Manufacturing apparatus and method for anisotropic fiber-reinforced concrete

Abstract

The method for manufacturing anisotropic fiber-reinforced concrete is notable in that the mortar structure is extruded with high-density, small-diameter fibers (9) arranged along the longitudinal direction of the structure.

Description

Technology Field

[0001] The present invention relates to an apparatus and method for manufacturing anisotropic fiber-reinforced concrete. Background Technology

[0002] As is generally known, fiber-reinforced concrete is cement or clay mortar reinforced with metal, vegetable, mineral, or synthetic fibers.

[0003] As is known by itself, even the addition of a very small amount of fiber to the mortar can improve the mechanical properties of the final concrete (nearly isotropy), particularly its resistance to shear force and cracking.

[0004] Also, as is well known, mortar can be locally reinforced by slender and oriented elements, steel, or composite rods, wires, electrical wires, etc., and the manufactured concrete can be imparted enhanced resistance to tensile force, preventing failure after the first crack caused by tensile force.

[0005] The present invention aims to provide an apparatus and method for manufacturing anisotropic fiber-reinforced concrete with improved mechanical properties compared to conventional technology.

[0006] The object of the present invention can be achieved by an extrusion additive manufacturing device for anisotropic fiber concrete comprising a multi-axis robot having a head equipped with an extrusion assembly including an extrusion nozzle for extruding a mortar comprising continuous fibers arranged in the longitudinal direction.

[0007] Due to these characteristics, continuous fibers within the mortar can be oriented in a desired direction to obtain an optimal fiber arrangement, and excellent resistance, particularly to tensile force, can be imparted to the final concrete structure.

[0008] According to the conventional technology of mixing and stirring fibers in a mortar batch before molding or extrusion, the fibers are randomly oriented, making it impossible to orient the fibers in a desired direction, and the maximum fiber ratio in the vertical cross-section of the structure was limited to 3% (if it exceeds 3%, the fibers clump together or a system error occurs). However, according to the extrusion principle of the concrete structure of the present invention, the fibers within the structure are oriented in the longitudinal direction, and a high fiber ratio in the vertical cross-section of the structure, typically 5 to 10% or more, can be obtained.

[0009] The continuous and mass introduction of fibers with diameters of tens of micrometers, distinct from typical millimeter-diameter fibers, enables the production of entirely different materials. These fiber / matrix assemblies allow for mechanical performance similar to existing composite materials, such as carbon and epoxy, in that bimaterials can be considered homogeneous at a specific scale, as they possess identical mechanical properties at all points of the tissue's cross-section.

[0010] This is because numerous fibers distributed nearly uniformly within the organization enable optimal force distribution, and while the numerous fibers absorb tensile force, the precise distribution of the matrix is ​​ensured by shear force.

[0011] This does not apply to structures that are reinforced by a small number of reinforcing elements (e.g., bars, fiber bundles) having a large cross-sectional area, where the characteristics of the reinforcing elements are more prominent than the characteristics of the mortar.

[0012] Therefore, this improved fiber distribution allows microcracks to be better dispersed, thereby preventing the formation of large macrocracks perpendicular to the hardened tissue. Furthermore, the improved fiber distribution allows for significantly different resistance to the tissue during the process (rheologically, in a new state), for example in additive manufacturing processes (dieless), as the mortar is better "held" thanks to the fibers favorable for deposition.

[0013] In addition, small-diameter fibers are easy to move with the mortar during the extrusion process because the contact surface with the mortar and the ratio of mass to stiffness with the mortar are favorable. Therefore, situations requiring high power to drive cables or thick fiber bundles can be easily avoided.

[0014] Finally, using fibers with a small diameter and low bending stiffness provides improved workability to the organization, for example, in that they can bend more during the lamination process.

[0015] In addition, the present invention relates to an apparatus comprising an extrusion assembly and a mortar mixer located on the upstream side of an extrusion nozzle.

[0016] In addition, the present invention relates to a device comprising an extrusion assembly including a bottleneck located between a mortar mixer and an extrusion nozzle.

