GRADES OF ORDINARY PORTLAND CEMENT

At present, Ordinary Portland Cement is available in three different grades in India as 33-grade (IS: 269–1989), 43-Grade (IS: 8112–1989) and 53-grade (IS: 12269–1987).

The numbers 33, 43 and 53 correspond to the 28-day compressive strength of cement-mortar as 33 MPa, 43 MPa and 53 MPa. The strengths are obtained from standard tests on cement–sand mortar specimens. These three grades are most commonly used in general concrete construction.

All the three grades of Ordinary Portland Cement are produced from the same basic materials. But higher strength is achieved by increasing the tricalcium silicate (C₃S) content and also by finer grinding of the clinker.

Physical properties of 33, 43 and 53 Grade Ordinary Portland Cement are shown in Table 6.4.

Table 6.4 Physical properties of OPC