Additive manufacturing of insulating building elements

Abstract

The invention relates to a method for obtaining a building element (1) by additive manufacturing, said building element (1) comprising at least one structural element (2) and at least one insulating element (3, 4), wherein dry mortar is mixed with mixing water in order to form a basic wet mortar, the basic wet mortar is delivered to a print head, and a stack of mortar layers is deposited continuously by moving the print head in order to form the at least one structural element (2) and the at least one insulating element (3, 4), the method being such that water foam is additionally added to the basic wet mortar during the delivery of the basic wet mortar to the print head before depositing a mortar layer belonging to the insulating element (3, 4).

Description

Technical Field

[0001] This invention relates to the field of construction. More particularly, it relates to the manufacture of insulated building components using additive manufacturing technology. Background Technology

[0002] Beyond their advantages in comfort and cost savings, building insulation is a key issue in both construction and renovation aimed at mitigating global warming. Therefore, it is fundamental for building components to have the lowest possible thermal conductivity. To address this issue, numerous technical solutions have been proposed for implementing various insulation elements (mineral wool, organic foam, etc.) associated with structural components (walls, ceilings, etc.).

[0003] This invention seeks to propose a new technology for manufacturing building components with improved thermal insulation.

[0004] Today, additive manufacturing technology is experiencing promising development in a wide range of technological fields. Also known as "3D printing," additive manufacturing is a method in which computer-controlled robots create three-dimensional objects by continuously depositing material layer by layer. These technologies particularly allow for the creation of objects with complex shapes.

[0005] Additive manufacturing has been used, for example, to manufacture structural components such as concrete walls.

[0006] For example, additive manufacturing of building components made of concrete or mortar allows for the integration, automation, and simplification of the design, planning, and construction processes. Other advantages of this technology include reduced labor costs, reduced material loss and consumption, elimination of trench boxes, and reduced project time and investment.

[0007] In known technologies, wet mortar, obtained by mixing dry mortar and water, is pumped and conveyed toward a printhead fixed to a robot or gantry crane, the movement of which is computer-controlled. Typically, a layer of wet mortar is deposited on top of a previously deposited layer through nozzle extrusion. The printhead moves continuously according to a predetermined pattern to create the final object. Summary of the Invention

[0008] This invention is proposed to obtain building components with thermal insulation functions through such technology.

[0009] Therefore, one object of the present invention is a method for obtaining building elements by additive manufacturing, the building elements comprising at least one structural element and at least one insulating element, wherein dry mortar is mixed with mixed water to form a base wet mortar, the base wet mortar is conveyed to a printhead, and stacked mortar layers are continuously deposited by moving the printhead to form the at least one structural element and the at least one insulating element, wherein the method is such that water foam is additionally added to the base wet mortar during conveying the base wet mortar to the printhead before depositing the mortar layer belonging to the insulating element.

[0010] Another object of the present invention is a building element comprising at least one structural element and at least one isolation element, which is obtained by the method according to the invention, or is simply obtainable by the method according to the invention.

[0011] Another object of the present invention is a system for implementing the method according to the invention. Such a system includes a mixing device capable of mixing dry mortar and mixed water to form a base wet mortar, a conveying device capable of conveying the base wet mortar to a printer, the printer including a printhead movable to deposit stacked mortar layers, a foam generating device capable of generating water foam, and a mixing device capable of mixing the base wet mortar and the water foam.

[0012] "Structural elements" refer to building components that fulfill structural functions or contribute to their enhancement. Regarding insulating elements, they add thermal and even acoustic isolation.

[0013] Structural elements are most commonly walls or wall components, especially facade walls or interior load-bearing walls. They can also be floor components. These elements are typically intended to be integrated into the building's structure. In fact, the presence of structural elements enables building components to perform this structural function.

[0014] In the case of walls, building elements preferably have height and width in a vertical plane (i.e., once the element is incorporated into the building) and thickness in a vertical direction along this vertical plane. Typically, each structural element and each insulating element extends in the vertical plane over the entire height and width of the structural element. These elements are then continuous with each other in the thickness of the building element. The structural and insulating elements are preferably in contact with each other such that the thickness of the wall is equal to the sum of the thicknesses of each of these elements. The structural elements may be rectangular or parallelogram in shape. However, other shapes are possible because additive manufacturing techniques enable a wide variety of shapes to be obtained.

