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Publication Number: FHWA-HRT-09-044
Date: October 2009

Integrity of Infrastructure Materials and Structures

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Table of Contents

FOREWARD

Corrosion-induced deterioration of both reinforced concrete and steel bridges exposed to chlorides is a pervasive problem that challenges the design of new structures and the maintenance of existing ones. Because of concerns regarding long-term serviceability of epoxy-coated reinforcing steel in bridge decks and substructures, enhanced attention has focused on these materials in recent years. An important consideration in the case of existing steel bridges is the development of monitoring methods and technologies for characterizing the deterioration rate. For exposed steel surfaces, determination of the as-constructed deterioration rates is critically important for maintenance schedules, especially for weathering steels. Furthermore, for new construction, specification of unpainted weathering versus painted steel bridges has important cost-performance implications. In addition, steel performance monitoring can be facilitated by sensor technologies where accessibility is difficult (e.g., suspension cables, box beams, and cable stays). This investigation was initiated for two purposes: (1) to evaluate stainless steel (SS) type 2304 (UNS S32304) as a corrosion-resistant reinforcement in concrete and (2) to develop sensor technology for characterizing corrosion rate on existing steel bridges in situ.

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 and the State of Florida assume no liability for its content or use thereof. This report does not constitute a standard, specification, or regulation.

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

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TECHNICAL REPORT DOCUMENTATION PAGE

1. Report No.
FHWA-HRT-09-044
2. Government Accession No. 3. Recipient's Catalog No.
N/A

4. Title and Subtitle
Integrity of Infrastructure Materials and Structures

5. Report Date
October 2009

6. Performing Organization Code
FAU-OE-CMM-0802

7. Author(s)
Richard D. Granata and William H. Hartt

8. Performing Organization Report No.

9. Performing Organizations Names and Addresses

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

10. Work Unit No.(TRAIS)
N/A

11. Contract or Grant No.
DTFH61-05-C-00003

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

14. Sponsoring Agency Code

15. Supplementary Notes
The Contracting Officer's Technical Representative (COTR) was Y.P. Virmani, HRDI-10.

16. Abstract
Corrosion of bridges, both of steel and reinforced concrete construction, constitutes a major maintenance problem for the
United States. In the case of reinforced concrete bridges, recent attention has focused on corrosion-resistant reinforcements because of concerns that epoxy-coatings, which are presently employed for corrosion protection, may not provide the
75- to 100-year service life that is now required for major structures. A component of this research addressed two aspects of serviceability of 2304 stainless steel (SS) (UNS S32304) as reinforcement in concrete bridges. The first aspect addressed concerns regarding possible susceptibility to stress corrosion cracking in chloride-contaminated pore water, and the second aspect focused on determination of the critical chloride concentration, CT, to initiate active corrosion. The latter effort involved both accelerated aqueous tests and longer-term exposure of reinforced concrete slabs. No stress corrosion cracking was detected, and a value was defined which CT exceeds.

In the case of steel bridges, an accelerated corrosion test was developed for weathering steel with a range of exposure conditions that demonstrated sensitivity to chloride environments. The protective oxide layer (patina) of weathering steel was degraded above 0.5 wt percent chloride. Above 1 wt percent chloride, the protective oxide could have been severely degraded. Sensors were able to indicate the corrosion rate of coupon material exposed to the same environment. Sensors allowed direct and immediate observation of the impact environmental changes had on corrosion rate. X-ray diffraction showed that the corrosion products produced in cyclic test chambers were similar to those observed under field conditions. Sensors were capable of monitoring corrosive conditions within suspension bridge cables and other steel bridge geometries that were difficult to access.

