Construction method for advance pre-burying of structural anchoring

Abstract

The application discloses a construction method for secondary structure steel bar planting advanced pre-burying, which comprises the following steps: S1, construction preparation and component prefabrication: calculating steel bar planting positions, quantity and depth according to drawings, prefabricating pre-burying boxes and adjustable supporting modules, the pre-burying boxes are provided with steel bar planting holes, and the adjustable supporting modules comprise concrete poles, cushion blocks and adjusting structural members; S2, on-site measurement, line laying and positioning: after main body structure beam reinforcement and column reinforcement binding are completed and a template is combined on one side, installation center lines of the pre-burying boxes and the cushion blocks are laid out; S3, assembly and fixation of the pre-burying device; the steel bar planting hole forming process is advanced to be completed before concrete pouring, so that dust, noise and vibration generated by traditional chemical steel bar planting after structure forming are avoided; the pre-burying boxes with blocking membranes are pre-buried in the main body structure beams, columns and walls, the blocking membranes are removed after concrete solidification, clean holes are obtained, secondary cleaning is not needed, the structural integrity is protected, and the construction environment is improved.

Description

Technical Field

[0001] This invention relates to the field of secondary structure rebar installation technology, and in particular to a construction method for advanced pre-embedding of rebar in secondary structures. Background Technology

[0002] In the field of construction engineering, secondary structural rebar installation is usually a subsequent process after the main structure is completed. Its technical background has long faced the contradiction between construction period and quality. Traditional construction techniques often employ the "post-drilling rebar installation method," which involves laying out the lines, mechanically drilling, cleaning the holes, and injecting adhesive to install the rebar after the main concrete has been poured and reached its strength. This process is not only cumbersome, but also generates significant dust pollution from drilling, and the hole depth and verticality are difficult to control precisely. During on-site construction, drilling often encounters the rebar within the main structure, requiring repeated drilling. Incomplete hole cleaning can easily lead to insufficient rebar anchorage. Another common method, the "direct rebar insertion method," avoids post-drilling, but directly inserting rebar during the main structure pouring stage often results in rebar displacement due to the impact of concrete pouring. Furthermore, exposed rebar on-site severely hinders subsequent formwork installation and concrete finishing work, posing significant safety hazards and rework risks. Especially in frame-shear wall structures, the positioning accuracy requirements for rebar installation at the beam bottom and wall junctions are extremely high. Existing technologies struggle to ensure both construction efficiency and finished product quality and operational safety. Summary of the Invention

[0003] The purpose of this invention is to address the shortcomings of existing technologies by proposing a construction method for pre-embedding rebar in secondary structures.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: A construction method for pre-embedding rebar in secondary structures includes the following steps: S1: Construction preparation and component prefabrication: Calculate the location, quantity and depth of rebar installation according to the drawings, prefabricate embedded boxes and adjustable support modules. The embedded boxes have rebar installation holes, and the adjustable support modules include concrete rods, pads and adjustment structural components. S2: On-site measurement, layout and positioning: After the main structure beam reinforcement and column reinforcement are tied and the formwork is closed on one side, mark the installation center line of the embedded box and pad block; S3: Assembly and fixing of the embedded device: Connect the embedded box to the concrete rod and the adjusting structure, install the pad on the ground or main structure through the positioning component, fix the pad to the formwork through the fixing component, put the assembled device into the steel cage, make the opening of the embedded box close to the inner surface of the formwork, and fix the concrete rod on the pad. S4: Firmness check and concrete pouring: Check the firmness of the installation and the integrity of the sealing membrane, and pour concrete after the formwork is closed; S5: Template Removal and Hole Cleaning: After template removal, before secondary structure construction, uncover or puncture the sealing membrane to expose the pre-embedded holes. If the sealing membrane is damaged, clean the dust inside the holes before proceeding with subsequent procedures. S6: Rebar installation: After processing the threads at the ends of the secondary structural rebars, screw them into the pre-embedded sleeves and tighten them, or inject rebar adhesive into the clean pre-embedded channels and then install the rebars.

[0005] Preferred option: The embedded box is prefabricated using fine stone concrete or high-strength mortar of the same grade as or one grade higher than the main structure, with 0.9 kg / m³ of PVA fiber added inside, and dovetail or wavy grooves prefabricated on the outside.

[0006] Furthermore: A straight threaded sleeve is pre-embedded in the pre-embedded box. The straight threaded sleeve is made of 45# steel, and its length is at least twice the diameter of the steel bar. The internal thread machining accuracy is 6H grade.

