Drilled pier air entrainment

[haynewp]

Is air entrainment normally used for drilled piers? Our specs on a project I have taken over have no air entrainment required but the piers will be exposed to mild freeze-thaw. Is it normally assumed the placement process for drilled piers will provide some minimal air entrainment itself?

 

[JAE]

Most of the piers I have designed over the years were buried deep enough not to worry about - or were in the south where no freezing occurred.

If you have freeze-thaw exposure I'd certainly consider it. I wouldn't count on natural air (usually 2 to 3%).

You could provide an option to allow the contractor to only use air in the top "x" feet of the pier but that adds all sorts of coordination challenges and adds to the possibility of missing air in some piers.

 

[Ron]

haynewp...air entrainment is often specified for drilled shafts for workability enhancement rather than freeze-thaw resistance. Entrained air helps to achieve a more consistent placement with less bleeding.

 

[haynewp]

I have a couple that are extending into the 18" frost depth for this area. I am hearing the standard "we've never done it before" when I first stated air entrainment is to be used for all the pier concrete.

I have told them they can use it in the first 18" only and they don't know yet how that will be handled (as JAE mentioned above it would be a problem). I see now that I should have dropped all the top of piers to below frost level.

 

[motorbiketocrank]

Also, if you have a heated structure, you'd only have to include air for piers around the building perimeter which have the exterior exposure. Entrapped air (from placement) doesn't really help with freeze/thaw like entrained air does.