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NATIONAL
NCHRP REPORT 597
COOPERATIVE
HIGHWAY
RESEARCH
PROGRAM
Development of a
Recommended Practice
for Use of Controlled Low-Strength
Material in Highway Construction
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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
J. Richard Capka, Federal Highway Administrator, U.S.DOT
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
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
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 January 2008.
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NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM
NCHRP REPORT 597
Development of a
Recommended Practice
for Use of Controlled Low-Strength
Material in Highway Construction
Kevin J. Folliard
Lianxiang Du
UNIVERSITY OF TEXAS AT AUSTIN
Austin, TX
David Trejo
Ceki Halmen
TEXAS A&M UNIVERSITY
College Station, TX
Scott Sabol
VERMONT TECHNICAL COLLEGE
Randolph Center, VT
Dov Leshchinsky
UNIVERSITY OF DELAWARE
Newark, DE
Subject Areas
Pavement Design, Management, and Performance
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 597
RESEARCH PROGRAM
Systematic, well-designed research provides the most effective Project 24-12(01)
approach to the solution of many problems facing highway ISSN 0077-5614
administrators and engineers. Often, highway problems are of local ISBN 978-0-309-09930-1
interest and can best be studied by highway departments individually Library of Congress Control Number 2008924534
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 597
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
Natalie Barnes, Editor
NCHRP PROJECT 24-12(01) PANEL
Field of Soils and Geology--Area of Mechanics and Foundations
Robert A. Burnett, New York State DOT, Albany, NY (Chair)
David Riley, Ohio DOT, Columbus, OH
Edward J. Hoppe, Virginia DOT, Charlottesville, VA
David J. Horhota, Florida DOT, Gainesville, FL
Theodore Maynard, Chicago, IL
Jon I. Mullarky, Chester, MD
Tommy E. Nantung, Indiana DOT, West Lafayette, IN
Tom Papagiannakis, University of TexasSan Antonio, San Antonio, TX
Michael Adams, FHWA Liaison
G. P. Jayaprakash, TRB Liaison
AUTHOR ACKNOWLEDGMENTS
The research reported herein was performed under NCHRP Project 24-12(01) by the University of
Texas at Austin (Department of Civil Engineering) and Texas A&M University (Department of Civil
Engineering). The work undertaken at Texas A&M University was under a subcontract from the University
of Texas.
Kevin J. Folliard, Associate Professor of Civil Engineering, was the principal investigator, and David
Trejo, Associate Professor of Civil Engineering, was the co-principal investigator. Other authors of this
report are Lianxiang Du, former Ph.D. student at the University of Texas at Austin, now Research Engi-
neer with the Texas Department of Transportation; Ceki Halmen, former Ph.D. student at Texas A&M
University, now post-doctoral researcher at the same institution; Scott Sabol, former director of the
Delaware Transportation Institute, now Associate Professor at Vermont Technical College; and Dov
Leshchinsky, Professor of Civil and Environmental Engineering at the University of Delaware.
The authors would like to acknowledge the assistance of a host of students, faculty, and staff at the
University of Texas at Austin and Texas A&M University.
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FOREWORD
By Edward T. Harrigan
Staff Officer
Transportation Research Board
This report summarizes the results of a project to evaluate the use of controlled low-
strength material (CLSM) in highway construction applications, in particular, as backfill,
utility bedding, and void fill and in bridge approaches. A key product presented herein is a
recommended practice for the use of CLSM that was validated through a series of full-scale
field experiments. The report will be of particular interest to materials and construction
engineers in state highway agencies and industry.
CLSM is a highly flowable material typically composed of water, cement, fine aggregates,
and, possibly, fly ash or other by-product materials. CLSM is used in a wide range of high-
way construction applications where its ability to flow into and fill voids without the need
for compaction provides significant benefits over the use of compacted fill.
As the use of CLSM has evolved, so has the need for well-founded methods and specifi-
cations for the design of CLSM and its control during placement as a backfill envelope or
fill material in specific highway applications. Ideally, these methods and specifications will
be based on achieving desired performance characteristics rather than merely producing a
material satisfying a recipe-type specification. Thus, development of these design and
construction methods and specifications presupposes a thorough understanding and
knowledge of how (1) the characteristics of CLSM constituents are related to composite
properties that control field performance and (2) key material properties may be monitored
in the field.
