Testing device for concrete chloride ion migration rule under tensile load and application

Abstract

The invention provides a test device for chloride ion migration law under concrete tensile load, which comprises a bottom plate, the left side and the right side of the top of the bottom plate are respectively provided with a fixed support, and N transparent box bodies and N + 1 traction assemblies are arranged between the two fixed supports, a prismatic concrete test block matched with the transparent box body in size is placed in each transparent box body; a resistance-type strain gauge is arranged at the top of the prismatic concrete test block, and the prismatic concrete test block is in communication connection with a strain measuring instrument through the resistance-type strain gauge; a hydraulic hollow jack is arranged on the left side of the top of the bottom plate and located on the left side of the fixed support on the same side, and a pressure sensor is connected to the left end of the hydraulic hollow jack and is in communication connection with a load displayer. The hydraulic hollow jack is additionally connected with a hydraulic loading pump; a spring baffle is arranged on the right side of the top of the bottom plate and located on the right side of the fixed support on the same side, and a reset spring is arranged between the spring baffle and the fixed support on the same side.

Description

Technical Field

[0001] The present invention relates to the technical field of reinforced concrete durability test, and in particular to a test device and application for testing the migration law of chloride ions under concrete tensile load. The present invention can be used to test and detect the migration law of chloride ions in concrete under long-term tensile load. Background Art

[0002] Reinforced concrete structures in the high-salinity areas of northwest my country and the eastern coastal areas are susceptible to chloride ion corrosion. Chloride ions will penetrate the concrete protective layer through driving factors such as diffusion, convection and electromigration, causing the steel passive film to fail, further forming electrochemical corrosion and accelerating steel corrosion. Steel corrosion will gradually cause cracking of the protective layer and a decrease in the bearing capacity of the structure, causing the structure to be destroyed before its designed service life, causing huge safety problems and economic losses.

[0003] Chloride ion corrosion of concrete is usually slow and is the result of the combined effects of load and environment. Different test designs lead to differences between test results and actual conditions. Load action is usually a simplified term for long-term load action, accompanied by the influence of time effects such as creep, while a rapid chloride ion penetration test after preloading cannot fully reflect the influence of time effects. Bending loads are easy to apply in tests and can simulate both compression and tension states, but the stress on the erosion path is linearly distributed, which violates the single variable principle and is suitable as a simplified simulation of thin-layer components. Concrete is often used as a compressive component, so corrosion tests under tension are rarely involved.

[0004] The test methods and devices need to consider and even demonstrate the similarity of materials, loads and environments. The test research needs to optimize the test methods and test devices to obtain an accurate description of the ion corrosion process due to factors such as different materials, holding time, load type and load level. The current application publication number CN116026693A of the chloride ion corrosion test device under axial tension uses a universal testing machine to apply a load to the concrete specimen. This load is an axial tension cyclic load, which is difficult to meet the requirements of long-term holding, and the local immersion of the side of the specimen with the solution may cause the corrosion solution to spread to other locations.

[0005] In the prior art, various statistical data of other load type test devices are as follows: Fig.12 As shown, it can be clearly seen that the data parameters reflected in the loading time, load type, load level and erosion mode, the current existing experimental devices cannot meet the experimental requirements of long-term axial tension loads, and cannot simulate or reflect the real situation through experimental results. Naturally, they cannot meet the gradually improving needs of concrete structure design and construction.

[0006] It is an inevitable process to continuously improve the test method of concrete durability. In order to meet the needs of durability problems in actual reinforced concrete projects, designing a test device and method for the migration law of chloride ions in concrete under long-term tensile load has become an urgent problem to be solved. Taking prestressed steel cylinder concrete pipe PCCP as an example, the direct and indirect losses caused by the insufficient durability of PCCP in North America and North Africa are beyond people's expectations.

[0007] Due to the effect of water pressure, the protective layer of PCCP is in a state of tension for a long time. In-depth research on the migration law of chloride ions in the protective layer of PCCP under the action of operating load in high-salinity areas is of great significance to the durability design and evaluation of PCCP.

[0008] Currently, there is no technical solution to the above-mentioned technical problems in the market. Summary of the invention

[0009] In view of the above technical problems in the related art, the present disclosure proposes a test device for the migration law of chloride ions under concrete tensile load, which can overcome the above shortcomings of the prior art.

