A test device and test method for studying the influence of freeze-thaw-dry-wet coupling on chloride ion permeability

Abstract

The present application relates to a kind of test device and test method for studying the influence of freeze-thaw-dry-wet coupling on chloride ion permeability, including test box, the inner cavity of test box is divided into test chamber for test and control chamber with refrigeration structure, lifting type bearing platform is installed in test chamber, and baffle is symmetrically arranged on two inner side walls of test chamber;Bearing platform is lifted in the direction perpendicular to the bottom surface of test chamber, when bearing platform is lowered to preset height, bearing platform bottom surface is in contact with baffle surface, and test chamber is divided into two airtight spaces, to provide single-side freeze-thaw environment for test piece;When bearing platform is raised to preset height, bearing platform bottom surface is separated from baffle surface, and two spaces in test chamber are communicated, to provide dry-wet cycle environment for test piece;The present application ensures that test can be in ideal coupling environment, and avoid the damage of test piece in transfer process, reduce the time cost of test and reduce economic cost.

Description

Technical Field

[0001] This invention relates to an experimental apparatus and method for studying the effect of freeze-thaw / wet-dry coupling on chloride ion permeability, belonging to the research field of concrete durability testing. Background Technology

[0002] The 21st century is the century of the ocean, and my country's marine industry has developed rapidly. However, marine corrosion occurs constantly, severely damaging marine facilities upon which the blue economy depends. Structures in cold coastal areas are subject to multiple factors, including freeze-thaw cycles and wet-dry cycles. Studies have shown that under the influence of freeze-thaw cycles and wet-dry cycles, the structural density, crack morphology, and extent of development of structures change, leading to varying degrees of increased chloride ion penetration, which seriously affects the service life and safe use of marine structures.

[0003] Currently, freeze-thaw cycles and wet-dry cycles for concrete are conducted using freeze-thaw machines and wet-dry cycle test chambers, respectively. However, wet-dry cycle test chambers are often designed for continuous wet-dry cycles, while in actual engineering practice, due to seasonal variations in effective wave height, the environment in which concrete is exposed to wet-dry cycles is characterized by discontinuous wet-dry interactions, i.e., intermittent exposure to wet-dry cycle conditions. This often results in temporal cross-coupling between wet-dry cycles and freeze-thaw cycles, making traditional test chambers unsuitable for practical applications. If both unilateral freeze-thaw tests and wet-dry cycle tests of concrete specimens are required, two testing machines are needed. Due to the low level of automation, it is impossible to guarantee that the tests will be conducted in an ideal coupled environment, and specimens are prone to damage during transfer, significantly increasing both time and economic costs. Summary of the Invention

[0004] This invention provides an experimental apparatus and method for studying the effect of freeze-thaw / wet-dry coupling on chloride ion permeability, enabling experimental research on the durability of concrete under natural conditions.

[0005] The technical solution adopted by this invention to solve its technical problem is:

[0006] An experimental apparatus for studying the effect of freeze-thaw-wet-dry coupling on chloride ion permeability includes a test chamber that can provide freeze-thaw and wet-dry conditions for the specimen;

[0007] The test chamber is divided into a test chamber for testing and a control chamber for refrigeration. A liftable platform is installed in the test chamber, which is parallel to the bottom surface of the test chamber. Baffles are symmetrically installed on the two inner side walls of the test chamber, which are also parallel to the bottom surface of the test chamber. In the direction parallel to the bottom surface of the test chamber, the distance between the two baffles is less than the length of the platform.

[0008] The platform moves up and down in a direction perpendicular to the bottom of the test chamber. When the platform descends to the preset height, the bottom surface of the platform contacts the surface of the baffle, and the test chamber is divided into two sealed spaces, providing a one-sided freeze-thaw environment for the specimen. When the platform rises to the preset height, the bottom surface of the platform separates from the surface of the baffle, and the two spaces in the test chamber are connected, providing a dry-wet cycle environment for the specimen.

[0009] An inlet is made on the side wall of the test chamber, and an outlet is made on the bottom surface of the test chamber;

[0010] Several infrared sensors arranged in sequence are installed on one side wall of the test chamber, a dryer is installed on the top of the test chamber, and a heating device is installed on the bottom of the test chamber.

