LOW CARBON CONSTRUCTION BINDER AND ASSOCIATED BUILDING MATERIAL

Abstract

The invention relates to a construction binder comprising: - 35% to 65% by weight of clinker, - 5% to 30% by weight of a calcined clay matrix, - 5% to 30% by weight of a raw clay matrix, and - 0.05% to 5% by weight of a deflocculating agent; and the mass ratio of the raw clay matrix to the calcined clay matrix is ​​0.2 to 7. The invention further relates to a construction material comprising a construction binder according to the invention.

Description

Title of the invention: LOW CARBON CONSTRUCTION BINDER AND ASSOCIATED BUILDING MATERIAL technical field

[0001] The invention relates to the field of construction and more particularly to that of low-carbon construction materials. In particular, it relates to a low-carbon construction binder comprising a raw clay matrix and a calcined clay matrix. Furthermore, the invention relates to a construction material produced from a construction binder according to the invention. Previous technique

[0002] Below, we describe the prior art known from which the invention was developed.

[0003] Cement is the second most consumed resource in the world, with over 4 billion tons produced annually worldwide. This consumption is constantly increasing, driven by the growing demand for housing and infrastructure. Cement is notably used in the manufacture of masonry elements that rely on cementitious materials as binders. Due to the ongoing development of new infrastructure in most countries of the world, there is a continuous demand for the supply of construction binders, particularly mineral resources for the production of cements, notably Portland cement. However, the production and use of Portland cement is associated with a high environmental footprint. The cement used in construction is generally Portland cement. It is a hydraulic binder that, when mixed with water, hardens and sets.After hardening, cement retains its strength and stability, even when exposed to water. A wide variety of cements are used worldwide. However, all conventional cements contain clinker, with percentages ranging from 5% for some blast furnace cements to a minimum of 95% for Portland cement, which is currently the most widely used cement in the world. Clinker is produced by firing a mixture composed of approximately 80% limestone and 20% aluminosilicates (such as clays). This firing process, called clinkerization, is generally carried out at temperatures exceeding 1200°C, making cement production a highly energy-intensive process. Furthermore, the chemical conversion of limestone into lime also releases carbon dioxide. Consequently, the cement industry generates approximately 8% of global CO2 emissions.

[0004] Indeed, it is estimated that the manufacture of a Portland-type construction binder generates on average 0.8 kg of CO2 per kg of Portland cement clinker produced. Various solutions have therefore been developed to try to replace, at least partially, certain components of the construction binders used in the production of Portland-type cements. These solutions primarily aim to reduce the carbon footprint.

[0005] A first solution, described in document no. EP3274315, relates to a construction material composition that allows the use of readily available and reactive materials, has a low environmental impact, and does not require lengthy and costly heat treatment. To this end, the construction material composition comprises a matrix containing mainly a compound based on "flash-fired" metakaolin, that is, metakaolin obtained by the rapid calcination of powdered clay at a temperature between 600°C and 900°C for a few seconds, followed by rapid cooling, and an alkaline activation solution. This composition further comprises a mass proportion of cement or clinker of less than 10%, while the alkaline activation solution comprises a source of sodium or potassium silicate and an alkaline base.The relative proportions of the activation solution and the matrix are such that the total sum in moles of sodium silicate and alkali base of the activation solution is between 3.5 and 5.5 mol / kg of matrix and the alkali activation solution has an overall sodium silicate to alkali base molar ratio between 1.25 and 1.65.

[0006] A second solution, described in document no. W02010130511, proposes a construction material comprising at least 65% by weight of Portland cement clinker, a calcined clay produced at a temperature between 500°C and 900°C and a carbonate ground to a specific surface area of ​​3000 - 15000 cm2 / g in which the weight ratio of the calcined clay material to the carbonate material is between 0.25 and 3. This construction material makes it possible to maintain a high mechanical strength, compared to Portland cement, and to reduce CO2 emissions during cement production.

[0007] Although these solutions allow the production of construction materials with mechanical strengths similar to those of Portland cement, such as CEM1 or CEM2 Portland cement, the composition of the construction binders used in these materials still requires excessive amounts of calcined components, such as calcined clays and / or Portland cement clinker. Therefore, the carbon footprint of these construction materials can still be improved. However, the main challenges lie in maintaining compressive strength at an early age (at 1 day) but also at 28 days, a rheology close to that of Portland cement type CEM 2 while reducing the carbon footprint of the construction material produced.

[0008] The invention aims to overcome the drawbacks of the prior art. In particular, the invention aims to provide a low-carbon construction binder with an improved carbon footprint and energy balance compared to prior art construction binders, while ensuring compressive strength and rheology close to those of CEM 2 type Portland cement.

[0009] The invention further aims to provide a low carbon construction material made from a construction binder according to the invention, said construction material having a compressive strength at least equivalent to that of Portland cement, an improved carbon and energy footprint compared to prior art construction materials. Summary of the invention

[0010] The invention aims to overcome these drawbacks.

[0011] The invention relates in particular to a construction binder comprising - 35% to 65% by weight of clinker, - 5% to 30% by weight of a calcined clay matrix, - from 5% to 30% by weight of a raw clay matrix, and - from 0.05% to 5% by weight of a deflocculating agent; and in that the mass ratio of the raw clay matrix to the calcined clay matrix is ​​from 0.2 to 7.

[0012] The combination of raw clay and, as a partial substitute, calcined clay reduces the carbon footprint compared to a conventional LC3-type construction binder, firstly by limiting the required content of calcined constituents, such as CEM 1-type cement or calcined clay matrix, and secondly by reducing the energy input needed to produce a construction material. Furthermore, a construction binder according to the invention also ensures the maintenance of an early-age compressive strength greater than 5 MPa, as well as improved rheology of the construction binder in its fresh state.

