GB2102338A

GB2102338A - A deformable or collapsible structure and method of using such a structure

Info

Publication number: GB2102338A
Application number: GB08215142A
Authority: GB
Inventors: Donald Jonathan Bissland
Original assignee: BELDALE INVESTMENTS Ltd
Current assignee: BELDALE INVESTMENTS Ltd
Priority date: 1981-05-27
Filing date: 1982-05-24
Publication date: 1983-02-02

Abstract

A deformable or collapsible structure which is rigid when dry and is deformable or collapsible under the action of moisture comprises two sheets (1,2) of material between which is sandwiched a separating medium (3) which fills at least a substantial part of the space between two sheets (1,2), the separating medium at least being attackable by water or other liquids. The invention also includes a method of using such a structure. <IMAGE>

Description

SPECIFICATION A deformable or collapsible structure and method of using such a structure This invention relates to a deformable or collapsible structure which is primarily designed for use in concrete casting operations and also to a method of building construction which uses such a structure when, for example, casting concrete parts of a building.

In modern times, the construction industry has made considerable use of concrete, such as in the production of foundations and in the construction of flooring. The techniques used have been applied to the construction of large scale buildings such as blocks or flats and industrial developments such as factories and offices as well as to the construction of private housing.

One difficulty which is encountered in building construction resides in the fact that there can, for various reasons, be movement of the ground upon which the structure rests. When this movement is serious, foundations can be shifted and concrete flooring can be either cracked or broken up or can be bodily lifted from the foundations. In the worst case, such a movement can cause total destruction of the building either directly or in that it has to be demolished for safety reasons.

Ground movement is a particular problem when constructing buildings on clay soil, for example. As is known, clay swells very substantially when wet and can cause, for example, a vertical movement of the ground level of 30 mm between its wet and dry states. Thus when building structures on this type of ground, it is often desirable to arrange for a void to be left beneath or around the concrete, at least initially to take up this movement.

It will also be appreciated that there are other conditions which also require there to be a void beneath or around the concrete structure, for example when it is necessary to allow soil beneath or around the structure to breathe.

The present invention seeks to provide a collapsible or deformable structure which is generally rigid but which can be caused to become deformable or collapsible under relative controlled conditions and also to provide a method of using such a structure.

According to the invention there is provided a deformable structure which is rigid when dry and is deformable or collapsible under the action of moisture, wherein the structure comprises two sheets of material sandwiching between them a separating medium which fills at least a substantial part of the space between the two sheets, at least the separating medium being attackable by water or other liquids.

Preferably the separating medium comprises a water soluble plastics material, suitably in the form of an expanded plastics foam. Alternatively, the separating medium may comprise an expanded inorganic foam which is water soluble.

The foam may be of open or closed cell type. One or more parts of the structure may be treated to provide delay in the action of the liquid by which it is attackable. The invention also includes a method of building using a deformable or.

collapsible structure such as that above referred to.

The invention will now be described in greater detail, by way of example, with reference to the drawings, in which: Figure 1 is a perspective view of one form of deformable or collapsible structure in accordance with the invention, and Figure 2 is a schematic view showing the use of the structure of Figure 1 in building construction.

Referring to the drawing, the deformable or collapsible structure comprises two sheets 1 and 2 of a suitable material such as chipboard, composition board, or hardboard. The two sheets 1 and 2 are separated by a separating medium 3, in the form of an expanded plastics material or an inorganic foam which are soluble in water.

The sheets of the structure may suitably be glued to the separating medium and this glue may if desired be water soluble also. Where the sheets 1 and 2 of the material are not porous e.g. when using hardboard, at least one sheet is perforated to permit the passage of moisture unless the arrangement is such that other means are provided for feeding the water to the separating medium 3. Examples of such soluble material are materials based on polyvinyl alcohol or soluble versions of inorganic foam material such as a soluble version of the foam sold by l.CI. under the designation IF70.

The material used may be either open celled or closed celled as desired.

Instead of providing a completely integral separating medium for the collapsible structure, the separating structure may be built up in blocks of foam material arranged in a suitable formation between the two sheets, a void, if desired being left between individual blocks. The type of construction used will depend upon the length of time it is necessary for the material to remain in its rigid state before deformable or collapse takes place.

If desired the water soluble material may be replaced by materials soluble in other than liquids so that absolute control of the deformable or collapsibility of the structure may be achieved.

Such liquids may include liquid detergents. Thus, using this type of material, in certain circumstances in which the collapsible structure may be required to remain in or on the ground for very long periods, e.g. for a number of weeks, to allow the construction of specialised steel work or piping prior to the pouring of the concrete, adequate control may still be achieved. Thus when it is desired to collapse or deform the structure, the appropriate liquid is fed to the structure at the appropriate time.

In use of the structure (Fig. 2), once the normal preparations of the site has been made, i.e. ground levelled and trenches dug, the structure is laid in the form of boards 20 to 23 with their water permeable surfaces 25 facing outwards, i.e. in the direction from which the moisture which is to deform or collapse the boards will come. Casting of the concrete can be carried out either by laying the concrete on top of a board (e.g. board 24) when a horizontal structure is required, or the boards (e.g. boards 21 to 23) may be used, for example, as bases and shuttering in trenches.

With suitable dimensioning of the materials used in producing the boards, the rigidity will remain during a period when it is necessary to set the concrete, i.e. a period normal in excess of 1 6 hours. Admission of moisture suitably takes place through the permeable surface of the boards. The periods of time which are required for the boards to remain rigid can be controlled by the suitable selection of the materials and the construction of the boards.

In special circumstances, one or more of the parts of the board may be treated to provide a delay in the action of the liquid by which it is attackable.

If instead of the situation with the normal building construction, it is desired to leave a void in situations where there is no significant moisture or little moisture available for deforming or collapsing the board, the board may be saturated with water from a separate source when it is desired to deform or collapse it. The size of the void can be increased by the removal of the exterior sheets together with any remaining undisintegrated separator, if desired.

From the above it can be seen that the described deformable or collapsible structure can be used to create a void by application of water or other suitable liquids to a separating medium attackable thereby.

Claims

1. A deformable or collapsible structure which is rigid when dry and is deformable or collapsible under the action of moisture, wherein the collapsible structure comprises two sheets of material sandwiching between them a separating medium which fills at least a substantial part of the space between the two sheets, the separating medium at least being attackable by water or other liquids.

2. A structure according to claim 1, wherein the separating medium comprises a soluble plastics material.

3. A structure according to claim 1 or 2, wherein the separating structure comprises an expanded plastics foam.

4. A structure according to claim 1, wherein the separating medium comprises an expanded inorganic foam which is water soluble.

5. A structure as claimed in any preceding claim, wherein the foam material of the separating structure may be of the open cell type.

6. A structure according to any one of claims 1 to 5, wherein the foam material of the separating structure is of the closed cell type.

7. A structure according to any one of claims 1 to 6 wherein one or more parts of the structure is or are treated to provide a delay in the action of the liquid by which it is attackable.

8. A method of building comprising laying a board formed of a collapsible or deformable structure according to any one of claims 1 to 6, as a base and/or shuttering for concrete and pouring concrete into or onto the mould parts formed by the deformable or collapsible board.

9. A method according to claim 8, wherein the mould structure formed from the deformable or collapsible board is lined with a water impermeable membrane so as to prevent water in the concrete from attacking the structure.

10. A collapsible or deformable structure substantially as described herein with reference to the drawing.

11. A method of building substantially as described herein with reference to the drawing.