Research, Development, and Technology

Turner-Fairbank Highway Research Center

6300 Georgetown Pike

McLean, VA 22101-2296

Multiple Corrosion-Protection Systems 

for Reinforced Concrete Bridge 

Components

Publication No. FHWA-HRT-11-060 November 2011
FOREWORD

Eleven systems combining epoxy-coated reinforcement (ECR) with another corrosion-protection 

system were evaluated using rapid macrocell, southern exposure, cracked beam, linear polarization

resistance, and field tests. The systems included bars that were pretreated with zinc chromate to 

improve the adhesion between the epoxy and the reinforcing steel, two epoxies with improved 

adhesion to the reinforcing steel, one inorganic corrosion inhibitor (calcium nitrite), two organic 

corrosion inhibitors, an epoxy-coated bar with a primer containing microencapsulated calcium 

nitrite, three epoxy-coated bars with improved adhesion combined with the corrosion inhibitor 

calcium nitrite, and multiple-coated (MC) bars with an initial 50-μm (2-mil) coating of 98 percent 

zinc and 2 percent aluminum followed by a conventional epoxy coating. The systems were 

compared with conventional uncoated reinforcement and conventional ECR. 

The results presented in this report indicate that the coated bars provided superior corrosion 

protection to the reinforcing steel. In addition, bars with damaged coatings initiated corrosion 

at several times the chloride contents within concrete and typically corroded at rates two orders 

of magnitude less than conventional reinforcement. Limited additional protection was achieved 

using bars with primer coating, MC bars, and concrete containing calcium nitrite and one of the 

organic corrosion inhibitors, although the latter resulted in reduced compressive strength and 

reduced resistance to surface scaling. 

Jorge E. Pagán-Ortiz

Director, Office of Infrastructure

Research and Development

Notice

This document is disseminated under the sponsorship of the U.S. Department of Transportation 

in the interest of information exchange. The U.S. Government assumes no liability for the use 

of the information contained in this document. This report does not constitute a standard, 

specification, or regulation.

The U.S. Government does not endorse products or manufacturers. Trademarks or 

manufacturers’ names appear in this report only because they are considered essential to the 

objective of the document.

Quality Assurance Statement

The Federal Highway Administration (FHWA) provides high-quality information to serve 

Government, industry, and the public in a manner that promotes public understanding. Standards 

and policies are used to ensure and maximize the quality, objectivity, utility, and integrity of its 

information. FHWA periodically reviews quality issues and adjusts its programs and processes to 

ensure continuous quality improvement.
TECHNICAL REPORT DOCUMENTATION PAGE

1. Report No.

FHWA-HRT-11-060

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

4. Title and Subtitle

Multiple Corrosion-Protection Systems for Reinforced Concrete Bridge 

Components

5. Report Date

November 2011

6. Performing Organization Code

7. Author(s)

David Darwin, JoAnn Browning, Matthew O’Reilly, Carl E. Locke Jr., 

and Y. Paul Virmani

8. Performing Organization Report No. 

SM Report No. 101

9. Performing Organization Name and Address

University of Kansas Center for Research, Inc. 

2385 Irving Hill Road 

Lawrence, KS 66045-7563

10. Work Unit No.

11. Contract or Grant No.

DTFH61-03-C-00131

12. Sponsoring Agency Name and Address

Office of Infrastructure Research and Development

Federal Highway Administration

6300 Georgetown Pike

McLean, VA 22101-2296

13. Type of Report and Period Covered

Final Report

September 2003–February 2011

14. Sponsoring Agency Code

15. Supplementary Notes

The Contracting Officer’s Technical Representative (COTR) was Y.P. Virmani, HRDI-60.

16. Abstract

Eleven systems containing epoxy-coated reinforcement (ECR) in combination with another corrosion-protection system are 

evaluated using the rapid macrocell, southern exposure, cracked beam, linear polarization resistance, and field tests. The systems 

include bars pretreated with zinc chromate to improve the adhesion between the epoxy and the reinforcing steel, two epoxies 

with improved adhesion to the reinforcing steel, one inorganic corrosion inhibitor (calcium nitrite), two organic corrosion 

inhibitors (Rheocrete® 222+ and HycreteTM), an epoxy-coated bar with a primer containing microencapsulated calcium nitrite, 

three epoxy-coated bars with improved adhesion combined with the corrosion inhibitor calcium nitrite, and multiple-coated (MC) 

bars with an initial 50- m (2-mil) coating of 98 percent zinc and 2 percent aluminum followed by a conventional epoxy coating. 

The systems are compared with conventional uncoated reinforcement and conventional ECR. The coatings on all bars are 

penetrated to simulate the effects of damage during fabrication and placement in the field. 

The results presented in this report indicate that the coated bars provide superior corrosion protection to the reinforcing steel and 

that bars with damaged coatings initiate corrosion at chloride contents within concrete that are several times greater and corrode 

at rates that are typically two orders of magnitude below those exhibited by conventional reinforcement. Limited additional 

protection is achieved using bars with the primer coating, MC bars, and concrete containing the corrosion inhibitors calcium 

nitrite and one of the organic corrosion inhibitors, although the latter resulted in reduced compressive strength and reduced

resistance to surface scaling. The differences in costs over a 75-year design life are relatively small for coated bars. Cracks in 

concrete directly over and parallel to the reinforcement, such as found in bridge decks, result in earlier corrosion initiation and 

higher corrosion rates than obtained with intact concrete for all systems. Epoxies that provide initially high adhesion to the 

underlying steel provide no advantage over conventional epoxy coatings. All coated bars that were evaluated exhibited corrosion 

losses at openings through the coating. A reduction in adhesion between an epoxy coating and the reinforcing steel occurs after a 

period of exposure to corrosive conditions. This reduction increases with increasing chloride content in the concrete and in the 

presence of cracks and decreases with the use of corrosion inhibitors, with the use of MC reinforcement, and with electrical 

isolation of the epoxy-coated bars from each other. Corrosion products form under the coating where adhesion has been reduced. 

For periods up to five years under exposure conditions representative of those in bridge decks, the reduction in adhesion between 

an epoxy coating and the reinforcing steel did not affect the rate at which coated bars corrode. 

17. Key Words

Adhesion, Chlorides, Concrete, Corrosion, Corrosion 

inhibitor, Durability, Epoxy-coated steel, Zinc-coated steel

18. Distribution Statement

No restrictions. This document is available to the public through 

the National Technical Information Service, Springfield, VA 

22161.

19. Security Classif. (of this report)

Unclassified

20. Security Classif. (of this page)

Unclassified

21. No of Pages

255

22. Price

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

C 

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 the International System of Units. Appropriate rounding should be made to comply with Section 4 of ASTM E380. 

(Revised March 2003)
iii

TABLE OF CONTENTS

CHAPTER 1. INTRODUCTION.................................................................................................1

CHAPTER 2. EXPERIMENTAL WORK ..................................................................................3

CORROSION-PROTECTION SYSTEMS...........................................................................3

Control Systems...................................................................................................................4

Epoxies with Increased Adhesion........................................................................................4

Corrosion Inhibitors.............................................................................................................4

Epoxies With Increased Adhesion Plus Calcium Nitrite .....................................................5

Multiple Coatings.................................................................................................................5

PRETEST EVALUATION OF EPOXY-COATED BARS .................................................5

Evaluation of Coating Thickness and Holidays...................................................................5

Cathodic Disbondment Tests...............................................................................................6

CORROSION TEST PROCEDURES...................................................................................9

Rapid Macrocell Tests .........................................................................................................9

Bench-Scale Tests..............................................................................................................15

Corrosion Initiation Beam Tests........................................................................................19

Linear Polarization Resistance Test...................................................................................20

Field Tests..........................................................................................................................21

Chloride Analysis...............................................................................................................29

Average Corrosion Rates Based on Losses After Corrosion Initiation .............................30

TEST PROGRAM .................................................................................................................32

Rapid Macrocell Test Program..........................................................................................33

Bench-Scale and Corrosion Initiation Test Programs........................................................33

Linear Polarization Resistance Test Program....................................................................33

Field Test Program.............................................................................................................33

CHAPTER 3. TEST RESULTS .................................................................................................35

RAPID MACROCELL TESTS............................................................................................35

Bare Bar Tests....................................................................................................................37

Mortar-Wrapped Bar Tests................................................................................................43

BENCH-SCALE TESTS .......................................................................................................48

Southern Exposure Tests....................................................................................................49

Cracked Beam Tests ..........................................................................................................77

Linear Polarization Resistance Tests.................................................................................93

Autopsy of Bench-Scale Test Specimens........................................................................101

FIELD TESTS......................................................................................................................108

Corrosion Losses..............................................................................................................110

Corrosion Rates Based on Losses After Corrosion Initiation..........................................127

Mat-to-Mat Resistance.....................................................................................................128

Autopsy of Field Test Specimens....................................................................................132
iv

CHAPTER 4. EVALUATION..................................................................................................143

COMPARATIVE PERFORMANCE ................................................................................143

Critical Chloride Corrosion Threshold (CCCT) ..............................................................143

Corrosion Rate .................................................................................................................147

Disbondment....................................................................................................................153

LIFE EXPECTANCY .........................................................................................................153

Time to Corrosion Initiation ............................................................................................154

Time to Cracking After Corrosion Initiation ...................................................................157

Time to First Repair.........................................................................................................167

COST EFFECTIVENESS...................................................................................................169

Initial Cost........................................................................................................................169

Repair Costs.....................................................................................................................173

Present Value ...................................................................................................................175

CHAPTER 5. CONCLUSIONS................................................................................................179

APPENDIX A. DISBONDMENT OF CONVENTIONAL EPOXY-COATED AND 

MC BARS IN RAPID MACROCELL TEST .........................................................................181

TEST RESULTS..................................................................................................................182

Corrosion Rate, Loss, and Potentials...............................................................................182

Visual Observations.........................................................................................................185

Disbondment Results.......................................................................................................187

Summary..........................................................................................................................192

APPENDIX B. CORROSION LOSS REQUIRED TO CRACK CONCRETE 

CONTAINING CONVENTIONAL, EPOXY-COATED, AND GALVANIZED 

REINFORCEMENT..................................................................................................................193

INTRODUCTION................................................................................................................193

EXPERIMENTAL PROCEDURE.....................................................................................193

Mixture Proportions.........................................................................................................193

Materials ..........................................................................................................................194

Specimens........................................................................................................................194

Test Procedure .................................................................................................................195

Fabrication .......................................................................................................................195

Test Program....................................................................................................................196

Finite Element Modeling of Corrosion Loss and Cracking.............................................196

EXPERIMENTAL RESULTS............................................................................................201

Conventional and Galvanized Reinforcement .................................................................201

ECR..................................................................................................................................206

FINITE ELEMENT RESULTS .........................................................................................209

DISCUSSION.......................................................................................................................225

ACKNOWLEDGMENTS.........................................................................................................229

REFERENCES...........................................................................................................................231
v

LIST OF FIGURES

Figure 1. Illustration. Cathodic disbondment test setup (after reference 13)...................................6

Figure 2. Illustration. Macrocell test with bare bar specimens........................................................9

Figure 3. Illustration. Macrocell test with mortar-clad specimens ................................................10

Figure 4. Illustration. Mortar-wrapped specimen containing conventional reinforcing bar..........10

Figure 5. Equation. Corrosion rate for iron....................................................................................11

Figure 6. Equation. Example of corrosion rate for iron.................................................................12

Figure 7. Equation. Corrosion rate for zinc ...................................................................................12

Figure 8. Equation. Corrosion current density...............................................................................12

Figure 9. Illustration. Bare bar and mortar-wrapped rapid macrocell specimens with cap to 

protect the exposed end of epoxy-coated bars...............................................................................13

Figure 10. Illustration. Southern exposure test specimen..............................................................15

Figure 11. Illustration. Cracked beam test specimen.....................................................................16

Figure 12. Illustration. Corrosion initiation beam test specimen...................................................19

Figure 13. Illustration. Sampling locations for initiation beam tests.............................................20

Figure 14. Equation. Corrosion current density.............................................................................20

Figure 15. Illustration. Field test specimens, top slab without cracks...........................................22

Figure 16. Illustration. Field test specimens, top slab with cracks................................................22

Figure 17. Illustration. Field test specimens, bottom slab .............................................................22

Figure 18. Illustration. Field test specimens, front and side views................................................23

Figure 19. Equation. Temperature correction in Celsius...............................................................24

Figure 20. Equation. Temperature correction in Fahrenheit..........................................................24

Figure 21. Illustration. Potential test points for conventional steel specimens..............................25

Figure 22. Illustration. Potential test points for epoxy-coated bar specimens with four test bars....25

Figure 23. Illustration. Potential test points for epoxy-coated bar specimens with two test bars ....25

Figure 24. Illustration. Shim holder for field specimens, top view ...............................................27

Figure 25. Illustration. Shim holder for field specimens, front view.............................................27

Figure 26. Illustration. Shim holder for field specimens, side view..............................................27

Figure 27. Graph. Individual corrosion losses based on total area of the top bars for field test 

specimens containing Rheocrete® in uncracked concrete, with corrosion initiation marked ........30

Figure 28. Graph. Individual corrosion losses based on total area of the top bars for field test 

specimens containing Rheocrete® in uncracked concrete, with lines connecting corrosion loss 

at initiation to corrosion loss at 250 weeks....................................................................................31

Figure 29. Graph. Individual corrosion loss based on exposed area of the top bars for southern 

exposure specimens containing epoxy-coated bars cast in concrete containing DCI, with lines 

connecting corrosion loss at initiation to corrosion loss at 96 weeks............................................31

Figure 30. Graph. Macrocell test, average corrosion rate for bare conventional, ECR, 

increased-adhesion ECR, and MC steel in simulated pore solution with 1.6 molal ion 

concentration of sodium chloride...................................................................................................38

Figure 31. Graph. Macrocell test, average corrosion rate for bare ECR, increased-adhesion 

ECR, and MC steel in simulated pore solution with 1.6 molal ion concentration of sodium 

chloride (adjusted y-axis)...............................................................................................................38

Figure 32. Graph. Macrocell test, average corrosion loss based on total area for bare 

conventional, ECR, increased-adhesion ECR, and MC steel in simulated pore solution with 

1.6 molal ion concentration of sodium chloride ............................................................................39
vi

Figure 33. Graph. Macrocell test, average corrosion loss based on area exposed at holes 

through coating for bare conventional, ECR, increased-adhesion ECR, and MC steel in 

simulated pore solution with 1.6 molal ion concentration of sodium chloride..............................40

Figure 34. Graph. Macrocell test, average corrosion potential at anode for bare conventional, 

ECR, increased-adhesion ECR, and MC steel in simulated pore solution with 1.6 molal ion 

concentration of sodium chloride...................................................................................................41

Figure 35. Graph. Macrocell test, average corrosion potential at cathode for bare conventional, 

ECR, increased-adhesion ECR, and MC steel in simulated pore solution with 1.6 molal ion 

concentration of sodium chloride...................................................................................................41

Figure 36. Photo. Bare conventional anode bar at 15 weeks showing corrosion products that 

formed below the surface of the solution.......................................................................................42

Figure 37. Photo. Bare ECR anode bar at 15 weeks showing corrosion products that formed 

at holes through the epoxy .............................................................................................................42

Figure 38. Photo. Bare MC anode bar with only epoxy penetrated at 15 weeks showing 

corrosion products that formed at holes through the epoxy...........................................................42

Figure 39. Graph. Macrocell test, average corrosion rate based on total area for mortar-wrapped 

conventional, ECR, ECR with calcium nitrite primer, and MC steel in simulated pore solution 

with 1.6 molal ion concentration of sodium chloride ....................................................................43

Figure 40. Graph. Macrocell test, average corrosion rate based on area exposed at holes through

coating for mortar-wrapped conventional ECR, ECR with calcium nitrite primer, and MC 

steel in simulated pore solution with 1.6 molal ion concentration of sodium chloride .................43

Figure 41. Graph. Macrocell test, average corrosion loss based on total area for mortar-wrapped

conventional, ECR, ECR with calcium nitrite, and MC steel in simulated pore solution with 

1.6 molal ion concentration of sodium chloride ............................................................................44

Figure 42. Graph. Macrocell test, average corrosion loss based on area exposed at holes through 

coating for mortar-wrapped conventional, ECR, ECR with calcium nitrite, and MC steel in 

simulated pore solution with 1.6 molal ion concentration of sodium chloride..............................45

Figure 43. Graph. Macrocell test, average corrosion potential at anode for mortar-wrapped 

conventional, ECR, ECR with increased adhesion, ECR cast with corrosion inhibitor, and 

ECR with calcium nitrite in simulated pore solution with 1.6 molal ion concentration of 

sodium chloride..............................................................................................................................46

Figure 44. Graph. Macrocell test, average corrosion potential at cathode for mortar-wrapped 

conventional, ECR, ECR with increased adhesion, ECR cast with corrosion inhibitor, and 

ECR with calcium nitrite in simulated pore solution with 1.6 molal ion concentration of 

sodium chloride..............................................................................................................................46

Figure 45. Graph. Macrocell test, average corrosion potential at anode for mortar-wrapped 

MC steel in simulated pore solution with 1.6 molal ion concentration of sodium chloride..........47

Figure 46. Graph. Macrocell test, average corrosion potential at cathode for mortar-wrapped

MC steel in simulated pore solution with 1.6 molal ion concentration of sodium chloride..........47

Figure 47. Photo. Conventional anode bar after removal of mortar at 15 weeks..........................48

Figure 48. Graph. Southern exposure test, average corrosion rates based on total area for 

conventional reinforcement and ECR............................................................................................56

Figure 49. Graph. Southern exposure test, average corrosion loss based on total area for 

conventional reinforcement and ECR............................................................................................57

Figure 50. Graph. Southern exposure test, average corrosion loss based on area exposed at 

holes through coating for ECR ......................................................................................................57
vii

Figure 51. Graph. Southern exposure test, corrosion potential of top mat for conventional 

reinforcement and ECR..................................................................................................................58

Figure 52. Graph. Southern exposure test, corrosion potential of bottom mat for conventional 

reinforcement and ECR..................................................................................................................59

Figure 53. Graph. Southern exposure test, mat-to-mat resistance for conventional 

reinforcement and ECR..................................................................................................................60

Figure 54. Graph. Southern exposure test, corrosion losses based on total area for 

conventional ECR and increased-adhesion ECR...........................................................................61

Figure 55. Graph. Southern exposure test, corrosion losses based on area exposed at holes 

through coating for conventional ECR and increased-adhesion ECR...........................................61

Figure 56. Graph. Southern exposure test, corrosion potential of top mat for conventional 

ECR and increased-adhesion ECR.................................................................................................62

Figure 57. Graph. Southern exposure test, corrosion losses based on area exposed at holes 

through coating for conventional ECR and ECR with inhibitors with bars containing four 

holes and concrete with w/c = 0.45................................................................................................63

Figure 58. Graph. Southern exposure test, corrosion losses based on area exposed at holes 

through coating for conventional ECR and ECR with inhibitors with bars containing 10 holes 

and concrete with w/c = 0.45 .........................................................................................................63

Figure 59. Graph. Southern exposure test, corrosion losses based on area exposed at holes 

through coating for conventional ECR and ECR with inhibitors with bars containing 10 holes 

and concrete with w/c = 0.35 .........................................................................................................64

Figure 60. Graph. Southern exposure test, corrosion potential of top mat for conventional 

ECR with and without corrosion inhibitor with bars containing four holes and concrete with 

w/c = 0.45 ......................................................................................................................................65

Figure 61. Graph. Southern exposure test, corrosion potential of top mat for conventional 

ECR with and without corrosion inhibitor with bars containing 10 holes and concrete with 

w/c = 0.45 ......................................................................................................................................65

Figure 62. Graph. Southern exposure test, corrosion potential of top mat for conventional 

ECR with and without corrosion inhibitor with bars containing 10 holes and concrete with 

w/c = 0.35 ......................................................................................................................................66

Figure 63. Graph. Southern exposure test, average corrosion losses based on area exposed at 

holes through coating for conventional ECR and ECR with and without increased adhesion 

and corrosion inhibitor...................................................................................................................67

Figure 64. Graph. Southern exposure test, corrosion potential of top mat for conventional ECR

with and without corrosion inhibitor and increased-adhesion ECR with corrosion inhibitor .......67

Figure 65. Graph. Southern exposure test, corrosion loss based on area exposed at holes through 

coating for conventional ECR and MC reinforcement with bars containing four holes ...............68

Figure 66. Graph. Southern exposure test, corrosion loss based on area exposed at holes through

coating for conventional ECR and MC reinforcement with bars containing 10 holes..................69

Figure 67. Graph. Southern exposure test, corrosion potential of top mat for conventional 

ECR and MC reinforcement with bars containing four holes........................................................70

Figure 68. Graph. Southern exposure test, corrosion potential of bottom mat for conventional 

ECR and MC reinforcement with bars containing four holes........................................................70

Figure 69. Graph. Southern exposure test, corrosion potential of top mat for conventional 

ECR and MC reinforcement with bars containing 10 holes..........................................................71
viii

Figure 70. Graph. Southern exposure test, corrosion potential of bottom mat for conventional 

ECR and MC reinforcement with bars containing 10 holes..........................................................71

Figure 71. Graph. Southern exposure test, average corrosion rates based on total area for 

conventional reinforcement in specimens without and with corrosion inhibitors.........................73

Figure 72. Graph. Southern exposure test, average corrosion losses based on total area for 

conventional reinforcement in specimens without and with corrosion inhibitors.........................73

Figure 73. Graph. Southern exposure test, corrosion potential of top mat for conventional 

reinforcement in specimens without and with corrosion inhibitors...............................................74

Figure 74. Graph. Southern exposure test, mat-to-mat resistance for conventional 

reinforcement in specimens without and with corrosion inhibitors...............................................75

Figure 75. Graph. Cracked beam test, average corrosion rates based on total area of control 

specimens for conventional reinforcement and ECR.....................................................................81

Figure 76. Graph. Cracked beam test, average corrosion loss based on total area of control 

specimens for conventional reinforcement and ECR.....................................................................82

Figure 77. Photo. Cracked beam specimen containing conventional reinforcing steel at end 

of 96-week test...............................................................................................................................83

Figure 78. Graph. Cracked beam test, average corrosion loss based on area exposed at holes 

through coating for ECR................................................................................................................84

Figure 79. Graph. Cracked beam test, average corrosion loss based on area exposed at holes 

through coating for conventional ECR and increased-adhesion ECR with bars containing 

four holes .......................................................................................................................................85

Figure 80. Graph. Cracked beam test, average corrosion loss based on area exposed at holes 

through coating for conventional ECR and increased-adhesion ECR with bars containing 

10 holes..........................................................................................................................................85

Figure 81. Graph. Cracked beam test, average corrosion loss based on area exposed at holes 

through coating for conventional ECR with and without corrosion inhibitors with bars 

containing four holes and concrete with w/c = 0.45 ......................................................................86

Figure 82. Graph. Cracked beam test, average corrosion loss based on area exposed at holes 

through coating for conventional ECR with and without corrosion inhibitors with bars 

containing 10 holes and concrete with w/c = 0.45.........................................................................87

Figure 83. Graph. Cracked beam test, average corrosion loss based on area exposed at holes 

through coating for conventional ECR with and without corrosion inhibitors with bars 

containing 10 holes and concrete with w/c = 0.35.........................................................................87

Figure 84. Graph. Cracked beam test, average corrosion loss based on area exposed at holes

through coating for conventional ECR and MC reinforcement with bars containing four holes.....88

Figure 85. Graph. Cracked beam test, average corrosion loss based on area exposed at holes

through coating for conventional ECR and MC reinforcement with bars containing 10 holes.....89

Figure 86. Graph. Cracked beam test, corrosion potential of top mat for conventional ECR 

and MC reinforcement with bars containing four holes ................................................................89

Figure 87. Graph. Cracked beam test, corrosion potential of bottom mat for conventional 

ECR and MC reinforcement with bars containing four holes........................................................90

Figure 88. Graph. Cracked beam test, corrosion potential of top mat for conventional ECR 

and MC reinforcement with bars containing 10 holes...................................................................90

Figure 89. Graph. Cracked beam test, corrosion potential of bottom mat for conventional 

ECR and MC reinforcement with bars containing 10 holes..........................................................91
ix

Figure 90. Graph. Cracked beam test, average corrosion losses based on the total area for 

conventional reinforcement in specimens containing corrosion inhibitors ...................................92

Figure 91. Graph. Cracked beam test, corrosion potential of top mat for conventional 

reinforcement in specimens containing corrosion inhibitors.........................................................92

Figure 92. Graph. Cracked beam test, mat-to-mat resistance for conventional reinforcement 

in specimens containing corrosion inhibitors ................................................................................93

Figure 93. Graph. Linear polarization test results for southern exposure specimens, average

corrosion loss based on total area for conventional reinforcement and conventional ECR ..........93

Figure 94. Graph. Linear polarization test results for southern exposure specimens, average

corrosion loss based on total area for conventional reinforcement and conventional ECR 

(different scale)..............................................................................................................................94

Figure 95. Graph. Southern exposure specimens, total versus macrocell corrosion loss based 

on total area for conventional reinforcement and area exposed at holes through coating for 

ECR with w/c = 0.45......................................................................................................................96

Figure 96. Graph. Southern exposure specimens, total versus macrocell corrosion loss based 

on total area for conventional reinforcement and area exposed at holes through coating for 

ECR with w/c = 0.45 (different scale) ...........................................................................................97

Figure 97. Graph. Cracked beam specimens, total versus macrocell corrosion loss based on 

total area for conventional reinforcement and area exposed at holes through coating for ECR 

with w/c = 0.45 or 0.35 ..................................................................................................................97

Figure 98. Graph. Southern exposure specimens, average total and macrocell corrosion rates 

based on losses after corrosion initiation based on total area for conventional reinforcement 

and area exposed at holes through coating for coated reinforcement, w/c = 0.45.......................100

Figure 99. Graph. Southern exposure specimens, average total and macrocell corrosion rates 

based on losses after corrosion initiation based on total area for conventional reinforcement 

and area exposed at holes through coating for coated reinforcement, w/c = 0.45 

(different scale)............................................................................................................................100

Figure 100. Graph. Cracked beam specimens, average total and macrocell corrosion rates 

based on losses after corrosion initiation based on total area for conventional reinforcement 

and area exposed at holes through coating for coated reinforcement, w/c = 0.45 or 0.35...........101

Figure 101. Photo. Conventional steel bars from southern exposure specimen after 96 weeks ....102

Figure 102. Photo. Conventional steel bars from cracked beam specimens after 96 weeks .......102

Figure 103. Photo. Conventional epoxy-coated bar from southern exposure specimen after 

96 weeks.......................................................................................................................................103

Figure 104. Photo. Conventional epoxy-coated bar from figure 103 after disbondment test......104

Figure 105. Photo. Conventional epoxy-coated top and bottom bars from southern exposure 

specimen containing calcium nitrite after 96 weeks....................................................................104

Figure 106. Photo. Conventional epoxy-coated top bar from southern exposure specimen 

containing HycreteTM after 96 weeks...........................................................................................104

Figure 107. Photo. DuPontTM high-adhesion epoxy-coated top and bottom bars from southern

exposure specimen after 96 weeks...............................................................................................104

Figure 108. Photo. MC top bar with holes through epoxy only from southern exposure 

specimen after 96 weeks..............................................................................................................105

Figure 109. Photo. MC top bar with holes penetrating both epoxy and zinc from southern 

exposure specimen after 96 weeks...............................................................................................105

Figure 110. Graph. Disbondment results for southern exposure specimens................................106
x

Figure 111. Graph. Disbondment results for cracked beam specimens.......................................106

Figure 112. Graph. Comparison of disbondment of top bars in southern exposure specimens 

cast in concrete with w/c = 0.35 and 0.45....................................................................................107

Figure 113. Graph. Comparison of disbondment of top bars in cracked beam specimens 

cast in concrete with w/c = 0.35 and 0.45....................................................................................107

Figure 114. Graph. Average chloride content at a depth of 25 mm (1 inch) versus w/c ratio 

at end of field tests.......................................................................................................................109

Figure 115. Graph. Average chloride content at a depth of 25 mm (1 inch) at end of field 

tests for uncracked field test specimens.......................................................................................110

Figure 116. Graph. Average chloride content at a depth of 25 mm (1 inch) at end of field 

tests for cracked field test specimens...........................................................................................110

Figure 117. Graph. Field test, average corrosion loss based on total area for conventional 

reinforcement and ECR................................................................................................................115

Figure 118. Graph. Field test, average corrosion loss based on exposed area for ECR ..............115

Figure 119. Graph. Field test, corrosion potential of top mat for conventional reinforcement 

and ECR.......................................................................................................................................116

Figure 120. Graph. Field test, corrosion potential of bottom mat for conventional 

reinforcement and ECR................................................................................................................116

Figure 121. Graph. Field test, average corrosion losses based on area exposed at holes through 

coating for conventional and increased-adhesion ECR without simulated cracks......................117

Figure 122. Graph. Field test, average corrosion losses based on area exposed at holes through

coating for conventional and increased-adhesion ECR with simulated cracks...........................118

Figure 123. Graph. Field test, corrosion potential of top mat for conventional and increasedadhesion ECR without simulated cracks......................................................................................118

Figure 124. Graph. Field test, corrosion potential of bottom mat for conventional and 

increased-adhesion ECR without simulated cracks.....................................................................119

Figure 125. Graph. Field test, corrosion potential of top mat for conventional and increasedadhesion ECR with simulated cracks...........................................................................................119

Figure 126. Graph. Field test, corrosion potential of bottom mat for conventional and 

increased-adhesion ECR with simulated cracks..........................................................................120

Figure 127. Graph. Field test, average corrosion losses based on area exposed at holes 

through coating for conventional ECR without and with corrosion inhibitors and without 

simulated cracks...........................................................................................................................121

Figure 128. Graph. Field test, average corrosion losses based on area exposed at holes 

through coating for conventional ECR without and with corrosion inhibitors and with 

simulated cracks...........................................................................................................................121

Figure 129. Graph. Field test, corrosion potential of top mat for conventional ECR without 

and with corrosion inhibitors and without simulated cracks .......................................................122

Figure 130. Graph. Field test, corrosion potential of bottom mat for conventional ECR 

without and with corrosion inhibitors and without simulated cracks..........................................122

Figure 131. Graph. Field test, corrosion potential of top mat for conventional ECR without 

and with corrosion inhibitors and with simulated cracks.............................................................123

Figure 132. Graph. Field test, corrosion potential of bottom mat for conventional ECR 

without and with corrosion inhibitors and with simulated cracks ...............................................123

Figure 133. Graph. Field test, average corrosion losses based on area exposed at holes 

through coating for conventional ECR and MC reinforcement without simulated cracks..........124
xi

Figure 134. Graph. Field test, average corrosion losses based on area exposed at holes 

through coating for conventional ECR and MC reinforcement with simulated cracks...............124

Figure 135. Graph. Field test, corrosion potential of top mat for conventional ECR without 

and with corrosion inhibitors and without simulated cracks .......................................................125

Figure 136. Graph. Field test, corrosion potential of bottom mat for conventional ECR 

without and with corrosion inhibitors and without simulated cracks..........................................125

Figure 137. Graph. Field test, corrosion potential of top mat for conventional ECR without 

and with corrosion inhibitors and with simulated cracks.............................................................126

Figure 138. Graph. Field test, corrosion potential of bottom mat for conventional ECR 

without and with corrosion inhibitors and with simulated cracks ...............................................126

Figure 139. Graph. Field test, mat-to-mat resistance for conventional reinforcement and ECR...129

Figure 140. Graph. Field test, mat-to-mat resistance for conventional and increased-adhesion 

ECR without simulated cracks.....................................................................................................129

Figure 141. Graph. Field test, mat-to-mat resistance for conventional and increased-adhesion

ECR with simulated cracks..........................................................................................................130

Figure 142. Graph. Field test, mat-to-mat resistance for conventional ECR without and with 

corrosion inhibitors and without simulated cracks ......................................................................130

Figure 143. Graph. Field test, mat-to-mat resistance for conventional ECR without and with 

corrosion inhibitors and with simulated cracks ...........................................................................131

Figure 144. Graph. Field test, mat-to-mat resistance for conventional ECR and MC 

reinforcement without simulated cracks......................................................................................131

Figure 145. Graph. Field test, mat-to-mat resistance for conventional ECR and MC 

reinforcement with simulated cracks...........................................................................................132

Figure 146. Photo. Field test specimen without simulated cracks containing conventional 

reinforcing steel at 250 weeks......................................................................................................133

Figure 147. Photo. Field test specimen without simulated cracks containing conventional 

reinforcing steel at 254 weeks......................................................................................................134

Figure 148. Photo. Field test specimen with simulated cracks containing conventional 

reinforcing steel at 250 weeks......................................................................................................134

Figure 149. Photo. Field test specimen with simulated cracks containing conventional 

reinforcing steel at 254 weeks......................................................................................................135

Figure 150. Photo. Top bars from field test specimen without simulated cracks containing 

conventional reinforcing steel at 254 weeks................................................................................136

Figure 151. Photo. Top bars from field test specimen with simulated cracks containing 

conventional reinforcing steel at 250 weeks................................................................................136

Figure 152. Photo. Field test specimen without simulated cracks containing conventional 

epoxy-coated steel at 254 weeks..................................................................................................136

Figure 153. Photo. Field test specimen with simulated cracks containing conventional 

epoxy-coated steel at 254 weeks..................................................................................................137

Figure 154. Photo. Field test specimen without simulated cracks containing conventional 

ECR and HycreteTM corrosion inhibitor at 250 weeks.................................................................137

Figure 155. Photo. Field test specimen with simulated cracks containing conventional ECR 

and HycreteTM corrosion inhibitor at 254 weeks .........................................................................138

Figure 156. Photo. Conventional epoxy-coated top bars from field test specimen containing 

Rheocrete® 222+ corrosion inhibitor without simulated cracks after 254 weeks.........................138
xii

Figure 157. Photo. High adhesion DuPontTM epoxy-coated top bars from field test specimen 

with simulated cracks after 250 weeks ........................................................................................139

Figure 158. Photo. MC top bars from field test specimen with simulated cracks after 

250 weeks.....................................................................................................................................139

Figure 159. Graph. Disbondment results for electrically connected bars in field test 

specimens without simulated cracks............................................................................................140

Figure 160. Graph. Disbondment results for electrically connected bars in field test 

specimens with simulated cracks.................................................................................................140

Figure 161. Graph. Comparison of disbondment values for electrically connected and 

electrically isolated bars in field test specimens without simulated cracks.................................141

Figure 162. Graph. Chloride content taken at cracks interpolated at a depth of 76.2 mm 

(3 inches) versus age for bridges with an AADT greater than 7,500 ..........................................155

Figure 163. Equation. Chloride content trendline........................................................................155

Figure 164. Equation. Average time to critical chloride threshold..............................................155

Figure 165. Graph. Comparison between average macrocell corrosion rates after corrosion 

initiation based on total area for bench-scale and field test specimens with conventional 

reinforcement in uncracked concrete ...........................................................................................158

Figure 166. Graph. Comparison between average macrocell corrosion rates after corrosion 

initiation based on total area for bench-scale and field test specimens with conventional 

reinforcement in cracked concrete ...............................................................................................158

Figure 167. Graph. Total versus macrocell corrosion rate after corrosion initiation for 

southern exposure specimens with conventional reinforcement .................................................161

Figure 168. Graph. Total versus macrocell corrosion rate after corrosion initiation for 

cracked beam specimens with conventional reinforcement.........................................................161

Figure 169. Graph. Total versus macrocell corrosion rate after corrosion initiation for 

southern exposure specimens with ECR......................................................................................162

Figure 170. Graph. Total versus macrocell corrosion rate after corrosion initiation for 

cracked beam specimens with ECR.............................................................................................162

Figure 171. Graph. Total versus macrocell corrosion rate after corrosion initiation for 

southern exposure specimens with MC reinforcement................................................................163

Figure 172. Graph. Total versus macrocell corrosion rate after corrosion initiation for 

cracked beam specimens with MC reinforcement.......................................................................163

Figure 173. Equation. Corrosion loss to crack concrete in SI units.............................................166

Figure 174. Equation. Corrosion loss to crack concrete in English units....................................166

Figure 175. Equation. Typical quantity of reinforcement............................................................169

Figure 176. Equation. Reinforcement cost for conventional steel...............................................169

Figure 177. Equation. Reinforcement cost for ECR, ECR(Dupont), and ECR(Valspar)............169

Figure 178. Equation. Reinforcement cost for ECR(Chromate) and ECR(primer/Ca(NO2)2)....169

Figure 179. Equation. Reinforcement cost for MC reinforcement ..............................................170

Figure 180. Equation. Costs for concrete placed with conventional reinforcement....................170

Figure 181. Equation. Costs for concrete placed with Rheocrete® inhibitor...............................170

Figure 182. Equation. Costs for concrete placed with calcium nitrite inhibitor..........................171

Figure 183. Equation. Costs for concrete placed with HycreteTM inhibitor.................................171

Figure 184. Equation. Total initial cost for decks with conventional steel..................................171

Figure 185. Equation. Total initial cost for decks with conventional steel and Rheocrete®

inhibitor........................................................................................................................................171
xiii

Figure 186. Equation. Total initial cost for decks with conventional steel and calcium 

nitrite inhibitor (DCI)...................................................................................................................171

Figure 187. Equation. Total initial cost for decks with conventional steel and HycreteTM 

inhibitor........................................................................................................................................171

Figure 188. Equation. Total initial cost for decks with ECR, ECR(Dupont), and 

ECR(Valspar)...............................................................................................................................172

Figure 189. Equation. Total initial cost for decks with ECR(Chromate) ....................................172

Figure 190. Equation. Total initial cost for decks with ECR and Rheocrete® inhibitor..............172

Figure 191. Equation. Total initial cost for decks with ECR and calcium nitrite inhibitor (DCI) ..172

Figure 192. Equation. Total initial cost for decks with ECR and HycreteTM inhibitor................172

Figure 193. Equation. Total initial cost for decks with ECR with primer...................................172

Figure 194. Equation. Total initial cost for decks with MC reinforcement.................................172

Figure 195. Equation. Total repair costs with silica fume overlay ..............................................174

Figure 196. Equation. Total repair costs with polymer overlay ..................................................174

Figure 197. Equation. Bridge rail modification cost....................................................................174

Figure 198. Equation. Approach guard rail cost..........................................................................174

Figure 199. Equation. Approach pavement work cost.................................................................175

Figure 200. Equation. Mobilization cost......................................................................................175

Figure 201. Equation. Traffic control and miscellaneous costs...................................................175

Figure 202. Equation. Total repair costs......................................................................................175

Figure 203. Equation. Present value ............................................................................................175

Figure 204. Graph. Rapid macrocell test, average corrosion rate based on total area of ECR 

and MC reinforcement .................................................................................................................182

Figure 205. Graph. Rapid macrocell test, average corrosion loss based on total area of ECR 

and MC reinforcement .................................................................................................................183

Figure 206. Graph. Rapid macrocell test, average anode potential of ECR and MC 

reinforcement ...............................................................................................................................183

Figure 207. Graph. Rapid macrocell test, average cathode potential of ECR and MC 

reinforcement ...............................................................................................................................184

Figure 208. Photo. Rapid macrocell test, M-ECR-1, 5 weeks, before disbondment test ............185

Figure 209. Photo. Rapid macrocell test, M-ECR-1, 5 weeks, after disbondment test ...............185

Figure 210. Photo. Rapid macrocell test, M-ECR-13, 40 weeks, before disbondment test ........185

Figure 211. Photo. Rapid macrocell test, M-ECR-21, 35 weeks, after disbondment test ...........185

Figure 212. Photo. Rapid macrocell test, M-MC-4, 10 weeks, before disbondment test............186

Figure 213. Photo. Rapid macrocell test, M-MC-4, 10 weeks, after disbondment test...............186

Figure 214. Photo. Rapid macrocell test, M-MC-5, 10 weeks (zinc depletion in regions 

surrounding damage sites) ...........................................................................................................186

Figure 215. Photo. Rapid macrocell test, M-MC-23, 40 weeks, before disbondment test..........186

Figure 216. Photo. Rapid macrocell test, M-MC-23, 40 weeks, after disbondment test.............187

Figure 217. Graph. Rapid macrocell test, disbonded area versus time for specimens with ECR ...190

Figure 218. Graph. Rapid macrocell test, disbonded area versus time for specimens with 

MC reinforcement........................................................................................................................190

Figure 219. Graph. Rapid macrocell test, disbonded area versus corrosion loss for specimens

with ECR......................................................................................................................................191

Figure 220. Graph. Rapid macrocell test, disbonded area versus corrosion loss for specimens

with MC reinforcement................................................................................................................191
xiv

Figure 221. Graph. Disbonded area versus time for ECR and MC reinforcement in simulated

pore solution without salt.............................................................................................................192

Figure 222. Illustration. Cracking specimen................................................................................195

Figure 223. Illustration. Damage patterns for ECR with two holes.............................................196

Figure 224. Illustration. Damage patterns for ECR with two half-rings .....................................196

Figure 225. Illustration. Two-dimensional finite element model of concrete to measure 

cracking behavior.........................................................................................................................197

Figure 226. Graph. Load-deflection behavior for nonlinear spring model, spring density of 

6,200 springs/m2 (4 springs/in2)...................................................................................................198

Figure 227. Equation. Corrosion loss conversion........................................................................198

Figure 228. Illustration. Two-dimensional finite element analysis model ..................................199

Figure 229. Illustration. Three-dimensional finite element analysis model (end view)..............199

Figure 230. Graph. Effect of mesh seed size on corrosion loss required to produce a 50-μm

(2-mil) crack.................................................................................................................................200

Figure 231. Illustration. Cross section of bar damage patterns for three-dimensional finite 

element models: full ring, half ring, and quarter ring..................................................................201

Figure 232. Graph. Average corrosion loss required to crack concrete for specimens with 

conventional and galvanized reinforcement ................................................................................202

Figure 233. Photo. Top side of bar in specimen Conv.-3, 51-mm (2-inch) cover, after autopsy...202

Figure 234. Photo. Bottom side of bar in specimen Conv.-3, 51-mm (2-inch) cover,

after autopsy.................................................................................................................................202

Figure 235. Photo. Side view of specimen Conv.-2, 25-mm (1-inch) cover, after autopsy 

(plane of crack visible above reinforcement)...............................................................................203

Figure 236. Photo. Top view of specimen Conv.-2, 25-mm (1-inch) cover, after autopsy.........203

Figure 237. Photo. Top side of bar in specimen Zn-2, 25-mm (1-inch) cover, after autopsy .....204

Figure 238. Photo. Bottom side of bar in specimen Zn-2, 25-mm (1-inch) cover, after autopsy ..204

Figure 239. Photo. Side view of specimen Zn-4, 25-mm (1-inch) cover, after autopsy..............204

Figure 240. Photo. Top view of specimen Zn-4, 25-mm (1-inch) cover, after autopsy ..............205

Figure 241. Photo. Staining on surface at crack initiation in galvanized reinforcement 

specimen, 25-mm (1-inch) cover.................................................................................................205

Figure 242. Photo. Top side of galvanized reinforcement, 25-mm (1-inch) cover, after 

autopsy at crack initiation ............................................................................................................206

Figure 243. Photo. Detail of top side of galvanized reinforcement, 25-mm (1-inch) cover, 

after autopsy at crack initiation....................................................................................................206

Figure 244. Photo. Bottom side of galvanized reinforcement, 25-mm (1-inch) cover, after 

autopsy at crack initiation ............................................................................................................206

Figure 245. Photo. Test bar from specimen ECR-2h-V-2 ...........................................................207

Figure 246. Photo. Crack initiation in specimen ECR-2r-H-2.....................................................208

Figure 247. Photo. Crack propagation in specimen ECR-2h-V-1 ...............................................208

Figure 248. Photo. Concrete surrounding test bar from specimen ECR-2h-V-1.........................209

Figure 249. Photo. Concrete surrounding test bar from specimen ECR-2r-H-2 .........................209

Figure 250. Graph. Corrosion loss to crack concrete versus cover for two-dimensional finite 

element model..............................................................................................................................210

Figure 251. Graph. Corrosion loss to crack concrete versus cover showing effect of bar 

diameter for two-dimensional finite element model....................................................................211

Figure 252. Equation. Suggested best-fit in SI units ...................................................................211
xv

Figure 253. Equation. Suggested best-fit in English units...........................................................211

Figure 254. Graph. Corrosion loss to crack concrete versus cover in two-dimensional finite 

element model with experimental data ........................................................................................213

Figure 255. Graph. Corrosion loss to crack concrete for uniform general corrosion based on 

experimental and finite element results versus predicted corrosion losses using figure 252 ......213

Figure 256. Equation. Alternate best-fit in SI units.....................................................................214

Figure 257. Equation. Alternate best-fit in English units............................................................214

Figure 258. Graph. Corrosion loss to crack concrete for uniform general corrosion based on 

experimental and finite element results versus predicting corrosion losses using figure 256 .....214

Figure 259. Graph. Corrosion loss to crack concrete for uniform general corrosion versus 

cover for two-and three-dimensional finite element model.........................................................217

Figure 260. Graph. Corrosion loss to crack concrete versus fraction of exposed area with 

best-fit line for 13-mm (0.5-inch)-diameter bar and 51-mm (2-inch) cover................................218

Figure 261. Graph. Corrosion loss to crack concrete xcrit versus cover C for 1,013-mm

2

(1.57-in2) corroding area..............................................................................................................219

Figure 262. Graph. Corrosion loss to crack concrete xcrit versus Lf with best fit line for

1,013-mm2 (1.57-in2

) corroding area ...........................................................................................219

Figure 263. Equation. Potential relationship between corrosion loss and variables in 

English units.................................................................................................................................220

Figure 264. Equation. Potential relationship between corrosion loss and variables in

SI units.........................................................................................................................................220

Figure 265. Graph. Corrosion loss to crack concrete for localized corrosion based on the finite 

element model results versus corrosion losses calculated by the equations in figure 263 and 

figure 264.....................................................................................................................................221

Figure 266. Graph. Corrosion loss in localized corrosion specimens versus corrosion loss 

predicted by the equation in figure 263 and figure 264 for three-dimensional finite element 

model and experimental data .......................................................................................................224

Figure 267. Graph. Corrosion loss in localized corrosion specimens versus corrosion loss 

predicted by the equation in figure 263 and figure 264 for three-dimensional finite element 

model and experimental data (revised scale)...............................................................................224

Figure 268. Equation. Torres-Acosta and Sagues’ corrosion loss to crack initiation..................225

Figure 269. Graph. Corrosion loss in localized corrosion specimens versus corrosion loss 

predicted by the equation in figure 268 with three-dimensional finite element model and 

experimental data .........................................................................................................................226

Figure 270. Graph. Corrosion loss in localized corrosion specimens versus corrosion loss 

predicted by the equation in figure 268 with three-dimensional finite element model and 

experimental data (revised scale).................................................................................................226

Figure 271. Graph. Ratio of experimentally derived corrosion loss to predicted corrosion loss 

versus corrosion loss to crack concrete based on experimental data ...........................................228

Figure 272. Graph. Ratio of finite element model-derived corrosion loss to predicted corrosion 

loss versus corrosion loss to crack concrete based on finite element model ...............................228
xvi

LIST OF TABLES

Table 1. Systems studied..................................................................................................................3

Table 2. Chemical analysis of steel by percent................................................................................4

Table 3. Coating thickness...............................................................................................................6

Table 4. Cathodic disbondment results............................................................................................8

Table 5. Concrete mixtures............................................................................................................18

Table 6. Kansas Department of Transportation (KDOT) salt usage history..................................23

Table 7. Properties of concrete batches for field tests...................................................................28

Table 8. Number of test specimens in test program.......................................................................32

Table 9. Corrosion loss at 15 weeks (μm) for rapid macrocell specimens based on total area..........36

Table 10. Corrosion loss at 15 weeks (μm) for rapid macrocell specimens based on area 

exposed at holes through coating...................................................................................................37

Table 11. Corrosion loss at 96 weeks (μm) for southern exposure specimens based on 

total area.........................................................................................................................................50

Table 12. Corrosion loss at 96 weeks (μm) for southern exposure specimens based on area 

exposed at holes through coating...................................................................................................51

Table 13. Chloride content at corrosion initiation (kg/m3) for southern exposure specimens...........52

Table 14. Chloride content at 96 weeks (kg/m3) for southern exposure specimens......................53

Table 15. Average corrosion rate (μm /year) based on losses after corrosion initiation for 

southern exposure specimens.........................................................................................................55

Table 16. Concrete properties for southern exposure and cracked beam specimens with 

uncoated bars and corrosion inhibitor in the concrete ...................................................................72

Table 17. Corrosion initiation results for bare bars in concrete without and with corrosion 

inhibitors (values at time of initiation)...........................................................................................76

Table 18. Corrosion loss at 96 weeks (μm) for cracked beam specimens based on total area.............78

Table 19. Corrosion loss at 96 weeks (μm) for cracked beam specimens based on area 

exposed at holes through coating...................................................................................................79

Table 20. Average corrosion rate (μm /year) based on losses after corrosion initiation for 

cracked beam specimens................................................................................................................80

Table 21. Total and macrocell corrosion loss at 96 weeks (μm) for southern exposure and 

cracked beam specimens expressed in terms of total bar area and area exposed at holes.............95

Table 22. Average total and macrocell corrosion rates (μm /year) based on losses after 

corrosion initiation for southern exposure and cracked beam specimens expressed in terms 

of total bar area and area exposed at holes ....................................................................................99

Table 23. Average chloride content (kg/m3) at a depth of 25 mm (1 inch) at end of field tests.....108

Table 24. Corrosion loss at end of field tests (μm) based on total area for specimens without 

simulated cracks...........................................................................................................................111

Table 25. Corrosion loss at end of field tests (μm) based on area exposed at holes through 

coating for specimens without simulated cracks .........................................................................112

Table 26. Corrosion loss at end of field tests (μm) based on total area for specimens with 

simulated cracks...........................................................................................................................113

Table 27. Corrosion loss at end of field tests (μm) based on area exposed at holes through 

coating for specimens with simulated cracks...............................................................................114

Table 28. Average corrosion rate (μm/year) based on losses after corrosion initiation for 

field test specimens without simulated cracks.............................................................................127
xvii

Table 29. Average corrosion rate (μm/year) based on losses after corrosion initiation for 

field test specimens with simulated cracks..................................................................................128

Table 30. Estimated time to cracking for instrumented bars on field test specimens 

containing conventional steel.......................................................................................................135

Table 31. Chloride content at corrosion initiation (kg/m3), taken as the CCCT..........................144

Table 32. Student’s t-test results ( values) for CCCT for bars without coatings cast in 

concrete with w/c = 0.45..............................................................................................................147

Table 33. Student’s t-test results ( values) for CCCT for bars with coatings cast in concrete 

with w/c = 0.45 ............................................................................................................................147

Table 34. Equivalent corrosion rates for conventional reinforcement with inhibitors (μm/year)......148

Table 35. Student’s t-test results ( values) for average corrosion rates based on corrosion

losses after corrosion initiation based on total area for bars without coatings from southern 

exposure tests...........................................................................................................................................149

Table 36. Student’s t-test results ( values) for average corrosion rates based on corrosion 

losses after corrosion initiation based on total area for bars without coatings from cracked 

beam tests.....................................................................................................................................149

Table 37. Student’s t-test results ( values) for average corrosion rates based on corrosion 

losses after corrosion initiation based on exposed area for bars with coatings from southern 

exposure tests...........................................................................................................................................150

Table 38. Student’s t-test results ( values) for average corrosion rates based on corrosion 

losses after corrosion initiation based on exposed area for bars with coatings from cracked 

beam tests.....................................................................................................................................150

Table 39. Student’s t-test results ( values) for average corrosion rates based on corrosion 

losses after corrosion initiation based on exposed area for bars with coatings from field test 

specimens with uncracked concrete.............................................................................................152

Table 40. Student’s t-test results ( values) for average corrosion rates based on corrosion 

losses after corrosion initiation based on exposed area for bars with coatings from field test 

specimens with cracked concrete.................................................................................................152

Table 41. Estimated time to corrosion initiation for corrosion-protection systems in a bridge 

deck with 76.2-mm (3-inch) cover on top reinforcing steel ........................................................156

Table 42. Equivalent field test specimen macrocell corrosion rates (μm/year) for bare bar 

corrosion-protection systems.......................................................................................................159

Table 43. Equivalent field test specimen macrocell corrosion rates (μm/year) for bare bar 

corrosion-protection systems based on effective area .................................................................160

Table 44. Estimated total corrosion rates in bridge decks (μm/year) for corrosion-protection 

systems.........................................................................................................................................165

Table 45. Estimated times to formation of initial delamination cracks after corrosion initiation

(propagation times) (years)..........................................................................................................167

Table 46. Time to first repair based on corrosion rate in cracked concrete (years).....................168

Table 47. Total in-place cost for reinforcement per unit area of bridge deck .............................170

Table 48. Total in-place cost for concrete per unit area of bridge deck ......................................171

Table 49. Total in-place cost for corrosion protection systems...................................................173

Table 50. Repair costs for bridge decks in South Dakota............................................................174

Table 51. Total costs ($/m2) over 75-year design life for corrosion-protection systems using 

time to first repair based on corrosion rates in cracked concrete.................................................176
xviii

Table 52. Total costs ($/yd2

) over 75-year design life for corrosion protection systems using 

time to first repair based on corrosion rates in cracked concrete.................................................176

Table 53. Rapid macrocell test program......................................................................................181

Table 54. Total and macrocell corrosion loss for selected rapid macrocell specimens...............184

Table 55. Disbonded area and corrosion loss for rapid macrocell specimens with ECR............188

Table 56. Disbonded area and corrosion loss for rapid macrocell specimens with MC 

reinforcement ...............................................................................................................................189

Table 57. Mix proportions for cracking specimens.....................................................................194

Table 58. Corrosion loss to cause cracking, number of specimens in test program....................196

Table 59. Effect of two-dimensional element type on corrosion loss..........................................200

Table 60. Effect of three-dimensional element type on corrosion loss........................................200

Table 61. Estimated uncorroded surface area of galvanized reinforcement................................204

Table 62. Average corrosion loss to crack concrete cover for specimens with ECR..................207

Table 63. Finite element results for two-dimensional model ......................................................210

Table 64. Corrosion loss to crack concrete (corrosion along entire bar length)..........................212

Table 65. Finite element results for three-dimensional model, 51-mm (2-inch) cover...............215

Table 66. Finite element results for three-dimensional model, 76-`mm (3-inch) cover..............216

Table 67. Constants m and b for best-fit curve xcrit = m(Af)b to corrosion loss versus Af plots ....218

Table 68. Results from other research: corrosion loss to crack concrete (localized corrosion)....222
1

CHAPTER 1. INTRODUCTION

There are nearly 600,000 bridges in the United States, and more than 6 percent are structurally 

deficient due to corrosion-related damage.(1,2) The estimated direct annual cost of corrosion is

$8.3 billion, and the estimated indirect cost to users due to traffic delays and lost productivity is 

equal to about 10 times this amount.

(2) Bridge decks represent a special problem because cracks 

directly over and parallel to reinforcing steel provide an avenue for deicing salts to rapidly reach 

the reinforcement. Chloride analysis from bridge decks indicates that the chloride content in 

concrete around cracks can exceed the critical chloride corrosion threshold of conventional steel 

reinforcement within the first year.(3) Thus, the reinforcing steel in these structures must be 

protected against corrosion at the time of construction.

For more than 35 years, the corrosion-protection system used in most reinforced concrete structures

has been epoxy-coated reinforcement (ECR) combined with increased concrete cover. This system 

has provided significant improvement over uncoated bars in the corrosion performance of reinforcing 

steel.(4,5)It has, however, not been without its critics.(6–8)Problems include the poor performance of 

ECR when the concrete remains saturated, such as in bridge piers in salt water, and the observation

that the epoxy tends to lose its adhesion to the steel over time. (See references 4, 6, 7, and 9–11.) 

This reduction in adhesion, or disbondment, while the epoxy coating is still intact on the 

reinforcement is accelerated when the concrete remains wet.

Despite observations that portions of ECR have rusted, the corrosion of epoxy-coated steel has 

not resulted in the need for repairs when used in structures such as bridge decks, which allow 

the concrete to occasionally dry, except in the case of a few well-documented nonstandard 

applications.(4,5,8) Because ECR is a good, but not perfect, corrosion-protection system, there is 

strong impetus to develop methods to improve its performance.

The objective of this research was to evaluate a number of techniques for making ECR more 

corrosion-resistant by using multiple corrosion-protection strategies for ECR in bridge decks as 

well as in bridge members in marine environments where salt, moisture, and high temperatures 

(tropical weather) are prevalent.

This report describes the results for systems including chemical pretreatments and epoxy 

formulations that increase the adhesion of the epoxy coating to the reinforcing steel, conventional

uncoated steel and conventional ECR with inorganic and organic corrosion inhibitors added to 

the concrete, reinforcement with a primer containing a microencapsulated corrosion inhibitor 

under a conventional epoxy coating, and bars coated with 98 percent zinc and 2 percent 

aluminum prior to epoxy application. 

3

CHAPTER 2. EXPERIMENTAL WORK

CORROSION-PROTECTION SYSTEMS

This study involved the evaluation of 11 systems in which ECR was combined with another 

corrosion-protection system. The research included seven bar types: one uncoated and six with a 

fusion-bonded epoxy coating fabricated from the same heat of steel. Uncoated conventional 

reinforcing steel and conventional ECR served as the controls. The multiple corrosion-protection 

systems included conventional ECR in conjunction with one of three corrosion inhibitors; bars 

that were treated with a primer coating containing microencapsulated calcium nitrite (a corrosion 

inhibitor) prior to coating with conventional epoxy; bars with improved adhesion between the epoxy

and the reinforcing steel, obtained through the use of either a zinc chromate pretreatment or special 

epoxies with higher adhesion; the combination of bars with an improved adhesion epoxy and the 

addition of calcium nitrite to the mortar or concrete; and bars with multiple coatings consisting of a

50-μm (2-mil) layer of 98 percent zinc and 2 percent aluminum that was, in turn, coated with a 

conventional epoxy. In addition, a second heat of conventional reinforcement was used to evaluate

the corrosion performance of uncoated steel cast in concrete containing one of the three corrosion

inhibitors used in the study. The systems are listed in table 1 along with the shorthand notation

used in this report.

Table 1. Systems studied.

