Shell- and hydraulic binder-based concrete compositions and method for producing furnishing and construction elements from these compositions

Abstract

The present invention relates to a concrete composition comprising a hydraulic binder, aggregate (G), water (E) and at least functional adjuvants, the hydraulic binder comprising a cement (C) and mineral fillers, and the functional adjuvants comprising a superplasticiser (S), an anti-air-entraining agent and a water repellent. According to the invention, the water-to-cement weight ratio W / C is between 0.15 and 0.6, and the aggregate comprises microfibres and shells, the amount of which in the concrete composition is given by an aggregate-to-hydraulic binder weight ratio G / C of between 0.1 and 2.5, the shells comprising a first category (G1) of shells with a size of between 3 mm and 6 mm, the amount of which is given by an aggregate-to-hydraulic binder weight ratio G1 / C of between 0.05 and 2.45, and a second category (G2) of shells with a size of less than 3 mm, the amount of which is given by an aggregate-to-hydraulic binder weight ratio G2 / C of between 0.05 and 2.5. The present invention also relates to a method for producing a fresh concrete, the composition of which is that of the concrete composition according to the invention, and to a method for producing a concrete object cured from the fresh concrete obtained according to this production method. Finally, the present invention also relates to a cured concrete object obtainable by means of this method and to the use thereof as an interior or exterior furnishing element, or as a sanitary element, construction element, floor or façade covering, or as a decorative object.

Description

DESCRIPTION Title of the invention: CONCRETE COMPOSITIONS BASED ON SHELLFISH AND HYDRAULIC BINDER AND METHOD FOR MANUFACTURING ELEMENTS OF FURNISHINGS AND CONSTRUCTION FROM THESE COMPOSITIONS Technical field of the invention [1] The field of the invention is that of concrete compositions based on shell products and hydraulic binders which are also mechanically resistant and impermeable to water and gases and the manufacture of furnishing and construction elements from these concretes. Technical background [2] Concrete is commonly used in the construction of buildings, including walls, foundations, roofs and floors of buildings, as well as bridges and roads, etc. It has the advantage of being easy to pour into predetermined areas or molds, and of supporting heavy loads such as vehicles and the weight of the structures themselves. [3] Conventional aggregates such as gravel and sand are traditionally used in the manufacture of concrete, which are taken directly from nature or from the recycling of demolition concrete. The extraction of these exhaustible resources from nature leads to degradation of soils and landscapes, and more generally of the fauna and flora present. [4] It is known to those skilled in the art to use, in concrete compositions, products and / or residues from the marine ecosystem. For example, Chinese patent application CN106149872 teaches a high-performance reinforced concrete composition based on coral aggregates and fibers. Although patent CN106149872 does not specifically indicate the nature of the corals used in its concretes, it is known to those skilled in the art that certain corals are calcareous or have a calcareous skeleton, as taught in particular by patent application CN112430040. However, corals or coral residues based on limestone are generally branched and porous (see Figures 1 and 2), which is not suitable for the manufacture of dense high-performance concrete. Indeed, Table 1 below (which is a comparative table of the characteristics of shells and corals determined by experimental tests) shows that the volume density of shell products is higher more than 25% higher than that of corals (e.g., coral 1, Table 1), or even more than double that of some corals (e.g., coral 2, Table 1). On the other hand, as far as the water absorption rate is concerned, it is, on average, for corals, three times the percentage of water absorption of shellfish products. [5] Table 1: Comparison of the volume density and water absorption rate of corals with those of different shell products. 6] Furthermore, the skilled person is aware of the use of other marine products to replace conventional aggregates in the manufacture of concrete. For example, the skilled person is aware of the use of shellfish products as aggregates in concrete compositions. These shellfish products are typically derived from harvests of empty shells of marine animals washed up at sea or recovered by fishermen or in restaurants, or from waste residues from the shellfish farming industry. Indeed, the French shellfish farming industry produces approximately 250,000 tonnes of shellfish each year. This results in a significant production of bulky waste of empty shells (particularly along marine coastlines), which must be disposed of and treated in order to limit the degradation of the landscape. This concerns, for example, empty shells of marine animals.The use of these shell products as aggregates in the manufacture of concrete makes it possible, on the one hand, to limit the extraction of sand from nature, and on the other hand, to recycle natural waste. Thus, international application WO2016 / 087720 describes the production of water-permeable concretes obtained from a mixture comprising crushed shell products. In the manufacturing process used to produce such concretes, part of the conventional aggregates is replaced by crushed marine shell products (comprising calcium carbonate) in order to produce permeable and mechanically resistant concretes. However, such concretes have the disadvantage of not being able to be considered as dense and high-performance concretes, in terms of compressive strength and flexural strength. In addition, such concretes are not impermeable to water and gases. Statement of the invention [7] In order to overcome the aforementioned drawbacks and obtain a dense, high-performance concrete, while addressing the problem of managing the treatment of shellfish waste and the recovery of renewable mineral resources (in particular from bio-mineralization with the capture of CO2 dissolved in seawater), without harming existing coral reefs and marine fauna, the inventors have developed concrete compositions in which all conventional aggregates are completely replaced by shellfish products, which make it possible to obtain materials with improved mechanical and environmental properties compared to the known solutions of the prior art, as well as concretes obtained from these compositions with water and gas impermeability properties, as well as properties of resistance to bending, compression,and improved chemicals compared to prior art solutions., [8] More particularly, the present invention relates to a concrete composition comprising a hydraulic binder, aggregates G, water E and at least functional additives, said hydraulic binder comprising a cement C and mineral fillers (or mineral additions), and optionally a colorant and / or a pigment, and said functional additives comprising a superplasticizing agent S, an anti-air entrainment agent (or anti-foaming agent) and a water-repellent agent, said concrete composition being characterized in that the total water / cement W / C mass ratio is between 0.15 and 0.6, and in that said aggregates comprise shells and microfibers, said shells originating from crushed shell products, the quantity of which in said concrete composition is given by an aggregate / cement G / C mass ratio of between 0.1 and 2.5, and preferably between 0.5 and 2.5, even better between 0.75 and 1.5,said shells being distributed as follows:, - a first category (Gl) of shells having a size between 3 mm and 6 mm and the quantity of which in said concrete composition is given by an aggregate / cement mass ratio Gl / C of between 0.05 and 2.45, and preferably between 0.1 and 2.25, - a second category (G2) of shells having a size less than 3 mm and the quantity of which in said concrete composition is given by an aggregate / cement mass ratio G2 / C of between 0.05 and 2.5, and preferably between 0.1 and 2.5. [9] Such a concrete composition makes it possible to manufacture hardened concrete objects with both high mechanical resistance properties and impermeability to water and gases.

