Device and method for directionally arranging steel fibers and self-repairing concrete in 3DPC (Three Dimensional Polycarbonate)

Abstract

The invention discloses a device and a method for directionally arranging steel fibers in 3DPC and self-repairing concrete, belongs to the technical field of concrete 3D printing, and adopts hollow steel fibers for adsorbing an acidophilic bacillus microbial crack repairing agent. In the printing process, the control precision and the arrangement mode of directional arrangement of the hollow steel fibers are controlled by additionally arranging a controllable magnetic field and programming, so that the hollow steel fibers magnetized by the magnetic field are directionally arranged along the magnetic field, move and penetrate through an interface between printing layers, and fiber connection is formed. When the component generates cracks, the hollow steel fibers are extruded to release the repairing agent containing the acidophilic bacillus microorganisms, the acidophilic bacillus microorganisms breathe aerobically to generate a metabolite CO2, and the metabolite CO2 reacts with Ca < 2 + > in the cement-based material to generate CaCO3 crystals to fill gaps and cracks.

Description

Technical Field

[0001] The present invention belongs to the technical field of concrete 3D printing, and specifically relates to a device and method for directional arrangement of steel fibers in 3DPC and self-repairing of concrete. Background Art

[0002] 3D printing technology, commonly known as additive manufacturing, is an intelligent manufacturing technology based on digital models that can achieve rapid prototyping by printing layer by layer. 3D printed concrete (3DPC) technology is a new intelligent building technology that builds building structures by stacking concrete materials layer by layer. The extrusion-based process is a widely used method in 3DPC technology, that is, the premixed concrete is transported to the container of the printer, extruded through the nozzle, and stacked layer by layer according to a predetermined program. Compared with the traditional casting molding process, 3DPC technology has the advantages of mold-free construction, high degree of automation, labor saving and time saving.

[0003] However, due to the particularity of the process and the limitations of the current technological development, it is not yet possible to achieve simultaneous printing of steel bars and concrete, resulting in poor bonding between concrete layers during the printing and stacking process, and the interface between layers becomes a weak link in structural damage. At the same time, due to the brittleness of concrete, cracks are inevitable. Cracks provide channels for the migration of water and corrosive ions, threatening the durability of the structure and increasing the maintenance cost of the structure. The "Five Laws" emphasize that the cost of structural maintenance is much higher than the design cost, and the cost of repair increases exponentially with deterioration. Traditional repair methods are often manual repairs, which are not timely and expensive. In recent years, the emerging microbial self-repair technology can make up for this limitation. The principle of microbial self-repair is to use microorganisms to mineralize the metabolites secreted by bacteria or fix CO2 in the air, and then react with Ca + The process of forming calcium carbonate. However, the alkaline environment of concrete is not suitable for the survival of microorganisms.

[0004] Therefore, how to solve the poor interlayer bonding strength of 3D printed concrete and repair cracks in components is a current hot research issue. Summary of the invention

[0005] In order to solve the technical problems existing in the background technology, the present invention aims to provide a device and method for directional arrangement of steel fibers and self-repair of concrete in 3DPC, using hollow steel fibers that adsorb acidophilic Bacillus microorganism crack repairing agents. During the printing process, the control accuracy and arrangement method of the directional arrangement of the hollow steel fibers are controlled by external controllable magnetic fields and programming, so that the hollow steel fibers magnetized by the magnetic field are directional arranged along the magnetic field, move, pass through the interface between the printed layers, and form fiber connections. When cracks appear in the component, the hollow steel fibers are squeezed to release the repairing agent containing acidophilic Bacillus microorganisms. The acidophilic Bacillus microorganisms produce metabolic products CO2 through aerobic respiration, which react with Ca in the cement-based material. 2+ The reaction generates CaCO3 crystals which fill the voids and cracks.

[0006] In order to solve the technical problem, the technical solution of the present invention is:

[0007] A device for directional arrangement of steel fibers in 3DPC and self-repairing of concrete, the device comprising: a hopper, a rotating shaft fixing rod, a rotating shaft blade, a printing nozzle, a nozzle rotating rod, a universal adjuster, a magnetic field generator, a controller and a DC power supply;

[0008] The discharge end of the hopper is connected to the printing nozzle through a rotating shaft fixing rod; the rotating shaft blade is installed inside the rotating shaft fixing rod and the printing nozzle, and the nozzle rotating rod passes through the hopper, the central axis of the rotating shaft blade and the printing nozzle in sequence;

[0009] The ejection end of the printing nozzle is connected to the magnetic field generator through a universal adjuster, and the universal adjuster is electrically connected to the controller through a control line. The magnetic field generator is distributed on both sides of the movement direction of the printing nozzle and is electrically connected to a DC power supply through a control line.

