A concrete multi-field coupling test device and test method

Abstract

This invention relates to the field of concrete testing technology, and provides a concrete multi-field coupling test device and method. The test device includes an axial loading component, a lateral exposure clamping component, a chemical medium circulation component, an electrical testing component, and a secondary enclosure component. The axial loading component applies an axial compressive load to the specimen. The lateral exposure clamping component is positioned on the non-compression side of the specimen, with its clamping force path independent of the axial compression surface, and together with the specimen, defines a local medium cavity. The chemical medium circulation component is fluidly connected to the local medium cavity. The electrical testing component includes an electromigration circuit, a four-terminal measurement circuit, and an isolation switching module. The isolation switching module connects two circuits in a time-sharing manner and connects the four-terminal measurement circuit after confirming that the residual voltage meets a threshold. The secondary enclosure component surrounds the test area. This invention provides a concrete multi-field coupling test device and method that can achieve both mechanical boundary fidelity and high-precision alternating electrical measurements in concrete durability testing.

Description

Technical Field

[0001] This invention relates to the field of concrete testing technology, specifically to a concrete multi-field coupling test device and test method. Background Technology

[0002] In concrete durability research, simulating the coupling effects of loads, chemical erosion, and electric fields under actual service conditions is crucial. In related technologies, multi-field coupling test devices typically apply chemical media through overall immersion or full surface wrapping. However, their clamping structures often occupy or constrain the axial bearing surface of the specimen, leading to distorted stress distribution and difficulty in accurately reflecting the material response under axial compression. Furthermore, during accelerated electromigration tests, strong electric field excitation generates significant polarization effects and residual potentials at the electrode interfaces. Directly measuring weak electrical signals such as resistivity or impedance is severely hampered by residual interference from the preceding strong electric field, significantly reducing measurement accuracy. Therefore, there is an urgent need for a high-precision multi-field coupling test device and method that can achieve localized chemical media exposure while ensuring the fidelity of the mechanical loading boundary and effectively eliminating electromigration polarization interference. Summary of the Invention

[0003] The purpose of this invention is to overcome the above-mentioned technical deficiencies and propose a concrete multi-field coupling test device and test method to solve the technical problems in related technologies where the mechanical loading boundary is easily interfered with by the fixture and the electrical measurement is easily affected by polarization in concrete durability testing.

[0004] To achieve the above-mentioned technical objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a concrete multi-field coupling test apparatus, comprising: an axial loading assembly configured to apply an axial compressive load to a concrete specimen; a lateral exposure clamping assembly disposed on the non-compression side of the concrete specimen, wherein the clamping force path of the lateral exposure clamping assembly is independent of the axial compression surface of the concrete specimen, and the lateral exposure clamping assembly and the concrete specimen together define a local medium cavity; a chemical medium circulation assembly fluidly connected to the local medium cavity; an electrical testing assembly including an electromigration circuit, a four-terminal measurement circuit, and an isolation switching module, wherein the isolation switching module is configured to connect the electromigration circuit and the four-terminal measurement circuit in a time-sharing manner, and to connect the four-terminal measurement circuit after disconnecting the electromigration circuit and confirming that the residual voltage meets a preset threshold condition; and a secondary enclosure assembly surrounding the test area of ​​the concrete specimen and the lateral exposure clamping assembly.

[0005] In some embodiments, the lateral exposure clamping assembly includes: an exposure box fitted to a first non-compression side of the concrete specimen; a clamping back plate disposed on a second non-compression side of the concrete specimen; and a clamping tie rod disposed outside the axial compression surface of the concrete specimen and connecting the exposure box and the clamping back plate.

[0006] In some embodiments, the lateral exposure clamping assembly further includes a closed-cell elastic sealing gasket, a perforated flow equalization plate, and an insulating liner; the closed-cell elastic sealing gasket is disposed between the exposure box and the concrete specimen, and the opening of the closed-cell elastic sealing gasket and the exposure box together define the local medium cavity; the perforated flow equalization plate is disposed within the local medium cavity and is configured to equalize the flow of the chemical medium entering the local medium cavity; the insulating liner is disposed on the inner wall of the exposure box and is configured to isolate the electric field; the exposure box is provided with a liquid supply connector and a liquid return connector, the chemical medium enters the local medium cavity through the liquid supply connector, is equalized by the perforated flow equalization plate, and flows out through the liquid return connector.

[0007] In some embodiments, the isolation switching module includes: a migration relay connected in series in the electromigration circuit; a measurement relay connected in series in the four-terminal measurement circuit; the migration relay and the measurement relay are interlocked; the electrical testing component further includes a residual voltage sampling unit electrically connected to the electrode of the electromigration circuit, the residual voltage sampling unit being configured to acquire the residual voltage of the electrode and output it to a synchronization controller to trigger the measurement relay to close when the residual voltage meets a preset threshold condition.

[0008] In some embodiments, the migration relay and the measurement relay are hardware cross-interlocked through normally closed contacts, preventing the electromigration circuit and the four-terminal measurement circuit from being simultaneously activated. The electrical testing assembly also includes an excitation protection unit connected between the programmable DC power supply and the migration relay, configured to provide overcurrent and overvoltage protection during the electromigration excitation phase. The residual voltage sampling unit includes an isolation sampling circuit that isolates and samples the voltage across the electrodes before the migration relay is disconnected and the measurement relay is closed, and transmits the sampling signal to the synchronization controller for threshold determination.

[0009] In some embodiments, the chemical medium circulation assembly includes: a thermostatic storage tank configured to store a chemical medium; a circulation pump configured to pump the chemical medium from the thermostatic storage tank to the local medium chamber; an online medium sensor group disposed on the return line, including at least one of a temperature sensor, a pH sensor, a conductivity sensor, and a target ion sensor, configured to detect state parameters of the chemical medium; a replenishment unit connected to the thermostatic storage tank; and a chemical closed-loop controller signal-connected to the circulation pump, the online medium sensor group, and the replenishment unit, configured to adjust the flow rate of the circulation pump and the replenishment volume of the replenishment unit based on the state parameters.

[0010] In some embodiments, the chemical medium circulation assembly further includes: a mechanical overpressure bypass valve, connected in parallel between the liquid supply line and the constant temperature storage tank, configured to independently release pressure when the line pressure exceeds the limit; a liquid supply check valve, disposed on the liquid supply line and located before the inlet of the local medium cavity; a return liquid regulating valve, disposed on the return liquid line and configured to regulate the return liquid flow rate; and a constant temperature heat exchanger, disposed on the liquid supply line and configured to regulate the temperature of the chemical medium entering the local medium cavity.

[0011] In some embodiments, the secondary enclosure assembly includes a secondary enclosure cavity and a removable cavity cover; the loading rod of the axial loading assembly passes through the removable cavity cover, and a dual dynamic sealing assembly is provided between the loading rod and the removable cavity cover; a leakage collecting annular groove is provided between the dual dynamic sealing assemblies, the leakage collecting annular groove is connected to a leakage detection connector, and the leakage detection connector is configured to monitor early leakage of the dual dynamic sealing assembly.

[0012] Secondly, the present invention also provides a method for multi-field coupling testing of concrete, using the multi-field coupling testing apparatus for concrete as described in the first aspect, comprising: applying an axial compressive load to a concrete specimen while maintaining lateral local exposure and chemical medium circulation; closing an electromigration circuit to perform electromigration excitation on the concrete specimen; disconnecting the electromigration circuit and entering a depolarization waiting state; after confirming that the residual electrode voltage of the concrete specimen meets a preset threshold condition, closing a four-terminal measurement circuit to perform four-terminal electrical measurements on the concrete specimen; repeating the alternating cycle of the electromigration excitation and the four-terminal electrical measurements, and simultaneously recording mechanical, chemical, and electrical data.

[0013] In some embodiments, the alternation cycle includes the following stages executed sequentially: Migration excitation stage: closing the migration relay and outputting DC power to connect the electromigration circuit, continuing for a preset migration time or disconnecting the migration relay after reaching a preset charge level; Double disconnection depolarization stage: keeping both the migration relay and the measurement relay disconnected, waiting for a preset depolarization time to allow the electrode polarization effect to decay; Residual voltage confirmation stage: acquiring the residual voltage across the electrodes through the residual voltage sampling unit, determining whether the residual voltage meets the preset threshold condition, and triggering a measurement enable signal if it does; Four-terminal measurement stage: responding to the measurement enable signal, closing the measurement relay, initiating four-terminal measurement sampling, acquiring resistivity or impedance data, disconnecting the measurement relay after sampling is completed, and returning to the migration excitation stage.

[0014] Compared with existing technologies, the present invention provides a concrete multi-field coupling test device and method that, by making the clamping force path of the laterally exposed clamping component independent of the axial bearing surface of the concrete specimen, constructs a closed loop of laterally sealed clamping force that is completely decoupled from the axial mechanical loading path. This structure avoids the occupation or constraint of the specimen bearing surface by traditional clamps, eliminates the interference of lateral clamping force on the axial stress distribution, thereby ensuring the fidelity of the mechanical loading boundary in the multi-field coupling test, and making the test results more realistically reflect the performance response of concrete under actual axial compression.

