Mortar composition for three-dimensional modeling

Abstract

The purpose is to provide a mortar composition for three-dimensional modeling that enables three-dimensional modeling without depending on temperature. The mortar composition for three-dimensional modeling contains cement, gypsum, and fine aggregate, and a mini-slump exhibits a slump reduction rate of 65% or more 10 minutes after kneading at 20°C in comparison to a mini-slump immediately after kneading.

Description

Mortar composition for three-dimensional modeling

[0001] The present invention relates to a mortar composition for three-dimensional molding used in the fields of civil engineering, construction and factory products.

[0002] In recent years, a new three-dimensional modeling technology has been proposed for producing large-scale structures, such as construction components, using cementitious materials like mortar and concrete. Using this technology, automated construction machines are already being used in Europe, the United States, and China to manufacture large structures on the scale of detached houses.

[0003] For example, Patent Document 1 discloses a three-dimensional modeling technique using cementitious materials, in which three-dimensional data created by a computer is cut at a predetermined thickness to create two-dimensional slice data, mortar mixed with an accelerator is sprayed onto a bed (table) while controlling the movement of a spray nozzle in the vertical and horizontal directions based on the two-dimensional slice data, the sprayed mortar is allowed to self-harden to form a solidified layer in the shape based on the two-dimensional slice data, and the process of forming such solidified layers is repeated to sequentially stack them up and down to form a shape. Patent Document 2 describes a material for creating molds for producing castings using a 3D printer, and discloses a material consisting of cement, sand, and a water-soluble silicate as an accelerator.

[0004] Japanese Patent Application Laid-Open No. 10-235623 U.S. Patent No. 8,211,226

[0005] The fluidity of cementitious materials used for construction applications changes over time due to factors such as temperature. If the fluidity is unstable, the discharge rate will be unstable, which can lead to reduced lamination accuracy and irregularities. Therefore, the fluidity has been stabilized by predicting the temporal change in fluidity in advance and adjusting the amount of admixture. For example, Patent Document 1 adds a quick-setting additive, and Patent Document 2 adds an accelerator. However, adjusting the amount of admixture depending on the environmental temperature during three-dimensional modeling is cumbersome, and a cementitious material that is not affected by environmental temperature is desired.

[0006] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a mortar composition for three-dimensional modeling that enables three-dimensional modeling independent of temperature.

[0007] After extensive research to solve the above problems, the present inventors have conceived the following invention and found that it can solve the above problems. Specifically, the present invention is as follows: [1] A mortar composition for 3D printing containing cement, gypsum, and fine aggregate, wherein the mini-slump 10 minutes after mixing at 20°C exhibits a slump reduction rate of 65% or more compared to the mini-slump immediately after mixing. [2] The mortar composition for 3D printing according to [1], wherein the gypsum contains 90% by mass or more of gypsum hemihydrate. [3] The mortar composition for 3D printing according to [1] or [2], further containing short fibers. [4] The mortar composition for 3D printing according to any one of [1] to [3], wherein the slump reduction rate is 90% or more. [5] The mortar composition for 3D printing according to any one of [1] to [4], wherein the content of a calcium aluminate compound in the mortar composition for 3D printing is 5% by mass or less. [6] The mortar composition for three-dimensional fabrication according to any one of [1] to [5], wherein the content of a water-reducing agent in the mortar composition for three-dimensional fabrication is 0.1 mass% or less.

[0008] According to the present invention, it is possible to provide a mortar composition for three-dimensional modeling that enables three-dimensional modeling independent of temperature.

[0009] [Mortar composition for three-dimensional modeling] The mortar composition for three-dimensional modeling of the present invention (hereinafter also referred to as "mortar composition") contains cement, gypsum, and fine aggregate, and at 20°C, the mini-slump 10 minutes after mixing shows a slump reduction rate of 65% or more compared to the mini-slump immediately after mixing.

[0010] (Cement) The cement contained in the mortar composition of the present invention is not particularly limited, and examples thereof include various Portland cements such as normal, early-strength, ultra-early-strength, low-heat, and medium-heat; various mixed cements obtained by mixing these Portland cements with blast furnace slag, fly ash, silica fume, etc.; environmentally friendly cements (ecocements) produced using municipal waste incineration ash or sewage sludge incineration ash as raw materials; commercially available fine particle cements; and white cements. Various cements can also be used in a finely powdered form. Furthermore, cements prepared by increasing or decreasing the amounts of components normally used in cement can also be used. Furthermore, combinations of two or more of these can also be used.