[0010] Furthermore, the hopper is a conical cylinder, or the upper part of the hopper is cylindrical and the lower part is conical.

[0011] Furthermore, the magnetic field generator adopts an electromagnet, which is a DC coil electromagnet, and the magnetic field strength is controlled by the current size.

[0012] Furthermore, the steel fiber is a hollow structure and is used for absorbing microbial liquid.

[0013] Furthermore, the universal adjuster comprises: a driving gear, a driven gear and a mechanical rod connected to the magnetic field generator;

[0014] The driving gear drives the driven gear to rotate, and the direction of the magnetic field generator is controlled by the mechanical rod to orient the steel fiber adsorbed with the microbial liquid.

[0015] A method for directional arrangement of steel fibers in 3DPC and self-repair of concrete, the method being applied to any of the above-mentioned devices, the method comprising:

[0016] S1: Perform structural design and finite element analysis on the target printed component to obtain the location where cracks may occur under the corresponding load. The system exports the design information of the component, including the structural design of the component, printing material information and the location where cracks may occur. Then, the programming software is used to generate printing codes, which are finally input into the controller of the 3D printer and the universal adjuster.

[0017] S2: Adding acidophilic Bacillus to a culture medium containing nutrients required by microorganisms, culturing the mixture in a shaker at 30°C for 36 hours and then centrifuging to obtain a microbial culture solution;

[0018] S3: placing the obtained microbial liquid in a reaction container, and then placing the hollow steel fiber therein for adsorption;

[0019] S4: Put the prepared printing material and the hollow steel fiber adsorbed with the microbial liquid into a mixer and mix them evenly, and then place them in a feeding device for programmable directional arrangement of steel fibers in 3D printing concrete and self-repair of concrete;

[0020] S5: Convert the input civilian AC power of 220V / 50Hz into a DC output of safe voltage 0-60V, 0-999Hz through a DC power supply, and then use the DC output voltage to connect an external electromagnet to form a magnetic field on the front and back sides of the steel fiber device in the programmable directional arrangement 3D printing concrete;

[0021] S6: Start the controller, DC power supply and universal regulator controller of the programmable directional arrangement of steel fibers in 3D printed concrete and the concrete self-repairing device, and print according to the code to obtain the self-repairing concrete with directional arrangement of steel fibers.

[0022] Furthermore, in step S2, the nutritional ingredients are beef extract, glucose, protein peptides, yeast extract and water.

[0023] Furthermore, in step S2, the microbial culture liquid is a culture liquid of Bacillus acidophilus, and the OD value of Bacillus acidophilus is 1.9-2.5.

[0024] Or the microbial bacterial liquid is composed of acidophilic Bacillus bacterial liquid and urea-containing nutrient solution: the OD value of the acidophilic Bacillus bacterial liquid is 1.9-2.5, and the acidophilic Bacillus bacterial liquid is incubated at -4-0°C for 12 hours and then mixed with the urea-containing nutrient solution to obtain the microbial bacterial liquid.

[0025] Furthermore, when cracks appear in concrete components due to stress, the hollow steel fibers that encapsulate microbial liquid inside are squeezed to release the liquid; external moisture and air penetrate through the cracks, providing a suitable living environment for acidophilic Bacillus; the bacteria colonize and multiply in the cracks, secrete urease through metabolic activities, and catalyze the hydrolysis of urea to produce ammonium carbonate; in the alkaline environment of concrete, ammonium carbonate further decomposes into carbonate ions and ammonium ions; subsequently, the carbonate ions combine with calcium ions in the cement hydration products to form calcium carbonate precipitates, ultimately achieving self-repair of the cracks.

[0026] Compared with the prior art, the advantages of the present invention are:

[0027] (1) The present invention can regulate the magnetic field control system during the 3D printing of concrete components, so that the steel fibers adsorbing microbial liquid in the concrete can pass through the interface, which can not only enhance the bonding force between the 3D printed concrete layers, but also can directional arrange the steel fibers according to different stress conditions and possible locations of cracks, thereby maximizing the utilization of the steel fibers.

