiet Pavement: Research and Issues : Research and Issues, Nova Science Publishers, Incorporated, 2010. ProQuest Ebook

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Figure 35. Chart. Final frost penetration profile for SMP site 46-0804 for the winter of 1999

Generate Frost Penetration Table To generate the frost penetration table FrostPen, click File > Create Frost Penetration Table, as shown in figure 36.

Figure 36. Screen capture. Create Frost Penetration Table option Long Life and Quiet Pavement: Research and Issues : Research and Issues, Nova Science Publishers, Incorporated, 2010. ProQuest Ebook

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APPENDIX B. EICM MODELING INPUTS Table 12. EICM Inputs Site_ID 16_1010 Start Year 1996 Start Month Sept. Length Analysis 3195 Period (day) Time Increment 1 Output (hour) Time Increment 0.1 Calculation (hour) Latitude 43.4 (degrees. minutes ) Longitude -112.07 (degree. minute) Short-wave 0.8 absorptivity Upper limit 32 freezing (°F) Lower limit 30.2 freezing (°F) Pavement Layer 1 Material Asphalt Thickness 5.2 (inches) Number of 5 elements Thermal 0.67 Conductivity (BTU/hr-ft-°F) Heat capacity 0.22 (BTU/lb-°F)

23_1026 1996 Sept. 3287

27-4040 1996 Sept. 3287

27_6251 1996 Sept. 3287

31_3018 1996 Sept. 3287

34_0506 1996 Sept. 3287

34_0902 1996 Sept. 3287

36_0801 1996 Sept. 3287

39_0901 1996 Sept. 3287

46_0804 1996 Sept. 3287

46_9187 1996 Sept. 3287

50_1002 1996 Sept. 3287

56_1007 1996 Sept. 3287

1

1

1

1

1

1

1

1

1

1

1

1

0.1

0.1

0.1

0.1

0.1

0.1

0.1

0.1

0.1

0.1

0.1

0.1

44.34

47.18

47.27

40.4

40.17

40.43

43.21

40.38

45.56

44.46

44.07

44.3

-70.17

-93.43

-94.54

-99.2

-74.51

-74.1

-77.55

-83.07

-100.25

-102.03

-73.1

-108.55

0.75

0.8

0.9

0.8

0.8

0.8

0.95

0.8

0.8

0.8

0.8

0.9

32

32

32

32

32

32

32

32

32

32

32

32

30.2

30.2

30.2

30.2

30.2

30.2

30.2

30.2

30.2

30.2

30.2

30.2

8.1

Asphalt 9

PCC 11.9

Asphalt 9.7

Asphalt 12.4

Asphalt 4.9

Asphalt 19.7

Asphalt 7.2

Asphalt 5.9

Asphalt 8.5

Asphalt 2.8

10

8

9

12

10

12

5

20

7

6

9

3

0.67

1

0.67

1

0.67

0.67

1.5

1.5

0.67

0.67

0.67

0.67

0.22

0.2

0.22

0.2

0.22

0.22

0.22

0.22

0.22

0.22

0.22

0.22

Asphalt 9.8

PCC

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Table 12. (Continued) Site_ID 16_1010 Unit Weight 148 (pcf) Pavement Layer 2 Material Asphalt Thickness 5.7 (inches) Number of 6 elements Thermal 0.67 Conductivity (BTU/hr-ft°F) Heat 0.22 Capacity (BTU/lb-°F) Unit Weight 148 (pcf) Soil Layer 1 Material A-1-a Thickness 12 (inches) Number of 12 Elements Porosity 0.25 Saturated 0.0583 permeability (ft/hr) Dry unit weight 127 (pcf) Dry thermal 0.8 conductivity (BTU/hr-ft°F) Dry heat 0.22 capacity (BTU/ft3-°F)

23_1026 148

27-4040 150

27_6251 148

31_3018 150

34_0506 148

34_0902 148

36_0801 148

39_0901 148

46_0804 148

46_9187 148

50_1002 148

56_1007 148

A-1-a 17.6

A-1-a

A-1-a 10.2

A-1-a 5.6

A-1-a

A-1-a

A-1-a

A-1-a

A-1-a

A-1-a

A-1-a

6

17

6

10

0.25 0.0583

0.25 0.0583

127

10

5

8.4

6

12

11

A-1-a 25.8

5

10

5

9

6

12

11

26

6

0.3 0.0583

0.25 0.0583

0.25 0.0583

0.25 0.0583

0.25 0.0583

0.25 0.0583

0.25 0.0472

0.1 0.0416

0.25 0.138

0.24 0.074

127

127

127

127

127

127

127

127

127

127.2

127.1

0.8

0.8

0.8

0.8

0.8

0.8

0.8

0.8

0.8

1.6

0.8

0.8

0.22

0.22

0.22

0.22

0.22

0.22

0.22

0.22

0.22

0.22

0.22

0.22

6.8

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Table 12. (Continued) Site_ID Initial VMC (/o) Fredlund–af Fredlund–bf Fredlund–cf Fredlund–hr Plasticity Index (PI) D60 (mm) Passing #4 (/o) Passing #200 (/o) Soil Layer 2 Material Thickness (inches) Number of Elements Porosity Saturated permeability (ft/hr) Dry unit weight (pcf) Dry thermal conductivity (BTU/hr-ft°F) Dry heat capacity (BTU/ft3-°F) Initial VMC (/o) Fredlund–af Fredlund–bf Fredlund– cf Fredlund–hr

16_1010 15.26 7.2555 1.234 0.83152 117.4

23_1026 15.26 7.2555 1.234 0.83152 117.4

27-4040 15.26 7.2555 1.234 0.83152 117.4

27_6251 2 7.2555 1.234 0.83152 117.4

31_3018 15.26 7.2555 1.234 0.83152 117.4

34_0506 15.26 7.2555 1.234 0.83152 117.4

34_0902 15.26 7.2555 1.234 0.83152 117.4

36_0801 15.26 7.2555 1.234 0.83152 117.4

39_0901 15.26 7.2555 1.234 0.83152 117.4

46_0804 15.26 7.05034 1.28391 0.83784 152.2

46_9187 8 6.94777 1.29552 0.83536 169.6

50_1002 15.08 7.33241 1.69057 0.81675 108

56_1007 15.07 7.2923 1 1.41089 0.82058 113.6

1

1

1

1

1

1

1

1

1

152.2

4

1

1

10.82 44.7

10.82 44.7

10.82 44.7

10.82 44.7

10.82 44.7

10.82 44.7

10.82 44.7

10.82 44.7

10.82 44.7

10.82 44.7

10.82 44.7

10.82 44.7

10.82 44.76.8

8.7

8.7

8.7

8.7

8.7

8.7

8.7

8.7

8.7

8.7

8.7

4

300

A-2-4 300

A-2-7 300

A-2-4 300

A-2-4 300

A-2-4 300

5

A-2-4 300

12

A-7-5 300

300

A-2-4 300

A-2-4 300

150

150

150

150

150

150

5

150

12

150

150

150

150

0.27 0.0004.39

0.29 0.000792

0.14 1.55E-06

0.29 1

0.26 0.00364

0.27 0.000439

0.25 0.04

0.27 0.000439

0.39 4.28E-06

0.38 3.29E-06

0.36 1.95E-05

0.27 0.000439

0.27 0.00326

123.4

120.2

120.8

119.8

124

123.4

127

123.4

102

104.8

107.9

123.4

123.1

0.8

0.8

0.8

3

0.8

0.8

0.8

0.8

0.8

0.8

0.8

0.8

0.8

0.22

0.22

0.22

0.22

0.22

0.22

0.22

0.22

0.22

0.22

0.22

0.22

0.22

18.39 9.28522 0.643865 3.09113 189.6

19.65 10.2125 0.3 3.72724 100

12 76.5824 0.926038 0.42491 500

19.77 5.74545 1.95497 0.71916 100

17.88 5.85556 1.8823 1.08956 110

18.39 9.28522 0.643865 3.09113 189.6

15.26 7.2555 1.234 0.83152 117.4

18.39 9.28522 0.643865 3.09113 189.6

32.69 125.312 0.57723 0.10524 500

31.24 117.641 0.621817 0.15556 500

39.57 108.409 0.68007 0.21612 500

18.39 9.28522 0.643865 3.09113 189.6

18.54 13.4953 0.567768 3.18708 160

A-2-4

A-1-a

A-7-5

A-6

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Table 12. (Continued) Site_ID Plasticity Index (PI) D60 (mm) Passing #4 (%) Passing #200 (%) Soil Layer 3 Material Thickness (inches) Number of Elements Porosity Saturated permeability (ft/hr) Dry unit weight (pcf) Dry thermal conductivity (BTU/hr-ft- °F) Dry heat capacity (BTU/ft3-°F) Initial VMC (%) Fredlund–af Fredlund–bf Fredlund–cf Fredlund–hr Plasticity Index (PI) D60 (mm) Passing #4 (%)

16_1010 2

23_1026 0

27-4040 14

27_6251 0

31_3018 1

34_0506 2

34_0902 1

36_0801 2

39_0901 24

46_0804 19

46_9187 16

50_1002 2

56_1007 1

0.3216 87.2 22.4

0.3216 87.2 22.4

5.73 55.4 27.4

2 87.2 10

0.3477 87.2 5

0.3216 87.2 22.4

10.82 44.7 8.7

0.3216 87.2 22.4

0.02798 94 70.5

0.02798 94 70.5

0.05364 93.5 63.2

0.3216 87.2 22.4

0.3038 87.2 30

A-2-4

A-7-5

300

300

150

150

0.27

0.39

0.000439

4.28E-06

123.4

102

0.8

0.8

0.22

0.22

18.39 9.28522 0.643865 3.09113 189.6 2

32.69 125.3 12 0.57723 0.105242 500 24

0.3216 87.2

0.02798 94

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Table 12. (Continued) Site_ID Passing #200 (%) Deep ground temperature (°F)

16_1010

23_1026

27-4040

27_6251

31_3018

34_0506

34_0902 22.4

36_0801

39_0901 70.5

46_0804

46_9187

50_1002

56_1007

51

48.1

40.88

40.55

51.43

53.74

55.25

47.85

54

44.87

48.13

46.4

46.03

1 inch = 25.4 mm 32 °F = 0 °C (Deduct 32, then multiply by 5, then divide by 9). Note: For soil layers, The Fredlund Soil Water Characteristic Curve model is used to relate soil suction to water content. Fredlund parameters af and hr have units of psi. Parameters of bf and cf are unitless. Parameter af is a measure of air entry, the soil suction at which the soil becomes less than 100-percent saturated. Parameters bf and cf determine the rate of change of moisture content versus suction as it transitions from saturated to unsaturated (no free water). hr defines the slope of the curve after free water is removed.

