Continuous manufacturing process for a low-density mineral foam

Abstract

Continuous production process of a mineral foam whose volumetric mass in dry state (d) is between 40 and 600 kg / m3, comprising the following steps: (i) mix ¤ cement; ¤ a water-reducing agent; ¤ between 0.5 and 10%, in % by mass with respect to the total mass of cement, of ultrafine particles having a liquid-solid contact angle between 30° and 140°, measured according to the procedure described in the description, and whose D50 is between 10 and 600 nm; ¤ water, with a water / cement mass ratio between 0.3 and 2.5; (ii) add to the mixture between 0.5 and 10% of a porogenic agent, in % by mass with respect to the mass of cement; (iii) place the mixture obtained in step (ii) on a support; (iv) allow the mixture to spread over the support.

Description

Continuous manufacturing process for a low-density mineral foam The present invention relates to a continuous manufacturing process for a low-density mineral foam based on cements, as well as to the use of this foam as an insulating material. Mineral foam is generally very advantageous for numerous applications due to its thermal insulation properties. Mineral foam refers to a foam-like material. This material is lighter than traditional concrete because of the pores or empty spaces it contains; it is also called cement foam. These pores or empty spaces are due to the presence of a gas in the mineral foam and can appear as bubbles. In fact, with 1 m³ of raw material, it is possible to manufacture approximately 5 m³ of finished product, that is, a material composed of 20% material and 80% gas (valid for an element with a volumetric mass of 400 kg / m³). Thus, mineral foam comprises a network of bubbles more or less separated from each other, that is, pockets of gas contained within a solid shell of mineral binder. The manufacture of mineral foams is a delicate process, as it involves the solidification of a liquid foam into a solid foam. This solid foam is initially a liquid foam—a network of air or gas bubbles surrounded by a hydraulic binder—which evolves over time into a solid mineral foam. Therefore, the manufacture of mineral foams requires a stage in the production of a stable liquid foam. The stability of the liquid foam is thus crucial, and it is advisable that the manufacturing process can control foam destabilization phenomena during setting, such as coalescence, Ostwald ripening, or drainage. These challenges are exacerbated when the manufacturing process is continuous, meaning the finished product is produced without interruption.Continuous manufacturing processes are well suited to an industrial environment and are recommended for factory or construction sites. Document FR 2986790 A1 discloses a continuous production process for a lightweight mortar for facades and floors. The material expands in situ during application. The challenge in producing continuous mineral foams in an industrial setting is therefore to manufacture a stable foam that mitigates these destabilization phenomena. However, known foam manufacturing processes do not allow for obtaining sufficiently stable foams. Furthermore, when this mineral foam is used as insulation material, it is advantageous that it can be sprayed onto a substrate, which can be horizontal, inclined, or vertical. It is therefore beneficial that the foam adheres to this substrate and remains attached until it solidifies. Indeed, when the foam is in a liquid state, it can flow under the effect of gravity, and it is important that once on its substrate, the foam does not flow or sag due to gravity. In order to meet user demands, it has become necessary to find a procedure for making a continuous mineral foam in an industrial or construction context, with easy placement of this foam. Therefore, the problem that the invention proposes to solve is to find a continuous production method for a mineral foam, which can remain in place when applied to a support regardless of the shape and inclination of the support. The invention also relates to a mineral foam that can be obtained according to the procedure of the invention. According to another object of the invention, the mineral foam according to the invention can be used as a construction material. For example, the mineral foam can be used as sprayed or non-sprayed insulation, or as a filling element in structures. The present invention seeks to provide new mineral foams that have one or more of the following characteristics: - The mineral foam according to the invention has excellent stability properties. In particular, it is possible to obtain a foam that can be sprayed and adhere to a substrate, regardless of the substrate's position and independent of gravitational forces; The mineral foam according to the invention has excellent thermal properties, and in particular very low thermal conductivity. Reducing the thermal conductivity of building materials is highly desirable as it allows for energy savings in heating for residential and commercial buildings. Furthermore, this reduction helps to minimize thermal bridges, particularly in multi-story buildings with internal thermal insulation, especially thermal bridges in intermediate floors. The present invention relates to a continuous process for producing a mineral foam whose dry density (d) is between 40 and 600 kg / m3, comprising the following steps: (i) mix to cement; to a water-reducing agent; between 0.5 and 10%, in % by mass with respect to the total mass of cement, of ultrafine particles having a liquid-solid contact angle between 30° and 140°, and whose D50 is between 10 and 600 nm; to water, with a water / cement mass ratio between 0.3 and 2.5; (ii) add to the mixture between 0.5 and 10% of a porogenic agent, in % by mass with respect to the mass of cement; (iii) place the mixture obtained in step (ii) on a support; (iv) allow the mixture to spread over the support. The cement suitable for making the mineral foam according to the process of the invention is preferably the cement described in accordance with European Standard NF EN 197-1 of April 2012 or mixtures thereof. The preferred cement suitable according to the invention is Portland cement CEM I, alone or in mixture with other cements such as those described in accordance with European Standard NF EN 197-1 of April 2012. Preferably, the mixture of step (i) of the process according to the invention comprises between 60 and 95% cement, preferably between 65 and 90%, by mass percentage with respect to the total mass of the mixture of step (i) without water. A calcium aluminate cement could also be suitable for producing the mineral foam according to the invention. This cement could comprise a mineralogical phase of C4A3, CA, C12A7, C3A, or CnAyCaF2, or mixtures thereof, such as, for example, Ciments Fondu®, sulfoaluminous cements, calcium aluminate cements according to European Standard NF EN 14647 of December 2006, the cement obtained from the clinker described in patent application WO 2006 / 