METHOD FOR CONSTRUCTING A WEARING COURSE

Abstract

The present invention relates to a method for constructing a road surface wearing course, comprising the following steps: preparing a cationic emulsion E1 of hydrocarbon binder, formulated from a hydrocarbon binder having a needle penetration at 25°C less than or equal to 100 1 / 10 mm; applying a layer of cold-mix asphalt to a suitable substrate; compacting the layer applied in step b); applying the cationic emulsion E1 from step a) to the surface of the asphalt layer compacted in step c). The present invention also relates to the wearing course thus obtained and the use of the cationic emulsion E1 of hydrocarbon binder to improve the early-age flaking resistance of cold-mix asphalt.

Description

Title of the invention: METHOD FOR CONSTRUCTING A WEARING LAYER FIELD OF INVENTION

[0001] The present invention falls within the field of road construction. It relates to a method for constructing a wearing course from cold-mix asphalt whose resistance to stripping / pulling under traffic is improved. STATE OF THE ART

[0002] The role of a pavement is to transfer the forces due to traffic onto the subgrade, distributing them appropriately. The pavement must have a thickness such that the vertical pressure transmitted to the subgrade is sufficiently low so that the subgrade can support it without damage.

[0003] A pavement is made up of superimposed layers with different mechanical properties. Generally, the following layers are encountered, starting from the ground:

[0004] - subgrade layer or soil treated with a hydraulic binder;

[0005] - most often, foundation layer;

[0006] - base layer which must be able to withstand the stresses resulting from traffic; and

[0007] - surface layer comprising the wearing layer.

[0008] The foundation and base layers together form the sub-base layer. The surface layer generally comprises, starting from the sub-base layer, a binder layer, which is however optional, and a wearing course.

[0009] The wearing course is the outermost layer, directly in contact with traffic. It protects the base from the effects of traffic, weather, and pollutants. It must offer good grip, reduce rolling noise, and blend in with the surrounding architecture.

[0010] Among the various materials used for the construction of wearing courses for roads, pavements and coatings for urban development, we find hydrocarbon mixes.

[0011] Two main families of hydrocarbon mixes can be distinguished: hot mixes and cold mixes. The latter are also called "cold mixes" or "emulsion mixes".

[0012] Hot mix asphalt is obtained by hot mixing of aggregates and a hydrocarbon binder. The aggregates are generally heated to a temperature above 100°C. This asphalt exhibits good coverage, workability, and mechanical properties after application and cooling. conforming to the expectations of the expert. The cohesion of these asphalts rises sharply and rapidly, occurring through cooling of the coating in a few hours.

[0013] Cold-mix asphalt is obtained by cold mixing of solid particles, possibly moistened, with a hydrocarbon binder emulsion, typically at temperatures close to ambient temperature, ranging from 10°C to 40°C. The use of a hydrocarbon binder emulsion allows for coating without drying or heating the solid particles due to the low viscosity of the hydrocarbon binder emulsion at ambient temperature. The cold production of these asphalt mixes significantly reduces energy consumption compared to that required for hot-mix asphalt production to dry and heat the solid particles. Cold-mix asphalt is recognized for reducing the environmental footprint of hydrocarbon asphalt during the road surface manufacturing process.

[0014] The manufacturing temperature of cold-mix asphalt, which is close to ambient temperature (the recommended minimum temperature is approximately 10°C, so the advantageous range is from 10°C to 40°C), gives the binder, after the emulsion breaks down, a very important role in the workability and compactability of the asphalt mix. Within this temperature range, the high viscosity of the binder reduces its fineness and the compactability of the asphalt mix, thus diminishing the mechanical properties of the resulting asphalt. Cold-mix asphalt mixes have certain drawbacks and technical limitations.

[0015] First, the reactivity of the hydrocarbon binder emulsion with solid particles sometimes leads to poor coating quality, particularly when the solid particles have a high fines content. Indeed, the more fines the granular fraction contains, the worse the distribution of the binder will be on the granular fraction (mainly on the larger particles). Furthermore, this coating defect can be exacerbated by the numerous handling operations of the asphalt mix (transport, passage through the screw conveyors of the paver, compaction), which lead to coating stripping problems due to abrasion of the binder film on the granular surfaces. These coating problems cannot be improved by increasing the water content of the mixture comprising the hydrocarbon binder emulsion and the solid particles. In fact, cold-mix asphalt mixes are very sensitive to the total water content of the mixture, which generates workability problems when it is too high.

[0016] Workability is also an inherent technical limitation of cold-mix asphalt. During the transport time of the asphalt between the mixing plant and the construction site, cohesion builds up following the rupture of the emulsion upon contact with the solid particles. While rapidly achieving high cohesion is desirable, excessively high cohesion reached too early can drastically reduce the workability period and make application of the asphalt difficult. This cohesion build-up is generally mitigated by several means, including reducing the binder content of the asphalt mix. The use of fluxing agents or very slow-release surfactants. These actions positively affect the workability of the asphalt during transport but also negatively affect the recovery of cohesion of the asphalt once it has been applied to the road surface.

[0017] Finally, cold mix asphalt is a material that evolves over time. These mixes transition from an initial, weakly bound state to a final, highly cohesive state through the combined effect of several progressive phenomena: emulsion coalescence, water expulsion, bonding of solid particles, increased cohesion due to binder fining during contact between coated particles, and compaction of the granular skeleton under traffic. This evolving cohesion characteristic of the asphalt mix often leads to early-age defects such as surface stripping and chipping due to the loss of aggregate under traffic. These defects impair the quality of the pavement (macrotexture, evenness, mechanical strength).

[0018] Furthermore, the use of Asphalt Aggregates (AA) in the formulation of cold-mix asphalt, an increasingly common practice, even at a content as low as 30% by mass, can lead to a significant lack of surface cohesion at an early age. This lack of cohesion generally results in pronounced feathering of these mixes at an early age, during the curing of the asphalt.

[0019] To limit problems of uneven bitumen film distribution across the entire granular fraction, the mixing step of the granular fractions and the emulsion binder can be sequenced. Sequencing methods are described in patents EP 0 384 094, EP 0 524 031, EP 0 781 887, and FR 2 960 890. However, sequencing involves significant industrial constraints, such as the need to use specific cold-mix asphalt plants equipped with a long mixer and two emulsion spray booms. Furthermore, despite the improved coating, this sequencing generally does not have a positive impact on the early-age cohesion of the asphalt mix. This technique therefore does not solve the problem of early-age brittleness in cold-mix asphalt.

[0020] In order to improve the performance of cold-mix asphalt, particularly with regard to coating, workability, and cohesion development, processes including a heating step have been proposed (see, for example, EP 0 552 574, FR 2 732 239, and EP 1 668 184). Heating cold-mix asphalt optimizes coating and workability and reduces the asphalt's tendency to evolve due to a more pronounced and rapid cohesion development. However, these heating techniques diminish the environmental benefits of cold-mix asphalt due to the significant energy consumption required to bring the asphalt to the desired temperature.

[0021] To improve the early resistance to flaking of cold-mix asphalt, resulting in particular from insufficient surface cohesion of the coating, it is possible to increase the binder content of the asphalt. However, this increase in binder content causes handling problems and does not allow for a sufficient level of resistance to flaking.

[0022] There remains a need to propose new solutions to improve the resistance to flaking at an early age of cold mixes used in the preparation of wearing courses, in particular regardless of the formula of the cold mix, without compromising on the workability of the cold bituminous mix or the macrotexture of the wearing course resulting from it. Description of the invention

[0023] According to a first aspect, the present invention relates to a method for constructing a wearing course of a road surface, comprising the following steps: a. prepare a cationic emulsion El of hydrocarbon binder, formulated from a hydrocarbon binder having a needle penetration at 25°C less than or equal to 100 1 / 10 mm; b. apply a layer of cold-mix asphalt onto a suitable surface; c. compact the layer implemented in step b); d. Apply the cationic emulsion El from step a) to the surface of the layer of compacted asphalt in step c).

[0024] The steps can be carried out in parallel and are not necessarily successive. In particular, steps b) and c) can be carried out before or during (i.e. in parallel) step a).

