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Publication Number: FHWA-HRT-07-043
Date: July 2007
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Multiple Corrosion Protection Systems for Reinforced Concrete Bridge Components

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FOREWORD

Eleven systems combining epoxy-coated reinforcement with another corrosion protection system are evaluated using the rapid macrocell, Southern Exposure, cracked beam, and linear polarization resistance tests. The systems include bars that are pretreated with zinc chromate to improve the adhesion between the epoxy and the reinforcing steel; two epoxies with improved adhesion to the reinforcing steel; one inorganic corrosion inhibitor, calcium nitrite; two organic corrosion inhibitors; an epoxy-coated bar with a primer containing microencapsulated calcium nitrite; the three epoxy-coated bars with improved adhesion combined with the corrosion inhibitor calcium nitrite; and multiple coated bars with an initial 50-micrometer (μm) (2-mil) coating of 98 percent zinc and 2 percent aluminum followed by a conventional epoxy-coating. The systems are compared with conventional uncoated reinforcement and conventional epoxycoated reinforcement. The results presented in this report represent the findings obtained during the first half of a 5-year study that includes longer-term ASTM G 109 and field tests.

Gary L. Henderson
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 and the State of Kansas assume no liability for its content or use thereof. This Report does not constitute a standard, specification, or regulation.

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

Quality Assurance Statement

The Federal Highway Administration (FHWA) provides high-quality information to serve Government, industry, and the public in a manner that promotes public understanding. Standards and policies are used to ensure and maximize the quality, objectivity, utility, and integrity of its information. FHWA periodically reviews quality issues and adjusts its programs and processes to ensure continuous quality improvement.

Technical Report Documentation Page

1. Report No.

    FHWA-HRT-07-043

2. Government Accession No.

3. Recipient’s Catalog No.

4. Title and Subtitle

    Multiple Corrosion Protection Systems for Reinforced Concrete Bridge Components

5. Report Date

    July 2007

6. Performing Organization Code

7.Author(s)

    David Darwin, JoAnn Browning, Carl E. Locke, Jr., and Trung V. Nguyen

8. Performing Organization Report No.

    SM Report No. 84

9. Performing Organization Name and Address

    University of Kansas Center for Research, Inc.
    2385 Irving Hill Road
    Lawrence, KS 66045-7563

10. Work Unit No.

11. Contract or Grant No.

    DTFH61-03-C-00131

12. Sponsoring Agency Name and Address

    Office of Federal Highway Administration
    6300 Georgetown Pike
    McLean, VA 22101-2296

13. Type of Report and Period Covered

    Interim Report
    September 2003–March 2006

14. Sponsoring Agency Code

15. Supplementary Notes

    Project Manager: Y. Paul Virmani, HRDI-10

16. Abstract

Eleven systems combining epoxy-coated reinforcement with another corrosion protection system are evaluated using the rapid macrocell, Southern Exposure, cracked beam, and linear polarization resistance tests. The systems include bars that are pretreated with zinc chromate to improve the adhesion between the epoxy and the reinforcing steel; two epoxies with improved adhesion to the reinforcing steel; one inorganic corrosion inhibitor, calcium nitrite; two organic corrosion inhibitors; an epoxy-coated bar with a primer containing microencapsulated calcium nitrite; the three epoxy-coated bars with improved adhesion combined with the corrosion inhibitor calcium nitrite; and multiple coated bars with an initial 50-μm (2-mil) coating of 98 percent zinc and 2 percent aluminum followed by a conventional epoxy-coating. The systems are compared with conventional uncoated reinforcement and conventional epoxy-coated reinforcement. The results presented in this report represent the findings obtained during the first half of a 5-year study that includes longer-term ASTM G 109 and field tests. In the short-term tests used to date, the epoxy-coatings evaluated provide superior corrosion protection to the reinforcing steel. The results also indicate that the bars will continue to perform well in the longer term, although the tests do not evaluate the effects of long-term reductions in the bond between the epoxy and the reinforcing steel. The corrosion rate on the exposed regions of damaged epoxy-coated reinforcement is somewhat higher than the average corrosion rate on the surface of uncoated reinforcement subjected to similar exposure conditions. The use of concrete with a reduced water-cement ratio improves the corrosion performance of both conventional and epoxy-coated reinforcement in uncracked concrete but has little effect in cracked concrete. Increased adhesion between the epoxy and reinforcing steel provides no significant improvement in the corrosion resistance of epoxy-coated reinforcement. It appears that corrosion inhibitors in concrete and the primer coating containing microencapsulated calcium nitrite improve the corrosion resistance of the epoxy-coated steel in uncracked concrete, but not in cracked concrete. The zinc coating on the multiple coated bars acts as a sacrificial barrier and provides some corrosion protection to the underlying steel in both uncracked and cracked concrete. The degree of protection, however, cannot be evaluated based on the results available to date.