[0013] According to other optional features, the construction binder according to the invention may include the following features taken alone or in combination: - Up to 25% by weight of a precursor. - The precursor includes a source of calcium carbonate. - The precursor is selected from: blast furnace slag, fly ash, silica fume, a natural or synthetic limestone filler, a siliceous filler, diatomite. - Calcium carbonate has a D50 between 0.1 micron and 5 microns. - Calcium carbonate includes vaterite. - The deflocculating agent is an organic deflocculating agent. - The clay matrix has a D50 approximately equal to 10 pm. - 35% by weight of clinker. - At most 65% by weight of clinker. - Between 35% and 50% by weight of clinker. - 20% by weight of precursor. - Between 15% and 20% by weight of precursor. - 5% by weight of calcined clay matrix. - At least 10% by weight of raw clay matrix. - At least 30% by weight of raw clay matrix. - The calcined clay matrix is ​​a flashed clay matrix. - The calcined clay matrix is ​​a natural pozzolanic rock. - The calcined clay matrix is ​​metakaolin. - The construction binder comprises at least: • 40% to 55% by weight of clinker, • up to 25% by weight of a precursor, • 5% to 15% by weight of a calcined clay matrix, • 15% to 30% by weight of a raw clay matrix, and • 0.05% to 2% by weight of a deflocculating agent; and in that the mass ratio of the raw clay matrix to the calcined clay matrix is ​​from 0.5 to 6. - The construction binder comprises at least: • 39% by weight of clinker, • 20% by weight of a precursor, • 10% by weight of a calcined clay matrix, • 30% by weight of a raw clay matrix, and • 1% by weight of a deflocculating agent. - The construction binder includes: • 39% by weight of clinker, • 20% by weight of a precursor, • 20% by weight of a calcined clay matrix, • 20% by weight of a raw clay matrix, and • 1% by weight of a deflocculating agent.

[0014] According to a second object, the invention further relates to a construction material comprising a construction binder according to the invention. Description of the implementation methods

[0015] Other features and advantages of the invention will be better understood from the following description and with reference to the accompanying drawings, given by way of illustration and not limitation.

[0016] Below, we describe a summary of the invention and the associated vocabulary, before presenting the disadvantages of the prior art, and finally showing in more detail how the invention remedies them.

[0017] In the following description, the term "% by weight" in relation to the construction binder should be understood as a proportion relative to the dry weight of the construction binder. The dry weight corresponds to the weight before the addition of water, for example, necessary for the formation of a construction material. When the % by weight values ​​are given as ranges, the limits are inclusive.

[0018] The term "clay matrix" in the context of the invention may refer to one or more rock materials based on phyllosilicates, hydrated silicates, or aluminosilicates with a lamellar structure, said clay matrix being composed at least in part of fine particles generally resulting from the alteration of silicates with a three-dimensional framework or from the precipitation of a supersaturated fluid. A clay matrix may thus comprise a mixture of such rock materials, which may, for example, include kaolinite, serpentine, pyrophyllite, talc, smectite, vermiculite, illite, glauconite, mica, chlorite, palygorskite, sepiolite, interstratified materials, or mixtures thereof (Alain Meunier, Clays, 2005). In addition, a clay matrix may contain silts or loams.A clay matrix can originate from, but is not limited to, construction site spoil, quarry fines, clay-limestone fines, washing fines, clay muds, overburden materials, clay excavation materials such as excavated soils, or sediments including dredging sediments and varves, phyllosilicate rocks and weathered materials such as turbidites, marls, pelites, ruffes, laterites, schists, mica schists.

[0019] The term "concrete" should be understood as a mixture of aggregates, possibly including sand, with a construction binder (for example, cement) and water, which has set. Thus, the term concrete can refer to a structural element formed from a mixture of aggregates, mineral or plant-based, possibly including sand, one or more admixtures, a construction binder, and water.

[0020] The expression "raw clay matrix" corresponds, in the context of the invention, to a clay matrix that has not undergone a calcination step. In particular, that is to say, it has not been subjected to any prior heat treatment. For example, this corresponds to a clay matrix that has not been subjected to a temperature increase. above 300°C, preferably above 200°C, and more preferably above 150°C. Indeed, the raw clay matrix may undergo a drying stage requiring a temperature increase generally equal to or less than 150°C, but no calcination stage. A raw clay matrix may preferably contain rock materials, such as kaolinite, serpentine, pyrophyllite, talc, smectite, vermiculite, illite, glauconite, mica, chlorite, palygorskite, sepiolite, interstratified materials, or mixtures thereof.

[0021] For the purposes of this invention, a "flocculant," "flocculant," or "flocculating agent" may refer to a compound capable of dissociating aggregates and colloids, particularly those in aqueous suspension. Flocculants have, for example, been used in drilling or oil extraction to make clay more fluid and facilitate extraction or drilling.

[0022] The term “binder” or “construction binder” in the context of the invention can be understood as a formulation that ensures the agglomeration of materials, particularly during the setting and subsequent hardening of a construction material. Thus, it specifically ensures the agglomeration of sand and other aggregates with the constituents of the binder. The binder according to the invention is, in particular, a hydraulic binder, meaning that hardening occurs upon contact with water.

[0023] The term “Portland cement” refers to a hydraulic binder composed primarily of hydraulic calcium silicates, the setting and hardening of which is made possible by a chemical reaction with water. Portland cement generally contains at least 95% clinker and a maximum of 5% secondary constituents such as alkalis (Na2O, K2O), magnesia (MgO), gypsum (CaSO4 • 2 H2O), or various traces of metals.

