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Suggested Citation:"Front Matter." National Academies of Sciences, Engineering, and Medicine. 2019. Field Verification of Proposed Changes to the AASHTO R 30 Procedures for Laboratory Conditioning of Asphalt Mixtures. Washington, DC: The National Academies Press. doi: 10.17226/25608.
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Suggested Citation:"Front Matter." National Academies of Sciences, Engineering, and Medicine. 2019. Field Verification of Proposed Changes to the AASHTO R 30 Procedures for Laboratory Conditioning of Asphalt Mixtures. Washington, DC: The National Academies Press. doi: 10.17226/25608.
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Suggested Citation:"Front Matter." National Academies of Sciences, Engineering, and Medicine. 2019. Field Verification of Proposed Changes to the AASHTO R 30 Procedures for Laboratory Conditioning of Asphalt Mixtures. Washington, DC: The National Academies Press. doi: 10.17226/25608.
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Suggested Citation:"Front Matter." National Academies of Sciences, Engineering, and Medicine. 2019. Field Verification of Proposed Changes to the AASHTO R 30 Procedures for Laboratory Conditioning of Asphalt Mixtures. Washington, DC: The National Academies Press. doi: 10.17226/25608.
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Suggested Citation:"Front Matter." National Academies of Sciences, Engineering, and Medicine. 2019. Field Verification of Proposed Changes to the AASHTO R 30 Procedures for Laboratory Conditioning of Asphalt Mixtures. Washington, DC: The National Academies Press. doi: 10.17226/25608.
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Suggested Citation:"Front Matter." National Academies of Sciences, Engineering, and Medicine. 2019. Field Verification of Proposed Changes to the AASHTO R 30 Procedures for Laboratory Conditioning of Asphalt Mixtures. Washington, DC: The National Academies Press. doi: 10.17226/25608.
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Suggested Citation:"Front Matter." National Academies of Sciences, Engineering, and Medicine. 2019. Field Verification of Proposed Changes to the AASHTO R 30 Procedures for Laboratory Conditioning of Asphalt Mixtures. Washington, DC: The National Academies Press. doi: 10.17226/25608.
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Suggested Citation:"Front Matter." National Academies of Sciences, Engineering, and Medicine. 2019. Field Verification of Proposed Changes to the AASHTO R 30 Procedures for Laboratory Conditioning of Asphalt Mixtures. Washington, DC: The National Academies Press. doi: 10.17226/25608.
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2019 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 RESEARCH REPORT 919 Field Verification of Proposed Changes to the AASHTO R 30 Procedures for Laboratory Conditioning of Asphalt Mixtures David Newcomb Edith Arámbula-Mercado Amy Epps Martin Mengge Yuan Texas a&M TransporTaTion insTiTuTe College Station, TX Nam Tran Fan Yin naTional CenTer for asphalT TeChnology auburn universiTy Auburn, AL Subscriber Categories Materials 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, and implementable research is the most effective way to solve many problems facing state departments of transportation (DOTs) administrators and engineers. Often, highway problems are of local or regional interest and can best be studied by state DOTs individually or in cooperation with their state universities and others. However, the accelerating growth of highway transporta- tion results in increasingly complex problems of wide interest to high- way authorities. These problems are best studied through a coordinated program of cooperative research. Recognizing this need, the leadership of the American Association of State Highway and Transportation Officials (AASHTO) in 1962 ini- tiated an objective national highway research program using modern scientific techniques—the National Cooperative Highway Research Program (NCHRP). NCHRP is supported on a continuing basis by funds from participating member states of AASHTO and receives the full cooperation and support of the Federal Highway Administration, United States Department of Transportation. The Transportation Research Board (TRB) of the National Academies of Sciences, Engineering, and Medicine was requested by AASHTO to administer the research program because of TRB’s recognized objectivity and understanding of modern research practices. TRB is uniquely suited for this purpose for many reasons: TRB maintains an extensive com- mittee structure from which authorities on any highway transportation subject may be drawn; TRB possesses avenues of communications and cooperation with federal, state, and local governmental agencies, univer- sities, and industry; TRB’s relationship to the National Academies is an insurance of objectivity; and TRB maintains a full-time staff of special- ists in highway transportation matters to bring the findings of research directly to those in a position to use them. The program is developed on the basis of research needs identified by chief administrators and other staff of the highway and transportation departments, by committees of AASHTO, and by the Federal Highway Administration. Topics of the highest merit are selected by the AASHTO Special Committee on Research and Innovation (R&I), and each year R&I’s recommendations are proposed to the AASHTO Board of Direc- tors and the National Academies. Research projects to address these topics are defined by NCHRP, and qualified research agencies are selected from submitted proposals. Administration and surveillance of research contracts are the responsibilities of the National Academies and TRB. The needs for highway research are many, and NCHRP can make significant contributions to solving 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 research 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 by going to http://www.national-academies.org and then searching for TRB Printed in the United States of America NCHRP RESEARCH REPORT 919 Project 09-52A ISSN 2572-3766 (Print) ISSN 2572-3774 (Online) ISBN 978-0-309-48073-4 Library of Congress Control Number 2019948869 © 2019 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, FRA, FTA, Office of the Assistant Secretary for Research and Technology, PHMSA, or TDC 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 research 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 National Academies of Sciences, Engineering, and Medicine. 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 Academies of Sciences, Engineering, and Medicine; or the program sponsors. The Transportation Research Board; the National Academies of Sciences, Engineering, and Medicine; and the sponsors of the National Cooperative Highway Research Program do not endorse products or manufacturers. Trade or manufacturers’ names appear herein solely because they are considered essential to the object of the report.

