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 represents 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.
All the grades are produced from the same basic materials, but higher strength is achieved by increasing the tricalcium silicate content and also by finer grinding of the clinker.
Indian Standard Code (IS: 456: 2000) permits the use of the following Portland cement for specific types of work.