Cement is a mixture of many chemical components. These chemical possesses different properties. Its content amount in cement changes basic physical properties of cement. This is why knowing chemical composition of cement is very important. Presently Portland cement is most commonly used cement in industry. Hence knowing the content of different chemicals in Portland cement is important.
Chemical Compositions in cement: –
CaO: – Calcium Oxide is Key ingredient in cement. this material is cheap and easily available. Excess CaO makes the cement unsound (i.e. cement expands) and hence it disintegrates. And it’s deficiency makes the cement to set quickly with development of actual strength.
SiO2: -Silica is second most important ingredient in cement. Sufficient quantity of silica helps for the formation of di-calcium and tri-calcium silicates which imparts strength to the cement. Excess silica in cement will increase the strength of cement but at the same time setting time of cement also increased.
Al2O3: – Alumina imparts quick setting property to the cement. It acts as a flux and lowers the clinkering temperature. Alumina in excess quantity reduces the setting time of cement but simultaneously reduces the strength of cement.
Fe2O3: – Iron Oxide increases the hardened cement stone flexural strength, and slightly decrease the compressive strength. Iron oxide particles, as produced for the construction industry, are 10 times finer than cement particles. When added into a concrete mix, the iron oxide particles actually surround and coat the cement particles.
MgO:- Magnesium is good to reduce burnability of cement. It increase the content of free lime in clinker and decrease the strength of cement.
K2O: – Potassium Oxide has the superior performances in terms of early strength and high strength.
Na2O: -Sodium Oxide is good for compressive strength. It increases with an increase in Na2O content
SO3: -Sulfur Trioxide increases the drying shrinkage for all cements. It reduces strength loss of cement concrete.
Quantity of Chemical Composites: –
- CaO (Calcium Oxide) – 58% – 67%
- SiO2 (Silica) – 20%-26%
- Al2O3 (Alumina) – 5% – 10%
- Fe2O3 (Iron Oxide) – 2% – 6%
- MgO (Magnesium) – 0.5% – 3%
- K2O (Potassium Oxide) – 0.5% – 1%
- Na2O (Sodium Oxide) – 0.5% – 1%
- SO3 (Sulfur Trioxide) – 0.5% – 1.5%
- Other Chemicals – 0.5% – 1.5%