Method for evaluating extrusion property of, method for evaluating self-support stability of, and method for selecting cement composition for additional manufacture, and cement composition for additional manufacture

Abstract

To provide a method for evaluating the extrusion property of a cement composition for additional manufacture with which the extrusion property can be easily evaluated.SOLUTION: A method for evaluating the extrusion property of a cement composition 30 for additional manufacture is provided. The method includes filling the cement composition 30 for additional manufacture into a mold 20 having an opening 21 into which an extrusion jig 10 can be inserted at one end and a discharge port 22 for filler at the other end, then extruding the cement composition 30 for additional manufacture filled into the mold 20 by using the extrusion jig 10 connected to a uniaxial compression tester, determining the relationship between displacement and extrusion pressure with the uniaxial compression tester, and calculating the average extrusion pressure on the basis of the relationship.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for evaluating the extrudability of a cement composition for additive manufacturing, a method for evaluating and selecting self-supporting stability, and a cement composition for additive manufacturing. [Background technology]

[0002] In recent years, methods have been proposed for using cement compositions to create shaped objects using additive manufacturing devices (3D printers). In additive manufacturing devices, the cement composition is extruded from a nozzle and built up layer by layer to create a shape. For this reason, cement compositions used in additive manufacturing are required to have the property of being able to extrude the cement composition from the nozzle without defects (i.e., extrudability) and the property of being able to build up the layered cement composition to a desired height without collapsing or being crushed (i.e., self-standing stability).

[0003] As a method for evaluating the properties of cement compositions for additive manufacturing, Patent Document 1 proposes a method using the ratio of zero-stroke flow / density of a hydraulic composition (cement composition) and the ratio of 15-stroke flow / density of a hydraulic composition. Patent Document 2 also proposes a method using vane shear strength and shear stress. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-90004 [Patent Document 2] Japanese Patent Application Publication No. 2023-176290 Summary of the Invention [Problem to be solved by the invention]

[0005] The method of Patent Document 1 evaluates extrudability and self-supporting stability using the flow value of the cement composition, but the evaluation of self-supporting stability is not sufficient. In particular, the index using the flow value does not necessarily have a good relationship with the number of layers that can be laminated of the cement composition. Furthermore, although the method of Patent Document 2 can evaluate the self-supporting stability, it is necessary to separately conduct a flow test to evaluate the extrudability.

[0006] The present invention has been made to solve the above problems, and aims to provide a method for evaluating the extrudability of a cement composition for additive manufacturing, which allows for easy evaluation of extrudability. Another aim of the present invention is to provide a method for evaluating the self-supporting stability of a cement composition for additive manufacturing, which allows for easy evaluation of self-supporting stability. A further aim of the present invention is to provide a cement composition for additive manufacturing that is excellent in extrudability and self-supporting stability, and a method for selecting such a cement composition. [Means for solving the problem]

[0007] The present inventors have conducted extensive research to solve the above problems, and have found that the average extrusion pressure and deformation coefficient of the additive manufacturing cement composition calculated by a uniaxial compression test are closely related to the extrudability and self-supporting stability of the additive manufacturing cement composition, respectively, and have completed the present invention. That is, the present invention is exemplified as follows.

