Self-healing performance of GGBFS based cementitious mortar with granulated activators exposed to a seawater environment

Concrete structures exposed to marine environments are susceptible to attack by harmful ions such as chloride, sulfate, etc. Ground granulated blast furnace slag (GGBFS) blended cementitious materials are used as a binder in coastal concrete structures. Cracks are generated at young ages due to shrinkage or other factors, which allow the ingress of harmful ions. Therefore, repair and maintenance of such structures is necessary to increase the service lives of these structures. Autogenous self-healing of the cement composites has proved to be an effective alternative method. It occurs when water comes in contact with the unhydrated cement particles and forms additional hydration products. In this study, cement mortar was prepared by replacing cement with GGBFS up to 50%. Granules of activators Ca(OH)2 and Na2SO4 were made and incorporated at different dosages. Physical and self-healing performance of the mortar specimens were evaluated via compressive strength, relative dynamic modulus of elasticity, ultrasonic pulse velocity and water permeability tests. The healing products were examined via electron microscopy, energy dispersive X-ray spectrometry, and microhardness tests. The results indicated that the specimens incorporating granulated Na2SO4 showed minimal self-healing performance while the self-healing efficiency of the specimens with Ca(OH)2 granules was significantly enhanced.