The basis for the classification of ordinary Portland cement (OPC) as grade 33, 43 and 53 as per IS 10262 is:
The basis for the classification of ordinary Portland cement (OPC) as grade 33, 43 and 53 as per IS 10262 is 28 day compressive strength.
General-purpose Portland Cements
The commonly used Portland cement in India is branded as 33-grade (IS: 269-1989), 43-grade (IS: 8112-1989) and 53-grade (IS: 12269-1987) having 28-days mean compressive strengths exceeding 33 MPa, 43 MPa, and 53 MPa, respectively.
All three grades of ordinary Portland cement are produced from the same materials. The higher strengths are achieved by increasing the tricalcium silicate (C3S) content and also by finer grinding of the clinker. The fineness of 53-grade cement obtained by Blaine s air permeability test is specified to be of the order of 350000 mm2/g.