New formulation for low-carbon construction binder, preparation process and construction materials

Abstract

The invention relates to a formulation for a low-carbon construction binder comprising, in dehydrated form, a raw clay matrix and a deflocculation agent. It also relates to a construction binder, a method for preparing this construction binder as well as to a construction material comprising the construction binder according to the invention. Abstract figure: FIGURE 1

Description

Title of the invention: New formulation for low-carbon construction binder, preparation process and construction materials

[0001] The invention relates to the field of construction materials, and more particularly to that of binders which can be used in construction. The invention relates to a formulation for a construction binder. The invention also relates to a method for preparing a construction binder, the construction binder as such and the use of such a binder in the production of construction materials. Prior art

[0002] Cement is the second most consumed resource in the world, with more than 4 billion tons of material produced each year worldwide and this consumption is constantly increasing driven by the growing demand for housing and infrastructure.

[0003] Cement is a generally hydraulic binder which, when mixed with water, hardens and sets. After hardening, the cement retains its strength and stability even when exposed to water. There is a wide variety of cements used throughout the world. However, all conventional cements contain clinker at a percentage ranging from 5% for certain blast furnace cements to a minimum of 95% for Portland cement, which is the cement most widely used in the world today.

[0004] Clinker is the result of firing a mixture of approximately 80% limestone and 20% aluminosilicates (such as clays). This firing, clinkerization, is carried out at a temperature of over 1200°C, so such a cement preparation process involves high energy consumption. In addition, the chemical conversion of limestone into lime also releases carbon dioxide. As a result, the cement industry generates approximately 8% of global CO2 emissions. Faced with this challenge, industry and researchers are investigating ways to reduce the impact of carbon dioxide emissions generated by the cement industry.

[0005] A first solution led to the creation of a cement plant operating from a combination of alternative fuels based on waste and technologies related to the capture and storage of carbon emitted during cement production, to achieve zero-emission status. However, these solutions are not yet available on an industrial scale and require heavy investments.

[0006] The preferred route concerns research into substitutes for Portland cement, which is far too energy-intensive. Indeed, the development of alternative construction binders, requiring lower energy consumption for their production would reduce the energy footprint of the entire construction industry (Maddalena, et al, “Can Portland cement be replaced by low-carbon alternative materials? A study on the thermal properties and carbon emissions of innovative Cements”, Journal of Cleaner Production 186; 2018; 933-942).

[0007] For example, a new hydraulic binder has been proposed that is similar to Portland cement but includes secondary constituents such as ash formed during the combustion of coal in power plants. However, the secondary constituents (ash, pozzolan, blast furnace slag) generally represent a maximum of 35% of the mixture and this composite Portland cement then includes at least 50% clinker. This remains too high a clinker content to constitute a real low-carbon alternative to Portland cement.

[0008] Hydraulic binders or cements based on metakaolin have also been proposed. Metakaolin is a dehydroxylated alumina silicate of general composition Al2Si2O7, it constitutes a largely amorphous dehydration product of kaolinite, of general formula Al2(OH)4Si2O5 which exhibits a strong pozzolanic activity. In general, the pozzolanic activity of a material can be defined as the capacity of a material, not possessing binding properties, but which in finely divided form and in the presence of moisture, reacts chemically with calcium hydroxide at room temperature to form compounds possessing binding properties. Kaolinitic clays are widely available in the Earth's crust and a heat treatment (eg from 600 to 800°C for a short period called "flashed") leads to the dehydroxylation of the crystalline structure of kaolinite to give metakaolin.The mixture of lime or sodium hydroxide and metakaolin during the hydration of the cement will induce a pozzolanic reaction. This reaction improves the binding properties of metakaolin-based cements. Due to these properties, metakaolin-based construction materials have been proposed, including flashed metakaolin combined with sodium hydroxide, as described in document FR3034094.

[0009] Furthermore, the use of uncalcined kaolinite or more broadly of raw clay matrix has been proposed for cements with lower carbon footprints (NA Hadi, “Geo Polymerization of Kaolin and Metakaolin Incorporating NaOH and High Calcium Ash”, Earth Science Research Vol. 5, No. 1; 2016). However, these cements, as described in document FR3016376, either had physical properties, such as improved mechanical strength, reduced capillary absorption, or reduced permeability to liquids, that were too low, or required the addition of a portion of Portland cement to be able to have acceptable mechanical properties.

[0010] Thus, there is a need for new formulations of construction binders having a low carbon footprint while having mechanical properties at least equivalent or even superior to the mechanical properties of cements commonly used in the construction field, such as CEM I, CEM II, CEM III, CEM IV and CEM V cements defined by standard NF EN 197-1. [Technical problem]

[0011] The invention therefore aims to remedy the drawbacks of the prior art. In particular, the invention aims to propose a formulation for a construction binder making it possible, on the one hand, to obtain a construction material with mechanical properties at least equivalent to Portland cement, and on the other hand to improve the comfort of the inhabitants compared to a concrete formed from Portland cement.

[0012] The invention further aims to propose a method for manufacturing a construction binder making it possible to reduce the emission of greenhouse gases, such as carbon dioxide emitted during the preparation of such a binder, while preserving the suitable mechanical characteristics of said binder relating to its use in the field of construction. The invention further relates to the use of a construction binder for the production of construction elements, capable of improving the comfort of inhabitants compared to conventional concrete and in particular the hygrothermal properties of buildings. [Brief description of the invention]

[0013] To this end, the invention relates to a formulation for construction binder comprising, in dehydrated form, a raw clay matrix and a deflocculation agent.

[0014] Thus, this dehydrated formulation is intended to replace, totally or partially, conventional cements such as Portland cement, lime, or even calcium aluminate cement ("Calcium Sulfoaluminate Cement" - CSA, in English terminology). As will be shown below, this formulation makes it possible to achieve mechanical performance identical to Portland cement (class C 25 / 30) while reducing greenhouse gas emissions by 30 to 85%, and more generally by around 50%.

[0015] In addition, the presence of a raw clay matrix allows better hygrothermal transfer and therefore better cooling and health properties of the construction using a binder derived from this formulation.

