WO2006131727A1

WO2006131727A1 - Particulate materials and method of obtaining thereof

Info

Publication number: WO2006131727A1
Application number: PCT/GB2006/002075
Authority: WO
Inventors: Jeffrey Alan Barnes
Original assignee: Total France SA
Current assignee: TotalEnergies Marketing Services SA
Priority date: 2005-06-07
Filing date: 2006-06-06
Publication date: 2006-12-14
Anticipated expiration: 2007-12-07
Also published as: EP1888841A1; GB0511532D0

Abstract

The amount of small particles of aggregate in a mass of aggregate is reduced by causing a binder, for example bitumen, to contact the small particles and preferentially adhere to them, thereby causing groups of small particles to coalesce and thereby define larger particles . As a result, the amount of small particles in the mass is reduced thereby allowing the mass of material to be used in surface dressing of roads or in other applications. A plant for carrying out the method comprises an aggregate hopper (4) for containing aggregate, a feeder (6) for feeding aggregate into a mixing chamber (8) wherein aggregate is contacted with a bitumen emulsion, and a conveyer (10) for feeding material from the chamber (8) to a stockpile.

Description

PARTICULATE MATERIALS AND METHOD OF OBTAINING THEREOF

PARTICULATE MATERIALS

This invention relates to particulate materials and particularly, although not exclusively, relates to a method of reducing the level of small particles in a mass of particulate material and a mass of particulate material treated in the method per se. Preferred embodiments relate to the treatment of aggregates for use in surface dressing of roads and other areas.

Aggregates produced in a quarry are screened using appropriate sieves to define individual masses of aggregate comprising particulates having sizes within predetermined ranges. However, dust or very fine particles of aggregate tend to adhere to larger aggregate particles and such fine particles need to be removed, otherwise their presence may lead to problems in downstream applications. Removal is achieved by a washing process, for example using water. However, the use of water and the disposal of contaminated water after the washing has environmental implications; and is wasteful of a natural product.

Similarly, during a surface dressing operation, for example of a road, a binder for example comprising bitumen is applied to a surface and then aggregate is applied over the binder and compacted. Thereafter, excess particles of aggregate are swept from the road. Such excess aggregate comprises both fines (e.g. dust) and large particles of aggregate. However, it cannot easily be used in a subsequent surface dressing due to the relatively high content of fine particles, for example particles which will pass through a sieve of mesh size of 63μm. In fact, the maximum permitted level of such fine particles for use in surface dressing is less than lwt%. If too high a level of fine particles is used, then a barrier is created between the aggregate and bitumen binder and that increases the risk of premature failure of the surface dressing. Consequently, the aggregate swept from the road is usually discarded. This has environmental implications; is wasteful of a natural resource; and, furthermore, there is a direct cost implication since a disposal tax is payable on any such discarded material.

It is an object of the present invention to address the above described problems.

According to the first aspect of the invention, there is provided a method of reducing the level of particles which will pass through a sieve of 63μm mesh size, the method comprising:

(i) selecting a mass of particulate material which includes first particles of a size which is such that they can pass through a sieve having a mesh size of 63μm;

(ii) treating the mass of particulate material to cause at least some of said first particles to aggregate to produce thereby second particles comprising a plurality of said first particles, wherein said second particles are bigger than said first particles and wherein treatment of said mass of particulate material includes a step of contacting the mass of material with a binder formulation. First particles may make up at least 0.5wt%, suitably at least lwt%, preferably at least 1.25wt%, more preferably at least 1.5wt%, especially at least 1.75wt% of said mass of particulate material selected in step (i) of the method. The amount of first particles of the type described in said mass of particulate material may be less than 10wt%, suitably less than 5wt%, preferably less than 4wt%, especially 3wt% or less.

Said mass of material selected in step (i) is suitably such that at least 95wt% thereof passes through a 20mm mesh. Preferably at least 98wt%, more preferably at least 99wt%, especially 100wt% passes through a 20mm mesh. For some countries, for example the U.K., the standard may require 100% to pass through a 14mm mesh.