[0011] The cement used in this embodiment has a Blaine specific surface area of ​​2,500 cm from the viewpoint of production cost and strength development. ２ / g or more 7,000cm ２ / g or less, and ２ / g or more 6,000cm ２ / g or less, and more preferably 3,000 cm ２ / g or more 4,500cm ２ In the present invention, the Blaine specific surface area value is determined in accordance with JIS R 5201:2015 (physical testing methods for cement).

[0012] The cement content in the mortar composition is preferably 10% by mass or more and 90% by mass or less, and more preferably 20% by mass or more and 80% by mass or less, from the viewpoint of stabilizing the fluidity (mini-slump) independent of temperature.

[0013] (Gypsum) Examples of gypsum contained in the mortar composition of the present invention include anhydrous gypsum, hemihydrate gypsum, and dihydrate gypsum. Other examples include natural gypsum, by-product gypsum, and gypsum obtained by heat treating these. These can also be used in combination. Among these, it is preferable to use hemihydrate gypsum from the viewpoint of stabilizing fluidity (mini-slump) independent of temperature.

[0014] The content of gypsum in the mortar composition is preferably 0.2% by mass or more and 10% by mass or less, more preferably 0.5% by mass or more and 8% by mass or less. Furthermore, when the above-mentioned gypsums are used in combination, the total gypsum preferably contains 90% by mass or more of gypsum hemihydrate, more preferably 95% by mass or more. The slump reduction rate described below can be adjusted by adjusting the amount of gypsum hemihydrate. By increasing the amount of gypsum hemihydrate, the slump reduction rate described below can be increased, and by decreasing the amount of gypsum hemihydrate, the slump reduction rate can be decreased. By making the amount of gypsum hemihydrate in the total gypsum 90% by mass or more, the slump reduction rate after 10 minutes of mixing at 20°C can be made 65% or more.

[0015] (Fine Aggregate) The fine aggregate contained in the mortar composition of the present invention may be the same as that used in ordinary cement mortar or concrete. That is, river sand, mountain sand, crushed sand, lime sand, silica sand, colored sand, sea sand, etc. may be used, and combinations of these may also be used.

[0016] The content of the fine aggregate is preferably 10 to 500 parts by mass, more preferably 50 to 400 parts by mass, and even more preferably 100 to 300 parts by mass, relative to 100 parts by mass of cement in the mortar composition. By setting the content of the fine aggregate at or above the lower limit, it is possible to reduce the drying shrinkage rate of the mortar, and by setting the content at or below the upper limit, it is possible to ensure appropriate softness and improve pumpability.

[0017] (Short Fibers) The short fibers contained in the mortar composition of the present invention are not an essential component of the mortar composition of the present invention, but are preferably contained. The inclusion of short fibers increases the frictional heat generated when the mortar composition of the present invention is pumped, thereby increasing the temperature of the mortar composition extruded from the nozzle tip and appropriately shortening the hardening time.

[0018] The short fibers contained in the mortar composition of the present invention can be any commercially available short fibers for cement admixture. Examples include vinylon fiber, acrylic fiber, nylon fiber, steel fiber, glass fiber, polypropylene fiber, polyethylene fiber, polyester fiber, and basalt fiber. These fibers can be used alone or in combination of two or more. Among these, vinylon fiber, which has a wide variety of fiber diameters and lengths, and nylon fiber, which has excellent dispersibility, are preferred.

[0019] Considering that the short fibers are premixed in advance, the average fiber length of the short fibers is preferably in the range of 5 to 15 mm. The average fiber diameter of the short fibers is preferably 20 to 250 μm, more preferably 100 to 250 μm. By setting the average fiber diameter within the above range, the short fibers are easy to obtain and can improve the pumpability of the mortar composition, thereby preventing deterioration of moldability or reduction in strength development. By setting the average fiber diameter of the short fibers to 20 μm or more, particularly 100 μm or more, the frictional heat generated when pumping the mortar composition increases, the temperature of the mortar composition discharged from the nozzle tip increases, and the curing time is suitably shortened, thereby achieving continuous, higher lamination.

