Cold Weather Concrete Mat

[Oilisking]

Hello all!

We are getting ready to pour a 3' thick mat on grade this week. Average temps for the pour days in the mid 20s, overnight lows in the teens. Based on the depth of the slab, I'm expecting some signifigant heat.

Right now the ground is not frozen, as temps are still around 40 degrees, but I expect it to be crusty on the pour date. Can I pour on a light crust, expecting the ground to thaw out quickly? I am "this close" to telling the contractor to heat the subgrade.

Also, is it worthwhile to cover the reinforcement without heating it?

FWIW, I am hesitant to heat the area due to the site restrictions, which would be poor for combustion heaters.

The contractor is confident that blankets are all that is needed. I am primarily concerned about the crunchy subgrade and any subsequent cracks/settling that may occur.

THANKS!

 

[CarlB]

I would think that covering the area, even with tarps, would retain some ground heat & prevent the "crust" from forming. With that thick of a pour, you're probably right that a thin frozen layer (say less than 1/4") would thaw very quickly and not be a concern. Not sure where to draw the line on frozen depth, as the greater the depth, the more possible loosening/loss of compaction and slower thawing.

 

[LHunter]

I would have the contractor heat the ground prior to the pour.

 

[Oilisking]

Thanks for the input. The ground is crunchy this morning and temps in the 30s. We will definitely be heating the area.

 

[beton1]

Insulated tarps or straw/other insulating material placed on surface (over tarp) beforehand are some other options. Sounds like you're on the way now. Keep in mind for next time.