Said mass of material selected in step (i) is suitably such that at least 80wt%, preferably at least 90wt%, more preferably at least 95wt%, especially at least 99wt% passes through a 15mm mesh.

Said mass of material selected in step (i) may be such that at least 5wt%, suitably at least 7wt%, preferably at least 10wt%, more preferably at least 12wt%, especially at least 15wt% can pass through a 6.3mm sieve. The level which can pass through a 6.3mm sieve may be less than 80wt%, suitably less than 60wt%, preferably less than 40wt%, especially 30wt% or less.

After treating the mass of particulate material as described in step (ii) , there is produced a mass of particulate material which will hereinafter be referred to as "said treated mass of particulate material".

Said treated mass of particulate material is suitably such that at least 95wt% thereof passes through a 20mm mesh. Preferably at least 98wt%, more preferably at least 99wt%, especially 100wt% passes through a 20mm mesh. For some countries, for example the U.K., the standard may require 100% to pass through a 14mm mesh.

Said treated mass of particulate material is suitably such that at least 80wt%, preferably at least 90wt%, more preferably at least 95wt%, especially at least 99wt% passes through a 15mm mesh.

Said treated mass of particulate material may be such that at least 5wt%, suitably at least 7wt%, preferably at least 10wt%, more preferably at least 12wt%, especially at least 15wt% can pass through a 6.3mm sieve. The level which can pass through a 6.3mm sieve may be less than 80wt%, suitably less than 60wt%, preferably less than 40wt%, especially 30wt% or less.

Preferably, substantially 100wt% of said treated mass of particulate material is able to pass through any sieve through which 100wt% of said mass of particulate material selected in step (i) is able to pass. Thus, preferably, the method described does not increase the size (e.g. through coalescence or agglomeration) of the largest particles in said mass of particulate material selected in step (i) but only increases the size of very small particles . Preferably, said second particles are no bigger than the biggest particles in said mass of particulate material selected in step (i) .

The ratio of the wt% of particles in said treated mass of material which are such that they can pass through a sieve having a mesh size of 63μm to the wt% of said first particles which are such that they can pass through a sieve having a mesh size of 63μm is suitably less than 0.5, preferably less than 0.3, more preferably less than 0.1.

References to a sieve having a mesh size of 63μm (or similar expressions) suitably refers to a sieve in accordance with BSEN410, Part 1 (2000) or ISO3310, Part 1

(2000) . Similarly, references to sieves having larger mesh sizes (or similar terms) may be in accordance with the aforementioned or with BSEN410, Part 2 (2000) or

ISO3310, Part 2 (2000) as applicable.

Said binder formulation may comprise any formulation suitable for binding first particles together which may be used in surface dressing of roads and other areas. Said binder formulation preferably includes a binder material which may comprise a natural or synthetic material.

Said binder material may have a penetration (measured in isolation from other components in the binder formulation), in accordance with EN1426* in the range 5 to 500 ¹Z₁₀ mm. Preferably, the penetration is in the range 5 to 350 ¹Zi₀ mm and, more preferably, is in the range 50 to 250 Vio mm. Said binder material may have a softening point, in accordance with EN1427** in the range 10 to 100⁰C, preferably in the range 30 to 80'

Said binder material may be any material suitable for binding aggregate together for use in surface dressing of roads and other areas. Said binder material may comprise a synthetic binder, a naturally-occurring binder or a modified naturally-occurring binder. For example, the binder may be selected from a synthetic binder, bitumen, a natural resin of vegetable origin or a modified natural resin of vegetable origin.

A said synthetic binder may be a clear and/or coloured binder, for example as sold under the trade mark KROMATIS (RTM) by Total France.

A said naturally-occurring binder or modified naturally occurring binder may be of vegetable origin. Such a binder is preferably exempt of any natural or synthetic elastomer, such as for instance polybutadiene, latex, styrene-butadiene rubber (SBR) , styrene-butadiene-styrene (SBS) , ethylene vinyl acetate (EVA) , etc, and of any thermoplastic polymer such as, for instance, polyolefins (polyethylene, polypropylene), polyamides and polyesters.

