Influence of nano-SiO2 and nano-TiO2 on early hydration process of cement: Hydration rate, hydration products microstructure, calcium ion solubility, and diffusion ability

This study aims to study the influence of Nano-SiO2 (NS) and Nano-TiO2 (NT) on the early hydration process of cement. The cement hydration rate, the morphology of the early age hydrated products, and concentration of calcium ions were evaluated. The results indicated that the volume of sediment in the cement paste incorporating nanomaterials increased at 24 h. The hydration area of cement increases by 52.9 %-76.0 % and 21.5 %-49.0 % corresponding to NS and NT, respectively. Moreover, NS promoted the formation of straw-like calcium silicate hydrate (C-S-H), while NT promoted the formation of radial C-S-H and improved the microstructure of cement. The calcium ion dissolution results indicate that after 5 min of hydration, the calcium ion concentrations in the NS1 % and NT1 % groups were 2.38 times and 1.63 times that of the control group, respectively. After 30 min, the calcium ion concentration in the NS1 % group decreased by 23.9 %, whereas it increased by 129.7 % and 34.1 % in the control and NT1 % groups, respectively. Both NS and NT significantly promoted calcium ion diffusion. NT exhibited a stronger ability to enhance calcium ion diffusion, increasing the diffusion concentration by up to 200.0 %.