Corrosion Resistant Alloys for

Reinforced Concrete 

Publication No. FHWA-HRT-07-039 July 2007

Research, Development, and Technology

Turner-Fairbank Highway Research Center

6300 Georgetown Pike

McLean, VA 22101-2296
Foreword 

Initial cost considerations have historically precluded widespread utilization of high performance 

(corrosion resistant) reinforcements such as stainless steels in bridge construction. However, 

with the advent of life-cycle cost analysis as a project planning tool and of a requirement that 

major bridge structures have a 75- to 100-year design life, the competitiveness of such steels has 

increased such 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-year) test yard exposures and accelerated 

laboratory experiments in simulated concrete pore waters are being performed. The ultimate 

objective is to, first, evaluate the corrosion properties and rank the different candidate materials 

and, second, develop tools whereby long-term performance in actual structures can be projected 

from short-term tests. This interim report presents results from the initial 3 years of an overall 

5-year program. 

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 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. 

FHWA-HRT-07-039 

2. Government Accession No. 3. Recipient's Catalog No. 

5. Report Date 

July 2007 

4. Title and Subtitle 

Corrosion Resistant Alloys for Reinforced Concrete 

6. Performing Organization Code 

FAU-OE-CMM-0601 

7. Author(s) 

William H. Hartt,* Rodney G. Powers,** Diane K. Lysogorski,* 

Virginie Liroux,* Y. Paul Virmani*** (See Boxes 9 and 12) 

8. Performing Organization Report No. 

9. Performing Organization Name and Address 10. Work Unit No. (TRAIS) 

*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 

11. Contract or Grant No. 

13. Type of Report and Period Covered 

Interim Report 

12. Sponsoring Agency Name and Address 

***Office of Infrastructure Research and Development 

 Federal Highway Administration 

 6300 Georgetown Pike 

 McLean, VA 22012 14. Sponsoring Agency Code 

15. Supplementary Notes 

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

16. Abstract 

Infrastructure deterioration, which includes corrosion of reinforcing steel in concrete bridges, has been identified as a major

economic and societal cost to the United States. For the past 30 years, epoxy-coated reinforcing steel (ECR) has been 

specified for reinforced concrete bridges exposed to deicing salts and coastal environments. Premature corrosion induced 

cracking of marine bridge substructures in Florida indicated, however, that ECR is of little benefit for this type of exposure;

and while performance of ECR in northern bridge decks has been generally good to-date (30-plus years), still the degree of 

corrosion resistance to be afforded in the long term to major structures with design lives of 75 to 100 years is uncertain. This 

concern, combined with increased utilization of life-cycle cost analysis in project planning and materials selection, has 

caused renewed interest in corrosion resistant reinforcements, stainless steels in particular. The present research study is 

being performed jointly by Florida Atlantic University and the Florida Department of Transportation to evaluate alloys that 

have been identified as candidate corrosion resistant reinforcements. These include MMFX-IITM (ASTM A 1035), solid 

stainless steels 3Cr12 (UNS-S41003), 2201LDX (ASTM A955-98), 2205 (UNS 31803), and two 316L (UNS S31603) 

alloys; and two 316 stainless steel clad black bar products. Black bar (ASTM A615) reinforcement was included for 

comparison purposes. Testing methods included three types of short-term exposures: (1) a previously developed method that 

involves cyclic exposure to synthetic pore solution (SPS) with incrementally increasing chlorides and then to moist air, (2) 

anodic potentiostatic exposure in SPS with incrementally increasing chlorides, and (3) potentiodynamic polarization scans in 

saturated Ca(OH)2 at different chloride concentrations. Long-term exposures involve four specimen types: (1) simulated 

deck slabs, (2) 3-bar columns, (3) macro-cell slab specimens, and (4) field columns. Specimen types (1) and (3) are being 

cyclically wet-dry ponded with a sodium chloride (NaCl) solution and are intended to simulate northern bridge decks 

exposed to deicing salts, whereas types (2) and (4) are partially submerged continuously, the former in a NaCl solution and 

the latter at a coastal marine site in Florida. This report details findings for the initial 3 years of this 5 year project.

17. Key Word 

Reinforced concrete, bridges, corrosion resistance, 

corrosion testing, high performance reinforcement, 

stainless steel, MMFX-IITM 

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 

132 

22. Price 

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

SI* (MODERN METRIC) CONVERSION FACTORS 

APPROXIMATE CONVERSIONS TO SI UNITS

Symbol When You Know Multiply By To Find Symbol 

LENGTH 

in inches 25.4 millimeters mm 

ft feet 0.305 meters m 

yd yards 0.914 meters m 

mi miles 1.61 kilometers km 

AREA 

in2 square inches 645.2 square millimeters mm2

ft2 square feet 0.093 square meters m2

yd2 square yard 0.836 square meters m2

ac acres 0.405 hectares ha

mi2 square miles 2.59 square kilometers km2

VOLUME 

fl oz fluid ounces 29.57 milliliters mL 

gal gallons 3.785 liters L 

ft3 cubic feet 0.028 cubic meters m3 

yd3 cubic yards 0.765 cubic meters m3 

NOTE: volumes greater than 1000 L shall be shown in m3

MASS 

oz ounces 28.35 grams g

lb pounds 0.454 kilograms kg

T short tons (2000 lb) 0.907 megagrams (or "metric ton") Mg (or "t") 

TEMPERATURE (exact degrees) o

F Fahrenheit 5 (F-32)/9 Celsius oC 

or (F-32)/1.8 

ILLUMINATION 

fc foot-candles 10.76 lux lx

fl foot-Lamberts 3.426 candela/m2 cd/m2

FORCE and PRESSURE or STRESS 

lbf poundforce 4.45 newtons N 

lbf/in2 poundforce per square inch 6.89 kilopascals kPa 

APPROXIMATE CONVERSIONS FROM SI UNITS 

Symbol When You Know Multiply By To Find Symbol 

LENGTH

mm millimeters 0.039 inches in 

m meters 3.28 feet ft 

m meters 1.09 yards yd 

km kilometers 0.621 miles mi 

AREA mm2

 square millimeters 0.0016 square inches in2 

m2 square meters 10.764 square feet ft2 

m2 square meters 1.195 square yards yd2 

ha hectares 2.47 acres ac

km2 square kilometers 0.386 square miles mi2 

VOLUME 

mL milliliters 0.034 fluid ounces fl oz 

L liters 0.264 gallons gal 

m3 cubic meters 35.314 cubic feet ft3 

m3 cubic meters 1.307 cubic yards yd3 

MASS 

g grams 0.035 ounces oz

kg kilograms 2.202 pounds lb

Mg (or "t") megagrams (or "metric ton") 1.103 short tons (2000 lb) T 

TEMPERATURE (exact degrees) o

C Celsius 1.8C+32 Fahrenheit oF 

ILLUMINATION 

lx lux 0.0929 foot-candles fc 

cd/m2 candela/m2 0.2919 foot-Lamberts fl

FORCE and PRESSURE or STRESS 

N newtons 0.225 poundforce lbf 

kPa kilopascals 0.145 poundforce per square inch lbf/in2

*SI is the symbol for th International System of Units. Approp e riate rounding should be made to comply with Section 4 of ASTM E380. 

(Revised March 2003)
iii 

TABLE OF CONTENTS 

1. INTRODUCTION ...................................................................................................................... 1

2. PROJECT OBJECTIVES ........................................................................................................... 5

3. EXPERIMENTAL PROCEDURE ............................................................................................. 7

ACCELERATED SCREENING TESTS .............................................................................. 7 

General ............................................................................................................................ 7 

Materials.......................................................................................................................... 7 

AST-1: Wet-Dry Exposures............................................................................................ 10 

Specimens ................................................................................................................ 10 

Test Procedure ......................................................................................................... 11 

AST-2A: Chloride Threshold Determinations ............................................................... 14 

AST-2B: Pitting Potential Determinations .................................................................... 16 

Specimens ................................................................................................................ 16 

Test Procedure ......................................................................................................... 17 

LONG-TERM TESTS ......................................................................................................... 19 

Specimen Design............................................................................................................ 19 

General..................................................................................................................... 19 

Simulated Deck Slabs .............................................................................................. 20 

Three Bar Columns.................................................................................................. 23 

Macro-Cell Slab Specimens..................................................................................... 26 

Field Columns.......................................................................................................... 27 

4. EXPERIMENTAL RESULTS AND DISCUSSION ............................................................... 33

SIMULATED PORE WATER PH DATA FOR AST-1 AND AST-2................................ 33 

AST-1................................................................................................................................... 33 

AST-2A................................................................................................................................ 45 

AST-2B................................................................................................................................ 48 

Open Circuit Potential................................................................................................... 48 

Scan Rate ....................................................................................................................... 51 

Surface Condition:......................................................................................................... 51 

Critical Pitting Potential................................................................................................ 52 

CORRELATIONS BETWEEN DIFFERENT SHORT-TERM TEST RESULTS............. 52 

RELATING [ ] − Cl (AST-2A) TO CHLORIDE THRESHOLD th

CONCENTRATIONS IN CONCRETE..................................................................... 55 

CONCRETE SPECIMENS ................................................................................................. 57 

General .......................................................................................................................... 57 

Simulated Deck Slab (SDS) Specimens.......................................................................... 57 

General..................................................................................................................... 57 

Black Bar Slabs........................................................................................................ 58 

Slabs Reinforced With MMFX-IITM Bars................................................................ 63 

Slabs Reinforced With 3Cr12 Bars.......................................................................... 77 

Slabs Reinforced With 2201 Bars............................................................................ 88 

Slabs Reinforced With 316 Solid and Clad (Stelax) Stainless Bars ...................... 101 

Chloride Concentration.......................................................................................... 103 

Three Bar Columns...................................................................................................... 103 

Square Three Bar Column Specimens ................................................................... 103 
iv 

Three Bar Tombstone Columns............................................................................. 105 

Macro-Cell Slab (MS) Specimens................................................................................ 105 

Field Columns.............................................................................................................. 107 

Correlation of Concrete Specimen Data With Results From Accelerated Testing...... 107 

5. CONCLUSIONS..................................................................................................................... 111

APPENDIX A ............................................................................................................................. 113

EXAMPLE PH CALCULATION ..................................................................................... 113 

APPENDIX B ............................................................................................................................. 115

EXAMPLE CALCULATION OF CORROSION RATE FROM 

POLARIZATION RESISTANCE............................................................................ 115 

APPENDIX C ............................................................................................................................. 117

EXAMPLE CALCULATION OF CORROSION RATE FROM WEIGHT 

LOSS DATA............................................................................................................. 117 

BIBLIOGRAPHY....................................................................................................................... 119
v 

LIST OF FIGURES 

Figure 1.1. Photo. Cracked and spalled marine bridge piling. .................................................. 2 

Figure 1.2. Schematic illustration. Various steps in deterioration of reinforced concrete 

due to chloride induced corrosion........................................................................... 3 

Figure 3.1. Photo. Straight, as-received, MMFX-IITM bar with epoxy-mounted ends and 

electrical lead. ....................................................................................................... 10 

Figure 3.2. Photo. Three bent, as-received Type 2201 stainless steel bars with electrical 

leads. ..................................................................................................................... 11 

Figure 3.3. Photo. Abraded MMFX-IITM specimen. ............................................................... 12 

Figure 3.4. Photo. Damaged MMFX-IITM specimen............................................................... 12 

Figure 3.5. Photo. AST-1 wet-dry exposure setup.................................................................. 12 

Figure 3.6. Photo. AST-1 specimens under test in the upper hold tank (figure 3.5)............... 13 

Figure 3.7. Schematic illustration. AST-2A experimentation................................................. 15 

Figure 3.8. Photo. AST-2A test system................................................................................... 15 

Figure 3.9. Photo. Test chamber with specimens.................................................................... 16 

Figure 3.10. Illustration and photo. Schematic illustration (a) and photograph (b) of the 

as-received, circumferential AST-2B test specimen............................................. 17 

Figure 3.11. Photo. Polished circumferential specimen............................................................ 18 

Figure 3.12. Schematic illustration. Polished cross section surface specimen.......................... 18 

Figure 3.13. Photo. Two polished cross section specimens. ..................................................... 18 

Figure 3.14. Photo. Test cell for potentiodynamic polarization measurements........................ 19 

Figure 3.15. Schematic illustration. CREV type simulated deck slab specimens..................... 22 

Figure 3.17. Graphic. Standard specimen nomenclature........................................................... 22 

Figure 3.18. Graphic. Nonstandard specimen nomenclature. ................................................... 23 

Figure 3.19. Photo. Ponded deck slab specimen under test. ..................................................... 24 

Figure 3.20. Photo. Perspective view of exposure site and specimens. .................................... 24 

Figure 3.21. Schematic illustration. Square three bar column specimen for each of the 

three bar configurations. ....................................................................................... 25 

Figure 3.22. Schematic illustration. Tombstone type three bar column specimen for each 

of the three bar configurations. ............................................................................. 25 

Figure 3.23. Photo. Three bar column specimens under exposure............................................ 26 

Figure 3.24. Schematic illustration. Geometry of the macro-cell slab type specimen with 

both bent and straight bars. ................................................................................... 27 

Figure 3.25. Photo. Macro-cell slab specimens under exposure............................................... 27 

Figure 3.26. Schematic illustration. Geometry of the field column type specimen. ................. 28 

Figure 3.27. Photo. Field column specimens under exposure at the Intracoastal Waterway 

site in Crescent Beach, FL. ................................................................................... 28 

Figure 4.1. Graph. Change in pH and [Cl-

] as a function of time for AST-1 and AST-2 

experiments........................................................................................................... 33 

Figure 4.2. Graph. Plot of polarization resistance versus exposure time for representative 

alloys during different AST-1 runs (numbers in parentheses).............................. 35 

Figure 4.3. Graph. Plot of polarization resistance versus exposure time for intermediate 

performing alloys and black bars during different AST-1 (number in 

parentheses after each alloy designation indicates different AST-1 runs............. 36 
vi 

Figure 4.4. Graph. Plot of polarization resistance versus exposure time for 2201 stainless 

steel AST-1 specimens with different surface preparation conditions. ................ 37 

Figure 4.5. Graph. Plot of polarization resistance versus exposure time for clad stainless 

steel AST-1 specimens.......................................................................................... 37 

Figure 4.6. Graph. Plot of polarization resistance versus exposure time for clad stainless 

steel AST-1 specimens in the intact, abraded (A), and damaged (D) 

conditions.............................................................................................................. 38 

Figure 4.7. Graph. Plot of polarization resistance for straight versus bent solid bars............. 39 

Figure 4.8. Graph. Plot of polarization resistance for straight versus bent clad bars.............. 39 

Figure 4.9. Graph. Comparison of corrosion rate measured by weight loss and calculated 

from polarization resistance for different solid bars............................................. 41 

Figure 4.10. Photo. Type 316 SS specimens subsequent to AST-1 testing. ............................. 42 

Figure 4.11. Photo. Type 2205 SS specimens subsequent to AST-1 testing. ........................... 42 

Figure 4.12. Photo. Type 2201 SS specimens subsequent to AST-1 testing. ........................... 43 

Figure 4.13. Photo. MMFX-IITM specimens subsequent to AST-1 testing............................... 43 

Figure 4.14. Photo. MMFX-IITM abraded specimens subsequent to AST-1 testing. ................ 44 

Figure 4.15. Photo. MMFX-IITM damaged specimens subsequent to AST-1 testing. .............. 44 

Figure 4.16. Photo. Black bar specimens subsequent to AST-1 testing.................................... 45 

Figure 4.17. Graph. Plot of current density versus [Cl-

] such that [ ] − Clth for alloys with 

intermediate corrosion resistance is revealed (specimens with B in the 

designation were bent). ......................................................................................... 46 

Figure 4.18. Graph. Plot of current density versus [Cl-

] such that [ ] − Clth for alloys with 

relatively high corrosion resistance is revealed. ................................................... 46 

Figure 4.19. Graph. Expanded scale plot of current density versus [Cl-

] for alloys with 

relatively high corrosion resistance is revealed. ................................................... 47 

Figure 4.20. Graph. Plot of current density versus exposure time for 10 specimens each of 

black bar and 3Cr12. Incremental Cl-

 additions are also shown........................... 48 

Figure 4.21. Graph. Expanded scale view of the current density versus exposure time data 

from figure 4.20. ................................................................................................... 49 

Figure 4.22. Graph. Plot of current density versus time for a series of 10 MMFX and 

2201 specimens polarized to +100 mVSCE. Incremental Cl-

 additions are 

also shown............................................................................................................. 49 

Figure 4.23. Graph. Plot of current density versus time for replicate MMFX-IITM 

specimens.............................................................................................................. 50 

Figure 4.24. Graph. Distribution of [ ] − Clth for four alloys based upon the 10 μA/cm2

 

current density criterion. ....................................................................................... 50 

Figure 4.25. Graph. Anodic CPP scans for as-received MMFX-IITM specimens in saturated 

Ca(OH)2 without Cl-

 at scan rates of 0.33, 1.00, and 5.00 mV/s. Arrows 

indicate direction of forward and reverse scans.................................................... 51 

Figure 4.26. Graph. Anodic CPP scans on as-received MMFX-IITM specimens with three 

surface conditions in saturated Ca(OH)2 without Cl-

 at 1.00 mV/s. Arrows 

indicate direction of forward and reverse scans.................................................... 52 

Figure 4.27. Graph. Critical pitting potential as a function of [Cl-

] for four bar types. ............ 53 

Figure 4.28. Graph. Plot of polarization resistance (AST-1) versus PREN for the test 

reinforcements....................................................................................................... 54 
vii 

Figure 4.29. Graph. Plot of polarization resistance (AST-1) versus [ ] − Clth (AST-2A).............. 55 

Figure 4.30. Graph. Plot of [ ] − Clth (AST-2A) versus PREN...................................................... 56 

Figure 4.31. Graph. Plot of [ ] − Clth (AST-2A) versus the corresponding threshold projected 

from literature data for pastes, mortars, and concrete........................................... 57 

Figure 4.32. Graph. Plot of potential versus exposure time for STD1 and STD2 concrete 

specimens with black bar reinforcement............................................................... 58 

Figure 4.33. Graph. Plot of macro-cell current density versus exposure time for STD1 

and STD2 concrete specimens with black bar reinforcement............................... 59 

Figure 4.34. Graph. Plot of potential versus exposure time for black bar STD1 concrete 

specimens with and without a simulated crack..................................................... 59 

Figure 4.35. Graph. Plot of macro-cell current density versus exposure time for black bar 

STD1 concrete specimens with and without a simulated crack............................ 60 

Figure 4.36. Graph. Plot of potential versus macro-cell current density for black bar 

reinforced concrete specimens.............................................................................. 60 

Figure 4.37. Photo. Exposed surface of specimen number 3-CCON-BB-2 after 377 days. ..... 61 

Figure 4.38. Photo. Traces of the upper three rebars and heavy corrosion products 

(specimen number 3-CCON-BB-1). ..................................................................... 62 

Figure 4.39. Photo. Trace of the upper rebars and heavy corrosion products on specimen 

number 1-STD1-BB-3. ......................................................................................... 62 

Figure 4.40. Graph. Plot of potential versus exposure time for STD1 concrete specimens 

with MMFX-IITM reinforcement in comparison to black bar results.................... 63 

Figure 4.41. Graph. Plot of macro-cell current density versus exposure time for STD1 

concrete specimens with MMFX-IITM reinforcement in comparison to black 

bar results.............................................................................................................. 64 

Figure 4.42. Graph. Plot of potential versus exposure time for STD1 and STD2 concrete 

specimens with MMFX-IITM reinforcement. ........................................................ 64 

Figure 4.43. Graph. Plot of macro-cell current density versus exposure time for STD1 and 

STD2 concrete specimens with MMFX-IITM reinforcement. ............................... 65 

Figure 4.44. Graph. Plot of potential versus exposure time for STD1 concrete specimens 

with black bar bottom mat and top mat MMFX-IITM reinforcement compared 

to ones with all MMFX-IITM bars. ........................................................................ 65 

Figure 4.45. Graph. Plot of macro-cell current density versus exposure time for STD1 

concrete specimens with black bar bottom mat and top mat MMFX-IITM 

reinforcement compared to ones with all MMFX-IITM bars................................. 66 

Figure 4.46. Graph. Plot of potential versus exposure time for STD1 concrete specimens 

with as-received and wire brushed (WB) MMFX-IITM reinforcement................. 66 

Figure 4.47. Graph. Plot of macro-cell current density versus exposure time for STD1 

concrete specimens with as-received and wire brushed (WB) MMFX-IITM 

reinforcement. ....................................................................................................... 67 

Figure 4.48. Graph. Plot of potential versus exposure time for STD1 concrete specimens 

with top mat crevice bars (splice) and MMFX-IITM reinforcement compared 

to ones with normal bar placement. ...................................................................... 67 

Figure 4.49. Graph. Plot of macro-cell current density versus exposure time for STD1 

concrete specimens with top mat crevice bars (splice) and MMFX-IITM 

reinforcement. ....................................................................................................... 68 
viii 

Figure 4.50. Graph. Plot of potential versus exposure time for STD1 concrete specimens 

with a simulated concrete crack and MMFX-IITM reinforcement compared 

to normal (uncracked) specimens. ........................................................................ 68 

Figure 4.51. Graph. Plot of macro-cell current density versus exposure time for STD1 

concrete specimens with a simulated concrete crack and MMFX-IITM 

reinforcement compared to normal (uncracked) specimens. ................................ 69 

Figure 4.52. Graph. Plot of potential versus exposure time for STD1 concrete specimens 

with a simulated concrete crack and MMFX-IITM reinforcement compared to 

ones with a simulated crack and top bar crevice (splice)...................................... 69 

Figure 4.53. Graph. Plot of macro-cell current density versus exposure time for STD1 

concrete specimens with a simulated concrete crack and MMFX-IITM 

reinforcement compared to ones with a simulated crack and top bar crevice 

(splice)................................................................................................................... 70 

Figure 4.54. Graph. Plot of potential versus exposure time for STD1 concrete specimens 

with a simulated concrete crack and MMFX-IITM reinforcement compared to 

ones with a simulated crack and black bottom bars.............................................. 70 

Figure 4.55. Graph. Plot of macro-cell current density versus exposure time for STD1 

concrete specimens with a simulated concrete crack and MMFX-IITM 

reinforcement compared to ones with a simulated crack and black bar bottom 

mat......................................................................................................................... 71 

Figure 4.56. Graph. Plot of potential versus macro-cell current density for MMFX-IITM 

reinforced specimens. ........................................................................................... 71 

Figure 4.57. Photo. Top surface of specimen 2-BCAT-MMFX-3 after 461 days of 

exposure. ............................................................................................................... 72 