[0008] [1] A method for evaluating the extrudability of an additive manufacturing cement composition, comprising: The method includes filling the additive manufacturing cement composition into a formwork having an opening at one end through which an extrusion tool can be inserted and a filler discharge outlet at the other end, extruding the additive manufacturing cement composition filled in the formwork using the extrusion tool connected to a uniaxial compression testing machine, determining the relationship between displacement and extrusion pressure using the uniaxial compression testing machine, and calculating the average extrusion pressure based on the relationship. [2] The method according to [1], wherein the average extrusion pressure is an average value of extrusion pressures at a displacement of 10 to 30 mm. [3] A method for evaluating the self-supporting stability of an additive manufacturing cement composition, comprising: A method comprising: preparing a molded body of the additive manufacturing cement composition; compressing the molded body using a uniaxial compression testing machine to determine the relationship between compressive stress and compressive strain; and calculating a deformation coefficient based on the relationship. [4] The method according to [3], wherein the deformation coefficient is the slope of a line connecting the point where the compressive stress is 0.5 kPa and the point where the compressive stress is half the uniaxial compressive strength in a graph showing the relationship between compressive stress (y-axis) and compressive strain (x-axis). [5] A method for selecting a cement composition for additive manufacturing, comprising: Selecting an additive manufacturing cement composition having an average extrusion pressure of 300 kPa or less and a deformation modulus of 0.05 MPa or more; The average extrusion pressure is calculated by the method described in [1] or [2] using a mold having an inner dimension of 5±0.5 cm in diameter and 10±1 cm in height and a discharge opening diameter of 1±0.1 cm; The deformation coefficient is calculated by the method described in [3] or [4] using a molded body having a diameter of 5±0.5 cm and a height of 10±1 cm. [6] A cement composition for additive manufacturing, in which the average extrusion pressure is 300 kPa or less when calculated using a formwork having an internal dimension of 5 cm in diameter and 10 cm in height and a discharge outlet diameter of 1 cm according to the method described in [1] or [2], and the deformation coefficient is 0.05 MPa or more when calculated using a molded body having a diameter of 5 cm and a height of 10 cm according to the method described in [3] or [4]. [Effects of the Invention]

[0009] According to the present invention, a method for evaluating the extrudability of a cement composition for additive manufacturing, which allows for easy evaluation of extrudability, can be provided. Furthermore, according to the present invention, a method for evaluating the self-supporting stability of a cement composition for additive manufacturing, which allows for easy evaluation of self-supporting stability, can be provided. Furthermore, according to the present invention, a cement composition for additive manufacturing having excellent extrudability and self-supporting stability, and a method for selecting the same, can be provided. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a cross-sectional schematic diagram for explaining a uniaxial compression test as a method for evaluating extrudability. [Figure 2] 1 is an example of a graph showing the relationship between displacement and extrusion pressure obtained by performing a uniaxial compression test on an additive manufacturing cement composition. [Figure 3] FIG. 1 is a cross-sectional schematic diagram for explaining a uniaxial compression test of the self-standing stability evaluation method. [Figure 4] 1 is an example of a graph showing the relationship between compressive strain and compressive stress obtained by performing a uniaxial compression test on a molded body of a cement composition for additive manufacturing. DETAILED DESCRIPTION OF THE INVENTION

[0011] The following is a detailed description of the embodiments of the present invention. The present invention is not limited to the following embodiments, and it should be understood that modifications and improvements made to the following embodiments based on the ordinary knowledge of those skilled in the art without departing from the spirit of the present invention are also within the scope of the present invention.

[0012] (1. Extrusion Evaluation Method) The method for evaluating the extrudability of the cement composition for additive manufacturing according to the embodiment of the present invention (extrudability evaluation method) is performed by a uniaxial compression test. The uniaxial compression test can be performed using a commercially available uniaxial compression tester equipped with a displacement meter and a load meter. For example, a universal physical property tester called a texture analyzer can be used as the uniaxial compression tester.

[0013] In this specification, "additive manufacturing" refers to the process of using a computer to calculate a sliced ​​two-dimensional cross-sectional shape based on data representing a shaped object, and then using the results to additively manufacture a material (cement composition). This additive manufacturing is carried out using an existing additive manufacturing device equipped with a nozzle that ejects the material and a pump that transports the material to the nozzle. In addition, in this specification, the term "cement composition" refers to a material containing water before hardening (for example, paste, mortar, and concrete).

[0014] FIG. 1 is a cross-sectional schematic diagram for explaining the uniaxial compression test of the extrudability evaluation method. As shown in Figure 1, the uniaxial compression test of the extrudability evaluation method is performed using an extrusion jig 10 connected to a uniaxial compression testing machine (not shown), and a mold 20. The mold 20 has an opening 21 at one end into which the extrusion jig 10 can be inserted, and a discharge port 22 for the filler at the other end. The extrusion jig 10 can be moved vertically by driving the uniaxial compression testing machine, and by inserting it through the opening 21 and moving it vertically downward, the filler filled in the mold 20 can be extruded from the discharge port 22.