System Abbreviation

Control

Conventional uncoated reinforcing bars Conv. and Conv.2

Conventional ECR ECR

Epoxies with increased adhesion

Chromate pretreatment ECR(Chromate)

DuPontTM coating ECR(DuPont)

Valspar® coating ECR(Valspar)

Corrosion inhibitors in mortar or concrete

Uncoated bars with Ca(NO2)2 Conv.2(DCI)

Uncoated bars with Hycrete Conv.2(HY)

Uncoated bars with Rheocrete® 222+ Conv.2(RH)

ECR with calcium nitrite ECR(DCI)

ECR with HycreteTM ECR(HY)

ECR with Rheocrete® 222+ ECR(RH)

3MTM primer containing calcium nitrite ECR(primer/Ca(NO2)2)

Epoxies with increased adhesion plus calcium nitrite in mortar or concrete

Chromate pretreatment ECR(Chromate)-DCI

DuPontTM coating ECR(DuPont)-DCI

Valspar® coating ECR(Valspar)-DCI

Bars with multiple coatings MC
4

Control Systems

Uncoated Conventional Steel (Conv.)

With the exception of the tests to evaluate uncoated bars in concrete containing corrosion 

inhibitors, all tests of both uncoated and coated bars involved the use of a single heat of

No. 16 (No. 5) Grade 420 (60) ASTM A615 reinforcing steel, identified as “Conv.”

(12)

The uncoated reinforcement used in the corrosion inhibitor tests is identified as “Conv.2.” 

Chemical analysis is shown in table 2.

Table 2. Chemical analysis of steel by percent.

Steel

Bar Size

No.

Heat

Number C Mn Si P S Cr Ni Mo Cu B

Conv. 16 (5) 231159 0.43 0.95 0.21 0.014 0.046 0.20 0.17 0.038 0.49 0.0005

Conv.2 16 (5) N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A

C = Carbon; Mn = Manganese; Si = Silicon; P = Phosphorus; S = Sulfur; Cr = Chromium; Mo = Molybdenum; 

Cu = Copper; N = Nitrogen; B = Boron. 

N/A indicates chemical analysis not available.

Conventional ECR

The conventional reinforcement coated with fusion-bonded thermoset epoxy used as the control 

was coated with ScotchkoteTM 413, manufactured by 3MTM.

Epoxies with Increased Adhesion

A number of techniques have been used to improve the adhesion of epoxy coatings to steel. 

Three systems were evaluated in this study. The first involved pretreatment of uncoated steel 

with zinc chromate prior to the application of the epoxy coating. This procedure is used in 

Canada for all ECR, but because it involves the use of hexavalent chromate, which presents a 

significant environmental problem, it is not widely used in the United States. As an alternative, 

DuPontTM and Valspar® have developed epoxy powders with improved adhesion to reinforcing 

steel that do not require pretreating the bars. The three systems are identified as ECR(Chromate), 

ECR(DuPont), and ECR(Valspar).

Corrosion Inhibitors 

Three corrosion inhibitors, one inorganic and two organic, were studied. Calcium nitrite is the 

most widely used inorganic corrosion inhibitor in U.S. practice. Because calcium nitrite acts as a 

set-accelerator, DCI® S, an admixture produced by Grace Construction Products that contains a 

retarder, was used in this study. The organic corrosion inhibitors were Rheocrete® 222+, a waterbased combination of amines and esters produced by BASF Admixtures, and HycreteTM, a salt of 

alkenyl-substituted succinic acid produced by Broadview Technologies for this study and now 

produced by Hycrete, Inc. A fourth system, in which the epoxy coating ScotchkoteTM 413 was 

applied to the bars after the application of a primer coating that contains microencapsulated calcium 

nitrite, was also evaluated. According to 3MTM, the system provides protection by releasing calcium

nitrite as the epoxy coating is damaged. The systems are identified, respectively, as ECR(DCI), 
5

ECR(HY), ECR(RH), and ECR(primer/Ca(NO2)2). The three corrosion inhibitors (DCI® S, 

HycreteTM, and Rheocrete®) were also studied in conjunction with conventional uncoated 

reinforcement and are identified as Conv.2(DCI), Conv.2(HY), and Conv.2(RH), respectively. 

Epoxies With Increased Adhesion Plus Calcium Nitrite

The three types of ECR with improved adhesion were also evaluated in mortar and concrete 

containing the corrosion inhibitor calcium nitrite. The systems are identified as ECR(Chromate)-

DCI, ECR(DuPont)-DCI, and ECR(Valspar)-DCI.

Multiple Coatings

Western Coating developed a patented process for multiple-coated (MC) bars that involves the 

application of a layer of 98 percent zinc and 2 percent aluminum to reinforcing steel using a 

thermal spray coating process prior to the application of the epoxy coating. The zinc layer has a 

nominal thickness of 50 μm (2 mil). Following application of the zinc, the bars in this study were 

coated with DuPontTM 8-2739 Flex West Blue, a conventional epoxy.

One applicator applied the epoxy to the conventional ECR and ECR(Valspar) bars. A second 

applicator handled the MC and ECR(DuPont) bars while two other applicators individually 

handled the ECR(Chromate) and ECR(primer/Ca(NO2)2) bars.

PRETEST EVALUATION OF EPOXY-COATED BARS

Prior to corrosion testing, the bars used in this study were evaluated for coating thickness and 

number of holidays. The bars were also evaluated for coating adhesion using the cathodic 

disbondment test in accordance with ASTM A775-04a and ASTM G8-96 (referred to hereafter 

as ASTM A775 and ASTM G8, respectively).

(13,14)

Evaluation of Coating Thickness and Holidays

The six types of ECR bars used in this study were evaluated for coating thickness and number of 

holidays. The results are summarized in table 3. All bars met the coating thickness requirements 

of ASTM A775 except the bars with the calcium nitrite primer coating, which tended to have larger 

percentages of coating measurements below 175 and 125 μm (6.89 and 4.92 mil) than the maximum

allowable values of 10 and 5 percent, respectively. 1 (13) Only the bars with the calcium nitrite primer

coating exhibited holidays, although the number of holidays was below the maximum allowable 

of 3 holidays/m (1 holiday/ft) specified in ASTM A775. The other five bar types exhibited no 

measurable holidays on full-size bars. Additional tests of small bar samples, however, indicated 

the presence of a small number of holidays on all bar types.

 1 The requirements for coating thickness measurements have changed since the initiation of this study, but with the exception of the bars with 

the calcium nitrite primer coating, it is expected that the bars in this study would meet the current coating thickness criteria (ASTM A775-07b).(15)
6

Table 3. Coating thickness.

Type of Bar

Number of 

Measurementsa

Maximum

(mm)

Minimum

(mm)

Average

(mm)

Coefficient of

Variation

ECR 4 bars, 144 locations 307 175 244 0.10

ECR(Chromate) 1 bar, 36 locations 241 175 213 0.07

ECR(DuPont) 1 bar, 36 locations 249 160 213 0.08

ECR(Valspar) 1 bar, 36 locations 262 175 226 0.11

ECR(primer/ 

Ca(NO2)2) 4 bars, 126 locations 264 102 188 0.16

MC 1 bar, 36 locations 251 213 236 0.04

1 μm = 0.0394 mil a Bars were 6.1 m (20 ft) long; 15 to 18 measurements were evenly spaced along each side of the test bar.

Cathodic Disbondment Tests

Cathodic disbondment tests involve the penetration of the epoxy coating on a test specimen using 

a 3-mm (0.12-inch)-diameter drill bit. The specimen is then immersed for 168 h in an electrolyte 

(3 percent sodium chloride) solution at 24 ±2 °C (75 ±3.6 °F) and maintained at a -1.5 V potential

difference with an anode, measured with respect to a saturated calomel electrode (SCE). The test 

setup, as described in ASTM A775, is shown in figure 1.

(13)

Figure 1. Illustration. Cathodic disbondment test setup (after reference 13).
7

An examination is performed immediately upon termination of the test. At the end of the test 

period, the test area is rinsed with warm tap water. The sample is immediately wiped dry, and the 

entire area of coating is visually examined at the edge of the intentional defect. A new defect, to 

serve as a reference, is drilled in a portion of the coated area that was not immersed. Two radial 

cuts at 90 degrees to each other and oriented 45 degrees with respect to the longitudinal axis of 

the bar are made through the coating, intersecting the center of both intentional defects, using a 

sharp, thin-bladed knife. An attempt is then made to lift the coating at both the reference defect 

and the submerged defect with the point of the knife. The bond at the reference defect is then 

used to judge the quality of the bond at the submerged holiday. Finally, the increase in radial 

area and total area of the disbonded coating at the submerged defect are measured and recorded. 

In this study, three rounds of cathodic disbondment tests were performed, with one specimen 

per round for each of the six types of ECR. Tests were also performed on conventional epoxycoated bars that had been used in a previous study. In accordance with ASTM A775, four radial 

measurements were taken of the disbonded region at 0, 90, 180, and 270 degrees with respect to 

the longitudinal axis of the bar, and the values were averaged.

(13) The cathodic disbondment tests 

were recorded in terms of both the area of the disbonded coating (in accordance with ASTM G8) 

and the average coating disbondment radius (four measurements).(14) The results are summarized 

in table 4. The area of the disbonded coating and the radius do not include the original penetration 

through the coating. As shown in table 4, the average coating disbondment radius was above 4 mm

(0.16 inches), the maximum allowed in annex A1 of ASTM A775, for the conventional ECR and 

ECR(Valspar) bars, indicating that these bars failed the coating disbondment requirements. The 

MC reinforcement, ECR(DuPont), ECR(Chromate), and ECR(primer/Na(NO2)2) bars met the 

coating disbondment requirements. Table 4 also shows that the conventional ECR exhibited the 

highest area of disbonded coating, with an average value of 178 mm2 (0.271 in2). The highadhesion Valspar® bars had an area of disbonded coating of 151 mm2 (0.230 in2

), followed by 

ECR with calcium nitrite primer at 67 mm2 (0.102 in2) and the high-adhesion DuPontTM bars at 

65 mm2 (0.099 in2

). The MC and ECR(Chromate) bars had the lowest areas of disbonded 

coating, with average values of 27 and 20 mm2 (0.041 and 0.030 in2), respectively. Like the 

conventional ECR used in this study, the conventional ECR from the previous study also exhibited 

an average disbondment radius, 5.5 mm (0.21 inches), that exceeded the 4 mm (0.16 inches)

allowed by ASTM A775; the disbonded area equaled 168 mm2 (0.256 in2).
8

Table 4. Cathodic disbondment results.

Type of Bar

Test 

No.

Thickness

(mm)

Coating Disbondment Radiusa

(mm)

Area of 

Disbonded 

Coatingb

(mm2 0 ) o 90o 180o 270o Average

ECR

1 NM 6.5 6.5 6 5.5 6.1 183

2 NM 6.5 5 3.5 4 4.8 133

3 249 6.5 6.5 7.5 6.5 6.8 219

Average 5.9 178

ECRc

1 300 5.5 6.5 5.5 5 5.6 170

2 274 5.5 4.5 4.5 5.5 5.0 161

3 241 6.5 5.5 5.5 5.5 5.8 174

Average 5.5 168

ECR(Chromate)

1 NM 0.5 1 0 0 0.4 6

2 NM 1 0.5 2 2.5 1.5 35

3 279 1.5 0.5 0.5 1.5 1.0 19

Average 1.0 20

ECR(DuPont)

1 NM 4 3 3.5 3.5 3.5 93

2 NM 1.5 1 1.5 1 1.3 19

3 224 3.5 4 3.5 4 3.8 83

Average 2.8 65

ECR(Valspar)

1 NM 4.5 4 4.5 4 4.3 133

2 NM 6 4.5 5.5 4.5 5.1 167

3 269 6.5 4.5 5.5 4.5 5.3 154

Average 4.9 151

ECR

(primer/Ca(NO2)2)

1 NM 1.5 2 2 2 1.9 58

2 NM 3.5 2.5 4.5 2.5 3.3 77

3 203 3 2.5 2.5 2.5 2.6 67

Average 2.6 67

MC

1 NM 2.5 1.5 1 1 1.5 22

2 NM 2 1.5 1.5 3 2.0 35

3 284 0.5 2.5 1.5 1.5 1.5 25

Average 1.7 27

1 μm = 0.0394 mil

1 mm = 0.039 inches

1 mm2 = 0.00155 in2

NM = Not measured

a Coating disbondment radius measured from edge of 3-mm (0.12-inch)-diameter hole. b Area of disbonded coating is the total area after disbondment minus the original area of a 3-mm (0.12-inch)-

diameter hole.

c Conventional ECR from previous study.

The criteria in annex A1 of ASTM A775 are qualification requirements for the epoxy coating 

itself and are not meant to be applied to production bars such as those used in this study. Thus,
9

although all bars did not all meet the qualification criteria, they are considered to be representative

of bars used in practice. Further, as observed in earlier tests by McDonald et al., the performance 

of the bars in the cathodic disbondment tests did not prove to be a predictor of their performance 

in the corrosion tests in this study.

(16)

CORROSION TEST PROCEDURES

The corrosion-protection systems in this study were evaluated using a combination of laboratory 

and field tests. The performance of each system was compared to that of conventional ECR and 

uncoated mild steel reinforcement. The tests included rapid macrocell tests, bench-scale tests, 

linear polarization resistance, and field tests. 

Rapid Macrocell Tests

Summary of Method

The response of the multiple corrosion-protection systems was first evaluated using the rapid 

macrocell test, originally developed at the University of Kansas under the Strategic Highway 

Research Program and since updated. (See references 17 through 26). The goal of the test is to 

obtain a realistic measure of the performance of corrosion-protection systems in a short time 

period. The basic test specimen consists of either a bare reinforcing bar or a bar clad in mortar 

(mortar-wrapped), as illustrated in figure 2 through figure 4. The procedures used for bare bars 

are incorporated in annex A2 of ASTM A955.(27) The contact surface between the mortar and the 

bar simulates the contact obtained between concrete and reinforcing bars in structures through 

the use of realistic water-cement and sand-cement ratios. 

Specimen

Simulated Pore

Solution with NaCl

Simulated Pore

 Solution

Styrofoam Support

Scrubbed Air

Anode Cathode

Terminal Box

Salt Bridge

Voltmeter

10 Ohm

V

Figure 2. Illustration. Macrocell test with bare bar specimens.
10 

Anode Cathode

Salt Bridge

Voltmeter

10 Ohm Resistor

V Terminal Box

Scrubbed Air

Simulated Pore Solution

with NaCl

Simulated Pore Solution

Mortar Fill

Mortar Fill

Lid Lid

Figure 3. Illustration. Macrocell test with mortar-clad specimens. 

154 mm

(6 in.)

127 mm

(5 in.)

30 mm

(1.2 in.)

No. 16 Copper Wire

Electrical Connection 10-24 Screw

No. 16 [No.5] Ba r

Mortar Cover 

Figure 4. Illustration. Mortar-wrapped specimen containing conventional reinforcing bar. 

The macrocell tests shown in figure 2 and figure 3 require two containers. The test specimen, 

either a bare or mortar-wrapped No. 16 (No. 5) bar, is placed in a 1.5-L (1.6-qt) container 

along with simulated pore solution containing a preselected concentration of sodium chloride 

(1.6 or 6.04 moles/kg (0.73 or 2.74 moles/lb) of solvent-ion (4.68 or 15 percent) concentration). 

Two specimens are placed in a second container and immersed in simulated pore solution with 

no chlorides added. For mortar-wrapped specimens, crushed mortar fill is added to the containers 

to more closely simulate the concrete environment. The solution depth exposes 76 mm (3.0 inches) 

of the bar (including the 13-mm (0.5-inch) plastic cap used to protect the end of epoxy-coated 
11

bars) below the level of the solution. The two containers are connected by a salt bridge, and the 

test specimen in the pore solution containing sodium chloride (anode) is electrically connected 

across a single 10-ohm resistor to the two specimens in the simulated pore solution (cathode). The

resistors are mounted between binding posts in a terminal box to consolidate the specimen wires. 

Air (scrubbed to remove carbon dioxide) is bubbled into the liquid surrounding the cathode to ensure

an adequate supply of oxygen. Plastic lids are placed just above the surface of the solution to hold the

specimens in place and reduce evaporation of the solution. Holes are cut in the lids to introduce the

specimens, a salt bridge, and the air supply. The air causes some evaporation, which is countered 

by adding deionized water to the container to maintain a constant volume of solution. The solutions

in both containers are changed once every 5 weeks to further protect against carbonation.2 The 

corrosion current and the rate of corrosion are determined by measuring the voltage drop across 

the resistor. The open circuit corrosion potentials of the cathode and anode are also measured 

with respect to an SCE after the circuit has been open for 2 h to allow the potentials to stabilize. 

The simulated pore solution, consisting of sodium hydroxide and potassium hydroxide, matches 

that obtained in a pore solution analysis.(28,29) Epoxy-coated steel is evaluated using specimens in 

which the coating is breached by four 3.2-mm (0.13-inch)-diameter holes to simulate defects in 

the epoxy coating (damaged area equals 1.0 percent of total exposed area in the solution). In the 

rapid macrocell test, bare conventional bars exhibit corrosion initiation within the first 24 h, and 

conventional bars cast in mortar exhibit corrosion within the first week. The tests last 15 weeks.

Corrosion Rate and Corrosion Loss

The corrosion rate of reinforcing steel (measured in the bench-scale and field tests as well as in 

the rapid microcell tests) indicates how fast reinforcing steel is oxidized. It may be expressed as 

a current density in microamps per square centimeter (μA/cm2), which is obtained by measuring 

the rate of electron flow from anodes to cathodes. Based on Faraday’s law, current density can be 

converted to another expression for corrosion rate, a rate of loss of metal from the surface of the 

steel in μm/year.

(30) The equation in figure 5 shows this conversion for iron.

i

nF

ia R = k = 11.6

Figure 5. Equation. Corrosion rate for iron.

Where:

R = Corrosion rate, given as rate of metal loss, μm/year.

i = Corrosion rate, given as current density, μA /cm2.

k = Conversion factor = 31.5 104 amp·μm s/μA cm·year.

(30)

a = Atomic weight of the metal = 55.8 g/mole for iron.

n = Number of electrons transferred = 2 for iron.

F = Faraday’s constant = 96,500 Coulombs/equivalent.

= Density of the metal, g/cm3 = 7.87 g/cm3 for iron.

 2 The 5-week interval was satisfactory to maintain the pH of the solutions above 13.3.
12 

For example, calculating corrosion loss for a bare conventional bar, a voltage drop of 0.70 mV 

across the 10-ohm resistor represents a total current of 70.0 μA. For a No. 16 (No. 5) bar and a 

solution depth of 76 mm (3.0 inches) (the values used in the test), the total surface area in contact 

with the solution (based on the nominal diameter of the bar and including the end of the bar) is 

4,021 mm2

 (6.233 in2), giving a current density i of 1.74 μA/cm2 (11.2 μA/in2). Applying the 

equation in figure 5 results in the equation in figure 6. 

R i   11.6 11.6 1.74 20.2 μm/year

Figure 6. Equation. Example of corrosion rate for iron. 

For zinc, the first coating layer on the MC bars, the equation in figure 5 becomes the equation in 

figure 7. 

15 0 ia R k .i

nF  

Figure 7. Equation. Corrosion rate for zinc. 

Where: 

a = Atomic weight of the metal = 65.38 g/mole for zinc. 

n = Number of electrons transferred = 2 for zinc. 

 = Density of the metal, g/cm3

 = 7.14 g/cm3 for zinc. 

For reinforced concrete bridge decks, the measurement of the macrocell current is generally not 

possible because the top and bottom mats of reinforcing steel are usually connected by steel wire 

ties and bar supports in the concrete slab. In laboratory tests that simulate the corrosion of steel 

in bridge decks, however, ties and bar supports are not used, and the macrocell current can be 

determined by measuring the voltage drop across a resistor that electrically connects the anode 

and the cathode through an external circuit, as shown in the equation in figure 8. 

RA

V i 

Figure 8. Equation. Corrosion current density. 

Where: 

i = Corrosion current density, A/cm2. 

V = Voltage drop across the resistor, mV. 

R = Resistance of the resistor, kilohms

A = Area of exposed metal on the anode bar, cm2. 

The measured macrocell current density and the calculated corrosion rate can be affected 

significantly by the test methods and the details of the test configuration such as the anode to 

cathode area ratio and the size of the resistor connecting the anode and the cathode.(31,16) Thus, 

the corrosion rate calculated from the measured macrocell current should be used only to compare 

the relative performance of corrosion-protection systems under same test conditions. 
13

Corrosion loss represents cumulative metal loss expressed in micrometers and is calculated by 

numerically integrating the corrosion rate.

Test Specimens

The specimens in the rapid macrocell test consist of 127-mm (5-inch)-long No. 16 (No. 5) 

reinforcing bars, either bare or embedded in mortar, as illustrated in figure 9 for epoxy-coated bars. 

Figure 9. Illustration. Bare bar and mortar-wrapped rapid macrocell specimens with cap 

to protect the exposed end of epoxy-coated bars.

The following procedure is used to fabricate the specimens: 

1. Preparation of reinforcing bars: One end of the bar is drilled and tapped 13 mm (0.5 inches) 

to accommodate a No. 10-24 machine screw. The sharp edges on the bar ends are removed by

grinding. Uncoated bars are cleaned with acetone to remove grease and dirt from the surface. 

ECR bars are cleaned with soap and water. The epoxy coating is penetrated by four 3.2-mm

(0.13-inch)-diameter holes to simulate defects in the coating. The holes are made to a depth 

of 0.5 mm (0.02 inches) using a 3.2-mm (0.13-inch)-diameter four-flute end mill. Two of the 

holes are placed at the midlength of the bars, and the other two are placed about 32 mm

(1.3 inches) from the untapped end, which is submerged in the solution. The submerged end 

is protected using a plastic cap filled with a repair epoxy. The four holes represent 1 percent 

damage to the evaluated area of the epoxy-coated bars. When a mortar-wrapped specimen is 

used, a prepared bare bar is symmetrically embedded in a 154 mm (6-inch)-long mortar cylinder.

The cylinder has a 30-mm (1.2-inch) diameter and provides a 7-mm (0.28-inch) mortar 

cover over the reinforcing bar. Mortar-wrapped bars are cast in a mold consisting of 

polyvinyl chloride (PVC) pipes and fittings.(24–26)

2. Casting: Mortar is placed in a cylindrical PVC mold in four layers. Each layer is rodded 

25 times using a 2-mm (0.08-inch) diameter rod, followed by vibration for 30 s on a vibration 

table with an amplitude of 0.15 mm (0.006 inches) and a frequency of 60 Hz. 

No. 16 Copper Wire

Electrical

 Connection 10-24 Screw

No. 16 [No.5] Rebar

127 mm

 (5 in.)

Epoxy Filled Plastic Cap

(Only for ECR bars)

Epoxy Filled Plastic Cap

(Only for ECR bars)

Protective 

Epoxy Coating

Mortar Cover

127 mm

 (5 in.)

No. 16 [No.5] Rebar

10-24 Screw

Electrical 

Connection

No. 16 Copper Wire

30 mm

(1.2 in.)

127 mm

 (5 in.) 154 mm

 (6 in.)

Bar Bar
14

3. Curing: Specimens are cured in the molds for 1 day at room temperature and then removed 

from the molds and cured in saturated lime water (pH 12.4) for 13 days to reach a passive 

condition. After this period, the specimens are surface-dried with compressed air and then 

vacuum dried for 1 day. 

4. Wiring and coating: For both bare and mortar-wrapped bars, a 16-gauge copper electrical 

wire is attached to the tapped end of each specimen with a 10-24 1/2 (13-mm (0.5-inch)-

long) screw. The electrical connection is then coated with two layers of Herberts-O’Brien 

epoxy for bare bars or two layers of Ceilgard 615TM epoxy for mortar-wrapped specimens. 

Test Materials

The following materials are used in rapid macrocell tests:

Simulated concrete pore solution: Simulated concrete pore solution is used at the cathode. 

One liter of the solution contains 974.8 g (34.39 oz) of distilled water, 18.81 g (0.6635 oz)

of potassium hydroxide, and 17.87 g (0.6303 oz) of sodium hydroxide, based on pore 

solution analysis by Farzammehr et al.(28,29)

Simulated concrete pore solution with sodium chloride: The solution was used at the 

anode and is prepared by adding 45.6 or 172.1 g (1.61 or 6.07 oz) of sodium chloride to 

1 L (0.3 gal) of the simulated concrete pore solution to obtain a 1.6 or 6.04 molal ion 

concentration solution, equal to a 0.8 or 3.02 molal sodium chloride solution.

Salt bridges: A salt bridge provides an ionic path between the cathode and the anode. It 

consists of a 0.45-m (1.5-ft)-long plastic tube filled with a conductive gel. To prepare a 

salt bridge, 4.5 g (0.16 oz) of agar, 30 g (1.1 oz) of potassium chloride, and 100 g (3.53 oz)

of distilled water are mixed and then heated over a hot plate until the solution starts to 

thicken. The heated mixture, enough to produce four salt bridges, is poured into plastic 

tubes using a funnel. The tubes then placed in boiling water for 1 h to firm the gel, 

keeping the ends of the tubes above the surface of the water. The gel in the salt bridges 

must be continuous, without interruption by air bubbles.

Mortar: The mortar has a water-cement (w/c) ratio of 0.5 and sand-cement ratio of 2.0 

by weight and is made with Type I/II portland cement (ASTM C150), distilled water, 

and ASTM C778 graded Ottawa sand.(32,33) The mix proportions represent the mortar 

constituent of concrete. The mortar is mixed in accordance with the procedures outlined 

in ASTM C305.(34)

Mortar fill: Mortar fill is placed in containers with mortar-wrapped specimens. The fill 

consists of the same mixture used in the test specimens. The fill is cast in a metal baking

sheet to a depth of about 25 mm (1 inch). The mortar in the sheet is air-cured at room 

temperature for 15 days and broken into 25- to 50-mm (1- to 2-inch) pieces prior to use.
15

Data Acquisition

A voltmeter with a 0.001 mV resolution is used to measure corrosion potential of the anode and 

cathode and the voltage drop across the 10-ohm resistor. In a typical test, the voltage drop tends to 

fluctuate between -0.003 and 0.003 mV when the corrosion current is close to zero. Only voltage 

drop readings outside of this region are used to evaluate the performance of the corrosionprotection systems. Values between -0.003 and 0.003 mV are treated as zero.

Bench-Scale Tests

During the past two decades, bench-scale tests such as the southern exposure, cracked beam, and

ASTM G109 tests have frequently been used to evaluate the corrosion performance of reinforcing

steel.(31,35,36) Of these tests, the southern exposure and cracked beam tests have proven to give 

useful data in a relatively short period. All three test methods were used in this study, but only 

the results for the first two are reported because they yielded useful data. The ASTM G109 test 

uses only a 3 percent sodium chloride solution and provides a much milder degree of exposure to 

the specimens. It yielded no useful information over a 4-year period, twice as long as that used 

for the southern exposure and cracked beam tests.

Southern Exposure Test

The specimen used in the southern exposure test consists of a small slab containing two mats of 

reinforcing steel (see figure 10).

(37)

64 mm

(2.5 in.)

64 mm

(2.5 in.)

V

178 mm

(7.0 in.)

25 mm (1.0 in.)

25 mm (1.0 in.)

57 mm

(2.25 in.)

64 mm

(2.5 in.)

57 mm

(2.25 in.)

305 mm

(12 in.)

15% NaCl solution

Voltmeter

Terminal Box

10 ohm

Figure 10. Illustration. Southern exposure test specimen.

The concrete is wet cured for 3 days and then air cured until the test begins at 28 days. The top 

mat consists of two No. 16 (No. 5) bars, and the bottom mat consists of four No. 16 (No. 5) bars. 

The mats are connected electrically across a 10-ohm resistor, a dam is placed around the edge of 
16 

the top surface (cast integrally with the specimen), and the sides of the concrete are sealed with 

epoxy. A 15 percent (6.04 molal ion) sodium chloride solution is placed inside the dam, allowing 

the chlorides to penetrate the concrete. The slabs are subjected to a 7-day alternate ponding and 

drying regime, with ponding at 23 ±2 C (73 ±3 F) for 4 days and drying at 38 C (100 F) 

(thus the name southern exposure) for 3 days. Prior to drying, the solution is removed from the 

upper surface using an industrial vacuum cleaner. The ponding and drying regime continued for 

12 weeks. The specimens were then subjected to continuous ponding for 12 weeks at 23 ±2 C 

(73 ±3 F) after which the alternate ponding and drying regime begins again. The two regimes 

continued for 96 weeks. Corrosion current and the corresponding corrosion rate are determined 

by measuring the voltage drop across the resistor. The corrosion potentials of the top and bottom 

bars are measured.3 Corrosion performance is also evaluated using monthly linear polarization 

resistance readings on selected specimens. The test provides a severe corrosion environment that 

is generally believed to simulate 15–20 years of exposure for marine structures under tropical 

conditions and 30–40 years of exposure for bridges within a 48-week period.(38) 

Upon corrosion initiation and at the conclusion of the tests, southern exposure specimens are 

sampled for chloride content using procedures described in the section on chloride analysis later 

in this chapter. 

Cracked Beam Test 

The cracked beam specimen is used to model the corrosion of reinforcing steel in which cracks 

directly expose the steel to deicing chemicals (see figure 11). The specimen is half the width of 

the southern exposure specimen, with one bar on top and two bars on the bottom. 

V

Voltmeter

Terminal Box

10 ohm

152 mm

(6.0 in.)

178 mm

(7.0 in.)

25 mm (1.0 in.)

25 mm (1.0 in.)

Figure 11. Illustration. Cracked beam test specimen. 

 3

 Corrosion potentials are measured with respect to an SCE on ponded specimens and a copper-copper sulfate (CSE) electrode for dry 

specimens. Potentials with respect to CSE are approximately 0.075 V more negative than those with respect to SCE. 
17

A crack is simulated parallel to and above the top reinforcing bar through the insertion of a 

0.3-mm (12-mil) stainless steel shim when the specimen is fabricated. The shim is removed 

within 12 h of casting, leaving a direct path for chlorides to the reinforcing steel and simulating 

the effects of a settlement crack over the bar. An integral dam is used in manner similar to that 

used for the southern exposure specimen around the upper surface of the specimen. Like the 

southern exposure specimen, the cracked beam specimen is subjected to cycles of wetting and 

drying with a 15 percent sodium chloride solution, continuing up to 96 weeks.

Specimen Fabrication

The following process is used to fabricate southern exposure and cracked beam specimens:

1. Reinforcing bar preparation: Each reinforcing bar is cut to a length of 305 mm

(12 inches). Both ends of the bar are drilled and tapped 13 mm (0.5 inches) to accommodate 

a No. 10-24 machine screw. The sharp edges on the bar ends are removed with a grinder. 

Uncoated bars are cleaned with acetone to remove grease and dirt from the surface. ECR bars 

are cleaned with soap and water. The epoxy coating is then penetrated by four or ten 3.2-mm

(0.125-inch)-diameter holes to simulate defects in the coating. The holes are made to a depth 

of 0.4 mm (16 mil) using a 3.2-mm (0.125-inch)-diameter four-flute end mill. Two or five 

holes are placed evenly along the length on each side of the bars. On the MC bars, specimens 

are evaluated with both layers penetrated and with only the epoxy penetrated. The epoxy is 

penetrated without damaging the zinc using a soldering gun set to a temperature of 205 °C

(400 °F), which is above the melting temperature of epoxy but below the melting temperature 

of zinc. The burned epoxy regions are cleaned with acetone. Four holes represent 0.21 percent 

damage, and 10 holes represent 0.52 percent damage to the exposed surface of the epoxycoated bar.

2. Form assembly: Formwork is made to cast the specimen in an inverted position. In this 

study, the forms consist of several pieces of 19-mm (0.75-inch)-thick plywood, including 

four sides and a bottom. Inside the mold, a smaller beveled wooden piece is bolted to the 

bottom to create the integral concrete dam after casting. For the cracked beam forms, a 

152-mm (6-inch)-long, 0.3-mm (0.012-inch)-wide longitudinal slot is made in the center of 

the beveled wood to accommodate a 0.3-mm (0.012-inch)-thick stainless steel shim. The shim 

projects 25 mm (1 inch) from the slot and just touches the test bar. After demolding, the shim 

is removed from the concrete to form the crack. All parts of the mold are fastened with angles 

and clamps. The inside corners are sealed with clay. The bars are supported by 10-24×1 

(25-mm (1.0-inch)-long) screws through 4.8-mm (0.19-inch)-diameter holes in two side pieces 

of the form. When epoxy-coated bars are tested, two of the holes in the coating face up and 

the other two face down.

3. Casting: Concrete is mixed in accordance with the requirements of ASTM C192 for 

mechanical mixing.(39) The concrete mixture proportions are given in table 5. The concretes 

have a w/c ratio of 0.45 or 0.35 and a nominal air content of 6 percent. The specimens are 

cast in two layers. Each layer is vibrated for 30 s on a vibrating table with an amplitude of 

0.15 mm (0.006 inches) and a frequency of 60 Hz. The concrete surface is finished with a 

wooden float.
18 

Table 5. Concrete mixtures. 

w/c 

Cement, 

kg/m3

Water, 

kg/m3

Fine 

Aggregate, 

kg/m3

Coarse 

Aggregate,

kg/m3

AirEntraining

Agent, 

mL/m3

DCI, 

L/m3

HycreteTM, 

kg/m3

Rheocrete®,

L/m3

SP, 

L/m3

0.45 

355 160 851 880 90 – – – – 

355 147.4 851 880 140 15 – – – 

355 154.0 851 880 35 – 8.0 – – 

355 155.7 851 880 300 – – 5 – 

0.35 

438 153 764 861 355 – – – 2.12 

438 140.4 764 861 740 15 – – 2.12 

438 145.6 764 861 330 – 9.9 – 2.25 

438 148.7 764 861 1,480 – – 5 2.25 

1 kg/m3 = 1.69 lb/yd3

1 mL/m3

 = 0.026 fl oz/yd3

1 L/m3

 = 0.202 gal/yd3

SP = Superplasticizer (Rheobuild® 1000 by BASF Admixtures, Inc.) 

– Not used. 

4. Curing: The specimens are cured in the mold for 24 h at room temperature, except the 

cracked beam specimens, which usually require earlier demolding (8–12 h) to facilitate the 

removal of the shim. Once removed from the mold, specimens are cured at room temperature 

in a plastic bag with water until 72 h after casting. The specimens are then removed from the 

bag and air-cured for 25 days. Testing starts 28 days after casting. 

5. Wiring and coating: Two days before testing begins, 16-gauge copper electrical wire is 

attached to one end of each bar embedded in the specimens with a 10-241/2 (13-mm (0.5-

inch)-long) screw. The other end of the bar is sealed with the same kind of screw. All four 

sides of the specimens, including the electrical connections, are then coated with two layers 

of epoxy such as Ceilgard 615TM or ThoRoc® SewerGuard® HBS. The epoxy is mixed and 

applied according to manufacturer’s recommendations. 

Test Materials 

The properties of the materials were as follows: 

 Cement: Type I/II portland cement. 

 Coarse aggregate: Crushed limestone with maximum size = 19 mm (0.75 inches), bulk 

specific gravity (SSD) = 2.58, absorption (dry) = 2.27 percent, unit weight = 1,536 kg/m3

(2,589 lb/yd3

). 

 Fine aggregate: Kansas River sand with bulk specific gravity (SSD) = 2.62, absorption 

(dry) = 0.78 percent, fineness modulus = 3.18. 

 Air-entraining agent: Daravair® 1400 by Grace Construction Products. 
19 

A 15 percent sodium chloride solution (6.04 molal ion concentration) was used to pond the test 

specimens: 600 mL (20.3 fl oz) to pond one southern exposure specimen and 300 mL (10.1 fl oz) 

to pond one cracked beam specimen. 

Data Acquisition 

The same voltmeter and rules for data conversion described for the rapid macrocell tests were 

used for the bench-scale tests. 

Corrosion Initiation Beam Tests 

The corrosion initiation beam test is used to determine the critical chloride corrosion threshold of 

a corrosion-protection system. While these data are also obtained from southern exposure specimens, 

corrosion initiation tests are terminated at the onset of corrosion, thus allowing a greater number of 

samples to be collected. The test was used in this study to evaluate conventional reinforcing steel 

cast in concrete containing corrosion inhibitors. The specimen is identical to the cracked beam 

specimen except that no intentional crack is placed above the reinforcement. The corrosion 

initiation beam specimen is shown in figure 12. 

 ~ 25 mm (1.0 in.)

178 mm

(7.0 in.)

152 mm

(6.0 in.)

10 ohm

V 63.5 mm

measured

Figure 12. Illustration. Corrosion initiation beam test specimen. 

The materials, fabrication, and testing procedures used in the corrosion initiation tests are 

identical to those used for the southern exposure and cracked beam tests with the exception of 

test duration. The w/c ratio is 0.45. 

For conventional reinforcing steel, corrosion initiation is considered to occur when either the 

macrocell corrosion rate first reaches a value greater than or equal to 0.3 μm/year (0.01 mil/year) 

or when the corrosion potential of the top mat of steel first shifts to a value more negative than 

-0.350 V with respect to a CSE. For zinc-coated steel, corrosion initiation is based on a corrosion 

rate of 0.3 μm/year (0.01 mil/year) or when a sharp change in corrosion potential is observed, 

with the former serving as the primary guide. 

(2.5 in.)
20

Once corrosion initiation occurs, testing is halted and concrete samples are taken for chloride 

analysis. A total of 20 samples are taken from each initiation beam, 10 from each side of the 

beam starting 40 mm (1.5 inches) from the edge and spaced at 25-mm (1-inch) intervals, as 

shown in the side view of the specimen in figure 13. For each sample, drilled holes are positioned 

so that the top of the holes and the top surface of the reinforcing bar are at the same level. To do 

this, the actual level of the top reinforcing bar in each specimen is measured. Concrete sampling 

and chloride analysis are preformed as described later in this chapter.

Figure 13. Illustration. Sampling locations for initiation beam tests.

Linear Polarization Resistance Test

A measure of both microcell and macrocell corrosion can be obtained with the polarization 

resistance test, which uses a noncorroding counter electrode and a reference electrode to establish a 

polarization curve by imposing a range of potentials on the metal and measuring the corresponding 

corrosion currents using a potentiostat. Polarization resistance measurements were obtained from 

selected bench-scale specimens throughout the test period.

Polarization resistance tests were used in this study to obtain the total corrosion rates for benchscale specimens. In the tests, current readings are taken during a short, slow sweep of bar potential. 

The sweep typically ranges from -20 to +20 mV relative to the open circuit potential Eoc. In this 

range, the current-versus-voltage curve is roughly linear. The slope of the linear region is 

proportional to the resistance of the metal. The total corrosion current density is obtained using 

the relationship shown in figure 14.

p

B i

R =

Figure 14. Equation. Corrosion current density.

305 mm [12 in.]

measured

38 mm

[1.5 in.]

38 mm

25.4 mm [1 in.] x 9 [1.5 in.]

top reinforcing bar
21

Where: 

i = Corrosion current density (A/cm2).

B = Stern-Geary constant (typically taken as 26 mV for both reinforcing steel and zinc in concrete).

Rp = Slope determined from the polarization curve (kilohms×cm

2

). 

The total corrosion rate in μm/year is calculated using the equations in figure 5 and figure 7 for 

iron and zinc, respectively. In this study, the tests are performed using a PC4/750 Potentiostat

and DC105 corrosion measurement system from Gamry Instruments. 

The tests for bench-scale specimens were performed every 4 weeks to obtain the total corrosion 

rates for the top mats with the bottom mats disconnected. In the tests, the top mat of reinforcing 

steel is used as the working electrode, an SCE immersed in salt solution on top of the specimen 

is used as the reference electrode, and a platinum strip immersed in the salt solution is used as 

the counter electrode.

The data file from a polarization resistance test is analyzed using the data analysis package provided 

with the DC105. This analysis software can read the data file and plot a graph based on the data 

in the file. When a new graph is created in this package, the user picks a range of voltage in the 

graph and the software automatically uses a linear fit of the data in the selected range to calculate 

the polarization resistance. The corrosion current density and corrosion rate can then be 

determined using the polarization resistance.

Field Tests

Using concrete slab test specimens stored outdoors, the field test is designed to obtain a measure 

of the performance of corrosion-protection systems under realistic exposure conditions. Like the 

bench-scale specimens, some field test specimens are uncracked and some have simulated cracks 

directly above and parallel to selected reinforcing bars. A dam made of weatherstripping is 

attached to the upper concrete surface to hold a salt solution that is ponded on the specimens 

every 4 weeks. Corrosion rate measurements are obtained for a minimum of 250 weeks.

Field test specimens consisted of a 1,219 × 1,219 × 165-mm (48 × 48 × 6.5-inch) concrete slabs with 

two mats of No. 16 (No. 5) reinforcing bars (see figure 15 through figure 18). Each mat contains 

seven bars in both the longitudinal and transverse directions with clear concrete covers 25 mm

(1 inch) from the top and bottom and 76 mm (3 inches) from the ends. Selected top and corresponding 

bottom bars are electrically connected across a 10-ohm resistor to form one test point.
22

1219 mm (48 in.)

1219 mm (48 in.)

1 3 5 7 (6 in.)

152 mm

Bar

Weatherstrip152 mm

(6 in.)

Figure 15. Illustration. Field test specimens, top slab without cracks. 1219 mm (48 in.)

1219 mm (48 in.)

152 mm

152 mm

305 mm (12 in.)

Bar

Crack

Weatherstrip

1 3 5 7 (6 in.)

(6 in.)

Figure 16. Illustration. Field test specimens, top slab with cracks. 1219 mm (48 in.)

1219 mm (48 in.) 152 mm

152 mm

Bar

1 3 5 7 (6 in.)

(6 in.)

Figure 17. Illustration. Field test specimens, bottom slab.
23

165 mm

1 3 5 7

165 mm

FRONT

SIDE

(6.5 in.) (6.5 in.)

229 mm

(9 in.)

229 mm

(9 in.) PVC Pipe

Figure 18. Illustration. Field test specimens, front and side views.

Test specimens are moved to the Adams Campus of the University of Kansas 7 days before 

testing. The specimens are spaced 0.914 m (3 ft) apart and placed 203 mm (8 inches) above the 

ground using 203 × 203 × 406-mm (8 × 8 × 16-inch) concrete blocks.

A 9.5-mm (0.375-inch)-thick dam made of weatherstrip tape is attached to the top concrete 

surface around the edges and sealed with silicone caulk to prevent leakage. The specimens are 

ponded with 3.3 L (0.87 gal) of 10 percent rock salt solution, which contains 0.30 kg (0.66 lb) of 

rock salt, every 4 weeks. Occasionally in winter, rock salt alone is used. 

The salt exposure program was based on Kansas salt usage history from 1998 to 2002, as shown 

in table 6.

(40) The average application rate was based on a total length of all driving lanes of 

33,742 km (20,967 mi) with an average lane width of 3.7 m (12 ft). The yearly average salt 

application was 0.66 kg/m2 (0.13 lb/ft2). 

Table 6. Kansas Department of Transportation (KDOT) salt usage history.(40)

Fiscal Year

Rock Salt Total

Average 

Application Rate

Metric Ton Ton kg/m2 lb/ft2

1998 86,507 95,374 0.71 0.14

1999 64,254 70,840 0.52 0.11

2000 58,583 64,588 0.48 0.1

2001 124,619 137,392 1.02 0.21

2002 67,673 74,609 0.55 0.11

Average 80,327 88,561 0.66 0.13

The KDOT Maintenance Manual provides general guidelines for salt applications in snow season.(41)

According to KDOT personnel, bridge decks receive four to five times the amount of salt applied to

the adjacent pavement to account for lower temperatures on bridge decks. To match the approximate

quantity of salt applied to bridge decks, four times the application rate of salt on pavements in 

Kansas, which is 2.64 kg/m2 (0.52 lb/ft2), is applied to field test specimens. This translates to

3.92 kg (8.32 lb) per specimen per year or 0.30 kg (0.66 lb) of rock salt every 4 weeks, the value 

used in the tests, as described above. 
24

The 16-gauge copper wires from the top mat bars are connected to red binding posts, and the 

wires from the bottom mat bars are connected to paired black binding posts. A switch was

connected to the red binding post through a 10-ohm resistor. The switches are turned on and off 

to control the electrical circuits. Binding posts of several specimens are centered together in a 

terminal box for testing convenience.

The test specimens are ponded with 3.3 L (0.87 gal) of 10 percent rock salt solution on the first 

day. Two weeks later, the voltage drops across the 10-ohm resistors are measured using a voltmeter. 

The circuits are then opened and the mat-to-mat resistances are recorded using an ohmmeter. The 

corrosion potentials are measured about 2 h after opening the circuits. Both anode and cathode 

corrosion potentials are measured with respect to a CSE. The circuits are closed after all the 

readings are taken. To achieve consistent measurements, specimens are watered before taking 

readings, usually about an hour before voltage drops. 

Corrosion potential varies with temperature, and temperatures fluctuate in the field.(42)

Therefore, a

correction factor must be applied to convert potential measurements taken in the field to a value 

corresponding to 22o C (72o F). For a CSE, the correction is shown in figure 19 and figure 20.

E = Eo + 0.9(T-22)

Figure 19. Equation. Temperature correction in Celsius.

E = Eo + 0.5(T-72)

Figure 20. Equation. Temperature correction in Fahrenheit.

Where:

T = Temperature, °C or °F.

Eo = Uncorrected corrosion potential reading, mV.

E = Temperature corrected corrosion potential reading, mV.

The test cycle is repeated every 4 weeks. The specimens are ponded at the same time readings are 

taken. After the specimens reach about 96 weeks, readings are taken every 8 weeks, but the 

ponding cycle is maintained at 4 weeks. 

Corrosion potentials are measured at fixed grid points on the top specimen surface, as shown in 

21 through figure 23. 
25 

1219 mm (48 in.) (6 in.)

(6 in.)

Bar

Weatherstrip

1

2

3

4

5

6

7

8

9

10

11

12

3 5 152 mm

152 mm

Figure 21. Illustration. Potential test points for conventional steel specimens. 

1219 mm (48 in.) 1357 (6 in.)

(6 in.)

Bar

Weatherstrip

1

2

3

4

5

6

7

8

9

10

11

12

152 mm

152 mm

Figure 22. Illustration. Potential test points for epoxy-coated bar specimens with four test bars. 1219 mm (48 in.)

1219 mm (48 in.) 152 mm

152 mm

Bar

Weatherstrip

1

2

3

4

5

6

3 5

(6 in.)

(6 in.)

Figure 23. Illustration. Potential test points for epoxy-coated bar specimens with two test bars. 
26

Specimen Fabrication

The following process is used to fabricate field test specimens:

1. Reinforcing bar preparation: Reinforcing bars are cut to 1,067 mm (42 inches), and the sharp 

edges at the ends are smoothed with a grinder. One end of the bar is drilled and tapped to a depth 

of 13 mm (0.5 inches) to accommodate a 10-24 stainless steel threaded bolt. Conventional 

bars are cleaned with acetone, and epoxy-coated bars are cleaned with soap and warm water 

and left to dry in the air. The coatings on the epoxy-coated and MC bars are penetrated with 

16 3.2-mm (0.125-inch)-diameter holes. The holes are drilled to a depth of 0.4 mm (16 mil) 

from the epoxy coating surface using a 3.2-mm (0.125-inch)-diameter four-flute drill bit 

mounted on a milling machine. Eight holes are evenly distributed on each side of the bar along 

the length. For MC bars, both the epoxy and zinc layers are penetrated. 

A 914-mm (36-inch)-long 14-gauge electrical copper wire is connected to the tapped end of 

the test bars with a 10-mm (0.375-inch) 10-24 stainless steel threaded bolt. The connection 

and all other exposed ends of epoxy-coated and MC bars are coated with 3MTM Rebar Patch 

epoxy. After the epoxy dried, a 76-mm (3-inch)-long heat-shrinkable tube is used to protect 

and direct the copper wire out of the specimen. Because 76 mm (3 inches) of the bar is 

covered by the tube, the holes in the epoxy represent 0.26 percent of the exposed bar surface. 

The interface between the shrinkable tube and the tapped end is patched with epoxy. As 

shown in figure 15 through figure 18, bars numbered 1, 3, 5, and 7 are connected across 

10-ohm resistors. In some early test specimens, only bars 3 and 5 were connected.

2. Form assembly: The forms used for the field test specimens are made of 19-mm (0.75-inch)-

thick plywood and held in position with wood screws and clamps. All corners are sealed with 

modeling clay from the inside to avoid leakage. The inside of the form is coated with mineral 

oil after cleaning to remove dust. The front and back form pieces are predrilled, and two 25-mm

(1-inch)-diameter holes are centered 229 mm (9 inches) away from the specimen sides. Two 

1.4-m (4.5-ft)-long PVC pipes are installed through holes perpendicular to the test bars, as 

shown in figure 18. Two 1.8-m (6-ft)-long No. 16 (No. 5) conventional bars are inserted into 

the PVC pipes to aid in lifting the specimens. 

Plastic chairs 25-mm (1-inch)-high are used to support bottom mat bars, and 108-mm

(4.25-inch)-high plastic chairs are used to support top mat bars to provide 25-mm (1-inch) 

clear concrete covers. Plastic rather than metal chairs are used to avoid unplanned electrical 

connections between the top and bottom bars. The steel within each mat is connected using 

conventional tie wire for conventional steels and plastic-coated tie wire for epoxy-coated steels. 

For specimens with simulated cracks from the top surface, 0.3-mm (12-mil)-thick, 305-mm

(12-inch)-long stainless steel shims are placed directly above and parallel to the test bars. The 

crack thickness is designed based on bridge deck crack surveys.(43) A shim holder is used to 

position stainless steel shims in place. It is made of plywood and structured as shown in 

figure 24 through figure 26. The stainless steel shims are attached to the top of the shim 

holder and the holder is attached into the form using wood screws.
27

Shim

holder

Specimen 

form305 mm (12 in.)

Specimen 

Figure 24. Illustration. Shim holder for field specimens, top view.

Stainless

steel 

shim Screw

Shim holder

Shim 

metal

610 mm (24 in.)

Specimen form

Figure 25. Illustration. Shim holder for field specimens, front view.

305 mm (12 in.)

Shim holder

Specimen 

form

Figure 26. Illustration. Shim holder for field specimens, side view.

3. Specimen Casting: Concrete is ordered from a local ready mix plant. The mixture 

proportions are the same as those shown in table 5 for the bench-scale specimens, with 

a w/c ratio of 0.45.

Concrete is consolidated during casting using an electric internal vibrator with a 33-mm

(1.375-inch)-diameter head. The upper surface is finished with a screed, followed by a 
28

bullfloat. For cracked specimens, a wooden float is used instead of a bullfloat. The stainless 

steel shims are removed from the concrete about 12 h after casting. 

During casting, concrete slump, temperature, unit weight, and air content are measured in 

accordance with ASTM standards. Test cylinders are made for each batch and stored with the 

specimens in a curing room and in a curing tank containing lime-saturated water. The cylinders

are tested at 28 days to determine compressive strength. Concrete batch information and the 

properties of the plastic and hardened concrete are summarized in table 7. As shown in the 

table, the concrete in the specimens containing Rheocrete® and HycreteTM exhibited reduced 

compressive strength compared to other specimens independent of w/c ratio. The reduced 

strengths may be explained in part by analyses of pore solutions in cement pastes by O’Reilly 

et al., who observed a marked increase in sulfate content at 7 days for pastes containing 

Rheocrete® and at both 1 and 7 days for cement pastes containing HycreteTM.

(44) These 

increases in sulfate content may also explain differences in the critical chloride corrosion 

threshold for concretes containing corrosion inhibitors, as discussed in chapter 3.

Table 7. Properties of concrete batches for field tests.

Batch

Steel Designationa

(No. of Specimens) w/c

Slump,

mm

Concrete

Temp.,

°C

Unit

Weight,

kg/m3

Air

Content,

Percent

Average Compressive

Strengthb, MPa

Curing 

Tank

Curing 

Room

With 

Specimens

1

Conv. (2), ECR (2),

ECR(Valspar) (2) 0.39 100 19 2,219 6.25 – 28.4 30.6

2

ECR(DuPont) (2),

ECR(Chromate) (2), MC (2) 0.43 100 19 2,319 5.00 – 35.7 37.4

3

ECR(primer/Ca(NO2)2) (2), 

Conv. (2), ECR (2) 0.41 50 28 2,307 4.00 – 34.4 36.9

4

ECR(Valspar) (2),

ECR(DuPont) (2),

ECR(Chromate) (2) 0.42 125 25 2,296 5.75 – 32.5 32.9

5

MC (2),

ECR(primer/Ca(NO2)2) (2) 0.44 110 23 2,291 5.25 32.8 32.6 33.2

6 ECR(DCI) (4) 0.48 210 22 2,255 7.25 35.3 30.9 29.6

7 ECR(DCI) (2) 0.40 25c 21 – 5.50 36.8 35.9 –

8 ECR(RH) (4) 0.44 165 23 2,295 5.50 29.1 28.5 28.1

9 ECR(HY) (4) 0.41 185 16 2,216 5.65 15.0 13.5 13.1

1 mm = 0.039 inches

°F = 1.8 °C + 32

1 kg/m3 = 1.69 lb/yd3

1 MPa = 145 psi

– Not used. a See table 1 for abbreviation definitions; MC bars have both zinc and epoxy layers penetrated; all epoxy-coated bars are 

penetrated with 16 surface holes.

b Average of three cylinders.

c A slump of 150 mm (6 inches) was measured at the ready-mix plant before transporting to the concrete lab.

4. Curing: The specimens are covered with saturated burlap and plastic sheeting in the laboratory

for 7 days, the curing period required by the Kansas Standard Specifications for State Road and 

Bridge Construction at the time the specimens were fabricated.(45)After 7 days, the specimens

are demolded, moved outdoors, and cured in air for 3 months prior to the initiation of the tests.
29

Chloride Analysis

The sampling and testing procedures to determine chloride ion concentration in bench-scale and 

corrosion initiation specimens were those adopted by Ji et al.(26) Pulverized concrete samples are 

obtained by drilling 6.4-mm (0.25-inch)-diameter holes in the side of the specimen using a rotary 

impact-type drill. Prior to sampling, the drilled concrete surface is cleaned three times, first using 

soap and water, then using tap water, and finally using deionized water. The surface is then dried 

using paper towels. Drilling positions are measured and marked. A 152-mm (6-inch)-long, 

6.4-mm (0.25-inch)-diameter drill bit is mounted to a heavy-duty drill. The specimen is drilled 

perpendicular to the reinforcing steel, parallel to the top surface of the specimen. The sample 

obtained from the first 13-mm (0.5-inch) depth contains epoxy coating from the exterior of the 

specimen and is discarded. The drilling continues to a depth of 63.5 mm (2.5 inches) to obtain 

approximately 4 g (0.15 oz) of powder. The pulverized concrete sample from each hole is 

collected using two pieces of copy paper and transferred to labeled plastic bags. The drill bit is 

cleaned before and between each sample to avoid contamination. A shop vacuum reserved for 

drilling is used during the procedure.

Four cores are taken from most field test specimens at end of life using an 89-mm (3.5-inch)-

diameter core drill bit and core drill to determine the chloride ion concentration. The cores are 

taken at the corners of the specimen, 230 mm (9 inches) from the edges. Cores that include

reinforcement are not analyzed to avoid measuring the effect of chloride buildup over the bars.

After coring, cores are stored at -18○ C (0○ F) to minimize chloride ion migration prior to sampling.

Concrete powder for sampling is obtained from the cores using a milling machine and a 32-mm

(1.25-inch)-diamond grit hole saw. The cores are mounted on a rotary table and the hole saw is 

positioned off center from the core bit so that when the rotary table is rotated the hole saw cuts a 

44-mm (2.5-inch)-diameter circle in the core. This path avoids sampling from the edge of the core,

where water from the core drill may affect the chloride content. Samples are obtained from different 

depths so that a depth profile of chloride content can be determined. The powder obtained from the 

top 4 mm (0.15 inches) of the core is discarded because of possible contamination from the core 

drill water. Samples are collected from 4–8 mm (0.15–0.30 inches), 8–13 mm (0.3–0.5 inches), 

13–19 mm (0.5–0.75 inches), 19–25 mm (0.75–1.0 inches), 25–29 mm (1–1.125 inches), 

29–32 mm (1.125–1.25 inches), and 38–41 mm (1.5–1.625 inches) with the aid of a vacuum 

filter collection system. 

Concrete samples are analyzed for water-soluble chloride content using procedure A from AASHTO 

T 260-94.(46)

Samples are boiled in deionized water to free any water-soluble chlorides. The solution 

is filtered, acidified with nitric acid, and titrated with silver nitrate. The potential of a chloride ionselective electrode is monitored throughout the titration. The change in potential with respect to 

the volume of silver nitrate is calculated, with the endpoint indicated by the inflection point of the

potential-volume curve—the point at which the greatest change in potential for a given incremental

addition of silver nitrate was observed. This procedure gives the chloride ion concentration in 

terms of percent chloride by weight of concrete. In this study, values are presented in kg/m3

(lb/yd3) by multiplying by the unit weight of concrete, taken as 2,246 kg/m3 (3,786 lb/yd3). 
30

Average Corrosion Rates Based on Losses After Corrosion Initiation

Corrosion-protection systems are typically compared based on average losses of metal from the 

surface (expressed as μm) over time for a given test method. These losses are a function of both 

the time to corrosion initiation and the corrosion rate following initiation. General comparisons 

do not necessarily require that the time of corrosion initiation be precisely indentified. To develop 

an estimate of the corrosion performance of a system in a structure such as a bridge deck, however, 

requires separate estimates for the time to corrosion initiation and the subsequent corrosion rate. 

Because corrosion rates fluctuate and each specimen is unique, using the combined average losses 

versus time underestimates both the average time to initiation (losses appear to increase at the 

earliest initiation time) and the average corrosion rate (losses start slowly because not all specimens

are corroding). To rectify this, bench-scale and field test specimens in this study are analyzed 

individually and the results are combined to determine the average corrosion rate for each system 

and specimen type.

To illustrate the process, the plots of macrocell corrosion loss versus time for the individual bars 

in the two field test specimens with conventional steel bars in uncracked concrete containing 

Rheocrete®, ECR(RH)-U-1 and ECR(RH)-U-2, are shown in figure 27. To determine the average 

corrosion rate for each bar, the point at which the corrosion loss begins to increase steadily is 

determined and marked, as shown by red arrows in the figure. The average corrosion rate for the 

bar is the slope of the line connecting this to the point representing the corrosion loss at the end 

of the test (see figure 28). The individual averages are combined to obtain the average for the 

system. Bars that show no increase in corrosion loss, such as ECR(RH)-U-2 (3), are excluded 

from the average.

1 μm = 0.0394 mil

Figure 27. Graph. Individual corrosion losses based on total area of the top bars 

for field test specimens containing Rheocrete® in uncracked concrete, 

with corrosion initiation marked.

