Effect of colloidal nano silica on the freeze-thaw resistance and air void system of portland cement concrete

Abstract

The present study investigates the impact of colloidal nano silica (CNS) on the freeze-thaw durability of concrete, with a particular focus on understanding the fundamental mechanism via a systematic analysis of the air void system. Experimental results suggest that the incorporation of CNS increases the total air content of the sample while reducing the average void size. This phenomenon can be attributed to the remarkable capacity of CNS to stabilize air bubbles within the concrete matrix, by a heightened viscosity and lower surface tension of the fresh concrete mixture. The increase in air void chambers facilitates the release of internal stress during freezing expansion, thereby enhancing the freeze-thaw resistance of the concrete. Additionally, the inclusion of CNS results in the formation of a denser cement matrix that improves the water impermeability of the concrete and prevents the ingress of water and other potentially corrosive substances.