[0015] The shape and size of the formwork 20 are not particularly limited, but it is preferable that the formwork 20 has internal dimensions of 5±0.5 cm in diameter and 10±1 cm in height, with the diameter of the discharge port 22 being 1±0.1 cm. Typically, a formwork 20 having internal dimensions of 5 cm in diameter and 10 cm in height, with the diameter of the discharge port 22 being 1 cm, can be used. The shape and size of the formwork 20 may be set according to the diameter of the aggregate contained in the cement composition to be evaluated and the diameter of the nozzle of the additive manufacturing device, but it is preferable that the ratio of the cross-sectional area of ​​the formwork 20 to the cross-sectional area of ​​the discharge port 22 be constant. Furthermore, the shape and size of the extrusion jig 10 are not particularly limited as long as it has outer dimensions that correspond to the inner dimensions of the mold 20 .

[0016] The mold 20 is filled with an additive manufacturing cement composition 30 whose extrudability is to be evaluated. The additive manufacturing cement composition 30 filled in the mold 20 is extruded by an extrusion jig 10. The moving speed of the extrusion jig 10 at this time is not particularly limited, but is preferably 10 to 30 mm / min. Typically, the moving speed of the extrusion jig 10 is 20 mm / min.

[0017] During extrusion, the relationship between the displacement and the extrusion pressure is determined using a uniaxial compression tester. The displacement can be measured using a displacement meter, and the extrusion pressure can be measured using a load meter. The extrusion pressure is the load generated during the extrusion of the additive manufacturing cement composition 30, converted into pressure. The relationship between the displacement and the extrusion pressure can be represented by a graph with the displacement on the x-axis and the extrusion pressure on the y-axis. An example of a graph showing the relationship between the displacement and the extrusion pressure obtained by performing the above-mentioned uniaxial compression test on the additive manufacturing cement composition 30 is shown in Figure 2. Note that this graph shows the results of a uniaxial compression test performed using a formwork 20 having internal dimensions of 5 cm in diameter and 10 cm in height, and a discharge port 22 with a diameter of 1 cm.

[0018] Next, the average extrusion pressure is calculated based on the relationship between the displacement and the extrusion pressure. As demonstrated in the examples described below, the average extrusion pressure can be used as an index for evaluating the extrudability of the additive manufacturing cement composition 30. For example, when a uniaxial compression test of the additive manufacturing cement composition 30 is performed using a formwork 20 having internal dimensions of 5 cm in diameter and 10 cm in height and a discharge port 22 with a diameter of 1 cm, if the average extrusion pressure is 300 kPa or less, preferably 200 kPa or less, the extrudability of the additive manufacturing cement composition 30 can be determined to be good. Here, in this specification, the term "average extrusion pressure" means the average value of the extrusion pressure when the displacement is 10 to 30 mm. It should be noted that when a mold 20 having a shape and size different from those described above is used, the reference value of the average extrusion pressure at which extrusion properties can be determined to be good may change.

[0019] The method for evaluating the extrudability of the cement composition for additive manufacturing according to an embodiment of the present invention can be performed by a uniaxial compression test, which is easier than evaluation by a flow test.

[0020] (2. Self-Standing Stability Evaluation Method) The method for evaluating the self-supporting stability of the cement composition for additive manufacturing according to the embodiment of the present invention (self-supporting stability evaluation method) is carried out by a uniaxial compression test, similar to the extrusion evaluation method described above. The uniaxial compression tester used for the uniaxial compression test can also be the same as that described above. FIG. 3 is a cross-sectional schematic diagram for explaining the uniaxial compression test of the self-standing stability evaluation method. The uniaxial compression test for the self-supporting stability evaluation method is performed in accordance with a general uniaxial compression test. Specifically, as shown in Fig. 3, the molded body 40 of the additive manufacturing cement composition is sandwiched between two pressure plates 50, and the molded body 40 is compressed by a uniaxial compression tester (not shown) connected to the upper pressure plate 50.