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REFERENCES [1] [2] [3]

[4] [5] [6] [7] [8] [9] [10]

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[11]

[12] [13] [14]

[15]

[16] [17] [18]

NOAA Manual NOS NGS 1. (1978). Geodetic Bench Marks, U.S. Department Of Commerce, NOAA, Rockville, MD, September. Boyd, D. W. (1973). Normal freezing and thawing degree-days for Canada. Environment Canada, Atmos. Environ., Rep. CL 14–73. Ali, H. A. & Tayabji, S. D. (1999). Determination of Frost Penetration in LTPP Sections, FHWARD-99-088, U.S. Department of Transportation, Federal Highway Administration, McLean, VA. FHWA, LTPP Seasonal Monitoring Program. (1994). Instrumentation Installation and Data Collection Guidelines, Report No. FHWA-RD-94-1 10, April. FHWA. (2000). LTPP Guidelines for SMP Phase II Equipment and Instrumentation Installation, SM35, April 10. FHWA (1999). LTPP SMP Phase II Monitoring, SM-31, December 7. LTPP Seasonal Monitoring Program SMP II Equipment Installation/De-Installation Reports prepared by LTPP Regional Contractor Offices for individual sites. Computed Parameters: Freeze/Thaw Monograph for LTPP. (1998). Publication No. FHWA-RD-98- 177. LTPP Information Management System, IMS Quality Control Checks, FHWA. Jiang, Y. J. & Tayabji, S. D., (1999). Analysis of Time Domain Reflectometry Data From LTPP Seasonal Monitoring Program Test Sections, Final Report, Publication No. FHWA-RD-99- 115, U.S. Department of Transportation, Federal Highway Administration, McLean, VA. Larson, G. & Dempsey, B. J., (1997). Enhanced Integrated Climatic Model, Version 2.0, Final Report, Contract DTFA MN/DOT 72114, Department of Civil Engineering, University of Illinois at Urbana-Champaign. Roberson and Siekmeier. (2000). Transportation Research Record 1709: Using a Multi-Segment TDR probe to Determine Frost Depth in Pavement Systems. Benson and Bosscher (1999). Remote Field Methods to Measure Frost Depths, in Field Instrumentations of Rock and Soil, ASTM 1358. Lytton, R. L., Pufahl, D. E., Michalak, C. H., Liang, H. S. & Dempsey, B. J. (1993). An Integrated Model of the Climatic Effects on Pavements, Report No. FHWA-RD-90-033, U.S. Department of Transportation, Federal Highway Administration, McLean, VA. Zou and Elkins. (1994). Pavement Responses to Seasonal Variations, Proceedings of the 4th International Conference on the Bearing Capacity of Roads and Airfields, Minneapolis, MN, July. E.C. Drumm & R. Meier. (2003). LTPP Data Analysis Daily and Seasonal Variations in In-situ Material Properties, NCHRP Web Document 60, November. C.A. Richter. (2003). Seasonal Variations in the Moduli of Unbound Pavement Layers, Report No. FHWA-RD-04-079, FHWA, August. Farrington, S. P., Gildea, M. L., Dougherty, D., Rizzo, Frost Penetration Prediction and Mapping, Final Report of Contract #984024, Agency of Transportation, State of Vermont.

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[19] Dempsey, B. J., Herlach, W. A. & Patel, A. J., (1985). The Climatic-MaterialsStructural Pavement Analysis Program, Final Report, FHWA/RD-84-1 15, Volume 3, Federal Highway Administration, Washington, DC. [20] Liu, S. J. & Lytton, R. L. (1985). Environmental Effects on Pavement Drainage, Volume IV, Report No. FHWA-DTFH61-87-C-00057, Federal Highway Administration, Washington, DC. [21] Guymon, G. L., Berg, R. L. & Johnston, T. C. (1986). Mathematical Model of Frost Heave and Thaw Settlement in Pavements, Report: U.S. Army Cold Regions Research and Engineering Laboratory. [22] D. Zollinger, S. Lee, J. Puccinelli, N. Jackson. (2008). Long Term Pavement Performance Computed Parameter: Moisture Content, Final Report, Publication No. FHWA-HRT-08-030, U.S. Department of Transportation, Federal Highway Administration, McLean, VA.

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In: Long Life and Quiet Pavement: Research and Issues ISBN: 978-1-60741-888-7 Editor: Gordon E. Daniels © 2010 Nova Science Publishers, Inc.

Chapter 5

LTPP BEYOND FY 2009: WHAT NEEDS TO BE DONE? United States Department of Transportation OVERVIEW

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This chapter summarizes the current status of the Long-Term Pavement Performance (LTPP) program and its major activities—data collection, data storage, data analysis, and product development. It describes the work that will be needed beyond 2009 to realize the full potential of the world’s most comprehensive pavement performance database and the benefits that will be accrued by capitalizing on the investment that has been made. The work that remains is as follows: 1. Provide ongoing security and maintenance of the LTPP database and manage the Materials Reference Library (MRL). 2. Continue to support LTPP database users. 3. Further develop the LTPP database including additional data collection and database refinements. 4. Continue data analysis and product development. Addressing these needs is included in the Federal Highway Administration’s (FHWA) planning for future infrastructure research and development as documented in Highways of the Future—A Strategic Plan for Highway Infrastructure Research and Development (FHWA-HRT-08-068). The LTPP program is an ongoing and active program. To obtain more information, LTPP data users should visit the LTPP Web site at http://www.fhwa.dot.gov/ pavement/ltpp. LTPP data requests, technical questions, and data user feedback can be submitted to LTPP customer service via e-mail at [email protected].

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INTRODUCTION The United States reaps a substantial return from investing approximately $40 billion a year in its pavements. As large as that figure seems, a recent article in Roads & Bridges puts the annual savings from the interstate system at $737 billion when considering “safety benefits, saved time, reduced fuel, and lower consumer costs.”[1] The LTPP program, the most comprehensive pavement research program ever undertaken, addresses the issue of how to optimize this recurring investment. The need for the LTPP program was first identified in the Transportation Research Board’s (TRB) America’s Highways: Accelerating the Search for Innovation.[2] This chapter, prepared by a panel of senior leaders in the transportation community, noted that highway pavements do not always live up to design expectations and recommended a “long-term field test that systematically covered a wide range of climate, soil, construction, maintenance, and loading conditions....”[2] In 1986, based on this recommendation, the American Association of State Highway and Transportation Officials (AASHTO) developed the plan for such a program to be included in the 5-year Strategic Highway Research Program (SHRP). The mission of the program, known now as the LTPP program, was to promote increased pavement life through the following: •

•

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•

Collecting and storing performance data from a large number of in-service highways in the United States and Canada over an extended period to support analysis and product development. Analyzing these data to describe how pavements perform and to explain why they perform as they do. Translating these insights into knowledge and usable engineering products related to pavement design, construction, rehabilitation, maintenance, preservation, and management.

Congress funded SHRP which was managed by the National Academy of Sciences as part of Federal- aid highway authorizing legislation in 1987. LTPP field data collection began in 1989. It was always understood that the achievement of the program’s objectives required that the program be continued over the long term. The long term, as originally envisioned, was a period of 20 years—the minimum duration necessary to establish a path to better roads. Therefore, as SHRP began to diminish, continuation of LTPP under the FHWA was formally authorized by Congress in the Intermodal Surface Transportation Efficiency Act (ISTEA) of 1991. In 1992, the FHWA assumed management and administrative responsibilities to continue LTPP and complete the planned pavement performance monitoring. In 2009, the LTPP program is reaching its 20-year monitoring milestone—a critical milestone in this national pavement research initiative similar to the end of the first 5-year SHRP program. A dataset reflecting two decades of data collection is available. Analysis results derived from the application of the data are also available to support advances in pavement engineering science, to provide valuable insights and innovations, and to form the basis for the products needed by State transportation departments and local and municipal agencies.

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The LTPP database is the program’s most important product; however, LTPP has produced or contributed to many other products that have benefited pavement engineering and pavement management practices. Other LTPP products that have been developed range from standardized data collection methods, to new engineering tools, to new pavement design methods. These advances are only the beginning as many significant activities, real benefits, and innovative products remain to be performed and developed after 2009. This chapter briefly summarizes the current status of LTPP and describes the work needed after 2009 to capitalize on the investment made in developing the world’s most comprehensive pavement research database. The purpose of this chapter is to provide LTPP’s stakeholders with a look ahead to the critical activities and products that need to be pursued beyond 2009 in order to reap the high return rewards of this unique and critical program that has and will continue to influence the way pavements are designed, built, and maintained.

LTPP IN 2009 LTPP requires activities in four main areas: data collection, data storage, data analysis, and product development. These activities are conducted in accordance with a well-defined plan developed in collaboration with LTPP’s primary stakeholders, the States, Canadian Provinces, academia, and industry. Accomplishments in each area derived from the substantial investment to date are discussed below.

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Data Collection The performance data collection effort is the largest and most comprehensive ever undertaken on in-service highway pavements. The LTPP experiment plan was developed in a collaborative manner to address the data analysis needs for various pavement types and was extensively peer reviewed by experts and highway agency practitioners.

