The present invention relates to a slab for use in the construction industry, especially to a modular construction slab, to a modular surface system including such slabs, and to a method of joining construction slabs.

It is well known in the construction industry to use slabs, especially concrete or concrete-derivative slabs, as building components. Such slabs find use as flooring components for buildings, public highways and the like. When two or more such known slabs are connected together, it is typically with some kind of internal tie that runs through the interior length and/or width of the slabs.

The problem with a system incorporating such slabs and ties is that, once the slabs have been joined together by the internal ties, if any adjustment, rectification or replacement of a slab or tie is required, the only way to access the tie to disconnect the appropriate slabs is by destroying at least a part of the slab and or tie as is necessary. This is both costly and time consuming because any part that has been even partially destroyed will typically need to be replaced, thereby rendering the system unavailable for a period of time until the rectification work has been completed.

It would therefore be desirable to provide an improved slab for use in the constructions industry, and an improved method of joining slabs, neither of which suffer from the aforementioned problems currently experienced. Accordingly, in a first aspect, the present invention provides a removable modular slab for use in the construction industry comprising: an upper surface, a lower surface opposed to the upper surface, and first and second opposing end surfaces between and substantially normal to the upper and lower surfaces, and a conduit extending from an aperture in the upper surface to an aperture in an end surface, wherein the slab is end-to-end abuttable with a second removable modular slab, said second slab having an upper surface, a lower surface opposed to the upper surface, and first and second opposing end surfaces between and substantially normal to the upper and lower surfaces, and said second slab being provided with one or both of: (i) a conduit extending from an aperture in the upper surface thereof to an aperture in an end surface thereof, and (ii) a cavity extending from an aperture in an end surface thereof into said second slab, whereby the conduit in the first-mentioned slab is mateable with the conduit in the second slab so as to form an elongate conduit through the ends of the two slabs, which is accessible through the apertures in the upper surfaces of each slab, and through which a first joining means is removably locatable to join the two slabs together, or the conduit in the first-mentioned slab is mateable with the cavity in the second slab so as to form an elongate cavity through the ends of the two slabs, which terminates within the second slab and which is only accessible through the aperture in the upper surface of the first-mentioned slab, into which a second joining means is removably locatable to join the two slabs together.

The first aspect of the invention also accordingly provides a second removable modular slab for use in the construction industry with the aforementioned removable modular slab of the preceding paragraph, said second slab comprising: an upper surface, a lower surface opposed to the upper surface, and first and second opposing end surfaces between and substantially normal to the upper and lower surfaces, and a cavity extending from an aperture in an end surface thereof into said second slab, wherein said second slab is end-to-end abuttable with the aforementioned slab, whereby the cavity is mateable with a conduit of the aforementioned slab so as to form an elongate cavity through the ends of the two slabs, which terminates within said second slab and which is only accessible through the aperture in the upper surface of the aforementioned slab, in which a second joining means is removably locatable to join the two slabs together.

Provision of a removable modular slab of this type is advantageous because, firstly, the modular aspect means that the slabs have reproducible and predictable dimensions, and so can be more easily and accurately aligned. Secondly, the slabs can be rapidly installed, whether during initial installation or subsequent replacement, and readily adjusted with minimal disruption and cost. In this regard, the upper surface of the slab is preferably an exposed surface, i.e. it is readily accessible, as are the apertures therein.

Preferably at least one of the first and second opposing end surfaces of one slab is profiled such that a cooperative joint is formable with a profiled end surface of the other slab when the two slabs are abutted together. Advantageously, the end surface profile of one slab includes a protrusion and the end surface profile of the other slab includes a corresponding concavity. Thus when the end surface of one slab and the end surface of the other slab are brought into abutment, the surfaces and profile mate so as to form an intimate joint. Through this joint, the elongate conduit or elongate cavity may extend, and thus also the first or second joining means for joining the two slabs.

