Unfilled grout pockets exposed to winter conditions

[shaneelliss]

We are in the middle of a project where there are large concrete column bases with large grout pockets for shear keys. Due to unforeseen circumstances we have to shut down construction until next spring. Our winters usually are cold and snowy mingled with temperatures that rise above freezing intermittently. My boss is worried that if we leave the grout pockets exposed to the elements (not covered or sealed) that water will accumulate in the grout pockets and break the concrete as it freezes. He wants to seal them up. I think that won't happen because they aren't sealed at the top and any expansion of the freezing water will just push the ice out the top of the pocket. I think if we don't get them sealed right water will get in there and by putting a lid on the space, we will create the problem my boss is worried about. What do you think? Will it be an issue to leave them open, or do we need to seal them closed?

 

[KootK]

I'm with your boss on this one. Having an outlet at the top won't eliminate lateral pressures. Conversely, it's unlikely that any cap would be stiff enough to exacerbate the lateral pressures.


Unless your pockets are close to edges, I doubt that you'd have problems leaving them exposed. I don't know how to quantify that however. You could grout the pockets with a lean mix that could be easily dug out at a later date. I've used this approach to protect exposed rebar.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[shaneelliss]

Some of the grout pockets are close to the edge. I have left a few glass bottles of liquid in the freezer to cool down for too long and had them freeze and they have never broken as long as there was room at the top for expansion. Based on this anecdotal evidence, my thought was that lateral pressures won't build up to anything significant unless it is restrained on all sides. KootK, it sounds like you have different experience?

I hadn't thought about using a lean mix to fill the holes. I was thinking of expanding spray foam or something. I'll have to look into that.

 

[kingnero]

fill the grout pockets with styrofoam (cut to size). Any water that gets in there, will compress the styrofoam when it freezes.

 

[KootK]

Yeah, I saw a few freezers messed up in college due to exploding beer but, honestly, I think that they may have actually been cans (surprising to me). Obviously, there is some lateral pressure with the top surface of the ice open to the air because something has to constrain the ice's natural tendency to dilate in all directions.

The question is simply how much lateral pressure. One thing that a bottle may have going for it is its limited width. The ice strain that you'd accumulate over, say, the Atlantic ocean would obviously be more than you'd get across the width of a beer bottle.

Google tells me that the maximum compressive strength of ice is about 25 MPa. And your shear keys must be designed for some lateral pressure since they are shear keys. Any chance their strong enough to resist 25 MPa? I guess that your keys may be designed to resist shear in only one direction which may or may not be oriented perpendicular to the concrete edges that concern us here.

kingnero's approach sounds pretty good to me, particularly if you throw a couple of 2x's over the top to keep the styrofoam from floating.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[racookpe1978]

Spray-in Home Depot/Lowes/Wally World expandable foam insulation?