[0021] The shape and size of the molded body 40 of the cement composition for additive manufacturing are not particularly limited, but it is preferably cylindrical with a diameter of 5±0.5 cm and a height of 10±1 cm. Typically, a cylindrical molded body 40 with a diameter of 5 cm and a height of 10 cm can be used. The shape and size of the molded body 40 may be set according to the diameter of the aggregate contained in the cement composition to be evaluated, but it is preferable that the ratio of the diameter to the height of the molded body 40 is constant (diameter / height = 1 / 2). The method for producing the molded product 40 of the additive manufacturing cement composition is not particularly limited, and it is sufficient to place the additive manufacturing cement composition 30 in a mold 20 of a predetermined size and then demold the composition. Demolding may be performed at any time taking into consideration use in an additive manufacturing device, but it is preferable to demold the composition 30 15 minutes after placing it in the mold 20.

[0022] The compression speed (movement speed of the upper pressure plate 50) is not particularly limited, but is preferably 10 to 30 mm / min. Typically, the compression speed is 20 mm / min.

[0023] During compression, the relationship between compressive stress and compressive strain is determined using a uniaxial compression testing machine. Compressive stress is measured with a load meter and displacement with a displacement meter, and the compressive strain is calculated from these results. The relationship between compressive stress and compressive strain can be represented by a graph with compressive strain on the x-axis and compressive stress on the y-axis. An example of a graph showing the relationship between compressive strain and compressive stress obtained by performing the above-mentioned uniaxial compression test on a molded body 40 of the additive manufacturing cement composition is shown in Figure 4. This graph shows the results of a uniaxial compression test performed on a cylindrical molded body 40 with a diameter of 5 cm and a height of 10 cm.

[0024] Next, the deformation coefficient is calculated based on the relationship between compressive stress and compressive strain. As demonstrated in the examples described below, the deformation coefficient can be used as an index for evaluating the self-supporting stability of the additive manufacturing cement composition 30. For example, when a uniaxial compression test is performed using a cylindrical molded body 40 having a diameter of 5 cm and a height of 10 cm, if the deformation coefficient is 0.05 MPa or more, preferably 0.10 to 0.80 MPa, the self-supporting stability of the additive manufacturing cement composition 30 can be determined to be good. In this specification, the "deformation modulus" refers to the slope of the line connecting the point where the compressive stress is 0.5 kPa and the point where the compressive stress is half the uniaxial compressive strength in a graph showing the relationship between compressive stress (y-axis) and compressive strain (x-axis). The uniaxial compressive strength refers to the maximum compressive stress in the region where the compressive strain is 15% or less. It should be noted that if the shape and size of the molded body 40 differ from those described above, the standard value of the deformation coefficient that determines whether the self-standing stability is good may change.

[0025] The method for evaluating the self-supporting stability of a cement composition for additive manufacturing according to an embodiment of the present invention can be performed by a uniaxial compression test, similar to the method for evaluating extrudability, and is therefore easier than conventional evaluations.

[0026] (3. Method for selecting cement composition for additive manufacturing) The method for selecting a cement composition for additive manufacturing according to an embodiment of the present invention can be performed using the above-described extrudability evaluation method and self-supporting stability evaluation method. This selection method also includes selecting a cement composition for additive manufacturing 30 with an average extrusion pressure of 300 kPa or less and a deformation coefficient of 0.05 MPa or more. In this selection, the average extrusion pressure is preferably 200 kPa or less and the deformation coefficient is preferably 0.10 to 0.80 MPa. However, in order to use the above-mentioned reference value for the average extrusion pressure, the above-mentioned extrudability evaluation method must be performed using a mold 20 having internal dimensions of 5±0.5 cm in diameter and 10±1 cm in height, with a discharge port 22 having a diameter of 1±0.1 cm. Similarly, in order to use the above-mentioned reference value for the deformation coefficient, the above-mentioned self-standing stability evaluation method must be performed using a molded body 40 having a diameter of 5±0.5 cm and a height of 10±1 cm.

[0027] If the average extrusion pressure exceeds 300 kPa, the pressure required to extrude the cement composition becomes too great, and the cement composition may not be sufficiently ejected from the nozzle of the additive manufacturing device. Also, if the deformation coefficient is less than 0.05 MPa, the cement composition may not be able to be stacked to a predetermined height, and may collapse or be crushed during stacking.