[0025] The El cationic emulsion is preferably applied before putting the wearing course back into circulation, preferably on the same day as the application of the cold mix asphalt or within a period of between 0 and 72h after application of the cold mix asphalt.

[0026] In the sense of the invention, the wearing course comprises a layer of cold-mix asphalt in direct contact with the residual binder from the application of the El cationic emulsion on the cold-mix asphalt.

[0027] Advantageously, during step d), the quantity of cationic emulsion El applied corresponds to a dosage of residual bituminous binder, determined according to standard NF EN 12272-1: October 2003, less than 240 g / m2, preferably within a range of 50 to 200 g / m2, more preferably from 50 to 150 g / m2.

[0028] Advantageously, the hydrocarbon binder of the cationic emulsion El has a needle penetration at 25°C less than or equal to 70 1 / 10 mm. In particular, the hydrocarbon binder of the cationic emulsion El has a needle penetration at 25°C ranging from 15 1 / 10 mm to 35 1 / 10 mm, advantageously from 20 1 / 10 mm to 35 1 / 10 mm.

[0029] Step d) is advantageously carried out before putting the wearing course back into circulation, preferably on the same day as step c) or within a period of between 0 and 72h after step c).

[0030] Cold-mix asphalt applied in step (b) can be prepared by mixing solid particles and an E2 emulsion of hydrocarbon binder, the solid particles comprising 80% to 100% by mass of asphalt aggregates relative to the total mass of solid particles.

[0031] Step b) may comprise the following successive substeps:

[0032] b' 1) recovery of asphalt aggregates from the milling of a pre-existing wearing course;

[0033] b'2) preparation of recycled asphalt mixes by mixing solid particles and a E2 emulsion of hydrocarbon binder, the solid particles comprising 80% to 100% by mass of asphalt aggregates from step b' 1) relative to the total mass of solid particles,

[0034] b'3) application on a suitable substrate, for example a base layer, of a layer of recycled asphalt obtained in step b'2);

[0035] steps b' 1), b'2) and b'3) are advantageously carried out in place, that is to say on the site of the construction site.

[0036] Advantageously, the asphalt applied in step b) is an asphalt having a conventional residual anhydrous binder content ranging from 3% to 6.5% by mass relative to the total mass of dry asphalt.

[0037] A second aspect of the invention relates to a cold-mix asphalt wearing course obtained by the process of the invention.

[0038] Advantageously, the average of the losses at 50 cycles of the asphalt at 21 days of the wearing course, test conducted with a normal tire force of 500 N, is less than or equal to 1500 g / m2, more advantageously less than or equal to 1000 g / m2, even more advantageously less than or equal to 800 g / m2, even more advantageously less than or equal to 500 g / m2, even more advantageously less than or equal to 200 g / m2.

[0039] Advantageously, the asphalt of the wearing course has an average depth of texture surface, determined according to standard NF EN 13036-1: September 2010, of at least 0.60 mm.

[0040] A third aspect of the invention relates to the use of a cationic emulsion El of hydrocarbon binder, formulated from a hydrocarbon binder, modified or not with polymers, having a needle penetration at 25°C less than or equal to 100 1 / 10 mm, on the surface of a layer of cold-mix asphalt to improve the resistance to early-age flaking of cold-mix asphalt.

[0041] Other aspects of the invention are as described below. DESCRIPTION OF THE FIGURES

[0042] [Fig. 1] is an illustration of a road surface comprising the wearing course obtained by the process of the invention.

[0043] From the ground up, the road surface comprises a subgrade or soil treated with a hydraulic binder and / or a foundation layer (5); a base course (4), optionally a binder course (3) and a wearing course (1 and 2). According to the invention, the wearing course comprises a layer of asphalt (2) coated with a hydrocarbon binder film (1). DEFINITIONS

[0044] The term "wearing course" defines a layer adapted to be in direct contact with people or objects moving on the road surface, in particular with vehicle wheels. The wearing course constructed using the method of the invention is intended to be subjected to traffic after its construction. It is not intended to be subsequently covered by another layer of asphalt.

[0045] The term “road surface” refers in particular to roads, pavements and surfaces for urban development.

[0046] The term "plumage" refers to the removal of gravel from the wearing course, often under the effect of traffic.

[0047] The term "early age" refers to the period extending from the application of the asphalt surface course until the asphalt reaches its final consistency. Asphalt at an early age has not yet reached its final consistency. The time required to reach this final consistency depends on weather conditions and can last up to approximately three months after the application of the asphalt surface course.

[0048] The term “hydrocarbon coating” refers to a mixture of solid particles, a hydrocarbon binder, and possibly dopes and / or additives.

[0049] In a "cold-mix asphalt", the binder is supplied in the form of an emulsion comprising a continuous aqueous phase in which the hydrocarbon binder particles are dispersed.

[0050] A “recycled in-place emulsion asphalt” designates a mixture of solid particles comprising generally 80% to 100% by mass, relative to the total mass of solid particles, of asphalt aggregates from the fragmentation of road surface layer removed during construction (hence the terms in place or on site) and a hydrocarbon binder emulsion.

[0051] The term "asphalt aggregates" refers to fragments of asphalt (a mixture of aggregates and bituminous binders) obtained from milling asphalt layers, crushing slabs extracted from asphalt pavements, or pieces of slabs asphalt mixes, asphalt waste, or surplus asphalt production (surplus production consists of materials coated or partially coated at the plant resulting from transitional manufacturing phases). These elements and other recycled products can reach dimensions of up to 31.5 mm.

[0052] By "solid particles", are designated all solid particles usable for the production of bituminous products, in particular for road construction.Examples of solid particles include mineral solid particles such as natural mineral aggregates (gravel, sand, fines) for example from quarries or gravel pits, recycled products such as asphalt aggregates, for example resulting from the recycling of materials recovered during road repairs or surpluses from asphalt plants, manufacturing waste, shingles (from the recycling of roofing membranes), aggregates from the recycling of road materials including concrete, slags in particular slag, shales in particular bauxite or corundum, rubber powders from the recycling of tires in particular, artificial aggregates of any origin and aggregates from for example bottom ash from municipal solid waste incineration (MSWI), as well as mixtures thereof in all proportions.

[0053] Solid particles typically include:

[0054] - elements smaller than 0.063 mm (filler or fines);

[0055] - sand whose elements are between 0.063 mm and 2 mm;

[0056] - gravel or aggregates, the elements of which have dimensions

[0057] * between 2 mm and 6 mm;

[0058] * greater than 6 mm.

[0059] The size of solid particles, in particular mineral solid particles, for example mineral aggregates, is measured by the tests described in standard NF EN 933-2 (July 2020 version).

[0060] The solid particles form the "granular fraction" of the asphalt mix. The "solid particles" are also referred to as the "0 / D fraction" (or "mineral 0 / D fraction" even though particles other than mineral particles may be present). This 0 / D fraction can be separated into two particle sizes: the 0 / d fraction and the d / D fraction.

[0061] A "d / D asphalt mix" is an asphalt mix comprising solid particles with a size ranging from d mm to D mm. Thus, in a 0 / 10 asphalt mix, the size of solid particles varies from > 0 mm to 10 mm. In a 2 / 10 asphalt mix, the size of solid particles varies from 2 mm to 10 mm.

[0062] The thinnest elements (the 0 / d fraction) will be those within the range between 0 and a maximum diameter that can be set between 2 and 6 mm (from 0 / 2 to 0 / 6), advantageously between 2 and 4 mm. The other elements (minimum diameter) greater than 2, 3, 4, 5 or 6 mm; and approximately up to 31.5 mm) constitute the fraction d / D.

[0063] The particle size distribution curve of the granular fraction can be continuous or discontinuous (i.e. with one or more particle size intervals that are underrepresented or absent in the solid fraction, thus creating cuts or discontinuities in the particle size distribution curve).

[0064] The term “binder” refers to the hydrocarbon binder, which is advantageously a bitumen.

