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N A T I O N A L C O O P E R A T I V E H I G H W A Y R E S E A R C H P R O G R A M NCHRP REPORT 779 Field Performance of Warm Mix Asphalt Technologies Randy West Carolina Rodezno Grant Julian NatioNal CeNter for asphalt teChNology Auburn, AL and Brian Prowell advaNCed Materials serviCes, llC Auburn, AL Bob Frank CoMpliaNCe MoNitoriNg serviCe Linwood, NJ Linda V. Osborn Tony Kriech heritage researCh group Indianapolis, IN Subscriber Categories Construction â¢ Environment â¢ Materials TRANSPORTAT ION RESEARCH BOARD WASHINGTON, D.C. 2014 www.TRB.org Research sponsored by the American Association of State Highway and Transportation Officials in cooperation with the Federal Highway Administration
NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM Systematic, well-designed research provides the most effective approach to the solution of many problems facing highway administrators and engineers. Often, highway problems are of local interest and can best be studied by highway departments individually or in cooperation with their state universities and others. However, the accelerating growth of highway transportation develops increasingly complex problems of wide interest to highway authorities. These problems are best studied through a coordinated program of cooperative research. In recognition of these needs, the highway administrators of the American Association of State Highway and Transportation Officials initiated in 1962 an objective national highway research program employing modern scientific techniques. This program is supported on a continuing basis by funds from participating member states of the Association and it receives the full cooperation and support of the Federal Highway Administration, United States Department of Transportation. The Transportation Research Board of the National Academies was requested by the Association to administer the research program because of the Boardâs recognized objectivity and understanding of modern research practices. The Board is uniquely suited for this purpose as it maintains an extensive committee structure from which authorities on any highway transportation subject may be drawn; it possesses avenues of communications and cooperation with federal, state and local governmental agencies, universities, and industry; its relationship to the National Research Council is an insurance of objectivity; it maintains a full-time research correlation staff of specialists in highway transportation matters to bring the findings of research directly to those who are in a position to use them. The program is developed on the basis of research needs identified by chief administrators of the highway and transportation departments and by committees of AASHTO. Each year, specific areas of research needs to be included in the program are proposed to the National Research Council and the Board by the American Association of State Highway and Transportation Officials. Research projects to fulfill these needs are defined by the Board, and qualified research agencies are selected from those that have submitted proposals. Administration and surveillance of research contracts are the responsibilities of the National Research Council and the Transportation Research Board. The needs for highway research are many, and the National Cooperative Highway Research Program can make significant contributions to the solution of highway transportation problems of mutual concern to many responsible groups. The program, however, is intended to complement rather than to substitute for or duplicate other highway research programs. Published reports of the NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM are available from: Transportation Research Board Business Office 500 Fifth Street, NW Washington, DC 20001 and can be ordered through the Internet at: http://www.national-academies.org/trb/bookstore Printed in the United States of America NCHRP REPORT 779 Project 9-47A ISSN 0077-5614 ISBN 978-0-309-30803-8 Library of Congress Control Number 2014949286 Â© 2014 National Academy of Sciences. All rights reserved. COPYRIGHT INFORMATION Authors herein are responsible for the authenticity of their materials and for obtaining written permissions from publishers or persons who own the copyright to any previously published or copyrighted material used herein. Cooperative Research Programs (CRP) grants permission to reproduce material in this publication for classroom and not-for-profit purposes. Permission is given with the understanding that none of the material will be used to imply TRB, AASHTO, FAA, FHWA, FMCSA, FTA, or Transit Development Corporation endorsement of a particular product, method, or practice. It is expected that those reproducing the material in this document for educational and not-for-profit uses will give appropriate acknowledgment of the source of any reprinted or reproduced material. For other uses of the material, request permission from CRP. NOTICE The project that is the subject of this report was a part of the National Cooperative Highway Research Program, conducted by the Transportation Research Board with the approval of the Governing Board of the National Research Council. The members of the technical panel selected to monitor this project and to review this report were chosen for their special competencies and with regard for appropriate balance. The report was reviewed by the technical panel and accepted for publication according to procedures established and overseen by the Transportation Research Board and approved by the Governing Board of the National Research Council. The opinions and conclusions expressed or implied in this report are those of the researchers who performed the research and are not necessarily those of the Transportation Research Board, the National Research Council, or the program sponsors. The Transportation Research Board of the National Academies, the National Research Council, and the sponsors of the National Cooperative Highway Research Program do not endorse products or manufacturers. Trade or manufacturersâ names appear herein solely because they are considered essential to the object of the report.
