Concrete - When to Pour

Old 01-10-03, 08:42 PM
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Concrete - When to Pour

Maybe someone on this forum could enlighten me...

A few days ago, myself and some buddies were discussing when you could actually pour concrete. It was my understanding that you could pour concrete at almost anytime, with the help of adding antifreeze. I have no idea where I got this from because all the local hardware stores dont recommend pouring below 32 F. Whats the deal? When is it to cold to actually pour concrete? Can anything be added to keeping it from freezing and cracking?

Old 01-10-03, 09:22 PM
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I am an inspector in the construction field and test concrete just about daily. All of the concrete publication specifications I've encountered do not allow placing concrete when the temperature is 36 and falling, but it can be placed at 33 and rising. No concrete is allowed to be placed on frozen soils and/or water. Not that these requirements have ever stopped any contractor from actually placing concrete!! All concrete is guaranteed ... guaranteed to crack! Proper placement with construction joints and not adding too much water are the key to keeping structurally damaging cracks from occuring. Of course, I work in the southeast where the temperatures do not stay below freezing for longer than a couple of weeks and mainly after dark. If the concrete you need to place is structural, i.e. footers, slab, etc. I would err on the side of caution and wait until the weather is more agreeable. If it does drop below freezing at night, place the concrete early in the day and once it has set (5-6 hours), cover with poly and hay or blankets to help keep it warm at least for the first 7 days to ensure a good cure. Heated blankets are the only thing I know about that will keep the concrete from freezing once you place it and they need to stay in place on the poly for the first 24 hours then cover with hay for the remaining 6 days.
Old 01-11-03, 10:22 PM
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I agree with onourown.

Specifications from the ACI (American Concrete Institute):

“Specifications for Structural Concrete”: “When the mean daily outdoor temperature is less than 40°F, the temperature of the concrete shall be maintained between 50°F and 70°F for the curing period.”

There is an interesting article about this subject at

Old 01-12-03, 04:25 AM
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Also, the specs I write for concrete for buildings do not allow the addition of antifreeze.


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