[0016] According to other optional characteristics of the formulation: - the raw clay matrix contains at least one mineral species selected from: Kaolinite, Illite, Smectite, Bentonite, Chlorite, Montmorillonite, Muscovite, Hallocyte, Sepiolite, Attapulgite, Vermiculite and so-called interstratified clays which are complex combinations of several clays. The presence of one or more of these mineral species in the binder formulation makes it possible to obtain a cement and more broadly a construction material with good mechanical properties, i.e. mechanical properties equivalent to the mechanical properties of a construction material containing Portland cement. Preferably, the raw clay matrix contains at least one mineral species selected from: Kaolinite, Illite, Smectite and Bentonite. - it comprises at least 80% by weight of raw clay matrix, preferably between 80 and 99.5% by weight, more preferably between 90 and 99% by weight. Such a quantity of raw clay matrix makes it possible to improve the mechanical properties of the materials constructed from this formulation. - the deflocculation agent is selected from: - a non-ionic surfactant such as a polyoxyethylene ether, - an anionic agent such as an anionic agent selected from: alkylaryl sulfonates, amino alcohols, carbonates, silicates, fatty acids, humates (eg sodium humates), carboxylic acids, lignosulfonates (eg sodium lignosulfonates), polyacrylates, phosphates or polyphosphates such as sodium hexametaphosphate, sodium tripolyphosphate, sodium orthophosphate, carboxymethylcelluloses and mixtures thereof; - a polyacrylate such as a polyacrylate selected from sodium polyacrylate or ammonium polyacrylate; - an amine such as an amine selected from: 2-amino-2-methyl-l-propanol; mono-, di- or triethanolamine; isopropanolamines (l-Amino-2-propanol, diisopropanolamine and triisopropanolamine) and N-alkylated ethanolamines; or - their mixtures.

[0017] These deflocculation agents allow good dispersion of clays and are suitable for clay matrices that can be used in construction. - the deflocculation agent represents at least 0.5% by weight of the raw clay matrix, preferably between 0.5 and 20% by weight of the raw clay matrix, more preferably between 1 and 10% by weight. Such a concentration makes it possible to improve the mechanical properties of the materials constructed from this formulation. - it includes: • from 80% to 99.5% by weight of raw clay matrix, and • from 0.5% to 20% by weight of deflocculation agent.

[0018] Such a formulation for construction binder makes it possible, in the case where such a formulation is used in conjunction with an activation composition, to obtain mechanical properties equivalent to Portland cement.

[0019] The invention further relates to a construction binder comprising the constituents of the construction binder formulation according to the invention and an activation composition. The activation composition makes it possible to give the construction binder its mechanical properties of interest and in particular to bind the clay sheets together.

[0020] According to other optional characteristics of the construction binder: - the activation composition is an alkaline activation composition. The alkaline composition may for example comprise a compound having a pKa greater than or equal to 10, more preferably greater than or equal to 12, even more preferably substantially equal to 14. - The activation composition comprises metal oxides. In particular, the metal oxides are present at a content of at least 2% by weight of the composition, preferably at least 5% by weight of the composition, even more preferably at least 10% by weight of the composition. Such a concentration makes it possible to improve the mechanical properties of the materials constructed from this formulation. - the metal oxides are selected from: iron oxides such as FeO, Fe3O4, Fe2O3, Fe2O3, alumina A12O3, manganese(II) oxide MnO, titanium(IV) oxide TiO2 and their mixtures. - the activation composition contains cement. The cement may, for example, be a CEM I type cement. - it includes: • from 50% to 89% by weight of raw clay matrix, • from 1% to 15% by weight of deflocculation agent, and • from 10% to 49% by weight of activation composition.

[0021] These quantities make it possible to obtain mechanical properties equivalent to Portland cement while presenting a much lower carbon footprint.

[0022] The invention further relates to a method of preparing a construction binder comprising the following steps: - Prepare a clay suspension comprising at least a raw clay matrix, a deflocculation agent and water, - Adding an activating composition to the clay suspension, said activating composition possibly being an alkaline activating composition and / or comprising metal oxides, and - Mix to obtain a construction binder.

[0023] According to other optional characteristics of the method: - it comprises a step of mixing the clay suspension so as to obtain a deflocculated clay suspension and the activation composition is added after the mixing step. - the construction binder comprises at least 50% by weight of raw clay matrix, preferably between 50 and 80% by weight. - the deflocculation agent represents at least 0.25% by weight of the construction binder, preferably at least 0.5% by weight of the construction binder, more preferably between 0.5 and 10% by weight of the construction binder. - the activation composition is present at a content of at least 10% by weight of binder. For example, metal oxides are present at a content of at least 10% by weight of binder.

[0024] The invention further relates to a construction material such as a mortar, a coating, a plaster, an insulator, a lightweight concrete, a prefabrication element, comprising the construction binder according to the invention.

[0025] The construction material according to the invention may further comprise one or more fillers, the fillers being for example chosen from mineral fillers or plant fillers. The fillers may be any fillers known to those skilled in the art in the field of construction materials. In particular, they may be selected from recycled or non-recycled aggregates, powders, sand, gravel, gravel, and / or fibers. The fibers may in particular be fibers of plant origin such as sawdust, wood shavings and fibers, straw, flax, perlite, cork or even hemp shiv. Preferably, the construction material according to the invention further comprises fibers of plant origin.

[0026] The building material may also include pigments.

[0027] The construction material according to the invention may further comprise an expanding or foaming agent, such as aluminum powder.

[0028] According to another aspect, the invention relates to the use of the construction binder according to the invention, for the production of covering elements, in particular floor coverings, such as tiles, slabs, paving stones or borders, wall coverings, such as interior or exterior facade elements, facing tiles, cladding elements, or roof coverings of the tile type, for the production of extruded or molded construction modules, such as bricks, or for the production of various extruded shapes.

[0029] The invention relates to the use of the construction binder according to the invention, for the production of composite materials, such as construction panels of the prefabricated panel type, prefabricated blocks such as door lintels or window, prefabricated wall elements, or any other prefabricated building element.