[0010] To achieve the above technical objectives, the technical solution of the present disclosure is implemented as follows: The first object of the present disclosure is to provide a test device for chloride ion migration law under concrete tensile load, which comprises a bottom plate, a fixed support is respectively arranged on the left and right sides of the top of the bottom plate, N transparent boxes and N+1 pulling components are arranged between the two fixed supports, and a prismatic concrete test block of a size suitable for the transparent box is respectively placed in each transparent box; A resistance strain gauge is arranged on the top of the prismatic concrete test block, and the prismatic concrete test block is communicatively connected with the strain measuring instrument via the resistance strain gauge; A hydraulic hollow jack is provided on the left side of the top of the bottom plate. The hydraulic hollow jack is located on the left side of the fixed support on the same side. A pressure sensor is connected to the left end of the hydraulic hollow jack. The pressure sensor is connected to the load display for communication. The hydraulic hollow jack is also connected to a hydraulic loading pump. A spring baffle is provided on the right side of the top of the bottom plate, the spring baffle is located on the right side of the fixed support on the same side, and a return spring is provided between the spring baffle and the fixed support on the same side; The hydraulic hollow jacks, the prismatic concrete test blocks and the spring baffle are arranged in a row along the top of the bottom plate, and are detachably connected to each other through a pulling assembly; the left and right side walls and the fixed support of the transparent box are respectively passed through by the adjacent pulling assemblies, and the left and right side walls and the fixed support of the transparent box are respectively provided with openings for the pulling assemblies to pass through, and the reset spring is sleeved on the pulling assembly connected to the spring baffle.

[0011] Preferably, N>=1.

[0012] Preferably, N is determined according to actual needs, and preferably, N=2. That is, 2 transparent boxes and 3 pulling components are provided between the two fixed supports. When N=2, the hydraulic hollow jack and the leftmost prismatic concrete test block, the two adjacent prismatic concrete test blocks, and the spring baffle and the rightmost prismatic concrete test block are connected respectively through a corresponding pulling component.

[0013] Preferably, a rolling pulley is provided at the bottom of the transparent box, and the transparent box reciprocates on the top of the bottom plate through the rolling pulley.

[0014] Preferably, the pulling assembly includes a universal bearing, a pull rod is provided at each of the left and right ends of the universal bearing, one end of the pull rod is detachably connected to the universal bearing, the other end of the pull rod is detachably connected to a hydraulic hollow jack or a prismatic concrete test block or a spring baffle, and the other end of the pull rod passes through an opening formed in a transparent box or a fixed support.

[0015] Preferably, the top of the prismatic concrete test block is sealed by a polyurea sealing material; Preferably, the opening of the transparent box is sealed.

[0016] Preferably, anchors are symmetrically provided at the left and right ends of the prismatic concrete test block, the anchors comprising a steel plate, a small anchor hole is symmetrically provided at each of the four corners of the steel plate and a large anchor hole is provided in the middle, a small anchor rod is correspondingly provided at each small anchor hole position, and the small anchor rod extends from the corresponding small anchor hole into the interior of the prismatic concrete test block; A large internal threaded rod is correspondingly provided at each large anchor hole position, and the large internal threaded rod extends from the large anchor hole to the inside of the prismatic concrete test block; The axial center lines of the small anchor rod and the large internal threaded rod are parallel to the axial center line of the prismatic concrete test block; The tie rod is provided with an external thread and is threadedly connected with the large internal thread rod, so as to realize the connection between the tie rod and the prismatic concrete test block. That is, the small anchor rod and the large internal thread rod are parallel to the long sides of the front, rear, top and bottom sides of the prismatic concrete test block.

[0017] Preferably, a sealing nut is provided at the opening of the transparent box, and the other end of the pull rod is connected to the prismatic concrete test block after passing through the sealing nut into the transparent box. The transparent box seals the opening through the sealing nut, thereby preventing the corrosive solution from leaking out from the inside of the transparent box through the opening.

[0018] Preferably, the sealing nut comprises an outer nut and an inner nut which are threadedly connected, the outer nut is sleeved on the inner nut, an oil seal is further arranged inside the sealing nut, and the corresponding pull rod passes through the outer nut, the inner nut and the oil seal.

[0019] The second object of the present disclosure is to provide an application of the test device for chloride ion migration law under concrete tensile load, which comprises the following steps: S1: Prepare several prismatic concrete test blocks with the same specifications; S2: Select M prismatic concrete test blocks from all prismatic concrete test blocks as limit test pieces; S3: Place the limit test pieces on the universal testing machine, stretch them slowly until they fail, record the failure load values, and then take the average of all failure load values ​​and define it as the axial tension limit load of the prismatic concrete specimen; S4: setting the corrosion test cycle T and the specified load P, selecting N prismatic concrete test blocks from the remaining prismatic concrete test blocks as corrosion test pieces, placing them in transparent boxes respectively, and completing the assembly of the test device; S5: Operate the hydraulic loading pump to keep all erosion test pieces, pulling components, hydraulic hollow jacks, pressure sensors and return springs in an axially consistent state; S6: Pour NaCl corrosion solution into all transparent boxes respectively, so that each corrosion test piece is soaked in the NaCl corrosion solution respectively; S7: operating the hydraulic loading pump, loading each erosion test piece to a specified load P by viewing the load display, and continuously testing and recording strain data of each erosion test piece by a strain gauge; S8: Periodic inspection to ensure that the concentration of NaCl erosion solution in each transparent box remains constant before and after, and the reading of the load display remains at the specified load P; S9: After the immersion time of each corrosion test piece reaches the corrosion test cycle T, the test device is closed, each corrosion test piece is taken out, and a number of core samples are extracted from the corroded position of each corrosion test piece; S10: Slice each core sample, record the depth of each slice inside the corrosion test piece, grind the slices into powder, test the chloride ion concentration of slices at different depths by titration, and draw a relationship curve between chloride ion penetration concentration and penetration depth; S11: Based on the relationship curve drawn in S10, the relevant chloride ion migration rules are finally summarized.

