CEMENT ingredients:Lime: is calcium oxide or calcium hydroxide. It is 61-67% of cementPresence of lime in a sufficient quantity is required to form silicates and aluminates of calcium which are mainly responsible for formation of Bogue’s compounds which imparts strength and cementing property. Deficiency of lime reduces strength of cement. Deficiency in lime CAUSES cement to set quickly.Silica: silicon dioxide (SiO2) is called as silica. it is present as 17-25% of cement.Sufficient quantity of silica should be present in cement as it imparts strength to the cement. Also, if it is present in HIGH quantity, it makes cement low heat hence safeguard against chemical action and heat resistant.Alumina: Alumina is Aluminium oxide (Al2O3). Alumina is present as 3-8% of cement and 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. It also increases heat of hydration.Magnesia: Magnesium Oxide (MgO) is called as Magnesia. It should not be present more than 2% in cement. Excess magnesia will reduce the strength of the cement. If present in limited quantity, it imparts strength.Iron oxide: (Fe2O3), Iron oxide imparts colour to cement. It is present as 1-6% of cement and acts as a flux. At a very high temperature, it imparts into the chemical reaction with calcium and aluminium to form tricalcium alumino-ferrite. Tricalcium alumino-ferrite imparts HARDNESS and strength to cement.Calcium Sulphate (gypsum): This is present in cement in the form of gypsum (CaSO4.2H2O) It slows down or retards the setting action of cement. Also, reduces the rate of heat of hydration.Alkaline: Should not be present more than 1%. Excess Alkaline matter causes efflorescence or white patches on the face of wall which can also LEAD to cracking of concrete.