Steel fiber embedding device and method for steel fiber reinforced 3D printing concrete interface performance

Abstract

The invention relates to a steel fiber embedding device and method for improving the interface performance of 3D printing concrete through steel fibers, an electromagnet cavity is formed in the upper portion of an embedding device body, a triangular limiting through groove is formed in one side of the lower portion of the embedding device body, and the combination face of the triangular limiting through groove and the embedding device body is a triangular continuous concave-convex wrinkled face; an iron core in the electromagnet cavity downwards extends out of the electromagnet cavity and extends to one side of the triangular limiting through groove; the length adjusting sheet slides up and down along the wrinkled surface and is magnetically connected with the iron core; a plurality of steel fibers are arranged in the triangular limiting through groove and are magnetically connected with the iron core, and the top ends of the steel fibers upwards abut against the lower portions of the length adjusting pieces; a steel fiber pressing plate is connected into the triangular limiting through groove through a bolt, and the steel fiber pressing plate presses the length adjusting sheet and the steel fiber; clamping units are symmetrically arranged at the lower part of the embedding device main body, and the two clamping units clamp the steel fiber embedding device on a test piece forming test mold. After steel fibers are arranged on the steel fiber embedding device, the steel fiber embedding device can be inserted into a bottom-layer test piece in the forming test mold.

Description

Technical Field

[0001] This invention relates to the field of intelligent construction technology, and in particular to a steel fiber embedding device and method for enhancing the interface performance of 3D printed concrete. Background Technology

[0002] As an emerging digital construction method, 3D printed concrete technology has shown great application potential in fields such as complex structure construction, emergency construction, and personalized construction due to its significant advantages such as high level of intelligence, high flexibility, free molding, and saving of formwork and labor.

[0003] However, 3D printing concrete requires layer-by-layer modeling, and this layer-by-layer stacking process results in numerous weakened interlayer interfaces within the printed component. These interfaces are weak points in the printed structure, with mechanical properties, especially tensile and shear properties, far lower than those of the concrete itself. This severely restricts the integrity, durability, and load-bearing capacity of the printed component, and is one of the key technical bottlenecks hindering the large-scale application of 3D printed concrete technology in load-bearing structures.

[0004] Therefore, in existing technologies, the technical approach of directionally arranging steel fibers in the interface layer to improve the interlayer interface performance has proven to be effective. In short, by arranging steel fibers in the interlayer interface of printed concrete, the bonding performance of the interlayer interface can be improved, thereby enhancing the overall mechanical properties of the printed concrete. However, the improvement effect can vary depending on various factors such as the type of steel fiber, geometric parameters like length and aspect ratio, embedment depth, and spacing, especially embedment depth and spacing.

[0005] In order to rationally select steel fiber types, scientifically evaluate their optimal combination with 3D printed concrete materials, and improve the service performance of structures, it is necessary to effectively test the mechanical properties of 3D printed concrete with steel fibers embedded in the interface layer. However, there is currently a lack of dedicated equipment and test methods to systematically and quantitatively evaluate the effect of steel fibers on improving the interlayer interface performance under 3D printing process conditions.

[0006] Previously, steel fibers were inserted manually, but this method was not standardized, making it difficult to accurately control the insertion depth and spacing, and the fibers might even be misaligned, hindering the work. Regularly embedded steel fibers can maximize the bonding performance between the fibers and concrete and effectively improve the tensile strength of the interface layer. Publication number CN217424952U discloses an experimental device for precisely controlling the embedding depth of steel fibers, which can precisely control the insertion depth and spacing of adjacent fibers; however, only one fiber can be inserted at a time, making the process cumbersome when inserting multiple fibers.

[0007] To this end, this invention develops a steel fiber embedding device that precisely embeds steel fibers at the interlayer interface of a specimen by simulating the 3D printing process. This device can effectively and conveniently control simulation parameters such as embedding depth and steel fiber spacing, and realize standardized testing of the interfacial bonding performance of 3D printed concrete with steel fibers distributed in the interlayer. This provides reliable experimental basis and technical support for optimizing raw material ratios, improving printing processes, and enhancing the overall performance of 3D printed concrete structures. Summary of the Invention

[0008] To address the issues of non-standard steel fiber embedding and cumbersome insertion operations in evaluating the interface performance of steel fiber reinforced 3D printed concrete, this invention provides a steel fiber embedding device and method for evaluating the interface performance of steel fiber reinforced 3D printed concrete. This method effectively achieves the directional arrangement of steel fibers, and the insertion depth and spacing are accurately controllable, improving the standardization of embedding. At the same time, it allows for batch insertion of steel fibers, avoiding repeated operations and improving the embedding efficiency of steel fibers.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A steel fiber embedding device for reinforcing the interface performance of 3D printed concrete with steel fiber reinforcement includes a steel fiber embedder and a matching specimen molding mold. The steel fiber embedder includes an embedder body, an electromagnet unit containing multiple iron cores, a length adjustment plate, a steel fiber pressure plate, and a clamping unit. The upper part of the embedder body has an electromagnet chamber to accommodate the electromagnet unit, and the lower side has a triangular limiting groove. The mating surface between the triangular limiting groove and the embedder body is a triangular continuous concave-convex pleated surface. The electromagnet unit is installed in the electromagnet cavity. Multiple iron cores in the electromagnet unit are evenly distributed in a straight line. The iron cores extend downward into the electromagnet cavity and extend to one side of the triangular limiting slot. The length adjustment piece is installed in the triangular limiting slot and is magnetically connected to the iron core, which ensures the fixation of the length adjustment piece. The length adjustment piece is in contact with the pleated surface of the triangular limiting slot and slides up and down along the pleated surface. Multiple steel fibers are also provided in the triangular limiting groove. Each steel fiber is magnetically connected to the iron core, and the top of the steel fiber rests against the length adjustment piece below, so that the position of the steel fiber can be restricted by the length adjustment piece. The steel fiber pressure plate is bolted to the triangular limiting groove, so that the steel fiber pressure plate can be easily installed and removed. The steel fiber pressure plate presses the length adjustment piece and multiple steel fibers. The clamping units are symmetrically arranged at both ends of the lower part of the embedding device body. The two clamping units cooperate to clamp the steel fiber embedding device on the specimen forming mold. The specimen forming mold includes a bottom mold and a top mold.

[0010] Furthermore, the electromagnet chamber is a rectangular cavity, with the top of the electromagnet chamber extending upwards through the main body of the implanter. A cover plate for opening and closing the electromagnet chamber is hinged to the top of the main body of the implanter. A handle recess is provided on the end face of the cover plate for the hand to grip the cover plate and flip it over. A locking component is provided between the cover plate and the main body of the implanter to control the flipping of the cover plate.

