PERMEABLE ASPHALT MIXES OBTAINED BY FILLING THE COMMUNICATING VOIDS OF AN OPEN ASPHALT MIX WITH A PERMEABLE MATERIAL CONSISTING OF SAND

Abstract

The present invention relates to a road surface comprising an open-cell asphalt mix whose interconnected voids are filled with a sand-based filler material. The present invention also relates to a method for preparing such a road surface comprising the steps of: (a) preparing an open-cell asphalt mix comprising interconnected voids; (b) filling the interconnected voids of the open-cell asphalt mix with sand or a sand suspension. The present invention also relates to the use of such a road surface for low-traffic roads, parking areas, and active mobility routes, such as cycle paths or pedestrian walkways.

Description

Title of the invention: PERMEABLE ASPHALT MIXES OBTAINED BY FILLING THE COMMUNICATING VOIDS OF AN OPEN ASPHALT MIX WITH A PERMEABLE MATERIAL CONSISTING OF SAND FIELD OF THE INVENTION

[0001] The present invention relates to a road surface comprising an open hydrocarbon asphalt whose communicating voids are filled by a filling material made of sand, its preparation process and its use for the preparation of low traffic roads, parking areas, soft mobility routes such as cycle paths or pedestrian walkways. BACKGROUND OF THE INVENTION

[0002] In order to facilitate vehicle traffic or parking, it is common practice to lay a surface covering on the ground that provides a suitable support for these uses, is durable, and is not degraded by these uses. Asphalt pavements and dense hydrocarbon mixes have commonly been used for this purpose, covering, for example, parking spaces or sidewalks.

[0003] While such coatings offer many advantages, particularly in terms of ease of installation, cost, flatness, and durability, they have the disadvantage of waterproofing surfaces, which poses both a problem of rainwater drainage and a lack of hydration of the underlying soils.

[0004] The use of open-cell asphalt mixes overcomes these drawbacks. Open-cell asphalt mixes remain permeable thanks to spaces, called "interconnecting voids," between the solid asphalt particles, allowing water and air to pass through. However, this type of asphalt suffers from reduced mechanical properties in terms of traffic resistance and durability, particularly due to the phenomenon of aggregate detachment from the surface of the permeable pavement, compared to asphalt pavements and dense asphalt mixes, which have few or no voids.

[0005] Thus, to obtain good mechanical properties, it is common practice to use a filler material, generally cement-based, to fill these spaces, or voids, between the solid particles of open-cell asphalt. However, environmental concerns are prompting manufacturers to seek alternatives to cement. Since cement production is responsible for significant CO2 emissions, more environmentally friendly alternatives deserve to be developed. Furthermore, such coatings do not necessarily offer acceptable drainage.

[0006] A need therefore remains for a method of preparing road surfaces which are easy to implement at a lower cost, have good permeability while maintaining satisfactory mechanical properties in accordance with those expected for such surfaces. BRIEF DESCRIPTION OF THE INVENTION

[0007] The invention relates to a road surface comprising an open hydrocarbon coating whose communicating voids are filled by a filling material made of sand.

[0008] The invention also relates to a method for preparing such a road surface comprising the steps of:

[0009] (a) preparation of an open hydrocarbon coating comprising voids communicants; (b) filling of communicating voids in open hydrocarbon asphalt with sand or an aqueous suspension of sand.

[0010] Other aspects of the invention are as described below and in the claims. DETAILED DESCRIPTION OF THE INVENTION

[0011] The inventors have made a surprising discovery: that open-cell asphalt mixes, whose interconnected voids are filled with a sand-based filler material, can be used to prepare permeable road surfaces that meet the required mechanical properties. These mechanical properties can be characterized by conventional asphalt mix tests (PCG (gyratory shear press), water resistance, rutting, cantabrian test, etc.) depending on the intended use.

[0012] The present invention thus relates to road surfacing comprising on the surface an open hydrocarbon coating whose communicating voids are filled by a filling material made of sand.

