WO2008116274A1

WO2008116274A1 - Formwork

Info

Publication number: WO2008116274A1
Application number: PCT/AU2008/000455
Authority: WO
Inventors: Ian Robert Ackland
Original assignee: Advanced Formwork Systems Pty Ltd
Priority date: 2007-03-28
Filing date: 2008-03-27
Publication date: 2008-10-02
Also published as: AU2007201341A1

Abstract

The present invention relates to formwork for forming at least part of a concrete wall. The formwork includes a pair of retainers between which wet concrete of the wall can be retained. One or more spacers extend between the retainers and each define at least one passage in which a floor rebar can be received. Separation means is provided for separating at least one of the retainers from the set concrete wall. The present invention also relates to a method for forming concrete walls using the formwork. The present invention has particular application in joining concrete walls and concrete slab floors.

Description

TECHNICAL FIELD

The present invention relates to formwork for forming at least part of a concrete wall. The present invention has particular, although not exclusive application in joining concrete walls to concrete slab floors.

BACKGROUND

Skyscrapers and other multi-storey buildings are typically constructed using concrete material. Many of these buildings have concrete walls between which concrete floors extend.

In order to reinforce the joint between a wall and a floor, an embedded plate may be provided in the wall from which reinforcement rods outwardly extend. This system is colloquially known as the "Rebox System". The concrete wall can be formed first, and then the concrete floor can be formed to abut the wall and receive the cantilevered reinforcement rods.

In practice, the cantilevered rods can bend under the weight of the poured floor concrete, and may be weakened or break in the process. On occasion, the embedded plates may even become dislodged from the wall altogether.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, there is provided formwork for forming at least part of a concrete wall, the formwork including: a pair of retainers between which wet concrete of the wall can be retained; one or more spacers for extending between the retainers and each defining at least one passage; and separation means for separating at least one of the retainers from the set concrete wall. The formwork provides a means for facilitating the formation of an improved joint between the wall and a floor, as reinforcement bars (i.e. rebars) of the floor may be passed into respective passages prior to pouring the floor concrete.

Each retainer may include a quadrilateral plate having inwardly beveled edges. Each retainer may define a plurality of inner wells for receiving respective spacers. Each retainer may define a plurality of outer recesses for receiving ends of respective fasteners. Each retainer may define a threaded hole in which a separation bolt of the separation means can be engaged.

Preferably, each retainer includes a plate formed from polyethylene (PE) or high density polyethylene (HDPE). Even more preferably, each plate is formed from Polystone 300™ supplied by Dotmar Engineering Plastic Products (see http://www.dotmar.com.au) or other like HDPE.

In one embodiment, each spacer is a conduit defining a single open passage. Alternatively, each spacer may be hollow and define a pair of oppositely extending passages separated by a common wall. The formwork may include a plurality of conduits. The formwork may include up to fourteen conduits.

The separation means may include a pair of separators for separating respective retainers from the set concrete wall. Each separator may include a threaded hole defined in a retainer. Each separator may further include a separation bolt for engaging in the threaded hole so that the retainer can be forced from the set concrete wall.

The formwork may further include one or more fasteners for extending through respective passages, and for fastening the retainers and spacers together. Each fastener may include a shaft having a threaded end to which a fastening nut can be engaged. Each shaft may be bent at an opposite end to the threaded end. According to another aspect of the present invention, there is provided a method for forming at least part of a concrete wall with formwork, the formwork including a pair of retainers between which one or more passage defining spacers can extend and separating means for separating at least one of the retainers from the wall, the method including the steps of: pouring wet concrete of the wall between the retainers to surround the spacers; and separating at least one of the retainers from the set concrete wall using the separating means.

According to another aspect of the present invention, there is provided formwork for forming at least part of a concrete wall, the formwork including: a pair of retainers between which wet concrete of the wall can be retained, each retainer including a plate formed from Polystone 300™ or another like grade of high density polyethylene; and one or more spacers for extending between the retainers and each defining at least one passage.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred features, embodiments and variations of the invention may be discerned from the following Detailed Description which provides sufficient information for those skilled in the art to perform the invention. The Detailed Description is not to be regarded as limiting the scope of the preceding Summary of the Invention in any way. The Detailed Description will make reference to a number of drawings as follows:

Figure 1 is a perspective view of formwork in accordance with an embodiment of the present invention;

Figure 2a is a partial front view of the formwork of Figure 1 ;

Figure 2b is a partial top view of the formwork of Figure 1 ; Figure 2c is a partial rear view of the formwork of Figure 1 ; and

Figures 3a-e are schematic side views of the formwork of Figure 1 showing the sequential steps involved with forming a concrete wall and floor.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

According to an embodiment of the present invention, there is provided formwork 10 (Figure 1) for forming the base part of a concrete wall 20 as shown in Figure 3.

