Pouring/curing concrete in cold weather

[Ryan Browne]

So, I'm finally ready to have the slab poured in an addition I'm putting on an existing pole barn on our property. Only problem is that the weather is unseasonably brisk. I hopefully have a guy lined up to pour the slab next monday when the high temp is 41. The low Sunday night is 31. He's talking about adding chloride to the mix, and the concrete company is using hot water. The low Monday night is forecast to be 22, and they just keep getting lower after that, including lows in the teens at the end of next week with highs below freezing.

My thought is to do the pour on Monday morning and then that night cover the slab with a sheet of plastic and then blow in some chopped straw using our bale chopper. It wouldn't be a problem to put down 6" even. I could leave that straw there for a few weeks if needed. I could also hang plastic on the walls, which do not have siding up yet and won't for a while. I did hear that the temps aren't supposed to stay this cold. The weather guesser on the radio suggested that mid-november will have highs in the 50s.

By the way, the slab is 16'x24' and 3.5" thick, reinforced with rebar. It's all pitched to a floor drain. There is a 7" deep lip around the first 10" of the perimeter.

Anyone got experience with this sort of stuff? I'd really like to get this poured yet this fall, but if it's gonna result in a crappy end product, obviously I would rather wait.

Thanks!
Ryan

 

[Cat 525]

Kevin Huskil l

 

[Stump Shot]

So, I'm finally ready to have the slab poured in an addition I'm putting on an existing pole barn on our property. Only problem is that the weather is unseasonably brisk. I hopefully have a guy lined up to pour the slab next monday when the high temp is 41. The low Sunday night is 31. He's talking about adding chloride to the mix, and the concrete company is using hot water. The low Monday night is forecast to be 22, and they just keep getting lower after that, including lows in the teens at the end of next week with highs below freezing.

My thought is to do the pour on Monday morning and then that night cover the slab with a sheet of plastic and then blow in some chopped straw using our bale chopper. It wouldn't be a problem to put down 6" even. I could leave that straw there for a few weeks if needed. I could also hang plastic on the walls, which do not have siding up yet and won't for a while. I did hear that the temps aren't supposed to stay this cold. The weather guesser on the radio suggested that mid-november will have highs in the 50s.

By the way, the slab is 16'x24' and 3.5" thick, reinforced with rebar. It's all pitched to a floor drain. There is a 7" deep lip around the first 10" of the perimeter.

Anyone got experience with this sort of stuff? I'd really like to get this poured yet this fall, but if it's gonna result in a crappy end product, obviously I would rather wait.

Thanks!
Ryan

That's a pretty good plan, keep it covered up plenty long for it to cure. Might want to put plastic on top of the straw as well.

 

[Ryan Browne]

That's a pretty good plan, keep it covered up plenty long for it to cure. Might want to put plastic on top of the straw as well.

Thanks Steve. One good thing about growing stuff in hoop houses is that one thing I've got plenty of is used sheet of plastic. I suppose I could get really fancy and make a compost pile on top of the slab!

 

[Stump Shot]

Thanks Steve. One good thing about growing stuff in hoop houses is that one thing I've got plenty of is used sheet of plastic. I suppose I could get really fancy and make a compost pile on top of the slab!

You can keep it from freezing the whole winter like that if you want to.

 

[huskihl]

Need to keep it dry and above freezing for a couple weeks. If it gets wet and stays wet, you need to double the amount of time. Make sure he pours it early enough so that it’s reasonably hard enough that night to put hay and tarps on it without messing up the finish

 

[huskihl]

Put hay down first and plastic over that. Keep the hay dry too

 

[Ryan Browne]

Dry straw and tarps I can do, no problem. So, yes to calcium chloride? And go ahead, or put it off until next year?

Here's what I'm worried about. He wants to pour Monday because it's supposed to snow tomorrow morning. Wish we could do it anyway though.

 

[huskihl]

Is it inside? Or can the walls, door openings, and ceiling be tarped off?

