Novel raw earth material, method for preparing same and use thereof as a construction material

Abstract

The present invention relates to the use, for the preparation of a water-resistant construction material, of a mold comprising mycelium formed by the hyphae arising from the growth of at least one fungus, the mold colonizing pores of a solid, previously shaped inorganic matrix, the inorganic matrix consisting of an assembly of mineral grains bound by clay, the clay ensuring the structural cohesion of the material, wherein each of the pores is formed by the space between adjacent mineral grains of the assembly, bound by clay and / or by the interstice between the clay particles, and wherein the matrix comprises a biopolymer as a substrate for the growth of the mold.

Description

[0001] New raw earth material, its preparation process and its use as a building material

[0002] technical field

[0003] The present invention relates to a new building material and its manufacturing process and its use as a building material.

[0004] State of the art

[0005] Global temperature increases exceeding 1.5°C will significantly exacerbate human vulnerabilities, including poverty, food insecurity, forced displacement, and political instability. Therefore, the construction sector must limit its widespread use of cement, which is responsible for 8–9% of global anthropogenic CO2 emissions. A low-carbon option is earthen building materials, an age-old material still used by 8–10% of the world's population. Primarily composed of earth, earthen materials offer numerous advantages, such as local availability, recyclability, hygrothermal comfort, and improved air quality. However, a major drawback of earthen materials is their low water resistance.To protect against the effects of rain and flooding, hydraulic binders such as lime or cement are often incorporated into earthen materials. However, these binders reduce recyclability, decrease hygrothermal comfort, and significantly increase the environmental costs of earthen materials, often making them unsuitable solutions. In contrast, incorporating natural materials into earthen materials, commonly used in traditional building techniques, increases water resistance with a very low impact on global warming.

[0006] One of the aims of the invention is the use of material of natural origin for the preparation of a building material.

[0007] One of the aims of the invention is to make available a new building material.

[0008] One of the aims of the invention is to provide a new material that solves the disadvantages of conventional earthen materials.

[0009] One of the aims of the invention is to provide a new water-resistant raw earth material.

[0010] One of the aims of the invention is to provide a material exhibiting physical and mechanical properties similar to raw earth materials.

[0011] Another objective of the invention is to provide a simple method for preparing such a building material.

[0012] Description of the invention

[0013] An object of the present invention relates to the use, for the preparation of a water-resistant building material, of a mold comprising mycelium formed by hyphae from the growth of at least one fungus, said mold colonizing pores of a solid, pre-formed inorganic matrix consisting of a set of mineral grains bound by clay ensuring the structural cohesion of said material, each of said pores being formed by the space between adjacent mineral grains of said set bound by clay and / or by the interstice between the clay particles, said matrix comprising a biopolymer as a growth substrate for said mold.

[0014] The inventors have surprisingly found that mold developing in the pores of an inorganic matrix made up of mineral grains and clay ensuring structural cohesion, such as raw earth materials, improves the water resistance of these biostabilized earth materials in terms of sorpivity with a reduction in water absorption by capillarity of the material, in terms of mass loss under water spray stress and in terms of durability under immersion in water of the material, being able to maintain its integrity for at least 2 to 24 hours.This is possible while preserving the structure and physical characteristics of the material which are governed by the inorganic matrix, resulting in minimal reductions in shrinkage (about 6%), density (about 1%), and having a minimal effect on mechanical properties (decrease in Young's dynamic modulus of about 10%, in flexural strength of about 5%, and in compressive strength of about 6%), remaining within the ranges of values ​​of raw earth materials.

[0015] For the purposes of this invention, "mold" means a collection of microscopic organisms, including fungi involved in the fermentation and decomposition of organic matter. Mold comprises the fungal reproductive structures and their mycelium.

[0016] Mold families are diverse and mostly belong to the Ascomycota taxon. The molds identified in French Guiana are from the Eurotiales and Onygenales orders. The Eurotiales include, in particular, the genus Aspergillus and the genus Penicillium / Talaromyces.

[0017] The term "mycelium" refers to the vegetative part or apparatus of fungi composed of filaments that are more or less branched.

[0018] The term “hyphae” refers to filamentous vegetative elements, composed of several elongated cells with a nucleus, partitioned by walls containing proteins, glucan, and chitin.

[0019] A "biopolymer" is defined as an organic material comprising a polymer derived from biomass. Biopolymers are produced by living organisms such as plants, animals, algae, fungi, and bacteria. By way of non-limiting examples, plant-based biopolymers are materials of plant origin comprising one or more polymers selected from cellulose, hemicellulose, lignin, polyphenols such as hydrolyzable or condensed tannins, amylose, amylopectin, alginate, agar, carrageenan, keratin, casein, collagen, albumin, pectin, xanthan gum, and chitosan.

[0020] The term "pre-formed" means that the solid inorganic matrix has a defined shape or morphology, which is predetermined before the growth of the mold and is maintained after the colonization of the pores by the mycelium, with the finished material having the same shape as the inorganic matrix.

[0021] Mineral grains are particles composed of inorganic matter, primarily resulting from the decomposition of parent rock, namely the superficial mineral layer of the Earth's crust. These grains are mainly composed of silicon, aluminum, and iron oxides. Mineral grains from soil can be classified according to their size as pebbles, gravel, sand, or silt.

[0022] By "clay" we mean a material made up of mineral particles less than 2 pm forming a cohesive whole allowing it to be a binding agent, mainly made up of two types of minerals, phyllosilicates (kaolinite, illite, smectite) and oxides (of silicon, iron: hematite / goethite, of aluminium / gibbsite)

[0023] Mineral grains, being charge-neutral, are generally not cohesive with each other, unlike clay whose particles interact with each other through various electrostatic interactions such as hydrogen bonds, ionic bonds and van der Waals forces, due to the presence of negative charges in phyllosilicate minerals and positive charges on oxidized minerals.

[0024] The mineral grains and clay thus form an inorganic granular matrix ensuring the structural cohesion of the solidified material, which can be pre-shaped.

[0025] The term "pores" refers to the empty spaces formed within the material, which may be open to the outside or closed. These empty spaces or cavities in inorganic granular material are formed by the non-cohesive grouping of mineral grains held together by clay as an inorganic binder, or by the interstices between the clay particles. Thus, each pore is delimited by adjacent mineral grains held together by clay, which acts as a cohesive agent, and / or by the clay particles themselves.

[0026] Mold develops on the surface of materials but also inside the material, as observed in micrographs; mold mycelium has the ability to spread inside the material through networks of open pores running through the material.

[0027] For the purposes of the present invention, the inorganic matrix consists of a major inorganic part, namely consisting of at least 85% by mass of inorganic matter, or at least 90% by mass, or at least 95% by mass, and a minor organic part, namely at most 15% by mass of organic matter, or at most 10% by mass, or at most 5% i.e.: the biopolymer and organic matter from the soil from which the inorganic matrix is ​​extracted.

[0028] The proportion "at least 85% by mass of inorganic matter" and the proportion "at most 15% by mass of organic matter" are calculated in relation to the total mass of the inorganic matrix as defined above.

[0029] The present invention highlights the fact that it is the biopolymer that enables the growth of the mold, and that the organic matter from the soil from which the inorganic matrix is ​​extracted is not involved in the growth of the mold, as shown in Example 5.

[0030] According to a particular embodiment, the invention relates to the use as defined above, in which said at least one mold fungus is a ubiquitous fungus, in particular uninoculated.

[0031] According to a particular embodiment, the invention relates to the use as defined above for the preparation of a water-resistant construction material, of a mold resulting from the growth of ubiquitous non-inoculated fungi, said mold comprising mycelium formed by the hyphae of said fungi, said mold colonizing pores of a solid, pre-formed inorganic matrix consisting of a set of mineral grains bound by clay ensuring the structural cohesion of said material, each of said pores being formed by the space between the adjacent mineral grains of said set, bound by clay and / or by the interstice between the clay particles, said matrix comprising a biopolymer as a growth substrate for said mold.

[0032] The term "ubiquitous fungi" refers to fungi whose spores are found everywhere in the environment, both inside and outside an enclosed space.

[0033] Advantageously, the local environment is used as a source of fungal spores for mycelial growth within the material. Therefore, there is no need for fungal selection, a material sterilization step to eliminate existing microorganisms, or an inoculation step with the selected fungus to generate mycelial growth for the preparation of a building material.

[0034] According to a particular embodiment, the invention relates to the use as defined above, in which said at least one mycelium-forming fungus is inoculated.

[0035] According to a particular embodiment, the invention relates to the use as defined above, in which said inorganic matrix is ​​prepared from raw earth from a natural soil, as the source of mineral and clay grains.

[0036] The terms "raw earth" or "earth-based material" refer to building materials composed primarily of soil, meaning they contain more than 90% soil by dry mass. These materials are generally reworked, unfired, and do not contain hydraulic binders such as cement or lime. The terms "soil" or "natural soil" refer to the raw material used for earth-based building materials. This material originates from the subsoil, located at the interface between living and non-living matter, encompassing all the material between the bedrock and the surface, more precisely, the layer beneath the topsoil. It is generally poor in organic matter, meaning less than 2% organic matter by dry mass. The soil used in earth-based materials can come from excavated soil, such as construction waste from earthworks or foundations, or be extracted from a quarry.It consists of a collection of solid minerals of varying compositions and sizes (pebbles, gravel, sand, silt, clay). It includes solid minerals, but also water and air in pores of different sizes, both open and closed.

[0037] Mineral grains from the soil include pebbles, gravel, sand and silt.

[0038] Advantageously, the soil is local (from French Guiana) in order to obtain a low carbon impact construction material.

[0039] Using natural soil as a raw material is advantageous for obtaining an earth-based material that is natural, ecological and inexpensive.

[0040] According to a particular embodiment, the invention relates to the use as defined above, in which said raw earth comprises from 90.0 to 100.0% by dry mass of soil, in particular 98% of soil.

[0041] The range "from 90.0 to 100.0%" includes the following ranges: from 90.0 to 91.0%, from 91.0 to 92.0%, from 92.0 to 93.0%, from 93.0 to 94.0%, from 94.0 to 95.0%, from 95.0 to 96.0%, from 96.0 to 97.0%, from 97.0 to 98.0%, from 98.0 to 99.0%, from 99.0 to 100.0%.

[0042] Using a material sourced primarily from the ground is advantageous.

[0043] According to a particular embodiment, the invention relates to the use as defined above, in which the density of the material varies from 1400 to 2200 kg / m³. 3 .

[0044] The range "from 1,400 to 2,200 kg / m³" 3 » includes the following ranges: 1400 to 1450 kg / m 3 1450 to 1500 kg / m 3 1500 to 1550 kg / m 3 1550 to 1160 kg / m 3 1600 to 1650 kg / m 3 1650 to 1700 kg / m 3 1700 to 1750 kg / m 3 1750 to 1800 kg / m 3 1800 to 1850 kg / m 3 , 1850 to 1900 kg / m 3 , 1900 to 1950 kg / m 3 , 1950 to 2000 kg / m3 2000 to 2050 kg / m 3 2050 to 2100 kg / m 3 2100 to 2150 kg / m 3 2150 to 2200 kg / m 3 .

[0045] Raw earth materials containing mycelium have a density or specific gravity similar to raw earth materials without mycelium, namely within the range of conventional earth building materials. The material's density is therefore dictated by that of the inorganic matrix.

[0046] According to a particular embodiment, the invention relates to the use as defined above, in which said inorganic matrix is ​​put into the form of a solid brick, said matrix representing from 65 to 85%, preferably more than 75%, by volume of said solid brick.

[0047] The term "brick" refers to a building element or unit with a predefined shape that allows it to be stacked or interlocked to form building walls. This defined shape is generally a rectangular parallelepiped.

[0048] The brick can be solid, meaning that it is made entirely of the material by volume. In this case, the solid raw earth brick is made up of 65 to 85% by volume of soil, i.e. the inorganic matrix, knowing that the pores represent 15 to 35% of the material with a size varying from 10 nm to 300 pm, in particular from 100 nm to 10 pm.

[0049] A brick is said to be hollow when a part inside is hollowed out and contains no material.

[0050] Advantageously, the inorganic matrix is ​​a solid raw earth brick in the form of a rectangular parallelepiped that is easy to shape.

[0051] According to a particular embodiment, the invention relates to the use as defined above, in which said inorganic matrix is ​​prepared from raw earth from a natural soil, as the source of mineral and clay grains, and in particular in which said inorganic matrix is ​​put into the form of a solid brick, said matrix representing from 65 to 85%, preferably more than 75%, by volume of said solid brick.

[0052] According to a particular embodiment, the invention relates to the use as defined above, in which the biopolymer represents from 0.1 to 5.0% by total mass of the inorganic matrix, preferably 2.0%. The range "from 0.1 to 5.0%" comprises the following ranges delimited by 0.1%, 0.5%, 1.0%, 2.0%, 3.0%, 4.0% and 5.0%.

[0053] Advantageously, the quantity of 0.1 to 5.0% by mass of biopolymer contained in the matrix allows both to be a source of nutrients for the growth of mold fungi and to be a natural additive allowing to improve the properties of the material such as mechanical properties.

[0054] According to a particular embodiment, the invention relates to the use as defined above, in which the biopolymer is derived from waste, in particular household, agricultural, forestry or industrial waste.

[0055] Using waste allows for its recovery.