[0030] The invention relates to the use of the construction binder according to the invention, for the production of insulation modules, such as partition panels, or lightweight insulating construction modules (with a density of less than 1.5 kg / L, preferably less than 1.2 kg / L, more preferably less than 1.0 kg / L, more preferably less than 0.7 kg / L)

[0031] The invention relates to the use of the construction binder according to the invention, for the production by additive manufacturing, such as by means of a 3D printer, of construction elements, buildings or houses, or decorative objects.

[0032] The invention relates to the use of the construction binder according to the invention in the form of a two-component system with either on the one hand the constituents in solid form, and on the other hand the constituents in liquid form, or the constituents in the form of two pastes, for the production of mastic, glue or sealing mortar.

[0033] Other advantages and characteristics of the invention will appear on reading the following description given by way of illustrative and non-limiting example, with reference to the appended Figures:

[0034] [Fig. 1] represents a diagram of the process for preparing a construction binder according to the invention. [Description of the invention]

[0035] In the remainder of the description, the term "% by weight" in relation to the raw clay matrix, the formulation, the binder or the construction material must be understood as being a proportion relative to the dry weight of the formulation, the binder or the construction material. The dry weight corresponds to the weight before the addition of water, for example, necessary for the formation of a construction binder.

[0036] The term “Dehydrated” within the meaning of the invention corresponds to a formulation comprising a reduced quantity of water and for example a water content of less than 20% by weight, preferably less than 10%, more preferably less than 5% and for example less than 1% by weight. The water content can be measured by any method known from the state of the art. It can for example be measured according to standard NF P 94 050 of September 1995 “Determination of the water content by weight of materials: Method by steaming”.

[0037] The term "clay matrix" means one or more rock materials based on hydrated silicates or aluminosilicates of lamellar structure, said clay matrix being composed of fine particles generally originating from the alteration of silicates with a three-dimensional framework, such as feldspars. A clay matrix may thus comprise a mixture of such rock materials which may, for example, consist of kaolinite, illite, smectite, bentonite, chlorite, vermiculite, metakaolin or mixtures thereof. The expression "raw clay matrix" corresponds, within the meaning of the invention, to a clay matrix which has not undergone a calcination step. In particular, that is to say, it has not undergone any prior heat treatment. For example, this corresponds to a clay matrix which has not undergone a temperature rise greater than 300°C, preferably greater than 200°C and more preferably a temperature greater than 150°C. Indeed, the raw clay matrix may undergo a heating step requiring a temperature rise generally substantially equal to 150°C but no calcination step.

[0038] The term "deflocculating agent" means any compound which, in aqueous suspension, will dissociate aggregates and colloids. Deflocculating agents have, for example, been used in the context of drilling or oil extraction to make clay more fluid and facilitate extraction or drilling.

[0039] The term "activation composition" means any composition having the function of accelerating the dispersion of an aluminosilicate source promoting the formation of stable hydrates with low solubility and the formation of a compact structure with these hydrates, thus increasing the mechanical resistance of the materials incorporating such an activation composition.

[0040] The term “substantially equal” within the meaning of the invention corresponds to a value varying by less than 20% compared to the compared value, preferably by less than 10%, even more preferably by less than 5%.

[0041] The inventor has developed a new formulation for a construction binder which could be advantageously, but not limited to, used as a replacement for Portland cement, lime or CSA.

[0042] A formulation according to the invention and more specifically a construction binder according to the invention have the advantage of having a carbon footprint at least twice as low as most of the construction binders, or hydraulic binders, most used in the world today (i.e. Portland Cement). Indeed, a construction binder according to the invention is mainly composed of a clay matrix, also called raw clay matrix, which has not undergone a calcination step, an energy-intensive step which also generates the emission of greenhouse gases and more particularly carbon dioxide.

[0043] In addition, a construction formulation or binder according to the invention has a lower clinker content than equivalent products and allows, with equivalent mechanical properties, to reduce CO2 emissions and production costs.

[0044] Advantageously, as will be presented in the examples, a construction binder according to the invention allows the manufacture of construction materials having mechanical properties at least equivalent to Portland cement and much superior to “low carbon” materials, such as those described previously.

[0045] Thus, according to a first aspect, the invention relates to a formulation for construction binder comprising, in dehydrated form, a raw clay matrix and a deflocculation agent.

[0046] As mentioned, the use of a raw clay matrix helps to reduce the environmental impact of the construction binder.

[0047] Deflocculation agents have already been used with clays. This is particularly the case in pottery and ceramics where the preparation of a slip in the liquid and undehydrated state may involve mixing a deflocculation agent with a clay matrix. This practice allows the clay to be fluidized to recover only the fine particles and is not intended or suitable for the preparation of a construction binder.

[0048] Here, without being limited by theory, the deflocculation agent can position itself at the interface of the layers constituting the raw clay matrix and destructure it. Thus, the use of a deflocculation agent will make it possible to obtain, from the raw clay matrix, a formulation comprising a destructured raw clay matrix and capable of forming, in the presence of an activation composition, a more efficient construction binder.

[0049] Such a formulation can be prepared extemporaneously or prepared on a production site and then possibly stored and then transported to the construction site.

[0050] Thus, the invention relates, for example, to a formulation for a construction binder, comprising a raw clay matrix and a deflocculation agent, which is stored and / or transported while awaiting its mixing with an activating composition, thus allowing the formation of a construction binder. In particular, the formulation can be stored in containers with a capacity of 0.5 L to 50 L.

[0051] We will present in detail the general and preferred characteristics of each of the constituents of the formulation according to the invention. Raw clay matrix

[0052] The raw clay matrix may for example comprise at least one mineral species selected from: Kaolinite, Illite, Smectite, Bentonite, Chlorite and Vermiculite.

[0053] Table 1 below presents the chemical characteristics of these mineral species.

