GB2501564A

GB2501564A - Reinforcing structure, eg for paved structures, with bamboo fibres

Info

Publication number: GB2501564A
Application number: GB1220439.2A
Authority: GB
Inventors: Matthew James Inman
Original assignee: ROAD SOLUTIONS Ltd
Current assignee: ROAD SOLUTIONS Ltd
Priority date: 2012-04-28
Filing date: 2012-11-14
Publication date: 2013-10-30
Anticipated expiration: 2032-11-14
Also published as: GB2501541A; GB201220439D0; GB201207576D0; EP2657402A1; GB2501564B; EP2657402B1

Abstract

A reinforcing structure 200 eg for a concrete or asphaltic road (101, fig.1), pavement or car park, comprises a first set of reinforcing elements 201A-201C and a second set of reinforcing elements 202A-202C connected together to form a grid 203. The reinforcing elements 201, 202, eg in the form of bundles, are formed from a composite material containing bamboo fibres, filaments or yarns in a binding matrix, eg a pre-impregnated (pre-preg) material. The binding matrix may comprise polymer modified asphalt, synthetic rubber, bamboo sap or resin, natural rubber. The reinforcing elements 201,202 may be connected by stitching 207, 209, by adhesive or by the binding matrix itself. The composite material may contain other fibres, eg of carbon, glass or polymeric material eg viscose. The reinforcing elements may be coated, eg with polymer modified asphalt, synthetic rubber or PVC, to prevent abrasion and protect from heat. A carrier layer, eg of geotextile material or bamboo-derived material, may be attached to one or each side of the grid.

Description

Reinforcing Structure

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority from United Kingdom Patent Application No. 12 07 576.8, filed 28 April 2D12, the entire disclosure of which is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a reinforcing structure and a method of manufacture of the same. The invention further relates to a paved structure including such a reinforcing structure.

2. Description of the Related Art

Reinforcing structures in the form of geosynthetics are currently used in paved structures to provide increased strength and function. Geosynthetics of this type have been developed with the aim of retarding the onset of reflective cracking thereby extending the maintenance cycle of asphalt overlays. They are known to provide sealing, reinforcement, stress relief and adhesive bonding. Conventional geosynthetics are composed of various man-made products and used as reinforcement within asphalt pavements. A problem with such man-made products is that they are not environmentally friendly and often suffer from large carbon footprints. Furthermore, these man-made products often include materials which are harmful to operatives in the field and require additional health and safety measures to be in place during manufacturing procedures and production methods.

BRIEF SUMMARY OF THE INVENTION

According to an aspect of the present invention, there is provided a reinforcing structure comprising: a first set of reinforcing elements, each said reinforcing element arranged substantially parallel to other reinforcing elements of said first set; a second set of reinforcing elements arranged at an angle to said first set of reinforcing elements; said first set of reinforcing elements are connected to said second set of reinforcing elements by a connection means; wherein each said reinforcing element is formed of a composite material comprising a plurality of bamboo fibres and a binding matrix.

According to a further aspect of the present invention, there is provided a paved surface comprising: a reinforcing structure comprising a first set of reinforcing elements arranged at an angle to a second set of reinforcing elements; said first set of reinforcing elements and said second set of lb reinforcing elements are connected by a connection means and each said set comprises plurality of bamboo fibres and a binding matrix; a first layer suitable for receiving said reinforcing structure; and a second layer configured to overlay said reinforcing structure, such that said reinforcing structure is positioned between said first layer and said second layer According to a still further aspect of the present invention, there is provided a method of manufacturing a reinforcing structure, comprising the steps of: extracting a plurality of bamboo fibres from natural bamboo by means of mechanical extraction; refining said plurality of bamboo fibres such that said plurality of bamboo fibres are substantially aligned; impregnating said plurality of bamboo fibres with a binding matrix to form a reinforcing element; arranging a first set of reinforcing elements such that each reinforcing element is substantially parallel to other reinforcing elements of said first set; arranging a second set of reinforcing elements at an angle to said first set of reinforcing elements; and connecting said first set of reinforcing elements and said second set of reinforcing elements together with a connection means.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows a typical installation scene for applying reinfordng products to a road; Figure 2 shows a portion of a reinforcing structure embodying an aspect of the present invention; Figure 3 shows an alternative embodiment to the reinforcing structure shown in Figure 2; Figure 4 shows a portion of a reinforcing structure suitable for use in the application of Figure 1; Figures 5a and 5b show a cross sectional view and an exploded isometric view respectively of a reinforcing structure comprising a single carrier layer; Figures 6a and 6b show a cross sectional view and an exploded isometric view respectively of a reinforcing structure comprising a first carrier layer and a second carrier layer; Figure 7 shows a cross sectional view of a typicai asphaltic paved structure embodying the present invention; Figure 8 shows a flow chart describing a method of producing a paved surface; Figure 9 shows an alternative reinforcing structure for use in the paved structures as previously described; Figure 10 shows a further example of a reinforcing structure for use in the paved structure of Figure 7; Figure 11 shows a flow chart detailing the manufacture of a reinforcing structure.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

Figure 1 An example embodying the present invention is shown in Figure 1.