[0065] The term "residual bituminous binder" or "residual bitumen" or "residual binder" refers to the binder / bitumen obtained after the water has been removed from an emulsion and, where applicable, the volatile components of a fluxed or fluidized binder / bitumen. It is the binder / bitumen recovered after decoating and solvent removal; it is free of all mineral matter. It corresponds to the binder, advantageously the bitumen, contained in the asphalt mix after coating and removal of water (and / or solvents where applicable).

[0066] The term "theoretical residual anhydrous binder" refers to the theoretical residual anhydrous binder consisting of the binder supplied by the emulsion and any asphalt aggregates used. The content is defined based on the theoretical composition of the asphalt mix.

[0067] The term “conventional residual anhydrous binder” refers to the hydrocarbon binder whose content is determined after successive drying operations at 110 ± 5 °C, until constant mass is reached, and after the test has been carried out according to standard NF EN 12697-1 (March 2020). The characteristics are determined after extraction according to standard NF EN 12697-3 (August 2013 version, since withdrawn). In the case of an emulsion without fluxant, the conventional residual anhydrous binder content is equal to the theoretical residual anhydrous binder content.

[0068] The term "total water content" refers to the ratio of the mass of water supplied by the solid particles, by the emulsion and by the added water to the mass of the dry solid particles and of conventional residual anhydrous binder, expressed as an external percentage (see the old standard NF P98-139).

[0069] The term “binder content” refers to the ratio of the mass of hydrocarbon binder to the total mass of the mixture, expressed as an internal percentage.

[0070] The term "theoretical residual anhydrous binder content" refers to the ratio of the mass of theoretical residual anhydrous binder to the total mass (mass of dry solid particles plus mass of conventional residual anhydrous binder), expressed as an internal percent (see the old standard NF P98-139).

[0071] The term "conventional residual anhydrous binder content" refers to the ratio of the mass of conventional residual anhydrous binder to the total mass (mass of dry solid particles plus mass of conventional residual anhydrous binder), expressed as an internal percent (see the former standard NF P98-139).

[0072] The term “external percent” refers to the percentage of binder relative to the mass of dry solid particles.

[0073] The term "internal percent" refers to the percentage of binder relative to the total mass of the mixture (solid particles, binder, any additives).

[0074] The term "spreading thickness" refers to the thickness of the layer of spread asphalt measured just behind the spreading device.

[0075] The "polymers" modifying the binder, in particular bitumen, referred to herein, may be chosen from natural or synthetic polymers. These include, for example, polymers from the elastomer or plastomer family, whether synthetic or natural, and, by way of example and not limitation:

[0076] - statistical, multi-sequenced or star-shaped copolymers of styrene and butadiene or isoprene in all proportions (in particular styrene-butadiene-styrene (SBS) block copolymers, styrene-butadiene (SB, SBR for styrene-butadiene rubber) block copolymers, styrene-isoprene-styrene (SIS) block copolymers or copolymers of the same chemical family (isoprene, natural rubber, etc.), possibly cross-linked in-situ,

[0077] - vinyl acetate and ethylene copolymers in all proportions,

[0078] - copolymers of ethylene and esters of acrylic, methacrylic acid or of maleic anhydride, ethylene and glycidyl-methacrylate copolymers and terpolymers, and polyolefins.

[0079] The "polymers" modifying the binder, in particular bitumen, can be chosen from recovered polymers, for example "rubber powders" or other compositions based on rubber reduced to pieces or powder, for example obtained from used tires or other polymer-based waste (cables, packaging, agricultural, etc.) or any other polymer commonly used for the modification of bitumens such as those mentioned in the Technical Guide written by the International Road Association (PIARC) and published by the Laboratoire Central des Ponts et Chaussées "Use of Modified Bituminous Binders, Special Bitumens and Bitumens with Additives in Road Pavements" (Paris, LCPC, 1999), as well as any mixture in any proportion of these polymers.

[0080] In the description of the invention, unless explicitly stated otherwise, the term "coating" means "cold-mixed hydrocarbon coating" and the term "binder" means "hydrocarbon binder". DETAILED DESCRIPTION OF THE INVENTION

[0081] Surprisingly, the inventors discovered that applying a cationic emulsion of hydrocarbon binder El, formulated from a hard hydrocarbon binder (i.e., a binder with a needle penetration of less than 100 1 / 10 mm), to the surface of a cold asphalt layer improves the The invention exhibits resistance to flaking at an early age in asphalt mixes. Furthermore, the wearing course possesses a macrotexture and coating quality that meet the expectations of those skilled in the art for a low- to high-traffic wearing course. In particular, the surface treatment of the present invention maintains a macrotexture suitable for producing such a wearing course. Moreover, the invention allows the use of a wider range of cold-mix asphalts, thus enabling the use of workable cold mixes. Finally, it is surprising to be able to obtain such properties with an El emulsion containing a low amount of residual binder.

[0082] The inventors have indeed discovered that it is possible to meet the surface coating and early-age flaking requirements of cold-mix asphalt more effectively than by increasing the overall binder content of the cold-mix asphalt, while maintaining excellent workability and a macrotexture suitable for use as a wearing course. The invention provides a surface treatment for asphalt mixes. Step a)

[0083] Step a) of the process consists of preparing a cationic emulsion El of hydrocarbon binder, from a hydrocarbon binder e having a needle penetration at 25°C, measured according to the method described in standard NF EN 1426, January 2018, less than or equal to 100 1 / 10 mm.

[0084] The hydrocarbon binder can be a pure or polymer-modified binder, in particular a pure or polymer-modified bitumen, the polymers being as defined above.

[0085] The hydrocarbon binder, in particular bitumen, advantageously has a needle penetration at 25 °C of less than or equal to 70 1 / 10 mm, more preferably less than or equal to 50 1 / 10 mm, more preferably less than or equal to 35 1 / 10 mm, in particular ranging from 15 1 / 10 mm to 35 1 / 10 mm, advantageously from 20 1 / 10 mm to 35 1 / 10 mm.

[0086] The binder grade can be defined by the penetrability class corresponding to the lower and upper limits of needle penetration at 25°C, measured according to standard NF EN 1426, January 2018. Thus, a 35 / 50 binder has a needle penetration at 25°C ranging from 35 to 50 1 / 10 mm. The binder used in the El emulsion is advantageously a binder, in particular a bitumen, of grade 70 / 100 or 35 / 50 or 20 / 30 or 15 / 25 or 50 / 70, more advantageously of grade 35 / 50 or 20 / 30 or 15 / 25 or 50 / 70, and even more advantageously of grade 35 / 50 or 20 / 30 or 15 / 25.

[0087] The harder the binder grade (the lower its penetration), the better the resistance to early-age flaking of the wearing course.

[0088] The binder content in the cationic emulsion El is in particular within a range of 50% to 71% by mass relative to the total mass of the emulsion, preferably ranging from 60% to 65%. This emulsion El can be used as is in step d) or diluted before step d). The dilution step makes it possible to achieve the target conventional residual anhydrous binder content per m² while using existing spreading equipment.

[0089] The cationic emulsion of binder El is prepared according to any conventional method of the art. In particular, it is obtained by dispersing binder droplets in an aqueous phase comprising one or more cationic surfactant (emulsifier) ​​compounds.

[0090] The emulsifier content in the cationic emulsion El is in particular in a range of 0.1% to 2%, preferably 0.15% to 1%, by mass relative to the total mass of the emulsion.

[0091] In one embodiment, the surfactant compound is an amine, in particular selected from alkylpolyamines, fatty amines, amidopolyamines, fatty-chain quaternary ammonium compounds, and combinations thereof. Trimethylpropylene diamine tallow is an example of an alkylpolyamine. Dimethylamine tallow is an example of a fatty amine.

[0092] Alkylpolyamines advantageously comprise one or two hydrocarbon radicals, saturated or unsaturated, comprising from 8 to 24 carbon atoms, more advantageously 12 to 22 carbon atoms, and / or its immediate cyclization derivatives as well as its oxyethylated or oxypropylated derivatives.

