CH721911A1 - Cement composition comprising microparticles of coal, process for its production and final material comprising such a composition - Google Patents

Abstract

The present invention covers a cementitious composition (30) comprising an organic material (20), and an inorganic material (10), as well as the process for its production and the final material comprising such a composition.

Description

technical field

[0001] The present invention relates to a biocarbon microparticle powder and a method for producing such a biocarbon powder from biomass. The present invention further relates to a cementitious composition comprising such a biocarbon powder and a method for its preparation.

State of the art

[0002] Concrete is among the most widely used man-made materials. It is responsible for eight to ten percent of global greenhouse gas (GHG) emissions. Cement plays a central role in concrete, being the active binding ingredient, but it is also the main contributor to CO₂ emissions. It is estimated that the production of one kg of standard Portland cement releases 0.5 to 0.9 kg of CO₂, of which approximately 60% is due to the chemical conversion of limestone into calcium oxide and 40% to the use of fossil fuels for clinker production.

[0003] It is desirable to have cement pastes with a lower environmental impact. However, it is also important that the new materials remain compatible with the means of production, distribution and use that underlie existing value chains, without requiring major changes to equipment or procedures commonly used in the cement and construction sectors.

[0004] In an attempt to decarbonize the industry, at least partially, cement producers use additional cementitious materials (ACMs) to limit the clinker content of Portland cement and reduce its greenhouse gas emissions. The most common ACMs are limestone, fly ash, granulated blast furnace slag, silica fume, calcium carbonate, and natural pozzolans such as calcined clays and metakaolin. In addition to reducing the energy requirements and CO₂ emissions of cement, in this case ordinary Portland cement, by partially replacing clinker, ACMs are also used to improve certain technical aspects of concrete such as permeability, durability, and workability. However, the quantity of available ACMs is limited, as is their capacity to reduce cement-related emissions, since only partial clinker substitution is viable.

[0005] Recently, the addition of biocarbon or biochar (BC) to concrete and mortars has gained popularity due to its effectiveness in reducing net CO₂ emissions associated with cement production. Biocarbon is produced by heating a renewable organic precursor (biomass) in the absence of oxygen. This stabilizes the carbon atoms and prevents them from being released back into the atmosphere. One tonne of biocarbon can sequester an amount of carbon equivalent to three tonnes of carbon dioxide. Biocarbon can therefore contribute to greenhouse gas reduction through two distinct mechanisms. If biocarbon is used in place of non-renewable materials, the release of new CO₂ into the atmosphere is avoided. Furthermore, thanks to its ability to lock renewable carbon atoms in a stable solid form, biocarbon is also effective in removing existing CO₂ from the atmosphere. For a specific application, the amount of CO₂ avoided and removed can be accurately determined by weighing the biocarbon and measuring its carbon content. For these reasons, biocarbon is considered an effective and reliable means of reducing GHGs in the short and medium term.

[0006] Biocarbons can exhibit a wide range of characteristics depending on the biomass source and the carbonization process used. Therefore, biocarbons can be included in concrete and cement formulations as an inert additive or as an active biofiller acting as an additional cementitious material. Biocarbon can replace a fraction of the inert materials, the binder, or both. Consequently, biocarbon has a much greater potential for reducing emissions associated with cement production and use than other alternative ingredients, since it allows for both avoidance and disposal pathways.

[0007] Biocarbon can be produced using two main families of technologies: slow pyrolysis and hydrothermal carbonization. Slow pyrolysis is characterized by slow heating rates (a few °C/min to a few tens of °C/min), medium temperatures (500-700 °C), and a long residence time (up to several hours). Hydrothermal carbonization is characterized by lower temperatures (180-300 °C), high pressures (tens of bars), and a similar duration. Biocarbon produced by pyrolysis is generally characterized by a higher carbon content, greater aromaticity, and greater porosity than hydrothermal carbon. High temperature and pressure, as well as a long residence time, are associated with a high energy demand.

[0008] Recent research suggests that the performance of biocarbon and cement mixtures, relating to mechanical properties, permeability, workability and shrinkage of the final product, among others, is optimal when the size of the biocarbon particles corresponds to the size distribution of the cement particles.

[0009] In general, the particle size of biocarbon is correlated with the particle size of the biomass used as feedstock, since neither pyrolysis nor conventional hydrothermal methods allow for particle size reduction simultaneously with thermochemical conversion. Therefore, to improve its characteristics, biocarbon must be ground in a subsequent mechanical step. This practice is very time- and energy-intensive. The two-step strategy of thermochemical conversion followed by size reduction is efficient on a small scale, but difficult to implement on an industrial scale because it presents numerous operational challenges.

[0010] There is therefore potential to improve the performance of mixed materials based on cement and carbonaceous material, both from the point of view of the properties of the final product and the production costs and the quantities of CO<2> emissions.

