EP2946037A1

EP2946037A1 - Apparatus for forming a joint

Info

Publication number: EP2946037A1
Application number: EP14705552.9A
Authority: EP
Inventors: Shaun Anthony Spurrell
Original assignee: Spurrell Shaun
Current assignee: SPURRELL, SHAUN ANTHONY
Priority date: 2013-01-18
Filing date: 2014-01-16
Publication date: 2015-11-25
Anticipated expiration: 2034-01-16
Also published as: WO2014111712A1; GB2511729A; BR112015016818A2; GB2511729B; BR112015016818B1; AU2014206674A1; ES2761578T3; GB201300928D0; AU2014206674B2; EP2946037B1

Abstract

Apparatus for forming a joint between concrete floor slab panels, with: • a divider plate (2); • a first top strip (3) connectable to the divider plate and a second top strip (4) frangibly connectable to the divider plate and/or the first top strip; each of the top strips comprising: • an elongate concrete engagement member (9); and • a top section comprising • an elongate top face presenting an elongate edge configurable to lie at the level of the top surface of a concrete panel; and • an elongate concrete abutment face extending from the elongate edge along the length of the relevant top strip, which abutment face is a continuous face adapted for concrete to be cast against; • wherein the abutment face extends downward from the elongate edge of the top face and the angle between the abutment face and the top surface of an abutting concrete panel is from 65° to 135°.

Description

APPARATUS FOR FORMING A JOINT

Field of the invention

The present invention relates to an apparatus for forming a joint between concrete floor slab panels, a concrete floor slab panel comprising the apparatus, a concrete floor comprising the apparatus, a method of manufacturing a concrete floor slab panel and a method of manufacturing a concrete floor.

Background to the invention

Concrete floor slabs are generally cast as adjoining slab panels and each slab panel is cast inside a formwork; this formwork defines a space in which to cast the concrete. The formwork may be constructed from timber, steel, aluminium, plastic or the like. The formwork may be removable, which means it is removed after the concrete has cured.

Alternatively, it may be leave-in-place formwork, which forms part of the resulting concrete structure, for example by providing at least part of an edge of a resulting concrete slab panel.

The formwork generally comprises one or more upright elongate divider plates, which the concrete is cast against. The divider plates ensure that the concrete is contained within the desired space. When a number of floor slab panels are cast next to one another to form a concrete floor or slab, the divider plates generally sit in between adjacent slab panels, and dowels or dowel plates, attached to the divider plates, are used to connect the slab panels together in order to transfer loads across the joint. During the casting of a concrete floor slab panel comprising leave-in-place formwork, the formwork should be positioned in such a way that the upper edges of the formwork coincide with the finished floor level (FFL), i.e. the level of the upper surface of the finished concrete floor slab.

The slab and formwork rest on a subbase. If the subbase level (SBL) varies, the formwork will rest on the subbase's highest point. Because of this, it is common practice in casting concrete floors to allow around 15 - 25 mm between the formwork and the subbase for clearance. Concrete floor slab thicknesses are usually in the range of 150 to 200 mm.

Formwork can be manufactured to desired thickness specifications, which is commonly done in 5 mm increments. If it is desired to cast a concrete slab with a thickness of, for example, 180 mm, formwork with a depth of 155 - 165 mm is normally used. In order to achieve the desired finished floor level (FFL), a divider plate can be suspended at the desired FFL using suspension means. Such suspension means can, for example, be a jack, or pins may be placed on both sides of the divider plate and studs, which are commonly present in an apparatus for forming the edge of a concrete floor slab, may be welded to these pins, thus suspending the divider plate at the desired FFL. In addition, wedges, adjustable feet and the like can be used to position the formwork in the desired manner against the subbase and hold it in place whilst the concrete is cast.

