GB2267676A - Moulded surfacing material incorporating natural stone - Google Patents

Abstract

A method of making a surfacing material such as a rectangular slab for use in domestic paving or other applications employs offcuts of natural stone embedded in a settable composition in a mould and, after moulding, the product is treated, for example by cutting, to expose clean surfaces of the natural material.

Description

METHOD OF MAKING SURFACING MATERIALS This invention relates to a method of making surfacing materials. An example of the application of the invention is to paving materials to be used in situations where so-called crazy paving has been used in the past, and for use in similar or related situations where a hardwearing surfacing material is needed for ground coverage to provide, for example, a clean surface for walking on. The invention is also applicable to surfacing materials for cladding buildings, related applications, and even more widely.

Previously known and proposed surfacing materials include crazy paving, natural york stone, and a whole range of synthetic surfacing materials, these latter including many based upon concrete compositions.

The shortcoRings of previously proposed and presently available surfacing materials include the labour-intensive nature of the process of laying crazy paving, the very high cost of york stone and other natural surfacing materials when supplied in acceptably large unit pieces, and the fact that presently available synthetic surfacing materials, including concrete moulded slabs of various kinds leave something to be desired in terms of appearance, at least to the extent that it is readily determinable visually and at a glance that these are indeed synthetic materials. This latter fact appears to arise despite the equally undoubted fact that concrete materials can be supplied in exactly the right colours to simulate at least some natural stone materials.A further factor relates to the need in paving and surfacing materials, at least for some applications, for sufficient strength to avoid cracking, and an acceptably smooth surface.

An object of the present invention is to provide a method of making a surfacing material, and indeed such a material thus-made which offers improvements in relation to one or more of the above-mentioned requirements or limitations of the prior art, or which provides a surfacing material incorporating natural materials, such as stone, which can be produced relatively cost-effectively, or such a material in which the natural material is readily treated to expose the attractive surface appearance of that material, or such a method in which the natural material is more efficiently bonded-into the whole, or which provides improvements generally.

According to the invention there is provided a method of making a surfacing material. It is hereby stated that not all features of this present paragraph are intended to be necessarily essential limitations of the broadest aspect of the invention claimed in the present application, or any application claiming priority therefrom. The method comprises providing pieces of natural material, providing also a slurry/mortar material to bond the pieces. The pieces are bonded to the slurry/mortar material in a mould. The moulded article is then treated to expose surfaces of the natural material.

The pieces of natural material may, for example, be offcuts of a natural stone material, such as york stone. Any other suitable and/or attractive natural material may be employed, or any mixture of such materials. By the use of off-cuts and the like, the cost of the natural material is very substantially reduced. For example, at the time of filing of the priority application the ratio of the cost of slabs of york stone, per square metre, to the cost of such stone provided on an off-cut basis is in the region of 10 to 1.

The slurry/mortar material will usually be concretebased. Any suitable such material may be employed, according to requirements. The expression "slurry/mortar" is intended to refer to any consistency of slurry or mortar, though at the time of filing the priority application it is thought that a consistency of more towards slurry is more likely to be appropriate than the consistency of conventional mortar.

As regards the moulding step, any suitable mould may be employed, the external dimensions of such being chosen in accordance with the requirements, so far as size is concerned, of the finished product. A typical application will be a rectangular slab provided in a range of sizes corresponding to those presently available for concrete slabs. The depth of the mould, corresponds to the required depth of the moulded element.

As regards the treatment step to expose the surface of the natural material, this will typically be by means of cutting, for example with conventionally available diamond or carbide-tipped cutting wheels, related cutting techniques, or indeed any more suitable techniques which may be or become available. Alternatively, it is envisaged that an alternative surface treatment step might be usable instead of a cutting technique, for example an abrasion step. In the case of a cutting step, and indeed likewise with an abrasion step, it will be understood that this step provides the finished product with a flat and smooth surface finish, eminently suitable for traditional surfacing tasks.

