Structure and construction method thereof

Abstract

To provide a structure and its construction method capable of increasing strength by suitably reinforcing a laminated boundary and coping with a three dimensional shape.SOLUTION: The structure 1 is formed by laminating a water-curable composition discharged from a nozzle of a 3D printer, and an acryl resin 5 is filled in a gap generated between laminated layers (curable material layers 2) of the water-curable composition. The method for constructing a structure includes a laminate construction step of discharging a water-curable composition from a nozzle of a 3D printer in a predetermined thickness to construct the laminate 3, an impregnation step of impregnating the laminate 3 with an acrylic monomer (acryl resin 5), and a polymerization step of polymerizing the acrylic monomer permeated between the laminated layers (curable material layers 2) of the laminate 3.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a structure and a method for constructing the same. [Background technology]

[0002] Examples of buried formwork that are produced by pouring concrete into a formwork include SEED Form, which is made by fiber-reinforcing a highly durable mortar with a low water-cement ratio; Ductal (registered trademark) Form, which is made from ultra-high-strength fiber-reinforced concrete; and PIC Form, which is made by impregnating a steel fiber-reinforced concrete plate with a polymer. Because these conventional buried formworks are produced by pouring concrete into the formwork, the formwork used for pouring is often a simple, inexpensive flat plate. On the other hand, there are cases where buried formwork with a three-dimensional shape other than a flat plate is required, but due to the increased manufacturing costs, such forms are rarely produced. In recent years, buried formwork with complex three-dimensional shapes has been produced using construction 3D printers that use a material extrusion method. When producing formwork using a construction 3D printer, a three-dimensional model is created in advance, and the formwork can be produced automatically based on slice-converted tool path data. Construction 3D printers can also extrude fresh cement-based materials and the like to build structures (see, for example, Patent Document 1). Using such construction 3D printers, buried formwork and structures with complex three-dimensional shapes, such as those with curved surfaces, can be constructed more inexpensively than when three-dimensional shapes are formed using buried formwork manufactured by conventional concrete pouring. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-184275 Summary of the Invention [Problem to be solved by the invention]

[0004] In conventional buried formwork and structures constructed using 3D printers, there are laminate boundaries, which can act as a migration route for deterioration factors that cause anisotropy in mechanical properties or reduce durability, and improvements are needed. In order to prevent the formation of discontinuous surfaces where the laminate boundaries become weak, the following methods can be considered. (1) Adjust the printing conditions Adjusting the build speed, the extrusion rate from the nozzle, or the build height of each layer can help prevent discontinuities from forming at the build interface, but these methods all have limitations and are only effective to a limited extent. (2) Maintaining the freshness of ingredients Maintaining the freshness of 3D printer materials over time is an important quality control point to prevent discontinuities at the layer interfaces. If the freshness deteriorates over time, there is a higher risk of discontinuities at the layer interfaces. While the above methods are effective in preventing the formation of discontinuities at the laminate interface, they cannot completely prevent the occurrence of discontinuities. Furthermore, all of these require trial and error and meticulous care, which is likely to lead to reduced productivity and increased costs. Therefore, we investigated a method for strengthening weak areas by taking advantage of the occurrence of discontinuities at the laminate interface, which are weak areas in terms of strength and durability. From this perspective, the present invention aims to provide a structure that can be adapted to a three-dimensional shape and that has improved strength and durability by suitably reinforcing the laminated boundary, and a method for constructing the same. [Means for solving the problem]

[0005] The first invention to solve these problems is a structure formed by layering a water-curable composition ejected from a nozzle of a 3D printer, characterized in that voids generated between the layers of the water-curable composition are filled with an acrylic resin. The "structure" of this invention refers to buildings, constructions, and structural members (including buried formwork) that are part of them, and is a broader concept of buried formwork. In other words, the "structure" includes not only structures formed as buried formwork, but also structures other than buried formwork that are formed in a block shape or other shape and that themselves serve as the main body. The structure of the present invention improves strength and durability because the acrylic resin easily penetrates into the gaps between the laminated layers through the discontinuous surfaces. In addition, the use of a 3D printer allows for the inexpensive construction of three-dimensional structures.