[0017] In addition, the present invention relates to an apparatus comprising means for an extrusion assembly to inject a hardening accelerating additive into a mortar.

[0018] In addition, the present invention relates to a device comprising an injection head positioned between a mortar mixer and a bottleneck portion for injecting a hardening-promoting additive.

[0019] In addition, the present invention relates to an extrusion nozzle comprising a radial bridge having an orifice formed therein for guiding fibers.

[0020] In addition, the present invention relates to a device comprising an extrusion nozzle and a peripheral orifice for guiding a fiber.

[0021] In addition, the present invention relates to a device comprising a magazine having a coil on which a fiber is wound, and a guide member for guiding the fiber from the coil to an extrusion nozzle.

[0022] In addition, the present invention relates to an extrusion-type additive manufacturing device for anisotropic fiber concrete according to the present invention, and to equipment including a system for supplying and pumping mortar to a mixer.

[0023] In addition, the present invention relates to an extrusion additive manufacturing method using an extrusion additive manufacturing device for anisotropic fiber concrete according to the present invention, wherein the fiber is guided into the interior of the mortar by the adhesion between the fiber and the mortar.

[0024] In addition, the present invention relates to an extrusion additive manufacturing method using an extrusion additive manufacturing device for anisotropic fiber concrete according to the present invention, wherein surface treatment and / or mechanical treatment is applied to the fibers before they are extruded together with mortar.

[0025] In addition, the present invention relates to an extrusion additive manufacturing method using an extrusion additive manufacturing device for anisotropic fiber concrete according to the present invention, wherein fibers with low bending stiffness are guided into the interior (or center; heart) of the mortar.

[0026] In addition, the present invention relates to an extrusion additive manufacturing method using an extrusion additive manufacturing device for anisotropic fiber concrete according to the present invention, wherein fibers with high bending stiffness are guided to the periphery of the mortar.

[0027] In addition, the present invention relates to an extrusion additive manufacturing method using an extrusion additive manufacturing device for anisotropic fiber concrete according to the present invention, wherein the fiber is selected from the group comprising carbon, metal, glass, basalt, polymer, single or bundled fibers.

[0028] In addition, the present invention relates to an extrusion additive manufacturing method using an extrusion additive manufacturing device for anisotropic fiber concrete according to the present invention, characterized in that, by injecting a hardening accelerating additive, the shear threshold of the mortar is increased by at least 6 times at the end of the extrusion nozzle compared to the area where the hardening accelerating additive is injected. Brief explanation of the drawing

[0029] Other features and advantages of the present invention will become clear by referring to the following description and the accompanying drawings. FIG. 1 is an overall perspective view of the equipment according to the present invention. FIG. 2 is a cross-sectional view of an extrusion assembly according to one embodiment of the present invention. Figure 3 is a side view of the extrusion nozzle of the extrusion assembly of Figure 2. Figure 4 is a perspective view of the extrusion nozzle of Figure 3. Figure 5 is a cross-sectional view along the VV line of the extrusion nozzle of Figure 3. Figure 6 is a drawing similar to Figure 2, showing the process of extruding a mixture of mortar and fibers. Figure 7 is a cross-sectional view of concrete extruded from an extrusion assembly according to Figure 2. FIG. 8 is a cross-sectional view of an extrusion assembly according to one embodiment of the present invention. Figure 9 is a side view of the extrusion nozzle of the extrusion assembly of Figure 8. Fig. 10 is a perspective view of the extrusion nozzle of Fig. 8. Figure 11 is a cross-sectional view along the line XI-XI of the extrusion nozzle of Figure 9. FIG. 12 is a drawing showing the process of extruding a mixture of mortar and fibers in an extrusion assembly according to FIG. 8. FIG. 13 is a cross-sectional view of concrete extruded from an extrusion assembly according to FIG. 8. FIG. 14 is a schematic diagram showing the addition of an additive to the extrusion assembly. Specific details for implementing the invention

[0030] In all drawings, identical or similar components or sets of components have been assigned identical or similar drawing numbers.

