Patent Description:
Void formers are commonly used for forming voids or hollows within concrete elements during casting. Such voids may advantageously:.

Void formers are also used to provide access openings or recesses in the surface of a cast concrete element. This may allow for operations to occur within the opening, including:.

Void formers are typically produced from expanded polystyrene (`EPS'), since it: is low-cost and lightweight, provides sufficient compressive strength, and allows for shaping (i.e. being cut to shape). However, EPS is bulky to transport and store. While EPS is recyclable, it yields only small amounts of polystyrene for re-use on a volume basis, making it costly and unpopular to recycle. EPS also fills voids created within the concrete, hampering or preventing any construction operations within the voids.

Alternatives to EPS exist as for example as described in: <CIT> and <CIT>.

<CIT> discloses void formers formed of spherical or semi-spherical plastic balls locked within metal lattices. The void formers may be incorporated into slab or precast concrete elements relatively simply. However, the modules remain bulky to transport and store; and void spaces are formed within concrete elements as multiple discrete and discontinuous spheres. The modules are not suitable for use in providing access openings in the surface of a concrete element.

<CIT> also discloses a displacement body for forming cavities in concrete elements. The displacement body comprises: a grid structure of intersecting longitudinal and transverse rods, and plastic sheets applied to both sides of the grid structure and connected to one another and the grid structure by welding and or heat shrinking. The displacement body is described as cost effective, light-weight and easily storable. However, as the displacement body is assembled though shrink wrapping and or plastic welding, it may be difficult to produce, resize and/or re-shape onsite. The disclosed displacement body does not appear suitable for use in providing access openings in the surface of a concrete element.

<CIT> discloses a void former unit, wherein void former elements are connected to form a passage between first and corresponding second openings.

Despite advances in void former technology, there remains an ongoing need to overcome certain disadvantages associated with the technology, such as:.

It is an object of the present invention to provide a void former which addresses one or more of the above-mentioned disadvantages.

When used in the specification and unless the context otherwise requires, the term 'concrete' is intended to relate not only to traditional Portland cement concretes but more broadly to any composite material involving a matrix of aggregate and a binder. Such concretes may include polymer concretes, asphalt concretes, hydraulic cement concretes generally, geopolymers, and other suitable building materials.

The reference in this specification to any prior publication, or information derived from it, or to any matter which is known, is not, and should not be taken as an acknowledgement or admission or any form of suggestion that the prior publication, or information derived from it, or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.

Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise" and variations thereof such as "comprises" and "comprising", will be understood to include the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or groups of integers or steps.

According to a first aspect of the invention, there is provided a void former unit suitable for forming a void in concrete elements comprising:.

In an embodiment, the first surface and the second surface are substantially flat.

In an embodiment, the first void former element and the second void former element are substantially identical.

In an embodiment, the first void former element comprises a lip extending outward from the first surface about a peripheral edge of the first void former element.

In an embodiment, the void former unit further comprises at least one side-edge void former element, wherein each side edge void former element connects the first void former element to the second void former element along a peripheral edge of the void former unit to at least partially enclose the void space surrounding the or each passage.

In an embodiment, the void former unit comprises a plurality of apertures to allow a small amount of concrete to seep through during pouring and curing of concrete. Optionally, apertures are only provided in the top surface of the void former unit.

In an embodiment, the first surface and/or the second surface each comprise surface indents or ribs to reinforce the corresponding first void former element and the second void former element, and / or enhance interface load transfer in a resulting concrete element. In an embodiment, at least some of the surface indents or ribs may operate as spacers to separate any reinforcement materials included in a resulting concrete element from the remainder of the void former unit.

In an embodiment, the void former unit further comprises one or more sleeve or positioning elements to in use slidably house or position one or more joint reinforcement bar(s).

In an embodiment, the first void former element is detachably connected to the second void former element. Further in an embodiment, an interlocking mechanism, such as a tongue and groove interlocking mechanism, detachably connects the first void former element to the second void former element. Alternatively, the first void former element and the second void former element are integrally joined or formed as a single unit.

In an embodiment, the first void former element and the second void former element are nestably stackable when not connected to one another.

In an embodiment, the concrete void former unit further comprises a hollow spacer element connecting the, or each, first opening to its corresponding second opening. In an embodiment the hollow spacer element is to be foldable to allow for stacking when not in use as part of the void former unit.

In an embodiment, the void former unit further comprises an insulating body located in a passage between a first opening and a corresponding second opening to improve thermal or sound insulation between the first surface and the second surface.