Figure 1. Geographic distribution of LTPP test sections Long Life and Quiet Pavement: Research and Issues : Research and Issues, Nova Science Publishers, Incorporated, 2010. ProQuest Ebook

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Data collection guides developed by SHRP and kept current by the FHWA explicitly define the data elements to be collected for each experiment and test section, the sampling and testing protocols to be employed, and the processes used to assess data quality and store records in the LTPP database. Data collection categories include climate, traffic volumes and loads, pavement layer types and thicknesses, material properties, and pavement condition (distress, longitudinal and transverse profile, and structural response). Some data are collected centrally, while others are the responsibility of the participating States or Provinces. Regardless of the collecting agency, a high priority is placed on the accuracy and completeness of the measurements. Of the 2,512 LTPP test sections located throughout the United States and Canada, 950 test sections are currently active. Figure 1 shows the geographic distribution of the test sections, while figure 2 shows the number of active test sections over time. Prior to 2005, most data collection activities occurred on a yearly cycle for each test section. However, data collection on in-service test sections was reduced from annual surveys to one round of testing between 2006 and 2008 due to budget constraints of the Safe, Accountable, Flexible, Efficient Transportation Equity Act: A Legacy for Users (SAFETEALU). This reduction in testing frequency, while a setback to the program, can be partially overcome with a return to more frequent data collection in the future. The remaining sections are those that are of most interest to pavement engineers, including many sections in the rehabilitation and structural factor experiments of the program.

Figure 2. Variation in number of active test sections over time

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Data Storage The LTPP database is the central facility for assembly, storage, maintenance, and dissemination of the collected data. The pavement performance database is LTPP’s principal operational tool, its most strategic product, and its legacy to its stakeholders and future generations of highway researchers and practitioners. The LTPP pavement performance database is supported by a traffic database and a large amount of ancillary information including test section photographs, videos, reports, raw data files, construction plans, data collection protocols, data processing guides, and other program documentation. The LTPP database is the largest and most comprehensive pavement performance research database ever created. At present, the database includes approximately 150 million records of data comprising 11,000 individual data elements stored in 460 tables. By virtue of its size and the evolutionary nature of its development, the database can be characterized as a complex data warehouse. Plans to simplify the database structure, add more commonly used computed parameters,1 improve access, and create a ready-for-analysis data structure have been deferred due to budget constraints. Therefore, in 2009, LTPP is delivering a data warehouse that is somewhat cumbersome to use properly and efficiently without extensive training and experience. Providing technical support to data users has been and will continue to be an important activity. The ancillary data and information are even more voluminous than the pavement performance database. The traffic database presently contains more than 1.5 billion raw traffic classification and weight measurement records. The central electronic ancillary information consisting of data and images not in the pavement performance or traffic databases currently includes 10,000 files. Over 12,000 35-mm black and white, high-quality film-strips of LTPP test sections are stored in the MRL. In addition, FHWA has created a central LTPP library at the Turner-Fairbank Highway Research Center (TFHRC) to store the more than 600 physical documents associated with the program, many of which have yet to be converted into a searchable electronic format. Plans to create an indexed electronic library containing all of this information were canceled due to program budget constraints.

Data Analysis Analysis of LTPP data, the key to producing benefits and products, began in earnest in 1992 with the evaluation of the then-current version of the AASHTO Guide for the Design of Pavement Structures.[3] That analysis confirmed the need for a new guide because it showed large discrepancies between predicted and actual performance. Since that initial analysis, a total of 90 LTPP data analysis reports have been published by SHRP, FHWA, and the National Cooperative Highway Research Program (NCHRP). Highlights of these reports can be found in the 2000 and 2004 Key Findings from LTPP Analysis, and many are available on the LTPP Web site http://www.fhwa.dot.gov/pavement/ ltpp/index.cfm.[4,5] In addition, States, Provinces, and universities have published countless reports, theses, and dissertations based on analysis of LTPP data.

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Data analysis serves several important functions. First, it provides the technical basis for identifying and developing tools and products that engineers and managers can use to design more cost-effective and better-performing pavements. It ensures that the data being collected are of the quality and completeness needed to find answers about how and why pavements perform as they do. It is also used to fill in data gaps, for example estimating cumulative traffic loads from short-term traffic monitoring measurements. Another major function of data analysis is to have experts centrally compute common parameters from the raw measurements so that future researchers do not have to expend limited research resources performing these same computations. The FHWA worked with the Data Analysis Expert Task Group (ETG) of the TRB to develop a strategic plan for LTPP data analysis. This plan was subsequently expanded and maintained with support of all of the TRB LTPP committees supporting the ETG. The plan lays out a long-term strategy for data analysis that recognizes both internal and external analytical needs, the current or anticipated data availability, and the building block process through which the major products of LTPP will be developed. The plan is a coordinated set of interrelated analyses, with some outcomes being inputs to others. FHWA maintains the plan by tracking analytical efforts completed, currently underway, and yet to be undertaken.2 To date, 66 of 116 identified projects have been completed through FHWA, NCHRP, or pooled fund projects. Due to funding limitations under SAFETEA-LU, only two formal data analysis projects have been supported with LTPP program funds for fiscal years 2005 to 2009. Over 40 LTPP analysis projects identified in the plan remain to be funded.

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Products and Benefits Documented outcomes of the LTPP program include many positive and wide ranging impacts. Long lasting and quality pavements contribute to the following: •

Country—Expanded economy.

•

Public—Increased safety, decreased congestion, and reduced user costs.

•

Environment—Reduced pollution.

•

Highway agencies—New and improved engineering practices and savings.

•

Education—Real world data for university curricula.

•

Industry—New equipment, manuals, calibrations, and lab procedures.

•

Research community—A national pavement performance database.

Products derived from LTPP have been flowing to State transportation departments and other segments of the highway community since the early years of the program. Initially, Long Life and Quiet Pavement: Research and Issues : Research and Issues, Nova Science Publishers, Incorporated, 2010. ProQuest Ebook

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these were methods, guidelines, and procedures for standardized testing and performance data collection. While these procedures were developed to meet LTPP data collection needs, their conversion into standard practices has been an AASHTO activity. Some products and benefits from LTPP already implemented in practice are based on best-practice construction specifications developed for the pavement experiments requiring new construction, while other products were developed from early analysis of LTPP data. The products and benefits derived from the LTPP program include improved data collection techniques, better data quality and quality assurance tools, new materials, testing protocols, software for selecting the most suitable and cost-effective asphalt binder for a particular site, pavement maintenance and repair manuals, a more efficient method for asphalt pavement layer temperature measurements, rigid pavement design software, the implementation of wider Portland cement concrete (PCC) slabs and narrower joints, and discontinued use of skewed joints. Also, the developers of the Mechanistic- Empirical Pavement Design Guide (M-E PDG), developed under the NCHRP 1-37A project and adopted by AASHTO in 2008, stated that it would have been impossible to develop the guide and nationally calibrate its prediction models without LTPP data.[5,6] Throughout the life of the LTPP program, significant efforts have been made to improve data accessibility for all potential users. At least once a year for more than a decade, standard data releases containing data from the LTPP database have been made available on CDs and/or DVDs. Since March 2003, DataPave Online has also made available a significant portion of the data contained in the LTPP database via the Web at http://www. ltppproducts.com. Another significant benefit of the LTPP program has been the introduction and use of LTPP data in university engineering curricula. Many engineering schools with pavement engineering classes have developed course curricula around the LTPP data and database. In addition to challenging students with computational problems based on real field data, this provides the benefit of introducing both professors and students to database manipulation tools, which is an emerging need for future engineers that is not presently provided in most engineering programs. Hundreds of undergraduate and graduate students have used the LTPP database as part of their pavement engineering coursework. More than 75 engineering graduates with advanced degrees based on analysis of LTPP data are now working in the profession. The funding dedicated to LTPP in SAFETEA-LU has not been sufficient to support both the development of LTPP-based products and the completion of the needed data collection. For this reason, LTPP product development activities are funded as part of FHWA’s broader Pavement Technology Program. In economic terms, the 2001 study An Investment Benefiting America’s Highways: The Long Term Pavement Performance Program (FHWA-RD-0 1-094) estimated that the use of just one LTPP product, the LTPPBind software for selection of the SuperPave® binder grade, can save as much as $50 million per year. Estimates of the value of this and other products of the program to date give the program annual benefit-to-cost ratios ranging from 5 to 10. The overall rate of return could be much greater with an appropriate investment in data analysis and product development.

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Lessons Learned to Date LTPP is a unique national research program whose operations model consists of providing research quality data for analysis. Data quality has been a prime concern in the development and operation of the LTPP program. LTPP is also unique in its magnitude and duration. Full documentation of the many lessons learned over the course of the last 20 years is beyond the scope of this chapter. However, within the context of planning for LTPP after 2009, the most important lessons learned to date are as follows: •

•

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•

•

•

Continued involvement of stakeholders is vital to the ultimate success of the LTPP program. Routine coordination and communication with participating highway agencies, for example, are of paramount importance. Without support from the States and Provinces, performance monitoring and other data collection activities on the LTPP test sections would not be possible. Furthermore, the program cannot afford to lose priority test sections due to a lack of interest by the highway agencies. Central management of core LTPP functions is required to achieve consistent, highquality data. Efficient execution of a program, such as LTPP, requires considerable planning and a predictable, uninterrupted stream of funding. While LTPP has received continued funding, there has been considerable disruption and uncertainty as to how much money would be available and when it would be available. This was the case, for example, over the nearly 2-year period of extensions and continuing resolutions under the TEA-21 highway legislation immediately prior to the SAFETEA-LU highway legislation. The adjustments in short- and long-term plans and priorities made necessary by funding uncertainties and shortfalls led to missed opportunities, as is the case with pavement performance monitoring and the delay of critical activities. The LTPP database is the program’s principal operational tool, its most strategic product, and its legacy to future generations of highway researchers and practitioners. LTPP’s efforts over the past two decades have focused primarily on the collection and efficient storage of high-quality data in the database. The database is a large data warehouse, not an analysis database. Successful navigation requires indepth knowledge that requires a substantial investment of time to develop. In addition, the database contains many raw data elements that must be combined or processed in some way to derive data sets suitable for analysis. In some cases, significant effort is required to extract and prepare the data for analysis. Therefore, refinements and enhancements to the database to significantly improve its accessibility are viewed high-priority needs to address after 2009. More than 20 years are required to fully document and understand the performance of high-performing in-service pavement structures. To understand why some pavements provide superior service beyond a 20-year design life, monitoring must be extended beyond 20 years.

