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Many of the problems with cold weather can be overcome by the ready mix producer. Here are a few things to keep in mind:
Hot water—Your ready mixed concrete producer will usually have, and use, hot water in the concrete when the weather turns cold. Most producers will try to have the concrete be at least 65°F when it leaves the plant, which is generally good enough depending on air temperature and thickness of the concrete element.
Specify the slump at less than 4 inches and use air entrained concrete to reduce bleeding.
Accelerators—Since colder weather leads to colder concrete, the set time can be delayed. Accelerators added to the concrete can keep it on schedule. Addition of 2% (by weight of cement) of calcium chloride is the traditional way to accelerate the hydration reaction—it is very effective and reasonably cheap. But—a big but—that much chloride can lead to corrosion of any steel embedded in the concrete (like rebar) and it can lead to a mottled surface appearance with colored concrete.
Thank you very much for your help.
Is there anything else we should know or be aware of when pouring concrete in the cold weather?