Self-leveling filler with low greenhouse potential

Description

Field of invention

[0001] The invention relates to a self-leveling filler with low global warming potential. State of the art

[0002] Mineral building materials, and in particular self-leveling compounds, contribute to climate-damaging CO₂ emissions, especially due to their mineral components (e.g., cement) and their organic ingredients (e.g., dispersion powders). For example, commercially available leveling compounds have global warming potential (GWP) values ​​between 0.26 and 0.51 kg CO₂ equivalent / kg.

[0003] To reduce the greenhouse gas potential of mineral building materials, the state of the art proposes adding so-called biochar to these materials. Such biochar, or "plant-based carbon," is produced by carbonizing plant or woody raw materials. Carbonization encompasses pyrolysis and various other processes, all of which involve gently heating plant material, sometimes under pressure, to increase its carbon content. The CO₂ originally absorbed by plants during their life cycle is removed from the atmosphere. Therefore, biochar acts as a carbon sink and makes a positive contribution when added to building products or fillers.

[0004] Such an approach is pursued, for example, in WO 2023 / 281220 A1, which describes cementitious compositions containing up to 30% carbonated biochar. This can achieve a CO₂ emission reduction of between 0.207 and 0.382 kg CO₂ equivalent / kg.

[0005] Furthermore, WO 2023 / 006136 A1 describes a process for producing concrete with an improved CO₂ balance, in which a mixture of binder, aggregate, and biochar is produced with the addition of an aqueous solvent. The biochar comprises between 1 and 30% of the total mixture. The use of biochar can improve the carbon balance of one cubic meter of concrete by up to 70%.

[0006] WO 2023 / 285501 discloses dry mortar compositions containing 10 to 50 wt% biomass ash, thereby enabling a reduction in CO₂ emissions of 20 to 35%. These dry mortar compositions are particularly suitable as tile adhesives.

[0007] The aforementioned disclosures generally disclose building material mixtures in which the CO₂ balance of the mixtures is improved by the addition of biochar or biomass ash. However, the biochar can significantly influence the properties of the building material mixtures. Particularly with self-leveling compound mixtures, it must be ensured that the self-leveling properties are maintained when the components of the compound mixture are changed. If simply mixing in any type of biochar results in a thick, viscous consistency lacking self-leveling properties, the problem of providing a self-leveling compound is considered unsolved. None of the aforementioned disclosures describe a compound containing biochar that exhibits self-leveling properties.

[0008] In addition to the above-mentioned publications, the following prior art is referenced: KR 100 841 781 B1 discloses a self-leveling cement-based floor leveling compound which may include charcoal powder. KR 2005 0004356 A describes a construction mortar with activated charcoal and wood charcoal. CN 111 943 578 A discloses a self-leveling concrete with charcoal powder. WO 2022 / 154774 A2 discloses a composite coating material with cement binder and carbon dust. CN 102 190 463 A describes an environmentally friendly, self-leveling cement-based material. FR 3 125 034 A1 discloses a cement composition with biochar.

[0009] Therefore, there is a need to develop a self-leveling compound with reduced global warming potential. Furthermore, there is a need for biochar that can be used to reduce the global warming potential of self-leveling compounds. Summary of the invention

[0010] In a first aspect, the present invention provides a self-leveling cement- or gypsum-based filler comprising 3 to 13 wt.% biochar, based on the dry weight of the self-leveling filler, wherein the biochar has a particle size d10 of at most 3.2 µm and a specific surface area of ​​at least 7800 cm² / g, wherein the particle size and the specific surface area are determined by laser granulometric measurement, and wherein the term "biochar" refers to materials produced by carbonization of plant and / or woody starting materials.

[0011] The inventors have surprisingly discovered that a self-leveling leveling compound can be produced solely by using biochar with a particle size (d10) of no more than 3.2 µm and a specific surface area of ​​at least 7800 cm² / g. Commercially available biochars that formally reduce the global warming potential (GWP) of leveling compounds can, when used in self-leveling floor compounds, lead to a loss of desirable application properties such as self-leveling. Furthermore, the use of 3 to 13 wt% of this biochar can reduce the GWP value, making the leveling compound not only climate-neutral but also capable of making a climate-positive contribution.

[0012] In a further aspect, the present invention provides for the use of biochar to reduce the global warming potential (GWP) of self-leveling cement- or gypsum-based fillers, wherein the biochar has a particle size d10 of at most 3.2 µm and a specific surface area of ​​at least 7800 cm² / g. As described above, the use of biochar with the aforementioned properties enables the self-leveling of the filler and a significant reduction in the GWP value.

[0013] Further aspects of the present invention can be found in the dependent claims and the detailed description. Detailed description of the invention Definitions

[0014] Unless otherwise defined, technical and scientific terms used herein shall have the same meaning as they are generally understood by a person skilled in the field of the invention.

[0015] Quantity specifications within the scope of the present invention refer to wt.%, unless otherwise specified or evident from the context.

[0016] Within the scope of the present invention, "self-leveling" and "self-leveling" can be used synonymously. As is generally known, "self-leveling" means that a water-based leveling compound spreads itself on a substrate and forms a level surface. Leveling compounds with self-leveling properties are commercially available and known in the prior art. Self-leveling leveling compounds are suitable for leveling substrates and, if necessary, as a preparation for the subsequent installation of a floor covering. In certain embodiments, a leveling compound is self-leveling if it has the ability to spread itself under its own weight. According to some embodiments, a leveling compound is self-leveling if it has a flow time of no more than 120 s and a spread of at least 11 cm, measured with a flow cup according to DIN 53211:1987-06 with a 6 mm nozzle.To measure the flow time and spread, the filler is mixed with water. Between 22 and 28% by weight of water can be added to the dry filler, based on the dry weight of the filler. "Dry" here means that the filler has not been mixed with water. According to some embodiments, a flow cup conforming to DIN 53211:1987-06 is used to measure the flow time and spread, with the difference that a 6 mm nozzle is used instead of the 4 mm nozzle specified in DIN 53211:1987-06. A detailed description of the determination of the flow time and spread is given below.