018569, or mixtures thereof. The calcium aluminate cement suitable for producing the mineral foam according to the invention could be in either crystalline or amorphous form. The preferred calcium aluminate cement according to the invention is Ciment Fondu®. Preferably, the cement in the mixture of step (i) of the process according to the invention has a Blaine specific surface area greater than or equal to 5000 cm² / g, more preferably greater than or equal to 6500 cm² / g. Preferably, the cement in the mixture of step (i) of the process according to the invention is a cement whose Blaine specific surface area is between 5000 and 9000 cm² / g. It is possible to use several cements with different Blaine specific surface values ​​in the mixture of step (i) of the process according to the invention. For example, a cement with a Blaine specific surface value greater than or equal to 5000 cm² / g can be mixed with a cement with a Blaine specific surface value less than or equal to 5000 cm² / g, for example, a Portland cement. The cement that can be used according to the present invention can be crushed and / or separated (by means of a dynamic separator) to obtain cement having a Blaine specific surface area greater than or equal to 5000 cm² / g. This cement can be classified as ultrafine. For example, the cement can be crushed according to two procedures. According to a first procedure, the cement or clinker can be crushed to a Blaine specific surface area of ​​between 5000 and 9000 cm² / g. In this first stage, a high-efficiency, second-generation, or third-generation separator, or a very high-efficiency separator, can be used to separate the cement with the desired fineness from the cement that does not have the desired fineness. This cement is then sent to the mill.According to a second process, cement can be passed through a very high efficiency separator, called a THF (very high fineness) separator, to separate cement particles with a Blaine specific surface area greater than or equal to the target fineness (the target fineness being greater than 5000 cm² / g) from cement particles with a Blaine specific surface area less than the target fineness. Cement particles with a Blaine specific surface area greater than or equal to the target fineness can be used as is. Cement particles with a Blaine specific surface area less than the target fineness can be separated or ground separately to obtain the desired Blaine specific surface area. Mills that can be used in both processes include, for example, a ball mill, a vertical mill, a roller mill, a horizontal mill (e.g., a Horomill© type), or a vertical stirred mill (e.g., a Tower Mill type). The mixture in step (i) of the procedure according to the invention could also contain calcium sulfate, which may be gypsum, anhydrous calcium sulfate, or calcium sulfate hemihydrate. The mixture in step (i) of the process according to the invention comprises a water-reducing agent, a plasticizer, or a superplasticizer. A water-reducing agent allows the amount of mixing water to be reduced by approximately 10 to 15% by mass for a given workability time. Examples of water-reducing agents include lignosulfonates, hydroxycarboxylic acids, carbohydrates, and other specific organic compounds, such as glycerol, polyvinyl alcohol, sodium aluminomethyl siliconate, sulfanilic acid, and casein (see Concrete Admixtures Handbook, Properties Science and Technology, VS Ramachandran, Noyés Publications, 1984). Superplasticizers belong to the new generation of water-reducing agents and allow for an approximate 30% reduction in the amount of mixing water by mass for a given workability time. As an example of a superplasticizer, PCP-type superplasticizers without an antifoaming agent can be cited. The term "PCP" or "polycarboxylate polyoxide" according to the present invention refers, among other things, to a copolymer of acrylic acids or methacrylic acids and their poly(ethylene oxide) (POE) esters. Preferably, the mixture of step (i) of the process according to the invention comprises between 0.01 and 1%, more preferably between 0.05 and 0.5% of a water-reducing agent, a plasticizer or a superplasticizer, the percentage being expressed by mass with respect to the mass of the mixture of step (i). When the water-reducing agent, plasticizer, or superplasticizer is used in solution, the amount is expressed as active material in the solution. According to one variant of the invention, the mixture in step (i) or step (ii) of the process according to the invention does not comprise any antifoaming agent, or any agent having the property of destabilizing an air-in-liquid emulsion. Some commercial superplasticizers may contain antifoaming agents and, consequently, these superplasticizers might not be suitable according to the invention. The mixture in step (i) or step (ii) of the process according to the invention may include a retarding agent. The retarding agent corresponds to the definition of a setting retarder mentioned in European Standard NF EN 934-2 of September 2002. According to a variant of the invention, the mixture of step (i) or step (ii) of the process according to the invention does not comprise any foaming agent. Preferably, the mixture in step (i) or step (ii) of the process according to the invention further comprises a transition metal salt, for example, a manganese salt or an iron salt. The transition metal salt can be considered a catalyst precursor that facilitates the decomposition of the porogenic agent into oxygen. Examples of catalyst precursors include manganese salts and oxides, such as permanganates and manganates, iron salts and oxides, cobalt salts and oxides, copper salts and oxides, molybdenum salts and oxides, tungsten salts and oxides, chromium salts and oxides, silver salts and oxides, and enzymes, preferably catalases. In some cases, the transition metal salt can be provided by the cement itself, particularly when dealing with cement containing a high iron content, whether in oxide form or not. The catalyst precursor can be selected in particular from among water-soluble manganese(II) salts, such as manganese(II) acetate, manganese(II) sulfate, manganese(II) chloride, and manganese(II) nitride. These salts can be decomposed, in a basic medium, into insoluble compounds comprising manganese in the +4 oxidation state, such as MnO2, which is a known catalyst for the decomposition of peroxides. The mixture of step (i) of the procedure according to the invention comprises between 0.5 and 10%, in % by mass with respect to the total mass of cement, of ultrafine particles having a liquid-solid contact angle between 30° and 140°, and whose d 50 is between 10 and 600 nm. Preferably, the mixture of step (i) of the procedure according to the invention comprises between 1 and 9%, in % by mass with respect to the total mass of cement, of ultrafine particles having a liquid-solid contact angle between 30° and 140°, and whose D50 is between 10 and 600 nm. Preferably, the mixture of step (i) of the procedure