Preparation method of prefabricated fair-faced concrete pipe piece and fair-faced concrete pipe piece prepared through method

Abstract

The invention belongs to the technical field of concrete prefabrication, particularly relates to a preparation method of a prefabricated fair-faced concrete pipe piece and the fair-faced concrete pipe piece prepared through the method, and aims to overcome the defects and deficiencies in the aspects of fair-faced concrete pipe piece reinforcement cage welding and concrete curing. The method comprises the following steps: (1) prefabricating a reinforcement cage; (2) mold cleaning; (3) brushing a release agent; (4) mounting an embedded part; (5) hoisting the reinforcement cage; (6) installing embedded parts and reinforcing steel bars at hand holes; (7) carrying out concealed acceptance; (8) concrete pouring; (9) surface finishing of a feed opening; (10) trowelling and surface finishing; (11) natural curing; (12) demolding and marking; (13) inspecting a finished product; (14) naturally curing a finished product; (15) the duct pieces are put in storage; (16) repairing the duct piece; and (17) the outer cambered surface is coated with protective paint. The machining efficiency of the steel reinforcement framework of the prefabricated pipe piece is improved, the one-time mold entering percent of pass of the steel reinforcement framework is improved, and the comprehensive production efficiency of the prefabricated bare concrete pipe piece is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of precast concrete, and specifically relates to a preparation method of precast fair-faced concrete segments and fair-faced concrete segments prepared by using this method. Background Art

[0002] Fair-faced concrete, also known as decorative concrete due to its strong decorative properties, does not require additional painting or external wrapping materials after casting. Compared with traditional concrete casting processes, it has high technical requirements for the surface flatness, smoothness, curing during the casting process, and coating.

[0003] Due to its advantages such as high stiffness, fast construction speed, and relatively small maintenance workload, steel-concrete tower barrels have gradually become the preferred solution for high tower structures. The precast segments formed by its high-strength concrete are connected by multi-piece circular bolts to form a complete ring, and the diameter of the complete ring gradually decreases for up-and-down connection to form the tower barrel base. As a permanent structure of above-ground buildings, the quality of the segments directly affects the overall quality and safety of the steel-concrete tower barrel and its durability.

[0004] Chinese Patent with the authorization announcement number CN 117484643 A discloses a production process of precast reinforced concrete segments. The process is as follows: including the following steps, according to the predetermined water-binder ratio and the theoretical dosage of binder materials, determine the dosage of each component in the raw materials of the concrete, and then mix to obtain the concrete; first, bind and weld to obtain a steel bar cage in the order of stirrups, bottom steel bars, and surface steel bars, and then on the steel bar cage, bind and weld to obtain a steel bar framework in the order of core rod reinforcing bars, ear-shaped reinforcing bars, hook-shaped reinforcing bars, waist reinforcing bars, end head reinforcing bars, and small material reinforcing bars; first install the formwork outside the steel bar framework, then install embedded parts and spring reinforcing bars on the steel bar framework according to the positions of the reserved holes of the formwork, then pour the concrete into the formwork, remove the formwork, and cure to obtain precast segments with embedded holes.

[0005] However, the above technical solutions have the following defects: (1) Since the steel bar cage of the segments is composed of various types of steel bars, and all the steel bars are gradually bound and formed manually, this process completely depends on the technical level of the operators. On the one hand, it is difficult to guarantee the quality, and on the other hand, the efficiency of welding and installing the steel bar cage into the formwork is relatively low; (2) In the above segment production process, the curing method adopts natural curing, and only basic regulations are made for the controlled time and temperature, without proposing clear curing methods and practices; (3) Due to the nature of the concrete itself, cracks that affect the structural performance, safety, and appearance will occur in the segments by this process method; (4) The finished product appearance inspection of the existing fair-faced concrete segments adopts manual naked-eye inspection, and the subjective factors lead to unreliable inspection results.

[0006] Compared with ordinary precast reinforced concrete segments, the precast process of fair-faced concrete segments requires higher standards, and it is urgent to solve the deficiencies and problems in the welding of steel reinforcement cages and the curing of concrete. Summary of the Invention

[0007] To solve the above problems in the prior art, namely the deficiencies and problems in the welding of steel reinforcement cages and the curing of concrete for fair-faced concrete segments, the present invention provides a method for preparing precast fair-faced concrete segments for a tower crane and the fair-faced concrete segments prepared by this method.