In an embodiment, the void former unit further comprises at least one side-edge void former element, wherein each side-edge void former element connects the first void former element to the second void former element along a peripheral edge of the void former unit to at least partially enclose the void space surrounding the or each passage.

In an embodiment, the void former unit is formed of injection-moulded plastic.

In an embodiment, the void former unit comprises a connection means to detachably connect the void former unit to like void former units. In an embodiment, the connection means comprises a interlocking mechanism, such as a tongue and groove interlocking mechanism.

In a second aspect of the invention, there is provided a concrete void former system comprising a plurality of concrete void former units according to a first aspect of the invention, wherein the void former units are connected together so as to provide a substantially continuously extended first surface; second surface, and void space extended between the extended first surface and the extended second surface, across multiple void former units.

In an embodiment, the void former system comprises at least one side-edge void former element, each side-edge void former element connecting a first void former element to its corresponding second void former element along a periphery of the void former system to at least partially enclose a void space formed within the void former system.

In an embodiment, at least one of the void former units comprises a first void former element which comprises a lip extending outward from the first surface of the first void former element about a peripheral edge of the first void former element.

In an embodiment, the concrete void former units are detachably connected to one another. In an embodiment, the detachable connections are formed by a tongue and groove inter-locking mechanism.

In a third aspect of the invention, there is provided a method of producing a concrete element comprising:.

In an embodiment, the method further comprises positioning reinforcing materials in the mould and in the passage(s) so as to reinforce the resulting concrete element.

In an embodiment, the method comprises configuring and/or positioning the void former unit or void former system in the mould to form an accessible void space within the outer surface the resulting concrete element. Further in an embodiment, the method comprises slidably housing one or more joint reinforcement bar(s) at least partially in the accessible void space such that it may reinforce a joint formed between two like concrete elements.

An embodiment according to the first aspect of the invention is now described by reference to <FIG> shows a void former unit <NUM> comprising a first void former element <NUM> (similar to that shown in <FIG>), and a second void former element <NUM> (similar to that shown in <FIG>).

<FIG> shows a first void former element <NUM> comprising a substantially flat, square first surface <NUM> and a first opening <NUM> in the first surface <NUM>. Opposite the first surface <NUM>, the first opening <NUM> projects downward to provide a position for detachably connecting the first void former element <NUM> to a second void former element <NUM>.

While the device is shown as having a square, substantially flat, first surface <NUM>, it is noted that other shapes may be utilized to for example allow for other geometries, including: curved or angled geometries. For example, where a curved concrete surface or element is desired, the first surface may be rounded accordingly. Rather than use a square geometry as shown in <FIG>, in certain embodiments other shaped may be used such as triangular, pentagonal, hexagonal. Shapes capable of forming tessellation with other void former elements <NUM> may be preferred for certain embodiments, but are not essential.

<FIG> shows a second void former element <NUM> comprising a substantially flat second surface <NUM>, and a second opening <NUM> in the second surface <NUM>. Opposite the second surface <NUM>, the second opening <NUM> projects upward to provide a mechanism for detachably connecting the second void former element <NUM> to a first void former element <NUM>.

As may be appreciated the second void former element <NUM> shown in <FIG> is actually identical to the first void former element <NUM> of <FIG>, such that a first void former element <NUM> may provide a second void element <NUM> by simply flipping the element over. Further, the first void former element <NUM> and the second void former element <NUM> are nestably stackable so as save storage and transport space when disconnected.

<FIG> shows a void former unit <NUM> comprising a first void former element <NUM> similar to that of <FIG> connected to the second void former element <NUM> similar to that of <FIG>. As shown, the void former unit provides a passage <NUM> between the first opening <NUM> and the second opening <NUM>. In use, concrete is poured into and cured within the passage <NUM> so as to provide a strut in a concrete element, while void space <NUM> is formed in the space surrounding the passage <NUM>. Without wishing to be bound by theory, the struts are believed to.

As shown in <FIG>, the first void former element <NUM> and the second void former element <NUM> are detachably connected by an interlocking tongue and groove style mechanism <NUM>. This mechanism may analogously be applied to detachably connect other elements of the void former unit <NUM> together. It may also be used to connect multiple void former units <NUM> together using a peripheral interlocking tongue and groove mechanism <NUM> surrounding the peripheral edge of the first void former element <NUM> and the second void former element <NUM>. While an interlocking mechanism as shown is preferable, other connection means are envisaged such as gluing, taping, welding, Velcro, or click-fit buttons. Joining as proposed is further exemplified in respect of <FIG>.

