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Re: Lightweight yet stiff fill ?

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Bill-
 You might want to use cellular concrete.  It is sometimes used as road fill and can be obtained with densities as low as about 22 pcf. Of course the 28 day compressive strength is only about 75 psi.  If you are only requiring it to act as a fill, this corresponds to putting a "very lightweight" soil fill in with a bearing strength of 10,800 psf.
 
I'll send you a product sheet from one manufacturer privately so you can see the properties.  It is typically foamed in place.  I encountered it because I needed something to fill a 9' diameter water tunnel being abandoned.
 
Bill Cain, S.E.
Berkeley CA
 
 
-----Original Message-----
From: Bill Allen, S.E. <T.W.Allen(--nospam--at)cox.net>
To: seaint(--nospam--at)seaint.org
Sent: Thu, 12 May 2005 11:02:17 -0700
Subject: RE: Lightweight yet stiff fill ?

The depth varies because of the slope of the existing roof and the ridiculous desire of the owner to have a level floor. I need something that can be poured or placed (i.e., liquid or granular) I believe.
 
T. William (Bill) Allen, S.E. (CA #2607)
ALLEN DESIGNS
Consulting Structural Engineers
V (949) 248-8588
F (949) 209-2509
 
-----Original Message-----
From: Paul Feather [mailto:pfeather(--nospam--at)SE-Solutions.net]
Sent: Thursday, May 12, 2005 10:58 AM
To: seaint(--nospam--at)seaint.org
Subject: Re: Lightweight yet stiff fill ?
 
Foam blocks.  We use them to vary floor heights frequently. 
 
----- Original Message -----
Sent: Thursday, May 12, 2005 10:23 AM
Subject: Lightweight yet stiff fill ?
 
I am working on a project where there is going to be an addition to an existing penthouse. The existing roof is concrete slab over metal joists. The new slab will be at least 6 inches above the existing roof slab and may be as much as 12 inches above at the low part of the roof. Due to the loading, I don’t want to fill the entire space with concrete. I would rather use a thin slab (4” lightweight; 3,000 psi w/#3 @ 15” E.W. or something close to that) over some lightweight material. My concern is the stiffness, of course. The use is residential, so there will not be any heavy loads on the slab, but I do not want the slab to “settle” too much. My first thought was pearlite or vermiculite, but I don’t know if either is stiff enough.
 
Any thoughts/recommendations would be appreciated.
 
T. William (Bill) Allen, S.E. (CA #2607)
ALLEN DESIGNS
Consulting Structural Engineers
V (949) 248-8588
F (949) 209-2509