A method for self-repairing of steel reinforced concrete structure rust expansion cracking

Abstract

The application discloses a reinforced concrete structure rust-expansion cracking self-repairing method, and relates to the technical field of intelligent materials and structures, which comprises a hollow steel bar filled with repairing microcapsules and a brittle trigger window preset on the surface of the hollow steel bar, a targeted repairing behavior for simulating a concrete crack, precise breaking of the brittle plug under crack stress and release of repairing components to realize instant sealing of the crack, and a crack sensing and positioning method based on the technology. The application realizes trigger type self-repairing and intelligent monitoring of rust-expansion cracks, realizes the whole process of release of the repairing agent triggered by crack stress to crack healing, realizes directional migration behavior of the repairing agent to the crack side, and has the advantages of targeting, high efficiency and sensing compared with the traditional method of randomly mixing repairing capsules in concrete.

Description

Technical Field

[0001] This invention belongs to the field of smart materials and structure technology, and in particular, it relates to a self-repair method for cracks in reinforced concrete structures, especially a self-repair method for rust expansion cracks in reinforced concrete structures. Background Technology

[0002] In the field of concrete structure durability and life-cycle maintenance research, self-healing technology, as a proactive maintenance method, is widely used to improve the long-term performance of reinforced concrete in corrosive environments. However, traditional concrete self-healing methods often involve directly incorporating repair microcapsules or microbial carriers during concrete mixing. While simple to implement, this method has a series of significant limitations. The shortcomings of traditional methods are particularly pronounced when dealing with the more damaging rust expansion cracking: rust expansion cracking originates from the surface of the reinforcing steel, exhibiting concealment and self-accelerating characteristics, while randomly distributed repair capsules cannot ensure a precise response in the early stages of crack initiation. Furthermore, existing methods generally lack the ability to perceive and assess the repair process, failing to determine whether repair has occurred or where it has occurred, leaving structural maintenance in a passive and uncertain state, greatly limiting the reliability and engineering application value of self-healing technology.

[0003] A review revealed numerous publicly available self-healing solutions for concrete cracks in corrosive environments, but no technologies claiming to self-heal rust-induced cracks were found. The publicly available solutions are listed below:

[0004] Chinese Patent CN116835902B discloses a rapid self-healing agent for cracks in marine reinforced concrete and its preparation method. The proposed rapid self-healing agent can be used for repairing concrete cracks in marine corrosive environments, but it lacks guiding technology for repairing rust-induced cracking. Chinese Patent CN116151001B discloses a design method for a carrier of a core-shell type repair agent for self-healing concrete cracks. The proposed core-shell type repair agent carrier can be used as a disaster-bearing crack repair liquid and for repairing concrete cracks in corrosive environments, but it lacks guiding technology for repairing rust-induced cracking. Chinese Patent CN116835901B also discloses a self-healing agent for concrete cracks suitable for marine corrosive conditions. The proposed self-healing agent can be used for repairing concrete cracks in marine corrosive environments, but it lacks guiding technology for repairing rust-induced cracking. Chinese patent CN120701160A discloses an intelligent infiltration grouting process and device for self-healing concrete cracks. The designed method can achieve active repair of the inside of concrete. However, this method requires a dense network of distributed optical fibers, PLA pipes and other vascular structures, as well as a series of real-time monitoring technologies, which are significantly different from the technology involved in this application.

[0005] Therefore, there is an urgent need for a self-healing method for rust expansion cracks in reinforced concrete structures that can realize the entire process from the release of the repair agent triggered by crack stress to crack healing, and achieve the directional migration behavior of the repair agent to the crack side. Summary of the Invention

[0006] The purpose of this invention is to provide a self-repair method for rust expansion and cracking in reinforced concrete structures, so as to solve the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A self-repair method for rust expansion cracks in reinforced concrete structures, characterized in that the method includes:

[0009] S1. Arrange the hollow steel bars in the mold of the reinforced concrete structure;

[0010] S2. Fill the cavity with a repair microcapsule mixture;

[0011] S3. A brittle trigger plug and sensing unit are pre-set on the surface of the hollow steel bar;

[0012] S4. Pour concrete into the mold of the reinforced concrete structure, and remove the mold after curing;

[0013] S5. After the cast-in-place reinforced concrete structure is installed in the corrosive environment, it is connected to the monitoring equipment and long-term monitoring is carried out.