[0011] Furthermore, the locking assembly includes a locking pin slot, a cover plate locking pin, and a cover plate clip. The locking pin slot is provided inside the body of the implanter. The cover plate locking pin is elastically slidably connected in the locking pin slot. One end of the cover plate locking pin extends out of the locking pin slot to the outside of the body of the implanter and is connected to a pull ring, which facilitates pulling the cover plate locking pin by the pull ring. The other end of the cover plate locking pin extends out of the locking pin slot to the electromagnet cavity. The cover plate is provided with a cover plate latch at the lower part of the cover plate. The cover plate latch extends vertically downward and connects to the locking tongue at the other end of the cover plate locking pin to facilitate the formation of a restraint. The main body of the embedding device is provided with a push-out groove, and a push-out spring is provided in the push-out groove. The push-out spring presses upward against the cover plate in the closed state. The upper ends of the embedding device body extend horizontally outward on both sides to form plate-shaped embedding device handles, which facilitate the handling and movement of the embedding device body.

[0012] Furthermore, the electromagnet unit includes a battery, wires, coils, an iron core, and a power switch. The battery is disposed in the electromagnet chamber via a battery box. The iron core is a rod with its lower end fixedly inserted into the body of the implanter and its upper end extending into the electromagnet chamber. The coil is wound around the upper end of each iron core. The battery, multiple coils, and the power switch are connected together via the wires. The power switch is located on the upper surface of the implanter body for easy manual operation to control whether the iron core generates magnetic force.

[0013] Furthermore, the cross-section of the triangular limiting groove is rack-shaped, and one side opposite to the folded surface of the triangular limiting groove penetrates the body of the embedder. The length adjustment piece is a continuously convex and concave plate. The thickness of the length adjustment piece is the same as the diameter of the steel fiber. The steel fiber is arranged in the recessed position of the folded surface of the triangular limiting groove, which ensures that the distance between two adjacent steel fibers is constant. The length adjustment piece and the steel fiber are arranged vertically and abut against each other, which limits the height of the steel fiber. The arrangement length between multiple steel fibers is not greater than the length of the length adjustment piece. The steel fiber extends downward out of the triangular limiting groove.

[0014] Furthermore, the steel fiber pressure plate is a long plate with a thick middle and thin ends. One side of the middle part of the steel fiber pressure plate has a continuous triangular concave-convex shape to form a pressing rack. The pressing rack is adapted to the length adjustment piece. Each protruding position of the pressing rack is recessed inward to form a triangular rack groove, and the rack groove abuts against the side wall of the steel fiber.

[0015] Furthermore, one end of the steel fiber plate has a left U-shaped groove, and one end of the embedding device body has a left limiting bolt arranged horizontally. The left limiting bolt passes through the triangular limiting through groove and through the left U-shaped groove, and is connected to a left nut, which facilitates the installation and fixation of the left end of the steel fiber plate. The other end of the steel fiber plate has a right U-shaped groove, and the length of the left U-shaped groove is less than the length of the right U-shaped groove. The other end of the embedding device body has a bolt shaft arranged vertically. The bolt shaft is rotatably connected to the embedding device body. A right limiting bolt is arranged horizontally on the bolt shaft. The right limiting bolt passes through the triangular limiting through groove and through the right U-shaped groove, and is connected to a right nut, which facilitates the installation and fixation of the right end of the steel fiber plate. Both the left nut and the right nut are wing nuts.

[0016] Furthermore, the clamping unit includes a base and a limiting slider, the limiting slider being elastically slidably connected to the base, and the limiting sliders in the two clamping units cooperate to clamp the bottom trial mold; The bottom and top test molds are arranged symmetrically and connected. The top test mold includes test mold side plates and test mold partitions. There are two test mold side plates, and multiple test mold partitions are arranged between the two test mold side plates. The bottom test mold has the same structure as the top test mold. The bottom test mold also includes a test mold base plate, and a test mold base plate is arranged between the two test mold side plates.

[0017] A method for embedding steel fibers to enhance the interfacial properties of 3D-printed concrete, based on the aforementioned embedding device, includes the following steps: Step 1: Prepare trial molds: Prepare trial molds for the specimen molding process, including one bottom mold and at least one top mold; Step 2, Installing Steel Fibers: After inserting the battery, activate the electromagnet unit to generate magnetism in the iron core; select a suitable length adjustment piece according to the specifications of the steel fiber, and attach the length adjustment piece to the upper part of the triangular limiting slot; flatten the surface of the piled steel fibers, and use the magnetism of the iron core to neatly attach the steel fibers into the triangular limiting slot, ensuring that the length adjustment piece and steel fiber are arranged vertically, and that the exposed length of the steel fiber is half of the total length; install the steel fiber pressure plate on the body of the embedder with bolts, and after tightening the bolts, the steel fiber pressure plate tightly presses against the steel fiber and length adjustment piece to achieve fixation; Step 3: Prepare 3D printed concrete base specimen: Print the mixed 3D printed concrete slurry into the assembled base specimen through the printer nozzle, fill it, place it on the vibration table to make the interior dense, and smooth the surface with a trowel. Step 4, Inserting steel fibers: Before the specimen initially sets, lift the main body of the embedding device with both hands, align it with the upper surface of the bottom specimen, and slowly press it down. Under the control of the clamping units at both ends of the lower part of the embedding device, the main body of the embedding device is accurately placed on the top surface of the bottom specimen. At this time, exactly half the length of all the steel fibers is inserted into the upper surface of the bottom specimen, completing the steel fiber embedding work. Step 5: Separate the steel fiber from the implant body: Hold the implant body with your left hand, ensuring it does not shift on the upper surface of the bottom specimen. Loosen the bolts and remove the steel fiber pressure plate. Turn off the electromagnet unit to remove the implant body's attraction to the steel fiber, thus reducing interference with the steel fiber already embedded on the surface of the bottom specimen. Then remove the length adjustment piece, and use both hands to slide the implant body horizontally along the bottom specimen, gradually moving it away from the steel fiber to remove the implant body. Step 6: Preparation of the whole specimen: Before the bottom specimen has set, the top specimen is installed on the bottom specimen mold. Then, the same concrete slurry as the bottom specimen is printed into the top specimen mold. After filling, the upper surface is smoothed with a trowel to form the whole 3D printed concrete specimen, which is used to test and evaluate the bonding performance of the 3D printed concrete interface layer.

[0018] The beneficial effects of the present invention through the above technical solution are: This invention features a rational structural design. The use of a steel fiber embedder improves the efficiency of inserting steel fibers into 3D-printed concrete interfaces, as well as the accuracy of embedding depth and spacing. This reduces experimental errors caused by uneven embedding depth and spacing, thus improving evaluation results. The electromagnet unit ensures a one-to-one correspondence between the iron core and the steel fiber, allowing the steel fiber to be quickly and accurately adsorbed at the designated position and preventing it from falling off, thereby improving the installation efficiency of the steel fiber on the embedder. The steel fiber is adsorbed at each recessed position on the wrinkled surface, ensuring accurate spacing between adjacent steel fibers.

