Long-Term Performance of Corrosion Inhibitors Used in Repair of Reinforced Concrete Bridge Components

PDF Version (4.41 MB)

PDF files can be viewed with the Acrobat® Reader®

FOREWORD

In 1987, the Strategic Highway Research Program (SHRP) launched a research effort to evaluate the effectiveness of using corrosion inhibitors as a means for mitigating corrosion in reinforced concrete bridge components. That project, completed in 1993, involved a laboratory study and field validation, and concluded that corrosion inhibitors could be applied successfully with field repair and rehabilitation techniques.
Although the SHRP study established the effectiveness of using corrosion inhibitors on concrete bridge components, it was not designed to ascertain the long-term effectiveness of the technology in mitigating corrosion. This follow-on study of the SHRP effort was initiated by the Federal Highway Administration (FHWA) in August 1994 and ended in July 1999. The primary goal of this study was to monitor the SHRP field sites for 5 years to determine the long-term effectiveness of corrosion inhibitors. An analysis of the results concluded that neither of the corrosion inhibitors evaluated in this study, using the specified repairs and exposed to the specific environments, provided any corrosion-inhibiting benefit.
This report will be of interest to engineers involved in bridge design, bridge performance evaluation and prediction, and bridge maintenance and rehabilitation.

NOTICE

This document is disseminated under the sponsorship of the U.S. Department of Transportation in the interest of information exchange. The U.S. Government assumes no liability for its contents or use thereof. This report does not constitute a standard, specification, or regulation.

The U.S. Government does not endorse products or manufacturers. Trade and manufacturers’ names appear in this report only because they are considered essential to the object of the document.

SI* (Modern Metric) Conversion Factors

TABLE OF CONTENTS

• 1.0. INTRODUCTION
  • 1.1. Project Background
  • 1.2. SHRP Laboratory Work
  • 1.3. SHRP Field Studies
  • 1.4. FHWA Follow-on Study
  • 1.5. Scope and Purpose
    • 1.5.1. Evaluation of Field Site
• 2.0. ELMWOOD AVENUE BRIDGE OVER NY ROUTE 198, BUFFALO, NY
  • 2.1. Structure Background
  • 2.2. Field Evaluation
  • 2.3. Test Results
    • 2.3.1. Visual Survey
    • 2.3.2. Delamination Survey
    • 2.3.3. Clear Concrete Cover Survey
    • 2.3.4. Corrosion Potential Survey
    • 2.3.5. Corrosion Rate Survey
    • 2.3.6. Chloride Ion Content Analysis
  • 2.4. Conclusions
• 3.0. STATE ROAD 2042 OVER I-81, WILKES BARRE, PA
  • 3.1. Structure Background
  • 3.2. Field Evaluation
  • 3.3. Test Results
    • 3.3.1. Visual Survey
    • 3.3.2. Delamination Survey
    • 3.3.3. Clear Concrete Cover Survey
    • 3.3.4. Corrosion Potential Survey
    • 3.3.5. Corrosion Rate Survey
    • 3.3.6. Chloride Ion Content Analysis
  • 3.4. Conclusions
• 4.0. HOOD CANAL BRIDGE, PORT GAMBLE, WA
  • 4.1. Structure Background
  • 4.2. Field Evaluation
  • 4.3. Test Results
    • 4.3.1. Visual Survey
    • 4.3.2. Delamination Survey
    • 4.3.3. Clear Concrete Cover Survey
    • 4.3.4. Corrosion Potential Survey
    • 4.3.5. Corrosion Rate Survey
    • 4.3.6. Chloride Ion Content Analysis
  • 4.4. Conclusions
• 5.0. TRUNK HIGHWAY (TH)-3 OVER SOUTHVIEW BOULEVARD IN ST. PAUL, MN
  • 5.1. Structure Background
  • 5.2. Field Evaluation
  • 5.3. Test Results
    • 5.3.1. Visual Survey
    • 5.3.2. Delamination Survey
    • 5.3.3. Clear Concrete Cover Survey
    • 5.3.4. Corrosion Potential Survey
    • 5.3.5. Corrosion Rate Survey
    • 5.3.6. Chloride Ion Content Analysis
  • 5.4. Conclusions
• 6.0. CONCLUSIONS
• 7.0. REFERENCES

LIST OF FIGURES

2-1. General view of the Elmwood Avenue bridge over NY Route 198, Buffalo, NY
2-2. Views of test sections on: (a) south pier (control), (b) middle pier (Cortec 2000), and (c) north pier (DCI)
3-1. General views of the SR 2042 bridge structures over I-81: (a) west bridge and (b) east bridge
3-2. General views of piers: (a) pier 1, (b) pier 2, (c) pier 3, and (d) field evaluation in progress
4-1. General views of the Hood Canal bridge
4-2. Partial views of test cells on the Hood Canal bridge: (a) cell 1D (control), (b) cell 2D (MCI 2020/2000), (c) cell 3D (Postrite/DCI)
5-1. TH-3 over the Southview Boulevard bridge: (a) structure and (b) deck5-1

