AU2006315015A1 - Cast in situ concrete slab - Google Patents

Description

WO 2007/056833 PCT/AU2006/001760 CAST IN SITU CONCRETE SLAB The present invention relates to cast in situ 5 concrete slabs, hereinafter referred to as "concrete slabs" for use in the building industry. The present invention relates particularly, although by no means exclusively, to concrete slabs for 10 use in the construction of mezzanine floors and floors for multi-storey buildings, including multi-storey car parks. The present invention also relates to assemblies of two or more components of concrete slabs. 15 In the context of the construction of floors, the term "concrete slabs" is understood herein to mean slabs that include (a) a base formed from a plurality of profiled decking sheets positioned in side-by-side and/or 20 end-to-end relationship as required; and (b) a layer of concrete on the base. Typically, in the context of the construction of floors, the term "concrete slabs" is understood herein to 25 mean slabs that also include reinforcement embedded in the concrete layer. The profiled decking sheets of the concrete slabs may contribute to the mechanical performance of the 30 concrete slabs. Specifically, the profiled decking sheets may act compositively with the concrete via mechanical bonding and therefore contribute to the bottom reinforcement of the concrete slabs. 35 Notwithstanding the above, the present invention extends to arrangements in which the profiled decking sheets do not make a contribution to the mechanical WO 2007/056833 PCT/AU2006/001760 -2 performance of the concrete slabs and the profiled decking sheets act as lost formwork only. Typically, concrete floor slabs are formed in situ 5 by (a) positioning a plurality of the profiled decking sheets onto a permanent support structure, such as a series of horizontal beams, and forming a continuous base (b) positioning formwork that defines the perimeter of the concrete slabs, (c) placing reinforcement, typically in 10 the form of flat sheets of steel mesh or bars, or both mesh and bars, on or in relation to the profiled decking sheets, and (d) finally pouring concrete onto the assembly of the decking sheets and reinforcement within the perimeter of the formwork and forming a layer of concrete. 15 Depending on a number of factors, including the form of the profiled decking sheets, the weight of concrete required to form a concrete slab, the span between adjacent permanent support members, deflection 20 limits, the concrete pour sequence, the number of spans, the means of fixing to the permanent support structure, and construction loads (other than wet concrete), the sheets may need to be propped temporarily between the permanent support members. 25 The term "profiled decking sheet" is understood herein to mean roll-formed sheets or brake pressed sheets that include at least one pan and side edge formations that enable adjacent sheets to be positioned together in 30 side-by-side relationship. In situations in which a profiled decking sheet includes two or more than two pans, the term "profiled decking sheet" is understood herein to include one or more 35 than one upstanding rib separating adjacent pans.

