i.e. if a concrete slab is 10m3 how many bags of cement are needed?
well, depending on the water:cement ratio that u desired to have.
You have to consider first or decide on the strenght or class of concrete.
Go to the store and check the bags of cement. Read the instructions and it should tell you the volume result from each bag. If you can't work it out, one of the guys in the store will do the math for you.
Length (in feet) x Width (in feet) x Height (aka Depth) of 2/3 foot (aka 8 inches); and divide the answer by [ 3 x 3 x 3 = ] 27 cubic feet per (cubic) yard = Volume needed. But as others said, you should get some advice; and probably someone to smooth it out, depending on where it is going and what it will be used for (floor in house v. driveway, etc) because you may need to allow for expansion joints, etc; and concrete truck drivers do not like hanging around ( because time is money, and the concrete starts hardening in the tumbler on the truck after a short time).
I am going to assume you are not asking about ready-mix concrete since you seem to understand the difference between cement and concrete. Concrete is a mixture of water, cement, and aggregate. The amount of cement in this mixture usually runs anywhere from 10 to 15 percent. A good rule of thumb is 6 bags of cement per cubic yard of concrete. Since you are asking about cubic meters instead of cubic yards all I can say is a cubic yard is about .76 of a cubic meter, a rough guess would then be a little less than 8 bags per cubic meter. All of this is based on an 80 lb bag. On the off chance you are asking about ready-mix concrete, then an 80 lb bag yields about .6 cubic feet of concrete. you are going to need a large pile of bags, 45 per cubic yard. Good luck with that!
