GB2415008A

GB2415008A - Building element such as a kerbstone

Info

Publication number: GB2415008A
Application number: GB0514268A
Authority: GB
Inventors: Ian John Geeson; Kevin Greaves; David Simpson
Original assignee: Aggregate Industries UK Ltd
Current assignee: Aggregate Industries UK Ltd
Priority date: 2003-07-01
Filing date: 2004-06-30
Publication date: 2005-12-14
Also published as: GB0514268D0

Abstract

The building element has a body with one surface defining at least one re-entrant portion 22 to provide for a reduction in weight of the building element, the re-entrant portion defined, in part, by side surfaces of upper 26 and lateral 28,30 reinforcement formations extending rearwardly at an angle of between 20 and 70 degrees from an inner portion 24 of the rear surface to a portion of the rear surface defining a back, in use, surface of the reinforcement formations. The re-entrant portion is preferably in the rear, in use, surface 12 of the building element so that it is concealed in use. The building element may include a number of re-entrant portions that are preferably all formed in one surface. The inner face of the re-entrant portion(s) may be flat and parallel to the front surface of the building element, sloped at an angle relative to the front surface or formed from a number of stepped portions. Guides, such as projections, indentations or score lines 34, may be provided on the building element, preferably on the rear surface, to assist the locating of the building element in use. The building element is preferably a concrete kerbstone. Also claimed is a method of forming a building element.

Description

24 1 5008 Building Elements The present invention relates to building

elements and particularly but not exclusively to kerbstones. The invention also relates to a method of forming building elements.

There is often a need for manual handling of building elements both on and off construction sites. Manual handling must however be carefully carried out to mitigate the potential for injury, and this is particularly so where the building elements are heavy. Indeed, current Health & Safety Regulations stipulate maximum weights manual labourers can lift alone, and this means that for heavier objects lifting apparatus has to be employed. However, this can be costly and inconvenient.

According to a first aspect of the present invention, there is provided a building element comprising a plurality of surfaces defining a body having substantially the same overall dimensions and composition as a known building unit, but one of said surfaces defining at least one reentrant portion to provide for a reduction in the weight of the building element and arranged so that in use the resistance of the element to impact on a further surface at least generally on an opposite side of the element to said one surface remains substantially the same as said known building unit.

According to a second aspect of the present invention there is provided a 2s building element comprising a plurality of surfaces defining a body, one of said surfaces defining at least one reentrant portion arranged to give the element at least substantially similar resistance to impact on a further surface thereof as it would have if said one surface had no reentrant portion(s) defined therein.

The reentrant portion in said surface is sufficiently large that the weight of the building element is significantly reduced relative to a similar known unit, and may provide a reduction of weight of up to 50%, preferably 10 - 40% and desirably approximately 20 to 25%.

The reentrant portion is preferably defined in a rear surface, which is concealed from view when the element is installed in position for use.

The reentrant portion preferably extends inwardly from the rear surface towards a front surface, and desirably the said further surface, of the element, preferably to a depth of between 10% and 70% and desirably about 30% according to certain embodiments of the invention and in other embodiments about 50 - 60% of the depth of the element between the rear and front surfaces.

The reentrant portion may extend over the majority of the rear surface. Preferably the reentrant portion is defined, in part, by an inner portion of the rear surface, which inner portion may be substantially flat and may be generally parallel to the said front surface.

The building element may comprise one or more reinforcement formations.

An upper reinforcement formation may extend along an upper surface of the building element and may extend in a rearward direction. One or more lateral reinforcement formations are preferably provided which may extend down one or more side surfaces of the building element and may extend in a rearward direction, preferably by a similar distance to the upper reinforcement formation.

The upper and lateral reinforcement formations may in part define the reentrant portion. Preferably side surfaces of the reinforcement formations defining the reentrant portion extend rearwardly from the said inner portion to a portion of the rear surface defining a back surface of the reinforcement formations. Preferably the side surfaces slope at an angle of between 20 and 70 degrees to the inner portion, and desirably at an angle of approximately 45 degrees.

The provision of these sloped side surfaces is believed to be particularly advantageous. A first advantage is that they facilitate production of the element as is discussed hereinafter. A second advantage is that the angle of the sloped surfaces facilitates dissipation of impact forces which the element is most likely to experience during use and against which the element should have certain resistance characteristics. This will be discussed in more detail later.

A plurality of reentrant portions may be provided, all of which may be provided in one surface, although in an alternative embodiment one or more reentrant portions may be provided in a plurality of surfaces. s

Where a plurality of reentrant portions is provided, the reentrant portions are preferably shaped and/or arranged so that the building element has good impact strength and thus resistance to damage from impacts on the further surface, which is preferably a front surface.

Preferably the reentrant portions are so shaped and/or arranged to give the element greatest impact resistance and thus resistance to damage from impacts generally mid-way along the length of the element. Where a plurality of reentrant portions is provided, each reentrant portion is preferably shaped and the plurality arranged so that the impact resistance of the building element decreases, preferably gradually, from the generally mid-way region towards each end of the element. Each reentrant portion may be shaped so that the strength of the building element decreases substantially linearly.

In a preferred embodiment, the inner portion of the or each reentrant portion slopes relative to the said front surface of the element. Preferably the inner portion of the or each reentrant portion slopes inwardly from the rear surface towards the front surface of the element in a direction away from the mid-way region. Desirably the or each inner portion slopes generally gradually and linearly inwardly from the rear surface towards the front surface. An inner portion may extend from the mid-way region on or near the rear surface, inwardly towards the front surface to a depth of between 40% and 70% and desirably about 50 - 60% of the distance between the rear and front surfaces.

