AU2003200942A1 - Method of constructing a concrete slab for building and formwork for the method - Google Patents

Description

P/00/011 Regulation 3.2 COMMONWEALTH OF AUSTRALIA Patents Act 1990 COMPLETE SPEC/FICAT/ON FOR A STANDARD PA TENT Name ofApplicant Actual//nventor(s): Address for Serv/ce: Inventfon T/tle:.

EVOLUTION INTERNATIONAL PTY LTD Paul Anthony Camilleri AHEARN FOX Patent Trade Mark Attorneys GPO Box 1149 Brisbane Queensland 4001 *METHOD OF CONSTRUCTING

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CONCRETE SLAB FOR A BUILDING AND FORMWORK FOR THE METHODN The following statement is a full description of this invention, including the best method of performing it known to us: METHOD OF CONSTRUCTING A CONCRETE SLAB FOR A BUILDING AND FORMWORK FOR THE METHOD This invention relates to a method of constructing a concrete slab floor for a building and formwork for the method.

The invention has particular application to the construction of concrete slab floors for dwelling houses and small commercial buildings although it may be useful also for larger buildings and other structures.

Concrete slabs for dwelling houses and small commercial buildings are typically constructed using temporary formwork which is made of timber or steel. Typically, such formwork is fabricated and assembled on site and then erected in a predetermined position to define the perimeter of the slab to be constructed. After the slab has been poured and cured sufficiently, the formwork is removed and often re-used on the next slab to be constructed. However, the next slab usually is a different size and shape and consequently the formwork has to be dismantled, cut to suit and reformed. Typically, only two or three slabs can be constructed using the reformed formwork and completely new formwork needs to be constructed for the next slab. Thus, present methods of constructing concrete slabs is more expensive than desirable.

One problem with the presently known methods of constructing concrete building slabs is that if the edge portion of the slab is not vibrated sufficiently during pouring, it will have voids and passages therein which give an appearance often called "bony" or "honeycombed". The existence of the voids and passages only becomes apparent after removal of the formwork when the bony edges can be seen. While the bony appearance is aesthetically displeasing, it also indicates an undesirably weak portion of the slab. Additionally, the voids and passages provide a path by which termites can access the house to be built on the slab from the ground below. While the bony appearance may be overcome by rendering, often the voids and passages are too deep to be completely filled by rendering and a path for termites remains which is not visible from outside the house.

One object of the present invention is to provide a method of constructing concrete slab floors for buildings which overcomes or ameliorates at least one of the aforementioned problems or at least provides a suitable alternative to present methods. Another object is to provide formwork suitable for carrying out the method of the invention.

With the foregoing in view the invention in one aspect resides broadly in formwork for constructing a concrete slab floor for a building, including: a first wall of metal adapted to form a first edge of the concrete slab to be constructed; and first anchoring means operatively connected to said first wall and adapted to engage in the concrete slab to be constructed to permanently anchor said first wall to the concrete slab.

Preferably, said first anchoring means is a portion of metal extending from said first wall contiguous therewith, said first wall and said first anchoring portion enclosing an acute angle therebetween. In such form, it is preferred that said first anchoring portion be continuous with said first wall such that the rounded edge extends fully about the perimeter of the slab, thereby stiffening the first wall in both the horizontal and vertical planes. Advantageously, in such form of the invention the rounded edge is also adapted to support a screeding board during laying of the slab.

Preferably, said first wall and said first anchoring means are respectively a first wall portion and a first anchoring portion of a strip of metal and said first anchoring portion extends from and is contiguous with said first wall portion and encloses an acute angle therewith.

Preferably, the formwork includes a second wall of metal adapted to form a second edge of the concrete slab to be constructed spaced from the first edge, said second wall being operatively connected to said first wall. Advantageously, such form of the invention provides for the construction of a typical on-ground slab for a dwelling house with a set-down around the floor for supporting a brick wall thereon. In such form, it is preferred that the formwork include second anchoring means connected to said second wall and adapted to engage in the concrete slab to be constructed to permanently anchor said second wall to the concrete slab. It that form it is also preferred that said second wall and said second anchoring means are respectively a second wall portion and a second anchoring portion of a strip of metal and said second anchoring portion extends from and is contiguous with said second wall portion and encloses an acute angle therewith. Preferably, said second anchoring portion is adapted to stiffen said second wall portion in the horizontal and vertical planes also and is adapted to support the second wall portion on a horizontal surface.

Preferably, said first wall and said second wall are connected by a third wall adapted to form a horizontal face of the slab to be constructed between the first edge and the second edge. Suitably such horizontal face is adapted to support brickwork thereon for forming the brick wall of a buiding, particularly a dwelling house.