After casting, concrete slabs display normal drying shrinkage. This shrinkage may be exacerbated when the temperature of the concrete is reduced, for example in the case of floor slabs for freezer stores. The shrinkage of concrete floor slabs is a slow process: it can take up to two years for a concrete slab to stop shrinking. The shrinkage of concrete slab panels generally results in the opening of the joints between the slab panels, due to each concrete slab panel shrinking away from the joint in a direction generally perpendicular to the longitudinal axis of the joint. The type of joint which is adapted to accommodate such shrinking, or contraction, of a concrete slab panel on one or each side of the joint is known as a "contraction joint". This is as opposed to an "expansion joint", which is adapted to accommodate expansion of a concrete slab panel on one or each side of the joint where the slab panels are cast with a preset gap between them, to allow thermal expansion of the slab panel, after contraction of the slab panel due to curing has taken place. EP 1389648 Al describes an apparatus for forming the edge of a concrete floor slab panel, the apparatus comprising a divider plate with a plurality of apertures, dowels for engaging through the apertures and sleeves for applying to the dowels, in which the divider plate is provided with means to adjust the height thereof above the subbase. The apparatus can also comprise edge rails supportable by the divider plate. Known apparatuses for forming a joint between concrete floor slab panels can use studs for anchoring to the concrete, i.e. connecting the apparatus with the concrete on either side, as shown in EP 1389648 Al. These studs are commonly spaced at regular intervals (about every 25 cm) along the length of the apparatus. However, in between the studs there is no anchorage of the apparatus to the concrete. Therefore, if, for example, the apparatus is cut to a particular length and the final section is cut just before a stud, there could be almost 25 cm of free apparatus not anchored to the concrete. There are some known systems which address the issue of intermittent engagement by providing an apparatus where a divider plate has been "wrapped around" at the top, resulting in a longitudinal planar surface, level with the top of the slab panel; and a longitudinal concrete-engaging downturn, which downturn is angled with respect to the horizontal and has regular cut-outs in it. Such a divider plate can be combined back-to-back with another identical divider plate, or with a shorter plate member which has a similar "wrap around" section at the top. These types of apparatuses are shown in, for example, WO 2005/103412 Al and WO 2010/094910 Al.

These systems provide continuous engagement to the concrete along the length of the apparatus through the downturn, but at the level of the top surface of the concrete slab panel these apparatuses do not contain a continuous face for the concrete to abut. As is known in the art, concrete is strong in compression, but weak in tension. This means that it is very difficult to get concrete to "thin out" over a radius, because thin sections of concrete, such as thin edges, are very likely to crack and spall. Therefore, if a downturn has a radius of curvature or a significant angle where it abuts the top surface of a concrete slab panel, the area where the concrete abuts the curve will be a potential spalling site.

It is an aim of the present invention to provide an apparatus for forming a joint between concrete floor slab panels, embodiments of which can enhance the performance

characteristics of the resulting concrete slab panels. Statements of the invention

According to a first aspect of the present invention there is provided an apparatus for forming a joint between concrete floor slab panels, the apparatus comprising:

a divider plate for bounding a side of a concrete floor slab panel; and

first and second top strips, the first top strip being connectable to the divider plate, and the second top strip being frangibly connectable to the divider plate and/or the first top strip; wherein each of the first and second top strips comprises:

an elongate concrete engagement member; and

a top section comprising

an elongate top face presenting an elongate edge configurable to lie at the level of the top surface of a concrete floor slab panel; and an elongate concrete abutment face extending from the elongate edge of the top face, which abutment face is a continuous face adapted for concrete to be cast against and which extends along the length of the relevant top strip;

the arrangement being such that in use after casting concrete, the elongate concrete abutment face extends downward from the elongate edge of the top face at an angle such that the angle between the abutment face and the top surface of an abutting concrete floor slab panel is from 65° to 135°.

The term "elongate", as used in the context of the concrete engagement member, the top face, the edge of the top face and/or the concrete abutment face, means that the relevant element has an elongate shape. Suitably, the longitudinal axis of the elongate element is, in use, positioned parallel to the longitudinal axis of the divider plate, and hence of the apparatus. The elongate concrete engagement member extends into the region where, in use, concrete would be cast, the arrangement being such that the top strips are securable to adjacent concrete floor slab panels by means of their respective concrete engagement members. The purpose of the "elongate concrete engagement member" is to engage with the concrete on each side of the apparatus. After the concrete has been cast, the elongate concrete engagement members on each of the top strips will be embedded into the concrete of the concrete slab panels on each side of the apparatus.

