The Development of Self-healing with Granulated Alkali-activator at High Volume Slag Mortar in Marine Environment

In order to protect the penetration from harmful ions such as chloride, sulfate and etc, Ground Granulated Blast-furnace Slag (GGBS) cementitious materials are used in coastal and marine environment. The concrete structure can often generate cracks at early stage under 28 days due to the dry-shrinkage or other factors. Thus, chloride ions is penetrated into cracks and then concrete structure is significantly affected by harmful ions. Thus, cracks promote the chloride ions ingress and then impair the durability of cementitious materials. Therefore, repair and maintenance on the crack formation are needed to reduce chloride induced corrosion. Instead of applying repair and maintenance, self-healing capability of concrete is effectively alternative method and strategy. self-healing materials are demonstrated properties of self-healing due to the composition of the cementitious materials. In order to achieve the healing, the presence of water is crucial factor for ongoing hydration of un-hydrated cement clinkers. In addition, CO2 is necessary to form calcium carbonate precipitation. In this study, the properties and efficiency of the self-healing with the granulated alkali-activator made with Ca(OH)2 and Na2SO4 is evaluated for crack healing under 300 ??m of cracks in seawater environment. Specimens with GGBS, OPC and silica fume were manufactured with or without the granulated alkali-activators. After that, it is immersed in seawater for evaluating self-healing performance. In addition, the physical properties and durability of the specimens with the granulated alkali-activators were evaluated with compressive strength, flow test, chloride ions penetration and carbonation test. Also, the self-healing of the specimens with the granulated alkali-activator was evaluated by microscope, water permeability test, relative dynamic modulus, ultrasonic pulse velocity method, Vickers hardness and SEM-EDS respectively. As the results, the compressive strength was indicated that it was decreased with the increase of the usage of the granulated alkali-activator in comparison with specimen without the granulated alkali-activator. Also, chloride ions penetration test presented the similar result with the compressive strength. It was indicated that the increase of the usage of the granulated alkali-activator could be affected to the strength and increase of the porosity. However, in case of the self-healing performance, it tends to present the opposite results. It was verified that cementitious materials with the granulated alkali-activator, exposed in marine environments, could be able to seal cracks. Self-healing performance was rapidly generated in case of the increase of the usage of the granulated alkali-activator. Consequentially, healing is generated by ongoing hydration, calcium carbonate precipitation as well as formation of C-H or portlandite on the surface of cracks. Therefore, it was verified that the use of the granulated alkali activator (Ca(OH)2) could be filled on the cracks with healing hydration products.Maste