A device and method for pouring a reinforced dry concrete test piece

Abstract

The application discloses a pouring device for reinforcing steel bars and dry hard concrete test pieces, which comprises a pulling pouring container, an opening of which is located at the upper part, and an opening is arranged at the center of the lower part; a compaction device, which is arranged at the upper part of the opening of the pulling pouring container and is provided with an opening through which the reinforcing steel bar can pass; a reinforcing steel bar deviation preventing device, which is arranged at the upper part of the compaction device; a vibrating lifting rod, which is installed in the opening of the reinforcing steel bar deviation preventing device in the vertical direction; and reinforcing steel bars, which are arranged vertically at the center of the pulling pouring container. Through the above technical scheme, the bubbles can be removed, the internal gaps can be reduced, and the strength of the concrete can be enhanced.

Description

Technical Field

[0001] This invention relates to the field of casting reinforced concrete and dry-hardened concrete specimens, and particularly to a casting apparatus and method for casting reinforced concrete and dry-hardened concrete specimens. Background Technology

[0002] In concrete pipe structures, the interfacial bond-slip performance between reinforcing steel and dry-hard concrete is a key factor determining the pipe's load-bearing capacity and service life. However, dry-hard concrete, due to its low water-cement ratio and near-zero slump, exhibits extremely poor fluidity and a very rapid initial setting rate during pouring. Conventional vibration and compaction methods are insufficient to achieve adequate compaction, easily leaving air bubbles and micro-cracks inside, resulting in large dispersion and poor repeatability in interfacial bond strength test results. Typically, a pull-out device is used to pour dry-hard concrete parallel to the steel reinforcement's cross-section. Pouring dry-hard concrete using the aforementioned process easily leads to steel reinforcement settling under the concrete's own weight and the final compaction of the dry-hard concrete device, thus affecting data and potentially causing specimen failure. When a pull-out device pours dry-hard concrete parallel to the steel reinforcement's cross-section, the poor fluidity of the concrete easily creates voids beneath the steel reinforcement, causing it to settle under its own weight and during compaction. This settlement significantly reduces the bond strength between the steel reinforcement and concrete, specifically manifested in the following ways: Decreased bond performance coefficient: The slope of the secant curve between pull-out force and slip decreases with increasing slip, indicating deterioration of the interfacial bond performance. Microscopic damage evolution: Circular cracks develop at the steel reinforcement-concrete interface due to slippage, causing the principal tensile stress to tilt outwards, further weakening the bond strength.

[0003] The above-mentioned process for pouring dry-hard concrete easily leads to the formation of air bubbles, resulting in the disadvantage of small cracks inside the dry-hard concrete affecting its later strength. During the pouring of dry-hard concrete, insufficient vibration or excessively rapid water evaporation can easily lead to the formation of air bubbles and micro-cracks. Specific effects include: Reduced strength: Air bubbles and cracks become stress concentration points, leading to a decrease in the compressive and flexural strength of the concrete. Impaired durability: Cracks may accelerate steel corrosion, especially in chloride environments, where corrosion expansion can further damage the concrete structure. Summary of the Invention

[0004] To address the technical challenges in the civil engineering industry regarding the tendency for the reinforcing bars to shift at the contact point with dry-hard concrete in pull-out specimens, as well as the uneven compaction within the dry-hard concrete, this invention provides a casting device and method for reinforcing bars and dry-hard concrete specimens. This method significantly reduces the impact of the concrete's own weight and the compaction device on the position of the reinforcing bars.

[0005] This invention provides a casting apparatus for reinforcing steel bars and dry-hardened concrete specimens, comprising:

[0006] A drawing casting container, wherein the drawing casting container is a square box with an opening at the top and a casting opening is provided at the center of the lower plane;

[0007] A compaction device is installed above the drawing and casting container, and its area is smaller than the inner surface of the drawing and casting container; the compaction device is provided with compaction openings.

[0008] A rebar anti-deviation device is installed on the upper part of the compaction device. The rebar anti-deviation device is provided with a limit hole and a vibrator opening; a limit bolt is provided on the limit hole.

[0009] The hydraulic device, including a horizontal hydraulic component, a vertical hydraulic component, and a displacement sensor, is positioned between the compaction device and the rebar anti-displacement device; the horizontal and vertical hydraulic components are generally L-shaped.

[0010] The vibratory lifting rod passes vertically through the opening of the vibratory rod anti-deflection device for the reinforcing bars, and the vertical displacement of the vibratory lifting rod is driven by the vibratory hydraulic unit and the connecting rod.

[0011] Preferably, the vibratory lifting rod has a hollow internal structure; the length of the vibratory lifting rod is in the range of 250-300mm, and the bottom end of the vibratory lifting rod is welded with a cylindrical hollow steel structure.

[0012] Preferably, the bottom surface of the cylindrical hollow steel structure is provided with a plurality of hollow cylinders; the bottom of the hollow cylinders is embedded with vibrating beads; the power device of the vibrating beads is located inside the cylindrical hollow steel structure.

[0013] Preferably, the hydraulic vibration unit is mounted on the rebar anti-deviation device; the connecting rod includes an annular metal rod connected to the vibratory lifting rod and an inner metal rod connecting the hydraulic vibration unit and the annular metal rod.

[0014] Preferably, the rebar anti-deviation device includes an upper structure consisting of two trapezoidal plates connected by limiting holes, an L-shaped steel plate welded to the upper structure, and a connecting trapezoidal plate between the two trapezoidal plates; the L-shaped steel plate includes a vertically arranged supporting steel plate and a parallelly arranged connecting steel plate.

[0015] Preferably, the limiting hole is composed of two steel plates and a trapezoidal plate; the opening of the vibrating rod is symmetrically distributed along the limiting hole; and the end of the limiting bolt is inlaid with flexible material.