In an alternative embodiment, an inner portion may comprise a sequence of interconnected step portions which together define a stepped surface of the inner portion. Each step portion may comprise a first surface which may be substantially flat and generally parallel to the front surface. Each step portion may further comprise a second surface which interconnects the first surfaces of successive step portions. The second surface may be sloped relative to the said front surface of the element. The second surface may be sloped at a similar angle to said front surface as said side surfaces. Preferably the general slope of the stepped inner portion is substantially the same as that of and as described above for the aforesaid linear sloped inner portion of the previous embodiment.

Where a plurality of reentrant portions is provided in a surface, reinforcing formations as aforesaid may define in part, one or more of these portions. A series of reentrant portions may be provided across a surface, with reinforcing formations defining, in part, each thereof. Preferably a series of three or more lateral reinforcing formations is provided, extending preferably generally mutually parallel to each other to define a series of two or more reentrant portions.

Preferably the aforesaid sloped inner portions define at least, in part an intermediate lateral reinforcement formation about the generally mid- way region of the element. Preferably lateral reinforcement formations extend from the forward-most region of the sloped surface, back to the rear surface, to define a side of each reentrant portion. Preferably one or more intermediate lateral reinforcing formations define a boundary between adjacent reentrant portions and the width of each of the said one or more intermediate reinforcing formations may be on average greater than, and preferably about twice that of the width of the lateral reinforcing formations extending down the one or more side surfaces of the building element. The, or at least one of the reentrant portions may open onto an in use lower most surface of the element.

The or at least one of the reentrant portions receives haunching, concrete, cement or other material to help secure the element in position for use, the location of the portion(s) acting to restrain the element from movement generally along an axis, and generally a longitudinal axis, when the element is impacted on said further surface at an acute angle relative to that axis Guide means may be provided for assisting with location of building material adjacent the building element. The guide means may comprise a projection. Alternatively, the guide means may comprise an indentation. As a yet further alternative, the guide means may comprise a score line. The guide means s may be provided on the rear surface of the building element and desirably on the back surface of one or more reinforcement formations. Preferably, the guide means is provided on the lateral reinforcing elements.

S The building element preferably comprises a kerbstone. Preferably the element is manufactured using cementitious material, such as concrete.

Preferably the material has a load bearing resistance or strength of at least 40 MPa (N/mm2), and desirably at least 50MPa (N/mm2).

Preferably the element has a length of approximately 457mm, a height of approximately 254mm, a depth of approximately 1 25mm and a weight of approximately 20kg or less. Preferably the reentrant portion extends to a depth of approximately 72mm.

The material may comprise fibres to strengthen the element, and may comprise plastic fibres to improve the impact resistance of the element.

According to a third embodiment of the present invention there is provided a building element comprising a plurality of surfaces defining a body having substantially the same composition and overall dimensions as a known building unit, one of said surfaces defining a reentrant portion to provide for a reduction in the weight of the building element whilst maintaining the strength and appearance of the element when in use substantially the same as said known building unit.

The building element may be as described in any of the preceding paragraphs.

According to a fourth aspect of the present invention, there is provided a kerbstone, at least one surface of the kerbstone being concealed in use, said surface defining a reentrant portion to provide for a reduction in the weight of the kerbstone relative to a conventional kerbstone of similar size and in-situ appearance.

The kerbstone preferably has at least substantially the same impact resistance, and in-use appearance as a like kerbstone of the same size and composition, but without said reentrant portion.

The kerbstone may comprise a building element as defined in any of the preceding paragraphs.

The invention further provides a kerbstone unit comprising a body in one surface of which is defined a reentrant portion arranged to give the element at least similar resistance to impact on a further surface of the body, when in use, as it would have if said one surface had no reentrant portion defined therein, the unit being locatable in use, alongside a similar such unit for replacement or as an alternative to a conventional kerbstone.

Preferably the unit has a length of approximately 457mm.

The unit may be approximately 20kg or less in weight. Prefereably a unit is comprised in a pair of preferably similar units for use in the replacement of a conventional kerbstone of approximately 915mm length.

The invention may further comprise a pair of kerbstone units as described above.

The or each kerbstone unit preferably comprises a building element as described above.

According to a fifth aspect of the present invention, there is provided a method of forming a building element as described in any of the preceding paragraphs, the method comprising: charging a mould with gettable material; locating a press tool in the mould and compressing material in the mould to form a body having at least one recess formed in a surface thereof, and allowing the material to set sufficiently to retain its shape in the form of a building element; and removing the press tool from the mould.

Preferably the recess is fommed by a formation on the press tool. The recess may be formed as a reentrant portion as described in any of the preceding paragraphs.

The material may be allowed to set further in or outside the mould.

Preferred embodiments of the present invention will now be described by way of example only and with reference to the accompanying drawings, in which: Fig. 1 is a diagrammatic view of a rear surface of a first building element according to the invention; Fig. 2 is a diagrammatic cross-sectional side view along line A-A of Fig. 1; Fig. 3 is a diagrammatic view of a front surface of the building element of Fig. 1; Fig. 4 is a diagrammatic view of a rear surface of a second building element according to the invention; Fig. 5 is a diagrammatic view of a rear surface of a third building element according to the invention; Fig. 6 is a view of from a bottom surface of a fourth building element; Fig. 7 is a view of from a bottom surface of a fifth building element; Fig. 8 is a view of from a bottom surface of a sixth building element; and Fig. 9 is a rear view of a seventh building element according to the present invention; Fig. 10 is a rear view of an eighth building element according to the present invention; Fig. 11 is a rear view of the elements of Figs. 9 and 10 in mutual location for use; Fig. 12 is a plan view of a ninth building element according to the present invention; Fig. 13 is a rear view of the element of Fig. 12; Fig. 14 is a plan view of a tenth building element according to the present invention; Fig. 15 is a rear view of the element of Fig. 14; and Fig. 16 is a diagrammatic view of an arrangement for forming a building element according to the invention.