Figure 1 shows a typical installation scene for applying reinforcing products to a road 101. It is appreciated that, in an alternative embodiment a pavement, car park or other paved surface can be substituted for the road. In the course of this specification, a paved surface is taken to mean a pavement car park, road or other firm surface suitable for walking or travelling on. The paved surface may comprise concrete or asphaltic material which may be planed or milled. As shown in the example of Figure 1, a reinforcing structure 102 is laid over a prepared layer 103. In the embodiment shown, reinforcing structure 102 is in the form of a grid comprising a plurality of bamboo strands and is configured to be positioned at any depth or layer of the road. In the embodiment shown in Figure 1, layer 103 is of the form of a previously laid paved structure. In an alternative embodiment, base layer 103 is a freshly laid layer of asphaltic mixture.

Reinforcing structure 102 is supplied to the site in rolls of the material before being rolled out and laid flat onto the surface of layer 103. The reinforcing structure is laid flat either by hand or by a suitable mechanical applicator. Once the reinforcing structure 102 has been laid, it can be brushed or rolled and smoothed as required to remove any ripples in the surface. It can also be cut on site as required, particularly around any ironworks present.

Once laid, one or more overlaying layers are positioned on top of reinforcing structure 102 to finalise the road structure. The overall road structure and method of laying the road will be discussed in further detail in Figures 7 and 8.

Figure 2 A portion of a reinforcing structure 200 suitable for use in the application s of Figure 1 is shown in Figure 2. Reinforcing structure 200 comprises a first set of bundles 201 which includes bundle 201A, bundle 201B and bundle 201C.

Bundle 201A is arranged substantially parallel to bundle 201B and bundle 201C.

Reinforcing structure 200 further comprises a second set of bundles 202, which includes bundle 202A, bundle 202B and bundle 202C. Second set of bundles 202 is arranged substantially perpendicular to the first set of bundles 201 in a grid 203. Grid 203 defines a plurality of holes 204, such as hole 204A. Hole 204A has a width indicated by arrow 205 and a length indicated by arrow 206. In the present embodiment, both the width and the length are substantially similar in size and are greater than 4mm in size.

Further, the width and the length are preferably less than 100 millimetres in size. For example, in an embodiment, the hole size is 12.5mm x 12.5mm. In an alternative embodiment the hole size is 25mm x 25mm and in a still further embodiment the hole size is 50mm x 50mm.

It is appreciated that alternative reinforcing structures that achieve the same objective include holes which are substantially rectangular in shape such that the width is greater than the length or vice versa.

In the embodiment shown, the outer diameter of each one of the first set of bundles 201 is 10mm, but in alternative embodiments, the bundles have a diameter between 2 and 30 millimetres. Similarly, the outer diameter of each one of the second set of bundles 202 is 10 millimetres, and, in a preferred embodiment is between 2 and 30 millimetres. The specific dimension selected is dependent on the structural requirements of the application in which the reinforcing structure 200 is used for.

Reinforcing structure 200 further comprises a connection means 207 which maintains the first set of bundles 201 and the second set of bundles 202 in grid 203. In this illustrated example, connection means 207 is in the form of stitching at a crossover point, such as crossover point 208 of bundle 201A and bundle 202A. Similarly, bundle 201C and 202C are connected together by connection means 209 (in the form of stitching) at crossover point 210. The stitching comprises a separate piece of material which is tied around the bundles to maintain the bundles in position. In this particular embodiment, the material used for the stitching is derived from bamboo. It is appreciated that similar stitching may or may not be present at any one of the crossover points as shown. It is further appreciated that the stitching may be any other suitable material which will maintain the bundles in position.

Each of the bundles which make up first set of bundles 201 and second set of bundles 202 comprise a plurality of strands of material derived from bamboo. In manufacture, a plurahty of strands of material derived from bamboo are obtained and combined to form each bundle. In this illustrated example, therefore, all of the strands of the material comprise a material derived from bamboo.

In some applications of the product, any one of bundles 201 or bundles 202 is provided with a coating which prevents abrasion of the strands when in use. The coating is also configured to protect the strands from excessive heat generated from an overlay of asphalt. An example of the coating is an asphaltic coating and in one such example the coating is polymer modified asphalt. However, in an alternative embodiment, the coating comprises synthetic rubber, for example SBR (styrene butadiene rubber). In a further embodiment, the coating is a polymeric coating such as polyvinyl chloride (PVC), polypropylene (PP) or polytetrafluoroethylene (PTFE).

It is appreciated that, while the portion of reinforcing structure 200 shows a first set of bundles 201 comprising three bundles, in alternative embodiments further bundles are present, with each bundle being positioned substantially parallel to other bundles of the same set. In a particular embodiment only two bundles are present which are arranged in a similar manner.

