GB2196681A - Members for casting concrete - Google Patents

Abstract

A member (1) useful for casting concrete in the formation of foundations such as beams or slabs, comprises a generally three sided compressible unit including base (2) and spaced upright sidewalls (3) any of which can include voids (7). Both walls are associated with support means (5,6) to resist outward displacement under load generated by concrete cast into the interior. Optional cover 10 and retaining clip 11 can be included and the units abutted or overlapped to form a concrete casting assembly. The compressible nature of the unit and/or the voids are for resisting the effects of ground 'heave' associated with clay soils. An impermeable membrane may cover the external faces of the unit to resist moisture but not ground heave. <IMAGE>

Description

SPECIFICATION Members for casting concrete This invention concerns members for casting concrete. More particularly it is concerned with a member suitable for casting concrete such as moulds, extrusions and the like, assemblies suitable for constructing concrete foundations and the use thereof in casting concrete. The invention may thus have principal application in the building and construction industry.

Concrete foundations are conventionally laid as slabs or beams at or below ground level to provide support for subsequently formed building structures. It is conventional to use ply or timber shuttering for constructing concrete slabs or beams.

Certain clay soils have a predisposition to expand and contract and this movement of soil is well known as ''ground heave" or "clay heave".

In sub-surface construction, the sides of excavations are frequently used for forming concrete giving poor accuracy and using an excess of concrete material. Ground beams formed in this manner, without an infill material, are at risk of damage or even collapse of the foundation sides during or after construction as a result of ground or clay heave.

Consequently, in such soil conditions it is necessary to accommodate the effects of heave, particularly when forming concrete ground beam foundations.

One commercial product used to counter effects of this heave is a cardboard structure known as CLAYBOARD (Trade Mark) manufactured by Dufaylite Developments Limited. This material collapses when wetted and is used as separate pieces on the soffit and sides of ground beams to take up soil expansion.

Apart from a high initial outlay, the material requires cutting from standard sheets which can be wasteful, and there are problems in using this material on site. The product may collapse prematurely by contacting ground water or wet concrete. However, the product requires wetting to induce loss of strength and so accommodate soil expansion without transferring potentially damaging forces. In certain cases it is recommended to cover CLAYBOARD with plastics sheeting involving further effort, costs and inconvenience.

There is available a grade of compressible expanded polystyrene supplied in standard sized sheet farms known as CLAYMASTER (Trade Mark) manufactured by Vencel Resil Limited. Whilst this product is reasonably convenient to use on site it does require cutting to size and has limited capacity to absorb expansion. Whilst both commercial products are useful in constructing the underside (soffit) of ground beams by casting concrete on top of them, the materials are not useful as site forms when they must be used in conjunction with shuttering or, alternatively, located in position after the concrete member has been cast.

It is from consideration of the existing techniques used in casting concrete that has led to the development of the present invention.

According to a first aspect of this invention there is provided a member suitable for casting of concrete comprising a base connected to a pair of spaced upright walls, the member formed from a compressible material, the external face of both walls having support means for resisting outward displacement thereof when concrete is poured into the member.

According to a second aspect of this invention there is provided a mould section, suitable for casting of concrete, comprising an elongate base and two elongate, upright side walls integrally formed with the base, the section formed from compressible polymeric-material and the external face of both side walls incorporating a linear recess in which part of an elongate, rigid support member can be inserted and maintained in position.

The external faces of the side walls and/or the base may include one or a series of voids and such void(s) may be defined by linear recesses such as grooves. The said grooves or depressions may be ribbed, and may extend longitudinally and/or laterally with respect to the base. The base and sidewalls may be seperable or integral. In separable form the member provides a fold-flat carrying and storage facility.

Preferably the linear recesses are defined by parts of the member which are integrally formed with the respective side wall. The member may inciude a channel formation at the top of both side walls in which a cover can be located if required. The member may be constructed from cellular, foamed or expanded material and it is preferred to use expanded polystyrene.

It should be noted that the invention includes within its scope an assembly of members in abutment or in overlapping engagement suitable for forming foundation work comprising beams and/or slabs, the assembly extending in any given pattern or arrangement.

Support means may comprise e.g. elongate timbers arranged to engage the sidewalls and be supported by other means such as clips.

