Fun Days, Cold Concrete

[Hay Dude]

One way to tell concrete froze is it will turn a tan-ish color. My uncle tried to squeeze in a block basement and it dropped into the low 20s. All the mortar joints were tan. I was very young and working for my dad on a weekend when we went to visit and my dad, a mason by trade, had to inform him it all had to be knocked down. Luckily it was only partially completed

 

[Diggin It]

Nawh, this is the usual dark grey to light grey. Temp only hit 30, maybe 29 and only for a few hours just before sunrise. It had several hours to cure before it got that low and we've been warmer than normal for a week or more so the ground was warm.

 

[Streetcar]

You should never pour concrete on frozen subgrade
Also cover the concrete as soon as it firm enough to not leave marks.
If you can leave tarp on for a week.

 

[s219]

I wanted to post a couple pics of what I did yesterday to protect some concrete pole barn footings from an overnight temperature of 20F. This was based on how we used to layer hay over the top of winter concrete pours back when I grew up in New England.

First off, these were 28-32" below grade, which helps a lot (our frostline here is 12"). Due to a rainy year, these holes begin to fill with water as soon as they are drilled, and that eventually covers the concrete -- which is OK for the concrete, but drastically slows the cure time. Because of that, the concrete needs extended protection.

After I poured the concrete, I placed a plastic grocery bag full of leaves on top of the footing. Then I dumped another handful of leaves on top of that to fill the hole about halfway.





On top of the leaves I placed scrap radiant barrier bubble wrap (comes in frozen food shipments my wife gets periodically).



Then on top of the hole is another layer of radiant barrier, a thick layer of scrap carpet or folded up tarp, a piece of cardboard, and a piece of wood to weigh it down.



I've use this method down to 20F temps and it has worked fine. I think having the concrete so far down in the ground makes this a lot easier than if it was a slab or shallow footing. Really, all this method does is provide a couple buffers between the ground temperature and the outside air temperature.