Brief summary of the invention

[0011] An object of the present invention is to provide a carbonaceous material, in this case a biocarbon, suitable for incorporation into an inorganic or mineral material, particularly a cementitious material. Such a carbonaceous material is preferably stable, i.e., non-biodegradable, or at least only slightly biodegradable so as to allow for the long-term sequestration of carbon. Such a material preferably offers sufficient mechanical strength to be incorporated into construction materials such as cement or concrete. Advantageously, such an organic material is incorporated in substantial proportions, in particular greater than 1%, 2%, 5%, 10%, or 20%, or even greater than 30% by mass, without degrading the mechanical properties of the resulting cement.

[0012] Another object of the invention is to provide a process or method for manufacturing carbonaceous materials, in particular biocarbons, that is faster and less expensive than currently used processes. The object is, in this instance, to provide a process applicable for the production of industrial quantities, such as more than one tonne or 10 tonnes or more per day per production unit, of biocarbon, or that can be industrialized in such proportions. The object of such a process is further to produce industrial quantities of carbonaceous materials while limiting CO₂ emissions, or even avoiding CO₂ emissions, preferably with a negative carbon balance if the sequestration of CO₂ equivalents in the carbonaceous material is greater than the CO₂ emitted during the implementation of the process.

[0013] Another object of the present invention is to provide a cementitious composition, in particular a cement or concrete, comprising a proportion of carbonaceous material that allows carbon to be sequestered within the cementitious material without significantly deteriorating its mechanical and/or physical characteristics. In this way, such a cementitious composition remains usable as a construction material. Advantageously, such a composition is clinker-free or contains a reduced or significantly reduced proportion of clinker, for example, less than 30% or 50%, compared to traditional Portland cement.

[0014] Another object of the present invention is to provide a production method or process for manufacturing a cementitious composition, such as cement or concrete, comprising a proportion of carbonaceous material, in particular biocarbon. Such a process aims to reduce the energy expenditure required for the production of cement and concrete, and consequently the associated CO₂ emissions. Such a process also aims to incorporate a proportion of carbonaceous material into the cementitious material in a sustainable manner, so as to sequester carbon within it. The proposed method advantageously allows for the production of a greater variety of cementitious compositions and broadens the possible applications of such compositions.

[0015] According to the invention, these goals are achieved, in particular by means of the compositions, biocarbons and processes which are the subject of the claims.

[0016] This solution offers, in particular, the advantage over the prior art of limiting the energy expenditure associated with the production of cement and concrete, and consequently the corresponding CO₂ emissions. The present solution also offers the advantage of sustainably sequestering carbon within the cement. The present invention makes it possible to vary and/or adapt the mechanical and physical properties of cements according to their applications.

Brief description of the figures

[0017] Examples of implementation of the invention are shown in the description illustrated by the following figures:

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Figure 1: Schematic representation of a step in the manufacturing process of a cementitious composition according to an embodiment of the present invention,

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Figure 2: Schematic representation of the process of producing organic matter according to an embodiment of the present invention.

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Figure 3: Schematic representation of the process for producing a final material, according to an embodiment of the present invention.

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Figure 4: Schematic perspective representation of a crusher according to an embodiment of the present invention.

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Figure 5: Schematic side view representation of a crusher according to an embodiment of the present invention.

Example(s) of an embodiment of the invention

[0018] With reference to Figure 1, the cementitious compositions 30 according to the present invention designate mixed compositions based on inorganic matter 10 on the one hand, and organic matter 20 on the other, which are homogeneously assembled. The term homogeneous is understood as designating a regular and interlocking distribution of the inorganic and organic matter, so as to avoid or limit the accumulation of either of the two materials within the cementitious compositions 30. The assembly of the two organic matter 20 and inorganic matter 10 is therefore equivalent to a mixture. The cementitious compositions 30 described herein are intended to be used in the production of final materials 40 (Figure 3) produced, for example, on a construction site. The final materials 40 are typically obtained by adding other products such as sand 31, water 32, gravel 33, and possibly additives to the cementitious compositions 30. The final materials40 thus constitute a construction or certain parts of a construction, such as a house or an apartment building. In particular, the final materials40 can refer to the structural elements of such a construction. The final materials40 are typically in solid and rigid form, unlike the powders of the cementitious compositions30 on the basis of which they are produced.

[0019] Cementitious compositions according to this description preferably include low carbon footprint cements, or so-called “low carbon” cements, such as those corresponding to standard NF 197-5 of 2021 or any other equivalent standard.

[0020] Inorganic material 10 comprises essentially, or even exclusively, inorganic materials. In particular, inorganic material 10 refers to mineral materials, including, notably, calcium, silicon, boron, aluminum, iron, sulfur, copper, potassium, magnesium, sodium, and phosphorus, in all their forms, including mixtures and oxidized derivatives such as carbonates, silicates, aluminates, sulfides, phosphates, and aluminosiliates, as well as their combination with ions such as hydroxide or halide ions. An inorganic material according to the present invention may, for example, consist mainly of calcium carbonate, commonly called limestone, and clay, in a mass proportion of approximately 70/30 to 90/10, preferably around 80/20. Other inorganic materials may be included in the inorganic material, such as sulfates, notably calcium sulfate, also known as gypsum, magnesium oxides, or ferric oxide. Preferably, the inorganic material corresponds to a known cement, for example, Portland cement, or Portland-type cement. The inorganic material is not limited to such a cement and more broadly designates any sealing or construction material such as mortar, concrete, tile adhesive, pure Portland cement, composite Portland cement, blast furnace cement, pozzolanic cement, and composite cement. In some embodiments, the inorganic material also designates plaster, lime, and any equivalents. The inorganic material 10 according to the present invention includes special cements such as low-clinker, so-called durable cements, for example LC3 cement known as "Limestone Calcined Clay Cement," or calcined clay and limestone cement, or earth cement such as raw clay cement, also known as "Raw Clay Cement." The inorganic material according to the present invention further includes geopolymers, in particular those based on aluminosilicate, phosphate, or zeolites.

