A stackable rail spacer configured to support a reinforcement

Abstract

A stackable rail spacer comprising two interconnected support cells, each support cell comprising a first and a second end surface. Each support cell further comprises a circumferential wall defining a central void of the support cell, the circumferential wall extending from the first to the second end surface, such that the circumferential wall tapers from the first end surface towards the second end surface, wherein the circumferential wall is provided with at least one aperture. The second end surface of each support cell is spaced apart from the second end surface of any neighbouring support cell. First closed curves formed by the first end surfaces of two neighbouring support cells overlap each other with respect to the longitudinal direction of the rail spacer such that a cross-section taken perpendicularly to said longitudinal direction cuts through the first end surfaces of both neighbouring support cells.

Description

TECHNICAL FIELD The present disclosure relates to a stackable rail spacer configured to support a reinforcement, such as a roll-out or mesh reinforcement, in concrete structures. BACKGROUND ART In order to achieve appropriate properties for concrete in various structural constructions, they are normally provided with some kind of reinforcement to increase the strength and to reduce the risk of cracking. The reinforcement may be individual reinforcement bars (rebars) made of steel or made of glass fibre reinforced plastic material. Further examples include welded mesh reinforcement, roll-out reinforcement, steel fibres or other. Unlike the example of steel fibres, which may be mixed into the concrete, some of the other examples, such as individual reinforcement bars, welded mesh reinforcement or roll-out reinforcement made of steel, should normally be placed at a certain height inside the concrete. In particular, said height should be a hight that results in desired physical properties for the concrete structure, and said height should also be such that a sufficient concrete cover is provided onto the reinforcement. The concrete cover is defined as the smallest distance between the reinforcement material and the concrete surface of the completed structure. This concrete cover reduces the risk of moisture reaching the reinforcement. In case moisture reaches a steel reinforcement, which is not of stainless character, then a corrosion process is initiated which may cause the concrete to break apart from the inside. Corrosion may, through its expansion, slowly damage the nearby concrete, which simplifies for more moisture to reach the reinforcement which in turn accelerates the corrosion process. Over time this will weaken the strength of the structure, and thus shorten its life expectancy or the time at which costly repairs need to be undertaken. It should thus be understood that a correctly provided concrete cover is important for the entire concrete structure. In order to facilitate the desired placement of the reinforcement 2 within the concrete structure, and thus the provision of the desired concrete cover, reinforcement spacers may be used. Such reinforcement spacers should suitably be made of a material which, in itself, does not facilitate ingress of moisture. Common materials used for reinforcement spacers include concrete, plastic and steel, but other materials may also be used. The choice of material is oftentimes dependent on local regulations, common practice and recommendations. However, the choice of material may also depend on the type of structure that is to be cast, the type of environment around the completed structure, the location within the structure where the spacers are to be placed, etc. Plastic is the most commonly used material for reinforcement spacers. Due to the risk of cracking of the concrete structure due to corrosion, reinforcement spacer made of steel are normally only used where the concrete cover is not negatively affected. Spacer made of concrete can be used in most types of structure. When it comes to reinforcement spacers made of concrete and reinforcement spacers made of plastic, greatest risk of moisture ingress is considered to be at the interface between the spacer and the surrounding concrete, and thus the ensuing risk of the moisture reaching the reinforcement as time passes. A concrete spacer of lower quality of concrete than the surrounding concrete, a plastic spacer made of a plastic material that is chemically unstable in the alkaline environment provided by wet concrete, or other factors, may have a negative effect on the life expectancy of the structure and its serviceability over time. The choice of type of material and the quality of the material may thus be of importance when spacers are to be selected for usage in a certain concrete structure. Similarly, when it comes to spacers made of steel that are to be placed directly onto a mould surface for concrete, it is normally better to select stainless steel than steel that may rust. Reinforcement spacers made of concrete may normally be used in most type of concrete structures and in combination with most types of reinforcements. They can withstand pressure, but are often heavy and therefore working with such spacers is often timeconsuming and laborious. Plastic spacers, on the other hand, are light-weight and they are often moulded into shapes that are adapted to the application of interest. Hereby, there usage will normally be cost 3 efficient and ergonomic. Furthermore, the production cost of such plastic spacers may be relatively low. Regardless of choice of material, reinforcement spacers may be configured as multi-zone spacers or as single-zone spacers. Multi-zone spacers, which may often be referred to as rail spacers, are intended to support more than one reinforcement bar, regardless if the reinforcement is in the form of roll-out or mesh reinforcement or in the form of individual reinforcement bars. Single-zone spacers, however, are intended to support only one reinforcement bar at the time (irrespective of the type of reinforcement, e.g. supporting only one bar of a mesh reinforcement). Single-zone spacers are in numbers more commonly used than multi-zone spacers, and are provided in a large variety of material and configurations. The most common type of multi-zone spacers is elongated, having a length that is considerably larger than its width. However, there are also multi-zone spacers having more of a square or circular shape. These may be used to support mesh reinforcement and are dimensioned to exceed the individual openings in the mesh that will currently be supported. Elongated multi-zone spacers may be provided in various shapes. For instance, they may be completely straight or snake-shaped. The normal approach for placing elongated multi-zone spacers is linearly and in more or less parallel rows. Thereafter, the reinforcement bars are positioned onto the spacers. In particular, the reinforcement bars are positioned in parallel with each other, but at an angle to the spacers. Depending on the length of the spacers and the distance between the reinforcement bars, one and the same spacer may in this way support two, three or more reinforcement bars lying next to each other. Oftentimes, it is desired to position the reinforcement bars as perpendicularly as possible relative to the elongated multi-zone spacers, thereby keeping down the material consumption. Similarly, welded mesh reinforcement can be placed directly onto multi-zone spacers. The length of the spacer exceeds the dimension of an individual mesh opening, and thereby mesh reinforcement is supported at several points of contact. Since the individual reinforcement bars of the mesh are welded into one large sheet, it is of less importance at which angle the spacers are placed relative to the mesh. Under certain circumstances, an elongated multi-zone spacer may also be used to support a roll-out reinforcement. A roll-out reinforcement normally comprises a plurality of substantially parallel reinforcement bars which are connected by bendable bands, wires, strings, or the like. The connecting bendable material allows the reinforcement bars to wound into a roll, wherein the individual reinforcement bars are provided at a predetermined distance from each other. The roll may suitably be wound around a circular core, which may facilitate the handling when unwinding the roll-out reinforcement at the worksite. A roll of roll-out reinforcement is normally lifted to the desired location by some sort of crane and is then properly aligned. After proper alignment, workers put the roll-out reinforcement in motion so as to unwind it from the core. Hereby, the reinforcement bars of the roll-our reinforcement are quickly and pa ra I Ie lly placed at their desired locations to cover a large surface. Roll-out reinforcements are thus handled differently from welded mesh reinforcement, the latter comprising longitudinal and transverse