Long-Term Performance of Corrosion Inhibitors Used in

Repair of Reinforced Concrete Bridge Components

Publication No. FHWA-RD-01-097

U.S. Department of Transportation

Federal Highway Administration

Research and Development

6300 Georgetown Pike

McLean, VA 22101-2296
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.

T. Paul Teng, P.E.

Director, Office of Infrastructure 

 Research and Development

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.



iv

TABLE OF CONTENTS

CHAPTER PAGE

1.0. INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1

1.1. Project Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1

1.2. SHRP Laboratory Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1

1.3. SHRP Field Studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1

1.4. FHWA Follow-on Study . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2

1.5. Scope and Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2

1.5.1. Evaluation of Field Sites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2

2.0. ELMWOOD AVENUE BRIDGE OVER NY ROUTE 198, BUFFALO, NY . . . . . . . . . 2-1

2.1. Structure Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

2.2. Field Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2

2.3. Test Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2

2.3.1. Visual Survey . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2

2.3.2. Delamination Survey . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4

2.3.3. Clear Concrete Cover Survey . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4

2.3.4. Corrosion Potential Survey . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-6

2.3.5. Corrosion Rate Survey . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-8

2.3.6. Chloride Ion Content Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-9

2.4. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-10

3.0. STATE ROAD 2042 OVER I-81, WILKES BARRE, PA . . . . . . . . . . . . . . . . . . . . . . . . 3-1

3.1. Structure Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1

3.2. Field Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-3

3.3. Test Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-3

3.3.1. Visual Survey . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-3

3.3.2. Delamination Survey . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-3

3.3.3. Clear Concrete Cover Survey . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-4

3.3.4. Corrosion Potential Survey . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-4

3.3.5. Corrosion Rate Survey. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-6

3.3.6. Chloride Ion Content Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-7

3.4. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-10

4.0. HOOD CANAL BRIDGE, PORT GAMBLE, WA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1

4.1. Structure Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1

4.2. Field Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-3

4.3. Test Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-3

4.3.1. Visual Survey . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-3

4.3.2. Delamination Survey . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-3

4.3.3. Clear Concrete Cover Survey . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-3

4.3.4. Corrosion Potential Survey . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-6

4.3.5. Corrosion Rate Survey . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-6

TABLE OF CONTENTS (continued)
v

CHAPTER PAGE

4.3.6. Chloride Ion Content Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-8

4.4. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-8

5.0. TRUNK HIGHWAY (TH)-3 OVER SOUTHVIEW BOULEVARD IN ST. PAUL, MN 5-1

5.1. Structure Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1

5.2. Field Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-2

5.3. Test Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-2

5.3.1. Visual Survey . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-2

5.3.2. Delamination Survey . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-3

5.3.3. Clear Concrete Cover Survey . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-3

5.3.4. Corrosion Potential Survey . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-4

5.3.5. Corrosion Rate Survey . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-5

5.3.6. Chloride Ion Content Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-5

5.4. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-8

6.0. CONCLUSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-1

7.0. REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-1
vi

LIST OF FIGURES

FIGURE PAGE

2-1. General view of the Elmwood Avenue bridge over NY Route 198, Buffalo, NY. . . . . 2-2

2-2. Views of test sections on: (a) south pier (control), (b) middle pier (Cortec 2000), 

and (c) north pier (DCI). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3

3-1. General views of the SR 2042 bridge structures over I-81: (a) west bridge and 

(b) east bridge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1

3-2. General views of piers: (a) pier 1, (b) pier 2, (c) pier 3, and (d) field evaluation 

in progress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2

4-1. General views of the Hood Canal bridge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1

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) . . . . . . . . . . . . . . . . . . . . . . . 4-2

5-1. TH-3 over the Southview Boulevard bridge: (a) structure and (b) deck . . . . . . . . . . . . 5-1
vii

LIST OF TABLES

TABLE PAGE

2-1. Delamination survey results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5 

2-2. Cover depth survey results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-6 

2-3. Corrosion potential summary (October 1994) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-7 

2-4. Corrosion potential summary (May 1997) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-7 

2-5. Corrosion potential summary (June 1998) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-7 

2-6. Corrosion rate results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-8 

2-7. Corrosion rate interpretation guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-9 

2-8. Total chloride ion content analysis (first visit) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-11

2-9. Total chloride ion content analysis (third visit) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-12

3-1. Delamination survey results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-4 

3-2. Cover depth survey results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-5 

3-3. Corrosion potential summary (November 1994) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-5 

3-4. Corrosion potential summary (May 1997) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-6 

3-5. Corrosion potential summary (September 1998) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-6 

3-6. Summary of corrosion rate measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-7 

3-7. Total chloride ion content data (first visit) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-8 

3-8. Total chloride ion content data (third visit) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-11

4-1. Delamination survey results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-4 

4-2. Clear concrete cover measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-5 

4-3. Summary of corrosion potential measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-6 

4-4. Corrosion rate measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-7 

4-5. Total chloride ion content data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-9 

5-1. Crack survey results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-3 

5-2. Cover survey results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-4 

5-3. TH-3 over Southview Boulevard bridge—corrosion potential summary . . . . . . . . . . 5-4 

5-4. Corrosion rates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-6 

5-5. TH-3 over Southview Boulevard bridge—chloride ion content . . . . . . . . . . . . . . . . . 5-7 
viii

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 corrosioninhibitor 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.
ix

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.
1-1

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 VCI1337 [MCI-2020] (organic surface-applied), Cortec VCI-1609 [MCI-2000] (organic admixture),

DCI (inorganic admixture), and sodium tetraborate (inorganic surface-applied).(1) Nine smallscale slabs were constructed representing different treatment conditions. The three surfaceapplied 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)
1-2

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 corrosioninhibitor 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
1-3

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.
2-1

2.0. ELMWOOD AVENUE BRIDGE OVER NY ROUTE 198, BUFFALO, NY

2.1. Structure Background

The Elmwood Avenue bridge over NY Route 198, Buffalo, NY, carries two northbound and two

southbound lanes of traffic. The bridge has four spans and is supported by three piers with four

circular columns each. Figure 2-1 shows a general view of the Elmwood Avenue bridge. 

Rehabilitation of the bridge (deck, approaches, sidewalks, piers, and abutments) started in March

1992, and was completed in October 1992. The substructure repair work was performed in

stages between these dates as weather permitted.

Personnel from the New York State Department of Transportation (NYSDOT) sounded the

substructure components prior to the rehabilitation work and determined the location and extent

of the hollow-sounding areas to be patched. Sawcuts, 19 mm deep, were cut along the borders of

the identified hollow-sounding areas and the concrete was removed to a depth of 19 mm below

the reinforcing steel with pneumatic hammers. The patch cavities were backfilled with concrete. 

The exposed reinforcing steel was severely corroded and was not cleaned before the concrete

was placed. Sound chloride-contaminated concrete adjacent to the patch areas was left in place.

Two corrosion-inhibitor admixtures were used, Cortec 2000 and DCI-S. The columns and pier

caps for each pier were patched. The middle pier, columns, and pier cap were patched with

concrete containing Cortec 2000 corrosion inhibitor admixture at a dosage rate of 1.2 kilograms

per cubic meter (kg/m3

). The north pier was patched with concrete containing DCI-S corrosioninhibitor admixture at a dosage rate of 29.9 liters per cubic meter (L/m3

). The columns and pier

cap of the south pier were patched with portland cement concrete and were designated as the

control.

Corrosion performance evaluations of the inhibitor admixtures had been limited to the south

faces of the three pier caps. A sounding survey conducted prior to rehabilitation indicated a

significant difference between the south and north faces of the three pier caps. The south faces

were more severely and uniformly delaminated than the north face of the pier caps. The

percentages of hollow-sounding areas in the south face for the control (south pier), Cortec

(middle pier), and DCI (north pier) pier caps were 51, 59, and 56, respectively. The percentages

of hollow-sounding areas in the north face for the control, Cortec, and DCI pier caps were 17,

40, and 22, respectively. To assess the effectiveness of the corrosion-inhibitor treatments,

corrosion performance evaluations were limited to equivalent areas on the west sections of the

south face of the three pier caps. Figures 2-2 through 2-5 show sections of the south pier, middle

pier, and north pier that were evaluated.
2-2

Figure 2-1. General view of the Elmwood Avenue bridge

over NY Route 198, Buffalo, NY.

2.2. Field Evaluation

Field evaluations were performed on the following dates:

First evaluation October 17-19, 1994 ~2 years after treatment

Second evaluation May 7-9, 1997 ~5 years after treatment

Third evaluation June 17-23, 1998 ~6 years after treatment

2.3. Test Results

The following sections describe the results of five standard surveys and the chloride ion content

analysis.