[0011] The refrigeration structure includes a loop consisting of an evaporator, a compressor, and a condenser. One port of the evaporator is connected to one port of the compressor, another port of the compressor is connected to one port of the condenser, and the other port of the condenser is connected to the other port of the evaporator. A filter and an expansion valve are installed sequentially on the pipe connecting the condenser and the evaporator. The output port of the evaporator is connected to the water inlet of the test chamber through a pipe.

[0012] A water tank and a control cabinet are also installed in the control chamber. The water tank is connected to the input port of the evaporator, and the control cabinet is electrically connected to the refrigeration structure, the support platform, the infrared sensor, the dryer, and the heating device.

[0013] The water outlet of the test chamber is connected to the water tank, and the water tank is also connected to the water tank through a pipeline;

[0014] As a further preferred embodiment of the present invention,

[0015] The outlet of the test chamber is positioned opposite the inlet of the water tank, and the test chamber and the water tank are connected by a second pipeline, on which a water pump is installed.

[0016] A water pump is installed on the pipeline between the evaporator and the water inlet of the test chamber;

[0017] The water tank and the evaporator are connected by a first pipe;

[0018] As a further preferred embodiment of the present invention, the support platform installed inside the test chamber is raised and lowered by means of a telescopic rod;

[0019] The telescopic rod consists of two rods, and each telescopic rod is simultaneously installed perpendicular to the support platform and the bottom surface of the test chamber.

[0020] As a further preferred embodiment of the present invention, sealing rubber strips are respectively provided on the bottom surface of the bearing platform near the end, and each baffle is provided with a sealing rubber strip near the bearing platform.

[0021] An insulation layer is installed on the inner wall of the test chamber;

[0022] As a further preferred embodiment of the present invention, movable constraint devices are respectively provided at two ends of the surface of the bearing platform, and the constraint devices are provided perpendicular to the surface of the bearing platform.

[0023] The test method using the aforementioned experimental apparatus for studying the effect of freeze-thaw / wet-dry coupling on chloride ion permeability includes the following steps when conducting a unilateral freeze-thaw test:

[0024] Step S11: Place the specimen on the bearing platform and use the moving constraint device to fix the specimen to the surface of the bearing platform;

[0025] Step S12: Operate the control cabinet, start the telescopic rod, and seal the sealing rubber strip on the bottom surface of the platform with the sealing rubber strip on the surface of the baffle, dividing the test chamber into two sealed spaces.

[0026] Step S13: The refrigerant in the water tank returns to the evaporator after passing through the evaporator, compressor, condenser, filter and expansion valve. At this time, the water pump between the evaporator and the water inlet of the test chamber is started to bring the cooled refrigerant into the test chamber through the water inlet of the test chamber.

[0027] Step S14: When the refrigerant injected into the sealed space below the platform in the test chamber reaches the preset height, the infrared sensor located on the side wall of the test chamber is triggered, the water outlet of the test chamber opens, and the refrigerant flows into the water tank, forming a liquid medium flow circulation.

[0028] Step S15: After the specimen has been frozen for the preset time, the control cabinet sends a shutdown command to the refrigeration structure, the water inlet is closed, until all the refrigerant in the test chamber flows into the water tank.

[0029] Step S16: Start the water pump on the second pipeline to input the refrigerant into the test chamber. The control cabinet sends an start command to the heating device to heat the refrigerant in the test chamber to the preset temperature and carry out the single-sided freeze-thaw test of the specimen.

[0030] The test method using the aforementioned experimental apparatus for studying the effect of freeze-thaw / wet-dry coupling on chloride ion permeability includes the following steps when conducting wet-dry cycle tests using the experimental apparatus:

[0031] Step S21: Place the specimen on the support platform and use the moving constraint device to fix the specimen to the surface of the support platform;

[0032] Step S22: Operate the control cabinet, start the telescopic rod, separate the sealing rubber strip on the bottom surface of the platform from the sealing rubber strip on the surface of the baffle, and connect the two sealed spaces in the test chamber.

