The present invention relates to a composition for modifying aggregate materials. The present invention also relates to coated aggregate and an aggregate admixture which is particularly suitable for use with an asphalt concrete, for example a Stone Matrix Asphalt concrete. A modified asphalt concrete is also provided.

Background to the Invention

Bituminous asphalt concrete suffers from cracking, potholing, ravelling and stripping and requires frequent repairs by patching. The regular degradation of bituminous asphalt is caused by exposure to thermal distress and photo-oxidation from UVA and Infrared. Oxidative ageing of the bituminous asphalt is an irreversible chemical reaction caused by oxidation of different components within the asphalt admixture. Oxidative ageing (and thus degradation) of the asphalt admixture is increased where the asphalt mixture contains a high void content.

US2012/0196959 describes an asphalt paving material which comprises 3 to 8% of asphalt binder formed from a base asphalt together with 0.25 to 10% by weight of an oxidised polyolefin. Addition of the polyolefin assist the asphalt to adhere to the aggregate in moist conditions.

GB1072056 describes the manufacture of road edging members, such as curbstones, formed from a combination of bitumen, an olefin polymer and a mineral filler formed from an admixture of stone chippings, stone dust and sand.

The present invention seeks to address the above issues and to reduce oxidative ageing of the asphalt concrete. Accordingly, the asphalt concrete is less susceptible to problems of "rutting" due to softening at warmer temperatures, and also less susceptible to "cracking" and "stone flying" due to the hardening caused by lower temperatures. One objective of the present invention is to reduce the damaging effects of thermal fluctuations which age the bituminous asphalt by absorption of light in the infrared spectrum and in the Ultraviolet spectrum.

A further objective of the present invention is to actively reduce the aging of the bitumen binder in asphalt concrete, by enabling the asphalt surface matrix to resist thermo-environmental and thermo-structural changes.

Summary of the Invention

The present invention provides a composition, suitable for use within an aggregate of an asphalt concrete.

The composition comprises:

80 to 95% by weight of an inorganic component,

3 to 5% by weight of polyisobutylene; and

2 to 15% by weight of an organic component comprising elastomer polymers of alkylene or isoalkylene, but excluding polyisobutylene, (for example propylene elastomers or ethylene propylene elastomers), wherein the combination of inorganic component, polyisobutylene and organic component sums to 100%, and wherein said inorganic component comprises:

60 to 90% by weight of soda lime glass, and

10 to 40% by weight of a geopolymer.

The present invention further provides an aggregate admixture comprising aggregate and the composition as described above. In one aspect, the aggregate particles can be at least partially coated with the composition described above. The coated particles are suitable for use as aggregate, for example are formed from stone, such as granite. The aggregate will typically be a gradated aggregate, as is commonly used for asphalt concrete. Typically, the aggregate particles will be of sieve size 20mm or smaller, for example 16mm or smaller. The present invention further provides an asphalt concrete comprising the composition and /or coated particles or aggregate admixture according to the invention.

Description of the Figures

Fig 1 illustrates a prior art and unmodified single stone aggregate (in stylised form for simplicity).

Fig.2 illustrates a single stone aggregate (in stylised form for simplicity) coated with the composition of the present invention.

Fig. 3 illustrates a prior art bituminous asphalt containing a mixture of bitumen and stone aggregate (in stylised form for simplicity).

Fig. 4 illustrates the bituminous asphalt mixture according to the present invention comprising the coated stone aggregate of Fig. 2 within the bitumen.

Detailed Description of the Invention

The composition, coated aggregate particles, modified aggregate admixture and asphalt concrete of the present invention are now described in further detail.

As noted above, the present invention provides a composition which can be admixed with or used as a coating onto particles for use within the aggregate of an asphalt concrete. The composition comprises:

80 to 95% by weight of an inorganic component,

3 to 5% by weight of polyisobutylene; and

2 to 15% by weight of an organic component comprising elastomer polymers of alkylene or isoalkylene, but excluding polyisobutylene, (for example propylene elastomers or ethylene propylene elastomers), wherein the combination of inorganic component, polyisobutylene and organic component sums to 100%, and wherein said inorganic component comprises:

60 to 90% by weight of soda lime glass, and

10 to 40% by weight of a geopolymer. Optionally, the composition consists of:

80 to 95% by weight of an inorganic component, 3 to 5% by weight of polyisobutylene; and

2 to 15% by weight of an organic component comprising elastomer polymers of alkylene or isoalkylene, but excluding polyisobutylene, (for example propylene elastomers or ethylene propylene elastomers), wherein the combination of inorganic component, polyisobutylene and organic component sums to 100%, and wherein said inorganic component comprises:

65 to 85% by weight of soda lime glass, and 15 to 35% by weight of a geopolymer.