[0013] By "surface," it is understood that the open-cell asphalt mix, whose interconnected voids are filled with a sand-based filler material, is in direct contact with the air. Thus, in the context of a road surface comprising several layers, the top layer, that is, the one directly in contact with the air, consists of an open-cell asphalt mix whose interconnected voids are filled with a sand-based filler material. In other words, the road surface of the invention comprises, as its surface layer, an open-cell asphalt mix whose interconnected voids are filled with a sand-based filler material. In certain embodiments, the road surface is single-layered, that is, consisting of an open-cell asphalt mix whose Communicating voids are filled with a filling material consisting of sand.

[0014] The open hydrocarbon coating whose communicating voids are filled by a filling material made of sand can also be defined as a permeable hydrocarbon coating made up of a hydrocarbon coating and a permeable material made of sand.

[0015] The road surface of the present invention has the characteristics generally expected for a wearing course (trafficability, compactability, water resistance).

[0016] Furthermore, the road surface of the invention has good permeability, enabling it to absorb and potentially store water, particularly rainwater. This property prevents water from accumulating on the surface of the pavement. In particularly hot and humid regions, which are becoming more frequent due to current climate change, the absorption and storage of rainwater within the pavement can also help prevent the formation of urban heat islands through the subsequent evaporation of the previously stored rainwater. Open bituminous asphalt

[0017] Open-mix asphalt can be prepared according to techniques well known to those skilled in the art.

[0018] The open-cell asphalt typically has a communicating void content of 15% to 40%, or 20% to 35%, preferably 30% to 35%, as measured by determination of apparent density according to EN 12697-6 (2012) or by gamma rays, according to EN 12697-7 (2014).

[0019] Open hydrocarbon asphalt is typically made up of solid particles coated with a bituminous binder.

[0020] The term “solid particles” refers to all solid particles usable for the production of hydrocarbon asphalt.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 recycled ballast, 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 the incineration of non-hazardous waste (MIDND), as well as mixtures thereof in all proportions.

[0021] The solid particles are chosen so as to have sufficient characteristics to withstand the stresses to which they are subjected. They generally have a granularity of 0 / d or d / D chosen for example from the classes 0 / 2, 0 / 4, 2 / 4, 2 / 6, 4 / 6, 6 / 10, 10 / 14, 14 / 20, 20 / 31.5, 20 / 40 and their mixtures.

[0022] Solid particles, in particular mineral solid particles, typically include:

[0023] - elements smaller than 0.063 mm (filler or fines); - elements with a size between 0.063 mm and 2 mm; - gravel or aggregates, the elements of which have the following dimensions: - between 2 mm and 6 mm; - greater than 6 mm. The size of solid particles, in particular mineral solid particles, is measured by the tests described in the standard NF EN 933-1 (May 2012 version).

[0024] The bituminous binder can be a pure bitumen (for example from class 10 / 20 to 70 / 100, for example 35 / 50 or 70 / 100), a bitumen containing gilsonite and / or natural asphalt, or a bitumen modified by polymers or by additives commonly used in the road sector, for example adhesion enhancers or vegetable or petrochemical waxes.

[0025] Bitumen-modifying polymers can be natural or synthetic. Examples include polymers from the elastomer family, whether synthetic or natural, and, by way of example and not limitation:

[0026] - 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) copolymers, styrene-isoprene-styrene (SIS) copolymers or copolymers of the same chemical family (isoprene, natural rubber,...), possibly cross-linked in-situ, - vinyl acetate and ethylene copolymers in all proportions, - copolymers of ethylene and acrylic acid esters (for example as described in WO2022 / 208035), methacrylic or maleic anhydride, ethylene and methacrylate copolymers and terpolymers of glycidyl- and polyolefins. Bitumen-modifying polymers can be recycled polymers, for example, "rubber dust" or other rubber-based compositions reduced to pieces or powder, obtained, for example, from used tires or other polymer-based waste (cables, packaging, agricultural waste, etc.), or any other polymer commonly used for bitumen modification, such as those listed in the Technical Guide written by the International Road Association (PIARC) and published by the French National Laboratory for Roads and Bridges (LNE) "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.