[0014] S6. After the reinforced concrete structure rusts and cracks, the brittle trigger plug will rupture, and the microcapsule mixture will be released in a directional manner.

[0015] S7, the sensing unit monitors the repair status and locates the cracks.

[0016] Preferably, before the hollow steel bars in step S1 are laid out, their cavities need to be cleaned and dried to ensure that there is no rust or debris inside, so as to ensure the long-term stability of the repair microcapsule mixture.

[0017] Preferably, the filling of the cavity with the repair microcapsule mixture in step S2 can be done by vacuum injection, specifically: first, seal one end of the hollow steel bar and connect the other end to the vacuum pump and the storage tank; start the vacuum pump to draw the cavity to a slightly negative pressure state; then, under the action of negative pressure, smoothly draw the repair microcapsule mixture from the storage tank into the cavity until it is full; after filling, temporarily seal the injection port.

[0018] Preferably, the repair microcapsule mixture can be preheated before filling to reduce its viscosity and promote the smoothness of the filling process.

[0019] Preferably, during operation, the microcapsule mixture within the cavity can be kept under pressure.

[0020] Preferably, in step S3, a brittle trigger plug is pre-set. Specifically, during the prefabrication stage, the trigger plug groove of the brittle trigger plug is aligned and pressed into the brittle trigger plug groove in the notch of the repair fluid on the surface of the hollow steel bar until the edge of the trigger plug is flush with or slightly convex to the surface of the steel bar. Subsequently, a constant static pressure is applied to the inside of the brittle trigger plug through the pressure tube, so that the thin ceramic sheet generates initial prestress and maintains a stable convex state.

[0021] Preferably, the installation of the sensing unit is performed simultaneously with or after the preset process of the brittle trigger plug. Specifically, the body of the sensing unit is fixed at a designated position in the middle of the hollow steel bar, and its signal lead can be laid along the groove on the surface of the steel bar and converged to a unified terminal at the end of the steel bar.

[0022] Preferably, in step S4, self-compacting concrete or a concrete mixture with a large slump should be used for concrete pouring. During pouring, the vibrator should be prevented from directly contacting the hollow reinforcing bars and their brittle trigger plugs to prevent accidental breakage. After pouring, standard curing is required, and the formwork should be removed after the concrete reaches the design strength.

[0023] Preferably, the monitoring device in step S5 is a multi-channel data acquisition instrument, which is connected to the terminal block of the sensing unit at the end of each hollow steel bar via a cable. The monitoring device can be set to a timed inspection or continuous monitoring mode, recording and storing the signal data of the sensing unit in real time.

[0024] Preferably, the mechanism by which rust expansion cracking triggers the brittle trigger plug rupture in step S6 is as follows: the volume expansion of the steel corrosion products generates circumferential tensile stress on the surrounding concrete, resulting in radial cracks in the concrete cover pointing towards the steel surface; when the cracks extend to the thin ceramic sheet of the brittle trigger plug, the stress on the protruding part of the thin ceramic sheet increases sharply, causing the thin ceramic sheet to rupture.

[0025] Preferably, the directional release process of the repair microcapsule mixture is as follows: after the thin ceramic sheet breaks, the repair microcapsule mixture in the hollow steel bar cavity flows out from the repair fluid gap under the combined action of the pre-placed slight positive pressure in the cavity and the capillary suction of the crack, and enters and fills the newly formed rust-swelling crack.

[0026] Preferably, in step S7, the sensing unit monitors the repair status and locates the crack. Specifically, the sensing unit is an acoustic emission sensor or a stress wave sensor. When the thin ceramic sheet cracks, a high-frequency stress wave is generated. The sensing unit captures the stress wave signal in this specific frequency band and records its occurrence time and waveform characteristics. By analyzing the signal arrival time, amplitude, and waveform, the monitoring device can determine the brittle-triggered plug rupture event and, based on the reinforcing bar number corresponding to the sensing unit and its relative position on the reinforcing bar, achieve coarse crack location. If multiple sensing units receive the same event signal, the location accuracy can be improved using a time-difference positioning method.