[0028] The method for selecting a cement composition for additive manufacturing according to an embodiment of the present invention allows for evaluation of both extrusion property and self-supporting stability through uniaxial compression testing, making it easier than ever to select a cement composition for additive manufacturing.

[0029] 4. Additive Manufacturing Cement Compositions The additive manufacturing cement composition (hereinafter abbreviated as "cement composition") according to an embodiment of the present invention has an average extrusion pressure of 300 kPa or less when calculated using the above-mentioned extrudability evaluation method using a formwork 20 having internal dimensions of 5 cm in diameter and 10 cm in height and a discharge outlet 22 with a diameter of 1 cm, and a deformation coefficient of 0.05 MPa or more when calculated using the above-mentioned self-standing stability evaluation method using a molded body 40 having a diameter of 5 cm and a height of 10 cm. The cement composition according to the embodiment of the present invention can improve extrudability and self-supporting stability by being configured as described above.

[0030] The composition of the cement composition according to the embodiment of the present invention is not particularly limited, but may include cement, an admixture, a fine aggregate, and water. Cement is a major component of cement compositions. The cement is not particularly limited, but various types of Portland cement, such as ordinary Portland cement, high-early-strength Portland cement, moderate-heat Portland cement, low-heat Portland cement, white Portland cement, and ultra-high-early-strength Portland cement, as well as ultra-rapid-hardening cement, blast-furnace cement, fly ash cement, alumina cement, and ecocement, can be used. These may be used alone or in combination of two or more. Among these, Portland cement is preferred from the viewpoint of availability. The content of cement in the cement composition is not particularly limited, but is preferably 70 to 100 mass %, more preferably 80 to 90 mass %, based on the total of the cement and the admixture. If the content is within such a range, a cement composition with good extrudability and self-supporting stability is easily obtained.

[0031] Admixtures are components that are effective in improving various properties. Examples of admixtures include silica fume, gypsum powder, blast furnace slag powder, molten coal slag powder, fly ash, limestone fine powder, siliceous powder, natural pozzolan, calcined clay, etc. These may be used alone or in combination of two or more. The content of the admixture in the cement composition is not particularly limited, but is preferably 30% by mass or less, more preferably 10 to 20% by mass, based on the total of the cement and the admixture. If the content is within this range, a cement composition with good extrudability and self-standing stability is easily obtained. As the admixture, silica fume is preferably used. The BET specific surface area of ​​silica fume is preferably 12 to 25 m 2 / g, more preferably 13 to 20m2 / g. If the BET specific surface area is outside the above range, it becomes difficult to obtain silica fume. It is also preferable to use limestone fine powder or siliceous powder as an admixture. The Blaine specific surface area of ​​these is preferably 2500 to 10000 cm 2 / g, more preferably 3000 to 9000 cm 2 / g, more preferably 3500 to 8000 cm 2 / g. The Blaine specific surface area is 2500 cm 2 If the viscosity is less than 10000 cm / g, the strength development of the cement composition will decrease. 2 If the kneading time exceeds 1 / g, the mixing time of the cement composition becomes long.

[0032] The fine aggregate is an effective component for reducing the calorific value of the cement composition. Examples of fine aggregate include limestone powder, river sand, mountain sand, land sand, sea sand, crushed sand, silica sand, slag fine aggregate, lightweight fine aggregate, recycled fine aggregate, etc. These may be used alone or in combination of two or more. The content of the fine aggregate in the cement composition is not particularly limited, but is preferably 50 to 150 parts by mass, more preferably 70 to 130 parts by mass, relative to 100 parts by mass of the total of the cement and the admixture. If the content is within such a range, a cement composition having good extrudability and self-supporting stability is easily obtained.

[0033] The water is not particularly limited, and tap water, recycled water, sludge water, etc. can be used. The water content in the cement composition is not particularly limited, but is preferably 15 to 40 parts by mass, more preferably 20 to 30 parts by mass, per 100 parts by mass of the total of cement and admixtures. A content within this range makes it easy to obtain a cement composition with good extrudability and self-supporting stability. The water content corresponds to the water-binder ratio (mass of water / total mass of cement and admixtures).