[0010] In particular, with regard to the mechanical properties, such hardened concrete objects may be considered as high-performance concrete objects (usually designated by the acronym BHP and having a compressive strength at 28 days of between 45 and 60 MPa) or very high-performance concrete objects (usually designated by the acronym BTHP and having a compressive strength at 28 days of more than 65 MPa). Such concrete construction objects obtained from a concrete composition according to the invention also have a flexural strength at 28 days of between 8 MPa and 15 MPa. In addition, such concrete construction objects obtained from a concrete composition according to the invention have a density (in particular of between 2000 and 2300 kg / m 3 ), which is lower than that of BHP objects known from the prior art (typically of the order of 2400 kg / m 3 and beyond).

[0011] The shells used have an aragonite and lamellar crystalline form, and are also very low in porosity compared to the corals used in prior art solutions. In addition, shell mother-of-pearl, the nanostructure of which is shown in Figure 3, provides increased resistance to concrete, particularly in terms of flexural strength. It has thus been discovered that such characteristics promote the improvement of the mechanical performance of concretes, thus allowing the production of high-performance concretes based on natural marine waste.

[0012] The aggregates of the concrete composition according to the invention comprise shells from crushed shell products and microfibers.

[0013] As shells originating from crushed shellfish products used as aggregates in the concrete composition according to the invention, mention may in particular be made, in a non-limiting manner, of mussel shells, oyster shells, scallop shells, abalone shells, periwinkle shells, whelk shells, clam shells, cockle shells, slipper limpets, and mixtures thereof, and more generally of all shells of marine or terrestrial animals.

[0014] In addition to the shells, the aggregates comprise microfibers which may be chosen from natural cellulose fibers, synthetic fibers, metal fibers, glass fibers, carbon fibers, and mixtures thereof. As commercial natural fibers which may be used in the context of the present invention, mention may for example be made of the natural microfibers marketed by the company CHRYSO under the brand names CHRYSO®Fibre UF 500. The quantity of microfibers MF in the concrete composition may preferably be defined by a microfiber / hydraulic binder MF / C mass ratio of between 0 and 0.005, preferably between 0 and 0.003, even more preferably between 0 and 0.00035.

[0015] Such small-sized fibers (with a diameter between 6 and 20 microns and a length between 300 microns and 15 mm, preferably between 300 microns and 6 mm) make it possible to improve the mechanical performance of concrete.

[0016] The hydraulic binder of the concrete composition according to the invention comprises a cement (C) and mineral fillers. As cements C which can be used in the context of the present invention, mention may be made of Portland cements (CEM I, II, III, IV, V, VI) as defined according to standard NF EN 197-1 of February 2001, aluminous cements, sulfo-aluminous cements, clay cements, cements based on calcined clays (for example LC3 cements) or geopolymers.

[0017] More preferably, a Portland cement may be used, and better still a CEM II Portland cement, such as that marketed by the company LAFARGE under the trade name Ciment Super Blanc CEM II / A-LL 42.5 N CE PM.

[0018] The total water / cement / cement mass ratio is between 0.15 and 0.6, and advantageously between 0.20 and 0.40, and better between 0.25 and 0.3.

[0019] As mineral fillers or additions CM which can be used in the context of the present invention, mention may be made of limestone fillers, fly ash, slag, silica fume, metakaolins, calcium carbonate as an industrial by-product, and their mixtures.

[0020] The quantity of mineral fillers CM in the concrete composition may preferably be defined by a mass ratio of dry mineral fillers / hydraulic binder CM / C of between 0 and 0.3, preferably between 0.05 and 0.25, better still between 0.075 and 0.15.

[0021] The hydraulic binder of the concrete composition according to the invention may comprise, in addition to the cement C and the mineral fillers, a colorant Co, the quantity of which in the concrete composition may preferably be defined by a colorant / cement Co / C mass ratio of between 0 and 0.3, preferably between 0.05 and 0.25, better still between 0.075 and 0.15. As colorants which may be used in the context of the present invention, mention may in particular be made of the commercial colorant VERT 2441 and the commercial colorant NOIR- 1932880 (or Indian Black), or the pigment Terre de Sienne® and blue pigments.

[0022] The functional additives of the concrete composition according to the invention comprise a superplasticizing agent S, an anti-air entrainment agent (or anti-foaming agent) AM and a water-repellent agent AH.

[0023] For the purposes of the present invention, the term “superplasticizing agent” means a water-reducing agent. As superplasticizing agents which can be used in the context of the present invention, mention may in particular be made of polycarboxylic compounds such as polycarboxylates, and in particular compounds combining a polycarbonate and a modified phosphonate, such as for example the compound marketed by the company CHRYSO under the brand CHRYSO®FLUID Optima 185. The quantity of superplasticizing agent (S) in the concrete composition may preferably be defined by a mass ratio of dry superplasticizing agent / hydraulic binder S / C of between 0 and 0.015, preferably between 0.001 and 0.0125, better still between 0.005 and 0.01.

