GB2460707A

GB2460707A - Polymer concrete aggregate

Info

Publication number: GB2460707A
Application number: GB0816689A
Authority: GB
Inventors: Peter Ridgway; Bernie Howes
Original assignee: Aco Technologies PLC
Current assignee: Aco Technologies PLC
Priority date: 2008-06-02
Filing date: 2008-09-12
Publication date: 2009-12-09
Also published as: GB0816689D0; GB0810009D0

Abstract

A polymer concrete aggregate is disclosed. In some examples, the aggregate comprises glass sand, which may comprise ground, crushed or otherwise broken down glass. The aggregate may comprise a mixture of gravel-sized particles, sand-sized particles, and fine filler particles, wherein at least a portion of at least one of the gravel-sized particles, sand-sized particles and fine filler particles may comprise glass sand. In some examples, at least a portion of the aggregate may comprise recycled materials.

Description

POLYMER CONCRETE

This invention relates to polymer concrete.

Polymer concrete is a composite construction material comprising aggregates bound together by a polymeric binder (instead of water and a cement binder, as used in cementitious concrete).

Polymer concrete provides advantages over conventional construction materials such as cementitious concrete. In particular, its superior mechanical properties enable pre-cast items to be produced that are lighter than the equivalent cement-based products. Polymer concrete also offers greater corrosion resistance to acids, alkalis, salt and other corrosive materials and, due to its low water content, better withstands freezing.

There is an increasing desire to incorporate recycled material such as plastic, paper, crushed concrete or glass, into manufactured products and materials in order to reduce waste. However, construction materials should not incorporate any components which compromise their flexural and compression strengths, nor their rheological properties (i.e. the behaviour of the material under stress particularly when in the fluid state). Indeed, attempts to incorporate glass in cementitious concrete have met with technical obstacles, and in particular the problem of Alkali-Silica Reaction (ASR).

ASR creates a gel that swells in the presence of moisture causing cracks and unacceptable damage to the concrete. Research also shows protective coatings to the glass would help resist ASR but this adds complexity and expense to the manufacturing process. Admixtures which suppress ASR can be included in the normal concrete mix but these have a negative effect on workability of the concrete.

Another way to overcome ASR is to include glass ground to fine texture or to replace part of the cement with metakaolin, which has a particle size which is smaller than that of cement. Glass concrete using metakaolin gives a Portlandite-free microstructure', enabling better durability and low shrinkage. As will be appreciated by the skilled person, Portlandite it is a common product of hydration (the curing process) of Portland cement (Portland cement is a commonly used type of cement) and is a colourless, hexagonal mineral consisting of calcium hydroxide which forms to provide a microstructure of small plates. The use of metakaolin prevents this microstructure from forming. However, no aggregate larger than 6mm can be used to achieve the new structure, which places a restriction on the aggregates used.

According to a first aspect of the present invention there is provided a polymer concrete aggregate comprising glass sand.

Glass is a non-reactive and solid material. It can help increase the flexural strength of construction materials. The term glass sand' used herein is intended to describe glass particles which may be produced for example by crushing, grinding, or otherwise breaking down waste glass (e.g. bottles and other container glass). Glass sand particles may be comparable in size to fine-filler materials, very fine sand, fine sand, coarse sand and/or gravel components used in known polymer concrete compositions. The glass sand particles may be sorted, for example by sieving, in to samples with particle sizes which are substantially equivalent to one or more of these component particle sizes.

For example, very fine sand particles may range in size between approximately 1/16- 1/8 mm. Fine sand particles may range in size between approximately 0.5 to 1mm.

Coarse sand particles may range in size between about 1mm and 3mm and gravel may range in size between about 3mm and 8mm.

