Cement is an important building material. It was first introduced in England in 1824 by Joseph Asphdin. It is also called Portland cement because it resembles with the natural limestone quarried in the Isle of Portland, England. Cement is a product obtained by combining a material rich in lime, CaO with other material such as clay which contains silica, SiO2 along with the oxides of aluminium, iron and magnesium. The average composition of Portland cement is : CaO, 50- 60%; SiO2, 20-25%; Al2O3, 5-10%; MgO, 2- 3%; Fe2O3, 1-2% and SO3, 1-2%. For a good quality cement, the ratio of silica (SiO2) to alumina (Al2O3) should be between 2.5 and 4 and the ratio of lime (CaO) to the total of the oxides of silicon (SiO2) aluminium (Al2O3) and iron (Fe2O3) should be as close as possible to 2. The raw materials for the manufacture of cement are limestone and clay. When clay and lime are strongly heated together they fuse and react to form ‘cement clinker’. This clinker is mixed with 2-3% by weight of gypsum (CaSO4·2H2O) to form cement. Thus important ingredients present in Portland cement are dicalcium silicate (Ca2SiO4) 26%, tricalcium silicate (Ca3SiO5) 51% and tricalcium aluminate (Ca3Al2O6) 11%