The Bureau of Indian Standards came forward to grade the ordinary portland cement into grade 33 cement, grade 43 cement and grade 53 cement.
After total de-control of cement industry in 1989 and abolishing of licensing system for setting up of cement plants in 1992, there has been phenomenal growth in the production of cement. With the many fold increase in the production of cement, cement manufacturers adopted and aggressive marketing strategy, each projecting their product as the best. Manufacturers of 53 grade cement invaded the market and created an impression amongst the consumers that 53 grade OPC could be used by them as it is the best cement and grade 33 and grade 43 cements, are inferior.

In fact, all cements are one and the same but for minor changes in the characteristics. By and large grade 33 cement would meet the structural requirements of ordinary and small scale consumers. 43 grade cement may be utilised for precast concrete production besides the sleeper manufact ...more

For slabs I think....a lower grade is used for other construction and a higher say 58 grade for bridges!!!! I m not sure but I think so!!!!