[0093] Alkylpolyamines advantageously conform to formula (II)

[0094] NRjR2-R3-(NR4-R5)x-NR6R7 (II)

[0095] in which:

[0096] - x is an integer from 0 to 3. Advantageously x equals 0;

[0097] - one or two of Rh R2, R6, R7, represents a hydrocarbon radical comprising of 8 to 24 carbon atoms, more advantageously 12 to 22 carbon atoms, saturated or unsaturated, linear or branched, possibly cyclized. This radical is advantageously derived from tallow fatty acids;

[0098] - the others of RB R2, R6, R7, each represent, independently, one of the other: a hydrogen atom; a hydrocarbon radical comprising from 1 to 6 carbon atoms, advantageously from 1 to 4 carbon atoms, more advantageously from 1 to 2 carbon atoms, saturated or unsaturated, linear or branched; or a radical -(CH2-CR8OH)ZH in which R8 is a hydrogen atom or a methyl radical, z is 1 or 2. Advantageously the others of Rh R2, R6, R7, represent a methyl or ethyl radical;

[0099] - R3 represents a hydrocarbon radical comprising from 1 to 6 carbon atoms, saturated or unsaturated, linear or branched. Advantageously R3 represents an ethylene or propylene radical;

[0100] - R4, R5 each represent, independently of each other: a hydrogen atom; a hydrocarbon radical comprising from 1 to 6 carbon atoms, advantageously from 1 to 4 carbon atoms, more advantageously from 1 to 2 carbon atoms, saturated or unsaturated, linear or branched; or a radical -(CH2-CR8OH)ZH in which R8 is a hydrogen atom or a methyl radical, z is 1 or 2. Advantageously R4, R5 represents a methyl or ethyl radical.

[0101] As an example, trimethylpropylene diamine tallow may be cited.

[0102] Fatty amines respond advantageously to formula (III)

[0103] NR9R10-Rn (III)

[0104] - R9 represents a hydrocarbon radical comprising 8 to 24 carbon atoms, more advantageously 12 to 22 carbon atoms, saturated or unsaturated, linear or branched, possibly cyclized. This radical is advantageously derived from tallow fatty acids;

[0105] - Rio, represents: a hydrogen atom; a hydrocarbon radical comprising of 1 to 6 carbon atoms, advantageously of 1 to 4 carbon atoms, more advantageously of 1 to 2 carbon atoms, saturated or unsaturated, linear or branched; or a radical -(CH2-CR8OH)ZH in which R8 is a hydrogen atom or a methyl radical, z is 1 or 2. Advantageously R10 represents a methyl or ethyl radical;

[0106] - Ru represents a hydrocarbon radical comprising from 1 to 6 carbon atoms, saturated or unsaturated, linear or branched. Advantageously Ru represents a methyl, ethyl or propyl radical.

[0107] As an example, dimethylamine tallow can be cited.

[0108] Amidopolyamines respond advantageously to formula (IV)

[0109] R1'CO-(NH-R1”)a-NH2 (IV)

[0110] in which:

[0111] - Ri' is a hydrocarbon residue, saturated or unsaturated, linear or branched, comprising 12 to 24 carbon atoms, advantageously 16 to 24 carbon atoms. This radical is advantageously derived from tall oil or tallow fatty acids;

[0112] - Ri” is an ethylene radical;

[0113] - a represents an integer from 2 to 5, preferably a equals 5;

[0114] and / or its immediate cyclization derivatives, in particular imidazoline derivatives.

[0115] Amidopolyamine is advantageously the reaction product(s) of a fatty acid such as Tall Oil or tallow with diethanolamine, and / or diethylenetriamine, and / or tetraethylenepentamine and / or triethylenetetramine.

[0116] Quaternary ammonium compounds may in particular be of formula (V)

[0117] (Rx)bN+(Ry)cY (V)

[0118] in which:

[0119] - Rx represents a hydrocarbon radical comprising 8 to 24 carbon atoms, more advantageously 12 to 22 carbon atoms, saturated or unsaturated, linear or branched, possibly cyclized;

[0120] - Ry represents an alkyl radical comprising from 1 to 6 carbon atoms, possibly hydroxylated, in particular methyl, ethyl, propyl, hydroxyethyl, hydroxypropyl;

[0121] - Y designates an anion of a mineral acid, in particular a chloride anion, or of a organic acid, in particular an acetate or formate anion;

[0122] - c is an integer equal to (4-b) and

[0123] - b can take the values ​​of 1, 2 or 3.

[0124] Among the surfactants relevant to this application, the following commercial products may be mentioned: - Dinoram®S (Ceca) or Redicote®E9 (Akzo Nobel): N alkyl tallow propylene diamine;

[0125] - Emulsamine®L 60 (Ceca): Preparation based on tallol fatty amide, N-(3- dimethylamino)propyls (> 50%) and Emulsamine®LZ (> 25%) with an aromatic hydrocarbon (> 1%) and diethanolamine (> 1%);

[0126] - Polyram®S (Ceca): N-alkyl tallow propylene polyamine with Dinoram®S (< 10%), alkyl tallow amines (Noram®S - < 5%), tallow nitrile (< 10%);

[0127] - Stabiram®MS 601 (Ceca): N-alkyl tallow dichloride solution of N-dimethyl aminopropyl N-trimethyl ammonium (> 50%) in a water / hexylene glycol (glycol > 20%) mixture with Dinoram®S (< 1%);

[0128] - Dinoram®O (Ceca): N-(C16 and C18 alkyl unsaturated)trimethyl diamine (oleic diamine);

[0129] - Emulsamine®640 (Ceca): Preparation based on tallol fatty amides (> 50%), of Dinoram®O (> 25%) and (Z)-octadec-9-enylamine (> 1%);

[0130] - Indulin®R 66 (Meadwestvaco): Tall oil fatty amides: N - [(dimethylamino)-3- propyl] ;

[0131] - Indulin®R 33 (Meadwestvaco): Tall oil fatty amides (N-[(dimethylamino)-3- propyl]) (75-90%), N-tallow alkyltrimethylenediamine (20-25%);

[0132] - Indulin®GE F2 (Meadwestvaco): Nonylphenol ethoxylate (25-35%), lignin alkaline (reaction produced with dimethylamine and formaldehyde) (15-20%), N-(C14-18 alkyl and C16-18 unsaturated)-trimethylenediamine (5-10%);

[0133] - Indulin®GE F2 (Meadwestvaco): C12-C14 ethoxylated alcohols (2.5-25%), Alkaline lignin (reaction produced with dimethylamine and formaldehyde) (10-20%), N-(C14-18 alkyl and C16-18 unsaturated)-trimethylenediamine (1-3%);

[0134] - Duomeen®TTM (Akzo Nobel): sulftrimethylpropylenediamine (90-100%), suifdimethylamine (5-10%);

[0135] - Redicote®404 (Akzo Nobel): tallol, reaction products with the tetraethylenepentamine (100%).

[0136] One or more of these surfactants may be used, alone or in mixtures.

[0137] The emulsifying composition may also include a non-ionic emulsifying agent. This agent may be chosen from the family of ethoxylated fatty alcohols, the hydrophobic part of the molecule being of the nonylphenol-, octylphenol-, cetyl, oleic, etc. type, the hydrophilic part being made up of several ethoxy groups.

[0138] The aqueous phase of the emulsion also comprises a sufficient quantity of a mineral or organic acid (for example: citric acid, acetic acid), advantageously a mineral acid. The acid ionizes the cationic functions, particularly amines, of the emulsifiers to allow their dissolution in water.

[0139] The acid content is adjusted to the emulsifier content to have a pH of the aqueous phase ranging from 1.5 to 3.0, advantageously from 1.8 to 2.5.

[0140] The acid is advantageously hydrochloric acid, phosphoric acid or a polyphosphoric acid. Step b)

[0141] This step b) corresponds to a spreading step.

[0142] In step b), the suitable substrate is any substrate suitable for receiving a wearing course. This substrate may, in particular, be a base course (or the layer closest to the surface when the base course comprises several layers), especially a base course possibly coated with a binder course. The substrate may also be the existing wearing course of the road surface restored by implementing the method according to the invention.

[0143] The layer of asphalt is advantageously applied, i.e. spread, using a grader or a paver.

[0144] The layer of asphalt applied in step b) advantageously has a thickness of at least 1.5 cm, advantageously a thickness ranging from 1.5 cm to 12 cm. This thickness corresponds to the spreading thickness.

