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NATIONAL NCHRP REPORT 673 COOPERATIVE HIGHWAY RESEARCH PROGRAM A Manual for Design of Hot Mix Asphalt with Commentary

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TRANSPORTATION RESEARCH BOARD 2011 EXECUTIVE COMMITTEE* OFFICERS CHAIR: Neil J. Pedersen, Administrator, Maryland State Highway Administration, Baltimore VICE CHAIR: Sandra Rosenbloom, Professor of Planning, University of Arizona, Tucson EXECUTIVE DIRECTOR: Robert E. Skinner, Jr., Transportation Research Board MEMBERS J. Barry Barker, Executive Director, Transit Authority of River City, Louisville, KY Deborah H. Butler, Executive Vice President, Planning, and CIO, Norfolk Southern Corporation, Norfolk, VA William A.V. Clark, Professor, Department of Geography, University of California, Los Angeles Eugene A. Conti, Jr., Secretary of Transportation, North Carolina DOT, Raleigh James M. Crites, Executive Vice President of Operations, Dallas-Fort Worth International Airport, TX Paula J. Hammond, Secretary, Washington State DOT, Olympia Adib K. Kanafani, Cahill Professor of Civil Engineering, University of California, Berkeley Susan Martinovich, Director, Nevada DOT, Carson City Michael R. Morris, Director of Transportation, North Central Texas Council of Governments, Arlington Tracy L. Rosser, Vice President, Regional General Manager, Wal-Mart Stores, Inc., Mandeville, LA Steven T. Scalzo, Chief Operating Officer, Marine Resources Group, Seattle, WA Henry G. (Gerry) Schwartz, Jr., Chairman (retired), Jacobs/Sverdrup Civil, Inc., St. Louis, MO Beverly A. Scott, General Manager and CEO, Metropolitan Atlanta Rapid Transit Authority, Atlanta, GA David Seltzer, Principal, Mercator Advisors LLC, Philadelphia, PA Lawrence A. Selzer, President and CEO, The Conservation Fund, Arlington, VA Kumares C. Sinha, Olson Distinguished Professor of Civil Engineering, Purdue University, West Lafayette, IN Daniel Sperling, Professor of Civil Engineering and Environmental Science and Policy; Director, Institute of Transportation Studies; and Interim Director, Energy Efficiency Center, University of California, Davis Kirk T. Steudle, Director, Michigan DOT, Lansing Douglas W. Stotlar, President and CEO, Con-Way, Inc., Ann Arbor, MI C. Michael Walton, Ernest H. Cockrell Centennial Chair in Engineering, University of Texas, Austin EX OFFICIO MEMBERS Peter H. Appel, Administrator, Research and Innovative Technology Administration, U.S.DOT J. Randolph Babbitt, Administrator, Federal Aviation Administration, U.S.DOT Rebecca M. Brewster, President and COO, American Transportation Research Institute, Smyrna, GA Anne S. Ferro, Administrator, Federal Motor Carrier Safety Administration, U.S.DOT John T. Gray, Senior Vice President, Policy and Economics, Association of American Railroads, Washington, DC John C. Horsley, Executive Director, American Association of State Highway and Transportation Officials, Washington, DC David T. Matsuda, Deputy Administrator, Maritime Administration, U.S.DOT Victor M. Mendez, Administrator, Federal Highway Administration, U.S.DOT William W. Millar, President, American Public Transportation Association, Washington, DC Tara O'Toole, Under Secretary for Science and Technology, U.S. Department of Homeland Security, Washington, DC Robert J. Papp (Adm., U.S. Coast Guard), Commandant, U.S. Coast Guard, U.S. Department of Homeland Security, Washington, DC Cynthia L. Quarterman, Administrator, Pipeline and Hazardous Materials Safety Administration, U.S.DOT Peter M. Rogoff, Administrator, Federal Transit Administration, U.S.DOT David L. Strickland, Administrator, National Highway Traffic Safety Administration, U.S.DOT Joseph C. Szabo, Administrator, Federal Railroad Administration, U.S.DOT Polly Trottenberg, Assistant Secretary for Transportation Policy, U.S.DOT Robert L. Van Antwerp (Lt. Gen., U.S. Army), Chief of Engineers and Commanding General, U.S. Army Corps of Engineers, Washington, DC Barry R. Wallerstein, Executive Officer, South Coast Air Quality Management District, Diamond Bar, CA *Membership as of March 2011.