[0006] The second invention of the present invention for solving the above-mentioned problems is a method for constructing a structure, comprising: a laminate construction step of constructing a laminate by ejecting a water-curable composition from a nozzle of a 3D printer at a predetermined thickness; an impregnation step of impregnating the laminate with an acrylic monomer; and a polymerization step of polymerizing the acrylic monomer that has penetrated between the layers of the laminate. According to the method for constructing a structure of the present invention, acrylic monomer is filled between the layers of the laminate in the impregnation process, and the acrylic monomer is polymerized in the polymerization process, thereby increasing the strength. In addition, the use of a 3D printer allows for the inexpensive construction of three-dimensional structures.

[0007] In the method for constructing a structure of the present invention, it is preferable that the polymerization step is performed by immersing the laminate in water glass, and that the method further comprises a washing step of washing the water glass after the polymerization step. According to such a method, since the laminate is immersed in water glass in the polymerization step, the acrylic monomer filled between the laminate layers does not flow out to the outside. [Effects of the Invention]

[0008] According to the structure and the method for constructing the structure of the present invention, the laminated boundary can be suitably reinforced to increase strength and also to accommodate three-dimensional shapes. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 2 is an enlarged view of a main part of the structure according to the embodiment. [Figure 2] FIG. 1 is a perspective view showing a structure formed as an embedded formwork. [Figure 3] 1 is a flowchart showing a method for constructing a structure according to an embodiment. [Figure 4] FIG. 10 is a diagram showing the state in which a core is extracted from a laminated block. [Figure 5] 1A and 1B are diagrams showing the state of loading on the core, where (a) shows vertical splits and (b) shows horizontal splits. [Figure 6] FIG. 10 is a diagram showing a state in which a laminate for a bending strength test is cut out from a laminate block. [Figure 7] 1 is a graph showing the results of a compressive strength test. [Figure 8] 1 is a graph showing the results of a splitting tensile strength test. [Figure 9] 1 is a graph showing the results of a bending strength test. DETAILED DESCRIPTION OF THE INVENTION

[0010] A structure and a method for constructing the same according to an embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 1 is an enlarged view of a main part of the structure, and FIG. 2 is a perspective view of a structure formed as an embedded formwork according to this embodiment. The "structure" of this invention refers to buildings, constructions, and structural components (including embedded formwork) that are part of them, and is a broader concept than embedded formwork. In other words, the "structure" includes not only structures formed as embedded formwork, but also structures other than embedded formwork that are formed in a block shape or other shape and that serve as the main body rather than a formwork itself. The structure in FIG. 1 is a block-shaped structure, and the structure in FIG. 2 is an embedded formwork.

[0011] First, the structure of the structure will be described. The structure described below has the same structure as the block-shaped structure of FIG. 1 and the structure formed as an embedded formwork of FIG. 2. As shown in FIG. 1, the structure 1 according to this embodiment includes a laminate 3 formed by laminating layers of water-curable composition ejected from a nozzle of a 3D printer. Gaps generated between the layers of water-curable composition (between the curable material layers 2, 2) are filled with acrylic resin 5.

[0012] The 3D printer used to construct the structure 1 is a construction printer, and for example, a robot arm type 3D printer is used. The robot arm type 3D printer includes a main body, a multi-stage robot arm, and a hardening material supply unit provided at the tip of the robot arm. The main body supports the robot arm. The robot arm is, for example, a six-axis robot. That is, the robot arm has multiple arms connected via rotatable connectors. The robot arm may be mounted on a self-propelled unit provided on the main body. The self-propelled unit is capable of ascending and descending (or moving up and down) and is provided to move the robot arm by self-propelling to a predetermined location along the ground surface. The 3D printer is controlled by a control device consisting of a computer, and is configured to drive the hardening material supply unit to a desired three-dimensional position.

