Silica Fume Introduction:

Silica fume (also known as Microsilica) is amorphous powdery silica (SiO2) collected by specifically designed dust collectors from the oxide silicon steam discharged through the flue in the process of smelting industrial silicon or silicon alloy. The average particle diameter of silica fume is 0.15 ~ 0.20 μ m; the specific surface area is 15000 ~ 20000m 2/kg, and it has strong surfactivity. The main ingredient of silica fume is amorphous silica. The rising furnace gas also carries impurities such as free C, Fe2O3, CaO, K2O, Na2O and so on. The color of silica powder varies with the increase of the content of C and Fe2O3, changing from white, off-white, gray, to dark gray. Silica fume directly undergoing dust collection is called prime fume, which has a bulk density of 150 ~ 300kg/m3. In order to facilitate transport and engineering applications, it is also possible to intensify the prime fume.

Functions of silica fume:

1. Admixture for cement or concrete Silica fume is able to fill the pores between the particles of cement, while generating gel after reacting with hydration products, and generating gel with alkaline magnesium oxide. In cement-based concrete, mortar and refractory casting materials, an appropriate amount of silica fume in it can play the following roles: 1. Significantly improve the resistances to pressure, folding, penetration, corrosion, impact and abrasion.

2. Retain water, and prevent separation and bleeding, to significantly reduce the resistance of concrete pumping.

3. Significantly extend the service life of concrete, especially in such harsh environments as chloride contamination erosion, sulfate erosion, high humidity and so on, in which it can improve the durability of concrete by twice or even higher times.

4. Significantly reduce dust from spray concrete and castable falling to the floor, and increase the thickness of single spray.

5. It is a necessary component of high-strength concrete, used in the existing C150 concrete engineering.

6. 5 times higher than the effect of cement; in common concrete and low cement castables, it can reduce costs and improve durability.

7. Effectively prevent the occurrence of concrete alkali aggregate reaction.

8. Improve the compactness of castable refractory materials. When coexisting with Al2O3, it can generate more mullite phase to enhance the high temperature strength, and thermal shock resistance.

9. Strong effect of volcanic ash: when mixed with concrete, it can have secondary hydration reaction with cement hydration products Ca (OH) 2 to form a gel product, to fill with the cement structure, improve the microstructure of slurry and improve the mechanical properties and durability of the hardened body.

10. Silica fume is amorphous spherical particles, which can improve the rheological property of concrete.

11. The average particle size of silica fume is relatively small, with a good filling effect. It can fill in the gap between cement particles and improve the concrete strength and durability.