[0027] Preferably, the sensing unit can also be a sensor based on the principle of electrical impedance, which works by monitoring the overall electrical impedance change of the hollow steel bar segment: when the brittle trigger plug ruptures and the repair agent is released, the conductive medium in the cavity of the steel bar segment is replaced by air, causing a sudden change in the local electrical impedance characteristics, which can indirectly determine that the repair agent has been released and confirm the approximate segment where the rupture occurred.

[0028] Furthermore, the hollow steel bar is embedded in the mold, and brittle trigger plugs are arranged at equal intervals on the surface of the hollow steel bar. The sensing unit is set in the middle of each hollow steel bar to monitor the time and location of the breakage and repair of the brittle trigger plugs.

[0029] Preferably, the hollow steel bar specifically refers to a threaded steel bar, including threads provided on its surface, wherein the thickness of the hollow wall is not less than 2 / 3 of the cross-sectional radius of the hollow steel bar, and the diameter of the steel bar cavity is not greater than 1 / 3 of the cross-sectional diameter of the hollow steel bar, for containing the repair microcapsule mixture, and the surface of the hollow wall is provided with repair fluid notches at equal intervals for locking the brittle trigger plug.

[0030] Preferably, the hollow reinforcing bar is a hot-rolled ribbed reinforcing bar, and the threads on its surface enhance the bond strength with concrete. The thickness of the hollow wall is 0.7-0.8 times the nominal radius of the reinforcing bar, ensuring sufficient cavity volume while ensuring that the overall mechanical properties of the reinforcing bar are not lower than those of solid reinforcing bars of the same specification. The diameter of the hollow cavity is 0.25-0.3 times the nominal diameter of the reinforcing bar.

[0031] Furthermore, the repair fluid notch includes a repair fluid notch constriction for introducing the repair microcapsule mixture into the brittle trigger plug and for feeding it into the interior of the reinforced concrete structure from the repair fluid notch expansion. The inner side of the repair fluid notch is also provided with a brittle trigger plug slot for locking the brittle trigger plug.

[0032] Preferably, the repair fluid notches are arranged at equal intervals along the axis of the reinforcing bars, with a spacing of 100-300 mm. The constricted opening of the repair fluid notch is located inside the cavity, with a diameter of 1-2 mm, serving to limit flow and provide initial guidance; the flared opening of the repair fluid notch is located outside the reinforcing bars, in a trumpet shape, with an opening diameter of 3-5 mm, facilitating the diffusion of the repair agent into the concrete.

[0033] Preferably, the trigger plug groove of the brittle trigger plug and the brittle trigger plug groove in the repair fluid gap adopt an interference fit or a micro-tapered fit to ensure that the plug does not shift or fall off during concrete pouring and curing.

[0034] Furthermore, the brittle trigger plug includes a trigger plug slot and a brittle trigger plug slot that are engaged together. The edge of the trigger plug contacts the surface of the hollow steel bar. A pressure tube passes through the edge of the trigger plug to increase the pressure inside the brittle trigger plug. The edge of the trigger plug holds a thin ceramic sheet in place to sense rust-induced cracks and release the repair microcapsule mixture.

[0035] Preferably, the thin ceramic sheet is made of alumina or silicon nitride ceramic material with a thickness of 0.2-0.5 mm. After the pressure tube is pre-pressurized, the port is fused or sealed with a check valve to maintain the internal pressure.

[0036] Furthermore, the thin ceramic sheet of the brittle trigger plug is driven to crack by the occurrence and expansion of rust-induced cracks, allowing the repair microcapsule mixture to flow from the hollow steel bar into the gaps of the rust-induced cracks and repair them.

[0037] Furthermore, the thin ceramic sheet of the brittle trigger plug protrudes towards the concrete side, and internal pressure is applied through the pressurization tube during placement to ensure that the thin ceramic sheet breaks towards the concrete side without breaking into the hollow steel bar, thus preventing the repair microcapsule mixture from flowing from the hollow steel bar into the gap of the rust-swelling crack due to debris blockage.

