Eighteen-year performance of epoxy-coated rebar in a tunnel structure subjected to a very aggressive chloride-contaminated environment

The increased use of deicing salts during winter is the major cause of corrosion of offshore reinforced concrete structures. Research in the early 1970s suggested that epoxy-coated reinforcing bars might be the solution to this problem. Epoxy-coating reinforcement (ECR) was well received by designers until concern about the effectiveness of the coating arose when bars in several bridges built in Florida in the early 1980s began to corrode after only a few years of service. The occurrence of this problem resulted in extensive research on the durability of structures built with ECR. This paper describes a corrosion study aimed at gaining a better understanding of the service life of ECR exposed to a chloride-contaminated environment. Corrosion monitoring has been periodically conducted on a roof of a tunnel structure built in 1984 to replace the roof made with uncoated bars that failed after 17 years of service. The present study summarizes the results of visual inspection and electrochemical testing carried out during the life of the new structure. Results indicate that after 18 years in a very aggressive environment, considering the combined action of chlorides and extreme changes in temperature, the structure is still in good condition and only a few locations show rust staining and cracking, presumably caused by corrosion of the steel reinforcement. Based on the results it would appear that fusion-bonded epoxy coating subjected to a chloride-laden environment does not provide total protection to the steel reinforcing. However, epoxy coatings have significantly extended the corrosion initiation period as compared to uncoated bars for structures subjected to a chloride environment.