Further advantageously, the protrusion and the concavity may be shaped such that the end surface of each (i.e. that surface which would lie flush with the remainder of the end surface of the slab if the protrusion were flattened or the concavity shrunk) is at an angle of 45° or less to the vertical, preferably less than 25°, further preferably less than 15° and most preferably in the range of from 1-5° to the vertical.

The end surface profile of one slab may extend along the length of the end surface of the slab, and correspondingly the other slab also. However, it is not essential that the mating surfaces have such an extent. Indeed, the end surface profile may extend only part-way along the length of the end surface of both slabs; the profile may be positioned towards the centre of the width of the end surface of the slabs or it may extend from one end of the end surface.

A removable modular slab according to the invention may have two identically profiled end surfaces, and as such will be referred to as a type-A slab. The other modular slab, against which a type-A slab is abuttable, may also have two identically profiled end surfaces, which are different from, but cooperable with, the type-A slab, and as such this other slab will be referred to as a type-B slab. A type-A slab may have, for example, two end surfaces that are each provided with a concavity, and a type-B slab may have, for example, two end surfaces that are each provided with a protrusion; the concavities and protrusions being of complementary and cooperative shape. With such type-A and type-B slabs, a row of multiple slabs following the pattern -A-B-A-B-A- B-(etc) may be provided.

Alternatively, a removable modular slab according to the invention may have two differently profiled end surfaces, and as such will be referred to as a type-C slab. The profile of one of the end surfaces of a type-C slab may be cooperable with the profile of the other end surface, such that one type-C slab is abuttable against a further type-C slab. For example one of the end surfaces of a type-C slab may be provided with a concavity whilst the other end surface may be provided with a protrusion. With such type-C slabs, a row of multiple slabs following the pattern -C-C-C-C-C-(etc) may be provided.

A removable modular slab as hereinbefore described may be pre-cast or pre-moulded from a construction material. Any suitable material known in the art may be used, however, concrete or a concrete-derivative material, such a glass-fibre reinforced concrete (GFRC) or glass-fibre reinforced plastic (GFRP) rebar, or a plastics material, may be preferred for its inherent strength, corrosion-resistance, and electrical current- resistance.

Preferably, a modular slab may have one or more voids, preferably longitudinal voids, provided within it, thereby reducing its weight compared to a full-density slab without compromising its strength. These voids may remain empty or may be filled with a lightweight filler material, such as an aerated/foamed rubber. Advantageously, this filler material may also absorb vibrations if and when the slab is subjected to vibrational forces. Additionally, a modular slab may comprise one or more channels in its first surface, which may be for drainage purposes and/or for accommodation of cables, such as electricity cables. Furthermore, longitudinal ducts may be provided alongside the one or more channels for accommodation of cables and/or into which surface water may drain. Moreover, the longitudinal ducts may be crossed by transverse ducts within the slab.

A second aspect of the present invention provides a modular surface system for use in the construction industry comprising two modular slabs, both having a conduit extending from an aperture in their upper surfaces to an aperture in their end surfaces, as hereinbefore described, and a first joining means to join the two slabs together, wherein the first joining means is removably eatable through the elongate conduit.

In practice, any number of modular slabs may be joined together in this manner, and indeed may be joined linearly, to form an elongate surface, or multi-directionally to form a more expansive surface area. Advantageously, the first joining means may be removably locatable in the elongate conduit. Furthermore, the first joining means may be adjustably locatable in the elongate conduit. In both cases, the ease of accessibility to the first joining means, as a result of the configuration of the conduits in the slabs, means that adjustment, alignment and replacement of a modular slab within this modular surface system is quick, easy and low cost.

Preferably, the elongate conduit is arcuate or parabolic; the conduit is open at both ends in the upper surfaces of two adjacent modular slabs and may arc between adjacent end surfaces of the slabs. Correspondingly, the first joining means may be a curved, tensionable cable or tie, or a flexible bar connector. As a cable is located in the elongate conduit via the upper surfaces in two adjacent modular slabs, the lower part of the cable may be subjected to tensile forces whilst the upper part of the cable may be subjected to compressive forces. Thus when a force is applied to the cooperative joint between the two slabs, the distribution of forces within the cable retains the alignment of the slabs. In this way, the slabs act collectively as a monolithic structure.

