Pouring concrete slab in cold temps

[SteelHorseHD]

I am getting ready to install the outdoor wood burner that I fixed up within the next two weeks. I want to pour a 4 inch slab that is 6' wide and 8' long. The temps here this weekend will be 41 F on Sunday with a low of 30. Monday will be 45 with a low of 25 Monday night. I would like to get the concrete poured on Sunday but the cold weather is making me a little nervous. Is there any way to avoid the negative effects of pouring concrete when it's cold outside? I planned on covering the concrete with plastic after it is hard enough. I am not extremely worried about the finish because it will only be used to set my OWB on and a little bit of firewood. Another thought was that I have a few 12" x 12" x 2" paver blocks that I could set the OWB on until spring if I had to but I would rather get it out of the way so I don't have to move the stove again. Any suggestions would get appreciated!

 

[JimVonBaden]

Mine was recently poured in the low 30's, and then it got colder.

Jim

 

[SteelHorseHD]

Mine was recently poured in the low 30's, and then it got colder.

Jim

No issues with it yet? Did you put plastic or anything over the top of it?

 

[JimVonBaden]

No issues with it yet? Did you put plastic or anything over the top of it?

I wasn't there when it was poured. Here it is late the next day. It was about 45° by then:

Jim

 

[LegacyIndustrial]

Your mason should know what to do.
If the weather warrants they will add anti-freeze (not the car type) to keep the water from freezing.

 

[SteelHorseHD]

Your mason should know what to do.
If the weather warrants they will add anti-freeze (not the car type) to keep the water from freezing.

I am planning on just pouring it myself with Quikcrete. I think I'll just got for it.

 

[TommyK]

I am planning on just pouring it myself with Quikcrete. I think I'll just got for it.

Concrete blankets. If you don't have access to those you can put down plastic and then cover with a thick layer of hay. Cover that with more plastic and weight it down so it doesn't blow away.

 

[canadiantim]

It's important that it doesn't freeze for the first 7 days. Blankets are likely the most you would need in your temps.

Normally during these temps an admixture would be added to accelerate the curing and air would be added to the mix as the voids allow for expansion and contraction without affecting the crystal structure. Quickcrete has a admixture available and I've pasted it below.

QUIKRETE® - Thermo-Lube®
... CLEANERS Thermo-Lube® QUIKRETE® Thermo-Lube® (No. 1905) is a winter admixture that provides thermal characteristics required for a faster set ...
www.quikrete.com/ProductLines/ThermoLube.as...

 

[racerbob4]

Concrete creates a small amount of heat by itself but a tarp and even some blankets will certainly help. I woudn't pour if its going to be much below 28 degrees as the low over night.

 

[ConCretin]

Concrete can be placed in low, even freezing temps quite successfully if you keep a couple things in mind.

First off, don't place concrete on a frozen sub grade and don't allow the concrete to freeze for a minimum of 48 hours.

Concrete generates heat as it hydrates. Providing some kind of insulated cover will retain the heat when ambient temps drop below freezing.

Low temps will slow down the setting process so start early in the day to give you the maximum time to get a decent finish.

You can add calcium (not recommended with rebar) or a non chloride accelerator. These products will accelerate hydration and decrease set times.

Make sure you ask for "air entrained" concrete. The plant will add an admixture that produces a matrix of tiny air bubbles which will greatly improve long term durability under freeze thaw conditions.

That's the jist of it. I think you'll be fine placing as planned.

 

[Cabby89]

Are you going to pour in small batches? Do you have any sort of mixer? I checked and 16 cu ft is a lot for one pour if you dont have equipment. That is 24 80lb bags.


Def. listen to the other advise about making sure your water does not freeze. I would also def. recommend a non chloride accelerator to help.

 

[SteelHorseHD]

wow! thanks for all of the information guys! It's supposed to snow now tomorrow and friday and get down into the teens so it's going to put this project on hold for a little bit. Maybe it will warm back up again before the end of the month. I might just do what I had talked about with the paver blocks until spring time that way I know there won't be any issues. My buddy has a mixer I am going to use when I do it but yes, that is a lot of 80 lb bags.

 

[darkk]

I poured a 6" x 7 1/2' x 28' front porch slab last year just before it snowed. Covered it with a borrowed concrete blanket. It snowed about 4 hrs after the pour. Left the blankets on for 8 days until the snow finally stopped and the weather went up to about 40 ish. Still looks good. Just make sure it's protected for a week or so.