[0007] Furthermore: A sealing film is affixed above the pre-embedded box. The sealing film has a three-layer structure: the outer layer is a high-toughness PE layer, the middle layer is an aluminum foil layer, and the inner layer is a silicone oil-coated release paper. It also has tear-off tabs on the edges.

[0008] As a preferred embodiment of the present invention: the concrete rod and the adjusting structure are provided with concrete grooves, which are annular, spiral, dovetail-shaped or barbed.

[0009] As a further embodiment of the present invention: the pad has a positioning element pre-embedded at the bottom or side, the positioning element being a positioning nail or a clamp, the upper end of the pad is provided with a screw with a fluorescent mark, and a cold-drawn wire mesh with a diameter of 4mm is added inside the pad.

[0010] As a further aspect of the present invention: In step S3, multiple embedded boxes are assembled in series, and multiple embedded boxes are connected by concrete rods and adjusting structural components. Multiple embedded boxes are fixed above a set of pads to achieve one-time pre-embedding of multiple rebars on the top of the wall.

[0011] Based on the aforementioned solution: when using an aluminum mold or steel mold system, the fasteners in step S3 are high-strength structural adhesive or 3M VHB tape, replacing nails for fixing.

[0012] Based on the aforementioned scheme: the concrete rod in step S3 is replaced with HRB400 ribbed steel bars with a diameter of 12mm or 10mm. One end of the ribbed steel bar is welded or threaded to the back of the embedded box, and the other end is tightly attached to the stirrups or the upper row of main bars of the beam and tied or spot-welded for fixation.

[0013] Based on the aforementioned scheme: In step S4, when pouring concrete, the vibrator should maintain a safe distance of at least 50mm from the embedded box, and fine aggregate concrete should be used, supplemented by an attached vibrator or manual tamping.

[0014] The beneficial effects of this invention are as follows: A construction method for pre-embedding rebar in secondary structures avoids the dust, noise, and vibration generated by drilling after the structure is formed by traditional chemical rebar installation by completing the rebar hole forming process before concrete pouring. By pre-embedding pre-hole boxes with sealing membranes in the beams, columns, and walls of the main structure, the sealing membrane can be removed after the concrete has solidified to obtain clean channels without the need for secondary cleaning, thus protecting the integrity of the structure and improving the construction environment.

[0015] A construction method for pre-embedding rebar in secondary structures is proposed. Through a modular device consisting of a pre-embedded box, an adjustable support module, and pads, the length and angle can be flexibly adjusted according to the beam width and the formwork system. The pads are fixed to the formwork or structural surface by positioning components, and the height can be finely adjusted with the screw marked with fluorescent markers. This method solves the problems of easy displacement and difficult fixing in traditional pre-embedding.

[0016] A construction method for pre-embedding rebar in secondary structures involves assembling multiple pre-embedded boxes in series using concrete rods and adjustable structural components to form an integral strip structure. After the wall reinforcement is tied, the strip is positioned and fixed on both sides of the formwork, enabling the one-time pre-embedding of multiple rebars at the top of the wall. This reduces the amount of work required for point-by-point positioning and improves construction speed and positional consistency.

[0017] A construction method for pre-embedding rebar in secondary structures involves prefabricating dovetail or wavy grooves on the outer wall of the pre-embedded box, which can be directly clamped onto the stirrups and tied with binding wire to prevent drift caused by concrete impact. This method is highly applicable and provides reliable fixation.

[0018] A construction method for pre-embedding rebar in secondary structures involves pre-embedding a straight-threaded sleeve matching the rebar specifications inside a pre-embedding box. After the concrete solidifies, the secondary structural rebar with pre-processed threads is directly screwed into the sleeve and tightened to the specified torque. The connection can be completed without rebar adhesive. The straight-threaded mechanical connection has more stable quality and completely eliminates the aging and durability problems of chemical adhesives. Attached Figure Description