2.3.1. Visual Survey

Visual surveys were conducted during all three visits. In October 1994, approximately 2 years

after the repair of the piers, the west section of the south face of all three pier caps appeared

sound and no spalls were observed. The patched areas, particularly those with inhibitor

treatments, were severely cracked. The observed cracking pattern was mud-flat cracking, typical

of drying shrinkage cracks. During the second and third visits (May 1997, and June 1998,

respectively), the drying shrinkage cracks appeared to be about the same. However, minor

spalling was observed in the three piers.
2-3

Figure 2-2. Views of test sections on: (a) south pier (control), 

 (b) middle pier (Cortec 2000), and (c) north pier (DCI). 

2.3.2. Delamination Survey

(a)

(b)

(c)
2-4

Delamination surveys were conducted during the first and third visits; results are presented in

table 2-1. The first evaluation (October 1994) revealed hollow-sounding areas in patches of all

three south face sections and in the original concrete within the south face sections of the control

and Cortec-treated pier cap faces. It was not determined whether the hollow-sounding areas

were the result of continued corrosion, drying shrinkage cracking, or disbondment of the patch

material. It was noted in the SHRP C-103 Field Validation report (Publication No. SHRP-S658) that difficulties were encountered in bonding the cast-in-place patch concrete to the original

concrete. Researchers detected hollow-sounding areas in patch concrete within weeks after the

repairs were completed. The researchers did not survey all of the patch areas and did not verify

that all hollow-sounding areas were repaired.

In general, the hollow-sounding areas increased between the first and third evaluations. The

increase in hollow-sounding areas with respect to the first evaluation was significant, especially

on the original concrete areas of the control pier and on patched areas of the treated piers. The

overall percentages of hollow-sounding areas for the control pier increased from 4.8 to 13.1; the

middle pier (Cortec 2000-treated) increased from 4.3 to 5.1 percent; and the north pier (DCItreated) increased from 6.0 to 13.6 percent.

An attempt was made to identify the cause(s) of the hollow-sounding areas. Several 7.6-

centimeter cores were collected from sound and deteriorated areas located in patches or original

concrete. Corrosion-induced delaminations were observed in some cores; bond failure between

the patch and the original concrete was observed in others.

2.3.3. Clear Concrete Cover Survey

A clear concrete cover survey was performed during the first evaluation using a cover meter. 

Readings were taken in the patch concrete, at the interface, and in the original concrete. The

results of the cover meter were verified at random locations with actual cover measurements at

drill holes. The results are shown in table 2-2. The average clear concrete cover for the middle

pier was greater than that for the south and the north piers.
2-5

Original Patch Original Patch Original Patch

South Pier 1.4 x 12.1 16.9 10.6 3 4 0.55 0.26 8.7 2.5 (Control)Middle Pier 1.4 x 12.1 16.9 3.9 3 2 0.18 0.55 1.4 14.1 (Cortec)North Pier 1.4 x 12.1 16.9 9.9 0 3 0.00 1.01 0.0 10.2 (DCI)South Pier 1.4 x 12.1 16.9 10.6 5 4 1.29 0.92 20.5 8.7 (Control)

Middle Pier 1.4 x 12.1 16.9 3.9 2 2 0.26 0.60 2.0 15.4 (Cortec)North Pier 1.4 x 12.1 16.9 9.9 1 10 0.09 2.20 1.3 22.2 (DCI)

Location

Survey 

Section, 

m

Survey

Area, 

m

2

Approx 

Patch Area, 

m

2

June, 1998

Evaluation 

Date

October, 1994

Number of Hollow 

Sounding Areas Hollow Sounding, m2 Hollow Sounding, % 

Table 2-1. Delamination survey results.
2-6

Table 2-2. Cover depth survey results.

Test Area Location Average Cover Depth, cm Combined

Average, cm

South Pier (control) Patch 4.27 4.57

Interface 4.50

Original 4.93

Middle Pier (Cortec) Patch 5.66 6.43

Interface 6.25

Original 7.39

North Pier (DCI) Patch 3.71 4.42

Interface 4.83

Original 4.72

2.3.4. Corrosion Potential Survey

Corrosion potential measurements were conducted as indicated by the American Society

for Testing and Materials (ASTM) C-876 during all three visits. The test areas were

approximately 1.4 x 12.1 m for the south pier, 1.4 x 5.5 m for the middle pier, and 1.4 x

9.2 m for the north pier. Potential measurements were taken on a 0.61-m grid on patched

(P) areas, interface (I), and original (O) concrete. However, the majority of the

measurements were located on patches and original concrete. According to ASTM C876, rebars with corrosion potentials less than -350 mV (millivolts measured against a

copper-copper sulfate electrode (CSE)) have a high probability of active corrosion. 

When the potentials are in the range of -200 mV to -350 mV, corrosion activity is

uncertain. Rebars with corrosion potentials that are greater than -200 mV have a low

probability of corrosion.

Summaries of corrosion potential measurements for the three visits are shown in tables 

2-3 through 2-5. Corrosion potential data should be analyzed with caution from inhibitor

treated areas, as the presence of inhibitor in the concrete can impact potential

measurements due to the formation of junction cells.
2-7

Table 2-3. Corrosion potential summary (October 1994).

Inhibitor

Treatment

Concrete

Type*

No. of

Measurements

Average

Potential

mV vs. CSE

Standard

Deviation

% Corrosion Potentials,

mV vs. CSE*

<-200 -200 to -350 >-350

Control Original

Patch

12

21

-400

-177

86

38

 0

71

25

29

75

 0

Cortec Original

Patch

 9

 8

-201

-138

48

62

56

87

44

13

 0

 0

DCI Original

Patch

13

17

-229

-198

31

62

15

59

85

41

 0

 0

* millivolts measured against a copper-copper sulfate electrode

Table 2-4. Corrosion potential summary (May 1997).

Inhibitor

Treatment

Concrete

Type*

No. of

Measurements

Average

Potential

mV vs. CSE

Standard

Deviation

% Corrosion Potentials,

mV vs. CSE*

<-200 -200 to -350 >-350

Control Original

Patch

14

21

-464

-216

98

50

 0

43

 7

52

93

 5

Cortec Original

Patch

11

 8

-281

-240

51

27

11

 0

89

100 

 0

 0

DCI Original

Patch

13

17

-269

-230

46

91

 0

53

83

35

17

12

* millivolts measured against a copper-copper sulfate electrode

Table 2-5. Corrosion potential summary (June 1998).

Inhibitor

Treatment

Concrete

Type*

No. of

Measurements

Average

Potential

mV vs. CSE

Standard

Deviation

% Corrosion Potentials,

mV vs. CSE*

<-200 -200 to -350 >-350

Control Original

Patch

14

21

-394

-112

139

 64

 7

86

25

14

68

 0

Cortec Original

Patch

11

 8

-235

-236

 67

 37

27

25

73

75

 0

 0

DCI Original

Patch

13

17

-254

-259

 45

 81

 0

31

86

56

14

13

* millivolts measured against a copper-copper sulfate electrode
2-8

In general terms, there was a slight increase in the active potentials for the control and DCItreated piers. The potentials for the Cortec-treated pier remained in the passive to uncertain

range.

2.3.5. Corrosion Rate Survey

Corrosion rate tests were conducted with an NBS-3LP corrosion rate device and measurements

were made at 31 locations (11 in the control section and 10 each in the Cortec- and DCI-treated

sections) during each of the three visits. Measurements were made on original concrete, on the

patches, and at the interface. Table 2-6 shows average corrosion rate values determined in each

of the test areas for all three visits.

Table 2-6. Corrosion rate results.

Location Concrete Type

Average Corrosion Rate, mA/m 2

 *

Oct. 1994 May 1997 June 1998

South Pier

(control)

Original 0.103 0.229 0.713

Interface 0.108 0.367 0.502

Patch 0.097 0.166 0.237

Middle Pier

(Cortec)

Original 0.170 0.284 0.417

Interface 0.219 0.429 0.247

Patch 0.554 0.795 0.658

North Pier

(DCI)

Original 0.161 0.092 0.245

Interface 0.189 0.206 0.426

Patch 0.379 0.533 0.920

* milliamps per square meter

1 mA/m2

 = 10.753 mA/ft2

The guidelines for interpreting corrosion rate data obtained with the NBS-3LP device are shown

in table 2-7.
2-9

Table 2-7. Corrosion rate interpretation guidelines.

Guidelines for Interpreting 3LP Corrosion Rate Data

Corrosion Current Density

(Icorr), mA/m2

 *

Predicted Time to Damage

less than 0.019 none

0.019 to 0.093 10 to 15 years

0.093 to 0.930 2 to 10 years

greater than 0.930 less than 2 years

 * milliamps per square meter

 1 mA/m2

 = 10.753 mA/ft2

As the corrosion rate varies significantly with temperature, the variation in data as a function of

time and a comparison between test sections provides more information than the actual

magnitude of the corrosion rate measurements. The highest rate of increase in corrosion rate

with time in patched areas was observed on the north pier (DCI-treated). Similarly, the highest

rate of change in original concrete and on the interface was observed on the south (control) pier. 