[0038] Furthermore, after the thin ceramic sheet of the brittle trigger plug breaks, some of the larger debris is attached to the crack opening, which, together with the repair microcapsule mixture, inhibits the propagation of the rust-induced cracks; some of the smaller debris enters the crack through the crack opening, which, together with the repair microcapsule mixture, fills the existing rust-induced cracks.

[0039] Furthermore, the repair microcapsule mixture mainly comprises a fluid repair fluid and self-healing microcapsules. In the early stage of rust expansion crack formation, the fluid repair fluid and the fragments of thin ceramic sheets fill and bond the cracks. When the rust expansion cracks expand a second time, the self-healing microcapsules repair the cracks.

[0040] Preferably, the fluid repair fluid in the repair microcapsule mixture is a low-viscosity epoxy resin or methyl methacrylate grouting material, which has good crack penetration.

[0041] Preferably, in the repair microcapsule mixture, the volume ratio of the fluidized repair fluid to the self-healing microcapsules is (3:1) to (5:1). In the early stages of rust-induced crack formation, the fluidized repair fluid first penetrates the crack and combines with thin ceramic fragments, initially solidifying within several hours to a day, achieving rapid repair. If the crack continues to expand due to corrosion, the expansion stress will rupture the self-healing microcapsules embedded in the repair or adjacent cracks, releasing their core material for secondary repair.

[0042] Furthermore, if the signal monitored by the sensing unit is a composite signal of rust expansion cracking and thin ceramic sheet rupture, it can be used as a criterion for preliminary repair of rust expansion cracks.

[0043] Preferably, if the signal monitored by the sensing unit is a composite signal of rust expansion cracking and thin ceramic sheet fracture, the specific criterion is as follows: the signal waveform first shows a low-frequency, long-duration energy envelope, corresponding to the process of concrete cracking, followed by a high-frequency, transient signal, corresponding to the brittle fracture of the ceramic sheet. When the monitoring device identifies this composite signal, it can be determined as a complete "crack triggering-repair agent release" event, indicating that the rust expansion crack has been detected and repair has been initiated, which can be used as a criterion for the initial repair of the rust expansion crack.

[0044] Preferably, the monitoring device has a remote data transmission function, which can send information such as crack location and repair trigger events to a cloud platform or maintenance personnel terminal, so as to realize intelligent remote health monitoring and maintenance management of the structure.

[0045] The technical effects and advantages of this invention are as follows:

[0046] 1. This invention uses hollow steel bars as a storage and delivery carrier for the repair agent, achieving integration of structural components and the repair system. Compared with traditional methods of randomly adding repair capsules to concrete or pre-embedding independent pipeline networks, this design does not require additional concrete space, does not interfere with the original reinforcement design, and improves the targetedness and efficiency of the repair.

[0047] 2. The brittle trigger plug mechanical triggering mechanism proposed in this invention enables targeted repair of rust expansion cracks. When steel corrosion causes radial cracks in concrete, the stress concentration at the crack tip can directly destroy the thin ceramic sheet at the corresponding location, triggering the release of the repair agent. It requires no external energy or complex control system, has high reliability and direct response, and is especially suitable for hidden damage such as rust expansion cracks.

[0048] 3. This invention utilizes the fragments generated after the thin ceramic sheet of the brittle trigger plug breaks as aggregate in the repair system. Larger ceramic fragments can remain at the crack opening, forming a physical barrier and immediately inhibiting the rapid propagation of the crack; while fine ceramic particles can penetrate deep into the crack with the repair fluid, serving as micro-aggregate to enhance the density and mechanical properties of the repair, thus achieving full utilization of the trigger component material.

[0049] 4. This invention enables the sensing of the repair status of rust-induced cracks. The repair agent is directionally released into the newly formed cracks through a pre-set notch, and the sensing unit integrated into the reinforcing steel can capture the rupture signal, realizing real-time recording of repair events and coarse location of the cracks. Attached Figure Description

[0050] Figure 1 This is a schematic diagram of the self-repair method for rust expansion and cracking in reinforced concrete structures according to the present invention.