[0033] Step S23: Start the water pump on the second pipeline, and the salt solution is introduced into the test chamber. When the salt solution reaches the preset height, the infrared sensor located on the side wall of the test chamber is triggered. At this time, the specimen is immersed in the salt solution, and the water pump on the second pipeline is turned off.

[0034] Step S24: After the specimen has been immersed in the salt solution for a preset time, the outlet of the test chamber is opened and the salt solution is delivered to the water tank.

[0035] Step S25: After the salt solution in the test chamber is drained, turn on the dryer to dry the specimen and conduct a wet-dry cycle test on the specimen.

[0036] The experimental method using the aforementioned experimental apparatus for studying the effect of freeze-thaw / wet-dry coupling on chloride ion permeability specifically includes the following steps:

[0037] Step S1: Based on the structural drawing, cast a concrete specimen;

[0038] Step S2: Select specimens that have reached the preset age and place them in the test chamber. Perform a freeze-thaw-wet-dry cross-coupling test using the test methods described in claims 6 and 7, wherein the number of freeze-thaw tests is set to n times and the number of wet-dry cycle tests is set to m times.

[0039] Step S3: Take out the specimen after the freeze-thaw-dry-wet cross-coupling test, use an AC impedance meter to test the AC impedance between two adjacent titanium metal probes, and analyze the resistivity of the solution in the pore layer. Determine the penetration depth of chloride ions based on the degree of difference in resistivity.

[0040] 9. The test method using the test apparatus for studying the effect of freeze-thaw-wet-dry coupling on chloride ion permeability as described in claim 8, characterized in that: the step of designing the specimen in step S1 is to insert titanium metal probes into the mold at a fixed distance, and then pour concrete into the mold.

[0041] The surface of the specimen is defined as the test surface, and epoxy resin is applied to the remaining surfaces of the specimen except for the test surface.

[0042] As a further preferred embodiment of the present invention, in step S2, the number of freeze-thaw tests is set to n times and the number of wet-dry cycle tests is set to m times. The n times and m times are set according to the annual average number of positive and negative temperature alternations in each coastal cold region based on meteorological data statistics.

[0043] By employing the above technical solutions, the present invention has the following beneficial effects compared to the prior art:

[0044] 1. The experimental apparatus provided by this invention will create experimental conditions that are cross-coupled between freeze-thaw cycles and wet-dry cycles;

[0045] 2. The test apparatus provided by the present invention can automatically switch between freeze-thaw test and wet-dry test by adjusting the height of the support platform within the same test apparatus, which can effectively avoid errors caused by manual operation.

[0046] 3. The test apparatus provided by the present invention, based on the same test apparatus, adjusts the number of cycles of freeze-thaw test and wet-dry test in a single coupled test to realistically and accurately simulate the climate conditions of different regions. Attached Figure Description

[0047] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0048] Figure 1 This is a perspective view of a preferred embodiment provided by the present invention;

[0049] Figure 2 This is a schematic diagram of the refrigeration structure provided by the present invention;

[0050] Figure 3 This is a schematic diagram of the experimental device provided by the present invention for conducting a unilateral freeze-thaw test;

[0051] Figure 4 This is a schematic diagram of the structure of the test device provided by the present invention for performing a wet-dry cycle test;

[0052] Figure 5 This is a schematic diagram of the specimen structure provided by the present invention.

[0053] In the diagram: 1 is the test chamber, 2 is the test cavity, 3 is the water tank, 4 is the first pipeline, 5 is the evaporator, 6 is the compressor, 7 is the expansion valve, 8 is the filter, 9 is the condenser, 10 is the water pump, 11 is the restraint device, 12 is the support platform, 13 is the telescopic rod, 14 is the baffle, 15 is the sealing rubber strip, 16 is the infrared sensor, 17 is the control cabinet, 18 is the second pipeline, 19 is the heating device, 20 is the dryer, 21 is the insulation layer, 22 is the test specimen, and 23 is the titanium metal probe. Detailed Implementation

[0054] The present invention will now be described in further detail with reference to the accompanying drawings. In the description of this application, it should be understood that the terms "left side," "right side," "upper part," "lower part," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. "First," "second," etc., do not indicate the importance of the components, and therefore should not be construed as a limitation of the present invention. The specific dimensions used in this embodiment are only for illustrating the technical solution and do not limit the scope of protection of the present invention.