Figure 4.58. Photo. Trace of the upper rebars and corrosion products on specimen 

number 1-STD1-MMFX-2.................................................................................... 72 

Figure 4.59. Photo. Trace of the upper rebars and corrosion products on specimen 

number 1-STD2-MMFX-2.................................................................................... 73 

Figure 4.60. Photo. Trace of the upper rebars and corrosion products on specimen 

number 2-WB-MMFX-1....................................................................................... 74 

Figure 4.61. Photo. Trace of the upper rebars and corrosion products on specimen 

number 3-CREV-MMFX-1. ................................................................................. 74 

Figure 4.62. Photo. Trace of the upper rebars and corrosion products on specimen 

number 1-CCON-MMFX-1.................................................................................. 75 

Figure 4.63. Photo. Trace of the upper rebars and corrosion products on specimen 

number 2-BCAT-MMFX-1. ................................................................................. 75 

Figure 4.64. Photo. Trace of the upper rebars and corrosion products on specimen 

number 2-CCNB-MMFX-1. ................................................................................. 76 

Figure 4.65. Photo. Trace of the upper rebars and corrosion products on specimen 

number 3-CCRV-MMFX-1. ................................................................................. 76 

Figure 4.66. Graph. Plot of potential versus exposure time for STD1 concrete specimens 

with 3Cr12 reinforcement compared to that for black bar.................................... 77 

Figure 4.67. Graph. Plot of macro-cell current density versus exposure time for STD1 

concrete specimens with 3Cr12 reinforcement compared to that for black bar. .. 78 

Figure 4.68. Graph. Plot of potential versus exposure time for STD1 and STD2 concrete 

specimens with 3Cr12 reinforcement. .................................................................. 78 
ix 

Figure 4.69. Graph. Plot of macro-cell current density versus exposure time for STD1 and 

STD2 concrete specimens with 3Cr12 reinforcement. ......................................... 79 

Figure 4.70. Graph. Plot of potential versus exposure time for STD1 concrete specimens 

with wire brushed compared to as-received 3Cr12 bars....................................... 79 

Figure 4.71. Graph. Plot of macro-cell current density versus exposure time for STD1 

concrete specimens with wire brushed compared to as-received 3Cr12 bars....... 80 

Figure 4.72. Graph. Plot of potential versus exposure time for STD1 concrete specimens 

with top mat bar crevice (splice) and 3Cr12 reinforcement compared to ones 

with normal bar placement.................................................................................... 80 

Figure 4.73. Graph. Plot of macro-cell current density versus exposure time for STD1 

concrete specimens with top mat bar crevice (splice) and 3Cr12 

reinforcement compared to ones with normal bar placement............................... 81 

Figure 4.74. Graph. Plot of potential versus exposure time for STD1 concrete specimens 

with a simulated concrete crack and 3Cr12 reinforcement compared to 

uncracked ones...................................................................................................... 81 

Figure 4.75. Graph. Plot of macro-cell current density versus exposure time for STD1 

concrete specimens with a simulated concrete crack and 3Cr12 reinforcement 

compared to uncracked ones................................................................................. 82 

Figure 4.76. Graph. Plot of potential versus exposure time for STD1 concrete specimens 

with black bar bottom mat and top mat 3Cr12 reinforcement compared to 

ones with all 3Cr12 bars. ...................................................................................... 82 

Figure 4.77. Graph. Plot of macro-cell current density versus exposure time for STD1 

concrete specimens with black bar bottom mat and top mat 3Cr12 

reinforcement compared to ones with all 3Cr12 bars. .......................................... 83 

Figure 4.78. Graph. Plot of potential versus exposure time for STD1 concrete specimens 

with a simulated concrete crack and 3Cr12 reinforcement compared to 

cracked ones with a simulated crack and top bar crevice (splice). ....................... 83 

Figure 4.79. Graph. Plot of macro-cell current density versus exposure time for STD1 

concrete specimens with a simulated concrete crack and 3Cr12 

reinforcement compared to cracked ones with a simulated crack and top 

bar crevice (splice)................................................................................................ 84 

Figure 4.80. Graph. Plot of potential versus macro-cell current density for 3Cr12 

reinforced specimens. ........................................................................................... 84 

Figure 4.81. Photo. Trace of the upper rebars and corrosion products on specimen 

number 1-STD1-3Cr12-1...................................................................................... 85 

Figure 4.82. Photo. Trace of the upper rebars and corrosion products on specimen 

number 1-STD2-3Cr12-1...................................................................................... 85 

Figure 4.83. Photo. Trace of the upper rebars and corrosion products on specimen 

number 1-WB-3Cr12-1......................................................................................... 86 

Figure 4.84. Photo. Trace of the upper rebars and corrosion products on specimen 

number 1-CREV-3Cr12-1..................................................................................... 86 

Figure 4.85. Photo. Trace of the upper rebars and corrosion products on specimen 

number 1-CCON-3Cr12-1. ................................................................................... 87 

Figure 4.86. Photo. Trace of the upper rebars and corrosion products on specimen 

number 1-BCAT-3Cr12-1..................................................................................... 87 
x 

Figure 4.87. Photo. Trace of the upper rebars and corrosion products on specimen 

number 1-CCRV-3Cr12-1. ................................................................................... 88 

Figure 4.88. Graph. Plot of potential versus exposure time for STD1 concrete specimens 

with 2201 reinforcement compared to data for black bar..................................... 89 

Figure 4.89. Graph. Plot of macro-cell current density versus exposure time for STD1 

concrete specimens with 2201 reinforcement compared to data for black bar..... 89 

Figure 4.90. Graph. Plot of potential versus exposure time for STD1 and STD2 concrete 

specimens with 2201 reinforcement. .................................................................... 90 

Figure 4.91. Graph. Plot of macro-cell current density versus exposure time for STD1 

and STD2 concrete specimens with 2201 reinforcement. .................................... 90 

Figure 4.92. Graph. Plot of potential versus exposure time for STD1 concrete specimens 

with wire brushed (WB) 2201 bars compared to ones with as-received 2201 

bars........................................................................................................................ 91 

Figure 4.93. Graph. Plot of macro-cell current density versus exposure time for STD1 

concrete specimens with wire brushed (WB) 2201 bars compared to ones 

with as-received 2201 bars.................................................................................... 91 

Figure 4.94. Graph. Plot of potential versus exposure time for STD1 concrete specimens 

with top mat crevice bars (splice) and 2201 reinforcement compared to ones 

with normal bar placement.................................................................................... 92 

Figure 4.95. Graph. Plot of macro-cell current density versus exposure time for STD1 

concrete specimens with top mat crevice bars (splice) and 2201 reinforcement 

compared to ones with normal bar placement. ..................................................... 92 

Figure 4.96. Graph. Plot of potential versus exposure time for STD1 concrete specimens 

with a simulated crack and 2201 reinforcement compared to uncracked ones..... 93 

Figure 4.97. Graph. Plot of potential versus exposure time for STD1 concrete specimens 

with a simulated crack and 2201 reinforcement compared to uncracked ones..... 93 

Figure 4.98. Graph. Plot of potential versus exposure time for STD1 concrete specimens 

with top mat 2201 bars and bottom mat black bar compared to ones with all 

2201 bars............................................................................................................... 94 

Figure 4.99. Graph. Plot of macro-cell current density versus exposure time for STD1 

concrete specimens with top mat 2201 bars and bottom mat black bar 

compared to ones with all 2201 bars..................................................................... 94 

Figure 4.100. Graph. Plot of potential versus exposure time for STD1 concrete specimens 

with a simulated concrete crack and 2201 reinforcement compared to ones 

with a simulated crack and black bottom bars...................................................... 95 

Figure 4.101. Graph. Plot of macro-cell current density versus exposure time for STD1 

concrete specimens with a simulated concrete crack and 2201 reinforcement 

compared to ones with a simulated crack and black bottom bars......................... 95 

Figure 4.102. Graph. Plot of potential versus exposure time for STD1 concrete specimens 

with a simulated crack and crevice at top bars (splice) and 2201 

reinforcement compared results for ones with cracked concrete and normal 

top bar placement.................................................................................................. 96 

Figure 4.103. Graph. Plot of macro-cell current density versus exposure time for STD1 

concrete specimens with a simulated crack and crevice at top bars (splice) 

and 2201 reinforcement compared results for ones with cracked concrete and 

normal top bar placement...................................................................................... 96 
xi 

Figure 4.104. Graph. Plot of potential versus macro-cell current density for 2201 reinforced 

specimens.............................................................................................................. 97 

Figure 4.105. Photo. Trace of the upper rebars and corrosion products on specimen 

number 1-STD1-2201-3........................................................................................ 97 

Figure 4.106. Photo. Trace of the upper rebars and corrosion products on specimen 

number 1-STD2-2201-2........................................................................................ 98 

Figure 4.107. Photo. Trace of the upper rebars and corrosion products on specimen 

number 1-WB-2201-1........................................................................................... 98 

Figure 4.108. Photo. Trace of the upper rebars and corrosion products on specimen 

number 1-CREV-2201-1....................................................................................... 99 

Figure 4.109. Photo. Trace of the upper rebars and corrosion products on specimen 

number 1-CCON-2201-1. ..................................................................................... 99 

Figure 4.110. Photo. Trace of the upper rebars and corrosion products on specimen 

number 1-BCAT-2201-1..................................................................................... 100 

Figure 4.111. Photo. Trace of the upper rebars and corrosion products on specimen 

number 1-CCNB-2201-1. ................................................................................... 100 

Figure 4.112. Photo. Trace of the upper rebars and corrosion products on specimen 

number 1-CCRV-2201-1. ................................................................................... 101 

Figure 4.113. Graph. Plot of average potential versus average macro-cell current density 

at each measurement time for three specimens of the four indicated 

reinforcement types............................................................................................. 102 

Figure 4.114. Graph. Plot of potential versus exposure time for STD1 and STD2 concrete 

specimens with 316.18, 316.17, and Stelax reinforcement compared to that 

for black bar in STD1 concrete........................................................................... 102 

Figure 4.115. Graph. Plot of macro-cell current density versus exposure time for STD1 

and STD2 concrete specimens with 316.18 reinforcement compared to ones 

with black bar in STD1 concrete. ....................................................................... 103 

Figure 4.116. Graph. Plot of chloride concentration at 2.54 cm below the exposed surface 

of STD1 concrete slabs versus exposure time. ................................................... 104 

Figure 4.117. Graph. Time-to-corrosion results for square 3-bar column specimens............... 104 

Figure 4.118. Graph. Example potential and current data for macro-cell slab specimens........ 106 

Figure 4.119. Graph. Time-to-corrosion results for the macro-cell slab specimens without 

a simulated crack................................................................................................. 106 

Figure 4.120. Graph. Time-to-corrosion results for the macro-cell slab specimens with a 

simulated crack. .................................................................................................. 108 

Figure 4.121. Graph. Plot of time-to-corrosion of reinforced concrete specimens as a 

function of [ ] − Clth as determined from accelerated testing. ................................. 108 

Figure 4.122. Photo. Example of corner cracking on a 2201 reinforced simulated deck slab 

specimen. ............................................................................................................ 109 

Figure 4.123. Graph. Chloride profile from each of two cores taken from STD1 concrete 

slabs after 136 days of exposure. ........................................................................ 110 
xii 

LIST OF TABLES 

Table 3.1. Listing of reinforcing steel types. ........................................................................... 9 

Table 3.2. Chemical composition of the rebar types................................................................ 9 

Table 3.3. Listing of AST-1 runs and the rebar and specimen type for each (“x” indicates 

that the indicated alloy was tested during that run, and “2” indicates two sets 

of triplicate specimens)......................................................................................... 14 

Table 3.4. Listing of each AST-2A run according to rebar type and number of specimens. 16 

Table 3.5. Listing of the number of AST-2B tests for each specimen type and surface 

condition. .............................................................................................................. 19 

Table 3.6. Concrete mix designs............................................................................................ 20 

Table 3.7. Listing of the various specimen types, variables, and nomenclature for each...... 19 

Table 3.8. Listing of specimens reinforced with 316.18 and 3Cr12...................................... 29 

Table 3.9. Listing of specimens with 2201 rebar (specimens in shaded cells not yet 

fabricated). ............................................................................................................ 29 

Table 3.10. Listing of specimens reinforced with MMFX-IITM............................................... 30 

Table 3.11. Listing of specimens reinforced with Stelax (specimens in shaded cells not yet 

fabricated). ............................................................................................................ 30 

Table 3.12. Listing of specimens reinforced with SMI (specimens in shaded cells not yet 

fabricated). ............................................................................................................ 31 

Table 3.13. Listing of specimens reinforced with black bar.................................................... 31 

Table 4.1. Average polarization resistance for each alloy during each 28-day period of 

six individual AST-1 runs..................................................................................... 34 

Table 4.2. Polarization resistance for each alloy averaged over the six individual AST-1 

runs........................................................................................................................ 35 

Table 4.3. Corrosion rate calculated from weight loss of individual specimens of each 

alloy at the end of the indicated NaCl exposure for the indicated run.................. 40 

Table 4.4. Average corrosion rate calculated from weight loss for each alloy during four 

individual AST-1 runs........................................................................................... 40 

Table 4.5. Listing of projected CT values for the corresponding [ ] − Clth from AST-2A. ........ 56 

Table 4.6. Calculated times-to-corrosion for concrete specimens. ...................................... 110 
1 

1. INTRODUCTION 

The United States has a major investment in its highway system, the operational performance of 

which, in conjunction with that of other transportation modes, is critical to the Nation’s 

economic health and societal functionality. While deterioration of structures with time is a 

normal and expected occurrence, the rate at which this has occurred for highway bridges since 

advent in the 1960s of a clear roads policy, as affected by winter application of deicing salts in 

northern locations, has been abnormally advanced and has posed significant challenges, both 

economically and technically. Also important is similar advanced deterioration of reinforced 

concrete bridges in coastal locations, both northern and southern, as a consequence of sea water 

or spray exposure. In both cases (deicing salts and marine exposure), the deterioration is a 

consequence of the aggressive nature of the chloride ion in combination with moisture and 

oxygen.1

 Over half of the total bridge inventory in the United States is of the reinforced concrete 

type, and these structures have proved to be particularly susceptible. A recent study2

 has 

indicated that the annual direct cost of corrosion to bridges is $5.9 to $9.7 billion. If indirect 

factors are included also, this cost can be as much as 10 times higher.3

 

As this problem has manifested itself during the past 40 or so years, technical efforts have been 

directed towards, first, understanding the deterioration mechanism and, second, developing 

prevention and intervention strategies. With regard to the former, steel and concrete are in most 

aspects mutually compatible, as exemplified by the fact that, in the absence of chlorides, the 

relatively high pH of concrete pore solution (pH ≈ 13.0-13.8) promotes formation of a protective 

oxide (passive) film such that corrosion rate is negligible and decades of relatively low 

maintenance result. In the presence of chlorides, even at concentrations at the steel depth as low 

as 0.6 kilograms per cubic meter (kg/m3) (1.0 pound per cubic yard (lb/yd3

)) (concrete weight 

basis),4

 the passive film may become locally disrupted and active corrosion commence. Once 

this occurs, solid corrosion products form progressively near the steel-concrete interface and lead 

ultimately to concrete cracking and spalling. Figure 1.1 shows a photograph illustrating such 

damage for the case of a coastal bridge piling. Because corrosion induced deterioration is 

progressive, inspections for damage assessment must be performed routinely; and present 

Federal guidelines require a visual inspection every 2 years.5

 If indicators of deterioration are 

not addressed, then public safety is at risk. As an example, corrosion induced concrete spalls 

occur as potholes in a bridge deck and contribute to unsafe driving conditions. In the extreme, 

structural failure and collapse result. 
2 

Figure 1.1. Photo. Cracked and spalled marine bridge piling. 

Corrosion induced deterioration of reinforced concrete can be modeled in terms of three 

component steps: (1) time for corrosion initiation, Ti, (2) time, subsequent to corrosion initiation, 

for appearance of cracking on the external concrete surface (crack propagation), Tp, and (3) time 

for surface cracks to progress into further damage and develop into spalls, Td, to the point where, 

if repairs and rehabilitations are not performed, the functional service life, Tf, is reached.6

 Figure 

1.2 illustrates these parameters schematically as a plot of cumulative damage versus time. Of the 

three component terms, Ti normally occupies the longest period and, as such, is the predominant 

factor in determining useful service life. Based upon the corrosion deterioration model 

represented by figure 1.2, methods of life-cycle cost analysis (LCCA) are now commonly 

employed to evaluate and compare different materials selection and design alternatives. This 

approach considers both initial cost and the projected life history of maintenance, repair, and 

rehabilitation that are required until the design life is reached. These are evaluated in terms of the 

time value of money, from which present worth is determined; and comparisons between 

different options can then be made on a cost normalized basis. 

In the early 1970s, research studies were performed that qualified epoxy-coated reinforcing steel 

(ECR) as an alternative to black bar;7,8

 and for the past 30 years ECR has been specified by most 

State Departments of Transportation (DOTs) for bridge decks and substructures exposed to 

chlorides. At the same time, ECR was augmented by use of low water-to-cement ratio (w/c) 

concrete, possibly with pozzolans or corrosion inhibitors (or both), and concrete covers of 

65 millimeters (mm) or more.9

 However, premature corrosion induced cracking of marine bridge 

substructures in Florida10,11,12,13 indicated that ECR is of little benefit for this type of exposure; 

and while performance of ECR in northern bridge decks has been generally good to-date (30-

plus years), still the degree of corrosion resistance afforded in the long term for major structures 

with design lives of 75 to 100 years is uncertain. In response to this, interest has focused during 

the past decade upon more corrosion resistant alternatives to ECR, stainless steels in particular. 
3 

Such corrosion resistant steels become particularly competitive on a life-cycle cost basis, since 

the higher initial expense of the steel per se may be recovered over the life of the structure via 

reduced repairs and rehabilitations. 

Figure 1.2. Schematic illustration. Various steps in deterioration 

of reinforced concrete due to chloride induced corrosion. 

The present research study is being performed jointly by Florida Atlantic University and the 

Florida Department of Transportation as a 6-year effort to evaluate the suitability of various 

corrosion resistant reinforcements for bridges exposed to chlorides. An initial phase of the study 

provided a critical literature review of corrosion resistant reinforcements.14 The present report 

details research findings during the initial 3 years of the project. Cumulative Damage 

Time

Ti 

Tf 

Tp 

Td 

5 

2. PROJECT OBJECTIVES 

Objectives for this research are as listed below: 

I. Determine the extent to which high performance metallic reinforcement has been employed 

in reinforced concrete bridges and other construction and critically review its performance. 

II. Identify candidate high performance metallic reinforcement types that are appropriate for 

concrete bridge construction. 

III. Perform an experimental program that consists of (1) accelerated short-term screening tests 

and (2) service realistic long-term exposures to establish data from which selection and 

service life of high performance metallic reinforcement in concrete can be projected. 

IV. Analyze the data from III and identify the utility and limitations of employing specific high 

performance metallic reinforcement in concrete bridge construction. 

The purpose of this report is to document accomplishments for the initial 3 years of this 6-year 

overall effort. Results pertaining to Objective I have been reported elsewhere, as noted above.14 

Progress for Objectives II through IV is described below. 

7 

3. EXPERIMENTAL PROCEDURE 

ACCELERATED SCREENING TESTS 

General 

Three categories of accelerated screening tests (ASTs)—wet-dry cycling (AST-1), chloride (Cl-

) 

threshold determinations (AST-2A), and pitting potential determinations (AST-2B)—were 

performed. The first of these, AST-1, was modeled after an earlier program15 and focused upon 

measurement of corrosion rate of rebar specimens upon exposure to repetitive 1.75 hours wet—

4.25 hours dry cycles for a total of 84 days. The test solution was 0.30N potassium hydroxide 

(KOH)—0.05N sodium hydroxide (NaOH) (pH ~ 13.40) simulated pore water that contained 

3.00 weight percent (w/o) sodium chloride (NaCl) (1.82 w/o chloride (Cl-

)) during the initial 28 

days exposure, 9.00 w/o NaCl (5.46 w/o Cl-

) for the next 28 days, and 15.00 w/o NaCl (9.10 w/o 

Cl-

) for the last 28 days. Corrosion rate of the different rebar specimens was determined by both 

weight loss and polarization resistance measurements. 

The second test method, AST-2A, consisted of continuous immersion of specimens in simulated 

pore solution of the same composition as for AST-1. In this case, however, no chlorides were 

present initially but were subsequently introduced incrementally as NaCl at time intervals 

ranging from one to several days. Also, AST-2A specimens were anodically polarized 

potentiostatically to +0.100 VSCE. For both AST-1 and AST-2A experiments, the test solution 

was periodically titrated for hydroxide (OH-

); and pH was then calculated using the equation, 

 (3.1) 

where γOH is the activity coefficient for OH-

, which was taken as 0.716 and [OH-] is molality of 

that species. An example calculation is provided in Appendix A. The purpose of these 

experiments was to determine the critical Cl-

 concentration for loss of passivity and onset of 

active corrosion. 

The AST-2B experiments, on the other hand, involved anodic potentiodynamic polarization 

scans upon individual specimens in deaerated, saturated calcium hydroxide (Ca(OH)2) with 

different chloride ion concentrations ([Cl-

]). The objective in this case was to determine the 

critical pitting potential for the different types of rebar. In effect, the AST-2B experiments are a 

sequel to the AST-2A, in that the former determined the potential for pitting at a given [Cl-

] and 

the latter the critical [Cl-

] at a specific potential (+0.100 VSCE in this case). 

Materials 

Table 3.1 lists the various steels that were acquired based upon a review of the literature and bar 

availability. The fact that Type 316L stainless steel (SS) was acquired from two sources resulted 

because Type 304SS was requested from one of these, but chemical analysis of the received 

material indicated that it qualified as Type 316LSS instead. Composition for all bars is shown in 

table 3.2. Bar size in all cases was number 5 (16 mm diameter). The two types of clad bars 

(Stelax and SMI) were fabricated by two distinct processes, the former by packing a stainless 

pH = 14+log (γOH · [OH -

]) 
8 

steel tube with steel scrap followed by rolling, and the latter by plasma applying stainless steel to 

a carbon steel billet and then rolling. Unless noted otherwise, bars were tested in the as-received 

surface condition subsequent to acetone cleaning. 
9

Table 3.1. Listing of reinforcing steel types. 

