ADDITIVE MANUFACTURING OF CONCRETE CONSTRUCTION ELEMENTS

Abstract

A method for obtaining a concrete construction element by additive manufacturing, in which superposed mortar layers are successively deposited so as to form two wall surfaces, opposite one another, so as to form a cavity, as well as a plurality of reinforcement elements each extending from one of the wall surfaces toward the cavity, each reinforcement element being in contact with neither the wall surface opposite to that from which it extends, nor with a reinforcement element extending from the opposite wall surface to that from which it extends.

Claims

1. A method for obtaining a concrete construction element by additive manufacturing, the method comprising successively depositing superposed mortar layers so as to form two wall surfaces, opposite one another, so as to form a cavity, as well as a plurality of reinforcement elements each extending from one of the two wall surfaces toward the cavity, each reinforcement element being in contact with neither the wall surface opposite to that from which it extends, nor with a reinforcement element extending from the opposite wall surface to that from which it extends.

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

3. The method according to claim 1, wherein at least one of the plurality of reinforcement elements comprises a first part extending linearly from one of the wall surfaces and transversely to said wall surfaces.

4. The method according to claim 3, wherein at least one of the plurality of reinforcement elements further comprises a second linear part extending from the first part and transversely thereto.

5. The method according to claim 4, wherein at least one of the plurality of reinforcement elements has a T-shaped or L-shaped profile.

6. The method according to claim 1, wherein two consecutive reinforcement elements extend from two different wall surfaces.

7. The method according to claim 6, wherein, in a plane of a wall surface, a ratio of the distance between two consecutive reinforcement elements extending from said wall surface to a distance between the wall surfaces is between 0.5 and 10.

8. The method according to claim 6, wherein a number of reinforcement elements per linear meter of construction element is between 1 and 5.

9. The method according to claim 1, further comprising filling the cavity with an insulating material.

10. The method according to claim 9, wherein the insulating material is selected from mineral foams, organic foams, mineral wools, mortars comprising a mineral binder and lightweight aggregates and insulators based on natural materials.

11. The method according to claim 1, wherein each reinforcement element is only in contact with the wall surface from which it extends, and where appropriate with an insulating material which fills the cavity.

12. The method according to claim 1, wherein the construction element only comprises a single cavity.

13. The method according to claim 1, wherein the construction element comprises two reinforcement elements each arranged along one of the two wall surfaces and forming a regular pattern, thereby delimiting a plurality of cells.

14. A concrete construction element capable of being obtained according to the method of claim 1, comprising two wall surfaces, opposite one another, so as to form a cavity, as well as a plurality of reinforcement elements produced integrally with said two wall surfaces and each extending from one of the two wall surfaces toward the cavity, each reinforcement element being in contact with neither the wall surface opposite to that from which it extends, nor with a reinforcement element extending from the opposite wall surface to that from which it extends.

15. The concrete construction element according to claim 14, the cavity of which is filled with an insulating material.

16. The method according to claim 7, wherein the ratio is between 2 and 8.

17. The method according to claim 8, wherein the number of reinforcement elements per linear meter of construction element is between 1 and 4.

18. The method according to claim 13, wherein the regular pattern is sinusoidal or broken lines.

19. The method according to claim 1, wherein each reinforcement element forms a closed curve, delimiting at least one cell.

20. The method according to claim 19, wherein the curve is closed on itself at one of the two wall surfaces.

Description

[0041] As explained in greater detail in the remainder of the text, for each layer the printer can first deposit a strip of mortar, referred to as outer strip, forming the outer envelope of the wall element, then an inner strip adjacent to the outer strip and in contact therewith, which comprises portions parallel to the outer strip, forming, with said outer strip, the wall surfaces, and portions extending toward the cavity, forming the reinforcement elements.

[0042] 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 in which the reinforcement elements delimit cells, said cells can also be filled with the insulating material, during the same step or a subsequent step.

[0043] The insulating material may for example be mineral or organic.

[0044] The insulating material is advantageously selected from mineral foams, organic foams, mineral wools, mortars comprising a mineral binder and lightweight aggregates and insulators based on natural materials, especially based on natural fibers (plant or animal fibers).

[0045] The filling method is adapted based on the selected material and may be carried out, depending on the case, by pouring, injecting or else spraying a pasty or granular material, or spraying precursor compounds of the material, which forms in situ inside the cavity. The filling method may be carried out by a robot, where appropriate by the same robot as that which carries out the 3D printing.

[0046] The mineral foams are especially silica foams or foams based on hydraulic binder, for example cement, mortar or concrete foams. These may especially be obtained by mixing wet concrete or mortar with an aqueous foam. In such a case, the filling step is preferably carried out by pouring the mineral foam in the pasty state into the cavity. The foam can subsequently harden inside the cavity. The filling step can be carried out before hardening of the wall element, especially simultaneously to 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.sup.3, especially less than 150 kg/m.sup.3, or even less than 100 kg/m.sup.3. The concrete foam may especially be the foam sold under the reference Airium by LafargeHolcim.