The elongate concrete abutment face is a continuous face adapted for concrete to be cast against which extends along the length of the relevant top strip. In use, the concrete can therefore abut the elongate abutment face in an uninterrupted manner, i.e. there are no protrusions from the abutment face which extend into the region where concrete would be cast. Suitably, the continuous concrete abutment face does not contain any apertures. The concrete can abut the elongate abutment face along the length of the relevant top strip. The invention provides an apparatus which allows continuous engagement with adjacent concrete floor slab panels on both sides of a joint, while at the same time providing a continuous face for the concrete to abut on each side of the joint, which can limit the risk of spalling. Therefore the apparatus can significantly enhance the performance characteristics of the resulting concrete floor slabs. Once cast, concrete slab panels are prone to shrinkage during curing which causes the edges of the adjacent slab panels to separate. This exposes the upper edge, or arris, of each individual slab panel to damage from loads such as from vehicles, including for example lorries or forklift trucks, passing across the joint. The top strips help to protect each arris from such damage, and improve the longevity of the slab at the joints.

Each top strip comprises a top section having an elongate top face. The top face is the face of the apparatus which would still be visible from above after the concrete has been cast. In an embodiment, the elongate top face of the top section of one or each top strip is at least 2 mm wide, or at least 3 mm wide, or at least 6 mm wide, or at least 8 mm wide. This can result in a stronger top section, and can allow more effective protection of the arris. In an embodiment, the elongate top face is from 3 mm to 20 mm wide, or from 3 mm to 15 mm wide, or from 3 mm to 12 mm wide, or from 3 mm to 10 mm wide, or from 6 mm to 20 mm wide, or from 6 mm to 15 mm wide, or from 6 mm to 12 mm wide, or from 6 mm to 10 mm wide, or from 7 mm to 20 mm wide, or from 7 mm to 15 mm wide, or from 7 mm to 12 mm wide, or from 7 mm to 10 mm wide, or from 8 mm to 20 mm wide, or from 8 mm to 15 mm wide, or from 8 mm to 12 mm wide, or from 8 mm to 10 mm wide. In an embodiment, the elongate top face is about 5 mm wide, or about 10 mm wide, or about 15 mm wide. The top section of each top strip also has an elongate concrete abutment face. In an embodiment, the elongate concrete abutment face of the top section of one or each top strip is at least 2 mm deep, or at least 3 mm deep, or at least 6 mm deep, or at least 8 mm deep. In an embodiment, the elongate concrete abutment face is from 3 mm to 20 mm deep, or from 3 mm to 15 mm deep, or from 3 mm to 12 mm deep, or from 3 mm to 10 mm deep, or from 6 mm to 20 mm deep, from 6 mm to 15 mm deep, or from 6 mm to 12 mm deep, or from 6 mm to 10 mm deep, or from 7 mm to 20 mm deep, from 7 mm to 15 mm deep, or from 7 mm to 12 mm deep, or from 7 mm to 10 mm deep, or from 8 mm to 20 mm deep, from 8 mm to 15 mm deep, or from 8 mm to 12 mm deep, or from 8 mm to 10 mm deep. In an embodiment, the elongate concrete abutment face is about 5 mm deep, or about 10 mm deep, or about 15 mm deep. For the avoidance of doubt, the distance indicated by "deep" means the distance from the elongate edge configurable to lie at the level of the top surface of a concrete floor slab panel to a lower elongate edge of the elongate concrete abutment face. The arrangement is such that in use after casting concrete, the elongate concrete abutment face extends downward from the elongate edge of the top face at an angle such that the angle between the abutment face and the top surface of an abutting concrete floor slab panel is from 65° to 135°. In other words, in use the elongate concrete abutment face extends downward from the elongate edge of the top face at an angle of from 25° away from true vertical in the direction where the angle between the abutment face and the top surface of an abutting concrete floor slab panel would be an acute angle (i.e. the angle between the abutment face and the top surface of an abutting concrete floor slab panel would be 65°) to 45° away from true vertical in the direction where the angle between the abutment face and the top surface of an abutting concrete floor slab panel would be an obtuse angle (i.e. the angle between the abutment face and the top surface of an abutting concrete floor slab panel would be 135°).

