Silica fume

History: First testing of silica fume in Portlandcementbased concretes in 1952 Silica fume initially lacked material for experimentation Silica fume is a byproduct of elemental silicon or ferrosilicon production Silica fume was vented into the atmosphere before environmental laws tightened Silica fume research in Norway highlighted its high strengths and low porosities Properties: Silica fume has ultrafine spherical particles less than 1 μm Bulk density ranges from 130 to 600 kg/m³ Specific gravity is typically 2.2 to 2.3 Specific surface area ranges from 15,000 to 30,000 m²/kg Silica fume is about 100 times smaller than average cement particles Production: Silica fume is a byproduct of producing silicon and ferrosilicon alloys Produced in electric arc furnaces using highpurity quartz and carbonaceous materials Carbothermic reduction process generates silica fume Silicon smelters collect silica fume for various applications Silica fume was previously discharged into the atmosphere Applications: Silica fume enhances compressive strength, bond strength, and abrasion resistance of concrete Reduces concrete permeability to chloride ions, protecting reinforcing steel Used in highperformance concrete for coastal regions and saltwater bridges Has applications in oil and gas operations, such as grout placement in wells Silica fume effects on concrete properties include workability and bleeding reduction Silicon carbide: Silica fume byproduct may be used to produce silicon carbide See also: Alkalisilica reaction Engineered cementitious composite Energetically modified cement (EMC) Fly ash Kaolinite