according to the invention comprises between 2 and 8%, by mass % with respect to the total mass of cement, of ultrafine particles having a liquid-solid contact angle between 30° and 140°, and whose D50 is between 10 and 600 nm. Preferably, the ultrafine particles of the mixture in step (i) of the process according to the invention are partially hydrophobic, for example by stearic acid. Functionalization is also possible. The ultrafine particles of the mixture in step (i) of the process according to the invention have a liquid-solid contact angle between 30° and 140°, preferably between 40° and 130°, even more preferably between 70° and 130°. This contact angle is also called the wetting angle. The term "contact angle" or "wetting angle" refers to the angle formed between a liquid / vapor interface and a solid surface. It is the angle formed between the interface of a liquid and the solid surface on which the liquid is deposited. A wall is generally considered hydrophilic when the static contact angle of a water droplet on the wall is less than approximately 30 degrees, and hydrophobic to varying degrees when the static contact angle of a distilled water droplet on the wall is greater than approximately 30 degrees and less than approximately 140 degrees. A wall is said to be superhydrophobic when the static contact angle of a distilled water droplet on the wall is greater than approximately 140 degrees.To produce a foam using the procedure according to the invention, it would be desirable that the ultrafine particles of the mixture in step (i) are not superhydrophobic, i.e., that they do not have a contact angle strictly greater than 140°. Preferably, the ultrafine particles of the mixture in step (i) of the process according to the invention are not hydrophilic. The ultrafine particles suitable according to the process of the invention have a D50 between 10 and 600 nm, preferably between 20 and 500 nm, and more preferably between 30 and 200 nm. The D50, also denoted Dv50, corresponds to the 50th percentile of the volume distribution of particle size, meaning that 50% of the volume consists of particles smaller than D50 and 50% of particles larger than D50. It should be noted that ultrafine particles generally comprise elementary particles with a diameter between 10 and 50 nm. These elementary particles can agglomerate to form agglomerated particles with a diameter between 40 nm and 150 nm. These agglomerated particles can then agglomerate to form aggregates with a diameter between 100 nm and 600 nm. The convenient ultrafine particles according to the procedure of the invention can be derived from one or more materials selected from among calcareous powders, precipitated calcium carbonates, natural and artificial pozzolans, pumice stones, crushed fly ash, hydrated silica, in particular the products described in document FR 2708592, and mixtures thereof. According to one variant, the mixture of step (i) of the process according to the invention further comprises a mineral addition such as a pozzolan, slag, calcium carbonate, fly ash, sand or mixtures thereof, and whose particles have a D50 between 0, 1 and 4 mm. Preferably, the mixture of step (i) of the process according to the invention may comprise between 15 and 50% mineral addition, preferably between 15 and 40%, even more between 20 and 35%, the percentages being expressed by mass with respect to the mass of the mixture of step (i). Preferably, the D50 of the mineral addition particles suitable for mixing in step (i) of the process according to the invention is between 0.2 and 500 pm, for example between 0.25 and 250 pm. The D50 of the mineral particles is preferably between 0.1 and 150 pm, more preferably between 0.1 and 100 pm. The mineral additions suitable for mixing in step (i) of the process according to the invention are selected from calcium carbonate, silica, crushed glass, solid or hollow glass balls, glass granules, expanded glass powders, silica aerogels, silica fumes, slags, crushed sedimentary silica sands, fly ash or pozzolanic materials or mixtures thereof. Suitable mineral additions for mixing in step (i) of the process according to the invention may be pozzolanic materials (for example, such as those defined in European Standard NF EN 197-1 of February 2001, paragraph 5.2.3), silica fumes (for example, such as those defined in European Standard NF EN 197-1 of February 2001, paragraph 5.2.7), slags (for example, such as those defined in European Standard NF EN 197-1 of February 2001, paragraph 5.2.2), materials containing calcium carbonate, for example, limestone (for example, such as that defined in European Standard NF EN 197-1, paragraph 5.2.6), siliceous additions (for example, such as those defined in the "Béton" standard NF P 18-509), fly ash (for example, such as those defined in European Standard NF EN 197-1 of February 2001), or other materials containing calcium carbonate, such as limestone (for example, such as that defined in European Standard NF EN 197-1, paragraph 5.2.6), or siliceous additions (for example, such as those defined in the "Béton" standard NF P 18-509). described in European standard NF EN 197-1 of February 2001 paragraph 5.2.4) or their mixtures. Fly ash is generally a powdery particle contained in the flue gases of coal-fired power plants. It is usually recovered by electrostatic or mechanical precipitation. The chemical composition of fly ash depends primarily on the chemical composition of the coal burned and the process used in the power plant from which it originates. The same applies to its mineralogical composition. The fly ash used according to the invention can be siliceous or calcic in nature. Slag is generally obtained by rapidly cooling the molten slag resulting from the smelting of iron ore in a blast furnace. Suitable slag for mixing in step (i) of the process according to the invention can be selected from granulated blast furnace slag according to European standard NF EN 197-1 of February 2001, paragraph 5.2.2. The silica fumes suitable for mixing in step (i) of the process according to the invention can be a material obtained by reducing high-purity quartz with carbon in electric arc furnaces used for the production of silicon and ferrosilicon alloys. The silica fumes are generally composed of spherical particles comprising at least 85% by mass of amorylic silica. Preferably, the silica fumes suitable for mixing in step (i) of the process according to the invention can be selected from the silica fumes according to European standard NF EN 197-1 of February 2001 paragraph 5.2.7. The pozzolanic materials suitable for mixing in step (i) of the process according to the invention may be natural siliceous or silicoaluminous substances, or a combination thereof. Among the pozzolanic materials, we can mention natural pozzolans, which are generally materials of volcanic origin or sedimentary rocks, and calcined natural pozzolans, which are thermally activated materials of volcanic origin, clays, schists, or sedimentary