Description

Title: Additive manufacturing of concrete construction elements

The invention relates to the field of construction. It relates more particularly to the manufacture of concrete construction elements by an additive manufacturing technique.

Also called “3D printing”, additive manufacturing is a method in which a computer-controlled robot manufactures three-dimensional objects by continuously depositing material layer after layer. These techniques make it possible in particular to manufacture objects having complex shapes.

The additive manufacturing of concrete or mortar elements makes it possible to integrate the design, planning and construction processes and to automate and rationalize the latter. Other advantages of this technology include a reduction in labor costs, a reduction in waste and material consumption, the elimination of formwork and a reduction in the duration of projects and investments.

In the present text, concrete or mortar is understood to mean a material comprising a hydraulic binder and aggregates. In known technologies, a wet mortar, obtained by mixing a dry mortar and mixing water, is pumped and conveyed to a printing head attached to a robot or a gantry whose movement is controlled by computer. . A layer of wet mortar is deposited over a layer of mortar previously deposited, generally by being extruded through a nozzle. The printhead is continuously moved in a predetermined pattern to produce the final object.

Additive manufacturing has, for example, been used to manufacture concrete walls by printing flat walls opposite and parallel to each other and, inside the cavity formed by these walls, a "zigzag" structure, therefore according to a broken line. forming alternately salient and re-entrant angles, connecting these two walls. The structure thus delimits a plurality of cavities separated from each other by a thickness of concrete. Patent KR 10-1911404 describes for example such walls comprising three walls each connected to the opposite wall by a zigzag structure.

The invention aims to manufacture construction elements, in particular wall elements, having both good mechanical strength, in particular in compression, in bending and in shear, and good performance in terms of thermal insulation.

To this end, the subject of the invention is a process for obtaining a concrete construction element by additive manufacturing, in which layers of superimposed mortar are successively deposited so as to form two walls, opposite one another. another so as to provide a cavity, as well as a plurality of reinforcing elements each extending from one of the walls towards the cavity, each reinforcing element being in contact neither with the wall opposite to that from which it extends ni with a reinforcing element extending from the wall opposite to that from which it extends.

The invention also relates to a concrete construction element, in particular obtained or likely to be obtained according to the process of the invention, comprising two walls opposite to each other so as to form a cavity, as well as a plurality of reinforcing elements made of material with said walls and each extending from one of the walls towards the cavity, each reinforcing element being in contact neither with the wall opposite to that from which it extends nor extends with a reinforcing element extending from the wall opposite that from which it extends.

The construction element will most often be a wall or a wall element, in particular for a facade or shear wall. It can also be a floor element. The element will generally be intended to be integrated into the structure of a building.

The successive deposition of superimposed layers of mortar is carried out so as to form two walls and a plurality of reinforcing elements. The reinforcing elements, printed with the walls and therefore made of material with them, make it possible to confer good mechanical strength on the construction element thus manufactured. The construction element preferably consists of two opposite walls and reinforcing elements, and optionally of an insulating material filling the cavity.

In the known walls, the zigzag structure also makes it possible to reinforce the wall, but it appears that this structure creates unfavorable thermal bridges between the opposite walls which it connects. In the patent KR 10-1911404 for example, each zigzag reinforcing element is in contact with opposite walls in pairs. Surprisingly, it has proved possible to considerably reduce these thermal bridges while maintaining an acceptable mechanical resistance of the wall. Being in contact neither with the wall opposite to that from which they extend, nor with a reinforcing element extending from said opposite wall, the reinforcing elements do not form a thermal bridge. By "opposite wall", we mean the wall immediately opposite, that is that is to say the wall directly facing that from which the reinforcing element extends. In other words, the reinforcing elements are not in contact with the opposite wall and with the reinforcing elements extending from the opposite wall, neither directly nor via an additional or intermediate wall, since such a wall would form a thermal bridge. In general, it must not be possible to cross the construction element in its thickness by passing only through mortar, except possibly at the lateral ends of the element. since such a wall would form a thermal bridge. In general, it must not be possible to cross the construction element in its thickness by passing only through mortar, except possibly at the lateral ends of the element. since such a wall would form a thermal bridge. In general, it must not be possible to cross the construction element in its thickness by passing only through mortar, except possibly at the lateral ends of the element.

