Cement is a binding
material which hardens in air and under water and is water-resistant after
hardening (hydraulic binding material) and which consists substantially of
compounds of calcium oxide (CaO) and silica (SiO2), Alumina (Al2O3) and iron
oxide (Fe2O3), while satisfying the requirements of the standards of strength
and soundness (constancy of volume).
The
raw material or the major part of the initial substances must be heated at least
to sintering,i.e. , the stage preceding fusion (1400 °C to 1450 °C ).Described
very briefly, cement manufacture therefore consists in crushing, grinding and
blending the raw materials, burning the raw mix to clinker, and grinding the
clinker to cement.
Mixed with aggregates (such as gravel or crushed stone) and water, cement reacts
in air and under water to form a rock hard and almost imperishable material
known as concrete, which can be cast and moulded into any desired shape for a
multitude of purposes.
