Structure Research > Structure Publications > FHWA-HRT-09-020

Corrosion Resistant Alloys for Reinforced Concrete, FHWA-HRT-09-020

April 2009

FOREWORD

Initial cost considerations have historically precluded widespread utilization of high performance (corrosion resistant) reinforcements, such as stainless steel in bridge construction. However, because of concerns regarding long-term serviceability of epoxy-coated reinforcing steel in northern and coastal bridge decks and substructures, advent of life cycle cost analysis as a project planning tool, and requirements that major bridge structures have a 75-100-year design life, the competitiveness of such steels has increased that enhanced attention has focused in recent years upon these materials.

This investigation was initiated to evaluate the corrosion resistance of various types of corrosion resistant reinforcement, including new products that are becoming available in bridge structures that are exposed to chlorides. Both long-term (4+ years) test yard exposures and accelerated laboratory experiments in simulated concrete pore waters are being performed. The ultimate objective was to, first, evaluate the corrosion properties and service life of the different candidate materials and, second, develop tools whereby long-term performance in actual structures can be projected from a short-term accelerated test. An interim report provided results from the initial three years of this overall 6-year program, and this report serves as a second interim report.

Cheryl Richter
Acting 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 Florida 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 Florida 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.
HRT-09-020

2. Government Accession No.

3. Recipient's Catalog No.

4. Title and Subtitle

Corrosion Resistant Alloys for Reinforced Concrete

5. Report Date

April 2009

6. Performing Organization Code

FAU-OE-CMM-0901

7. Author(s)

William H. Hartt,* Rodney G. Powers,** Francisco Presuel Marino,* Mario Paredes,** Ronald Simmons,** Hui Yu,* Rodrigo Himiob,*
Y. Paul Virmani*** (See boxes 9 and 12)

8. Performing Organization Report No.

9. Performing Organization Name and Address

*Florida Atlantic University-Sea Tech Campus, 101 North Beach
Road, Dania Beach, FL 33004

**Florida Department of Transportation-State Materials Office,
5007 NE 39th Street, Gainesville, FL 32609

***Office of Infrastructure Research and Development

Federal Highway Administration
6300 Georgetown Pike
McLean, VA 22012

10. Work Unit No. (TRAIS)

11. Contract or Grant No.

12. Sponsoring Agency Name and Address

Office of Infrastructure Research and Development
Federal Highway Administration
6300 Georgetown Pike
McLean, VA 22012

13. Type of Report and Period Covered

Interim Report

14. Sponsoring Agency Code

15. Supplementary Notes

Contracting Officer's Technical Representative (COTR): Y.P. Virmani, HRDI-10

16. Abstract

Deterioration of concrete bridges because of reinforcing steel corrosion has been recognized for 4-plus decades as a major technical and economic challenge for the United States. As an option for addressing this problem, renewed interest has focused on corrosion resistant reinforcements, stainless steels in particular. The present research study was performed jointly by Atlantic University and the Florida Department of Transportation to evaluate reinforcements of this type. These included solid stainless steels 3Cr12 (UNS-S41003), 2101LDX (ASTM A955-98), 2304 (UNS-S31803), 2205 (UNS 31803), two 316L (UNS S31603) alloys, two 316 stainless steel clad black bar products, and ASTM A1035 commonly known as MMFX 2. Black bar (ASTM A615) reinforcement provided a baseline for comparison purposes. Results from short-term tests and preliminary results from long-term exposure of reinforced concrete slabs were presented in the first interim report for this project. This second interim report provides longer-term data and analyses of chloride exposures that involved four different types of reinforced concrete specimens, two of which were intended to simulate northern bridge decks exposed to deicing salts and the remaining two to marine substructure elements. Three different concrete mix designs were employed, and specimen types included combinations with a (1) simulated concrete crack, (2) bent top bar, (3) corrosion resistant upper bar(s) and black steel lower bars, and (4) intentional clad defects such that the carbon steel substrate was exposed. Cyclic wet-dry ponding with a sodium chloride (NaCl) solution was employed in the case of specimens intended to simulate northern bridge decks, and continuous partial submergence in either a NaCl solution or at a coastal marine site in Florida was used for specimens intended to represent a coastal bridge substructure. The exposures were for periods in excess of 4 years. The candidate alloys were ranked according to performance, and an analysis is reported that projects performance in actual concrete structures.

