AU784695B2 - Formwork for casting concrete and method for doing same - Google Patents

Description

P/00/011 28/5/91 Regulation 3.2(2)

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION STANDARD PATENT Application Number: Lodged: Invention Title: FORMWORK FOR CASTING CONCRETE AND METHOD FOR DOING SAME The following statement is a full description of this invention, including the best method of performing it known to us E" Y I FORMWORK FOR CASTING CONCRETE AND METHOD FOR DOING SAME FIELD OF THE INVENTION This invention relates to modular, formwork bodies for casting concrete and other curable construction materials. However, the casting formwork may be used for other purposes as explained below.

BACKGROUND OF THE INVENTION Re-usable concrete formwork moulds are known in the art. These normally consist of two- or multi-part re-usable steel or fibreglass mould components that can be braced together to form a casting cavity corresponding in shape to the desired building element. These moulds are typically of a fixed length and shape.

For concrete casting of larger structures, the mould walls are usually thick plates, which may be reinforced by steel rods and the like, in order to withstand the substantial weight of the concrete slurry prior to curing, thus resulting in heavy and bulky formwork moulds that require auxiliary (motorised) equipment to erect.

The joining of the mould halves is also time consuming. Known structures are also very expensive to manufacture, due to the strength requirements of the materials employed.

Whilst in many building structures, such as houses, apartment blocks and the like, ceiling heights are standardised, many applications exist where columns or pillars are used that require structures of variable height. In order to cast such columns or pillars using re-usable formwork components, it is necessary to stack, brace and cross-fasten a plurality of mould halves if a single cast operation is to be performed. Alternatively, incremental height casting may be employed, i.e. a first length of pillar is cast and a subsequent length portion is cast onto the previous one after the lower portion has set, using the same mould. However, this is a very time-consuming method.

Spirally formed plastic, steel cardboard tubing has also been used in the casting of round concrete pillars or casting concrete with a fibrous cement tube.

However, the inside surface of cardboard tubing usually renders a low-grade finish of the cast structure, which requires further rendering to be performed on the cast pillar. Existing spirally wound tubing used for casting is also generally circular in section, making it unsuitable for casting pillars with other crosssections.

2 Columns of square cross-section are typically cast in moulds constructed from timber, or similar materials. This method of construction also tends to be labour and time consuming and dimensional accuracy of successive pillar castings is not always ensured due to the need of erecting formwork from scratch each time a pillar is cast.

Australian Patent No. 696707 discloses a composite tube and method of manufacturing thereof. The tube consists of a foamed, tubular core with inner and outer surface liners. The tube can be formed to define a pillar-like casting cavity with a desired cross-section circular, square, polygonal); the casting formwork is manufactured using internal and external moulds with desired crosssections. The continuous outer liner of the composite tube is designed to withstand the hoop-stress resulting from filling of the internal cavity of the tubular mould, thereby providing a strong, yet light-weight component which can be used to cast concrete columns of quite substantial height.

One drawback of this type of formwork tubing is that once the concrete (or other casting material) has set, the peripherally closed tubular formwork has to be radially cut and pulled from the cast pillar or column. Formwork tubing that has been cut in this manner cannot be re-used without an additional bracing mantle, since the exterior lining that provides hoop strength for the formwork has been breached. As the tubing formwork disclosed in the Patent is relatively expensive in comparison with more traditional methods of forming concrete columns, it would be advantageous if the present invention could provide an alternate construction of similar type which would enable the formwork to be reused, thereby reducing overall casting costs.

Accordingly, it is an object of the present invention to provide a modular, re-usable formwork mould, and a method of manufacturing thereof, that has flexibility in regards to both length and cross-sectional shape and which is relatively inexpensive to manufacture, and which can be used to carry out multiple castings.Summary of the invention SUMMARY OF THE INVENTION According to one aspect, the present invention provides formwork for casting pillar-like or column-like structures, having at least two complementary mould segments that have an inner foam core that is at least partly covered with a liquid-impervious skin or liner. The mould segments define, when assembled, a moulding cavity open towards an upper and a lower end of the formwork. The formwork further includes a bracing member disposed to surround and restrain the assembled mould segments, and fasteners arranged to secure, preferably by tensioning, the bracing member, in order to hold the assembled mould segments together and resist displacement during casting.