[0024] The term "metal oxides" may, in the context of the invention, refer to a composition comprising metal oxides such as aluminates. In particular, a construction binder according to the invention may comprise a metal oxide composition including more than 25% by weight of metal oxides, preferably more than 30% by weight of metal oxides, more preferably more than 40% by weight of metal oxides, and even more preferably more than 45% by weight of metal oxides. For example, the metal oxide composition may include more than 2% by weight of aluminate, preferably more than 5% by weight of aluminate, more preferably more than 7% by weight of aluminate, and even more preferably more than 10% by weight of aluminate. Furthermore, the metal oxides may be, or include, alkali-earth oxides.For example, the composition of metal oxides may include more than 10% by weight of calcium oxide, preferably more than 20% by weight of calcium oxide, in a more Preferably, more than 25% by weight of calcium oxide, and even more preferably, more than 30% by dry weight of calcium oxide. The composition of metal oxides may include chemical species that are not metal oxides. For example, the composition of metal oxides may be replaced by aluminum or silicon oxides, with, for example, more than 10% by weight of aluminum or silicon oxide, preferably more than 20% by weight of aluminum or silicon oxide, more preferably more than 25% by weight of aluminum or silicon oxide, and even more preferably more than 30% by weight of aluminum or silicon oxide. These mass concentrations can be readily measured by a person skilled in the art using conventional techniques for the determination of metal oxides or aluminum or silicon oxides.In particular, the term "metal oxide composition" refers to a composition comprising more than 50%, preferably more than 70%, more preferably more than 80%, and even more preferably more than 90%, of metal oxides and / or aluminum or silicon oxides, including aluminates. Preferably, a metal oxide composition will be a slag from metallurgy, such as blast furnace slag, or fly ash. The "metal oxide" composition is preferably a composition of calcined metal oxides. That is to say, it has undergone a high-temperature treatment. This high-temperature treatment may be natural or artificial; in the latter case, it is a high-temperature treatment.The high-temperature step may, for example, correspond to treatment at a temperature greater than or equal to 400°C, preferably greater than or equal to 750°C and more preferably greater than or equal to 900°C; and even more preferably greater than 1000°C. The metal oxide composition of a composition or building element may be determined by X-ray fluorescence (“Standard Test Methods for Chemical Analysis of Hydraulic Compounds” December 2022; ASTM Cl 14-18 or according to EN ISO 29581-2:2010).

[0025] The term "substantially equal" in the meaning of the invention corresponds to a value varying by less than 20% from the compared value, preferably by less than 10%, even more preferably by less than 5%.

[0026] The term "clinker" or "Portland clinker" refers to a constituent of cement and is obtained by firing a mixture composed of approximately 80% limestone and 20% aluminosilicates (such as clays). This firing process, clinkerization, is generally carried out at a temperature exceeding 1200°C, which is particularly energy-intensive and generates significant greenhouse gas emissions. The clinker is generally ground and then mixed with 5% gypsum, anhydrite, and / or bassanite to produce CEM1 type Portland cement.

[0027] The term "D50" refers to the median diameter at which 50% (by volume or mass, preferably by volume) of the grains, particles, aggregates, or sediments are smaller than a given diameter. For example, if a sieving and sedimentation analysis method indicates a D50 = 5.8 mm, then 50% of the particles in the sample (by volume or mass, preferably by volume) are larger than 5.8 mm and 50% are smaller than 5.8 mm. D50 is generally used to represent the particle size of a group of particles. D50 can be measured by any method known to a person skilled in the art. D50 is preferably measured according to ASTM D422-63, XP P 94-041 (1995), NF ISO 11277 (2020), NF EN ISO 17892-4 (2018) or ASTM D6913-04 (2009) or especially for fine particles ISO 13320:2020 (e.g. D10 or <65 pm).

[0028] The construction sector must evolve to optimize its productivity while addressing societal and environmental challenges. In this context, research laboratories and manufacturers have proposed low-carbon construction binders containing reduced amounts of Portland clinker, or have attempted to replace Portland clinker with other calcined components that have a lower carbon footprint than Portland clinker. However, these mixtures still contain high amounts of Portland clinker and / or calcined components.

[0029] Indeed, even when construction binders do not contain Portland clinker, they still comprise nearly 50% by weight of the construction binder in calcined components and have the disadvantage of not having a mechanical resistance equivalent to that of Portland cement of type CEM1 or CEM2.

[0030] However, it is becoming increasingly urgent to reduce the carbon footprint of the construction sector and to further limit the use of Portland cement or Portland clinker, or even to replace Portland cement / clinker with other components having a lower or even zero carbon footprint. To address this, the inventors have developed a construction binder comprising specific proportions of clinker, raw and calcined clay matrix that allow for a reduction in the quantity of clinker and calcined clay matrix compared to construction binders containing clinker and / or calcined components, while exhibiting a 1-day mechanical strength of at least 5 MPa, preferably 10 MPa, and a 28-day mechanical strength of at least 30 MPa, preferably 40 MPa.

[0031] Thus, the invention relates in particular to a low-carbon construction binder comprising clinker, a calcined clay matrix, a raw clay matrix, and a deflocculating agent. Furthermore, the mass ratio of the raw clay matrix to the calcined clay matrix is ​​from 0.2 to 7.

[0032] The construction binder according to the invention can be prepared extemporaneously or prepared on a production site and then possibly stored and transported to the construction site.

[0033] We will present in detail the general and preferred characteristics of each of the constituents of the formulation according to the invention.

[0034] Raw clay matrix

[0035] The raw clay matrix may, for example, comprise at least one mineral species selected from: Illite, Kaolinite, Smectite, Vermiculite, Chlorite, Montmorillonites, Muscovite, Halloysite, Sepiolite, and Palygorskite.

[0036] Preferably, the raw clay matrix comprises at least two types of clay selected from: Illite, Kaolinite, Smectite, Vermiculite, Chlorite, Montmorillonite, Muscovite, Halloysite, Sepiolite, Interstratified clays, Pyrophyllite, Talcs, Serpentines, and Palygorskite. This includes so-called interstratified clays, which are complex combinations of several clays. Even more preferably, the raw clay matrix comprises at least one mineral species selected from: Kaolinite, Illite, Smectite, Palygorskite, Sepiolite, Chlorite, Montmorillonite, and Vermiculite.