[0051] Figure 2 This is a schematic diagram of the self-healing specimen for rust expansion and cracking of reinforced concrete structure before casting, according to the present invention.

[0052] Figure 3 This is a schematic diagram of the self-healing specimen for rust expansion and cracking of reinforced concrete structure after casting, according to the present invention.

[0053] Figure 4 This is a schematic diagram of the hollow steel bar structure of the present invention.

[0054] Figure 5 This is a schematic diagram of the clamp structure of the hollow steel bar of the present invention.

[0055] Figure 6 This is a schematic diagram of the brittle trigger plug structure of the present invention.

[0056] Figure 7 This is a schematic diagram of the brittle trigger plug and the hollow steel bar combined together according to the present invention.

[0057] In the diagram: 1. Hollow steel bar; 11. Thread; 12. Hollow wall; 13. Steel bar cavity; 14. Repair fluid notch; 141. Repair fluid notch closing; 142. Repair fluid notch flaring; 143. Brittle trigger plug groove; 2. Brittle trigger plug; 21. Trigger plug groove; 22. Trigger plug edge; 23. Pressure tube; 24. Thin ceramic sheet; 3. Sensing unit; 4. Mold; 5. Reinforced concrete structure; 6. Monitoring equipment; 7. Repair microcapsule mixture. Detailed Implementation

[0058] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0059] First Embodiment

[0060] To address the issues of random distribution of repair agents and inability to target the source of rust-induced cracks in traditional self-healing technologies, this embodiment details a specific implementation method that uses hollow steel bars as an integrated repair carrier.

[0061] (1) Preparation of hollow steel bars (1). HRB400 grade hot-rolled ribbed steel bars with a nominal diameter of 20 mm were selected as the base material. A through cavity (13) with a diameter of 6 mm was machined in the center of the steel bar. The minimum wall thickness of the steel bar after processing was 7 mm. After processing, the inner wall of the cavity (13) was sandblasted to remove rust and cleaned with alcohol, and dried until the internal relative humidity was less than 5% to ensure that the cavity was clean and dry.

[0062] (2) Process repair fluid notches (14) on the surface of the reinforcing bar. Process repair fluid notches (14) at equal intervals of 150 mm in the groove of the thread (11) on the surface of the reinforcing bar. Each notch consists of an inner constriction (141) and an outer flare (142). The constriction (141) is a circular hole with a diameter of 1.5 mm, which communicates with the cavity (13); the flare (142) is a bell mouth with an opening diameter of 4 mm and a cone angle of 60°, which leads to the outside of the reinforcing bar. A ring-shaped brittle trigger plug groove (143) with a depth of 0.5 mm is machined on the inner side of the flare (142).

[0063] (3) Arrange the steel bars inside the mold. The prepared hollow steel bars (1) are used as the main reinforcing bars and are tied and fixed in the rectangular beam mold (4) with dimensions of 150mm×200mm×1200mm according to the design drawings of the reinforced concrete beam. When arranging, ensure that the bell-shaped openings of all repair fluid notches (14) face the concrete cover. Use clamps to accurately position the steel bars to prevent displacement during pouring.

[0064] Second Embodiment

[0065] To address the issues of storage stability and injection efficiency of the repair agent, this embodiment details the filling process of the repair agent.

[0066] (1) Prepare the repair microcapsule mixture (7). The mixture may consist of the following components: 80% of the total volume of a fluid repair liquid base, made of low-viscosity waterborne epoxy resin, with a compressive strength greater than 60 MPa after curing; and 20% of the total volume of self-healing microcapsules. The two components are mechanically stirred at low speed for 30 minutes in a constant temperature environment of 25°C until they are mixed evenly to obtain the repair microcapsule mixture (7). Before use, preheat it to further increase its fluidity.

[0067] (2) The hollow steel bar (1) is filled with the mixture using the vacuum injection method. One end of the steel bar that has been placed in Example 1 is sealed with a special sealing head with a shut-off valve, and the other end is connected to the vacuum buffer tank, the vacuum pump and the constant pressure storage tank for storing the preheated mixture in sequence through a hose. The vacuum pump is started to draw the entire system to negative pressure and expel the residual gas in the cavity. Then, the valve connected to the storage tank is slowly opened, and the repair microcapsule mixture (7) is steadily drawn into the cavity (13) of the steel bar by using the pressure difference, and then the valve is closed.

