To pour a 9ft.x9ft.x4inch concrete floor.

Hello casinorose39

The information is located here:http://209.85.173.104/search?q=cache:xRV2NcEpO58J:www.concrete.net.au/pdf/Volume.pdf+dry+mix+concrete+volume+weight&hl=en&ct=clnk&cd=6&gl=nz&client=firefox-a

For some reason the main weblink is not presently working, so use the above link.

You want your answer in Imperial measure, and the website above is in metric measure.

But you need to do something for yourself, don't you, so happy converting.

Kind Regards....

you will need enough 80 lb bags to fill a void of 27 cubic ft, or 3 yards of redi-mix from a local plant, which would be easier and more consitant for a better slab.

sorry, i was distracted by my dogs, i meant 1 yard, 3x3x3=27-1 cubic yard- good luck!

My arithmetic works out to 27 cubic feet, but that is equivalent to 1 cubic yard. I agree that with that quantity it is a whole lot easier to have it delivered in a truck rather than mixing it by hand... unless you have a pretty big crew to finish it while you are mixing and pouring. Otherwise by the time you have it poured, the starting end is getting pretty stiff and might not be workable.

Bill

Another thought that comes to mind is that if you are framing the slab with 2x4s, The 4 inch dimension is only 3 !/2 inches. Also if you do not know what a "scree" is, you might want to do some research at the public library. This has to do with the finishing of the concrete.

Bill

Hello Sciesis2

<"....if you do not know what a "scree" is, you might want to do some research at the public library. This has to do with the finishing of the concrete.">

A "Scree" is a covering of loose rocks or stones on a slope of a mountain.

The slope is then called a "Scree Slope".

The person at left is crossing or "traversing" a "scree slope".

A "Screed" is a levelling tool, generally a long straight metal bar, which is moved from side to side rapidly, at the same time moving forward slowly, to level the concrete surface of a path, floor, roof, roadway or similar.

There are power-operated screeds, also the more common type used by one or two persons.

Hope that explains the difference.

Kind Regards....

9 x 9 x ¹/₃ = 27 cuft. The bags may have printed on them the made-up volume/bag, else ask the supplier how many bags for 27 cuft (1 'yard' of concrete).

I don't know what kind of yards you do have over there but, down here in Houston, it takes a lot much more than 27 cuft to get a yard of concrete!

We have heard that everything is bigger in Texas, but to be nice, I will refrain from telling my Texan joke.....

Don't be shy, I like a bit of flattery

Do you really want to hear it? its NOT flattery......

I got it from your first mentioning of the joke, but I cannot conceive that a kind person like you would say anything unflattering about anybody (even from Texas)

P.S. I intend to pour a 6'x6'x4" slab and I remembered that we do have good answers on this subject. This is how I found your answer. Sorry for the delay.

Everyone gets jokes told about them at some point, the Texan joke always made me laugh, but a friend of mine in Denver ( a Texan!, many live in Colorado!!), did not find the joke appealing at all!! His problem!!

But maybe I had better keep it to myself anyway.....

Only if you have a large yard....

27 ft³ =1yd³ in the western US also, or 3 ft x3 ftx3ft =1 yd³

27 ft³ =1yd³ in the western US also, or 3 ft x3 ftx3ft =1 yd³

^{3 x 3 x 3 I understand but..still not enough for my yard}

Well, you didn't ask for my opinion, but that never stops a true Buttinski. That's too big a slab to pour with readimix - the first pour will long since be set up before you get to the last. As a rule, somewhere in the neighborhood of about 20 bags is all you want to pour.

Keep it wet and it won't set...float 2" of water on top...use expansion joint material/fiber board works great then mix second pour. Keep water on top for 5-6 days will set well and cure evenly.

Hmm, so how does concrete set underwater. You have 90 minutes to place concrete and grade the surface, unless you add a retarding compound.

I believe it sets much slower and the result is also then significantly stronger.

Years ago when concrete yachts were "in" you had to keep them wet for a long time with the "curing" phase....

No do not bother to ask, I would not set foot in one, I like boats that have positive buoyancy even when holed!!!

Conversely, drying quickly reduces the strength of concrete significantly. The use of a plastic foil between the concrete and the ground for a slab, not only stops groundwater rising later, it also improves the strength by slowing down the loss of water during curing.....covering with another plastic foil at this time not only gives some protection when frosty, but also improves the strength by keeping water in longer....

Builders are notorious for not following such methods as they feel they are losing time, which is why I would recommend someone who is having building done, to be around and keep a watchfully eye!!! It saves a lot of aggravation and money later.....a digital camera is also a good idea.....