reinforcement bars that have been welded into a common meshed sheet. These sheets are rigid and cannot be wound into a roll without deforming the reinforcement bars. Using a deformed meshed reinforcement would result in increased risk of incorrect concrete cover and should therefore be avoided. A roll of roll-out reinforcement is often heavy, sometimes weighing several tonnes. Initially, at the start of the unwinding procedure, this heavy roll will initially provide its load to a low number of spacers. The load on these spacers will gradually become reduced as the roll-out reinforcement is being unwound from the core and is rolled out onto other spacers. The weight of the reinforcement will thus become distributed to more spacers. In order to allow the roll-out reinforcement to be rolled out in its entirety and without interruption or with as few interruptions as possible, a long rail should desirably be provided having an extension corresponding to that of the reinforcement when it has been completely rolled-out. Such a long rail is normally achieved by placing two or more elongated multi-zone spacers (rail spacers) in a row, sometimes interconnected, sometimes edge to edge, onto the mould surface, but they may also be provided somewhat displaced sideways and with a minor longitudinal overlap. If a rail is not provided in such way, there is a risk of discontinuance in the rail, i.e. a space between two spacers, which may result in the roll, or an individual reinforcement bar of the roll, drops down to the mould surface between the two spacers, or which may result in one or more individual reinforcement bars hanging in the space between the two spacers. In either case, this means an increased risk of the structure obtaining an incorrect concrete cover, or that you will have a time-consuming work to do to correct the misplacement. It is thus important that the roll-out reinforcement is supported by spacers along its entire extension. Due to the initially high load exerted by a roll of roll-out reinforcement, it is common to use multi-zone spacers of concrete, although a correctly configured multi-zone spacer in plastics or steel could work as well. There are seldom any specific requirements that one or the other material should be used; it is rather for the user to decide based on the conditions of each individual work project. A well-working multi-zone spacer of plastic material has the advantage of presenting a considerably lower weight than a corresponding spacer made of concrete. As should be understood, an advantage of roll-out reinforcement is the time-saving that can be made by allowing such a roll containing the connected reinforcement bars to be rolled out on top of a continuous rail of multi-zone spacers in a quick and efficient manners. However, even though the application of a roll-out reinforcement onto the spacers may be time-saving compared to other alternatives, such as mesh or loose reinforcement bars, the preparatory work of positioning the reinforcement spacers properly to allow for such a roll-out to be effectively performed, has in contrast been quite time-consuming. It would be desirable to not only provide spacers which can be relatively quickly positioned and distributed at a worksite in preparation for receiving a roll-out reinforcement, but also to provide spacers which additionally have sufficient strength to be able to carry the initial heavy load of a wound roll-out reinforcement before it has been rolled out. SUMMARY OF THE INVENTION An object of the present invention is to provide spacers which are strong enough to support a roll-out reinforcement, and which spacers may not necessarily but suitably be distributed by means of an ergonomic dispensing tool. The inventor has realized that by making spacers stackable, without any mutual lateral displacement, and without being fixed to each other, one or more through-holes may be provided (suitably having one or more predefined dimensions) through a stack of spacers which may receive a dispensing tool, thereby enabling the spacers to be dispensed in a time-efficient manner. In order to make the spacers stackable, there should be some suitable feature which guides one spacer into a correct nondisplaced position relative to another spacer when stacking them. Such a feature may suitably be or include walls of the spacers, suitably with some irregular shape. For example, inclined walls may be advantageous for making the spacer stackable. However, inclined spacer walls that are subjected to a load generally have lower weight bearing capacity than vertical spacer walls. In view of the initially high load of a roll-out reinforcement on the spacers, the inferior weight bearing capacity of an inclined wall may be of concern unless it is compensated in some manner. The inventor has realized that by configuring the spacer with a plurality of more or less closed cells, the weight bearing capacity of the inclined walls may be compensated for. The closed cells provide stability and increased strength. The inventor has also realized that for an elongated spacer, providing the spacer with a plurality of smaller cells results in higher strength than just having a single larger cell. The weight bearing capacity may be varied in dependence on different hole patterns in the inclined walls. Such holes may also facilitate concrete to embrace the support cells. Thus, in view of the above, the inventor has realized that by providing a rail spacer having two or more interconnected support cells, which together form an integral support sequence of support cells, wherein each support cell is provided with an inclined wall, a rail spacer may be provided which is not only stackable, but which also have a sufficient weight bearing capacity to support the initially heavy load of a wound roll-out reinforcement. This general inventive concept will be discussed in more detail in the following. According to an aspect of the general inventive concept, there is provided a stackable rail spacer configured to support a reinforcement, such as a roll-out or mesh reinforcement, in concrete structures, the stackable rail spacer comprising two or more interconnected support cells which together form an integral sequence of support cells arranged one after another, wherein each support cell comprises: - a first end surface forming a first closed curve, - a second end surface forming a second closed curve, wherein for each support cell, one of said first and second end surfaces is configured to face, and allow at least a portion of that end surface to be placed on, a support surface for the stackable rail spacer, such that the other one of said first and second end surfaces faces away from the support surface for the stackable rail spacer and allows at least a portion of that other end surface to support a reinforcement, wherein each support cell further comprises: - a circumferential wall defining a central void of the support cell, the circumferential wall extending from the first end surface to the second end surface, wherein the perimeter of the second closed curve is smaller than the perimeter of the first closed curve such that the circumferential wall tapers from the first end surface towards the second end surface, wherein the circumferential wall is provided with at least one aperture, wherein the second end surface of each support cell is spaced apart from the second end surface of any neighbouring support cell, wherein the integral sequence of support cells arranged one after another defines a longitudinal direction of the rail spacer, wherein the first closed curves formed by the first end surfaces of two neighboring support cells overlap each other with respect to said longitudinal direction such that a cross-section taken perpendicularly to said longitudinal direction cuts through the first end surfaces of both neighboring support cells. A technical benefit of this stackable rail spacer is its combined stackability (provided by the tapered circumferential walls of the support cells) and its weight bearing capacity (improved by the provision of the sequence of support cells), making it particularly useful for a worksite that intends to produce a concrete structure with embedded roll-out reinforcement. However, it should be understood that although the stackable rail spacer, which is stackable for timeefficient dispensing, while also having appropriate weight bearing capacity, is particularly advantageous for providing support to a roll-out reinforcement, the rail spacer can also be used for supporting other types of reinforcements, such as mesh reinforcement or even 8 individual reinforcement bars. Put differently, although the stackable rail spacer overcomes drawbacks related to worksites using roll-out reinforcements, the stackable rail spacer is not limited to such usage, but may advantageously be used to support other kinds of reinforcements as well. Because the stackable rail spacer is formed by the plurality of support cells