silicaafume

Silica fume, also called micro silica or amorphous silica, is a byproduct of silicon and ferrosilicon alloy production in electric arc furnaces. It consists of extremely fine, spherical silica particles and is typically sold as a dry powder or slurry.

Chemically, it is predominantly SiO2 with trace oxides. The particles are submicron in size and have a very high surface area, which makes silica fume highly reactive as a pozzolanic material used in cementitious systems.

In cement-based systems, silica fume acts as a micro filler and pozzolanic, reducing porosity and capillary permeability, increasing early and long-term strength, and improving durability and resistance to alkali–silica reactions. Typical dosing ranges from a few percent up to about 15% by cement mass, often with superplasticizers to maintain workability.

Beyond concrete, it is used in refractory materials, high-performance polymers, coatings, ceramics, and some rubber compounds to enhance strength, abrasion resistance, and chemical durability.

Handling requires controls to limit dust exposure, as inhalation of fine silica dust poses health risks. Protective equipment and dust-management practices are recommended, and standards such as ASTM C1240 govern silica fume use in concrete.