"Cold-applied, thin-layer structural base course coating, its manufacturing process and road surfacing comprising said base course coating"

Abstract

The present invention relates to a structural base course coating composed of one or more base layers, each base layer comprising, by mass relative to its total mass: - 50% to 90% asphalt aggregates comprising, by mass relative to its total mass, a residual bituminous binder content ranging from 3% to 8%; - 0% to 48% sand; - 2% to 10% hydraulic binder, characterized in that each base layer, after compaction, has a thickness strictly less than 15 cm and is free of added bituminous binder. The present invention also relates to a cold-forming process for said base course coating, as well as to a road surface. Figure for the abstract: no figure

Description

Title of the invention: "Cold-formed, thin-layer structural base course coating, its manufacturing process and road surfacing comprising said base course coating" Technical field of the invention

[0001] The present invention relates to the field of road surfacing.

[0002] In particular, the present invention relates to a base layer comprising asphalt aggregates, corrective sand and a binder, the base layer having an unusual thickness which is strictly less than 15 cm.

[0003] The invention also relates to a road surface comprising said base layer. State of the art

[0004] Asphalt road pavements are composed of a superposition of several layers on the subgrade to be covered: a subgrade layer covered with a base course classically composed of a base course and a foundation course, on which a surface course is deposited, also usually formed of a two-layer comprising a bonding layer and a wearing course or a single-layer (wearing course only).

[0005] In particular, the foundation and base layers forming the subgrade must perform the following functions: during pavement construction, they must provide the surface layers with a load-bearing, homogeneous, and well-graded support. They may occasionally serve as a temporary wearing course during pavement construction. Finally, they provide thermal protection for the underlying platform and give the pavement its mechanical resistance to the vertical loads induced by traffic.

[0006] In France, it is well known that base layers are either based on bitumen and are called "black formulations", or based on hydraulic binder and are called "white formulations".

[0007] Bituminous base layers known as "black" are generally made up of Bituminous Gravel (GB) or High Modulus Asphalt (EME), the normative reference of which is NF EN 13108-1 published in May 2017. They are manufactured hot at a temperature ranging from 120°C to 170°C in a continuous or discontinuous asphalt plant.

[0008] Bituminous gravel (GB) is usually composed of a mixture of bitumen and crushed aggregates, most often with a continuous particle size distribution. Currently, the particle sizes used are 0 / 14 mm, and less frequently 0 / 20 mm. The bitumen content of these products systematically exceeds 4% (mass of bitumen relative to the mass of bituminous gravel expressed as a percentage), reaching 5% for the highest-performing GB. The bitumen grades usually used are 35 / 50 or 20 / 30. As a base course or foundation course, GB is applied in a thickness range of 8 to 16 cm; these thicknesses are specified in the design standard NFP 98-086 published in December 2019.These base layers constructed with aggregates can comprise two or even three layers of aggregates, each with a typical thickness of 8 to 14 cm and a 0 / 14 mm particle size, resulting in a total thickness of up to 35 cm in road applications and considerably more in the area of ​​special platforms used by special vehicles such as reach stackers. In this context, it is standard practice to use the Alizé software (sizing software) for design under special loads.

[0009] The EME comprises a mixture of crushed aggregates of the same particle size as those composing the GB (average diameter limited to 20 mm or preferably 14 mm) with a harder bitumen than that used for the GB (grade 10 / 20 or 15 / 25, or even 20 / 30). If necessary, a grade 35 / 50 is acceptable, but in this case, it is generally supplemented with components to stiffen the bituminous mixture. Furthermore, the binder content of EME is higher than in GB (between 5.2 and 6% by mass relative to the total mass of the EME). EME formulations thus exhibit a high stiffness modulus and superior resistance to fatigue and rutting than GB. EME therefore makes it possible to form a base course with a thickness similar to that formed with GB.Thus, the base layers in EME (Electrical Materials Engineering) can comprise two layers (base / foundation), each with a thickness ranging from 6 cm to 15 cm, for a total thickness of up to 26 cm in road applications and considerably more in the area of ​​so-called special platforms, on which special vehicles such as Reach Stackers operate. In this context, it is also agreed to use the Alizé software (sizing software) for dimensioning under special loads.

[0010] White base layers, based on hydraulic binders, unlike black formulations, are manufactured cold at temperatures less than or equal to 50°C, generally at room temperature.

[0011] They may, for example, correspond to the Ertalh® product marketed by EIFFAGE. This product is obtained from a mixture of 0 / 20 aggregates resulting from the crushing and screening of recycled asphalt (i.e., asphalt aggregates), sand and / or It consists of gravel and a hydraulic binder. This hydraulic binder-based base course is usually laid in one or two layers (base course and / or sub-base) with a minimum application thickness of 15 cm. Such a base course, known as a "white" base course, can thus have a total thickness of up to 48 cm in road construction and much greater in the case of special platforms, on which special vehicles such as reach stackers operate. In this context, it is also standard practice to use the Alizé software (sizing software) for design under special loads.

[0012] The Guide to the Application of Standards for the National Road Network published by the Ministry of Equipment, Transport and Housing, SETRA / LCPC, "Roadbeds in Untreated Gravel and Materials Treated with Hydraulic and Pozzolanic Binders" of December 1998, indicates that the average thickness of a layer after compaction should not exceed 32 cm. The rigidity and low deformability before failure of materials treated with a hydraulic or pozzolanic binder lead to the prohibition of any layer less than 15 cm thick, even on the lightest traffic areas.In the case where the base is made in two layers, the minimum thickness of the foundation layer, if it is treated with a hydraulic or pozzolanic binder, shall be greater than or equal to 20 cm in the case of a PF2 platform, shall be greater than or equal to 18 cm in the case of a platform greater than or equal to PF3, shall be greater than or equal to 15 cm in the case of a platform greater than or equal to PF4 or in the case of a base layer implemented on a foundation layer.