[0020] Preferably, M depends on actual needs, and preferably, M = 3. M = 3 means that 3 prismatic concrete test blocks are selected as limit test pieces to calculate the axial tensile limit load of the prismatic concrete test blocks by the average value method.

[0021] Preferably, the concentration of the NaCl etching solution is determined according to actual needs, preferably 1%-5%.

[0022] Preferably, each transparent box is provided with NaCl etching solutions of the same or different concentrations, that is, the concentrations of NaCl etching solutions in different transparent boxes can be different or the same, so as to meet the needs of chloride ion testing at different concentrations.

[0023] Preferably, the specified load P<axial tensile limit load. During implementation, each corrosion test piece is loaded to a specified load P, which should be less than the axial tensile limit load it can withstand.

[0024] Preferably, the corrosion test period T depends on actual needs, preferably, T>=60 days.

[0025] Preferably, the eroded location of the erosion test piece used for sampling is preferably an unsealed erosion surface of a prismatic concrete test block.

[0026] Compared with the prior art, the present invention has the following beneficial effects: (A) The present invention has an independent loading device and a load display, and can carry out tests without the help of the existing universal loading equipment in the laboratory. The device occupies a small area and can hold multiple sets of the same equipment to carry out research on different influencing factors at the same time, which can meet the needs of long-term load holding and immersion.

[0027] (B) Compared with the existing pre-loading and then soaking technology, the present disclosure realizes the corrosion of chloride salts while the concrete test block is loaded, which is closer to the actual project.

[0028] (C) Compared with the technique of partial immersion during loading, the present invention immerses the entire test piece in the solution, which is closer to the requirement of one-dimensional corrosion.

[0029] (D) Compared with the prior art, the present invention is simple to operate and does not require much maintenance during long-term loading. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present disclosure or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present disclosure. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0031] Figure 1 Schematic diagram of the application of the test device described in the present disclosure.

[0032] Figure 2 It is a stereoscopic diagram of the partial structure of the test device described in the present disclosure (the prismatic concrete test block, pressure sensor, hydraulic loading pump, and strain gauge are omitted).

[0033] Figure 3These are the front view, top view, left view and right view of the partial structure of the test device described in the present invention (the prismatic concrete test block, pressure sensor, hydraulic loading pump and strain gauge are omitted).

[0034] Figure 4 It is a schematic diagram of the coordination of the base plate and the fixed support described in the present invention.

[0035] Figure 5 It is a schematic diagram of the structure of the prismatic concrete test block (including anchors) described in the present invention.

[0036] Figure 6 It is a three-dimensional diagram of the combination of the prismatic concrete test block (including anchor), polyurea sealing material, tie rod, and resistive strain gauge described in the present disclosure.

[0037] Figure 7 yes Figure 6 Display diagrams and three-dimensional cross-sectional diagrams from other perspectives of the combination.

[0038] Figure 8 It is a schematic diagram of the prismatic concrete test block described in the present disclosure before and after being placed in a transparent box.

[0039] Fig. 9 It is a partial display diagram of the transparent box, prismatic concrete test block, and pulling assembly (pull rod, universal bearing) described in the present invention.

[0040] Fig.10 Schematic diagram of the sealing nut described in the present invention.

[0041] Fig.11 It is a schematic diagram of extracting a core sample from a corrosion test piece in S9 described in the present disclosure.

[0042] Fig.12 It is the statistical data of the load holding time, load type, load level and erosion mode of the current test device in the prior art.

[0043] In the figure: 1, bottom plate; 101, channel steel; 2, fixed support; 3, universal bearing; 4, prismatic concrete test block; 401, small anchor rod; 402, stainless steel plate with holes; 403, large internal threaded rod; 404, unsealed erosion surface; 405, polyurea sealing material; 5, pull rod; 6, hydraulic hollow jack; 7, pressure sensor; 8, load display; 9, hydraulic loading pump; 10, rolling pulley; 11, transparent box; 12, resistance strain gauge; 13, strain gauge; 14, erosion solution; 15, sealing nut; 1501, outer nut; 1502, inner nut; 1503, oil seal; 16, reset spring; 17, spring baffle; 18, core sample. DETAILED DESCRIPTION

[0044] The following will be combined with the drawings in the embodiments of the present disclosure to clearly and completely describe the technical solutions in the embodiments of the present disclosure. Obviously, the described embodiments are only part of the embodiments of the present disclosure, rather than all the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by ordinary technicians in this field belong to the scope of protection of the present disclosure.

