Cement, as a binding material, is a very important building material. Almost every construction work requires cement. Therefore, composition of cement is a matter of great interest for engineers. For understanding cement composition, one must know the functionality of Cement ingredients. By altering the amount of an ingredient during cement production, one can achieve a desired cement quality. 

cement ingradients

There are eight major ingredient of cement. The general percentage of these ingredients in cement is given below:

 Ingredient

Percentage 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 Ingredients

The main features of these Cement ingredients along with their functions and usefulness or harmfulness are given below:

  1. Function of Lime: Lime is calcium oxide or calcium hydroxide.
    • Presence of lime in a sufficient quantity is required to form silicates and aluminates of calcium.
    • Deficiency in lime reduces the strength of cement.
    • Deficiency in lime causes cement to set quickly.
    • Excess lime make cement unsound.
    • Excessive presence of lime cause cement to expand and disintegrate.

       

  2. SilicaSilicon dioxide is known as silica, chemical formula SiO2.
    • Sufficient quantity of silica should be present in cement to dicalcium and tricalcium silicate.
    • Silica imparts strength to cement.
    • Silica usually present to the extent of about 30 percent cement.

       

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  3. Alumina: Alumina is Aluminium oxide. Chemical formula is Al2O3.
    • Alumina imparts quick setting property to the cement.
    • Clinkering temperature is lowered by the presence of requisite quantity of alumina.
    • Excess alumina weaken the cement.

       

  4. Magnesia: Magnesium Oxide. Chemical formula is MgO.
    • Magnesia should not be present more than 2% in cement.
    • Excess magnesia will reduce the strength of the cement.

       

  5. Iron oxide: Chemical formula is Fe2O3.
    • Iron oxide imparts color to cement.
    • It acts as a flux.
    • At a very high temperature it imparts into chemical reaction with calcium and aluminum to form tricalcium aluminoferrite.
    • Tricalcium aluminoferrite imparts Hardness and strength to cement.

       

  6. Calcium Sulfate: Chemical formula is CaSO4
    .
    • This is present in cement in the form of gypsum(CaSO4.2H2O)
    • It slows down or retards the setting action of cement.

       

  7. Sulfur Trioxide: Chemical formula is SO3
    .
    • Should not be present more than 2%.
    • Excess Sulfur Trioxide causes cement to unsound.

       

  8. Alkaline:
    • Should not be present more than 1%.
    • Excess Alkaline matter causes efflorescence.

Summery of the article:

  • What are the ingredients of the cement?
  • Describe the cement composition.
  • What are the functions of different cement ingredients?
  • What are the functions of lime in cement?
  • What are the functions of Silica in cement?
  • What are the functions of alumina in cement?
  • What are the functions of Magnesia in cement?
  • What are the functions of Iron oxide in cement?

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