[0021] The inorganic material 10 is used in the context of the present invention in the form of powders, obtained by grinding and cooking processes, such as those commonly used, or other more specific processes. Dry, wet, or mixed processes may, for example, be used. The process used for the production of inorganic material powder may include one or more homogenization phases, in particular by stirring.

[0022] The specific surface area of the inorganic powder 10 is between 2000 and 7000 cm²/g, preferably between 2700 and 5500 cm²/g or in the range of 2800 to 5000 cm²/g. The apparent density of the inorganic powder 10, including the voids between the powder particles, is in the range of 800 kg/m³ to 1200 kg/m³, preferably in the range of 1000 kg/m³ to within 2% or 5%. The absolute density of the inorganic powder 10, determined without taking into account the interstitial voids between the particles, is on the order of 2.5 g/cm³ to 3.5 g/cm³, preferably between 2.8 g/cm³ and 3.2 g/cm³ or between 2.9 g/cm³ and 3.15 g/cm³. The particle size of the inorganic powder 10, within the scope of the present invention, is between 0.1 micrometers and 200 micrometers, preferably between 0.5 and 100 micrometers, depending on their composition and method of production. The particles can be of fine size such as 1 to 10 micrometers, or 1 to 5 micrometers, or of a higher granulometry such as 30 to 80 micrometers or on the order of 40 to 60 micrometers.

[0023] The organic matter 20 included in the cementitious compositions 30 of the present invention is used in powder form. In this way, the powder(s) of organic matter 20 can easily be mixed and homogenized with the inorganic matter 10. Organic matter 20 is understood to be derived from the living world, in particular from the plant world. The term organic matter is equivalent to carbonaceous matter or biocarbon, even if the matter constituting it is not 100% carbonaceous. Organic matter 20 may in fact include a small proportion of mineral salts or other so-called inorganic elements. Typically, the organic matter 20 according to the present invention may comprise up to 2%, 3%, 5%, or less than 10% by mass of inorganic elements naturally present in the plant kingdom.

[0024] The particle size of the organic material powder 20 is preferably calibrated according to the particle size of the inorganic material powder 10. It can also be determined according to the expected properties of the final composition and/or material 40. In one embodiment, the average particle size of the organic material 20 is the same as, or similar to, that of the inorganic material particles 10. An average particle size of the organic material 20 that differs by less than 10% or less than 5% from the average particle size of the inorganic material 10 is considered here to be similar to that of the inorganic material particles 10. Alternatively, the average particle size of the organic material 20 is smaller than that of the inorganic material particles 10. For example, it may correspond to 10% to 80% of the average particle size of the inorganic material 10. It can be determined to correspond to approximately 20%, 30%, 50%, or 60% of the average size of the inorganic matter particles.10 In this way, the organic matter particles20 easily fit into the natural interstices of the inorganic matter.10 Alternatively, the average size of the organic matter particles20 can be determined to be significantly larger than that of the inorganic matter particles.10 For example, it can be more than 20%, 30%, 50%, or even 80% larger than the average size of the inorganic matter particles.10

[0025] Although the average particle size of organic matter 20 can be determined relative to that of inorganic matter 10, as indicated above, it can also be defined in absolute terms. In this case, the organic matter 20 can be obtained or used in the form of a homogeneous powder with an average particle size between 1 micrometer and 100 micrometers, preferably between 5 and 90 micrometers or between 40 and 60 micrometers. Alternatively, different particle sizes can be considered. A fine powder with an average particle size of less than 30 micrometers, or between 30 and 1 micrometer, can be considered, as well as an intermediate particle size of around 50 micrometers, or between 40 and 60 micrometers, or a larger particle size of between 70 and 100 micrometers or around 80 micrometers. The dimensions stated above are subject to a tolerance that a person skilled in the art will be able to assess. The dimensions can be determined with a tolerance of 5% or 10%, for example. Organic matter powders can be obtained with the required particle size by sieving through one or more calibrated sieves. For example, a 60-micrometer sieve yields a powder whose particle size is entirely less than 60 micrometers on the one hand, and entirely greater on the other, when it remains on the sieve. Double sieving allows control over the particle size distribution range. Alternatively, or in addition, the particle size and size distribution can be determined by microscopy or any other suitable method.

