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fthurber
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# Posted: 28 Nov 2010 10:41
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My son and I poured 2 sonatubes worth of cement a couple of days ago but the temps went below freezing the last two nights (as low as about 25). Will the cement be OK? It was the typical consumer grade Quikcrete gravel / cement mix.
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fooboo
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# Posted: 28 Nov 2010 18:14
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With the limited info you've provided, I'd say you are in a borderline gray area about whether it will be successful. If the water in the concrete freezes, it will prevent the concrete from hardening and crack the concrete. I hope you get lucky and the concrete was able to complete it's chemical reactions before the freezing temps kicked in. I'd say you have a 50/50 chance. If I had to bet though, I'd bet you're going to have to redo the pour because the sonotubes are not that big around and the freezing temps probably got all the way into the middle of the tube.
You'll know if it failed because there will be cracks or chunks will fall off the pier once you remove the sonotube.
FYI, You're not supposed to pour when it's under 40F (unless you're going to constantly heat the area while the concrete is curing). To do that, you would thaw out the ground before you pour, and then use blankets and tarps to insulate the concrete while it cures and maybe even use a propane heater under the blankets if it is really cold. There are additives that help concrete cure in cold weather. I don't remember what they are because I usually use a concrete truck and just tell them I'm pouring in cold weather and they change the mix. I think they add more cement and air. In any event, you have to insulate and/or heat the area for several days so the concrete will have it's critical chemical reaction, which won't occur in freezing temps.
One way to do sonotubes in cold weather is to dig the hole, put a 55 gal drum upside down over the hole with a propane heater inside for a few hours to thaw out the ground. Set the sonotube and rebar, use hot water for the concrete mix and then pour the concrete mix into the sonotubes. Put the inverted 55 gal drum back over the sonotube. Rig up a 100 watt light bulb and slip that under the 55 gal drum. Cover the entire drum with a couple of blankets from the house and then cover all that with a tarp. That will keep everything warm enough to cure the concrete. This won't work in really cold weather - like below zero temps - but it will work if you are dropping into the 20's at night and it's getting up above freezing during the day. Hope it helps....
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fasenuff
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# Posted: 28 Nov 2010 18:59
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CALCIUM CHLORIDE
that is the chemical used to "heat" the concrete. Caution when using it though because too much will cause the concrete to over heat and dry out too fast and it will crumble. I have poured many slabs below freezing and never had a problem but use of calcium chloride and insulating blankets make the difference. If you use heat take care not too direct the heat directly on the concrete because there again it may dry too fast. Use indirect heat and not too much. The blankets can be rented at a lot of rental stores and construction supply stores. They are big enough that one per pier should do it in your case.
The calcium will create a lot of heat which the blankets will hold in and unless it is extremely cold should be enough.
Like fooboo said it is a toss up if the piers will be good or not but a couple days of set up time and you may be good.
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MtnDon
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# Posted: 28 Nov 2010 21:03
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Calcium chloride is a concrete accelerant. It accelerates the cement hydration promoting early strength. The concrete can setup in as little as one third the normal time.
The use of calcium chloride is not all pluses though. The addition of calcium chloride can lead to increased corrosion of reinforcing steel. This is most apparent in concrete in wet or damp service like foundations and slabs. The concrete will not test to as high a strength as concrete without the admixture, with everything else being equal.
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elkdiebymybow
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# Posted: 17 Jan 2011 18:09 - Edited by: elkdiebymybow
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At 25, that really isn't too cold. Had you used insulating blankets or provided other protection you would have been perfectly fine. The Earth would provide enough warmth under insulating blankets to prevent a hard freeze at 25 degrees. With that said, I have been around a lot of concrete work in cold temperatures and haven't seen much of a problem with footings or foundations. I would steer clear of any finished flat work in temperatures below 45 degrees unless you don't care about a quality job and want to do it twice.
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