[0068] (3) Sealing and pressure maintenance. After filling, quickly remove the filling equipment and immediately seal the filling port. A certain positive pressure can be maintained in the cavity, which is conducive to the release of the subsequent repair agent.

[0069] Third Embodiment

[0070] However, in practice, especially in reinforced concrete structures with long service lives, the fluidity of the mixture filling the hollow steel bars (1) decreases, thereby losing its function in repairing rust-induced cracks. In addition, in some cases, the solidified mixture can back-block the hollow steel bars (1), which poses a challenge to the implementation of this invention.

[0071] Therefore, to address the long-term performance issues of the repair microcapsule mixture (7), this embodiment provides a long-term alternative solution for the repair microcapsule mixture (7). A low-viscosity waterborne epoxy resin is selected as the base carrier liquid. This resin is chemically stable without the addition of a curing agent. Subsequently, two types of microcapsules, A and B, are incorporated. Type A microcapsules contain conventional concrete repair agents, while type B microcapsules encapsulate curing agents, which can cure the low-viscosity waterborne epoxy resin at the cracks.

[0072] During this process, the B-type microcapsule will not be damaged during the flow process inside the hollow steel bar (1). Instead, it will be near the thin ceramic sheet (24). When the thin ceramic sheet (24) is induced to be damaged by the new crack, the B-type microcapsule is easily broken along with it, causing the curing agent and epoxy resin to mix near the new crack and flow into the interior of the new crack, playing the role of bonding and curing the crack, and wrapping the A-type microcapsule in the cured epoxy resin to achieve the function of secondary repair.

[0073] Fourth embodiment

[0074] To achieve accurate detection and triggering of rust expansion cracks, this embodiment details the installation of the brittle trigger plug and its sensing unit.

[0075] (1) Install the brittle trigger plug (2). The main body of the brittle trigger plug (2) is made of engineering plastic, and the trigger plug groove (21) at its bottom is designed with a 1° micro-taper, which is interference fit with the brittle trigger plug groove (143) on the reinforcing bar. During installation, the plug body is pressed vertically into the groove (143) of the repair fluid notch (14) until its trigger plug edge (22) is flush with the threaded surface of the reinforcing bar. The pressure tube (23) on the plug body is a stainless steel capillary tube with an inner diameter of 0.8 mm.

[0076] (2) Installation and pre-stressing of the thin ceramic sheet (24). The thin ceramic sheet (24) is a ceramic disc with a thickness of 0.3 mm and a diameter slightly larger than the inner diameter of the trigger plug opening (22). The ceramic sheet is placed inside the opening, so that it is naturally slightly convex with the convex surface facing the concrete side. Then, the pressure controller is connected through the pressure tube (23) and the pressure is slowly increased to increase the convexity of the ceramic sheet and generate a stable prestress state. After holding the pressure for 5 minutes, the port of the pressure tube (23) is sealed with a laser spot welder.

[0077] (3) Install the sensing unit (3). In this example, an acoustic emission sensor is selected as the sensing unit (3). The sensor body is glued and fixed to the flat, unthreaded part in the middle of the reinforcing bar using epoxy adhesive. The sensor's signal wire is inserted into a moisture-proof flexible tube, laid along the small groove reserved on the surface of the reinforcing bar, and finally led out from the end of the mold and connected to a junction box. Each reinforcing bar sensor has a unique number.

[0078] Fifth Embodiment

[0079] To ensure the successful molding of concrete components with built-in intelligent systems, this embodiment details the concrete construction process.

[0080] (1) Concrete preparation. Self-compacting concrete with a strength grade of C40 is used to ensure high fluidity of the concrete and a slump expansion of 650mm, without the need for strong vibration.