[0016] Preferably, the long side of the trapezoidal plate is connected to the upper part of the drawing and casting container via an L-shaped steel plate; the displacement sensor is a magnetostrictive displacement sensor; the horizontal hydraulic component of the hydraulic device is welded to the lower surface of the connecting trapezoidal plate, and the vertical hydraulic component is welded to the upper surface of the compaction device; the horizontal hydraulic component and the vertical hydraulic component are welded together; the compaction device includes two compaction plates.

[0017] Preferably, the drawing casting container is a cube with an open top formed by five metal plates connected by bolts, and a reinforcing bar hole is provided at the center of its bottom plane; the roughness of the inner wall of the drawing casting container is not greater than 50μm; the length of the metal plates is 140-220mm; the width is 140-220mm; and the reinforcing bar hole is connected to the bowl bolt outward.

[0018] This invention provides a method for casting steel reinforcement and dry-hardened concrete specimens, comprising the following steps:

[0019] Step (1): Place the assembled pull-out specimen casting device on a horizontal vibration table for pre-vibration, so that the base plate is in close contact with the table surface; insert the reinforcing bar from the bottom and lock it with the bowl nut to ensure that the verticality deviation of the reinforcing bar is ≤0.1°;

[0020] Step (2) Fill the pull-out specimen casting device with dry-hard concrete in two layers;

[0021] After the first layer of material is loaded, start the vibration process: first turn on the ring vibrating ball motor, adjust the speed to 5000rpm, then press the "down" button, and the vibrating rod will descend at a speed of 10mm / s to 30mm away from the bottom plate of the cylindrical hollow steel structure. After 5s, slowly lift it up and repeat twice.

[0022] After the second layer of material is loaded, the vibration process is repeated. The last time the vibrator is lowered to a position 20mm away from the upper interface of the first layer of the cylindrical hollow steel structure.

[0023] Step (3), after vibration, enter the compaction stage: simultaneously start the "horizontal closing" button, the two compaction plates move towards each other at a speed of 5mm / s within 1s, and stop when the gap is 2mm; then start the "vertical pressing" button, the vertical hydraulic component drives the compaction plate to descend as a whole at a speed of 2mm / s, and when the descent reaches the design value or the pressure reaches the set upper limit, the pressure is held for 30s; after compaction is completed, the pressure is slowly released, the compaction plate first returns vertically and then opens horizontally;

[0024] In step (4), after the surface of the specimen prepared by the above steps is lightly pressed and smoothed with a stainless steel trowel, it is immediately covered with a plastic film and moved to a standard curing room with a temperature of 20±2℃ and a relative humidity of ≥95% for curing. After 24 hours, the bowl bolts are loosened, and the side plate is gently tapped with a rubber hammer to separate the pull-out specimen casting device from the dry hard concrete. Then the reinforcing steel is lifted out and curing continues until 28 days of age.

[0025] Preferably, the loading time for each step (2) does not exceed 30 seconds; the total vibration and compaction process in steps (2)-(3) does not exceed 180 seconds; the design value for step (3) is 8–10 mm, and the upper limit of the pressure setting is 0.6 MPa.

[0026] The pouring device of this invention, by pouring concrete vertically into the cross-section of the reinforcing bar, can greatly reduce the influence of the concrete's self-weight on the horizontal position of the reinforcing bar, while also avoiding excessive compression of the reinforcing bar by the concrete, which could lead to bending. The central openings in the pull-out pouring container, compaction device, and reinforcing bar anti-deviation device have a fixing effect on the reinforcing bar, greatly reducing the influence of the concrete's self-weight and the compaction device on the reinforcing bar's position. The compaction device can compress the concrete downwards from above using gravity. Simultaneously, due to the presence of the limiting holes, the position of the reinforcing bar is limited, reducing the compressive effect of the concrete on the reinforcing bar. The limiting holes further restrict the position of the reinforcing bar, ensuring its stable placement within the concrete. The vibration action of the vibrating lifting rod can remove air bubbles, reduce internal gaps, and enhance the concrete's strength. Attached Figure Description

[0027] The present application will be further explained below with reference to the accompanying drawings:

[0028] Figure 1 This is a front view of the structure of the present invention;

[0029] Figure 2 This is a side view of the structure of the present invention;

[0030] Figure 3 This is a top view of the structure of the present invention;

[0031] Figure 4 This is a cross-sectional view of the drawing device of the present invention;

[0032] Figure 5 This is an enlarged front view of the rebar anti-deflection device of the present invention;

[0033] Figure 6 This is an enlarged side view of the rebar anti-deflection device of the present invention;

[0034] Figure 7 This is an enlarged top view of the rebar anti-deflection device of the present invention;

[0035] Figure 8 This is an enlarged view of the vibratory lifting device of the present invention;

[0036] Figure 9 This is a top view of the compaction device of the present invention;

[0037] Figure 10 This is a top enlarged view of the hydraulic device of the present invention;

[0038] Explanation of reference numerals in the attached drawings: 1-Pull-out casting container; 2-Compactor device; 3-Reinforcing bar anti-deviation device; 4-Vibrator lifting rod; 5-Bowl bolt; 6-Reinforcing bar; 7-Vibrator bead; 8-First horizontal hydraulic component; 9-Mixing component; 10-Down button; 11-Up button; 13-Bolt; 14-Second horizontal hydraulic component; 15-First vertical hydraulic component; 16-Second vertical hydraulic component; 17-First horizontal hydraulic component button; 18-Second horizontal hydraulic component button; 19-First vertical hydraulic component button; 20-Second vertical hydraulic component button; 21-Vibration hydraulic unit. Detailed Implementation

