Corrosion Evaluation of Iowa Bridge Decks AWS
Corrosion and Chloride Evaluation of Iowa Bridge Decks Scott Neubauer, P.E.
Bridge Maintenance and Inspection Engineer Iowa Department of Transportation Office of Bridges and Structures
Scope of Project • Bridges with epoxy coated reinforcing in the deck. • Bridges on a “corridor” that could be bundled together.
• Determine depth of chlorides in decks. • Is chloride concentration at reinforcing level above corrosion limits?
• Determine what type of overlay is appropriate
Service Life Analysis • Six bridges were used to determine the service life expected for these decks.
• Reinforcing depth surveys were conducted using a pachometer.
• Petrographic analysis was performed on 1 core per bridge.
• Condition of epoxy coating was evaluated in 3 locations on each bridge.
Scope of Work
Non-Service Life Bridges • Bridge plans, current inspection reports, and other relevant condition data were reviewed.
• Spall, delamination, and patch quantities were determined by the Iowa DOT. • A concrete cover survey was performed on each deck (24 to 36 readings per deck). • Core locations were selected and marked using ground penetrating radar (GPR). A
total of 24 cores (4 per bridge) were collected. All cores were extracted and patched by a local coring company, then shipped to the SCS laboratory for further testing.
• All cores were used for chloride content analysis. From each of these cores, concrete powder samples were collected at four depths to measure the chloride profile. Chloride content of each sample (96 total) was tested per AASHTO T-260.
• Based on available corrosion data, viable preservation/repair options to mitigate future corrosion and extend the service life of each structure were identified.
Scope of Work
Service Life Bridge Evaluation •
Bridge plans, current inspection report, and other relevant condition data were reviewed.
•
Spall, delamination, and patch quantities were determined by the Iowa DOT and provided by WHKS.
•
A concrete cover survey was performed on the deck using a pachometer (120 readings per bridge).
•
Core locations were selected and marked using ground penetrating radar (GPR). A total of 74 cores were collected. All cores were extracted and patched by a local coring company, then shipped to the SCS laboratory for further testing.
•
Cores were used for chloride content analysis. From each of these cores, concrete powder samples were collected at eight depths to measure the chloride profile. Chloride content of each sample was performed per AASHTO T-260.
•
Three of the chloride cores in each bridge were intentionally drilled through top mat ECR. These rebar samples were extracted from the cores for analysis of the coating quality.
•
One core in each bridge was used for petrographic analysis (per ASTM C856 and C457) to evaluate the concrete quality and performance.
•
Laboratory and field data were used in the NCHRP 558 service life model to estimate future corrosion-related concrete damage.
•
Viable preservation/repair options to mitigate corrosion and extend the service life of the structure were identified. Life cycle cost of each option was compared in order to select the most cost-effective option.
Service Life Analysis Results
Bridge ID
Avg. Cover
4525.1S009 6697.3S009 6609.3S009 5521.8S018 2166.2S018 8416.3S018
2.82 in. 2.74 in. 2.84 in. 2.53 in. 3.38 in. 2.74 in.
Average Chloride Content @ Rebar Level 1500 ppm 1000 ppm 1300 ppm 2400 ppm 500 ppm 250 ppm
ASR Present Yes Yes Yes Yes Yes Yes
Epoxy Air Coating Entrainment Rating 5 5 4 2 3 3
7.60 % 7.10 % 4.40 % 9.00 % 6.50 % 7.40 %
Year Built
Life Cycle Cost
1976 1992 1978 1993 1987 1989
$129,175 Epoxy Overlay $197,630 Dense Concrete Overlay $119,463 Epoxy Overlay $127,355 Dense Concrete Overlay $73,785 Epoxy Overlay $158,314 Dense Concrete Overlay
Repair Type
Repair Life 15 Years 20 Years 15 Years 20 Years 15 Years 20 Years
Chloride Content at Rebar Level
Chloride Content at Rebar Level
Chloride Content at 0.75” Depth
Epoxy Coating Evaluation
Epoxy Coating Evaluation
Epoxy Coating Evaluation
ASR Evaluation
ASR Evaluation
Average Chloride Content for 11 bridges vs. Age
Epoxy Overlays % Chloride Depth Ranges (in.)
