After replacing cement with silica fume, its function is similar to fly ash, which can improve the workability of concrete mixture, reduce the heat of hydration, improve the corrosion resistance, frost resistance and impermeability of concrete, and inhibit the alkali-aggregate reaction, and its effect is much better than that of fly ash. SiO2 in silica fume can react with Ca (OH) 2 at an early stage to produce hydrated calcium silicate. Therefore, replacing cement with silica fume can improve the early strength of concrete.
Although the replacement of cement with silica fume is generally 5% – 15%, the cement slurry will become very viscous when it exceeds 20%. The water consumption for concrete mixing increases with the addition of silica fume. Therefore, when silica fume is added to concrete, water reducer must be added at the same time, so as to obtain the best effect. Silica fume can improve the pumping performance of concrete and can withstand more vibration without segregation. In addition, silica fume can improve the fluidity of concrete. Using the same pouring method, silica fume concrete can have a slump of 500px higher than ordinary concrete. Silica fume concrete is very sensitive to early shrinkage cracks, and special attention should be paid to the control of curing conditions.
At present, silica fume has been widely used, and is mainly used for preparing high-strength and ultra-high-strength concrete, high impermeability concrete, underwater anti-dispersion concrete and other required concrete.