Optionally the inorganic component of the composition comprises: 60 to 80% by weight of soda lime glass, and 20 to 40% by weight of a mixture of geopolymer.

The organic component and polyisobutylene together form 5 to 20% by weight of the total composition.

The polyisobutylene (butyl rubber) for use in the composition of the invention is a thick viscous liquid which remains flexible at temperatures down to a freezing point of -54 ^Q C. The function of the polyisobutylene is to act as a binder and tackifier to the solid inorganic mineral content of the formula and as an anti-aging/anti- embrittlement modification of the bitumen binder of the aggregates to form asphalt road surfaces. The polyisobutylene also enables the bitumen binder of the aggregates to resist embrittlement brought on by freezing road surface temperatures in extreme climates. The polyisobutylene is generally in a liquid form. The weight average molecular weight (MW Mn) of the polyisobutylene can range from 950 to 2400, for example from 1000 to 1500. A MW Mn of 1200-1400 can be used, for example around 1250-1350, such as 1300. The polyisobutylene can be hydrogenated. Due to its fully saturated hydrocarbon backbone, polyisobutylene is inert and highly resistant to degradation, especially by oxygen and ozone. The low glass transition temperature (Tg) of polyisobutylene, measures in the range of -73 to -65 °C dependent upon molecular weight and provides it with strong low temperature properties.

The organic component comprising 2 to 15% by weight of the composition comprises elastomer polymers of alkylene or isoalkylene and is a different polymer to polyisobutylene. The organic component may optionally comprise one or more waxes. Optionally an anti-oxidant can also be included as part of the organic component. Optionally, the elastomer polymer in the organic component is cured to improve tensile strength and modulus. Optionally, the elastomer polymer is an alkylene polymer. Suitable elastomers include ethylene propylene-based elastomers. Optionally the elastomer is present in an amount of up to 8% by weight of the overall composition, for example in an amount of 5-7% by weight of the overall composition. Preferred elastomers may be hydrogenated or nonhydrogenated polymers of alkylene or isoalkylene such as polybutene, polypropylene, polyethylene, polybutadiene or polyisoprene, polyalphaolefin, polyester, and polyacrylate and its copolymers. Optionally the polymers may be polypropylene or polyethylene based polymers or copolymers. Propylene-based elastomers are one suitable option, in particular propylene-ethylene elastomers, for example formed from isotactic propylene units with random ethylene distribution. Preferably the propylene elastomer has a low viscosity of below 4000 mPa.s at 190 ^Q C. One commercially available option is Viscomaxx® 8780 of ExxonMobil.

The organic component can also comprise one or more waxes, for example a polyethylene wax or a mixture of different polyethylene waxes. Optionally the waxes can be present in an amount of up to 2% by weight of the overall composition. One suitable wax is E1 1 B of Deurex GmbH.

The organic component can also comprise one or more anti-oxidants. One suitable example is tetrakis[methylene-3-(3,5-di-tert-butyl-4-hydroxyphenyl)prop ionate] methane, which is commercially available as Songnox® CS 1010. Other antioxidants can alternatively be used.

The soda lime glass can conveniently be formed with a majority component of silicon dioxide and can include one or more of sodium oxide, calcium oxide, magnesium oxide and/or aluminium oxide. Traces of other metals, including heavy metals, or their oxides can also be present, for example in amounts up to 5% by weight. An exemplary composition is formed from (% by weight) SiC>2 (68 to 75%), Na ₂ O (12 to 18%), CaO (7 to 12%), MgO (0 to 5%), AI2O3 (0 - 2.5%), and optionally heavy metal trace elements, for example in a total amount of up to 1 % by weight. The heavy metal trace elements can be, for example Pb, As and/or Sb. The trace elements will typically be present at an amount of 200ppm or less. Preferably, the glass content of composition of the present invention is characterized in that particles are formed by oxides selected from the group consisting of SiO, BO, POs, GeO2, ASOs, ASO, Sb2O, and their mixtures thereof, and more preferably SiO. Alternatively, the glass particles may be solid glass beads, typically of micron or sub-micron size.

