Effect of steel corrosion pattern on RC beam performance

Chloride-induced corrosion in reinforced concrete leads to a reduction of the steel cross-section and deterioration of the steel–concrete bond. In this paper, experimental results are presented in order to clarify the respective influence of these degradations on beam serviceability (deflection). Pitting corrosion simulations were performed and two naturally corroded beams (14 and 23 years old) were analysed. Corrosion simulations have shown that the reduction in steel cross-section due to local pitting corrosion does not affect serviceability. Increased deflection is due to deterioration of the steel-concrete bond (reduction of concrete tension stiffening). Experimental results obtained on two corroded beams broken and analysed after 14 years and 23 years of chloride exposure showed that, during the natural chloride-induced corrosion process, the corrosion pattern evolves in relation to the corrosion cracking. Localised pitting corrosion is responsible for the initiation of corrosion cracking. Then, as the width of the cracks develops, general corrosion becomes gradually the main corrosion pattern. According to these experimental results, a mechanical model is proposed for serviceability assessment, which takes into account the evolution of the corrosion pattern from local pitting corrosion to general reinforcement corrosion.