Designation./Spec. Common Design. As-Rec’d. Cond. Microstructure PREN1 

263 S

UNS-S31603 Type 316LSS Pickled2 Austenitic 244 DUNS-S31803 Type2205SS As-Rolled Duplex (Austinite plus Ferrite) 35 GeASTM A955-98 Type 2201LDXSS As-Rolled Lean Duplex (Austinite plus Ferrite) 25 GeASTM A615, Grade 75 MMFX-II As-Rolled Microcomposit austenite-martensite. 9 MM

- Nouvinox Pickled 316 Clad/Carbon Steel Core - Ste- SMI Pickled 316 Clad/Carbon Steel Core - CM

UNS-S41003 Type 3Cr12SS Pickled Ferritic 12 AmASTM A615 Black Bar As-Rolled Ferrite/Pearlite 0 Ge

1 PREN (Pitting Resistance Equivalent Number) where PREN = %Cr + 3.3⋅ %Mo +16 ⋅ %N . 2 Pickled with HF and Nitric acid per ASTM A380. 3 Subsequently designated as 316.16. 4 Subsequently designated as 316.18. 

Table 3.2. Chemical composition of the rebar types. 

Alloy C Mn P S Si Cr Ni Mo 

Type 316LSS(316.16) 0.03 1.55 0.025 0.001 0.59 18.43 10.06 2.08 0Type 316LSS(316.18) 0.03 1.66 0.026 0.005 0.42 16.97 10.07 2.15 0Type2205SS 0.029 1.68 0.028 0.004 0.63 21.58 4.8 2.64 Type 2201LDXSS 0.04 4.70 0.019 0.001 0.80 22.47 1.68 0.24 0MMFX-II 0.05 0.45 0.012 0.015 0.23 9.30 0.10 0.03 0Type 3Cr12SS 0.04 0.38 0.018 0.024 0.71 11.69 0.50 0.09 0Black Bar 0.3 1.22 0.013 0.032 0.26 0.21 0.19 0.04 
10 

AST-1: Wet-Dry Exposures 

Specimens 

Both straight and bent rebar specimens were tested in this phase of the program. The former 

were sectioned directly from the as-received rebars to a length of 152 mm. In the latter case (bent 

bar specimens), the rebar was bent 180o

 to a radius that was four times the bar diameter. 

Specimens were acquired by then sectioning the bent portion of the rebar such that the 

circumferential length was approximately 200 mm. An electrical lead was mechanically attached 

to one end of each specimen via a screw and drilled and tapped hole. Specimens were then 

cleaned and the ends encapsulated with West System Brand marine epoxy type 105 and hardener 

type 207, a commercially available slow cure epoxy. Figures 3.1 and 3.2 show photographs of 

these two specimen types. In addition, MMFX-IITM and clad bars were prepared in surface 

abraded (A) and surface damaged (D) conditions. For clad bars, the intention in testing 

specimens with the A and D surface preparations was to evaluate possible effects of two degrees 

Figure 3.1. Photo. Straight, as-received, Stelax bar 

with epoxy-mounted ends and electrical lead. 
11 

Figure 3.2. Photo. Three bent, as-received Type 2201 stainless 

steel bars with electrical leads. 

of clad disruption on corrosion performance. The A condition did not penetrate the cladding, 

whereas the D condition did. Also, because MMFX-IITM is a relatively new alloy that involves 

proprietary thermo-mechanical processing, the possibility was considered that corrosion 

properties of the near surface might differ from the bulk. Abrasion (condition A) involved 

pressing the side surface of a rebar specimen for 30 seconds against a rotating round steel wire 

brush that was mounted in a drill press. This resulted in two, approximately two cm diameter 

abraded areas on each rebar specimen, as shown in figure 3.3. The D condition, on the other 

hand, involved drilling a 4.8 mm diameter hole to a depth of three mm on a bar side. Figure 3.4 

shows a photograph of a specimen prepared in this manner. Type 2201 stainless steel specimens 

were tested as-rolled (unpickled) and in addition with surface blasting using (1) steel shot, (2) 

stainless steel shot, and (3) silica sand. 

Test Procedure 

Figure 3.5 shows a photograph of this test system, which consisted of two polyethylene 

chambers, an elevated one in which rebar specimens were suspended and a lower one which 

served as a reservoir for the solution during the nonsubmerged period of each cycle. A timer and 

solenoid valve controlled the solution exchange between chambers. Figure 3.6 is a photograph of 

specimens under test. The exposure chamber was covered such that a high relative humidity was 

maintained during the dry period in order to maximize test severity during this 
12 

Figure 3.3. Photo. Abraded MMFX-IITM specimen. 

Figure 3.4. Photo. Damaged MMFX-IITM specimen. 

Figure 3.5. Photo. AST-1 wet-dry exposure setup. 
13 

Figure 3.6. Photo. AST-1 specimens under test in the upper hold tank (figure 3.5). 

phase. Triplicate specimens of a given material and specimen type were tested in a particular run. 

Polarization resistance (PR) measurements were made periodically on the rebar specimens 

during the submerged phase of the exposures using a Gamry CMS100 potentiostat with a scan 

rate of 0.33 mV/sec and polarizations of ±0.020 V referenced to the free corrosion potential. 

Prior to scanning, rebar potential was monitored for 300 seconds or until any potential variations 

were less than 0.1 mV/sec. From the measured PR, corrosion rate, CR, was calculated using a 

modified form of the Stern-Geary equation, 

PR

B

n F

Z CR 3.15 107 ⋅ ⋅ ⋅ρ = ⋅ ⋅ , (3.2) 

where Z is atomic weight, n is the number of electrical equivalents, F is Faraday’s constant, ρ is 

alloy density, and B is a constant that depends on the Tafel constants. In the present 

determinations, B was taken as 0.052 V for the metals that were assumed to be corroding 

passively (316, 2205, 2201, and 3Cr12) and 0.026 V for the actively corroding ones (MMFXIITM and black bar). An example calculation is provided in Appendix B. 

In addition, one rebar specimen of each material was removed at the completion of each 28-day 

period for weight loss determination. The average CR over the exposure duration was 

determined from before and after specimen weight measurements using the expression, 

ρ A T

W CR ⋅ ⋅ = , (3.3) 

where W is weigh loss, ρ is metal density, A is exposed rebar specimen surface area, and T is 

exposure time. An example calculation is provided in Appendix C. Overall, there were five 

separate AST-1 runs with the rebar and specimen type for each being as listed in table 3.3. This 

indicates that a total of 267 specimens were tested, with anywhere from 24 to 69 specimens 

being exposed in a particular run. Multiple runs on the same rebar type were performed to 

confirm run-to-run PR and corrosion rate reproducibility. Also, for a given run there were 
14 

triplicate specimens of the alloys tested. The lack of a pattern with regard to what rebars were 

exposed in a particular run was due, in part, to delays in acquiring some of the materials. 

Table 3.3. Listing of AST-1 runs and the rebar and specimen type for 

each (“x” indicates that the indicated alloy was tested during that run, 

and “2” indicates two sets of triplicate specimens). 

1 6

Material S S B S B S B S B S

Black Bar x x x x x x x - -

MMFX-II x x x x x - - x - -

MMFX-II(A) x x x x x - - x - -

MMFX-II(D) x x x x x - - x - -

3Cr12 - - - - - x(2) x(2) x - -

Type2201 x x x x x x x x - -

Type 2205 xxxxxxxx- -

Type 2201P x x - x - x - x - -

Type 2201(Fe Blast) - - - - - x- x- -

Type 2201(SS Blast) - - - - - x- x- -

Type 2201(Sand Blast) - - - - - x- x- -

Type 316.16 - - - - - x(2) x(2) x - -

Type 316.18 xxxxxxx- - -

Clad/Nouvinox - xxxxx- x- x

Clad/Nouvinox(A) - x - x - x - - - x

Clad/Nouvinox(D) - x - x - x - - - x

Clad /SMI - - - - - - - x - x

Clad/SMI(A) - - - - - - - x - x

Clad/SMI(D) - - - - - - - x - x

AST-1 Run Number

2345

AST-2A: Chloride Threshold Determinations 

The specimen type in this case was the same straight 152 mm long number 5 rebar employed in 

AST-1. The test procedure involved concurrent exposure of 20 rebar specimens which were 

potentiostatically polarized using a single, locally designed and constructed potentiostat. Current 

to each rebar specimen was calculated from the voltage drop across an individual 10-ohm 

resistor that was in series with each specimen. Chloride as NaCl was incrementally added to the 

simulated pore solution at time intervals of from one to several days. Figure 3.7 shows a 

schematic representation of this test system, and figure 3.8 provides a photograph. Figure 3.9 is a 

photograph of specimens under test. The rationale behind this approach considers that the 

polarized potential (+0.100 VSCE) is about 100 mV more positive than the upper value of the free 

corrosion (half-cell) potential that is likely to occur for rebar in concrete under outdoor 

atmospheric or splash zone exposure. As such, the critical chloride concentration (threshold) to 

cause loss of rebar passivity and onset of active corrosion, [ ] − Clth , should be less at this potential 

(+0.100 VSCE) than in actual service, thereby providing a conservative determination of this 

parameter. A current density of 10 μA/cm2

 was defined as indicative of corrosion initiation; and 
15 

Figure 3.8: Photograph of the AST-2A test system. 

Test 

Chamber 

Data 

Acquisition 

System

Potentiostat 

the corresponding [Cl-] was taken as [ ] − Clth . While this current density is somewhat arbitrary, it is 

the same as has been employed by others in similar experiments.17 The chloride threshold 

concentration is an important parameter for projection of time-to-corrosion, maintenance 

planning, and life-cycle cost analysis for reinforced concrete structures. 

 

Figure 3.7. Schematic illustration. AST-2A experimentation. 

Figure 3.8. Photo. AST-2A test system. 

Potentiostat 

Reference 

Electrode 

Counter Electrode 

Data Acquisition System 
16 

Figure 3.9. Photo. Test chamber with specimens. 

An initial, trial AST-2A run employed either one or two rebar specimens for six of the alloys. 

Subsequent runs employed 10 identical specimens of two rebar types. Table 3.4 provides a 

listing of these for the three runs that have been completed (total of 52 specimens). The relatively 

large number of specimens of each alloy in the latter two runs serves as a basis for statistical 

treatment of the resulting [ ] − Clth data. Thus, considering that [ ] − Clth is a statistically distributed 

parameter and that the results from this study can be related to actual service in concrete, then it 

should be possible to project the percentage of rebar for which corrosion initiates at a given [Cl-

]. 

This is directly related to practice in the sense that repairs and rehabilitations are often initiated 

in response to a certain percentage of substructure spalling or deck delamination. 

Table 3.4. Listing of each AST-2A run according to rebar type and number of specimens. 

1 1 1 2 2 2 11 1 1

2 - - 10 - - 10 - - -

3 10 10 - - - - - - -

AST-2A Run 

Number 316.18 MMFXIITM

MMFXIITM (A) 3Cr12 MMFXIITM (D) BB 2201 2205 316.16

Number of Specimens

AST-2B: Pitting Potential Determinations 

Specimens 

Three types of specimens, defined according to orientation and preparation of the exposed 

surface, were tested in order to determine the respective pitting potentials. These included (1) 

longitudinally oriented rebar specimens that were similar to the AST-1 and AST-2A ones except 

that length was 30 mm with (a) the as-received surface condition and (b) a machined and 600 grit 

polished surface condition and (2) sectioned rebar specimens where the cross-section (machined 
17 

and 600 grit polished) was exposed. The objective of employing multiple specimen orientations 

and surface conditions was to determine any effect these might have upon corrosion properties. 

Figures 3.10 through 3.13 show schematic illustrations and photographs of these three specimen 

types. Four rebar types, 316.16, 2201, MMFX-IITM, and 3Cr12, were tested using this protocol. 

Test Procedure 

These experiments utilized a one liter glass container with a threaded Teflon-lined lid. Five holes 

were drilled in the lid for insertion of electrical leads and tubing for nitrogen gas purging. Each 

of the leads and the tubing were mounted in a sealed rubber stopper which was fitted into the lid. 

The immersion solution for the rebar specimens was saturated Ca(OH)2 containing 0 to 10 w/o 

NaCl (0-6.07 w/o Cl-

). The rebar specimen potential normally stabilized after about 20 minutes 

of high purity nitrogen gas purging of the solution. Purging continued throughout the 

experiments. Figure 3.14 provides a photograph of the test cell. The same Gamry system as for 

the AST-1 experiments (see above) was employed to perform the scans. These were initiated at a 

potential of −0.600 VSCE in order to reduce surface oxides and reduce any effect of these on 

electrochemical response. The scans proceeded positively to +1.000 VSCE or 2.00 mA/cm2

, 

whichever occurred first. This assured that a relatively broad potential range was covered. The 

scan was then reversed and terminated at −0.500 V SCE. The forward and reverse scan rates were 

both 0.50 mV/s, but a limited number of experiments were performed at 0.33 and 1.00 mV/s. A 

minimum of three replicate experiments was performed for each set of variables with each scan 

using a newly prepared specimen. Table 3.5 lists the number of tests for each rebar and specimen 

type and surface condition. A total of 116 scans were performed. 

Exposed 

Circumferential 

Surface 

50 

Epoxy 

16 

Electrical 

Connection 

30 

10 Dimensions 

in mm 

(a) (b) 

Figure 3.10. Illustration and photo. Schematic illustration (a) and 

photograph (b) of the as-received, circumferential AST-2B test specimen. 
18 

Figure 3.11. Photo. Polished circumferential specimen. 

Figure 3.12. Schematic illustration. Polished cross section surface specimen. 

Epoxy 

Polished cross 

section 

Electrical 

lead

Figure 3.13. Photo. Two polished cross section specimens. 

End mount 

epoxy 

Specimen 

50 mm 

Epoxy 

Polished 

Cross Section 

15 mm 
19 

Counter 

Electrode 

Mesh 

Specimen 

SCE 

Figure 3.14. Photo. Test cell for potentiodynamic polarization measurements. 

Table 3.5. Listing of the number of AST-2B tests for each specimen type and surface 

condition. 

0.05 0.50 1.00 2.00 5.00 10.00

Cross Section/Polished 0.50 - 3 - - - -

Circumferential/Polished 0.50 - 3 - - - -

0.33 - 3 - - - -

0.50 3 3 3 4 3 4

1.00 - 3 - - - -

3Cr12 Circumferential/As-Received 0.50 33643 4

Circumferential/As-Received 0.50 34434 3

Circumferential/Pickled 0.50 3 4 3 3 3 5

316.16 Circumferential/As-Received 0.50 33334 3

MMFX-IITM

Circumferential/As-Received

2201

Number of Specimens

Rebar Type Specimen Type/Surface 

Condition

Scan Rate, 

mV/sec.

Concentration, w/o NaCl

LONG-TERM TESTS 

Specimen Design 

General 

Four different types of reinforced concrete specimens, designated (1) simulated deck slabs 

(SDS), (2) two different types of three bar column specimens (designations S3BC and 3BTC),1

(3) macro-cell slabs (MS), and (4) field columns (FC), were fabricated by the Florida 

 

1

 The S3BC designation signifies a square column specimen with three rebars, and 3BTC indicates a 

tombstone column (rectangular cross section) specimen with three rebars. Each is described 

subsequently in detail. 
20 

Department of Transportation State Materials Office (FDOT-SMO) in Gainesville. Three 

concrete mix designs, designated (1) STD1 (5 bags cement and 0.5 w/c) which yields a high 

permeability concrete, (2) STD2 (7 bags of cement and 0.41 w/c) which results in moderate 

permeability, and (3) STD3 (7 bags of cement and 0.50 w/c) which is of intermediate 

permeability, were employed. Target mix designs are listed in table 3.6. The various corrosion 

resistant alloy types in addition to black bar (table 3.1) were used as reinforcement. Table 3.7 

provides a listing of the different specimen types and bar configurations that were prepared, each 

of which is discussed in detail below. The clad bars were placed in the as-received condition 

with and without intentional damage (3 mm diameter clad penetrations spaced 25 mm apart). 

Specimens were cured subsequent to casting and prior to exposure for a minimum of 6 months in 

a warehouse with no temperature or humidity control. All bars were nominally 16 mm in 

diameter (number 5) and, unless noted otherwise, had the as-received surface finish (table 3.1). 

Table 3.6. Concrete mix designs. 

Material STD1 STD2 STD3

Cement (Bags) 5 7 7

Cement, kg 213 300 300

Water, kg 107 122 149

Water/Cement 0.5 0.41 0.5

Fine Aggregate (silica sand), kg 652 540 489

Coarse Aggregate (limestone), kg 753 753 747

Simulated Deck Slabs 

The simulated deck slab (SDS) specimens were fabricated with six bars; three of which comprised a top 

mat and three the bottom mat, as illustrated schematically in figure 3.15. Concrete cover for all bars was 

25 mm; and triplicate specimens were prepared for each bar type and specimen variable, as described 

below. Concrete mix designs STD1 and STD2 were employed but with most specimens being prepared 

using the former. Because of material inventory limitations, no Stelax bars with intentional clad damage 

were included in this phase of the study. Five different modifications to the above standard slab 

configuration have been prepared to date and are under test, as listed and described below. 

1. Slabs with black bottom bars (designated BCAT). For these, the bottom mat was comprised 

of black bars whereas the top bars were one of the corrosion resistant alloys. 

2. Slabs with a simulated concrete crack (designated CCON). In fabrication of these specimens, 

a 1.6 mm thick stainless steel shim was placed vertically in the form on top of and 

perpendicular to the upper bars at their center. The shim was removed subsequent to the 

initial concrete set. 

3. Slabs with bar crevice (splice) (designated CREV). In this case, two bars that overlapped for 

a portion of their length replaced each of the three single top bars in the standard specimen. 

Hence, the top mat of reinforcement consisted of six rebars instead of three, as was the case 

for the other slab types. Cover for each of the bar pairs was maintained at 25 mm. Figure 

3.16 illustrates this specimen type schematically. 

4. Slabs with a bar crevice (splice) per configuration (3) but with a simulated concrete crack 

also (designated CCRV). 

5. Slabs with a simulated concrete crack and black bar cathode (designated CCNB). 
21

Table 3.7. Listing of the various specimen types, variables, and nomenclature for each

Specimen 

Designation Description 

STD1 STD1 concrete mix. 

STD2 STD2 concrete mix. STD3 STD3 concrete mix. 

BCAT STD1 concrete, bottom mat black steel. CCON STD1 concrete mix, simulated concrete crack. 

CCNB STD1 concrete mix, bottom mat (cathode) black bars, simulated concrete crack. 

CREV STD1 concrete mix, top bar crevice. 

CCRV STD1 concrete mix, simulated concrete crack, top bar crevice. 

STD1 concrete mix, top bar bent STD3 concrete mix, top bar bent 

BNTB STD1 concrete mix, top bar bent, bottom bars black steel. CBNT STD1 concrete mix, simulated concrete crack, top bar bent. CBNB STD1 concrete mix, simulated concrete crack, bottom bars black steel, top bar bent. 

STD1 concrete mix, one bar elevated. STD3 concrete mix, one bar elevated. 

WB STD1 concrete mix, top bars wire brushed. 

ARWB STD1 concrete mix, top bars as received. 

USDB STD1 concrete mix, 3 mm diameter clad holes 25 mm apart on top bars. 

UBDB STD1 concrete mix, 3 mm diameter clad holes 25 mm apart on top bars, top bar bent. 

CSDB STD1 concrete mix, simulated concrete crack, 3 mm diameter clad holes 25 mm apart. CBDB STD1 concrete, cracked concrete, 3 mm diameter clad holes 25 mm apart on top bars, top bar bent. BCCD STD1 concrete mix, 3 mm diameter clad holes 25 mm apart on top bars, bottom bars black steel. 

ACID STD1 concrete mix, top bars lab pickled, cathode as received. 

BENT

ELEV

* SDS: Simulated deck slab. 

S3BC: Square 3-bar column. 3BTC: 3-bar tombstone column. MS: Macroslab FC: Field column. 
22 

Figure 3.15. Schematic illustration. Standard simulated deck slab specimens. 

Figure 3.16. Schematic illustration. CREV type simulated deck slab specimens. 

Because the specimens were fabricated over a period of time, they were delivered to FAU on 

three separate occasions. The following example illustrates the nomenclature that was adapted to 

identify a standard specimen: 

 1-STD2-316(18)-3 

Figure 3.17. Graphic. Standard specimen nomenclature. 

There were three Specimen Lot Numbers corresponding to one of the three groups of specimens 

that were delivered to FAU by FDOT at different times. Likewise, designation of specimens that 

were nonstandard (BCAT, CCON, ...) is illustrated by the following example: 

Specimen 

Lot Number 

Concrete 

Mix Design 

Type 

Reinforcement 

Type 

Specimen 

Number 

NaCl 

Pond 

All 

dimensions in 

cm. 

30

30

15

All 

dimensions in 

cm.

2

30

26

30

NaCl 

Pond 
23 

Specimen 

Type 

3-CREV-3Cr12-2 

Figure 3.18. Graphic. Nonstandard specimen nomenclature. 

Thus, the latter identifies this as simulated deck slab specimen number 2 with 3Cr12 

reinforcement in the crevice configuration from lot 3. The default mix design (no indication) was 

STD1. 

Once slabs were delivered to FAU, their condition between the different lots was normalized by 

placement in air conditioned space for 2 months. During this time, a hard electrical connection 

was established between bars in each of the two mats of each slab using a stainless steel wire in 

conjunction with a screw and drilled and tapped hole in each bar end. The wires from each mat 

were normally connected; but the circuit was periodically interrupted during the exposures and a 

10 Ω resistor temporarily inserted. This allowed measurement of the voltage drop between the 

mats from which macro-cell current was calculated. This current was then divided by the surface 

area of the three top bars to obtain current density. The specimen sides were epoxy coated, and a 

plastic bath with a vented lid was attached to the top concrete surface in preparation for ponding 

with a salt water solution. Exposure for the three sets of specimens commenced on June 9, 

August 5, and October 30, 2003, respectively. Salt water ponding consisted of a 1-week wet— 

1-week dry cycle with 15 w/o NaCl (9.10 w/o Cl-

). Figure 3.17 shows a single specimen under 

test, and figure 3.18 is a perspective view of the test site. 