[0017] According to some embodiments, the term "dry weight" refers to the weight of the powdered and / or dry filler. In some embodiments, "powdered filler" means that the filler has not been mixed with water. In certain embodiments, the term "dry filler" means that the filler has a moisture content of less than 1.2 wt.%, preferably less than 1.1 wt.%, and more preferably less than 1.0 wt.%, based on the dry weight of the filler. The moisture content of the filler is determined using the drying method (gravimetric moisture measurement) by comparing the weight of the sample before and after drying at 40 °C. A detailed description of the determination of the moisture content of fillers is given below.

[0018] According to certain embodiments, the "self-leveling compound" refers to a dry mix and / or powder mix of a leveling compound before it is mixed with water. According to some embodiments, the self-leveling compound refers to a leveling compound that has already been mixed with water.

[0019] In the context of the present invention, the terms "biochar," "bio-char," and "plant charcoal" can be used synonymously. Plant charcoals are materials produced by the carbonization of plant and / or woody feedstocks. In some embodiments, "carbonization" is the pyrolysis of plant material. Plant material can be heated and / or heated under pressure to increase its carbon content. The CO₂ originally absorbed by plants during their life cycle prior to carbonization is removed from the atmosphere. Therefore, plant charcoals act as carbon sinks (negative CO₂ emissions) and, when added to product compositions, lead to a reduced CO₂ footprint. Generally, plant charcoals can have a carbon content of ≥ 75% by weight.-%, based on the total weight of the biochar, have a particle size of ≤ 1 mm, an ash content of < 15%, a water content of < 10% and a specific surface area of ​​at least 3000 cm² / g.

[0020] In some embodiments, the leveling compound is a floor leveling compound. According to certain embodiments, the leveling compound is a self-leveling compound. Within the scope of the present invention, leveling compounds can be cement-based ("cementitious leveling compounds") and / or gypsum-based ("calcium sulfate-bound leveling compounds"). The determining factor is the inorganic binder with the highest proportion in the respective product. In particular, the leveling compound of the present invention can be a cementitious leveling compound or a calcium sulfate-bound leveling compound, as defined in TKB Data Sheet 9, dated July 2019, Chapter 4.1.

[0021] In the context of the present invention, the abbreviation "GWP" stands for "Global Warming Potential." The GWP value of a chemical compound, component, or mixture is a measure of its relative contribution to the greenhouse effect. GWP is generally understood to be the sum of all greenhouse gases absorbed or emitted over the considered phases of the product life cycle. The greenhouse gas fluxes are thus combined into the common unit: kg CO2 - equivalents / kg The data is converted and summed. The product-specific GWP is calculated according to the calculation rules of the DIN EN 15804:2012+A2:2019 standard. Life cycle phases A1 to A3 of the standard can be considered, and both primary and secondary data can be included. In some embodiments of the present invention, the GWP value is determined according to DIN EN 15804:2012+A2:2019.

[0022] "Particle size x10" and "particle size d10", "particle size x50" and "particle size d50", "particle size x90" and "particle size d90", as well as "particle size x99" and "particle size d99" can be used synonymously. As is generally known, the particle size d10, d50, d90, or d99 of a powdered substance or mixture refers to the value at which 10%, 50%, 90%, or 99% of the particles are smaller than a specific particle size. In some embodiments, the particle size refers to the equivalent diameter of the particles. The particle size d10, d50, d90, and / or d99 are determined by laser granulometric measurement.According to certain embodiments, a Heywood factor of 1 and / or a theoretical density of 1 g / cm³ is assumed for determining the particle sizes d10, d50, d90, d99 and / or the specific surface area by means of laser granulometric measurement. For determining the particle sizes d10, d50, d90, d99 and the specific surface area by means of laser granulometric measurement, an ideal spherical geometry of the particles is assumed.

[0023] As is generally known, mixing fillers refers to blending the dry filler with water. The amount of water required for mixing is usually specified by the manufacturer. This water is also called "mixing water" or "add-on water" and refers to the water that must be added during the mixing and preparation of the filler to make it workable and initiate the setting process. A professional can easily determine the required amount of mixing water through a few simple tests if it is not already specified by the manufacturer in the respective technical documentation for the filler. In certain formulations, the terms "mixing" and "blending" are used interchangeably.

[0024] A first aspect of the invention relates to a self-leveling cement- or gypsum-based filler comprising 3 to 13 wt.% biochar, based on the dry weight of the self-leveling filler, wherein the biochar has a particle size d10 of at most 3.2 µm and a specific surface area of ​​at least 7800 cm² / g. The particle size d10 and the specific surface area are determined by laser granulometric measurement.

[0025] In extensive studies, the inventors surprisingly discovered that only biochars with a particle size d10 of no more than 3.2 µm and a specific surface area of ​​at least 7800 cm² / g result in self-leveling fillers. Self-leveling fillers could not be produced using biochars with particle sizes d10 larger than 3.2 µm and specific surface areas smaller than 7800 cm² / g. In particular, the use of 3 to 13 wt% of these biochars can reduce the global warming potential (GWP) of the self-leveling fillers. In some embodiments, a negative GWP value, for example -0.05 kg CO₂ equivalent / kg, can even be achieved, resulting not only in a climate-neutral filler but also in a filler with a negative CO₂ footprint.Thus, the present invention provides a filler with excellent self-leveling properties and a significantly reduced CO2 footprint.

