Abstract
Since the Florida Keys incident in 1986, effectiveness of epoxy coated reinforcing steel (ECR) has been questioned among corrosion professionals and transportation officials. One of the key controversies is whether ECR can be effective corrosion resistant under the disbonded coating condition. A school of experts claim that as soon as the epoxy coating disbonds, the ECR no longer provides adequate corrosion protection. According to others, however, excellent field performance records for nearly 30 years and several significant laboratory studies proved that, despite universally accepted disbondment phenomenon, ECR is still the best and economic corrosion protection system for the northern bridge decks and its corrosion resistance expects to improve because newer decks contain ECRs in both top and bottom mats.
The present lab study is being performed to investigate corrosion behavior of ECRs having various conditions including coating disbondment. Poor quality concrete with w/c = 0.55 and a HPC mix containing blast furnace slag were used to cast seven 6 in. x 6 in. x 12 in. long prism specimens, which were exposed to an accelerated test environment called Southern Exposure. Test variables include artificial defect size, coating disbondment, clear cover, concrete quality, and bar type of bottom mat. For control purpose, prisms with black steel and defect-free virgin ECRs were also made.
Corrosion behaviors have been monitored in terms of open circuit potential, macro-cell current, and impedance. Emphasis is given to the disbonded ECRs and their performance is compared to others without coating disbondment and black bars. An equivalent circuit modeling technique is also utilized to analyze the experimental EIS data to simulate corrosion mechanism of ECRs exhibiting various conditions. This paper reports the preliminary test results obtained up to 153 days in concrete.