[0054] [Tables 1] Matrix Clayey Raw Type of clay Composition Illite (K,H3O)(Al,Mg,Fe)2(Si,Al)4O10[(OH)2,(H2O)] Smectite / M ontmorillonite (Na,Ca)o.3(Al,Mg)2Si4010(OH)2, n H2O Kaolinite Al2Si2O5(OH)4 Metakaolin Anhydrous Al2Si2O5(OH)4 Bentonite (Na,Ca)o.3(Al,Mg)2Si4010(OH)2

[0055] Preferably, a formulation according to the invention comprises at least 80% by weight of raw clay matrix, more preferably at least 90% by weight of raw clay matrix. Indeed, the formulation for construction binder according to the invention has the advantage of being able to comprise a high quantity of raw clay matrix without this altering the mechanical properties of the construction materials resulting therefrom.

[0056] Furthermore, preferably, a formulation according to the invention comprises at most 98% by weight of raw clay matrix, more preferably at most 96% by weight of raw clay matrix. Indeed, the formulation for construction binder according to the invention also comprises at least one deflocculation agent then limiting the proportion of raw clay matrix in the formulation.

[0057] Thus, in particular, a formulation according to the invention may comprise between 80 and 99.5% by weight of raw clay matrix, preferably between 90 and 99% by weight or between 80 and 98% by weight of raw clay matrix, more preferably between 85 and 97% by weight of raw clay matrix, and even more preferably between 90 and 96% by weight of raw clay matrix. Deflocculation agent

[0058] Many compounds can act as deflocculation agents and many are generally known to those skilled in the art.

[0059] In the context of the invention, the deflocculation agent is in particular a non-ionic surfactant such as a polyoxyethylene ether. The polyoxyethylene ether may for example be selected from: a lauryl poly(oxyethylene) ether.

[0060] The deflocculation agent may also be an anionic agent such as an anionic surfactant. In particular, the anionic agent may be selected from: alkylaryl sulfonates, amino alcohols, carbonates, silicates, fatty acids, humates (e.g. sodium humates), carboxylic acids, lignosulfonates (e.g. sodium lignosulfonates), polyacrylates, phosphates or polyphosphates such as sodium hexametaphosphate, sodium tripolyphosphate, sodium orthophosphate, carboxymethylcelluloses and mixtures thereof.

[0061] The deflocculation agent may also be a polyacrylate. It may then be selected, for example, from sodium polyacrylate and ammonium polyacrylate.

[0062] The deflocculation agent may also be an amine selected for example from: 2-amino-2-methyl-l-propanol; mono-, di- or triethanolamine; isopropanolamines (l-Amino-2-propanol, diisopropanolamine and triisopropanolamine) and N-alkylated ethanolamines.

[0063] The deflocculation agent may also be a silicate such as sodium silicate, sodium metasilicate or sodium trisilicate.

[0064] Alternatively, the deflocculation agent may be a mixture of compounds, such as a mixture comprising at least two compounds selected from: non-ionic surfactant, anionic agent, polyacrylate, amine and organophosphorus compound.

[0065] In particular, the deflocculation agent may be a mixture of sodium silicate and sodium carbonate.

[0066] Preferably, the deflocculation agent is selected from: a lignosulphonate (eg sodium lignosulphonate), a polyacrylate, a humate and mixtures thereof.

[0067] The deflocculation agent is preferably in the form of a salt.

[0068] However, the invention cannot be limited to the deflocculating agents mentioned above; any type of deflocculating agent known to those skilled in the art can be used instead of the said deflocculating agents mentioned above.

[0069] In particular, the deflocculation agent represents at least 0.5% by weight of the raw clay matrix, preferably at least 1% by weight of the raw clay matrix, more preferably at least 2% by weight of the raw clay matrix, even more preferably at least 3% by weight of the raw clay matrix, and for example at least 4% by weight of the raw clay matrix. Indeed, with such concentrations of deflocculation agent, the binder formulation according to the invention can then be used in combination with an activating composition to form a material with advantageous mechanical properties.

[0070] Furthermore, the deflocculation agent represents at most 20% by weight of the raw clay matrix, preferably at most 10% by weight of the raw clay matrix. Indeed, too high a concentration is not necessary to form a material with advantageous mechanical properties.

[0071] In particular, the deflocculation agent represents between 0.5 and 20% by weight of the raw clay matrix, preferably between 1 and 10% by weight of the raw clay matrix, more preferably between 3 and 10% by weight of the raw clay matrix and even more preferably between 4 and 10% by weight of the clay matrix. raw.

[0072] According to another aspect, the invention relates to a construction binder comprising the constituents of the construction binder formulation according to the invention and an activating composition.

[0073] It is the addition of the activation composition, in conjunction with the raw clay matrix and the deflocculating agent, which will give the construction binder its mechanical properties of interest.

[0074] The construction binder can advantageously take the form of a two-component multi-component system, that is to say, it can comprise its constituents, namely raw clay matrix, deflocculating agent and activation composition, in a juxtaposed form.

[0075] In particular, before a mixing step necessary for the effective use of the construction binder, the construction binder may be prepared in such a way that the activating composition is not in contact with the raw clay matrix and / or the deflocculation agent. Such a characteristic has the advantage of being able to improve the stability of the construction binder before its use.

[0076] For example, the construction binder may correspond to the combination of a mixture corresponding to the binder formulation according to the invention and an activation composition placed in another container. In a two-component or multi-component system, either the constituents may not all be in the same form (e.g. liquid, solid or paste) or the constituents are in the form of a paste or they are placed in different containers.

[0077] Without being limited by theory, the activation composition will allow the formation of a network between the clay sheets which will provide its mechanical properties to the construction binder according to the invention.

[0078] The activation composition is for example present at a content of at least 10% by weight of the construction binder, preferably at least 15% by weight of the construction binder, more preferably at least 20% by weight of the construction binder, even more preferably at least 25% by weight of the construction binder, and for example at least 30% by weight of the construction binder.

[0079] Furthermore, the activating composition may represent at most 50% by weight of the construction binder, preferably at most 45% by weight of the construction binder, and more preferably at most 40% by weight of the construction binder.

