Corrosion Resistant Alloys for Reinforced Concrete
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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 assumes no liability for the use of the information contained in this document.
The
U.S. Government does not endorse products or manufacturers. Trademarks or manufacturers' names appear in this report only because they are considered essential to the objective of the 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-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
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6. Performing Organization Code
FAU-OE-CMM-0901
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| 7. Author(s)
William H. Hartt,* Rodney G. Powers,** Francisco Presuel Marino,* Mario Paredes,** Ronald Simmons,** Hui Yu,* Rodrigo Himiob,* |
8. Performing Organization Report No.
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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
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10. Work Unit No. (TRAIS)
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| 11. Contract or Grant No.
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| 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
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14. Sponsoring Agency Code
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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.
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| 17. Key Words
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 |
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19. Security Classification
(of this report)
Unclassified
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20. Security Classification
(of this page)
Unclassified
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21. No. of Pages
146
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22. Price |
| Form DOT F 1700.7 |
Reproduction of completed page authorized |
SI (Modern Metric) Conversion Factors
TABLE OF CONTENTS
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 Ti for the four indicated reinforcements
Figure 27. Graph. Weibull cumulative distribution plot of Ti for STD and USDB MMFX-2 reinforcements
Figure 28. Graph. Weibull cumulative distribution plot of Ti 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 Ti for STD1-MS specimens with improved performance reinforcements
Figure 36. Graph. Weibull CDF plot of Ti 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 Ti for MS-STD2 specimens that exhibited a well-defined corrosion initiation
Figure 43. Chart. Ti 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 Ti for 3BTC-STD2 specimens for each reinforcement
Figure 58. Graph. Cumulative probability plot of Ti for 3BTC-STD3 specimens with each reinforcement
Figure 59. Graph. Cumulative probability plot of Ti for 3BTC-3Cr12 specimens
Figure 60. Graph. Cumulative probability plot of Ti for 3BTC-MMFX-2 specimens
Figure 61. Graph. Cumulative probability plot of Ti 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 CT in units of kg Cl- per m3 of concrete
Figure 82. Graph. Weibull cumulative distribution of CT 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. CT determined from accelerated aqueous solution testing versus CT from SDS concrete specimens
Figure 85. Graph. CT determined from accelerated aqueous solution testing versus Ti 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 Ti 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. Ti data for SDS/STD1 specimens with improved performance reinforcements (see table 4 for specimen designation nomenclature)
Table 13. Listing of Ti for improved performance reinforcements and Ti ratio to BB for SDS-STD 1 specimens at 2 percent, 10 percent, and 20 percent active
Table 14. Listing of Ti for improved performance reinforcements and Ti 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 Ti followed by measureable macrocell corrosion
Table 20. Ratio of Ti for CRR that did not initiate corrosion to the mean Ti for BB specimens
Table 21. Listing of Ti values for MS-STD1 specimens with improved performance reinforcements
Table 22. Listing of Ti values (days) for MS specimens with improved performance reinforcements other than STD
Table 23. Listing of Ti values for MS-STD2 specimens with improved performance reinforcements
Table 24. Listing of Ti (alloy)/Ti (BB) for STD2-MS-MMFX-2 and -2101 reinforced specimens
Table 25. Listing of Ti 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 Ti (alloy)/Ti (BB) for high performance reinforced MS specimens
Table 43. Listing of 3BTC specimens with improved performance reinforcements and the Ti for each
Table 44. Ti data and Ti (alloy)/Ti (BB) at 2 percent, 10 percent, and 20 percent cumulative active for improved performance 3BTC specimens in STD2 concrete
Table 45. Ti data at 2 percent, 10 percent, and 20 percent cumulative active for 3BTC specimens with improved performance reinforcements in STD3 concrete
Table 46. Ti data at 2 percent, 10 percent, and 20 percent cumulative active for 3BTC specimens reinforced with 3Cr12
Table 47. Ti data at 2 percent, 10 percent, and 20 percent cumulative active for 3BTC specimens reinforced with MMFX-2
Table 48. Ti 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. De values calculated from core [Cl-] data
Table 59. Listing of CT (kg/m3) for the improved performance reinforcements and black bar and CT (alloy)/CT (BB)
Table 60. Projected [Cl-] at the bar depth for the different reinforcement types after the indicated times
Table 61. Listing of CT data (wt percent) from accelerated aqueous solution testing
Table 62. Listing of high alloyed specimens that were autopsied.
Table 63. Listing of Ti, propagation time (Tp), and total time of testing for BB and improved performance bars in MS specimens.
Table 64. Comparison of Ti 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
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Microampere, unit of current |
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