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NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM NCHRP REPORT 673 A Manual for Design of Hot Mix Asphalt with Commentary Advanced Asphalt Technologies, LLC Sterling, VA Subscriber Categories Highways Materials Research sponsored by the American Association of State Highway and Transportation Officials in cooperation with the Federal Highway Administration TRANSPORTATION RESEARCH BOARD WASHINGTON, D.C. 2011 www.TRB.org

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NATIONAL COOPERATIVE HIGHWAY NCHRP REPORT 673 RESEARCH PROGRAM Systematic, well-designed research provides the most effective Project 9-33 approach to the solution of many problems facing highway ISSN 0077-5614 administrators and engineers. Often, highway problems are of local ISBN 978-0-309-15564-9 interest and can best be studied by highway departments individually Library of Congress Control Number 2011927831 or in cooperation with their state universities and others. However, the 2011 National Academy of Sciences. All rights reserved. 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 COPYRIGHT INFORMATION cooperative research. Authors herein are responsible for the authenticity of their materials and for obtaining In recognition of these needs, the highway administrators of the written permissions from publishers or persons who own the copyright to any previously American Association of State Highway and Transportation Officials published or copyrighted material used herein. initiated in 1962 an objective national highway research program Cooperative Research Programs (CRP) grants permission to reproduce material in this employing modern scientific techniques. This program is supported on 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, a continuing basis by funds from participating member states of the FMCSA, FTA, or Transit Development Corporation endorsement of a particular product, Association and it receives the full cooperation and support of the method, or practice. It is expected that those reproducing the material in this document for Federal Highway Administration, United States Department of 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 Transportation. from CRP. The Transportation Research Board of the National Academies was requested by the Association to administer the research program because of the Board's recognized objectivity and understanding of NOTICE modern research practices. The Board is uniquely suited for this purpose as it maintains an extensive committee structure from which 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 authorities on any highway transportation subject may be drawn; it the Governing Board of the National Research Council. possesses avenues of communications and cooperation with federal, The members of the technical panel selected to monitor this project and to review this state and local governmental agencies, universities, and industry; its report were chosen for their special competencies and with regard for appropriate balance. relationship to the National Research Council is an insurance of 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 objectivity; it maintains a full-time research correlation staff of by the Governing Board of the National Research Council. specialists in highway transportation matters to bring the findings of The opinions and conclusions expressed or implied in this report are those of the research directly to those who are in a position to use them. researchers who performed the research and are not necessarily those of the Transportation The program is developed on the basis of research needs identified Research Board, the National Research Council, or the program sponsors. by chief administrators of the highway and transportation departments The Transportation Research Board of the National Academies, the National Research and by committees of AASHTO. Each year, specific areas of research Council, and the sponsors of the National Cooperative Highway Research Program do not needs to be included in the program are proposed to the National endorse products or manufacturers. Trade or manufacturers' names appear herein solely because they are considered essential to the object of the report. 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

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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. On 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. Charles M. Vest 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, on its own initiative, to identify issues of medical care, research, and education. Dr. Harvey V. Fineberg 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 Academy's 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. Charles M. Vest 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 Board's 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

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COOPERATIVE RESEARCH PROGRAMS CRP STAFF FOR NCHRP REPORT 673 Christopher W. Jenks, Director, Cooperative Research Programs Crawford F. Jencks, Deputy Director, Cooperative Research Programs Edward T. Harrigan, Senior Program Officer Melanie Adcock, Senior Program Assistant Eileen P. Delaney, Director of Publications Hilary Freer, Senior Editor NCHRP PROJECT 9-33 PANEL Field of Materials and Construction--Area of Bituminous Materials Frank Fee, NuStar Asphalt Refining, LLC, Moylan, PA (Chair) Jon A. Epps, Texas Transportation Institute - Texas A&M, College Station, TX Kee Y. Foo, California DOT, Sacramento, CA Kenneth W. Fults, KWF Pavement Consulting, Round Rock, TX Larry Ilg, Oregon DOT, Salem, OR Leslie Ann McCarthy, Villanova University, Villanova, PA Larry L. Michael, Hagerstown, MD Jennifer R. Williams, Arkansas SHTD, Little Rock, AR James M. Winford, Jr., Prairie Contractors, Inc., Westlake, LA John Bukowski, FHWA Liaison Thomas Harman, FHWA Liaison John D'Angelo, Other Liaison David E. Newcomb, National Asphalt Pavement Association Liaison Frederick Hejl, TRB Liaison

