Cold Weather Pour - Masonry - Contractor Talk

Cold Weather Pour

 
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Old 12-14-2019, 02:16 PM   #1
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Cold Weather Pour


While the best practices for cold weather pours are well established, I have a project that seems like it is probably Ok but...
This is a small 12"X12"X 20' in ground footing using bagged ready mix and #4 rebar that will support an above grade 2' max retaining wall. I plan to pour the footing now and complete the job in the spring.
The temperature will be fluctuating between 35 and 55 degrees for the next 2 weeks. This area rarely experiences freezing temperatures other than occasional freezing temps for a few hours in the early morning.
What will happen if I just pour the footing in this temperature range?
Will the extra long cure time and/or low temperatures weaken the concrete to the point the it will matter on a structure with such insignificant loading?
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Old 12-14-2019, 02:32 PM   #2
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Re: Cold Weather Pour


I would pour it, when it's hard enough to walk on, cover it with poly, fill the trench with straw and fold the poly back over the straw to try and keep it dry, or just do it in the Spring.

My biggest worry would be having a trench open all Winter and some unsuspecting fella step into it and get hurt.

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Old 12-14-2019, 02:46 PM   #3
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Re: Cold Weather Pour


While I see how erosion around the site could certainly be a problem, you think rain could damage the concrete that will be mostly set and very hard by the time the next rains start up?
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Old 12-14-2019, 02:52 PM   #4
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Re: Cold Weather Pour


No, rain won't hurt the concrete, I was concerned about frost. An open trench with a footing in it will most likely get frost heave in the Winter here, and it doesn't all that cold where I live.

I read your first post again, you don't get frost so I would not be concerned about that then.
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Old 12-14-2019, 10:51 PM   #5
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Re: Cold Weather Pour


Use Hot water.....

Heat the ground BEFORE the pour....

Blankets, the WHOLE winter...or straw....

Add 2-4 Pounds of type II Portland Cement for every 80 lb. premix bag of concrete...~ 1 to 2 "extra" 1/4 bbls of Cement per yard = quicker time to frost proof concrete + more heat from curing....

Buy 5000 Psi mix.....

Add about 0.5% to Portland weight, calcium chloride?

Cover with a piece of 2" FOAM BOARD?

Even a piece of clear plastic poly/ reinforced shelter poly/ tar paper, would act a a "green house" and warm the crete in the daytime, and keep the wind off it at nighttime = never freezing.


20' cubic of crete = ~30 80 lb bags of ready mix = .75 yards = 2400 lbs more or less.

An Army field expedient is to cover it with dirt till spring then power wash....
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Last edited by Fouthgeneration; 12-14-2019 at 10:54 PM.
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Old 12-15-2019, 03:14 AM   #6
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Re: Cold Weather Pour


Good info.
The question remains:
Will the extra long cure time and/or low temperatures weaken the concrete to the point the it will matter on a structure with such insignificant loading?
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Old 12-15-2019, 08:32 AM   #7
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Re: Cold Weather Pour


Concrete cure is a chemical process. Theoretically, it forever gets stronger with age. It does however need some moisture to keep the chemical process going. The exception to this is allowing the concrete to freeze. Freezing pulverizes it's structure and can potentially turn it to powder. In practical terms, keep it from freezing in 1st month with blankets, or straw, & make sure you have a way to stop flooding.
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Old 12-15-2019, 11:21 AM   #8
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Re: Cold Weather Pour


Check out Mike Day's channel on YT. He's been pouring at freezing temps for about a month now in Maine. Maybe some pointers there.

https://www.everything-about-concrete.com/
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Old 12-15-2019, 02:13 PM   #9
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Re: Cold Weather Pour


Concrete is poured all winter long all across the world. Jeep it from freezing for 72 hrs and you are good to go.

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Old 12-17-2019, 08:13 AM   #10
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Re: Cold Weather Pour


Bagged mix is garbage.


Get it batched with the right amount of air in it, use high early cement, and cover it up for a couple weeks.
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Old 12-17-2019, 08:15 AM   #11
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Re: Cold Weather Pour


Quote:
Originally Posted by Fouthgeneration View Post
Use Hot water.....

Heat the ground BEFORE the pour....

Blankets, the WHOLE winter...or straw....

Add 2-4 Pounds of type II Portland Cement for every 80 lb. premix bag of concrete...~ 1 to 2 "extra" 1/4 bbls of Cement per yard = quicker time to frost proof concrete + more heat from curing....

Buy 5000 Psi mix.....

Add about 0.5% to Portland weight, calcium chloride?

Cover with a piece of 2" FOAM BOARD?

Even a piece of clear plastic poly/ reinforced shelter poly/ tar paper, would act a a "green house" and warm the crete in the daytime, and keep the wind off it at nighttime = never freezing.


20' cubic of crete = ~30 80 lb bags of ready mix = .75 yards = 2400 lbs more or less.

An Army field expedient is to cover it with dirt till spring then power wash....
Isn't calcium a big no-no when there is steel in it?

My plant has a "steel safe" accelerator that is used for wall pours and slabs with steel....of course it costs more though.

I prefer a high early cement if it doesn't need to have any special finish, the stuff starts to get hard an hour after it leaves the chute, no matter how cold it is.
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Old 12-18-2019, 07:22 AM   #12
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Re: Cold Weather Pour


Since you are in an area that doesn't experience frost or frozen ground, you are good to go.
The extended time is no problem at all. Concrete reaches 50% strength in 24 hours, 90% in 7 days, and 100% in 28 days.
(There will be some people say it never fully reaches 100% and will say the concrete in Hoover dam is still curing. Maybe so, but 28 days is still pretty close to 100%.)

If your area would freeze, then you would need to cover the footing, as the frost would get under the footing and cause it to heave.
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Old 12-18-2019, 07:23 AM   #13
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Re: Cold Weather Pour


Quote:
Originally Posted by NYCB View Post
I prefer a high early cement if it doesn't need to have any special finish, the stuff starts to get hard an hour after it leaves the chute, no matter how cold it is.
I poured High Early concrete over 20 years ago. As soon as the last semi was done unloading, we tore out a large slab, re-poured it, and the next morning, semis were unloading again. The concrete is still there, with minimal cracks.

Worked well.
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Old 12-18-2019, 08:04 PM   #14
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Re: Cold Weather Pour


Quote:
Originally Posted by builditguy View Post
I poured High Early concrete over 20 years ago. As soon as the last semi was done unloading, we tore out a large slab, re-poured it, and the next morning, semis were unloading again. The concrete is still there, with minimal cracks.

Worked well.
You have to know what you are working with though, fine for walls, footers and work that only needs a rough finish (like for cows to walk on)

If you plan on power troweling it, you're gonna have a bad day.

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