WO 2007/056833 PCT/AU2006/001760 -3 Typically, currently available profiled decking sheets used in concrete slabs are supplied cut to lengths in the range of 0.4 to 19.5 m and widths in the range of 0.3 to 1.2 m. The maximum unsupported spans of profiled 5 decking sheets used in concrete slabs are currently 6 m or more. At least in part, the above-described maximum length and maximum width are set by issues relating to the 10 structural performance of the profiled decking sheets as formwork, particularly the extent to which the profiled decking sheets can support the weight of wet concrete on sheets. 15 The present invention is based on a realisation that longer unsupported spans and/or wider structural decking sheets can be used in concrete slabs by spacing the concrete layer above the pans of profiled decking sheets and forming a space between the pans of the 20 profiled decking sheets and the concrete layer. According to one aspect of the present invention there is provided a concrete slab that includes: 25 (a) a base formed from a plurality of profiled decking sheets positioned side by side, with each decking sheet including one pan and side edge formations that enable adjacent sheets to be positioned in side by 30 side relationship, and (b) a layer of concrete spaced above the pans of the base. 35 According to another aspect of the present invention there is provided a concrete slab that includes: WO 2007/056833 PCT/AU2006/001760 -4 (a) a base formed from a plurality of profiled decking sheets positioned side by side, with each decking sheet including two or more than two pans, an upstanding rib 5 separating adjacent pans, and side edge formations that enable adjacent sheets to be positioned in side by side relationship, and 10 (b) a layer of concrete spaced above the pans of the base. Preferably the concrete layer is spaced at least 40 mm above the pans of the profiled decking sheets in a 15 situation in which the thickness of the concrete slab is at least 140 mm. More preferably the concrete layer is spaced at least 60 mm above the pans of the profiled decking sheets 20 in a situation in which the thickness of the concrete slab is at least 180 mm. Preferably the concrete slab includes a means that spaces the concrete layer above the pans of the base. 25 Preferably the spacing means resists lateral deflection of side edge formations and/or ribs of the profiled decking sheets under load, for example an applied load of wet concrete. 30 The spacing means may be one or more than one plate that extends between and is connected to adjacent side edge formations and/or ribs of the profiled decking sheets and forms a raised base for the concrete layer. 35 Preferably the spacing means includes at least one block of a lightweight material positioned on at least WO 2007/056833 PCT/AU2006/001760 -5 one of the pans of at least one of the profiled decking sheets so that the block or blocks forms a raised base for the concrete layer. 5 The lightweight material may be any suitable material. By way of example, the lightweight material is polystyrene foam. 10 Preferably (a) the block of the lightweight material and (b) the side edge formations and/or the ribs of the decking sheets on opposite sides of the block are mechanically interlocked or otherwise engaged together to 15 resist lateral deflection of side edge formations and/or ribs of the profiled decking sheets under load. Adhesives are one example of a form of engagement between the block of the lightweight material and the side 20 edge formations and/or the ribs of the decking sheets The block of the lightweight material and the side edge formations and/or the ribs of the decking sheets may become mechanically interlocked together after there 25 has been a predetermined amount of lateral deflection of the side edge formations and/or the ribs of the decking sheets in response to load on the profiled decking sheets due to weight of wet concrete that is poured onto the profiled decking sheets in the process of forming a 30 concrete slab. When the block of the lightweight material is mechanically interlocked or otherwise engaged with the side edge formations and/or the ribs of the profiled 35 decking sheets, it is not necessary that the block be adhered or otherwise secured to the pans of the decking sheets.

WO 2007/056833 PCT/AU2006/001760 -6 Preferably the block or blocks of the lightweight material at least substantially cover the surface of the pans of the decking sheets. Consequently, there is no 5 upward hydrostatic pressure on the block or blocks when the concrete is wet. The block or blocks of the lightweight material may be the same length as the profiled decking sheets. 10 Alternatively, the block or blocks of the lightweight material may be shorter than the lengths of the profiled decking sheets and be positioned in end to end relationship on the pans of the decking sheets - to 15 allow concrete to be placed in compression where necessary and to achieve full capacity of shear studs or other means of connecting the profiled decking sheets to a permanent support structure. 20 Preferably the side edge formations and/or the ribs of the profiled decking sheets are at least 50 mm high. More preferably the side edge formations and/or 25 the ribs of the profiled decking sheets are at least 60 mm high. Preferably the block or blocks of the lightweight material have a height that is at least 70% of 30 the height of the side edge formations and/or ribs of the decking sheets. Preferably the block or blocks of the lightweight material are at least 50 mm high. 35 Preferably the side edge formations and/or the ribs of the decking sheets are relatively high so as to WO 2007/056833 PCT/AU2006/001760 -7 provide an effective mechanical interlock with concrete of the concrete slab. Preferably the side edge formations are formed to 5 allow engagement of side edge formations of adjacent profiled decking sheets that inhibits vertical and/or horizontal separation of the sheets. The side edge formations may be formed so that 10 the side edge formations of adjacent profiled decking sheets engage each other in overlapping relationship. By way of further example, the side edge formations may be formed so that the side edge formations 15 of adjacent profiled decking sheets engage without overlapping of the formations. An example of such an arrangement is one in which the side edge formations include a web that extends upwardly from a pan and includes a rib that is shaped so that the ribs of side 20 edge formations of adjacent profiled decking sheets interlock. Such an arrangement is disclosed in International applications PCT/AU01/01446 (WO02/38885) and PCT/AU2004/000366 (W02004/085085) and the disclosure in these International applications is incorporated herein by 25 cross-reference. Preferably, the profiled decking sheets are pre cambered along the length of the sheets. 30 Preferably the profiled decking sheets are pre cambered along the length of the sheets so that the pans of the sheets form flat, horizontal surfaces when wet concrete is poured to form the concrete slab. 35 Preferably the concrete slab further includes reinforcement, such as steel mesh, embedded in the concrete.

