Fastener for concrete flooring joint

Abstract

The invention provides a one-piece fastener for securing a first joint component and a second joint component together to assemble a concrete flooring joint, such as an expansion joint. The one-piece

Description

TECHNICAL FIELD This invention relates to a concrete flooring joint, a fastener for securing joint components of a concrete flooring joint, and methods of assembly and installation of a concrete flooring joint. BACKGROUND Concrete flooring joints are used to form large concrete floors, for example concrete floors suitable for industrial applications such as warehouses or factories. Concrete flooring joints separate adjacent concrete flooring slabs from one another, and ensure adequate protection of arris edges at gaps that necessarily form between adjacent slabs as a result of contraction of concrete material during curing. Known concrete flooring joints comprise frangible fasteners to retain components of the joint together during transportation and installation, but to fracture under tension during curing of the concrete material as a gap between the concrete flooring slabs to either side of the joint opens up. Such frangible fasteners typically comprise a nylon bolt, a nut and an alignment bush. SUMMARY OF THE INVENTION In general terms, the invention provides a one-piece fastener for securing a first joint component and a second joint component together to assemble a concrete flooring joint. The one-piece fastener is preferably frangible, such that it is configured to fail under tension after installation. The fastener preferably comprises a cam surface configured to cause the fastener to be pre-tensioned as the fastener is rotated through an angle. In this way, the first and second joint components become clamped together. A first aspect of the invention provides a concrete flooring joint comprising a first joint component and a second joint component connected to the first joint component by one or more fasteners, each fastener comprising: a shaft; a head at a first end of the shaft, the head engaging the first joint component; and a tail at a second end of the shaft, the tail comprising a cam surface engaging the second joint component, whereby rotation of the shaft causes the first and second joint components to be urged together as a result of interaction between the cam surface and the second joint component. This arrangement is a significant improvement over known fastener solutions for concrete flooring joints, as described above. In particular, the joint assembly process is faster, providing efficiency gains. Users can be sure of providing a fastener pre-tension within acceptable margins by simply ensuring that the fastener is turned through a specified angle (for example, a quarter turn), so that there is no need for monitoring of fastener torque levels or other means of controlling fastener pre-tension. Assembly is also significantly more straightforward, since the fasteners can be fastened from one side of the joint assembly, with no need to access a nut or other connecting part at another side of the joint assembly. Also, parts inventory is minimised, since a single fastener replaces bolt, nut and alignment bush. The or each fastener is preferably a one-piece fastener. That is, the fastener preferably comprises no threaded portion, and no component configured to attach to the shaft via a threaded portion. The fastener is preferably formed as one unitary part, optionally by injection moulding. The shaft is preferably frangible, such that it is configured to fracture after installation. By frangible it is meant that the fastener is configured to maintain its structural integrity during assembly, transportation and installation of the concrete flooring joint, but to fail under tension after installation, once the tensile force reaches or exceeds a threshold commensurate with the separation forces applied to the first and second joint components during concrete curing. An appropriate tensile force threshold may be at or greater than 1200N, preferably at or less than 1700N, most preferably 1500N. In preferred embodiments the concrete flooring joint comprises a divider plate connected to the first joint component or the second joint component, the divider plate being configured to retain a poured concrete product. The divider plate may comprise an upper portion and an adjustable lower portion configured to move relative to the upper portion to adjust a height of the joint. The first and second joint components preferably each comprise an upper face configured to be aligned with a finished floor level of a concrete flooring material retained by the concrete flooring joint in use. The upper faces of the first and second joint components are preferably aligned in the same plane as one another. The first and second joint components preferably each comprise one or more apertures therethrough, for accommodating the or each fastener. The one or more apertures may be configured such that alignment of each aperture of the first joint with a respective aperture of the second joint results in alignment of upper faces of the first and second joint components. Such alignment may be achieved by insertion of a respective fastener through the aperture. In use, pourable concrete flooring material is poured to both sides of the concrete flooring joint to form adjacent first and second concrete flooring slabs. The first joint component is engaged with the first concrete flooring slab and the second joint component is engaged with the second concrete flooring slab. For example, the first and second joint components may comprise anchor members or other features configured to enhance engagement with the concrete material of the respective concrete flooring slab. As the concrete flooring material cures it contracts, causing the first and second joint components to be urged away from one another, so that tensile forces are applied to the one or more fasteners, eventually leading to failure of the one or more fasteners. The cam surface preferably extends radially outwardly from the shaft, the cam surface wrapping around at least a portion of a perimeter of the shaft such that it progressively becomes closer to the head. The cam surface may be generally perpendicular to the shaft. The cam surface may be arranged such that rotation in either a clockwise direction or an anti-clockwise direction causes the first and second joint components to be urged together. The one or more apertures of the first joint component and / or the second joint component are preferably shaped such that the tail of each fastener can pass through a respective one of the one or more apertures in a first angular orientation of the shaft, but be prevented from passing through the aperture in a second angular orientation of the shaft. In this way, a straightforward turn of the fastener from the first angular orientation to the second angular orientation provides a secure connection between the first and second joint components. Thus the one or more apertures may be configured to permit clear passage therethrough of the tail of the one or more fasteners when a respective fastener is appropriately angularly positioned so that tail and aperture are aligned in the first angular orientation, but to prevent passage therethrough of the tail after the shaft is rotated to the second angular orientation so that the tail and aperture are out of alignment. The one or more apertures preferably comprise slotted apertures having an elongate shape. For example, the one or more slotted apertures preferably have a width (in a direction aligned with the desired finished floor level) that is greater than their height (in a direction perpendicular to the desired finished floor level). The one or more slotted apertures may have any appropriate shape suitable for engagement with the shape of the tail of the one or more fasteners. For example, the one or more slotted apertures may have a generally rectangular or oblong shape, optionally with rounded ends. The one or more slotted apertures may have a width that is greater than a longest dimension of the fastener tail in cross-section at a plane perpendicular to an axis of the shaft, preferably at least 20% greater than a longest dimension of the fastener tail. This may correspond to a width that is at least 2 times that of a width of the shaft, optionally at least 3 times that of a width of the shaft, further optionally at least 5 times that of a width of the shaft. The width of the one or more slotted apertures may be smaller than 100mm, preferably 50mm or smaller, or most preferably 40mm or smaller. The one or more slotted apertures may have a height that is generally equal to or up to 20% greater than, preferably 10% greater than, a width of the shaft. The height of the one or more slotted apertures is preferably smaller than a longest dimension of the fastener tail in cross-section at a plane perpendicular to an axis of the shaft. In some embodiments the shaft of the or each fastener comprises a pair of axially-aligned opposing flat faces. For example, the flat faces may be defined by parallel tangential planes that bisect a circumference of a cylindrical body of the shaft. In such embodiments, the one or more slotted apertures may have a height that is equal to or up to 20% greater than, preferably 10% greater than, a distance between the opposing flat faces. Movement of the shaft between the first angular orientation and the second angular orientation preferably comprises an angular movement of between 20 degrees and 160 degrees, preferably between 30 degrees and 150 degrees, more preferably between 40 degrees and 140 degrees, more preferably between 50 degrees and 130 degrees, more preferably between 60 degrees and 120 degrees, more preferably between 70 degrees and 110 degrees, more preferably between 80 degrees and 100 degrees, most preferably between 85 degrees and 95 degrees. In some embodiments each of the one or more fasteners comprises one or more stop members projecting radially outwardly from the shaft. The or each stop member may comprise a stop face extending along a first plane generally tangential to the shaft. The stop preferably face abuts or otherwise is located adjacent to a perimeter wall of a respective one of the one or more apertures in the second angular orientation of the shaft. Thus, the one or more stop members serve to resist rotation of the shaft beyond the second angular orientation. In such embodiments the one or more stop members may each comprise a lead-in face extending along a second plane at an angle to the first plane. The lead-in face preferably abuts or otherwise is located adjacent to the perimeter wall in the first angular orientation of the shaft. The angle preferably corresponds to an angular difference between the first angular orientation and the second angular orientation. The lead-in face may serve to guide the shaft through the aperture during initial insertion in the first angular orientation. The shaft of each of the one or more fasteners may comprise a pair of opposing flat faces extending in an axial direction between the head and the tail, and the lead-in face of each of the one or more stop members may be generally co-planar with a respective flat face of the shaft. This arrangement provides a particularly effective means of guiding the shaft through the aperture during initial insertion in the first angular orientation. Each of the one or more fasteners may comprise one or more anti-rotation bump members projecting outwardly from the shaft. The one or more anti-rotation bump members preferably abut or otherwise are adjacent the perimeter wall in the second angular orientation of the shaft to resist rotation of the shaft from the second angular orientation towards the first angular orientation. In this way, the anti-rotation bump members resist unwanted loosening, or unfastening, of the fastener. In arrangements in which the shaft of each of the one or more fasteners comprises a pair of opposing convex faces extending in an axial direction between the head and the tail, each of the one or more anti-rotation bump members may project outwardly from a respective one of the convex faces. This provides a particularly effective position for the anti-rotation bump members. The shaft preferably comprises a pair of opposing flat faces extending in an axial direction between the head and the tail. The shaft preferably also comprises a pair of opposing convex faces extending in an axial direction between the head and the tail. A distance between the pair of flat faces is preferably up to 20% less than a distance between the pair of opposing convex faces, most preferably up to 10% less than a distance between the pair of opposing convex faces. The pair of opposing flat faces enable particularly straightforward insertion of the tail through the one or more apertures in the first angular orientation by enabling either