The National Academy of Sciences is a private, nonprofit, self-perpetuating society of distinguished scholars engaged in scientific and engineering research, dedicated to the furtherance of science and technology and to their use for the general welfare. Upon the authority of the charter granted to it by the Congress in 1863, the Academy has a mandate that requires it to advise the federal government on scientific and technical matters. Dr. Ralph J. Cicerone is president of the National Academy of Sciences. The National Academy of Engineering was established in 1964, under the charter of the National Academy of Sciences, as a parallel organization of outstanding engineers. It is autonomous in its administration and in the selection of its members, sharing with the National Academy of Sciences the responsibility for advising the federal government. The National Academy of Engineering also sponsors engineering programs aimed at meeting national needs, encourages education and research, and recognizes the superior achievements of engineers. Dr. C. D. Mote, Jr., is president of the National Academy of Engineering. The Institute of Medicine was established in 1970 by the National Academy of Sciences to secure the services of eminent members of appropriate professions in the examination of policy matters pertaining to the health of the public. The Institute acts under the responsibility given to the National Academy of Sciences by its congressional charter to be an adviser to the federal government and, upon its own initiative, to identify issues of medical care, research, and education. Dr. Victor J. Dzau is president of the Institute of Medicine. The National Research Council was organized by the National Academy of Sciences in 1916 to associate the broad community of science and technology with the Academyâs purposes of furthering knowledge and advising the federal government. Functioning in accordance with general policies determined by the Academy, the Council has become the principal operating agency of both the National Academy of Sciences and the National Academy of Engineering in providing services to the government, the public, and the scientific and engineering communities. The Council is administered jointly by both Academies and the Institute of Medicine. Dr. Ralph J. Cicerone and Dr. C. D. Mote, Jr., are chair and vice chair, respectively, of the National Research Council. The Transportation Research Board is one of six major divisions of the National Research Council. The mission of the Transporta- tion Research Board is to provide leadership in transportation innovation and progress through research and information exchange, conducted within a setting that is objective, interdisciplinary, and multimodal. The Boardâs varied activities annually engage about 7,000 engineers, scientists, and other transportation researchers and practitioners from the public and private sectors and academia, all of whom contribute their expertise in the public interest. The program is supported by state transportation departments, federal agencies including the component administrations of the U.S. Department of Transportation, and other organizations and individu- als interested in the development of transportation. www.TRB.org www.national-academies.org
C O O P E R A T I V E R E S E A R C H P R O G R A M S CRP STAFF FOR NCHRP REPORT 779 Christopher W. Jenks, Director, Cooperative Research Programs Christopher Hedges, Manager, National Cooperative Highway Research Program Edward T. Harrigan, Senior Program Officer Anthony P. Avery, Senior Program Assistant Eileen P. Delaney, Director of Publications Sharon Lamberton, Editor NCHRP PROJECT 9-47A PANEL Field of Materials and ConstructionâArea of Bituminous Minerals Bouzid Choubane, Florida DOT, Gainesville, FL (Chair) Kim A. Willoughby, Washington State DOT, Olympia, WA Cathrina Barros, California DOT, Sacramento, CA German Claros, Rodriguez Engineering, Houston, TX Colin Franco, Rhode Island DOT, Providence, RI Kim J. Jenkins, University of Stellenbosch, Matieland, South Africa Julie E. Kliewer, Arizona DOT, Phoenix, AZ Howard S. Marks, National Asphalt Pavement Association, Lanham, MD Jorge A. Prozzi, University of TexasâAustin, Austin, TX Ronald A. Sines, Oldcastle Materials, Leominster, MA Matthew Corrigan, FHWA Liaison Nelson H. Gibson, FHWA Liaison Frederick Hejl, TRB Liaison