[0055] As described in the background section, current single-sided freeze-thaw tests and wet-dry cycle tests on concrete specimens are conducted using two testing machines. This method was previously not widely adopted due to its application to marine structures. However, with the rapid development of my country's marine industry, specialized research is needed. Therefore, the initial purpose of this application is to provide a structure that integrates freeze-thaw tests and wet-dry cycle tests while ensuring a certain level of accuracy.

[0056] like Figure 1 The image shows an experimental apparatus provided in this application for studying the effect of freeze-thaw-wet-dry coupling on chloride ion permeability, including a test chamber 1, which can provide freeze-thaw and wet-dry conditions for the specimen 22;

[0057] The test chamber is divided into a test chamber 2 for testing and a control chamber with a refrigeration structure. A platform 12 is installed in the test chamber. The platform is parallel to the bottom surface of the test chamber. Baffles 14 are symmetrically arranged on the two inner side walls of the test chamber. The baffles are also parallel to the bottom surface of the test chamber. In the direction parallel to the bottom surface of the test chamber, the distance between the two baffles is less than the length of the platform.

[0058] The platform moves up and down in a direction perpendicular to the bottom of the test chamber. When the platform descends to the preset height, the bottom surface of the platform contacts the surface of the baffle, and the test chamber is divided into two sealed spaces, providing a one-sided freeze-thaw environment for the specimen. When the platform rises to the preset height, the bottom surface of the platform separates from the surface of the baffle, and the two spaces in the test chamber are connected, providing a dry-wet cycle environment for the specimen.

[0059] In other words, a key innovation of the experimental apparatus designed in this application lies in meeting the requirements of both types of tests simply by raising and lowering the platform, combined with a cooling structure. It should be noted that since the experimental apparatus designed in this application is intended to simulate the annual average positive and negative temperature alternation in cold coastal regions, switching between two test cycles, and given that the annual temperature difference is not very frequent, the use of platform raising and lowering to simulate the relevant test environment fully meets the actual usage conditions and service life requirements.

[0060] The following is a detailed description of the specific structure of the test device. These structures are designed to meet different test requirements. A water inlet is opened on the side wall of the test chamber, and a water outlet is opened on the bottom surface of the test chamber. Several infrared sensors 16 arranged in sequence are also installed on one side wall of the test chamber. A dryer 20 is installed on the top of the test chamber, and a heating device 19 is installed on the bottom surface of the test chamber. Figure 2As shown, the refrigeration structure includes a loop consisting of an evaporator 5, a compressor 6, and a condenser 9. One port of the evaporator is connected to one port of the compressor, the other port of the compressor is connected to one port of the condenser, and the other port of the condenser is connected to the other port of the evaporator. A filter 8 and an expansion valve 7 are installed sequentially on the pipe connecting the condenser and the evaporator. The output port of the evaporator is connected to the water inlet of the test chamber through a pipe.

[0061] A water tank 3 and a control cabinet 17 are also installed in the control chamber. The water tank is connected to the input port of the evaporator, and the water outlet of the test chamber is connected to the water tank. The water tank is also connected to the test chamber via a pipeline. The control cabinet (located in...) Figure 1 The design (from the right side of the viewpoint) serves as a central control command transmitter. The control cabinet includes a display screen, power button, refrigeration unit button, heating unit button, and dryer button. The lifting platform and restraint device 11 are also controlled by knobs on the control cabinet.

[0062] The test chamber and the water tank are also connected by a pipeline, namely the second pipeline 18, and a water pump 10 is installed on the second pipeline; a water pump is installed on the pipeline between the evaporator and the water inlet of the test chamber; the water tank and the evaporator are connected by the first pipeline 4.