[0020] Short fibers in the form of bundled fibers, in which monofilaments are bundled together with a binder, are preferred over monofilament fibers, as this allows for a larger number of fibers to be incorporated. The number of short fibers per gram is preferably 5,000 or more. By having a number of short fibers per gram of 5,000 or more, the reinforcing effect and initial crack suppression effect of the short fibers can be exhibited. The number of fibers per gram of short fibers is calculated using the following formula, where fineness (dtex) is the weight (g) per 10,000 m of monofilament: Number of fibers (fibers / g) = [1 / (fineness / 10,000 (m))] / average fiber length (m / fiber). The amount of short fibers used is preferably 0.1 to 1.0 parts by mass, more preferably 0.2 to 0.5 parts by mass, per 100 parts by mass of cement and fine aggregate combined. By using an amount within the above range, a reinforcing effect can be exhibited and pumping can be improved.

[0021] (Calcium Aluminate Compound) The mortar composition of the present invention preferably contains 5% by mass or less of calcium aluminate compounds, and more preferably contains substantially no calcium aluminate compounds. The phrase "substantially free of calcium aluminate compounds" means that calcium aluminate compounds and their raw materials are not actively added, and refers to a content below the impurity level contained in raw materials. Specifically, the content is, for example, 1% by mass or less. Because calcium aluminate compounds act as hardening accelerators, when calcium aluminate compounds are contained, the mortar composition begins to harden rapidly after mixing is stopped. Therefore, it is preferable to use calcium aluminate compounds in combination with a set retarder. However, when calcium aluminate compounds, which are hardening accelerators, are contained in combination with a set retarder, the fluidity after mixing varies depending on the temperature, making it necessary to adjust the amount of set retarder added. In this embodiment, the desired fluidity can be ensured by including gypsum hemihydrate. Therefore, even when the calcium aluminate compound content is 5% by mass or less, or preferably substantially absent, there is no need to add a set retarder. Therefore, the mortar composition can be produced without adjusting the amount of setting retarder added depending on the environmental temperature during three-dimensional shaping.

[0022] (Water-reducing agent) The mortar composition of the present invention preferably contains 0.1% by mass or less of a water-reducing agent, and more preferably contains substantially no water-reducing agent. The phrase "substantially does not contain a water-reducing agent" means that a water-reducing agent is not actively added, and refers to a content below the level of impurities contained in raw materials, etc. Specifically, for example, it is 0.02% by mass or less. A water-reducing agent is added to ensure the fluidity of a mortar composition. However, the water-reducing agent may reduce the slump reduction rate, making it impossible to ensure the desired fluidity. Therefore, the content of the water-reducing agent is preferably 0.1% by mass or less.

[0023] (Other Components) In the present invention, various additives such as antifoaming agents, anticorrosive agents, antifreeze agents, shrinkage reducing agents, inorganic minerals such as bentonite and sepiolite, anion exchangers such as hydrotalcite, polymer emulsions, etc. can be added within the range that does not impair application and the performance of the hardened body. Furthermore, it is also possible to use inorganic powders with hydration activity such as blast furnace slag, silica fume, and fly ash, apart from those pre-mixed with cement.

[0024] The mortar composition for three-dimensional modeling of the present invention is mixed with water to prepare a wet material, which is then used for three-dimensional modeling. The amount of water used is preferably 20 to 70 parts by mass, more preferably 30 to 60 parts by mass, per 100 parts by mass of cement. By using water in the above range, the mortar composition can be easily mixed and its self-supporting properties can be ensured.

[0025]

[0033] Next, a three-dimensional modeling method using the mortar composition will be described. The three-dimensional modeling method can be classified into a mixing step of the mortar composition, a pumping step of the mortar composition, and a three-dimensional modeling step using controlled nozzle movement.

[0026] The method for mixing the mortar composition is not particularly limited, and the mortar composition can be mixed using a commercially available mixer, such as a pan mixer, a forced twin-screw mixer, or a continuous mixing mixer pump that combines a mixer and a pressure pump (a rotary positive displacement single-shaft eccentric screw pump).