[0015] Therefore, this invention applies additive manufacturing technology to construct structural or support elements of building components and at least one isolation element.

[0016] This invention allows for the adjustment of the final mortar density from the same dry mortar so that structural and insulating elements can be constructed using the same printing system, and in particular, the same printhead.

[0017] Therefore, when the printhead deposits a mortar layer belonging to structural elements, water foam is typically not added. The wet mortar reaching the printhead is then the base wet mortar. However, when the printhead deposits a mortar layer belonging to insulating elements, a certain amount of water foam is first added to the base wet mortar. This allows for adjustment of the final mortar density and thus provides insulation properties to the elements. The wet mortar reaching the printhead is then a mixture of base wet mortar and water foam.

[0018] This is typically achieved without adding water foam to each structural element. Therefore, a dense mortar layer is obtained, which is particularly capable of fulfilling its structural function. Preferably, the mortar layer belonging to the structural elements has a density of at least 2000 kg / m² after hardening (especially after 28 days). 3 Especially at least 2100 kg / m 3 This density is preferably less than or equal to 2500 kg / m³. 3 .

[0019] At least one, or even each, insulating element is obtained by adding water foam. Therefore, a less dense mortar layer is obtained compared to the mortar layer belonging to the structural elements. The density of the mortar layer belonging to at least one insulating element after hardening (especially after 28 days) is preferably at most 1500 kg / m³. 3 Especially up to 1200 kg / m 3 .

[0020] According to one embodiment, the building element includes an insulating element whose density, after hardening (particularly after 28 days), is at most 100 kg / m³. 3 This component will have excellent thermal insulation properties.

[0021] According to another embodiment, the building element includes an insulating element with a density of 700 and 1500 kg / m³ after hardening (particularly after 28 days). 3 Between, especially 800 and 1200 kg / m 3 Between. This element will have moderate thermal insulation performance.

[0022] A preferred embodiment combines two of the foregoing embodiments. In this case, the building element includes a structural element, a first insulating element, and a second insulating element, the second insulating element having a density greater than that of the first insulating element. In this method, the amount of water foam added to the base wet mortar when obtaining the first insulating element is greater than the amount of water foam added to the base wet mortar when obtaining the second insulating element. Preferably, the mortar layer belonging to the first insulating element has a hardened density of at most 100 kg / m³. 3 The mortar layer, which belongs to the second isolation element, has a hardened density of 700 and 1500 kg / m³. 3 Between. In the case of a wall, the building elements preferably include a supporting element starting from the outside of the wall, followed by a first insulating element, and then a second insulating element.

[0023] In an alternative to this preferred embodiment, only the second isolating element is obtained by additive manufacturing. The first isolating element is obtained by pouring constituent material into the cavity formed by the structural element and the second isolating element. The pouring step can be performed using a robot.

[0024] According to one embodiment of the invention, the structural and insulating elements are formed sequentially. The mortar delivery device then advantageously includes a single hose for delivering wet mortar to a single printhead, which prints each element (structural or insulating) one by one. Therefore, the system preferably includes a single pump and a single hose, with water foam added during the formation of the insulating element and stopped during the formation of the structural element.

[0025] According to one embodiment of the invention, the structure and the isolation element are formed simultaneously. The mortar delivery device then advantageously includes multiple hoses, each hose delivering wet mortar to a different printhead or to a different chamber of the same printhead, with water foam added only in the hose delivering the base wet mortar intended to form the isolation element. Each hose may be connected to the same pump or to different pumps.

[0026] Dry mortar refers to a powder mixture. Dry mortar preferably includes at least one mineral binder, preferably hydraulic, such as selected from silicate cement, alumina cement, sulfoaluminate cement, quicklime, ground granulated blast furnace slag, fly ash, and mixtures thereof. The hydraulic binder is advantageously silicate cement or even includes such cement. The mineral binder may also be gypsum-based or a geopolymer binder.