[0019] The length adjustment piece of the present invention can also be fixed by the adsorption of the iron core, and the length adjustment piece can slide up and down along the folded surface to adjust its position. Since the steel fiber is at the bottom of the length adjustment piece, the extension length of multiple steel fibers can be uniformly controlled by adjusting the position of the length adjustment piece, thereby facilitating the consistency of the steel fiber embedment depth.

[0020] The steel fiber clamping plate of this invention can effectively restrict the steel fibers, and combined with the magnetic attraction of the iron core, ensures the fixation of the steel fibers and prevents them from moving during the embedding process. The left limiting bolt is fixedly connected to the body of the embedding device, while the right limiting bolt is movably connected to the body of the embedding device via a rotating shaft. When the steel fiber clamping plate is used to tighten the steel fibers, neither the left nor the right wing nut needs to be removed from the limiting bolts, which improves the efficiency of installing the steel fiber clamping plate and avoids the loss of the wing nuts after they come off.

[0021] The present invention features clamping units on both sides of the implanter body, which improves the speed and accuracy of placing the implanter on the surface of the bottom specimen and facilitates precise control of the steel fiber embedding depth and planar spacing. Specifically, when the implanter body with the steel fibers laid out is pressed from above onto the bottom specimen in the mold, the clamping units on both sides precisely control the position of the implanter body above the specimen, allowing the steel fibers to be accurately inserted into predetermined positions, thus achieving precise control of the embedding depth and spacing.

[0022] The principle of the locking assembly of the present invention is as follows: when the cover plate is pressed down, the cover plate locking pin and the cover plate clip can be interlocked under the action of the locking pin spring to prevent the cover plate from detaching from the top of the embedding device body; when the cover plate locking pin is pulled outward, the cover plate clip disengages from the cover plate locking pin, and the free end of the cover plate can be flipped under the action of the ejection spring.

[0023] The embedding device handle of this invention facilitates operations such as moving the embedding device body and inserting steel fibers into the lower surface of the specimen. The iron core extends to one side of the triangular limiting groove to generate sufficient attraction for the steel fibers, facilitating rapid placement. The thickness of the length adjustment piece can be set according to the length and diameter of the steel fiber; if the length is sufficient, it can be omitted. The length adjustment piece allows for precise control of the embedding depth of the steel fiber in the specimen interface layer.

[0024] Compared to manual embedding of steel fibers, this invention uses an embedding device to embed the steel fibers, which reduces the error of manual embedding and makes the embedding depth and spacing more accurate and reliable. Based on the magnetic adsorption of the steel fibers, a pressure plate further compresses the steel fibers, ensuring that the steel fibers do not easily move or rotate during insertion and preventing skewness. Attached Figure Description

[0025] Figure 1 This is a front view of the steel fiber embedding device for the steel fiber reinforced 3D printed concrete interface performance of the present invention.

[0026] Figure 2 This is a side view of the steel fiber embedding device for the steel fiber reinforced 3D printed concrete interface performance of the present invention.

[0027] Figure 3 This is a top view of the steel fiber embedding device for the steel fiber reinforced 3D printed concrete interface performance of the present invention.

[0028] Figure 4 This is a schematic diagram of the locking component of the steel fiber embedding device for the steel fiber reinforced 3D printed concrete interface performance of the present invention.

[0029] Figure 5 This is a top view of the length adjustment piece of the steel fiber embedding device for the steel fiber reinforced 3D printed concrete interface performance of the present invention.

[0030] Figure 6 This is a front view of the length adjustment piece of the steel fiber embedding device for the steel fiber reinforced 3D printed concrete interface performance of the present invention.

[0031] Figure 7 This is a top view of the steel fiber pressure plate of the steel fiber embedding device for steel fiber reinforced 3D printed concrete interface performance according to the present invention.

[0032] Figure 8 This is a front view of the steel fiber pressure plate of the steel fiber embedding device for steel fiber reinforced 3D printed concrete interface performance according to the present invention.

[0033] Figure 9 This is a front view of the steel fiber pressure plate of the steel fiber embedding device for the steel fiber reinforced 3D printed concrete interface performance of the present invention, in the installation state.

[0034] Figure 10 This is a top view of the steel fiber pressure plate of the steel fiber embedding device for steel fiber reinforced 3D printed concrete interface performance according to the present invention, showing the installation state of the steel fiber pressure plate.

[0035] Figure 11 This is a schematic diagram of the clamping unit of the steel fiber embedding device for the steel fiber reinforced 3D printed concrete interface performance of the present invention.

[0036] Figure 12 This is a schematic diagram of the test mold for the steel fiber embedded device for reinforcing the interface performance of 3D printed concrete with steel fiber reinforcement according to the present invention.

[0037] Figure 13 This invention relates to the installation of a steel fiber embedder and a bottom mold in a method for embedding steel fibers to enhance the interface performance of 3D printed concrete.

[0038] Figure 14 This is a schematic diagram of a 3D printed concrete specimen after molding, based on the steel fiber embedding method for improving the interfacial performance of steel fiber reinforced 3D printed concrete according to the present invention.

[0039] Figure 15 This is a schematic diagram of the full curve of debonding load-opening displacement of the interface layer of a 3D printed concrete specimen, which is a steel fiber embedding method for improving the interface performance of steel fiber reinforced 3D printed concrete according to the present invention.

[0040] The attached diagram is labeled as follows: 1 is the ejector spring, 101 is the ejector block, 2 is the handle recess, 3 is the cover plate, 4 is the rotating shaft collar, 5 is the cover plate rotating shaft, 6 is the cover plate locking pin, 61 is the limiting block, 7 is the embedding device body, 8 is the left limiting bolt, 9 is the left nut, 10 is the base, 11 is the steel fiber, 12 is the bottom specimen, 13 is the test mold side plate, 14 is the test mold bottom plate, 15 is the ejector groove, 16 is the cover plate clip, 17 is the battery, 18 is the iron core, 19 is the power switch, 20 is the embedding device handle, 21 is the wire, and 22 is the wire. 23 is the bolt shaft, 24 is the right limit bolt, 25 is the right nut, 26 is the notch, 27 is the steel fiber pressure plate, 28 is the length adjustment piece, 29 is the locking pin spring, 30 is the test mold partition, 31 is the locking pin slot, 32 is the clamping rack, 33 is the electromagnet chamber, 34 is the limit spring, 35 is the guide rod, 36 is the limit slider, 37 is the triangular limit through slot, 371 is the pleated surface, 38 is the rack slot, 39 is the left U-shaped groove, 40 is the right U-shaped groove, 41 is the upper specimen, and 42 is the specimen interface layer. Detailed Implementation

[0041] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings: like Figures 1-12 As shown, the steel fiber embedding device for enhancing the interface performance of 3D printed concrete includes a steel fiber embedder and a matching specimen molding mold. The steel fiber embedder is used to insert steel fibers 11 into the specimen molding mold.