[0145] The asphalt is preferably applied, advantageously spread, in a thickness ranging from 1.5 cm to 10 cm, more preferably from 2 cm to 4 cm or from 3 cm to 6 cm or from 5 cm to 10 cm.

[0146] Typically, the spreading of asphalt is done at a temperature ranging from 10°C to 40°C.

[0147] The advantage of the invention is that it is possible to use a wide range of cold-mix asphalts during this step b).

[0148] For example, hydrocarbon asphalt can be: - an asphalt mix meeting the specifications given for emulsion-based bituminous concretes in the Cerema technical guide. Factory-made emulsion-based asphalt mixes, Bron: Cerema, 2020, collection: ISBN: 978-2-37180-456-2; - an asphalt mix meeting the specifications given for emulsion-treated aggregates in the Cerema technical guide. Factory-made emulsion-treated asphalt mixes, Bron: Cerema, 2020, ISBN: 978-2-37180-456-2; - an asphalt mix meeting the specifications given in the SETRA technical guide, cold in-place recycling of old pavements, 2003, ISBN: 2-11-093430-1.

[0149] Thus, advantageously, during this step b) a workable asphalt mix is ​​spread. The asphalt mix applied during step b) advantageously has a workability, also called Nynas workability, measured according to standard NF EN 12697-53, September 2019, under conditions adapted to cold mix asphalt, i.e. after a curing time at 18°C ​​and 55% humidity for 4 hours without a material recovery step, within a range of 50 to 300 N, preferably from 100 to 200 N.

[0150] In particular, it is not necessary to increase the binder content in the asphalt mix. Advantageously, the conventional residual anhydrous binder content varies from 3% to 6.5% by mass relative to the total mass of the asphalt mix after drying, advantageously from 3% to 6%, more advantageously from 3% to 5.5%, and even more advantageously from 3% to 5%.

[0151] The total water content of the asphalt mix varies advantageously from 3% to 10%, more advantageously from 5% to 8%.

[0152] Cold-mixed hydrocarbon coatings applied in the process of the present invention are obtained according to methods well known to those skilled in the art by mixing solid particles and a hydrocarbon binder emulsion.

[0153] The coating is in particular prepared by mixing: - 4.5% to 10% by mass, relative to the total mass of the mixture, of an E2 hydrocarbon binder emulsion; - 90% to 95.5% by mass, relative to the total mass of the mixture, of solid particles; - where applicable, water from the supply; - additives if applicable.

[0154] The binder of the E2 emulsion includes any hydrocarbon binder of fossil, vegetable or synthetic origin usable for the production of cold-mix asphalt. It is advantageously a bitumen.

[0155] The hydrocarbon binder may be a soft to hard binder, advantageously of a grade ranging from 10 / 20 to 160 / 220, in particular from 50 / 70 to 160 / 220.

[0156] The hydrocarbon binder can be pure or modified by the addition of polymer, as defined above. In addition, the binder, pure or modified by polymers, can be additively treated, in particular by the addition of additives commonly used in the road construction field, for example adhesion enhancers, handling additives, vegetable or petrochemical waxes, fluxing agents, fluidizing agents, and mixtures of these additives.

[0157] Binder emulsions used in the road construction industry are predominantly cationic in nature. The European standard EN 13808:2013 defines the technical specifications for cationic bitumen emulsions used in road construction, road infrastructure maintenance, airports, and other pavements. This European standard applies to bitumen emulsions, fluxed bitumen emulsions, polymer-modified bitumen emulsions, and polymer-modified fluxed bitumen emulsions, which also include latex-modified bitumen emulsions.

[0158] Any surfactant, advantageously cationic, may be used. In particular, the surfactants described above for the El emulsion may be used.

[0159] In a known manner, the aqueous phase of the emulsion may include a mineral or organic acid.

[0160] The E2 emulsion comprises in particular 60% to 71%, in particular 62% to 67%, by mass of binder relative to the total mass of the emulsion.

[0161] The solid particles are as defined above.

[0162] Advantageously, the maximum dimension of the gravel or aggregates (D) is less than or equal to 20 mm, more advantageously less than or equal to 16 mm, even more advantageously less than or equal to 14 mm, even more advantageously less than or equal to 12.5 mm, even more advantageously less than or equal to 10 mm.

[0163] Advantageously, the minimum dimension of the solid particles is greater than 0 mm.

[0164] Advantageously, at least 10% by mass, advantageously at least 20% by mass of the solid particles pass through the 2 mm mesh sieve. Advantageously, less than 60% by mass, advantageously less than 50% by mass of the solid particles pass through the 2 mm mesh sieve.

[0165] Advantageously, at least 1% by mass, advantageously at least 3% by mass of the solid particles pass through the 0.063 mm mesh sieve. Advantageously, less than 15% by mass, advantageously less than 10% by mass of the solid particles pass through the 0.063 mm mesh sieve.

[0166] Advantageously the asphalt is an asphalt 0 / 6 or 0 / 10 or 0 / 14 or 0 / 20, advantageously 0 / 10 or 0 / 6.

[0167] It is also possible to consider asphalt mixes having a break in the distribution curve of their solid particles, such as for example asphalt mixes free of 0 / 2 fraction.

[0168] The solid particles are advantageously chosen from mineral solid particles, for example natural mineral aggregates, asphalt aggregates and their mixtures.

[0169] In one embodiment of the invention, the solid particles comprise 80% to 100% by mass, relative to the total mass of the solid particles, of aggregates of coated materials.

[0170] The invention makes it possible to use, as a coating, recycled in-place emulsion-treated asphalt.

[0171] Depending on the climatic conditions, the dryness of the solid fraction, water, called supply water, can be added to the solid particles before mixing with emulsion E2.

[0172] The total water content of the asphalt mixes varies advantageously from 3% to 10%, more advantageously from 5% to 8%.

[0173] The mixture may also include a minor amount of hydraulic binder in combination with the E2 emulsion. By "minor amount" is meant that the residual hydraulic binder content is less than or equal to 2% by mass relative to the total mass of the asphalt mix, preferably less than 1%. Advantageously, said hydraulic binder is selected from Portland cement, lime, slurry of lime, magnesia, synthetic or natural calc-magnesium compounds such as dolomites, magnesian limes or dolomitic limes, calcium and / or magnesium silicate or aluminate cements, or any other hydraulic binder well known to those skilled in the art.

[0174] The hydraulic binder can be introduced either during the mixing of the different components of the coating, or prior to the solid particles or the emulsion binder before coating, subject to the compatibility and stability of the hydraulic binder in the aqueous dispersion.

[0175] The mixing of solid particles and hydrocarbon binder emulsion can be done just before laying, i.e. on site / on construction site, or in asphalt plants.

[0176] Advantageously, the cold-mix asphalts applied in step b) of the process of the invention are emulsion-based asphalts prepared in asphalt plants.

[0177] In some embodiments, the cold-mix asphalts applied in step b) may be emulsion-treated asphalts.

[0178] Step b) may include the following substeps:

[0179] bl) manufacture in a mixer or using an in-place reprocessing machine, by simple or sequential coating method, of the solid fraction described above with the E2 emulsion of a cold hydrocarbon mix as described above;

[0180] b2) spreading of the cold-mix asphalt prepared in step bl), advantageously using a grader or a paver, to form a layer with a thickness of at least 1.5 cm.

[0181] The coating, during step bl), can be simple or sequenced as described in patents EP 0 384 094, EP 0 524 031, EP 0 781 887 and FR 2 960 890. Preferably, step bl) is carried out without sequencing, i.e. the coating is simple. A preliminary step of wetting or drying the solid particles may optionally be implemented.

[0182] The coating is advantageously carried out at ambient temperature, that is to say at a temperature typically ranging from 10°C to 40°C.

[0183] Advantageously, the process for preparing the coatings does not include a heating or pre-heating step.

[0184] In a first embodiment of the invention, the cold-mix asphalt is prepared in a mixer. This mixer may be on site (i.e., on the construction site) or at the plant, i.e., in the asphalt mixing plant.