F O R E W O R D This report compares material properties and field performance of warm mix asphalt (WMA) and control hot mix asphalt (HMA) pavement sections constructed at 14 locations across the United States between 2006 and 2010. Thus, the report will be of immediate inter- est to materials engineers in state highway agencies and the asphalt pavement construction industry. Over the past decade, the use of WMA for asphalt pavement construction has dramati- cally increased in the United States. WMA, which offers the potential to lower energy demand during production and construction, reduce emissions at the plant and the paver, and increase allowable haul distances, is seen as an alternative to HMA. However, questions remain about the long-term performance and durability of WMA pavements. The objectives of NCHRP Project 9-47A were to (1) compare the short-term performance of WMA and control HMA pavements, (2) examine relationships among engineering prop- erties of WMA binders and mixes and the field performance of pavements constructed with WMA technologies, (3) compare production and laydown practices between WMA and HMA pavements (including necessary plant adjustments to optimize plant operations when producing WMA), and (4) provide relative emissions measurements of WMA technologies and conventional HMA technologies. The research was performed by the National Center for Asphalt Technology, Auburn University, Auburn, Alabama, with major assistance from Advanced Materials Services, LLC, Auburn, Alabama; Heritage Research Group, Indianap- olis, Indiana; and Compliance Monitoring Service, Linwood, New Jersey. Performance and material property data were obtained from 14 field projects. Eight proj- ects were documented and sampled at their initial construction in 2010 and 2011 and after approximately 2 years in service. Another six projects constructed between 2006 and 2008 were documented and evaluated after 3 to 5 years in service. Each of the 14 projects included single- or multiple-WMA technology pavement sections and an HMA control section. A total of 12 WMA technologies were investigated, including asphalt foaming additives, plant foaming units, chemical additives, and organic additives. All projects used âdrop inâ WMA mix designs where the WMA technology was used with an existing HMA mix design with no significant changes to the binder content or other aspects of the mix design. Except for the reduced mixing and compaction temperatures for WMA, there were no substantial differences in the production and laydown practices of WMA and HMA. In-service performance of WMA and HMA in all projects was virtually identical, with little or no rutting, no evidence of moisture damage, and very little indication of transverse or longitu- dinal cracking. Energy use, plant and paver emissions, and worker exposure to fumes were extensively measured at three multiple-WMA technology projects. Compared to HMA, By Edward T. Harrigan Staff Officer Transportation Research Board
the reduced temperatures used in WMA production and laydown yielded lower energy consumption and emissions and reduced worker exposure to respirable fumes. Overall, then, no penalties and some potential benefits were observed in the short term when WMA replaced HMA. The key finding of laboratory testing of WMA binders and mixtures from the projects sampled at construction was the expected lower stiffness of the WMA materials that would have potential effects on pavement rutting and cracking. However, the equivalent perfor- mance of the WMA and HMA pavement sections over several years of service suggests that these differences in material properties, when present, were not great enough to affect the relative performances of HMA and WMA. This report fully documents the research in two parts bound in one report. Part 1 includes an appendix on Falling Weight Deflectometer Testing; Part 2 includes an appendix on Documenting Emissions and Energy Reductions of WMA and Conventional HMA During Plant and Paving Operations.