[0034] The cement composition according to the embodiment of the present invention may further contain a water-reducing admixture and / or a setting accelerator, if necessary. The water reducing agent is a component that disperses cement to improve fluidity and thereby improve extrusion properties. Examples of the water-reducing agent include air-entraining water-reducing agents, high-performance water-reducing agents, high-performance air-entraining water-reducing agents, etc. These may be used alone or in combination of two or more. The content of the water-reducing agent in the cement composition is not particularly limited, but is preferably 3.0 parts by mass or less, more preferably 0.8 to 2.0 parts by mass, relative to 100 parts by mass of the total of cement and admixture. If the content is within this range, a cement composition with good extrudability is likely to be obtained.

[0035] The quick-setting admixture is a component that improves the self-standing stability. Examples of the quick-setting admixture include aluminum-based quick-setting admixtures such as aluminum sulfate and aluminum silicate, aluminate-based quick-setting admixtures, calcium aluminate-based quick-setting admixtures, etc. These may be used alone or in combination of two or more. The content of the quick-setting admixture in the cement composition is not particularly limited, but is preferably 2.5 parts by mass or less, more preferably 0.5 to 2.0 parts by mass, relative to 100 parts by mass of the total of cement and admixture. If the content is within this range, a cement composition with good self-standing stability is likely to be obtained.

[0036] The cement composition may further contain components known in the art, such as coarse aggregate, fibers, grinding aids, antifoaming agents, shrinkage reducing agents, set accelerators, and set retarders, without interfering with the scope of the present invention.

[0037] The cement composition can be produced by mixing the above components. The mixing means is not particularly limited, and a mixer generally used for mixing mortar, concrete, etc. can be used. Specifically, a vertical mixer, horizontal mixer, Nauta mixer, tilting mixer, forced mixer, twin-shaft mixer, etc. can be used. [Example]

[0038] The present invention will be described in detail below with reference to examples, but the present invention should not be construed as being limited to these examples.

[0039] [Raw materials used] Cement: Ordinary Portland cement Admixture: Silica fume (BET specific surface area: 16.5m 2 / g) Fine aggregate: Silica sand No. 6 Water reducing agent: High performance water reducing agent (polycarboxylic acid type) Accelerator: Aluminum sulfate aqueous solution (reagent) Water: Tap water

[0040] [Preparation of cement composition] The components were blended in the proportions shown in Table 1 and mixed in a mixer to prepare cement compositions. The resulting cement compositions were evaluated as follows.

[0041] [Average extrusion pressure] A uniaxial compression test was conducted using a formwork with internal dimensions of 5 cm diameter and 10 cm height, and a discharge port diameter of 1 cm. A commercially available texture analyzer was used as the uniaxial compression tester. Specifically, the cement composition was filled into the formwork, and then extruded by moving an extrusion tool connected to the texture analyzer at a speed of 20 mm / min, and the relationship between the displacement and the extrusion pressure was determined. Next, the average extrusion pressure was calculated based on this relationship.

[0042] Deformation Coefficient The cement composition was filled into a mold with internal dimensions of 5 cm diameter and 10 cm height, and then demolded after 15 minutes to obtain a cylindrical molded body with a diameter of 5 cm and a height of 10 cm. Next, a uniaxial compression test was performed on the molded body using the same texture analyzer as above. Specifically, the molded body was sandwiched between two pressure plates, and compressed by moving the upper pressure plate connected to the texture analyzer at a speed (compression speed) of 20 mm / min, and the relationship between compressive stress and compressive strain was determined. Next, the deformation modulus was calculated based on this relationship.

[0043] [Extrusion] The extrudability of the cement composition was evaluated using an additive manufacturing device (3D printer) equipped with a cartridge containing the cement composition, a piston (77 mm diameter) inserted into the cartridge so that the cement composition can be extruded, and a nozzle (16 mm nozzle diameter) that can extrude (spit out) the cement composition by driving the piston. In this evaluation, if the cement composition could be extruded from the nozzle, it was represented as ○ (good extrudability), and if the cement composition could not be extruded from the nozzle, it was represented as × (poor extrudability).