Three Bar Columns 

Two different versions of this type specimen, the square 3-bar column (S3BC) and the 3-bar 

tombstone column (3BTC), were prepared. Each of these has three bar geometries: normal, bent, 

and elevated. The two configurations (S3BC and 3BTC) are illustrated schematically in figures 

3.19 and 3.20, respectively, where the S3BC specimens were fabricated using concrete mixes 

STD1 and STD2 and the 3BTC using STD2 and STD3 (table 3.6). Initially, the square geometry 

only (S3BC) was to be employed; but subsequent to these being prepared, the 3BTC was 

developed, considering the fact that chlorides can reach the reinforcement from three sides rather 

than one which provides a more severe exposure. The normal reinforcement configuration has 

been employed by the FDOT for more than 10 years and was intended to provide baseline data 

that can be compared to results from previous studies. On the other hand, the bend bar 

configuration was considered particularly relevant in the case of the stainless clad and possibly 

the MMFX-IITM reinforcements. The elevated bar geometries were intended to provide different 

anode-cathode area ratio of bars and, possibly, enhance macro-cell activity. Six specimens of 

each rebar type were prepared and exposed for each test condition. Subsequent to curing, these 

were partially submerged in a 3.5 w/o NaCl solution to a depth of 152 mm for the purpose of 

facilitating formation of an electrochemical macro-cell on each of the long bars. Figure 3.21 

shows the outside screen room at the FDOT-SMO facility (north central Florida) where the 

specimens are exposed. 

Specimen 

Lot No. 

Reinforcement 

Type 

Specimen 

No. 
24 

Figure 3.19. Photo. Ponded deck slab specimen under test. 

Figure 3.20. Photo. Perspective view of exposure site and specimens. 
25 

Figure 3.21. Schematic illustration. Square three bar column specimen for 

each of the three bar configurations. 

Figure 3.22. Schematic illustration. Tombstone type three bar column 

specimen for each of the three bar configurations. 

All dimensions 

in mm 

Cathode 

51 

152 

546 

165 64 

Water Level Normal Bent Elevated 

165 64 165 64 

Anode 

All 

dimensions 

152 

610 

120 120 

120 120 

120 

120 

Water Level Normal Bent Elevated 
26 

Figure 3.23. Photo. Three bar column specimens under exposure. 

Once exposure was initiated, the individual bar potentials in each of the two specimen types 

(S3BC and 3BTC) were measured monthly. In addition, for the 3-bar tombstone columns 

(3BTC) macro-cell current between the two long bars (anode) in each specimen and the short bar 

(cathode) was measured. The potential of all three bars coupled together was also measured. 

These readings were acquired daily using a custom designed data acquisition system. Specimen 

exposure was terminated upon concrete cracking or visible corrosion product bleed-out. 

Macro-Cell Slab Specimens 

Specimens of this type were fabricated with the reinforcement having been wire brushed, 

although one set was prepared using the bars as-received. Two bar configurations, straight and 

bent, were employed, as illustrated by figure 3.22. The macro-cell slab STD1 specimens were 

made with and without a simulated crack, but specimens based upon the STD2 concrete mix 

were standard (no crack). Subsequent to curing, the specimens were inverted; and a 76 x 152 mm 

pond was attached to what had been the bottom cast face. Specimens were exposed to 14 days 

wet—14 days dry cyclic ponding with 3.0 w/o NaCl solution until corrosion induced cracking 

occurred. Figure 3.23 shows the exposure arrangement, which was similar to the one for the 3-

bar columns. As was done for the 3-bar columns, macro-cell current between the top single bar 

(anode) and lower four electrically connected bars (cathode) was recorded daily via a data 

acquisition system, whereas potential measurements were only made manually on a monthly 

basis. 
27 

Figure 3.24. Schematic illustration. Geometry of the macro-cell slab type 

specimen with both bent and straight bars. 

Figure 3.25. Photo. Macro-cell slab specimens under exposure. 

Field Columns 

These specimens were made using the STD1 concrete mix design only and with all bars in the 

as-received condition. Figure 3.24 is a schematic drawing that illustrates the specimen geometry. 

Each bar is electrically isolated from the others. The columns have been exposed in the intercoastal waterway at Crescent Beach, FL by burying the bottom 1.2 m in bottom soil such that 

mean high water is 1.8 m from the specimen bottom; however, placement was delayed because 

of environmental permitting issues and only commenced in September 2005. Figure 3.25 is a 

photograph of the specimens and exposure site. Polarization resistance and potential of each 

individual bar was measured at the time of initial exposure. These measurements are to be 

obtained every 6 months until corrosion cracking or visible corrosion product bleed out is 

observed. 

114

280 114

Normal Bent Bar 

All dimensions in mm 
28 

Tables 3.8 through 3.13 list the number of specimens for each specimen configuration and type 

of reinforcement (316.18 and 3Cr12, 2201, MMFX-IITM, Stelax, SMI, and black bar). 

Figure 3.26. Schematic illustration. Geometry of the field column type specimen. 

Figure 3.27. Photo. Field column specimens under exposure 

at the Intracoastal Waterway site in Crescent Beach, FL. 

3.05 m 152 152 

Epoxy Coating

Test box with insulated 

lead wires to bars

1.52 m

Where not indicated, 

dimensions in mm 
29 

Table 3.8. Listing of specimens reinforced with 316.18 and 3Cr12. 

Description SDS S3BC 3BTC MS FC

STD1 mix design, standard specimen. 3 6 - 6 3

STD3 mix design, standard specimen. 3 3 3 3 -

STD2 mix design, standard specimen. - - 6 - -

STD1-BCAT. 3 - - 3 -

STD1-CCON. 3 - - 3 -

STD1-CCNB. 3 - - 3 -

STD1-CREV. 3 - - - -

STD1-CCRV. 3 - - - -

STD1-BENT. - 3 - 3 -

STD3-BENT. - - 3 - -

STD1-BNTB. - - - 3 -

STD1-CBNT. - - - 3 -

STD1-CBNB. - - - 3 -

STD1-ELEV. - 3 - - -

STD3-ELEV. - - 3 - -

STD1-WB. 3 - - - -

STD1-ARWB. - - - 3 -

Total 24 15 15 33 3

TOTAL 90

Table 3.9. Listing of specimens with 2201 rebar (specimens in shaded cells not 

yet fabricated). 

Description SDS S3BC 3BTC MS FC

STD1 mix design, standard specimen. 36-63

STD3 mix design, standard specimen. 3333-

STD2 mix design, standard specimen. --6--

STD1-BCAT. 3--3-

STD1-CCON. 3--3-

STD1-CCNB. 3--3-

STD1-CREV. 3----

STD1-CCRV. 3----

STD1-BENT. - 3 3 3 -

STD3-BENT. --3--

STD1-BNTB. ---3-

STD1-CBNT. ---3-

STD1-CBNB. ---3-

STD1-ELEV. - 3 3--

STD3-ELEV. --3--

STD1-WB. 3----

STD1-ARWB. - - - 3 -

STD1-ACID. 3---

STD1-ABRD 3

30 15 15 33 3

TOTAL 96
30 

Table 3.10. Listing of specimens reinforced with MMFX-IITM. 

Description SDS S3BC 3BTC MS FC

STD1 mix design, standard specimen. 3 6 - 6 3

STD2 mix design, standard specimen. 3 3 3 3 -

STD3 mix design, standard specimen. - - 6 - -

STD1-BCAT. 3 - - 3 -

STD1-CCON. 3 - - 3 -

STD1-CCNB. 3 - - 3 -

STD1-CREV. 3 ----

STD1-CCRV. 3 ----

STD1-BENT. -3-3-

STD3-BENT . - - 3 - -

STD1-BNTB. --- 3 -

STD1-CBNT. --- 3 -

STD1-CBNB. --- 3 -

STD1-ELEV. -3---

STD3-ELEV. - - 3 - -

STD1-WB. 3 ----

STD1-ARWB. --- 3 -

STD1-USDB. 3 - - 3 -

STD1-ACID. 3 ----

STD1-ABRD. 3 ----

33 15 15 36 3

TOTAL: 102

Table 3.11. Listing of specimens reinforced with Stelax (specimens in shaded 

cells not yet fabricated). 

Description SDS S3BC 3BTC MS FC

STD1 mix design, standard specimen. 3 6 - 6 3

STD2 mix design, standard specimen. 3 3 3 3 -

STD3 mix design, standard specimen. - - 6 - -

STD1-CCON. 3 - - 3 -

STD1-CREV. 3 ----

STD1-CCRV. 3 ----

STD1-BENT. - 3 3 3 -

STD3-BENT . - - 3 - -

 STD1-CBNT. --- 3 -

STD1-ELEV. - 3 3 - -

STD3-ELEV. - - 3 - -

STD1-WB. 3 ----

STD1-ARWB. --- 3 -

STD1-USDB. 3 - - 3 -

STD1-UBDB. --- 3 -

STD1-CSDB. 3 - - 3 -

STD1-CBDB. --- 3 -

STD1-BCCD. 3 - - 3 -

STD1-ACID. 3 ----

STD1-ABRD. 3 ----

STD1-CVNC . 3 ----

36 15 15 36 3

TOTAL: 105
31 

Table 3.12. Listing of specimens reinforced with SMI (specimens in shaded cells not yet 

fabricated). 

Description SDS S3BC 3BTC MS FC

STD1 mix design, standard specimen. 3 - - 6 3

STD2 mix design, standard specimen. 3 - 3 3 -

STD3 mix design, standard specimen. - - 6 - -

STD1-CCON. 3 - - 3 -

STD1-CREV. 3 ----

STD1-CCRV. 3 ----

STD1-BENT. ---3-

STD3-BENT . - - 3 - -

 STD1-CBNT. --- 3 -

STD1-ELEV. -----

STD3-ELEV. - - 3 - -

STD1-WB. 3 ----

STD1-ARWB. --- 3 -

STD1-USDB. 3 - - 3 -

STD1-UBDB. --- 3 -

STD1-CSDB. 3 - - 3 -

STD1-CBDB. --- 3 -

STD1-BCCD. 3 - - 3 -

STD1-ABRD. 3 ----

STD1-CVNC . 3 ----

33 0 15 36 3

TOTAL: 87

Table 3.13. Listing of specimens reinforced with black bar. 

Description SDS S3BC 3BTC MS FC

STD1 mix design, standard specimen. 36-93

STD2 mix design, standard specimen. 3663-

STD3 mix design, standard specimen. --6--

CCON - STD1, Cracked concrete. 3 - -3 -

9 12 12 15 3

TOTAL: 51

33 

4. EXPERIMENTAL RESULTS AND DISCUSSION 

SIMULATED PORE WATER PH DATA FOR AST-1 AND AST-2 

Figure 4.1 plots simulated pore water pH versus time for representative AST-1 and AST-2A 

experiments. Both sets of data approximately superimpose and show a progressive pH decrease 

with time from an initial value of 13.28 (AST-1) to a final of 13.12. This reflects a contribution 

of the common ion effect from addition of chlorides and possibly carbonation, the former being 

evidenced by the step decrease in pH of the AST-1 solution pH at 28 and 56 days (times at which 

[Cl-

] was increased). This pH decrease is not a significant concern for interpretation of the AST1 data, but it is important for projection of [ ] − Clth , since this parameter is a function of Cl-

 to OHratio. 

13.0

13.1

13.2

13.3

13.4

13.5

0 10 20 30 40 50 60 70 80

Exposure Time, days

pH

0

1

2

3

4

5

6

7

8

9

10

Chloride Concentration, w/o

pH, AST-1

pH, AST-2A

[Cl-], AST-1

[Cl-], AST-2A

Figure 4.1. Graph. Change in pH and [Cl-] as a function of time for 

AST-1 and AST-2 experiments. 

AST-1 

Table 4.1 lists the average PR for straight bar specimens of each alloy during the successive 

28-day exposures of the six individual AST-1 runs. Likewise, table 4.2 shows the average PR for 

the individual straight bar specimens of each alloy. Figure 4.2 plots polarization resistance, PR, 

versus exposure time for straight, as-received bars and illustrates the range of behavior and data 

scatter that characterized these measurements. Thus, PR data scatter was relatively large (in 

excess of one order of magnitude) for the most resistant alloy represented here (316.18 as well as 

for 2205); but the overall trend was generally constant with time. Data scatter was less and 

conformed to a downward trend with time for MMFX-IITM, 3Cr12, and black bars. This probably 

reflects localized passive film instabilities in the case of 3Cr12; however, these were probably 
34 

less of a factor, if a factor at all, for the actively corroding MMFX-IITM and black bars for which 

progressive oxygen concentration polarization was controlling. The decrease in PR with time, 

where this occurred, reflects an effect of time per se rather than increased [Cl-

], since the decay 

showed no abrupt changes at the times of Cl-

 additions. 

Table 4.1. Average polarization resistance for each alloy during each 

28-day period of six individual AST-1 runs. 

316(18) 2201P MMFX MMFX-A MMFX-D BB

3% NaCl 1.89E+06 6.59E+04 5.43E+04 5.43E+04 3.83E+04 2.16E+03

9% NaCl 1.71E+06 5.71E+04 1.98E+04 2.78E+04 2.13E+04 1.26E+03

15% NaCl 2.83E+06 3.07E+04 1.39E+04 1.29E+04 1.73E+04 8.15E+02

Average Polarization Resistance (Run 1), ohm/cm2

316(18) 2201 2201P MMFX MMFX-A MMFX-D BB

3% NaCl 3.19E+06 5.78E+04 8.13E+04 5.82E+04 7.30E+04 3.75E+04 2.71E+03

9% NaCl 4.18E+06 5.42E+04 5.85E+04 2.55E+04 3.04E+04 3.03E+04 1.68E+03

15% NaCl 6.60E+06 4.98E+04 1.49E+05 1.29E+04 1.41E+04 2.92E+04 8.86E+02

Average Polarization Resistance (Run 2), ohm/cm2

316(18) 2205 2201 2201P MMFX MMFX-A MMFX-D BB

3% NaCl 3.97E+06 6.83E+04 5.91E+04 5.30E+04 5.87E+04 3.69E+04 3.06E+04 2.37E+03

9% NaCl 2.84E+06 7.37E+04 7.01E+04 4.84E+04 2.01E+04 1.31E+04 1.66E+04 1.19E+03

15% NaCl 3.57E+06 6.85E+04 4.75E+04 3.08E+04 1.15E+04 8.18E+03 1.00E+04 9.00E+02

Average Polarization Resistance (Run 3), ohm/cm2

316(16) 316(16) 3Cr12 3Cr12 Stelax Stelax-A Stelax-D

3% NaCl 1.54E+06 2.61E+06 3.75E+04 4.57E+04 2.40E+04 4.45E+04 2.94E+04

9% NaCl 2.02E+06 1.52E+06 2.78E+04 2.52E+04 1.05E+04 1.76E+04 7.18E+03

15% NaCl 1.65E+06 2.22E+06 1.19E+04 1.31E+04 9.76E+03 1.81E+04 4.71E+03

Average Polarization Resistance (Run 4), ohm/cm2

316(16) 3Cr12 Stelax Stelax-A Stelax-D SMI SMI-A SMI-D

3% NaCl 1.50E+06 3.59E+04 9.51E+04 5.72E+04 2.58E+04 3.06E+05 2.91E+05 1.65E+05

9% NaCl 2.24E+06 2.95E+04 5.46E+04 5.80E+04 1.26E+04 3.03E+05 3.38E+05 1.32E+04

15% NaCl 6.88E+05 1.83E+04 5.74E+04 3.63E+04 1.16E+04 1.78E+05 1.77E+05 1.23E+04

Average Polarization Resistance (Run 5), ohm/cm2

SMI SMI-A SMI-D SMI SMI-A SMI-D

3% NaCl 6.09E+05 4.59E+05 7.45E+04 7.83E+05 3.59E+05 8.49E+04

9% NaCl 4.58E+05 4.09E+05 2.26E+04 5.63E+05 4.52E+05 1.37E+04

15% NaCl 2.87E+05 4.14E+05 1.45E+04 1.59E+05 6.72E+05 1.26E+04

Average Polarization Resistance (Run 6), ohm/cm2
35 

Table 4.2. Polarization resistance for each alloy averaged over 

the six individual AST-1 runs. 

316(18) 316(16) 2205 2201 2201P MMFX MMFX-A MMFX-D

3% NaCl 3.E+06 2.E+06 7.E+04 6.E+04 7.E+04 6.E+04 5.E+04 4.E+04

9% NaCl 3.E+06 2.E+06 7.E+04 6.E+04 5.E+04 2.E+04 2.E+04 2.E+04

15% NaCl 4.E+06 2.E+06 7.E+04 4.E+04 7.E+04 1.E+04 1.E+04 2.E+04

3Cr12 BB Stelax Stelax-A Stelax-D SMI SMI-A SMI-D

3% NaCl 4.E+04 2.E+03 5.E+04 5.E+04 2.E+04 6.E+05 4.E+05 1.E+05

9% NaCl 3.E+04 1.E+03 3.E+04 3.E+04 1.E+04 4.E+05 4.E+05 2.E+04

15% NaCl 1.E+04 9.E+02 4.E+04 2.E+04 7.E+03 2.E+05 4.E+05 1.E+04

Average Polarization Resistance (all runs), ohm/cm2

1.00E+02

1.00E+03

1.00E+04

1.00E+05

1.00E+06

1.00E+07

1.00E+08

0 10 20 30 40 50 60 70 80 90 100

Exposure Time, days

Polarization Resistance, Ohm.c

m

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

9.0

10.0

Chloride Concentration, w/

316.18(1) 2205(1) MMFX(1) Black(1)

316.18(2) 2205 (2) MMFX (2) Black(2)

316.18(3) 2205(3) MMFX(3) Black(3)

3Cr12(5) 3Cr12(6-1) 3Cr12 (6-2) ClFigure 4.2. Graph. Plot of polarization resistance versus exposure time for representative 

alloys during different AST-1 runs (numbers in parentheses). 

Figure 4.3 reproduces the 2205, MMFX-IITM, 3Cr12, and black bar data from figure 4.2 but with 

results for 2201 added. The more expanded PR scale allows these results to be viewed in greater 

detail. This shows that PR for 2205, 2201, MMFX-IITM, and 3Cr12 were in the range 

104

 to 105 Ω·cm2, with 2205 occupying the upper bound, MMFX-IITM ad 3Cr12 the lower, and 

2201 intermediate. The black bar data, on the other hand, are in the range 103

 to 104 Ω·cm2. As 

noted above, PR for MMFX-IITM, 3Cr12, and black bar decreased with exposure time, whereas 

values for 2205 tended to remain constant. The 2201 data are intermediate in that these exhibit a 

slight downward trend during the third phase of the exposure. The data in each case are from 
36 

three different runs; and it was concluded from the reproducibility between these for the different 

rebar types that any run-to-run variations were within the range of inherent data scatter. 

1.00E+02

1.00E+03

1.00E+04

1.00E+05

1.00E+06

0 10 20 30 40 50 60 70 80 90 100

Exposure Time, days

Polarization Resistance, ohm.cm2

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

9.0

10.0

Chloride Concentration, w/o

2205(1-3) 2201 (1-3)

MMFX(1-3) Black Bar(1-3)

3Cr12(5-6) ClFigure 4.3. Graph. Plot of polarization resistance versus exposure time for intermediate 

performing alloys and black bars during different AST-1 (number in parentheses 

after each alloy designation indicates different AST-1 runs. 

Figure 4.4 plots PR versus exposure time for 2201 stainless steel specimens with different 

surface preparations, including as-received (see table 3.1), steel shot (Fe) blasted, stainless steel 

(SS) shot blasted, and silica sand blasted. The data referenced as “Jensen Beach” pertain to 2201 

reinforcement that was acquired from a bridge construction site in Jensen Beach, FL, and was 

from the same heat as the other 2201 specimens; but the Jensen Beach bars had been silica sand 

surface blasted. These bars experienced about 6 weeks of uncovered atmospheric exposure 

approximately 1 km inland prior to being acquired. The sand blasted specimens exhibit PR 

values that approach being an order of magnitude greater than the as-received and metal blasted 

ones but with a trend where the former merged with the latter as the 84-day exposure progressed. 

Figure 4.5 plots PR versus exposure time for the two 316 stainless steel clad bars (Stelax and 

SMI), in comparison to data for solid 316 stainless steel bars. The results show that PR for the 

SMI bars averaged about one order of magnitude below that for the solid SS bars but with some 

data overlap. Data for the Stelax are about two orders of magnitude below those for the solid 

bars. Differences in surface condition are thought to be responsible for these variations. 

Likewise, figure 4.6 shows this same clad bar data along with results for the abraded (A) and 

damaged (D) surface conditions. Little difference is apparent between intact and abraded bars; 

but the damaged clad resulted in the lowest PR values, which were generally the same for both 

clad bar types. 
37 

1.00E+04

1.00E+05

1.00E+06

0 10 20 30 40 50 60 70 80 90

Exposure Time, days

Polarization Resistance, ohm.cm2

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

9.0

10.0

Chloride Concentration, w/o

2201-As-Received 2201-Fe Blasted

2201-SS Blasted 2201-Sand Blasted

2201 - Jensen Beach ClFigure 4.4. Graph. Plot of polarization resistance versus exposure time for 2201 

stainless steel AST-1 specimens with different surface preparation conditions. 

1.00E+03

1.00E+04

1.00E+05

1.00E+06

1.00E+07

1.00E+08

0 10 20 30 40 50 60 70 80 90 100

Exposure Time, days

Polarization Resistance, ohm.cm2

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

9.0

10.0

Chloride Concentration, w/o

Stelax (2)

Stelax(3)

Stelax(4)

SMI

SMI(6-1)

SMI(6-2)

316.18(1)

316.18(2)

316.18(3)

ClFigure 4.5. Graph. Plot of polarization resistance versus exposure time for 

clad stainless steel AST-1 specimens. 
38 

1.00E+03

1.00E+04

1.00E+05

1.00E+06

1.00E+07

0 10 20 30 40 50 60 70 80 90

Exposure Time, days

Polarization Resistance, ohm.cm2

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

9.0

10.0

Chliride Concentration, w/o

Stelax Stelax(D)

Stelax(A) SMI

SMI(D) SMI(A)

ClFigure 4.6. Graph. Plot of polarization resistance versus exposure time for clad stainless 

steel AST-1 specimens in the intact, abraded (A), and damaged (D) conditions. 

Figure 4.7 plots PR for straight versus bent solid bars. If both specimen types had the same 

corrosion rate, then PR for each should be the same and the data lay along the 1:1 line. In 

general, such a correlation is apparent but with some displacement to higher PR (lower corrosion 

rate) for the bent bars. The reason for this is unclear. Likewise, figure 4.8 shows a similar plot for 

the two types of clad bars. Here also, the data track has a 1:1 correlation but with more scatter 

than for the solid bars. Consistent with figure 4.6, the undamaged SMI bars exhibit PRs about an 

order of magnitude greater than for the Stelax ones. Also, damage apparently had only a modest 

effect on PR of Stelax bars but reduced PR for SMI bars to the same range as for the damaged 

Stelax. 