a loose fit between the opposing flat faces and the one or more apertures in the first angular orientation, or a close fit between the opposing flat faces and the one or more apertures in the first angular orientation that enables sliding of the shaft within the one or more apertures. Rotation of the fastener to the second angular orientation enables a close or interference fit between the pair of opposing convex faces and the one or more apertures in the second angular orientation, such that accurate alignment between the respective one or more apertures of the first joint member and the second joint member is achieved. In use, the opposing flat faces are preferably generally aligned with walls of the one or more apertures in the first angular orientation. In embodiments in which the one or more apertures comprise a slotted aperture, a height (in a direction perpendicular to the finished floor level) of the slotted aperture of the slotted aperture is generally equal to or up to 20% greater than, preferably up to 10% greater than, a distance between the pair of opposing flat faces. The height of the slotted aperture may alternatively, or in addition, be generally equal to a distance between the opposing convex faces, or a diameter of the shaft. The cam surface may comprise a first cam surface portion and a second cam surface portion, the second cam surface portion being radially symmetrical with the first cam surface portion about an axis of the shaft. In this way, the tensile loads within the fastener are shared equally between the first and second cam surface portions. In other embodiments, the cam surface may comprise a plurality of cam surface portions, each of the cam surface portions being radially symmetrical with the other cam surface portions about an axis of the shaft. The tail may comprise first and second portions extending radially outwardly from the shaft, the first portion carrying the first cam surface portion, and the second portion carrying the second cam surface portion. This arrangement is particularly suitable where the tail has an elongate shape generally corresponding to an elongate shape of a slotted aperture through the first and second joint components. For example, the first and second portions may be arranged at either ends of a longest dimension of the tail. In some embodiments the tail has a shortest dimension in a radial direction that generally corresponds to a shortest dimension of the shaft in the radial direction, and the tail has a longest dimension in the radial direction that is greater than the shortest dimension of the shaft in the radial direction. Preferably, the cam surface extends radially outwardly from the shaft, the cam surface comprising a first cam surface portion sloping from a first position at a perimeter of the shaft to a second position at the perimeter of the shaft, the second position being closer to the head of the fastener than the first position. In some embodiments the first and second positions may be co-incident, such that the cam surface extends around the entire perimeter of the shaft. Alternatively, the first and second positions may be spaced apart around the perimeter. The cam surface preferably also comprises a second cam surface portion sloping from a third position at a perimeter of the shaft to a fourth position at the perimeter of the shaft, the fourth position being closer to the head of the fastener than the third position. The first, second, third and fourth positions are preferably located in series around the perimeter of the shaft. The first position and third position are preferably equidistant from the head, and the second position and fourth position are preferably equidistant from the head. This arrangement serves to provide radial symmetry of the first and second cam surfaces, such that tensile loads within the fastener are shared equally between the first and second cam surfaces. The shaft preferably comprises a stress concentration feature configured to promote failure of the fastener at the stress concentration feature. In particular, the stress concentration may be configured to cause fracture of the shaft when the fastener is subjected to tensile forces above the tensile force threshold. The stress concentration feature may comprise a surface discontinuity, shoulder, change in cross-sectional shape or other feature of the shaft at which stress concentrations will be experienced when the fastener is subjected to a tensile force. For example, the stress concentration feature may comprise a recessed groove extending around a perimeter of the shaft, preferably around an entire perimeter of the shaft. The recessed groove may be generally V-shaped in cross-section. The tail preferably comprises one or more first frangible ribs projecting from the cam surface towards the head, the or each first frangible rib being configured to fracture when subjected to compression during fastening of the fastener. For example, the first frangible ribs may comprise radially-aligned ribs extending in a radial direction from the shaft. The first frangible rubs may extend from the shaft across the cam surface. The first frangible ribs may be configured to fail under compression during installation, to ensure correct alignment of the first and second joint components. The first frangible ribs mitigate for tolerance deviations in the thicknesses of the first and second joint components. For example, at some tolerance cases the first frangible ribs may be fractured as a result of interaction with the adjacent face of the first or second joint component as the fastener is tightened, and at other tolerance cases the first frangible ribs engage with that adjacent face to ensure an adequate pre-tension in the fastener. The or each fastener preferably comprises a tool interface for receiving a fastening tool, the tool interface having an opening in the head of the fastener and a recessed cavity extending from the opening into the shaft, the recessed cavity including a tool-engaging portion configured to engage with a fastening tool to permit transmission of torque from the fastening tool to the tool-engaging portion, wherein the tool-engaging portion extends into the shaft. By extending the tool-engaging portion into the shaft, torque transmitted to the fastener by the fastening tool is transmitted directly to the shaft. Alternative arrangements in which the tool-engaging portion extends into the head only, and not the shaft, may be vulnerable to unplanned failures at the head-shaft interface during fastening. In particularly preferred arrangements in which the shaft comprises a stress concentration feature configured to promote failure of the fastener at the stress concentration feature, the tool-engaging portion is preferably located between the stress concentration feature and the tail, and optionally not between the stress concentration feature and the head. This arrangement avoids unintentional fracturing of the fastener at the stress concentration feature during fastening of the fastener. The shaft preferably comprises one or more second frangible ribs projecting from the shaft, the or each second frangible rib being configured to fracture when subjected to compression during fastening of the fastener. For example, the second frangible ribs may comprise axially-aligned frangible ribs extending along the shaft in an axial direction. The second frangible ribs may be configured to fail under compression during installation, to ensure correct alignment of the first and second joint components. The second frangible ribs mitigate for tolerance deviations in a size (e.g. diameter) of the shaft of the or each fastener, and a height of the or each aperture in the first and second joint components through which a respective shaft passes. Such mitigation is particularly important in arrangements in which it is important to accurately control the relative positions of apertures in the first joint component with apertures in the second joint component, in order to accurately control a position of upper faces of the first and second joint component that are aligned with the finished floor level such that they are exposed after installation of the concrete floor. The skilled reader will recognise that it is necessary for there to be a close fit (or interference fit) between the shaft and the apertures in order for the upper faces to be maintained in close alignment during and after assembly of the joint. For example, at some tolerance cases the second frangible ribs may be fractured as a result of interaction with the walls of the aperture as the fastener is tightened, and at other tolerance cases the second frangible ribs engage with walls of the aperture to ensure an adequate fit between shaft and aperture. In all tolerance cases the apertures are thereby aligned to ensure alignment of the upper surfaces of the first and second joint components. A second aspect of the invention provides a fastener for forming a concrete flooring joint according to the first aspect, the fastener comprising: a shaft; a head at a first end of the shaft, the head being configured to engage the first joint component; and a tail at a second end of the shaft, the tail comprising a cam surface configured to engage the second joint component, whereby rotation of the shaft causes the first and second joint components to be urged together as a result of interaction between the cam surface and the second joint component in use. The fastener may have any of the features described herein in relation to any aspect of the invention. A third aspect of the invention provides a method of assembling a concrete flooring joint comprising a first joint component, a second joint component, and one or more fasteners, each fastener having: a shaft; a head at a first end of the shaft; and a tail at a second end of the shaft, the tail comprising a cam surface, the method comprising the steps of: inserting the one or more fasteners through the first joint component and the second joint component so that the head engages the first joint component; and rotating the one or more fasteners to cause the cam surface of the tail to engage the second joint component, the first and second joint components being urged together as a result of interaction between the cam surface and the second joint component. The first and second joint components may each comprise one or more apertures therethrough, and the step of inserting the one or more fasteners through the first joint component and the second joint component may include passing the tail of the one or more fasteners through a respective aperture in a first angular orientation, and the step of rotating the one or more fasteners may include rotating the shaft to a second angular orientation in which the tail is prevented from passing through the aperture. Thus, the apertures may be configured to permit clear passage therethrough of the tail of the one or more fasteners when a respective fastener is appropriately angularly positioned so that tail and aperture are aligned in the first angular orientation, but to prevent passage therethrough of the tail after the shaft is rotated to the second angular orientation so that the tail and aperture are out of alignment. The one or more apertures may comprise slotted apertures as described herein. The tail may comprise one or more first frangible ribs projecting from the cam surface towards the head, and the step of rotating the one or more fasteners may include fracturing the one or more first frangible ribs. The shaft may comprise one or more second frangible ribs projecting from the shaft, and the step of rotating the one or more fasteners may include fracturing the one or more second frangible ribs. The first joint component, second joint component, and one or more fasteners may have any of the features described herein in relation to any aspect of the invention. A fourth aspect of the invention provides a method of forming a concrete floor, comprising the steps of: providing a concrete flooring joint according to the first aspect or a concrete flooring joint assembled according to the third aspect; pouring a curable concrete flooring material to a first side of the concrete flooring joint adjacent the first joint component to form a first concrete flooring slab; pouring a curable concrete flooring material to a second side of the concrete flooring joint adjacent the second joint component to form a second concrete flooring slab; and curing the curable concrete material to cause separation of the first joint component and the second joint component and consequential fracture of the one or more fasteners at the shaft. The first joint component, second joint component, and one or more fasteners may have any of the features described herein in relation to any aspect of the invention. Throughout the description and claims of this specification, the words "comprise" and "contain" and variations of the words, for example "comprising" and "comprises", mean "including but not limited to", and do not exclude other components, integers or steps. Moreover the singular encompasses the plural unless the context otherwise requires: in particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise. Preferred features of each aspect of the invention may be as described in connection with any of the other aspects. Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and / or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and / or features of any embodiment can be combined in any way and / or 5 combination, unless such features are incompatible. BRIEF DESCRIPTION OF THE DRAWINGS One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is an isometric view of a fastener according to a first embodiment of the invention; Figures 2 and 3 are further isometric views of the fastener of Figure 1; Figure 4 is a top view of the fastener of Figure 1; Figure 5 is a bottom view of the fastener of Figure 1; Figure 6 is a partial cross-sectional view of the fastener of Figure 1, taken along a longitudinal axis of the fastener; Figure 7 is an isometric view of a section of a first concrete flooring joint comprising the fastener of Figure 1; Figures 8 and 9 are detail views of the first concrete flooring joint; Figure 10 is a detail view comprising a partial cross-sectional view of the first concrete flooring joint, taken along a longitudinal axis of one of the fasteners; Figure 11 is an isometric view of a section of a second concrete flooring joint comprising the fastener of Figure 1; Figures 12 and 13 are detail views of the second concrete flooring joint; Figure 14 is a detail view comprising a partial cross-sectional view of the second concrete flooring joint, taken along a longitudinal axis of one of the fasteners; Figure 15 is an isometric view of a section of a third concrete flooring joint comprising the fastener of Figure 1; Figures 16 and 17 are detail views of the third concrete flooring joint; Figure 18 is a detail view comprising a partial cross-sectional view of the third concrete flooring joint, taken along a longitudinal axis of one of the fasteners; Figure 19 is an isometric view of a section of a fourth concrete flooring joint comprising the fastener of Figure 1; Figures 20 and 21 are detail views of the fourth concrete flooring joint; Figure 22 is a detail view comprising a partial cross-sectional view of the fourth concrete flooring joint, taken along a longitudinal axis of one of the fasteners; Figure 23 is an isometric view of a fastener according to a second embodiment of the invention; Figures 24A and B are a front view and a side view, respectively, of the fastener of Figure 23; Figures 25A and B are partial cross-sectional views of the fastener of Figure 23, taken along lines A-A and B-B, respectively, indicated in Fig. 24B; and Figures 26A and B are a top view and a bottom view, respectively, of the fastener of Figure 23. DETAILED DESCRIPTION The present invention relates to a frangible one-piece fastener 100, 600 for temporarily clamping first and second joint components of a concrete flooring joint together for the purpose of maintaining a desired configuration during storage, transportation and installation. In the figures, a first embodiment of the fastener 100 is illustrated on its own (in Figures 1 to 6) and in combination with four differently-configured concrete flooring joints 200, 300, 400, 500 (in Figures 7 to 21). A second embodiment of the fastener 600 is illustrated on its own (in Figures 23 to 26), but can likewise be assembled with the concrete flooring joints 200, 300, 400, 500. The skilled reader will understand that there is a wide variety of configurations of concrete flooring joints available in the market, and that the fastener 100, 600 may be incorporated into concrete flooring joints other than those illustrated herein. The first embodiment is illustrated in Figures 1 to 22. The fastener 100 comprises a shaft 10 subtended by a head 30 and a tail 50. The head 30 is generally circular in cross-section, while the tail 50 has a generally elongate shape in cross-section, as discussed below. The fastener 100 is formed in one unitary piece from plastics material. Suitable materials include polymers. Examples of suitable materials are nylon or polyamide nylon (PA), including PA6, PA12, PA6C, PA63 or PA66. Other suitable materials include high-density polyethylene (HDPE or PE-HD), polypropylene (PP), or polycarbonate (PC). The plastics material may be fibre-reinforced, for example reinforced with glass, carbon or aramid fibres. The fastener 100 may be formed by injection moulding, additive manufacturing, machining from stock material, or by any other suitable means. While the fastener 100 of the embodiments is formed from plastics material, the skilled reader will understand that other materials may be used instead. For example, the fastener 100 may be formed from metal such as steel, stainless steel, Inconel, titanium, aluminium, or any suitable metal or metal 12 alloy. For example, the metal fastener 100 may be machined from stock material or cast. In some such arrangements the metal fastener may not be formed in one piece, but may instead be assembled from a plurality of parts joined by welding or other suitable means. A tool interface 70 comprises a recessed cavity 72 that extends from an opening 74 in the head 30, through the head 30 and into the shaft 10. In use, a hex key tool (not shown; also known as an Allen key) is inserted into the tool interface 70 and operated to control the rotational position of the shaft 10. The entrance portion 76 of the recessed cavity 72 is generally circular in cross-section and sized to ensure clear passage of the hex key tool. The base portion 78 of the recessed cavity 72 has a series of flat walls such that it is hexagonal in cross-section, and sized to engage a corresponding hex key tool to enable the transfer of torque from the tool to the fastener 100. The skilled reader will understand that in other embodiments the tool interface 70 may be configured according to any known tooling interface format. For example, the tool interface may instead comprise a series of flat walls to an external face of the head 30 to form a hex head or similar configuration to accommodate fastening with a torque wrench or similar tool. The shaft 10 is generally cylindrical. In the illustrated example the shaft comprises a pair of opposing flat faces 12 extending along its longitudinal extent at opposite radial positions. The flat faces 12 are defined by parallel tangential planes that bisect the circumference of the cylindrical body of the shaft 10. A distance between the flat faces 12 is preferably up to 10% less than a diameter of the shaft 10. In use, the flat faces 12 facilitate alignment of the fastener 100 within the slotted aperture into which it is assembled, as described further below. The shaft 10 also includes a recessed groove 14 extending around the shaft's periphery. The function of the recessed groove 14 is to provide a stress concentration feature, with the intention that, in use, the frangible fastener 100 will fail under tension by fracturing of the shaft at the recessed groove 14. The shape and configuration of the recessed groove 14 is selected to ensure failure at or above a threshold tensile force applied to the shaft 10. In this way, the shaft 10 maintains its structural integrity during assembly, transportation and installation of a concrete flooring joint 200, 300, 400, 500, but fails under tension under the higher tensile forces experienced during curing of concrete poured to either side of the joint during use, as described below. In the illustrated embodiments, the recessed groove 14 has a generally V-shaped cross section, but any shape or configuration sufficient to provide stress concentration feature may be appropriate. In some embodiments a feature other than a recessed groove 14 may be appropriate, such as a series of recesses arranged around the shaft 10, a shoulder feature, or other discontinuity or change in geometry. In the illustrated embodiments the tool interface 70 is configured such that the base portion 78 (i.e. the part of the tool interface 70 that engages the hex key tool) is positioned between the recessed groove 14 and the tail 50, and not between the recessed groove 14 and the head 74. In this way, torque applied to the fastener 100 during fastening using the hex key tool is transmitted directly to the tail 50 and the portion of the shaft 10 between the recessed groove 14 and the tail 50, with minimal torque being applied to the head 30 or to the shaft 10 at the head 30 or in the region of the recessed groove 14. This avoids unintentional fracturing of the fastener 100 at the recessed groove during installation of the fastener 100 into the concrete flooring joint 200, 300, 400, 500. The tail 50 is generally pill-shaped in a cross-section taken at a plane perpendicular to a longitudinal axis of the shaft 10. For example, the cross-sectional shape may be a stadium, discorectangle or obround shape, i.e. a shape comprising a rectangle with opposite edges subtended by semicircles. In other embodiments the tail 50 may have a different cross-sectional shape, such as a square, rectangular or oblong shape, optionally with rounded corners. In the illustrated embodiments the longest dimension of the tail 50 in cross-section (in a plane perpendicular to an axis of the shaft 10) is generally equal to the diameter of the head 30, and the shortest dimension in cross-section is smaller than the diameter of the head 30, as seen best in Figure 5. This shape enables the tail 50 to pass through a slotted aperture 114, 214, 340, 440 (described below) having a height (in a direction perpendicular to a finished floor level) and a width (in a direction aligned with the finished floor level). The shortest dimension of the tail 50 is thus generally equal to or less than the height of the slotted aperture 114, 214, 340, 440. The longest dimension of the tail 50 is thus generally less than the width of the slotted aperture 114, 214, 340, 440, and greater than the height of the slotted aperture 114, 214, 340, 440. In this way, once the tail 50 passes through the slotted aperture, rotation of the shaft 10 will ensure that the tail 50 and slotted aperture are no longer aligned, so that the fastener is retained by the slotted aperture 114, 214, 340, 440. The tail 50 comprises a cam surface 52 opposed to an underside face of the head 30, such that, in use, the first and second joint components of the concrete flooring joint are clamped therebetween. The pill-shaped cross-sectional shape of the tail 50 provides for two opposing limbs projecting outwardly from the shaft 10. The cam surface 52 comprises a first cam surface portion 54 carried by one of the limbs, and a second cam surface portion 56 carried by the other of the limbs. The first cam surface portion 54 and second cam surface portion 56 each have rotational symmetry with the other, about the longitudinal axis of the shaft 10. The skilled reader will understand that in other embodiments the cam surface 52 may not be divided into two portions, but instead may be formed in one unitary part, or alternatively divided into three or more portions. The cam surface 52 extends radially outwardly from the shaft 10, such that as it wraps around the shaft 10 it progressively becomes closer to the head 30. That is, the cam surface 52 provides a ramped surface extending around the shaft 10. Each of the first cam surface portion 54 and the second cam surface portion 56 provides a corresponding ramped surface that work in tandem together as the shaft 10 is rotated. The first cam surface portion 54 slopes progressively from a first radial position Pl at a perimeter of the shaft 10 to a second radial position P2 at a perimeter of the shaft, the second radial position P2 being closer to the head 30 than the first radial position Pl. Similarly, the second cam surface portion 56 slopes progressively from a third radial position P3 at a perimeter of the shaft 10 to a fourth radial position P4 at a perimeter of the shaft, the fourth radial position P4 being closer to the head 30 than the third radial position P3. The first radial position Pl and third radial position P3 are equidistant from the head 30, while the second radial position P2 and fourth radial position P4 are equidistant from the head 30; this arrangement ensures that the first 54 and second 56 cam surface portions have radial symmetry with one another, and that tensile loads within the fastener 100 are shared equally between the two opposing limbs of the tail 50. The skilled reader will observe that in the first embodiment the cam surface 52 is configured to require rotation of the shaft 10 in an anti-clockwise direction during fastening, from the first angular orientation to the second angular orientation. It is envisaged that in other embodiments, such as