GB2331540A - Pavement construction - Google Patents

Abstract

A pavement construction and a method of forming a pavement construction is intended to give rise to a durable construction which has an attractive surface finish. This is achieved by laying aggregate X which is a mixture of stone and binder on a base C. Mortar M is then applied to the mixture, the mortar comprising cement and microsilica particles. The mortar covers the surface and penetrates into voids within the aggregate mixture. The surface is then ground to expose the stone and provide a smooth attractive finish simulating terrazo tiling.

Description

5353GB 1 2331540 PAVEMENT CONSTRUCTION This invention relates to pavement

constructions and in particular, but not exclusively, to flooring intended to have a hard durable construction but which is also attractive to the eye.

1 Hitherto pavement constructions for shopping areas, hotels and other public areas have used tiles to achieve an attractive finish but such surfaces are expensive to create due to the need to lay the tiles individually over large areas which may be irregular in shape, incorporate slopes and steps and which may require to be load bearing for wei 11 lity vehicles or other Z) loads.

It has been proposed to provide load bearing surfaces incorporating asphalt aggregates which are covered with a layer of mortar which are relatively easy to lay but which do not present an attractive surface finish.

An object of the invention is to provide a pavement construction which obviates disadvantages of existing constructions.

According to the invention a method of laying a pavement comprises applying a layer of an aggregate to a base layer which aggregate is a mixture of stone particles or pieces and a binder, such as asphalt, so that the mixture has voids within the layer, applying mortar to the layer of aggregate mixture so that the mortar covers said layer and enters voids within said mixture, allowing the mortar to set, and grinding down the resulting surface of aggregate and mortar so that mortar and aggregate are exposed at said surface to give a relatively smooth surface with visible aggregate and mortar.

The binder used maybe clear or translucent asphalt which has a light colour compatible with the desired further surface finish rather than a black or dark finish of conventional asphalt.

5353GB 2 Preferably the mortar comprises microsilica material, cement, water, with some quartzsand and plasticiser.

The microsilica material includes silica particles of very small size. These particles may be one hundred times smaller in size than the particles of cement in the mortar. This admixture of cement and silica particles improves the packing density of the mortar compared with conventional cement mortar. However other mortar may also find application in the method.

Preferably the mortar layer is applied with a curing agent to obtain controlled hardening of the mortar layer.

Conveniently after an initial grinding operation of the aggregate and mortar a further 0 application of mortar may be made to the surface to ensure an even finish to the surface. Such further application may be followed by a further surface grinding and polishing application to obtain the desired surface finish, taking account of the desired properties of the pavement, such as slippiness and polish.

By the selection of a suitable mortar colour and stone for the stone particles or pieces in the aggregate a pavement surface may be achieved having the desired characteristics, such as the 0 appearance of terrazzo flooring. This is obtained without dark asphalt material being exposed at the surface.

In most cases mortar in a layer in the range of 2-6cms thick is sufficient. This would normally be laid on a layer of aggregate mixture of some 10-20cms thickness. To obtain a hard impervious base the asphalt/aggregate layer may be applied to a layer of 10-30cms of concrete or bitumen which in turn would be conveniently laid on a layer of gravel of, say, 1030cms thickness. The sub layers and their thicknesses would depend on the loads and duties required of the pavement composition.

5353GB 3 Laying of the asphalt aggregate mixture can be by conventional equipment for laying asphalt 0 W for pavement construction and the mortar layer can be applied to the asphalt aggregate by the use of a pump and manual spreading using, say, rubber edged scrapers. Moreover conventional surface grinding machines can be used for achieving the desired finish.

The pavement finds particular application in situations in which an attractive surface finish is required such as in shopping areas, hotels and other situations in which a decorative effect, usually achieved by tiling, is required.

According to another aspect of the invention a pavement construction made according to the method of the invention, comprises a layer of aggregate which is a mixture of stone particles or pieces and a binder on which mortar is laid, the mortar filling voids in the mixture, the construction having a surface which comprises ground down stone particles or pieces in the aggregate to provide a smooth surface of stone and mortar.

The mortar comprises cement and microsilica particles of very small size.

Optionally a flirther superficial upper layer of mortar is present which has been ground down to produce the finished pavement surface.

The binder may be asphalt and the asphalt may incorporate clear bitumen which is translucent bitumen not having a dark or black colour, or it may be dark bitumen.

