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Re: Lightweight yet stiff fill ?

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You might want to contact Cell-Crete Corporation (626)357-3500, you might be able to use styrofoam (polystyrene) under the structural slab, possibly elastizell (20 psf to 120 psf) for the fill with a structural concrete topping. You might be able able to eliminate the metal deck and pour the structural slab directly over the elastizell.  You could design the 4" slab to span as a simple beam between concrete curbs downward every 10 - 12 feet each way that would provide shear transfer of the concrete mass to the existing slab.  Perlite, Vermiculite do not function at all well if you are thinking of using them as the final wearing surface, they need to be protected by a wearing surface.  Elastizell has been used for a lot of fill applications.
Mike Cochran
In a message dated 5/12/2005 10:24:36 A.M. Pacific Standard Time, T.W.Allen(--nospam--at) writes:

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)


Consulting Structural Engineers

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