Table 4.3 lists the average corrosion rate for runs 1 through 4 (weight loss determinations were 

not made for runs 5 and 6) calculated from weight loss for specimens of each alloy (equation 3.3) 

at the end of the indicated 28-day period. Likewise, table 4.4 shows the average corrosion rate 

for each alloy averaged over the different runs in cases where the same alloy was used in 

different runs. Figure 4.9 shows a comparison between these corrosion rates as calculated from 

weight loss and from PR (equation 3.2). Data for the intermediate performers (3Cr12, 

MMFX-IITM, 2201, and 2205) generally track the 1:1 trend; however, the PR based corrosion 

rate for black bars exceeds that from weight loss with the opposite trend being apparent for 316, 

both by almost an order of magnitude. The B value for 316 would have to increase to 0.40 V and 

the black bar decrease to 0.008 V, both of which seem unrealistic, to bring these two data sets to 

the 1:1 line. A possible explanation for data displacement from the 1:1 line is that PR in the 

present experiments reflects corrosion rate during the submerged portion of the wet-dry cycle, 

whereas weight loss averaged attack during both periods. Reconciling the two sets of data on this 
39 

basis requires then that corrosion rate of the 316 was greater during the nonsubmerged phase and 

black bar greater during the submerged phase. 

1.00E+02

1.00E+03

1.00E+04

1.00E+05

1.00E+06

1.00E+07

1.00E+02 1.00E+03 1.00E+04 1.00E+05 1.00E+06 1.00E+07

Polarization Resist. (Bent), ohm.cm2

Polarization Resist. (Straight), ohm.cm2

MMFX D

MMFX

2201

2205

316.18(2)

Black Bar

3Cr12

Figure 4.7. Graph. Plot of polarization resistance for straight versus bent solid bars. 

1.00E+03

1.00E+04

1.00E+05

1.00E+06

1.00E+07

1.00E+03 1.00E+04 1.00E+05 1.00E+06 1.00E+07

Polarization Resist. (Bent), ohm.cm2

Polarization Resist. (Straight), ohm.cm2

Stelax 

Stelax(D)

SMI

SMI(D)

Figure 4.8. Graph. Plot of polarization resistance for straight versus bent clad bars. 
40 

Table 4.3. Corrosion rate calculated from weight loss of individual specimens of 

each alloy at the end of the indicated NaCl exposure for the indicated run. 

316(18) 2201 2201P MMFX MMFX-A MMFX-D BB

3% NaCl 0.004 0.005 0.006 0.013 0.009 0.009 0.070

9% NaCl 0.001 0.007 0.008 0.015 0.010 0.016 0.063

15% NaCl 0.001 0.004 0.003 0.017 0.007 0.012 0.058

Corrosion Rate (Run 1), mmpy

316(18) 2205 2201 2201P MMFX MMFX-A MMFX-D

3% NaCl 0.005 0.013 0.020 0.008 0.013 0.008 0.001

9% NaCl 0.002 0.007 0.010 0.005 0.011 0.007 0.009

15% NaCl 0.001 0.004 0.008 0.004 0.015 0.012 0.012

Corrosion Rate (Run 2), mmpy

316(18) 2205 2201 2201P MMFX MMFX-A MMFX-D BB

3% NaCl 0.003 0.006 0.003 0.012 0.008 0.016 0.009 0.057

9% NaCl 0.001 0.005 0.007 0.006 0.011 0.017 0.013 0.052

15% NaCl 0.001 0.004 0.005 0.004 0.013 0.014 0.013 0.040

Corrosion Rate (Run 3), mmpy

316(16) 316(16) 3Cr12 3Cr12

3% NaCl 0.001 0.001 0.026 0.025

9% NaCl 0.002 0.001 0.020 0.018

15% NaCl 0.001 0.001 0.024 0.019

Corrosion Rate (Run 4), mmpy

Table 4.4. Average corrosion rate calculated from weight 

loss for each alloy during four individual AST-1 runs. 

316(18) 316(16) 2205 2201 2201P

3% NaCl 0.004 0.001 0.008 0.009 0.009

9% NaCl 0.001 0.001 0.005 0.008 0.006

15% NaCl 0.001 0.001 0.004 0.005 0.004

MMFX MMFX-A MMFX-D 3Cr12 BB

3% NaCl 0.011 0.011 0.006 0.025 0.070

9% NaCl 0.012 0.011 0.013 0.019 0.057

15% NaCl 0.015 0.011 0.012 0.021 0.048

Corrosion Rate, mmpy

_______________________ 

1 mA/m2

 = 0.1 μA/cm2 = 0.0011 mm/year = 1.15 μm/year = 0.043 mils/year. 
41 

1.00E-05

1.00E-04

1.00E-03

1.00E-02

1.00E-01

1.00E+00

1.00E-05 1.00E-04 1.00E-03 1.00E-02 1.00E-01 1.00E+00

Corrosion Rate (Wt. Loss), mmpy

Corrosion Rate (PR), mmpy

316.18

316.16

2205

2201

MMFX

M M FX-A

M M FX-D

3Cr12

BB

Figure 4.9. Graph. Comparison of corrosion rate measured by weight loss 

and calculated from polarization resistance for different solid bars. 

Figures 4.10 through 4.16 show photographs of representative specimens subsequent to testing. 

In each case, testing of the uppermost specimen in the photographs was terminated after 28 days, 

the middle one after 56 days, and the one at the bottom after 84 days or slightly later. With the 

exception of the 316 reinforcement, all three specimens of which appear pristine, there was a 

general trend whereby specimens appeared more corroded with successive 28-day exposures. 

The visual appearances generally conform to the PR and weight loss results in that bars with 

more corrosion products typically exhibited lower PR and higher weight loss. 

___________________________ 

1 mA/m2

 = 0.1 μA/cm2 = 0.0011 mm/year = 1.15 μm/year = 0.043 mils/year. 
42 

Figure 4.10. Photo. Type 316 SS specimens subsequent to AST-1 testing. 

Figure 4.11. Photo. Type 2205 SS specimens subsequent to AST-1 testing. 
43 

Figure 4.12. Photo. Type 2201 SS specimens subsequent to AST-1 testing. 

Figure 4.13. Photo. MMFX-IITM specimens subsequent to AST-1 testing. 
44 

Figure 4.14. Photo. MMFX-IITM abraded specimens subsequent to AST-1 testing. 

Figure 4.15. Photo. MMFX-IITM damaged specimens subsequent to AST-1 testing. 
45 

Figure 4.16. Photo. Black bar specimens subsequent to AST-1 testing. 

AST-2A 

Figure 4.17 plots current density to maintain a potential of +100 mVSCE versus [Cl-

] for an initial 

experiment (run number 1, table 3.4) that involved one specimen of each alloy except MMFXIITM with various surface conditions included where applicable. Only the initial time scale is 

shown here so that activation time of bars with relatively poor and intermediate corrosion 

resistance could be more accurately discerned. Initially, current density was several μA or less 

for all bar types. Corrosion was defined as having initiated when current density reached 10 

μA/cm2, and the [Cl-] at which this occurred is indicated from the right Y axis. This reveals that 

the black bar specimen activated in response to the initial Cl-

 increment (0.30 w/o), followed by 

the 3Cr12 at 0.60 w/o Cl-

, various MMFX-IITM specimens in the range 0.60-1.30 w/o Cl-, and 

2201 at 1.30 w/o Cl-

. The 2205 and 316 specimens exhibited current densities below the defined 

activation threshold (10 μA/cm2

) for all Cl- increments shown here. Similarly, figure 4.18 plots 

data from this same experiment at longer times and higher [Cl-

], where activation for some of the 

more corrosion resistant bars occurred. While some data are obscured, it can be seen that the 

single damaged Stelax bar activated at 2.12 w/o Cl-

 and the damaged SMI at 6.37 w/o Cl-. 
46 

0

5

10

15

20

0 100 200 300 400 500 600

Time, hours

Current Density, 

μA/cm2

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

Chloride Concentration, w/ooo

SMI D SMI A SMI 

Stelax A Stelax D Stelax 

316-18 316-16 MMFX B A

MMFX A MMFX B D MMFX B

MMFX 2201 P 2201

2205 3Cr12 BB

ClFigure 4.17. Graph. Plot of current density versus [Cl-

] such that [ ] − Clth for alloys 

with intermediate corrosion resistance is revealed (specimens with B in 

the designation were bent). 

0

5

10

15

20

400 500 600 700 800 900 1000 1100 1200

Time, hours

Current Density, 

μA/cm2

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

Chloride Concentration, w/ooo

SMI D SMI A SMI 

Stelax A Stelax D Stelax 

316-18 316-16 2205

ClFigure 4.18. Graph. Plot of current density versus [Cl-

] such that [ ] − Clth

for alloys with relatively high corrosion resistance is revealed. 
47 

Performance was mixed for the other clad bar specimens with an abraded and an undamaged 

SMI specimen activating at 5.16 and 6.37 w/o Cl-

, respectively. Post exposure observations 

indicated that in the former case the abrasion penetrated the cladding; and in the latter, attack 

initiated underneath the end sealing epoxy. Corrosion also occurred underneath the epoxy for the 

bar designated as Stelax B (bent), which also activated at 6.37 w/o Cl-

, and at cladding breaks 

caused by bending. Figure 4.19 provides extends the scale from figure 4.18 to longer times so 

that data for the best performers can be viewed in greater detail. Thus, maximum current density 

for the two 316, Stelax, and SMI bars was less than one μA/cm2

 except in cases where there was 

intentional damage (D) or where the end sealing of the clad bars failed. Data for the 2205 bar 

beyond about 850 hours was cyclic with a maximum current density of about five μA/cm2

. As 

such, performance of the latter alloy in AST-2A was considerably better than in AST-1. 

Thresholds for the more corrosion resistant bars may have been higher if pH had been 

maintained constant (see figure 4.1). The experiment was terminated after approximately 1,150 

hours because of a power shutdown mandated in September 2004 by Hurricane Frances. 

0.0

0.2

0.4

0.6

0.8

1.0

400 500 600 700 800 900 1000 1100 1200

Time, hours

Current Density, μA/cm2

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

Chloride Concentration, w/ooo

SMI D SMI A SMI 

Stelax A Stelax D Stelax 

316-18 316-16 2205

ClFigure 4.19. Graph. Expanded scale plot of current density versus [Cl-

] for alloys 

with relatively high corrosion resistance is revealed. 

Second and third AST-2A experiments were performed for the purpose of better defining [ ] − Clth

for black bar, 3Cr12, MMFX-IITM and 2201. This involved concurrently testing 10 bars of the 

individual alloys and using smaller Cl-

 increments than for the initial run. Specimens were 

preconditioned in the simulated pore water at +100 mVSCE for 5 days before the first Cl-

 addition. 

Testing of individual specimens was in some cases terminated once current density exceeded 10 

μA/cm2. Figures 4.20 and 4.21 show plots of current density versus exposure time for black and 

3Cr12 specimens, the latter with a more expanded vertical axis for better resolution. Likewise, 

figure 4.22 presents results for MMFX-IITM and 2201. Because of data clutter and the fact that 
48 

[ ] − Clth was reached earlier for MMFX-IITM specimens, figure 4.23 shows data for the latter 

specimens only. The above plots exhibit noise as a consequent of repetitive passive film 

breakdown and repair. Also, apparent is the arbitrariness of the 10 μA/cm2

 criterion. Irrespective 

of this, figure 4.24 presents a cumulative distribution plot of [ ] − Clth for each of the four alloys. 

AST-2B 

Open Circuit Potential 

In general, free corrosion potential for specimens in these tests decreased during the initial 400 

seconds of exposure by on average about 100 mV and decayed more gradually or remained 

constant thereafter. No definitive relationship between this potential and [Cl-

] was apparent; 

however, the decay at a given [Cl-

] was generally reproducible. 

0

50

100

150

200

250

300

0 50 100 150 200 250 300 350 400

Exposure Time, hours

Current Density, 

μA/cm2

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

Chloride Concentration, w/o

BB (1) BB (2) BB (3)

BB (4) BB (5) BB (6)

BB (7) BB (8) BB (9)

BB (10) 3Cr12 (1) 3Cr12 (2)

3Cr12 (3) 3Cr12 (4) 3Cr12 (5)

3Cr12 (6) 3Cr12 (7) 3Cr12 (8)

3Cr12 (9) 3Cr12 (10) w%ClFigure 4.20. Graph. Plot of current density versus exposure time for 10 specimens 

each of black bar and 3Cr12. Incremental Cl-

 additions are also shown. 
49 

0

5

10

15

20

25

30

0 50 100 150 200 250 300 350 400

Exposure Time, hours

Current Density, 

μA/cm2

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

Chloride Concentration, w/o

BB (1) BB (2) BB (3)

BB (4) BB (5) BB (6)

BB (7) BB (8) BB (9)

BB (10) 3Cr12 (1) 3Cr12 (2)

3Cr12 (3) 3Cr12 (4) 3Cr12 (5)

3Cr12 (6) 3Cr12 (7) 3Cr12 (8)

3Cr12 (9) 3Cr12 (10) w%ClFigure 4.21. Graph. Expanded scale view of the current density versus 

exposure time data from figure 4.20. 

0

5

10

15

20

25

30

0 200 400 600 800 1000 1200

Exposure Time, hours

Current Density, 

μA/cm2

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

Chloride Concentration, w/o

2201(1) 2201(2)

2201(3) 2201(4)

2201(5) 2201(6)

2201(7) 2201(8)

2201(9) 2201(10)

MMFX(1) MMFX(2)

MMFX(3) MMFX(4)

MMFX(5) MMFX(6)

MMFX(7) MMFX(8)

MMFX(9) MMFX(10)

Chloride Content

Figure 4.22. Graph. Plot of current density versus time for a series of 10 MMFX and 

2201 specimens polarized to +100 mVSCE. Incremental Cl- additions are also shown. 
50 

0

5

10

15

20

25

0 50 100 150 200 250 300 350 400

Exposure Time, hours

Current Density, 

μA/cm2

0.0

0.5

1.0

1.5

2.0

Chloride Concentration, w/o

MMFX(1) MMFX(2)

MMFX(3) MMFX(4)

MMFX(5) MMFX(6)

MMFX(7) MMFX(8)

MMFX(9) MMFX(10)

Chloride Content

Figure 4.23. Graph. Plot of current density versus time for replicate MMFX-IITM 

specimens. 

0

2

4

6

8

10

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

Chloride Concentration, w/o

Cummulative Number of Active Specimens

BB

3Cr12

2201

MMFX

Figure 4.24. Graph. Distribution of [ ] − Clth for four alloys based 

upon the 10 μA/cm2

 current density criterion. 
51 

Scan Rate 

Figure 4.25 presents cyclic potentiodynamic polarization (CPP) scans for cross section polished 

MMFX-IITM specimens in saturated Ca(OH)2 without Cl-

 showing that current density at a given 

potential increased with increasing scan rate. Similar to the potentiostatic procedure (AST-2A), 

the critical pitting potential, Epit, was defined as the potential corresponding to a current density 

of 10 μA/cm2

. The scans illustrate the arbitrariness of this definition, however, in that a small 

change in this criterion could alter Epit by as much as several hundred millivolts. 

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0.0001 0.001 0.01 0.1 1 10 100 1000

Current Density, μA/cm2

Potential, VSCE

5.00 mV/sec

1.00 mV/sec

0.33 mV/sec

Figure 4.25. Graph. Anodic CPP scans for as-received MMFX-IITM specimens 

in saturated Ca(OH)2 without Cl-

 at scan rates of 0.33, 1.00, and 5.00 mV/s. 

Arrows indicate direction of forward and reverse scans. 

Surface Condition 

Figure 4.26 presents CPP scans for MMFX-IITM specimens in saturated Ca(OH)2 with 0.50 w/o 

Cl-

 and shows that Epit for the specimen with the as-received surface finish was more negative 

than for the 600 grit polished ones by about 200 mV or more based on the 10 μA/cm2

 criterion. 

A similar trend was disclosed for 2201. Surface effects were not studied in the case of the other 

bars. This result by itself indicates that bars with as-rolled mill scale have inferior pitting 

resistance to ones where this is removed, as is generally known; however, surface cleaning 

methods such as pickling and blasting negatively affect cost and from this standpoint render 

corrosion resistant reinforcement less competitive. 
52 

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0.0001 0.001 0.01 0.1 1 10 100 1000

Current Density, μA/cm2

Potential, VSCE

Circumferential As-Received

Circumferential Polished

Cross Section Polished

Figure 4.26. Graph. Anodic CPP scans on as-received MMFX-IITM specimens 

with three surface conditions in saturated Ca(OH)2 without Cl- at 

1.00 mV/s. Arrows indicate direction of forward and reverse scans. 

Critical Pitting Potential 

From CPP scans performed on 3Cr12, MMFX-IITM, 2201, and 316.16, Epit was determined as a 

function of [Cl-

] with results being as shown in figure 4.27. This reveals that, for the bar types 

represented here, Epit for 3Cr12 is the most active and for 316.16 the most noble with the average 

for MMFX-IITM and 2201 being essentially the same. That this latter finding does not agree with 

results from AST-2A (figure 4.24) may have resulted because of the sensitive dependence of Epit

on [Cl-

] in the 0-1.0 w/o Cl- range in saturated Ca(OH)2 (pH ~ 12.45) and the fact that the 

potentiostatic tests were in synthetic pore solution (pH ~ 13.2). 

CORRELATIONS BETWEEN DIFFERENT SHORT-TERM TEST RESULTS 

The Pitting Resistance Equivalent Number, PREN (alternatively, PRE), as defined by the 

expression, 

PREN = w/oCr + 3.3 · w/oMo + x · w/oN 

 (4.1) 

(w/o is weight percent of the indicated element and x is commonly chosen as 16), is widely 

employed for selection of stainless steels in applications where corrosion by pitting is a concern. 

PREN values for the reinforcements employed in the present study are listed in table 3.1. 

Polarization resistance (PR), on the other hand, is an electrochemical parameter that is inversely 
53 

-0.40

-0.20

0.00

0.20

0.40

0.60

0.80

01234567

Chloride Concentration, weight percent

Critical Pitting Potential, V (SCE)

3Cr12 MMFX

2201 316.16

Series5 Series6

Series7 Series8

3CR12

MMFX

2201

316.16

Figure 4.27. Graph. Critical pitting potential as a function of [Cl-] for four bar types. 

proportional to uniform corrosion rate. An attempt was made to correlate the AST-1 PR results 

with the respective PREN for the different alloys. To this end, figure 4.28 plots PR versus PREN 

for the relevant alloys. The results reveal almost two orders of magnitude difference in PR 

between 2201 and 316.18 despite the fact that the PREN for each is about the same. Also, 2205 

has the highest PREN, but its PR is comparable to that for 2201 and is also well below that of 

316.18. These differences may be a consequence of the 316.18 having been pickled, whereas 

2201 and 2205 were tested in the as-rolled condition (MMFX-IITM and black bar also were tested 

as-rolled). On the other hand, PR of 2201 specimens with various surface treatments (AST-1 

tests) did not vary greatly from that of the as-received material (figure 4.4). Also, corrosion of 

the 2201 and 2205 specimens appeared to be uniform in the AST-1 exposures rather than by 

pitting (see figures 4.11 and 4.12); and this being the case, a pitting index (PREN) may not 

apply. An added contributing factor to the lack of correlation may be that the PREN parameter is 

empirical and was established based upon exposure in acidic and marine environments rather 

than alkaline ones. Nonetheless, a trend of increasing PR with increasing PREN is apparent if the 

316.18 datum is ignored. 
54 

1.0E+04

1.0E+05

1.0E+06

1.0E+07

0 5 10 15 20 25 30 35 40

PREN

Polarization Resistance, Ohm.cm2

316.18

2205

2201

MMFX

3Cr12

Figure 4.28. Graph. Plot of polarization resistance (AST-1) versus PREN for 

the test reinforcements. 

Figure 4.29 shows a plot of average PR (AST-1) versus [ ] − Clth (AST-2A) for solid bars and 

reveals a trend of increasing threshold with increasing PR for alloys of low and intermediate 

corrosion resistance with an apparent relatively abrupt transition in [ ] − Clth from relatively low to 

high at a PR near 6·104 Ω·cm2

. Again, the distinction in performance of 2205 in these two tests is 

apparent in that this alloy exhibited a relatively high [ ] − Clth ; but PR was intermediate and in the 

same range as the 2201 and MMFX-IITM reinforcements. This may reflect the fact that these two 

parameters (PR and [ ] − Clth ) were measured under different exposure conditions and that they 

represent different aspects of bar response (uniform corrosion rate for the former and the 

threshold condition for passive film breakdown for the latter). It can be reasoned also that pH of 

the residual, high [Cl-

] moisture on AST-1 bars during the periods of atmospheric exposure was 

reduced and that this affected behavior during the submerged periods. If this was the case, then 

PR values for the bar types other than 316 are indicative of postactivation corrosion, whereas for 

316 [ ] − Clth reflects a criterion for active corrosion initiation. 
55 

1.0E+03

1.0E+04

1.0E+05

1.0E+06

1.0E+07

0123456

Critical Chloride Concentration (AST-2A), w/o

Polarization Resistance (AST-1), 

Ohm.cm2 

316.18 2205 2201

MMFX 3Cr12 BB

Threshold PR

Figure 4.29. Graph. Plot of polarization resistance (AST-1) versus [ ] − Clth (AST-2A). 

Figure 4.30 plots [ ] − Clth (AST-2A) versus PREN and again shows lack of a consistent trend by 

the better performers to the extent that data are available. While the results indicate a transition 

of [ ] − Clth from low to high at about PREN 25, additional tests on other alloys are required to 

confirm that this constitutes a true performance demarcation. 

The [Cl-

] corresponding to an Epit of +100 mVSCE from AST-2B experiments was compared with 

the [ ] − Clth determinations for the AST-2A ones. Thus, [ ] − Clth at this potential for 3Cr12 in AST-1 

was estimated from figure 4.27 as 0.25 w/o for MMFX-IITM and 0.30 w/o for 2201. These values 

are less than those from AST-2A (0.9 w/o for MMFX-IITM and 2.0 w/o for 2201, see above); 

however, this is not unexpected given that pH of the electrolyte was lower in AST-2B than AST2A (saturated Ca(OH)2 compared to synthetic pore solution). Also, the Epit data are based on 

relatively few data points; and these fall in a range where Epit was relatively sensitive to [Cl-

]. 

RELATING [ ] − Clth (AST-2A) TO CHLORIDE THRESHOLD CONCENTRATIONS IN 

CONCRETE 

Relating the presently determined [ ] − Clth values from the AST-2A experiments to Cl-

 thresholds 

in actual concrete, CT, is difficult since, first, the free Cl-

 concentration in the cement pore water, 

[Cl-

]f, is not a simple function of CT and, second, CT depends upon numerous factors including 

water/cement ratio, cement content and composition, exposure conditions, and others. 