The mould segments are provided with complementary abutment surfaces along a longitudinal axis thereof, such that the segments can be joined in a juxtapositioned manner, thereby forming the internal cavity that corresponds in cross-section with the desired shape of the pillar or column to be cast with the mould.

There is advantageously provided a seal for preventing leakage of the cast material, or other associated fluids, through the abutment interfaces of said mould segments. Such seal may be formed by coating the abutment surfaces with a waterproof elastic material such that when the mould halves are braced, a leakproof sealing edge is formed. The complementary surfaces may preferably be indexed to facilitate the correct positioning of the mould segments in forming the formwork. Said complementary surfaces may also preferably feature complementary indentations and protrusions, such as longitudinal ridges and valleys that interlock to help prevent liquid egress from the mould. The abutment surfaces may also be adapted to receive a gasket to help prevent liquid egress from the closed mould at the abutting edge surfaces.

Whilst the bracing member could simply consist of a plurality of steel or reinforced plastic bands that are tensioned about the closed mould segments and secured, in a preferred form the bracing member is a single sheet of waterimpervious, fibre-reinforced material of sufficient dimension to envelop, preferably in an overlapping manner, the circumference of the assembled mould segments along the entire length thereof. The free longitudinal ends of the bracing material may preferably be releasably secured together via a clamping or locking mechanism. The locking mechanism must be capable of holding the free edges of the bracing sheet together with sufficient force to resist the weight of the material that is to be cast into the assembled mould segments.

Preferably, the longitudinal free edges of the bracing material sheet joint along a line perpendicular to the circumference of the mould that does not coincide with any of the abutment interfaces at the mould segments. This arrangement is conducive in keeping any liquid egress from the concrete contained within the bracing material sheet which cloaks (sheathes) the mould segments.

Advantageously, the bracing sheet is fastened permanently to one of the mould segments, in particular along the entire length of the mould segment.

The present invention provides a light-weight structure for use as concrete formwork that has sufficient strength to support a column of fluid concrete as it sets. The mould may then be disassembled by releasing the clamping mechanism, folding back the bracing material sheet and removing the mould segments from the set concrete column without destroying the strength, or the waterproof nature of any of the segments. Therefore, the same construction may subsequently be re-used in forming further concrete column sections.

The lined foam construction of each of the segments allows a variety of different cross-sectional shapes to be constructed. Such make-up of the segments is also more cost effective than metal or fibreglass constructions known in the art.

Preferably, the core of the mould segments is formed from polystyrene.

Polystyrene may be readily cut by computer-assisted machine, or laser, cutting) into any desired shape, and is lightweight, stiff and strong. Polyurethane foam may alternatively be used, however this requires the mould segment cores to be moulded into the desired shape.

Preferably, the liquid impervious skin of each core is a sprayed, solventless, high build polyurethane or polyurea coating. These materials offer the advantage of fast curing, fast manufacture and are solvent-free. This helps to prevent adverse reaction with the foam core. These materials also have good impact resistance, assisting in extending the life of the mould segments. They allow a smooth finish to the cast concrete, negating the need for further finishing.

The fact that they are liquid-applied allows the optional incorporation of reinforcing mesh or cloth, if required. Advantageously, the entire foam core is so covered.

Alternatively, the waterproof liner may be formed from a material selected from the group including polyester; paint; epoxy resin; laminated, extruded or spray-applied plastic; laminated foil; waterproof paper; ceramic; latex; or other liquid-impervious lining designed to improve the durability, and the re-usable life, of the internal core material of the mould segment.

Preferably, the outer bracing material sheet is a sprayed, solventless high build polyurethane that is reinforced by the inclusion of a woven, high-tensile strength material. Preferably the woven material is selected from the group comprising polyester, polypropylene, polyethylene, PVC, hessian and fibreglass.