having its inclined walls, a sufficiently high weight bearing capacity may be achieved by making the stackable rail spacer of a plastic material. This provides the additional advantage of further promoting timeefficiency, since a stack of plastic spacers may weigh less than a stack of spacers of other and heavier material, and may thus be more easily be carried around a worksite for time-efficient dispensing. Thus, according to at least one example embodiment, the stackable rail spacer is made of plastic material. It should be understood that since both the first end surface and the second end surface of each cell form a closed curve, either one of them may, depending on the reinforcement that will be supported, be facing upwards to receive the reinforcement. Although it may be advantageous to let the smaller second end surface face an upper reinforcement and the larger end surface face the spacer support surface, in particular for heavy-weight reinforcements, it should be understood that it would also be conceivable to turn the spacer the other way around if, under certain circumstances, that would be considered practical for any particular situation. As mentioned above, the first closed curves formed by the first end surfaces of two neighboring support cells overlap each other with respect to said longitudinal direction such that a cross-section taken perpendicularly to said longitudinal direction cuts through the first end surfaces of both neighboring support cells. Hereby, the first end surface can provide contact along the entire longitudinal direction. This may be advantageous when placing the rail spacer between two layers of reinforcement, the first end surface providing good support along the entire longitudinal direction, since there are no gaps in that direction. The overlapping of the first end surfaces, together with the tapered circumferential wall allows the second end surfaces to come closer to each other. Indeed, if desired, an effective overlapping of the second end surfaces is also possible, which may be beneficial since it can ensure a desired distance between two layers of reinforcements when the wires / bars of the 9 reinforcement extend perpendicularly to the longitudinal direction of the rail spacer. Furthermore, the rails spacer may hereby conveniently be placed with either the first end surfaces or the second end surfaces facing a support surface. Also, hereby, a roll-out reinforcement may be easily rolled out on either one of the end surfaces, as desired. The fact that the rails spacer has a longitudinal direction means that it may be regarded as at least somewhat elongated. Elongated rail spacers are particularly advantageous for rolling out a roll-out reinforcement. Although in some example embodiments, the support cells may be arranged to form a straight line, it should be understood that this is not mandatory. In case of, for example, the rail spacer comprising three, four or more support cells arranged one after another, these may be arranged in for example a zig-zag or snake-shaped sequence, wherein a longitudinal direction of the rail spacer as a whole would still be clearly identifiable. Such zigzag or snake-shapes may be advantageous as these may, compared to linear shapes, reduce the risk of linear weakening in the concrete as well as the risk of crack formation. Such crack formation may for example occur if a foundation for a house is cast and the ground underneath the foundation settles over time. The circumferential wall of each support cell may have an inside surface facing the central void and an outside surface facing away from the central void. As mentioned before, the circumferential wall of each support cell is provided with at least one aperture. Such an aperture or apertures will extend through the wall so that concrete may flow through the aperture from the outside of the support cell to the central void on the inside of the support cell. Hereby, both the inside and outside surface of the circumferential wall may be covered by concrete. The first and second end surfaces of each support cell may, seen from a horizontal perspective, be planar, but do not necessarily need to be such. For instance, either one of the first and second end surfaces, or even both end surfaces may be provided with one or more local recesses indentations, notches or the like. Such recesses may, for instance, be configured to receive reinforcement bars. Similarly, one or both end surfaces may be provided with one or more local ridges, protrusions, etc. It should furthermore be understood that the stackable rail spacer may be placed onto different kinds of support surfaces. For instance, either one of the first and second end 10 surfaces of the support cell may be placed onto a support surface in the form of a mould surface for the concrete, or onto a support surface in the form of a raised mesh. As mentioned above, the stackable rail spacer comprises two or more interconnected support cells. The number of interconnected support cells in the stackable rail spacer may, for example, be five, seven, nine or eleven. An odd number of support cells may be advantageous because the most centrally located support cell may conveniently be used for mounting to a dispensing tool, with equal number of support cells on either side of the dispensing tool, thereby providing good balance. However, the stackable rail spacer may, at least in some example embodiments comprise an even number of support cells. Furthermore, although some example embodiments of the stackable rail spacer may advantageously be mountable to a dispensing tool, this may not be the case for other example embodiments which may instead be distributed by hand. According to at least one example embodiment, said longitudinal direction of the rail spacer may correspond to an x-axis in an x,y,z Cartesian coordinate system, wherein the second end surfaces of two neighboring support cells are spaced apart by a space such that, at said space, - a first imaginary geometrical plane can be drawn to extend as a first yz-plane in the Cartesian coordinate system such that it extends tangentially to the second end surface of one of said neighboring support cells, and - a second imaginary geometrical plane can be drawn to extend as a second yz-plane in the Cartesian coordinate system such that it extends tangentially to the second end surface of the other neighboring support cell, wherein the second end surfaces of the two neighboring support cells are dimensioned such that any separating distance, with respect to said longitudinal direction, between the first and the second imaginary geometrical planes is smaller than the radius of a wire or rod of the reinforcement to be supported. In other words, even though there may be a separating distance in the longitudinal direction between the second end surfaces of two neighboring support cells, it may suitably be small enough to prevent a wire or rod of the reinforcement to fall down into the space between the second end surfaces. Thus, in this example embodiment a wire or rod of the reinforcement can either be supported by just one second end surface of a support cell, or it can be supported simultaneously by the second end surfaces of two neighboring support cells. From 11 a manufacturing perspective it may be advantageous to allow a space to be present between the second end surfaces of two neighboring support cells. By limiting the extent of such a space, the second end surfaces can still provide a reliable support for a reinforcement along the longitudinal extension of the rail spacer. Thus, a person placing the reinforcement onto the rail spacer does not need to worry about misaligning the reinforcement with respect to said space. For completeness, it may be pointed out that any yz-plane in a Cartesian coordinate system extends perpendicularly to the x-axis in a Cartesian coordinate system. According to at least one example embodiment, the second end surfaces of the two neighboring support cells are dimensioned such that any separating distance, with respect to said longitudinal direction, between the first and the second imaginary geometrical planes is smaller than 16 mm, suitable smaller than 4 mm. This is advantageous as commonly used reinforcement rods are often dimensioned with radii in the range of 4 - 16 mm. According to at least one example embodiment, the second end surfaces of two neighboring support cells are dimensioned so that a cross-section taken perpendicularly to said longitudinal direction includes the respective second end surface of both neighboring support cells. In other words, two neighboring support cells may be arranged in an overlapping relationship such that a reinforcement bar which is positioned onto the rail spacer, and which extends perpendicularly to the longitudinal direction of the rail spacer, can simultaneously be supported by the second end surfaces of two neighboring support cells. Thus, the fact that the second end surface of each support