[0056] According to a particular embodiment, the invention relates to the use as defined above, in which the biopolymer is derived from leaf, cactus, grass or tannin.

[0057] According to a particular embodiment, the invention relates to the use as defined above, in which the building material is biostabilized and comprises inactivated mycelium formed from biologically inert hyphae.

[0058] Advantageously, the hyphae retain their structure, namely they maintain their filamentous appearance, observable by microscopy.

[0059] Advantageously, the hyphae retain their cellular structure, namely the cell wall of the cells constituting them is maintained, analysis by IR spectroscopy making it possible to identify the compounds constituting the cell wall of the hyphae such as proteins, polysaccharides and lipids.

[0060] According to a particular embodiment, the invention relates to the use as defined above, in which the material is biostabilized, after growth of the mold in the pores of the matrix, by inactivation of the mycelium of said mold.

[0061] The term "biostabilization of a material" refers to a treatment that renders the material biologically inert; it corresponds to the biological inactivation of the material by eliminating the microorganisms present or by halting the biological processes of fermentation, degradation, and growth of microorganisms within the material. Thus, the biostabilized material is biologically inactivated.

[0062] The biological inactivity of the material can be verified by assessing the absence of CO2 carbon dioxide release from the fungi, confirming that the mold fungi are indeed inert.

[0063] "Mycelium inactivation" refers to a treatment that inactivates the fungus, namely stopping the growth of the mycelium and preventing the production and release of fungal spores.

[0064] The term “biologically inert hyphae” refers to hyphae which, although retaining their filament structure, are not capable of growing or reproducing, i.e., not susceptible to multiplying.

[0065] According to a particular embodiment, the invention relates to the use as defined above, in which said mold is biostabilized by heat treatment at a temperature of 65 to 120 °C, preferably 80 °C, for more than 12 hours, in particular for 48 hours.

[0066] Advantageously, heat treatment allows biostabilization throughout the entire volume of the material, particularly in the pores by thermal conduction.

[0067] The range "from 65 to 120°C" includes the ranges delimited by: 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C and 120°C.

[0068] The "more than 12h" range includes the duration ranges delimited by: 12h, 24h, 48h, 72h.

[0069] It is understood that the duration can be adjusted by a person skilled in the art according to the volume of material to be treated; a large volume will require a longer heat treatment. According to a particular embodiment, the invention relates to the use as defined above, in which said mold is biostabilized by heat treatment at a temperature of 80°C for 48 hours.

[0070] According to a particular embodiment, the invention relates to the use as defined above, in which the building material is biostabilized and comprises inactivated mycelium formed of biologically inert hyphae, and in particular in which the material is biostabilized, after growth of the mold in the pores of the matrix, by inactivation of the mycelium of said mold, and in particular in which said mold is biostabilized by heat treatment at a temperature of 65 to 120 °C, preferably 80 °C, for more than 12 hours, in particular for 48 hours.

[0071] Another object of the invention relates to an intermediate earth composite material comprising or consisting of: an inorganic earth matrix derived from soil, solid and previously shaped, consisting of a set of mineral grains bound by clay ensuring the structural cohesion of the material, a biopolymer present in said matrix, mold present in pores of the matrix, each pore being formed by the space between the adjacent mineral grains of said set bound by clay and / or by the interstice between the clay particles.

[0072] This material, which is not biostabilized, namely containing mold in the pores, constitutes an intermediate material in the preparation of the finished construction material.

[0073] According to a particular embodiment, the invention relates to a material as defined above, in which said mold is generated by at least one fungus having said biopolymer as its growth substrate.

[0074] According to a particular embodiment, the invention relates to a material as defined above, said at least one fungus being a ubiquitous fungus, in particular uninoculated.

[0075] According to a particular embodiment, the invention relates to a material as defined above, said at least one fungus being an inoculated fungus.

[0076] It is understood that the mold fungus in question can be selected and intentionally inoculated.

[0077] Another object of the invention relates to a composite material for construction, comprising or consisting of: an inorganic earth matrix derived from natural soil, solid and previously shaped, made up of a set of mineral grains bound by clay ensuring the structural cohesion of the material, a biopolymer present in said matrix, mycelium present in pores of said matrix, each pore being formed by the space between the adjacent mineral grains of said set, bound by clay and / or by the interstice between the clay particles, said mycelium being derived from mold generated by the growth of hyphae of at least one fungus having as a growth substrate said biopolymer present in the matrix, and said material being biostabilized and comprising inactivated mycelium in which the hyphae are biologically inert.Advantageously, the biopolymer is both the source allowing the growth of mold fungi and a stabilizer of the material.

[0078] The term "stabilizer" refers to an additive that strengthens the structural cohesion of the material or its properties, particularly mechanical ones.

[0079] The biopolymer can advantageously serve as an additional binder to maintain the cohesion of mineral grains in the inorganic granular matrix.

[0080] Advantageously, the hyphae retain their structure, namely they maintain their filamentous appearance, observable by microscopy.

[0081] Advantageously, the hyphae retain their cellular structure, namely the wall of the elongated cells constituting them is maintained, analysis by IR spectroscopy making it possible to identify the compounds constituting the cell wall of the hyphae such as proteins, polysaccharides and lipids.

[0082] Advantageously, mold mycelium differs from selected fungal mycelia of the prior art in its structure and composition. Indeed, the biopolymer influences the fungal population of the mold, and consequently the mold mycelium and the structure of the hyphae. This can be observed by fluorescence microscopy, as the mycelium is known to exhibit autofluorescence under UV excitation. Autofluorescence in the hyphae can vary depending on the properties and content of different chitin components, as well as on the specific proteins, flavins, lipofuscins, porphyrins, and lignins in their cell walls.

[0083] According to a particular embodiment, the invention relates to a material as defined above, in which said at least one fungus is ubiquitous, in particular not inoculated.

[0084] According to a particular embodiment, the invention relates to a construction material as defined above, comprising or consisting of: an inorganic earth matrix of natural soil, solid and previously shaped, made up of a set of mineral grains bound by clay ensuring the structural cohesion of the material, a biopolymer present in said matrix, mycelium present in pores of said matrix, each pore being formed by the space between the adjacent mineral grains of said set, bound by clay and / or by the interstice between the clay particles, said mycelium being derived from mold generated by the growth of hyphae of ubiquitous non-inoculated fungi having said biopolymer as a growth substrate, and said material being biostabilized and comprising inactivated mycelium in which the hyphae are biologically inert.

[0085] Advantageously, the spores of mold fungi come from the ambient environment and are neither selected nor inoculated.

[0086] According to a particular embodiment, the invention relates to a material as defined above, in which from 1.0 to 95.0% of the pore volume are filled with mycelium.

[0087] The construction material according to the invention comprises pores filled with mycelium resulting from mold growth on the biopolymer as a substrate, which influences its growth. It is understood that a portion of the matrix pores are colonized by mycelial hyphae that can use the network of open pores to penetrate the material. The closed pores of the inorganic matrix generally do not constitute a favorable environment for mycelial growth.

[0088] The range "from 1.0 to 95%" includes the ranges delimited by: 1.0%, 2.0%, 3.0%, 4.0%, 5.0%, 6.0%, 7.0%, 8.0%, 9.0%, 10.0%, 15.0%, 20.0%, 25.0%, 30.0%, 35.0%, 40.0%, 45.0%, 50.0%, 55.0%, 60.0%, 65.0%, 70.0%, 75.0%, 80.0%, 85.0%, 90.0%, 95.0%.

[0089] Advantageously, from 2.0 to 90.0% of the pore volume is filled with mycelium.

[0090] Advantageously, 15.0 to 50.0% of the pore volume is filled with mycelium. According to a particular embodiment, the invention relates to a material as defined above, in which 0.2 to 95.0% of the material's surface is covered by mold mycelium.

[0091] Advantageously, from 2.0 to 90.0% of the material surface is covered by mold mycelium.

[0092] Advantageously, 15.0 to 50.0% of the material surface is covered by mold mycelium.

[0093] Mold mycelium has a greenish or black appearance, visually recognizable, allowing its presence to be identified and the mycelium coverage to be assessed on the surface of the material.

[0094] According to a particular embodiment, the invention relates to a material as defined above, in which the inorganic matrix is ​​made from raw earth from a natural soil, as the source of the mineral and clay grains of said matrix.

[0095] According to a particular embodiment, the invention relates to a material as defined above, in which said mineral grains comprise pebbles, gravel, sand and silt.

[0096] Advantageously, the said mineral grains are derived from a natural soil, preferably local. Advantageously, the clay is derived from a natural soil, preferably local.

[0097] It is understood that the choice of soil will determine the population of mineral grains (pebbles, gravel, sand, silt) and the composition and properties of the clay as a binder. Consequently, the choice of soil conditions the size and size distribution of the pores in the earthen building material.

[0098] Mineral grains can have a wide range of sizes, making it possible to avoid handling them to select them by size, particularly by sieving.

[0099] According to a particular embodiment, the invention relates to a material as defined above, in which said natural soil comprises more than 95% by mass of sand, clay and silt.

[0100] The range "over 95%" includes ranges delimited by 95.0%, 96.0%, 97.0%, 98.0%, 99.0% and 100.0%.

[0101] According to a particular embodiment, the invention relates to a material as defined above, in which said natural soil comprises more than 95% by mass of pebbles, gravel, sand, clay and silt.

[0102] According to a particular embodiment, the invention relates to a material as defined above, in which said natural soil comprises more than 95% by mass of gravel, sand, clay and silt.

[0103] Advantageously the soil is used without reworking, in particular without selection of mineral grain sizes by sieving.

[0104] According to a particular embodiment, the invention relates to a material as defined above, in which the inorganic matrix represents 65 to 85%, preferably 75%, by volume of the material. It is understood that the inorganic matrix is ​​a porous material with a porosity of 15 to 35%.

[0105] According to a particular embodiment, the invention relates to a material as defined above, in which the total volume of the pores represents 15 to 35% by volume of the material.

[0106] A total pore volume of 15 to 35% by volume of the material is typically that of raw earth materials.

[0107] The "total pore volume" of the material refers to the volume of the material subtracted from the volume of the inorganic matrix, which is the sum of the volumes of the mineral grains and the clay that constitutes the matrix. The total pore volume corresponds to the sum of the volumes of open and closed pores relative to the inorganic granular matrix; that is, this volume also includes the volume of pores filled by the mycelium.

[0108] According to a particular embodiment, the invention relates to a material as defined above, in which the pore size ranges from 10 nm to 300 pm, in particular from 100 nm to 100 pm. It is understood that the distribution of the pore size depends on that of the mineral grain size. The range "from 10 nm to 300 pm" includes the ranges delimited by 10 nm, 50 nm, 100 nm, 250 nm, 500 nm, 750 nm, 1 µm, 2 µm, 5 pm and 10 µm, 50 µm, 100 µm, 200 µm, 300 pm.

[0109] It is understood that the average size lies within these ranges and that a portion of the pores, on the order of 1.0 to 5.0%, may be outside this size range.

[0110] According to a particular embodiment, the invention relates to a material as defined above, wherein the material has a density of 1400 to 2200 kg / m³ 3 .

[0111] A density of 1400 to 2200 kg / m³ 3constitutes the density of the finished materials in classic earth construction.

[0112] According to a particular embodiment, the invention relates to a material as defined above, wherein the inorganic matrix is ​​made from raw earth extracted from natural soil, as the source of the mineral and clay grains of said matrix, and / or wherein said natural soil comprises more than 95% by mass of sand, clay, and silt, and / or wherein the inorganic matrix represents 65% to 85%, preferably 75%, by volume of the material, and / or wherein the material has a density of 1400 to 2200 kg / m³ 3 .

[0113] According to a particular embodiment, the invention relates to a material as defined above, wherein the material has a density of 1600 to 1950 kg / m³ 3 .

[0114] The density of the material of the invention is governed essentially by that of the raw earth and not by that of the mycelium and its substrate, allowing it to stand out from the matrix materials made up mainly of mycelium of the prior art.

[0115] The range "from 1600 to 1950 kg / m³" 3 » includes the following ranges: 1600 to 1625 kg / m 3 , 1625 to 1650 kg / m 3 1650 to 1675 kg / m 3 1675 to 1700 kg / m 3 1700 to 1725 kg / m 3 1725 to 1750 kg / m 3 , 1750 to 1775 kg / m 3 1775 to 1800 kg / m 3 1800 to 1825 kg / m 3 , 1825 to 1850 kg / m 3 , 1850 to 1875 kg / m 3 , 1875 to 1900 kg / m 3 , 1900 to 1925 kg / m 3 , 1925 to 1950 kg / m 3 .

[0116] According to a particular embodiment, the invention relates to a material as defined above, in which the biopolymer represents from 0.1 to 5.0% by total mass of the inorganic matrix, in particular 2.0%.

[0117] It is understood that for an inorganic matrix made from soil, the total mass of the inorganic matrix corresponds to the dry mass of the soil, made up of the mass of mineral grains and clay.

[0118] According to a particular embodiment, the invention relates to a material as defined above, in which the biopolymer is a biopolymer of plant origin.

[0119] According to a particular embodiment, the invention relates to a material as defined above, in which the biopolymer comprises at least one compound selected from cellulose, hemicellulose, lignin, polyphenols such as hydrolyzable or condensed tannins, amylose, amylopectin, alginate, agar, carrageenan, keratin, casein, collagen, albumin, pectin, xanthan gum, chitosan.