17. Key Words
Reinforced concrete, Reinforcing steel, Stainless steel, Bridges, Corrosion resistance, Atmospheric corrosion, Steel, Corrosion sensors

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
85

22.Price

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

Metric Coversion Table

TABLE OF CONTENTS

CHAPTER 1. INTRODUCTION
STEEL FOR CONCRETE REINFORCEMENT
STEEL FOR STRUCTURES AND CABLES

CHAPTER 2. RESEARCH COMPONENT #1: 2304 SS REINFORCING BARS IN CHLORIDE-CONTAMINATED ENVIRONMENTS
OBJECTIVE
MATERIAL

CHAPTER 3. RESEARCH APPROACH #1
TASK 1.1. STRESS CORROSION CRACKING

Procedure
TASK 1.2. CORROSION PROPERTIES OF TYPE 2304 SS REINFORCEMENT
Accelerated Corrosion Test Procedure
Reinforced Concrete Exposures

CHAPTER 4. RESULTS AND DISCUSSION #1
TASK 1.1. STRESS CORROSION CRACKING

TASK 1.2. CORROSION PROPERTIES OF TYPE 2304 SS REINFORCEMENT
Accelerated Corrosion Test Procedure
Reinforced Concrete Exposures

CHAPTER 5. RESEARCH STUDY #1 FINDINGS

CHAPTER 6. RESEARCH STUDY #2: HIGHWAY BRIDGE STEEL COMPONENTS SUBJECT TO SIMULATED ATMOSPHERIC EXPOSURE
OBJECTIVE
Material

CHAPTER 7. RESEARCH APPROACH #2
TASK 2.1. LABORATORY TEST METHOD FOR PRODUCTION OF PROTECTIVE AND NONPROTECTIVE OXIDE LAYERS IN CHLORIDE ENVIRONMENTS
Wet/Dry Cycle
Exposure Tests
Coupon Preparation
Weight Loss
X-ray Diffraction Analyses
TASK 2.2. CORROSION RATES OF ACCELERATED TEST SPECIMENS USING GALVANIC SENSORS
Approach
Sensor Design
Zero Resistance Ammeter Data Logger
Sensor Active Area
Sensor Anode Fabrication
Sensor Cathode Fabrication
Electrode Separator
Sealer
Sensor Electrical Connection
Exposure Testing
TASK 2.3. DEVELOPMENT OF PROTOTYPE CABLE CORROSION SENSORS
Cable Sensors
Cable Sensor Tests
XRD for Cable Sensor Tests

CHAPTER 8. RESULTS AND DISCUSSION #2
TASK 2.1. LABORATORY TEST METHOD FOR PRODUCTION OF PROTECTIVE AND NONPROTECTIVE OXIDE LAYERS IN CHLORIDE ENVIRONMENTS
Weight Loss
First Set Test
Influence of Sodium Chloride
Influence of Wetting Time
Second Set Test
XRD and Corrosion Rate
Weathering Steel—15-Cycle Exposure with Protective Patina
Weathering Steel—30–Cycle Exposure with Protective Patina
Weathering Steel—30–Cycle Exposure with Nonprotective Patina Exposed to High Chloride Concentration
Weathering Steel—30–Cycle Exposure with Nonprotective Patina Exposed to High Time of Wetness
Carbon Steel—30–Cycle Exposure with Nonprotective Patina Exposed to High Chloride Concentration
Analyses of Carbon and Weathering Steel Corrosion Products
Summary of XRD Analysis
TASK 2.2. CORROSION RATES OF ACCELERATED TEST SPECIMENS USING GALVANIC SENSORS
Reaction to Humidity and Salt Application
Corrosion Rate Determination
RESULTS OF TASK 2.3. PROTOTYPE CABLE CORROSION SENSORS
Cable Sensor Response to Test Conditions
XRD Results for Cable Test Specimens

CHAPTER 9. RESEARCH STUDY #2 FINDINGS

CHAPTER 10. CONCLUSIONS

APPENDIX
CALCULATIONS
Example 1. Convert Weight/Area (Corrosion in g/inches2) to mils (or mm)Corrosion Penetration
Example 2. Conversion of ZRA Current to Coulombs
Example 3. Conversion of Sensor Output (µA) to Corrosion Rate (mpy or mmpy)
Example 4. Comparison of Mass Loss and Sensor Results in Terms of Penetration