[0027] Dry mortar preferably includes aggregates. These aggregates are particularly siliceous, calcareous, and / or dolomite aggregates. It may also include lightweight aggregates, that is, those with a density of less than 200 kg / m³. 3The apparent density. Lightweight aggregates are particularly selected from perlite, vermiculite, expanded glass beads, expanded polystyrene beads, microspheres, expanded silicates, aerogels, and mixtures thereof. Taking into account the reduced cross-section of the pumping device and the nozzle of the printhead, the maximum size of the aggregate is preferably no greater than 3 mm, particularly no greater than 2 mm and even no greater than 1 mm. The maximum size can be varied, for example, by screening.

[0028] Dry mortar preferably includes at least one additive, particularly selected from superplasticizers, thickeners, accelerators, and retarders. Dry mortar advantageously includes inorganic thickeners, such as expanded clay, which can increase the static elastic limit of wet mortar. Accelerators and retarders allow for adjustment of the time required for the hydraulic binder to set and harden.

[0029] The composition of the dry mortar is preferably adjusted in such a way that the base wet mortar exhibits thixotropic behavior. Preferably, the viscosity of the base wet mortar increases by at least 50% within one second after the wet mortar leaves the printhead nozzle. The base wet mortar thus possesses low viscosity for high shear rates, allowing it to be easily pumped and carried, but its structural stability increases immediately upon leaving the nozzle of the printhead, thus enabling it to support the overlay layer before setting and hardening. This deposition on the still-wet mortar layer improves adhesion between successive layers and therefore improves the final mechanical strength of the building element.

[0030] Dry mortar is mixed with a water mixture to form a base wet mortar. The water mixture can be simply water, or water containing one or more additives, particularly organic additives such as surfactants, dispersed or suspended in a solution.

[0031] The mixing ratio can be adjusted if necessary, depending on the characteristics of the components; that is, the ratio between the amount of water and the amount of dry mortar (by weight). Alternatively, the mixing ratio can be the same for all components. The mixing ratio is preferably at most 0.5, particularly between 0.05 and 0.20.

[0032] The wet mortar has a viscosity and can be pumped and delivered to the printhead. Pumping can be carried out, for example, by means of a screw pump. Delivery is typically carried out in a hose. The delivery device therefore preferably includes a pump, particularly a screw pump, and at least one hose.

[0033] At least for the production of isolation components, water foam is added to the base wet mortar during the delivery of the base wet mortar to the printhead.

[0034] The mixing of water foam and base wet mortar is preferably accomplished using a static mixer. Therefore, the mixing device is preferably a static mixer.

[0035] Water foam is preferably added between the pump and the printhead, ideally as close to the printhead as possible to maintain the foam's structure. However, adding it too close to the printhead can be detrimental to the uniform mixing of the water foam and the base mortar.

[0036] The amount of water foam relative to the amount of base wet mortar is preferably automatically adjusted. In particular, it is adjusted based on the desired density in the area of ​​interest. The ratio between the volume of added water foam and the volume of base wet mortar is preferably between 0.5 and 15, particularly between 1 and 12.

[0037] For example, for 100 kg / m after hardening 3 The density of the mortar, the ratio between the volume of added water foam and the volume of the base wet mortar is typically about 10. For hardened 800 kg / m³ 3 The ratio between the density of the water foam and the volume of the base wet mortar is typically about 1.3.

[0038] Water foam is obtained, for example, by stirring water and a foaming agent (or foam stabilizer) and then introducing a gas, particularly air, by stirring, foaming, or pressure injection. The intermediate diameter of the water foam is preferably at most 400 µm, and particularly at most 200 µm.

[0039] Foaming agents are, for example, surfactants. According to a preferred example, they are surfactants derived from proteins or amino acids.

[0040] According to another example, water foam comprises a mixture of cationic and anionic surfactants, with the cationic surfactant being a quaternary ammonium salt (especially a halide) and the anionic surfactant being a C10-C24 carboxylate (especially an alkali metal salt), such as potassium stearate.

[0041] According to yet another example, water foams include, in particular, silica nanoparticles, which possess foam-stabilizing properties. Such foams are called "Pickler foams." The silica nanoparticles can also be stabilized by surfactants.