cell is spaced apart from the second end surface of any neighboring support cell does not necessarily mean that the spacing-apart is in the longitudinal direction; it can be in a direction transversely or obliquely to the longitudinal direction. In such case, when there is no space between neighboring support cells with respect to the longitudinal direction of the rail spacer, a reliable support for a reinforcement may be provided anywhere from the first to the last second end surface along the sequence of interconnected support cells. According to at least one example embodiment, the shape of the second closed curve is elongated, the shape of the second closed curve having a maximum length which is larger than its maximum width, the maximum width being measured perpendicularly to the maximum length. Although various shapes are conceivable for the second closed curve, an 12 advantage of such an elongated shape (for example oval, elliptical or similar shape) may be that the previously discussed overlapping relationship (with respect to the longitudinal direction of the rail spacer) between two neighboring support cells may conveniently be achieved by designing the support cells with such an elongated shape. As a purely illustrative example, the ratio between the maximum length and maximum width of the second closed curve may be approximately 2:1. Suitably, the ratio may be larger than 2:1, such as for example 3:1. According to at least one example embodiment, said maximum length of the shape of the second closed curve extends in a direction obliquely to said longitudinal direction of the rail spacer. By letting the second end surface of each support cell be directed in this way, the previously discussed overlapping relationship may be effectively obtained, and thus a reliable support for reinforcements may be achieved. Analogously to the above discussed examples of the second closed curve having an elongated shape, the first closed curve may also have an elongated shape. This will be discussed in relation to some of the following example embodiments. Thus, according to at least one example embodiment, the shape of the first closed curve is elongated, the shape of the first closed curve having a maximum length which is larger than its maximum width, the maximum width being measured perpendicularly to the maximum length. By designing the first closed curve elongated, and by having the tapering of the circumferential wall from the first end surface to the second end surface, the second closed curve may also be elongated. As a purely illustrative example, the ratio between the maximum length and maximum width of the first closed curve may be approximately 2:1. Suitably, the ratio may be larger than 2:1, such as for example 3:1. According to at least one example embodiment, said maximum length of the shape of the first closed curve extends obliquely to said longitudinal direction of the rail spacer. Configuring the rail spacer with obliquely extending first closed curves may facilitate the formation of the previously discussed common continuous end surface of the rail spacer. In particular, the common continuous end surface may be achieved by configuring neighboring obliquely extending first closed curves somewhat overlappingly with each other. Furthermore, the 13 oblique feature allows the rail spacer as a whole to be formed into a less linear product. A completely linear product may increase the risk of formation of cracks in the concrete. According to at least one example embodiment, portions of the first end surfaces of at least two support cells may form part of a common continuous end surface of the rail spacer, wherein said common continuous end surface defines a third closed curve which circumscribes all the first closed curves formed by the first end surfaces of said at least two support cells. Such a common continuous end surface formed by the first end surfaces of at least two support cells provides for stability, in particular in implementations when it is intended to face and be positioned on a support surface, such as a mould surface. A large continuous common end surface reduces the risk of the rail spacer sinking into the support surface (in case the support surface is soft), and is therefore particularly advantageous when carrying the initial heavy load of a wound roll-out reinforcement. The fact that the common continuous end surface may define a third closed curve which circumscribes the first closed curves of said at least two support cells, and that this common continuous end surface is formed by portions of the first end surfaces, means that at least some section of each first closed curve of said at least two support cells is also part of the third closed curve, while one or more other sections of each first closed curve of said at least two support cells is not part of the third closed curve. According to at least one example embodiment, portions of the first end surface of all the support cells form part of said common continuous end surface, wherein the third closed curve defined by said common continuous end surface circumscribes all the first closed curves formed by the first end surfaces of all the support cells. Having a common continuous end surface formed by portions of the first end surfaces of all the support cells provides for even greater stability, in particular in implementations when it is intended to face and be positioned on a support surface, such as a mould surface. As mentioned previously, a large continuous common end surface reduces the risk of the rail spacer sinking into the support surface (in case the support surface is soft), and is therefore particularly advantageous when carrying the initial heavy load of a wound roll-out reinforcement. A further advantage is that a large continuous common end surface makes the rail spacer as a whole more rigid in the longitudinal direction, which in turn may be an advantage when a dispensing tool is used, as discussed elsewhere in this disclosure. The fact that the common continuous end surface 14 defines a third closed curve which circumscribes the first closed curves of all the support cells, and that this common continuous end surface is formed by portions of the first end surfaces, means that at least some section of each first closed curve is also part of the third closed curve, while one or more other sections of each first closed curve is not part of the third closed curve. According to at least one exemplary embodiment, each support cell may be provided with one or more collars, wherein said one or more collars project from at least one of said first end surface and said second end surface. A technical benefit may include that such a collar may improve the stability and the strength of the support cell. The collar may be an inwardly extending or an outwardly extending collar. The strength and stability may be further increased by providing supporting ridges between the collar and the wall. Such supporting ridges may fixate the collar in a defined angle in relation to the adjacent wall of a support cell. A further advantage with providing such supporting ridges is that it reduces the risk of two rail spacers in a stack of rail spacers getting stuck to each other. The risk of stacked rail spacers becoming stuck to each other may in particular be present for support cells having a circumferential wall that extends at a small angle of inclination. While a small angle of inclination may be advantageous from a strength perspective, the risk of getting stuck to a neighbouring rail spacer in a stack is increased. Therefore, by providing supporting ridges between the collar and the circumferential wall, the supporting ridges may form abutments for the next rail spacer in the stack, resulting in some play between the walls of neighbouring rail spacers in the stack. Such small play between the walls of neighbouring rail spacers may efficiently avoid the above-mentioned sticking effect. A further advantage with providing a collar is that the collar may increase the contact area of the rail spacer against the support surface. According to at least one example embodiment, the circumferential wall of each support cell has an inside surface facing the central void and an outside surface facing away from the central void, wherein the rail spacer further comprises, between any neighboring support cells, at least one stiffening bridge extending from the outside surface of the circumferential wall of one of the neighboring support cells to the outside surface of the circumferential wall of the other one of the neighboring support cells. In case of a long rail spacer, if it is lifted in the middle, the two ends of the rail spacer may sag if the rail spacer is not stiff enough. For 15 instance, if a stack of rail spacers is held in the middle by a dispensing tool, the sagging may result in different wall angles in different support cells with respect to a vertical plane. The stacked walls may therefore tend