0.0 - 0.5 0.5 - 1.0 1.0 - 1.5 1.5 - 2.0 Year Built Bridge ID 0.083 0.070 0.046 1981 2887.2R020 #1 0.083 0.103 0.093 0.037 2887.2R020 #2 0.103 0.096 0.079 1988 3100.2R020 #1 0.159 0.106 3100.2R020 #2 0.108 0.096 0.073 0.086 3104.0R020 #1 0.156 0.137 No Test No Test 1988 3104.0R020 #2 0.083 0.053 0.089 0.043 3193.5R020 #1 0.141 0.136 0.172 0.065 1986 3193.5R020 #2 0.125 0.078 0.080 0.065 3193.5R020 #3 0.269 0.314 0.330 0.233
Dense Concrete Overlays % Chloride Depth Ranges (in.) Bridge ID 0.0 - 0.5 0.5 - 1.0 1.0 - 1.5 1.5 - 2.0 Year Built 1054.2L020 #1 0.104 0.083 0.069 0.080 1978 1054.2L020 #2 0.167 0.272 0.168 0.113 1054.2R020 #1 0.116 0.149 0.119 0.125 1978 1054.2R020 #2 0.163 0.216 0.174 No Test 3100.2L020 #1 0.175 0.163 0.198 0.161 1988 3100.2L020 #2 0.116 0.179 0.209 0.207 3104.0L020 #1 0.100 0.233 0.113 0.083 1987 3104.0L020 #2 0.193 0.206 0.211 0.160 3116.5R020 #1 0.322 0.258 0.161 0.049 1995 3116.5R020 #2 0.108 0.121 0.112 0.092 3116.5R020 #3 0.360 0.309 0.219 0.123 3194.0L020 #1 0.070 0.098 0.156 0.116 1987 3194.0L020 #2 0.139 0.343 0.382 0.340 3194.0R020 #1 0.117 0.100 0.063 0.039 1987 3194.0R020 #2 0.321 0.393 0.233 0.145
Epoxy Overlays % Chloride Depth Ranges (in.) Bridge ID 7133.9R060 #2 7133.9R060 #3 7133.9R060 #4 7133.9R060 #5 7133.9R060 #6 7137.0R060 #1 7137.0R060 #2 7137.0R060 #3 7137.0R060 #4 7249.5R060 #1 7249.5R060 #2 7249.5R060 #4 7249.5R060 #5 7253.5R060 #1 7253.5R060 #2 7253.5R060 #4 7253.5R060 #5 7253.5R060 #6
0.0 - 0.5 0.5 - 1.0 1.0 - 1.5 1.5 - 2.0 Year Built 0.055 0.161 0.129 0.056 0.129 0.105 0.086 0.170 0.151 0.046 0.066 0.120 0.249 0.056 0.080 0.147 0.152 0.070
0.073 0.133 0.123 0.123 0.088 0.110 0.088 0.093 0.166 0.056 0.071 0.078 0.145 0.100 0.118 0.062 0.068 0.063
0.043 0.114 0.120 No Test 0.061 0.084 0.039 0.056 0.068 0.026 0.043 0.110 0.109 0.070 0.059 0.059 0.042 0.163
0.027 0.033 0.053 No Test 0.029 0.038 0.016 0.023 0.140 0.033 0.026 0.157 0.039 0.027 0.032 0.030 0.019 0.037
2005
2004
2006
2006
Results • Chloride concentrations are higher than anticipated. • Minimal concrete removal and thin epoxy overlays are not the dominant option.
• Epoxy reinforcing corrosion is not a problem. • Program most bridges for dense concrete overlays with concrete removal of 1.75 inches.
• Concrete removal of 1.75 inches will remove a significant amount of chloride contaminated concrete.
• Thin epoxy overlays are considered when chloride
concentrations of 1800 ppm are not deeper than 0.5 inches.
Questions?
Scott Neubauer, P.E.
