WO2007039887A2

WO2007039887A2 - A method of constructing a roof or floor slab

Info

Publication number: WO2007039887A2
Application number: PCT/IB2006/053667
Authority: WO
Inventors: Michael Robert Hull; Hendrik Floris Mostert
Original assignee: Michael Robert Hull; Hendrik Floris Mostert
Priority date: 2005-10-06
Filing date: 2006-10-06
Publication date: 2007-04-12
Also published as: WO2007039887A3; ZA200803837B

Abstract

The invention relates to a method of constructing a roof or floor slab for domestic, commercial, or industrial buildings. The method includes erecting a support grid (10) of a plurality of elongate, laterally spaced, parallel, longitudinally extending, pre-cast reinforced concrete beams (12, 14, 16), and a plurality of orthogonally disposed elongate pre-cast reinforced concrete cross ribs (18 to 28) interconnecting adjacent pairs of beams. A plurality of openings (46) is defined by the upper edges of the interconnecting beams (12, 14, 16) and cross ribs (18 to 28). The method includes laying pre-cast reinforced concrete shutter panels (44) over the openings, the panels (44) being supported along their peripheries by the upper edges of the beams (12, 14, 16) and cross ribs (18 to 28) defining the openings. The method further includes pouring a layer (66) of a settable cementitious material onto the shutter panels (44) and allowed to set to form a concrete layer.

Description

A METHOD OF CONSTRUCTING A ROOF OR FLOOR SLAB

THIS INVENTION relates to building construction. The invention relates in particular to a method of constructing a roof or floor slab for domestic, commercial, or industrial buildings. The invention extends also to in situ formwork for casting a concrete roof or floor slab, and to a pre-cast elongate reinforced concrete beam. The invention extends still further to a pre-cast elongate cross rib of reinforced concrete, to a support grid, and to a concrete slab.

The invention provides broadly a method of constructing a floor or roof slab which includes: erecting a support grid of a plurality of elongate, laterally spaced, parallel, longitudinally extending, pre-cast reinforced concrete beams, and a plurality of orthogonally disposed elongate pre-cast reinforced concrete cross ribs interconnecting adjacent pairs of beams, a plurality of openings being defined by the upper edges of the interconnecting beams and cross ribs; and laying pre-cast reinforced concrete shutter panels over the openings, the panels being supported along their peripheries by the upper edges of the beams and cross ribs defining the openings. The cross ribs may have a length which equals the longitudinal spacing between the cross ribs, thereby ensuring that the openings and hence the shutter panels are generally square.

The beams and the cross ribs may have rebates along their operative upper edges, thereby to provide recessed seats around the peripheries of the openings, to accommodate the shutter panels with clearance. The interconnection between the beams and cross ribs may be provided by bolting them together.

In order to achieve the bolting, the beams may have longitudinally spaced transverse passages at a spacing corresponding to the longitudinal spacing between the cross ribs, and the cross ribs may have opposed screw threaded socket members at their ends. Bolts having screw threaded shanks may pass through the transverse passages in the beams and then screwed into the screw threaded socket members at the ends of the cross ribs.

The socket members at the opposing ends of the cross ribs may be interconnected by reinforcing steel rods embedded within the cross ribs.

The cross ribs between adjacent pairs of beams, may be longitudinally staggered relative to each other. A layer of a settable cementitious material may be poured onto the shutter panels and allowed to set to form a concrete layer.

Reinforcing steel wire mesh may be laid over the shutter panels, before the pouring of the settable cementitious material to form the concrete layer.

The invention extends also to in situ formwork for casting a concrete roof or floor slab, which formwork includes: a plurality of elongate pre-cast reinforced concrete beams arranged in parallel laterally spaced longitudinally extending relationship; a plurality of longitudinally spaced, elongate, pre-cast reinforced concrete cross ribs orthogonally interconnecting adjacent pairs of beams, a plurality of longitudinally and laterally spaced openings being thus defined between the upper edges of the beams and cross ribs; and pre-cast reinforced concrete shutter panels located in position over the openings, thereby to form in situ formwork for the casting of a concrete slab.

The beams, cross ribs and shutter panels, may have the features described above with reference to the method for constructing a concrete floor or roof slab. The concrete of the beams, cross ribs, and the shutter panels, may be of high strength concrete, and their reinforcement may include a fibrous material, such as steel fibers. Instead, or in addition, fibers of other materials may be employed.

