Ordinary Portland cement (OPC) is by far the most important type of cement. Prior to 1987, there was only one grade of OPC which was governed by IS 269-1976. After 1987 higher grade cement were introduced in India.
Types of Ordinary Portland Cement
The Ordinary portland cement (OPC) was classified into three grades, namely 33 grade, 43 grade and 53 grade depending upon the strength of the cement at 28 days when tested as per IS 4031- 1988.
If the 28 days strength is not less than 33N/mm2, it is called 33-grade cement, if the strength is not less than 43N/mm2, it is called 43-grade cement, and if the strength is not less then 53 N/mm2, it is called 53-grade cement. But the actual strength obtained by these cement at the factory is much higher than the BIS specifications.
Advantages and Use of Ordinary portland cement
It has been possible to upgrade the qualities of cement by using high-quality limestone, modern equipment, closer on line control of constituents, maintaining better particle size distribution, finer grinding and better packing. Generally, the use of high-grade cement offers many advantages for making stronger concrete.
Although they are little costlier than low-grade cement, they offer 10-20% savings in cement consumption and also they offer many other hidden benefits. One of the most important benefits is the faster rate of development of strength. In modern construction activities, higher grade cement has become so popular that 33-grade cement is almost out of the market
The manufacture of OPC is decreasing all over the world in view of the popularity of blended cement on account of lower energy consumption, environmental pollution, economic and other technical reasons. In advanced western countries, the use of OPC has come down to about 40 percent of the total cement production.
Amount of OPC used in India
In India for the year 1998- 99 out of the total cement production i.e., 79 million tons, the production of OPC in 57.00 million tons i.e., 70%. The production of PPC is 16 million tones i.e., 19% and slag cement are 8 million tons i.e., 10%. In the years to come the use of OPC may still come down, but all the same, the OPC will remain as an important type for general construction.