[0026] According to certain embodiments, the self-leveling compound comprises 5 to 12 wt.% and preferably 6 to 10 wt.% biochar, based on the dry weight of the self-leveling compound. In some embodiments, the biochar has a particle size d10 of at most 3.0 µm and preferably at most 2.9 µm. According to some embodiments, the biochar has a specific surface area of ​​at least 8000 cm² / g, preferably at least 8150 cm² / g. The effects and advantages mentioned above are particularly pronounced in these embodiments.

[0027] In certain embodiments, the biochar can have a particle size d10 of at least 2.5 µm, preferably at least 2.7 µm. According to some embodiments, the biochar can have a specific surface area of ​​at most 9500 cm² / g, preferably at most 8500 cm² / g. These embodiments further improve the application-related properties of the filler.

[0028] According to certain embodiments, the biochar has a particle size d50 of at most 16.7 µm, preferably at most 16.4 µm. In some embodiments, the biochar has a particle size d50 of at least 15.8 µm, preferably at least 16.0 µm. The particle size d50 is determined by laser granulometric measurement. In these embodiments, the advantages and effects mentioned above are particularly pronounced.

[0029] In some embodiments, the biochar has a particle size d90 of at most 71.0 µm, preferably at most 69.0 µm. In certain embodiments, the biochar has a particle size d90 of at least 65.5 µm, preferably at least 66.5 µm. According to certain embodiments, the biochar has a particle size d99 of at most 135.0 µm, preferably at most 132.0 µm. In some embodiments, the biochar has a particle size d99 of at least 125.0 µm, preferably at least 127.0 µm. The particle size d90 and / or d99 is determined by laser granulometric measurement. According to these embodiments, the self-leveling properties of the filler can be further improved.

[0030] According to certain embodiments, the biochar has a water content of 3.7 to 5.8 wt.%, preferably 3.9 to 4.5 wt.%, based on the total weight of the biochar. In some embodiments, the water content of the biochar is determined by oven drying at 40 °C. In some embodiments, the biochar has an ash content of 4.60 to 5.00 wt.%, preferably 4.65 to 4.80 wt.%, based on the total weight of the biochar. According to some embodiments, the ash content is determined by thermogravimetric analysis. The application-related properties of the filler are further improved by these embodiments. In some embodiments, the biochar has a carbon content of at least 78 wt.%, based on the total weight of the biochar.

[0031] In certain embodiments, biochar can replace a portion of a filler in a self-leveling filler. According to some embodiments, the self-leveling filler further comprises a filler, wherein the total content of biochar and filler is 40 to 80 wt.%, preferably 45 to 70 wt.%, based on the dry weight of the self-leveling filler. The weight ratio between biochar and filler (biochar:filler) can be 0.05:1 to 0.50:1, preferably 0.10:1 to 0.25:1, and more preferably 0.12:1 to 0.20:1. These embodiments further improve the application-related properties of the filler.

[0032] According to some embodiments, the self-leveling compound has a GWP value of at most 0.1 kg CO₂ equivalent / kg, preferably at most 0.08 kg CO₂ equivalent / kg. The use of biochar thus reduces the global warming potential of the self-leveling compound.

[0033] In certain embodiments, the self-leveling filler has a flow time of no more than 120 s and / or a spread of at least 11 cm, measured with a flow cup with a 6 mm nozzle. In particular, the flow cup can be a flow cup according to DIN 53211:1987-06 with a 6 mm nozzle. According to some embodiments, the flow time is determined according to DIN 53211:1987-06, using a mixed filler instead of the paints, coatings, and similar coating materials measured in DIN 53211:1987-06, and using a flow cup with a 6 mm nozzle. In some embodiments, a mixed filler is obtained by adding 22 to 28 wt.%, in particular 23 to 27 wt.%, to the dry filler.-% water is mixed, based on the dry weight of the filler, optionally with the resulting mixture being homogenized for 30 to 60 s, in particular 45 s, using a laboratory stirrer at 18 to 20 °C. "Dry" here means that the filler has not been mixed with water. According to certain embodiments, the flow cup is filled with the mixed filler 30 seconds (s) after the filler has been mixed. This means that 30 s are allowed between mixing the filler and filling the flow cup. In some embodiments, the flow of the mixed filler from the flow cup is started 15 s after the flow cup has been filled. The start of the flow of the mixed filler is also referred to as "flow start" in the context of the present invention.In particular, the run-out time can be determined according to the procedure described in the paragraph below, "Determination of the run-out time (in seconds (s)) and the spread measurement (in centimeters (cm))."

[0034] According to some embodiments, the spread is determined after the flow time has been determined, with the spread of the filler being determined 4 minutes after the start of flow. In certain embodiments, the spread is determined by carrying out the flow time determination as described above, collecting the filler flowing through the flow cup on a plate covered with millimeter paper, and reading the flow radius covered by the collected filler on the glass plate from the millimeter paper 4 minutes after the start of flow. In particular, the spread can be determined according to the procedure described in the paragraph below, "Determination of the flow time (in seconds (s)) and the spread (in centimeters (cm))."

[0035] According to some embodiments, the self-leveling compound comprises, in addition to the biochar defined above, cement, a CaSO₄ binder, fillers, and additives. In some embodiments, the self-leveling compound consists of cement, a CaSO₄ binder, fillers, additives, and biochar. According to these embodiments, the self-leveling compound refers to a dry mix of a leveling compound before it is mixed with water. In certain embodiments, the self-leveling compound consists of cement, a CaSO₄ binder, fillers, additives, biochar, and water. According to these embodiments, the self-leveling compound refers to a leveling compound that has been mixed with water.These embodiments can further improve the self-leveling properties of the filler and further promote rapid drying and setting of the filler.