[0008] The technical solution of the present invention includes:

[0009] A method for preparing precast fair-faced concrete segments, comprising the steps of: Step (1) Precasting of the steel reinforcement cage; Step (2) Cleaning of the mold; Step (3) Coating of the release agent; Step (4) Installation of embedded parts; Step (5) Hoisting of the steel reinforcement cage; Step (6) Installation of embedded parts and steel bars at the manhole; Step (7) Hidden acceptance; Step (8) Concrete pouring; Step (9) Finishing the pouring opening; Step (10) Smoothing and finishing; Step (11) Natural curing; Step (12) Demoulding marking; Step (13) Final inspection of the finished product; Step (14) Natural curing of the finished product; Step (15) Warehousing of the segments; Step (16) Repair of the segments; Step (17) Coating of protective paint on the outer arc surface;

[0010] Among them, in step (1), the precasting of the steel reinforcement cage includes a material preparation stage, and the material preparation stage includes

[0011] Step (1.1.1) Splitting the segment steel reinforcement cage into upper and lower layer circular ribs, upper and lower layer longitudinal hooked bars, end dark columns, dark columns above the manhole, longitudinal hooked bars at the manhole, and circular rib steel bar components at the manhole, and splitting each component into steel bar members, including stirrups, hooks, spring bars and bent-up bars at the casing, and lifting point strengthening bars;

[0012] Step (1.1.2) Straightening, cutting, bending the stirrups, bending the arcs, bending, and coiling the springs of each steel bar member to process them into semi-finished products for standby;

[0013] Step (1.1.3) Spot-welding the upper and lower layer longitudinal U-shaped bars into a closed integral bar according to the requirements of the segment thickness;

[0014] Step (1.1.4) The end dark columns and the dark columns above the manhole are pre-bundled and formed in advance by four hooked bars and stirrups according to the segment thickness and the angle of the manhole.

[0015] As an alternative technical solution, in step (1), the precasting of the steel reinforcement cage further includes an assembly stage, and the assembly stage includes

[0016] Step (1.2.1) Placing the lower layer circular ribs one by one according to the positioning checkpoints of the steel bar formwork rack;

[0017] Step (1.2.2): Vertically spot-weld the closed integral ribs to the lower-layer circular ribs according to the longitudinal positioning points of the steel bar formwork.

[0018] Step (1.2.3): Place the end concealed columns and the concealed columns above the manholes, and tie them to the lower-layer circular ribs, with one set on each side symmetrically.

[0019] Step (1.2.4): After placing the longitudinal hooked ribs at the manhole, place the upper-layer circular ribs and tie them to the steel bars in contact surfaces of the closed integral ribs, end concealed columns, and concealed columns above the manholes.

[0020] Step (1.2.5): Install the stirrups of the circular ribs at the manhole. The stirrups are semi-closed. After installation, weld them into a whole, and the welding adopts intelligent CO2 gas shielded welding.

[0021] Step (1.2.6): Finally, install the stirrups, spring ribs, bent-up ribs, and lifting point reinforcement bars at the casing to form a steel reinforcement cage.

[0022] Step (1.2.7): The steel bar team pastes the identification. After internal quality inspection and acceptance by the quality inspector, the identification is carried out.

[0023] As an alternative technical solution, in the repair of the segment in step (18), corresponding repair methods are adopted according to the width and depth of the cracks.

[0024] As an alternative technical solution, when the crack width does not exceed 0.2 mm, the crack depth does not exceed 10 mm and does not exceed the steel bar surface, and the crack does not exceed the waterproof seal groove, fill the crack with AB glue and repeatedly rub and press until the repaired part is flat. After reaching the set strength, polish it smooth and shiny with sandpaper; when the crack width exceeds 0.2 mm, or the crack depth exceeds 10 mm, or the crack depth exceeds the steel bar surface, choose the grooving and embedding method for repair, that is, first open a "V"-shaped or "U"-shaped groove. The opening angle of the "V"-shaped groove is 45°, the groove width is 10 mm, and the depth reaches the position without cracks. Then fill the groove with AB glue and repeatedly rub and press until the repaired part is flat. After reaching the set strength, polish it smooth and shiny with sandpaper; for cracks with a width exceeding 0.3 mm or a depth exceeding the steel bar protection layer, use the low-pressure syringe grouting method for treatment. The selected repair material is epoxy resin mortar. After cleaning and blocking the crack, use a low-pressure grouting device to pour the epoxy resin mortar into the crack.