In use the angle between the abutment face and the top surface of an abutting concrete floor slab panel can therefore be a right angle, an acute angle or an obtuse angle. In an embodiment, in use after casting concrete, the elongate concrete abutment face extends downward from the elongate edge of the top face at an angle such that the angle between the abutment face and the top surface of an abutting concrete floor slab panel is from 70° to 135°, or from 75° to 135°, or from 80° to 135°, or from 85° to 135°, or from 65° to 130°, or from 70° to 130°, or from 75° to 130°, or from 80° to 130°, or from 85° to 130°, or from 65° to 125°, or from 70° to 125°, or from 75° to 125°, or from 80° to 125°, or from 85° to 125°, or from 65° to 120°, or from 70° to 120°, or from 75° to 120°, or from 80° to 120°, or from 85° to 120°, or from 65° to 115°, or from 70° to 115°, or from 75° to 115°, or from 80° to 115°, or from 85° to 115°, or from 65° to 110°, or from 70° to 110°, or from 75° to 110°, or from 80° to 110°, or from 85° to 110°, or from 65° to 105°, or from 70° to 105°, or from 75° to 105°, or from 80° to 105°, or from 85° to 105°, or from 65° to 100°, or from 70° to 100°, or from 75° to 100°, or from 80° to 100°, or from 85° to 100°, or from 65° to 95°, or from 70° to 95°, or from 75° to 95°, or from 80° to 95°, or from 85° to 95°. In an embodiment, in use after casting concrete, the elongate concrete abutment face extends downward from the elongate edge of the top face at an angle such that the angle between the abutment face and the top surface of an abutting concrete floor slab panel is from 90° to 135°, i.e. the angle between the abutment face and the top surface of an abutting concrete floor slab panel is a right angle or an obtuse angle. In an embodiment, the angle between the abutment face and the top surface of an abutting concrete floor slab panel is from 90° to 130°, or from 90° to 125°, or from 90° to 120°, or from 90° to 115°, or from 90° to 110°, or from 90° to 105°, or from 90° to 100°, or from 90° to 95°. In an embodiment, in use after casting concrete, the elongate concrete abutment face extends downward from the elongate edge of the top face at an angle such that the angle between the abutment face and the top surface of an abutting concrete floor slab panel is from 65° to 90°, i.e. the angle between the abutment face and the top surface of an abutting concrete floor slab panel is a right angle or an acute angle. In an embodiment, the angle between the abutment face and the top surface of an abutting concrete floor slab panel is from 70° to 90°, or from 75° to 90°, or from 80° to 90°, or from 85° to 90°.

In an embodiment, in use after casting concrete, the elongate abutment face extends vertically downward from the elongate edge of the top face. This means that the angle between the abutment face and the top surface of an abutting concrete floor slab panel is a right angle, i.e. about 90°. In this embodiment, the elongate concrete abutment face can therefore lie parallel to the divider plate. This arrangement means that the section of concrete which abuts the abutment face can be at least as thick as the abutment face is deep, and typically there is no thinning of concrete along the abutment face, thus limiting the risk of spalling.

In an embodiment, the top section of one or each top strip comprises an elongate Dutch fold or folds. Such a fold can strengthen the top section. As mentioned above, concrete slab panels are prone to shrinkage during curing, which causes adjacent slab panels to separate, leaving a gap between them. In order to ensure that the apparatus remains connected to the concrete on each side of the gap, in order to be able to transfer loads across the joint, and in order to be able to protect the arris of each slab panel, it is important to ensure that the apparatus is firmly anchored to the concrete of each slab panel. This is achieved by means of the elongate concrete engagement member on each of the two top strips.

In an embodiment, the elongate concrete engagement member of one or each top strip contains a plurality of apertures. Such apertures allow the elongate concrete engagement members to become more strongly embedded in the concrete during casting and curing, and therefore help to fix the top strips, and hence the apparatus, in position relative to the concrete.

As stated above, each of the first and second top strips comprises an elongate concrete engagement member and a top section, which top section comprises an elongate top face and an elongate concrete abutment face.

In an embodiment, one or each top strip further comprises a connection section in between the top section and the concrete engagement member. In an embodiment, the arrangement is such that in use after casting concrete, the connection section lies parallel or substantially parallel to the divider plate.

Throughout this specification, unless expressly stated otherwise, the term "substantially parallel" is to be understood as being at an angle of less than 20° away from true parallel. In an embodiment, this is less than 19°, less than 18°, less than 17°, less than 16°, less than 15°, less than 14°, less than 13°, less than 12°, less than 11°, less than 10°, less than 9°, less than 8°, less than 7°, less than 6°, less than 5°, less than 4°, less than 3°, less than 2°, or less than 1° away from true parallel. Any angle away from true parallel can be to either side of true parallel. In an alternative embodiment, the concrete engagement member of one or each top strip extends from a lower elongate edge of the elongate concrete abutment face.

The apparatus according to the first aspect of the invention comprises a divider plate and first and second top strips, the first top strip being connectable to the divider plate, and the second top strip being frangibly connectable to the divider plate and/or the first top strip. The divider plate and the two top strips are thus three distinct components.