[0027] The pump used to pump the mortar composition is not particularly limited as long as it can pump the mortar composition without degrading its quality. However, a rotary positive displacement uniaxial eccentric screw pump is preferred. Rotary positive displacement uniaxial eccentric screw pumps, also known as mono pumps or snake pumps, are capable of constant pumping without pulsation compared to squeeze pumps, and the discharge rate can be adjusted by controlling the motor rotation speed. Furthermore, due to their structure, rotary positive displacement uniaxial eccentric screw pumps are considered to be more likely to increase the temperature of the wet material being pumped. This allows the curing reaction of the wet material to proceed in a short time, improving self-supporting stability and allowing for a larger continuous stack height. Specifically, rotary positive displacement uniaxial eccentric screw pumps have a rotor corresponding to the male thread and a stator corresponding to the female thread. When the rotor is inserted into the stator, a sealed space called a cavity (e.g., the space between the rotor and the stator) is formed in the gap. As the rotor rotates within the stator, a strong suction force is generated, and the cavity moves toward the discharge side, thereby continuously transporting the material. During transfer, for example, the rotor rotates eccentrically around the central axis of the stator while revolving around the axis. It is believed that when the material in the first cavity moves to the previous (discharge) cavity due to suction force, it is heated by frictional resistance with the stator surface. By utilizing this heating phenomenon, it is possible to achieve three-dimensional shaping with superior self-standing stability while ensuring usable life. For example, a rotary positive displacement uniaxial eccentric screw pump is exemplified in paragraphs 0063-0064 of International Publication No. 2014 / 142239.

[0028] The pressure-transfer piping can be a flexible hose with a pressure resistance of 2 to 4 MPa or a combination of metal piping in part, and although it depends on the set discharge rate, the piping diameter is preferably an inner diameter of 20 to 50 mm. There are no particular limitations on the length of the pressure-transfer piping, but a length of 20 m or less is preferred in consideration of pumpability.

[0029] A nozzle is provided at the discharge portion of the mortar composition (the tip of the pressure-transport pipe). The diameter of the discharge port is not particularly limited, but may be set appropriately depending on the diameter of the aggregate used and the stacking width. For example, if the aggregate diameter is 5 mm or less and the stacking width is 50 mm or less, the diameter of the discharge port is preferably 8 to 15 mm. The shape of the discharge port is not particularly limited, but examples include circular, elliptical, rectangular, cross, and star shapes, and a brim may be provided around the discharge port to impart smoothness to the surface of the discharged wet material. In these cases, the discharge port is provided perpendicular to the bed, but in some cases, the discharge port may be provided horizontally.

[0030] The horizontal and vertical movement of the nozzle is preferably controlled by, for example, fixing the nozzle to a robot arm or a portal plotter and controlling it by computer. For example, a method is possible in which three-dimensional data created by a computer is cut at a predetermined thickness to create two-dimensional slice data, and the spray nozzle is controlled to move horizontally (vertically, horizontally, diagonally, etc.) based on the two-dimensional slice data while ejecting wet material from the nozzle onto the bed and moving the nozzle vertically, thereby repeatedly layering and forming the desired shape. The nozzle movement speed is not particularly limited and can be changed depending on the layer width. When the amount of mortar composition ejected is constant, slowing the speed increases the layer width, and increasing the speed decreases the layer width.

[0031] [Physical Properties of Mortar Composition for 3D Fabrication] (Slump Reduction Rate) The mortar composition for 3D fabrication of the present invention exhibits a slump reduction rate of 65% or more at 20°C, in terms of the mini-slump 10 minutes after mixing, compared to the mini-slump immediately after mixing. In the present invention, the mini-slump (MS) can be measured in accordance with JIS A 1171. The temperature at which the mini-slump is measured, 20°C, is the ambient temperature. The mortar composition for measuring the mini-slump is prepared, for example, by mixing for 30 seconds at a high speed using a mortar mixer in accordance with JIS R 5201. The mini-slump immediately after mixing is specifically a value measured within 1 minute after mixing the mortar composition for 30 seconds.

[0032] In addition, in this embodiment, the slump reduction rate (%) 10 minutes after mixing can be determined by the following equation: Slump reduction rate (%) = [mini-slump (immediately after mixing) - mini-slump (after a predetermined time has elapsed (10 minutes))] / [mini-slump (immediately after mixing)] × 100.

[0033] In this embodiment, the slump reduction rate after 10 minutes at 20° C. is 65% or more, preferably 90% or more, and more preferably 95% or more. As described above, the mortar composition of this embodiment can stabilize the fluidity (mini-slump) regardless of temperature. Therefore, by making the slump reduction rate after 10 minutes at 20° C. 65% or more, the slump reduction rate after 10 minutes can be made 65% or more even in the temperature range of 5° C. to 40° C. By making the slump reduction rate after 10 minutes 65% or more, the fluidity after 10 minutes can be suppressed. Therefore, when performing three-dimensional modeling, a mortar composition is discharged from a nozzle, and after the fluidity is lost, the mortar composition is discharged again and layered, thereby producing a shaped object.

[0034] The present invention will be described in more detail below using examples and comparative examples, but the present invention is not limited to the following examples and comparative examples as long as they do not deviate from the spirit of the present invention.

