Abstract:
An anti-spalling edging comprising: a metal strip  21,31  adapted for concrete to be cast against, a return  22,32  along a top edge of the strip and forming a corner with the metal strip, a down-turn  23,33  from the edge of the return spaced from the strip and cut-outs in  26,36  the down-turn for anchoring it in the concrete and an elongate metallic member  201,202  extending in the corner, fixed to the strip and the return for reinforcement of the anti-spalling edge at the corner.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is for entry into the U.S. National Phase under §371 for International Application No. PCT/GB2013/000071 having an international filing date of Feb. 22, 2013, and from which priority is claimed under all applicable sections of Title 35 of the United States Code including, but not limited to, Sections 120, 363, and 365(c), and which in turn claims priority under 35 USC 119 to United Kingdom Patent Application No. 1203580.4 filed on Feb. 29, 2012. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an anti-spalling edging, in particular, though not exclusively for concrete. 
     2. Description of the Related Art 
     Concrete is strong in compression, but weak in tension. Small sections are liable to fail in shear. The result is that edges of concrete slabs are liable to spall, that is the edge is liable to crack away, generally at angle. 
     The problem can be relieved to an extent by a flat steel edging, with may form part of a joint allowing contraction of the slabs on setting and thermal expansion. Flat steel strip can become bent away from the concrete, thus the original problem is not really solved. The steel strip can be reinforced against such bending away by provision of an in-turned edge or return level with the top of the slab. This protects the edge of the slab, but loading, deflections and impact can allow the free edge of the return to lift. This gives rise to another set of problems. In turn the free edge can be turned down and provided with cut-outs for its anchoring in the slab. 
     Again there is a problem, in that the down-turn has a radius of curvature at its abutment with the top surface of the concrete, which creates yet another potential spalling site. 
     In our International Application No WO 2010/094910 (Our &#39;910 Application), we have described and claimed an anti-spalling edging comprising:
         a metal strip adapted for concrete to be cast against,   a return along a top edge of the strip,   a down-turn from the edge of the return spaced from the strip,   cut-outs in the down-turn for anchoring it in the concrete;
 
wherein:
   the cut-outs are so arranged as to provide faces, extending through the return and generally in the direction of the edging, against which faces the concrete abuts when cast level with the outer surface of the return.       

     In our &#39;910 Application, we envisaged that anti-spalling advantage could be obtained if the faces were non-planar, such as being S or W shaped when viewed in plan, preferably the faces are flat and face directly away from a bend connecting the metal strip to the return. We preferred in the direction of the edging, the transverse faces to predominate compared with fingers of the down-turn extending down between the cut-outs. 
     We envisaged that the fingers might not joined at their distal ends, but we preferred to join them at their distal ends to stabilise them during installation and casting of the concrete. Members joining the fingers are important for holding the finger from drawing upwards of the concrete. 
     We envisaged that the metal strip would be of steel galvanised before or after is punching of its cut-outs. However, it could also be of stainless steel, mild steel or plastics materials. 
     In the preferred embodiment of our &#39;910 Application, a pair of anti-spalling edgings were normally to be provided as a “joint” between two sections of concrete slab, the two metal strips abutting with the returns extending in opposite directions on laying of the concrete and separating on curing. The joint would normally include dowels extending into the two sections of the slab, for vertical load transfer in use; the dowels may be any type of dowels and indeed are optional. Furthermore, a single anti-spalling edging might be used, particularly at an edge. 
     In testing this joint with admittedly-heavy, localised repetitive loading, we have experienced impacting of the return below neighbouring regions of the edge and the concrete not subjected to the localised load. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is to provide an improved anti-spalling edging. 
     According to the invention there is provided an anti-spalling edging comprising:
         a metal strip adapted for concrete to be cast against,   a return along a top edge of the strip and forming a corner with the metal strip,   a down-turn from the edge of the return spaced from the strip and   cut-outs in the down-turn for anchoring it in the concrete
           the cut-outs being so arranged as to provide faces, extending through the return and generally in the direction of the edging, against which faces the concrete abuts when cast level with the outer surface of the return and   
           an elongate metallic member extending in the corner, fixed to the strip and/or the return for reinforcement of the anti-spalling edge at the corner.       

