Autogenous Self-healing of Alkali-Activated Materials: A Review

Alkali-activated materials (AAMs) are introduced as promising green materials with less carbon dioxide (CO₂) footprints rather than ordinary Portland cement (OPC) in concrete production. Moreover, as innovative, durable, and sustainable materials, AAMs exhibited superior mechanical properties and durability performances comparable to OPC. AAMs have advantageous characteristics (i.e., high early-age strength, high strength development, high chemical resistance, severe environmental conditions, etc.). Those intrinsic features have promoted AAMs in diverse applications, including repair approaches. Furthermore, from a sustainability perspective, self-healing as an inherent feature of AAMs should be addressed when considering those materials for repair purposes. AAMs have been deduced to be potentially self-healed autogenously and autonomously. Autogenous healing is defined as the ability of concrete to heal cracks over the long term without any manual interference. Autonomous healing, by which the induced cracks will be plugged using engineered materials embedded inside the mixture during casting. This paper focused on the autogenous self-healing of AAMs, the extent of self-healing, and factors affecting self-healing efficiency. Also, determination and quantification of self-healing were demonstrated as well.