TITLE: A rigid composite material FIELD: The invention relates to a rigid building material at least partially comprised of particulate recycled glass used to produce a mouldable composite material that may be used to 5 manufacture shaped objects including roofing tiles, paving slabs, decorative panels. The composite material may also be used as an aggregate in the manufacture of concrete. BACKGROUND Accumulating piles of collected rubbish contain some recyclable materials. There is a continual search to find a method of gainfully using the separable materials such as plastic, 10 glass and paper that are accumulated by recycling. Known methods include collection and processing of paper, glass and plastic materials to form at least part of new products or materials. Materials so produced may be variously substituted for or combined with conventional elements in manufacturing or construction. Composite materials are known in manufacturing and construction. Some such include 15 settable compositions incorporating hard aggregates, with final properties reflecting both elements. Concrete is an example. Also known are fibreglass and carbon composites. PROBLEM TO BE SOLVED To find a practical use for waste glass such as in the form of bottles, and produce a material that can be used to manufacture useful products. 20 OBJECT An object of the present application is to provide a cheap and rigid material of use in structures such as buildings or panels, or at least to provide the public with a useful choice. SUMMARY OF INVENTION In a first broad aspect the invention provides a method to utilize waste glass and produce a 25 material that can be used to manufacture building products such as roofing tiles, paving tiles or garden ornaments; the method including the steps of: 1 Receiving waste glass Crushing or otherwise forming the glass into granules having size distribution appropriate for forming a tough composite material, 30 Optionally washing the glass, Providing a thermoplastics material; Optionally sourcing the thermoplastics material from waste plastics; preferably sorted by plastic type; Shredding the thermoplastics material, 35 Heating at least the glass to a temperature greater than the melting point of the thermoplastics material, Feeding the glass and thermoplastics material into a moulding device such that they become mixed either before entry or within the moulding device, Optionally further heating the mixture 40 Moulding the mixture into shapes. Optionally the moulded shapes are discrete objects selected from a list including artificial aggregate, paving slabs, field tiles, drain tiles, roofing tiles, slate-like roofing tiles, paving kerbstones, bird baths, planters, fencing panels, and garden ornaments. Optionally the mixing stage is carried out under reduced pressure so that inclusion of bubbles 45 in the composition is minimised. Alternatively the mixing stage involves (a) extrusion of a sheet of melted plastic polymer, superimposition of a layer of heated, crushed glass over the melted plastic sheet, and then pressing the heated, crushed glass into the melted plastic sheet. Optionally the moulding device comprises or includes an extrusion device capable of 50 producing extended rods from an aperture. In a second broad aspect the invention provides a method for combining waste glass with thermoplastics to produce useful objects or materials. 2 In a third broad aspect the invention provides a composition comprised of granules of glass intimately mixed with, and suspended within a solidified thermoplastics matrix. 55 Preferably the proportion of glass in the composition, by weight, is about 75 %. Optionally the glass content is in a range of from 16 % to 75 % by weight. Preferably the glass content has a particle size between 0.5 mm to 5 mm in diameter. Alternatively, the glass content has a particle size of at least 0.5 mm in diameter. Optionally the glass content is comprised of glass having a selected colour. 60 Preferably the thermoplastics matrix is comprised of a plastics material selected from a range including without limitation: high density polyethylene (HDPE), polyethylene terephthalate (PET), polyester (PE), polyethyletherketone (PEEK), polystyrene (PS), polyvinylidene chloride (PVDC). Preferably the selected plastics material, if a mixture, for any given composition is 65 substantially all of a similar melting point. Optionally some of the glass may be substituted by plastics of a higher melting point which does not form the matrix. Optionally the plastics content is comprised of plastics fragments having a selected colour. Preferably the plastics content is washed, dried, optionally compressed, and shredded into a 70 manageable size before melting. PREFERRED EMBODIMENT The description of the invention to be provided herein is given purely by way of example and is not to be taken in any way as limiting the scope or extent of the invention. 