[0031] Referring to FIG. 1, FIG. 1 illustrates equipment for manufacturing fiber-reinforced concrete according to the present invention.

[0032] As illustrated in FIG. 1, the equipment according to the present invention includes a commercially available 6-axis robot (1, 6-axis robot), manufactured, for example, by ABB.

[0033] The head (3) of the 6-axis robot (1) is equipped with a device according to the present invention. The device according to the present invention is supplied on one side by a mortar pump (7) and on the other side by a continuous fiber (9) that comes out of a coil (11) installed in a magazine (13) and is guided by a plurality of guide members (15a, 15b, 15c).

[0034] Continuous fibers can be formed from, for example, carbon, metal, glass, basalt, polymers, or combinations thereof. Continuous fibers have small diameters in the micrometer range, smaller than millimeters (except for metals, which can be up to 100 micrometers). These fibers are typically bundled in the thousands to form a cluster, which can constitute a diameter in the millimeter range.

[0035] The coil (11) may be rotated only by the traction of the fiber (11), or may be rotated by motor drive.

[0036] Referring to FIG. 2, FIG. 2 shows an extrusion assembly (5) of a device according to one embodiment of the present invention.

[0037] In FIG. 2, the direction of circulation of the mortar and fibers is indicated by arrow F. Hereinafter, the terms "upstream" and "downstream" will be understood based on arrow F.

[0038] The embodiment illustrated in FIG. 2 is particularly suitable for fibers (9) that have relative stiffness, that is, have high resistance to flexural stresses. These sufficiently stiff fibers are well fixed in position relative to each other, penetrate well into the tissue, and are evenly distributed in the cross-section of the tissue including the central part. An apparatus suitable for more flexible fibers is described later with reference to FIGS. 8 through 13.

[0039] The extrusion assembly (5) is formed in a cylindrical shape and includes a mortar mixer (17) on the upstream side, which is equipped with a mixing impeller (19) that is rotated by a motor (not shown) inside. The mixer (17) extends to a conical bottleneck (21) located on the downstream side of the mixer (17).

[0040] The bottleneck (21) extends to an extrusion nozzle (23) located downstream of the bottleneck (21). The lower part of the extrusion nozzle (23) is formed in a cylindrical shape with a diameter smaller than that of the mixer (17).

[0041] As illustrated in FIGS. 2 to 5, the extrusion nozzle (23) has a peripheral protrusion (25) located on the upstream side of the extrusion nozzle (23). The peripheral protrusion (25) is provided with peripheral orifices (27) that are regularly distributed in the circumferential and axial directions.

[0042] As shown in FIG. 6, these peripheral orifices (27) are provided to receive fibers (9) coming from coils (11) arranged in the magazine (13) shown in FIG. 1.

[0043] The operating mode of the equipment according to the present invention is derived directly from the foregoing description.

[0044] This equipment enables the production of anisotropic fiber-reinforced concrete structures coming out of the extrusion nozzle (23) by extrusion.

[0045] The robot (1) moves the end (29) of the extrusion nozzle (23) to an area where the fiber-reinforced concrete structure is to be deposited. The area may be, for example, a location where a concrete wall is to be manufactured through a deposition process, that is, through the superposition of fiber-reinforced concrete structures.

[0046] Mortar (e.g., a mixture of cement or clay containing aggregate) is introduced into a mortar pump (7), sent to a mixer (17) of an extrusion assembly (5), and mixed by an impeller (19).

[0047] If necessary, various additives to adjust the physical and / or chemical properties of the mortar may be added to the mortar in the mixer (17), particularly to ensure perfect compatibility and adhesion with the fiber (9).

[0048] The parameters of stirring the mortar in the mixer (17) (time, speed, etc.) are adjusted to match the rheological characteristics of the mortar, such as the target appropriate viscosity and shear threshold.