In a preferred form, said first wall and said first anchoring means are respectively a first wall portion and a first anchoring portion of a strip of metal and said first anchoring portion extends from and is contiguous with said first wall portion and encloses an acute angle therewith, said second wall and said second anchoring means are respectively a second wall portion and a second anchoring portion of said strip of metal and said second anchoring portion extends from and is contiguous with said second wall portion and encloses an acute angle therewith, and said third wall is a third wall portion of said strip of metal contiguous with said first wall portion and said second wall portion. In such form it is preferred that said third wall portion has a plurality of openings therein.

In another aspect the invention resides broadly in a method of constructing a concrete slab floor for a building, including: providing formwork as previously described; erecting said formwork in a predetermined position to form a retaining wall for the concrete to be poured; securing said formwork in said predetermined position; and pouring concrete within said formwork to form the concrete slab floor.

Preferably, said method includes ensuring that the concrete forms about said anchoring means and anchors said formwork to the concrete slab. In a case where the formwork has a third wall portion with openings therein, the openings are arranged to prevent the entrapment of air under the third wall portion and to provide visual access to the set-down portion of the slab.

Advantageously, the concrete can be vibrated more if the edge portion is found to be honeycombed.

The terms "upper", "lower",' "top", "bottom", "side", "horizontal", "vertical" and the like are used herein to describe the formwork in the normal in-use position and are not intended to limit the use of the invention to any particular orientation.

Further the term "horizontal" is to be understood as meaning generally horizontal and the term "vertical" is to be understood as meaning generally vertical.

In order that the invention can be more easily understood and put into practical effect reference will now be made to the accompanying drawings, wherein: Fig. 1 is a pictorial representation of a piece of metal formwork according to the invention; Fig. 2 is an end elevation of the piece of formwork of Fig.

1; Fig. 3 is a prefabricated corner piece of formwork according to the invention adapted to connect two pieces of the formwork shown in Fig. 1; Fig. 4 is a plan view of a concrete slab constructed according to the present invention; Fig. 5 is a sectional elevation of part of the slab along line Fig. 6 is a pictorial representation of another piece of formwork according to the invention; Fig. 7 is a cross-sectional elevation of a site prior to pouring a concrete slab according to the invention; Fig. 8 is a cross- sectional elevation of a concrete slab constructed on the site shown in Fig. 7; and Fig. 9 is a pictorial representation of another piece of formwork according to the invention.

The piece of formwork 10 illustrated in Fig. 1 is constructed of sheet steel and has a first vertical wall portion 11 adapted to form a first edge 17 of the concrete slab 20 shown in Fig. 5, a second vertical wall portion 13 adapted to form a second edge 18 of the slab and a horizontal wall portion 16 extending between the first and second wall portions which is adapted to form the upper face 19 of the set down 21 of the slab.

The three wall portions are formed by folding an elongate piece of sheet steel at two spaced apart lines along its full length.

Similarly, two anchoring portions 12 and 14 are provided at adjacent the free edges of the first and second wall portionns respectively by folding the sheet along its length again so that the two spaced apart edge portions enclose an angle of 45Q with the adjacent first and second wall portions respectively. Each fold line forms a smooth rounded edge which in the case of the edge at the junction of the first wall portion and the first anchoring portion forms the upper edge of the formwork when in use and provides an edge on which a screeding board may be moved for screeding off the concrete slab after it has been poured. The other edge at the junction of the second vertical face 13 and the second anchoring portion provides a smooth rounded edge which is adapted to rest on the pre-prepared ground surface for the slab.

In cases where a film of plastic moisture barrier is first laid on the ground surface, the rounded edge advantageously is adapted to slide easily on the plastic while being placed in the desired position without damage to the plastic film.

In order to construct the slab 20, lengths of formwork of -8the type shown in Fig.1 are connected together by using internal or external corner pieces generally of the type shown in Fig. 3 as Item 22. Corner pieces for corners of other angles also can be provided. The formwork is erected to form the perimeter of the slab 20 in the desired predetermined position and braced where required to retain the wet concrete when it is poured. Once the concrete has sufficiently cured, the bracing is removed and the formwork remains anchored to the concrete and forms an edge wall of the slab. Suitably, the anchoring portions are fully embedded in the concrete and form a barrier which extends up to (shorter or longer if desired) into the concrete thereby also preventing the establishment of termite tracks between the first, second and third wall portions and the concrete.

The formwork 30 illustrated in Fig. 6 is very similar to the formwork 10 shown in Fig. 1 and has first, second and third wall portions 31, 33, and 36 corresponding to wall portions 11, 13 and 16 and a first anchoring portion 32 corresponding to portion 12 but does not have a second anchoring portion as in formwork However, formwork 30 also has a plurality of spaced apart openings 35 in the third wall portion 36, the openings being adapted to vent the set-down of the slab as it is being poured thereby preventing the formation of voids and passages in the set-down which would give a honeycombed or bony appearance.