75 Throughout this specification unless the text requires otherwise, the word "comprise" and variations such as "comprising" or "comprises" will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps. Each document, reference, patent application or patent cited in this text is expressly incorporated herein in their entirety by reference. Reference to 3 80 cited material or information cited in the text should not be understood as a concession that the material or information was part of the common general knowledge or was known in New Zealand or in any other country. In particular, the range of plastics named is a function of current availability. The person skilled in the art will be aware that the availability of plastics may change, as when new 85 plastic blends are invented or discovered, or when the price of currently available plastics changes, and will therefore read references to specific plastics as including a broad range of functionally similar plastics. DRAWINGS Fig 1: shows a flow chart for making shaped articles according to the invention. 90 PRODUCTION PROCESS Product: Objects comprised of an artificial compound consisting of crushed glass and plastic polymer. A product moulding material: Exposed aggregate and coloured aggregate. STEP 1: Crushing the glass The glass to be used will be either glass that is reject glass from the manufacturing process or 95 glass that has been collected from recycling operations. Most of the glass will be from bottles but some glass may be sheet glass or other glass products. Glass which is contaminated is preferably avoided, although a washing and drying step may be useful. The glass will first be crushed to have a mean particle size between 0.5 mm to 5 mm in 100 diameter. This size is a guideline and for some applications such as paving slabs a larger particle size may be used. The larger the size of the product to be manufactured, the larger the size of the glass particle may be. One preferred type of glass crusher uses patterned rollers or dies to break the glass into cubic rather than elongated shapes. 4 A set of screens to sieve the crushed glass should be placed under the crusher to ensure that 105 the particle size is consistent about the desired range. Larger pieces can be returned to the crusher and smaller particles may be used in some other way. Optionally the glass can be tumbled in order to smooth sharp edges, although it may be preferable to mould shapes (see later) so that they include an overall coating of plastics. STEP 2: Heating the glass 110 The next step is to ensure that the crushed glass is heated and dry. If water is not removed, it will turn to steam during the process. This steam would produce flaws in the end product and could cause extreme damage to an extrusion moulding plant. The crushed glass is then transferred to a heating chamber where the glass is heated to a temperature higher than the melting point of the plastic polymer. This is to ensure that there 115 is a firm bond between the plastic polymer and the crushed glass. It is also to ensure that the temperature of the molten plastic polymer is not lowered by the introduction of the crushed glass STEP 2A: Optionally melting the plastic polymer 120 The plastic may be separately heated to a softening point by conventional methods. A moving hot and preferably inert gas having a controlled temperature may be preferable. Many plastics cannot tolerate a temperature much above their melting point, else decomposition sets in. One practical method is to feed the plastic polymer pellets into an extrusion moulding machine. The molten plastic polymer could then be extruded as a continuous thin sheet. 125 STEP 3: Mixing the heated, crushed glass with plastic polymer and (possibly) colorant. This step mixes the plastic polymer with the heated crushed glass. Polymers such as polyethylene terephthalate (PET), polyester (PE), polyethyletherketone (PEEK), polystyrene (PS), polyvinylidene chloride (PVDC), or other plastic resins with a 130 high melting point are preferred. High density polyethylene (HDPE) may also be used. A list of thermoplastics available from refuse collections at this date may be superseded in the 5 future. At this time, it is recommended that virgin plastic resins are used as this will produce a consistent product, but suitably advanced refuse separation procedures, whether manual or not, may be able to provide reasonably pure plastics of at least a common melting point, if 135 not a common chemical composition. Plastic that has already been recycled and homogenised may be used for some applications. For example, the ratio of plastic resin to crushed glass will vary from one part polymer resin to three parts of crushed glass to one part plastic polymer to five parts glass