rocks. Preferably, the pozzolanic materials suitable for mixing in step (i) of the process according to the invention can be selected from the pozzolanic materials according to European standard NF EN 197-1 of February 2001 paragraph 5.2.3. Preferably, the suitable mineral additions for mixing in step (i) of the process according to the invention may be limestone powders and / or slags and / or fly ash and / or silica fumes. Preferably, the suitable mineral additions for mixing in step (i) of the process according to the invention are limestone powders and / or slags. Other suitable mineral additions for mixing in step (i) of the process according to the invention are calcareous, siliceous or silico-calcareous powders, or mixtures thereof. The mineral additions suitable for mixing in step (i) of the procedure according to the invention may come partly or entirely from the cement when it is a composite cement. The mixture in step (i) of the process according to the invention comprises water. The water-to-cement mass ratio is between 0.45 and 1.3, preferably between 0.5 and 1.2, and more preferably between 0.6 and 0.8. This overall water-to-cement ratio may vary, for example, due to the water demand of the ultrafine particles or mineral additions when used. This overall water-to-cement ratio is defined as the mass ratio between the quantity of water (E) and the mass of all cements (C). According to one variant, the mixture of step (i) of the procedure according to the invention may comprise hydraulic lime. Preferably, the mixture of step (i) of the procedure according to the invention does not comprise light granules as described in accordance with European standard NF EN 206-1 of April 2004, for example perlite. According to another variant of the invention, the mixture in step (i) of the process according to the invention does not comprise lightweight fillers, for example polystyrene balls. Step (ii) of the procedure according to the invention comprises adding to the mixture of step (i) between 0.5 and 10% of a porogenic agent, in % by mass with respect to the mass of cement. Preferably, step (ii) of the procedure according to the invention comprises the addition of between 2 and 8% of a porogenic agent. The porogenic agent added in step (ii) of the process according to the invention may be a hydrogen peroxide solution, a peroxomonosulfuric acid solution, a peroxodisulfuric acid solution, an alkali peroxide solution, an alkaline earth peroxide solution or an organic peroxide solution such as peroxoacetic acid or peroxobenzoic acid, or a suspension of aluminum particles or mixtures thereof. Preferably, the porogenic agent is hydrogen peroxide. Preferably, it is hydrogen peroxide with a concentration between 8% and 35%. At the end of step (ii) of the process according to the invention, a mixture is obtained. This mixture can be prepared according to the process of the invention using a device comprising tubes, optionally of different sizes, forming a conduit. This conduit may or may not include a mechanical mixing aid, such as a static mixer. The reaction between the porogenic agent and the transition metal salt (catalyst precursors) and / or the cement begins immediately, and a fraction of the total oxygen is released immediately, such that the conduit contains bubbles. At the outlet of the conduit, the mixture containing a fraction of bubbles is intended to be poured immediately into a mold or projected onto a support. In this operation of discharging the mixture from the conduit, this mixture is not fractionated. Preferably, the mixture obtained in step (ii) of the procedure according to the invention is not fractionated. The expression "not fractionated" generally means that the mixture comes out of the channel in the form of a jet and retains its integrity, and in particular is not sprayed onto the mold or support, although some occasional droplets may form when contact with the support takes place. Step (iii) of the procedure according to the invention comprises placing the mixture obtained in step (ii) onto a support. This placement step can be performed without using spray nozzles or an equivalent. Furthermore, this placement can be performed without using elements at the outlet of the device. Indeed, spraying will generally result in the mixture becoming fragmented or forming droplets. Placement can be done by allowing the mixture obtained in step (ii) to flow naturally onto the support. This way, the naturally flowing mixture is not propelled or accelerated, which could destabilize it and cause droplets to form. Preferably, in step (iii) the mixture is placed without using any spray nozzle. Preferably, step (iii) of the procedure according to the invention is carried out without spraying. According to one variant of the invention, step (iii) can be repeated to obtain successive or superimposed layers. Preferably, the most recently deposited layer is placed on top of a layer that has already acquired mechanical strength through cement hydration. The support used in step (iii) of the procedure according to the invention can be vertical, horizontal, inclined, or in any position. It can also be a receptacle, a mold, a hollow or solid building block, a hollow or solid wall, a ceiling, or a floor (recovery or insulation sub-plate). The support used in step (iii) of the procedure according to the invention can be treated prior to the placement of the mixture obtained in step (ii). According to one variant, the procedure according to the invention further uses a cement hydration accelerator, which is present either in the mixture of step (i) or (ii), or on the surface of the support of step (iii). Preferably, the mixture of step (i) of the procedure according to the invention further comprises a cement hydration accelerator, for example calcium chloride. When a cement hydration accelerator is present in the mixture of step (i) or (ii), it is preferably a calcium salt, such as calcium chloride. The cement hydration accelerator can be continuously integrated before step (iii) of the process according to the invention. When a cement hydration accelerator is present on the surface of the support in stage (iii), it is preferably aluminum sulfate. The cement hydration accelerator can be introduced in stage (i) before or after the addition of water, or sprayed onto the support in stage (iii). Water can be applied to the substrate used in step (iii) of the process according to the invention before step (iii). Other additives can also be used in the process according to the invention, such as colored pigments, hydrophobic agents, or decontaminating agents (e.g., zeolites or titanium dioxide). In step (iv) of the process according to the invention, the mixture is expanded. This expansion begins as soon as the porogenic agent reacts chemically, i.e., in step (ii), and is completed in step (iv). The aerated mineral foam thus obtained can be smoothed and have a thickness greater than 1 cm. It is then set to obtain a solid mineral foam. This