In a preferred embodiment of the invention, the method includes providing a base layer of concrete in the mould.

This base layer of concrete provides a strong flat base for the moulded product, the base not needing to include any natural material, as it is not seen in use.

After the base layer of concrete, or related product, the natural material is then inserted into the mould. This may be done by hand-placement followed, if necessary, by tapping the pieces into the already-present settable composition.

Then, the settable composition, such as mortar/slurry may be poured around or over the pieces of natural material.

The material in the mould may then be allowed to set or cure, and then follows the treatment step to provide an exposed surface on some at least of the pieces of natural material. The setting or curing period will usually comprise more than one day, or generally a period of 5 to 10 days, 7 days being preferred.

An important preferred feature of the invention is to provide the materials within the mould in a generally symmetrical configuration so that the treatment stage, when performed by cutting through the sandwich produces 2 elements each having a cut surface in which the natural material is exposed. These elements need not be symmetrical, but a symmetrical relationship has advantages. In the case where a concrete or other material base is provided in the moulded element, then, effectively, the natural material is provided in a "sandwich" between two such layers, and the cutting step is performed through the middle of the sandwich.

Thus, one aspect of the invention provides a moulded block, slab or surfacing element containing a natural material which has been cut or otherwise treated to expose that material.

Another aspect of the invention provides a surfacing material in which an embedded natural material is bonded by a settable composition and cut or otherwise treated to reveal a clean exposed surface.

A third aspect of the invention provides for the use of pieces of natural material in a settable composition and bonded thereto by that composition and treated to expose clean surfaces thereof.

There is a tremendous range of synthetic paving slabs on the market, but really none of these compares in quality with natural stone slabs. The present invention provides slabs that are visually 95 per cent natural material, to be produced. Initial costings indicate that these can be produced at less than one tenth of the cost of york stone slabs, per unit area.

Apart from york stone, other materials can be used in the method according to the invention, including limestone, slate, marble, granite etc.

If desired, slabs of a far greater size than conventional paving slabs can be produced. These would be suitable for wall-panelling applications.

Likewise, the thickness of the slabs can be varied in accordance with specific requirements.

The idea of filling the joints between the pieces of natural materials with slurry/mortar not only bonds these pieces together, but also creates a bond between the slurry/mortar or other settable composition and the natural material itself, thus eliminating the need for any other procedure to enhance adhesion.

The colour of the settable composition may be chosen to emphasise and contrast with the colour of the natural material, or to blend-in with it, the former emphasising the "crazy paving" effect, and the latter tending to give the effect of whole flag stones.

An embodiment of the invention will now be described by way of example with reference to the accompanying drawings in which : Fig 1 shows a prospective view of a moulded article forming an intermediate product in the method of the invention, the article being ready for dividing by sawing to produce two paving slabs; Fig 2 shows a paving slab, of the kind which can be produced from the article of Fig 1, after the cutting step; Fig 3 shows, on a much smaller scale, an area of paving laid with slabs produced in accordance with Figs 1 and 2, and showing on the left hand side slabs in which the "crazy paving" effect is emphasised, and on the right hand side slabs in which this effect is unemphasised.

As shown in Fig 1, a moulded article or block 10 comprises an integral bonded assembly of upper and lower concrete layers 12, 14, and an intermediate layer 16 of a natural material, such as york stone.

Block 10 is produced by a method comprising the following steps.

Firstly, a rectangular mould is provided, corresponding in size to the block 10. Into this mould, firstly, a layer of concrete is placed in the bottom of the mould, and having a thickness chosen according to the use of the finished product.

Domestic usage slabs would require less thickness than public footpaths.

Next, the concrete layer is compacted to the required thickness The third step comprises taking randomly-shaped pieces of a natural material, such as stone and laying these flat in the mould, on top of the concrete. This produces what might be called a "crazy paving" effect. The pieces of natural material are then tapped firmly into the concrete.