[0080] In particular, the activation composition may represent between 10 and 50% by weight of the construction binder, preferably between 15 and 50% by weight of the construction binder, more preferably between 1 and 10% by weight of the construction binder, even more preferably between 2 and 8% by weight of the construction binder and for example between 2 and 5% by weight of the construction binder.

[0081] In particular, the activation composition may comprise metal oxides and / or be an alkaline activation composition.

[0082] Preferably, the metal oxides are transition metal oxides.

[0083] More preferably, the metal oxides are selected from: oxides iron such as FeO, Fe3O4, Fe2O3, Fe2O3, alumina A12O3, manganese (II) oxide MnO, titanium (IV) oxide TiO2 and mixtures thereof.

[0084] The metal oxides may preferably come from a composition of blast furnace slags, for example formed during the production of cast iron from iron ore.

[0085] The metal oxides are present at a content of at least 2% by weight of the construction binder, preferably at least 5% by weight of the construction binder, more preferably at least 10% by weight of the construction binder.

[0086] When the activating composition is an alkaline activating composition. The alkaline composition may preferably comprise a compound having a pKa greater than or equal to 10, more preferably greater than or equal to 12, even more preferably substantially equal to 14.

[0087] The alkaline composition may, for example, comprise an organophosphorus compound such as sodium tripolyphosphate designated by the acronym NaTPP.

[0088] In particular, the activating composition may comprise a mixture of sodium hydroxide and sodium silicate.

[0089] Advantageously, the activation composition may be an alkaline activation composition further comprising metal oxides. As will be shown in the examples, construction binders prepared from such an activation composition have good mechanical properties. Thus, preferably, the activation composition may comprise metal oxides and at least one compound having a pKa greater than or equal to 10.

[0090] In addition to the raw clay matrix, the deflocculating agent and the activating composition, the construction binder may contain flashed or non-flashed metakaolin, cement, lime and / or plaster.

[0091] Despite the possible presence of such additives, preferably, the raw clay matrix represents at least 30% by weight of the construction binder, preferably at least 40% by weight of the construction binder, preferably between 40 and 80% by weight, even more preferably between 50 and 60% by weight.

[0092] Similarly, the deflocculation agent may represent at least 0.25% by weight of the construction binder, preferably at least 0.5% by weight of the construction binder, more preferably at least 1% by weight of the construction binder, even more preferably at least 1.5% by weight of the construction binder, and for example at least 2% by weight of the construction binder.

[0093] Furthermore, the deflocculation agent may represent at most 20% by weight of the construction binder, preferably at most 15% by weight of the construction binder, and more preferably at most 10% by weight of the construction binder.

[0094] In particular, the deflocculation agent may represent between 0.25 and 10% by weight of the construction binder, preferably between 0.5 and 10% by weight of the construction binder, more preferably between 1 and 10% by weight of the construction binder, even more preferably between 2 and 8% by weight of the construction binder and for example between 2 and 5% by weight of the construction binder.

[0095] In a particular embodiment, a construction binder according to the invention comprises: - from 30% to 80% by weight of raw clay matrix, - from 1% to 10% by weight of deflocculation agent, and - from 10% to 50% by weight of an activation composition.

[0096] Preferably, a construction binder according to the invention comprises: - from 50% to 75% by weight of raw clay matrix, - from 1% to 10% by weight of deflocculation agent, and - from 15% to 50% by weight of an activation composition.

[0097] More preferably, a construction binder according to the invention comprises: - from 50% to 70% by weight of raw clay matrix, - from 2% to 5% by weight of deflocculation agent, and - from 15% to 45% by weight of an activation composition.

[0098] More preferably, a construction binder according to the invention comprises: - from 50% to 60% by weight of raw clay matrix, - from 2% to 5% by weight of deflocculation agent, and - from 25% to 45% by weight of metal oxides.

[0099] Even more preferably, a construction binder according to the invention comprises: - from 30% to 80% by weight of raw clay matrix, - from 1% to 10% by weight of deflocculation agent, - from 10% to 40% by weight of metal oxides, and - from 2% to 15% by weight of a strong base.

[0100] Furthermore, the mass ratio of water to dry matter of the composition referred to here as construction binder is controlled and is preferably less than 1, advantageously substantially equal to 0.6.

[0101] According to another aspect, the invention relates to a method for preparing a construction binder. Such a method according to the invention, illustrated in [Fig.l], has the advantage of being a so-called low-carbon method, that is to say one whose greenhouse gas emissions, such as in particular carbon dioxide emissions, are reduced in relation to greenhouse gas emissions from known construction binder preparation processes. Such reductions in greenhouse gas emissions are linked in particular to the absence of a calcination step which is particularly energy-intensive.

[0102] The method comprises in particular the preparation 110 of a clay suspension comprising at least one raw clay matrix, a deflocculation agent and water. As previously, the raw clay matrix may comprise at least one mineral species selected from: Kaolinite, Illite, Smectite, Bentonite, Chlorite, Montmorillonite, Muscovite, Hallocyte, Sepiolite, Attapulgite, Vermiculite and so-called interstratified clays which are complex combinations of several clays.

[0103] During the preparation step 110 of the suspension, the water can be added so that the ratio between the mass of water and the mass of construction binder is less than 1 and for example between 0.4 and 0.8. In addition, the water can advantageously be added after the raw clay matrix and the deflocculation agent have been dry mixed.

[0104] Advantageously, the raw clay matrix used during the step 110 of preparing the clay suspension may come from earth excavated near the construction site. Thus, the method of preparing the construction binder may comprise a step of excavating earth comprising a raw clay matrix prior to the preparation 110 of a clay suspension. Furthermore, in this case, the method may comprise a step of preparing the excavated earth, said preparation being able for example to comprise: drying, grinding, sieving, storage.

[0105] Thus, the preparation of construction binder according to the invention can allow the preparation of a site concrete made at least in part from raw material originating from the construction site. Such characteristics further contribute to reducing the environmental footprint of the concrete produced.

[0106] Preferably, the method according to the invention may comprise, following the preparation of the clay suspension, a step 120 of mixing the clay suspension so as to obtain a dispersed or deflocculated clay suspension.