[0024] Such superplasticizers have the advantage of promoting the reduction of the air content of the concrete (including the formation of bubbles), the reduction of the Water / Cement ratio, as well as increasing the fluidity of the concrete.

[0025] As water-repellent agents (WA) that can be used in the context of the present invention, mention may be made, for example, of the product marketed by the company CHRYSO under the brand CHRYSO®Fuge B4. The hydro gives concrete a high resistance to rising water by capillary absorption and reduces, or even eliminates, the penetration of water under pressure. The fine hydrophobic particles that constitute it combine with the lime in the cement to form micelles that obstruct the capillaries of the medium and prevent water penetration. The quantity of water-repellent agent in the concrete composition may preferably be defined by a dry water-repellent agent / hydraulic binder WA / C mass ratio of between 0 and 0.02, preferably between 0.00021 and 0.01, better still between 0.001 and 0.0032.

[0026] As anti-air entrainment agents (or anti-foam agents) AM which can be used in the context of the present invention, mention may for example be made of the product marketed by the company Sika under the brand name SikaControl®-800 Param ent. The quantity of anti-air entrainment agent in the concrete composition may preferably be defined by an AM / C mass ratio of between 0 and 0.02, preferably between 0.002 and 0.01, better still between 0.001 and 0.0015.

[0027] The functional additives of the concrete composition according to the invention may also optionally comprise a latex. As a latex that can be used in the context of the present invention, mention may for example be made of the product marketed by the company Sika under the brand name SikaLatex® 360 (L). The quantity of dispersing agent in the concrete composition may preferably be defined by a dry latex / hydraulic binder L / C mass ratio of between 0 and 0.01, preferably between 0 and 0.003, better still between 0 and 0.0005.

[0028] In addition to the aforementioned functional admixtures, the concrete composition according to the invention may further comprise one or more other functional admixtures chosen from internal curing agents, anti-cracking agents, anti-shrinkage agents, accelerators, retarders and mixtures thereof.

[0029] The present invention also relates to a method for manufacturing fresh concrete having the concrete composition according to the invention, said method comprising a step B) of formulating the fresh concrete, which comprises the following successive sub-steps: - BO) a step of introducing, into a mixer, shells belonging to the two categories G1 and G2 and microfibers, then mixing the whole; - Bl) a step of introducing water into the mixer, for pre-wetting said shells, then mixing followed by a waiting phase to allow the impregnation of water into said shells of categories G1 and G2; - B2) a step of introducing, into the mixer, a cement (C) and mineral fillers and optionally a colorant and / or a pigment, then mixing; - B3) a step of introducing water for mixing and a superplasticizing additive (S) into the mixer, then mixing; - B4) a step of introducing an anti-air entrainment agent (or anti-foam agent) and / or a water-repellent agent into the mixer, then mixing until fresh concrete is obtained.

[0030] The shells (in particular first and second category products) originating from shell products, the cement, the mineral fillers, where appropriate the colorant and / or pigment, the functional additives (comprising in particular a superplasticizing agent (S), an anti-air entrainment or anti-foaming agent and a water-repellent agent) as well as their respective quantities in the fresh concrete composition thus obtained are as described previously.

[0031] Advantageously, the method for manufacturing fresh concrete according to the invention may further comprise, before step B) of formulating the fresh concrete, a step A) of preparing the shells comprising the following successive sub-steps - AO) collection of shellfish products and, where appropriate, in the case of scallops, elimination of tendon remains, then natural or accelerated fermentation; - Al) elimination of foreign bodies present in said shells; - A2) washing said shells with water; - A3) heat treatment of said shells at a temperature between 120°C and 200°C for at least 20 minutes; - A4) crushing and grinding of the shells thus heat-treated; - A5) separation of the heat-treated, crushed and ground shells into a first category (Gl) of shells having a size between 3 mm and 6 mm and the quantity of which in said concrete composition is defined by a mass ratio of Gl shells / Gl / C cement between 0.05 and 2.45, and preferably between 0.1 and 2.25, and a second category (G2) of shells having a size less than 3 mm and the quantity of which in said concrete composition is defined by an aggregate / cement mass ratio G2 / C of between 0.05 and 2.5, and preferably between 0.1 and 2.5.

[0032] Advantageously, fermentation when natural can consist of inerting the shells by storing them outdoors for 2 to 6 weeks to allow for initial degradation of the remaining organic matter present in or on the shells. Advantageously, fermentation when accelerated allows for the decomposition of the organic matter in the shells during which the shells are stacked at a height of a few meters for a period of 2 to 6 weeks. Forced aeration by continuous ventilation of air from bottom to top in order to accelerate decomposition is maintained during the treatment.

[0033] Sub-step A1) is followed by sub-step A2) of washing the shells with water, for example in a tubular washer.

[0034] The washing sub-step A2) is followed by a heat treatment A3) of the shells at a temperature between 120°C and 200°C, preferably for approximately 20 to 30 minutes, to kill all traces of bacteria. This heat treatment (or drying) can advantageously be carried out in a continuously operating rotary oven / dryer.

[0035] Alternatively, step A2) of washing is followed by an antibacterial chemical treatment with caustic soda (NaOH, 1.5% to 5% by mass in water at room temperature, from less than 15h h to 65h), or a biological treatment by immersion in a natural environment with the introduction of crabs, shrimps or fish to eliminate the animal flesh, or by burial treatment. In addition to these treatments, it is possible to carry out a treatment by gamma ray ionization.

[0036] It has been observed that using sodium hydroxide at 4.5%-5% by mass during antibacterial chemical treatment reduces the time required for treatment. A sodium hydroxide concentration of 4.5% by mass can eliminate all traces of bacteria in less than 15 hours.

