I came across this type of cement grade first time
here in India there are 5 OPC type cement available in market
33 Grade
43 Grade
43S Grade
53 Grade and
53S Grade
Grade of cement with number in general defines its compressive strength which it can achieved at 28 days if tested as per the guidelines stated in IS code.
So if i say 53 Grade cement it must achieve a 53mpa strength at 28 days (this is meaning of grade)
there are 2 more grade with letter "S" at end
it says our production is for 43 grade of cement
but we have achieve more fineness than expected as per IS code and hence it will achieve the more strength than that of specified grade.
Hope you understood what i said.