Influence of Nano-SiO2 and Nano-TiO2 on properties and microstructure of cement-based materials

This study investigated the effect of Nano-SiO2 (NS) and Nano-TiO2 (NT) on the mechanical properties and microstructure of cement paste. Nanomaterials type and dosage are considered. Apparent viscosity, compressive strength and flexural strength were tested. Moreover, the microstructure, composition, and pore structure were analyzed. Incorporating NS and NT can enhance the apparent viscosity of cement paste. The apparent viscosity increases as the content of nanomaterials increases. The apparent viscosity of the NS group is higher than that of the NT group. The ideal dosages for maximizing compressive strength are 1 % NS or 0.1 % NT. NS and NT can enhance the early hydration reaction, and NS and NT could increase the orientation of hydrated product Ca (OH)2. Nanomaterials are incorporated into the interstitial spaces of cement-based materials to establish nucleation sites, which partially restrict the crystallization orientation of calcium hydroxide crystals. The nanomaterials enhance the density of the C-S-H and boost hydration levels. Ca(OH)2 content was reduced by 3.3 % in the NS group, whereas NT increased it by 1.3 %. Additionally, NS and NT improved the pore structure, reducing porosity from 10.1 % to 16.7%. NS and NT have different properties and should be selected according to the performance requirements of cement-based materials.