The first joining means is preferably fastenable and tensionable at the upper surfaces of each slab, providing easy access to said first joining means in the event that realignment or replacement of one or more slabs is required.

The second aspect of the present invention also accordingly provides a modular surface system for use in the construction industry comprising two modular slabs, one having a conduit extending from an aperture in its upper surface to an aperture in its end surface and one having a cavity extending from an aperture in its end surface into is body, as hereinbefore described, and a second joining means to join the two slabs together, wherein the second joining means is removably locatable in the elongate cavity. Again, any number of modular slabs may be joined together in this manner, and indeed may be joined linearly, to form an elongate surface, or multi-directionally to form a more expansive surface area.

Advantageously, the second joining means may be removably locatable in the elongate cavity. Furthermore, the second joining means may be adjustably locatable in the elongate cavity. In both cases, the ease of accessibility to the second joining means, as a result of the configuration of the mating conduit and cavity in the slabs, means that adjustment, alignment and replacement of a modular slab within this modular surface system is quick, easy and low cost.

Preferably, the elongate cavity is arcuate, parabolic or linear; the cavity is open at one end only in the upper surface of one of the adjacent modular slabs and terminates in the body of the other slab. Correspondingly, the second joining means may be a curved, tensionable cable or tie, or a flexible bar connector.

The second joining means is preferably anchored at the terminal end of the elongate cavity within one slab and tensionable at the upper surface of the other slab, providing easy access to said second joining means in the event that realignment or replacement of one or more slabs is required.

As described above, a modular slab may be of one of three types: type-A, type-B or type-C. A modular surface system according to the invention may comprise both type- A and type-B cooperative modular slabs. Alternatively however, the system may comprise just the one type of slab: type-C.

A modular surface system according to the invention may be used widely in the construction industry. However, it finds particular use as a railway or metro track support. Typically a railway is constructed from a foundation or sub-grade material on top of which a layer of ballast is laid. The purpose of the ballast layer is to provide a level substrate for the sleepers to be laid upon, and then for the railways tracks themselves to be fastened to the sleepers. The problem with this construction is that the ballast layer and the sleepers are prone to degradation due to the elements, i.e. water, snow and ice can penetrate, leading to track misalignment. Realignment of such a track is often costly and time-consuming, and accompanied by significant delays to rail traffic, thereby reducing track availability and capacity.

Use of a modular surface system as a railway track support minimises these problems by replacing the sleepers with modular slabs. The railway track may be supportable on the first surfaces (typically the upper surfaces) of the modular slabs, which themselves may be laid directly onto an existing ballast layer as a foundation. Alternatively, the foundation may be in the form of recycled or hydraulically stabilised ballast, or it may simply be earth. The ballast layer would be mostly covered and protected from the elements by the slabs, and the improved joining means between the slabs thereby creates a contiguous structure.

Alternatively, the metro track may be embedded into the first surface (typically the upper surface) of the slabs.

In practice, a plurality of modular slabs may be joined with joining means to form a monolithic railway/metro track support, without the need for additional concrete to provide strength, as a long-term solution and alternative to ballasted railway tracks. This may be particularly advantageous in tunnels, crossovers and switches, level crossings and in locations where poor ground conditions exist; also for light rail applications in urban areas (for example the Docklands' Light Railway) where rapid installation is essential to minimise disruption to traffic in the locality.

Of course, there are may other uses for a modular slab and a modular surface system according to the invention, including, without limitation, as flooring in a building, for a highway, in airports (such as for a runway) and at ports or freight terminals (to form the hardstanding). Furthermore, the invention may have non-horizontal (or at least, non- ground) applications, for example in the walls of retaining structures and for temporary or emergency structures.