[0013] The hardening material supply unit forms the hardening material layer 2 by extruding the hardening material (hydraulic composition). The hardening material supply unit is equipped with a nozzle that can extrude the hardening material while mixing in a flexible short fiber reinforcement material. The hardening material of this embodiment is a cement-based hydraulic composition such as mortar or rapid hardening concrete. The hardening material is not limited to the above materials, and other types of hydraulic composition may also be used. A known example of another type of hydraulic composition is so-called geopolymer. Geopolymer is a hydraulic composition that uses an alkaline solution and a powder whose main component is aluminum silicate.

[0014] The nozzle that dispenses the curable material has a diameter of, for example, 25 mm. In this case, the width of the curable material layer 2 dispensed from the nozzle is 25 mm. The amount of curable material dispensed from the nozzle is set by the control device so that the height of the curable material layer 2 is, for example, 10 mm. In this manner, in this embodiment, for example, a curable material with a width of 25 mm and a height of 10 mm is dispensed from the nozzle, and the next curable material is dispensed sequentially onto the width direction side of the dispensed curable material, thereby forming one layer of curable material layer 2 with a desired width (see FIG. 1). Note that the shape of the dispensed curable material is not limited to the above; the width dimension can be changed by changing the diameter of the nozzle, and the height dimension can be changed by changing the amount of curable material dispensed.

[0015] The short fiber reinforcing material to be mixed into the hardening material and extruded together with the hardening material can be steel fiber, resin fiber such as polypropylene or polyethylene, carbon fiber, etc. Note that instead of the short fiber reinforcing material, wire made of reinforcing fiber such as carbon fiber or glass fiber, A continuous reinforcing material such as a metal wire or a resin wire can also be used.

[0016] The shape of the structure 1 is formed according to the desired shape. The structure 1 is formed by creating a three-dimensional structure model in advance using a 3D printer, converting it into tool path data, and then controlling the stacking program to perform automatic modeling. Figure 1 shows the structure 1 in which the hardening material layer 2 is formed in a flat plate shape. A robot arm unit moves the hardening material supply unit in a plane according to the shape of the structure 1, forming each hardening material layer 2. The hardening material layer 2 is formed to a predetermined width dimension by moving the hardening material supply unit in parallel multiple times. In the structure 1 formed by the 3D printer, there is a layer boundary between the hardening material layers 2, 2, and the gap at the layer boundary is filled with acrylic resin 5. The method of filling the acrylic resin 5 will be described later.

[0017] FIG. 2 shows a structure 1 used as an embedded formwork. Embedded formwork consisting of the structure 1 is used to construct various structures (for example, FIG. 2 shows an embedded formwork for a column) such as columns, beams (girders), walls, bridge piers, and dam inspection galleries. The structure 1 of this embodiment has an arc-shaped cross section corresponding to the shape of the structure (for example, a column) to be constructed using the embedded formwork. The structure 1 includes a laminate 3 made of multiple hardening material layers 2 stacked in the height direction. Acrylic resin 5 is filled in the gaps between the hardening material layers 2, 2. The inner surface of the structure 1 may be formed with a wave-shaped recess 7 to improve adhesion with the concrete poured inside.

[0018] Next, a method for constructing a structure according to an embodiment will be described. Fig. 3 is a flowchart showing the method for constructing a structure. The method for constructing such a structure includes a laminate construction step, an impregnation step, a polymerization step, and a washing step.

[0019] The laminate construction process (S1 to S3) is a process in which a water-curable composition is discharged from the nozzle of a 3D printer at a predetermined thickness to construct the laminate 3. In the laminate construction process, first, a model of a three-dimensional structure is created in advance using the 3D printer and converted into tool path data (step S1). Then, based on the tool path data, a robot arm unit and a hardening material supply unit are controlled to automatically model the laminate 3 (step S2). At this time, the hardening material is placed in a hopper and pressure-fed to the nozzle by a pump, where it is supplied to the hardening material supply unit.