The first top strip is connectable to the divider plate. The components may, for example, be frangibly connectable or permanently connectable.

In an embodiment, the first top strip is connected to the divider plate. The components may, for example, be frangibly connected or permanently connected. The second top strip is frangibly connectable to the divider plate and/or the first top strip. In an embodiment, the second top strip is frangibly connected to the divider plate and/or the first top strip. In an embodiment, the second top strip is frangibly connectable to the divider plate. In an embodiment, the second top strip is frangibly connected to the divider plate.

In an embodiment, the second top strip is frangibly connectable to the first top strip. In an embodiment, the second top strip is frangibly connected to the first top strip.

In an embodiment, the second top strip is frangibly connectable to the divider plate and the first top strip. In an embodiment, the second top strip is frangibly connected to the divider plate and the first top strip. In an embodiment, the first top strip is connected to the divider plate, and the second top strip is frangibly connected to the divider plate and/or the first top strip.

When the top strips and the divider plate are connected, the connection between the divider plate and the first top strip, or between the divider plate and the first and second top strips, is located in the region towards the top of the divider plate; at least the bottom part of the divider plate extends out beyond the top strips. In use after casting concrete, the top strips will sit at or near the surface of a concrete floor slab, providing a continuous face for the concrete to abut on each side of the joint and ensuring that the apparatus remains firmly anchored to the concrete on both sides of the joint, while the divider plate extends further down towards the subbase or even rests on the subbase, allowing the divider plate to fulfil its usual function of helping to retain the concrete within the desired space.

In an embodiment, the top part of the divider plate is positioned in between the first and second top strips. In an embodiment, the divider plate and the first and second top strips are connected via yieldable fixings.

In an embodiment, the divider plate is adapted to support the first top strip. In an embodiment, the first and second top strips are connected via yieldable fixings. Yieldable fixings fail under tension as shrinking occurs during the curing process and the top strips of adjacent slab panels are drawn apart. In an embodiment, the yieldable fixings comprise low tensile strength bolts. .Examples of such low tensile strength bolts are bolts formed from nylon, the threads of which will become stripped under shrinkage forces, or the shanks of which will fail under tension.

In an embodiment, one or each top strip is formed from an elongate flat section of material.

In an embodiment, one or each top strip is formed from a metal such as, for example, steel. In an embodiment, one or each top strip is unitary. This means that the elongate concrete engagement member and the top section (comprising the elongate top face and the elongate concrete abutment face) are integral in a single component.

In an embodiment, one or each top strip is formed from a single sheet of metal by rolling and/or folding. The top strips may be arranged to mate with each other along linear or non-linear edges. In an embodiment, the top strips are arranged to mate with each other along linear edges. In an embodiment, the top strips are arranged to mate with each other along non-linear edges, such as curved edges.

The divider plate can be conventional in construction, for example as in EP 1389648 or similar.

In an embodiment, the divider plate is an elongate flat section of material.

In an embodiment, the divider plate is non-deformable. This means that the material from which the divider plate is made is not compressible by the concrete once the concrete has been cast on one or both sides of the divider plate.

In an embodiment, the divider plate is formed from a metal such as, for example, steel. This can result in a divider plate of high mechanical strength, capable of withstanding the forces acting upon it during the casting of concrete.

In an embodiment, the divider plate comprises a longitudinal fold at the top edge and/or the lower edge of the divider plate. Such a fold can, for example, be a longitudinal L-fold, a longitudinal J-fold, a longitudinal V-fold or a Dutch fold (where the divider plate is completely folded back on itself). Such a fold can strengthen the divider plate.

In an embodiment, the divider plate comprises one or more apertures. In an embodiment, the apparatus further comprises one or more dowels or dowel plates for engaging through the one or more apertures. These act to connect the resulting concrete slab panels together and to provide a method of load transfer between adjacent slab panels.

The apparatus according to the first aspect of the invention can be used to form, for example, prefabricated four-way intersections, three-way "T" intersections, corner units and loading dock corners. According to a second aspect of the present invention there is provided a concrete floor slab panel comprising the apparatus according to the first aspect of the invention .

According to a third aspect of the present invention there is provided a concrete floor comprising the apparatus according to the first aspect of the invention or the slab panel according to the second aspect of the invention. According to a fourth aspect of the present invention there is provided a method of manufacturing a concrete floor slab panel, comprising the steps of

(i) setting up the apparatus according to the first aspect of the invention to form at least part of an edge of a space for casting concrete; and

(ii) casting concrete in the space.

