There are specific temp mixtures and additives to allow for low temp pours

The additives are expensive iirc

If your contractor knows what he is doing I would defer to him BUT I would not do this on any of our projects.

A couple of comments...

Concrete curing is actually a exothermic reaction and gives off heat when it cures. The problem is usually not the first night but the second and third night when the majority of the reaction has been completed but there is still a significant amount of water in the mix.

Yes you can use additives but they only lower the acceptable temperature range by a couple of degrees.

Code in VA requires 2" of foam board (R-10) to go 2 feet deep around the perimeter AND also 2 feet horizontally to create a thermal break from the exterior. This is for living spaces so may not apply to your case. Either way it is much colder where you are and 4" deep won't be enough.

The obvious thing about concrete is once it's poured you have to deal with it regardless...why risk it?

quote:

Originally posted by smlsig:
The problem is usually not the first night but the second and third night when the majority of the reaction has been completed but there is still a significant amount of water in the mix.

This is what he was explaining to me this morning. The second and third days are the important ones.

Also, to be clear, the ground is not frozen. It will frost as the temps drop at night though. With plenty of warmth indoors (the building is insulated well), the foam around the edges, and possibly some black plastic with straw around the outside, he's not worried.

Of course this is all contingent on me being able to get the heater in there and hooked up. If everything goes as planned, the electrician and propane guys will be out early next week, so...we'll see. The way my luck goes it's anyone's guess.

Some concrete pads have radiant heating tubes run through them. That would probably be extreme for what you need, but if you were able to keep it at 60 degrees for a few days the temperature wouldn't be an issue.