[0027] Open-mix asphalt can be hot-mix asphalt, warm-mix asphalt (30°C cooler than hot-mix), or semi-warm-mix asphalt (50°C cooler than hot-mix). The manufacture and application of such asphalt mixes are well known to those skilled in the art. They are laid using traditional road construction methods.

[0028] Hot mix asphalt is obtained by hot mixing of solid particles, such as those described above, for example aggregates, and a binder. This binder can be pure or modified bitumen (for example, with the addition of polymer(s)), a pure or modified vegetable binder, or a synthetic binder of petroleum origin. The solid particles (aggregates) are heated, generally to a temperature above 100°C.

[0029] Warm or semi-warm asphalt mixes are mixes applied at temperatures approximately 30 to 50°C lower than the temperatures applied for hot asphalt mixes.

[0030] Open-cell asphalt can be compacted. However, the compaction intensity will be controlled to maintain a communicating void content of 15% to 40% before filling with the filler material.

[0031] The total hydrocarbon binder content is 2.5% to 7%, advantageously 3% to 5%, by weight relative to the weight of the solid particles.

[0032] Open-cell asphalt pavement can be applied to any base course, preferably to an infiltrating substrate typically having a permeability ranging from 10³ to 10⁶ m / s, for example 10⁴ m / s. Permeability is typically measured using a double-ring open infiltrometer according to standard NF X30-418 of December 2012 or using a single or double-ring closed infiltrometer according to standard NF X30-420 of August 2007. The base course can be untreated aggregate (GNT), a free-draining asphalt concrete, or a permeable pavement. Depending on the intended use, the pavement can also be applied directly to a subgrade or a soil and stone mixture, with the soil and stone mixture being preferred for pedestrian and bicycle paths.

[0033] Thus, in certain embodiments, the road surface of the present invention consists of a surface layer (upper layer) made of an open-cell bituminous mixture whose interconnected voids are filled by a filling material made of sand resting on a layer (lower layer) selected from the group consisting of untreated gravel, a draining bituminous gravel (GB) and a draining concrete.

[0034] The bituminous coating generally has a thickness varying from 2 cm to 15 cm, preferably from 4 cm to 10 cm, even more preferably from 5 cm to 7 cm cm. Filling material

[0035] In the context of the present invention, the communicating voids of the open-cell asphalt are filled with a filler material made of sand. Such a material has the advantage of being permeable.

[0036] The term "sand" refers to solid particles consisting of elements having a particle size distribution (d / D) ranging from 0 / 1 mm to 0 / 4 mm. The sand according to the invention typically has a filler or fines content (elements smaller than 0.063 mm) ranging from 0% to 15%, preferably from 2% to 5%, by weight relative to the total weight of the sand. Such a filler content allows the sand used as a filling material to be easy to handle, particularly for introduction into communicating voids, while remaining permeable. The sand according to the invention includes, for example, homometric sands, that is, sands having elements of very similar, or even identical, sizes. The sand according to the invention includes, but is not limited to, quarry sand, alluvial sand, gravel pit sand, Fontainebleau sand and dune sand, insofar as these sands have a grain size as specified above.

[0037] The sand may have a water content ranging from 0 to 15% by weight relative to the total weight of the sand.

[0038] It is understood that, according to the invention, the filling material is free of any component other than the previously defined sand. The filling material is thus free of cement, silt, binder, in particular synthetic resin-type binder (e.g., epoxy or acrylic), or any other additive.