As shown in <FIG>, the first void former element <NUM> and the second void former element <NUM> each comprise apertures <NUM> to allow small amounts of concrete to seep through, which:.

It is envisaged that other components of the void former unit <NUM> may also comprise apertures <NUM> as for example shown in <FIG>, which are now discussed.

In the embodiment shown in <FIG>, the void former unit <NUM> further comprises a hollow spacer element <NUM>, which separates the first void former element <NUM> from the second void former element <NUM>, thereby adjusting the length of the resulting passage <NUM> and the height of the surrounding void space <NUM>. Variations in void space <NUM> thickness may therefore be accommodated via the use of different length hollow spacer elements <NUM>. In <FIG>, the void former unit <NUM> is partially assembled to demonstrate the detachable nature of the connection between the hollow spacer element <NUM> and the first void former element <NUM>.

<FIG> shows a foldable hollow spacer element <NUM> according to an embodiment of the invention. The foldable hollow spacer element <NUM> comprises a fold line <NUM> along its length, and is split apart opposite the fold line <NUM>. When not in use the hollow spacer element <NUM> may be unfolded as shown in <FIG> to allow for stacking during storage.

<FIG> shows another hollow spacer element <NUM> similar to that of <FIG>, however the hollow spacer element <NUM> comprises three distinct fold lines <NUM>. It is believed that the embodiment shown in <FIG> provides a flatter profile for stacking than that of <FIG>, while potentially being easier to manufacture.

Each of the void former elements may be manufactured using plastic via injection moulding techniques, but other methods can be used such as thermoforming, 3D printing and CNC routing, particularly where bespoke geometries are required. To ensure fire performance, plastic void former elements should be kept sufficiently isolated from exposure to fire.

Other types of material could also be used to form void former elements, such as sheet-metal, in which case production processes could include stamping and pressing. Particularly where a strong material such as steel or glass reinforced plastic is used, the void former unit <NUM> may contribute to the overall strength / reinforcement of the concrete element. Otherwise, the stiffness of the void former elements must at least be sufficient to resist hydrostatic pressures from the concrete in its wet state and resist other minor loads during manufacturing operations.

In an embodiment, the adopted materials would be sourced sustainably such as via the recycling of waste.

<FIG> shows another embodiment of a first void former element <NUM> in which the first surface <NUM> of the first void former element is ribbed to provide additional structural strength to the first void former unit <NUM>, as well as providing further contact between the first surface <NUM> and setting concrete. In the embodiment shown the first opening <NUM> also projects further away from the first surface <NUM>, such that substantial distances can be obtained between the first surface <NUM> and second surface <NUM> of a void former unit <NUM> without requiring a hollow spacer element <NUM>. <FIG> shows first void former elements <NUM>, demonstrating the manner in which the projection of the first opening <NUM> may vary between embodiments of the invention. Joining of first void former elements <NUM> and second void former elements <NUM> as shown in <FIG> to form a void former unit <NUM> is demonstrated in <FIG>.

<FIG> shows a first void former element <NUM> according to an embodiment of the invention in which the first surface <NUM> comprises indentations <NUM> to enhance the interface load transfer capability during and after concrete casting. As shown, the indentations <NUM> may project outward from the first surface <NUM>. In an embodiment, such indentations <NUM> may space reinforcement materials from the remainder of the first surface <NUM> during casting, thus allowing adequate flow of concrete around the reinforcement materials.

<FIG> shows a first void former element <NUM> according to another embodiment of the invention, in which the indentations project inward from the first surface <NUM>. The indentations <NUM> may in themselves comprise apertures <NUM>, which are believed to further relieve hydrostatic pressure, and enhance interface load transfer capabilities.

While indentations <NUM> are shown in respect of a first void former element <NUM>, they can be equally applied in respect of a second void former element <NUM> (which may be identical to the first void former element <NUM> as previously described).

<FIG> demonstrate a void former unit <NUM> in which the first void former element <NUM> comprises more than one first opening <NUM>, and the second void former element <NUM> correspondingly comprises more than one second opening <NUM>. The void former unit <NUM> thereby comprises multiple passages <NUM> to allow for larger void former units <NUM> to reduce the number of void former units required in a given void former system <NUM>. In <FIG> the void former unit <NUM> provides four passages <NUM>, while in <FIG> the void former unit <NUM> provides nine passages <NUM>.