[0028] (2) The present invention uses hollow steel fibers instead of ordinary steel fibers as carriers to absorb acidophilus Bacillus liquid under negative pressure conditions. When cracks appear in the component, the hollow steel fibers are squeezed to release the acidophilus Bacillus liquid. The acidophilus Bacillus microorganisms undergo aerobic respiration to produce a metabolic product, CO2, which reacts with Ca in the cement-based material. 2+ The reaction generates CaCO3 crystals which fill the voids and cracks.

[0029] (3) Compared with traditional repair methods, including surface repair, grouting and other artificial repair methods, it is more environmentally friendly, economical and efficient. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 A schematic diagram of a printing nozzle for a device for programmable directional arrangement of steel fibers in 3D printed concrete and self-repair of concrete provided in an embodiment of the present invention;

[0031] Figure 2 The fiber distribution of the concrete cross section printed by the device for programmable directional arrangement of steel fibers in 3D printed concrete and self-repair of concrete provided in the implementation case of the present invention;

[0032] Figure 3 A structural diagram of a universal regulator for a device for programmable directional arrangement of steel fibers in 3D printed concrete and self-repair of concrete provided in an embodiment of the present invention;

[0033] Figure 4 A printing flow chart of a device for programmable directional arrangement of steel fibers in 3D printed concrete and self-repair of concrete provided for an implementation case of the present invention;

[0034] Figure 5 This is a diagram of the self-repair mineralization mechanism of Bacillus acidophilus;

[0035] Figure 6 Plan and perspective views of the schematic diagram for manufacturing hollow steel fibers.

[0036] Reference numerals:

[0037] 1. hopper, 2. shaft fixing rod, 3. shaft blade, 4. printing nozzle, 5. nozzle rotating rod, 6. universal adjuster, 7. magnetic field generator, 8. controller, 9. DC power supply, 10. iron sheet (1), 11. iron sheet (2), 12. epoxy resin adhesive; 601. driving gear, 602. driven gear, 603. mechanical rod. DETAILED DESCRIPTION

[0038] The specific implementation mode of the present invention is described below in conjunction with embodiments:

[0039] It should be noted that the structures, proportions, sizes, etc. shown in this specification are only used to match the contents disclosed in the specification so that people familiar with this technology can understand and read them, and are not used to limit the conditions under which the present invention can be implemented. Any structural modification, change in proportional relationship or adjustment of size should still fall within the scope of the technical content disclosed in the present invention without affecting the effects and purposes that can be achieved by the present invention.

[0040] At the same time, the terms such as "upper", "lower", "left", "right", "middle" and "one" cited in this specification are only for the convenience of description and are not used to limit the scope of implementation of the present invention. Changes or adjustments to their relative relationships should be regarded as the scope of implementation of the present invention without substantially changing the technical content.

[0041] Embodiment 1:

[0042] The present invention provides a device for programmable directional arrangement of steel fibers in 3D printed concrete and self-repair of concrete, such as Figure 1 As shown, the 3D printer print head includes a hopper 1, and the bottom of the hopper 1 is connected to the print nozzle 4 through a rotating shaft fixing rod 2; a rotating shaft blade 3 is also provided between the hopper 1 and the print nozzle 4; and the nozzle rotating rod 5 passes through the hopper 1, the central axis of the rotating shaft blade 3, and the print nozzle 4 in sequence. The hopper is a conical cylinder, or the upper part of the hopper is cylindrical and the lower part is conical. The print head is connected to a magnetic field generator 7 through a universal adjuster 6, and the universal adjuster is connected to a controller 8 through a control line. The magnetic field generator is arranged on both sides of the front and rear of the print nozzle movement direction, and is connected to a DC power supply 9 through a control line.

[0043] exist Figure 2In the structure, the steel fiber runs through the upper and lower concrete strips in the middle, and the steel fibers at both ends present an angle. When the component is stressed and cracks are generated, the hollow steel fiber is squeezed to release the microbial liquid adsorbed in it. The aerobic respiration of Bacillus acidophilus microorganisms produces a metabolic product CO2, which reacts with Ca in the cement-based material. 2+ The reaction generates CaCO3 crystals which fill the voids and cracks.

[0044] like Figure 3 As shown, the interior of the universal adjuster is composed of a driving gear 601, a driven gear 602 and a mechanical rod 603 connected to the magnetic field generator 7. The driving gear 601 drives the driven gear 602 to rotate, and controls the direction of the magnetic field generator 7 through the mechanical rod 603 to orient the steel fiber adsorbed with microbial liquid.