to stick together more, making it more difficult to release the lowest rail spacer from the stack. By making the first end surface as such with sufficient stiffness, this potential problem may be avoided. Another option may be to have different wall angles in different support cells of the rail spacer in order to compensate for any sagging of the rail spacer. Yet another option is providing the above exemplified stiffening bridges. Such stiffening bridges may have any suitable shape, such as straight, arched, or any other suitable shape. According to at least one example embodiment, the stackable rail spacer may further comprise a locking element enabling the rail spacer to be locked to a mating locking element of another rail spacer. By locking several rail spacers to each other a continuous rail may be obtained on to which a roll-out reinforcement may be rolled-out. Such mating locking elements may be engaged to each other in any suitable manner. For example, the locking elements may be snap-locked to each other in a vertical direction, for instance, lowering one locking element towards the other. However, other ways of engaging the locking elements are also possible, such as approaching one rail spacer in the longitudinal direction towards another rail spacer. According to at least one example embodiment, the stackable rail spacer may further comprise visually distinctive markings indicating appropriate placements of individual reinforcement bars. For instance, the visually distinctive markings may be distributed such that each support cell comprises at least one visually distinctive marking on at least one of its first and second end surfaces, however, other distributions are also conceivable. The visually distinctive markings may, for instance, be clearly distinguishable lines, numbers, etc. According to at least one example embodiment, the first end surface may comprise recesses, enabling portions of the first end surface on either side of each recess to straddle across a reinforcement wire / bar while the reinforcement wire / bar is received in the recesses. A technical benefit may include that the rail spacer may be placed onto a mesh reinforcement in a manner reducing the risk for unwanted movements, while also providing support to an overhead reinforcement. According to at least one example embodiment, the rail spacer may further comprise a plurality of locking tabs, wherein each locking tab is provided at a respective one of said recesses and is arrangeable in a locking position that prevents a straddled reinforcement wire / bar from accidently leaving said recess. This is advantageous as it may save time by avoiding the use of separate fastening means if it is desired to fixate the rail spacer. According to at least one example embodiment, at least one of said recesses is defined by a pair of resilient locking portions that are spaced apart by a separating distance, wherein when a reinforcement wire / bar that has a larger diameter than said separating distance is inserted into the recess, then the resilient locking portions become deformed by and adapted to the dimension of the reinforcement wire / bar, thereby preventing a straddled reinforcement wire / bar from accidently leaving said recess. This is advantageous as the locking will be automatically achieved as the reinforcement wire / bar is being inserted into the recess. It should be understood that in other example embodiments the second end surface may instead or additionally be provided with the above-mentioned recesses, enabling overhead reinforcement to rest in such recesses in the second end surface. This also reduces the risk of movements of the overhead reinforcement. According to at least one example embodiment, the rail spacer may further comprise spikes or pins projecting from the first and / or second end surface to counteract movement of the stackable rail spacer when concrete flows to the stackable rail spacer. Alternatively, such spikes or pins may project from a collar in either direction (e.g. upwards or downwards). Such spikes or pins may contribute to the stability of the rail spacer and may also counteract movement and / or deformation when the spacer is subjected to load from above. Furthermore, in case of a soft and uneven support surface, spikes or pins may be allowed to sink down into the support surface without resulting in a negative effect on the concrete cover. Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a / an / the part, portion, element, component, arrangement, device, etc." are to be interpreted openly as referring to at least one instance of the part, portion, element, component, arrangement, device, etc., unless explicitly stated otherwise. Further features of, and advantages with, the present inventive concept will become apparent when studying the appended claims and the following description. The skilled person realizes that different features of the present inventive concept may be combined to create embodiments other than those described in the following, without departing from the scope of the present inventive concept. BRIEF DESCRIPTION OF THE DRAWINGS Figs, la and lb illustrate a stackable rail spacer in accordance with at least a first example of this disclosure. Figs. 2a and 2b illustrate a stackable rail spacer in accordance with at least a second example of this disclosure. Fig. 3a illustrates a stackable rail spacer in accordance with at least a third example of this disclosure. Fig. 3b is a detailed view of the stackable rail spacer of Fig. 3a. Figs. 4a and 4b illustrate a stackable rail spacer in accordance with at least a fourth example of this disclosure. Fig. 5 illustrates a stackable rail spacer in accordance with at least a fifth example of this disclosure. Fig. 6 is a detailed view of a stackable rail spacer in accordance with at least some examples of this disclosure. Fig. 7 illustrates a stackable rail spacer in accordance with at least a sixth example of this disclosure. Fig. 8 illustrates a stackable rail spacer in accordance with at least a seventh example of this disclosure. 18 DETAILED DESCRIPTION Figs, la and lb illustrate a stackable rail spacer 1 in accordance with at least a first example of this disclosure. The stackable rail spacer 1 is configured to support a reinforcement, such as a roll-out or mesh reinforcement, in concrete structures. As shown in Figs, la and lb, the stackable rail spacer 1 comprises two interconnected support cells 2a, 2b which together form an integral sequence of support cells 2a, 2b arranged one after another. Although only two support cells 2a, 2b are illustrated in this example, it should be understood that in other examples, the stackable rail spacer 1 may have more than two interconnected support cells 2a, 2b which together form an integral sequence of support cells arranged one after another. As illustrated in Fig lb, each support cell 2a, 2b comprises a first end surface 4 forming a first closed curve (as indicated by the dotted lines). As illustrated in Fig. la, each support cell 2a, 2b comprises a second end surface 6 forming a second closed curve (as indicated by the dotted lines). Thus, it can be understood that Fig. la is a perspective view in which an observer faces the second end surfaces 6 of the support cells 2a, 2b, whereas Fig. lb is a perspective view in which the observer faces the first end surfaces 4 of the support cells 2a, 2b. The stackable rail spacer 1 may, in practical use, be oriented with either one of the end surfaces 4, 6 facing upwards. For instance, the first end surfaces 4 may face, and allow at least a portion of each first end surface 4 to be placed on, a support surface for the stackable rail spacer 1. In such cases, the second end surfaces 6 face away from the support surface for the stackable rail spacer 1 and allow at least a portion of each second end surface 6 to support a reinforcement. Conversely, in some cases, the second end surfaces 6 may face, and allow at least a portion of each second end surface 6 to be placed on, a support surface for the stackable rail spacer 1. In such cases, the first end surfaces 4 face away from the support surface for the stackable rail spacer 1 and allow at least a portion of each first end surface 4 to support a reinforcement. Each support cell 2a, 2b comprises a circumferential wall 8. The circumferential wall 8 defines a central void 10 of the support cell 2a, 2b. The circumferential wall 8 extends from the first end surface 4 to the second end surface 6. As can be seen in Figs, la and lb, the perimeter of the second closed curve (formed by the second end surface 6) is smaller than the perimeter of the first closed curve (formed by the first end surface 4). In other words, in this illustration, the 19 parallelograms formed by the dotted lines are larger for each first end surface 4 as compared to for each second end surface 6. Although parallelogram shapes have been illustrated for the end surfaces 4, 6 in this example, it should be