[0013] Indeed, to date, the so-called white base layers have a thickness ranging from 15 cm to 32 cm, for reasons of compactness, cohesion and implementation, as highlighted in the application guide for the standards mentioned above.

[0014] Although prior art base course formulations are satisfactory, there is still a need and a demand for new formulations that are easy to implement, more economical and have a reduced carbon footprint, while exhibiting good mechanical performance.

[0015] In particular, there is a need to provide base course (so-called white) formulations exhibiting excellent durability, good fatigue resistance and excellent modulus, while also presenting a satisfactory economic balance.

[0016] The aim of the present invention is thus to provide a new base coat coating that meets at least partially the aforementioned needs. Presentation of the invention

[0017] To this end, the present invention relates to a base layer coating composed of one or more base layer(s), each base layer comprising, by mass, relative to its total mass:

[0018] - from 50% to 90% of asphalt aggregates comprising, by mass, relative to its mass total, a residual bituminous binder content ranging from 3% to 8%;

[0019] - from 0% to 48% sands;

[0020] - 2% to 10% hydraulic binder,

[0021] characterized in that each base layer, after compaction, has a thickness strictly less than 15 cm and is free of added bituminous binder.

[0022] The Applicant discovered that a base course coating, known as a "white" base course, could be formed, surprisingly and unexpectedly because it contradicts the best road construction practices outlined in the current Standards Application Guides, with a compaction thickness of less than 15 cm. Indeed, it discovered that the residual bitumen content already present in the asphalt aggregates gave the base course coating a certain viscoelasticity. The cold-mixed base course coating according to the invention could thus be characterized by the same properties as a bitumen-based formulation, namely a hot-mixed "black" formulation. It discovered that the base course coating according to the invention surprisingly exhibits excellent durability, good resistance to fatigue, and resistance to micro-deformation.

[0023] In particular, the base coat coating according to the invention is more economical than the black formulations described above because it is cold-formulated. Furthermore, it offers equivalent mechanical performance for a similar application thickness to said black formulations (namely, a thin layer).

[0024] Other non-limiting and advantageous characteristics of the base coat coating according to the invention, taken individually or in all technically possible combinations, are as follows:

[0025] - each base layer has, after compaction, a thickness less than or equal to 14 cm, in particular less than or equal to 13 cm and typically less than or equal to 12 cm;

[0026] - the coating is composed of at least two superimposed base layers one to the other so as to form a bilayer;

[0027] - when it is composed of several layers of base, at least two layers of seat, said seat layer covering has a total thickness strictly less than 30 cm, preferably less than or equal to 29 cm, in particular less than or equal to 28 cm and typically less than or equal to 25 cm;

[0028] - the hydraulic binder is chosen from one or more of the following compounds: a clinker, blast furnace slag, siliceous or calcic fly ash, lime, gypsum, a geosynthesis binder based on an alkaline activator and a silico-aluminous compound, pozzolans activated by lime or a sulfo-calcic compound, calcined clays of the metakaolin type, crushed limestones, steel slags, biomass or paper mill ash, calcined shales;

[0029] - the asphalt aggregate has, by mass, relative to its total mass, a content of residual bituminous binder, from 3.5% to 7.5% and typically from 4.0% to 7.0%;

[0030] - the coating exhibits a compactness, measured in the laboratory according to NF standards EN 13286-2 and NP EN 12697-29, which is greater than or equal to 95% of a reference value, named OPM, which is measured according to the NF EN 13286-2 standard;

[0031] - the base layer(s) comprising said coating have:

[0032] * a stiffness modulus measured according to standard NF EN 12697-26 (Annex A or C) greater than or equal to 5,000 MPa, preferably greater than or equal to 9,000 MPa, in particular greater than or equal to 11,000 MPa (by way of example, the stiffness modulus of said coating is equivalent to a GB2 / GB3 (9,000 MPa <<11,000 MPa), or a GB4 (11,000 MPa < < 14,000 MPa), or an EME (>14,000 MPa), such as greater than or equal to 12,500 MPa and typically greater than or equal to 13,000 MPa),

[0033] * a fatigue resistance, measured according to standard NF EN 12697-24, greater than or equal to 80 pDef, preferably greater than or equal to 90 pDef, in particular greater than or equal to 100 pDef.

[0034] The present invention also relates to a cold manufacturing process for a base coat coating as described above, comprising the following successive steps:

[0035] (a) the preparation of a base coat formulation comprising, by mass, relative to its total mass:

[0036] - from 50% to 90% of asphalt aggregates;

[0037] - from 0% to 48% sands (usually having a grain size of 0 / 4 mm);

[0038] - from 2% to 10% hydraulic binder,

[0039] (b) the spreading of said base layer formulation via a spreader of road surface on a subgrade layer intended to receive a base course;

[0040] (c) compaction via a compactor (such as a compactor commonly used for form the embankment layers with base layers such as a single-drum vibratory roller or an asphalt roller commonly used to form base layers and wearing courses such as a tandem roller), of this base layer thus formed so as to obtain a thickness strictly less than 15 cm;

[0041] (d) where appropriate, repeating steps (a) to (c), so as to form a coating comprising several superimposed seating layers, such as at least two superimposed seating layers.

