TRANSPORTATION RESEARCH BOARD 2025 EXECUTIVE COMMITTEE*

OFFICERS

Chair: Leslie S. Richards, Professor of Practice, University of Pennsylvania, Philadelphia

Vice Chair: Joel M. Jundt, Secretary of Transportation, South Dakota Department of Transportation, Pierre

Executive Director: Victoria Sheehan, Transportation Research Board, Washington, DC

MEMBERS

James F. Albaugh, President and CEO, The Boeing Company (retired), Scottsdale, AZ

Carlos M. Braceras, Executive Director, Utah Department of Transportation, Salt Lake City

Douglas C. Ceva, Vice President, Customer Lead Solutions, Prologis, Inc., Jupiter, FL

Nancy Daubenberger, Commissioner of Transportation, Minnesota Department of Transportation, St. Paul

Marie Therese Dominguez, Commissioner, New York State Department of Transportation, Albany

Garrett Eucalitto, Commissioner, Connecticut Department of Transportation, Newington

Andrew Fremier, Executive Director, Metropolitan Transportation Commission, San Francisco, CA

Martha Grabowski, Professor Emerita, Information Systems, Le Moyne College, Madden College of Business & Economics, Cazenovia, NY

Randell Iwasaki, President and CEO, Iwasaki Consulting Services, Walnut Creek, CA

Carol A. Lewis, Professor, Transportation Studies, Texas Southern University, Houston

Scott C. Marler, Director, Iowa Department of Transportation, Ames

Ricardo Martinez, Adjunct Professor of Emergency Medicine, Emory University School of Medicine, Decatur, GA

Russell McMurry, Commissioner, Georgia Department of Transportation, Atlanta

Craig E. Philip, Research Professor and Director, VECTOR, Department of Civil and Environmental Engineering, Vanderbilt University, Nashville, TN

Steward T.A. Pickett, Distinguished Senior Scientist, Cary Institute of Ecosystem Studies, Millbrook, NY

Susan A. Shaheen, Professor and Co-Director, Transportation Sustainability Research Center, University of California, Berkeley

Marc Williams, Executive Director, Texas Department of Transportation, Austin

EX OFFICIO MEMBERS

Bryan Bedford, Administrator, Federal Aviation Administration, Washington, DC

Michael R. Berube, Deputy Assistant Secretary for Sustainable Transportation, U.S. Department of Energy, Washington, DC

Tariq Bokhari, Acting Administrator, Federal Transit Administration, Washington, DC

Steven G. Bradbury, Deputy Secretary, U.S. Department of Transportation, Washington, DC

Steven Cliff, Executive Officer, California Air Resources Board, Sacramento

Drew Feeley, Acting Administrator, Federal Railroad Administration, Washington, DC

LeRoy Gishi, Chief, Division of Transportation, Bureau of Indian Affairs, U.S. Department of the Interior, Germantown, MD

Firas Ibrahim, Director, Office of Research, Development, and Technology, Office of the Assistant Secretary for Research and Technology (OST-R), Washington, DC

Jason Kelly, Deputy Commanding General for Civil Works and Emergency Operations, U.S. Army Corps of Engineers, Washington, DC

Sandra Knight, President, WaterWonks, LLC, Washington, DC

Ben Kochman, Acting Administrator, Pipeline and Hazardous Materials Safety Administration, Washington, DC

Niloo Parvinashtiani, Engineer, Mobility Consultant Solutions, Iteris Inc., Fairfax, VA, and Chair, TRB Young Members Coordinating Council

Gloria Shepherd, Acting Deputy Administrator, Federal Highway Administration, Washington, DC

Karl Simon, Director, Transportation and Climate Division, U.S. Environmental Protection Agency, Washington, DC

Paul P. Skoutelas, President and CEO, American Public Transportation Association, Washington, DC

Jim Tymon, Executive Director, American Association of State Highway and Transportation Officials, Washington, DC

Sang Yi, Acting Administrator, U.S. Maritime Administration, Washington, DC

__________________

^* Membership as of August 2025.

NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM

NCHRP SYNTHESIS 657

Full-Depth Reclamation

CURRENT PRACTICES

A Synthesis of Highway Practice

Jo E. Sias

Sias Consulting, LLC

Nottingham, NH

University of New Hampshire

Durham, NH

Eshan V. Dave

Kaleigh Miech

Ebubechukwu Al-Ihekwaba

University of New Hampshire

Durham, NH

Subscriber Categories

Design • Materials • Pavements

Research sponsored by the American Association of State Highway and Transportation Officials in cooperation with the Federal Highway Administration

2025

NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM

Systematic, well-designed, and implementable research is the most effective way to solve many problems facing state department of transportation (DOT) 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 transportation results in increasingly complex problems of wide interest to highway 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 initiated 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.

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 TRBʼs recognized objectivity and understanding of modern research practices. TRB is uniquely suited for this purpose for many reasons: TRB maintains an extensive committee 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, universities, and industry; TRBʼs relationship to the National Academies is an insurance of objectivity; and TRB maintains a full-time staff of specialists 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 FHWA. Topics of the highest merit are selected by the AASHTO Special Committee on Research and Innovation (R&I), and each year R&Iʼs recommendations are proposed to the AASHTO Board of Directors, the FHWA, 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 oversight of research contracts are the responsibilities of NCHRP.

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.

NCHRP SYNTHESIS 657

Project 20-05, Topic 55-04
ISSN 0547-5570
ISBN 978-0-309-99545-0
Library of Congress Control Number 2025946041

© 2025 by the National Academy of Sciences. National Academies of Sciences, Engineering, and Medicine and the graphical logo are trademarks of the National Academy of Sciences. All rights reserved.

COPYRIGHT INFORMATION

Authors herein are responsible for the originality and accuracy 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.

The National Academy of Sciences (NAS) grants permission to reproduce written material in this publication for classroom and non-commercial purposes subject to the rights of any third parties and appropriate attribution. Permission is given with the understanding that none of the material will be used to imply NAS, TRB, AASHTO, APTA, FAA, FHWA, FTA, GHSA, or NHTSA endorsement of a particular product, method, or practice. For other uses of the written material, users must request permission from the National Academies Press.

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.

This material is based upon work supported by the FHWA under Agreement No. 693JJ32350025. Any opinions, findings, and conclusions or recommendations expressed or implied in this document 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 specifications. 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 manufacturersʼ names or logos appear herein solely because they are considered essential to the object of the report.

Published reports of the

NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM

are available from

National Academies Press
500 Fifth Street, NW, Keck 360
Washington, DC 20001

(800) 624-6242

and can be ordered through the Internet by going to

https://nap.nationalacademies.org

Printed in the United States of America

The National Academy of Sciences was established in 1863 by an Act of Congress, signed by President Lincoln, as a private, nongovernmental 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. Tsu-Jae Liu 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 program divisions of the National Academies of Sciences, Engineering, and Medicine. The mission of the Transportation Research Board is to mobilize expertise, experience, and knowledge to anticipate and solve complex transportation-related challenges. The Boardʼs varied activities annually engage about 8,500 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 departments of transportation, 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.

COOPERATIVE RESEARCH PROGRAMS

CRP STAFF FOR NCHRP SYNTHESIS 657

Monique R. Evans, Director, Cooperative Research Programs

Waseem Dekelbab, Deputy Director, Cooperative Research Programs, and Manager, National Cooperative Highway Research Program

Trey Joseph Wadsworth, Senior Program Officer

Tijhuana Stapleton, Senior Program Assistant

Natalie Barnes, Director of Publications

Heather DiAngelis, Associate Director of Publications

NCHRP PROJECT 20-05 PANEL

Joyce N. Taylor, Maine Department of Transportation, Augusta, ME (Chair)

