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NATIONAL NCHRP REPORT 621 COOPERATIVE HIGHWAY RESEARCH PROGRAM Acceptance Tests for Surface Characteristics of Steel Strands in Prestressed Concrete
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TRANSPORTATION RESEARCH BOARD 2008 EXECUTIVE COMMITTEE* OFFICERS CHAIR: Debra L. Miller, Secretary, Kansas DOT, Topeka VICE CHAIR: Adib K. Kanafani, Cahill Professor of Civil Engineering, University of California, Berkeley EXECUTIVE DIRECTOR: Robert E. Skinner, Jr., Transportation Research Board MEMBERS J. Barry Barker, Executive Director, Transit Authority of River City, Louisville, KY 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, Executive Vice President, Planning, and CIO, Norfolk Southern Corporation, Norfolk, VA William A.V. Clark, Professor, Department of Geography, University of California, Los Angeles David S. Ekern, Commissioner, Virginia DOT, Richmond Nicholas J. Garber, Henry L. Kinnier Professor, Department of Civil Engineering, University of Virginia, Charlottesville Jeffrey W. Hamiel, Executive Director, Metropolitan Airports Commission, Minneapolis, MN Edward A. (Ned) Helme, President, Center for Clean Air Policy, Washington, DC Will Kempton, Director, California DOT, Sacramento Susan Martinovich, Director, Nevada DOT, Carson City 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 Neil J. Pedersen, Administrator, Maryland State Highway Administration, Baltimore 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., Chairman (retired), Jacobs/Sverdrup Civil, Inc., St. Louis, MO C. Michael Walton, Ernest H. Cockrell Centennial Chair in Engineering, University of Texas, Austin Linda S. Watson, CEO, LYNXCentral Florida Regional Transportation Authority, Orlando 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 Joseph H. Boardman, Federal Railroad Administrator, U.S.DOT Rebecca M. Brewster, President and COO, American Transportation Research Institute, Smyrna, GA Paul R. Brubaker, Research and Innovative Technology Administrator, U.S.DOT George Bugliarello, Chancellor, Polytechnic University of New York, Brooklyn, and Foreign Secretary, National Academy of Engineering, Washington, DC Sean T. Connaughton, Maritime Administrator, U.S.DOT LeRoy Gishi, Chief, Division of Transportation, Bureau of Indian Affairs, U.S. Department of the Interior, Washington, DC 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 Carl T. Johnson, Pipeline and Hazardous Materials Safety Administrator, U.S.DOT J. Edward Johnson, Director, Applied Science Directorate, National Aeronautics and Space Administration, John C. Stennis Space Center, MS David Kelly, Acting Administrator, National Highway Traffic Safety Administration, U.S.DOT Thomas J. Madison, Jr., Administrator, Federal Highway Administration, U.S.DOT William W. Millar, President, American Public Transportation Association, Washington, DC James S. Simpson, Federal Transit Administrator, U.S.DOT Robert A. Sturgell, Acting Administrator, Federal Aviation Administration, 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 *Membership as of October 2008.
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NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM NCHRP REPORT 621 Acceptance Tests for Surface Characteristics of Steel Strands in Prestressed Concrete Andrew E. N. Osborn WISS JANNEY ELSTNER ASSOCIATES INC. New York, NY John S. Lawler James D. Connolly WISS JANNEY ELSTNER ASSOCIATES INC. Northbrook, IL Subject Areas Bridges, Other Structures, and Hydraulics and Hydrology · 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. 2008 www.TRB.org
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NATIONAL COOPERATIVE HIGHWAY NCHRP REPORT 621 RESEARCH PROGRAM Systematic, well-designed research provides the most effective Project 10-62 approach to the solution of many problems facing highway ISSN 0077-5614 administrators and engineers. Often, highway problems are of local ISBN: 978-0-309-11761-6 interest and can best be studied by highway departments individually Library of Congress Control Number 2008910409 or in cooperation with their state universities and others. However, the © 2008 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 621 Christopher W. Jenks, Director, Cooperative Research Programs Crawford F. Jencks, Deputy Director, Cooperative Research Programs Edward T. Harrigan, Senior Program Officer Eileen P. Delaney, Director of Publications Hilary Freer, Senior Editor NCHRP PROJECT 10-62 PANEL Field of Materials and Construction--Area of Specifications, Procedures, and Practices William N. Nickas, Corven Engineering, Inc, Tallahassee, FL (Chair) Gary DeWitt, Colorado DOT, Evans, CO Ahmad M. Itani, University of Nevada - Reno, Reno, NV Jose A. Lopez, Plainsboro, NJ Mohsen Shahawy, SDR Engineering Consultants, Inc., Tallahassee, FL Thomas C. Stout, Texas DOT, Austin, TX Paul Virmani, FHWA Liaison Frederick Hejl, TRB Liaison AUTHOR ACKNOWLEDGMENTS The research reported herein was performed under NCHRP Project 10-62 by Wiss Janney Elstner Asso- ciates Inc. (WJE), Kansas State University (KSU), StressCon Corporation Inc. (SC), Lehigh University (LU), and Northwestern University (NU). At WJE, the principal investigator was Andrew Osborn. The co-principal investigators were James Con- nolly and John Lawler. Major assistance to the project was provided by Sunyoung Hong, Richard Cechner, John Fraczek, Mark Moore, and Donald Pfeifer. The hard work of Leo Zegler, Ryan Keesbury, Susanne Papas, Kim Steiner, Dave Dunkman, and the rest of the staff of WJE is also gratefully acknowledged. At KSU, the research work was performed under the direction of Robert Peterman. At SC, the research work was performed under the direction of Donald Logan. At LU, the research was performed under the direction of Eric Kaufman. At NU, the research work was carried out by Bruce Ankenman. The assistance of all these individuals is gratefully acknowledged.