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LTPP BEYOND 2009 The LTPP database that is delivered in 2009—the culmination of the originally-planned 20-year monitoring period for the LTPP test sections—has enormous potential as the foundation for improvement in pavement engineering and management procedures and practices. While some of that potential has already been realized, full realization will require work beyond 2009. The additional work currently identified as necessary to take full advantage of the investment already made in LTPP is as follows: 1. Provide ongoing security and maintenance of the LTPP database and manage the MRL. 2. Continue to support LTPP database users. 3. Further develop the LTPP database including additional data collection and database refinements. 4. Continue data analysis and product development.

Security and Maintenance of the LTPP Database The LTPP data have been available to all potential users since the first public release of data in May 1999. The LTPP database is expected to remain an important resource for pavement performance research for decades to come. However, this expectation can only be realized if mechanisms are put into place to ensure that the database and supporting information remain accessible to all. Accomplishing this will require the following:

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•

•

Arrangements for secure storage of backup copies of the database and updates of the database software and hardware needed to keep pace with changing data storage technology technology, newly discovered data issues, and new ways to characterize data. This work includes expansion and development of the auxiliary information management system. Maintenance of the MRL established as part of the SHRP Asphalt Research Program. Although not solely an LTPP activity, the MRL is an important component of the work required to secure the LTPP data by virtue of the fact that it is the repository for material samples and 35-mm film distress records from LTPP test sections.

History offers an important lesson in this regard. The 1957 American Association of State Highway Officials (AASHO) Road Test data were used by researchers and engineers in the Federal Government, State transportation departments, and industry associations for many years after the completion of the test. However, a majority of its data were lost due to a fire at the public university that volunteered to house the data. Avoiding a similar loss of the LTPP data will require positive action to secure continued access to LTPP data and information after 2009. Providing for security and maintenance of the LTPP database will assure that it remains accessible to any and all potential users. This is the minimum level of functionality needed to assure progress toward full achievement of the potential of LTPP. Without adequate

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investment in these activities, the potential of the LTPP database to contribute to advancements in pavement engineering will be gradually eroded and eventually lost.

Materials Reference Library The original MRL was established in the late 1980s in Austin, TX, as part of the original SHRP. The purpose of the MRL was to create a central storage/warehouse facility for asphalt cements and aggregates selected for use by the Asphalt Research Program of SHRP and pavement and subsurface materials from both the General Pavement Studies (GPS) and Specific Pavement Studies (SPS) experiments of the LTPP program. This has made it possible to link the results of past, present, and future research of national significance. Over time, materials from other FHWA and national pavement research activities such as the FHWA Crumb Rubber Modifier Project, Accelerated Loading Facility (ALF), and the WesTrack Project were also stored in the MRL. Material from the National Center for Asphalt Technology (NCAT) and the Western Research Institute (WRI) research work will be stored there in the near future. From 2003 to 2006, materials from the MRL have been used to support 32 national highway research projects. Samples from the LTPP test sections added to the MRL enable the application of as-yet undeveloped test methods to LTPP materials, thereby enabling updates of the LTPP data to reflect new technologies. These samples have and will continue to make it possible to clearly understand the relationships among studies including LTPP through its use of common materials.

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Support Users of the LTPP Database For the past decade, researchers throughout the world have successfully applied LTPP data to address a broad array of pavement engineering problems. Among the keys to their success has been the availability of technical support to answer their questions, point them to the documentation they need to understand the data applicable to their problem, and otherwise help them successfully navigate and manipulate the LTPP database to obtain the appropriate data. Over 5,000 requests for LTPP data or technical assistance have been processed by LTPP. Given the complexity of the LTPP database, continuing to provide technical support to data users is important to maximize the success and efficiency of those who apply the LTPP data to address pavement engineering problems. User support may take several different forms and the level of support provided may depend on the intended use of the data as illustrated below through the following sample scenarios: •

For studies of national significance, such as the NCHRP 1-37 effort that developed the new M-E PDG, user support may entail: (1) face-to-face meetings with the contract team to clearly understand their data needs and required format as well as to suggest the best source of those data within the LTPP database, (2) custom extractions from the LTPP database to provide the needed data in the appropriate format, and (3) ongoing technical support to ensure a clear understanding of the

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•

•

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LTPP data by the contractor team and to clarify issues that may arise from their usage. In the case of State and local highway agencies, user support could focus on the generation of custom data extraction routines that would generate data sets for selected location(s) that could be used to calibrate the M-E PDG for local conditions. User support would also likely entail general technical support to ensure a clear understanding of the LTPP data provided and to clarify issues that may arise from their usage. Support may include training for government agencies, industry, academia, and local agencies. For example, LTPP has developed a professor training workshop that familiarizes and engages professors who teach pavement engineering courses with the LTPP database and real pavement analysis problems. For university students working on their theses, dissertations, or other university or State- sponsored research projects, user support could include: (1) provision of the standard LTPP database release along with the required documentation, (2) recommendations on where to find the needed data within the database structure, and (3) clarification of data-related questions and issues.

The above examples are just a few of many possible scenarios, but they illustrate that the actual form and level of user support will depend on the nature of the request and from where it originates. In addition to the above, keeping track of data requests and suggestions made by data users to improve either the customer support functions or the database itself is also a vital function associated with user support (i.e., the feedback mechanism).

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Further Develop the LTPP Database While the LTPP database is already an unprecedented resource for deriving answers about how and why pavements perform, its value could be improved significantly through targeted investment in its further development. Two areas of investment warrant consideration: (1) additional monitoring of selected LTPP test sections to improve its potential for answering the most critical performance questions facing pavement engineers and (2) refinement of the database to make it easier to use. More details concerning these opportunities are listed below.

Test Section Monitoring A total of 950 LTPP test sections remain in active service in 2009 (see figure 2). Among these test sections, some have been constructed or rehabilitated within the past decade in several of the SPS-2 projects, while some are long-lived structures still in good condition, and others are monitored as LTPP test sections both before and after rehabilitation. Continued performance monitoring of these sections will be needed to fully answer the questions they were selected to address. For example, many of the SPS-2 experimental sites have been in service for fewer than 15 years as of 2009. In addition, 172 of the original 207 (83 percent) SPS-2 test sections are still active in 2009. Similarly, 155 of the presently active GPS-6 and -7 (asphalt concrete

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(AC) overlay on AC and PCC pavements, respectively) experimental test sections have been in service for 10 years or less as of 2009. An opportunity for continued monitoring that warrants consideration is the collection of permanent distress records for those test sections that remain in service. This activity was highly recommended by the TRB LTPP Committee for pursuit prior to 2009, but it was not completed due to budgetary constraints. One area where continued LTPP test section monitoring is already provided for to some degree is the continued collection of traffic data for selected SPS test sections. This work is part of the LTPP SPS Traffic Data Collection Pooled Fund Study. Table 1 provides more specifics as to the benefits that may be derived through additional monitoring of severalsubsets of the LTPP test sections that remain in service as well as what will be lost if monitoring is not continued.

Database Refinements The LTPP database that is delivered in 2009 is best described as a large data warehouse. While the LTPP database is well documented, successful navigation requires in-depth knowledge that develops only after a substantial investment of time. In addition, the LTPP database contains many raw data elements that must be combined or processed to derive data sets suitable for analysis. Several activities have been identified as having the potential to make the LTPP database easier to use, which include the following:

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• • • •

• • • •

Creating a consolidated pavement surface distress time history dataset. Developing consolidated transverse profile indices. Consolidating data tables. Generating additional computed parameters (e.g., layer moduli derived from deflection data, hot mix asphalt dynamic modulus values from existing laboratory test results, etc.). Creating ready-to-use analysis datasets. Improving the data quality labeling system. Interpreting test section images. Enhancing electronic documentation for the program.

Pursuit of these enhancements would significantly improve the accessibility of the LTPP database to those not intimately involved in its development and bring the LTPP database into better compliance with section 515 of the Treasury and General Government Appropriations Act for fiscal year 2001 (Public Law 106-554; H.R. 5658). Section 515 directs the Office of Management and Budget (OMB) to issue governmentwide guidelines that “provide policy and procedural guidance to Federal agencies for ensuring and maximizing the quality, objectivity, utility, and integrity of information (including statistical information) disseminated by Federal agencies.” Funding restrictions preclude pursuit of these enhancements prior to 2010.

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Table 1. Summary of economic analysis results Monitoring of LTPP Test Sections SPS-1 and -2

Benefits of Additional Data Collection Improved ability to derive definitive results concerning the impact of design features on pavement performance.

SPS-8

Assessment of the effects of loading and environment on pavement life. This work cannot begin until sufficient distress (serviceability loss) has accumulated on the SPS-8 test section pavements. Improved design, construction, and maintenance procedures for AC overlays, which will result in longer and/or more economical renewed pavement life. Performance data required to develop, verify, and calibrate designs for long- life, highperformance pavements and to manage and maintain those new pavements. Future analysts will have the opportunity to revisit test section condition on the basis of objective records. Potential for interpretation/reinterpretation of images based on improved distress definitions/ criteria.

GPS-6 and -7 SPS-5, -6, and -9 (AC overlay)

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GPS-1, -2, -3, -4, and -5 (long life)

Permanent distress records for LTPP

What Is Lost if Monitoring is Not Continued Research conclusions that are drawn will be founded on incomplete performance histories,and the results may be misleading in relation to longterm performance. The opportunity to quantitatively evaluate the performance impact of environmental factors absent of heavy loads, which is critical for pavement design and performance models. Knowledge required for improving the design, construction, and maintenance of AC overlays. Knowledge required for designing, managing, and maintaining long-life, highperformance pavements.