expansion corresponds to the gaseous release following the chemical reaction of the porogenic agent, possibly in the presence of a catalyst. When the porogenic agent is peroxide-based, the decomposition reaction of the porogenic agent carried out in the presence of a catalyst is an exothermic reaction that generates dioxygen and water. Indeed, it is known that the decomposition of peroxides is accelerated in the presence of a metal. The mixture in step (i) can be prepared using mixers commonly used for making cement slurries. This could be a slurry mixer, a cement plant mixer, a mixer described in European standard NF EN 196-1 of April 200, Paragraph 4.4, or a planetary mixing mixer. The mixture for step (i) can be prepared by introducing the different materials in powder form into the mixer. The powders are mixed to obtain a homogeneous mixture. Water is then introduced into the mixer. Next, the mineral particles and adjuvants, such as water-reducing agents, plasticizers, superplasticizers, accelerators, thixotropic agents, viscosifying agents, water-retaining agents, or retarders (when present in the mineral foam formulation), are added. The resulting paste is mixed to obtain a cement grout mixture. Preferably, the mixtures of stage (i) or (ii) are kept under agitation with the help of the deflocculant paddle, throughout the duration of the mineral foam manufacturing process according to the invention. The procedure according to the invention can be implemented on site by installing a foaming system directly on site, or implemented in a prefabrication plant. The invention also relates to a mineral foam that can be obtained according to the procedure of the invention. Preferably, the mineral foam produced according to the invention has a dry density of between 50 and 600 kg / m³, more preferably between 60 and 500 kg / m³, and even more preferably between 70 and 450 kg / m³. It should be noted that the density of the mineral foam in its fresh state (wet density) differs from the density of the mineral foam in its dry state, i.e., after setting (density of the hardened material). The density of the mineral foam in its fresh state is always greater than the density of the foam in its dry state. The invention offers the advantage that the mineral foam according to the invention is very light, and in particular has a very low density. The invention offers as another advantage that the mineral foam according to the invention has excellent stability properties. In particular, the bubbles that make up the mineral foam in its fresh state degrade very little after being poured into the mold or deposited onto the support. The support can be of different natures and different forms. The substrate can be a receptacle that is to be filled. In this case, it is intended to fill masonry blocks with the mineral foam according to the invention. For example, these could be masonry blocks, terracotta blocks, or aerated concrete blocks that will be filled with the foam according to the invention. The substrate can also be a wall that is to be coated with the mineral foam according to the invention. For example, it could be a concrete slab, cast concrete, a masonry block wall, a terracotta block wall, an aerated concrete block wall, or a wall coated with mortar or other materials. The substrate can be made of various materials such as concrete, terracotta, plaster, raw wood, a sheet of cement, cardboard, or any other material used in construction. The substrate can be treated or coated with a first layer of mineral foam according to the invention. The substrate may be treated before the foam is applied. The treatment may consist, for example, of one or more water sprays, the application of setting accelerator solutions such as aluminum sulfate, the application of bonding primer layers, or any other solution of a physical or chemical nature that accelerates the setting of the cement at the interface between the substrate and the mix, improves the adhesion of the mix to the substrate, or increases the roughness of the substrate. The invention offers another advantage: the mineral foam according to the invention has excellent thermal properties, and in particular, very low thermal conductivity. Reducing the thermal conductivity of building materials is highly desirable as it allows for energy savings in heating for residential and commercial buildings. Furthermore, the mineral foam according to the invention provides good insulation performance even at low thicknesses, thus preserving habitable surfaces and volumes. Thermal conductivity (also called lambda(A)) is a physical quantity that characterizes the behavior of materials when heat transfer by conduction occurs. Thermal conductivity represents the amount of heat transferred per unit area per unit time under a temperature gradient.In the International System of Units, thermal conductivity is expressed in watts per meter kelvin (W m⁻¹K⁻¹). Conventional or traditional concretes have a thermal conductivity between 1.3 and 2.1, measured at 23°C and 50% relative humidity. The mineral foam according to the invention has a thermal conductivity between 0.03 and 0.5 W / mK, preferably between 0.04 and 0.15 W / mK, more preferably between 0.045 and 0.10 W / mK The invention offers as another advantage that the mineral foam according to the invention has good mechanical properties, and in particular good compressive strength compared to known mineral foams. The mineral foam according to the invention exhibits a compressive strength of between 0.04 and 5 MPa, preferably between 0.05 and 2 MPa, and more preferably between 0.05 and 1 MPa. The invention also relates to the use of the mineral foam according to the invention as a construction material. For example, the mineral foam according to the invention can be poured onto walls, floors, and ceilings during construction. It is also envisaged to manufacture prefabricated elements from the foam according to the invention, such as blocks and panels, in a prefabrication plant. The mineral foam according to the invention can be poured onto walls during construction work. The invention also relates to the use of the mineral foam according to the invention as an insulation material, in particular as a thermal or sound insulation material. Advantageously, the mineral foam according to the invention allows, in certain cases, the replacement of glass wool, mineral wool, asbestos, or polystyrene and polyurethane insulation. Advantageously, the mineral foam according to the invention can be used as a filler for an empty or hollow space in a building, wall, partition, masonry block (for example, a brick), floor, or ceiling. Such composite building materials or elements comprising the mineral foam according to the invention are also objects of the invention per se. Advantageously, the mineral foam according to the invention can be used as a plugging material. Advantageously, the mineral foam according to the invention can be used as a facade cladding, for example, to insulate