17. Key Words

    adhesion, chlorides, concrete, corrosion, corrosion
    inhibitor, durability, epoxy-coated steel, zinc-coated
    steel

18. Distribution Statement
   No restrictions. This document is available to  the public through the National Technical Information Service, Springfield, VA 22161.

19. Security Classif. (of this report)

    Unclassified

20. Security Classif. (of this page)

    Unclassified

21. No. of Pages

    92

22. Price

Form DOT F 1700.7 (8-72) Reproduction of completed pages authorized.

Metric Conversion Chart


TABLE OF CONTENTS

 

1. INTRODUCTION

2. EXPERIMENTAL WORK
     CORROSION PROTECTION SYSTEMS
          Control Systems
          Epoxies With Increased Adhesion
          Corrosion Inhibitors
          Epoxies With Increased Adhesion Plus Ca(NO2)2
          Multiple Coatings
     PRETEST EVALUATION OF EPOXY-COATED BARS
          Evaluation of Coating Thickness and Holidays
          Cathodic Disbondment Tests
     CORROSION TEST PROCEDURES
          Rapid Macrocell Tests
          Bench-Scale Tests
          Linear Polarization Resistance Test
     TEST PROGRAM
          Rapid Macrocell Test Program
          Bench-Scale Test Program
          Bench-Scale Test Program
          Linear Polarization Resistance Test Program

3. TEST RESULTS
     RAPID MACROCELL TESTS
          Bare Bar Tests
          Mortar-Wrapped Bar Tests
     BENCH-SCALE TESTS
          Southern Exposure Tests
          Cracked Beam Tests
     LINEAR POLARIZATION RESISTANCE TESTS

4. EVALUATION

5. INTERIM CONCLUSIONS

ACKNOWLEDGEMENTS

REFERENCES


LIST OF FIGURES

Figure 1. Diagram. Schematic of macrocell test with bare bar specimens

Figure 2. Diagram. Schematic of macrocell test with mortar-clad specimens

Figure 3. Diagram. Mortar-wrapped specimen containing a conventional reinforcing bar

Figure 4. Diagram. Rapid macrocell specimens: (a) bare bar and (b) mortar-wrapped specimens with cap to protect the exposed end of epoxy-coated bars

Figure 5. Diagram. Southern Exposure test specimen

Figure 6. Diagram. Cracked beam test specimen

Figure 7a. Graph. Macrocell test—average corrosion rate. Bare conventional, epoxy-coated, increased adhesion ECR, and multiple coated steel in simulated pore solution with 1.6 m ion NaCl

Figure 7b. Graph. Macrocell test—average corrosion rate. Bare conventional, epoxy-coated, increased adhesion ECR, and multiple coated steel in simulated pore solution with 1.6 m ion NaCl

Figure 8a. Graph. Macrocell test—average corrosion loss. Bare conventional, epoxy-coated, increased adhesion ECR, and multiple coated steel in simulated pore solution with 1.6 m ion NaCl

Figure 8b. Graph. Macrocell test—average corrosion loss based on area exposed at holes through coating. Bare epoxy-coated, increased adhesion ECR, and multiple coated steel in simulated pore solution with 1.6 m ion NaCl

Figure 9a. Graph. Macrocell test—average corrosion potential, anode. Bare conventional, epoxy-coated, increased adhesion ECR, and multiple coated steel in simulated pore solution with 1.6 m ion NaCl

Figure 9b. Graph. Macrocell test—average corrosion potential, cathode. Bare conventional, epoxy-coated, increased adhesion ECR, and multiple coated steel in simulated pore solution with 1.6 m ion NaCl

Figure 10. Photo. Bare conventional anode bar, at 15 weeks, showing corrosion products that formed below the surface of the solution

Figure 11. Photo. Bare ECR anode bar, at 15 weeks, showing corrosion products that formed at holes though the epoxy

Figure 12. Photo. Bare MC anode bar with only epoxy penetrated, at 15 weeks, showing corrosion products that formed at holes though the epoxy

Figure 13a. Graph. Macrocell test—average corrosion rate. Mortar-wrapped conventional, epoxy-coated, ECR with calcium nitrite primer, and multiple coated steel in simulated pore solution with 1.6 m ion NaCl

