Concrete and cold-ish weather

Fabrik8

Fabrik8

Overcomplicator
Joined
May 27, 2015
Location
Huntersville
I know some of you people do a lot with concrete, and I don't.

I need to make a new footing/landing/whatever for our rickety-ass front porch steps, and re-pour the connecting section of walkway, and it's December. Truthfully, it's going to be a little while until I come up with something interesting to make, and figure out whether I need a structural engineer because "prescriptive design" is not in my vocabulary. That will just push things toward the next slightly colder months. Damn 200lbf lateral load requirement for the guard post is messing up my lovely open-riser design (have to add a tension tie, somewhere), and then there's the 46inch tread span with a 3X or 4X tread.

Anyway, is pouring concrete in Charlotte winter a good idea? I'm not looking for a way to make it happen in winter if it's not a good idea. If this is a matter of "Wait until March and then you don't have to worry about anything", that is an acceptable answer as well.
 
Last edited:
Fabrik8 said:
I know some of you people do a lot with concrete, and I don't.

I need to make a new footing/landing/whatever for our rickety-ass front porch steps, and re-pour the connecting section of walkway, and it's December. Truthfully, it's going to be a little while until I come up with something interesting to make, and figure out whether I need a structural engineer because "prescriptive design" is not in my vocabulary. That will just push things toward the next slightly colder months. Damn 200lbf lateral load requirement for the guard post is messing up my lovely open-riser design (have to add a tension tie, somewhere), and then there's the 46inch tread span with a 3X or 4X tread.

Anyway, is pouring concrete in Charlotte winter a good idea? I'm not looking for a way to make it happen in winter if it's not a good idea. If this is a matter of "Wait until March and then you don't have to worry about anything", that is an acceptable answer as well.
Click to expand...
Use hot water and accelerator. Tarp over it and put jet heater so it tents up. Cold weather never stopped pooring precast at metromont.

Sent from my SM-G892A using Tapatalk
 
They don’t stop pouring concrete in the winter, they just use warm water and accelerator. Sometimes calcium. No big deal really, just a slower process and a mix that is harder to “push” around and finish. I watched 65 yards go down today.
 
warm water always helps. I've poured when it was snowing in charlotte and never had an issue. You have to watch the nighttime temps though, usually during the day is warm enough to pour and finish. Instead of a tarp, I would go with burlap. We always used burlap when it was this cold and it works well.
 
As stated above. Calcium and cover it. I work with an old guy who is a concrete wizard. He swears covering it in burlap speeds the process. Doesn’t sound like you’re pouring a lot nor on a time crunch. You could probably pour it and let it do it’s thang and be fine. I’m pouring 20 yards on Friday. We’re not doing anything special at all. In a perfect world we’d like some calcium, but the boss is too cheap, so we’ll get it done without.
 
We do concrete in cold weather all the time. There are lots of provisions for cold weather concreting.

make sure ground isn’t frozen with heaters and blankets. Straw works in a pinch.
Hot water
Calcium
And blankets and heaters to keep the concrete at temp (~70) while curing. Concrete puts off heat while curing, so blankets and heaters will help it.

be careful while placing as it can fall asleep on you if it’s too cold. So it basically slows down on setting up and finishing takes forever. Calcium helps with this.

there are lots of resources online regarding cold weather concrete practices. We poured maybe 2500CY last winter in temps from 15* to 30* and were successful. Got any questions, send me a message and I’ll answer however I can.
 
Lots of blankets and heaters.

if it gets too cold, it will fall asleep and not cure enough to finish. Finishing when this happens usually causes the paste to rise and aggregate to fall. And the top portion cures before the bottom. And when the bottom finally cures, the top 1/4” or so starts to pop off. It’s a hell of a mess.
 
this is what happens when the concrete falls asleep in 20* weather by not keeping it at temperature while placing and finishing.
CD14E46A-BE56-42A8-9190-D38125428187.jpeg
 
tknopp said:
^^^
Don't want that.
Click to expand...


Not at all, especially on a slab for a shop. This was just a small 12 sq ft area, which was the smallest damaged area of about 10 areas on this one pour. This single pour was about 90,000 sq ft.

The contractor made a few adjustments and was all good the next several, similar pours.
 
When I poured my garage floor it was barely above freezing that day we covered it with black plastic and then hay and left it covered for a couple weeks because it below freezing for several days and it cured out well. it has been 15 years now and it is holding up well.
 
They also make what we used to call High strength/Early set. Just more chemicals & cement. Used mostly in high rise buildings & winter months. Contractors might pour a floor at midnight, & be pulling the forms & setting up the next floor, within 12 hours! Call your concrete supplier, & see what they suggest. Your most economical way, is just wait for a couple of above freezing days, to pour!
 
Back
Top