[0042] In general, steps (a) to (c) are carried out at ambient temperature, namely at the temperature of the external environment where the base coat coating according to the invention is intended to be deposited. In general, the ambient temperature ranges from -5°C to 40°C, preferably from 10°C to 30°C and typically from 15°C to 25°C. According to the invention, an ambient temperature ranging from 5°C to 40°C includes the following values ​​and any interval between these values ​​(in °C): -5; 4; -3; -2; -1; 0; 1; 2; 3; 4; 5; 6; 7; 8; 9; 10; 11; 12; 13; 14; 15; 16; 17; 18; 19; 20; 21; 22; 23; 24; 25; 26; 27; 28; 29; 30; 31; 32; 33; 34; 35; 36; 37; 38; 39; 40.

[0043] The present invention also relates to a road surface intended to cover a ground comprising successively, starting from the ground:

[0044] a form layer coating,

[0045] a base layer coating disposed on said sub-base layer coating,

[0046] a surface layer coating, disposed on said base layer coating and which is itself generally composed of a two-layer system comprising a binder layer and a wearing course,

[0047] characterized in that said base layer coating corresponds to the base layer coating as defined above.

[0048] Of course, the different features, variants and embodiments of the invention can be combined with each other in various ways insofar as they are not incompatible or mutually exclusive.

[0049] For the remainder of the description, unless otherwise specified, the indication of a range of values ​​"from X to Y" or "between X and Y" in the present invention is understood to include the values ​​X and Y.

[0050] Hereinafter, the mention "strictly less than Z", unless otherwise specified, is understood as not including the value of Z.

[0051] According to the invention, unless otherwise stated, the various characteristics of the invention have been measured according to the standards mentioned below. Detailed description of the invention

[0052] In addition, various other features of the invention will become apparent from the accompanying description, which illustrate non-limiting embodiments of the invention. A. Base layer coating

[0053] The Applicant company has focused on the development of new base course coatings, in particular "white" base course coatings based on hydraulic binder and free of added bitumen, which have a balance reduced carbon compared to hot- or cold-processed bituminous structural products (i.e., black formulations), which are more economical and intended for cold application. In particular, it has focused on developing new base course coatings suitable for and / or configured to form road surfaces for light and heavy vehicles, or even special loads such as Reach Stackers, while offering a certain level of durability (adequate mechanical performance).

[0054] To this end, the base layer coating according to the invention is composed of one or more base layer(s), each base layer comprising, by mass, relative to its total mass:

[0055] - from 50% to 90% of asphalt aggregates comprising, by mass, relative to its mass total, a residual bituminous binder content ranging from 3% to 8%;

[0056] - from 0% to 48% of sands generally having a grain size of 0 / 2 or 0 / 4 and preferably a particle size of 0 / 4mm;

[0057] - from 2% to 10% hydraulic binder,

[0058] characterized in that said base layer has, after compaction, a thickness strictly less than 15 cm and is free of added bituminous binder.

[0059] By "free from added bituminous binder", it is understood that the base course according to the invention comprises a portion of bituminous binder that is already present in the asphalt aggregates; however, no additional bituminous binder, referred to as added bituminous binder or new / virgin bituminous binder, is added to the composition of the base course according to the invention.

[0060] In particular, each base layer has, after compaction, a thickness less than or equal to 14 cm, in particular less than or equal to 13 cm and typically less than or equal to 12 cm.

[0061] According to the invention, "a thickness strictly less than 15 cm" includes the following values ​​and any interval between these values ​​(in cm): 14.5; 14.0; 13.5; 13.0; 12.5; 12.0; 11.5; 11.0; 10.5; 10.0; 9.5; 9.0; 8.5; 8.0; 7.5; 7.0; etc.

[0062] Due to its characteristics, and in particular its high content of reclaimed asphalt pavement (RAP) containing a residual bituminous binder, the base course exhibits a certain viscoelasticity that allows it to be considered not as a "white" formulation whose studied parameters do not include temperature (i.e., measurements of thickness, Young's modulus, etc.), but as a "black" formulation whose parameters do, on the contrary, include temperature, such as measurements of the complex modulus, fatigue resistance, and resistance to micro-deformation. The Applicant thus discovered, contrary to expectations, that such a base course exhibited excellent mechanical performance and that it could therefore have a thickness exceeding 15 cm, as previously mentioned. explicitly in the application standards guide, but on a lower thickness, strictly less than 15 cm, such as 12 cm.

[0063] According to one embodiment of the invention, the seat layer coating may comprise a single seat layer, namely be formed by a single seat layer having a thickness strictly less than 15 cm.

[0064] According to another embodiment of the invention, the base layer coating may comprise several base layers. Indeed, it may comprise a superposition of two or more base layers in direct contact with each other, each base layer having the composition / formulation mentioned above and a thickness strictly less than 15 cm after compaction. For example, the base layer coating may be formed of a bilayer of base layers such that the total thickness of said bilayer does not exceed 30 cm (i.e., strictly less than 30 cm).

[0065] In general, when said seat layer covering is composed of at least two seat layers, it has a total thickness strictly less than 30 cm, preferably less than or equal to 29 cm, in particular less than or equal to 28 cm and typically less than or equal to 25 cm. According to the invention, a "total thickness strictly less than 30 cm" includes the following values ​​and any interval between these values ​​(in cm): 29; 28; 27; 26; 25; 24; 23; 22; 21; 20; 19; 18; 17; 16; 15; 14; 13; 12; etc.

[0066] As mentioned above, the base layer or layers forming the base layer coating are formed of a hydraulic binder and aggregates (i.e., asphalt aggregates and sands).

[0067] In particular, the hydraulic binder suitable for the present invention can be chosen from one or more of the following compounds: clinker, blast furnace slag, siliceous or calcic fly ash, lime, gypsum, a geosynthesis binder based on an alkali activator and a silico-aluminous compound, pozzolans activated by lime or a sulfo-calcic compound, calcined clays of the metakaolin type, crushed limestones, steel slags, biomass or paper mill ash, calcined shales or any other equivalent binder whose composition allows a hydraulic setting to be obtained.