A naturally-occurring binder which may be used in a natural or modified form may comprise exudates from vegetables. Exudates may be of fossil origin or so-called harvest origin. They may be used as such (natural resins) or be transformed chemically (modified natural resins) . When they are produced by vegetables existing currently, they form renewable raw materials . Among the purely natural and modified harvest resins, one may quote the accroid resins, the dammar, the purely natural and modified natural rosins, the rosin esters, the rosin soaps and the metal resinates. Among the natural rosins, one may quote the fir and wood and tall oil rosins, such as tall oil pitch. Among the modified natural rosins, one may quote the hydrogenated, dismutated, polymerised and maleated rosins. Among the rosin esters, one may quote the esters of glycerol and of natural, hydrogenated, dismutated, polymerised and maleated rosins, and the esters of pentaerythritol and of natural and hydrogenated rosins. Among the metal resinates, one may quote the metal carboxylates, for instance of Ca, Zn, Mg, Ba, Pb, Co, obtained from natural or modified rosins, the calcium resinates, the zinc resinates and the mixed resinates composed of calcium and of zinc.

A said naturally-occurring binder or modified naturally occurring binder may be as described in US2004/0260057 and EP1466878A, the contents of which are incorporated herein by reference.

Said binder material preferably comprises bitumen. In this case, said binder formulation preferably comprises a bitumen formulation.

Said binder formulation (especially when in the form of a bitumen formulation) preferably comprises an emulsion.

Said binder formulation suitably includes less than 90wt%, preferably less than 80wt%, more preferably less than 70wt% of binder material (e.g. bitumen) . The amount of binder material in said binder formulation may be at least 30wt%, preferably at least 40wt%, more preferably at least 50wt%. Preferably, said binder formulation includes 45 to 70wt% binder material (e.g. bitumen) .

Said binder formulation preferably includes a surface active agent, for example an emulsifier. Suitably, said formulation includes at least 0.5wt%, preferably at least lwt%, more preferably at least 1.5wt%, especially at least 2wt% of said surface active agent. The formulation may include less than 4wt% of said surface active agent. Preferably, the sum of the wt% of surface active agent (if more than one is provided) is as described for said surface active agent. Preferably, however said formulation includes a single type of surface active agent.

Said surface active agent is preferably a cationic surfactant. It may comprise an amine moiety such as alkylamine derivatives, mixtures of alkylamidopolyamines and quaternary ammonium salts, or alklypropylenepolyamine compounds such as N-tallow-propylenepolyamines . This type of surface active agent is cationic. Bitumen emulsions with anionic or non-ionic surface active agents may be used, depending the nature of the aggregates

Said binder (e.g. bitumen) formulation is preferably a cationic emulsion.

Said binder (e.g. bitumen) formulation suitably includes at least 25wt%, preferably at least 35wt% water. The amount of water may be less than 60wt%, preferably less than 50wt%, more preferably less than 45wt%. Said binder (e.g. bitumen) formulation may include an acid, for example a protic acid such as hydrochloric acid.

In a preferred embodiment, said binder formulation (especially bitumen formulation) includes 50 to 70wt%

(preferably 55 to 65wt%) binder material (especially bitumen), 1.5 to 5wt% (preferably 2 to 4wt%) surface active agent (s) and 25wt% to 50wt% (preferably 31 to

45wt%) water.

Suitably, at least 92wt%, preferably at least 94wt%, more preferably at least 96wt%, especially at least 97wt% of the mass of particulate material is selected and contacted with said binder formulation and any other materials used in the method. Preferably, less than 99wt%, more preferably less than 98wt% of particulate material is selected for contact in the method.

The ratio of the wt% of said mass of particulate material to the wt% of binder material (e.g. bitumen) contacted with said mass of particulate material in the method may be at least 150, is preferably at least 175, is more preferably at least 200 and is especially at least 225.

Said ratio may be less than 350, is suitably less than 325, is preferably less than 300, is more preferably less than 275 and, especially, is less than 250.

The ratio of the wt% of said mass of particulate material to the wt% of water contacted with said mass of particulate material in the method may be at least 20, is preferably at least 25, is more preferably at least 35 and, especially, is at least 40. The ratio may be less than 50, preferably less than 45. Preferably, the method includes the step of mixing said mass of particulate material and said binder formulation

(e.g. bitumen formulation) . Mixing may be carried out for less than 5 minutes, preferably less than 2 minutes, more preferably less than 1 minute.