[0081] (2) Concrete pouring. The mixed self-compacting concrete is slowly and continuously poured into one end of the mold (4), relying on its own weight to flow and fill the entire mold space. The use of an immersion vibrator is strictly prohibited to avoid the vibration energy acting directly on the brittle trigger plug (2) and causing it to break. Only light tapping on the outside of the mold is allowed to assist in venting.

[0082] (3) Curing and demolding. After pouring, cover the concrete surface with plastic film to retain moisture, and let it stand in a standard curing room at 20±2℃ for 24 hours before demolding. After demolding, continue to place the concrete beam (5) in the standard curing room and sprinkle water for curing until 28 days. During the curing period, regularly check the exposed sensing unit (3) lead wire ends to ensure they are intact.

[0083] Sixth Embodiment

[0084] To verify the long-term performance of the system in corrosive environments, this embodiment details the monitoring and accelerated corrosion test.

[0085] (1) Install monitoring equipment (6). Install the cured concrete beam (5) onto the three-point bending test frame. Connect the signal line of the sensing unit (3) led out from each steel bar to a 16-channel acoustic emission signal acquisition instrument. Set the acquisition parameters as follows: sampling frequency 1MHz, threshold value 40dB, and the system is set to continuous monitoring mode.

[0086] (2) Setting up an accelerated corrosion environment. To accelerate the corrosion and rust expansion cracking process of the reinforcing steel, an "electrically accelerated corrosion method" was adopted. Wires were welded to the hollow reinforcing bars (1) at both ends of the concrete beam (5) and connected to a DC constant current power supply as the anode. Sponges soaked in 5% NaCl solution were arranged around the concrete beam, and a stainless steel plate was placed as the cathode. A DC current of constant density was applied. This environment simulated the severe corrosion conditions of chloride salt intrusion.

[0087] Seventh Embodiment

[0088] This embodiment describes the entire process of the system being triggered and completing repair under accelerated corrosion.

[0089] (1) Formation and triggering of rust expansion cracks. After the anodic reaction accelerates the corrosion, the anodic reaction causes rust to continuously form on the surface of the steel bar, resulting in volume expansion. About 15 days later, under a microscope, the first fine radial crack with a width of about 0.05 mm was found on the surface of the concrete cover corresponding to the location of the steel bar. The crack extends exactly to the location of a brittle trigger plug (2).

[0090] (2) Brittle trigger plug rupture and repair agent release. The crack tip generates local compressive stress concentration on the protruding thin ceramic sheet (24). When the stress exceeds the strength of the ceramic sheet, the ceramic sheet undergoes brittle fracture. After fracture, the micro-positive pressure pre-stored in the hollow steel bar (13) and the capillary suction of the crack itself work together to drive the repair microcapsule mixture (7) to flow out rapidly through the repair liquid notch (141) and into the newly formed crack through the funnel-shaped flare (142).

[0091] (3) Fragment synergistic repair. The broken ceramic piece forms several fragments, with larger fragments remaining at the crack opening and smaller fragments flowing into the depths of the crack with the repair fluid. The fluid epoxy resin base liquid quickly penetrates the crack and initially solidifies within 24 hours, bonding and fixing the ceramic fragments, thus forming the initial seal for the crack.

[0092] Eighth embodiment

[0093] This embodiment demonstrates how the system detects repair events and evaluates the repair results.

[0094] Signal capture and event identification. At the moment the brittle trigger plug (2) breaks, the integrated acoustic emission sensor captures a set of distinctive signals. The waveform recorded by the monitoring device (6) shows that: first, there is a low-frequency energy envelope, corresponding to the concrete cracking process, followed by a short-duration, high-frequency transient signal, corresponding to the brittle fracture of the ceramic sheet. Based on this, it is determined that a rust expansion cracking-repair event has occurred.

Claims

1. A self-repair method for rust expansion and cracking in reinforced concrete structures, characterized in that, The method includes: S1. Arrange the hollow steel bars (1) in the mold (4) of the reinforced concrete structure; S2. Fill the cavity with a repair microcapsule mixture (7); S3. A brittle trigger plug (2) and a sensing unit (3) are pre-set on the surface of the hollow steel bar (1); S4. Concrete is poured into the mold (4) of the reinforced concrete structure, and the mold is removed after curing. S5. After the cast reinforced concrete structure (5) is installed in the corrosive environment, it is connected to the monitoring equipment (6) and long-term monitoring is carried out. S6. After the reinforced concrete structure (5) rusts and cracks, the brittle trigger plug (2) is triggered to rupture, and the microcapsule mixture (7) is directionally released. S7, the sensing unit monitors the repair status and locates the cracks.