Fourthly, a mixture of sand and cement with any required colouring agent, is mixed into the form of a slurry and poured between the joints of the pieces of natural material. The surplus slurry is then removed.

Fifthly, a further layer of concrete is placed on top of the pieces of stone, and this layer is compacted, as in the case of the first layer.

The sixth step comprises allowing the concrete and slurry to set, for a period of, for example, about 24 hours, where upon the moulded article is released from the mould.

Finally, at from 5 to 10 days after commencing moulding, the block 10, with its upper and lower concrete layers 12, 14 and its intermediate layer 16 of natural material is sawn through, in a plane parallel to the upper surface 18 of the slab, thereby producing the cut slab 20, which is ready for use after curing has been completely finished.

In Fig 2, it can be seen that the pieces 22 of natural stone material fairly closely inters it with each other, and thus the lines 24 between them, in which the slurry composition is introduced, are relatively narrow. This is not an essential requirement of the invention, and it is to be understood that manual input, and thus cost, in relation to the product is not unduly increased by a requirement for closely interfitting pieces of stone or other natural material. In principle, relatively random dispositions of the pieces can be accepted, though manual placement of the pieces in generally one plane is to be preferred, for economy and other reasons.

As shown in Fig 3, an area 26 has been surfaced with slabs 20 produced in accordance with the above method. The slabs 20 in the left hand portion of the drawing have a slurry/mortar mix bonding the pieces of natural material together and which has a colour contrasting therewith, so as to emphasise the "crazy paving" effect. On the right hand side of the drawing the slurry/mortar mixture is chosen to match that of the natural material, so as to produce the effect of all natural material.

As seen in Fig 3, the slabs 20 are of generally rectangular configuration, varying in size considerably, according to requirements.

Amongst modifications which could be made in the above embodiment are the use of completely randomly-distributed natural stone material in the central layer 16, these being simply poured into the mould so as to be sandwiched between the upper and lower concrete layers. Provided it can be accepted that this technique will allow more of the concrete composition to be visible in the finished product, the result is greater simplicity of production, and thus lower cost.

Claims (16)

CLAIMS :

1 A method of making a surfacing material comprising providing pieces of a natural material, providing also a slurry/mortar material to bond the pieces, the method comprising causing the pieces to be bonded to the slurry/mortar material in a mould, and then treating the moulded article to expose surfaces of the natural material.

2 A method according to claim 1 wherein said natural material comprises offcuts of a natural stone material.

3 A method according to claim 1 or claim 2 wherein said slurry/mortar material is concrete-based.

4 A method according to any one of the preceding claims wherein the consistency of said slurry/mortar material is nearer to that of a slurry than to a conventional mortar.

5 A method according to any one of the preceding claims wherein the shape of said moulded article is rectangular.

6 A method according to any one of the preceding claims wherein the treatment step to expose the surface of the natural material comprises cutting.

7 A method according to any one of claims 1 to 5 wherein said treatment step to expose the surface of the natural material comprises an abrasion step.

8 A method according to any one of the preceding claims wherein a base layer of concrete is provided in the mould, and the natural material is then inserted into the mould and the settable composition is poured around or over the pieces of the natural material.

9 A method according to claim 8 wherein a second base layer of concrete is provided in the mould on top of said settable composition, so as to provide a symmetrical configuration in the moulded product.

10 A method of making a surfacing material substantially as described herein with reference to the accompanying drawings.

11 A method according to any one of claims 1 to 10 wherein said slurry/mortar material is replaced by an alternative settable composition.

12 A surfacing material made by a method according to any one of the preceding claims.

13 A moulded block, slab or surfacing element containing a natural material which has been cut or otherwise treated to expose said material.

14 A surfacing material in which an embedded natural material is bonded by a settable composition and cut or otherwise treated to reveal a clean exposed surface.

15 A method for the use of pieces of natural material in a settable composition and bonded thereto by that composition and treated to exposed clean surfaces thereof.

16 A moulded block, slab or surfacing element substantially as described herein with . reference to the accompanying drawings.