GB2286616A

GB2286616A - Indicator sheet for use when removing or laying a road surface

Info

Publication number: GB2286616A
Application number: GB9402969A
Authority: GB
Inventors: Stephen Bernard Murphy
Original assignee: Individual
Current assignee: Individual
Priority date: 1994-02-16
Filing date: 1994-02-16
Publication date: 1995-08-23
Anticipated expiration: 2014-02-16
Also published as: GB2286616B; GB9402969D0

Abstract

An indicator sheet for indicating the remaining thickness of road layer on removal of part of the road comprises a substantially flat sheet of material which produces a highly visible debris when damaged or broken up. The road suitably comprises a waterproof membrane (5) laid on a substrate (1), a sand carpet layer (4), the indicator sheet (6), a base layer (10) and a tarmacadam surface layer (3). The indicator sheet is preferably in the form of a plastics mesh structure. <IMAGE>

Description

BRIDGE DECK IDENTIFICATION SCREEN The present invention relates to a depth indicator for a road surface, and particularly, although not exclusively to a depth indicator for a road surface on a bridge deck.

Conventionally, when a road surface is laid over a road bridge deck, in order to protect the deck from water damage, a waterproof membrane is laid over the bridge deck structure prior to laying the road surface.

Over the waterproof membrane is then laid a "red sand carpet" layer, followed by a base layer and a wearing course, which usually comprises a black tarmacadam top surface. The "red sand carpet" comprises a red tarmac layer of depth around 50 mm.

When it is necessary to replace or remove the base layer and wearing course, or otherwise cut into the road surface, a motorised planing machine is used to cut into and remove the surface of the tarmac. The planing machine is provided with a plurality of grinding/sawing discs arranged in parallel on a cutting drum, which rotates to cut into the tarmac road surface. The debris from the road surface is ejected, via a conveyor, to an adjacent truck for removal from site.

As the planing machine cuts into the surface wearing course and base layer and the red sand carpet is reached, pieces of the red sand carpet are thrown up and collected by the planing machine and are visible by the operative working the machine as the red sand carpet debris is passed along a conveyor to the waiting truck. Appearance of the red sand carpet debris indicates that the drum is set to a depth such as to cut through the wearing course and base layer, into the red carpet, and giving a warning not to cut any deeper in order to avoid damage of the waterproof membrane underneath.

However, the above method of laying a red sand carpet under a tarmac road surface layer has a disadvantage that the red sand carpet is expensive, and is not particularly visually distinctive in debris form, when mixed in with debris of the wearing course and base layer.

Specific embodiments and methods of the present invention aim to alleviate some of the above problems.

According to one aspect of the present invention there is provided a method of laying a road surface comprising: laying a waterproof membrane; forming a lower road layer over the waterproof membrane; laying a sheet of indicator material over the lower road layer; and forming ar upper road layer over the indicator sheet and over the lower road layer.

Preferably the method comprises a method of laying a road onto the deck of a bridge.

According to a second aspect of the present invention, there is provided an indicator sheet for including in a road, for indicating a remaining thickness of road layer upon removal of part of the road, the indicator sheet comprising a substantially flat sheet of material selected so as to produce a highly visible debris when damaged or broken up.

Preferably, the indicator sheet comprises a mesh structure.

Preferably, the mesh comprises a plurality of apertures in te sheet, the apertures selected in area, length and width to allow bonding of the upper and lower road layers through the apertures.

Preferably, the indicator sheet comprises a light coloured material. This may make the indicator sheet highly or readily visible in debris form, when mixed in with debris of the upper and/or lower road layers.

Preferably, the indicator sheet comprises a plastics material.

Preferably, the indicator sheet comprises a relatively brittle material, which produces a plurality of highly visible particles or fragments, upon planing of or break up of the sheet.

The indicator sheet may be supplied on a roll. The indicator sheet may be rolled out over the surface of the lower road layer prior to laying of the upper road layer.

The indicator sheet may comprise a material selected for its thermo setting properties, so that the indicator sheet adopts a pliable state within a first range of temperatures encountered under normal outdoor weather conditions, for example in the range -10" to 300C, so as to be manageable in the form of a roll of sheet material in the first temperature range for laying over the lower road layer. The indicator sheet material may undergo a transition, to become relatively brittle when experiencing a temperature above the first range, for example, when a layer of hot tarmac, comprising the upper road layer, is formed on top of the indicator sheet. The heat contained in the upper road layer may cause the indicator sheet material to undergo a transition from the pliable, plastic state to a relatively brittle state.In the brittle state, the indicator sheet may readily fragment into a plurality of pieces or into a dust upon damage of the indicator sheet.

