Abstract: “In this study, effects of nano-silica (nano-SiO2), micro-silica (micro-SiO2) and fly ash on chloride penetration, sulfate resistance and water permeability were investigated based on the results of electrical indication of concrete’s ability to resist chloride iron penetration test (ASTM standard C1202-10) and length change of hydraulic cement mortars exposed to a sulfate solution test (ASTM standard, C1012-02). The addition of nano-silica (nano-SiO2), micro-silica (micro-SiO2) and fly ash in concrete causes a remarkable reduction in chloride iron permeability. These effects may be due to primarily to microstructural changes both in the cement paste phase and in the interracial zone around aggregates. In concrete with nano-silica (nano-SiO2) and micro-silica (micro-SiO2), Nano-SiO2 can behave as nucleus tightly bond with cement hydrates. A stable gel structures can be formed and the mechanical properties of hardened cement paste can be improved when a smaller amount of these materials”

Keywords: nano-silica, micro-silica, durability of concrete, chloride penetration, sulfate resistance