[0120] According to a particular embodiment, the invention relates to a material as defined above, in which the plant biopolymer comprises at least one compound selected from cellulose, hemicellulose, lignin and polyphenols.

[0121] According to a particular embodiment, the invention relates to a material as defined above, in which the biopolymer is derived from leaf, cactus, grass or tannin.

[0122] According to a particular embodiment, the invention relates to a material as defined above, in which the biopolymer is in the form of particles with an average size of 50 pm to 1 mm, in particular 250 pm. The range "from 50 pm to 1 mm" includes the ranges delimited by 50 pm, 100 pm, 150 pm, 200 pm, 250 pm, 300 pm, 400 pm, 500 pm, 600 pm, 700 pm, 800 pm, 900 pm, 1 mm.

[0123] According to a particular embodiment, the invention relates to a material as defined above, in which the biopolymer represents from 0.1 to 5.0% by total mass of the inorganic matrix, in particular 2.0%, and in particular in which the biopolymer is a biopolymer of plant origin, and in particular, in which the plant biopolymer comprises at least one compound selected from cellulose, hemicellulose, lignin and polyphenols, and in particular, in which the biopolymer is in the form of particles of average size from 50 pm to 1 mm, in particular 250 pm.

[0124] According to a particular embodiment, the invention relates to a material as defined above, in which part of the mineral grains have a size ranging from centimeter to millimeter.

[0125] This wide range of sizes, from centimeter to millimeter, can be obtained using gravel and sand from natural soil.

[0126] According to a particular embodiment, the invention relates to a material as defined above, in which the size of the mineral grains of the matrix is ​​less than or equal to 2.0 mm.

[0127] Such a size of mineral grains in the soil used to prepare the matrix can be obtained by sieving.

[0128] The size of a mineral grain is defined here as the largest of the grain dimensions.

[0129] According to a particular embodiment, the invention relates to a material as defined above, in which the sorpivity of the material is from 0.020 to 0.500 kg.m 2 .s- 1 / 2 .

[0130] The range "from 0.020 to 0.500" includes the ranges delimited by the values ​​0.020; 0.050; 0.100; 0.200; 0.300; 0.400; 0.500.

[0131] This value is typical of raw earth materials.

[0132] According to a particular embodiment, the invention relates to a material as defined above, in which the sorpivity of the material is less than 0.100 kg.m 2 .s- 1 / 2 .

[0133] Sorptivity refers to a material's ability to absorb or release water by capillary action. Sorptivity can be measured using the following capillary action test:

[0134] Capillary absorption was evaluated on three test samples following the procedures described in Y. Du et al. (Construction and Building Materials 323 (2022) 126571), S. Guihéneuf et al. (Mater. Struct. 53 (2020)), and CTS Beckett et al. (Construction and Building Materials 242 (2020) 118098). The lateral sides of the samples were sealed with aluminum tape, and the lower surface was covered with Whatman filter paper to prevent physical degradation, while the upper surfaces were left uncovered. The samples were placed on a sponge in a container filled with tap water to the top of the sponge, and the mass of the samples was measured at various time intervals over a period of 1 hour.The capillary absorption of water is calculated by dividing the mass change by the contact area, and the sorpivity of water is calculated using a linear fit of the capillary absorption plot with respect to the square root of time, as has been done in previous studies by Y. Du et al.

[0135] According to a particular embodiment, the invention relates to a material as defined above, in which the mass loss after a continuous water spray test for 10 min at a pressure of 2 bars and a flow rate of 12 L / min under a plane inclined at an angle of 30°C to the vertical is less than 2% by mass, in particular less than 0.5% by mass of the material.

[0136] The range of "less than 2%" includes the ranges delimited by: 0.0%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%. Mass loss under water spray can be evaluated according to the procedures described in M. Ouedraogo et al. (Journal of Building Engineering 23 (2019) 250-258), and in H. Bamogo et al. (Chemistry Africa (2023)).

[0137] The test consists of spraying water droplets at a pressure of 2 bar and a constant flow rate of 12 L / min for 10 minutes onto the material placed on a plane inclined at an angle of 30° to the vertical. The percentage of mass loss of the material is then evaluated using the equation:

[0138] M o - M, Mass loss (%) = - x 100

[0139] M o in which

[0140] Mo is the initial mass of the dried sample and

[0141] Ms the mass of the sample after spray testing after complete drying.

[0142] According to a particular embodiment, the invention relates to a material as defined above, in which said material retains its integrity for at least 24 hours when immersed in water.

[0143] By "integrity" we understand that the material retains its physical integrity and presents a form identical to the initial non-immersed material, without visual observation of cracks or disintegration of the matrix structure of the material after immersion.

[0144] Water immersion resistance can be assessed by an immersion test performed on three samples following the procedure described in CTS Beckett et al. (Construction and Building Materials 242 (2020) 118098), in Y. Kulshreshtha et al. (Construction Technologies and Architecture, Trans Tech Publications Ltd, Switzerland, 2022), and in RN Pachamama et al. (Materials 17 (2024)). Each sample is fully immersed for 24 hours in a plastic tray filled with 450 ml of tap water at a laboratory temperature of 25 °C. Images are captured using a 12-megapixel camera at various time intervals to monitor sample disintegration. An analysis is performed on the visual effects observed in the images.

[0145] Soil material samples are photographed after 5 minutes, 2 hours and 24 hours of immersion and classified as "undamaged" or "damaged" depending on the presence of cracks or disintegration.

[0146] According to a particular embodiment, the invention relates to a material as defined above, in which the dynamic Young's modulus of the material is from 800 to 6500 MPa.

[0147] The range "from 800 to 6500 MPa" includes the ranges of values ​​delimited by: 800 MPa, 1000 MPa, 1500 MPa, 2000 MPa, 2500 MPa, 3000 MPa, 3500 MPa, 4000 MPa, 4500 MPa, 5000 MPa, 5500 MPa, 6000 MPa, 6500 MPa.

[0148] This range of values ​​is typical of raw earth materials.

[0149] The dynamic Young's modulus of the material can be evaluated using the pulse excitation technique (ASTM E1876-2). A multimedia microphone (HSM6, Velleman) is connected to an oscilloscope (DSOX1204A 100 MHz) with an integrated Fast Fourier Transform (FFT) to determine the resonant frequency of the earth materials. The dynamic Young's modulus was then calculated using the equation.

[0150] Dynamic Young's modulus (P a) = 0.9465 in which: m is the mass of the sample (g), b the width of the sample (mm), L the length of the sample (mm), t the thickness of the sample (mm), ff the fundamental resonance frequency of the bar in bending (Hz) and T1 a correction factor for the finite thickness of the sample (L / t>20).

[0151] According to a particular embodiment, the invention relates to a material as defined above, in which the flexural strength of the material is from 0.1 to 2.0 MPa. The range "0.1 to 2.0 MPa" includes the ranges of values ​​delimited by: 0.1 MPa, 0.3 MPa, 0.5 MPa, 1.0 MPa, 1.5 MPa, 2.0 MPa.

[0152] This range of flexural strength values ​​is typical of raw earth materials.

[0153] Flexural strength can be assessed by flexural strength tests carried out on three samples using a 10 kN sensor at a constant speed of 10 N / s.

[0154] According to a particular embodiment, the invention relates to a material as defined above, in which the compressive strength of the material is from 0.5 to 5.0 MPa.

[0155] The range "0.5 to 5.0 MPa" includes the ranges of values ​​delimited by: 0.5 MPa, 1.0 MPa, 1.5 MPa, 2.0 MPa, 2.5 MPa, 3.0 MPa, 3.5 MPa, 4.0 MPa, 4.5 MPa, 5.0 MPa.

[0156] This range of compressive strength values ​​is typical of raw earth materials.

[0157] Compressive strength can be assessed by compression strength tests carried out on six semi-prismatic samples, each tested at a constant speed of 200 N / s using a 10 kN sensor.

[0158] According to a particular embodiment, the invention relates to a material as defined above, in which the inorganic matrix is ​​formed from a soil having an iron content of 0.5 to 30.0% by mass and an aluminum content of 0.5 to 35.0% by mass, as determined by ICP-OES analysis. The chemical elemental analyses of the material can be performed by inductively coupled plasma atomic emission spectrometry (ICP-OES), a technique known to those skilled in the art.

[0159] According to a particular embodiment, the invention relates to a material as defined above, in which the inorganic matrix is ​​made from a soil having an iron content of 1.0 to 10.0% by mass, in particular 7%, and an aluminium content of 0.5 to 20.0% by mass, in particular 12.0%, by ICP-OES analysis.

[0160] According to a particular embodiment, the invention relates to a material as defined above, in which the inorganic matrix is ​​made from a soil having an iron content of 15.0 to 30.0% by mass, in particular 19%, and an aluminium content of 20.0 to 35.0% by mass, in particular 29%, by ICP-OES analysis.

[0161] According to a particular embodiment, the invention relates to a material as defined above, in which the biostabilized building material exhibits respiration generating a CO2 flux less than or equal to 0.03 pmol.m 2 .s -1 .

[0162] A low rate or absence of respiration is an indicator that the mold mycelium is inactivated and the hyphae are biologically inert.

[0163] The CO2 flux characterizing the respiration of microorganisms can be evaluated as follows:

[0164] The CO2 flux is measured with humidity correction using the Ultraportable Greenhouse Gas Analyzer (UGGA, Los Gatos Research Inc., Mountain View, USA). The UGGA is connected to a 3.01 L custom-made PVC chamber, operating in a closed loop, and incorporating an internal fan to mix the air inside.

[0165] Material samples, each with a surface area of ​​approximately 288 cm² 2 are placed on a triangular plastic base inside the chamber to prevent any obstruction of the surface.

[0166] During a measurement period of 30 minutes, the CO2 concentration was recorded every 9 seconds and used to calculate the CO2 flux using the following equation:

[0167] PV ACO2

[0168] CO2- flux x - x - R x TS At in which

[0169] CO2 flux is the CO2 efflux rate of the analyzed soil material sample (pmol.m2 .s _ 1 ),

[0170] P is atmospheric pressure (Pa), V is the volume of the chamber (m³) 3 ),

[0171] S is the surface area of ​​the earth bricks (m 2 ),

[0172] R is the universal gas constant (kg.m 2 . s -2 K -1 . mol -1 ),

[0173] T is the initial temperature of the air chamber (K),

[0174] ACO2 is the variation of the water-corrected mole fraction of CO2 (pmol.mol) -1 ) and At is the duration of the measurement (s).

[0175] The mean and standard deviation are determined by analyzing the CO2 flux of three material samples.

[0176] Another object of the invention relates to a building brick comprising or made of a building material as defined above.

[0177] Advantageously, the said building brick is a solid brick.

[0178] According to a particular embodiment, the invention relates to a brick as defined above, in which the surface of the brick is covered from 0.2 to 95.0% by mold mycelium.

[0179] Advantageously, from 2.0 to 90.0% of the brick surface is covered by mold mycelium.

[0180] Advantageously, 15.0 to 50.0% of the brick surface is covered by mold mycelium.

[0181] Mold mycelium has a greenish or black appearance, visually recognizable, allowing its presence to be identified and the mycelium coverage to be assessed on the surface of the material, particularly through image processing.

[0182] According to a particular embodiment, the invention relates to a brick as defined above, in which said brick is in the form of a rectangular parallelepiped.

[0183] The rectangular parallelepiped is an easily malleable shape.

[0184] According to a particular embodiment, the invention relates to a brick as defined above, in which said brick is in the form of a rectangular parallelepiped of dimension:

[0185] Length 15 to 16 cm,

[0186] Width of 3.5 to 4 cm,

[0187] Height of 3.5 to 4 cm,

[0188] These dimensions are those of standard bricks.

[0189] Advantageously, the dimensions of the brick correspond to the standard dimensions of earthen bricks.

[0190] According to a particular embodiment, the invention relates to a brick as defined above, in which said brick is solid and formed from a material consisting of: an inorganic matrix, made from raw earth from soil, as the source of the mineral and clay grains of said matrix; a biopolymer derived from a leaf, at a rate of 2.0% by total mass of the organic matrix, mixed with the clay of said matrix; and mycelium present in pores of the matrix, each pore being formed by the space between adjacent mineral grains of said assembly, bound by clay and / or by the interstices between the clay particles, said mycelium being derived from mold generated by the growth of hyphae of ubiquitous, uninoculated fungi having said biopolymer as their growth substrate; and said material being biostabilized and comprising inactivated mycelium in which the hyphae are biologically inert.

[0191] By way of non-limiting example, the leaf-derived polymer is from the leaves of Octoea guianensis.

[0192] According to a particular embodiment, the invention relates to a brick as defined above, in which said brick is solid and formed from a material consisting of: an inorganic matrix, made from raw earth extracted from soil, as the source of the mineral and clay grains of said matrix; a biopolymer derived from cactus, at a rate of 2.0% by total mass of the organic matrix, mixed with the clay of said matrix; and mycelium present in pores of the matrix, each pore being formed by the space between adjacent mineral grains of said assembly, bound by clay and / or by the interstices between the clay particles, said mycelium being derived from mold generated by the growth of hyphae of ubiquitous, uninoculated fungi having said biopolymer as their growth substrate; and said material being biostabilized and comprising inactivated mycelium in which the hyphae are biologically inert.

