ORDINARY PORTLAND CEMENT AND ITS CONSTITUENTS

Ordinary Portland Cement and Its Constituents.

Ordinary portland cement is one of the most widely used cement worldwide.This type of cement is manufactured to powder by mixing limestone and other raw materials which consists of argillaceous,calcareous and gypsum.

The ingredients are mixed in proportion of about two parts of calcareous materials to one part of argillaceous materials and then crushed and ground in ball mill in a dry state or mixed in wet state.The dry powder or wet slurry is then brunt in a rotary kiln at a temperature between 1400 degree C to 1500 degree C.The clinker obtained from the kiln is first cooled and then passed on to ball mills where gypsum is added and it is ground to requisite fineness acccording to the class of product.

This cement is available in market in three grades namely OPC 33,OPC 43 and OPC 53.It was developed by Joseph Aspdin in 1824 due to the similarity in colour and its quantity when it harden like Portland Stone.Portland stone is white grey limestone in island of Portland Dorset.

The Constituents of Portland Cement.

CONSTITUENTS	PERCENTAGE
Lime   (CaO)	60 To 67 %
Silica  (SiO2)	17 To 25 %
Alumina (Al2O3)	3 To 8 %
Calcium Sulphate (CaSO4)	3 To 4 %
Iron Oxide (Fe2O3)	0.5 To 6%
Magnesia (MgO)	0.1 To 4%
Sulphur Trioxide (SO3)	1 To 3 %
Alkalies (Na2 + K2O)	0.5 To 1.3 %

Uses of Portland Cement;

• Used in general construction purposes.
• Used in masonry work.