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NATIONAL
NCHRP REPORT 648
COOPERATIVE
HIGHWAY
RESEARCH
PROGRAM
Mixing and Compaction
Temperatures of Asphalt
Binders in Hot-Mix Asphalt
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TRANSPORTATION RESEARCH BOARD 2010 EXECUTIVE COMMITTEE*
OFFICERS
CHAIR: Michael R. Morris, Director of Transportation, North Central Texas Council of Governments, Arlington
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NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM
NCHRP REPORT 648
Mixing and Compaction Temperatures
of Asphalt Binders in Hot-Mix Asphalt
Randy C. West
Donald E. Watson
Pamela A. Turner
NATIONAL CENTER FOR ASPHALT TECHNOLOGY
Auburn, AL
John R. Casola
MALVERN INSTRUMENTS INC.
Westborough, MA
Subscriber Categories
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.
2010
www.TRB.org
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NATIONAL COOPERATIVE HIGHWAY NCHRP REPORT 648
RESEARCH PROGRAM
Systematic, well-designed research provides the most effective Project 9-39
approach to the solution of many problems facing highway ISSN 0077-5614
administrators and engineers. Often, highway problems are of local ISBN 978-0-309-11825-5
interest and can best be studied by highway departments individually Library of Congress Control Number 2010923478
or in cooperation with their state universities and others. However, the © 2010 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. Such approval reflects the
possesses avenues of communications and cooperation with federal, Governing Board's judgment that the program concerned is of national importance and
state and local governmental agencies, universities, and industry; its appropriate with respect to both the purposes and resources of the National Research
Council.
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The members of the technical committee selected to monitor this project and to review this
objectivity; it maintains a full-time research correlation staff of
report were chosen for recognized scholarly competence and with due consideration for the
specialists in highway transportation matters to bring the findings of balance of disciplines appropriate to the project. The opinions and conclusions expressed
research directly to those who are in a position to use them. or implied are those of the research agency that performed the research, and, while they have
been accepted as appropriate by the technical committee, they are not necessarily those of
The program is developed on the basis of research needs identified
the Transportation Research Board, the National Research Council, the American
by chief administrators of the highway and transportation departments Association of State Highway and Transportation Officials, or the Federal Highway
and by committees of AASHTO. Each year, specific areas of research Administration, U.S. Department of Transportation.
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Committee and the Governing Board of the National Research Council.
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surveillance of research contracts are the responsibilities of the National Cooperative Highway Research Program do not endorse products or manufacturers. Trade
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The needs for highway research are many, and the National
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Published reports of the
NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM
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Printed in the United States of America
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COOPERATIVE RESEARCH PROGRAMS
CRP STAFF FOR NCHRP REPORT 648
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
Margaret B. Hagood, Editor
Andréa Briere, Editor
NCHRP PROJECT 09-39 PANEL
Field of Materials and Construction--Area of Bituminous Materials
Rita B. Leahy, Asphalt Pavement Association of California, Sacramento, CA (Chair)
John H. Tenison, AMEC Earth & Environmental, Albuquerque, NM
Paul J. Hoelscher, Texas DOT, Abilene, TX
Gayle N. King, GHK, Inc., The Woodlands, TX
Michael W. Longshaw, Kansas DOT, El Dorado, KS
Louay N. Mohammad, Louisiana State University, Baton Rouge, LA
Allen H. Myers, Kentucky Transportation Cabinet, Frankfort, KY
Nelio J. Rodrigues, Connecticut DOT, Rocky Hill, CT
John D'Angelo, FHWA Liaison
Nelson H. Gibson, FHWA Liaison
Frederick Hejl, TRB Liaison
AUTHOR ACKNOWLEDGMENTS
The research reported herein was performed under NCHRP Project 9-39 by the National Center for
Asphalt Technology, Auburn University. Randy C. West, Director, was the principal investigator and Donald
E. Watson, Lead Research Engineer at the National Center for Asphalt Technology, was the co-principal
investigator. John Casola, Product Sales Manager at Malvern Instruments, and Pamela Turner, Assistant
Research Engineer at the National Center for Asphalt Technology, were key contributors to the research
and preparation of this report. The authors thank Fred Mazzeo of Malvern Instruments for providing
rheological testing and analysis and Saeed Maghsoodloo, Auburn University, for experimental design and
statistical analysis. The authors thank Jason Moore and all of the staff of the National Center for Asphalt
Technology who worked on this project. The authors thank the Federal Highway Administration Turner-
Fairbank Highway Research Center for binder testing and the asphalt binder suppliers who provided mate-
rials and information for this project.
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FOREWORD
By Edward Harrigan
Staff Officer
Transportation Research Board
This report identifies improved test methods for determining laboratory mixing and
compaction temperatures of modified and unmodified asphalt binders. The report will be
of immediate interest to materials engineers in state highway agencies and the hot-mix
asphalt (HMA) construction industry.
