New concrete question?

[Astross89]

I have my new slab (24x35x10 shop. FL) starting tomorrow. When it is poured and finished. Do I need to do anything like keep it moist? I thought I have seen about slow curing. If so. How long before I should I spray it with water?

Thank you.

 

[ConCretin]

The best method is to keep the slab moist for a week or so. You can can spray or pond it with water or cover it with poly or a curing fabric like ConKure. You could also spray on a chemical curing compound.

The goal is simply to prevent the mix water in the concrete from evaporating prematurely. This water is needed to allow to concrete to gain full strength.

 

[Jlbc212]

Spray a light mist over the finished concrete to dampen it. Then cover the entire surface with 4mil poly. The 4mil poly will "stick" to the moist surface and keep it damp. If the slab is exposed to the sun, periodic removal and re-damping of the surface may be necessary. Every slab I've ever done I try to leave the poly in place for a month.

 

[skulldrinker]

I placed my lawn sprinkler in the middle and turned it on everytime it was about to dry up. You'll be doing that alot if the hot sun is out.

 

[6768rogues]

Put curing sealer on it as soon as possible. It will slow the cure and is better than putting water on it. If you do it soon enough, it will penetrate the surface and make it resistant to dusting later.
As concrete cures, a matrix is formed and pores open up. Curing sealer closes some of those pores, slowing the cure.

 

[cory58]

Built my garage in 2 phases. Concrete guy didn't tell me about keeping first phase wet while curing. Three weeks later - shrinkage crack across 75% of the slab. I used free tarps from Harbor Freight to cover the second phase for a week after pouring. No cracks.


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[Astross89]

How soon can/should I cover it? 1hr, 12hr, 24hrs? No idea. Thank you all for the help.

 

[ConCretin]

As soon as saw cuts are done and you can walk on it. The sooner the better

 

[NUTTSGT]

As soon as saw cuts are done and you can walk on it. The sooner the better

You guys cutting the day you pour Doug ?

 

[ConCretin]

You guys cutting the day you pour Doug ?

Hey Eric. It's been tough over the last few months when you are trying to get a finish on the concrete and get it covered but generally yes. There are times when you just can't but the saving grace is that the concrete is setting pretty slowly so shrinkage cracks are forming more slowly.

 

[SALIV8]

My concrete guy didn't spray or cover it at all and I have no cracks. I didn't keep it wet or do a thing.

And it was poured in hot weather, in a pole barn with huge door openings.

 

[Astross89]

Last question. How long should I make sure they wait before the metal building gets installed on top of the concrete?

 

[Falcon67]

I poured on Friday, kept wet until Sunday. Here, they don't water foundations - they just put 'em down and go. You get small cracks here whether you like it or not. When I poured mine the slab stayed over 100F, 130F when it dried out.

As for wait, the house next door has 92 yards in the foundation. Pour started at 6:30AM. The boards were off by 4 PM. I think the framers showed up about 5 days later. Your slab takes usually 30 days to fully cure. I poured on 7/24 and put lumber on it on 8/8. Would have been sooner but had to wait on material bids to come back.

 

[brownbagg]

i like to lay a soaker hose on the concrete and then cover the whole slab with plastic, keep it wet for seven days.

 

[77Birdman]

Best thing to do is spray a curing compound on as soon as the trowel machines are done and it can be walked on. Cut the joints with a soft cut saw and its done! No need to keep it wet after doing that. The concrete will be cured more than enough to work off of after a day, two if you want. I wouldn't put any machines on it for a week or so though. I have placed many a slab large and small with this method to great success.

 

[mcbane]

Last question. How long should I make sure they wait before the metal building gets installed on top of the concrete?

I wouldnt allow a light vehicle on the slab until at least 7 days have passed. The slab would be around 65% strength by then. The thing to avoid is putting a forklift or other heavy construction equipment on it. If that is necessary wait at least a few weeks.

 

[Astross89]

I appreciate everything. Nothing will go on the slab for probably 30 days. So I got plenty of time full to fully cure.