The outer bracing material shall be of sufficient hoop strength to maintain the desired shape of the mould when a force is applied from the inside of the mould, such as when the mould is filled with liquid concrete.

Preferably, the ends of the bracing material sheet are releasably and resiliently joined by providing eyelets at opposing locations on both ends of the sheet wrap. The opposing eyelets are linked and tied by looping a tensionadjustable metal cable tie through the eyelets, and releasably tightening the loop in known manner. Successive eyelets are similarly locked together down the length of the mould using additional metal cable ties until the entirety of the edges are evenly and securely fixed.

The outer bracing member may alternatively feature metal bars resiliently attached or received within a fold along the length of the longitudinal free edges sheet of the bracing material sheet, in order to facilitate engagement of releasable clamping means. Preferably, the releasable clamping means is a simple clamp.

Alternatively, the releasable clamping means may consist of a ratchet mechanism that is adapted to draw the ends of the bracing material together, thereby tightening (tensioning) the bracing material sheet evenly around the mould segments. The releasable clamping means may be reinforced by use of steel bands encircling the bracing material.

Another aspect of the present invention provides a method of casting a (concrete) column, including the steps of: arranging two mould segments, conforming to any one of the embodiments described above, in opposite abutment so as to form a formwork having an internal cavity that has a cross-sectional shape that conforms with the intended shape of the column; wrapping the flexible bracing sheet around the circumference of both mould segments, securing (preferably by tensioning) same about the closed mould segments and fastening the free edges of the bracing material sheet releasably together; pouring liquid concrete (or other castable, building material) into the cavity formed between the two moulded segments; allowing the concrete (or other material) to cure sufficiently for it to be able to support its own mass; releasing the clamping force applied to the bracing sheet; and removing the two mould segments from the sides of the column thus formed.

Preferably, an additional water-impervious lining could be provided inside the mould cavity, wherein the longitudinal edges of said lining do not coincide with the position of the abutment interfaces of the mould segments, thereby assisting in preventing liquid egress from the mould.

The present invention provides a concrete column mould, which is lightweight yet strong, and is relatively inexpensive to manufacture. It is also suitable for relatively simple on site manufacture and may easily be sized to enable the manufacture of concrete columns of varying lengths. The entire assembly is susceptible of re-use on multiple concrete pourings.

The invention described above has the advantage of being relatively simple to erect and disassemble, compared with the prior art. For example, a square column formed by conventional techniques would take approximately man-hours to erect, whereas the present invention is expected to take approximately 0.25 0.5 man-hours.

The invention, when utilised as a concrete formwork structure, is selfsupporting, and does not require a secondary supporting structure. This is a further improvement on the prior art.

The mould segments may be provided in modular lengths, e.g. 0.3m, 0.6m, 1.2m, 2.4m. These may be combined and joined to easily provide various mould heights. This flexibility is not possible with prior art moulds.

Most pre-formed tubes are relatively light and therefore occupy large volumes. The invention allows nesting of the mould segments. This significantly increases the length per unit volume ratio achievable in transport and storage, thereby significantly reducing the associated costs.

The invention does not require a purpose-built internal and external mould to produce each different size or shape of mould segment that is desired.

Therefore, capitalisation costs are lower than, for example, the manufacture of tubes described in Australian Patent No. 696707. The invention also allows lower material stocks to be held in inventory by the mould segment manufacturer, due to the same base materials being required for all of the different size and shape mould segments to be manufactured.

The formwork may also serve as a permanent protective shield when mounted/assembled around in-ground drainage or service pipes.

A single, non-limiting preferred embodiment of the invention will now be described with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a perspective view of an embodiment of the invention, wherein the complementary mould segments are adapted to form concrete formwork for casting a square concrete column, and wherein the complementary mould segments are shown in a disassembled state; Figure 2 is a perspective view of the concrete formwork, with the mould segments shown in complementary abutment, and the bracing sheet material is secured around the periphery of the mould.