[0019] The accompanying drawings, which form part of this application, are used to provide a further understanding of the application and to make other features, objects, and advantages of the application more apparent. The illustrative embodiments and descriptions of this application are used to explain the application and do not constitute an undue limitation of the application. In the drawings: Figure 1 This is a schematic diagram of a construction method for pre-embedding rebar in secondary structures proposed in this invention. Figure 2 This is a schematic diagram of the pre-embedding of rebar at different elevations of the main structure, which is a construction method for pre-embedding rebar in secondary structures proposed in this invention. Figure 3This is a schematic diagram of a double-rebar hole pre-embedded box for a construction method for advanced pre-embedding of rebar in secondary structures proposed in this invention. Figure 4 This is a schematic diagram of the series connection of the pre-embedded boxes in a construction method for pre-embedding rebar in secondary structures proposed in this invention. Figure 5 This is a schematic diagram of the pre-embedded box and the grooved surface of the concrete pole, which are part of a construction method for pre-embedding rebar in secondary structures proposed in this invention. Figure 6 This is a schematic diagram of the two-layer arrangement of the double-rebar hole pre-embedded box in a construction method for advanced pre-embedding of rebar in secondary structures proposed in this invention. Figure 7 This is a schematic diagram of the two-layer arrangement of a single rebar hole pre-embedded box for a construction method for advanced pre-embedding of rebar in secondary structures proposed in this invention.

[0020] Figure label: 1. Rebar hole; 2. Embedded box; 3. Concrete rod; 4. Spacer block; 5. Positioning component; 6. Adjustment structure component; 7. Concrete groove; 8. Sealing membrane. Detailed Implementation

[0021] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0022] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate for the embodiments of this application described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0023] In this application, the terms "upper," "lower," "left," "right," "front," "rear," "top," "bottom," "inner," "outer," "middle," "vertical," "horizontal," "lateral," and "longitudinal" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are primarily for the purpose of better describing this application and its embodiments, and are not intended to limit the indicated device, element, or component to having a specific orientation, or to be constructed and operated in a specific orientation.

[0024] Furthermore, in addition to indicating location or positional relationship, some of the aforementioned terms may also have other meanings. For example, the term "above" may also be used in some cases to indicate a certain dependency or connection relationship. Those skilled in the art can understand the specific meaning of these terms in this application based on the specific circumstances.

[0025] In addition, the term "multiple" should mean two or more.