[0039] When it is stated that the interconnecting voids are filled with a sand-based filler material, it should be understood that the interconnecting voids are filled to saturation with sand. Asphalt mixes may retain a small amount of void space, but this remains very low. Thus, the structure of the asphalt mix is ​​homogeneous throughout its thickness. There is no formation of sub-layers within the asphalt mix. Preparation process

[0040] The road surface according to the present invention can be prepared by a preparation process comprising the steps of:

[0041] (a) preparation of an open hydrocarbon coating comprising voids communicants; (b) filling of communicating voids in open bituminous asphalt with sand or an aqueous suspension of sand.

[0042] Step (a) can be implemented using techniques well known to those skilled in the art, in particular using the methods described above for asphalt mixes Hot, lukewarm or semi-warm.

[0043] During step (b), the communicating voids of the open hydrocarbon coating are filled with sand or an aqueous suspension of sand.

[0044] When it is stated that the filling is carried out with sand, this means with sand alone, that is, in the absence of any other components or additives. The sand is as defined previously. In this embodiment, when the filling material is sand alone, a hydraulic compaction step is advantageously carried out after step (b) of filling the communicating voids. By hydraulic compaction, it is understood that water is added to the sand filling the communicating voids to compact it. If necessary, step (b) followed by hydraulic compaction can be repeated several times until the communicating voids are saturated ("to refusal") with filling material.

[0045] Preferably, in step (b), the communicating voids are filled using an aqueous sand suspension. The use of an aqueous sand suspension can facilitate the filling of the communicating voids, as it increases the fluidity of the sand. Typically, the mass content of sand in the aqueous suspension varies from 60% to 90%.

[0046] Typically, the application of the filling material is carried out to refusal (i.e. in such a way as to saturate the communicating voids).

[0047] The application is typically carried out using a construction broom or a squeegee, such as a rubber squeegee, typically after cooling of the open hydrocarbon asphalt.

[0048] Depending on the interconnected void content of the open-cell asphalt mix, it may be necessary, following step (b), to vibrate using a vibrating plate or roller to aid the penetration of the sand or aqueous sand suspension to refusal. This vibration step is particularly useful when the filler material is sand, especially very dry sand. This vibration step can be carried out between step (b) and the hydraulic compaction step as described above, simultaneously with the hydraulic compaction step, or following the hydraulic compaction step.

[0049] Furthermore, the coating of the present invention exhibits good permeability. It is understood that immediately after its manufacture, particularly when prepared using a sand suspension, the coating may not exhibit the desired permeability. Nevertheless, it will be readily understood that the water that may saturate the sand at the time of coating preparation evaporates over time, rendering the coating permeable.

[0050] Thus, the coating of the present invention exhibits both the characteristics of a bituminous coating in terms of mechanical properties and the characteristics of an asphalt mix that is open in terms of permeability.

[0051] The road surfaces of the present invention are particularly suitable for low traffic roads, parking areas, soft mobility routes, such as cycle paths or pedestrian walkways.

[0052] The road surfaces of the present invention are typically horizontal and preferably have a slope of less than 5%, preferably less than 3%. Such a characteristic promotes water drainage and improves the durability of the surface. EXAMPLES

[0053] Construction of parking lot and access road

[0054] A road surface according to the invention, with an area of ​​650m2, was produced according to the following steps: - Manufacture and implementation of an open 0 / 40 hydrocarbon asphalt. - Filling of communicating voids with 0 / 2 mm sand. Coated

[0055] The coating used is composed as follows (% by mass relative to the total mass of solid particles):

[0056] - 20 / 40 (Quartzite): 83%, - 0 / 4 (Quartzite): 12%, - Filler (limestone): 2%, - Bitumen (50 / 70): 3%. The particle size distribution curve of the final mixture has the following characteristics (% by mass relative to the total mass of solid particles):

[0057] - Passing at 63 pm: 5%, - Passing at 2 mm: 11%, - Passing at 4 mm: 16%, - Passing at 20 mm: 32%, - Passing at 31.5 mm: 62%, - Passing at 40 mm: 99%.

