Performance and Mechanism Analysis of Nano-silica Sol Modified Cement-based Materials

In view of the problems of low early strength and weak deformation resistance of ordinary cement-based materials, the cement-based materials were modified by nano-silica sol. The nano-silica sol was charasterized by means of electro-hydraulic servo universal testing, X-ray diffraction, and scanning electron microscopy. The fluidity, stone rate, uniaxial compressive strength, elastic modulus, hydration products, and microstructure of cement-based materials with different water-cement ratios were evaluated. The results show that when the content of silica sol is within 0.5% and the water-cement ratio is less than 1.0, the fluidity of cement slurry can be significantly improved, and the maximum increase is 20.24%. The stone formation rate increases with the increase of nano-silica sol admixture, and the silica sol increases the stone formation rate of slurry with water-cement ratio greater than 0.7 significantly, with a maximum increase of 24.49%. When the content of silica sol is 2%, the compressive strength of the stone body increases the most. The effect of increasing the strength gradually weakens. The incorporation of nano-silica sol promotes the early hydration reaction of cementitious, and reacts with the hydration products to produce hydrated calcium silicate gel (C—S—H) and makes the microscopic morphology more dense, so that the early compressive strength and elastic modulus of the stone body are significantly increased. Nano-silica sol promotes the hydration reaction by shortening the induction period and providing nucleation sites for C—S—H in the particle voids, which improves the performance of cementitious materials.