[0026] According to one embodiment, several organic matter powders 20 of different particle sizes can be mixed in varying proportions. For example, the organic matter 20 of a cementitious composition may comprise approximately 10% of a fine-particle powder, corresponding, for example, to about 20% or 30% of the average particle size of the inorganic matter 10, or to an average size of approximately 20 to 30 micrometers, the remainder of the powder having a particle size comparable or identical to that of the inorganic matter 10, or an intermediate size of approximately 40 to 60 micrometers. The combinations are, of course, adaptable according to requirements, particularly in terms of the mechanical strength of the final material 40.

[0027] The requirements take into account the amount of carbon to be sequestered. According to one embodiment, the average particle size of the organic matter20 is determined so as to sequester a maximum of CO₂ without impacting the mechanical strength of the final material, or impacting it only minimally, within a given tolerance range. To this end, a 10% reduction in compressive strength may be considered acceptable if, in return, the CO₂ sequestration exceeds a predetermined threshold. In addition to compressive strength, other parameters may be considered, such as the permeability, density, porosity, albedo, or color of the final material40, as well as a combination of these parameters. The values of the measured physical parameters are preferably determined with respect to the corresponding values of a known cementitious material consisting exclusively of inorganic matter. Portland cement may be taken as a reference in this case.

[0028] For the purposes of the present invention, organic matter 20 refers to plant material that has undergone at least one thermal transformation process, i.e., heating that transforms it into biocarbon. The carbon content is greater than 60% by mass, preferably greater than 70% by mass, or even greater than 80% by mass. The mass proportion of oxygen relative to carbon is on the order of 0.5 or less, preferably less than 0.4, or even less than 0.3. The organic matter according to the present invention further results from a grinding process that transforms it into powder. The specific surface area of the organic matter powder 20 is on the order of 20 m²/g or less, typically 15 m²/g or less, 7 m²/g or less, 5 m²/g or less, and in particular on the order of 4 m²/g or 2 m²/g. Thus, the porosity of the organic matter is significantly lower than that of most biocarbon-type materials. The specific surface area is determined according to the Brunauer-Emmett-Teller method, also known as the BET method. Based on the particle sizes, the organic matter 20 can be described as micro-biocarbon or micro-biocarbon particles. In one respect, the high carbon content of the organic matter allows for a reduction in net carbon dioxide emissions. Specifically, one kilogram of organic matter according to the present invention captures the equivalent of 2.5 kilograms of CO₂. According to another aspect, the organic matter20 according to the present invention is non-degradable or not significantly degradable, particularly due to its low oxygen content. It thus allows for the long-term sequestration of carbon in inorganic matter.

[0029] The specific surface area of organic matter particles20 is lower than that of conventional biocarbons produced by pyrolysis, which are porous. Consequently, the adsorption of additives onto the particles is limited or even impossible. Adsorption-desorption cycles of organic pollutants are thus limited or even impossible. Conventional carbons cannot be used for such applications, particularly due to their greater porosity. The low porosity of the organic matter particles20 according to the present invention also offers the advantage of not separating from the inorganic matter particles10 during the various stages of cement or concrete preparation, including during the final sealing or construction stages in the field, leading to the final product40. The organic matter particles20 according to the present invention preferably have a density close to that of the inorganic matter10. The density of organic matter particles 20 represents, for example, at least 30%, 40%, 50%, 60%, or 80% of the density of inorganic matter particles 10. The same proportions can be applied to the absolute density. Alternatively, or in addition, the absolute density of organic matter particles 20 is greater than 1 g/cm³, preferably on the order of 1.2 g/cm³ or more, or even 1.4 g/cm³ or more, or 1.6 g/cm³ or more. The absolute density of organic matter particles 20 according to this description may, for example, be between 1.1 g/cm³ and 2.5 g/cm³, or between 1.2 g/cm³ and 1.7 g/cm³.

[0030] According to one embodiment, the absolute density of the organic matter particles 20 in a cementitious composition 30 is greater than 1.2 g/cm³, or even greater than 1.4 g/cm³, or between 1.2 g/cm³ and 1.7 g/cm³, and that of the inorganic matter particles 10 is between 2 g/cm³ and 3.5 g/cm³, or in the range of 3.1 g/cm³ to 3.2 g/cm³. According to another embodiment, the absolute density of the organic matter particles 20 is that indicated above, and that of the cement particles is less than 3 g/cm³, or even less than 2.5 g/cm³, or even less than 2 g/cm³, particularly in the case where the inorganic matter is based on zeolites.

[0031] Figure 2 schematically illustrates the production of organic matter according to the present invention. Biomass 21 is subjected to a heating step using a suitable heating device 102, such as a furnace or equivalent. In one embodiment, the biomass 21 can be circulated in a heating loop by means of a carrier fluid. In a preferred embodiment, the heating is carried out at atmospheric pressure at a temperature between 200°C and 400°C, or between 250°C and 350°C. Depending on the process conditions, a higher pressure may be observed locally, particularly when the biomass 21 is circulated. The biomass 21 is further subjected to a grinding step using a suitable grinder 101.

