The Process
Cement is one
of the most natural of all manufactured products because its raw
materials come from the ground. Here we show you how it is
made.
In very simple terms, you take a mixture of finely ground
limestone or chalk, clay and sand and heat it almost to melting
point in a large rotating kiln. The cement clinker that emerges is
then ground to a powder with about five per cent gypsum, added to
control the setting time of the end-product.
The manufacturing process depends on the moisture content of the
raw materials. Chalk has a high moisture content and chalk-based
processes tend to be less energy efficient than those based on hard
limestone.
The description that follows is of the
limestone-based process.