[0107] This step of mixing 120 of the clay suspension can advantageously but not limitatively be carried out in a device selected from: a mixer and a mixer truck or more generally within any device suitable for mixing a clay suspension for the production of a construction binder.

[0108] This step of mixing 120 the clay suspension, before adding the activation composition, can be carried out over a period of at least 10 seconds, preferably at least 30 seconds, more preferably at least 60 seconds.

[0109] Furthermore, this step of mixing 120 the clay suspension, before adding the activation composition, can be carried out over a period of at most 24 hours, preferably at most 12 hours, more preferably at most 6 hours.

[0110] The method also comprises a step 130 of adding an activation composition to the clay suspension. As detailed previously, the activation composition may comprise metal oxides and / or be an alkaline activation composition.

[0111] The method comprises a step 140 of homogenization, or mixing, so as to obtain a construction binder.

[0112] Before, concomitantly or after the addition of the activation composition, the method according to the invention may comprise the addition of additives or materials making it possible to modify the mechanical properties of the final construction material.

[0113] The added materials may, for example, be recycled or non-recycled aggregates, chosen from fillers, powders, sand, gravel, gravel, and / or fibers, and possibly pigments.

[0114] The method may also include the addition of a plasticizer. The plasticizer may, for example, be a polyacrylate, a polynaphthalene sulfonate, a polycarboxylate, or a polyphosphonate.

[0115] The method may also include the addition of fibers. The fibers are, for example, selected from: plant fibers such as cotton, linen, hemp, cellulose, bamboo, miscanthus fibers, synthetic fibers such as metal, glass, carbon, polypropylene fibers and their mixtures. The presence of fibers can allow the formation of a construction material with improved mechanical and insulating properties.

[0116] The method may also include the addition of aggregates. The aggregates are, for example, selected from: gravel, crushed concrete, recycled concrete and mixtures thereof.

[0117] The method may also include the addition of an additive. The additive is, for example, selected from: a synthetic or natural rheological maintaining agent, an anti-shrinkage agent, a water-retaining agent, an air-entraining agent, a synthetic resin and mixtures thereof.

[0118] The preparation of a construction binder according to the invention will include in particular the addition of sand and water. The sand may optionally come from excavated material, particularly in the case of “site” concrete. The sand may also be desert sand.

[0119] The construction materials obtained can for example be selected from: mortars, coatings, or plasters.

[0120] Thus, according to another aspect, the invention relates to a construction material formed from the construction binder according to the invention.

[0121] Furthermore, the invention relates to a construction binder obtained from the method according to the invention. The invention relates to a construction material obtained from the method according to the invention.

[0122] The invention allows in particular the manufacture of: - insulating construction material: from a construction binder according to the invention with the addition of light aggregates of the “plant or porous” type; - lightweight concrete: from a construction binder according to the invention with the addition of a foaming agent such as aluminum powder. This will trap air in the material and improve its insulating properties; - Prefabrication elements: manufacture of concrete blocks or slabs in the factory from the construction binder according to the invention; and - Insulation modules.

[0123] Thus, the invention also relates to the use of the construction binder according to the invention, for the production of covering elements, for the production of extruded or molded construction modules, or more generally for the production of various extruded shapes.

[0124] The covering elements may, for example, be selected from floor coverings, such as tiles, slabs, paving stones or borders, wall coverings, such as interior or exterior facade elements, facing tiles, cladding elements, or roof coverings of the tile type. The extruded or molded construction modules, for their part, are, for example, bricks.

[0125] The invention also relates to the use of the construction binder according to the invention, for the production of composite materials, prefabricated blocks,

[0126] Composite materials are, for example, construction panels of the prefabricated panel type, while prefabricated blocks are, for example, door or window lintels, prefabricated wall elements, or any other prefabricated construction element.

[0127] The invention also relates to the use of the construction binder according to the invention, for producing insulation modules, such as partition panels, or lightweight insulating construction modules. These insulation modules have, for example, a density of less than 1.5 kg / L, preferably less than 1.2 kg / L, more preferably less than 1.0 kg / L and even more preferably less than 0.7 kg / L.

[0128] The invention also relates to the use of the construction binder according to the invention, for implementing additive manufacturing. In particular, the implementation of additive manufacturing can be carried out by means of an automated 3D construction system such as a 3D printer. Such additive manufacturing can allow the manufacture of construction elements, buildings or houses, or even decorative objects.

[0129] As illustrated by the examples below, the present invention provides a solution based on a mixture of raw clay matrix, deflocculating agent and activating composition to provide a construction binder with mechanical properties similar to the standard while having a reduced carbon footprint. EXAMPLES: Preparation of a construction binder:

[0130] In all the examples presented below, the formulations according to the invention are prepared according to an identical protocol, namely that a dry premix is ​​made between a raw clay matrix and a deflocculating agent in predetermined quantities, then water is added and the solution is mixed at low speed, that is to say substantially at six hundred revolutions per minute for thirty seconds. Then, an activating composition is added to the premix and then the premix is ​​mixed at high speed, that is to say at approximately one thousand five hundred revolutions per minute for three minutes.

[0131] The mass ratio of water to dry matter in the composition (also called construction binder) is adjusted to a value substantially equal to 0.6.

[0132] The construction binder thus formed is then poured into a mold and left to mature at room temperature, i.e. approximately 20 degrees Celsius for twenty-eight days.

[0133] Methodology for measuring the mechanical properties of construction binders:

[0134] Once maturation is complete, the construction binder is removed from the mold and the mechanical strength is measured. The mechanical strength of a construction binder is understood to mean its compressive strength, such compression being measured according to standard NF EN 196-1, for a cylinder 40 millimeters in diameter and 80 millimeters in height and is expressed in Mega Pascal (MPa).

[0135] Comparison of the construction binders according to the invention with known construction binders:

[0136] Table 2 below shows, for different types of construction binders, known formulations and a formulation according to the invention. The mass of the components relating to each formulation is expressed as a percentage of the total mass of the construction binder (dry weight).