The National Academy of Sciences was established in 1863 by an Act of Congress, signed by President Lincoln, as a private, non- governmental institution to advise the nation on issues related to science and technology. Members are elected by their peers for outstanding contributions to research. Dr. Marcia McNutt is president. The National Academy of Engineering was established in 1964 under the charter of the National Academy of Sciences to bring the practices of engineering to advising the nation. Members are elected by their peers for extraordinary contributions to engineering. Dr. John L. Anderson is president. The National Academy of Medicine (formerly the Institute of Medicine) was established in 1970 under the charter of the National Academy of Sciences to advise the nation on medical and health issues. Members are elected by their peers for distinguished contributions to medicine and health. Dr. Victor J. Dzau is president. The three Academies work together as the National Academies of Sciences, Engineering, and Medicine to provide independent, objective analysis and advice to the nation and conduct other activities to solve complex problems and inform public policy decisions. The National Academies also encourage education and research, recognize outstanding contributions to knowledge, and increase public understanding in matters of science, engineering, and medicine. Learn more about the National Academies of Sciences, Engineering, and Medicine at www.national-academies.org. The Transportation Research Board is one of seven major programs of the National Academies of Sciences, Engineering, and Medicine. The mission of the Transportation Research Board is to increase the benefits that transportation contributes to society by providing leadership in transportation innovation and progress through research and information exchange, conducted within a setting that is objective, interdisciplinary, and multimodal. The Board’s varied committees, task forces, and panels 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 individuals interested in the development of transportation. Learn more about the Transportation Research Board at www.TRB.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 AUTHOR ACKNOWLEDGMENTS The research reported herein was performed under NCHRP Project 09-52A by the Texas A&M Transportation Institute, a member of the Texas A&M University System. Dr. David Newcomb, senior research engineer at the Texas A&M Transportation Institute, was the project director and principal investigator. Other authors of this report are Dr. Amy Epps Martin, Dr. Edith Arámbula-Mercado, and Ms. Mengge Yuan from the Texas A&M Transportation Institute; and Dr. Fan Yin and Dr. Nam Tran from the National Center for Asphalt Technology. The Western Research Institute, the University of Nevada Reno, and Iowa State University were very generous in allowing the research team to share their field sites and for providing critical information to the research team. A substantial debt of gratitude is owed the state departments of transportation of Texas, New Mexico, Wyoming, Iowa, South Dakota, and Florida, and the cities of Indianapolis, Indiana, and Odessa, Texas, for their willingness to provide test sections and support. The following contractors provided a great deal of assistance in achieving the goals of the project: J.H. Hamilton Construction Co. (New Mexico); Rieth-Riley Construction Co. (Indiana); Reese-Albert Construction Co. (Odessa, Texas); Manatts, Inc. (Iowa); Commercial Asphalt Co. (South Dakota); McGarvin-Moberly Construction Co. (Wyoming); Duval Asphalt (Florida); and Ramming Paving Co. (Texas). The authors would like to acknowledge Dr. Jon Epps from the Texas A&M Transportation Institute for his contributions to this report. CRP STAFF FOR NCHRP RESEARCH REPORT 919 Christopher J. Hedges, Director, Cooperative Research Programs Lori L. Sundstrom, Deputy Director, Cooperative Research Programs Edward T. Harrigan, Senior Program Officer Anthony P. Avery, Senior Program Assistant Eileen P. Delaney, Director of Publications Natalie Barnes, Associate Director of Publications Kami Cabral, Editor NCHRP PROJECT 09-52A PANEL Field of Materials and Construction—Area of Bituminous Materials Frank Fee, Frank Fee, LLC, Media, PA (Chair) Cathrina Barros, California DOT, Sacramento, CA Peter C. Capon, Rieth-Riley Construction, Inc., Goshen, IN Timothy R. Clyne, Minnesota DOT, Roseville, MN Joseph R. DeVol, Washington State DOT, Tumwater, WA John E. Grieco, Massachusetts DOT, Hopkinton, MA Scott A. Schram, Iowa DOT, Ames, IA Annette G. Smith, PQ Corporation, Malvern, PA Vivek Tandon, University of Texas at El Paso, El Paso, TX James A. Williams, III, Mississippi DOT, Jackson, MS Jack Youtcheff, FHWA Liaison Kent R. Hansen, Liaison