Referring to the drawings, there is shown generally a building element 10, 40, 50, 100, 200, 300, 400, 500 and 600 in the form of a kerbstone, the building element comprising a plurality of surfaces, for example a rear surface 12, an upper surface 14, two side surfaces 16, a lower surface 18 and a front surface 20. The plurality of surfaces 12, 14, 16, 18, 20 define a body having substantially the same overall dimensions as a known building element, for example a known kerbstone, but one of said surfaces defines a reentrant portion 22 whereby the weight of the building element 10, 40, 50, 100, 200, 300, 400, 500, 600 is reduced but the impact resistance to impact, and the appearance of the element 10, 40, 50, 100, 200, 300, 400, 500, 600 when in use, are at least substantially the same as a said known kerbstone.

In more detail, Fig. 1 illustrates a first building element 10 in which a reentrant portion 22 is defined in the rear surface 12 of the element 10. The element has overall dimensions equivalent to known kerbstones so that the building element 10 of the present invention can be used as a replacement or alternative to known, heavier elements. One known standard size of kerbstone is 457 mm long and so element 10 is also 457 mm long, as measured between the S side surfaces 16. The rear surface 12 would nominally be concealed from view when the element 10 is in position for use and the front surface 20, which has the same appearance as the front surface of a known building element, is arranged to be visible when the element is in position for use. The element 10 is also manufactured from the same material, generally concrete, as similar known elements. In this way, the element 10 has the same composition, and overall appearance in use, as a known building element.

The reentrant portion 22 extends over the majority of the rear surface 12 of the element 10, and extends inwardly in a forward direction towards the front surface 20 of the element 10 by a distance of about 30% of the depth of the element 10 measured between the front and rear surfaces 20, 12. However, this distance can be varied between about 10% and 70%.

An inner portion 24 of the rear surface 12 of the element 10 defines in part the reentrant portion 22, and the inner portion 24 is generally flat and parallel to the front surface 20 of the element 10. In the embodiment illustrated in Figs. 1 to 3, the lower region 23 of the reentrant portion 22 opens out onto the lower surface 18 of the element 10.

An upper reinforcing formation 26 and two lateral reinforcing formations 28, 30, are provided to ensure that the building element 10 has the same structural strength as a known building element formed of the same material and having the same overall dimensions, but not including a reentrant portion 22. The upper reinforcing formation 26 extends along and defines in part the upper surface 14 between the side surfaces 16 of the element 10 and the lateral reinforcing formations 28, 30 extend down and define in part the side surfaces 16 of the element between the upper and lower surfaces 14, 18. The upper and lateral reinforcement formations 26, 28, 30 all extend by the same distance from the element 10 in a rearward direction.

Each of the reinforcement formations 26, 28, 30 has an outer surface 31, defined by an outer portion of the rear surface 12 of the element 10, and a sloped side surface 32 which slopes at an angle of about 45 degrees from the rear surface 31 to the inner portion 24 of the rear surface 12. This angle can be varied within the range of 20 to 70 degrees according to desired characteristics of the element 10. In the embodiment shown in Figs. 1 to 3, the width of the outer surface 31 of each reinforcing formation 26, 28, 30, is about 28 mm and the distance between the outer most point of the sloped side surface 32, where it meets the outer surface 31, and the inner most point where it meets the inner portion 24, is about 20 mm.

In the event of impact of the element 10 when in situ for use by an object, for example a vehicle tyre when the element 10 is a kerbstone, this is most likely to be received by the front surface 20. The sloped side surfaces 32 help reduce stress concentration at the boundary between the inner portion 24 and the reinforcing formations 26, 28, 30, by facilitating dissipation of the impact forces within the element 10. This is believed to reduce the likelihood of failure of the element 10 in the event the usual sort of impact that kerbstones are expected to experience in use and to help provide the element with substantially the same strength and impact resistance as a said heavier element of the same overall size and composition. Providing the reinforcing formations 26, 28, 30 with sloped side surfaces 32 also facilitates moulding of the element 10, as discussed hereinafter.

As best seen in Fig. 1, guide means in the form of score lines 34 are provided on the outer surface 31 of each lateral reinforcing formation 28, 30 towards the upper end thereof. The score lines 34 may for example be located approximately 70 mm from the upper surface 14 of the element 10. When the element 10 is a kerbstone, for example, the score lines 34 provide a guide to assist with location of adjacent building material, such as paving slabs or haunching (not shown). It is not essential that the guide means take the form of score lines 34, and any suitable visual marker such as a projection or indentation may be provided. The upper reinforcing formation 26 may be formed to provide the guide means, which may comprise a lower edge of the reinforcing formation 26.

In use, the building element 10 can be used as a kerbstone in all conventional applications for known kerbstones, such as delineating walkways and roadways. Each element 10 is installed in position for use in generally the same way as conventional, solid kerbstones, with the front surface being exposed, at least in part, and the rear surface hidden by the presence of haunching, pointing, paving and the like. A long series of elements 10 will generally be positioned end on end again in generally conventional manner.

The opening of the reentrant portion 22 at the lower region 23 facilitates location of the element 10 by allowing it to easily bed into soft base-material such as concrete on which the element 10 is generally sited for use. As the element 10 is so positioned the base-material enters into the reentrant portion 22 to help bed- in and secure the element 10. The location of the base material, such as haunching into the portion 22 also helps to secure the element 10 against movement, when impacted with glancing blows. In use, the most likely of type of impact a kerbstone element 10 will experience is an impact at an angle to its longitudal axis. Impacts at an acute angle to this axis may act to try to move the element in a generally longitudal direction. The location of the base material in the portion 22 helps to resist such undesirable movement and thus maintain the integrity of the kerb.