Additionally, the glass particles may further include modifiers selected from the group consisting of KO, Na ₂ O, CaO, BaO, PbO, ZnO, VOs, ZrO, BiO, AI2O, oxides of Ti, oxides of Th, and mixtures thereof.

The soda lime glass will normally be in particulate form and can have a particle size (average diameter) of 300 pm or less, for example can be from 1 to 300 pm, for example can be from 1 to 200 pm, for example from 1 to 120 pm, for example from 50 to 120 pm, for example from 70 to 100 pm.

In one embodiment, the glass particles have an average diameter of 0.05 micron to 1 .5 micron, more preferably 0.75 micron.

The geopolymer can be any inorganic material with covalently bonded, noncrystalline networks. The geopolymer can be a ceramic material. The geopolymer can be a phyllosilicate, such as talc, mica or kaolin. The geopolymer can be a hydrous kaolin (china clay), for example can be Polwhite™ E, for example as supplied by Imerys. The geopolymer can be an alumina phyllosilicate and for example may be formed from a clay mineral such as a kaolin or kaolinite in which the structure has been changed upon thermal removal of structural water or by high-energy grinding. The geopolymer can conveniently be selected from a hydrosodalite-based geopolymer poly(sialate), or any of the serpentine mineral groups (i.e. antigorite, chrysotile and lizardite), silica-based geopolymer, sialate link and siloxo link in poly(siloxonate) Si :AI>5, kaolinite / hydrosodalite-based geopolymer, poly(sialate) Si:AI=1 :1 , Meta kaolin MK-750-based geopolymer, poly(sialate-siloxo) Si :AI=2: 1 , water glass-based geopolymer, poly(siloxonate), soluble silicate, Si :AI=1 :0, calcium-based geopolymer, (Ca, K, Na)-sialate, Si:AI=1 , 2, 3 rock-based geopolymer, poly(sialate-multisiloxo) 1 < Si:AI<5 silica-based geopolymer, sialate link and siloxo link in poly(siloxonate) Si :AI>5 fly ash-based geopolymer, ferro-sialate-based geopolymer, phosphate-based geopolymer, AIPO4-based geopolymer, organic-mineral geopolymer. The geopolymer is preferably a hydrosodalite-based geopolymer poly(sialate).

Optionally, the geopolymer includes 0 to 5% (by weight of the inorganic component) of an additive selected from a boron compound (typically a borate salt such as sodium borate, boron trioxide or diboron trioxide) or a magnesium aluminium phyllosilicate (such as attapulgite). Thus, the inorganic component can be formed of, for example:

60 to 90% by weight of soda lime glass, and

5 to 40% by weight of a phyllosilicate (such as kaolin) and

0 to 5% by weight of either a boron compound or a magnesium aluminium phyllosilicate.

Optionally, the inorganic component can be formed of: 60 to 90% by weight of soda lime glass, and 5 to 39% by weight of a phyllosilicate (such as kaolin) and 1 to 5% by weight of either a boron compound or a magnesium aluminium phyllosilicate.

Optionally, the inorganic component can be formed of: 60 to 90% by weight of soda lime glass, and 5 to 37% by weight of a phyllosilicate (such as kaolin) and 3 to 5% by weight of either a boron compound or a magnesium aluminium phyllosilicate. The magnesium aluminium phyllosilicate has formula (Mg,AI)2Si40io(OH)-4(H20). Suitable magnesium aluminium phyllosilicates include palygorskite or attapulgite. Inclusion of magnesium aluminium phyllosilicate can be beneficial where the asphalt concrete is intended to be used in a location which experiences a high level of rainfall (for example the west coast of Scotland).

The composition of the present invention is conveniently provided in the form of a free-flowing powder formulation.

The composition of the present invention can maintain its stability (i.e. , will not separate) even when stored for a period of over a year, for example 1 to 2 years, for example 18 months.