WO 2007/056833 PCT/AU2006/001760 -8 The reinforcement may be pretensioned. The reinforcement may be welded or otherwise 5 connected to the side edge formations and/or the ribs of the profiled decking sheets to increase the resistance to lateral deflection under load. According to another aspect of the present 10 invention there is also provided an assembly of: (a) a profiled decking sheet that includes one pan and side edge formations that enable adjacent sheets to be positioned in side by 15 side relationship and form a base of a concrete slab; and (b) a means for spacing a layer of concrete above the pan of the profiled decking 20 sheet. According to another aspect of the present invention there is also provided an assembly of: 25 (a) a profiled decking sheet that includes two or more than two pans and an upstanding rib separating adjacent pans, and side edge formations that enable adjacent sheets to be positioned in side by side relationship 30 and form a base of a concrete slab; and (b) a means for spacing a layer of concrete above the pans of the profiled decking sheet. 35 Preferably the spacing means resists lateral deflection of side edge formations and/or ribs of the WO 2007/056833 PCT/AU2006/001760 -9 profiled decking sheets under load, for example the applied load of wet concrete The spacing means may be one or more than one 5 plate that extends between and is connected to adjacent side edge formations and/or ribs of the profiled decking sheet and forms a raised base for the concrete layer. Preferably the spacing means includes at least 10 one block of a lightweight material that mechanically interlocks or otherwise mechanically engages side edge formations and/or ribs of the decking sheet on opposite sides of the block or blocks and forms a raised base for the concrete layer. 15 Preferably the profiled decking sheet is pre cambered along its length. According to another aspect of the present 20 invention there is also provided a method of manufacturing the above-described assembly of a profiled decking sheet and at least one block of a lightweight material mechanically interlocked together that includes the steps of: 25 (a) passing a flat strip of steel successively through a series of roll-forming stands of a roll former and progressively roll forming the profiled decking sheet, and 30 (b) positioning the block or blocks of the lightweight material on sections of the steel strip that are ultimately roll formed into the pan or pans of the profiled 35 decking sheet upstream of roll forming stands that form the side edge formations and/or the ribs into shapes that WO 2007/056833 PCT/AU2006/001760 - 10 mechanically interlock with the block or blocks and thereby forming a means for spacing a concrete layer above the pan or pans. 5 The above-described assembly is a convenient form of module that can be manufactured off-site and transported to site. 10 The present invention is described further by way of example with reference to Figure 1 which is a cross section of one embodiment of a part of a concrete slab in accordance with the present invention. 15 The concrete slab shown in Figure 1 includes: (a) a continuous base formed from a plurality of profiled decking sheets 3 positioned side by side, with each decking sheet 3 20 including one flat pan 5 and side edge formations 7 that enable adjacent sheets 3 to be positioned in side by side relationship, as shown in the figure, 25 (b) a plurality of blocks 9 of a lightweight material in the form of polystyrene foam positioned on the pans 5 of the profiled decking sheets 3 so that the blocks 9 define a means for spacing a layer of 30 concrete 11 described hereinafter above the pans 5 of the base and resist inward deflection of side edge formations 7 under load; 35 (c) reinforcement in the form of a steel mesh 11 positioned above the side edge WO 2007/056833 PCT/AU2006/001760 - 11 formations 7 of the profiled decking sheets 3; and (d) the above-mentioned layer of concrete 11 5 spaced above the base. The base 3 is supported by a plurality of permanent support members (not shown). 10 The main criteria for the lightweight material is that it be lightweight and form a raised platform for the concrete layer above the pans 5 and be capable of providing resistance to lateral buckling, typically inward movement, of the side edge formations 7 under load during 15 construction stage when the profiled decking sheets function as formwork and to provide sufficient interlock to improve dynamics/damping during in service stage after the concrete has set). 20 Polystyrene foam is one of a number of suitable materials. In the arrangement shown in Figure 1 the blocks 9 cover the entire upper surface of the pans 5 of the 25 profiled decking sheets 3. The profiled decking sheets 3 are typically 4-9 m in length. The blocks 9 of the lightweight material may be the same length as the profiled decking sheets 3 or may be 30 considerably shorter in length and positioned in end to end relationship along the entire length of each of the sheets. The sides of the blocks 9 are shaped to be 35 complementary to the shapes of the side edge formations 7 so that the blocks 9 and the formations 7 are mechanically interlocked together.

