Cement is the most essential material Nowadays. Before we know the Chemical composition of cement we have to basic terms of Cement. So let's start.
What is Cement?
Cement is a type of Adhesive and Cohesive material obtained by burning and grinding calcareous and argillaceous material at very high temperatures and grinding the clinker.
Cement is commonly used as a binding material with a particle size of 75-150 microns. Its general ingredients are mainly Calcareous rocks (65%) and Argillaceous Rocks (35%).
Chemical Composition of Cement
- Lime(Cao)60-65%-Its main functions are strength and Soundness control, deficiency reduces the strength. High Lime content generally increases the setting time and strength.
- Silica(SiO2)17-25%-It is responsible for quick setting. Excess quantity reduces strength and slow setting.
- Alumina(Al2O2)3-8%-It is responsible for quick setting if in excess then lowers strength.
- Magnesia(MgO)0.5-6%-It is responsible for colour and hardness and an excess quantity of it causes unsoundness.
- Gypsum(2-5%)-It is used as a retarder.
- Sulphur(SO3)-It imparts soundness. The quantity of Sulphur trioxide (SO3)in OPC Cement should not be more than 3%.
- Alkalies(0.2-1%)-It causes Efflorescence and accelerates the setting of cement paste.