In a further aspect, the present invention further provides particles at least partially coated with the composition described above. The particles are suitable for forming aggregate, for example are formed from stone, such as granite. The aggregate particles can have a diameter of 20mm or less, for example 15mm or less. Optionally, the coated particles will be the “large aggregate” or “coarse aggregate” portion of a standard aggregate gradated mixture. For example, the aggregate particles may be typically sized between 1 mm and 20mm, for example may be sized between 2mm and 16mm, for example may be sized between 4mm and 16mm. An aggregate of a suitable diameter would generally be conveniently selected by sieving using a sieve with an appropriately sized mesh, and selecting the component which passes through the sieve. The powder coating composition is simply admixed with the aggregate for a time sufficient for allow the aggregate to become at least partially coated with the coating composition. The time required for coating will typically be in the order for minutes, for example 5 to 30 minutes. Optionally the aggregate is substantially uniformly dispersed with the composition of the invention. Typically, 1 to 10% by weight, for example 1 to 5% by weight of the composition, for example 1 .5 to 3 % by weight of the composition (relative to the total admixture formed) is added to the aggregate. For example, to form 100kg of the coated aggregate, 1 to 10kg of the composition can be added to 90 to 99kg of aggregate. In some mixtures, at least 50% of the surface area of the aggregate will be coated with the coating composition of the present invention. However even at low levels of coating, for example coating 10% or even 5% or 2% or 1% of the surface area of the aggregate can provide benefits regarding the longevity of the resultant asphalt concrete. Where the aggregate is intended for use within an asphalt concrete, the aggregate is conveniently coated with the composition of the present invention prior to addition of the bitumen binder.

The coated aggregate has been demonstrated to exhibit improved wet-out by the bitumen and to result in significantly higher mechanical strength of the resultant asphalt concrete.

In a further aspect, the present invention further provides an aggregate admixture for use within an asphalt concrete, wherein said admixture comprises the composition described above admixed with standard aggregate. The aggregate is formed from particles which are suitable for forming aggregate, for example are formed from stone, such as granite. The aggregate particles can have a diameter of 20mm or less, for example 16mm or less. For example, the aggregate particles may be typically sized between 1 mm and 16mm. An aggregate of a suitable diameter range would generally be conveniently selected by sieving using a sieve with an appropriately sized mesh, and selecting the component which passes through the sieve. Optionally the aggregate is a gradated aggregate. Optionally, the aggregate can be the coarse fraction only, i.e. , having gradated particles with diameters of from 2mm to 20mm, for example from 4mm and 16mm. The composition of the present invention can be simply admixed with the aggregate to form the aggregate admixture. Typically, 1 to 10% by weight, for example 1 to 5% by weight of the composition, for example 1 .5 to 3 % by weight of the composition (relative to the total admixture formed) is added to the aggregate. For example, to form 100kg of the admixture, 1 to 10kg of the composition can be added to 90 to 99kg of aggregate. Optionally the aggregate is mixed with composition to form a uniform admixture. Where the admixture is intended for use within an asphalt concrete, the admixture is conveniently formed prior to addition of the bitumen binder. The aggregate admixture of the present invention has been demonstrated to exhibit improved wet-out by the bitumen and to result in significantly higher mechanical strength of the resultant asphalt concrete.

Additionally, the asphalt concrete is less susceptible to problems of "rutting" due to softening at warmer temperatures, and also less susceptible to "cracking" and "stone flying" due to the hardening caused by lower temperatures.

The asphalt concrete formed has improved ability to resist thermo-environmental and thermo-structural changes. For example, the asphalt concrete of the present invention can provide a Marshall Quotient of at least 7.0 kN/mm, for example a Marshall Quotient of at least 8kN/mm or 9kN/mm, or even a Marshall Quotient of at least 10kN/mm.

Accordingly, the present invention further provides a method of forming a coated aggregate, wherein the composition of the present invention is admixed with aggregate. Typically, 1 to 10% by weight, for example 1 to 5% by weight of the composition, for example 1 .5 to 3% by weight of the composition (relative to the total admixture formed) is added to the aggregate. For example, to form 100kg of the admixture, 1 to 10kg of the composition can be added to 90 to 99kg of aggregate. The mixture is stirred until uniformity is achieved and at least a portion of the aggregate is at least partially coated with the composition. Generally, the mixing step can be conducted at ambient temperature, however gentle heating of the composition (for example to 100 ^Q C) to reduce viscosity can be beneficial. Optionally the aggregate can be subjected to gentle heating (to aid drying thereof) in the conventional manner prior to addition of the composition of the invention.

Additionally, the present invention further provides a method of forming an aggregate admixture, wherein the composition of the present invention is admixed with aggregate. Typically, 1 to 10% by weight, for example 1 to 5% by weight of the composition, for example 1 .5 to 3 % by weight of the composition (relative to the total admixture formed) is added to the aggregate. For example, to form 100kg of the admixture, 1 to 10kg of the composition can be added to 90 to 99kg of aggregate. The mixture is stirred until uniformity is achieved. Generally, the mixing step can be conducted at ambient temperature, however gentle heating of the composition (for example to 100 ^Q C) to reduce viscosity can be beneficial. Optionally the aggregate can be subjected to gentle heating (to aid drying thereof) in the conventional manner prior to addition of the composition of the invention.

