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2021 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 RESEARCH REPORT 958 Electrochemical Test Methods to Evaluate the Corrosion Potential of Earthen Materials Kenneth L. Fishman McMahon & Mann consulting EnginEEring and gEology, P.c. Buffalo, NY Soheil Nazarian Shane Walker Arturo Bronson thE univErsity of tExas at El Paso El Paso, TX Subscriber Categories Construction â¢ Geotechnology â¢ Materials 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, and implementable research is the most effective way to solve many problems facing state departments of transportation (DOTs) administrators and engineers. Often, highway problems are of local or regional interest and can best be studied by state DOTs individually or in cooperation with their state universities and others. However, the accelerating growth of highway transporta- tion results in increasingly complex problems of wide interest to high- way authorities. These problems are best studied through a coordinated program of cooperative research. Recognizing this need, the leadership of the American Association of State Highway and Transportation Officials (AASHTO) in 1962 ini- tiated an objective national highway research program using modern scientific techniquesâthe National Cooperative Highway Research Program (NCHRP). NCHRP is supported on a continuing basis by funds from participating member states of AASHTO and receives the full cooperation and support of the Federal Highway Administration (FHWA), United States Department of Transportation, under Agree- ment No. 693JJ31950003. The Transportation Research Board (TRB) of the National Academies of Sciences, Engineering, and Medicine was requested by AASHTO to administer the research program because of TRBâs recognized objectivity and understanding of modern research practices. TRB is uniquely suited for this purpose for many reasons: TRB maintains an extensive com- mittee structure from which authorities on any highway transportation subject may be drawn; TRB possesses avenues of communications and cooperation with federal, state, and local governmental agencies, univer- sities, and industry; TRBâs relationship to the National Academies is an insurance of objectivity; and TRB maintains a full-time staff of special- ists in highway transportation matters to bring the findings of research directly to those in a position to use them. The program is developed on the basis of research needs iden- tified by chief administrators and other staff of the highway and transportation departments, by committees of AASHTO, and by the FHWA. Topics of the highest merit are selected by the AASHTO Special Committee on Research and Innovation (R&I), and each year R&Iâs recommendations are proposed to the AASHTO Board of Direc- tors and the National Academies. Research projects to address these topics are defined by NCHRP, and qualified research agencies are selected from submitted proposals. Administration and surveillance of research contracts are the responsibilities of the National Academies and TRB. The needs for highway research are many, and NCHRP can make significant contributions to solving 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 research 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 by going to https://www.nationalacademies.org and then searching for TRB Printed in the United States of America NCHRP RESEARCH REPORT 958 Project 21-11 ISSN 2572-3766 (Print) ISSN 2572-3774 (Online) ISBN 978-0-309-67377-8 Library of Congress Control Number 2021930399 Â© 2021 National Academy of Sciences. All rights reserved. COPYRIGHT INFORMATION 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, FTA, GHSA, NHTSA, or TDC 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 research report was reviewed by the technical panel and accepted for publication according to procedures established and overseen by the Transportation Research Board and approved by the National Academies of Sciences, Engineering, and Medicine. The opinions and conclusions expressed or implied in this report are those of the researchers who performed the research and are not necessarily those of the Transportation Research Board; the National Academies of Sciences, Engineering, and Medicine; the FHWA; or the program sponsors. The Transportation Research Board; the National Academies of Sciences, Engineering, and Medicine; and the sponsors of 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 the report.