[0026] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments. Example

[0027] A construction method for pre-embedding rebar in secondary structures, such as... Figure 1 As shown, it includes the following steps: S1: Construction preparation and component prefabrication. First, accurately calculate the location, quantity, and depth of rebar installation in the main structure beams, columns, and walls based on the drawings for secondary structures such as infill walls and structural columns. Subsequently, based on the calculation results, embedded box 2 is manufactured and selected. Embedded box 2 is made of fine stone concrete or high-strength mortar of the same grade as or one grade higher than that of the main structure. C35 fast-hardening high-strength self-compacting mortar is preferred, with 0.9 kg / m³ of PVA fiber added to resist cracking. The specifications are changed according to the beam height and the height of the protective layer. The preferred specifications are 50mm×50mm×220mm or 60mm×60mm×220mm. Rebar holes 1 are opened in embedded box 2. Dovetail or wavy grooves can be prefabricated on the outside of embedded box 2 to increase the mechanical interlocking force with the post-poured concrete and prevent pull-out. This facilitates the fixing of the device and prevents the embedded box 2 from drifting due to impact during concrete pouring. Preferably, a straight threaded sleeve can be embedded for reinforcement. The internal straight threaded sleeve can be made of 45# steel, with specifications matching the reinforcing bars to be implanted. The internal thread of the sleeve has a machining accuracy of 6H grade, and its length is at least twice the diameter of the reinforcing bar. At the same time, the rebar hole 1 and the upper and lower end faces of the embedded box 2 are flush. The upper surface of the embedded box 2 is firmly attached with an easy-to-tear and remove sealing film 8. When rebar is installed on a 100mm wide wall, two rebar holes 1 can be opened on one embedded box 2. The sealing film 8 adopts a three-layer structure: an outer high-toughness PE layer for protection against damage, a middle aluminum foil layer for light blocking and heat insulation, and an inner silicone oil-coated release paper with an unadhesive tear-off tab at the edge. Preferably, the sealing film 8 can be a kraft paper tape composite PE film. Furthermore, the adjustable support module is prefabricated, comprising a concrete rod 3, a pad 4, and an adjusting structural component 6. One end of the concrete rod 3 can be pre-embedded or welded with a connecting nut. The adjusting structural component 6 has mortise and tenon structures at both ends and can be designed in multiple shapes for connection at various angles. The two ends of the adjusting structural component 6 can be connected to the concrete rod 3 using mortise and tenon structures. Concrete grooves 7 are cut into the concrete rod 3 and the adjusting structural component 6 to enhance the bonding strength between the concrete and the concrete rod 3 and the adjusting structural component 6 during concrete pouring. The concrete grooves 7 can be in various shapes such as ring, spiral, dovetail, or barb, improving the bonding strength with the concrete while also enhancing the mechanical anchoring effect. During prefabrication, positioning components 5 can be pre-embedded in the bottom or side of the pad block 4. The positioning components 5 can be positioning tops or clamps, etc., to install the pad block 4 on the ground, slab formwork, or main structural beams, columns, and wall reinforcement. At the same time, the upper end of the pad block 4 can be fitted with a screw rod corresponding to the nut pre-embedded on the concrete rod 3. The screw rod can be marked with fluorescent markers to indicate the distance, which facilitates fine-tuning of the installation position of the concrete rod 3. The concrete pad block 4 is preferably 50mm×50mm×50mm, with a compressive strength grade of not less than C35, and a 4mm diameter cold-drawn wire mesh is added inside to prevent it from breaking when nails are driven in. The fastener can be a 30mm long cement nail that penetrates the pad 4 and protrudes 15mm outwards, and is used to embed about 1cm into the wooden mold, which is both firm and easy to remove. S2: On-site measurement, layout and positioning; After the beam and column reinforcement of the main structure is tied and the formwork is closed on one side, according to the construction drawings, accurately lay out the installation center lines of all embedded boxes 2 and the installation center lines of pads 4 on the ground on the other side or on the closed formwork. Use a laser level or theodolite to transfer the control line to the steel cage, and mark the specific position of the embedded box 2 on the stirrups with a marker to ensure that the vertical and horizontal position deviations are no more than ±3mm. S3: Assembly and fixing of the embedded device; First, connect the prefabricated embedded box 2 with the concrete rod 3 and the adjusting structure 6. Adjust the length of the adjusting structure 6 according to the beam width at the marked position so that the total length of the support rod is slightly larger than the installation space. At the same time, install the pad 4 on the ground or the main structural beam, column, or wall through the positioning piece 5. When assembling and fixing multiple embedded boxes 2, they can be assembled in series. By using the concrete rod 3 in conjunction with the adjusting structure 6 to connect multiple embedded boxes 2, multiple embedded boxes 2 can be fixed above a set of pads 4. After the wall reinforcement is tied, the strip is positioned as a whole and fixed to the formwork on both sides to achieve one-time pre-embedding of multiple rebars at the top of the wall. The pad 4 is inserted into the wooden template using fasteners to achieve precise fixation, and then hammered in for reinforcement. Nails are preferred as fasteners. If the main structure uses an aluminum or steel mold system, high-strength structural adhesive or pre-applied high-adhesion 3M VHB tape can be used. After removing the release paper, press the pad 4 firmly onto the marked point on the metal template and hold the pressure for 10-15 seconds to complete the positioning. The assembled device is then placed into the steel cage, so that the opening of the box is in close contact with the inner surface of the wooden or aluminum mold to be molded. Then the concrete rod 3 installed on the other end of the adjusting structure 6 is installed on the pad 4. Preferably, the concrete rod 3 can be fixed on the pad 4 using a tenon and mortise structure or a nut and screw structure. When fixing the pre-embedded box 2, first attach the concrete rod 3 tightly to the upper main reinforcement or stirrup of the main structural beam, and then tie it fully with tie wire, with no less than 3 intersection points, to prevent the box from floating or shifting to the side during pouring. Preferably, the pre-fabricated slots on the outer wall of the embedded box 2 can be used to directly attach the slots to the beam stirrups or horizontal distribution bars, and then tied with tie wires. If the beam height exceeds 800mm, the concrete rod 3 can be adjusted by adding the adjusting structural component 6 to make it bidirectionally adjustable. That is, adjustable support rods are set at both the upper and lower ends of the embedded box 2 to support the two sides of the formwork and ensure multi-directional stability. Preferably, when multiple embedded boxes 2 need to be embedded at different heights within the same main body, the bottoms of the two embedded boxes 2 can be connected by concrete rods 3, and an additional concrete rod 3 can be installed on one side of the lower embedded box 2 to fix the bottom. This allows the upper and lower embedded boxes 2 to be fixed to each other during pouring, further preventing the embedded boxes 2 from shaking and shifting due to impact during pouring. S4: Firmness inspection and concrete pouring; Before closing the formwork, the quality inspector checks the installation firmness and positional accuracy of each embedded device, and focuses on checking whether the sealing membrane 8 is intact. After the acceptance is qualified, the final formwork is closed. When pouring concrete, the vibrator should maintain a safe distance of at least 50mm in the area of ​​the embedded device. It is strictly forbidden to directly vibrate the box body. Fine aggregate concrete should be used and supplemented with an attached vibrator or manual tamping to ensure that the concrete around the box is dense and does not damage the internal structure. S5: Template removal and duct cleaning; After the concrete has solidified, the opening above the embedded box 2 is clearly exposed on the concrete surface; Before the secondary structure construction, use tools to peel off or puncture the sealing film 8 on the surface, and the internal embedded sleeve duct will be exposed. The duct is clean, dry and free of dust, and no secondary cleaning is required. S6: Prepare the straight thread end of the secondary structural steel bar to be planted in advance, clean it and screw it directly into the pre-embedded sleeve exposed in S5. Tighten it to the specified torque with pipe wrench to complete the connection. Straight thread mechanical connection installation can completely replace chemical anchoring adhesive. When using plain round steel bars or unprocessed threads, anchoring adhesive can be injected into the clean pre-embedded sleeve ducts, and anchoring can be carried out in accordance with traditional chemical anchoring.

