thanks equimo i think your reply was just what i was looking for.
the concrete grade actualy specifies the cube strenght in 28 days.grade 30(G30)means 30N/mm2 strenght whereas the concrete mix ratios stands for cement ratio to sand to coarse aggregate.but i still wonder if we can achieve such...
i would like to know how the different concrete grades relate to concrete mixes.for example what concrete mix do i use to achieve a concrete grade 25,as well as grade 15,25,30.
concrete mixes include 1:2:4, 1:3:6, etc