Steel-concrete interface influence on chloride threshold for corrosion – Empirical reinforcement to theory

Reinforcement corrosion is a common cause for reinforced concrete structure deterioration. One of the main causes for reinforcement corrosion is chloride ingress to the concrete. Published work hint at a relationship between susceptibility to chloride induced corrosion and the interface between the concrete and the rebar, known as the steel–concrete interface (SCI). This paper presents an investigation of the relationship between the chloride threshold for chloride-induced corrosion and the properties of the SCI around embedded rebar. The relationship was investigated using 16 different concrete mixes. SCI properties were extracted using automated image analysis. The chloride threshold was found to decrease with the distance between the rebar surface and the concrete solids. In the case of horizontal rebar, the chloride threshold decreased with SCI thickness as well. These results agree with the theory of concentration polarization in localized corrosion and may explain the variety of chloride threshold values reported in the literature.