Concrete incorporating at least a portion of biochar in its composition

Abstract

Concrete incorporating at least a portion of biochar in its composition. The invention relates to a concrete for the production of low-carbon buildings or building elements, characterized in that the composition incorporates at least a portion of biochar as an aggregate in addition to cement and water. Figure to be published with the abstract: no figure

Description

Title of the invention: Concrete incorporating at least a portion of biochar in its composition

[0001] The present invention relates to the field of low carbon constructions and construction elements and more particularly to the field of low carbon concretes for the construction of buildings.

[0002] In the context of the fight against climate change, regulatory constraints have emerged to reduce greenhouse gas emissions. While the transport sector is the primary target of these measures, the building sector is also impacted by these constraints. Indeed, the assessment of greenhouse gas reduction is not solely based on energy consumption but also on carbon footprint, that is, the measurement of the volume of carbon dioxide (CO2) emitted by the combustion of fossil fuels, carbon dioxide being the main greenhouse gas contributing to global warming.

[0003] In the construction sector, carbon footprint performance is measured over the entire life cycle of the building, from its construction phase to its demolition. This assessment is thus carried out based on various criteria, including the coherence of the construction, the limitation of carbon-based energy sources for the building's operation, and even the utilization of carbon storage.

[0004] In construction, the use of concrete constitutes a significant source of carbon-based energy. Indeed, the production of conventionally composed concrete, for example from CEM II / A 52.5R cement, sand, gravel, and water, can generate a carbon footprint of approximately 203 kg of CO2 per cubic meter produced. Therefore, to overcome this constraint, mixtures incorporating ground wood have been developed to obtain new compositions corresponding to wood-based concretes. Such wood-based concretes do indeed make it possible to obtain concretes with a negative carbon footprint. However, this reduction in carbon footprint compared to conventionally composed concrete is also accompanied by a significant reduction in the compressive strength of the wood-based concrete compared to conventionally composed concrete.Therefore, the solution provided by introducing wood into the composition of concrete forces a reduction in its scope of application within the context of construction operations.

[0005] The present invention aims to overcome these drawbacks by proposing a technical solution with a negative carbon footprint that compensates for the lack of decarbonization of other construction operations that may occur on a construction site, while also meeting the compressive strength requirements encountered in a wide range of construction operations.

[0006] The invention thus relates to a concrete for the production of low carbon construction or construction elements, characterized in that the composition incorporates at least a portion of biochar as an aggregate in addition to cement and water.

[0007] The invention also relates to a structural construction unit intended for filling and / or manufacturing precast wall or precast slab, characterized in that this unit is made of concrete according to the invention.

[0008] The invention will be better understood from the following description, which relates to various preferred embodiments, given by way of non-limiting example, and explained, with reference to the accompanying tables, in which:

[0009] [Fig.1] represents a summary table of different characteristics of an example of concrete according to the first particular range of concrete according to the invention.

[0010] [Fig.2] represents a summary table of different characteristics of an example of concrete according to the second particular range of concrete according to the invention.

[0011] [Fig.3] represents a summary table of different characteristics of an example of concrete according to the third particular range of concrete according to the invention.

[0012] [Fig.4] represents a summary table of different characteristics of an example of concrete according to the fourth particular range of concrete according to the invention.

[0013] The present invention relates to a concrete for the production of low-carbon buildings or building elements, characterized in that the composition incorporates at least a portion of biochar as an aggregate in addition to cement and water. Biochar, also known as charcoal or plant-based charcoal, is a compound obtained by the pyrolysis of biomass and which allows carbon retention in the form of an inert product with a high carbon density compared to other products or compounds. This inertness of biochar ensures carbon storage and retention without risk of release, for as long as necessary. By its properties, biochar constitutes a total or partial substitute for aggregates which, mixed with cement, contribute to the composition and production of concrete.Thus, while a conventional concrete mix comprises, in addition to cement, sand and gravel, the concrete mix according to the invention also includes biochar as a replacement for all or part of the sand and gravel. Furthermore, the biochar incorporated into the concrete mix may also be combined with one or more fines or fillers, which may include aggregates, for example, of the powder type. of stone or calcium carbonates or even silica fume, and whose fineness is, for example, on the order of 0 to 125 pm.

[0014] According to an embodiment corresponding to a variant of the concrete of the invention, the biochar comprises a particle size of between 0 and 5 mm, preferably in the range of 0 to 2 mm. This particle size of the biochar is chosen so that the biochar optimally substitutes for the aggregates, sand and / or gravel, which it replaces.