The invention extends further to a pre-cast elongate reinforced concrete beam which includes a series of transverse passages through it spaced longitudinally along its length; the passages being adapted in use to receive bolts passing through them, opposing edges which in use will be the upper edges of the beam, being provided with rebates.

The invention extends still further to a pre-cast elongate cross rib of reinforced concrete, having embedded therein screw threaded socket members engagable by screw threaded shanks of bolts passing through the transverse passages of a beam as defined above.

A reinforcing rod within the cross rib, may interconnect the threaded socket members.

Opposing edges which in use will be the upper edges of the cross rib, may be provided with rebates.

The invention extends yet further to a support grid which includes: a plurality of elongate concrete beams as defined above, arranged in transversely spaced longitudinally extending parallel relationship; a plurality of cross ribs as defined above, arranged orthogonally to the beams in longitudinally spaced relationship between adjacent pairs of beams, the beams and cross ribs being arranged such that the passages in the beams are aligned with the threaded socket members of the cross ribs; and bolts having screw threaded shanks passing through the passages of the beams, and screw threadedly engaging the screw threaded socket members at the ends of the cross ribs, thereby interconnecting the beams and cross ribs to form a support grid having openings defined between interconnecting beams and cross ribs.

The invention even provides a concrete slab which includes a support grid as defined above; pre-cast reinforced concrete shutter panels over the support grid openings; and a concrete layer over the shutter panels and support grid.

The concrete layer may have embedded within it reinforcement in the form of a steel wire mesh. Before the casting of the concrete layer, the mesh may be raised clear of the shutter panels and supported by supports spaced longitudinally along the beams. The supports may be in the form of metallic pins cast in a longitudinally spaced relationship in such a manner that ends of the pins protrudes from the beam and stands proud there from. The support grid may include an elongated bar attached to the ends of the pins or shear pins, the wire mesh being placed on top of the elongated bar which avoids interference from the pins with the wire mesh facilitating ease of installation.

The formwork may also include tiles or secondary panels having an similar shape as that of the shutter panels, each tile being for lying flat concentrically face-to-face on top of the shutter panel, the tile being sized so as to, in use, conceal a central part of the shutter panel, a remaining exposed part of the shutter panel thus forming a brim around the tile before pouring of the settable cementitious material to form the concrete layer.

Further features of the invention will become apparent from the following description by way of example with reference to the accompanying diagrammatic drawings.

Figure 1 shows a three-dimensional view of a part of in situ formwork, in accordance with the invention;

Figure 2 shows a three-dimensional view of part of a concrete slab constructed with in situ formwork, in accordance with the invention;

Figure 3 shows a cross section of a slab made in accordance with the method of the invention; the section being taken as at H-II in Figure 2; Figure 4 shows a three-dimensional view of one end of a cross rib forming part of a support grid, in accordance with the invention; and

Figure 5 shows a three-dimensional view of one end of a beam forming part of a support grid, in accordance with the invention.

Referring to Figure 1 of the drawings, reference numeral 10 indicates generally a support grid in accordance with the invention. The support grid 10, is made up of a plurality of elongate laterally spaced parallel longitudinally extending pre-cast reinforced concrete beams 12, 14 and 16, and by a plurality of orthogonally disposed elongate pre-cast reinforced concrete cross ribs 18, 20, 22, 24, 26 and 28. The cross ribs 18 to 22, interconnect the adjacent pair of beams 12 and 14, whereas the cross ribs 24, 26, and 28, interconnect the adjacent pair of beams 14 and 16. It will be noted that the cross ribs 24, 26, and 28, are in staggered relationship relative to the cross ribs 18, 20, 22.

The interconnection between the beams 12, 14, 16 and the various cross ribs 18 to 28, is described with reference to Figure 3 of the drawings. The beams 14, 16 are provided with transverse passages 14.1 and 16.1 to accommodate bolts 30, 32 passing along the passages. The bolts 30, 32 have screw threaded shanks 30.1 and 32.1 , engaging with screw threaded socket members 34 and 36 embedded in the ends of cross rib 26 (and the other cross ribs). The screw threaded socket members 34 and 36, are interconnected by a reinforcing rod 38 embedded within the cross rib 26. The beam 14 has rebated regions 14.2 and 14.3. The beam 16 similarly has rebated regions 16.2 and 16.3. The cross rib 26 has similar rebated regions 26.2 and 26.3 as indicated in Figure 3 of the drawings with reference to cross rib 26. The rebated regions on the beams 14, 16, and cross ribs 26, serve to provide a recessed seat indicated by reference numeral 40 and 42 for a shutter panel 44, the seat 40, 42, serving to locate the shutter panel 44 in position over the opening 46 defined between adjacent beams 14, 16, and the cross rib 26. The other openings 48, 50, 52 and so on, are ail similarly covered with shutter panels 44, so that when the in situ formwork has been finally completed, a full deck is provided onto which a concrete layer 60 can be poured with or without mesh reinforcement 62.

