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NATIONAL
NCHRP REPORT 673
COOPERATIVE
HIGHWAY
RESEARCH
PROGRAM
A Manual for Design of Hot Mix
Asphalt with Commentary
OCR for page R2
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
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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
