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Re: Flowable Backfill

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"Flowable Backfill" is a more technical phrase for "lean concrete slurry."
It is usually stronger than compacted soil and has one to three sacks of
conrete (94 lbs each) for each curbic yard.  The remainder of the mix is
sand and water.   Relative compaction has no real meaning for this material
so don't specify any. Since it is cemented, its strength characteristics are
more dependent upon water / cement ratio than density.

If you tell the plant a one-sack or three-sack slurry, they'll know what
you're talking about.  Take cylinders and have a testing lab determine the
compressive strength of the mix.  The geotech can duplicate this mix in the
lab if it wants to check compressibility and shear strength.  It is
excellent for filling-in void spaces that conventional compaction equipment
or "powder-puffs or wackers" can't reach.

Tom Bayne
----- Original Message -----
From: "Ed Fasula" <tibbits2(--nospam--at)metro.lakes.com>
To: <seaint(--nospam--at)seaint.org>
Sent: Monday, August 28, 2000 3:33 PM
Subject: Flowable Backfill


> We're designing the reinforced concrete cap for a cylindrical fiberglass
wetwell.  The mfgr. calls for the cap slab to bear on perimeter compacted
soil.  Since the cap will be at grade with heavy truck traffic, I asked the
geotechnical engineer to spec the backfill & compaction.
>
> He recommended "flowable backfill."  Which I understand as basically a
weak mix of concrete.  We called a couple of ready-mix plants and they were
not familiar with it.  Can someone give us the pros & cons of this stuff and
a design mix or a lead to one?  Is it safe to just give the mix design to
the plant and have them treat it as a typical concrete order?
>
> Regards,
>
> Ed Fasula E.I.T.
>
>
>
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