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FOREWORD By Edward T. Harrigan Staff Officer Transportation Research Board This report presents a mix design manual for hot mix asphalt (HMA) that incorporates the many advances in materials characterization and mix design technology developed since the conclusion of the Strategic Highway Research Program (SHRP). The report will be of immediate interest to materials engineers in state highway agencies and industry. At the conclusion of SHRP in 1993, the Superpave system of HMA mix design and analy- sis was envisioned to include both novel volumetric design procedures and a suite of per- formance tests supported by performance models for judging the quality of candidate mix designs on the basis of their predicted long-term in-service behavior. Since that time, the Superpave volumetric design method has been thoroughly validated and widely imple- mented in routine practice throughout the HMA industry as AASHTO R 35, Superpave Volumetric Design for Hot Mix Asphalt (HMA): AASHTO M 323, Superpave Volumetric Mix Design; and their supporting standard specifications and methods of test. Unfortu- nately, however, the SHRP performance models proved unreliable, the performance test equipment was complex and expensive, and the planned Superpave performance evalua- tion was not fully or widely implemented. In the past decade, more robust and reliable HMA performance tests, models, and equipment were delivered through coordinated research projects sponsored by NCHRP and FHWA. Of particular utility are the Mechanistic-Empirical Pavement Design Guide (MEPDG) and software developed and implemented in NCHRP Projects 1-37A and 1-40 and the simple performance tests and equipment developed in NCHRP Projects 9-19 and 9-29. Thus, the opportunity was presented to develop a new mix design method incorporating (1) features that were intended to be part of the Superpave system, including performance test- ing and performance predictions, and (2) the products of research on HMA materials char- acterization and mix design. This new mix design method is foreseen as an eventual successor to the Superpave system. The objective of NCHRP Project 9-33 was to develop a new, improved mix design method for HMA (including dense-graded, open-graded, and gap-graded mixes) in the form of a manual of practice for use by engineers and technicians in the public and private sectors. The project was carried out by Advanced Asphalt Technologies, LLC, Sterling, Virginia. The man- ual also includes a mix design method for warm mix asphalt (WMA) that codifies the key findings of the recently completed NCHRP Project 9-43. In the course of the research, the project team critically reviewed the worldwide literature on HMA materials and mix design since the conclusion of SHRP and, when necessary to resolve specific issues, conducted limited laboratory testing and analysis. Several detailed drafts of the manual were critically evaluated by the NCHRP project panel and several FHWA

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expert technical groups and subsequently revised by the project team. This report presents the final version of the manual; the manual's key features are (1) a single mix design method applicable to dense-graded, open-graded, and gap-graded HMA and WMA; (2) the applica- tion of a range of performance tests and criteria to estimate potential permanent deforma- tion, fatigue cracking, and low-temperature cracking behavior of HMA and WMA mix designs; (3) integration of mix and structural design through the use of the MEPDG software to validate HMA performance for specific combinations of pavement structure, climate, and traffic; and (4) the extensive use of examples to illustrate all facets of the mix design method. Detailed technical discussion to support the methodologies and processes included in the manual are presented in the commentary included herein as Appendix A. Besides the manual and commentary, the project team delivered HMA Tools a comprehensive software program written in Microsoft Excel spreadsheet format that is capable of carrying out all computations and analyses required to conduct and document a mix design; A 1-day training course to introduce the mix design method to practitioners; and A draft specification and practice in AASHTO standard format for volumetric mix design of dense-graded HMA that reflect the procedures presented in the manual. The project final report included the manual and commentary as Appendixes A and B and four additional appendixes: Appendix C: Course Manual Appendix D: Draft Specification for Volumetric Mix Design of Dense-Graded HMA Appendix E: Draft Practice for Volumetric Mix Design of Dense-Graded HMA Appendix F: Tutorial The project final report and Appendixes C through F are available as NCHRP Web-Only Document 159. HMA Tools and the training course materials are available for download at http://apps.trb.org/cmsfeed/TRBNetProjectDisplay.asp?ProjectID=967.