According to a fifth aspect of the present invention there is provided a method of manufacturing a concrete floor, comprising the steps of

(ii) casting concrete in the space;

wherein steps (i) and (ii) are performed more than once.

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 moieties, additives, 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. Other features of the invention will become apparent from the following examples. Generally speaking the invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims and drawings). Thus features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. Moreover unless stated otherwise, any feature disclosed herein may be replaced by an alternative feature serving the same or a similar purpose.

Where upper and lower limits are quoted for a property, then a range of values defined by a combination of any of the upper limits with any of the lower limits may also be implied.

Specific description

Embodiments of the present invention will now be further described with reference to the accompanying figures, of which:

Figure 1 shows a perspective view of a first embodiment of the apparatus of the invention. Figure 2 shows an area cross-sectional view of the embodiment of Figure 1 perpendicular to its length, after concrete has been cast on both sides of the apparatus, with the second top strip abutting the divider plate.

Figure 3 shows an area cross-sectional view of the embodiment of Figure 1 perpendicular to its length, after concrete has been cast on both sides of the apparatus, with the second top strip moved away from the divider plate and the first top strip, in the direction perpendicular to the longitudinal axis of the joint.

Figure 4 shows a perspective view of a second embodiment of the apparatus of the invention. As shown in Figures 1 to 4, the apparatus 1 broadly comprises a divider plate 2, a first top strip 3 and a second top strip 4.

The divider plate 2 is an elongate flat section of steel, with a longitudinal J-fold 5 at its lower edge. The divider plate 2 comprises apertures 6 along its length at regular intervals. The apertures 6 are adapted to receive dowel plates 7. On one side of the divider plate 2, the dowel plates 7 are encased in dowel sleeves 8, which, in use, allow movement of the concrete as it sets and shrinks.

The top strips 3, 4 are elongate sections of steel. Each top strip 3, 4 is unitary.

Each top strip 3, 4 contains an elongate concrete engagement member 9 extending into the region where, in use, concrete would be cast. Each concrete engagement member 9 contains a plurality of apertures 10.

Each top strip 3, 4 further contains a top section 11. The top section 11 has an elongate top face 12. The top face 12 is the face of the apparatus which would still be visible from above after the concrete has been cast. The top face 12 presents an elongate edge 13 which in use will lie at the level of the top surface of a concrete floor slab panel. The top section 11 also has an elongate concrete abutment face 14 extending vertically downward from the elongate edge 13 of the top face 12. As can be seen from Figures 2 and 3, this means that in use after casting concrete, the angle between the abutment face 14 and the top surface of an abutting concrete floor slab panel is about 90°. The elongate concrete abutment face 14 lies parallel to the divider plate 2. The concrete abutment face 14 provides a continuous face for the concrete to abut; the concrete can abut the elongate abutment face 14 along the length of the relevant top strip in an uninterrupted manner. The concrete abutment face 14 does not contain any apertures.

In the embodiments shown, each top strip 3, 4 contains a connection section 15 which lies parallel to the divider plate 2. Holes 16 are present in the connection sections 15 of top strips 3, 4 and in the divider plate 2; the top strips 3, 4 and the divider plate 2 can be connected together by putting low tensile bolts 17 through these holes 16.

In the first embodiment, shown in Figures 1-3, the top section 11 of each top strip 3, 4 is formed by a simple Dutch fold. In this arrangement, if the steel from which the top strips 3, 4 are formed is 3mm thick, this will result in an elongate top face 12 which is about 6 mm wide. The elongate concrete abutment face 14 can be as deep as is desired, for example about 10 mm deep.

In the second embodiment, shown in Figure 4, the top section 11 of each top strip 3, 4 is formed by a Dutch fold which has been folded out, away from the divider plate 2, resulting in a Dutch fold approximately perpendicular to the connection section 15 of each top strip 3, 4. In this arrangement, if the steel from which the top strips 3, 4 are formed is 3 mm thick, this will result in an elongate concrete abutment face 14 which is about 6 mm deep. The elongate top face 12 can be as wide as is desired, for example about 10 mm wide.