Referring firstly to Figure 1 , the formwork 10 (or former) includes a pair of like plate retainers 2 between which wet concrete of the wall 20 can be retained. A quartet of plastic conduits 4 act as spacers and extend between the spaced apart retainers 2, although in other embodiments up to fourteen conduits 4 may be provided. Each conduit 4 defines an open ended passage in which a floor rebar can be horizontally received. In use, a sea of wall concrete surrounds the conduits 4. The formwork 10 further includes a pair of separators 12 (Fig. 2b) for separating respective retainers 2 from the set concrete wall 20. Upon separation of the retainers 2 from the wall 20, the floor rebars can be provided into respective conduit passages prior to pouring wet floor concrete. A detailed description of the formwork 10 is provided below.

As can best be seen in Figure 1 , each retainer 2 includes a rectangular (or square) plate having four inwardly beveled edges 8. The beveled edges 8 facilitate the formation of a concavity in the base part of the wall 20 into which the floor concrete can be poured, as described in detail below. Each rectangular plate is formed from high density polyethylene (HDPE) so as to facilitate reusability of the formwork 10. The applicant has found that forming the plates from Polystone 300™_, supplied by Dotmar Engineering Plastic Products (see http://www.dotmar.com.au), is highly desirable whereby sticking of the concrete to the plates is minimal. The following table sets out a number of physical properties of Polystone 300™ that have been found to be suitable:

Broadly, the material is a natural, white or black, high-density polyethylene. It is to be appreciated that any such polyethylene is suitable for forming the rectangular plates. Key features of the material should be that it is weldable, substantially weatherproof and have a significant resistance to chemical attack. As a result, the material inhibits the adherence of concrete to itself. As shown in Figure 2b, each retainer 2 defines a plurality of inner wells 14 for snugly receiving respective conduits 4. Each retainer 2 further defines a plurality of outer slotted recesses 16 for receiving ends 22, 24 of respective fasteners 6. Each fastener 6 includes an elongate shaft which is bent at one end to define a bent head 22 and has a threaded tail 24. The bent head 22 is located in a slotted recess 16 of one retainer 2, the shaft extends through the conduit passage, and the tail 24 is located in a corresponding a slotted recess 16 of the other retainer 2.

Each fastener 6 further includes a fastening nut 26 for engaging with the threaded tail 24 so that the retainers 2 and conduits 4 can be fastened together. The bent head 22 is received within the slotted recess 16 which restricts the rotation of the head 22 as the nut 26 is loosened or tightened (Figure 2a). Furthermore, each slotted recess 16 defines an enlarged head 18 to facilitate access to the nut 26 for loosening or tightening (Figure 2c).

Turning to Figure 2b, the formwork 10 includes a pair of separators 12 for separating the retainers 2 from the set concrete wall 20. Each separator 12 include a countersunk and threaded hole 28 defined by a retainer 2. Each separator 12 further includes a separation bolt 30 for engaging in the threaded hole 28 so that the retainer 2 can be forced from the set concrete wall 20. Typically, each retainer 2 includes a rectangular PE plate, and a threaded bush (or nut) 32 embedded in the plate and which defines the threaded hole 28.

A method for forming the concrete wall 20 with the formwork 10 is now described in detail below with reference to Figure 3.

As shown in Figure 3a, a lower wall 34 of a multi-storey building is initially formed. The assembled formwork 10 is then fixed in position upon the lower wall 34. A pair of planar shutters 36 is then located on either side of the lower wall 34 (and the formwork 10) to form a mould into which wet wall concrete can be poured. As shown in Figure 3b, wet concrete 38 is then poured from above into the cavity defined between the shutters 36. The wet concrete 38 surrounds the conduits 4 of the formwork 10 between the retainers 2.

Turning to Figure 3c, the wet concrete 38 is allowed to set and forms the upper wall 20. Once the concrete 38 sets, the shutters 36 are removed from the walls 20, 34. A user then disengages fastening nuts 26 from the threaded shafts of fasteners 6. The user then engages separation bolts 30 in the threaded holes 28 defined by the retainers 2 which force the retainers 2 to separate from the set concrete wall 20. The conduits 6 remain fixed in the wall 20. Concavities are formed in the base of the upper wall 20 where the retainers 2 were previously located.

As shown in Figure 3d, reinforcing bars (rebars) 40 are horizontally passed through respective conduits 6.