17. Key Word

Reinforced Concrete, Bridges, Corrosion Resistance, Corrosion Testing, High Performance Reinforcement, Stainless Steel, MMFX-2

18. Distribution Statement

No restrictions. This document is available to the public through NTIS, Springfield, VA 22161

19. Security Classif. (of this report)

Unclassified

20. Security Classif. (of this page)

Unclassified

21. No. of Pages
146

22. Price

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

SI (Modern Metric) Conversion Factors

1.0 INTRODUCTION

2.0 Project Objective

3.0 MATERIALS AND EXPERIMENTAL PROCEDURES

4.0 RESULTS AND DISCUSSION

5.0 CONCLUSIONS

REFERENCES

LIST OF FIGURES

Figure 1. Photo. A cracked and spalled marine bridge piling

Figure 2. Graph. Schematic illustration of the various steps in deterioration of reinforced concrete due to chloride-induced corrosion

Figure 3. Chart. Representation of the sequential steps involved in the design process

Figure 4. Chart. Schematic representation of benefits that can be derived from CRR

Figure 5. Chart. Standard SDS specimens

Figure 6. Chart. Example nomenclature for standard specimens

Figure 7. Chart. Example nomenclature for non-standard specimens

Figure 8. Chart. Schematic illustration of the CREV type simulated deck slab specimens

Figure 9. Photo. View of a mold for a CCRV-SMI specimen prior to concrete pouring

Figure 10. Photo. Two SDS specimens under exposure

Figure 11. Photo. SDS specimens under exposure in the outdoor test yard

Figure 12. Chart. Geometry of the macrocell slab type specimen with both bent and straight bars

Figure 13. Photo. Three MS specimens under exposure

Figure 14. Photo. MS slab specimens under exposure

Figure 15. Chart. 3BTC specimen for each of the three bar configurations

Figure 16. Photo. Type 304 rebars of the bent configuration in a mold prior to concrete placement

Figure 17. Photo. 3BTC specimen

Figure 18. Photo. 3BTC specimens under exposure

Figure 19. Chart. Geometry of the field column type specimen

Figure 20. Photo. Field column specimens under exposure at the Intracoastal Waterway site in Crescent Beach, FL

Figure 21. Chart. Concrete sectioning for SDS specimens

Figure 22. Chart. Concrete sectioning for 3BTC specimens

Figure 23. Chart. SDS specimen milling along rebar trace to acquire powdered concrete for chloride analysis

Figure 24. Graph. Potential versus time for specimens reinforced with MMFX-2 steel indicating times that individual bars became active and were isolated (L—left bar; C—center bar; R—right bar)

Figure 25. Graph. Macrocell current versus time for specimens reinforced with MMFX-2 steel indicating times that individual bars became active and were isolated (L—left bar; C—center bar; R—right bar)

Figure 26. Graph. Weibull cumulative distribution plot of T_i for the four indicated reinforcements

Figure 27. Graph. Weibull cumulative distribution plot of T_i for STD and USDB MMFX-2 reinforcements

Figure 28. Graph. Weibull cumulative distribution plot of T_i treating all STD and USDB-MMFX-2 reinforced specimens as a single population

Figure 29. Graph. Macrocell current history for 316 reinforced slabs with BB lower steel

Figure 30. Graph. Current-time history for SDS-SMI specimens that initiated corrosion

Figure 31. Graph. Potential and macrocell current results for MS-STD1-BB specimens

Figure 32. Graph. Potential and macrocell current results for MS-STD1-3Cr12 specimens

Figure 33. Graph. Potential and macrocell current results for MS-STD1-MMFX-2 specimens