[0063] As mentioned above, the platform needs to be able to lift and lower to meet the testing requirements. In the preferred embodiment provided in this application, the platform installed inside the testing chamber is lifted and lowered via a telescopic rod 13. The telescopic rod consists of two rods, each perpendicular to both the platform and the bottom surface of the testing chamber. The telescopic rod may include a hollow rod, within which a sliding rod is slidably connected via a slider groove. The extension and retraction are achieved by the sliding rod sliding up and down within the hollow rod.

[0064] During the test, the separation and connection of the two sealed spaces in the test chamber are achieved by raising and lowering the platform. Especially during the separation, it is necessary to ensure a tight connection between the platform and the baffle. Therefore, sealing rubber strips 15 are installed on the bottom surface of the platform near the end, and sealing rubber strips are installed on each baffle near the platform.

[0065] An insulation layer 21 is installed on the inner wall of the test chamber. This insulation layer can be heat-resistant rock wool or foamed cotton.

[0066] When the specimen is placed on the platform for testing, in order to ensure the stability of the specimen, movable constraint devices are set at two ends of the platform surface, and the constraint devices are set perpendicular to the platform surface. The distance between the two constraint devices can be adjusted to limit the specimen. Here, the constraint device can be a plate-shaped structure made of the same material as the platform.

[0067] Since the experimental setup designed in this application needs to meet two experimental environments, the simulation methods for the two experimental environments will be analyzed separately here. Figure 3 As shown, when using a testing apparatus to conduct a unilateral freeze-thaw test, the following steps are included:

[0068] Step S11: Place the specimen on the bearing platform and use the moving constraint device to fix the specimen to the surface of the bearing platform;

[0069] Step S12: Operate the control cabinet, start the telescopic rod, and seal the sealing rubber strip on the bottom surface of the platform with the sealing rubber strip on the surface of the baffle, dividing the test chamber into two sealed spaces.

[0070] Step S13: The refrigerant in the water tank returns to the evaporator after passing through the evaporator, compressor, condenser, filter and expansion valve. At this time, the water pump between the evaporator and the water inlet of the test chamber is started to bring the cooled refrigerant into the test chamber through the water inlet of the test chamber.

[0071] Step S14: When the refrigerant injected into the sealed space below the platform in the test chamber reaches the preset height, the infrared sensor located on the side wall of the test chamber is triggered, the water outlet of the test chamber opens, and the refrigerant flows into the water tank, forming a liquid medium flow circulation.

[0072] Step S15: After the specimen has been frozen for the preset time, the control cabinet sends a shutdown command to the refrigeration structure, the water inlet is closed, until all the refrigerant in the test chamber flows into the water tank.

[0073] Step S16: Start the water pump on the second pipeline to input the refrigerant into the test chamber. The control cabinet sends an start command to the heating device to heat the refrigerant in the test chamber to the preset temperature and conduct a one-sided freeze-thaw test on the specimen.

[0074] Figure 4 As shown, when using a test apparatus to conduct a wet-dry cycle test, the following steps are included:

[0075] Step S21: Place the specimen on the support platform and use the moving constraint device to fix the specimen to the surface of the support platform;

[0076] Step S22: Operate the control cabinet, start the telescopic rod, separate the sealing rubber strip on the bottom surface of the platform from the sealing rubber strip on the surface of the baffle, and connect the two sealed spaces in the test chamber.

[0077] Step S23: Start the water pump on the second pipeline, and the salt solution is introduced into the test chamber. When the salt solution reaches the preset height, the infrared sensor located on the side wall of the test chamber is triggered. At this time, the specimen is immersed in the salt solution, and the water pump on the second pipeline is turned off.

[0078] Step S24: After the specimen has been immersed in the salt solution for a preset time, the outlet of the test chamber is opened and the salt solution is delivered to the water tank.

[0079] Step S25: After the salt solution in the test chamber is drained, turn on the dryer to dry the specimen and conduct a wet-dry cycle test on the specimen.