the second embodiment, the cam surface 52 may be configured to require rotation of the shaft 10 in a clockwise direction during fastening. The fastener 100 also includes a series of axially-aligned frangible ribs 16 distributed around the external curved surface of the shaft 10. There are six axially-aligned frangible ribs 16 in the illustrated embodiments, but in other embodiments there may be more, or fewer, ribs 16. The axially-aligned frangible ribs 16 are configured to fail under compression during installation, to ensure correct alignment of the first and second joint components, as described further below. In addition to the axially-aligned frangible ribs 16, the fastener 100 also includes a pair of radially-aligned frangible ribs 58 comprising upstanding elongate ribs projecting from the cam surface 52, one from the first cam surface portion 54 and the other from the second cam surface portion 56. The radially-aligned frangible ribs 58 are configured to fail under compression during installation, to ensure correct alignment of the first and second joint components, as described further below. The axially-aligned frangible ribs 16 and radially-aligned frangible ribs 58 each have a generally triangular cross-sectional shape, with a broader base narrowing to an apex. Other cross-sectional shapes may be appropriate. For example, any a cross-sectional shape with an aspect ratio of less than 1, so that the ribs have a height that is greater than their width. Such cross-sectional shapes ensure that the ribs 16, 58 are configured to fracture under compression during installation. Figures 7 to 10 illustrate a first concrete flooring joint 200 comprising the frangible one-piece fastener 100. The first joint 200 comprises a first top strip 110 (first joint component) and a second top strip 112 (second joint component) fastened together by a plurality of frangible one-piece fasteners 100. The shaft 10 of each fastener 100 passes through slotted apertures 114 in the first 110 and second 112 top strips. The slotted apertures 114 are shaped and sized to permit clear passage therethrough of the tail 50 of the fasteners 100 when the fastener is appropriately angularly positioned so that tail 50 and slotted aperture 114 are aligned, but to prevent passage therethrough of the tail 50 after the shaft 10 is rotated so that the tail 50 and slotted aperture 114 are out of alignment. In particular, the height of the slotted apertures 114 may generally correspond to, or be up to 10% greater than, a width of the shaftlO, for example a diameter of the shaft 10 or a distance between the pair of opposing flat faces 12. In this way, both tail 50 and shaft 10 are able to readily slide though the slotted apertures 50 when the fastener 100 is orientated so that the pair of flat faces 12 are generally aligned with the upper and lower walls of the slotted apertures 50, i.e. when the tail 50 and slotted aperture 114 are aligned. The head 30 is unable to pass through the slotted apertures 114 in all angular positions of the fastener 100. The first concrete flooring joint 200 comprises a divider plate 120 that acts in use to separate a first concrete flooring slab (not shown) from a second concrete flooring slab (not shown). The divider plate 120 comprises an upper divider plate portion 122 which is welded (or otherwise affixed) to the first top strip 110 (but not the second top strip 112) and extends downwardly therefrom, and a lower divider plate portion 124. The lower divider plate portion 124 comprises a series of vertically aligned slots 126 through each of which a rivet 128 passes. The rivets 128 fasten the upper 122 and lower 124 divider plate portions together such that some movement between the lower divider plate portion 124 and upper divider plate portion 122 is possible by sliding of the rivets 128 within their respective slots 126. The lower divider plate portion 124 comprises a foot in the form of a laterally-projecting flange 125. Each of the first 110 and second 112 top strips comprises an elongate member with a rectangular cross-section. They are fastened together such that they have two mating faces, and each of their upper faces 116 is aligned in a plane that is co-incident with a finished flooring level of a concrete floor formed using the joint 200. In this way, the upper faces 116 are exposed in the finished concrete floor, and provide arris protection for the first and second concrete flooring slabs. The first top strip 110 is welded (or otherwise affixed) to the upper divider plate portion 122 of the divider plate 120. A first series 130 and a second series 132 of anchor members (shear studs) are welded to each of the first 110 and second 112 top strips, respectively, so that the first 130 and second 132 series of anchor members project outwardly from the top strips and away from one another. Each anchor member 130, 132 comprises an elongate rod with a projecting head. In use, the anchor members 130, 132 become embedded within the concrete material of the first and second concrete flooring slabs, respectively, in order to anchor the first top strip 110 into the first concrete flooring slab and the second top strip 112 into the second concrete flooring slab. A first series 140 and a second series 142 of load transfer plates are welded to opposing faces of the upper divider plate portion 122 of the divider plate 120. The first series of load transfer plates 140 projects away from the first top strip 110. Similarly, the second series of load transfer plates 142 projects away from the second top strip 112. Each load transfer plate 140, 142 comprises a plate projecting at a right angle to a longitudinal plane of the divider plate 120. The load transfer plates 140, 142 are generally rectangular in the illustrated embodiments, but other shapes are envisaged, including triangular or trapezoidal shapes. Each of the second series of load transfer plates 142 is encased within a plastic sleeve 144 so that the sleeve 144 is able to slide relative to the load transfer plate 142. In use, the first series of load transfer plates 140 are embedded within the concrete material of the first concrete flooring flab, and the sleeves 144 of the second series of load transfer plates 142 are embedded within the concrete material of the second concrete flooring slab. The load transfer plates 140, 142 provide for the transfer of bending loads between the first and second concrete flooring slabs in use. This helps to prevent undesirable damage to the concrete slabs in the region of the joint that might otherwise occur as heavy vehicles travel across the joint. The first joint 200 is assembled by orienting the fasteners 100 with the slotted apertures 114, inserting the fasteners 100 therethrough, and using a hex key tool (not shown) to rotate each fastener 100 so that the tail 50 becomes mis-aligned with the respective slotted aperture 114. As each fastener 100 is rotated, the cam surface 52 engages the second top strip 112 (in the illustrated embodiment; in other embodiments, the cam surface 52 may engage the first top strip 110). The shape of the cam surface 52 causes the fastener 100 to become progressively pre-tensioned such that the first top strip 110 and second top strip 112 become clamped together with a progressively increasing clamping force. In the illustrated embodiments, a rotation of the fastener 100 through an angle of approximately 800-100 degrees, i.e. a quarter turn or around 90 degrees, achieves the desired level of pre-tensioning of the fastener 100. In other embodiments, the cam surface 52 may be configured to achieve the desired level of pre-tensioning by rotation of the fastener 100 through a different angle. The skilled reader will understand that the particular angle is not material, though they will recognise that a quarter turn (i.e. an angle or approximately 80-100 degrees, or around 90 degrees) is particularly straightforward to put into practice and ideally suited to embodiments in which the fastener 100 is installed through a slotted aperture 114. During installation of the fasteners 100, the axially-aligned frangible ribs 16 act to ensure accurate alignment of the upper faces 116 of the first 110 and second 112 top strips. The slotted apertures 114 are accurately machined to ensure a tight tolerance between their hole centres and the upper faces 116. However, the skilled reader will recognise that it is necessary for there to be a close fit (or interference fit) between the shaft 10 and the slotted apertures 114 in order for the upper faces 116 to be maintained in close alignment during and after assembly of the joint. Moreover, the skilled reader will recognise that there will necessarily be a degree of manufacturing tolerance for the height of the slotted apertures 114 themselves, and for the diameter of the shaft 10 of the fasteners 100. The axially-aligned frangible ribs 16 provide a means for mitigating for these manufacturing tolerances. If the height of the slotted apertures 114 is at the maximum end of its allowable tolerance range and the diameter of the shaft 10 is at the minimum end of its allowable tolerance range, the axially-aligned frangible ribs 16 ensure an adequate fit between shaft 10 and slotted aperture 114. Conversely, if the height of the slotted apertures 114 is at the minimum end of its allowable tolerance range and the diameter of the shaft 10 is at the maximum end of its allowable tolerance range, the axially-aligned frangible ribs 16 will be fractured as a result of interaction between the ribs 16 and the walls of the slotted aperture 114 as the fastener 100 is tightened, such that an adequate fit between shaft 10 and slotted aperture 114 is attained. During installation of the fasteners 100, the radially-aligned frangible ribs 58 mitigate for tolerance deviations in the thickness of the first 110 and second 112 top strips. The skilled reader will recognise that there will necessarily be a degree of manufacturing tolerance for the thickness of the first 110 and second 112 top strips, and for the length of the shaft 10 of the fastener 100 (i.e. the distance between the head 30 and the cam surface 52). The radially-aligned frangible ribs 58 provide a means for mitigating these manufacturing tolerances. In particular, if the thickness of the first 110 and second 112 top strips is at the maximum end of its allowable tolerance range and the length of the shaft 10 is at the minimum end of its allowable tolerance range, the radially-aligned frangible ribs 58 can be fractured as a result of interaction between the ribs 58 and the adjacent face of the second top strip 112 (or first top strip 110) as the fastener 100 is tightened, such that an adequate pre-tension in the fastener 100 is achieved. Conversely, if the thickness of the first 110 and second 112 top strips is at the minimum end of its allowable tolerance range and the length of the shaft 10 is at the maximum end of its allowable tolerance range, the radially-aligned frangible ribs 58 engage with the adjacent face of the second top strip 112 (or first top strip 110) to ensure an adequate pre-tension in the fastener 100. The fasteners 100 remain installed and intact during storage, transportation and installation of the joint 200, serving to retain the joint 200 in the configuration illustrated in the figures, and in particular to maintain alignment of the upper faces 116 of the first 110 and second 112 top strips. However, the fasteners 100 fail after installation and during curing of pourable concrete material in the first and second concrete flooring slabs, by fracturing of the shaft 10 at the recessed groove 14 as described below. During installation, the assembled joint 200 is located so that the upper faces 116 of the first 110 and second 112 top strips are aligned with the desired finished floor level. Jacks or other suspension means may be used to ensure correct alignment. The lower portion of the divider plate 122 is then adjusted by sliding of the rivets 128 within the vertical slots 126 so that the flange 128 engages a sub-floor (not shown) on top of which the first and second concrete flooring slabs are to be formed. The first concrete flooring slab is formed by pouring curable concrete material to a first side of the divider plate 120 so that the first series of anchor members 130 and first series of load transfer plates 140 are embedded in the concrete material. As the concrete material cures, it contracts. The first series of anchor members 130 embedded in the concrete material ensure that the first top strip 110 and the divider plate 120 remain in close contact with a joint-side face of the first concrete slab. The second concrete flooring slab is formed by pouring curable concrete material to a second side of the divider plate 120 so that the second series of anchor members 132 and the sleeves 144 of the second series of load transfer plates 142 are embedded in the concrete material. Again, as the concrete