No objective record of pavement distress condition will exist for dates after 2005.

Data Analysis and Product Development The greatest way to derive benefit—the real payoff—from the LTPP database is to first apply the data and then develop products from what is learned through its application. While it is likely that individual researchers and organizations around the world will continue to apply the LTPP data on an ad hoc basis for as long as it remains accessible to them and applicable to questions of interest, the greatest and most immediate impact will be achieved if an integrated and programmatic approach to analysis (such as that defined in the Strategic Plan for LTPP Data Analysis) is pursued in an organized fashion and accompanied by a similarly coordinated and organized program of product development. More specifics concerning the work that is needed are provided next.

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Data Analysis The Strategic Plan for LTPP Data Analysis provides the framework, organization, and classification matrix for LTPP-related research projects. The plan identifies the following seven strategic objective areas: • • • • •

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• •

Traffic characterization and prediction. Materials characterization. Determination of environmental effect in pavement design and performance prediction. Evaluation and use of pavement condition data in pavement management. Development of pavement response and performance models applicable to pavement design and performance prediction. Maintenance and rehabilitation strategy selection and performance prediction. Quantification of the performance impact of specific design features such as drainage and prerehab surface preparation.

More than 60 analysis projects defined in the plan have been completed, and over 300 research papers have been submitted to the TRB using LTPP data. Numerous agencies have initiated follow-up research and/or implementation activities within their jurisdictions to take advantage of the LTPP efforts. However, 40 defined research projects remain to be performed, and some analysis outcomes are not ready for development of research problem statements since the underlying research will not have been performed. In addition, second looks at early findings from LTPP data are recommended to determine if the short-term trends were correct. It is also important to recognize that while national needs drove the analysis program defined in the Strategic Plan for LTPP Data Analysis, the plan does not encompass all of the needs to which the data are applicable. LTPP data, for example, are also applicable to some of the needs identified in the Concrete Pavement (CP) Roadmap, the National Asphalt Roadmap, and, to a lesser degree, the Pavement Preservation Roadmap.[7–9] Many of the studies outlined in these strategic roadmaps will be difficult to perform without the use of LTPP data.

Product Development The LTPP program was established to enable the development of new pavement engineering and pavement management products. While LTPP has created many products during the course of its mission, the most significant products will be derived after the full performance history of the test sections has been documented and complete suites of quality data are available in the LTPP pavement performance database. As noted by the TRB LTPP Committee in its 2001 report Fulfilling the Promise of Better Roads: The fact that LTPP data are being used does not indicate that the job is complete. Pavement distresses observed in the studies so far are primarily confined to the lighter duty test sections. To learn the lessons required to design long-life, high-performance pavements, we must continue to track the performance of the more structurally robust test sections. It is their performance that will yield the requisite knowledge to develop, verify, and calibrate designs demanded by 21st century highway networks; their performance that will teach us

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how to manage and maintain these new pavements. If LTPP stops now, we will have only learned how to build and maintain 20th century pavements better.[10]

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Other Considerations The post-2009 activities described in the preceding paragraphs are critical activities to fully complete the LTPP program. Those activities can be expanded to further extend the usefulness of the LTPP program. The value of the LTPP database could be enhanced through the addition of new materials test data and other inputs required by the M-E PDG, in particular the level 1 inputs. Dynamic modulus testing of asphalt mixes and asphalt binder characterization testing in accordance with the M-E PDG input requirements, for example, would facilitate the calibration of the existing performance models at the State and local level while at the same time providing the necessary data for future calibration and validation of the existing models or the development of improved performance models. Also, improved traffic loading and volume estimates from the LTPP test sections could contribute to M-E PDG implementation. At a higher level, completion of LTPP does not fully address the need for long-term monitoring of pavement performance. America’s Highways: Accelerating the Search for Innovation, Special Report 202, the 1978 Surface Transportation Act and the FHWA LongTerm Monitoring Study of the early 1980s clearly established the need for long-term or continuous pavement monitoring.[2] The fulfillment of that need began with the LTPP program. However, many new technologies have evolved over the past two decades, including SuperPave®, the new M-E PDG, new construction technologies, and new materials. As a result, further long-term monitoring of pavement performance is warranted. The LTPP processes, procedures, and database could certainly serve as the spring board for such longterm monitoring programs.

SUMMARY The first 20 years of data collection, data storage, data analysis, and product development have already provided LTPP stakeholders with a number of high priority outcomes from the program. However, the work is not yet complete. Working with stakeholders, FHWA has identified the work that remains to be done and estimated the cost of completing that work. The required activities fall under the following four strategic work areas: 1. Provide ongoing security and maintenance of the LTPP database and manage the MRL. 2. Continue to support LTPP database users. 3. Further develop the LTPP database including additional data collection and database refinement. 4. Continue data analysis and product development.

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United States Department of Transportation Some of the benefits to be reaped through these activities will include the following: • • • •

Improved ability to derive definitive results concerning the impact of design features on pavement performance. Ability to assess the effects of loading and environment on pavement life. Improved design, construction, and maintenance procedures for AC overlays, which will result in longer and/or more economical renewed pavement life. Increasxed knowledge required to develop, verify, and calibrate designs for long-life, high-performance pavements and to manage and maintain those new pavements.

Stakeholders of the LTPP program can be assured that plans to continue the program are a prime consideration of FHWA’s future research and technology strategy. The Long-Term Infrastructure Performance Strategy outlined in Highways of the Future—A Strategic Plan for Highway Infrastructure Research and Development (FHWA-HRT-08-068) is intended to build upon the foundation that has been established through the LTPP program.[11] LTPP, as well as the continuation of the recently initiated Long-Term Bridge Performance program authorized under SAFETEA-LU and pursuit of infrastructure performance data collection needs, are central to FHWA’s strategies for fulfilling the mission of better roads for our Nation.

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THE LONG-TERM PAVEMENT PERFORMANCE (LTPP) PROGRAM The LTPP program incorporates two major studies—SPS and GPS. The primary goal of SPS experiments is to conduct detailed analysis of specific performance factors of newly constructed pavements and overlays. In contrast, the primary goal of GPS experiments is to analyze performance factors of existing pavements and overlays. Table 2. SPS experiment analyses of newly constructed pavements and overlays SPS Test SPS-1 SPS -2 SPS -3 SPS -4 SPS -5 SPS -6 SPS -7 SPS -8 SPS -9P/ SPS -9A

Experiment Analyses of Newly Constructed Pavements and Overlays strategic study of structural Factors for Flexible Pavements strategic study of structural Factors for Rigid Pavements Preventive Maintenance Effectiveness of Flexible Pavements Preventive Maintenance Effectiveness of Rigid Pavements Rehabilitation of AC Pavements Rehabilitation of Jointed Portland Cement Concrete (JPCC) Pavements Bonded PCC overlays of Concrete Pavements study of Environmental Effects in the Absence of Heavy Loads Validation and Refinements of superPave® Asphalt specifications and Mix Design Process/ superPave® Asphalt Binder study

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Table 3. GPS experiment analyses of existing pavements and overlays GPS Test GPS-1 GPS-2 GPS-3 GPS-4 GPS-5 GPS-6 GPS-7 GPS-9

Experiment Analyses of Existing Pavements and Overlays AC Pavement on Granular Base AC Pavement on Bound Base Jointed Plain Concrete Pavement (JPCP) Jointed Reinforced Concrete Pavement (JRCP) Continuously Reinforced Concrete Pavement (CRCP) AC overlay on AC Pavement AC overlay on PCC Pavement Unbonded PCC overlay on PCC Pavement

REFERENCES

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[1]

Wilkins, W. (2006). “A Clay Mold—Two Commissions Working to Improve System,” Roads & Bridges, 4(11). [2] America’s Highways: (1984). Accelerating the Search for Innovation, Special Report 202, Transportation Research Board, National Research Council, Washington, DC. [3] AASHTO Guide for Design of Pavement Structures, (1986) American Association of State Highway and Transportation Officials, Washington, DC. [4] Key Findings from LTPP Analysis: 1990–1999, Report No. FHWA-RD-00-085, Federal Highway Administration, Washington, DC. [5] Key Findings from LTPP Analysis: 2000–2003, Report No. FHWA-HRT-04-032, Federal Highway Administration, Washington, DC. [6] 2002 Pavement Design Guide, (2000) Report No. FHWARD-00- 129, Federal Highway Administration, Washington, DC. [7] (2005). Long-Term Plan for Concrete Pavement Research and Technology—The Concrete Pavement Roadmap: Volume II, Tracks, Report No. FHWA-HRT- 05-053, Federal Highway Administration, Washington, DC. [8] National Asphalt Roadmap: A Commitment to the Future, (2007). NAPA Special Report 194, National Asphalt Pavement Association, Lanham, MD. [9] Transportation System Preservation Research, Development, and Implementation Roadmap, (2008) Federal Highway Administration, Washington, DC. [10] Fulfilling the Promise of Better Roads: A Report of the TRB Long-Term Pavement Performance Committee, (2001).Transportation Research Board, the National Academies, Washington, DC. [11] Highways of the Future—A Strategic Plan for Highway Infrastructure Research and Development, (2008). Report No. FHWA-HRT-08-068, Federal Highway Administration, Washington, DC.

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End Notes 1

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2

Computed parameters are values derived from the raw data that are stored in the LTPP database for use in subsequent analysis. Examples of computed parameters include International Roughness Index (IRI) values computed from longitudinal profile data as a measure of pavement roughness, backcalculated pavement layer moduli derived through analysis of pavement deflection data to characterize the structural characteristics of the pavement layers, and moisture content estimates derived from interpretation of raw data from Time Domain Reflectometry (TDR) probes. See the Strategic Plan for LTPP Data Analysis (http://www. fhwa. dot. Gov /pavement/ ltpp/ stratplan/ strategic.cfm).

