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RE: Lean concrete as structural fill?

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This is frequently called controlled density fill (cdf).  I've used it
before but I just can't recall the specs for it.  I think we specced 500
psi and/or one sack of cement per cubic yard.  There was no course
aggregate in our mix, just sand.  In my case, the ready mix company had
no problem supplying it.  I used it to fill below a partially exposed
footing that had been undercut.  There was insufficient space to place
compacted earth below the footing and the cdf worked well.  If you spec
it right, it is also "diggable" if you need to remove some of it in the
future.

Bob Garner, S.E.

-----Original Message-----
From: Jim Wilson [mailto:wilsonengineers(--nospam--at)yahoo.com]
Sent: Wednesday, July 06, 2005 12:29 PM
To: seaint(--nospam--at)seaint.org
Subject: Lean concrete as structural fill?

We are working with a contractor who has asked to use
lean concrete as structural fill under footings and
slabs for a single story building.  Through google
searches, I've come up with matches to lean concrete,
cement bound material (CBM) and flowable backfill.
Are these all essentially the same product?  They
don't appear to be well defined in terms of material
properties, though I found one reference to 500psi
minimum strength.  The flowable fill I have worked
with in the past was 700psi. Also, these products are
only mentioned in the context as being used for
roadway sub-bases.  I'm guessing they are not commonly
used in building construction because they are
relatively costly compared to gravel backfills.

By comparison to regular gravels, this seems very
acceptable as structural fill, but I'm looking for a
second opinion.  And is there an appropriate spec or
even a product name to call this material for building
use?

Regards,
Jim Wilson, PE
Stroudbsurg, PA

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