Ordinary Portland Cement - Materials and Production

Cement (hydraulic and non-hydraulic) is a substance which sets and hardens independently, and can bind other materials together. Cement is the most important construction material which is used in the production of mortar and concrete.

Cement is produced by heating together calcareous material (containing calcium carbonate) such as limestone  and argillaceous material (silica and alumina) such as clay, shale etc from 1400 to 1550�C in a kiln, in a process known as calcination. The resulting product is a hard substance, called 'clinker', which is then ground with a small amount of gypsum(4% to 6%) into a powder to make Ordinary Portland Cement (OPC), the most common type of cement  used.

Ordinary Portland Cement (non-hydrated) consists of the following compounds;

Tricalcium silicate C3S                      (50%)

Dicalcium silicate C2S                      (25%)

Tricalcium aluminate C3A                  (12%)

Tetracalcium alumino ferrite C4AF      (8%)

Gypsum                                           (3.5%)

Other compounds                              (1.5%)

• Retarding admixtures
• Accelerating admixtures
• Super plasticizers
• Water reducing admixtures
• Air-entraining admixtures

OPC is a hydraulic cement which gains the binding property by hydration (mixing with water) and solidifies gradually with time. The process of solidification of cement is termed as setting of cement. The setting time of cement depends on the type of cement.

Types of portland cement as per ASTM

Type I     Normal

Type II    Moderate sulphate resistant

Type III    High early strength

Type IV   Low heat of hydration

Type V    High sulphate resistant

Type IA   Normal air-entraining

Type IIA   Moderate sulphate resistant, air entraining

Type IIIA  High early strength, air entraining

Physical properties of ordinary portland cement

Know more about, fineness, soundness, density, hydration, setting and strength etc