Pouring concrete in the cold

[kebo]

You should not pour it on a surface which is frozen. Sometimes you have to make an enclosure and heat it to thaw the granulars and soil.

You need to order the concrete heated i.e. made with hot water so when it arrives on the job site it is protected for a while.

Concrete generates heat as it cures, but a limited amount when the slab is thin

You need to have a 6' high wind barrier in place to stop wind sweeping across the surface. I would consider insulating the forms in some fashion. Often straw is used.

You need to have insulated tarps on hand. Essentially like bubble wrap in tarp form. Put them over the surface as soon as finishing is completed.

If it is going to be very cold, the tarps should be elevated above the concrete and heat added to the enclosure.

Do NOT use an open flame heater as they produce CO2 which is harmful to the quality of the concrete.

You need to keep the concrete above freezing for at least 7 days, preferably more as the curing time is 28

The sooner you stop keeping the concrete warm, the curing process stops until the temp rises so it will not have its full strength.

You need to have a way to monitor the temp within the enclosure so if things are starting to get close to freezing temps, you can take more drastic action.

Leave the forms on as long as possible to protect the concrete edges.

Only on large projects would pouring in cold weather be done to stay on schedule. It involves risks and extra costs to wait for a break in the weather.
This link would be a good reference:

Cold Weather Concreting

Dave M7040

Who knew what pouring concrete in cold weather was so complicated? I guess that is something we don't have to deal with in the south very much.

 

[Tractor Seabee]

Hot weather concreting can also be complicated; to get optimum results.

Ron

 

[Streetcar]

Cold weather requires protection from freezing until concrete has strength to resist ice forces.
Hot weather can cause flash curing

 

[Texasmark]

You should not pour it on a surface which is frozen. Sometimes you have to make an enclosure and heat it to thaw the granulars and soil.

You need to order the concrete heated i.e. made with hot water so when it arrives on the job site it is protected for a while.

Concrete generates heat as it cures, but a limited amount when the slab is thin

You need to have a 6' high wind barrier in place to stop wind sweeping across the surface. I would consider insulating the forms in some fashion. Often straw is used.

You need to have insulated tarps on hand. Essentially like bubble wrap in tarp form. Put them over the surface as soon as finishing is completed.

If it is going to be very cold, the tarps should be elevated above the concrete and heat added to the enclosure.

Do NOT use an open flame heater as they produce CO2 which is harmful to the quality of the concrete.

You need to keep the concrete above freezing for at least 7 days, preferably more as the curing time is 28

The sooner you stop keeping the concrete warm, the curing process stops until the temp rises so it will not have its full strength.

You need to have a way to monitor the temp within the enclosure so if things are starting to get close to freezing temps, you can take more drastic action.

Leave the forms on as long as possible to protect the concrete edges.

Only on large projects would pouring in cold weather be done to stay on schedule. It involves risks and extra costs to wait for a break in the weather.
This link would be a good reference:

Cold Weather Concreting

Dave M7040

I'm not a concrete guy but I had a slab poured for a room addition to my house and we like to never got it to setup. Contractor said he forgot to tell the pit to add Calcium to the mix.

 

[Texasmark]

Hot weather concreting can also be complicated; to get optimum results.

Ron

I've seen it too covered to keep the sun off it while curing in hot weather. also saw a guy watering down the slab for the same reason I guess.

 

[bcp]

Long ago, in a hot, dry climate, i used to see new slabs surrounded with a dirt berm, then flooded for several days.

Bruce

 

[Tractor Seabee]

Water curing is always best. Concrete core samples are stored in a controlled temp water bath up to the time they are tested.

There are projects where piping embedded in concrete and hot water circulated in winter or cold water circulated in summer. The "heat of hydration" generated in concrete can destroy it before it cures unless controlled to save or remove as necessary.

Ron

 

[bdog]

I still have the insulated blankets on it. I lifted up a corner yesterday and it is really wet under there. Water droplets on the surface of the concrete and bottom of the blanket. Should make for a really good cure. I plan to remove it Monday which will be 7 days.

 

[Texasmark]

Water curing is always best. Concrete core samples are stored in a controlled temp water bath up to the time they are tested.

There are projects where piping embedded in concrete and hot water circulated in winter or cold water circulated in summer. The "heat of hydration" generated in concrete can destroy it before it cures unless controlled to save or remove as necessary.

Ron

The Hoover dam was an example of planning for, and dealing with that. Interesting how they worked around the problem.

 

[dirtydan]

Back in the late 80s I was a batch manager for a Ready Mix outfit that poured weights for a pipeline in northern Minnesota. Our cut off point was 20 below zero anything above that we worked below that we didn't. It takes quite a bit to get things going at 20 below zero trucks ran all night, loader also, and the generator plant did too. We used 190 degree water and lots of calcium cloride. Since oil is lighter than water they needed weights to put over the pipeline when it runs through the swamps. Each weight was two cubic yards. The crew put tarps and heated the weights for I really don't remember how long but a day or two. Our job was just to supply the concrete. As we recirculated the 190 degree water back into the swamp this made turtles and frogs come out of hibernation in the middle of winter in northern Minnesota quite a strange thing.