The National Academy of Sciences was established in 1863 by an Act of Congress, signed by President Lincoln, as a private, non- governmental institution to advise the nation on issues related to science and technology. Members are elected by their peers for outstanding contributions to research. Dr. Marcia McNutt is president. The National Academy of Engineering was established in 1964 under the charter of the National Academy of Sciences to bring the practices of engineering to advising the nation. Members are elected by their peers for extraordinary contributions to engineering. Dr. John L. Anderson is president. The National Academy of Medicine (formerly the Institute of Medicine) was established in 1970 under the charter of the National Academy of Sciences to advise the nation on medical and health issues. Members are elected by their peers for distinguished contributions to medicine and health. Dr. Victor J. Dzau is president. The three Academies work together as the National Academies of Sciences, Engineering, and Medicine to provide independent, objective analysis and advice to the nation and conduct other activities to solve complex problems and inform public policy decisions. The National Academies also encourage education and research, recognize outstanding contributions to knowledge, and increase public understanding in matters of science, engineering, and medicine. Learn more about the National Academies of Sciences, Engineering, and Medicine at www.nationalacademies.org. The Transportation Research Board is one of seven major programs of the National Academies of Sciences, Engineering, and Medicine. The mission of the Transportation Research Board is to provide leadership in transportation improvements and innovation through trusted, timely, impartial, and evidence-based information exchange, research, and advice regarding all modes of transportation. The Boardâs varied activities annually engage about 8,000 engineers, scientists, and other transportation researchers and practitioners from the public and private sectors and academia, all of whom contribute their expertise in the public interest. The program is supported by state transportation departments, federal agencies including the component administrations of the U.S. Department of Transportation, and other organizations and individuals interested in the development of transportation. Learn more about the Transportation Research Board at www.TRB.org.
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 AUTHOR ACKNOWLEDGMENTS The research reported herein was performed under NCHRP Project 21-11 by McMahon & Mann Consulting Engineering and Geology, P.C. (McMahon & Mann) and the University of Texas at El Paso (UTEP). K. L. Fishman, Ph.D., P.E., of McMahon & Mann was the principal investigator, and Profes- sors S. Nazarian, Ph.D., P.E.; S. Walker, Ph.D., P.E.; and A. Bronson, Ph.D., of UTEP were co-principal investigators. Personnel from McMahon & Mann, including Cody Coonradt; Jim Bojarski, P.E.; Chad Giesler; Jon Whiting; Brad Armstrong, P.E.; Kaitlyn Murray, P.E.; and Sonia Pang assisted with the literature review, sampling, and data analyses for the project. Dr. Hamid Fakhri of McMahon & Mann was instrumental in implementing the verification study conducted in Phase III of this research and in preparing this report. We are grateful to the many graduate and undergraduate research assistants at UTEP who undertook the extensive laboratory test program that was a large part this research, including Jose Luis Arciniega Aguilar, Diana Cabrara, Troy Svede, Mathew Gonzales, Luisa Morales, Daniela Hernandez, Yadira Calderas, Miguel Perez, and Luis Lemus. The lab technicians at UTEP, including Jose Garibay, Sergio Rocha, and Cesar Tirado are also acknowledged for their contributions to the laboratory test program as well as for collecting information from the Texas sites incorporated into the implementation study conducted during Phase III. CRP STAFF FOR NCHRP RESEARCH REPORT 958 Christopher J. Hedges, Director, Cooperative Research Programs Lori L. Sundstrom, Deputy Director, Cooperative Research Programs Edward T. Harrigan, Senior Program Officer Anthony P. Avery, Program Associate Eileen P. Delaney, Director of Publications Natalie Barnes, Associate Director of Publications Janet M. McNaughton, Senior