[0045] like Figure 1-12 As shown, in order to facilitate the understanding of the above technical solutions of the present disclosure, the above technical solutions of the present disclosure are described in detail below through specific usage methods.

[0046] The first object of the present disclosure is to provide a test device for chloride ion migration law under concrete tensile load, which comprises a bottom plate 1, a fixed support 2 is respectively arranged on the left and right sides of the top of the bottom plate 1, N transparent boxes 11 and N+1 pulling components are arranged between the two fixed supports 2, and a prismatic concrete test block 4 of a size suitable for it is placed in each transparent box 11; A resistance strain gauge 12 is provided on the top of the prismatic concrete test block 4, and the prismatic concrete test block 4 is communicatively connected with a strain measuring instrument 13 via the resistance strain gauge 12; A hydraulic hollow jack 6 is provided on the left side of the top of the bottom plate 1. The hydraulic hollow jack 6 is located on the left side of the fixed support 2 on the same side. A pressure sensor 7 is connected to the left end of the hydraulic hollow jack 6. The pressure sensor 7 is connected to the load display 8 for communication. The hydraulic hollow jack 6 is also connected to a hydraulic loading pump 9. A spring baffle 17 is further provided on the right side of the top of the bottom plate 1. The spring baffle 17 is located on the right side of the fixed support 2 on the same side. A return spring 16 is provided between the spring baffle 17 and the fixed support 2 on the same side. The hydraulic hollow jack 6, the prismatic concrete test blocks 4, and the spring baffle 17 are arranged in a row along the top of the bottom plate 1 in sequence, and are detachably connected to each other through a pulling assembly; the left and right side walls and the fixed support 2 of the transparent box 11 are respectively passed through by adjacent pulling assemblies, and the left and right side walls and the fixed support 2 of the transparent box 11 are respectively provided with openings for the pulling assemblies to pass through, and the reset spring 16 is sleeved on the pulling assembly connected to the spring baffle 17.

[0047] In one embodiment, N>=1.

[0048] In one embodiment, N is determined according to actual needs, preferably, N=2. That is, two transparent boxes 11 and three pulling components are provided between the two fixed supports 2. When N=2, the hydraulic hollow jack 6 and the leftmost prismatic concrete test block 4, the two adjacent prismatic concrete test blocks 4, and the spring baffle 17 and the rightmost prismatic concrete test block 4 are connected by a corresponding pulling component respectively.

[0049] In one embodiment, a rolling pulley 10 is provided at the bottom of the transparent box 11 , and the transparent box 11 reciprocates on the top of the bottom plate 1 via the rolling pulley 10 .

[0050] In a certain embodiment, the pulling assembly includes a universal bearing 3, and a pull rod 5 is provided at each of the left and right ends of the universal bearing 3. One end of the pull rod 5 is detachably connected to the universal bearing 3, and the other end of the pull rod 5 is detachably connected to the hydraulic hollow jack 6 or the prismatic concrete test block 4 or the spring baffle 17. The other end of the pull rod 5 passes through an opening formed in the transparent box 11 or the fixed support 2.

[0051] In one embodiment, the top of the prismatic concrete test block 4 is sealed by a polyurea sealing material 405; In one embodiment, the opening of the transparent box 11 is sealed.

[0052] In one embodiment, anchors are symmetrically provided at the left and right ends of the prismatic concrete test block 4, and the anchors include a steel plate 402, and a small anchor hole is symmetrically provided at each of the four corners of the steel plate 402, and a large anchor hole is provided in the middle, and a small anchor rod 401 is correspondingly provided at each small anchor hole position, and the small anchor rod 401 extends from the corresponding small anchor hole to the inside of the prismatic concrete test block 4; A large internal threaded rod 403 is correspondingly provided at each large anchor hole position, and the large internal threaded rod 403 extends from the large anchor hole to the inside of the prismatic concrete test block 4; The axial center lines of the small anchor rod 401 and the large internal threaded rod 403 are parallel to the axial center line of the prismatic concrete test block 4; The tie rod 5 is provided with an external thread and is threadedly connected with the large internal thread rod 403, so as to realize the connection between the tie rod 5 and the prismatic concrete test block 4. That is, the small anchor rod 401 and the large internal thread rod 403 are parallel to the long sides of the front, rear, top and bottom sides of the prismatic concrete test block 4.

[0053] In one embodiment, a sealing nut 15 is provided at the opening of the transparent box 11, and the other end of the pull rod 5 is connected to the prismatic concrete test block 4 after passing through the sealing nut 15 into the transparent box 11. The transparent box 11 seals the opening through the sealing nut 15, thereby preventing the corrosive solution from leaking out from the inside of the transparent box 11 through the opening.