[0032] Figures 4 and 5 illustrate an example of a grinder usable for grinding biomass21. In this particular case, the grinder also serves as a device for circulating the carrier fluid and the biomass21. The grinder may include a drive assembly140 comprising a rotor141 and a stator142. The rotation of the rotor via its drive shaft143 allows the fluids to be drawn from the circuit and circulated. The rotor includes for this purpose a drive head 144 embedded in a part of the stator 142. The fluids of the circuit, including the carrier fluid and the biomass 21, are thus forced to pass between the drive head 144 and the stator 142. According to one embodiment, the drive head 144 and/or the stator 142 is provided with drive means such as blades, or reliefs adapted to drive the fluids. For example, the drive head 144 can be cylindrical or semi-cylindrical, the wall of which is notched with one or more slots forming rotor channels 145. Alternatively or in addition, the stator 142 can be cylindrical, arranged concentrically with the drive head, the wall of which is notched with one or more slots forming stator channels 146. The number, shape, and arrangement of the stator and rotor channels can be adapted as required. For example, they can be oriented parallel to the drive axis 143.

[0033] In addition to the fluid entrainment effect, the crusher is adapted to condition the biomass into elements of a specific size, such as less than 10 cm, less than 5 cm, or less than 1 cm, as required, or even smaller. In one embodiment, the biomass 21 can be loaded into a conversion tank (not shown) without significant prior crushing, provided that it can be circulated. The circulation device is adapted to the particle size required for the organic matter obtained from the biomass 21. For example, the stator 146 and/or rotor 145 channels can be sized accordingly. The largest elements of the biomass 21 are thus sheared during their entrainment. Alternatively, or in addition, an adequate gap is provided between the drive head 144 and the stator 142.

[0034] According to one embodiment, several shredders are arranged in series so as to break down the biomass into increasingly finer elements. According to another embodiment, a shredder according to the present invention comprises several stages, that is to say, several rotors and several stators, thereby increasing the shredding efficiency.

[0035] Other types of grinders can be considered. However, an important aspect of the present invention lies in the simultaneous heating and grinding steps described above. The biomass 21 can be circulated in a conversion unit 100 combining both the heating device 102 and the grinder 101. Thus, the organic matter 20 can be obtained rapidly in a single conversion step in the form of a powder such as that described above. The heating time is typically on the order of a few minutes, for example, less than 10 minutes, or 5 minutes, or even 2 or 3 minutes. Such a heating time is significantly shorter than that of slow pyrolysis, such as that mentioned in the preamble, which generally requires several hours of heating at high temperatures. Furthermore, the pressure required for the process of the present invention remains low, unlike conventional hydrothermal processes, which generally require several tens of bars.

[0036] In addition to combining heat treatment and particle size sizing of organic matter particles 20 in a single step, the present process offers the advantages of a short heating time (a few minutes), temperatures below 400°C, and low pressures close to atmospheric pressure. The process therefore differs from currently known rapid methods such as rapid pyrolysis, which requires temperatures above 500°C.

[0037] A variety of biomass 21 can be used. Depending on the requirements, certain types of plant biomass may be preferred, such as woody materials rather than green parts. Pre-treatments such as drying or dehydration may be carried out before the production of organic matter powder 20. Alternatively or in addition, a sieving step may be carried out after grinding to refine the particle size distribution, for example.

[0038] Depending on the required particle size, the grinder is calibrated accordingly. A grinder specifically adapted to the required particle size can be implemented in the conversion unit. Alternatively, a grinder can be modular, at least within certain limits, so as to produce particles of a predetermined size. Alternatively, or in addition, a biomass conversion unit can contain several grinders, each usable depending on the required particle size.

[0039] The one-step process thus minimizes energy expenditure and the resulting CO₂ emissions. Furthermore, the thermal energy can be obtained from renewable sources such as a solar furnace or a renewable electricity source. Alternatively, or in addition, heating can be obtained, at least partially, by burning gases from biomass conversion.⁴⁹

[0040] A device such as that described in patent application WO2024IB54752, the contents of which are fully incorporated by reference in this application, may be used. This does not, however, preclude other devices, provided that they allow the heating and grinding steps to be combined to obtain the organic matter particles 20 described above.

[0041] The present invention further covers a cementitious composition 30 comprising an amount of inorganic matter 30 and an amount of organic matter 20 as described herein. The cementitious compositions 30 according to the present invention are preferably in the form of a homogeneous powder, the particle size of which corresponds to that described above. The proportions of organic matter 20 relative to inorganic matter can vary according to requirements in a ratio between 1/99 and 40/60, such as 2/98 and 40/60, or even higher, on the order of 50/50. Preferably, the proportions are in a ratio of 5/95 to 35/65 or 10/90 to 30/70.