[0137] [Tables2] Formulations Binder CEM1 (Reference e) HP2A1 (Reference e) CMT (Reference e) MUP1 Raw Clay Matrix 0.0% 0.0% 75.0% 55.0% Deflocculating Agent 0.0% 0.0% 0.0% 3.0% Activation Composition 0.0% 65.0% 10.0% 42.0% Metakaolin 0.0% 35.0% 0.0% 0.0% Cement CEM1 100.0% 0.0% 15.0% 0.0% Compressive Strength (M Pa) 45 42 25 45 Estimated Carbon Footprint High Medium Medium Low

[0138] Thus, Table 2 presents the mechanical strengths of known construction binders (CEM1, HP2A1, CMT binder) and not forming part of the invention, such as the CEM1 type construction binder better known under the name of “Portland” cement whose compressive strength is of the order of 45 MPa.

[0139] The HP2A1 formulation can be obtained by following the teachings of patent application FR3034094. The HP2A1 type construction binder comprises 35% by weight of Metakaolin obtained by calcination of kaolin, 65% by weight of an activation composition. Thus the mechanical resistance relative to such a construction binder, of the order of 42 MPa, is lower than the resistance of the Portland type construction binder.

[0140] Finally, the CMT construction binder, obtained by following the teachings of patent application FR3016376, comprises 75% by weight of raw clay matrix, 10% by weight of an activation composition comprising in particular lime and 15% by weight of Portland type cement. The mechanical strength associated with such a binder comprising a majority of raw clay matrix is ​​of the order of 25 MPA and therefore has a compressive strength significantly lower than that of Portland or HP2A1 type construction binders.

[0141] Table 2 also shows a MUP1 formulation according to the invention. It is important to note that this formulation comprising 3% deflocculating agent, although comprising a majority of raw clay matrix, has a mechanical resistance identical to the mechanical resistance of Portland cement. Importance of deflocculating agent

[0142] Table 3 below shows a known formulation HP2A_X02 and a formulation according to the invention MUP2.

[0143] [Tables3] Formulations HP2A2 (Reference) MUP2 Raw Clay Matrix 54% 51% Deflocculating Agent 0% 3% Alkaline Silicate Solution 23% 16% Metakaolin 18% 20% LHF 5% 10% Compressive Strength (M Pa) 27 43

[0144] The HP2A2 type construction binder comprises 54% by weight of raw clay matrix, 23% by weight of an activation composition (alkaline silicate solution), 18% by weight of metakaolin and 5% of LHF. Such a formulation can in particular be derived from the teaching of patent application FR3034094. The mechanical strength associated with such a binder is of the order of 27 MPa.

[0145] On the contrary, the MUP2 binder obtained according to the invention and comprising a substantially identical composition except for the presence of a 3% deflocculating agent has a mechanical strength of 43 MPa. Such strength can be considered equivalent to that of a Portland Cement.

[0146] Table 4 below shows the formulation according to the invention already presented MUP1 and an equivalent formulation to which the deflocculating agent has not been added.

[0147] [Tables4] Formulations MUP1 CMT2 (Reference) Raw Clay Matrix 55.0% 57.1% Deflocculating Agent 3.0% 0.0% Activation Composition 41.5% 42.9% Compressive Strength (M Pa) 45 25

[0148] This comparison shows that a formulation according to the invention can achieve a mechanical strength of 45 MPa while the same formulation without deflocculating agent (CMT2) only has a mechanical strength of 25 MPa. As described previously, the presence of a deflocculating agent in combination with the raw clay matrix and the activation composition makes it possible to improve the mechanical strength of a construction binder.

[0149] Use of a combination of metal oxides and an alkaline activating composition:

[0150] Table 5 below details the formulation of several construction binders according to the invention. These construction binders differ in particular in that some comprise an alkaline activation composition (a NaTPP solution in this case) and others Portland cement.

[0151] [Tables5] Formulations MUP1 MUP3 MUP4 MUP5 Raw Clay Matrix 55.3% 54.6% 54.0% 51.3% Deflocculating Agent 3.2% 2.7% 3.1% 2.9% LHF 38.6% 17.5% 31.9% 18.8% NaTPP 2.9% 0.0% 11.0% 0.0% Cement CEM1 0.0% 25.2% 0.0% 27.0% Compressive Strength (MPa) 45 41 45 42

[0152] Table 5 shows that the formulations comprising a mixture: - blast furnace slag (BFS) which contains metal oxides and - sodium tripolyphosphate

[0153] have mechanical resistances at 45 MPa, identical to Portland cement.

[0154] Equivalent formulations in which the alkaline activation composition has been replaced by CEM1 cement have sufficient but slightly lower mechanical strengths.

[0155] Concrete formulation from a construction binder according to the invention:

[0156] Table 6 below details the formulation of several concretes including a concrete reference concrete formed from Portland cement (B-Portland) and concretes formed from construction binder according to the invention (MUP_BA1, MUP_BA2, MUP_BA3). These concretes differ in particular by the nature of the raw clay matrix, by the nature of the deflocculating agent and by the activation compositions used.

[0157] [Tableauxô] B-Portla nd MUP_BA1 MUP_BA2 MUP_BA3 Cement CEM I 52.5 N kg / m3 (%m / lia nt) 240 (100%) 84 (26%) 0 0 Argile Nature / aquitaine kaolinite bentonite kg / m3 (%m / lia nt) 165 (55%) 178 (54%) Deflocculating agent Nature / sodium humides lignosulfonate sodium polyacrylate kg / m3 (%m / lia nt) 0 10 (3%) 10 (3%) 10 (3%) Activation composition Nature / LHF LHF (40%) + NaOH + Nature (27%) NaTTP (26%) kg / m3 (%m / lia nt) 0 54 (16%) 101 (31%) 141 (43%) Metakaolin kg / m3 (%m / lia nt) 0 0 54 (16%) 0 Superplasticizer Nature Time 1 2 Time 12 Time 12 kg / m 2.64 2.64 2.64 Sand 0-4 kg / m3 900 900 900 900 Granules 4-12 kg / m3 780 780 780 780 Water kg / m2 38 39 41

[0158] As shown in Table 6, the concretes according to the invention have compressive strengths equivalent to the compressive strengths obtained with a concrete formed with Portland cement. Thus, the present invention makes it possible to form a low-carbon construction binder, from a raw clay matrix, having sufficient mechanical properties to make it a construction material meeting the majority of the sector's needs.