Preferably, after contact of said mass of material with said binder formulation (e.g. bitumen formulation) in step (ϋ) the level of water is reduced in order to prepare said treated mass of particulate material. The level of water may be reduced by allowing it to evaporate. After sufficient water has been removed, the treated mass of material thereby defined will appear to be substantially dry and comprise freely flowable particles.

The amount of water in said treated mass of particulate material is suitably less than 5wt%, preferably less than 4wt%, more preferably less than 3wt%, especially less than 2wt%.

The method of the first aspect may be carried out wherever required, for example at a quarry or on material reclaimed from road building.

According to a second aspect of the present invention, there is provided a treated mass of particulate material which has been treated in accordance with said first aspect. A said treated mass of particulate material may comprise second particles which are an aggregation of first particles, wherein said first particles are such that they would, if not aggregated, be able to pass through a sieve having a mesh size of 63μm. Said first particles are suitably held together by binder material (e.g. bitumen) .

Said treated mass of particulate material preferably comprises particles which are not aggregated; and which are not held together by binder materials (e.g. bitumen).

Preferably, at least 90wt%, more preferably at least 95wt% of said treated mass of particulate material comprises particles which are not aggregated. Said treated mass of particulate material may include at least lwt%, preferably at least 1.5wt% of aggregated first particles.

Said first particles, said second particles and/or said treated mass of particulate material may have any feature of the aforementioned components (for example ability to pass through specified sieves) as described in accordance with the first aspect.

Said treated mass of particulate material preferably comprises second particles which are coated with binder materials (e.g. bitumen); and other particles which are not coated with binder material (e.g. bitumen) .

According to a third aspect of the invention, there is provided a method of dressing a surface, for example for building a roadway (e.g. for vehicular or pedestrian travel) the method comprising contacting a surface to be dressed with a treated mass of particulate material according to the second aspect and/or as made according to said first aspect. The method preferably includes contacting a surface to be dressed with a binder and contacting the binder with a said treated mass of particulate material. Said binder preferably comprises any binder material referred to herein. It may be the same type of binder material as used in said treated mass of particulate material. Preferably, said binder used in surface dressing and in said treated mass of particulate material comprises bitumen.

The invention extends to the use of a treated mass of particulate material according to said second aspect and/or as described according to said first aspect in dressing a surface, for example in the surface dressing of a surface to define a roadway.

The invention extends to a surface, for example a roadway which has been surface dressed as described herein.

Any feature of any aspect of any invention or embodiment described herein may be combined with any feature of any aspect of any other invention or embodiment described herein mutatis mutandis.

Specific embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which:

Figure 1 is a schematic representation of a plant for preparing a mass of particulate material having a reduced level of small particles; and

Figure 2 is a graph comparing a mass of particulate material treated as described herein to an untreated material . In general terms, the amount of small particles in a mass of particulate material is reduced by causing a binder to contact the small particles and preferentially adhere to them, thereby causing groups of small particles to coalesce and thereby define larger particles. As a result, the amount of small particles in the mass is reduced thereby allowing the mass of material to be used in surface dressing or other applications as desired.

The mass of particulate material treated in the manner described may be obtained from any source. For example, it may comprise virgin aggregate obtained directly from a quarry. Such aggregate may be screened so that it nominally comprises only aggregate particles within a certain size range. However, inevitably some dust, comprising small particles, will be associated with the mass of material. The level of such dust may be reduced using the treatment described herein. In one embodiment, the virgin aggregate may not be washed to any significant degree to remove dust prior to treatment in the method described and so the generation and disposal of contaminated water, as described in the introduction of the present specification, may be obviated.

Alternatively, the mass of particulate material may comprise excess chippings and dust, swept up after a surface dressing operation.

The mass of particulate material or aggregate may be any material which may be used in surface dressing of roadways or the like. Such materials are preferably in accordance with BS-EN 13043 (2002) . For example, material may be gritstone, stone chippings, recycled stone limestones, synthetic particles (e.g crumb rubber), recycled particles and/or steel slag.