In use, the divider plate 2 and the top strips 3, 4 are suspended at the desired FFL using support means, which can include suspension means such as, for example, a jack. The jack can be secured to the subbase, for example via a pin. Additional pins can also be placed in the ground next to the divider plate, and wedges can be placed between these pins and the divider plate 2, in order to secure the apparatus to the subbase in a desired location and prevent movement caused by the thrust of the concrete. At this stage, the apparatus will form at least part of an edge of a space for casting concrete. The entire edge may be formed by the apparatus, and the remaining edges may also be formed by further units of the apparatus. Once the space for casting concrete has been defined by the edges, i.e. the formwork has been set up, concrete is poured into the space. Concrete is first cast on the other side of the divider plate 2 from the jack. After this concrete has set sufficiently, the jack, pins and wedges are removed. After this concrete is cast on the remaining side of the apparatus.

Once the concrete has been cast, the top strips 3, 4 are firmly anchored to the concrete by means of their concrete engagement members 9 which have become embedded in the concrete. In addition, the arris of each concrete slab panel is protected. The concrete abuts the elongate abutment face 14 along the entire length of each top strip.

The concrete slab panels will display normal drying shrinkage. As the concrete on each side of the joint shrinks, the top strips 3, 4 move apart since they are anchored to the concrete. During this process, the dowel plates 7 will slide in the dowel sleeves 8, so as a gap opens up between the slab panels. The divider plate will stay on the side of the first top strip 3. The apparatus of the invention can allow continuous engagement with adjacent concrete floor slab panels on both sides of a joint, while at the same time providing a continuous face for the concrete to abut on each side of the joint, which can limit the risk of spalling. Therefore the apparatus can significantly enhance the performance characteristics of the resulting concrete floor slabs. In addition, the invention can provide a relatively light apparatus which has the required rigidity and stiffness, improving the ease of use and hence the ease of manufacturing concrete floors.

Claims

1. An apparatus for forming a joint between concrete floor slab panels, the apparatus comprising: a divider plate for bounding a side of a concrete floor slab panel; and first and second top strips, the first top strip being connectable to the divider plate, and the second top strip being frangibly connectable to the divider plate and/or the first top strip; wherein each of the first and second top strips comprises: an elongate concrete engagement member; and a top section comprising an elongate top face presenting an elongate edge configurable to lie at the level of the top surface of a concrete floor slab panel; and an elongate concrete abutment face extending from the elongate edge of the top face, which abutment face is a continuous face adapted for concrete to be cast against and which extends along the length of the relevant top strip; the arrangement being such that in use after casting concrete, the elongate concrete abutment face extends downward from the elongate edge of the top face at an angle such that the angle between the abutment face and the top surface of an abutting concrete floor slab panel is from 65° to 135°.

2. The apparatus of claim 1, wherein the elongate top face of the top section of one or each top strip is at least 6 mm wide.

3. The apparatus of any one of the preceding claims, wherein the elongate concrete abutment face of the top section of one or each top strip is at least 6 mm deep.

4. The apparatus of any one of the preceding claims, wherein in use after casting concrete, the elongate concrete abutment face extends downward from the elongate edge of the top face at an angle such that the angle between the abutment face and the top surface of an abutting concrete floor slab panel is from 80° to 135°.

5. The apparatus of claim 4, wherein the angle between the abutment face and the top surface of an abutting concrete floor slab panel is from 90° to 135°.

6. The apparatus of any one of the preceding claims, wherein the top section of one or each top strip comprises an elongate Dutch fold.

7. The apparatus of any one of the preceding claims, wherein one or each top strip further comprises a connection section in between the top section and the concrete engagement member.

8. The apparatus of claim 7, the arrangement being such that in use after casting concrete, the connection section lies parallel or substantially parallel to the divider plate.

9. The apparatus of any one of the preceding claims, wherein the first top strip is connected to the divider plate, and the second top strip is frangibly connected to the divider plate and/or the first top strip.

10. The apparatus of any one of the preceding claims, wherein the top part of the divider plate is positioned in between the first and second top strips.

11. The apparatus of any one of the preceding claims, wherein the divider plate is adapted to support the first top strip.

12. The apparatus of any one of the preceding claims, wherein the divider plate is non- deformable.

13. A concrete floor slab panel comprising the apparatus according to any one of claims 1-12.

14. A concrete floor comprising the apparatus according to any one of

claims 1-12 or the slab panel of claim 13.

15. A method of manufacturing a concrete floor slab panel, comprising the steps of (i) setting up the apparatus according to any one of claims 1-12 to form at least part of an edge of a space for casting concrete; and

(ii) casting concrete in the space.