Nonetheless, Li and Sagüés18 summarized [Cl-

]f data for black bar from the literature, most of 

which were determined by pore water expression (PWE) using water saturated cement pastes, 

mortars, and concretes, and correlated these with the corresponding CT values that were reported. 
56 

0

1

2

3

4

5

6

0 5 10 15 20 25 30 35 40

PREN

Critical Chloride Concentration, w/oooo

316.18

2205

2201

MMFX

3Cr12

BB

Figure 4.30. Graph. Plot of [ ] − Clth (AST-2A) versus PREN. 

In the present analysis, it was assumed that the [ ] − Clth values determined from the AST-2A 

experiments are comparable with the [Cl-

]f values summarized by Li and Sagüés. On this basis, 

figure 4.31 shows a plot of [ ] − Clth (AST-2A) versus the corresponding threshold projected for 

concrete. Here, the two curves are the upper and lower limits of the literature [Cl-

]f − CT data, 

and the [ ] − Clth are plotted as the midpoints of the CT extremes. Also, is reported as molarity, M, 

since the PWE data employed this unit of measure. Table 4.5 lists the values for [ ] − Clth and CT

that are plotted in figure 4.31. Such an analysis does not, of course, constitute an explicit 

[ ] − Clth − CT correlation since the values for the latter parameter are inferred based upon a trend of 

historically reported results. 

Table 4.5. Listing of projected CT values for the corresponding [ ] − Clth from AST-2A.

Reinforcement , M Average CT from Literature, weight percent cement

BB 0.08 0.54

3Cr12 0.15 0.80

MMFX-IITM 0.27 1.10

2201 0.35 1.30

[ ] − Clth
57 

0

0.1

0.2

0.3

0.4

0.5

0.0 0.5 1.0 1.5 2.0

Chloride Threshold, weight percent cement

Chloride Threshold, 

M

BB

3Cr12

MMFX-IITM

2201

Figure 4.31. Graph. Plot of [ ] − Clth (AST-2A) versus the corresponding threshold 

projected from literature data for pastes, mortars, and concrete. 

CONCRETE SPECIMENS 

General 

Data from potential measurements and, for some specimen types, macro-cell current density 

(calculated from voltage drop across a 10 Ω resistor between the two rebar mats) were evaluated 

as a function of exposure time as indicators of, first, the onset of corrosion and, second, corrosion 

rate subsequent to activation. Not all corrosion resistant reinforcement types have yet been 

investigated because of acquisition problems during the initial two project years and resultant 

delays in specimen fabrication and curing. Findings for each of the specimen types for which 

data are available are presented and discussed below. 

Simulated Deck Slab (SDS) Specimens 

General 

The data for this specimen type must be qualified because no isolation of the reinforcement 

where it exited the concrete, other than the epoxy coating on the side concrete surfaces, was 

provided. In many cases, corrosion was apparent at the steel-concrete exterior interface; and this 

could have affected both potential and macro-cell current. Besides the three specimen sets 

mentioned earlier, a fourth set has been prepared with heat shrink tubing around the bars where 
58 

these emerge from the concrete to determine the extent to which this lack of isolation affected 

performance. 

Black Bar Slabs 

Figures 4.32 and 4.33 show plots of potential and macro-cell current density as a function of 

exposure time for the standard (no simulated crack) black bar slabs. Figure 4.32 indicates that, 

according to the −280 mVSCE criterion, the STD1 bars (w/c 0.50) became active within weeks of 

initiating the Cl-

 exposure. Also, corrosion has activated on bars in two of the three STD2 (w/c 

0.41) slabs; however, the timing of this is not definitive in that, while potential for the former 

two specimens tended to more negative values between 100 and 150 days, this subsequently 

moderated with potential varying in the -200 to -300 mVSCE range to about 450 days. 

Subsequently, a more negative trend with time reoccurred. The macrocell current density data 

(Figure 4.32) correlate with the potential data in that high current density corresponds to 

relatively negative potential. 

Figures 4.34 and 4.35 show potential and macro-cell current density data for black bar specimens 

with and without a simulated crack. The data indicate that potential was more negative and 

current density higher initially for the cracked specimens compared to the uncracked ones but 

with the data merging at longer times, which is consistent with chlorides having immediate 

access, or nearly so, to steel in the cracked concrete case. However, as chlorides migrated into 

the uncracked concrete specimens by diffusion and became more concentrated at the steel depth, 

distinctions between the two data sets moderated. 

Typically, potential tended to be more negative and macro-cell current density greater when 

-700

-600

-500

-400

-300

-200

-100

0

0 100 200 300 400 500 600 700

Exposure Time, days

Potential, V (SCE)

1-STD1-BB-1

1-STD1-BB-2

1-STD1-BB-3

1-STD2-BB-1

1-STD2-BB-2

1-STD2-BB-3

Figure 4.32. Graph. Plot of potential versus exposure time for STD1 and STD2 

concrete specimens with black bar reinforcement. 
59 

-1.00

-0.50

0.00

0.50

1.00

1.50

2.00

0 100 200 300 400 500 600 700

Exposure Time, days

Macrocell Current Density, 

μA/cm2

1-STD2-BB-1

1-STD2-BB-2

1-STD2-BB-3

1-STD1-BB-1

1-STD1-BB-2

1-STD1-BB-3

Figure 4.33. Graph. Plot of macro-cell current density versus exposure time for STD1 

and STD2 concrete specimens with black bar reinforcement. 

-700

-600

-500

-400

-300

-200

-100

0

0 100 200 300 400 500 600 700

Exposure Time, days

Potential, V (SCE)

1-STD1-BB-1

1-STD1-BB-2

1-STD1-BB-3

3-CCON-BB-1

3-CCON-BB-2

3-CCON-BB-3

Figure 4.34. Graph. Plot of potential versus exposure time for black bar STD1 

concrete specimens with and without a simulated crack. 
60 

-1.00

-0.50

0.00

0.50

1.00

1.50

2.00

0 100 200 300 400 500 600 700

Exposure Time, days

Macrocell Current Density, 

μA/cm2

1-STD1-BB-1

1-STD1-BB-2

1-STD1-BB-3

3-CCON-BB-1

3-CCON-BB-2

3-CCON-BB-3

Figure 4.35. Graph. Plot of macro-cell current density versus exposure time for 

black bar STD1 concrete specimens with and without a simulated crack. 

-700

-600

-500

-400

-300

-200

-100

0

1.00E-04 1.00E-03 1.00E-02 1.00E-01 1.00E+00 1.00E+01

Macrocell Current Density, μA/cm2

Potential, V (SCE)

1-STD2-BB-1

1-STD2-BB-2

1-STD2-BB-3

1-STD1-BB-1

1-STD1-BB-2

1-STD1-BB-3

3-CCON-BB-1

3-CCON-BB-2

3-CCON-BB-3

Figure 4.36. Graph. Plot of potential versus macro-cell current density 

for black bar reinforced concrete specimens. 
61 

measurements were made during the wet portion of the ponding cycle compared to the dry, both 

for black bar and the other reinforcement types discussed below. This accounts for the saw-tooth 

pattern that is apparent in much of the data. The effect is more apparent in the case of cracked 

concrete specimens than for the uncracked. 

Figure 4.36 plots potential versus macro-cell current density for the black bar specimens. Since 

potential became more negative and macro-cell current density increased with exposure (figures 

4.32 through 4.35), increasing time is from upper left to lower right. The data generally conform 

to a common band irrespective of w/c or presence of a simulated crack and differences between 

individual specimens, as viewed in the potential and macro-cell versus time formats (figures 4.32 

through 4.35). However, results for the STD2 specimens do not extend as far down the trend 

band as do the other two specimen sets, consistent with these having maintained more positive 

potentials and developed less macro-cell current than the STD1 mix specimens. Also, the 

cracked concrete specimen data occupy only the relatively negative potential—high current 

density regime, consistent with a relatively high current density having occurred soon after 

exposure. Such a representation (potential versus current density) facilitates comparison of 

performance of the different specimen and bar types, as discussed subsequently. 

Figure 4.37 shows a typical example of the black bar slabs after 377 days of exposure, in this 

case for a CCON type specimen. This shows rust surface staining emanating from the simulated 

crack and occurrence of an actual crack above one of the bars (circled). Several black bar slabs 

were subsequently autopsied by partially saw cutting and then splitting the concrete along the 

plane of the upper three bars. Figure 4.38 is a photograph of the trace of the upper side of the top 

rebars on the sectioned concrete face of specimen number 3-CCON-BB-1 after 566 days of 

exposure. Likewise, figure 4.39 shows the appearance of the upper bar traces for specimen 

number 1-STD-BB-3 after 707 days. Prior to sectioning, this specimen had been cored for ClFigure 4.37. Photo. Exposed surface of specimen 

number 3-CCON-BB-2 after 377 days. 
62 

Figure 4.38. Photo. Traces of the upper three rebars and 

heavy corrosion products (specimen number 3-CCON-BB-1). 

Figure 4.39. Photo. Trace of the upper rebars and heavy 

corrosion products on specimen number 1-STD1-BB-3. 

analyses, as evidenced by the two core holes that are seen in the figure. In both cases, 

considerable corrosion product buildup is apparent. 
63 

Slabs Reinforced With MMFX-IITM Bars 

Figures 4.40 and 4.41 show potential and macro-cell current density results, respectively, for the 

STD1 MMFX-IITM bar slabs in comparison to the black bar slabs (figures 4.32 and 4.33). The 

initial potential decrease was similar for both bar types; however, this does not necessarily mean 

that time-to-corrosion was the same since different reinforcement types may have different 

potential criterion for activation. Current density, once corrosion initiated, was less for the 

MMFX-IITM reinforcement compared to black bar by about a factor of five (figure 4.41). This is 

consistent with potential of the MMFX-IITM bars having remained more positive that the black 

bars thereby resulting is reduced driving force for current flow. Likewise, figures 4.42 and 4.43 

show similar plots for MMFX-IITM reinforced STD2 concrete specimens in comparison to the 

STD1 ones. These reveal more positive potentials and lower current densities for the lower w/c 

concrete (STD2) compared to the higher (STD1). Figures 4.44 through 4.55 show potential and 

macro-cell current density plots for specimens with, respectively, black bar cathode (BCAT), 

wire brushed bars (WB), top bar crevice or splice (CREV), cracked concrete (CCON), cracked 

concrete and crevice (CCRV), and cracked concrete and black bar cathode (CCNB). The effect 

of each of these factors on corrosion initiation and propagation is summarized in figure 4.56 

which plots potential versus macro-cell current density for a single specimen in each category. 

As noted above for the comparable black bar specimens (figure 4.36), the data conform to a 

common trend, albeit with scatter, with data for the cracked concrete specimens (CCON and 

CCNB) generally falling in the relatively negative potential—high current density regime 

(similar to the comparable black bar specimens). Macro-cell current density data for the wire 

brushed bar specimens are generally less than for the other MMFX-IITM specimen types (see also 

figure 4.45). 

-700

-600

-500

-400

-300

-200

-100

0

0 100 200 300 400 500 600 700

Exposure Time, days

Potential, V (SCE)

1-STD1-MMFX-1

1-STD1-MMFX-2

1-STD1-MMFX-3

1-STD1-BB-1

1-STD1-BB-2

1-STD1-BB-3

Figure 4.40. Graph. Plot of potential versus exposure time for STD1 concrete 

specimens with MMFX-IITM reinforcement in comparison to black bar results. 
64 

-1.00

-0.50

0.00

0.50

1.00

1.50

2.00

0 100 200 300 400 500 600 700

Exposure Time, days

Macrocell Current Density, 

μA/cm2

1-STD1-BB-1

1-STD1-BB-2

1-STD1-BB-3

1-STD1-MMFX-1

1-STD1-MMFX-2

1-STD1-MMFX-3

Figure 4.41. Graph. Plot of macro-cell current density versus exposure time for STD1 

concrete specimens with MMFX-IITM reinforcement in comparison to black bar results. 

-700

-600

-500

-400

-300

-200

-100

0

0 100 200 300 400 500 600 700

Exposure Time, days

Potential, V (SCE)

1-STD1-MMFX-1

1-STD1-MMFX-2

1-STD1-MMFX-3

1-STD2-MMFX-1

1-STD2-MMFX-2

1-STD2-MMFX-3

Figure 4.42. Graph. Plot of potential versus exposure time for STD1 and STD2 

concrete specimens with MMFX-IITM reinforcement. 
65 

-1.00

-0.50

0.00

0.50

1.00

1.50

2.00

0 100 200 300 400 500 600 700

Exposure Time, days

Macrocell Current Density, 

μA/cm2

1-STD1-MMFX-1

1-STD1-MMFX-2

1-STD1-MMFX-3

1-STD2-MMFX-1

1-STD2-MMFX-2

1-STD2-MMFX-3

Figure 4.43. Graph. Plot of macro-cell current density versus exposure time 

for STD1 and STD2 concrete specimens with MMFX-IITM reinforcement. 

-700

-600

-500

-400

-300

-200

-100

0

0 100 200 300 400 500 600 700

Exposure Time, days

Potential, V (SCE)

1-STD1-MMFX-1

1-STD1-MMFX-2

1-STD1-MMFX-3

2-BCAT-MMFX-1

2-BCAT-MMFX-2

2-BCAT-MMFX-3

Figure 4.44. Graph. Plot of potential versus exposure time for STD1 

concrete specimens with black bar bottom mat and top mat MMFX-IITM 

reinforcement compared to ones with all MMFX-IITM bars. 
66 

-1.00

-0.50

0.00

0.50

1.00

1.50

2.00

0 100 200 300 400 500 600 700

Exposure Time, days

Macrocell Current Density, 

μA/cm2

2-BCAT-MMFX-1

2-BCAT-MMFX-2

2-BCAT-MMFX-3

1-STD1-MMFX-1

1-STD1-MMFX-2

1-STD1-MMFX-3

Figure 4.45. Graph. Plot of macro-cell current density versus exposure time 

for STD1 concrete specimens with black bar bottom mat and top mat 

MMFX-IITM reinforcement compared to ones with all MMFX-IITM bars. 

-700

-600

-500

-400

-300

-200

-100

0

0 100 200 300 400 500 600 700

Exposure Time, days

Potential, V (SCE)

1-STD1-MMFX-1

1-STD1-MMFX-2

1-STD1-MMFX-3

2-WB-MMFX-1

2-WB-MMFX-2

2-WB-MMFX-3

Figure 4.46. Graph. Plot of potential versus exposure time for STD1 concrete 

specimens with as-received and wire brushed (WB) MMFX-IITM reinforcement. 
67 

-1.00

-0.50

0.00

0.50

1.00

1.50

2.00

0 100 200 300 400 500 600 700

Exposure Time, days

Macrocell Current Density, 

μA/cm2

2-WB-MMFX-1

2-WB-MMFX-2

2-WB-MMFX-3

1-STD1-MMFX-1

1-STD1-MMFX-2

1-STD1-MMFX-3

Figure 4.47. Graph. Plot of macro-cell current density versus exposure time for STD1 

concrete specimens with as-received and wire brushed (WB) MMFX-IITM reinforcement. 

-700

-600

-500

-400

-300

-200

-100

0

0 100 200 300 400 500 600 700

Exposure Time, days

Potential, V (SCE)

1-STD1-MMFX-1

1-STD1-MMFX-2

1-STD1-MMFX-3

3-CREV-MMFX-1

3-CREV-MMFX-2

3-CREV-MMFX-3

Figure 4.48. Graph. Plot of potential versus exposure time for STD1 

concrete specimens with top mat crevice bars (splice) and MMFX-IITM 

reinforcement compared to ones with normal bar placement. 
68 

-1.00

-0.50

0.00

0.50

1.00

1.50

2.00

0 100 200 300 400 500 600 700

Exposure Time, days

Macrocell Current Density, 

μA/cm2

3-CREV-MMFX-4

3-CREV-MMFX-5

3-CREV-MMFX-6

1-STD1-MMFX-1

1-STD1-MMFX-2

1-STD1-MMFX-3

Figure 4.49. Graph. Plot of macro-cell current density versus exposure time for STD1 

concrete specimens with top mat crevice bars (splice) and MMFX-IITM reinforcement. 

-700

-600

-500

-400

-300

-200

-100

0

0 100 200 300 400 500 600 700

Exposure Time, days

Potential, V (SCE)

1-STD1-MMFX-1

1-STD1-MMFX-2

1-STD1-MMFX-3

3-CCON-MMFX-1

3-CCON-MMFX-2

3-CCON-MMFX-3

Figure 4.50. Graph. Plot of potential versus exposure time for STD1 

concrete specimens with a simulated concrete crack and MMFX-IITM 

reinforcement compared to normal (uncracked) specimens. 
69 

-1.00

-0.50

0.00

0.50

1.00

1.50

2.00

0 100 200 300 400 500 600 700

Exposure Time, days

Macrocell Current, 

μA/cm2

3-CCON-MMFX-1

3-CCON-MMFX-2

3-CCON-MMFX-3

1-STD1-MMFX-1

1-STD1-MMFX-2

1-STD1-MMFX-3

Figure 4.51. Graph. Plot of macro-cell current density versus exposure time 

for STD1 concrete specimens with a simulated concrete crack and 

MMFX-IITM reinforcement compared to normal (uncracked) specimens. 

-700

-600

-500

-400

-300

-200

-100

0

0 100 200 300 400 500 600

Exposure Time, days

Potential, V (SCE)

3-CCON-MMFX-1

3-CCON-MMFX-2

3-CCON-MMFX-3

3-CCRV-MMFX-1

3-CCRV-MMFX-2

3-CCRV-MMFX-3

Figure 4.52. Graph. Plot of potential versus exposure time for STD1 concrete 

specimens with a simulated concrete crack and MMFX-IITM reinforcement 

compared to ones with a simulated crack and top bar crevice (splice). 
70 

-1.00

-0.50

0.00

0.50

1.00

1.50

2.00

0 100 200 300 400 500 600

Exposure Time, days

Macrocell Current Density, 

μA/cm2

3-CCON-MMFX-1

3-CCON-MMFX-2

3-CCON-MMFX-3

3-CCRV-MMFX-1

3-CCRV-MMFX-2

3-CCRV-MMFX-3

Figure 4.53. Graph. Plot of macro-cell current density versus exposure time for STD1 

concrete specimens with a simulated concrete crack and MMFX-IITM reinforcement 

compared to ones with a simulated crack and top bar crevice (splice). 

-700

-600

-500

-400

-300

-200

-100

0

0 100 200 300 400 500 600 700

Exposure Time, days

Potential, V (SCE)

3-CCON-MMFX-1

3-CCON-MMFX-2

3-CCON-MMFX-3

2-CCNB-MMFX-1

2-CCNB-MMFX-2

2-CCNB-MMFX-3

Figure 4.54. Graph. Plot of potential versus exposure time for STD1 concrete 

specimens with a simulated concrete crack and MMFX-IITM reinforcement 

compared to ones with a simulated crack and black bottom bars. 
71 

-1.00

-0.50

0.00

0.50

1.00

1.50

2.00

0 100 200 300 400 500 600 700

Exposure Time, days

Macrocell Current Density, 

μA/cm2

2-CCNB-MMFX-1

2-CCNB-MMFX-2

2-CCNB-MMFX-3

3-CCON-MMFX-1

3-CCON-MMFX-2

3-CCON-MMFX-3

Figure 4.55. Graph. Plot of macro-cell current density versus exposure time for 

STD1 concrete specimens with a simulated concrete crack and MMFX-IITM 

reinforcement compared to ones with a simulated crack and black bar bottom mat. 

-700

-600

-500

-400

-300

-200

-100

0

1.00E-04 1.00E-03 1.00E-02 1.00E-01 1.00E+00 1.00E+01

Current Density, μA/cm2 

Potential, V (SCE)

1-STD1-MMFX

3-CCON-MMXF

3-CCRV-MMFX

3-CREV-MMFX

2-WB-MMFX

2-BCAT-MMFX

2-CCNB-MMFX'

Figure 4.56. Graph. Plot of potential versus macro-cell current 

density for MMFX-IITM reinforced specimens. 
72 

Figure 4.57 shows a photograph that was taken of the exposed surface of a MMFX-IITM 

specimen (specimen number 2-BCAT-MMFX-3) during the dry phase of the ponding cycle after 

461 days. The surface is rust stained, and the concrete has cracked above one of the three bars. 

Likewise, Figures 4.58 through 4.65 show the appearance of the upper bar traces for one 

specimen each of the STD1, STD2, WB, CREV, CCON, BCAT, CCNB, and CCRV 

configurations. Because specimens were exposed at three different times but autopsied at the 

same time, the exposure time varied (566 to 707 days). Irrespective of this, a visual comparison 

of the standard STD1 and CCON black bar (figures 4.39 and 4.38, respectively) and companion 

MMFX-IITM specimens (figures 4.62 and 4.58, respectively) reveals considerably less corrosion 

for the latter, consistent with the corresponding current density data as discussed above. The 

visual extent of the corrosion products (figures 4.58 through 4.65) is generally consistent with 

magnitude of the long-term current density (higher current density, more corrosion). Bar traces 

on the autopsied MMFX-IITM BCAT specimen exhibited the greatest amount of corrosion 

product and had the highest current density at long-term. With the exception of the BCAT 

specimens, current density of the three specimen set of each type exhibited relatively little 

scatter. 

Figure 4.57. Photo. Top surface of specimen 

2-BCAT-MMFX-3 after 461 days of exposure. 
73 

Figure 4.58: Photograph of the trace of the upper rebars and corrosion products on 

specimen no. 1-STD1-MMFX-2. 

Figure 4.59. Photo. Trace of the upper rebars and corrosion 

products on specimen number 1-STD2-MMFX-2. 

Figure 4.58. Photo. Trace of the upper rebars and 

corrosion products on specimen number 1-STD1-MMFX-2. 
74 

Figure 4.60. Photo. Trace of the upper rebars and corrosion 

products on specimen number 2-WB-MMFX-1. 

Figure 4.61. Photo. Trace of the upper rebars and 

corrosion products on specimen number 3-CREV-MMFX-1. 
75 

Figure 4.62. Photo. Trace of the upper rebars and 

corrosion products on specimen number 1-CCON-MMFX-1. 

Figure 4.63. Photo. Trace of the upper rebars and 

corrosion products on specimen number 2-BCAT-MMFX-1. 
76 

Figure 4.64. Photo. Trace of the upper rebars and 

corrosion products on specimen number 2-CCNB-MMFX-1. 