[0015] Simultaneously, a time-division isolation mechanism is established between the electromigration high-voltage circuit and the four-terminal measurement low-voltage circuit through the isolation switching module in the electrical testing component, and residual voltage confirmation logic is introduced as a precondition for circuit switching. After disconnecting the electromigration circuit, the system does not immediately connect the measurement circuit, but first confirms that the residual voltage of the electrode has decayed to meet the preset threshold condition, thereby reducing the interference of electrode polarization effect and residual electric field on high-precision resistivity or impedance measurement, and improving the test accuracy and data reliability of electrical parameters under multi-field coupling conditions.

[0016] Furthermore, by employing a secondary enclosure component and a dual-stage dynamic seal on the loading rod in conjunction with a leakage collection ring groove, a multi-level safety protection system is formed, effectively preventing the risk of leakage of chemical media during long-term dynamic loading. Combined with the closed-loop control of the chemical media circulation component and the mechanical overpressure bypass protection, the stability of the test environment parameters and the safety of equipment operation are ensured, meeting the stringent requirements of long-cycle multi-field coupling tests. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of a concrete multi-field coupling test device in one embodiment of the present invention; Figure 2 This is a schematic diagram of the structure of a secondary enclosure component in one embodiment of the present invention; Figure 3This is a schematic diagram of the structure of a dual-channel dynamic sealing assembly in one embodiment of the present invention; Figure 4 This is a schematic diagram of the structure of a laterally exposed clamping assembly in one embodiment of the present invention; Figure 5 This is an exploded view of the exposed box and its internal structure in one embodiment of the present invention; Figure 6 This is a schematic diagram of the composition of a chemical medium circulation component in one embodiment of the present invention; Figure 7 This is a schematic diagram of the composition of an electrical testing component in one embodiment of the present invention; Figure 8 This is a timing diagram of multi-field synchronous control, data acquisition, safety interlocking and cyclic testing in one embodiment of the present invention; Figure 9 This is a flowchart illustrating a concrete multi-field coupling test method in one embodiment of the present invention.

[0018] Explanation of reference numerals in the attached figures: 1. Axial loading assembly; 1a. Servo actuator; 1b. Load sensor; 1c. Loading rod; 1d. Self-aligning upper equalizing plate; 1e. Lower equalizing plate; 2. Lateral exposure clamping assembly; 21. Exposure box; 21a. Exposure window; 22. Clamping back plate; 23. Clamping pull rod; 24. Disc spring compensation assembly; 25. Closed-cell elastic sealing gasket; 26. Liquid supply connector; 27. Liquid return connector; 28. Perforated flow equalization plate; 29. ​​Insulating liner; 3. Chemical medium circulation assembly; 31. Thermostatic storage tank; 32. Circulation pump; 33. Online medium sensor group; 34. Liquid replenishment unit; 35. Chemical closed-loop controller; 3a. Liquid supply shut-off valve; 3b. Mechanical overpressure bypass valve; 3c. Liquid supply check valve; 3d. Liquid return regulating valve; 3e. Thermostatic heat exchanger; 3f. Sampling valve; 3g. Metering pump; 3h. Filter; 3i. Flow meter; 3j. Pressure transmitter; 4. Electrical testing components; 41. Electromigration circuit; 42. Four-terminal measurement circuit; 43. Isolation switching module; 431. Migration relay; 432. Measurement relay; 44. Residual voltage sampling unit; 44a. Isolation sampling circuit; 45. Excitation protection unit; 46. Programmable DC power supply; 47. Measuring instrument; 48. Synchronization control components; 481. Synchronization controller; 482. Mechanical acquisition unit; 483. Chemical acquisition unit; 484. Electrical acquisition unit; 485. Safety monitoring unit; 486. Alarm and shutdown unit; 5. Secondary enclosure assembly; 51. Secondary enclosure cavity; 51a. Cleaning inlet; 51b. Cleaning outlet; 52. Removable cavity cover; 6. Localized media cavity; 7. Base; 8. Top plate; 9. Column; 10. Horizontal beam; 11. Double-seal assembly; 111. Sealing gland; 112. Sealing scraper ring; 113. Upper U-shaped dynamic seal; 114. Lower U-shaped dynamic seal; 115. Leakage collection annular groove; 116. Seal element; 12. Leak detection connector; 13. Guide sleeve; 14. Sealing electrode feedthrough; 15. Sealing sensor feedthrough; 16. Lowest point drain valve; 17. Displacement sensor; 18. First field electrode; 19. Second field electrode; 20. Four-probe assembly; 20a. Probe; 100. Concrete specimens. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the invention.

[0020] Please see Figure 1 This invention provides a concrete multi-field coupling test device, which can be used to solve the problems of mechanical boundaries being easily interfered with by clamps and electrical measurements being easily affected by polarization in multi-field coupling tests. In this embodiment, the device includes an axial loading component 1, a lateral exposure clamping component 2, a chemical medium circulation component 3, an electrical testing component 4, and a secondary enclosure component 5. The axial loading component 1 can be used to apply axial compressive load to the concrete specimen 100; the lateral exposure clamping component 2 is set on the non-compression side of the concrete specimen 100, and its clamping force path is independent of the axial compression surface of the concrete specimen 100, and can jointly define the local medium cavity 6 with the concrete specimen 100; the chemical medium circulation component 3 is fluidly connected to the local medium cavity 6, and is responsible for delivering, recovering and regulating the chemical medium to the local medium cavity 6 to maintain the chemical environment parameters (such as concentration, temperature, flow rate, etc.) required for the test; the electrical testing component 4 is used to perform electrical measurements on the concrete specimen 100 and has a time-division isolation function based on residual voltage confirmation; the secondary enclosure component 5 surrounds the test area of ​​the concrete specimen 100 and the lateral exposure clamping component 2, which can form a relatively closed safety protection space to prevent accidental leakage of chemical medium from polluting the external environment or damaging the precision loading equipment, and provide a physical barrier for temperature and humidity control within the test area. In this way, the components work together to build a comprehensive testing platform that provides high fidelity in mechanical loading, controllable chemical environment, and high precision in electrical measurement. On this testing platform, the mechanical loading path and the lateral clamping path can be spatially decoupled, and the electrical test has a time-division isolation mechanism based on residual voltage confirmation, which helps to achieve high-fidelity and high-precision multi-field coupling tests on concrete.

[0021] In some embodiments, such as Figure 1 As shown, the device also includes a base 7, a top plate 8, and multiple columns 9. Each column 9 can be vertically fixed to the upper surface of the base 7 and can be connected to the top plate 8, which is arranged parallel to the base 7. At the same time, a horizontally arranged crossbeam 10 is fixedly installed on the side of the top plate 8 near the base 7. The aforementioned axial loading component 1 can be installed on the crossbeam 10 and can apply an axial compressive load to the concrete specimen 100 on the base 7 in the vertical direction to achieve axial loading.

[0022] For example, in combination Figure 1 and Figure 2 The axial loading assembly 1 may include a servo actuator 1a fixedly mounted on the crossbeam 10. The output end of the servo actuator 1a is connected to a loading rod 1c via a load sensor 1b. The end of the loading rod 1c away from the load sensor 1b is connected to a self-aligning upper pressure equalizing plate 1d. Correspondingly, a lower pressure equalizing plate 1e is also fixedly mounted on the base 7. The lower pressure equalizing plate 1e can be used to support the concrete specimen 100, and the lower pressure equalizing plate 1e and the self-aligning upper pressure equalizing plate 1d are located on the upper and lower sides of the concrete specimen 100, respectively. In practical applications, the servo actuator 1a can drive the self-aligning upper pressure equalizing plate 1d to move downward and compress the upper surface of the concrete specimen 100 through the load sensor 1b and the loading rod 1c, thereby cooperating with the lower pressure equalizing plate 1e to apply an axial compressive load to the concrete specimen 100. Of course, although the device adopts the above-described vertical loading structure in this embodiment, it can also adopt a horizontal or other loading structure in other embodiments, as long as it can apply a stable and measurable axial compressive load to the concrete specimen 100.

[0023] In some embodiments, please refer to Figure 1-2 The secondary enclosure component 5 is mounted on the base 7 and completely surrounds the test area where the concrete specimen 100 is located, providing a relatively enclosed and safe protective space for the specimen. In this embodiment, the secondary enclosure component 5 may include a secondary enclosure cavity 51 and a removable cavity cover 52. The secondary enclosure cavity 51 may be a cavity structure with an open top and a hollow interior, which can be fixedly mounted on the base 7. The removable cavity cover 52 can be detachably fixed to the top opening of the secondary enclosure cavity 51 by bolts to seal the secondary enclosure cavity 51.