An asphalt concrete is typically formed using coarse gradated aggregate, a fine aggregate (such as sand), an optional filler, and bitumen binder. The composition of the present invention can be used with the coarse aggregate fraction of the asphalt concrete. Finer aggregate (for example sand) and optionally filler can be included together with the bitumen binder or asphalt in the known manner. The filler material can be any conventional filler used in conventional asphalt cement compositions, for example limestone. Alternatively, the composition of the present invention can be used in combination with both the fine aggregate (sand) and coarse aggregate, in other words the composition can be used with the whole gradated aggregate to be used to form the asphalt concrete.

In a yet further aspect, the present invention further provides an asphalt concrete composition comprising coated particles according to the invention (i.e., coated aggregate) in combination with a bitumen binder. The coated particles are at least partially coated with the composition of the invention. Optionally the asphalt concrete composition can further comprise uncoated aggregate, i.e., will have a combination of coated and uncoated aggregate together within the aggregate component with a bitumen binder. For some asphalt concretes, a portion of the coarse aggregate fraction (for example 1 to 5% by weight of the total coarse aggregate) is coated with the composition of the present invention, which is then combined with uncoated coarse aggregate and optionally with finer aggregate particles such as sand and filler before mixing with the bitumen binder. For other asphalt concretes, a portion of the total aggregate fraction comprising both fine and coarse aggregate is coated with the composition of the present invention (for example 1 to 5% by weight of the total aggregate is coated), and uncoated aggregate and optionally filler are then added before mixing with the bitumen binder. The filler material can be any conventional filler used in conventional asphalt cement compositions, for example limestone. In one embodiment the total aggregate component of the asphalt concrete can be formed from 1 to 20% by weight of the coated aggregate according to the invention and from 80% to 99% of uncoated aggregate, for example from 1 to 10 % by weight of the coated aggregate, for example from 1 to 5 % by weight of the coated aggregate.

Optionally the coated aggregate is gradated, i.e. , has a continuous range of diameter sizes within the aggregate size range, which is typically from 0.5mm to 20mm, for example 1 mm to 16mm. In one embodiment, the asphalt concrete composition of the present invention comprises 5 to 8 % by weight of the coating composition of the present invention and 92 to 95 % by weight of the total aggregate and bitumen asphalt mix. As noted above, the relationship between the aggregate gradation and the bitumen binder has been noted to be significantly improved through use of the coating on a fraction on the aggregate (either of coarse aggregate only or the total gradated aggregate) according to the invention. Modification of the aggregate gradation (rather than the bitumen binder) enables improved asphalt concrete surface durability.

In a yet further aspect, the present invention further provides an asphalt concrete composition comprising the composition according to the invention in combination with an aggregate and a bitumen binder. Optionally the asphalt concrete composition can further comprise conventional filler. The composition of the invention can conveniently be combined with the aggregate as described above for the aggregate admixture. For some asphalt concretes, only the coarse aggregate fraction is combined with the composition of the present invention, which is then combined with the finer aggregate particles (such as sand), and optionally a filler, before mixing with the bitumen binder. For other asphalt concretes, the total aggregate comprising both fine and coarse aggregate is admixed with the composition of the present invention as described above. Optionally uncoated aggregate and/or a filler can then be added before mixing with the bitumen binder. The filler material can be any conventional filler used in conventional asphalt cement compositions, for example limestone. In one embodiment the asphalt concrete can be formed from 92 to 95% by weight of the aggregate admixture according to the invention and from 5 to 8 % by weight of the bitumen binder (such as asphalt). Optionally the aggregate is gradated, i.e., has a continuous range of diameter sizes within the aggregate size range, which is typically from 0.5mm to 20mm, for example 1 mm to 16mm. As noted above, the relationship between the aggregate gradation and the bitumen binder has been noted to be significantly improved through use of the coating on a fraction on the aggregate (either of coarse aggregate only or the total gradated aggregate) according to the invention. Modification of the aggregate gradation (rather than the bitumen binder) enables improved asphalt concrete surface durability.