It will be appreciated that the initial grinding operation of the surface can give rise to some unevenness which may call for a flu-ther mortar layer to be applied to the surface to ensure the requisite smoothness for the finished surface. Thereafter a further grinding operation produces a surface having the desired slip characteristics and polished finish. Such finish will depend upon the location and duties which the pavement has to perform.

5353GB 4 Further features of the invention will appear from the following description of an

0 embodiment of the invention given by way of example only and with reference to the drawings, in which:

Ficy. 1 shows a typical pavement construction, not to scale, and 0 Figs 2, 3 and 4 show stages in creating the desired surface for the pavement construction.

In Fig I there is shown an example of pavement construction according to the invention. In this case the construction includes a sub base A, a gravel base G applied over the sub base A and a further layer C applied over the gravel base G. A further layer C may be a layer of lean mix concrete for obtaining a strong pavement construction when pavement loads will be heavy and the layer C may be of a thickness according to the anticipated load. Alternatively the layer C may comprise a bituminous asphalt base course when lighter loads are anticipated or the layer C may be omitted depending on anticipated loadings, sub base conditions or the required flexibility of construction.

Typically the gravel layer G will have a thickness of 10-25cms. The layer C may be formed of concrete having a thickness of 10-25cms or of bituminous asphalt of a similar thickness or of a thickness around 16cms. The base A may have a thickness of 10-30cms or may be the actual ground surface.

The layers G and C may be laid by conventional methods which are not part of the present invention, for example the gravel layer may be tipped and levelled, the concrete layer C may be poured and levelled or, if the layer C is of asphalt, it may be laid by a conventional asphalt laying machine or paver, or by hand in more inaccessible areas.

Over the layer C is laid an binder and stone aggregate material to form layer X of 10-20MM in thickness, the aggregate including particles, pieces or other discrete stone material selected according to the desired finish of the pavement and of a size between 6-15nim to give a void ratio of about 25% within the matrix. By way of example the stone may be granite chippings 5353G9 of which the granite is of mixed colours and composition, such pieces or particles being dispersed throughout the mixture. The mixture may incorporate binder of conventional dark bitumen. Alternatively the binder used may be so-called "clea?'bitumen which is of light colour with translucent properties.

The layer X is applied to the layer C by conventional asphalt laying equipment to produce 0 a layer having a thickness in the range 10-20cm. in which-stone particles or pieces are exposed in the upper surface surrounded by and, to some extent, covered by the asphalt material, see Fig 2.

The binder material in the layer X may be asphalt incorporating bitumen of the conventional dark or black kind or the asphalt may contain "clear" bitumen or bitumen having translucent properties and which is of light colour. There is next applied, after cooling of the asphalt, 0 0 as an upper layer on the layer X a relatively thin layer M of mortar. The layer M may be cernentitious mortar to which pigment may have been added according to the desired colour of the surface finish. Preferably the mortar is of a special kind incorporating microsilica particles which are very small sized particles of silica (up to one hundred times smaller than the associated cement particles) which ensures a higher packing density of the mortar. In particular such mortar comprises Portland cement, microsilica, superplasticiser and fine quartz sand. Of these components the microsilica may be amorphous silicon dioxide produced as a product of filtered smoke condensation from the production of ferrosilicium and is in the from of very small spherical particles. The superplasticiser may be sodium polydiniaphtenemethanesulphonate. The microsilica particles replace most of the conventional sand used in mortar mixes and the microsilica particles are of a mean diameter of around 0. 1 micrometer and of spherical shape. The microsilica particles which react with calcium dioxide in the cement and provides a microstructure which is very dense and becomes denser in the hydration phase. Alternatively a polymer cement mortar may be used. The mortar may be of the kind sold under the trade mark DENSIPHALT by DENSIT A/S.

5353GB 6 The mortar layer M may be applied in semi-liquid form first pumping the mortar onto the surface and then using a kind of brush having a rubber edge by which the mortar is spread over the layer X penetrating the surface voids in the asphalt. After application the mortar M may be applied with a curing compound to achieve curing of the mortar at the desired rate to achieve a relatively smooth surface without cracking or other deterioration. (A suitable curing compound is DENSIT (registered trade mark) from Densit A/S). It will be seen that the layer M envelopes and surrounds any particles or pieces -of stone in the layer X which stand proud of the surface so that such protrusions are incorporated in the layer M. If necessary, with certain kinds of mortar, vibration may be applied to the mortar to ensure that full penetration into the surface voids is achieved, for example by a vibrating roller, but this step is not usually necessary as the mortar will penetrate the voids by flowing into the voids.

