GB2336607A

GB2336607A - Slab construction

Info

Publication number: GB2336607A
Application number: GB9808773A
Authority: GB
Inventors: Alexander George Maitland
Original assignee: Birchwood Omnia Ltd
Current assignee: Birchwood Omnia Ltd
Priority date: 1998-04-25
Filing date: 1998-04-25
Publication date: 1999-10-27
Also published as: GB9808773D0

Abstract

A method of constructing a concrete slab comprises the steps of (i) preforming a thin concrete slab (17) the underside of which may form a ceiling for a space below, the slab having a plurality of upstanding projections (18), (ii) placing the slab on a support structure (22,23 - fig 5), (iii) positioning reinforcing means in the form of a mesh (19) above the thin concrete slab, (iv) pouring concrete (20) onto the slab to form a thicker slab with the reinforcing means embedded therein. Polypropylene reinforcement fibres may also be introduced into the concrete of the preformed slab to increase its resistance to fracture during the above method of construction.

Description

2336607 SLAB CONSTRUCTIO The invention relates to the construction of

concrete slabs, for example to provide a floor in a building or other structure, with the underside of the floor providing a ceiling for a space below.

In one conventional method forming such slabs, it is necessary to arrange main support beams in spaced apart parallel fashion, resting on metal props. Secondary support beams are then arranged on top of the main support beams, spaced apart and parallel but running at 900 to the main support beams. Plywood formwork is then fixed on top of the secondary support means and concrete is poured onto the plywood to a depth to form a concrete slab of a desired thickness. Steel bar or wire reinforcement is incorporated in the lower and upper part of the slab to provide a reinforced or prestressed concrete slab.

Once the slab has set the unsightly plywood and all support beams are stripped away to provide a ceiling finish on the underside of the slab.

Difficulties can be encountered in satisfactorily supporting the reinforcement at the desired height during the pouring of the concrete.

The invention provides a method of constructing a concrete slab comprising preforming a relatively thin concrete slab, the slab having a plurality of upstanding projections, placing the slab on an underlying support structure, positioning reinforcing means above the thin concrete slab, and pouring concrete onto the slab to form a thicker slab with the reinforcing means embedded therein.

A top layer of reinforcing means may be positioned on the upstanding projections and may comprise reinforcing mesh.

A lower layer of reinforcing means, for example steel bars or wires, may be incorporated below the reinforcing mesh and may be supported by spacing pieces above the top of the thin concrete slab.

The underlying support structure may comprise parallel timber or metal beams.

The beams may be spaced at 2 m to 3 m centres. The beams are preferably spaced at 2 metre centres.

The support beams may be laid directly onto metal support props.

The preformed slab may be lifted into position by attaching lifting means to the projections.

The projections preferably comprise at least two parallel lattices.

The lattices are preferably of metal.

The lattices may be spaced at centres of 200 mm to 600 mm.

The lattices are preferably spaced at 400 mm centres.

The depth of the preformed slab may be in the range 25 mm to 35 mm, a preferred depth being 30 mm.

Preformed slabs may be provided in any desired lengths and widths, to suit the particular construction project. The width may be 1-3 metres, a preferred width being 2.4 metres. The slabs can span distances of up to 10 metres.

Reinforcement fibres may be introduced into the concrete of the preformed slab, during the preforming of the slab, to reduce the risk of cracking during manufacture and erection of the slabs.

The fibres may also improve impact resistance, making for a more robust product.

The fibres are preferably of polypropylene.

The invention includes a slab when manufactured by the method designed above.

By way of example, specific embodiments of the invention will now be described, with reference to the accompanying drawings, in which:- Figure 1 is a perspective cut away view illustrating a prior art method;

Figure 2 is a diagrammatic cross section through the prior art slab of Figure 1;

Figure 3 is a perspective view of the preformed slab used in an embodiment of the invention, looking in the direction of the upwardly projecting lattices; Figure 4 is a diagrammatic cross section illustrating the positioning of the slab of Figure 3; Figure 5 is a cut away perspective view through this embodiment of 5 slab according to the invention; and Figure 6 is a diagrammatic cross section through the slab of Figure 5.

To construct a concrete floor in a building or other structure according to the prior art methods shown in Figures 1 and 2, main support beams 10 are provided, the beams being spaced apart and parallel, and usually arranged on metal props 11.

Secondary support beams 12 are provided at right angles to the beams 10 and these beams are covered with plywood sheets 13.

