Impact of Ca/(Si+Al) ratio of calcium aluminosilicate hydrate (C-A-S-H) gel on chloride adsorption for evaluating durability of reinforced concrete

Abstract

Cement-based materials have been using in various application of reinforced concrete structural components as well as in nuclear waste repositories. The ingress of detrimental ions and consequent chemical reactions pose severe threat to the durability of cementitious materials. The chloride-induced corrosion in concrete structures is one of serious durability problems. In the penetration of chloride into concrete, it is necessary to consider both binding and diffusion of chloride. The adsorption of chloride on the surface calcium silicate hydrate (C-S-H) gel, main hydration product of cement, controls the binding of chloride in cement-based materials. It has been reported that a partial substitution of Portland cement by ground granulated blast furnace slag(GGBFS) increase the chloride adsorption and form C-A-S-H gel. The physicochemical and surface electrical properties of C-A-S-H gel are significantly different from the properties of C-S-H gel. Therefore, in this study, chloride adsorption behavior on C-A-S-H gel is analyzed by experimental techniques. The C-A-S-H gel with different Ca/ (Si+Al) ratios was synthesized and their structure and active surface site were analyzed by 29Si MAS-NMR and 27Al MAS-NMR. And zeta potential of C-A-S-H gel in various suspensions were measured and the chloride adsorption experiment was conducted on C-A-S-H gel.