Structurization of cement systems with nanodispersed silica stabilized with acetate ions

Abstract

The influence of a modifying additive in the form of silica sol stabilized with acetate ions on the structure and properties of cement stone has been studied. The mechanism of structure formation in the system of “cement-nanodispersed silica (NDS) stabilized with acetate ions” is proposed. It includes two aspects. In the initial period of hydration the crystallization of calcium hydroacetoaluminates occurs, the rate of their formation being higher than the rate of ettringite formation. Their crystals have some micro-reinforcing effect on cement stone, increasing its density and strength. The nanodisperse silica in combination with the calcium hydroacetoaluminates is directly involved in the structurization of cement stone, colmataging the pores. Si4+ atoms, building-in in the structure of portlandite phases, increase the impermeability of cement stone. The generation of calcium hydroacetoaluminates leads to the formation of the primary carcass, providing the strength development of cement stone in the early stages of hardening. It is established that adding the modifier results in pore redistribution in size: a decline in the amount of macropores and an increase in the quantity of the gel pores and submicropores (5-0.1 µm) at a constant micropore volume (0.1-20 µm).