-15

-10

-5

0

5

10

15

20

25

30

0 25 50 75 100 125 150 175 200 225 250

CORROSION LOSS, μm

TIME (weeks)

ECR(RH)-U-1 (1) ECR(RH)-U-1 (2) ECR(RH)-U-1 (3) ECR(RH)-U-1 (4)

ECR(RH)-U-2 (1) ECR(RH)-U-2 (2) ECR(RH)-U-2 (3) ECR(RH)-U-2 (4)
31

1 μm = 0.0394 mil

Figure 28. Graph. Individual corrosion losses based on total area of the top bars 

for field test specimens containing Rheocrete® in uncracked concrete, 

with lines connecting corrosion loss at initiation to corrosion loss at 250 weeks.

As shown in figure 29 for three southern exposure specimens containing epoxy-coated bars (with 

four holes through the epoxy) cast in concrete with a w/c ratio of 0.45 containing corrosion 

inhibitor DCI, some specimens exhibit corrosion loss (the result of short periods of measureable

corrosion) and extended periods with no corrosion without having a measureable corrosion rate 

over time. In figure 29, the corrosion rate after corrosion initiation can be measured for only one 

of three specimens (ECR-DCI-4h-45-2). 

1 μm = 0.0394 mil

Figure 29. Graph. Individual corrosion loss based on exposed area of the top bars for 

southern exposure specimens containing epoxy-coated bars cast in concrete containing 

DCI, with lines connecting corrosion loss at initiation to corrosion loss at 96 weeks.

-15

-10

-5

0

5

10

15

20

25

30

0 25 50 75 100 125 150 175 200 225 250

CORROSION LOSS, μm

TIME (weeks)

ECR(RH)-U-1 (1) ECR(RH)-U-1 (2) ECR(RH)-U-1 (3) ECR(RH)-U-1 (4)

ECR(RH)-U-2 (1) ECR(RH)-U-2 (2) ECR(RH)-U-2 (3) ECR(RH)-U-2 (4)

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

0 12 24 36 48 60 72 84 96

CORROSION LOSS, μm 

TIME (weeks)

ECR(DCI)-4h-45-1 ECR(DCI)-4h-45-2 ECR(DCI)-4h-45-3
32

TEST PROGRAM

The test program, summarized in table 8, compared the corrosion performance of the 11 multiple 

corrosion-protection systems with that of conventional reinforcing steel and conventional ECR

and compared the effectiveness of corrosion inhibitors when used with conventional reinforcing 

steel. As shown in the table, rapid macrocell and bench-scale tests were used for all multiple 

corrosion-protection systems, but all versions of the tests were not used for every system. In all, 

the work included 126 macrocell tests, 117 southern exposure tests, 93 cracked beam tests, 

30 corrosion initiation beams, 42 field tests, and 32 corrosion-loss-to-crack-concrete tests.

Table 8. Number of test specimens in test program.

System

Test

Macrocell

SEb CBb FTSc Bare

Mortarwrappeda

Control

Uncoated barsd 6 6 15e 9 4f

ECR 6 6 18e,g 9 4f

Epoxies with increased adhesion

Chromate pretreatment 6 6 6 6 4f

DuPont coating 6 6 6 6 4f

Valspar coating 6 6 6 6 4f

Corrosion inhibitors in mortar or concrete

Uncoated bars with calcium nitrited – – 3 3 –

Uncoated bars with Rheocrete® 222+ d – – 3 3 –

Uncoated bars with HycreteTM d – – 3 3 –

ECR with calcium nitrite – 6 9g 9g 6f

ECR with Rheocrete® 222+ – 6 9g 9g 4f

ECR with HycreteTM – 6 9g 9g 4f

3MTM primer containing calcium nitrite – 6 9g 9g 4f

Epoxies with increased adhesion plus calcium nitrite in mortar or concrete

Chromate pretreatment – 6 3h – –

DuPontTM coating – 6 3h – –

Valspar® coating – 6 3h – –

Bars with multiple coatings

Both layers penetrated 6 6 6 6 4f

Epoxy only penetrated 6 6 6 6 –

SE = southern exposure; CB = cracked beam; FTS = field test specimen

– No tests. a w/c = 0.5. Specimens with four 3.2-mm (0.125-inch)-diameter holes in coating. b w/c = 0.45. ECR systems tested using 3, 6, or 12 specimens with four 3.2-mm (0.125-inch)-diameter holes in 

coating and three specimens with 10 3.2-mm (0.125-inch)-diameter holes in coating. c w/c = 0.45. ECR systems tested with 16 3.2-mm (0.125-inch)-diameter holes in coating. d Six or 12 corrosion initiation specimens also tested. e Twelve specimens with w/c = 0.45 and three specimens with w/c = 0.35. f Half without and half with cracks over the test bars. g Includes three additional specimens with w/c = 0.35 and 10 3.2-mm (0.125-inch)-diameter holes in coating. h Three specimens with four 3.2-mm (0.125-inch)-diameter holes in coating.
33

Rapid Macrocell Test Program

As shown in table 8, the rapid macrocell test with mortar-wrapped specimens was used for all 

multiple protection systems, while the macrocell test with bare bars was not used to evaluate the 

effects of corrosion inhibitors. The macrocell tests for the bare and mortar-wrapped specimens for 

the MC system included bars with penetrations through both layers as well as bars in which only 

the outer layer of epoxy had been penetrated. The coating on each bar in the rapid macrocell tests 

was penetrated by four 3.2-mm (0.125-inch)-diameter holes, representing damage to 1.0 percent of 

the bar area exposed to solutions in these tests. Six specimens were used for each system. 

Bench-Scale and Corrosion Initiation Test Programs

Southern exposure, cracked beam, and corrosion initiation tests were used to compare the 

performance of corrosion-protection systems cast in concrete. A w/c ratio of 0.45 was used in all 

cases. In addition, concrete with a w/c ratio of 0.35 was used to evaluate the performance of the 

corrosion inhibitors (as well as the control specimens) because the corrosion protection provided 

by calcium nitrite relative to that of other corrosion inhibitors has been observed to improve as 

the w/c ratio and permeability of the concrete decrease.

(47) The coatings on bars in the benchscale tests were penetrated with 4 or 10 holes with a diameters 3.2 mm (0.125 inches), 

representing damage to 0.21 or 0.52 percent of the bar surface, respectively.

Linear Polarization Resistance Test Program

Linear polarization resistance measurements were performed on a single southern exposure and 

cracked beam specimen for each configuration and corrosion-protection system in the study (see 

table 8). The results were used in conjunction with the readings obtained from the macrocell,

bench-scale, and field tests to characterize the performance of the corrosion-protection systems.

Field Test Program

Field test specimens were used to compare conventional reinforcing steel and conventional ECR 

steel to epoxy-coated bars with increased adhesion, epoxy-coated bars with corrosion inhibitors, 

and MC bars with both layers penetrated. Four specimens were included for each category, except

there were six epoxy-coated bar specimens with calcium nitrite. Half of the specimens had 

simulated cracks above top reinforcing bars. ECR was cast with 16 3.2-mm (0.125-inch)-

diameter holes in the coating, representing 0.24 percent of the bar surface.

Following the rapid macrocell, bench-scale, and field tests, specimens were photographed to 

record cracking and corrosion products visible on the exterior of concrete or mortar and on 

reinforcing steel and surrounding cementitious materials after the removal of concrete or mortar. 

Following the bench-scale and field tests, coatings were evaluated for disbondment, and concrete 

samples were taken to analyze for chloride contents. 

35

CHAPTER 3. TEST RESULTS

The test results presented in this chapter demonstrate that conventional fusion-bonded epoxy coating 

significantly reduces the corrosion of reinforcing steel. Epoxy-coated bars initiate corrosion at 

chloride contents that are generally several times greater and corrode at rates that are typically 

two orders of magnitude below those exhibited by conventional reinforcement. The results show 

that cracks in concrete directly over and parallel to the reinforcement, such as found in bridge 

decks, result in earlier corrosion initiation and higher corrosion rates than obtained with intact 

concrete for all systems tested.

Epoxies that provide initially high adhesion to the underlying steel provide no advantage in terms 

of improved corrosion performance or improved adhesion when used in concrete. Using concrete 

with a reduced w/c ratio (and thus, lower permeability) lowers the corrosion rate for both 

conventional reinforcement and ECR under all conditions in intact concrete but provides only 

limited corrosion protection, at best, in the presence of cracks, which allow direct access of chlorides

to reinforcing bars. Corrosion inhibitors consistently provided improved corrosion protection 

when used in conjunction with conventional reinforcement and ECR in intact concrete but to a 

lesser degree in cracked concrete. Corrosion inhibitors had a greater relative effect on uncoated 

than on coated reinforcement. Bars with an MC system consisting of 98 percent zinc and 2 percent

aluminum and conventional epoxy exhibit high corrosion rates in cases when the concrete is often 

wet but corrosion rates similar to those exhibited by conventional ECR under conditions similar 

to those in bridge decks; the metallic coating corrodes in preference to the underlying steel, 

providing some additional protection. All coated bars exhibited corrosion losses at openings 

through the coating. The reduction in adhesion between an epoxy coating and the reinforcing steel 

(often referred to as disbondment) that occurs after a period of exposure to corrosive conditions 

increases with increasing chloride content in the concrete and in the presence of cracks and 

decreases with the use of corrosion inhibitors, with the use of MC reinforcement, and with 

electrical isolation of the epoxy-coated bars from each other. Corrosion products form under the 

disbonded coating. Disbondment does not affect the rate at which coated bars corrode. 

RAPID MACROCELL TESTS

All systems were evaluated using rapid macrocell tests. The bare bar test, however, was not used 

to evaluate corrosion inhibitors. The results presented in this section represent the average of six 

specimens. The epoxy on all bars was penetrated with four 3.2-mm (0.125-inch)-diameter holes, 

representing 1.0 percent of the total area in contact with the solution, as previously described.

Corrosion losses (total thickness of metal lost due to corrosion calculated by integrating the 

corrosion rate) for the individual specimens in the rapid macrocell test are summarized in 

table 9 and table 10, which express the results based on the total area of the bars in contact 

with the test solutions and on the area of steel exposed by the four holes through the coating 

on each epoxy-coated bar.
36

Table 9. Corrosion loss at 15 weeks (μm) for rapid macrocell specimens based on total area.

Steel Designationa

Specimen

Average

Standard

1 2 3 4 5 6 Deviation

Controls

Conv. 7.1 5.3 4.7 7.4 6.5 5.2 6.0 1.12

Mb-Conv. 5.8 6.7 3.5 3.8 3.8 5.4 4.8 1.33

ECR 0.256 0.649 0.215 0.381 0.494 0.018 0.336 0.222

M-ECR 0.000 0.000 0.000 0.000 -0.004 0.000 -0.001 0.001

Epoxies with increased adhesion

ECR(Chromate) 0.101 0.000 0.000 0.000 0.000 0.055 0.026 0.043

M-ECR(Chromate) 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000

ECR(DuPont) 0.000 0.438 0.336 0.361 0.425 0.418 0.330 0.166

M-ECR(DuPont) 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000

ECR(Valspar) 0.266 0.389 0.599 0.083 0.056 0.499 0.315 0.221

M-ECR(Valspar) 0.000 -0.003 0.000 0.000 0.000 0.000 0.000 0.001

Corrosion inhibitors in mortar

M-ECR(DCI) 0.000 -0.003 0.000 0.000 0.000 0.000 0.000 0.001

M-ECR(RH) 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000

M-ECR(HY) 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000

M-ECR(primer/Ca(NO2)2) 0.000 0.000 0.000 0.000 0.008 0.009 0.003 0.004

Epoxies with increased adhesion plus calcium nitrite in mortar

M-ECR(Chromate)-DCI 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000

M-ECR(DuPont)-DCI 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000

M-ECR(Valspar)-DCI 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000

Bars with multiple coatings

MC(both layers penetrated) 0.043 0.041 0.007 0.007 -0.038 0.023 0.014 0.030

M-MC(both layers penetrated) -0.004 0.001 0.001 0.000 -0.011 0.000 -0.002 0.005

MC(only epoxy penetrated) 0.064 0.022 0.108 0.050 0.039 0.060 0.057 0.029

M-MC(only epoxy penetrated) 0.020 0.030 0.017 0.024 0.006 0.022 0.020 0.008

1 μm = 0.0394 mil a See table 1 for abbreviation definitions. b M prefix indicates mortar-wrapped specimen, otherwise bare bar specimen.
37

Table 10. Corrosion loss at 15 weeks (μm) for rapid macrocell specimens 

based on area exposed at holes through coating.

Steel Designationa

Specimen

Average

Standard

1 2 3 4 5 6 Deviation

Controls

Conv. – – – – – – – –

Mb-Conv. – – – – – – – –

ECR 25.6 64.9 21.5 38.1 49.4 1.8 33.6 22.2

M-ECR 0.000 0.000 0.000 0.000 -0.352 0.000 -0.059 0.144

Epoxies with increased adhesion

ECR(Chromate) 10.14 0.00 0.00 0.00 0.04 5.49 2.61 4.29

M-ECR(Chromate) 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000

ECR(DuPont) 0.0 43.8 33.6 36.1 42.5 41.8 33.0 16.6

M-ECR(DuPont) 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000

ECR(Valspar) 26.6 38.9 59.9 8.3 5.6 49.9 31.5 22.1

M-ECR(Valspar) 0.000 -0.282 0.000 0.000 0.000 0.000 -0.047 0.115

Corrosion inhibitors in mortar

M-ECR(DCI) 0.000 -0.282 0.000 0.000 0.000 0.000 -0.047 0.115

M-ECR(RH) 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000

M-ECR(HY) 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000

M-ECR(primer/Ca(NO2)2) 0.000 0.000 0.000 0.000 0.774 0.925 0.283 0.441

Epoxies with increased adhesion plus calcium nitrite in mortar

M-ECR(Chromate)-DCI 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000

M-ECR(DuPont)-DCI 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000

M-ECR(Valspar)-DCI 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000

Bars with multiple coatings

MC(both layers penetrated) 4.26 4.13 0.65 0.66 -3.82 2.27 1.36 2.99

M-MC(both layers penetrated) -0.35 0.12 0.08 0.00 -1.06 0.00 -0.20 0.45

MC(only epoxy penetrated) 6.35 2.21 10.78 5.00 3.86 6.03 5.70 2.91

M-MC(only epoxy penetrated) 1.96 2.97 1.66 2.37 0.57 2.18 1.95 0.81

1 μm = 0.0394 mil

– No test. a See table 1 for abbreviation definitions. b M prefix indicates mortar-wrapped specimen, otherwise bare bar specimen.

Bare Bar Tests

The average corrosion rates for the systems evaluated using bare bars are shown in figure 30 and 

figure 31. The two figures differ in the scale of the vertical axis. The corrosion rate represents the 

average based on the total area exposed to the test solution.
38

0

5

10

15

20

25

30

35

40

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

CORROSION RATE, μm/year

TIME, weeks

Conv. ECR MC(both layers penetrated)

MC(only epoxy penetrated) ECR(Dupont) ECR(Chromate)

ECR(Valspar)

1 μm = 0.0394 mil

Figure 30. Graph. Macrocell test, average corrosion rate for bare conventional, ECR, 

increased-adhesion ECR, and MC steel in simulated pore solution with 1.6 molal ion 

concentration of sodium chloride.

-25

0

25

50

75

100

125

150

175

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

CORROSION RATE, μm/year

TIME, weeks

ECR MC(both layers penetrated) MC(only epoxy penetrated)

ECR(Dupont) ECR(Chromate) ECR(Valspar)

1 μm = 0.0394 mil

Figure 31. Graph. Macrocell test, average corrosion rate for bare ECR, increased-adhesion 

ECR, and MC steel in simulated pore solution with 1.6 molal ion concentration of sodium 

chloride (adjusted y-axis).

The results indicate that conventional steel corroded at a much higher rate than any of the epoxycoated bars in the test, with a rate that ranged between 7 and 40 μm/year (0.3 and 1.6 mil/year) 
39

during the 15-week test. Based on corrosion rate, the epoxy-coated bars fell into two groups, 

with conventional ECR, ECR(DuPont), and ECR(Valspar) corroding at an average rate between 

0.5 and 1.7 μm/year (0.02 and 0.067 mil/year) and ECR(Chromate) and the MC bars (both layers

penetrated and only epoxy penetrated) corroding at an average rate between -0.1 and 0.6 μm/year

(-0.004 and 0.02 mil/year). The negative corrosion rate, which indicates more oxidation at the 

cathode than at the anode, may be explained by the amphoteric nature of zinc. As demonstrated 

in the figures, corrosion rates varied significantly from week to week. Conventional reinforcement 

exhibited significant increases in corrosion between weeks 5 and 6 and between weeks 10 and 11,

when the solutions were changed.

Total corrosion losses, which are calculated by integrating the corrosion rate over the test period, 

are shown in figure 32 and figure 33 and in table 9 and table 10. Figure 32 expresses the losses 

based on the total area of the bars in contact with the text solutions, while figure 33 expresses the 

losses in terms of the area of steel exposed by the holes through the epoxy coating, which for 

macrocell specimens equals the values based on total bar surface multiplied by a factor of 100. 

Over the 15-week period, total losses for conventional steel equaled approximately 6 μm

(0.2 mil). For conventional ECR, ECR(DuPont), and ECR(Valspar), total losses ranged from

0.31 and 0.34 μm (0.012 and 0.013 mil) based on total area and between 31 and 34 m (1.2 and 

1.3 mil) based on exposed area. For the ECR(Chromate) and MC bars, total losses were below 

0.057 μm (0.0022 mil) based on total area and 5.7 μm (0.22 mil) based on exposed area. The low 

macrocell corrosion rates for the MC bars resulted because the test measures macrocell rather 

than microcell corrosion and because, as an amphoteric material, zinc is attacked by the alkaline 

solution at the cathode (with twice that area of the anode) as well as by the combined alkaline 

and salt solution at the anode, reducing the net macrocell current. 

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

TIME, weeks

CORROSION LOSS, μm

Conv. ECR MC(both layers penetrated) MC(only epoxy penetrated) ECR(Dupont) ECR(Chromate) ECR(Valspar)

1 μm = 0.0394 mil

Figure 32. Graph. Macrocell test, average corrosion loss based on total area for bare 

conventional, ECR, increased-adhesion ECR, and MC steel in simulated pore solution with

1.6 molal ion concentration of sodium chloride.
40

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

CORROSION LOSS, μm

TIME, weeks

ECR MC(both layers penetrated) MC(only epoxy penetrated)

ECR(Dupont) ECR(Chromate) ECR(Valspar)

1 μm = 0.0394 mil

Figure 33. Graph. Macrocell test, average corrosion loss based on area exposed at holes 

through coating for bare conventional, ECR, increased-adhesion ECR, and MC steel 

in simulated pore solution with 1.6 molal ion concentration of sodium chloride.

The corrosion potentials shown in figure 34 and figure 35 (anode and cathode bars disconnected 

for 2 h) provide additional information on the behavior of the specimens. With the exception of 

ECR(Chromate), all specimens exhibited corrosion potentials at the anode more negative than 

-0.275 V with respect to an SCE (approximately equivalent to -0.350 V for a CSE), indicating 

that the bars were undergoing active corrosion. In contrast to bars with only steel exposed to the 

test solutions, the MC bars initially exhibited corrosion potentials of approximately of -1.200 V

at both the anode and cathode, indicating active corrosion of the zinc layer. The MC bars with 

both layers of coating penetrated reached a corrosion potential of about -0.500 V after 3 weeks, 

indicating that the effect of the zinc surrounding the holes had been largely reduced and that the 

exposed area of steel was governing the corrosion process. In contrast, the MC bars with only the 

epoxy penetrated maintained a significantly more negative corrosion potential than the other anode 

bars, indicating that the zinc was still providing some protection for the underlying steel for a 

significant portion of the test period. Interestingly, the corrosion potentials of the MC cathode 

bars are similar to those at the anode throughout the test period. The fact that the MC cathode 

bars never reached a corrosion potential more positive than -0.275 V, as exhibited by all of the 

other bars, suggests that the zinc continues to contribute to the performance of the system over 

time. With the exception of ECR(Chromate), the corrosion potentials exhibited by the other 

corrosion-protection systems showed a strong similarity to that of uncoated conventional 

reinforcement, indicating that the differences in observed corrosion rates shown in figure 30

and figure 31 are primarily based on the role of the epoxy coating in limiting the exposed bar 

surface at both the anode and the cathode. In terms of total metal loss, that effect is significant

(see table 9, table 10, figure 32, and figure 33).
41

-1.2

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

TIME, weeks

CORROSION POTENTIAL, V

Conv. ECR MC(both layers penetrated) MC(only epoxy penetrated) ECR(Dupont) ECR(Chromate) ECR(Valspar)

Figure 34. Graph. Macrocell test, average corrosion potential at anode for bare 

conventional, ECR, increased-adhesion ECR, and MC steel in simulated pore solution 

with 1.6 molal ion concentration of sodium chloride.

-1.2

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

TIME, weeks

CORROSION POTENTIAL, V

Conv. ECR MC(both layers penetrated) MC(only epoxy penetrated) ECR(Dupont) ECR(Chromate) ECR(Valspar)

Figure 35. Graph. Macrocell test, average corrosion potential at cathode for bare 

conventional, ECR, increased-adhesion ECR, and MC steel in simulated pore solution 

with 1.6 molal ion concentration of sodium chloride.

As a general rule in the bare bar tests, the corrosion rates for ECR based on the area exposed at the 

holes through the coating were significantly higher than they were for conventional reinforcement

based on the total area of the bar (see table 9 and table 10). This behavior, however, does not 

necessarily mean that corrosion losses on damaged regions of ECR are higher than local metal 

losses due to corrosion on uncoated conventional reinforcement because the losses recorded for 
42

uncoated conventional steel represent values that are averaged over the full contact surface. In 

practice, corrosion losses on uncoated bars are not uniformly distributed over the bar surface but

may be much greater in some areas than in others. In addition, the losses calculated for coated bars 

may include losses that occur under the coating, instead of just on the exposed regions.

The test specimens were evaluated visually following the tests, and all specimens in the group 

exhibited significant corrosion, as shown in figure 36, figure 37, and figure 38 for conventional 

reinforcement, conventional ECR, and MC with only the epoxy layer penetrated, respectively. 

Figure 38 shows that the zinc was fully consumed on the MC bars in spite of the fact that the 

total corrosion loss on the exposed area based on the macrocell current (shown in figure 33) 

amounted to less than 6 μm (0.2 mil) for a coating that was 50 μm (2 mil) thick. This observation 

demonstrates the impact of microcell corrosion, which was not measured in this test, on the loss 

of zinc and indicates that macrocell measurements may underestimate total corrosion losses.

Figure 36. Photo. Bare conventional anode bar at 15 weeks showing corrosion products 

that formed below the surface of the solution.

Figure 37. Photo. Bare ECR anode bar at 15 weeks showing corrosion products 

that formed at holes through the epoxy.

Figure 38. Photo. Bare MC anode bar with only epoxy penetrated at 15 weeks showing 

corrosion products that formed at holes through the epoxy.

In addition to the tests described above, bare ECR and MC bars were subjected to extended rapid 

macrocell tests using 6.04 molal ion sodium chloride solutions for periods of up to 40 weeks with the 

goal of evaluating the relative disbondment characteristics of conventional ECR and MC bars under

the severe exposure conditions produced in the test as a function of corrosion loss and time. The 

results of that evaluation, reported in detail appendix A, demonstrate that in the rapid macrocell test

with a high chloride concentration, the specimens with MC reinforcement show greater corrosion 

losses than the specimens with conventional ECR but that MC reinforcement shows significantly 

less disbondment than ECR, both as a function of corrosion loss and as a function of time.
43

Mortar-Wrapped Bar Tests

The corrosion rates using mortar-wrapped specimens for conventional steel, conventional ECR, 

ECR(primer/Ca(NO2)2), and MC bars with both layers penetrated and only the epoxy penetrated 

are shown in figure 39 and Figure 40. In figure 40, the corrosion rate is based on the exposed 

area at the holes through the coating. 

0.0

5.0

10.0

15.0

20.0

25.0

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

TIME, weeks

CORROSION RATE, μm/year

Conv. ECR ECR(primer/Ca(NO2)2)

MC(both layers penetrated) MC(only epoxy penetrated)

1 μm = 0.0394 mil

Figure 39. Graph. Macrocell test, average corrosion rate based on total area for mortarwrapped conventional, ECR, ECR with calcium nitrite primer, and MC steel in simulated 

pore solution with 1.6 molal ion concentration of sodium chloride.

-10.0

-5.0

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

40.0

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

TIME, weeks

CORROSION RATE, μm/year

ECR ECR(primer/Ca(NO2)2)

MC(both layers penetrated) MC(only epoxy penetrated)

1 μm = 0.0394 mil

Figure 40. Graph. Macrocell test, average corrosion rate based on area exposed at holes 

through coating for mortar-wrapped conventional ECR, ECR with calcium nitrite primer, 

and MC steel in simulated pore solution with 1.6 molal ion concentration of sodium chloride.
44

The corrosion rate based on total area for conventional steel started at approximately 2.5 μm/year

(0.098 mil/year), increasing to about 21 μm/year (0.83 mil/year) at week 9, and remained between

18 and 23 μm/year (0.71 and 0.91 mil/year) thereafter. As shown in figure 40, conventional ECR

exhibited essentially no corrosion during the test, while the corrosion current exhibited by the 

other test specimens shown in the figure was relatively minor. The MC bars with only the epoxy 

penetrated exhibited a high corrosion rate between weeks 2 and 5; the rate decreased to zero after 

week 5. The other systems tested, including ECR with improved adhesion (ECR(Chromate)), 

ECR(DuPont), ECR(Valspar)), ECR in mortar with a corrosion inhibitor (calcium nitrite, 

Rheocrete® 222+ or HycreteTM), and the three epoxies with improved adhesion in mortar with 

calcium nitrite, exhibited no corrosion in the test.

Corrosion losses based on total and exposed areas for the systems that did exhibit corrosion are 

shown in figure 41 and figure 42, respectively. Corrosion losses at 15 weeks for all specimens 

are presented in table 9 and table 10. Total losses for conventional steel amounted to 4.8 μm

(0.19 mil) at 15 weeks, compared to values of less than 0.02 μm (0.0008 mil) based on total area 

for other systems and amounted to less than 2 μm (0.08 mil) for the MC bars with only the epoxy 

penetrated and less than 0.5 μm (0.02 mil) for the other systems based on exposed area. 

0.0

1.0

2.0

3.0

4.0

5.0

6.0

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

TIME, weeks

CORROSION LOSS, μm

Conv. ECR ECR(primer/Ca(NO2)2)

MC(both layers penetrated) MC(only epoxy penetrated)

1 μm = 0.0394 mil

Figure 41. Graph. Macrocell test, average corrosion loss based on total area for 

mortar-wrapped conventional, ECR, ECR with calcium nitrite, and MC steel in simulated 

pore solution with 1.6 molal ion concentration of sodium chloride.
45

-0.5

0.0

0.5

1.0

1.5

2.0

2.5

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

TIME, weeks

CORROSION LOSS, μm

ECR ECR(primer/Ca(NO2)2)

MC(both layers penetrated) MC(only epoxy penetrated)

1 μm = 0.0394 mil

Figure 42. Graph. Macrocell test, average corrosion loss based on area exposed at holes 

through coating for mortar-wrapped conventional, ECR, ECR with calcium nitrite, and 

MC steel in simulated pore solution with 1.6 molal ion concentration of sodium chloride.

The average corrosion potentials during the tests, shown in figure 43 through figure 46, demonstrate 

that at the anode, only those steels that exhibited some corrosion loss (see table 9 and table 10) 

had corrosion potentials more negative than -0.275 V, with the exception of ECR(Chromate) in 

mortar containing calcium nitrite (ECR(Chromate)-DCI), which dropped below -0.275 V after 

week 12. The potential of the ECR(primer/Ca(NO2)2) bars, which did exhibit corrosion, dropped 

to approximately -0.400 V at 7 weeks, maintaining that value thereafter. The MC specimens with 

both layers penetrated and with only epoxy penetrated, exhibited progressively more negative 

potentials as the test progressed (see figure 43 and figure 44). For the MC bars with both layers 

penetrated, the corrosion potential started at approximately -0.400 V, dropping to a value somewhat 

more negative than -0.700 V at 15 weeks at both the anode and the cathode. The MC bars with 

only epoxy penetrated started at approximately -0.600 V, ending at a value equal to that for the 

same bars with both layers penetrated. The corrosion potentials of the cathodes for the MC bar 

tests started at only slightly more positive values than exhibited by the anodes, dropping to values

between -0.600 and -0.800 V at 15 weeks. These results suggest that the MC bars started the tests 

in a passive condition and became relatively more active as the simulated pore solutions, both 

with and without sodium chloride, penetrated the mortar. The zinc provided protection during the 

test for both types of damage to the coating. 
46

-0.7

-0.6

-0.5

-0.4

-0.3

-0.2

-0.1

0.0

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

TIME, weeks

CORROSION POTENTIAL, V

Conv. ECR ECR(Rheocrete) ECR(DCI) ECR(Hycrete) ECR(primer/Ca(NO2)2) ECR(Dupont) ECR(Chromate) ECR(Valspar) ECR(Dupont)-DCI ECR(Chromate)-DCI ECR(Valspar)-DCI

Figure 43. Graph. Macrocell test, average corrosion potential at anode for mortar-wrapped 

conventional, ECR, ECR with increased adhesion, ECR cast with corrosion inhibitor, and 

ECR with calcium nitrite in simulated pore solution with 1.6 molal ion concentration of

sodium chloride.

-0.70

-0.60

-0.50

-0.40

-0.30

-0.20

-0.10

0.00

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

TIME, weeks

CORROSION POTENTIAL, V

Conv. ECR ECR(Rheocrete) ECR(DCI) ECR(Hycrete) ECR(primer/Ca(NO2)2) ECR(Dupont) ECR(Chromate) ECR(Valspar) ECR(Dupont)-DCI ECR(Chromate)-DCI ECR(Valspar)-DCI

Figure 44. Graph. Macrocell test, average corrosion potential at cathode for mortarwrapped conventional, ECR, ECR with increased adhesion, ECR cast with corrosion 

inhibitor, and ECR with calcium nitrite in simulated pore solution with 1.6 molal ion 

concentration of sodium chloride.
47

-0.9

-0.8

-0.7

-0.6

-0.5

-0.4

-0.3

-0.2

-0.1

0.0

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

TIME, weeks

CORROSION POTENTIAL, V

MC(both layers penetrated) MC(only epoxy penetrated)

Figure 45. Graph. Macrocell test, average corrosion potential at anode for mortar-wrapped 

MC steel in simulated pore solution with 1.6 molal ion concentration of sodium chloride.

-0.9

-0.8

-0.7

-0.6

-0.5

-0.4

-0.3

-0.2

-0.1

0.0

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

TIME, weeks

CORROSION POTENTIAL, V

MC(both layers penetrated) MC(only epoxy penetrated)

Figure 46. Graph. Macrocell test, average corrosion potential at cathode for mortar-wrapped

MC steel in simulated pore solution with 1.6 molal ion concentration of sodium chloride.

At the conclusion of the tests, the mortar was removed and the bars were inspected for evidence 

of corrosion. The uncoated conventional steel bars exhibited corrosion, as shown in figure 47, 

while none of the epoxy-coated bars exhibited any corrosion products.
48

Figure 47. Photo. Conventional anode bar after removal of mortar at 15 weeks.

The results shown in table 9, table 10, and figure 27 through figure 35 indicate several things about

the corrosion process for steel with a damaged epoxy coating. As mentioned for the bare bar 

tests, the epoxy coating significantly reduced total corrosion losses. But more than that, the tests 

demonstrated that, even with a relatively homogenous material like the mortar used, the chloride 

concentrations at the surface of the bar are likely to vary, providing concentrations high enough 

to initiate corrosion at some locations but not high enough at all locations. This is clearly the case 

for mortar-wrapped conventional steel, as shown in figure 47, where the corrosion products are 

distributed nonuniformly across the bar surface. The exposed steel at locations where epoxy is 

damaged should begin to corrode at the same chloride concentration as uncoated conventional steel. 

When this does not occur, as demonstrated in these tests, it is likely that the chloride concentration 

at the location of the damaged epoxy has not reached the critical chloride threshold. Thus, even 

damaged ECR will have an advantage over conventional steel because all locations that are 

damaged may not be subjected to chloride concentrations high enough to cause corrosion, while 

under the same conditions for uncoated steel, the chloride concentration would be high enough to 

initiate corrosion somewhere on the bars. 

The test results also suggest that if this test is to be used to evaluate the corrosion protection 

provided by damaged epoxy coating (as opposed to systems with uncoated bars for which it 

provides a consistent measure of corrosion resistance), the severity of the exposure conditions 

should be increased, such as would be provided by an increased number of penetrations in the 

epoxy or by an increase in the concentration of chloride in the solution at the anode.(31) In the 

end, the test results for the mortar-wrapped rapid macrocell tests provide a general comparison 

of the performance of the systems studied.

BENCH-SCALE TESTS

The results of the southern exposure and cracked beam tests provide a detailed picture of the 

performance of the corrosion-protection systems in this study. The systems, as reported in the 

following sections, were compared based on average values for a minimum of three specimens 

for each configuration and corrosion-protection system. Six southern exposure and cracked beam 

specimens were used for conventional reinforcing steel and conventional ECR with four holes 

through the epoxy cast in concrete with a w/c ratio of 0.45 (ECR-4h-45). 
49

Southern Exposure Tests

Test results expressed in terms of corrosion loss provide an overall view of system performance. 

Values based on the total area of the bar in contact with concrete and on the exposed area at holes 

in the epoxy are presented in table 11 and table 12, respectively. For these tests, the corrosion 

rates and losses based on the exposed area at the holes for bars with 4 and 10 penetrations 

through the epoxy on each bar are, respectively, 480 and 192 times the corrosion rate based on 

total bar area. As noted in the tables, two of the six epoxy-coated bars with four holes through 

the epoxy cast in concrete with a w/c ratio of 0.45 (ECR-4h-45) and a number of other individual 

specimens with different types of epoxy are not included in the averages because the corrosion 

rates remained essentially zero throughout the tests. The low corrosion rate on individual epoxycoated bars resulted from the highly variable chloride content in the concrete. As observed for 

the mortar-wrapped rapid macrocell specimens with epoxy-coated bars, if the chloride content 

adjacent to the damage site on the bar is not high enough, corrosion will not be induced. In 

contrast, uncoated bars have a much larger exposed area, any part of which is susceptible to a 

chloride content high enough to induce corrosion. Variations in concrete quality can also play a 

role, and such variations occurred on this project, as described in the interim report.(48) The 

original southern exposure specimens containing conventional and conventional ECR had a 

lower than desired w/c ratio. As a result, those tests were repeated and provided the results in this 

report. The results through 96 weeks for the original conventional and conventional ECR are 

reported by Draper et al.(49)

Table 13 and table 14 summarize the average chloride content at a depth of 25 mm (1 inch) in the 

southern exposure specimens at corrosion initiation and at the conclusion of the 96-week test 

period. The average values at corrosion initiation are weighted based on the number of samples 

taken per specimen and are used subsequently in this report to estimate the time to corrosion 

initiation in bridge decks.
50

Table 11. Corrosion loss at 96 weeks (μm) for southern exposure specimens

based on total area.

Steel Designationa

Specimen

Average

Standard

1 2 3 4 5 6 Deviation

Controls 

Conv.-45 7.23 5.59 6.71 6.06 7.48 9.44 7.083 1.352

Conv.2-45 14.31 13.79 15.23 14.44 0.731

Conv.-35 1.05 4.22 1.10 2.121 1.817

ECR-4h-45 0.038 -0.011b -0.011b 0.011 0.011 0.001 0.015 0.016

ECR-10h-45 0.019 0.008 0.023 0.017 0.008

ECR-10h-35 0.011 0.003 0.010 0.008 0.004

Epoxies with increased adhesion

ECR(Chromate)-4h-45 0.004 0.015 0.035 0.018 0.016

ECR(Chromate)-10h-45 0.011 0.068 0.123 0.067 0.056

ECR(DuPont)-4h-45 0.031 0.017 0.030 0.026 0.008

ECR(DuPont)-10h-45 0.029 0.060 0.050 0.046 0.016

ECR(Valspar)-4h-45 0.039 0.015 0.044 0.032 0.016

ECR(Valspar)-10h-45 0.054 0.044 0.090 0.063 0.024

Corrosion inhibitors in concrete

Conv.2(DCI)-45 9.63 7.28 8.88 8.60 1.200

Conv.2(RH)-45 3.11 2.29 4.79 3.40 1.276

Conv.2(HY)-45 1.24 1.59 1.82 1.55 0.292

ECR(DCI)-4h-45 0.002 0.008 0.002 0.004 0.003

ECR(DCI)-10h-45 -0.002b 0.020 0.016 0.018 0.003

ECR(DCI)-10h-35 0.012 0.001 0.008 0.007 0.006

ECR(RH)-4h-45 0.000 0.030 -0.002b 0.015 0.021

ECR(RH)-10h-45 0.001 -0.011b 0.003 0.002 0.001

ECR(RH)-10h-35 0.002 0.005 0.003 0.003 0.001

ECR(HY)-4h-45 -0.001b -0.002b -0.002b 0.000 –

ECR(HY)-10h-45 0.003 -0.001b 0.003 0.003 0.000

ECR(HY)-10h-35 0.006 -0.002b -0.001b 0.006 –

ECR(primer/Ca(NO2)2)-4h-45 0.005 0.012 0.026 0.014 0.011

ECR(primer/Ca(NO2)2)-10h-45 0.031 0.137 0.022 0.064 0.064

ECR(primer/Ca(NO2)2)-10h-35 0.003 0.002 0.001 0.002 0.001

Epoxies with increased adhesion plus calcium nitrite in concrete

ECR(Chromate)-DCI-4h-45 0.002 -0.000b 0.018 0.010 0.011

ECR(DuPont)-DCI-4h-45 -0.000b -0.001b 0.001 0.001 –

ECR(Valspar)-DCI-4h-45 0.000 0.002 0.033 0.012 0.019

Bars with multiple coatings

MC(both layers penetrated)-4h-45 0.030 0.013 0.016 0.020 0.009

MC(both layers penetrated)-10h-45 0.055 0.229 0.153 0.146 0.088

MC(only epoxy penetrated)-4h-45 0.012 0.007 -0.001 0.006 0.006

MC(only epoxy penetrated)-10h-45 0.001 0.021 0.026 0.016 0.013

1 μm = 0.0394 mil

– No standard deviation.

Blank cells indicate no specimen tested.

a See table 1 for abbreviation definitions. 4h = bar with four holes through epoxy, 10h = bar with 10 holes through 

epoxy. 35 = concrete with w/c = 0.35, 45 = concrete with w/c = 0.45. b Excluded from average.
51

Table 12. Corrosion loss at 96 weeks (μm) for southern exposure specimens 

based on area exposed at holes through coating.

Steel Designationa

Specimen

Average

Standard

1 2 3 4 5 6 Deviation

Controls 

ECR-4h-45 18.44 -5.26b -5.32b 5.07 5.18 0.70 7.35 7.68

ECR-10h-45 3.66 1.58 4.41 3.21 1.47

ECR-10h-35 2.03 0.55 1.83 1.47 0.80

Epoxies with increased adhesion

ECR(Chromate)-4h-45 2.11 7.28 16.89 8.76 7.50

ECR(Chromate)-10h-45 2.04 12.99 23.66 12.90 10.81

ECR(DuPont)-4h-45 14.71 7.99 14.32 12.34 3.77

ECR(DuPont)-10h-45 5.52 11.50 9.68 8.90 3.07

ECR(Valspar)-4h-45 18.76 7.00 20.97 15.58 7.51

ECR(Valspar)-10h-45 10.33 8.53 17.22 12.03 4.58

Corrosion inhibitors in concrete

ECR(DCI)-4h-45 0.99 3.62 0.84 1.82 1.57

ECR(DCI)-10h-45 -0.37b 3.90 3.17 3.53 0.52

ECR(DCI)-10h-35 2.25 0.11 1.49 1.29 1.08

ECR(RH)-4h-45 0.00 14.46 -0.74b 7.23 10.23

ECR(RH)-10h-45 0.27 -2.08b 0.63 0.45 0.26

ECR(RH)-10h-35 0.48 0.94 0.52 0.65 0.26

ECR(HY)-4h-45 -0.39b -0.95b -1.13b 0.00 –

ECR(HY)-10h-45 0.65 -0.20b 0.66 0.65 0.01

ECR(HY)-10h-35 1.17 -0.30b -0.17b 1.17 –

ECR(primer/Ca(NO2)2)-4h-45 2.18 5.63 12.35 6.72 5.17

ECR(primer/Ca(NO2)2)-10h-45 6.02 26.41 4.32 12.25 12.29

ECR(primer/Ca(NO2)2)-10h-35 0.61 0.48 0.17 0.42 0.22

Epoxies with increased adhesion plus calcium nitrite in concrete

ECR(Chromate)-DCI-4h-45 1.06 -0.21b 8.59 4.82 5.33

ECR(DuPont)-DCI-4h-45 -0.21b -0.49b 0.28 0.28 –

ECR(Valspar)-DCI-4h-45 -0.07b 1.16 16.08 8.62 10.55

Bars with multiple coatings

MC(both layers penetrated)-4h-45 30.47 30.75 21.96 27.73 5.00

MC(both layers penetrated)-10h-45 100.15 136.15 109.50 115.3 18.68

MC(only epoxy penetrated)-4h-45 8.96 25.20 13.51 15.89 8.38

MC(only epoxy penetrated)-10h-45 5.06 34.37 12.70 17.37 15.20

1 μm = 0.0394 mil

– No standard deviation.

Blank cells indicate no specimen tested.

a See table 1 for abbreviation definitions. 4h = bar with four holes through epoxy, 10h = bar with 10 holes through 

epoxy. 35 = concrete with w/c of 0.35, 45 = concrete with w/c of 0.45. b Excluded from average.
52

Table 13. Chloride content at corrosion initiation (kg/m3) for southern exposure specimens.

Steel Designationa

Samples per 

Specimenb

Specimen

Average

Standard 

1 2 3 4 5 6 Deviation

Controls 

Conv.-45 6 0.65 1.07 0.38 1.38 0.39 0.66c 0.77 0.39

Conv.2-45 6 1.58c 0.66c 0.48 0.88 0.65

Conv.-35 2 1.93d 0.75 1.90 1.69 0.80

ECR-4h-45 6 1.54 0.99 * 3.52 † 2.48 2.13 1.11

ECR-10h-45 2 3.43 9.26e 8.36 7.57 2.62

ECR-10h-35 3 † † † † †

Epoxies with increased adhesion

ECR(Chromate)-4h-45 2 5.54 8.30f 8.47 7.56 2.56

ECR(Chromate)-10h-45 2 2.44 3.73 † 3.08 0.91

ECR(DuPont)-4h-45 2 8.77 7.73 4.24 6.91 2.37

ECR(DuPont)-10h-45 2 1.56 2.17 5.41d 3.99 1.96

ECR(Valspar)-4h-45 2 8.17 7.25f 7.15 7.48 1.31

ECR(Valspar)-10h-45 2 5.11 2.77 † 3.94 1.65

Corrosion inhibitors in concrete

Conv.2-DCI-45 6 2.88 3.03 5.26 3.72 1.12

Conv.2-RH-45 6 1.97c 2.26 2.24 2.16 0.76

Conv.2-HY-45 6 † 0.82 0.62 1.21 0.24

ECR(DCI)-4h-45 2 4.52 † 5.74d 5.44 1.36

ECR(DCI)-10h-45 2 † 5.78 7.29 6.53 1.06

ECR(DCI)-10h-35 2 2.18 2.67 1.41 2.09 0.64

ECR(RH)-4h-45 6 3.44 2.17f 3.38 3.16 0.96

ECR(RH)-10h-45 2 † * 4.01 4.01 –

ECR(RH)-10h-35 2 * 1.52 0.73 1.13 0.56

ECR(HY)-4h-45 6 † 1.19 † 1.19 –

ECR(HY)-10h-45 2 0.79 * 1.03 0.91 0.17

ECR(HY)-10h-35 2 0.60 0.43d 0.35f 0.44 0.24

ECR(primer/Ca(NO2)2)-4h-45 2 4.47 † 3.51 3.99 0.68

ECR(primer/Ca(NO2)2)-10h-45 2 6.36 13.80 7.47 9.21 4.01

ECR(primer/Ca(NO2)2)-10h-35 6 * 1.48 * 1.48 –

Epoxies with increased adhesion plus calcium nitrite in concrete

ECR(Chromate)-DCI-4h-45 2 2.26 1.20 4.86 2.77 1.88

ECR(DuPont)-DCI-4h-45 2 3.91 3.50d 11.4f 5.73 3.65

ECR(Valspar)-DCI-4h-45 2 * 1.56 9.13 5.35 4.13

Bars with multiple coatings

MC(both layers penetrated)-4h-45 2 † † 0.71 0.71 –

MC(both layers penetrated)-10h-45 2 † 1.48 0.96 1.22 0.37

MC(only epoxy penetrated)-4h-45 2 0.69 1.75 2.63 1.69 0.97

MC(only epoxy penetrated)-10h-45 2 5.26 2.53 † 3.90 1.92

1 kg/m3 =1.69 lb/yd3

* Corrosion initiation not recorded. 

† Information not available.

– No standard deviation.

Blank cells indicate no specimen tested.

a See table 12 for abbreviation definitions. b Unless otherwise noted. 

c Five samples analyzed; d Six samples analyzed; e Four samples analyzed; f Three samples analyzed.
53

Table 14. Chloride content at 96 weeks (kg/m3) for southern exposure specimens.

Steel Designationa

Specimen

Average

Standard

1 2 3 4 5 6 Deviation

Controls 

Conv.-45 10.65 13.16 7.09 8.51 8.08 9.01 9.42 2.18

Conv.2-45 4.53 3.88 6.02 4.81 1.09

Conv.-35 5.96 8.31 5.74 6.67 1.43

ECR-4h-45 6.92 6.83 9.42 8.15 7.79 6.13 7.54 1.17

ECR-10h-45 12.38 13.31 13.34 13.01 0.55

ECR-10h-35 5.96 8.31 5.74 6.67 1.43

Epoxies with increased adhesion

ECR(Chromate)-4h-45 13.14 15.98 13.74 14.29 1.50

ECR(Chromate)-10h-45 11.34 19.49 9.24 13.35 5.42

ECR(DuPont)-4h-45 12.82 17.49 10.98 13.76 3.36

ECR(DuPont)-10h-45 14.46 15.64 10.74 13.61 2.56

ECR(Valspar)-4h-45 14.34 13.39 23.93 17.22 5.83

ECR(Valspar)-10h-45 17.71 18.79 8.12 14.87 5.88

Corrosion inhibitors in concrete

Conv.2(DCI)-45 4.73 8.87 8.00 12.11 3.67

Conv.2(RH)-45 4.43 3.97 4.47 7.22 0.47

Conv.2(HY)-45 3.13 2.45 3.23 4.94 0.72

ECR(DCI)-4h-45 † † † – –

ECR(DCI)-10h-45 † † † – –

ECR(DCI)-10h-35 7.97 4.53 2.45 4.98 2.79

ECR(RH)-4h-45 3.74 7.76 5.88 5.79 2.01

ECR(RH)-10h-45 7.74 4.99 6.49 6.41 1.38

ECR(RH)-10h-35 1.56 2.94 3.73 2.74 1.10

ECR(HY)-4h-45 2.76 3.04 4.74 3.51 1.07

ECR(HY)-10h-45 1.78 2.89 3.73 2.80 0.98

ECR(HY)-10h-35 0.74 1.61 2.23 1.53 0.75

ECR(primer/Ca(NO2)2)-4h-45 9.25 9.93 10.25 9.81 0.51

ECR(primer/Ca(NO2)2)-10h-45 9.83 9.19 11.53 10.18 1.21

ECR(primer/Ca(NO2)2)-10h-35 1.69 2.81 2.73 2.41 0.62

Epoxies with increased adhesion plus calcium nitrite in concrete

ECR(Chromate)-DCI-4h-45 7.86 6.42 7.44 7.24 0.74

ECR(DuPont)-DCI-4h-45 7.95 6.06 8.35 7.45 1.23

ECR(Valspar)-DCI-4h-45 8.35 4.93 8.19 7.16 1.93

Bars with multiple coatings

MC(both layers penetrated)-4h-45 11.13 10.22 11.76 11.04 0.77

MC(both layers penetrated)-10h-45 12.76 12.56 12.79 12.70 0.12

MC(only epoxy penetrated)-4h-45 8.85 15.37 9.84 11.35 3.52

MC(only epoxy penetrated)-10h-45 11.62 13.23 11.21 12.02 1.07

1 kg/m3 =1.69 lb/yd3

† Information not available.

– No standard deviation.

Blank cells indicate no specimen tested.

a See table 12 for abbreviation definitions.
54

The chloride contents at corrosion initiation, 0.77 and 0.88 kg/m3 (1.30 and 1.48 lb/yd3), are within

the expected range of 0.60 to 1.20 kg/m3 (1.0 to 2.0 lb/yd3) for conventional steel cast in concrete 

with w/c of 0.45 and somewhat higher, 1.69 kg/m3 (2.85 lb/yd3

), in concrete with w/c of 0.35. 

With the notable exception of bars cast in concrete containing the corrosion inhibitor HycreteTM

(discussed later in this section), chloride contents at corrosion initiation for epoxy-coated bars and 

conventional bars cast in concrete containing a corrosion inhibitor are above, and in most cases 

well above, 1.20 kg/m3 (2.0 lb/yd3

). The high value for epoxy-coated bars again emphasizes the 

effects of local variations in chloride content near damaged areas on epoxy-coated bars.

The chloride contents at 96 weeks for concretes without corrosion inhibitors with w/c of 0.45 

range from 4.8 to 17.2 kg/m3 (8.1 to 29.0 lb/yd3); with just one exception (ECR-4h-45), these 

values exceed 11 kg/m3 (18.5 lb/yd3) only for specimens containing bars coated with epoxies 

with increased adhesion and bars with multiple coatings. The chloride contents at 96 weeks for 

concretes with corrosion inhibitors range from 2.4 to 10.1 kg/m3 (4.1 to 17.1 lb/yd3

). As observed 

in earlier studies, the chloride values exhibit considerable scatter within individual specimens as 

well as from specimen to specimen, with the latter demonstrated in the tables.(50)

The variation in chloride contents and corrosion performance observed in these tests provides 

insight into the variability in corrosion performance observed in the field, where bridge decks 

reinforced with uncoated bars have provided service lives that range from 4 to 40 years for

bridges in the same environment. That variability may be due to differences in concrete quality, 

both local and global, which can significantly affect the rate of chloride penetration. 

Average corrosion rates for the southern exposure specimens, which are based on losses after 

corrosion has initiated, are summarized in table 15. For bars without coatings, the corrosion rates 

are expressed in terms of the total bar area, and for bars with coatings, the corrosion rates are 

expressed in terms of the area exposed at holes through the coating. As noted in chapter 2, there 

are a number of specimens with epoxy-coated bars for which no corrosion was observed, meaning 

that the specimens did not exhibit a measureable corrosion rate over time. This may be true even 

though a net corrosion loss was recorded (see table 11 and table 12). 
55

Table 15. Average corrosion rate (μm/year) based on losses after corrosion initiation

for southern exposure specimens.

Bars Without Coatings—Corrosion Rate Based on Total Area

Steel Designationa

Specimen

Average

Standard

1 2 3 4 5 6 Deviation

Controls

Conv.-45 5.35 4.41 5.10 6.04 5.82 7.40 5.69 1.01

Conv.2-45 10.7 9.74 10.0 10.1 0.49

Conv.-35 5.99 8.68 1.61 5.43 3.57

Corrosion inhibitors in concrete

Conv.2(DCI)-45 7.81 5.11 7.09 6.67 1.40

Conv.2(RH)-45 2.57 2.60 3.56 2.91 0.56

Conv.2(HY)-45 0.791 1.03 1.92 1.25 0.60

Bars With Coatings—Corrosion Rate Based on Exposed Area

Steel Designation

4 holes 10 holes

Average

Standard

1 2 3 1 2 3 Deviation

Controls

ECR-45 13.6 b b 5.98 18.4 12.710.43 5.32 6.74c 5.09c bc

ECR-35 1.49 b 2.35 1.92 0.61

Epoxies with increased adhesion

ECR(Chromate) b 13.0 18.1 1.18 11.6 20.5 12.9 7.48

ECR(DuPont) 13.8 24.3 b 4.72 7.79 11.2 12.4 7.51

ECR(Valspar) 15.5 5.91 44.0 12.3 6.52 17.4 16.9 14.0

Corrosion inhibitors in concrete

ECR(DCI)-45 b 9.36 b b 11.8 2.33 7.81 4.90

ECR(DCI)-35 2.32 b 1.16 1.74 0.82

ECR(RH)-45 b b 5.94 b 11.3 b 8.63 3.80

ECR(RH)-35 b 0.558 b 0.558 -

ECR(HY)-45 b b b b b 0.674 0.674 -

ECR(HY)-35 1.08 b b 1.080 -

ECR(primer/Ca(NO2)2)-45 b 3.66 22.0 6.56 24.4 6.39 12.6 9.79

ECR(primer/Ca(NO2)2)-35 b 1.41 b 1.41 -

Epoxies with increased adhesion plus calcium nitrite in concrete

ECR(Chromate)-DCI-45 b b 10.3 10.3 -

ECR(DuPont)-DCI-45 b b b b -

ECR(Valspar)-DCI-45 b b 5.97 5.97 -

MC 5.55d 22.7d 36.9d 6.57d 23.1d 7.52d31.6 26.2

19.6e 29.2e 13.1e 65.9e 80.7e 68.8e

1 μm = 0.0394 mil

– No standard deviation.

Blank cells indicate no specimen tested.

a See table 1 for abbreviation definitions. 35 = concrete with w/c of 0.35, 45 = concrete with w/c of 0.45. b No corrosion observed. c Specimens 4, 5, and 6. 

d Both layers penetrated. 

e Only epoxy penetrated.
56

In the following sections, a description of the results for the southern exposure tests of the control 

specimens is followed by those for the multiple corrosion-protection systems. The chapter also covers 

a study of uncoated conventional reinforcement cast in concrete containing corrosion inhibitors.

Control Specimens

The control specimens for this study consisted of conventional steel cast in concrete with w/c ratios 

of 0.45 (Conv.-45) and 0.35 (Conv.-35), conventional ECR cast in concrete with w/c of 0.45 with

4 holes (ECR-4h-45) or 10 holes (ECR-10h-45) through the epoxy, and conventional ECR cast 

in concrete with w/c of 0.35 with 10 holes through the epoxy (ECR-10h-35). The corrosion rates 

based on total area in contact with the concrete are shown in figure 48. The figure shows that, as 

seen in the rapid macrocell test, corrosion proceeds at a much higher rate for uncoated than for 

coated reinforcement, with the latter corroding at well below 1 percent of the rate of the former, 

a rate that is about equal to the ratio of the area exposed at the holes to the total area of the bars. 

The lower w/c ratio provides additional protection to conventional steel, with significant corrosion 

starting at about 48 weeks for the concrete with w/c of 0.35, compared to 24 weeks for the concrete

with w/c of 0.45. The corrosion rate for the Conv.-45 specimens reached a maximum of 7.2 μm/year

(0.28 mil/year) at 94 weeks, but generally varied between 6 and 7 μm/year (0.24 and 0.28 mil/year)

during the final 24 weeks of the test. The corrosion rate of the Conv.-35 specimens reached a 

maximum of approximately 4.2 μm/year (0.17 mil/year) at 87 weeks while exhibiting a nearly 

constant rate between 3.9 and 4.2 μm/year (0.15 and 0.17 mil/year) between week 83 and the end 

of the test.

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

0 12 24 36 48 60 72 84 96

CORROSION RATE, μm/year 

TIME, weeks

Conv.-45 Conv.-35 ECR-4h-45 ECR-10h-45 ECR-10h-35

1 μm = 0.0394 mil

Figure 48. Graph. Southern exposure test, average corrosion rates based on total area 

for conventional reinforcement and ECR.

The average total corrosion losses for the systems are plotted in figure 49 and figure 50, which, 

like figure 48, show the effect of the lower w/c ratio in delaying corrosion initiation and lowering 
57

corrosion losses. The average losses at the end of the tests equaled 7.1 and 2.1 μm (0.28 and 

0.083 mil) for the Conv.-45 and Conv.-35 specimens, respectively. 

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

0 12 24 36 48 60 72 84 96

CORROSION LOSS, μm 

TIME (weeks)

Conv.-45 Conv.-35 ECR-4h-45 ECR-10h-45 ECR-10h-35

1 μm = 0.0394 mil

Figure 49. Graph. Southern exposure test, average corrosion loss based on total area 

for conventional reinforcement and ECR.

-1.0

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

0 12 24 36 48 60 72 84 96

CORROSION LOSS, μm

TIME (weeks)

ECR-4h-45 ECR-10h-45 ECR-10h-35

1 μm = 0.0394 mil

Figure 50. Graph. Southern exposure test, average corrosion loss based on area exposed at 

holes through coating for ECR.
58

The corrosion losses for the epoxy-coated bars based on the area exposed at the holes through 

the coating are shown in figure 50. As for the conventional steel, the lower w/c ratio provided 

additional corrosion protection, with losses at 96 weeks for the ECR-10h-35 specimens equal to 

about 50 percent of the losses for the ECR-10h-45 specimens. The losses based on exposed area 

for the ECR-4h-45 specimens are considerably higher (7.2 μm (0.28 mil)), more than twice those 

based on exposed area for the ECR-10h-45 specimens. The losses based on total area, however, 

are nearly identical at 0.015 and 0.017 μm (0.00059 and 0.00067 mil) for the specimens with 

4 and 10 holes, respectively. As shown in table 11, table 12, and table 15, the scatter for the 

conventional ECR specimens is quite high, as it is for a number of other systems. As a result, the 

difference in corrosion between ECR-4h-45 and ECR-10h-45 is not statistically significant. The 

difference is statistically significant between ECR-10h-45 and ECR-10h-35. The negative corrosion 

exhibited between weeks 12 and 36 for the ECR-4h-45 specimens is the result of measurements 

of very low currents caused by low levels of oxidation on the exposed regions of the four bottom 

bars before corrosion initiates on the two top bars, resulting in current flow that makes the bottom

bars appear to be anodes. Once chloride reaches the top bars, the nature of the corrosion reverses, 

which occurs at about week 30 based on the average corrosion loss versus time relationship shown

in figure 50. The flat regions on the corrosion loss curves may be the result of corrosion products 

temporarily blocking the small exposed areas on the bars.