material cures, it contracts. The second series of anchor members 132 embedded in the concrete material ensure that the second top strip 112 remains in close contact with a joint-side face of the second concrete slab, and the sleeves 144 slide over each of the second series of load transfer plates 142 to enable the divider plate 120 to remain in close contact with the joint-side face of the first concrete slab as described above. As a result, a gap opens up between the first 110 and second 112 top strips, and the fasteners 100 consequently fail in tension by fracturing of the shafts 10 at the recessed groove 14. The first 110 and second 112 top strips protect the arris edges of the first and second concrete flooring slabs that would otherwise be vulnerable to cracking or crumbling as heavy vehicles travel across the gap between the slabs after installation. The load transfer plates 140, 142 further reduce damage in this vulnerable region of the concrete, by providing for the transfer of bending loads between the first and second concrete flooring slabs as vehicles travel across the joint. Figures 11 to 14 illustrate a second concrete flooring joint 300 comprising the frangible one-piece fastener 100. The second concrete flooring joint 300 is identical to the concrete flooring joint 200 described above and illustrated in Figures 7 to 10, with the exception of the differences described below. Like features are indicated by the same reference numerals, and the description will be focused on those features which differ from the first concrete flooring joint 200. The second concrete flooring joint 300 comprises a first top strip 210 (first joint component) and a second top strip 212 (second joint component) fastened together by a plurality of frangible one-piece fasteners 100. As in the first concrete flooring joint 200, the shaft 10 of each fastener 100 passes through slotted apertures 214 in the first 210 and second 212 top strips. The slotted apertures 214 are shaped and sized to permit clear passage therethrough of the tail 50 of the fasteners 100 when the fastener is appropriately angularly positioned so that tail 50 and slotted aperture 214 are aligned, but to prevent passage therethrough of the tail 50 after the shaft 10 is rotated so that the tail 50 and slotted aperture 214 are out of alignment. In particular, the height of the slotted apertures 214 may generally correspond to, or be up to 10% greater than, a width of the shaft 10, for example a diameter of the shaft 10 or a distance between the pair of opposing flat faces 12. In this way, both tail 50 and shaft 10 are able to readily slide though the slotted apertures 50 when the fastener 100 is orientated so that the pair of flat faces 12 are generally aligned with the upper and lower walls of the slotted apertures 50, i.e. when the tail 50 and slotted aperture 214 are aligned. The head 30 is unable to pass through the slotted apertures 214 in all angular positions of the fastener 100. The concrete flooring joint 200 comprises a divider plate 220 that acts in use to separate a first concrete flooring slab (not shown) from a second concrete flooring slab (not shown). The divider plate 220 comprises an upper divider plate portion 222 which is welded to the first top strip 210 (but not the second top strip 212) and extends downwardly therefrom, and a lower divider plate portion 224. The lower divider plate portion 224 comprises a series of vertically aligned slots 226 through each of which a rivet 228 passes. The rivets 228 fasten the upper 222 and lower 224 divider plate portions together such that some movement between the lower divider plate portion 224 and upper divider plate portion 222 is possible by sliding of the rivets 228 within their respective slots 226. The lower divider plate portion 224 comprises a foot in the form of a laterally-projecting flange 225. The first 210 and second 212 top strips each comprise an elongate member with a rectangular cross-section, and each has a wave-form profile such that at their mating faces they undulate between corresponding peaks and troughs. The upper faces 216 of the first 210 and second 212 top strips are aligned in a plan that is co-incident with a finished flooring level of a concrete floor formed using the joint 300. The upper faces 216 thus together provide a wave-form shape corresponding to the wave-form profile of the first 210 and second 212 top strips. The second joint 300 is assembled and installed as described above with reference to the first joint 200. In this way, as the pourable concrete material of the first and second concrete flooring slabs contracts during curing, the first 210 and second 212 top strips become separated from one another to form a gap therebetween, and the frangible fasteners 100 fracture at the recessed groove 14 as a result. The first series of anchor members 130 embedded in the concrete material of the first concrete flooring slab ensure that the first top strip 210 and the divider plate 120 remain in close contact with a joint-side face of the first concrete slab. Similarly, the second series of anchor members 132 embedded in the concrete material ensure that the second top strip 212 remains in close contact with a joint-side face of the second concrete slab, and the sleeves 144 slide over each of the second series of load transfer plates 142 to enable the divider plate 220 to remain in close contact with the joint-side face of the first concrete slab as described above. As a result, a gap opens up between the first 210 and second 212 top strips, and the fasteners 100 consequently fail in tension by fracturing of the shafts 10 at the recessed groove 14. Whereas the first joint 200 provides a gap in a straight line, the second joint 300 provides a gap having a wave-form shape. This wave-form shape can provide particularly good protection for the arris edges of the first and second concrete flooring slabs. In particular, loads from heavy vehicles travelling across the gap between the slabs after installation may be better distributed across the joint, reducing areas of stress concentrations. Thus, the first 210 and second 212 top strips protect the arris edges of the first and second concrete flooring slabs that would otherwise be vulnerable to cracking or crumbling. Figures 15 to 18 illustrate a third concrete flooring joint 400 comprising the frangible one-piece fastener 100. The third concrete flooring joint 400 is identical to the first concrete flooring joint 200 and second flooring joint 300 described above and illustrated in Figures 7 to 10 and 11 to 14, respectively, with the exception of the differences described below. Like features are indicated by the same reference numerals, and the description will focus on those features which differ from the first 200 and second 300 concrete flooring joints. Instead of first and second top strips, the third concrete flooring joint 400 comprises a first top plate assembly 310 (first joint component) and a second top plate assembly 320 (second joint component) fastened together by a plurality of frangible one-piece fasteners 100. The concrete flooring joint 200 comprises a divider plate 330 that acts in use to separate a first concrete flooring slab (not shown) from a second concrete flooring slab (not shown). The divider plate 330 comprises an upper divider plate portion 332 and a lower divider plate portion 334. The lower divider plate portion 334 comprises a series of vertically aligned slots 336 through each of which a rivet 338 passes. The rivets 338 fasten the upper 332 and lower 334 divider plate portions together such that some movement between the lower divider plate portion 334 and upper divider plate portion 332 is possible by sliding of the rivets 338 within their respective slots 336. The lower divider plate portion 334 comprises a foot in the form of a laterally-projecting flange 335. The first top plate assembly 310 comprises a first top wave plate 311, a first intermediate plate 312 and a first anchor member 313. The first anchor member 313 comprises an elongate component with a vertical web portion 314, a horizontal web portion 315 extending from an upper edge of the vertical web portion 314, an upper flange portion 316 and a series of lower flange portions 317. The vertical web portion 314 engages the upper divider plate portion 332, and the horizontal web portion 315 engages the first intermediate plate 312. Each lower flange portion 317 comprises a generally rectangular member projecting outwardly from a lower edge of the vertical web portion 314, and each has a plurality of apertures 318 therethrough. The upper flange portion 316 comprises an elongate member projecting outwardly from an outer edge of the horizontal web portion 315 and has a series of apertures 319 therethrough. The upper 316 and lower 317 flange portions and their respective apertures 318, 319 provide anchor means that are embedded in the concrete material of the first concrete flooring slab in use, and thereby promote reliable engagement of the first top plate assembly 310 with the concrete material of the first concrete flooring slab. The first top wave plate 311 comprises an elongate planar plate-like member with a waveform edge profile at an interface with the second top wave plate 321 of the second top plate assembly 320, as described below. The first intermediate plate 312 is sandwiched between the first top wave plate 311 and the horizontal web portion 315 of the first anchor member 313. Rivets pass through the first top wave plate 311, first intermediate plate 312, and the horizontal web portion 315 of the first anchor member 313 to provide a permanent connection between the first top wave plate 311, first intermediate plate 312 and first anchor member 313. The first intermediate plate 312 comprises an elongate planar platelike member with a generally linear edge profile at an interface with the second intermediate plate 322, as described below. The second top plate assembly 320 comprises a second top wave plate 321, a second intermediate plate 322 and a second anchor member 323. The second anchor member 323 comprises an elongate component with a vertical web portion 324, a horizontal web portion 325 extending from an upper edge of the vertical web portion 324, an upper flange portion 326 and a series of lower flange portions 327. The vertical web portion 324 engages the upper divider plate portion 332, and the horizontal web portion 325 engages the second intermediate plate 322. Each lower flange portion 327 comprises a generally rectangular member projecting outwardly from a lower edge of the vertical web portion 324, and each has a plurality of apertures 328 therethrough. The upper flange portion 326 comprises an elongate member projecting outwardly from an outer edge of the horizontal web portion 325 and has a series of apertures 329 therethrough. The upper 326 and lower 327 flange portions and their respective apertures 328, 329 provide anchor means that are embedded in the concrete material of the second concrete flooring slab in use, and thereby promote reliable engagement of the second top plate assembly 320 with the concrete material of the second concrete flooring slab. The second top wave plate 321 comprises an elongate planar plate-like member with a wave-form edge profile at an interface with the first top wave plate 311 of the first top plate assembly 320, as described below. The second intermediate plate 322 is sandwiched between the second top wave plate 321 and the horizontal web portion 325 of the second anchor member 323. Rivets pass through the second top wave plate 321, second intermediate plate 322, and the horizontal web portion 325 of the second anchor member 323 to provide a permanent connection between the second top wave plate 321, second intermediate plate 322 and second anchor member 323. The second intermediate plate 322 comprises an elongate planar plate-like member with a generally linear edge profile at an interface with the first intermediate plate 312 and laterally offset from the wave-form interface of the first 311 and second 321 top wave plates, as described below. Each of the vertical web portions 314, 324 of the anchor members 310, 320 comprises a plurality of slotted apertures 340 through each of which a respective one of the plurality of frangible one-piece fasteners 100 passes. The slotted apertures 340 are shaped and sized to permit clear passage therethrough of the tail 50 of the fasteners 100 when the fastener is appropriately angularly positioned so that tail 50 and slotted aperture 340 are aligned, but to prevent passage therethrough of the tail 50 after the shaft 10 is rotated so that the tail 50 and slotted aperture 340 are out of alignment. In particular, the height of the slotted apertures 340 may generally correspond to, or be up to 10% greater than, a width of the shaft 10, for example a diameter of the shaft 10 or a distance between the pair of opposing flat faces 