[0020] Thereafter, the laminate 3 is cured (step S3). For example, when wet curing is performed, the laminate 3 is covered with a vinyl sheet, a humidifier is installed inside, and humid curing is performed for 24 hours. Thereafter, the laminate 3 is wrapped in a water-soaked curing mat and cured for 3 days. Thereafter, the laminate 3 is placed in a constant temperature and humidity room at a temperature of 20°C and a relative humidity of 70%, and cured for up to 28 days. Note that this curing is just one example, and the temperature, humidity, and curing period can be changed as appropriate. Furthermore, when constructing a structure to be applied to an actual structure, curing may not be performed.

[0021] The impregnation step (S4 to S5) is a step of impregnating the laminate 3 with an acrylic monomer. The impregnation step involves two steps: drying and degassing, and monomer impregnation. Drying and degassing are performed by placing the laminate 3 in a low vacuum environment of about 20 mmHg for two hours (step S4). Monomer impregnation is performed by impregnating the laminate 3 with a low-viscosity acrylic monomer (e.g., methyl methacrylate (MMA)) (step S5). Specifically, the laminate 3 is immersed in the acrylic monomer for 16 hours. The acrylic monomer contains a polymerization initiator. The polymerization initiator is an azo-based radical polymerization initiator, such as ABN-R (manufactured by Japan Finechem Co., Ltd.).

[0022] The polymerization step (S6) is a step of polymerizing the acrylic monomer that has permeated between the layers of the laminate. In this polymerization step, the laminate 3 is immersed in water glass (sodium silicate) at a temperature of 70°C or higher for 4 hours to polymerize the acrylic monomer (step S6). The acrylic monomer is polymerized by the polymerization initiator contained in the acrylic monomer. In the polymerization step, the laminate 3 is immersed in water glass, which has a higher viscosity than warm water, so the laminate 3 is wrapped, which makes it possible to prevent the acrylic monomer from seeping out.

[0023] The washing step (S7) is a step of washing away the water glass. In the washing step, after the polymerization step is completed, the laminate 3 is immersed in warm water at a temperature of 70°C or higher for 3 hours to wash away the water glass from the surface of the laminate 3 (step S7). Through these steps, the structure 1 having the configuration of this embodiment is completed.

[0024] Next, we will explain the mechanical performance tests conducted on specimens manufactured by the method for constructing the structure 1 of this embodiment. Three mechanical performance tests were conducted: a compressive strength test, a splitting tensile strength test, and a bending strength test. Fig. 4 is a diagram showing the state in which a core is taken from a laminated block, and Fig. 5 is a diagram showing the state in which a load is applied to the core. (a) is a diagram showing the method for a longitudinal splitting tensile test, (b) is a diagram showing the method for a transverse splitting tensile test, and Fig. 6 is a diagram showing the state in which a laminate for a bending strength test is cut out from a laminated block. Fig. 7 is a graph showing the results of the compressive strength test, Fig. 8 is a graph showing the results of the splitting tensile strength test, and Fig. 9 is a graph showing the results of the bending strength test.

[0025] For the compressive strength test, as shown in FIG. 4, a test piece 10 having a diameter of 100 mm and a height of 200 mm was taken from the upper surface of the laminate 3 by a wet method, and both end surfaces were polished before the test.

[0026] In the compressive strength test, two types of specimens were created for the 28-day-old cast specimen and the 3D-printed specimen, one with and one without impregnation, and the compressive strength was measured. As shown in Figure 7, the cast specimen without impregnation had a compressive strength of 90.0 (N / mm 2 ), and the compressive strength of the printed specimen without impregnation was 71.6 (N / mm 2 ) The compressive strength of the impregnated specimen was 156.2 (N / mm 2 ), and the compressive strength of the impregnated printed specimen was 186.7 (N / mm 2) From the above results, without impregnation, the compressive strength of the printed specimen was 80% of that of the cast-in specimen, meaning that the printed specimen had a lower compressive strength. With impregnation, the compressive strength of the cast-in specimen was 173% of that of the cast-in specimen without impregnation, and the compressive strength of the printed specimen was 207% of that of the cast-in specimen without impregnation. In other words, with impregnation, the compressive strength was greater than without impregnation, and the rate of increase in compressive strength was greater for the printed specimen than for the cast-in specimen. This is thought to be due to the following reason. In other words, when comparing the cast-in specimen without impregnation and the printed specimen, the printed specimen has discontinuous gaps at the layer boundaries, which act as weak spots and reduce its strength. With impregnation, on the other hand, these weak spots become filling paths for the impregnating material, and the impregnating material selectively penetrates the weak spots, contributing to an increase in strength.

