Ok, so i've got 2 concrete slabs to lay, one is 5.4m x 5.4m and the other is 5m x 5m, both 4" thick. Q1. how much concrete will i need, i get it to around 3 cube per room. Q2 this is the killer, because of where i'm doing this we can't get a premix in so it's got to be done by hand so how much sand, stone and cement am i gonna need. Q3 where can i get a new back from when i've done all this mixing lol Thanks Martin.