Effect of nano-silica on the mechanical and transport properties of lightweight concrete

•The effect of nano-silica on transport properties of LWC is firstly reported.•Interfacial transition zone became more compact and denser with nano-silica.•Nano-silica can increase compressive strength and lower porosity of LWC.•Resistance to water and chloride ion were both improved at 1% nano-silica.•Both pure cement and 60% slag cement LWC showed similar results.

This paper investigated the influence of nano-silica (NS) on the mechanical and transport properties of lightweight concrete (LWC). The resistance of LWC to water and chloride ions penetration was enhanced despite strength marginally increased. Water penetration depth, moisture sorptivity, chloride migration and diffusion coefficient was reduced by 23% and 49%, 23% and 10%, 5% and 0%, 22% and 12% compared to the two reference LWC mixes (pure cement and 60% slag blended cement), respectively with 1% NS. Such improvements were attributed to more compact microstructures because the micropore system was refined and the interface between aggregates and paste was enhanced.