[0027] For the splitting tensile strength test, two types of test specimens were created, one with and one without impregnation, for a 28-day-old cast-in test specimen and one printed with a 3D printer, and the tensile strength was measured. For the printed test specimen 10 created with a 3D printer, tests were conducted on vertical splitting (see Figure 5), which compresses along the extension direction of the acrylic resin 5, and horizontal splitting (see Figure 5), which compresses in a direction perpendicular to the rear extension direction of the acrylic resin 5 of the printed test specimen.

[0028] As shown in Figure 8, the tensile strength of the unimpregnated specimen was 4.13 (N / mm 2 ), and the tensile strength of the unimpregnated printed specimen under longitudinal loading was 2.64 (N / mm 2 ), and under cross-grain loading, the tensile strength is 4.62 (N / mm 2 ) for the impregnated specimen, the tensile strength was 7.31 (N / mm 2 ), and the tensile strength of the unimpregnated printed specimen under longitudinal loading was 6.71 (N / mm 2 ) and under cross-grain loading, the tensile strength is 11.89 (N / mm 2) From the above results, without impregnation, the tensile strength of the printed specimen was 64% of that of the driven specimen under longitudinal loading, and 112% of that of the driven specimen under transverse loading. The tensile strength of the printed specimen under longitudinal loading was lower than that of the driven specimen, and the tensile strength of the printed specimen under transverse loading was higher than that of the driven specimen. With impregnation, the tensile strength of the driven specimen was 177% of that of the driven specimen without impregnation, and the tensile strength of the printed specimen was 162% of that of the driven specimen under longitudinal loading, and 288% of that of the driven specimen under transverse loading. In other words, with impregnation, the tensile strength of all specimens was greater than that of the non-impregnated, poured specimens. In particular, when comparing the tensile strength of the printed specimens with and without impregnation, the increase in tensile strength under longitudinal loading (tensile strength with impregnation / tensile strength without impregnation) was 2.54 times, and the increase in tensile strength under transverse loading (tensile strength with impregnation / tensile strength without impregnation) was 2.57 times, indicating that the increase in tensile strength was significant under both longitudinal and transverse loading. Furthermore, under transverse loading, the tensile strength of the printed specimens without impregnation was similar to that of the poured specimens, but with impregnation, the tensile strength of the printed specimens was significantly greater than that of the poured specimens, demonstrating the remarkable effect of impregnation. This is thought to be due to the following reasons. In other words, because the short fibers are uniformly aligned in the cross grain direction when printed, the weak areas at the laminate boundaries are strengthened, and the crack dispersion effect of the short fibers mixed in throughout the core is exerted, which is thought to have increased the strength.The reason why the strength does not increase as much when printed and impregnated with longitudinal loading as when impregnated with transverse loading is that the short fibers are aligned in the longitudinal direction (vertical direction) and do not cross the laminate boundaries, so the crack dispersion effect of the short fibers is not effective against the penetration of vertical cracks.However, because the weak areas at the laminate boundaries are strengthened in this case as well, it is thought that a strength roughly equivalent to that of the impregnated specimens was obtained.

