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NATIONAL
NCHRP REPORT 555
COOPERATIVE
HIGHWAY
RESEARCH
PROGRAM
Test Methods for
Characterizing Aggregate Shape,
Texture, and Angularity
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TRANSPORTATION RESEARCH BOARD 2007 EXECUTIVE COMMITTEE*
OFFICERS
CHAIR: Linda S. Watson, CEO, LYNXCentral Florida Regional Transportation Authority, Orlando
VICE CHAIR: Debra L. Miller, Secretary, Kansas DOT, Topeka
EXECUTIVE DIRECTOR: Robert E. Skinner, Jr., Transportation Research Board
MEMBERS
J. Barry Barker, Executive Director, Transit Authority of River City, Louisville, KY
Michael W. Behrens, Executive Director, Texas DOT, Austin
Allen D. Biehler, Secretary, Pennsylvania DOT, Harrisburg
John D. Bowe, President, Americas Region, APL Limited, Oakland, CA
Larry L. Brown, Sr., Executive Director, Mississippi DOT, Jackson
Deborah H. Butler, Vice President, Customer Service, Norfolk Southern Corporation and Subsidiaries, Atlanta, GA
Anne P. Canby, President, Surface Transportation Policy Partnership, Washington, DC
Nicholas J. Garber, Henry L. Kinnier Professor, Department of Civil Engineering, University of Virginia, Charlottesville
Angela Gittens, Vice President, Airport Business Services, HNTB Corporation, Miami, FL
Susan Hanson, Landry University Professor of Geography, Graduate School of Geography, Clark University, Worcester, MA
Adib K. Kanafani, Cahill Professor of Civil Engineering, University of California, Berkeley
Harold E. Linnenkohl, Commissioner, Georgia DOT, Atlanta
Michael D. Meyer, Professor, School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta
Michael R. Morris, Director of Transportation, North Central Texas Council of Governments, Arlington
John R. Njord, Executive Director, Utah DOT, Salt Lake City
Pete K. Rahn, Director, Missouri DOT, Jefferson City
Sandra Rosenbloom, Professor of Planning, University of Arizona, Tucson
Tracy L. Rosser, Vice President, Corporate Traffic, Wal-Mart Stores, Inc., Bentonville, AR
Rosa Clausell Rountree, Executive Director, Georgia State Road and Tollway Authority, Atlanta
Henry G. (Gerry) Schwartz, Jr., Senior Professor, Washington University, St. Louis, MO
C. Michael Walton, Ernest H. Cockrell Centennial Chair in Engineering, University of Texas, Austin
Steve Williams, Chairman and CEO, Maverick Transportation, Inc., Little Rock, AR
EX OFFICIO MEMBERS
Thad Allen (Adm., U.S. Coast Guard), Commandant, U.S. Coast Guard, Washington, DC
Thomas J. Barrett (Vice Adm., U.S. Coast Guard, ret.), Pipeline and Hazardous Materials Safety Administrator, U.S.DOT
Marion C. Blakey, Federal Aviation Administrator, U.S.DOT
Joseph H. Boardman, Federal Railroad Administrator, U.S.DOT
John A. Bobo, Jr., Acting Administrator, Research and Innovative Technology Administration, U.S.DOT
Rebecca M. Brewster, President and COO, American Transportation Research Institute, Smyrna, GA
George Bugliarello, Chancellor, Polytechnic University of New York, Brooklyn, and Foreign Secretary, National Academy of Engineering,
Washington, DC
J. Richard Capka, Federal Highway Administrator, U.S.DOT
Sean T. Connaughton, Maritime Administrator, U.S.DOT
Edward R. Hamberger, President and CEO, Association of American Railroads, Washington, DC
John H. Hill, Federal Motor Carrier Safety Administrator, U.S.DOT
John C. Horsley, Executive Director, American Association of State Highway and Transportation Officials, Washington, DC
J. Edward Johnson, Director, Applied Science Directorate, National Aeronautics and Space Administration, John C. Stennis Space Center, MS
William W. Millar, President, American Public Transportation Association, Washington, DC
Nicole R. Nason, National Highway Traffic Safety Administrator, U.S.DOT
Jeffrey N. Shane, Under Secretary for Policy, U.S.DOT
James S. Simpson, Federal Transit Administrator, U.S.DOT
Carl A. Strock (Lt. Gen., U.S. Army), Chief of Engineers and Commanding General, U.S. Army Corps of Engineers, Washington, DC
*Membership as of March 2007.