In one embodiment, the glass sand comprises ground glass. The use of ground glass is advantageous as it makes a use of commonly and readily available material which may be manufactured from waste glass, which is often relatively inexpensive. It is increasingly the case that governmental and other policies require the inclusion of recycled materials in manufactured or construction products as well as in new construction projects. For example, the UK Olympic Delivery Authority intends to ensure that at least 20 percent of the materials used in the 2012 Olympics project as a whole are recycled. The use of ground glass in concrete may assist manufacturers in meeting targets set by such policies.

In some embodiments, glass sand comprises up to about 32% or 33% by total dry weight of the aggregate. It has been found that increasing the amount of glass sand up to about 32 or 33% by dry weight of the aggregate does not compromise the flexural or compression strength of the polymer concrete. In other embodiments, glass sand may comprise a lower or higher proportion of the aggregate, for example, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100%. As will be appreciated by the skilled person, the above stated proportions are intended to cover values of a few percent (perhaps up to 10%) either side of those specified, in particular as there are generally manufacturing variations in the mix of a concrete aggregate of several percent.

In some embodiments, glass sand comprises between about 5% and about 32% or between about 10% and about 32% by dry weight of the aggregate. In other embodiments, glass sand comprises between about 15% and about 32% or between about 20% and about 32% by dry weight of the aggregate. The upper limits may, in each case, be for example about 33% or may be higher as outlined above. This allows an appreciable amount of glass to be used, which may be advantageous particularly if the glass is waste glass, without compromising the strength of the concrete. In examples where the concrete need not be as strong, the aggregate may comprise higher proportions of glass sand.

The aggregate may comprise a mixture of gravel-sized particles, sand-sized particles, and fine filler particles, and at least a portion of at least one of the gravel-sized particles, sand-sized particles, and fine filler particles comprises glass sand. In some embodiments each of the gravel-sized or sand-sized particles may be replaced in their entirety by glass sand. The term gravel' used herein is intended to refer to gravel, crushed stone, recycled crushed concrete, recycled brick and other construction waste.

The aggregate may comprise: (i) 0-45% by dry weight gravel-sized particle (ii) 0-45% by dry weight coarse sand-sized particles (iii) 0-85% by dry weight fine sand-sized particles (iv) 0-20% by dry weight fine filler particles Alternatively, the aggregate may comprise: (i) 0-45% by dry weight gravel-sized particle (ii) 15-60 % by dry weight coarse sand-sized particles (iii) approximately 25% by dry weight fine sand-sized particles (iv) approximately 15% by dry weight calcium carbonate.

These proportions are found in known polymer concrete mixes and will therefore be familiar to the skilled person, which may reduce production risks. Calcium carbonate is an example of a fine filler material.

According to a second aspect of the present invention there is provided a polymer concrete aggregate, wherein at least a portion of the aggregate comprises recycled materials.

The aggregate may comprise a mixture of gravel-sized particles, sand-sized particles, and fine filler particles, and at least a portion of at least one of the gravel-sized particles, sand-sized particles, and fine filler particles comprises recycled material(s). Each of the gravel-sized or sand-sized particles may be replaced in their entirety by recycled material(s).

The recycled material may comprise one or more of the following: colliery spoil; gypsum, pulverised fuel ash (PFA), china clay waste (e.g. ball clay waste), slag (e.g. basic oxygen furnace (steel), blast furnace (iron), electric arc furnace (steel)), spent railway track ballast, recovered asphalt plainings, slate waste, crushed/ground/broken down glass waste, incinerator bottom ash from waste to energy plants, crushed fired ceramic waste, ground rubber crumb from scrap tyres, brick dust, crushed waste bricks, spent foundry sand, plastic, paper, crushed concrete block, crushed polymer concrete residues, synthetic aggregates produced from incinerated waste streams, aluminium flume, incinerated sewage sludge ash, road drain silt, ferrous foundry slag, non-ferrous foundry slag.

According to a third aspect of the invention, there is provided a polymer concrete composition comprising an aggregate according to the first or second aspect of the invention and a polymeric binding agent.