a building from the outside. In this case, the mineral foam according to the invention can be covered with a finishing coating. The invention also relates to a system comprising the mineral foam according to the invention. The foam can be present in the system as an insulating material. It can be poured vertically between two walls, selected, for example, from concrete slabs, brick walls, plasterboard, wood panels (such as oriented strand board), or fiber cement panels, the assembly forming the system. The system according to the invention is advantageously able to resist or reduce air and thermohydric transfers, that is, this element has a controlled permeability to transfers of air, water in the form of vapor or liquid. The system according to the invention preferably comprises at least one frame or structural element. This frame can be made of concrete (posts / beams), metal (studs or rails), wood, plastic or composite material, or synthetic material. The mineral foam according to the invention can also cover a lattice-type structure (plastic, metal), for example, or a pillar or beam of a building. The system according to the invention can be used to make or manufacture a cladding, an insulation system, or a partition, for example a partition wall, a distribution partition, or a counter-partition. The invention also relates to a construction element comprising the mineral foam according to the invention. When the mineral foam according to the invention is intended to be sprayed onto a vertical wall, this wall may be provided with elements that facilitate the foam's adhesion, for example, metal or plastic-based frameworks, whether or not separate from the wall and attached to it. Vertical supports may be positioned along the wall to serve as anchor points for the frameworks. These frameworks may consist of simple horizontal cables. Figure 1 is a diagram illustrating the principle of measuring a contact angle between a water droplet and a surface. Figure 2 is a schematic illustrating an example of how to implement a device for the procedure according to the invention. In the example shown in Figure 2, the device comprises a tank equipped with an agitator (1), a first pump (3), a first tube (4), a static mixer (5), a second pump (6), a container (7), a second tube (8), an outlet element (9), and a support (10). The mixture (2) is the mixture from stage (i) and is contained in the tank (1). The porogenic agent is contained in the container (7). They are pumped continuously and independently by pumps (3) and (6) and mixed by means of the static mixer (5). The tube (8) and the outlet element (9) form a pipeline that may include supplementary elements of different cross-sections and lengths.The dimensions (L1) and (D1) of the pipe (8) and the dimensions (L2) and (D2) of the outlet element (9) are chosen so that the pressure losses in the pipeline remain compatible with the flow characteristics, such as the flow rates and velocities at the outlet of the pipeline, and with the pumping means. The pipe (8) and the outlet element (9) are also chosen based on the rate of oxygen release in the pipeline, and in particular the ratio between the expected release in the pipeline and the expected release after the outlet (11) of the pipeline, and the regularity of the flow. Generally, the diameter (D2) of the end portion of the pipeline (outlet (11)) is chosen as a means of regulating the foam ejection velocity while maintaining the integrity of the jet. In the density range according to the invention, the expansion is not complete at the outlet of the pipeline (11) and terminates at the support (10).Generally, at least 20% of the expansion over the support (10) remains to be completed. Other ways of implementing a device to carry out the procedure according to the invention can be foreseen. Procedure for measuring a wetting or contact angle Figure 1 illustrates the principle of measuring a wetting angle between a solid surface 10 of a concrete sample 12 and a droplet 14 of a liquid deposited on the surface 10. The liquid / gas interface between the droplet 14 and the ambient air is designated by reference 16. Figure 1 is a section along a plane perpendicular to the surface 10. In the cut plane, the wetting angle α corresponds to the angle, measured from inside the liquid droplet 14, between the surface 10 and the tangent T to the interface 16 at the point of intersection between the solid 10 and the interface 16. To measure the wetting angle, sample 12 is placed in a room at a temperature of 20°C and a relative humidity of 50%. A water droplet 14 with a volume of 2.5 pl is placed on the surface 10 of sample 12. The angle is measured using an optical procedure, for example, a drop shape analysis device, such as the DSA 100 device marketed by Krüss. The measurements are repeated five times, and the average of these five measurements is the value of the contact angle measured between the water droplet and the support. Laser granulometry procedure The particle size distribution curves of the different powders are obtained from a Mastersizer 2000 type laser granulometer (year 2008, serial number MAL1020429) marketed by the Malvern company. The measurement is performed in a suitable medium (e.g., aqueous) to disperse the particles; the particle size must be between 1 pm and 2 mm. The light source consists of a red He-Ne laser (632 nm) and a blue diode (466 nm). The optical model is the Fraunhofer model, and the calculation matrix is ​​of the polydisperse type. First, a background noise measurement is performed with a pump speed of 2000 rpm, an agitator speed of 800 rpm, and a noise measurement taken for 10 seconds, in the absence of ultrasound. It is then verified that the laser light intensity is at least 80% and that a decreasing exponential curve is obtained for the background noise. If this is not the case, the cell lenses must be cleaned. A first measurement is then performed on the sample with the following parameters: pump speed of 2000 rpm, agitator speed of 800 rpm, no ultrasound, and a darkening limit between 10% and 20%. The sample is immersed to achieve a darkening level slightly above 10%. After the darkening stabilizes, the measurement is taken with a fixed immersion interval of 10 seconds. The measurement duration is 30 seconds (30,000 diffraction images analyzed). The resulting particle size distribution should take into account the fact that some of the powder may be agglomerated. A second measurement is then performed (without emptying the tank) using ultrasound. The pump speed is set to 2500 rpm, the agitator speed to 1000 rpm, and the ultrasound is emitted at 100% power (30 watts).This regime is maintained for 3 minutes, after which the initial parameters are returned: pump speed of 2000 rpm, agitator speed of 800 rpm, and no ultrasound. After 10 seconds (to evacuate any air bubbles), a 30-second measurement is taken (30,000 images analyzed). This second measurement corresponds to a powder deagglomerated by ultrasonic