Figure 13b. Graph. Macrocell test—average corrosion rate based on area exposed at holes through coating. Mortar-wrapped conventional epoxy-coated, ECR with calcium nitrite primer, and multiple coated steel in simulated pore solution with 1.6 m ion NaCl

Figure 14a. Graph. Macrocell test—average corrosion loss. Mortar-wrapped conventional, epoxy-coated, ECR with calcium nitrite, and multiple coated steel in simulated pore solution with 1.6 m ion NaCl

Figure 14b. Graph. Macrocell test—average corrosion loss based on area exposed at holes through coating. Mortar-wrapped conventional, epoxy-coated, ECR with calcium nitrite, and multiple coated steel in simulated pore solution with 1.6 m ion NaCl

Figure 15a. Graph. Macrocell test—average corrosion potential, anode. Mortar-wrapped conventional, epoxy-coated reinforcement, epoxy-coated reinforcement with increased adhesion, epoxy-coated reinforcement cast with corrosion inhibitor, and ECR with calcium nitrite in simulated pore solution with 1.6 m ion NaCl

Figure 15b. Graph. Macrocell test—average corrosion potential, cathode. Mortar-wrapped conventional, epoxy-coated reinforcement, epoxy-coated reinforcement with increased adhesion, epoxy-coated reinforcement cast with corrosion inhibitor, and ECR with calcium nitrite in simulated pore solution with 1.6 m ion NaCl

Figure 16a. Graph. Macrocell test—average corrosion potential, anode. Mortar-wrapped multiple coated steel in simulated pore solution with 1.6 m ion NaCl

Figure 16b. Graph. Macrocell test—average corrosion potential, cathode. Mortar-wrapped multiple coated steel in simulated pore solution with 1.6 m ion NaCl

Figure 17. Photo. Conventional anode bar after removal of mortar, at 15 weeks

Figure 18. Graph. Southern Exposure test—average corrosion rates based on the total area for conventional and epoxy-coated reinforcement, w/c = 0.35 or 0.45, ponded with 15 percent NaCl solution. Bars with coatings contain four or 10 holes

Figure 19a. Graph. Southern Exposure test—average corrosion loss based on total area for conventional and epoxy-coated reinforcement, w/c = 0.35 or 0.45, ponded with 15 percent NaCl solution. Bars with coatings contain four or 10 holes

Figure 19b. Graph. Southern Exposure test—average corrosion loss based on area exposed at holes through coating for epoxy-coated reinforcement, w/c = 0.35 or 0.45, ponded with 15 percent NaCl solution. Bars with coatings contain four or 10 holes

Figure 20a. Graph. Southern Exposure test—corrosion potential, top mat, for conventional and epoxy-coated reinforcement, w/c = 0.35 or 0.45, ponded with 15 percent NaCl solution. Bars with coatings contain four or 10 holes

Figure 20b. Graph. Southern Exposure test—corrosion potential, bottom mat, for conventional and epoxy-coated reinforcement, w/c = 0.35 or 0.45, ponded with 15 percent NaCl solution. Bars with coatings contain four or 10 holes

Figure 21a. Graph. Southern Exposure test—corrosion losses based on area exposed at holes through coating for conventional epoxy-coated and increased adhesion epoxycoated reinforcement, w/c = 0.45, ponded with 15 percent NaCl solution. Bars with coatings contain four holes

Figure 21b. Graph. Southern Exposure test—corrosion losses based on area exposed at holes through coating for conventional epoxy-coated and increased adhesion epoxy-coated reinforcement, w/c = 0.45, ponded with 15 percent NaCl solution. Bars with coatings contain 10 holes

Figure 22. Graph. Southern Exposure test—corrosion potential, top mat, for conventional epoxy-coated and increased adhesion epoxy-coated reinforcement, w/c = 0.45, ponded with 15 percent NaCl solution. Bars with coatings contain four holes

Figure 23a. Graph. Southern Exposure test—corrosion losses based on area exposed at holes through coating for conventional epoxy-coated reinforcement and with inhibitors, w/c = 0.45, ponded with 15 percent NaCl solution. Bars with coatings contain four holes

Figure 23b. Graph. Southern Exposure test—corrosion losses based on area exposed at holes through coating for conventional epoxy-coated reinforcement and with inhibitors, w/c = 0.45, ponded with 15 percent NaCl solution. Bars with coatings contain 10 holes

Figure 23c. Graph. Southern Exposure test—corrosion losses based on area exposed at holes through coating for conventional epoxy-coated reinforcement and with inhibitors, w/c = 0.35, ponded with 15 percent NaCl solution. Bars with coatings contain 10 holes