[0193] By way of non-limiting example, the cactus-derived polymer is, for instance, the cladodes of Hylocereus polyrhizus.

[0194] According to a particular embodiment, the invention relates to a brick as defined above, in which said brick is solid and formed from a material consisting of: an inorganic matrix, made from raw earth extracted from soil, as the source of the mineral and clay grains of said matrix; a biopolymer derived from grass, at a rate of 2.0% by total mass of the organic matrix, mixed with the clay of said matrix; and mycelium present in pores of the matrix, each pore being formed by the space between adjacent mineral grains of said assembly, bound by clay and / or by the interstices between the clay particles, said mycelium being derived from mold generated by the growth of hyphae of ubiquitous, uninoculated fungi having said biopolymer as their growth substrate; and said material being biostabilized and comprising inactivated mycelium in which the hyphae are biologically inert.

[0195] By way of non-limiting example, the grass-derived polymer is a grass sample containing three species belonging to the following families: Poaceae, Fabaceae and Cyperaceae.

[0196] According to a particular embodiment, the invention relates to a brick as defined above, in which said brick is solid and formed from a material consisting of: an inorganic matrix, made from raw earth from soil, as the source of the mineral and clay grains of said matrix; a biopolymer derived from tannin, at a rate of 2.0% by total mass of the organic matrix, mixed with the clay of said matrix; and mycelium present in pores of the matrix, each pore being formed by the space between adjacent mineral grains of said assembly, bound by clay and / or by the interstices between the clay particles, said mycelium being derived from mold generated by the growth of hyphae of ubiquitous, uninoculated fungi having said biopolymer as their growth substrate; and said material being biostabilized and comprising inactivated mycelium in which the hyphae are biologically inert.

[0197] By way of non-limiting example, the polymer derived from tannin is a chestnut tannin powder, extracted from the wood of chestnut trees (Castanea sativà).

[0198] According to a particular embodiment, the invention relates to a brick as defined above, the inorganic matrix being made from a soil having an iron content of 1.0 to 10.0%, in particular 7%, and an aluminium content of 0.5 to 20.0%, in particular 12.0%, by ICP-OES analysis.

[0199] Advantageously the soil comprises: 25.0 to 35.0% by mass of clay, 5.0 to 15.0% by mass of silt, 55.0 to 65.0% by mass of sand. Advantageously the soil comes from quarries near Mana in French Guiana.

[0200] According to a particular embodiment, the invention relates to a brick as defined above, in which the inorganic matrix is ​​made from a soil having an iron content of 15.0 to 30.0%, in particular 19%, and an aluminium content of 20.0 to 35.0%, in particular 29%, by ICP-OES analysis.

[0201] Advantageously, the soil comprises: 15.0 to 25.0% by mass of clay, 35.0 to 45.0% by mass of silt, and 35.0 to 45.0% by mass of sand.

[0202] Advantageously, the soil comes from quarries near Sinnamary in French Guiana.

[0203] Another object of the invention relates to a process for preparing a building material as defined above, comprising the following steps: shaping an inorganic earth matrix from a soil using a mortar comprising a mixture of mineral grains, clay, water and a biopolymer; inducing the proliferation of mold from at least one fungus under humid atmospheric conditions allowing the formation of mycelium in pores of said shaped inorganic matrix, to obtain an intermediate material consisting of the inorganic matrix containing mold mycelium in pores; biostabilizing said intermediate material by stopping the proliferation of the mold in order to obtain inactivated mycelium formed of biologically inert hyphae, in particular by heat treatment, to obtain said building material.

[0204] The term "mortar" or "fresh mortar" refers to the mixture comprising mineral grains, clay, water, and possibly a biopolymer. The mortar has a suitable consistency for shaping in a mold before drying to form a solid material. Thus, the mortar is the mixture prior to shaping the material, and this material is a finished, solidified earth material with a defined morphology.

[0205] By "humid atmosphere" we mean the pressure, temperature and humidity conditions that allow mold growth.

[0206] Advantageously, biostabilization allows the structure of the hyphae to be preserved in the form of filaments.

[0207] Advantageously, biostabilization allows the cellular structure of the hyphae to be preserved.

[0208] According to a particular embodiment, the invention relates to a process for preparing a construction material as defined above, comprising the following steps: shaping an inorganic earth matrix from a soil using a mortar comprising a mixture of mineral grains, clay, water and a biopolymer; inducing the proliferation of mold from ubiquitous fungi under humid atmospheric conditions allowing the formation of mycelium in the pores of said shaped inorganic matrix, to obtain an intermediate material consisting of the inorganic matrix containing mold mycelium in pores; biostabilizing said intermediate material by stopping the proliferation of the mold in order to obtain inactivated mycelium formed of biologically inert hyphae, in particular by a heat treatment, to obtain said construction material.

[0209] In this embodiment, the mold growth originates from ubiquitous fungi. The present method of this embodiment of the invention has the advantage of not requiring fungal selection for mycelium growth, thus avoiding the steps of fungal selection, fungal inoculation, and sterilization of the medium prior to fungal inoculation. According to a particular embodiment, the invention relates to a method as defined above, comprising a step of inoculating said at least one fungus of said mold before inducing the mold proliferation step.

[0210] In this alternative embodiment of the process of the invention, mold growth originates from at least one mold fungus that is inoculated. The present process of the invention has the advantage of facilitating mold colonization in the pores and / or influencing the fungal population within the mold.

[0211] According to a particular embodiment, the invention relates to a process as defined above, comprising a preliminary step of preparing said mortar by mixing mineral grains, clay, water and the biopolymer.

[0212] According to a particular embodiment, the invention relates to a process as defined above, in which the inorganic matrix is ​​shaped into a building brick.

[0213] According to a particular embodiment, the invention relates to a process as defined above, in which said building brick is solid, said matrix representing from 65 to 85%, preferably more than 75% by volume of said solid brick.

[0214] According to a particular embodiment, the invention relates to a process as defined above, in which the inorganic matrix is ​​shaped into a building brick, and in particular in which said building brick is solid, said matrix representing from 65 to 85%, preferably more than 75% by volume of said solid brick.

[0215] According to a particular embodiment, the invention relates to a method as defined above, in which said building brick is hollow.

[0216] According to a particular embodiment, the invention relates to a process as defined above, in which said mortar contains a hydraulic binder, in particular chosen from cement or lime.

[0217] It is possible to strengthen the cohesion of the material by incorporating a fraction of hydraulic binder which allows to reduce their use.

[0218] According to a particular embodiment, the invention relates to a process as defined above, in which the mortar is prepared from raw earth taken from natural soil, as the source of mineral and clay grains.

[0219] According to a particular embodiment, the invention relates to a process as defined above, in which the mortar is prepared from an inorganic natural soil comprising less than 2.0% by mass of organic matter relative to the total mass of the soil, as the source of mineral and clay grains.

[0220] According to a particular embodiment, the invention relates to a process as defined above, in which the mortar is prepared from a soil having: 15.0 to 35.0% clay by total mass of the soil, 5.0 to 45.0% silt by total mass of the soil, 35.0 to 65.0% sand by total mass of the soil.

[0221] According to a particular embodiment, the invention relates to a process as defined above, in which the mortar is prepared from a soil having: a liquid limit of 40.0 to 50.0% and a plastic limit of 20.0 to 30.0%. According to a particular embodiment, the invention relates to a process as defined above, in which the mortar is prepared from a soil having a specific surface area of ​​10 to 30 m². 2 / g.

[0222] According to a particular embodiment, the invention relates to a process as defined above, in which the mortar is prepared from a soil having an iron content of 0.5 to 30.0% and an aluminum content of 0.5 to 35.0% by mass, by ICP-OES analysis.

[0223] According to a particular embodiment, the invention relates to a process as defined above, in which the mortar is prepared from a soil having a silicon content of 20.0 to 80.0% by mass, by ICP-OES analysis, in particular of about 36% and about 75%.

[0224] According to a particular embodiment, the invention relates to a process as defined above, in which the mortar is prepared from a soil having an iron content of 1.0 to 10.0%, in particular 7%, and an aluminum content of 0.5 to 20.0% by mass, in particular 12.0%, by ICP-OES analysis.

[0225] Advantageously, the soil comprises: 25.0 to 35.0% clay by mass, 5.0 to 15.0% silt by mass, and 55.0 to 65.0% sand by mass.

[0226] Advantageously, the soil comes from quarries near Mana in French Guiana.

[0227] According to a particular embodiment, the invention relates to a process as defined above, in which the mortar is prepared from a soil having an iron content of 15.0 to 30.0% by mass, in particular 19%, and an aluminium content of 20.0 to 35.0% by mass, in particular 29%, by ICP-OES analysis.

[0228] Advantageously, the soil comprises: 15.0 to 25.0% by mass of clay, 35.0 to 45.0% by mass of silt, and 35.0 to 45.0% by mass of sand.

[0229] Advantageously, the soil comes from quarries near Sinamary in French Guiana.

[0230] According to a particular embodiment, the invention relates to a process as defined above, in which the mortar comprises 15 to 40% by mass of water.

[0231] According to a particular embodiment, the invention relates to a process as defined above, in which the mortar is prepared from raw earth taken from natural soil, as the source of mineral and clay grains, and in particular in which the mortar comprises 15 to 40% by mass of water.

[0232] According to a particular embodiment, the invention relates to a process as defined above, in which the biopolymer in the mortar represents from 0.1 to 5.0% by total mass of the inorganic matrix.

[0233] According to a particular embodiment, the invention relates to a process as defined above, in which the biopolymer comprises at least one compound selected from cellulose, hemicellulose, lignin, polyphenols such as hydrolyzable or condensed tannins, amylose, amylopectin, alginate, agar, carrageenan, keratin, casein, collagen, albumin, pectin, xanthan gum, chitosan.

[0234] According to one particular embodiment, the invention relates to a process as defined above, wherein the biopolymer comprises at least one polymer selected from cellulose, hemicellulose, lignin, and polyphenols. According to another particular embodiment, the invention relates to a process as defined above, wherein the biopolymer is selected from leaves, cactus, herbs, or tannin.

[0235] By way of non-limiting example, the leaf-derived polymer is from the leaves of Octoea guianensis.

[0236] By way of non-limiting example, the cactus-derived polymer is, for instance, the cladodes of Hylocereus polyrhizus.

[0237] By way of non-limiting example, the grass-derived polymer is a grass sample containing three species belonging to the following families: Poaceae, Fabaceae and Cyperaceae.

[0238] By way of non-limiting example, the polymer derived from tannin is a chestnut tannin powder, extracted from the wood of chestnut trees (Castanea sativà).

[0239] According to a particular embodiment, the invention relates to a process as defined above, in which the biopolymer is derived from waste, preferably from household, forestry, agricultural or industrial waste.

[0240] According to a particular embodiment, the invention relates to a process as defined above, in which the biopolymer mixed in the mortar is in the form of particles of average size from 50 pm to 1 mm, in particular 250 pm.

[0241] According to a particular embodiment, the invention relates to a process as defined above, in which the biopolymer in the mortar represents from 0.1 to 5.0% by total mass of the inorganic matrix, and in particular in which the biopolymer comprises at least one polymer selected from cellulose, hemicellulose, lignin and polyphenols, and in particular in which the biopolymer is selected from leaves, cactus, herbs or tannin, and in particular in which the biopolymer mixed in the mortar is in the form of particles of average size from 50 pm to 1 mm, in particular 250 pm.

[0242] According to a particular embodiment, the invention relates to a process as defined above, in which the biopolymer mixed in the mortar is in the form of a powder of particles obtained by atomizing a solution of the biopolymer.

[0243] According to a particular embodiment, the invention relates to a process as defined above, in which the proliferation of molds is achieved:

[0244] - at a temperature of 25.0 to 35.0 °C

[0245] - and / or from 50.0 to 98.0% relative humidity (RH)

[0246] - and / or for a period of 5 to 30 days.

[0247] The range "from 25 to 35°C" includes the temperature ranges delimited by: 25.0°C, 26.0°C, 27.0°C, 28.0°C, 29.0°C, 30.0°C, 31.0°C, 32.0°C, 33.0°C, 34.0°C, 35.0°C.

[0248] The range "from 50.0 to 98.0%" includes the ranges of values ​​delimited by: 50.0%, 55.0%, 60.0%, 65.0%, 70.0%, 75.0%, 80.0%, 85.0%, 90.0%, 95.0%, 98.0%.

[0249] The "5 to 30 days" range includes the ranges of periods delimited by: 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29 and 30 days.

[0250] A person skilled in the art is able to determine the conditions that promote mold growth and to adjust the pressure, temperature, humidity level and duration accordingly.

[0251] According to a particular embodiment, the invention relates to a process as defined above, in which the material is biostabilized by a heat treatment at a temperature of 65 to 120°C, preferably 65 to 80°C, for 12 to 72 hours, preferably 48 hours.

[0252] Advantageously, heat treatment allows biostabilization throughout the entire volume of the material, particularly in the pores by thermal conduction.

[0253] It is understood that the duration can be adjusted by a person skilled in the art according to the volume of material to be treated; a large volume will require a longer heat treatment. This step allows for fungal inactivation of the material, as well as drying.

[0254] According to a particular embodiment, the invention relates to a process as defined above, comprising a step of removing the mold containing the inactivated mycelium on the surface of the biostability material.

[0255] Once the material has achieved biostability, the inactivated fungi present on the surface can be removed, for example by dusting with a brush.