Claims

Claims

1. A construction binder comprising a raw clay matrix, a deflocculation agent and further an activating composition, said binder comprising metal oxides at a content of at least 10% by weight of the binder and the activating composition is an alkaline activating composition comprising a compound having a pKa greater than or equal to 10, more preferably greater than or equal to 12, even more preferably substantially equal to 14.

2. Construction binder according to claim 1, characterized in that the raw clay matrix comprises at least one mineral species selected from: Kaolinite, Illite, Smectite, Bentonite, Chlorite, Montmorillonite, Muscovite, Hallocyte, Sepiolite, Attapulgite, Vermiculite and so-called interstratified clays which are complex combinations of several clays.

3. Construction binder according to one of claims 1 or 2, characterized in that the deflocculation agent is selected from: - a non-ionic surfactant such as a polyoxyethylene ether; - an anionic agent such as an anionic agent selected from: alkylaryl sulfonates, amino alcohols, carbonates, silicates, fatty acids, humates (eg sodium humates), carboxylic acids, lignosulfonates (egsodium lignosulfonates), polyacrylates, phosphates or polyphosphates such as sodium hexametaphosphate, sodium tripolyphosphate, sodium orthophosphate, carboxymethylcelluloses and mixtures thereof; - a polyacrylate such as a polyacrylate selected from sodium polyacrylate or ammonium polyacrylate; - an amine such as an amine selected from: 2-amino-2-methyl-l-propanol; mono-, di- or triethanolamine; isopropanolamines (l-Amino-2-propanol, diisopropanolamine and triisopropanolamine) and N-alkylated ethanolamines; or - mixtures thereof.

4. Construction binder according to any one of the preceding claims, characterized in that the raw clay matrix, the deflocculating agent and the activating composition form a two-component or multi-component system.

5. Construction binder according to any one of claims 1 to 4, characterized in that the metal oxides are selected from: iron oxides such as FeO, Fe3O4, Fe2O3, alumina A12O3, manganese(II) oxide MnO, titanium(IV) oxide TiO2 and mixtures thereof.

6. Construction binder according to any one of claims 1 to 5, characterized in that the metal oxides come from a composition of blast furnace slag, for example formed during the production of cast iron from iron ore.

7. Construction binder according to any one of the preceding claims, characterized in that the activating composition comprises cement.

8. Construction binder according to any one of the preceding claims, characterized in that the raw clay matrix represents at least 30% by weight of the construction binder.

9. Construction binder according to any one of the preceding claims, characterized in that it comprises: - from 50% to 89% by weight of raw clay matrix, - from 1% to 15% by weight of deflocculation agent, and - from 10% to 49% by weight of activation composition.

10. Construction binder according to any one of claims 1 to 8, characterized in that it comprises: - from 30% to 80% by weight of raw clay matrix, - from 1% to 10% by weight of deflocculation agent, - from 10% to 40% by weight of metal oxides, and - from 2% to 15% by weight of a strong base.

11. Construction binder according to any one of claims 1 to 8, characterized in that the deflocculation agent represents at least 0.5% by weight of the raw clay matrix.

12. Construction binder according to any one of claims 1 to 8, characterized in that the deflocculation agent represents at least 1% by weight of the raw clay matrix.

13. Construction binder according to any one of claims 1 to 12, characterized in that said construction binder comprises at least 80% by weight of raw clay matrix.

14. A method (100) of preparing a construction binder comprising the following steps: - Prepare (110) a clay suspension comprising at least one raw clay matrix, a deflocculation agent and water, - Add (130) an activation composition to the clay suspension, said activation composition is an alkaline activation composition comprising a compound having a pKa greater than or equal to 10, more preferably greater than or equal to 12, even more preferably substantially equal to 14, and - Mix (140) so as to obtain a construction binder, said construction binder further comprising at least 10% by weight of metal oxides.

15. Preparation method according to claim 14, characterized in that it comprises a step of mixing (120) the clay suspension so as to obtain a deflocculated clay suspension and in that the activation composition is added after the mixing step (120).

16. Construction material such as a mortar, a coating, a plaster, an insulator, a lightweight concrete, a prefabrication element, comprising the construction binder according to any one of claims 1 to

17. read. Construction material according to claim 16, characterized in that it further comprises one or more fillers, the fillers being for example chosen from mineral fillers or vegetable fillers.

18. Construction material according to one of claims 16 or 17, characterized in that it further comprises an expanding or foaming agent, such as aluminum powder.

19. Use of the construction binder according to any one of claims 1 to 13, for the production of covering elements, in particular floor coverings, such as tiles, slabs, paving stones or borders, wall coverings, such as interior or exterior facade elements, facing tiles, cladding elements, or roof coverings of the tile type, for the production of extruded or molded construction modules, such as bricks, or for the production of various extruded shapes.

20. Use of the construction binder according to any one of claims 1 to 13, for the production of composite materials, such as construction panels of the prefabricated panel type, prefabricated blocks such as door or window lintels, prefabricated wall elements, or any other prefabricated building element.

21. Use of the construction binder according to any one of claims 1 to 13, for the production of insulation modules, such as partition panels, or lightweight insulating construction modules (with a density of less than 1.5 kg / L, preferably less than 1.2 kg / L, more preferably less than 1.0 kg / L, more preferably less than 0.7 kg / L)

22. Use of the construction binder according to any one of claims 1 to 13, for the production by additive manufacturing, such as by means of a 3D printer, of construction elements, buildings or houses, or decorative objects.

23. Use of the construction binder according to any one of claims 1 to 13, in the form of a two-component system with either on the one hand the constituents in solid form, and on the other hand the constituents in liquid form, or the constituents in the form of two pastes, for the production of mastic, glue or sealing mortar.

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