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CHAPTER SOURCES

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The following chapters have been previously published: Chapter 1 – This is an edited, excerpted and augmented edition of a United States Department of Transportation, Federal Highway Administration publication, Report No. FHWA-IF-08-004, dated July 2007. Chapter 2 – This is an edited, excerpted and augmented edition of a United States Department of Transportation, Federal Highway Administration publication, Report No. FHWA-PL-07-027, dated August 2007. Chapter 3 – This is an edited, excerpted and augmented edition of a United States Department of Transportation, Federal Highway Administration publication, Publication No. FHWA-HRT-08-035, dated March 2008. Chapter 4 – This is an edited, excerpted and augmented edition of a United States Department of Transportation, Federal Highway Administration publication, Publication No. FHWA-HRT-08-057, dated November 2008. Chapter 5 – This is an edited, excerpted and augmented edition of a United States Department of Transportation, Federal Highway Administration publication, Publication No. FHWA-HRT-09-052, dated 2009.

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INDEX

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A  academics, 104, 106 accessibility, 307, 308, 312 accounting, 156, 164 achievement, 302, 309 adjustment, 55, 179, 185, 186, 187, 188, 199, 205 Africa, 143 age, 59, 63, 104, 143 aggregates, 24, 25, 26, 38, 40, 41, 42, 44, 46, 66, 86, 87, 94, 95, 97, 109, 110, 111, 114, 115, 118, 310 algorithm, 63, 179, 181, 224, 242, 246, 255, 256, 257, 258, 261, 263, 290 alternatives, 45, 55, 59, 66, 70, 76, 77, 78, 81, 115, 118 ambient air, 264 ambient air temperature, 264 amplitude, 163, 211, 219 APL, 43, 112 applied research, 140 ash, 42, 94, 95, 97, 100, 111, 117 assessment, ix, 42, 70, 106, 112, 148, 263, 282 assignment, 57, 70, 248, 249, 252, 255, 261, 263, 291 Australia, 32, 33, 34, 37, 48, 49 Austria, 37, 39, 40, 41, 42, 44, 46, 50, 51, 53, 54, 60, 61, 62, 63, 64, 65, 66, 78, 79, 85, 86, 87, 88, 95, 96, 98, 103, 109, 110, 111, 112, 114, 115, 126, 127, 128, 144, 145, 146 authority, 52, 64 availability, 118, 249, 263, 280, 310

B  background, 11, 204, 243, 264 background information, 204, 264 background noise, 11 Bangladesh, 49

barriers, 2, 11, 54, 100, 101 basilar membrane, 3 behavior, 43, 102, 113, 143, 250 Belgium, 37, 40, 41, 43, 44, 50, 52, 53, 54, 65, 66, 67, 68, 80, 81, 82, 85, 88, 89, 90, 91, 96, 97, 98, 99, 100, 104, 109, 110, 112, 114, 128, 129, 144, 145, 146 bending, 95 beneficial effect, 101 blocks, 12, 13, 15 bonding, 46, 99, 115 broadband, 7 Bulgaria, 49 buttons, 226, 284, 285, 287, 289, 291

C  calcium, 35, 107 calibration, 156, 166, 168, 169, 170, 171, 179, 181, 182, 183, 187, 191, 195, 196, 197, 198, 204, 205, 206, 207, 218, 225, 246, 315 Canada, v, x, 26, 31, 33, 34, 36, 37, 38, 40, 41, 43, 48, 49, 50, 53, 54, 55, 56, 74, 84, 94, 97, 101, 120, 121, 142, 230, 277, 298, 302, 304 cast, 97, 218 cell, 17, 70, 257, 258, 290, 291 certification, 44, 113, 118, 119 CIA, 144 City, 140 classes, 70, 71, 72, 76, 79, 82, 94, 307 classification, 156, 305, 314 cleaning, 99 close relationships, 71 closure, 91, 97, 100 codes, 193, 195 collaboration, 106, 303 combined effect, x, 230 commodity, 12 communication, 308

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322 community, x, 37, 45, 46, 47, 48, 49, 55, 105, 113, 114, 230, 282, 302, 306 compatibility, 26, 27, 68, 104, 118, 255, 256 competition, 12, 60 complexity, 14, 310 compliance, 312 components, 7, 10, 21, 46, 70, 115, 154, 163, 183, 191, 206, 208, 223, 225 composition, 70 compounds, 12, 86, 103, 107 compression, 41, 110 computation, ix, 148, 149, 156, 176, 179, 182, 194, 195, 200, 206, 208 computer program, ix, x, 57, 74, 149, 156, 175, 231 computing, 157, 161, 170, 175, 224 conductivity, 147, 151, 161, 162, 163, 164, 165, 166, 176, 179, 180, 183, 192, 193, 200, 205, 207, 208, 226, 246, 264, 294, 295, 296 conductor, 215 conductors, 151, 215 confidence, 170 configuration, 198 conformity, 44, 114 confusion, 9 congestion, 37, 39, 40, 46, 49, 50, 65, 69, 72, 91, 108, 109, 306 Congress, 302 conifer, 52, 53 conservation, 210 consolidation, 42, 111 consultants, 51, 70, 104, 105, 106 consulting, 37, 102, 103, 106, 143 consumption, 55, 63, 68 continuity, 210 contour, x, 217, 230 control, ix, 12, 23, 40, 42, 43, 71, 72, 85, 110, 112, 149 convergence, 179 conversion, 4, 27, 160, 307 correlations, 235 corrosion, 75, 92, 118, 119 cost effectiveness, 23 cost saving, 45, 114 cost-benefit analysis, 63 costs, 27, 38, 39, 47, 48, 55, 56, 57, 59, 60, 66, 67, 69, 70, 81, 89, 108, 117, 118, 205, 302, 306 covering, 86, 143, 278 CPB, 18 crack, 40, 93, 110 credit, 56, 59, 84 curing, 86, 87, 91, 93, 103

Index currency, 55 Czech Republic, 65

D  Danube River, 53 data analysis, x, xi, 231, 235, 252, 254, 255, 262, 278, 280, 301, 303, 305, 306, 307, 309, 315 data availability, 147, 229, 238, 306 data collection, xi, 11, 12, 43, 112, 169, 171, 206, 225, 233, 234, 238, 281, 301, 302, 303, 304, 305, 307, 308, 309, 315, 316 data processing, 193, 223, 225, 264, 305 data set, 285, 308, 311, 312 data structure, 305 decision-making process, 12 decisions, 27, 116, 242 deficiency, 40, 109 definition, 8, 12, 47, 63, 220, 248 deformation, 142 delivery, viii, 32, 140 Denmark, 70 density values, 182, 184, 193, 195, 196, 204, 208, 225 dependent variable, 220 deposits, 26, 54 depression, 243 derivatives, 220, 221 designers, 46 detection, 233, 243 developed countries, 48, 49, 54 developed nations, 54 dielectric constant, ix, 148, 151, 153, 154, 155, 156, 157, 161, 162, 163, 164, 165, 166, 167, 168, 169, 170, 171, 173, 176, 179, 180, 182, 183, 187, 191, 192, 193, 196, 197, 198, 200, 205, 207, 208, 209, 224, 225, 226, 235 dielectric permittivity, 151 dielectrics, 166, 183, 207 differentiation, 209 dispersion, 161, 163 disseminate, 105 distress, 61, 75, 85, 97, 304, 309, 312, 313 distribution, 82, 256, 303, 304 divergence, 210, 251 division, 105, 140, 142 dosage, 42, 111 downsizing, 56, 69 draft, 19, 20 drainage, 40, 47, 74, 88, 109, 119, 142, 314 drying, 118, 204, 246 durability, 13, 23, 24, 25, 27, 42, 43, 46, 85, 94, 104, 107, 112, 113, 116, 142 duration, 119, 302, 308

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Index dykes, 53

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E  economic activity, 54 economic development, 48 economic evaluation, 74 Education, 306 educational experience, viii, 2 elasticity, 103 electric charge, 209, 210 electric current, 209 electric field, 209, 214, 216 electrical conductivity, 161, 162 electrical properties, 161, 208 electrodes, 233, 263, 264, 265, 281 electromagnetic, 148, 151, 152, 153, 154, 176, 209, 210, 211, 212, 214, 215, 216 electromagnetic fields, 209, 211, 212 electromagnetic waves, 214 e-mail, viii, xi, 32, 301 employees, 44, 91, 105, 113, 141 energy, 5, 6, 7, 10, 54, 68, 72, 245 England, 33, 52, 53, 71, 72, 73 environment, 22, 23, 28, 29, 39, 102, 105, 108, 211, 223, 313, 316 environmental conditions, 149 environmental effects, 193 environmental factors, 149, 223, 313 environmental impact, 70 environmental issues, 39, 46, 108, 115 erosion, 82 estimating, 170, 205, 208, 225, 282, 306 EU, 35, 39, 42, 43 Europe, v, 2, 3, 24, 27, 28, 31, 32, 33, 34, 35, 36, 38, 42, 43, 45, 46, 48, 49, 51, 53, 54, 66, 68, 72, 89, 105, 106, 111, 113, 114, 115 European Commission, 44 European Community, 43, 44 European Union, 29, 35, 39, 54, 64, 65, 70, 72, 94, 106 evening, 97, 98 exchange rate, 55 execution, 31, 257, 308 experimental design, 149, 237 expertise, 2, 31, 74, 140

F  failure, 117, 118, 240 Falkland Islands, 71 fatigue, 24, 83 favorite son, 3 feedback, xi, 42, 112, 301, 311

