Compositon Of Cement & Cement Compositon Ratio
Cement is considered as one of the vital building material that is mainly used as a binding material. The engineers should have sufficient knowledge about the composition of cement. For this purpose, the knowledge regarding the functionality of cement components is required. In order to obtain the required cement quality, the amount of cement component has to be modified.
Composition of Cement
The cement comprises of eight major components with the following percentage.
Components and their ratios in cement :-
- 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 Components
The prime features of these cement components together with their functions and utility or harmfulness are as follow :
- Lime stands for calcium oxide or calcium hydroxide.
- The existence of lime should be sufficient to develop silicates and aluminates of calcium.
- Shortage of lime leads to minimizing the strength of property to the cement.
- Scarcity in lime triggers setting of the cement rapidly.
- With too much lime, the cement becomes unsound.
- With too much lime, the cement is extended and disintegrated.
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- Silicon dioxide is defined as silica and its chemical formula is SiO2.
- There should be adequate quantity of silica should be present in cement to dicalcium and tricalcium silicate.
- Silica transmits strength to cement.
- Silica normally exists to the extent of about 30 percent cement.
- Alumina stands for Aluminium oxide. The chemical formula is Al2O3.
- Alumina provides rapid setting property to the cement.
- Clinkering temperature is reduced by the existence of the necessary quantity of alumina.
- With excessive alumina, the strength of the cement is reduced.
- It is known as Magnesium Oxide. The chemical formula is MgO.
- Magnesia should not be exist in excess of 2% in cement.
- With excessive magnesia, the strength of the cement is decreased.
- Chemical formula is Fe2O3.
- Iron oxide provides color to cement.
- It functions as a flux.
- At a very high temperature, it makes chemical reaction with calcium & aluminum and develops tricalcium alumino-ferrite to provide hardness and strength to cement.
- Chemical formula is CaSO4
- It exists in cement in the form of gypsum(CaSO4.2H2O)
- It delays or retards the setting action of cement.
- Chemical formula is SO3
- It should not exist in excess of 2%.
- Excess Sulfur Trioxide leads the cement to unsound.
- It should not exist in excess of 1%.
- Excess Alkaline matter leads to efflorescence.