Effect of Nano-silica Addition on the Mechanical Properties and Thermal Conductivity of Cement Composites

Abstract

This research article presents the mechanical properties and thermal conductivity of cement-based composite containing nano-silica. The effects of nano-silica particle size (12 nm, 50 nm and 150 nm) and concentration (1 - 5 wt.%) were systematically investigated. The compressive strength increases with certain amount of nano-silica due to the highly reactive nature of nano-silica which accelerates cement hydration reaction. Excessive nano-silica, on the other hand, leads to the decrease in strength since nano-silica absorb water required for cement hydration. This results in the creation of air void and lowers the bulk density. The maximum strength is obtained for the cement paste with 50 nm nano-silica of 4 wt.%. The compressive strength increases more than 50% in comparison to the control cement paste. For thermal conductivity measurement, adding nano-silica reduces thermal conductivity of the cement paste. The most effective agent for thermal resistivity is the 12 nm nano-silica due to the higher volume percent of air void formation. The thermal conductivity experimental results fit well with the theoretical models: the series model and the Maxwell’s model.