Bridge Maintenance and Inspection Engineer Iowa Department of Transportation Office of Bridges and Structures Phone: 515-239-1165 E-Mail: [email protected]
Bridge Maintenance and Inspection Engineer Iowa Department of Transportation Office of Bridges and Structures
Scope of Project • Bridges with epoxy coated reinforcing in the deck. • Bridges on a “corridor” that could be bundled together.
• Determine depth of chlorides in decks. • Is chloride concentration at reinforcing level above corrosion limits?
• Determine what type of overlay is appropriate
Service Life Analysis • Six bridges were used to determine the service life expected for these decks.
• Reinforcing depth surveys were conducted using a pachometer.
• Petrographic analysis was performed on 1 core per bridge.
• Condition of epoxy coating was evaluated in 3 locations on each bridge.
Scope of Work
Non-Service Life Bridges • Bridge plans, current inspection reports, and other relevant condition data were reviewed.
• Spall, delamination, and patch quantities were determined by the Iowa DOT. • A concrete cover survey was performed on each deck (24 to 36 readings per deck). • Core locations were selected and marked using ground penetrating radar (GPR). A
total of 24 cores (4 per bridge) were collected. All cores were extracted and patched by a local coring company, then shipped to the SCS laboratory for further testing.
• All cores were used for chloride content analysis. From each of these cores, concrete powder samples were collected at four depths to measure the chloride profile. Chloride content of each sample (96 total) was tested per AASHTO T-260.
• Based on available corrosion data, viable preservation/repair options to mitigate future corrosion and extend the service life of each structure were identified.
Scope of Work
Service Life Bridge Evaluation •
Bridge plans, current inspection report, and other relevant condition data were reviewed.
•
Spall, delamination, and patch quantities were determined by the Iowa DOT and provided by WHKS.
•
A concrete cover survey was performed on the deck using a pachometer (120 readings per bridge).
•
Core locations were selected and marked using ground penetrating radar (GPR). A total of 74 cores were collected. All cores were extracted and patched by a local coring company, then shipped to the SCS laboratory for further testing.
•
Cores were used for chloride content analysis. From each of these cores, concrete powder samples were collected at eight depths to measure the chloride profile. Chloride content of each sample was performed per AASHTO T-260.
•
Three of the chloride cores in each bridge were intentionally drilled through top mat ECR. These rebar samples were extracted from the cores for analysis of the coating quality.
•
One core in each bridge was used for petrographic analysis (per ASTM C856 and C457) to evaluate the concrete quality and performance.
•
Laboratory and field data were used in the NCHRP 558 service life model to estimate future corrosion-related concrete damage.
•
Viable preservation/repair options to mitigate corrosion and extend the service life of the structure were identified. Life cycle cost of each option was compared in order to select the most cost-effective option.
Service Life Analysis Results
Bridge ID
Avg. Cover
4525.1S009 6697.3S009 6609.3S009 5521.8S018 2166.2S018 8416.3S018
2.82 in. 2.74 in. 2.84 in. 2.53 in. 3.38 in. 2.74 in.
Average Chloride Content @ Rebar Level 1500 ppm 1000 ppm 1300 ppm 2400 ppm 500 ppm 250 ppm
ASR Present Yes Yes Yes Yes Yes Yes
Epoxy Air Coating Entrainment Rating 5 5 4 2 3 3
7.60 % 7.10 % 4.40 % 9.00 % 6.50 % 7.40 %
Year Built
Life Cycle Cost
1976 1992 1978 1993 1987 1989
$129,175 Epoxy Overlay $197,630 Dense Concrete Overlay $119,463 Epoxy Overlay $127,355 Dense Concrete Overlay $73,785 Epoxy Overlay $158,314 Dense Concrete Overlay
Repair Type
Repair Life 15 Years 20 Years 15 Years 20 Years 15 Years 20 Years
Chloride Content at Rebar Level
Chloride Content at Rebar Level
Chloride Content at 0.75” Depth
Epoxy Coating Evaluation
Epoxy Coating Evaluation
Epoxy Coating Evaluation
ASR Evaluation
ASR Evaluation
Average Chloride Content for 11 bridges vs. Age
Epoxy Overlays % Chloride Depth Ranges (in.)