Figure 34. Graph. Potential and macrocell curent results for MS-STD-1-2101 specimens

Figure 35. Graph. Cumulative probability plot of T_i for STD1-MS specimens with improved performance reinforcements

Figure 36. Graph. Weibull CDF plot of T_i for MS-STD1, -BCAT, -BENT, -BNTB, -UBDB, and -USDB specimens

Figure 37. Graph. Potential versus time for STD2 black bar MS specimens

Figure 38. Graph. Macrocell versus time for STD2 black bar MS specimens

Figure 39. Graph. Potential versus time for STD2 3Cr12 MS specimens

Figure 40. Graph. Macrocell current versus time for STD2 3Cr12 MS specimens

Figure 41. Graph. Potential and macrocell current versus time for STD2 MMFX-2 MS specimens

Figure 42. Graph. Normal CDF plot of T_i for MS-STD2 specimens that exhibited a well-defined corrosion initiation

Figure 43. Chart. T_i for BB and an improved performance reinforcement in STD1 and STD2 concretes

Figure 44. Graph. Potential and macrocell current history for MS-STD1-316.16 specimens

Figure 45. Graph. Potential and macrocell current history for MS-STD1-316.18 specimens

Figure 46. Graph. Potential and macrocell current history for MS-STD1-304 specimens

Figure 47. Graph. Potential and macrocell current history for MS-STD1-STAX specimens

Figure 48. Graph. Potential and macrocell current history for MS-STD1-SMI specimens

Figure 49. Graph. Potential and macrocell current history for MS-CCNB-316.16 specimens

Figure 50. Graph. Potential and macrocell current history for MS-CCNB-304 specimens

Figure 51. Graph. Potential and macrocell current history for MS-CSDB-SMI specimens

Figure 52. Graph. Potential and macrocell current history for MS-USDB-SMI specimens

Figure 53. Graph. Potential and macrocell current between indicated bars for 3BCT-BB specimen A

Figure 54. Graph. Potential and macrocell current between indicated bars for 3BCT-BB specimen B

Figure 55. Graph. Potential and macrocell current between indicated bars for 3BCT-BB specimen D

Figure 56. Graph. Potential and macrocell current between indicated bars for 3BCT-BENT-3Cr12-C

Figure 57. Graph. Cumulative probability plot of T_i for 3BTC-STD2 specimens for each reinforcement

Figure 58. Graph. Cumulative probability plot of T_i for 3BTC-STD3 specimens with each reinforcement

Figure 59. Graph. Cumulative probability plot of T_i for 3BTC-3Cr12 specimens

Figure 60. Graph. Cumulative probability plot of T_i for 3BTC-MMFX-2 specimens

Figure 61. Graph. Cumulative probability plot of T_i for 3BTC-2101 specimens

Figure 62. Graph. Potential and macrocell current versus time for 3BTC-SMI-specimen B in STD3 concrete

Figure 63. Graph. Potential and macrocell current versus time for 3BTC-316.16-ELEV specimen A

Figure 64. Graph. Potential versus exposure time plot for field columns with BB reinforcement

Figure 65. Graph. Potential versus exposure time plot for field columns with 3Cr12 reinforcement

Figure 66. Graph. Potential versus exposure time plot for field columns with MMFX-2 reinforcement

Figure 67. Graph. Potential versus exposure time plot for field column with 2101 reinforcement

Figure 68. Graph. Potential versus exposure time plot for field columns with 316.16 reinforcement

Figure 69. Graph. Potential versus exposure time plot for field columns with 304 reinforcement

Figure 70. Graph. Potential versus exposure time plot for field columns with SMI reinforcement

Figure 71. Graph. Polarization resistance versus exposure time plot for field columns with improved performance reinforcements

Figure 72. Graph. Polarization resistance versus exposure time plot for field columns with high alloy reinforcements

Figure 73. Graph. Plot of polarization resistance versus potential for field columns with improved performance reinforcements