[0256] According to a particular embodiment, the invention relates to a process as defined above, comprising a step of storing the construction material at a temperature of 20 to 30°C, preferably 25°C, at a humidity level of 50 to 70% relative humidity, preferably 60% relative humidity, for 5 to 10 days.

[0257] Once the mold is inactivated, the storage conditions no longer allow the growth of mold fungi.

[0258] According to a particular embodiment, the invention relates to a process as defined above for preparing a raw earth construction brick comprising the following steps: shaping an inorganic raw earth matrix in the form of a rectangular parallelepiped from a mortar comprising a mixture of soil, water and a biopolymer derived from leaves, preferably Octoea guianensis leaves, at a rate of 2.0% by mass relative to the total mass of the soil; inducing the proliferation of mold from ubiquitous fungi under humid atmospheric conditions at a temperature of 30.0 °C, at a relative humidity (RH) of 98.0% and for a period of 21 days, allowing the formation of mycelium in the pores of said shaped inorganic matrix, to obtain an intermediate material consisting of the inorganic matrix containing mold mycelium in pores,the biostabilization of said intermediate material by stopping the proliferation of mold in order to obtain inactivated mycelium formed of biologically inert hyphae, by heat treatment at a temperature of 80°C for 48 hours to obtain said construction material.

[0259] According to a particular embodiment, the invention relates to a process as defined above for preparing a raw earth construction brick comprising the following steps: shaping an inorganic raw earth matrix in the form of a rectangular parallelepiped from a mortar comprising a mixture of soil, water and a biopolymer derived from cacti, preferably from Hylocereus polyrhizus cladodes, at a rate of 2.0% by mass relative to the total mass of the soil; inducing the proliferation of mold from ubiquitous fungi under humid atmospheric conditions at a temperature of 30.0 °C, at a relative humidity (RH) of 98.0% and for a period of 21 days, allowing the formation of mycelium in the pores of said shaped inorganic matrix, to obtain an intermediate material consisting of the inorganic matrix containing mold mycelium in pores,the biostabilization of said intermediate material by stopping the proliferation of mold in order to obtain inactivated mycelium formed of biologically inert hyphae, by heat treatment at a temperature of 80°C for 48 hours to obtain said construction material.

[0260] According to a particular embodiment, the invention relates to a process as defined above for preparing a raw earth construction brick comprising the following steps: shaping an inorganic raw earth matrix in the form of a rectangular parallelepiped from a mortar comprising a mixture of soil, water and a biopolymer derived from grass, preferably grass of three species belonging to the following families: Poaceae, Fabaceae and Cyperaceae, at a rate of 2.0% by mass relative to the total mass of the soil, inducing the proliferation of mold from ubiquitous fungi under humid atmospheric conditions at a temperature of 30.0 °C, at a relative humidity of 98.0% RH and for a period of 21 days, allowing the formation of mycelium in the pores of said shaped inorganic matrix,To obtain an intermediate material consisting of an inorganic matrix containing mold mycelium in pores, the biostabilization of said intermediate material by stopping mold proliferation to obtain inactivated mycelium formed from biologically inert hyphae, by heat treatment at a temperature of 80°C for 48 hours to obtain said construction material.

[0261] According to a particular embodiment, the invention relates to a process as defined above for preparing a raw earth construction brick comprising the following steps: shaping an inorganic raw earth matrix in the form of a rectangular parallelepiped from a mortar comprising a mixture of soil, water and a biopolymer derived from tannin, preferably a chestnut tannin powder, extracted from chestnut wood (Castanea sativa), at a rate of 2.0% by mass relative to the total mass of the soil, inducing the proliferation of mold from ubiquitous fungi under humid atmospheric conditions at a temperature of 30.0 °C, at a relative humidity (RH) of 98.0% and for a period of 21 days, allowing the formation of mycelium in the pores of said shaped inorganic matrix,To obtain an intermediate material consisting of an inorganic matrix containing mold mycelium in pores, the biostabilization of said intermediate material by stopping mold proliferation to obtain inactivated mycelium formed of biologically inert hyphae, by heat treatment at a temperature of 80°C for 48 hours to obtain said construction material.

[0262] According to a particular embodiment, the invention relates to a process as defined above for preparing a raw earth brick, in which the mortar is prepared from a soil having: an iron content of 1.0 to 10.0% by mass, in particular 7%, and an aluminum content of 0.5 to 20.0% by mass, in particular 12.0%, by ICP-OES analysis, comprising: o 25.0 to 35.0% by mass of clay o 5.0 to 15.0% by mass of silt o 55.0 to 65.0% by mass of sand.

[0263] Advantageously, the soil comes from quarries near Mana in French Guiana.

[0264] According to a particular embodiment, the invention relates to a process as defined above for preparing a raw earth brick, in which the mortar is prepared from a soil: having an iron content of 15.0 to 30.0% by mass, in particular 19%, and an aluminum content of 20.0 to 35.0% by mass, in particular 29%, by ICP-OES analysis, comprising o 15.0 to 25.0% by mass of clay o 35.0 to 45.0% by mass of silt o 35.0 to 45.0% by mass of sand.

[0265] Advantageously, the soil comes from quarries near Sinamary in French Guiana.

[0266] FIGURES Figure 1 schematically represents an earth brick comprising a biopolymer and water-resistant inactivated mycelium which includes an earth matrix derived from soil formed of mineral grains bound by clay and comprising pores which are filled with mycelium, the mycelium being made up of hyphae formed of cells with elongated nuclei, the cell wall of the hyphae comprising proteins, glucan and chitin.

[0267] Figure 2 shows the normalized ATR-FTIR spectra of biopolymers from leaf, cactus, grass and tannin.

[0268] Figure 3 shows photographs of the visual evolution over time at 0, 2, 5, 9, 14 and 21 days of wet curing of an earth material from soil S comprising a biopolymer from cactus.

[0269] Figure 4 shows a photograph of one side of a sample of soil material S with cactus after wet curing and the image transformed into black and white to assess the percentage of mold coverage on the surface of the material.

[0270] Figure 5 represents the percentage of visual surface coverage by mold after wet curing for earth materials from soil M (left histogram) or soil S (right histogram) not containing biopolymer (Control) and containing a biopolymer from leaf, cactus, grass and tannin.

[0271] Figure 6 represents micrographs of materials from soil M (part a) or soil S (part b) containing a biopolymer from leaf or cactus, after dry curing or wet curing, showing, by arrows, the presence of mycelium hyphae for materials that have undergone wet curing.

[0272] Figure 7 represents the setup for evaluating CO2 flux of a material comprising a chamber approximately 17.5 cm wide and 12.5 cm high in which the sample is hermetically sealed inside using a gasket and a plastic plate, the chamber being connected to a CO2 flux analyzer and a computer.

[0273] Figure 8 represents the results of the CO2 flux generated by materials not containing biopolymer (Control) and containing a biopolymer derived from leaf, cactus, grass and tannin for materials from soil M (left part) and from soil S (right part).

[0274] Figure 9 represents the normalized ATR-FTIR spectra of recovered mycelia for materials containing cactus, grass and tannin biopolymer for materials from soil and from soil S after wet curing.

[0275] Figure 10 shows the ratio of the IR peak intensities of amide-l at 1640 cm⁻¹ -1 and the amide-ll at 1545 cm -1 , of chitin (1375 cm -1 ) compared to that of polysaccharides (1040 cm -1 ) for materials containing a biopolymer of cactus, grass and tannin for materials from soil and from soil S after wet curing.

[0276] Figure 11 shows the diagrams of the water resistance tests, diagram a) representing the capillary absorption test in which the 4x4x8cm specimen of the material is placed on a sponge to measure the mass change; diagram b) representing the immersion test in which the 4x4x8cm specimen of the material is immersed in water; diagram c) representing the water spray resistance test in which the 4x4x16cm specimen of the material is placed on an inclined plane at an angle of 30° to the vertical at an average distance of 40 cm from the source of the water droplets at a pressure of 2 bars and a constant flow rate of 12 L / min for 10 minutes.

[0277] Figure 12 shows the sorpivity results (kg nr s -1 / 2) of the capillarity test for materials prepared with soil M (left part) or with soil S (right part), without biopolymer (Control) or containing the respective biopolymers leaf, cactus, grass and tannin, with a dry cure or with a wet cure.

[0278] Figure 13 represents the mass loss results as a mass percentage after the water spray resistance test for materials prepared with soil M (left part) or with soil S (right part), without biopolymer (Control) or containing the respective biopolymers leaf, cactus, grass and tannin, with dry curing or with wet curing and the visual appearance of the samples.

[0279] Figure 14 represents the results indicating whether the sample is "intact" or "destroyed" according to the reference images (images in the lower part) after an immersion time of 5 min, 2 h and 24 h, for materials prepared with soil M (left part) or with soil S (right part), without biopolymer (Control) or containing the respective biopolymers leaf, cactus, grass and tannin, with a dry cure or with a wet cure and the visual appearance of the samples.

[0280] Figure 15 shows the values ​​of volumetric shrinkage (%), mass, and density (kg / m³). 3 ) materials prepared with soil M (left part) or with soil S (right part), without biopolymer (Control) or containing the respective biopolymers leaf, cactus, grass and tannin, with a dry cure or with a wet cure.

[0281] Figure 16 represents, as a function of the water content of the mortar used to prepare the materials, the volumetric shrinkage (upper part), the dry mass (centred part) and the dry density (lower part) for materials prepared with soil M or with soil S, without biopolymer or containing the respective biopolymers leaf, cactus, grass and tannin, with a dry cure or with a wet cure.

[0282] Figure 17 represents the values ​​of dynamic Young's modulus (MPa), flexural strength (MPa) and compressive strength (MPa) of materials prepared with soil M (left part) or with soil S (right part), without biopolymer (Control) or containing the respective biopolymers leaf, cactus, grass and tannin, with dry curing or with wet curing.

[0283] EXAMPLES

[0284] Example 1 - Biopolymers

[0285] Four different biopolymers, derived respectively from leaf, cactus, grass, and tannin, were used in the preparation of the materials. The selection of these biopolymers was based on traditional recipes and local availability; in particular, the biopolymers derived from leaf, cactus, and grass were prepared from industrial, agricultural, or household waste.

[0286] • Leaf: The leaves of Octoea guianensis, a tree species native to the forests of French Guiana, were chosen for their high mucilage content. These leaves were a by-product of a local cosmetics company that uses leaf mucilage in shampoo production. The leaves were in the form of a mixture of water, mucilage gel, and pieces of Octoea guianensis leaves. The mixture was completely dry before use.

[0287] • Cactus: Cladodes of Hylocereus polyrhizus were collected during the post-harvest pruning period in a field near Macouria, French Guiana. The freshly cut cladodes were washed and stripped of their spines and stems. • Grass: Freshly cut grass was collected on the campus of the University of French Guiana in Kourou on mowing day. The grass sample included three species belonging to the following families: Poaceae, Fabaceae, and Cyperaceae.

[0288] • Tannin: The chestnut tannin powder was sourced from Kingtree (Arras, France). These tannins were extracted from wood of sustainably managed chestnut trees (Castanea sativa) in southern France. The extraction process involved water extraction followed by evaporation and spray drying.

[0289] Biopolymer materials derived from leaves, cactus and grass were collected locally, dried at 40°C until the mass stabilized, mechanically ground and sieved to a size of 250 µm.

[0290] The pH was measured by mixing the biopolymer powder with distilled water at a concentration of 74 g / L, a concentration close to that used to prepare a mortar. The pH was 4.80 for the leaf solution, 4.08 for the cactus solution, 5.48 for the grass solution, and 2.95 for the tannin solution.

[0291] The chemical composition of the biopolymer powder was evaluated using ATR-FTIR (Attenuated Total Reflectance-Fourier Transformed Infrared) spectrometry on the four biopolymer powders in the wavelength range of 400-4000 cm⁻¹ 1 , with a resolution of 4 cm' 1on ground samples dried at 40°C. All spectra underwent baseline correction and min-max normalization and are shown in Figure 2.

[0292] Example 2 - Floors

[0293] Two soil samples were used. The soil samples were collected from lateritic quarries near Mana and Sinamary in French Guiana and designated M and S, respectively. These soils were analyzed, and their main characteristics are summarized in Table 1 according to L. Walter et al. (Case Studies in Construction Materials 20 (2024) e02709). The main difference between the soils is the lower concentration of iron and aluminum oxide in soil M than in soil S. The soils were air-dried and sieved to a 2 mm size before use.

[0294] Table 1 - Composition and physico-chemical characterization of soils M and S

[0295] Example 3 - Material preparation

[0296] The material formulations were prepared by mixing the biopolymers with the soil at a concentration of 2% biopolymer by mass relative to the soil.

[0297] In total, 10 formulations were prepared, including: one formulation per soil type serving as a control, i.e., not containing biopolymer.

[0298] 4 formulations with soil M comprising respectively biopolymers from leaves, cactus, herbs and tannin, 4 formulations with soil S comprising respectively biopolymers from leaves, cactus, herbs and tannin.

[0299] The biopolymers were first dissolved in distilled water for 3 minutes.

[0300] Next, the biopolymer solution was mixed with the soil containing the mineral grains and clay, for 2 minutes at a low speed of 62.5 rpm, then for 3 minutes at a high speed of 125 rpm.