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FOREWORD By Edward T. Harrigan Staff Officer Transportation Research Board This report provides practical tests to identify and measure residues on the surface of steel pre-stressing strands and to establish thresholds for residue types found to affect the strength of the strand's bond to concrete. Key products presented here are four test methods suitable for use in a quality assurance program for the manufacture of steel pre- stressing strand. The report will be of particular interest to bridge engineers in state high- way agencies and industry and to suppliers of steel pre-stressing strand. In the 1980s, tests conducted on uncoated and epoxy-coated steel pre-stressing strands found that the measured transfer and development lengths of the uncoated strands were in excess of lengths computed using the equation in the AASHTO standard specifications. These results raised concerns that the AASHTO equation was not conservative enough for modern strands with larger diameter and higher ultimate tensile strength. As a result, a 60% increase in the development length over the length computed using the AASHTO equation was implemented. As part of the investigation of possible causes for the discrepancy between measured and computed development lengths, attention was drawn to variations in the surface condition of strands used throughout the United States. The presence of surface residues--e.g., rust, lubricants used in manufacturing processes, or corrosion inhibitors--suggested a possible source for the wide scatter that was observed in bond test data. There is a need for (1) practical tests to quantify the surface condition of steel pre- stressing strands and (2) quality assurance criteria based on these tests to control the effect of strand surface condition on bond strength. Under NCHRP Project 10-62, "Accept- ance Tests for Surface Characteristics of Steel Strands in Pre-Stressed Concrete," Wiss, Janney, Elstner Associates, Inc. was assigned the tasks of (1) identifying the common types of residues on steel pre-stressing strands, (2) developing practical tests to measure deleterious strand residues and estimate their effect on the performance of the strand- concrete bond, and (3) preparing a practical quality assurance procedure for strand acceptance. The research team designed and conducted a program of laboratory experiments to accomplish these tasks. Residues commonly found on pre-stressing strands after manufac- ture and as a result of the strand exposure to the elements during storage and transport were identified. A wide variety of chemical and physical test methods for measuring the levels of such residues were evaluated for accuracy, speed, and ease of use. The results of promising methods were correlated to the results of transfer length testing and limited mechanical pull out testing to establish performance thresholds.
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Four test methods showed satisfactory correlation with bond in concrete or mortar or both and are recommended for inclusion in a quality assurance program for steel pre- stressing strand: 1. Weight Loss on Ignition, 2. Contact Angle Measurement After Lime Dip, 3. Change in Corrosion Potential, and 4. Organic Residue Extraction with Fourier Transform Infrared Analysis. Further, the following combinations of the methods above provided better correlation with bond in concrete or mortar or both than the methods used individually: 1. Weight Loss on Ignition combined with Contact Angle Measurement After Lime Dip and Change in Corrosion Potential, 2. Contact Angle Measurement After Lime Dip combined with Change in Corrosion Potential, and 3. Contact Angle Measurement After Lime Dip combined with Organic Residue Extrac- tion (100% stearate only). This report presents the main text of the contractor's final report of the project and two appendices: (1) Evaluation of Mechanical and Chemical Test Methods (Appendix B) and (2) Specifications for Standard Surface Test Methods (Appendix C). The following three appendices are available upon request to NCHRP: 1. Appendix A: Review of Strand Bond Literature; 2. Appendix D: Supplemental Investigations of Strand Bond; and 3. Appendix E: Bibliography of Strand Bond.
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CONTENTS 1 Summary 3 Chapter 1 Introduction 3 Background to Strand Bond Uncertainty 4 Manufacture and Surface Condition of Prestressing Strand 4 Pretreatment and Lubrication 7 Residual Film 8 Research Objectives 8 Organization of Document 9 Chapter 2 Research Approach 9 Overview 9 Industry Survey 9 Quality Control Program Development 10 Quality Control Program Overview 10 Evaluation of Proposed Surface and Chemical Test Methods 13 Proposed Quality Control Test Methods 17 Statistical Evaluation of Results 19 Supplemental Investigations of Strand Bond 20 Chapter 3 Findings and Applications 20 Findings of Industry Survey 20 Lubricant Manufacturers 20 Strand Manufacturers 21 Findings of Supplemental Investigations 21 Findings of Evaluation of Test Methods 21 Mechanical Testing 22 Chemical and Surface Testing 25 Test Methods and Precision Testing 25 Development of Thresholds 29 Interpretation of Elemental Analyses Relative to Manufacturing Processes 31 Interpretation and Applications 31 Development of Quality Control Program for Strand Bond 32 Thresholds 33 Computational Tool 35 Chapter 4 Conclusions and Recommendations 36 Future Work 37 References
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38 Appendix A Review of Strand Bond Literature 39 Appendix B Evaluation of Mechanical and Chemical Test Methods 123 Appendix C Specifications for Standard Surface Test Methods 129 Appendix D Supplemental Investigations of Strand Bond 130 Appendix E Bibliography of Strand Bond