Those low temps scare me

 

[stihl livin]

Ryan you mentioned you could wait till next year and for the new building I’d wait just so you don’t have issues. One thing I’ve learned though is if we have a wet spring you might not get to pour as early as you’d like. Maybe try and get the building up first but I now this is a freestanding building and you are thickening the ends of the slab to act as your footings so that’s not possible. Wish I had better help for you

 

[exSW]

You are in a building that you ca seal up?You have ample quality straw and plastic. Concrete makes it's own heat. I'd go for it. And have many times.Does it have southern exposure?

 

[Ryan Browne]

Morning gentlemen, thanks for the replies.

The building is currently not enclosed. I have girters up and trusses on. I could definitely enclose the walls with plastic and run a heater. It does get good sunshine. The roof is questionable. It's possible that I could get the purlins on in the next few days and get steel up in the first few days of next week.

Waiting until next year would not hinder the rest of the building. Not putting up stud walls or anything. I guess that perimeter ditch is just to reinforce the slab as I understand it, not really a footing. Only problem is that we start washing vegetables in April. That's what this addition is for, and we'd sure love to be in there right away in spring instead of washing outside for the first month.

 

[kingOFgEEEks]

puts civil engineer hat on

As long as the concrete has reached 'final set' before it freezes, the ultimate strength of the concrete won't be affected by slight freezing. What it will do, however, is change the cure time of the concrete. Basically, every concrete mix is aiming for a certain strength at 28 days. Every minute that the concrete spends below freezing between the final set and 28 days doesn't count, and you will need to add to the 28 days time period.

I echo Kevin - get it poured and set, then cover and keep it as warm as you can. You will have plenty of heat coming off the concrete for the first 24-48 hours, and then after that, your insulation will keep things warmer, but maybe not thawed. If you can swing the expense of a glycol heater for a week, it would cure your headaches:

 

[cgraham1]

Concrete makes it's own heat.

This^

The drying process actually puts off heat... if it’s right around freezing, that should be enough to keep the concrete from freezing, especially if you cover it with plastic/straw.

We build all winter around here, and with low temps generally in the high teens to low 20s and I’ve only ever seen/heard of one slab freezing.... But it was a mess and you definitely want to avoid that.

 

[huskihl]

This^

The drying process actually puts off heat... if it’s right around freezing, that should be enough to keep the concrete from freezing, especially if you cover it with plastic/straw.

We build all winter around here, and with low temps generally in the high teens to low 20s and I’ve only ever seen/heard of one slab freezing.... But it was a mess and you definitely want to avoid that.

It’s a little different when it gets to 20 at night and 45-60 the next day.
Concrete gets the heat pulled out of it pretty quick when the ground temp is 35 and the air stays below 25 for a few weeks. 2” of snow won’t melt off it when it’s 30 the next day

 

[Wilhelm]

Hot air gas cannon?

 

[Ryan Browne]

Well, it was warm and sunny today. I covered the pad with clear greenhouse plastic and just now I covered it with some concrete blankets a neighbor offered. The soil temp outside the building is 34-35 and the pad is at 40-42. The low tonight is right around freezing, so hopefully I stay close to 40 under the blankets. I'm gonna plan on getting the blankets and maybe straw on tomorrow night after we pour and then think about making a heated tent on Tuesday.

 

[Ryan Browne]

Concrete got poured at noon today. It's still 37 degrees here and I stapled some plastic halfway up the walls to keep the breeze off it. Not dry enough for blankets yet, but I'm gonna give it a couple hours and probably put them on them.

 

[Ryan Browne]

Alright, it's all tucked in under blankets. It's set up pretty good it seems. I'll probably blow some hay in there tomorrow.

 

[Stump Shot]

Alright, it's all tucked in under blankets. It's set up pretty good it seems. I'll probably blow some hay in there tomorrow.

We poured a garage slab this time of year and covered it up with those blankets for the entire winter so it was ready in spring and could work while road limits were on. It never did freeze the entire winter, got covered up with snow and pulled heat from the earth I guess.