[0042] According to one embodiment, the proportion of organic matter relative to inorganic matter is in a mass ratio of between 5/95 and 40/60, the organic matter comprises at least 60% by mass of carbon, a molar ratio of oxygen to carbon of 0.5 or less, and a surface area of 20 m²/g or less. According to another example, the proportion of organic matter relative to inorganic matter is in a mass ratio of between 1/99 and 40/60, or between 2/98 and 40/60, the organic matter comprises at least 60% by mass of carbon, a molar ratio of oxygen to carbon of 0.5 or less, and a surface area of 20 m²/g or less. According to another embodiment, the proportion of organic matter to inorganic matter is in a mass ratio between 2/98 and 40/60, or between 5/95 and 40/60, the organic matter comprises at least 60% by mass of carbon, a molar proportion of oxygen/carbon of 0.5 or less, and a surface area of 5 m<2>/g or less.

[0043] The incorporation of organic matter 20 into the cementitious compositions 30 of the present invention makes it possible, in particular, to reduce CO₂ emissions without significantly degrading the compressive strength of the final materials 40. The incorporation of 5 parts of biocarbon as described herein into a cementitious composition 30 reduces CO₂ emissions by 20% while maintaining 90% of the compressive strength. The incorporation of 10 parts of biocarbon according to the present invention into a cementitious composition 30 reduces CO₂ emissions by 40% and maintains the compressive strength at 80% of its value compared to a traditional cement without biocarbon. For 20 grams of biocarbon per 100 grams of cementitious composition 30, CO₂ emissions are reduced to only 30%, while the compressive strength of the final product 40 remains at 70% of its reference value. With 30 parts of biocarbon for 100 parts of cement composition 30, CO<2> emissions are totally offset and the compressive strength of the final product40 remains at 68% of its reference value.

[0044] The proportions of organic matter20 can thus be adapted according to the expected strengths of the final materials40. Elements requiring the greatest resistance to compression can contain an amount of organic matter20 limited to 5 or 10% by mass, while structurally less demanding elements can contain up to 30% by mass of biocarbon20, or even more.

[0045] The present invention also covers a process for producing cementitious compositions 30 such as those described herein. The process includes a step of selecting or producing biocarbon particles whose size and specific surface area at least correspond to the required values. Such values can be determined beforehand either empirically, through testing, or via modeling, or by a combination of modeling and actual testing. Such tests and/or simulations make it possible, for example, to determine the size of organic matter particles 20 relative to the size of inorganic matter particles 10 as a function of the compressive strength of the final material 40, or as a function of the acceptable amount of CO₂ emission, or as a function of the proportion of organic matter incorporated in the cementitious composition 30. Multi-parameter lookup tables can, for example, be developed to facilitate the determination of the parameters.

[0046] The process for manufacturing such cementitious compositions 30 includes the step of selecting or producing the inorganic material in the form of a powder of suitable particle size. The inorganic material 10 advantageously corresponds to a Portland-type cement, but may be different. For example, a specific cement may be required for a particular application. Preferably, the characteristics of the organic material 20 are determined based on those of the selected inorganic material 10. Although the reverse is conceivable, it is not the preferred approach.

[0047] The process for producing cementitious compositions 30 includes a step of mixing a proportion of organic matter 20, in the form of a powder of suitable particle size, with inorganic matter 10, also in powder form. The proportion is determined according to the criteria stated above. The mixing can be carried out using a tank 200 (Figure 1) or any other suitable container and a mechanical mixing means 201 until satisfactory homogeneity is achieved. The tank can be stationary and contain mixing propellers driven by a rotary motor. Alternatively, the tank can be rotating and have baffles or mixing fins on its internal walls. Vibration and/or tipping means can be provided. The organic matter 20 and inorganic matter 10 can be poured simultaneously into the tank 200 or arranged in alternating layers, or in other ways as required. Organic matter 20 and inorganic matter 10 can be conveyed via conveyor chains. They can also be premixed during their conveying to the tank 200, for example by adding one to the other on the conveyor belts. Any suitable mixing system can be used provided it allows the organic matter 20 and inorganic matter 10 to be homogenized in the required proportions.

[0048] The process may optionally include post-mixing steps. A sieving step may, for example, be envisaged in the case where the particles of organic matter 20 and inorganic matter 10 must be of the same size.

[0049] In addition to compressive strength and CO₂ emissions, parameters such as water permeability or the porosity of the final material 40 can be considered. The particle sizes of the inorganic 10 and organic 20 materials can be matched to adapt such parameters. For example, the particle size of the organic 20 materials can be reduced relative to that of the inorganic 20 materials to fill as many gaps as possible and thus increase the compactness of the final material 40. Trade-offs can therefore be made to optimize both compressive strength, the porosity of the final material 40, and CO₂ emissions. Alternatively, or in addition, parameters such as the thermal conductivity of the final material 40, the setting rate of the cementitious composition, and the long-term strength of the final material 40 can also be optimized by adding an appropriate amount of organic matter according to the present invention.

[0050] According to one aspect, the organic matter 20 included in the cementitious compositions 30 of the present invention can be adapted to modify the rheology of such compositions so as to be used in three-dimensional printing applications.

[0051] The cementitious composition according to the present invention may have a density identical or similar to the density of the inorganic material alone, or less than the density of the inorganic material by a value of less than 30%, or less than 20%, or even less than 10%. These values may apply to the apparent density or to the absolute density.

