Cement, as a binding material, is a very important building material. Almost every construction work requires cement. Therefore, the composition of cement is a matter of great interest to 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 the desired cement quality.

cement ingradients
Ingredients of Cement

What is Cement Made of - Composition of Cement

There are eight major ingredients in cement. The following image is showing the ingredients of cement: 

cement ingredients

The general percentage of these ingredients of which cement is made of is given below:


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. Lime: Lime is calcium oxide or calcium hydroxide.
    • The presence of lime in a sufficient quantity is required to form silicates and aluminates of calcium.
    • Deficiency in lime reduces the strength of the property to the cement.
    • Deficiency in lime causes the cement to set quickly.
    • Excess lime makes cement unsound.
    • The excessive presence of lime causes the cement to expand and disintegrate.


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


  4. Alumina: Alumina is Aluminium oxide. The chemical formula is Al2O3.
    • Alumina imparts quick setting property to the cement.
    • Clinkering temperature is lowered by the presence of the requisite quantity of alumina.
    • Excess alumina weakens the cement.

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

  6. 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 the chemical reaction with calcium and aluminum to form tricalcium alumino-ferrite.
    • Tricalcium alumino-ferrite imparts hardness and strength to cement.

  7. 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.

  8. Sulfur Trioxide: Chemical formula is SO3
    • It should not be present for more than 2%.
    • Excess Sulfur Trioxide causes the cement to unsound.

  9. Alkaline:
    • It should not be present more than 1%.
    • Excess Alkaline matter causes efflorescence.

Chemical Formulas of Cement Materials

Cement is made of different chemical components as discussed above. Cement chemical composition is dependent on the chemical composition of these ingredients.  These components have their own chemical formula. There is no specific chemical formula for cement itself.

The followings are the chemical formula for major components of cement.

  • Lime -Ca(OH)₂
  • Silica - SiO2
  • Alumina - Al2O3
  • Magnesia - MgO
  • Iron oxide - Fe2O3
  • Calcium Sulfate - CaSO4
  • Sulfur Trioxide - SO3
  • Alkaline - "X"(OH) 2

Summary of the article:

By reading this article on cement components, you are now capable to answer the following questions.

  • What are the ingredients of cement?
  • What is Cement made of?
  • What is in cement powder?
  • What's in cement?
  • What's cement made of?
  • What are portland cement ingredients?
  • Describe the cement composition.
  • What makes cement?
  • What is cement made out of?
  • What chemicals are in cement? 
  • What is cement made of chemically?
  • What are the contents of cement?
  • What are the functions of different portland 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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