[0042] The steel fiber implanter includes an implanter body 7, an electromagnet unit containing multiple iron cores 18, a length adjustment plate 28, a steel fiber pressure plate 27, and a clamping unit, such as... Figures 1-3 As shown. The upper sides of the implant body 7 extend horizontally outward to form plate-shaped implant handles 20, which facilitate the movement of the implant body 7. An electromagnet chamber 33 is provided in the upper part of the implant body 7. The electromagnet chamber 33 is a rectangular cavity, and the top of the electromagnet chamber 33 extends upward through the implant body 7, so that the electromagnet chamber 33 is an open cavity at the top.

[0043] To achieve the sealing of the electromagnet chamber 33, a cover plate 3 for opening and closing the electromagnet chamber 33 is hinged to the top of the embedding body 7. During installation, the cover plate 3 has cover plate pivots 5 at both ends, and pivot collars 4 are provided on both sides of the top of the embedding body 7. The cover plate pivots 5 and pivot collars 4 correspond one-to-one, with the corresponding cover plate pivots 5 extending into the pivot collars 4 and rotatably connected to them, thus achieving the installation of the cover plate 3. After installation, the cover plate 3 can be flipped. Before flipping, the cover plate 3 seals the electromagnet chamber 33; after flipping, the electromagnet chamber 33 can be opened. To facilitate opening the cover plate 3, two handle recesses 2 are provided on one end face of the cover plate 3 for manually gripping the cover plate 3 to achieve flipping, meaning that the rotation of the cover plate 3 can be controlled manually by gripping the handle recesses 2.

[0044] To lock the cover plate 3 and prevent it from being easily opened, a locking assembly is provided between the cover plate 3 and the embedding device body 7. This locking assembly controls the rotation of the cover plate 3. Figure 4 As shown, in this embodiment, the locking assembly includes a locking pin slot 31, a cover plate locking pin 6, and a cover plate clip 16. The main body 7 of the implanter has a locking pin slot 31, and the cover plate locking pin 6 is elastically slidably connected in the locking pin slot 31. Specifically, the cover plate locking pin 6 has a prism structure to prevent the cover plate locking pin 6 from rotating circumferentially. A limit block 61 is provided on the cover plate locking pin 6. A locking pin compression spring 29 is sleeved on the cover plate locking pin 6 between the limit block 61 and one end of the locking pin slot 31. The locking pin compression spring 29 tends to elongate, thereby pushing the limit block 61 to press tightly against the other side of the locking pin slot 31.

[0045] One end of the cover plate locking pin 6 extends out of the locking pin slot 31 to the outside of the embedding device body 7 and is connected to a pull ring. The pull ring facilitates pulling the cover plate locking pin 6 outward, and the locking pin compression spring 29 is compressed when pulled. The other end of the cover plate locking pin 6 extends out of the locking pin slot 31 to the electromagnet chamber 33. In the initial state, under the push of the locking pin compression spring 29, the cover plate locking pin 6 tends to move horizontally to the right, so that the other end of the cover plate locking pin 6 is always located in the electromagnet chamber 33.

[0046] Meanwhile, a cover plate latch 16 is provided at the lower part of the cover plate 3. The cover plate latch 16 extends vertically downward and connects to the locking tongue at the other end of the cover plate locking pin 6. Specifically, the lower end of the cover plate latch 16 is bent into a hook shape, and the other end of the cover plate locking pin 6 has an arc surface. In this way, the other end of the cover plate locking pin 6 cooperates with the lower end of the cover plate latch 16 to achieve a connection and lock, thus restricting the cover plate 3 from rotating. When the cover plate locking pin 6 is pulled outward, the cover plate locking pin 6 disengages from the cover plate latch 16, unlocking the cover plate 3, which can then be flipped open. When the cover plate 3 is pressed down, the cover plate locking pin 6 and the cover plate latch 16 interlock under the action of the locking pin spring 29, preventing the cover plate 3 from detaching from the top of the embedding device body 7.

[0047] To facilitate the opening of the cover plate 3, a vertically arranged ejector groove 15 is provided on the main body 7 of the implanter. An ejector spring 1 is installed in the ejector groove 15, and the ejector spring 1 presses upward against the cover plate 3 when it is in the closed state. That is, the ejector spring 1 is a compression spring. The lower end of the ejector spring 1 is connected and fixed to the bottom of the ejector groove 15, and an ejector block 101 is provided at the upper end of the ejector spring 1. The ejector block 101 abuts against the cover plate 3 to prevent the cover plate 3 from shaking. In the initial state, the ejector spring 1 is in a compressed state under the pressure of the cover plate 3. Once the cover plate locking pin 6 and the cover plate clip 16 are disengaged, the ejector spring 1 pushes the cover plate 3 to flip open.

[0048] An electromagnet unit is installed inside the electromagnet chamber 33. The electromagnet unit includes a battery 17, wires 21, coils 22, iron cores 18, and a power switch 19. The battery 17 can be a dry cell battery. The battery 17 is installed inside the electromagnet chamber 33 via a battery box, meaning the battery box is located inside the electromagnet chamber 33, and the motor is installed inside the battery box. The multiple iron cores 18 in the electromagnet unit are evenly distributed in a straight line. Each iron core 18 is a rod, and a coil 22 is wound around the upper end of each iron core 18.

[0049] The battery 17, multiple coils 22, and power switch 19 are connected in series via wire 21. The power switch 19 is located outside the electromagnet chamber 33 and is positioned on the upper surface of the implant body 7, near the implant handle 20 on one side, for easy manual operation. Operating the power switch 19 allows for easy control of the entire circuit's conduction. Once the circuit is active, the coils 22 are energized, generating magnetism on each iron core 18, which can attract related components.

[0050] A triangular limiting groove 37 is formed on one side of the lower part of the implant body 7. This is equivalent to cutting off one side of the lower part of the implant body 7 to form the triangular limiting groove 37, resulting in the implant body 7 being wider at the top and narrower at the bottom. The cross-section of the triangular limiting groove 37 is rack-shaped, and the two corresponding sides of the triangular limiting groove 37 are a toothed surface and a flat surface, respectively. The mating surface between the triangular limiting groove 37 and the implant body 7 is a triangular continuous concave-convex pleated surface 371, which is also the toothed surface. At the same time, the side opposite to the pleated surface 371 of the triangular limiting groove 37 penetrates through the implant body 7, so the lower part of the implant body 7 is completely open.

