Use of Recycling Agents in Asphalt Concrete Mixtures (2022)

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Use of Recycling Agents in Asphalt Concrete Mixtures A Synthesis of Highway Practice Jo E. Sias Eshan V. Dave Runhua Zhang University of New Hampshire Durham, NH 2022 Research sponsored by the American Association of State Highway and Transportation Officials in cooperation with the Federal Highway Administration Subscriber Categories Highways • Construction • Materials 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 SYNTHESIS 586

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 by going to https://www.mytrb.org/MyTRB/Store/default.aspx Printed in the United States of America NCHRP SYNTHESIS 586 Project 20-05, Topic 52-17 ISSN 0547-5570 ISBN 978-0-309-68695-2 Library of Congress Control Number 2022937083 © 2022 by the National Academy of Sciences. National Academies of Sciences, Engineering, and Medicine and the graphical logo are trade- marks of the 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. Cover photo credit: Runhua Zhang NOTICE 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 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 does not develop, issue, or publish standards or speci- fications. The Transportation Research Board manages applied research projects which provide the scientific foundation that may be used by Transportation Research Board sponsors, industry associations, or other organizations as the basis for revised practices, procedures, or specifications. 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. 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.

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.

CRP STAFF FOR NCHRP SYNTHESIS 586 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 Jo Allen Gause, Senior Program Officer Deborah Irvin, Program Coordinator Natalie Barnes, Director of Publications Heather DiAngelis, Associate Director of Publications Doug English, Senior Editor NCHRP PROJECT 20-05 PANEL Joyce N. Taylor, Maine Department of Transportation, Augusta, ME (Chair) Socorro “Coco” A. Briseno, California Department of Transportation (retired), Sacramento, CA Anita K. Bush, Nevada Department of Transportation, Carson City, NV Joseph D. Crabtree, Kentucky Transportation Center, Lexington, KY Mostafa Jamshidi, Nebraska Department of Transportation, Lincoln, NE Cynthia L. Jones, Ohio Department of Transportation, Columbus, OH Jessie X. Jones, Arkansas DOT, Little Rock, AR Brenda Moore, North Carolina Department of Transportation, Raleigh, NC Ben T. Orsbon, South Dakota Department of Transportation, Pierre, SD Randall R. Park, Avenue Consultants, Taylorsville, UT Brian Worrel, Iowa Department of Transportation, Ames, IA Jack D. Jernigan, FHWA Liaison Jim T. McDonnell, AASHTO Liaison Stephen F. Maher, TRB Liaison TOPIC 52-17 PANEL Judith B. Corley-Lay, Pittsboro, NC Stacey D. Diefenderfer, Virginia Department of Transportation, Charlottesville, VA Adam J.T. Hand, University of Nevada, Reno, Reno, NV Thomas A. Kane, New York State Department of Transportation, Albany, NY Jacob D. Lautanen, Ohio Department of Transportation, Columbus, OH Robert C. Rea, Nebraska Department of Transportation, Lincoln, NE Jesus Alberto Sandoval-Gil, Arizona Department of Transportation, Phoenix, AZ David J. Mensching, FHWA Liaison Nelson H. Gibson, TRB Liaison 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

