Preparation method of high-strength and high-durability 3D printing concrete

Abstract

The invention relates to a preparation method of high-strength and high-durability 3D printing concrete applied to the field of concrete preparation. The preparation method comprises the following steps: S1, preparing materials; s3, uniformly stirring high-alumina cement, fine aggregate and glass fibers through a stirrer, then adding the mixing water containing the silane carbon dots, continuously stirring for 4-6 minutes until the mixture is uniform to obtain a 3D printing material, assisting dry-wet mixing and stirring through a lifting stirring assembly in the stirrer in the stirring process, and intercepting and crushing agglomerates in real time; s4, the 3D printing material in the S3 is put into a charging barrel of an extrusion type 3D printer for extrusion printing, and 3D printing concrete is obtained, silane-containing carbon dots are prepared through a two-step hydrothermal method, the stability and durability of the 3D printing concrete are improved, silane grafting efficiency is higher, the 3D printing concrete is more environmentally friendly, in the dry-wet mixing process in the S3, a stirring machine is adopted to be matched with a lifting stirring assembly, and the stirring efficiency is improved. The interference of insoluble lumps on the quality of the concrete is reduced.

Description

Technical Field

[0001] This invention relates to a method for preparing concrete, and more particularly to a method for preparing high-strength, high-durability 3D-printed concrete for application in the field of concrete preparation. Background Technology

[0002] 3D-printed concrete is an innovative construction technology that builds structures by layering materials. In the field of lightweight building materials, it offers significant advantages: achieving superior thermal insulation performance while substantially reducing material usage and construction costs. Combined with digital design, this technology can manufacture lightweight components with complex geometries, providing new solutions for building weight reduction and energy conservation.

[0003] In recent years, 3D printed concrete technology has been successfully applied to lightweight building materials such as walls. However, in marine engineering, high-rise buildings or extreme climate environments, problems such as delamination and excessive carbonization depth are prone to occur, resulting in a significant decrease in structural durability. In addition, the existing concrete cement has high carbon emissions and easy permeability issues that urgently need to be addressed.

[0004] Chinese invention patent CN113372075B discloses a 3D-printed concrete and its preparation method, as well as a 3D-printed column template. The printed components have good compressive and bending resistance, low cracking rate, and are easy to promote and apply. It uses sulfoaluminate cement, which can improve corrosion resistance, frost resistance, and impermeability.

[0005] Chinese invention patent CN114656225B discloses a method for preparing 3D printed concrete, which solves the problems of insufficient water and poor curing inside 3D printed concrete, and the problem of low interlayer bond strength in 3D printed concrete.

[0006] In the current process of preparing concrete for printing, aggregates and fibers need to be dry-mixed first, followed by wet-dry mixing with water. During this process, the small amount of water added at the beginning, when mixed with a large amount of dry-mixed products, easily forms clumps that are wet on the surface and dry inside. This makes it easy to form insoluble substances during subsequent mixing. In order to enhance the mixing effect, it is necessary to extend the mixing time of the concrete. However, such long-term shearing action will damage the fibers. Therefore, the residual insoluble substances have an adverse effect on the quality of the concrete. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to address the issues of low thixotropy of concrete, poor structural stability, insufficient adaptability to printing complex shapes, and insufficient dissolution of dry powder particles during mixing, which are problems existing in the prior art.

[0008] To address the above problems, this invention provides a method for preparing high-strength, high-durability 3D-printed concrete, comprising the following steps: S1. Material preparation: Prepare the ingredients according to the following mass percentages: High-alumina cement: 40%-50%; Mixing water: 12%-16%; Silane-containing carbon points: 0.01%-1.0%; Fine aggregate: 30%-40%; Glass fiber: 0.5%-2.0%; S2. Preparation of silane-containing carbon dots, the specific steps are as follows: S21. After mixing glucose, deionized water and ethanol evenly, transfer them to a high-pressure reactor and react at 160-180°C for 3-4 hours. After cooling to room temperature, the initial product is obtained. S22. Purify the initial product to obtain carbon dots; S23. Dissolve γ-aminopropyltriethoxysilane in a mixture of ethanol and water, and stir at room temperature for 2-3 h to generate silanol; S24. Add the carbon dots prepared in S22, stir evenly, transfer to a high-pressure reactor, react at 160-200°C for 8-10 hours, and then purify to obtain silane-containing carbon dots. S3. Mix high-alumina cement, fine aggregate and glass fiber evenly with a mixer, then add mixing water containing silane carbon dots, and continue mixing for 4-6 minutes until uniform to obtain 3D printing material. During the mixing process, the lifting mixing component in the mixer assists in the dry and wet mixing, and intercepts and breaks up lumps in real time. S4. Place the 3D printing material from S3 into the barrel of the extrusion 3D printer and extrude it to obtain 3D printed concrete.