[0051] It should be noted that the iron core 18 extends downward into the electromagnet chamber 33 and extends to one side of the triangular limiting groove 37. That is, the lower end of the iron core 18 is fixedly inserted into the body 7 of the embedder and close to the folded surface 371 of the triangular limiting groove 37 so as to form a sufficient attraction to the steel fiber 11, which is conducive to the quick placement of the steel fiber 11. The upper end of the iron core 18 extends into the electromagnet chamber 33.

[0052] like Figure 5As shown, the length adjustment piece 28 is mainly used to precisely control the embedding depth of the steel fiber 11 in the interface layer 42 of the specimen. The length adjustment piece 28 is a continuously bent plate. It is set in the triangular limiting groove 37 and magnetically connected to the iron core 18 to prevent it from falling off. Because the length adjustment piece 28 is continuously bent, it can fit against the folded surface 371 of the triangular limiting groove 37, and it can slide vertically up and down along the folded surface 371. The length adjustment piece 28 comes in different sizes and has different thicknesses to accommodate steel fibers 11 of different diameters. It is required that the thickness of the length adjustment piece 28 is consistent with the diameter of the steel fiber 11.

[0053] Multiple steel fibers 11 are also provided within the triangular limiting groove 37. Each steel fiber 11 is positioned in the recessed area of ​​the pleated surface 371 of the triangular limiting groove 37, ensuring accurate spacing between adjacent steel fibers 11. Each steel fiber 11 is magnetically connected to the iron core 18. The top of each steel fiber 11 rests against the lower part of the length adjusting plate 28, meaning the length adjusting plate 28 and the steel fibers 11 are arranged vertically and abut against each other. Figure 6 As shown; the length of the arrangement between multiple steel fibers 11 is not greater than the length of the length adjustment piece 28, and the steel fibers 11 extend downwards into the triangular limiting groove 37 and protrude from the body of the embedder 7.

[0054] In this embodiment, a steel fiber pressure plate 27 is bolted into the triangular limiting groove 37. With the length adjustment piece 28 and the steel fiber 11 both being magnetically attracted and fixed, the steel fiber pressure plate 27 can press the length adjustment piece 28 and multiple steel fibers 11 together to achieve reliable fixation again.

[0055] like Figure 7 and Figure 8 As shown, the steel fiber pressure plate 27 is a long plate, thicker in the middle and thinner at both ends. Since the length adjustment piece 28 has a continuously bent structure, to accommodate it, one side of the middle portion of the steel fiber pressure plate 27 has a triangular, continuously convex-concave shape forming a clamping rack 32. The clamping rack 32 fits the length adjustment piece 28, but the length of the steel fiber pressure plate 27 is greater than the length of the length adjustment piece 28. Furthermore, to clamp the steel fiber 11, each protruding position of the clamping rack 32 is recessed inward, forming an obtuse-angled triangular rack groove 38. The rack groove 38 abuts against the side wall of the steel fiber 11, facilitating clamping of the steel fiber 11. Therefore, the steel fiber pressure plate 27 can simultaneously clamp both the steel fiber 11 and the length adjustment piece 28.

[0056] During installation, both ends of the steel fiber pressure plate 27 are connected to the body 7 of the embedder. For example... Figure 9 and Figure 10As shown in the figure, specifically, one end of the steel fiber pressing plate 27 is provided with a left U-shaped groove 39, and the opening of the left U-shaped groove 39 faces left; one end of the embedder main body 7 is horizontally provided with a left limit bolt 8. After the left limit bolt 8 passes through the triangular limit through groove 37 and passes through the left U-shaped groove 39, a left nut 9 is connected. The left nut 9 is a butterfly nut. After tightening the left nut 9, the steel fiber pressing plate 27 can be pressed.

[0057] Meanwhile, the other end of the steel fiber pressing plate 27 is provided with a right U-shaped groove 40, and the length of the left U-shaped groove 39 is less than the length of the right U-shaped groove 40. The other end of the embedder main body 7 is vertically provided with a bolt rotating shaft 23. The bolt rotating shaft 23 is rotatably connected to the embedder main body 7. A right limit bolt 24 is horizontally arranged on the bolt rotating shaft 23. After the right limit bolt 24 and the bolt rotating shaft 23 are connected and combined, the cross section is in the shape of "丄". The right limit bolt 24 and the left limit bolt 8 are arranged at intervals and in parallel. The right limit bolt 24 can rotate horizontally. After the right limit bolt 24 passes through the triangular limit through groove 37 and passes through the right U-shaped groove 40, a right nut 25 is connected. The left nut 9 and the right nut 25 have the same structure and are both butterfly nuts. Through the cooperation of the left nut 9 and the right nut 25, the steel fiber pressing plate 27 can be jointly pressed, so that the steel fiber pressing plate 27 presses the length adjusting piece 28 and the steel fiber 11 again.

[0058] In order to install the steel fiber embedder on the specimen forming test mold, clamping units are symmetrically arranged at both ends of the lower part of the embedder main body 7. The two clamping units cooperate to clamp the steel fiber embedder on the specimen forming test mold. The clamping unit is used to accurately control the position of the embedder on the 3D printing concrete specimen forming test mold, so as to accurately regulate the embedding spacing of the steel fiber 11 in the specimen interface layer 42. As Figure 11 shown, the clamping unit includes a base 10 and a limit slider 36. The base 10 is a plate body. The base 10 is arranged at the end of the triangular limit through groove 37, and the base 10 is fixedly connected to the embedder main body 7 upward.

[0059] A limit slider 36 is elastically slidably connected to the base 10. Specifically, the limit slider 36 is a right trapezoidal block, and the width of the limit slider 36 decreases successively from top to bottom. The limit slider 36 is arranged below the steel fiber pressing plate 27. One end of the limit slider 36 is provided with a rectangular guide rod 35. One end of the guide rod 35 passes through the base 10, and a pin shaft can be arranged at one end of the guide rod 35 to prevent the guide rod 35 from detaching from the base 10. A limit spring 34 is sleeved on the guide rod 35 between the base 10 and the limit slider 36. Furthermore, under the push of the limit spring 34, the limit sliders 36 in the two clamping units approach each other.

[0060] Note: Since there is a base 10 at the end of the triangular limiting groove 37, the steel fiber pressure plate 27 is installed with both ends abutting against the base 10, and a notch 26 is opened on the base 10 on the right side. This notch 26 corresponds to the right limiting bolt 24. The purpose is to prevent the base 10 from affecting the horizontal rotation of the right limiting bolt 24. The right limiting bolt 24 can rotate through this notch 26.