323 fibers, 21, 23, 24 fillers, 95, 104, 142 finance, 35, 65, 73 financial support, 43, 113 financing, viii, 32, 39, 54, 59, 60, 64, 108 flexibility, 45, 70, 114 flooding, 53 fluctuations, 237, 238, 240, 245 focusing, 24 food, 49, 68 foreign technologies, viii, 31, 36 France, 34, 37, 65, 68, 70, 72 freeze-thaw cycles, x, 230, 271, 276, 280 freezing, ix, 85, 94, 95, 230, 234, 235, 237, 239, 240, 241, 242, 243, 245, 246, 248, 249, 250, 253, 255, 256, 258, 261, 278, 281, 283, 290, 291, 293, 298 friction, 12, 26, 30, 44, 46, 59, 61, 63, 64, 68, 89, 92, 97, 114, 116, 117, 143 frost heave, ix, 75, 230, 244 frost resistance, 143 fuel, 49, 54, 63, 69, 302 fulfillment, 315 funding, 11, 12, 54, 58, 306, 307, 308 funds, viii, 31, 36, 54, 56, 65, 306 fusion, 249, 254

G  gasoline, 68, 72 General Motors, 19 generation, 13, 14, 15, 19, 290, 311 geography, 53 geology, 141 Georgia, 37, 137, 141 Germany, 33, 37, 39, 40, 41, 42, 43, 44, 46, 50, 53, 54, 58, 59, 70, 72, 75, 76, 77, 78, 85, 94, 95, 97, 102, 103, 109, 110, 111, 112, 113, 114, 115, 122, 123, 124, 125, 126, 142 Gibraltar, 71 GNP, 35, 48 goals, 37, 46 government, iv, 36, 54, 55, 56, 57, 59, 64, 69, 70, 72, 88, 102, 103, 104, 105, 116, 143, 311 GPS, 310, 311, 313, 316, 317 grading, 46, 115, 118 graduate students, 307 graph, 162, 238, 260, 278, 285, 290, 291 gravity, 182 Great Britain, 53 gross national product, 35, 48 groups, viii, 7, 29, 32, 44, 57, 95, 106, 113, 141, 143 growth, 49, 50

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Index

guidance, 23, 25, 26, 91, 93, 102, 106, 139, 246, 260, 312 guidelines, 11, 93, 95, 104, 105, 106, 142, 143, 252, 307, 312

H  harmonization, 44, 113 hearing loss, 6 heat, 103, 240, 243, 246, 248, 249, 250, 254, 256, 294, 295, 296 heat capacity, 246, 294, 295, 296 heat loss, 240 heat release, 250 heat transfer, 256 heating, 204 height, 7, 11, 19, 21, 49, 83, 235 higher quality, 66 highway system, 56 highways, 2, 10, 23, 54, 55, 65, 69, 102, 135, 302 House, 132, 133, 134, 135, 136 housing, 49, 50 human experience, 4 humidity, 8 hydroelectric power, 54

instruction, 104 instruments, 15, 223 integration, 106, 217, 219 integrity, 255, 312 interaction, 2, 14, 117 interactions, 18, 107 interest rates, 55 interface, 2, 256, 284 interval, 190, 200 intervention, 38, 69, 82, 108 investment, xi, 65, 69, 74, 76, 117, 301, 302, 303, 307, 308, 309, 310, 311, 312 Israel, 49 iteration, 165, 177, 179, 181

J  Japan, 2, 32, 33, 35, 48, 49 jobs, 91 joints, 38, 40, 41, 74, 75, 77, 78, 79, 80, 81, 82, 83, 85, 86, 87, 88, 91, 100, 101, 109, 110, 111, 118, 120, 142, 152, 307 judgment, 55, 242, 252 justification, 167

K 

I 

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Kenya, 143 ideal, 21, 205, 261 identification, 20, 97, 148, 165, 190, 191, 192, 199, 200, 222, 281 identity, 210, 213 image, 103, 106 images, 305, 312, 313 implementation, vii, viii, 1, 22, 32, 36, 44, 103, 114, 282, 307, 314, 315 imports, 95 in transition, 201, 240 INCE, 29 inclusion, 50, 193, 199, 208, 280 income, 64, 65 independence, 49 independent variable, 157, 220 India, 49, 53 indication, 7, 239 indices, ix, 148, 312 industry, vii, 1, 29, 43, 44, 45, 50, 52, 57, 59, 66, 68, 70, 72, 84, 102, 104, 106, 113, 114, 116, 140, 141, 143, 303, 309, 311 infrastructure, xi, 35, 48, 49, 50, 105, 301, 316 INS, 191 insight, 49, 198 inspectors, 44, 113 institutions, 43, 113

L  land, x, 12, 53, 66, 230, 278 land use, 12 Latin America, 34 leadership, 143 legend, 238 legislation, 302, 308 life cycle, 27, 61, 117 lifespan, 71 limestone, 95 limitation, 162, 238, 263 line, ix, 2, 11, 148, 162, 163, 171, 176, 209, 214, 215, 216, 217, 218, 224, 246 listening, vii, 2, 4 loans, 60 local government, viii, 32, 60, 105 logging, 54 longevity, 36 Louisiana, 140 lower prices, 49

M  magnetic field, 209, 213, 214, 216, 217, 218 magnetic resonance, 107

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Index maintenance, viii, ix, xi, 32, 36, 37, 38, 39, 41, 43, 47, 48, 56, 58, 59, 61, 62, 65, 66, 67, 68, 69, 70, 71, 73, 74, 91, 97, 101, 102, 104, 105, 106, 108, 111, 112, 117, 120, 141, 142, 230, 301, 302, 305, 307, 309, 313, 315, 316 management, viii, ix, 32, 36, 39, 40, 43, 56, 58, 59, 62, 63, 64, 66, 67, 74, 105, 108, 109, 112, 116, 119, 141, 230, 302, 303, 308, 309, 314 manipulation, 265, 307 manufacturer, 118 mapping, 64 market, 44, 55, 82, 105, 113, 143 market share, 105 matrix, 24, 25, 45, 115, 165, 166, 179, 182, 220, 221, 222, 249, 314 measurement, x, 5, 8, 18, 19, 20, 85, 102, 143, 150, 162, 166, 190, 192, 204, 206, 207, 231, 245, 252, 253, 259, 260, 261, 262, 265, 269, 278, 281, 283, 291, 305 measures, 4, 49, 60, 107, 118, 193, 199 mechanical properties, 43, 113, 208 media, 211 melting, 249, 283 merchandise, 49 Miami, 49 Microsoft, 198, 224, 256 microstructure, 51, 107 Middle East, 49 migration, 243 mixing, 94, 155, 156 mobility, 105 model, ix, 18, 22, 55, 59, 60, 63, 70, 82, 83, 91, 148, 155, 156, 157, 158, 162, 164, 166, 168, 169, 170, 171, 176, 181, 183, 195, 200, 201, 204, 207, 222, 223, 224, 245, 246, 250, 259, 282, 297, 308 modeling, 12, 29, 39, 109, 143, 242, 243, 246, 248, 250, 251, 256, 282, 283, 293 models, ix, 8, 59, 63, 106, 148, 149, 155, 156, 157, 175, 180, 205, 206, 207, 208, 224, 245, 246, 313, 314, 315 modules, 74 modulus, 103, 312, 315 moisture state, 164 money, 308 Montana, 236, 238, 239, 273 motion, 19, 20

N  nanometer, 107 nanometers, 107 nanotechnology, 51, 106, 107, 108, 113 nation, 54

325 national debt, 39, 108 National Research Council, 317 natural gas, 54, 68, 72 Netherlands, 33, 35, 37, 39, 40, 41, 42, 44, 50, 52, 53, 54, 66, 68, 69, 71, 82, 83, 91, 92, 93, 97, 101, 104, 105, 109, 110, 111, 114, 129, 130, 131, 145, 146 network, 39, 49, 53, 54, 56, 58, 60, 62, 63, 64, 65, 66, 67, 69, 71, 72, 74, 76, 81, 106, 109, 116, 217 New Zealand, 33, 48 next generation, 37, 283 N-N, 281 noise, vii, 1, 2, 3, 5, 7, 8, 9, 10, 11, 12, 13, 14, 15, 18, 19, 20, 21, 22, 23, 24, 26, 27, 28, 29, 30, 39, 43, 44, 46, 65, 66, 68, 69, 72, 85, 89, 90, 93, 101, 102, 108, 112, 114, 115, 117, 118, 143 North America, 27, 30, 55, 147 North Sea, 53 Northern Ireland, 71, 72 Norway, 95

O  objectives, ix, 148, 231, 302 objectivity, 312 observations, 39, 41, 45, 109, 110, 114, 206, 220, 221, 248 Office of Management and Budget, 312 oil, 54, 68, 72 Oklahoma, 141 operating system, 224 operator, 209, 210 optimization, 63 order, 5, 7, 10, 11, 20, 23, 155, 156, 157, 158, 182, 195, 198, 208, 209, 213, 216, 223, 226, 249, 256, 257, 303 organ, 16, 105 outliers, 155 overlay, 26, 43, 47, 61, 66, 73, 80, 81, 98, 99, 100, 101, 112, 312, 313, 317 oversight, 59, 104

P  Pacific, 52 Pakistan, 49 parameter, viii, x, 21, 63, 148, 168, 176, 179, 204, 206, 207, 229, 231, 237, 255, 280, 281, 282 parameter estimates, 204, 206, 207 parameters, viii, x, 147, 148, 152, 157, 158, 161, 162, 164, 165, 175, 179, 180, 181, 182, 193,