[0049] And, the mortar is pressed into the bottleneck (21) by the impeller (19), and the mortar is provided with a shear force that contributes to the good homogeneity of the mixture.

[0050] When the mortar reaches the nozzle (23), the mortar comes out of the coil (11) and meets the fiber (9) guided into the interior of the surrounding orifice (27) by the guide members (15a, 15b, 15c).

[0051] Advantageously, during the manufacturing process of the fiber or during the process in which the fiber is unwound from the coil (11) and reaches the surrounding orifice (27), various physicochemical treatments (surface attack, pre-impregnation, etc.) or mechanical treatments (tensioning, taking up play, etc.) may be applied to the fiber, including single fibers, threads, wires, or bundles of threads or wires of small diameter (i.e., in micrometers), to optimize the adhesion between the fiber and the mortar.

[0052] By performing the above treatment, the mortar can move and circulate together with the fibers (9) within the extrusion nozzle (23). The characteristics of the nozzle (length, inner diameter, etc.) are determined so that the mortar can have a shear threshold sufficient to offset the relative velocity of the fibers of the mortar.

[0053] It should be understood that the fibers can move together with the mortar only by the adhesive force of the fibers (9) to the mortar.

[0054] Accordingly, the structure of fiber-reinforced concrete can be obtained at the outlet of the end (29) of the nozzle (23), and the general cross-section is shown in FIG. 7. In the embodiment shown in FIG. 7, the fibers (9) are uniformly distributed throughout the cross-section of the matrix (31) of the mortar that hardens after a specific time.

[0055] Generally, unlike conventional anisotropic fiber-reinforced concrete, where the fiber ratio in the cross section is difficult to exceed 3% and the fibers are distributed more randomly, according to the method of extruding mortar with continuous fibers (9) according to the present invention, the fiber ratio aligned along the axial direction of the structure relative to the matrix (31) in the cross section can be 5 to 10% or more. Accordingly, the density of aligned fibers in concrete is improved compared to conventional technology, and as a result, the structure of the anisotropic mortar can have different mechanical properties and improved performance in the direction in which the structure is formed rather than in the transverse direction.

[0056] Theoretically, a greater fiber density can be obtained, except for the physical limit that the distance between fibers cannot be smaller than the largest aggregate contained in the mortar and that the distance between fibers must be minimized to improve fiber density.

[0057] Various variables can be adjusted, for example, the mixing time and speed of the mortar in the mixer (17), the geometric shape of the bottleneck (21), the density and geometric distribution of the surrounding orifice (27), the diameter and length of the nozzle (23), the characteristics and amount of additives added to the mortar, the properties of the fibers (9), and the characteristics of the treatment applied to the fibers (9), so that the concrete structure obtained at the outlet of the extrusion nozzle (23) can have the desired physical and chemical properties (especially rheological properties).

[0058] The ratio between the cross-section of the extrusion nozzle (23) and the cross-section of the fiber (9) characterizes the density of the fiber in the desired matrix (31).

[0059] FIGS. 8 to 13 illustrate an extrusion assembly (5) of a device according to another embodiment of the present invention suitable for fibers that are relatively flexible, i.e., have low bending stiffness.

[0060] According to one embodiment of the present invention, an orifice (21) for guiding the fiber (9) is formed in the radial bridge (33). As a result, the fibers are distributed radially from the outer edge to the center of the extrusion nozzle (23), and a matrix (31) of mortar in which the fibers are arranged like rays of sunlight can be obtained as shown in FIG. 13. Such a device enables improved guidance compared to the device shown in FIG. 4 through 6 for harder fibers. The distribution of the orifice in the radial bridge (33) enables the flexible fibers to penetrate the center of the mortar structure (the mortar moves through the white triangular empty space between the radial bridges (33) shown in FIG. 11), and prevents the fibers from being pushed outward by the flow of the mortar (which may occur in the device shown in FIG. 4 through 10).