[0068] As is known, a hydraulic binder is generally found in the form of a mineral powder which, once combined with water, becomes a setting paste that hardens progressively in air as well as underwater. Two characteristics distinguish it from cement:

[0069] • a setting kinetic adapted to road construction site conditions (setting time of handling, time to return to service, etc.), and climatic conditions (seasonality);

[0070] • a reduced environmental impact thanks to the possibility of using a binder hydraulic clinker-based (i.e., cement) mixed with lime-activated pozzolans or a sulfo-calcium compound, calcined clays of the metakaolin type which are able to reduce the carbon impact of the coating thus formed.

[0071] The hydraulic binder generally has the characteristics defined in the two standards NF EN 13282-1 and 13282-2.

[0072] According to one feature of the invention, the hydraulic binder is chosen from clinker, blast furnace slag or a mixture thereof.

[0073] Preferably, the hydraulic binder has an apparent density greater than or equal to 0.8 t / m3, preferably greater than or equal to 1 t / m3 and typically greater than or equal to 2.8 t / m3.

[0074] In general, the hydraulic binder comprises, by mass, relative to its total mass, 50% or more, preferably 60% or more, and typically 65% ​​or more, of blast furnace slag. According to the invention, "50% or more" includes the following values ​​and any interval between these values ​​(in %): 50; 55; 60; 65; 70; 75; 80; 85; 90; 95; 100.

[0075] According to another feature of the invention, the hydraulic binder can be a geosynthesis binder based on an alkaline activator and a silico-aluminous compound and can for example correspond to the binder described in patent FR 3 028 509 in the name of the Applicant.

[0076] According to another feature of the invention, the hydraulic binder can be a clinker and / or blast furnace slag mixed with at least one of the following compounds: lime-activated pozzolans or a sulfo-calcium compound or even calcined clays of the metakaolin type.

[0077] Generally, the hydraulic binder is prepared in the factory. It can correspond to a finished product and be distributed ready for use.

[0078] A possible additive may be necessary depending on the type of hydraulic binder used to improve workability or, on the contrary, accelerate setting, for example.

[0079] An admixture is a product whose incorporation in small doses (less than 5% of the mass of the hydraulic binder) into concrete, mortar, grout, or treated aggregate during mixing or before placement causes modifications to the properties of the mixture, in its fresh or hardened state. Admixtures conform to standard NF EN 934, Part 2. By way of example, the following admixtures are suitable for the present invention: plasticizers such as Sika® Plastiment® or Chryso® Plast Delta; superplasticizers such as SikaPlast® Techno® or Chryso® Optima; retarders such as SikaTard® or ChrysoTard®; and a setting accelerator such as SikaCem or ChrysoXel®.

[0080] According to the invention, the hydraulic binder represents, by mass, relative to the total mass of the base layer / each base layer composing said base coating, from 2% to 10%, preferably from 3% to 7% and typically from 2.5% to 6%. According to the invention, "from 2% to 10%" includes the following values ​​and any interval between these values ​​(in %): 2; 2.5; 3; 3.5; 4; 4.5; 5; 5.5; 6; 6.5; 7; 7.5; 8; 8.5; 9; 9.5; 10.

[0081] Generally, the base layer coating according to the invention is free of added bitumen.

[0082] Then, the base layer or layers forming the base layer coating also include natural, artificial or recycled aggregates meeting in particular the standards NF EN 13043 and NF P 18-545.

[0083] The term "natural aggregate" refers to an aggregate that has not undergone any deformation other than mechanical (reduction by crushing). The term "artificial aggregate" refers to an aggregate resulting from an industrial process involving thermal or other transformations.

[0084] The term “recycled aggregate” refers to an aggregate obtained by mechanical treatment of an inert inorganic material previously used in construction.

[0085] According to the invention, one of the aggregates forming the base course according to the invention is the asphalt concrete aggregate, hereinafter referred to as AE. AE corresponds to a pavement demolition product and thus designates an aggregate derived from demolition products (such as asphalt from old pavements that have been crushed and / or milled). AEs comply with the NF EN 13108-8 standard.

[0086] According to the invention, the AE represents, by mass, relative to the total mass of the base layer(s) forming the seat covering, from 50% to 90%, preferably from 55% to 80% and typically from 60% to 75%. According to the invention, "from 50% to 90%" includes the following values ​​and any interval between these values ​​(in %): 50; 51; 52; 53; 54; 55; 56; 57; 58; 59; 60; 61; 62; 63; 64; 65; 66; 67; 68; 69; 70; 71; 72; 73; 74; 75; 76; 77; 78; 79; 80; 81; 82; 83; 84; 85; 86; 87; 88; 89; 90.

[0087] In general, the AEs have an apparent particle size of the type 0 / 6; 0 / 8; 0 / 10; 0 / 12.5; 0 / 14; 0 / 16; 0 / 18; 0 / 20; 0 / 25 or 0 / 31.5 mm or a mixture thereof and preferably have an apparent particle size of the type 0 / 6mm to 0 / 14mm.

[0088] They are incorporated into the formulation preferably with an apparent particle size of the type 0 / 14 mm.

[0089] According to the invention, the base layer(s) forming the base course comprise sands with a particle size of up to 0 / 6 mm and preferably 0 / 4 mm. The sands may be, without limitation: sands, fine-grained sands, or a mixture thereof. The aggregates used may be road aggregates conforming to the following standards: NF EN 13043 in Europe and ASTM C33 in North America.

