All About Civil Engineering : Chemical Constituents of cement

Chemical Constituents of cement

Percentage of various ingredients for the manufactures of Portland cement should be as follows:

Lime (CaO)

· Major constituent and Proportion needs to maintained carefully,

· Excess makes the cement unsound and cause the cement to expand and disintegrate,

· Deficiency in lime reduces in strength and cement sets quickly.

Silica (SiO₂)

· It is an important ingredient of cement and imparts strength to the cement due to the formation of dicalcium and tricalcium silicates.

· Excess provides greater strength but prolongs the setting time.

Alumina (Al₂O₃)

· Imparts quick setting quality to the cement,

· Acts as a flux and lowers the clinkering temperature,

· Alumina in excess reduces the strength of cement.

Iron Oxide (Fe₂O₃)

· Provides colour, hardness and strength to cement.

Calcium Sulphate (CaSO₄)

· Present in the form of gypsum,

· Increase in the initial setting time of cement.

Magnesium Oxide (MgO)

· Imparts hardness and colour to the cement,

· Excess makes the cement unsound.

Sulphur Oxide (SO₃)

· Makes the cement sound.