by weight. Other ratios of glass to plastic may be used. 140 The more plastic that is used, the smoother the finished product will be. The mixture may have colorant added to produce bright colours, such as red, green, white or blue, to enable the finished product to be used for decorative purposes, particularly exposed aggregate panels, paving stones, roof tiles or plant pots . Preferred colorants will be stable to light. Ultraviolet light absorbers may be added to the mixture to reduce the effect of sunlight on products that 145 are subject to continuous exposure to sunlight. One such absorber is carbon black. Flame retardants may also be added for products requiring a higher fire safety rating. A mixture of the heated glass and the plastic polymer may be fed into an extruder and mixed. Where the melted plastic polymer is extruded from an extruder, a layer of heated, crushed glass may be spread over the melted plastic sheet. The heated, crushed glass is then pressed 150 into the melted plastic sheet. Alternatively, the melted plastic may be fed into a mixer - such as a Banbury mixer - the heated glass is also fed into the mixer and processed until the materials have blended. Further heating may be applied to assist with handling and bonding of the mixture. As one option, the heating process may be carried out under a vacuum, or a vacuum and 155 centrifugation step, or a centrifugation step of the melted composition alone may be added to this process in order that entrapped air bubbles are removed. In another option, entrapped air is not a disadvantage since it lightens the resulting composition. (Air content was not taken into account when determining preferred ratios of glass to thermoplastics). 6 Another alternative, is when the melted plastic is extruded from the extrusion moulding 160 machine, the heated glass is add to the melted plastic and the mixture is fed into a second extrusion moulding machine to complete the mixing process STEP 4: Forming the product. Many products such as paving slabs, field tiles, slate roofing tiles, or paving kerbs, may be 165 produced direct from the die on the extruder. A concrete aggregate may also be produced directly from the extrusion moulder. By "concrete aggregate" we mean large granules, short rods, and other shapes that may be substituted in part or completely for conventional aggregate which is usually crushed rocks. By adding a colourant, this concrete aggregate may by be manufactured in a colour selected 170 from a range for use as a coloured exposed aggregate panel or paving slab. It is recommended that any concrete made using this aggregate is used only for non-structural purposes. Other products such as roofing tiles, drain tiles, bird baths, planters, or garden ornaments could be produced by transferring the hot extruded mixture into a compression moulding 175 machine. It will be appreciated that it is more convenient to form the composition into final shapes while molten, since the combination of glass and thermoplastics may be difficult to cut or shape when cold. This property can be an advantage for security fences or security panels. It has been found that if the particulate glass is heated preferably up to a plastics working 180 temperature and at least to 300 degrees Celsius prior to being mixed with the thermoplastic constituents, bonding is greatly improved. While an explanation of this effect is not yet confirmed, it may be in part that the thermoplastics flows better around the glass, and also that the film of water usually present over any glass surface is caused to evaporate by the heat. 185 This leads to the possibility of feeding both pre-heated particulate glass and shredded or granular thermoplastics as a mixture into the same extrusion machine, thereby simplifying the steps involved in the process described above. 7 Products such as garden ornaments and planters may be produced by mixing the heated glass and the polymer and feeding the mixture into the rotational moulding machine and rotating 190 the mould until the product is formed. RESULTS Tests have been carried out to assess the material properties of the invention. Compression Test 195 A test was carried out by Opus. A concrete mix was purchased and one test was with the aggregate in the mix. The aggregate in the concrete mix was sieved out, and the aggregate replaced with an aggregate made from the glass/plastic mix. A compression test was carried on the two samples to compare how the concrete varied with the different aggregates. Age Average Length Design Density Compressive (days) diameter (mm) Strength Strength (mm) (MPa) (MPa) Readymix Concrete, 7 51.8 96.7 17.5 2300 7.5 conventional aggregate Readymix Concrete, 7 50.1 100.5 17.5 1930 7.5 glass/plastic aggregate 200 The glass/plastic aggregate produced concrete lighter by 400 kg per ton, with equal compressive strength. A further compression test was carried out by Opus. Samples of the material itself was molded into a tube that was twice as high as it was wide. The samples were then compression tested (results supplied by Dave G Hotham of Opus). 