Underslab void forms
Underslab void forms
(OP)
We are involved with an office building project located in an area underlain by highly plastic clay. We have recommended a traditional belled pier and suspended slab approach of dealing with the potential for soil heave. However, the project team is now debating the merits of conventional cardboard void forms vs. the foam type product as the void form. Can anyone with experience with the two different materials comment about the pros and cons?





RE: Underslab void forms
RE: Underslab void forms
You have AT LEAST enough stiffness to support the wet weight of concrete so that is probably most of the dead load pushing up on your slab when the soil heaves.
RE: Underslab void forms
RE: Underslab void forms
RE: Underslab void forms
RE: Underslab void forms
This will kill your slab, compared to simple gravity design, I would think.
I just think this is all easily avoided by using traditional void forms.
RE: Underslab void forms
With highly plastic clay, it is unlikely that you will have heave once the building is enclosed; the soil tends to dessicate and shrink.
I usually use the foam type for grade beams (a product called 'Frost Cushion') Foam can have a crushing strength of several psi and may be problematic with slabs. I've done reports on beams that have heaved when conventional cardboard was used and the void filled with water.
Dik