[0037] Table 1 below presents the chemical characteristics of these mineral species. [Tables 1] Matrix Clayey Raw Type of clay Composition Illite (K,H3O)(Al,Mg,Fe)2(Si,Al)4O10[(OH)2,(H2O)] Smectite (Na,Ca)0.3(Al,Mg)2Si4O10(OH)2, n H2O Kaolinite Al2Si2O5(OH)4 Bentonite (Na,Ca)0.3(Al,Mg)2Si4O10(OH)2 Vermiculite (Mg,Ca)0j7(Mg,Fe,Al)6(Al,Si)8O22(OH)4j n H2O Chlorite (Fe,Mg,Al)6(Si,Al)4O10(OH)8 Muscovite KAl2(AlSi3O10) (OH,F)2 Halloysite Al2Si2O5(OH)4 Sepiolite Mg4Si6O15(OH)2, n H2O Palygorskite (Mg,Al,Fe3+)5[Si8O20](OH)2 (OH2)4n H2O

[0038] In addition, the raw clay matrix may also include Montmorillonite and / or so-called interstratified clays which are complex combinations (at the atomic scale) of several clays.

[0039] The type of clay can be determined by methods known to a person skilled in the art. In particular, X-ray diffractometry can be used after specific sample preparation according to the so-called oriented plate method (see Thiry et al. - 2013 - Technique for preparing clay minerals for analysis by X-ray diffraction and introduction to the interpretation of diagrams). For example, the following conditions can be used: - Equipment: Diffractometer, for example a BRUKER D8 ADVANCE (Bragg-Brentano geometry); for example with the following settings: Copper Tube (X Kal ~ 1.54 Å) Generator power: 40 kV, 40 mA; Primary optics: fixed slit 0.16°; Soller slit 2.5°; Secondary optics: Soller slit 2.5°; LynXeye XE-T detector - Acquisition parameters: Scanning from 4 to 70°20; Scanning speed of 0.03°20 / second, Counting time: between 20 min and 60 min per step; Rotating sample.

[0040] The raw clay matrix may preferably correspond, at least in part, to excavated clay soil, preferably uncalcined excavated clay soil, such as treated raw excavated clay soil. The raw clay matrix may advantageously have been treated, such treatment being selected from: grinding, sorting, sieving, and / or drying. Preferably, the raw clay matrix used in the binder has been ground.

[0041] Preferably, a construction binder according to the invention comprises at least 5% by weight of raw clay matrix, and more preferably at least 15% by weight of raw clay matrix. Indeed, the construction binder according to the invention has the advantage of being able to contain a high quantity of raw clay matrix without altering the mechanical properties of the construction materials.

[0042] In addition, preferably, the construction binder according to the invention comprises at most 30% by weight of raw clay matrix, more preferably at most 25% by weight of raw clay matrix.

[0043] Thus, in particular, a construction binder according to the invention comprises between 5% and 30% by weight of raw clay matrix, preferably between 10% and 28% by weight or between 15% and 27% by weight of raw clay matrix, more preferably between 20% and 26% by weight of raw clay matrix, and even more preferably between 22% and 25% by weight of raw clay matrix.

[0044] Advantageously, the raw clay matrix may comprise crushed raw clay. Preferably, the raw clay matrix may have a D50 less than or equal to 500 pm, preferably less than or equal to 250 pm, more preferably less than or equal to 100 pm, or even more preferably less than or equal to 50 pm.

[0045] Furthermore, the raw clay matrix may have a D50 greater than or equal to 0.1 pm, preferably greater than or equal to 1 pm, more preferably greater than or equal to 10 pm, or even more preferably greater than or equal to 20 pm, and even more preferably greater than 40 pm. This helps to limit the stress on industrial production equipment dedicated to grinding.

[0046] More preferably, the raw clay matrix may have a D50 between 10 µm and 500 µm, preferably between 15 µm and 250 µm, more preferably between 20 µm and 150 µm, or even more preferably between 20 µm and 50 µm. The presence of clay ground to achieve such diameters can improve the performance of the construction binder and the construction material according to the invention.

[0047] Advantageously, the raw clay matrix may comprise at least 2% by weight of silt particles, preferably at least 4% by weight, and more preferably at least 6% by weight. For example, the raw clay matrix may comprise at most 50% by weight of silt particles, preferably at most 30% by weight, and more preferably at most 20% by weight. The silt particles are, in particular, particles having a diameter between 2 µm and 63 µm.

[0048] The raw clay matrix may comprise at least 1% by weight of sand, preferably at least 2% by weight, and more preferably at least 3% by weight. For example, the raw clay matrix may comprise at most 70% by weight of sand, preferably at most 50% by weight, and more preferably at most 40% by weight. For example, the raw clay matrix may comprise from 1% to 70% by weight of sand particles, preferably from 2% to 50% by weight, and more preferably from 3% to 40% by weight. The sand corresponds in particular to particles having a diameter between 63 µm and 2 mm.

[0049] Preferably, the raw clay matrix comprises clay contents, in the mineralogical sense of the term, of at least 10% by dry weight, more preferably at least 20% by dry weight, and even more preferably at least 30% by dry weight. However, a raw clay matrix comprising low clay contents, in the mineralogical sense, may be used. In particular, the raw clay matrix may consist of fine clay-limestone or clay-siliceous / quartz material comprising at least 50% by dry weight of limestone, silica, or quartz, preferably at least 60%, more preferably at least 70%, or even more preferably at least 80% by dry weight of limestone, silica, or quartz.

[0050] Calcined clay matrix

[0051] The calcined clay matrix can be a raw clay material which has previously undergone heat treatment, preferably at a temperature of at least 450°C and at most 900°C, or in a "flash" calcination process according to Anglo-Saxon terminology at temperatures between 800°C and 1100°C.