When a series of elements 10 has been positioned end on end, which may be facilitated by locating them along a line of string or similar, with the lateral reinforcing formations assisting location by providing contacting points for the string, haunching or similar mixes of concrete, gravel, hardcore, shippings or like material is bedded in behind the elements, generally up to the level of the guide means 34 to preferably enter into the reentrant portion to secure the elements 10 in position. Entry of such materials into the reentrant position adds further strength to the element 10 when in situ not only to impact resistance to a full-on impact on the front surface 20 but also to key the element 10 in position to resist movement under the influence of glancing impacts on the element generally along the axis of the element with which the impact forms an acute angle, such as the longitudal axis of the element.

The provision of the reentrant portion provides a significant reduction in S the weight of the element 10 when compared to conventional kerbstones of the same size and material. The reduction in weight can be as high as 50%. In this embodiment, the weight reduction is in the order of 20 to 25%. The concealment of the reentrant portion when the element is in position for use provides the element 10 with the same external appearance as conventional equivalent kerbstones.

The element 10 can therefore be used to replace damaged conventional kerbstones, as well as for producing new kerbs of conventional appearance.

Conventional kerbstones are generally manufactured of cementitious material with a load bearing resistance of approximately 40MPa (N/mm2). The element 10 can be made of such material.

However, where desired the load resistance of material used may be greater than 40MPa. Although the basic material of the element 10 is the same as a conventional kerbstone. i.e. concrete, the impact resistance may be increased by increasing the amount of cement in the material. In a particularly preferred embodiment the load bearing resistance of the material used is at least MPa (N/mm2). However, the external appearance of the material is substantially the same as that of a conventional kerbstone.

The element 10 has a length of approximately 457mm, a height of approximately 254mm, a depth of approximately 1 25mm and a weight of approximately 20kg, or less. The reentrant portion extends into the body to a depth of approximately 72mm.

The element 10 is approximately half the length of a standard full length concrete kerbstone of UK standard specification. In use, two similar elements 10 would be sited in longitudinal alignment, one against the other to provide an alternative to or a replacement for such a standard full length herb.

The main advantage of the present invention is therefore the significant reduction in weight of the element 10 which facilitates handling of the element 10, particularly manual handling, and this helps with compliance with Health and Safety Regulations, as well as mitigating the risk of injury through lifting, whilst the element retains the same general outward appearance, strength and impact resistance characteristics as equivalent conventional kerbstones, especially when to in position for use.

Fig. 4 illustrates a second building element 40 according to the invention in which features corresponding to those described with respect to the first building element 10 of Figs.1 to 3 are given corresponding reference numerals.

The building element 40 is similar to the building element 10 except that is approximately twice as long (914 mm) and the rear surface 12 thereof defines two reentrant portions 22, which are separated by an intemmediate lateral reinforcing formation 42 providing a partition between the adjacent portions 22.

The intermediate formation 42 extends between the upper reinforcement formation 26 and the lower surface 18 of the element 10 at a position generally mid-way between side surfaces 16, and is parallel to the lateral reinforcing formations 28, 30. The outer surface 44 is of greater width than and ideally about twice that of the outer surfaces 31 of either of the lateral reinforcing formations 28, 30, with the width being in the order of 40 mm. The intermediate formation 42 also includes sloped side surfaces 32, the dimensions and angles of which are the same as the sloped side surfaces of the lateral reinforcement formations 28, 30.

The building element 40 has a length of about 914 mm, which is greater than the length of the first building element 10. The provision of an intermediate lateral reinforcement formation 42 between the two reentrant portions 22 ensures that the desired structural strength and impact resistance of the element 40 is maintained and that it is at least substantially the same as a building element having the same overall dimensions, including length, and constructed of the same material but not having reentrant portions 22. Importantly, the generally mid-way location of the intermediate reinforcement formations provides the element with sufficient strength to generally resist the usual types of impacts that the front surface of the element 40 may experience in use.

The building element 40 is installed for use in similar manner to conventional kerbstones. When placed end on end, the lateral formations 28 of one element 40 abut a similar formation 28 on the other, to define a combination reinforcement formation (not shown) of similar size to the intermediate formation 42. They may be bonded together using cementitious material or the like. The provision of combination reinforcement formation in this way helps to ensure the strength of the kerbs produced by the elements 40, along the length thereof.

As a still further embodiment of the present invention an element (not shown) similar to element 40 is provided having a single reentrant portion with no intermediate reinforcement formation 42.

Fig. 5 illustrates a third building element 50 which is again of similar construction to the first and second building elements 10, 40 and in which corresponding features are given corresponding reference numerals.

The building element 50 is of greater length than either of the first or second building elements 10, 40, the length of the element 50 being about 1.5 m.

In order to maintain the structural strength and impact resistance desired of the element 50, two intermediate lateral reinforcement formations 42 are provided which define three reentrant portions 22 in the rear surface 12 of the element 50.

The dimensions of each of the intermediate formations 42 are as discussed above in relation to the second building element 40.

A lifting formation 41 is provided in the lowermost edge 43 of each of the reentrant portions 22. Each formation 41 is located generally centrally within the respective reentrant portion and symmetrically about the centre of balance of the element 50. In use, the formations 41 receive straps or similar lifting apparatus (not shown), and provide recesses in which such straps engage to facilitate lifting and handling of the element 50 using lifting apparatus.

