Air entrainment in grout 1

[maverik709]

I have about 2-5 inches of grout going into the bottom of a clarifier. The bottom of the clarifer may be in freeze/thaw conditions. The grout would be a 9 bag mix (23% cement, 10% water, 67% fine aggregate, all by weight). The grout supplier is telling me that they have never added an air entrainment agent to any grout mix of theirs and that they can't get the air content about 2% in this mix.

In general, is air entrainment in grout a good idea?
Anyone have experience with air entrainment agents in grout? Anyone know of any standards for adding air entrainment in grout?

 

[bjb]

When I have done a clarifier, what we specify on the bottom we refer to as a bonded concrete topping, consisting of type II cement, 3/8" max aggregate, and fibermesh. We also specify an air content of 6 percent, and require that a ready-mix supplier will provide it. I have seen similar specs from other engineers.

In ACI 350-01, in the commentary to section 4.2, they talk about tanks containing water or wastewater as being a moderate exposure. It seems to me though that it would be extremely rare for the grout at the bottom of the tank to ever see a significant number of freeze-thaw cycles. I don't think that if un-air entrained grout were to experience a low number of freeze-thaw cylces that it would significantly deteriorate, especially since it is unlikely that any freeze-thaw cycles would be consecutive. Having said that, I think it is a good idea to have air entrainment in the grout, and it seems to be the intention of ACI 350-01 in my opinion.

Also, try contacting either ACI or PCA and see what they have to say.