Lime stone is the raw material used for making Cement. it is taken from the quarries and is brought to the factory in lorries or wagons. Here it passes’ through various machines and gets crushed into small chips. The conveyor belt carries the small chips to the storage yard.
Not only limestone but also any material rich is calcium carbonate can be used as raw material for making cement. Some factories use sea-shells also as raw material. Wherever lime stone is available in large quantities they were used for making cement.
Then the crushed stone is passed through the tub mills inside the tub mills there are three chambers in which there are steel balls of various sizes to grind the limestone. The limestone chips are fed into these mills along with the required amount of laterite and water. As the mills rotate, the limestone chips pass through these chambers and get ground into a mixture called ‘slurry’.
Slurry is a mixture of powdered limestone, laterite and water. When the steel balls become thin by constant use, they are replaced by new ones.
The slurry is fed into a huge basin called the mixture basin. This basin shakes the mixture continuously. The mixture will get hard and become solid if it is not stirred constantly. This constant shaking prevents it from becoming hard. Now the mixture is ready for being burnt in kilns.
There are gigantic rotating tubes, the kilns to burn the slurry into cement. They rotate slowly and they are lined normally with bricks which can stand high temperatures. The bricks are used on account of their resistance to heat. The slurry from the mixture basin is pumped into the upper end of the kiln while finely powdered coal is fired with great force from the lower end.
The slurry pumped into the kiln gets dried and burnt on account of the very high temperature of about 1490° inside the kiln. During this process the slurry undergoes a chemical change and becomes cement, small quantity of gypsum is added and the mixture is ground into fine powdered cement. Then they are packed in jute bags, stitched and branded in the factory itself.
Cement can be easily mixed with sand and used as plastering material.