Figure 74. Graph. Plot of polarization resistance versus potential for field columns with high alloy reinforcements

Figure 75. Photo. Cracking on a BB reinforced field column after 735 days of exposure

Figure 76. Photo. Cracking on a 2101 reinforced field column after 735 days of exposure

Figure 77. Graph. Chloride concentrations as a function of depth into concrete as determined from cores taken from the indicated specimens

Figure 78. Graph. Chloride concentrations determined from a core and millings for specimen 5-STD-1-3Cr12-2

Figure 79. Graph. Chloride concentrations determined from a core and millings for MMFX-2 reinforced specimens

Figure 80. Graph. Chloride concentrations determined from a core and millings for 2101 reinforced specimens

Figure 81. Graph. Weibull cumulative distribution of C_T in units of kg Cl- per m³ of concrete

Figure 82. Graph. Weibull cumulative distribution of C_T in units of wt percent Cl- referenced to cement

Figure 83. Graph. Previously reported chloride threshold concentrations as determined from aqueous solution potentiostatic tests

Figure 84. Graph. C_T determined from accelerated aqueous solution testing versus C_T from SDS concrete specimens

Figure 85. Graph. C_T determined from accelerated aqueous solution testing versus T_i for STD2-MS concrete specimens

Figure 86. Photo. Upper R bar trace of dissected specimen 5-STD1-BB-1 showing localized corrosion products (circled)

Figure 87. Photo. Upper L bar trace of dissected specimen 5-STD1-BB-1 showing corrosion products

Figure 88. Photo. Specimen 2-BCAT-316-1 prior to dissection (red markings identify specimen for removal)

Figure 89. Photo. Top R bar and bar trace of specimen 2-BCAT-316-1 subsequent to dissection

Figure 90. Photo. Lower L BB and bar trace of specimen 2-BCAT-316-1 subsequent to dissection

Figure 91. Photo. Specimen 2-CCNB-316-2 prior to dissection (red markings identify specimen for removal)

Figure 92. Photo. Top C bar and bar trace of specimen 2-CCNB-316-2 subsequent to dissection

Figure 93. Photo. Lower R bar and bar trace of specimen 2-CCNB-316-2 subsequent to dissection

Figure 94. Photo. Top L bar and bar trace of specimen 4-BCCD-SMI-1 subsequent to dissection

Figure 95. Photo. Lower R bar and bar trace of specimen 4-BCCD-SMI-1 subsequent to dissection

Figure 96. Photo. Top C bar and bar trace of specimen 4-CSDB-SMI-1 subsequent to dissection

Figure 97. Photo. Top R bar and bar trace of specimen 4-CSDB-SMI-1 subsequent to dissection

Figure 98. Photo. Top L bar and bar trace of specimen 4-CSDB-SMI-1 subsequent to dissection

Figure 99. Photo. Specimen 6-BCAT-304-2 prior to dissection

Figure 100. Photo. Top C bar and bar trace of specimen 6-BCAT-304-2 subsequent to dissection

Figure 101. Photo. Lower right BB and bar trace of specimen 6-BCAT-304-2 subsequent to dissection

Figure 102. Photo. Top C bar and bar trace of specimen 6-CCNB-304-1 subsequent to dissection

Figure 103. Photo. Lower left BB and bar trace of specimen 6-CCNB-304-1 subsequent to dissection

Figure 104. Photo. Top L bar pair and bar pair trace of specimen 6-CVNC-SMI-1 subsequent to dissection

Figure 105. Photo. Top bar and bar trace for specimen MS-MMFX-2-A

Figure 106. Photo. Top bar and bar trace for specimen MS-MMFX-2-B

Figure 107. Photo. Top bar and bar trace for specimen MS-MMFX-2-C

Figure 108. Photo. Top bent bar trace in concrete for specimen MS-CBDB-MMFX-2-A

Figure 109. Photo. Top bent bar from specimen MS-CBDB-MMFX-2-C after removal

Figure 110. Photo. Top bent bar from specimen MS-BTNB-316-C after removal

Figure 111. Photo. Localized corrosion on the top bent bar from specimen MS-CBNB-316-B