0.0 - 0.5 0.5 - 1.0 1.0 - 1.5 1.5 - 2.0 Year Built Bridge ID 0.083 0.070 0.046 1981 2887.2R020 #1 0.083 0.103 0.093 0.037 2887.2R020 #2 0.103 0.096 0.079 1988 3100.2R020 #1 0.159 0.106 3100.2R020 #2 0.108 0.096 0.073 0.086 3104.0R020 #1 0.156 0.137 No Test No Test 1988 3104.0R020 #2 0.083 0.053 0.089 0.043 3193.5R020 #1 0.141 0.136 0.172 0.065 1986 3193.5R020 #2 0.125 0.078 0.080 0.065 3193.5R020 #3 0.269 0.314 0.330 0.233
Dense Concrete Overlays % Chloride Depth Ranges (in.) Bridge ID 0.0 - 0.5 0.5 - 1.0 1.0 - 1.5 1.5 - 2.0 Year Built 1054.2L020 #1 0.104 0.083 0.069 0.080 1978 1054.2L020 #2 0.167 0.272 0.168 0.113 1054.2R020 #1 0.116 0.149 0.119 0.125 1978 1054.2R020 #2 0.163 0.216 0.174 No Test 3100.2L020 #1 0.175 0.163 0.198 0.161 1988 3100.2L020 #2 0.116 0.179 0.209 0.207 3104.0L020 #1 0.100 0.233 0.113 0.083 1987 3104.0L020 #2 0.193 0.206 0.211 0.160 3116.5R020 #1 0.322 0.258 0.161 0.049 1995 3116.5R020 #2 0.108 0.121 0.112 0.092 3116.5R020 #3 0.360 0.309 0.219 0.123 3194.0L020 #1 0.070 0.098 0.156 0.116 1987 3194.0L020 #2 0.139 0.343 0.382 0.340 3194.0R020 #1 0.117 0.100 0.063 0.039 1987 3194.0R020 #2 0.321 0.393 0.233 0.145
Epoxy Overlays % Chloride Depth Ranges (in.) Bridge ID 7133.9R060 #2 7133.9R060 #3 7133.9R060 #4 7133.9R060 #5 7133.9R060 #6 7137.0R060 #1 7137.0R060 #2 7137.0R060 #3 7137.0R060 #4 7249.5R060 #1 7249.5R060 #2 7249.5R060 #4 7249.5R060 #5 7253.5R060 #1 7253.5R060 #2 7253.5R060 #4 7253.5R060 #5 7253.5R060 #6
0.0 - 0.5 0.5 - 1.0 1.0 - 1.5 1.5 - 2.0 Year Built 0.055 0.161 0.129 0.056 0.129 0.105 0.086 0.170 0.151 0.046 0.066 0.120 0.249 0.056 0.080 0.147 0.152 0.070
0.073 0.133 0.123 0.123 0.088 0.110 0.088 0.093 0.166 0.056 0.071 0.078 0.145 0.100 0.118 0.062 0.068 0.063
0.043 0.114 0.120 No Test 0.061 0.084 0.039 0.056 0.068 0.026 0.043 0.110 0.109 0.070 0.059 0.059 0.042 0.163
0.027 0.033 0.053 No Test 0.029 0.038 0.016 0.023 0.140 0.033 0.026 0.157 0.039 0.027 0.032 0.030 0.019 0.037
2005
2004
2006
2006
Results • Chloride concentrations are higher than anticipated. • Minimal concrete removal and thin epoxy overlays are not the dominant option.
• Epoxy reinforcing corrosion is not a problem. • Program most bridges for dense concrete overlays with concrete removal of 1.75 inches.
• Concrete removal of 1.75 inches will remove a significant amount of chloride contaminated concrete.
• Thin epoxy overlays are considered when chloride
concentrations of 1800 ppm are not deeper than 0.5 inches.
Questions?
Scott Neubauer, P.E.
Bridge Maintenance and Inspection Engineer Iowa Department of Transportation Office of Bridges and Structures Phone: 515-239-1165 E-Mail: [email protected]