[0080] Finally, the effect of freeze-thaw / wet-dry coupling on chloride ion permeability was tested using the above-described experimental method. Before the test, the specimen preparation method was determined. Titanium metal probes 23 were inserted into the mold at fixed intervals. Then, concrete was poured into the mold to form a specimen as shown in the image. Figure 5 The specimen shown is defined as the test surface; the remaining surfaces of the specimen, excluding the test surface, are coated with epoxy resin. The test specifically includes the following steps:

[0081] Step S1: Based on the structural drawing, cast a concrete specimen;

[0082] Step S2: Select specimens that have reached the preset age and place them in the test chamber. Use the test method described in claims 6 and 7 to conduct a freeze-thaw-wet cross-coupling test, wherein the number of freeze-thaw tests is set to n times and the number of wet-dry cycles is set to m times. n and m are set according to the annual average number of positive and negative temperature alternations in each coastal cold region based on meteorological data statistics.

[0083] Step S3: Take out the specimen after the freeze-thaw-dry-wet cross-coupling test, use an AC impedance meter to test the AC impedance between two adjacent titanium metal probes, and analyze the resistivity of the solution in the pore layer. Determine the penetration depth of chloride ions based on the degree of difference in resistivity.

[0084] Those skilled in the art will understand that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the same meaning as in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless defined as herein.

[0085] The meaning of "and / or" as used in this application includes situations where each exists alone or both exist simultaneously.

[0086] The term "connection" as used in this application can mean a direct connection between components or an indirect connection between components through other components.

[0087] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. An experimental apparatus for studying the effect of freeze-thaw / wet-dry coupling on chloride ion permeability, characterized in that: Includes a test chamber that provides freeze-thaw and wet / dry conditions for the specimen; The test chamber is divided into a test chamber for testing and a control chamber for refrigeration. A liftable platform is installed in the test chamber, which is parallel to the bottom surface of the test chamber. Baffles are symmetrically installed on the two inner side walls of the test chamber, which are also parallel to the bottom surface of the test chamber. In the direction parallel to the bottom surface of the test chamber, the distance between the two baffles is less than the length of the platform. The platform moves up and down in a direction perpendicular to the bottom of the test chamber. When the platform descends to the preset height, the bottom surface of the platform contacts the surface of the baffle, and the test chamber is divided into two sealed spaces, providing a one-sided freeze-thaw environment for the specimen. When the platform rises to the preset height, the bottom surface of the platform separates from the surface of the baffle, and the two spaces in the test chamber are connected, providing a dry-wet cycle environment for the specimen. An inlet is made on the side wall of the test chamber, and an outlet is made on the bottom surface of the test chamber; Several infrared sensors arranged in sequence are installed on one side wall of the test chamber, a dryer is installed on the top of the test chamber, and a heating device is installed on the bottom of the test chamber. The refrigeration structure includes a loop consisting of an evaporator, a compressor, and a condenser. One port of the evaporator is connected to one port of the compressor, another port of the compressor is connected to one port of the condenser, and the other port of the condenser is connected to the other port of the evaporator. A filter and an expansion valve are installed sequentially on the pipe connecting the condenser and the evaporator. The output port of the evaporator is connected to the water inlet of the test chamber through a pipe. A water tank and a control cabinet are also installed in the control chamber. The water tank is connected to the input port of the evaporator, and the control cabinet is electrically connected to the refrigeration structure, the support platform, the infrared sensor, the dryer, and the heating device. The water outlet of the test chamber is connected to the water tank, and the water tank is also connected to the water tank through a pipeline; The platform installed inside the test chamber is raised and lowered by telescopic rods; there are two telescopic rods, and each telescopic rod is simultaneously set perpendicular to the platform and the bottom surface of the test chamber. Sealing rubber strips are installed on the bottom surface of the base near the end, and sealing rubber strips are installed on each baffle near the base; an insulation layer is installed on the inner wall of the test chamber. Movable restraint devices are installed at both ends of the foundation surface, and the restraint devices are installed perpendicular to the foundation surface.

2. The experimental apparatus for studying the effect of freeze-thaw / wet-dry coupling on chloride ion permeability according to claim 1, characterized in that: The outlet of the test chamber is positioned opposite the inlet of the water tank. The test chamber and the water tank are also connected by a second pipeline, on which a water pump is installed. A water pump is also installed on the pipeline between the evaporator and the inlet of the test chamber. The water tank and the evaporator are connected by a first pipe.