[0045] Among them, the universal adjuster plays a key role in the present invention and is mainly responsible for the following functions:

[0046] 1. Realize three-dimensional directional control

[0047] Multi-directional freedom: The universal adjuster can be freely adjusted in multiple axes, allowing the print head to be precisely adjusted according to the predetermined path and angle, thereby achieving programmable directional arrangement of steel fibers. This flexibility helps to optimize the arrangement of steel fibers according to the stress conditions of the component to enhance the mechanical properties of concrete.

[0048] 2. Ensure the consistency of steel fiber orientation

[0049] Coordination of driving and driven gears: The coordinated operation of the driving gear and the driven gear in the universal adjuster can effectively and synchronously adjust the orientation of the print head, thereby ensuring that during the printing process, no matter how the print head moves, the steel fibers can always be arranged at a predetermined angle and direction, avoiding randomness and confusion, thereby improving the overall quality and performance of the component.

[0050] 3. Dynamic adjustment and feedback system

[0051] Real-time monitoring and adjustment: Through the feedback of the controller, the universal regulator can receive real-time monitoring data from the printing process, such as the fluidity of concrete, interlayer adhesion, etc., and automatically adjust the direction of the print head for dynamic compensation. This mechanism ensures that during the printing process, even if there are changes in external factors (such as temperature, humidity, etc.), the printing path and steel fiber layout can be adjusted to ensure the quality of the final concrete component.

[0052] 4. Cooperate with magnetic field generator

[0053] Local magnetic field regulation: The combination of the universal regulator and the magnetic field generator further enhances the control of the direction of the steel fibers. By precisely adjusting the direction and strength of the magnetic field, the steel fibers can be oriented during the printing process, which will have a positive impact on the physical and chemical properties of the fibers and their adhesion to concrete, improving their strength and toughness.

[0054] 5.Support self-repair function

[0055] Combined with microbial release: The universal regulator's control mechanism not only helps to orient the steel fibers during printing, but also releases microbial liquid through the movement of the mechanical rod when the steel fibers are stressed, thereby promoting the self-healing function of concrete. This mechanism ensures that after cracks occur, microorganisms can be released in time to react with the concrete substrate to form self-healing CaCO3 crystals, effectively filling gaps and cracks.

[0056] The design and implementation of the universal adjuster not only improves the directional arrangement accuracy of steel fibers in 3D printed concrete, but also, through linkage with the magnetic field generator, gives the printing process more intelligence and flexibility, ultimately helping to improve the overall performance and self-healing ability of concrete components.

[0057] like Figure 4 As shown, this embodiment provides a method for programmable directional arrangement of steel fibers in 3D printed concrete and self-repair of concrete, including the following steps:

[0058] S1: Structural design and finite element analysis are performed on the components to be printed. The locations where cracks may occur under the corresponding loads are obtained through analysis. The system exports the design information of the components, including the structural design of the components, printing material information and the locations where cracks may occur. Then, programming software is used for programming to generate printing codes, which are finally input into the controllers of the 3D printer and the universal adjuster.

[0059] S2: Add acidophilic Bacillus to the culture medium, which contains the nutrients required by the microorganisms. The mixture is cultured in a shaker at 30°C for 36 hours and then centrifuged.

[0060] S3: The final microbial liquid is placed in a reaction container, and then the hollow steel fiber is placed therein for adsorption.

[0061] S4: Put the prepared printing material and the hollow steel fiber adsorbed with microbial liquid into a mixer and mix them evenly, and then place them in the feeding device of the device for programmable directional arrangement of steel fibers in 3D printing concrete and self-repair of concrete.

[0062] S5: The input civilian AC power of 220V / 50Hz is converted into a DC output of safe voltage 0-60V, 0-999Hz through a DC power supply. Then, the DC output voltage is used to connect an external electromagnet to form a magnetic field on the front and back sides of the steel fiber device in the programmable directional arrangement 3D printing concrete.

[0063] S6: Start the controller, DC power supply and universal regulator controller of the device for programmable directional arrangement of steel fibers and self-repair of concrete in 3D printing concrete, and print according to the code to obtain self-repairing concrete with directional arrangement of steel fibers.

[0064] The magnetic field generator is an electromagnet, and the magnitude of the magnetic field it generates is controlled by adjusting the magnitude of the current.

