Roles of nano-silica and micro-silica in durability of concrete

It has been proven by various studies that adding micro-silica (MS) alone or nano-silica (NS) alone can provide significant beneficial effects on the durability of concrete. In theory, MS and NS may also be added together, but up to now, such possible combined usage of MS and NS for improving the durability of concrete has not been deeply explored. In this paper, the individual and combined roles of MS and NS in the chloride and carbonation resistance of concrete were investigated by producing a series of concrete mixes containing varying MS, NS and water contents for rapid chloride permeability test and carbonation test. It was found that the single addition of MS or NS can significantly improve the chloride and carbonation resistance, but combined addition of MS and NS can further enhance the sulphate and chloride resistance.