DESCRIPTION OF PREFERRED EMBODIMENT Referring to Figure 1, the formwork should consists of essentially two mould segments or halves 1 and a bracing sheet 4 secured to one mould half and disposed to envelop both in the closed state of the formwork.

The shape of the mould segments 1 is determined by their intended use.

For concrete formwork to cast pillars or columns, the external and internal crosssection of the mould may generally be circular, however other shapes may be required (such as an ovular external cross-section where a rectangular internal cavity is required).

The mould segments include a polystyrene foam core 3. The core 3 will typically be cut to shape by a computer-aided profile cutter, or moulded. The foam core 3 of each of the mould segments 1 must be of sufficient strength to withstand the compressive force of a liquid concrete column by maintaining the internal profile shape during the pouring and curing of the concrete.

A lining or surfacing material 2 is applied to all surfaces of the mould segments 1, possibly with the exception of the top and bottom faces of the core 3.

The protective core surface lining is preferably a spray-applied, solvent-free polyurethane high-build coating. This material offers short curing time and therefore low manufacturing times. The absence of solvent ensures the coating does not adversely react with the foam material in the core. This material also offers good impact resistance and durability, and therefore a relatively long working life. This material also allows a smooth surface finish on the concrete column, including the ability to provide precise ornamental detail in the moulding, if required.

For concrete formwork applications, the internal profile of the mould segment will correspond to the external dimensions and shape of the concrete column to be constructed. Generally, two mould halves will be cut or moulded to produce two mould segments which, when abutted together at their complementary abutment faces, form a tube having the desired internal crosssectional shape of the concrete column to be cast. In the embodiment of Figure 1, the mould segments 1 are adapted to form a basically square column, with bevelled edges.

Referring further to figure 1, an outer bracing sheet 4 that features metal tubes or rods 5 received within folds at the free height-wise extending edges is attached glued) to the outside of one mould segment. However, it is typically not attached over the entire outer side of the mould segment, thereby to allow the outer layer to be "peeled back". The mould halves 1 have two height-wise extending abutment surfaces 6, 7 providing two mould separation lines. The abutment surfaces may be indexed to allow a juxtapositioned assembly of the mould halves (not illustrated). Similarly, the joining surfaces 6, 7 may be provided with a seal to prevent egress of fluid from the interior mould cavity through the mould line interfaces.

It will be appreciated by those skilled in the art that the form of the mould segments is not limited to any particular length or internal diameter or external diameter. It will also be appreciated by those skilled in the art that the internal and external profiles of the mould segments are also not limited to any particular shape.

The core foam material 3 is cut to the desired shape and size by computerassisted machine tools. The spray-applied, solvent-free high-build polyurethane external coating 2 is then applied to the inner and outer surfaces of the mould segment cores 3. Both mould segments are formed in this way.

The outer bracing sheet 4, formed from spray-applied, solvent-free highbuild polyurethane reinforced with polyester mesh 4 is then glued on to the outer coating 2 on the surface of one of the mould segments 3.

The free, reinforced ends of the outer wrap 4 are evenly tensioned against each other and joined, using a fastener susceptible to resisting the weight force of the liquid concrete, which tends to force the mould segments apart. As shown exemplarily in Figure 2, the metal bars 5 of the bracing sheet 4 are releasably secured by a clamp 8, others (not shown) being disposed along the height of the structure.

Once the mould structure is in place, the liquid concrete may be poured in to the cavity formed by the mould. After the usual setting and curing stages, the clamps 8 are released and the bracing sheet 4 is peeled back such that the mould segments 3 are able to be removed from the completed concrete column.

Claims (19)

1. Formwork for casting pillar-like or column-like structures, having at least two complementary mould segments that have an inner foam core that is at least partly covered with a liquid-impervious skin or liner, wherein said mould segments define, when assembled, a moulding cavity open towards an upper and a lower end of the formwork, and wherein the formwork further includes a bracing member disposed to surround and restrain the assembled mould segments, and fasteners arranged to secure, preferably by tensioning, the bracing member, in order to hold the assembled mould segments together and resist displacement during casting.