[0025] As an alternative technical solution, in the segment repair in step (18), for the case of exposed reinforcement, after flushing the exposed reinforcement on the surface clean, use AB glue to level and compact the exposed reinforcement part. Or when the exposed reinforcement is deeper, first chisel off the weak concrete and protruding particles, wash it clean, install a formwork, and pour and compact it with micro-expansion fine aggregate concrete with a strength grade one higher than that of the structural concrete and cure it.

[0026] As an alternative technical solution, in the segment repair in step (18), for the cases of root rot or knocked-off corners, first chisel off the loose stones at the place, brush it clean with a wire brush, rinse it with water and wet it sufficiently, and then repair it neatly with AB glue.

[0027] As an alternative technical solution, in the segment repair in step (18), for the concrete protruding from the structural surface, chisel it off after the strength reaches 50%, and level the surface with a grinding machine.

[0028] As an alternative technical solution, in the finished product inspection in step (13), it includes an intelligent auxiliary inspection step. The intelligent auxiliary inspection first uses a laser scanner to construct a point cloud model of the outer surface of the segment finished product, and then compares the obtained point cloud model with a preset BIM model, and obtains a quality report according to the comparison result.

[0029] As an alternative technical solution, in the leveling and finishing in step (10), it includes

[0030] Step (10.1) Initial leveling: When the concrete in the mold reaches nearly the initial setting, open the flip cover on the mold, use an automatic leveling machine to fill the pits and lift the slurry on the segment surface for initial leveling, and use a screed bar to remove the excess concrete on the surface to make the concrete surface smooth and free of impurities;

[0031] Step (10.2) Secondary leveling: After the initial leveling is completed, use a trowel for secondary plastering to make the segment surface keep the arc surface flat and without unevenness, and remove the excess concrete at the four sides of the mold to ensure that the finished segment has no flash and burrs;

[0032] Step (10.3) Tertiary finishing: When the concrete surface has a slight indentation when gently pressed with a finger and the hand is not sticky to the surface concrete, perform the third finishing, and use a trowel to smear and press to make the outer arc surface of the segment smooth and flat.

[0033] As an alternative technical solution, in the concrete pouring in step (8), the concrete contains the following raw material mass ratios: cement 434 kg / m 3 , fly ash 93 kg / m 3 , microbeads 56 kg / m 3 , natural sand 616 kg / m 3 , silica fume 37 kg / m 3 , 5 - 10 mm crushed stone 359 kg / m 3, 780 kg / m of 10 - 20 mm gravel 3 , 10 kg / m of high - performance water - reducing agent 3 , 117 kg / m of water 3 , After the concrete is mixed, measure the slump on - site and control it within 170 ± 20 mm, and measure the temperature when entering the mold not less than 20 °C.

[0034] A precast fair - faced concrete segment, and the precast fair - faced concrete segment is prepared by the preparation method as described above.

[0035] Advantages of the present invention:

[0036] (1) Through the optimization of the steel bar framework structure of the precast fair - faced concrete segment, disassembling the structure of the steel bar framework and adopting the grouped assembly method, on the one hand, the processing efficiency of the steel bar framework is accelerated, on the other hand, the qualified rate of the steel bar framework entering the mold at one time is improved, the rework rate of the steel bar framework process is reduced, and the comprehensive production efficiency of the precast fair - faced concrete segment is improved.

[0037] (2) On the basis of meeting the quality requirements of the fair - faced concrete segment, using the low - cost curing process of the new fair - faced concrete segment to ensure the reasonable control of the temperature difference between the inside and outside of the precast segment, the atmospheric temperature difference and the cooling rate, and using the hydration heat reaction of the concrete segment itself to enhance the strength of the component, reduce the risk of cracks that may exist on the surface of the segment, and thus reduce the processing cost of the component.

[0038] (3) Aiming at the common crack phenomenon of concrete segments in the processing and production process of precast fair - faced concrete segments, a repair method based on different crack parameters is provided. On the one hand, the finished product rate of the segment components is improved through crack repair, on the other hand, the increase in the processing cost of the segments caused by the scrapping of the segments due to cracks is reduced. At the same time, through the repair of cracks with various different parameters, the surface smoothness of the fair - faced concrete segments is improved, and the processing quality of the precast concrete segments is improved. Description of the drawings

[0039] By reading the detailed description of the non - restrictive embodiments with reference to the following drawings, other features, purposes and advantages of the present application will become more obvious:

[0040] Figure 1 is the process flow chart of the processing of the precast fair - faced concrete segment of the present invention;

[0041] Figure 2 is the structural schematic diagram of the precast fair - faced concrete segment of the present invention;

[0042] Figure 3 is the structural schematic diagram of the steel bar framework of the precast fair - faced concrete segment of the present invention;

[0043] Figure 4 It is a schematic structural diagram of the end of the circumferential steel bars;

[0044] Figure 5 It is a schematic structural diagram of the reinforcement arrangement of the manhole.