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NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM
NCHRP REPORT 555
Test Methods for
Characterizing Aggregate Shape,
Texture, and Angularity
E. Masad, T. Al-Rousan, J. Button, and D. Little
TEXAS TRANSPORTATION INSTITUTE
College Station,TX
AND
E. Tutumluer
UNIVERSITY OF ILLINOIS AT URBANA-CHAMPAIGN
Urbana, IL
Subject Areas
Pavement Design, Management, and Performance · Materials and Construction
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.
2007
www.TRB.org
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NATIONAL COOPERATIVE HIGHWAY NCHRP REPORT 555
RESEARCH PROGRAM
Systematic, well-designed research provides the most effective Project 4-30A
approach to the solution of many problems facing highway ISSN 0077-5614
administrators and engineers. Often, highway problems are of local ISBN: 978-0-309-09882-3
interest and can best be studied by highway departments individually Library of Congress Control Number 2007926566
or in cooperation with their state universities and others. However, the © 2007 Transportation Research Board
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 PERMISSION
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.
relationship to the National Research Council is an insurance of
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.
needs to be included in the program are proposed to the National Each report is reviewed and accepted for publication by the technical committee according
Research Council and the Board by the American Association of State to procedures established and monitored by the Transportation Research Board Executive
Committee and the Governing Board of the National Research Council.
Highway and Transportation Officials. Research projects to fulfill these
needs are defined by the Board, and qualified research agencies are The Transportation Research Board of the National Academies, the National Research
Council, the Federal Highway Administration, the American Association of State Highway
selected from those that have submitted proposals. Administration and and Transportation Officials, and the individual states participating in the National
surveillance of research contracts are the responsibilities of the National Cooperative Highway Research Program do not endorse products or manufacturers. Trade
Research Council and the Transportation Research Board. or manufacturers' names appear herein solely because they are considered essential to the
object of this report.
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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COOPERATIVE RESEARCH PROGRAMS
CRP STAFF FOR NCHRP REPORT 555
Christopher W. Jenks, Director, Cooperative Research Programs
Crawford F. Jencks, Deputy Director, Cooperative Research Programs
Amir N. Hanna, Senior Program Officer
Eileen P. Delaney, Director of Publications
Natassja Linzau, Editor
Beth Hatch, Editor
NCHRP PROJECT 4-30A PANEL
Field of Materials and Construction--Area of General Materials
D. Stephen Lane, Virginia DOT (Chair)
Guy Cautillo, Ontario Ministry of Transportation, Canada
Ervin L. Dukatz, Jr., Mathy Construction, Onalaska, WI
Kee Y. Foo, California DOT
Caroline Herrera, Texas DOT
David W. Jahn, DWJ Resources, LLC, Cincinnati, OH
Richard C. Meininger, Columbia, MD
William Sheftick, Bowser-Morner, Inc., Springfield, IL
William H. Skerritt, New York State DOT
Linbing Wang, Virginia Polytechnic Institute and State University
Leslie Ann McCarthy, FHWA Liaison
G.P. Jayaprakash, TRB Liaison
AUTHOR ACKNOWLEDGMENTS
The research reported herein was performed under NCHRP Project 4-30A by the Texas Transportation
Institute, Texas A&M University; and the Department of Civil and Environmental Engineering, Univer-
sity of Illinois at Urbana-Champaign. Texas A&M University is the contractor of this study. The University
of Illinois served as a subcontractor.
Eyad Masad, Assistant Professor of Civil Engineering, Texas A&M University, was the principal investi-
gator; the work was done under his general supervision. Other authors of this report are Taleb Al-Rousan,
Research Assistant at Texas Transportation Institute (currently an Assistant Professor at the Hashemite
University in Jordan); Joe Button, Head of the Materials and Pavement Division, Texas Transportation
Institute; Dallas Little, Professor, Texas Transportation Institute; and Erol Tutumluer, Associate Professor,
University of Illinois.
The researchers would like to extend their gratitude to all the individuals who provided direction and
guidance in this project and also to thank all individuals and agencies that gave permission to include their
test methods in this study.
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FOREWORD
By Amir N. Hanna
Staff Officer
Transportation Research Board
This report presents a methodology for classifying aggregates based on the distribution
of shape, texture, and angularity characteristics and recommends a test method for measur-
ing these characteristics to help improve specifications for aggregates used in highway pave-
ments. The test method measures shape, texture, and angularity characteristics of aggregates
used in hot-mix asphalt, hydraulic cement concrete, and unbound base and subbase layers
of highway pavements, and it is appropriate for use in central and field laboratories. This
report will be of particular interest to materials engineers, researchers, and others concerned
with the design and construction of flexible and rigid pavements.
The properties of coarse and fine aggregates used in hot-mix asphalt (HMA) and
hydraulic cement concrete and unbound base and subbase layers are very important to the
performance of the pavement system in which they are used. Particle shape, texture, and
angularity are among the aggregate properties that have significant effects on performance.