[0036] In some embodiments, the cement is selected from alumina cement, Portland cement, calcium sulfoaluminate cement, and combinations thereof. In particular, the cement may be a mixture of alumina cement and Portland cement. In some embodiments, the alumina cement may have the chemical composition of 36–44 wt.% Al₂O₃, 34–42 wt.% CaO, 2–8 wt.% SiO₂, and 12–20 wt.% Fe₂O₃, based on the total weight of the alumina cement. In particular, the alumina cement may have the chemical composition 4-6 wt% SiO₂, 38-42 wt% Al₂O₃, 13-17 wt% Fe₂O₃, 36-40 wt% CaO or 3-5 wt% SiO₂, 38-42 wt% Al₂O₃, 14-18 wt% Fe₂O₃, 35-38 wt% CaO, based on the total weight of the alumina cement. The alumina cements may also contain up to 1.5 wt% MgO and up to 0.4 wt% SO₃, based on the total weight of the respective alumina cement.Suitable alumina cements include, for example, ISTRA40, LUMNITE MG4, and Ternal RG. According to certain embodiments, the Portland cement has the chemical composition of 18-25 wt.% SiO₂, 2-6 wt.% Al₂O₃, 1-4 wt.% Fe₂O₃, 62-69 wt.% CaO, and 2-5 wt.% SO₃, based on the total weight of the Portland cement. In particular, Portland cement may have the chemical composition 21-24 wt.% SiO2, 3-5 wt.% Al2O3, 1-2 wt.% Fe2O3, 63-68 wt.% CaO, 3-4 wt.% SO3 or 19-20 wt.% SiO2, 5-7 wt.% Al2O3, 2-3 wt.% Fe2O3, 63-64 wt.% CaO, 3-4 wt.% SO3, based on the total weight of the Portland cement. Suitable Portland cements include, for example, Milke Plus CEM I 52.5 R, Milke Premium CEM I 52.5 R, and Schwenk CEM I 52.5 R. In certain embodiments, the calcium sulfoaluminate cement has the chemical composition 5-10 wt.% SiO₂, 15-25 wt.% Al₂O₃, 1-5 wt.% Fe₂O₃, 30-50 wt.% CaO, 15-25 wt.%-% SO3, based on the total weight of the calcium sulfoaluminate cement. In particular, the calcium sulfoaluminate cement can have the chemical composition 6 wt% SiO2, 22 wt% Al2O3, 1 wt% Fe2O3, 35 wt% CaO, 16 wt% SO3, based on the total weight of the calcium sulfoaluminate cement. A suitable calcium sulfoaluminate cement is, for example, AliCEM.

[0037] In some embodiments, the CaSO₄ binder is selected from the group consisting of calcium sulfate hemihydrate (calcium sulfate α-hemihydrate and / or calcium sulfate β-hemihydrate), calcium sulfate anhydrite, calcium sulfate dihydrate, and combinations thereof. Preferably, the CaSO₄ binder is calcium sulfate α-hemihydrate.

[0038] In certain embodiments, the fillers are selected from the group consisting of sand, limestone flour, dolomite, and combinations thereof. In preferred embodiments, the fillers are selected from the group consisting of sand, limestone flour, and combinations thereof. In further preferred embodiments, the fillers are a combination of sand and limestone flour. The sand can be quartz sand and / or have a particle size of 0.06 to 0.3 mm. In some embodiments, the limestone flour has a particle size of 0 to 90 µm. In certain embodiments, the particle size of the sand and / or the limestone flour is determined via sieve residues. These embodiments further improve the application-related properties of the filler.

[0039] According to some embodiments, the additives are selected from the group consisting of dispersible powder, accelerators, retarders, rheology additives, and combinations thereof. In preferred embodiments, the additives are a combination of dispersible powder, retarders, rheology additives, and accelerators. In some embodiments, the dispersible powder is selected from the group consisting of ethylene-vinyl acetate copolymers, ethylene-vinyl versatate copolymers, styrene acrylates, and combinations thereof. In preferred embodiments, the dispersible powder is an ethylene-vinyl acetate copolymer. In certain embodiments, the accelerator is selected from the group consisting of alkali carbonates, alkali sulfates, or combinations thereof. According to preferred embodiments, the accelerator is an alkali carbonate, in particular lithium carbonate.According to certain embodiments, the retarder is selected from the group consisting of fruit acids, phosphates, polyphosphates, alkali gluconates, saccharides, alkali tartrates, or combinations thereof. The fruit acids may be tartaric acid or citric acid. In preferred embodiments, the retarder is citric acid. According to certain embodiments, the rheology additives are selected from the group consisting of thickeners, liquefiers, and combinations thereof. In particular, the rheology additives may be a combination of thickener and liquefier. In some embodiments, the liquefier is a comb polymer based on poly(meth)acrylic acid with polyethylene oxide side chains (PCEs, polycarboxylate ethers). In preferred embodiments, the liquefier is polycarboxylate ether. According to some embodiments, the thickener is an amide-based polyelectrolyte with sulfonic acid groups.In these embodiments, the aforementioned advantages and effects are particularly pronounced.

[0040] In some embodiments, the self-leveling compound is cement-based and, in addition to the biochar defined above, comprises 15 to 45 wt.%, preferably 20 to 30 wt.%, and more preferably 22 to 25 wt.% cement; 5 to 15 wt.%, preferably 6 to 10 wt.%, and more preferably 7 to 9 wt.% CaSO₄ binder; 40 to 75 wt.%, preferably 50 to 60 wt.%, and more preferably 53 to 57 wt.% fillers; and 1 to 8 wt.%, preferably 2 to 7 wt.%, and more preferably 3 to 5 wt.% additives, based on the dry weight of the self-leveling compound. These embodiments further improve the self-leveling properties of the compound and promote rapid drying and setting. According to certain embodiments, the self-leveling cement-based screed consists of the aforementioned components, wherein the weight percentages (wt.-%) add up to a total of 100% by weight. According to these embodiments, the self-leveling compound refers to a dry mix of a filler compound before it is mixed with water.