The polymeric binding agent may be a polymeric resin. The resin may be selected from a group of resins including polyester, epoxy, acrylic, vinyl, polyurethane and phenolic resins. As will be familiar to the skilled person, acrylic resins include polymethyl methacrylate. Polyester resins include the subclasses orthophthalic ployester resins, isophthalic polyester resins, and dicyclpentadiene polyester resins According to a fourth aspect of the invention, there is provided a cured polymer concrete composition according to the third aspect of the invention.

Any aspect of the invention described above may incorporate features of other aspects of the invention as appropriate and as will be appreciated by the person skilled in the art.

Embodiments of the invention are now described by way of example only.

Figure 1 shows a graph which illustrates the flexural strength of samples of a glass sand polymer concrete composition; Figure 2 shows a graph which illustrates the flexural strength of glass sand polymer concrete compositions; and Figure 3 shows a graph which illustrates the flexural strength of polymer concrete compositions with recycled content.

Polymer concrete is a mix of aggregates and a polymer binder. Concrete aggregates are granular materials ranging in particle size from gravel through various grades of sand to fine filler flour-like materials. Mixed aggregate materials are placed in a mould or void and the binder, which is often a resin binder, is introduced into the mixed aggregate materials and left to cure. For example, the dry mix may be injected with the resin and the whole mixed using a rotating screw feed. Accelerators may be added to reduce curing times, perhaps along with other additives such as hardeners and admixtures. The term admixture' encompasses a variety of materials which may be added to change properties or the appearance of the concrete, for example colour pigments.

Polymer concrete cure involves a chemical reaction called cross-linking, which forms a polymer matrix around the materials included in an aggregate, which bind aggregate particles of up to 8mm in size. The bond strength achieved between the polymer matrix and the aggregate materials is achieved in a different manner to cementitious concrete, which relies on a hydration process and interaction between the different aggregate materials.

As is known to the skilled person, the proportions of particles of each size are chosen with regard to desired properties of the concrete. The properties are partially dependent on the packing' of the aggregate material, as follows. In a mould filled to the brim with gravel, there will be air gaps between the gravel particles. Mixing in some finer material, such as coarse sand, will fill up some of the space between the gravel particles and reduce the total volume of the air gaps. Adding fine sand and then a fine filler material will reduce the volume of air still further. This will result in a dry mix which is closely packed and a polymeric binder which is poured onto the mix will coat particles rather than falling straight through the mix and pooling at the base of the mould. A closely packed material may also exhibit high compressive strength (although this is partly dependent on the binder used).

In a first embodiment, some or all of at least one of the gravel-sized, coarse sand-sized, fine sand-sized and fine filler size particles are replaced by ground glass. In this example, the ground glass is recycled glass which has been ground, cleaned and sieved to separate it into samples which match the size of gravel, coarse sand, fine sand and/or fine filler particles in known concrete mixes. As will be familiar to the skilled person, the cleaning process may comprising washing with water or some other liquid medium, or may comprise "airwashing" in which unwanted surface contamination is blown away by air during the grinding process, or some other cleaning process. In other examples, the glass may be crushed or formed into particles some other way (e.g. by being broken or smashed) The range of quantity of each material is presented in Table 1.

Table I

Material Particle size Amount Gravel 3 mm -8 mm 0-45% by dry weight Gravel-like glass sand 3 mm -8 mm 0-45% by dry weight Coarse sand 1 mm -3 mm 0-45% by dry weight Coarse glass sand 1 mm -3 mm 0-45% by dry weight Fine sand 0.5 mm -1 mm 0 -85% by dry weight Fine glass sand 0.5 mm -1 mm 0 -85% by dry weight Fine filler (flour-like materials) <0.5 mm 0-20% by dry weight Fine filler (flour-like ground glass) <0.5 mm 0-20% by dry weight Resin -Ca. 10 -16% by total weight Accelerator -Ca. 0.1 -1% by total weight Hardener -Ca. 0.1 -1% by total weight Admixtures -Ca. 0 -1% by total weight As can be appreciated from Table 1, recycled glass can form part of the composition in various ways. For example, recycled glass can provide part or all of the gravel-sized particles. Alternatively or additionally, it can provide part or all of the coarse sand-sized particle, the fine sand-sized particles and/or the fine filler material.

