Pouring a 12'x16'x4" slab with bags of concrete.

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Old 06-23-15, 04:00 PM
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Pouring a 12'x16'x4" slab with bags of concrete.

I am pouring a slab that is 12'x16'x4 inches. It's about 2.37 yards or 130 60lb bags. The homeowner bought the bags months ago and can no longer return them. However they are still soft. It will be just me and an electric cement mixer. I would like to think I could pour it all in one long day but probably not. I'm thinking about doing one half one day and the other half the next day. If I do this, what is the best way to make the joint. My plan is to section off the halves and pour the first half leaving rebar sticking out and then the next day remove the board and pour the other half. Any advice? Thanks.
 
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Old 06-23-15, 04:12 PM
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I'm not the pro here.... just an observation based on experience. If that is an outside slab then it needs to be broken up by expansion joints anyway.

That's some pretty ambitious mixing and pouring.
 
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Old 06-23-15, 04:29 PM
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At least 90% of how a slab turns out and if it sags or cracks is in the prep work.
Has all the organic matter been removed?
Has it been dug out so you can have a turned down slab on the outside.
Has the fact that the slab needs needs to be at least 6" above grade been accounted for?
There is no need for a wire or rebar in a properly prepped slab.
I'd pass on doing this job if it was me.
 
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Old 06-23-15, 04:37 PM
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Ambitious is right! *IF* you could maintain the pace of mixing one bag every 3 minutes and spend 3 minute pouring and smoothing it, you would be at it for 8 hours straight... for 2 days.

Not to mention that you will have cold joints between each bag you mix, it will probably not be the best looking pad.
 
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Old 06-23-15, 05:59 PM
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I just finished pouring a 5x5 slab with rebar for a base to begin building a outdoor wood burning pizza oven. 12 bags (80lbs) in a mixer in 100 degree heat and it just about killed me. Lost 5 lbs of body weight in the process. 130 bags Ambitious is an understatement. Factor in extra for Gatoraid.
 
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Old 06-23-15, 06:00 PM
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Not going to happen as you have outlined. I've done some small jobs with bags of concrete and vowed I'd pay the short load charge any time. If you can get a truck in there, 3 yards would probably be a short load, but well worth the peace of mind let alone the over the top effort to mix that much in a mixer. Plus, with premix you would be able to pour this yourself and be done in a day.

If any moisture has gotten to those bags then there is the potential for a poor mix. The bags may seem soft, but how would you remove it and start over?

Personally, and I'm not a concrete pro, I would at least lay down some wire. I would also add a one foot haunch around the perimeter with at least two pieces of rebar. I would also hire an experienced helper, concrete does not wait for you.

Let's see what more pros have to say.

Bud
 
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Old 06-23-15, 06:59 PM
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When I first started in the industry, the contractor I worked for had a 1.5 bag gas mixer and did all his slabs and basements by hand. 130 bags would take 3 of us a good 8-10 hour day to pour going non stop.

Even if you are talking 130 bags of premixed ( which I assume is the case based on your yard calculation) As someone who has literally poured thousands of bags like this the best advice I can give is to not walk, but run away as fast as you can. Truse me, that is not a one man job.
 
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Old 06-23-15, 07:00 PM
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Did 65 bags with three helpers making a porch and ramp at my church. Took nearly 6 hours. Did have a short break between pouring and troweling.
That was all we wanted for that day.
Mixer didn't give out, but we did.
If you can't get help, then don't try it.

RR
 
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Old 06-24-15, 03:44 AM
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Concrete work is hard work especially if you've not done much of it before! 40 yrs ago I poured an 8x12 slab mixing it in wheelbarrows and survived, 25 yrs ago I poured an 8x15 slab using an electric mixer and barely survived, 10-12 yrs ago I helped a friend pour 8 yards [truck] and didn't think I was going to survive. Point being it is hard work! I would definitely check on pricing to have a truck deliver, probably not as much price difference as you think.
 
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Old 06-24-15, 11:10 AM
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Just poured the first 70 bags by myself in 2 hours. Feeling tough and dumb right about now. I let the homeowner know some of the concerns you guys mentioned but he said to do it anyway. Thanks for the advice. This will be the first and last time I do something like this.
 
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Old 06-24-15, 11:13 AM
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Be sure to add the chiropractor charges into your bill . 70 in two hours, you are doing fantastic. Is the owner helping?

Bud
 
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Old 06-24-15, 11:17 AM
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No the owner isn't helping. Fortunately I didn't have to move the mixer much and the pallets of concrete were right next to me. Just screeded it and am going to sweep it. Definitely going to wait til tomorrow to do the other half. That's is if I can walk tomorrow.
 
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Old 06-24-15, 12:14 PM
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One of the best tools I ever bought was a bull float. A three foot wide trowel on the end of a sectional pole. You can smooth out a 15' pour from one side. They do rent them and the finish is about what you want for a patio or garage floor.

My back is hurting just reading about yours.

I have a short story. My neighbor decided to pour the patio around his in-the-ground pool. The problem was, he couldn't get a truck behind his house so needed to wheelbarrow some 20 yards of concrete about 200' to get it back there. Wet concrete has to be one of the most difficult materials to move in a wheelbarrow. We started with about 8 pairs of hands, a couple were very experienced. Dropped to 6 rather quickly, then 4 of us had to work under the lights to finish it up. Usually you can't remember pain, but in this case the memory comes back all too quickly.

Bud
 
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Old 06-24-15, 12:26 PM
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Yeah, I can't imagine that much in a wheelbarrow. I'd like to get a float but I haven't used one and thought if I tried it this time I'd do more harm than good. I'll probably get one and practice on something at my house.
 
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Old 06-24-15, 01:09 PM
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60 bags in two hours?? You must be using premix bags.
 
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Old 06-24-15, 04:04 PM
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you can drop that word, ' probably ', from your vocabulary right now,,,what rebar ? there's no rebar in a 4" slab ? for conc to properly embed rebar, according to aci, you'll have 2" above AND 2" below - that's 4 1/2",,, the only advice worthwhile is hire a hispanic bucket brigade,,, guys, this isn't a serious thread
 
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Old 06-26-15, 07:08 AM
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ah yes...a troll on every forum. should be a universal law.
 
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