In general, the corrosion rate data do not differentiate between the treated areas and the control.

2.3.6. Chloride Ion Content Analysis

Total chloride ion content analysis as per the standard American Association of State Highway

and Transportation Officials (AASHTO) T-260(3) method was conducted during the first and

third visits. Powdered samples (at 1.27-cm intervals from the top surface to beyond the depth of

the embedded steel) were obtained from cores collected from original concrete, patched areas,

and the interface. The chloride content analysis results from the first and third visits are given in

tables 2-8 and 2-9, respectively.

The chloride content in the various test areas has increased in a span of about 4 years, from the

first evaluation in October 1994 to the third evaluation in June 1998. The chloride content at the

average level of the reinforcing steel (5.1 cm) was above the corrosion threshold for all piers. 

The average chloride content at the level of the reinforcing steel in patched areas was

approximately 50 percent higher on the treated piers than on the control pier. The average

chloride content at the steel depth in patched and interface areas for the treated and control piers

was approximately 3 to 4 times the chloride corrosion threshold.
2-10

2.4. Conclusions

All patched areas, particularly those treated with the inhibitor, had suffered shrinkage cracking. 

The cause of shrinkage cracking was not determined in this study. Immediately after the

installation of the repairs, hollow-sounding areas were detected. The formation of hollowsounding areas was attributed to lack of bonding between the patch material and the original

concrete. Generally, bond failure occurs soon after the installation of new concrete and does not

continue to occur with time. The size and number of hollow-sounding areas in patches

continued to increase with time. This suggests that a process other than bond failure was

responsible for the increase in hollow-sounding areas. Some cores extracted from patches in the

control pier and the treated piers exhibited ongoing corrosion and consequent formation of

delamination.

The average corrosion rate measurements in patched areas and original areas were of a

magnitude that can result in corrosion-induced damage in 2 to 10 years. The variation in average

corrosion rates with time suggests that corrosion continued unabated in the patches of the control

area and the treated areas. Also, the corrosion rate in the patches of the control area and the area

treated with the DCI inhibitor increased with time; it varied with time for the patches treated

with the Cortec inhibitor. Corrosion was ongoing in the original concrete and was increasing

with time. The corrosion rates at the interface between the patches and the original concrete in

treated areas were similar to or higher than that for the control area.

Sufficient levels of chloride ions were present everywhere to ensure continuation of corrosion. 

The cracking of the patches probably aided the ingress of chloride ions (CI) into the patches and

reached such high levels of concentration within 6 years of completion of the repairs.

Considering that corrosion has continued unabated in patches of inhibitor-treated areas at similar

or higher rates than the control, it may be concluded that the inhibitors did not provide any

protection against corrosion. 
2-11

Table 2-8. Total chloride ion content analysis (first visit).

Location x,y 

Coordinates, m

Concrete

Type

Cl Sample

Depth, cm

Cover

Depth, cm

Cl Ion

Content,

ppm*

South Pier

(control)

0.43, 0.46 Original

1.27

2.54

3.81

5.08

3.43

1226

 766

 664

 409

10.9, 0.38 Interface

1.27

2.54

3.81

5.08

4.06

1660

1762

1405

1201

5.02, 0.40 Patch

1.27

2.54

3.81

5.08

4.32

766

255

281

281

Middle Pier

(Cortec)

0.62, 0.43 Interface

1.27

2.54

3.81

5.08

5.33

639

741

894

817

1.54, 0.40 Patch

1.27

2.54

3.81

5.08

4.83

792

409

358

332

North Pier

(DCI)

6.95, 1.05 Interface

1.27

2.54

3.81

5.08

5.33

4802

2963

3448

2478

2.58, 0.40 Patch

1.27

2.54

3.81

5.08

3.30

1149

 741

 383

 332

* ppm = parts per million
2-12

Table 2-9. Total chloride ion content analysis (third visit).

Location x,y 

Coordinates, m

Concrete

Type

Cl Sample

Depth, cm

Cover

Depth, cm

Cl Ion Content,

ppm

South Pier

(control)

0.54, 0.46 Original

1.27

2.54

3.81

5.08

6.35

7.62

3.43

1541

1542

1162

 834

 601

 421

10.9, 0.46 Interface

1.27

2.54

3.81

5.08

6.35

7.62

4.06

1773

1542

1588

1505

 926

1133

5.08, 0.46 Patch

1.27

2.54

3.81

5.08

6.35

7.62

4.32

357

245

222

144

323

338

Middle Pier

(Cortec)

0.77, 0.46 Interface

1.27

2.54

3.81

5.08

6.35

7.62

5.33

 792

 580

1320

 865

 990

 788

3.0, 0.24 Patch

1.27

2.54

3.81

5.08

6.35

7.62

4.83

1522

 927

 634

 537

 541

 472

North Pier

(DCI)

6.92, 1.08 Interface

1.27

2.54

3.81

5.08

6.35

7.62

5.33

3124

3542

2161

1881

1129

 699

2.77, 0.37 Patch

1.27

2.54

3.81

5.08

6.35

7.62

3.30

2942

1664

1047

 604

 465

 435

3-1

3.0. STATE ROAD 2042 OVER I-81, WILKES BARRE, PA

3.1. Structure Background

The Pennsylvania State Road (SR) 2042 bridge consists of two three-span structures and carries

traffic in an east-west direction over the north and southbound lanes of I-81. The west bridge

carries SR 2042 traffic over southbound I-81, and the east bridge carries SR 2042 traffic over

northbound I-81. Each bridge is approximately 43 m long and 12 m wide, consisting of two

3.66-m-wide traffic lanes and two 2.44-m-wide breakdown lanes. Piers are numbered 1 through

4 from east to west. Piers 1 and 2 are on the east bridge, and piers 3 and 4 are on the west

bridge. Figures 3-1 (a) and (b) show general views of the west bridge and the east bridge,

respectively.

Figure 3-1. General views of the SR 2042 bridge structures over I-81:

 (a) west bridge and (b) east bridge.

Piers 1, 2, and 3 were selected for SHRP C-103 field trial installation of shotcrete/corrosioninhibitor repair systems. Areas of unsound concrete were delineated and removed to a depth of

19 millimeters (mm) below the reinforcing steel level with pneumatic hammers before repairs

were begun. The exposed steel was sandblasted to near-white metal prior to application of the

shotcrete and inhibitor treatment. In all patch repair areas, a wire mesh was tied to the

reinforcing steel mat.

Pier 1 was used as the control. The repair cavities on this pier were backfilled with a standard

shotcrete mix without any inhibitor treatment.

Pier 2 was repaired with shotcrete admixed with DCI inhibitor added at a rate of 1.9 liters (L) per

bag of cement (approximately 4.99 L/m3

 of concrete). In addition, four spray applications of

Postrite (a 15-percent calcium-nitrite solution) were applied to the repair cavities with exposed

steel prior to backfilling with inhibitor-treated shotcrete. The surface of the repair cavity for

each application was sprayed until it was saturated. The second application was done

(a) (b)
3-2

(d)

approximately 2 hours after the initial application, the third 8 hours after the initial application,

and the final application was done immediately prior to the application of the shotcrete.

Pier 3 was repaired with shotcrete treated with Cortec MCI 2000 inhibitor. The MCI 2000

admixture was added at a rate of 0.18 L per bag of cement (approximately 1.2 L/m3

 of concrete).

All testing was limited to equal areas of 7.6 m2 on one face of each of the three pier caps. The

east face was chosen for piers 1 and 2, and the west face was chosen for pier 3.

Figures 3-2 (a-c) show the test areas on piers 1, 2, and 3, respectively, while figure 3-2 (d) shows

testing in progress utilizing a snooper.

Figure 3-2. General views of piers: 

 (a) pier 1, (b) pier 2, (c) pier 3, and (d) field evaluation in progress.

(a) (b)

(d)

(c)
3-3

3.2. Field Evaluation

A total of three field evaluations were performed in this study on the following dates:

First evaluation November 16-18, 1994 ~2 years after treatment

Second evaluation May 5-6, 1997 ~5years after treatment

Third evaluation September 29-30, 1998 ~6 years after treatment

3.3. Test Results

Six types of information were gathered. These results are discussed below.

3.3.1. Visual Survey

During the first visit, the concrete surface of the three pier caps did not have spalls. All patched

areas on the three pier caps were cracked. Detailed mapping of the cracks was not performed. 

Cracks generally occurred along patch perimeters and the crack pattern within patched areas was

typical of drying shrinkage cracking. Cracking was not observed in the original concrete areas. 

