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55.1 CEMENT

Cement is a general name given to a powdered material which initially have plastic flow when mixed with water, but sets into a hard solid structure in several-hour with varying degree of strength and bonding properties. It was discovered in 1824 by an English Meson Joseph Aspdine.

Chemically, cement is fine ground mixture of calcium aluminates mid silicates of varying composition which hardens into a rigid solid mass after treatment with water. It is called portland cement because of the resemblance of the hardened mass to portland rock, a famous building stone of England.

Composition of Portland Cement

Portland-Cement is a, dirty greyish heavy powder containing calcium aluminates and silicates. The silicates and aluminates which form more than 90% of the cement are:

  • Tricalcium silicate (3CaO.SiO2)
  • Dicalcium silicate (2CaO.SiO2)
  • Tricalcium aluminate (3CaO.Al2O3)
  • Tetra calcium alumino ferrite (4CaO.Al2O3.Fe2O3)

Of these, tricalcium silicate is most important.