ABOUT THE NCHRP SYNTHESIS PROGRAM Highway administrators, engineers, and researchers often face problems for which information already exists, either in documented form or as undocumented experience and practice. This infor- mation may be fragmented, scattered, and unevaluated. As a consequence, full knowledge of what has been learned about a problem may not be brought to bear on its solution. Costly research findings may go unused, valuable experience may be overlooked, and due consideration may not be given to recommended practices for solving or alleviating the problem. There is information on nearly every subject of concern to highway administrators and engineers. Much of it derives from research or from the work of practitioners faced with problems in their day- to-day work. To provide a systematic means for assembling and evalu ating such useful information and to make it available to the entire highway community, the American Association of State High- way and Transportation Officials—through the mechanism of the National Cooperative Highway Research Program—authorized the Transportation Research Board to undertake a continuing study. This study, NCHRP Project 20-05, “Synthesis of Information Related to Highway Practices,” searches out and synthesizes useful knowledge from all available sources and prepares concise, documented reports on specific topics. Reports from this endeavor constitute an NCHRP report series, Synthesis of Highway Practice. This synthesis series reports on current knowledge and practice, in a compact format, without the detailed directions usually found in handbooks or design manuals. Each report in the series provides a compendium of the best knowledge available on those measures found to be the most successful in resolving specific problems. FOREWORD By Jo Allen Gause Staff Officer Transportation Research Board The use of recycled asphalt materials (RAM), including reclaimed asphalt pavement and reclaimed asphalt shingles, has a number of potential engineering, economic, and environmental benefits in the highway construction industry. However, using some of these materials in new asphalt mixtures may compromise cracking resistance. To avoid this problem, asphalt mixtures containing RAM may require the use of a softer binder or recycling agents (RA). The objective of this synthesis is to docu- ment state department of transportation (DOT) practices and procedures related to the use of RAs in asphalt mixtures containing RAM. Information for this study was gathered through a literature review, a survey of state DOTs, and follow-up interviews with selected agencies. Five case examples provide additional information on the topic. Jo E. Sias, Eshan V. Dave, and Runhua Zhang, University of New Hampshire, collected and syn- thesized the information, and wrote the report. The members of the topic panel are acknowledged on page iv. This synthesis is an immediately useful document that records practices that were accept- able within the limitations of the knowledge available at the time of its preparation. As progress in research and practice continues, new knowledge will be added to that now at hand.

1 Summary 3 Chapter 1 Introduction 3 1.1 Background 3 1.2 Synthesis Objective 4 1.3 Study Approach 5 1.4 Organization of Report 7 1.5 Definitions 8 Chapter 2 Literature Review of Use of Recycling Agents in Asphalt Mixtures 8 2.1 Introduction 8 2.2 Definition and General Types of Recycling Agents 9 2.3 Factors Affecting the Performance or Effectiveness of Recycling Agents 13 2.4 Current Methods and Practices for Evaluation of RA-Treated Binder Blends 17 2.5 Current Methods and Practices for Evaluation of RA-Treated Asphalt Mixtures 23 2.6 Long-Term Performance of RA-Treated Asphalt Materials 25 2.7 Sustainability Assessment Related to Use of RAs 27 2.8 Summary 29 Chapter 3 Survey on Practices for Use of Recycling Agents in Asphalt Mixtures 29 3.1 Introduction 29 3.2 State of the Practice Related to the Use of RAM Including RAP and RAS in Asphalt Mixtures 34 3.3 Experience of RA Use in Asphalt Mixtures 39 3.4 RA Type and Dosage Determination and Verification 43 3.5 QA Aspects for Asphalt Mixtures with RA 43 3.6 Performance Evaluation of Asphalt Binder and Mixtures with RA 45 3.7 Other Applications of RAs 47 3.8 Challenges and Plans for Use of RA 48 3.9 Summary 51 Chapter 4 Case Examples of Practices for Use of Recycling Agents in Asphalt Mixtures 51 4.1 Introduction 51 4.2 Delaware Department of Transportation Case Example 53 4.3 Oklahoma Department of Transportation Case Example 54 4.4 Nebraska Department of Transportation Case Example 57 4.5 Washington State Department of Transportation Case Example 59 4.6 Virginia Department of Transportation Case Example 61 4.7 Summary C O N T E N T S

62 Chapter 5 Summary of Major Findings 62 5.1 Summary of Findings 63 5.2 Identified Gaps in Knowledge and Future Research Needs 65 References 72 Appendix A Agency Survey Questions 89 Appendix B Agency Survey Responses (DOTs) 105 Appendix C Agency Survey Responses (CPTAs) 116 Abbreviations 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.nap.edu) retains the color versions.