Visual observations of the three piers during the second visit did not show much change

compared to the first evaluation. During the third visit, approximately 2.5 m of new cracks were

documented in the patch areas of pier 3 (treated with Cortec 2000). These cracks did not appear

to be caused by drying shrinkage. Outside the survey area of pier 3, corrosion products were

visible in the original concrete. The shrinkage cracks on the other two piers remained the same. 

Spalls were not visible on any of the three pier caps.

3.3.2. Delamination Survey

During the first visit, hollow-sounding areas were detected in the patched areas and original

concrete of pier 2 (treated with DCI Postrite). The hollow-sounding areas were 0.372 m2

 and

0.093 m2

 for the patched and original concrete, respectively. During the third visit, 0.093 m2 of

hollow-sounding area in the original concrete was found on pier 1 (control). The hollowsounding area in the original concrete on pier 2 remained the same. However, the hollowsounding area in the patched section on pier 2 was found to be somewhat less than that

documented during the first visit. This discrepancy resulted from a confusion of the grids

marked on the surface of the test area. Drawings of the delaminations suggest that the

delaminations increased with time. No hollow-sounding sections were identified on pier 3

(treated with Cortec 2000). Table 3-1 summarizes the delamination survey results.
3-4

Table 3-1. Delamination survey results.

Location/Treatment Survey Date

No. of HollowSounding AreasHollow-Sounding

Surface Area, m2

Original Patched Original Patched

Pier 1, East Face

(control)

November 1994

0 0 0 0 

Pier 2, East Face

(Postrite, DCI) 2 4 0.093 0.372

Pier 3, West Face

(MCI 2000) 0 0 0 0 

Pier 1, East Face

(control)

September 1998

1 0 0.093 0 

Pier 2, East Face

(Postrite, DCI) 3 4 0.093 0.186

Pier 3, West Face

(MCI 2000) 0 0 0 0 

Notes:

Survey section in each case is (1.07 x 7.41)m = 7.93 m2

Original = original concrete

Patch = patch concrete placed in October 1992

3.3.3. Clear Concrete Cover Survey

A clear concrete cover survey was performed during the first evaluation using a cover meter. 

Readings were taken in the patch concrete, at the interface, and in the original concrete. The

results of the cover meter were verified at random locations, with actual cover measurements at

drill holes. The results are shown in table 3-2. The average clear concrete cover for the middle

pier was greater than for the south and the north piers.

3.3.4. Corrosion Potential Survey

Corrosion potential measurements were conducted according to ASTM C-876(4) during all three

visits. Potential measurements were taken on a 0.61-m grid on patched (P) areas, interface (I),

and original (O) concrete. However, the bulk of the measurements were for patched and original

concrete. Summaries of corrosion potential measurements for the three visits are shown in tables

3-3 through 3-5. Guidelines for interpretation of corrosion potentials were discussed earlier.

Table 3-2. Cover depth survey results.
3-5

Location/

Treatment

x, y

Coordinates, m

Cover Depth,

cm

Average

Cover

Depth, cm

Average

Pre-Construction

Depth, cm

Pier 1, East

Face

(control)

O (0.79, 0.61)

O (7.47, 0.91)

I (2.06, 0.91)

I (4.64, 1.07)

6.35

5.33

2.67

4.95

4.83 5.18

Pier 2, East

Face

(Postrite, DCI)

O (3.78, 0.40)

O (7.26, 0.61)

I (2.10, 0.67)

I (14.51, 0.76)

4.83

6.99

5.33

6.10

5.82 6.22

Pier 3, West

Face

(MCI 2000)

O (1.89, 0.31)

O (7.53, 0.46)

I (3.05, 0.46)

I (4.79, 0.92)

6.60

6.73

4.57

4.95

5.72 5.77

Notes:

O = original concrete; I = interface of original and patch concrete

(0,0) coordinate is at the southern top corner of pier cap; x is measured in the northerly direction,

and y measured in the southerly direction

Table 3-3. Corrosion potential summary (November 1994).

Location/

Treatment

Concrete

Type

No. of

Potential

Measurements

Average

Potential,

mV vs.

CSE

Standard

Deviation

% Corrosion Potentials,

mV vs. CSE*

<-

200 -200 to -350 >-350

Pier 1, East Face

(control)

O

P

12

12

-249

 -52

 70

 48

 25

100

75

 0

 0

 0

Pier 2, East Face

(Postrite, DCI)

O

P

13

10

-202

-218

127

 86

 62

 60

23

20

15

20

Pier 3, West Face

(MCI 2000)

O

P

12

12

-209

 -91

 92

 48

 33

100

67

 0

 0

 0

O = original concrete; P = patch concrete

* millivolts measured against a copper-copper sulfate electrode

Table 3-4. Corrosion potential summary (May 1997).
3-6

Location/

Treatment

Concrete

Type

No. of

Potential

Measurements

Average

Potential,

mV vs.

CSE

Standard

Deviation

% Corrosion Potentials,

mV vs. CSE*

<-200 -200 to -350 >-350

Pier 1, East Face

(control)

Original

Patch

14

12

-282

 -74

 83

 55

 21

100

57

 0

21

 0

Pier 2, East Face

(Postrite, DCI)

Original

Patch

13

10

-242

-246

126

 83

 31

 40

46

30

23

30

Pier 3, West Face

(MCI 2000)

Original

Patch

11

12

-202

 -98

 98

 64

 45

 92

55

 8

 0

 0

* millivolts measured against a copper-copper sulfate electrode

Table 3-5. Corrosion potential summary (September 1998).

Location/

Treatment

Concrete

Type

No. of

Potential

Measurements

Average

Potential,

mV vs.

CSE

Standard

Deviation

% Corrosion Potentials,

mV vs. CSE*

<-200 -200 to -350 >-350

Pier 1, East Face

(control)

Original

Patch

20

16

-239

 -60

 70

 53

25

94

75

 6

 0

 0

Pier 2, East Face

(Postrite, DCI)

Original

Patch

23

11

-207

-242

 98

108

48

55

39

18

13

27

Pier 3, West Face

(MCI 2000)

Original

Patch

21

15

-246

 -70

 91

 54

24

93

66

 7

10

 0

* millivolts measured against a copper-copper sulfate electrode

3.3.5. Corrosion Rate Survey

Corrosion rate tests were conducted on all three visits. An NBS-3LP (linear polarization)

corrosion rate device was used and measurements were made at a total of 18 locations (6

measurements per pier). On each pier, two measurements were made in the original concrete, at

patch areas, and at the interface of the original and patch concrete. The results are presented in

table 3-6. Corrosion rate measurements made on the original concrete taken prior to the

rehabilitation in October 1992 are also included. However, it should be mentioned that the

locations for the 1992 corrosion rate measurements were not the same as for the 1994-1998

measurements. The corrosion rate measurements obtained in the patch areas were not accurate

because: (1) no reinforcing steel layout information was available, and (2) the calculated

corrosion rate values did not take into account the polarized area of the mesh. The relative

difference in the data can be used to study the impact of inhibitors in mitigating corrosion.

Table 3-6. Summary of corrosion rate measurements.
3-7

Location Concrete

Type

Corrosion Rate, mA/m2

Oct. 1992 Nov. 1994 May 1997 Sept. 1998

Pier #1

(control)

O

P

I

0.248 0.166

0.077

0.160

0.178

0.064

0.315

0.084

0.120

0.154

Pier #2

(Postrite/DCI)

O

P

I

0.977 0.194

0.136

0.201

0.162

0.119

0.276

0.092

0.108

0.111

Pier #3

(MCI 2000)

O

P

I

1.107 0.390

0.099

0.130

0.286

0.066

0.363

0.777

0.118

0.428

1 mA/m2 = 10.753 mA/ft2

O = original concrete; P = patch concrete placed in 1992; I = interface of original and patch 

It should be noted that the corrosion rates measured on the original concrete in October 1992,

shortly after rehabilitation, were quite high. However, the locations were not the same as those

used in the subsequent measurements from 1994 to 1998. Corrosion rates in patched areas had

practically remained stable and were similar for all three piers, whereas at the patch/original

concrete interface, corrosion rate data from pier 3 exhibited a significantly larger increase than

that for the other two piers.

3.3.6. Chloride Ion Content Analysis

During the first visit in November 1994, powdered concrete samples were collected from the

original concrete, patches, and interface areas from each of the three piers (a total of nine

locations). At each location, 4 samples were collected at progressive increments of 13 mm down

from the surface for a total of 36 samples. The chloride analyses data for the first visit are

presented in table 3-7. Data collected prior to rehabilitation are also included in table 3-7. The

three pier caps had high chloride contamination before rehabilitation. Chloride contents near the

depth of the reinforcing steel were 6 to 13 times the corrosion threshold level (260 ppm). Two

years after rehabilitation, chloride contents were very high at the interface areas, demonstrating

that high chloride-contaminated concrete was left adjacent to patch areas. The patch concrete

chloride content was low. The chloride content of pier 2 in the original concrete after 2 years

was well above the corrosion threshold level.
3-8

Table 3-7. Total chloride ion content data (first visit).