Each reinforcing element is preferably in contact only with the wall from which it extends. As explained in the rest of the text, however, it is not excluded that the reinforcing elements are in contact with any insulating material filling the cavity. A reinforcement element can also be in contact with another reinforcement element which would extend from the same wall as it. In this text, contact means direct contact.

Unlike known walls, in which the zigzag structure delimits a plurality of separate cavities, the reinforcing elements of the construction element according to the invention are generally such that the construction element only comprises a single cavity. As indicated in the following text, this cavity can be filled with an insulating material. The presence of a single cavity, in addition to the advantage it provides in terms of thermal insulation, facilitates the filling process.

The cavity is normally such that a line can be drawn through it through the whole building element in a horizontal plane (with the element positioned as printed) and in the general direction of the walls without pass through layer of mortar.

Preferably, the walls are flat and parallel to each other. Alternatively, the walls can have any shape, such as curved shapes or even broken lines.

The walls preferably have a rectangular shape, therefore having a width and a length. However, other shapes are possible.

Generally, due to the use of the additive manufacturing technique, which requires the deposition of superimposed layers, at least one, in particular each, reinforcing element extends, in the plane of the wall, linearly and according to a dimension of Wall. Most often, each reinforcing element has a profile extending substantially along the axis normal to the plane of the mortar layers. In the case of rectangular walls, at least one, in particular each, reinforcing element may extend, in the plane of the wall, along the width or along the length of the walls. In its end use, the wall element can be placed so that its width or its length is arranged vertically, so that the reinforcing elements can extend vertically or horizontally.

The shape and distribution of the reinforcing elements influence the mechanical strength and the thermal insulation properties of the construction element obtained.

Preferably, each reinforcing element has an identical shape. Alternatively, the construction element may comprise reinforcing elements having different shapes.

The reinforcing elements can be arranged periodically or not.

According to an advantageous embodiment, at least one, in particular each, reinforcing element comprises a first part extending linearly from one of the walls and transversely to said walls. The angle formed by this first part and by the wall is preferably between 75 and 105°, in particular between 80 and 100°, or even between 85 and 95°. This angle is advantageously a right angle. When the wall is not planar, the angle can be measured by taking into account the plane tangent to the wall in the area from which the element extends.

In the direction of extension of the first part (transversely to the walls), the ratio between the length of this first part and the distance between the walls is preferably between 0.2 and 0.8, in particular between 0.3 and 0.7.

According to this mode, at least one, in particular each, reinforcing element can form a wing projecting with respect to the wall from which it extends. The wing may in particular have a rectangular profile.

At least one, in particular each reinforcing element, may also comprise a second linear part extending from the first part and transversely thereto. The reinforcing element may for example have a T or L profile. The ratio between the length of this second part and the distance between the walls is preferably between 0.1 and 0.7, in particular between 0.2 and 0.6. By "transversely" is not necessarily meant the angle between the first and the second part is a right angle. The angle b between the first and the second part is preferably between 70 and 110°, in particular between 80 and 100°. It can be a right angle, as in the case of elements having an L or T profile.

According to another embodiment, at least one, in particular each, reinforcing element forms a closed curve, in particular on itself, at the level of one of the walls, delimiting at least one cell. In this case, the wall element comprises several cavities: the single cavity delimited by the walls and the cells located inside the reinforcing elements.

Preferably, in order to optimize the mechanical strength of the construction element, whatever the shape of the reinforcing elements, two consecutive reinforcing elements extend from two different walls. The construction element then comprises a plurality of reinforcing elements extending alternately from each of the walls.

In the plane of one of the walls, the ratio between the distance between two consecutive reinforcing elements extending from the wall concerned and the distance between the walls is preferably between 0.5 and 10, in particular between 2 and 8.

In order to ensure a good compromise between thermal and mechanical, the number of reinforcing element per linear meter of construction element is preferably between 1 and 5, in particular between 1 and 4, or even between 2 and 3 ( terminals included).

According to another embodiment, the construction element comprises two reinforcing elements each arranged along one of the walls, and preferably over the entire length of said walls, and forming a periodic pattern, for example sinusoidal or in broken lines. , thus delimiting a plurality of cells.