The member may further comprise one or more elongate clips which not only extend the width of the channel defined by the base and sidewalls but also located around and assist the support means.

In order to provide further reinforcement the member may be additionally supported by one or more stakes also useful in maintaining any elongate timbers present in e.g. a recess in the upper parts of the external surface of each sidewall.

The scope of this invention further embraces the use of members or assemblies as defined above in a method of casting concrete and method of in-situ casting of concrete by casting concrete into a member or assembly as defined.

In order that the invention may be illustrated and readily carried into effect, embodiments thereof will now be described by way of example only with reference to the accompanying drawings and in which: Figure 1 is an isometric view of one form of member as a moulded unit, Figure 2 is a sectional view of a similar moulded unit, and Figure 3 illustrates an assembly of members in engagement for subsequent casting of concrete.

in general, whether the members are used on the surface or below ground in an excavation they should be placed on a prepared surface i.e. bladed flat and reasonably level with any unevenness or undulations levelled out with a thin bedding of e.g. sand.

Referring firstly to Fig. 1 of the drawings, the moulded member 1 comprises elongate base 2, integrally formed upright side walls 3 and elongate linear recesses 4. Because the member has integrally formed side walls there are no joints between the base and side wall, the member being continuous compressible expanded polystyrene. The linear recesses 4 are rectangular and formed in the upper parts of the external faces of walls 3, the recesses filled by rigid supports 5. These supports are conveniently in the form of timbers 5 and/or 6, the support member 6 acting as packing.

The underside of the base 2 and the external faces of the sidewalls have a plurality of longitudinal and/or linear grooves 7 (shown only in the base) the grooves acting as voids to accommodate horizontal and/or vertical ground or clay heave forces by way of pressure relief zones. Such heave conditions can be further taken up by the compressible nature of the material from which the member 1 is formed.

The upper parts 8 of the member define a recess 4 within which support member(s) are or can be inserted.

Each side wall has a channel formation 9 within which a cover 10 may be seated. The cover may be made of expanded polystyrene or other suitable material. A steel clip 11 is used to maintain support members 5 (and packing 6) in position and hence limit outward displacement of sidewalls 3. The ends of such clips curve under the base of each support 5.

These clips 11 may be made from thin gauge steel formed at one end and bent on site at the other end to accommodate any given width of channel and any variations in the size of support means. The clips and support members (including packing and/or stakes) may be reusable and thus advantageous in phased constructions. The purpose of all support means for the sidewalls is to restrain outward displacement and consequent disfigurement of the member and any concrete foundation being formed therein. It will be appreciated that considerable load will be applied to the sidewalls by the weight of concrete cast into the channel within the member. In order to close the channel at each end of a member suitable covers, such as wooden boards (not shown) may be included and held in position by appropriate means.

As shown in Fig. 2 the member 1 has thicker portions 8 which define linear recesses 4. This arrangement may be less preferred than the arrangement of Fig. 1 in view of the bulk of material. The member is shown beiow ground 13 level, stakes 12 being inserted into the ground 13 immediately adjacent the sidewall support means and/or adjacent the ends of the clips 11.

Referring to Fig. 3 of the drawings an assembly of members is shown in predetermined array for casting of concrete to form appropriate foundation work. The arrangement also illustrates various joints that may be used to form assemblies or non-linear members.

Corner sections may be cut to a mitre and joined in abutment as at 14. Extensions of the same width may be butt-jointed as shown at 15. Where it is desired to increase the width of ground beam to be formed, this may be effected by means of overlap engagement shown at 16. This assembly more clearly shown an array of regularly spaced longitudinal grooves 7 in both side walls of the mould section but lateral such grooves might be preferred. The arrangements of additional packing 6, cover 10 and clip 11 have been omitted for clarity.

It will thus be appreciated that members and assemblies according to the invention are useful in the construction of formers for casting concrete, especially ground beams. The member, which may be rectangular, may be made to standard widths and lengths and may be of relatively lightweight construction. In use, the members may be regarded as disposable, being used only once and left in position. In the construction of ground beams this is partly for convenience but also to provide a compressible infill medium to the slides and soffit of the cast beams, which medium is capable of absorbing the expansive effects of ground or clay heave.