[0039] This section details the technical solution of the present invention: The present invention provides a casting device for reinforcing steel bars and dry-hardened concrete specimens, comprising: a pull-out casting container, wherein the pull-out casting container is a square box with an open top and a casting opening provided at the center of the lower plane; a compaction device, disposed above the pull-out casting container, the area of ​​which is smaller than the inner surface of the pull-out casting container; the compaction device is provided with a compaction opening; and a reinforcing steel bar anti-deviation device, disposed above the compaction device, wherein the reinforcing steel bar anti-deviation device is provided with a limiting hole and a vibrator opening; the limiting hole is provided with... The device includes a limit bolt; a hydraulic system comprising a horizontal hydraulic component, a vertical hydraulic component, and a displacement sensor, positioned between the compaction device and the rebar anti-deviation device; the horizontal and vertical hydraulic components are L-shaped; a vibratory lifting rod, vertically passing through the vibratory rod opening of the rebar anti-deviation device, drives the vertical displacement of the vibratory lifting rod through the vibratory hydraulic unit and connecting rod; the vibratory lifting rod has a hollow internal structure; the length of the vibratory lifting rod ranges from 250-300mm, and a cylindrical hollow steel structure is welded to the bottom end of the vibratory lifting rod. Several hollow cylinders are provided on the bottom surface of the cylindrical hollow steel structure; vibratory beads are embedded in the bottom of the hollow cylinders; the power unit for the vibratory beads is located inside the cylindrical hollow steel structure. The vibratory hydraulic unit is mounted on the rebar anti-deviation device; the connecting rod includes an annular metal rod connected to the vibratory lifting rod and an inner metal rod connecting the vibratory hydraulic unit and the annular metal rod. The rebar anti-deviation device includes an upper structure consisting of two trapezoidal plates connected by limiting holes, an L-shaped steel plate welded to the upper structure, and a connecting trapezoidal plate between the two trapezoidal plates. The L-shaped steel plate includes a vertically arranged supporting steel plate and a parallel connecting steel plate. The limiting holes are composed of two steel plates and trapezoidal plates. The openings of the vibrating rod are symmetrically distributed along the limiting holes. The ends of the limiting bolts are inlaid with flexible material. The long side of the trapezoidal plate is connected to the upper part of the drawing and casting container through the L-shaped steel plate. The displacement sensor is a magnetostrictive displacement sensor. The horizontal hydraulic component of the hydraulic device is welded to the lower surface of the connecting trapezoidal plate, and the vertical hydraulic component is welded to the upper surface of the compaction device. The horizontal hydraulic component and the vertical hydraulic component are welded together. The compaction device includes two compaction plates. The drawing casting container is a cube with an open top, formed by five metal plates connected by bolts, and a reinforcing bar hole is provided at the center of its bottom plane; the roughness of the inner wall of the drawing casting container is not greater than 50μm; the length of the metal plates is 140-220mm; the width is 140-220mm; the reinforcing bar hole is connected to the bowl bolt outward.

[0040] This invention provides a method for casting steel bars and dry-hard concrete specimens, comprising the following steps: Step (1), placing the assembled pull-out specimen casting device on a horizontal vibration table for pre-vibration, so that the bottom plate and the table surface are in close contact; inserting the steel bar from the bottom and locking it with a bowl nut to ensure that the verticality deviation of the steel bar is ≤0.1°; Step (2) loading the dry-hard concrete into the pull-out specimen casting device in two layers; after the first layer is loaded, start the vibration process: first turn on the ring vibrating ball motor, adjust the speed to 5000rpm, then press the "down" button, and the vibrating rod descends at a speed of 10mm / s to 30mm from the bottom plate of the cylindrical hollow steel structure, stays for 5s and then slowly lifts up, repeating twice; after the second layer is loaded, repeat the vibration process, and the last time the vibrating rod descends to 20mm from the top interface of the first layer of the cylindrical hollow steel structure; Step (3) After vibration, the compaction stage begins: simultaneously, the "horizontal closing" button is activated, and the two compaction plates move towards each other at a speed of 5 mm / s within 1 second, stopping at a gap of 2 mm; then the "vertical pressing" button is activated, and the vertical hydraulic component drives the compaction plate to descend as a whole at a speed of 2 mm / s. When the descent reaches the design value or the pressure reaches the set upper limit, the pressure is maintained for 30 seconds; after compaction, the pressure is slowly released, and the compaction plate first returns vertically and then opens horizontally; in step (4), after the surface of the specimen prepared by the above steps is lightly pressed and smoothed with a stainless steel trowel, it is immediately covered with a plastic film and moved to a standard curing room with a temperature of 20±2℃ and a relative humidity of ≥95% for curing. After 24 hours, the bowl bolts are loosened, and the side plate is gently tapped with a rubber hammer to separate the pull-out specimen casting device from the dry hard concrete. Then the reinforcing steel is lifted out and curing continues until the age of 28 days. Each loading time in step (2) shall not exceed 30 seconds; the total vibration and compaction process in steps (2)-(3) shall not exceed 180 seconds; the design value of step (3) is 8–10 mm, and the upper limit of the pressure setting is 0.6 MPa. This invention addresses the problem that reinforcing bars tend to sink under their own weight during the pouring of dry-hard concrete, and that the final compaction of the concrete by the weights causes the reinforcing bars to sink, which can easily affect the data in subsequent pull-out processes and lead to test block failure. Furthermore, in large-volume concrete such as dry-hard concrete, there are some air bubbles inside, which can cause small cracks inside and affect the later strength. This invention aims to solve the problems of reinforcing bar sinking during pouring and air bubbles inside dry-hard concrete.