12. In this way, both tail 50 and shaft 10 are able to readily slide though the slotted apertures 340 when the fastener 100 is orientated so that the pair of flat faces 12 are generally aligned with the upper and lower walls of the slotted apertures 340, i.e. when the tail 50 and slotted aperture 340 are aligned. The head 30 is unable to pass through the slotted apertures 340 in all angular positions of the fastener 100. The third concrete flooring joint 400 is assembled as described above with reference to the first joint 200 and second joint 300. The method of installation is similar, but with some small differences as described below. The frangible one-piece fasteners 100 maintain correct relative positions of first 310 and second 320 top plate assemblies with the divider plate 330 throughout assembly, transportation and installation. During installation, the assembled joint 400 is located so that the upper faces of the first 311 and second 321 top wave plates are aligned with the desired finished floor level. Jacks or other suspension means may be used to ensure correct alignment. The lower portion of the divider plate 332 is then adjusted by sliding of the rivets 338 within the vertical slots 336 so that the flange 338 engages a sub-floor (not shown) on top of which the first and second concrete flooring slabs are to be formed. The first concrete flooring slab is formed by pouring curable concrete material to a first side of the divider plate 330 so that the upper flange portion 316 and lower flange portion 317 of the first anchor member 313, and the first series of load transfer plates 140, are embedded in the concrete material. As the concrete material cures, it contracts. The first anchor member 313 embedded in the concrete material ensures that the first top plate assembly 310 and the divider plate 330 remain in close contact with a joint-side face of the first concrete slab. The second concrete flooring slab is formed by pouring curable concrete material to a second side of the divider plate 330 so that the upper flange portion 326 and lower flange portion 327 of the second anchor member 323, and the sleeves 144 of the second series of load transfer plates 142, are embedded in the concrete material. Again, as the concrete material cures, it contracts. The second anchor member 323 embedded in the concrete material ensures that the second top plate assembly 320 remains in close contact with a joint-side face of the second concrete slab, and the sleeves 144 slide over each of the second series of load transfer plates 142 to enable the divider plate 330 to remain in close contact with the joint-side face of the first concrete slab as described above. As a result, a wave-form shaped gap opens up between the first 311 and second 321 top plates, and the fasteners 100 consequently fail in tension by fracturing of the shafts 10 at the recessed groove 14. The wave-form interface between the first 311 and second 321 top wave plates serves to minimise regions of stress concentration across the joint in the finished floor. This waveform interface is laterally offset from the straight interface between the first 312 and second 322 intermediate plates, so that the first intermediate plate 312 provides a continuous base beneath the wave-form interface in use. This arrangement serves to prevent debris from falling into the gap between the first and second concrete flooring slabs in use. Figures 19 to 22 illustrate a fourth concrete flooring joint 500 comprising the frangible one-piece fastener 100. The fourth concrete flooring joint 500 is identical to the third concrete flooring joint 400 described above and illustrated in Figures 15 to 18, respectively, with the exception of the differences described below. Like features are indicated by the same reference numerals, and the description will focus on those features which differ from the third 400 concrete flooring joint. Like the third concrete flooring joint 400, the fourth concrete flooring joint comprises a first top plate assembly 410 (first joint component) and a second top plate assembly 420 (second joint component) fastened together by a plurality of frangible one-piece fasteners 100. The concrete flooring joint 200 comprises a divider plate 330 that acts in use to separate a first concrete flooring slab (not shown) from a second concrete flooring slab (not shown). The divider plate 330 comprises an upper divider plate portion 332 and a lower divider plate portion 334. The lower divider plate portion 334 comprises a series of vertically aligned slots 336 through each of which a rivet 338 passes. The rivets 338 fasten the upper 332 and lower 334 divider plate portions together such that some movement between the lower divider plate portion 334 and upper divider plate portion 332 is possible by sliding of the rivets 338 within their respective slots 336. The lower divider plate portion 334 comprises a foot in the form of a laterally-projecting flange 335. The first top plate assembly 410 comprises a first top wave plate 411 and a first anchor member 413. There is no intermediate plate. The first anchor member 413 comprises an elongate component with a vertical web portion 414, a horizontal web portion 415, an upper flange portion 416 and a series of lower flange portions 417. The vertical web portion 414 engages the upper divider plate portion 332, and the horizontal web portion 415 engages the first top wave plate 411. Each of the lower flange portions 417 comprises a generally trapezoidal-shaped member projecting outwardly from a lower edge of the vertical web portion 414. The upper flange portion 416 comprises an elongate member projecting outwardly from an outer edge of the horizontal web portion 415, and has a series of apertures 419 therethrough. The upper 416 and lower 417 flange portions provide anchor means that are embedded in the concrete material of the first concrete flooring slab in use, and thereby promote reliable engagement of the first top plate assembly 410 with the concrete material of the first concrete flooring slab. The first top wave plate 411 comprises an elongate planar plate-like member with a waveform edge profile at an interface with the second top wave plate 421 of the second top plate assembly 420. Rivets pass through the first top wave plate 411 and the horizontal web portion 415 of the first anchor member 413 to provide a permanent connection therebetween. The second top plate assembly 420 comprises a second top wave plate 421 and a second anchor member 423. There is no intermediate plate. The second anchor member 423 comprises an elongate component with a vertical web portion 424, a horizontal web portion 425, an upper flange portion 426 and a series of lower flange portions 427. The vertical web portion 424 engages the upper divider plate portion 332, and the horizontal web portion 425 engages the second top wave plate 421. Each of the lower flange portions 427 comprises a generally trapezoidal-shaped member projecting outwardly from a lower edge of the vertical web portion 324. The upper flange portion 426 comprises an elongate member projecting outwardly from an outer edge of the horizontal web portion 425 and has a series of apertures 429 therethrough. The upper 426 and lower 427 flange portions provide anchor means that are embedded in the concrete material of the second concrete flooring slab in use, and thereby promote reliable engagement of the second top plate assembly 420 with the concrete material of the second concrete flooring slab. The second top wave plate 421 comprises an elongate planar plate-like member with a wave-form edge profile at an interface with the first top wave plate 411 of the first top plate assembly 420. Rivets pass through the second top wave plate 421, and the horizontal web portion 425 of the second anchor member 423 to provide a permanent connection therebetween. Each of the vertical web portions 414, 424 of the anchor members 410, 420 comprises a plurality of slotted apertures 440 through each of which a respective one of the plurality of frangible one-piece fasteners 100 passes. The slotted apertures 440 are shaped and sized to permit clear passage therethrough of the tail 50 of the fasteners 100 when the fastener is appropriately angularly positioned so that tail 50 and slotted aperture 440 are aligned, but to prevent passage therethrough of the tail 50 after the shaft 10 is rotated so that the tail 50 and slotted aperture 440 are out of alignment. In particular, the height of the slotted apertures 440 may generally correspond to, or be up to 10% greater than, a width of the shaft 10, for example a diameter of the shaft 10 or a distance between the pair of opposing flat faces 12. In this way, both tail 50 and shaft 10 are able to readily slide though the slotted apertures 340 when the fastener 100 is orientated so that the pair of flat faces 12 are generally aligned with the upper and lower walls of the slotted apertures 440, i.e. when the tail 50 and slotted aperture 340 are aligned. The head 30 is unable to pass through the slotted apertures 440 in all angular positions of the fastener 100. The fourth concrete flooring joint 500 is assembled as described above with reference to the first joint 200, second joint 300 and third joint 400. The method of installation is the same as that described above with reference to the third joint 400. The frangible one-piece fasteners 100 maintain alignment between the first 410 and second 420 plate assemblies and the divider plate 330 during assembly, transportation and installation of the joint 500. After installation, the fasteners 500 fracture at the recessed groove 14 to allow a gap to open up at the wave-form interface between the first 411 and second 421 top wave plates. This wave-form interface serves to minimise regions of stress concentration across the joint in the finished floor. The second embodiment is illustrated in Figures 23 to 26. The fastener 600 of the second embodiment has many features in common with the fastener 100 of the first embodiment, and like features are identified using the same reference numerals. Description of such features in relation to the first embodiment apply equally to the second embodiment. The fastener 600 comprises a shaft 10 subtended by a head 30 and a tail 50. The head 30 is generally circular in cross-section, while the tail 50 has a generally elongate shape in crosssection, as discussed below. The fastener 600 is formed in one unitary piece from plastics material. Suitable materials include polymers. Examples of suitable materials are nylon or polyamide nylon (PA), including PA6, PA12, PA6C, PA63 or PA66. Other suitable materials include high-density polyethylene (HDPE or PE-HD), polypropylene (PP), or polycarbonate (PC). The plastics material may be fibre-reinforced, for example reinforced with glass, carbon or aramid fibres. The fastener 600 may be formed by injection moulding, additive manufacturing, machining from stock material, or by any other suitable means. While the fastener 600 of the embodiments is formed from plastics material, the skilled reader will understand that other materials may be used instead. For example, the fastener 600 may be formed from metal such as steel, stainless steel, Inconel, titanium, aluminium, or any suitable metal or metal alloy. For example, the metal fastener 600 may be machined from stock material or cast. In some such arrangements the metal fastener may not be formed in one piece, but may instead be assembled from a plurality of parts joined by welding or other suitable means. A tool interface 70 comprises a recessed cavity 72 that extends from an opening 74 in the head 30, through the head 30 and into the shaft 10. In use, a hex key tool (not shown; also known as an Allen key) is inserted into the tool interface 70 and operated to control the rotational position of the shaft 10. The entrance portion 76 of the recessed cavity 72 is generally circular in cross-section and sized to ensure clear passage of the hex key tool. The base portion 78 of the recessed cavity 72 has a series of flat walls such that it is hexagonal in cross-section, and sized to engage a corresponding hex key tool to enable the transfer of torque from the tool to the fastener 600. The skilled reader will understand that in other embodiments the tool interface 70 may be configured according to any known tooling interface format. For example, the tool interface may instead comprise a series of flat walls to an external face of the head 30 to form a hex head or similar configuration to accommodate fastening with a torque wrench or similar tool. The shaft 10 is generally cylindrical. In the illustrated example the shaft comprises a pair of opposing flat faces 12 extending along its longitudinal extent at opposite radial positions. The flat faces 12 are defined by parallel tangential planes that bisect the circumference of the cylindrical body of the shaft 10. A distance between the flat