Application of a self-healing mechanism in concrete to reduce chloride ingress through cracks

Chloride induced corrosion of reinforcing steel is one of the most important damage mechanisms of reinforced concrete structures. The appearance of cracks in reinforced concrete structures will accelerate the ingress of chlorides and therefore cause a higher risk for corrosion and its propagation. In this research, autonomous healing of cracks by encapsulated polyurethane was investigated as a possible method to reduce chloride ingress through cracks. Therefore, uncracked, cracked, and healed concrete specimens were subjected to a high concentration NaCl solution for exposure periods of 7, 19, and 52 weeks. Chloride profiles were determined in the crack region after each exposure period. The resulting chloride profiles showed that the autonomous crack healing mechanism formed a partial barrier which prevented the immediate ingress of chlorides through cracks. At depths below the surface larger than 12 mm, a self-healing efficiency of at least 70% was found for all exposure periods. Due to this big reduction in chloride concentration, a much lower amount of chlorides will reach the steel reinforcement through the cracks. This will postpone the time to corrosion initiation and reduce the corrosion rate of the steel reinforcement. Consequently, the use of self-healing concrete will have important benefits for the durability of reinforced concrete structures in marine environments