Figure 24a. Graph. Southern Exposure test—corrosion potential, top mat, for conventional epoxy-coated reinforcement with and without corrosion inhibitor, w/c = 0.45, ponded with 15 percent NaCl solution. Bars with coatings contain four holes

Figure 24b. Graph. Southern Exposure test—corrosion potential, top mat, for conventional epoxy-coated reinforcement with and without corrosion inhibitor, w/c = 0.45, ponded with 15 percent NaCl solution. Bars with coatings contain 10 holes

Figure 24c. Graph. Southern Exposure test—corrosion potential, top mat, for conventional epoxy-coated reinforcement with and without corrosion inhibitor, w/c = 0.35, ponded with 15 percent NaCl solution. Bars with coatings contain 10 holes

Figure 25. Graph. Southern Exposure test—average corrosion losses based on area exposed at holes through coating for conventional epoxy-coated and epoxy-coated rebar with and without increased adhesion and DCI-S corrosion inhibitor, w/c = 0.45, ponded with 15 percent NaCl solution. Bars with coatings contain four drilled holes

Figure 26. Graph. Southern Exposure test—corrosion potential, top mat, for conventional epoxy-coated reinforcement with and without DCI-S corrosion inhibitor and increased epoxy-coated reinforcement with DCI-S corrosion inhibitor, w/c = 0.45, ponded with 15 percent NaCl solution. Bars with coatings contain four holes

Figure 27a. Graph. Southern Exposure test—corrosion loss based on area exposed at holes through coating for conventional epoxy-coated and multiple-coated reinforcement, w/c = 0.45, ponded with 15 percent NaCl solution. Bars with coatings contain four holes

Figure 27b. Graph. Southern Exposure test—corrosion loss based on area exposed at holes through coating for conventional epoxy-coated and multiple-coated reinforcement, w/c = 0.45, ponded with 15 percent NaCl solution. Bars with coatings contain 10 holes

Figure 28a. Graph. Southern Exposure test—corrosion potential, top mat, for conventional epoxy-coated and multiple-coated reinforcement, w/c = 0.45, ponded with 15 percent NaCl solution. Bars with coatings contain four holes

Figure 28b. Graph. Southern Exposure test—corrosion potential, bottom mat, for conventional epoxy-coated and multiple-coated reinforcement, w/c = 0.45, ponded with 15 percent NaCl solution. Bars with coatings contain four holes

Figure 29a. Graph. Southern Exposure test—corrosion potential, top mat, for conventional epoxy-coated and multiple-coated reinforcement, w/c = 0.45, ponded with 15 percent NaCl solution. Bars with coatings contain 10 holes

Figure 29b. Graph. Southern Exposure test—corrosion potential, bottom mat, for conventional epoxy-coated and multiple-coated reinforcement, w/c = 0.45, ponded with 15 percent NaCl solution. Bars with coatings contain 10 holes

Figure 30. Graph. Cracked beam test—average corrosion rates based on the total area of control specimens for conventional and epoxy-coated reinforcement, w/c = 0.35 or 0.45, ponded with 15 percent NaCl solution. Bars with coatings contain four or 10 holes

Figure 31a. Graph. Cracked Beam test—average corrosion loss based on total area of control specimens for conventional and epoxy-coated reinforcement, w/c = 0.35 or 0.45, ponded with 15 percent NaCl solution. Bars with coatings contain four or 10 holes

Figure 31b. Graph. Cracked Beam test—average corrosion loss based on area exposed at holes through coating for epoxy-coated reinforcement, w/c = 0.35 or 0.45, ponded with 15 percent NaCl solution. Bars with coatings contain four or 10 holes

Figure 32a. Graph. Cracked Beam test—average corrosion loss based on area exposed at holes through coating for conventional epoxy-coated and increased adhesion epoxy-coated reinforcement, w/c = 0.45, ponded with 15 percent NaCl solution. Bars with coatings contain four holes

Figure 32b. Graph. Cracked Beam test—average corrosion loss based on area exposed at holes through coating for conventional epoxy-coated and increased adhesion epoxy-coated reinforcement, w/c = 0.45, ponded with 15 percent NaCl solution. Bars with coatings contain 10 holes

Figure 33a. Graph. Cracked Beam test—average corrosion loss based on area exposed at holes through coating for conventional epoxy-coated reinforcement with and without corrosion inhibitor, w/c = 0.45, ponded with 15 percent NaCl solution. Bars with coatings contain four holes

Figure 33b. Graph. Cracked Beam test—average corrosion loss based on area exposed at holes through coating for conventional epoxy-coated reinforcement with and without corrosion inhibitor, w/c = 0.45, ponded with 15 percent NaCl solution. Bars with coatings contain 10 holes

