1) What is cement?

Cement is a powder, which by hydraulic reaction (i.e. with water) forms a solid and cohesive mass.

2) Which are the most common types of cement available in the market?

The most common types of cement available in the market are:
Ordinary Portland cement (OPC): The standard, grey cement used for most purposes.

Rapid Hardening Portland cement: Chemically very similar, but ground finer. Sets as slowly as OPC, but its gains quick strength more so after it sets.

Sulphate Resisting Portland cement (SRPC): Cement used for underground work, particularly with "aggressive" i.e. sulphate containing groundwater.

High Alumina Cement (HAC): A special type of cement that develops rapid strength and possesses high chemical resistance. It can also be utilised for refractory concretes, e.g. in steelworks, using the white version. A phenomenon known as "inversion” occurs in HAC when it gets hot and wet it disintegrates.

3) What is Portland Cement?

Portland Cement is a blend of finely pulverized clinkers, manufactured by burning materials containing lime, alumina, iron and silica in pre-determined proportion at very high temperatures. Normally, gypsum or its derivatives are added during the grinding stages for set control.

4) What are the raw materials used in the manufacturers of Portland cement?

The two main raw materials employed during the manufacturer of Portland cement are calcareous materials like limestone, chalk, shells or marl and argillaceous materials like clay and shale (rich in silica).

5) How is Portland Cement made?

The calcareous and argillaceous raw materials along with the other additives are mixed and finely ground. This is intimately blended and fired in a rotary kiln at very high temperatures in the range of 1450 °-1500°C. The product formed in the kiln is known as clinker. Theses clinkers are allowed to cool and then ground to fine powder along with small percentage of gypsum (4-5%). This finely blended powder is known as Portland cement.

6) Can cement irritate my hands?

Some people are rather more sensitive to the free lime than others. It may cause some irritability if it comes in contact with the eyes. As such no long- term health problems occur, but it is possible that cracked skin will leave you more prone to dermatitis.

7) What is the difference between cement and concrete?

Cement is a finely ground powder composed mainly of limestone and silica that react with water to harden. Concrete is a blend of cement powder, sand, gravel, water and sometimes chemicals, which are mixed together and placed in forms for construction purposes.

8) Will concrete harden under water?

Portland cement is hydraulic cement. This means that it sets and hardens faster due to a chemical reaction with water. As a result, it will also harden under water.

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