[0009] In the above-mentioned method for preparing high-strength and high-durability 3D printed concrete, a mixer is used in conjunction with a lifting mixing component to achieve real-time interception and crushing of clumps. This reduces the interference of insoluble clumps on the quality of concrete during dry and wet mixing. Furthermore, a two-step hydrothermal method is used to prepare silane-containing carbon dots, which improves the stability and durability of 3D printed concrete and makes silane grafting more efficient and environmentally friendly.

[0010] Furthermore, the silane carbon dots in S2 are spherical with a particle size distribution range of 2-20 nm. The oxygen-containing and nitrogen-containing functional groups on the surface of the silane carbon dots in S2 include one or more of OH, C=O, C=C, Si-O-Si, Si-OH and NH. The diameter of the circular printing nozzle on the surface of the 3D printer barrel in S4 is 20-50 mm. The volume ratio of ethanol to water in the mixture of ethanol and water in S23 is 10-5:1.

[0011] Furthermore, the S3 high-strength and high-durability 3D printing material adds auxiliary cementitious materials to replace part of the cement content. The auxiliary cementitious materials are one or more of the following: fly ash, silica fume, limestone powder, metakaolin, slag powder, and steel slag powder.

[0012] Furthermore, the mixer in S3 is used for dry and wet mixing of materials. The mixer is equipped with a top cover plate, and a drive motor and a diversion pipe are installed on the top of the top cover plate. The top cover plate has an annular groove inside. The lifting and mixing assembly includes a reciprocating screw. The reciprocating screw is fixedly connected to an outer cover rod near the bottom surface via a connecting rod. Multiple sets of mixing rods are arranged on the surface of the outer cover rod. A movable sleeve is threadedly connected to the surface of the reciprocating screw. A movable ring is rotatably connected to the surface of the movable ring. A sieve plate is slidably connected to the surface of the outer cover rod. The sieve plate has a through groove matching the mixing rod inside. A closing assembly for the mixing rod to pass through the sieve plate is installed inside the through groove. A grinding assembly is rotatably connected inside the annular groove to grind the lumps that are wet on the surface and dry inside that are screened out from the sieve plate. The diversion pipe is used to divert the mixing water into the mixer for dry and wet mixing after the dry materials are mixed.

[0013] Furthermore, the closing assembly includes a rotating plug rod rotatably installed inside the through groove, and the rotating plug rod has a through groove for accommodating the stirring rod through the sieve plate. The cross-sectional length and width of the through groove are the same as the length and diameter of the stirring rod, respectively. A drive motor is fitted inside the movable ring, and the output end of the drive motor is connected to the end of the rotating plug rod through a short rod. The inner wall of the sieve plate is fitted with a constraint rod. The outer cover rod has a strip groove inside and constraint rods spaced apart from the strip groove. A lifting block matching the strip groove is installed on the surface of the movable ring near the bottom.

[0014] Furthermore, the lifting block is used to lift the rotating plug rod, and the cross-sectional width of the lifting block is not greater than the cross-sectional width of the strip groove.

[0015] Furthermore, the grinding assembly includes an output rotor connected to the output end of the drive motor. A rotating component is fixedly mounted on the surface of the output rotor. An I-shaped movable plate is slidably connected through the interior of the rotating component. A spring telescopic column is connected to the top of the movable plate, and the top of the spring telescopic column is movably connected to the interior of the annular groove through a hinge ball. The height of the movable plate is greater than the diameter of the rotating component.

[0016] Furthermore, the output rotor and the reciprocating screw are connected by a reducer. When the moving sleeve moves to the top thread position of the reciprocating screw, the movable plate presses the spring telescopic column upward to compress it to its minimum value.

[0017] Furthermore, the cross-sectional thickness of the through groove after it is rotated 90 degrees is less than the thickness of the sieve plate, and the projection of the stirring rod in the vertical direction is the same as the projection of the through groove in the vertical direction.

[0018] Furthermore, an electromagnetic ring is embedded in the top wall of the annular groove, the movable plate is made of magnetic material, and a displacement sensor for monitoring the movement and lifting status of the movable plate is installed inside the movable plate.