The indicator sheet may become brittle through ageing, over a period of time.

Preferably, the lower road layer comprises a black sand carpet.

The black sand carpet may comprise a black tarmacadam or road aggregate layer.

Preferably, the upper road layer comprises a wearing course and/or base layer.

The part of the road removed may comprise the base layer and wearing course, or just the wearing course, and the remaining thickness of road may comprise the sand carpet layer.

Preferably, the upper road layer comprises a wearing course, and may comprise a base layer.

Preferably, the indicator sheet is adhesive backed, so that when the sheet is laid onto the sand carpet, the sheet sticks to the sand carpet and will not blow away under force of wind, or will not significantly move when the upper road layer, eg. a tarmacadam layer, is laid over the indicator sheet. Suitably, the indicator sheet may be backed by a layer of tar. The layer of tar may be lightly coloured to enhance visibility of the tar layer.

The indicator sheet material may itself form a continuous waterproof membrane, for protecting the bridge structure from water damage.

Suitably, the indicator sheet is of a relatively light colour, compared to black tarmacadam.

Preferably the indicator sheet comprises a plastics sheet, suitably a uPVC sheet.

Specific embodiments and methods according to the invention may replace the use of a red sand carpet by way of introducing a self adhesive bright coloured plastics or similar mesh, overlaid onto a black sand carpet which is less expensive and more readily available than a red sand carpet.

Preferably the indicator sheet is self adhesive in order to roll out the sheet onto the sand carpet and for the sheet to itself steady until the remainder of the road is applied, notwithstanding damp conditions. Once in position, the sheet may resist distortion due to heat transmitted by the upper road layer material. Over a period of time, the road base and wearing course may become worn and require replacement. A planing machine may be set in order to recover the wearing course and base materials without affecting the black sand carpet, the black sand carpet protecting the waterproof membrane.

When the planer contacts the indicator sheet, the sheet preferably shreds becoming noticeable in the conveyor planing debris, and therefore indicating a depth of planing and thereby preventing deep cut damage to the membrane or deck structure.

For a better understanding of the invention, and to show how embodiments and example methods of the same may be carried into effect, reference will now be made, by way of example, to the accompanying diagrammatic drawings, in which: Figure 1 shows schematically a cross section of a bridge deck section surfaced according to a specific method of the present invention; and Figure 2 shows in schematic view a mesh according to specific embodiment of the present invention.

Referring to figures 1 and 2 of the accompanying drawings, a deck section of a bridge 1, for example a suspension bridge, carries a road 2. The road comprises a wearing course, eg. an upper road surface layer 3 of tarmacadam, a base layer 10, laid over a sand carpet layer 4, covering a waterproof membrane 5 which is laid directly onto an upper surface of the bridge deck structure 1. The sand carpet layer 4 comprises a conventional black tarmacadam road sub layer. Between the base layer and the sand carpet layer 4 is laid an indicator sheet 6 according to a specific embodiment of the present invention, in the form of a plastics mesh structure. The sand carpet need not be a red sand carpet, and for reasons of economy is preferably not a red sand carpet, but rather a black sand carpet.

Referring to figure 2 of the accompanying drawings, an indicator sheet 20 according to a specific embodiment of the present invention is shown, in the form of a mesh sheet. The mesh, which is adapted for laying on top of the sand carpet 4 covering the waterproof membrane 5, is preferably of a plastics material, and is capable of becoming relatively brittle with heat or ageing, so that upon damage by a planing machine, or by cutting with for example a circular saw, the mesh fractures into a multiplicity of small fragments, which are distributed by the action of the planer or saw, and collected with the debris of the wearing course and base layer.

The mesh is coloured a light or bright colour, for example fluorescent green or orange, so that the fragments of the mesh are highly visible against the dark background of the tarmacadam surface layer. Preferably the mesh is of a thickness in the range 2 mm to 2 cm, and may be formed in an elongate sheet which may be supplied on a roll. Preferably the roll is of width of the order of 2 to 5 metres, such that when the sand carpet 4 is laid, the mesh can be rolled out over the sand carpet prior to laying of the base layer and wearing course. A suitable plastics material may be uPVC.