The corrosion potentials for the top and bottom mats of steel are shown in figure 51 and figure 52,

respectively. For the top mat, the average corrosion potential for the ECR-10h-35 bars remained

more positive than -0.350 V with respect to a CSE throughout the test, indicating a low probability 

of corrosion. The corrosion potentials dropped below -0.350 V at weeks 26, 51, 49, and 52 for 

Conv.-45, Conv.-35, ECR-4h-45, and ECR-10h-45, respectively. 

-0.80

-0.60

-0.40

-0.20

0.00

0 12 24 36 48 60 72 84 96

CORROSION POTENTIAL, V 

TIME, weeks

Conv.-45 Conv.-35 ECR-4h-45 ECR-10h-45 ECR-10h-35

Figure 51. Graph. Southern exposure test, corrosion potential of top mat for conventional 

reinforcement and ECR.
59

-0.80

-0.60

-0.40

-0.20

0.00

0 12 24 36 48 60 72 84 96

CORROSION POTENTIAL, V 

TIME, weeks

Conv.-45 Conv.-35 ECR-4h-45 ECR-10h-45 ECR-10h-35

Figure 52. Graph. Southern exposure test, corrosion potential of bottom mat for 

conventional reinforcement and ECR.

The corrosion potentials for the bottom mat of reinforcement remained more positive than -0.350 V

with respect to a CSE throughout the test for Conv.-35 and ECR-10h-35. The potential dropped

below -0.350 V at weeks 33, 50, and 56 for Conv.-45, ECR-4h-45 and ECR-10h-45, respectively, 

indicating that chlorides penetrated to the level of the bottom mat for those specimens. 

The values of mat-to-mat resistance for the five systems are shown in figure 53, which illustrates 

a key difference between systems with coated and uncoated bars. The resistance between the top 

and bottom steel bars was similar for Conv.-45 and Conv.-35 throughout the 96-week test period, 

ranging from low values of 126 and 166 ohms, respectively, at week 1 to high values of 588 ohms

at week 85 for Conv.-45 and 586 ohms at week 72 for Conv.-35, with values rising for about the 

first 60 weeks and then leveling off. The values for the epoxy-coated bars also rose early in the 

test, leveling off somewhat earlier—between 42 and 50 weeks. The major difference from the 

uncoated bars, however, is the much higher resistance provided by the epoxy coating, with initial 

readings of 2,099, 742, and 924 ohms for ECR-4h-45, ECR-10h-45, and ECR-10h-35, respectively.

The respective high resistance values were 13,247 ohms at week 36, 6,710 ohms at week 51, and 

5,989 ohms at week 82. As observed for the uncoated bars, w/c ratio had little effect on the matto-mat resistance and the number of openings in the coating had a major effect, with the bars 

with 4 holes in the coating exhibiting more than twice the mat-to-mat resistance as those with 

10 holes. A high mat-to-mat resistance represents a high resistance to ionic current and 

represents a major advantage to coated reinforcement. 
60

0

2000

4000

6000

8000

10000

12000

14000

0 12 24 36 48 60 72 84 96

MAT-TO-MAT RESISTANCE, ohms

TIME, weeks

Conv.-45 Conv.-35 ECR-4h-45 ECR-10h-45 ECR-10h-35

Figure 53. Graph. Southern exposure test, mat-to-mat resistance for conventional

reinforcement and ECR.

Epoxies with Improved Adhesion

Comparisons of the corrosion losses for conventional ECR-4h-45 and ECR-10h-45 and the 

corresponding specimens of ECR(Chromate), ECR(DuPont), and ECR(Valspar) based on total 

and exposed area are shown in figure 54 and figure 55, respectively. The figures demonstrate 

that increased adhesion between the epoxy and reinforcing steel provides no benefits under the 

exposure conditions provided by these tests. In fact, by the end of tests, all of the bars with the 

higher adhesion epoxies exhibited greater average corrosion losses on the exposed area than the 

conventional ECR specimens. At 96 weeks, the average chloride contents of the specimens 

containing bars with the higher adhesion epoxies ranged from 13.6 to 17.2 kg/m3 (22.9 to 

29.0 lb/yd3) compared with about 7.5 kg/m3 (12.7 lb/yd3) for the specimens containing 

conventional epoxy-coated steel with 4 holes through the epoxy and for the specimens 

containing conventional epoxy-coated reinforcement with 10 holes through the coating. The 

variation in corrosion losses exhibited in both figures, however, is likely due to variations in 

the chloride content along the surface of the individual bars. As shown in table 11 and table 12, 

the variability in test results can often be explained by a very high reading on a single specimen. 

This is true for ECR(Chromate)-4h-45, ECR(Chromate)-10h-45, ECR(Valspar)-4h-45, and 

ECR(Valspar)-10h-45. As shown in figure 56, a plot of corrosion potential for the top mats, the 

systems exhibited average corrosion potential below -0.350 V by 45 weeks with the exception 

of conventional ECR (ECR-4h-45), which remained above this value until week 50. 
61

-2

0

2

4

6

8

10

12

14

16

18

0 12 24 36 48 60 72 84 96

CORROSION LOSS, μm

TIME (weeks)

ECR-4h-45 ECR(Chromate)-4h-45 ECR(DuPont)-4h-45 ECR(Valspar)-4h-45

1 μm = 0.0394 mil

Figure 54. Graph. Southern exposure test, corrosion losses based on total area 

for conventional ECR and increased-adhesion ECR.

0

3

6

9

12

15

0 12 24 36 48 60 72 84 96

CORROSION LOSS, μm

TIME (weeks)

ECR-10h-45 ECR(Chromate)-10h-45 ECR(DuPont)-10h-45 ECR(Valspar)-10h-45

1 μm = 0.0394 mil

Figure 55. Graph. Southern exposure test, corrosion losses based on area exposed

at holes through coating for conventional ECR and increased-adhesion ECR. 
62

-0.80

-0.60

-0.40

-0.20

0.00

0 12 24 36 48 60 72 84 96

CORROSION POTENTIAL, V

TIME, weeks

ECR-4h-45 ECR(Chromate)-4h-45 ECR(DuPont)-4h-45 ECR(Valspar)-4h-45

Figure 56. Graph. Southern exposure test, corrosion potential of top mat for conventional 

ECR and increased-adhesion ECR.

ECR Used in Conjunction with Corrosion Inhibitors

Corrosion losses based on exposed area for conventional ECR cast in concrete without a 

corrosion inhibitor and cast in concrete with calcium nitrite, Rheocrete® 222+, and HycreteTM

are shown in figure 57, figure 58, and figure 59 for bars with 4 holes in the epoxy and concrete 

with w/c of 0.45, bars with 10 holes through the epoxy in concrete with w/c of 0.45, and bars 

with 10 holes cast in concrete with w/c of 0.35, respectively. The figures also include the results 

for conventional ECR with a primer containing microencapsulated calcium nitrite. 
63

-1

0

1

2

3

4

5

6

7

8

0 12 24 36 48 60 72 84 96

CORROSION LOSS, μm

TIME (weeks)

ECR-4h-45 ECR(DCI)-4h-45 ECR(RH)-4h-45

ECR(HY)-4h-45 ECR(primer/Ca(NO2)2)-4h-45

1 μm = 0.0394 mil

Figure 57. Graph. Southern exposure test, corrosion losses based on area exposed 

at holes through coating for conventional ECR and ECR with inhibitors with bars 

containing four holes and concrete with w/c = 0.45.

-4

0

4

8

12

16

0 12 24 36 48 60 72 84 96

CORROSION LOSS, μm

TIME (weeks)

ECR-10h-45 ECR(DCI)-10h-45 ECR(RH)-10h-45

ECR(HY)-10h-45 ECR(primer/Ca(NO2)2)-10h-45

1 μm = 0.0394 mil

Figure 58. Graph. Southern exposure test, corrosion losses based on area exposed 

at holes through coating for conventional ECR and ECR with inhibitors with bars 

containing 10 holes and concrete with w/c = 0.45.
64

0.00

0.50

1.00

1.50

2.00

2.50

3.00

0 12 24 36 48 60 72 84 96

CORROSION LOSS, μm

TIME (weeks)

ECR-10h-35 ECR(DCI)-10h-35 ECR(RH)-10h-35

ECR(HY)-10h-35 ECR(primer/Ca(NO2)2)-10h-35

1 μm = 0.0394 mil

Figure 59. Graph. Southern exposure test, corrosion losses based on area exposed 

at holes through coating for conventional ECR and ECR with inhibitors with bars 

containing 10 holes and concrete with w/c = 0.35. 

Figure 57 through figure 59 and table 11 through table 15 show that corrosion inhibitors improve the

corrosion performance of ECR in uncracked concrete. They also show that a lower w/c ratio, which 

results in a lower chloride level in the concrete due to reduced permeability, enhances the performance 

of the corrosion inhibitors. This observation is especially apparent for ECR(primer/Ca(NO2)2). 

The large differences observed in this case are likely due to the limited quantity of nitrite, which is 

available only from the exposed primer where the epoxy is penetrated. This limited quantity of nitrite

is consumed in a shorter period of time in concrete with a w/c ratio of 0.45 than in concrete with a 

w/c of 0.35 due to the higher chloride concentration at the bar surface for the higher w/c ratio 

concrete. In contrast, the quantity of nitrite available was considerably higher for all ECR(DCI) 

specimens because the calcium nitrite was added to the concrete. Overall, specimens containing 

a corrosion inhibitor exhibited the same or less corrosion than exhibited by the conventional 

ECR specimens with the single exception of the ECR(primer/Ca(NO2)2)-10h-45 specimens.

The corrosion potentials exhibited by the top mats for the test specimens are shown in figure 60

through figure 62. The figures indicate that most of the specimens containing a corrosion 

inhibitor experienced corrosion potentials more negative than -0.350 V with respect to a 

CSE during the course of the test. The exceptions were ECR(HY)-4h-45, ER(HY)-10h-45, 

and ECR(primer/Ca(NO2)2)-10h-35. 
65

-0.80

-0.60

-0.40

-0.20

0.00

0 12 24 36 48 60 72 84 96

CORROSION POTENTIAL, V

TIME (weeks)

ECR-4h-45 ECR(DCI)-4h-45 ECR(RH)-4h-45

ECR(HY)-4h-45 ECR(primer/Ca(NO2)2)-4h-45

Figure 60. Graph. Southern exposure test, corrosion potential of top mat for conventional 

ECR with and without corrosion inhibitor with bars containing four holes and concrete 

with w/c = 0.45.

-0.80

-0.60

-0.40

-0.20

0.00

0 12 24 36 48 60 72 84 96

CORROSION POTENTIAL, V

TIME (weeks)

ECR-10h-45 ECR(DCI)-10h-45 ECR(RH)-10h-45

ECR(HY)-10h-45 ECR(primer/Ca(NO2)2)-10h-45

Figure 61. Graph. Southern exposure test, corrosion potential of top mat for conventional 

ECR with and without corrosion inhibitor with bars containing 10 holes and concrete 

with w/c = 0.45.
66

-0.80

-0.60

-0.40

-0.20

0.00

0 12 24 36 48 60 72 84 96

CORROSION POTENTIAL, V

TIME (weeks)

ECR-10h-35 ECR(DCI)-10h-35 ECR(RH)-10h-35

ECR(HY)-10h-35 ECR(primer/Ca(NO2)2)-10h-35

Figure 62. Graph. Southern exposure test, corrosion potential of top mat for conventional 

ECR with and without corrosion inhibitor with bars containing 10 holes and concrete 

with w/c = 0.35.

Epoxy Coating with Improved Adhesion Cast in Concrete Containing Calcium Nitrite

A limited number of specimens (four holes in the epoxy with w/c of 0.45) were tested for each of 

the three epoxies with improved adhesion cast in concrete containing calcium nitrite. As observed

in the other tests with concrete containing corrosion inhibitors, the bars with improved adhesion 

exhibited improved corrosion resistance in the presence of calcium nitrite, as shown in figure 63,

and exhibited improved corrosion performance compared to conventional ECR in concrete with 

calcium nitrite with the exception of ECR(Valspar) after 60 weeks. At the conclusion of the tests, 

losses based on the area exposed at the holes through the epoxy ranged from 0.28 μm (0.011 mil)

for ECR(DuPont)-DCI-4h-45 to 8.62 μm (0.339 mil) for ECR(Valspar)-DCI-4h-45. The scatter 

in the data shown in table 12 indicates that these values did not differ in a statistically meaningful 

way from each other. The corrosion potentials for the top mats in these tests are shown in figure 

64. The average corrosion potential dropped below -0.350 V by the end of the test in all cases 

with the exception of ECR(Valspar)-DCI-4h-45, which exhibited the highest corrosion losses in 

spite of its relatively more positive corrosion potential. 
67

-4

-2

0

2

4

6

8

10

0 12 24 36 48 60 72 84 96

CORROSION LOSS, μm

TIME (weeks)

ECR-4h-45 ECR(DCI)-4h-45 ECR(Chromate)-DCI-4h-45

ECR(DuPont)-DCI-4h-45 ECR(Valspar)-DCI-4h-45

1 μm = 0.0394 mil

Figure 63. Graph. Southern exposure test, average corrosion losses based on area exposed 

at holes through coating for conventional ECR and ECR with and without increased 

adhesion and corrosion inhibitor.

-0.80

-0.60

-0.40

-0.20

0.00

0 12 24 36 48 60 72 84 96

CORROSION POTENTIAL, V

TIME (weeks)

ECR-4h-45 ECR(DCI)-4h-45 ECR(Chromate)-DCI

ECR(DuPont)-DCI ECR(Valspar)-DCI

Figure 64. Graph. Southern exposure test, corrosion potential of top mat for conventional ECR 

with and without corrosion inhibitor and increased-adhesion ECR with corrosion inhibitor. 
68

Bars with Multiple Coatings

The corrosion losses for MC bars are compared with those for conventional ECR in figure 65 and 

figure 66 for bars with 4 and 10 holes, respectively. The specimens with MC bars consistently 

exhibited greater corrosion losses than those with conventional ECR. The MC bars with both 

layers penetrated exhibited average corrosion losses on the exposed area of 27.7 μm (1.09 mil)

(for 4 holes) and 115 μm (4.53 mil) (for 10 holes) at the conclusion of the tests compared to 

values of 7.4 and 3.2 μm (0.29 and 0.13 mil) for conventional ECR. The respective values with 

only the epoxy penetrated were 15.9 and 17.4 μm (0.626 and 0.685 mil), as shown in figure 65, 

figure 66, and table 12.

-3

0

3

6

9

12

15

18

21

24

27

30

0 12 24 36 48 60 72 84 96

CORROSION LOSS, μm

TIME (weeks)

ECR-4h-45 MC(both layers penetrated)-4h-45 MC(only epoxy penetrated)-4h-45

1 μm = 0.0394 mil

Figure 65. Graph. Southern exposure test, corrosion loss based on area exposed at holes 

through coating for conventional ECR and MC reinforcement with bars containing four holes. 
69

0

30

60

90

120

150

0 12 24 36 48 60 72 84 96

CORROSION LOSS, μm

TIME (weeks)

ECR-10h-45 MC(both layers penetrated)-10h-45 MC(only epoxy penetrated)-10h-45

1 μm = 0.0394 mil

Figure 66. Graph. Southern exposure test, corrosion loss based on area exposed at holes 

through coating for conventional ECR and MC reinforcement with bars containing 10 holes.

The average corrosion potentials for the top and bottom mat are shown in figure 67 and figure 68

for bars with 4 holes and in figure 69 and figure 70 for bars with 10 holes through the epoxy. The 

top mat corrosion potentials were similar for the cases in which both layers were penetrated and 

in which only the epoxy was penetrated, differing most widely during the first 10–20 weeks of 

the tests. For the top mats, the values were more negative than those for conventional ECR until 

the final 24 weeks of the tests for bars with 4 holes and the final 36 weeks for bars with 10 holes 

through the epoxy coating. The values for the MC bars ranged between -0.200 and -0.500 V 

between the beginning of the tests and week 10, stabilizing between -0.500 and -0.600 V after 

week 20. The autopsy results (described later) show that both the zinc coating and the underlying 

conventional reinforcement participated in corrosion by the end of the tests. 
70

-0.80

-0.60

-0.40

-0.20

0.00

0 12 24 36 48 60 72 84 96

CORROSION POTENTIAL, V

TIME (weeks)

ECR-4h-45 MC(both layers penetrated)-4h-45 MC(only epoxy penetrated)-4h-45

Figure 67. Graph. Southern exposure test, corrosion potential of top mat 

for conventional ECR and MC reinforcement with bars containing four holes.

-0.80

-0.60

-0.40

-0.20

0.00

0 12 24 36 48 60 72 84 96

CORROSION POTENTIAL, V

TIME (weeks)

ECR-4h-45 MC(both layers penetrated)-4h-45 MC(only epoxy penetrated)-4h-45

Figure 68. Graph. Southern exposure test, corrosion potential of bottom mat 

for conventional ECR and MC reinforcement with bars containing four holes. 
71

-0.80

-0.60

-0.40

-0.20

0.00

0 12 24 36 48 60 72 84 96

CORROSION POTENTIAL, V

TIME (weeks)

ECR-10h-45 MC(both layers penetrated)-10h-45 MC(only epoxy penetrated)-10h-45

Figure 69. Graph. Southern exposure test, corrosion potential of top mat 

for conventional ECR and MC reinforcement with bars containing 10 holes.

-0.80

-0.60

-0.40

-0.20

0.00

0 12 24 36 48 60 72 84 96

CORROSION POTENTIAL, V .

TIME (weeks)

ECR-10h-45 MC(both layers penetrated)-10h-45 MC(only epoxy penetrated)-10h-45

Figure 70. Graph. Southern exposure test, corrosion potential of bottom mat

for conventional ECR and MC reinforcement with bars containing 10 holes.

Conventional Steel with Corrosion Inhibitors

Although the corrosion inhibitors used in this study have been evaluated previously, it became 

clear as the study proceeded that the high level of corrosion protection provided by even damaged 

epoxy coatings made it difficult to distinguish between the performance of the three inhibitors.(51–56)
72

With that in mind, the inhibitors were evaluated using southern exposure, cracked beam, and 

corrosion initiation tests containing uncoated conventional reinforcement to gain an improved 

understanding of their performance using the same test procedures as used to evaluate the 

multiple corrosion-protection systems in the this study. The properties of the concrete and the 

results of the southern exposure and corrosion initiation tests are reported here, and the results of 

the cracked beam tests are reported with the results of the other cracked beam tests. 

The properties of the concrete in the corrosion initiation beam specimens are summarized in

table 16. The somewhat lower strength exhibited by the concrete containing Rheocrete® 222+

, 

30.4 MPa (4,410 psi), and the greatly reduced strength of the concrete containing HycreteTM, 

14.2 MPa (2,060 psi), compared to the strengths of concrete without a corrosion inhibitor and 

concrete containing calcium nitrite, 35.8 and 40.0 MPa (5,190 and 5,810 psi), respectively, were 

also observed in the field test specimens (see table 7).

Table 16. Concrete properties for southern exposure and cracked beam specimens with 

uncoated bars and corrosion inhibitor in the concrete.

Specimen 

Designation

Slump,

mm

Air Content,

percent

Compressive 

Strengtha,

MPa

Standard 

Deviation,

MPa

Coefficient of 

Variation

Conv.2 55 5.25 35.8 2.35 0.07

Conv.2(DCI) 95 5 40.0 3.65 0.09

Conv.2(RH) 50 4 30.4 4.45 0.15

Conv.2(HY) 90 5.25 14.2 1.93 0.14

1 mm = 0.039 inches

1 MPa = 145 psi

a Average of eight cylinders cured in saturated limewater.

The southern exposure tests were performed using the second heat of conventional steel cast in 

concrete with a w/c ratio of 0.45. Figure 71 compares the corrosion rates of the specimens without 

a corrosion inhibitor with those with concrete containing Rheocrete® 222+

, calcium nitrite, 

and HycreteTM, designated as specimens Conv.2-45, Conv.2(RH)-45, Conv.2(DCI)-45, and 

Conv.2(HY)-45, respectively. The specimens without a corrosion inhibitor exhibited the earliest 

corrosion initiation and highest corrosion rate, which ranged between 8 and 15 μm/year (0.3 and 

0.59 mil/year) from week 26 through the end of the test; the only exception occurred at week 34,

where the Conv.2(DCI)-45 specimens exhibited a higher corrosion rate. The Conv.2(DCI)-45 

specimens exhibited corrosion rates between 3.5 and 9.5 μm/year (0.14 and 0.37 mil/year) after 

week 33, while the Conv.2(RH)-45 and Conv.2(HY)-45 specimens exhibited respective corrosion 

rates of 2 to 4 and 0.5 to 2 μm/year (0.08–0.2 and 0.02–0.08 mil/year) between week 33 and the 

conclusion of the test. The corrosion losses for the specimens are shown in figure 72. At 96 weeks, 

losses of 14.4, 8.4, 3.4, and 1.4 μm (0.567, 0.33, 0.13, and 0.055 mil) were observed for the 

Conv.2-45, Conv.2(RH)-45, Conv.2(DCI)-45, and Conv.2(HY)-45 specimens, respectively. 
73

-2

0

2

4

6

8

10

12

14

16

0 12 24 36 48 60 72 84 96

CORROSION RATE, μm/year

TIME, weeks

Conv.2-45 Conv.2(RH)-45 Conv.2(DCI)-45 Conv.2(HY)-45

1 μm = 0.0394 mil

Figure 71. Graph. Southern exposure test, average corrosion rates based on total area 

for conventional reinforcement in specimens without and with corrosion inhibitors. 

0

2

4

6

8

10

12

14

16

0 12 24 36 48 60 72 84 96

CORROSION LOSS, μm

TIME, weeks

Conv.2-45 Conv.2(RH)-45 Conv.2(DCI)-45 Conv.2(HY)-45

1 μm = 0.0394 mil

Figure 72. Graph. Southern exposure test, average corrosion losses based on total area 

for conventional reinforcement in specimens without and with corrosion inhibitors. 

The average corrosion potentials of the top bars with respect to CSE are shown in figure 73. The 

initially rising corrosion potentials of the top bars for all four systems indicate increasing passivity

through week 14, at which point the specimens without a corrosion inhibitor and those containing 

calcium nitrite began to exhibit progressively more negative potentials, dropping below a value 
74

of -0.350 V at week 24. The Conv.2(RH)-45 and Conv.2(HY)-45 specimens continued to exhibit 

increasing passivity until weeks 23 and 26, respectively. The specimens with Rheocrete® and 

HycreteTM in the concrete exhibited a negative spike in corrosion potential at week 34, which 

may be an aberration in the data. The specimens containing Rheocrete® dropped below a corrosion 

potential of -0.350 V at week 48 and remained there for the balance of the tests. Specimens 

containing HycreteTM dropped below a corrosion potential of -0.350 V in week 48, exhibiting 

corrosion potentials between -0.299 and -0.388 V for the balance of test.

-0.8

-0.6

-0.4

-0.2

0.0

0 12 24 36 48 60 72 84 96

CORROSION POTENTIAL, V

TIME, weeks

Conv.2-45 Conv.2(RH)-45 Conv.2(DCI)-45 Conv.2(HY)-45

Figure 73. Graph. Southern exposure test, corrosion potential of top mat for conventional 

reinforcement in specimens without and with corrosion inhibitors. 

The resistance between the top and bottom mats of steel, or mat-to-mat resistance, was measured 

on a weekly basis for all test specimens in this study. For most specimens, mat-to-mat resistance

is not included in this report but is presented by Draper et al.(49) It is presented for this group of 

specimens because it represents a measure of the ion conductivity of the concrete and provides 

insight into how the inhibitors function. 

The mat-to-mat resistance for the southern exposure specimens is presented in figure 74. It is 

noteworthy that the value of the resistance is nearly identical for the Conv.2-45, Conv.2(RH)-45, 

and Conv.2(DCI)-45 specimens throughout the test period, beginning at approximately 100 ohms,

increasing through week 84 to a peak of approximately 600 ohms (860 ohms for the DCI specimens), 

and then dropping toward values between 300 and 600 ohms by week 96. In contrast, the specimens

containing HycreteTM exhibited progressively higher resistance throughout the test period, reaching 

a maximum value of 2,700 ohms at week 90, with values in excess of 1,175 ohms between weeks 78

and 96. The increase in resistivity from the reduction in concrete permeability provided by 

HycreteTM played a key role in minimizing the macrocell corrosion measured in this test.
75

0

300

600

900

1200

1500

1800

2100

2400

2700

3000

0 12 24 36 48 60 72 84 96

MAT-TO-MAT RESISTANCE, ohms

TIME, weeks

Conv.2-45 Conv.2(RH)-45 Conv.2(DCI)-45 Conv.2(HY)-45

Figure 74. Graph. Southern exposure test, mat-to-mat resistance for conventional 

reinforcement in specimens without and with corrosion inhibitors. 

Corrosion initiation tests are used to obtain a measure of the critical chloride corrosion threshold

for corrosion-protection systems. The results of the tests for bare bars cast in concrete containing 

corrosion inhibitors are summarized in table 17. The initial tests were performed with the first 

heat of conventional steel (Conv.) in specimens containing Rheocrete®, DCI® S, and HycreteTM. 

Over the course of those tests, the values for the critical chloride threshold for the specimens 

containing HycreteTM were observed to be exceptionally low, averaging 0.43 kg/m3 (0.72 lb/yd3), a

value below that observed for conventional steel, which typically ranged from 0.60 to 1.20 kg/m3

(1 to 2 lb/yd3). To follow up, a second series of specimens was evaluated using Conv.2 steel cast 

in concrete without and with HycreteTM. The critical chloride corrosion threshold observed in the 

second series for HycreteTM (Conv.2(HY)), 0.51 kg/m3 (0.86 lb/yd3), closely matches the value 

in the initial series. In addition to corrosion thresholds, table 17 shows the individual and average

values of time to initiation and the corrosion rate and corrosion potential during the week in which

corrosion was initially observed, along with the standard deviations for corrosion threshold. The 

values of standard deviation and coefficient of variation for each specimen represent the variation

observed for individual samples within the specimen. The values of standard deviation and 

coefficient of variation for each group of specimens were calculated based on the individual 

specimen averages. This is why the coefficient of variation is consistently greater for the 

individual samples than for each group of samples.
76

Table 17. Corrosion initiation results for bare bars in concrete without and 

with corrosion inhibitors (values at time of initiation).

Specimena

Time to

Initiation, 

weeks

Rate,

μm/year

Potentiala

,

V

Averageb,

kg/m3

Standard

Deviation,

kg/m3

Conv.2-1 16 1.50 -0.383 1.23 1.09

Conv.2-2 16 0.404 -0.339 0.88 0.67

Conv.2-3 28 0.922 -0.300 0.42 0.80

Conv.2-4 16 0.869 -0.309 1.45 1.44

Conv.2-5 – – – – –

Conv.2-6 23 0.389 -0.229 0.54 0.41

Average 19.8 0.90 0.44

Conv.(DCI)-1 43 0.945 -0.337 2.05 0.56

Conv.(DCI)-2 31 0.297 -0.293 1.59 0.40

Conv.(DCI)-3 20 1.166 -0.344 1.39 0.65

Conv.(DCI)-4 23 0.815 -0.331 1.63 0.33

Conv.(DCI)-5 25 0.511 -0.362 2.10 0.66

Conv.(DCI)-6 17 1.684 -0.376 1.19 0.38

Average 26.5 1.66 0.36

Conv.(RH)-1 16 0.320 -0.301 1.27 0.65

Conv.(RH)-2 14 2.614 -0.421 0.57 0.39

Conv.(RH)-3 20 0.853 -0.357 0.94 0.41

Conv.(RH)-4 21 0.800 -0.397 1.23 0.54

Conv.(RH)-5 26 0.953 -0.404 2.13 1.04

Conv.(RH)-6 20 0.979 -0.457 1.77 0.79

Average 19.5 1.32 0.56

Conv.(HY)-1 16 0.549 -0.320 0.33 0.26

Conv.(HY)-2 26 1.349 -0.391 0.24 0.08

Conv.(HY)-3 48 0.343 -0.314 0.54 0.74

Conv.(HY)-4 12 0.549 -0.348 0.41 0.30

Conv.(HY)-5 52 1.158 -0.344 0.71 0.50

Conv.(HY)-6 17 0.457 -0.299 0.37 0.32

Average 28.5 0.43 0.17

Conv.2(HY)-1 58 0.137 -0.218 0.67 0.43

Conv.2(HY)-2 – – – – –

Conv.2(HY)-3 68 0.899 -0.21 0.47 0.35

Conv.2(HY)-4 24 0.823 -0.294 0.34 0.25

Conv.2(HY)-5 42 2.87 -0.222 0.25 0.21

Conv.2(HY)-6 50 3.76 -0.362 0.69 0.33

Average 48.4 0.51 0.31

1 μm = 0.0394 mil

1 kg/m3 =1.69 lb/yd3

– Initiation was missed. a With respect to an SCE. b Individual specimen averages and standard deviations based on 20 samples per specimen. Overall 

averages and standard deviations based on specimen averages. 
77

The specimens containing HycreteTM exhibited the longest time to initiation, 28.5 and 48.4 weeks

for the Conv.(HY) and Conv.2(HY) specimens, respectively, followed by the Conv.(DCI), 

Conv.(RH), and Conv.2 specimens at 26.5, 19.5, and 19.8 weeks, respectively. The conventional 

steel specimens exhibited an average critical chloride corrosion threshold of 0.90 kg/m3 (1.52 lb/yd3),

matching earlier results at the University of Kansas using similar specimens but different heats 

of conventional steel.(50) The specimens containing Rheocrete® and DCI® S exhibited critical 

corrosion thresholds of 1.32 and 1.66 kg/m3 (2.22 and 2.80 lb/yd3), respectively. 

To explain the very low corrosion threshold for the conventional steel in concrete containing 

HycreteTM, O’Reilly et al. used a pore press to extract pore solution from cement paste specimens 

without inhibitors and with each of the inhibitors used in this study.(44) As described in chapter 2, 

they observed a marked increase in sulfate content at both 1 and 7 days for cement pastes containing 

HycreteTM and at 7 days for pastes containing Rheocrete®. Along with chlorides, sulfates can 

reduce the passivity of reinforcing steel and may explain the very low critical chloride corrosion 

threshold for HycreteTM and the observation that Rheocrete® produces a corrosion threshold 

below that provided by calcium nitrite.(57)

Cracked Beam Tests

The performance of the corrosion-protection systems in the cracked beam tests is presented in this

section. The losses at 96 weeks based on total and exposed area on the ECR bars are summarized 

in table 18 and table 19. The average corrosion rates after corrosion initiation are summarized in 

table 20. Unlike the corrosion rates for the southern exposure specimens shown in table 15, 

corrosion was observed for all but one specimen, specimen 1 for ECR(HY)-45 with 10 holes 

through the epoxy. 
78

Table 18. Corrosion loss at 96 weeks (μm) for cracked beam specimens based on total area.

Steel Designationa

Specimen

Average

Standard

1 2 3 4 5 6 Deviation

Controls 

Conv.-45 17.56 8.53 7.29 15.40 15.16 14.46 13.06 4.15

Conv.2-45 44.39 22.74 22.62 29.92 12.54

Conv.-35 11.48 6.02 7.51 8.34 2.82

ECR-4h-45 0.04 0.07 0.02 0.07 0.04 0.01 0.04 0.02

ECR-10h-45 0.026 0.083 0.032 0.047 0.031

ECR-10h-35 0.132 0.124 0.162 0.139 0.020

Epoxies with increased adhesion

ECR(Chromate)-4h-45 0.066 0.058 0.099 0.074 0.022

ECR(Chromate)-10h-45 0.026 0.140 0.480 0.216 0.236

ECR(DuPont)-4h-45 0.124 0.137 0.054 0.105 0.045

ECR(DuPont)-10h-45 0.128 0.127 0.297 0.184 0.098

ECR(Valspar)-4h-45 0.172 0.071 0.009 0.084 0.082

ECR(Valspar)-10h-45 0.081 0.039 0.254 0.125 0.114

Corrosion inhibitors in concrete

Conv.2(DCI)-45 32.09 26.39 21.56 26.68 5.273

Conv.2(RH)-45 24.58 18.26 22.63 21.82 3.236

Conv.2(HY)-45 8.635 6.314 7.845 7.60 1.180

ECR(DCI)-4h-45 0.025 0.048 0.007 0.026 0.021

ECR(DCI)-10h-45 0.044 0.155 0.039 0.079 0.065

ECR(DCI)-10h-35 0.124 0.095 0.449 0.223 0.197

ECR(RH)-4h-45 0.062 0.314 0.047 0.141 0.150

ECR(RH)-10h-45 0.240 0.134 0.138 0.171 0.060

ECR(RH)-10h-35 0.096 0.302 0.136 0.178 0.109

ECR(HY)-4h-45 0.010 0.005 0.092 0.036 0.049

ECR(HY)-10h-45 0.002 0.116 0.062 0.060 0.057

ECR(HY)-10h-35 0.144 0.159 0.278 0.194 0.073

ECR(primer/Ca(NO2)2)-4h-45 0.016 0.008 0.028 0.017 0.010

ECR(primer/Ca(NO2)2)-10h-45 0.152 0.059 0.084 0.098 0.048

ECR(primer/Ca(NO2)2)-10h-35 0.416 0.315 0.589 0.440 0.139

Bars with multiple coatings

MC(both layers penetrated)-4h-45 0.489 0.262 0.379 0.377 0.114

MC(both layers penetrated)-10h-45 0.214 1.269 0.532 0.672 0.541

MC(only epoxy penetrated)-4h-45 0.141 0.161 0.581 0.294 0.248

MC(only epoxy penetrated)-10h-45 0.159 0.106 0.398 0.221 0.156

1 μm = 0.0394 mil

Blank cells indicate no specimen tested.

a See table 1 for abbreviation definitions. 4h = bar with four holes through epoxy, 10h = bar with 10 holes through 

epoxy. 35 = concrete with w/c = 0.35, 45 = concrete with w/c = 0.45.
79

Table 19. Corrosion loss at 96 weeks (μm) for cracked beam specimens based on area 

exposed at holes through coating.

Steel Designationa

Specimen

Average

Standard

1 2 3 4 5 6 Deviation

Controls 

ECR-4h-45 17.0 34.1 8.0 33.1 20.3 7.0 19.9 11.8

ECR-10h-45 5.0 16.0 6.1 9.0 6.0

ECR-10h-35 25.3 23.8 31.1 26.7 3.8

Epoxies with increased adhesion

ECR(Chromate)-4h-45 31.5 28.0 47.5 35.7 10.4

ECR(Chromate)-10h-45 5.0 26.9 92.3 41.4 45.4

ECR(DuPont)-4h-45 59.4 66.0 26.0 50.4 21.4

ECR(DuPont)-10h-45 24.6 24.4 57.0 35.3 18.8

ECR(Valspar)-4h-45 82.6 34.2 4.3 40.4 39.5

ECR(Valspar)-10h-45 15.6 7.5 48.8 24.0 21.9

Corrosion inhibitors in concrete

ECR(DCI)-4h-45 12.1 22.9 3.2 12.7 9.9

ECR(DCI)-10h-45 8.4 29.8 7.6 15.3 12.6

ECR(DCI)-10h-35 23.8 18.2 86.3 42.8 37.8

ECR(RH)-4h-45 29.6 150.6 22.5 67.6 72.0

ECR(RH)-10h-45 46.1 25.7 26.6 32.8 11.6

ECR(RH)-10h-35 18.5 58.0 26.2 34.3 20.9

ECR(HY)-4h-45 4.8 2.4 44.0 17.1 23.4

ECR(HY)-10h-45 0.3 22.4 12.0 11.6 11.0

ECR(HY)-10h-35 27.7 30.6 53.4 37.2 14.1

ECR(primer/Ca(NO2)2)-4h-45 7.8 3.8 13.2 8.3 4.7

ECR(primer/Ca(NO2)2)-10h-45 29.2 11.4 16.1 18.9 9.2

ECR(primer/Ca(NO2)2)-10h-35 79.9 60.5 113.2 84.5 26.6

Bars with multiple coatings

MC(both layers penetrated)-4h-45 234.9 125.8 182.1 181.0 54.6

MC(both layers penetrated)-10h-45 41.1 243.7 102.1 129.0 104.0

MC(only epoxy penetrated)-4h-45 64.9 76.0 278.8 139.9 120.4

MC(only epoxy penetrated)-10h-45 30.5 20.7 76.4 42.5 29.7

1 μm = 0.0394 mil

Blank cells indicate no specimen tested.

a See table 1 for abbreviation definitions. 4h = bar with four holes through epoxy, 10h = bar with 10 holes through 

epoxy. 35 = concrete with w/c = 0.35, 45 = concrete with w/c = 0.45.
80

Table 20. Average corrosion rate (μm/year) based on losses after corrosion initiation for 

cracked beam specimens.

Bars Without Coatings—Corrosion Rate Based on Total Area

Steel Designationa

Specimen

Average

Standard

1 2 3 4 5 6 Deviation

Controls

Conv.-45 9.42 4.50 3.82 8.32 8.18 7.74 7.00 2.27

Conv.2-45 24.6 12.2 12.1 16.3 7.16

Conv.-35 7.72 5.05 6.34 6.37 1.34

Corrosion inhibitors in concrete

Conv.2(DCI)-45 17.5 14.4 11.6 14.5 2.96

Conv.2(RH)-45 13.6 9.80 12.4 11.9 1.96

Conv.2(HY)-45 4.91 3.44 4.16 4.17 0.74

Bars With Coatings—Corrosion Rate Based on Exposed Area

Steel Designation

4 holes 10 holes

Average

Standard

1 2 3 1 2 3 Deviation

Controls

ECR-45 8.57 18.3 2.63 2.29 9.20 3.69 8.07 5.86 13.8c 12.2c 1.99c

ECR-35 11.8 12.4 16.9 13.7 2.79

Epoxies with increased adhesion

ECR(Chromate)-45 14.1 11.9 29.1 2.37 14.3 50.4 20.4 17.0

ECR(DuPont)-45 33.5 48.5 14.5 13.2 14.7 31.1 25.9 14.2

ECR(Valspar)-45 41.1 16.9 0.770 8.28 4.62 26.6 16.4 15.3

Corrosion inhibitors in concrete

ECR(DCI)-45 6.19 18.9 16.6 4.58 16.7 4.10 11.2 6.90

ECR(DCI)-35 13.1 27.6 47.2 29.3 17.1

ECR(RH)-45 12.7 15.3 17.8 27.1 14.2 15.1 17.0 5.21

ECR(RH)-35 10.1 31.7 14.3 18.7 11.45

ECR(HY)-45 1.87 6.98 25.5 b 13.3 6.37 10.8 9.18

ECR(HY)-35 15.1 17.7 30.9 21.2 8.47

ECR(primer/Ca(NO2)2)-45 2.38 13.5 5.74 15.6 6.02 9.19 8.73 5.03

ECR(primer/Ca(NO2)2)-35 43.6 32.9 61.6 46.0 14.5

Bars with multiple coatings

MC 36.8d 44.7d 169d 16.2d 10.5d 39.7d

68.6 51.9 129e 68.7e 98.7e 21.8e 132e 55.5e

1 μm = 0.0394 mil

Blank cells indicate no specimen tested. a See table 1 for abbreviation definitions. 35 = concrete with w/c = 0.35, 45 = concrete with w/c = 0.45. b No corrosion observed. c Specimens 4, 5, and 6. 

d Both layers penetrated. e Only epoxy penetrated.
81

Control Specimens

The average corrosion rates and corrosion losses based on the total area of the reinforcing bars 

are shown in figure 75 and figure 76, respectively, for cracked beam specimens with conventional 

reinforcing steel and conventional ECR steel. The specimens with ECR have 4 or 10 holes through

the epoxy for the concrete with a w/c ratio of 0.45 and 10 holes through the epoxy for concrete 

with a w/c ratio of 0.35. Because the simulated crack provides direct access to the top reinforcing 

bars for the 15 percent sodium chloride solution, significant corrosion rates, on the order of 

10 μm/year (0.4 mil/year), were observed early in the test for specimens containing conventional 

steel at both w/c ratios. Throughout the test period, the lower w/c ratio appears to have provided

some protection, likely the result of lower concrete permeability, which reduces access of oxygen

and moisture to the cathode. At both w/c ratios, however, the corrosion rate is significant, with 

average rates on the order of 6 to 9 μm/year (0.2 to 0.4 mil/year) for specimens with w/c of 0.45 

and 2 to 8 μm/year (0.08 to 0.3 mil/year) after week 10 for specimens with w/c of 0.35. The 

corrosion rates decreased from the high initial values as a result of the accumulation of corrosion 

products within the crack. The average macrocell corrosion rates shown in table 20 are 7.00 and 

6.37 μm/year (0.276 and 0.251 mil/year) for the Conv.-45 and Conv.-35 specimens, respectively.

0

3

6

9

12

15

0 12 24 36 48 60 72 84 96

CORROSION RATE, μm/year

TIME, weeks

Conv.-45 Conv.-35 ECR-4h-45 ECR-10h-45 ECR-10h-35

1 μm = 0.0394 mil

Figure 75. Graph. Cracked beam test, average corrosion rates based on total area of control 

specimens for conventional reinforcement and ECR. 
82

0

3

6

9

12

15

0 12 24 36 48 60 72 84 96

CORROSION LOSS, μm

TIME (weeks)

Conv.-45 Conv.-35 ECR-4h-45 ECR-10h-45 ECR-10h-35

1 μm = 0.0394 mil

Figure 76. Graph. Cracked beam test, average corrosion loss based on total area of control 

specimens for conventional reinforcement and ECR.

Occasionally, individual specimens exhibited large increases in corrosion rate. This increase was 

due to the accumulated corrosion products exerting enough stress on the concrete to widen the 

crack, again providing direct access of the sodium chloride solution to the top reinforcing bar. 

Corrosion rates increased somewhat during the last 12 weeks of the tests for specimens with both 

w/c ratios. Figure 76 and table 18 show that the average corrosion losses were 13.1 and 8.3 μm

(0.516 and 0.33 mil) at the end of the 96-week test. These values are below the nominal value of 

25 μm (0.98 mil) required to crack concrete. However, by the end of the test, a number of 

specimens produced a high enough quantity of corrosion products to cause severe cracking, as 

shown in figure 77, which also allowed the sodium chloride solution to reach the lower bars. The 

observed cracking was likely due to nonuniformity in deposition of the corrosion products, 

which is evident in the section describing the autopsy of the bench-scale specimens. Overall, 

figure 75, figure 76, and table 20 indicate a small advantage for a lower w/c ratio for cracked 

concrete and a significant reduction in corrosion loss provided by epoxy coating. 
83

Figure 77. Photo. Cracked beam specimen containing conventional reinforcing steel 

at end of 96-week test.

Corrosion losses as a function of exposed area are plotted versus time for the ECR specimens in

figure 78. The bars with 10 holes through the epoxy cast in concrete with w/c of 0.35 (ECR-10h-35)

exhibited two to three times the losses of the same bars cast in concrete with w/c of 0.45 (ECR10h-45). The bars with four holes through the epoxy in concrete with w/c of 0.45 (ECR-4h-45) 

exhibited corrosion losses between those for the two other specimen types. The results represent 

the average of six specimens for ECR-4h-45 and three specimens for the others. For the epoxycoated bars, there does not appear to be an advantage based on a reduced w/c ratio. The corrosion 

losses for the ECR bars based on exposed area are 1 to 4 times the average values observed for 

the uncoated conventional bars.
84

0

5

10

15

20

25

30

0 12 24 36 48 60 72 84 96

CORROSION LOSS, μm

TIME (weeks)

ECR-4h-45 ECR-10h-45 ECR-10h-35

1 μm = 0.0394 mil

Figure 78. Graph. Cracked beam test, average corrosion loss based on area exposed 

at holes through coating for ECR.

Epoxies with Improved Adhesion

The total corrosion losses based on exposed area for the bars coated with the improved adhesion 

epoxies are compared with losses for conventional ECR in figure 79 and figure 80 for bars with

4 and 10 holes, respectively. As observed in the southern exposure tests, these results indicate 

that the improved adhesion epoxies provided no advantage with respect to conventional ECR 

under severe exposure conditions. In fact, the corrosion losses for bars with improved adhesion 

epoxies were at least 1.7 times those for bars with conventional epoxy for both 4 holes (35.4 to 

50.4 μm (1.39 to 1.98 mil) versus 19.9 μm (0.783 mil)) and 10 holes (24.0 to 41.4 μm (0.945 to 

1.63 mil) versus 9 μm (0.4 mil)).
85

0

6

12

18

24

30

36

42

48

54

60

0 12 24 36 48 60 72 84 96

CORROSION LOSS, μm

TIME (weeks)

ECR-4h-45 ECR(Chromate)-4h-45 ECR(DuPont)-4h-45 ECR(Valspar)-4h-45

1 μm = 0.0394 mil

Figure 79. Graph. Cracked beam test, average corrosion loss based on area exposed at 

holes through coating for conventional ECR and increased-adhesion ECR with bars 

containing four holes.

0

10

20

30

40

50

0 12 24 36 48 60 72 84 96

CORROSION LOSS, μm

TIME (weeks)

ECR-10h-45 ECR(Chromate)-10h-45 ECR(DuPont)-10h-45 ECR(Valspar)-10h-45

1 μm = 0.0394 mil

Figure 80. Graph. Cracked beam test, average corrosion loss based on area exposed at 

holes through coating for conventional ECR and increased-adhesion ECR with bars 

containing 10 holes.
86

ECR Used in Conjunction with Corrosion Inhibitors 

Corrosion losses for cracked beam specimens with conventional ECR cast in concrete with 

corrosion inhibitors or for ECR bars with primer containing microencapsulated calcium nitrate 

are shown in figure 81 and figure 82 for specimens with 4 and 10 holes through the epoxy on 

bars cast in concrete with w/c of 0.45 and in figure 83 for with 10 holes through the epoxy cast in 

concrete with w/c of 0.35. Unlike the results for intact concrete in the southern exposure test, the 

presence of a corrosion inhibitor did not provide an advantage in severely cracked concrete as 

represented by the cracked beam specimen, where chlorides have direct access to the reinforcing 

steel. Except for ECR (DCI)-4h-45 and ECR (primer/Ca(NO2)2)-4h-45, the corrosion losses are 

the same or greater for the specimens with a corrosion inhibitor in the concrete or in a primer 

below the coating than for the conventional ECR specimens. 

0

10

20

30

40

50

60

70

0 12 24 36 48 60 72 84 96

CORROSION LOSS, μm

TIME (weeks)

ECR-4h-45 ECR(DCI)-4h-45 ECR(RH)-4h-45

ECR(HY)-4h-45 ECR(primer/Ca(NO2)2)-4h-45

1 μm = 0.0394 mil

Figure 81. Graph. Cracked beam test, average corrosion loss based on area exposed 

at holes through coating for conventional ECR with and without corrosion inhibitors 

with bars containing four holes and concrete with w/c = 0.45.
87

0

10

20

30

40

0 12 24 36 48 60 72 84 96

CORROSION LOSS, μm 

TIME (weeks)

ECR-10h-45 ECR(DCI)-10h-45 ECR(RH)-10h-45

ECR(HY)-10h-45 ECR(primer/Ca(NO2)2)-10h-45

1 μm = 0.0394 mil

Figure 82. Graph. Cracked beam test, average corrosion loss based on area exposed 

at holes through coating for conventional ECR with and without corrosion inhibitors 

with bars containing 10 holes and concrete with w/c = 0.45.

0

10

20

30

40

50

60

70

80

90

100

0 12 24 36 48 60 72 84 96

CORROSION LOSS, μm

TIME (weeks)

ECR-10h-35 ECR(DCI)-10h-35 ECR(RH)-10h-35

ECR(HY)-10h-35 ECR(primer/Ca(NO2)2)-10h-35

1 μm = 0.0394 mil

Figure 83. Graph. Cracked beam test, average corrosion loss based on area exposed 

at holes through coating for conventional ECR with and without corrosion inhibitors 

with bars containing 10 holes and concrete with w/c = 0.35. 
88

Bars with Multiple Coatings

The corrosion losses for the bars with multiple coatings are compared with those for conventional

ECR in figure 84 and figure 85 for bars with 4 and 10 holes through the coatings, respectively. 

Both figures show that the highest corrosion losses were attained by the MC bars with both 

layers penetrated followed by those with only the epoxy layer penetrated and then by conventional 

ECR. For the specimens with four holes in the epoxy coating, the respective average losses based 

on exposed area were 181, 140, and 20 μm (7.13, 5.51, and 0.79 mil) at the conclusion of tests. 

For the specimens with 10 holes, the respective values were 129, 43, and 9 μm (5.08, 1.7, and 

0.4 mil) at the conclusion of tests. Corrosion losses less than 50 μm (2 mil), the thickness of the 

zinc coating, exhibited by the MC(only epoxy penetrated)-10h-45 specimens may indicate that 

the coating was not penetrated. However, as observed for the rapid macrocell specimens, the 

values shown do not reflect the effects of microcell corrosion, which increases metal loss. Losses 

greater than 50 μm (2 mil) indicate that the zinc was penetrated, which was demonstrated when 

the bars were autopsied, as discussed later in this chapter.

0

25

50

75

100

125

150

175

200

0 12 24 36 48 60 72 84 96

CORROSION LOSS, μm 

TIME (weeks)

ECR-4h-45 MC(both layers penetrated-4h-45) MC(only epoxy penetrated)-4h-45

1 μm = 0.0394 mil

Figure 84. Graph. Cracked beam test, average corrosion loss based on area exposed 

at holes through coating for conventional ECR and MC reinforcement with bars 

containing four holes.
89

0

30

60

90

120

150

0 12 24 36 48 60 72 84 96

CORROSION LOSS, μm

TIME (weeks)

ECR-10h-45 MC(both layers penetrated)-10h-45 MC(only epoxy penetrated)-10h-45

1 μm = 0.0394 mil

Figure 85. Graph. Cracked beam test, average corrosion loss based on area exposed at holes

through coating for conventional ECR and MC reinforcement with bars containing 10 holes.

The corrosion potentials for the specimens are shown in figure 86 and figure 87 for bars with 

4 holes and in figure 88 and figure 89 for bars with 10 holes. For both the MC and ECR bars, the 

top bars reached a potential of about -0.600 V and sustained that value throughout the test period 

while the corrosion potential of the bottom bars remained between -0.200 and -0.400 V for most of 

the test for the MC specimens with 4 holes through the epoxy and between -0.200 and -0.450 V for

the MC specimens with 10 holes through the epoxy. The corrosion potential of the ECR specimens

remain between -200 and -400 V for specimens with both 4 and 10 holes through the epoxy. 

-0.80

-0.60

-0.40

-0.20

0.00

0 12 24 36 48 60 72 84 96

CORROSION POTENTIAL, V

TIME (weeks)

ECR-4h-45 MC(both layers penetrated) MC(only epoxy penetrated)

Figure 86. Graph. Cracked beam test, corrosion potential of top mat for conventional 

ECR and MC reinforcement with bars containing four holes. 
90

-0.80

-0.60

-0.40

-0.20

0.00

0 12 24 36 48 60 72 84 96

CORROSION POTENTIAL, V

TIME (weeks)

ECR-4h-45 MC(both layers penetrated) MC(only epoxy penetrated)

Figure 87. Graph. Cracked beam test, corrosion potential of bottom mat for conventional 

ECR and MC reinforcement with bars containing four holes.

-0.80

-0.60

-0.40

-0.20

0.00

0 12 24 36 48 60 72 84 96

CORROSION POTENTIAL, V

TIME (weeks)

ECR-10h MC(both layers penetrated)-10h MC(only epoxy penetrated)-10h

Figure 88. Graph. Cracked beam test, corrosion potential of top mat for conventional 

ECR and MC reinforcement with bars containing 10 holes.
91

-0.80

-0.60

-0.40

-0.20

0.00

0 12 24 36 48 60 72 84 96

CORROSION POTENTIAL, V

TIME (weeks)

ECR-10h MC(both layers penetrated)-10h MC(only epoxy penetrated)-10h

Figure 89. Graph. Cracked beam test, corrosion potential of bottom mat for conventional 

ECR and MC reinforcement with bars containing 10 holes.

Conventional Steel with Corrosion Inhibitors

The corrosion losses for the cracked beam specimens containing conventional steel cast in concrete

with corrosion inhibitors and for the control specimens without a corrosion inhibitor are qualitatively

similar to those observed for the matching southern exposure specimens. As shown in table 20

and figure 90, the highest average corrosion losses were exhibited by the specimens without a 

corrosion inhibitor (Conv.2-45) (29.7 μm (1.17 mil) at 96 weeks), followed by the specimens 

containing calcium nitrite, Rheocrete® 222+, and HycreteTM (Conv.2(DCI)-45, Conv.2(RH)-45, 

and Conv.2(HY)-45), with losses of 26.4, 21.7, and 7.5 μm (1.04, 0.854, and 0.29 mil), respectively. 

Although qualitatively the same, the average losses for the cracked beam specimens containing 

Rheocrete® and calcium nitrite were much closer to the average loss for the specimens without a 

corrosion inhibitor than were the average losses for the specimens containing HycreteTM, indicating

that HycreteTM provided measurably better macrocell corrosion protection to bare bars in cracked 

concrete than the other two inhibitors. All of the losses were significantly higher than observed 

in the southern exposure tests. The corrosion potentials for the top mats of steel are shown in 

figure 91, with all specimens exhibiting an average potential more negative than -0.400 V at 

week 1 except the specimens containing HycreteTM, which dropped below -0.400 V at week 6. 

Similar to the southern exposure specimens, the cracked beam specimens containing HycreteTM

exhibited significantly higher mat-to-mat corrosion resistance than the other specimens 

beginning at about week 24 (see figure 92).
92

0

5

10

15

20

25

30

35

0 12 24 36 48 60 72 84 96

TIME, weeks

CORROSION LOSS, μm

Conv.2-45 Conv.2(RH)-45 Conv.2(DCI)-45 Conv.2(HY)-45

1 μm = 0.0394 mil

Figure 90. Graph. Cracked beam test, average corrosion losses based on the total area 

for conventional reinforcement in specimens containing corrosion inhibitors. 

-0.8

-0.6

-0.4

-0.2

0.0

0 12 24 36 48 60 72 84 96

TIME, weeks

CORROSION POTENTIAL, V

Conv.2-45 Conv.2(RH)-45 Conv.2(DCI)-45 Conv.2(HY)-45

Figure 91. Graph. Cracked beam test, corrosion potential of top mat for conventional 

reinforcement in specimens containing corrosion inhibitors.
93

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

0 12 24 36 48 60 72 84 96

TIME, weeks

MAT-TO-MAT RESISTANCE, ohms

Conv.2-45 Conv.2(RH)-45 Conv.2(DCI)-45 Conv.2(HY)-45

Figure 92. Graph. Cracked beam test, mat-to-mat resistance for conventional 

reinforcement in specimens containing corrosion inhibitors.

Linear Polarization Resistance Tests

Linear polarization resistance tests provide values of the total corrosion rate (microcell plus 

macrocell), often expressed as corrosion current density. For ease of comparison with the macrocell 

results presented in this chapter, the corrosion current densities have been converted to corrosion 

rates using the equations in figure 5 or figure 7 and integrated to obtain corrosion losses. As an 

example, the total corrosion losses for conventional steel (Conv.-45 and Conv.-35) and conventional 

ECR (ECR-4h-45, ECR-10h-45, and ECR-10h-35) in the southern exposure tests based on linear 

polarization resistance readings are shown in figure 93 and figure 94. 

0

5

10

15

20

25

30

0 12 24 36 48 60 72 84 96

TIME (weeks)

CORROSION LOSS (μm) .

Conv.-45 Conv.-35 ECR-4h-45 ECR-10h-45 ECR-10h-35

1 μm = 0.0394 mil

Figure 93. Graph. Linear polarization test results for southern exposure specimens, average

corrosion loss based on total area for conventional reinforcement and conventional ECR.
94

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.16

0.18

0.20

0 12 24 36 48 60 72 84 96

TIME (weeks)

CORROSION LOSS (μm) .

Conv.-45 Conv.-35 ECR-4h-45 ECR-10h-45 ECR-10h-35

1 μm = 0.0394 mil

Figure 94. Graph. Linear polarization test results for southern exposure specimens, 

average corrosion loss based on total area for conventional reinforcement and 

conventional ECR (different scale).

The total losses at 96 weeks for the southern exposure and cracked beam tests are summarized in 

table 21 based on both total and exposed area (as explained in chapter 2, each of these values 

represents a single specimen). For comparison, the average macrocell losses at 96 weeks presented

in table 11, table 12, and table 20 are shown side-by-side with the total losses. As expected, the 

losses based on the linear polarization results are, in nearly all cases, higher than those obtained 

based on macrocell current. This is true in 33 out of 34 cases for the southern exposure tests and 

in 30 out of 31 cases for the cracked beam test. As observed for macrocell losses, total corrosion 

losses are noticeably higher for the cracked beam test than for the southern exposure test. 
95

Table 21. Total and macrocell corrosion loss at 96 weeks (μm) for southern exposure and 

cracked beam specimens expressed in terms of total bar area and area exposed at holes.