[0054] In a certain embodiment, the sealing nut 15 includes an outer nut 1501 and an inner nut 1502 that are threadedly connected. The outer nut 1501 is sleeved on the inner nut 1502. An oil seal 1503 is also provided inside the sealing nut 15. The corresponding pull rod 5 passes through the outer nut 1501, the inner nut 1502, and the oil seal 1503.

[0055] In one embodiment, two channel steels 101 may be welded to the bottom of the base plate 1 to improve the bending rigidity.

[0056] In one embodiment, the bottom plate 1 can be treated for corrosion by boiling black and painting.

[0057] In one embodiment, six leveling screws may be provided at the four corners of the base plate 1 to ensure that the device is placed flat on the ground.

[0058] In one embodiment, the base plate 1 may be provided with multiple rows of connection holes corresponding to the fixed supports 2 at the left and right ends, and the fixed supports 2 are also provided with corresponding connection holes, so as to facilitate the adjustment of the position of the fixed supports 2 and adapt to more prismatic concrete test blocks 4 of different sizes.

[0059] In one embodiment, the universal bearing 3 can be designed as a socket-and-spigot type, and can be detachably connected to the pull rod 5 through a latch pin. The socket-and-spigot joint can retain a movable space to ensure that the bearing remains horizontal when subjected to force during testing.

[0060] In one embodiment, the pressure sensor 7 is preferably a spoke-type weighing sensor. The pressure sensor 7 has a diameter of 105 mm, a height of 37 mm, a measuring range of 5 t, and a center threaded hole subjected to force, and the load size is displayed by means of a load display 8. In a certain embodiment, the reset spring 16 can provide reset elasticity because it is restricted between the right fixed support 2 and the spring baffle 17. When implementing, it should be noted that the reset spring 16 should have sufficient rigidity, so that even if the prismatic concrete test block 4 reaches the strength of the axial tension limit load, it can ensure that the experimental device can still be reset after the prismatic concrete test block 4 is removed, and the compression range during loading does not exceed the jacking range of the hydraulic hollow jack 6. The precautions here are common knowledge.

[0061] In one embodiment, the strain gauge 13 is preferably an intelligent static strain gauge with built-in single-chip microcomputer for management, key operation, and dual-window display. Preferably, the strain gauge 13 satisfies the requirements of arbitrary bridge grouping at each measuring point, electronic switch switching measuring point, simultaneous display of force and strain, high-reliability silicone keyboard operation, AC and DC power supply, convenient full setting function, fixed point, scanning and other measurement functions, and supports single-machine, USB-connected, and multi-machine network measurement.

[0062] In one embodiment, the size of the bottom plate 1 is preferably 1500×200×40 mm, and the material is preferably steel.

[0063] In one embodiment, the prismatic concrete test block 4 is preferably a test block cast with a given concrete mix ratio, and anchors are placed at both ends of the test block during casting, such as Figure 5 As shown. The anchor is preferably made of stainless steel. The small anchor rod 401 is 80 mm long and fixed on the perforated stainless steel plate 402. The large internal threaded rod can be 90 mm long and can be fixed in the middle of the perforated stainless steel plate 402. The anchor is used to make the prismatic concrete test block 4 more uniformly stressed during stretching.

[0064] In one embodiment, the pull rod 5 is preferably a stainless steel straight rod with a diameter of 20 mm, which can be used to connect the prismatic concrete test block 4, the universal bearing 3, the spring baffle 17 and the pressure sensor 7, and can pass through the openings of the fixed support 2 and the transparent box 11.

[0065] In a certain embodiment, the specifications of the hydraulic hollow jack 6 are preferably 223 mm in outer diameter, 117 mm in inner diameter, and 223 mm in height. It can be connected to the pressure sensor 7 via a pull rod 5, and the hydraulic hollow jack 6 can be manually pressurized using a hydraulic loading pump 9.

[0066] In a certain embodiment, the transparent box 11 can be made of polypropylene (plastic material) with a thickness of 5 mm. The connection position with the pull rod 5 can be sealed by a sealing nut 15; a plurality of rolling pulleys 10 are arranged at the bottom to minimize the friction generated during the shaft pulling process, while ensuring that the transparent box 11 and the hydraulic hollow jack 6 remain level.

[0067] In one embodiment, the rolling pulley 10 and the sealing nut 15 are preferably made of non-metallic material.

[0068] In one embodiment, the structure of the sealing nut 15 can be as follows: Fig.10 As shown, it adopts a double nut and double rubber ring design, with an oil seal added in the middle. Rotating the outer nut can prevent the corrosion solution from leaking and can prevent the pull rod 5 from being subjected to axial force. After assembling the test device, the sealing nut 15 can be used to ensure the sealing of the connection between the transparent box 11 and the pull rod 5.

[0069] In one embodiment, the coil spring 16 is confined between the fixed support 2 and the spring baffle 17; it has sufficient rigidity to ensure that it returns to its original state after unloading even if the test block reaches the ultimate tensile strength, and the compression range during loading does not exceed the jacking range of the hydraulic hollow jack 6.