[0041] According to certain embodiments, the self-leveling compound is cement-based and, in addition to the plant-based charcoal defined above, comprises 10 to 30 wt.%, preferably 12 to 18 wt.%, and further preferably 13 to 16 wt.% alumina cement; 5 to 15 wt.%, preferably 6 to 12 wt.%, and further preferably 7 to 10 wt.% Portland cement; 5 to 15 wt.%, preferably 6 to 10 wt.%, and further preferably 7 to 9 wt.% CaSO₄ binder; 10 to 25 wt.%, preferably 13 to 21 wt.%, and further preferably 14 to 20 wt.% limestone flour; 30 to 50 wt.%, preferably 35 to 45 wt.%, and further preferably 37 to 43 wt.% sand; and 1 to 8 wt.%, preferably 2 to 7 wt.%, and further preferably 3 to 5 wt.% additives, based on the dry weight of the self-leveling filler.These embodiments further improve the self-leveling properties of the leveling compound and promote rapid drying and setting. According to certain embodiments, the cement-based self-leveling compound consists of the aforementioned components, with the total weight percentages (wt%) adding up to 100 wt%. According to these embodiments, the self-leveling compound refers to a dry mix of the compound before it is mixed with water. In certain embodiments, the cement-based self-leveling compound can be mixed with 20 to 30 wt%, preferably 25 to 28 wt%, of water, based on the dry weight of the self-leveling compound.

[0042] In some embodiments, the self-leveling cement-based screed comprises as additives 1 to 5 wt.%, preferably 2 to 4 wt.% and further preferably 2.5 to 3.5 wt.% dispersion powder, 0.05 to 0.5 wt.%, preferably 0.1 to 0.4 wt.% and further preferably 0.15 to 0.30 wt.% accelerator, 0.05 to 0.5 wt.%, preferably 0.1 to 0.4 wt.% and further preferably 0.25 to 0.35 wt.% retarder, 0.1 to 1.0 wt.%, preferably 0.2 to 0.8 wt.% and further preferably 0.4 to 0.6 wt.% rheology additives, based on the dry weight of the self-leveling screed.

[0043] According to certain embodiments, the rheology additives consist of a thickener and a liquefier. The weight ratio between thickener and liquefier (thickener:liquefier) ​​can be 5:1 to 1:5, preferably 5:2 to 2:5, and more preferably 3:2 to 2:3. These embodiments further improve the application-related properties of the filler.

[0044] In some embodiments, the self-leveling compound is gypsum-based and, in addition to the biochar defined above, comprises 0.5 to 7.5 wt.%, preferably 1 to 6 wt.%, and more preferably 2 to 5 wt.% cement; 30 to 60 wt.%, preferably 35 to 50 wt.%, and more preferably 41 to 47 wt.% CaSO₄ binder; 30 to 55 wt.%, preferably 35 to 50 wt.%, and more preferably 37 to 45 wt.% fillers; and 1 to 8 wt.%, preferably 1.5 to 5 wt.%, and more preferably 2 to 4 wt.% additives, based on the dry weight of the self-leveling compound. These embodiments further improve the self-leveling properties of the compound and promote rapid drying and setting. According to certain embodiments, the self-leveling gypsum-based filler consists of the aforementioned components, wherein the weight percentages (wt.-%) add up to a total of 100 wt.%. According to these embodiments, the self-leveling compound refers to a dry mix of a leveling compound before it is mixed with water. In certain embodiments, the gypsum-based self-leveling compound can be mixed with 20 to 30 wt.%, preferably 22 to 25 wt.% water, based on the dry weight of the self-leveling compound.

[0045] According to certain embodiments, the self-leveling filler is gypsum-based and, in addition to the plant charcoal defined above, comprises 0.4 to 5 wt.%, preferably 1 to 4.5 wt.%, and further preferably 2 to 4 wt.% alumina cement; 0.1 to 2.5 wt.%, preferably 0.5 to 2 wt.%, and further preferably 0.7 to 1.5 wt.% Portland cement; 30 to 60 wt.%, preferably 35 to 50 wt.%, and further preferably 41 to 47 wt.% CaSO₄ binder; 20 to 30 wt.%, preferably 22 to 28 wt.%, and further preferably 23 to 27 wt.% limestone flour; 10 to 25 wt.%, preferably 14 to 23 wt.%, and further preferably 16 to 20 wt.% sand; and 1 to 8 wt.%, preferably 1.5 to 5 wt.%, and further preferably 2 to 4 wt.% Additives based on the dry weight of the self-leveling filler.These embodiments further improve the self-leveling properties of the filler and promote rapid drying and setting. According to certain embodiments, the gypsum-based self-leveling filler consists of the aforementioned components, with the total weight percentages (wt%) adding up to 100 wt%. According to these embodiments, the self-leveling filler refers to a dry mix of filler before it is mixed with water.

[0046] In some embodiments, the self-leveling gypsum-based filler comprises as additives 0.5 to 4 wt.%, preferably 1 to 3 wt.% and further preferably 1.5 to 2.5 wt.% dispersion powder, 0.05 to 0.5 wt.%, preferably 0.1 to 0.4 wt.% and further preferably 0.15 to 0.30 wt.% accelerator, 0.05 to 0.5 wt.%, preferably 0.1 to 0.4 wt.% and further preferably 0.25 to 0.35 wt.% retarder, 0.1 to 1.0 wt.%, preferably 0.2 to 0.8 wt.% and further preferably 0.4 to 0.6 wt.% rheology additives, based on the dry weight of the self-leveling filler.

[0047] According to certain embodiments, the rheology additives consist of a thickener and a liquefier. The weight ratio between thickener and liquefier (thickener:liquefier) ​​can be 5:1 to 1:5, preferably 5:2 to 2:5, and more preferably 3:2 to 2:3. These embodiments further improve the application-related properties of the filler.