Editor NCHRP PROJECT 21-11 PANEL Field of Soils and GeologyâTesting and Evaluation of Soils Kathryn F. Griswell, California Department of Transportation, Sacramento, CA (Chair) James J. Brennan, Kansas Department of Transportation, Kansas City, KS Marcus J. Galvan, Foresight Planning & Engineering Services, LLC, Austin, TX Robert A. Gladstone, Association for Mechanically Stabilized Earth, Reston, VA Leslie Myers McCarthy, Federal Highway Administration, Washington, DC Darin L. Sjoblom, Utah Department of Transportation, South Weber, UT Marta Vasquez, Baton Rouge, LA John J. Yzenas, Jr., J Yzenas Consulting, LLC, Hobart, IN Jennifer E. Nicks, FHWA Liaison
We received considerable assistance in procuring samples of fill for the laboratory test program from the New York State Department of Transportation (DOT), the North Carolina DOT, the Florida DOT, the Expanded Shale, Clay and Slate Institute (ESCSI), and from contractors and aggregate suppliers in New York, South Carolina, and British Columbia and Alberta, Canada. Samples of fill were obtained from in-service mechanically stabilized earth structures and involved the use of excavation equipment, drilling equipment, traffic control, associated crews, and utility clearances that were donated as part of the assistance provided by these agencies. The following personnel from these agencies contributed to the study: From the New York State DOT: Joe DiGregorio, P.E., Structure Foundations Section Supervisor; Chris Nebral, P.E., Geo technical Engineer, Geotechnical Engineering Bureau; Joe Santamaria, P.E., Regional Engineer, and Tim Wolff, P.E., Assistant Geotechnical Engineer, Region 2; Darryl Byers, P.E., Geotechnical Engineer, Region 4; Todd Nelson, P.E., Geotechnical Engineer, Region 5; John Wheeler, Construction, Region 8; and Aquifer Drilling and Testing, Inc., drilling contractor, Region 8. From the North Carolina DOT: Brian Hunter, Cabell Garbee, and Todd Whittington, Materials and Test Unit; Mohammed Mulla, Ph.D., P.E., Scott Hidden, P.E., and John Pilipchuk, P.E., Geotechnical Engineering Unit; Kyle Brashear, Quality Assur- ance Supervisor, North Carolina East District; and Martin Marietta, Clark Quarry, New Bern, North Carolina. From the Florida DOT: Rodrigo Herrera, P.E., Structures Design Office; David Horhota, Ph.D., State Geotechnical Materials Engineer, State Materials Office; Ron Simmons, Lab Managerâ Corrosion, State Materials Office; and the District 5 Ocala Operations Office. From the South Carolina DOT: John Johnson, P.E., Project Manager, CDM Smith, Inc., Horry County Department of Public Works. From Canada: Brian Bennett, Project Manager, Windley Contracting, Ltd., Nanaimo, British Columbia; and Barre Johnson, Kiewit Graham Ledcor Constructors, Calgary, Alberta. From ESCSI: Bill Wolfe and Jack Moore. Monica Ruiz and Richard Izzo of the Texas DOT; Matthew Van Wicklen and Jacob Fuentes, P.E., of Raba Kistner Consultants, Inc.; and Joe DiGregorio, P.E., Structure Foundations Section Supervisor, and Brett Dening, Supervisor, Soils Engineering Laboratory of the New York State DOT, graciously facilitated access to sites included in the implementation study for Phase III, provided much-needed background information for the sites, and performed sampling and laboratory testing for comparison with the results from the research team. The authors are sincerely grateful to the members of the Association for Mechanically Stabilized Earth (AMSE) for their helpful comments, discussions, and feedback during the course of this research. AUTHOR ACKNOWLEDGMENTS (Continued)
NCHRP Research Report 958: Electrochemical Test Methods to Evaluate the Corrosion Potential of Earthen Materials presents a protocol for evaluating the corrosion potential of earthen materials in contact with steel highway structures. Thus, the report will be of imme- diate interest to engineers in state and local transportation agencies with responsibility for the construction and maintenance of buried or embedded steel elements within retaining walls, earth embankments, and bridge foundations, abutments, and approaches. Electrochemical properties of earthen materials are used to characterize their poten- tial for corrosion of buried or embedded steel elements in highway structures. Electro- chemical properties are typically evaluated with