Microsilica is collected and processed by a special collection device in the process of industrial electric furnace smelting industrial silicon production and ferrosilicon at high temperatures. In the escaping smoke and dust. The content of SiO2 accounts is about 90%, the particle size is very small. And the average particle size is almost nanometer level, so it is called micro-silica fume.
According to the content of SiO2, micro silica can be divided into Four Types:
SiO2≥85%, the typical value is more than 88%, mainly used for concrete and low-grade refractories;
SiO2≥90%, the typical value is about 92%, used for concrete and general refractories;
SiO2≥92%, the typical value is about 94%, mostly used for medium and high-grade refractories;
SiO2≥97%, typical value above 97%, mostly used for high-grade refractories.
Applications of Silica Fume
Silica fume is the best performance of all admixtures, and it is also the most expensive admixture. According to different applications, the main uses of silica fume are Cement or Concrete Admixtures, Refractory Additives, Metallurgical Pellet Binders and Chemical Product Dispersants.
Cement or Concrete Admixture
Silica fume can fill the pores between the cement particles, and at the same time form a gel with the hydration product, and react with the alkaline material magnesium oxide to form a gel. In cement-based concrete, mortar and refractory castables, adding an appropriate amount of silica fume can play the following roles:
- Significantly improve the compression resistance, bending resistance, impermeability, corrosion resistance, impact resistance and wear resistance.
- It has the functions of retaining water, preventing segregation, bleeding, and greatly reducing the resistance of concrete pumping.
- Significantly prolong the service life of the concrete. Especially in harsh environments such as chloride pollution, sulfate corrosion, and high humidity, the durability of concrete can be doubled or even several times higher.
- Greatly reduce the landing ash of sprayed concrete and castables, and increase the thickness of a single spraying layer.
- It is a necessary component of high-strength concrete and has been used in engineering applications of C150 concrete.
- It has about 5 times the effect of cement, and it can reduce costs and improve durability when applied in ordinary concrete and low-cement castables.
- Effectively prevent the alkali-aggregate reaction.
- Improve the compactness of castable refractories. When coexisting with Al2O3, it is easier to generate a mullite phase, which enhances its high-temperature strength and thermal shock resistance.
- It has a strong pozzolanic effect. When mixing concrete, it can undergo a secondary hydration reaction with the cement hydration product Ca(OH)2 to form a cementitious product, fill the cement stone structure, improve the microstructure of the slurry, and improve the Mechanical properties and durability of hardened bodies.
- Micro silica fume is an amorphous spherical particle, which can improve the rheological properties of concrete.
- The average particle size of micro-silica fume is relatively small, and it has a good filling effect, which can be filled between the gaps of cement particles to improve the strength and durability of concrete.
High-quality silica fume is mainly used as high-performance refractory castables, preformed unit, ladle materials, air bricks, self-flowing refractory castables and dry and wet spray materials. Microsilica has the characteristics of high fluidity, low water storage, high density and high strength.
Metallurgical Pellet Binder
The silica fume is mixed with water to make pellets and then dried or sintered naturally without additional binder. The pellets have few impurities and can be returned to the electric furnace as smelting materials.
Chemical Product Dispersant
In order to prevent the agglomeration of some chemical synthetic powders, micro silica fume powder can be used to replace the more expensive treatment materials, instead of part of the dispersed isolation and or to increase the effect, it is widely used in fine pesticides, fertilizers, fire extinguishing agents and other products.