understood that many other shapes are also conceivable, such as oval or eye-shaped as illustrated in some of the other examples herein. As can be seen in Figs, la and lb due to the above-mentioned difference in perimeter between the first and second closed curves, the circumferential wall 8 tapers from the first end surface 4 towards the second end surface 6. As can be seen in Fig. lb, portions of the first end surfaces 4 of the two support cells 2a, 2b form part of a common continuous end surface of the rail spacer 1. Thus, in this example, each one of the first end surfaces 4 form a respective small parallelogram surface. One of the short sides of each parallelogram is shared by both support cells 2a, 2b. The opposite short sides, however, form together with all the long sides the common continuous end surface. Thus, in this example, the common continuous end surface defines a third closed curve which circumscribes the first closed curves formed by the first end surfaces 4 of the two support cells 2a, 2b. As best seen in Fig. la, the second end surface 6 of one of the support cells 2a is spaced apart from the second end surface 6 of the other one of the support cells 2b. In examples in which more than two support cells are included in the stackable rail spacer, then the second end surface of each support cell is spaced apart from the second end surface of any neighbouring support cell. The circumferential wall 8 is provided with apertures 9 for allowing concrete to flow from outside of the support cells 2a, 2b to the inside, i.e. into the central void 10. The first closed curves formed by the first end surfaces 4 of the two support cells 2a, 2b overlap each other with respect to the longitudinal direction of the rail spacer, such that a cross-section C taken perpendicularly to said longitudinal direction cuts through the first end surfaces 4 of both support cells 2a, 2b. Indeed, in this example, the two support cells 2a, 2b share the first end surface 4 in the middle of the rail spacer 1. Figs. 2a and 2b illustrate a stackable rail spacer 100 in accordance with at least a second example of this disclosure. In particular, Fig. 2a illustrates a side view, whereas Fig. 2b 20 illustrates a perspective view. In this example, the stackable rail spacer 100 comprises a plurality of interconnected support cells 102 which together form an integral sequence of support cells 102 arranged one after each other. In this example, seven support cells 102 are illustrated as forming the stackable rail spacer 100, however, other number of support cells are also conceivable. An odd number of support cells may be advantageous in case a dispensing tool is used for dispensing one rail spacer at a time from a stack of rail spacers. In such case, the central support cell may suitably be used for mounting to the dispensing tool, such that an equal number of support cells extend on both sides thereof for providing good balance. Analogously to the example in Figs, la and lb, the example in Figs. 2a and 2b (as well as the other examples herein) illustrates that for each support cell 102, its circumferential wall 108 tapers from the first end surface 104 towards the second end surface 106. Furthermore, portions of the first end surfaces 104 of at least two support cells 102 may form part of a common continuous end surface of the rail spacer 100, although in other examples this may not be necessary. The common continuous end surface defines a third closed curve which circumscribes all the first closed curves formed by the first end surfaces 104 of said at least two support cells 102. In the specific example of Figs. 2a and 2b, portions of the first end surfaces 104 of each support cell 102 form part of a common continuous end surface of the rail spacer 100. Thus, in this specific example, the common continuous end surface defines a third closed curve which circumscribes all the first closed curves formed by the first end surfaces 104 of all the support cells 102. Furthermore, the second end surface 106 of each support cell 102 is spaced apart from the second end surface 106 of any neighbouring support cell 102. Fig. 2a illustrates that in relation to an x,y,z Cartesian coordinate system, the integral sequence of support cells 102 arranged one after another may define a longitudinal direction of the rail spacer 100 which corresponds to the x-axis in the x,y,z Cartesian coordinate system. Fig. 2a also illustrates that the second end surfaces 106 of two neighbouring support cells 102 may be spaced apparat by a space 112. At said space 112, a first imaginary geometrical plane Pl may be drawn to extend as a first yz-plane in the Cartesian coordinate system such that it extends tangentially to the second end surface 106 of one of said neighbouring support cells 102. A second imaginary geometrical plane P2 may be drawn to extend as a second yz-plane in the Cartesian coordinate system such that it extends tangentially to the second end surface 106 of the other neighbouring support cell 102. The second end surfaces 106 of the two neighbouring support cells 102 may be dimensioned such that the separating distance, with respect to the longitudinal direction (i.e. the x-direction in Fig. 2a), between the first and the second imaginary geometrical planes Pl, P2 is smaller than the radius of a wire or rod of the reinforcement to be supported. In particular, the second end surfaces 106 of the two neighbouring support cells 102 may suitably be dimensioned such that the separating distance, with respect to the longitudinal direction (i.e. the x-direction in Fig. 2a), between the first and the second imaginary geometrical planes Pl, P2 is smaller than 16 mm, suitably smaller than 4 mm. As already discussed in this disclosure, it may sometimes be desirable to use a dispensing tool for dispensing a stack of rail spacers. To this end, as further indicated in Fig. 2b, the stackable rail spacer may suitably have a mounting feature which facilitates it to be mounted to a dispensing tool. In this example, the central support cell is provided with a mounting feature which includes a ring 114 through which a dispensing tool may be inserted. In this example the ring 114 is provide adjacent to the second end surface 106 of the central support cell 102. As can be further seen in Figs. 2a and 2b the stackable rail spacer 100 may further comprise optional spikes or pins 116 projecting from the first and second end surfaces 104,106 to counteract movement of the stackable rail spacer 100 when concrete flows to the stackable rail spacer 100. Although Figs. 2a and 2b illustrates spikes or pins 116 provided on both the first and the second end surfaces 104,106, in other examples, there may be spikes or pins 116 provided on only one of the first and second end surfaces 104,106. In further examples, spikes or pins may be completely omitted. As further illustrated in the example of Figs. 2a and 2b, and also in other examples, each support cell 102 may suitably be provided with one or more apertures 109 for allowing concrete to flow into the centre of the support cell 102. Fig. 3a illustrates a stackable rail spacer 200 in accordance with at least a third example of this disclosure. In this example the spikes or pins 216 are only projecting from the second end surface. As can be seen in the example of Fig. 3a, the first end surface 204 may comprise recesses 220, enabling portions of the first end surface 204 on either side of each recess 220 to straddle across a reinforcement wire / bar while the reinforcement wire / bar is received in the recesses 220. The example of Fig. 2a-2b, shows similar recesses 120. Fig. 3b is a detailed view of the stackable rail spacer 200 of Fig. 3a. As can be seen in this detailed view, some of the recesses 220 may be defined by, or comprise, a pair of locking portions 222 that are spaced apart by a separating distance. When a reinforcement wire / bar that has a larger diameter than said separating distance is inserted into the recess 220, then the resilient locking portions 222 become deformed by and adapted to the dimension of the reinforcement wire / bar, thereby preventing a straddled reinforcement wire / bar from accidently leaving the recess 220. Figs. 4a and 4b illustrate a stackable rail spacer 300 in accordance with at least a fourth example of this disclosure. In particular, Fig. 4a is a top view in which the first end surfaces 304 have been arranged to face the observer, whereas Fig. 4b is a top view in which the second end surfaces 306 have been arranged to face the observer. Starting with Fig. 4a, it can be seen that, for each support cell 302, the first end surface 304 forms a first closed curve which may have a shape that is elongated. In particular, the shape of the first closed curve may have a maximum length LI which is larger than a maximum width Wl, the maximum width W1 being measured perpendicularly to the maximum length LI. As can also be seen in Fig. 4a, the maximum length LI of the shape of the