[0019] In summary, this application employs a reciprocating screw-driven dynamic sieve plate structure to achieve real-time interception and crushing of clumps. Combined with a flip-over through-slot design, it ensures continuous mixing. Furthermore, the grinding assembly utilizes the shear force generated by the speed difference to perform secondary crushing of the clumps. A spring-loaded movable plate forms adaptive pressure, enhancing the compaction effect. The overall mechanical synergy effectively eliminates mixing dead zones, reduces material porosity, and enables the concrete to achieve superior density and interfacial bonding strength, meeting the dual requirements of 3D printing for material flowability and molding precision. Moreover, the concrete obtained by this method is prepared using a two-step hydrothermal method to produce silane-containing carbon dots, meeting the requirements of low-carbon and sustainable development. The resulting concrete is suitable for printing structures with various complex geometries, including vertical, suspended, and large-span buildings. Attached Figure Description

[0020] Figure 1 This is a flowchart illustrating the preparation process of the first embodiment of this application; Figure 2 This is a transmission electron microscope (TEM) image of a silane carbon dot-containing structure according to the first embodiment of this application. Figure 3 This is the Fourier transform infrared (FTIR) spectrum of the silane carbon dots in the first embodiment of this application; Figure 4 This is a schematic diagram of the overall structure of the second and third embodiments of this application; Figure 5 These are internal structural diagrams of the mixer according to the second and third embodiments of this application; Figure 6 This is an installation diagram of the grinding assembly, reducer, outer cover rod, and sieve plate according to the second and third embodiments of this application; Figure 7 For this application Figure 6 Enlarged view of point A in the middle; Figure 8 This is a mounting diagram of the movable coil and drive motor in the second and third embodiments of this application; Figure 9 These are structural diagrams of the grinding assembly according to the second and third embodiments of this application; Figure 10 This is a structural diagram of the reciprocating lead screw and outer cover rod according to the second and third embodiments of this application; Figure 11The diagram shows the sieve plate, through groove, and rotating plug rod structure of the second and third embodiments of this application. Figure 12 This is a diagram showing the state of the through groove after the rotating plug rod is rotated 90 degrees in the second and third embodiments of this application; Figure 13 These are diagrams showing the state of the sieve plate before and after passing the stirring rod during the upward movement of the sieve plate in the second and third embodiments of this application. Figure 14 This is a state diagram showing the screen plate moving up to the topmost stirring rod and contacting the grinding assembly to perform the corresponding grinding operation in the second and third embodiments of this application; Figure 15 This is a structural diagram of the electromagnetic ring according to the third embodiment of this application.

[0021] Explanation of the labels in the diagram: 1. Mixer; 2. Drain pipe; 3. Drive motor; 4. Annular groove; 5. Grinding assembly; 51. Output rotating rod; 52. Rotating component; 53. Movable plate; 54. Spring telescopic column; 6. Sieve plate; 7. Mixing rod; 8. Reducer; 9. Outer cover rod; 91. Constraint rod; 92. Strip groove; 10. Reciprocating lead screw; 11. Movable ring component; 12. Drive motor; 13. Rotating plug rod; 131. Through groove; 14. Electromagnetic ring. Detailed Implementation

[0022] The three embodiments of this application will now be described in detail with reference to the accompanying drawings.

[0023] First implementation method: Figure 1 A method for preparing high-strength, high-durability 3D-printed concrete is shown, comprising the following steps: S1. Material preparation: Prepare the ingredients according to the following mass percentages: High-alumina cement: 40%-50%; Mixing water: 12%-16%; Silane-containing carbon points: 0.01%-1.0%; Fine aggregate: 30%-40%; Glass fiber: 0.5%-2.0%; The appropriate high-alumina cement from the prior art shall be selected by those skilled in the art for batching, such as aluminate cement with an alumina content of 50%-60%; Specifically, in the prior art, fluidity is improved by increasing the content of silicate cement, but the resulting high heat of hydration exacerbates the risk of temperature cracking. In this application, high-alumina cement is used in conjunction with the addition of silane carbon dots to ensure fluidity and corrosion resistance.

[0024] S2. Preparation of silane-containing carbon dots, the specific steps are as follows: S21. After mixing glucose, deionized water and ethanol evenly, transfer them to a high-pressure reactor and react at 160-180°C for 3-4 hours. After cooling to room temperature, the initial product is obtained. S22. Purify the initial product to obtain carbon dots; S23. Dissolve γ-aminopropyltriethoxysilane in a mixture of ethanol and water, and stir at room temperature for 2-3 h to generate silanol; S24. Add the carbon dots prepared in S22, stir evenly, transfer to a high-pressure reactor, react at 160-200°C for 8-10 hours, and then purify to obtain silane-containing carbon dots. S3. Mix high-alumina cement, fine aggregate and glass fiber evenly through mixer 1, then add mixing water containing silane carbon dots, and continue mixing for 4-6 minutes until uniform to obtain 3D printing material. During the mixing process, the lifting mixing component in mixer 1 assists in the dry and wet mixing, and intercepts and breaks up lumps in real time. S4. Place the 3D printing material from S3 into the barrel of the extrusion 3D printer and extrude it to obtain 3D printed concrete.

