Epoxy‐coated reinforcement in concrete structures: Results of a Swiss pilot project after 24 years of field exposure

Abstract

Reinforced concrete is the most common construction material of civil infrastructure. In severe environment, e.g., chloride exposure, concrete deterioration can occur with consequences on the durability of the structure. The use of epoxy‐coated reinforcement is a strategy to control chloride‐induced reinforcement corrosion, particular by prolonging the initiation and propagation phase. The epoxy‐coating acts as a physical barrier to chlorides and the electrolyte concrete. However, the effectiveness of the strategy in chloride environment and the corrosion performance of ECR in presence of coating defects is investigated by condition assessment of a Swiss pilot project after 24 years of field exposure.

Corrosion performance of mild steel and epoxy coated rebar in concrete under simulated harsh environment

“…The potential of ECRCD suggested that the small damages to epoxy were not able to initiate the corrosion at the steel surface. Keßler et al (2016) suggested that the damages will only be harmful in the case where a macro-cell is formed between these damages and an uncoated rebar or other defected portion. Then these defects could act as a cathode and cause disbondment of epoxy near the damaged surface.…”

“…The salt spraying on highways to melt the snow caused corrosion problems in the bridges in North America and other countries with cold climate. To overcome this problem, a research was initiated by the National Institute of Standards in the USA, in the early 1970s, which resulted in epoxy-coated reinforcing bars (Manning, 1996; Keßler et al , 2016). The optimum thickness required for corrosion protection, bond strength, and creep requirement was established to be 0.18 ± 0.05 millimeter (mm) (Manning, 1996).…”

“…However, Keßler et al (2016) suggested otherwise, after evaluating the parapet of a 24-year-old ECR-reinforced concrete bridge in Switzerland. The bridge was a Swiss pilot project to test the effect of ECR on the durability of RC structures.…”

“…The pre-defined defects on the ECRs form macro-cells with uncoated rebar if there is an electrical connection. This causes the cathodic disbondment of epoxy at defects (Keßler et al , 2016). Most of the bridges built in the USA had only the upper reinforcement layer of ECR and the bottom layer was of uncoated bare bars (BB).…”

“…Epoxy was difficult to be removed in the knife-peel test. Although the outcomes of studies are mixed, it has been established to date that the durability of civil infrastructure could be enhanced in conditions in which the corrosion problem is imminent (Khaled et al , 1998; Pyc, 1998; Keßler et al , 2016).…”