Meredith Emily Hill, Maryland Department of Transportation, Hanover, MD

Jessie X. Jones, Arkansas Department of Transportation, Little Rock, AR

Raymond J. Khoury, Virginia Department of Transportation, Richmond, VA

James Murphy, Nevada Department of Transportation, Carson City, NV

Debra A. Nelson, New York State Department of Transportation, Albany, NY

James S. Nelson, Iowa Department of Transportation, Ames, IA

Jesus Alberto Sandoval-Gil, Arizona Department of Transportation, Phoenix, AZ

Cynthia J. Smith, Mississippi Department of Transportation, Jackson, MS

Jean M. Wallace, Minnesota Department of Transportation, St. Paul, MN

Mary Huie, FHWA Liaison

TOPIC 55-04 PANEL

Cathrina Barros, California Department of Transportation, Sacramento, CA

Ruben Carrasco, Texas Department of Transportation, Austin, TX

Brian K. Diefenderfer, Virginia Transportation Research Council, Charlottesville, VA

Colin A. Franco, Warwick, RI

Daba Gedafa, University of North Dakota, Grand Forks, ND

Jusang Lee, Indiana Department of Transportation, West Lafayette, IN

Chud Lundgreen, Washington State Department of Transportation, Pasco, WA

Kimberly R. Lyons, South Carolina Department of Transportation, Columbia, SC

Raquel Moraes, National Center for Asphalt Technology, Auburn, AL

Jason M. Dietz, FHWA Liaison

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 information 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 evaluating such useful information and to make it available to the entire highway community, the American Association of State Highway 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 Trey Joseph Wadsworth
Staff Officer
Transportation Research Board

The objective of this synthesis is to document practices used by state departments of transportation (DOTs) regarding the use of full-depth reclamation (FDR). FDR is a method to recycle in-place asphalt material for reconstruction and rehabilitation of flexible pavements. The synthesis documents state DOT classification of FDR types, site selection, specifications and guidelines for FDR mix design, and test methods to evaluate FDR quality.

This synthesis gathered information through a literature review, a survey of DOTs, and follow-up interviews with selected DOTs. Five case examples examine the specific practices regarding use of FDR. Additional survey responses from non-state DOTs are available in Appendix C.

Dr. Jo Sias, of Sias Consulting, LLC, led a team that collected and synthesized 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 acceptable within the limitations of the knowledge available at the time of its preparation.

CONTENTS

Summary

Chapter 1 Introduction

1.1 Background

1.2 Synthesis Objective

1.3 Study Approach

1.4 Organization of the Report

Chapter 2 Literature Review on Practices and Guidelines for Use of Full-Depth Reclamation

2.1 Background and Introduction

2.2 Project Selection, Benefits, and Limitations for Full-Depth Reclamation

2.3 Properties and Characterization Methods

2.4 Stabilization Methods

2.5 Mix Design

2.6 Structural Design of Pavements with FDR

2.7 Construction Processes, Quality Assurance Procedures, and Requirements for Opening to Traffic and Surfacing

2.8 Performance of FDR Projects

2.9 Summary

Chapter 3 Survey on Practices and Guidelines for Use of Full-Depth Reclamation

3.1 Introduction

3.2 State of the Practice

3.3 Use of Stabilizing Agents in FDR

3.4 Pavement Design with FDR Layers

3.5 Mix Design and Construction of FDR

3.6 Post-Construction for FDR

3.7 Identification of Challenges and Future Plans

3.8 Summary

Chapter 4 Case Examples of Practices for Use of Full-Depth Reclamation

4.1 Introduction

4.2 California Department of Transportation Case Example

4.3 Idaho Transportation Department Case Example

4.4 Minnesota Department of Transportation Case Example

4.5 Vermont Agency of Transportation Case Example

4.6 Virginia Department of Transportation Case Example

4.7 Summary

Chapter 5 Summary of Major Findings and Future Needs

5.1 Summary of the Findings

5.2 Identified Gaps in Knowledge and Future Research Needs

References 

Abbreviations 

Appendix A Agency Survey Questions 

Appendix B Agency Survey Responses (DOTs) 

Appendix C Other Agency Survey Responses 

Appendix D Results of Contractor Survey on Full-Depth Reclamation Construction Practices