F O R E W O R D By Edward T. Harrigan Staff Officer Transportation Research Board This report presents the outcomes of an extended field verification of proposed changes to AASHTO R 30, Standard Practice for Mixture Conditioning of Hot-Mix Asphalt (HMA), originally identified in NCHRP Report 815: Short-Term Laboratory Conditioning of Asphalt Mixtures (NCHRP Project 09-52). It will be of immediate interest to materials engineers in state highway agencies and the construction industry with responsibility for design and production of hot mix asphalt (HMA) and warm mix asphalt (WMA). Laboratory conditioning of asphalt mixtures during the mix design process to simulate their short-term aging influences the selection of the optimum asphalt content. In addi- tion, long-term conditioning affects the mixture and binder stiffness, deformation, and strength evaluated with fundamental characterization tests to assess mixture performance. The current standard conditioning procedure, AASHTO R 30, Standard Practice for Mix- ture Conditioning of Hot-Mix Asphalt (HMA), was developed over two decades ago and was reviewed to determine whether it required updating to address today’s asphalt materials and mix production processes. The objectives of NCHRP Project 09-52A were to (1) verify the laboratory conditioning procedures for asphalt mixtures in NCHRP Report 815 with field data obtained over an extended service period, (2) revise the long-term aging model in NCHRP Report 815, and (3) re-examine the effects of the factors identified in NCHRP Project 09-52 on the aging characteristics of asphalt mixtures. The research was performed by the Texas A&M Trans- portation Institute, Texas A&M University, College Station, Texas, in association with the National Center for Asphalt Technology, Auburn, Alabama. The in-situ aging of HMA and WMA field projects constructed and followed for 1 to 2 years in NCHRP Project 09-52 was further evaluated for up to 4 to 5 years in NCHRP Project 09-52A. These field data were used to test whether long-term oven aging (LTOA) of loose asphalt mix for 5 days at 85°C (185°F) better simulated long-term field aging than the current aging of compacted asphalt mix at the time and temperature called for in AASHTO R 30. NCHRP Report 815 had found that an initial field performance period of 1 to 2 years (depending on the specific project climate) of aging is well simulated by 5 days of oven aging at 85°C (185°F). This finding called into question the original recommendation incorporated in AASHTO R 30 from research conducted by the Strategic Highway Research Program, that is, that these conditions were equivalent to 5 to 10 years of field aging. The results of NCHRP Project 09-52A suggest that a better approach to LTOA could be aging loose mix at 85°C (185°F) for 5 days before compacting. For the field sites included in the project, this laboratory conditioning equates to 7 to 10 years of aging for warmer climates and 12 to 14 years for cooler climates.

The key outcome of this research is that the current LTOA procedure in AASHTO R 30 is not realistic; replacing the aging of a compacted specimen with aging of loose mix for 5 days at 85°C (185°F) before compaction for testing should be considered by the AASHTO Committee on Materials and Pavements.

C O N T E N T S Note: Photographs, figures, and tables in this report may have been converted from color to grayscale for printing. The electronic version of the report (posted on the web at www.trb.org) retains the color versions. 1 Summary 3 Chapter 1 Introduction 3 Background 4 Previous Research—NCHRP Project 09-52 5 Literature Review 8 Project Objectives and Scope 9 Chapter 2 Experimental Design 9 Field Site Selection 9 Specimen Preparation 12 Laboratory Tests 14 Chapter 3 Findings and Applications 14 Global Models 15 MR Stiffness Ratio 27 IDEAL-CT Results 30 Chapter 4 Conclusions and Suggested Research 30 Conclusions 31 IDEAL-CT 32 Suggested Research 33 References 34 Appendix A Resilient Modulus Stiffness and Air Void Content Values for All Field Sites

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Laboratory conditioning of asphalt mixtures during the mix design process to simulate their short-term aging influences the selection of the optimum asphalt content. In addition, long-term conditioning affects the mixture and binder stiffness, deformation, and strength evaluated with fundamental characterization tests to assess mixture performance. The current standard conditioning procedure, AASHTO R 30, Standard Practice for Mixture Conditioning of Hot-Mix Asphalt, was developed over two decades ago.

In reviewing whether to update the standard, TRB’s National Cooperative Highway Research Program (NCHRP) Research Report 919: Field Verification of Proposed Changes to the AASHTO R 30 Procedures for Laboratory Conditioning of Asphalt Mixtures seeks to (a) develop a laboratory short-term aging protocol to simulate the aging and asphalt absorption of an asphalt mixture during production and transportation based on factors thought to affect aging, and (b) develop a laboratory longer-term aging protocol to simulate the aging of the asphalt mixtures after construction.

The key outcome of the research is that the current long-term oven aging (LTOA) procedure in AASHTO R 30 is not realistic. Replacing the aging of a compacted specimen with aging of loose mix for 5 days at 85°C (185°F) before compaction for testing should be considered by the AASHTO Committee on Materials and Pavements.

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