[0061] As can be understood from the above perspective, according to the present invention, fibers are perfectly distributed in the longitudinal direction, so that a fiber-reinforced concrete structure having adjustable physicochemical properties can be obtained before setting the mortar according to the application in which the mortar is used.

[0062] When the mortar hardens, it has properties similar to a composite of the matrix and, in particular, the geometrically arranged fibers, allowing for the formation of an anisotropic fiber-reinforced concrete structure with significantly improved resistance to various stresses (especially tensile stresses) compared to fiber-reinforced concrete according to conventional technology.

[0063] In particular, according to the present invention, the risk of cracking in anisotropic fiber-reinforced concrete can be significantly limited.

[0064] Referring to FIG. 14, a hardening accelerating additive (34) may be added to the mortar (31) before the mortar is applied through the end (29) in the extrusion assembly (5) so that the mortar (31) may set quickly after being applied to the support (36). The support (36) may be, for example, a previously applied mortar structure.

[0065] Under these conditions, by adding an accelerator that enables the deposition process to be performed at an appropriate speed, the mortar applied by the nozzle (23) on the mortar previously applied by the same nozzle can be supported on the already positioned mortar.

[0066] The addition of the additive (34) enables the creation of a mortar at the end (29) that is flexible enough to be slightly broken or compressed on a support (36) that is nearly perpendicular to the nozzle (23). The support (36) may be a layer previously applied by 3D printing.

[0067] This low concentration allows for a larger or smaller angle between the nozzle and the support during application, and prevents the application from bending due to additional rotation around the axis of the nozzle. This additional rotation may be necessary when the tissue coming out of the end (29) has a high concentration, thereby having a shape that is complementary to the shape of the nozzle. If no additive is added at the height of the head (39), the material coming out of the outlet of the mixer (17) must have a high concentration to enable the deposition of layers, which does not allow for breakage during the application process.

[0068] As illustrated in FIG. 14, according to the 3D printing process, the nozzle (23) has a direction nearly perpendicular to the support (36) and moves in a direction parallel to the support (36). The fact that the nozzle (23) produces a flexible material ensures proper application of the tissue. In addition, the fact that the material contains an additive (34) ensures proper and rapid production of a rigid support that forms a stable base for accepting other mortar tissues.

[0069] That is, by adding an additive, a mortar can be used that is very flexible at the moment it comes out of the nozzle (23) and is guaranteed to harden quickly after application.

[0070] In fact, the additive (34) is added as late as possible so that the mortar is flexible when it comes out of the nozzle but hardens quickly after application.

[0071] As such, as illustrated in FIG. 14, the additive (34) is added directly to the mortar (31) from the extrusion assembly (5). The additive (34) is contained within a receiver (37) that can be supported by the extrusion assembly (5) and is injected into the mortar (31) from the downstream side of the mixer (17) and the upstream side of the bottleneck (21). In practice, the additive (34) is transferred from the receiver (37) to the mortar (31) through a duct (38) located inside the mortar (31), and an injection head (39) is mounted at one end to ensure the diffusion of the additive in the flow of the mortar (31) coming out of the mixer (17) and moving to the bottleneck (21).

[0072] The fact that the injection head (39) is elevated relative to the liquid mortar (31) enables the fibers (9) that are subsequently guided to be impregnated more effectively. This constitutes an important condition for the mechanical function of the anisotropic concrete, and impregnation is most effective when the mortar is in a liquid state.

[0073] The fact that a mortar whose viscosity increases rapidly after passing through the injection head (39) by the addition of an accelerator is used ensures a significant shear force between the mortar and the fiber, thereby enabling the fiber (9) to be pulled by the flow of the mortar (31) and allowing the coil to be unwound without the help of an external device.

[0074] In fact, the mortar has a viscosity with a shear threshold of approximately 100 Pa when it reaches the height of the injection head (39), and the viscosity of the mortar increases to a viscosity with a shear threshold between approximately 600 Pa and 1000 Pa at the end (29) of the nozzle (23), for example, when the nozzle has a length of 10 cm. The shear threshold at the end (29) decreases as the nozzle (23) lengthens and the distance over which the fibers are pulled by the mortar increases.

