Micro-silica powder, also called silica micro-powder, is also called silica fume, silica fume or ultrafine silica powder.
Micro-silica powder is a kind of ultra-fine siliceous powder material formed by the rapid oxidation and condensation of SiO2 and Si gas produced by metallurgical electric furnace at a high temperature above 2000 ℃ and oxygen in the air.
1. Physical and chemical properties of microsilica
1. Micro silica fume:
The appearance is gray or off-white powder, and the refractoriness is >1600℃. Bulk density: 200～250 kg/cubic meter.
The chemical composition of micro-silica powder is shown in the following table:
Chemical properties of micro-silica fume
2. Fineness of micro silicon powder:
The micro-silica powder has a fineness of less than 1μm accounting for more than 80%, the average particle size is 0.1-0.3μm, and the specific surface area is 20-28m2/g. Its fineness and specific surface area are about 80-100 times that of cement and 50-70 times that of fly ash.
3. Particle shape and mineral phase structure:
During the formation process of micro-silica powder, due to the effect of surface tension in the process of phase change, amorphous spherical particles of amorphous phase are formed, and the surface is relatively smooth, and some are agglomerates of multiple spherical particles sticking together . It is a volcanic ash material with a large specific surface area and high activity. For materials mixed with micro-silica powder, tiny spheres can play a lubricating effect.
Second, the role of silica
The micro-silica fume can fill the pores between 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 the cement-based concrete, mortar and refractory castables, mixing appropriate amount of micro-silica fume can play the following roles:
1. Significantly improve compression resistance, flexural resistance, impermeability, corrosion resistance, impact resistance and wear resistance.
2. It has the functions of retaining water, preventing segregation and bleeding, and greatly reducing the resistance of concrete pumping.
3. Significantly prolong the service life of concrete. Especially in harsh environments such as chloride pollution erosion, sulfate erosion, and high humidity, the durability of concrete can be doubled or even several times higher.
4. Significantly reduce the floor dust of sprayed concrete and castables, and increase the thickness of a single spray layer.
5. It is a necessary component of high-strength concrete, and C150 concrete has been used in engineering.
6. It has about 5 times the effect of cement. It can reduce costs and improve durability when used in ordinary concrete and low cement castables.
7. Effectively prevent the occurrence of concrete alkali aggregate reaction.
8. Improve the compactness of castable refractories. When coexisting with Al2O3, it is easier to form mullite phase, which increases its high temperature strength and thermal shock resistance.
PUDA silica packing machine:
PUDA has three kinds of packing machines for silica, one is open bag packing machine with screw feeder. the second is valve bag packing machine with screw feeder, the third is valve bag vacuuming packing machine. Uaually common silica powder can ba packed well by the former two machines. The last one is for ultra light material.