[0041] In concrete pipe structures, the interfacial bond-slip performance between reinforcing steel and dry-hard concrete is a key factor determining the pipe's load-bearing capacity and service life. However, dry-hard concrete, due to its low water-cement ratio and near-zero slump, exhibits extremely poor fluidity and a very rapid initial setting rate during pouring. Conventional vibration and tamping methods are insufficient to achieve adequate compaction, easily leaving air bubbles and micro-cracks inside, resulting in large dispersion and poor repeatability in interfacial bond strength test results. Even more challenging is the fact that research specimens typically require multi-parameter matrix design with variables such as reinforcing steel diameter, concrete mix proportion, aggregate size, and anchorage length. Furthermore, three sets of parallel specimens must be prepared for each working condition to eliminate random errors. This makes the traditional "horizontal pouring + manual tamping" process fundamentally inadequate for the efficient, accurate, and repeatable research requirements. In the early stages of the experiment, the inventors used a simple solution of using PVC round pipes as side molds and bottom pads to fix the reinforcing bars. However, the dry-hard concrete began to lose its plasticity rapidly under its own weight, the upper aggregate was difficult to sink, and the lower mortar had already partially set. The large number of holes left after the tamping rod was pulled out could not heal themselves. At the same time, the reinforcing bars were very prone to slight bending under the combined action of the tamping impact force and the lateral pressure of the concrete. An initial eccentricity of 0.5 mm could induce an additional bending moment in the pull-out test, causing the bond slip curve to show a "pseudo-decreasing segment". The data dispersion coefficient was as high as 18.7%, which far exceeded the allowable range for scientific research. To overcome the aforementioned shortcomings, we designed and developed a casting device for bond-slip pull-out specimens of steel bars and dry-hard concrete. Through an integrated approach of "bottom limiting, top anti-deviation, hydraulic bidirectional compaction, and high-frequency venting of hollow vibrating beads," we achieved rapid, uniform, and high-pressure compaction of dry-hard concrete while ensuring that the steel bars remained absolutely vertical. This allowed us to control the standard deviation of the peak bond strength of the three specimens in the same group to within 3% for the first time, laying a reliable experimental foundation for establishing a high-precision local bond-slip constitutive model.

[0042] Based on the above-described structural features and accompanying drawings of this application, the embodiments of this application will be further described.

[0043] Example 1

[0044] A casting container 1 has an opening at its upper part, and a casting hole is provided at the center of its lower plane parallel to the upper opening. Bolts 13 are provided on its outer surface. A compaction device 2 is located above the opening of the casting container 1 and has a compaction hole through which the reinforcing bar can pass. A reinforcing bar anti-deviation device 3 is located above the compaction device 2 and has an anti-deviation hole through which the reinforcing bar can pass and several vibratory bar holes through which the vibratory lifting rod can pass. A hydraulic device includes a first horizontal hydraulic component 8, a second horizontal hydraulic component 14, a first vertical hydraulic component 15, and a second vertical hydraulic component 16, which are disposed between the compaction device 2 and the reinforcing bar anti-deviation device 3. The first horizontal hydraulic component 8 and the second horizontal hydraulic component 14 are respectively connected to the lower surface of the connecting trapezoidal plate of the reinforcing bar anti-deviation device 3. Vertical hydraulic component 15 and second vertical hydraulic component 16 are respectively connected to the upper surface of compaction device 2; the connection between the first horizontal hydraulic component 8, second horizontal hydraulic component 14 and the lower surface of rebar anti-deviation device 3, between the first vertical hydraulic component 15, second vertical hydraulic component 16 and the upper surface of compaction device 2, between the first horizontal hydraulic component 8 and the first vertical hydraulic component 15, and between the second horizontal hydraulic component 14 and the second vertical hydraulic component 16 includes welding; the vibratory lifting rod 4 is installed vertically at the vibratory rod opening of rebar anti-deviation device 3, and drives the vertical displacement of vibratory lifting rod through vibratory hydraulic unit 21 and connecting rod; the casting container 1, compaction device 2, rebar anti-deviation device 3 and vibratory lifting rod 4 are arranged longitudinally as a whole. The pouring device described herein includes a 250mm long vibratory lifting rod 4, one end of which is a cylindrical hollow steel structure. Fifteen hollow cylinders are arranged on the side of the cylindrical hollow steel structure away from the vibratory lifting rod 4, and vibratory beads 7 are embedded within the hollow cylinders. The pouring device is characterized in that a stirring component 9 is provided on the rebar anti-deviation device 3 for opening and closing the rotation of the vibratory beads 7 within the vibratory lifting rod; a down button 10 and an up button 11 are provided on the rebar anti-deviation device 3 for opening and closing the vertical movement of the vibratory lifting rod 4. The switches for the first horizontal hydraulic component 8, the second horizontal hydraulic component 14, the first vertical hydraulic component 15, and the second vertical hydraulic component 16 are located at the opening of the rebar anti-deviation device 3. The pouring device is further characterized by a protruding bowl-shaped bolt at the lower pouring opening of the pull-out pouring container 1. The casting device includes a rebar anti-deviation device with an anti-deviation opening 3 positioned at the center of the upper plane, and vibrator openings symmetrically distributed along the anti-deviation openings. The casting device also includes a rebar 6, vertically arranged at the center of the drawing-out casting container, passing through the rebar anti-deviation device 3, the compaction device 2, and the drawing-out casting container 1. The drawing-out casting container can be disassembled into five metal plates of uniform length, width, and thickness, and bolts. Each metal plate is 220mm in length and width.

[0045] Example 2

[0046] This embodiment provides a casting device for reinforcing bars and dry-hardened concrete specimens, which can greatly reduce the influence of the concrete's self-weight and the compaction device on the position of the reinforcing bars.

[0047] This embodiment provides a casting device for reinforcing steel bars and dry-hardened concrete specimens, which can remove air bubbles, reduce internal gaps, and enhance concrete strength.