[0042] Due to the addition of water foam, the mortar contains a large amount of gas, particularly air, trapped within the mineral matrix, and therefore exhibits low thermal conductivity, especially by reducing heat transfer through convection and conduction. The thermal conductivity of the insulating element after hardening (particularly after 28 days) is preferably at most 60 mW·m. -1 .K -1 Ideally, it is approximately 40 mW·m. -1 .K -1 .

[0043] The printhead specifically includes nozzles through which wet mortar (base wet mortar, possibly with added water foam) is extruded. The extrusion nozzles are preferably positioned less than 100 mm from the underlying layer. The printer is, for example, an industrial robot or gantry crane carrying the printhead, and its movement is controlled by a computer. The computer specifically includes a recording medium storing a set of data or a 3D model, as well as instructions that, when executed by the computer, guide it in controlling the movement of the printhead (track, speed, etc.) and other parameters of the method, such as the ratio between the amount of water foam and the amount of base wet mortar, or the mixing ratio (i.e., the ratio between the amount of mixed water and the amount of dry mortar).

[0044] Printing speeds typically range from 30 to 1000 mm / s, particularly from 50 to 300 mm / s. The thickness (or height, since here it refers to the vertical dimension) of the mortar layer is preferably between 5 and 40 mm, particularly between 10 and 20 mm. The width of the mortar layer is preferably between 10 and 300 mm, particularly between 20 and 100 mm.

[0045] This method may also include adding a setting and / or hardening accelerator or rheology modifier to the wet mortar prior to deposition. The addition can be done at or near the nozzle, just before extrusion. Alternatively, the accelerator or rheology modifier can be added immediately on the surface of the layer after deposition. Setting accelerators are, for example, aluminum sulfate or lithium salts, depending on the type of hydraulic binder used. Rheology modifiers, for example, allow the mortar to acquire thixotropic properties. The addition of a setting accelerator or rheology modifier allows the mortar layers to solidify rapidly, enabling them to withstand the weight of the overlay without deformation.

[0046] Building components may also include reinforcing members. These members are intended to mechanically reinforce the component, or are preferably deposited during the printing of mortar layers. They may be deposited horizontally or vertically within the thickness of the mortar layers and then extend into several mortar layers. The reinforcing members are, for example, made of steel.

[0047] Building components can be prefabricated elements intended to be assembled on-site, for example, using mortar, to form the interior or exterior walls of a building (e.g., interior load-bearing walls). Components can also be manufactured directly on-site to form complete walls of a building.

[0048] The lateral dimensions of the building elements are preferably between 1 and 4 m, particularly between 1 and 3 m. The thickness is preferably at most 70 cm, particularly between 20 and 50 cm.

[0049] The thermal resistance of building components is preferably between 3.0 and 5.0 m. 2 Between .K / W. Attached Figure Description

[0050] Figure 1A specific and non-limiting embodiment of the invention is shown.

[0051] Figure 2 An example of a system according to the present invention is illustrated schematically. Detailed Implementation

[0052] Figure 1 A schematic top view of a building element 1 obtained by the method of the present invention is shown, in this example, a wall.

[0053] Wall 1 here takes the form of a rectangular parallelepiped with a thickness e and a width L. This is merely an example, and it goes without saying that additive manufacturing technology allows for a variety of shapes.

[0054] In use, wall 1 includes structural elements 2 that contact a first isolating element 3, which in turn contacts a second isolating element 4, starting from the outside of the building. Each of these elements extends over the entire height and width of the wall.

[0055] The density after 28 days of hardening is greater than 2000 kg / m³ for structural element 2. 3 For the first isolation element 3, the weight is less than 100 kg / m 3 And for the second isolation element 4 at 700 and 1200 kg / m 3 Between. The second insulating element 4 is therefore more in the form of a lighter wall, while the first insulating element 3 is more in the form of mineral foam.

[0056] This wall 1 is aided by Figure 2 The printing system 20, schematically depicted in the diagram, includes:

[0057] - Mixing device 22 for mixing dry mortar and mixed water,

[0058] - Includes a conveying device with a threaded pump 24, which facilitates the pumping and conveying of the base wet mortar obtained thereby in the hose 25.

[0059] - A foam generating device 26 facilitates the generation of water foam, wherein foam is inserted into a hose 25 after the pump 24.

