A new approach to determine the chloride threshold initiating corrosion: Preliminary results

Abstract

The initiation of corrosion by chlorides is traditionally based on the existence of a threshold that would lead to corrosion. Almost all existing approaches considered implicitly that corrosion induced by chlorides is uniform and take not into account the intrinsic localized character of corrosion in reinforced concrete structures. This work aims to implement a new test protocol that takes explicitly into account the localized nature of chlorides-induced corrosion by inducing physical separation between anode and cathode thus permitting to measure the corrosion current. The anodic part allows to test different levels of chlorides and the cathodic part to highlight the ohmic (limiting ionic current by low porosity) and cathodic (restricting access to oxygen due to saturation of porosity, low porosity, dioxygen consumption by additions) control of corrosion. The chloride threshold is set on the basis of a threshold corrosion current that is considered acceptable with respect to the structure’s life. The first results provide a preliminary idea of the variation of corrosion rate in function of chlorides content. This method also highlights the influence of surface condition of the steel-concrete interface on the corrosion current.