LIST OF TABLES

2-1. Delamination survey results
2-2. Cover depth survey results
2-3. Corrosion potential summary (October 1994)
2-4. Corrosion potential summary (May 1997)
2-5. Corrosion potential summary (June 1998)
2-6. Corrosion rate results
2-7. Corrosion rate interpretation guidelines
2-8. Total chloride ion content analysis (first visit)
2-9. Total chloride ion content analysis (third visit)
3-1. Delamination survey results
3-2. Cover depth survey results
3-3. Corrosion potential summary (November 1994)
3-4. Corrosion potential summary (May 1997)
3-5. Corrosion potential summary (September 1998)
3-6. Summary of corrosion rate measurements
3-7. Total chloride ion content data (first visit)
3-8. Total chloride ion content data (third visit)
4-1. Delamination survey results
4-2. Clear concrete cover measurements
4-3. Summary of corrosion potential measurements
4-4. Corrosion rate measurements
4-5. Total chloride ion content data
5-1. Crack survey results
5-2. Cover survey results
5-3. TH-3 over Southview Boulevard bridge—corrosion potential summary
5-4. Corrosion rates
5-5. TH-3 over Southview Boulevard bridge—chloride ion content

EXECUTIVE SUMMARY

In 1987, the Strategic Highway Research Program (SHRP), mandated by the United States Congress under section 128 of the Surface Transportation and Uniform Relocation Assistance Act, launched multiple research efforts to study all aspects of reinforced concrete deterioration. One of the projects (SHRP C-103) under the Structures portion of SHRP evaluated the effectiveness of using corrosion inhibitors to mitigate corrosion in reinforced concrete bridge components. This project, which
concluded in 1993, involved a laboratory study and field validation.

Under the field validation program, several field sites were established to evaluate the effectiveness of two of the corrosion-inhibitor systems identified in the laboratory study on mitigating corrosion of reinforced concrete bridge components. The two systems were spray-on applications of Postrite and/or DCI® admixture (calcium nitrite-based inorganic inhibitors), and spray-on MCI®2020 and/or MCI®2000 admixture (amine-based organic inhibitors). Two bridge structures were selected for deck trials and four bridges were selected for substructure trials. However, only five of the six structures were included in the project. The Maryland site was not treated with inhibitors as planned because of lack of funds and was excluded from the SHRP study. The field validation study concluded that corrosion inhibitors could be successfully applied with field repair and rehabilitation techniques.

A follow-on study of the SHRP effort was initiated by the Federal Highway Administration (FHWA) in August 1994. The primary objective of this multitask FHWA project, which ended in July 1999, was to determine the effectiveness of cathodic protection, electrochemical chloride extraction, and corrosion-inhibitor treatment systems installed during the SHRP effort. This was to be achieved through long-term evaluation of 32 field test sites in the United States and one Canadian Province, as well as a number of laboratory concrete slab specimens.

One task the FHWA program required was monitoring the long-term performance of corrosion- inhibitor treatments on selected components of five bridges that were treated and evaluated under the SHRP C-103 project. These bridges were located in:

• Saint Paul, MN
• Buffalo, NY
• Wilkes Barre, PA
• Christiansburg, VA
• Port Gamble, WA

The structure in Virginia was eliminated from this study after the first evaluation because the design of the test areas would not allow a fair assessment of the inhibitor performance. . Three evaluations over a period of 5 years were conducted on structures in Minnesota, New York, and Pennsylvania; two evaluations were performed on the structure in Washington State.

On each structure, three similar test areas were delineated. Repairs were performed in these test areas using the same materials and procedures, with the exception of the inclusion of corrosion inhibitors in two of the three areas. The third test area was designated a control area. Postrite and/or the DCI admixture system was used in the repairs on one test area and MCI 2020 and/or MCI 2000 admixture was used in the repairs on the other test area.

An analysis of the results of visual and delamination surveys, half-cell potential surveys, corrosion rate measurements, and total chloride ion content determination concluded that neither of the corrosion inhibitors evaluated in this study, using the specified repairs and exposed to the specific environments, provided any corrosion-inhibiting benefit.

With the exception of the Port Gamble test site, shrinkage cracking plagued repairs in all other sites. The concrete surrounding the patched areas was contaminated with chloride ions to varying degrees. In some sites, shrinkage cracking allowed faster ingress of chloride ions into the repair patches. In all four sites, the results of the visual and delamination surveys and corrosion rate measurements showed no difference between patches containing corrosion inhibitors and those that did not.

1.0. INTRODUCTION

1.1. Project Background

In 1987, the Strategic Highway Research Program (SHRP), mandated by the U.S. Congress under section 128 of the Surface Transportation and Uniform Relocation Assistance Act, launched multiple research efforts to study all aspects of reinforced concrete deterioration. One of the projects (SHRP C-103) under the Structures portion of SHRP evaluated the effectiveness of using corrosion inhibitors to mitigate corrosion in reinforced concrete bridge components. This project, which concluded in
1993, involved a laboratory study and field validation.