[0037] The shells thus heat-treated are then crushed and ground, for example in a grinder (for example a hammer mill, or a tooth or ball mill or any equivalent system)

[0038] At the end of step A4) of crushing and grinding, step A5) of separating the heat-treated, crushed and ground shells into the two aforementioned categories G1 and G2 is carried out. This separation A5) can, for example, be carried out on a vibrating screen capable of separating shells having a size between 3 mm and 6 mm (category G1) and shells having a size less than 3 mm (category G2).

[0039] Once the aggregates have been prepared, the second step B) of the fresh concrete manufacturing process is carried out, which consists of the formulation of the fresh concrete. This second step B) includes the following sub-steps: - BO) a step of introducing, into THE mixer, microfibers (for example commercial microfibers CHRYSO®Fibre UF-500) and shells belonging to the two categories G1 and G2, then mixing the whole and advantageously for one minute; - Bl) a step of introducing water (so-called pre-wetting water) into the mixer, for pre-wetting the shells of categories G1 and G2,: the quantity of pre-wetting water being determined by the absorption rate of the shells; then mixing (for example one minute), followed by a waiting phase to allow the impregnation of the water into said shells of categories G1 and G2 (for example for 5 to 10 minutes); - B2) a step of introducing, into the mixer, a cement (for example white cement CEM n / A-LL 42.5 N) and mineral fillers (for example the commercial products Betocarb HP, D, F or UF from OMYA), and optionally a colorant (for example the commercial colorant VERT 2441) and / or a pigment, which are as defined previously, then mixing (in particular for 1 to 2 minutes); - B3) a step of introducing water (so-called mixing water) for mixing and a superplasticizing additive S (for example the commercial product CHRYSO®Fluid Optima 185) into the mixture of shells, cement and water obtained at the end of step B2), then mixing (preferably for 1 to 2 minutes); - B4) a step of introducing an anti-air entrainment agent (or anti-foam agent) (for example the commercial product SikaControl®-800 Parement) into the fresh concrete and / or a water-repellent agent (for example the commercial product CHRYSO®Fuge B4), then mixing the mixture thus obtained preferably for 1 to 2 minutes).

[0040] Advantageously, the method according to the invention may further comprise, between steps B3) and B4), a step of introducing a latex as a functional adjuvant. This latex is as defined above. The introduction of the latex is followed by kneading of the mixture thus obtained (preferably for 1 to 2 minutes).

[0041] The fresh concrete obtained at the end is typically characterized at the end of step B4 of the process according to the invention for manufacturing fresh concrete. To do this, the slump and fresh spread are measured using a cone (top diameter = 100 mm, bottom diameter = 119 mm, height = 135 mm) according to standard NF EN 12350-2. In addition, the density and air content of the fresh concrete are also measured using an aerometer according to standard EN 459-2 and EN 1015-7.

[0042] Fresh concrete obtained by the process according to the aforementioned invention can be used for the manufacture of a hardened concrete object.

[0043] The resulting concretes are self-compacting with low air content. To this end, the applicant has also developed a process for manufacturing a hardened concrete object, comprising the following steps: - CO) where appropriate, a step of preparing a mold by spraying a release agent (for example the commercial product CHRYSO® DEM BIO 21 DVE) onto the surface of said mold intended to be in contact with the fresh concrete; - Cl) pouring and distributing in said mold fresh concrete as obtained by the process as described in the present description, with manual or mechanical vibration to remove air bubbles from the concrete; - C2) curing of the concrete, at room temperature and with a residual humidity of 100% for 48 hours; - C3) demoulding or stripping of the hardened concrete object thus obtained, at ambient temperature and humidity; then hardening and drying at ambient temperature and humidity; - C4) machining of said hardened concrete object (preferably 7 days after the end of step C3) comprising the dimensional rectification of said object (for example either using a disc or by abrasion, and the polishing or sanding of its surface.

[0044] The composites of the concretes obtained are distributed horizontally in the form of a "layer cake" (see for example figures 11 to 13) of low thickness (less than 3 mm), and have a higher density and lower porosity compared to the solutions described in the prior art. This microstructure gives the shells improved mechanical resistance (flexural and compressive strength) allowing the production of self-compacting concrete.

[0045] As a mold, a mold with a frame made of HDPE (High Density Polyethylene) or steel can be used. This mold is prepared by spraying a release agent onto the surface of the mold to form a thin, even layer. Alternatively, an intrinsically non-stick mold, such as silicone, can be used: in this case, a layer of release agent is not necessary.

[0046] As for the surface polishing of step C4, this can be carried out using a polishing machine to obtain the desired final finish: to obtain a matte or non-slip finish: use of polishing grains of dimensions 100 / 200 / 500 (grain size defined according to the standard of the European Federation of Abrasive Producers); To obtain a satin finish: use polishing grits of sizes 100 / 200 / 500 / 1000 / 2000; To obtain a glossy finish: use polishing grits of sizes 100 / 200 / 500 / 1000 / 2000 / 3000, then use a polishing tool.

[0047] The hardened concrete object is characterized at the end of step C4). To this end, the density of the concrete is measured by weighing, and the mechanical properties of the hardened concrete (compressive and flexural strengths) are determined according to the NF EN 196-1 method: Test methods for cements - Part 1: Determination of strengths.

[0048] Finally, the present invention also relates to a hardened concrete object obtainable by the method of manufacturing a hardened concrete object according to the invention. The hardened concrete object according to the invention may be in the essentially two-dimensional panel form or in the form of a three-dimensional object.

[0049] By obj and in essentially two-dimensional form, is meant, within the meaning of the present invention, a panel-type object.

[0050] For the purposes of the present invention, an object in essentially three-dimensional form is understood to mean an object comprising a curved or angular surface, or a sculpture of the art object type.

