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TRANSPORTAT ION RESEARCH BOARD WASHINGTON, D.C. 2007 www.TRB.org N A T I O N A L C O O P E R A T I V E H I G H W A Y R E S E A R C H P R O G R A M NCHRP REPORT 555 Subject Areas Pavement Design, Management, and Performance â¢ Materials and Construction 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 A N D E. Tutumluer UNIVERSITY OF ILLINOIS AT URBANA-CHAMPAIGN Urbana, IL Research sponsored by the American Association of State Highway and Transportation Officials in cooperation with the Federal Highway Administration
NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM Systematic, well-designed research provides the most effective approach to the solution of many problems facing highway administrators and engineers. Often, highway problems are of local interest and can best be studied by highway departments individually or in cooperation with their state universities and others. However, the 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 cooperative research. In recognition of these needs, the highway administrators of the American Association of State Highway and Transportation Officials initiated in 1962 an objective national highway research program employing modern scientific techniques. This program is supported on a continuing basis by funds from participating member states of the Association and it receives the full cooperation and support of the Federal Highway Administration, United States Department of Transportation. The Transportation Research Board of the National Academies was requested by the Association to administer the research program because of the Boardâs recognized objectivity and understanding of modern research practices. The Board is uniquely suited for this purpose as it maintains an extensive committee structure from which authorities on any highway transportation subject may be drawn; it possesses avenues of communications and cooperation with federal, state and local governmental agencies, universities, and industry; its relationship to the National Research Council is an insurance of objectivity; it maintains a full-time research correlation staff of specialists in highway transportation matters to bring the findings of research directly to those who are in a position to use them. The program is developed on the basis of research needs identified by chief administrators of the highway and transportation departments and by committees of AASHTO. Each year, specific areas of research needs to be included in the program are proposed to the National 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 NCHRP REPORT 555 Project 4-30A ISSN 0077-5614 ISBN: 978-0-309-09882-3 Library of Congress Control Number 2007926566 Â© 2007 Transportation Research Board COPYRIGHT PERMISSION Authors herein are responsible for the authenticity of their materials and for obtaining written permissions from publishers or persons who own the copyright to any previously published or copyrighted material used herein. Cooperative Research Programs (CRP) grants permission to reproduce material in this 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, FMCSA, FTA, or Transit Development Corporation endorsement of a particular product, method, or practice. It is expected that those reproducing the material in this document for 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 from CRP. NOTICE 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 the Governing Board of the National Research Council. Such approval reflects the Governing Boardâs judgment that the program concerned is of national importance and appropriate with respect to both the purposes and resources of the National Research Council. The members of the technical committee selected to monitor this project and to review this report were chosen for recognized scholarly competence and with due consideration for the balance of disciplines appropriate to the project. The opinions and conclusions expressed 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 Transportation Research Board, the National Research Council, the American Association of State Highway and Transportation Officials, or the Federal Highway Administration, U.S. Department of Transportation. Each report is reviewed and accepted for publication by the technical committee according to procedures established and monitored by the Transportation Research Board Executive Committee and the Governing Board of the National Research Council. The Transportation Research Board of the National Academies, the National Research Council, the Federal Highway Administration, the American Association of State Highway and Transportation Officials, and the individual states participating in the National Cooperative Highway Research Program do not endorse products or manufacturers. Trade or manufacturersâ names appear herein solely because they are considered essential to the object of this report.
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 ConstructionâArea 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. C O O P E R A T I V E R E S E A R C H P R O G R A M S
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, âTest Methods for Characterizing Aggregate Shape, Tex- ture, and Angularity,â Texas A&M University of College Station was assigned the objective of identifying or developingâfor use in central and field laboratoriesâsuitable 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 methodsâ accuracy, repeatability, reproducibility, ease of use, and ease of interpretation F O R E W O R D By Amir N. Hanna Staff Officer Transportation Research Board
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 methodâthe Aggregate Imaging System (AIMS)âwas recommended for implementation. 4. Developed a methodology to classify aggregates based on the distribution of characteristicsâ not average valuesâfor use in materials selection and specifications. 5. Prepared a draft protocol for a proposed âStandard Method of Test for Shape, Angularity, and Texture of Aggregate Particles Using the Aggregate Imaging System (AIMS)â 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 agencyâs 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
C O N T E N T S 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