[0029] For the bending strength test, two types of test specimens were created, one without impregnation and one with impregnation, for a 28-day-old cast test specimen and one printed test specimen created using a 3D printer, and bending strength was measured. For the printed test specimen 12 created using a 3D printer, the test specimen (see Figure 6) had the extension direction of the acrylic resin 5 (the direction of nozzle movement) as the longitudinal direction, and tests (loaded in the strong axis direction) were performed both without impregnation and with impregnation, and for the test specimen (not shown) had the extension direction of the acrylic resin 5 as the transverse direction, tests (loaded in the weak axis direction) were performed with impregnation.

[0030] As shown in Figure 9, the flexural strength of the unimpregnated specimen was 3.95 (N / mm 2 ), and the bending strength of the unimpregnated printed specimen under strong axial loading was 5.30 (N / mm 2 ) The impregnated specimen had a bending strength of 10.91 (N / mm 2 ), and the flexural strength of the impregnated printed specimen under strong axial loading was 13.11 (N / mm 2 ) and the bending strength is 14.96 (N / mm 2) From the above results, without impregnation, the bending strength of the printed specimen was 134% of that of the cast-in specimen under strong axial loading, and was higher than that of the cast-in specimen under strong axial loading. With impregnation, the bending strength of the cast-in specimen was 276% of that of the cast-in specimen without impregnation, 332% of that of the cast-in specimen under strong axial loading, and 378% of that of the cast-in specimen under weak axial loading. In other words, with impregnation, the bending strength of all specimens was higher than that of the cast-in specimen without impregnation, and the bending increase rate of the printed specimen was more than three times that of the strong axial and weak axial loading. In particular, the bending strength increase rate was greatest when the printed specimen was loaded in the weak axial direction. This is thought to be due to the following reason: the printed specimen has the most weak areas at the laminate boundaries, which are more susceptible to impregnation, and therefore weak areas can be reinforced efficiently. Specifically, impregnation not only strengthens the laminate boundary, but also penetrates into the layers inside the laminate boundary, increasing their strength. This is why the strength of the stamped test specimen also increased. The more weak points there are, such as in the printed test specimen, the easier it is for the acrylic to penetrate deep into the interior of the specimen, effectively increasing the strength of both the laminate boundary and the laminated parts.

[0031] As described above, according to the structure 1 and the method for constructing the structure 1 of this embodiment, the gaps between the cured material layers 2 are filled with acrylic resin 5, which effectively reinforces the laminate boundaries. This increases the compressive strength, tensile strength, and bending strength of the structure 1. Furthermore, strengthening the discontinuous surfaces (laminar boundaries), which are weak areas, leads to blocking of migration paths for deterioration factors that cause a decrease in durability, thereby improving durability. Furthermore, because a 3D printer is used, the three-dimensional structure 1 can be constructed inexpensively and easily. According to the method for constructing the structure 1 of this embodiment, the polymerization step is performed while the laminate 3 is immersed in water glass, so that the acrylic resin 5 filled between the hardening material layers 2 is less likely to leak out.

[0032] Although the embodiments for carrying out the present invention have been described above, the present invention is not limited to the above-described embodiments, and appropriate design changes are possible within the scope of the present invention. For example, In the above embodiment, the structure 1 serving as the buried formwork has an arc-shaped cross section, but is not limited to this and may have, for example, a U-shaped or L-shaped cross section. The present invention is also particularly suitable for buried forms for making structural members. [Explanation of symbols]

[0033] 1 structure 2 Hardened material layer 3 Laminate 5. Acrylic resin

Claims

1. A structure formed by laminating a water-curable composition discharged from a nozzle of a 3D printer, The gaps generated between the layers of the water-curable composition are filled with an acrylic resin. A structure characterized by:

2. a laminate construction step of constructing a laminate by discharging a water-curable composition from a nozzle of a 3D printer to a predetermined thickness; an impregnation step of impregnating the laminate with an acrylic monomer; a polymerization step of polymerizing the acrylic monomer that has penetrated between the layers of the laminate. A method for constructing a structure.

3. The polymerization step is carried out by immersing the laminate in water glass, The method further includes a washing step of washing the water glass after the polymerization step.

3. The method for constructing a structure according to claim 2.

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