[0051] The present invention also relates to the use of the hardened concrete object according to the invention or capable of being used as an interior furnishing element (in particular furniture tops, worktops, splashbacks, bar or restaurant counters, or exterior (such as floor slabs, pool bottoms and edges, outdoor benches and benches, slabs or facades, etc.), or a sanitary element such as a bathroom sink top or a shower tray, a bathtub), an architectural construction element, or a floor or facade covering (for buildings, or bridges, roads, roundabouts), or a decorative object.

[0052] Advantageously, such construction objects obtained from a concrete composition according to the invention may have a mechanical compressive strength of at least 30 MPa, preferably between 30 MPa and 70 MPa, and preferably a mechanical flexural strength of at least 8 MPa, and a density (in particular between 2100 and 2400 kg / m 3 , preferably between 2100 and 2270 kg / m 3 ).

[0053] Advantageously, the concrete construction objects obtained from a concrete composition according to the invention have a flexion / compression ratio greater than 15%, preferably greater than 20%.

[0054] Other advantages and features of the present invention will result from the description which follows, given by way of non-limiting example and with reference to the drawings and examples.

[0055] Brief description of the figures Other characteristics and advantages of the invention will appear during the reading of the detailed description which follows for the understanding of which reference will be made to the appended drawings in which: - Figure 1 is a photograph showing a whole coral; - figure 2 a photograph showing another whole coral; - figure 3 is a photograph of the nanostructure of the mother-of-pearl of shells cited in the work of BARTHELAT, 2014; - Figure 4 is a photograph showing a whole mussel shell as used in step A) of preparing shells as defined in the present description; - Figure 5 is a photograph showing a whole oyster shell as used in step A) of preparing shells as defined in the present description; - Figure 6 is a photograph showing a whole oyster shell as used in step A) of preparing shells as defined in the present description; - Figure 7A is a photograph showing mussel shell aggregates comprising sizes between 1.5 μm and 3 mm (corresponding to the second category of shells G2) obtained at the end of step A) of preparation of shells as defined in the present description; - figure 7B is a photograph showing mussel shell aggregates comprising sizes between 3 μm and 6 mm (corresponding to the second category of shells Gl) obtained at the end of step A) of preparation of shells as defined in the present description; - figure 8 A is a photograph showing oyster shell aggregates comprising sizes between 1.5 m and 3 mm (corresponding to the second category of shells G2) obtained at the end of step A) of preparation of shells as defined in the present description; - figure 8B is a photograph showing oyster shell aggregates comprising sizes between 3 μm and 6 mm (corresponding to the second category of shells Gl) obtained at the end of step A) of preparation of shells as defined in the present description; - figure 9A is a photograph showing scallop shell aggregates comprising sizes between 0.5 μm and 3 mm (corresponding to the second category of shells G2) obtained at the end of step A) of preparation of shells as defined in the present description; - figure 9B is a photograph showing scallop shell aggregates comprising sizes between 3 μm and 6 mm (corresponding to the second category of shells Gl) obtained at the end of step A) of preparation of shells as defined in the present description; - figure 10 is a photograph showing the spreading of a concrete comprising scallop shells and having improved fluidity compared to the solutions described in the prior art, this concrete being obtained at the end of step B) of the process for manufacturing fresh concrete as described in the present description; - Figure 11 is a photograph of a hardened concrete panel of mussel shells (of categories Gl and G2, such as those shown in Figures 7A and 7B) obtained by the manufacturing method described in the present description; - Figure 12 is a photograph of a hardened concrete panel of oyster shells (of categories Gl and G2, such as those shown in Figures 8A and 8B) obtained by the manufacturing method described in the present description, and - Figure 13 is a photograph of a hardened concrete panel of scallop shells (of categories Gl and G2, such as those shown in Figures 9A and 9B) obtained by the manufacturing method described in the present description. EXAMPLES