2. The self-repair method for rust expansion cracking in reinforced concrete structures according to claim 1, characterized in that, The hollow steel bar (1) is built into the mold (4), the brittle trigger plugs (2) are arranged at equal intervals on the surface of the hollow steel bar (1), and the sensing unit (3) is set in the middle of each hollow steel bar (1) to monitor the time and location of the brittle trigger plug (2) breakage repair. The hollow steel bar (1) specifically refers to a threaded steel bar, including threads (11) provided on its surface, wherein the thickness of the hollow wall (12) is not less than 2 / 3 of the cross-sectional radius of the hollow steel bar (1), and the diameter of the steel bar cavity (13) is not greater than 1 / 3 of the cross-sectional diameter of the hollow steel bar (1), for containing the repair microcapsule mixture (7), and repair fluid notches (14) are arranged at equal intervals on the surface of the hollow wall (12) for locking the brittle trigger plug (2); The repair fluid notch (14) includes a repair fluid notch closing (141) for introducing the repair microcapsule mixture (7) into the brittle trigger plug (2) and sending it into the interior of the reinforced concrete structure (5) from the repair fluid notch expansion (142). The repair fluid notch (14) is also provided with a brittle trigger plug slot (143) on the inner side for locking the brittle trigger plug (2). The brittle trigger plug (2) includes a trigger plug slot (21) and a brittle trigger plug slot (143) that are locked together. The trigger plug opening (22) is in contact with the surface of the hollow steel bar (1). The pressure tube (23) passes through the trigger plug opening (22) to increase the pressure inside the brittle trigger plug (2). The trigger plug opening (22) holds the thin ceramic sheet (24) in place to sense rust expansion cracks and release the repair microcapsule mixture (7).

3. The self-repair method for rust expansion cracking in reinforced concrete structures according to claim 1, characterized in that, The thin ceramic sheet (24) of the brittle trigger plug (2) is driven to crack by the occurrence and expansion of rust expansion cracks, so that the repair microcapsule mixture (7) flows from the hollow steel bar (1) into the gap of the rust expansion crack and repairs the rust expansion crack.

4. The self-repair method for rust expansion and cracking in reinforced concrete structures according to claim 1, characterized in that, The thin ceramic sheet (24) of the brittle trigger plug (2) protrudes toward the concrete side and is subjected to internal pressure through the pressure tube (23) during placement to ensure that the thin ceramic sheet (24) breaks toward the concrete side without breaking into the hollow steel bar (1), which would prevent the repair microcapsule mixture (7) from flowing from the hollow steel bar (1) into the gap of the rust-inflated crack due to debris blockage.

5. The self-repair method for rust expansion cracking in reinforced concrete structures according to claim 1, characterized in that, After the thin ceramic sheet (24) of the brittle trigger plug (2) breaks, some of the larger debris generated adheres to the crack opening and acts as aggregate together with the repair microcapsule mixture (7) to inhibit the expansion of the rust-induced cracks. The smaller debris generated enters the crack through the crack opening and, together with the repair microcapsule mixture (7), fills the existing rust-induced cracks.

6. The self-repair method for rust expansion cracking in reinforced concrete structures according to claim 1, characterized in that, The repair microcapsule mixture (7) mainly includes a fluid repair liquid and self-healing microcapsules. In the early stage of rust expansion crack formation, the fluid repair liquid and the fragments of thin ceramic sheets (24) fill and bond the crack. When the rust expansion crack expands for the second time, the self-healing microcapsules repair the crack.

7. The self-repair method for rust expansion cracking in reinforced concrete structures according to claim 1, characterized in that, If the signal monitored by the sensing unit (3) is a composite signal of rust expansion crack opening and thin ceramic sheet (24) rupture, it can be used as a criterion for the initial repair of rust expansion crack.

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