DEAR ALL

I WANT TO KNOW ABOUT A VERY BASIC QUESTION ABOUT CEMENT

1. WHY THE BIS STANDARDS SELECTED 3DAY,7 DAY & 28 STRENGTH TESTING ? WHY NOT OTHER DAYS OR MONTHS OR YEARS?

2. WHY CEMENT GRADES ARE 33,43 & 53 OR 63 GRADE , WHY NOT 35 OR 45 ETC.PLEASE DO REPLY IN DETAIL .

 

THANKS

RAJU