dispersion. Each measurement is repeated at least twice to verify the stability of the result. The device is calibrated before each work session using a standard sample (Sifraco C10 silica) with a known particle size distribution curve. All measurements presented in the description and the advertised ranges correspond to values ​​obtained using ultrasound. Blaine specific surface area measurement procedure The specific surface area of ​​different materials is measured as follows. The Blaine procedure at 20°C with a relative humidity not exceeding 65% using a Blaine Euromatest Sintco apparatus in accordance with European standard EN 196-6. Before measuring the specific surface area, the wet samples are dried in an oven to a constant mass at a temperature between 50 and 150°C (the dried product is then ground to obtain a powder whose maximum particle size is less than or equal to 80 pm). Examples The process according to the invention was put into practice to make mineral foams of formulas 391, 390-a, 390-by, and 400. A comparative example 389 was also made to highlight the advantageous aspects of the process according to the invention. Materials The cement used is Portland cement CEMI 52, R from the Lafarge Saint Pierre la Cour cement plant. The letter "R" corresponds to the definition in the NF EN 197-1 standard, April 2012 version. This cement was crushed to obtain a Blaine specific surface area of ​​8000 cm² / g. The water-reducing agent is a new-generation, highly water-reducing superplasticizer based on modified polycarboxylate, marketed under the name Chr y so Fluid Premia 180 and supplied by Chr y so. The dry extract of Premia 180 is 50% by mass. The water-reducing agent does not contain any antifoaming agent. The ultrafine particles are precipitated calcium carbonate particles marketed as Socal 312 and sourced from Solvay PCC. These ultrafine particles have a contact angle ranging from 90° to 130°, as measured according to the procedure described above, and a particle D50 of 40 nm, as measured using the procedure described in EP1 740649. The transition metal salt is manganese sulfate monohydrate from Sigma Aldrich. The mineral addition is a limestone powder marketed as BL200 Orgon and sourced from Omya for formulas 389, 391, 390-a and 390-b, and Dunkirk slag (Origin: Arcelor) for formula 400. The D50 of BL200 is 6 pm, and the D50 of the slag is 14.2 pm. The cement hydration accelerator is aluminum sulfate with a concentration of 1 mol / l prepared from hydrated aluminum sulfate (14H2O) powder from the company VWR. The porogenic agent is 30% hydrogen peroxide from the company VWR. The water is tap water. Materials used Rayneri Mixers - A Rayneri R 602 EV (2003) mixer. The mixer consists of a frame on which drums ranging from 10 to 60 liters are positioned. The 10-liter drum was used with a paddle-type blade adapted to the drum's volume. This blade rotates on its own axis and rotates planetaryly around the drum's axis. Pumps - One Seepex™ type MD 006-24 offset screw pump (I) delivery no. 244920. - One Seepex™ type MD 006-24 offset screw pump (ll) delivery no. 278702. Static mixer - A static mixer composed of 32 Kenics-type helical elements of 19 mm diameter, referenced 16La632 in ISOJET I. Production of mineral foams Preparation of the paste for formulas 389, 391, 390-ay, 390-b The paste is prepared by mixing the compounds in Table I in the respective proportions indicated in this table. The paste is then mixed with water in a planetary mixer (Rayneri brand) for 5 minutes. The density of the foam is measured in its fresh state after expansion. Table 1 * The values ​​are percentages expressed as mass relative to the mass ** percentages by mass with respect to the mass of cement *** mass relationship Before applying the foam to a supporting masonry wall, the wall is treated, using a sprayer, by spraying a 1 mol / l aluminum sulfate solution. The paste is then continuously pumped by a screw pump (Seepex brand (I)) into a 15 mm diameter main pipeline. Simultaneously, the aqueous hydrogen peroxide solution is pumped by another screw pump (Seepex brand (II)) and continuously injected into the pipeline carrying the paste. The respective pumping rates are shown in Table 2. Mixing between the paste and the solution is accelerated by a static mixer located in the main pipeline immediately downstream of the hydrogen peroxide injection point. The pipeline downstream of the static mixer is 5.5 m long. Table 2 The pipeline is equipped with an applicator (diameter adapter) that increases the diameter of the outlet tubing to 20 mm over a length of 20 cm. The paste exiting the applicator is observed to be only partially aerated (less than 50% of the total oxygen fraction is incorporated into the paste at this point), and its expansion continues after application. The paste is deposited onto the wall solely by the outlet jet, which maintains its integrity up to the point of application. The density of the foam is measured in its fresh state after expansion. The wall is coated by gradually varying the position of the deposit point until the wall is completely covered by the foam after full expansion. This results in a layer approximately 3 cm thick. The system is left as is until the cement begins to set, which takes approximately 2 hours and 30 minutes at room temperature. The foam deposition process is repeated a second time, under exactly the same conditions as the first time. A second layer of approximately 3 cm is applied. The paste is then floated to smooth out any irregularities and give it a finished appearance. Preparation of the paste for formula 400 The paste is prepared by mixing the following components, the percentages being expressed by mass: 71.46% of crushed cement until a Blaine specific surface of 8000 cm2 / g is achieved. 22.2% Dunkirk slag 4.80% of treated ultrafine particles (Solvay PCC Socal 312) 1.6% manganese sulfate monohydrate 0.4% of a Premia 180 superplasticizer 4.5%, calculated with respect to the cement, of H2O2 is added in the form of a 30% solution. II. Analysis of the mineral foam 11.1 Thermal conductivity of mineral foams Thermal conductivity (λ) was measured using a thermal conductivity measuring device: a CT-meter supplied by Alphis-ERE (50 Ω resistor, 50 mm probe cable). The measurement was performed on samples dried at 45°C to constant mass. The sample was then cut into two equal pieces using a saw. The measuring probe was placed between the two flat faces of these two sample halves (the sawn sides). Heat was transferred from the source to the thermocouple through the material surrounding the probe. The temperature rise of the thermocouple was measured over time, allowing the thermal conductivity of the sample to be calculated. 11.2 Density of mineral foams The wet density of the foamed cement grouts was measured by weighing the cubes at the time of pouring and after complete expansion. The dry density of the samples was measured on samples dried at 45°C to constant mass, always by weighing the cubes. Table 3