[0052] Preferably, the calcined clay material is dehydroxylated into an amorphous material while the formation of high-temperature aluminosilicate crystalline phases such as mullite is prevented.

[0053] The calcined clay matrix is ​​preferably amorphous, and has pozzolanic activity.

[0054] Furthermore, the calcined clay matrix may comprise at least 5% by weight of metal oxides, preferably at least 10% by weight of metal oxides, preferably at least 20% by weight of metal oxides, and even more preferably at least 30% by weight of metal oxides. The calcined clay matrix may further comprise up to 70% by weight of metal oxides, preferably up to 60% by weight of metal oxides.

[0055] The calcined clay matrix can be formed with all the clay matrices mentioned above. The calcined clay matrix may comprise, by way of non-limiting example, at least one mineral species selected from: Metakaolin, Metalillite, and / or Metamontmorillonite. Preferably, the clay matrix that has been calcined comprises kaolinite and / or illite. Thus, preferably, the calcined clay matrix consists of metakaolin or metalillite.

[0056] According to a preferred embodiment of the present invention, the calcined clay matrix is ​​composed of metakaolin. Metakaolin is a material resulting from the calcination of kaolinite or minerals that are rich in kaolinite, for example, that have a kaolinite content of at least 20% by weight, preferably at least 25% by weight, and even more preferably at least 30% by weight.

[0057] Preferably the calcined clay matrix is ​​a flashed clay matrix, such as, for example, metakaolin obtained from a flash calcination.

[0058] Alternatively, the calcined clay matrix can be derived from a natural pozzolanic rock, that is to say formed by volcanic basaltic projections or of similar composition or more generally from any substance which has "pozzolanic properties", that is to say which has an ability to combine, at room temperature and in the presence of water, with lime or portlandite to give very poorly soluble hydrates.

[0059] Preferably, a construction binder according to the invention comprises at least 5% by weight of calcined clay matrix, more preferably at least 15% by weight of calcined clay matrix. Indeed, the construction binder according to the invention has the advantage of being able to contain a small amount of clay matrix. raw without altering the mechanical properties of the construction materials.

[0060] In addition, preferably, the construction binder according to the invention comprises at most 30% by weight of calcined clay matrix, more preferably at most 25% by weight of calcined clay matrix.

[0061] Thus, in particular, a construction binder according to the invention comprises between 5% and 30% by weight of calcined clay matrix, preferably between 10% and 25% by weight or between 10% and 20% by weight of calcined clay matrix, more preferably between 12.5% ​​and 20% by weight of calcined clay matrix, and even more preferably between 12.5% ​​and 15% by weight of calcined clay matrix.

[0062] Preferred mass ratio

[0063] As illustrated in the examples, the applicant discovered that certain mass ratios between the raw clay matrix and the calcined clay matrix of the construction binder made it possible to obtain advantageous mechanical strength properties at early age and at 28 days.

[0064] Advantageously, in a construction binder according to the present invention, the calcined clay matrix and the raw clay matrix are present in such a quantity that the mass-weight ratio of the raw clay matrix to the calcined clay matrix is ​​between 0.33 and 3 (inclusive). Indeed, as illustrated in the examples, such mass ratios make it possible to obtain a high Rc at Ij (e.g., greater than 7 MPa) while maintaining an Rc at 28j of at least 30 MPa.

[0065] Deflocculating agent

[0066] Many compounds can act as deflocculating agents and many are generally known to those skilled in the art.

[0067] The presence of one or more deflocculating agent(s) can improve the performance of the material formed from the construction binder.

[0068] In the context of the invention, a construction binder may include an organic deflocculating agent, advantageously a deflocculating polymer. According to the present invention, an organic deflocculating agent comprises at least one carbon atom and preferably at least one carbon-oxygen bond.

[0069] The deflocculating polymer may be a non-ionic surfactant such as a polyoxyethylene ether. The polyoxyethylene ether may, for example, be selected from: a poly(oxyethylene) lauryl ether.

[0070] The deflocculating polymer can also be an anionic agent such as an anionic surfactant. In particular, the anionic agent can 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 that sodium hexametaphosphate, sodium tripolyphosphate, sodium orthophosphate, carboxymethylcelluloses and mixtures thereof.

[0071] The deflocculant polymer can also be a polyacrylate. It can then be selected, for example, from sodium polyacrylate and ammonium polyacrylate.

[0072] The deflocculant polymer can also be an amine selected for example from: 2-amino-2-methyl-l-propanol; mono-, di or tri ethanolamine, isopropanolamines (l-Amino-2-propanol, diisopropanolamine, triisopropanolamine) and N-alkyl ethanolamines.

[0073] Preferably, the deflocculating polymer is selected from: a lignosulfonate (e.g., sodium lignosulfonate), a polyacrylate, a humate, and mixtures thereof.

[0074] Preferably, the deflocculating polymer is selected from: a lignosulfonate (e.g. sodium lignosulfonate), a polyacrylate, a humate, a polycarboxylate such as an ether polycarboxylate, and mixtures thereof.

[0075] More preferably, the deflocculating polymer comprises a humate, a lignosulfonate and / or a polyacrylate.

[0076] The deflocculating agent can also be a silicate such as sodium silicate, sodium metasilicate or sodium trisilicate.

[0077] Alternatively, the deflocculating 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.

[0078] In particular, the deflocculating agent may be a mixture of sodium silicate and sodium carbonate.

[0079] The deflocculating agent is preferably in the form of a salt.

[0080] However, the invention cannot be limited to the deflocculants mentioned above; any type of deflocculant known to a person skilled in the art can be used in place of the aforementioned deflocculants.

[0081] The deflocculating agents usable according to the present invention may take a solid or liquid form.

