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Old 12-05-2009, 09:24 PM   #1
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curing concrete slab


I just poured a concrete slab (10' x 16' and 12" thick around the edge, 8" deep in the middle, with lots of rebar---it took almost 5 and 1/2 cubic yards of concrete, which included glass fibers, etc.). I'd done a couple of smaller slabs, but this was too intimidating, so and I paid some guy to finish it. Since it'll eventually be used as a garage he put a smooth finish in it. Anyways, it seems he did a good job, so no complaints there.

My concern here is with the curing. The finishing guy suggested that we just leave it alone---he was adamant that we put no water on the surface and he didn't want me to cover it with a plastic sheet, no nothing. The concrete was poured about 36 hours ago, and the temperature was in the 50s for about the first 8 hours or so, but since then it's been in the 40s, with high humidity the whole time. Tonight the low temp is supposed to be 36 degrees with a chance of a light frost. Tomorrow night it's supposed to rain, and the rain will continue off and on for a few days and the temps will in the 40s during the days with 30s at night (freezing is highly unlikely here, but we do get the occasional frost.

So, I'm wondering if I should do anything. I've read a lot, but the advice out there doesn't seem to be too consistent, so I'm confused (as usual...). In particular, is doing nothing a reasonable approach? Thanks.

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Old 12-05-2009, 10:46 PM   #2
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curing concrete slab


I would say the finishing guy is correct. At the temperatures you quoted, there is no excessive evaporation, so no need to spread any water on the concrete. You said it was humid out, raining in fact, and the temperature is above freezing, so the concrete will cure very well without any help from burlap bags, and there is no real need to cover it at all.

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Old 12-06-2009, 12:10 AM   #3
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curing concrete slab


Agreed - good parameters and conditions for the slab to cure.
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Old 12-06-2009, 06:46 AM   #4
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curing concrete slab


me, too - go back to bed ! ! !

ps - did you joint the slab or is it intended for controlled environment space ? ? ?
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Old 12-06-2009, 10:48 AM   #5
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curing concrete slab


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Originally Posted by itsreallyconc View Post
me, too - go back to bed ! ! !

ps - did you joint the slab or is it intended for controlled environment space ? ? ?
Thanks for all of the advice---I'll be glad to go back to bed!

Yes, there is a control joint across the center. Here are few pictures...
Attached Thumbnails
curing concrete slab-slab3.jpg   curing concrete slab-slab4.jpg   curing concrete slab-slab1.jpg  
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Old 12-06-2009, 04:47 PM   #6
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curing concrete slab


You sure your DIY?? Nice looking job and rebar I might add.

Take his advise do nothing you already did enough.


OH! did you oil them forms to get them off easy??
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Old 12-06-2009, 04:54 PM   #7
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curing concrete slab


Just a late question -

Is the control joint sawed deep enough ot is it just a decorative tooled joint?

Dick
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Old 12-07-2009, 04:20 AM   #8
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if sawed, current specs're thickness/4 OR thickness/3,,, 8" slab would get a sawed jnt of 2 2/3" OR 2",,, then again, since soff-cut saw/method, that's kind of been relax'd,,, i'm old school so hand me a saw
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Old 12-07-2009, 11:16 AM   #9
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Originally Posted by concretemasonry View Post
Just a late question -

Is the control joint sawed deep enough ot is it just a decorative tooled joint?

Dick
It's tooled and not too deep---less than 1" and the concrete in the center is at least 7" deep. Should it be sawed deeper? That doesn't sound like it would be an easy thing to do...
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Old 12-07-2009, 11:28 AM   #10
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Originally Posted by SULTINI View Post
You sure your DIY?? Nice looking job and rebar I might add.

Take his advise do nothing you already did enough.


OH! did you oil them forms to get them off easy??
The groundwork (including rebar) was all done by me. However, I wimped out and hired somebody to finish it. Having seen most of the finishing process (I had to miss some of it due to that pesky real job of mine...), I wouldn't hesitate to attempt it myself if I ever have something like this again, particularly if a super-smooth finish is not required.

A couple of final questions:

How long should I wait before using the pad? It's been 3 days since it was poured, with cool temps (40s and 30s) and rainy/snowy. I'm in no hurry and want to be sure I don't damage it, so I was thinking I'd wait a week before I touch it. Even then, I won't be parking a car on it or anything like that. For this winter it's just going to be covered by a "portable garage" (basically, a glorified tent) and used for light to moderate storage.

Second, is there anything that I should do to treat the concrete surface before using it? Thanks.
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Old 12-07-2009, 12:46 PM   #11
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A week should be fine for light storage (quad, snowmobile, etc) but I would wait an additional week before parking a car on it. As for the curing process, I'm on board with everyone else here... just leave it alone, grab a beer and watch it cure As for control joints, get a concrete-cutting blade for your circular saw, and GRAB A DUST MASK (you don't want to be breathing that stuff) - do it when the wind's not blowing. You also don't have to throw tarps over all the nearby plants and shrubs... only cover the ones you don't want to die. The concrete dust is a real plant & shrub killer. Follow the above formula for depth of cut. If you want to REALLY err on the side of caution (and you still have plenty of blade left , snap a chalk line and cut another one down the middle. They'll be little dust & dirt catchers, but it's better that having a crack develop. You can always fill the cut lines with a non-hardening caulk after if the dirt bothers you.
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Old 12-08-2009, 10:06 AM   #12
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Looks great. Did you put a base under the concrete, or do you just have naturally sandy soil? Also, what are the two holes in the middle for, and what did you use to bend the rebar?
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Old 12-08-2009, 06:45 PM   #13
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What will you be storing on this slab? Just curious.
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Old 12-10-2009, 12:11 PM   #14
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Looks great. Did you put a base under the concrete, or do you just have naturally sandy soil? Also, what are the two holes in the middle for, and what did you use to bend the rebar?
Drainage is good here and so a local concrete guy told me not to bother with any sand or gravel underneath. This is earthquake country, and it seems to be fairly common to add a few holes to help keep things from shifting when the ground shakes a little bit. As for bending the 1/2" rebar, I did that all by hand. It was a workout---I felt like I was wrestling and anaconda.
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Old 12-10-2009, 12:17 PM   #15
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Originally Posted by MI-Roger View Post
What will you be storing on this slab? Just curious.
For now, it's going to be covered with a "portable garage" (a tent-like thing) and we'll put usual garage stuff in there. Most important of all, it'll be used to keep the pellets for our pellet stove dry. Eventually, we should have enough storage that we can use it as a real garage, although it's probably only practical for a relatively small car.

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