[0025] Specifically, compared to the one-step hydrothermal method for preparing silanized carbon dots provided by the existing patent CN113174255B, the two-step hydrothermal method used in this application for preparing silane-containing carbon dots results in higher silane grafting efficiency.

[0026] The prepared silane-containing carbon dots can significantly improve the rheological and interfacial properties of 3D printed concrete (e.g., Figures 2-3 (As shown). On the one hand, silane-containing carbon dots enhance rheological properties through the ball-bearing effect and steric hindrance effect. Specifically, silane-containing carbon dots are spherical particles with lubricity, which can exert the ball-bearing effect; silane-containing carbon dots can adsorb onto the surface of cement particles, exert steric hindrance, disperse cement particles, and thus release free water encapsulated in cement particle clusters.

[0027] On the other hand, silane-containing carbon dots enhance interfacial properties through nucleation, bridging, and chemical bonding effects. Specifically, during cement hydration, the carbon nuclei of silane-containing carbon dots exert the nucleation effect of nanomaterials, further promoting cement hydration and generating more hydration products, thereby reducing porosity and enhancing interfacial properties. Silane-containing carbon dots form a flexible chemical bond network between glass fibers and cement, transferring the tensile load borne by the fibers to the matrix. When the matrix cracks, the elastic network formed by silane can delay crack propagation. The alkoxy groups of silane-containing carbon dots hydrolyze in a humid environment to generate silanol groups (Si-OH), which condense with silanol groups (Si-OH) on the surface of glass fibers to form Si-O-Si covalent bonds, achieving chemical modification of the fiber surface.

[0028] Furthermore, the flexibility of silane molecular chains can reduce interfacial rigidity and decrease stress concentration. During the layer-by-layer deposition process in 3D printing, silanes can also alleviate interlayer shear stress and improve the overall structural stability.

[0029] The silane carbon dots in S2 are spherical with a particle size distribution range of 2-20 nm. The oxygen-containing and nitrogen-containing functional groups on the surface of the silane carbon dots in S2 include one or more of OH, C=O, C=C, Si-O-Si, Si-OH and NH. The diameter of the circular printing nozzle on the surface of the 3D printer barrel in S4 is 20-50 mm. The volume ratio of ethanol to water in the mixture of ethanol and water in S23 is 10-5:1.

[0030] The S3 high-strength and high-durability 3D printing material adds auxiliary cementitious materials to replace part of the cement. The auxiliary cementitious materials are one or more of the following: fly ash, silica fume, limestone powder, metakaolin, slag powder, and steel slag powder. Example

[0031] S1: 2.5g glucose, 50mL deionized water and 50mL ethanol were stirred evenly and then transferred to a high-pressure reactor. The mixture was reacted at 170°C for 3.5h and cooled to room temperature to obtain the initial product. S11. The initial product was subjected to purification steps such as centrifugation (8000 rpm, 15 min), dialysis, rotary evaporation, and freeze drying to obtain carbon dots; S12. Dissolve 10 mL of γ-aminopropyltriethoxysilane in 100 mL of an ethanol / water mixture with a volume ratio of 9:1, adjust the pH to 4.5, and stir at room temperature for 2.5 h to hydrolyze γ-aminopropyltriethoxysilane to generate silanol. S13. Add the prepared carbon dots, stir evenly, and then transfer to a high-pressure reactor. React at 180°C for 9 hours. S14. After centrifugation (8000 rpm, 15 min), dialyzing, rotary evaporation, and freeze drying, silane-containing carbon dots were obtained. S2: Weigh 0.5g of the silane-containing carbon dots prepared above, add it to 160mL of mixing water, and stir evenly; mix 500g of high-alumina cement, 320g of fine aggregate and 20g of glass fiber evenly, then add the silane-containing carbon dots mixing water, and stir continuously in a mixer for 5min until uniform to obtain 3D printing material. S3: Place the above high-strength and high-durability 3D printing material into the barrel of an extrusion 3D printer (the diameter of the printing nozzle is 40mm), and use the circular nozzle to extrude and print to obtain 3D printed concrete.

[0032] Comparative Example 1 Mix 500g of high-alumina cement, 320g of fine aggregate and 20g of glass fiber evenly, then add 160mL of mixing water and stir continuously in a mixer for 5 minutes until uniform to obtain 3D printing material. Then put it into the barrel of an extrusion 3D printer (the diameter of the printing nozzle is 40mm) and use a circular nozzle to extrude and print to obtain 3D printed concrete. Other steps are the same as in the example.