Typically, the mass of particulate material will initially comprise greater than lwt% of particles of a size less than 63μm (i.e. greater than lwt% pass through a sieve of mesh size 63μm) since such a material is generally regarded as inappropriate for use in surface dressing; and treatment in the manner described herein can make the material usable in surface dressing.

The binder used to contact the small particles may comprise a bitumen. The bitumen may comprise a pure bitumen, fluxed bitumen or a bitumen modified by polymers. A pure or natural bitumen may be understood as being the product obtained particularly as the residue from distillation under vacuum of crude oil and the extraction of asphalt from this residue. As an alternative, the binder may be completely or in part made of synthetic or other natural materials (or modified natural materials) including but not limited to elastomers, thermoplastic polymers, modified or non-modified vegetable oils and resins. Thus, the binder used to treat the small particles may be completely or in part made of synthetic or natural materials.

In one embodiment, a bitumen emulsion is used to treat the mass of particulate material and the emulsion is suitably cationic in nature or is otherwise selected on the basis of its compatibility with the particulate material to be treated. Furthermore, the emulsion suitably has a breaking value (measured as described in European Standard prEN 13075-1 of November 2001) of greater than 200. Such an emulsion is able to disperse within the mass of particulate material to coat the small particles before it breaks .

The binder (e.g. bitumen part of a bitumen emulsion when used) is suitably selected so that it is similar or compatible with the binder (e.g. bitumen) used to bind particulate matter in a surface dressing operation in which the mass of particulate material treated in the method may be used. This may improve adhesion between the binder used in surface dressing and the particulate material. Additionally, the binder (in the surface dressing or emulsion) may be selected according to the climate in which it may be used. If too hard a binder is used, there will be a risk of low temperature failure of the surface dressing; if too soft a binder is used there may be a risk of hot weather softening which could lead to premature softening of the surface dressing.

In the treatment method, binder (e.g. bitumen emulsion) at ambient temperature (about 2O⁰C) and the mass of particulate material are contacted and mixed. The amount and type of binder (e.g. bitumen emulsion) mixed with particulate material is selected so that the binder (e.g. bitumen) generally only adheres to the small particles which have a relatively high surface area, compared to larger particles included within the mass of material. Small particles with adherent binder (e.g. bitumen) will, with further mixing, contact and coalesce with other similar small particles so that particles are formed which comprise a multiplicity of small particles bound together by binder (e.g. bitumen). The total amount of binder

(e.g. bitumen) in the binder (e.g. bitumen) emulsion is selected according to the amount of small particles in the mass of particulate material. If there is too much binder present, then more than just the small particle will be caused to coalesce which may make the material unworkable; if too little binder is present the smaller particles may be insufficiently coated with binder to cause them to coalesce satisfactorily. In a preferred embodiment, the weight of binder (e.g. bitumen) in the binder (e.g. bitumen) emulsion is no greater than 75% (and preferably is about 50%) of the weight of small particles (i.e. those which pass through a 75μm mesh) in the mass of particulate material .

Additionally, to allow adequate mixing of the binder (e.g. bitumen) emulsion and the mass of particulate material, the total water content in the mixture is suitably greater than 2wt% and less than 5wt%.

Mixing of the binder (e.g. bitumen) emulsion and particulate material should be minimised to minimise abrasion within the mixture and generation of further small particles. At the completion of the treatment and after water has evaporated, a product may be produced which comprises substantially clean-looking relatively large particles together with coalesced smaller particles which, when the binder comprises bitumen, appear as brown/black particles. The material is granular; appears to be relatively dry; and is free flowing. The aforementioned applies particularly to mixtures which include less than 3wt% water (before evaporation) .

Mixtures with greater than 3wt% water may, when the binder comprises bitumen, appear brown after drying since, in this case, bitumen from the emulsion is better dispersed around larger aggregate.

A plant for carrying out the method described herein is shown in Figure 1. Referring to the figure, the plant 2 comprises an aggregate hopper 4 for containing a mass of particulate material; a feeder 6 for feeding particulate material towards and into a mixing chamber 8 and a conveyor 10 for feeding material from the chamber 8 to a stockpile.

