Backfill with flowable fill between shoring and basement wall

[EngMan40]

The basement wall has a geocomposite sheet drain (geotextile and drainage core)

Any comment on the following claims:

1. that the flowable fill will clog the drainage by seeping through the geotextile when placed wet due to cement particles smaller than geotextile AOS.
2. that the flowable fill being a solid material will act as a barrier to groundwater and cause hydrostatic buildup behind the wall and drainage won't see groundwater at all.
3. that the flowable fill will crack eventually after it is set so it will allow groundwater to seep through.
4. that the flowable fill should be placed in small lifts to prevent overstressing the wall.

 

[BridgeSmith]

If you're talking about the material I understand as "flowable fill" (concrete slurry), I believe statements 1 and 2, at least, are correct, which should be enough to make this plan a non-starter.

That said, whether statement 3 is true depends on the support provided by the foundation under the flowable fill.

Statement 4 being true or false depends on the capacity of the wall, but yes, you would have to consider the full hydrostatic pressure (assume 145 pcf, unless a more exact density is provided) of the flowable fill for the depth of the lifts. I believe the set-up time for flowable fill is considerably longer than for normal concrete, also.

Rod Smith, P.E., The artist formerly known as HotRod10

 

[ACtrafficengr]

This is based only on a seminar I saw, and I don't have any direct experience with the stuff.
You may want to look into cellular concrete. Depending on the foaming agent used, it can be porous or impervious, and density can be controlled so statement 4 won't be a problem.

My glass has a v/c ratio of 0.5

Maybe the tyranny of Murphy is the penalty for hubris. -

http://xkcd.com/319/

 

[MTNClimber]

Cellular concrete should work but I would talk to a rep to make sure your concern #1 isn't an issue.

 

[SlideRuleEra]

EngMan40 - Flowable fill is fairly permeable, it does not have to crack for water to slowly pass through it. Don't rely on it waterproofing. It's made from (microscopically spherical) coal fly ash, sand, cement and water - nothing like "clay" that could significantly retard water passing through it.

Agree that hydrostatic pressure during placement of flowable fill is a consideration.

We started using flowable fill at our electric generating stations when it was first being introduced in the early 1990s (since we "produced" flyash, and wanted to help create a market). Flowable fill was used as backfill on top of buried concrete ductbanks, so they could be easily dug up later for modifications.

http://www.SlideRuleEra.net