[0044] [Self-supporting stability] A cement composition lamination test was conducted using the additive manufacturing device (3D printer). Specifically, using the additive manufacturing device, the cement composition was extruded while moving the nozzle over the loading platform (base) at a speed of 25 mm / s, and a laminate (modeled object) was produced by stacking multiple layers with a thickness of 10 mm and a circumference of 280 mm per layer. In this evaluation, the number of layers that could be stacked without collapsing or crushing during stacking (number of layers that could be stacked) was determined as the result. If the number of layers that could be stacked was 10 or more (stack height of 50 mm or more), it could be determined that the self-standing stability was good.

[0045] The results of the above evaluations are shown in Table 1.

[0046] [Table 1]

[0047] As shown in Table 1, cement compositions with an average extrusion pressure of 300 kPa or less and a deformation modulus of 0.05 MPa or more had good extrusion properties and self-supporting stability. In contrast, the cement composition of Comparative Example 1 had insufficient extrudability due to a high average extrusion pressure, and thus the self-supporting stability could not be evaluated. In Comparative Example 2, the raw materials could not be mixed, and a cement composition could not be obtained. In Comparative Example 3, the deformation modulus was too low, and therefore the self-standing stability was insufficient.

[0048] As can be seen from the above results, the present invention can provide a method for evaluating the extrudability of a cement composition for additive manufacturing, which allows for easy evaluation of extrudability. The present invention can also provide a method for evaluating the self-supporting stability of a cement composition for additive manufacturing, which allows for easy evaluation of self-supporting stability. Furthermore, the present invention can provide a cement composition for additive manufacturing that has excellent extrudability and self-supporting stability, and a method for selecting such a cement composition. [Explanation of symbols]

[0049] 10 Extrusion jig 20 Formwork 21 Opening 22 Outlet 30 Cement composition for additive manufacturing 40 Molded body 50 Pressure Plate

Claims

1. 1. A method for evaluating the extrudability of an additive manufacturing cement composition, comprising: The method includes filling the additive manufacturing cement composition into a formwork having an opening at one end through which an extrusion tool can be inserted and a filler discharge outlet at the other end, extruding the additive manufacturing cement composition filled in the formwork using the extrusion tool connected to a uniaxial compression testing machine, determining the relationship between displacement and extrusion pressure using the uniaxial compression testing machine, and calculating the average extrusion pressure based on the relationship.

2. The method according to claim 1, wherein the average extrusion pressure is an average value of extrusion pressures for a displacement of 10 to 30 mm.

3. 1. A method for evaluating the free-standing stability of an additive manufacturing cement composition, comprising: A method comprising: preparing a molded body of the additive manufacturing cement composition; compressing the molded body using a uniaxial compression testing machine to determine the relationship between compressive stress and compressive strain; and calculating a deformation coefficient based on the relationship.

4. 4. The method according to claim 3, wherein the deformation modulus is the slope of a line connecting a point where the compressive stress is 0.5 kPa and a point where the compressive stress is half the uniaxial compressive strength in a graph showing the relationship between compressive stress (y-axis) and compressive strain (x-axis).

5. 1. A method for selecting a cement composition for additive manufacturing, comprising: Selecting an additive manufacturing cement composition having an average extrusion pressure of 300 kPa or less and a deformation modulus of 0.05 MPa or more; The average extrusion pressure is calculated by the method according to claim 1 or 2 using a mold having an inner dimension of 5±0.5 cm in diameter and 10±1 cm in height, and an outlet diameter of 1±0.1 cm; 5. A method according to claim 3 or 4, wherein the deformation coefficient is calculated using a molded body having a diameter of 5±0.5 cm and a height of 10±1 cm.

6. A cement composition for additive manufacturing, wherein the average extrusion pressure is calculated using the method of claim 1 or 2 using a formwork having internal dimensions of 5 cm in diameter and 10 cm in height and a discharge outlet diameter of 1 cm, and the average extrusion pressure is 300 kPa or less, and the deformation coefficient is calculated using the method of claim 3 or 4 using a molded body having a diameter of 5 cm and a height of 10 cm, and the deformation coefficient is 0.05 MPa or more.

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