Function Of Cement Ingredients

The ingredients of ordinary cement, as mentioned above, perform the following functions:

(1) Lime (CaO): This is the important ingredient of cement and its proportion is to be carefully maintained. The lime in excess makes the cement unsound and causes the cement to expand and disintegrated. On the other hand, if lime is in deficiency, the strength of cement is decreased and it causes cement to set quickly.

(2) Silica (SiO₂): This is also an important ingredient of cement and it gives or imparts strength of the cement due to the formation of dicalcium and tricalcium silicates. If silica is present in excess quantity the strength of cement increases but at the same time, its setting time is prolonged.

(3) Alumina (Al₂O₃): This ingredient imparts quick setting property to the cement. It acts as a flux and it lowers the clinkering temperature. However the high temperature is essential for the formation of a suitable type of cement and hence the alumina should not be present in excess amount as it weakens the cement.


(4) Calcium sulphate (CaSO₄): This ingredient is in the form of gypsum and its function is to increase the initial setting time of cement.

(5) Iron oxide (Fe₂O₃): This ingredient imparts color, hardness and strength to the cement.

(6) Magnesia (MgO): This ingredient, if present in small amount, imparts hardness and color