Corrosion of embedded metals in concrete can be greatly reduced by placing crackfree concrete with low permeability and sufficient concrete cover. Lowpermeability concrete can be attained by decreasing the water to cementitious materials ratio of the concrete and the use of pozzolans and slag.
Semiconductorgrade silicon is used in the manufacture of silicon chips and solar cells. Fumed silica is used as a filler in the cement and refractory materials industries, as well as in heat insulation and filling material for synthetic rubbers, polymers and grouts. Silica is used in ceramics and in making glass.