[0015] According to another example, which corresponds to a variant embodiment of a first particular range of concrete according to the invention and whose characteristics can be combined with those of the examples detailed above, the concrete has a composition free of gravel and comprises, by mass percentage, between 25% and 50% biochar and at most 20% cement. Preferably, the mass percentage of biochar is between 30% and 50% and ideally between 40% and 50%. As an example of an embodiment, the composition can comprise, by mass percentage, 9.59% cement, for example a CEM IEB 52.5 N type cement with 31.19% filler, 41.19% biochar and 18% water. The production of concrete with such a composition has a negative carbon balance of around -1455 kg of CO2 / m3, as well as a density of around 1283.5 kg / m3.In addition to a more favorable carbon footprint, concrete with such a composition also has a lower density than conventional concrete, which is around 2338 kg / m3.

[0016] According to another example of the production of concrete with such a composition, it is likely that it will not require any steam curing operation as part of its production.

[0017] According to another example corresponding to a particular embodiment of this first range of concrete according to the invention, seven days after pouring concrete of this composition, this concrete exhibits a compressive strength of at least 0.5 MPa or 0.5 x 10⁶ Pascals, or even, preferably, a compressive strength of at least 3.4 MPa or 3.4 x 10⁶ Pascals. Therefore, concrete according to this particular first range is suitable for use as a particularly relevant formwork material as an alternative to polystyrene blocks usually integrated into the thickness of slabs, paving elements, or precast walls. Similarly, concrete according to this particular first range constitutes an interesting material for the production of elements forming structural units, for example, in the form of slabs, intended for filling precast walls or slabs.For example, in the context of making pancakes whose volume. Each individual batch is around 10.5 litres, each of the cakes produced has a negative carbon footprint of around -15.5 kg of CO2.

[0018] It should also be noted that the invention also relates to a structural construction unit intended for filling and / or manufacturing precast walls or slabs, characterized in that this unit is made of concrete according to the invention, i.e. incorporating biochar, and more particularly a concrete whose composition corresponds to that of this first range of concrete according to the invention.

[0019] According to another example, which corresponds to a variant embodiment of a second specific range of concrete according to the invention and whose characteristics can be combined with those of some of the examples detailed above, the concrete has a gravel-free composition comprising, by mass percentage, between 35% and 60% biochar and at most 60% cement. Preferably, the mass percentage of biochar is between 40% and 60%, and ideally between 45% and 60%. Such a composition has a higher biochar content than in the first specific range but also allows for higher levels of mechanical strength. Similarly, this composition can also be completely free of fines or fillers. As an example of an embodiment, the composition can comprise, by mass percentage, 37% cement, for example, a CEM IP A 52 type cement.5R, 47% biochar and 16% water. The production of concrete with such a composition has a negative carbon balance of around -1434 kg of CO2 / m3, as well as a density of around 1261.7 kg / m3.

[0020] It should be noted that, during the first eighteen hours after pouring / molding, a concrete according to this second particular range is likely to require a curing operation at 35°Celsius.

[0021] According to another example, which corresponds to a particular embodiment of this second range of concrete according to the invention, twenty-eight days after pouring, the concrete exhibits a compressive strength of at least 14 MPa or 14 x 10⁶ Pascals. According to a more specific implementation example, which can be obtained in particular with a concrete whose composition is detailed above, the concrete exhibits a compressive strength of approximately 14.3 MPa or 14.3 x 10⁶ Pascals at seven days and approximately 17.8 MPa or 17.8 x 10⁶ Pascals at twenty-eight days. Therefore, a concrete according to this second particular range can be used as a construction material for the construction of unreinforced structures, as well as an alternative material to wood-concrete type concretes.

[0022] According to another example, which corresponds to a variant embodiment of a third particular range of concrete according to the invention and whose characteristics can be combined with those of some of the examples detailed previously, the concrete has a composition comprising gravel and, by mass percentage, between 5% and 12% biochar and at most 30% cement, or even 25% cement. Such a composition incorporates biochar while allowing for higher levels of mechanical strength than in the first and second ranges of concrete. Thus, the concrete has a composition in which a portion of the sand in conventional concrete is replaced by biochar, for example, so that the biochar and sand are present in similar or even identical volumes.As an example, the mix design is free of reinforcing steel and may include, by mass percentage, 14.43% cement, for example, a CEM II / A 52.5 R type cement, with 6.2% biochar, 19.24% sand, 52.91% gravel, and 7.22% water. The production of concrete with this composition results in a negative carbon footprint of approximately -181 kg CO2 / m3, and a density of approximately 2158 kg / m3. Therefore, concrete with such a composition has a lower density than conventional concrete while also having a negative carbon footprint.

[0023] It should be noted that, during the first sixteen hours after pouring / molding, a concrete according to this particular third range is likely to require a curing operation at 35°Celsius.

