1. Cement

2. Ordinary Portland cement is obtained by mixing of calcareous materials (such as limestone /chalk) & argillacious material (clay/shale containing silica & alumina) burning the mixture in rotary kiln at very high temperature to produce clincker

3. Stages of manufacture of cement 1.Mixing of raw materials 2.Burning 3.Grinding

4. Raw materials-composition MaterialPercentage (%) Lime (Cao)60 to 65 silica (SiO2)20 to 25 Alumina (Al2O3)3 to 8 Iron oxide (Fe2O3)2 to 4 Magnesia (MgO)1 to 4

5. Manufacture of cement There are three main operations involved 1.Mixing of raw materials 2.Burning 3.Grinding

6. Mixing of raw materials a.)Dry process b.)Wet process In this method, the calcareous materials such as limestone & argillaceous materials such as clay are separated reduced in size of about 25mm in crushers. After drying, these materials are grounded in ball mills. This powder is then stored in hoppers. Then they are mixed in correct proportions.

8. Wet process