The provision of lifting formations has only been illustrated in relation to element 50 as currently an element of this size when manufactured fromcementitious material is too heavy for manual lifting. The other elements discussed herein, including 10, 40 are generally sufficiently light to be manually lifted, although such lifting formations 41 could be provided in one or more of these elements to facilitate lifting by apparatus, if desired.

Figs. 6, 7 and 8 illustrate further building elements 100, 200, 300 according to the invention which are similar to the building element 40 of Fig. 4 in size and corresponding features have again been given corresponding reference numerals. Like the building element 40, each of the building elements TOO, 200, 300 includes two reentrant portions 22 defined in a rear surface 12 of the element. However, each reentrant portion 22 is shaped to provide the element 100, 200, 300 with its greatest impact resistance and strength generally mid-way between its side surfaces 16 in the mid-way region 102, and gradually reducing strength in the direction away from the midway region towards the side surfaces 16. This is important to produce elements of sufficient impact resistance and strength to perfomm their intended function satisfactorily, whilst enabling the desired reduction in weight to be achieved In more detail and referring firstly to Fig. 6, the inner portion 24 of each reentrant portion 22 of the building element 100 is substantially flat and slopes inwardly away from the rear surface 12 towards the front surface 20 of the element 100. Each inner portion 24 slopes generally linearly away from the central region 102 towards a respective side region 104 of the element 100, and this linear sloping is believed to be particularly advantageous for reasons which will be discussed later. When each inner portion 24 approaches a respective side surface 16 in a side region 104, it merges smoothly as shown at 105 into the sloped side surface 32 of a respective lateral reinforcing formation 28, 30. Each inner portion 24 extends inwardly of the element 100 to a distance of between 40% and 70% and desirably about 50% and 60% of the distance between the rear and front surfaces 12, 20.

The configuration of the elements 100 and the reentrant portions are such that the element 100 is able to bear substantially the same loads and therefore bear substantially the same impacts as a similar such unit without the reentrant portions formed therein. The element 10 is therefore believed to provide the optimum strength to weight ratio using conventional materials and composition for the production of kerbstones.

Referring to Fig. 7, the building element 200 also includes two reentrant portions 22 in which the inner portion 24 of each reentrant portion 22 generally slopes inwardly away from the rear surface 12 of the element 200 towards the front surface 20. However, in this embodiment, each inner portion 24 comprises a stepped surface 202 which is defined by a plurality of interconnected step portions 204. Each step portion 204 has a first surface 206 which is flat and generally parallel to the front surface 20 of the element 200, and a second surface 208 which is sloped relative to the front surface 20 and which interconnects the first surfaces 206 of adjacent step portions 204. The angle of slope may be about the same as the angle of slope of the side surfaces 32. The general slope of the stepped inner portion of this embodiment is substantially the same as that of the linear sloped inner portion as described with reference to Fig. 6. The inner portion of this embodiment also extends into the element 200 a similar distance as that of the embodiment of Fig. 6.

Referring to Fig. 8, the element 300 includes two reentrant portions 22, the inner portion 24 of each reentrant portion 22 including first and second portions 24a, 24b. The first portion 24a is substantially flat and slopes inwardly away from the rear surface 12 towards the front surface 20 of the element 300. The gradient of the first portion 24a is greater than the gradient of the inner portion 24 of the element 100 of Fig. 6. A relatively short distance away from the central region 102, the first portion 24a merges into the second portion 24b which is substantially flat and parallel to the front surface 20 of the element 300. In this embodiment the inner portions 24 extend to between 20 and 50%, and desirably about 30 - 40% of the distance between the rear and front surfaces 12,20.

It has been appreciated by the applicant that for elements of lengths between 600 and 1200 mm, it is important to provide intermediate reinforcing formations 42 to provide the elements with the necessary impact resistance and strength for satisfactory performance in use whilst enabling the desired reduction in weight to be achieved. In kerbstones of generally standard length (U.K.

standard full length kerbstones are 914 mm long) the provision of an intermediate reinforcing fommation generally mid-way along the length of the kerbstone provides the kerbstone with the requisite strength and resistance to damage from impacts on the front surface thereof during use, not only to perform satisfactory in use, but to meet current British Standard Safety Tests. Upon impact of the front surface 20 of a building element approximately mid-way between the side surfaces 16 in the central region 102, the element is subjected to greatest stress forces in the midway region 102, and these forces gradually reduce towards the side surfaces 16. Moreover, the stress forces have been found to decrease in a generally linear manner away from the central region 102 towards the side regions 104, and thus there is the greatest potential for failure of an element in the central region 102, with the likelihood of failure decreasing from the central region 10 towards the side regions 104.

The building elements 100, 200, 300 all take account of this potential failure model by the provision of reentrant portions 22 which provide for the elements to have greatest strength in the mid-way region 102, where the stress forces on an element can be the greatest. The side regions 104 will be located adjacent to and supported by an equivalent element (which is most often the case when the elements are kerbstones lined end-on-end to delineate a kerb) or otherwise secured, in use, which arrangement provides the necessary strength and impact resistance at the ends. In view of the fact that the stress forces experienced by the element are believed to decrease generally linearly in a direction away from the central region 102 towards a respective side region 104, the element 100 of Fig. 6 is believed to be particularly advantageous since the constant and linear slope of each inner portion 24 is designed to track the profile of the stress forces within the element when impacted centrally, and thereby provides the element 100 with a decreasing amount of material away from the central region 102 towards the side regions 104, and hence with the optimum combination of strength and reduced weight. Each element 100, 200, 300 is believed to have substantially the same load bearing characteristics and resistance to impact as conventional kerbstones of equivalent material and composition, or indeed as they would have if they did not comprise the reentrant portions, both in use and also in isolation when subjected to test conditions away from location for use.