[0024] Based on this, the lower equalizing plate 1e of the aforementioned axial loading assembly 1 can be disposed inside the secondary containment cavity 51 and can be fixedly disposed at the bottom of the secondary containment cavity 51. In practical applications, after the removable cavity cover 52 is opened, the concrete specimen 100 can enter the secondary containment cavity 51 through the top opening of the secondary containment cavity 51 and be stably placed on the lower equalizing plate 1e. At the same time, the self-aligning upper equalizing plate 1d of the axial loading assembly 1 can be disposed inside the secondary containment cavity 51 and positioned above the concrete specimen 100; the loading rod 1c can pass through the removable cavity cover 52 and connect to the self-aligning upper equalizing plate 1d inside the secondary containment cavity 51. At this time, the axial loading assembly 1 can perform axial loading on the concrete specimen 100 inside the secondary containment cavity 51.

[0025] It should be understood that the secondary enclosure 51 can form a closed test space, and its removable cover 52 facilitates the loading, unloading, and maintenance of the specimen. A static sealing gasket can be provided between the mating surface of the removable cover 52 and the secondary enclosure 51. This static sealing gasket can form a reliable static sealing interface after the removable cover 52 is locked, preventing chemical vapors or aerosols in the secondary enclosure 51 from escaping from the mating surface. Since the loading rod 1c needs to perform high-frequency, long-stroke axial reciprocating motion under the drive of the servo actuator 1a to apply dynamic loads to the specimen, the interface between it and the stationary removable cover 52 is the weakest potential leakage point in the entire enclosure system.

[0026] In some embodiments, a sealing assembly can be provided between the loading rod 1c and the removable cavity cover 52 to dynamically seal the gap between the loading rod 1c and the removable cavity cover 52, addressing the aforementioned potential leakage points. For example, the top surface of the removable cavity cover 52 is provided with a groove surrounding the loading rod 1c, and the sealing assembly can be integrally embedded in this groove. Furthermore, the sealing assembly can be a double-layer dynamic sealing assembly 11.

[0027] Specifically, such as Figure 3 As shown, Figure 3 This is a schematic diagram of the structure of the dual-channel dynamic sealing assembly 11 in one embodiment of the present invention; wherein, Figure 3 (a) is a partial structural diagram of the connection between the loading rod 1c and the detachable cavity cover 52; Figure 3 (b) is an exploded view of the dual-channel dynamic sealing assembly 11; Figure 3(c) is a top view of the dual-channel dynamic seal assembly 11. At this time, the dual-channel dynamic seal assembly 11 may include a sealing gland 111, which has an open bottom and is embedded in the groove mentioned above. It can be detachably fixed to the removable cavity cover 52 by fasteners. The sealing gland 111 and the bottom surface of the groove form an annular cavity. In this annular cavity, a sealing scraper ring 112, an upper U-shaped dynamic seal 113, and a lower U-shaped dynamic seal 114 are stacked sequentially from top to bottom. The sealing scraper ring 112 is sleeved on the outside of the loading rod 1c. It can remove dust, particles, or liquid film adhering to the surface of the loading rod 1c when it reciprocates, preventing external contaminants from entering the dynamic seal 116 below. The upper U-shaped dynamic seal 113 and the lower U-shaped dynamic seal 114 are arranged at intervals along the axial direction of the loading rod 1c and sleeved on the outside of the loading rod 1c. They are both made of wear-resistant, low-friction polyurethane or fluororubber material. Their U-shaped openings face the pressure source direction (i.e., the inside of the secondary enclosure cavity 51). The pressure of the medium inside the cavity makes the sealing lip tightly adhere to the surface of the loading rod 1c, forming a self-tightening sealing effect.

[0028] Furthermore, the aforementioned dual-channel dynamic seal assembly 11 may also include a leakage collecting annular groove 115. The leakage collecting annular groove 115 surrounds the loading rod 1c and is located between the upper U-shaped dynamic seal 113 and the lower U-shaped dynamic seal 114. The leakage collecting annular groove 115 is an annular component, with an annular groove on the side near the upper U-shaped dynamic seal 113, allowing the side of the upper U-shaped dynamic seal 113 near the leakage collecting annular groove 115 to be embedded in the annular groove. In this case, the annular groove can be used to collect the chemical medium that seeps out after the upper U-shaped dynamic seal 113 wears down. Simultaneously, the leakage collecting annular groove 115 is connected to an external leakage detection connector 12 through an internal radial channel. The leakage detection connector 12 can be fixed to the removable cavity cover 52 or the secondary enclosure cavity 51, and can be used to monitor early leakage of the dual-channel dynamic seal assembly 11. In this embodiment, if the upper U-shaped dynamic seal 113 experiences a slight leakage due to long-term wear, the leaked chemical medium will not immediately overflow the device but will first be trapped in the leakage collecting annular groove 115. At this time, the lower U-shaped dynamic seal 114 remains intact and effective, serving as the final safety barrier. Simultaneously, the leak detection connector 12, connected to the leak collection annular groove 115, can detect the accumulation of media within the groove in real time. For example, a level probe, humidity sensor, or conductivity probe 20a can be installed at the leak detection connector 12. When liquid is detected in the leak collection annular groove 115 or an abnormal increase in conductivity is detected, the synchronous controller 481 can determine that the first seal has experienced early failure and trigger a graded alarm or preventative shutdown maintenance command. This allows operators to intervene promptly within the "window period" before the second seal (i.e., the lower U-shaped dynamic seal 114) is damaged and before external leakage occurs, helping to improve the operational safety and equipment reliability of long-cycle multi-field coupling tests.

[0029] Meanwhile, a guide sleeve 13 can be provided below the loading rod 1c in the double-channel dynamic seal assembly 11. The guide sleeve 13 can be fixedly installed inside the sealing gland 111 or fixedly installed on the inner wall of the shaft hole of the removable cavity cover 52 for the loading rod 1c to pass through. It is sleeved on the outside of the loading rod 1c and can provide guidance and support for the reciprocating motion of the loading rod 1c. The inner wall of the guide sleeve 13 and the outer circle of the loading rod 1c can be precision fitted to ensure the linearity of the movement of the loading rod 1c and reduce the uneven wear of the corresponding sealing lip on the double-channel dynamic seal assembly 11 caused by radial runout, thereby extending the service life of the double-channel dynamic seal assembly 11. In addition, a sealing element 116 (such as a sealing spacer or sealing ring) can be provided on the side of the loading rod 1c away from the double-channel dynamic seal assembly 11 to further improve the sealing effect.

[0030] Furthermore, such as Figure 2 As shown, multiple functional interfaces can be integrated into the cavity wall of the secondary enclosure 51. For example, a sealed electrode feedthrough 14 and a sealed sensor feedthrough 15 are provided on one side of the cavity wall. The sealed electrode feedthrough 14 and the sealed sensor feedthrough 15 can respectively power the migration electrode cable and the sensor cable through the cavity wall. They can use corrosion-resistant sealing fillers or O-ring structures to maintain the airtightness of the secondary enclosure 51 while allowing flexible cable routing and preventing chemical vapors from escaping from the cable penetrations. On this basis, a cleaning inlet 51a and a corresponding cleaning outlet 51b can be provided on the other side of the cavity wall (e.g., the side opposite to the side where the feedthrough is located). This is used to clean and flush the interior of the secondary enclosure 51 or purge and replace it with inert gas before the test, and to remove residual chemical media in the cavity after the test, providing the necessary interface conditions for maintenance and atmosphere control during long-term tests. Meanwhile, a minimum point drain valve 16 can be installed at the bottom of the secondary enclosure cavity 51. After the test, the minimum point drain valve 16 can be used to drain the condensate accumulated in the secondary enclosure cavity 51 or the liquid that has been accidentally leaked, preventing long-term liquid accumulation from causing corrosion of the cavity or microbial growth. In addition, a displacement sensor 17 can be installed on the side wall of the secondary enclosure cavity 51. The displacement sensor 17 is close to the concrete specimen 100 and can be electrically connected to the mechanical acquisition unit 482 via wired or wireless means. In practical applications, the displacement sensor 17 can monitor the deformation of the concrete specimen 100 under axial load in real time, and its measurement signal can be transmitted to the mechanical acquisition unit 482, providing data support for the plotting of stress-strain curves and the calculation of elastic modulus.

[0031] In some embodiments, please refer to Figure 1-2The laterally exposed clamping assembly 2 can be disposed inside the secondary enclosure cavity 51. It can be disposed on the non-compression side of the concrete specimen 100, and its clamping force path is independent of the axial compression surface of the concrete specimen 100. A local medium cavity 6 is jointly defined between the laterally exposed clamping assembly 2 and the concrete specimen 100. Here, "non-compression side" refers to the surface of the concrete specimen 100 that does not directly bear axial pressure during axial loading. "Clamping force path independent of the axial compression surface" means that the lateral clamping force generated by the laterally exposed clamping assembly 2 during fixing and sealing is entirely borne by the structure of the assembly itself, forming a self-balancing closed-loop force. This clamping force will not be transmitted, superimposed, or interfered with on the axial compression surfaces at the upper and lower ends of the concrete specimen 100. This arrangement achieves mechanical decoupling of the concrete specimen 100, avoiding the stress concentration or distribution distortion problems caused by the occupation or constraint of the compression surface by traditional clamps, and ensuring the purity of axial mechanical data. Meanwhile, the localized medium cavity 6 formed by the component and the surface of the specimen allows the chemical medium to act only on a specific local area of ​​the specimen, rather than immersing the specimen as a whole, thus enabling a more accurate simulation of the service conditions of concrete components subjected to localized erosion in actual engineering.