REFERENCES

LIST OF FIGURES

Figure 1. Photo. 2304 SS bar after bending
Figure 2. Illustration. A bent specimen in the restrained position
Figure 3. Photo. Test tank with cover
Figure 4. Photo. Top view of two specimens with C-clamps in the test tank
Figure 5. Photo. High temperature experiment arrangement
Figure 6. Photo. Straight as-received 2304 SS bar with epoxy-mounted ends and an electrical lead
Figure 7. Illustration. Accelerated experimental arrangement
Figure 8. Photo. Test system
Figure 9. Illustration. Simulated deck slab specimen design
Figure 10. Photo. SDS specimens reinforced with 2304 SS under test
Figure 11. Graph. Accelerated corrosion test data
Figure 12. Graph. Cumulative distribution plot of CT for 2304 SS from accelerated testing
Figure 13. Graph. Potential data for the 2304 SS-reinforced concrete specimens
Figure 14. Graph. Macrocell current data for the 2304 SS-reinforced concrete specimens
Figure 15. Graph. Concrete chloride concentration profiles determined from 10 cores
Figure 16. Chart. Standard SAE J2334 cyclic test with five cycles/week
Figure 17. Photo. CARON® environmental chamber for cyclic SAE J2334 tests
Figure 18. Photo. Specimens on holder rack and in soak tank
Figure 19. Graph. Example of X-ray powder diffraction spectrum
Figure 20. Illustration. Atmospheric corrosion sensor (Model FAU2)
Figure 21. Illustration. Anode detail for atmospheric corrosion sensor
Figure 22. Photo. Data logger incorporating a ZRA
Figure 23. Graph. Sensor output for 0.7-inch active anode steel washer diameter for one SAE J2334 cycle in the standard solution
Figure 24. Graph. Sensor output for 0.8-inch active anode steel washer diameter for one SAE J2334 cycle in the standard solution
Figure 25. Photo. Bottom side of a sensor mounted on its holder experiencing under-paint corrosion
Figure 26. Photo. Four sensors set up on the cross-shaped holding rack
Figure 27. Photo. Components and fabrication of the cable sensor
Figure 28. Photo. Completion of the cable sensor
Figure 29. Graph. First test of corrosion sensor wetted, dried out, rewetted, and redried
Figure 30. Illustration. Cable specimen showing arrangement of strands and sensors
Figure 31. Graph. A606 corrosion as a function of the concentration of NaCl
Figure 32. Graph. SAE1010 corrosion as a function of the concentration of NaCl
Figure 33. Graph. Relative corrosion between A606 and SAE1010
Figure 34. Graph. A606 corrosion as a function of chloride concentration during a one soak/cycle exposure
Figure 35. Graph. A606 corrosion as a function of chloride concentration during a two soak/cycle exposure
Figure 36. Graph. SAE1010 corrosion as a function of chloride concentration during a one soak/cycle experiment
Figure 37. Graph. SAE 1010 corrosion as a function of chloride concentration during a two soak/cycle experiment
Figure 38. Graph. Relative corrosion versus NaCl concentration during exposure to a one soak/cycle environment
Figure 39. Graph. A606 corrosion as a function of chloride concentration at pH 6
Figure 40. Graph. A606 corrosion as a function of chloride concentration at pH 8
Figure 41. Graph. SAE1010 corrosion as a function of chloride concentration at pH 6
Figure 42. Graph. SAE1010 corrosion as a function of chloride concentration at pH 8
Figure 43. Graph. Corrosion of A606 and SAE1010 versus chloride concentration for the second test set
Figure 44. Graph. Relative corrosion versus chloride concentration
Figure 45. Graph. Output for a Cu-A606 atmospheric corrosion sensor using soaking solution 3-1
Figure 46. Graph. Output for Cu-A606 sensor during a 15-cycle test
Figure 47. Graph. Corrosion of A606 versus NaCl concentration
Figure 48. Graph. Corrosion (weight loss) of A606 coupons and calculated mass-loss for A606 sensors versus NaCl concentration for 15-cycle exposure
Figure 49. Graph. Corrosion (weight loss) of SAE1010 coupons and calculated mass-loss for SAE1010 sensors versus NaCl concentration for 15-cycle exposure
Figure 50. Graph. Response of cable sensor before and after dilute Harrison solution
Figure 51. Graph. Response of cable sensor during constant 50-percent RH exposure after dilute Harrison solution
Figure 52. Graph. Response of cable sensor during constant 100-percent RH exposure after dilute Harrison solution
Figure 53. Graph. XRD pattern of steel rods in cable sensor bundle after single soak in dilute Harrison solution and exposure in cyclic chamber for 40 days