The set time and cure time are different. The set time is the time in which it must be placed before substantial reaction and solidification occurs, this is usually about 2 hours or less from the time water was added (The ACI require placement within 90 minutes). The cure time is the time it takes the concrete to develop strength. Wet curing concrete allows it to dissipate the heat of hydration and form crystals slower, allowing a less porous and stronger internal structure. The standard is to develop strength with in 28 day (this is when you break cylinders to determine the strength), unless a retarding agent is used, ultimate strength is 56 days (though it will continue to cure a little even after that).

Of particular note, i believe most ships when holed will not have positive bouyancy, since even the wooden yachts have a large amounth of metal inside them.

Weight of bag divided by 133.33 will give you cubic ft of coverage.

80 lb ÷ 133.33 = .60 cubic ft.

9ft * 9ft * 4in = 27 cubic ft

27 cubic ft ÷ .60 cubic ft = 45 bags

Thanks for the conversion. I was going to guess at 2/3 cu. foot per bag (which is close to your .6). I have a couple of used bags in the side yard which I could look at but it is cold, dark, and pouring down rain here. So Thanks again

Bill

This may seem extravagant but in all my years i have yet to have a cracked foundation or wall.

That's commendable if you are not a professional of the concrete.

Thank you indel. No not a professional in the concrete business just a D.I.Y home builder sometimes. Elec Eng LC my field, tool and die making second.

Hmm, intersting. In my 12 years as a CE, I have seen many cracked foundations and slabs. However, I am usually called in when these things occur to investigate. Nearly every major failure in a concrete system has been because of improper compaction or moisture conditioning of the supporting subgrade materials, or the use of inappropriate materials or thickness of materials (Usually an issue that occurs on expansive native subgrades). Frequently, when there is something wrong with a concrete slab, usually (With a couple of exceptions) I have found it is not the slab or footings. Flaws in the concrete work are usually detectable within 14 days or less and can easily be seen. Frequently what I have found is the flaws that arise after construction, the major flaws, are something buried that a contractor thought was not visible and would be hard to implicate as a cause (wet spots, variable compaction across the slab, thinning out of the engineered fills, contaminated or unsuitable fills). contractors are very aware that flaw in construction that people can not readily observe are more important to address than those that are hidden from public view.

Ratios (cement, sand, gravel) are: 1:2.5:3 for floors, light duty, like driveway etc.

Best is to re-bar lightly with 1/4 bars (#2b bar)...4" thickness is just right for this application.

The final volume of the wet concrete mix is approximately 2/3's of the dry mix. you have all the info you need to calculate your mixture.

Wangito.

Why tie all that bar when you can use heavy screen?

It is only a matter of saying. For me, re-bar could be anything: re-bar plain suspended bar, mesh, screen anything you want. I said this, because the poster didn't specify his intended usage.

Wangito.

Personally, on slabs on/in the ground, I use heavy mesh and tie it well in to anything surrounding it that is already there, I actually overdo the mesh etc.. according to a friend of mine who sometimes helps by watching me!!!

Not that I do this very often you understand, but I hate ever having to do something (anything!!) twice and that rarely happens!!

In my new garage floor extension(14" thick to match original floor as well as filling in a depression behind the garage caused by removing two small trees), I put two thick mats, one on the rubble I had packed in and well vibrated an another around the middle, tied to several bricks.

Both meshes were wired to very long wood screws which were placed 3/4 of their length in screw anchors in the side of the old floor slab....it has been there now about 18 years, with three walls built on it to extend the garage further, no cracks or separations. You cannot even see the join anymore, though I know where it is!!

Hello Andy!

You wrote;

"But I hate ever having to do something (anything!!) twice and that rarely happens!!"

How about Well, doesn't matter, let's forget it.

Wangito.

There is no need for concrete calculators,websites and ad nausem.

1. Figure out volume required.

2. Check any Ready mix concrete bag. It will tell you on the bag how

many cubic metres or cubic feet it will fill when mixed to the directions.

3. Divide your volume by the bag's volume = # of bags needed.

UFG

168 lbs per cubic ft 27 cf 56.7

You have received excellent help already, but my one concern is that a 4 inch thickness is pretty thin......to my mind it needs stiffening up or thickening up or both.....thats my 2 cents worth!!!

I guess you are weighing in then?

Well I did not see at that point anyone saying that 4" with no strengthening, is mostly too thin for anything....we have also had people with garage floors of this thickness that started to break up......since I posted, someone else has basically said the same thing.