The beams have longitudinal reinforcing rods 64. Likewise, the cross ribs have reinforcing rods 66 extending longitudinally along the length of the cross ribs. In addition to such reinforcement, the beams 14 and 16, and the cross rib 26 have reinforcement of steel fibers 68. The concrete panels 44 also have reinforcing with steel fibers.

The invention have the advantage that the components making up the support grid 10, can be prefabricated at a position remote from a work site, and can then be transported to the work site, and assembled there. The reinforcing 62 of the beams, may be pre-stressed so as to improve the beam strength of the beams 12, 14, 16, and so on.

It will be understood, that the design of a floor slab may require the use of more than the three beams 12, 14, 16 showed in Figure 1 of the drawings. The dimensions of the beams, and the cross ribs, their pre-stressing, can all be matched to the size of the slab required. Generally the sizes of the openings 46, will be such as to enable panels 44 to be manhandled by workers. Thus the Applicant has found, that a panel 44, of one square meter, and having a thickness of say 30 mm can be manhandled by a worker and laid in position. The Applicant has found that the other components making up the support grid can also be manhandled into position.

The formwork 10, in this embodiment of the invention, also includes a tile 50.1 is laid flat concentrically face-to-face on top of the shutter panel 44, the tile 50.1 being sized so as to, in use, conceal a central part of the shutter panel 44, a remaining exposed part 50.2 of the shutter panel thus form a brim around the tile 50.1 before pouring of the settable cementitious material to form the concrete layer. Space between adjacent tiles 50.1 is thus filled with the poured concrete end may further contribute to structural strength of the slab. The tile is made from a material having a density lower than that of water. The Applicant has found that such materials assist in thermal and sound isolation. A polystyrene material or the like can be used.

The beams 12 to 15 also include pin supports or shear pins protruding from the beams 12 to 15 for bonding. Conveniently, a rod or bar may be connected to the protruding ends of the pins, say by arc welding, in which case the wire mesh 62 can be positions on top of the bar and slid in position, the bars or rods thus avoiding interference between the wire mesh and the pins. The shear pins further facilitates bonding of the concrete layer to the beams.

The reinforcing steel may include rods selected from the Y-bar or high- tension steel bars specified series of steel rods having a suitable diameter. Instead, steel wire cable having a suitable strand count and overall diameter may be selected. The selected reinforcing steel bars or rods may be pre-stress, eg. It may be pre-stressed to between 15% and 70% of its yield strength, depending the application.

In accordance with the invention, and keeping in mind the pre-cast and manhandleable nature of the pre-cast beams, cross ribs and shutter panels, it is desirous to employ a light weight high strength settable cementitious mixture. The settable cementitious mixture may be composed to provide a cured concrete having an average density of between 2400 and 2700 kg/m^Λ3 and a compressed strength of between 80 and 120 mpa.

The mixture may include cementitious material or any other hydraulic binder, for example Cem I 42.5R or Cem I 52.5 as covered by the standard SANS 197 or any Cem Il 42.5 or 32.5R covered by the same SANS standard specification.

A Pozzelanic material, having a high content of Silica oxides and which is able to react with the Calcium hydroxide that forms when a hydraulic binder reacts with water, may also form part of the mixture, for example fly ash {a process waste product) silica fume (a process waste product in the manufacturing of non-ferrous metals), GGBFS (a waste product in the manufacturing of steel) or any suitable natural pozzelans like zeolite or volcanic ash.

Fine or coarse aggregate stone can be used, or a combination of the two depending on the application. The mixture can be manufactured with only fine aggregate as specified by SABS 1083 standard specification, passing a size 4,75 mm sieve. Typically, materials can be any aggregates as specified by SABS 1083 suitable for the use in concrete Admixtures suitable for the use in concrete to change the wet and dry properties of the concrete may also form part to the mixture, the admixtures being suitable for facilitating molding or forming of the required beam, cross rib or shutter panel. Typical admixtures are accelerators, retarders, plasticizers, super plasticizers, and the like.

The fibres used can be either steel, synthetic or naturally occurring plant- like materials, or any combination, suitable for the use in concrete to improve the properties of the set concrete as well as preventing the wet concrete from cracking during setting.