     Preferably as in Our &#39;910 application the cut-outs being so arranged as to provide faces, extending through the return and generally in the direction of the edging, against which faces the concrete abuts when cast level with the outer surface of the return. 
     Normally the reinforcement will be substantially the same width as the return and welded into the corner. Whilst other sections can be envisaged such as triangular or square cross section complementary in shape to the shape of the corner, with close matching of radius of the inside corner of the metal strip, we prefer to use reinforcing bar, for its ready availability. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       To help understanding of the invention, specific embodiments thereof will now be described by way of example and with reference to the accompanying drawings, in which: 
         FIG. 1  is cross-sectional view of a joint including two anti-spalling edgings in accordance with the invention of Our &#39;910, the edgings being improved in accordance with the present invention, 
         FIG. 2  is a perspective view of the joint, 
         FIG. 3  is a view similar to  FIG. 1  of another joint improved by reinforcement in accordance with the invention, 
         FIG. 4  is a scrap view of the reinforcement of the edgings of the joint of  FIG. 3 , 
         FIG. 5  is a view similar to  FIG. 2  of the joint of  FIG. 3 , 
         FIG. 6  is a view similar to  FIG. 3  (but from the other end of the joint) of a modified improved joint and 
         FIG. 7  is a view similar to  FIG. 5  of the modified joint. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to the drawings, a joint  1  including a pair of anti-spalling edgings  2 , 3 . Both have:
     metal strips  21 , 31 , the first being deep and the second being shallow,   returns  22 , 32  along the top edges of the strips, facing in opposite directions from the central plane P of the joint,   down-turns  23 , 33  extending down from the edges of the returns,   cut-outs  24 , 34  in the down-turns,   the cut-outs defining:
       edges  25 , 35  in the returns which face outwards from the plane P,   fingers  26 , 36  of the down-turns extending down between the edges, the fingers being narrow and the edges being wide,   connections  27 , 37  at the bottom of the fingers.   
       

     The two anti-spalling edgings are lightly connected together with frangible fixings  5 , below the level of the connections. 
     The deep metal strip  21  extends to or close to the base of the slab into which the joint is to be laid. It has a return  28  and up-stand  29  for stiffening it. These features are both optional and may be used separately. The shallow strip  31  also has a return  38 , which is angled slightly away from the top return  32 . The return  38  has a series of apertures  39 . As shown these are of a similar size to the cut-outs  34 , but they can be either large or more usually smaller. Beneath the return  38 , the deep strip has flat plate dowels  6  welded to it at punched cut-outs  7 . On the shallow strip side, the dowels are enclosed in sleeves  8 , which allow the dowel to withdraw from the slab portion in which they extend. The dowels are not essential to the working of the invention, and embodiments can be envisaged without dowels. 
     In accordance with the present invention, lengths of reinforcing bar  101 , 111  are welded into the corners  102 , 112  between the metal strips  21 , 31  and the returns  22 , 32 . 
     To install the joint, it is set up to form the edge of a slab portion S 2 , that is with the top of the return at the intended finished height of the slab. It can be temporarily secured by means that form no part of this invention. The slab portion is laid. Once it has cured to a green state, the temporary securement is removed and the portion S 3  of the slab on the second side is laid. During laying, the concrete forms against the edges  25 , 35  in a manner that is not prone to spalling. The concrete is able to rise against the underside of the returns and the reinforcing bars  101 , 111 , since air can flow out at the edges. Further air escape cut-outs  10  can be provided in the returns  22 , 32 . Under heavy, repetitive loading, such as to cause break up to the top surfaces of the slabs, the returns  22 , 32  are supported at the original level of the top surfaces for appreciably longer than would be the case in the absence of the reinforcement provided by the reinforcing bars. 
     In our initial testing, we have used reinforcing bar that is substantially the same diameter, preferably 8-10 mm, as the width of the returns, with the radius of curvature of the corners matching that of the bar. 
     Turning now to  FIG. 3 , there is shown an edging having alternative reinforcing members in the form of a triangular rolled steel fillet  201 , 202 . The fillets have a radius of curvature  203  at their right angle corners complementary to that  204  of the corner of the edging between the strips  21 , 31  and the returns  22 , 32 . The fillet&#39;s radius of curvature can be slightly larger, so as not to hold the fillet away from the corner of the edging, nor so much larger as to leave an appreciable gap allowing deformation of the edging in service. This can be achieved by arranging for the minimum of the tolerance range of the fillet&#39;s radius of curvature to exceed the maximum of the tolerance range of the radius of curvature of the corner. Thus one face  205  of the fillet abuts the strip and the other  206  abuts the return. The fillet is welded in place at intervals along its and the edging&#39;s length, as typically shown at  208 . It is shaped to allow air rising during vibration of the poured concrete to rise up under the angled face  209  of the fillet and escape through the anti-spalling cut-outs  24 , 34 . The cut-outs  10  in the return  22 , 32  would be obscured and are not provided. In the preferred embodiment, the face  209  is angled at 50° to the vertical in use, i.e. 50° to the metal strip abutted by the fillet&#39;s face  205 . It could be angled from 65° to 15°, and particularly between 55° and 45°. 50° provides a compromise between economy of material and robust reinforcement. 
     The invention is not intended to be restricted to the details of the above described embodiments. For instance, as shown in  FIGS. 6 and 7 , both strips  121 ,  131  are of the same depth, normally the full depth of the slabs. Thus both could have plain returns and up-stands as  28 , 29 , but in practice, they have returns  122 , 132  along their bottom edges, up-turns  123 , 133  extending up from the edges of the returns and cut-outs  124 , 134  in the up-turns. Two lines of frangible fixings  105  are provided. These modifications provides significantly more stiffness to the joint, which is advantageous in handling prior to installation. Whilst there is some scope for the joint to be placed upside-down, it is provided with a line of apertures  151  for known supports to hold the joint at installation height. Such support ensures that the joint is installed the right way up, with the reinforcing fillets uppermost. 
     One further modification is the provision of gussets  152  for assisting in ensuring that dowels  106  are welded square to the strips.