[0070] The second object of the present disclosure is to provide an application of the test device for chloride ion migration law under concrete tensile load, which comprises the following steps: S1: Prepare a number of prismatic concrete test blocks 4 with the same specifications; S2: firstly select M prismatic concrete test blocks 4 from all prismatic concrete test blocks 4 as limit test pieces; S3: The limit test pieces are placed on the universal testing machine respectively, and slowly stretched until failure, and the failure load values ​​are recorded respectively. Then, the average value of all the failure load values ​​is taken and defined as the axial tension limit load of the prismatic concrete specimen 4; S4: setting the corrosion test cycle T and the specified load P, selecting N prismatic concrete test blocks 4 from the remaining prismatic concrete test blocks 4 as corrosion test pieces, placing them in the transparent box 11 respectively, and completing the assembly of the test device; S5: operate the hydraulic loading pump 9 to keep all the erosion test pieces, the pulling assembly, the hydraulic hollow jack 6, the pressure sensor 7 and the return spring 16 in an axially consistent state; S6: Pour NaCl corrosion solution into all transparent boxes 11 respectively, so that each corrosion test piece is soaked in the NaCl corrosion solution respectively; S7: operate the hydraulic loading pump 9, load each erosion test piece to a specified load P by viewing the load display 8, and continuously test and record the strain data of each erosion test piece by the strain gauge 13; S8: Periodic inspection to ensure that the concentration of the NaCl erosion solution in each transparent box 11 remains constant before and after, and the reading of the load display 8 remains at the specified load P; S9: After the immersion time of each corrosion test piece reaches the corrosion test cycle T, the test device is closed, each corrosion test piece is taken out, and a number of core samples 18 are extracted from the corroded position of each corrosion test piece; S10: Slice each core sample 18, record the depth of each slice inside the corrosion test piece, grind the slices into powder, test the chloride ion concentration of slices with different depths by titration method, and draw a relationship curve between chloride ion penetration concentration and penetration depth; S11: Based on the relationship curve drawn in S10, the relevant chloride ion migration rules are finally summarized.

[0071] In one embodiment, M is determined according to actual needs, and preferably, M = 3. M = 3 means that three prismatic concrete test blocks 4 are selected as limit test pieces to calculate the axial tensile limit load of the prismatic concrete test blocks 4 by the average value method.

[0072] In one embodiment, the concentration of the NaCl etching solution is determined according to actual needs, and is preferably 1%-5%.

[0073] In one embodiment, NaCl etching solutions of the same or different concentrations are respectively configured in each transparent box 11. That is, the concentrations of NaCl etching solutions in different transparent boxes 11 can be different or the same, so as to meet the needs of chloride ion testing at different concentrations.

[0074] In one embodiment, the specified load P is less than the axial tensile limit load. During implementation, each corrosion test piece is loaded with a specified load P, which should be less than the axial tensile limit load it can withstand.

[0075] In one embodiment, the corrosion test period T depends on actual needs, preferably, T>=60 days.

[0076] In one embodiment, the corroded location of the corrosion test piece used for sampling is preferably the unsealed corroded surface 404 of the prismatic concrete test block 4 .

[0077] In order to more fully illustrate the implementation process of the disclosed method, the following implementation examples may be referred to: (Step 1) Cast a batch of prismatic concrete test blocks 4 with anchors as described above.

[0078] (Step 2) Randomly select 3 test blocks as limit test pieces, conduct limit axial tension test, and determine the ultimate tensile strength of the prismatic concrete test block 4.

[0079] (Step 3) The selected limit test pieces are placed on a universal testing machine, stretched slowly until failure, and the failure load values ​​are recorded respectively. Then, the average value of all failure load values ​​is taken and defined as the axial tension limit load of the prismatic concrete specimen 4. The meaning of the axial tension limit load is the ultimate tensile strength of the prismatic concrete specimen 4.

[0080] (Step 4) Set the corrosion test cycle T and the specified load P, select two more prismatic concrete test blocks 4 from the remaining prismatic concrete test blocks 4 as corrosion test pieces, place them in two transparent boxes 11 respectively, and complete the full assembly of the test device. Pay attention to the connection firmness of the corrosion test piece, the resistance strain gauge 12, and the strain gauge 13. The specified load P is set to 60% of the axial tension limit load. The corrosion test cycle T is the predetermined corrosion test duration.

[0081] (Step 5) Check whether all erosion test pieces, pulling components, hydraulic hollow jacks 6, pressure sensors 7 and reset springs 16 are in axially consistent state. If not, operate the hydraulic loading pump 9 to load appropriately, so that all erosion test pieces, pulling components, hydraulic hollow jacks 6, pressure sensors 7 and reset springs 16 are in axially consistent state.

[0082] (Step 6) Add 5% NaCl solution into the transparent box 11, so that each corrosion test piece is immersed in the NaCl corrosion solution.

