In extreme weather they tend not to pour, but I think the limiting factor is is more worker safety and comfort than the concrete not setting properly. Concrete hardening is actually a exothermic calcification reaction and therefore creates quite a bit of its own heat. I think they run into more problems in extreme heat where they actually have to douse the concrete with water for days afterwards to keep it cool enough for the reaction to continue evenly.
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Harry C - Urbanize Chicago- My Flickr stream HRC_OakPark
The man who trades freedom for security does not deserve nor will he ever receive either. B Franklin.
Wish I could go. Best of luck everyone and thanks for toughing the elements. Bring a jug of cocoa with maybe a little something extra in there to keep you warm and toasty. Haha.