Silica fume

History:
– First testing of silica fume in Portland-cement-based concretes in 1952
– Silica fume initially lacked material for experimentation
– Silica fume is a by-product 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 high-purity 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 high-performance 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:
– Alkali-silica reaction
– Engineered cementitious composite
– Energetically modified cement (EMC)
– Fly ash
– Kaolinitehttps://en.wikipedia.org/wiki/Silica_fume