Self-healing concrete with a microencapsulated healing agent

We have developed a concrete material exhibiting self-healing properties and corrosion inhibition. This system involves a sodium silicate solution stored in polyurethane microcapsules present in the concrete matrix. The sodium silicate, released when the capsules are ruptured by propagating cracks, reacts with the calcium hydroxide in cement and produces a C-S-H gel that partially heals the cracks. Compressive strength is unaffected by the presence of capsules. Samples are stressed to the point of incipient failure in a three-point bend system, and retested after one week. The load at failure in the capsule-containing samples is 26% of the original value, while the samples without capsules displayed a recovery of 10%. The capsule-containing samples displayed ductility, in contrast to brittle failure in the control samples. They also show a significant reduction in corrosion. The flexural strength recovery, the improved toughness and the attenuation of corrosion make it a promising material for construction.