Figure 112. Photo. Corrosion at an intentional clad defect on the top bent bar from specimen MS-CBDB-SMI-B

Figure 113. Photo. Corrosion at a second intentional clad defect on the top bent bar from specimen MS-CBDB-SMI-B

Figure 114. Photo. Specimen 3BTC-STD2-BB-B after sectioning and opening along the two longer bars

Figure 115. Photo. Specimen 3BTC-STD2-2101-C after sectioning and opening along the two longer bars

Figure 116. Graph. Comparison of T_i at 2 percent to 20 percent activation for BB and an improved performance bar under conditions relevant to actual structures

LIST OF TABLES

Table 1. Listing of reinforcements that were investigated

Table 2. Composition of the reinforcements

Table 3. Concrete batch mix design

Table 4. Listing of the various specimen types, variables, and the nomenclature for each

Table 5. Listing of SDS specimens in lots 4-6

Table 6. Listing of specimens reinforced with 316.18 and 3Cr12

Table 7. Listing of specimens with 2101 rebar

Table 8. Listing of specimens reinforced with MMFX-2

Table 9. Listing of specimens reinforced with Stelax

Table 10. Listing of specimens reinforced with SMI

Table 11. Listing of specimens reinforced with black bar

Table 12. T_i data for SDS/STD1 specimens with improved performance reinforcements (see table 4 for specimen designation nomenclature)

Table 13. Listing of T_i for improved performance reinforcements and T_i ratio to BB for SDS-STD 1 specimens at 2 percent, 10 percent, and 20 percent active

Table 14. Listing of T_i for improved performance reinforcements and T_i ratio to BB for SDS-STD 1 specimens at 2 percent, 10 percent, and 20 percent active based on all MMFX-2 specimens

Table 15. Listing of exposure times and macrocell current data for Type 316SS SDS reinforced slabs

Table 16. Listing of exposure times and macrocell current data for Type 304SS reinforced slabs

Table 17. Corrosion activity for Stelax reinforced SDS specimens

Table 18. Listing of SMI reinforced SDS specimens and macrocell current results

Table 19. Results for SMI reinforced SDS specimens that exhibited a defined T_i followed by measureable macrocell corrosion

Table 20. Ratio of T_i for CRR that did not initiate corrosion to the mean T_i for BB specimens

Table 21. Listing of T_i values for MS-STD1 specimens with improved performance reinforcements

Table 22. Listing of T_i values (days) for MS specimens with improved performance reinforcements other than STD

Table 23. Listing of T_i values for MS-STD2 specimens with improved performance reinforcements

Table 24. Listing of T_i (alloy)/T_i (BB) for STD2-MS-MMFX-2 and -2101 reinforced specimens

Table 25. Listing of T_i for STD1G and STD1-MS specimens along with the three specimen average for each of the two exposures

Table 26. Listing of maximum and minimum macrocell currents for high alloy STD1-MS specimen

Table 27. Maximum and minimum macrocell currents for Type 316.16 specimens other than STD1 and STD2

Table 28. Maximum and minimum macrocell currents for Type 304 specimens other than STD1 and STD2

Table 29. Maximum and minimum macrocell currents for SMI specimens other than STD1 and STD2

Table 30. Corrosion rate calculations for STD1-MS specimens with relatively high current excursions

Table 31. Corrosion rate calculations for the STD2-MS specimens with relatively high current excursions

Table 32. Corrosion rate calculations for CCON-MS specimens with relatively high current excursions

Table 33. Corrosion rate calculations for BENT-MS specimens with relatively high current excursions

Table 34. Corrosion rate calculations for the BCAT-MS specimen with relatively high current excursion

Table 35. Corrosion rate calculations for CBNT-MS specimens with relatively high current excursion