The beams may be manufactured from a mixture comprising the following ingredients, expressed as a ratio of weight relative to each other,

Range Preferable

Cement 430-500 450

Pozzfill 50-80 70

CSF 30-40 35

Sand 1000-1200 1050

Stone 650-900 700

Admix A 4-5 4.3

Admix B 0.4-0.5 0.45

Fibre A 1-2 1.0

Fibre B 40-80 55 Similarly, the cross ribs and shutter panels may be manufactured from a mixture comprising the following ingredients, also express as a ratios of weight relative to each other,

Range Preferable

Cement 300-400 330

Pozzfill 40-70 50

CSF 20-40 25

Sand 1000-1200 1150

Stone 650-900 925

Admix A 3-4.5 3.1

Admix B 0.3-0.5 0.33

Fibre A 0.1-0.2 0.1

Fibre B 30-60 40

Advantageously, and in accordance with the invention, a roof or floor slab can be constructed which, generally, has a floor thickness and weight which is less than would typically expected with other methods of construction. Moreover, the Applicant believes that a lightweight floor system comprising high-strength pre-cast beams, cross ribs and shutter panels as described, facilitates manhandeling of the components and may even result in a reduced construction cost. A fairly large span in the order of five meters can be achieved without supports other than the supports at a periphery of the floor slab.

Claims

CLAIMS:

1. A method of constructing a floor or roof slab, which method includes: erecting a support grid of a plurality of elongate, laterally spaced, parallel, longitudinally extending, pre-cast reinforced concrete beams, and a plurality of orthogonally disposed elongate pre-cast reinforced concrete cross ribs interconnecting adjacent pairs of beams, a plurality of openings being defined by the upper edges of the interconnected beams and cross ribs; and laying pre-cast reinforced concrete shutter panels over the openings, the panels being supported along their peripheries by the upper edges of the beams and cross ribs defining the openings.

2. A method as claimed in claim 1, in which the cross ribs have a length which equals the longitudinal spacing between the cross ribs, thereby ensuring that the openings and hence the shutter panels are generally square.

3. A method as claimed in claim 1 or 2, in which the beams have rebates along their operative upper edges, thereby to provide recessed seats around the peripheries of the openings, to accommodate the shutter panels with clearance.

4. A method as claimed in anyone of the claims 1 to 3 inclusive, in which the interconnection between the beams and cross ribs is provided by bolting them together.

5. A method as claimed in claim 4, in which the beams have longitudinally spaced transverse passages at a spacing corresponding to the longitudinal spacing between the cross ribs; and in which the cross ribs have opposed screw threaded socket members at their ends, so that bolts having screw threaded shanks passing through the transverse passages in the beams are screwed into the screw threaded socket members at the ends of the cross ribs, thereby to bolt the beams and cross ribs together to form the support grid.

6. A method as claimed in claim 5, in which the socket members in the opposing ends of the cross ribs are interconnected by reinforcing steel rods embedded within the cross ribs.

7. A method as claimed in anyone of the claims 1 to 6 inclusive, in which the cross members between adjacent pairs of beams, are longitudinally staggered relative to each other.

8. A method as claimed in anyone of the claims 1 to 7 inclusive, in which a layer of a settable cementitious material is poured onto the shutter panels and allowed to set to form a concrete layer.

9. A method as claimed in claim 8, in which a reinforcing mesh is laid over the shutter panels, before the pouring of the settable cementitious material to form the concrete layer.

10. A method as claimed in claim 8 or 9, in which a tile is laid flat concentrically face-to-face on top of the shutter panel, the tile being sized so as to, in use, conceal a central part of the shutter panel, a remaining exposed part of the shutter panel thus form a brim around the tile before pouring of the settable cementitious material to form the concrete layer.

11. A method as claimed in claim 10, in which the tile is formed of a material having a density lower than that of water.

12. In situ formwork for casting a concrete roof or floor slab, which formwork includes: a plurality of elongate pre-cast reinforced concrete beams arranged in parallel laterally spaced longitudinally extending relationship; a plurality of longitudinally spaced, elongate, pre-cast reinforced concrete cross ribs orthogonally interconnecting adjacent pairs of beams, a plurality of longitudinally and laterally spaced openings being thus defined between the upper edges of the beams and cross ribs; and pre-cast reinforced concrete shutter panels located in position over the openings, thereby to form in situ formwork for the casting of a concrete slab.

13. Formwork as claimed in claim 12, in which the cross ribs have a length which equals the longitudinal spacing between the cross ribs, the openings and hence the shutter panels being generally square.