[0090] Sands generally correspond to any rock in the form of small, unbound grains with a dimension of up to 4 mm. These aggregates generally have an actual density measured according to standard NF EN 1097-6 greater than 2000 kg / m3 and even greater than 2500 kg / m3 and a relative bulk density measured according to standard NF EN 1097-3 between 1.2 and 1.7.

[0091] As used here, the dimension of a particle, and more generally of a constituent of a granular mixture, corresponds to its diameter if that constituent is spherical. If the constituent is not spherical, its dimension corresponds to the length of its primary axis, that is, the longest straight line that can be drawn between one end of that constituent and an opposite end.

[0092] According to the invention, the sands represent, by mass, relative to the total mass of the base layer(s) forming the base course, from 0% to 48%, preferably from 10% to 45% and typically from 15% to 37%. According to the invention, "from 0% to 48%" includes the following values ​​and any interval between these values ​​(in %): 0; 1; 2; 3; 4; 5; 6; 7; 8; 9; 10; 11; 12; 13; 14; 15; 16; 17; 18; 19; 20; 21; 22; 23; 24; 25; 26; 27; 28; 29; 30; 31; 32; 33; 34; 35; 36; 37; 38; 39; 40; 41; 42; 43; 44; 45; 46; 47; 48.

[0093] The Applicant discovered that, when present, this sandy fraction contributes to the workability of the pavement by mixing with the hydraulic binder and the residual binder present in the asphalt aggregates. Its optimized quantity allows it to fill the vast majority of the gaps between the coarsest elements in the finished product, without causing them to separate.

[0094] The aggregate forming the base layer(s) may also include, in addition to aggregates and sands, one or more gravels. The addition of the latter aims to obtain a granular recomposition enabling improved mechanical performance. The gravels may have the following particle sizes: 2 / 6; 4 / 6; 4 / 8; 6 / 10; 6 / 14; 10 / 14. The proportion of the gravel(s) will be from 0% to 40%, preferably from 10% to 30%, and typically from 10% to 25%. According to the invention, "from 0% to 40%" includes the following values ​​and any interval between these values ​​(in %): 0; 1; 2; 3; 4; 5; 6; 7; 8; 9; 10; 11; 12; 13; 14; 15; 16; 17; 18; 19; 20; 21; 22; 23; 24; 25; 26; 27; 28; 29; 30; 31; 32; 33; 34; 35; 36; 37; 38; 39; 40. The base layer coating preferably has the following characteristics.

[0095] In general, the seat covering has a laboratory-measured compactness greater than or equal to 95% of the OPM (Modified Proctor Optimum) reference. According to the invention, the OPM reference, or "density reference," which corresponds to the highest dry density associated with a water content, is determined according to standard NF EN 13286-2. Then, the density of a sample taken on-site or, where applicable, from a laboratory mold, is compared with this OPM reference. Furthermore, the closer the laboratory-measured compactness is to 100%, the better the results. Specifically, the density of the sample, also called the "test specimen," is measured geometrically: the weight and dimensions of the specimens allow for the calculation of an apparent density (mva). For asphalt mixes, the NF EN 12697-29 standard defines the methods for measuring the density of the test specimen (apparent density mva):

[0096] % empty in the test tube = [Mva / OPM Reference] - 1

[0097] Compactness % = [Mva / OPM Reference] ».

[0098] This characteristic gives the base layer coating according to the invention excellent mechanical performance which also meets the required requirements and;

[0099] According to another feature of the invention, the seat covering has a direct tensile strength Rtd at 360j ranging from 0.8 MPa to 2.7 MPa, preferably ranging from 0.8 to 2.0 MPa and typically from 0.9 to 1.5 measured according to standard NF EN 13286-40 or NF EN 13286-42.

[0100] Also, the seat covering has a stiffness modulus, measured according to standard NF EN 13826-43, greater than or equal to 5000 MPa, preferably greater than or equal to 9000 MPa, in particular greater than or equal to 11000 MPa, such as greater than or equal to 12500 MPa and typically greater than or equal to 13000 MPa; preferably, the stiffness modulus ranges from 5000 MPa to 20000 MPa, advantageously from 8000 to 18000 MPa and typically from 9000 to 16000; thus in general, the stiffness modulus is equivalent to a GB2 / GB3 (9000 MPa <<11000 MPa), or a GB4 (11000 MPa << 14000 MPa), or an EME (>14000 MPa).

[0101] According to another feature of the invention, the seat covering has a fatigue resistance greater than or equal to 80 pDef, preferably greater than or equal to 90 pDef, in particular greater than or equal to 100 pDef, and typically greater than or equal to 130 pDef; in particular the fatigue resistance ranges from 100 pDef to 150 pDef and typically ranges from 110 pDef to 140 pDef measured according to standard NF EN 12697-24; thus, preferably the fatigue resistance ranges from 80 pDef to 150 pDef, so as to be equivalent to a GB2 (> 80 pDef), GB3 (> 90 pDef), or a GB4 (>100 pDef), or an EME 2 (>130 pDef).

[0102] B. Method for manufacturing the base layer coating

[0103] The present invention also relates to a method for manufacturing a base coat coating as defined above, comprising the following successive steps:

[0104] (a) the preparation of a base coat formulation comprising, by mass, relative to its total mass:

[0105] - from 50% to 90% asphalt aggregates;

[0106] - from 0% to 48% of sands usually having a grain size of 0 / 4 mm;

[0107] - 2% to 10% hydraulic binder,

[0108] (b) spreading said base layer formulation via a spreader road surface on a subgrade layer intended to receive a base course;

[0109] (c) compaction via a compactor, for example of the Monoball or tandem type, of this base layer thus formed so as to obtain a thickness strictly less than 15 cm (after compaction);

[0110] (d) where appropriate, repeating steps (a) to (c), so as to form a coating comprising at least two superimposed base layers.