A third aspect of the present invention provides a method of removably joining two construction slabs, each having an upper surface, a lower surface opposed to the upper surface, and first and second opposing end surfaces between and substantially normal to the upper and lower surfaces, and each having a conduit extending from an aperture in the upper surface thereof to an aperture in an end surface thereof, the method comprising end-to-end abutting the two slabs, such that the conduit in one slab is mateable with the conduit in the other slab so as to form an elongate conduit through the ends of the two slabs, and removably locating a first joining means through the elongate conduit such that each end of the first joining means is accessible via the upper surface of each slab. The third aspect of the present invention also accordingly provides a method of removably joining two construction slabs, each having an upper surface, a lower surface opposed to the upper surface, and first and second opposing end surfaces between and substantially normal to the upper and lower surfaces, one slab having a conduit extending from an aperture in the upper surface thereof to an aperture in an end surface thereof and the other slab having a cavity extending from an aperture in an end surface thereof into said slab, the method comprising end-to-end abutting the two slabs, such that the conduit in one slab is mateable with the cavity in the other slab so as to form an elongate cavity through the ends of the two slabs, and removably locating a second joining means through the elongate cavity which terminates within the other slab such that the second joining means is only accessible via the upper surface of the first slab.

This method of joining is applicable with the modular slabs according to the first aspect of the invention, and in the modular surface system according to the second aspect of the invention. However it is also applicable to other slabs which facilitate access to a joining means through their upper surfaces, which in the case of retaining structures or emergency structures, may be outer vertical or substantially vertical surfaces. The method further comprises the steps of subsequently anchoring/fastening and tensioning the joining means, which avoids the need to use jointing materials to harden or cure before the slab construction is brought into use.

To aid understanding, the present invention will now be more particularly described, by way of non-limiting example, with reference to and as shown in the accompanying (schematic) drawings in which:

Figure 1 is a perspective view of a modular slab according to the invention;

Figure 2 is an end elevation of the modular slab shown in Figure 1 ;

Figure 3 is a perspective view of an alternative modular slab according to the invention; Figure 4 is an end elevation of the modular slab shown in Figure 3;

Figure 5 is a perspective view of the end surfaces of two modular slabs according to the invention (shown in Figures 1 to 4);

Figure 6 is a side elevation of a plurality of modular slabs according to the invention (shown in Figures 1 to 5); Figure 7 is a perspective view of a further alternative modular slab to that shown in Figures 1 to 4;

Figure 8 is a side elevation of a plurality of modular slabs according to the invention (shown in Figure 7);

Figure 9 is a side elevation of a modular surface system according to the invention; Figure 10 is a transverse section through a modular slab according to the invention; Figure 11 is a transverse section through an alternative modular slab according to the invention;

Figure 12 is a perspective view of a plurality of modular slabs according to the invention;

Figure 13 is a perspective view of an alternative form of the modular slab shown in Figure 1 ;

Figure 14 is an end elevation of the modular slab shown in Figure 13;

Figure 15 is a side elevation of a variant of the modular surface system shown in Figure 9; and

Figure 16 is a transverse section through a yet further alternative modular slab according to the invention.

Figures 1 and 2 show a modular slab 10 comprising a first surface, in the form of an upper surface 11 , a second surface, in the form of a lower surface 12 and two opposing end surfaces 13. The slab 10 is elongate in the direction between the two end surfaces

13. The end surfaces 13 of the slab 10 are each profiled to form a concavity 16. This profile extends part-way along the length of, and is centred on, the end surface 13.

Located within the concavity 16 are four apertures 14, which correspond to a further four apertures 15 located in the upper surface 11 of the slab 10, adjacent to the end surface 13. A conduit 19 (shown in dotted outline) extends between each pair of apertures, joining them.

Slab 10 also comprises longitudinal voids 17 (shown in dotted outline) which may be filled with foamed rubber to both reduce the overall weight of slab 10 (compared to a similar slab formed without voids) and to dampen any vibrations through it without compromising its strength. Additionally, a central elongate channel 18 is provided along the longitudinal axis of the slab, along with drainage outlets 18a, for drainage of surface water which may otherwise stagnate on the slab's upper surface 11. On either side of channel 18 within the body of slab 10, two longitudinal ducts 18b may be provided, along with optional transverse ducts 18c.