Steel Designationa

Based on Total Area Based on Exposed Area

Southern Exposure Cracked Beam Southern Exposure Cracked Beam 

Total Macrocell Total Macrocell Total Macrocell Total Macrocell

Controls 

Conv.-45 27.1 7.1 166.8 13.1 NA NA NA NA

Conv.2-45 20.5 14.4 49.2 29.9 NA NA NA NA

Conv.-35 2.50 2.121 130.8 8.34 NA NA NA NA

ECR-4h-45 0.030 0.007 0.645 0.041 14.44 3.13 310.0 19.91

ECR-10h-45 0.143 0.017 0.500 0.047 27.44 3.21 96.06 9.04

ECR-10h-35 0.038 0.008 0.842 0.139 7.25 1.47 161.8 26.70

Epoxies with increased adhesion

ECR(Chromate)-4h-45 0.029 0.018 1.727 0.074 14.13 8.76 829.7 35.66

ECR(Chromate)-10h-45 0.281 0.067 0.550 0.216 54.07 12.90 105.7 41.40

ECR(DuPont)-4h-45 0.106 0.026 0.525 0.105 50.92 12.34 252.1 50.44

ECR(DuPont)-10h-45 0.287 0.046 1.883 0.184 55.22 8.90 361.7 35.30

ECR(Valspar)-4h-45 0.221 0.032 1.912 0.084 105.92 15.58 918.2 40.35

ECR(Valspar)-10h-45 0.450 0.063 1.714 0.125 86.43 12.02 329.2 23.95

Corrosion inhibitors in concrete

Conv.2(DCI)-45 12.15 8.599 132.8 26.68 NA NA NA NA

Conv.2(RH)-45 4.613 3.398 62.12 21.82 NA NA NA NA

Conv.2(HY)-45 2.611 1.549 27.383 7.598 NA NA NA NA

ECR(DCI)-4h-45 0.056 0.004 0.788 0.026 26.82 1.79 378.6 12.72

ECR(DCI)-10h-45 0.256 0.012 1.288 0.079 49.08 2.23 247.3 15.26

ECR(DCI)-10h-35 0.020 0.007 0.203 0.223 3.83 1.29 38.90 42.75

ECR(RH)-4h-45 0.002 0.010 2.225 0.141 0.96 4.58 1069 67.59

ECR(RH)-10h-45 0.024 -0.002 1.164 0.171 4.55 -0.39 223.5 32.80

ECR(RH)-10h-35 0.018 0.003 0.654 0.178 3.40 0.65 125.6 34.25

ECR(HY)-4h-45 0.005 -0.002 0.357 0.036 2.25 -0.82 171.4 17.06

ECR(HY)-10h-45 0.013 0.002 0.880 0.060 2.52 0.37 169.1 11.55

ECR(HY)-10h-35 0.069 0.001 0.973 0.194 13.21 0.23 186.8 37.22

ECR(primer/Ca(NO2)2)-4h-45 0.033 0.014 0.902 0.017 15.77 6.72 433.0 8.28

ECR(primer/Ca(NO2)2)-10h-45 0.029 0.064 1.030 0.098 5.55 12.25 197.8 18.89

ECR(primer/Ca(NO2)2)-10h-35 0.008 0.002 2.034 0.440 1.54 0.42 390.8 84.50

Epoxies with increased adhesion plus calcium nitrite in concrete

ECR(Chromate)-DCI-4h-45 0.080 0.007 – – 15.35 1.26 – –

ECR(DuPont)-DCI-4h-45 0.010 0.000 – – 1.95 -0.06 – –

ECR(Valspar)-DCI-4h-45 0.004 0.012 – – 0.70 2.29 – –

Bars with multiple coatings

MC(both layers penetrated)-4h-45 0.931 0.058 1.436 0.377 447.3 27.70 690.0 181.0

MC(both layers penetrated)-10h-45 1.859 0.628 3.647 0.672 357.0 120.6 700.5 129.0

MC(only epoxy penetrated)-4h-45 0.803 0.033 3.769 0.294 385.9 15.88 1810.5 141.3

MC(only epoxy penetrated)-10h-45 0.681 0.090 1.657 0.221 130.7 17.36 318.2 42.36

1 μm = 0.0394 mil

NA = Not applicable

– No specimen. a See table 1 for abbreviation definitions. 4h = bar with four holes through epoxy, 10h = bar with 10 holes through epoxy. 35 = concrete 

with w/c of 0.35, 45 = concrete with w/c of 0.45.
96

The results for total (linear polarization resistance) and macrocell corrosion are shown for the 

southern exposure tests in figure 95 and figure 96 (w/c = 0.45) and for the cracked beam tests in 

figure 97 (w/c = 0.45 and 0.35). Losses for conventional steel, including conventional steel cast 

in concrete with corrosion inhibitors, are based on total area, while losses for ECR are based on 

the area exposed at holes through the coating and represent the average for specimens with 4 and 

10 holes. The figures demonstrate that corrosion losses for conventional reinforcement based on 

total area are of the same order of magnitude as those for ECR based on exposed area, but, as 

discussed for the bare-bar rapid macrocell tests, the average corrosion losses based on total area 

for uncoated bars are generally lower than those based on exposed area for epoxy-coated bars. 

The figures also demonstrate that, overall, the relative performance of the systems is similar 

whether based on microcell or macrocell corrosion current.

-2

8

18

28

38

48

58

68

78

0 100 200 300 400 500

Macrocell Corrosion Loss, μm 

Total Corrosion Loss, μm

Conv. - 45

ECR-4h and 10h-45

ECR(RH)-4h and 10h-45

ECR(DCI)-4h and 10h-45

ECR(HY)-4h and 10h-45

ECR(primer/Ca(NO2)2)-4h and 10h-45

MC(Only epoxy penetrated)-4h and 10h-45

MC(both layers penetrated)-4h and 10h-45

ECR(Chromate)-4h and 10h-45

ECR(DuPont)-4h and 10h-45

ECR(Valspar)-4h and 10h-45

ECR(Chromate)-DCI-4h-45

ECR(DuPont)-DCI-4h-45

ECR(Valspar)-DCI-4h-45

Conv.2-45

Conv.2(RH)-45

Conv.2(DCI)-45

Conv.2(HY)-45

1 μm = 0.0394 mil

Figure 95. Graph. Southern exposure specimens, total versus macrocell corrosion loss 

based on total area for conventional reinforcement and area exposed at holes through 

coating for ECR with w/c = 0.45.
97

-2

0

2

4

6

8

10

12

14

16

18

0 20 40 60 80 100

Macrocell Corrosion Loss, μm 

Total Corrosion Loss, μm

Conv. - 45

ECR-4h and 10h-45

ECR(RH)-4h and 10h-45

ECR(DCI)-4h and 10h-45

ECR(HY)-4h and 10h-45

ECR(primer/Ca(NO2)2)-4h and 10h-45

MC(Only epoxy penetrated)-4h and 10h-45

MC(both layers penetrated)-4h and 10h-45

ECR(Chromate)-4h and 10h-45

ECR(DuPont)-4h and 10h-45

ECR(Valspar)-4h and 10h-45

ECR(Chromate)-DCI-4h-45

ECR(DuPont)-DCI-4h-45

ECR(Valspar)-DCI-4h-45

Conv.2-45

Conv.2(RH)-45

Conv.2(DCI)-45

Conv.2(HY)-45

1 μm = 0.0394 mil

Figure 96. Graph. Southern exposure specimens, total versus macrocell corrosion loss 

based on total area for conventional reinforcement and area exposed at holes through 

coating for ECR with w/c = 0.45 (different scale).

0

20

40

60

80

100

120

140

160

0 200 400 600 800 1000 1200 1400

Macrocell Corrosion Loss, μm 

Total Corrosion Loss, μm

Conv. - 45

ECR-4h and 10h-45

ECR(DCI)-4h and 10h-45

ECR(HY)-4h and 10h-45

ECR(RH)-4h and 10h-45

ECR(primer/Ca(NO2)2)-4h and 10h-45

MC(Only epoxy penetrated)-4h and 10h-45

MC(both layers penetrated)-4h and 10h-45

ECR(Chromate)-4h and 10h-45

ECR(DuPont)-4h and 10h-45

ECR(Valspar)-4h and 10h-45

Conv.2-45

Conv.2(RH)-45

Conv.2(DCI)-45

Conv.2(HY)-45

Conv.-35

ECR-10h-35

ECR(DCI)-10h-35

ECR(HY)-10h-35

ECR(RH)-10h-35

ECR(primer(Ca(NO2)2))-10h-35

1 μm = 0.0394 mil

Figure 97. Graph. Cracked beam specimens, total versus macrocell corrosion loss based on 

total area for conventional reinforcement and area exposed at holes through coating for 

ECR with w/c = 0.45 or 0.35.
98

Total losses were highest for the MC bars and significantly lower for other systems in intact 

concrete, as shown in figure 95 and figure 96. These figures do not show the results for the 

southern exposure specimens with concrete with a w/c ratio of 0.35; if plotted, those results 

would appear in a grouping with macrocell losses between 0.6 and 2.1 μm (0.02 and 0.083 mil) 

and total losses between 2.5 and 13.2 μm (0.098 and 0.520 mil).

Figure 95 through figure 97 illustrate the relative performance of the systems, with the more 

effective systems exhibiting data points closer to the origin. Based on corrosion losses in the 

southern exposure and cracked beam tests as the measure of performance, all of the systems 

incorporating ECR appear to perform well in intact concrete, with the exception of the MC bars. 

In cracked concrete, all systems exhibited significantly higher losses and wider scatter in both 

total and macrocell corrosion, as shown in figure 97. When compared based on total area of 

steel, the systems involving conventional reinforcement both with and without a corrosion 

inhibitor did not perform as well as the systems with ECR or MC reinforcement. 

Table 22 compares the average corrosion rates based on losses after corrosion initiation 

calculated using the linear polarization results with those calculated based on macrocell 

corrosion (see table 15 and table 20). The macrocell corrosion rates represent the individual 

specimens for which the linear polarization resistance readings were taken. As observed for 

corrosion losses, the corrosion rates based on the linear polarization results are, in nearly all cases,

higher than those obtained based on macrocell current. This is true in 32 out of 34 cases for the 

southern exposure tests and in all 31 cases for the cracked beam test. Also similar to losses, 

corrosion rates are much higher for the cracked beam test than for the southern exposure test. 

The total and macrocell corrosion rates are compared for the southern exposure tests in figure 98

and figure 99 (w/c = 0.45) and for the cracked beam tests in figure 100 (w/c = 0.45 and 0.35). 

Following the format used for figure 96 and figure 97, corrosion rates for uncoated bars are 

based on total area while the rates for coated bars are based on the area exposed at holes through 

the coating and represent the average for specimens with 4 and 10 holes. Observations based 

on corrosion rates are similar to those based on losses, with corrosion rates for conventional 

reinforcement based on total area somewhat lower but of the same order of magnitude as those 

for ECR based on exposed area. When based on total area, the systems with conventional 

reinforcement, with and without a corrosion inhibitor, do not perform as well as the systems with 

ECR or MC reinforcement.
99

Table 22. Average total and macrocell corrosion rates (μm/year) based on losses after 

corrosion initiation for southern exposure and cracked beam specimens expressed 

in terms of total bar area and area exposed at holes.

Steel Designationa

Based on Total Area Based on Exposed Area

Southern Exposure Cracked Beam Southern Exposure Cracked Beam

Total Macrocell Total Macrocell Total Macrocell Total Macrocell

Controls

Conv.-45 20.5 7.40 90.3 7.74 NA NA NA NA

Conv.2-45 17.0 10.7 30.6 24.6 NA NA NA NA

Conv.-35 2.07 1.61 73.03 6.34 NA NA NA NA

ECR-4h-45 0.028 b 0.562 0.004 13.2 b 269.6 1.99

ECR-10h-45 0.152 0.066 0.358 0.019 29.2 12.7 68.8 3.69

ECR-10h-35 0.030 0.012 1.197 0.088 5.72 2.35 229.9 16.9

Epoxies with increased adhesion

ECR(Chromate)-4h-45 0.021 b 1.008 0.029 10.3 b 483.6 14.1

ECR(Chromate)-10h-45 0.199 0.006 0.368 0.012 38.2 1.18 70.6 2.37

ECR(DuPont)-4h-45 0.112 0.029 0.309 0.070 53.9 13.8 148.4 33.5

ECR(DuPont)-10h-45 0.242 0.025 1.261 0.069 46.5 4.72 242.2 13.2

ECR(Valspar)-4h-45 0.193 0.032 1.218 0.086 92.5 15.5 584.6 41.1

ECR(Valspar)-10h-45 0.399 0.064 1.116 0.043 76.7 12.3 214.3 8.28

Corrosion inhibitors in concrete

Conv.2(DCI)-45 9.79 7.81 106.6 17.5 NA NA NA NA

Conv.2(RH)-45 3.82 2.57 48.34 13.6 NA NA NA NA

Conv.2(HY)-45 1.82 0.791 18.2 4.91 NA NA NA NA

ECR(DCI)-4h-45 0.045 b 0.421 0.035 21.7 b 202.3 16.6

ECR(DCI)-10h-45 0.227 0.012 0.754 0.021 43.5 2.33 144.7 4.10

ECR(DCI)-10h-35 0.022 0.006 0.239 0.246 4.28 1.16 46.0 47.2

ECR(RH)-4h-45 0.001 0.012 1.25 0.037 0.581 5.94 601.3 17.8

ECR(RH)-10h-45 0.015 b 0.658 0.079 2.86 b 126.3 15.1

ECR(RH)-10h-35 0.011 b 0.920 0.074 2.09 b 176.7 14.3

ECR(HY)-4h-45 0.002 b 0.215 0.053 1.19 b 103.0 25.5

ECR(HY)-10h-45 0.011 0.004 0.468 0.033 2.09 0.674 89.8 6.37

ECR(HY)-10h-35 0.049 b 1.37 0.161 9.44 b 263.9 30.9

ECR(primer/Ca(NO2)2)-4h-45 0.028 0.046 0.509 0.012 13.3 22 244.3 5.74

ECR(primer/Ca(NO2)2)-10h-45 0.037 0.033 0.608 0.048 7.04 6.39 116.7 9.19

ECR(primer/Ca(NO2)2)-10h-35 0.004 b 2.80 0.321 0.741 b 537.6 61.6

Epoxies with increased adhesion plus calcium nitrite in concrete

ECR(Chromate)-DCI-4h-45 0.036 0.021 – – 17.1 10.3 – –

ECR(DuPont)-DCI-4h-45 0.004 b – – 2.12 b – –

ECR(Valspar)-DCI-4h-45 0.001 b – – 0.423 b – –

Bars with multiple coatings

MC(both layers penetrated)-4h-45 0.572 0.027 0.809 0.206 274.5 13.1 388.1 98.7

MC(both layers penetrated)-10h-45 1.32 0.358 2.04 0.289 254 68.8 391.2 55.5

MC(only epoxy penetrated)-4h-45 0.518 0.077 2.12 0.352 248.8 36.9 1018.8 169

MC(only epoxy penetrated)-10h-45 0.506 0.039 2.33 0.207 97.2 7.52 448.2 39.7

1 μm = 0.0394 mil

NA = Not applicable; – No specimen. a See table 1 for abbreviation definitions. 4h = bar with four holes through epoxy, 10h = bar with 10 holes through epoxy. 

35 = concrete with w/c of 0.35, 45 = concrete with w/c of 0.45. b No corrosion observed.
100

0

5

10

15

20

25

30

35

40

45

0 100 200 300

Macrocell Corrosion Rate, μm/yr 

Total Corrosion Rate, μm/yr

Conv. - 45

ECR-4h and 10h-45

ECR(RH)-4h and 10h-45

ECR(DCI)-4h and 10h-45

ECR(HY)-4h and 10h-45

ECR(primer/Ca(NO2)2)-4h and 10h-45

MC(Only epoxy penetrated)-4h and 10h-45

MC(both layers penetrated)-4h and 10h-45

ECR(Chromate)-4h and 10h-45

ECR(DuPont)-4h and 10h-45

ECR(Valspar)-4h and 10h-45

ECR(Chromate)-DCI-4h-45 

ECR(DuPont)-DCI-4h-45

ECR(Valspar)-DCI-4h-45

Conv.2-45

Conv.2(RH)-45

Conv.2(DCI)-45

Conv.2(HY)-45

1 μm = 0.0394 mil

Figure 98. Graph. Southern exposure specimens, average total and macrocell corrosion 

rates based on losses after corrosion initiation based on total area for conventional 

reinforcement and area exposed at holes through coating for coated reinforcement, w/c = 0.45. 

y = 0.1529x

0

2

4

6

8

10

12

14

16

18

20

0 20 40 60 80 100

Macrocell Corrosion Rate, μm/yr 

Total Corrosion Rate, μm/yr

Conv. - 45

ECR-4h and 10h-45

ECR(RH)-4h and 10h-45

ECR(DCI)-4h and 10h-45

ECR(HY)-4h and 10h-45

ECR(primer/Ca(NO2)2)-4h and 10h-45

MC(Only epoxy penetrated)-4h and 10h-45

MC(both layers penetrated)-4h and 10h-45

ECR(Chromate)-4h and 10h-45

ECR(DuPont)-4h and 10h-45

ECR(Valspar)-4h and 10h-45

ECR(Chromate)-DCI-4h-45 

ECR(DuPont)-DCI-4h-45

ECR(Valspar)-DCI-4h-45

Conv.2-45

Conv.2(RH)-45

Conv.2(DCI)-45

Conv.2(HY)-45

1 μm = 0.0394 mil

Figure 99. Graph. Southern exposure specimens, average total and macrocell corrosion 

rates based on losses after corrosion initiation based on total area for conventional 

reinforcement and area exposed at holes through coating for coated reinforcement, w/c = 0.45

(different scale). 
101

0

20

40

60

80

100

120

0 200 400 600 800

Macrocell Corrosion Rate, μm/yr 

Total Corrosion Rate, μm/yr

Conv. - 45

ECR-4h and 10h-45

ECR(RH)-4h and 10h-45

ECR(DCI)-4h and 10h-45

ECR(HY)-4h and 10h-45

ECR(primer/Ca(NO2)2)-4h and 10h-45

MC(Only epoxy penetrated)-4h and 10h-45

MC(both layers penetrated)-4h and 10h-45

ECR(Chromate)-4h and 10h-45

ECR(DuPont)-4h and 10h-45

ECR(Valspar)-4h and 10h-45

Conv.2-45

Conv.2(RH)-45

Conv.2(DCI)-45

Conv.2(HY)-45

Conv.-35

ECR-10h-35

ECR(RH)-10h-35

ECR(DCI)-10h-35

ECR(HY)-10h-35

ECR(primer/Ca(NO2)2)-10h-35

1 μm = 0.0394 mil

Figure 100. Graph. Cracked beam specimens, average total and macrocell corrosion rates 

based on losses after corrosion initiation based on total area for conventional reinforcement 

and area exposed at holes through coating for coated reinforcement, w/c = 0.45 or 0.35.

The results in table 22 are used in chapter 4 to estimate total corrosion rates as a function of 

macrocell corrosion rates for the field tests, for which linear polarization resistance data are 

not available. 

The relative performance of the systems can be judged further based on the autopsies of the 

specimens, performed after completion of the tests and based on the performance of the field test 

specimens. As discussed in chapter 4, the tests demonstrated that the coated-bar systems under 

evaluation would serve well in practice. 

Autopsy of Bench-Scale Test Specimens

Following the tests, the specimens were evaluated for staining and cracking and autopsied to observe

the degree of corrosion on the reinforcing steel. With the exception of the cracked beam specimens

containing conventional steel, little cracking or staining was observed on the surface of the benchscale test specimens. Upon removal of the concrete, the degree of corrosion damage was observed. 

Figure 101 illustrates the extent of corrosion damage at 96 weeks to conventional steel (Conv.) in 

the southern exposure tests. The two top bars (at the left of the figure) exhibited varying degrees 

of corrosion along their lengths. The four bottom bars exhibited little if any corrosion damage. In 

contrast, the cracked beam specimen containing conventional steel, shown previously in figure 77, 

exhibited stains on the top and sides as well as a crack that extended from the original simulated 

crack in the center top of the specimen. The cause of the crack extension is shown figure 102, 

where the top bar shows highly nonuniform but major corrosion with the volume of corrosion 

products clearly adequate to cause crack extension. The bottom bars exhibited corrosion, as well, 

especially the center bar in the figure.
102

Figure 101. Photo. Conventional steel bars from southern exposure specimen after 96 weeks.

Figure 102. Photo. Conventional steel bars from cracked beam specimens after 96 weeks.

Upon removal of the concrete from epoxy-coated bars, the epoxy coating was observed to be 

intact on all specimens, although some specimens exhibited blisters, as shown in figure 103. This 

figure shows a top bar from a southern exposure specimen containing conventional ECR. Holes 

placed in the epoxy prior to the test are shown to the center left and right in the figure, while the 

blister in the epoxy is shown at the center. Corrosion products are apparent at both the left and 

the right penetrations. 
103

Figure 103. Photo. Conventional epoxy-coated bar from southern exposure specimen

after 96 weeks.

To evaluate the bond between the epoxy and the steel, a radial 45-degree cut was made with a 

knife at the center of selected openings at the intentionally damaged areas. Following the same 

procedure described in chapter 2 for the cathodic disbondment tests, an attempt was made to lift 

the coating at these locations. If the bond between the coating and the steel was in good 

condition, the epoxy could not be removed. 

The bar surface was inspected for corrosion products following disbondment. In most cases, the 

bar surface appeared black or dark brown, suggesting corrosion in the absence of oxygen. Within 

an hour, the color typically changed to orange or light brown as the corrosion products were 

exposed to oxygen.

The total area of coating disbondment was used to evaluate the bond between the epoxy coating 

and the steel. Figure 104 shows the bar from figure 103 shortly after disbondment at one of the 

penetrations. Figure 105 shows top and bottom bars after disbondment for bars cast in concrete 

containing calcium nitrite. The greater disbondment exhibited by the top bar compared to the 

bottom bar is typical. Corrosion products were present at the left penetration and in the disbonded

region on the bar. Figure 106 shows a top bar in a southern exposure specimen cast with concrete 

containing HycreteTM. In this case, corrosion products were apparent at the left penetration, and 

the epoxy coating exhibited significant disbondment at the penetration near the center of the image 

but no disbondment at the penetration to the right of the image. Figure 107 illustrates a bar coated 

with an epoxy (ECR(DuPont)) that initially provided improved adhesion. The upper bar in the 

image, a top bar in the specimen, underwent complete disbondment while the lower bar in the 

image, a bottom bar in the specimen, underwent only partial disbondment. For the top bar, all 

three penetrations in the epoxy exhibited corrosion products, which were also apparent in the 

disbonded region. MC bars with holes through the epoxy only and with holes penetrating both 

the epoxy and zinc layers are shown in figure 108 and figure 109, respectively. Corrosion products 

were present at the points where the epoxy was penetrated. Both bars exhibited varying degrees 

of disbondment. In all cases, some corrosion products were observable within the disbonded 

region. For the MC bars, the zinc, the more active metal, was seen to preferentially corrode under 

the epoxy coating, thus protecting the underlying steel.

Blister in epoxy

Holes placed in epoxy
104

Figure 104. Photo. Conventional epoxy-coated bar from figure 103 after disbondment test.

Figure 105. Photo. Conventional epoxy-coated top and bottom bars from southern 

exposure specimen containing calcium nitrite after 96 weeks.

Figure 106. Photo. Conventional epoxy-coated top bar from southern exposure specimen 

containing HycreteTM after 96 weeks.

Figure 107. Photo. DuPontTM high-adhesion epoxy-coated top and bottom bars from 

southern exposure specimen after 96 weeks. 
105

Figure 108. Photo. MC top bar with holes through epoxy only from southern exposure 

specimen after 96 weeks.

Figure 109. Photo. MC top bar with holes penetrating both epoxy and zinc from southern 

exposure specimen after 96 weeks.

In addition to visual inspection, the disbonded area on the bars was measured using a grid of 

2.5-mm (0.1-inch) squares printed on a transparent plastic sheet superimposed on the disbonded 

region. For each southern exposure and cracked beam specimen, one bar each from the top and 

bottom mats was chosen to measure disbondment. Disbondment tests were performed at two 

locations on the upper surface of each bar. When the disbonded area extended a distance greater 

than 14.7 mm (0.58 inches) in all directions, the bar was said to exhibit total disbondment. Damage 

locations that exhibited total disbondment were assigned to disbonded area of 680 mm

2 (1.05 in2

), 

the approximate area of the circle with a 14.7-mm (0.58-inch) radius.

Figure 110 and figure 111 show the disbonded areas for bars in the southern exposure and 

cracked beam specimens, respectively, cast with concrete with a w/c ratio of 0.45. In the 

uncracked concrete, disbondment greater than 515 mm2 (0.8 in2

) was observed on the top mat 

of steel for the conventional ECR specimens as well as for all bars with improved adhesion 

between the epoxy and the steel cast in concrete without an inhibitor, with a maximum values 

in excess of 680 mm

2 (1.05 in2

) for the ECR(DuPont) bars. Less disbondment was observed for 

the MC bars and for all bars cast in concrete containing corrosion inhibitors, including those with 

improved adhesion cast in concrete containing calcium nitrite. The bars in concrete containing 

HycreteTM exhibited the least disbondment. Disbondment in the bottom mat was below 130 mm

2

(0.2 in2) for all bars, with MC bars and epoxy-coated bars cast in concrete containing inhibitors 

showing less bottom mat disbondment than the control and improved adhesion bars. 

In cracked concrete, a disbonded area greater than 515 mm2 (0.8 in2

) was observed for the top bars 

in all specimens except MC bars, which exhibited an average disbonded area of approximately 

355 mm2 (0.55 in2). ECR(Chromate) specimens exhibited total disbondment. All bottom-mat bars 

in the cracked beam specimens exhibited increased disbondment compared to bars in uncracked 

concrete with the exception of the MC bars, which exhibited somewhat less.
106

0

100

200

300

400

500

600

DISBONDED AREA, mm2

Top Bar Bottom Bar

1 mm2 = 0.00155 in2

Figure 110. Graph. Disbondment results for southern exposure specimens.

0

100

200

300

400

500

600

DISBONDED AREA, mm2

Top Bar Bottom Bar

1 mm2 = 0.00155 in2

Figure 111. Graph. Disbondment results for cracked beam specimens.

Figure 112 and figure 113 compare the disbondment of bars in southern exposure and cracked 

beam specimens cast in concrete with a w/c ratio of 0.35 with that for similar specimens cast 

with a w/c ratio of 0.45. As shown in figure 112, the average disbonded areas for bars in the 

southern exposure specimens with w/c of 0.35 ranged from 11 percent (ECR(RH)) to 76 percent 
107

(ECR(DCI)) of the values for the southern exposure specimens with w/c of 0.45. In contrast,

figure 113 shows that little difference was observed for the cracked beam specimens as a 

function of w/c ratio, emphasizing both the negative impact of cracks on disbondment and 

the inability of a lower w/c ratio to limit disbondment in the presence of cracks.

0

100

200

300

400

500

600

Disbonded Area, mm2

w/c = 0.45 w/c = 0.35

1 mm2 = 0.00155 in2

Figure 112. Graph. Comparison of disbondment of top bars in southern exposure 

specimens cast in concrete with w/c = 0.35 and 0.45.

0.0

100.0

200.0

300.0

400.0

500.0

600.0

Disbonded Area, mm2

w/c=0.45 w/c=0.35

1 mm2 = 0.00155 in2

Figure 113. Graph. Comparison of disbondment of top bars in cracked beam specimens 

cast in concrete with w/c = 0.35 and 0.45.
108

FIELD TESTS

The field tests provided a highly realistic evaluation of corrosion-protection systems. The test 

specimens were designed to match bridge decks. The key difference was the use of a 25-mm

(1-inch) top cover, which provides earlier corrosion initiation than obtained with the 150-mm

(3-inch) top cover typically used in practice for bridge decks. Four specimens were used to 

evaluate each corrosion-protection system except those cast with the corrosion inhibitor 

calcium nitrite, for which six specimens were used. 

As shown in table 7 in chapter 2, the field tests specimens were cast in nine batches. Half of the 

specimens were cast without cracks and half of the specimens contained simulated cracks over 

four of the seven top reinforcing bars. The coating on epoxy-coated bars was penetrated by 16 

3.2-mm (0.125-inch)-diameter holes to simulate defects in the coating. Rock salt in solution or 

solid form was applied every 4 weeks to provide a salt application rate matching that used on 

bridge decks in Kansas, as described in chapter 2. At the conclusion of the tests (250 or 254 weeks

after initial exposure), chloride samples were obtained from cores taken at the four corners of 

each specimen in batches 3 through 9. The chloride contents for those specimens at a depth of 

25 mm (1 inch) are listed in table 23. The chloride content for the specimens in batch 1 was 

extrapolated from vacuum drill samples taken at 213 weeks. No data is available for batch 2. 

Table 23. Average chloride content (kg/m3

) at a depth of 25 mm (1 inch) at end of field tests.

Batch Specimena Uncracked Cracked

1b Conv.-1, ECR-1, ECR(Valspar)-1 4.40 4.40

2 ECR(Chromate)-1, ECR(DuPont)-1, MC-1 – –

3

Conv.-2 1.97 3.85

ECR-2 3.22 2.18

ECR(primer/Ca(NO2)2)-1 – –

4

ECR(Chromate)-2 3.53 4.89

ECR(DuPont)-2 4.78 4.43

ECR(Valspar)-2 3.03 4.82

5 ECR(primer/Ca(NO2)2)-2 9.86 8.36

MC-2 8.92 8.78

6 ECR(DCI)-1 8.30 9.67

ECR(DCI)-2 7.73 9.03

7 ECR(DCI)-3 8.26 5.20

8 ECR(RH)-1 9.34 8.49

ECR(RH)-2 6.23 7.56

9 ECR(HY)-1 0.55 1.12

ECR(HY)-2 0.29 1.10

1 kg/m3 = 1.69 lb/yd3

– No data. a See table 1 for abbreviation definitions. b Extrapolated from vacuum drill samples taken at 213 weeks.

The chloride content at a depth of 25 mm (1 inch) is plotted versus the w/c ratio in figure 114 for 

the seven batches for which data are available not including the concrete in batch 9, which 
109

contained HycreteTM. HycreteTM was excluded because, as observed for the southern exposure 

tests, the chloride content of the specimens containing HycreteTM was very low (0.77 kg/m3

(1.30 lb/yd3

)). As expected, the figure shows a general trend of increasing chloride content 

with increasing w/c ratio. The variation in w/c ratio between batches is the result of variations 

in the quality of the ready-mix concrete delivered for casting the specimens and is typical of 

the range of properties obtained in the field. Overall, the average chloride contents differed 

markedly, ranging from 0.77 kg/m3 (1.30 lb/yd3

) for the concrete containing HycreteTM to 

2.81 kg/m3 (4.73 lb/yd3

) for batch 3 and 8.73 kg/m3 (14.7 lb/yd3) for batch 5 for concretes 

without a corrosion inhibitor. Extreme values for individual specimens ranged from a low of 

0.29 kg/m3 (0.49 lb/yd3) for uncracked HycreteTM specimen 2 to a high of 9.86 kg/m3 (16.6 lb/yd3) 

for uncracked ECR(primer/Ca(NO2)2) specimen 2. The chloride contents for the individual 

specimens are shown graphically in figure 115 and figure 116 for specimens without and with 

cracks, respectively. Because the chloride samples were taken from the corners of the specimens, 

the values of chloride content do not reflect the effect of the cracks. They are best used as a 

measure of the permeability of the concrete. 

2

3

4

5

6

7

8

9

10

0.35 0.4 0.45 0.5

CHLORIDE CONTENT, kg/m3

W/C RATIO

1 kg/m3 = 1.69 lb/yd3

Figure 114. Graph. Average chloride content at a depth of 25 mm (1 inch) versus w/c ratio 

at end of field tests.
110

* * *

0

2

4

6

8

10

12

CHLORIDE CONTENT, kg/m3

1 kg/m3 = 1.69 lb/yd3

* Extrapolated from vacuum drill data taken at 213 weeks.

Figure 115. Graph. Average chloride content at a depth of 25 mm (1 inch) at end of field 

tests for uncracked field test specimens.

* * *

0

2

4

6

8

10

12

CHLORIDE CONTENT, kg/m3

1 kg/m3 = 1.69 lb/yd3

* Extrapolated from vacuum drill data taken at 213 weeks.

Figure 116. Graph. Average chloride content at a depth of 25 mm (1 inch) at end of field 

tests for cracked field test specimens.

Corrosion Losses

The corrosion losses based on the total area of the bar in contact with the concrete and on the 

exposed area at the holes in the epoxy are presented in table 24 and table 25 for specimens without

cracks and in table 26 and table 27 for specimens with cracks. The data represent two or four bars

per specimen, as shown in the tables. As noted on the tables, negative values of corrosion loss 

are excluded from the average values of loss.
111

Table 24. Corrosion loss at end of field tests (μm) based on total area for specimens 

without simulated cracks.

Steel Designationa

Exposure Time

(weeks)

Test Bar

Averageb

Standard

1 2 3 4 Deviation

Controls

Conv. (1) 250 3.67 2.49 3.08 0.833

Conv. (2) 254 0.142 1.17 0.657 0.728

ECR (1) 250 0.024 0.069 0.046 0.032

ECR (2) 254 0.016 0.008 -0.005c 0.004 0.009 0.006

Bars with increased adhesion

ECR(Chromate) (1) 250 0.015 0.013 0.014 0.001

ECR(Chromate) (2) 254 0.047 -0.042c -0.006c 0.025 0.036 0.016

ECR(DuPont) (1) 250 0.028 0.014 0.021 0.010

ECR(DuPont) (2) 254 0.016 0.007 0.011 0.037 0.018 0.013

ECR(Valspar) (1) 250 0.009 0.024 0.016 0.010

ECR(Valspar) (2) 254 0.025 -0.009c 0.100 0.041 0.055 0.040

Corrosion inhibitors in concrete

ECR(DCI) (1) 250 0.031 0.038 0.019 0.030 0.030 0.008

ECR(DCI) (2) 254 0.062 0.097 0.045 0.017 0.055 0.033

ECR(DCI) (3) 254 0.035 0.034 0.007 0.023 0.025 0.013

ECR(RH) (1) 250 0.068 0.048 0.016 0.045 0.044 0.022

ECR(RH) (2) 254 -0.003c -0.008c -0.004c 0.029 0.029 –

ECR(HY) (1) 250 -0.001c 0.003 0.011 0.047 0.020 0.023

ECR(HY) (2) 254 0.022 0.017 0.033 0.025 0.024 0.007

ECR(primer/Ca(NO2)2) (1) 250 0.000 0.020 0.033 0.028 0.027 0.007

ECR(primer/Ca(NO2)2) (2) 254 0.070 0.030 0.024 0.046 0.042 0.020

Bars with multiple coatings

MC (1) 250 0.024 0.023 0.024 0.001

MC (2) 254 0.047 0.008 0.007 0.049 0.028 0.023

1 μm = 0.0394 mil

– No standard deviation.

Blank cells indicate that the test bar was not present. a See table 1 for abbreviation definitions. All epoxy-coated bars are penetrated with 16 surface holes. b Based on top mat only.

c Excluded from average.
112

Table 25. Corrosion loss at end of field tests (μm) based on area exposed at holes through 

coating for specimens without simulated cracks.

Steel Designationa

Exposure Time

(weeks)

Test Bar

Averageb

Standard

1 2 3 4 Deviation

Controls

ECR (1) 250 9.25 27.0 18.1 12.6

ECR (2) 254 6.27 3.29 -2.04c 1.62 3.73 2.36

Bars with increased adhesion

ECR(Chromate) (1) 250 5.72 5.02 5.37 0.498

ECR(Chromate) (2) 254 18.4 -16.5c -2.34c 9.93 14.2 5.99

ECR(DuPont) (1) 250 11.1 5.57 8.32 3.90

ECR(DuPont) (2) 254 6.39 2.87 4.47 14.4 7.03 5.10

ECR(Valspar) (1) 250 3.49 9.18 6.33 4.02

ECR(Valspar) (2) 254 9.72 -3.49c 38.9 16.0 21.5 15.4

Corrosion inhibitors in concrete

ECR(DCI) (1) 250 12.2 14.8 7.57 11.9 11.6 3.00

ECR(DCI) (2) 254 24.1 37.7 17.5 6.46 21.4 13.1

ECR(DCI) (3) 254 13.8 13.3 2.59 9.00 9.66 5.18

ECR(RH) (1) 250 26.6 18.7 6.06 17.6 17.3 8.47

ECR(RH) (2) 254 -1.34c -3.12c -1.69c 11.2 11.2 –

ECR(HY) (1) 250 -0.458c 1.25 4.42 18.3 7.99 9.07

ECR(HY) (2) 254 8.59 6.69 13.1 9.76 9.52 2.67

ECR(primer/Ca(NO2)2) (1) 250 -0.141c 7.73 12.9 11.0 10.5 2.62

ECR(primer/Ca(NO2)2) (2) 254 27.1 11.6 9.53 17.9 16.5 7.91

Bars with multiple coatings

MC (1) 250 9.54 8.81 9.17 0.515

MC (2) 254 18.4 2.94 2.89 18.9 10.8 9.10

1 μm = 0.0394 mil

– No standard deviation.

Blank cells indicate that the test bar was not present. a See table 1 for abbreviation definitions. All epoxy-coated bars are penetrated with 16 surface holes. b Based on top mat only.

c Excluded from average.
113

Table 26. Corrosion loss at end of field tests (μm) based on total area for specimens with 

simulated cracks.

Steel Designationa

Exposure time

(weeks)

Test Bar

Averageb

Standard

1 2 3 4 Deviation

Controls

Conv. (1) 250 2.26 6.71 4.49 3.14

Conv. (2) 254 4.01 3.34 3.68 0.475

ECR (1) 250 0.015 0.065 0.040 0.035

ECR (2) 254 0.056 0.171 0.044 0.042 0.078 0.062

Bars with increased adhesion

ECR(Chromate) (1) 250 0.039 0.030 0.035 0.006

ECR(Chromate) (2) 254 0.099 0.066 0.051 0.061 0.069 0.021

ECR(DuPont) (1) 250 0.026 0.050 0.038 0.017

ECR(DuPont) (2) 254 0.048 0.029 0.066 0.234 0.094 0.095

ECR(Valspar) (1) 250 0.071 0.177 0.124 0.075

ECR(Valspar) (2) 254 0.023 0.064 0.018 0.153 0.064 0.062

Corrosion inhibitors in concrete

ECR(DCI) (1) 250 0.043 0.065 0.079 0.072 0.065 0.015

ECR(DCI) (2) 254 0.023 0.041 0.074 0.064 0.050 0.023

ECR(DCI) (3) 254 0.105 0.124 0.004 0.020 0.063 0.060

ECR(RH) (1) 250 0.073 0.084 0.038 0.059 0.063 0.020

ECR(RH) (2) 254 0.066 0.057 0.073 0.074 0.068 0.007

ECR(HY) (1) 250 0.044 0.019 0.008 -0.006c 0.024 0.018

ECR(HY) (2) 254 0.005 0.020 -0.006c -0.004c 0.013 0.011

ECR(primer/Ca(NO2)2) (1) 250 0.006 0.017 0.046 0.009 0.019 0.018

ECR(primer/Ca(NO2)2) (2) 254 0.016 0.043 0.041 0.067 0.042 0.021

Bars with multiple coatings

MC (1) 250 0.044 0.056 0.050 0.008

MC (2) 254 0.074 0.061 0.074 0.021 0.057 0.025

1 μm = 0.0394 mil

Blank cells indicate that the test bar was not present. a See table 1 for abbreviation definitions. All epoxy-coated bars are penetrated with 16 surface holes. b Based on top mat only.

c Excluded from average.
114

Table 27. Corrosion loss at end of field tests (μm) based on area exposed at holes through 

coating for specimens with simulated cracks.

Steel Designationa

Exposure time

(weeks)

Test Bar

Averageb

Standard

1 2 3 4 Deviation

Controls

ECR (1) 250 5.72 25.2 15.5 13.8

ECR (2) 254 21.9 66.8 17.1 16.4 30.6 24.3

Bars with increased adhesion

ECR(Chromate) (1) 250 15.3 11.7 13.5 2.52

ECR(Chromate) (2) 254 38.7 25.9 19.9 23.7 27.1 8.16

ECR(DuPont) (1) 250 10.2 19.6 14.9 6.64

ECR(DuPont) (2) 254 18.7 11.3 25.6 91.4 36.8 36.9

ECR(Valspar) (1) 250 27.8 69.2 48.5 29.3

ECR(Valspar) (2) 254 8.9 24.9 7.06 59.6 25.1 24.4

Corrosion inhibitors in concrete

ECR(DCI) (1) 250 16.8 25.3 30.7 28.1 25.2 6.02

ECR(DCI) (2) 254 9.00 15.9 28.9 24.9 19.7 8.96

ECR(DCI) (3) 254 40.9 48.5 1.48 7.96 24.7 23.4

ECR(RH) (1) 250 28.3 32.7 14.8 23.0 24.7 7.70

ECR(RH) (2) 254 25.9 22.4 28.4 28.7 26.4 2.92

ECR(HY) (1) 250 17.2 7.31 3.31 -2.47c 9.27 7.15

ECR(HY) (2) 254 1.95 7.85 -2.24c -1.55c 4.90 4.17

ECR(primer/Ca(NO2)2) (1) 250 2.27 6.55 18.0 3.59 7.59 7.14

ECR(primer/Ca(NO2)2) (2) 254 6.38 16.8 16.0 26.0 16.3 8.00

Bars with multiple coatings

MC (1) 250 17.1 21.8 19.5 3.32

MC (2) 254 28.9 23.8 28.7 8.24 22.4 9.75

1 μm = 0.0394 mil

Blank cells indicate that the test bar was not present. a See table 1 for abbreviation definitions. All epoxy-coated bars are penetrated with 16 surface holes. b Based on top mat only.

c Excluded from average.

Control Specimens

As with the bench-scale tests, the control specimens for the field tests consisted of conventional 

reinforcement and conventional ECR cast in concrete without and with cracks. Due to the more 

realistic, milder exposure conditions obtained in the field, the corrosion rates were about one-fourth 

those observed in the bench-scale tests. The average corrosion losses based on exposed area for 

the control specimens without and with simulated cracks over the top bars are shown in figure 117

over a period of 250 weeks. The losses for the conventional ECR specimens are shown in figure 118.

Uncracked specimens are denoted with a “U” and cracked specimens are denoted with a “C” in 

the figures. The graphs show that specimens with cracks began to corrode earlier and at a higher 

rate than those with intact concrete and that the ECR bars corroded at a much slower rate than 

conventional reinforcement. Based on total bar area, average losses at 250 weeks ranged from 

3.99 μm (0.157 mil) for conventional steel specimens with cracks and 1.86 μm (0.0732 mil) for 
115

conventional steel specimens without cracks to less than 0.055 μm (0.0022 mil) for ECR 

specimens. Based on exposed area, the ECR specimens exhibited losses of 10.7 and 22.1 μm

(0.421 and 0.870 mil) at 250 weeks for specimens without and with simulated cracks, respectively.

As shown in figure 118, the specimens without cracks exhibited negative corrosion between 

weeks 72 and 152, at which point the net losses became positive. Based on the shape of the 

curve, corrosion appears to have initiated, on average, at week 144. In contrast, the specimens 

with simulated cracks exhibited corrosion initiation at week 76.

0.0

1.0

2.0

3.0

4.0

5.0

0 25 50 75 100 125 150 175 200 225 250

CORROSION LOSS, μm

TIME, weeks

Conv.-U Conv.-C ECR-U ECR-C

1 μm = 0.0394 mil

Figure 117. Graph. Field test, average corrosion loss based on total area for conventional 

reinforcement and ECR.

-3.0

0.0

3.0

6.0

9.0

12.0

15.0

18.0

21.0

24.0

0 25 50 75 100 125 150 175 200 225 250

CORROSION LOSS, μm

TIME, weeks

ECR-U ECR-C

1 μm = 0.0394 mil

Figure 118. Graph. Field test, average corrosion loss based on exposed area for ECR.
116

The average corrosion potentials for the top and bottom bar mats are shown in figure 119 and 

figure 120, respectively, with the potentials cycling between high and low values as the moisture 

content and temperature conditions of the specimens varied. The top bars had average corrosion 

potentials more negative than -0.350 V with respect to a CSE with the exception of the ECR 

specimens without simulated cracks. As shown in figure 120, the corrosion potentials of the bars 

in the bottom mats remained above -0.350 V with the exception of the conventional steel 

specimens with cracks at week 112. 

-0.70

-0.60

-0.50

-0.40

-0.30

-0.20

-0.10

0.00

0 25 50 75 100 125 150 175 200 225 250

CORROSION POTENTIAL, V

TIME, weeks

Conv.-U Conv.-C ECR-U ECR-C

Figure 119. Graph. Field test, corrosion potential of top mat for conventional 

reinforcement and ECR.

-0.70

-0.60

-0.50

-0.40

-0.30

-0.20

-0.10

0.00

0 25 50 75 100 125 150 175 200 225 250

CORROSION POTENTIAL, V

TIME, weeks

Conv.-U Conv.-C ECR-U ECR-C

Figure 120. Graph. Field test, corrosion potential of bottom mat for conventional 

reinforcement and ECR.
117

Epoxies with Improved Adhesion

The corrosion performance of the bars with improved adhesion epoxies, ECR(Valspar),

ECR(DuPont), and ECR(Chromate), is compared to that of the conventional ECR in figure 121

and figure 122 based on exposed area for field test specimens without and with simulated cracks, 

respectively. A comparison of the two figures shows that the corrosion rate of the specimens with 

simulated cracks was 3 to 5 times the value for specimens without cracks. The results also indicate

little difference in the performance of the specimens based on average corrosion loss, although, 

as shown in table 24 through table 27, significant scatter is evident between results for individual 

specimens for both uncracked and cracked specimens. At 250 weeks, ECR(Valspar) exhibited the 

highest average corrosion losses, 12.8 and 36.5 μm (0.504 and 1.44 mil), while ECR(DuPont)

exhibited the lowest loss for uncracked specimens, 3.75 μm (0.148 mil) and ECR(Chromate) 

exhibited the lowest loss for cracked specimens, 20.1 μm (0.791 mil). Considering the very low 

corrosion losses based on total bar area, however, there is little practical difference in behavior as 

a function of the degree of adhesion between the epoxy coating and the underlying steel. As observed

for the bench-scale specimens and in other studies, the results demonstrate that improved performance

in the cathodic disbondment test does not correlate with improved corrosion performance.(16)

-4.0

-2.0

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

0 25 50 75 100 125 150 175 200 225 250

CORROSION LOSS, μm

TIME, weeks

ECR-U ECR(Chromate)-U ECR(DuPont)-U ECR(Valspar)-U

1 μm = 0.0394 mil

Figure 121. Graph. Field test, average corrosion losses based on area exposed at holes 

through coating for conventional and increased-adhesion ECR without simulated cracks.
118

-5.0

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

40.0

0 25 50 75 100 125 150 175 200 225 250

CORROSION LOSS, μm

TIME, weeks

ECR-C ECR(Chromate)-C ECR(DuPont)-C ECR(Valspar)-C

1 μm = 0.0394 mil

Figure 122. Graph. Field test, average corrosion losses based on area exposed at holes 

through coating for conventional and increased-adhesion ECR with simulated cracks.

The average corrosion potentials for the top and bottom mats of reinforcement in specimens 

without cracks are shown in figure 123 and figure 124. None of the top bars exhibited a potential 

more negative than -0.350 V at any time during the test, and only one bottom mat, ECR(Chromate)

at week 100, reached an average corrosion potential more negative than -0.350 V. In contrast, 

figure 125 and figure 126 show that all of the epoxy-coated bars in specimens with simulated cracks

reached corrosion potentials more negative than -0.350 V by week 72. The corrosion potentials of 

the bottom mats of steel for the same specimens were generally more positive than -0.350 V, but at

some point during the tests, all bottom mats reached average corrosion potentials below that value.

-0.70

-0.60

-0.50

-0.40

-0.30

-0.20

-0.10

0.00

0 25 50 75 100 125 150 175 200 225 250

CORROSION POTENTIAL, V

TIME, weeks

ECR-U ECR(Chromate)-U ECR(DuPont)-U ECR(Valspar)-U

Figure 123. Graph. Field test, corrosion potential of top mat for conventional and 

increased-adhesion ECR without simulated cracks.
119

-0.70

-0.60

-0.50

-0.40

-0.30

-0.20

-0.10

0.00

0 25 50 75 100 125 150 175 200 225 250

CORROSION POTENTIAL, V

TIME, weeks

ECR-U ECR(Chromate)-U ECR(DuPont)-U ECR(Valspar)-U

Figure 124. Graph. Field test, corrosion potential of bottom mat for conventional and 

increased-adhesion ECR without simulated cracks.

-0.70

-0.60

-0.50

-0.40

-0.30

-0.20

-0.10

0.00

0 25 50 75 100 125 150 175 200 225 250

CORROSION POTENTIAL, V

TIME, weeks

ECR-C ECR(Chromate)-C ECR(DuPont)-C ECR(Valspar)-C

Figure 125. Graph. Field test, corrosion potential of top mat for conventional and 

increased-adhesion ECR with simulated cracks.
120

-0.70

-0.60

-0.50

-0.40

-0.30

-0.20

-0.10

0.00

0 25 50 75 100 125 150 175 200 225 250

CORROSION POTENTIAL, V

TIME, weeks

ECR-C ECR(Chromate)-C ECR(DuPont)-C ECR(Valspar)-C

Figure 126. Graph. Field test, corrosion potential of bottom mat for conventional and 

increased-adhesion ECR with simulated cracks.

Overall, the corrosion potentials of the bottom and top mats of steel became progressively more 

positive during the last 50 weeks of the test, perhaps because the deposition of corrosion products 

at some of the penetrations limited access of oxygen and moisture. It is not clear that the changes 

in potential translated into a change in corrosion rate, although the corrosion rates (based on the 

slope of the corrosion loss curves) during the last 25 to 50 weeks are, in most cases, below the 

average rate of corrosion over the final 100 weeks of the test. 

ECR Used in Conjunction with Corrosion Inhibitors

Average corrosion losses based on exposed area for conventional ECR cast in concrete without a 

corrosion inhibitor and cast in concrete with calcium nitrite, Rheocrete® 222+, and HycreteTM, as 

well as bars with microencapsulated calcium nitrite primer are shown in figure 127 and figure 128.

At 250 weeks for specimens without simulated cracks, the ECR(HY) specimens exhibited the 

lowest average corrosion loss based on exposed area, 8.2 μm (0.32 mil), while ECR(RH) exhibited

the highest loss, 14.2 μm (0.559 mil). Several bars exhibited negative corrosion values, with 

ECR(RH) exhibiting a negative loss as late as week 172. Based on the slope of the corrosion loss 

curves, however, it appears that all specimens were undergoing corrosion by week 124. With the 

exception of specimens containing HycreteTM, the specimens containing corrosion inhibitors 

exhibited chloride contents 1.5 to 2 times that exhibited by the concrete in the specimens with 

conventional ECR (see table 23). The difference is likely a function of the higher w/c ratios of 

the specimens containing a corrosion inhibitor (see table 7).

As shown in figure 128, the specimens with simulated cracks exhibited a wider range in corrosion 

loss than those without cracks. The ECR(HY) specimens exhibited the lowest average corrosion loss

at 250 weeks, 8.04 μm (0.317 mil), based on exposed area, followed by the ECR(primer/Ca(NO2)2)

specimens at 11.93 μm (0.4697 mil) (very close to the value observed in the ECR(primer/Ca(NO2)2)

specimens without cracks) and then by the ECR, ECR(DCI), and ECR(RH) specimens, with 

average losses of 22.1, 23.0, and 23.6 μm (0.870, 0.906, and 0.929 mil), respectively.
121

-6.0

-4.0

-2.0

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

16.0

0 25 50 75 100 125 150 175 200 225 250

CORROSION LOSS, μm

TIME, weeks

ECR-U ECR(RH)-U ECR(DCI)-U ECR(HY)-U ECR(primer/Ca(NO2)2)-U

1 μm = 0.0394 mil

Figure 127. Graph. Field test, average corrosion losses based on area exposed at holes 

through coating for conventional ECR without and with corrosion inhibitors and without 

simulated cracks.

-5.0

0.0

5.0

10.0

15.0

20.0

25.0

0 25 50 75 100 125 150 175 200 225 250

CORROSION LOSS, μm

TIME, weeks

ECR-C ECR(RH)-C ECR(DCI)-C ECR(HY)-C ECR(primer/Ca(NO2)2)-C

1 μm = 0.0394 mil

Figure 128. Graph. Field test, average corrosion losses based on area exposed at holes 

through coating for conventional ECR without and with corrosion inhibitors and with 

simulated cracks.

The corrosion potentials for specimens without simulated cracks are shown in figure 129 and 

figure 130, and the corrosion potentials for specimens with simulated cracks are shown in figure 131

and figure 132. For the specimens without simulated cracks, the corrosion potentials of the top mats

of steel remained more positive than -0.350 V for ECR, ECR(DCI), ECR(HY), and ECR(RH) 
122

throughout the tests while dropping below -0.350 V for ECR(primer/Ca(NO2)2) for two readings 

during the 250-week test period. The corrosion potential of the bottom mat of reinforcement was 

more positive than -0.350 V in all cases. Once again, in contrast to uncracked concrete, the 

corrosion potentials in the top mats for all systems in specimens with simulated cracks were 

more negative than -0.350 V during the test. For the bottom mat, the corrosion potential was 

more negative than -0.350 V only for ECR(RH) and only between weeks 160 and 172.

-0.70

-0.60

-0.50

-0.40

-0.30

-0.20

-0.10

0.00

0 25 50 75 100 125 150 175 200 225 250

CORROSION POTENTIAL, V

TIME, weeks

ECR-U ECR(RH)-U ECR(DCI)-U ECR(HY)-U ECR(primer/Ca(NO2)2)-U

Figure 129. Graph. Field test, corrosion potential of top mat for conventional ECR without 

and with corrosion inhibitors and without simulated cracks.

-0.70

-0.60

-0.50

-0.40

-0.30

-0.20

-0.10

0.00

0 25 50 75 100 125 150 175 200 225 250

CORROSION POTENTIAL, V

TIME, weeks

ECR-U ECR(RH)-U ECR(DCI)-U ECR(HY)-U ECR(primer/Ca(NO2)2)-U

Figure 130. Graph. Field test, corrosion potential of bottom mat for conventional ECR 

without and with corrosion inhibitors and without simulated cracks.
123

-0.70

-0.60

-0.50

-0.40

-0.30

-0.20

-0.10

0.00

0 25 50 75 100 125 150 175 200 225 250

CORROSION POTENTIAL, V

TIME, weeks

ECR-C ECR(RH)-C ECR(DCI)-C ECR(HY)-C ECR(primer/Ca(NO2)2)-C

Figure 131. Graph. Field test, corrosion potential of top mat for conventional ECR without 

and with corrosion inhibitors and with simulated cracks.

-0.70

-0.60

-0.50

-0.40

-0.30

-0.20

-0.10

0.00

0 25 50 75 100 125 150 175 200 225 250

CORROSION POTENTIAL, V

TIME, weeks

ECR-C ECR(RH)-C ECR(DCI)-C ECR(HY)-C ECR(primer/Ca(NO2)2)-C

Figure 132. Graph. Field test, corrosion potential of bottom mat for conventional ECR 

without and with corrosion inhibitors and with simulated cracks.

Bars with Multiple Coatings

The corrosion losses for the bars with multiple coatings are compared with those for conventional

ECR in figure 133 and figure 134 for bars without and with simulated cracks over the reinforcement, 

respectively. The hole through the coatings on the MC bars in the field tests penetrated both the 

zinc and the epoxy layers. Unlike the results observed for the bench-scale tests, where the MC bars

exhibited significantly more corrosion than the conventional ECR bars, the corrosion losses for the

MC bars were slightly below those for the ECR bars in the field test, with average corrosion losses 

at 250 weeks of 10.0 and 10.7 μm (0.394 and 0.421 mil) for MC and ECR bars, respectively, in 
124

specimens without cracks and 20.1 and 22.1 μm (0.791 and 0.870 mil), respectively, for MC and 

ECR bars in specimens with simulated cracks over the bars. The relative behavior of the MC bars in

the field and bench-scale tests suggests that MC reinforcement performs much like conventional 

ECR under exposure conditions similar to those in bridge decks, even providing an advantage 

since the initial losses represent corrosion of the zinc coating rather than the underlying steel, but 

will provide no significant advantage in cases where the concrete is often saturated, such as in 

marine environments.

-2.0

0.0

2.0

4.0

6.0

8.0

10.0

12.0

0 25 50 75 100 125 150 175 200 225 250

CORROSION LOSS, μm

TIME, weeks

ECR-U MC-U

1 μm = 0.0394 mil

Figure 133. Graph. Field test, average corrosion losses based on area exposed at holes 

through coating for conventional ECR and MC reinforcement without simulated cracks.

0.0

5.0

10.0

15.0

20.0

25.0

0 25 50 75 100 125 150 175 200 225 250

CORROSION LOSS, μm

TIME, weeks

ECR-C MC-C

1 μm = 0.0394 mil

Figure 134. Graph. Field test, average corrosion losses based on area exposed at holes 

through coating for conventional ECR and MC reinforcement with simulated cracks.
125

The corrosion potentials for specimens without and with cracks are shown in figure 135 through 

figure 138. The corrosion potentials were initially more negative than -0.350 V for the top mats 

of steel for MC bars in specimens both without and with simulated cracks and somewhat more 

negative (-0.500 V) for specimens with cracks than those without cracks (-0.400 V).

-0.70

-0.60

-0.50

-0.40

-0.30

-0.20

-0.10

0.00

0 25 50 75 100 125 150 175 200 225 250

CORROSION POTENTIAL, V

TIME, weeks

ECR-U MC-U

Figure 135. Graph. Field test, corrosion potential of top mat for conventional ECR without 

and with corrosion inhibitors and without simulated cracks.

-0.70

-0.60

-0.50

-0.40

-0.30

-0.20

-0.10

0.00

0 25 50 75 100 125 150 175 200 225 250

CORROSION POTENTIAL, V

TIME, weeks

ECR-U MC-U

Figure 136. Graph. Field test, corrosion potential of bottom mat for conventional ECR 

without and with corrosion inhibitors and without simulated cracks.
126

-0.70

-0.60

-0.50

-0.40

-0.30

-0.20

-0.10

0.00

0 25 50 75 100 125 150 175 200 225 250

CORROSION POTENTIAL, V

TIME, weeks

ECR-C MC-C

Figure 137. Graph. Field test, corrosion potential of top mat for conventional ECR without 

and with corrosion inhibitors and with simulated cracks.

-0.70

-0.60

-0.50

-0.40

-0.30

-0.20

-0.10

0.00

0 25 50 75 100 125 150 175 200 225 250

CORROSION POTENTIAL, V

TIME, weeks

ECR-C MC-C

Figure 138. Graph. Field test, corrosion potential of bottom mat for conventional ECR 

without and with corrosion inhibitors and with simulated cracks.

The top mat corrosion potential for specimens both without and with cracks became more positive 

toward the end of tests, reaching values in the range of -0.300 to -0.350 V. The corrosion potential 

of the bottom mats of steel started close to -0.350 V for specimens both without and with simulated

cracks, rising to values more positive than -0.150 V by the end of the 250-week test. This behavior

suggests that the zinc exposed at the penetrations through the coating dominated the behavior early 

in the test, but the effect diminished by the end of the test period, with the underlying steel 

dominating the behavior of the bottom mat.
127

Corrosion Rates Based on Losses After Corrosion Initiation

The average corrosion rates based on losses after corrosion initiation are summarized in table 28

and table 29 for field test specimens without and with simulated cracks, respectively. The rates 

are expressed in terms of total area for bars without coatings and in terms of exposed area for 

bars with coatings. The rates shown in the tables provide a good representation of corrosion rates 

expected in bridge decks because both the exposure conditions and structural design of the 

specimens closely match those of bridge decks in Kansas.

Table 28. Average corrosion rate (μm/year) based on losses after corrosion initiation for 

field test specimens without simulated cracks.