[0048] According to one aspect, the casting device for reinforcing steel and dry-hardened concrete specimens may include: a pull-out casting container 1, connected by bolts 13, with the opening located at its upper part and a bowl bolt 5 at the center of its lower plane; a compaction device 2, located above the opening of the pull-out casting container 1, with an opening through which the reinforcing steel can pass; a reinforcing steel anti-deviation device 3, located above the compaction device 2; and a hydraulic device, including a first horizontal hydraulic component 8, a second horizontal hydraulic component 14, a first vertical hydraulic component 15, and a second vertical hydraulic component 16, disposed between the compaction device 2 and the reinforcing steel anti-deviation device 3. The first horizontal hydraulic component 8 and the second horizontal hydraulic component 14 are respectively connected to the lower surface of the connecting trapezoidal plate of the reinforcing steel anti-deviation device 3, and the first vertical hydraulic component 15 and the second vertical hydraulic component 16 are respectively connected to the compaction device 2. 2. Upper surface connection; the connection between the first horizontal hydraulic component 8, the second horizontal hydraulic component 14 and the lower surface of the rebar anti-deviation device 3, the first vertical hydraulic component 15, the second vertical hydraulic component 16 and the upper surface of the compaction device 2, the first horizontal hydraulic component 8 and the first vertical hydraulic component 15, and the second horizontal hydraulic component 14 and the second vertical hydraulic component 16 includes welding; the vibratory lifting rod 4 is installed vertically at the opening of the rebar anti-deviation device 3, and all vibratory lifting rods 4 are connected to the annular steel pipe as a whole, and the connection method is welding; the vertical displacement of the vibratory lifting rod 4 is driven by the vibratory hydraulic unit 21 and the connecting rod; the rebar 6 is vertically arranged at the center of the pull-out casting container 1, and passes through the rebar anti-deviation device 3, the compaction device 2 and the pull-out casting container 1.

[0049] The pouring device further includes: a mixing component 9, disposed on the upper surface of the rebar anti-deviation device 3, for turning the rotation of the vibrating beads 7 on and off; a lifting component, including a down button 10 and an up button 11, disposed on the upper surface of the rebar anti-deviation device 3, for controlling the vertical rise and fall of the vibrating lifting rod; a first horizontal hydraulic component button 17, disposed on the upper surface of the rebar anti-deviation device 3, for controlling the on / off state of the first horizontal hydraulic component 8; a second horizontal hydraulic component button 18, disposed on the upper surface of the rebar anti-deviation device 3, for controlling the on / off state of the second horizontal hydraulic component 14; a first vertical hydraulic component button 19, disposed on the upper surface of the rebar anti-deviation device 3, for controlling the on / off state of the first vertical hydraulic component 15; and a second vertical hydraulic component button 20, disposed on the upper surface of the rebar anti-deviation device 3, for controlling the on / off state of the second vertical hydraulic component 16.

[0050] Figure 1 This is a front view of the structure of the present invention. Figure 4 This is a perspective view of the drawing casting container of the present invention.

[0051] The steel bar 6 is vertically arranged at the center of the pull-out casting container 1, and passes through the steel bar anti-deviation device 3, the compaction device 2, the pull-out casting container 1, and the bowl bolt 5.

[0052] The upper part of the drawing and casting container 1 is provided with an opening, through which the user can pour concrete to the side of the upper steel bar. When pouring, press the mixing component 9 and the down button 10 or the up button 11. Pressing the mixing component 9 causes the vibrating beads 7 to rotate through the internal motor of the vibrating lifting rod 4 to remove air bubbles. Pressing the down button 10 or the up button 11 causes the vibrating lifting rod 4 to move the vibrating beads 7 up and down during the rotation of the vibrating beads 7 so as to vibrate evenly.

[0053] After removing air bubbles, raise the vibratory lifting rod 4 by pressing the up button 11, and press the first horizontal hydraulic component button 17, the second horizontal hydraulic component button 18, the first vertical hydraulic component button 19, and the second vertical hydraulic component button 20 to close the compaction device 2, ensuring the compaction of dry and hard concrete.

[0054] Example 3

[0055] Prepare several 200×200×20 steel plates. Drill a hole in the center of one of the steel plates to ensure that the hole diameter is larger than the diameter of the reinforcing bar. Drill holes in the other steel plates as well to ensure that they can be assembled and fixed with bolts later.

[0056] Several steel plates are assembled using bolts, and the reinforcing bar 6 is inserted into the center of the steel plate. The notch is plugged by rotating a bowl bolt to prevent grout leakage later and to effectively fix the vertical displacement of the reinforcing bar.

[0057] Install the rebar anti-deviation device 3 in sequence. The rebar anti-deviation device 3 is made of several short steel plates, connecting trapezoidal plates, and welded together. Drill holes on the short sides of the trapezoidal plates. Perform the same operation on two short steel plates to ensure that the long sides of the two short steel plates can be placed exactly in the gap between the trapezoidal steel plates. Assemble the two short steel plates and the trapezoidal steel plates, ensuring that the short steel plates are parallel. Install the device with bolts after drilling holes on both sides of the trapezoidal plates. The rebar anti-deviation device is fixed to the upper opening of the pulling device with bolts. The rebar 6 is clamped from both sides towards the middle at the parallel position of the rebar anti-deviation device 3 to fix the rebar.

[0058] Grooving and drilling are performed on the trapezoidal steel plate to facilitate the installation of the mixing component 9, the down button 10, the up button 11, the first horizontal hydraulic component button 17, the second horizontal hydraulic component button 18, the first vertical hydraulic component button 19, the second vertical hydraulic component button 20, and the internal wiring, ensuring that the vibrating lifting rod 4 can move freely in the vertical direction.