[0028] This method advances the process of forming the anchor hole from after the concrete has solidified to after the rebar is tied and before the concrete is poured, completely eliminating the dust, noise and vibration of drilling in the later stage, and saving the construction period of drilling and cleaning in the original anchor method. At the same time, the modular combination of pre-embedded box 2, adjustment structure 6 and pad block 4 is adopted, which can flexibly adapt to different beam widths and different formwork systems, and solves the problems of inaccurate position, difficulty in fixing and easy deviation due to concrete impact of traditional pre-embedded methods. Meanwhile, by covering the surface of the anchor hole 1 with a sealing film 8, the cleanliness of the pre-embedded channel during concrete pouring, vibration and subsequent construction is ensured, guaranteeing the bonding strength of the anchor in the later stage. At the same time, the insertion of a sleeve with internal threads can eliminate the need for anchor adhesive, realize mechanical connection and make the quality more reliable. Example

[0029] A construction method for pre-embedding rebar in secondary structures, such as... Figure 1-7 As shown, for areas with particularly dense reinforcement, the concrete rod 3 in step S3 can be replaced with ribbed steel bars with a diameter of 12mm, which can be directly spot-welded to the main beam reinforcement to form a stable support system and prevent displacement during pouring.

[0030] At this point, step S3 is as follows: Select HRB400 ribbed steel bars with a diameter of 12mm or 10mm as replacement concrete rod 3. The diameter selection is determined according to the beam cross-section size; use 10mm for beam width ≤ 200mm and 12mm for beam width > 200mm to ensure that the strut has sufficient rigidity to resist the lateral pressure during concrete pouring; cut the steel bars to a length 30-40mm shorter than the clear distance of the beam cross-section at the installation location. This shortening is reserved for the connectors at both ends and the fine-tuning mechanism. For example, with a beam clearance of 250mm, the length of the cut steel bars is approximately 210-220mm. Then, the ends of the cut steel bars are lightly ground with an angle grinder to remove burrs, and the surface oxide scale is cleaned with a wire brush to ensure smooth fit with subsequent connectors. To connect with the ribbed steel bars, metal ear plates or internally threaded sleeves can be pre-installed on the side wall of the embedded box 2 during manufacturing. Then, one end of the cut ribbed steel bar is welded to the center of the back of the embedded box 2. The welding is done using double-sided spot welding, with a weld length of not less than 20mm. Alternatively, external threads can be machined at the end of the steel bar for direct threaded connection, enabling detachment. The assembled device is then placed into the reinforcing cage, with the opening of the embedded box 2 facing the side to be molded. The ribbed steel bar struts are then tightly attached to the stirrups or upper main reinforcement bars of the beam, and tied with double-strand wire at least three times, each twisted at least three times. If the struts are horizontal, they are tied to the stirrups; if they are vertical, they are tied to the main reinforcement bars. For areas with particularly dense reinforcement and high vibration force, the ribbed steel bar struts can be directly spot-welded to the main beam reinforcement.

[0031] Replacing the precast concrete pole 3 with ribbed steel bars cut on site allows for the direct use of leftover short steel bar ends on the construction site. This can be done as needed, with almost no increase in material costs. There is no need for pre-fabrication and curing, which does not take up construction time. At the same time, it is easy to weld and facilitates the installation of embedded boxes 2 in areas with dense steel bars.

[0032] It is important to note that the anchoring hole must be used with a prefabricated anchoring box and sleeve. If a sleeve is not used, the anchoring hole itself must have threads. Otherwise, without a sleeve and without threads, the rebar pull-out test cannot be completed.