[0045] Reference numerals:

[0046] 1 - Precast concrete segment; 2 - Bolt connection hole; 3 - Operation hole; 4 - Embedded part; 5 - Drainage groove; 6 - Ring reinforcement; 7 - Longitudinal hook reinforcement; 8 - Tie bar; 9 - End hidden column; 10 - Hidden column above the manhole; 11 - Stirrup of the ring reinforcement at the manhole; 12 - Spring reinforcement at the casing; 14 - Bent-up reinforcement at the casing. Specific embodiments

[0047] The present application will be further described in detail below with reference to the accompanying drawings and embodiments. It can be understood that the specific embodiments described herein are only used to explain the related invention and do not limit the invention. Additionally, it should be noted that for the sake of description, only the parts related to the relevant invention are shown in the drawings.

[0048] It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. The present application will be described in detail below with reference to the drawings and in combination with the embodiments.

[0049] The present invention provides a method for preparing precast fair-faced concrete segments, and precast fair-faced concrete segments prepared by using this preparation method.

[0050] Figure 1 The following shows a schematic production flow diagram of the method for preparing the precast fair-faced concrete segments of the present invention. Specifically, it includes: The processing part of the steel cage: including inspection and submission of steel bar raw materials for inspection, steel bar cutting, forming of main steel bars, binding of the hidden column steel cage, forming of the steel cage, self-inspection of the steel cage, quality inspection of the steel cage, rectification of non-conformities, and standby after passing. The mold part: including mold cleaning, mold assembly, mold precision detection, leveling, and application of release agent. Then, the precast steel cage is put into the mold, embedded parts are installed, the protective layer is positioned, concealed acceptance is carried out, rectification is carried out for non-conformities, and the mold is closed after passing. Inspection of concrete raw materials, concrete mixing, making test blocks, inspection of the strength of test blocks, and invalidation of non-conformities. Pour the qualified concrete, vibrate it, perform three smoothings and three rubbings, cure it, confirm the demolding conditions, return to the curing link if unqualified, perform finished product demolding and component numbering if qualified. Inspection of finished products, repair of non-conformities, inspection after repair, and scrapping if still unqualified. Final product inspection is qualified, stored indoors for maintenance, transferred to the yard for maintenance, surface treatment of the finished segment, factory inspection, and loaded and shipped. Figure 2 The following shows a structural schematic diagram of the precast fair-faced concrete segment of the present invention. It includes a precast concrete segment 1, bolt connection holes 2, operation holes 3, embedded parts 4, and drainage grooves 5. Figure 3 It is a structural schematic diagram of the steel bar cage of the precast fair-faced concrete segment of the present invention. Figure 4 It is a structural schematic diagram of the end of the circumferential steel bar. Figure 5 It is a structural schematic diagram of the reinforcement of the manhole. Welding of the steel bar cage: The split-type segment steel bar cage is disassembled, mainly divided into upper and lower layer circular bars 6, upper and lower layer longitudinal hooked bars 7, tie bars 8, end dark columns 9, dark columns above the manhole 10, longitudinal hooked bars at the manhole, stirrups 11 of the circular bar at the manhole, hook bars, spring bars 12 at the casing, bent-up bars 14 at the casing, and lifting point reinforcement bars, etc. Classify and process the steel bars according to the disassembled ones, and process the steel bar raw materials into semi-finished products for standby through straightening, shearing, hoop bending, arc bending, bending, and spring coiling processes. Among them, the upper and lower layer longitudinal U-shaped bars are spot-welded into a closed integral bar according to the segment thickness requirements. Among them, the end dark columns 9 and the dark columns 10 above the manhole are mainly pre-bundled and formed by four hooked bars and stirrups according to the segment thickness and the angle of the manhole. The specific processing method includes: First step, place the lower layer circular bars one by one according to the positioning points of the steel bar mold frame. Second step, vertically spot-weld the closed integral bar to the lower layer circular bars according to the longitudinal positioning points of the steel bar mold frame. Third step, place the end dark columns 9 and the dark columns 10 above the manhole, and tie them to the lower layer circular bars, with one set on each side symmetrically. Fourth step, after placing the longitudinal hooked bars at the manhole, place the upper layer circular bars, and tie them to the contacting steel bars of the closed integral bar, the end dark columns 9, and the dark columns 10 above the manhole. Fifth step, install the stirrups 11 of the circular bar at the manhole. The stirrups are semi-closed. After installation, weld them into a whole, and the welding uses intelligent CO2 gas shielded welding. Sixth step, finally install the hook bars, the spring bars 12 at the casing, the bent-up bars 14 at the casing, and the lifting point reinforcement bars to form the steel bar cage. Seventh step, the steel bar team pastes the identification. After internal quality