Pour it out boys!

I'd wait. That ain't a cheap pour.

Wait. Waiting only costs you a few days. A failure on the slab due to weather issues will cost a helluva lot more.

With the correct additives, it will be a non-issue. However, if you're concerned then just push it back.

Nope.

Either they add blankets or don't place the concrete. Don't budge.

With additives, I wouldn't have an issue with it. Concrete is poured all year long in all sorts of weather.

Needs to be 40 degrees and rising to pour. Personally I wouldn't.

S.A. Aggie said:

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Why are you even pouring Mid January? March is the safe bet for that kind of $$.

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Mr Expert do you even read what you just wrote? So concrete companies just shut down during January and February? SA. Aggie says that no one in Texas is pouring slabs until March. Got it. The whole foundation construction industry says thank you for letting them take a couple months off.

40 degrees and rising is the rule of thumb we always used when I was a construction manager

AgRyan04 said:

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40 degrees and rising is the rule of thumb we always used when I was a construction manager

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Yea I was in stucco contraction. 40 and rising was rule of thumb but that was on 1/4" stucco or plaster, not a multi foot slab. The cure would be my concern over 72 hours or so.

Blankets or wait, IMHO

Jbob04 said:

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With additives, I wouldn't have an issue with it. Concrete is poured all year long in all sorts of weather.

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It is placed in cold weatger when cold weather procedures and precautions are used. That means heat, blankets and cold weather admixtures.

Throw concrete on the ground - especially as thin as this slab - without implementing cold weather techniques and you end up with a garbage product.

Also, if it isnt cured right it will be crap as well. You dont just put it on the ground and walk away and magically it is good.

To add to that, 1 hour from batching us hitting the danger zone for time. We reject trucks after 45 mins. I have seen it start to flash at just over an hour before. Higher psi mix has more portland, more susceptible to flashing.

The biggest question is who is the concrete supplier? If the concrete isn't good when it gets there, it doesn't matter the temperature. That temperature with a good supplier shouldn't matter. Your finishers.need to know what they are doing also.

Hirsch 94 said:

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The biggest question is who is the concrete supplier? If the concrete isn't good when it gets there, it doesn't matter the temperature. That temperature with a good supplier shouldn't matter. Your finishers.need to know what they are doing also.

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False.

Absolutely no. Too many variables. That's too much money to gamble with.

If the plants are open, we generally pour…..BUT, temps during the 3 days afterwards dictate how you protect the product. Concrete curing is a chemical reaction that can be affected by temps and in the "too cold" scenario we use blankets and sometimes heaters when heating from below.
The admixture will speed up the heat of hydration process, so that coupled with blankets - I would go for it. Without blankets and 20 degree temps within the first 48 hours, I would push the pour.
Without proper protection in the extreme cold, the concrete close to the surface has potential of curing problems.

southernskies said:

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I'm placing 300yds this morning. 36F. I've also placed in snow. It can be done with proper planning

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It can be done, sure. I've put many thousands of yards down in cold weather.

But as the OP said - his contractor isn't doing anything to prep for the cold before or after. So no way in hell would I place the concrete.

TENTEX said:

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Admixtures & Blankets. Make sure the finishers are aware of the admixtures so the slab doesn't flash on them and harden up before they get to finish it.

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This.

They should be using both in tandem at those temperatures. Admixtures can't replace loss of heat in a cold snap.

I bet if you tell him you're pushing the pour he will find some blankets. Sounds like he needs to get some money in the bank after the start of the new year and is finding anything he can bill for to keep payroll going.

Unless there is some sort of financial loss situation here like an LD involved, I would not do this. Folks in North Dakota probably have the blankets and knowledge to do this correctly. Probably not so much around here. Sort of like how they handle iced up roads in Texas opposed to areas that frequently deal with it.

mhnatt said:

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Still leaning towards not pouring on Friday.

We did however pour a separate smaller slab two days ago (Monday morning).

While we are on the subject, here is that slab now on day 2. I have a slight concern of the spots (is this a sign of temperatures in the past few days?) and also the pooling of water at one corner but am thinking it is likely okay.

PS - bollards were placed for the planned 18' wide doors.

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Those are probably just bird ponds in the slab, not unusual especially in barns, larger flatwork, etc.

You should be water curing your slabs! Get burlap blankets on that concrete and saturate it.