Figs. 9 to 11 show a further kerbstone 400 according to this invention which comprises two sections 400a (Fig. 9) and 400b (Fig. 10). The first section 400a is of generally similar configuration to the element 10 at Figs.1 to 3, but the upper surface 14a slopes from one side 16aa to the other side 16ab, and the reinforcing formation 26a and surface 32a slope correspondingly. A reentrant portion 22a is thereby provided in the rear surface 12a in generally similar manner as described above with the upper side to the reentrant portion 22a sloped in the direction of one side to the other.

The second section 400b is shown in Fig. 10 and is of generally similar shape to section 400a, in that its upper surface 14b of the reinforcing formation 26b is sloped thereby providing the reentrant portion 22b with a sloped upper side. The length of the section 400b may be greater than the length of the section 400a and the height of the section 400b at its highest point is approximately the same as the height of the first section 400a at its lowest point.

Preferably the overall weight of 400a is substantially the same as the unit 400b.

The features shared between the units 400a and 400b are marked with the same reference numerals, with corresponding suffixes. Similar features shared with other embodiments are given corresponding reference numerals.

The two units 400a, 400b locate together as shown in Fig. 11, for use as a sloping section in a kerb arrangement. Such sloped sections have particular use in areas where the height of the kerb is desired to be lowered relative to the kerbs general height, for example to facilitate access over the kerb such as for vehicular access. When the sections 400a, 400b are aligned, end on end, the respective slopes extend in the same direction with the highest point on the sloped surface of unit 400b generally coinciding with the lowest point on the sloped surface of the unit 400a such that the kerbstone 400 has a smooth, sloped upper surface 14.

The reinforcing formations 28a, 30a, 28b and 30b are generally as described above in relation to Figs. 1 to 3, and when the sections are in alignment for use as shown in Fig. 11, the combination reinforcement 33 formed therebetween is located in an off-centre location along the length of the kerbstone 400, being located closer to the side surface 16aa than to the side surface 16bb.

The relatively low height of the section 400b when compared to the section 400a provides the section 400b with greater inherent impact resistance characteristics than section 400b, thereby enabling the length of section 400b to be greater than that of section 400a, whilst maintaining a resultant impact strength similar to that of section 400a. Further, this enables the sections 400a, 400b to have approximately the same weight, which facilitates handling.

Referring to Figs. 12 and 13, a further building element 500 according to a further aspect of the present invention comprises a radius kerb unit generally curved along its length when viewed in plan (Fig.12). Radius kerb units are used to provide curves or bends in kerb arrangements. A series of such kerb units can be arranged end on end to provide a longer, curve or bend, or alternatively the units can be aligned with a straight kerbstone units to provide a kerb arrangement with a desired profile.

It will be appreciated that the curvature of such radius unit used can be varied within the scope of the present invention, but all such units 500 have a reentrant portion 22 defined in the rear surface thereof in a similar manner as described above. Features shared with previous embodiments are referenced with the same numerals.

The reentrant portion 522 is defined by side surfaces 32 and an inner portion 24 which in this embodiment is preferably curved to follow the general curvature of the unit 500.

S With regard to Figs. 14 and 15, a still further building element 600 according to the present invention comprises a comer unit having a curved shape when viewed in plan primarily to extend around and form a corner in a kerb arrangement. The unit 600 is curved to provide an approximately 90 corner, but it will be appreciated that any desired curvature can be, be provided for within the to scope of the present invention.

Again, this element 600 has a reentrant portion 22 defined in, curved rear surface 631 thereof. Again many of the features of this element are shared with previous embodiments and are referenced with the same numerals.

The reentrant portion 622 is defined by side surfaces 32 and a curved inner portion 24, the curvature of which follows the general curvature of the unit 600. The respective side surfaces 32 extend at an angle of approximately 45 to the respective sides 16.

Referring to Fig. 16, the building elements 10, 4O, 50, 100, 200, 300, 400, 500, 600 according to the invention may be formed by charging a mouid 62 with gettable material 60, such as concrete. The mould 62 defines the upper, side, lower and front surfaces 14, 16, 18, 20 of the building element 10, 40, 50, 100, 200, 300, 400, 500, 600. A press tool 64 is then located in the mould 62 to compress the material 60. The tool 64 is removed from the mould 62 when the material has set sufficiently to define one or more reentrant portions 22 in the rear surface 12 of the element 10, 40, 50, 100, 200, 300, 400, 500, 600. The material is then allowed to further set either within or outside the mould to form the desired building element 10, 40, 50, 100, 200, 300, 400, 500, 600. The rear surface 12 defines one or more reentrant portions 22, as determined by the configuration of the press tool 64 or the number of press tools 64 used.

Providing the reinforcing formations with sloping side surfaces 32, and in particular surfaces at an angle of about 45 degrees, is advantageous as it facilitates removal of the of the press tool from 64 the material.

There is thus provided building elements 10, 40, 50, 100, 200, 300, 400, 500, 600 which when formed from the same material as similar known building element with the same overall dimensions and in use appearance as said known equivalent elements, are of substantially lighter weight and thus considerably easier to handle and also cheaper to produce having less material therein than to known elements. The provision of one or more reentrant portions can also make the building element according to the invention easier to handle by providing a convenient location for the hands. Moreover, providing the reentrant portions 22 with sloped inner portions 24 is particularly advantageous in order to provide necessary strength and impact resistance whilst at the same time minimising weight.