[0082] In particular, the deflocculating agent represents at least 0.05% by weight of the construction binder, preferably at least 0.1% by weight of the construction binder, preferably at least 0.25% by weight of the construction binder, more preferably at least 0.5% by weight of the construction binder, more preferably at least 0.5% by weight of the construction binder, even more preferably at least 0.8% by weight of the construction binder and for example at least 1% by weight of the construction binder.

[0083] Furthermore, the deflocculating agent represents at most 5% by weight of the construction binder, preferably at most 4% by weight of the construction binder, more preferably at most 3% by weight of the construction binder, and even more preferably at most 2% by weight of the construction binder. Indeed, too high a concentration is not necessary to form a material with advantageous mechanical properties.

[0084] In particular, the deflocculating agent represents between 0.05% and 5% by weight of the construction binder, preferably between 0.1% and 4% by weight of the construction binder, more preferably between 0.25% and 3% by weight of the construction binder, even more preferably between 0.5% and 2% by weight of the construction binder, and even more preferably between 0.8% and 2% by weight of the construction binder, and even more preferably between 0.9% and 2% by weight of the construction binder.

[0085] Precursor

[0086] The construction binder according to the invention may include a precursor. Without being limited by theory, the role of the precursor is to contribute to the mechanical strength of the construction material.

[0087] The precursor may comprise a source of carbonates, with or without silicates. In particular, the precursor may comprise sodium or potassium carbonate. The sodium or potassium carbonate may further be mixed with sodium or potassium silicate.

[0088] Preferably, the precursor may comprise a source of calcium carbonate. The source of calcium carbonate may correspond to a solid material composed mainly of carbonate minerals such as calcite or dolomite.

[0089] By way of illustrative examples, the carbonate source may be limestone, dolomite, chalk, aragonite or vaterite.

[0090] Alternatively, the limestone may also be magnesium carbonate and / or a mixture of magnesium carbonate and dolomite.

[0091] Preferably, the limestone is a natural limestone primarily composed of calcium carbonate with various polymorphs, such as calcite and / or aragonite, but also containing a certain amount of magnesium carbonate and / or dolomite. The limestone may also be a clayey limestone or a natural marl.

[0092] In addition, the precursor may comprise a siliceous filler or "quartz flour". By way of example, the siliceous filler may comprise corpuscular silica and kaolinite.

[0093] The precursor may also include calcined shale, diatomite, phonolite, paper mill mud ash, or crushed glass.

[0094] In addition, the precursor may comprise at least 30% by weight of calcium oxide or at least 30% by weight of calcium carbonate.

[0095] As an alternative or in addition, the precursor may further comprise blast furnace slags, fly ash, incineration ash, volcanic ash, silica fume, a limestone filler for example a micronized limestone filler of a known type, or a combination thereof.

[0096] The precursor may further exhibit a specific particle size distribution, for example, a D50 characterizing the particle size whereby 50% of the volume (or mass) of the precursor has a particle size distribution less than 25 microns and 50% of the volume (or mass) of the precursor has a particle size distribution greater than 5 microns. Alternatively, the precursor may exhibit a specific particle size distribution, for example, an average particle size distribution characterizing the average diameter of the particles between 5 microns and 50% of the volume (or mass) of the precursor has a particle size distribution greater than 5 microns.

[0097] Alternatively, the precursor, such as calcium carbonate, may have a specific particle size distribution, for example an average particle size distribution characterizing the average diameter of the particles between 0.1 micron and 100 microns, preferably between 0.1 micron and 5 microns.

[0098] When the precursor is calcium carbonate, it can be made up of vaterite.

[0099] Calcium carbonate may thus comprise at least 10% by weight of vaterite; or at least 20% by weight of vaterite; or at least 30% by weight of vaterite; or at least 40% by weight of vaterite; or at least 50% by weight of vaterite; or at least 60% by weight of vaterite; or at least 70% by weight of vaterite; or at least 80% by weight of vaterite; or at least 90% by weight of vaterite; or at least 95% by weight of vaterite; or at least 99% by weight of vaterite.

[0100] Vaterite, in the presence of water, forms aragonite. Vaterite can be obtained by any type of method known to those skilled in the art.

[0101] In the invention, when the precursor is present, it may be present at a content of at least 1% by weight of the construction binder, preferably at a content of at least 10% by weight of the construction binder, even more preferably at a content of at least 15% by weight of the construction binder.

[0102] In addition, preferably, the construction binder according to the invention comprises at most 25% by weight of precursor, more preferably at most 20% by weight of precursor.

[0103] Thus, in particular, a construction binder according to the invention can comprise between 1% and 25% by weight of precursor, preferably between 10% and 25% by weight of precursor, more preferably between 15% and 20% by weight of precursor.

[0104] Clinker

[0105] The construction binder according to the invention further comprises clinker.

[0106] Clinker is obtained by firing a mixture composed of approximately 80% limestone and 20% aluminosilicates. This firing, known as clinkerization, is generally carried out at a temperature exceeding 1200°C. As previously mentioned, clinker may also contain up to 5% gypsum. The role of gypsum is to provide sulfates that slow the setting of the cement. Although gypsum is commonly used in conjunction with Portland clinker to produce CEM 1, any other constituent that provides sulfates and slows the setting of the cement could be used in addition to or as a replacement for gypsum, such as bassanite or anhydrite.

[0107] By way of non-limiting example, the clinker may be "Portland" clinker. Portland clinker consists of at least two-thirds by mass of calcium silicates (3CaO • SiO2: C3S and 2CaO • SiO2: C2S), the remaining portion consisting of phases containing aluminum and iron, and free lime (CaO) not exceeding 2%. The mass ratio (CaO) / (SiO2) is generally greater than or equal to 2.

[0108] Preferably, a construction binder according to the invention comprises at least 35% by weight of clinker, more preferably at least 40% by weight of clinker.

[0109] In addition, preferably, the construction binder according to the invention comprises at most 60% by weight of clinker, more preferably at most 65% by weight of clinker.