[0048] A second aspect of the present invention relates to the use of biochar for reducing the global warming potential (GWP) of self-leveling cement- or gypsum-based fillers, wherein the biochar has a particle size d10 of at most 3.2 µm and a specific surface area of ​​at least 7800 cm² / g. As described above, the use of biochar with these properties enables the self-leveling of the filler and significantly reduces the GWP value. The above statements regarding the first aspect of the invention apply analogously here. Manufacturing process of the self-leveling filler

[0049] The self-leveling compound according to the invention can be produced by successively mixing the aforementioned components of the self-leveling compound in any order or by simultaneously mixing them in a mixing device customary for this purpose. The components include, in particular, biochar, cement, CaSO₄ binder, fillers, additives, and optionally water. The above statements regarding the first aspect of the invention apply analogously here.

[0050] Alternatively or additionally, a formulation of a self-leveling compound known in the prior art can be used, wherein a proportion of a filler contained in the self-leveling compound is replaced by the biochar described above. The above statements regarding the first aspect of the invention apply analogously here. Determination of the run-out time (in seconds (s)) and the spread (in centimeters (cm))

[0051] To determine the flow time and spread, an Erichsen aluminum flow cup, model 243 / II, with a 6 mm nozzle, a stopwatch with a second hand, a 30 x 30 cm glass plate or larger, graph paper, a 500 ml mixing container, and a Vollrath laboratory stirrer EWTHV 0.5 with a disc stirrer, approximately 65 mm in diameter, can be used. The graph paper should be waterproof (protective cover or laminated). For easier reading, concentric circles should be drawn at 1 cm intervals and marked on the graph paper with the corresponding radius. The flow cup can be fixed on a stand at a height of 17.5 cm, which corresponds to an 11 cm drop height for the mixed material. The base of the stand should be outside the glass plate below to allow sufficient surface area for the filler to spread. Then, 500 g of filler with a density of 23 to 27 g / kg can be added.Add -% water, based on the dry weight of the filler, to the mixing vessel and then homogenize for 45 seconds using a laboratory stirrer (mixing temperature approx. 18-20 °C). Then proceed as follows: Place the flow cup in a stand on the work surface. Position a sheet of graph paper underneath it (the center of the paper must be vertically below the nozzle). Place a dry glass plate on top. 30 seconds after mixing the filler, fill the flow cup to the brim and cover the nozzle with a finger. Scrape off any excess material with a small glass plate or a spatula. After another 15 seconds from the start of filling, and a total of 45 seconds after mixing the filler, begin the flow start: Remove your finger from the nozzle opening and simultaneously start a stopwatch with your other hand.Now, observe how long the mass flows from the beaker. When the flow stops abruptly, stop the timer. This time at which the flow stops corresponds to the flow time.

[0052] Following the described procedure for determining the flow time, the spread radius covered by the collected filler material on the glass plate can be read from the millimeter paper 4 minutes after the flow starts. The spread radius is read at four positions approximately 90° apart and averaged (reading accuracy 1 mm). The average value is rounded down to the nearest millimeter. Determination of the water content of biochar (in wt.%, based on the total weight of the biochar)

[0053] To determine the water content of biochar, a stainless steel drying tray with a diameter of approximately 10 cm and a height of approximately 1.5 cm, a Binder drying oven model ED 115, and a Mettler Toledo laboratory balance model XS6002SDR can be used, proceeding as follows: Weigh 50 to 100 g of biochar into the drying tray, recording the weight. Then, place the drying tray containing the biochar in the drying oven (preheated to 40 °C) and dry until a constant weight is achieved. Determine the weight of the sample using the laboratory balance. Divide the weight loss by the dry weight of the initial sample and then multiply by 100 to obtain the water content. Determination of the moisture content of fillers (in wt.%, based on the powder weight of the filler)

[0054] A drying oven can be used to determine the moisture content of powdered fillers. A drying temperature of 40 °C is set, and a sample of approximately 100 g of the powdered filler is used. The measurement is stopped when the weight reaches a constant level, but no later than after 24 hours. Weight is considered constant when two consecutive measurements show a weight difference of no more than 0.02 g. The weight loss, divided by the dry weight of the initial sample and then multiplied by 100, yields the determined moisture content. Determination of the particle size distribution, the particle sizes d10, d50, d90 and d99 (in micrometers (µm)) and the specific surface area (in square centimeters per gram (cm² / g))

[0055] To determine the particle size distribution and particle sizes d10, d50, d90, and d99, a Sypatec HELOS type H2321 laser granulometer with a measuring range R4: 0.5 / 1.6...350 µm and a RODOS dry disperser can be used, proceeding as follows. Approximately 5 g of the sample is placed in the hopper of the sample feeder. The following parameters can be set: primary pressure = 1 bar, vacuum = 65 mbar, 0% rotational speed, feed rate of the vibrating feeder 60%, bed height 1.00 mm, hopper gap 1 mm. The measurement begins at an optical concentration of 2.1% and ends at a concentration < 1.9% for 5 s or after 99 s at the latest. The measurement is performed in HLRD mode (high-resolution diffraction mode). A theoretical density of 1 and a Heywood factor of 1 are assumed. The evaluation is performed using Windox 5.10.0.4. Determination of the ash content of biochar (in wt.%, based on the total weight of the biochar)

[0056] To determine the ash content, a Netzsch STA 449 C thermogravimeter can be used, proceeding as follows. The ash residue (residual mass at 1150°C) is determined by thermogravimetric analysis of the biochar using a Netzsch Jupiter STA 449C apparatus. For this purpose, a temperature range of 30–1150°C is traversed under an air-nitrogen flux (air:nitrogen / 30:20) with a heating rate of 10 K / min (30–550°C) and 20 K / min (550–1150°C). Data analysis can be performed using the Netzsch Proteus software. Determination of flexural and compressive strengths (in Newtons per square millimeter (N / mm²))