These properties vary widely with the type and source of aggregates and processing vari-
ables. However, current aggregate specifications do not address, in a direct manner, the
measurement of these properties, thus leading to inconsistent interpretation and use of test
results. Also, a thorough evaluation of available methods for measuring aggregate shape,
texture, and angularity characteristics has not been performed to identify appropriate meth-
ods. Without this information, a rational recommendation for incorporating such test
methods in aggregate specifications can not be made. Thus, research was needed to evalu-
ate potential test methods and identify or develop suitable test methods for measuring rel-
evant properties in central and field laboratories, and to develop recommendations to help
improve specifications for aggregates used in highway pavements.
Under NCHRP Project 4-30A, "Test Methods for Characterizing Aggregate Shape, Tex-
ture, and Angularity," Texas A&M University of College Station was assigned the objective
of identifying or developing--for use in central and field laboratories--suitable test methods
for measuring shape, texture, and angularity characteristics of aggregates used in HMA,
hydraulic cement concrete, and unbound base and subbase layers of highway pavements.
The research focused on the characteristics of coarse aggregates with limited consideration
given to the characteristics of fine aggregates. To accomplish this objective, the researchers
performed the following tasks:
1. Reviewed and synthesized information relevant to available test methods for measuring
aggregate characteristics.
2. Conducted tests using 13 different coarse aggregates and 5 different fine aggregates to evaluate
test methods' accuracy, repeatability, reproducibility, ease of use, and ease of interpretation
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of results, and considered other factors, such as cost, readiness for implementation, portabil-
ity, and applicability for the different aggregate sizes and types. Based on this information,
13 potential test methods were selected for further evaluation and ranking.
3. Used an Analytical Hierarchy Process for evaluating and ranking potential test methods; the
highest ranked method--the Aggregate Imaging System (AIMS)--was recommended for
implementation.
4. Developed a methodology to classify aggregates based on the distribution of characteristics--
not average values--for use in materials selection and specifications.
5. Prepared a draft protocol for a proposed "Standard Method of Test for Shape, Angularity,
and Texture of Aggregate Particles Using the Aggregate Imaging System (AIMS)" for consid-
eration by AASHTO.
In the methodology described in this report, aggregate characteristics are represented by
cumulative distribution functions and not by average values to better represent the effects
of blending and crushing of aggregates. This approach helps better explore the influence of
different crushing and blending processes, facilitate quality control, identify possible effects
on performance, and improve specifications. The proposed method of test, recommended
for implementation, can be used to measure aggregate shape, texture, and angularity char-
acteristics that relate to performance and thus it provides a means for evaluating and select-
ing aggregates used in paving materials. The test procedure will be particularly useful to
highway agencies and is recommended for consideration and adoption by AASHTO as a
standard test method.
Appendixes B through E contained in the research agency's final report are not published
herein. These appendixes are accessible on the web as NCHRP Web-Only Document 80 at
http://trb.org/news/blurb_detail.asp?id=7276. These appendixes are titled as follows:
Appendix B: Review of Aggregate Characteristics Affecting Pavement Performance
Appendix C: Image Analysis Methods for Characterizing Aggregate Shape Properties
Appendix D: Test Methods for Measuring Aggregate Characteristics
Appendix E: Photographs of Aggregate Samples
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CONTENTS
1 Summary
3 Chapter 1 Introduction and Research Approach
3 Project Background
3 Research Objective
3 Scope of Study
4 Research Approach
4 Evaluation of Test Methods
5 Experimental Design and Statistical Analysis
5 Ranking and Recommendation of Test Methods
6 Chapter 2 Findings
6 Evaluation of Merits and Deficiencies of Test Methods
9 Aggregate Selection
11 Experimental Design and Statistical Analysis
11 Evaluation of Repeatability and Reproducibility
13 Evaluation of Accuracy
20 Cost and Operational Characteristics of Test Methods
21 Ranking of Test Methods Using the Analytical Hierarchy Process
21 Background on the Process
22 Program Description
26 AHP Ranking of Test Methods
27 Fine Aggregate Angularity
29 Coarse Aggregate Texture
29 Coarse Aggregate Shape
33 X-Ray Computed Tomography of Aggregates
36 Statistical-Based Methodology for Classification of Aggregates
36 Analysis and Results
45 Chapter 3 Interpretation, Appraisal, and Applications
45 Test Methods
45 Use of Aggregate Acceptance Tests in Specifications
47 Chapter 4 Conclusions and Suggested Research
47 General Conclusions
48 Applicability and Suggested Research
49 References
A-1 Appendix A
B-1 Appendixes B, C, D, and E