[0110] Thus, in particular, a construction binder according to the invention comprises between 35% and 65% by weight of clinker, preferably between 40% and 60% by weight or between 45% and 60% by weight of clinker, more preferably between 45% and 55% by weight of clinker, and even more preferably between 45% and 50% by weight of clinker.

[0111] In a particular embodiment, a construction binder according to the invention comprises: - 40% to 55% by weight of clinker, - 15% to 25% by weight of a precursor, - 5% to 15% by weight of a calcined clay matrix, - 15% to 30% by weight of a raw clay matrix, and - from 0.05% to 2% by weight of a deflocculating agent; the mass ratio of the raw clay matrix to the raw clay matrix is ​​from 0.2 to 7.

[0112] In another particular embodiment, a construction binder according to the invention comprises: - 39% by weight of clinker, - 20% by weight of a precursor, preferably the precursor is a limestone filler, - 10% by weight of a calcined clay matrix, - 30% by weight of a raw clay matrix, and - 1% by weight of a deflocculating agent.

[0113] In another particular embodiment, a construction binder according to the invention comprises: - 39% by weight of clinker, - 20% by weight of a precursor, preferably a calcareous filler, - 20% by weight of a calcined clay matrix, - 20% by weight of a raw clay matrix, and - 1% by weight of a deflocculating agent.

[0114] In another particular embodiment, a construction binder according to the invention comprises: - 39% by weight of clinker, - 20% by weight of a precursor, preferably a calcareous filler, - 25% by weight of a calcined clay matrix, - 5% by weight of a raw clay matrix, and - 1% by weight of a deflocculating agent.

[0115] In another particular embodiment, a construction binder according to the invention comprises: - 50% by weight of clinker, - 30% by weight of a calcined clay matrix, - 20% by weight of a raw clay matrix, and - 1% by weight of a deflocculating agent.

[0116] Thus, according to another aspect, the invention relates to a construction material formed from the low carbon construction binder according to the invention.

[0117] The low-carbon construction binder according to the invention allows, in particular, the manufacture of insulating building materials: from a construction binder according to the invention with the addition of lightweight aggregates of a "vegetable 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 allow air to be trapped in the material and improve its insulating properties; prefabricated elements: manufacturing of concrete blocks or slabs in a factory from the construction binder according to the invention; and insulation modules. Examples

[0118] Preparation of a construction binder:

[0119] In all the examples presented below, the construction binders according to the invention are prepared according to an identical protocol, namely that a dry premix is ​​carried out between clinker, a raw clay matrix, a calcined clay matrix, a precursor (except for one of the examples which does not contain one) and a deflocculating agent in predetermined quantities, then water is added and the solution is mixed at low speed, i.e. approximately 100 revolutions per minute for 90 seconds. Then, water and aggregates are added to the construction binder and mixed at low speed, i.e. approximately 100 revolutions per minute for 45 seconds in order to obtain a construction material.

[0120] Alternatively, the dry premix can be carried out by first mixing the raw clay matrix, the calcined clay matrix and the deflocculating agent, and then by adding clinker and precursor (if present).

[0121] The water-to-dry-matter mass ratio of the composition (also called construction binder) is adjusted to a value between 0.4 and 0.6. In the examples, the construction material, a mortar, comprises 25% by weight of binder, 75% by weight of sand; this mixture being completed with water for a water-to-dry-matter mass ratio of the binder adjusted to a value of 0.4.

[0122] The mortar based on the construction binder thus formed is then poured into two separate molds and then left to mature at room temperature, i.e. about 20 degrees Celsius for twenty-four hours for the first mold and undergoes a water cure at 20 °C for twenty-eight days for the second mold.

[0123] Alternatively, the mortar can be poured into a mold and then left to cure for less than twenty-four hours in a curing stage, at ambient temperature, i.e. about 25 degrees Celsius, or preferably under heat treatment. During this curing stage, the mold can be sealed or the top layer of the building material can be coated with a curing compound to limit / prevent evaporation.

[0124] Methodology for measuring the consistency of construction binders:

[0125] Once the constituents have been mixed, the consistency, hereinafter referred to as rheology, of the freshly mixed mortars is determined by means of measuring the spread value with a cone as described in standard NF EN 1015-3.

[0126] Methodology for measuring the mechanical properties of construction binders:

[0127] Once the maturation is complete, the mechanical resistance is measured. Mechanical resistance of a construction binder means its resistance to compression, such compression being measured according to standard NF EN 196-1, for a prism of 40 millimeters on each side and 160 millimeters in length and is expressed in Mega Pascals (MPa).

[0128] Comparison of the construction binders according to the invention with known construction binders:

[0129] Table 2 below presents different types of known construction binders. The mass of the components relating to each formulation is expressed as a percentage of the total mass of the construction binder (dry weight).

[0130] [Tables2] CEM2-A (Reference) LC3 (Reference) REF1 REF2 CEM I (mixture of 95% Clinker and 5% Soft Gypsum) 80% 50% 50% 50% Precursor 20% Limestone Filler 20% Limestone Filler 20% Limestone Filler 20% Limestone Filler Calcined Clay Matrix 0% 30% 0% 15% Raw Clay Matrix 0% 0% 30% 15% Deflocculating Agent 0% 0% 0% 0% Rheology by Cone Spread (mm) 110 100 100 100 Compressive Strength (MPa) at 24h >15 10 3 5 Compressive Strength (MPa) at 28 days >50 45 12 25 Estimated Carbon Footprint Reduction compared to CEM 2 A na 15% 25% 20% Raw clay / calcined clay ratio na na na 1

[0131] Thus, Table 2 presents the mechanical resistances of known construction binders (CEM2 binder, LC3, REF1 and REF2) and not part of the invention, such as the CEM2 type construction binder better known as Portland limestone cement whose compressive strength is on the order of 50 MPa.