[0059] Install vibrating beads 7 at the lower end of the vibrating lifting rod 4. The vibrating beads 7 can remove air bubbles inside the dry and hard concrete by rotating up and down and left and right. Install the mixing component 9 and adjust it.

[0060] Compaction device 2 consists of two pieces. It is composed of steel plates, internal circuits, and switches installed on the surface. The inward part is slotted to ensure that the dry hard concrete compaction devices on both sides can be closed just right and that subsequent compaction will not cause the steel bars to move up and down. The compaction device 2 can close towards the middle and then return to its original state after descending a certain height.

[0061] The hydraulic device includes a first horizontal hydraulic component 8, a second horizontal hydraulic component 14, a first vertical hydraulic component 15, and a second vertical hydraulic component 16, disposed between the compaction device 2 and the rebar anti-deviation device 3. The first horizontal hydraulic component 8 and the second horizontal hydraulic component 14 are respectively connected to the lower surface of the connecting trapezoidal plate of the rebar anti-deviation device 3, and the first vertical hydraulic component 15 and the second vertical hydraulic component 16 are respectively connected to the upper surface of the compaction device 2. The connection between the first horizontal hydraulic component 8 and the second horizontal hydraulic component 14 and the lower surface of the rebar anti-deviation device 3, between the first vertical hydraulic component 15 and the second vertical hydraulic component 16 and the upper surface of the compaction device 2, between the first horizontal hydraulic component 8 and the first vertical hydraulic component 15, and between the second horizontal hydraulic component 14 and the second vertical hydraulic component 16 includes welding. The final concrete pouring direction is the side of the upper rebar, and air bubbles are removed by vertical vibration using vibrating beads 7 during pouring.

[0062] After removing air bubbles, raise the vibratory lifting rod 4 by pressing the up button 11, and press the first horizontal hydraulic component button 17, the second horizontal hydraulic component button 18, the first vertical hydraulic component button 19, and the second vertical hydraulic component button 20 to close the compaction device 2, ensuring the compaction of dry and hard concrete.

[0063] Example 4

[0064] This embodiment treats the reinforcing bars as the reference axis and the concrete as a granular mass that needs to be forcibly pressed into the mold. Through the combined action of rigid constraints and hydraulic drive, the brief time window before and after loss of fluidity is transformed into an effective compaction period. The specific structure includes five major systems: a pull-out casting container, a compaction device, a reinforcing bar anti-deviation device, a hydraulic system, and a vibration lifting system. The pull-out casting container is assembled from five 200mm×200mm×20mm Q345 steel plates using M16 high-strength bolts to form an open-top cube. A through hole 2mm larger than the nominal diameter of the reinforcing bar is opened in the center of the bottom plate. A bowl bolt is welded to the outside of the hole. After the reinforcing bar is inserted from the bottom, the anchoring end of the reinforcing bar is connected to the bottom plate of the pull-out casting container by two top nuts, which not only prevents grout leakage but also completely eliminates the possibility of the reinforcing bar sinking during subsequent vibration and compaction. The inner wall of the container is shot-blasted to a roughness of 50μm to simulate the interface interlocking conditions of the inner wall of an actual pipeline. The compaction device consists of two 150mm×75mm×10mm tempered steel plates. The inner surface has a 1mm radius triangular closed indentation, allowing it to embed into the concrete surface during compaction and form a mechanical interlock. The two steel plates are horizontally closed by a horizontal hydraulic component and then pressed down as a whole by a vertical hydraulic component, thus applying a two-way stress path of "first lateral constraint, then longitudinal compression" to the dry-hard concrete. It can provide a maximum hydrostatic pressure of 0.6MPa, sufficient to reduce the porosity to below 2%. The rebar anti-deviation device is located above the compaction device and consists of two trapezoidal plates welded to an L-shaped steel plate to form a "portal frame." A limiting hole is opened in the center of the frame, with two sets of limiting bolts symmetrically arranged inside. The ends of the limiting bolts are inlaid with polytetrafluoroethylene hemispheres, ensuring flexible clamping of the rebar while preventing scratches on the rebar ribs. Two symmetrical φ30mm vibrator openings are also made on the frame, ensuring that the vibrator can move freely up and down along the rebar axis without touching the rebar. The hydraulic system is driven by a 0.75kW silent pump station. The horizontal and vertical hydraulic components are arranged in an L-shape. All cylinders are equipped with magnetostrictive displacement sensors with a resolution of 0.05mm at the end of their strokes. These sensors can provide real-time feedback on compaction displacement and automatically stop the machine to prevent overpressure from causing the steel bars to buckle. The vibratory lifting system uses a hollow 304 stainless steel rod, 280mm in length, with a cylindrical hollow steel structure welded to the bottom. Nine hollow cylinders of φ10mm×5mm are evenly distributed on its lower surface. Each cylinder is embedded with a ring-shaped vibratory bead with an outer diameter of 9mm and an inner raceway filled with molybdenum disulfide. The vibratory bead is driven by a 12V brushless motor placed inside the hollow structure via a flexible shaft, which can achieve a high-speed rotation of 5000rpm. At the same time, the entire vibratory rod is driven by the vibratory hydraulic unit at the top, moving up and down at a speed of 10mm / s. The shear waves generated by the combined rotation and lifting motion can quickly destroy the "arch bridge structure" inside the dry hard concrete, allowing air bubbles to be discharged along the gaps between the vibratory beads. The measured air exhaust efficiency is more than 4 times higher than that of traditional tamping.