The non-glass aggregates in this example are selected from the following group: sand, gravel, crushed stone, slag, silt. In other examples, other materials may also be used which may be resistant to compressive stress.

A portion of the aggregates in the composition may be replaced with other materials, in particular but not exclusively with recycled materials, such as colliery spoil; gypsum, pulverised fuel ash (PFA), china clay waste (e.g. ball clay waste), slag (e.g. basic oxygen furnace (steel), blast furnace (iron), electric arc furnace (steel)), spent railway track ballast, recovered asphalt plainings, slate waste, incinerator bottom ash from waste to energy plants, crushed fired ceramic waste, ground rubber crumb from scrap tyres, brick dust, crushed waste bricks, spent foundry sand, ground plastic wastes, fine paper wastes, crushed concrete block wastes, crushed polymer concrete residues, synthetic aggregates produced from incinerated waste streams, aluminium flume, incinerated sewage sludge ash, road drain silt, ferrous foundry slag, non-ferrous foundry slag.

In one sample, the composition is as set out in Table 2:

Table 2

Component % by wt %by Dry Wt % by % by Dry (No (No Liquid Vol Liquid Components) components) Gravel 39.23% 45.00% 34.61% 45.33% Fine sand 21.79% 25.00% 18.74% 24.54% Calcium Carbonate 13.08% 15.00% 11.07% 14.50% Glass Coarse sand 13.08% 15.00% 11.93% 15.63% Resin 12.45% 0 22.80% 0 Accelerator 0.12% 0 0.28% 0 Hardener 0.25% 0 0.56% 0 Total Wet Wt 100.00% 100.00% 100.00% 100.00% The square symbols in all the Figures represent the Arithmetic Mean of the test results obtained for a particular material with the upper (diamond) and lower (triangle) symbols representing the 95% confidence limits that the true Mean lies between the values depicted.

Figure 1 shows the results of testing 6 samples of the mix shown in Table 2. The graph of Figure 1 can be read in the context of BS EN standard 1433 which relates to concrete for use in construction in the UK and Europe. This standard requires that the average flexural bending strength of the materials exceed 22 Newtons/mm2. All of the samples meet this standard.

Examples of the strength of five different polymer concrete compositions are shown in Figure 2, which shows the effect of providing a proportion of the coarse sand and the gravel-sized particles as ground glass coarse sand-sized particles on the flexural strength of the resulting cured concrete.

In other examples, the gravel could be replaced by gravel-sized glass sand particles with similar results. However, in this example, coarse sand sized particles were used as this means that only a single sample of glass sand particles is required. As can readily be appreciated, the coarse sand-sized particles must be stored separately from the gravel sized particles. Therefore, if gravel is replaced with gravel sized particles and coarse sand is replaced with Coarse Glass Sand CGS (i.e. coarse sand-sized particles), there would need to be an additional materials storage silo and handling system. Providing such systems and apparatus is costly.

Specifically, the mixes shown in Figure 2 are set out in Table 3 below:

