What is cement?

Cement is a fine, soft, powdery-type substance. It is made from a mixture of elements that are found in natural materials such as limestone, clay, sand and/or shale. When cement is mixed with water, it can bind sand and gravel into a hard, solid mass called concrete. Cement is usually gray. White cement can also be found but it is usually more expensive than gray cement.

1. Cement mixed with water, sand and gravel, forms concrete.
2. Cement mixed with water and sand, forms cement plaster.
3. Cement mixed with water, lime and sand, forms mortar.
Cement powder is very, very fine. One kilo (2.2 lbs) contains over 300 billion grains. The powder is so fine it will pass through a sieve capable of holding water.
In India, Ordinary Portland Cement (OPC) is manufactured in three grades, viz. 33 grade, 43 grade and 53 grade, the numbers indicating the compressive strength obtained after 28 days, when tested as per the stipulated procedure.
Apart from OPC, there are several other types of cement, most of them meant for special purposes, e.g. sulphate resistant cement, coloured cement, oil well cement, etc. However, there are some general purpose cements, the commonest one being Portland Pozzolana Cement (PPC).