Characterisation of chloride transport and reinforcement corrosion in concrete under cyclic wetting and drying by electrical resistivity

Concrete prisms were made with four cement types including cements with fly ash and/or blast furnace slag and three water-to-cement (w/c) ratios. Chloride penetration and corrosion of rebars were stimulated by subjecting prisms to cyclic loading with salt solution and drying. Concrete resistivity, steel potentials and corrosion rates were measured up to one year of age. Chloride penetration profiles were determined after salt loading. It was found that the resistivity of a particular concrete reflects its properties with regard to chloride penetration, corrosion initiation (probability of corrosion) and corrosion propagation (corrosion rate). Blending the cement with blast furnace slag, fly ash or both is beneficial with regard to delaying the onset of corrosion and subsequently limiting its severity under simulated de-icing salt load. The fly ash cement shows increased resistivity compared to Portland cement from eight weeks. Cement with a high percentage of slag develops a significantly higher resistivity after one week.