[0056] The following examples illustrate the invention, without however limiting its scope. PRODUCTS AND RAW MATERIALS - hydraulic binder: Portland cement CEM II, such as that marketed by the company LAFARGE under the trade name Ciment Super Blanc CEM II / A-LL 42.5 N CE PM (absolute density 3.1); - water (for pre-wetting aggregates and mixing concrete) - conventional aggregates (for comparison): ■ gravel with a grain size between 6 and 20 mm; ■ sand with a grain size between 0.1 and 4 mm; - crushed shellfish products: ■ oyster shells with a grain size between 3 and 6 mm (H3-6); ■ oyster shells with a grain size between 0.5 and 3 mm (HO, 5-3); ■ mussel shells with a grain size between 3 and 6 mm (M3-6); ■ mussel shells with a grain size between 0.5 and 3 mm (MO, 5-3); ■ scallops with a grain size between 3 and 6 mm (SJ3-6); ■ scallop shells sand with a grain size between 0.5 and 3 mm (SJ0.5-3); - adjuvants: ■ superplasticizer: product marketed by the company CHRYSO under the brand CHRYSO®FLUID Optima 185 (23.6% dry matter); ■ latex: product marketed by the company Sika under the brand SikaLatex® 360 (30% dry matter); ■ water-repellent agent: product marketed by CHRYSO under the brand CHRYSO®Fuge B4 (6.8% dry matter); anti-air entrainment agents: products marketed either by Sika under the brand SikaControl®-800 or by CHRYSO under the brand CHRYSO® AB 42. The dry matter content of the anti-air entrainment agents is 100%; - mineral fillers: ■ limestone fillers: compounds marketed by the company Omya under the brands Betocarb® HP, Betocarb® F, Betocarb® UF and Betoflow® D; - microfibers: ■ natural microfibers marketed by the company CHRYSO under the brands CHRYSO®Fibre UF 500; ■ synthetic microfibers marketed by the company CHRYSO under the brands CHRYSO® FIBRIN 23 D; - colorants: ■ Pigment Green 2441: colorant based on a mixture of baryta sulfate and nitroso green, with an absolute density of 4.1, marketed by the company MOULIN A COULEURS; ■ BLACK- 1932880 (Indian Black): dye marketed by the company ULTIBAT. It is a mixture of Fe2O3, SiO2, CaO, MgO, AI2O3 and FeO, with an absolute density of 5.17. MATERIAL USED FOR THE MANUFACTURE OF CONCRETE COMPOSITIONS AND THE CHARACTERIZATION OF CONCRETE PANELS - for manufacturing: ■ a mixer, which can be either a KitchenAid® brand mixer with a volume of 6 liters and 6 mixing speeds and a maximum capacity of 2.2 liters of fresh concrete or a mixer (BARON® brand) for production (100 liters and 300 liters volume); ■ molds for the production of panels (surface dimensions from 30 x 30cm to 200 x 100cm and thickness from 12 mm to 40 mm) comprising a plywood or steel base and high-density polymer (HDPE) edges; - for characterization: ■ a mini-icon with a top diameter of 100 mm, a bottom diameter of 119 mm, and a height of 135 mm for measuring the spread and slump of fresh concrete (see characterization tests); ■ a manual mortar aerometer referenced STDME027, marketed by the company STDE and complying with standard EN 459-2, to measure the air content and the density of fresh concrete; ■ 4 cm x 4 cm x 16 cm molds for measuring flexural and compressive strengths according to standard NF EN 196-1 “Cement testing methods - Part 1: Determination of strengths.”; ■ a cylindrical cardboard ZIPPLER® test tube from SPINNLER produced according to French standard NF EN 12390-1 to measure the porosity of hardened concrete; CHARACTERIZATION TESTS - measurement of the spread of fresh concrete: according to standard NF EN 12350-8 with the mini cone; the spread test consists of carrying out the following steps; the mini cone is placed upside down and held on a steel plate with a hard, non-absorbent surface; the mini cone is filled with fresh concrete; the mini cone is leveled with a rod; the mini cone is immediately lifted vertically and gently by 4 cm, turning it a little to unmold it; the very fluid concrete sinks completely and spreads in the form of a pancake on the spreading table; the largest diameter is measured as well as the diameter associated with it perpendicular. The spread is the average of these two diameters which must not differ by more than 5 cm. - measurement of the slump of fresh concrete (or Abrams cone slump test): according to standard NF EN 12350-2; this test consists of carrying out the following steps: - the cone is filled with fresh concrete in three batches. Each time, each layer is pricked with 25 blows using the rod; - the cone is leveled with a rod; - then the cone is lifted immediately, vertically and gently, turning it a little to unmold it; and - the slump of fresh concrete is measured by measuring the difference between the height of the cone and the height of the pile of fresh concrete. - measurement of the density p (kg / m3) of fresh concrete: p (kg / m3) = mass (kg) / volume (m 3 ) ; - measurement of the flexural and compressive strength of hardened concrete: carried out according to standard NF EN 196-1 “Test methods for cements - Part 1: Determination of strengths”. This measurement also makes it possible to determine the Rf / Rc ratio of hardened concrete; - measurement of the porosity of hardened concrete: carried out according to the SIA 162-1 method Test No. 7 (specimen diameter 7 cm, height 14 cm); - measurement of the water permeability of hardened concrete: according to Method SIA 262 / 1 Annex A (specimen diameter 7cm, height 14cm). EXAMPLE 1: PREPARATION AND CHARACTERIZATION OF SHELLS ACCORDING TO THE METHOD OF THE INVENTION (STEP A)

[0057] The crushed shell products are sorted and prepared according to step A of the process according to the invention, as follows: Stage AO: Collection of shellfish and decomposition of organic animal flesh - Collection of poor quality shellfish with animal bodies that are either dead or partially decomposed or from the food processing industry; - Natural decomposition by inerting (optional) of the shellfish by storing them for 2 to 6 weeks outside to allow initial degradation of the remains of organic matter present in or on the shellfish; - Accelerated decomposition by fermentation (optional) to decompose the organic matter of the shells during which the shells are stacked to a height of a few meters for a period of 2 to 6 weeks. Forced aeration by continuous ventilation of air from the bottom up to accelerate decomposition is maintained during treatment. - With the exception of the scallop, the shells containing the remaining tendons (ligament) of the shell are removed manually. Step Al: Elimination of foreign bodies (plastic, wood, metal, stones, etc.) present in the shells. Step A2: Washing the shellfish with water in a tubular washer. Step A3: Heat treatment and drying of the shellfish in a continuous rotary oven / dryer at a temperature between 120°C and 200°C for approximately 20 to 30 minutes to kill all traces of bacteria. Step A4: Crushing and grinding of shells using a hammer / tooth / ball mill or other equivalent systems. Step A5: Separation of the shells into three particle size fractions by a vibrating sieve (G1: from 3 mm to 6 mm as shown in Figures 7B, 8B and 9B - G2: from 0.5 mm to 3 mm as shown in Figures 7 A, 8 A, and 9 A - Fines: particle size less than 0.5 mm). Step A6: Measurement of water absorption rate of shellfish aggregates using the pycnometer method. Step A7: Packaging of fractions G1 and G2 either in 25 kg bags or in 0.5 tonne to 1 tonne containers and storing the clean and dry shell aggregates in a dry place for the production of concrete. EXAMPLE 2: PREPARATION OF FRESH AND HARDENED CONCRETE COMPOSITIONS ACCORDING TO THE INVENTION BASED ON OYSTER SHELLS AND PRODUCTION OF PANELS WITH THESE COMPOSITIONS

