Impact of TiO₂ Nanoparticles on Drying Shrinkage of Hardened Cement Paste

Abstract

This paper reports the influence of nano-TiO₂ on hydration reactions and drying shrinkage behavior during the first drying process of hardened cement pastes. Cement pastes containing 3 wt% nano-TiO₂ (by external addition) in cement and reference samples were prepared with water to cement ratios (W/C) of 0.40 and 0.55. The results of experiments on samples hydrated for 6 months show that in the mature state of hydration, the addition of TiO₂ retards the reaction of belite and slightly reduces the precipitation of portlandite in both W/C ratios. Regarding the formation of C-S-H, the addition of TiO₂ increases the mean chain silicate length in C-S-H in the saturated state, and nano-TiO₂ is present in the vicinity of low density (LD) C-S-H during the hydration process. The drying shrinkage of the cement paste with nano-TiO₂ in the first drying process is larger than the reference sample when W/C = 0.55, but the opposite occurs when W/C = 0.40. This is explained by the increased precipitation of low density C-S-H due to the addition of nano-TiO₂ when W/C = 0.55; however, when W/C = 0.40 the amount of LD C-S-H in the sample with nano-TiO₂ does not increase due to their being less space for precipitation in the sample.