As per Indian Standard IS:4031-PART 6-1988, Code of practice for COMPRESSIVE STRENGTH OF HYDRAULIC CEMENT.
Compressive strength of cement is determined by compressive strength test on mortar cubes compacted by means of a standard vibration machine. The Standard sand as per IS:650 (Ennore, TN) is used for the preparation of cement mortar. The specimen is in the form of cubes 70.6mm*70.6mm*70.6mm. (IS 1080:1982)
IS 650: 1992 “ Specification for Standard Sand for Testing of Cement”
IS 10080:1982 “ Specification for Vibration Machine for casting standard Cement Mortar Cubes “ with Amendments Clause 3.4
The compressive strength attained in N/Sq.mm at 28 days age when a standard cube of 70.6mm*70.6mm*70.6mm is subjected to standard compressive test is termed as Grade of Cement.
Thus, the OPC 43 grade cement should attain the compression strength of 43MPa within 28 days of setting.
And similarly he OPC 53 grade cement should attain the compression strength of 53MPa within 28 days of setting.
Further the diffrence between the grade of cements is elobarted based on production, use and application in below.
43 Grade OPC
The 43 grade OPC is the most popular general-purpose cement in the country today. The production of 43 grade OPC is nearly 50% of the total production of cement in the country.
43 Grade OPC can be used for the following applications:
+ General Civil Engineering construction work.
+ RCC works(preferably where grade of concrete is up to M-30).
+ Precast items such as blocks, tiles, pipes etc.
+ Asbestos products such as sheets and pipes.
+ Non-structural works such as plastering, flooring etc.
53 Grade OPC
53 Grade OPC is a higher strength cement to meet the needs of the consumer for higher strength concrete. As per BIS requirements the minimum 28 days compressive strength of 53 Grade OPC should not be less than 53 MPa. For certain specialized works, such as pre-stressed concrete and certain items of precast concrete requiring consistently high strength concrete, 53 grade OPC is found very useful. 53 grades OPC produce higher-grade concrete at very economical cement content. In concrete mix design, for concrete M-20 and above grades a saving of 8 to 10 % of cement may be achieved with the use of 53 grade OPC.
In concrete major strength is from coarse aggregate. strength of coarse aggregate is more than concrete. If you observe concrete compression test, it the cement mortar mix that fails to crack initially. So to increase the strength of concrete we have to add more cement. the maximum stress the cement can take is indicated by grade of cement. So 43 grade can be used for rcc upto M30 grade and also brickwork. 53 grade grade can be used anywhere but 53 grade cement has more heat of hydration and less setting time. so we don’t use for brickwork.
Currently 43 grade manufacturing is stopped by many companies as 53 grade can be used every where. The difference of cost between two grades will be around 5rs only. composition difference will not be there in two grades only difference is in fineness. 53 grade is more fine.