faces 12 is preferably up to 10% less than a diameter of the shaft 10. In use, the flat faces 12 facilitate alignment of the fastener 600 within the slotted aperture into which it is assembled, as described further below. The shaft 10 also includes a recessed groove 14 extending around the shaft's periphery. The function of the recessed groove 14 is to provide a stress concentration feature, with the intention that, in use, the frangible fastener 600 will fail under tension by fracturing of the shaft at the recessed groove 14. The shape and configuration of the recessed groove 14 is selected to ensure failure at or above a threshold tensile force applied to the shaft 10. In this way, the shaft 10 maintains its structural integrity during assembly, transportation and installation of a concrete flooring joint 200, 300, 400, 500, but fails under tension under the higher tensile forces experienced during curing of concrete poured to either side of the joint during use, as described below. In the illustrated embodiments, the recessed groove 14 has a generally V-shaped cross section, but any shape or configuration sufficient to provide stress concentration feature may be appropriate. In some embodiments a feature other than a recessed groove 14 may be appropriate, such as a series of recesses arranged around the shaft 10, a shoulder feature, or other discontinuity or change in geometry. In the illustrated embodiments the tool interface 70 is configured such that the base portion 78 (i.e. the part of the tool interface 70 that engages the hex key tool) is located between the recessed groove 14 and the tail 50, and not between the recessed groove 14 and the head 74. In this way, torque applied to the fastener 600 during fastening using the hex key tool is transmitted directly to the tail 50 and the portion of the shaft 10 between the recessed groove 14 and the tail 50, with minimal torque being applied to the head 30 or to the shaft 10 at the head 30 or in the region of the recessed groove 14. This avoids unintentional fracturing of the fastener 600 at the recessed groove during installation of the fastener 600 into the concrete flooring joint 200, 300, 400, 500. The tail 50 is generally pill-shaped in a cross-section taken at a plane perpendicular to a longitudinal axis of the shaft 10. For example, the cross-sectional shape may be a stadium, discorectangle or obround shape, i.e. a shape comprising a rectangle with opposite edges subtended by semicircles. In other embodiments the tail 50 may have a different cross-sectional shape, such as a square, rectangular or oblong shape, optionally with rounded corners. In the illustrated embodiments the longest dimension of the tail 50 in cross-section (in a plane perpendicular to an axis of the shaft 10) is generally equal to the diameter of the head 30, and the shortest dimension in cross-section is smaller than the diameter of the head 30, as seen best in Figure 26B. This shape enables the tail 50 to pass through a slotted aperture 114, 214, 340, 440 (described above) having a height (in a direction perpendicular to a finished floor level) and a width (in a direction aligned with the finished floor level). The shortest dimension of the tail 50 is thus generally equal to or less than the height of the slotted aperture 114, 214, 340, 440. The longest dimension of the tail 50 is thus generally less than the width of the slotted aperture 114, 214, 340, 440, and greater than the height of the slotted aperture 114, 214, 340, 440. In this way, once the tail 50 passes through the slotted aperture, rotation of the shaft 10 will ensure that the tail 50 and slotted aperture are no longer aligned, so that the fastener is retained by the slotted aperture 114, 214, 340, 440. The tail 50 comprises a cam surface 52 opposed to an underside face of the head 30, such that, in use, the first and second joint components of the concrete flooring joint are clamped therebetween. The pill-shaped cross-sectional shape of the tail 50 provides for two opposing limbs projecting outwardly from the shaft 10. The cam surface 52 comprises a first cam surface portion 54 carried by one of the limbs, and a second cam surface portion 56 carried by the other of the limbs. The first cam surface portion 54 and second cam surface portion 56 each have rotational symmetry with the other, about the longitudinal axis of the shaft 10. The skilled reader will understand that in other embodiments the cam surface 52 may not be divided into two portions, but instead may be formed in one unitary part, or alternatively divided into three or more portions. The cam surface 52 extends radially outwardly from the shaft 10, such that as it wraps around the shaft 10 it progressively becomes closer to the head 30. That is, the cam surface 52 provides a ramped surface extending around the shaft 10. Each of the first cam surface portion 54 and the second cam surface portion 56 provides a corresponding ramped surface that work in tandem together as the shaft 10 is rotated. The skilled reader will observe that in the second embodiment the cam surface 52 is configured to require rotation of the shaft 10 in a clockwise direction during fastening, from a first angular orientation to a second angular orientation. It is envisaged that in other embodiments, like the first embodiment, the cam surface 52 may be configured to require rotation of the shaft 10 in an anti-clockwise direction during fastening. The fastener 600 also includes a pair of opposed stop members 610 projecting radially outwardly from a mid region of the shaft 10. Each stop member 610 comprises a generally-wedge-shaped body with two planar faces subtended by a right angle, including a lead-in face 612 and a stop face 614. During installation, each lead-in face 612 generally abuts a perimeter wall of the aperture 114, 214, 340, 440 in the first angular orientation, and each stop face 614 generally abuts the perimeter wall in the second angular orientation. In this way, the lead-in face 612 serves to aid alignment of the fastener as it is inserted into the aperture 114, 214, 340, 440 in the first angular orientation, and after rotation of the shaft to the second angular orientation the stop face 614 serves to resist further clockwise rotation. The lead-in face 612 of each stop member 610 is generally aligned with, preferably planar with, a respective one of the flat faces 12 of the shaft 10. The stop face 614 of each stop member 610 extends at a right angle to the respective lead-in face 612, so that it lies along a plane generally tangential with the convex face of the shaft 10, to form a generally axially-extending linear interface 616 with the convex face. Each stop member 610 has an axial length that is small compared to the axial length of the shaft 10. For example, each stop member 610 may have an axial length of less than half the axial length of the shaft 10. The stop members 610 are illustrated as being discrete from, i.e. not directly joined to, the head 30 and the tail 50 of the fastener 60. In other embodiments, the stop members 610 may extend partially or wholly along the axial length of the shaft 10, from the head 30 or the tail 50. The fastener 600 further includes a pair of anti-rotation bump members 620, each comprising an elongate rib member projecting from the outer cylindrical surface of the shaft 10. Each anti-rotation bump member 620 is aligned generally axially. In other embodiments the anti-rotation bump members 620 may comprise any type of projecting feature such as a pimple, step or shoulder. The anti-rotation bump members 620 are located on the shaft 12 so that they generally abut the perimeter wall of the respective aperture 114, 214, 340, 440 in the second angular orientation, to thereby resist rotation of the shaft 10 towards the first angular rotation. Thus, the anti-rotation bump members 620 serve to prevent unwanted loosening of the fastener 600 after installation. In the illustrated arrangement each anti-rotation bump member 620 is located generally mid-way between a respective one of the flat faces 12 and a respective one of the linear interfaces 616 discussed above. The frangible one-piece fastener 600 of the second embodiment is installed into a concrete flooring joint 200, 300, 400, 500 in a similar manner as described above in relation to the fastener 100 of the first embodiment. Features of the concrete flooring joints 200, 300, 400, 500, and the methods of installing the fastener 100, described above apply equally to the fastener 600 of the second embodiment. The following description is focused on the features that differ, for the sake of brevity. In use, each fastener 600 is assembled with the concrete flooring joint 200, 300, 400, 500 by orienting the fasteners 600 with the slotted apertures 114, 214, 340, 440, inserting the fasteners 100 therethrough, and using a hex key tool (not shown) to rotate each fastener 30 600 clockwise so that the tail 50 becomes mis-aligned with the respective slotted aperture 114, 214, 340, 440. This corresponds to rotation of the shaft from the first angular orientation to the second angular orientation. As each fastener 100 is rotated, the cam surface 52 engages the first joint component or second joint component (such as the second top strip 112 or first top strip 110, in the example of the joint 200). The shape of the cam surface 52 causes the fastener 100 to become progressively pre-tensioned such that the first joint component and second joint component become clamped together with a progressively increasing clamping force. A rotation of the fastener 600 through an angle of approximately 90 degrees, i.e. a quarter turn, achieves the desired level of pre-tensioning of the fastener 600. The skilled reader will understand that the particular angle is not material, though they will recognise that a quarter turn (i.e. an angle of approximately 80-100 degrees, or around 90 degrees) is particularly straightforward to put into practice and ideally suited to embodiments in which the fastener 100 is installed through a slotted aperture 114, 214, 340, 440. During installation, the stop members 610 and anti-rotation bump members 620 together act to ensure 90 degree rotation of the fastener 600. As the shaft 10 rotates through 90 degrees from the first angular orientation to the second angular orientation, the stop face 614 of each of the stop members 610 moves into a mating contact with a perimeter wall of the slotted aperture 114, 214, 340, 440. This mating contact is readily verifiable by the installer, who is thus able to easily determine that the fastener has been correctly installed through 90 degrees. This mating contact also provides a means of maintaining the correct installation position of the fastener 600 thereafter, by resisting further rotation in a clockwise direction. The anti-rotation bump members 620 further aid in maintaining the correct installation position of the fastener. The torque applied by the hex tool during installation is sufficient to cause the anti-rotation bump members 620 to be slid across the perimeter wall of the slotted aperture 114, 214, 340, 440, so that in the second angular orientation the antirotation bump members 620 are generally adjacent to the perimeter wall such that they abut the perimeter wall or are separated from the perimeter wall by only a small gap. In this position, the anti-rotation bump members 620 provide sufficient resistance to rotation towards the first angular orientation (i.e. resistance to anti-clockwise rotation) to prevent unintentional unfastening during handling, transportation etc. That is, after installation, some torque may be inadvertently applied to the fastener 600, but it is envisaged that this will be insufficient to overcome the resistance of the anti-rotation bump members 620. The fasteners 600 remain installed and intact during storage, transportation and installation of the joint 200, 300, 400, 500, serving to retain the joint 200, 300, 400, 500 in the configuration illustrated in the figures, and in particular to maintain alignment of the first and second joint members. However, the fasteners 600 fail after installation and during curing of pourable concrete material in the first and second concrete flooring slabs, by fracturing of the shaft 10 at the recessed groove 14 as described above. 5 It is envisaged that fasteners 600 according to the second embodiment may incorporate axially-aligned frangible ribs 16 and / or radially-aligned frangible ribs 58 as described in relation to the first embodiment. Similarly, it is envisaged that fasteners 100 according to the first embodiment may incorporate stop members 610 and / or anti-rotation bump members 620 according to the 10 second embodiment. The skilled reader will understand that the embodiments illustrated herein and described above represent only examples of how the invention may be put into effect, and that the scope of the invention is defined by the appended claims.