[0024] According to another example, which corresponds to a particular embodiment of this third range of concrete according to the invention, twenty-eight days after pouring, the concrete exhibits a compressive strength of at least 30 MPa or 30 x 10⁶ Pascals. According to a more specific implementation example, which can be obtained in particular with a concrete whose composition is detailed above, the concrete exhibits a compressive strength of approximately 35.1 MPa or 35.1 x 10⁶ Pascals at seven days and approximately 40.7 MPa or 40.7 x 10⁶ Pascals at twenty-eight days.

[0025] According to another example, which corresponds to a variant embodiment of a fourth particular range of concrete according to the invention and whose characteristics can be combined with those of some of the examples detailed previously, the concrete has a composition comprising gravel and biochar as the only aggregates and, by mass percentage, between 12% and 30% biochar and at most 30% cement. Preferably, the mass percentage of biochar is at least 15%. Thus, the concrete has a composition in which the biochar completely replaces the sand in conventional concrete. By way of an example embodiment, The mix design is free of fibers and sand and is likely to include, by mass percentage, 16.59% cement, for example, a CEM II / A 52.5 R type cement with 14.27% biochar, 60.84% ​​gravel, and 8.30% water. The production of concrete with this composition results in a negative carbon footprint of approximately -586 kg CO2 / m³, as well as a density of approximately 1916 kg / m³. Furthermore, concrete with such a composition has a lower density than conventional concrete while also exhibiting a negative carbon footprint.

[0026] It should be noted that, during the first sixteen hours after pouring / molding, a concrete according to this particular fourth range is likely to require a curing operation at 35°Celsius.

[0027] According to another example, which corresponds to a particular embodiment of this fourth range of concrete according to the invention, twenty-eight days after pouring, the concrete exhibits a compressive strength of at least 20 MPa, or 20 x 10⁶ Pascals. According to a more specific implementation example, which can be obtained in particular with a concrete whose composition is detailed above, the concrete exhibits a compressive strength of approximately 21 MPa, or 21 x 10⁶ Pascals, at seven days and approximately 25.9 MPa, or 25.9 x 10⁶ Pascals, at twenty-eight days.

[0028] It should be noted that, given their respective compressive strengths, concretes produced according to these third and fourth specific ranges are suitable for use as construction materials for reinforced or unreinforced load-bearing structures and for application in precast walls, precast slabs, and / or solid walls. Similarly, these third and fourth specific ranges are suitable for use as construction materials for solid slabs.

[0029] Within the framework of the invention, the mechanical strength of each of these different types of concrete can be adjusted by modifying the quantity of cement in the proportions specific to each of the particular concrete ranges detailed above. Indeed, the compressive strength of the concrete can be improved by increasing the quantity of cement in the corresponding concrete mix. Such an increase in cement impacts the carbon footprint of the concrete produced. However, it should be noted that the additional CO2 released by this additional cement is amply offset by the significant negative carbon footprint of the biochar. In fact, it should be recalled that while the carbon footprint of cement is positive and on the order of 680 kgCO2 per tonne, the carbon footprint of biochar is negative, on the order of -2934 kgCO2 / tonne. Therefore, an addition The amount of cement in the composition of concrete only slightly affects the significant carbon deficit provided by biochar.

[0030] The invention also relates to a construction or portion of a construction without reinforcement characterized in that it incorporates concrete according to the invention or incorporating a composition as detailed previously for the second, third and fourth particular ranges of concrete.

[0031] Similarly, the invention also relates to a construction or portion of a construction provided with reinforcement characterized in that it incorporates concrete according to the invention or incorporating a composition such as is detailed previously for the third and fourth particular ranges of concrete.

[0032] Of course, the invention is not limited to the embodiment described and shown in the accompanying drawings. Modifications remain possible, particularly with regard to the composition of the various elements or by substitution of technical equivalents, without departing from the scope of protection of the invention.

Claims

Demands

1. Concrete for the production of low carbon construction or construction elements, characterized in that the composition incorporates at least a portion of biochar as an aggregate in addition to cement and water so that the concrete has a composition comprising gravel and biochar as the only aggregates and, by mass percentage, between 12% and 30% biochar and at most 30% cement.

2. Concrete according to claim 1, characterized in that the biochar comprises a particle size between 0 and 5 mm.

3. Concrete according to one of claims 1 or 2, characterized in that, twenty-eight days after pouring, the concrete has a mechanical compressive strength of at least 20 MPa (106 Pascals).

4. Construction or portion of construction without reinforcement characterized in that it incorporates concrete according to one of claims 1 to 3.

5. Construction or portion of construction provided with reinforcement characterized in that it incorporates concrete according to one of claims 1 to 3.