8 Major Cement Ingredients & their functions
Cement is a useful binding material for any construction. Cement is very essential for every construction work. So, the engineers must have sound knowledge on composition of cement as well as the functionality of Cement ingredients. In order to obtain optimal cement quality, modify the amount of a component throughout cement production.
Cement contains eight major components. The common ratios of these components in cement are provided below:
- Lime 60-65
- Silica 17-25
- Alumina 3-8
- Magnesia 1-3
- Iron oxide 0.5-6
- Calcium Sulfate 0.1-0.5
- Sulfur Trioxide 1-3
- Alkaline 0-1
Functions of Cement Ingredients
Described below the major features of these Cement ingredients together with their functions and effectiveness:
1. Function of Lime: Lime stands for calcium oxide or calcium hydroxide.
- Existence of lime in an adequate quantity is necessary to develop silicates and aluminates of calcium.
- Scarcity in lime decreases the cement strength.
- Scarcity in lime turns cement to be arranged rapidly.
- Surplus lime turns cement unsound.
- Surplus lime cause cement to expand and disintegrate.
2. Silica: Silicon dioxide is called silica, chemical formula SiO2.
- Adequate quantity of silica should be available in cement to dicalcium and tricalcium silicate.
- Silica imparts strength to cement.
- Silica normally exists to the extent of about 30 percent cement.
3. Alumina: Alumina refers to Aluminium oxide. Chemical formula is Al2O3.
- Alumina transmits rapid setting property to the cement.
- Clinkering temperature is reduced by the existence of necessary quantity of alumina.
- Surplus alumina make the cement feeble.
4. Magnesia: Magnesia stands for Magnesium Oxide. Chemical formula is MgO.
- Magnesia should not be over 2% in cement.
- Surplus magnesia will decrease the power of the cement.
5. Iron oxide: Chemical formula is Fe2O3.
- Iron oxide imparts color to cement.
- It performs as a flux.
- At a very extreme temperature it passes on chemical reaction with calcium and aluminum to develop tricalcium aluminoferrite.
- Tricalcium aluminoferrite passess on rigidity and firmness to cement.
6. Calcium Sulfate: Chemical formula is CaSO4
- It is included in cement as gypsum(CaSO4.2H2O)
- It delays or checks the setting action of cement.
7. Sulfur Trioxide: Chemical formula is SO3
- Should not surpass 2%.
- Excess Sulfur Trioxide causes cement to unsound.
- Should not be present more than 1%.
- Surplus Alkaline leads to efflorescence.