The Asphalt Institute (AI) procedure for determining mixing and compaction tempera-
tures of asphalt binders was developed for penetration- and viscosity-graded asphalt
cements used in the United States until the 1990s. Since that time, the use of modified,
performance-graded asphalt binders in HMA paving has increased significantly, especially
on high-volume traffic routes. The AI procedure often requires heating of modified binders
to unrealistically high temperatures that can potentially damage the asphalt binder. To over-
come this problem, highway agencies usually rely on the modifier suppliers to recommend
mixing and compaction temperatures, a circumstance that can produce mixed results.
The objective of this research was to identify or develop a simple, rapid, and accurate lab-
oratory procedure--suitable for routine use--for determining the mixing and compaction
temperatures of both unmodified and modified asphalt binder. The research was performed
by the National Center for Asphalt Technology, Auburn University, Auburn, Alabama with
the support of Malvern Instruments Inc., Westborough, Massachusetts.
In the course of the research, the project team evaluated existing and emerging methods to
determine temperatures that will provide satisfactory aggregate coating during laboratory mix-
ing and appropriate laboratory specimen compaction without degrading the asphalt binder and
identified two improved, equally effective test methods. These tests, termed (1) the phase angle
method and (2) the steady shear flow viscosity (SSFV) method, provide reasonable, consistent
mixing and compaction temperatures that correlate well with the results of HMA coating,
workability, and compactability tests for both binder types. The phase angle and SSFV mea-
surements are made with the dynamic shear rheometer (DSR), already widely used in asphalt
laboratories for measuring binder stiffnesses over a range of temperatures and frequencies.
This report includes four appendices as follows:
· Appendix A: Responses of Survey on Agency Specifications Regarding Mixing and Com-
paction Temperatures;
· Appendix B: Mix Design Data for Base Mix and Other Compaction Experiment Mixes;
· Appendix C: Draft AASHTO Standard for Steady Shear Flow and Phase Angle Methods; and
· Appendix D: Statistical Analyses of the Steady Shear Flow and Phase Angle Methods.
The draft standard methods of test are under consideration for possible adoption by the
AASHTO Highway Subcommittee on Materials.
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CONTENTS
1 Summary
5 Chapter 1 Background
5 Introduction
5 Literature Search
5 A Note on Units of Viscosity
6 Background on the Development of Mixing and Compaction
Temperature Criteria
8 Effect of Temperature on Degradation of Asphalt Binders
9 Mixing and Compaction Temperatures for Modified Asphalt Binders
10 Survey of Current Practices for Determining Mixing and Compaction
Temperatures
13 Recent Research on Proposed New Methods for Determining Mixing
and Compaction Temperatures
13 Zero Shear Viscosity
14 Extrapolated High Shear Rate Viscosity
14 Steady Shear Flow
14 Shear Rate Dependency
15 Extensional Viscosity
15 Equivalent Mixture Properties
15 Workability
16 Shear Rates During Mixing and Compaction
19 Summary of Key Findings from the Literature Review
20 Chapter 2 Research Approach
20 Experimental Plan
20 Approach
20 Overview of the Experimental Research Plan
22 Materials
22 Organization of the Test Plan
23 Part 1: Binder Tests
23 Part 2: Mixture Tests
24 Description of Tests
24 Binder Tests
30 Mixture Tests
31 Summary of Research Plan
33 Chapter 3 Findings and Applications
33 Experimental Results
33 Binder Testing
33 Binder Grading
33 High Shear Rate Viscosity Method
33 Steady Shear Flow Method
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33 Phase Angle Method
34 SEP Tests
37 Results of Re-Graded Binders
37 MSCR Tests
37 Analysis of Binder Degradation
43 Mixture Testing
43 Mixture Coating Tests
45 Mixture Coating Tests with Incompletely Dried Aggregate
46 Workability Tests
47 Compaction Tests
53 Indirect Tensile Creep Compliance and Strength
59 Correlation of Mixing and Compaction Temperatures
66 Comparison of SSF and Phase Angle Methods
68 Validation Experiment Results and Analysis
72 Chapter 4 Conclusions and Recommendations
72 Summary of Key Findings
73 Recommendation of a New Method for Determining Mixing and Compaction
Temperatures
73 Recommendations for Further Work
73 Independent Validation
74 Refinement of the SSF and Phase Angle Methods
74 Interlaboratory Studies
74 Training
76 References
A-1 Appendix A Responses of Survey on Agency Specifications
Regarding Mixing and Compaction
Temperatures
B-1 Appendix B Mix Design Data for Base Mix and Other
Compaction Experiment Mixes
C-1 Appendix C Draft AASHTO Standard for Steady Shear Flow
and Phase Angle Methods
D-1 Appendix D Statistical Analyses of the Steady Shear Flow and
Phase Angle Methods