[0033] Comparative Example 2 Weigh 0.5g of carbon dots and add them to 160mL of mixing water, and stir evenly. Mix 500g of high-alumina cement, 320g of fine aggregate and 20g of glass fiber evenly, then add the carbon dots and mixing water, and continue stirring in a mixer for 5 minutes until uniform to obtain carbon dot-containing 3D printing material. Then put it into the barrel of an extrusion 3D printer (the diameter of the printing nozzle is 40mm), and use a circular nozzle to extrude and print to obtain carbon dot-containing 3D printed concrete. Other steps are the same as in the example.

[0034] To prove that the product prepared in S2 of the example contains silane carbon dots, it was characterized by TEM and FTIR, such as... Figure 2 As shown, the prepared product is spherical and well-dispersed, with a particle size distribution range of 5-20 nm. Figure 3 As shown, the peak at 1599 cm⁻¹ belongs to a C=C bond, confirming the existence of the sp₂C structure. Furthermore, the peaks at 1122 cm⁻¹ and 908 cm⁻¹ belong to Si-O-Si and Si-OH bonds, respectively, confirming that the silane has been successfully grafted onto the carbon dots. Therefore, the above characterization confirms that the prepared product contains silane-containing carbon dots.

[0035] To demonstrate the good rheological properties of the 3D-printed concrete prepared in Example S4, the spread of the 3D-printed concrete prepared in Example 1, Comparative Example 2 was tested using the jump-table method specified in GB / T2419-2005 "Method for Determination of Flowability of Cement Mortar". Furthermore, to demonstrate the excellent strength and durability of the 3D-printed concrete prepared in Example S4, the interlaminar splitting strength, compressive strength, tensile strength, and chloride ion penetration coefficient of the 3D-printed concrete prepared in Example 1, Comparative Example 2 were tested after 28 days of curing, following the methods specified in T / CECS786-2020 "Technical Specification for 3D Printing of Concrete". The test results are shown in Table 1.

[0036] Table 1 Comparison of strength and durability of three types of 3D printed concrete sample Expansion (mm) Interlaminar splitting strength (MPa) Compressive strength (MPa) Tensile strength (MPa) <![CDATA[Chloride ion permeability coefficient (×10 -12 )]] Example 205 3.2 45.4 5.6 10.1 Comparative Example 1 183 1.8 39.2 3.2 14.7 Comparative Example 2 191 2.3 42.3 4.0 12.8 As shown in Table 1, Comparative Example 2 exhibits greater scalability than Comparative Example 1, while the Example exhibits the greatest scalability. Specifically, the scalability of Comparative Example 2 and the Example is increased by 4.4% and 12.0% respectively compared to Comparative Example 1. This indicates that the 3D printed concrete prepared in the Example has the best rheological properties, confirming that silane-containing carbon dots can significantly improve the rheological properties of 3D printed concrete. Furthermore, compared to Comparative Example 1, Comparative Example 2 exhibits higher strength and a lower chloride ion permeability coefficient, while the Example exhibits the highest strength and the lowest chloride ion permeability coefficient.

[0037] Specifically, compared to Comparative Example 1, Comparative Example 2 showed increases in interlaminar splitting strength, compressive strength, and tensile strength of 27.8%, 7.9%, and 25.0%, respectively, while a decrease in chloride ion permeability coefficient of 12.9%. In contrast, the examples showed increases in interlaminar splitting strength, compressive strength, and tensile strength of 2 of 3D printed concrete of 2 of 3D printed concrete of 77.8%, 15.8%, and 75.0%, respectively, while a decrease in chloride ion permeability coefficient of 31.3%. This indicates that the 3D printed concrete prepared in the examples possesses excellent strength and durability, confirming that silane-containing carbon dots can significantly improve the interfacial properties of 3D printed concrete.

[0038] Second implementation method: Figures 4-8 and Figure 10 As shown, the mixer 1 in S3 is used for dry and wet mixing of materials. The mixer 1 has a top cover plate, on the top of which a drive motor 3 and a drain pipe 2 are installed. An annular groove 4 is provided inside the top cover plate. A lifting mixing assembly is installed inside the mixer 1, including a reciprocating screw 10. An outer cover rod 9 is fixedly connected to the reciprocating screw 10 near its bottom surface via a connecting rod. Multiple sets of mixing rods 7 are arranged on the surface of the outer cover rod 9. A movable sleeve is threaded onto the surface of the reciprocating screw 10. A movable ring 11 is rotatably connected to the surface of the movable sleeve. A sieve plate 6 is slidably connected to the surface of the outer cover rod 9 and fitted onto the surface of the movable ring 11. A through groove matching the mixing rods 7 is arranged inside the sieve plate 6. A closing assembly for the mixing rods 7 to pass through the sieve plate 6 is installed inside the through groove. Figure 11 As shown, the closing assembly includes a rotating plug rod 13 rotatably mounted inside the through groove, and the interior of the rotating plug rod 13 is provided with a through groove 131 for accommodating the stirring rod 7 passing through the sieve plate 6; The annular groove 4 is rotatably connected to a grinding assembly 5, which is used to grind the lumps that are wet on the surface and dry on the inside that are screened out from the surface of the sieve plate 6. The diversion pipe 2 is used to divert the mixing water into the mixer 1 for dry and wet mixing after the dry materials are mixed.

