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I want to put a concrete slab in my shed. I know I can get sakrete, but, I don't think that is what I want, I want the mix that I add sand (2 parts) and gravel (3 parts) to, and a way to figure out how many bags of this mix I am going to need. If my formula is wrong, let me know too, thank you in advance.
All I know is concrete comes in different mixes.
A 5 bag mix means 5 bags of cement, 90 lbs each, to 1 Cubic Yard on sand, gravel etc. You can add small rocks to this to make it go farther.
5 bag is used for a floor like yours at 3½" thick.
6 bag or more is used if you are going to have cars or pickups on it. 5" thick
Large trucks & heavy equipment need 6" or more + rebars.
Your slab should have wire mesh in it.
If I remember right, mixing in a small home mixer you need 2 shovels of cement & 10 of sand or gravel. Rocks are extra, don't count in the 10.
Becareful not to add to many rocks. Do a little & soon you will get the hang of it. That' all a professioal is; experience.
Good Luck,
Bernie
I was just reading today in my chicken book that you can acutally mix dirt with the cement to make a floor. Don't even need the sand/gravel. Now, that is for Chickens mind you, depending on what you're putting in your shed would make a difference how strong you needed to make it.
I'm a bit new still to DG, and just stumbled across this thread. Having worked in the ready-mix concrete biz since 2000, I'd like to shed a little light on this subject. Concrete isn't a real difficult thing, but it can be messed up just as easy as baking a cake. For simple 3500 psi concrete(most residential construction), mix is roughly 625 lbs sand, 885 lbs rock and 260 lbs cement and add water to make 1/2 cubic yard. All cement does is bind the rock and sand together like glue, with microscopic air pockets that allow it to flex in the freeze/thaw cycle. You cannot use just dirt to have any strength- to many micro organisms that will die, decay and leave weaking pockets. When adding water, only enough to be like a thick pancake batter. To much water weakens concrete, so you don't want soup. Don't add water to top surface of concrete before finishing off, as this can lead to flaking(all that "good" cream you pulled to the surface has no strength and will flake off). For anything requiring more than a couple of yards, best to order from a ready mix company. For a simple shed, I would certainly use the pre mixed bags. A 5'x4'x4" is only .25 yard of crete. Large patios(beyond 4x4) and drives need to be reinforced with either fibermesh or steel. For cars and RVs, a 4" slab is sufficient at 3500 psi. The steel and fibermesh doesn't particularly strengthen the concrete as much as it allows it to flex as a whole(stabilization,like foundation walls), and thus preventing cracking. Hope this helps, and can use your local readymix company website for more info.