[0032] For example, in conjunction with the appendix Figure 4 , Figure 4 This is a schematic diagram of the structure of the laterally exposed clamping assembly 2 in one embodiment of the present invention; wherein, Figure 4 (a) is a front view of the concrete specimen 100 and the laterally exposed clamping assembly 2; Figure 4 (b) is a bottom view of the concrete specimen 100 and the laterally exposed clamping assembly 2; Figure 4(c) is a schematic diagram of the four-probe assembly 20 on a non-bearing side of the concrete specimen 100. In this case, the lateral exposure clamping assembly 2 may include an exposure box 21, a clamping back plate 22, and a clamping rod 23; wherein the exposure box 21 is fitted against the first non-bearing side of the concrete specimen 100, and the clamping back plate 22 is disposed on the second non-bearing side of the concrete specimen 100, the two being arranged opposite each other to clamp the specimen. The clamping rod 23 connects the exposure box 21 and the clamping back plate 22, and the clamping rod 23 is disposed outside the axial bearing surface of the concrete specimen 100, avoiding the stress areas where the upper and lower ends of the concrete specimen 100 directly contact the equalizing plates (i.e., the self-aligning upper equalizing plate 1d and lower equalizing plate 1e). For example, for a standard cubic specimen, four clamping rods 23 can be provided. These four clamping rods 23 can be divided into two groups, which can be distributed on the third and fourth non-bearing sides of the concrete specimen 100, respectively, and located outside the projection range of the upper and lower bearing surfaces of the concrete specimen 100. Taking the two clamping rods 23 on the third non-bearing side as an example, these two clamping rods 23 can be located on the upper and lower sides of the concrete specimen 100, respectively, and each clamping rod 23 can have its ends connected to the exposure box 21 and the clamping back plate 22 via a bracket. Furthermore, the two clamping rods 23 on the fourth non-bearing side can be symmetrically arranged with the two clamping rods 23 on the third non-bearing side, which will not be elaborated further here.

[0033] Furthermore, the connecting chain of the clamping rod 23 is also equipped with a disc spring compensation group 24. The disc spring compensation group 24 can be connected in series between the end of the clamping rod 23 and the exposed box 21 or the clamping back plate 22, and can be composed of several stacked disc springs. It can be used to provide elastic compensation under the preload of the clamping rod 23. In practical applications, the disc spring compensation group 24, with its elastic energy storage characteristics, can automatically compensate for the loss of preload, maintain the stability of the sealing pressure of the local medium cavity 6, and thus reduce the leakage of chemical media.

[0034] It should be noted that if the tie rod passes through or occupies the bearing surface, the lateral preload will generate additional frictional constraints or local compressive stress concentration on the bearing surface, causing the values ​​measured by the load sensor 1b to include non-pure axial compression components, thereby distorting the mechanical boundary conditions in the multi-field coupling test. By externalizing the clamping tie rod 23, the lateral exposure clamping assembly 2 can construct an independent clamping system that is completely decoupled from the axial mechanical loading chain, ensuring that the axial stress distribution of the concrete specimen 100 remains pure and conforms to the theoretical calculation model while applying chemical medium exposure. Furthermore, it should be understood that although this embodiment adopts a symmetrical arrangement of four clamping tie rods 23, in other embodiments, the number, cross-sectional shape, and specific arrangement of the clamping tie rods 23 can be adjusted according to the specimen size and sealing pressure requirements, as long as the core principle that its force path does not interfere with the axial bearing surface is met.

[0035] For example, in combination Figure 4 and Figure 5 The aforementioned exposure box 21 has an internal cavity, and an exposure window 21a is provided on the side of the exposure box 21 closest to the concrete specimen 100. The side of the exposure box 21 with the exposure window 21a is attached to the first non-pressure-bearing side of the specimen, and together with the concrete specimen 100, it defines the aforementioned local medium cavity 6. Simultaneously, the lateral exposure clamping assembly 2 also includes a closed-cell elastic sealing gasket 25, which can be disposed between the exposure box 21 and the concrete specimen 100. The opening of the closed-cell elastic sealing gasket 25 and the exposure window 21a of the exposure box 21 together define the local medium cavity 6, and can improve the sealing performance of the contact area between the exposure box 21 and the specimen. In this embodiment, the closed-cell elastic sealing gasket 25 can be made of a corrosion-resistant, low-compression-permanent-deformation closed-cell foam material, which can not only adapt to the micro-roughness of the concrete surface to achieve reliable sealing, but also provide uniform contact pressure under the clamping force applied by the clamping rod 23, preventing chemical media leakage.

[0036] Furthermore, the exposure box 21 is equipped with a liquid supply connector 26 and a liquid return connector 27 on the side facing away from the specimen. The chemical medium can be introduced into the local medium cavity 6 through the liquid supply connector 26 and can flow out through the liquid return connector 27. During this process, the chemical medium can contact the specimen through the exposure window 21a of the exposure box 21 and cause chemical corrosion to the specimen. At the same time, the liquid supply connector 26 and the liquid return connector 27 can be connected to the external chemical medium circulation component 3 to realize dynamic renewal and closed-loop control of the medium. This configuration can continuously replenish the consumed reactants and remove corrosion products to maintain a constant erosion driving force on the specimen, thereby simulating the durability degradation process of concrete under long-term service conditions.

[0037] Furthermore, the lateral exposure clamping assembly 2 may also include a perforated flow equalization plate 28, which is disposed within the local medium cavity 6 and can be used to equalize the flow of the chemical medium entering the local medium cavity 6. Specifically, the perforated flow equalization plate 28 is fixedly disposed inside the exposure box 21, parallel to the adjacent surface of the specimen and directly facing the liquid inlet (i.e., the liquid supply connector 26) of the exposure box 21. At this time, the perforated flow equalization plate 28 is located between the liquid inlet (i.e., the aforementioned liquid supply connector 26) of the exposure box 21 and the adjacent surface of the specimen, and has a plurality of micropores or guide grooves distributed on it. When the chemical medium is injected into the exposure box 21 by the liquid supply connector 26, the perforated flow equalization plate 28 can improve the flow distribution within the local medium cavity 6, avoid the fluid directly scouring the surface of the specimen and causing abnormal local erosion rates, and also ensure the consistency of ion concentration and temperature throughout the local medium cavity 6, thereby improving the repeatability of experimental data. In addition, the lateral exposure clamping assembly 2 may also include an insulating liner 29, which may be disposed on the inner wall of the exposure box 21. The insulating liner 29 can be used to isolate the test electric field, so as to strictly limit the electric field inside the concrete specimen 100 and on the effective transmission path between the electrodes, thereby ensuring the accuracy of the electrical test.

[0038] In some embodiments, please refer to Figure 4-5 A first field electrode 18 (E1) is fixedly disposed inside the local dielectric cavity 6, and a second field electrode 19 (E2) is fixedly disposed inside the pressing back plate 22. The first field electrode 18 is parallel to the adjacent surfaces of the concrete specimen 100 and is parallel to the second field electrode 19. At this time, the first field electrode 18 and the second field electrode 19 are located on opposite sides of the specimen, and can be used to apply an electromigration excitation voltage to establish a transverse electric field inside the specimen to drive the directional migration of ions.

[0039] Meanwhile, a four-probe assembly 20 is provided on the third or fourth non-compression side of the concrete specimen 100. The four-probe assembly 20 includes four probes 20a, which can be mounted on the concrete specimen 100 via probe supports. Each probe 20a is equipped with a spring-loaded structure. In this embodiment, the four probes 20a can be configured using the Wenner four-probe 20a configuration. The four probes 20a can be arranged at equal intervals along a straight line and can be sequentially labeled E3 / C1, E4 / P1, E5 / P2, and E6 / C2. The two outer probes 20a (E3, E6) can serve as current injection terminals, and the two inner probes 20a (E4, E5) can serve as potential measurement terminals. Thus, the resistivity calculation depends only on the probe 20a spacing and the measured voltage-current ratio, which helps simplify the data processing flow and improve measurement accuracy.

[0040] It should be noted that, combining the first field electrode 18 (E1), the second field electrode 19 (E2), and the four probes 20a (E3 to E6) of the four-probe assembly 20a, a total of six electrodes are configured on the surface of the concrete specimen 100. These six electrodes form a complete electrode numbering system from E1 to E6. E1 and E2 serve as field electrodes to establish a transverse electromigration field, while E3 to E6, as the four-probe assembly 20, collect potential signals in localized areas on the specimen surface. Their spatial separation avoids interference from the excitation current path on measurement accuracy. During this process, the spring-loaded structure ensures that each probe 20a maintains a constant contact pressure with the concrete surface, adapting to minor deformations of the specimen surface during the test and maintaining stable electrical contact.