[0065] For S1, the structural design of the printed component first involves drawing a model diagram of the component on CAD according to the structural dimensions, and importing it into the printer system. The system automatically generates a printing path based on the model diagram.

[0066] Abaqus was used to perform finite element analysis on the components to simulate the stress conditions of the components under different loads, obtain the locations where cracks occurred, and then Python was used for programming to obtain the code.

[0067] The length of the hollow steel fiber used needs to be determined according to the printing layer height, and the longest length cannot exceed the printing layer height.

[0068] For S2, the enrichment medium included beef extract 3.0 g / L, peptone 5.0 g / L, and NaCl 5.0 g / L.

[0069] For S2, the enrichment and separation steps include: weighing 30g of acidophilic Bacillus sample, placing it in 100mL enrichment medium, adding MnSO4.H2O at a concentration of 0.005g / L to the medium in order to increase the number of bacterial transformation spores. The medium was placed on a shaker at 30°C, 170rmp for 36h, and then centrifuged at 15°C for 10min to obtain fresh spores. The spores were then dispersed in 0.9% saline. The final bacterial concentration was 10 10 Microbial culture liquid with a concentration of about 10 cells / mL.

[0070] For S3, the hollow steel fiber was placed under a negative pressure of -0.06 MPa to adsorb the concentrated bacterial solution, and the adsorption stopped after 4 hours.

[0071] The freshly mixed concrete is poured into the nozzle hopper, and the freshly mixed concrete is squeezed out from the lower end of the nozzle by the rotation of the nozzle rotating rod.

[0072] For S6, after the 3D printing device is started, the DC power supply and the universal regulator start working at the same time. The DC power supply generates a magnetic field. During the printing process, the universal regulator adjusts the direction of the magnetic field to achieve fiber orientation of concrete in different parts. After the printing is completed, the DC power supply and the universal regulator controller are turned off at the same time.

[0073] like Figure 5 As shown in the figure, when cracks appear in concrete components due to stress, the hollow steel fibers encapsulating the microbial liquid inside are squeezed and release the liquid. External moisture and air penetrate through the cracks, providing a suitable living environment for acidophilic Bacillus. The bacteria colonize and multiply in the cracks, secrete urease through metabolic activities, and catalyze the hydrolysis of urea to produce ammonium carbonate. In the alkaline environment of concrete, ammonium carbonate is further decomposed into carbonate ions (CO3 2- ) and ammonium ions (NH4 + Subsequently, carbonate ions react with calcium ions (Ca 2+ ) combine to form calcium carbonate (CaCO3) precipitation, ultimately achieving self-repair of cracks.

[0074] like Figure 6 As shown, the fiber size used in the present invention is 3mm in diameter and 10mm in length. Two iron sheets with a length of 500mm, a diameter of 3mm and a thickness of 2mm and having a certain curvature and good ductility are used. The iron sheets are bonded by epoxy resin adhesive and mechanically cut into 10mm long steel fibers after solidification. Then negative pressure adsorption is performed, and after adsorption is completed, the two ends of the steel fiber are sealed with epoxy resin adhesive. In order to improve the mechanical properties of the steel fiber, a layer of concrete is sprayed on its outer surface.

[0075] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge scope of ordinary technicians in this field without departing from the purpose of the present invention.

[0076] Many other changes and modifications may be made without departing from the concept and scope of the present invention.It should be understood that the present invention is not limited to the specific embodiments, and the scope of the present invention is defined by the appended claims.

Claims

1. A device for directional arrangement of steel fibers in 3DPC and self-repairing of concrete, characterized in that: The device comprises: a hopper (1), a rotating shaft fixing rod (2), a rotating shaft blade (3), a printing nozzle (4), a nozzle rotating rod (5), a universal adjuster (6), a magnetic field generator (7), a controller (8) and a direct current power supply (9); The discharge end of the hopper (1) is connected to the printing nozzle (4) via a rotating shaft fixing rod (2); the rotating shaft blade (3) is installed inside the rotating shaft fixing rod (2) and the printing nozzle (4), and the nozzle rotating rod (5) passes through the hopper (1), the central axis of the rotating shaft blade (3) and the printing nozzle (4) in sequence; The ejection end of the printing nozzle (4) is connected to a magnetic field generator (7) via a universal adjuster (6); the universal adjuster (6) is electrically connected to a controller (8) via a control line; the magnetic field generator (7) is distributed on both sides of the movement direction of the printing nozzle (4) and is electrically connected to a DC power supply (9) via a control line.