[0039] The length and width of the cross-section of the channel 131 are the same as the length and diameter of the stirring rod 7, respectively. Figure 8As shown, a drive motor 12 is fitted inside the movable ring 11, and the output end of the drive motor 12 is connected to the end of the rotating plug rod 13 via a short rod.

[0040] The inner wall of the sieve plate 6 is fitted and connected to the constraint rod 91. The inner wall of the outer cover rod 9 is provided with a strip groove 92 and constraint rods 91 arranged at intervals with the strip groove 92. The surface of the movable ring 11 near the bottom is equipped with a lifting block that matches the strip groove 92. The lifting block is used to lift the rotating blocking rod 13, and the cross-sectional width of the lifting block is not greater than the cross-sectional width of the strip groove 92.

[0041] Figure 6 and Figure 9 The grinding assembly 5 is shown to include an output rotating rod 51 connected to the output end of the drive motor 3. A rotating component 52 is fixedly mounted on the surface of the output rotating rod 51. An I-shaped movable plate 53 is slidably connected through the interior of the rotating component 52. A spring telescopic column 54 is connected to the top of the movable plate 53, and the top of the spring telescopic column 54 is movably connected to the interior of the annular groove 4 through a hinge ball. The height of the movable plate 53 is greater than the diameter of the rotating component 52.

[0042] Figure 7 As shown, the output rotary rod 51 and the reciprocating screw 10 are connected by a reducer 8. When the moving sleeve moves to the top thread position of the reciprocating screw 10, the movable plate 53 presses the spring telescopic column 54 upward to compress it to the minimum value.

[0043] Figure 12 As shown, the cross-sectional thickness of the through groove 131 after being rotated 90 degrees is less than the thickness of the sieve plate 6, and the projection of the stirring rod 7 in the vertical direction is the same as the projection of the through groove 131 in the vertical direction.

[0044] Specifically, during the corresponding wet and dry mixing operation, the silane carbon point mixing water is introduced into the mixer 1 through the diversion pipe 2 for mixing. In the initial stage of mixing, due to the small amount of water but large amount of dry material, lumps with wet surface and dry interior (hereinafter referred to as lumps) are easily generated. In subsequent mixing, it is difficult to mix thoroughly. Therefore, the drive motor 3 drives the output rod 51 to rotate. Under the action of the reducer 8, the rotation speed of the output rod 51 and the reciprocating screw 10 are not the same.

[0045] During the rotation of the reciprocating screw 10, the outer cover rod 9 can be driven to rotate synchronously. While the outer cover rod 9 rotates and drives the stirring rod 7 to rotate for mixing, the sieve plate 6 can also rotate synchronously with the outer cover rod 9 due to the interlocking connection of the constraint rod 91. Since one end of the rotating blocking rod 13 inside the sieve plate 6 is rotatably connected to the inside of the through groove, and the other end is rotatably connected to the movable ring 11 located inside the outer cover rod 9 through a short rod, the movable ring 11 will also rotate when the outer cover rod 9 moves. Therefore, when the reciprocating screw 10 rotates and drives the moving sleeve on the surface to move up and down, the sieve plate 6 can perform corresponding up and down movements and corresponding rotation operations (the moving sleeve and the movable ring 11 are rotatably connected, so the rotation of the movable ring 11 will not affect the moving sleeve).

[0046] During the upward movement of the sieve plate 6 driven by the rotation of the reciprocating screw 10, the through groove 131 inside the rotating plug rod 13 is in a horizontal state, which can block the through groove, allowing the sieve plate 6 to screen and intercept clumps during its upward movement. When passing the stirring rod 7 (because the rotation speed of the sieve plate 6 and the stirring rod 7 is the same, they are relatively stationary), the drive motor 12 drives the rotating plug rod 13 to rotate, causing the through groove 131 to change from a horizontal state to a vertical state (e.g., Figure 12 As shown), so that the stirring rod 7 on the surface of the outer cover rod 9 can pass through. After passing the stirring rod 7, the through groove 131 returns to a horizontal state and continues the bottom-up screening operation of clumps (as shown). Figure 13 (As shown).