In section in a plane transverse to the walls, in other words in the plane of the layers of mortar, the thickness of the walls is preferably between 10 and 200 mm, in particular between 40 and 120 mm. The thickness of the structural elements is preferably between 20 and 100 cm, in particular between 30 and 80 cm.

The lateral dimensions of the construction element are preferably between 1 and 4 m, in particular between 1 and 3 m.

The mortar preferably comprises a hydraulic binder and aggregates.

The wet mortar, of pasty consistency, is formed by mixing with water a dry mortar. By dry mortar is meant a powdery mixture. After setting and hardening, the final mortar is called hardened mortar, or “concrete”.

The hydraulic binder is preferably chosen from Portland cements, aluminous cements, sulphoaluminous cements, hydrated lime, ground granulated blast furnace slags, fly ash and mixtures thereof. The hydraulic binder preferably comprises a Portland cement. It is advantageously made of Portland cement.

The aggregates are preferably chosen from siliceous, limestone, dolomitic aggregates and mixtures of the latter. The maximum size of the aggregates is preferably at most 3 mm, in particular at most 2 mm and even at most 1 mm, taking into account the reduced section of the pumping device and of the nozzle of the head of impression.

The dry mortar preferably comprises at least one additive, chosen in particular from superplasticizers, thickeners, accelerators and retarders. The dry mortar advantageously comprises inorganic thickeners, for example swelling clays, capable of increasing the elastic limit at rest of the wet mortar. The accelerators and retarders make it possible to adjust the time required for the setting and hardening of the hydraulic binder.

The composition of the dry mortar is preferably adjusted so that the wet mortar exhibits thixotropic behavior. Preferably, the viscosity of the wet mortar increases by a factor of at least 50 only one second after the wet mortar leaves the printing nozzle. The wet mortar then exhibits low viscosity at high shear rates so that it can be easily pumped and conveyed, but exhibits an immediate increase in structural stability as soon as it leaves the print head nozzle, allowing thus to support the overlying layers before setting and hardening. This deposition on a layer of mortar that is still wet improves the adhesion between the successive layers, and therefore the final mechanical strength of the wall element. By contrast,

The method includes the successive deposition of superimposed layers of mortar. As indicated above, the layers are preferably deposited on an underlying layer which has not yet set or hardened.

The method preferably comprises a step of mixing a dry mortar composition with water in order to obtain a wet mortar, of pasty consistency. The wet mortar is preferably pumped and conveyed, usually in a pipe, to the print head of a printer. The print head notably comprises a nozzle through which the wet mortar is extruded. The printer is for example an industrial robot or a gantry, carrying the print head, and whose movement is controlled by a computer. The computer comprises in particular a recording medium in which is stored a set of data or 3D model as well as instructions, which when executed by the computer lead the latter to control the movement (trajectory, speed, etc.).

The printing speed is typically 30 to 1000 mm/s, in particular 50 to 300 mm/s. The thickness (or height, since it is a question here of the dimension in the vertical direction) of the layers of wet mortar is preferably between 5 and 40 mm, in particular between 10 and 20 mm. The width of the layers of mortar is preferably between 10 and 100 mm, in particular between 20 and 60 mm.

As explained in more detail later in the text, for each layer the printer can first lay down a strip of mortar, called the external strip, forming the outer envelope of the wall element, then an internal strip adjacent to the outer strip and in contact with it, which comprises portions parallel to the outer strip, forming with the latter the walls, and portions extending towards the cavity, forming the reinforcing elements.

Preferably, the method further comprises a step of filling the cavity (or at least part of the cavity) with an insulating material. In the case where the reinforcing elements delimit cells, the latter can also be filled with the insulating material, during the same step or a subsequent step.

The insulating material can for example be inorganic or organic.

The insulating material is advantageously chosen from mineral foams, organic foams, mineral wools, mortars comprising a mineral binder and light aggregates and insulators based on natural materials, in particular based on natural fibers (vegetable or animal).

The filling process is adapted according to the material chosen and can implement, depending on the case, the flow, the injection or even the projection of a pasty or granular material, or the projection of precursor compounds of the material, which forms in situ inside the cavity. The filling process can be implemented by a robot, if necessary by the same robot as that which performs the 3D printing.