3. The test method using the experimental apparatus described in claim 1 for studying the effect of freeze-thaw / wet-dry coupling on chloride ion permeability, characterized in that: When using a testing apparatus to conduct a unilateral freeze-thaw test, the following steps are included: Step S11: Place the specimen on the bearing platform and use the moving constraint device to fix the specimen to the surface of the bearing platform; Step S12: Operate the control cabinet, start the telescopic rod, and seal the sealing rubber strip on the bottom surface of the platform with the sealing rubber strip on the surface of the baffle, dividing the test chamber into two sealed spaces. Step S13: The refrigerant in the water tank returns to the evaporator after passing through the evaporator, compressor, condenser, filter and expansion valve. At this time, the water pump between the evaporator and the water inlet of the test chamber is started to bring the cooled refrigerant into the test chamber through the water inlet of the test chamber. Step S14: When the refrigerant injected into the sealed space below the platform in the test chamber reaches the preset height, the infrared sensor located on the side wall of the test chamber is triggered, the water outlet of the test chamber opens, and the refrigerant flows into the water tank, forming a liquid medium flow circulation. Step S15: After the specimen has been frozen for the preset time, the control cabinet sends a shutdown command to the refrigeration structure, the water inlet is closed, until all the refrigerant in the test chamber flows into the water tank. Step S16: Start the water pump on the second pipeline to input the refrigerant into the test chamber. The control cabinet sends an start command to the heating device to heat the refrigerant in the test chamber to the preset temperature and conduct a one-sided freeze-thaw test on the specimen.

4. The test method using the experimental apparatus described in claim 1 for studying the effect of freeze-thaw / wet-dry coupling on chloride ion permeability, characterized in that: When using a testing apparatus to conduct a wet-dry cycle test, the following steps are included: Step S21: Place the specimen on the support platform and use the moving constraint device to fix the specimen to the surface of the support platform; Step S22: Operate the control cabinet, start the telescopic rod, separate the sealing rubber strip on the bottom surface of the platform from the sealing rubber strip on the surface of the baffle, and connect the two sealed spaces in the test chamber. Step S23: Start the water pump on the second pipeline, and the salt solution is introduced into the test chamber. When the salt solution reaches the preset height, the infrared sensor located on the side wall of the test chamber is triggered. At this time, the specimen is immersed in the salt solution, and the water pump on the second pipeline is turned off. Step S24: After the specimen has been immersed in the salt solution for a preset time, the outlet of the test chamber is opened and the salt solution is delivered to the water tank. Step S25: After the salt solution in the test chamber is drained, turn on the dryer to dry the specimen and conduct a wet-dry cycle test on the specimen.

5. The test method using the test apparatus described in claim 3 or 4 for studying the effect of freeze-thaw / wet-dry coupling on chloride ion permeability, characterized in that: Specifically, the following steps are included: Step S1: Based on the structural drawing, cast a concrete specimen; The steps for designing the specimen in step S1 are as follows: insert titanium metal probes into the mold at fixed intervals, then pour concrete into the mold; define the surface of the specimen as the test surface, and apply epoxy resin to the remaining surface of the specimen except for the test surface. Step S2: Select specimens that have reached the preset age and place them in the test chamber for freeze-thaw-wet-dry cross-coupling test, wherein the number of freeze-thaw tests is set to n times and the number of wet-dry cycle tests is set to m times; Step S3: Take out the specimen after the freeze-thaw-dry-wet cross-coupling test, use an AC impedance meter to test the AC impedance between two adjacent titanium metal probes, and use an impedance-resistivity conversion model to analyze the pore solution resistivity of the corresponding layer of the adjacent probes. Determine the penetration depth of chloride ions based on the difference in resistivity of each layer.

6. The test method using the experimental apparatus described in claim 5 for studying the effect of freeze-thaw / wet-dry coupling on chloride ion permeability, characterized in that: In step S2, the number of freeze-thaw tests is set to n times, and the number of wet-dry cycle tests is set to m times. The n times and m times are set based on the annual average number of positive and negative temperature alternations in each coastal cold region, as statistically analyzed from meteorological data.

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