I have poured a few slabs in my time, learnt with my Dad when I was about 4 years old, helped him build a garage that is still in use today!!! The doors he handmade have been replaced with an "over and under" door, thats all!!! 58 years ago!!!

I have poured two slabs here, one joining onto an old slab of the garage, that was 20 years ago and there is still no crack between the old and the (relatively!) new. I used a lot of matting and drove 8" wood screws into screw anchors that I had drilled in the side of the old slab and wired the piece of screw sticking out to the heavy mats....even built 3 new walls on it as I extended the garage, still hasn't moved or cracked....but I do believe in heavy duty!!!

Sounds like you have a ton of good advice already, so this will be brief. To sumarize, you are looking at about one cubic yard, which weighs around 4000 lbs, which is equal to 50-80 lb bags. That is a lot for a small backyard mixer. One advantage to ready mix is that you will get better air entrainment, and entrained air is important to the durability of the finished concrete. You will also get better concrete if you order 4000 psi (6-bag) mix, this will be stronger and last longer and not cost that much more. Don't pour the mix too soupy, keep the slump to no more than 3 or 4 inches. The ready mix driver will understand what that means. The drier the mix is that can still be worked, the better the concrete will be. Ideally the water/cement ratio will be no more than 0.45. Also, you want to consider adding some steel reinforcing in the form of a welded wire fabric, 6x6 W1.4xW1.4 (6" mesh, ~1/8" wire size). This will control temperature and shrinkage cracking. I also agree with other opinions that say that 4" is a little thin for a slab. However, it would be OK if you have a good compacted crushed stone base (6" to 8", 100% crushed stone, No. 2 or No. 1, or 3/4" minus crusher run), on at least a foot of compacted clean well drained gravel. If this is a garage floor, increase the thickness to 6" and the mesh reinforcement to a 4x4 W1.4xW1.4 . If the loads are really heavy you might want to go 8" thick and use No. 4 bars top and bottom on a 1 foot pattern for structural reinforcing, the same is true if you have a poor base or subgrade. (units are US units, convert to SI as/if necessary). Hope this helps, follow the other good tips and good luck on the project.

Good advise given by all and 4" is fine for building a lawn shed, barbie, sauna and a pad to park a sedan or utility trailer/RV upon.

Use of lathe, wire mesh, screen or I've used a mattress inner spring assembly (:

Ask your building supply or rental for use of a concrete vibrator to remove air bubbles as this will make a stronger pad.

Many concrete or building supply centers offer concrete delivery from 1/4 yard which is about as much as one man could manage at any one time, they mix according to application specs or your preference. Bulk delivery also makes blending a color more feasible.

Bulk delivery is the only way, I totally agree.....

I recently helped my brother in law pour some concrete to increase the deck area around his pool.From my experience in that endeavor I will offer the following unsolicited advice.The 80lb bags get heaver as the day gets longer. I can't explain the physics of it. ( perhaps some one here can provide a formula?) but its true, TRUST ME! There were 3 of us working on the pool deck expansion and we all agreeded that 60lb is the way to go. We poured about 6900lbs total that day. We started with 60lb bags but did not have enough. We had to finish with 80lb bags and by the time we poured the last bag I'm sure it weighed at least 110lb. It will cost a little more but your back will appreciate the investment.

Good Luck

Hello casinorose39

Remember how concrete actually sets.

NOT by drying.

Concrete sets by needle sharp crystals growing through the aggregate/sand mixture.

When curing is complete, the matrix is very strong in compression, but weak in tension - that is why steel reinforcing (strong in tension) is used.

So for strength long term, you need:

1. Correct mixture of Cement/sand/aggregate
   
2. Steel reinforcing - in correct place in the slab
   
3. Concrete to be kept damp during the curing time = 28 days or more

A finished slab of concrete is a wonderful sight to behold, more if you mixed, poured, screeded it and then waited for the slab to cure fully.

If you intend a waterproof concrete, add to the mixing water a water-miscible latex, (check your supplier for the correct proportions of water/latex), to make waterproof concrete.

Ordinary concrete to actually dry out after the cure is completed, takes approximately one month per inch of concrete slab thickness, plus one month.

If you intend ceramic tiling or laying slate on the slab, for a four inch slab, it will be five months (4 + 1 = 5), before the water which is required for the complete crystallisation process, leaves the slab.

For those interested, concrete and epoxy resins have the similar process of growing matrices of long-chain molecules throughout the setting mixture, to make a strong article.

Kind Regards....

Perhaps the yard refers to ale.

Kind Regards....