[0083] (Step 7) Operate the hydraulic loading pump 9, and load each corrosion test piece to the specified load P by viewing the load display 8, and continuously test and record the strain data of each corrosion test piece through the strain gauge 13. The strain data comes from the induction transmission of the resistance strain gauge 12.

[0084] (Step 8) Periodic inspection to ensure that the concentration of the NaCl erosion solution in each transparent box 11 remains constant before and after, and the reading of the load display 8 remains at the specified load P. Note: If the load decreases during the loading process, press the loading pump to replenish the pressure in time to ensure that it is maintained at the specified load P; if the concentration of the NaCl solution changes during the immersion process, it should be handled in time.

[0085] (Step 9) When the erosion reaches the erosion test cycle T, the test device is closed, each erosion test piece is taken out, and a number of core samples 18 are extracted from the eroded position of each erosion test piece. A water drill can be used to drill the core sample 18 on the erosion surface of each erosion test piece.

[0086] (Step 10) Slice each core sample 18 separately, record the depth of each slice inside the corrosion test piece, then grind the slices into powder, use titration method to test the chloride ion concentration of slices with different depths, and draw a relationship curve between chloride ion penetration concentration and penetration depth.

[0087] (Step 11) Based on the relationship curve drawn by S10, the relevant chloride ion migration rules are finally summarized.

[0088] During the implementation process, multiple experimental devices can be used to carry out different tests on the same batch of test blocks. The tests may include a blank control group, different NaCl solution concentrations, different holding sizes, different holding times, different concrete mix ratios, etc. By drawing a curve showing the relationship between chloride ion intrusion concentration and intrusion depth, the difference in the curve can be compared for different material ratios, immersion times, and load sizes. More suitable concrete materials can be selected to explore the migration law of chloride ions under different loads and holding times. To summarize the migration law of chloride ions, we can summarize accurate and reliable general laws of chloride ion migration in concrete under real load conditions based on the law of non-steady-state diffusion and the plastic damage relationship of concrete under load.

[0089] In summary, through the unique design of the present invention, compared with the prior art, the present invention has the following beneficial effects: (A). The present invention has an independent loading device and a load display, and can carry out tests without the help of the existing universal loading equipment in the laboratory. The device occupies a small area, and can place multiple sets of the same equipment to carry out research on different influencing factors at the same time, which can meet the needs of long-term loading and immersion. (B). Compared with the existing pre-loading and re-immersion technology, the present invention realizes chloride salt erosion while loading the concrete test block, which is closer to the actual project. (C). Compared with the technology of local immersion during loading, the present invention immerses the entire test block in the solution, which is closer to the requirement of one-dimensional erosion. (D). Compared with the prior art, the present invention is simple to operate and does not require too much maintenance during long-term loading.

[0090] The above description is only a preferred embodiment of the present disclosure and is not intended to limit the present disclosure. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present disclosure should be included in the protection scope of the present disclosure.

Claims

1. A test device for chloride ion migration law under concrete tensile load, characterized in that: It comprises a bottom plate (1), wherein a fixed support (2) is respectively arranged on the left and right sides of the top of the bottom plate (1), N transparent boxes (11) and N+1 pulling components are arranged between the two fixed supports (2), and a prismatic concrete test block (4) of a size suitable for the transparent box (11) is respectively placed in each of the transparent boxes (11); the N>=1; A resistance strain gauge (12) is provided on the top of the prismatic concrete test block (4), and the prismatic concrete test block (4) is communicatively connected to the strain measuring instrument (13) via the resistance strain gauge (12); A hydraulic hollow jack (6) is further provided on the left side of the top of the base plate (1), and the hydraulic hollow jack (6) is located on the left side of the fixed support (2) on the same side. A pressure sensor (7) is connected to the left end of the hydraulic hollow jack (6), and the pressure sensor (7) is in communication connection with a load display (8); the hydraulic hollow jack (6) is further connected to a hydraulic loading pump (9); A spring baffle (17) is further provided on the right side of the top of the bottom plate (1), the spring baffle (17) is located on the right side of the fixed support (2) on the same side, and a return spring (16) is provided between the spring baffle (17) and the fixed support (2) on the same side; The hydraulic hollow jack (6), the prismatic concrete test blocks (4), and the spring baffle (17) are arranged in a row along the top of the bottom plate (1), and are detachably connected to each other via a pulling assembly; the left and right side walls of the transparent box (11) and the fixed support (2) are respectively penetrated by the adjacent pulling assemblies, and the left and right side walls of the transparent box (11) and the fixed support (2) are respectively provided with openings for the pulling assemblies to pass through, and the reset spring (16) is sleeved on the pulling assembly connected to the spring baffle (17).

2. The test device for chloride ion migration law under concrete tensile load according to claim 1 is characterized in that: The N=2, that is, a total of two transparent boxes (11) and three pulling components are arranged between the two fixed supports (2).