Experimental section

[0052] General procedures: The mortars were prepared according to the following procedure. If the mix formulation so requires, the gravel was introduced into the mixer first, followed by the cement and biocarbon. The solids were then mixed to ensure good homogeneity. Finally, water was added to the mixture, and the resulting mixture was stirred until completely homogeneous. For mixes requiring a superplasticizer, the calculated amount was added after 80% of the required water had already been added. The remaining 20% of water was added after the superplasticizer.

[0053] The mixtures obtained were poured into cubic or cylindrical molds. After filling the molds to the brim, the samples were briefly compacted using a portable vibrating device and the open face was sealed with a transparent plastic film and stored in a temperature and humidity controlled chamber for hardening.

[0054] For all tests and specimens, the type of cement used is CEM II A-LL 42.5 N. When used, the superplasticizer (SP) is Sika ViscoCrete®-20 easy.

[0055] The batch of biocarbon used for these tests was prepared from wheat straw residue using CarboRefine's proprietary conversion technology. The particle size is less than 50 µm (sieve test). The average particle length is 11.6 ± 10.5 µm and the average particle width is 6.2 ± 5.7 µm (microscopic calibration).

[0056] Several cementitious compositions 30 are prepared by mixing Portland cement with organic matter powder 20 in varying proportions listed in Table 1. Sample E5 contains 5 g of organic matter 20 per 100 g of cementitious composition 30, sample E10 contains 10 g of organic matter 20 per 100 g of composition, sample E15 contains 15 g of organic matter 20 per 100 g of composition, sample E20 contains 20 g of organic matter 20 per 100 g of composition, and sample E30 contains 30 g of organic matter 20 per 100 g of composition. The quantities are expressed in the table in kg/m³.

Table 1

[0057] Reference

1384

0

554

0.40

E 5 (5%)

1319

66

527

0.40

E 10 (9%)

1185

118

533

0.45

E 15 (13%)

1105

166

525

0.48

E 20 (17%)

1036

207

518

0.50

E 30 (23%)

880

264

528

0.60

[0058] Table 2 shows the estimated CO₂ emitted for each composition and the compressive strength expressed in absolute values. The CO₂ emissions are calculated on the basis of the assumption that one kg of cement, corresponding to the inorganic matter (20), releases 0.75 kg of CO₂ and that 1 kg of biocarbon stores 2.5 kg of CO₂.

Table 2

[0059] Reference

1038

37.6

E 5 (5%)

824

33.6

E 10 (9%)

594

30.5

E 15 (13%)

414

27.8

E 20 (17%)

260

26

E 30 (23%)

0

25.5

[0060] Table 3 shows the CO<2>emitted estimate for each of the compositions, as well as the compressive strength expressed in relative values with respect to the reference not containing organic matter20.

Table 3

[0061] Reference

100

100

E 5 (5%)

79

89

E 10 (9%)

61

81

E 15 (13%)

43

74

E 20 (17%)

28

69

E 30 (23%)

0

68

[0062] Table 4 describes the composition of a sample E10' comprising 10g of organic matter per 100g of composition, which also includes gravel:

Table 4

[0063] Reference

321.1

0.0

1911.2

188.6

0.6

E 10' (10%)

313.1

34.8

1863.7

183.9

0.6

[0064] Table 5 shows the compressive strength expressed in N/mm<2> over periods of 7 days and 28 days, of composition E10':

Table 5:

[0065] Reference

25.1

34.6

E 10' (10%)

22.8

30.5

[0066] Table 6 represents the compressive strength of composition E10' expressed as a relative value with respect to the reference.

Table 6:

[0067] Reference

73%

100%

E 10' (10%)

66%

88%

[0068] After adding 10% biocarbon to the total binder content, the compressive strengths of the samples remained at 90% and 88% of those of the reference at 7 and 28 days, respectively. At the same time, the addition of biocarbon reduced net CO₂ emissions from 240.8 kgCO₂/m³ to 147.8 kgCO₂/m³, representing a reduction of 39%.

[0069] Table 7 describes the composition of samples E5b, E10b, and E20b, comprising 5 g, 10 g, and 20 g of organic matter per 100 g of composition, respectively, which also includes superplasticizer (SP). The amount of organic matter is substantially the same in all samples. The values in the table are expressed in kg/m³. The fluidity of the mixtures was equalized using a modified polycarboxylate-based superplasticizer. The results indicate that it is possible to partially replace a substantial amount of cement with biocarbon without compromising the key characteristics of the final material.

Table 7

[0070] Reference

1397.5

0.0

4.2

545.0

0.40

E 5b (5%)

1330.8

66.5

9.1

514.1

0.40

E 10b (9%)

1270.7

127.1

13.1

486.3

0.40

E 20b (17%)

1109.0

221.8

25.2

458.7

0.44

[0071] Table 8 describes the compressive strength of compositions E5b, E10b and E20b, expressed in N/mm<2>

Table 8

[0072] Reference

60

E 5b

59

E10b

57.9

E20b

39.5

[0073] Table 9 describes the compressive strength of compositions E5b, E10b and E20b, expressed as a relative value with respect to the reference.