The present invention is not limited to any particular type or grade of bitumen binder or asphalt. Any bitumen binder or asphalt which is considered suitable to form asphalt concrete may also be used in the present invention. Use of the composition of the present invention in combination with the aggregate (either in admixture or coating the aggregate) has the advantage that less bitumen binder or asphalt is required to achieve a suitable asphalt concrete, as compared to an equivalent asphalt concrete using standard aggregate alone. For example, the weight of binder required can be reduced by at least 10%.

A further advantage of this invention is in the

1. High durability

2. Better water resistance properties

3. Increased resistance to cracks and stripping

4. Increased resistance to deformation

5. Higher rigidity of the resultant asphalt concrete.

Moreover, this change in the aggregate formulation and the addition of the uniquely polymerised mineral antioxidation particle reinforcement composite of this invention, has shown to increase the dynamic stability of over current industry performance by 235% (See Table 1 in the Examples).

The present invention further provides a method of forming an asphalt concrete wherein at least 1% of said aggregate fraction is replaced with the coated aggregate of the present invention. Optionally from 1 to 20% of the aggregate fraction for the concrete is replaced with the coated aggregate of the present invention for example from 1 to 10 % by weight of the aggregate fraction, for example from 1 to 5 % by weight of the aggregate fraction is replaced with the coated aggregate of the present invention. The method comprises admixing the aggregate mixture (comprising both coated and uncoated aggregate) together with a bitumen binder or asphalt, and optionally together with filler material. The method can be limited to a concrete where only the coarse aggregate has been coated in accordance with the present invention, wherein coarse aggregate fraction has a sieve size of from 4mm to 20mm (or 16mm).

An alternative method of preparing the asphalt concrete can utilise an admixture of aggregate and the composition of the present invention and combining with a bitumen binder or asphalt, and optionally together with filler material.

The present invention will now be further described with reference to the following, non-limiting examples and figures.

With reference to the figures, Fig. 1 illustrates a prior art and unmodified single stone aggregate (1 ). The single stone aggregate is shown in stylised form for simplicity, but can be any shape and is typically irregular in shape. The aggregate (1 ) is formed of a piece of stone or other hardcore (3) having a surface (2). The aggregate can have a particle sieve size of 4mm to 16mm. In use, the aggregate (1 ) is bound together with other aggregate in gradated size (not shown in Fig. 3 for simplicity) to form an asphalt concrete (1 1 ), as shown stylised form in Fig. 3. The voids or interstices between each aggregate (1 ) are at least partially filled with a bitumen binder or asphalt (4). Remaining air spaces or voids are not separately shown for simplicity.

Fig. 2 illustrates a coated single stone aggregate (10) according to the present invention. The single stone aggregate (10) is shown in stylised form for simplicity, but can be any shape and is typically irregular in shape. The aggregate (10) can have a particle sieve size of 4mm to 16mm. The single stone aggregate (10) is coated at its surface (2) with a layer of the coating composition (20) of the present invention. Specifically, the coating composition (20) comprises multiple micron and sub-micron particles (25) which together at least partially coat the aggregate (10) and provide multiple surface bonding sites for the bitumen binder or asphalt (4), as shown in Fig. 4. Multiple copies of the coated aggregate (10) in gradated sizes are located in the bitumen binder or asphalt (4) form the modified asphalt concrete (40) of the present invention.

Preferred or alternative features of each aspect or embodiment of the invention apply mutatis mutandis to each other aspect or embodiment of the invention (unless the context demands otherwise).

All documents referred to herein are incorporated by reference. Any modifications and/or variations to described embodiments that would be apparent to one of skill in art are hereby encompassed. Whilst the invention has been described herein with reference to certain specific embodiments and examples, it should be understood that the invention is not intended to be unduly limited to these specific embodiments or examples.

Examples

Example 1 : Production of a Coating Composition

Glass beads of a soda lime glass powder were added into a Z-blade mixer. Soda lime glass microsphere are suitable, for example microsphere having a tapped density of 1 .57g/cc, and with an average particle size of 70 to 100 microns. The glass composition can comprise SiC>2 (68 - 75%), Na2O (12 - 18%), CaO (7 - 12%), MgO (0 - 5%), and AI2O3 (0 - 2.5%), with all percentages being by weight. Heavy metal trace elements may be present.

A kaolin-based geopolymer is then added into the mixer. The ratio (by weight) of the soda lime glass powder to the kaolin geopolymer was 4:1 (i.e. , 80% by weight glass powder and 20% by weight geopolymer). These ingredients were mixed together to produce the inorganic component according to the invention.