Table 3

_________ GSAI GSA2 GSA3 GSA4 GSA5 % Vol of 0% 25.0% 50.0% 75.0% 100.0% Gravel Replaced by

CGS _______ _______ _______ _______ _______

WetWt% %bywt %bywt %bywt %bywt %bywt Gravel 39.46% 29.69% 19.86% 9.96% 0.00% Fine Sand 21.92% 22.00% 22.07% 22.14% 22.07% Calcium 13.15% 13.20% 13.24% 13.28% 13.24% Carbonate ___________ ___________ ___________ ___________ ___________ CGS 12.56% 22.17% 31.84% 41.58% 51.70% Glass fines 0.00% 0.00% 0.00% 0.00% 0.00% Resin 12.53% 12.57% 12.61% 12.65% 12.61% Accelerator 0.13% 0.13% 0.13% 0.13% 0.13% Hardener 0.25% 0.25% 0.25% 0.25% 0.25% Total Wet Wt 100.00% 100.00% 100.00% 100.00% 100.00% Dry WT % %by Dry %by Dry %by Dry %by Dry %by Dry _______ Wt Wt Wt Wt Wt Gravel 45.31% 34.11% 22.83% 11.46% 0.00% Fine Sand 25.17% 25.27% 25.36% 25.46% 25.36% Calcium 15.10% 15.16% 15.22% 15.28% 15.22% Carbonate ___________ ___________ ___________ ___________ ___________ CGS 14.42% 25.46% 36.59% 47.81% 59.42% Total 100.00% 100.00% 100.00% 100.00% 100.00% Vol% Wet % by Vol % by Vol % by Vol % by Vol % by Vol Gravel 34.80% 26.10% 17.40% 8.70% 0.00% Fine Sand 18.84% 18.84% 18.84% 18.84% 18.73% Calcium 11.13% 11.13% 11.13% 11.13% 11.07% Carbonate ___________ ___________ ___________ ___________ ___________ Glass Coarse 11.45% 20.15% 28.85% 37.56% 46.58% sand ___________ ___________ ___________ ___________ ___________ Resin 22.92% 22.92% 22.92% 22.92% 22.78% Accelerator 0.28% 0.28% 0.28% 0.28% 0.28% Hardener 0.56% 0.56% 0.56% 0.56% 0.56% Total Wet Vol 100.00% 100.00% 100.00% 100.00% 100.00% Vol% dry % by Dry % by Dry % by Dry % by Dry % by Dry ___________ Vol Vol Vol Vol Vol Gravel 45.65% 34.24% 22.83% 11.41% 0.00% Fine Sand 24.72% 24.72% 24.72% 24.72% 24.52% Calcium 14.61% 14.61% 14.61% 14.61% 14.49% Carbonate ___________ ___________ ___________ ___________ ___________ Glass Coarse 15.02% 26.44% 37.85% 49.26% 60.98% sand ___________ ___________ ___________ ___________ ___________ Total Dry Vol 100.00% 100.00% 100.00% 100.00% 100.00% Strength (N/mm2) _________ _________ _________ _________ _________ Mean Flex 22.52 22.87 22.49 20.41 18.37 Strength Lowervalue 21.40 21.65 21.80 18.94 21.88 Upper Value 23.63 24.08 23.19 21.88 20.12 As can be seen from this Figure, the flexural strength of the concrete reduces as glass provides a greater proportion of the mix.

If a trend line is plotted on Figure 2, it can be seen that the concrete meets the BS EN 1433 standard of 22 Newtons/mm2 for a percentage of glass by total dry weight of up to about 32%. At this point, 52% of the gravel-sized particles are provided by glass particles. Mixes with about 33% glass by weight have also been found to meet the BS EN 1433 standard. Above this value, the material is weaker than 22 Newtons/mm2 and therefore may not be suitable for certain projects. However, these compositions could be strengthened in order to meet this or other standards with the inclusion of a hardener or the like which may allow for higher glass sand proportions in an aggregate.

In a further embodiment, some or all of the coarse sand-sized particles are replaced by ground glass. The range of quantity of each material is presented in Table 4.

Table 4

Material Particle size Amount Gravel 3 mm -8 mm 0-45 % by dry weight Coarse glass sand 1 mm -3 mm 14 or 15%-60 % by dry weight Fine sand 0.5 -1 mm 25 % by dry weight Calcium carbonate <0.5mm 15 % by dry weight Resin 10-15% by total weight Accelerator Approx. 0.15-0.5 % by total weight Hardener Approx. 0.3 -1 % by total weight Admixtures 0 -1 % of total weight This range of material has been selected as being similar to standard mixtures, which may reduce production risks. As is demonstrated by Figures 1 and 2, this range includes appreciable levels of recycled material and still provides the strength requirements of the standard. Providing a proportion of the aggregate as glass which has been crushed /ground or otherwise broken down may also be cost-advantageous in some cases glass may be cheaper than the equivalent sand or gravel particles.