AASHTO Standard Methods T 288 through T 291. These methods are based upon procedures originally developed and applied to agron- omy. They neither consider the different characteristics of materials used in transportation- related construction nor distinguish issues inherent in specific highway applications. These limitations create issues such as project delays, the necessity of using more-expensive sources of backfill, and lower quality of the finished product. Under NCHRP Project 21-11, âImproved Test Methods and Practices for Characterizing Steel Corrosion Potential of Earthen Materials,â McMahon & Mann Consulting Engineer- ing and Geology, P.C., was tasked with the identification of new or improved laboratory and field test methods for measuring the electrochemical properties of earthen materials surrounding buried or embedded steel elements. The research was to identify test methods appropriate for assessing the corrosion potential of earthen materials for different highway applications and was to result in improved AASHTO standards or recommendations for the use of alternative methods, or both. The research included a comprehensive literature review that informed a series of lab- oratory experiments to assess the capabilities and limitations of existing and improved AASHTO, ASTM, and state department of transportation test methods for measuring soil resistivity, pH, and sulfate and chloride salt content accurately and precisely. The promising test methods were incorporated in a draft AASHTO standard practice that was successfully implemented as a shadow specification on two bridge reconstruction projects in New York and two mechanically stabilized earth retaining wall construction projects in Texas. The key outcome of this research is the proposed AASHTO Standard Practice: Electro- chemical Test Methods to Evaluate the Corrosion Potential of Earthen Materials. This practice is presented in the appendix to this report. F O R E W O R D By Edward T. Harrigan Staff Officer Transportation Research Board
1 Summary 7 Chapter 1 Background 7 1.1 Introduction 7 1.2 Research Objectives 8 1.3 Review of Current Practices for the Characterization of the Corrosion Potential of Earthen Materials 8 1.3.1 Factors Affecting the Corrosion Potential of Geomaterials 9 1.3.2 Current Laboratory Test Methods 10 1.3.3 Comparison of Different Resistivity Test Methods 13 1.3.4 Limitations of Current Test Methods 14 1.4 Knowledge Gaps and Study Purpose 15 Chapter 2 Research Approach 15 2.1 Introduction 15 2.2 Phase I 15 2.2.1 Task 1. Information Search 15 2.2.2 Task 2. Identify Limitations of Approaches for Characterizing Materials 15 2.2.3 Task 3. Develop Detailed Work Plan 16 2.2.4 Task 4. Submit Interim Report 16 2.3 Phase II 16 2.3.1 Task 5. Conduct Work Plan Approved in Task 4 16 2.3.2 Task 6. Prepare Work Plan for Field Trials 16 2.4 Phase III 16 2.4.1 Task 7. Implement Work Plan for Field Trials 16 2.4.2 Task 8. Propose Protocol 16 2.4.3 Task 9. Prepare Final Report 17 Chapter 3 Laboratory Measurements 17 3.1 Introduction 17 3.2 Description of Data Set 25 3.3 Comparison of Results from Different Test Methods 25 3.3.1 Resistivity 31 3.3.2 Salt Content 34 3.3.3 Correlation Between Salt Content and Resistivity 36 3.3.4 Measurements of pH C O N T E N T S
37 3.4 Characterization of Corrosion Potential and Correlation with Corrosion Rates 38 3.4.1 Correlation Between Resistivity and Performance Data 43 3.4.2 Classification of Soil Corrosivity 48 3.5 Recommended Protocol 51 Chapter 4 Field Measurements 51 4.1 Introduction 51 4.2 Description of Data Set 54 4.3 Results 54 4.3.1 Resistivity Measured by Soil Box Test 55 4.3.2 Resistivity Measured by Field Tests Using Wenner Technique 60 4.3.3 Other Electrochemical Properties 62 4.4 Comments and Suggestions from Owners 63 4.5 Conclusions 64 Chapter 5 Conclusions and Needs for Future Research 64 5.1 Main Conclusions 65 5.2 Recommendations for Future Research 67 Abbreviations and Acronyms 68 References 70 Appendix Proposed AASHTO Standard Practice: Electrochemical Test Methods to Evaluate the Corrosion Potential of Earthen Materials Note: Photographs, figures, and tables in this report may have been converted from color to grayscale for printing. The electronic version of the report (posted on the web at www.trb.org) retains the color versions.