Mineral foams are in particular silica foams or hydraulic binder-based foams, for example cement, mortar or concrete foams. The latter can in particular be obtained by mixing mortar or wet concrete with an aqueous foam. In such a case, the filling step preferably implements the flow of the mineral foam in the pasty state inside the cavity. The foam can then harden inside the cavity. The filling step can be carried out before hardening of the wall element, in particular simultaneously with the manufacture of the wall element, or after hardening of the wall element. After hardening, the mineral foam preferably has a density of less than 200 kg/m 3 ,, or even less than 100 kg/m 3 . The concrete foam may in particular be the foam marketed under the reference Airium by the company LafargeHolcim.

The organic foams are, for example, polyurethane or polyisocyanurate foams. Such foams can be formed in situ inside the cavity, the filling step then implementing the simultaneous spraying of an isocyanate compound and an alcohol inside the cavity.

The mineral wools are in particular glass wool, rock wool or even slag wool. It may in particular be blowing wool (or wool in bulk), that is to say in the form of flakes. In this case, the filling step implements the projection of said flakes inside the cavity. Mineral wools can be combined with a hydraulic binder, in particular cementitious.

Mortars comprising a mineral binder and light aggregates also make it possible to confer insulating properties. The mineral binder is preferably a hydraulic binder, for example a Portland cement. The lightweight aggregates preferably have a density of at most 200 kg/m 3 . The lightweight aggregates are preferably chosen from expanded polystyrene beads, aerogels, perlite, expanded glass beads, vermiculite, expanded clays, cork and cenospheres.

Insulators based on natural materials are in particular based on cellulosic materials (cork, wood fibres, cellulose fibres, etc.) or based on animal wool (sheep's wool, etc.).

Whatever the method used, the presence of a single cavity can simplify the filling step, allowing for example the use of a single possibly fixed filling nozzle rather than having to use either a nozzle per cavity or a mobile nozzle in front of be moved to successively fill the cavities.

When it exhibits adhesion with the mortar constituting the walls and the reinforcing elements, the insulating material can play a structural role and thus improve the mechanical properties of the construction element. This is the case, for example, when the insulating material comprises an inorganic, in particular hydraulic, binder. The method according to the invention can then comprise a step of cutting out the lateral ends of the element. It is thus possible to remove the concrete edges formed during printing and improve the thermal performance of the wall element.

The building element may also include reinforcing pieces which are not integral with the walls and which may extend between these walls. These parts can in particular be mechanically fixed to the walls after or during the manufacture of the construction element. They will preferably be made of polymeric material in order to limit thermal bridges.

The construction elements can be prefabricated elements, intended to be assembled on the construction site, for example by means of a mortar, in order to form the exterior or interior walls (for example the shear walls) of a building. The elements can also be manufactured directly on the construction site and form the complete wall of the building.

The invention and its advantages will be better understood with the aid of the following description, with reference to the appended FIGS. 1 to 10, of non-limiting examples of construction elements. These are wall elements in this case, but they could be other types of construction elements.

The wall elements exemplified here are rectangular parallelepipedic elements comprising two planar walls parallel to each other extending along an XZ plane, also called “plane of the walls”. In the present text, “plane of the walls” is qualified as any plane parallel to the plane XZ. The Y axis is the axis orthogonal to the plane of the walls. The Z axis is the axis orthogonal to the layer plane (XY plane).

Figures 1 to 10 show part of these elements in section along the XY plane in order to illustrate different examples of reinforcing elements. The ends of the elements are not shown: when printing, the ends form, for example, a return along the Y axis connecting the two walls. As indicated above, these ends can in some cases be cut out, and therefore no longer be present in the final wall element.

In all the cases shown, the reinforcing elements extend linearly, in the plane of the walls, along the Z axis (normal to the plane of the layers). In other words, the reinforcement elements are cylinders of generatrix Z. The position and shape of a reinforcement element along the X axis does not depend on the height along the Z axis. The additive manufacturing technique, however, allows slightly different designs: the reinforcement elements can for example only extend over part of the height of the walls (along the Z axis) and/or the position of the reinforcement elements along the X axis or the shape of the elements reinforcement can depend on the height along the Z axis.

In all the cases shown, the reinforcing elements are arranged periodically. However, it is possible to proceed otherwise, the additive manufacturing method being able to produce the most varied and complex geometries.