[0301] After mixing, a fresh mortar was obtained. The consistency of the fresh mortar was assessed using a cone penetrometer. Based on previous studies, a penetration depth of 6 to 7 mm was targeted to define the required water content that allows for maximum compressive strength of the soil materials. If the penetration depth was less than 6 mm or greater than 7 mm, the procedure was repeated from the beginning, increasing or decreasing the water content accordingly. The water content used for the different formulations ranged from 21 to 36% by total weight of the composition. This is reported in Table 2 below for the different polymer and soil formulations.

[0302] Table 2: Water content of formulations as a percentage by total weight of the mortar composition.

[0303] The fresh mortar of each formulation was then poured into 24 prismatic samples (4x4x16 cm) 3 ) and stored directly in an oven at 50°C to allow for quick unmolding in 6 hours.

[0304] After demolding, the 24 samples were divided into two groups. Half of the samples underwent a 21-day dry cure in an oven at 50 °C, while the other half underwent a 21-day wet cure in a climate chamber at 30 °C with 98% relative humidity (RH). The wet cure condition (30 °C / 98% RH) was selected to promote mold growth.

[0305] After the 21-day curing period, all samples were dried at 80°C in an oven for 48 hours to ensure complete drying and fungal inactivation.

[0306] All samples were stored at 25°C with 60% RH for five days prior to material characterization.

[0307] Example 4: Visual analysis for the presence of mold

[0308] Methods

[0309] The characterization of the presence of molds on samples that underwent wet curing was carried out visually by photography and by image analysis during wet curing at 0, 2, 5, 9, 14 and 21 days.

[0310] Results

[0311] All biostabilized materials containing a biopolymer showed visual mold growth after the wet curing process.

[0312] Photographs of the samples confirm the presence of mold, particularly in formulations containing cactus (Figure 3) and tannin. Varying colors and appearances of mold growth were observed after 21 days of wet curing. Mold colonization times varied depending on the biopolymers used. For example, cactus biopolymers induced visible mold within two days of curing, while leaf biopolymers did not show mold growth until after nine days.

[0313] Conclusions

[0314] Significant variations were observed in both the extent of mold growth and its chemical composition depending on the different formulations.

[0315] The choice of biopolymer used affects the composition and quantity of mold mycelium. In comparison, the type of soil has little effect.

[0316] The low mold growth observed in samples prepared with a substrate derived from Octoea guianensis leaves, compared to three other substrates, including the grass substrate (also composed of lignocellulosic compounds), can be attributed to the antifungal, antimicrobial, and antiproliferative properties of Octoea species. Conversely, the cactus extract, rich in carbon, nitrogen, phosphorus, and minerals, induced the strongest mold growth, supporting the usefulness of cactus cladodes from species like Opuntia as fungal or microbial culture media. Surprisingly, significant mold growth was induced by tannin, a biopolymer known for its antifungal properties. Certain fungal species, such as Aspergillus and Penicillium, are capable of producing tannase enzymes that degrade chestnut tannin.This suggests that mold species naturally present in the laboratory environment can effectively degrade chestnut tannins.

[0317] Example 5: Visual analysis of surface colonization of materials by mycelium

[0318] Method

[0319] The proportion of the sample surface covered with mold mycelium was evaluated by image processing and analysis, after 21 days of wet curing.

[0320] For each sample, the four identical faces were photographed (4x16 cm). 2 ) using a 12-megapixel camera placed at a fixed distance and under homogeneous lighting conditions.

[0321] Using ImageJ software, the image was cropped to the dimensions of the sample, and then the "color threshold" was manually adjusted for each photograph to differentiate the mycelium from the uncontaminated sample surface. The image was then converted to black and white using the "make binary" command: the black area corresponds to the mycelium zone and the white area to the uncontaminated part (see Figure 4).

[0322] Finally, the proportion of the black area (mycelium coating) was measured as calculated in Laborel-Préneron et al. (Environ. 142 (2018) 11-21). The mean and standard deviation of the mycelium coating area were determined from the analysis of 16 images per formulation.

[0323] Results

[0324] The extent of mold mycelium coating on the surfaces of soil materials was quantified using image analysis, following the methodologies described above. The results are shown in Figure 5, part a) for materials with soil M, part b) for materials with soil S, and in Tables 3 and 4.

[0325] Table 3: Surface mold recovery rate according to image analysis of formulations with soil M of materials after wet curing as a percentage of the sample surface.

[0326] Table 4: Surface mold recovery rate according to image analysis of formulations with soil S of materials after wet curing as a percentage of the sample surface.

[0327] Conclusions

[0328] The control materials, i.e., those without biopolymer, showed no visible mold growth (0% mycelium coating). This confirms that soils M and S alone lack the organic matter necessary for mold development.

[0329] The assessed value of the visible surface mycelium coating varied from 2% to 87% for all formulations (Fig. 5). The addition of biopolymers consistently promoted mold growth in both soils.

[0330] More specifically, leaves induced minimal mycelium coating (less than 2%), while cactus, grass, and tannin resulted in significantly larger coatings, with more than 50%, 3%, and 16% coating, respectively.

[0331] The mycelial coating was uniformly higher in samples prepared with soil M compared to those made with soil S.

[0332] These results demonstrate the dual role of biopolymers as nutrient sources and the impact of abiotic soil properties, such as particle size, on mold growth dynamics.

[0333] Example 6: Analysis of the internal microstructure to determine the presence of mycelium

[0334] Method

[0335] To check for the suspected presence of mold mycelium in the pores of soil materials after wet curing, sample cores of all material formulations were examined using an optical microscope at 5X magnification with UV excitation.

[0336] The microstructure of the soil material was analyzed using an optical microscope (5X magnification) with UV illumination (400 nm). UV excitation was used to enhance the observation of the mycelium in the sample, as mycelium is known to exhibit autofluorescence under UV excitation. For each sample, at least 80 images were taken, and the overall image was then reconstructed using Microvision Instruments' Ellix software.

[0337] Many plants and microorganisms contain molecules that autofluorescent under UV excitation. Analyzing the color of these autofluorescent components can provide information about their molecular composition.

[0338] The control samples, composed solely of soil, did not show autofluorescent compounds after dry or wet curing, as these samples lack autofluorescent organic components.

[0339] Result

[0340] Effect of the biopolymer after a wet cure compared to a dry cure

[0341] Blue-violet autofluorescent components, in the form of interconnected filament networks, were observed in all samples of raw earth materials biostabilized after wet curing (Fig. 6). Emitting blue to violet hues, these filamentous structures are characteristic of fungal mycelium under UV excitation. Variations in the structure and coloration of the mycelium were observed between the different formulations of the earth material.

[0342] This result suggests the involvement of different fungal species in the different formulations, which was also the conclusion of the ATR-FTIR analysis (see example 7). Indeed, autofluorescence in hyphae can vary depending on the properties and content of different chitin components, as well as on the specific proteins, flavins, lipofuscins, porphyrins, and lignins in their cell walls.

[0343] Conclusion

[0344] Overall, systematic observation of the mycelium at the core of all biostabilized samples after wet curing confirmed that the mycelium penetrates deeply into the core of the sample. These observations helped explain the significant effect of the mycelium observed in this study on the physical, mechanical, and water-resistance properties of the biostabilized raw earth materials (Examples 9 to 13).

[0345] Example 7 - Metabolic activity - Evaluation of CO2 content

[0346] Method

[0347] Carbon dioxide production, a key by-product of fungal metabolism, serves as a measure to assess and quantify metabolic activity or fungal biomass under various conditions and substrates.

[0348] Thus, mold growth was measured by the CO2 flux produced by their respiration. CO2 fluxes were measured with humidity correction using the Ultraportable Greenhouse Gas Analyzer (UGGA, Los Gatos Research Inc., Mountain View, USA). The UGGA was connected to a homemade 3.01 L PVC chamber, operating in a closed loop, and incorporating an internal fan to mix the air inside.

[0349] Material samples, each with a surface area of ​​approximately 288 cm2, were placed on a triangular plastic base inside the chamber to avoid obstruction of the surface (see Fig. 7).

[0350] During a measurement period of 30 minutes, the CO2 concentration was recorded every 9 seconds and used to calculate the CO2 flux using the following equation #1. in which

[0351] CO2 flux is the CO2 efflux rate of the analyzed soil material sample (pmol.m 2 .s _ 1 ),

[0352] P is atmospheric pressure (Pa).

[0353] V is the volume of the chamber (m 3 ),

[0354] S is the surface area of ​​the earth bricks (m 2 ),

[0355] R is the universal gas constant (kg.m 2 . s -2 K -1 . mol -1 ),

[0356] T is the initial temperature of the air chamber (K),

[0357] ACO2 is the variation of the water-corrected mole fraction of CO2 (pmol.mol) -1 ) and At is the duration of the measurement (s).

[0358] The mean and standard deviation were determined by analyzing the CO2 flux of three material samples per formulation.

[0359] Results

[0360] The results of CO2 flux generated by the materials are reported in Figure 8, part a) for materials containing soil M, part b) for materials containing soil S and in Tables 5 and 6.

[0361] Table 5: CO2 flux generated by the materials of the formulations with soil M after wet curing.

[0362] Table 6: CO2 flux generated by the materials of the formulations with soil S after wet curing.

[0363] Conclusion

[0364] In this study, the CO2 flux of soil materials after 21 days of wet curing varied from 0.03 to 1.56 pmol.m 2 .s-1, which corresponds to the CO2 flux values ​​generally observed in forest soils. Materials produced without biopolymers from both soils exhibited a similar CO2 flux of approximately 0.03 pmol.m 2 .s-1. Since no visible mold growth was observed in these samples, the minimal CO2 flux was attributed to the respiration of unseen microorganisms. The addition of biopolymers therefore resulted in a significant increase in CO2 flux. This increase indicates an increase in microbial and fungal populations.

[0365] Among the biopolymers evaluated, cactus resulted in the largest increase in CO2 flux, followed by grass, tannin, and leaves on both soils.

[0366] Example 8: Characterization of the mycelium

[0367] Method

[0368] ATR-FTIR spectroscopy was used to characterize the chemical nature of mold mycelium collected from the surface of biostabilized soil materials. The chemical composition of the mold mycelium was analyzed by infrared spectroscopy. A mold mycelium sample was carefully removed from the surface of the soil material for each formulation, ensuring that no mineral grains were collected to avoid interference with the analysis. The mycelium samples were then directly subjected to ATR-FTIR analysis in the 4000-400 cm⁻¹ range. 1 with a resolution of 4 cm' 1 .

[0369] To compare the composition of mold mycelium with that commonly used in mycelium-based materials, three infrared ratios were measured from the spectra: amide-l / polysaccharides, amide-ll / polysaccharides and chitin / polysaccharides.

[0370] Results

[0371] The ATR-FTIR spectra of the molds in the materials are shown in Figure 9.

[0372] Table 7 shows the detailed allocation of peaks according to the references below.

[0373] - M. Haneef et al. Advanced Materials From Fungal Mycelium: Fabrication and Tuning of Physical Properties, Sci. Rep. 7 (2017) 41292.

[0374] - FA Saif et al., Identification and characterization of Aspergillus species of fruit rot fungi using microscopy, FT-IR, Raman and UV-Vis spectroscopy, Spectrochim. Acta A Mol. Biomol. Spectrosc. 246 (2021) 119010. - M. Jones et al., Sustainable mycelium-derived chitinous thin film, TWENTY-SECOND INTERNATIONAL CONFERENCE ON COMPOSITE MATERIALS, nd https: / / www.researchgate.net / publication / 334852017

[0375] - BS Gupta et al., Application of ATR-FTIR Spectroscopy to Compare the Cell Materials of Wood Decay Fungi with Wood Mold Fungi, International Journal of Spectroscopy 2015 (2015). https: / / doi.Org / 10.1 155 / 2015 / 521938.

[0376] Table 7: Assignment of peaks in ATR-FTIR spectra of molds in materials

[0377] The ATR-FTIR spectra of the mold samples from the materials showed a typical fungal absorbance, indicative of lipids (3000-2800 cm⁻¹). -1 ), of protein (1650-1300 cm -1 ), of nucleic acids (1255-1245 cm -1 ) and polysaccharides (1200-900 cm -1 ).

[0378] Analysis of the peak intensities of amide-l at 1640 cm -1 and the amide-ll at 1545 cm -1 ), of chitin (1375 cm -1 ) compared to that of polysaccharides (1040 cm -1) is reported in Figure 10 and Table 8 for molds from materials containing a biopolymer of cactus, grass or tannin.

[0379] Table 8: Ratio of IR intensities of molds from materials with cactus, leaf and tannin biopolymers after wet curing.

[0380] In the protein absorption band, amide I (1645-1635 cm-1) and amide II (1550-1545 cm-1) were clearly observed in the mycelium sample in different proportions.

[0381] Spectral analyses gave consistent results on mycelium samples from the same group of biopolymers, confirming that the biopolymer substrate has a greater impact on the chemical structure of mold mycelium than the soil type (M. Pavlik et al. Curr. Microbiol. 77 (2020) 2374-2384; Z. Tacer-Caba et al., Mater. Des. 192 (2020) 108728).