[0058] Different fresh concrete compositions based on oyster shells according to the invention are prepared in accordance with the method of the invention, and comprise the following steps (step B): Step B0: introduce all of the aggregates (G1 and / or G2) of shells as prepared in example 1 and micro-fibers (CHRYSO®Fiber UF-500) into a concrete mixer (KitchenAid® or BARON® as mentioned above) and mix for 1 minute; Step B1: Introduce the pre-wetting water (the amount of pre-wetting water is determined by the absorption rate of the aggregates) into the mixer and mix for 1 minute then leave the water impregnation in the aggregates for 5 to 10 minutes; Step B2: introduce all of the cement (White Cement CEM II / A-LL 42.5 N), mineral fillers (Betocarb HP, D, F or UF from OMYA) and / or colorants (VERT 2441) into the mixer then mix for 1 to 2 minutes; Step B3: introduce the mixing water and superplasticizer (CHRYSO®Fluid Optima 185) mixture into the mixer and mix for 1 to 2 minutes; Step B'3: introduce the Latex (Sika®Latex-360) into the mixer then mix for 1 minute; Step B4: introduce the anti-air entrainment agent (or anti-foam) (SikaControl®-800 Facing) then the water-repellent agent (CHRYSO®Fuge B4) into the mixer, then mix for 1 to 2 minutes;

[0059] The fresh concrete (see for example Figure 10) thus obtained is characterized in accordance with the test methods indicated previously.

[0060] Then the fresh concrete thus obtained is poured into the molds (panel type) and the concrete is cured, in accordance with the process described below: Step CO: preparation of a panel mold by spraying a release agent (CHRYSO®Dem Bio 21 - DVE) onto the inner surface of said mold so as to form a thin, homogeneous layer; Step C1: pouring and distributing in said mold the fresh concrete as obtained by the method according to the invention, with manual or mechanical vibration to remove air bubbles from the concrete. For the measurements of the flexural and compressive strengths of the hardened concrete, the procedure will be to pour and distribute fresh concrete in the 4 cm x 4 cm x 16 cm molds with manual vibration or using a vibrating rod to remove air bubbles from the concrete; Step C2: hermetically seal said mold, then cure the concrete, at room temperature and with a residual humidity of 100% for 48 hours; then obtain, after setting, a hardened concrete panel; Step C3: demoulding of objects in the form of panels or test pieces 4 cm x 4 cm x 16 cm at room temperature and humidity. Step C4: machining the concrete panels (see figures 11 to 13), preferably from 7 days, thus obtained at the end of step C3, for example by dimensional rectification, either using a disc or by abrasion, and by carrying out a surface polishing of the hardened concrete objects (panels) using a polishing machine to obtain the desired final finish: to obtain a matte or non-slip finish: use polishing grains of dimensions 100 / 200 / 500 (grain size defined according to the standard of the European Federation of Abrasive Producers); to obtain a satin finish: use polishing grains of dimensions 100 / 200 / 500 / 1000 / 2000; to obtain a glossy finish: use polishing grains of dimensions 100 / 200 / 500 / 1000 / 2000 / 3000, then use a polishing tool.

[0061] The different concrete compositions prepared according to the process described above are detailed in Table 2 below, with the respective quantities of the different ingredients as is and the characterization of the fresh and hardened concrete according to the test methods indicated previously:

[0062] Table 2: Concretes made from oyster shells EXAMPLE 3: PREPARATION OF FRESH CONCRETE COMPOSITIONS ACCORDING TO THE INVENTION BASED ON MUSSEL SHELLS (STEPS B AND C) AND PRODUCTION OF PANELS WITH THESE COMPOSITIONS

[0063] Different compositions of fresh concrete based on mussel shells are prepared in accordance with the process of the invention, in the same way as in Example 2. The different compositions of concrete thus prepared are detailed in Table 3 below, with the respective quantities of the different ingredients as is and the characterization of the fresh concrete and the hardened concrete thus obtained, according to the test methods indicated previously:

[0064] Table 3: Concretes made from mussel shells EXAMPLE 4: PREPARATION OF FRESH AND HARDENED CONCRETE COMPOSITIONS ACCORDING TO THE INVENTION BASED ON SCALLOPS (STEPS B AND C) AND PRODUCTION OF PANELS WITH THESE COMPOSITIONS

[0065] Different fresh concrete compositions based on scallop shells are prepared in accordance with the process of the invention, in the same manner as in Examples 2 and 4.

[0066] The different concrete compositions thus prepared are detailed in Table 4 below, with the respective quantities of the different ingredients as is and the characterization of the fresh and hardened concrete according to the test methods indicated previously:

[0067] Table 4: Concretes made from scallop shells EXAMPLE 5: EFFECT OF UF500 FIBER DOSAGE ON THE CHARACTERISTICS OF MUSSEL SHELL-BASED CONCRETE

[0069] Different concretes based on mussel shells were prepared according to the method of the present description, and in which the quantity of microfibers was varied. The compositions of these concretes are given in Table 5 below.

[0070] Microfiber-free RM3-6 52 concrete is a concrete produced for comparison with the concretes according to the invention (RM3-6_53, RM3-6_54, RM3-6_55, and RM3-6_56) with microfibers.

[0071] Table 5: Effect of adding UF500 fiber on the characteristics of concrete based on mussel shells

[0072] Mechanical characterization tests show that the addition of microfibers to a concrete made from mussel shells leads to an improvement in strength, particularly in the average flexural strength, compared to a concrete made from shells without cellulose fiber. UF-500. Therefore, the addition of microfibers to shell-based concrete allows the increase of the Rf / Rc ratio, reflecting the achievement of better mechanical performances of the concrete than those obtained without microfibers. EXAMPLE 6 (COMPARATIVE): COMPOSITIONS OF FRESH CONCRETE ACCORDING TO THE PRIOR ART BASED ON SCALLOPS AND PRODUCTION OF PANELS WITH THESE COMPOSITIONS

[0073] Different permeable concretes based on scallop shells are prepared in accordance with the teaching of French patent WO2016 / 087720. The different concrete compositions thus prepared are detailed in Table 6 below with the respective quantities of the different ingredients as is and the characterization of the fresh and hardened concrete according to the test methods indicated previously.