14. Formwork as claimed in claim 12 or 13, in which the beams and cross ribs have rebates along their upper edges thereby providing recessed seats accommodating the shutter panels with clearance.

15. Formwork as claimed in anyone of claims 12 to 14 inclusive, in which the interconnection between beams and cross ribs is by having them bolted together.

16. Formwork as claimed in claim 15, in which the beams have longitudinally spaced transverse passages through them at a spacing corresponding to the longitudinal spacing between the cross ribs; in which the cross ribs have opposed screw threaded socket members at their ends; and in which the bolts having screw treaded shanks passing through the transverse passages in the beams are screw threadedly engaged with the screw threaded socket members at the ends of the cross ribs.

17. Formwork as claimed in claim 16, in which the socket members at the ends of the cross ribs, are fast with opposing ends of reinforcing steel rods embedded in the cross ribs.

18. Formwork as claimed in anyone of claims 12 to 17 inclusive, in which the cross ribs between adjacent pairs of beams are longitudinally staggered relative to each other.

19. Formwork as claimed in anyone of claims 12 to 18 inclusive, in which the concrete of the beams, cross ribs, and the shutter panels, is high strength concrete.

20. Formwork as claimed in anyone of claims 12 to 19, in which the reinforcement of the beams, cross ribs, and shutter panels, includes fibers.

21. Formwork as claimed in claim 20, in which the fibers are formed of a material selected from the group comprising: metal, synthetic, and plant.

22. A pre-cast elongate reinforced concrete beam which includes a series of transverse passages through it spaced longitudinally along its length, the passages being adapted in use to receive bolts passing through them; and in which the opposing edges which in use will be the upper edges of the beam, are provided with rebates.

23. A pre-cast elongate cross rib of reinforced concrete, which cross rib includes at its opposing ends embedded therein screw threaded socket members engagable by screw threaded shanks of bolts passing through the transverse passages of a beam as claimed in claim 22.

24. A cross rib as claimed in claim 23, in which a reinforcing rod within the cross rib, interconnects the threaded socket members.

25. A cross rib as claimed in claim 23 or 24, in which opposing edges which in use will be the upper edges of the cross rib, are provided with rebates.

26. A support grid which includes: a plurality of elongate concrete beams arranged in transversely spaced longitudinally extending parallel relationship; a plurality of cross ribs as claimed in claim 23, 24 or 25, arranged orthogonally to the beams in longitudinally space relationship between adjacent pairs of beams, the beams and cross ribs being arranged such that the passages in the beams are aligned with the threaded socket members of the cross ribs; and bolts having screw threaded shanks passing through the passages of the beams, and screw threadedly engaging the screw threaded socket members in the ends of the cross ribs, thereby interconnecting the beams and cross ribs to form the support grid so that it has openings defined by the operatively upper edges of the interconnected beams and cross ribs, thereby to permit laying of shutter panels over the openings.

27. A concrete slab which includes a support grid as claimed in claim 26; pre-cast reinforced concrete shutter panels over the support grid openings; and a concrete layer over the shutter panels and grid support.

28. A slab as claimed in claim 25, in which the concrete layer has embedded within it reinforcement in the form of a mesh.

29. A slab as claimed in claim 28, in which the mesh is steel wired mesh, and in which the steel wire mesh is raised by support pins protruding from the beams prior to pouring of the concrete layer,

30. A slab as claimed in any one of claims 27 to 29, in which tiles are (aid flat concentrically face-to-face on top of shutter panels laid over openings defined by upper edges of a support grid, the tiles being sized so as to, in use, conceal a central part of the shutter panels, a remaining exposed part of the shutter panels thus forming a brim around the tile before pouring of a settable cementitious material to form the concrete layer.

31. A method of constructing a floor or roof slab as claimed in claim 1 , substantially as herein described and illustrated.

32. In situ formwork for casting a concrete roof or floor slab as claimed in claim 12, substantially as herein described and illustrated.

33. A pre-cast elongate reinforced concrete beam as claimed in claim 22, substantially as herein described and illustrated.

34. A pre-cast elongate cross rib of reinforced concrete as claimed in claim 23, substantially as herein described and illustrated.

35. A support grid as claimed in claim 26, substantially as herein described and illustrated.

36. A concrete slab as claimed in claim 27, substantially as herein described and illustrated.

37. A new method, a new formwork, a new concrete beam, a new cross rib, a new support grid, or a new concrete slab, substantially as herein described.