Manual on Service Life of Corrosion-Damaged Reinforced Concrete Bridge Superstructure Elements (2006)

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TRANSPORTAT ION RESEARCH BOARD WASHINGTON, D.C. 2006 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 558 Subject Areas Bridges, Other Structures, and Hydraulics and Hydrology • Materials and Construction • Maintenance Manual on Service Life of Corrosion-Damaged Reinforced Concrete Bridge Superstructure Elements Ali Akbar Sohanghpurwala CONCORR, INC. Sterling, VA 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 Board’s 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 558 Price $32.00 Project 18-6A ISSN 0077-5614 ISBN-13: 978-0-309-09862-5 ISBN-10: 0-309-09862-9 Library of Congress Control Number 2006932123 © 2006 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 Board’s 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 manufacturers’ names appear herein solely because they are considered essential to the object of this report.

CRP STAFF FOR NCHRP REPORT 558 Robert J. Reilly, Director, Cooperative Research Programs Crawford F. Jencks, Manager, NCHRP Amir N. Hanna, Senior Program Officer Eileen P. Delaney, Director of Publications Beth Hatch, Editor NCHRP PROJECT 18-6A PANEL Field of Materials and Construction—Area of Concrete Materials Stanley W. Woods, Wisconsin DOT (ret.) (Chair) H. Martin Laylor, Blue Road Research, Tualatin, OR (formerly Oregon DOT) Harry A. Capers, Jr., New Jersey DOT Gerardo G. Clemena, Virginia Transportation Research Council, Charlottesville, VA (ret.) Timothy Kennelly, California Department of Water Resources, Sacramento, CA Larry M. Sessions, Florida DOT Paul Virmani, FHWA Liaison Frank N. Lisle, TRB Liaison AUTHOR ACKNOWLEDGMENTS The work reported herein was performed under NCHRP Project 18-6A by CONCORR, Inc. The prin- cipal investigator and author of this report is Ali Akbar Sohanghpurwala, principal of CONCORR, Inc. The author expresses his sincere gratitude to Dr. John P. Broomfield, Consulting Corrosion Engineer, United Kingdom, who assisted in preparing a section of the manual and provided field data for use in the project; Dr. Amara Loulizi of Virginia Polytechnic Institute, Blacksburg, Virginia, who assisted in the delineation of the climatic zones; and Dr. Brian Deifenderfer, formerly an employee of CONCORR, Inc., who is presently working for the Virginia Transportation Research Council, for his assistance in the prepa- ration of the manual. 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 is a manual that provides step-by-step procedures for assessing the condi- tion of corrosion-damaged bridge elements. It also includes procedures that can be used to estimate the expected remaining life of reinforced concrete bridge superstructure elements and to determine the effects of maintenance and repair options on their service life. This manual should be of interest to state engineers and others involved in the design, construc- tion, and maintenance of highway bridges. Corrosion-induced deterioration of reinforced concrete bridge superstructure elements is a common and costly problem in the United States. A rational decision regarding main- tenance, repair, or replacement of such deteriorated elements must take into account the condition of the element, the extent of deterioration, the expected remaining service life, and the impact of alternative maintenance and repair options on the service life of such ele- ments. However, available publications do not provide reliable procedures for evaluating the existing condition of corrosion-damaged elements or approaches for comparing the effectiveness of maintenance and repair alternatives. Without such information, the selec- tion of the optimum repair strategy cannot be ensured, leading to the application of a less desirable and often more costly repair strategy. Thus, research was needed to identify suit- able procedures for assessing the condition of corrosion-damaged bridge elements, estimat- ing the expected remaining service life of such elements, and determining the effects of maintenance and repair options on their service life. Relevant background information was provided by Michigan State University under NCHRP Project 18-6; subsequent work and manual development was performed under NCHRP Project 18-6A. Under NCHRP Project 18-6A, “Service Life of Corrosion-Damaged Reinforced Concrete Superstructure Elements,” CONCORR, Inc., of Sterling, Virginia, was assigned the objec- tive of developing a manual, for consideration and adoption by AASHTO, that provides step-by-step procedures for (1) assessing the condition of reinforced concrete bridge super- structure elements subjected to corrosion-induced deterioration, (2) predicting the remain- ing service life of such elements, and (3) quantifying the service life extension for such ele- ments expected from alternative maintenance and repair options. The research was limited to concrete bridge superstructure elements reinforced only with epoxy-coated and/or “black” reinforcing steel and did not include prestressed concrete elements or concrete ele- ments reinforced with other steel types. To accomplish this objective, the researchers performed the following tasks: 1. Developed a protocol for condition assessment of reinforced concrete bridge superstructure elements; F O R E W O R D By Amir N. Hanna Staff Officer Transportation Research Board

