Self-healing of microcracks in Engineered Cementitious Composites under sulfate and chloride environment

Hydraulic structures are subject to high risk of deterioration associated with cracking and sulfate-chloride attack. Application of Engineered Cementitious Composites (ECC) with self-controlled tight microcracks and self-healing capacities could potentially lead to enhanced durability performance of hydraulic structures even after the formation of cracks under combined environmental and mechanical loadings. This research experimentally investigated the self-healing behavior of ECC under aggressive sulfate and chloride conditions. Resonant frequency (RF) and mechanical properties including stiffness, first cracking strength, ultimate tensile strength and tensile strain capacity were experimentally determined for ECC specimens that were preloaded to 1% strain and exposed to sulfate and sulfate-chloride solutions to simulate the service environment of hydraulic structures. The performance of ECC was found not to be adversely affected by the aggressive solutions. Instead, self-healing of the microcracks was observed leading to partial recovery of the mechanical properties. It was also found that ECC tends to heal faster and more completely in sulfate solutions than in water. These results demonstrate that ECC material remains durable under sulfate-chloride environment, which is beneficial for improving the long-term performance of hydraulic structures in such aggressive environments.