In operation of the plant 2, pre-screened chippings 10, for example having a maximum specified size and containing relatively small particles, are delivered to the aggregate hopper 4. From hopper 4 the chippings are feed via feeder 6 into mixing chamber 8 wherein they are contacted and mixed with a bitumen emulsion at a predetermined wt% ratio of chippings to emulsion. After a predetermined mixing time in which small particles within the chippings coalesce, the material is fed via conveyor 10 to a stockpile for storage prior to use, for example in surface dressing.

The following specific examples illustrate the method described herein. Examples 1, 2, and 3 hereinafter may be compared with Examples Cl, C2 and C3 respectively to show the effect the treatment described herein has on the level of small particles in a mass of particulate material.

In the following examples, unless otherwise stated, 250/330 bitumen, in accordance with BSW EN 12591:2000, was used together with an emulsifier formulation comprising, in solution, . a polyamine emulsifier (3.4wt%), 28wt% concentration hydrochloric acid (0.73wt%) and water (95.87wt%). The finished bitumen emulsion comprises 250/330 bitumen (59wt%) , emulsifier formulation (1.35wt%), hydrochloric acid (0.29wt%) and water (to 100wt%) .

Examples 1 and Cl

A mass of 10mm gritstone was divided into two equal parts and one part (Example 1) comprising 10kg was mixed in a 25kg pan mixer with 2.0wt% water and 0.7wt% of the bitumen emulsion at ambient temperature (20⁰C) for 20 seconds. Water in the formulation evaporates at a rate dependent on ambient conditions. On visual inspection, at the end of mixing, the mixture comprised larger particles of material and brown/black particles which comprised smaller particles which were bound together by bitumen.

The second part (Example Cl) of the 10mm gristone was not treated in the manner described above.

The treated material of Example 1 and the untreated material of Example Cl were tested in a Vialit Plate Shock Test. This test is used to assess the adhesion of aggregate complete with its dust to the surface dressing emulsion and to compare adhesion of aggregate after treatment of aggregate as described herein to allow a determination of any improvement or deterioration in adhesivity of aggregate caused by the treatment. Any improvement in % retained shows that the large aggregate is better adhered to the surface dressing binder. Additionally, untreated and treated materials were compared to establish the level of particles of size less than 63μm using test EN933-1

Results of tests undertaken are provided in table 1. The Vialit adhesion test results indicate improved mechanical adhesion from 90% retained to 100% retained. This implies that there is an improvement in bonding between the large aggregate and the surface dressing bitumen. Additionally the tests show that the level of particles of size less than 63μm has been reduced from 1.20wt% to 0.24 wt%. Thus, whereas the material of Example Cl included too high a level of small particles for it to be used in surface dressing, the material of Example 1 has a much lower level and can be used in such an application. Furthermore, since even some of the small particles in the material of Example 1 may carry at least some bitumen coating, they may be more readily bound into a surface dressing compared to identical material which does not carry such a coating.

Example 2 and C2

Following generally the procedure of Examples 1 and Cl, βmm recycled stone was treated with 0.5wt% of bitumen emulsion (Example 2) and compared to an identical sample of untreated material (Example C2) . Results for tests undertaken are provided in Table 1 from which it will be noted that there is a substantial reduction in the level of small particles in the treated material of Example 2. Examples 3 and C3

Following generally the procedure of Examples 1 and Cl, 10mm steel slag was treated with 0.7wt% bitumen emulsion

(Example 3) and compared to an identical sample of untreated material (Example C2) with results being provided in Table 1. In addition, the graph of figure 2 was constructed to illustrate the effect treatment has on particle sizes. It will be noted that, for the treated material of Example 3, 0.13% passes through a 0.08mm sieve, compared to 1.52% for the Example C3 material. Similarly, 2.27% passes through a 5mm sieve for the Example 3 material compared to 10.12% for the Example C3 material. Thus, it is clear that the level of smaller particles has been reduced by the treatment described in Example 3.