acceptance, it is handed over to the quality inspector for acceptance and then for identification. The specific processes of other processing operations in the preparation method of the precast fair-faced concrete segment of the present invention include: Mold cleaning: The operator uses a special splitting tool to thoroughly clean the residual concrete blocks and mud on the inner side of the upper cover of the mold; the inner cavity of the mold is blown clean with a compressed air machine; finally, it is wiped clean with a rag; Coating the release agent: The operator first checks and confirms that the mold has been completely cleaned, and then uses a spray gun to evenly spray the pre-prepared water-based release agent on the inner surface of the mold, and wipes it evenly with a clean rag to leave a thin layer; Installation of embedded parts: According to the requirements of the drawing, install the climbing frame embedded parts and lightning protection embedded parts on the bottom surface of the mold, and install the lifting embedded parts on the side of the mold. All positions of the embedded parts are clearly marked on the outside of the mold; Hoisting of the steel cage: Use a special lifting tool to hoist the finished steel cage tied with spacers arranged in a plum blossom shape into the mold, and use a crowbar to adjust the thickness requirements of the protective layer on the upper, lower, left and right sides. Appropriately increase cement spacers locally to make the position of the steel cage meet the requirements; Installation of embedded parts and steel bars at the manhole: Put the mandrel with a rubber hose on the spring bar, insert it into the hole of the reserved fixing block, and tighten it to be installed in place with the mold. Finally, install the bent-up bars at the manhole and the reinforcing bars at the lifting points; Hidden acceptance: Check and confirm the installation quality of the embedded parts and the steel cage, the tightening degree of the bolts, and the thickness of the protective layer. After passing the acceptance, close the mold covers on both sides. The tightening bolts of the covers must be tightened to the specified torque, and a hidden acceptance record form shall be formed and photographed for preservation; In this embodiment, the specified torque is 300 N·M. Concrete pouring: The concrete mixture is automatically loaded, metered, and stirred by the mixer according to the set high-strength concrete mix ratio. After the mixture is completed, the discharge port is opened to the hopper, and it is transported to the fixed formwork production area. The hopper is lifted by the overhead crane to the pouring port of the mold to start placing the concrete. While placing the concrete, the vibrator in the middle of the mold is turned on. When the concrete fills the bottom plate of the mold, all vibrators are turned on for layered vibration. Stop placing the concrete when the concrete reaches the top plate of the mold and there is a little overflow. Stop vibrating when there are no more bubbles on the surface of the concrete; After the pouring and vibrating operators complete the above work, hand it over to the finishing personnel and start the pouring operation of the next mold. Finishing at the discharge port: The finishing personnel use a shovel and a screed to remove and level the excess concrete at the discharge port, and cover it with a plastic film for curing. Initial screeding: When the concrete in the mold reaches nearly the initial setting stage, open the upper cover of the mold, and use an automatic screeding machine to fill the pits and lift the slurry on the surface of the segment for initial screeding. Use a screed to remove the excess concrete on the surface to make the surface of the concrete smooth and free of impurities. Second screeding: After the initial screeding is completed, use a trowel for second screeding to make the surface of the segment keep the arc surface flat and without unevenness, and remove the excess concrete on the four sides of the mold to ensure that the finished segment has no flash and burrs; Three - time surface finishing: The third - time surface finishing is carried out when the concrete surface has a slight indentation when gently pressed with a finger and the hand does not stick to the surface concrete. Use a trowel to smear and press to make the outer arc surface of the segment smooth and flat; Natural curing after pouring: In spring, summer, and autumn, use plastic film to cover for static - stop and moist curing. The film should be closely attached to the concrete surface, and the film area should be slightly larger than the concrete surface area. Fix the four corners of the film with clips. When the weather temperature is 5 - 20°C, an additional layer of geotextile should be added on the plastic film for heat preservation; In winter, use plastic film + thermal insulation quilt (2 - 3 cm thick) + geotextile for three - layer covering and curing. The covering should be airtight. The temperature inside the insulation layer is mainly increased by the heat generated by the hydration heat of the segment itself. When necessary, use double - layer cotton quilts, electric blankets, hot air blowers and other facilities to increase the curing temperature of the segment. Demoulding identification: Use a rebound hammer to rebound the segment. When the rebound strength of the segment reaches 40 Mpa, the component is ready for demoulding. In winter, first use a temperature gun to measure the concrete surface temperature, then uncover the first - layer geotextile, open the four ends of the mold, let the second - layer thermal insulation quilt hang down for static - stop, use a temperature gun to measure the