Figure 4.65. Photo. Trace of the upper rebars and 

corrosion products on specimen number 3-CCRV-MMFX-1. 
77 

Slabs Reinforced With 3Cr12 Bars 

Figures 4.66 through 4.79 present potential and macro-cell current density plots for specimens 

reinforced with 3Cr12.2

 For the standard STD1 specimens (figures 4.66 and 4.67), the 

corresponding black bar data are shown for comparison; and these reveal that, while the initial 

potential decay was approximately the same for the two reinforcements, macro-cell current 

density for the 3Cr12 reinforcement, once corrosion initiated, increased more gradually and to a 

steady-state value about three times lower than for the black bar specimens. Figure 4.80 shows a 

plot of potential versus macro-cell current density for specimens reinforced with 3Cr12 that 

includes representative data for each of the specimen types. As for the black bar and MMFX-II 

specimens, a common data band is apparent; however, in this case the band is more narrow and 

largely limited to a potential-current density regime rather than extending from upper left to 

lower right. The highest current densities occurred for specimens with concrete cracks (CCON 

and CCRV); however, this occurred also in the case for the black bar cathode (BCAT) 

specimens. 

Photographs of the upper bar traces of autopsied specimens are shown in figures 4.81 through 

4.87. These indicate that specimens STD1, STD2, CREV, and BCAT exhibited relatively heavy 

localized corrosion products on one bar compared to the WB, CCON, and CCRV specimens for 

which corrosion was relatively light. As for the MMFX-IITM specimens, the appearance of the 

corrosion products is in general agreement with the long-term current density data (higher 

current density greater corrosion products). 

-700

-600

-500

-400

-300

-200

-100

0

0 100 200 300 400 500 600 700

Exposure Time, days

Potential, V (SCE)

1-STD1-BB-1

1-STD1-BB-2

1-STD1-BB-3

1-STD1-3Cr12-1

1-STD1-3Cr12-2

1-STD1-3Cr12-3

Figure 4.66. Graph. Plot of potential versus exposure time for STD1 concrete 

specimens with 3Cr12 reinforcement compared to that for black bar. 

 

2

 Due to an error during specimen fabrication, six BCAT and no CCNB specimens with this 

reinforcement were prepared. 
78 

-1.00

-0.50

0.00

0.50

1.00

1.50

2.00

0 100 200 300 400 500 600 700

Exposure Time, days

Macrocell Current Density, 

μA/cm2

1-STD1-3Cr12-1

1-STD1-3Cr12-2

1-STD1-3Cr12-3

1-STD1-BB-1

1-STD1-BB-2

1-STD1-BB-3

Figure 4.67. Graph. Plot of macro-cell current density versus exposure time for STD1 

concrete specimens with 3Cr12 reinforcement compared to that for black bar. 

-600

-500

-400

-300

-200

-100

0

0 100 200 300 400 500 600 700

Exposure Time, days

Potential, V (SCE)

1-STD1-3Cr12-1

1-STD1-3Cr12-2

1-STD1-3Cr12-3

2-STD2-3Cr12-1

2-STD2-3Cr12-2

2-STD2-3Cr12-3

Figure 4.68. Graph. Plot of potential versus exposure time for STD1 

and STD2 concrete specimens with 3Cr12 reinforcement. 
79 

-1.00

-0.50

0.00

0.50

1.00

1.50

2.00

0 100 200 300 400 500 600 700

Exposure Time, days

Macrocell Current Density, 

μA/cm2

1-STD1-3Cr12-1

1-STD1-3Cr12-2

1-STD1-3Cr12-3

2-STD2-3Cr12-1

2-STD2-3Cr12-2

2-STD2-3Cr12-3

Figure 4.69. Graph. Plot of macro-cell current density versus exposure time 

for STD1 and STD2 concrete specimens with 3Cr12 reinforcement. 

-600

-500

-400

-300

-200

-100

0

0 100 200 300 400 500 600 700

Exposure Time, days

Potential, V (SCE)

1-STD1-3Cr12-1

1-STD1-3Cr12-2

1-STD1-3Cr12-3

3-WB-3Cr12-1

3-WB-3Cr12-2

3-WB-3Cr12-3

Figure 4.70. Graph. Plot of potential versus exposure time for STD1 concrete 

specimens with wire brushed compared to as-received 3Cr12 bars. 
80 

-1.00

-0.50

0.00

0.50

1.00

1.50

2.00

0 100 200 300 400 500 600 700

Exposure Time, days

Macrocell Current Density, 

μA/cm2

1-STD1-3Cr12-1

1-STD1-3Cr12-2

1-STD1-3Cr12-3

3-WB-3Cr12-1

3-WB-3Cr12-2

3-WB-3Cr12-3

Figure 4.71. Graph. Plot of macro-cell current density versus exposure time for 

STD1 concrete specimens with wire brushed compared to as-received 3Cr12 bars. 

-600

-500

-400

-300

-200

-100

0

0 100 200 300 400 500 600 700

Exposure Time, days

Potential, V (SCE)

1-STD1-3Cr12-1

1-STD1-3Cr12-2

1-STD1-3Cr12-3

3-CREV-3Cr12-1

3-CREV-3Cr12-2

3-CREV-3Cr12-3

Figure 4.72. Graph. Plot of potential versus exposure time for STD1 concrete 

specimens with top mat bar crevice (splice) and 3Cr12 reinforcement 

compared to ones with normal bar placement. 
81 

-1.00

-0.50

0.00

0.50

1.00

1.50

2.00

0 100 200 300 400 500 600 700

Exposure Time, days

Macrocell Current Density, 

μA/cm2

1-STD1-3Cr12-1

1-STD1-3Cr12-2

1-STD1-3Cr12-3

3-CREV-3Cr12-1

3-CREV-3Cr12-2

3-CREV-3Cr12-3

Figure 4.73. Graph. Plot of macro-cell current density versus exposure time 

for STD1 concrete specimens with top mat bar crevice (splice) and 3Cr12 

reinforcement compared to ones with normal bar placement. 

-600

-500

-400

-300

-200

-100

0

0 100 200 300 400 500 600 700

Exposure Time, days

Potential, V (SCE)

1-STD1-3Cr12-1

1-STD1-3Cr12-2

1-STD1-3Cr12-3

3-CCON-3Cr12-1

3-CCON-3Cr12-2

3-CCON-3Cr12-3

Figure 4.74. Graph. Plot of potential versus exposure time for STD1 concrete specimens 

with a simulated concrete crack and 3Cr12 reinforcement compared to uncracked ones. 
82 

-1.00

-0.50

0.00

0.50

1.00

1.50

2.00

0 200 400 600 800

Exposure Time, days 

Current Density, 

μA/cm2

3-CCON-3Cr12-1 3-CCON-3Cr12-2

3-CCON-3Cr12-3 1-STD1-3Cr12-1

1-STD1-3Cr12-2 1-STD1-3Cr12-3

Figure 4.75. Graph. Plot of macro-cell current density versus exposure time 

for STD1 concrete specimens with a simulated concrete crack and 

3Cr12 reinforcement compared to uncracked ones. 

-600

-500

-400

-300

-200

-100

0

0 100 200 300 400 500 600 700

Exposure Time, days

Potential, V (SCE)

1-STD1-3Cr12-1

1-STD1-3Cr12-2

1-STD1-3Cr12-3

3-BCAT-3Cr12-1

3-BCAT-3Cr12-2

3-BCAT-3Cr12-3

3-BCAT-3Cr12-4

3-BCAT-3Cr12-5

3-BCAT-3Cr12-6

Figure 4.76. Graph. Plot of potential versus exposure time for STD1 concrete 

specimens with black bar bottom mat and top mat 3Cr12 reinforcement 

compared to ones with all 3Cr12 bars. 
83 

-1.00

-0.50

0.00

0.50

1.00

1.50

2.00

0 100 200 300 400 500 600 700

Exposure Time, days

Macrocell Current Density, 

μA/cm2

1-STD1-3Cr12-1 1-STD1-3Cr12-2 1-STD1-3Cr12-3

3-BCAT-3Cr12-1 3-BCAT-3Cr12-2 3-BCAT-3Cr12-3

3-BCAT-3Cr12-4 3-BCAT-3Cr12-5 3-BCAT-3Cr12-6

Figure 4.77. Graph. Plot of macro-cell current density versus exposure time 

for STD1 concrete specimens with black bar bottom mat and top mat 

3Cr12 reinforcement compared to ones with all 3Cr12 bars. 

-600

-500

-400

-300

-200

-100

0

0 100 200 300 400 500 600

Exposure Time, days

Potential, V (SCE)

3-CCON-3Cr12-1

3-CCON-3Cr12-2

3-CCON-3Cr12-3

3-CCRV-3Cr12-1

3-CCRV-3Cr12-2

3-CCRV-3Cr12-3

Figure 4.78. Graph. Plot of potential versus exposure time for STD1 concrete 

specimens with a simulated concrete crack and 3Cr12 reinforcement compared 

to cracked ones with a simulated crack and top bar crevice (splice). 
84 

-1.00

-0.50

0.00

0.50

1.00

1.50

2.00

0 100 200 300 400 500 600

Exposure Time, days

Macrocell Current Density, 

μA/cm2

3-CCON-3Cr12-1

3-CCON-3Cr12-2

3-CCON-3Cr12-3

3-CCRV-3Cr12-1

3-CCRV-3Cr12-2

3-CCRV-3Cr12-3

Figure 4.79. Graph. Plot of macro-cell current density versus exposure time for STD1 

concrete specimens with a simulated concrete crack and 3Cr12 reinforcement 

compared to cracked ones with a simulated crack and top bar crevice (splice). 

-700

-600

-500

-400

-300

-200

-100

0

1.00E-04 1.00E-03 1.00E-02 1.00E-01 1.00E+00 1.00E+01

Current Density, μA/cm2 

Potential, V (SCE)

1-STD1-3Cr12-1

3-CCON-3Cr12-1

3-CCRV-3Cr12-2

3-CREV-3Cr12-1

3-WB-3Cr12-1

3-BCAT-3Cr12-1

2-STD2-3Cr12-1

Figure 4.80. Graph. Plot of potential versus macro-cell current density for 

3Cr12 reinforced specimens. 
85 

Figure 4.81. Photo. Trace of the upper rebars and 

corrosion products on specimen number 1-STD1-3Cr12-1. 

Figure 4.82. Photo. Trace of the upper rebars and 

corrosion products on specimen number 1-STD2-3Cr12-1. 
86 

Figure 4.83. Photo. Trace of the upper rebars and 

corrosion products on specimen number 1-WB-3Cr12-1. 

Figure 4.84. Photo. Trace of the upper rebars and 

corrosion products on specimen number 1-CREV-3Cr12-1. 
87 

Figure 4.85. Photo. Trace of the upper rebars and 

corrosion products on specimen number 1-CCON-3Cr12-1. 

Figure 4.86. Photo. Trace of the upper rebars and 

corrosion products on specimen number 1-BCAT-3Cr12-1.
88 

Figure 4.87. Photo. Trace of the upper rebars and 

corrosion products on specimen number 1-CCRV-3Cr12-1. 

Slabs Reinforced With 2201 Bars 

Figures 4.88 through 4.91 show potential and macro-cell current density plots for standard 

specimens reinforced with 2201. Here, the initial potential decay was more gradual than for the 

black bar specimens; and current density subsequent to initiation was less by a factor of 2 to 3. 

Figures 4.92 through 4.103 show plots for the other specimen variables. Figure 4.104 presents 

potential versus macro-cell current density data for specimens reinforced with 2201 that includes 

representative data for each of the specimen types. As for the other bar types, all data conform to 

a common trend but occupy different regimes therein. As such, the upper current densities of the 

trend band occurred for the crevice specimens (CCON and CCRV), whereas the wire brushed 

ones were at the lower bound. Some of the black cathode (BCAT) current densities occurred at 

values below the lower band bound. This apparently reflects the fact that potential remained 

relatively positive for one of the three specimens (see figure 4.98). 

Figures 4.105 through 4.112 show photographs of the upper bar traces of autopsied specimens 

(one specimen from each group of three) for each of the specimen variables. These indicate that, 

more so than for the black bar, MMFX-IITM, and 3Cr12, corrosion tended to initiate on the bars 

near the specimen side faces. Unlike the bar types evaluated above, corrosion products were 

more extensive on the STD2 than STD1 specimen (compare figures 4.105 and 4.106), which is 

inconsistent with the current density data (figure 4.91). The reason for this is unclear but may be 

related to the corrosion preferential attack at the bar ends. In addition to the STD2 specimen, 

products were extensive on at least one bar of the CREV, CCON, and BCAT specimens. 

Consequently, of the rebar types MMFX-IITM, 3Cr12, and 2201, the autopsied CREV and BCAT 

specimens in each case exhibited heavy corrosion product accumulation on at least one of the 

three bars. 
89 

-700

-600

-500

-400

-300

-200

-100

0

0 100 200 300 400 500 600 700

Exposure Time, days

Potential, V (SCE)

1-STD1-BB-1

1-STD1-BB-2

1-STD1-BB-3

1-STD1-2201-1

1-STD1-2201-2

1-STD1-2201-3

Figure 4.88. Graph. Plot of potential versus exposure time for STD1 concrete 

specimens with 2201 reinforcement compared to data for black bar. 

-1.00

-0.50

0.00

0.50

1.00

1.50

2.00

0 100 200 300 400 500 600 700

Exposure Time, days

Macrocell Current Density, 

μA/cm2

1-STD1-2201-1

1-STD1-2201-2

1-STD1-2201-3

1-STD1-BB-1

1-STD1-BB-2

1-STD1-BB-3

Figure 4.89. Graph. Plot of macro-cell current density versus exposure time for STD1 

concrete specimens with 2201 reinforcement compared to data for black bar. 
90 

-700

-600

-500

-400

-300

-200

-100

0

0 100 200 300 400 500 600 700

Exposure Time, days

Potential, V (SCE)

1-STD1-2201-1

1-STD1-2201-2

1-STD1-2201-3

1-STD2-2201-1

1-STD2-2201-2

1-STD2-2201-3

Figure 4.90. Graph. Plot of potential versus exposure time for STD1 and 

STD2 concrete specimens with 2201 reinforcement. 

-1.00

-0.50

0.00

0.50

1.00

1.50

2.00

0 100 200 300 400 500 600 700

Exposure Time, days

Macrocell Current Density, 

μA/cm2

1-STD2-2201-1

1-STD2-2201-2

1-STD2-2201-3

1-STD1-2201-1

1-STD1-2201-2

1-STD1-2201-3

Figure 4.91. Graph. Plot of macro-cell current density versus exposure time for 

STD1 and STD2 concrete specimens with 2201 reinforcement. 
91 

-700

-600

-500

-400

-300

-200

-100

0

0 100 200 300 400 500 600 700

Exposure Time, days

Potential, V (SCE)

1-STD1-2201-1

1-STD1-2201-2

1-STD1-2201-3

2-WB-2201-1

2-WB-2201-2

2-WB-2201-3

Figure 4.92. Graph. Plot of potential versus exposure time for STD1 concrete specimens 

with wire brushed (WB) 2201 bars compared to ones with as-received 2201 bars. 

-1.00

-0.50

0.00

0.50

1.00

1.50

2.00

0 100 200 300 400 500 600 700

Exposure Time, days

Macrocell Current Density, 

μA/cm2

1-STD1-2201-1

1-STD1-2201-2

1-STD1-2201-3

2-WB-2201-1

2-WB-2201-2

2-WB-2201-3

Figure 4.93. Graph. Plot of macro-cell current density versus exposure 

time for STD1 concrete specimens with wire brushed (WB) 2201 bars 

compared to ones with as-received 2201 bars. 
92 

-700

-600

-500

-400

-300

-200

-100

0

0 100 200 300 400 500 600 700

Exposure Time, days

Potential, V (SCE)

1-STD1-2201-1 1-STD1-2201-2

1-STD1-2201-3 3-CREV-2201-1

3-CREV-2201-2 3-CREV-2201-3

Figure 4.94. Graph. Plot of potential versus exposure time for STD1 concrete 

specimens with top mat crevice bars (splice) and 2201 reinforcement 

compared to ones with normal bar placement. 

-1.00

-0.50

0.00

0.50

1.00

1.50

2.00

0 100 200 300 400 500 600 700

Exposure Time, days

Macrocell Current Density, 

μA/cm2

1-STD1-2201-1

1-STD1-2201-2

1-STD1-2201-3

3-CREV-2201-1

3-CREV-2201-2

3-CREV-2201-3

Figure 4.95. Graph. Plot of macro-cell current density versus exposure time 

for STD1 concrete specimens with top mat crevice bars (splice) and 2201 

reinforcement compared to ones with normal bar placement. 
93 

-700

-600

-500

-400

-300

-200

-100

0

0 100 200 300 400 500 600 700

Exposure Time, days

Potential, V (SCE)

1-STD1-2201-1

1-STD1-2201-2

1-STD1-2201-3

3-CCON-2201-1

3-CCON-2201-2

3-CCON-2201-3

Figure 4.96. Graph. Plot of potential versus exposure time for STD1 concrete specimens 

with a simulated crack and 2201 reinforcement compared to uncracked ones. 

-1.00

-0.50

0.00

0.50

1.00

1.50

2.00

0 100 200 300 400 500 600 700

Exposure Time, days

Macrocell Current Density, 

μA/cm2

1-STD1-2201-1

1-STD1-2201-2

1-STD1-2201-3

3-CCON-2201-1

3-CCON-2201-2

3-CCON-2201-3

Figure 4.97. Graph. Plot of potential versus exposure time for STD1 concrete specimens 

with a simulated crack and 2201 reinforcement compared to uncracked ones. 
94 

-450

-400

-350

-300

-250

-200

-150

-100

-50

0

0 100 200 300 400 500 600 700

Exposure Time, days

Potential, V (SCE)

2-BCAT-2201-1

2-BCAT-2201-2

2-BCAT-2201-3

1-STD1-2201-1

1-STD1-2201-2

1-STD1-2201-3

Figure 4.98. Graph. Plot of potential versus exposure time for STD1 concrete specimens 

with top mat 2201 bars and bottom mat black bar compared to ones with all 2201 bars. 

-1.00

-0.50

0.00

0.50

1.00

1.50

2.00

0 100 200 300 400 500 600 700

Exposure Time, days

Macrocell Current Density, 

μA/cm2

2-BCAT-2201-1

2-BCAT-2201-2

2-BCAT-2201-3

1-STD1-2201-1

1-STD1-2201-2

1-STD1-2201-3

Figure 4.99. Graph. Plot of macro-cell current density versus exposure time for 

STD1 concrete specimens with top mat 2201 bars and bottom mat black 

bar compared to ones with all 2201 bars. 
95 

-700

-600

-500

-400

-300

-200

-100

0

0 100 200 300 400 500 600 700

Exposure Time, days

Potential, V (SCE)

3-CCON-2201-1 3-CCON-2201-2

3-CCON-2201-3 2-CCNB-2201-1

2-CCNB-2201-2 2-CCNB-2201-3

Figure 4.100. Graph. Plot of potential versus exposure time for STD1 

concrete specimens with a simulated concrete crack and 2201 reinforcement 

compared to ones with a simulated crack and black bottom bars. 

-1.00

-0.50

0.00

0.50

1.00

1.50

2.00

0 100 200 300 400 500 600 700

Exposure Time, days

Macrocell Current Density, 

μA/cm2

3-CCON-2201-1

3-CCON-2201-2

3-CCON-2201-3

2-CCNB-2201-1

2-CCNB-2201-2

2-CCNB-2201-3

Figure 4.101. Graph. Plot of macro-cell current density versus exposure time 

for STD1 concrete specimens with a simulated concrete crack and 2201 

reinforcement compared to ones with a simulated crack and black bottom bars. 
96 

-700

-600

-500

-400

-300

-200

-100

0

0 100 200 300 400 500 600

Exposure Time, days

Potential, V (SCE)

3-CCON-2201-1 3-CCON-2201-2

3-CCON-2201-3 3-CCRV-2201-1

3-CCRV-2201-2 3-CCRV-2201-3

Figure 4.102. Graph. Plot of potential versus exposure time for STD1 concrete specimens 

with a simulated crack and crevice at top bars (splice) and 2201 reinforcement 

compared results for ones with cracked concrete and normal top bar placement. 

-1.00

-0.50

0.00

0.50

1.00

1.50

2.00

0 100 200 300 400 500 600

Exposure Time, days

Macrocell Current Density, 

μA/cm2

3-CCON-2201-1 3-CCON-2201-2

3-CCON-2201-3 3-CCRV-2201-1

3-CCRV-2201-2 3-CCRV-2201-3

Figure 4.103. Graph. Plot of macro-cell current density versus exposure time for STD1 

concrete specimens with a simulated crack and crevice at top bars (splice) and 2201 

reinforcement compared results for ones with cracked concrete and normal top bar 

placement. 
97 

-700

-600

-500

-400

-300

-200

-100

0

1.00E-04 1.00E-03 1.00E-02 1.00E-01 1.00E+00 1.00E+01

Current Density, μA/cm2 

Potential, V (SCE)

1-STD2-2201-1

1-STD1-2201-1

3-CCON-2201-1

3-CCRV-2201-3

3-CREV-2201-1

2-WB-2201-1

2-BCAT-2201-1

2-CCNB-2201-1

Figure 4.104. Graph. Plot of potential versus macro-cell current density 

for 2201 reinforced specimens. 

Figure 4.105. Photo. Trace of the upper rebars and 

corrosion products on specimen number 1-STD1-2201-3. 
98 

Figure 4.106. Photo. Trace of the upper rebars and 

corrosion products on specimen number 1-STD2-2201-2. 

Figure 4.107. Photo. Trace of the upper rebars and 

corrosion products on specimen number 1-WB-2201-1. 
99 

Figure 4.108. Photo. Trace of the upper rebars and 

corrosion products on specimen number 1-CREV-2201-1. 

Figure 4.109. Photo. Trace of the upper rebars and 

corrosion products on specimen number 1-CCON-2201-1. 
100 

Figure 4.110. Photo. Trace of the upper rebars and 

corrosion products on specimen number 1-BCAT-2201-1. 

Figure 4.111. Photo. Trace of the upper rebars and 

corrosion products on specimen number 1-CCNB-2201-1. 
101 

Figure 4.112. Photo. Trace of the upper rebars 

and corrosion products on specimen number 1-CCRV-2201-1. 

Figure 4.113 compares on a single plot the average macro-cell current density versus average 

potential data for each three specimen set (standard specimens only) of reinforcement types 

black bar, 3Cr12, MMFX-IITM, and 2201 and illustrates that these conform to different trends. 