[0061] In this embodiment, the specimen molding mold is used as a mold for 3D printing concrete, such as... Figure 12 As shown, the specimen molding mold includes a bottom mold and a top mold. The bottom mold and the top mold are arranged symmetrically and connected vertically. The limiting sliders 36 in the two clamping units cooperate to clamp the bottom mold. The cross-section of the top mold is approximately a hollow isosceles trapezoidal structure that runs vertically through the top and bottom, but the top mold is inverted. The top mold includes mold side plates 13 and mold partitions 30. There are two mold side plates 13, and multiple mold partitions 30 are arranged between the two mold side plates 13.

[0062] The bottom mold has the same structure as the top mold, but the bottom mold also includes a mold base plate 14, which is located between the two mold side plates 13. In this way, the cross-section of the bottom mold is approximately a hollow isosceles trapezoidal structure with an opening at the top, and the bottom mold is upright.

[0063] like Figures 13-15 As shown, the method for embedding steel fibers to enhance the interfacial properties of 3D-printed concrete includes the following steps: Step 1: Prepare the test mold: Prepare the test mold for the specimen. Assemble the test mold side plate 13, test mold bottom plate 14 and test mold partition plate 30 as required to form a 3D printed concrete specimen molding mold, including a bottom mold and at least one top mold, for later use.

[0064] Step 2, Install steel fiber 11: Pull the cover plate locking pin 6, and the free end of the cover plate 3 will disengage from the top surface of the rear side wall of the electromagnet chamber 33 under the action of the ejector spring 1. Insert your finger into the handle socket 2 to lift the cover plate 3, take out the old battery 17, insert the new battery 17, and then close the cover plate 3. At this time, the cover plate locking pin 6 is connected to the cover plate clip 16 and locks the cover plate 3.

[0065] After inserting battery 17, turn on power switch 19 to start electromagnet unit and put it into working state. At this time, iron core 18 generates magnetic force. Select a length adjustment piece 28 of appropriate size according to the specifications of steel fiber 11 and attach the length adjustment piece 28 to the upper part of triangular limiting through groove 37.

[0066] The surface of the piled steel fibers 11 is leveled, and the steel fibers 11 are neatly adsorbed into the triangular limiting groove 37 by the magnetism of the iron core 18, ensuring that the length adjustment piece 28 and the steel fibers 11 are arranged vertically, and that the length of the steel fibers 11 exposed to the outside is half of the total length. Specifically, the implant body 7 is lifted with both hands so that the side with the adsorbed length adjustment piece 28 rests against the pile of steel fibers 11. At this time, the triangular limiting groove 37 is horizontally downward. Under the adsorption of the iron core 18, at least one steel fiber 11 can be adsorbed in each recess of the triangular limiting groove 37. Then, the implant body 7 is placed on a platform, with the triangular limiting groove 37 horizontally upward. The position and number of steel fibers 11 are manually arranged to ensure they are neatly distributed within the triangular limiting groove 37. Alternatively, each steel fiber 11 can be adsorbed into each recess of the triangular limiting groove 37 one by one.

[0067] The steel fiber pressure plate 27 is installed on the body 7 of the implanter with bolts. After tightening the bolts, the steel fiber 11 is pressed against the length adjustment piece 28 to achieve fixation. Specifically, the position of the left nut 9 is adjusted so that the left U-shaped groove 39 of the steel fiber pressure plate 27 can easily engage the left limit bolt 8 without being too loose. Then, the right limit bolt 24 is rotated around the bolt pivot 23 until it is just engaged in the right U-shaped groove 40. The left nut 9 and the right nut 25 are tightened simultaneously with both hands, and the steel fiber 11 is fixed to the body 7 of the implanter by pressing the steel fiber pressure plate 27.

[0068] Step 3, Preparation of 3D Printed Concrete Substrate Specimen 12: The mixed 3D printed concrete slurry is printed into the assembled substrate specimen through the printer nozzle. After filling, it is placed on a vibration table to make the interior dense, and the surface is smoothed with a trowel.

[0069] Step 4, Inserting Steel Fibers 11: Before the specimen initially sets, lift the inserter body 7 with both hands using the inserter handle 20, align it with the upper surface of the bottom specimen 12, and slowly press it down. Under the control of the clamping units at both ends of the lower part of the inserter body 7, the inserter body 7 is precisely positioned on the top surface of the bottom specimen mold. At this time, exactly half the length of all steel fibers 11 is inserted into the upper surface of the bottom specimen 12, completing the insertion of steel fibers 11. Figure 13 As shown.

[0070] Step 5: Separate the steel fiber 11 from the implant body 7: Hold the implant body 7 with your left hand, ensuring that the implant body 7 does not shift on the upper surface of the bottom specimen 12. After loosening the bolts, remove the steel fiber pressure plate 27. Specifically, first loosen the left nut 9 with your right hand, then loosen the right nut 25 and rotate it 90 degrees to the right. At this time, the steel fiber pressure plate 27 is completely disengaged from the right limit bolt 24. Lift the steel fiber pressure plate 27 from the right side and pull it out from the left limit bolt 8.

[0071] By turning off the electromagnet unit via power switch 19, the embedding device body 7 loses its attraction to the steel fibers 11, thereby reducing interference with the steel fibers 11 already embedded on the surface of the bottom specimen 12. Then, remove the length adjustment piece 28, and then use both hands to slide the embedding device body 7 horizontally along the bottom specimen 12, gradually moving it away from the steel fibers 11, thus removing the embedding device body 7. At this point, one row of steel fibers 11 has been embedded. Steps 2, 4, and 5 can be repeated to embed multiple rows of steel fibers 11 in the bottom specimen 12.

[0072] Step 6: Preparation of the overall specimen: Before the bottom specimen 12 has fully set, install the top mold on the bottom mold, then print the same concrete slurry as the bottom specimen 12 into the top mold. After filling, smooth the upper surface with a trowel to form the entire 3D printed concrete specimen. Figure 14 As shown, this is used to test and evaluate the bonding performance of the interface layer of 3D printed concrete. The entire 3D printed concrete specimen includes at least one upper specimen 41, one lower specimen 12, and one interface layer, and the interface layer contains at least one row of steel fibers 11.

[0073] The above steel fiber embedding method was used to conduct experiments, and the results are as follows: 1. Raw materials The main raw materials used include aluminate cement, recycled brick powder, nano silica, sodium sulfate, standard sand, water-reducing agent and water.

[0074] (1) Aluminate cement The CA50-Ⅲ aluminate cement produced by Zhengzhou Jianai Co., Ltd. was used. Its physical properties and chemical composition meet the requirements of "Aluminate Cement" (GB / T201-2015). The chemical composition is shown in Table 1, and the physical properties are shown in Table 2.

[0075] (2) Recycled brick powder The main chemical components of recycled brick powder are shown in Table 3.

