Autogenous Self-Healing: A Better Solution for Concrete

Self-healing can be defined as the ability of a material to repair inner damage without any external intervention. In the case of concrete, the process can be autogenous, based on optimized mix composition, or autonomous, when using additionally incorporated capsules containing a healing agent and/or bacteria spores. The first process uses unhydrated cement particles as the healing material while the other utilizes a synthetic material or bacteria released into the crack from a broken capsule or activated through access of water and oxygen. The critical reviewing of both methods indicates that the autogenous self-healing is more efficient, more cost effective, safer, and easier to implement in full-scale applications. Nevertheless, a better understanding of the mechanism and factors affecting the effectiveness of the process is needed. The main weaknesses of the autonomous method were identified as loss of workability, worsened mechanical properties, low efficiency and low probability of the healing to occur, low survivability of the capsules and bacteria in harsh concrete environment, very high price, and lack of full-scale evaluation.