Steel Designationa Specimen

Bar

Average

Standard 

1 2 3 4 Deviation

Bars without coatings—corrosion rate based on total area

Controls

Conv.

1 1.55 0.77

0.882 0.62

2 b 0.322

Bars with coatings—corrosion rate based on exposed area

Controls

ECR

1 9.86 10.1

5.68 4.21

2 0.587 4.90 b 2.97

Bars with increased adhesion

ECR(Chromate)

1 4.86 2.50

4.83 3.35

2 10.4 b 1.97 4.40

ECR(DuPont)

1 5.35 2.95

5.14 5.99

2 0.710 5.35 1.41 17.0

ECR(Valspar)

1 2.38 9.77

9.11 4.90

2 15.0 b 12.0 6.39

Corrosion inhibitors in concrete

ECR(DCI)

1 3.58 3.69 1.64 2.73

2 6.62 10.3 4.95 1.41 4.26 2.81

3 4.47 7.86 0.904 2.96

ECR(RH)

1 10.2 5.24 6.49 3.97

5.43 3.68

2 1.49 0.856 b 9.72

ECR(HY)

1 1.82 b 1.75 6.09

2.89 1.62

2 1.52 3.74 3.11 2.18

ECR(primer/Ca(NO2)2)

1 b 1.89 4.25 2.60

4.49 2.95

2 10.3 3.78 2.36 6.22

Bars with multiple coatings

MC

1 5.54 6.58

6.31 3.39

2 11.9 6.35 1.29 6.68

1 μm = 0.0394 mil

Blank cells indicate that the test bar was not present. a See table 1 for abbreviation definitions. b No corrosion observed. 
128

Table 29. Average corrosion rate (μm/year) based on losses after corrosion initiation for 

field test specimens with simulated cracks.

Steel Designationa Specimen

Bar

Average

Standard 

1 2 3 4 Deviation

Bars without coatings—corrosion rate based on total area

Controls

Conv.

1 0.482 1.65

0.939 0.61

2 0.897 0.731

Bars with coatings—corrosion rate based on exposed area

Controls

ECR

1 2.91 10.3

8.13 7.82

2 5.76 22.6 4.58 5.72

Bars with increased adhesion

ECR(Chromate)

1 5.06 5.79

8.94 8.65

2 25.6 6.43 6.31 11.4

ECR(DuPont)

1 3.79 5.72

6.50 4.05

2 10.8 2.30 12.8 7.10

ECR(Valspar)

1 3.76 11.6

7.64 4.93

2 7.19 16.5 8.46 1.99

Corrosion inhibitors in concrete

ECR(DCI)

1 3.20 4.97 8.67 8.22

2 1.62 10.1 7.52 5.51 5.79 3.60

3 0.634 0.500 7.95 10.6

ECR(RH)

1 9.92 8.34 6.07 7.74

8.38 1.64

2 11.2 8.38 7.68 7.78

ECR(HY)

1 6.12 2.06 12.0 b

4.32 4.31

2 2.12 2.28 b 1.36

ECR(primer/Ca(NO2)2)

1 9.28 2.22 4.75 b

4.65 2.13

2 1.78 4.25 3.90 6.40

Bars with multiple coatings

MC

1 5.64 10.9

8.11 5.29

2 1.47 5.89 6.40 14.2

1 μm = 0.0394 mil

Blank cells indicate that the test bar was not present. a See table 1 for abbreviation definitions. b No corrosion observed. 

Mat-to-Mat Resistance 

The average mat-to-mat resistance results for the field test specimens are shown in figure 139 though

figure 145. Uncracked specimens are denoted with a “U” and cracked specimens are denoted with 

a “C” in the figures. As observed in figure 53 for the southern exposure specimens, the high resistance

provided by the epoxy coating was also apparent for the field test specimens, as shown in figure 139, 

which compares mat-to-mat resistance for conventional reinforcement and conventional ECR in 

specimens without and with simulated cracks. The highest resistances were exhibited by ECR in 

concrete containing corrosion inhibitors Rheocrete® and HycreteTM, as shown in figure 142 and 

figure 143.
129

0

2500

5000

7500

10000

12500

15000

17500

20000

0 25 50 75 100 125 150 175 200 225 250

MAT-TO-MAT RESISTANCE, ohms

TIME, weeks

Conv.-U Conv.-C ECR-U ECR-C

Figure 139. Graph. Field test, mat-to-mat resistance for conventional reinforcement and ECR.

0

2500

5000

7500

10000

12500

15000

17500

20000

0 25 50 75 100 125 150 175 200 225 250

MAT-TO-MAT RESISTANCE, ohms

TIME, weeks

ECR-U ECR(Chromate)-U ECR(DuPont)-U ECR(Valspar)-U

Figure 140. Graph. Field test, mat-to-mat resistance for conventional and increasedadhesion ECR without simulated cracks.
130

0

2500

5000

7500

10000

12500

15000

17500

20000

0 25 50 75 100 125 150 175 200 225 250

MAT-TO-MAT RESISTANCE, ohms

TIME, weeks

ECR-C ECR(Chromate)-C ECR(DuPont)-C ECR(Valspar)-C

Figure 141. Graph. Field test, mat-to-mat resistance for conventional and increasedadhesion ECR with simulated cracks.

0

2500

5000

7500

10000

12500

15000

17500

20000

0 25 50 75 100 125 150 175 200 225 250

MAT-TO-MAT RESISTANCE, ohms

TIME, weeks

ECR-U ECR(RH)-U ECR(DCI)-U ECR(HY)-U ECR(primer/Ca(NO2)2)-U

Figure 142. Graph. Field test, mat-to-mat resistance for conventional ECR without and 

with corrosion inhibitors and without simulated cracks.
131

0

2500

5000

7500

10000

12500

15000

17500

20000

0 25 50 75 100 125 150 175 200 225 250

MAT-TO-MAT RESISTANCE' ohms

TIME, weeks

ECR-C ECR(RH)-C ECR(DCI)-C ECR(HY)-C ECR(primer/Ca(NO2)2)-C

Figure 143. Graph. Field test, mat-to-mat resistance for conventional ECR without and 

with corrosion inhibitors and with simulated cracks.

0

2500

5000

7500

10000

12500

15000

17500

20000

0 25 50 75 100 125 150 175 200 225 250

MAT-TO-MAT RESISTANCE, ohms

TIME, weeks

ECR-U MC-U

Figure 144. Graph. Field test, mat-to-mat resistance for conventional ECR and MC 

reinforcement without simulated cracks.
132

0

2500

5000

7500

10000

12500

15000

17500

20000

0 25 50 75 100 125 150 175 200 225 250

MAT-TO-MAT RESISTANCE, ohms

TIME, weeks

ECR-C MC-C

Figure 145. Graph. Field test, mat-to-mat resistance for conventional ECR and MC 

reinforcement with simulated cracks.

For all bar types, the mat-to-mat resistance rose over time, reached a peak, and then declined or, 

in a few cases, leveled off. The times at which each bar type reached the peak resistance differ, 

but a similarity between resistances in specimens without and with cracks for the same bar type 

is clear. Causes for the decrease in the resistance may include deterioration of concrete, increase 

in ionic conductivity resulting from the increased chloride content, and for the coated bars systems, 

disbondment or other damage to the coating. The figures illustrating corrosion loss versus time 

for the field test specimens indicate little change in the corrosion rates in the latter stages of the 

tests, suggesting that decreases in mat-to-mat resistance or any damage accompanying the 

decreases did not result in an increase in corrosion rate for these specimens.

Autopsy of Field Test Specimens

At the conclusion of the field tests at 250 or 254 weeks, specimens were evaluated for staining 

and cracking and autopsied to evaluate the nature of any corrosion on the reinforcing steel 

following the same procedures used for the southern exposure and cracked beam specimens. 

Epoxy-coated bars were evaluated for disbondment. As previously described, specimens in 

batches 3 through 9 were cored to measure the chloride content at the end of the tests. 

The specimens both without and with simulated cracks containing conventional reinforcing steel 

exhibited staining and cracking of the concrete, as shown in figure 146 through figure 149. The 

age at crack initiation for each bar instrumented to measure corrosion was estimated from photos 

of each specimen taken approximately annually beginning at the third year of testing. The age at 

cracking was assumed to be the average of the specimen age in the last photograph where no 

cracking was observed above the test bar and the specimen age in the first photograph where 

cracking was observed. The values for the four field test specimens containing conventional steel 

are listed in table 30. Also, as shown in the figures, the cracks were primarily parallel to the top 
133

reinforcing bars. This cracking occurred in spite of the fact that the average macrocell corrosion

loss did not exceed 6.7 μm (0.26 mil) on any individual bar, a value that is below 25 μm (0.98 mil), 

the corrosion loss typically needed to crack concrete with 25 mm (1 inch) of cover over the 

reinforcing steel.(44) An explanation is provided for conventional steel specimens without and 

with simulated cracks in figure 150 and figure 151, which show that some of the top bars had 

corrosion losses well above 25 μm (0.98 mil) and that the corrosion products were not uniformly 

distributed over the surface of the bars. In reference to the latter point, a visual inspection of 

the conventional reinforcement from the field test specimens at the end of testing indicated that 

corrosion covered only about one-third of the total of bar area in uncracked concrete and about 

40 percent of the total bar area in cracked concrete. Thus, although the average corrosion losses 

based on macrocell corrosion remained well below 25 μm (0.98 mil), enough of the bar surface 

underwent corrosion adequate to crack the concrete. In addition, the losses given in table 24

and table 26 represent macrocell losses rather than total losses, which, as discussed with the 

linear polarization resistance results for the bench-scale tests, are several times greater than the 

macrocell losses. This information is used in chapter 4 to estimate the time to cracking on 

bridge decks. As illustrated in figure 152 and figure 153, none of the field test specimens 

containing coated reinforcement exhibited cracking of the concrete. 

Figure 146. Photo. Field test specimen without simulated cracks containing conventional 

reinforcing steel at 250 weeks.
134

Figure 147. Photo. Field test specimen without simulated cracks containing conventional 

reinforcing steel at 254 weeks.

Figure 148. Photo. Field test specimen with simulated cracks containing conventional 

reinforcing steel at 250 weeks.
135

Figure 149. Photo. Field test specimen with simulated cracks containing conventional 

reinforcing steel at 254 weeks.

Table 30. Estimated time to cracking for instrumented bars on field test specimens 

containing conventional steel.

Specimen-Bara Estimated Time to 

Cracking (weeks)

Conv. (1)-U-1 227

Conv. (1)-U-2 183

Conv. (2)-U-1b –

Conv. (2)-U-2 222

Conv. (1)-C-1 227

Conv. (1)-C-2c –

Conv. (2)-C-1 171

Conv. (2)-C-2 171 a Number in parentheses is specimen number (U = 

specimen without simulated cracks; C = specimen

with simulated cracks; final number is bar number.) b No cracking observed. c Cracking occurred prior to first photo.
136

Figure 150. Photo. Top bars from field test specimen without simulated cracks containing 

conventional reinforcing steel at 254 weeks.

Figure 151. Photo. Top bars from field test specimen with simulated cracks containing 

conventional reinforcing steel at 250 weeks.

Figure 152. Photo. Field test specimen without simulated cracks containing conventional 

epoxy-coated steel at 254 weeks.
137

Figure 153. Photo. Field test specimen with simulated cracks containing conventional 

epoxy-coated steel at 254 weeks.

The only other observation of interest relative to the appearance of the concrete deals with the 

specimens cast with corrosion inhibitor HycreteTM. Those specimens uniformly exhibited scaling 

of the upper surface for specimens both without and with simulated cracks, as shown in figure 154

and figure 155. This result suggests that additional work is needed to establish criteria to preclude a 

loss of durability when Hycrete is used.

Figure 154. Photo. Field test specimen without simulated cracks containing conventional 

ECR and HycreteTM corrosion inhibitor at 250 weeks.
138

Figure 155. Photo. Field test specimen with simulated cracks containing conventional ECR 

and HycreteTM corrosion inhibitor at 254 weeks.

All bars were removed from the specimens, and the outermost epoxy-coated bars were evaluated 

for disbondment, including all top and bottom bars in specimens without cracks and all electrically 

connected top and bottom bars in specimens with cracks. Disbondment was checked at two points 

on the upper side of each bar using the procedures described for the bench-scale specimens. In 

the description that follows, bars that were electrically connected between the top and bottom 

mats are distinguished from those that were electrically isolated. 

Figure 156 and figure 157 show bars following the disbondment tests. Figure 156 shows bars 

coated with conventional reinforcement cast in concrete containing Rheocrete®, and figure 157

shows bars coated with the high-adhesion DuPontTM coating. The figures are typical of observations

made in the field test specimens for all types of ECR and demonstrate that corrosion occurred 

both at the points where the epoxy was penetrated and under the epoxy coating. Figure 158

shows disbondment results for an MC bar, with a loss of the zinc coating under the epoxy and 

subsequent corrosion of the steel. 

Figure 156. Photo. Conventional epoxy-coated top bars from field test specimen containing 

Rheocrete® 222+ corrosion inhibitor without simulated cracks after 254 weeks.
139

Figure 157. Photo. High adhesion DuPontTM epoxy-coated top bars from field test specimen 

with simulated cracks after 250 weeks.

Figure 158. Photo. MC top bars from field test specimen with simulated cracks after 250 weeks.

The average values of disbondment for the electrically connected top and bottom bars for specimens

without and with simulated cracks over the reinforcement are shown in figure 159 and figure 160,

respectively. For specimens without cracks, the average values of disbondment for individual 

specimens with the same corrosion protection systems were quite similar in a number of cases 

and quite different in others. Specifically, conventional ECR, ECR(HY), ECR(Valspar), 

ECR(DuPont), and ECR(Chromate) exhibited low values of disbondment for the top bars for both

specimens. In contrast, ECR(primer/Ca(NO2)2), ECR(DCI), ECR(RH), and MC bars exhibited 

significantly higher disbondment for some but not all of the specimens. The scatter is, in all 

likelihood, typical of what would be observed in bridge decks. ECR(primer/Ca/NO2)2 specimens 1 

and 2 and ECR specimen 2 exhibited the highest disbondment among bottom bars, at 127, 102, 

and 110 mm2 (0.20, 0.16, and 0.17 in2

), respectively, but the bottom bars in most specimens 

exhibited significantly less disbondment and, in many cases, no disbondment was observed.
140

0

100

200

300

400

500

600

DISBONDED AREA, mm2

Top Bars Bottom Bars

1 mm2 = 0.00155 in2

Figure 159. Graph. Disbondment results for electrically connected bars in field test 

specimens without simulated cracks.

0

100

200

300

400

500

600

DISBONDED AREA, mm2

Top Bars Bottom Bars

1 mm2 = 0.00155 in2

Figure 160. Graph. Disbondment results for electrically connected bars in field test 

specimens with simulated cracks.
141

Figure 160 shows that, as with the cracked beam specimens, the field test specimens with 

simulated cracks over the reinforcement exhibited significantly more disbondment than the 

specimens without simulated cracks. All specimens had average top bar disbondment values in 

excess of 317 mm2 (0.49 in2), and all groups except conventional ECR and ECR(primer/Ca/NO2)2

had at least one specimen with average disbondment in excess of 606 mm2 (0.94 in2). One specimen

for ECR(DCI), ECR(RH), ECR(Valspar), and ECR(DuPont) and both bars for ECR(HY) exhibited

total disbondment of the top bars. As observed in the cracked beam specimens, MC reinforcement 

exhibited very low disbondment on the bottom mat of steel.

Figure 161 compares the disbondment for top bars in specimens without cracks that are electrically

connected with adjacent bars that are electrically isolated. Without exception, the electrically 

isolated bars exhibited less disbondment and, in most cases, much less disbondment than the bars 

that were electrically connected. This bodes well for ECR because epoxy-coated bars are 

electrically isolated in the vast majority of cases in bridge decks. 

As observed with respect to the drop in mat-to-mat resistance toward the end of the test period, 

disbondment does not appear to have affected the corrosion rate of the field test specimens.

0

100

200

300

400

500

600

DISBONDED AREA, mm2

Electrically Connected Electrically Isolated

1 mm2 = 0.00155 in2

Figure 161. Graph. Comparison of disbondment values for electrically connected and 

electrically isolated bars in field test specimens without simulated cracks.

143

CHAPTER 4. EVALUATION

In this chapter, the experimental results presented in chapter 3 are compared and used to develop 

estimates of the life expectancy and cost effectiveness of the systems.

The comparative performance of the systems is measured based on the chloride content required to 

initiate corrosion, the average corrosion rate based on corrosion losses after corrosion initiation, 

and, in the case of coated bars, disbondment of the coating from the surface of the reinforcement.

Estimates of life expectancy and cost effectiveness are determined using a typical monolithic bridge

deck with a thickness of 216 mm (8.5 inches) and concrete cover of 76 mm (3 inches) over the top

layer of reinforcing steel. Life expectancy depends on the time to first repair. Cost effectiveness is 

based on the sum of the cost of a new bridge deck and the cost of repairs over a 75-year service life.

The results show that fusion-bonded epoxy coatings significantly improve not only corrosion 

resistance but also life expectancy and cost effectiveness of reinforcing steel and that additional 

protection provides only limited additional improvement. Some corrosion inhibitors and the 

multiple zinc-epoxy coating extend the time to first repair, but differences in the costs over a 

75-year design life are relatively small for coated bars.

COMPARATIVE PERFORMANCE

The systems under study are compared based on the chloride content required to initiate corrosion, 

also known as the critical chloride corrosion threshold (CCCT); the corrosion rate after initiation; 

and disbondment or separation of the coating from the surface of the reinforcement as it is subjected

to a corrosive environment in concrete. The first two criteria can be used to provide an estimate 

of the life expectancy and, in turn, the cost effectiveness of structures such as bridge decks. 

Disbondment represents a noteworthy aspect of system performance, although its impact on life 

expectancy and cost effectiveness remains unclear. 

Critical Chloride Corrosion Threshold (CCCT)

Table 31 lists the CCCT for each corrosion-protection system for bars cast in concrete with a w/c

ratio of 0.45. The table also lists the number of samples and standard deviations. The standard 

deviations account for the effect of combining groups of data. 
144

Table 31. Chloride content at corrosion initiation (kg/m3), taken as the CCCT.

Steel Designationa

Southern

Exposure

Initiation

Beam

Total Number

of Samples

Weighted

Average

Standard

Deviation

Bars without coatings

Controls

Conv. 0.77 0.94 156 0.90 0.479

Conv.2 0.88 1.00 118 0.98 0.822

Conv. Average 274 0.94 0.673

Corrosion inhibitors in concrete

Conv.(DCI) – 1.49 120 1.49 0.604

Conv.2(DCI) 3.72 – 18 3.72 1.69

Conv.(DCI) Average 138 1.78 1.02

Conv.(RH) – 1.23 120 1.23 0.839

Conv.2(RH) 2.16 – 18 2.16 0.708

Conv.(RH) Average 138 1.35 0.769

Conv.(HY) – 0.37 120 0.37 0.267

Conv.2(HY) 1.19 0.51 118 0.61 0.317

Conv.(HY) Average 238 0.49 0.425

Bars with coatings

Control and epoxies with increased adhesion

ECR 4.31 – 28 4.31 1.14

ECR(Chromate) 5.69 – 11 5.69 2.88

ECR(DuPont) 4.97 – 16 4.97 3.33

ECR(Valspar) 6.08 – 11 6.08 2.90

ECR Average 66 5.00 3.17

Conventional epoxy and epoxies with increased adhesion plus calcium nitrite in concrete

ECR(DCI) 5.80 – 12 5.80 1.24

ECR(Chromate)-DCI 2.77 – 6 2.77 1.87

ECR(DuPont)-DCI 5.73 – 11 5.73 1.58

ECR(Valspar)-DCI 5.35 – 4 5.35 0.179

ECR(DCI) Average 33 5.17 2.71

Corrosion inhibitors other than calcium nitrite in concrete

ECR(RH) 4.10 – 17 4.10 1.45

ECR(HY) 1.08 – 10 1.08 0.673

ECR(primer/Ca(NO2)2) 7.11 – 10 7.11 4.04

Bars with multiple coatings

MC 2.00 – 16 2.00 1.79

1 kg/m3 = 1.69 lb/yd3

– No specimens. a See table 1 for abbreviation definitions. 

A w/c ratio of 0.35 was used for five systems: conventional steel, conventional ECR, and 

conventional ECR cast in concrete with each of the three corrosion inhibitors (calcium nitrite, 

Rheocrete®, and HycreteTM), but CCCT values for these systems are not used for this comparison. 

As shown in table 13, no data are available for conventional ECR cast in concrete with a w/c
145

ratio of 0.35. For each of the systems with a corrosion inhibitor in concrete with a w/c ratio of 

0.35, six or fewer samples were taken in total. The corrosion threshold for conventional steel cast 

in concrete with a w/c ratio of 0.35 is about twice that of conventional steel cast in concrete with 

a w/c ratio of 0.45, while the corrosion threshold is lower at a w/c ratio of 0.35 than at a w/c ratio 

of 0.45 for the systems with ECR and a corrosion inhibitor. For these reasons, the effect of w/c

ratio on corrosion threshold is considered to be uncertain based on the current test results and 

will not be addressed further.

In table 31, the values for conventional steel without and with the corrosion inhibitors calcium 

nitrite, Rheocrete®, and HycreteTM include values from both southern exposure specimens and 

initiation beams. The values for coated bars include chloride contents only from southern exposure 

specimens. The values for bars with 4 and 10 holes through the coating are combined and weighted

based on the number of samples collected. As observed in chapter 3, the CCCTs for bars with 

coatings are consistently several times the CCCTs for bars without coatings. The higher thresholds

of the coated bars, all of which have penetrations in the coating, are in all likelihood due to the 

lack of uniformity of the chloride content in the concrete and the low probability that a region of 

locally high chloride content will coincide with the point on a bar where the coating is penetrated.

Looking at the individual CCCT values, conventional reinforcement Conv. has an average CCCT 

of 0.90 kg/m3 (1.52 lb/yd3

) while conventional reinforcement Conv.2 has an average CCCT of 

0.98 kg/m3 (1.65 lb/yd3). The two values are combined to obtain a weighted average CCCT for 

conventional reinforcement of 0.94 kg/m3 (1.58 lb/yd3). Similarly, the values for Conv. and Conv.2

reinforcement in concrete containing the corrosion inhibitors calcium nitrite, Rheocrete®, and 

HycreteTM are combined to obtain CCCT values of 1.78, 1.35, and 0.49 kg/m3 (3.00, 2.28, and 

0.83 lb/yd3), respectively. The reason for the low CCCT for HycreteTM is discussed in chapter 3. 

Conventional ECR exhibits an average CCCT of 4.31 kg/m3 (7.26 lb/yd3

) while the systems 

with ECR and increased adhesion have CCCT values ranging from 4.97 to 6.08 kg/m3 (8.38 to 

10.3 lb/yd3). The use of an increased-adhesion epoxy should not affect the chloride threshold of 

the system, and data for the high-adhesion bars are treated as representing the same population as 

conventional ECR; therefore, the CCCT values for conventional ECR and ECR with increased 

adhesion are averaged to produce a single CCCT of 5.00 kg/m3 (8.43 lb/yd3

). 

Among the specimens with ECR and inhibitors, ECR in concrete with calcium nitrite (combining 

the results for conventional epoxy and the epoxies with increased adhesion) had a CCCT of 

5.17 kg/m3 (8.69 lb/yd3

), just above the CCCT for ECR alone. ECR in concrete with Rheocrete®, 

however, exhibited a CCCT of 4.10 kg/m3 (6.93 lb/yd3

), which is lower than the CCCT for 

ECR in concrete with no inhibitor. ECR in concrete with HycreteTM has a CCCT of 1.08 kg/m3

(1.82 lb/yd3), well below that of ECR in concrete with no inhibitor (5.00 kg/m3 (8.45 lb/yd3)). 

Relatively speaking, this is similar to conventional reinforcement in concrete containing HycreteTM, 

which exhibits a CCCT of 0.49 kg/m3 (0.83 lb/yd3) compared to a CCCT of 0.94 kg/m3 (1.59 lb/yd3)

for conventional steel in concrete with no inhibitors. With a CCCT of 7.11 kg/m3 (12.0 lb/yd3), 

ECR(primer/Ca(NO2)2) has the highest corrosion threshold of any of the systems tested. The 

high CCCT value for ECR(primer/Ca(NO2)2) may be due to the fact that the primer places the 

corrosion inhibitor directly in contact with the steel surface. 
146

In the southern exposure test, MC reinforcement exhibits a CCCT of 2.00 kg/m3 (3.38 lb/yd3), 

which is lower than that of ECR. A study examining the CCCT of galvanized reinforcement,

however, found that galvanized steel has an average critical chloride corrosion threshold of 

1.52 kg/m3 (2.57 lb/yd3), about 50 percent higher than the value for conventional reinforcement, 

which suggests that a higher value, such as that used for conventional ECR, would be more 

appropriate for MC bars.(50)

Because the CCCT values given in table 31 are, in some cases, based on a small number of samples,

Student’s t-test can be used to determine if the differences are the statistically significant. 

Student’s t-test compares the means and variances of two data sets to determine the probability 

that any differences in the mean values could have arisen by chance; that is, that differences in the 

mean values μ1 and μ2 are due to natural variability, not differences in the systems. For example, 

= 0.05 indicates a 5 percent chance that the test will incorrectly identify (or a 95 percent chance

of correctly identifying) a statistically significant difference in sample means when, in fact, there 

is no difference. For this analysis, a two-tailed test is performed, meaning that there is a probability 

of /2 that μ1 is greater than μ2 and /2 that μ1 is less than μ2 when, in fact, μ1 and μ2 are equal. 

An value of 0.20 is used as the threshold for statistical significance. If is greater than 0.20, 

the systems are considered to be performing in a similar manner. It is worthwhile to note that a 

threshold of 0.20 is higher than often selected and values of 0.02, 0.05, and 0.10 are more 

common. An value of 0.20 is used here to restrict the number of cases in which systems are 

treated as similar.

The results of the Student’s t-test are summarized in table 32 and table 33 for bare and coated 

bars, respectively. The tables show that all of the differences for bare bars are statistically 

significant with < 0.001. For the coated bars, all of the differences are statistically significant 

with < 0.162, with two exceptions: the differences in chloride threshold between conventional 

ECR and ECR(DCI) (5.00 and 5.17 kg/m3 (8.45 and 8.69 lb/yd3)) and between ECR(DCI) and 

ECR (RH) (5.17 and 4.10 kg/m3 (8.69 and 6.93 lb/yd3)). Furthermore, the value of for the 

difference between the corrosion thresholds for ECR and ECR(RH) is fairly high at 0.162. 

Because concrete with Rheocrete® raises the CCCT of conventional reinforcement relative to 

conventional reinforcement in concrete without an inhibitor and because there is no reason to 

expect that Rheocrete® would have a negative effect when used with ECR, it would seem 

appropriate to consider ECR cast in concrete with Rheocrete® as having a CCCT no lower than 

that of conventional ECR alone. As mentioned earlier in this section, a CCCT of 2.00 kg/m3

(3.38 lb/yd3

) for MC reinforcement appears to be low because galvanized bars have a higher 

CCCT than conventional bars. Thus, even though the differences between the CCCT for MC 

reinforcement and other coated bars are statistically significant, it would also seem appropriate to 

apply the CCCT of conventional ECR to the MC reinforcement.
147

Table 32. Student’s t-test results ( values) for CCCT for bars without coatings 

cast in concrete with w/c = 0.45.

Steel Designationa

CCCT, 

kg/m3 Conv. Conv.(RH) Conv.(DCI) Conv.(HY)

CCCT (kg/m3) 0.94 1.78 1.35 0.49

Conv. 0.94 1 2.89E-28 9.55E-11 1.40E-12

Conv.(DCI) 1.78 2.89E-28 1 6.06E-05 2.12E-39

Conv.(RH) 1.35 9.55E-11 6.06E-05 1 5.16E-25

Conv.(HY) 0.49 1.40E-12 2.12E-39 5.16E-25 1

1 kg/m3 = 1.69 lb/yd3

Bold indicates statistical significance.

a See table 1 for abbreviation definitions.

Table 33. Student’s t-test results ( values) for CCCT for bars with coatings 

cast in concrete with w/c = 0.45.

Steel

Designationa

CCCT,

kg/m3 ECR ECR(DCI) ECR(RH) ECR(HY)

ECR

(primer/

Ca(NO2)2) MC

CCCT (kg/m3) 5.00 5.17 4.10 1.08 7.11 2.00

ECR 5.00 1 0.470 0.162 0.001 0.029 0.044

ECR(DCI) 5.17 0.470 1 0.344 4.26E-04 0.009 0.055

ECR(RH) 4.10 0.162 0.344 1 6.59E-05 0.003 0.107

ECR(HY) 1.08 0.001 4.26E-04 6.59E-05 1 2.71E-04 0.089

ECR(primer/Ca(NO2)2) 7.11 0.029 0.009 0.003 2.71E-04 1 0.006

MC 2.00 0.044 0.055 0.107 0.089 0.006 1.000

1 kg/m3 = 1.69 lb/yd3

Bold indicates statistical significance.

a See table 1 for abbreviation definitions.

Corrosion Rate

The systems can be compared based on corrosion rate for both bench-scale and field test 

specimens. As with the chloride threshold comparisons, emphasis is placed on results for 

concretes with a w/c ratio of 0.45. 

The average corrosion rates based on corrosion losses after corrosion initiation for the bench-scale 

specimens are presented in chapter 3 in table 15 and table 20 for the southern exposure and cracked

beam specimens and table 28 and table 29 for field test specimens without and with simulated 

cracks over the reinforcing steel. The tables include the number of specimens or bars for which 

the data is obtained as well as the standard deviation, providing a summary for corrosion rate that 

is equivalent to that presented for chloride content at corrosion initiation in table 31. 

To aid in comparisons dealing with conventional reinforcement without and with corrosion inhibitors

in the concrete, a modification is made to the data. Table 34 lists bench-scale macrocell corrosion

rates for Conv. reinforcement without inhibitors and Conv.2 reinforcement without and with 

inhibitors. The bench-scale macrocell corrosion rates for Conv.2 reinforcement were 10.1 and 
148

16.3 μm/year (0.398 and 0.642 mil/year) in uncracked and cracked concrete (southern exposure 

and cracked beam specimens), respectively, about twice the respective a rates for Conv. 

reinforcement (5.69 and 7.00 μm/year (0.224 and 0.276 mil/year)). All inhibitors reduced the 

corrosion rate of Conv.2 reinforcement compared to Conv.2 reinforcement with no inhibitor, but in

cracked concrete, Conv.2(RH) and Conv.2(DCI) show corrosion rates greater than those observed 

for Conv. reinforcement. It is assumed that if the inhibitors had been used in conjunction with the 

earlier tests on Conv. reinforcement, the resulting corrosion rates would have been less than the 

corrosion rates measured for Conv. reinforcement with no inhibitor. Since all other protection 

systems (uncoated and coated) used the same heat of steel as Conv. reinforcement and because 

the mat-to-mat resistance values for the Conv.2 southern exposure and cracked beam specimens

are lower than for the corresponding Conv. specimens (which would lead to higher corrosion 

rates), the only way to achieve a fair comparison between systems is to reduce the corrosion rates 

for the systems with Conv.2 reinforcement with inhibitors by the ratio of the Conv.2 corrosion 

rate to the Conv. corrosion rate.(44,58) The designation Conv.* is used when referring to the

modified corrosion rate data for conventional reinforcement in concrete with corrosion inhibitors.

The modified corrosion rates for these systems are presented in table 34. Based on the modified 

corrosion rates, the estimated rates for Conv.*(RH) are 1.64 and 5.13 μm/year (0.0646 and 

0.202 mil/year) in uncracked and cracked concrete, respectively. Likewise, the estimated rates 

for Conv.*(DCI) are 3.77 and 6.24 μm/year (0.148 and 0.246 mil/year) and are 0.706 and 

1.80 μm/year (0.0278 and 0.0709 mil/year) for Conv.*(HY).

Table 34. Equivalent corrosion rates for conventional reinforcement with inhibitors (μm/year).

Steel

Designation Concretea

Macrocell 

Corrosion 

Rate

Ratio of 

Conv.2 to 

Conv. Rate

Modified 

Corrosion 

Rate (Conv.*)b

Corrosion rate (total area)

Conv. U 5.69 NA NA

C 7.00 NA NA

Conv.2 U 10.1 1.77 5.69

C 16.3 2.32 7.00

Conv.2(RH) U 2.91 1.77 1.64

C 11.90 2.32 5.13

Conv.2(DCI) U 6.67 1.77 3.77

C 14.50 2.32 6.24

Conv.2(HY) U 1.25 1.77 0.706

C 4.17 2.32 1.80

1 μm = 0.0394 mil

NA = Not applicable

a U = Uncracked concrete (southern exposure), C = cracked concrete (cracked beam). b Estimated corrosion rate in conjunction with Conv. reinforcement.

To determine the statistical significance of the differences in corrosion rates between corrosionprotection systems, the two-tailed Student’s t-test is again used with > 0.20 indicating that the 

observed differences are not statistically significant and that systems can be considered to perform

in a similar manner. Bare bars, for which corrosion rates are presented based on total area, are 
149

examined separately from coated bars, for which corrosion rates are based on exposed area. The 

systems are compared first based on bench-scale results and then based on the field test results.

Table 35 and table 36 list the values of based on comparisons of corrosion rates for corrosionprotection systems with bare bars in southern exposure and cracked beam specimens, respectively.

To prepare the tables, the corrosion rates and standard deviations for conventional reinforcement 

with inhibitors are scaled by the ratio of Conv.2 corrosion rate to Conv. corrosion rate prior to 

analysis, as shown in table 34. The comparisons for the southern exposure tests show that, at 

5.69 μm/year (0.224 mil/year), the corrosion rate is highest for Conv., followed by Conv.*(DCI),

Conv.*(RH), and Conv.*(HY), with values of 3.77, 1.64, and 0.706 μm/year (0.148, 0.0646, and 

0.0278 mil/year), respectively. All differences are statistically significant with < 0.025. The 

comparisons for the cracked beam tests, however, show that while the order of the corrosion 

rates is the same as for the southern exposure specimens with values of 7.00, 6.24, 5.15 and 

1.80 μm/year (0.276, 0.246, 0.203, and 0.0709 mil/year) for Conv., Conv.*(DCI), Conv.*(RH), 

and Conv.*(HY), respectively, only the rate for Conv.*(HY) differs with statistical significance 

from the other values.

Table 35. Student’s t-test results ( values) for average corrosion rates based on corrosion

losses after corrosion initiation based on total area for bars without coatings from southern 

exposure tests.

Steel Designationa

Corrosion 

Rate,

μm/year Conv.

Conv.*

(RH)

Conv.*

(DCI)

Conv.*

(HY)

Corrosion Rate (μm/year) 5.69 1.64 3.77 0.706

Conv. 5.69 1 9.4E-06 0.005 1.5E-06

Conv.*(RH) 1.64 9.4E-06 1 0.012 0.025

Conv.*(DCI) 3.77 0.005 0.012 1 0.004

Conv.*(HY) 0.706 1.5E-06 0.025 0.004 1

1 μm = 0.0394 mil

Bold indicates statistical significance.

a See table 1 for abbreviation definitions.

Table 36. Student’s t-test results ( values) for average corrosion rates based on corrosion 

losses after corrosion initiation based on total area for bars without coatings from cracked 

beam tests.

Steel

Designationa

Corrosion 

Rate, 

μm/year Conv.

Conv.*

(RH)

Conv.*

(DCI)

Conv.*

(HY)

Corrosion Rate (μm/year) 7.00 5.15 6.24 1.80

Conv. 7.00 1 0.22 0.31 0.004

Conv.*(RH) 5.15 0.22 1 0.28 0.003

Conv.*(DCI) 6.24 0.31 0.28 1 0.004

Conv.*(HY) 1.80 0.004 0.003 0.004 1

1 μm = 0.0394 mil

Bold indicates statistical significance.

a See table 1 for abbreviation definitions.
150

Table 37 and table 38 list the values of for comparisons of corrosion-protection systems with 

coated bars in the southern exposure and cracked beam tests, respectively. Since only one 

southern exposure specimen with HycreteTM initiated corrosion, a statistical analysis cannot 

be performed for that system.

Table 37. Student’s t-test results ( values) for average corrosion rates based on corrosion 

losses after corrosion initiation based on exposed area for bars with coatings from southern 

exposure tests.

Steel Designationa

Corrosion 

Rate

(μm/year) ECR

ECR

(DCI)

ECR

(RH)

ECR

(HY)

ECR

(primer/

Ca(NO2)2)

ECR

(Chromate)

ECR

(DuPont)

ECR

(Valspar) MC

Corrosion Rate (μm/year) 10.43 7.81 8.63 0.674 12.61 12.86 12.37 16.93 31.63

ECR 10.43 1 0.500 0.274 – 0.649 0.544 0.628 0.313 0.071

ECR(DCI) 7.81 0.500 1 0.291 – 0.468 0.344 0.391 0.324 0.150

ECR(RH) 8.63 0.274 0.291 1 – 0.613 0.569 0.529 0.977 0.471

ECR(HY) 0.674 – – – – – – – – –

ECR(primer/Ca(NO2)2) 12.61 0.621 0.468 0.613 – 1 0.964 0.966 0.577 0.140

ECR(Chromate) 12.86 0.544 0.344 0.569 – 0.964 1 0.919 0.576 0.142

ECR(DuPont) 12.37 0.628 0.391 0.529 – 0.966 0.919 1 0.532 0.132

ECR(Valspar) 16.93 0.313 0.324 0.977 – 0.577 0.576 0.532 1 0.220

MC 31.63 0.071 0.150 0.471 – 0.140 0.142 0.132 0.220 1

1 μm = 0.0394 mil

Bold indicates statistical significance.

a See table 1 for abbreviation definitions.

Table 38. Student’s t-test results ( values) for average corrosion rates based on corrosion 

losses after corrosion initiation based on exposed area for bars with coatings from cracked 

beam tests.

Steel Designationa

Corrosion 

Rate

(μm/year) ECR

ECR

(DCI)

ECR

(RH)

ECR

(HY)

ECR

(primer/

Ca(NO 2)2)

ECR

(Chromate)

ECR

(DuPont)

ECR

(Valspar) MC

Corrosion Rate (μm/year) 8.07 11.2 17.0 10.8 8.73 20.4 25.9 16.4 68.6

ECR 8.07 1 0.364 0.014 0.506 0.826 0.064 0.005 0.158 0.005

ECR(DCI) 11.2 0.364 1 0.145 0.938 0.497 0.250 0.046 0.465 0.027

ECR(RH) 17.0 0.014 0.145 1 0.211 0.026 0.720 0.243 0.893 0.067

ECR(HY) 10.8 0.506 0.938 0.211 1 0.645 0.292 0.072 0.494 0.041

ECR(primer/Ca(NO2)2) 8.73 0.826 0.497 0.026 0.645 1 0.140 0.019 0.270 0.021

ECR(Chromate) 20.4 0.064 0.250 0.720 0.292 0.140 1 0.554 0.680 0.064

ECR(DuPont) 25.9 0.005 0.046 0.243 0.072 0.019 0.554 1 0.290 0.097

ECR(Valspar) 16.4 0.158 0.465 0.893 0.494 0.270 0.680 0.290 1 0.045

MC 68.6 0.005 0.027 0.067 0.041 0.021 0.064 0.097 0.045 1

1 μm = 0.0394 mil

Bold indicates statistical significance. a See table 1 for abbreviation definitions.
151

The comparison between rates for the southern exposure test shows that only MC reinforcement, 

corroding at nearly 3 times the rate of conventional ECR, has a corrosion rate that is significantly 

different from that of the other systems ( < 0.20). ECR(HY) is also assumed to have a statistically

significant difference in corrosion rate compared to the other systems because the corrosion rate 

of ECR(HY), 0.674 μm/year (0.0265 mil/year), is over an order of magnitude lower than any of 

the other systems. 

The results for the cracked beam tests show no statistically significant differences between ECR, 

ECR(DCI), ECR(HY), and ECR(primer/Ca(NO2)2) ( > 0.20), although it is worth noting that 

the corrosion rate for conventional ECR, 8.07 μm/year (0.318 mil/year), is the lowest rate 

obtained for any of the systems in the cracked beam tests and that both conventional ECR and 

ECR(primer/Ca(NO2)2) exhibited lower rates in the cracked beam tests than in the southern 

exposure tests, highlighting some of the variability inherent in corrosion tests. ECR(RH), 

ECR(Chromate), ECR(DuPont), and ECR(Valspar) show significant differences in performance 

relative to ECR, with corrosion rates greater than that for ECR. In practice, however, there is no 

reason to expect that a corrosion inhibitor or an epoxy with increased adhesion will increase the 

corrosion rate. The greater corrosion rates observed are likely due to variations in the test or in 

concrete quality. The corrosion rate of the MC bars, 68.6 μm/year (2.70 mil/year), is significantly 

different from that of all of the other systems—over 2 times the next closest value, 25.9 μm/year

(1.02 mil/year) for ECR(DuPont) and over 8 times greater than that of conventional ECR 

(8.07 μm/year (0.318 mil/year)). 

The results of Student’s t-test for the field test specimens are shown in table 39 and table 40

for uncracked and cracked concrete, respectively. The analysis does not include bare bar systems 

because the only bare bar system evaluated using the field test specimens was conventional steel. 

The comparisons between average macrocell corrosion rates based on losses after corrosion 

initiation in uncracked concrete show no statistically significant differences in rates for ECR, 

ECR(RH), ECR(DCI), ECR(primer/Ca(NO2)2), ECR(Chromate), and ECR(DuPont) ( > 0.20). 

Although the rates for ECR(Valspar) and MC are statistically different from other corrosionprotection systems, they are not statistically different from conventional ECR, and these 

differences are likely due to variations in concrete quality. In addition, the corrosion rate for 

MC reinforcement (6.31 μm/year (0.248 mil/year)) is only 11 percent higher than that of 

conventional ECR (5.68 μm/year (0.224 mil/year)), compared to 3 times higher in the southern 

exposure tests. At 2.89 μm/year (0.114 mil/year), the corrosion rate for ECR(HY) is 68 percent 

of the next closest corrosion rate and is statistically different from the rates for ECR, ECR(RH), 

ECR(Valspar), and MC.
152

Table 39. Student’s t-test results ( values) for average corrosion rates based on corrosion 

losses after corrosion initiation based on exposed area for bars with coatings from field test 

specimens with uncracked concrete.

Steel

Designationa

Corrosion 

Rate

(μm/year) ECR

ECR

(DCI)

ECR

(RH)

ECR

(HY)

ECR

(primer/

Ca(NO2)2)

ECR

(Chromate)

ECR

(DuPont)

ECR

(Valspar) MC

Corrosion Rate (μm/year) 5.68 4.26 5.43 2.89 4.49 4.83 5.14 9.11 6.31

ECR 5.68 1 0.425 0.915 0.136 0.574 0.732 0.949 0.269 0.763

ECR(DCI) 4.26 0.425 1 0.446 0.256 0.871 0.726 0.563 0.020 0.176

ECR(RH) 5.43 0.915 0.446 1 0.120 0.606 0.778 0.989 0.166 0.636

ECR(HY) 2.89 0.136 0.256 0.120 1 0.233 0.209 0.295 0.010 0.033

ECR(primer/Ca(NO2)2) 4.49 0.574 0.871 0.606 0.233 1 0.856 0.708 0.067 0.301

ECR(Chromate) 4.83 0.732 0.726 0.778 0.209 0.856 1 0.836 0.145 0.463

ECR(DuPont) 5.14 0.949 0.563 0.989 0.295 0.708 0.836 1 0.305 0.750

ECR(Valspar) 9.11 0.269 0.020 0.166 0.010 0.067 0.145 0.305 1 0.305

MC 6.31 0.763 0.176 0.636 0.033 0.301 0.463 0.750 0.305 1

1 μm = 0.0394 mil

Bold indicates statistical significance.

a See table 1 for abbreviation definitions. 

Table 40. Student’s t-test results ( values) for average corrosion rates based on corrosion 

losses after corrosion initiation based on exposed area for bars with coatings from field test 

specimens with cracked concrete.

Steel

Designationa

Corrosion 

Rate

(μm/year) ECR

ECR

(DCI)

ECR

(RH)

ECR

(HY)

ECR

(primer/

Ca(NO2)2)

ECR

(Chromate)

ECR

(DuPont)

ECR

(Valspar) MC

Corrosion Rate (μm/year) 8.13 5.79 8.38 4.32 4.65 8.94 6.50 7.64 8.11

ECR 8.13 1 0.275 0.923 0.234 0.200 0.745 0.656 0.733 0.918

ECR(DCI) 5.79 0.275 1 0.072 0.448 0.475 0.126 0.501 0.415 0.258

ECR(RH) 8.38 0.923 0.072 1 0.024 0.004 0.554 0.416 0.577 0.947

ECR(HY) 4.32 0.234 0.448 0.024 1 0.862 0.144 0.269 0.241 0.181

ECR(primer/Ca(NO2)2) 4.65 0.200 0.475 0.004 0.862 1 0.112 0.216 0.190 0.137

ECR(Chromate) 8.94 0.745 0.126 0.554 0.144 0.112 1 0.424 0.486 0.643

ECR(DuPont) 6.50 0.656 0.501 0.416 0.269 0.216 0.424 1 0.893 0.675

ECR(Valspar) 7.64 0.733 0.415 0.577 0.241 0.190 0.486 0.893 1 0.774

MC 8.11 0.918 0.258 0.947 0.181 0.137 0.643 0.675 0.774 1

1 μm = 0.0394 mil

Bold indicates statistical significance.

a See table 1 for abbreviation definitions. 

The analysis of the cracked field test specimens shows that the corrosion rates for ECR, ECR(DCI), 

ECR(RH), ECR (HY), ECR(Chromate), ECR(DuPont), ECR(Valspar), and MC are not significantly

different ( > 0.20). The rates for two systems combining ECR with inhibitors in the concrete, 

ECR(DCI) and ECR (HY), and ECR(primer/Ca(NO2)2) are lower and significantly different from 

at least two other systems. The rate for ECR(DCI) is significantly different from the rates for 

ECR(RH) and ECR(Chromate); the rate for ECR(HY) is significantly different from the rates for 
153

ECR(RH) ECR(Chromate) and MC; and the rate for ECR(primer/Ca(NO2)2) is significantly 

different from the rates for ECR, ECR(RH), ECR(Chromate), ECR(Valspar), and MC. As 

observed for the uncracked field test specimens, the specimens containing MC bars had a 

corrosion rate (8.11 μm/year (0.319 mil/year)) that was close to that of conventional ECR

(8.13 μm/year (0.320 mil/year)).

Disbondment

The disbondment results are summarized in figure 110 through figure 112 for the bench-scale 

specimens and in figure 159 through figure 161 for the field test specimens. In all cases, the top 

bars exhibited far more disbondment than the bottom bars, indicating that higher chloride content,

higher moisture content, or a combination of the two results in increased disbondment. The southern 

exposure specimens cast with one of the corrosion inhibitors exhibited significantly less disbondment

than those cast in concrete without an inhibitor. The same observation does not hold for the cracked

beam specimens or for the field test specimens, with or without cracks. The tests uniformly show 

that when cast in the same quality of concrete, bars with high adhesion epoxies exhibit no 

reduction in disbondment compared to conventional ECR bars.

Bars in cracked concrete exhibited far more disbondment than those in uncracked specimens in 

both the bench-scale and field tests. Bottom bars fared better in uncracked concrete than in cracked

concrete, presumably because of the higher chloride content lower in the specimens in the presence

of a crack. 

Bars in southern exposure specimens with a w/c ratio of 0.35 consistently exhibited less disbondment

than bars in southern exposure specimens with a w/c ratio of 0.45, in some cases exhibiting no 

disbondment (see figure 112). The results were mixed for bars in cracked beam specimens. As 

shown in figure 112, the ECR(primer/Ca(NO2)2) and ECR(DCI) bars cast in concrete with w/c of 

0.35 exhibited no disbondment, while ECR, ECR(RH), and ECR(HY) exhibited nearly the same 

disbondment as those in the specimens with the higher w/c ratio. MC bars exhibited somewhat 

less disbondment than for the other systems. This trend is especially true for the bottom bars in 

concrete with cracks (see figure 111 and figure 160). Finally, as shown in figure 153, top bars that 

were electrically isolated (bars not connected across a 10-ohm resistor to a bottom bar in the same 

specimen) exhibited far less disbondment than those that were connected, indicating the negative 

impact of macrocell corrosion and the importance of maintaining electrical isolation between 

coated bars in reinforced concrete structures.

LIFE EXPECTANCY

The life expectancy of a bridge deck (the structure used to compare life expectancy and cost

effectiveness in this study) is based on an estimate of the time to first repair combined with

the time between repairs to establish the present cost of a deck over a 75-year design life. In 

many cases, the time to first repair is based on experience. For example, the South Dakota 

Department of Transportation (SDDOT) has estimated that the time to first repair for bridge 

decks containing conventional steel is 10 years under harsh environmental conditions and 

25 years in arid conditions.(23) The latter matches the time to first repair estimated by the 

KDOT.

(23,36) In 2001, the time to first repair for bridge decks containing ECR was estimated to 

be 35 and 40 years by KDOT and SDDOT, respectively. The estimate for decks with ECR was
154

based on the fact that, as of the 2001, no bridge decks containing ECR had required repair due to 

corrosion-induced damage since its first use in the late 1970s.

(36) Other estimates of time to first 

repair use models that are based on the time required for chloride to diffuse through uncracked 

concrete.(59–62) Models of this type usually include a preselected time for the corrosion products 

to cause the concrete to crack following corrosion initiation. Diffusion-based models have two 

key drawbacks: (1) they do not account for the role played by cracks in the concrete in allowing 

rapid penetration of chlorides to the level of the reinforcing steel and (2) a preselected time for 

the corrosion products to cause the concrete to crack is not based on actual corrosion rates. 

Because surveys of bridge decks with ages ranging from several months to over 20 years 

demonstrate that reinforced concrete bridge decks exhibit significant cracking parallel to and 

directly above the reinforcing bars, estimates of time to first repair are based principally 

on corrosion in the presence of cracks. (See references 3, 43, and 63–66.)

The procedures used in the current analysis are based on field and laboratory evidence addressing

corrosion initiation and propagation in cracked concrete combined with experience with deck 

repair. Using this approach, the time to first repair depends on: (1) the time required for the

chloride content of the concrete to reach the critical chloride initiation threshold for the system, 

(2) the time required after initiation for corrosion products to cause cracking and spalling of the 

concrete cover, and (3) the time between first cracking and the time that the repair is made. 

Time to Corrosion Initiation

The time to corrosion initiation is estimated based on chloride contents measured at crack 

locations on bridge decks in Kansas and the CCCT (water-soluble chloride content) for each 

corrosion-protection system, as previously discussed.

(3,43,67)

The chloride contents in bridge decks are based on two studies.(43,67) In those studies, chloride 

samples were obtained in bridge decks using a vacuum drill. The samples were obtained in 

increments of 19 mm (0.75 inches) to a depth of 95 mm (3.8 inches) both at and away from 

cracks in bridge decks primarily in northeast Kansas. Figure 162 shows the relationship between 

the average chloride content at crack locations interpolated to a depth of 76.2 mm (3 inches) 

versus age for bridges with an average annual daily traffic (AADT) greater than 7,500 (high 

traffic bridges).(3) The decks in the survey were cast monolithically and with high-density 

conventional and silica fume overlays. Figure 162 demonstrates that the chloride content at 

cracks is independent of the type of deck.
155

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

9.0

10.0

11.0

12.0

0.0

0.6

1.2

1.8

2.4

3.0

3.6

4.2

4.8

5.4

6.0

6.6

7.2

0 24 48 72 96 120 144 168 192 216 240

Age, months

Conventional Overlay 5% Silica Fume Overlay 7% Silica Fume Overlay

Monolithic Linear (All)

y = 0.0187x + 0.4414

Chloride Content at 76.2, kg/m3

Chloride Content at 76.2, lb/yd3

1 kg/m3 = 1.69 lb/yd3

Figure 162. Graph. Chloride content taken at cracks interpolated at a depth of 76.2 mm

(3 inches) versus age for bridges with an AADT greater than 7,500.

Based on the data shown in figure 162, the chloride content C (in kg/m3) can be expressed as a 

function of age at the time of sampling T (in months) by the trendline shown in the equation in

figure 163.

C = 0.0187 T + 0.4414

Figure 163. Equation. Chloride content trendline.

Using the equation in figure 163, the average time to reach a specific critical chloride threshold Tc

can be expressed as a function of the critical chloride threshold Cc, as shown in figure 164.

Tc = (Cc – 0.4414) / 0.0187

Figure 164. Equation. Average time to critical chloride threshold.

Table 31 lists the chloride contents at corrosion initiation (from table 13 and table 17), taken as 

the CCCT, for each corrosion-protection system in this study cast in concrete with a w/c ratio of 

0.45, a realistic value for bridge decks. The values are combined and weighted based on the 

number of samples collected.

The CCCT values listed in table 31, with some modifications, are used in conjunction with figure 

164 to determine the time to corrosion initiation for each corrosion-protection system.

The values, expressed in years, are listed in table 41.
156

Table 41. Estimated time to corrosion initiation for corrosion-protection systems in a 

bridge deck with 76.2-mm (3-inch) cover on top reinforcing steel.

Steel Designationa

Chloride 

Threshold,

kg/m3b

Age at Corrosion 

Initiation in Bridge Decks,

years

Bars without coatings

Control

Conv. 1.58 2.2

Corrosion inhibitors in concrete

Conv.(DCI) 3.00 6.0

Conv.(RH) 2.28 4.1

Conv.(HY) 0.83 0.2 (1.0)c

Bars with coatings

Control

ECR 8.29 20.0

Epoxies with increased adhesion

ECR(Chromate) 8.29 20.0

ECR(DuPont) 8.29 20.0

ECR(Valspar) 8.29 20.0

Corrosion inhibitors in concrete

ECR(DCI) 8.29 20.0

ECR(RH) 8.29 20.0

ECR(HY) 1.82 2.8

ECR(primer/Ca(NO2)2) 12.0 29.7

Bars with multiple coatings

MC 4.92 20.0

1 kg/m3 = 1.69 lb/yd3

a See table 1 for abbreviation definitions. b See text for explanation of differences of values from those in table 31. c Rounded up from 0.2 years.

As shown in the table, the system combining uncoated conventional bars with concrete containing

HycreteTM has the lowest calculated time to initiation of corrosion, 0.2 years. Because salt is not 

applied to bridge decks until the first winter, this value is rounded up to 1 year. Conventional 

reinforcement with no inhibitor initiates corrosion after 2.2 years. Rheocrete® and calcium nitrite 

extend the initiation time of conventional reinforcement to 4.1 and 6.1 years, respectively.

Based on the statistical analysis of chloride threshold values presented earlier in this chapter for 

systems with coated bars, the differences in CCCT value for ECR, the three types of ECR with 

increased adhesion, and ECR with calcium nitrite or Rheocrete® added to the concrete are not 

significant. Therefore, the values are averaged (weighted based on the number of samples) to 

obtain a single CCCT value, 4.92 kg/m3 (8.29 lb/yd3

). Because galvanized reinforcement has a 

higher corrosion threshold than conventional reinforcing steel, the CCCT value obtained in the 

southern exposure tests for MC bars, 2.00 kg/m3 (3.37 lb/yd3

), is considered unrealistic.(50) Thus, 
157

the threshold used for most of the other coated bars, 4.92 kg/m3 (8.29 lb/yd3), is used for the MC 

reinforcement, as well. For this value of CCCT, the time to corrosion initiation is 20.0 years. The 

use of the calcium nitrite primer under the epoxy significantly increases the time to 29.7 years, the

highest of any of the systems in this study. ECR with HycreteTM initiates corrosion after 2.8 years.

Time to Cracking After Corrosion Initiation

The time required to generate enough corrosion products to crack concrete is a function of the 

total corrosion rate and the corrosion loss required to cause cracking. The latter is a function of 

the bar size and the concrete cover. (See references 44 and 68–71.) Total corrosion rates will be 

covered first. To do this, equivalent field test macrocell corrosion rates must be calculated for 

conventional reinforcement cast in concrete with corrosion inhibitors because corrosion rates in 

field test specimens serve as the basis for calculating the time to cracking and because field tests 

were not performed on conventional reinforcement cast in concrete with corrosion inhibitors.

Equivalent Field Test Corrosion Rates for Conventional Reinforcement Cast in Concrete with 

Corrosion Inhibitors

As shown in chapter 3, corrosion rates and losses were consistently lower in the field test specimens 

than in the bench-scale specimens. Because the results for the field test specimens serve as the 

basis for the life-cycle and cost-effectiveness calculations and because field test specimens were 

not used for conventional reinforcement cast in concrete with corrosion inhibitors, an estimate of 

corrosion rates in field test specimens is needed for these systems. This is done using the ratio of 

the field test to bench-scale macrocell corrosion rates for conventional reinforcement in concrete 

without and with cracks above the reinforcement. Figure 165 and figure 166 compare the average 

macrocell corrosion rates after corrosion initiation based on total area for the field test and 

bench-scale specimens containing conventional reinforcement in uncracked and cracked concrete,

respectively. The figures also show the range in the rates for each type of specimen. As shown, 

the average macrocell corrosion rates in the field test specimens equal 15.5 and 13.4 percent of 

the rates in the bench-scale specimens in uncracked and cracked concrete, respectively. These 

values are used to convert the corrosion rates shown in table 34 to equivalent macrocell 

corrosion rates in field tests shown in table 42.
158

y = 0.155x

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

1.1

1.2

1.3

0 2 4 6 8

FTS Corrosion Rate, μm/yr

Bench-scale Corrosion Rate, μm/yr

Conv.-U

1 μm = 0.0394 mil

Figure 165. Graph. Comparison between average macrocell corrosion rates after corrosion 

initiation based on total area for bench-scale and field test specimens with conventional 

reinforcement in uncracked concrete.

y = 0.134x

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

1.1

1.2

0 2 4 6 8 10

FTS Corrosion Rate, μm/yr

Bench-scale Corrosion Rate, μm/yr

Conv.-C

1 μm = 0.0394 mil

Figure 166. Graph. Comparison between average macrocell corrosion rates after corrosion 

initiation based on total area for bench-scale and field test specimens with conventional 

reinforcement in cracked concrete.
159

Table 42. Equivalent field test specimen macrocell corrosion rates (μm/year) for bare bar 

corrosion-protection systems.