[0382] The intensity ratios in Table 8 correspond to the intensities of the most significant peaks attributed to proteins (amide-l at 1640 cm -1 and amide-ll at 1545 cm -1 ), to chitin (1375 cm -1 ) and to polysaccharides (1040 cm -1 ) (Fig. 9). The relative ratios observed were as follows: amide-l / polysaccharides ranged from 0.8 to 3.9, amide-ll / polysaccharides ranged from 0.3 to 1.9 and chitin / polysaccharides ranged from 0.2 to 0.9.

[0383] The chitin / polysaccharide ratios are consistent with those found in studies on mycelial materials or studies on molds by E. Elsacker et al (PLoS One 14 (2019) e0213954), M. Haneef et al. (Advanced Materials From Fungal Mycelium: Fabrication and Tuning of Physical Properties, Sci. Rep. 7 (2017) 41292), BS Gupta et al. (International Journal of Spectroscopy 2015 (2015)) and ME Antinori et al. (ACS Appl. Bio Mater. 3 (2020) 1044-1051). However, the amide-l / polysaccharide and amide-ll / polysaccharide ratios for mold samples collected on grass and cactus-containing materials were particularly high, often exceeding 1.These values ​​are higher than those generally reported in previous studies on mycelium materials or molds, indicating that the mold growing on grass or cactus has a high protein content, as evidenced by comparing the amide-1 / polysaccharide and amide-1 / polysaccharide ratios with those found in other articles on mycelium materials. For example, in the article by Haneef et al. (Advanced Materials from Fungal Mycelium: Fabrication and Tuning of Physical Properties, Sci. Rep. 7 (2017) 41292), the amide-1 / polysaccharide ratio is 0.3 and 0.5, whereas the mold analysis of the materials of the present invention shows an amide-1 / polysaccharide ratio between 0.8 and 3.8.

[0384] Example 9: Water resistance - capillary action test

[0385] Water resistance was assessed using capillary action tests.

[0386] The capillary action test, also known as capillary water absorption, is a well-established method for assessing the water absorption resistance of earth materials. Capillary water absorption can lead to the dissociation of earth materials, thereby compromising the integrity of the earth matrix structures.

[0387] Method

[0388] Three test samples per formulation were sawn in half to give half-samples. Capillary absorption was evaluated on three half-test samples following the procedures described in Y. Du et al. (Construction and Building Materials 323 (2022) 126571), in S. Guihéneuf et al. (Mater. Struct. 53 (2020)) and CTS Beckett et al. (Construction and Building Materials 242 (2020) 118098).

[0389] The lateral sides of the samples were sealed with aluminum tape and the lower surface was covered with Whatman filter paper to prevent physical degradation, while the upper surfaces were left open. The samples were placed on a sponge in a container filled with tap water to the top of the sponge, and the mass of the samples was measured at different time intervals over 1 hour (Figure 11a). The capillary absorption of water was calculated by dividing the mass change by the contact area, and the sorpivity of water was calculated using a linear fit of the capillary absorption plot to the square root of time, as performed in previous studies by Y. Du et al.

[0390] Results

[0391] The sorpivity results of materials prepared with soil M, without biopolymer or containing the respective biopolymers leaf, cactus, grass and tannin, with a dry cure or with a wet cure are reported in Figure 12 and Table 9.

[0392] The sorpivity results of materials prepared with soil S, without biopolymer or containing the respective biopolymers leaf, cactus, grass and tannin, with a dry cure or with a wet cure are reported in Figure 12 and Table 10.

[0393] Table 9: Sorptivity of materials prepared with soil M

[0394] Table 10: Sorptivity of materials prepared with soil S

[0395] In this study, sorpivity, measured from the linear fit of water absorption by cumulative capillarity, showed typical values ​​for raw earth materials ranging from 0.066 to 0.177 kg.m 2 .s- 1 / 2 .

[0396] Without biopolymer, both soils showed similar sorpivity, of approximately 0.14 kg nr s -1 / 2 .

[0397] Effect of the biopolymer after a dry treatment:

[0398] Biopolymers had varying effects on sorpivity depending on the soil type. For soil M, leaves and tannin significantly reduced sorpivity by approximately 39% and 51%, respectively, while grass and cactus reduced it by only 0.1% and 8%.

[0399] Conversely, for soil S, leaves increased sorpivity by approximately 20%, while cactus, grass, and tannin slightly reduced it by approximately 16%, 4%, and 26%, respectively. The sorpivity of soil S showed a negative linear correlation with dry density (R 2 = 0.85) and with the compressive strength (R 2 = 0.91).

[0400] Effect of the biopolymer after wet curing compared to dry curing:

[0401] Compared to dry curing, the four materials with biopolymers, after wet curing, significantly reduced sorpivity by approximately 28%. All samples of biostabilized raw earth material exposed to wet curing (except for the soil S sample prepared with the biopolymer sheet) exhibited consistently low sorpivity, below 0.09 kg / m³. 2 .s- 1 / 2. All biostabilized raw earth materials exposed to wet curing, including mycelium, showed a consistently lower sorpivity than the corresponding material that underwent dry curing, i.e. not containing mycelium.

[0402] Example 10: Water resistance - Water spray test

[0403] Water resistance was assessed by the spray test.

[0404] Rain erosion was simulated using a spray test device to determine the impact of rain on soil material formulations.

[0405] This test measured the mass loss after continuous spraying of a sample of the soil material with tap water for 10 minutes at a constant pressure and flow rate. It was carried out following the procedures described in M. Ouedraogo et al. (Journal of Building Engineering 23 (2019) 250-258), and in H. Bamogo et al. (Chemistry Africa (2023)).

[0406] The test consisted of spraying water droplets at a pressure of 2 bar and a constant flow rate of

[0407] 12 L / min for 10 minutes on the material placed on an inclined plane at an angle of 30° to the vertical according to the diagram in Figure 11 b).

[0408] The percentage of mass loss of the material was then evaluated using the following equation:

[0409] M o — M s Mass loss (%) = - x 100

[0410] M o in which

[0411] Mo is the initial mass of the dried sample and

[0412] Ms the mass of the sample after spray testing after complete drying.

[0413] Results

[0414] The mass loss results of materials prepared with soil M, without biopolymer or containing the respective biopolymers leaf, cactus, grass and tannin, with dry curing or with wet curing are reported in Figure 13 (top part) and Table 11.

[0415] The sorpivity results of materials prepared with soil S, without biopolymer or containing the respective biopolymers leaf, cactus, grass and tannin, with a dry cure or with a wet cure are reported in Figure 13 (lower part) and Table 12.

[0416] Table 11: Mass loss of materials prepared with soil M

[0417] Table 12: Mass loss of materials prepared with soil S

[0418] Conclusions

[0419] Significant differences in mass loss were observed between the materials with soils M and S without biopolymers: the material with soil M without biopolymers underwent a substantial mass loss of approximately 35%, while the material with soil S underwent only a mass loss of approximately 5%. This difference was attributed to the higher proportion of iron and aluminum oxides in soil S.

[0420] Effect of the biopolymer after a dry treatment:

[0421] The four biopolymers reduced mass loss by 87% when mixed with soil M. In contrast, for soil S, leaves and tannin reduced mass loss by 17%, while cactus and grass increased it. This result is unexpected, as grass—a lignocellulosic biopolymer—and cactus—a mucilage-rich extract—have been described for their stabilizing effect against rain erosion.

[0422] Effect of the biopolymer after wet curing compared to dry curing:

[0423] Compared to a dry cure, the four biopolymers after the wet cure significantly reduced mass loss by approximately 64%.

[0424] With the exception of the material from soil S prepared with the biopolymer sheet, which exhibited a mass loss of less than 2%, all biostabilized raw earth materials containing a biopolymer, subjected to wet curing, showed a very low mass loss of less than 0.5%. All biostabilized raw earth materials, subjected to wet curing and containing mycelium, showed a consistently low mass loss (less than 2%), less than or equal to that of the corresponding material that underwent dry curing, i.e., did not contain mycelium.

[0425] These results were unexpected and interesting for biostabilized raw earth materials, which generally exhibit much lower water resistance. Even more surprising is that the biopolymers that reduced water resistance after dry curing significantly improved it after wet curing.

[0426] For example, cactus increased mass loss from 5% to 18% after dry curing, but provided almost no mass loss for materials exposed to wet curing. This significant improvement in water resistance after wet curing was attributed to the presence of mold mycelium in the soiled materials.

[0427] Example 11: Immersion Test

[0428] The immersion test assessed the integrity of the soil material when fully submerged in water to characterize its behavior under flood conditions. This simple test is commonly used to characterize stabilized soil materials.

[0429] The immersion test was carried out on three half-samples following the procedure described in CTS Beckett et al. (Construction and Building Materials 242 (2020) 118098), in Y. Kulshreshtha et al. (Construction Technologies and Architecture, Trans Tech Publications Ltd, Switzerland, 2022) and in RN Pachamama et al. (Materials 17 (2024)).

[0430] Each sample was fully immersed for 24 hours in a plastic tray filled with 450 ml of tap water at a room temperature of 25 °C (Figure 11b). Images were captured using a 12-megapixel camera at various time intervals to monitor sample disintegration. An analysis was performed on the visual effects observed in the images.

[0431] In this study, samples of soil material were photographed after 5 minutes, 2 hours and 24 hours of immersion and classified as "intact" or "destroyed" according to the presence of cracks or disintegration as shown in Figure 14 (lower part).

[0432] Result

[0433] The results of visual analysis of the integrity of materials prepared with soil M, without biopolymer or containing the respective biopolymers leaf, cactus, grass and tannin, with a dry cure or with a wet cure are reported in Figure 14 (left part) and Table 13.

[0434] The results of visual analysis of the integrity of materials prepared with soil M, without biopolymer or containing the respective biopolymers leaf, cactus, grass and tannin, with a dry cure or with a wet cure are reported in Figure 14 (right part) and Table 14.

[0435] Table 13: Immersion time before destruction of materials prepared with soil M

[0436] Table 14: Immersion time before destruction of materials prepared with soil S

[0437] Conclusion

[0438] Without biopolymers, both soil materials used as controls were completely destroyed after only 5 minutes of immersion.

[0439] Effect of the biopolymer after wet curing compared to dry curing: The four materials containing biopolymer, after wet curing, showed a longer immersion time before destruction compared to the corresponding material that underwent dry curing. All biostabilized materials containing biopolymer, exposed to wet curing, resisted disintegration for at least 24 hours after immersion. Example 12 - Physical Properties

[0440] The physical properties were characterized by volumetric shrinkage, dry mass and dry density.

[0441] Method

[0442] The materials were characterized after five days of storage under ambient conditions (25°C, 50% RH). The volume and dry mass of nine samples per formulation were measured using calipers (± 0.05 mm) and a balance (± 0.05 g), respectively. Volumetric shrinkage was expressed as the average percentage change in volume between the fresh (after shaping with fresh mortar) and hardened states of 4x4x16 cm³ samples. The dry density was then calculated by dividing the dry mass by the volume.

[0443] Results

[0444] The values ​​of the physical properties obtained from the materials prepared with soil M (left part) or with soil S (right part), without biopolymer or containing the respective biopolymers leaf, cactus, grass and tannin, with a dry cure or with a wet cure are presented in Figure 15 for volumetric shrinkage (top part), for dry mass (middle part) and for dry density (bottom part).

[0445] Tables 15 and 16 respectively report the mass in grams of the material samples taken from soils M and S.

[0446] Tables 17 and 18 respectively report the density (Kg / m³) 3 ) samples of materials taken respectively from soils M and S.

[0447] Tables 19 and 20 respectively report the volumetric shrinkage as a percentage of material samples from soils M and S.

[0448] Table 15: Mass of soil material samples M

[0449] Table 16: Mass of soil material samples S

[0450] Table 17: Density of soil material samples M

[0451] Table 18: Density of soil material samples S

[0452] Table 19: Removal of material samples from soil M

[0453] Figure 16 represents, as a function of the water content of the mortar used to prepare the materials, the volumetric shrinkage (upper part), the dry mass (middle part) and the dry density (lower part) for materials prepared with soil M or with soil S, without biopolymer or containing the respective biopolymers leaf, cactus, grass and tannin, with a dry cure or with a wet cure.

[0454] Conclusion

[0455] Volumetric shrinkage varies from 8% to 14%, dry mass from 360 to 430 g, and dry density from 1621 to 1885 kg / m³. 3 for all formulations with and without biopolymer, with and without the presence of mold mycelium.

[0456] These results are consistent with properties commonly measured in soil materials indicating that the density of the composite material with mycelium is governed by that of its inorganic matrix.

[0457] Effect of the biopolymer after dry-to-dry curing:

[0458] For a given soil, shrinkage showed a positive linear correlation with the initial water content of the mortar (Fig. 16 – upper part). In contrast, both dry mass and dry density showed negative linear correlations with the initial water content (Fig. 16 – middle and lower parts). These results are consistent with classical findings, indicating that a higher initial water content leads to a lower fresh density, thus reducing both dry mass and dry density. Furthermore, the higher initial water content induces increased evaporation of the finished materials, resulting in greater shrinkage. The biopolymer-containing sheet materials from both soils M and S were prepared with a mortar having the highest initial water content of approximately 33%, which resulted in the highest shrinkage of approximately 13% of the finished materials.Conversely, the mortar formulations with tannin, prepared from the two soils M and S, exhibited the lowest initial water content of approximately 23%, resulting in the lowest shrinkage of approximately 10% of the finished materials.

[0459] The effect of biopolymers on the physical properties of volumetric shrinkage, dry mass and dry density appears to result mainly from their effect of increasing or reducing the initial water content.