[0111] Preferably, steps (a) to (c) are carried out at ambient temperature, meaning that these steps do not require external heating. Indeed, the aggregates do not need to be preheated, nor do other aggregates present, such as sands and gravels. Step (a) of preparing the formulation is thus carried out without external heat input, as are the spreading and compaction steps.

[0112] In particular, at the end of step (c), the base layer coating according to the invention has a compactness measured in the laboratory according to standard NF EN 13286-2 greater than or equal to 95% of the OPM (Modified Procter Optimum) reference.

[0113] By way of example, compaction step (c) is carried out using a VT2 type vibratory tandem roller such as the Bomag Asphalt Manager BW174 with a mass of 10 tonnes, combined with a small Hamm HD-10 type vibratory tandem roller with a mass of 2.5 tonnes. The number of passes is generally between 2 and 8 with varying amplitudes using the BW174 roller and between 2 and 4 passes with the HD-10 roller. A PI to P3 type pneumatic tire roller may optionally be used to further improve the surface finish, for example, with 8 to 20 passes.

[0114] Thus, the base coat coating according to the invention is generally manufactured cold, namely at ambient temperature (5-30°C), which gives it a definite advantage (economic, ecological) compared to the black formulations (i.e.: EME and GB) described above.

[0115] Of course, the various embodiments described above for the base layer coating also apply to this manufacturing process of said coating.

[0116] The spreader and the compactor are well known to those skilled in the art and will not be detailed below. C. Road surface

[0117] The present invention also relates to a road surface intended to cover a floor comprising successively from the ground:

[0118] a form layer coating,

[0119] a base layer coating disposed on said sub-base layer coating,

[0120] a surface layer coating, disposed on said base layer coating and which is itself generally composed of a two-layer system comprising a binder layer and a wearing course,

[0121] characterized in that said base layer coating corresponds to the base layer coating as defined above.

[0122] Of course, the various embodiments described above for the base course coating and its manufacturing process also apply to the road surface and will not be repeated below

[0123] Of course, the different features, variants and embodiments of the invention can be combined with each other in various ways insofar as they are not incompatible or mutually exclusive. Examples

[0124] A1 Examples of base layer formulations

[0125] Formulations for base coat were made from the raw materials illustrated in Table 1.

[0126] [Tables 1] hmimiaseurs Grabat 1 Aggregate of wW (A£> w summer cannasses fta^és pmentant urs granstom-Wa ds I mm ©s'abat i Satdss W CæmptW das Cataâes et Matédsw (CŒ) | CCM i Grabat 1 Gravion hdW tca^atre) cœ Binder bttwmeax | ds grade TOTAL | Binder | Wtasga ds dft&er and da tastssr of high towatu vc^psudaut su 1 fwduh ROC VOS w î hlàhag® cempta&ant ds 58¾ of the^ar of foemeam gmate J AS .. 1

[0127] In particular, from the raw materials mentioned above, eight base layer compositions according to the invention, the formulations of which are illustrated in Table 2 below, were prepared cold, namely at ambient temperature (ranging from 15°C to 30°C) in a treated gravel plant.

[0128] This power plant has the parameters described below. - The dosing of materials is carried out in 5 dosing hoppers (11 m3) with weight information in the control cabin, they are equipped with skimming grids (two of them are weight-based and are equipped with vibrators). - The hydraulic binders are stored in two vertical silos with capacities of 37 m3 and 61 m3. They are equipped with vibrators. Transfer to the gravimetric feeder is carried out by screws whose operation is controlled by the buffer hopper. - The dosage of hydraulic binders is carried out in a gravimetric doser. - The mixing takes place in a mixer equipped with two horizontal shafts with a capacity of 275 tonnes / hours. - The water is stored in a buffer tank and metered by a centrifugal pump using an electronic flow meter programmed from the control cabin (flow rate 5 to 30 m3 / h). - Storage and distribution are carried out using a storage hopper (30 m3) equipped with a vibrator. The processed materials are loaded into trucks and weighed on the electronic weighbridge which is located directly under the loading hopper. - The control software allows continuous monitoring of: the formula manufactured, the weight of the quantity manufactured, the instantaneous weight of each constituent, the quantity of powder introduced into the manufacturing process, and the quantity of water introduced into the manufacturing process. - The control station is equipped with a synoptic display, centralized information (% water; instantaneous flow rates), a control microprocessor with memory for 20 formulas, two video display screens, and a recording system to list the characteristics of each batch.

[0129] Two comparative formulations of Bituminous Gravel (GB) according to the prior art were also prepared from the raw materials mentioned above in a hot mix (gas) at 160°C. For this purpose, two comparative GB compositions, the formulations of which are also illustrated in Table 2 below, were hot-mixed in a temperature-controlled mixer at the mix. The 35 / 50 grade bitumen was heated to a temperature of 160°C, and the aggregates (i.e., asphalt pavement aggregates, gravel, and sand) were pre-measured in containers and heated to 160°C before being introduced with the heated bitumen into the mixer for 30 seconds.