In the embodiment of Figure 2, the strands of each bundle comprise a fibre or plurality of fibres of bamboo material. It is appreciated however, that in alternative embodiments, the strands of bamboo comprise filaments or a plurality of filaments. Alternatively, the strands of bamboo may comprise a yarn or a plurality of yarns.

is While the embodiment herein describes bundles made entirely from material derived from bamboo, in an alternative embodiment, the bundles 201 and 202 further comprise a second material which is combined with the bamboo strands. This second material is any suitable structural material, such as carbon fibre, fibre glass or a polymeric material such as viscose fibres or rayon.

Figure 3 An alternative embodiment to the reinforcing structure shown in Figure 2 is shown in Figure 3. In this illustrated example, a portion of reinforcing structure 300 comprises a first set of bundles 301 and a second set of bundles 302. Each bundle (301A, 301B, 301C, 301D, 301E and 301F) is arranged substantially parallel to each of the other bundles of the set. In this embodiment, each bundle is also paired with another bundle, that is, for example, bundle 301A is paired with bundle 301B such that bundle 301A is positioned a shorter distance from bundle 301B than to any of the other bundles. Bundle 301A and bundle 301B are also arranged substantially parallel to each other. Each pair is also arranged substantially parallel to the other pairs of the reinforcing structure 300.

Second set of bundles 302 is also arranged such that each bundle (302A, 302B, 302C and 302D) has been paired with another bundle of second set 302. For example, bundle 3024 is paired with bundle 302B and bundle ID 302C is paired with bundle 302D. Second set of bundles 302 is arranged substantially perpendicular to the first set of bundles 301 First set of bundles 301 and second set of bundles 302 are also arranged in a grid 303. Grid 303 defines holes, such as hole 304A and hole 304B. Hole 304A has a width 305 and a length 306. As shown, the width and length are substantially similar in size and define a substantially square hole. In the present embodiment the holes are at least 4mm x 4mm square, and, preferably, less than 100mm x 100mm square. In an example, the holes are 12.5mm x 12.5mm in size. In another embodiment the hole length is 25mm and the hole width is 25mm. In a further embodiment, the size of the hole is 50mm x 50mm.

In alternative examples it is appreciated that the holes are substantially rectangular and the widths and lengths are unequal distances. Both the widths and lengths, however, are preferably between 4 millimetres and 100 millimetres in size.

In order to maintain first set of bundles 301 and second set of bundles 302 in grid 303, connection means 307 is used. Connection means 307 is in the form of stitching, with stitches used at crossover points, such as crossover

I

point 308, of any one of the first set of bundles 301 with any one of the second set of bundles 302. In this illustrated example, crossover point 308 indicates where bundles 302C and 302D cross bundles 301E and 301F. As shown, six separate stitches are used to maintain the grid in position. It is appreciated that any other number of stitches can be used as appropriate. The material used for the stitching is a material derived from bamboo.

Each of the bundles shown in Figure 3 comprises a plurality of strands of material derived from bamboo. In the example shown, the strands of material are entirely composed of fibres of bamboo.

In some applications of the product, any one of bundles 301 or bundles 302 is provided with a coating which prevents abrasion of the strands when in use. The coating is also configured to protect the strands from excessive heat generated from an overlay of asphalt. An example of the coating is an asphaltic coating and in one such example the coating is polymer modified asphalt. However, in an alternative embodiment, the coating comprises synthetic rubber, for example SBR (styrene butadiene rubber). In a further embodiment, the coating is a polymeric coating such as polyvinyl chloride (PVC), polypropylene (PP) or polytetrafluoroethylene (PTFE).

In an alternative embodiment to that shown in Figure 3, the strands which make up the bundles comprise both material derived from bamboo and fibre glass. The fibre glass is similar to the type used in conventional paved reinforcing structures. It is understood that different types of fibre glass that are suitable for the purpose can also be used.

In a further embodiment, the strands which make up the bundles comprise both material derived from bamboo and viscose fibres. The viscose fibres can be bamboo derived viscose or an alternative form of viscose. It is further appreciated that the strands may, for example, comprise material derived from bamboo and a combination of fibre glass and viscose fibres.

Similarly, the bamboo fibres may be combined with any other suitable structural material, such as carbon or aramid fibres or an alternative polymeric material such as rayon.

It is further appreciated that, while the embodiment described comprises fibres of bamboo, the fibres may be replaced with filaments or yarns of bamboo to achieve the same result.

With reference to the pairing of bundles described previously in this Figure, in an alternative embodiment, more than two bundles are grouped together. In one example, each set of bundles comprises a plurality of grouped bundles wherein each group comprises two or more bundles positioned in relative close proximity to each other. Each group of bundles may also be positioned such that the groups define a hole substantially similar to those previously described.

Figure 4 * Figure 4 shows a portion of a reinforcing structure 400 suitable for use in the application of Figure 1. A section of a grid 401 of reinforcing structure 400 includes a first set of bundles 402 and a second set of bundles 403 arranged to form the grid 401. The arrangement and composition of the bundles is substantially similar to that previously described in Figure 2.