As can be seen in Fig. 7, the formwork 30 is braced by a bracing member 37 which is pegged to the ground by pegs 38 for -9securing the formwork in the pre-determined desired position. As can also be seen in Fig. 7, prior to erecting the formwork, screw piles 39 are driven into the ground to support the edge beam 41 of the slab and steel reinforcing bars 42 are arranged in known manner. Once the concrete is poured, the concrete cures to form the slab 40 as shown in Fig. 8 and a timber frame 43 is then erected adjacent the upper edge of the slab and a brick wall 44 is erected on the upper face of the set-down defined by wall portion 36. The formwork remains in situ and its outer face forms the edge of the slab. The formwork of Fig. 1 can be used in the same manner.

The piece of formwork 50 illustrated in Fig, 9 is similar to the formwork 30 shown in Fig. 6 in that it has first, second and third wall portions 51, 53, and 56 corresponding to wall portions 31, 33, and 36 and a first anchoring portion 52 corresponding to anchoring portion 32. However, formwork 50 also has a base wall portion 54 adapted to rest on the ground and an inner wall portion 57 upstanding from the base wall portion spaced from and parallel to the second wall portion and an internal anchoring portion 58 extending from the rear wall portion 57 and enclosing an angle of 45 degrees therewith. The formwork 50 is adapted to form the edge beam 55 and set-down portion of the slab shown in Fig. 8 with the inner wall portion preventing the loose soil or sand 59 under the slab from flowing into the cavity formed for the edge beam.

While the foregoing description has been given by way of illustrative example of the invention, it will be understood that the invention may be embodied in many other forms and all such forms are deemed to fall within the broad scope and ambit of the invention as defined by the appended claims.

Claims (15)

1. Formwork for constructing a concrete slab floor for a building, including: a first wall of metal adapted to form a first edge of the concrete slab to be constructed; and first anchoring means operatively connected to said first wall and adapted to engage in the concrete slab to be constructed to permanently anchor said first wall to the concrete slab.

2. Formwork according to Claim 1, wherein said first wall and said first anchoring means are respectively a first wall portion and a first anchoring portion of a strip of metal and said first anchoring portion extends from and is contiguous with said first wall portion and encloses an acute angle therewith.

3. Formwork according to Claim 2, wherein said first anchoring portion is continuous with said first wall portion.

4. Formwork according to Claim 3, wherein said first anchoring portion is adapted to stiffen said first wall portion in the horizontal and vertical planes. Formwork according to Claim 3, wherein the junction of said first wall portion and said first anchoring portion provides a -12- first rounded edge adapted to support a screeding board.

6. Formwork according to claim 5, wherein said first rounded edge extends fully about the perimeter of the slab.

7. Formwork according to any one of the preceding claims, including a second wall of metal adapted to form a second edge of the concrete slab to be constructed spaced from the first edge, said second wall being operatively connected to said first wall.

8. Formwork according to Claim 7, including second anchoring means connected to said second wall and adapted to engage in the concrete slab to be constructed to permanently anchor said second wall to the concrete slab.

9. Formwork according to Claim 8, wherein said second wall and said second anchoring means are respectively a second wall portion and a second anchoring portion of a strip of metal and said second anchoring portion extends from and is contiguous with said second wall portion and encloses an acute angle therewith. Formwork according to Claim 9, wherein said second anchoring portion is continuous with said second wall portion. -13- 11ii. Formwork according to Claim 10, wherein said second anchoring portion is adapted to stiffen said second wall portion in the horizontal and vertical planes.

12. Formwork according to Claim 10, wherein the junction of said wall portion and said anchoring portion provides a second rounded edge adapted to support the second wall portion on a horizontal surface.

13. Formwork according to Claim 10, wherein said second rounded edge extends fully about the perimeter of the slab.

14. Formwork according to any one of Claims 7 to 13, wherein said first wall and said second wall are connected by a third wall adapted to form a horizontal face of the slab to be constructed between the first edge and the second edge. Formwork according to Claim 14, wherein said first wall and said first anchoring means are respectively a first wall portion and a first anchoring portion of a strip of metal and said first anchoring portion extends from and is contiguous with said first wall portion and encloses an acute angle therewith, said second wall and said second anchoring means are respectively a second wall portion and a second anchoring portion of said strip of metal and said second anchoring portion extends from and is -14- contiguous with said second wall portion and encloses an acute angle therewith, and said third wall is a third wall portion of said strip of metal contiguous with said first wall portion and said second wall portion.

16. Formwork according to Claim 15, wherein said third wall portion has a plurality of openings therein.

17. A method of constructing a concrete slab floor for a building, including: providing formwork as defined by any one of the preceding claims; erecting said formwork in a predetermined position to form a retaining wall for the concrete to be poured; securing said formwork in said predetermined position; and pouring concrete within said formwork to form the concrete slab floor.

18. A method according to Claim 17, including ensuring that the concrete forms about said anchoring means and anchors said formwork to the concrete slab.

19. Formwork as hereinbefore described with reference to the accompanying drawings. A method of constructing a concrete slab floor as hereinbefore described with reference to the accompanying drawings. Dated this 11th Day of March, 2003. EVOLUTION INTERNATIONAL PTY LTD By their Patent Attorneys AHEARN FOX