[0076] (3) Nano silica The technical specifications of nano-SiO2 are shown in Table 4.

[0077] (4) Sodium sulfate Anhydrous sodium sulfate (analytical grade AR500), purity >99%, is a white crystalline solid.

[0078] (5) Fine aggregate The fine aggregate is quartz standard sand, and its performance indicators are shown in Table 5.

[0079] (6) Water-reducing agent Polycarboxylate superplasticizer with a water content ≤3%, an air content of 1.5%~6%, a chloride ion content ≤0.05%, and a water reduction rate ≥40%.

[0080] (7) Water The test water was tap water, and all indicators met the requirements of the "Standard for Water Used in Concrete" (JGJ 63-2006).

[0081] (8) Steel fiber The steel fibers are straight ordinary steel fibers (CS) and hooked refractory steel fibers (RS), and their characteristic parameters are shown in Table 6.

[0082] Matrix raw material proportions The proportions of the raw materials used are shown in Table 7. Using the above specimen preparation method, a total of 7 groups of dog-bone 3D-printed concrete interfacial bonding tension specimens with dimensions of 80mm×40mm×90mm were prepared. The effects of CS and RS steel fibers on the interfacial tension performance under fiber-free, single-row, double-row, and triple-row embedding conditions were studied.

[0083] 3. Test Results 3.1 Tensile strength The test results of the interfacial bond tensile strength of 3D printed concrete are shown in Table 8.

[0084] Note: SF-0 is the control group without fibers. The numbers 1, 2, and 3 represent the number of rows of embedded steel fibers, with 7 steel fibers per row.

[0085] The results show that the deviation rate of the three strength test values ​​in each group from the mean value does not exceed 10%, indicating that the test method has a certain degree of reliability and feasibility.

[0086] It can also be seen that the type and dosage of steel fibers have a significant impact on the interfacial bond tensile strength. When the interfacial layer is embedded with 1, 2, and 3 rows of round straight ordinary steel fibers (CS), the interfacial bond strength increases by 5.5%, 40%, and 75%, respectively. However, when the interfacial layer is embedded with 1, 2, and 3 rows of hooked refractory steel fibers (RS), the interfacial bond strength increases by 12%, 54%, and 90%, respectively. Under the same conditions of embedding 1, 2, and 3 rows of steel fibers, RS can increase the interfacial bond strength by 6.2%, 10%, and 8.3% compared to CS.

[0087] 3.2 Tensile stress-strain curve Figure 15 The full curve of debonding load-opening displacement of the interfacial layer in 3D-printed concrete specimens is presented. It can be seen that the type of steel fiber has a significant impact on the full curve of debonding load-opening displacement of the interfacial layer in 3D-printed concrete specimens. For specimen SF-0 without embedded steel fibers, and specimens CS-1, CS-2, and CS-3 with 1, 2, and 3 rows of round straight ordinary steel fibers (CS) embedded respectively, the full curve has only one peak point and no obvious downward segment. However, for specimens RS-1, RS-2, and RS-3 with 1, 2, and 3 rows of hook-shaped refractory steel fibers (RS) embedded respectively, the full curve has two peak points and shows obvious re-strengthening and downward segments. This indicates that the type and dosage of steel fibers have a significant impact on the interfacial bonding performance of 3D-printed concrete specimens, further demonstrating the feasibility of the experimental apparatus and method of this invention.

[0088] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Therefore, all equivalent changes or modifications made to the structure, features and principles described in the claims of the present invention should be included within the scope of the present invention.

Claims

1. A steel fiber embedding device for reinforcing the interface properties of 3D-printed concrete with steel fiber reinforcement, comprising a steel fiber embedder and a matching specimen molding mold, characterized in that, The steel fiber implant includes an implant body (7), an electromagnet unit containing multiple iron cores (18), a length adjustment plate (28), a steel fiber pressure plate (27), and a clamping unit. The implant body (7) has an electromagnet chamber (33) on the upper part and a triangular limiting groove (37) on one side of the lower part. The joint surface between the triangular limiting groove (37) and the implant body (7) is a triangular continuous concave-convex pleated surface (371). The electromagnet unit is installed inside the electromagnet chamber (33). Multiple iron cores (18) in the electromagnet unit are evenly distributed in a straight line. The iron cores (18) extend downward into the electromagnet chamber (33) and extend to one side of the triangular limiting groove (37). The length adjustment piece (28) is installed in the triangular limiting groove (37) and is magnetically connected to the iron core (18). The length adjustment piece (28) is in contact with the pleated surface (371) of the triangular limiting groove (37) and slides up and down along the pleated surface (371). Multiple steel fibers (11) are also provided in the triangular limiting groove (37). Each steel fiber (11) is magnetically connected to the iron core (18). The top of the steel fiber (11) is pressed upward against the length adjustment piece (28). The steel fiber pressure plate (27) is bolted in the triangular limiting groove (37). The steel fiber pressure plate (27) presses the length adjustment piece (28) and multiple steel fibers (11). The clamping units are symmetrically arranged at both ends of the lower part of the embedding device body (7). The two clamping units cooperate to clamp the steel fiber embedding device on the specimen molding mold. The specimen molding mold includes a bottom mold and a top mold.

2. The steel fiber embedding device for reinforcing the interface properties of 3D printed concrete with steel fiber reinforcement according to claim 1, characterized in that, The electromagnet chamber (33) is a rectangular cavity. The top of the electromagnet chamber (33) extends upward through the body of the implanter (7). The top of the body of the implanter (7) is hinged with a cover plate (3) for opening and closing the electromagnet chamber (33). A handle recess (2) is provided on the end face of the cover plate (3) for the hand to hold the cover plate (3) to achieve flipping. A locking component is provided between the cover plate (3) and the body of the implanter (7) to control the flipping of the cover plate (3).

3. The steel fiber embedding device for reinforcing the interface properties of 3D printed concrete with steel fiber reinforcement according to claim 2, characterized in that, The locking assembly includes a locking pin slot (31), a cover plate locking pin (6), and a cover plate clip (16). The locking pin slot (31) is provided in the body of the implanter (7). The cover plate locking pin (6) is elastically slidably connected in the locking pin slot (31). One end of the cover plate locking pin (6) extends out of the locking pin slot (31) to the outside of the body of the implanter (7) and is connected to a pull ring. The other end of the cover plate locking pin (6) extends out of the locking pin slot (31) to the inside of the electromagnet chamber (33). The cover plate (3) is provided with a cover plate clip (16) at the lower part. The cover plate clip (16) extends vertically downward and is connected to the other end of the cover plate locking pin (6) with a locking tongue. The body of the implanter (7) is provided with a push-out groove (15). A push-out spring (1) is provided in the push-out groove (15). The push-out spring (1) presses upward against the cover plate (3) in the closed state. The upper two sides of the implanter body (7) extend horizontally outward to form a plate-shaped implanter handle (20).