205 Concrete Samples Cast Date Density (kg/m 3 ) Compressive Strength (MPa) 29/05/13 2050 3.9 30/05/13 2040 9.1 8 Plastic / Glass Samples Test Number Compressive Strength (MPa) 1 18.3 2 16.2 3 14.0 4 14.6 Tensile Strength A second test was carried out by Materials Testing Laboratories Ltd to test the tensile 210 strength. A sample of the material was cut into approximately 15mm strips and the strips tested for tensile strength. The material is very strong when in the formed sheet, but loses strength when cut. The following is the result of the tensile test Test report 37441/3 using a JJ Lloyd Tensile Testing Machine, type T5000 with a precision transducer model ST 50040 on 22 April 2003, sample identified as "Long HDPE" Standard 215 used: ASTM D790/1999 Flexural Strength Test S = 3PL / 2bd 2 x (Span 80mm) Sample Thickness d Width b Maximum P failure (load) (S) in (S) in (mm) (mm) (N) MPa PSI 1 16.57 14.00 576.3 18.0 2609 2 17.22 14.58 599.7 17.0 2414 3 15.23 13.19 411.3 16.0 2340 4 17.16 14.41 570.9 16.0 2342 5 16.31 14.48 584.7 18.0 2642 Average values 549.0 17.0 2469 9 Modulus of Elasticity in Bending / M.O.E EB = L 3 M /4 Def bd 3 (Span 80 mm) Sample Thickness d Width b Secant Modulus Deflection M.O.E (mm) (mm) (N) (mm) (MPa) 1 16.57 14.00 576.3 1.7 681 2 17.22 14.58 599.7 1.0 1031 3 15.23 13.19 411.3 1.5 753 4 17.16 14.41 570.9 1.3 772 57 16.31 14.48 584.7 1.6 745 Test report 37441/2 using a JJ Lloyd Tensile Testing Machine, type T5000 with a precision 220 transducer model ST 50040 on 22 April 2003, sample identified as "Short HDPE" Standard used: ASTM D790/1999. Test speed 10 mm/ minute. Flexural Strength test S = 3PL/2bd 2 x (Span 80 mm) Sample Thickness d Width d Maximum P failure (load) (S) in (S) in (mm) (mm) (N) MPa PSI 1 14.39 13.45 346.8 15.0 2167 2 14.43 14.37 279.7 12.0 12733 3 13.86 13.51 461.1 21.0 3092 4 14.81 14.33 384.9 15.0 2131 5 14.50 13.03 261.5 11.0 1661 Average values 350.0 15.0 2157 10 Modulus of Elasticity in Bending / M.O.E EB = L 3 M /4 Def bd 3 (Span 80 mm) Sample Thickness d Width d Secant Deflection M.O.E (mm) (mm) Modulus (mm) (MPa) (N) 1 14.39 13.45 346.8 1.7 652 2 14.43 14.37 279.7 0.9 981 3 13.86 13.51 461.1 1.5 1094 4 14.81 14.33 384.9 1.3 814 5 14.50 13.03 261.5 1.6 527 225 Insulation Test Two tests of insulation properties were privately conducted. A sheet of the material 10 mm thick was placed first on a block of ice and the temperature at each side measured. Ambient temperature was 14'C. The same sample was then placed 2.5 cm above a 230'C element. The sample did not soften. Time Elapsed (minutes) Ice side temperature (*C) Open side temperature (*C) 0 15 14 15 3.5 9.8 30 3.5 4.5 230 Time Elapsed (minutes) Element side temperature (*C) Open side temperature (*C) 0 19 14 5 47 29 10 87 65 15 106 95 20 118 95 30 126 102 11 Fastening Methods Method Result Nail A 15 cm sample had a nail driven into it. There needed to be a firm strike, but the nail was driven through the sample with no splitting of the sample. Screw A PK self-tapping screw was screwed Into the sample. There was a tendency for the screw to go off line but there was no splitting of the sample. Drill A hole was drilled through the sample. The drill used was metal drill and the sample was very easily drilled. RESULTS AND ADVANTAGES 235 The compound may be used as a "thermoplastic decorative gravel" or as a "thermoplastic building material" in which the glass emulates the aggregate of concrete and the plastics material emulates the hardened cement. The invention provides a decorative artificial gravel to be included in concrete driveways, footpaths, paving slabs and wall panels. 240 The invention provides a method to manufacture products such as roof tiles, garden omaments, fencing panels, paving tiles out of a waste material. The product produced is durable, colorful and hardwearing. It can be nailed or screwed to secure it in position or to other materials. It can be drilled to facilitate nailing or screwing. The invention provides a way to consume waste material such as glass, including bottle glass, 245 window glass, and lead glass from CRT monitors without incurring the cost of disposal, while at the same time consuming waste plastics such as PET from bottled beverages.. Finally it will be understood that the scope of this invention as described and/or illustrated herein is not limited to the specified embodiments. Those of skill will appreciate that various modifications, additions, known equivalents, and substitutions are possible without departing 250 from the scope and spirit of the invention as set forth in the following claims. 12