The indicator sheet may comprise a material selected for its thermo setting properties, so that the indicator sheet may be pliable within a first range of temperatures encountered under normal outdoor weather conditions, for example in the range -10" to 30"C, so as to be manageable in the form of a roll of sheet material, in the first temperature range for laying over the lower road aggregate layer, 4, and may become relatively brittle when in contact with the hot sand carpet, or when a layer of hot tarmac, comprising the upper road surface layer or wearing course, is formed on the laid out indicator sheet, the heat contained in the sand carpet or road surface layer causing the indicator sheet material to undergo a transition from a pliable, plastic state to the relatively brittle state.In the brittle state, the indicator sheet may readily fragment into a plurality of pieces or into a dust upon damage of the indicator sheet.

Preferably, the indicator sheet is supplied precoated with an adhesive backing, to allow the sheet to readily adhere to the sand carpet. A suitable adhesive backing may comprise tar or bitumen.

In use, a road surface can be laid according to a specific method of the present invention as follows.

Firstly the waterproof membrane 5 is laid over the bridge deck structure 1, and the sand carpet layer 4 is laid over the waterproof membrane in conventional manner.

Then an indicator sheet according to a specific embodiment of the present invention is laid flat on the upper surface of the sand layer 4, to form a substantially continuous membrane covering the whole of the sand surface. The sheet may be laid in strips from a plurality of rolls, or may be laid in a single roll, or alternatively may be laid in sheets. Preferably the sheet covers the whole surface of the sand 4, but alternatively the sheet may be distributed in spaced apart strips or sheets, over the surface of the sand carpet, at periodic distances, for example spaced apart by 1 or 2 feet. The base and upper road surface tarmac wearing course layer 3 is then laid in conventional manner, over the sheet 6.

The road, when formed may then be used over its conventional lifetime. When the road surface needs to be removed, a planing machine may then be set to cut into the wearing course and base layer. The depth of cut of the planing machine may be gauged by the appearance of small fragments of the mesh structure in the debris of the cut road, giving an indication visually of the depth of planing, and thus avoiding damage to the waterproof membrane underneath.

Where the indicator sheet is provided in the form of a mesh, the size and spacing of the apertures in the mesh are preferably selected so as to provide adequate adhesion between the base layer and/or wearing course and the underlying sand carpet, by virtue of connection of the sand carpet and the base layer and/or wearing course via the apertures. Different meshes, having different sizes of aperture compared with mesh membrane wall may be provided in different embodiments of the indicator sheet, for use at different road locations. For example, an area of road near a set of traffic lights may require a different size aperture mesh to a straight stretch of motorway, in order to provide greater bonding between the wearing course and sand carpet where the road surface undergoes greater lateral forces cause by vehicles braking.

Whilst a method of producing a road has herein been described with reference particularly to a road formed on a bridge deck, a method of laying a road and/or indicating the depth of removal of a road surface in accordance with the invention is not necessarily restricted to use on bridges.

Specific embodiments and methods of the present invention may have an advantage of providing a cheaper road surface for a bridge structure, since the sand layer 4 may comprise ordinary building sand or black sand, rather than more expensive red sand. This may significantly reduce the cost of laying the road surface.

A further advantage is that, as the mesh throws up a large number of fine highly visible dust particles when sawn or cut, much better indication of depth may be obtained than with using a red sand layer.

Whilst a specific embodiment in the form of a mesh is described herein above, other embodiments of the invention may include a continuous sheet membrane of a brittle material, which easily fragments upon the mechanical action of sawing, cutting or grinding the material to produce a highly or brightly coloured fine dust or particles upon the incidence of the mechanical action, which readily transported to the surface of the road, to act as a cut depth indicator.

The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings), may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

1. A method of laying a road surface comprising: laying a waterproof membrane; forming a lower road layer over the waterproof membrane; laying a sheet of indicator material over the lower road layer; and forming an upper road layer over the indicator sheet and over the lower road layer.

2. A method of laying a road surface as in claim 1, comprising a method of laying a road onto the deck of a bridge.

3. An indicator sheet for including in a road laid according to the method of any one of claims 1 or 2, for indicating a remaining thickness of road layer on removal of part of the road, the indicator sheet comprising a substantially flat sheet of material selected so as to produce a highly visible debris when damaged or broken up.