3. The test device for chloride ion migration law under concrete tensile load according to claim 1 is characterized in that: A rolling pulley (10) is provided at the bottom of the transparent box (11), and the transparent box (11) moves back and forth on the top of the bottom plate (1) via the rolling pulley (10).

4. The test device for chloride ion migration law under concrete tensile load according to claim 1, characterized in that: The pulling assembly includes a universal bearing (3), and a pull rod (5) is provided at each of the left and right ends of the universal bearing (3). One end of the pull rod (5) is detachably connected to the universal bearing (3), and the other end of the pull rod (5) is detachably connected to the hydraulic hollow jack (6) or the prismatic concrete test block (4) or the spring baffle (17). The other end of the pull rod (5) passes through an opening formed in the transparent box (11) or the fixed support (2).

5. The test device for chloride ion migration law under concrete tensile load according to claim 1, characterized in that: The top of the prismatic concrete test block (4) is sealed by a polyurea sealing material (405); The opening of the transparent box (11) is sealed.

6. The test device for chloride ion migration law under concrete tensile load according to claim 5, characterized in that: Anchors are symmetrically provided at the left and right ends of the prismatic concrete test block (4), the anchors comprising a steel plate (402), the steel plate (402) having a small anchor hole symmetrically provided at each of the four corners and a large anchor hole provided in the middle, a small anchor rod (401) corresponding to each small anchor hole, and the small anchor rod (401) extending from the corresponding small anchor hole into the interior of the prismatic concrete test block (4); A large internal threaded rod (403) is correspondingly provided at each large anchor hole position, and the large internal threaded rod (403) extends from the large anchor hole into the interior of the prismatic concrete test block (4); The axial center lines of the small anchor rod (401) and the large internally threaded rod (403) are parallel to the axial center line of the prismatic concrete test block (4); The tie rod (5) is provided with an external thread and is threadedly connected to the large internal thread rod (403), thereby achieving connection between the tie rod (5) and the prismatic concrete test block (4).

7. The test device for chloride ion migration law under concrete tensile load according to claim 5, characterized in that: A sealing nut (15) is provided at the opening of the transparent box (11), and the other end of the pull rod (5) penetrates into the transparent box (11) through the sealing nut (15) and is connected to the prismatic concrete test block (4).

8. The test device for chloride ion migration law under concrete tensile load according to claim 7, characterized in that: The sealing nut (15) comprises an outer nut (1501) and an inner nut (1502) which are threadedly connected. The outer nut (1501) is sleeved on the inner nut (1502). An oil seal (1503) is further provided inside the sealing nut (15). The corresponding pull rod (5) passes through the outer nut (1501), the inner nut (1502) and the oil seal (1503).

9. Application of the test device for chloride ion migration law under concrete tensile load according to claims 1-8, characterized in that: The following steps are involved: S1: preparing a plurality of prismatic concrete test blocks (4) of the same specifications; S2: Selecting M prismatic concrete test blocks (4) from all the prismatic concrete test blocks (4) as limit test pieces; S3: placing the limit test pieces on a universal testing machine respectively, slowly stretching them until they fail, recording the failure load values ​​respectively, and then taking the average value of all the failure load values ​​and defining it as the axial tensile limit load of the prismatic concrete test block (4); S4: setting the corrosion test cycle T and the specified load P, selecting N prismatic concrete test blocks (4) from the remaining prismatic concrete test blocks (4) as corrosion test pieces, placing them in the transparent box (11) respectively, and completing the entire assembly of the test device; S5: operating the hydraulic loading pump (9) to keep all the erosion test pieces, the pulling assembly, the hydraulic hollow jack (6), the pressure sensor (7) and the return spring (16) in an axially consistent state; S6: pouring NaCl etching solution into all the transparent boxes (11) respectively, so that each of the etching test pieces is soaked in the NaCl etching solution respectively; S7: operating the hydraulic loading pump (9), loading each of the erosion test pieces to the specified load P by viewing the load display (8), and continuously testing and recording the strain data of each of the erosion test pieces by using the strain gauge (13); S8: Periodically check to ensure that the concentration of the NaCl etching solution in each of the transparent boxes (11) remains constant, and the reading of the load display (8) remains at the specified load P; S9: After the immersion time of each corrosion test piece reaches the corrosion test period T, the test device is closed, each corrosion test piece is taken out, and a plurality of core samples (18) are extracted from the corroded position of each corrosion test piece; S10: Slice each of the core samples (18) and record the depth of each slice inside the corrosion test piece, then grind the slices into powder, test the chloride ion concentration of the slices at different depths by titration, and draw a relationship curve between the chloride ion penetration concentration and the penetration depth; S11: Based on the relationship curve drawn in S10, the relevant chloride ion migration rules are finally summarized.

10. The use according to claim 9, characterized in that: The M=3; The concentration of the NaCl erosion solution is 1%-5%; Each of the transparent boxes (11) is respectively provided with NaCl etching solutions of the same or different concentrations; The specified load P < the axial tension limit load; The corrosion test period T>=60 days.

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