Claims

1. A continuous process for producing a mineral foam with a dry density (d) between 40 and 600 kg / m³, comprising the following steps: (i) mixing cement; a water-reducing agent; between 0.5 and 10% by mass of the total cement mass of ultrafine particles having a liquid-solid contact angle between 30° and 140°, measured according to the procedure described herein, and whose D50 is between 10 and 600 nm; and water, with a water / cement mass ratio between 0.3 and 2.5; (ii) adding to the mixture between 0.5 and 10% by mass of a porogenic agent with respect to the cement mass; (iii) placing the mixture obtained in step (ii) onto a support; (iv) allowing the mixture to expand onto the support. 2.A process according to claim 1, wherein the cement in the mixture of step (i) is a cement having a Blaine specific surface area of ​​between 5000 and 9000 cm² / g.

3. A process according to any one of the preceding claims, wherein there is no foaming agent in the mixture of step (i) or (ii).

4. A process according to any one of the preceding claims, wherein the mixture of step (i) or step (ii) further comprises a transition metal salt, for example a manganese salt or an iron salt.

5. A process according to any one of the preceding claims, wherein the mixture of step (i) further comprises a mineral addition such as a pozzolan, slag, calcium carbonate, fly ash, sand, or mixtures thereof, the particles of which have a D50 of between 0.1 and 4 mm. 6.A process according to any one of the preceding claims, wherein the porogenic agent added in step (ii) is a hydrogen peroxide solution, a peroxomonosulfuric acid solution, a peroxodisulfuric acid solution, an alkali peroxide solution, an alkaline earth peroxide solution, or an organic peroxide solution such as peroxoacetic acid or peroxobenzoic acid, or a suspension of aluminum particles or mixtures thereof.

7. A process according to any one of the preceding claims, wherein the mixture of step (i) further comprises a cement hydration accelerator, for example, calcium chloride.

8. A process according to any one of the preceding claims, wherein the mixture obtained in step (ii) is not fractionated.

9. A process according to any one of the preceding claims, wherein in step (iii), the mixture is placed without the use of any spray nozzle.

10. A method according to any one of the preceding claims, wherein step (iii) is carried out without spraying.

11. A method according to any one of the preceding claims, wherein the substrate used in step (iii) is pre-treated before the application of the mixture obtained in step (ii).

12. Mineral foam obtainable according to the method of claims 1 to 11.

13. Use of the mineral foam according to claim 12 as an insulation material, in particular as a thermal or sound insulation material.

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