Table 36. Corrosion rate calculations for CBNB-MS specimens with relatively high current excursions

Table 37. Corrosion rate calculations for CSDB-MS specimens with relatively high current excursions

Table 38. Corrosion rate calculations for CCNB-MS specimens with relatively high current excursions

Table 39. Corrosion rate calculations for CCNB-MS specimens with relatively high current excursions

Table 40. Corrosion rate calculations for the BCAT-MS specimen with relatively high current excursions

Table 41. Listing of maximum and minimum macrocell currents for MS-STD1G specimens

Table 42. Listing of exposure times and T_i (alloy)/T_i (BB) for high performance reinforced MS specimens

Table 43. Listing of 3BTC specimens with improved performance reinforcements and the T_i for each

Table 44. T_i data and T_i (alloy)/T_i (BB) at 2 percent, 10 percent, and 20 percent cumulative active for improved performance 3BTC specimens in STD2 concrete

Table 45. T_i data at 2 percent, 10 percent, and 20 percent cumulative active for 3BTC specimens with improved performance reinforcements in STD3 concrete

Table 46. T_i data at 2 percent, 10 percent, and 20 percent cumulative active for 3BTC specimens reinforced with 3Cr12

Table 47. T_i data at 2 percent, 10 percent, and 20 percent cumulative active for 3BTC specimens reinforced with MMFX-2

Table 48. T_i data at 2 percent, 10 percent, and 20 percent cumulative active for 3BTC specimens reinforced with 2101

Table 49. Maximum and minimum macrocell currents recorded for the high alloy reinforcement 3BTC specimens

Table 50. Summary of field observations for cracks that developed on field column specimens

Table 51. Listing of [Cl^-] results for black bar reinforced specimens as acquired from coring

Table 52. Listing of [Cl^-] results for 3Cr12 reinforced specimens as acquired from cores

Table 53. Listing of [Cl^-] results for 3Cr12 reinforced specimens as acquired from millings

Table 54. Listing of [Cl^-] results for MMFX-2 reinforced specimens as acquired from
coring. 95

Table 55. Listing of [Cl-] results for MMFX-2 reinforced specimens as acquired from milling

Table 56. Listing of [Cl^-] results for 2101 reinforced specimens as acquired from coring

Table 57. Listing of [Cl^-] results for 2101 reinforced specimens as acquired from and milling

Table 58. D_e values calculated from core [Cl^-] data

Table 59. Listing of C_T (kg/m³) for the improved performance reinforcements and black bar and C_T (alloy)/C_T (BB)

Table 60. Projected [Cl^-] at the bar depth for the different reinforcement types after the indicated times

Table 61. Listing of C_T data (wt percent) from accelerated aqueous solution testing

Table 62. Listing of high alloyed specimens that were autopsied.

Table 63. Listing of T_i, propagation time (T_p), and total time of testing for BB and improved performance bars in MS specimens.

Table 64. Comparison of T_i values for STD-SDS and -MS specimens.

List of Abbreviations and Symbols

Acronym
3BTC	3-Bar tombstone columns
BB	Black bar
CDF	Cumulative distribution function
CRR	Corrosion resistant reinforcements
DOT	Department of transportation
ECR	Epoxy-coated reinforcing steel
ERF	Gaussian error function
FAU	Florida Atlantic University
FC	Field columns
FDOT-SMO	Florida Department of Transportation State Materials Office
LCCA	Life-cycle cost analysis
MS	Macrocell slabs
SDS	Simulated deck slabs
w/c	Water-to-cement ratio

Symbol
	Mathematical symbol indicating a partial derivative
	Ohm, unit of electrical resistance
A	Microampere, unit of current

FHWA-HRT-09-020

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Corrosion Resistant Alloys for Reinforced Concrete, FHWA-HRT-09-020

April 2009

FOREWORD

Notice

Quality Assurance Statement

Technical Report Documentation Page

TABLE OF CONTENTS

LIST OF FIGURES

LIST OF TABLES

List of Abbreviations and Symbols