Figures 3 and 4 show a modular slab 20 similar to slab 10 shown in Figures 1 and 2, in that slab 20 comprises a first surface, in the form of an upper surface 21 , a second surface, in the form of a lower surface 22 and two opposing end surfaces 23. The slab 20 is elongate in the direction between the two end surfaces 23. Slab 20 also comprises longitudinal voids 27 (shown in dotted outline) which may be filled with foamed rubber to both reduce the overall weight of slab 20 (compared to a similar slab formed without voids) and to dampen any vibrations through it without compromising its strength. Additionally, a central elongate channel 28 is provided along the longitudinal axis of the slab, along with drainage outlets 28a, for drainage of surface water which may otherwise stagnate on the slab's upper surface 21. On either side of channel 28 within the body of slab 20, two longitudinal ducts 28b may be provided, along with optional transverse ducts 28c.

Slab 20 differs from slab 10 in that the end surfaces 23 of the slab 20 are each profiled to form a protrusion 26. This profile extends part-way along the length of, and is centred on, the end surface 23. Located on the protrusion 26 are four apertures 24, which correspond to a further four apertures 25 located in the upper surface 21 of the slab 20, adjacent to the end surface 23. A conduit 29 (shown in dotted outline) extends between each pair of apertures, joining them.

For the avoidance of doubt, although only four conduits have been described with reference to slabs 10 and 20, any number of conduits as is deemed necessary to secure two slabs together may be provided. The conduits may be of varying diameter and may be dissimilar to one another, dependent upon the degree of tension to be applied to the joining means (tensionable cable). Figure 5 shows two modular slabs 10,20, and in particular the manner in which the two slabs are end-to-end abuttable. Slab 10 is as shown in Figures 1 and 2, whilst slab 20 is as shown in Figures 3 and 4. When slabs 10,20 are brought into end-to-end contact, protrusion 26 fits snugly into concavity 16 to form an intimate joint. In this joint, the conduits (not shown) that extend between the apertures 14,24 in the end surfaces 13,23 and the apertures 15,25 in the upper surfaces 11 ,21 of each slab 10,20 meet and are aligned such that an elongate conduit (not shown), which extends from the upper surface 11 of slab 10 to the upper surface 21 of slab 20, is formed.

Figure 6 illustrates how a number of slabs 10 are joined to a number of slabs 20 to form a continuous monolithic surface. It is clear that should a slab 10 need to be removed from the system, it could be upwardly removed simply and in a nondestructive manner. The slabs 10,20 may be a pair of type-A, having identically profiled protrusions on their end surfaces, and type-B, having identically profiled concavities on their end surfaces, slabs. The advantage with this configuration is that, should it be necessary, a type-B slab can be lifted outwardly of the system and away from its adjacent type-A slabs. Alternatively, the slabs 10,20 may both be type-C slabs, having a protrusion formed on one end surface and a concavity formed on the opposing end surface. Furthermore, although the slabs 10,20 have been described as having only two of their end surfaces profiled, it is possible that one or both of their long-edge surfaces could also be profiled to enable joints to be formed at all four edges.

Turning now to Figure 7, this shows an alternative slab 30, which is quite similar to slabs 10,20, in that it comprises a first surface, in the form of an upper surface 31 , a second surface, in the form of a lower surface 32 and two opposing end surfaces 33a, 33b, between and substantially normal to the first and second surfaces. The slab 30 is elongate in the direction between the two end surfaces 33a, 33b. The end surface 33a of the slab 30 is however profiled to form a protrusion 36 (rather than a concavity). This profile extends along the full length of the end surface 33a. End surface 33b is profiled to form a concavity 36b, which also extends along the full length of surface 33b. Located on end surface of the protrusion 36 are four apertures 34, which correspond to a further four apertures 35 located in the upper surface 31 of the slab 30, adjacent to the end surface 33. A conduit 39 (shown in dotted outline) extends between each pair of apertures, joining them.