Table 9:

[0074] Reference

100

E 5b

98

E10b

97

E20b

66

[0075] Table 10 describes the composition of samples E5c, E10c, and E20c, comprising 5 g, 10 g, and 20 g of organic matter per 100 g of composition, respectively, which also includes gravel and superplasticizer SP. The different samples contain the same amount of water. The values in the table are expressed in kg/m³.

Table 10:

[0076] Reference

913.1

0.0

1897.3

2.7

531.1

0.60

E 5c (5%)

881.3

44.1

1831.2

6.0

509.6

0.60

E 10c (9%)

851.9

85.2

1770.1

8.8

489.9

0.60

E 20c (17%)

799.1

159.8

1660.5

13.1

455.1

0.60

[0077] Table 11 describes the compressive strength of compositions E5c, E10c and E20c, expressed in N/mm<2>.

Table 11

[0078] Reference

31.9

E 5c

31.9

E10c

22.2

E20c

15.9

[0079] Table 12 describes the compressive strength of compositions E5c, E10c and E20c, expressed as a relative value with respect to the reference.

Table 12:

[0080] Reference

100

E 5c

100

E10c

70

E20c

50

Reference numbers used in the figures

[0081] 10 Inorganic material 20 Organic material 21 Biomass 30 Cementitious composition 40 Final material 100 Conversion unit 101 Crusher 102 Heating device 140 Drive assembly 141 Rotor 142 Stator 143 Drive shaft 144 Drive head 145 Rotor channels 146 Stator channels 200 Tank 201 Mixing means

Claims (14)

1. Cementitious composition (30) comprising: - a quantity of inorganic matter (10), and - a quantity of organic matter (20), in which the proportion of organic matter relative to inorganic matter is in a mass ratio between 1/99 and 40/60, the organic matter comprises at least 60% by mass of carbon, a molar ratio of oxygen/carbon of 0.5 or less, and a surface area of 20 m²/g or less. 2. Cementitious composition according to claim 1, wherein the organic (20) and inorganic (10) matter are in powder form, wherein the particle size of the inorganic matter is between 0.1 micrometer and 200 micrometers and the particle size of the organic matter (20) is between 1 micrometer and 100 micrometers. 3. Composition according to claim 2, wherein the average size of the organic matter particles (20) is identical or similar within 10% to that of the inorganic matter particles (10). 4. Composition according to claim 2, wherein the average size of the organic matter particles (20) is selected from small particles, between 1 and 30 micrometers, intermediate particles between 40 and 60 micrometers, large particles between 70 and 100 micrometers, or a mixture of such types of particles. 5. Composition according to any one of claims 1 to 4, wherein the absolute density of the organic matter particles (20) is greater than 1 g/cm<3>, and/or represents more than 30% or 50% of the absolute density of the inorganic matter particles (10). 6. Composition according to any one of claims 1 to 5, wherein the inorganic material comprises limestone and clay in mass proportions between 60/40 and 90/10. 7. Composition according to any one of claims 1 to 6, wherein the inorganic material is of the Portland cement type. 8. A process for producing a cementitious composition (30) according to any one of claims 1 to 7, comprising the steps of: – Selecting or producing a quantity of inorganic material (10) in powder form having an average particle size of between 0.1 micrometers and 200 micrometers, – Selecting or producing a quantity of organic material (20) in powder form, having an average particle size of between 1 micrometer and 100 micrometers, – Mixing the powders of organic material (20) and inorganic material (10) such that the proportion of organic material relative to inorganic material is in a mass ratio of between 1/99 and 40/60, in which the carbon content of the organic material (20) is greater than 60% by mass, the oxygen/carbon molar ratio is 0.5 or less, and its surface area is 5 m²/g or less. 9. A method according to claim 8, wherein the step of mixing the powders of organic (20) and inorganic (10) material is carried out by mechanical mixing using rotating blades or tanks and/or by vibration and/or by conveying. 10. A method according to any one of claims 8 and 9, wherein the step of producing a quantity of organic matter (20) in powder form, having an average particle size of between 1 micrometer and 100 micrometers, is carried out by thermal treatment of biomass (21) at a temperature between 200°C and 400°C at atmospheric pressure for a period of less than 10 minutes, concomitant with the grinding of the biomass (21), so as to directly produce particles of the required size at the end of the thermal treatment. 11. Method according to claim 10, said biomass being dispersed in a carrier fluid and circulated in a conversion loop comprising a grinder adapted for grinding organic matter (20). 12. Organic matter particles (20) comprising at least 60% by mass of carbon, an oxygen/carbon molar ratio of 0.5 or less, and a surface area of 5 m<2>/g or less. 13. Organic matter particles (20) according to claim 12, having an absolute density greater than 1 g/m<3>. 14. Final material (40) comprising the composition according to any one of claims 1 to 7, sand and water, the final material having a compressive strength between 60% and 90% of the compressive strength of a final material not comprising organic matter (20).