[0130] [Tables2] Comp.1 G830 Comp,2 GB?Ü Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example S Compounds Percentage by weight Percentage by weight Aggregates Are, coated 7fits 70% 70% 7D% 90% 50% 82.50% 50% 40% Gs^sna-tats v serges Sands (limestone) 27% - 25% 27% .25% 0¾ 48% 12.50% 30% 3'3% Gravif-!« S.'W 16% 10% - - - - - - 7% 12.50% Gravitations W14 (chales ire) 23.50% 18.50% - - - - - - - 12.56% Binder nydret:-tiQLie - - (RülJ VDS> 3% (ROC VGS) (ROC AS) 10% (ROC VOS.) 2% (RO >7 VDS) £.¾ (ROC VOS) tïRQC V'DS) 5% (ROC AS) Bstumr-newt binder contribution 3.50¾ 1.50% Total bituminous binder 5% 5% 37% 3.7% 3.7%. 4.7% 2.6% 4.3% 3.1% 2.1% Parameters Faaâeatipp temperature 160¾ 160¾ Am-& ta nie Am-biarste Ambra rite Ambient Ambient Ambient Ambient Ambient Am-bianie Ou::} of pmduc-îioa Hot ro-bage station (gas? Hot ro-bage station (gas) Central MHZ (electric) Central MHL (electric) Central (éiec-Irigsæ? Centime MHL <é îec-inque) Centrale MHL (SteC-iriqsje) Cenfmte mhl (éiec-irsqtse) Cents-ale MHS (electric:, Centrale tri HL (electrical) E pass r(c:Tîj 12 12 12 ■2 12 12 12 12. 12 12 Densities in place tore paciîés 2.35 T;%3 94% 2.35 w 94% 2.20 T.'m5 (tw-H-ide) 35% to 99% 2.20 T?m3 (hts-msde) 95% to 99% 2.20 Tire2 (hu-midej 95% to 99% 2.28 TMS (bs-tnide) 95% to 99% 2.20 T / m2 (hu-msie) 95% to 99% 2.23 T / m3 (b u-msde) 95% to 99% 2.20 T / m3 (hç-reice) 95% to 99% 2.20 rim1 (iw-rndei 95% to 99% Target state Bearing capacity of self Ps > SOMPà PF2 PF2 PF2 PF2 PF2 PF2 PF2 PF2 PF 2 PF2 .

[0131] For laboratory testing (molds of test specimens):

[0132] The resulting base materials were then weighed in a cylindrical mold of appropriate dimensions before being compacted according to NF EN 13286-53 (static compaction) or NF EN 13286-52 (vibrocompression). The target mass is calculated based on the Proctor OPM reference (NF EN 13286-2), and a compaction greater than or equal to 95% of this reference is required to meet the necessary mechanical performance.

[0133] For the stiffness modulus (NF EN 12697-26) and fatigue (NF EN 12697-24) tests, plates are molded to obtain a compactness close to that of cylindrical specimens.

[0134] For the implementation of the experimental plate (coated):

[0135] Tests were carried out to implement experimental boards in order to form base layers on a PF2 type substrate using the formulations in Examples 1 and 3 of Table 2. The boards were implemented following the protocol below:

[0136] - manufacturing in a treated gravel plant of the formulations of examples 1 and 3;

[0137] - transport by truck and application with a paver of a base coat on the PF2 shape layer;

[0138] - compaction of this base layer thus formed so as to obtain a thickness 12 cm via a tandem (double drum) compactor in order to compact the base layer.

[0139] Also, the results of these tests were extrapolated for the formulations of examples 4 and 5 (the results are estimated to + / - 20%).

[0140] A.2 Results: evaluation of the behavior of the base layer (tests of laboratory)

[0141] The following mechanical performances were tested for the compositions according to the invention:

[0142] Direct tensile strength Rtd (NF EN 13286-40 or NF EN 13286-42)

[0143] The standard NF EN 13286-40 or NF EN 13286-42 is used to determine the direct tensile strength Rtd. This involves measuring the breaking stress of a treated material subjected to direct tension (NF EN 13286-40) or the breaking stress of a cylindrical specimen subjected to a compressive force applied on two opposite generatrices (NF EN 13286-2).

[0144] This tensile strength and the modulus of elasticity (see below, this value being measured during the tensile test) allow for the dimensioning of a pavement.

[0145] The higher the Rtd value, the better the mechanical resistance of the tested composition.

[0146] Determination of the modulus of elasticity Etd (NF EN 13286-43)

[0147] The NF EN 13286-43 standard describes the method to be followed to measure Etd. The modulus of elasticity provides information on the behavior of the tested material subjected to stresses and characterizes the stiffness of the material.

[0148] The higher the modulus of elasticity Etd, the less the material deforms under stress and, consequently, the more rigid it is.

[0149] Determination of the stiffness modulus (NF EN 12697-26, Annex A or C)

[0150] This test is used for pavement design. A trapezoidal specimen is subjected to repeated linear deformation at a temperature of 15°C and a loading frequency of 10 Hz (Annex A). The stiffness modulus is derived from the relationship between the maximum stress and the strain. maximum measured. This measurement can be carried out on cylindrical test specimens at 15°C and 124 ms (Annex C).

[0151] Determination of fatigue resistance (NF EN 12697-24, Annex A)

[0152] This test is used for pavement design. A trapezoidal specimen is subjected to an imposed deformation at a temperature of 10°C and a loading frequency of 25 Hz. When the initial modulus of the specimen is reduced by half, the specimen is considered to have failed. The number of cycles is recorded. The test is repeated on batches of specimens to derive a fatigue line, and the deformation that allows reaching one million cycles is considered the final result.