In the example shown in Figure 4, reinforcing structure 400 further includes a carrier layer 404 which is made of a geotextile material. Carrier layer 404 is a stress absorbing membrane interlayer (SAMI) which is preferably a spun bonded, needle punched or needle bonded material derived from bamboo.

Carrier layer 404 has a mass per unit area of 100 grams per metre squared (100 g/m2) and a tensile strength of between five and fifteen kilonewtons per metre squared (5-15 kN/m2). These values are configured to allow the carrier layer to provide a physical barrier from the underlying layer and become saturated with bitumen or asphalt to provide a bond with the S overlying layer. For example, the saturation point for I OOg of carrier matérial is in the region of 0.7 to 1.1 litres per metre square (0.7-1.1 l/m2).

In alternative embodiments, the mass per unit area of the carrier layer is between twenty-five and three hundred grams per metre squared (25-300 gIm2). In preferred embodiments, the mass per unit area of the carrier layer is fifty to a hundred grams per metre squared (50-100 g/m2).

In the embodiment shown in Figure 4, the geotextile carrier layer 404 is attached to the grid 401 by stitching to form a single composite material 405.

The stitching is also configured to maintain the grid 401 in position as described previously. The stitching includes a plurali of rows of substantially parallel stitches 406 and a plurality of substantially diagonal stitches 407 positioned between the rows of substantially parallel stitches 406. The stitches are achieved using suitable knitting machines known in the art for this purpose.

In an alternative embodiment, the grid 401 and the carrier layer 404 are attached by gluing with the two materials combined to form a single material suitable for use in reinforcing a road structure.

The geotextile composite material 405 not only provides both physical and chemical protection for the grid 401 and the bundles 402 and 403 which form the grid, it further provides a backing material which supports the grid when being installed. During installation, the composite material also assists in maintaining the grid in position before asphalt is laid on the top.

Figures 5A and 5B Figures 5A and 58 show a cross sectional view and an exploded isometric view respectively of a reinforcing structure 500 akin to that shown in Figure 4. In this embodiment, reinforcing structure 500 comprises a grid 501 and a single carrier layer 502.

Grid 501 is configured to be substantially similar to any one of the embodiments described in preceding Figures 2, 3 and 4. Carrier layer 502 is substantially similar to that described in Figure 4 and comprises material derived from bamboo. In a preferred embodiment, carrier layer 502 comprises bamboo derived material only. Alternatively carrier layer 502 further comprises a second material such as glass fibres or viscose fibres.

Grid 501 is attached to carrier layer 502 by stitching, gluing or any other suitable means. In the embodiment shown, carrier layer 502 is attached to a first side 503 of grid 501 with second side 504 remaining exposed to the bitumen or asphaltic layers configured to be laid on top of the reinforcing structure.

Figures 6A and 68 In contrast to that shown in Figure 5, Figures 6A and 6B show a cross sectional view and an exploded isometric view respectively of a reinforcing structure 600 comprising a grid 601, a first carrier layer 602 and a second carrier layer 603.

Grid 601 is configured to be substantially similar to any one of the embodiments described in preceding Figures 2, 3 and 4. Both first carrier layer 602 and second carrier layer 603 are substantially similar to the carrier layer described in Figure 4 and comprise material derived from bamboo. In a preferred embodiment, each carrier layer comprises bamboo derived material only. In a further embodiment, each carrier layer comprises a second material, for example, glass fibres or viscose fibres. It is appreciated that, dependent on site requirements, each carrier layer can be substantially different to the other in composition, and may comprise a combination of the above.

Referring back to Figure 6, first carrier layer 602 is attached to a first side 604 of grid 601, while second carrier layer 603 is attached to a second side 605 of grid 601. Second carrier layer 603 is also positioned in a substantially parallel plane to first carrier layer 602.

Grid 601 is attached to carrier layer 602 by stitching, gluing or any other suitable means. Grid 601 is also attached to carrier layer 603 by any suitable method including, but not limited to, stitching or gluing.

In the embodiment of Figure 6, a coating is not required on the bundles of grid 601 as the carrier layers 602 and 603 provide the required physical and chemical protection from the asphaltic layers which sandwich reinforcing structure 600 when in use in a paving structure. Carrier layers 602 and 603 are configured to protect grid 601 from abrasion and heat during the laying of hot bitumen. In some applications where stresses are particularly high, however, a suitable coating is used to provide additional protection.

In an embodiment, second carrier laydr 603 has a thickness greater than first carrier layer 602. When positioned in the road or paved structure, the thicker carrier layer is configured to be positioned closest to the surface allowing the upper thicker carrier layer to provide heat insulation. In a preferred embodiment, the upper thicker carrier layer has a mass per unit area of between one hundred and three hundred grams per metre squared (100-300 g/m2). In contrast, the lower thinner carrier layer has a mass per unit area of between fifty and a hundred grams per metre squared (50-1 00 gIm2).