As an alternative to the bitumen emulsion described, for a 160/220 bitumen, an emulsifier formulation comprising polyamine emulsifier (2.9wt%), hydrochloric acid (2.5wt%) and water to balance may be used which provides a bitumen emulsion comprising 160/220 bitumen (62wt%) , polyamine emulsifier (l.lwt%), hydrochloric acid (0.95wt%) and water (to 100wt%) .

The process described may be carried out at any time, for example well in advance of performing a surface dressing operation, which is likely to make logistics flexible in site scale operations. Table 1

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

Claims

1. A method of reducing the level of particles which will pass through a sieve of 63μm mesh size, the method comprising:

(ii) treating the mass of particulate material to cause at least some of said first particles to aggregate to produce thereby second particles comprising a plurality of said first particles, wherein said second particles are bigger than said first particles and wherein treatment of said mass of particulate material includes a step of contacting the mass of material with a binder formulation.

2. A method according to claim 1, wherein first particles make up at least 1.25 wt% and less than 10 wt% of said mass of particulate material.

3. A method according to claim 1 or claim 2, wherein said mass of particulate material selected in step (i) is such that at least 98 wt% passes through a 20mm mesh.

4. A method according to any preceding claim, wherein said mass of particulate material selected in step (i) is such that at least 5 wt% can pass through a 6.3mm mesh.

5. A method according to any preceding claim, wherein after treating the mass of particulate material as described in step (ii) , there is provided a mass of particulate material, hereinafter referred to as "said treated mass of particulate material", wherein said treated mass of particulate .material is such that at least 95 wt% thereof passes through a 20mm mesh.

6. A method according to any preceding claim, wherein substantially 100 wt% of said treated mass of particulate material is able to pass through any sieve through which 100 wt% of said mass of particulate material selected in step (i) is able to pass.

7. A method according to any preceding claim, wherein said binder formulation includes a binder material which comprises a natural or synthetic material.

8. A method according to any preceding claim, wherein said binder material has a penetration (measured in isolation from other components in the binder formulation) , in accordance with EN1426* in the range 5 to

9. A method according to any preceding claim, wherein said binder material has a softening point, in accordance with EN1427**, in the range 10 to 100°C.

10. A method according to any preceding claim, wherein said binder is selected from a synthetic binder, bitumen, a natural resin of a vegetable origin or a modified natural resin of vegetable origin.

11. A method according to any preceding claim, wherein said binder material comprises bitumen.

12. A method according to any preceding claim, wherein said binder formulation includes at least 30 wt% and less than 90 wt% of binder material.

13. A method according to any preceding claim, wherein said binder formulation includes a surface active agent.

14. A method according to any preceding claim, wherein said binder formulation comprises a cationic emulsion.

15. A method according to any preceding claim, wherein said binder formulation includes 50 to 70 wt% binder material, 1.5 to 5 wt% surface active agent (s) and 25 to 50 wt% water.

16. A method according to any preceding claim, wherein the ratio of the wt% of said mass of particulate material to the wt% of binder material contacted with said mass of particulate material in the method is at least 150 and is less than 350; and the ratio of the wt% of said mass of particulate material to the wt% of water contacted with said mass of particulate material in the method is at least 20 and is less than 50.

17. A method according to any preceding claim, wherein the amount of water in said treated mass of particulate material is less than 5 wt%.

18. A treated mass of particulate material comprising second particles which are an aggregation, held together by a binder material, of first particles, wherein said first particles are such that they would, if not aggregated, be able to pass through a sieve having a mesh size of 63μm.

19. A treated mass according to claim 18, which comprises particles which are not aggregated; and which are not held together by a binder material.

20. A treated mass according to claim 18 or claim 19, wherein said first particles comprise aggregate and said binder material comprises bitumen.

21. A method of dressing a surface, the method comprising contacting a surface to be dressed with a treated mass of particulate material made in a method according to any of claims 1 to 17 or being as described in any of claims 18 to 20.

22. The use of a treated mass of particulate material made in a method according to any of claims 1 to 17 and/or as described according in any of claims 18 to 20 in dressing a surface.

23. A surface which has been dressed with a treated mass of particulate material as described in any of claims 18 to 20.