Turning to Figure 3e, floor concrete is then poured to form the floor 42 of a particular level in the multi-storey building and fills the concavities in the base of the upper wall 20. The rebars 40 extend through the wall 20 and provide a sturdy joint between the wall 20 and floor 42. Furthermore, the rebars 40 are resistant to bending or becoming dislodged from the wall 20 during the pouring of the floor concrete as they are fully supported by the conduits 4 (and the wall 20).

A person skilled in the art will appreciate that many embodiments and variations can be made without departing from the ambit of the present invention.

In the foregoing embodiment, each conduit 4 was a spacer defining a single open passage through which the rebars 40 could pass through entirely. In alternative embodiments, each spacer may be hollow and define a pair of oppositely extending passages separated by a common internal wall. In yet another embodiment, each spacer need only define a single passage having a closed end and would be suitable for use in forming outer walls of the building, when the rebars 40 need not entirely pass through the wall.

In the preferred embodiment, each retainer 2 included an embedded threaded bush 32 defining the threaded hole 28. In an alternative embodiment, the bush may be replaced by a metal plate defining a hole with which the separation bolt 30 can engage.

In the preferred embodiment, fasteners 6 were provided for fastening the formwork 10 together. In an alternative embodiment, the fasteners need not be provided as the formwork 10 can be held together during the pouring of concrete by the shutters 36.

In the preferred embodiment, the formwork 10 was used to form the base part of upper wall 20. In an alternative embodiment, the retainers 2 of the formwork 10 may be enlarged to form the whole upper wall 20, thereby removing the need for shutters 36.

In one embodiment, the shaft of the fastener 6 may be threaded along its entire length. Accordingly, the shaft may engage with a complementary threaded hole defined by the retainer 2 (on the floor of enlarged head 18 of slotted recess 16) and then be bent to form the bent head 22.

In compliance with the statute, the invention has been described in language more or less specific to structural or methodical features. It is to be understood that the invention is not limited to specific features shown or described since the means herein described comprises preferred forms of putting the invention into effect. The invention is, therefore, claimed in any of its forms or modifications within the proper scope of the appended claims appropriately interpreted by those skilled in the art.

Claims

The claims defining the invention are as follows:

1. Formwork for forming at least part of a concrete wall, the formwork including: a pair of retainers between which wet concrete of the wall can be retained; one or more spacers for extending between the retainers and each defining at least one passage; and separation means for separating at least one of the retainers from the set concrete wall.

2. Formwork as claimed in claim 1, wherein each retainer includes a quadrilateral plate having inwardly beveled edges.

3. Formwork as claimed in claim 1 , wherein each retainer defines a plurality of inner wells for receiving respective spacers.

4. Formwork as claimed in claim 1 , wherein each retainer defines a plurality of outer recesses for receiving ends of respective fasteners.

5. Formwork as claimed in claim 1 , wherein each retainer defines a threaded hole in which a separation bolt of the separation means can be engaged.

6. Formwork as claimed in claim 1 , wherein each retainer includes a plate formed from polyethylene (PE) or high-density polyethylene (HDPE).

7. Formwork as claimed in claim 6, wherein each plate is formed from Polystone 300™ or another like grade of PE.

8. Formwork as claimed in claim 1 , wherein each spacer is a conduit defining a single open ended passage.

9. Formwork as claimed in claim 8, wherein the formwork includes a up to fourteen conduits.

10. Formwork as claimed in claim 1 , wherein the separation means includes a pair of separators for separating respective retainers from the set concrete wall.

11. Formwork as claimed in claim 10, wherein each separator includes a threaded hole defined in a retainer.

12. Formwork as claimed in claim 11 , wherein each separator further includes a separation bolt for engaging in the threaded hole so that the retainer can be forced from the set concrete wall.

13. Formwork as claimed in claim 1 , further including one or more fasteners for extending through respective passages, and for fastening the retainers and spacers together.

14. Formwork as claimed in claim 13, wherein each fastener includes a shaft defining a threaded end to which a fastening nut can be engaged.

15. Formwork as claimed in claim 14, wherein each shaft is bent at an opposite end to the threaded end.

16. A method for forming at least part of a concrete wall with formwork, the formwork including a pair of retainers between which one or more passage defining spacers can extend and separating means for separating at least one of the retainers from the wall, the method including the steps of: pouring wet concrete of the wall between the retainers to surround the spacers; and separating at least one of the retainers from the set concrete wall using the separating means.

17. Formwork for forming at least part of a concrete wall, the formwork including: a pair of retainers between which wet concrete of the wall can be retained, each retainer including a plate formed from Polystone 300™ or another like grade of high density polyethylene; and one or more spacers for extending between the retainers and each defining at least one passage.