concrete surface temperature to reach about 35°C, then uncover the thermal insulation quilt for static - stop, use a temperature gun to measure the concrete surface temperature to reach about 25°C, and finally uncover the plastic film to ensure that the temperature difference between the final concrete surface temperature and the external temperature ≤ 20°C; In spring, summer, and autumn, use a temperature gun to measure the concrete surface temperature. When the temperature difference between the concrete surface temperature and the external temperature ≤ 20°C, uncover the plastic film. Remove the core rods at both ends of the mold in the specified order, open the side mold and end mold, and use a vacuum suction cup to lift the segment from the mold, move it to the turning machine, and use special tools to remove the sliders at the hand - hole. After applying butter at the lifting points, turn it 90 degrees. The operator marks the production date and type information of the segment as required. Finished product inspection: The content includes: the appearance quality, dimensional deviation, and identification check of the segment finished product, including using intelligent inspection methods and forming records; Intelligent inspection includes: Scanning the finished - product segment with a laser scanner to establish a three - dimensional point - cloud model, comparing the point - cloud model with the preset BIM model, and judging whether the finished - product segment is qualified based on the comparison result; Three - dimensional point - cloud model technology uses sensing devices such as laser scanners to obtain the position coordinate information of each point of an object, which can infinitely approximate the shape and contour of the object. BIM model (Building Information Modeling) is a building engineering full - life - cycle management technology based on three - dimensional digitization. It realizes collaborative optimization in design, construction, and operation and maintenance stages by integrating structured data. Its core value lies in constructing an intelligent model containing geometric and attribute information, supporting multi - party collaboration and improving engineering efficiency. Natural curing of finished products: They are hoisted by crane to the cooling area in the workshop, and fully wrapped with film and cotton felt for at least 7-14 days. Pipe segment storage: transport the upper pipe segments to the outdoor yard, place three square timbers evenly at the bottom, stack the pipe segments vertically, and keep a gap of at least 0.6m between the pipe segments. Repair: The contents include: the crack width does not exceed 0.2mm, the crack depth does not exceed 10mm and does not exceed the surface of the steel bar, the crack does not exceed the waterproof sealing groove (excluding the corresponding position on the side of the waterproof sealing groove), and the crack will affect the appearance. This type of crack repair uses a gray spatula dipped in Sika AB glue (selected according to the season) to rub repeatedly until the repair area is flat and the crack is filled. After reaching a certain strength, it is polished with sandpaper to make it smooth and bright. If the crack width exceeds 0.2mm, or the crack depth exceeds 10mm, or the crack depth exceeds the surface of the steel bar, choose the chiseling and filling method, first open a "V" or "U" groove with a 45° groove angle, a groove width of 10mm, and a depth to a crack-free position; then fill the "V" or "U" groove with Sika AB glue (selected according to the seasonal temperature). After reaching a certain strength, it is polished with sandpaper to make it smooth and bright. For cracks that are wider (>0.3mm) and deeper than the steel bar protective layer, low-pressure needle grouting is used, and epoxy resin slurry is used as the repair material. For pores and rough surfaces, the rough surface is first thoroughly moistened with water, and then epoxy mortar with the same concrete grade is used to smooth and polish the rough surface. After the repair, geotextile is applied for moisturizing and curing. For leaking reinforcement, the surface is rinsed clean and the leaking reinforcement area is smoothed and compacted with Sika AB glue (selected according to seasonal temperature). If the leak is deep, the weak concrete and protruding particles should be chiseled out, cleaned, and the formwork should be installed. The concrete should be rammed densely with micro-expansive fine stone concrete with a strength grade higher than the structural concrete, and then carefully maintained. For the concrete protruding from the structural surface, wait until the strength reaches 50% before chiseling it off and smooth the surface with a grinder. For rotten roots and chipped corners, first chisel off the loose stones there, clean them with a wire brush, rinse with clean water and fully moisten them, then fill them with Sika AB glue (selected according to seasonal temperature), and for the concrete protruding from the structural surface, wait until the strength reaches 50% before smoothing it with a grinder. Apply protective paint to the outer curved surface: Use a wire brush or sandpaper to clean the outer curved surface of the pipe segment, fill the hollow part of the pipe segment, confirm that the outer curved surface is flat and dry, then brush or roll it, or airlessly spray it with a primer (Konsitu concrete protection special primer). Wait half a day in summer and one day in winter. After the primer solidifies, brush or roll it, or airlessly spray it with a topcoat (Konsitu concrete decorative anti-corrosion protection topcoat). The pipe segment must not be exposed to water during the whole process.