Steel

Designationa Concretea

Benchscale 

Corrosion 

Rate

Equivalent FTS 

Corrosion Rate

b

FTS(Conv.) U NA 0.882

C NA 0.939

Conv.*(RH) U 1.64 0.255

C 6.34 0.939

Conv.*(DCI) U 3.77 0.584

C 6.34 0.939

Conv.*(HY) U 0.706 0.109

C 1.80 0.241

1 μm = 0.0394 mil

FTS = Field test specimen

NA = Not applicable

a See table 1 for abbreviation definitions. U = uncracked concrete, C = cracked concrete. b Estimated using a ratio of FTS to bench-scale rate of 0.155 in uncracked concrete and 0.134 in 

cracked concrete.

The corrosion rates for bare bar systems assume the entire area of steel is corroding; however, 

autopsy results from field test specimens indicated corrosion occurs in localized regions on the 

bars (see figure 150 and figure 151). As discussed in chapter 3, a visual inspection of conventional

reinforcement from field test specimens at the end of testing indicated that corrosion covers only 

about one-third the total area of bars in uncracked concrete and about 40 percent of the total area 

of bars in cracked concrete. Because corrosion only occurs on limited regions of the bar, the 

corrosion rates for bare bars in uncracked and cracked concrete are multiplied by 3 and 2.5, 

respectively, to obtain a macrocell corrosion rate based on effective area for these systems. The 

results are listed in table 43. As before, conventional reinforcement in concrete with no inhibitor 

has the greatest corrosion rates based on effective area in both uncracked and cracked concrete, 

2.65 and 2.35 μm/year (0.104 and 0.0925 mil/year), respectively. Conv.*(HY) has the lowest 

corrosion rates based on effective area in uncracked and cracked concrete, 0.328 and 0.602 μm/year

(0.0129 and 0.0237 mil/year), respectively. These adjustments appear to be appropriate not only 

based on the observed area undergoing corrosion but also based on the time to cracking observed 

for the Conv. field test specimens, as discussed in chapter 3.
160

Table 43. Equivalent field test specimen macrocell corrosion rates (μm/year) for bare bar 

corrosion-protection systems based on effective area.

Steel Designationa Concretea

FTS Corrosion Rate 

(Total Area)b

FTS Corrosion Rate 

(Effective Area)c

Conv. U 0.882 2.65

C 0.939 2.35

Conv.*(RH) U 0.255 0.765

C 0.939 2.35

Conv.*(DCI) U 0.584 1.75

C 0.939 2.35

Conv.*(HY) U 0.109 0.328

C 0.241 0.602

1 μm = 0.0394 mil

FTS = Field test specimen

a See table 1 for abbreviation definitions. U = uncracked concrete, C = cracked concrete. b See table 42. c Estimated using a ratio of 3 in uncracked concrete and 2.5 in cracked concrete.

Total Corrosion Rates

The field test specimens provide realistic models of bridge decks in terms of both configuration 

and exposure. Because the measurements are based on macrocell corrosion, which represents 

only a portion of the total corrosion loss, a comparison of the linear polarization resistance and 

macrocell corrosion results for the southern exposure and cracked beam specimens is used in 

conjunction with macrocell readings from the field tests to estimate the total corrosion rates in 

the field tests, and thus, in bridge decks.

To estimate the relationships between the macrocell and total corrosion rates for the different 

systems and degrees of exposure evaluated in this study, the average corrosion rates based on 

losses after corrosion initiation for southern exposure (table 15) and cracked beam (table 20) 

specimens are compared with the average corrosion rates based on total corrosion losses after 

corrosion initiation as measured using linear polarization resistance (table 22). Because of 

differences in exposure and corrosion mechanisms, separate comparisons are made for southern 

exposure and cracked beam specimens for uncoated bars, epoxy-coated bars, and MC bars.

The relationships between total and macrocell corrosion rates are shown in figure 167 and 

figure 168 for the bench-scale specimens containing uncoated bars, in figure 169 and figure 170

for specimens containing epoxy-coated bars, and in figure 171 and figure 172 for specimens 

containing MC bars. In each pair of figures, the first represents the results for the southern 

exposure specimens and the second represents the results for the cracked beam specimens. The 

figures show trend lines originating at the origin, which give the ratio of total to macrocell 

corrosion rate. As shown in figure 167 and figure 168 for conventional reinforcement, the total 

corrosion rates average 1.79 and 3.49 times macrocell corrosion rates for southern exposure and 

cracked beam specimens, respectively. The multiples are 3.15 and 12.36 for epoxy-coated bars 

and 4.90 and 5.82 for the MC bars.
161

y = 1.79x

0

5

10

15

20

25

0 5 10 15 20

Total Corrosion Rate, μm/yr

Macrocell Corrosion Rate, μm/yr

Conv.

Conv.2

Conv.2(RH)

Conv.2(DCI)

Conv.2(HY)

1 μm = 0.0394 mil

Figure 167. Graph. Total versus macrocell corrosion rate after corrosion initiation for 

southern exposure specimens with conventional reinforcement.

y = 3.49x

0

20

40

60

80

100

120

0 10 20 30

Total Corrosion Rate, μm/yr

Macrocell Corrosion Rate, μm/yr

Conv.

Conv.2

Conv.2(RH)

Conv.2(DCI)

Conv.2(HY)

1 μm = 0.0394 mil

Figure 168. Graph. Total versus macrocell corrosion rate after corrosion initiation for 

cracked beam specimens with conventional reinforcement.
162

y = 3.15x

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30

Total Corrosion Rate, μm/yr

Macrocell Corrosion Rate, μm/yr

ECR-10d

ECR(Chromate)-10d

ECR(DuPont)-4d

ECR(DuPont)-10d

ECR(Valspar)-4d

ECR(Valspar)-10d

ECR(RH)-4d

ECR(DCI)-10d

ECR(HY)-10d

ECR(primer/Ca(NO2)2)-4d

ECR(primer/Ca(NO2)2)-10d

1 μm = 0.0394 mil

Figure 169. Graph. Total versus macrocell corrosion rate after corrosion initiation for 

southern exposure specimens with ECR.

y = 12.36x

0

100

200

300

400

500

600

700

0 20 40 60

Total Corrosion Rate, μm/yr

Macrocell Corrosion Rate, μm/yr

ECR-4d

ECR-10d

ECR(Chromate)-4d

ECR(Chromate)-10d

ECR(DuPont)-4d

ECR(DuPont)-10d

ECR(Valspar)-4d

ECR(Valspar)-10d

ECR(RH)-4d

ECR(RH)-10d

ECR(DCI)-4d

ECR(DCI)-10d

ECR(HY)-4d

ECR(HY)-10d

ECR(primer/Ca(NO2)2)-4d

ECR(primer/Ca(NO2)2)-10d

1 μm = 0.0394 mil

Figure 170. Graph. Total versus macrocell corrosion rate after corrosion initiation for 

cracked beam specimens with ECR.
163

y = 4.90x

0

50

100

150

200

250

300

350

400

0 20 40 60 80

Total Corrosion Rate, μm/yr

Macrocell Corrosion Rate, μm/yr

MC(only epoxy 

penetrated)-4h

MC(only epoxy 

penetrated)-10h

MC(both layers 

penetrated)-4h

MC-(both layers 

penetrated)-10h

1 μm = 0.0394 mil

Figure 171. Graph. Total versus macrocell corrosion rate after corrosion initiation for 

southern exposure specimens with MC reinforcement.

y = 5.82x

0

200

400

600

800

1000

1200

0 50 100 150 200

Total Corrosion Rate, μm/yr

Macrocell Corrosion Rate, μm/yr

MC(only epoxy 

penetrated)-4h

MC(only epoxy 

penetrated)-10h

MC(both layers 

penetrated)-4h

MC(both layers 

penetrated)-10h

1 μm = 0.0394 mil

Figure 172. Graph. Total versus macrocell corrosion rate after corrosion initiation for 

cracked beam specimens with MC reinforcement.
164

As demonstrated in chapter 3, figure 167 through figure 172 show that corrosion rates are

significantly higher for cracked concrete (cracks directly above and parallel to the reinforcement) 

than for uncracked concrete. The figures also show that the total corrosion rate is a higher multiple

of the macrocell corrosion rate for coated bars than for uncoated bars and that the multiple is 

consistently higher for cracked concrete than for uncracked concrete. The multiples are closest 

between uncracked and cracked concrete for the MC bars, in all likelihood due to the combined 

effects of the amphoteric nature (corrodes in alkaline as well an acidic conditions) of zinc and the 

galvanic protection provided by the zinc.

The multiples developed in figure 167 through figure 172 are applied to the field test macrocell 

corrosion rates, including the equivalent rates for conventional bars cast in concrete containing 

corrosion inhibitors, to develop estimates of total corrosion rates in bridge decks. The macrocell 

corrosion rates used for the coated bars are based on the statistical analyses presented earlier in 

the chapter. Because the differences in corrosion rate are not statistically significant, an average 

macrocell rate based on exposed area of 5.66 μm/year (0.223 mil/year) is used for all but one 

system in uncracked concrete; the corrosion rate for that system, ECR(HY), (2.89 μm/year

(0.114 mil/year)) does exhibit a statistically significant difference. Based on the results of the 

analysis for bars in cracked concrete, an average macrocell corrosion rate of 7.95 μm/year

(0.313 mil/year) on an exposed area equal to that provided by a 3.2-mm (0.125-inch)-diameter 

penetration is used for conventional ECR, ECR with increased adhesion, ECR with corrosion 

inhibitor Rheocrete® in the concrete, and MC bars. Rates of 5.79, 4.32, and 4.65 μm/year (0.228, 

0.170, and 0.183 mil/year) are used, respectively, for ECR in concrete with the corrosion inhibitors

calcium nitrite and HycreteTM and ECR with primer containing microencapsulated calcium nitrite. 

In the latter case, it is unlikely the calcium nitrite provided by the primer would be adequate for 

the full time to first repair. Thus, for purposes of the analysis, a corrosion rate equal to that used 

for conventional ECR is assumed beginning 10 years after corrosion initiation. The estimated 

total corrosion rates in bridge decks are shown in table 44.
165

Table 44. Estimated total corrosion rates in bridge decks (μm/year) for corrosionprotection systems.

Steel Designationa Concreteb

Macrocell 

Corrosion Ratec

Estimated Total 

Corrosion Rated

Corrosion rate (total area)

Conv. U 2.65 4.74

C 2.35 8.19

Conv.*(RH) U 0.765 1.37

C 2.35 8.19

Conv.*(DCI) U 1.75 3.14

C 2.35 8.19

Conv.*(HY) U 0.328 0.588

C 0.602 2.10

Corrosion rate (exposed area)

ECR U 5.66 17.8

C 7.95 98.3

ECR(Chromate) U 5.66 17.8

C 7.95 98.3

ECR(DuPont) U 5.66 17.8

C 7.95 98.3

ECR(Valspar) U 5.66 17.8

C 7.95 98.3

ECR(RH) U 5.66 17.8

C 7.95 98.3

ECR(DCI) U 5.66 17.8

C 5.79 71.6

ECR(HY) U 2.89 9.1

C 4.32 53.4

ECR(primer/Ca(NO2)2) U 5.66 17.8

C 4.65 57.5e

MC U 5.66 27.7

C 7.95 46.3f

1 μm = 0.0394 mil a See table 1 for abbreviation definitions. b U = uncracked concrete, C = cracked concrete. c Macrocell corrosion rates for field test specimens.

d Macrocell corrosion rates multiplied by a ratio of 1.79, 3.15, and 4.90 for bare, coated, and 

MC bars in uncracked concrete and by 3.49, 12.36, and 5.82 for bare, coated, and MC bars 

in cracked concrete.

e Rate converts to value for ECR 10 years after corrosion initiation. 

f Rate converts to value for ECR after 50-μm (1.9-mil) zinc layer is consumed.

For systems with bare bars in uncracked concrete, Conv. has the highest total corrosion rate, 

4.74 μm/year (0.187 mil/year), while Conv.*(HY) has the lowest estimated total corrosion rate, 

0.588 μm/year (0.0231 mil/year). For systems with bare bars in cracked concrete, Conv. has the 

greatest total corrosion rate, 8.19 μm/year (0.322 mil/year), and Conv.*(HY) again has the lowest 

estimated total corrosion rate, 0.0827 mil/year (2.10 μm/year).
166

For systems with coated bars in uncracked concrete, conventional ECR, ECR with increased 

adhesion, and ECR with Rheocrete® are assigned total corrosion rates of 17.8 and 98.3 μm/year

(0.701 and 3.87 mil/year) in uncracked and cracked concrete, respectively. ECR with calcium 

nitrite is assigned total corrosion rates of 17.8 and 71.6 μm/year (0.701 and 2.82 mil/year) in 

uncracked and cracked concrete, and ECR with primer containing microencapsulated calcium 

nitrite is assigned total corrosion rates of 17.8 and 57.5 μm/year (0.701 and 2.26 mil/year) in 

uncracked and cracked concrete (the latter for the first 10 years, at which point it changes to 

98.3 μm/year (3.87 mil/year), the value for conventional ECR). MC has a higher corrosion rate 

than ECR in uncracked concrete, 27.7 μm/year (1.09 mil/year), but a lower corrosion rate than 

ECR in cracked concrete, 46.2 μm/year (1.82 mil/year); this is due to the difference in multipliers 

compared to bars without the zinc coating under the epoxy. This behavior will govern until the 

50-μm (2-mil) zinc layer is consumed, after which the bar is treated as corroding as conventional

ECR. ECR with HycreteTM has estimated total corrosion rates in both uncracked and cracked 

concrete of 9.1 and 53.4 μm/year (0.36 and 2.10 mil/year), respectively.

Corrosion Loss to Cause Concrete Cracking

A number of experimental studies have been performed to determine the corrosion loss on steel 

reinforcing bars required to crack (or delaminate) concrete. (See references 44 and 67–71.) All 

included corrosion of bare bars, and two included bars on which only a portion of the bar surface 

could corrode.(44,71) One of those efforts was conducted in concert with this study and included 

finite element analyses to supplement the experimental data.(44) Based on this work, which is 

summarized in appendix B, the corrosion loss in μm or mil required to crack concrete can be 

expressed as shown in figure 173 and figure 174.

[ ] 1

0.38 0.1 0.6

2

25.4 45 0.2 3

÷ = + ÷ f

f

A

f f

A C

crit D L A

x

Figure 173. Equation. Corrosion loss to crack concrete in SI units.

1

0.38 0.1 0.6

2

0.53 0.6 3

÷ = + ÷ f

f

A

f f

A

crit D L A

C

x

Figure 174. Equation. Corrosion loss to crack concrete in English units.

Where:

xcrit = Corrosion loss at crack initiation, μm or mil.

C = Cover, mm or inches.

D = Bar diameter, mm or inches.

Lf = Fractional length of bar corroding, Lcorroding/Lbar.

Af = Fractional area of bar corroding, Acorroding/Abar.

For a conventional steel No. 16 (No. 5) bar with a concrete cover of 76.2 mm (3.0 inches), Lf = 

Af = 1.0, and the value of xcrit is 56 μm (2.2 mil). For a No. 16 (No. 5) epoxy-coated bar with a 

damage pattern equal to that used for the field test specimens (3-mm (0.125-inch)-diameter holes 
167

spaced at 0.124 m (4.9 inches) on each side of the bar), the fractional length of exposed bar Lf is 

0.024, the fractional area of exposed bar Af is 0.0023, and the value of xcrit is 2,430 μm (95.7 mil).

For the purposes of the analysis, the bars in bridge decks are assumed to have the same damage 

pattern as the bars in the field tests.

Propagation Time

The time from corrosion initiation to initial delamination of the concrete cover due to the formation

of stress-induced cracks caused by expansive corrosion products (propagation time) for each system 

is found by dividing the corrosion losses required to crack concrete, calculated above, by the 

estimated total corrosion rates listed in table 44. Because bridge decks inevitably develop cracks over 

and parallel to the reinforcement due to settlement of plastic concrete and shrinkage of the hardened 

concrete, the comparisons using the corrosion rates in cracked concrete should provide a more 

accurate representation of corrosion in bridge decks and are used for the balance of the analysis.

The estimated times to first cracking after corrosion initiation are presented in table 45. Based on 

the corrosion rate in cracked concrete, ECR with HycreteTM has the longest propagation time, 

about 46 years, while the other coated bar systems have propagation times ranging from 25 to 

34 years. Conventional reinforcement cast in concrete with HycreteTM has a propagation time of 

about 27 years. The other systems involving conventional reinforcement cast in concrete without 

and with a corrosion inhibitor have propagation times of 6.8 years.

Table 45. Estimated times to formation of initial delamination cracks after corrosion 

initiation (propagation times) (years).

Steel

Designationa

Cracked

Concrete

Conv. 6.8

Conv.*(RH) 6.8

Conv.*(DCI) 6.8

Conv.*(HY) 26.6

ECR 24.8

ECR(Chromate) 24.8

ECR(DuPont) 24.8

ECR(Valspar) 24.8

ECR(RH) 24.8

ECR(DCI) 34.0

ECR(HY) 45.6

ECR(primer/Ca(NO2)2) 28.9

MC 33.6 a See table 1 for abbreviation definitions. 

Time to First Repair

The time to first repair for each corrosion- protection system is found by combining the time to 

corrosion initiation, the time to initial delamination cracking of the concrete after corrosion 
168

initiation, and the time between first cracking to the time when the deck is repaired. The latter 

period is based on the observation that a bridge deck is not fully repaired when the first crack 

forms. Rather, the bridge typically undergoes a series of short-term temporary repairs. To 

account for the period of temporary repairs, a 10-year delay between first cracking and repair is 

assumed based on the experience of the KDOT.

Table 46 compares expected times to first repair for all corrosion-protection systems based on 

the corrosion rate in cracked concrete. As shown in the table, conventional reinforcement has an 

expected time to first repair of 19 years, which is within the range of 10 to 25 years predicted by 

KDOT and SDDOT maintenance engineers.(23) Among systems with conventional reinforcement 

with inhibitors, conventional reinforcement used in conjunction with concrete containing Rheocrete®

and calcium nitrite have expected times to first repair of 21 and 23 years, slightly greater than those 

observed for conventional reinforcement without inhibitors. At 38 years, conventional reinforcement

used in conjunction with concrete containing HycreteTM has more than twice the age to first repair 

as conventional reinforcement with no inhibitor. ECR and ECR with increased adhesion have 

expected times to first repair of 55 years compared to the 35 to 40 years estimated by KDOT and 

SDDOT.(23) Most bridges containing ECR have not yet reached this age. Systems containing 

ECR used in concrete containing corrosion inhibitors have times to first repair ranging from 55 to 

69 years, with ECR with calcium nitrite and ECR with primer containing microencapsulated calcium 

nitrite giving the longest times at 64 and 69 years, respectively. Systems with MC reinforcement 

have an expected time to first repair of 56 years. Thus, based in the assumption that cracked 

concrete will dominate corrosion behavior, all systems will require at least one repair during the 

assumed 75-year design life of the deck.

Table 46. Time to first repair based on corrosion rate in cracked concrete (years).

Steel Designationa

Time to 

Initiationb

Time from 

Initiation to 

Crackingc

Time from 

Cracking to 

Repaird

Expected 

Time to 

First Repair

Conv. 2.2 6.8 10 19

Conv.*(RH) 4.0 6.8 10 21

Conv.*(DCI) 6.0 6.8 10 23

Conv.*(HY) 1.0 26.6 10 38

ECR 20.0 24.8 10 55

ECR(Chromate) 20.0 24.8 10 55

ECR(DuPont) 20.0 24.8 10 55

ECR(Valspar) 20.0 24.8 10 55

ECR(RH) 20.0 24.8 10 55

ECR(DCI) 20.0 34.0 10 64

ECR(HY) 2.8 45.6 10 58

ECR(primer/Ca(NO2)2) 29.7 28.9 10 69

MC 20.0 25.5 10 56 a See table 1 for abbreviation definitions. b See table 41. c See table 45 for cracked concrete.
169

COST EFFECTIVENESS

A 75-year economic life is used to compare the costs associated with the various corrosionprotection systems for a typical bridge deck. A 46-m (150-ft)-long, 11-m (36-ft)-wide, 216-mm

(8.5-inch)-thick bridge deck is used in the analysis. Costs include those for initial construction 

and repair over the 75-year period. With the exception of steel and admixture prices, costs are 

based on experience in Kansas and South Dakota for the years 2004 through 2008. Prices during 

this period are considered to be more indicative of the long term than prices between 2008 and 

2011, which are representative of a depressed construction market. User costs are not included in 

the analysis.

Initial Cost

The material costs for reinforcement and inhibitors used in this analysis are provided by the material

suppliers. For conventional reinforcement, the base cost is $0.77/kg ($0.35/lb). ECR and ECR 

with increased adhesion from DuPontTM and Valspar® have a base cost of $0.99/kg ($0.45/lb). 

ECR with chromate pretreatment and ECR with the calcium nitrite primer have a base cost of 

$1.10/kg ($0.50/lb). MC reinforcement has a base cost of $1.65/kg ($0.75/lb). A placement cost 

of $1.14/kg ($0.52/lb) is used for all reinforcement. A steel reinforcement density of 163 kg/m3

(275 lb/yd3) is used, based on the average quantity of steel used in 12 bridge decks constructed 

in Kansas between 2004 and 2007.(58) A 216-mm (8.5-inch)-thick bridge deck requires 35.2 kg/m2

(64.9 lb/yd2

) of steel based on the surface area of deck, as shown in figure 175.

2

3 35.2 kg/m typical deck

0.216 m

m

163 kg =

Figure 175. Equation. Typical quantity of reinforcement.

Using the required reinforcement per unit surface area determined using the equation in figure 175, 

the reinforcement costs for each system are calculated, as shown in the equations in figure 176

through figure 179 and listed in table 47.

2

2 $67.23/ m

m

35.2 kg

kg

$1.91 =

Figure 176. Equation. Reinforcement cost for conventional steel.

2

2 $74.98/ m

m

35.2 kg

kg

$2.13 =

Figure 177. Equation. Reinforcement cost for ECR, ECR(Dupont), and ECR(Valspar).

2

2 $78.85 / m

m

35.2 kg

kg

$2.24 =

Figure 178. Equation. Reinforcement cost for ECR(Chromate) and ECR(primer/Ca(NO2)2).
170

2

2 $98.21/ m

m

35.2 kg

kg

$2.79 =

Figure 179. Equation. Reinforcement cost for MC reinforcement.

Table 47. Total in-place cost for reinforcement per unit area of bridge deck.

Steel Designationa

Reinforcement Cost Reinforcement Used Total Cost

$/kg $/lb kg/m2 lb/yd2 $/m2 $/yd2

Conv. 1.91 0.87 35.2 64.9 67.23 56.35

ECR 2.13 0.97 35.2 64.9 74.98 62.84

ECR(Chromate) 2.24 1.02 35.2 64.9 78.85 66.08

ECR(DuPont) 2.13 0.97 35.2 64.9 74.98 62.84

ECR(Valspar) 2.13 0.97 35.2 64.9 74.98 62.84

ECR(primer/Ca(NO2)2) 2.24 1.02 35.2 64.9 78.85 66.08

MC 2.79 1.27 35.2 64.9 98.21 82.31 a See table 1 for abbreviation definitions.

The base in-place cost of concrete with no inhibitors used in this study is $735.75/m3 ($562.51/yd3)

based on costs between 2004 and 2007, updated to July 2008.(58,72) For corrosion inhibitors, the 

dosage rates are the rates used in this study and are based on manufacturer recommendations. 

Rheocrete® costs $6.08/L ($23.00/gal) and has dosage rate of 5 L/m3 (1 gal/yd3), equal to $30.40/m3

($23.00/yd3) over the base cost of the concrete. DCI® S costs $1.32/L ($5.00/gal) and has a dosage

rate of 15 L/m3 (3 gal/yd3

), equal to $19.80/m3 ($15/yd3). HycreteTM costs $4.95/L ($18.75/gal) 

and has a dosage rate of 7.6 L/m3 (1.54 gal/yd3). To counteract the reduction in strength and low 

freeze-thaw resistance observed in concrete containing HycreteTM, an additional 35.6 kg/m3

(60 lb/yd3

) of portland cement at $0.138/kg ($0.0625/lb) is added, for a cost of $42.53/m3

($32.63/yd3

) for HycreteTM over the in-place cost of conventional concrete.1

Assuming a 216-mm (8.5-inch)-thick bridge deck, 0.216 m3 of concrete are required per 1-m

2

(0.236 yd3 per 1-yd2) surface area of deck. Concrete costs for all corrosion-protection systems 

per unit surface area are calculated using the equations in figure 180 through figure 183 and are 

shown in table 48. 

2

3 $158.92 / m

typical deck

0.216 m

m

$735.74 =

Figure 180. Equation. Costs for concrete placed with conventional reinforcement.

2

3 3 $165.49 / m

typical deck

0.216 m

m

$30.40

m

$735.75

+ ÷ =

Figure 181. Equation. Costs for concrete placed with Rheocrete® inhibitor.

 1 The addition of 60 lb/yd3 (35.6 kg/m3

) is an estimate and is not based on laboratory or field observations. 
171

2

3 3 $163.20 / m

typical deck

0.216 m

m

$19.80

m

$735.75

+ ÷ =

Figure 182. Equation. Costs for concrete placed with calcium nitrite inhibitor.

3

3 $4.91cement / m

kg

$0.137

m

35.9 kg of cement =

3 3 3 $4.91cement / m + $735.75 concrete/ m = $740.66 / m

2

3 3 $168.11/ m

typical deck

0.216 m

m

$37.62

m

$740.66

+ ÷ =

Figure 183. Equation. Costs for concrete placed with HycreteTM inhibitor.

Table 48. Total in-place cost for concrete per unit area of bridge deck.

Steel

Designationa

Concrete Cost Inhibitor Cost Concrete Use Total Cost

$/m3 $/yd3 $/m3 $/yd3 m3/m2 yd3/yd2 $/m2 $/yd2

Conv. 735.75 562.51 – – 0.216 0.236 158.92 132.75

RH 735.75 562.51 30.40 23.00 0.216 0.236 165.49 138.18

DCI 735.75 562.51 19.80 15.00 0.216 0.236 163.20 136.29

HYa 740.66 566.29 37.62 28.88 0.216 0.236 168.11 140.46

– Indicates no inhibitor used. a Additional 35.9 kg/m3 (60 lb/yd3

) cement added to counteract strength reduction.

The total initial cost, equal to the sum of reinforcement and concrete costs, for each system is 

shown in figure 184 through figure 194 and table 49.

216-mm Concrete Deck + Conventional Steel = $158.92/m2 + $67.23/yd2 = $226.15/m2

Figure 184. Equation. Total initial cost for decks with conventional steel.

216-mm Concrete Deck with Rheocrete + Conventional Steel

= $165.49/m

2 + $67.23/m2 = $232.72/m2

Figure 185. Equation. Total initial cost for decks with conventional steel and

Rheocrete® inhibitor.

216-mm Concrete Deck with DCI + Conventional Steel

= $168.11/m2 + $67.23/m2 = $230.43/m2

Figure 186. Equation. Total initial cost for decks with conventional steel and

calcium nitrite inhibitor (DCI).

216-mm Concrete Deck with Hycrete + Conventional Steel

= $163.20/m2 + $67.23/m2 = $235.34/m2

Figure 187. Equation. Total initial cost for decks with conventional steel and

HycreteTM inhibitor.
172

216-mm Concrete Deck + Epoxy-Coated Reinforcement

= $158.92/m2 + $74.98/m

2 = $233.90/m2

Figure 188. Equation. Total initial cost for decks with ECR, ECR(Dupont), and 

ECR(Valspar).

216-mm Concrete Deck + Epoxy-Coated Reinforcement with Chromate 

= $158.92/m

2 + $78.85/m2 = $233.90/m2

Figure 189. Equation. Total initial cost for decks with ECR(Chromate).

216-mm Concrete Deck with Rheocrete + Epoxy-Coated Reinforcement

= $165.49/m

2 + $74.98/m2 = $240.46/m2

Figure 190. Equation. Total initial cost for decks with ECR and Rheocrete® inhibitor.

216-mm Concrete Deck with DCI + Epoxy-Coated Reinforcement

= $163.20/m2 + $74.98/m2 = $238.17/m2

Figure 191. Equation. Total initial cost for decks with ECR and calcium nitrite inhibitor

(DCI).

216-mm Concrete Deck with Hycrete and extra cement + Epoxy-Coated Reinforcement

= $168.11/m

2 + $74.98/m2 = $243.08/m2

Figure 192. Equation. Total initial cost for decks with ECR and HycreteTM inhibitor.

216-mm Concrete Deck + Epoxy-Coated Reinforcement with primer

= $158.92/m

2 + $78.85/m2 = $237.77/m2

Figure 193. Equation. Total initial cost for decks with ECR with primer.

216-mm Concrete Deck + Multiple-coated reinforcement

= $158.92/m2 + $98.21/m2 = $257.13/m2

Figure 194. Equation. Total initial cost for decks with MC reinforcement.
173

Table 49. Total in-place cost for corrosion protection systems.

Steel Designationa

Reinforcement Cost Concrete Cost Total Cost

$/m2 $/yd2 $/m2 $/yd2 $/m2 $/yd2

Conv. 67.23 56.35 158.92 132.75 226.15 189.10

Conv.(DCI) 67.23 56.35 163.20 136.29 230.43 192.64

Conv.(RH) 67.23 56.35 165.49 138.18 232.72 194.53

Conv.(HY) 67.23 56.35 168.11 140.46 235.34 196.81

ECR 74.98 62.84 158.92 132.75 233.90 195.59

ECR(Chromate) 78.85 66.08 158.92 132.75 237.77 198.83

ECR(DuPont) 74.98 62.84 158.92 132.75 233.90 195.59

ECR(Valspar) 74.98 62.84 158.92 132.75 233.90 195.59

ECR(DCI) 74.98 62.84 163.20 136.29 238.17 199.13

ECR(RH) 74.98 62.84 165.49 138.18 240.46 201.02

ECR(HY) 74.98 62.84 168.11 140.46 243.08 203.30

ECR(primer/Ca(NO2)2) 78.85 66.08 158.92 132.75 237.77 198.83

MC 98.21 82.31 158.92 132.75 257.13 215.06 a See table 1 for abbreviation definitions. 

A deck with conventional reinforcement has the lowest initial in-place cost, $226.15/m2

($189.10/yd2). This increases to $233.90/m2 ($195.59/yd2) for ECR, which exceeds the cost of a 

deck with conventional steel and calcium nitrite or Rheocrete® at $230.43/m2 ($192.64/yd2

) or 

$232.72/m2 ($194.53/yd2) but is less than the cost of a deck with conventional steel and 

HycreteTM at $235.34/m2 ($196.81/yd2

). At $257.13/m2 ($215.06/yd2), a deck with MC 

reinforcement has the highest in-place cost of all systems with an epoxy coating. 

Repair Costs

Repair costs for a typical 216-mm (8.5-inch) bridge deck were obtained from KDOT. Current 

data include repair of bridge decks with conventional reinforcement only because bridge decks 

constructed since the late 1970s have been constructed using ECR and have not needed repair as 

of the date of this report. It is estimated that repair costs of bridge decks with ECR will be similar 

to those for decks with conventional reinforcement. Based on experience in Kansas and South 

Dakota, repairs are assumed to last for 25 years.

(23)

In Kansas, repair consists of applying either a silica fume or polymer overlay to the deck. Repair 

costs include a unit cost for the overlay and machine preparation, costs for mobilization and 

traffic control, and patching costs based on the percentage of decks that received partial or full 

depth repairs, 5 and 17 percent, respectively. Based on an analysis of bid costs from 2008 

through 2010, total repair costs are given in figure 195 and figure 196.
174

Total repair costs (silica fume overlay)

= Total overlay deck + machine preparation + mobilization & traffic control

+ partial-depth repair + full-depth repair

= $47/m

2 + $30/m2 + $89/m2 + (17% x $247/m2

) + (5% x $335/m

2

)

($39/yd2 + $25/yd2 + $75/yd2 + (17% x $207/yd2) + (5% x $281/yd2))

= $224/m2 ($188/yd2)

Figure 195. Equation. Total repair costs with silica fume overlay.

Total repair costs (polymer overlay)

= Total overlay deck + machine preparation + mobilization & traffic control

+ partial-depth repair + full-depth repair

= $52/m

2 + $0/m2 + $89/m2 + (2% x $247/m2

) + (1% x $335/m

2

)

(($44/yd2 + $0/yd2 + $75/yd2 + (2% x $207/yd2) + (1% x $281/yd2))

= $175/m2 ($147/yd2)

Figure 196. Equation. Total repair costs with polymer overlay.

The current KDOT repair costs are compared with a previous analysis based on costs obtained 

from SDDOT, which are based on an average of costs for bridge deck repair projects for the year

2006.(72) A typical repair project includes costs for removing deleterious concrete and replacing 

with a low-slump dense concrete overlay, bridge rail modifications, approach guard rail 

replacement, approach pavement work, mobilization, traffic control, and other miscellaneous 

costs. Costs were determined per square yard for the 46-m (150-ft)-long deck described at the 

beginning of this section. A summary of the repair costs is shown in table 50 and described in 

figure 197 through figure 202.

Table 50. Repair costs for bridge decks in South Dakota.(75)

Item Unit Cost Cost/yd2 Unit Cost Cost/m2

Low slump dense concrete overlay Per yd2 $130.00 $130 Per m2 $155.00 $155

Bridge rail modification Per linear ft $62.00 $31 Per linear m $814.00 $37

Approach guard rail Lump sum $16,500.00 $28 Lump sum $16,500.00 $34

Approach pavement work Lump sum $17,000.00 $28 Lump sum $17,000.00 $34

Mobilization Lump sum $25,000.00 $42 Lump sum $25,000.00 $50

Traffic control and misc. Lump sum $20,000.00 $33 Lump sum $20,000.00 $39

Total repair costs $292 $349

1 m = 1.09 yd = 3.28 ft 

2 $37 / m

11 m deck width

1

bridge

2 sides

m

$814 =

Figure 197. Equation. Bridge rail modification cost.

2

2 $34 / m

506 m

typical bridge

project

$16,500 =

Figure 198. Equation. Approach guard rail cost.
175

2

2 $34 / m

506 m

typical bridge

project

$17,000 =

Figure 199. Equation. Approach pavement work cost. 

2

2 $50 / m

506 m

typical bridge

project

$25,000 =

Figure 200. Equation. Mobilization cost.

2

2 $39 / m

506 m

typical bridge

project

$20,000 =

Figure 201. Equation. Traffic control and miscellaneous costs.

Total repair costs = Total overlay deck + bridge rail modification + approach guard rail 

+ mobilization + traffic control and misc.

= $155/m2 + $37/m2 + $34/m2 + $34/m2 + $50/m2 + $39/m2

($130/yd2 + $31/yd2 + $28/yd2 + $28/yd2 + $42/yd2 + $33/yd2

)

= $349/m2 ($292/yd2)

Figure 202. Equation. Total repair costs.

A comparison of the repair costs provided by KDOT for 2008 through 2010 ($224/m2 or $175/m2

($188/yd2 or $147/yd2)) and those provided by SDDOT for 2006 ($349/m2 ($292/yd2)) shows 

that costs have significantly decreased in the current economic climate. Because the current 

highly competitive environment in the construction industry is not expected to be long term, the 

higher costs for 2006 analysis are used in this study.

Present Value 

The total life cycle cost of each corrosion-protection system is calculated using the times to first 

repair for systems in cracked concrete listed in table 46. Cost effectiveness is based on the initial 

cost of the deck and the present value of future repair costs. The present value is calculated as 

shown in figure 203, where P is the present value, F is the future cost of a repair ($349/m2

($292/yd2)), i is the discount rate, and n is the time to repair.

n P=F(1+i)

Figure 203. Equation. Present value.

For this study, discount rates of 2, 4, and 6 percent are assumed. As the most realistic, the value 

2 percent is used for most of the discussion that follows.

Table 51 and table 52 list the estimated costs over a 75-year design life using the time to first 

repair based on the corrosion rate in cracked concrete. Under this scenario, all of the corrosionprotection systems must be repaired at least once during the 75-year design life. Conventional 

reinforcement in concrete without a corrosion inhibitor and conventional reinforcement in 

concrete with the inhibitors calcium nitrite (DCI) and Rheocrete® must be repaired three times, 

and conventional reinforcement in concrete with the inhibitor HycreteTM must be repaired twice. 

All of the coated-bar systems must be repaired once during the 75-year design life of the deck.
176

Table 51. Total costs ($/m2) over 75-year design life for corrosion-protection systems using 

time to first repair based on corrosion rates in cracked concrete.

Steel Designationa

Initial 

Cost, 

$/m2

Time to Repair, 

years

Repair 

Cost,

$/m2

Present Cost, $/m2

1 2 3 i=2% i=4% i=6%

Conv. 226 19 44 69 349 700 477 374

Conv.*(DCI) 230 23 48 73 349 670 446 349

Conv.*(RH) 233 21 46 71 349 690 466 366

Conv.*(HY) 235 38 63 – 349 502 345 283

ECR 234 55 – – 349 351 274 248

ECR(Chromate) 238 55 – – 349 355 278 252

ECR(DuPont) 234 55 – – 349 351 274 248

ECR(Valspar) 234 55 – – 349 351 274 248

ECR(DCI) 238 64 – – 349 336 266 246

ECR(RH) 240 55 – – 349 358 281 255

ECR(HY) 243 58 – – 349 353 278 255

ECR(primer/Ca(NO2)2) 238 69 – – 349 327 261 244

MC 257 56 – – 349 373 296 271

– No repair required. a See table 1 for abbreviation definitions. 

Table 52. Total costs ($/yd2) over 75-year design life for corrosion protection systems using 

time to first repair based on corrosion rates in cracked concrete.

Steel Designationa

Initial 

Cost,

$/yd2

Time to Repair,

years

Repair 

Cost,

$/yd2

Present Cost, $/yd2

1 2 3 i=2% i=4% i=6%

Conv. 189 19 44 69 292 586 399 313

Conv.*(DCI) 193 23 48 73 292 560 373 291

Conv.*(RH) 195 21 46 71 292 577 390 306

Conv.*(HY) 197 38 63 – 292 420 288 237

ECR 196 55 – – 292 294 229 207

ECR(Chromate) 199 55 – – 292 297 232 211

ECR(DuPont) 196 55 – – 292 294 229 207

ECR(Valspar) 196 55 – – 292 294 229 207

ECR(DCI) 199 64 – – 292 281 223 206

ECR(RH) 201 55 – – 292 299 235 213

ECR(HY) 203 58 – – 292 295 233 213

ECR(primer/Ca(NO2)2) 199 64 – – 292 274 219 204

MC 215 56 – – 292 312 248 226

– No repair required. a See table 1 for abbreviation definitions. 

Because it requires three repairs and has the lowest time to first repair, conventional 

reinforcement without corrosion inhibitors in the concrete has the highest present cost, $700/m2

($586/yd2) at a 2 percent discount rate. Conventional reinforcement used in conjunction with 
177

concrete containing calcium nitrite and Rheocrete® has present costs of $670/m

2 and $690/m2

($560/yd2 and $577/yd2), respectively. Conventional reinforcement used in conjunction with 

concrete containing Hycrete has the lowest present cost among systems with conventional 

reinforcement, $502/m2 ($420/yd2

), but is less cost effective than any of the coated bar systems.

ECR in concrete with the calcium nitrite primer is the most cost-effective protection system, with 

a present cost of $327/m2 ($274/yd2) at a discount rate of 2 percent. ECR with calcium nitrite is 

the next most efficient system with a present cost of $336 m

2 ($281/yd2

) at a discount rate of 

2 percent. Conventional ECR, as well as increased adhesion epoxies from DuPontTM and 

Valspar®, have present costs of $351/m2 ($294/yd2

) at a discount rate of 2 percent. ECR(HY) 

and ECR(Chromate) have present costs of $353/m2 and $355/m2 ($295/yd2 and $297/yd2) at a 

discount rate of 2 percent; however, at a discount rate of 6 percent, ECR(Chromate) is more 

cost effective than ECR(HY). MC reinforcement has a present cost of $373/m2 ($312/yd2) at a 

2 percent discount rate. The total spread in cost for the coated bar systems is $46/m2 ($38/yd2

), 

or about 12 percent of the highest price. Considering the level of uncertainty inherent in the 

analysis, the differences in present costs for coated bar systems are not significant. However, 

the differences in the number of projected repairs and the differences in present costs between 

uncoated and coated bars systems are significant.

179

CHAPTER 5. CONCLUSIONS

The following conclusions are based on the results and analyses presented in this report:

Conventional fusion-bonded epoxy coatings significantly improve the corrosion resistance,

life expectancy, and cost effectiveness of reinforcing steel in severe climates such as 

bridge decks requiring application of deicing chemicals.

Coated bars with damaged coatings initiate corrosion at chloride contents within concrete

that are several times greater and corrode at rates that are typically two orders of magnitude

below those exhibited by conventional reinforcement. 

Limited additional protection and extension of the time to first repair are achieved using 

bars with a primer coating containing microencapsulated calcium nitrite underneath a 

conventional epoxy coating, multiple coated (MC) bars with a 50-μm (2-mil) coating of 

98 percent zinc and 2 percent aluminum underneath a conventional epoxy coating, and 

concrete containing corrosion inhibitors calcium nitrite and HycreteTM. The differences in 

the costs over a 75-year design life are relatively small for coated bars. Concrete containing 

HycreteTM may exhibit lower compressive strength and reduced resistance to surface scaling

compared to concretes with other inhibitors or without an inhibitor unless modified, such 

as through an increase in cement content. As a result, additional research is required to 

establish criteria that will preclude a loss of durability when HycreteTM is used.

Conventional reinforcement in concrete containing a corrosion inhibitor has a longer 

service life and is more cost effective than conventional reinforcement in concrete 

without a corrosion inhibitor but has a shorter service life and is less cost effective than 

any of the coated bar systems evaluated.

Cracks in concrete directly over and parallel to the reinforcement, such as found in bridge 

decks, result in earlier corrosion initiation and higher corrosion rates than obtained with 

intact concrete for all systems.

Epoxies that provide initially high adhesion to the underlying steel provide no advantage 

in terms of improved corrosion performance or improved adhesion when used in concrete. 

Using concrete with a reduced water-cement (w/c) ratio lowers the corrosion rate for both 

conventional reinforcement and epoxy-coated reinforcement (ECR) under all conditions 

in intact concrete but provides only limited corrosion protection when cracks allow direct 

access of chlorides to reinforcing bars. 

Corrosion inhibitors consistently provide improved corrosion protection when used in 

conjunction with conventional reinforcement and ECR in intact concrete but to a lesser 

degree in cracked concrete. 

Corrosion inhibitors have a greater relative effect on uncoated than on coated reinforcement. 
180

Reinforcement with a multiple coating consisting of 98 percent zinc and 2 percent 

aluminum and conventional epoxy exhibits high corrosion rates in cases when the 

concrete is often wet but exhibits corrosion rates similar to those exhibited by conventional

ECR under conditions similar to those in bridge decks; the metallic coating corrodes in 

preference to the underlying steel, providing some additional protection. 

All coated bars that were evaluated exhibit corrosion losses at openings through the 

coating. A reduction in adhesion between an epoxy coating and the reinforcing steel 

occurs after a period of exposure to corrosive conditions. This reduction increases with 

increasing chloride content in the concrete and in the presence of cracks and decreases 

with the use of corrosion inhibitors, with the use of MC reinforcement, and with electrical 

isolation of the epoxy-coated bars from each other. Corrosion products form under the 

coating where adhesion has been reduced.

For periods up to 5 years under exposure conditions representative of those in bridge 

decks, the reduction in adhesion between an epoxy coating and the reinforcing steel did 

not affect the rate at which coated bars corrode. 
181

APPENDIX A. DISBONDMENT OF CONVENTIONAL EPOXY-COATED AND MC

BARS IN RAPID MACROCELL TEST

In addition to the rapid macrocell tests described in the body of the report, 24 ECR and 24 MC 

rapid macrocell tests using 6.04 molal ion (15 percent) concentration sodium chloride solution 

were used to compare the disbondment characteristics of conventional ECR and MC bars under 

the severe exposure conditions produced in the test as a function of corrosion loss and time. The 

specimens consisted of a single ECR or MC bar as the anode and two bare steel bars as the cathode.

Every 5 weeks, three specimens were pulled from testing and a disbondment test was performed 

on the anode. The schedule of testing is shown in table 53. In addition, five control specimens of 

each type were placed in simulated pore solution with no chlorides to track disbondment in the 

absence of chlorides. Disbondment was performed using the procedures described in chapter 2 

for the cathodic disbondment test. Measurements are expressed in terms of the total area of 

disbonded material at each test point.

Table 53. Rapid macrocell test program.

ECR MC

Specimen 

Designation

Weeks 

Tested

Specimen 

Designation

Weeks 

Tested

M-ECR-1 5 M-MC-1 5

M-ECR-2 5 M-MC-2 5

M-ECR-3 5 M-MC-3 5

M-ECR-4 10 M-MC-4 10

M-ECR-5 10 M-MC-5 10

M-ECR-6 10 M-MC-6 10

M-ECR-7a 15 M-MC-7 15

M-ECR-8 15 M-MC-8 15

M-ECR-9 15 M-MC-9 15

M-ECR-10 20 M-MC-10 20

M-ECR-11 20 M-MC-11 20

M-ECR-12 20 M-MC-12 20

M-ECR-13a 40 M-MC-13 25

M-ECR-14 25 M-MC-14 25

M-ECR-15 25 M-MC-15 25

M-ECR-16 25 M-MC-16 30

M-ECR-17 30 M-MC-17 30

M-ECR-18 30 M-MC-18 30

M-ECR-19a 40 M-MC-19 35

M-ECR-20 30 M-MC-20 35

M-ECR-21 35 M-MC-21 35

M-ECR-22 35 M-MC-22a 40

M-ECR-23 35 M-MC-23a 40

M-ECR-24 40 M-MC-24a 40

Control specimens in simulated pore solution (no salt)

M-ECR-A 10 M-MC-A 10

M-ECR-B 20 M-MC-B 20

M-ECR-C 25 M-MC-C 30

M-ECR-D 30 M-MC-D 35

M-ECR-E 35 M-MC-E 40 a Linear polarization resistance tests performed on this specimen.
182

TEST RESULTS

The duration of the test ranged from 5 to 40 weeks. The purpose of the test program was to 

establish a relationship between corrosion loss, time, and disbondment of the epoxy coating for 

conventional ECR and MC reinforcement.

Corrosion Rate, Loss, and Potentials

The average macrocell corrosion rates based on total area for macrocell specimens with ECR and 

MC reinforcement are shown in figure 204. During the first five weeks of testing, the specimens 

with MC reinforcement exhibited significantly higher corrosion rates than the specimens with 

conventional ECR. A slight increase in corrosion rate was observed for the MC specimens 

between weeks 15 and 20. The corrosion rates were otherwise comparable to those observed in 

conventional ECR.

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

40.0

0 5 10 15 20 25 30 35 40

CORROSION RATE, μm/yr

TIME, weeks

M-ECR M-MC

1 μm = 0.0394 mil

Figure 204. Graph. Rapid macrocell test, average corrosion rate based on total area of 

ECR and MC reinforcement.

The average corrosion losses based on average corrosion rates for the macrocell specimens with 

ECR and MC reinforcement are shown in figure 205. The increased corrosion rate observed for 

MC reinforcement from weeks 0 to 5 and weeks 15 to 20 resulted in a greater overall corrosion 

loss at 40 weeks (7.55 μm (0.297 mil) compared to 5.43 μm (0.214 mil) for ECR) as well as 

greater losses throughout the test.
183

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

0 5 10 15 20 25 30 35 40

CORROSION LOSS, μm

TIME, weeks

M-ECR M-MC

1 μm = 0.0394 mil

Figure 205. Graph. Rapid macrocell test, average corrosion loss based on total area of ECR 

and MC reinforcement.

The average anode and cathode potentials with respect to an SCE are shown in figure 206 and 

figure 207, respectively, for specimens with conventional ECR and MC reinforcement. At the

anode, the corrosion potentials of both ECR and MC were more negative than -0.500 V for most 

of the test. The MC specimens showed a more negative anode potential than the ECR specimens 

for the first 27 weeks of testing. After 27 weeks, the corrosion potentials of the specimens with 

MC and ECR were comparable.

-1.2

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0 5 10 15 20 25 30 35 40

CORROSION POTENTIAL, V

TIME, weeks

M-ECR M-MC

Figure 206. Graph. Rapid macrocell test, average anode potential of ECR and MC 

reinforcement.
184

-0.40

-0.35

-0.30

-0.25

-0.20

-0.15

-0.10

-0.05

0.00

0 5 10 15 20 25 30 35 40

CORROSION POTENTIAL, V

TIME, weeks

M-ECR M-MC

Figure 207. Graph. Rapid macrocell test, average cathode potential of ECR and MC 

reinforcement.

At the cathode, the corrosion potentials of the specimens with both ECR and MC reinforcement 

were approximately -0.200 V at the start of the test. For the ECR specimens, the corrosion 

potential gradually decreased to approximately -0.350 V by week 40, whereas the corrosion 

potential of the MC specimens remained at approximately -0.200 V until week 36, when it 

decreased to -0.300 V over a four-week period.

Linear polarization resistance measurements were performed on selected specimens on a 

monthly basis. The total corrosion losses calculated from the linear polarization readings are 

compared to the macrocell corrosion losses in table 54. On average, the total corrosion losses 

were 4.0 times greater than macrocell corrosion losses, with the ratio of total to macrocell 

corrosion loss ranging from 1.45 (M-ECR-7) to 8.41 (M-ECR-13).

Table 54. Total and macrocell corrosion loss for selected rapid macrocell specimens.

Specimen

Age 

(weeks)

Corrosion Loss (μm)

Microcell Total

M-ECR-7 15 2.83 1.95

M-ECR-13 40 55.2 6.56

M-ECR-19 40 19.1 4.95

M-MC-22 40 18.2 7.64

M-MC-23 40 35.4 7.83

M-MC-24 40 31.0 9.04

1 μm = 0.0394 mil
185

Visual Observations

For the ECR specimens, corrosion products were visible at some damage sites after 5 weeks of 

testing (see figure 208), with moderate amounts of disbondment observed at some damage sites 

(see figure 209). Other damage sites on the ECR bars tested at 5 weeks showed no disbondment.

The ECR bars tested for 10 weeks or longer showed disbondment at all damage sites. For the 

ECR specimens tested for 30 weeks or longer, corrosion products were observed at all damage 

sites (see figure 210), with the disbonded region covering much of the area of the bar (see 

figure 211). The ECR bars removed after 30 to 40 weeks of testing showed severe disbondment 

at all damage sites (see figure 211).

Figure 208. Photo. Rapid macrocell test, M-ECR-1, 5 weeks, before disbondment test.

Figure 209. Photo. Rapid macrocell test, M-ECR-1, 5 weeks, after disbondment test.

Figure 210. Photo. Rapid macrocell test, M-ECR-13, 40 weeks, before disbondment test.

Figure 211. Photo. Rapid macrocell test, M-ECR-21, 35 weeks, after disbondment test.

For the MC specimens, those removed after 5 or 10 weeks of testing showed no signs of iron 

corrosion products (see figure 212) in contrast to specimens with ECR, which showed visible 
186

corrosion products after 5 weeks. Disbondment tests on the MC bars revealed minimal 

disbondment on specimens removed from testing after 5 or 10 weeks (see figure 213). Regions 

where disbondment did occur on the MC bars showed a ring of darkened metal around the 

damage site, indicating the zinc in this region has been consumed (see figure 214). The MC 

specimens began to show dark orange iron corrosion products by week 15, with all three of the 

MC specimens removed at week 40 showing dark iron corrosion products (see figure 215). The 

disbondment tests performed at 40 weeks on the MC bars showed moderate disbondment at all 

damage sites (see figure 216). The corrosion products in the disbonded regions of the MC bars 

consist of a central circle of dark iron corrosion products around the damage site surrounded by a 

larger region of light gray corrosion products, most likely from corroding zinc.

Figure 212. Photo. Rapid macrocell test, M-MC-4, 10 weeks, before disbondment test.

Figure 213. Photo. Rapid macrocell test, M-MC-4, 10 weeks, after disbondment test.

Figure 214. Photo. Rapid macrocell test, M-MC-5, 10 weeks (zinc depletion in regions 

surrounding damage sites).

Figure 215. Photo. Rapid macrocell test, M-MC-23, 40 weeks, before disbondment test.

Zinc depletion
187

Figure 216. Photo. Rapid macrocell test, M-MC-23, 40 weeks, after disbondment test.

In general, damage sites with visible corrosion products tended to exhibit greater disbondment 

than damage sites with no visible corrosion products for both ECR (figure 209) and MC (figure 216).

Both the disbonded area and visible corrosion increased with time. The corrosion products at the 

damage sites were dark orange or brown in color. Corrosion products underneath disbonded 

epoxy were initially black (figure 209), but turned dark orange with exposure to air as the 

corrosion products oxidized.

Disbondment Results

Disbonded area and corrosion loss for the ECR and MC bars are summarized in table 55 and 

table 56, respectively. Figure 217 and figure 218 show average disbonded area at a damage site 

as a function of time for ECR and MC reinforcement, respectively. A best fit line is plotted for 

each set of data. Based on the best fit lines, disbondment of ECR progressed at about twice the rate 

of disbondment of MC reinforcement, with ECR showing increases in disbonded area averaging 

10.8 mm2

/week (0.0167 in2/week) compared to 5.32 mm2/week (0.0082 in2/week) for MC 

reinforcement. It should be noted that disbondment at a given age varies widely for individual 

specimens of both types, especially at later ages.
188

Table 55. Disbonded area and corrosion loss for rapid macrocell specimens with ECR.

Specimen Week

Average

Disbonded Area,

mm2

Corrosion

Loss,

μm

Disbondment

Rate,

mm2/week

Disbondment

Rate,

mm2

/μm

M-ECR-1 5 35.5 0.359 7.10 98.8

M-ECR-2 5 16.1 0.318 3.23 50.7

M-ECR-3 5 37.1 0.233 7.42 159.2

M-ECR-4 10 74.2 0.638 7.42 116.3

M-ECR-5 10 158.1 0.513 15.8 308.1

M-ECR-6 10 133.9 1.29 13.4 103.8

M-ECR-7 15 116.1 1.92 7.74 60.5

M-ECR-8 15 154.8 0.428 10.3 361.8

M-ECR-9 15 187.1 3.35 12.5 55.8

M-ECR-10 20 175.8 4.99 8.79 35.2

M-ECR-11 20 338.7 4.59 16.9 73.8

M-ECR-12 20 140.3 4.71 7.02 29.8

M-ECR-13 40 456.5 4.94 11.4 92.4

M-ECR-14 25 567.7 3.73 22.7 152.2

M-ECR-15 25 187.1 1.04 7.48 179.9

M-ECR-16 25 408.1 2.16 16.3 188.9

M-ECR-17 30 232.3 3.35 7.74 69.3

M-ECR-18 30 162.9 2.37 5.43 68.7

M-ECR-19 40 261.3 4.64 6.53 56.3

M-ECR-20 30 198.4 5.75 6.61 34.5

M-ECR-21 35 874.2 6.24 25.0 140.1

M-ECR-22 35 222.6 5.41 6.36 41.1

M-ECR-23 35 598.4 3.27 17.1 183.0

M-ECR-24 40 241.9 5.38 6.05 45.0

1 mm2 = 0.00155 in2

1 μm = 0.0394 mil
189

Table 56. Disbonded area and corrosion loss for rapid macrocell specimens 

with MC reinforcement.

Specimen Week

Average 

Disbonded Area,

mm2

Corrosion 

Loss,

μm

Disbondment 

Rate,

mm2

/week

Disbondment 

Rate,

mm2

/μm

M-MC-1 5 9.7 1.11 1.94 8.7

M-MC-2 5 4.8 1.73 0.968 2.8

M-MC-3 5 21.0 1.3 4.19 16.1

M-MC-4 10 41.9 1.97 4.19 21.3

M-MC-5 10 43.5 3.42 4.35 12.7

M-MC-6 10 50.0 3.17 5.00 15.8

M-MC-7 15 77.4 4.97 5.16 15.6

M-MC-8 15 54.8 1.99 3.66 27.6

M-MC-9 15 74.2 2.98 4.95 24.9

M-MC-10 20 133.9 6.12 6.69 21.9

M-MC-11 20 125.8 4.19 6.29 30.0

M-MC-12 20 69.4 3.03 3.47 22.9

M-MC-13 25 162.9 3.58 6.52 45.5

M-MC-14 25 137.1 2.86 5.48 47.9

M-MC-15 25 146.8 6.61 5.87 22.2

M-MC-16 30 116.1 5.48 3.87 21.2

M-MC-17 30 98.4 3.13 3.28 31.4

M-MC-18 30 156.5 3.93 5.22 39.8

M-MC-19 35 117.7 6.89 3.36 17.1

M-MC-20 35 129.0 6.73 3.69 19.2

M-MC-21 35 308.1 8.64 8.80 35.7

M-MC-22 40 127.4 7.64 3.19 16.7

M-MC-23 40 177.4 7.83 4.44 22.7

M-MC-24 40 301.6 9.04 7.54 33.4

1 mm2 = 0.00155 in2

1 μm = 0.0394 mil
190

y = 10.838x + 5.2611

0

100

200

300

400

500

600

700

800

900

1000

0 5 10 15 20 25 30 35 40

Disbonded Area, mm2

TIME, weeks

1 mm2 = 0.00155 in2

Figure 217. Graph. Rapid macrocell test, disbonded area versus time for specimens with ECR.

y = 5.3213x - 7.8341

0

100

200

300

400

500

600

700

800

900

1000

0 5 10 15 20 25 30 35 40

Disbonded Area, mm2

TIME, weeks

1 mm2 = 0.00155 in2

Figure 218. Graph. Rapid macrocell test, disbonded area versus time for specimens 

with MC reinforcement.