Figure 7 A cross sectional view of a typical asphaltic paved structure or road section embodying the present invention is shown in Figure 7. Paved structure 701 comprises a plurality of layers including an underlying section 702, a reinforcing structure 703 and an overlaying section 704.

Reinforcing structure 703 is positioned between underlying section 702 and overlaying section 704. Preferably, the reinforcing structure 702 is positioned as far down in the paved structure as possible to provide maximum support to over section 704. Reinforcing structure 703 comprises a textile layer comprising a plurality of bamboo strands. The reinforcing structure 703 is substantially similar to ahy one of the reinforcing structures previously described and is configured to prevent movement and cracking from the underlying layers from dissipating to the overlying layers when placed in position.

In an embodiment, underlying section 702 comprises a plurality of layers of varying compositions. In the illustrated example, the underlying section comprises a base layer 705 and two sub base layers 706 and 707.

Base layer 705 comprises large aggregate material and contacts a first side 708 of reinforcing structure 702. First sub base layer 706 comprises a small stone layer, for example a Type 1 sub base. Second sub base layer 707 comprises a large stone sub base layer, for example a Type 2 sub base. In an alternative embodiment, the second sub base layer 707 is omitted.

Overlaying section 704 also comprises a plurality of layers of varying compositions. As shown, overlaying section 704 comprises a lower layer (or binder course) 709 and a surface course 710. Lower layer 709 is an asphaltic layer and is configured to be in contact with a second side 711 of reinforcing structure 703. It is anticipated that surface course 710 is a further asphaltic layer which is configured to wear through use. Surface course 710 will be replaced over periods of time due to expected wear and tear. In particular, without reinforcing structure 703 in place, surface course 710 is highly susceptible to cracking.

S The paved structure further comprises a bond coat 712 which is positioned between base layer 705 and reinforcing structure 703. The bond coat comprises pure bitumen or bitumen emulsion or a polymer modified bitumen solution. It is appreciated that an alternative polymer modified solution could be used.

Typically, overlaying section 704 is between eighty-five and one hundred and fifty millimetres (85-150 mm) thick, which corresponds to a thickness of reinforcing structure 703 of two to forts' millimetres (2-40 mm).

It is appreciated that the number of layers present in underlying section 702 varies depending on the application required depending on the load bearing capacity requirements (such as the Californian Bearing Ratio (CBR)) of the paved structure. Similarly, overlaying section 704 may comprise any number of suitable layers dependent on the application requirements. In a particular embodiment, underlying section 702 comprises a single layer of

suitable material.

Similarly, overlaying section 704 may comprise a single layer of asphaltic material. In an example embodiment, surface course 710 is the only layer of overlaying section 704 and is configured to be in contact with second side 711 of reinforcing structure 703.

Figure 8 Figure 8 shows a flow chart describing a method of producing a paved surface.

At step 801 the base layer of the paved surface is prepared. In an example where the base layer is an existing asphaltic or concrete pavement, the surface can be levelled to provide a clean and smooth surface most suitable for laying the reinforcing layer. In an alternative example the base layer has been freshly laid and this step forms part of the standard procedure for laying the base layer.

At this stage, any cracks or other joints are sealed with suitable fillers as necessary and further repairs can be made to ensure a uniform level surface.

A further regulating layer may be added if the surface is particularly damaged.

The surface is then cleaned as required before moving onto the next step.

At step 802 a uniform layer of a bond coat comprising bitumen is applied or sprayed to leave a residual coating seven hundred millilitres per metre square (700 mlIrn2). In an embodiment, a hot bitumen road emulsion of the type K1-70 (which includes around 70% bitumen and 30% water) is sprayed at a rate of around 1 litre per metre squared (1 11m2). This rate is increased for surfaces with greater porosity. The bitumen is also configured to saturate the reinforcing layer to enable the reinforcing layer to become an integral piece of the paving structure.

The bond coat may alternatively comprise pure bitumen or bitumen emulsion or a polymer modified solution. In an embodiment, a polymer modified bitumen solution is used.

Spraying of the bond coat is achieved by means of a calibrated spray tanker which enables a uniform spread of the bond coat. Alternatively, the spraying can be achieved by use of hand-held tools, such as a hand lance sprayer.

At step 803, the reinforcing structure is installed over the top of the bond coat layer. The reinforcing structure comprises a textile layer comprising a plurality of bamboo strands. It is appreciated that any one of the reinforcing structures discussed previously may be used for this purpose. The reinforcing structure is positioned by rolling it out and laid flat onto the prepared surface.

The surface is brushed under sufficient tension to ensure the reinforcing S structure is laid flat onto the base layer. In an embodiment, the hot bitumen road emulsion is allowed to cure prior to laying any further layers.

In an embodiment where the reinforcin structure comprises two carrier layers, the upper carrier layer may not be fully saturated by the bond coat, particularly where the upper carrier layer is thicker than the lower carrier layer.

In this case, the reinforcing structure can be oversprayed with emulsion until saturation occurs and prior to step 804 being conducted.