[0047] After the sieve plate 6 moves above the uppermost stirring rod 7, it continues to move upwards (because the threaded area on the surface of the reciprocating screw 10 has not yet ended, such as...). Figure 10 As shown), at this time, the clumps on the surface of the sieve plate 6 will gradually approach the bottom of the naturally drooping movable plate 53 in the rotating grinding assembly 5. Since the rotation speed of the movable plate 53 is different from that of the sieve plate 6, the clumps on the surface of the sieve plate 6 can be crushed. Combined with the mixing water flowing out from the upper drainage pipe 2, a targeted dissolution and mixing operation can be achieved.

[0048] As the sieve plate 6 continues to move upward, its surface lifts the movable plate 53. The upward movement of the movable plate 53 then creates a squeezing effect on the spring telescopic column 54, allowing the movable plate 53 to continue its squeezing contact with the surface of the sieve plate 6. Utilizing the difference in rotational speed, targeted mixing and dissolving operations continue until the spring telescopic column 54 is compressed to its minimum value. At this point, the threaded area on the surface of the reciprocating screw 10 ends, and the sieve plate 6 is about to move downward, awaiting the next round of screening, lifting, and crushing operations (such as...). Figure 14 (As shown).

[0049] When the movable plate 53 rotates, the spring telescopic column 54 rotates synchronously in the annular groove 4, so the rotation operation of the grinding assembly 5 can proceed normally.

[0050] During the downward movement of the sieve plate 6, if the mixer 1 is still in the initial dry-wet mixed state (that is, the state in which clumps are very easy to form), the clumps formed during the previous screening and lifting process of the sieve plate 6 will be squeezed downward as the sieve plate 6 moves downward. As the sieve plate 6 approaches the bottom of the mixer 1, the rotating sieve plate 6 will form a squeezing and grinding effect.

[0051] The third implementation method: Figure 15 As shown, an electromagnetic ring 14 is embedded in the top wall of the annular groove 4, the movable plate 53 is made of magnetic material, and a displacement sensor for monitoring the movement and lifting status of the movable plate 53 is installed inside the movable plate 53.

[0052] Unlike the second embodiment, this embodiment mainly adds an electromagnetic ring 14 and a displacement sensor, and adjusts the material of the movable plate 53.

[0053] Specifically, when the movable plate 53 performs the corresponding grinding operation on the surface of the screen plate 6, when passing through the through groove, due to the defect between the rotating blocking rod 13 and the through groove, the lower end of the movable plate 53 may fall into the defect and prevent the rotation from continuing. At this time, the displacement sensor can detect that the movable plate 53, which has been moving upward (because it has been continuously lifted by the screen plate 6), suddenly falls. At this time, the electromagnetic ring 14 is activated to drive the movable plate 53 to move upward and restore it to the state of being horizontal with the surface of the screen plate 6, and continue to perform stable grinding operation.

[0054] In light of current practical needs, the above-described embodiments adopted in this application are not limited to these. Any changes made within the scope of knowledge possessed by those skilled in the art without departing from the concept of this application still fall within the protection scope of this invention.

Claims

1. A method for preparing high-strength, high-durability 3D-printed concrete, characterized in that, Includes the following steps: S1. Material preparation: Prepare the ingredients according to the following mass percentages: High-alumina cement: 40%-50%; Mixing water: 12%-16%; Silane-containing carbon points: 0.01%-1.0%; Fine aggregate: 30%-40%; Glass fiber: 0.5%-2.0%; S2. Preparation of silane-containing carbon dots, the specific steps are as follows: S21. After mixing glucose, deionized water and ethanol evenly, transfer them to a high-pressure reactor and react at 160-180°C for 3-4 hours. After cooling to room temperature, the initial product is obtained. S22. Purify the initial product to obtain carbon dots; S23. Dissolve γ-aminopropyltriethoxysilane in a mixture of ethanol and water, and stir at room temperature for 2-3 h to generate silanol; S24. Add the carbon dots prepared in S22, stir evenly, transfer to a high-pressure reactor, react at 160-200°C for 8-10 hours, and then purify to obtain silane-containing carbon dots. S3. Mix high-alumina cement, fine aggregate and glass fiber evenly with mixer (1), then add mixing water containing silane carbon points and continue mixing for 4-6 minutes until uniform to obtain 3D printing material. During the mixing process, the lifting mixing component in mixer (1) assists in dry and wet mixing and intercepts and breaks up lumps in real time. S4. Place the 3D printing material from S3 into the barrel of the extrusion 3D printer and extrude it to obtain 3D printed concrete.