<FIG> demonstrate a void former unit <NUM> in which elements such as the first void former element <NUM> and the second void former element <NUM> are separate components that may be connected together However, it may be appreciated that the void former unit <NUM> may be provided as a single integrally formed unit, such as via injection moulding or 3D printing. Alternatively, the void former unit <NUM> may be assembled from separate components such that, for example two components form respective halves of the void former unit <NUM> by also forming two halves of the first void former element <NUM>, the second void former element <NUM> and any other part of the void former unit <NUM>. While not shown, this may be envisaged as splitting a void former unit <NUM> similar to that of <FIG> or <FIG> in half vertically.

An embodiment of the invention according to its second aspect is now described by reference to <FIG> shows a partially completed void former system <NUM> comprising a plurality of void former units <NUM> detachably connected to one another to provide an extended first surface <NUM>, an extended second surface <NUM> (not shown), as well as a single, continuous void space <NUM>. This is achieved by connecting first void former elements <NUM> to adjacent first void former elements <NUM>, and likewise second void former elements <NUM> to adjacent second void former elements <NUM>. To ensure that concrete does not enter the void space <NUM>, the void former system <NUM> further comprises a plurality of side-edge void former e <NUM>, each detachably connecting a first void former element <NUM> to its corresponding second void former element <NUM> along a periphery of the void former system <NUM>. As shown, first void former elements <NUM> along one side of the void former system comprise a lip <NUM> extending upward about a peripheral edge of the extended first surface <NUM> to prevent concrete from flowing over the lip <NUM>. Void former units <NUM> comprising the lipped first void former elements <NUM> may therefore cooperate with a mould to provide an access opening in a cast concrete element, as explained further with reference to <FIG>. <FIG> shows a void former system <NUM> ready for use in a mould.

<FIG> show an alternative embodiment of the void former unit <NUM> and void former system <NUM> in which the first surface <NUM> of each first void former element <NUM> comprises opening portions <NUM> at each corner of its perimeter. Thus, when forming a void former system <NUM>, cooperative openings are formed as first void former elements <NUM> are connected together. The opening portions <NUM> may provide the additional benefit of providing a mechanism to connect first void former elements <NUM> together through mutual connection to a single hollow spacer element <NUM>. In this embodiment the perimeter of the first void former element <NUM> does not necessarily comprise any interlocking mechanism <NUM>.

<FIG> shows the joining of a first void former element <NUM> and a second void former element <NUM>, in which both void former elements are configured according to the embodiments shown in <FIG>. As shown, the first opening <NUM> and the second opening <NUM> project such that a substantial distance is achieved between the first surface <NUM> and the second surface <NUM> without requiring a hollow spacer element <NUM>. Consistent with the embodiments shown in <FIG>, the first surface <NUM> and the second surface <NUM> are each ribbed to provide increased structural support and increased contact with concrete. Similarly, the side-edge void former element <NUM> shown is also ribbed to provide increased structural support and increased contact with concrete.

A method of forming precast concrete elements <NUM> in a match-casting mould using a void former system <NUM> is now described with reference to <FIG>. The disclosed match-casting system allows for multiple concrete elements <NUM> to be cast together, transported separately to a construction site, and then connected together onsite as part of a construction project. While a match-casting mould is exemplified, the person skill in the art will appreciate that concrete elements may otherwise be cast in any number of moulding / casting configurations including single element batch casting.

A cross section of an empty match-casting mould <NUM> is shown in <FIG>. The mould <NUM> enables production of more than one concrete element at a time in a match-casting arrangement, whereby the concrete elements are separated by shutters <NUM> in the mould <NUM>.

Reinforcement <NUM> is firstly placed in the mould <NUM> as shown in <FIG>. As shown, reinforcement <NUM> is placed on either side of the shutter <NUM> to provide for two separate cast concrete elements <NUM>. Reinforcement is typically provided in two directions, using reinforcement bars, mesh, pre-stressing wires, metal fibres and/or other such suitable fibrous materials.

A void former system <NUM> is then placed over the reinforcement <NUM> as shown in <FIG>. In the embodiment shown, the void former system <NUM> includes void former units <NUM> comprising opposing first void former elements <NUM> with lips <NUM>, which cooperate with the shutter <NUM> to separate the cast concrete elements <NUM>. As shown in <FIG>, the separated concrete elements <NUM> share a common void space in the mould, which is left open by the gap formed between the opposing first void former elements <NUM> with lips <NUM>.