At step 804, one or more layers are applied over the reinforcing structure. In an embodiment, a binding course is laid first over the reinforcing structure with a surface layer laid above the binding course. The surface course is compacted asphalt overlay and should have a minimum thickness of 40mm. In a particular embodiment, the thickness of the overlay is 50mm.

Figure 9 An alternative reinforcing structure 900 which could be used in the paved structures as previously described and in accordance with the application of Figure 1 is shown in Figure 9. The reinforcing structure 900 comprises a set of reinforcing elements 901 with each reinforcing element arranged in a substantially parallel position relative to each of the other reinforcing elements of the set as shown. In this illustrated example, reinforcing element 901A is positioned substantially parallel to reinforcing element 9016 and reinforcing element 901C.

Reinforcing structure 900 further includes a second set of reinforcing elements 902 which are arranged at an angle to set of reinforcing elements 901. In this illustrated example, the angle is approximately 90°. In other embodiments, however, the angle is any suitable angle for the application in question.

The set of reinforcing elements 901 and the set of reinforcing elements 902 are connected to each other by connection means 903. In the embodiment of Figure 9, the connection means comprises stitching which holds each of the reinforcing elements together at crossover points, such as crossover point 904. Alternative connection means are used in other examples, such as those described in Figure 10.

As shown, the reinforcing elements 901 and 902 are spaced such that holes, such as hole 904, are defined between them. In alternative embodiments, the reinforcing elements are positioned such that there are no visible holes between the reinforcing elements. For example, in an embodiment, reinforcing element 902A overlaps with reinforcing element 902B and reinforcing element 902B also overlaps with reinforcing element 902C.

Thus, the sets of reinforcing elements may form a continuous structure without spaces between the elements.

In the embodiment of Figure 9, each reinforcing element 901 and 902 is formed of a composite material comprising a plurality of bamboo fibres and a binding matrix. The binding matrix is any suitable material which can be used in combination with the plurality of bamboo fibres to form a composite material.

For example, in an embodiment, the binding matrix is an asphaltic coating and comprises polymer modified asphalt or a bitumen emulsion. In an example embodiment, the binding matrix is produced from a naturally occurring source, and comprises natural resins or material derived from bamboo. In an embodiment, the binding matrix is bamboo sap. In a further embodiment, the binding matrix comprises rubberwood sap or a natural rubber component. In another embodiment, the binding matrix comprises a synthetic rubber! for example, SBR (styrene butadiene rubber). In a further embodiment, the binding matrix comprises a polymeric material such as polyvinyl chloride (PVC), polypropylene (PP) or polytetrafluoroethylene (PTFE), As a part of the composite material, the binding matrix not only works to bind the reinforcing bamboo fibres together, but also works as a coating to provide physical and chemical protection to the bamboo fibres. The binding matrix therefore advantageously works to prevent abrasion of the bamboo fibres and avoids damage to the reinforcing structure from the heat generated from the overlay of asphalt (as described in the paved structure of Figure 7).

In an embodiment, the composite material further comprises fibres of a second material in addition to the bamboo fibres such that the composite material may also include fibres of viscose, glass fibres, carbon fibres or other suitable fibres as previously described.

In a particular embodiment, the composite material is a pre-impregnated (pre-preg) material. Thus, the fibres are aligned and impregnated with the binding matrix and partially cured to produce a pre-preg material suitable for the reinforcing structure. This process is explained in further detail inFigurell.

Figure 10 A further example of a reinforcing structure suitable for use in the paved structure of Figure 7 and in accordance with the application shown in Figure 1 is shown in Figure 10. Reinforcing structure 1000 comprises a first set of reinforcing elements 1001 which are arranged substantially parallel to the other reinforcing elements of the set. In this illustrated example, reinforcing element IOOIA is positioned substantially parallel to reinforcing element 10018 and reinforcing element IOOIC.

Reinforcing structure 1000 further comprises a second set of reinforcing elements 1002 which are arranged at an angie to the reinforcing elements of the first set 1001. In this illustrated embodiment, the angle is approximately 900. However, it is appreciated that other suitable angles may be used depending on the requirements of the application.

In an embodiment, each reinforcing element (1001 and 1002) is formed of a composite material comprising a plurality of bamboo fibres and a binding matrix. The reinforcing elements are connected by a connection means, which, in an embodiment may be similar to the example shown in previous Figure 9 and include stitching. However in the embodiment shown in Figure 101 the connection means is configured to be part of the binding matrix itself. In this embodiment, the binding matrix is configured to be tacky in texture, such that each reinforcing element can be positioned in place and fixed together by forcing the reinforcing elements together. In a further embodiment, a suitable adhesive is used to maintain the reinforcing elements in position with each of the reinforcing elements being glued together.

In the embodiment shown, reinforcing elements 1001 and 1002 are spaced such that holes, such as hole 1003, are defined between them.

However, in an embodiment, it is preferable to not have spaces between the reinforcing elements and so the reinforcing elements are positioned so as to not create holes or gaps between them. Thus, a reinforcing structure may take the appearance of a continuous sheet of material without holes.

