Effect of the specific surface area of nano-silica particle on the properties of cement paste

Two types of nano-silica with specific surface areas of 100 m2/g (NS-100) and 470 m2/g (NS-470) were used to investigate the effect of the specific surface area on the properties of cement paste. The mercury intrusion porosimetry results show that NS-470 nano-silica is more effective in improving the pore structure, which mainly reduces the gel pores and large pores. The attenuated-total-reflection spectrums illustrate that NS-470 nano-silica can be covered with more Si-OH groups, leading to the higher reactivity to accelerate the hydration reaction. The calorimetry results indicate that NS-470 nano-silica can more effectively prolong the acceleration period, and increase the exothermic rate and late hydration degree. The hydration kinetics simulation indicates that NS-470 nano-silica makes the hydration reaction quickly enter the diffusion stage. Based on the results of microanalysis, the mechanism of how the specific surface area influences the function of nano-silica in cement paste is proposed. [Display omitted] •Different specific surface area of nano-silica has different improvement effect.•Higher specific surface area of nano-silica can be covered with more Si-OH groups.•Nano-silica with higher specific surface area can change the hydration process.•Nano-silica with higher specific surface area can prolong the acceleration period.•Nano-silica with higher specific surface area reduces gel pores and large pores.