2. Developed a model for corrosion initiation for use in projecting future damage; 3. Developed a model for estimating expected remaining service life that incorporated the con- cept of Susceptibility Index––an approach for interpreting the distribution of chloride ions in the concrete; 4. Presented the remaining service life estimation process as computational software in the form of a Visual Basic–driven Excel spreadsheet to facilitate use; 5. Conducted tests on three bridges and used the results in modeling the corrosion process and in validating the model’s ability to project future deterioration; 6. Provided guidance on the service life that may be attainable with different corrosion control, repair, and rehabilitation techniques; and 7. Organized relevant information in the form of a manual to facilitate use by practitioners. The manual presented herein provides a systematic approach for assessing the condition of corrosion-damaged reinforced concrete bridges and comparing the effects of alternative repair strategies on service life; it is recommended for consideration and adoption by AASHTO. The research agency’s final report contains the data used in the development and validation of the service life model described in this manual; it is not published herein. The report is avail- able on the web as NCHRP Web-Only Document 88 at http://trb.org/news/blurb_detail. asp?id=6150. Also, the computational software (Excel spreadsheet) for the service life estima- tion process is available on the web at http://trb.org/news/blurb_detail.asp?id=6149.

C O N T E N T S ix Preface 1 Chapter 1 Introduction 2 Objective and Audience 2 Manual Organization 3 Chapter 2 Condition Evaluation of Superstructure Elements 3 Introduction 4 Development of an Evaluation Protocol 5 Test Methods and Test Techniques 5 Visual Survey 6 Delamination Survey 8 Cover Depth Measurements 8 Chloride Ion Content Analysis 9 Electrical Continuity Testing 9 Corrosion Potential Survey 10 Corrosion Rate Measurement 10 Petrographic Analysis 11 Selection of Tests for Corrosion Condition Evaluation 13 Chapter 3 Service Life Modeling 13 Introduction 13 Basis of a Model 14 Exposure to Chloride Ions 14 Diffusion of Chloride Ions 15 Corrosion Initiation 15 Time to Damage 16 Diffusion Models Proposed in Literature 17 Model Development 17 Model for Black Steel 19 Model for Epoxy-Coated Rebar 19 Susceptibility Index (SI) 21 Chapter 4 Selection of Corrosion Mitigation Alternatives 21 Introduction 24 Formulation of a Repair and Corrosion Control Strategy 26 Chapter 5 Extension of Service Life with Repair and Corrosion Mitigation Options 26 Local Corrosion Control Systems 26 Patching Materials 27 Reinforcing Bar Coatings 28 Repair of Epoxy-Coated Reinforcing Steel 28 Corrosion Inhibitors

30 Corrosion Inhibitor Patching (Superstructure Elements) 30 Global Corrosion Control Systems 30 Overlays 31 Membranes 32 Sealers and Surface Coatings 33 Corrosion Inhibitor Overlays (Bridge Decks) 34 Cathodic Protection Systems 34 Electrochemical Chloride Extraction 37 Chapter 6 Procedure For Design of Repair and Corrosion Control System 37 Overview of Procedures for Designing Repair and Corrosion Control System 39 Preliminary Corrosion Condition Evaluation (PCCE) 39 In-Depth Corrosion Condition Evaluation 39 Sampling Size 40 Service Life Modeling and Susceptibility Index 40 Selection of Repair and Corrosion Control System 42 Planning for Corrosion Condition Evaluation 44 Chapter 7 Field Evaluation Procedures 44 Grid Stationing 44 Visual Survey 44 Delamination Survey 45 Cover Depth Measurements 45 Continuity Testing—Direct Current Method 47 Core Sampling—Chloride Ion Distribution 48 Core Sampling—Epoxy-Coated Rebar 48 Core Sampling—Petrographic Core Extraction 48 Corrosion Potential Survey 49 Corrosion Rate Measurement Survey 49 Carbonation Testing 49 Patching Excavated Areas 50 Chapter 8 Laboratory Evaluation Procedures 50 Evaluation, Storage, and Preparation of Epoxy-Coated Rebar Cores 50 Pre-Extraction Procedures 50 Extraction of Epoxy-Coated Rebar from the Core 50 Bar Selection and Preparation 50 Visual Inspection of Epoxy-Coated Bars 51 Holiday Detection 51 Coating Adhesion 51 Preparation of Chloride Cores 52 Setting the Chloride Core 52 Powdering the Chloride Core 53 Service Life Model Procedure 53 Preparing Macros for Use in Microsoft Excel 53 Bridge Information Page 54 Core Processing Page 55 Distributions Page 55 Model Results Page 56 Cl Distribution Page 57 References