2. The formwork of claim 1, wherein the mould segments are provided with complementary abutment surfaces along a longitudinal axis thereof, such that the segments can be joined in juxtapositioned manner and thereby form the internal cavity that corresponds in cross-section with the desired shape of the pillar or column to be cast with the mould.

3. The formwork of either of claims 1 or 2, wherein there is provided a seal for preventing leakage of the cast material, or other associated fluids, through the abutment interfaces of said mould segments.

4. The formwork of claim 3, wherein the seal is formed by the coating of said abutment surfaces with a waterproof elastic material, such that when the mould halves are braced, a leak-proof sealing edge is formed.

The formwork of claim 4, wherein said abutment surfaces are indexed to facilitate the correct positioning of the mould segments in forming the formwork.

6. The formwork of claim 5, wherein said abutment surfaces may also be adapted to receive a gasket to help prevent liquid egress from the closed mould at the abutting surfaces. 1 ~3L.:

7. The formwork of any preceding claim, wherein said bracing member is a single sheet of water-impervious, fibre-reinforced material of sufficient dimension to envelop the circumference of the assembled mould segments along the entire length thereof.

8. The formwork of claim 7, wherein the longitudinal edges of the bracing member is be releasably secured together via a clamping or locking mechanism.

9. The formwork of claim 8, wherein said bracing member is positioned around the outer surface of the mould so as to ensure that the longitudinal edges of the bracing member are not positioned adjacent to the abutting surfaces of the mould.

The formwork of claim 9, wherein the bracing member is attached permanently to one of the mould segments.

11. The formwork of any preceding claim, wherein the core of the mould segments is formed from polystyrene or from polyurethane foam.

12. The formwork of any preceding claim, wherein the liquid impervious skin is formed from a material selected from the group comprising polyester; paint; epoxy resin; laminated, extruded or spray-applied plastic; laminated foil; waterproof paper; ceramic; latex; polyurethane or polyurea.

13. The formwork of claim 12, wherein the liquid impervious skin is formed from a sprayed, solventless, high build polyurethane or polyurea coating.

14. The formwork of any preceding claim, wherein the bracing member is a sprayed, solventless high build polyurethane that is reinforced by the inclusion of a woven, high tensile strength material.

The formwork of claim 14, wherein the woven material is selected from the group comprising polyester, polypropylene, polyethylene, PVC, hessian, woven steel and fibreglass.

16. The formwork of any preceding claim, wherein the ends of the bracing member are releasably joined by providing eyelets at opposing locations on both ends of the sheet wrap, opposing pairs of said eyelets being linked and tied by looping a tension-adjustable metal cable tie through the eyelets, and releasably tightening the loop.

17. The formwork of any preceding claim, wherein the bracing member features metal bars attached or received within a fold along the length of the longitudinal ends of the bracing member, in order to facilitate the releasable clamping together of said longitudinal ends.

18. The formwork of claim 14, wherein releasable clamping is effected by a ratchet mechanism that is adapted to draw the ends of the bracing material together, thereby tightening (tensioning) the bracing material sheet evenly around the mould segments.

19. A method of casting a column, including the steps of: arranging casting formwork according to any of claims 1 to 18 at the site of the column; wrapping the flexible bracing member around the circumference of the mould segments; securing, preferably by tensioning, the bracing member about the closed mould segments; fastening the free edges of the bracing member sheet releasably together; pouring liquid concrete into the cavity formed between the moulded segments; allowing the concrete to cure sufficiently for it to be able to support its own mass; releasing the fastening applied to the bracing member; and removing the two mould segments from the sides of the column thus formed. DATED this 27 t day of May 2002 EZYTUBE PTY LTD WATERMARK PATENT TRADE MARK ATTORNEYS 290 BURWOOD ROAD HAWTHORN VICTORIA 3122 AUSTRALIA CJS/ALH/ES I 1