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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