[0185] In a second embodiment of the invention, the cold-mix asphalt is prepared using an in-place recycling machine. In this embodiment, the solid particles comprise asphalt aggregates resulting from the fragmentation of the previous road surface removed, in particular by milling, during the construction work.

[0186] In a particular embodiment of this second variant, the bituminous coating layer is a layer of in-place recycled emulsion material. In this embodiment, step b) typically comprises the following substeps:

[0187] b' 1) recovery of asphalt aggregates from the milling of the pre-existing wearing course;

[0188] b'2) preparation of recycled asphalt mixes by mixing solid particles and a E2 emulsion of hydrocarbon binder, the solid particles comprising 80% to 100% by mass of asphalt aggregates from step b' 1) relative to the total mass of solid particles,

[0189] b'3) application on the base layer of a layer of recycled asphalt obtained at step b'2);

[0190] steps b' 1), b'2) and b'3) are advantageously carried out in place, that is to say on the site of the construction.

[0191] In-place emulsion recycling consists of recycling all or part of a pavement with a binder emulsion, with or without the addition of new solid particles. In-place emulsion recycling includes, in particular, a first step of pavement deconstruction, for example by milling the top layer, possibly followed by a crushing step to obtain asphalt aggregates of suitable size. The asphalt aggregates obtained, possibly supplemented with new solid particles, are mixed with a binder emulsion E2 and the resulting asphalt is applied to the pavement as a top layer.

[0192] In this embodiment, the content of conventional residual anhydrous binder, including the binder recovered from the asphalt aggregates forming part of the solid particles, is typically within a range of 3% to 6.5% by mass relative to the total mass of the asphalt after drying, advantageously 3% to 6%, more advantageously 3% to 5.5%, even more advantageously 3% to 5%. Step c)

[0193] Step c) of the process of the invention consists of a compaction step of the layer of asphalt applied during step b) by any means known to the person skilled in the art.

[0194] This step follows directly from step b); that is to say, there is advantageously no other step between steps b) and c) nor any voluntary pause or waiting time (other than that resulting from the normal spacing between construction equipment).

[0195] Most often, the compactor follows directly the grader or the paver.

[0196] The compacted asphalt layer advantageously has a thickness ranging from 1.5 cm to 12 cm, more preferably from 2 cm to 3 cm or from 3 cm to 5 cm or from 5 cm to 8 cm.

[0197] The void content of the compacted asphalt layer, determined by geometric measurement, advantageously varies from 5% to 30%, more advantageously from 12% to 20%. Indeed, the asphalt can be an open or a closed asphalt.

[0198] The asphalt mix advantageously has a void content threshold, of the fresh mix after compaction in the gyratory shear press (GSP), determined according to standard NF P98-252: June 1999, meeting at least one of the following performance criteria: at 25 gyrations: less than or equal to 26; at 40 gyrations: less than or equal to 20; at 60 gyrations: less than or equal to 15; at 100 gyrations: less than or equal to 18.

[0199] The asphalt mix advantageously has a percentage of voids (%), determined according to standard NF P98-251-4: August 2004, compaction method no. 2, less than or equal to 22.

[0200] The asphalt mix advantageously has very good water resistance. In particular, the asphalt mix meets the water resistance specifications required for a cold-mix asphalt for wearing courses (BBE) in the IDRRIM guide on asphalt mixes. to factory-made emulsion. More specifically, the water resistance value rl8 / R18 according to the Duriez test (NF P98-251-4) is greater than or equal to 0.70 and the water resistance value r35 / R35 is greater than or equal to 0.80. Step d)

[0201] Step d) of the process of the invention consists of applying a cationic emulsion of binder El, as described above, to the layer of asphalt compacted in step c). This step corresponds to a surface treatment of the compacted asphalt. This step can also be called the spreading step.

[0202] By "on the surface", it is understood that the cationic emulsion of binder El is applied directly over the layer of asphalt prepared in step b) and then compacted in step c) which is in contact with the air. When several layers of asphalt have been prepared in step b), these layers are superimposed and the emulsion El is applied over the top layer, i.e. the one in contact with the air at the end of step b) and then c).

[0203] Advantageously, there is no graveling step before or after step d).

[0204] The quantity of emulsion El applied corresponds to a dosage of conventional residual hydrocarbon binder strictly less than 250 g / m2, advantageously less than or equal to 240 g / m2, more advantageously ranging from 50 g / m2 to 200 g / m2, more preferably from 50 to 150 g / m2, even more preferably from 50 to 100 g / m2. This content is determined according to the "carpet tiles" method of standard NF EN 12272-1: October 2003.

[0205] Step d) may include a step dl) of diluting the emulsion El prepared in step a). The binder content in the diluted cationic emulsion El is in particular in a range of 10% to 60% by mass relative to the total mass of the diluted emulsion, preferably in a range of 30% to 50%.

[0206] The emulsion subsequently applied will then be the diluted El emulsion.

[0207] The residual binder layer of the El emulsion is, in particular, homogeneous, that is to say, it has a uniform thickness over its entire surface. In particular, the layer of bituminous asphalt is uniformly covered by the residual binder layer of the El emulsion and does not include any area where the asphalt is in direct contact with the air.

[0208] Step d) is typically carried out within a limited time following step c) to allow for rapid traffic reintroduction while providing early resistance to stripping of the asphalt. Step d) is carried out before the road surface is returned to traffic. Preferably, step d) is carried out a few hours, for example from 2 hours, to a few days, for example up to 3 days, after the application of the asphalt in step c), preferably from 2 to 6 hours after step c).

[0209] In a preferred embodiment, the application of the El binder cationic emulsion to the surface of a cold-mix asphalt layer is carried out by spraying.

[0210] According to the invention, the application of the El binder cationic emulsion to the surface of the cold mix asphalt layer makes it possible to obtain a resistance to stripping of the resulting wearing course, evaluated via the mass loss by stripping according to the DSD test (Darmstadt Scuffing Device - XP CEN / TS 12697-50-Annex B), more effective than for the same layer of cold mix asphalt not covered with the El emulsion.

[0211] Indeed, the average of the losses at 50 cycles of the asphalt at 21 days (normal force of the tire of 500 N) is at least divided by 1.5 when the surface treatment is implemented, advantageously at least divided by 2, more advantageously at least divided by 2.5, more advantageously at least divided by 3, more advantageously at least divided by 3.5, even more advantageously at least divided by 4.

[0212] Advantageously, the average loss at 50 cycles of the 21-day asphalt mix is ​​less than or equal to 1500 g / m², more advantageously less than or equal to 1000 g / m², even more advantageously less than or equal to 800 g / m², even more advantageously less than or equal to 500 g / m², even more advantageously less than or equal to 200 g / m². The average loss at 50 cycles advantageously ranges from 0 g / m² to 1000 g / m², advantageously from 0 g / m² to 800 g / m², advantageously from 0 g / m² to 500 g / m², advantageously from 0 g / m² to 200 g / m².

[0213] The asphalt mix obtained at the end of the process has a very good coating quality. The asphalt mix is ​​thus advantageously of class El according to standard NF P 98 / 257-1 of August 2004, corresponding to a percentage of the surface area of ​​the solid particles covered by the binder greater than or equal to 97%. The binder is derived from the E2 emulsion and the EL emulsion.

[0214] The process of the invention makes it possible to obtain a wearing course suitable for low to high traffic intensity. In particular, the asphalt mix obtained at the end of the process has a surface macro-texture conforming to that expected for a wearing course, notably evaluated by measuring the mean surface texture depth (MST), carried out according to standard NF EN 13036-1 of September 2010. The asphalt mix obtained at the end of the process therefore has an MST of at least 0.60 mm in most cases. The MST of the asphalt mix obtained at the end of the process thus provides early-age adhesion conforming to that expected for a final wearing course.

[0215] The process of the invention may optionally include a step e), after step d), of sandblasting the residual binder layer of the El emulsion, i.e., applying a thin layer of sand. This step provides additional micro-roughness which can be useful for improving the adhesion of the wearing course, particularly in winding or accident-prone areas.

[0216] Fig. 1 illustrates the wearing course obtained by the process of the invention comprising a layer 2 of cold-mix asphalt covered with a layer 1 of residual binder from the El binder emulsion, directly in contact with the ambient air.