Location/

Treatment x, y Coordinates, m Chloride SampleDepth, cm

Chloride Ion

Content, ppm

Pier 1, East Face

(control)

O (1.22, 0.61)*

1.27

2.54

3.81

5.08

1379

2810

2018

2043

O (4.27, 0.61)*

1.27

2.54

3.81

5.08

1967

2401

3295

2810

O (7.47, 0.92)

1.27

2.54

3.81

5.08

 674

 0

 138

 23

I (4.64, 1.07)

1.27

2.54

3.81

5.08

3780

3826

2087

2304

P (6.19, 0.92)

1.27

2.54

3.81

5.08

 56

 89

 49

 31

Pier 2, East Face

(Postrite/DCI)

O (0.61, 0.61)*

1.27

2.54

3.81

5.08

3934

2273

3167

2427

O (1.83, 0.61)*

1.27

2.54

3.81

5.08

3091

3372

3065

1890

Notes:

* Preconstruction data

O = original concrete; P = patch concrete placed in 1992; I = interface of original and patch

concrete

(0,0) coordinate is at the southern top corner of pier cap; x measured in the northerly direction

and y measured in the southerly direction
3-9

Table 3-7. Total chloride ion content data (first visit) (continued).

Location/

Treatment x, y Coordinates, m Chloride SampleDepth, cm

Chloride Ion

Content, ppm

Pier 2, East Face

(Postrite/DCI)

O (3.78, 0.40)

1.27

2.54

3.81

5.08

2248

3775

3484

3096

I (2.10, 0.67)

1.27

2.54

3.81

5.08

1995

1829

 628

 411

P (2.71, 0.61)

1.27

2.54

3.81

5.08

 15

 59

 28

 28

Pier 3, West Face

(MCI 2000)

O (4.97, 0.92)*

1.27

2.54

3.81

5.08

5006

5722

4342

4036

O (2.44, 0.92)*

1.27

2.54

3.81

5.08

4138

4521

3678

3014

O (7.53, 0.46)

1.27

2.54

3.81

5.08

 401

 289

 255

 64

I (4.97, 0.92)

1.27

2.54

3.81

5.08

2766

4950

2996

3428

P (4.76, 0.85)

1.27

2.54

3.81

5.08

 166

 0

 64

 299

Notes:

* Preconstruction data

O = original concrete; P = patch concrete placed in 1992; I = interface of original and patch

concrete

(0,0) coordinate is at the southern top corner of pier cap; x measured in the northerly direction

and y measured in the southerly direction
3-10

During the third visit, chloride samples were collected from nine locations adjacent to the

locations used on the first visit. At each location, 4 samples were collected at progressive

increments of 13 mm down from the surface for a total of 36 samples. The chloride analyses

data for the third visit are presented in table 3-8.

3.4. Conclusions

All patches on the control pier and the treated piers were experiencing shrinkage cracking. By

the third evaluation, additional cracks had developed in the patches treated with Cortec inhibitor. 

Rust staining that originated in a crack at the patch concrete interface of a patch treated with the

Cortec inhibitor was noted in the third evaluation. Hollow-sounding areas were observed on the

patch of the pier treated with DCI inhibitor and they increased with time.

The chloride ion content at the steel depth in the patches was below the threshold required to

initiate corrosion. 

Corrosion rate measurements in patched areas were not accurate, because the correct surface area

of the steel subjected to the measurement could not be determined. But the trends in the

corrosion rate measurements indicated that corrosion rates in the patched areas remained

relatively constant with time in the control pier and the treated piers, and the rates for the treated

patches and the control patches were similar. Corrosion rates at the interface were generally

higher than those in the patches.

The signs of ongoing corrosion in the patches of the treated areas and at the interfaces suggest

that the inhibitors were not providing any protection.
3-11

Table 3-8. Total chloride ion content data (third visit).

Location/

Treatment x, y Coordinates, m Chloride SampleDepth, cm

Chloride Ion

Content, ppm

Pier 1, East Face

(control)

O

1.27

2.54

3.81

5.08

 733

 493

 212

 87

I

1.27

2.54

3.81

5.08

1579

1551

1212

 902

P

1.27

2.54

3.81

5.08

 54

 45

 93

 212

Pier 2, East Face

(Postrite/DCI)

O

1.27

2.54

3.81

5.08

3525

3666

3012

2820

I

1.27

2.54

3.81

5.08

1692

2256

1500

1128

P

1.27

2.54

3.81

5.08

 87

 62

 0

 42

Pier 3, West Face

(MCI 2000)

O

1.27

2.54

3.81

5.08

 240

 129

 53

 70

I

1.27

2.54

3.81

5.08

1410

4373

2816

3125

P

1.27

2.54

3.81

5.08

2111

 128

 89

 216

Notes:

O = original concrete; I = interface; P = patch 
4-1

4.0. HOOD CANAL BRIDGE, PORT GAMBLE, WA

4.1. Structure Background

The Hood Canal bridge, located west of Seattle, WA, is a primary link to the Olympic Peninsula. 

The 2397-m-long pontoon bridge carries Washington Route 104 traffic across the Hood Canal,

which contains brackish tidal water. Due to the extreme depth of the natural canal, greater than

92 m at mid-channel, the structure was designed as a floating bridge that opens at the center to

allow passage of ship traffic. The roadway is elevated above the pontoon decks. The bridge

substructure, columns, and crossbeams are supported by the pontoons. Figures 4-1 (a) and (b)

show general views of the Hood Canal bridge.

Figure 4-1. General views of the Hood Canal bridge.

The floating bridge was constructed in 1961. In 1979, the western half of the bridge sank in a

storm and was subsequently replaced. Corrosion of the concrete reinforcing steel in the pontoon

decks and substructure members is evident throughout the older eastern half of the floating

bridge. Previous repairs to the eastern half of the bridge included patching of the pontoon decks,

columns, and crossbeams, and the coating of these surfaces with epoxy. Even though the

pontoon decks are about 1.5 m above high tide, they are constantly exposed to wind-blown

brackish water mist, especially on the southern side of the decks. Water tends to pond on the

deck surface. As a result, corrosion has continued unabated in the original and repaired concrete

areas.

In July 1992, the three southern pontoon deck cells (1D, 2D, and 3D) of pontoon S on the eastern

half of the bridge, each measuring 3.66 m by 9.14 m, were selected as a SHRP C-103 corrosioninhibitor-treatment field-trial site. Delaminated areas on these cells were identified and

delineated. Hollow-sounding areas in cells 1D, 2D, and 3D were found to be 8.9, 25.6, and 30.4

percent, respectively. Deteriorated concrete from the delaminated areas was removed to a depth

of about 19 mm below the top reinforcing steel and the cavities backfilled with non-air-entrained

cementitious patching material. The exposed reinforcing steel in all three cells was sandblasted

to near-white metal on the day of patching. Immediately prior to the placement of the repair

concrete, patch cavities were painted with a neat cement slurry. Cell 1D had no inhibitor

(a) (b)
4-2

treatment and was designated as the control. Corrosion inhibitor treatment was applied to the

patches in cells 2D and 3D. Cell 1D had 11 patches, cell 2D had 13 patches, and cell 3D had 9

patches. The size of the patches ranged from 0.072 m2 to 2.6 m2. Figures 4-2 (a), (b), and (c)

show partial views of the test locations.

Figure 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).

Cortec MCI 2020/2000 was used as the corrosion-inhibitor system in cell 2D. Cell 3D was

treated with the Postrite/DCI inhibitor system. Cortec 2020 was sprayed on the exposed

reinforcing steel prior to the placement of the patch concrete, and Cortec 2000 was added to the

patch concrete at a rate of 1.2 kg/m3

. Care was taken during the spraying of Cortec 2020 to

avoid contact with substrate concrete, because Cortec 2020 has been reported to cause a

detrimental reduction in bond strength. For the 3D cell repairs, Postrite was sprayed on the

exposed reinforcing steel and substrate concrete prior to the placement of the repair concrete,

which contained DCI at a dosage rate of 39.94 L/m3

.

4.2. Field Evaluation

(a) (b)

(c)
4-3

Field evaluations were conducted under the FHWA contract and done on the following dates:

First evaluation November 5 and 6, 1994 ~2 years after treatment

Second evaluation June 25 and 26, 1996 ~4 years after treatment

A limited evaluation consisting of visual and delamination surveys was conducted under the

SHRP program in October 1993. The observations from the 1993 survey are also included here. 

4.3. Test Results

The six types of results collected are presented below.

4.3.1. Visual Survey

Visual inspections were performed in October 1993, November 1994, and June 1996, about 1.3

years, 2.4 years, and 4 years after the repairs were completed. During the October 1993

inspection, no cracking or spalling was observed in the control, Cortec, or Postrite/DCI cells. 