C O N T E N T S P A R T 1 Engineering Properties and Field Performance of Warm Mix Asphalt Technologies 3 Chapter 1 Background 3 Introduction 4 Project Objectives 4 Scope 4 Report Organization 4 Summary of Energy Usage, Emissions Measurements, and Fume Exposure of WMA Compared to Conventional HMA 5 Fuel Usage 5 Stack Emissions 5 Worker Exposure 5 Findings and Suggested Revisions to Practice 6 Performance of WMA Experimental Sections at Accelerated Pavement Test Facilities 6 NCAT Test Track 10 University of California Pavement Research Center 13 MnROAD 15 Summary of WMA Evaluations at Accelerated Pavement Testing Facilities 16 Chapter 2 Experimental Plan 16 Introduction 16 Field Projects: Production and Construction Documentation 16 Existing and New Projects 16 WMA Technologies Evaluated 18 Production and Construction Information 19 Performance Monitoring 19 Initial Testing for Structural Homogeneity 19 Field Performance Data Collection 19 Field Performance Prediction 21 Laboratory Testing of Field Mixes 21 Engineering Properties 21 Recovered Binder Performance Grade 22 Mixture Stiffness 22 Moisture Susceptibility 22 Fatigue Cracking 23 Thermal Cracking 23 Permanent Deformation 23 Summary of Laboratory Performance Testing 23 Mix Design Verifications 23 Determination of Optimum Asphalt Content 24 Coating
25 Compactability 25 Moisture Susceptibility 25 Rutting Resistance 25 Summary Comparisons 26 Chapter 3 WMA Field Projects 26 Existing Projects 26 St. Louis, Missouri 30 Iron Mountain, Michigan 34 Silverthorne, Colorado 39 Franklin, Tennessee 45 Graham, Texas 49 George, Washington 54 New Projects 54 Walla Walla, Washington 62 Centreville, Virginia 69 Rapid River, Michigan 77 Baker, Montana 84 Munster, Indiana 95 Jefferson County, Florida 102 New York, New York 110 Casa Grande, Arizona 118 Comparison of Observed and Predicted Performance of WMA and HMA for New Projects 118 Rutting 120 Longitudinal, Top-Down Cracking 121 Thermal Cracking 122 Summary of Performance Prediction Comparisons 122 Practical Guidelines for Production and Placement of WMA 122 Stockpile Moisture Content 122 Maintaining Adequate Baghouse Temperatures 124 Burner Performance 124 Producing Mixes with RAP and RAS 124 Placement Changes 125 Compaction 126 Chapter 4 Engineering Properties of HMA and WMA 126 Binder Properties 131 Mixture Properties 131 Mix Moisture Contents 131 Densities 136 Binder Absorption 138 Dynamic Modulus 146 Flow Number 146 Tensile Strength 151 Tensile Strength Ratio 153 Hamburg Wheel Tracking Test 156 Fatigue 161 Indirect Tension Compliance and Strength 161 Comparison of Lab Test Results and Field Performance 162 Rutting 163 Moisture Damage
164 Fatigue Cracking 166 Low Temperature Cracking 168 Chapter 5 WMA Project Mix Verification 168 Determination of Optimum Asphalt Content 168 Rapid River, Michigan 168 Baker, Montana 168 Munster, Indiana 169 New York, New York 173 Jefferson County, Florida 173 Summary Comparisons 176 Coating 178 Compactability 178 Moisture Susceptibility 179 Flow Number Test 180 Proposed Revisions to the Draft Appendix to AASHTO R 35 185 Chapter 6 Cost Analysis of WMA 188 Chapter 7 Findings 188 Production and Construction of WMA 188 Energy and Emissions 189 Short-Term WMA Field Performance 189 Engineering Properties of WMA 190 Predicted Performance 191 Mix Design Verification 191 Suggestions for Modifying Practice 191 Mix Design 191 Production 191 Other Research 192 References 194 Appendix Falling Weight Deflectometer Testing P A R T 2 Effects of WMA on Plant Energy and Emissions and Worker Exposures to Respirable Fumes 205 Chapter 1 Background and Problem Statement 205 Experimental Plan 207 Chapter 2 Energy Usage 207 Background on Energy Used to Produce HMA and WMA 209 Research Approach 210 Results and Discussion 210 Fuel Savings 210 Distribution of Fuel Savings 213 Comparison of Measured and Predicted Fuel Savings 213 Influence of Aggregate Moisture Content 215 Summary 215 Recommendations
216 Chapter 3 Stack Emissions 216 Reported Emissions Reductions from WMA 216 Research Approach 217 Results and Discussion 217 Carbon Dioxide 217 Carbon Monoxide and Volatile Organic Compounds 220 Sulfur Dioxide 221 Nitrogen Oxides 221 Formaldehyde 221 PM-10 223 Summary 223 Recommendations 224 Chapter 4 Worker Exposure 224 Background 225 Research Approach 225 Study Population 225 Study Design 225 Collection and Analysis of Breathing Zone Samples 226 Results 231 Discussion 232 Summary 233 Chapter 5 Findings and Conclusions 233 Findings 233 Fuel Usage 233 Stack Emissions 234 Worker Exposure 234 Conclusions 235 References 237 Appendix Documenting Emissions and Energy Reductions of WMA and Conventional HMA During Plant and Paving Operations