Concrete 14 is then poured on.to the plywood 13 to a desired depth, and is allowed to set.

This prior art method suffers from at least two disadvantages.

Firstly, in order to provide a sightly underside for the ceiling of the space below, the plywood 13 and support beams and props 10, 11, 12 have to be stripped away after the slab has set.

Secondly, for strength purposes it is necessary to incorporate into the poured concrete lower and upper structural reinforcement. These reinforcements are illustrated in the more detailed cross sectional view of Figure 2, the lower reinforcement being referenced 15 and the upper reinforcement being referenced 16. Special arrangements have to be made to provide support, at least for the upper reinforcement mesh 16, to hold it in position while the concrete sets.

The method according to this embodiment of the invention employs a preformed relatively thin slab 17 shown in detail in Figure 3.

The slab 17 may contain polypropylene reinforcement fibres and a 10 small amount of steel to facilitate handling and transportation.

The slab also has upstanding projections in the form of parallel lattices 18.

The slab shown in Figure 3 is preformed with a high quality finish on the underside and as this relatively thin slab forms part of the final construction, the step of stripping away plywood formwork is eliminated.

Furthermore, the upstanding lattices 18 provide a support for the upper 20 reinforcement as shown at 19 in Figure 4.

As shown in Figure 5, the slab 17 can be laid directly onto main support beams 22 resting on metal props 23. The concrete 20 is then poured onto the preformed slab 17 to complete the construction.

As shown in the cross section view in Figure 6, the construction can incorporate not only upper mesh reinforcement 19 but also lower steel reinforcement 21.

The slab shown in Figure 3 can readily be lowered into position by attaching crane hooks to the lattices 18 at appropriate locations. With suitable craneage, areas of 100 square metres per hour are achievable.

The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in. this specification (including any accompanying claims, abstract and drawings), may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

1. A method of constructing a concrete slab comprising preforming a relatively thin concrete slab, the slab having a plurality of upstanding projections, placing the slab on an underlying support structure, positioning reinforcing means above the thin concrete slab, and pouring concrete onto the slab to form a thicker slab with the reinforcing means embedded therein.

2. A method as claimed in claim 1, in which a top layer of reinforcing means is positioned on the upstanding projections.

3. A method as claimed in Claim 2, in which the top layer of reinforcing means is reinforcing mesh.

4. A method as claimed in Claim 2 or Claim 3, in which a lower layer of reinforcing means is incorporated below the top layer of reinforcing means.

5. A method as claimed in Claim 4, in which the lower layer of reinforcing means comprises steel bars or wires.

6. A method as claimed in Claims 4 or 5, in which the lower layer of reinforcing means is supported by spacing pieces above the top of the thin concrete slab.

7. A method as claimed in any preceding claim, in which the underlying support structure comprises parallel timber or metal beams.

8. A method as claimed in Claim 7, in which the beams are spaced at 2 metre to 3 metre centres.

9. A method as claimed in Claim 8, in which the beams are spaced at 2 metre centres.

10. A method as claimed in any of Claims 7 to 9, in which the support beams are laid directly onto metal support props.

11. A method as claimed in any preceding claim, in which the preformed slab is lifted into position by attaching lifting means to the projections.

12. A method as claimed in any preceding claim, in which the projections comprise at least two parallel lattices.

13. A method as claimed in Claim 12, in which the lattices are of metal.

14. A method as claimed in Claims 12 or 13, in which the lattices are spaced at centres of 200 millimetres to 600 millimetres.

15. A method as claimed in Claim 14, in which the lattices are spaced at 400 millimetre centres.

16. A method as claimed in any preceding claim, in which the depth of the 25 preformed slab is in the range 25 millimetres to 35 millimetres.

17. A method as claimed in Claim 16, in which the depth is 30 millimetres.

-918. A method as claimed in any preceding claim, in which the width of the preformed slab is in the range 1 metre to 3 metres.

19. A method as claimed in Claim 18 in which the width is 2.4 metres.

20. A method as claimed in any preceding claim, in which the preformed slabs span distances of up to 10 metres.

21. A method as claimed in any preceding claim, in which reinforcement fibres are introduced into the concrete of the preformed slab, during the performing of the slab, to reduce the risk of cracking during manufacture and erection of the slabs.

22. A method as claimed in Claim 21, in which the fibres are of polypropylene.

23. A method substantially as described herein with reference to the accompanying drawings.

24. A slab when manufactured by a method as claimed in any one of the preceding claims.