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Hardcore underneath reinforced floor slab with Cellcore

Discussion in 'Building' started by ChrisZx, 3 Aug 2018.

  1. ChrisZx


    16 Nov 2016
    Thanks Received:
    United Kingdom
    On our floor slab (5.4m x 4.2m) design we have 225mm of cellcore underneath our reinforced slab (A193 50mm from bottom). The slab is thicker at the edges and rests on the inside of the foundation...so this makes it a suspended slab, right?

    The design also has a layer of sand-blinded hardcore underneath the cellcore, but why?

    My understanding is that the Cellcore is there to protect against ground heave (of which I think there will be none, but that's a different story) and designed to crush when an upward force is applied so that the force is not transferred to the slab. But what if the ground has already swelled up when the floor is built. When it shrinks, would there not be a void underneath the slab?

    So how does the substrate affect anything? Surely the whole point of this design is that the movement of the ground does not affect that slab. So long as the ground can support the cellcore whilst the slab cures, is that not enough?

    I read something from the manufacturers of cellcore that says "Cellcore should be placed on a firm level surface which will ensure uniform loading on the legs. A layer of concrete blinding will usually be necessary to achieve this condition"

    So it's just to protect the legs? I think I could smooth the ground enough to take our puny residential slab.

    I'm a bit confused by it, anyone got any experience/thoughts?
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