[0047] The organic foams are for example polyurethane or polyisocyanurate foams. Such foams may be formed in situ inside the cavity, with the filling step then being carried out by the simultaneous spraying of an isocyanate composition and an alcohol into the cavity.

[0048] The mineral wools are especially glass wools, rock wools or else slag wools. They may especially be blowing wools (or loose wool), i.e. be in the form of flakes. In this case, the filling step is carried out by spraying said flakes into the cavity. The mineral wools may be combined with a hydraulic binder, especially a cementitious binder.

[0049] The mortars comprising a mineral binder and lightweight 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.sup.3. The lightweight aggregates are preferably selected from expanded polystyrene beads, aerogels, perlite, expanded glass beads, vermiculite, expanded clays, cork and cenospheres.

[0050] The insulators based on natural materials are especially based on cellulosic materials (cork, wood fibers, cellulose fibers, etc.) or based on animal wools (sheep's wool, etc.).

[0051] Regardless of the method employed, the presence of a single cavity can simplify the filling step, making it possible for example to use a single, optionally stationary, filling nozzle, rather than having to use either one nozzle per cavity or a mobile nozzle which has to be moved in order to successively fill the cavities.

[0052] When it adheres to the mortar constituting the wall surfaces and the reinforcement elements, the insulating material may have a structural function and thus improve the mechanical properties of the construction element. This is the case for example when the insulating material comprises a mineral binder, especially a hydraulic mineral binder. The method according to the invention may then comprise a step of cutting off the lateral ends of the element. It is then possible to remove the concrete edges formed during the printing and to improve the thermal performance of the wall element.

[0053] The construction element may also comprise reinforcing pieces which are not integral with the wall surfaces and which may extend between these wall surfaces. These pieces may especially be mechanically attached to the wall surfaces after or during the manufacture of the construction element. They will preferably be made of polymeric material in order to limit thermal bridges.

[0054] The construction elements may be prefabricated elements, intended to be assembled on the building site, for example by means of a mortar, in order to form the external or internal walls (for example interior load-bearing walls) of a building. The elements may also be manufactured directly on the building site and form the complete wall of the building.

[0055] The invention and the advantages thereof will be better understood using the following description, with reference to the appended FIGS. 1 to 10, of nonlimiting examples of construction elements. In the case in point, these are wall elements, but they could be other types of construction elements.

[0056] The wall elements exemplified here are rectangular parallelepipedal elements comprising two planar wall surfaces which are parallel with one another and extend along a plane XZ, also referred to as plane of the wall surfaces. In this text, plane of the wall surfaces is defined as any plane parallel to the plane XZ. The Y axis is the axis orthogonal to the plane of the wall surfaces. The Z axis is the axis orthogonal to the plane of the layers (plane XY).

[0057] FIGS. 1 to 10 depict part of these elements in section along the plane XY in order to illustrate different examples of reinforcement elements. The ends of the elements are not shown: during printing, the ends form for example a return along the Y axis connecting the two walls. As indicated above, these ends may in some cases be cut off, and therefore no longer be present in the final wall element.

[0058] In all the cases shown, the reinforcement elements extend linearly, in the plane of the wall surfaces, along the Z axis (normal to the plane of the layers). In other words, the reinforcement elements are cylinders with the generatrix Z. The position and the shape of a reinforcement element along the X axis does not depend on the height along the Z axis. Nevertheless, the technique of additive manufacturing allows for slightly different designs: the reinforcement elements may for example only extend over a part of the height of the wall surfaces (along the Z axis) and/or the position of the reinforcement elements along the X axis or the shape of the reinforcement elements may depend on the height along the Z axis.

[0059] In all the cases shown, the reinforcement elements are arranged regularly. It is nevertheless possible to proceed differently, since the additive manufacturing method is able to produce highly varied and highly complex geometries.

[0060] 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, especially between 30 and 80 cm.

[0061] FIG. 1 illustrates a part of a wall element 100 according to the prior art, which comprises a single reinforcement element 110 along a broken line forming alternately protruding and recessed angles and connecting the two walls 120 and 130. This type of wall element is generally manufactured by printing, for a given layer, first the wall surfaces 120 and 130 (and also the lateral edges, not shown), then the reinforcement element 110, and repeating this step. Patent KR 10-1911404 describes a variant of this type of wall, in which the structure is doubled; the wall then comprising three wall surfaces and two zigzag reinforcement elements each connecting two opposite wall surfaces.

[0062] FIG. 2 shows a part of a wall element 1 according to an embodiment of the invention.

