Silica fume, also known as microsilica, It is an amorphous (non-crystalline) polymorph of silicon dioxide, silica. It is an ultrafine powder collected as a by-product of the silicon and ferrosilicon alloy production. Silica fume is an ultrafine material with spherical particles less than 1 μm in diameter, the average being about 0.15 μm, which have supperpower activity index. This makes it approximately 100 times smaller than the average cement particle. The bulk density of silica fume depends on the degree of densification in the silo and varies from 240kgs/m3 (undensifhed) to 720 kgs/m3（densifhed） The main field of application is concrete, grouts and mortars as well as refractory, cearamic ,oil well grouting, shotcrete,repair products.
Test report
High Performance Concrete (HPC) containing silica fume has been identified as one of the more important advanced materials necessary in the effort to rebuild the nation's infrastructure. In addition to increased strength and enhanced durability,HPC produced with silica fume delivers increased toughness, increased resistance to abrasion, corrosion and chemicals, sustainability and life-cycle cost efficiencies.
Silica fume will protect concrete against deicing salts, seawater, traffic and heavy impact. Rebar corrosion activity and concrete deterioration are virtually eliminated, which minimizes maintenance expense.
High-strength concrete enhanced with silica fume provides architects and engineers with greater design flexibility.Traditionally used in high-rise buildings for the benefit of smaller columns (increasing usable space) high-strength concrete containing silica fume is often used in precast and prestressed girders allowing longer spans in structural bridge designs.