It has been found that the use of rigid supports 5 strengthens the members and sustains the pressure from wet concrete. One rigid support member may extend the length of more than one mould section as shown in Fig.

3. Voids may be formed in the external walls of the member not only to absorb the expansive forces of ground heave but also to reduce the quantity of material that needs to be employed. The internal faces may be smooth and the dimensions manufactured to close tol erance. Standard sizes may be supplied to suit a variety of sizes of square or rectangular ground beams. A series of members may be butt-jointed using adhesive tape to effect a seal for receiving concrete. For ground beam intersections the members may be mitred or adapted to suit requirements.

The present members may be useful in excavations in the ground or on the surface depending upon the particular level of construction. They may be convenient to use in installation and assembly by simply cutting to size.

The steel clips described above are useful in preventing outward displacement of the side walls during the concrete stage and also serve to restrain the support members 5. They also provide a suspension point for initial positioning and can secure any cover when required.

The cover can protect against freezing in cold weather and reduce evaporation in warm or windy conditions.

It is possible to form holes for the passage of e.g. service pipes or electrical fittings through the finished concrete beam or slab contained within the channel defined by the member or an assembly thereof, since expanded polystyrene as the compressible material is easy to cut and shape. To vary the dimension of any beam to be formed, e.g.

from a standard to a non-standard size or section, an internal lining comprising layer(s) of compressible material can be used as the base and/or one or both side walls. For convenience the lining may comprising sheet(s) of polystyrene.

The (U-shaped) channel member could be manufactured in three parts. The base section would be formed with two longitudinal rebates near the edges, into which would slot the upright sidewalls. The present voides provided along the outer surfaces would be formed longitudinally as well, as a series of continuous ribs.

Apart from the manufacturing benefits it would be easier to store and deliver the member flat for assembly before use.

The alternative embodiment of the present invention may lack the strength and rigidity of a wholly-formed continuous member but it represents a possible alternative to a moulded unit.

A method of preventing the external voids from becoming choked with backfill during construction, removing their effectiveness as far as clay heave is concerned, has been devised. One way of carrying this out would be by glueing a thin water impermeable, such as polythene, membrane over the exterior surfaces of the member of sufficient strength to maintain the voids during construction, but yield under any prolonged lateral and/or upward pressure.

Claims (14)

1. A member suitable for casting of concrete comprising a base connected to a pair of spaced upright walls, the member formed from a compressible material, the external face of both walls having support means for resisting outward displacement thereof when concrete is poured into the member.

2. A member as claimed in Claim 1 in which one or more voids are present in the base and/or the external faces of the walls.

3. A member as claimed in Claim 2 comprising a series of optionally ribbed grooves extending longitudinally and/or laterally with respect to the base.

4. A member as claimed in any preceding claim constructed of polymeric material which is optionally cellular, foamed or expanded.

5. A member as claimed in Claim 4 in which the base and walls are constructed of expanded polystyrene.

6. A member as claimed in any preceding claim in which the base and walls are separable.

7. A member as claimed in any preceding claim in which the base and/or walls comprise a moulding or extrusion.

8. A member as claimed in Claim 1 in the form of a mould section comprising an elongate base and two elongate, upright sidewalls integrally formed with the base, the section formed from compressible polymeric material and the external face of both sidewalls incorporating a linear recess in which part of an elongate, rigid support member can be inserted and maintained in position.

9. A member as claimed in any preceding claim in which the means for resisting displacement comprise one or more elongate support members adapted to be located against an upper part of the external face of each wall.

10. A member as claimed in any preceding claim including one or more of the following: a cover part to rest on the upper edges of the walls, a retaining clip to resist wall displacement under load, and a supporting stake.

11. A member as claimed in any one of Claims 2 to 10, including a water-impermeable membrane such as plastics sheeting secured thereto to partly or fully cover the void(s).

12. A member as claimed in any preceding claim containing concrete or in combination with a concrete foundation member.

13. An assembly for constructing concrete foundation comprising a plurality of members as claimed in any preceding claim wherein two or more thereof are in end-to-end abutment or in overlapping engagement.

14. Use of a member as claimed in any one of Claims 1 to 12 or of an assembly as claimed in Claim 13 in a method of casting concrete.