Under NCHRP Project 24-12(01), "Controlled Low-Strength Material for Backfill, Util-
ity Bedding, Void Fill, and Bridge Approaches," the University of Texas--Austin and its
major subcontractor, Texas A&M University, were assigned the tasks of (1) defining the
properties of CLSM necessary for its satisfactory use as backfill, utility bedding, and void fill,
and in bridge approaches; (2) developing, for these applications, test methods and specifi-
cation criteria for the performance-related properties of CLSM, including its corrosion
potential and possible environmental impact; (3) identifying how the properties of its con-
stituent materials influence the performance of CLSM; (4) developing field methods to
monitor in-place properties of CLSM for construction acceptance; and (5) preparing design
criteria and construction guidelines for CLSM that take advantage of its properties for back-
fill, utility bedding, void fill, and bridge approaches.
The research team designed and conducted a major program of laboratory and field
experiments to accomplish these tasks. The results of this experimental program demon-
strated that CLSM is an effective, innovative material providing excellent short- and long-
term performance in all applications of interest. As with any highway construction mate-
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rial, CLSM must be used in conjunction with a good quality acceptance program and with
an awareness of its unique properties in order to avoid improper usage.
The research also provided guidance on potential problems with the use of CLSM and
precautions to avoid them. For example, excessive long-term strength gain of CLSM can
lead to difficulties in its future excavation. Excessive strength gain was most commonly
observed when fly ash was used as a CLSM component, especially in hot weather. Another
issue of concern was the potential for corrosion of metallic pipe in CLSM. In general,
embedding pipe in CLSM was found to reduce the potential for its corrosion due to the
reduced permeability of CLSM compared with compacted fill as well as beneficial changes
in pH and resistivity of pore solutions in the CLSM microstructure.
This report presents the full text of the contractor's final report of the project and three
of the five appendices, which present the test methods (Appendix B), specifications (Appen-
dix C), and practice (Appendix D) recommended for implementation. The corrosion study
(Appendix A) and implementation plan (Appendix E) are available as NCHRP Web-Only
Document 116 on the TRB website (www.trb.org/news/blurb_detail.asp?id=8714).
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CONTENTS
1 Summary
3 Chapter 1 Introduction and Scope
3 Introduction
3 Research Objectives
4 Overview of Report
5 Chapter 2 State of the Art and Current Practice
5 Introduction
5 Historical Background
5 Materials
5 Portland Cement
6 Supplementary Cementitious Materials
6 Aggregates
7 Water
7 Chemical Admixtures
7 Other Materials Used in CLSM
7 Mixture Proportions
8 Batching, Mixing, and Transporting
8 Properties of CLSM
8 Fresh CLSM Properties
9 Hardened CLSM Properties
11 Durability and Environmental Issues Related to CLSM
14 CLSM Applications
14 Backfill
14 Utility Bedding
14 Void Fill
14 Bridge Approaches
14 Other CLSM Applications
14 Summary of 1998 Questionnaire
14 CLSM Usage by State DOTs
16 Quality Assurance and Quality Control
16 Summary
17 Chapter 3 Laboratory Testing Program
17 Introduction
17 Research Approach
17 Materials
18 Mixture Proportions
21 Testing Program
21 Overview
21 Mixing Procedure
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24 Fresh CLSM Test Methods
26 Hardened CLSM Test Methods
30 Durability Test Methods
33 Results and Discussion
33 Fresh Properties
35 Hardened CLSM Properties
49 Durability Test Methods
59 Summary
61 Chapter 4 Field Evaluations of CLSM
61 Introduction
61 Research Approach
61 Field Testing Plan
62 Field Test at the University of TexasAustin
62 Introduction
62 Materials and Mixture Proportions
63 Experimental Program
63 Results and Findings
67 Excavation Study at NRMCA (Silver Spring, Maryland)
67 Introduction
67 Background Information
67 Testing Program
67 Results and Discussion
69 Field Test at Hamilton County, Ohio
69 Introduction
69 Experimental Program
71 Construction
71 Test Results
72 Field Test at East Bay Municipal Utility District
72 Introduction
73 Materials and Mixture Proportions
73 Experimental Program
73 Test Results
75 Field Evaluation of CLSM for Bridge Approach Repair (TxDOT)
75 Introduction
75 Research Program
80 Monitoring of Backfill Materials
81 Monitoring of Field Performance
82 Field Test at Texas A&M University
82 Introduction
83 Site Layout and Construction
85 Testing Program
86 Test Results
87 Long-Term Corrosion Testing
87 Summary of Key Findings from Field Tests
89 Chapter 5 Conclusions and Suggested Research
89 Conclusions
90 Suggested Research
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91 References
A-1 Appendix A Corrosion Study
B-1 Appendix B Recommended Test Methods for CLSM
C-1 Appendix C Recommended Specifications for CLSM
D-1 Appendix D Recommended Practice for CLSM
E-1 Appendix E Implementation Plan
