In fact, they belong to a substance but differ in the name. the difference between silica fume powder and microsilica, Silica fume is more focused on silica in the form of dust because its bulk density is relatively small, about 200-320 Kg/m3, and is usually used to indicate that there is no encrypted silica fume. Micro-silica powder is more focused on particle morphology, and the bulk density is relatively large, generally 320-680Kg/m3. It means that the silica fume after encryption is more appropriate.
silica fume properties
According to the SiO₂ content of silica fume powder, we divide the product into 85%–97% different specifications. The average particle size of the silica fume is 0.1-0.15 μm, which is a few percents of the average particle size of the cement. The silica fume properties and chemical composition are as follows:
From: amorphous silica powder
Color: grayish white (the natural state is white, as the density increases, the color gradually deepens)
Specific surface area: 15000 – 27000 m2/kg
Bulk density: 220 – 630kg/m3
Activity index: ≥120%
Water demand ratio: ≤125%
Silica fume is used in concrete and has the following advantages:
(1) Manufacture of high-strength concrete (above C70), significantly improving the strength and pumping performance of concrete;
(2) Manufacture of high impermeability (≥ P30), self-waterproof concrete structure, used in the basement of subways, tunnels, and high-rise buildings;
(3) Manufacture of marine and chemical concrete, due to its high density, effectively prevent the penetration and erosion of sulfate and chloride ions on concrete, and avoid corrosion of concrete reinforcement, thereby prolonging the life of concrete;
(4) In water conservancy, highway and bridge engineering projects, concrete not only needs the above basic indicators but also has very strict requirements for wear resistance and erosion resistance. It is necessary to incorporate micro silicon powder;
(5) Micro-silica powder has strong activity and water-reducing performance, and is suitable for admixtures of early-strength and high-strength concrete required for rapid construction; high-strength shotcrete for supporting during tunnel, subway and large-scale foundation pit construction Additives; admixtures for concrete used in underwater construction projects (eg piers, dams, rigs, etc.);
Silica fume powder has been used to improve refractory materials for more than 40 years.
Silica fume powder for refractory materials will have the following characteristics:
Improve the fluidity of the cast refractory material, reduce the water consumption, make it easy to form, and greatly improve the production efficiency;
Due to the interstitial effect of the ultrastructure, the compactness and strength of the refractory material are greatly improved;
The silica fume powder has high activity, and the mullite phase is more easily formed on the premise of the presence of the
Al₂O₃ component, so that the high-temperature strength and thermal shock resistance of the refractory material are remarkably improved.