[0057] The flexural and compressive strengths can be determined according to DIN EN 13892-2:2002. Examples

[0058] The invention will be explained in more detail below with reference to various examples. However, the invention is not limited to these examples. Production of self-leveling cement-based fillers

[0059] Table 1 lists formulations of self-leveling cement-based leveling compounds. The prior art formulation shown refers to a commercially available self-leveling cement-based leveling compound without biochar. Examples 1 and 2 are exemplary formulations of cement-based leveling compounds according to the invention. The comparative examples are formulations of cement-based leveling compounds that do not contain the biochar according to the invention. The abbreviation "BK" stands for biochar. Ethylene-vinyl acetate copolymer was used as the dispersion powder, an alkali carbonate as the accelerator, citric acid as the retarder, a polycarboxylate ether and an amide-based polyelectrolyte with sulfonic acid groups as rheology additives, calcium sulfate α-hemihydrate as the CaSO₄ binder, ISTRA 40 alumina cement, and Schwenk CEM I 52.5 R Portland cement. With the exception of the GWP data, the figures are given in percent by weight (wt.-%), based on the dry weight of the respective filler. Table 1: Compositions of exemplary self-leveling cement-based screeds and their GWP values. All values, except for the GWP data, are given as weight percent (wt%) based on the dry weight of the respective screed. Components State of the art 1 Example 1 Example 2 Comparative example 1 Comparative example 2 Comparative example 3 Comparative example 4 Comparative example 5 alumina fused cement 14 14 14 14 14 14 14 14 Portland cement 9 9 9 9 9 9 9 9 CaSO4 binder 8 8 8 8 8 8 8 8 BK-1 0 8 10 0 0 0 0 0 BK-2 0 0 0 10 0 0 0 0 BK-3 0 0 0 0 10 0 0 0 BK-4 0 0 0 0 0 10 0 0 BK-5 0 0 0 0 0 0 10 0 BK-6 0 0 0 0 0 0 0 10 Limestone flour 0 - 90 µm 26 18 16 16 16 16 16 16 Sand 0.06 - 0.3 mm 39 39 39 39 39 39 39 39 Dispersion powder 3 3 3 3 3 3 3 3 accelerator 0,2 0,2 0,2 0,2 0,2 0,2 0,2 0,2 Delayer 0,3 0,3 0,3 0,3 0,3 0,3 0,3 0,3 Rheology additives 0,5 0,5 0,5 0,5 0,5 0,5 0,5 0,5 sum 100 100 100 100 100 100 100 100 mixing water 26 26 27 27 27 27 27 27 GWP [kg CO2 eq / kg] 0,31 0,064 0,002 0,002 0,002 0,002 0,002 0,002 GWP reduction [%] - 79 99 99 99 99 99 99 Production of self-leveling gypsum-based fillers

[0060] Table 2 lists formulations of self-leveling gypsum-based fillers. The prior art formulation given refers to a commercially available self-leveling gypsum-based filler without biochar. Example 3 is an exemplary formulation of a gypsum-based filler according to the invention. Comparative Example 6 is a formulation of a gypsum-based filler that does not contain the biochar according to the invention. The abbreviation "BK" stands for biochar. Ethylene-vinyl acetate copolymer was used as the dispersion powder, an alkali carbonate as the accelerator, citric acid as the retarder, a polycarboxylate ether and an amide-based polyelectrolyte with sulfonic acid groups as rheology additives, calcium sulfate α-hemihydrate as the CaSO₄ binder, ISTRA 40 alumina cement, and Schwenk CEM I 52.5 R Portland cement. With the exception of the GWP data, the figures are given in percent by weight (wt.-%), based on the dry weight of the respective filler. Table 2: Compositions of exemplary gypsum-based self-leveling compounds and their GWP values. With the exception of the GWP data, all values ​​are given as weight percent (wt%) based on the dry weight of the respective compound. Components State of the art 2 Example 3 Comparative example 6 alumina fused cement 3 3 3 Portland cement 1 1 1 CaSO4 binder 45 45 45 BK-1 0 6 0 BK-2 0 0 6 BK-3 0 0 0 BK-4 0 0 0 BK-5 0 0 0 BK-6 0 0 0 Limestone flour 0 - 90 µm 30 24 24 Sand 0.06 - 0.3 mm 18 18 18 Dispersion powder 2 2 2 accelerator 0,2 0,2 0,2 Delayer 0,3 0,3 0,3 Rheology additives 0,5 0,5 0,5 sum 100 100 100 mixing water 23 24 24 GWP [kg CO2 eq / kg] 0,26 0,075 0,075 GWP reduction [%] - 71 71 Characterization of the biochars BK-1 to BK-6

[0061] The particle sizes d10, d50, d90 and d99, the particle size distribution, the specific surface area, the water content and the ash content were determined for the plant-based charcoals BK-1 to BK-6 used in the exemplary fillers described above. The determination methods are described above. Table 3: Characterization of the biochars BK-1 to BK-6. BK No. Part.gr. d10 [µm] Part.gr. d50 [µm] Part.gr. d90 [µm] Part.gr. d99 [µm] Specific surface area [cm² / g] Water content [wt.%] Ash content [wt.%] BK-1 2,85 16,21 67,33 129,98 8280 4,1 4,7 BK-2 3,65 17,43 64,63 120,96 7232 1,9 9,4 BK-3 9,63 94,21 227,01 311,02 3425 0,9 13,3 BK-4 3,49 18,33 74,87 137,32 7291 7,9 9,7 BK-5 5,44 26,06 99,79 204,6 5215 3,5 4,1 BK-6 6,48 36,3 136,35 237,18 4384 2,6 4,5 Testing the functionality and self-leveling properties of the fillers