For black bar slabs, it was considered that active corrosion commenced once potential dropped to 

−280 mVSCE, at which point the average macro-cell current density was about 0.26 μA/cm2

. If it 

is assumed that this same current density denotes onset of active corrosion for the other 

reinforcement types as well, then the corresponding potentials are −390, −350, and −195 mVSCE

for 3Cr12, MMFX-IITM, and 2201, respectively. These potentials were achieved after 35 days 

(black bar), 64 to 140 days (3Cr12), 91 to 140 days (MMFX-IITM), and 64 to 94 days (2201). 

Slabs Reinforced With 316 Solid and Clad (Stelax) Stainless Bars 

Figures 4.114 and 4.115 show plots of potential and macro-cell current density, respectively, for 

the standard solid and Stelax clad stainless steel specimens in comparison to that for the black 

bar ones. This reveals a general trend where potential of the stainless steel specimens tended to 

become more positive with exposure time with all specimens conforming to a common band. 

Macro-cell current density has remained nil throughout the exposures. Data for the BCAT, 

CREV, CCON, CCRV, and CCNB specimen types are not presented since potentials conformed 

to the same scatter band as for the standard specimens (figure 4.114), and macro-cell current 

density was nil in all cases. 

Thus, for the standard specimen simulated deck slab configuration the reinforcement types rank 

from best to worst, as: 

316 ≈ Stelax >> 2201 > MMFX-IITM > 3Cr12 > Black Bar. (4.2) 
102 

-700

-600

-500

-400

-300

-200

-100

0

1.00E-02 1.00E-01 1.00E+00 1.00E+01

Current Density, μA/cm2

Potential, V (SCE)

2201

MMFX

3Cr12

BB

Figure 4.113. Graph. Plot of average potential versus average macro-cell current density at 

each measurement time for three specimens of the four indicated reinforcement types. 

-700

-600

-500

-400

-300

-200

-100

0

0 100 200 300 400 500 600 700

Exposure Time, days

Potential, V (SCE)

1-STD2-316(18)-1

1-STD2-316(18)-2

1-STD2-316(18)-3

1-STD1-316(18)-1

1-STD1-316(18)-2

1-STD1-316(18)-3

1-STD1-BB-1

1-STD1-BB-2

1-STD1-BB-3

3-STD1-316(17)-1

3-STD1-316(17)-2

3-STD1-316(17)-3

1-STD1-Stelax-1

1-STD1-Stelax-2

1-STD1-Stelax-3

Figure 4.114. Graph. Plot of potential versus exposure time for STD1 

and STD2 concrete specimens with 316.18, 316.17, and Stelax 

reinforcement compared to that for black bar in STD1 concrete. 
103 

-1.00E+00

-5.00E-01

0.00E+00

5.00E-01

1.00E+00

1.50E+00

2.00E+00

0 100 200 300 400 500 600 700

Exposure Time, days

Macrocell Current Density, 

μA/cm2

1-STD2-316(18)-1 1-STD2-316(18)-2 1-STD2-316(18)-3

1-STD1-316(18)-1 1-STD1-316(18)-2 1-STD1-316(18)-3

1-STD1-BB-1 1-STD1-BB-2 1-STD1-BB-3

Figure 4.115. Graph. Plot of macro-cell current density versus exposure time 

for STD1 and STD2 concrete specimens with 316.18 reinforcement 

compared to ones with black bar in STD1 concrete. 

Chloride Concentration 

At several times during the exposures, 76 mm diameter cores were taken at the mid-spacing 

between bars in two of the reinforced STD1 concrete slabs and from blank (nonreinforced) slabs 

that underwent the same ponding as the reinforced ones. The cores were then sliced, the slices 

ground to powder, and the powder analyzed for acid soluble [Cl-

] using the FDOT standard 

method.19 Figure 4.116 shows the results as a plot of [Cl-

] versus time and indicates that sorption 

probably contributed to transport of this species in the early stages of the exposures ([Cl-

] = 0.65 

kg/m3

 after a single ponding cycle (14 days)). Also apparent is that relatively high Clconcentrations resulted during the time frame of the exposures ([Cl-

] ≈ 5 kg/m3 after about 100 

days and 10 kg/m3

 after 300 days). 

Three Bar Columns 

Square Three Bar Column Specimens 

Figure 4.117 presents a time-to- corrosion (defined as potential achieving −280 mVSCE) bar 

graph for all the S3BC specimens, where each bar in the plot represents the average of two or 

more specimens. In the case where corrosion has commenced for only one specimen, the total 

number of days of exposure is shown. The data indicate the following: 

1. Black bar specimens had the shortest time-to-corrosion irrespective of mix design. This 

includes all six STD1 and STD2 specimens. 
104 

0

4

8

12

16

20

0 100 200 300 400 500 600 700

Exposure Time, days

Chloride Concentration, kg/m333 

Blank

1-STD1-BB-3

1-STD-MMFX-II-2

Figure 4.116. Graph. Plot of chloride concentration at 2.54 cm below the 

exposed surface of STD1 concrete slabs versus exposure time. 

3 Bar Square Sample Geometry

0

100

200

300

400

Days to -280mV vs SCE

Alloys, as received 

surface condition

 2201, mill scale

 316, pickled

 3CR12, pickled

 BB, mill scale

 MMFX, mill scale

Control - Straight Bar Bent Bar Elevated Bar

Very High Permeability Concrete (STD1)

Control - Straight Bar 

Moderate Permeability Concrete (STD2)

Notes:

All bars as received.

365 days of total exposure.

Graph presents time to half-cell potential crossing -280mV vs SCE. 

 Not all samples in the set have shown signs of corrosion.

Number of Failed Samples 2/3 Total Number of Samples

6/6

0/6

6/6

6/6

6/6

0/3

3/3

3/3 3/3

1/3 0/3

3/3

0/3 0/3 0/3

3/3

6/6

0/3

Figure 4.117. Graph. Time-to-corrosion results for square 3-bar column specimens. 
105 

2. All 3Cr12 specimens initiated corrosion, irrespective of mix design and specimen type. 

3. Specimens reinforced with MMFX-IITM exhibited performance that was equivalent to 3Cr12 

in the most aggressive conditions (control and bent bar groups) but outperformed 3Cr12 in 

the least aggressive cases (elevated bar and STD2 standard). 

4. The 2201 reinforced specimens exhibited greater times-to-corrosion for all bars except 316. 

5. Irrespective of concrete quality and specimen type, only 316 stainless steel has not initiated 

corrosion. 

6. Bending the anode bar did not appear to have any effect on the time-to-corrosion of 316 and 

2201 stainless steel reinforcements; but time-to-corrosion of 3Cr12 and MMFX-IITM was 

reduced by 47 and 41 percent, respectively. 

7. Elevating the bar in the three bar columns resulted in a greater time-to-corrosion compared to 

the normal configuration (figures 3.19 and 3.20). However, all 3Cr12 and one 2201 specimen 

initiated corrosion in this configuration. 

8. All reinforcement types performed better in the STD2 concrete than STD1 except for black 

bar, for which no difference was observed. 

9. The following ranking resulted based on the time required for potential to shift to −280 

mVSCE or more negative (best to worst): 

316 >> 2201 > MMFX-IITM > 3Cr12 > Black Bar.

(4.3)

This is the same as for the simulated deck slab specimens, as indicated above, given that 

Stelax bars were not included in the three bar column test matrix. 

Three Bar Tombstone Columns 

Exposure of these specimens only commenced recently; and so there has been insufficient time 

to acquire meaningful results. 

Macro-Cell Slab (MS) Specimens 

Figure 4.118 shows a graph of typical potential and current trends with exposure time for macrocell slab specimens (MMFX-IITM in uncracked STD1 concrete in this case). The same criterion 

for defining corrosion initiation and time-to-corrosion was used as for the square three bar 

column specimens (potential ≤ −280 mVSCE). However, in cases where a measurable macro-cell 

current increase occurred at a different time, corrosion initiation was defined as the time at which 

this current was detected. For this specimen group, specimen A initiated corrosion at 212 days, B 

at 69 days, and C after 231 days, for an average of 171 days. 

Figure 4.119 shows time-to-corrosion data for STD1 MS specimens without a simulated crack. 

Based upon these results, the following conclusions were reached: 
106 

Macro-Cell Slabs

Days to Failure

Potential and Current vs Age

 Uncracked Concrete, Control Group, MMFX

-500

-450

-400

-350

-300

-250

-200

-150

-100

-50

0

0 25 50 75 100 125 150 175 200 225 250

Age (Days)

Potential (mV vs SCE)

-150

-125

-100

-75

-50

-25

0

Current (uA)

Potential A Potential B Potential C

Current A Current B Current C

69 days 

212 days 

231 days 

Figure 4.118. Graph. Example potential and current data for macro-cell slab specimens. 

Macrocell Slab Specimens

Time to Corrosion, Uncracked Concrete

0

100

200

300

400

Average Days to Corrosion

Number of Failed Specimens 2/3 Total Number of Specimens

3/3

0/3

2/3

3/3

3/3

0/3

3/3

0/3 0/3

1/3

2/3

0/3

3/3

3/3

2/3

1/3

2/3

0/3

3/3

0/3 0/3

3/3

Control

Black Steel

Cathode Bent Anode

Black Steel

Cathode, Bent 

Anode

Anode as Received, 

not wire brushed

Notes:

All bars wire brushed.

371 days of total exposure.

Graph presents the average days to failure of 3 specimens. 

 Not all specimens in the set have shown signs of corrosion.

Alloys, as received surface 

condition

 2201, mill scale

 316, pickled

 3CR12, pickled

 BB, mill scale

 MMFX, mill scale

 STAX, Sand Blasted

Figure 4.119. Graph. Time-to-corrosion results for the macro-cell slab specimens 

without a simulated crack. 
107 

1. Control STD1 specimens reinforced with black steel exhibited the shortest time-to-corrosion 

(black steel was not included in the other specimen types except as the cathode bar in the 

black steel cathode group). Ranking of the different reinforcements in the standard or control 

specimens was as listed below (best to worst): 

 316 ≈ Stelax > 3Cr12 > 2201 >MMFX-IITM> Black Bar. 

 (4.4) 

This ordering is the same as for the simulated deck slab and three bar column specimens with 

the exception that 3Cr12 outperformed 2201 and MMFX-IITM. Apparently, the fact that bars 

in the macro-cell slab specimens were wire brushed was responsible for this, although it 

cannot be ruled out that the difference in specimen design also may have been a factor. This 

performance reordering is surprising in the sense that wire brushing of the pickled 3Cr12 was 

of greater benefit than wire brushing of the as-rolled 2201. Time-to-corrosion of MMFX-IITM 

was essentially the same in each of the two surface conditions. 

2. Reinforcements 3Cr12, MMFX-IITM, and 2201 in the BCAT specimen configuration, 

exhibited greater times-to-corrosion than the corresponding controls. The reason for this 

improvement is unclear but will be investigated when the specimens are autopsied. 

3. The 3Cr12, MMFX-IITM, and 2201 reinforcements in the BNTB configuration (see table 3.7) 

all exhibited greater times-to-corrosion than did the respective controls (the improvement 

may not be significant in the case of 3Cr12), suggesting that the advantageous feature of 

either the BENT or BCAT configuration was retained in combination. 

4. The best performance for each specimen type was exhibited by the 316 reinforcement. 

However, corrosion apparently initiated in one of the 316 BNTB specimens after 

approximately 260 days. 

Figure 4.120 shows results for specimens with a simulated crack using the same format as in 

figure 4.119. This indicates that time-to-corrosion for black bar and 3Cr12 reinforced specimens 

was either relatively short (control specimens) or nil (BCAT and BENT configurations). The 

same was true for MMFX-IITM in the BNTB specimens. Otherwise, time-to-corrosion for the 

MMFX-IITM and 2201 specimens was comparable in general terms with that for the uncracked 

specimens. With the one exception noted above, none of the 316 reinforced specimens have 

initiated corrosion. 

Field Columns 

The field columns have been exposed for only 4 months. Currently, initial readings are all that 

are available, so there are no observations that can be made at this time. 

Correlation of Concrete Specimen Data With Results From Accelerated Testing 

Figure 4.121 shows a plot of time-to-corrosion for simulated deck slab and square three bar 

column specimens as a function of [ ] − Clth , as determined from the AST-2A experiments. This 

reveals a general trend where, with the exception of the 2201 simulated deck slab data, time-to- 
108 

Macrocell Slab Specimens

Time to Corrosion, Cracked Concrete

0

100

200

300

400

2201

316

3CR12

BB

MMFX

2201

316

3CR12

MMFX

2201

316

3CR12

MMFX

2201

316

3CR12

MMFX

Average Days to Corrosion

Number of Failed Specimens 2/3 Total Number of Specimens

Control

Black Steel

Cathode Bent Anode

Black Steel

Cathode, Bent 

Anode

3/3

0/3

3/3 3/3

2/3 2/3

0/3

3/3

2/3

1/3

0/3 0/3

3/3 3/3 3/3

2/3

3/3

 Alloys

 2201

 316

 3CR12

 BB

 MMFX

Notes:

All bars wire brushed.

371 days of total exposure.

Graph presents the average days to failure of 3 specimens. 

 Not all specimens in the set have shown signs of corrosion.

Figure 4.120. Graph. Time-to-corrosion results for the macro-cell slab specimens 

with a simulated crack. 

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 50 100 150 200 250 300

Time-to-Corrosion, days

Chritical Chloride Conc. (AST-2A), w/o

BB(3-Bar)

3Cr12(3-Bar)

M M FX(3-Bar)

2201(3-Bar)

BB(SDS)

3Cr12(SDS)

M M FX(SDS)

2201(SDS)

Figure 4.121. Graph. Plot of time-to-corrosion of reinforced concrete specimens 

as a function of [ ] − Clth as determined from accelerated testing. 
109 

corrosion increased in proportion to [ ] − Clth . The error bands for the three bar column data 

correspond to one standard deviation, whereas for the simulated deck slabs these correspond to 

the data range. In comparing results for the two specimen types, the fact that corrosion of the 

simulated deck slab rebars may have initiated at or near the concrete interface because isolation 

was not provided here may have affected the results for these specimens. For most bar types in 

these specimens, concrete cracking, once this occurred, was along the line of the reinforcement; 

however, in the specific case of the 2201 specimens, cracking often occurred diagonally at the 

corners. This appeared to have resulted from corrosion of rebar near the concrete surface. Figure 

4.122 is a photograph of an example case of this cracking. Subject to this limitation, the fact that 

time-to-corrosion increased in proportion to [ ] − Clth supports applicability of the AST-2A 

potentiostatic test method for projecting long-term reinforced concrete corrosion performance. 

Crack 

Figure 4.122. Photo. Example of corner cracking on a 2201 

reinforced simulated deck slab specimen. 

A calculation of time-to-corrosion, Ti, of STD1 concrete specimens was made based upon the 

[ ] − Clth projected for concrete from the AST-2A data (figure 4:31) using the one-dimensional 

solution for Fick’s second law, 

[ ]

⎥

⎥

⎦

⎤

⎢

⎢

⎣

⎡

⋅ = −

− −

s 0 e i

s th

2 D T

x erf

C C

C Cl

, (4.5) 
110 

where Cs is [Cl-

] at the exposed concrete surface, C0 is the initial [Cl-] in the concrete, and De is 

the effective diffusion coefficient. A determination of De was made from the average of two Clprofiles obtained after 136 days of exposure (see figure 4.116), which are shown in figure 4.123, 

using a least squares best fit algorithm to equation 4.4. This yielded a De of 3.20·10-11 m2

/s. 

Inputs to the Fick’s second law solution, in addition to this value for De, were cover 2.54·10-2 m 

and Cs 18 kg/m3

. Table 4.6 lists the calculated time-to-corrosion for black bar, 3Cr12, MMFXIITM, and 2201. The projected times-to-corrosion are in general agreement with the measured 

values for concrete specimens (figure 4.121) with the exception of the 2201 reinforced simulated 

deck slab specimens, the reason being as discussed above. 

0.00

4.00

8.00

12.00

16.00

0.00 1.00 2.00 3.00 4.00 5.00

Depth into Concrete, cm

Chloride Concentration, kg/m 333

Core 1

Core 2

Figure 4.123. Graph. Chloride profile from each of two cores taken 

from STD1 concrete slabs after 136 days of exposure. 

Table 4.6. Calculated times-to-corrosion for concrete specimens. 

Bar Type Cth, w/o cement (Figure 4:30) Calculated Time-to-Corrosion, days

BB 0.65 81

3Cr12 0.88 99

MMFX 1.22 128

2201 1.34 138
111 

5. CONCLUSIONS 

Both short-term laboratory experiments in simulated pore solutions and long-term exposure of 

concrete specimens reinforced with corrosion resistant rebars exposed to chlorides were 

performed. The reinforcements included UNS-S31603 (Type 316L stainless steel (SS)), UNS31803 (Type 2205 SS), ASTM A055-98 (Type 2201LDX SS), UNS-S41003 (Type 3Cr12 SS), 

ASTM A615, Grade 75 (MMFX-IITM), two 316 SS clad steels (Stelax and SMI), and ASTM 

A615 (black bar). The following conclusions were reached based on results during the initial 

3 years of this 5-year study: 

1. For Accelerated Screening Test-1 (AST-1), which involved measurement of polarization 

resistance and weight loss of bars exposed to repetitive 1.75 hours wet—4.25 hours dry 

cycles in synthetic pore solution with chlorides for a total of 84 days, 316L SS solid bars 

performed best and black bars the worst. Corrosion rate for the other bars was intermediate 

and shared a common scatter band. Performance of the clad bars was mixed in that data for 

some specimens without intentional clad defects approached that of the solid 316L SS, 

whereas with clad defects polarization resistance approached that of the black bars. 

2. Accelerated Screening Test-2A (AST-2A) involved exposure of specimens that were 

potentiostatically polarized to +100 mVSCE in synthetic pore water to which chlorides were 

incrementally added. Corrosion initiation was defined as having occurred when current 

density reached 10 μA/cm2

. For bars that became active, the average critical Clconcentration for corrosion, [ ] − Clth , was 0.25 weight percent (w/o) Cl-

 (black bar), 0.47 w/o 

Cl-

 (3Cr12), 0.87 w/o Cl- (MMFX-IITM), and 1.06 w/o Cl- (2201). By comparison of the 

presently determined [ ] − Clth values with those from the literature that were acquired using 

pore water expression from specimens for which companion chloride thresholds in concrete, 

CT, were available, CT of black bar was projected as 0.54 w/o, for 3Cr12 0.80 w/o, for 

MMFX-IITM 1.10 w/o, and 2201 1.30 w/o (cement weight basis). A comparison between the 

AST-1 and AST-2A data indicated that rebars with a polarization resistance greater than 

6·104

 ohm·m2 had a [ ] − Clth greater than 5 w/o, whereas below this [ ] − Clth was about 1 w/o or 

less. It was unclear if the [ ] − Clth could be predicted from the Pitting Resistance Equivalent 

Number (PREN). 

3. Three types of reinforced concrete specimens, simulated deck slabs, three bar columns, and 

macro-cell slabs, have been under either continuous or cyclic wet-dry ponding with a NaCl 

solution for over 600 days. Similar to the accelerated tests, the best corrosion resistance was 

exhibited by the 316L reinforcement (both solid and clad); however, no 2205 SS bars have 

been tested in concrete. For bars with poor or intermediate performance in the accelerated 

tests (black bar, 3Cr12, MMFX-IITM, and 2201), time-to-corrosion in concrete increased in 

proportion to [ ] − Clth as determined in the accelerated AST-2A tests. The ranking (best to 

worst) was: 

 316 ≈ Stelax >> 2201 > MMFX-IITM > 3Cr12 > Black Bar, 

 (4.2) 
112 

except for the macro-cell slab specimens where the 3CR12 exhibited longer times-tocorrosion than either 2201 or MMFX-IITM. This may have been because these bars were wire 

brushed; however, if this is the explanation, then wire brushing the pickled 3Cr12 resulted in 

greater corrosion resistance enhancement than wire brushing the as-rolled 2201 or MMFXIITM. 

4. In general, time-to-corrosion of the different reinforcements in concrete increased in direct 

proportion to the chloride threshold that was determined by accelerated testing (AST-2A). 

5. Additional data are still being collected for the concrete specimens with various types of 

reinforcement that remain under test. Final analysis based on non-destructive data and 

observed condition of dissected specimens may change the ranking which will be 

documented in the final report. 
113 

APPENDIX A 

EXAMPLE PH CALCULATION 

From equation 3.1, 

 pH = 14+log (γOH·[OH-]), 

 (3.1) 

where γOH is the activity coefficient for OH-

, which was taken as 0.7, and [OH-] is molality of 

that species. Thus, assuming [OH-] = 0.1, 

 pH = 14+log (0.7⋅0.1) = 14+(· 1.15) = 12.85.

115 

APPENDIX B 

EXAMPLE CALCULATION OF CORROSION RATE FROM POLARIZATION 

RESISTANCE 

Corrosion rate, CR, was calculated from the measured polarization resistance, PR, using a 

modified form of the Stern-Geary equation, 

PR

B

n F

Z CR 3.15 10

7

⋅ ⋅ ⋅ρ = ⋅ ⋅ , (3.2) 

where Z is atomic weight, n is the number of electrical equivalents, F is Faraday’s constant, ρ is 

alloy density, and B is a term the value for which depends on the Tafel constants. For the case of 

black bar reinforcing steel, a typical measured value for PR was 103 Ω⋅cm2

. Thus, with values for 

the other constants as, 

 Z = 56 grams/mol, 

 n = 2 equivalents, 

 F = 96,500 Coulombs/mol⋅equivalent, 

 ρ = 7.87 grams/cm3, and 

 B = 0.026 V, 

3 10

0.026

2 96,500 7.87

56

CR 3.15 107

⋅

⋅ ⋅

= ⋅ ⋅ = 0.03 cm/year = 0.3 mm/year 

 = 12 mils/year. 

117 

APPENDIX C 

EXAMPLE CALCULATION OF CORROSION RATE FROM WEIGHT LOSS DATA 

The average corrosion rate, CR, over the exposure duration was determined from before and 

after specimen weight measurements using the expression, 

ρ A T

W CR ⋅ ⋅ = , (3.3) 

where W is weigh loss, ρ is metal density, A is exposed rebar specimen surface area, and T is 

exposure time. From the density of iron (steel) and typical experimental parameters: 

 W = 1.6 grams 

 ρ = 7.87⋅106 grams/m3, 

 A = 76⋅10-4 m2

, and 

 T = 0.0767 years (28 days), 

7.87 10 76 10 0.0767

1.6

CR

6 4 ⋅ ⋅ ⋅ ⋅

= −

 = 349⋅10-6 m/year 

 = 0.39 mm/year = 15 mils/year. 

119 

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HRDI-10/07-07(700)E

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