[0075] More generally, the properties of the mortar, the accelerating additive, and the flow rate of the mortar are advantageously adjusted so that the shear threshold between the area where the additive is injected and the end (29) of the nozzle (23) increases by at least 6 times. Explanation of the symbols

[0076] 1: Multi-axis robot 3: Head 5: Extrusion Assembly 7: Mortar Pump 9: Fiber 11: Coil 13: Magazine 15a, 15b, 15c: Absence of guidance 17: Mixer 19: Mixing impeller 21: Bottleneck 23: Compression nozzle 25: Peripheral protrusion 27: Peripheral orifice 29: End 31: Matrix 33: Radial bridge 34: Curing accelerator 36: Support 37: Receptor 38: Duct 39: Head

Claims

Claim 1 An extrusion additive manufacturing method for anisotropic fiber-reinforced concrete comprising a multi-axis robot (1) having a head (3) equipped with an extrusion assembly (5) including an extrusion nozzle (23) for extruding a mortar (31) containing continuous fibers (9) arranged in the longitudinal direction and means for injecting a hardening accelerating additive (34) into the mortar (31), wherein, upon injection of the hardening accelerating additive (34), the shear threshold of the mortar (31) is increased by at least 6 times at the end (29) of the extrusion nozzle (23) compared to the area where the hardening accelerating additive (34) is injected. Claim 2 A method for extrusion lamination of anisotropic fiber-reinforced concrete, characterized in that, in claim 1, the extrusion assembly (5) includes a mortar mixer (17) located upstream of the extrusion nozzle (23). Claim 3 In claim 2, the extrusion assembly (5) is characterized by including a bottleneck (21) located between the mortar mixer (17) and the extrusion nozzle (23), in an extrusion lamination method for anisotropic fiber-reinforced concrete. Claim 4 delete Claim 5 In claim 3, the means for injecting the hardening accelerating additive (34) comprises an injection head (39) positioned between the mortar mixer (17) and the bottleneck (21) to inject the hardening accelerating additive (34), characterized in that it is an extrusion-type additive processing method for anisotropic fiber-reinforced concrete. Claim 6 A method for extrusion lamination of anisotropic fiber-reinforced concrete, characterized in that, in claim 1, the extrusion nozzle (23) includes a radial bridge (33) having an orifice (27) formed therein for guiding the fiber (9). Claim 7 A method for extrusion lamination of anisotropic fiber-reinforced concrete, characterized in that, in claim 1, the extrusion nozzle (23) includes a peripheral orifice (27) for guiding the fiber (9). Claim 8 The extrusion lamination method of anisotropic fiber-reinforced concrete according to claim 1, characterized by including a magazine (13) having a coil (11) around which the fiber (9) is wound, and guide members (15a, 15b, 15c) for guiding the fiber (9) from the coil (11) to the extrusion nozzle (23). Claim 9 The extrusion lamination method of anisotropic fiber-reinforced concrete, characterized in that, in claim 2, it includes the step of providing a system for supplying and pumping the mortar (31) to the mixer (17). Claim 10 An extrusion lamination method for anisotropic fiber-reinforced concrete, characterized in that, in claim 1, the fiber (9) is guided into the interior of the mortar (31) by adhesion between the fiber (9) and the mortar (31). Claim 11 A method for extrusion lamination of anisotropic fiber-reinforced concrete, characterized in that, in claim 1, the fiber (9) is subjected to surface treatment and / or mechanical treatment before being extruded together with the mortar (31). Claim 12 A method for extrusion lamination of anisotropic fiber-reinforced concrete, characterized in that, in claim 1, the fiber (9) is guided to the center of the mortar (31). Claim 13 delete Claim 14 The extrusion lamination method of anisotropic fiber-reinforced concrete according to claim 1, wherein the fiber (9) is selected from the group including carbon, metal, glass, basalt, polymer, single or bundled fibers. Claim 15 delete

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