2. The method for preparing high-strength, high-durability 3D-printed concrete according to claim 1, characterized in that, The silane carbon dots in S2 are spherical with a particle size distribution range of 2-20 nm. The oxygen-containing functional groups and nitrogen-containing functional groups on the surface of the silane carbon dots in S2 include one or more of OH, C=O, C=C, Si-O-Si, Si-OH and NH. The volume ratio of ethanol to water in the mixture of ethanol and water in S23 is 10-5:

1.

3. The method for preparing high-strength, high-durability 3D-printed concrete according to claim 1, characterized in that, The high-strength, high-durability 3D printing material in S3 uses an auxiliary cementitious material to replace part of the cement content. The auxiliary cementitious material is one or more of the following: fly ash, silica fume, limestone powder, metakaolin, slag powder, and steel slag powder.

4. The method for preparing high-strength, high-durability 3D-printed concrete according to claim 1, characterized in that, The mixer (1) in S3 is used for dry and wet mixing of materials. The mixer (1) is equipped with a top cover plate. A drive motor (3) and a drain pipe (2) are installed on the top of the top cover plate. An annular groove (4) is provided inside the top cover plate. The lifting and stirring assembly includes a reciprocating screw (10). An outer cover rod (9) is fixedly connected to the reciprocating screw (10) near the bottom surface by a connecting rod. Multiple stirring rods (7) are arranged on the surface of the outer cover rod (9). A movable sleeve is threadedly connected to the surface of the reciprocating screw (10). A rotating sleeve is rotatably connected to the surface of the movable sleeve. The movable ring (11) has a sieve plate (6) that is slidably connected to the surface of the outer cover rod (9) on its surface. The sieve plate (6) has a through groove that matches the stirring rod (7) inside. The through groove has a closing assembly for the stirring rod (7) to pass through the sieve plate (6) inside. The annular groove (4) has a grinding assembly (5) that is rotatably connected inside. The grinding assembly is used to grind the lumps that are wet on the surface and dry inside that are screened out from the surface of the sieve plate (6). The drain pipe (2) is used to drain the mixing water into the mixer (1) for dry and wet mixing after the dry materials are mixed.

5. The method for preparing high-strength, high-durability 3D-printed concrete according to claim 4, characterized in that, The closing assembly includes a rotating plug rod (13) rotatably installed inside the through groove, and the rotating plug rod (13) has a through groove (131) for accommodating the stirring rod (7) through the sieve plate (6). The cross-sectional length and width of the through groove (131) are the same as the length and diameter of the stirring rod (7), respectively. The movable ring (11) is fitted with a drive motor (12), and the output end of the drive motor (12) is connected to the end of the rotating plug rod (13) through a short rod. The inner wall of the sieve plate (6) is fitted with a constraint rod (91). The outer cover rod (9) has a strip groove (92) and constraint rods (91) spaced apart from the strip groove (92). The surface of the movable ring (11) near the bottom is fitted with a lifting block that matches the strip groove (92).

6. The method for preparing high-strength, high-durability 3D-printed concrete according to claim 5, characterized in that, The lifting block is used to lift the rotating plug rod (13), and the cross-sectional width of the lifting block is not greater than the cross-sectional width of the strip groove (92).

7. The method for preparing high-strength, high-durability 3D-printed concrete according to claim 4, characterized in that, The grinding assembly (5) includes an output rotating rod (51) connected to the output end of the drive motor (3). A rotating component (52) is fixedly installed on the surface of the output rotating rod (51). A movable plate (53) with an I-shaped cross section is slidably connected through the interior of the rotating component (52). A spring telescopic column (54) is connected to the top of the movable plate (53). The top of the spring telescopic column (54) is movably connected to the interior of the annular groove (4) through a hinge ball. The height of the movable plate (53) is greater than the diameter of the rotating component (52).

8. The method for preparing high-strength, high-durability 3D-printed concrete according to claim 4, characterized in that, The output rotating rod (51) and the reciprocating screw (10) are connected by a reducer (8). When the moving sleeve moves to the top thread position of the reciprocating screw (10), the moving plate (53) presses the spring telescopic column (54) upward to compress it to the minimum value.

9. The method for preparing high-strength, high-durability 3D-printed concrete according to claim 5, characterized in that, The cross-sectional thickness of the through groove (131) after being rotated 90 degrees is less than the thickness of the sieve plate (6), and the projection of the stirring rod (7) in the vertical direction is the same as the projection of the through groove (131) in the vertical direction.

10. The method for preparing high-strength, high-durability 3D-printed concrete according to claim 7, characterized in that, An electromagnetic ring (14) is embedded in the top wall of the annular groove (4). The movable plate (53) is made of magnetic material, and a displacement sensor for monitoring the movement and lifting status of the movable plate (53) is installed inside the movable plate (53).

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