first closed curve may extend obliquely to the longitudinal direction of the rail spacer 300. This can also be seen in other examples that have already been discussed above, such as for instance in Fig. 2b, Fig. 3a and Fig. 3b. As also shown in Fig. 4a, the first closed curves formed by the first end surfaces 304 of two neighbouring support cells 302 overlap each other with respect to the longitudinal direction of the rail spacer, such that a cross section C taken perpendicularly to the longitudinal direction cuts through the first end surfaces 304 of both neighbouring support cells 302.Thus, the first end surfaces 304 of the rail spacers 300 may provide areas of contact along the longitudinal direction without any gaps as seen in the longitudinal direction. In other words, if a wire / rod of a reinforcement is positioned to extend perpendicularly to the longitudinal direction of the rail spacer 300, then a contact with a first end surface 304 can be ensured. It should be understood, that if the examples in Figs. 2a, 2b and 3a, 3b would be shown in a corresponding top view as in Fig. 4a, then a corresponding cross section C taken perpendicularly to the longitudinal direction would cut through the first end surfaces of neighboring support cells in the same way as illustrated in Fig. 4a. Turning now to Fig. 4b, it can be seen that, for each support cell 302, the second end surface 306 forms a second closed curve which may have a shape that is elongated. In particular, the shape of the second closed curve may have a maximum length L2 which is larger than its maximum width W2, the maximum width W2 being measured perpendicularly to the maximum length L2. As can also be seen in Fig. 4b, the maximum length L2 of the shape of the second closed curve may extend obliquely to the longitudinal direction of the rail spacer 300. Fig. 5 illustrates a stackable rail spacer 400 in accordance with at least a fifth example of this disclosure. Similarly to Fig. 2a, the example in Fig. 5 is also illustrated in a side view. However, unlike the example in Fig. 2a, the second end surfaces 406 of neighbouring support cells 402 are not dimensioned to be separated with respect to the longitudinal direction. Instead, Fig. 5 illustrates that the second end surfaces 406 of two neighbouring support cells 402 may be dimensioned such that a cross-section taken perpendicularly to the longitudinal direction of the rail spacer may include the respective second end surface 406 of both neighbouring support cells 402. In other words, no gap can be seen in this side view at the level of the second end surfaces 406. Fig. 6 is a detailed view of a stackable rail spacer 500 in accordance with at least some examples of this disclosure. The circumferential wall 508 of each support cell 502 has an inside surface 508a that facing the central void 510. Although the inside surface is not seen in Fig. 6, it may be considered to correspond to, or be similar to, an inside surface 208a illustrated in Fig. 3b. However, Fig. 6 clearly illustrates an outside surface 508b facing away from the central wall 508. Furthermore, as illustrated in Fig. 6, the rail spacer 500 may further comprise, between any neighbouring support cells 502, at least one stiffening bridge 524 extending from the outside surface 508b of the circumferential wall 508 of one of the neighbouring support cells 502 to the outside surface 508b of the circumferential wall 508 of the other one of the neighbouring support cells 502. Fig. 7 illustrates a stackable rail spacer 600 in accordance with at least a sixth example of this disclosure. In this example, two support cells 602 are illustrated, however, the following discussion is also applicable to higher number of support cells. The first end surface 604 and the second end surface 606 of each support cell 602 are substantially planar, apart from some local areas in the second end surface 606 being provided with recesses 620. The planar areas of the first end surface 604 and the second end surface 606 of each support cell 602 should be substantially parallel with each other. Thus, if reinforcement bars / wires are placed on the planar areas of one of first and second end surfaces 604, 606 and the other end surface rests on the ground or some other support surface, then the concrete layer that will be formed, will have a uniform thickness along the length of the rail spacer 600, and also be parallel with the ground / support surface. Similarly, providing the rail spacer 600 between two levels of reinforcement bars / wires so that the bars / wires contact the planar areas of the first and second end surfaces 604, 606, a uniform and parallel concrete layer may be achieved. However, as has been explained previously in this disclosure, recesses may advantageously be used to receive wires / bars. In examples in which such receiving recesses are provided, the recesses should be arranged in such way that they do not affect the ability of the rail spacer to enable a uniform concrete layer to be formed along its length. In the example illustrated in Fig. 7, the distance between the recesses 620, as seen in the longitudinal direction (x-direction) of the rail spacer 600, is synchronized with the distance between the two reinforcement wires of a mesh. This distance between the recesses 620 should be consistent along the length of the rail spacer 600. Hereby, it can be avoided that some wires / rods of the reinforcement are received in recesses 620 while others rest on the planar areas. Depending on the length of the individual support cells 602, each support cell 602 may be provided with a recess 620 at one, two or more locations with respect to the longitudinal direction of the rail spacer 600. Each recess 620 may suitably have an extension which is perpendicular to the longitudinal direction of the rail spacer 600, so that the wires / bars received in the recesses 620 extend perpendicularly to the longitudinal direction of the rail spacer 600 (i.e. extend in the z-direction). Furthermore, since a wire / bar will extend across a support cell 602, recesses 620 should suitably be provided in pairs, such that there is one recess 620 on either side of the support cell 602. As illustrated in Fig. 7, the walls of each recess 620 may suitably be substantially vertical (extending in the y-direction), and if desired, the recesses 620 may have a rounded bottom. In case of a rounded bottom, the radius of the reinforcement wire / bar should not exceed the radius of the bottom of the recess 620. The depth of each recess 620 should suitably be the same for each recess 620 of the rail spacer 600 so as to obtain a consistent height level for the reinforcement bars / wires. In other words, the received wires / bars should, along the length of the rail spacer 600, be at the same level relative to, for example, a support surface or the ground. Fig. 8 illustrates a stackable rail spacer 700 in accordance with at least a seventh example of this disclosure. In this example, the recesses 720 are provided in the first end surface 704 and the recesses 720 have a substantially rectangular or square cross-section, i.e. without a rounded bottom. Furthermore, while Fig. 7 showed that each support cell 602 may be provided at two locations with respect to the longitudinal direction of the rail spacer 600, in the example of Fig. 8, the recesses 720 are provided at three locations. Thus, the recesses 720 in the example in Fig. 8, may be used for a reinforcement having relatively smaller meshes, and the recesses 620 in the example in Fig. 7 may be used for a reinforcement having relatively larger meshes. Although Fig. 7 and Fig. 8 have only illustrated recesses provided in one of the end surfaces, it should be understood that in other examples, the rail spacer may be provided with recesses in both the first and the second end surface. List of reference numerals: 1: stackable rail spacer 2a: support cell 2b: support cell 4: first end surface 6: second end surface 8: circumferential wall 9: aperture 10: central void 100: stackable rail spacer 102: support cell 104: first end surface 106: second end surface 108: circumferential wall 109: aperture 112:space 114: ring 116: spike / pin 120: recess 200: stackable rail spacer 204: first end surface 208a: inside surface 216: spike / pin 220: recess 222: resilient locking portions 300: stackable rail spacer 302: support cell 304: first end surface 306: second end surface 400: stackable rail spacer 402: support cells 406: second end surfaces 500: stackable rail spacer 502: support cell 508: circumferential wall 508a: inside surface 508b: outside surface 510: central void 524: stiffening bridge 600: stackable rail spacer 602: support cell 604: first end surface 606: second end surface 620: recess 700: stackable rail spacer T1 first end surface 720:recess Pl: first imaginary geometrical plane P2: second imaginary geometrical plane 5 LI: maximum length Wl: maximum width C: cross-section L2: maximum length W2: maximum width 10