[0051] In the description of the present invention, the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., which indicate directions or positional relationships, are based on the directions or positional relationships shown in the drawings. This is only for the convenience of description and does not indicate or imply that the device or element must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of the present invention. In addition, the terms "first", "second", "third" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0052] In addition, it should be noted that in the description of the present invention, unless otherwise clearly specified and limited, the terms "mounted", "connected", "coupled" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0053] The term "comprising" or any other similar term is intended to cover non-exclusive inclusion, so that a process, method, article or device / equipment comprising a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes the elements inherent in these processes, methods, articles or devices / equipment.

[0054] So far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will fall within the protection scope of the present invention.

Claims

1. A preparation method for precast fair-faced concrete segments, characterized in that, It includes the following steps: step (1) prefabrication of the steel reinforcement cage; step (2) cleaning of the mold; step (3) application of the release agent; step (4) installation of the embedded parts; step (5) hoisting of the steel reinforcement cage; step (6) installation of the embedded parts and steel bars at the manhole; step (7) concealed acceptance; step (8) concrete pouring; step (9) finishing of the material discharging opening; step (10) troweling and finishing; step (11) natural curing; step (12) demoulding identification; step (13) finished product inspection; step (14) natural curing of the finished product; step (15) storage of the segment; step (16) repair of the segment; step (17) application of protective paint on the outer arc surface. Among them, in step (1), the prefabrication of the steel reinforcement cage includes a material preparation stage, and the material preparation stage includes step (1.1.1) splitting the segment steel reinforcement cage into upper and lower layer circular ribs, upper and lower layer longitudinal hooked bars, end dark columns, dark columns above the manhole, longitudinal hooked bars at the manhole, and circular rib steel bar components at the manhole, and splitting each component into steel bar members, including stirrups, hooks, spring bars and bent-up bars at the casing, and lifting point reinforcement bars; step (1.1.2) straightening, cutting, bending the stirrups, bending the arcs, bending, and coiling the springs of each steel bar member to process them into semi-finished products for standby; step (1.1.3) spot-welding the upper and lower layer longitudinal U-shaped bars into a closed integral bar according to the segment thickness requirement; step (1.1.4) pre-bind the end dark column and the dark column above the manhole with four hooked bars and stirrups according to the segment thickness and the angle of the manhole in advance.

2. The preparation method of a precast fair-faced concrete segment according to claim 1, characterized in that: In the said step (1), the prefabrication of the steel reinforcement cage also includes an assembly stage, and the assembly stage includes step (1.2.1) placing the lower layer circular ribs one by one according to the positioning clamping points of the steel bar formwork; step (1.2.2) vertically spot-welding the closed integral bar on the lower layer circular ribs according to the longitudinal positioning points of the steel bar formwork; step (1.2.3) placing the end dark column and the dark column above the manhole, and binding them with the lower layer circular ribs, with one set on each side symmetrically; step (1.2.4) after placing the longitudinal hooked bars at the manhole, place the upper layer circular ribs, and bind the steel bars in contact with the closed integral bar, end dark column, and dark column above the manhole; step (1.2.5) install the stirrups of the circular ribs at the manhole, the stirrups are semi-closed, and after installation, weld them into a whole, and the welding adopts intelligent CO2 gas shielded welding; step (1.2.6) finally install the hooks, spring bars and bent-up bars at the casing, and lifting point reinforcement bars to form the steel reinforcement cage; step (1.2.7) the steel bar team pastes the identification, and after internal quality acceptance, it is handed over to the quality inspector for acceptance and then the identification is carried out.