To 900g of this admixture were added the following:

30g Polyisobutylene

7.5g Non-polar polyethylene wax (in granular form)

52.5g Propylene-based elastomer and

10g Antioxidant. The total admixture weighed 1 kg.

A suitable anti-oxidant is tetrakis[methylene-3-(3,5-di-tert-butyl-4- hydroxyphenyl)propionate] methane. Other anti-oxidants can alternatively be used.

The ingredients were then stirred together to form an exemplary composition according to the present invention having a uniform consistency.

Example 2: Formation of Modified Aggregate

The composition of Example 1 was admixed with coarse stone aggregate, namely granite chips with a diameter of 16mm or less. 2.1% by weight of the composition of Example 1 was mixed with the aggregate to form a modified aggregate, in which at least some of the aggregate particles are at least partially coated with the composition.

Example 3: Testing of Asphalt Concrete

The tests set out in Table 1 were conducted on the modified aggregate formed in Example 2.

Standard AC13 Asphalt was used as a control. This contained a coarse aggregate with a diameter of 14mm or less admixed with fine aggregate of sand. Aggregate size was selected by screening in the usual manner. The control sample was a standard AC13 grade mix and contained 34.7 % coarse aggregate of granite, 63.3% fine aggregate and 2.1% filler (Limestone, from LKAB Minerals). The bitumen or asphalt had a softening point of 55 ^Q C and was Puma 40/60.

The test sample and the control sample asphalts were mixed in accordance with BS EN 12697-35:2004, A1 :2007.

Specimen preparation by impact compactor was conducted in accordance with BS EN 12697-30:2012.

Results for the standard AC13 asphalt (control) and for the asphalt concrete using the modified aggregate are shown in Table 1 . Table 1 : Properties of Asphalt Concrete

Example 4: Testing of Asphalt Concrete The composition of Example 1 was used to form a modified aggregate having the following particle size and distribution:

34.7% by weight coarse aggregate (RAP aggregate).

63.3% by weight fine aggregate (sand); and

2.1% by weight filler (Limestone, LKAB Minerals, 87% with particle size 0.063mm or less). The particle size distribution for the coarse aggregate (determined in accordance with BS EB 933-1 :2012) for the coarse aggregate is set out in Table 2 below:

Table 2: Overall Grading of Coarse Aggregate The particle size distribution for the fine aggregate (determined in accordance with BS EB 933-1 :2012) is set out in Table 3 below:

Table 3: Overall Grading of Fine Aggregate To form the modified aggregate, 2.1 kg of the composition of Example 1 was admixed with the 97.9kg of the aggregate mixture. An equivalent aggregate mixture without the composition of Example 1 was also prepared for use as a control sample. The test sample asphalts were mixed in accordance with BS EN 12697-35:2004, A1 :2007. Specimen preparation was by impact compactor in accordance with BS EN 12697-30:2012. The bitumen or asphalt used had a softening point of 55 ^Q C and was Puma 40/60. The bitumen binder content for Hot Rolled Asphalt (HRA) surface course mixtures was varied, using the modified aggregate or control aggregate in accordance with the protocol set out in BS EN 13108-4 - BS 594987:2015 (Annex H). Binder content is given as a percentage by weight relative to the total mix of the asphalt concrete. The Marshall test was conducted in accordance with BS EN 12697- 34:2012.

The results for the control (unmodified) aggregate are shown in Table 4. Table 4: Physical properties of Asphalts containing the control (unmodified) aggregate using Different Bitumen Binder Quantities:

The optimum binder content for the control (unmodified) aggregate was determined to be 6.5% bitumen.

The results for the modified/coated aggregate are shown in Table 5. Table 5: Physical properties of Asphalts containing the Modified/Coated Aggregate of using Different Bitumen Binder Quantities: It was determined that a binder content of 5.5% bitumen (w/w) provided the best balance of properties for the asphalt cement using the composition of the present invention.

The results show that asphalt cement formed using the composition of the present invention exhibited improved properties as demonstrated by the increased Marshall

Quotient and the increased mean corrected stability values as compared to the asphalt cement using the control aggregate. Accordingly, a modified/coated aggregate according to the present invention will require less bitumen to form an asphalt concrete with the required mechanical and thermo-structural properties as compared to the equivalent asphalt concrete using a standard aggregate.