In a further embodiment, and to increase strength of the reinforcing structure as required, the reinforcing elements 1001 and 1002 are layered on top of other ieinforcing elements and stacked to increase the thickness of the reinforcing structure as a whole.

The binding matrix of the embodiment in Figure 10 is any suitable material which can be used in combination with the plurality of bamboo fibres to form a composite material. For example, in an embodiment, the binding matrix is an asphaltic coating and comprises polymer modified asphalt or a bitumen emulsion. In an example embodiment, the binding matrix is produced from a naturally occurring source, and comprises natural resins or material derived from bamboo. In an embodiment, the binding matrix is bamboo sap. In a further embodiment the binding matrix comprises rubberwood sap or a natural rubber component. In another embodiment, the binding matrix comprises a synthetic rubber, for example, SBR (styrene butadiene rubber). In a further embodiment, the binding matrix comprises a polymeric material such as polyvinyl chloride (PVC), polypropylene (PP) or polytetrafluoroethylene (PTFE).

As a part of the composite material, the binding matrix not only works to bind the reinforcing bamboo fibres together, but also works as a coating to provide physical and chemical protection to the bamboo fibres. The binding matrix therefore advantageously works to prevent abrasion of the bamboo fibres and avoids damage to the reinforcing, structure from the heat generated from the overlay of asphalt (as described in the paved structure of Figure 7).

In a particular embodiment, the composite material is a pre-impregnated (pre-preg) material. Thus, the fibres are aligned and impregnated with the binding matrix and partially cured to produce a pre-preg material suitable for the reinforcing structure. This process is explained in further detail in Figure 11.

In a further embodiment, the reinforcing structures shown in both Figures 9 and 10 further comprise carrier layers in a similar manner to the embodiments shown in Figures 5 and 6. In a preferred embodiment, each carrier layer is made of a geotextile material and is a stress absorbing membrane interlayer (SAMI) which is preferably a spun bonded, needle punched or needle bonded material derived from bamboo.

in an example embodiment, the reinforcing structure further comprises a single carrier layer which is attached to a first side of at least one of the reinforcing elements. In a further embodiment, the reinforcing structure comprises a further carrier layer, which is attached to a second side of a least one of the reinforcing elements. In this example, the further carrier layer is positioned in a substantially parallel plane to the first carrier layer.

In a particular embodiment, one of the carrier layers has a greater thickness than the other carrier layer such that the thicker layer can be utilised to enable increased protection for the reinforcing elements from the hot bitumen which overlays the reinforcing structure when laid as part of a paved structure.

Figure 11 Figure 11 shows a flow chart detailing the manufacture of a reinforcing structure comprising a composite grid in accordance with the embodiments described in Figures 9 and 10.

At step 1101 long length bamboo fibres are obtained from natural bamboo by means of mechanical extraction. In a preferred embodiment, the mechanical extraction is purely mechanical and does not include the addition of chemicals or the use of high temperatures so as to prevent damage or weakening of the bamboo fibres. Bamboo fibres of up to 35 cm in length are obtained from the length between the nodes of the natural bamboo by this method.

In an alternative embodiment, the bamboo fibres are extracted from natural bamboo by steam explosion utilising high pressures and temperatures as known in the art. Further embodiments include chemical extraction of the bamboo fibres from natural bamboo by utilising high concentrations of sodium hydroxide (NaOH).

Once the bamboo fibres have been extracted from the culm of the natural bamboo, the fibres are cleaned and aligned at step 1102. For manufacture of unidirectional composites, the bamboo fibres are combed and arranged such that the fibres are aligned substantially parallel to each other.

At step 1103, a suitable binding matrix is added. The binding matrix is any suitable material which binds the fibres together and provides a degree of protection from the hot asphaltic mixture of the paved structure. In a preferred embodiment, the binding matrix is an asphaltic coating and comprises polymer modified asphalt or a bitumen emulsion. Alternatively! in an embodiment, the binding matrix is produced from a naturally occurring source, and comprises natural resins or material derived from bamboo. In one embodiment, the binding matrix is bamboo sap. In a further embodiment, the binding matrix comprises rubberwood sap or includes a natural rubber component.

In a further embodiment, the binding matrix comprises a synthetic rubber, for example, SBR (styrene-butadiene rubber). In a still further embodiment, the binding matrix comprises a polymeric material such as polyvinyl chloride (PVC)! polypropylene (PP), maleic anhydride grafted polypropylene (MAPP) or polytetrafluoroethylene (PTFE). Alternatively, in an embodiment the binding matrix comprises epoxy resin.

In an embodiment, layers of bamboo fibres are positioned between layers of film of the binding matrix material before at least partially curing and/or melting. The bamboo fibres and binding matrix in combination are then compression moulded at step 1104 such that the binding matrix is partially cured to form pre-preg composite reinforcing elements. In a preferred embodiment, the bamboo fibres and binding matrix are heated while compression moulded to enable the fibres and matrix to form suitable bonds, It is appreciated that the film of binding matrix can be any of the aforementioned materials described previously and suitable for the particular application.