3. The preparation method of a precast fair - faced concrete segment according to claim 1, wherein: In the repair of segment in step (18), corresponding repair methods are adopted according to the width and depth of the cracks: when the crack width does not exceed 0.2 mm, the crack depth does not exceed 10 mm and does not exceed the surface of the steel bars, and the crack does not exceed the waterproof sealing groove, use AB glue to fill the crack, and repeatedly rub and press until the repaired part is flat. After reaching the set strength, polish it with sandpaper until it is smooth and clean; when the crack width exceeds 0.2 mm, or the crack depth exceeds 10 mm, or the crack depth exceeds the surface of the steel bars, choose the chiseled groove and inlay method for repair, that is, first open a "V" - shaped or "U" - shaped groove, the opening angle of the V - shaped groove is 45°, the groove width is 10 mm, and the depth reaches the position without cracks. Then fill the groove with AB glue, and repeatedly rub and press until the repaired part is flat. After reaching the set strength, polish it with sandpaper until it is smooth and clean; for cracks with a width exceeding 0.3 mm or a depth exceeding the steel bar protection layer, use the low - pressure syringe grouting method for treatment. The repair material selected is epoxy resin mortar. After the cracks are cleaned and blocked, use low - pressure perfusion equipment to pour epoxy resin mortar into the cracks.

4. The preparation method of a precast fair-faced concrete segment according to claim 3, characterized in that: In the repair of segment in step (18), for the situation of exposed steel bars, after washing the exposed steel bars on the surface clean, use AB glue to level and compact the exposed steel bar part. Or when the exposed steel bars are deeper, first chisel off the weak concrete and protruding particles, wash them clean, install the formwork, and pour and compact with micro - expanded fine aggregate concrete with a strength grade one higher than that of the structural concrete and cure.

5. A method for preparing precast fair-faced concrete segments according to claim 4, characterized in that: In the repair of segment in step (18), for the situation of root rot or knocked - off corners, first chisel off the loose stones at the place, brush them clean with a wire brush, wash them with clean water and fully moisten them, and then repair them neatly with AB glue.

6. The preparation method of a precast fair-faced concrete segment according to claim 3, characterized in that: In the repair of segment in step (18), for the concrete protruding from the structural surface, chisel it off after the strength reaches 50%, and level the surface with a grinding machine.

7. A method for preparing precast fair-faced concrete segments according to claim 1, characterized in that: In the finished product inspection in step (13), it includes an intelligent auxiliary inspection step. The intelligent auxiliary inspection first uses a laser scanner to construct a point cloud model of the outer surface of the segment finished product, and then compares the obtained point cloud model with the preset BIM model, and obtains a quality report according to the comparison result.

8. A method for preparing precast fair-faced concrete segments according to claim 1, characterized in that: In the screeding and finishing in step (10), it includes Step (10.1) Initial screeding: When the concrete in the mold reaches near the initial setting, open the upper cover of the mold, and use an automatic screeding machine to fill the pits and lift the slurry on the surface of the segment for initial screeding. Use a scraping bar to remove the excess concrete on the surface, so that the concrete surface is smooth and free of impurities. Step (10.2) Secondary screeding: After the initial screeding is completed, use a trowel for secondary screeding to make the surface of the segment keep the arc surface flat and without unevenness, and remove the excess concrete on the four sides of the mold to ensure that the finished segment has no flash and burr. Step (10.3) Tertiary finishing: When the concrete surface has a slight indentation when gently pressed with a finger and the hand is not sticky to the surface concrete, perform the third finishing, and use a trowel to smear and press to make the outer arc surface of the segment smooth and flat.

9. The preparation method of a precast fair-faced concrete segment according to claim 1, characterized in that: In step (8) of concrete pouring, the concrete contains the following raw material mass ratios: cement 434 kg / m 3 , fly ash 93 kg / m 3 , microbeads 56 kg / m 3 , natural sand 616 kg / m 3 , silica fume 37 kg / m3, 5 - 10 mm crushed stone 359 kg / m 3 , 10 - 20 mm crushed stone 780 kg / m 3 , high-performance water reducer 10 kg / m 3 , water 117 kg / m 3 After the concrete is mixed, the slump is measured on-site and controlled within 170 ± 20 mm, and the temperature of the concrete entering the formwork is measured to be not less than 20°C.

10. A precast fair-faced concrete segment, characterized in that: The precast fair - faced concrete segment is prepared by the preparation method described in claim 1.

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