4. An indicator sheet according to claim 3, comprising a mesh structure.

5. A mesh according to claim 4, comprising a plurality of apertures in the sheet, the apertures selected in area, length and width to allow bonding of the upper and lower road layers through the apertures.

6. An indicator sheet according to any one of claims 3 to 5, comprising a light coloured material, which makes the indicator sheet highly or readily visible in debris form, when mixed in with debris of the upper and/or lower road layers.

7. An indicator sheet according to any one of claims 3 to 6, comprising a plastics material.

8. An indicator sheet according to any one of claims 3 to 7, comprising a relatively brittle material, which produces a plurality of highly visible particles or fragments, upon planing of or breaking up of the sheet.

9. An indicator sheet according to any one of claims 3 to 8 supplied on a roll, the indicator sheet may be rolled out over the surface of the lower road layer prior to laying out of the upper road layer.

10. An indicator sheet according to any one of claims 3 to 9, comprising a material selected for its thermo setting properties, so that: the indicator sheet adopts a pliable state within a first range of temperatures encountered under normal outdoor weather conditions, for example in the range -10 C to 300C, so as to be manageable in the form of a roll of sheet material in the first temperature range for laying over the lower road layer; the indicator sheet material undergoes a transition, to become relatively brittle when experiencing a temperature above the first range, for example, when a layer of hot tarmac, comprising the upper road layer, is formed on top of the indicator sheet;; the heat contained in the upper road layer causes the indicator sheet material to undergo a transition from the pliable, plastic state to a relatively brittle state; and in the brittle state the indicator sheet readily fragments into a plurality of pieces or into a dust upon damage of the indicator sheet.

11. An indicator sheet according to any one of claims 3 to 10 which becomes brittle through ageing over a period of time.

12. A lower road layer laid according to the method of either of claims 1 or 2, comprising a black sand carpet.

13. A black sand carpet according to claim 12, comprising a black tarmacadam or road aggregate layer.

14. An upper road layer laid according to the method of either of claims 1 or 2, comprising a wearing course and/or base layer.

15. A part of a road to be removed as claimed in claim 3, comprising the base layer and wearing course, or just the wearing course, and the remaining thickness of road comprises the sand carpet layer.

16. An upper road layer laid according to the method of claim 1, comprising a wearing course and a base layer.

17. An indicator sheet according to any one of claims 3 to 11 with an adhesive back, such that when the sheet is laid onto a sand carpet, the sheet sticks to the sand carpet and will not blow away under force of wind, or will not significantly move when the upper road layer, e.g. a tarmacadam layer is laid over the indicator sheet.

18. An indicator sheet according to claim 17 backed by a layer of tar, the layer of tar is lightly coloured to enhance visibility of the tar layer.

19. An indicator sheet according to claim 3 which forms a continuous waterproof membrane for protecting the bridge structure from water damage.

20. An indicator sheet according to claim 19 which is of a light colour compared to black tarmacadam.

21. An indicator sheet according to either of claims 19 or 20 comprising a plastics sheet, suitably a uPVC sheet.

22. A sheet of indicator material and a method of laying a road surface according to any one of the preceding claims to replace the use of a red sand carpet by way of introducing a self-adhesive bright coloured plastics or similar mesh, overlaid onto a black sand carpet.

23. An indicator sheet according to any one of claims 3 to 11 or 17 to 21, in which the sheet is self adhesive in order to roll out the sheet onto the sand carpet and for the sheet to steady itself until the remainder of the road is applied, notwithstanding damp conditions, in position the sheet resists distortion due to heat transmitted by the upper road layer material.

24. A method of removing a road surface in which a planing machine is set in order to recover the wearing course and base materials without affecting the black sand carpet, the black sand carpet protecting the waterproof membrane. When the planer contacts the indicator sheet, the sheet preferably shreds, becoming noticeable in the conveyor planing debris, and therefore indicating a depth of planing and thereby preventing deep cut damage to the membrane or deck structure.

25. A method of laying a road surface as hereinbefore described with reference to the accompanying drawings.

26. An indicator sheet as hereinbefore described with reference to the accompanying drawings.

27. A method of removing a road surface as hereinbefore described with reference to the accompanying drawings.