[0041] In some embodiments, please refer to Figure 1 and Figure 6 The chemical medium circulation component 3 can be located on the outside of the base 7 and can be in fluid communication with the local medium cavity 6. Its main function is to deliver, recover, and regulate the chemical medium to the local medium cavity 6 to maintain the chemical environmental parameters (such as concentration, temperature, flow rate, etc.) required for the experiment. In this embodiment, the chemical medium circulation component 3 may include a constant-temperature storage tank 31, a circulation pump 32, an online medium sensor group 33, a replenishment unit 34, and a chemical closed-loop controller 35. The constant-temperature storage tank 31 can be used to store the chemical medium and can serve as the source and buffer container for the entire circulation system. The outlet of the constant-temperature storage tank 31 is connected to the liquid supply connector 26 on the exposure box 21 via a liquid supply pipeline. The circulation pump 32 is located on the pipeline between the constant-temperature storage tank 31 and the liquid supply connector 26 and can be used to drive the chemical medium from the constant-temperature storage tank 31 to the exposure box 21. Meanwhile, the return connector 27 of the exposure box 21 is connected to a return pipeline, and the end of the return pipeline away from the exposure box 21 is connected to the return port of the constant temperature storage tank 31. The aforementioned online medium sensor group 33 can be installed on this return pipeline. Based on this, the chemical closed-loop controller 35 can be electrically connected to at least the circulation pump 32 and the online medium sensor group 33 respectively; the replenishment unit 34 can be connected to the inlet of the constant temperature storage tank 31 via a pipeline. In practical applications, the circulation pump 32 can pump the chemical medium from the constant temperature storage tank 31 to the local medium chamber 6, providing the power required for fluid circulation; the online medium sensor group 33 can be used to detect the state parameters of the chemical medium; the chemical closed-loop controller 35 can at least control the operation of the circulation pump 32 based on the acquired state parameters; the replenishment unit 34 can be used to replenish the consumed reactants or adjust the concentration of the constant temperature storage tank 31.

[0042] Furthermore, such as Figure 6As shown, a supply shut-off valve 3a is connected in series on the outlet pipe of the constant temperature storage tank 31. This supply shut-off valve 3a can serve as the main switch for the supply pipeline, used to cut off the fluid passage between the storage tank and the downstream pipeline during system maintenance, pipeline repair, or emergency shutdown. The supply shut-off valve 3a is located upstream of the circulating pump 32, so that when the circulating pump 32 stops running, closing the supply shut-off valve 3a can prevent the medium in the storage tank from continuing to flow to the test piece side due to gravity or siphon effect.

[0043] Meanwhile, the chemical medium circulation assembly 3 also includes a mechanical overpressure bypass valve 3b, a supply check valve 3c, a return regulating valve 3d, and a constant-temperature heat exchanger 3e. In this embodiment, the mechanical overpressure bypass valve 3b is connected in parallel between the supply pipeline and the constant-temperature storage tank 31, and it can be used to independently relieve pressure when the pipeline pressure exceeds the limit. The mechanical overpressure bypass valve 3b can adopt a purely mechanical spring or diaphragm structure, without relying on any electrical signals or controller commands. When the supply pressure rises abnormally due to pipeline blockage, valve malfunction, or specimen crack closure, the mechanical overpressure bypass valve 3b can automatically open, directly guiding the excess medium back to the constant-temperature storage tank 31, thereby preventing pipeline rupture or pump damage.

[0044] The supply check valve 3c can be installed on the supply pipeline and located before the inlet of the local medium chamber 6. When the circulating pump 32 stops working or the system is depressurized, the supply check valve 3c can prevent the liquid in the local medium chamber 6 from flowing back into the supply pipeline due to gravity or back pressure, thus preventing the medium from flowing back through the supply pipeline and also preventing air from entering the pipeline system and affecting the stability of subsequent startup. The return regulating valve 3d can be installed on the return pipeline. It can be used to regulate the return flow rate and can be electrically connected to the aforementioned chemical closed-loop controller 35. In practical applications, the chemical closed-loop controller 35 can adjust the opening of the return regulating valve 3d according to the acquired state parameters, thereby balancing the flow matching between the supply and return liquids. Especially when changing media of different viscosities or adjusting the flow rate range, the return regulating valve 3d can help maintain the pressure stability in the local medium chamber 6 and prevent overflow caused by poor return or negative pressure cavitation caused by excessively fast return. Meanwhile, the return liquid line is also connected to a sampling valve 3f via a sampling line. The sampling valve 3f can be used to collect return liquid samples during the test for offline analysis (such as ion chromatography or chemical titration), or to drain the residual medium in the line after the test.

[0045] Based on this, a constant-temperature heat exchanger 3e can be installed on the liquid supply line. The constant-temperature heat exchanger 3e can be used to regulate the temperature of the chemical medium entering the local medium chamber 6. Since the electromigration process itself generates Joule heat, coupled with fluctuations in ambient temperature, the surface temperature of the specimen is prone to deviating from the set value. The constant-temperature heat exchanger 3e, located at the final stage before the medium enters the specimen, can precisely heat or cool the medium, offsetting heat loss or electromigration heat effects from preceding pipelines, ensuring that the temperature of the medium reaching the specimen surface strictly meets the test requirements. In addition, a filter 3h, a flow meter 3i, and a pressure transmitter 3j can be installed on the liquid supply line as needed. The filter 3h can be used to filter the chemical medium entering the local medium chamber 6; the flow meter 3i can be electrically connected to the chemical closed-loop controller 35, which can be used to collect flow data; the pressure transmitter 3j can be electrically connected to the chemical closed-loop controller 35, which can be used to monitor the fluid pressure in the liquid supply line in conjunction with the chemical closed-loop controller 35 to achieve closed-loop control.

[0046] Furthermore, such as Figure 6 As shown, the online medium sensor group 33 includes at least one of a temperature sensor, a pH sensor, a conductivity sensor, and a target ion sensor, which can be used to detect one or more state parameters of the chemical medium. Meanwhile, the replenishment unit 34 can be a replenishment tank or a concentrate tank, and its outlet is connected to a metering pump 3g via a pipeline. The outlet of the metering pump 3g is connected to the inlet of the constant temperature storage tank 31 via a pipeline. Based on this, the chemical closed-loop controller 35 can be electrically connected to the aforementioned circulation pump 32, online medium sensor group 33, and metering pump 3g, and can also be electrically connected to the supply shut-off valve 3a, return regulating valve 3d, mechanical overpressure bypass valve 3b, and constant temperature heat exchanger 3e. It can perform centralized closed-loop regulation of the entire fluid transport network based on the state parameters obtained by the online medium sensor group 33. For example, the chemical closed-loop controller 35 can control the heating or cooling power output of the constant temperature heat exchanger 3e according to the temperature deviation fed back by the online medium sensor group 33, adjust the injection volume of the metering pump 3g in the replenishment unit 34 according to the concentration deviation, and coordinate the speed of the circulation pump 32 and the opening of the return liquid regulating valve 3d according to the flow deviation, thereby realizing multi-parameter coordinated and stable control of chemical medium temperature, concentration, flow rate and pH value.

[0047] It should be noted that, since the online medium sensor group 33 can collect the medium state flowing out of the local medium cavity 6 in real time and feed the data back to the chemical closed-loop controller 35, the chemical closed-loop controller 35 can dynamically adjust the speed of the circulation pump 32 to change the flow rate, or control the metering pump 3g in the replenishment unit 34 to inject concentrated liquid or pure water to correct the concentration, based on the deviation between the preset target value and the actual detection value. In this way, the closed-loop control mechanism can effectively compensate for the drift of medium parameters caused by specimen absorption, chemical reaction consumption, or evaporation, ensuring that the driving force of chemical erosion acting on the surface of the concrete specimen 100 remains constant and controllable throughout the entire long-cycle multi-field coupling test, thereby improving the repeatability and scientific validity of the test data. It should be understood that the specific selection of the online medium sensor group 33 can be flexibly configured according to the test purpose. For example, when studying chloride ion erosion, the focus is on chloride ion concentration and conductivity, while when studying acidic medium erosion, the focus is on pH value monitoring.

[0048] In some embodiments, please refer to Figure 1 and Figure 7 The aforementioned electrical testing component 4 can be disposed on the outside of the base 7. It includes an electromigration circuit 41, a four-terminal measurement circuit 42, and an isolation switching module 43. The isolation switching module 43 can connect the electromigration circuit 41 and the four-terminal measurement circuit 42 in a time-sharing manner, and can connect the four-terminal measurement circuit 42 after disconnecting the electromigration circuit 41 and confirming that the residual voltage meets the preset threshold condition. In this embodiment, the electromigration circuit 41 can be connected to a programmable DC power supply 46 and the aforementioned first field electrode 18 (E1) and second field electrode 19 (E2). When the electromigration circuit 41 is connected, the first field electrode 18 and the second field electrode 19 can apply a DC electric field (e.g., 30V) to the concrete specimen 100, driving the erosion ions (e.g., chloride ions) to migrate directionally in the concrete pore solution to accelerate the erosion process. The four-terminal measurement circuit 42 can connect the measuring instrument 47 (such as a four-terminal resistivity or impedance measuring instrument 47) to the four-probe assembly 20 (E3-E6) mentioned above. When the four-terminal measurement circuit 42 is turned on, the resistivity or impedance of concrete can be measured by the measuring instrument 47 to characterize the internal ion transport characteristics and micro-damage state of the material.

