United States Department of Transportation
i
Field performance of epoxy-coated reinforcing steel in Virginia bridge decks.
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2000-02-01
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[PDF-1.84 MB]
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Abstract:In this study, the corrosion protection performance of epoxy-coated reinforcing steel
(ECR) was evaluated using approximately 250 concrete cores from 18 bridge decks in Virginia.
The decks were 2 to 20 years old at the time of the investigation. The deck field inspections
included a crack survey and cover depth determination in the right traffic lane. A maximum of
12 cores with the top reinforcement randomly located in the lowest 12th percentile cover depth
were taken from each bridge deck. Because of the safety concerns associated with taking cores
from the lower steel mat, and to minimize damage to the bridge, a maximum of only 3 cores
were taken through the truss bars. The laboratory evaluation of the concrete cores included a
visual examination and a determination of the carbonation depth, moisture content, absorption,
percent saturation, and chloride content at a 13-mm depth. The rapid chloride permeability test
was also performed for the surface and base concrete on samples obtained from the cores taken
through the truss bars to determine chloride permeability. The ECR inspection consisted of a
visual examination, a damage evaluation, and a determination of coating thickness and adhesion.
The condition of the steel underneath the epoxy coating was also evaluated.
Adhesion loss of the epoxy coating to the steel surface was detected in all but one deck
that was 4 years old and older. The epoxy coatings were debonding from the reinforcing bars.
Whereas a bonded coating can be expected to protect the steel, a debonded coating allows
chlorides, moisture, and oxygen to reach the steel and initiate a rapid corrosion mechanism.
Reinforcing bars in various stages of adhesion loss showed visible signs of a corrosion process
underneath the coating, suggesting that ECR will provide little or no additional service life for
concrete bridge decks in comparison to bare steel. Other systems that will provide longer
protection against chloride-induced corrosion of the reinforcing steel with a higher degree of
reliability should be considered.
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