Corrosion of concrete reinforcement and electrochemical factors in concrete patch repair

Abstract

Corrosion of concrete reinforcement at a patch repair is a complex problem, and current knowledge of its mechanism is quite limited. This review examined the correlation between two corrosion mechanisms, macrocell and microcell corrosion, from fundamental electrochemical principles. It was found that both mechanisms could play significant roles in inducing corrosion damage, contrary to the prevailing opinion that macrocell corrosion is the main deterioration mechanism in patch repair. This has practical implications that need to be considered for an effective and durable repair. A review of the studies done to date also enabled the identification of the key factors in patch repair controlling the corrosion characteristics. Corrosion could occur at different locations in the vicinity of the patch — substrate, interface, or patch area — depending on the respective electrochemical environments induced by the repair material properties and treatments, as well as the in-service exposure and mechanical loading. The review indicates that much of the needed research should focus on identification of corrosion mechanisms to effect successful patch repair in reinforced concrete structures.Key words: patch repair, substrate, corrosion, macrocell corrosion, microcell corrosion.