[0062] The setting time, spread, compressive strength, and flexural strength of the leveling compounds of Examples 1-3, Comparative Examples 1-6, and the prior art 1-2 were determined according to the methods described in detail above. The amount of mixing water used for each leveling compound is shown in Tables 1 and 2. For a leveling compound to be self-leveling or self-healing, and thus functional in the context of the present invention, the setting time must not exceed 120 s and the spread must be at least 11 cm. Furthermore, leveling compounds should have a compressive strength of at least 16 N / mm² and a flexural strength of at least 3 N / mm². The results are shown in Table 4. Table 4: Results of the determination of the flow time, spread, compressive strength and flexural strength of the fillers of examples 1-3, comparison examples 1-6 and the state of the art 1-2. filler Discharge time [s] Spread dimension [cm] Compressive strength [N / mm²] Flexural strength [N / mm²] Result State of the art 1 34 12,2 32 8 Functional Example 1 70 12,2 32 9 Functional Example 2 55 12 31 8 Functional Comparative example 1 240* 9,0 25 6 Not functional Comparative example 2 240* 9,0 26 6 Not functional Comparative example 3 240* 9,0 27 6 Not functional Comparative example 4 150 10,0 27 6 Not functional Comparative example 5 150 10,5 27 6 Not functional State of the art 2 33 12,5 37 8 Functional Example 3 46 12,9 35 8 Functional Comparative example 6 160 10,6 25 6 Not functional *Test aborted after 240 s because the material did not flow through the nozzle within the specified time of 4 minutes.

[0063] As the results above demonstrate, a leveling compound with the desired self-leveling functionality can only be achieved using the biochar "BK-1". This biochar differs from the biochars used in the comparison examples in its particle size distribution, particularly in the particle size d10, and in its specific surface area. It is evident that by using a biochar with a particle size d10 of no more than 3.2 µm and a specific surface area of ​​at least 7800 cm² / g, leveling compounds with self-leveling properties can be obtained.

Claims

1. Self-levelling compound based on cement or gypsum, comprising 3 to 13 wt% of biochar, based on the dry weight of the self-levelling compound, wherein the biochar has a particle size d10 of at most 3.2 µm and a specific surface area of at least 7800 cm2 / g, wherein the particle size and the specific surface area are determined by laser granulometric measurement, and wherein the term "biochar" refers to materials that are produced by carbonization of plant-based and / or wood-like starting materials.

2. Self-levelling compound according to claim 1, wherein the biochar has a particle size d50 of at most 16.7 µm.

3. Self-levelling filling compound according to one of claims 1 or 2, wherein the self-levelling compound has a GWP value ("Global Warming Potential") of at most 0.1 kg CO2 equivalent / kg, determined in accordance with DIN EN 15804:2012+A2:2019.

4. Self-levelling compound according to any one of the preceding claims, comprising 5 to 12 wt% of biochar, based on the dry weight of the self-levelling compound.

5. Self-levelling compound according to any one of the preceding claims, wherein the biochar has a particle size d10 of at least 2.5 µm.

6. Self-levelling compound according to any one of the preceding claims, wherein the biochar has a specific surface area of at most 9500 cm2 / g.

7. Self-levelling compound according to any one of the preceding claims, wherein the self-levelling compound has a efflux time of at most 120 s, measured using a flow cup having a 6 mm nozzle according to DIN 53211: 1987-06 and / or a flow spread of at least 11 cm.

8. Self-levelling compound according to any one of the preceding claims, wherein the self-levelling compound further comprises cement, CaSO4 binder, fillers and additives, optionally wherein the cement is selected from calcium aluminate cement, Portland cement, calcium sulfoaluminate cement and combinations thereof, further optionally wherein the fillers are selected from limestone powder, sand and combinations thereof, further optionally wherein the additives are selected from dispersion powders, accelerators, retarders, rheology additives and combinations thereof.

9. Self-levelling compound according to any one of the preceding claims, wherein the self-levelling compound is based on cement and further comprises 15 to 45 wt% of cement, 5 to 15 wt% of CaSO4 binder, 40 to 75 wt% of fillers and 1 to 8 wt% of additives, based on the dry weight of the self-levelling compound.

10. Self-levelling compound according to any one of the preceding claims, wherein the self-levelling compound is based on cement and further comprises 10 to 30 wt% of calcium aluminate cement, 5 to 15 wt% of Portland cement, 5 to 15 wt% of CaSO4 binder, 10 to 25 wt% of limestone powder, 30 to 50 wt% of sand and 1 to 8 wt% of additives, based on the dry weight of the self-levelling compound.

11. Self-levelling compound according to any one of claims 1 to 8, wherein the self-levelling compound is based on gypsum and further comprises 0.5 to 7.5 wt% of cement, 30 to 60 wt% of CaSO4 binder, 30 to 55 wt% of fillers and 1 to 8 wt% of additives, based on the dry weight of the self-levelling compound.

12. Self-levelling compound according to any one of claims 1 to 8, wherein the self-levelling compound is based on gypsum and further comprises 0.4 to 5 wt% of calcium aluminate cement, 0.1 to 2.5 wt% of Portland cement, 30 to 60 wt% of CaSO4 binder, 20 to 30 wt% of limestone powder, 10 to 25 wt% of sand and 1 to 8 wt% of additives, based on the dry weight of the self-levelling compound.

13. Use of biochar to reduce the global warming potential (GWP) of self-levelling compounds based on cement or gypsum, wherein the biochar has a particle size d10 of at most 3.2 µm and a specific surface area of at least 7800 cm2 / g, wherein the particle size and the specific surface area are determined by laser granulometric measurement, and wherein the term "biochar" refers to materials that are produced by carbonization of plant-based and / or wood-like starting materials.