[0063] This element comprises a first wall surface 2 and a second wall surface 4, housing a cavity 3. In the example shown, the section of each wall surface in a sectional plane XY is formed by two adjacent mortar strips: an outer strip and an inner strip 6. For a given layer (a given level along the Z axis), the printer moves in the plane XY and may for example first print the outer strip 5 (including the ends, not shown), which forms the outer contour of the wall element, then, inside the area defined by the outer strip 5, the inner strip 6.

[0064] This inner strip 6 comprises parts extending along the X axis, which together form part of the wall surface, and parts which extend from the wall surfaces in the direction Y, in other words the reinforcement elements.

[0065] The wall element comprises a plurality of reinforcement elements 21, 41, each having a T-shaped profile and extending from one of the wall surfaces 2, 4, toward the cavity 3. Each reinforcement element comprises a first linear part 21a, 41a extending from a wall surface 2, 4 in the plane YZ (orthogonal to the plane of the wall surfaces) and also a second linear part 21b, 41b extending from the first part 21a, 41a in the plane XZ, thus in a plane parallel to the plane of the wall surfaces.

[0066] The plurality of reinforcement elements comprises a first plurality of reinforcement elements 21 extending from the first wall surface 2 and a second plurality of reinforcement elements 41 extending from the second wall 4. The reinforcement elements are arranged alternately, each reinforcement element from one of the first and the second plurality being directly surrounded by two reinforcement elements of the other plurality.

[0067] In the example depicted, the transverse arms of the T (second parts 21b and 41b) are all in the same plane, here the mid plane between the two wall surfaces, schematically depicted by a dashed line.

[0068] The reinforcement elements are only in contact with the wall surface from which they extend. As shown in the figure, they are not in contact either with the other wall surface or with any other reinforcement element.

[0069] FIG. 3 depicts a variant in which the transverse arms of the T are in two different planes, parallel to the planes of the wall surfaces. More specifically, the transverse arms of the reinforcement elements 21b, 41b of the first (21), or second (41), respectively, plurality of reinforcement elements are in a first plane, or a second plane, respectively, parallel to the plane of the wall surfaces.

[0070] FIG. 4 depicts yet another variant in which the transverse arms of the T (21b and 41b) are elongated, such that the transverse arms 21b of the first reinforcement element 21 are partially facing the arms 41b of the second, adjacent, reinforcement elements 41.

[0071] FIG. 5 depicts another variant, in which the reinforcement elements 21 and 41 have an L-shaped profile. Each reinforcement element thus comprises a first part (21a, 41a) and a second part (21b, 41b), the second part forming a return of the first part.

[0072] FIG. 6 depicts a variant in which the reinforcement elements 21 and 41 form linear fins protruding from the wall surfaces. Each reinforcement element comprises here only a first linear part (21a, 41a), in other words has an I-shaped profile.

[0073] FIG. 7 depicts a variant in which each reinforcement element 22 and 42 forms a curve which is closed on itself at the wall surface from which it extends, thereby delimiting a cell.

[0074] In the various variants presented, the reinforcement elements are arranged alternately, each reinforcement element from one of the first and the second plurality being directly surrounded by two reinforcement elements of the other plurality.

[0075] FIG. 8 shows another embodiment in which the wall element only comprises two reinforcement elements, a first reinforcement element 22 arranged along the first wall surface 2, and a second reinforcement element 42 arranged along the second wall 4. The first reinforcement element 22 forms a regular pattern, in this case sinusoidal, facing the second reinforcement element 42.

[0076] FIG. 9 shows a variant of the embodiment of FIG. 8, in which the two regular patterns are offset by half a period.

[0077] In the embodiment of FIGS. 8 and 9, the printer may, for example, in the plane XY, first print the wall surfaces 2 and 4 which form the outer contour of the wall element, then, inside the area defined by these wall surfaces, the reinforcement elements 22 and 42.

[0078] FIG. 10 shows a variant in which the reinforcement elements 21 and 41 consist of a succession of broken lines.

[0079] Digital simulations made it possible to compare the equivalent thermal conductivity of wall elements according to the invention (geometry of the type depicted in FIG. 2) with that of a wall element according to the prior art (zigzag geometry of the type depicted in FIG. 1). Depending on the case, the cavities were filled with a polyurethane foam (thermal conductivity of 22 mW.Math.m.sup.1.Math.K.sup.1) or with glass wool (thermal conductivity of 35 mW.Math.m.sup.1.Math.K.sup.1). The hardened mortar has a thermal conductivity of 750 mW.Math.m.sup.1.Math.K.sup.1.

[0080] In the case of the wall according to the prior art, the equivalent thermal conductivity was 200 mW.Math.m.sup.1.Math.K.sup.1 with polyurethane foam filling, and 220 mW.Math.m.sup.1.Math.K.sup.1 with glass wool filling.

[0081] In the case of the wall according to the invention, the equivalent thermal conductivity was 100 mW.Math.m.sup.1.Math.K.sup.1 and 140 mW.Math.m.sup.1.Math.K.sup.1, respectively.