At step 1105 the pre-preg composite reinforcing elements are aligned as required into a grid or similar form, such as those illustrated in Figures 9 and 10, such that a composite reinforcing structure is obtained. The reinforcing elements may be split into a first set and a second set. The first set of reinforcing elements are then arranged such that each reinforcing element is positioned substantially parallel to the other reinforcing elements in the set.

The second set of reinforcing elements are then arranged at an appropriate angle to the first set of reinforcing elements before the two sets are connected together with appropriate connection means. The connection means may take the form of stitching, gluing or other adhesive. In an embodiment, the connection means is that of the binding matrix itself which is used to maintain the reinforcing elements in position.

Once arranged, the reinforcing composite can be used as part of a paved structure such as those described herein.

Claims

Claims What we claim is: 1. A reinforcing structure comprising: a first set of reinforcing elements, each said reinforcing element arranged substantially parallel to other reinforcing elements of said first set; a second set of reinforcing elements arranged at an angle to said first set of reinforcing elements; said first set of reinforcing elements are connected to said second set of reinforcing elements by a connection means; wherein each said reinforcing element is formed of a composite material comprising a plurality of bamboo fibres and a binding matrix.
2. A reinforcing structure according to claim 1 wherein said binding matrix comprises polymer modified asphalt.
3. A reinforcing structure according to claim I wherein said binding matrix comprises a synthetic rubber.
4. A reinforcing structure according to claim 1 wherein said binding matrix comprises a polymeric material.
5. A reinforcing structure according to claim 1 wherein said binding matrix comprises naturally occurring bamboo sap or resin.
6. A reinforcing structure according to claim 1 wherein said binding matrix comprises a natural rubber component.
7. A reinforcing structure according to any previous claim wherein said connection means comprises said binding matrix.
8. A reinforcing structure according to claim I wherein said angle is approximately 9QO
9. A reinforcing structure according to claim 1 wherein said composite material further comprises fibres of a second material.
10. A reinforcing structure according to claim 1 further comprising a first carrier layer attached to a first side of at least one of said reinforcing elements.
II. A reinforcing structure according to claim 10 further comprising a second carrier layer attached to a second side of said at least one of said reinforcing elements, said second carrier layer positioned in a substantially parallel plane to said first carrier layer.
12. A reinforcing structure according to claim 11 wherein said second carrier layer has a thickness greater than said first carrier layer.
13. A reinforcing structure according to claim II wherein any one of said first carrier layer or said second carrier layer comprises material derived from bamboo.
14. An asphaltic paving structure comprising a reinforcing structure in accordance with any previous claim.
15. A paved surface comprising: a reinforcing structure comprising a first set of reinforcing elements arranged at an angle to a second set of reinforcing elements; said first set of reinforcing elements and said second set of reinforcing elements are connected by a connection means and each said set comprises plurality of bamboo fibres and a binding matrix; a first layer suitable for receiving said reinforcing structure; and a second layer configured to overlay said reinforcing structure, such that said reinforcing structure is positioned between said first layer and said second layer
16. A paved surface according to claim 15, wherein said binding matrix comprises polymer modified asphalt.
17. A paved surface according to claim 15 wherein said binding matrix comprises a synthetic rubber.
18. A paved surface according to claim 15 wherein said matrix comprises a polymeric material.
19. A paved surface according to claim 15, wherein said reinforcing structure further comprises a first carrier layer attached to a first side of at least one of said reinforcing elements.
20. A paved surface according to claim 15, wherein said reinforcing structure further comprises a second carrier layer attached to a second side of said at least one of said reinforcing elements, said second carrier layer positioned in a substantially parallel plane to said first carrier layer.
21. A method of manufacturing a reinforcing structure, comprising the steps of: extracting a plurality of bamboo fibres from natural bamboo by means of mechanical extraction; refining said plurality of bamboo fibres such that said plurality of bamboo fibres are substantially aligned; impregnating said plurality of bamboo fibres with a binding matrix to form a reinforcing element; arranging a first set of reinforcing elements such that each reinforcing element is substantially parallel to other reinforcing elements of said first set; arranging a second set of reinforcing elements at an angle to said first set of reinforcing elements; and connecting said first set of reinforcing elements and said second set of reinforcing elements together with a connection means.
22. A method of manufacturing a reinforcing structure according to claim 21, further comprising the step of: attaching a first carrier layer to a first side of at least one of said reinforcing elements.
23. A method of manufacturing a reinforcing structure according to claim 22, further comprising the step of: attaching a second carrier layer to a second side of said at least one of said reinforcing elements such that said second carrier layer is positioned in a substantially parallel plane to said first carrier layer.
24. A reinforcing structure as described herein with reference to the accompanying Figures.s
25. A paved surface as described herein with reference to the accompanying Figures.
26. A method of manufacturing a reinforcing structure as described herein with reference to the accompanying Figures.