Cavity former

Abstract

A cavity former 10 for use in forming a cavity in a concrete slab is disclosed. The cavity former comprises a support member which supports the weight of a person standing on the cavity former or of wet concrete bearing down on the array until the concrete has cured sufficiently to support itself. The array is reconfigurable between a compact state for stacking with other similarly configured arrays to facilitate transport and an expanded state to define a volume about which the wet concrete is poured. The cavity former 10 has a cover 34 which is engageable with the array to distribute the weight onto the array elements and prevent wet concrete flowing into the volume defined by the elements in the expanded state.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application claims the benefit of Australian patent application serial no. 2003903688, filed Jul. 16, 2003. The disclosure of the above application is incorporated herein by reference. FIELD OF THE INVENTION [0002] This invention relates to concrete slabs and foundations. More specifically, the invention relates to an apparatus for forming a hollow cavity in a slab or foundation. BACKGROUND OF THE INVENTION [0003] The practice of using cavity formers as space filling members in the preparation of a concrete slab or foundation is an existing technique for reducing the amount of concrete required to form a slab or foundation. While the reduced concrete content in a slab having hollow cavities serves to reduce the cost of the slab, it also advantageously allows the slab to be built on unstable soil as expanding soils will flow into the formed cavities. Such cavities also assist the easy placement of electrical and plumbing conduits th...

AI Technical Summary

Benefits of technology

[0007] In accordance with the invention, it has been recognised that transport of cavity formers would be more convenient were the formers, collectively, to have a less voluminous state than their volume ready for the concrete to be poured. This less voluminous state is achievable by providing a suitable structural configuration which is stackable and which also enables the cavity former to meet the weight support requirements mentioned above. In a particularly advantageous application of the invention, such a structural configuration permits the formation of the cavity former from a degradable material.

[0010] (b) cover means detachably engageable with the member for distributing said weight onto the member and preventing flow of said concrete into the member;

[0014] (b) cover means detachably engageable with the array for distributing said weight onto the array elements and preventing the flow of wet concrete between said; and

[0024] In the preferred embodiment, a lattice arrangement is provided by an integrally formed matrix of cell walls, each cell wall having a V-shape in cross section, and wherein the matrix defines a plurality of cells. The structural strength of the support member may be improved by forming each cell with a floor on the same side of the member as the channels

[0030] (b) cover means integrally formed with said elements for distributing said weight onto the elements and preventing the flow of wet concrete between the elements;

[0032] Advantageously, cavity formers according to both the first and second aspects of the invention are made of a degradable material to facilitate disintegration of the cavity former over time to leave a cavity within the formed concrete slab. For example, the degradable material may be cardboard or fibreboard. If necessary, the cardboard or fibreboard may have a coating to slow the diffusion of moisture into the member and thereby prolong the weight bearing capacity of the member. In the preferred embodiment, the support member comprises paper pulp without a coating and the cover means comprises cardboard or fibreboard having a coating for slowing moisture diffusion.

Problems solved by technology

Polystyrene overcomes this limitation, but it has the disadvantage that, when cut into smaller shapes for cavities of smaller sizes, large quantities of fine polystyrene particles are often generated.

Such polystyrene particles present an environmental problem because they are easily scattered by a breeze.

Furthermore, polystyrene pods do not disintegrate to more completely form the cavity and this presents a disposal and environmental problem when the slab is partially or wholly demolished or reshaped.

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