Silica fume is a highly pozzolanic material that is used to
enhance mechanical and durability properties of concrete. It may
be added directly to concrete as an individual ingredient or in
a blend of portland cement and silica fume. Interest in the use
of silica fume resulted from the strict enforcement of air-
pollution measures designed to stop release of the material into
the atmosphere. Initial use of silica fume in concrete was
mostly for cement replacement,along with water-reducing
admixtures. Eventually,the availability of high-range water-
reducing admixtures(superplasticizers) allowed new possibilities
for the use of silica fume to produce high levels of
performance. * Reduces concrete permeability * Increases
concrete strength * Improves resistance to corrosion