[0033] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A construction method for pre-embedding rebar in secondary structures, comprising the following steps: S1: Construction preparation and component prefabrication: Calculate the location, quantity and depth of rebar installation according to the drawings, and prefabricate the embedded box (2) and adjustable support module. The embedded box (2) has rebar installation holes (1). The adjustable support module includes a concrete rod (3), a pad (4) and an adjustment structure (6). S2: On-site measurement, layout and positioning: After the main structure beam reinforcement and column reinforcement are tied and the formwork is closed on one side, the installation center line of the embedded box (2) and the pad (4) is laid out; S3: Assembly and fixing of the embedded device: Connect the embedded box (2) with the concrete rod (3) and the adjusting structure (6), install the pad (4) on the ground or main structure through the positioning component (5), fix the pad (4) to the template through the fixing component, put the assembled device into the steel cage, make the opening surface of the embedded box (2) close to the inner surface of the template, and fix the concrete rod (3) on the pad (4); S4: Firmness check and concrete pouring: Check the firmness of the installation and the integrity of the sealing membrane (8), and pour concrete after the formwork is closed; S5: Template removal and duct cleaning: After template removal, before secondary structure construction, uncover or puncture the sealing membrane (8) to expose the pre-embedded duct. If the sealing membrane is damaged, clean the ash inside the duct before proceeding with the subsequent procedures. S6: Rebar installation: After processing the threads at the ends of the secondary structural rebars, screw them into the pre-embedded sleeve and tighten them, or inject rebar adhesive into the clean pre-embedded channel and then install the rebars.

2. The construction method for pre-embedding rebar in secondary structures according to claim 1, characterized in that, The embedded box (2) is prefabricated using fine stone concrete or high-strength mortar of the same grade as or one grade higher than the main structure, with 0.9 kg / m³ of PVA fiber added inside, and dovetail or wave-shaped slots prefabricated on the outside.

3. The construction method for pre-embedding rebar in secondary structures according to claim 2, characterized in that, The pre-embedded box (2) contains a straight threaded sleeve, which is made of 45# steel and has a length of at least twice the diameter of the steel bar. The internal thread machining accuracy is 6H grade.

4. The construction method for pre-embedding rebar in secondary structures according to claim 3, characterized in that, The pre-embedded box (2) is attached with a sealing film (8). The sealing film (8) has a three-layer structure: the outer layer is a high-toughness PE layer, the middle layer is an aluminum foil layer, and the inner layer is a silicone oil-coated release paper. The edges are provided with tear-off tabs.

5. The construction method for pre-embedding rebar in secondary structures according to claim 1, characterized in that, The concrete rod (3) and the adjusting structure (6) are provided with concrete grooves (7), which are annular, spiral, dovetail-shaped or barbed.

6. A construction method for pre-embedding rebar in secondary structures according to claim 5, characterized in that, The pad (4) has a positioning component (5) pre-embedded at the bottom or side. The positioning component (5) is a positioning nail or a clamp. The upper end of the pad (4) is provided with a screw with a fluorescent mark. A cold-drawn wire mesh with a diameter of 4mm is added inside the pad (4).

7. The construction method for pre-embedding rebar in secondary structures according to claim 1, characterized in that, In step S3, multiple embedded boxes (2) are assembled in series. Multiple embedded boxes (2) are connected by concrete rods (3) and adjusting structural components (6). Multiple embedded boxes (2) are fixed above a set of pads (4) to achieve one-time pre-embedding of multiple rebars on the top of the wall.

8. The construction method for pre-embedding rebar in secondary structures according to claim 1, characterized in that, When using an aluminum or steel mold system, the fasteners in step S3 are high-strength structural adhesive or 3M VHB tape, replacing nails for fixing.

9. A construction method for pre-embedding rebar in secondary structures according to claim 8, characterized in that, The concrete rod (3) in step S3 is replaced with HRB400 ribbed steel bars with a diameter of 12mm or 10mm. One end of the ribbed steel bar is welded or threaded to the back of the embedded box (2), and the other end is tightly attached to the stirrups or the upper row of main bars of the beam and tied or spot-welded.

10. A construction method for pre-embedding rebar in secondary structures according to claim 1, characterized in that, In step S4, when pouring concrete, the vibrator should maintain a safe distance of at least 50 mm from the embedded box (2), and fine stone concrete should be used with the aid of an attached vibrator or manual tamping.

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