Figure 33c. Graph. Cracked Beam test—average corrosion loss based on area exposed at holes through coating for conventional epoxy-coated reinforcement with and without corrosion inhibitor, w/c = 0.35, ponded with 15 percent NaCl solution. Bars with coatings contain 10 holes

Figure 34a. Graph. Cracked Beam test—average corrosion loss based on area exposed at holes through coating for conventional epoxy-coated and multiple-coated reinforcement, w/c = 0.45, ponded with 15 percent NaCl solution. Bars with coatings contain four holes

Figure 34b. Graph. Cracked Beam test—average corrosion loss based on area exposed at holes through coating for conventional epoxy-coated and multiple-coated reinforcement, w/c = 0.45, ponded with 15 percent NaCl solution. Bars with coatings contain 10 holes

Figure 35a. Graph. Cracked beam test—corrosion potential, top mat, for conventional epoxy-coated and multiple-coated reinforcement, w/c = 0.45, ponded with 15 percent NaCl solution. Bars with coatings contain four holes

Figure 35b. Graph. Cracked beam test—corrosion potential, bottom mat, for conventional epoxy-coated and multiple-coated reinforcement, w/c = 0.45, ponded with 15 percent NaCl solution. Bars with coatings contain four holes

Figure 36a. Graph. Cracked beam test—corrosion potential, top mat, for conventional epoxy-coated and multiple-coated reinforcement, w/c = 0.45, ponded with 15 percent NaCl solution. Bars with coatings contain 10 holes

Figure 36b. Graph. Cracked beam test—corrosion potential, bottom mat, for conventional epoxy-coated and multiple-coated reinforcement, w/c = 0.45, ponded with 15 percent NaCl solution. Bars with coatings contain 10 holes

Figure 37a. Graph. Linear polarization test results for Southern Exposure specimens—average corrosion loss based on total area for conventional reinforcement and conventional epoxy-coated reinforcement, w/c = 0.35 or 0.45, ponded with 15 percent NaCl solution. Bars with coatings contain four or 10 holes

Figure 37b. Graph. Linear polarization test results for Southern Exposure specimens—average corrosion loss based on total area for conventional reinforcement and conventional epoxy-coated reinforcement, w/c = 0.35 or 0.45, ponded with 15 percent NaCl solution. Bars with coatings contain four or 10 holes

Figure 38a. Graph. Southern Exposure specimens—microcell versus macrocell corrosion loss based on total area for conventional reinforcement and area exposed at holes through coating for epoxy-coated reinforcement, w/c = 0.45, ponded with 15 percent NaCl solution. Results for epoxy-coated bar specimens based on average results for bars with coatings containing four and 10 holes

Figure 38b. Graph. Southern Exposure specimens—microcell versus macrocell corrosion loss based on total area for conventional reinforcement and area exposed at holes through coating for epoxy-coated reinforcement, w/c = 0.45, ponded with 15 percent NaCl solution. Results for epoxy-coated bar specimens based on average results for bars with coatings containing four and 10 holes

Figure 39. Graph. Cracked beam specimens—microcell versus macrocell corrosion loss based on total area for conventional reinforcement and area exposed at holes through coating for epoxy-coated reinforcement, w/c = 0.45 or 0.35, ponded with 15 percent NaCl solution. Results for epoxy-coated bar specimens with w/c = 0.45 based on average results for bars with coatings containing four and 10 holes

LIST OF TABLES

Table 1. Systems under study

Table 2. Chemical analysis of steel, percent

Table 3. Coating thickness

Table 4. Cathodic disbondment results

Table 5. Concrete mixtures

Table 6. Test program—number of specimens

Table 7a. Corrosion loss at 15 weeks (in μm) for rapid macrocell specimens based on total area

Table 7b. Corrosion loss at 15 weeks (in μm) for rapid macrocell specimens based on area exposed at holes through coating

Table 8a. Corrosion loss at 56 weeks (in μm) for Southern Exposure specimens based on total area

Table 8b. Corrosion loss at 56 weeks (in μm) for Southern Exposure specimens based on area exposed at holes through coating

Table 9a. Corrosion loss at 56 weeks (in μm) for cracked beam specimens based on total area

Table 9b. Corrosion loss at 56 weeks (in μm) for cracked beam specimens based on area exposed at holes through coating

Table 10. Microcell and macrocell corrosion loss at 56 weeks (in μm) for Southern Exposure and cracked beam specimens based on total area and area exposed at holes through coating

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