Various modifications may be made without departing from the scope of the present invention. For example, the or each reentrant portion 22 may have a different configuration to that shown in the drawings. The building element 10, 40, 50, 100, 200, 300, 400, 500, 600 may be an element other than a kerbstone. Any number of reentrant portions 22 may be defined by the rear surface 12 of the element 10, 40, 50, 100, 200, 300, 400, 500, 600. The reinforcing formations may not comprise sloping side surfaces, or may have side surfaces which slope at angles other than those indicated. Reinforcing fibres such as plastic fibres may be comprised in the material of the elements.

Whilst endeavoring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance, it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings, whether or not particular emphasis has been placed thereon.

Claims

Claims: 1. A buildng element comprising a plurality of surfaces defining a

body having substantially the same overall dimensions and made of the same material(s) as a known building unit, one of said surfaces defining at least one reentrant portion to provide for a reduction in the weight of the building element, the reentrant portion defined, in part, by side surfaces of upper and lateral reinforcement formations l() extending rearwardly at an angle of between 20 and 70 degrees from an inner portion of the rear surface to a portion of the rear surface defining a back surface of the reinforcement formations, the arrangement of the side surfaces being such that in use the resistance of the element to impact on a further surface at least generally on an opposite side of the element to said one surface remains substantially the I S same as said known building unit.
2. A building element as claimed in claim 1, in which the reentrant portion in said surface is sufficiently large that the weight of the building element is significantly reduced relative to a similar known unit. 2()
3. A building element as claimed in claim 2, in which the reentrant portion provides a reduction of weight of up to 50%.
4. A building element as claimed in claim 3, in which the reentrant portion provides a reduction of weight of between 10-40%.
5. A building element as claimed in claim 3, in which the reentrant portion provides a reduction of weight of between 20-25%.

3()
6. A building element as claimed in any preceding claim, in which the reentrant portion is defined in a rear surface, which Is concealed from view when the element is installed in position for use.
7. A building element as claimed in claim 6, in which the reentrant portion extends inwardly from the rear surface towards a front surface which is desirably said further surface of the element, preferably to a depth of between 10% and 70% of the depth of the element between the rear and front surfaces
8. A building element as claimed in claim 7, in which the reentrant portion extends to a depth of between 50 and 60%.
9. A building element as claimed in claim 7, in which the reentrant portion l () extends to a depth of approximately 30%.
10. A building element as claimed in any of claims 6 to 9, in which the reentrant portion extends over the majority of the rear surface.

l
11. A building element as claimed in any of claims 6 to 10, in which the reentrant portion is defined, in part, by the inner portion of the rear surface.
12. A building element as claimed in claim 11, in which the inner portion is substantially flat. 2()
13. A building element as claimed in claim 11 or claim 12, in which the inner portion is generally parallel to the said front surface.
14. A building element as claimed in any preceding claim, in which the upper reinforcement formation extends along an upper surface of the building element.
15. A building element as claimed in any preceding claim, in which the upper reinforcement formation extends in a rearward direction.

3()
16. A building element as claimed in any preceding claim, in which the or each lateral reinforcement formations extend down one or more side surfaces of the building element.
17. A building element as claimed in claim 16, in which the lateral formation(s) extend in a rearward direction.
18. A building element as claimed in claim 17, in which the lateral formations extend by a similar distance to the upper reinforcement formation.
19. A building element as claimed in any preceding claim, in which the side surfaces slope at an angle of approximately 45 degrees.
20. A building element as claimed in any preceding claim, in which a plurality of reentrant portions is provided.
21. A building element as claimed in claim 20, in which all of the reentrant portions are provided in one surface.
22. A building element as claimed in claim 20 or claim 21, in which the reentrant portions are shaped and/or arranged so that the building element has good impact strength and thus resistance to damage from impacts on the further surface.

2()
23. A building element as claimed in claim 22, in which the reentrant portions are so shaped and/or arranged to give the element greatest impact resistance and thus resistance to damage from impacts generally mid-way along the length of the element.
24. A building element as claimed in claim 23, in which each reentrant portion is shaped and the plurality arranged so that the impact resistance of the building element decreases from the generally mid-way region towards each end of the element.

3()
25. A building element as claimed in claim 24, in which the impact resistance decreases gradually.
26. A building element as claimed in claim 24 or claim 25, in which each reentrant portion is shaped so that the strength of the building element decreases substantially linearly.
27. A building element as claimed in any preceding claim, in which the inner portion of the or each reentrant portion slopes relative to the said further surface of the element.
28. A building element as claimed claim 27, in which the inner portion of the or to each reentrant portion slopes inwardly from the rear surface towards the further surface of the element in a direction away from the mid-way region of the length of the element.
29. A building element as claimed in claim 28, in which the or each inner portion slopes generally gradually and linearly inwardly from the rear surface towards the front surface.
30. A building element as claimed in claim 29, in which an inner portion extends from the mid-way region on or near the rear surface, inwardly towards the front surface to a depth of between 40% and 70% of the distance between the rear and front surfaces.
31. A building element as claimed in claim 30, in which the inner portion extends to a depth of between 50-60% of the distance between the rear and front surfaces.
32. A building element as claimed in any preceding claim, in which an inner portion comprises a sequence of interconnected step portions which together define a stepped surface of the inner portion.
33. A building element as claimed in claim 32, in which each step portion comprises a first surface which is substantially flat and generally parallel to the front surface.
34. A building element as claimed in claim 33, in which each step portion further comprise a second surface which interconnects the first surfaces of successive step portions.

s
35. A building element as claimed in claim 34, in which the second surface is sloped relative to the said front surface of the element.
36. A building element as claimed in claim 35, in which the second surface is sloped at a similar angle to said front surface as said side surfaces.
37. A building element as claimed in claim 35 or 36, in which the general slope of the stepped inner portion Is substantially the same as that of the aforesaid linear sloped inner portion.
38. A building element as claimed in any of claims 20 to 37, in which reinforcing formations as aforesaid define in part, one or more of the reentrant portions.
39. A building element as claimed in claim 38, in which a series of reentrant portions is provided across a surface, with reinforcing formations defining, in part, 2() each thereof.
40. A building element as claimed in claim 39, in which a series of three or more lateral reinforcing formations is provided, extending generally mutually parallel to each other to define a series of two or more reentrant portions.
41. A building element as claimed in claim 40, in which the aforesaid sloped inner portions define at least, in part an intermediate lateral reinforcement formation about the generally mid-way region of the element.

