Silica fume is a byproduct of producing silicon metal or ferrosilicon alloys. One of the most beneficial uses for silica fume is in concrete. Concrete containing silica fume can have very high strength and can be very durable.
Silica fumes consist primarily of amorphous (non-crystalline) silicon dioxide (SiO2). The individual particles are extremely small, approximately 1/100th the size of an average cement particle. Because of its fine particles, large surface area, and the high SiO2 content, silica fume is a very reactive pozzolan when used in concrete.
Since the 1980s, silica fume has been used extensively around the world to produce high performance concrete. Today, more than 10 million cubic metres of concrete containing silica fume is placed each year.
| STC Microsilica® | ||
|---|---|---|
| Mandatory chemical and physical requirements | ||
| R940 | R970 | |
| SiO2(%) | 92 - 94 | 93 - 97 |
| C(%) | < 2.0 | < 1.0 |
| Fe2O3(%) | < 0.6 | < 0.6 |
| Al2O3(%) | < 0.6 | < 0.6 |
| CaO(%) | < 0.8 | < 0.6 |
| Na2O+K2O(%) | < 0.6 | < 0.5 |
| Moisture(%) | < 2.0 | < 2.0 |
| Loss on Ignition @ 950°C(LOI)(%) | < 3.0 | < 2.0 |
| Coarse Particles > 45μm(%) | < 5.0 | < 3.0 |
| Bulk Density(kg/m3)-undensified | 300 - 450 | 300 - 450 |
| Fluidity(mm) | Good(>120mm) | Execllent(>150mm) |