How much concrete do I need.?
Question:If I am going a concrete slab how much concrete do I need for 10x12 at four inches. How many yard already mixed or how many bags of portland type N do I need if I mix it myself. Please help me
Answers:
Concrete is sold by the cubic yard, which is equal to 27 cubic feet. (3X3X3). Most companies have a minimum delivery amount, and to be honest with you, a 10'X12' slab, 4" thick isn't enough to be delivered in my area. You're only looking at 40 cubic feet, (10'X12'/3), so that comes up to less than two cubic yards. However, mixing that much concrete by hand, is going to be a big deal. I'd reccommend pouring it yourself, if you have any experience with concrete, but you'll need to rent a portable mixer to do it right. Be sure to put some sort of metal reinforcement in it (fence, mesh or what have you), and if it's going to be outside, give it a broom finish to keep it from getting too slick in rain or if you're in the midwest or north, the winter. When you rent the concrete mixer, rent a bull float if you don't have access to one. A bull float looks like a flat piece of wood or metal to which is attached a long handle. If you don't want to float it by hand, rent a power float, but beware, laying a good quality concrete pad isn't as easy as it looks, and if you don't do it right, you'll hate yourself afterwards. Might be best to see if you have a friend or friend of a friend that has experience in this, and barter with them to have them help you. I'm sure you have some skills you can trade them for their help.
I was a construction manager for a couple or three years, and the concrete thing can be a handful.
Best of luck.
At a 10 x 12 size having it poured would be the easiest, unless you have a slab party.
Assume and 60 lb bag (premix) is about 1.5 cu. ft. Calculate that out with your dimensions dividing the cubic by 3 @ 4 inches deep.
It will be 1.5 yards of concrete. if you mix portland the mix is 6 bags of portland to 1 yard of sand. so you will need 9 bags and 1.5 yards of sand. You can also add gravel to the cement. this will add strength and take up space. for example 6 bags portland 1 yard sand and 1/2 yard of gravel.
tiandro is right and gives a very good answer. But instead of going thru all of that, why not just increase the depth (thickness) of the slab so it requires the minimum 2 cubic yards? That will save you from the back breaking job of mixing it yourself.
Keep in mind that concrete set up fairly quickly, so once you start mixing, you can't stop till the job is done.
This is why I don't answer concrete questions anymore.
Answers like this.."if you mix portland the mix is 6 bags of portland to 1 yard of sand."
6 sack concrete for a residential slab are you nuts..
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To answer the question call your local rental yard and see if they have a "spin buggy" this is a small motorized tow-able mixer that they fill at the yard and usually holds 1 1/4 yards. you can get the balance in premixed bags an mix them in the buggy if you need them.
I would order out 1 3/4 yards, (theoretically 1 1/2 yards will be just enough - but I always allow for a little more that may not come out of the truck, sometimes I dug too deep, what ever -
They;re going to hit you extra for a "short yardage" load anyway, I ask for 4000", Type "N", with 15 % fly ash. .
If this is going to be an exterior slab on grade, I'd have them add 6% air entrainement . If the slab is going to have a float or broom flinsh, (Not a hard trowel finish, (Have them add 1 1/2 # @ yard of fiber mesh to the mix). Fiber mesh polypropeline fibers act a binders to hold the concrete together much like reinforcing steel.
If the slab is gling to be hard trowel finsihed , I'd omit the fiber mesh, and have the redi-mix plant deliver 120 S.F. of 6 x 6 10 WWF with redi-mic concrete. 6x6x10 is "wire mesh" . It is "temperature steel that will help hold the slab together as it hydrates, (cures). Roll outr the mesh flat, and connect together by cliping wires from edges of mesh together. You will want to suspend the "Mesh" in the center of the 4" slab .
After you get the slab poured, in the form, struck off, floated, edged, and finished, I recommend that you cut in two expansion joints in the fresh concrete - one each way centerd in the slab to form 4 equal sections - each 5'-0" x 6'-0" ..
Curing. You can wet cure concrete or chemically cure it, I prefer the chemical cure - because you do it once and your done. Go to a DIY Center or your Local Hardware and get a 1/2 gallon or gallon or concrete CURE - NOT sealer , and a cheap 6": brush and a roller & roller pan kit & a cheap wood extension handle (like a broom handle). Dump the cure in the roller pan and roll the roller in the cure and roll it out over the slab (follow mfg instructions). When your done thow the roller & pan away, keep the handle.
Keep the remaining cure. Use the brush and remaining cure to seal the edges of the slab, when you strip the edge forms in the next day of so. Then toss the brush, and recyle any remaining cure.
Good luck.
You need exactly a yard and a half. Use 4000 psi exterior mix w/ entrained air. Pour it out, use a straightedge to screed it flat, then float it to bring the cream to the top of the slab and broom it.
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