4. The steel fiber embedding device for reinforcing the interface properties of 3D printed concrete with steel fiber reinforcement according to claim 1, characterized in that, The electromagnet unit includes a battery (17), a wire (21), a coil (22), an iron core (18), and a power switch (19). The battery (17) is installed in the electromagnet chamber (33) through a battery box. The iron core (18) is a rod. The lower end of the iron core (18) is fixedly inserted into the body of the implanter (7), and the upper end of the iron core (18) extends into the electromagnet chamber (33). The upper end of each iron core (18) is wound with the coil (22). The battery (17), multiple coils (22), and power switch (19) are connected together through the wire (21). The power switch (19) is located on the upper surface of the body of the implanter (7).

5. The steel fiber embedding device for reinforcing the interface properties of 3D printed concrete with steel fiber reinforcement according to claim 1, characterized in that, The triangular limiting groove (37) has a toothed cross-section, and the side opposite to the folded surface (371) of the triangular limiting groove (37) penetrates the body of the implanter (7). The length adjustment piece (28) is a plate with continuous concave and convex bends. The thickness of the length adjustment piece (28) is the same as the diameter of the steel fiber (11). The steel fiber (11) is arranged in the recessed position of the folded surface (371) of the triangular limiting groove (37). The length adjustment piece (28) and the steel fiber (11) are arranged vertically and abut against each other. The arrangement length between multiple steel fibers (11) is not greater than the length of the length adjustment piece (28). The steel fiber (11) extends downward out of the triangular limiting groove (37).

6. The steel fiber embedding device for reinforcing the interface properties of 3D-printed concrete with steel fiber reinforcement according to claim 1, characterized in that, The steel fiber pressure plate (27) is a long plate with a thick middle and thin ends. One side of the middle part of the steel fiber pressure plate (27) has a continuous triangular concave-convex shape to form a pressing toothed rack (32). The pressing toothed rack (32) is adapted to the length adjustment piece (28). Each protruding position of the pressing toothed rack (32) is recessed inward to form a triangular toothed groove (38). The toothed groove (38) abuts against the side wall of the steel fiber (11).

7. The steel fiber embedding device for reinforcing the interface properties of 3D printed concrete with steel fiber reinforcement according to claim 6, characterized in that, The steel fiber pressure plate (27) has a left U-shaped groove (39) at one end, and a left limiting bolt (8) is horizontally arranged at one end of the implant body (7). The left limiting bolt (8) passes through the triangular limiting through groove (37) and through the left U-shaped groove (39) and is connected to a left nut (9). The steel fiber pressure plate (27) has a right U-shaped groove (40) at the other end. The length of the left U-shaped groove (39) is less than the length of the right U-shaped groove (40). The implant body (7) has a bolt shaft (23) vertically arranged at the other end. The bolt shaft (23) is rotatably connected to the implant body (7). A right limiting bolt (24) is horizontally arranged on the bolt shaft (23). The right limiting bolt (24) passes through the triangular limiting through groove (37) and through the right U-shaped groove (40) and is connected to a right nut (25). The left nut (9) and the right nut (25) are both wing nuts.

8. The steel fiber embedding device for reinforcing the interface properties of 3D printed concrete with steel fiber reinforcement according to claim 1, characterized in that, The clamping unit includes a base (10) and a limiting slider (36). The limiting slider (36) is elastically slidably connected on the base (10). The limiting slider (36) in the two clamping units cooperate to clamp the bottom test mold. The bottom and top test molds are arranged symmetrically and connected. The top test mold includes a test mold side plate (13) and a test mold partition (30). There are two test mold side plates (13), and multiple test mold partitions (30) are provided between the two test mold side plates (13). The bottom test mold has the same structure as the top test mold. The bottom test mold also includes a test mold base plate (14), and a test mold base plate (14) is provided between the two test mold side plates (13).

9. A method for embedding steel fibers to enhance the interfacial properties of 3D-printed concrete, characterized in that, The embedding device according to any one of claims 1-8 includes the following steps: Step 1: Prepare trial molds: Prepare trial molds for the specimen molding process, including one bottom mold and at least one top mold; Step 2, Install steel fiber (11): After inserting the battery (17), start the electromagnet unit to make the iron core (18) generate magnetic force; select the appropriate length adjustment piece (28) according to the specifications of the steel fiber (11), and attach the length adjustment piece (28) to the upper part of the triangular limiting groove (37); flatten the surface of the piled steel fiber (11), and use the magnetism of the iron core (18) to neatly attach the steel fiber (11) to the triangular limiting groove (37), ensuring that the length adjustment piece (28) and the steel fiber (11) are arranged vertically, and the length of the exposed steel fiber (11) is half of the total length; install the steel fiber pressure plate (27) on the body of the embedder (7) with bolts, tighten the bolts, and the steel fiber (11) presses the steel fiber (11) and the length adjustment piece (28) together to achieve fixation; Step 3: Prepare 3D printed concrete bottom layer specimen (12): Print the mixed 3D printed concrete slurry into the assembled bottom layer specimen through the printer nozzle, fill it, place it on the vibration table to make the interior dense, and smooth the surface with a trowel. Step 4, Inserting steel fibers (11): Before the specimen initially sets, lift the body of the embedder (7) with both hands and press it down slowly on the upper surface of the bottom specimen (12). Under the control of the clamping units at both ends of the lower part of the embedder body (7), the embedder body (7) is precisely placed on the top surface of the bottom specimen. At this time, ½ of the length of all the steel fibers (11) is inserted into the upper surface of the bottom specimen (12), completing the insertion of steel fibers (11). Step 5: Separate the steel fiber (11) from the implant body (7): Hold the implant body (7) with your left hand to ensure that the implant body (7) does not shift on the upper surface of the bottom specimen (12). Loosen the bolts and remove the steel fiber pressure plate (27). Turn off the electromagnet unit to make the implant body (7) lose its attraction to the steel fiber (11), thereby reducing the interference to the steel fiber (11) that has been embedded on the surface of the bottom specimen (12). Then remove the length adjustment piece (28), and then use both hands to control the body of the implanter (7) to slide horizontally along the bottom specimen (12) and gradually move away from the steel fiber (11) to remove the body of the implanter (7); Step 6, Preparation of the whole specimen: Before the bottom specimen (12) is fully set, the top specimen is installed on the bottom specimen mold. Then, the same concrete slurry as the bottom specimen (12) is printed into the top specimen mold. After filling, the upper surface is smoothed with a trowel to form the whole 3D printed concrete specimen, which is used to test and evaluate the bonding performance of the 3D printed concrete interface layer.

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