Self-healing and rebar corrosion performance of cracked engineered cementitious composites exposed to wet coral sand environment

Abstract

Wet coral sand environment on islands and reefs features high humidity and abundance in aggressive fluids and gases, thus posing a great threat to the durability of reinforced concrete structures. In this study, engineered cementitious composites (ECCs) with strain-hardening and self-healing characteristics are proposed as a potential cover material in wet coral sand exposure. The autogenous self-healing capability of cracked ECCs was evaluated by the visual crack morphology as well as water permeability, and their rebar corrosion performance over a period of one and a half years was investigated based on electrochemical tests. The results show that cracks with initial width up to 70 μm are able to completely close within one day, probably due to the efficient precipitation of calcium carbonate and further hydration of cement. Compared with the uncracked control, the 0.4 %, 1.0 % and 1.6 % strained ECCs can be healed up to 100 %, 93.4 % and 60.5 % at 30 days, respectively. The water permeability coefficient of the strained ECC decreases rapidly in the first 30 days, and then stabilizes in the later stages. Moreover, the load-carrying capacity of preloaded ECC beams is recovered, exhibiting comparable performance to the uncracked controls after the same exposure periods. The corrosion current densities of steel bars suggest an active corrosion conditions. Both of the corrosion current densities and mass losses of rebar show lower values at decreased strain level, which is closely related to the width and number of cracks that reach the reinforcement.