[0049] During this process, a "residual voltage confirmation" can be introduced through the isolation switching module 43 as a prerequisite for safety and accuracy. After the system completes the electromigration excitation, it will not immediately start the four-terminal measurement, but will first monitor the residual voltage decay at both ends of the electrodes. Only when the residual voltage drops below the preset safety threshold will the four-terminal measurement circuit 42 be allowed to be connected. This helps to eliminate the interference of strong electric field polarization on weak electrical measurements and further improves the test accuracy and data reliability of electrical parameters under multi-field coupling conditions.

[0050] For example, such as Figure 7As shown, the isolation switching module 43 may include a migration relay 431 (K1) and a measurement relay 432 (K2). In this embodiment, the migration relay 431 is connected in series in the electromigration circuit 41 and can be used to control the on / off state of the programmable DC power supply 46 and the test specimen electrode; the measurement relay 432 is connected in series in the four-terminal measurement circuit 42 and can be used to control the on / off state of the measuring instrument 47 and the test specimen probe 20a. Meanwhile, the electrical testing assembly 4 also includes a residual voltage sampling unit 44 for use with the isolation switching module 43. The residual voltage sampling unit 44 can be electrically connected to the electrode of the electromigration circuit 41 and can monitor the potential state at both ends of the electrode in real time. The migration relay 431 and the measurement relay 432 can be interlocked. The residual voltage sampling unit 44 can collect the residual voltage of the electrode and output it to the synchronous controller 481 to trigger the measurement relay 432 to close when the residual voltage meets a preset threshold condition. In practical applications, the migration relay 431 is responsible for opening and closing the high-energy excitation channel, and the measurement relay 432 is responsible for opening and closing the weak signal acquisition channel. An interlocking mechanism prevents both channels from conducting simultaneously. The residual voltage sampling unit 44 acts as a safety gate for switching from the "excitation state" to the "measurement state," allowing the measurement circuit to connect only when the polarization potential at the electrode interface decays to a safe range that does not affect measurement accuracy. This not only protects the measuring instrument 47 from high-voltage surges but also ensures the authenticity of the acquired resistivity or impedance data, avoiding measurement errors caused by the superposition of polarization voltages.

[0051] Furthermore, to enhance system safety and reliability, the migration relay 431 and the measuring relay 432 can be hardware cross-interlocked via normally closed contacts, preventing the electrical migration circuit 41 and the four-terminal measuring circuit 42 from being simultaneously activated. Specifically, in the circuit connection, the normally closed contact of the measuring relay 432 is connected in series in the coil drive circuit of the migration relay 431, and vice versa. In practical applications, as long as either relay is in the energized state, its normally closed contact will open, thereby forcibly cutting off the power supply path of the other relay at the electrical level. Thus, the hardware-based cross-interlocking of the migration relay 431 and the measuring relay 432 provides a higher level of safety. Even if the synchronous controller 481 program malfunctions, crashes, or issues erroneous commands due to electromagnetic interference, it can prevent the two circuits from activating simultaneously, reducing the risk of instrument burnout due to high voltage accidentally entering a low voltage circuit.

[0052] Furthermore, in combination Figure 7 and Figure 8All legal operating states of the isolation switching module 43 can include: State A, where the migration relay 431 is open and the measurement relay 432 is open, corresponding to the depolarization waiting and residual voltage confirmation stage. At this time, the specimen electrodes are completely isolated from all external active circuits and are in a floating state; State B, where the migration relay 431 is closed and the measurement relay 432 is open, corresponding to the electromigration excitation stage, where the programmable DC power supply 46 applies a DC electric field to the specimen; State C, where the migration relay 431 is open and the measurement relay 432 is closed, corresponding to the four-terminal measurement stage, where the measuring instrument 47 connects to the probe 20a for data acquisition; State D, where the migration relay 431 is closed and the measurement relay 432 is closed simultaneously. This state is marked as a prohibited state because the simultaneous connection of the high-voltage circuit and the low-voltage measurement circuit will cause the measuring instrument 47 to be damaged by a high-voltage impact. At the same time, the state machine logic in the synchronous controller 481 strictly constrains all state transitions to use State A as an intermediate transition. That is, when switching from State B to State C, the depolarization waiting and residual voltage confirmation of State A must be completed first, and direct jumps between State B and State C are prohibited.

[0053] Based on this, the electrical testing assembly 4 may further include an excitation protection unit 45, which can be connected between the programmable DC power supply 46 and the migration relay 431. It can provide overcurrent and overvoltage protection during the electromigration excitation phase. In this embodiment, the excitation protection unit 45 may include protective elements such as fast-acting fuses, self-resetting fuses, or electronic current-limiting circuits, and may be located upstream of the migration relay 431. Thus, during electromigration, if the concrete specimen 100 experiences an abnormal current surge due to crack expansion or localized breakdown, or if transient high voltage is generated due to poor contact, the excitation protection unit 45 can respond in milliseconds and cut off or limit the output, preventing the fault from escalating and damaging the power supply or specimen.

[0054] Furthermore, the residual voltage sampling unit 44 may include an isolation sampling circuit 44a. This circuit can isolate and sample the voltage across the electrodes before the migration relay 431 is disconnected and the measuring relay 432 is closed, and transmit the sampled signal to the synchronization controller 481 for threshold determination. Specifically, during the "double-disconnect depolarization phase" after the migration excitation ends, both the migration relay 431 and the measuring relay 432 are disconnected. At this time, the electrodes are completely physically isolated from the external power supply and the measuring instrument 47, and are in a floating state. Within this specific time window, the isolation sampling circuit 44a can non-destructively acquire the residual potential across the electrodes using a high-input-impedance isolation amplifier. It should be understood that because there may be arcing or transient interference at the moment the relay operates, and the excitation current of the measuring instrument 47 itself will change the electrode potential after the measuring relay 432 is closed, only by performing isolation sampling during the double-disconnect silence period can the most accurate polarization attenuation curve be obtained. Simultaneously, the synchronization controller 481 can make real-time judgments based on this sampled value. Only when the residual voltage is lower than a preset threshold (e.g., 1mV or other values ​​set according to the test accuracy) will it output an allow signal to trigger the measurement relay 432 to close. In this way, it can be ensured that each four-terminal measurement is performed under the premise of a relatively stable electrochemical environment at the electrode interface, thereby eliminating the interference of the preceding strong electric field polarization effect on the subsequent weak electrical signal measurement and improving the characterization accuracy of electrical parameter evolution in multi-field coupling experiments.

[0055] Furthermore, although this embodiment describes a relay-based hardware interlocking and isolation sampling scheme, in other embodiments, alternative forms such as solid-state relays, analog switches, and high-precision ADC sampling can be used to achieve the same functional logic, as long as the core timing and safety requirements of "power-off confirmation-measurement" are met.

[0056] Furthermore, in combination Figure 1 and Figure 8The concrete multi-field coupling test device may also include a synchronization control component 48, used to coordinate the operation of various components and record multi-field coupling test data. The synchronization control component 48 includes a synchronization controller 481 and mechanical acquisition units 482, chemical acquisition units 483, and electrical acquisition units 484 connected to it. The mechanical acquisition unit 482 is connected to the servo actuator 1a and the load sensor 1b, and can be used to acquire mechanical parameters such as axial load, displacement of the loading rod 1c, and specimen deformation in real time. The chemical acquisition unit 483 is connected to the chemical closed-loop controller 35, and can be used to acquire chemical parameters such as medium temperature, concentration, pH value, and conductivity in real time. The electrical acquisition unit 484 is connected to the measuring instrument 47 and the residual voltage sampling unit 44, respectively, and can be used to acquire electrical parameters such as resistivity, impedance, and residual voltage in real time. Under the unified scheduling of the synchronization controller 481, the three acquisition units can synchronously record the data of their respective physical fields with precise timestamps, ensuring strict alignment of mechanical, chemical, and electrical data in the time dimension, providing a complete data foundation for subsequent multi-field coupling response analysis.

[0057] Meanwhile, the synchronous control component 48 may also include a safety monitoring unit 485 and an alarm shutdown unit 486. When the safety monitoring unit 485 detects faults such as overload, overpressure, overtemperature, loss of current, leakage or electrical abnormality, the alarm shutdown unit 486 immediately disconnects the power supply and relay, and performs safety operations such as stopping liquid replenishment, stopping circulation or controlled unloading according to the fault type, so as to ensure the safe operation of long-term unattended tests.