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326 201, 204, 205, 206, 207, 208, 217, 223, 224, 225, 231, 246, 250, 252, 268, 283, 297, 305, 306, 312, 318 partnership, 36, 59, 64, 65, 68, 72, 73 PCA, 36, 142 peer review, 303 penalties, 85 per capita GNP, 48, 49, 65 percentile, 264 performance indicator, 118, 119 performance prediction, viii, 147, 148, 314 permeability, 118, 153, 154, 161, 163, 164, 179, 211, 294, 295, 296 permittivity, 151, 161, 162, 163, 164, 179, 207, 211, 215 phase diagram, 184 physical properties, 182 pilot projects, viii, 32, 59 planning, viii, xi, 32, 37, 68, 104, 105, 301, 308 plants, 95, 100, 105 plasticity, 264 PMS, 36, 58, 128 pollution, 2, 306 polymer, 24, 102, 119 polymer modifiers, 24 polymers, 21, 23 polypropylene, 77 polyvinyl chloride, 233 poor performance, ix, 230 population, 2, 49, 50, 51, 54, 65, 72 population density, 2, 51 porosity, 20, 21, 24, 159, 169, 184, 185, 186, 187 ports, 49 Portugal, 145 poverty, 48 power, 49, 217 power relations, 217 precipitation, 52, 53 prediction, viii, 8, 63, 147, 148, 194, 222, 223, 243, 245, 246, 248, 249, 250, 251, 264, 282, 307, 314 prediction models, 63, 307 preference, 55 present value, 57, 70 president, 141, 142, 143 pressure, 3, 4, 6, 7, 8, 19, 72, 196 prevention, 118, 119 PRI, 85 prices, 50, 68 private sector, viii, 32, 37, 55, 139 probe, 107, 150, 152, 153, 154, 155, 161, 162, 164, 176, 182, 190, 191, 192, 233, 234, 235, 238, 257, 264, 265, 290, 298

Index process control, 42, 112 producers, 102, 103, 104 production, 12, 84, 97 profit, 105 profits, 59, 105 programming, 175, 198 propagation, 8, 154, 155, 214 propane, 204 protocol, 73 public limited company, 64 public policy, 72 public-private partnerships, 36, 39, 55, 56, 58, 59, 65, 68, 69, 108, 117 Puerto Rico, 140 pulse, 119, 151 purchasing power, 49 PVC, 233

Q  quality assurance, 43, 46, 88, 102, 112, 115, 119, 193, 261, 307 quality control, 26, 27, 43, 84, 88, 112, 119, 148, 233 quality improvement, 140

R  radar, 162 radio, 3, 20 radius, 215, 216 rain, 7, 53, 149 rainfall, 53, 264 random errors, 166 range, 4, 6, 8, 24, 48, 52, 53, 70, 74, 93, 104, 107, 143, 156, 157, 168, 170, 176, 177, 179, 195, 198, 204, 206, 245, 249, 289, 302, 303 rate of return, 307 reactivity, 107, 118, 143 reading, 190, 246, 250, 260, 263 reason, 11, 70, 76, 307 recognition, 56, 81 reconstruction, 37, 46, 47, 59, 60, 65, 70, 75, 89, 141 recycling, 45, 60, 65, 66, 89, 114 reflection, 103, 165, 166 reflectivity, 147, 151, 162, 164, 165, 166, 176, 179, 180, 183, 192, 193, 200, 205, 207, 208, 226 region, 50, 52, 61, 65, 66, 67, 68, 76, 157, 212, 238, 278 regression, 63, 155, 156, 157, 166, 200, 204, 220, 221, 222, 235 regression equation, 157, 200, 235

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Index

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rehabilitation, 37, 38, 46, 47, 55, 56, 57, 97, 99, 108, 117, 120, 140, 141, 142, 143, 302, 304, 311, 314 reinforcement, 82, 93, 118, 119 relationship, 107, 116, 155, 159, 160, 169, 196, 197, 205, 206, 223 relative prices, 49 relevance, 36, 233 reliability, 38, 47, 75 relief, 39, 108 repair, 37, 43, 46, 47, 60, 75, 84, 97, 100, 112, 120, 307 Requirements, 224 residual error, 222, 223 residual matrix, 166 resistance, x, 3, 59, 68, 74, 85, 86, 87, 95, 102, 118, 151, 231, 234, 263, 264, 281, 283 resolution, 224 resource management, 105 resources, vii, viii, 1, 32, 306 retardation, 46, 115 revenue, 54, 59, 65 risk, 39, 72, 93, 108 rods, 152, 153, 161 rolling, 2, 53, 85 Romania, 49 roughness, 43, 63, 84, 85, 112, 318 routines, 256, 311 rubber, 12, 14, 21, 23, 24, 26 rubber compounds, 12 RVS, 36, 61, 78, 145

S  SAFETEA-LU, 304, 306, 307, 308, 316 safety, viii, 13, 23, 26, 27, 32, 37, 39, 40, 46, 56, 63, 89, 100, 101, 102, 105, 108, 109, 139, 302, 306 salinity, 193, 245, 248, 262, 263 salt, 75, 243 salts, x, 230 sampling, 102, 170, 171, 304 saturation, ix, 94, 148, 159, 160, 169 savings, viii, 32, 55, 302, 306 schema, 23 school, 68, 307 Seasonal Monitoring Program, x, 183, 223, 227, 229, 230, 233, 298 security, xi, 301, 309, 315 seed, 181 selecting, 45, 76, 114, 115, 269, 286, 307 sensing, 4 sensitivity, 6, 70, 71, 76, 166, 206, 222

327 sensors, 21, 56, 57, 149, 160, 187, 196, 201, 225, 254, 283 separation, 40, 46, 81, 82, 109, 115 severity, 243, 269 shape, 95, 164, 207, 258 shares, 64 sharing, viii, 11, 32, 39, 48, 108 shoulders, 40, 75, 85, 109, 119 signals, 151, 162 silica, 35, 41, 42, 43, 95, 97, 100, 104, 107, 110, 111, 112, 113, 118 skeleton, 25 skilled personnel, 106 slag, 42, 94, 95, 96, 97, 111 sleep disturbance, 30 smoothness, 26, 29, 43, 59, 61, 85, 86, 89, 92, 112, 117, 118 sodium, 42, 111 software, 39, 40, 58, 62, 63, 64, 70, 74, 82, 109, 110, 143, 198, 224, 231, 233, 256, 282, 284, 307, 309 solid state, 250 South Africa, 34, 35 South Dakota, 141, 236, 241, 258, 259, 260, 275, 276 Soviet Union, 54, 60 space, 35, 105, 151, 157, 163, 164, 179, 209, 211, 212, 213, 214, 224 specific gravity, 156, 160, 168, 182, 183, 186, 191, 207, 225 specific surface, 243 speech, 12 speed, 5, 7, 9, 10, 18, 26, 47, 59, 64, 91, 153, 154, 155 speed of light, 153, 154, 155 sports, 21 Spring, 239, 272, 273, 274, 275, 276 stakeholders, 27, 303, 305, 308, 315 standard deviation, 84 standard error, 156 standardization, 105 standardized testing, 307 standards, 44, 45, 56, 61, 72, 74, 92, 94, 102, 103, 104, 113, 115, 139, 142 statistics, 53, 54, 235, 264 steel, 40, 75, 78, 81, 82, 83, 84, 88, 91, 102, 110, 118, 119, 152 storage, xi, 234, 301, 303, 305, 308, 309, 310, 315 strategies, 36, 38, 47, 62, 316 stress, 83, 282 structural characteristics, 229, 270, 318 students, 307

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Index

subjectivity, 240, 242, 252, 263 summer, 12, 52, 53, 237, 240, 242, 283 suppliers, 105, 106 surface friction, 63, 64 surface layer, 21, 90, 96, 152 susceptibility, 68 sustainable development, 105 Sweden, 37, 49 Switzerland, 49, 52, 131, 132 synthesis, vii, 1, 107

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T  team members, viii, 32, 36, 37, 51, 117 technical assistance, 140, 310 technology transfer, 103, 139, 143 TEM, 148, 216, 217 tensile strength, 95 term plans, 308 terminals, 119 test data, 170, 315 test procedure, 22 thermal expansion, 118 thermal properties, 246 threshold, 10, 240, 248, 256, 259 time commitment, 36 time domain reflectometry, x, 147, 148, 149, 223, 230 time increment, 246 time series, 201, 290, 291 tolls, 56, 59, 64, 65, 73 tracking, 280, 306 tracks, vii, 2, 21, 47, 71, 72 trade, viii, 32, 43, 54, 113 trade and research groups, viii, 32 training, 44, 103, 104, 105, 106, 113, 116, 140, 142, 305, 311 training programs, 44, 106, 113 transactions, 56 transformation, 217 transition, 84, 92, 196, 198, 242, 248, 253 transition period, 248

W  Wales, 71, 72 warrants, 48, 312 wave propagation, 155, 216 wealth, 48, 49 wear, 66, 79, 87 wind, 19, 265

transitions, 242, 297 translation, 145, 146 transmission, ix, 148, 162, 163, 164, 171, 209, 214, 215, 218, 224 transport, viii, 32, 35, 50, 105 transportation, vii, viii, x, 1, 2, 31, 32, 35, 36, 37, 105, 140, 230, 302, 306, 309 transportation industry, vii, 1 trial, 27, 41, 66, 84, 111 turbulence, 10 Turkey, 49, 144, 145, 146

U  UK, 227 uniform, 5, 27, 84, 104, 214 unions, 104 United Kingdom, 37, 39, 40, 43, 50, 52, 53, 54, 70, 71, 72, 73, 74, 84, 93, 105, 132, 133, 134, 135, 136 United States, viii, x, 2, 32, 36, 37, 38, 39, 40, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 65, 68, 81, 115, 118, 140, 230, 302, 304, 319 universities, 101, 102, 305 university students, 311 urban areas, 2, 37, 47, 54

V  vacuum, 15, 153, 154 validation, 170, 171, 172, 173, 174, 175, 200, 205, 315 variability, 205, 206 variables, 8, 63, 157, 211, 220 variance, 156, 220 vector, 179, 182, 209, 210, 211, 213, 221 vehicles, 2, 5, 10, 18, 53, 55, 56, 61, 65, 69, 72, 74, 89, 92 velocity, 119, 151, 153, 154, 155, 214 violent crime, 48

winter, viii, 32, 38, 47, 52, 53, 67, 68, 75, 102, 117, 204, 237, 238, 241, 242, 245, 249, 252, 260, 261, 262, 270, 283, 289, 290, 291, 292 workers, 44, 113 working groups, 104, 105 World War I, 60

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