Effect of nano-silica on the hydration and microstructure of grey and white cement

This paper discusses the effects of nano-silica (NS) particles with an average diameter of 15 and 50 nm on the hydration, setting time, compressive strength, drying process and microstructure of grey and white cement. The cement was partially substituted by 1.0 wt% of NS. The results show that NS was able to promote cement hydration and shorten the induction period determined by low-field nuclear magnetic resonance, and that the smaller the average particle size of NS, the shorter the setting time. The effect of NS on the improvement of compressive strength mainly manifested in the early stage (3 d). In addition, the introduction of NS with a diameter of 15 and 50 nm could reduce the water-loss rate of hardened samples during drying and decreased the porosity of the system. Furthermore, the content of calcium hydroxide was reduced by introducing NS particles measuring 15 and 50 nm in diameter. Finally, the addition of NS could refine the grain size and improve the morphology of calcium silicate hydrate gel.