[0153] The results are as follows: Comp.l GB30 Comp.2 GB70 Example 1 Example î Example 4 Extrapolation Example 5 Extrapolation MLH Cylindrical specimens (no sawing) Compaction method Gyrocompact Vibrai static Vlbra / estic VMroZstatic Vibro / static Compaction 92% 2 95¾ 109% 100% 100% 100% RM. in MPa (NF EN 13286- 0.9 - 0.8 0.4 1 Etd, in MPa (NF EN 13286-43) 1700 6300 11000 14000 ± 20% (11200 < 16300) 7000 ± 20% (5600 5 5 8409) Asphalt Cylindrical specimens (sawing to remove edges) Compaction method Gyrocompact Static Gyrocompact Static Static Compaction 95.5% 96% 100% 100% 100% 100% Modulus of stiffness NF EN 12697-26 C 15eC - direct reading, in MPa 13000 12660 15700 13500 13000 ± 20% (14400 LL 21600) 300± 20% (6400 £ £ 9699) Trapezoidal, 360° sawing C LCPC plate compactor LCPC cooper LCPC - - Compaction 96.0% 96% 96% 97% - Stiffness modulus in MPa NF EN 12697-26 A, 13000 13700 13600 10600 Fatigue NF EM 12697-24 A 116 122 127 112 - - [Painting 3]

[0154] Thus, contrary to what is taught in the literature in the road field, the base layers according to the invention exhibit a mechanical resistance and a fatigue resistance at least similar to those of the EME and GB commonly used to date, and this for the same layer thickness after compaction.

[0155] The carbon footprint, carried out using the Seve software commonly used in the field (and which is described in the publication of the Institute for Roads, Streets and Infrastructure for Mobility, Technical Opinion No. 160, dated September 2013), compositions according to the invention and comparative compositions are as follows: Comp.1 Comp.2 Example 1 TSC mixture 160 160 - CumbusSNs burner Gas Gas Gsz Electricity Thickness Cm 12 12 12 Quantity manufactured T 0.28 0.28 0.26 Density 2.33 2.33 2.19 Extraction MP Kg CCT4 10.50 4.50 23.58 Transport Kg CO. t 2.26 1.05 1.05 Manufacturing Kg 18.15 21.30 'm es Preparation AE Kg COst G.45 1.05 1.05 Total production Kg CO»t 31.35 27.90 26.88 Total CO? Kg / m^ 8.77 7.80 7.07 [Painting 4]

[0156] Thus, the base layers according to the invention based on hydraulic binder are more environmentally friendly than base layers made on the basis of bituminous binder.

Claims

Demands

1. Base course coating composed of one or more base course(s), each base course comprising, by mass, relative to its total mass: - from 50% to 90% of asphalt aggregates comprising, by mass, relative to its total mass, a residual bituminous binder content ranging from 3% to 8%; - from 0% to 48% of sands; - from 2% to 10% of hydraulic binder, characterized in that each base course has, after compaction, a thickness strictly less than 15 cm and is free from added bituminous binder.

2. A base layer coating according to claim 1, wherein each base layer has, after compaction, a thickness less than or equal to 14 cm, in particular less than or equal to 13 cm and typically less than or equal to 12 cm.

3. Base layer coating according to claim 1 or 2, characterized in that it is composed of at least two base layers which are superimposed one on top of the other so as to form a bilayer.

4. A seat layer coating according to any one of the preceding claims, wherein when composed of several seat layers, including at least two seat layers, said seat layer coating has a total thickness strictly less than 30 cm, preferably less than or equal to 29 cm, in particular less than or equal to 28 cm and typically less than or equal to 25 cm.

5. Base course coating according to any one of the preceding claims, wherein the hydraulic binder is selected from one or more of the following compounds: clinker, blast furnace slag, siliceous or calcic fly ash, lime, gypsum, a geosynthetic binder based on an alkali activator and a silico-aluminous compound, pozzolans activated by lime or a sulfo-calcic compound, calcined clays of the metakaolin type, crushed limestones, steel slags, biomass or paper mill ash, calcined shales.

6. Base course coating according to any one of the preceding claims, wherein the asphalt aggregate presents, in niasse, relative to its total mass, a residual bituminous binder content of 3.5% to 7.5% and typically of 4.0% to 7.0%.

7. Base layer coating according to any one of the preceding claims, characterized in that it has a compactness, measured in laboratory according to standards NF EN 13286-2 and NP EN 12697-29, which is greater than or equal to 95% relative to a reference value, named OPM, which is measured according to standard NF EN 13286-2.

8. Base layer coating according to any one of the preceding claims, characterized in that the base layer or layers composing said coating has: a stiffness modulus measured according to standard NF EN 12697-26 (Annex A or C) greater than or equal to 5,000 MPa, preferably greater than or equal to 9,000 MPa, in particular greater than or equal to 11,000 MPa and a fatigue resistance measured according to standard NF EN 12697-24 greater than or equal to 80 pDef, preferably greater than or equal to 90 pDef, in particular greater than or equal to 100 pDef.

9. A cold manufacturing process for a base course coating according to any one of claims 1 to 8, comprising the following successive steps: (a) preparing a base course formulation comprising, by mass, relative to its total mass: - 50% to 90% asphalt aggregates; - 0% to 48% sands; - 2% to 10% hydraulic binder, (b) spreading said base course formulation via a road surfacing spreader onto a subgrade layer intended to receive a base course; (c) compacting this base course thus formed via a compactor to obtain a thickness strictly less than 15 cm; (d) where appropriate, repeating the steps (a) of preparation, (b) of spreading and (c) of compaction, so as to form a coating comprising several superimposed base layers, such as at least two superimposed base layers.

10. A manufacturing process according to claim 9, characterized in that the steps (a) of preparation, (b) of spreading and (c) of compaction are carried out at ambient temperature.

11. Road pavement intended to cover a ground comprising successively from the ground: a subbase layer, a base course layer placed on said subbase layer, a surface layer layer placed on said base course layer and which is itself generally composed of a two-layer comprising a binder layer and a wearing course, characterized in that said base course layer corresponds to the base course layer layer according to any one of claims 1 to 8.