Claims

1. A concrete flooring joint comprising a first joint component and a second joint component connected to the first joint component by one or more fasteners, each fastener comprising:a shaft;a head at a first end of the shaft, the head engaging the first joint component; anda tail at a second end of the shaft, the tail comprising a cam surface engaging the second joint component, whereby rotation of the shaft causes the first and second joint components to be urged together as a result of interaction between the cam surface and the second joint component.

2. A concrete flooring joint according to claim 1, wherein the cam surface extends radially outwardly from the shaft, the cam surface wrapping around at least a portion of a perimeter of the shaft such that it progressively becomes closer to the head.

3. A concrete flooring joint according to claim 1 or claim 2, wherein the first joint component and / or the second joint component comprise one or more apertures, the tail of each fastener being shaped such that it can pass through a respective one of the one or more apertures in a first angular orientation of the shaft, but be prevented from passing through the aperture in a second angular orientation of the shaft.

4. A concrete flooring joint according to claim 3, wherein movement of the shaft between the first angular orientation and the second angular orientation comprises an angular movement of between 20 degrees and 160 degrees, preferably between 30 degrees and 150 degrees, more preferably between 40 degrees and 140 degrees, more preferably between 50 degrees and 130 degrees, more preferably between 60 degrees and 120 degrees, more preferably between 70 degrees and 110 degrees, more preferably between 80 degrees and 100 degrees, most preferably between 85 degrees and 95 degrees.

5. A concrete flooring joint according to claim 3 or claim 4, wherein each of the one or more fasteners comprises one or more stop members projecting radially outwardly from the shaft, the or each stop member comprising a stop face extending along a first plane generally tangential to the shaft, the stop face abutting a perimeter wall of a respective one of the one or more apertures in the second angular orientation of the shaft to resist rotation of the shaft beyond the second angular orientation.

6. A concrete flooring joint according to claim 5, wherein the one or more stop members each comprise a lead-in face extending along a second plane at an angle to the first plane, 33the lead-in face abutting the perimeter wall in the first angular orientation of the shaft, the angle preferably corresponding to a difference between the first angular orientation and the second angular orientation.

7. A concrete flooring joint according to claim 6, wherein the shaft of each of the one or more fasteners comprises a pair of opposing flat faces extending in an axial direction between the head and the tail, and the lead-in face of each of the one or more stop members is generally co-planar with a respective flat face of the shaft.

8. A concrete flooring joint according to any of claims 3 to 7, wherein each of the one or more fasteners comprises one or more anti-rotation bump members projecting outwardly from the shaft, the one or more anti-rotation bump members abutting the perimeter wall in the second angular orientation of the shaft to resist rotation of the shaft from the second angular orientation towards the first angular orientation.

9. A concrete flooring joint according to claim 7, wherein the shaft of each of the one or more fasteners comprises a pair of opposing convex faces extending in an axial direction between the head and the tail, and wherein each of the one or more anti-rotation bump members projects outwardly from a respective one of the convex faces.

10. A concrete flooring joint according to any preceding claim, wherein the shaft comprises a pair of opposing flat faces extending in an axial direction between the head and the tail, the shaft optionally further comprising a pair of opposing convex faces extending in an axial direction between the head and the tail.

11. A concrete flooring joint according to any preceding claim, wherein the cam surface comprises a first cam surface portion and a second cam surface portion, the second cam surface portion being radially symmetrical with the first cam surface portion about an axis of the shaft.

12. A concrete flooring joint according to claim 11, wherein the tail comprises first and second portions extending radially outwardly from the shaft, the first portion carrying the first cam surface portion, and the second portion carrying the second cam surface portion.

13. A concrete flooring joint according to any preceding claim, wherein the shaft comprises a stress concentration feature configured to promote failure of the fastener at the stress concentration feature.

14. A concrete flooring joint according to claim 13, wherein the stress concentration feature comprises a recessed groove extending around a perimeter of the shaft, optionally around an entire perimeter of the shaft.

15. A concrete flooring joint according to any preceding claim, wherein the tail comprises one or more first frangible ribs projecting from the cam surface towards the head, the or each first frangible rib being configured to fracture when subjected to compression during fastening of the fastener.

16. A concrete flooring joint according to any preceding claim, wherein the fastener comprises a tool interface for receiving a fastening tool, the tool interface having an opening in the head of the fastener and a recessed cavity extending from the opening into the shaft, the recessed cavity including a tool-engaging portion configured to engage with a fastening tool to permit transmission of torque from the fastening tool to the tool-engaging portion, wherein the tool-engaging portion extends into the shaft.

17. A concrete flooring joint according to claim 16, wherein the shaft comprises a stress concentration feature configured to promote failure of the fastener at the stress concentration feature, and wherein the tool-engaging portion is located between the stress concentration feature and the tail.

18. A concrete flooring joint according to any preceding claim, wherein the shaft comprises one or more second frangible ribs projecting from the shaft, the or each second frangible rib being configured to fracture when subjected to compression during fastening of the fastener.

19. A concrete flooring joint according to any preceding claim, wherein the one or more fasteners are each formed as one unitary part, optionally by injection moulding.

20. A fastener for forming a concrete flooring joint according to any of claims 1 to 19, the fastener comprising:a shaft;a head at a first end of the shaft, the head being configured to engage the first joint component; anda tail at a second end of the shaft, the tail comprising a cam surface configured to engage the second joint component, whereby rotation of the shaft causes the first and second joint components to be urged together as a result of interaction between the cam surface and the second joint component in use.

21. A method of assembling a concrete flooring joint comprising a first joint component, a second joint component, and one or more fasteners, each fastener having: a shaft; a head at a first end of the shaft; and a tail at a second end of the shaft, the tail comprising a cam surface, the method comprising the steps of:inserting the one or more fasteners through the first joint component and the second joint component so that the head engages the first joint component; androtating the one or more fasteners to cause the cam surface of the tail to engage the second joint component, the first and second joint components being urged together as a result of interaction between the cam surface and the second joint component.

22. A method according to claim 21, wherein the first and second joint components each comprise one or more slotted apertures therethrough, and the step of inserting the one or more fasteners through the first joint component and the second joint component includes passing the tail of the one or more fasteners through a respective slotted aperture in a first angular orientation, and the step of rotating the one or more fasteners includes rotating the shaft to a second angular orientation in which the tail is prevented from passing through the slotted aperture.

23. A method according to claim 21 or claim 22 wherein the tail comprises one or more first frangible ribs projecting from the cam surface towards the head, and the step of rotating the one or more fasteners includes fracturing the one or more first frangible ribs.

24. A method according to any of claims 21 to 23, wherein the shaft comprises one or more second frangible ribs projecting from the shaft, and the step of rotating the one or more fasteners incudes fracturing the one or more second frangible ribs.

25. A method of forming a concrete floor, comprising the steps of:providing a concrete flooring joint according to any of claims 1 to 19;pouring a curable concrete flooring material to a first side of the concrete flooring joint adjacent the first joint component to form a first concrete flooring slab;pouring a curable concrete flooring material to a second side of the concrete flooring joint adjacent the second joint component to form a second concrete flooring slab; andcuring the curable concrete material to cause separation of the first joint component and the second joint component and consequential fracture of the one or more fasteners at the shaft.

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