Replies

1. 
   calvin_ | Dec 08, 2000 05:30am | #1

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   It's protected in the ground and concrete produces some heat initially after it was poured. I would think you'll be ok tonite. I might be concerned with under it. Don't need that to freeze and heave. Concrete experts autta be by soon to quell your fears or send you out with a blanket. Best of luck on the upcoming work. Maybe it'll warm up.

1. 
   David_Thomas | Dec 08, 2000 05:59am | #2

   *Jed: The concern is that if the concrete freezes before developing full strength (which it gets mostly in 3 days and pretty close in a week), water freezing within it will cause cracks that hurt the structure and make the surface look bad.The good news: As Calvin says, concrete produces heat (from hydration) while curing. The sheeting and hay were good ideas. If it really was a 2-4" slump (a 12" cone of concrete inverted, only slumps 2 to 4 inches) then it be stronger concrete than a mix with too much water. Was it really stiff? Hope so.The longer you can keep it warm, the more fully it will cure and the higher strength it will have. Also, the warmer you get it, the faster it will cure. I'd lay multiple layers of sheeting with a couple inches of hay over each one to create better dead air space. Can you put any heat into the space under the insulation? Throw in a few hair dryers on extension cords. Make a tent of sheeting and operate a heater or stove or stove of some sort. Run garden hose all around and run hot water through it (at maybe 0.5 gpm so your water heater can keep up).I poured my garage slab at 15F but had radiant tubing in it and 2" of blue foam on top. Ran hot water through it and got it up to 75F the next day. Cured just fine. You might well be okay with what you have done so far. But it would be a pain if the surface spalled or you got any big cracks. Do what's easy to improve your chances. The longer it stays warm, the closer to that 3000 psi spec you'll get. -David

1. 
   Gabe_Martel | Dec 08, 2000 02:56pm | #3

   *You're okay with what you've done so far.Important that the ground wasn't frozen underneath, and witht the precautions you have taken you will be fine.Get those walls up asap and backfill asap and all will be fine.Gabe

1. 
   blue_eyed_devil_ | Dec 08, 2000 04:00pm | #4

   *Jed, You're fine. That covering will keep the footings from freezing all winter.Heat rises from the earth and is trapped by the straw. I've seen it muddy under straw in the worst of winter.blue

1. 
   Johnnie_Browne | Dec 09, 2000 03:15am | #5

   *As a lab tech, no problem. It really need to be below freezing for couple days before anything happens and that really only with an elevated slab where wind can get under it. footing are no really a problem. Like other rematked. concrete will generate enough heat to keep from freezing.

2. 
   Jed_C. | Dec 09, 2000 04:20am | #6

   *Thank you all for your kind reassurances. Will be able to sleep tonight for the first time in days.

3. 
   Gabe_Martel | Dec 10, 2000 03:06am | #7

   *Then again.........Maybe it will freeze.Gabe

4. 
   Pete_Draganic | Dec 10, 2000 03:14am | #8

   *How deep into the earth is the concrete and is it in a trench or open pit? Did you have calcium added to the concrete mix for cold weather curing? If it is fairly deep (below your frostline) and covered, I would say you are safe as the ground temperature maintains itself around 55 degrees or so once you get so deep.Pete Draganic

2. 
   Jed_C. | Dec 10, 2000 03:14am | #9

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   Gentlemen: I'm a woodworker, not a builder, so my knowledge of concrete could fit into a thimble. I just poured a footing today for a small addition to our house, in temperatures slightly below freezing (upper 20 deg. F). The mix was a warm-water, 3000 lb., 3/4" aggregate, 2-4 slump with 4.5-7.5 air, whatever the hell that means. Forms are 2X12's, 24" wide with 2 courses of #4 rebar running horizontally and L-shaped verticals every couple of feet. After screeding the top, I covered them with #6 mil. plastic and topped that with about a foot of fluffed-up hay. The thermometer reads 16 deg. F. right now, and I just keep watching it drop. Am I in trouble?