[0460] Effect of the biopolymer after wet curing compared to dry curing:

[0461] For both soils, wet curing resulted in: a slight decrease in shrinkage of approximately 6% and a slight decrease in dry density of approximately 1%, compared to dry curing. However, no significant difference was observed in dry mass based on the curing process. As previously observed, wet curing consistently promoted mold growth.

[0462] The reduced shrinkage indicates that the mold mycelium, present in the soil pores, physically prevented the soil material from contracting during evaporation. Since the dry mass remained unchanged during the curing process, this suggests that the mass of biopolymer consumed by the mold mycelium closely matches the fungal biomass produced. Therefore, the minor changes in dry density were attributed to the reduced shrinkage following wet curing. Less shrinkage resulted in a higher volume for the same mass, leading to a decrease in dry density. Overall, wet curing and mold growth had a minimal effect on the physical density properties of the soil materials while maintaining and improving their water resistance.

[0463] Example 13 - Characterization of mechanical properties

[0464] Method

[0465] The mechanical properties were evaluated using three separate experiments: dynamic Young's modulus, flexural strength, and compressive strength.

[0466] The dynamic Young's modulus was tested on nine prismatic samples using the pulse excitation technique (ASTM E1876-2). A multimedia microphone (HSM6, Velleman) was connected to an oscilloscope (DSOX1204A 100 MHz) with an integrated Fast Fourier Transform (FFT) to determine the resonant frequency of the earth materials. The dynamic Young's modulus was then calculated using the equation.

[0467] Dynamic Young's modulus (P a) = 0.9465 where: m is the mass of the sample (g), b is the width of the sample (mm),

[0468] L is the length of the sample (mm), t is the thickness of the sample (mm), ft is the fundamental resonance frequency of the bar in bending (Hz) and

[0469] T1 is a correction factor for the finite thickness of the sample (L / t>20).

[0470] Flexural strength tests were performed on three samples using a 10 kN sensor at a constant speed of 10 N / s. Compressive strength tests were performed on six semi-prismatic samples, each tested at a constant speed of 200 N / s using a 10 kN sensor.

[0471] Results

[0472] The values ​​of the mechanical properties obtained from the materials prepared with soil M (left part) or with soil S (right part), without biopolymer or containing the respective biopolymers leaf, cactus, grass and tannin, with a dry cure or with a wet cure are presented in Figure 17 for the dynamic Young's modulus (top part), for the flexural strength (center part) and the compressive strength (bottom part).

[0473] Tables 21, 22 and 23 respectively report the dynamic Young's modulus, flexural strength and compressive strength of the material samples from soil M.

[0474] Tables 24, 25 and 26 respectively report the dynamic Young's modulus, flexural strength and compressive strength of the material samples from soil S.

[0475] Table 21: Dynamic Young's modulus (MPa) of soil material samples M

[0476] Table 22: Flexural strength (MPa) of soil material samples M

[0477] Table 23: Compressive strength (MPa) of soil material samples M

[0478] Table 24: Dynamic Young's modulus (MPa) of soil material samples S

[0479] Table 25: Flexural strength (MPa) of soil material samples S

[0480] Table 26: Compressive strength (MPa) of material samples from soil S

[0481] For all formulations, the dynamic Young's modulus varies from 852 to 6089 MPa, the flexural strength varies from < 0.3 to 1.9 MPa and the compressive strength varies from 0.73 to 4.25 MPa.

[0482] These values ​​are consistent with those reported for raw earth materials containing biopolymers.

[0483] The dynamic Young's modulus showed a positive linear correlation with compressive strength (R 2 = 0.91) and the flexural strength (R 2 = 0.74).

[0484] Soil S consistently shows higher resistance than soil M. On average, soil M has a dynamic modulus of 2100 MPa, a flexural strength of 0.8 MPa and a compressive strength of 1.6 MPa, while soil S has on average a dynamic modulus of 4000 MPa, a flexural strength of 1.5 MPa and a compressive strength of 3.2 MPa.

[0485] Effect of the biopolymer after curing:

[0486] The effect of the biopolymer on mechanical strength varies depending on the soil type. For soil M, all four biopolymers significantly increased strength, while for soil S, only cactus and tannin showed such an effect. More specifically, tannin led to the greatest improvement in compressive strength for soil M, reaching approximately 2.75 MPa, while for soil S, cactus achieved a compressive strength of approximately 4.2 MPa.

[0487] Effect of the biopolymer after wet curing compared to dry curing:

[0488] For mold-containing materials from two soil types, M and S, and from all biopolymer formulations, wet curing resulted, compared to dry-cured materials: a slight decrease in Young's dynamic modulus of approximately 10%, a slight decrease in flexural strength of approximately 5% (measured only for soil S), and a slight decrease in compressive strength of approximately 6%. Overall, wet curing with accompanying mold growth had a minimal effect on the mechanical properties of the soil-containing biopolymer materials, while maintaining and improving the materials' water resistance. Example 14 - Conclusions

[0489] The mold that develops during a wet curing process (35°C, 98% RH, 21 days) in the pores of an inorganic matrix made up of mineral grains and clay ensuring structural cohesion, such as raw earth materials, improves the water resistance of these biostabilized earth materials:

[0490] - in terms of sorpativity, with a reduction in the material's water absorption,

[0491] - in terms of mass loss under water spray stress and

[0492] - in terms of durability under immersion in water of the material, being able to maintain its integrity for at least 24 hours.

[0493] This is achieved while preserving the structure and physical characteristics of the material which are governed by the inorganic matrix, resulting in minimal reductions in shrinkage, density, and having a minimal effect on mechanical properties.

[0494] Indeed, as demonstrated in the examples, compared to mold-free biopolymer-containing materials obtained during dry curing, the four biopolymer-containing materials after wet curing induced mold growth in the pores of the material by using the biopolymer as a substrate, which plays a role in the mycelium population derived from the fungi.

[0495] These materials containing ubiquitous fungal mycelium significantly reduced sorpivity by approximately 28% and mass loss by approximately 64%, while also extending the immersion time before destruction. All biostabilized soil materials exposed to wet curing (with the exception of the material from soil S with the leaf biopolymer) exhibited consistently low sorpivity, less than 0.09 kg / m³. 2 .s- 1 / 2, a very low mass loss, less than 0.5%, and resisted disintegration for at least 24 hours after immersion.

[0496] These above properties, conferred on the materials, are obtained through mycelium and biopolymers while resulting in minimal reductions in shrinkage (approximately 6%), density (approximately 1%), and having a minimal effect on mechanical properties with a decrease in Young's dynamic modulus of approximately 10%, flexural strength of approximately 5%, and compressive strength of approximately 6%, however with values ​​within the desired ranges of raw earth materials.

[0497] Overall, wet curing accompanied by mold growth had a minimal effect on the mechanical properties of the earth-based materials containing biopolymer, while ensuring and improving the water resistance of the materials.

[0498] These results demonstrate the significant potential of using mold mycelium to improve the water resistance of biostabilized earth mortar. In particular, mold growth consistently improved water resistance, even when the biopolymer itself had detrimental effects.

[0499] This demonstrates that incorporating various organic elements, such as plant compost, grass clippings, or agricultural waste, into earth mortar to promote mold growth from ubiquitous fungi that do not need to be inoculated, followed by heat treatment to biostabilize the material, can be a simple and cost-effective method for producing highly water-resistant earth materials.

Claims

DEMANDS 1. Use for the preparation of a water-resistant building material, of a mold comprising mycelium formed by hyphae from the growth of at least one fungus, said mold colonizing pores of a solid, pre-formed inorganic matrix consisting of a set of mineral grains bound by clay ensuring the structural cohesion of said material, each of said pores being formed by the space between adjacent mineral grains of said set bound by clay and / or by the interstice between clay particles, said matrix comprising a biopolymer as a growth substrate for said mold.

2. Use according to claim 1 for the preparation of a water-resistant building material, of a mold resulting from the growth of uninoculated ubiquitous fungi, said mold comprising mycelium formed by the hyphae of said fungi, said mold colonizing pores of a solid, pre-formed inorganic matrix consisting of a set of mineral grains bound by clay ensuring the structural cohesion of said material, each of said pores being formed by the space between adjacent mineral grains of said set bound by clay and / or by the interstice between the clay particles, said matrix comprising a biopolymer as a growth substrate for said mold.

3. Use according to any one of claims 1 or 2, wherein said inorganic matrix is ​​prepared from raw earth from a natural soil, as the source of mineral and clay grains, and in particular wherein said inorganic matrix is ​​put into the form of a solid brick, said matrix representing from 65 to 85%, preferably more than 75%, by volume of said solid brick.

4. Use according to any one of claims 1 to 3, wherein the biopolymer represents from 0.1 to 5.0% by total mass of the inorganic matrix, preferably 2.0%.

5. Use according to claim 1, wherein the building material is biostabilized and comprises inactivated mycelium formed of biologically inert hyphae, and in particular wherein the material is biostabilized, after growth of the mold in the pores of the matrix, by inactivation of the mycelium of said mold, and in particular wherein said mold is biostabilized by heat treatment at a temperature of 65 to 120 °C, preferably 80 °C, for more than 12 hours, in particular for 48 hours.

6. Composite material for construction, comprising or consisting of: an inorganic earth matrix derived from natural soil, solid and previously shaped, consisting of a set of mineral grains bound together by clay ensuring the structural cohesion of the material, a biopolymer present in said matrix, mycelium present in pores of said matrix, each pore being formed by the space between the adjacent mineral grains of said set, bound together by clay and / or by the interstice between the clay particles, said mycelium being derived from mold generated by the growth of hyphae of at least one fungus having as a growth substrate said biopolymer present in the matrix, and said material being biostabilized and comprising inactivated mycelium in which the hyphae are biologically inert.

7. Material according to claim 6, comprising or consisting of: an inorganic matrix of earth from a natural soil, solid and previously shaped, made up of a set of mineral grains bound by clay ensuring the structural cohesion of the material, of a biopolymer present in said matrix, of mycelium present in pores of said matrix, each pore being formed by the space between adjacent mineral grains of said assembly, bound together by clay and / or by the interstice between clay particles, said mycelium being derived from mold generated by the growth of hyphae of ubiquitous uninoculated fungi having said biopolymer as a growth substrate, and said material being biostabilized and comprising inactivated mycelium in which the hyphae are biologically inert.

8. A material according to claim 6 or 7, wherein the inorganic matrix is ​​constituted from raw earth obtained from natural soil, as the source of the mineral and clay grains of said matrix, and / or wherein said natural soil comprises more than 95% by mass of sand, clay, and silt, and / or wherein the inorganic matrix represents 65 to 85%, preferably 75% by volume, of the material, and / or wherein the material has a density of 1400 to 2200 kg / m³ 3 .

9. Material according to any one of claims 6 to 8, wherein the biopolymer represents from 0.1 to 5.0% by total mass of the inorganic matrix, in particular 2.0%, and in particular wherein the biopolymer is a biopolymer of plant origin, and in particular, wherein the plant biopolymer comprises at least one compound selected from cellulose, hemicellulose, lignin and polyphenols, and in particular, wherein the biopolymer is in the form of particles of average size from 50 pm to 1 mm, in particular 250 pm.

10. Construction brick comprising or made of a construction material according to any one of claims 6 to 9.

11. A method for preparing a building material according to any one of claims 6 to 9, comprising the following steps: shaping an inorganic earth matrix from a soil using a mortar comprising a mixture of mineral grains, clay, water and a biopolymer; inducing the proliferation of mold from at least one fungus under humid atmospheric conditions enabling the formation of mycelium in pores of said shaped inorganic matrix, to obtain an intermediate material consisting of the inorganic matrix containing mold mycelium in pores; biostabilizing said intermediate material by stopping the proliferation of the mold in order to obtain inactivated mycelium formed of biologically inert hyphae, in particular by heat treatment, to obtain said building material.

12. A process according to claim 11, comprising the following steps: shaping an inorganic earth matrix from a soil from a mortar comprising a mixture of mineral grains, clay, water and a biopolymer, inducing the proliferation of mold from ubiquitous fungi under humid atmospheric conditions enabling the formation of mycelium in the pores of said shaped inorganic matrix, to obtain an intermediate material consisting of the inorganic matrix containing mold mycelium in pores, biostabilizing said intermediate material by stopping the proliferation of the mold in order to obtain inactivated mycelium formed of biologically inert hyphae, in particular by a heat treatment, to obtain said construction material.

13. A method according to any one of claims 11 to 12, wherein the inorganic matrix is ​​shaped into a building brick, and in particular wherein said building brick is solid, said matrix representing from 65 to 85%, preferably more than 75% by volume of said solid brick.

14. A process according to any one of claims 11 to 13, wherein the mortar is prepared from raw earth taken from natural soil, as the source of mineral and clay grains, and in particular wherein the mortar comprises from 15 to 40% by mass of water.

15. A process according to any one of claims 11 to 14, wherein the biopolymer in the mortar represents from 0.1 to 5.0% by total mass of the inorganic matrix, and in particular wherein the biopolymer comprises at least one polymer selected from cellulose, hemicellulose, lignin and polyphenols, and in particular wherein the biopolymer is selected from leaves, cactus, herbs or tannin, and in particular wherein the biopolymer mixed in the mortar is in the form of particles of average size from 50 pm to 1 mm, in particular 250 pm.

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