Cement: Raw Material, History, Chemical Composition, Functions of Compound.

Content outline

  • Introduction to Cement and its history.
  • Raw Material.
  • Chemical components
  • Chemical composition (Oxide compound and Bogue compound).
  • The function of Oxide compound.
  • The function of Bogue compound.

What is Cement?

Cement is a construction material that has cohesive and adhesive properties in the availability of water. Joseph Apsdin of Uk is a First person who invent Cement in 1824 A.D. He named the cement i.e. Portland cement because the natural stone that occurs for the manufacturing of cement is from the Place called Portland of England.

Raw Material used in Cement

a)  Limestone (Caco3

b) Sand (Sio2)

c). Stale clay (SiO2, Al2O3, Fe2O3)

Chemical Components

a). Calcium (Ca)

b). Silicon (Si)

c). Aluminum (Al)

d). Iron (Fe)

Chemical Components of Cement

There are two components i.e. Calcareous and Argillaceous components.

Calcareous Components (Lime CaO)

a). Limestone

b)  Chalk

c)  Marble shells

d) Lime sludge

          Argillaceous Components (SiO2, Al2O3, Fe2O3)

a) Clay

b) Shale

c). Rock

d) Blast furnace slag

e) Marl

Chemical Composition of Cement

  1. Oxide Compound
Oxide CompoundComposition Percentage
Lime(Cao)60-65%
Silica(SiO2)17-25%
Alumina(Al2O3)3-8%
Iron(Fe2O3)0.5-6%
Magnesia(MgO)0.5-4%
  • Bogue Compound
Bogue CompoundComposition Percentage
Tri calcium silicate25-50%
Di calcium Silicate25-40%
Tri calcium Aluminate5-11%
Tetra calcium Alumina- Ferrite8-14%

Functions of Oxide Compound

Lime(CaO)

Advantage

  • Gives binding property.
  • The addition of Lime controls strength and soundness.

Disadvantage

Lack or Deficiency of the percentage of lime in Cement reduces the strength and setting time.

Silica(SiO2)

Advantage

  • The function of Silica is to give strength.

Disadvantage

  • Lack of Silica slows the setting time of concrete.

Alumina(Al2O3)

Advantage

  • Responsible of Quick setting time.

Disadvantage

  • Excess of Alumina reduces the strength of cement.

Iron Oxide(Fe2O3)

  • Since the color of cement is grey. The function of Iron oxide is to give grey color.

Magnesia ( MgO)

  • It also imparts color and Hardness. If the amount of magnesia is excess then it causes cracks in mortar and concrete and unsoundness.

Functions of Bogue Compound

Tricalcium Silicate (C3S)

  • The chemical formula of Tricalcium silicate is 3CaO.SiO2.
  • The Chemical reaction of C3S with water can be expressed as

C3S+water = C-S-H + C-H + heat

  • Percentage of Tricalcium silicate in the range of 25-45%.
  • It gives early strength.
  • C3S hydrates rapidly produce high heat and develop early strength and hardness.

Diacalcium Silicate (C2S)

  • Chemical formula of Diacalcium Silicate is 2CaO.Sio2.
  • Slow heat of hydration than C3S.
  • Responsible for increase in strength beyond 7 day. At later stages, Its Contribution irrespective of strength and hardness is same as C3S.

Tricalcium Aluminates ( C3A)

  • Chemical formula of Tricalcium Aluminates is 3CaO.Al2O3.
  • Percentage of C3A is is 5-11%.
  • Responsible for Rapid setting.
  • An increase in C3A in cement reduces the setting time and lowers the ultimate strength, the heat of hydration.

Tetra calcium Alumina-Ferrite (C4AF)

  • The chemical formula of Tetra calcium Alumina – Ferrite is 4CaOAl2.Fe2O3.
  • Percentage of C4Af in cement is 8-14% (Normally 9%).
  • Responsible for rapid setting but generates less heat.
  • Increase in C4AF content reduces the strength slightly.

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