[0058] Laboratory results showed good compactability and a theoretical void percentage at 40 gyrations of 26.1% (test standard 12697-31). Filling material

[0059] This is a 0 / 2mm alluvial sand. This sand has the advantage of coming from a gravel pit and being naturally almost free of fines.

[0060] Indeed, the mass content of fines (% passing 63pm) in the sand is less than 2%.

[0061] Its mass water content is 7%. Support

[0062] The 0 / 60mm alluvial support (Seine alluvium) is poor in fines, has a modulus under static plate loading (EV2 measured according to standard NF P94-117-1 of April 2000) greater than 50 MPa and a permeability K of 10 4 to 105 m / s measured according to standard NF X30-418 of December 2012 or according to standard NF X30-420 of August 2007. Manufacturing and application of open asphalt

[0063] 70 t of open-mix asphalt as defined above were produced in Asphalt plant. After approximately 1 hour of transport, the open asphalt was primarily laid using a paver, with some areas laid manually. The asphalt layer thickness is between 5 cm and 6 cm over an area of ​​approximately 650 m².

[0064] The installation is carried out with simple compaction using a smooth tandem roller (i.e. without vibration).

[0065] Measurements taken on site allow us to estimate the percentage of voids in place in the asphalt layer as being greater than 25%.

[0066] After complete cooling, the open asphalt was then filled with sand as described above.

[0067] The sand was spread over the exposed asphalt and then swept to work it into the interconnecting voids. A fine spray of water was then applied to allow for hydraulic settling. This operation was repeated two to three times, depending on the area, until the sand refused to settle (no more sand was allowed to settle). No particular impact was observed from the initial water content of the sand, given that it is subsequently saturated during placement by the spraying operations.

[0068] The absence of water retention on the construction site allows the drainage of the coating to be assessed. Visual observations over time

[0069] After several weeks of implementation of reopening to traffic (Heavy Goods Vehicles to a traffic class T5, i.e. to less than 25 heavy goods vehicles per day): - no surface degradation is observed (no detachment of the largest elements under the effect of traffic), - The sand in the open asphalt remains in place and does not accumulate in the low points of the construction site. - the permeability behavior of the whole is very satisfactory under autumn rains.

Claims

Claims

1. Road surface comprising an open hydrocarbon coating on the surface, the communicating voids of which are filled with a filling material consisting of sand.

2. Road surface according to claim 1, characterized in that the open hydrocarbon coating has a content of communicating voids ranging from 15% to 40%, or from 20% to 35%, preferably from 30% to 35%.

3. Road surface according to claim 1 or 2, characterized in that the hydrocarbon coating has a thickness varying from 2 cm to 15 cm, preferably from 4 cm to 10 cm, even more preferably from 5 cm to 7 cm.

4. Road surface according to any one of claims 1 to 3, characterized in that the hydrocarbon coating is applied to an infiltrating support, preferably an untreated gravel (GNT), a draining bitumen gravel (GB) or a draining concrete.

5. Road surface according to any one of claims 1 to 4, in which the open hydrocarbon coating is a hot, warm or semi-warm coating.

6. A method of preparing a road surface according to any one of claims 1 to 5 comprising the steps of: (a) preparing an open hydrocarbon mix comprising communicating voids; (b) filling the communicating voids of the open hydrocarbon mix with sand or a sand suspension.

7. Method according to claim 6, characterized in that the filling of the communicating voids of the open hydrocarbon coating is carried out with sand.

8. Method according to claim 7, characterized in that a hydraulic compaction step is carried out following step (b).

9. Method according to any one of claims 6 to 8, characterized in that the filling of the communicating voids is carried out to refusal.

10. Use of a road surface according to any one of claims 1 to 5 for low-traffic traffic lanes, parking areas, soft mobility lanes, such as cycle paths or pedestrian lanes.