There are 3 standards in india
2. M20( 1:1.5:3)
3 M15 ( 1:2:4)
M20 is the minimum for PCC and RCC for Residentail building
But as you say about 1;3;3 In this mix sand contents are more and this mix is OVER SANDED and as much sand than requirement reduce the strength. Generally contractor use over sanded for easy finish.