[0060] - Mixing device 27, more specifically a stationary mixer connected to hose 25, for mixing base mortar and water foam,

[0061] - A printhead 28, including nozzles, allows wet mortar to be extruded through the nozzles to deposit a layer of wet mortar 11 on top of a previously deposited mortar layer 12. The movement of the printhead 28 is performed by a computer-controlled robot.

[0062] Dry mortar consists of silicate cement and siliceous fine aggregate. The mixing ratio is 0.12 to obtain the base wet mortar.

[0063] The structural and insulating elements are formed sequentially. The structural element 2 is first formed from overlapping mortar layers 12, the width of which is equal to the thickness of the layers. During this fabrication, no water foam is added to the base wet mortar. In the second step, the second insulating element is formed separately from the structural element to create a cavity. During this fabrication, water foam is added to the base wet mortar, with the volume ratio of the water foam to the base wet mortar being approximately 1.3. In the third step, the first insulating element is poured into the cavity.

[0064] Alternatively, the first isolation element can be produced through additive manufacturing, just like the structural element and the second isolation element.

Claims

1. A method for obtaining a building element (1) by additive manufacturing, the building element (1) comprising a structural element (2), a first isolation element (3), and a second isolation element (4), wherein dry mortar is mixed with mixed water to form a base wet mortar, the base wet mortar is conveyed to a printhead (28), and stacked mortar layers (11, 12) are continuously deposited by moving the printhead (28) to form the structural element (2), the first isolation element (3), and the second isolation element (4), the method being such that water foam is additionally added to the base wet mortar during conveying the base wet mortar to the printhead (28) before depositing the mortar layers belonging to the first isolation element (3) and the second isolation element (4); in, The structural element (2) and the first isolation element (3) and the second isolation element (4) are formed sequentially; the structural element (2) is first formed from overlapping mortar layers, during which water foam is not added to the base wet mortar; in a second step, the second isolation element (4) is formed separately from the structural element (2) to create a cavity, during which water foam is added to the base wet mortar; In the third step, the first isolation element (3) is formed into the cavity.

2. The method according to claim 1, wherein the building element (1) is a wall.

3. The method according to claim 1 or 2, wherein the mortar layer belonging to the structural element (2) has a hardened density of at least 2000 kg / m³. 3 .

4. The method according to claim 3, wherein the mortar layer belonging to the structural element (2) has a hardened density of at least 2100 kg / m³. 3 .

5. The method according to claim 1 or 2, wherein the mortar layer belonging to the first isolation element (3) and the second isolation element (4) has a hardened density of at most 1500 kg / m³. 3 .

6. The method according to claim 5, wherein the density of the first insulating element (3) after hardening is at most 100 kg / m³. 3 .

7. The method according to claim 5, wherein the density of the second insulating element (4) after hardening is between 700 and 1500 kg / m³. 3 between.

8. The method according to claim 7, wherein the density of the second insulating element (4) after hardening is between 800 and 1200 kg / m³. 3 between.

9. The method according to claim 1 or 2, wherein the second isolation element (4) has a density greater than that of the first isolation element (3), and the amount of water foam added to the base wet mortar when the first isolation element (3) is obtained is greater than the amount of water foam added to the base wet mortar when the second isolation element (4) is obtained.

10. The method according to claim 9, wherein the mortar layer belonging to the first insulating element (3) has a hardened density of at most 100 kg / m³. 3 The mortar layer belonging to the second isolation element (4) has a hardened density of 700 and 1500 kg / m³. 3 between.

11. The method according to claim 1 or 2, wherein the amount of water foam is automatically adjusted relative to the amount of base wet mortar.

12. The method according to claim 1 or 2, wherein the dry mortar comprises at least one hydraulic binder.

13. The method according to claim 12, wherein the at least one hydraulic binder is selected from silicate cement, alumina cement, sulfoaluminate cement, quicklime, ground granulated blast furnace slag, fly ash, and mixtures thereof.

14. The method according to claim 1 or 2, wherein the mixing of the water foam and the base wet mortar is accomplished using a static mixer (27).

15. The method according to claim 1 or 2, wherein the first isolation element (3) is poured into the cavity.

16. The method according to claim 1 or 2, wherein the first isolation element (3) is produced by additive manufacturing.

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