After applying the layer M the mortar sets and a grinder is applied to the surface to grind down the mortar and protruding stone pieces or particles so that a relatively smooth surface is produced on which the stone particles or pieces interspersed over the area of mortar, see Fig 4, are exposed and visible.

After this grinding operation there may be certain surface irregularities and spaces and to achieve a smoother surface a further application of mortar may be made to the surface of layer M to even out the surface using a similar application method to the previous mortar surface.

When the further mortar has cured a final grinding operation is applied to the surface and the surface is polished as required. Such grinding takes account of whether the surface needs to be anti-slip or have other surface characteristics according to the purpose of the pavement.

In Fig 2 there is shown enlarged the layer X after it has been laid in which there are prominent on the surface the stone pieces S protruding above the level of the associated asphalt. In Fig 3 there is shown the surface of Fig 2 to which a layer of mortar M has been applied. In Fig 4 is shown the surface of Fig 3 after grinding the layer M and pieces S.

53530t3 7 It will be seen that the pavement composition provides the ability to change the colour of the 0 surface, its texture, and the pattern achieved so as to achieve a surface pattern required for a particular application. In addition a seamless continuous surface is achieved which can be laid up to the edges of the pavement and can be blended into ramps and other inclined areas, or steps, and it is also possible to repair discrete areas of the surface by removing the material from that area and re-laying and treating the area in the described sequence. Moreover the pavement provides the possibility of being very hard wearing and load bearing. It is quick to lay and has a short curing time. The surface, beingjointless, is also impermeable and cost effective, especially compared with the alternative methods of tiling surfaces currently employed in a shopping environment in stores, shopping malls, and in hotels etc. The surface can be provided with the desired anti-slip characteristics which can be varied over the pavement. At the edges the pavement can be provided with a similar surface to give edge coving or other upstanding profiles. Similarl steps can be provided with the nose and edge 1 y details of a similar finish. Conventional equipment can be used to lay the layers of the composition and to give the desired finish to the upper surface. The surface is resistant to attack by products such as petroleum, most acids and is sealed and impermeable before and after it is finished. It is also particularly hygienic and easily cleaned.

53534,ti 8

Claims (12)

CLAIMS 1. A method of laying a pavement comprises applying a layer of an aggregate to a base layer 1 In, which aggregate is a mixture of stone particles or pieces and a binder, such as asphalt, so that the mixture has voids within the layer, applying mortar to the layer of aggregate mixture so that the mortar covers said layer and enters voids within said mixture, allowing the mortar to set, and grinding down the resulting surface of aggregate _and mortar so that mortar and aggregate are exposed at said surface to give a relatively smooth surface with visible aggregate and mortar.

1

2. A method according to claim 1 wherein the mortar comprises cement, microsilica particles of very small size, and water.

3. A method according to claim 2 wherein the microsilica particles are spherical in shape having a mean diameter of the order of 0. 1 micrometer.

4. A method according to claim2 or 3 wherein the microsilica comprises amorphous silicon dioxide.

1.

1

5. A method according to any one of the preceding claims wherein the aggregate mixture comprises bitumen and/or copolymer and stone pieces or particles and the aggregate is firmed by roller after the layer of aggregate is laid down.

6. A method according to any one of the preceding claims wherein the mortar is applied in semi-liquid form and is smoothed over the surface of the aggregate mixture to penetrate into the voids within the mixture layer.

7. A method according to any one of the preceding claims wherein the aggregate mixture r> and the mortar has a thickness in the range of 10-25cms.

8. A pavement construction made according to the method of the invention, comprising a 0 5353GB 9 layer of aggregate which is a mixture of stone particles or pieces and a binder on which mortar is laid, the mortar fillin voids in the mixture, the construction having a surface which 9 0 comprises ground down stone particles or pieces in the ag egate to provide a smooth surface Ogr of stone and mortar.

9. A pavement construction according to claim 8 wherein the mortar comprises cement and microsilica particles of very small size.

10. A pavement construction according to claim 9 wherein the microsilica particles are spherical having a mean diameter of the order of 0. 1 micrometer and the microsilica comprises amphorous silica dioxide.

11. A pavement construction according to claim 8, 9 or 10 wherein the layer of aggregate mixture and the associated mortar has a thickness in the range 2-20cms.

12. A pavement construction substantial as described with reference to the drawings.