The width of the complete wall element, along the X axis, is for example between 1 and 3 m. The height of the wall element, along the Z axis, is for example between 1 and 3 m. The thickness of the wall element, along the Y axis, is for example between 20 and 100 cm, in particular between 30 and 80 cm.

[Fig. 1] illustrates part of a wall element 100 according to the prior art, which comprises a single reinforcing element 110 along a broken line forming alternately salient and re-entrant angles and connecting the two walls 120 and 130. The manufacture of this type of wall element is generally produced by printing, for a given layer, first the walls 120 and 130 (as well as the side edges not shown) then the reinforcing element 110 and repeating this step. Patent KR 10-1911404 describes a variant of this type of wall, in which this structure is doubled, the wall then comprising three walls and two zigzag reinforcement elements each connecting two opposite walls.

[Fig. 2] represents part of a wall element 1 according to one embodiment of the invention.

This element comprises a first wall 2 and a second wall 4 forming a cavity 3. In the example illustrated, the section of each wall in an XY cutting plane is formed by two adjacent strips of mortar, an outer strip 5 and a strip inner layer 6. For a given layer (a given level along the Z axis), the printer moves in the XY plane and can for example first print the outer band 5 (including the ends not shown), which forms the outer contour of the wall element, then, inside the zone defined by the outer band 5, the inner band 6. This inner band 6 comprises parts extending along the axis X, which together make part of the wall, and parts which extend from the walls in the Y direction, in other words the reinforcing elements.

The wall element comprises a plurality of reinforcing elements 21, 41 each having a T-shaped profile and extending from one of the walls 2, 4, towards the cavity 3. Each reinforcing element comprises a first linear part 21a, 41a extending from a wall 2, 4 in the YZ plane

(Orthogonal to the plane of the walls) as well as a second linear part 21b, 41b extending from the first part 21a, 41a in the XZ plane, therefore in a plane parallel to the plane of the walls.

The plurality of reinforcement elements comprises a first plurality of reinforcement elements 21 extending from the first wall 2 and a second plurality of reinforcement elements 41 extending from the second wall 4. reinforcing elements are arranged alternately, each reinforcing element of one of the first and second plurality being directly flanked by two reinforcing elements of the other plurality.

In the example shown, the transverse branches of the Ts (second parts 21b and 41b) are all in the same plane, here the median plane of the two walls, shown schematically by a dotted line.

The reinforcing elements are only in contact with the wall from which they extend. As illustrated in the figure, they are in contact neither with the other wall nor with any other reinforcing element.

[Fig .3] shows a variant, in which the transverse branches of the T are in two different planes, parallel to the planes of the walls. More precisely, the transverse branches of the reinforcing elements 21b, 41b of the first (21), respectively second (41), plurality of reinforcing elements are in a first plane, respectively second plane, parallel to the plane of the walls.

[Fig. 4] represents yet another variant, in which the transverse branches of the Ts (21b and 41b) are elongated, so that the transverse branches 21b of the first reinforcing elements 21 are partially opposite the branches 41b of the adjacent second reinforcing elements 41 .

[Fig. 5] illustrates another variant, in which the reinforcing elements 21 and 41 have an L-shaped profile. Each reinforcing element therefore comprises a first part (21a, 41a) and a second part (21b, 41b), the second part forming a return of the first part.

[Fig. 6] shows a variant in which the reinforcing elements 21 and 41 form linear flanges projecting from the walls. Each reinforcing element here comprises only a first linear part (21a, 41a), in other words has an I-shaped profile.

[Fig. 7] represents a variant in which each reinforcing element 22 and 42 forms a curve closed on itself at the level of the wall from which it extends, thereby delimiting a cell.

In the various variants presented, the reinforcing elements are arranged alternately, each reinforcing element of one of the first and second plurality being directly flanked by two reinforcing elements of the other plurality.

[Fig. 8] illustrates another embodiment in which the wall element comprises only two reinforcement elements, a first reinforcement element 22 arranged along the first wall 2, and a second reinforcement element 42 arranged along the second wall 4. The first reinforcing element 22 forms a periodic pattern, here sinusoidal, facing the second reinforcing element 42.

[Fig. 9] illustrates a variant of the embodiment of FIG. 8, in which the two periodic patterns are offset by a half-period.