However, a 0.3-m-long crack was observed in patch # 2 in the Postrite/DCI cell during the

November 1994 inspection. The crack appeared to be caused by drying shrinkage. No further

cracks were documented during the 1996 evaluation.

4.3.2. Delamination Survey

Delamination surveys were conducted in October 1993 and November 1994. Due to inclement

weather, the delamination survey could not be conducted during the 1996 evaluation. The

results of the delamination survey are presented in table 4-1. Hollow-sounding areas were first

detected 1.3 years after patching in the Cortec cell (cell 2D) and after 2.4 years in the control and

Postrite/DCI cells (cells 1D and 3D, respectively). During the 1994 evaluation, hollow-sounding

areas were detected in 2 of the 11 patches in cell 1D; 2 of the 13 patches in cell 2D; and 3 of the

9 patches in cell 3D. The corresponding delaminations were computed to be 2.2, 5.2, and 12.2

percent, respectively. The hollow-sounding areas in cell 2D increased in size between the first

and second evaluations.

4.3.3. Clear Concrete Cover Survey

Table 4-2 presents the patch cover depths measured at about 3 days (July 1992) and 2.4 years

(November 1994) after repair. The cover depths measured in July 1992 and November 1994

were in general agreement and showed that cover depths were shallow in all three cells. The

average cover depths for cells 1D, 2D, and 3D were 3.35, 3.53, and 3.10 cm, respectively. The

original concrete cover depths prior to repair were also shallow, with averages of 2.90, 2.87, and

3.10 cm for cells 1D, 2D, and 3D, respectively.

Table 4-1. Delamination survey results.
4-4

Cell Patch

No.

Patch

Area,

m2

Hollow Sounding per Patch Hollow Sounding for Each Cell

Oct. 1993 Nov. 1994 Oct. 1993 Nov. 1994

m2 % m2 % m2 % m2 %

1 D

(control)

1

2

3

4

5

6

7

8

9

10

11

0.07

0.29

0.14

0.20

0.42

0.59

0.26

0.16

0.50

0.24

0.48 0.07 15.3

0.07 2.2

2 D

(Cortec

MCI

2020/2000)

1

2

3

4

5

6

7

8

9

10

11

12

13

0.38

0.28

0.33

0.27

0.11

0.20

0.36

0.35

0.25

2.31

1.30

1.46

0.28

0.011

0.030

4.1

8.2

0.15

0.25

57.4

70.7

0.041 0.5 0.408 5.2

3 D

(Postrite/

DCI)

1

2

3

4

5

6

7

8

9

0.40

0.60

0.69

0.74

0.99

0.28

2.59

0.62

1.23

0.31

0.19

0.50

31.1

30.0

40.7

0.995 12.2

Table 4-2. Clear concrete cover measurements.
4-5

Cell Patch No. Cover Depth, cm

July 1992 Nov. 1994

1 D

(control)

 1

 2

 3

 4

 5

 6

 7

 8

 9

10

11

Average

Std. Dev.

3.96

2.34

3.35

3.35

2.74

2.74

4.06

2.84

3.15

4.98

4.47

3.45

0.81

4.45

–

–

–

2.92

–

–

2.54

2.79

–

4.06

3.35

0.84

2 D

(Cortec MCI 2020/2000)

 1

 2

 3

 4

 5

 6

 7

 8

 9

10

11

12

13

Average

Std. Dev.

4.98

3.25

3.76

4.67

–

4.06

2.84

3.56

3.15

4.06

–

3.66

3.76

3.78

0.64

–

–

3.43

–

–

4.32

–

3.18

3.56

–

3.15

–

–

3.53

0.48

3 D

(Postrite/DCI)

1

2

3

4

5

6

7

8

9

Average

Std. Dev.

4.17

5.99

3.56

5.69

2.74

3.35

2.64

4.17

2.84

3.91

1.22

2.67

–

3.56

–

4.32

–

2.54

–

2.41

3.10

0.81

4.3.4. Corrosion Potential Survey
4-6

Potential measurements were made at the center of each patch in the respective cells. Table 4-3

presents a summary of the corrosion potential distribution in the three cells measured just prior

to repair and about 1.3 years, 2.4 years, and 4 years after repair. 

Corrosion potentials were mostly in the active range before the repairs were performed, but were

less active with time after the repairs. However, as apparent from table 4-3, a significant

percentage of the potentials remained in the active range for the inhibitor-treated patches as

compared to the control patches.

Table 4-3. Summary of corrosion potential measurements.

Cell No. Date No. of

Potential

Measurements

Average

Potential,

mV vs.

CSE

Standard

Deviation

% Corrosion Potentials, 

mV vs. CSE**

<-200 -200 to -350 >-

350

1 D

(control)

July 1992*

Oct. 1993 

Nov. 1994 

June 1996 

11

11

11

11

-440

-260

-266

-270

104

48

36

97

 0

 0

 9

18

27

91

91

73

73

 9

 0

 9

2 D

(Cortec MCI

2020/2000)

July 1992*

Oct. 1993 

Nov. 1994 

June 1996 

13

12

13

13

-474

-307

-353

-352

91

97

104

123

 0

25

 8

 8

15

25

46

54

85

50

46

38

3 D

(Postrite/DCI)

July 1992*

Oct. 1993 

Nov. 1994 

June 1996 

 9

 9

 9

 9

-436

-298

-285

-260

69

70

58

83

 0

11

 0

33

22

56

78

44

78

33

22

22

* Pretreatment data

** millivolts measured against a copper-copper sulfate electrode

4.3.5. Corrosion Rate Survey

The corrosion rate measurements were made with an NBS-3LP device at the center of selected

patches; results are presented in table 4-4. The average corrosion rates in all three test cells had

progressively increased from the pre-repair values.
4-7

Table 4-4. Corrosion rate measurements.

Cell Patch No.

Corrosion Rate, mA/m2

July 1992 Oct. 1993 Nov. 1994 June 1996

1 D

(control)

 1

 2

 3

 4

 5

 6

 7

 8

 9

10

11

Average

0.042

0.149

0.095

0.299

0.254

0.265

0.323

0.320

0.292

0.384

0.196

0.183

0.310

0.521

0.319

0.619

0.220

0.279

0.465

0.955

0.508

2 D

(Cortec MCI

2020/2000)

 1

 2

 3

 4

 5

 6

 7

 8

 9

10

11

12

13

Average

0.379

0.443

0.411

0.369

0.379

0.410

0.246

0.264

0.358

0.338

0.248

0.589

0.777

0.356

0.304

0.455

0.333

0.992

0.718

0.540

0.303

0.578

3 D

(Postrite/DCI)

1

2

3

4

5

6

7

8

9

Average

0.347

0.135

0.247

0.243

0.370

0.443

0.277

0.283

0.246

0.324

 0.407

0.950

 0.432

 0.697

 0.640

 0.625

0.512

1.143

0.990

0.443

0.998

0.817

* Pretreatment data

1 mA/m2

 = 10.753 mA/ft2
4-8

Corrosion rates were higher for the inhibitor-treated patches than for the control. The

Postrite/DCI-treated patches had the highest average corrosion rates and the largest increase 

with time.

4.3.6. Chloride Ion Content Analysis

The chloride content of the test cells was not determined before the November 1994 field

evaluation, and no chloride data were collected in 1996. Data collected in 1994 are presented in

table 4-5. The rate of chloride ingress into the patched areas appeared to be fairly rapid. The

chloride content near the steel depth in the patches, as well as in the original concrete, was

greater than the minimum threshold value of 260 ppm required to initiate corrosion.

4.4. Conclusions

With the exception of one crack observed during the first evaluation in a patch treated with

Cortec inhibitor, no other cracking was noted in the patches. Delaminations were first detected

in patches treated by the Cortec inhibitor and, with time, delaminations were noted in the control

patches and patches treated with the DCI inhibitor.

The chloride ion content at the steel depth in patches generally exceeded the threshold required

to initiate corrosion.

Average corrosion rates in patches increased with time for the patches in the control area and the

treated patches, and were higher in treated patches than in the control patches. Also, the increase

in corrosion rate with time in the treated patches was higher than that for the control patches.

Clear evidence of ongoing corrosion in inhibitor-treated patches indicated that the inhibitors

were not providing any protection.
4-9

Table 4-5. Total chloride ion content data.

