Cold Weather Concrete Pour

[lakeroadster]

Is there a definitive answer as to if pouring concrete in freezing weather is acceptable.

When I say acceptable I define that as concrete that is just as strong as it would be if it were poured during warm weather.

5" thick concrete, 3,000 psi strength for my 30' x 44' pole barn. Building will get a 2 post lift, so meeting the specifications is a big deal for me as my life depends on the quality of the concrete.

GC says no problem, they can bring in portable heaters. Building is done, but has ridge vents and soffit vents. So keeping heat in the building now is a fools errand, IMO.

I told him we would wait until spring.

Weather looks like this:

 

[SunsetsAndFriends]

If you wait until more favorable temperatures, you will not be fighting the cold or worrying about it either. On the other hand, you could call the redi-mix concrete supplier in your area and ask them about ad mixtures, etc., and their opinion.

I would probably wait.

 

[Rookie2]

Spring is best !IMO
Call the concrete supplier, there are chemicals the they can add other than calcium I think.
Some concrete guys use blankets.

ask to see a floor pour he did last winter.

 

[joes169]

I'm assuming when you say open soffits and vents, you literally just have a steel sided shell. If that's the case, I would not pour with that forecast, the low's at night are too low. A tin shell with open soffits and ridge cap is hard to heat.......

 

[machsnell]

Structurally in the middle of slab where lift would be you would get the strength but it will freeze with those Temps and trying to finish and cover very difficult.

If you can wait. WAIT. Easier on everyone. I can believe the contractor wants to pour it with those Temps. Not to mention having to protect the subgrade before the pour.

Fools errand for sure. You are correct. Wait wait wait. We have had real issues finishing in cold weather and won't unless we are being forced to and get a release for spalling surface.

Blankets and accelerators and hot water only do so much.

Your Temps are going to be cold

Sent from my SM-G900V using Tapatalk

 

[Dick in Wisconsin]

Are you going to eventually insulate the walls and ceiling? If so, why don't you do that. And then consider pouring. But by then the ground under the slab might be frozen.

I would wait. Sounds like you're not pressed to get it poured.

 

[matt_i]

The calcium chloride makes it setup faster, helps keep the guys from not staying there until 12pm at night. Problem is more corrosive to reinforcing steel. There is a glycol-based additive they can use as well.

The cheapest way to heat is those jet engine heaters. Which definitely produce heat. But at the expense of all the combustion moisture being entrained in the exhaust stream. In other words, humidity is going up dramatically, not to mention the bleed water in the concrete...and you will probably be adding to it keeping the surface wet.

I would want to heat with the electrically heated concrete blankets. Then, no extra humidity, but get the job done with no worries. Probably more expensive to rent as well.....

If your life is dependent on the quality of the floor, hopefully you added a significant amount of reinforcing steel.

 

[lakeroadster]

.... If your life is dependent on the quality of the floor, hopefully you added a significant amount of reinforcing steel.

Opinions vary. Can you back that statement up with factual data and specifications?

• Re-bar adds zero "strength" to the concrete, actually makes it weaker in a slab on grade design as the steel is a discontinuity in the slab and thus becomes stress risers.
  
• If the concrete cracks, the re-bar adds stability (i.e. reinforcing bar) to the concrete to keep it from lifting, separating, etc.
  
• Rotary, the manufacturer, says 4-1/4" thick 3000 psi concrete.
  
• Got a reinforcing steel design for a new pour slab, not a retrofit?
  
• How do you ensure the reinforcing steel will not interfere with drilling of the anchor bolts for the lift?
  

At my previous shop, I used fiber additives, no rebar, and followed Rotary's specifications. It worked great. There are thousands of lifts installed onto concrete "slab on grade" which have no reinforcing steel, so it's a proven design.

 

[Ponchoguy]

Is there a definitive answer as to if pouring concrete in freezing weather is acceptable.

When I say acceptable I define that as concrete that is just as strong as it would be if it were poured during warm weather.

5" thick concrete, 3,000 psi strength for my 30' x 44' pole barn. Building will get a 2 post lift, so meeting the specifications is a big deal for me as my life depends on the quality of the concrete.

GC says no problem, they can bring in portable heaters. Building is done, but has ridge vents and soffit vents. So keeping heat in the building now is a fools errand, IMO.

I told him we would wait until spring.

Weather looks like this:

Wait. My 64' long x 20' wide x 10' wide, 8" thick, 3500 psi driveway was poured in August of last year, here in NYC (see my other thread). No cracks thus far (knocks on Fibermesh reinforced concrete...)

 

[rancherbill]

Is there a definitive answer as to if pouring concrete in freezing weather is acceptable.

I wouldn't do it. I had concrete fail in temperatures that were not as low as yours.

My concrete guy ordered with 'winter heat" which is hot water and a chemical mix and who know what else. It never reached ultimate hardness.

Looking at those temperatures, the only way I'd have it done is if you heat for a week to get the ground warmed up before pouring.

 

[plugers]

When I used to pour, we would board up the door, pile straw around the outside and staple plastic to the ceiling. You would have to heat for a couple days prior and make sure all the frost is out of the ground or it will leave a void underneath come spring. Once the concrete hits 26 degrees, even chloride doesn't help, the chemical reaction stops.

If you can wait until spring and have other stuff you can do, it would be advisable. If frost in in the ground, you really want to get that out and the ground compacted before pouring.