Claims

1. A stackable rail spacer configured to support a reinforcement, such as a roll-out or mesh reinforcement, in concrete structures, the stackable rail spacer comprising two or more interconnected support cells which together form an integral sequence of support cells arranged one after another, wherein each support cell comprises:- a first end surface forming a first closed curve,- a second end surface forming a second closed curve,wherein for each support cell, one of said first and second end surfaces is configured to face, and allow at least a portion of that end surface to be placed on, a support surface for the stackable rail spacer, such that the other one of said first and second end surfaces faces away from the support surface for the stackable rail spacer and allows at least a portion of that other end surface to support a reinforcement, wherein each support cell further comprises:- a circumferential wall defining a central void of the support cell, the circumferential wall extending from the first end surface to the second end surface, wherein the perimeter of the second closed curve is smaller than the perimeter of the first closed curve such that the circumferential wall tapers from the first end surface towards the second end surface, wherein the circumferential wall is provided with at least one aperture, wherein the second end surface of each support cell is spaced apart from the second end surface of any neighbouring support cell, wherein the integral sequence of support cells arranged one after another defines a longitudinal direction of the rail spacer,wherein the first closed curves formed by the first end surfaces of two neighboring support cells overlap each other with respect to said longitudinal direction such that a cross-section taken perpendicularly to said longitudinal direction cuts through the first end surfaces of both neighboring support cells.

2. The stackable rail spacer according to claim 1, wherein said longitudinal direction of the rail spacer corresponds to an x-axis in an x,y,z Cartesian coordinate system, wherein, the second end surfaces of two neighboring support cells are spaced apart by a space such that, at said space,- a first imaginary geometrical plane can be drawn to extend as a first yz-plane in the Cartesian coordinate system such that it extends tangentially to the second end surface of one of said neighboring support cells, and- a second imaginary geometrical plane can be drawn to extend as a second yz-plane in the Cartesian coordinate system such that it extends tangentially to the second end surface of the other neighboring support cell,wherein the second end surfaces of the two neighboring support cells are dimensioned such that any separating distance, with respect to said longitudinal direction, between the first and the second imaginary geometrical planes is smaller than the radius of a wire or rod of the reinforcement to be supported.3 The stackable rail spacer according to claim 2, wherein the second end surfaces of the two neighboring support cells are dimensioned such that any separating distance, with respect to said longitudinal direction, between the first and the second imaginary geometrical planes is smallerthan 16 mm, suitable smallerthan 4 mm.

4. The stackable rail spacer according to any one of claims 1-3, wherein the second end surfaces of two neighboring support cells are dimensioned so that a cross-section taken perpendicularly to said longitudinal direction includes the respective second end surface of both neighboring support cells.

5. The stackable rail spacer according to any one of claims 1-4, wherein the shape of the second closed curve is elongated, the shape of the second closed curve having a maximum length which is larger than its maximum width, the maximum width being measured perpendicularly to the maximum length.

6. The stackable rail spacer according to claim 5, wherein said maximum length of the shape of the second closed curve extends in a direction obliquely to said longitudinal direction of the rail spacer.

7. The stackable rail spacer according to any one of claims 1-6, wherein the shape of thefirst closed curve is elongated, the shape of the first closed curve having a maximum length which is larger than its maximum width, the maximum width being measured perpendicularly to the maximum length.

8. The stackable rail spacer according to claim 7, wherein said maximum length of the shape of the first closed curve extends obliquely to said longitudinal direction of the rail spacer.

9. The stackable rail spacer according to any one of claims 1-8, wherein portions of the first end surfaces of at least two support cells form part of a common continuous end surface of the rail spacer, wherein said common continuous end surface defines a third closed curve which circumscribes all the first closed curves formed by the first end surfaces of said at least two support cells.

10. The stackable rail spacer according to claim 9, wherein portions of the first end surfaces of all the support cells form part of said common continuous end surface, wherein the third closed curve defined by said common continuous end surface circumscribes all the first closed curves formed by the first end surfaces of all the support cells.

11. The stackable rail spacer according to any one of claims 1-10, wherein the circumferential wall of each support cell has an inside surface facing the central void and an outside surface facing away from the central void, wherein the rail spacer further comprises, between any neighboring support cells, at least one stiffening bridge extending from the outside surface of the circumferential wall of one of the neighboring support cells to the outside surface of the circumferential wall of the other one of the neighboring support cells.

12. The stackable rail spacer according to any one of claims 1-11, wherein the first end surface comprises recesses, enabling portions of the first end surface on either side of each recess to straddle across a reinforcement wire / bar while the reinforcement wire / bar is received in the recesses.

13. The stackable rail spacer according to claim 12, wherein at least one of said recesses is defined by a pair of resilient locking portions that are spaced apart by a separating distance, wherein when a reinforcement wire / bar that has a larger diameter than said separating distance is inserted into the recess, then the resilient locking portions become deformed by and adapted to the dimension of the reinforcement wire / bar, thereby preventing a straddled reinforcement wire / bar from accidently leaving said recess.3114. The stackable rail spacer according to any one of claims 1-13, further comprising spikes or pins projecting from the first and / or second end surface to counteract movement of the stackable rail spacer when concrete flows to the stackable rail spacer.

Images