Once the void former system is in place, reinforcing stud assemblies <NUM> may be positioned within passages <NUM> in the void former system <NUM> (as shown in <FIG>). While stud assemblies <NUM> are exemplified, other suitable reinforcement material may be used, such as reinforcing fibres. In an embodiment, no reinforcement material need be used. Further reinforcement <NUM> is placed over the void former system <NUM> to reinforce the top layer of the two concrete elements <NUM> (as shown in <FIG>). While not shown, it is envisaged that the mould may allow for more than one layer of void former systems <NUM> such that the concrete element <NUM> is provided with, for example, three horizontal layers of concrete separated by two void spaces. Concrete elements of such configuration are exemplified by <FIG>.

In <FIG> wet concrete is poured into the mould <NUM> and over the void former system <NUM>. The concrete flows though the passages <NUM> and into to the bottom of the mould <NUM>, thereby forming a bottom layer of concrete. The concrete will then fill the passages <NUM> and in turn the top layer above the void former system <NUM>. Concrete is not poured into the void space <NUM> shared between the two concrete elements <NUM> at this stage. That is, it is not poured into gap formed between the opposing first void former elements <NUM> with lips <NUM>.

After the concrete is poured it is allowed to set and cure in the mould <NUM>. Once the concrete has obtained sufficient strength the cast concrete elements <NUM> may be removed from the mould <NUM> as shown in <FIG>. While not shown, the cast concrete elements <NUM> may be separated and transported to a construction site where they may be again positioned in alignment to each other.

Prior to transport, or at the construction site, a concrete element <NUM> may be loaded with at least one, in an embodiment multiple joint-reinforcement bars <NUM> positioned within its void space <NUM> (see <FIG>). The joint-reinforcement bars <NUM> reinforce the connection between connected concrete elements <NUM>, and when the concrete element <NUM> is positioned next to another concrete element <NUM>, the joint reinforcement bars <NUM> are slid into the corresponding void space of the other concrete element <NUM> as shown in <FIG>.

Concrete is then poured into the gap between concrete elements <NUM>. As concrete is poured into the gap it fills the void space shared by the two concrete elements <NUM>, thereby connecting the two concrete elements <NUM> together as shown in <FIG>.

While not shown in <FIG>, it will be appreciated that the entirety of the void space <NUM> formed within a concrete element <NUM> by the void former system <NUM> need not be filled to join the two concrete elements <NUM>. In fact, to do so may prevent many of the advantages of forming void spaces in concrete elements as previously discussed. To prevent concrete from completely filling a void space, the void former system <NUM> may for example incorporate side-edge void former elements <NUM> which internally divide the void space <NUM> into an accessible void space in the surface of the concrete element <NUM>, and an internal void space. Upon joining two like concrete elements <NUM> only the two accessible void spaces are filled with concrete such that the joined construction element still comprises unfilled internal void spaces.

In an embodiment (shown in <FIG>), the void former system <NUM> may comprise one or more sleeve elements <NUM>, within which one or more joint reinforcement bar(s) <NUM> may be slidably positioned such that, in use the joint reinforcement bar(s) <NUM> slides from a storage position to a reinforcing position within the accessible voids of adjacent concrete elements <NUM>. Use of the sleeve elements <NUM> allows for two particular advantages:.

The sleeve elements <NUM> may be provided completely within a void space <NUM> of a void former system <NUM> (as shown in <FIG>), or it may extend beyond the void space <NUM> such that concrete is cast about the sleeve elements <NUM> (within which the joint reinforcement bar(s) <NUM> is slidably housed) when the concrete element <NUM> is first cast (as shown in <FIG>).

As shown in <FIG> concrete elements <NUM> may joined together at various angles to one another. For example, concrete elements <NUM> may be joined in parallel (as shown in <FIG>), or concrete elements <NUM> may be joined perpendicular to one another (as shown in <FIG> and <FIG>). In the embodiments shown, joint reinforcement bars <NUM> are, rather than being housed in sleeve elements <NUM> slidably housed by two adjacent mesh walls <NUM> within a concrete element <NUM> (rather than through use of sleeves). Also, access holes <NUM> are provided in the outer surface of the concrete element <NUM> to provide access to the join reinforcement bars <NUM>. Access holes <NUM> can be provided by simply blocking out a volume during concrete casting using a removable wooden block or similar.