2. A 3DPC steel fiber directional arrangement and concrete self-repairing device according to claim 1, characterized in that: The hopper (1) is a conical cylinder, or the upper part of the hopper (1) is cylindrical and the lower part is conical.

3. The device for directable arrangement of steel fibers and self-repairing concrete in 3DPC according to claim 1, characterized in that: The magnetic field generator (7) adopts an electromagnet, which is a DC coil electromagnet, and the magnetic field strength is controlled by the current.

4. The device for directional arrangement of steel fibers and self-repairing concrete in 3DPC according to claim 1, characterized in that: The steel fiber adopts a hollow structure and is used for absorbing microbial liquid.

5. The device for directional arrangement of steel fibers and self-repairing concrete in 3DPC according to claim 1, characterized in that: The universal adjuster (6) comprises: a driving gear (601), a driven gear (602) and a mechanical rod (603) connected to the magnetic field generator (7); The driving gear (601) drives the driven gear (602) to rotate, and the direction of the magnetic field generator (7) is controlled by the mechanical rod (603) to orient the steel fiber adsorbed with the microbial liquid.

6. A method for directional arrangement of steel fibers in 3DPC and self-repairing of concrete, characterized in that: The method is applied to the device described in any one of claims 1 to 5, and the method comprises: S1: Perform structural design and finite element analysis on the target printed component to obtain the location where cracks may occur under the corresponding load. The system exports the design information of the component, including the structural design of the component, printing material information and the location where cracks may occur. Then, the programming software is used to generate printing codes, which are finally input into the controller of the 3D printer and the universal adjuster. S2: Adding acidophilic Bacillus to a culture medium containing nutrients required by microorganisms, culturing the mixture in a shaker at 30°C for 36 hours and then centrifuging to obtain a microbial culture solution; S3: placing the obtained microbial liquid in a reaction container, and then placing the hollow steel fiber therein for adsorption; S4: Put the prepared printing material and the hollow steel fiber adsorbed with the microbial liquid into a mixer and mix them evenly, and then place them in a feeding device for programmable directional arrangement of steel fibers in 3D printing concrete and self-repair of concrete; S5: Convert the input civilian AC power of 220V / 50Hz into a DC output of safe voltage 0-60V, 0-999Hz through a DC power supply, and then use the DC output voltage to connect an external electromagnet to form a magnetic field on the front and back sides of the steel fiber device in the programmable directional arrangement 3D printing concrete; S6: Start the controller, DC power supply and universal regulator controller of the programmable directional arrangement of steel fibers in 3D printed concrete and the concrete self-repairing device, and print according to the code to obtain the self-repairing concrete with directional arrangement of steel fibers.

7. A method for directional arrangement of steel fibers in 3DPC and self-repairing of concrete according to claim 6, characterized in that: In step S2, the nutritional ingredients are beef extract, glucose, protein peptides, yeast extract and water.

8. A method for directional arrangement of steel fibers in 3DPC and self-repairing of concrete according to claim 6, characterized in that: In the step S2, the microbial culture liquid is a culture liquid of Bacillus acidophilus, and the OD value of Bacillus acidophilus is 1.9-2.

5.

9. A method for directional arrangement of steel fibers in 3DPC and self-repairing of concrete according to claim 6, characterized in that: Or the microbial bacterial liquid is composed of acidophilic Bacillus bacterial liquid and urea-containing nutrient solution: the OD value of the acidophilic Bacillus bacterial liquid is 1.9-2.5, and the acidophilic Bacillus bacterial liquid is incubated at -4-0°C for 12 hours and then mixed with the urea-containing nutrient solution to obtain the microbial bacterial liquid.

10. A method for directional arrangement of steel fibers in 3DPC and self-repairing of concrete according to claim 6, characterized in that: The method further comprises: When cracks appear in concrete components due to stress, the hollow steel fibers that encapsulate microbial liquid inside are squeezed to release the liquid; external moisture and air penetrate through the cracks, providing a suitable living environment for acidophilic Bacillus; the bacteria colonize and multiply in the cracks, secrete urease through metabolic activities, and catalyze the hydrolysis of urea to produce ammonium carbonate; in the alkaline environment of concrete, ammonium carbonate further decomposes into carbonate ions and ammonium ions; then, the carbonate ions combine with calcium ions in the cement hydration products to form calcium carbonate precipitates, ultimately achieving self-repair of the cracks.

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