The functions of different ingredients of Cement are as follows:
1) Lime (CaO): This is the major constituent of cement. If lime content in cement is high it makes cement unsound and causes the cement to expand and disintegrate. If lime content in cement is low the strength of cement is decreased and cement sets quickly. And if lime is in the right proportion it makes cement sound and strong.
2) Silica (SiO2): This is an important ingredient of cement. It gives strength to the cement due to the formation of dicalcium and tricalcium silicates. Excess quantity of Silica provides greater strength to cement but it also extends the duration of setting time.
3) Alumina (Al2O3): It gives quick setting quality to the cement. An excess amount of alumina reduces the strength of cement.
4) Calcium Sulphate (CaSO4): Calcium Sulphate helps in increasing the initial settling time of cement. It is present in the form of gypsum.
5) Iron Oxide (Fe2O3): Iron Oxide basically provides Strength, colour and hardness to the cement. It also helps the fusion of raw materials during the manufacture of cement.
6) Magnesium Oxide(MgO): Magnesium Oxide in cement if presented in correct amount it imparts hardness and colour to cement but if the amount is high then it makes the cement unsound.
7) Sulphur Trioxide (SO3): Excess of Sulphur Trioxide makes cement unsound.
8) Alkalies: Alkalies should be present in small quantities.Alkalies in excess will cause efflorescence.
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