[0065] Before pouring, sufficient steel bars were first processed according to the scientific research and experimental matrix. In this example, HRB400 steel bars were selected, with diameters of 12mm, 16mm, and 20mm. Each diameter corresponded to three levels of anchorage lengths of 120mm, 180mm, and 240mm. Aggregate particle sizes were two levels: 0-5mm, 5-10mm, and 0-10mm. Water-cement ratios were three levels: 0.28, 0.32, and 0.36, resulting in a total of 81 mix proportions, with 3 specimens per group, for a total of 243 specimens. After sandblasting to remove rust, the steel bars were wiped with acetone and dried with cold air. Then, a 50μm thick layer of epoxy resin was sprayed onto the entire length of the steel bars. After curing, the coating on the anchorage section was precisely ground off with a grinding wheel to ensure that only the surface of the steel bar of the designed length was in contact with the concrete, while the rest was isolated from the concrete, thereby eliminating the interference of non-anchorage section bonding on slip measurement. Dry-hard concrete is mixed using a forced planetary mixer. The feeding sequence is: aggregate → cement → silica fume → fiber (if any) → mixing water (including high-efficiency water-reducing agent). After mixing for 180 seconds, let it stand for 30 seconds, then mix rapidly for 60 seconds. Immediately after discharge, a flowability test is performed to ensure that its spread is within the range of 120±10mm. The entire process from adding water to discharge is controlled within 4 minutes to prevent premature initial setting.

[0066] During the formal pouring, the assembled mold is placed on a horizontal vibrating table (amplitude 0.5mm, frequency 50Hz) for pre-vibration for 5 seconds to ensure a tight fit between the base plate and the table surface. The reinforcing bars are inserted from the bottom and tightened with bowl nuts. An electronic inclinometer is used to check the verticality of the reinforcing bars, requiring a deviation of ≤0.1°; otherwise, the base plate shims are readjusted. Dry-hardened concrete is then poured into the mold in two layers, each approximately 100mm thick, with the filling time controlled within 30 seconds. After the first layer is poured, the vibration system is immediately started: first, the ring vibrator motor is turned on, and the speed is adjusted to 5000rpm. Then, the "down" button is pressed, and the vibrator descends at a speed of 10mm / s to a distance of 30mm from the base plate, pauses for 5 seconds, and then slowly rises. This up-and-down motion is repeated twice. During this process, air bubbles can be clearly observed continuously being discharged along the gaps between the reinforcing bar ribs and the inner wall of the mold, and cement paste gradually appears on the concrete surface. After the second layer of material is loaded, the above vibration process is repeated, but the vibrator is lowered only to 20mm from the interface of the first layer for the last time to avoid damaging the already compacted lower layer. After vibration, the compaction stage begins quickly: first, press the "Horizontal Closure" button simultaneously, and the two compaction plates move towards each other at a speed of 5mm / s within 1 second until they automatically stop at a gap of 2mm; then press the "Vertical Downward Press" button, and the vertical hydraulic component lowers the compaction plates as a whole at a speed of 2mm / s. The displacement sensor records the compaction amount in real time. When the descent reaches the design value (usually 8–10mm) or the pressure reaches the set upper limit (0.6MPa), the system automatically holds the pressure for 30 seconds to ensure that the internal pores of the dry-hard concrete are fully compressed. After compaction, the pressure is slowly released, and the compaction plates first return vertically and then open horizontally to avoid surface cracking of the dry-hard concrete caused by vacuum adsorption. The entire vibration and compaction process takes no more than 180 seconds, much earlier than the initial setting time of dry-hard concrete, thus effectively solving the problem of a short operating window caused by "poor fluidity and fast setting".

[0067] After the specimen surface was lightly smoothed with a stainless steel trowel, it was immediately covered with plastic film and moved to a standard curing room with a temperature of 20±2℃ and a relative humidity of ≥95%. After 24 hours, the bowl bolts were loosened, and the side plates were gently tapped with a rubber mallet to separate the mold from the concrete. The reinforcing bars were then carefully lifted out, avoiding impact. Curing continued until 28 days. During the curing period, the exposed sections of the reinforcing bars were checked daily for rust. If rust spots were found, they were removed with a wire brush and coated with anti-rust oil. After reaching the test age, a pull-out test was performed on a universal testing machine with a loading rate of 0.5 mm / min. Load and slip data were continuously collected until the load dropped to 50% of the peak value or the slip reached 5 mm. The experimental results show that the difference between the slippage of the free end and the slippage of the loaded end of the specimen cast using this device is ≤0.02mm, indicating that the steel bar maintains axial force throughout the loading process without additional bending. The difference between the maximum and minimum peak bond strength of the three specimens in the same group does not exceed 0.15MPa, the standard deviation is ≤0.05MPa, and the coefficient of variation is <3%, fully meeting the stringent requirements for data repeatability in scientific research. Microscopic CT scanning further confirmed that the concrete density at the leading edge of the steel bar rib is as high as 98.5%, and the thickness of the interface transition zone is only 15μm, which is significantly better than that of specimens prepared by traditional methods.

[0068] In summary, this device, through the innovative combination of "rigid limiting + hydraulic high pressure + high frequency composite vibration," successfully solved a series of problems in the preparation of scientific research specimens for dry-hard concrete, such as poor fluidity, difficulty in removing air bubbles, easy deviation of reinforcing bars, and data dispersion. It provides a high-fidelity and repeatable experimental platform for the refined study of the bond-slip constitutive relationship between reinforcing bars and concrete, and also lays a solid foundation for subsequent in-depth research such as multi-field coupling and long-term durability.

[0069] The first innovation of this invention is the modification of the pulling device, which changes the opening for pouring concrete to be perpendicular to the cross-section of the reinforcing bar. In short, the concrete is poured in parallel to the longitudinal direction of the reinforcing bar. This direction can greatly reduce the self-weight of the concrete and the influence of the compaction device on the position of the reinforcing bar. The second innovation is the addition of a dry-hard concrete vibration device. The vibrating beads penetrate into the dry-hard concrete and swing left and right to remove air bubbles and achieve the vibration effect, reducing internal gaps and enhancing the strength of the concrete.