[0058] Please see Figure 8 and Figure 9 This invention also provides a method for multi-field coupling testing of concrete. This method can be executed based on the aforementioned multi-field coupling testing device and aims to acquire high-fidelity multi-physics response data in a dynamically coupled environment through specific timing control logic. Specifically, the method includes the following steps: Step S100: Perform a sealing self-test. Specifically, before formal loading and the start of the test cycle, the system first automatically detects the airtightness of the secondary enclosure cavity 51. The synchronous controller 481 determines whether there is a leak in the cavity by monitoring the changes in the readings of the pressure sensor inside the cavity; at the same time, it checks the status of the leak detection connector 12 of the double-channel dynamic sealing assembly 11 at the loading rod 1c to confirm that there are no early leakage signals. If the sealing self-test fails, the system will prevent the execution of subsequent steps and trigger an alarm to ensure that the test is carried out in a safe, sealed environment.

[0059] Step S200: Perform medium stabilization. Specifically, after the sealing self-test passes, the chemical medium circulation component 3 is activated, allowing the chemical medium to circulate between the constant-temperature storage tank 31 and the local medium chamber 6. The online medium sensor group 33 monitors parameters such as temperature, conductivity, and pH at the return end in real time. Once the fluctuation rate of each parameter is less than a preset threshold and remains stable for at least a preset time, it is determined that the medium environment has reached thermodynamic and chemical steady state, and subsequent loading and testing steps can proceed. This step ensures that the chemical erosion driving force is in a controlled and stable state at the start of the test, eliminating data deviations caused by initial unevenness of the chemical medium or the temperature not reaching the set value.

[0060] Step S300: An axial compressive load is applied to the concrete specimen 100 while maintaining lateral local exposure and chemical medium circulation. Specifically, after completing the aforementioned preparatory steps of sealing self-check and medium stabilization, this step can be used to establish the steady-state boundary conditions for the multi-field coupled test. During execution, a predetermined axial compressive load is first applied to the concrete specimen 100 via a servo loading system. This load can be a constant value or a load applied according to a specific spectrum and maintained at a target level to simulate the continuous compressive stress state borne by actual engineering structures. Simultaneously, the chemical medium circulation system continues to operate, maintaining dynamic flow of the corrosive medium at a specific concentration and temperature within the lateral local exposure area of ​​the specimen.

[0061] In step S400, the electromigration circuit 41 is closed to apply electromigration excitation to the concrete specimen 100. Specifically, under the premise of stable mechanical and chemical boundaries, the control system triggers the closure of the migration switch in the isolation switching module 43, connecting the programmable DC power supply 46 to the electrodes at both ends of the specimen (i.e., the first field electrode 18 and the second field electrode 19), thus activating the electromigration circuit 41. During this stage, the DC electric field applied to the specimen drives the erosion ions (such as chloride ions) to migrate directionally in the concrete pore solution, thereby accelerating the erosion process or simulating stray current corrosion conditions. The execution duration of this step can be controlled by a preset time parameter or triggered by an accumulated charge threshold to accommodate the differences in transport characteristics of concrete with different mix proportions. At this time, the system is in an electromigration excitation state, and significant electrochemical reactions and polarization charges accumulate at the electrode interfaces.

[0062] In step S500, the electromigration circuit 41 is disconnected, and the system enters a depolarization waiting state. Specifically, when the electromigration excitation reaches the preset endpoint, the control system immediately disconnects the migration switch, cutting off the external power supply. However, due to the capacitive effect of concrete as a porous medium and the double-layer characteristics of the electrode interface, significant polarization potentials and transient currents remain inside the specimen and on the electrode surface at the moment of power failure. If measurements are performed directly at this time, these residual signals will severely distort the true resistivity or impedance readings. Therefore, this step specifically sets a "depolarization waiting state," that is, a physical silent time window is maintained between the switching intervals of the two circuits. During this window period, both the electromigration circuit 41 and the four-terminal measurement circuit 42 remain disconnected, allowing the charge at the electrode interface to dissipate naturally and the concentration polarization to gradually subside, creating electrochemical steady-state conditions for subsequent high-precision measurements.

[0063] In step S600, after confirming that the residual voltage of the electrodes of the concrete specimen 100 meets the preset threshold condition, the four-terminal measurement circuit 42 is closed to perform four-terminal electrical measurements on the concrete specimen 100. Specifically, during or at the end of the depolarization waiting period, the system monitors the potential decay across the electrodes in real time through the residual voltage sampling unit 44. Only when the detected residual voltage amplitude drops below the preset safety threshold (e.g., 1mV or other set values ​​according to measurement accuracy requirements) is it determined that the polarization interference has been eliminated, thereby triggering the measurement switch to close and initiating four-terminal resistivity or impedance sampling. In this way, by making residual voltage confirmation a necessary prerequisite for measurement initiation, it can be ensured that each set of electrical data is acquired in a pure electrochemical background, which helps to improve the reliability of multi-field coupling test data.

[0064] Step S700 involves repeating the alternating cycle of electromigration excitation and four-terminal electrical measurements, while simultaneously recording mechanical, chemical, and electrical data. Specifically, steps S400 to S600 constitute a complete electrical testing sub-cycle, which is continuously and automatically executed throughout the long-cycle test. In each cycle, utilizing the multiple acquisition units (i.e., mechanical acquisition unit 482, chemical acquisition unit 483, and electrical acquisition unit 484), the system not only records the current resistivity or impedance value but also simultaneously acquires corresponding multi-dimensional parameters such as axial load, displacement, medium concentration, temperature, and pH value, and assigns a precise timestamp to all data. After each alternating cycle, the system performs a data evaluation step, assessing the quality of the multi-source data acquired in the current cycle, including checking whether the resistivity data is within a reasonable range and whether the residual voltage decay curve conforms to the expected decay law. If abnormal data is detected, the system can adaptively adjust the migration excitation intensity or depolarization duration of subsequent cycles, or mark abnormal data points for subsequent analysis. By employing this high-frequency alternating testing and simultaneous recording of multi-source data, researchers can capture the dynamic trajectory of concrete performance degradation under erosion-load coupling, such as identifying the temporal correlation between resistivity abrupt changes and microcrack initiation. It should be understood that although this embodiment describes a standard alternating cycle process, in practical applications, the duration, threshold settings, and cycle frequency of each stage can be adaptively adjusted according to the experimental purpose. As long as the core temporal logic of "power off - depolarization - residual pressure confirmation - measurement" is followed, it should be covered within the scope of protection of this invention.

[0065] In some embodiments, the aforementioned alternation cycle may include the following stages executed sequentially: a migration excitation stage, a double-disconnect depolarization stage, a residual voltage verification stage, and a four-terminal measurement stage. Combined with Figure 8 and Figure 9 The specific implementation mechanisms for each stage are as follows: During the migration excitation phase, the migration relay 431 is closed and a DC power supply is output, connecting the electromigration circuit 41. The migration relay 431 is then disconnected after a preset migration time or when a preset charge is reached. Specifically, the synchronous controller 481 sends a command to the isolation switching matrix to drive the bipolar migration relay 431 to engage, while simultaneously controlling the programmable DC power supply 46 to output according to a set voltage or current mode. The termination condition for this phase can employ dual criteria: for experiments studying ion transport rates, a "preset migration time" can be used as the endpoint to ensure comparability of different specimens within the same time window; conversely, for experiments studying total erosion or electrochemical equivalent, a "preset charge" can be used as the endpoint, i.e., the real-time integrated current value. The output is immediately cut off when the accumulated coulomb count reaches the target value, thereby eliminating deviations in actual charge due to differences in specimen resistance. Regardless of the termination condition used, the system will forcibly disconnect the migration relay 431 at the end of this phase, switching from a high-energy injection state to a high-blocking circuit state.

[0066] Following this, the double-disconnect depolarization stage begins, with both migration relay 431 and measuring relay 432 remaining disconnected, awaiting a preset depolarization time to allow the electrode polarization effect to decay. "Double disconnection" means that both migration relay 431 and measuring relay 432 are physically released, at which point the concrete specimen 100 and its electrode system are completely electrically isolated from all external active circuits and are in a floating state. At this time, utilizing the dielectric relaxation characteristics of concrete as a porous medium and the self-discharge effect of the electrode interface, the double-layer charge and concentration polarization potential accumulated under the strong electric field can be passively dissipated. This avoids the load effect of the input impedance of the measuring instrument 47 on the polarization decay process, allowing the residual voltage to naturally decrease according to the material's inherent time constant. Furthermore, the preset depolarization time should be set greater than the maximum expected relaxation time constant of the specimen under the current moisture content and damage state, for example, it can be set to between 30 and 300 seconds, to ensure that the vast majority of polarization components have decayed to an acceptable level.