Further embodiments are now discussed with reference to Figure 3. In the concrete compositions of these embodiments, some or all of at least one of the gravel-sized, coarse sand-sized, fine sand-sized and fine filler particles are provided by recycled materials.

Figure 3 shows the flexural strength of various polymer concrete mixes each of which includes recycled material. The compositions are set out in Table 5 below and the strengths of each composition are set out in Table 6. The recycled component in each composition is indicated in the left hand column and the percentage of this component is noted in the column indicating which of the gravel, course sand, fine sand or fine filler (in these examples, the fine filler is calcium carbonate) it replaces.

Table 5

Gvl C'rse Fine Fine Gvl C'rse Fine Fine Resin Sand Sand Filler RepI Sand Sand Filler __________ _____ ______ ______ ______ ______ RepI RepI RepI ______ Plastic 0% 18% 29% 18% 18% 0% 0% 0% 17% Beads Glass 38% 0% 17% 10% 0% 23% 0% 0% 12% Source A 0 -5mm ___ ____ ____ ____ ____ ____ ___ ___ ____ Glass 39% 0% 22% 13% 0% 13% 0% 0% 12% Source A 1 -3mm sieved Glass ______ _______ _______ _______ _______ _______ ______ ______ _______ Glass 39% 13% 0% 13% 0% 0% 22% 0% 12% Source A 0 -1mm sieved Glass ______ _______ _______ _______ _______ _______ ______ ______ _______ Glass 39% 0% 13% 0% 1% 13% 9% 13% 13% Source B 0 -3mm inc flour ______ _______ _______ _______ _______ _______ ______ ______ _______ Glass 39% 0% 0% 13% 0% 13% 22% 0% 12% Source B 0 -3mm sands ______ _______ _______ _______ _______ _______ ______ ______ _______ Glass 39% 0% 0% 13% 0% 13% 22% 0% 12% Source B 0 -3mm sieved ______ _______ _______ _______ _______ _______ ______ ______ _______ Glass 40% 0% 0% 13% 0% 13% 20% 0% 13% Source B 0 -3mm sieved ______ _______ _______ _______ _______ _______ ______ ______ _______ Crushed 0% 13% 23% 14% 42% 1% 0% 0% 7% Porcelain As Supplied ______ _______ _______ _______ _______ _______ ______ ______ _______ Crushed 0% 15% 25% 15% 31% 0% 0% 0% 14% Porcelain 3-8 ______ _______ _______ _______ _______ _______ ______ ______ _______ Recycled 41% 14% 0% 14% 0% 0% 18% 0% 13% Polymer concrete 0.1 -1mm ___ ____ ____ ____ ____ ____ ___ ___ ____ Recycled 41% 0% 23% 14% 0% 9% 0% 0% 13% Polymer concrete 1-3mm

Table 6

Mean Lower UpperValue ________________________________ Strength Value ___________ BS EN Std 22.00 18.00 26.00 Plastic Beads 8.34 7.39 9.30 Glass Source A 0 -5mm 20.78 19.03 22.53 Glass Source A 1 -3mm sieved Glass 25.28 24.16 26.41 Glass Source A 0 -1mm sieved Glass 20.69 19.56 21.82 Glass Source B 0 -3mm inc flour 8.16 4.01 12.30 Glass Source B 0 -3mm sands 17.81 16.01 19.62 Glass Source B 0 -3mm sieved 16.85 16.24 17.46 Glass Source B 0-3mm sieved 16.58 15.88 17.28 Crushed Porcelain As Supplied 4.75 2.57 6.94 Crushed Porcelain 3-8mm 8.90 8.43 9.37 Recycled Polymerconcreteo.1 -1mm 14.07 12.84 15.30 Recycled Polymer concrete 1-3mm 23.43 19.68 27.18 It will be understood that the above description of a preferred embodiment is given by way of example only and that various modifications may be made by those skilled in the art.