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CONTENTS 1 Chapter 1 Introduction 4 Chapter 2 Background 4 Materials Used in Making Asphalt Concrete 5 Asphalt Concrete Pavements 7 How Asphalt Concrete Pavements Fail 10 Asphalt Concrete Mixtures 12 HMA Mix Design Methods 15 Chapter 3 Asphalt Binders 17 Performance Grading of Asphalt Binders--Overview 17 Performance Grading--Test Methods 22 Performance Grading--Specification 24 Critical Temperatures, Specification Values, and Reliability 26 Practical Selection of PG Binder Grades for HMA Mix Design 28 Chapter 4 Aggregates 28 Aggregate Particle Size Distribution 33 Aggregate Specific Gravity and Absorption 38 Aggregate Specification Properties 43 Source Aggregate Properties 46 Chapter 5 Mixture Volumetric Composition 46 Composition Factors 53 Mixture-Specific Gravity 56 Volumetric Analysis 65 Chapter 6 Evaluating the Performance of Asphalt Concrete Mixtures 66 Mixture Composition and Performance 71 Laboratory Testing 82 Performance Predictions Using the AASHTO Mechanistic-Empirical Pavement Design Guide (MEPDG) 91 Chapter 7 Selection of Asphalt Concrete Mix Type 91 Pavement Structure and Construction 95 Important Factors in Mix Selection 98 Recommended Mix Types Note: Many of the photographs, figures, and tables in this report 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.

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101 Chapter 8 Design of Dense-Graded HMA Mixtures 101 Other Mix Design Methods 106 Overview of Design Method 107 Step 1. Gather Information 108 Step 2. Select Asphalt Binder 111 Step 3. Determine Compaction Level 111 Step 4. Select Nominal Maximum Aggregate Size 112 Step 5. Determine Target VMA and Design Air Void Content 114 Step 6. Calculate Target Binder Content 114 Step 7. Calculate Aggregate Content 114 Step 8. Proportion Aggregates for Trial Mixtures 124 Step 9. Calculate Trial Mix Proportions by Weight and Check Dust/Binder Ratio 128 Step 10. Evaluate and Refine Trial Mixtures 145 Step 11. Compile Mix Design Report 148 Chapter 9 Reclaimed Asphalt Pavement 148 General Mixture Design Considerations for RAP 150 Overview of the Mixture Design Process with RAP 151 A Note on General Methods of Handling RAP 151 Using HMA Tools to Design HMA Mixes with RAP 152 RAP Sampling 153 Blending and Variability 161 RAP Aggregate Properties 164 RAP Binder Properties 170 Handling RAP Materials in the Laboratory 174 Chapter 10 Design of Gap-Graded HMA Mixtures 174 Overview of GGHMA Mix Design Procedure 176 Step 1--Materials Selection 179 Step 2--Trial Gradations 188 Step 3--Selection of Optimum Gradation 189 Step 4--Refine Design Asphalt Binder Content 189 Step 5--Conduct Performance Testing 191 Trouble Shooting GGHMA Mix Designs 194 Chapter 11 Design of Open-Graded Mixtures 195 Overview of PFC Mix Design Procedure 195 Step 1--OGFC Materials Selection 198 Step 2--Trial Gradations 203 Step 3--Selection of Optimum Gradation 203 Step 4--Selection of Optimum Asphalt Binder Content 205 Step 5--Moisture Susceptibility 205 Trouble Shooting PFC Mix Designs 207 Chapter 12 Field Adjustments and Quality Assurance of HMA Mixtures 207 Adjusting Laboratory HMA Mix Designs for Plant Production 211 Quality Control of HMA

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225 Commentary to the Mix Design Manual for Hot Mix Asphalt 226 Chapter 1 Introduction 227 Chapter 2 Background 228 Chapter 3 Asphalt Binders 229 Chapter 4 Aggregates 231 Chapter 5 Mixture Volumetric Composition 232 Chapter 6 Evaluating the Performance of Asphalt Concrete Mixtures 240 Chapter 7 Selection of Asphalt Concrete Mix Type 241 Chapter 8 Design of Dense-Graded HMA Mixtures 253 Chapter 9 Reclaimed Asphalt Pavement 265 Chapter 10 Design of Gap-Graded HMA Mixtures 266 Chapter 11 Design of Open-Graded Mixtures 267 Chapter 12 Field Adjustments and Quality Assurance of HMA Mixtures 271 References