[0067] Subsequently, a residual voltage confirmation phase is executed. The residual voltage across the electrodes is acquired by the residual voltage sampling unit 44, and it is determined whether the residual voltage meets the preset threshold condition. If it does, a measurement enable signal is triggered. Specifically, after the double-disconnect depolarization phase ends (or at the end of the overlap with the depolarization phase), the isolation sampling circuit 44a in the residual voltage sampling unit 44 continuously acquires the open-circuit potential between the first field electrode 18 and the second field electrode 19 at a preset sampling frequency (e.g., 100Hz). The synchronous controller 481 processes the acquired voltage sequence in real time. The judgment logic can use the absolute threshold method (e.g., residual voltage amplitude less than 1mV) or the relative change rate method (e.g., voltage change rate of 5 consecutive sampling points less than 0.01mV / s). Only when the judgment result is true will the system generate an internal "measurement enable signal" as the gating condition for state machine transition. If the threshold is not met after the maximum waiting time limit, the system will record an abnormal flag and skip the current measurement or trigger an alarm to prevent deadlock caused by internal short circuits or electrode failure. In this way, the risk of "measurement with defects" caused by the inability of fixed delay to adapt to fluctuations in operating conditions can be eliminated, ensuring the purity of each set of electrical data.

[0068] Finally, the four-terminal measurement phase begins. In response to the measurement enable signal, the measurement relay 432 is closed, initiating four-terminal measurement sampling to acquire resistivity or impedance data. After sampling is complete, the measurement relay 432 is disconnected, and the system returns to the migration excitation phase. Specifically, once the measurement enable signal is received, the synchronous controller 481 immediately drives the measurement relay 432 to engage, connecting the measuring instrument 47 to the four-probe assembly 20. During the measurement window, the measuring instrument 47 can perform single rapid sampling or multi-cycle averaging sampling to further improve the signal-to-noise ratio. After sampling is complete, the system first disconnects the measurement relay 432, returning the specimen to an electrically isolated state. Then, based on a preset cycle count or total duration, it determines whether to continue the next round of testing. If continued, the state machine seamlessly transitions back to the migration excitation phase, starting a new alternation cycle; if terminated, a safety unloading and data saving procedure is executed.

[0069] It should be noted that although this embodiment describes the strict sequential execution of the four stages, in practical applications, the duration, threshold parameters and sampling strategies of each stage can be flexibly adjusted through configuration files. The migration excitation intensity or depolarization duration of the next cycle can even be adaptively modified based on the measurement results of the previous cycle. As long as the core timing logic of "excitation-isolation depolarization-residual voltage confirmation-measurement" is followed, it should be covered within the protection scope of this invention.

[0070] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A concrete multi-field coupling test device, characterized in that, include: An axial loading assembly is configured to apply an axial compressive load to a concrete specimen; A laterally exposed clamping assembly is disposed on the non-compression side of the concrete specimen. The clamping force path of the laterally exposed clamping assembly is independent of the axial compression surface of the concrete specimen. The laterally exposed clamping assembly and the concrete specimen together define a local medium cavity. A chemical medium circulation assembly is in fluid communication with the local medium cavity; An electrical testing assembly includes an electromigration circuit, a four-terminal measurement circuit, and an isolation switching module. The isolation switching module is configured to time-division multiplex the electromigration circuit and the four-terminal measurement circuit, and to connect the four-terminal measurement circuit after disconnecting the electromigration circuit and confirming that the residual voltage meets a preset threshold condition. A secondary enclosure assembly surrounds the test area of ​​the concrete specimen and the laterally exposed clamping assembly.

2. The concrete multi-field coupling test device according to claim 1, characterized in that, The laterally exposed clamping assembly includes: An exposure box is attached to the first non-bearing side of the concrete specimen. A clamping back plate is disposed on the second non-bearing side of the concrete specimen; and A clamping tie rod is positioned outside the axial bearing surface of the concrete specimen and connects the exposure box and the clamping back plate.

3. The concrete multi-field coupling test device according to claim 2, characterized in that, The lateral exposure clamping assembly further includes a closed-cell elastic sealing gasket, a perforated flow equalization plate, and an insulating liner; the closed-cell elastic sealing gasket is disposed between the exposure box and the concrete specimen, and the opening of the closed-cell elastic sealing gasket and the exposure box together define the local medium cavity; the perforated flow equalization plate is disposed in the local medium cavity and is configured to equalize the flow of the chemical medium entering the local medium cavity; the insulating liner is disposed on the inner wall of the exposure box and is configured to isolate the electric field; the exposure box is provided with a liquid supply connector and a liquid return connector, the chemical medium enters the local medium cavity through the liquid supply connector, is equalized by the perforated flow equalization plate, and flows out through the liquid return connector.

4. The concrete multi-field coupling test device according to claim 1, characterized in that, The isolation switching module includes: A migration relay, connected in series in the electromigration circuit; and A measuring relay is connected in series in the four-terminal measuring circuit; The migration relay and the measurement relay are interlocked. The electrical testing assembly also includes a residual voltage sampling unit electrically connected to the electrode of the electromigration circuit. The residual voltage sampling unit is configured to collect the residual voltage of the electrode and output it to the synchronization controller to trigger the measurement relay to close when the residual voltage meets a preset threshold condition.

5. The concrete multi-field coupling test device according to claim 4, characterized in that, The migration relay and the measurement relay are cross-locked by normally closed contacts, so that the electrical migration circuit and the four-terminal measurement circuit cannot be connected at the same time. The electrical testing assembly also includes an excitation protection unit connected between the programmable DC power supply and the migration relay, configured to provide overcurrent and overvoltage protection during the electromigration excitation phase. The residual voltage sampling unit includes an isolation sampling circuit. Before the migration relay is disconnected and the measurement relay is closed, the isolation sampling circuit performs isolated sampling of the voltage across the electrode and transmits the sampling signal to the synchronization controller for threshold determination.

6. The concrete multi-field coupling test device according to claim 1, characterized in that, The chemical medium circulation assembly includes: Thermostatic liquid storage tanks are configured to store chemical media; A circulation pump is configured to pump the chemical medium from the thermostatic storage tank to the local medium chamber; An online medium sensor group, installed on the return liquid line, includes at least one of a temperature sensor, a pH sensor, a conductivity sensor, and a target ion sensor, and is configured to detect the state parameters of the chemical medium. The replenishment unit is connected to the constant-temperature storage tank; and A chemical closed-loop controller, which is signal-connected to the circulating pump, the online medium sensor group, and the replenishment unit, is configured to adjust the flow rate of the circulating pump and the replenishment amount of the replenishment unit based on the state parameters.

7. The concrete multi-field coupling test device according to claim 6, characterized in that, The chemical medium circulation assembly also includes: A mechanical overpressure bypass valve is connected in parallel between the liquid supply line and the constant temperature liquid storage tank, and is configured to independently relieve pressure when the line pressure exceeds the limit; A liquid supply check valve is installed on the liquid supply pipeline, located before the inlet of the local medium chamber; A return flow regulating valve, disposed on the return flow line, is configured to regulate the return flow rate; and A constant-temperature heat exchanger, installed on the liquid supply line, is configured to regulate the temperature of the chemical medium entering the local medium chamber.

8. The concrete multi-field coupling test device according to claim 1, characterized in that, The secondary enclosure assembly includes a secondary enclosure cavity and a removable cavity cover; the loading rod of the axial loading assembly passes through the removable cavity cover, and a double dynamic sealing assembly is provided between the loading rod and the removable cavity cover; a leakage collection annular groove is provided between the double dynamic sealing assemblies, and the leakage collection annular groove is connected to a leakage detection connector, which is configured to monitor early leakage of the double dynamic sealing assembly.

9. A multi-field coupling test method for concrete, characterized in that, The concrete multi-field coupling test apparatus as described in any one of claims 1-8 includes: Axial compressive load was applied to the concrete specimens while maintaining lateral local exposure and chemical media circulation; A closed electromigration loop is used to apply electromigration excitation to the concrete specimen. Disconnect the electromigration circuit and enter the depolarization waiting state; After confirming that the residual electrode voltage of the concrete specimen meets the preset threshold condition, the four-terminal measurement circuit is closed, and four-terminal electrical measurements are performed on the concrete specimen. The alternating cycle of the electromigration excitation and the four-terminal electrical measurement is repeated, and mechanical, chemical and electrical data are recorded simultaneously.

10. The concrete multi-field coupling test method according to claim 9, characterized in that, The alternation cycle includes the following phases executed sequentially: Migration excitation phase: Close the migration relay and output DC power to connect the electric migration circuit, and disconnect the migration relay after a preset migration time or after reaching a preset amount of power. Double disconnection depolarization stage: Keep both the migration relay and the measurement relay disconnected, and wait for a preset depolarization time to allow the electrode polarization effect to decay; Residual voltage confirmation stage: The residual voltage across the electrodes is collected by the residual voltage sampling unit, and it is determined whether the residual voltage meets the preset threshold condition. If it does, a measurement enable signal is triggered. Four-terminal measurement stage: In response to the measurement enable signal, the measurement relay is closed, four-terminal measurement sampling is initiated, resistivity or impedance data is acquired, and after sampling is completed, the measurement relay is disconnected and the process returns to the migration excitation stage.

Images