WO 2007/056833 PCT/AU2006/001760 - 12 The blocks 9 sit on the pans 5 and are not adhered to or otherwise secured to the pans 5. 5 The profiled decking sheets 3 are generally C shaped and are as disclosed in International applications PCT/AU01/01446 (WO02/38885) and PCT/AU2004/000366 (W02004/085085). 10 The profiled decking sheets 3 include relatively high side edge formations 7 and thereby form a significant mechanical interlock with the concrete. In effect, each profiled decking sheet 3 and the 15 blocks 9 of the lightweight material on the sheet 3 form a module. These modules can be produced off-site as part of a method of roll-forming the profiled decking sheets and thereafter be conveniently transported to a construction site. Alternatively, the profiled decking sheets 3 and 20 the blocks 9 of the lightweight material can be separately supplied to a construction site and assembled on the site. The blocks of the lightweight material reduce the amount of wet concrete required and therefore reduce the 25 overall weight of concrete slabs and lateral buckling resistance. In addition to the above advantages, the blocks of the lightweight material facilitate improved vibrations 30 performance due to extra damping provided by the material. In addition to the above advantages, the concrete slab has comparable strength to conventional concrete slabs that do not have the blocks of the lightweight 35 material because only concrete in tension is replaced with the lightweight material and the remaining concrete that is on top of the lightweight material is in compression WO 2007/056833 PCT/AU2006/001760 - 13 under load. It is equivalent to external reinforcement bottom pans (tensile reinforcement) are separated from concrete in compression by the lightweight material increased capacity and stiffness of concrete slab due to 5 increased lever arm. In summary, the present invention makes it possible to avoid the use of props for longer spans, minimise weight, minimise deflections, minimise slab 10 thicknesses, and minimise concrete. Many modifications may be made to the embodiment of the present invention described above without departing from the spirit and scope of the invention. 15 By way of example, whilst the embodiment described above includes profiled decking sheets 3 having single pans 9, the present invention is not so limited and extends to any suitable profiled decking sheet having 20 multiple pans separated by internal ribs. In addition, whilst the whilst the embodiment described above include profiled decking sheets 3 that have relatively high side edge formations 7, the present 25 invention is not sop limited and the side edge formations 7 may be any suitable height.

Claims (20)

1. A concrete slab that includes: 5 (a) a base formed from a plurality of profiled decking sheets positioned side by side, with each decking sheet including one pan and side edge formations that enable adjacent sheets to be positioned in side by side relationship, and 10 (b) a layer of concrete spaced above the pans of the base.

2. A concrete slab that includes: 15 (a) a base formed from a plurality of profiled decking sheets positioned side by side, with each decking sheet including two or more than two pans, an upstanding rib separating adjacent pans, and side edge formations 20 that enable adjacent sheets to be positioned in side by side relationship, and (b) a layer of concrete spaced above the pans of the base. 25

3. The slab defined in claim 1 or claim 2 wherein the concrete layer is spaced at least 40 mm above the pans of the profiled decking sheets in a situation in which the thickness of the concrete slab is at least 140 mm. 30

4. The slab defined in claim 1 or claim 2 wherein the concrete layer is spaced at least 60 mm above the pans of the profiled decking sheets in a situation in which the thickness of the concrete slab is at least 180 mm. 35 WO 2007/056833 PCT/AU2006/001760 - 15 5. The slab defined in any one of the preceding claims wherein the concrete slab includes a means that spaces the concrete layer above the pans of the base.