[0074] Table 6: Concretes based on scallop shells according to the prior art (WO2016 / 087720)

Claims

CLAIMS 1. Concrete composition comprising a hydraulic binder, aggregates (G), water (E) comprising pre-wetting water and mixing water and being defined as total water, and at least functional admixtures, said hydraulic binder comprising a cement (C) and mineral fillers, and optionally a colorant and / or a pigment, and said functional admixtures comprising a superplasticizing agent (S), an anti-air entrainment agent and a water-repellent agent, said concrete composition being characterized in that the total water / cement W / C mass ratio is between 0.15 and 0.6, and in that said aggregates comprise shells and microfibers, said shells originating from crushed shell products, the quantity of which in said concrete composition is given by an aggregate / cement G / C mass ratio of between 0.1 and 2.5, said shells being distributed as follows: - a first category (Gl) of shells having a size between 3 mm and 6 mm and the quantity of which in said concrete composition is given by an aggregate / cement mass ratio Gl / C of between 0.05 and 2.45, - a second category (G2) of shells having a size less than 3 mm and the quantity of which in said concrete composition is given by an aggregate / cement mass ratio G2 / C of between 0.05 and 2.

5.

2. Composition according to claim 1, according to which the total water / cement W / C mass ratio is between 0.20 and 0.

40.

3. Composition according to any one of claims 1 and 2, according to the mass ratio G / C is between 0.5 and 2.5, even better between 0.75 and 1.

5.

4. Composition according to any one of claims 1 to 3, according to which the Gl / C mass ratio is between 0.1 and 2.

25.

5. Composition according to any one of claims 1 to 4, according to which the mass ratio G2 / C is between 0.1 and 2.

5.

6. Composition according to any one of claims 1 to 5, according to which the shells are chosen from mussel shells, oyster shells, scallop shells, abalone shells, periwinkle shells, whelk shells, clam shells, cockle shells, slipper limpets, and mixtures thereof.

7. Composition according to any one of claims 1 to 6, according to which said cement is chosen from Portland cements (CEM I, II, III, IV, V, VI), aluminous cements, sulfo-aluminous cements, cements based on calcined clays, or geopolymers, and is preferably a Portland cement.

8. Composition according to any one of claims 1 to 7, according to which said mineral fillers are chosen from limestone fillers, fly ash, slag, silica fume, metakaolins, calcium carbonate as an industrial by-product, and mixtures thereof.

9. Composition according to any one of claims 1 to 8, according to which said microfibers are chosen from natural cellulose fibers, synthetic fibers, metal fibers, glass fibers, carbon fibers, and mixtures thereof.

10. Composition according to any one of claims 1 to 9, according to which said functional adjuvants further comprise a latex.

11. Method for manufacturing fresh concrete whose composition is as defined according to any one of claims 1 to 10, said method comprising a step B) of formulating the fresh concrete, which comprises the following successive sub-steps: - B0) a step of introducing, into a mixer, shells belonging to the two categories G1 and G2 and microfibers, then mixing the whole; - Bl) a step of introducing water into the mixer, for pre-wetting said shells, then mixing followed by a waiting phase to allow the impregnation of water into said shells of categories G1 and G2; - B2) a step of introducing, into the mixer, a cement (C) and mineral fillers and optionally a colorant and / or a pigment, then mixing; - B3) a step of introducing water for mixing and a superplasticizing additive (S) into the mixer, then mixing; - B4) a step of introducing an anti-air entrainment agent and / or a water-repellent agent into the mixer, then mixing until fresh concrete is obtained.

12. Method according to claim 11, further comprising, before step B) of formulating the fresh concrete, a step A) of preparing the shells comprising the following successive sub-steps: - AO) collection of shellfish products and, where appropriate, in the case of scallops, elimination of tendon remains, then natural or accelerated fermentation; - Al) elimination of foreign bodies present in said shells; - A2) washing said shells with water; - A3) heat treatment of said shells at a temperature between 120°C and 200°C for at least 20 minutes; - A4) crushing and grinding of the shells thus heat-treated; - A5) separation of the heat-treated, crushed and ground shells into a first category (Gl) of shells having a size between 3 mm and 6 mm and the quantity of which in said concrete composition is defined by a mass ratio of Gl shells / Gl / C cement of between 0.05 and 2.45, and preferably between 0.1 and 2.25, and a second category (G2) of shells having a size less than 3 mm and the quantity of which in said concrete composition is defined by an aggregates / G2 / C cement mass ratio of between 0.05 and 2.5, and preferably between 0.1 and 2.

5.

13. Method according to any one of claims 11 and 12, further comprising, between steps B3) and B4), the introduction of a latex, followed by kneading of the mixture thus obtained.

14. Method of manufacturing a hardened concrete object, comprising the following steps: - C0) where appropriate, a step of preparing a mold by spraying a release agent onto the surface of said mold intended to be in contact with the fresh concrete; - Cl) pouring and distributing in said mold fresh concrete as obtained by the method according to any one of claims 11 to 13, with manual or mechanical vibration; - C2) curing of the concrete, at room temperature and with a residual humidity of 100% for 48 hours; - C3) demoulding or stripping of the hardened concrete object thus obtained, at ambient temperature and humidity; then hardening and drying at ambient temperature and humidity; - C4) machining of said hardened concrete object including dimensional rectification of said object, and polishing or sanding of its surface.

15. Hardened concrete object obtained by the manufacturing process as defined according to claim 14.

16. Concrete object according to claim 15, in the form of an essentially two-dimensional panel or in the form of a three-dimensional object.

17. Use of said object according to claim 16, as an interior or exterior furnishing element, or a sanitary element, or a construction element, a floor or facade covering, or even a decorative object.

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