Hydration and microstructures of concrete containing raw or densified silica fume at different curing temperatures

The hydration and microstructures of concrete containing silica fume (SF) cured with different temperatures were studied by measuring the mechanical properties of concrete, determining the content of non-evaporable water and calcium hydroxide, and investigating the pore structure of matrix and the porosity of concrete. The results show that the improving influence of raw SF on the macro properties of concrete and hydration degree of hardened paste are more obvious than that of densified SF. The difference between the influence of the two kinds of SF on the properties of concrete is reduced by the elevated temperature curing. The early-age steam curing tends to excite the hydration at early ages and hinder the hydration of binders at later ages. The addition of both raw and densified SF helps to reduce the content of CH. Raw SF can refine the pore structure of paste while the content of >50 nm pores increases with the addition of densified SF. Elevated temperature curing helps to reduce the porosity and increase the proportion of 4.5-50 nm micropores in the hardened paste.