Cell Patch No. Steel Depth,

cm

Sample

Depth, cm

Cl Content,

ppm

1 D

(control)

Patch #5 2.92 1.27

2.54

3.81

1775

 445

 450

Patch #11 4.06 1.27

2.54

3.81

2036

1130

 368

Near Patch #11* 1.27

2.54

3.81

2665

2220

1353

2 D

(Cortec MCI 2020/2000)

Patch #3 3.43 1.27

2.54

3.81

1217

 379

 176

Patch #8 3.18 1.27

2.54

3.81

2151

1435

 565

Near Patch #8* 1.27

2.54

3.81

3223

3350

2309

3 D

(Postrite/DCI)

Patch #3 3.56 1.27

2.54

3.81

1013

 499

 266

Patch #9 2.41 1.27

2.54

3.81

 719

 366

 258

Near Patch #3* 1.27

2.54

3.81

2409

1524

1072

* Original concrete

5-1

5.0. TRUNK HIGHWAY (TH)-3 OVER SOUTHVIEW BOULEVARD 

IN ST. PAUL, MN

5.1. Structure Background

The TH-3 bridge over Southview Boulevard is located in south St. Paul, MN. TH-3 (recently

renamed TH-52) is a main northbound arterial carrying southern traffic into St. Paul. The bridge

was built in 1973 and is approximately 50 m long and 14 m wide, with one breakdown lane and

two traffic lanes. The breakdown and right traffic lanes are approximately 3.35 m and 3.65 m

wide, respectively. There is also a 0.92-m-wide shoulder adjoining the left traffic lane. Spans 1,

2, and 3 are 13.5 m, 23.0 m, and 12.5 m long, respectively. The deck, parapets, and substructure

are cast-in-place reinforced concrete. The superstructure consists of precast, prestressed Ibeams. Figures 5-1 (a) and (b) show general views of the structure and deck, respectively.

Figure 5-1. TH-3 over the Southview Boulevard bridge: (a) structure and (b) deck.

The deck was rehabilitated and overlaid with a 5.08-cm Low-Slump Dense Concrete (LSDC)

mix in May-June 1992. About 3.81 cm of the original chloride-contaminated concrete was

milled off to the top layer of reinforcing steel and unsound areas were removed with a pneumatic

hammer. The entire deck surface was sandblasted to remove laitances prior to placement of the

overlay. 

Two corrosion-inhibitor treatment methods were used in rehabilitation of the deck. Cortec MCI

2000 (an organic amine) was used in span 1 and was added to the overlay concrete at a rate of

1.2 L/m3

. Span 2 was treated with DCI (calcium nitrite), which was added to the overlay

concrete at a rate of 19.96 L/m3

. In addition, span 2 received three spray-on applications of

Postrite (a 15-percent solution of calcium nitrite) prior to the placement of the DCI-treated

overlay. The application rate for Postrite was about 3.75 L/m3

. Span 3 was designated as the

control span and was overlaid with standard Minnesota Department of Transportation (MNDOT)

LSDC mix.

(a) (b)
5-2

5.2. Field Evaluation

Field evaluations were performed on the following dates:

First evaluation October 5-7, 1994 ~2.4 years after treatment

Second evaluation August 1-2, 1996 ~4.3 years after treatment

Third evaluation May 12-13, 1998 ~6.0 years after treatment

Some data collected in May 1992 (prior to the rehabilitation) and in May 1994 (about 2 years

after the inhibitor treatment) are also included in this report for comparison.

5.3. Test Results

The results of six types of data collection are presented below.

5.3.1. Visual Survey

The visual survey results (crack-length measurements) for all three evaluations are presented in

table 5-1.

During the first evaluation, the concrete surface of the right traffic and breakdown lanes

appeared to be sound. However, some longitudinal cracking was observed on the deck surface. 

Span 1 (Cortec 2000 treatment) exhibited larger cracks than span 2 (Postrite/DCI treatment) and

span 3 (control). The crack frequencies for spans 1, 2, and 3 were 0.265 m/m2, 0.004 m/m2, and

0.053 m/m2

, respectively. All the cracks appeared to be caused by drying shrinkage. It should

be mentioned that no cracking was observed in August 1992, about 3 months after placement of

the overlay. Crack surveys were not performed between August 1992 and October 1994.

During the second evaluation, a visual survey of the right traffic lanes and the breakdown lanes

was performed. Crack lengths in the right traffic lane were found to increase significantly since

the first evaluation in October 1994. The DCI-treated span (span 2) exhibited significantly less

cracking than the other two spans. Crack frequencies for the right lane of spans 1, 2, and 3 were

0.309 m/m2

, 0.018 m/m2, and 0.280 m/m2, respectively. Crack frequencies for the breakdown

lane of spans 1, 2, and 3 were 0.034 m/m2

, 0.020 m/m2, and 0.051 m/m2, respectively.

During the third evaluation, the right traffic and breakdown lanes were found to be in good

condition, with the exception of small areas that showed light scaling. A significant increase in

crack length was evident in the breakdown lane of span 1 and span 3. Overall, the DCI- treated

span exhibited less cracking than the other two spans, though there was an increase in the crack

frequency when compared to the second evaluation. Crack frequencies for the right traffic lane

were 0.309 m/m2, 0.069 m/m2, and 0.280 m/m2 for spans 1, 2, and 3, respectively, and for the

breakdown lane of spans 1, 2, and 3 were 0.131 m/m2, 0.024 m/m2, and 0.211 m/m2, respectively.
5-3

Table 5-1. Crack survey results.

Date Span Location Inhibitor

Treatment

Area

Surveyed,

m2

Total

Crack

Length, m

Crack

Frequency,

m/m2

Oct. 1994

1 Right lane Cortec 48.36 12.80 0.265

2 Right lane DCI 84.44 0.30 0.004

3 Right lane None 45.76 2.44 0.053

Aug. 1996

1

1

Right lane

Breakdown lane

Cortec

Cortec

48.36

44.36

14.94

 1.52

0.309

0.034

2

2

Right lane

Breakdown lane

DCI

DCI

84.44

77.38

 1.52

 1.52

0.018

0.020

3

3

Right lane

Breakdown lane

None

None

45.76

41.94

12.80

 2.13

0.280

0.051

May 1998

1

1

Right lane

Breakdown lane

Cortec

Cortec

48.36

44.36

14.94

 5.79

0.309

0.131

2

2

Right lane

Breakdown lane

DCI

DCI

84.44

77.38

 5.79

 1.83

0.069

0.024

3

3

Right lane

Breakdown lane

None

None

45.76

41.94

12.80

 8.84

0.280

0.211

5.3.2. Delamination Survey

No hollow-sounding areas were detected during any of the three evaluations.

5.3.3. Clear Concrete Cover Survey

The concrete cover depth survey results are shown in table 5-2. The mean cover depths for the

Cortec (span 1), Postrite/DCI (span 2), and control (span 3) locations were 7.16, 6.50, and 7.95

cm, respectively. The variability of cover depths was the least for the Postrite/DCI span, with a

coefficient of variation (CV) of 5.8 percent, and the greatest for the control span with a CV of

14.0 percent. The control span cover depth variability was considered to be typical.
5-4

Table 5-2. Cover survey results.

Date Span Inhibitor

Treatment

No. of

Measurement

s

Mean

Depth, cm

Standard

Deviation, cm

CV,%

Oct. 1994

1

2

3

Cortec

DCI

None

35

35

35

7.16

6.50

7.95

0.66

0.38

1.12

 9.2

 5.8

14.0

CV = Coefficient of variation

5.3.4. Corrosion Potential Survey

Corrosion potential measurements were conducted on a 0.61-m grid following ASTM C-876

during all three evaluations; the summary results are shown in table 5-3.

Table 5-3. TH-3 over Southview Boulevard bridge—corrosion potential summary

Date Span Inhibitor

Treatment No.**

Average

Potential

mV vs.

CSE

Standard

Deviation

% Potentials, mV vs. CSE***

<-200 -200 to -350 >-350

May

1992*

1

2

3

None

None

None

456

779

448

-145

-120

-137

77

71

75

91

97

93

9

3

7

0

0

0

Oct.

1994

1

2

3

Cortec

DCI

None

196

193

181

-142

 -89

-150

35

30

50

94

100 

88

6

0

12 

0

0

0

Aug.

1996

1

2

3

Cortec

DCI

None

245

369

223

-162

-132

-174

44

56

57

82

88

75

18 

12 

25 

0

0

0

May

1998

1

2

3

Cortec

DCI

None

244

413

215

-172

-147

-173

74

79

69

62

86

76

37 

10 

21 

1

4

3

* = Pretreatment data

** = Total number of measurements

*** millivolts measured against a copper-copper sulfate electrode
5-5

The corrosion potential data interpretation guidelines have been discussed previously. It can be

seen from Table 5-3 that the corrosion potentials were mostly in the passive range before the

rehabilitation. About 2 years after the rehabilitation (first evaluation), the corrosion potential

distribution was approximately the same. During the second evaluation, a shift was noticed in

the corrosion potential distribution toward the uncertain range for all three spans; however, no

active potentials were encountered. During the third evaluation, some active potentials were

found that amounted to 1 percent, 4 percent, and 3 percent for spans 1, 2, and 3, respectively. 

Overall, the corrosion activity on this structure can be categorized as low.