Furthermore, slab 30 comprises a central elongate channel 38 along the longitudinal axis of the slab 30, along with drainage outlets 38a. Optionally transverse ducts 38c may be provided within the body slab 30 also. Slab 30 may be described as a type-C slab, having a protrusion formed on one end surface and a concavity formed on the opposing end surface. When slab 30 is end-to-end abutted with a further slab, this further slab would be profiled to form a concavity, which extends along the full length of its end surface, and which is provided with correspondingly located apertures and conduits, thereby forming a -C-C-C-C-(etc) type modular system, as is illustrated in Figure 8.

Figure 9 shows a modular surface system 40 comprising, in this instance, two slabs 10,20 of the type herein described. Slabs 10,20 are end-to-end abutted to form a cooperative joint 43, such that the individual conduits 19,29 in each slab meet and join to form an elongate conduit 44, which extends between the two slabs 10,20. Through conduit 44 a first joining means 42, in the form of a flexible wire cable which can be made to follow an arcuate path, is located. Each end of the joining means 42 is provided with fastening and tensioning means 45 to lock the slabs 10,20 into position and to provide strength to the joint 43. Cooperative joint 43 is profiled such that the end surfaces 13,23 that form the concavity 16 and protrusion 26 respectively lie at an angle of 5-10° to the vertical (as is shown by the angle Θ annotated on the drawing). By providing the surfaces of the joint in this manner it is believed that the two slabs 10,20 are easier to align when laying the system 40.

Any two or more slabs 10,20 may be joined according to the following:

prepare a surface, for example a sub-soil layer (not shown) and a top-ballast layer (not shown), by levelling it;

lay two slabs 10,20 in end-to-end abutment such that their profiled surfaces 13,23 meet and a plurality of elongate conduits 44 are formed between the two;

locate a joining means, for example a cable 42, in each elongate conduit 44 by feeding it through an aperture 15 in the upper surface 11 of slab 10 until it appears through the corresponding aperture 25 in the upper surface 21 of slab 20; and

affix fastening and tensioning means 45 to each accessible end of each cable 42 to lock them into position and subsequently apply tension to them, which will tighten the joint 43 between the two slabs 10,20.

This method is equally applicable to the laying and joining of two or more slabs 30. Figure 10 shows the slab 10 of Figures 1 and 2 in use as a railway track support. Slab 10 is laid on a foundation surface (not shown) and is provided with a railway track 50 and a fixing 51 for fixing the track 50 to the upper surface 1 of slab 10. Instead of using GFRP concrete, a reinforcement rod 52 is provided within the body of slab 10, in this instance adjacent to the lower surface 12 of the slab and extending up the side of the slab. Rod 52 could continue around ducts 18b and adjacent the upper surface 11 of the slab to form a reinforcement loop. As an additional safety feature, slab 10 includes an optional raised portion 54, which extends longitudinally down each side of the upper surface 11 , and is located outboard of track 50. Should a train travelling on tracks 50 become de-railed, raised portion 54 should prevent said train from toppling over and coming off the slab track, thereby further increasing rail safety.

Figure 1 1 also shows the slab 10 of Figures 1 and 2 in use as a railway support. Slab

10 is again provided with a railway track 50 and a fixing 51 , however the upper surface 11 has been modified to include a raised-profile portion 101 - the centre of the slab is of greater depth when viewed in section compared to the outer edges of the slab, with tapering of the depth from the centre to the outer edges. Furthermore, upper surface

11 is provided with two longitudinal recesses 102 which accommodate the track 50 and fixing 51 components. In this way, the track 50 is effectively embedded in the slab 10, which may be especially useful when a railway track needs to be lowered to increase the clearance when laid in a tunnel or under a bridge, or at level crossings and locomotive maintenance yards, where it allows for maintenance work to take place as a result of the access possible with normal road vehicles. Figure 12 illustrates a network 60 of slabs which are joined to form a more expansive surface area than would be achieved by merely joining slabs end-to-end. In Figure 12 there are provided different types of slabs, having profiles formed on end surfaces and/or side surfaces as necessary to enable connections to be made to adjacent slabs as appropriate. In particular, Figure 12 shows:

- slabs 61 having profiles in the form of a pair of protrusions 62 on one end surface 63 and one side surface 64,

slab 65 having profiles in the form of a pair of concavities 66 formed in both end surfaces 67 and one side surface, and

slab 68 having profiles in the form of a pair of protrusions 69 formed in both end surfaces 70 and both side surfaces. Apertures 71 and conduits 72 are appropriately located such that elongate conduits 72 are formed when the different slabs are abutted, enabling joining of said slabs in two directions (i.e. in an x-direction and in a y-direction) thereby formed a mosaic of slabs. In the case of a network 60, the slabs may be square-shaped rather than elongate.

Figures 13 and 14 show a modular slab 10' which is very similar to modular slab 10 shown in Figure 1 and 2; the similarity is such that like features have been provided with like reference numerals in Figure 13 and 14, however denoted with a prime symbol ('). The difference between slab 10' and slab 10 is in the end profile of the slabs resulting from the profile of channel 18' in slab 10' and channel 18 in slab 10. Figure 13 and 14 clearly show a taller height profile along both longitudinal edges defining channel 18', through which longitudinal ducts 18b' are provided.

Figure 15 shows a modular surface system 40' which is an alternative to modular surface system 40 shown in Figure 9. Like features have been provided with like reference numerals in Figure 15, however denoted with a prime (') or double prime (") symbol. The main difference between the systems shown in Figures 9 and 15 is in the second joining means 42' and corresponding alternative form of slab 10". Slab 10" comprises a cavity 70 which extends from an aperture (not shown) in end surface 13" into the body of slab 10" and is provided therein with a tension-fixing anchoring ferrule 71. Slabs 10", 20 are end-to-end abutted to form a cooperative joint 43', such that the cavity 70 and conduit 29 in each slab meet and join to form an elongate cavity 72, which extends between the two slabs 10", 20. Into cavity 72 a second joining means 42', in the form of a flexible wire cable or GFRP curved bar which can be made to follow an arcuate path, is located. The first end of cable/curved bar 42' screw-threads into ferrule 71 to anchor the cable into position, whilst the other end of the cable/curved bar 42' is provided with fastening and tensioning means 45' to lock the slabs 10", 20 into position and to provide strength to the joint 43'.

Cooperative joint 43' is again profiled such that the end surfaces 13", 23 that form the concavity 16" and protrusion 26 respectively lie at an angle of 5-10° to the vertical (as is shown by the angle Θ annotated on the drawing). By providing the surfaces of the joint in this manner it is believed that the two slabs 10", 20 are easier to align when laying the system 40'. Figure 16 show a modular slab 10'" which is very similar to modular slab 10 shown in Figure 11 ; the similarity is such that like features have been provided with like reference numerals in Figure 16, however denoted with a triple prime symbol ("'). The difference between slab 10"' and slab 10 is in the end profile of the slabs. Figure 16 shows slab 10"' in use as a metro slab for city light rail systems. Slab 10"' is again provided with a rail/fixing component 50"' and a fixing 51"', however the upper surface 11 "' has been modified to include two outer raised-profile portions 101 "' - the edges of the slab 10"' are of greater depth when viewed in section compared to the centre of the slab, which allows for the laying (in the shallower area) of road surfacing materials (not shown). Furthermore, upper surface 11"' is provided with two longitudinal recesses 102"' which accommodate the track 50"' and fixing 51 "' components. In this way, the track 50"' is effectively embedded in the slab 10"', which may be especially useful as a metro track located in a highway or city streets. The modular slab 10"' can accommodate numerous ducts 17"' for cables associated with a metro system and recesses 102"' that are provided with drainage outlets 103, 104, 105 to allow for the collection, escape and drainage of surface and sub-surface collected water.