P R E F A C E Corrosion-induced deterioration of reinforced concrete bridge superstructure elements is a common and recurring problem in the United States. A rational decision regarding mainte- nance, repair, or replacement of such deteriorated elements must take into account the condi- tion of the element, the extent of deterioration, the expected remaining service life, and the impact of alternative maintenance and repair options on service life of such elements. However, available publications do not provide reliable procedures for evaluating the existing condition of corrosion-damaged elements or approaches for comparing the effectiveness of maintenance and repair alternatives. Without such information, the process of selecting the optimum repair strategy becomes difficult. Thus, a need was felt for the development of suitable procedures for assessing the condition of corrosion-damaged bridge elements, estimating the expected remaining service life of such elements, and determining the effects of maintenance and repair options on their service life. To meet this need, The National Cooperative Highway Research Program (NCHRP) initiated NCHRP Project 18-6A, “Service Life of Corrosion-Damaged Reinforced Concrete Superstruc- ture Elements.” The objective of the project was to develop a manual, for consideration and adoption by AASHTO, that provides step-by-step procedures for the following: 1. Assessing the condition of reinforced concrete bridge superstructure elements subjected to corrosion-induced deterioration. 2. Predicting the remaining service life of such elements. 3. Quantifying service life extension for such elements expected from alternative maintenance and repair options. This manual was developed as part of this project. The scope of the manual is limited to con- ventionally reinforced bridge superstructure elements. The first five chapters of the manual dis- cuss the state of the art and lay out the logic for the proposed protocols for assessing condition, predicting remaining service life, and, to some degree, quantifying the service life extension when certain alternatives are used in the repair and rehabilitation of bridge superstructure ele- ments. The remaining three chapters of the manual provide step-by-step procedures for imple- menting the protocols developed in the first five chapters. The protocol for condition assessment developed in this effort is integrated into the require- ments of the National Bridge Inspection Standards (NBIS), thereby making the implementation of the protocol easier for local, state, and federal agencies. The requirements of condition assess- ment have been kept to a minimum, recognizing the scarcity of resources experienced by almost all governmental agencies. A well-defined procedure is proposed that would allow the owner agencies to perform minimal assessment to obtain sufficient information on their bridge super- structure elements and to plan the allocation of resources. ix

xA mathematical model was developed for the initiation of corrosion on both black and epoxy- coated rebars. This model allows the users to estimate past progression of damage and project the development of future damage in terms of percent damage of the surface area under consid- eration. This approach allows each user to develop the criteria for end of service life that suits specific needs. A copy of the code (a macro in a spreadsheet) developed specifically to validate the model during the project is also made available for the users and can be accessed at http://trb.org/news/blurb_detail.asp?id=6149. This macro was not designed for public distri- bution and may not be as user friendly as desired; familiarity of using a spreadsheet program is required to use this macro. Chapter 8 deals with step-by-step procedures for using the macro. In addition to the service life model, a new concept of Susceptibility Index was developed. In the past, many agencies have attempted to develop and use numerous complicated decision- making matrixes to identify applicable corrosion control systems. The Susceptibility Index developed in this project allows the use of a number to describe the distribution of chloride ions in the concrete element at the steel depth and to identify the applicable corrosion mitigation sys- tems. The proposed correspondence between the Susceptibility Index and corrosion control sys- tems should be considered as a suggestion and should be modified as required. Based on a literature survey, an attempt has been made to provide some guidance with respect to additional service life that may be attainable using various corrosion control and repair and rehabilitation techniques. Sufficient information from independent sources was not available to provide a conclusive figure for additional service life for many of the technologies discussed in the manual. Additional service life attainable with any specific corrosion control or repair and rehabilitation technique is dependent on many factors. The most important of these factors is the applicability of that particular technique to the subject structure based on its corrosion condition, presence of other deterioration processes, and the exposure environment. In addi- tion, the quality of the design and the application of the technique also significantly impact performance. The mathematical model developed in this effort was validated against three bridge structures located in different environments in the United States. Two evaluations were conducted 2 years apart to ascertain the condition of the structure. The results of the first evaluation were used to model the corrosion process and to calibrate the model, and the results of the second evaluation were used to validate the ability of the model to project future deterioration. The results of the validation can be found in the appendix of the final report, which is available online as NCHRP Web-Only Document 88 at http://trb.org/news/blurb_detail.asp?id=6150. This manual is intended to be used by personnel with training and experience in repair and rehabilitation of reinforced concrete structures suffering from corrosion-induced deterioration. The application of the protocol in the manual will require the expertise and experience of both engineering and maintenance staff.