Precast concrete elements <NUM> as shown in <FIG> may be joined together to form a larger construction element, which can be used as a horizontal concrete floor element as shown in <FIG> and <FIG>, or a vertical concrete wall element as shown in <FIG>. This may be in turn used to create a floor construction as exemplified in <FIG>.

In an alterative to pre-cast concrete construction techniques, void former units <NUM> may be used in situ to form larger construction elements by pouring concrete onsite. That is, the void former units <NUM> may be laid out onsite with concrete poured thereover to produce items such as: ground-bearing slabs, foundation pads, building cores, and pavements.

Where geometry does not match the modular grid precisely, it is intended that geometry differentials be established at the construction geometry perimeter (e.g. slab perimeter edges) using an edge shutter formwork method. Similarly, zones of the geometry can be remain free of the void former system to accommodate other nongrid dimensions and construction details such as; column connections, recesses, steps, penetrations, lifting fixings, façade fixings, service fixings, etc..

Alternatively, cast concrete blocks <NUM> can be created using void former units <NUM> according to an embodiment of the invention exemplified in <FIG>. The blocks <NUM> can be used much like standard bricks but provide for larger void spaces, allowing the blocks <NUM> to be lighter than standard bricks. Like standard bricks, the blocks can then be used to construct walls such as retaining walls. Compared to traditional bricks, the blocks are much lighter and use less concrete to produce. Traditional brick-laying methodologies may be modified to the lay the blocks in to a wall or similar. In an embodiment, concrete may be poured into the continuous void formed in a block wall laid using the blocks <NUM>. Alternatively, the void space <NUM> can be filled with insulation via means such as injection of expanding foam or blown fibres.

In another embodiment, a concrete element <NUM> can be produced with further improved insulative properties as exemplified by <FIG>. As such in <FIG>, passages <NUM> within void former units <NUM> may include a body of insulative material <NUM>, such as polystyrene, which provides a thermal barrier within the passage <NUM> and between a first surface <NUM> and a second surface <NUM> of the void former unit <NUM>. In use, the body of insulative material <NUM> joins to but otherwise substantially separates concrete formed on either side of the passage <NUM> and the void former unit <NUM>. When used as part of a concrete element <NUM>, bodies of insulative material <NUM> may be found in one, some or all passages <NUM> to improve insulative properties from one side of the concrete element <NUM> to the other (i.e. by reducing heat and/or sound flow through passages <NUM>). In embodiments comprising a hollow spacer element <NUM>, a body of insulative material <NUM> may be placed in the hollow spacer element <NUM> to thermally insulate one side of the hollow spacer element <NUM> from the other. Additionally, the void space <NUM> can be filled with insulation via means such as injection of expanding foam or blown fibres.

For construction elements that require voids to provide multiple functions, multiple layers of void space can be provided as shown in <FIG>. For example, void space <NUM> can be left empty or filled with insulation, and void space <NUM> can be left empty of filled with concrete. In this way, a first layer of void former units <NUM> otherwise incorporating void space <NUM> may provide the greater insulative properties, while a second layer of void former units <NUM> otherwise incorporating void space <NUM> may provide the greater structural properties.

The construction elements including the void former elements can be used with other similar components or in combination with a wide range of other components such as; 'Hollowcore' planks, solid precast walls and columns, in situ concrete, steel beams, etc. The overall construction shall typically result in buildings and other civil engineering forms.

Claim 1:
A void former unit (<NUM>) suitable for forming a void in a concrete element comprising:
(a) a first void former element (<NUM>), the first void former element (<NUM>) comprising a first surface (<NUM>) and at least one first opening (<NUM>) in the first surface (<NUM>);
(b) a second void former element (<NUM>), the second void former element (<NUM>) comprising a second surface (<NUM>) opposite the first surface (<NUM>) and at least one second opening (<NUM>) in the second surface (<NUM>), each second opening (<NUM>) corresponding to a first opening (<NUM>) in the first surface (<NUM>), wherein
the first void former element (<NUM>) and the second void former element (<NUM>) are connected to form a passage (<NUM>) between each first opening (<NUM>) and its corresponding second opening (<NUM>), and a single void space (<NUM>) surrounding the or each passage (<NUM>), and further wherein
the void former unit (<NUM>) is modular in shape to allow for multiple void former units (<NUM>) to be connected together, thereby substantially continuously extending:
(c) the first surface (<NUM>);
(d) the second surface (<NUM>); and
(e) the void space (<NUM>) between the first surface (<NUM>) and the second surface (<NUM>), across multiple void former units (<NUM>).