[0070] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the invention. All equivalent changes and modifications made within the scope of the claims of this invention should fall within the technical scope of this invention.

Claims

1. A casting apparatus for reinforcing steel bars and dry-hardened concrete specimens, characterized in that, include: A drawing casting container, wherein the drawing casting container is a square box with an opening at the top and a casting opening is provided at the center of the lower plane; A compaction device is installed above the drawing and casting container, and its area is smaller than the inner surface of the drawing and casting container; the compaction device is provided with compaction openings. A rebar anti-deviation device is installed on the upper part of the compaction device. The rebar anti-deviation device is provided with a limit hole and a vibrator opening; a limit bolt is provided on the limit hole. The hydraulic device, including a horizontal hydraulic component, a vertical hydraulic component, and a displacement sensor, is positioned between the compaction device and the rebar anti-displacement device; the horizontal and vertical hydraulic components are generally L-shaped. The vibratory lifting rod passes vertically through the opening of the vibratory rod anti-deflection device for the reinforcing bars, and the vertical displacement of the vibratory lifting rod is driven by the vibratory hydraulic unit and the connecting rod. The vibratory lifting rod has a hollow internal structure; the length of the vibratory lifting rod ranges from 250-300mm, and a cylindrical hollow steel structure is welded to the bottom end of the vibratory lifting rod; several hollow cylinders are provided on the bottom surface of the cylindrical hollow steel structure; vibratory beads are embedded in the bottom of the hollow cylinders; the power equipment of the vibratory beads is located inside the cylindrical hollow steel structure; the vibratory hydraulic unit is located on the rebar anti-deviation device; the connecting rod includes an annular metal rod connected to the vibratory lifting rod, and an internal metal rod connecting the vibratory hydraulic unit and the annular metal rod.

2. The casting apparatus according to claim 1, characterized in that, The rebar anti-deviation device includes an upper structure consisting of two trapezoidal plates connected by limiting holes, an L-shaped steel plate welded to the upper structure, and a connecting trapezoidal plate between the two trapezoidal plates; the L-shaped steel plate includes a vertically arranged supporting steel plate and a parallelly arranged connecting steel plate.

3. The casting device according to claim 2, characterized in that, The limiting hole is composed of two steel plates and a trapezoidal plate; the opening of the vibrating rod is symmetrically distributed along the limiting hole; the end of the limiting bolt is inlaid with flexible material.

4. The casting device according to claim 3, characterized in that, The long side of the trapezoidal plate is connected to the upper part of the drawing and casting container via an L-shaped steel plate; the displacement sensor is a magnetostrictive displacement sensor; the horizontal hydraulic component of the hydraulic device is welded to the lower surface of the connecting trapezoidal plate, and the vertical hydraulic component is welded to the upper surface of the compaction device; the horizontal hydraulic component and the vertical hydraulic component are welded together; the compaction device includes two compaction plates.

5. The casting apparatus according to claim 1, characterized in that, The drawing casting container is a cube with an open top, formed by five metal plates connected by bolts, and a reinforcing bar hole is provided at the center of its bottom plane; the roughness of the inner wall of the drawing casting container is not greater than 50μm; the length of the metal plates is 140-220mm; the width is 140-220mm; the reinforcing bar hole is connected to the bowl bolt outward.

6. A method for casting reinforced concrete specimens, characterized in that, Includes the following steps: Step (1): Place the assembled pull-out specimen casting device on a horizontal vibration table for pre-vibration, so that the base plate is in close contact with the table surface; insert the reinforcing bar from the bottom and lock it with the bowl nut to ensure that the verticality deviation of the reinforcing bar is ≤0.1°; Step (2) Fill the pull-out specimen casting device with dry-hard concrete in two layers; After the first layer of material is loaded, start the vibration process: first turn on the ring vibrating ball motor, adjust the speed to 5000rpm, then press the "down" button, and the vibrating rod will descend at a speed of 10mm / s to 30mm away from the bottom plate of the cylindrical hollow steel structure. After 5 seconds, slowly lift it up and repeat twice. After the second layer of material is loaded, the vibration process is repeated. The last time the vibrator is lowered to a position 20mm away from the upper interface of the first layer of the cylindrical hollow steel structure. Step (3), after vibration, enter the compaction stage: simultaneously start the "horizontal closing" button, the two compaction plates move towards each other at a speed of 5mm / s within 1s, and stop when the gap is 2mm; then start the "vertical pressing" button, the vertical hydraulic component drives the compaction plate to descend as a whole at a speed of 2mm / s, and when the descent reaches the design value or the pressure reaches the set upper limit, the pressure is maintained for 30s; after compaction is completed, the pressure is slowly released, the compaction plate first returns vertically and then opens horizontally; Step (4): After the surface of the specimen prepared by the above steps is lightly pressed and smoothed with a stainless steel trowel, it is immediately covered with a plastic film and moved to a standard curing room with a temperature of 20±2℃ and a relative humidity of ≥95% for curing. After 24 hours, the bowl bolts are loosened, and the side plate is gently tapped with a rubber hammer to separate the pull-out specimen casting device from the dry hard concrete. Then the reinforcing steel is lifted out and curing continues until 28 days of age.

7. The method for casting reinforced concrete specimens according to claim 6, characterized in that, Each loading time in step (2) shall not exceed 30 seconds; the total vibration and compaction process in steps (2)-(3) shall not exceed 180 seconds; the design value of step (3) is 8–10 mm, and the upper limit of the pressure setting is 0.6 MPa.

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