Figure 219 and figure 220 show disbonded area versus macrocell corrosion loss for ECR and 

MC reinforcement, respectively. The ECR showed greater disbondment at a given corrosion loss 

than the MC reinforcement. On average, the disbondment of the ECR increased by 56.3 mm2

(2.21 in2

) for every 1 μm (1 mil) of corrosion loss, compared to an average increase of 26.5 mm

2

(1.04 in2

) for every 1 μm (1 mil) of corrosion loss for the MC bars. The difference in disbondment 

rate between ECR and MC reinforcement was more pronounced in specimens with low corrosion 
191

losses. For epoxy-coated bars with less than 2.0 μm (0.079 mil) of corrosion loss, the disbondment 

rate ranged from 50.7 to 308.1 mm2/μm (2.00 to 12.1 in2/mil) of loss, with an average rate of 

159.9 mm2

/μm (6.30 in2/mil). For the MC bars with less than 2.0 μm (0.078 mil) of corrosion 

loss, the disbondment rate ranged from 2.80 to 27.6 mm2/μm (0.11 to 1.09 in2/mil) of loss, with 

an average rate of 15.3 mm

2

/μm (0.60 in2/mil).

y = 56.321x + 81.057

0

100

200

300

400

500

600

700

800

900

1000

0 2 4 6 8 10

Disbonded Area, mm2

CORROSION LOSS, μm

1 mm2 = 0.00155 in2

1 μm = 0.0394 mil

Figure 219. Graph. Rapid macrocell test, disbonded area versus corrosion loss for 

specimens with ECR.

y = 26.473x - 7.6083

0

100

200

300

400

500

600

700

800

900

1000

0 2 4 6 8 10

Disbonded Area, mm2

CORROSION LOSS, μm

1 mm2 = 0.00155 in2

1 μm = 0.0394 mil

Figure 220. Graph. Rapid macrocell test, disbonded area versus corrosion loss for 

specimens with MC reinforcement.
192

In addition to the rapid macrocell specimens, five epoxy-coated bars and five MC bars with 

damaged regions identical to those used in the rapid macrocell test were exposed to a simulated 

pore solution without salt to determine the disbondment of the coatings with time in the absence 

of chlorides and chloride-induced corrosion. The results are shown in figure 221. At 10 weeks, the 

MC bars had a disbonded area of 25.8 mm2 (0.0394 in2), whereas ECR exhibited no disbondment. 

However, at 20 weeks, the ECR and MC reinforcement exhibited the same degree of disbondment

in the absence of corrosion, and at later ages, specimens with ECR exhibited greater disbonded 

areas than specimens with MC reinforcement. For both ECR and MC bars, disbondment at 

40 weeks in the absence of chlorides was 20–25 percent of the values observed at 40 weeks 

in bars subjected to chloride-induced corrosion.

0

20

40

60

80

100

120

0 5 10 15 20 25 30 35 40

Disbonded Area, mm2

TIME, weeks

M-ECR M-MC

1 mm2 = 0.00155 in2

Figure 221. Graph. Disbonded area versus time for ECR and MC reinforcement in 

simulated pore solution without salt.

Summary

For the rapid macrocell test, the specimens with MC reinforcement showed greater corrosion losses 

than the specimens with conventional ECR. However, MC reinforcement showed significantly less 

disbondment than ECR, both as a function of corrosion loss and as a function of time.
193

APPENDIX B. CORROSION LOSS REQUIRED TO CRACK CONCRETE CONTAINING 

CONVENTIONAL, EPOXY-COATED, AND GALVANIZED REINFORCEMENT

INTRODUCTION

The corrosion of steel reinforcement in concrete is a destructive process for both the steel and the 

concrete. The corrosion products of steel occupy several times the volume of solid steel, resulting

in cracking and spalling of the concrete cover once a sufficient amount of corrosion loss has 

occurred. Several prior studies have worked to establish a relationship between corrosion loss 

and cracking of concrete cover for uncoated conventional reinforcement.(68–71) In addition, 

Torres-Acosta and Sagues examined the effects of localized corrosion, although the corroding 

areas were much larger than the area typically exposed due to damage to ECR.

(71)

Limited research has been performed on the amount of corrosion loss required to crack concrete 

for galvanized reinforcement. Sergi, Short, and Page found that the corrosion product of zinc is often

zinc oxide.(73) The volume of zinc oxide is only 1.5 times that of solid zinc, whereas the volume 

of ferric oxide is 3 times that of solid steel, indicating that the corrosion loss required to crack 

concrete for specimens with galvanized reinforcement should be greater than the corrosion loss 

required to crack concrete with conventional reinforcement.(74,75)However, under certain conditions,

zinc can also form zinc hydroxychloride II, which has 3.6 times the volume of solid zinc.(73,74)

The 

formation of zinc hydroxychloride II will result in corrosion losses for galvanized reinforcement at

the onset of cracking similar to those observed for conventional reinforcement. Rasheeduzzafar 

et al. studied conventional and galvanized reinforcement cast in concrete with chloride contents 

at casting ranging from 2.4 to 19.2 kg/m3 (4 to 32 lb/yd3

).(76)Rasheeduzzafar et al. found specimens

containing galvanized reinforcement took longer to crack concrete than specimens containing 

conventional reinforcement; however, the corrosion loss at crack initiation was not determined. 

The research described in this appendix examines the corrosion losses required to crack concrete 

cover for conventional, galvanized, and damaged epoxy-coated reinforcement. Specimens with 

conventional and galvanized reinforcement were tested at varying covers to establish a relationship 

between corrosion loss and cracking for conventional and galvanized reinforcement. ECR was 

tested at 25-mm (1-inch) cover with varying damage patterns to determine the effect of the 

damaged area on corrosion loss required to crack concrete. Two- and three-dimensional finite 

element models were created to test the corrosion loss to crack concrete for multiple combinations

of cover and damaged area. The results from the finite element models are compared with 

experimental results from this and other studies, and an expression is developed relating 

damaged area, concrete cover, and corrosion loss to cause cracking.

EXPERIMENTAL PROCEDURE

Mixture Proportions

The mixture proportions used in the concrete for all specimens are shown in table 57. The 

materials used are as follows: 

Cement: Type I/II portland cement.

Water: Municipal tap water.
194

Fine aggregate: Kansas River sand. Bulk specific gravity (SSD) = 2.62, absorption = 

0.8 percent, fineness modulus = 2.51.

Coarse aggregate: Crushed limestone with a nominal maximum size of 19 mm

(0.75 inches), bulk specific gravity (SSD) = 2.58, absorption = 2.3 percent, 

unit weight = 95.9 lb/ft3 (1,536 kg/m3

).

Salt: Sodium chloride, added to mix water as specified in table 57.

Air entraining agent: Daravair® 1400, manufactured by W.R. Grace.

The mixture includes salt equivalent to 2 percent chlorides by weight of cement to destabilize the 

passive layer of the reinforcement and increase the ionic conductivity of the concrete. The salt is

dissolved in the mix water prior to casting.

Table 57. Mix proportions for cracking specimens.

Cement, 

kg/m3

(lb/yd3)

Water, 

kg/m3

lb/yd3

Fine 

Aggregate, 

kg/m3

(lb/yd3)

Coarse 

Aggregate, 

kg/m3

(lb/yd3)

Sodium 

Chloride, 

kg/m3

(lb/yd3)

Air 

Entraining

Agent, 

L/m3 (oz/yd3)

356 (598) 160 (269) 854 (1,435) 883 (1,484) 11.7 (19.8) 2.66 (68.9)

Materials

The following materials are used in the cracking tests described in this appendix:

Wire: External specimen connections from the reinforcing steel to the terminal box are 

made with 16-gauge multistrand copper wire.

Multimeter: A multimeter is used to measure current flow to each specimen.

Power supply: A power supply is used to drive the corrosion of the test bar. A galvanostat is

used for conventional and galvanized reinforcement. A 30-V power supply is used for ECR. 

The change in equipment is necessitated by the higher resistance of specimens with ECR.

Stainless steel screws/washers: Screws and washers are used to hold reinforcement in 

place in formwork and to connect wires to specimens during testing. 

Specimens

A schematic of the cracking specimens is shown in figure 222. Cracking specimens are beam 

specimens, 152 mm (6 inches) wide by 305 mm (12 inches) long. Specimen height is dependent 

on the concrete cover. The top bar is the test bar and consists of conventional, galvanized, or 

epoxy-coated reinforcement. The bottom bars are pickled 2205 duplex stainless steel. All bars 

are No. 16 (No. 5) reinforcing steel. Specimens are connected to a power supply to drive 

corrosion on the test bar and are kept ponded with deionized water.
195

Figure 222. Illustration. Cracking specimen.

A total of 34 specimens were tested in five series. Series 1 consisted of beams with conventional 

and galvanized reinforcement with 25-mm (1-inch) concrete cover. Series 2 consisted of beams 

with conventional and galvanized reinforcement with 13-mm (0.5-inch) concrete cover. Series 3 

tested conventional and galvanized reinforcement with 51-mm (2-inch) cover. Series 4 tested 

damaged ECR with 25-mm (1-inch) concrete cover. Series 5 tested two specimens with galvanized

reinforcement and 25-mm (1-inch) cover, with specimens removed from testing at crack initiation. 

Testing continued on series 1, 2, and 3 until the crack reached a width of 0.508 mm (0.02 inches). 

Testing continued on series 4 until the crack spanned the full length of the specimen because the 

lower corrosion rate of specimens containing ECR made it impractical to continue the test until 

the crack reached a width of 0.508 mm (0.02 inches).

Test Procedure

The test begins 14 days after the specimens are cast. During the test, the current to each specimen 

is measured daily. Dividing the measured current by the surface area of the test bar (or the damaged 

area for ECR) gives the corrosion current density, which is used to determine corrosion rate using

Faraday’s equation (see chapter 2). Specimens are monitored daily for staining and cracking. The 

corrosion loss at staining, crack initiation, and propagation of the crack to the full specimen 

length are recorded. In addition, the crack width as a function of corrosion loss is tracked for 

specimens with conventional and galvanized reinforcement. 

Fabrication

Specimen fabrication for cracking specimens follows the preparation procedure for bench-scale 

specimens outlined in chapter 2, with two exceptions. ECR is damaged in either a two-hole or 

152 mm [6 in.]

Variable

Direction of Current + - G

152 mm

[6 in.]

25.4 mm [1 in.]
196

two half-ring pattern, as shown in figure 223 and figure 224. Specimens are also cured in molds 

for 14 days as opposed to the curing procedure used for bench-scale specimens.

 

 

 

102 mm [4 in.] 102 mm [4 in.] 102 mm [4 in.]

 Top View Side View

 

Damage Damage

 

Ø3 mm [Ø0.125 in.] Ø3 mm [Ø0.125 in.]

Figure 223. Illustration. Damage patterns for ECR with two holes.

102 mm [4 in.] 102 mm [4 in.] 102 mm [4 in.]

 Top View Side View

 (b)

Damage Damage

 

 

 

3 mm [0.125 in.] 3 mm [0.125 in.]

 

Figure 224. Illustration. Damage patterns for ECR with two half-rings.

Test Program

The test program is summarized in table 58. The conventional and galvanized reinforcement 

were tested with 13-mm (0.5-inch), 25-mm (1-inch), and 51-mm (2-inch) concrete covers. The

galvanized reinforcement had a nominal coating thickness of 0.15 mm (6 mil). The ECR, with 

coating thickness ranging from 0.20 to 0.27 mm (8 to 10.5 mil) and an average of 0.25 mm

(9.7 mil), was tested using a 25-mm (1-inch) cover with two damage patterns, as previously 

described. 

Table 58. Corrosion loss to cause cracking, number of specimens in test program.

System

Cover

13 mm

(0.5 inches)

25 mm

(1 inch)

51 mm

(2 inches)

Uncoated bars (Conv.) 4 4 4

Galvanized bars (Zn) 4 6a 4

ECR-2 hole damage pattern

Horizontal alignment (ECR-2h-H) – 2 –

Vertical alignment (ECR-2h-V) – 2 –

ECR-2 ring damage pattern

Horizontal alignment (ECR-2r-H) – 2 –

Vertical alignment (ECR-2r-V) – 2 –

– No data. a Two specimens removed from testing at crack initiation.

Finite Element Modeling of Corrosion Loss and Cracking

To further study the relationship between corrosion loss and cracking, two- and three-dimensional 

finite element models were created using ABAQUS 6.9.(77) The two-dimensional models were 

used to model uniform corrosion of a reinforcing bar. The three-dimensional models were tested 
197

with uniform corrosion over the entire bar, as well as with areas of localized corrosion. The model

represents a slab with mirror symmetry about the axis of the reinforcement (see figure 225). The 

crack is assumed to propagate along the vertical boundary of the model centered on the reinforcing

bar. A series of nonlinear springs were used to provide horizontal restraint along the plane of the 

crack to represent the nonlinear behavior of the concrete as it cracks. 

152 mm [6.0 in.]

152 mm [6.0 in.]

Bar Diameter (Varies)

Point A Cover (Varies)

Figure 225. Illustration. Two-dimensional finite element model of concrete to measure 

cracking behavior.

The properties of the springs were based on measurements of fracture energy of concrete. Darwin et 

al. tested notched beams in center-point loading.(78) Fracture energy was calculated by determining

the area under the load-deflection curves for each specimen. Darwin et al. found that for concretes

older than 5 days, fracture energy is governed by coarse aggregate properties and is independent 

of w/c ratio, compressive strength, and age of concrete. The spring properties were adjusted to 

provide a fracture energy of 61 N/m (0.35 lb/in), comparable to the value reported by Darwin 

et al.(78) The initial stiffness of the springs provided an elastic modulus of 27.6 GPa (4,000 ksi) 

and a peak tensile stress of 2.76 MPa (400 psi). The spring behavior for a spring density of 

6,200 springs/m2 (4 springs/in2

) is shown in figure 226. 
198

0.0001, 100

0, 0 0.02, 0

0.005, 20

0

20

40

60

80

100

120

0 0.005 0.01 0.015 0.02 0.025

Deflection, in.

Load, lb.

1 lb = 2.228 N

1 inch = 25.4 mm

Figure 226. Graph. Load-deflection behavior for nonlinear spring model, spring density of 

6,200 springs/m2 (4 springs/in2).

Material away from the plane of the crack was assumed to be linear and elastic, with an elastic 

modulus of 27.6 GPa (4,000 ksi) and a Poisson’s ratio of 0.2. Corrosion was assumed to occur 

uniformly over the entire surface of the conventional and galvanized bars and over the localized 

damaged regions of the epoxy-coated bars. The buildup of corrosion products was represented by 

applying a uniform deflection normal to the reinforcing bar surface. The volume ratio of corrosion 

products to corrosion loss n was assumed to be 3.0 based on work by Suda et al.(75)

A visible crack

was assumed to have formed when the horizontal deflection at the top surface of the model (point A 

in figure 225) reached 25 μm (1.0 mil). With the model symmetry, this corresponds to a 50-μm

(2.0-mil)-wide crack. The displacement at the surface of the concrete at the location of the 

reinforcing bar required to cause the formation of the crack (Δcrit) was converted to a corrosion 

loss (xcrit) using the equation in figure 227. The term in the denominator (n-1) accounts for the 

volume of the reinforcing bar that is converted to corrosion product.

1 = n

x crit

crit

Figure 227. Equation. Corrosion loss conversion.

Figure 228 and figure 229 show typical finite element model meshes used for the two- and threedimensional models. The model dimensions are shown in figure 225. For the two-dimensional 

finite element models, concrete covers of 6.4, 13, 19, 25, 38, 51, 76, and 102 mm (0.25, 0.5, 0.75, 1, 

1.5, 2, 3, and 4 inches) and bar diameters of 13, 19, and 25 mm (0.5, 0.75, and 1 inches) were 

evaluated. For the three-dimensional finite element models, concrete covers of 51 and 76 mm (2 

and 3 inches) and bar diameters of 13, 19, and 25 mm (0.5, 0.75, and 1 inches) were used. The 

two-dimensional model had a unit length, and the three-dimensional model had a length of 

508 mm (20 inches). 
199

Figure 228. Illustration. Two-dimensional finite element analysis model.

Figure 229. Illustration. Three-dimensional finite element analysis model (end view).

Trial models were run for both the two- and three- dimensional models to determine the effect of 

mesh type on model performance (see table 59 and table 60). In both cases, the mesh type had no 

significant effect on the model performance, so the default meshes for the two- and threedimensional models (quad-dominated and hex, respectively) were used. 
200

Table 59. Effect of two-dimensional element type on corrosion loss.

Mesh Type

Corrosion Loss to Produce 

a 50-μm Crack, μm

Quad 38.99

Quad-dominated 38.48

Tri 38.74

1 μm = 0.0394 mil

Table 60. Effect of three-dimensional element type on corrosion loss.

Mesh Type

Corrosion Loss to Produce 

a 50-μm Crack, μm

Hex 64.5

Hex-dominated 64.2

Wedge 64.8

Tet 65.4

1 μm = 0.0394 mil

Trial models were also run to determine the effect of mesh seed size on model performance. The 

mesh seed size was increased until the finite element model results were affected (see figure 230).

A 6.4 mm (0.25-inch) mesh was chosen, as it was the largest mesh size for which the finite 

element model results were not affected.

38

38.2

38.4

38.6

38.8

39

39.2

39.4

39.6

0 0.125 0.25 0.375 0.5 0.625 0.75 0.875 1

Corrosion Loss, μm

Mesh Seed Size, in.

1 μm = 0.0394 mil

Figure 230. Graph. Effect of mesh seed size on corrosion loss required 

to produce a 50-μm (2-mil) crack.

The two-dimensional model was used to analyze uniform corrosion over the entire bar surface. 

For the three-dimensional model, three damage patterns were analyzed for each combination of 

cover and bar diameter, as shown in figure 231. The first damage pattern simulates corrosion 

along the entire circumference of the bar. Models with this damage pattern are designated FR 

(full ring corrosion pattern). The second damage pattern simulates corrosion along half the bar 
201

circumference and is designated HR. The third damage pattern simulates corrosion along onequarter of the bar circumference and is designated QR. The length of the FR damage pattern 

along the bar ranged from 3.2 to 508 mm (0.125 to 20 inches). The length of the HR damage 

pattern along the bar ranged from 3.2 to 203 mm (0.125 to 8 inches), and the length of the QR 

damage pattern along the bar ranged from 1.6 to 203 mm (0.0625 to 8 inches).

Figure 231. Illustration. Cross section of bar damage patterns for three-dimensional finite 

element models: full ring, half ring, and quarter ring.

EXPERIMENTAL RESULTS

Conventional and Galvanized Reinforcement

The values of corrosion loss to initiate cracking for conventional and galvanized reinforcement 

are shown in figure 232, with the standard deviation represented by error bars. For all concrete 

covers, galvanized reinforcement required significantly greater corrosion losses to crack the 

concrete cover than did conventional reinforcement. For 13-mm (0.5-inch) cover, conventional 

reinforcement required an average corrosion loss of 10.6 μm (0.417 mil) to crack the concrete 

cover, compared to 45.9 μm (1.81 mil) for galvanized reinforcement. For 25-mm (1-inch) cover, 

conventional reinforcement required an average corrosion loss of 22.4 μm (0.882 mil) to crack 

the concrete cover, compared to 49.7 μm (1.91 mil) for galvanized reinforcement, and for 51-mm

(2-inch) cover, conventional reinforcement required an average corrosion loss of 29.7 μm (1.17 mil)

to crack the concrete cover, compared to 68.0 μm (2.68 mil) for galvanized reinforcement. For 

conventional reinforcement, increasing the cover from 13 to 51 mm (0.5 to 2 inches) nearly 

tripled the corrosion loss required to crack concrete from 10.6 to 29.7 μm (0.417 to 1.17 mil), an 

increase of 19.1 μm (0.752 mil). For galvanized reinforcement, the loss increased by 48 percent 

from 45.9 to 68.0 μm (1.81 to 2.68 mil), an increase of 22.1 μm (0.870 mil).
202

0

10

20

30

40

50

60

70

80

90

13 mm (0.5 in.) 25 mm (1 in.) 51 mm (2 in.)

Cover

Corrosion Loss (μm) 

Conv. Zn

1 μm = 0.0394 mil

Figure 232. Graph. Average corrosion loss required to crack concrete for specimens with 

conventional and galvanized reinforcement.

Autopsy results from all specimens with conventional reinforcement showed heavy corrosion 

losses over the entire bar surface (see figure 233 and figure 234). Staining was apparent in the 

concrete surrounding the reinforcement. Figure 235 shows a side view of the concrete around the 

reinforcement split along the plane of the crack. Orange corrosion products are visible in regions 

where the staining reached the surface. In figure 236, greenish-black corrosion products are visible

in regions isolated from the atmosphere. All photos were taken immediately after autopsy.

Figure 233. Photo. Top side of bar in specimen Conv.-3, 51-mm (2-inch) cover, after autopsy.

Figure 234. Photo. Bottom side of bar in specimen Conv.-3, 51-mm (2-inch) cover, 

after autopsy.
203

Figure 235. Photo. Side view of specimen Conv.-2, 25-mm (1-inch) cover, after autopsy

(plane of crack visible above reinforcement).

Figure 236. Photo. Top view of specimen Conv.-2, 25-mm (1-inch) cover, after autopsy.

The autopsy found that galvanized reinforcement exhibited signs of pitting corrosion. Some regions

of the test bar exhibited heavy corrosion products, while in other sections, the galvanized coating 

was unaffected (see figure 237 and figure 238). Most of the uncorroded regions were located on 

the top face of the bar, a result of the bottom side of the bar having more even exposure to the ions

migrating from the bottom bars. Measurements with a coating thickness gauge showed no significant 

loss in the areas that appear uncorroded. Visual estimations of uncorroded surface areas were 

performed on all bars after autopsy, and results appear in table 61. The bars with 13-mm

(0.5-inch) cover showed the greatest average uncorroded area, 29 percent, likely due to the 

decreased cover interfering with ion transport to the top side of the bar. The bars with 25- and 

51-mm (1- and 2-inch) cover showed average uncorroded areas of 6 and 13 percent, respectively. 

The corrosion products on the concrete surrounding the galvanized reinforcement resembled

those seen in specimens with conventional reinforcement, indicating that the bulk of corrosion 

products applying pressure to the surrounding concrete are corrosion products of iron and not 

those of zinc (see figure 239 and figure 240).

Top Surface Plane of crack
204

Figure 237. Photo. Top side of bar in specimen Zn-2, 25-mm (1-inch) cover, after autopsy.

Figure 238. Photo. Bottom side of bar in specimen Zn-2, 25-mm (1-inch) cover,

after autopsy.

Table 61. Estimated uncorroded surface area of galvanized reinforcement.

Specimen

Estimated Uncorroded Area,

percent

Cover

13 mm

(0.5 inch)

25 mm

(1 inch)

51 mm

(2 inch)

Zn-1 30 8 5

Zn-2 30 5 10

Zn-3 40 5 50

Zn-4 15 5 30

Average 29 6 13

Figure 239. Photo. Side view of specimen Zn-4, 25-mm (1-inch) cover, after autopsy.

Uncorroded Zinc

Corroded Steel

Corroded Steel
205

Figure 240. Photo. Top view of specimen Zn-4, 25-mm (1-inch) cover, after autopsy.

To determine if the pitting observed on galvanized reinforcement was also present at crack initiation,

two additional specimens with galvanized reinforcement and 25-mm (1-inch) cover were cast 

and autopsied at the onset of cracking. Greenish-black corrosion products were visible along the 

crack at the upper surface of the specimens (see figure 241). The corrosion products turned orange 

about 2 h after exposure to air. The autopsy revealed pitting and localized corrosion on the bars 

similar to that observed in the specimens autopsied after the crack had propagated and widened

(see figure 242 and figure 243). As previously discussed, uncorroded regions were more common 

on the top than the bottom side of the test bar (see figure 244). These results suggest that cracking

of the concrete due to corrosion of the galvanized reinforcement did not result due to the buildup 

of zinc corrosion products but rather due to the formation of corrosion products from the 

intermetallic steel-zinc layers or from the underlying steel.

Figure 241. Photo. Staining on surface at crack initiation in galvanized reinforcement 

specimen, 25-mm (1-inch) cover.
206

Figure 242. Photo. Top side of galvanized reinforcement, 25-mm (1-inch) cover, after 

autopsy at crack initiation.

Figure 243. Photo. Detail of top side of galvanized reinforcement, 25-mm (1-inch) cover,

after autopsy at crack initiation.

Figure 244. Photo. Bottom side of galvanized reinforcement, 25-mm (1-inch) cover, after 

autopsy at crack initiation.

ECR

The corrosion losses required to crack concrete cover for specimens containing damaged ECR 

are shown in table 62. The losses are presented based on both the total area of the bar and the 

damaged (exposed) area in the epoxy. The bars with two half-rings had a nominal exposed area 

ten times greater than the bars with two holes in the epoxy; however, autopsy results revealed

significant blistering on bars with holes in the epoxy (see figure 245). Blistering was also present 

on the bars with the half-rings but was less severe and exposed less than the area exposed by the 

rings. Table 62 reflects an estimate of the increased exposed area from the blistered regions for 

all specimens. Ignoring the blistered regions, specimens with two half-rings had an exposed area 

of 150.8 mm2 (0.234 in2

) and specimens with two holes had an exposed area of 15.8 mm2 (0.024 in2).
207

Table 62. Average corrosion loss to crack concrete cover for specimens with ECR.

Specimen

Exposed Area 

(Including Blisters),

mm2

Corrosion Loss 

Based on Total 

Area, μm

Corrosion Loss 

Based on Exposed 

Area, μm

ECR-2 hole damage pattern

ECR-2h-H-1 188.3 10.14 730

ECR-2h-H-2 233.5 10.10 587

ECR-2h-H Average 10.12 659

ECR-2h-V-1 181.8 11.67 874

ECR-2h-V-2 201.1 7.58 510

ECR-2h-V Average 9.70 692

ECR-2 ring damage pattern

ECR-2r-H-1 208.9 6.07 421

ECR-2r-H-2 234 5.87 363

ECR-2r-H Average 5.97 392

ECR-2r-V-1 254 6.22 354

ECR-2r-V-2 208.9 6.15 426

ECR-2r-V Average 6.18 390

1 mm2 = 0.00155 in2

1 μm = 0.0394 mil

Figure 245. Photo. Test bar from specimen ECR-2h-V-2.

Table 62 shows no significant difference in the corrosion loss required to crack the concrete 

cover between the specimens with the damage pattern oriented horizontally or vertically. The 

corrosion losses on both the total and exposed areas indicate that the corrosion loss required to 

crack the concrete cover increases as exposed area decreases. Based on total and exposed area 

including blisters, the specimens with two holes in the epoxy required somewhat less than twice 

the corrosion loss to crack the concrete cover as the specimens with two half-rings in the epoxy. 

Figure 246 shows a specimen at crack initiation. Figure 247 shows a specimen with the crack 

spanning the length of the specimen. No specimens containing ECR showed signs of surface staining

during the test. After testing, however, staining was observed on the concrete surrounding the 

damaged regions in the epoxy when the specimens were autopsied (see figure 248 and figure 249).
208

Figure 246. Photo. Crack initiation in specimen ECR-2r-H-2.

Figure 247. Photo. Crack propagation in specimen ECR-2h-V-1.

Crack

Crack
209

Figure 248. Photo. Concrete surrounding test bar from specimen ECR-2h-V-1.

Figure 249. Photo. Concrete surrounding test bar from specimen ECR-2r-H-2.

FINITE ELEMENT RESULTS

The corrosion losses that cause a 50-μm (2-mil)-wide crack to form at the surface of the specimen

based on the two-dimensional finite element analyses are shown in table 63. The corrosion losses 

are plotted as a function of concrete cover in figure 250. The results suggest a linear relationship 

(for covers between 6 and 102 mm (0.25 and 4 inches)) between concrete cover and corrosion 

loss required to cause cracking. A slight dependence on bar diameter is also noted; figure 251

shows best-fit lines for each of the three bar diameters over the range of covers from 19 to 

76 mm (0.75 to 3 inches). 

Staining
210

Table 63. Finite element results for two-dimensional model.

Cover, 

mm

Bar Diameter, 

mm

Corrosion Loss to 

Crack Concretea, μm

6.4 12.7 19.7

13 12.7 20.3

25 12.7 26.0

38 12.7 35.6

51 12.7 45.1

76 12.7 59.5

9.5 19 19.7

19 19 25.4

38 19 33.7

57 19 45.1

76 19 56.5

13 25.4 20.3

25 25.4 26.7

51 25.4 40.6

76 25.4 51.1

102 25.4 76.2

1 mm = 0.039 inches

1 μm = 0.0394 mil a 50-μm (0.002-inch) crack width.

0

10

20

30

40

50

60

70

80

90

0 1 2 3 4 5

Corrosion Loss, μm .

Cover, in.

0.5 in. bar 0.75 in. bar 1 in. bar

1 μm = 0.0394 mil

1 inch = 25.4 mm

Figure 250. Graph. Corrosion loss to crack concrete versus cover for two-dimensional finite 

element model.
211

y = 15.99x + 11.62

y = 13.97x + 13.97

y = 12.22x + 15.03

0

10

20

30

40

50

60

70

0 0.5 1 1.5 2 2.5 3 3.5 4

Corrosion Loss, μm

Cover, in.

0.5 in. bar 0.75 in. bar 1 in. bar

Linear (0.5 in. bar) Linear (0.75 in. bar) Linear (1 in. bar)

1 μm = 0.0394 mil

1 inch = 25.4 mm

Figure 251. Graph. Corrosion loss to crack concrete versus cover showing effect of bar 

diameter for two-dimensional finite element model.

Table 63 and figure 251 show that as cover increases, bars with smaller diameters require somewhat

greater corrosion losses to crack concrete than bars with larger diameters for covers between 25 

and 76 mm (1 and 3 inches). An analysis of the data suggests the equation in figure 252 as a 

best-fit expression. The English equivalent is presented in figure 253.

=1.8 +7.5÷ 0.38 D

C

xcrit

Figure 252. Equation. Suggested best-fit in SI units.

=0.53 +1÷ 0.38 D

C

xcrit

Figure 253. Equation. Suggested best-fit in English units.

Where:

xcrit = Corrosion loss at crack initiation, μm or mil.

C = Cover, mm or inches.

D = Bar diameter, mm or inches. 

To verify the accuracy of the two-dimensional finite element model, the results obtained from the

model are compared with experimental results presented in this appendix along with experimental

results obtained by Saeki et al., Rasheeduzzafar et al., Alonso et al., and Torres-Acosta and 

Sagues for corrosion along the full length of conventional reinforcement. (See references 68, 69, 
212

71, and 79.) The data from these sources are shown in table 64. The experimental data are plotted 

along with the finite element results in figure 254. Data presented in this appendix are labeled 

“KU.” Other data are identified by the first author. A best-fit line for the results from the finite 

element model is also shown. While there is much scatter in the experimental data, the corrosion 

loss required to crack concrete, as predicted by the finite element model, provides an excellent 

representation of the bulk of the experimental data.

Table 64. Corrosion loss to crack concrete (corrosion along entire bar length).

Study

Cover,

mm

Diameter, 

mm

Corrosion 

Loss, μm

Torres-Acosta and 

Sagues(71)

39 13 35.9

39 13 31.1

Alonso et al.(69)

20 16 15

15 8 20

30 16 25

30 16 28

30 16 30

50 16 31

50 12 51

70 16 55

70 10 68

20 16 25

20 16 18

Rasheeduzzafar et 

al.(68)

19 13 33

19 13 26

19 13 34

38 13 32

38 13 30

38 13 47

38 13 38

38 13 27

38 13 27

50 13 70

50 13 71

50 13 74

50 13 61

60 13 67

Saeki et al.(79)

31.75 9.5 42

31.75 12.7 34

31.75 19 23

31.75 25 13

1 mm = 0.039 inches

1 μm = 0.0394 mil
213

0

10

20

30

40

50

60

70

80

90

0 1 2 3 4 5

Corrosion Loss, μm 

Cover, in.

Finite Element Model Rasheeduzzafar KU

Alonso Saeki Torres-Acosta

Linear (All FEA)

1 μm = 0.0394 mil

1 inch = 25.4 mm

Figure 254. Graph. Corrosion loss to crack concrete versus cover in two-dimensional finite 

element model with experimental data.

To determine its accuracy, the results predicted by the equation in figure 252 are compared with 

experimental results and finite element model results in figure 255. 

0

10

20

30

40

50

60

70

80

0 20 40 60 80

Corrosion Loss Based on FEM and Experimental 

Data, μm 

Corrosion Loss Based on Equation, μm 

FEM

Torres-Acosta

Alonso

Rasheeduzzafar

KU

Saeki

1 μm = 0.0394 mil

Figure 255. Graph. Corrosion loss to crack concrete for uniform general corrosion based 

on experimental and finite element results versus predicted corrosion losses using figure 252.
214

The proposed equation overestimates the corrosion loss required to crack concrete for most cases 

in which the actual corrosion loss required to crack the concrete is less than 45 μm (1.78 mil). 

An alternate equation is proposed in figure 256 and figure 257 that provides a somewhat more 

conservative estimate of the corrosion loss required to crack concrete (see figure 258).

=1.8 +4.5÷ 0.38 D

C

xcrit

Figure 256. Equation. Alternate best-fit in SI units. 

=0.53 +0.6÷ 0.38 D

C

xcrit

Figure 257. Equation. Alternate best-fit in English units.

Where:

xcrit = Corrosion loss at crack initiation, μm or mil.

C = Cover, mm or inches.

D = Bar diameter, mm or inches. 

0

10

20

30

40

50

60

70

80

0 20 40 60 80

Corrosion Loss Based on FEM and Experimental 

Data, μm 

Corrosion Loss Based on Equation, μm 

FEM

Torres-Acosta

Alonso

Rasheeduzzafar

KU

Saeki

1 μm = 0.0394 mil

Figure 258. Graph. Corrosion loss to crack concrete for uniform general corrosion based 

on experimental and finite element results versus predicting corrosion losses using figure 256.

The corrosion losses to cause cracking based on the three-dimensional finite element model are 

shown in table 65 and table 66. The models with a 51-mm (2-inch) cover and a 203-mm (8-inch) 

and 508-mm (20-inch) length of bar corroding show similar corrosion losses at crack initiation. 

The behavior of the three-dimensional finite element model under full-bar-length (508 mm
215

(20 inches)) corrosion is compared to that of the two-dimensional finite element model in figure 259.

The corrosion losses to cause cracking obtained from these models are similar. The differences in 

corrosion loss to crack concrete between two- and three-dimensional models is less than 1 μm

(0.039 mil), with the exception of models with a 25-mm (1-inch)-diameter bar and 76-mm (3-inch) 

cover, which show a 2.9-μm (0.11-mil) or 5.7 percent difference in corrosion loss to cause cracking. 

Table 65. Finite element results for three-dimensional model, 51-mm (2-inch) cover.

Corrosion Pattern

13-mm (0.5-in.) Bar Diameter 19-mm (0.75-in.) Bar Diameter 25-mm (1-in.) Bar Diameter

Exposed 

Area,

mm2 (in2

)

Corrosion 

Loss at 

Cracking, 

μm

Exposed 

Area, 

mm2 (in2

)

Corrosion 

Loss at 

Cracking, 

μm

Exposed 

Area,

mm2 (in2

)

Corrosion 

Loss at 

Cracking, 

μm

Full Ring

508 mm (20 in.) length 10,134 (15.7) 46 15,201 (23.6) 43 20,268 (31.4) 40

203 mm (8 in.) length 4,054 (6.28) 57 6,080 (9.42) 44 8,107 (12.6) 41

102 mm (4 in.) length 2,027 (3.14) 79 3,040 (4.71) 57 4,054 (6.28) 56

51 mm (2 in.) length 1,013 (1.57) 159 1,520 (2.36) 133 2,027 (3.14) 80

25 mm (1 in.) length 507 (0.785) 330 760 (1.18) 254 1,013 (1.57) 144

13 mm (0.5 in.) length 253 (0.392) 483 380 (0.589) 381 507 (0.785) 281

6.4 mm (0.25 in.) length 127 (0.196) 659 190 (0.295) 508 253 (0.392) 361

3.2 mm (0.125 in.) length 63.3 (0.098) 851 95 (0.147) 658 127 (0.196) 502

Half Ring

102 mm (4 in.) length 1,013 (1.57) 178 1,520 (2.36) 152 2,027 (3.14) 88

51 mm (2 in.) length 507 (0.785) 273 760 (1.18) 229 1,013 (1.57) 150

25 mm (1 in.) length 253 (0.392) 425 380 (0.589) 347 507 (0.785) 279

13 mm (0.5 in.) length 127 (0.196) 635 190 (0.295) 502 253 (0.392) 418

6.4 mm (0.25 in.) length 63.3 (0.098) 904 95.0 (0.147) 704 127 (0.196) 572

3.2 mm (0.125 in.) length 31.7 (0.049) 1,228 47.5 (0.074) 973 63.3 (0.098) 784

Quarter Ring

102 mm (4 in.) length 507 (0.785) 216 760 (1.18) 191 1,013 (1.57) 170

51 mm (2 in.) length 253 (0.392) 337 380 (0.589) 292 507 (0.785) 259

25 mm (1 in.) length 127 (0.196) 546 190 (0.295) 470 253 (0.392) 404

13 mm (0.5 in.) length 63.3 (0.098) 861 95.0 (0.147) 737 127 (0.196) 622

6.4 mm (0.25 in.) length 31.7 (0.049) 1,293 47.5 (0.074) 1,090 63.3 (0.098) 890

3.2 mm (0.125 in.) length 15.8 (0.025) 1,969 23.8 (0.037) 1,562 31.7 (0.049) 1,226

1.6 mm (0.0625 in.) length 7.9 (0.012) 2654 11.8 (0.018) 2,223 15.8 (0.025) 1,930

1 μm = 0.0394 mil
216

Table 66. Finite element results for three-dimensional model, 76-`mm (3-inch) cover.

Corrosion Pattern

13-mm (0.5-in.) Bar Diameter 19-mm (0.75-in.) Bar Diameter 25-mm (1-in.) Bar Diameter

Exposed 

Area,

mm2 (in2

)

Corrosion

Loss at 

Cracking,

μm

Exposed 

Area, 

mm2 (in2

)

Corrosion 

Loss at 

Cracking,

μm

Exposed 

Area, 

mm2 (in2

)

Corrosion 

Loss at 

Cracking, 

μm

Full Ring

508 mm (20 in.) length 10,134 (15.7) 57 15,201 (23.6) 56 20,268 (31.4) 54

203 mm (8 in.) length 4,054 (6.28) 102 6,080 (9.42) 152 8,107 (12.6) 83

102 mm (4 in.) length 2,027 (3.14) 216 3,040 (4.71) 267 4,054 (6.28) 108

51 mm (2 in.) length 1,013 (1.57) 445 1,520 (2.36) 406 2,027 (3.14) 267

25 mm (1 in.) length 507 (0.785) 660 760 (1.18) 584 1,013 (1.57) 446

13 mm (0.5 in.) length 253 (0.392) 927 380 (0.589) 813 507 (0.785) 611

6.4 mm (0.25 in.) length 127 (0.196) 1,295 190 (0.295) 1,067 253 (0.392) 853

3.2 mm (0.125 in.) length 63.3 (0.098) 1,689 95 (0.147) 1,321 127 (0.196) 1,116

Half Ring

102 mm (4 in.) length 1,013 (1.57) 368 1,520 (2.36) 356 2,027 (3.14) 328

51 mm (2 in.) length 507 (0.785) 559 760 (1.18) 521 1,013 (1.57) 483

25 mm (1 in.) length 253 (0.392) 838 380 (0.589) 762 507 (0.785) 693

13 mm (0.5 in.) length 127 (0.196) 1,219 190 (0.295) 1,118 253 (0.392) 968

6.4 mm (0.25 in.) length 63.3 (0.098) 1,676 95.0 (0.147) 1,461 127 (0.196) 1,283

3.2 mm (0.125 in.) length 31.7 (0.049) 2,261 47.5 (0.074) 1,842 63.3 (0.098) 1,689

Quarter Ring

102 mm (4 in.) length 507 (0.785) 508 760 (1.18) 445 1,013 (1.57) 394

51 mm (2 in.) length 253 (0.392) 737 380 (0.589) 622 507 (0.785) 610

25 mm (1 in.) length 127 (0.196) 1,067 190 (0.295) 927 253 (0.392) 902

13 mm (0.5 in.) length 63.3 (0.098) 1,626 95.0 (0.147) 1,308 127 (0.196) 1,270

6.4 mm (0.25 in.) length 31.7 (0.049) 2,350 47.5 (0.074) 1,791 63.3 (0.098) 1,702

3.2 mm (0.125 in.) length 15.8 (0.025) 3,226 23.8 (0.037) 2,502 31.7 (0.049) 2,273

1.6 mm (0.0625 in.) length 7.9 (0.012) 4,343 11.8 (0.018) 3,543 15.8 (0.025) 3,226

1 μm = 0.0394 mil
217

0

10

20

30

40

50

60

70

80

90

0 1 2 3 4 5

Corrosion Loss, μm

Cover, in.

2D-0.5 in. bar 2D-0.75 in. bar 2D-1 in. bar

3D-0.5 in. bar 3D-0.75 in. bar 3D-1 in. bar

1 μm = 0.0394 mil

1 inch = 25.4 mm

Figure 259. Graph. Corrosion loss to crack concrete for uniform general corrosion versus 

cover for two-and three-dimensional finite element model.

The number of variables studied in the three-dimensional finite element model makes plotting 

all data points on a single plot impractical. Instead, data subsets holding as many variables 

constant as possible are analyzed to determine the effect of a variable on the corrosion loss 

required to crack concrete. Furthermore, corroding area, bar diameter, length of corroding region, 

and damage pattern are not independent variables—specifying any three variables restricts the 

fourth to a single value. For this analysis, the effect of cover, bar diameter, corroding area, and 

corroding length are analyzed with the goal of creating an equation that reduces to figure 256 in 

the case of general corrosion. Corroding area is expressed as a fraction of the total area of the bar, 

Af (Af = Acorroding/Abar). Corroding length is expressed as a fraction of the total length of the bar, 

Lf (Lf = Lcorroding/Lbar).

The corrosion loss to crack concrete is plotted versus exposed area for a 13-mm (0.5-inch)-

diameter bar with 51-mm (2-inch) cover in figure 260. A curve of the form xcrit = m(Af)

b is fit to 

the data. Table 67 summarizes the values of m and b for all three-dimensional finite element 

models. Based on table 67, it may be reasonably assumed the constant b is equal to -0.6, while 

the constant A is dependent on other variables.
218

xcrit = 41.108(Af)-0.602

R2 = 0.9828

0

500

1000

1500

2000

2500

3000

3500

0 0.2 0.4 0.6 0.8 1 1.2

Corrosion Loss, μm

Af

1 μm = 0.0394 mil

Figure 260. Graph. Corrosion loss to crack concrete versus fraction of exposed area with 

best-fit line for 13-mm (0.5-inch)-diameter bar and 51-mm (2-inch) cover.

Table 67. Constants m and b for best-fit curve xcrit = m(Af)b to corrosion loss versus Af plots.

Bar Diameter, 

mm (inches)

Cover, 

mm (inches) m b

13 (0.5) 51 (2) 41.11 -0.602

19 (0.75) 51 (2) 34.20 -0.597

25 (1) 51 (2) 26.60 -0.600

13 (0.5) 76 (3) 85.11 -0.587

19 (0.75) 76 (3) 78.97 -0.592

25 (1) 76 (3) 60.65 -0.589

Figure 261 shows the relationship between corrosion loss and cover for all bars with a corroding 

area of 1,013 mm2 (1.57 in2). Similar plots were analyzed for other exposed areas. For bars with 

a fixed damage pattern and diameter, increasing the cover from 51 to 76 mm (2 to 3 inches) 

approximately doubles the corrosion loss required to crack concrete. This suggests that for 

localized corrosion, the corrosion loss required to crack concrete is proportional to cover 

squared. For larger corroding areas, the relationship between corrosion loss and cover becomes 

linear, as shown in figure 252 and figure 256.
219

xcrit = 100.96C1.7095

xcrit = 77.44C1.8511

xcrit = 50.00C2.1103

0

100

200

300

400

500

600

700

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5

Corrosion Loss, μm

Cover, in.

FR, D = 0.5 in. FR, D = 1 in. HR, D = 0.5 in.

HR, D = 1 in. QR, D = 0.5 in. QR, D = 1 in.

1 μm = 0.0394 mil

1 inch = 25.4 mm

Figure 261. Graph. Corrosion loss to crack concrete xcrit versus cover C for 1,013-mm2

(1.57-in2) corroding area.

Figure 262 shows the relationship between corrosion loss and fractional corroding length 

Lf (Lf = Lcorroding/Lbar) for all bars with a corroding area of 1013 mm2 (1.57 in2

). Similar 

plots are analyzed for other lengths. A best-fit power line to the data suggests a relationship 

between corrosion loss and fractional corroding length to the -0.1 power.

xcrit = 451.95(Lf)-0.086

R2 = 0.9672

0

100

200

300

400

500

600

700

0 0.1 0.2 0.3

Corrosion Loss, μm

Lf

1 μm = 0.0394 mil

Figure 262. Graph. Corrosion loss to crack concrete xcrit versus Lf with best fit line for 

1,013-mm2 (1.57-in2

) corroding area.
220

Based on the data presented, the equations in figure 263 and figure 264 represent a potential 

relationship between corrosion loss and the variables in this study. The term 3Af

-1 is required for 

localized corrosion and reduces to 1 for general corrosion. 

1

0.38 0.1 0.6

2

0.53 0.6 3

÷ = + ÷ f

f

A

f f

A

crit D L A

C

x

Figure 263. Equation. Potential relationship between corrosion loss and variables in 

English units. 

[ ] 1

0.38 0.1 0.6

2

25.4 45 0.2 3

÷ = + ÷ f

f

A

f f

A C

crit D L A

x

Figure 264. Equation. Potential relationship between corrosion loss and variables in 

SI units.

Where:

xcrit = Corrosion loss at crack initiation, mil or μm.

C = Cover, inches or mm.

D = Bar diameter, inches or mm. 

Lf = Fractional length of bar corroding, Lcorroding/Lbar.

Af = Fractional area of bar corroding, Acorroding/Abar.

Figure 265 compares the corrosion losses for the finite element models with the corrosion losses 

predicted by the equation. There is some scatter, but the equations in figure 263 and figure 264

provide a reasonable match with the results obtained from the finite element model.
221

0

200

400

600

800

1000

1200

1400

1600

1800

2000

0 500 1000 1500 2000

Corrosion Loss Based on FEM, μm

Corrosion Loss Based on Equation, μm

1 μm = 0.0394 mil

Figure 265. Graph. Corrosion loss to crack concrete for localized corrosion based on 

the finite element model results versus corrosion losses calculated by the equations

in figure 263 and figure 264.

To further verify the accuracy of the equations in figure 263 and figure 264, the corrosion loss 

predicted by the equation is compared to the experimental data for localized corrosion of ECR, 

as well as experimental results presented by Rasheeduzzafar et al., Alonso et al., and TorresAcosta and Sagues, which are summarized in table 68.

(68,69,71) Data for generalized corrosion of 

steel are also included in the analysis to check the accuracy of the equation for bars with large 

corroding areas. The comparison is presented in figure 266 and figure 267 along with the 

comparison for the three-dimensional finite element model results shown in figure 265.
222

Table 68. Results from other research: corrosion loss to crack concrete 

(localized corrosion).

Cover, mm

Diameter, 

mm

Exposed 

Area, mm2

Bar Area, 

mm2

Exposed 

Length, 

mm

Bar 

Length, 

mm

Corrosion 

Loss, μm

Torres-Acosta and Sagues(72)

27.6 21 2,105 16,757 32 254 48.3

27.6 21 2,105 16,757 32 254 66.4

40.3 21 2,738 20,122 42 305 88.2

40.3 21 2,738 20,122 42 305 69.6

65.7 21 4,486 26,785 68 406 76.5

65.7 21 4,486 26,785 68 406 121.8

40.3 21 2,764 20,122 42 305 55.2

40.3 21 2,764 20,122 42 305 68.9

40.3 21 1,260 13,393 19 203 141.2

40.3 21 1,260 13,393 19 203 70.6

40.3 21 2,738 20,122 42 305 60.3

40.3 21 2,738 20,122 42 305 65.0

40.3 21 22,827 26,785 346 406 28.4

40.3 21 22,827 26,785 346 406 7.2

27.5 21 1,649 26,785 25 406 30.8

40.3 21 1,649 26,785 25 406 61.6

45 13 4,084 16,581 100 406 84.0

45 13 1,021 16,581 25 406 336.0

38 13 4,084 16,581 100 406 49.8

38 13 4,084 16,581 100 406 49.8

13 13 4,084 16,581 100 406 31.1

13 13 1,021 16,581 25 406 37.3

13 13 1,021 16,581 25 406 49.8

13 13 4,084 16,581 100 406 3B2

28.8 13 796 16,581 20 406 207.4

30.3 13 796 16,581 20 406 111.7

39 13 15,928 16,581 390 406 35.9

39 13 15,928 16,581 390 406 31.1

39 13 1,593 16,581 39 406 151.6

39 13 1,593 16,581 39 406 159.6

39 13 327 16,581 8 406 233.3

39 13 327 16,581 8 406 272.2

27.5 6.4 603 8,163 30 406 63.2

26.5 6.4 603 8,163 30 406 8B3

39 13 1,593 16,581 39 406 271.2

39 13 1,593 16,581 39 406 191.5

39 13 1,593 16,581 39 406 159.6

39 13 1,593 16,581 39 406 151.6
223

Table 68. Results from other research: corrosion loss to crack concrete 

(localized corrosion)—Continued.

Cover, mm

Diameter, 

mm

Exposed 

Area, mm2

Bar Area, 

mm2

Exposed 

Length, 

mm

Bar 

Length, 

mm

Corrosion 

Loss, μm

Alonso et al.(70)

19 1B6 17,448 17,448 381 381 15

15.2 8.0 9,550 9,550 381 381 20

30.4 16.0 19,101 19,101 381 381 25

30.4 16.0 19,101 19,101 381 381 28

30.4 16.0 19,101 19,101 381 381 30

49.4 15.9 19,024 19,024 381 381 31

49.4 11.8 14,041 14,041 381 381 51

68.4 15.5 18,558 18,558 381 381 55

68.4 9.8 11,665 11,665 381 381 68

19 1B6 17,448 17,448 381 381 25

19 1B6 17,448 17,448 381 381 18

29 38.1 91,207 91,207 381 381 3

Rasheeduzzafar et al.(69)

20 13 22,462 22,462 550 550 33

20 13 22,462 22,462 550 550 26

20 13 22,462 22,462 550 550 34

35 13 22,462 22,462 550 550 32

35 13 22,462 22,462 550 550 30

35 13 22,462 22,462 550 550 47

35 13 22,462 22,462 550 550 38

35 13 22,462 22,462 550 550 27

35 13 22,462 22,462 550 550 27

50 13 22,462 22,462 550 550 70

50 13 22,462 22,462 550 550 71

50 13 22,462 22,462 550 550 74

50 13 22,462 22,462 550 550 61

60 13 22,462 22,462 550 550 67

1 mm = 0.039 inches

1 mm2 = 0.00155 in2

1 μm = 0.0394 mil
224

0

20

40

60

80

100

120

140

160

180

200

0 50 100 150 200

Corrosion Loss Based on FEM and Experimental Data, μm

Corrosion Loss Based on Equation, μm

FEM

Torres-Acosta

Alonso

Rasheeduzzafar

KU

1 μm = 0.0394 mil

Figure 266. Graph. Corrosion loss in localized corrosion specimens versus corrosion loss 

predicted by the equation in figure 263 and figure 264 for three-dimensional finite element 

model and experimental data.

0

200

400

600

800

1000

1200

1400

1600

1800

2000

0 500 1000 1500 2000

Corrosion Loss Based on FEM and Experimental Data, μm

Corrosion Loss Based on Equation, μm

FEM

Torres-Acosta

Alonso

Rasheeduzzafar

KU

1 μm = 0.0394 mil

Figure 267. Graph. Corrosion loss in localized corrosion specimens versus corrosion loss 

predicted by the equation in figure 263 and figure 264 for three-dimensional finite element 

model and experimental data (revised scale).
225

Figure 266 covers the range of the experimental data in table 68. There is a moderate degree of 

scatter for both the finite element model and experimental results, but the finite element model 

generally agrees with the experimental data. The equations in figure 263 and figure 264 provide 

a generally conservative estimate of the corrosion loss required to crack concrete based on both 

the experimental and finite element results; that is, in most cases, the equations in figure 263 and 

figure 264 underestimate the loss required to cause a crack to form.

The finite element models extend well beyond the range of experimental data (see figure 267); 

additional testing will be needed to verify the accuracy of the finite element model in this range. 

The KU specimens with actual corrosion losses between 350 and 900 μm (14 and 35 mil) represent

the epoxy-coated bars with half-rings and holes in the epoxy. Figure 263 and figure 264 are very 

conservative for these specimens, predicting losses of approximately 200 μm (7.8 mil), compared

to the 350 and 900 μm (14 and 35 mil) range in actual losses. The equation is most conservative 

for the epoxy-coated specimens with two holes in the epoxy; these specimens are shown as open 

circles in figure 267, as the uncertainty in the exposed area due to blistering of the epoxy calls 

the accuracy of these data points into question.

DISCUSSION

Torres-Acosta and Sagues derived an expression, shown in figure 268, relating bar cover, bar 

diameter, and localized corrosion length with the corrosion loss required for crack initiation 

based on experimental results.(71)

2

=11.0 +1÷

L

C

D

C

xcrit

Figure 268. Equation. Torres-Acosta and Sagues’ corrosion loss to crack initiation.

Where:

xcrit = Corrosion loss at crack initiation, μm.

C = Cover, mm.

D = Bar diameter, mm.

L= Length of exposed steel, mm.

Figure 269 and figure 270 compare the corrosion losses predicted by the equation with the 

experimental data for localized corrosion of ECR presented in table 62, as well as the finite 

element results and the experimental results presented by Rasheeduzzafar et al., Alonso et al., 

and Torres-Acosta and Sagues, as done for the equations in figure 263 and figure 264 in figure 

266 and figure 267.

(68,69,71)
226

0

20

40

60

80

100

120

140

160

180

200

0 50 100 150 200

Corrosion Loss Based on FEM and Experimental Data, μm

Corrosion Loss Based on Torres-Acosta Equation, μm

FEM

Torres-Acosta

Alonso

Rasheeduzzafar

KU

1 μm = 0.0394 mil

Figure 269. Graph. Corrosion loss in localized corrosion specimens versus corrosion loss 

predicted by the equation in figure 268 with three-dimensional finite element model and 

experimental data.

0

200

400

600

800

1000

1200

1400

1600

1800

2000

0 500 1000 1500 2000

Corrosion Loss Based on FEM and Experimental Data, μm

Corrosion Loss Based on Torres-Acosta Equation, μm

FEM

Torres-Acosta

Alonso

Rasheeduzzafar

KU

1 μm = 0.0394 mil

Figure 270. Graph. Corrosion loss in localized corrosion specimens versus corrosion loss 

predicted by the equation in figure 268 with three-dimensional finite element model and 

experimental data (revised scale).
227

Comparing figure 266 and figure 269 shows that for bars that require less than 50 μm (2 mil) of 

loss to crack concrete, the equations in figure 263 and figure 264 and the equation in figure 268

perform comparably. However, the equation developed by Torres-Acosta is less conservative 

based on both experimental and finite element model results for bars that require greater than 

50 μm (2 mil) of loss to crack concrete; that is, the corrosion loss required to crack concrete 

predicted by the equation in figure 268 is greater than the corrosion loss required to crack concrete

in the test specimens and for many of the finite element results. The equations in figure 263 and 

figure 264, in contrast, are more conservative with respect to many of the experimental specimens.

The equation in figure 268 overestimates a significant portion of the experimental results obtained

by Torres-Acosta and Sagues, in one case predicting a corrosion loss of 173 μm (6.81 mil) for 

a specimen that only required 63 μm (2.48 mil) of loss to crack concrete. For all experimental 

specimens with actual losses greater than 60 μm (2.4 mil), the equation in figure 268 overestimates

the corrosion loss requited to crack concrete for over 75 percent of the specimens. In comparison,

the equation in figure 263 and figure 264 overestimates the corrosion loss to crack concrete for 

only 14 percent of the specimens with actual losses greater than 60 μm (2.4 mil).

Comparing the two expressions based on results from the finite element model suggests that the 

equation in figure 268 becomes increasingly inaccurate and unconservative for bars that require 

very large corrosion losses to crack concrete (see figure 270). Furthermore, results from the finite 

element models where greater than 1,200 μm (47 mil) of loss is required to crack concrete do not 

appear in figure 270, as the equation in figure 268 predicts that greater than 2,000 μm (79 mil) of 

loss is required to crack the concrete.

The ratio of experimentally obtained corrosion losses required to crack concrete to the corrosion 

losses obtained by the two equations is also used to judge the degree of conservatism in each 

equation. A ratio less than 1.0 indicates an unconservative estimate for that specimen. Figure 271

and figure 272 compare this ratio for each equation based on corrosion losses obtained from 

experimental and finite element model results, respectively. Over the range of available experimental

data, the two equations perform comparably, with the equations in figure 263 and figure 264 being 

more conservative for systems where actual losses exceeded 50 μm (2 mil). As previously discussed,

the available experimental data involves exposed areas far larger than those typically observed on

damaged ECR. The specimens with damaged ECR tested as part of this study developed blisters 

that greatly increased the exposed area; therefore, only finite element model results are available 

for small exposed areas. Over the range of finite element model data, the equation in figure 268

rapidly becomes unconservative, as noted by the large percentage of ratios of finite element 

model-predicted corrosion losses to figure 268-predicted losses that are much less than 1.0 for 

models with expected corrosion losses greater than 500 μm (20 mil). In contrast, the equations in

figure 263 and figure 264 do not exhibit this behavior. Therefore, the equations in figure 263 and

figure 264 are used to determine the corrosion loss required to crack concrete for damaged ECR.
228

0

0.5

1

1.5

2

2.5

3

0 100 200 300 400

Ratio of Experimental to Equation 

Corrosion Loss

Corrosion Loss Based on Experimental Data, μm

equation in figure 

263 and figure 264

equation in figure 

268

1 μm = 0.0394 mil

Figure 271. Graph. Ratio of experimentally derived corrosion loss to predicted corrosion 

loss versus corrosion loss to crack concrete based on experimental data.

0

0.5

1

1.5

2

2.5

3

0 500 1000 1500 2000 2500 3000

Ratio of FEM to Equation Corrosion 

Loss

Corrosion Loss Based on FEM, μm

equation in figure 

263 and figure 264

equation in figure 

268

1 μm = 0.0394 mil

Figure 272. Graph. Ratio of finite element model-derived corrosion loss to predicted 

corrosion loss versus corrosion loss to crack concrete based on finite element model.
229

ACKNOWLEDGMENTS

Additional funding was provided by the University of Kansas and the Kansas Department of 

Transportation under Contract Nos. C1131 and C1281, with technical oversight by Dan Scherschligt,

Don Whisler, Michael Ingalls, the Concrete Reinforcing Steel Institute, DuPont Powder Coatings,

3M Corporation, Valspar Corporation, BASF Admixtures, Inc., W.R. Grace and Co., Broadview 

Technologies, Inc., Western Coating, Inc., and LRM Industries. Former graduate students at the 

University of Kansas who contributed to this project include Dr. Javier Balma, Dr. Jianxin Ji, 

Dr. Lien Gong, Dr. Guohui Guo, and Dr. Lihua Xing, as well as masters students Sean R. Hughes,

Jason L. Draper, and W. Joseph Sturgeon.

231

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