In the embodiment of Figures 8 and 9, the printer can for example, in the XY plane, first print the walls 2 and 4, which form the outer contour of the wall element, then, at the inside the area defined by these walls, the reinforcing elements 22 and 42.

[Fig. 10] illustrates a variant in which the reinforcing elements 21 and 41 consist of a succession of broken lines.

Numerical simulations made it possible to compare the equivalent thermal conductivity of wall elements according to the invention (geometry of the type shown in FIG. 2) with that of a wall element according to the prior art (zigzag geometry, type of that represented in figure 1). Depending on the case, the cavities were filled with polyurethane foam (thermal conductivity of 22 mW.nr 1 .Ki 1 ) or with glass wool (thermal conductivity of 35 mW.m^.K -1 ). The hardened mortar has a thermal conductivity of 750 mW.nr 1 .Kl 1 .

In the case of the wall according to the prior art, the equivalent thermal conductivity was 200 mW.m^.K -1 with a polyurethane foam filling and 220 mW.nr 1 .K _1 with a glass wool filling .

In the case of the wall according to the invention, the equivalent thermal conductivity was respectively 100 mW.m^.K -1 and 140 mW.nr 1 .K -1 .

Claims

1. Process for obtaining a concrete construction element (1) by additive manufacturing, in which layers of superimposed mortar are successively deposited so as to form two walls (2, 4), opposite to each other. another so as to provide a cavity (3), as well as a plurality of reinforcing elements (21, 41, 22, 42) each extending from one of the walls (2, 4) towards the cavity (3 ), each reinforcing element (21, 41, 22, 42) being in contact neither with the wall (2, 4) opposite that from which it extends nor with a reinforcing element (21, 41, 22 , 42) extending from the opposite wall (2, 4) to that from which it extends.

2. Method according to claim 1, such that the building element (1) is a wall element.

3. Method according to one of the preceding claims, wherein at least one reinforcing element (21, 41) comprises a first part (21a, 41a) extending linearly from one of the walls and transversely to said walls (2, 4).

4. Method according to the preceding claim, wherein at least one reinforcing element (21, 41) further comprises a second linear part (21b, 41b) extending from the first part (21a, 41a) and transversely thereto. this.

5. Method according to the preceding claim, in which at least one reinforcing element (21, 41) has a T or L profile.

6. Method according to one of the preceding claims, wherein two consecutive reinforcing elements (21, 41) extend from two different walls (2, 4).

7. Method according to the preceding claim, such that in the plane of a wall (21, 41), the ratio between the distance between two consecutive reinforcing elements (21, 41) extending from this wall and the distance between the walls (2, 4) is preferably between 0.5 and 10, in particular between 2 and 8.

8. Method according to one of claims 6 or 7, such that the number of reinforcing element per linear meter of construction element is between 1 and 5, in particular between 1 and 4.

9. Method according to one of the preceding claims, further comprising a step of filling the cavity with an insulating material.

10. Method according to the preceding claim, in which the insulating material is chosen from mineral foams, organic foams, mineral wools, mortars comprising a mineral binder and light aggregates and insulators based on natural materials.

11. Method according to one of the preceding claims, such that each reinforcing element (21, 41, 22, 42) is only in contact with the wall (2, 4) from which it extends, and the if necessary with an insulating material filling the cavity (3).

12. Method according to one of the preceding claims, such that the construction element (1) comprises only a single cavity (3).

13. Method according to one of claims 1, 2, 9 or 10, such that the construction element (1) comprises two reinforcing elements (22, 42) each arranged along one of the walls (2, 4 ) and forming a periodic pattern, for example sinusoidal or in broken lines, thus delimiting a plurality of cells.

14. Concrete construction element (1) obtainable according to the method of one of the preceding claims, comprising two walls (2, 4), opposite to each other so as to form a cavity ( 3), as well as a plurality of reinforcing elements (21, 41, 22, 42) made of material with said walls (2, 4) and each extending from one of the walls (2, 4) towards the cavity (3), each reinforcing element (21, 41, 22, 42) being in contact neither with the wall (2, 4) opposite to that from which it extends nor with a reinforcing element (21 , 41, 22, 42) extending from the opposite wall (2, 4) to that from which it extends.

15. Concrete construction element (1) according to the preceding claim, the cavity (3) of which is filled with an insulating material.