Long-Term Aging of Asphalt Mixtures for Performance Testing and Prediction: Phase III Results (2021)

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2021 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 973 Long-Term Aging of Asphalt Mixtures for Performance Testing and Prediction PHASE III RESULTS Y. Richard Kim Cassie Castorena Nooralhuda F. Saleh Elizabeth Braswell Michael Elwardany Farhad Yousefi Rad North Carolina State University Raleigh, NC Subscriber Categories Design • Materials • Pavements 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 (FHWA), United States Department of Transportation, under Agree- ment No. 693JJ31950003. 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 iden- tified by chief administrators and other staff of the highway and transportation departments, by committees of AASHTO, and by the FHWA. 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 https://www.mytrb.org/MyTRB/Store/default.aspx Printed in the United States of America NCHRP RESEARCH REPORT 973 Project 09-54 ISSN 2572-3766 (Print) ISSN 2572-3774 (Online) ISBN 978-0-309-67416-4 Library of Congress Control Number 2021942866 © 2021 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, FTA, GHSA, NHTSA, 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; the FHWA; 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 or logos 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.nationalacademies.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 provide leadership in transportation improvements and innovation through trusted, timely, impartial, and evidence-based information exchange, research, and advice regarding all modes of transportation. The Board’s varied activities annually engage about 8,000 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 CRP STAFF FOR NCHRP RESEARCH REPORT 973 Christopher J. Hedges, Director, Cooperative Research Programs Lori L. Sundstrom, Deputy Director, Cooperative Research Programs Waseem Dekelbab, Associate Program Manager, National Cooperative Highway Research Program Edward Harrigan, Senior Program Officer Anthony Avery, Senior Program Assistant Natalie Barnes, Director of Publications Heather DiAngelis, Associate Director of Publications NCHRP PROJECT 09-54 PANEL Field of Materials and Construction—Area of Bituminous Materials Dean A. Maurer, Lewisberry, PA (Chair) Bouzid Choubane, Florida Department of Transportation, Gainesville, FL Shongtao Dai, Minnesota Department of Transportation, Maplewood, MN Dale S. Decker, Dale S. Decker, LLC, Eagle, CO Charlie Pan, Nevada Department of Transportation, Carson City, NV Murari M. Pradhan, Arizona Department of Transportation, Phoenix, AZ Maria Carolina Rodezno, National Center for Asphalt Technology (NCAT), Auburn, AL Mansour Solaimanian, Pennsylvania State University, University Park, PA Jack S. Youtcheff, Jr., FHWA Liaison Nelson H. Gibson, TRB Liaison

This report presents methods to accurately condition asphalt mixtures to match their long-term aging in service. Thus, the report will be of immediate interest to engineers in state and local transportation agencies and those in industry with responsibility for evaluat- ing the performance of asphalt mixtures. Accurately characterizing the in situ aging of asphalt pavement materials over their long- term service life is of utmost importance to the implementation of mechanistic-empirical pavement design and analysis methods. Current pavement performance prediction models vary in their ability and level of sophistication for numerically simulating the increased stiffness of asphalt materials from oxidative aging and the competing reduction in modulus caused by accumulated pavement damage and deterioration. For the past 25 years, the most used method for aging asphalt materials for performance testing for input to prediction models has been the long-term procedure in AASHTO R 30, Standard Practice for Mixture Conditioning of Hot Mix Asphalt. AASHTO R 30 prescribes the aging of compacted asphalt mixture specimens at 85°C for 5 days, a time and tempera- ture combination that the original Strategic Highway Research Program (SHRP) research estimated—based on limited field calibration—to reflect a critical duration of field exposure from 5 to 10 years. However, an accumulation of laboratory and field data since the end of SHRP has demonstrated that a single time-temperature combination cannot reasonably simulate the effects of the range of climates found throughout the United States. Further, these data suggest that this single combination even underestimates the level of asphalt pavement aging that occurs in as little as 5 years in many climates. Research to develop new or improved long-term conditioning methods that reflect the aging of asphalt mixtures more accurately was warranted. Under NCHRP Project 09-54, “Long-Term Aging of Asphalt Mixtures for Performance Testing and Prediction,” North Carolina State University was tasked with developing a practical laboratory aging method to simulate more accurately the long-term in situ aging of asphalt mixtures for the purposes of performance testing and prediction. The research was conducted in three phases. The findings and results of Phases I and II were published in 2018 in NCHRP Research Report 871: Long-Term Aging of Asphalt Mixtures for Performance Testing and Prediction. This report presents the findings and results of Phase III. The research improved upon the proposed long-term aging procedure by developing a new, simplified Climatic Aging Index (CAI) to determine the necessary duration of asphalt loose mix conditioning for a specific project location. It carried out a field calibration and validation of the previously developed Pavement Aging Model (PAM). The PAM predicts the |G*| value of an asphalt binder at F O R E W O R D By Edward Harrigan Staff Officer Transportation Research Board

any field aging duration, pavement depth, and climate. Finally, the research produced an Asphalt Mixture Aging-Cracking (AMAC) Model that translates changes in binder |G*| predicted from PAM to changes in mixture linear viscoelastic and fatigue properties. The key outcomes of this research are (1) a Proposed Standard Method of Test for Long- Term Conditioning of Hot Mix Asphalt (HMA) for Performance Testing in the attachment at the end of the report, which incorporates the CAI to determine the required long-term conditioning duration that reflects the desired field aging in terms of age, climate, and depth; (2) the PAM in Table 9 of the report; and (3) the AMAC Model in Chapter 6 of the report.

1 Chapter 1 Introduction 2 Objectives and Scope 4 Report Organization 5 Chapter 2 Previous Research Conducted Under the Original NCHRP Project 09-54 5 Selection of Aging Index Properties 6 Selection of the Long-Term Aging Method 6 Climate-Based Determination of Predefined Aging Durations 14 Chapter 3 Refinement of the Climate-Based, Predefined Laboratory Aging Durations 14 Research Approach 18 Findings and Applications 28 Summary 29 Chapter 4 Refinement of the Pavement Aging Model (PAM) 29 Research Approach 35 Findings and Applications 58 Summary 60 Chapter 5 Development of Procedures to Estimate the PAM Inputs Using Standard Binder Aging Methods and PG 60 Research Approach 62 Findings and Applications 76 Summary 77 Chapter 6 Development of a Framework to Predict Changes in Asphalt Mixture Performance Due to Oxidative Aging 77 Research Approach 88 Findings and Applications 117 Summary 120 Chapter 7 Conclusions and Suggested Research 120 Refinement of the Climate-Based, Predefined Aging Durations 121 Refinement of the Pavement Aging Model 121 Development of Procedures to Estimate the PAM Inputs Using Standard Binder Aging Methods and Performance Grades 122 Development of a Framework to Predict Changes in Asphalt Mixture Performance Due to Oxidative Aging 122 Suggested Research 124 References C O N T E N T S

127 Appendix A Investigation into the Effects of Asphalt Mixture Morphology on Pavement Aging 134 Appendix B Estimation of the Material-Specific Parameters of RAP-Containing Mixtures Given Individual Virgin and RAP Parameters 140 Appendix C Prediction of Mixture Properties Through the Rate of Change of Model Coefficients 170 References for Appendices A, B, and C 171 Attachment Proposed Standard Method of Test for Long-Term Conditioning of Hot Mix Asphalt (HMA) for Performance Testing 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.