[0035] Experimental Example 1 A mortar composition was prepared according to the formulation in Table 1 below, and mixed for 30 seconds at high speed using a mortar mixer conforming to JIS R 5201. The mini-slump immediately after mixing and after 10 minutes were measured to determine the slump reduction rate. The experiment was carried out at an ambient temperature shown in Table 1. The mini-slump immediately after mixing was measured within 1 minute after mixing for 30 seconds.

[0036] (Materials used) Cement: Ordinary Portland cement, commercially available Gypsum (a): Hemihydrate gypsum, commercially available, manufactured by Yoshino Gypsum Co., Ltd., product number D-YN·H Gypsum (b): Anhydrous gypsum, commercially available, manufactured by Mitsubishi Materials Corporation The content of hemihydrate gypsum in the gypsum was adjusted by combining gypsum (a) and gypsum (b). Fine aggregate: Silica sand, commercially available, manufactured by Nippyo Mining Co., Ltd., product number N50 Short fiber: Vinylon fiber, commercially available, manufactured by Kuraray Co., Ltd., product number RECS7x6 Calcium aluminate: Commercially available special grade reagent CaCO ３ , Al ２ O ３ The above were mixed in a predetermined ratio, heated and melted at about 2000°C using a high-frequency furnace, quenched in water, and pulverized to prepare a product (amorphous, CaO / Al ２ O ３ Molar ratio 2.0, Blaine specific surface area 5500 cm ２ / g) Water reducing agent: polycarboxylic acid type, commercially available product, manufactured by BASF Japan Ltd., product number Melflux AP101F

[0037] In addition, a three-dimensional modeling experiment was conducted using the produced mortar compositions, and the lamination property (three-dimensional modeling property) was evaluated. The ambient temperature was 20°C. The three-dimensional modeling mortar compositions of Test Nos. 1-1 to 1-10 were added to a continuous mixing mixer pump, continuously mixed, pumped, and discharged from the nozzle tip via a flexible hose, thereby forming a three-dimensional model. In the evaluation of lamination property, a continuous stacking height of 30 cm or more was considered to be pass (◯ in Table 1), and a height of less than 30 cm was considered to be fail (× in Table 1).

[0038] The system and modeling conditions used in the 3D modeling experiment are as follows: (System) Continuous kneading mixer pump: manufactured by m-tec Pressure feed hose: 4 MPa pressure-resistant flexible hose (manufactured by PFT, inner diameter 1 inch, pressure feed piping distance 10 m) Nozzle: Homemade, nozzle outlet diameter 12 mm (circular) Robot arm: A modified robot arm (product name "MOTOMAN-MA2010") manufactured by Yaskawa Electric Corporation was used with a nozzle fixed to the tip of the arm.

[0039] (Modeling conditions) Shape of three-dimensional modeling object: hollow cylinder (inner diameter 29 cm, height of mortar composition for three-dimensional modeling per layer 1 to 2 cm, layer width (wall thickness) approximately 20 mm) Discharge amount of mortar composition for three-dimensional modeling: 0.3 m ３ / hr Nozzle movement speed: 180 mm / min Nozzle vertical movement distance: 15 mm

[0040]

[0041] By using the mortar composition for three-dimensional modeling of the present invention, the fluidity (slump reduction rate) can be stabilized regardless of temperature, so there is no need to adjust the composition of the mortar composition for three-dimensional modeling depending on the temperature, and it can be suitably used for the manufacture of civil engineering and construction components, etc.

Claims

1. A mortar composition for three-dimensional modeling, which contains cement, gypsum, and fine aggregate, and which, at 20°C, exhibits a slump reduction rate of 65% or more in the mini-slump 10 minutes after mixing, compared to the mini-slump immediately after mixing.

2. The mortar composition for three-dimensional modeling according to claim 1, wherein the gypsum contains 90% by mass or more of hemihydrate gypsum.

3. The mortar composition for three-dimensional modeling according to claim 1 or 2, further comprising short fibers.

4. A mortar composition for three-dimensional modeling according to claim 1 or 2, wherein the slump reduction rate is 90% or more.

5. A mortar composition for three-dimensional modeling according to claim 1 or 2, wherein the content of the calcium aluminate compound in the mortar composition for three-dimensional modeling is 5 mass% or less.

6. A mortar composition for three-dimensional modeling according to claim 1 or 2, wherein the content of the water reducing agent in the mortar composition for three-dimensional modeling is 0.1 mass% or less.

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