5.3.5. Corrosion Rate Survey

Corrosion rate tests were conducted during all three evaluations with an NBS-3LP corrosion rate

device and measurements were made at 32 locations (8 in span 1, 16 in span 2, and 8 in span 3). 

The results are shown in table 5-4 which also includes some data obtained in May 1992 before

rehabilitation. The guidelines for interpreting corrosion rate data obtained with the 3LP device

were discussed in an earlier section of this report.

The average corrosion rate in all three spans before rehabilitation was quite high (in the range of

5.70 to 7.27 μA/cm2

). The rates decreased significantly after about 2 years, as reflected by the

data collected during the first evaluation in October 1994. However, there was no significant

difference in the corrosion rates in the inhibitor-treated and untreated spans. Most corrosion rate

measurements obtained for spans 1 and 2 during the second evaluation were comparable to

measurements obtained during the first evaluation. The corrosion rate measurements obtained

for span 3 were suspect, probably due to a measurement error; thus, they are not reported here. 

Data obtained during the third evaluation showed an increase in the average rates for span 3

(control), while the average rates for spans 1 and 2 remained about the same.

The corrosion rate measurements may be considered as moderately high as per the interpretation

guidelines. However, they were not consistent with the largely passive corrosion potentials

measured on the deck surface and the low levels of chloride measured at the depth of the

reinforcing steel (see section below).

5.3.6. Chloride Ion Content Analysis

Powdered concrete samples were collected with a hammer drill from 15 different locations (5 on

each span) during the first evalutation. At four locations on each span, sampling was at the

approximate average steel depth, while at one location in each case, samples were collected at

nominal 1.27-cm increments down to the average steel depth. The powdered samples were

analyzed for total chloride ion content using the standard AASHTO T-260 procedure. The

results are shown in table 5-5. As mentioned earlier, the average cover depths for the Cortec

(span 1), DCI (span 2), and control (span 3) locations were 7.16, 6.50, and 7.95 cm, respectively.
5-6

Table 5-4. Corrosion rates.

Location x, y Coordinates,

m

Corrosion Rate, mA/m2

June 1992 Oct. 1994 Aug. 1996 May 1998

Span 1

(Cortec 2000)

0.92, 2.44

4.58, 5.49

2.75, 6.71

0.92, 9.76

6.41, 9.76

5.80, 14.03

2.14, 12.20

5.19, 12.20

Average

0.325

0.418

0.468

0.736

0.703

0.804

–

–

0.576

0.200

0.110

0.176

0.249

0.215

0.153

0.179

0.160

0.180

0.140

0.052

0.163

0.171

0.163

0.076

0.175

0.055

0.125

0.106

0.051

0.129

0.144

0.092

0.152

0.243

0.088

0.126

Span 2

(DCI)

0.92, 15.25

2.75, 17.08

4.27, 18.30

5.19, 18.91

1.53, 22.57

6.10, 22.57

3.97, 25.01

2.44, 27.45

4.27, 30.50

5.19, 30.50

6.10, 30.50

0.31, 30.50

2.14, 32.33

5.80, 33.55

3.97, 35.99

6.41, 27.45

Average

0.359

0.471

–

0.351

0.399

–

0.614

–

–

–

–

–

0.557

0.468

0.404

0.556

0.497

0.164

0.219

0.125

0.115

0.216

0.170

0.160

0.311

0.153

0.139

0.176

0.100

0.265

0.182

0.147

0.226

0.173

0.177

0.265

0.148

0.136

0.292

0.136

0.169

0.257

0.195

0.148

0.174

0.195

0.250

0.166

0.166

0.204

0.187

0.005

0.003

0.012

0.014

0.304

0.203

0.220

0.305

0.208

0.140

0.259

0.267

0.299

0.198

0.238

0.242

0.232

Span 3

(control)

0.92, 37.21

3.36, 39.04

4.27, 42.09

6.41, 43.92

3.36, 45.14

0.92, 45.75

4.27, 47.58

6.10, 47.58

Average

0.325

0.418

–

0.469

0.736

0.703

–

–

0.530

0.220

0.218

0.154

0.240

0.224

0.249

0.168

0.241

0.215

–

–

–

–

–

–

–

–

–

0.490

0.485

0.280

0.424

0.509

0.709

0.288

0.487

0.459

Notes: 

1 mA/m2 = 10.753 mA/ft2

(0,0) coordinate is at the southeast corner of the structure; x is measured in a westerly direction and y

is measured in a northerly direction
5-7

Table 5-5. TH-3 over Southview Boulevard bridge—chloride ion content.

Span No. Location

(x, y Coordinates, m)

Cl Sample

Depth, cm

Total Cl Ion

Content, ppm

1 (Cortec)

Right traffic lane (6.41, 9.76)

Breakdown lane (0.92, 2.44)

Right traffic lane (2.75, 8.54)

Right traffic lane (4.58, 5.49)

Right traffic lane (5.80, 14.03)

1.27

2.54

3.81

5.08

6.35

7.62

7.62

7.62

7.62

7.62

1573

 274

 61

 72

 276

 138

 481

 28

 49

 92

2 (DCI)

Right traffic lane (5.80, 33.55)

Right traffic lane (6.41, 27.45)

Right traffic lane (3.97, 35.99)

Breakdown lane (0.31, 30.50)

Breakdown lane (2.14, 32.33)

1.27

2.54

3.81

5.08

6.35

7.62

6.35

6.35

6.35

6.35

 558

 61

 79

 417

 350

 92

 87

 253

 3

 161

3 (control)

Right traffic lane (6.41, 43.92)

Right traffic lane (3.36, 39.04)

Right traffic lane (3.36, 45.14)

Breakdown lane (0.92, 37.21)

Breakdown lane (0.92, 45.75)

1.27

2.54

3.81

5.08

6.35

7.62

8.89

8.89

8.89

8.89

8.89

1197

 269

 74

 31

 69

 110

 41

 33

 28

 143

 59

Note:

The average chloride content at the average steel depth prior to rehabilitation was below the

threshold level of 260 ppm.
5-8

The average steel depths for spans 1 and 3 were approximately 7.62 cm; span 2 was

approximately 6.35 cm. Total chloride ion content at the average steel depth in span 1 (except

for one location) was below the minimum threshold value of the 260 ppm required to initiate

corrosion of steel embedded in concrete. A similar situation was evidenced in span 2. In span 3

(control), the chloride ion content was much below the threshold value. Limited chloride

analysis was also carried out during the third evaluation and showed the same trends. The

results are not reported here.

The chloride content at the average steel depth in the right traffic lane before rehabilitation of the

bridge deck in May-June 1992 was below the minimum threshold value of 260 ppm for all three

spans.

5.4. Conclusions

Cracking of the overlay was prevalent in all spans and increased with time. The span treated

with the Cortec inhibitor exhibited the highest crack density, followed by the control, and the

DCI-treated span exhibited the least amount of cracking. No delaminations were detected in any

evaluations.

The average corrosion rates were in a range that could result in damage in 2 to 10 years and any

corrosion would increase with time. The average corrosion rates in the inhibitor-treated spans

were higher than the control span. The corrosion rates were probably exaggerated due to deep

cover over the reinforcing steel.

The chloride ion content at the steel depth prior to the installation of the repairs was below the

threshold and the corrosivity of the environment was mild. It was difficult to judge the

performance of the inhibitors at this site. 
6-1

6.0. CONCLUSIONS

Based on the findings of the long-term evaluations, the following conclusions were reached:

1. In three out of the four structures evaluated in this study, the control areas and the treated

areas experienced shrinkage cracking.

2. Signs of ongoing corrosion in patched areas treated with corrosion inhibitors were noted

in three out of the four structures.

3. The corrosion inhibitors did not provide any protection against corrosion in the

environments in which they were evaluated.
7-1

7.0. REFERENCES

1. I.L. Qadi, B.D. Prowell, R.E. Weyers, T. Dutta, H. Gouro, and N. Berke. Concrete

Bridge Protection and Rehabilitation: Chemical and Physical Techniques, Corrosion

Inhibitors and Polymers, Publication No. SHRP-S-666, Strategic Highway Research

Program, National Research Council (NRC), Washington DC, 1993.

2. B.D. Prowell, R.E. Weyers, and I.L. Qadi. Concrete Bridge Protection and

Rehabilitation: Chemical and Physical Techniques, Field Validation, Publication No.

SHRP-S-658, SHRP, NRC, Washington DC, 1993.

3. Standard Method for Sampling and Testing for Chloride Ion in Concrete and Concrete

Raw Materials, T-260, American Association of State and Highway Transportation

Officials, Washington, DC, 1994.

4. Standard Test Methods for Half-Cell Potentials of Uncoated Reinforcing Steel in

Concrete: C-876, In Annual Book of ASTM Standards - Construction; American Society

for Testing and Materials, Philadelphia, PA. 1991.