1.2. SHRP Laboratory Work

The laboratory portion of the SHRP study evaluated 17 corrosion-inhibiting systems for reinforced concrete bridge components. Based on the initial evaluation, five corrosion inhibitors were selected for further testing. These were Alox 901 (organic surface-applied), Cortec VCI-1337 [MCI-2020] (organic surface-applied), Cortec VCI-1609 [MCI-2000] (organic admixture), DCI (inorganic admixture), and sodium tetraborate (inorganic surface-applied).(1) Nine small-scale slabs were constructed representing different treatment conditions. The three surface-applied corrosion inhibitors were also tested on salvaged portions of a deck slab from a bridge replacement project on I-80 in Pennsylvania. It was determined from the evaluation of these slabs that the use of Alox and Cortec on the deck slab resulted in a reduction of corrosion activity regardless of the pretreatment corrosion rate. DCI was found to be effective in reducing corrosion activity for specimens with low pretreatment corrosion rates. The benefits from the use of sodium borate were not as evident when compared to the control slabs.

1.3. SHRP Field Studies

Under the field validation program, several field sites were established to evaluate the effectiveness of two of the corrosion-inhibitor systems identified in the laboratory study on mitigating corrosion of reinforced concrete bridge components. The two systems were spray-on applications of Postrite and/or DCI admixture (calcium-nitrite based inorganic inhibitors), and spray-on MCI 2020 and/or MCI 2000 admixture (amine-based organic inhibitors). Two bridge structures were selected for deck trials and four for substructure trials. However, only five of the six structures were included in the project. The Maryland site was not treated with inhibitors as planned because of lack of funds and thus was excluded from the SHRP study. The field validation study concluded that corrosion inhibitors could be successfully applied with field repair and rehabilitation techniques. Although Postrite/DCI showed promising results in some cases, long-term corrosion assessment data were needed to draw any firm conclusions on the effectiveness of inhibitor-modified concrete systems.(2)

1.4. FHWA Follow-On Study

A follow-on study of the SHRP effort was initiated by the Federal Highway Administration (FHWA) in August 1994. The primary objective of this multitask FHWA project, which ended in July 1999, was to determine the effectiveness of cathodic protection, electrochemical chloride extraction, and corrosion inhibitor treatment systems installed during the SHRP effort. This was to be achieved through long-term evaluation of 32 field test sites in the United States and one Canadian Province, as well as a number of laboratory concrete slab specimens. The secondary objective of this research was to identify the most appropriate laboratory and field test method(s) for evaluating and monitoring the performance of the corrosion-control techniques and procedures involved in the project.

One task the FHWA program required was monitoring the long-term performance of corrosion- inhibitor treatments on selected components of five bridges that were previously treated with inhibitor and evaluated under the SHRP Contract C-103. These bridges are in the States of Minnesota, New York, Pennsylvania, Virginia, and Washington.

1.5. Scope and Purpose

Although the SHRP study established the effectiveness of using corrosion inhibitors on concrete bridge components, it was not designed to ascertain the long-term effectiveness of the technology in mitigating corrosion. As mentioned above, the primary goal of this study was to monitor the five field sites for 5 years to determine the long-term effectiveness of corrosion inhibitors.

Fifteen field evaluations were planned, three visits to each site (years 1, 3, and 5).

1.5.1. Evaluation of Field Sites

The details for each site, along with the monitoring results, are discussed individually later in this report. The following work was conducted during the site visits:

1. Review of past reports.
2. Visual inspection.
3. Sounding (delamination) survey.
4. Concrete cover measurements.
5. Corrosion potential measurements.
6. Corrosion rate measurements.
7. Chloride content analysis.

To assess the long-term performance of the field inhibitor sites, it was not considered necessary to perform all of the above tasks during each of the three visits. Thus, cover depth measurements were performed only during the first visit and delamination surveys were performed during the first and third visits.

The Christiansburg, VA, site was dropped from the program after the first visit for the following reasons:

• As suggested by the limited delamination and chloride ion concentration data, the control and treated areas on the deck may not have been in the same corrosion condition at the start of the study.
• The size of the control areas on the deck and substructure were inadequate.
• The control area on the deck was bordered by an expansion joint. Generally, on bridge decks, corrosion-induced damage is more prominent at the expansion joints.
• Some sections of the control area on the column were not exposed to the same environment as the treated areas. The treated areas were exposed to contaminated water run-off, whereas some regions of the control area were not exposed to any contaminated water run-off.
• The region of the control area above and below the plugged and patched areas on the column may have been exposed to different amounts of contaminated water run-off.

A separate report for one evaluation of the Christiansburg site was issued in July 1995; the results of that evaluation are not included in this study. Three visits each were made to sites at St. Paul, MN; Buffalo, NY; and Wilkes Barre, PA. Only two visits were made to the Port Gamble, WA, site because the last installment of contract funds was not available.