[0217] These asphalt mixes allow for a return to traffic in less than 24 hours, more advantageously within 12 hours after spreading, even more advantageously within 6 hours after spreading, even more advantageously within 2 to 4 hours after spreading.

[0218] The invention also relates to a cold-mix asphalt wearing course obtained by the process as described above.

[0219] This wearing course comprises a layer 2 of cold-mix asphalt, as obtained by step b) of the process, directly coated with a layer of residual binder from the binder emulsion El described previously.

[0220] Layer 2 has a thickness ranging from 2 cm to 8 cm after step c)

[0221] Layer 2 has a void content, determined by geometric measurement, ranging from 5% at 30% after step c), more advantageously from 12 to 20%.

[0222] Layer 1 and layer 2 together form the coating of the wearing course according to the invention.

[0223] The asphalt mix for the wearing course according to the invention has a very good coating quality. The asphalt mix is ​​advantageously of class El according to standard NF P 98 / 257-1 of August 2004, corresponding to a percentage of the solid particle surface covered by the binder greater than or equal to 97%. The binder is derived from E2 emulsion and EL emulsion.

[0224] The asphalt mix of the wearing course according to the invention has very good resistance to flaking, as described above. Advantageously, the average loss at 50 cycles (normal tire force of 500 N) of the asphalt mix at 21 days is less than or equal to 1500 g / m2, more advantageously less than or equal to 1000 g / m2, even more advantageously less than or equal to 800 g / m2, even more advantageously less than or equal to 500 g / m2, even more advantageously less than or equal to 200 g / m2. The average loss at 50 cycles of the asphalt at 21 days varies advantageously from 0 g / m2 to 1000 g / m2, advantageously from 0 g / m2 to 800 g / m2, advantageously from 0 g / m2 to 500 g / m2, advantageously from 0 g / m2 to 200 g / m2.

[0225] The asphalt mix of the wearing course according to the invention has a surface macro-texture conforming to that expected for a wearing course, in particular evaluated by the measurement of the average depth of texture surface (PMT), according to standard NF EN 13036-1: September 2010. The asphalt mix of the wearing course according to the invention therefore has a PMT of at least 0.60 mm.

[0226] The invention also relates to the use of a cationic emulsion of hydrocarbon binder El formulated from a hydrocarbon binder, advantageously a Bitumen, having a needle penetration at 25°C of 100 1 / 10 mm or less, is applied to the surface of a cold-mix asphalt layer to improve resistance to stripping, particularly at an early age but also during the aging of the surface course. Thanks to the residual binder layer of the resulting El emulsion, the long-term stripping resistance of the surface course is also improved, extending its service life.

[0227] The El emulsion and the hydrocarbon coating are as described above.

[0228] The performance of the wearing course, macrotexture and resistance to feathering in particular, is evaluated shortly after the construction of the wearing course, i.e. at a period ranging from 24 hours to 3 months.

[0229] The application of the cationic emulsion of hydrocarbon binder El on the surface of a layer of cold asphalt makes it possible in particular to increase the resistance to stripping, that is to say to reduce the mass loss at the tear-off of the asphalt, measured according to the DSD test, by 20%, 50%, 70%, 90% or 95% depending on the residual binder content of the emulsion El obtained and the grade of the binder used, compared to the same layer of asphalt not covered with the emulsion.

[0230] The present invention also relates to a method for improving the early-age resistance to flaking of cold-mix asphalt comprising the following steps: a. Preparation of a cationic emulsion El of hydrocarbon binder, formulated from a hydrocarbon binder, advantageously from a bitumen, modified or not with polymers, having a needle penetration at 25°C less than or equal to 100 1 / 10 mm b. apply a layer of cold-mix asphalt onto a suitable surface; c. compact the layer implemented in step b); d. Apply the cationic emulsion El from step a) to the surface of the layer of compacted asphalt in step c). METHODS Needle penetration

[0231] The needle penetration at 25 °C of the binder is measured according to the method described in standard NF EN 1426, January 2018. Residual binder content

[0232] The content of conventional residual anhydrous binder, during the preparation of the asphalt mix, is determined according to the protocol described in the DEFINITIONS section.

[0233] The residual binder dosage, determined after application of the El emulsion, is calculated according to the "carpet tile" method of standard NF EN 12272-1: October 2003. Workability:

[0234] The workability test of cold-mix asphalt is carried out by applying the conditions of the standard NF EN 12697-53 of September 2019 adapted to cold-mix asphalt, i.e. after a curing time at 18°C ​​and 55% humidity for 4 hours without a material recovery stage.

[0235] This handling ability is also known as Nynas handling. Resistance to tearing / plucking - DSD test

[0236] Resistance to tearing / plucking is determined by applying a modified protocol of the DSD (Darmstadt Scuffing Device) test, which is currently the subject of a draft experimental standard XP CEN / TS 12697-50-Annex B.

[0237] The modified conditions of Fessais DSD are as follows: • Tire pressure: 3 bar • Sample conditioned at 25°C • Vertical load of 500 N • Weighing of mass loss every two cycles during the first 10 cycles, then weighing of mass loss every ten cycles during the last 40 cycles up to a total of 50 cycles.

[0238] The results correspond to the average of the results obtained for 4 test specimens. Void content (geometric method)

[0239] The void content is calculated with the apparent geometric density determined according to standard NF EN 12697-6 operating method D and the actual density. Coating evaluation

[0240] The coating assessment was carried out based on the notation described in standard NF P 98-257-1 of August 2004, using slabs prepared for the DSD test (before abrasion). The adaptation consists of using the same notation as the standard but assessing the coating from a compacted asphalt slab and not from loose asphalt.

[0241] The rating scale as defined in standard NF P 98-257-1 of August 2004 is as follows:

[0242] [Tables 1] Coating Quality Class Percentage of Surfaces Covered Coating Qualification E1 ■é 97% Complete E2 90 to 96% Very Good E3 75 to 89% Average E4 <75% Poor EXAMPLES Emulsions El:

[0243] Various cationic emulsions with 65% by mass of bitumen, comprising a bitumen of varying hardness, were prepared on the basis of the following components; the contents are expressed in kg per tonne of emulsion:

[0244] [Tables2] Emulsion No. ABC Binder: Bitumen Supplier: Exxon Total Grade: 70 / 100 35 / 53 20 / 30 Content (kg / t) 650 Aqueous Phase: Cationic Surfactant Supplier: Arkema Name: Owws Content (kg / t) 1.6 Acid Nature: UQâ 37% Content (kg / t) 1.3 Water (kg / t) 347.1

[0245] Dinoram S: cationic surfactant (mixture comprising more than 90% alkyl propane-1,3-diamine, CAS: 1219010-04-4)

[0246] These emulsions were prepared using a laboratory Atomix C mill.

[0247] The El emulsions are obtained by diluting these emulsions with water to prepare cationic emulsions of bitumen with 40% bitumen. Cold-mix asphalt 0 / 10:

[0248] A cationic emulsion of bitumen E2 is prepared on the basis of the following components; the contents are expressed in kg per tonne of emulsion:

[0249] [Tables3] Bitumen Binder Supplier Exxon Grade 70 / WQ Content (kgd) 6S0 Aqueous Phase Cationic Surfactant Content (kgd) 11 Acid Nature HQ at 37% Content (kg / t) 3.7 Water (kg / t) 335 3

[0250] These emulsions were prepared using a laboratory Atomix C mill.

[0251] The mineral solid particles comprise, by mass relative to the total mass of the dry particles:

[0252] - 37.0% Dussac 0 / 2 sand;

[0253] - 20.0% Dussac 2 / 6 aggregates;

[0254] - 43.0% Dussac 6 / 10 aggregates.

[0255] The 0 / 2 cut corresponds to the fraction 0 / d. The 2 / 6 and 6 / 10 cuts form together the d / D fraction. These solid particles allow the manufacture of a 0 / 10 cold-mix asphalt.

[0256] The mineral solid particles are characterized by a 0.063 mm sieve size of 5.2% and a 2 mm sieve size of 35.5% (the percentages are mass percentages).