LIST OF TABLES

Table 1. Listing of information for 2304 SS
Table 2. Composition for 2304 SS
Table 3. Concrete mix design
Table 4. Chloride concentrations at activation in accelerated tests
Table 5. Alloying elements and Legault-Leckie corrosion index of the steels
Table 6. Compositions of soak solutions for the first test set
Table 7. Compositions of soaking solutions for the second test set
Table 8. Reference peak angles and intensities for the main iron oxidation products
Table 9. Solution compositions used for sensor exposure tests
Table 10. Cathode-anode combinations for the atmospheric corrosion sensors
Table 11. Tests for cable interstitial sensor
Table 12. Exposure chart for the first exposure test on coupons 01–96
Table 13. Exposure chart for the second set tests on coupons 01–48 (one soak only)
Table 14. Observed major peak intensities using XRD and corrosion rates
Table 15. Cumulative microampere hourly value readings (µAh) recorded by sensor type during 15 cycles
Table 16. Percentage corrosion components in specimens determined by XRD

ABBREVIATIONS AND SYMBOLS

Abbreviations

ASTM   ASTM International, also known as American Society for Testing and Materials
CNC   Computerized numerical control
DOT   Department of transportation
ECR   Epoxy-coated reinforcing
EDAX   Energy dispersive analysis by X-ray
ERF   Gaussian error function
FAU   Florida Atlantic University
FDOT   Florida Department of Transportation
FDOT-SMO   Florida Department of Transportation State Materials Office
FHWA   Federal Highway Administration
LCCA   Life-cycle cost analysis
mmpy   Millimeters per year
mpy   Mils per year (thousands of inch corrosion penetration)
mV   Millivolt
N   Normal (chemical concentration unit, 1 equivalent per 1 liter of solution)
pcy   Pounds per cubic yard
PREN; PRE   Pitting resistance equivalent number
PVC   polyvinyl chloride
RH   Relative humidity
SAE   Society for Automotive Engineers
SEM   Scanning electron microscopy
SCE   Saturated calomel electrode
SDS   Simulated deck slabs
SS   Stainless steel
w/c   water-to-cement ratio
wt   percent Weight percent
XRD   X-ray diffraction
ZRA   Zero resistance ammeter

Symbols

α   Greek letter alpha
β   Greek letter beta
γ   Greek letter gamma
θ   Greek letter theta
Δ   Greek letter delta 
π   Greek letter pi
Ω   Ohm
μA   Microamperes
a   Atomic weight
A   Exposed area of the coupon
As   Exposed area of the sensor
Cn   Cumulative coulomb reading
CRA606   Corrosion rate for A606
CRrelative   Relative corrosion rate
CRSAE1010   Corrosion rate for SAE1010
Cs   Cl- concentration at the concrete surface
CT   Initiation of corrosion
De   Effective diffusion coefficient
F   Faraday constant
ILL   Index (Legault-Leckie)
Ii   the average microampere reading
Ix   Intensity in X-ray spectrum
m   Mass
mn   Mass loss of the coupons after n cycles
n   Number of equivalents
t   Sampling rate
T   Time
x   Depth

 

 

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