[0132] The LC3 formulation can be obtained by following the instructions of patent EP2429966. The LC3 type construction binder comprises 30% by weight of Metakaolin obtained by calcination of kaolin, 50% by weight of CEM 1, and 20% of a limestone filler. Thus, the relative mechanical strength of such a construction binder, on the order of 45 MPa, is close to the strength of the CEM2 type construction binder.

[0133] Finally, the construction binders REF1 and REF2, obtained by following the teachings of patent application EP2429966, but by replacing all or part of the calcined clay matrix with a raw clay matrix. These tests show a sharp decrease The mechanical strength (12 MPa) is achieved when the construction binder does not contain (REF1) a calcined clay matrix, and the mechanical strength (25 MPa) is higher (REF2), but significantly lower than the CEM2 and LC3 references, when the construction binder contains a raw clay matrix and a calcined clay matrix in equivalent proportions. Therefore, the absence of a calcined clay matrix or its presence in equivalent proportions with a raw clay matrix does not allow for the production of concrete with adequate mechanical properties.

[0134] Table 3 below presents different types of construction binders according to the invention (MTU01 to MTU05). The mass of the components relating to each formulation is expressed as a percentage of the total mass of the construction binder (dry weight). The construction binders presented below differ in particular in that the proportions of raw and calcined clay matrices are greater or lesser; one example of a construction binder also includes blast furnace slag as a precursor. [Tables 3] MTU01 MTU02 MTU03 MTU04 MTU05 CEM I (mixture of 95% Clinker and 5% ground Gypsum) 39% 39% 39% 32% 49% Precursor 20% Icarus filler 20% Icarus filler 20% Icarus filler 20% Icarus filler 0% Calcined clay matrix 20% 30% 10% 23.6% 30% Raw clay matrix 20% 10% 30% 23.6% 20% Deflocculating agent 1% 1% 1% 0.8% 1% Cone spread rheology (mm) 190 140 200 160 170 Compressive strength (MPa) at 24 h 10 10 8 7 11 Compressive Strength (MPa) at 28 days 42 47 40 30 41 Estimated Carbon Footprint Reduction compared to CEM II A 35% 30% 40% 50% 25% Raw Clay / Calcined Clay Ratio 1 0.33 3 1 0.67

[0135] As shown in Table 3, the construction binders according to the invention exhibit compressive strengths equivalent to or even greater than those obtained with concrete made with CEM2 cement or LC3 type cement. Thus, the present invention makes it possible to produce a low-carbon construction binder by further limiting the proportions of clinker and calcined clay matrix used. This further reduces the carbon footprint and energy balance of these construction binders compared to CEM2 and LC3 type low-carbon binders, making them a construction material that meets the majority of the sector's needs.Finally, the construction binders according to the invention have the advantage of exhibiting improved rheology compared to reference construction binders, which include a calcined and / or raw clay matrix and early age compressive strength, allowing them to be used for the formation of all types of construction materials such as thin (less than 200 mm thick) or thick slabs, more generally for masonry work of any kind in reinforced or prestressed concrete.

Claims

Demands

1. Construction binder comprising: - 35% to 65% by weight of clinker, - 5% to 30% by weight of a calcined clay matrix, - 5% to 30% by weight of a raw clay matrix, and - 0.05% to 5% by weight of a deflocculating agent; and in that the mass ratio of the raw clay matrix to the calcined clay matrix is ​​0.2 to 7.

2. Construction binder according to claim 1, said binder further comprising up to 25% by weight of a precursor.

3. Construction binder according to claim 2, the precursor comprises a source of calcium carbonate.

4. Construction binder according to claim 2 or 3, wherein the precursor is selected from: blast furnace slags, fly ash, silica fume, a natural or synthetic limestone filler, a siliceous filler, diatomite.

5. Construction binder according to any one of claims 3 or 3 and 4, wherein the calcium carbonate has a D50 between 0.1 pm and 5 pm.

6. Construction binder according to any one of claims 3 to 5, wherein the calcium carbonate comprises vaterite.

7. Construction binder according to any one of claims 1 to 6, wherein the deflocculating agent is an organic deflocculating agent.

8. Construction binder according to any one of claims 1 to 7, wherein the raw clay matrix has a D50 greater than or equal to 1 pm, preferably greater than or equal to 10 pm, and less than or equal to 50 pm.

9. Construction binder according to any one of claims 1 to 8, said binder comprising between 35% and 50% by weight of clinker.

10. Construction binder according to any one of claims 1 to 9, said binder comprising at least 10% by weight of raw clay matrix.

11. Construction binder according to any one of claims 1 to 9, said binder comprising at least 30% by weight of clay matrix flood.

12. Construction binder according to any one of claims 1 to 11, wherein the calcined clay matrix is ​​metakaolin.

13. Construction binder according to any one of claims 1 to 9, said binder comprising at least: - from 40% to 55% by weight of clinker, - up to 25% by weight of a precursor, - from 5% to 15% by weight of a calcined clay matrix, - from 15% to 30% by weight of a raw clay matrix, and - from 0.05% to 2% by weight of a deflocculating agent; and in that the mass ratio of the raw clay matrix to the calcined clay matrix is ​​from 0.5 to 6.

14. Construction binder according to any one of claims 1 to 9, said binder comprising: - 39% by weight of clinker, - 20% by weight of a precursor, - 10% by weight of a calcined clay matrix, - 30% by weight of a raw clay matrix, and - 1% by weight of a deflocculating agent.

15. Construction binder according to any one of claims 1 to 9, said binder comprising: - 39% by weight of clinker, - 20% by weight of a precursor, - 20% by weight of a calcined clay matrix, - 20% by weight of a raw clay matrix, and - 1% by weight of a deflocculating agent.

16. Construction material comprising a construction binder according to any one of claims 1 to 15.