3()
42. A building element as claimed in claim 39 or claim 40, in which lateral reinforcement formations extend from the forward-most region of the sloped surface, back to the rear surface, to define a side of each reentrant portion.
43. A building element as claimed in either of claims 41 or 42, in which one or more intermediate lateral reinforcing formations define a boundary between adjacent reentrant portions.
44. A building element as claimed in claim 43, in which the width of each of the said one or more intermediate reinforcing formations is on average greater than that of the width of the lateral reinforcing formations extending down the one or more side surfaces of the building element.

I ()
45. A building element as claimed in claim 44, in which the width of the intermediate reinforcing formation(s) is about twice the width of the lateral reinforcing formaton(s).
46. A building element as claimed in any preceding claim, in which the, or at least IS one of the reentrant portions opens onto an in use lower most surface of the element.
47. A building element as claimed in any preceding claim, in which guide means are provided for assisting with location of building material adjacent the building 2() element.
48. A building element as claimed in claim 47, in which the guide means comprises a projection.
49. A building element as claimed in claim 47, in which the guide means comprises an indentation.
50. A building element as claimed in claim 47, in which the guide means comprises a score line. 3()
51. A building element as claimed in any of claims 47 to 50, in which the guide means is provided on the rear surface of the building element.
52. A building element as claimed in any of claims 47 to 51, in which the guide means is provided on the back surface of one or more reinforcement formations.
53. A building element as claimed in claim 52, in which the guide means is provided on the lateral reinforcing elements.
54. A building element as claimed in any preceding claim, in which the building element comprises a kerbstone.

l()
55. A building element as claimed in any preceding claim, in which the element is made of cementitious material, such as concrete.
56. A building element as claimed in claim 55, in which the material has a load bearing resistance of at least 40MPa (N/mm2).
57. A building element as claimed in claim 56, in which the material has a load bearing resistance of at least 50MPa (Nmm2).
58. A building element as claimed in any preceding claim in which the element 9() has a length of approximately 457mm, a height of approximately 254mm, a depth of approximately 125mm and a weight of approximately 20kg or less.
59. A building element as claimed in claim 58, in which the reentrant portion extends to approximately 72mm into the body.
60. A building element as claimed in any preceding claim, in which the material from which the element is made comprises fibres, such as plastic fibres, to improve the impact resistance of the element.

3()
61. A building element comprising a plurality of surfaces defining a body, one of said surfaces defining at least one reentrant portion arranged to give the element at least substantially similar resistance to impact on a further surface thereof as it would have if said one surface had no reentrant portion(s) defined therein.
62. A building element comprising a plurality of surfaces defining a body having substantially the same composition and overall dimensions as a known building unit, one of said surfaces defining a reentrant portion to provide for a reduction in the weight of the building element whilst maintaining the strength and appearance of the element when in use substantially the same as said known building unit.
63. A building element as claimed in claim 61 or claim 62, the element being as defined in any of claims 1 to 60.

l()
64. A kerbstone, at least one surface of the kerbstone being concealed in use, said surface defining a reentrant portion to provide for a reduction in the weight of the kerbstone relative to a conventional kerbstone of similar size and in-situ appearance.
65. A kerbstone as claimed in claim 64, in which the kerbstone has at least substantially the same impact resistance, and in-use appearance as a like kerbstone of the same size and composition, but without said reentrant portion.
66. A kerbstone as claimed in claim 64 or claim 65, in which the kerbstone 2() comprises a building element as defined in any of claims 1 to 61.
67. A kerbstone unit comprising a body in one surface of which is defined a reentrant portion arranged to give the element at least similar resistance to impact on a further surface of the body when in use, as it would have if said one surface had no reentrant portion defined therein, the unit being locatable, in use, alongside a similar such unit for replacement or as an alternative to a conventional kerbstone of approximately 91 5mm length.
68. A kerbstone unit as claimed in claim 67 in which the unit comprises a building 3() element substantially as claimed in any of claims 1 to 63.
69. A method of forming a building element as described in any of the preceding paragraphs, the method comprising: charging a mould with gettable material; locating a press tool in the mould and compressing material in the mould to form a body having at least one recess formed in a surface thereof, and allowing the material to set sufficiently to retain its shape in the form of a building element; and removing the press tool from the mould. s
70. A method as claimed in claim 69, in which the recess is formed by a formation on the press tool.
71. A method as claimed in claim 70, in which the recess is formed as a reentrant I () portion as described in any of claims 1 to 68 above.
72. A building element substantially as hereinbefore described with reference to any of the accompanying drawings.
73. A kerbstone substantially as hereinbefore described with reference to any of the accompanying drawings.
74. A kerbstone unit substantially as hereinbefore described with reference to any of the accompanying drawings. 2()
75. A method substantially as hereinbefore described with reference to any of the accompanying drawings.
76. Any novel subject matter or combination including novel subject matter disclosed herein, whether or not within the scope of or relating to the same invention as any of the preceding claims.