[0257] Cold-mix asphalt is prepared by mixing this E2 emulsion and mineral solid particles in a parallel shaft mixer from SR Consulting to prepare 30 kg batches.

[0258] The manufacture of cold-mix asphalt is carried out by direct mixing method, without sequencing of the 0 / d and d / D fractions. The mixing of the mineral solid particles in the presence of the emulsion is carried out for 15 seconds.

[0259] The RI coating is prepared by mixing 7.4 ppc by mass of the E2 emulsion relative to the dry mass of mineral solid particles and 100% by dry mass of mineral solid particles.

[0260] The R2 coating is prepared by mixing 7.5 ppc (parts per cent by weight) of E2 emulsion with 100% by mass of mineral solid particles.

[0261] The R3 coating is prepared by mixing 7.8 ppc of E2 emulsion with 100% by mass of mineral solid particles.

[0262] The R4 coating is prepared by mixing 8.5 ppc of E2 emulsion for 100% by mass of mineral solid particles.

[0263] The characteristics of the prepared cold-mix asphalt are given in the following table:

[0264] [Tables4] Asphalt termite number RI R2 R3 R4 Bitumen emulsion - content 74 œ 7.5 SK 7.8 œ 8.5 Total water content 8.0 8.0 œ 8.0 Conventional residual anhydrous top content 4.53% 4 37% 4.85% 5 21% ManiabiBé 121 120 îGG 220

[0265] RI coatings therefore have a lower residual binder content than R2, R3 and R4 coatings. Sample preparation for the DSD test

[0266] The resistance to tearing / plucking of the coatings was analyzed according to the DSD test.

[0267] The samples are prepared according to the protocol having the following successive steps: • Production of two batches of 30 kg of cold-mix asphalt 0 / 10 RI or R2 or R3 or R4 described above; • Production of two cold-mix asphalt slabs by compaction to 18% voids, applying the following dimensions for each slab: 400 mm * 600 mm * 40 mm; • Curing of the hydrocarbon asphalt slabs at cold temperature for 7 days at 35°C and 20% humidity; • Sawing of the cold-mix asphalt slabs after 7 days of curing to make 4 cold-mix asphalt test specimens with dimensions: 260 mm *260 mm *40 mm; • Additional curing of the cold-mix asphalt test specimens for 7 days at 35°C and 20% humidity; • Application or not of a surface treatment by applying with a brush to the surface of the test specimen a defined quantity of cationic emulsion of bitumen El (A, B or C) with 40% bitumen so as to achieve the dosage of residual bitumen indicated in the following table; • Additional curing of the cold asphalt test specimens for 7 days at 35°C and 20% humidity to obtain a total curing of the cold asphalt of 21 days at 35°C and 20% humidity.

[0268] At the end of this protocol: - a resistance test to plucking is carried out by applying the modified protocol of the DSD test described in the METHODS section; - an evaluation of the coating grade was also carried out by applying the protocol described in the METHODS section;

[0269] Details of the products evaluated and the results obtained are shown in the following table:

[0270] [Tables5] Product Number PI P2 P3 P4 P5 P8 P? PS P9 Asphalt Mix Formula RI R2 R3 R4 RI R1 RI R1 R3 Surface Treatment Emulsion El ABGBB Conventional Residual Bitumen Dosage (g / m?) y .1 ï 100 100 100 150 100- Results Feather Resistance - DSD Test Average Losses at 50 Cycles (gW) 2404 2327 1855 909 1437 651 184 117 717 Coating Grade Coating Quality Class E3 E2 E2 El El El El El El Adhesion - Depth Macrotexture (NF EN 13038-1) PMT (mm) 0.95 0f86 0.8o 0.82 / LOI Jf 0J4 y

[0271] Products P1 to P4 are comparative examples in which no bitumen emulsion El was applied to the surface of the asphalt. Products P5 to P9 are products according to the invention.

[0272] The results show that a very significant reduction in mass loss by tearing of cold-mix asphalt is indeed made possible by the use of a surface treatment with bitumen emulsion at a residual bitumen dosage of less than 240 g / m2.

[0273] In particular, this surface treatment is much more effective at limiting stripping than increasing the binder content of the cold-mix asphalt. Indeed, products P6 to P9 show better results than product P4.

[0274] The results also show that a bitumen with a needle penetration measured at 25°C of less than 100 l / 10mm (grade 70 / 100) significantly limits the losses during the removal of the asphalt layer. It is observed that this Pull-off loss is further limited when the bitumen used in the El cationic emulsion is hard. Indeed, products P6 (emulsion B with a grade 35 / 50 bitumen) and P7 (emulsion C with a grade 20 / 30 bitumen) show improved results compared to product P5 (emulsion A with a grade 70 / 100 bitumen).

[0275] The use of a surface treatment (products P5 to P9) also makes it possible to obtain coating scores equal to or even higher than the formulas without surface treatment (PI to P4) with the added considerable advantage of the 4h workability of the product compared to product P4 which certainly has a good coating score but suffers from insufficient workability.

[0276] Finally, the use of a surface treatment (product P8) with a conventional residual anhydrous binder dosage of 150 g / m2 ensures a PMT value suitable for use in a wearing course.

Claims

Demands

1. Method for constructing a wearing course of a road pavement, comprising the following steps: a. prepare a cationic emulsion El of hydrocarbon binder, formulated from a hydrocarbon binder having a needle penetration at 25°C less than or equal to 100 1 / 10 mm; b. apply a layer of cold-mix asphalt to a suitable substrate; c. compact the layer laid in step b); a. apply the cationic emulsion El from step a) to the surface of the asphalt layer compacted in step c).

2. A method according to claim 1, wherein, during step d), the quantity of cationic emulsion El applied corresponds to a dosage of residual bituminous binder, determined according to standard NF EN 12272-1: October 2003, of less than 240 g / m2, preferably within a range of 50 to 200 g / m2, more preferably from 50 to 150 g / m2.

3. A method according to claim 1 or 2, wherein the hydrocarbon binder of the cationic emulsion El has a needle penetration at 25°C less than or equal to 70 1 / 10 mm.

4. A method according to any one of the preceding claims, wherein the hydrocarbon binder of the cationic emulsion El has a needle penetration at 25°C ranging from 15 1 / 10 mm to 35 1 / 10 mm, advantageously from 20 1 / 10 mm to 35 1 / 10 mm.

5. A method according to any one of the preceding claims, wherein step d) is carried out before the wearing course is put back into circulation, preferably on the same day as step c) or within a period of between 0 and 72h after step c).

6. A process according to any one of the preceding claims, wherein the cold-mix asphalts applied in step b) are prepared by mixing solid particles and an E2 hydrocarbon binder emulsion, the solid particles comprising from 80% to 100% by mass of asphalt aggregates relative to the total mass of solid particles.

7. A method according to the preceding claim, wherein step b) comprises the following successive substeps: b'1) recovery of asphalt aggregates from the milling of a pre-existing wearing course; b'2) preparation of recycled asphalt by mixing solid particles and an E2 emulsion of hydrocarbon binder, the solid particles comprising from 80% to 100% by mass of asphalt aggregates from step b'1) relative to the total mass of the solid particles, b'3) application on a suitable support, for example a base course, of a layer of recycled asphalt obtained in step b'2); steps b'1), b'2) and b'3) are advantageously carried out in place, i.e. on the site.

8. A process according to any one of the preceding claims, wherein the asphalt applied in step b) is an asphalt having a conventional residual anhydrous binder content of 3% to 6.5% by mass relative to the total mass of dry asphalt.

9. Wearing course based on cold-mix asphalt obtained by the process as defined in the preceding claims.

10. Wearing course according to claim 9, wherein the asphalt has an average texture surface depth, determined according to standard NF EN 13036-1: September 2010, of at least 0.60 mm.

11. Use of a cationic emulsion El of hydrocarbon binder, formulated from a hydrocarbon binder having a needle penetration at 25°C less than or equal to 100 1 / 10 mm, on the surface of a compacted cold-mix asphalt layer to improve the early-age stripping resistance of a road surface course obtained by the process defined by claims 1 to 8.

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