In some embodiments, the concrete mix may be used to form pre-cast building elements such as drainage channels and kerbs. As will be appreciated from the foregoing, it may be particularly advantageous to incorporate recycled material into products which cannot otherwise contain recycled material (e.g. products formed purely of concrete, rather than those which contain, for example, cast iron or stainless steel elements which may more often comprise recycled components), as this may allow the use of a concrete in a project with a recycled component target.

Claims

CLAIMS1. A polymer concrete aggregate comprising glass sand.
2. The aggregate of claim 1 wherein the aggregate comprises up to 32% by weight glass sand.
3. The aggregate of claim 1 or claim 2 wherein the aggregate comprises from about 10% to about 32% by weight glass sand.
4. The aggregate of any preceding claim wherein the aggregate comprises from about 20% to about 32% by weight glass sand.
5. The aggregate of claim 1 wherein the aggregate comprises up to about 33% by weight glass sand.
6. The aggregate of any preceding claim, wherein the aggregate comprises a mixture of gravel-sized particles, sand-sized particles, and fine filler particles, and at least a portion of at least one of the gravel-sized particles, sand-sized particles, and fine filler particles comprises glass sand.
7. The aggregate of claim 6 in which at least one of the gravel-sized particles, sand-sized particles, and fine filler particles consists of glass sand.
8. The aggregate of claim 6 or claim 7 wherein the aggregate comprises: (i) 0-45% by dry weight gravel-sized particle (ii) 0-45% by dry weight coarse sand-sized particles (iii) 0-85% by dry weight fine sand-sized particles (iv) 0-20% by dry weight fine filler particles.
9. The aggregate of any of claims 6 to 7 in which the aggregate comprises: (i) 0-45% by dry weight gravel-sized particle (ii) 15-60 % by dry weight coarse sand-sized particles (iii) approximately 25% by dry weight fine sand-sized particles (iv) approximately 15% by dry weight calcium carbonate.
10. The aggregate of any preceding claim in which the glass sand comprises ground waste glass.
11. The aggregate of claim 10 in which the ground glass comprises at least one sample of waste glass of a predetermined size range.
12. A polymer concrete aggregate wherein at least a portion of the aggregate comprises recycled materials.
13. A polymer concrete aggregate according to claim 12 in which the recycled materials comprise one or more of the following: colliery spoil; gypsum, pulverised fuel ash (PFA), china clay waste (e.g. ball clay waste), slag (e.g. basic oxygen furnace (steel), blast furnace (iron), electric arc furnace (steel)), spent railway track ballast, recovered asphalt plainings, slate waste, crushed/ground/broken down glass waste, incinerator bottom ash from waste to energy plants, crushed fired ceramic waste, ground rubber crumb from scrap tyres, brick dust, crushed waste bricks, spent foundry sand, plastic, paper, crushed concrete block, crushed polymer concrete residues, synthetic aggregates produced from incinerated waste streams, aluminium flume, incinerated sewage sludge ash, road drain silt, ferrous foundry slag, non-ferrous foundry slag.
14. A polymer concrete composition comprising aggregate according to any proceeding claim and a polymeric resin.
15. The composition of claim further comprising at least one of: an admixture, a hardener.
16. The composition of any preceding claim wherein the polymeric binder is a polymeric resin selected from a group consisting of polyester, epoxy, acrylic and vinyl resins.
17. A polymer concrete aggregate substantially as described herein and as illustrated in the accompanying Figures.
18. A polymer concrete composition substantially as described herein and as illustrated in the accompanying Figures.