Pouring concrete in sections for storage building


Old 11-30-16, 09:05 AM
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Pouring concrete in sections for storage building

Hello All,

I want to pour a foundation (10 x 13ft) with redi-mix concrete and need to do such in sections, basically three 4 x 10ft sections. I am using some rebar around the perimeters and a few in the middle in addition to wire mesh.

**How should I do the expansion joints? Should I use something like Reflectix which I'm not sure exactly how to use it. Otherwise, should I just use a 1 x 4 between sections, and simply caulk the expansion joints after removing the 1 x 4's?

**Secondly. Is it ok to pour the dry concrete mix on the ground and wet it as I go -versus- mixing and then pouring it? As long as the dry mix becomes wet I don't see how it would matter but I'm no concrete man?

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Old 11-30-16, 02:29 PM
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For such a small pour, you could probably get by with just the mesh, but it never hurts to be overly built Between the slabs you can use 1/2" foam if that is available, or even sill seal foam, since the pours are so small. You can leave the foam or if it is below the edge of the pour you can use an elastomeric sealant in the crack or even Butyl rubber in a tube.

You cannot mix the concrete dry as you describe. That is only reserved for mail box posts You need to mix the concrete in a wheelbarrow or mixing flat in accordance to the instructions on the bag for the right consistency. Too wet or too dry will cause problems later on such as spalling or cracking.
Old 11-30-16, 04:23 PM
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Even though it is a small slab, for 4" thick you are talking about 100 60 lb bags of concrete (or 75 80 lb bags). Even if you do it in three batches, you will have a hard time hand mixing 33 bags of concrete fast enough to avoid problems with the first part being too set to finish by the time you have done all the mixing.

Rent a concrete mixer, you will be glad you did.
Old 12-01-16, 03:44 AM
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Check the price of delivered redi-mix (not the bags). If the truck can get close you can do this all in one pour and be done in a couple of hours. With forms around the perimeter and a screed board across the top this can be an easy one man job. Add in all of the advice you can get here and a bull float and you will be sipping the drink of your choice and smiling at the results.

Old 12-01-16, 11:40 AM
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10' x 13' x 4" = 130sf / 2sf per 80# bag = 65b here @ $4 per bag ($260),,, our 3 guys mix, place, & finish 90b in a day (160sf) w/1.5b elec conc mixer (rent the orange 1),,, we usually groove jnts here in atl,,, our redi-mix min del's 5cy @ $120 per cy,,, yours requires 1.61 cy,,, i wouldn't task 1 of our guys to do the work by himself

neither aci, engineer, nor anyone else recommends/specifies mesh in a 4" slab,,, it must be at the slab's vertical midpoint +/- 5% - that's only .1" or, as concreteists often say, 'v f tight',,, + ALL steel should be covered by 2" of conc top & bottom
Old 12-01-16, 12:19 PM
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@ stadry, I agree with most of the math and especially the comment on pulling the mesh up to mid point, never happens. But the op should still check as the price on the mix can vary and most delivery companies will have a small load charge option.

As for one guy doing the work, if the truck can get close enough to chute the entire pad, I'm 69 and not really good with concrete but would do that by myself any day. Of course having a couple of friends over to help with the beer would make it all go much better. IMO, all of the real work is in getting the forms and rebar set.

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