5

6. The slab defined in claim 5 wherein the spacing means resists lateral deflection of side edge formations and/or ribs of the profiled decking sheets under load, for example an applied load of wet concrete. 10

7. The slab defined in claim 5 or claim 6 wherein the spacing means is one or more than one plate that extends between and is connected to adjacent side edge formations and/or ribs of the profiled decking sheets and forms a raised base for the concrete layer. 15

8. The slab defined in claim 5 or claim 6 wherein the spacing means includes at least one block of a lightweight material positioned on at least one of the pans of at least one of the profiled decking sheets so that the block 20 or blocks forms a raised base for the concrete layer.

9. The slab defined in claim 8 wherein the lightweight material is polystyrene foam. 25

10. The slab defined in claim 8 or claim 9 wherein (a) the block of the lightweight material and (b) the side edge formations and/or the ribs of the decking sheets on opposite sides of the block are mechanically interlocked or otherwise engaged together to resist lateral deflection 30 of side edge formations and/or ribs of the profiled decking sheets under load.

11. The slab defined in claim 10 wherein the block of the lightweight material and the side edge formations and/or 35 the ribs of the decking sheets become mechanically interlocked together after there has been a predetermined amount of lateral deflection of the side edge formations WO 2007/056833 PCT/AU2006/001760 - 16 and/or the ribs of the decking sheets in response to load on the profiled decking sheets due to weight of wet concrete that is poured onto the profiled decking sheets in the process of forming a concrete slab. 5

12. The slab defined in any one of claims 8 to 11 wherein the block or blocks of the lightweight material at least substantially cover the surface of the pans of the decking sheets. 10

13. The slab defined in any one of claims 8 to 12 wherein the block or blocks of the lightweight material have a height that is at least 70% of the height of the side edge formations and/or ribs of the decking sheets. 15

14. The slab defined in any one of claims 8 to 13 wherein the block or blocks of the lightweight material are at least 50 mm high. 20

15. An assembly of: (a) a profiled decking sheet that includes one pan and side edge formations that enable adjacent sheets to be positioned in side by side relationship and form a base of 25 a concrete slab; and (b) a means for spacing a layer of concrete above the pan of the profiled decking sheet. 30

16. An assembly of: (a) a profiled decking sheet that includes two or more than two pans and an upstanding rib separating adjacent pans, and side edge formations that enable 35 adjacent sheets to be positioned in side by side relationship and form a base of a concrete slab; and WO 2007/056833 PCT/AU2006/001760 - 17 (b) a means for spacing a layer of concrete above the pans of the profiled decking sheet.

17. The assembly of claim 15 or claim 16 wherein the 5 spacing means resists lateral deflection of side edge formations and/or ribs of the profiled decking sheets under load, for example the applied load of wet concrete

18. The assembly of any one of claims 15 to 17 wherein 10 the spacing means is one or more than one plate that extends between and is connected to adjacent side edge formations and/or ribs of the profiled decking sheet and forms a raised base for the concrete layer. 15

19. The assembly of any one of claims 15 to 17 wherein the spacing means includes at least one block of a lightweight material that mechanically interlocks or otherwise mechanically engages side edge formations and/or ribs of the decking sheet on opposite sides of the block 20 or blocks and forms a raised base for the concrete layer.

20. A method of manufacturing the assembly of a profiled decking sheet and at least one block of a lightweight material mechanically interlocked together that includes 25 the steps of: (a) passing a flat strip of steel successively through a series of roll-forming stands of a roll former and progressively roll forming the profiled decking sheet, 30 and (b) positioning the block or blocks of the lightweight material on sections of the steel strip that are ultimately roll formed into the pan or pans of the 35 profiled decking sheet upstream of roll forming stands that form the side edge formations and/or the ribs into shapes that mechanically interlock with the block or WO 2007/056833 PCT/AU2006/001760 - 18 blocks and thereby forming a means for spacing a concrete layer above the pan or pans.