An experimental apparatus for detecting chloride ion migration in concrete under tensile load and its application.

Abstract

This disclosure provides an experimental apparatus for measuring the migration law of chloride ions in concrete under tensile load. The apparatus includes a base plate, with fixed supports on both the left and right sides of the top of the base plate. Between the two fixed supports are N transparent boxes and N+1 tensioning components. Each transparent box contains a prism-shaped concrete specimen of appropriate size. A resistance strain gauge is mounted on the top of the prism-shaped concrete specimen, and the specimen is communicatively connected to a strain gauge measuring instrument via the strain gauge. A hydraulic hollow jack is located on the left side of the top of the base plate, to the left of the fixed support on the same side. A pressure sensor is connected to the left end of the hydraulic hollow jack, and the pressure sensor is communicatively connected to a load display. A hydraulic loading pump is also connected to the hydraulic hollow jack. A spring baffle is located on the right side of the top of the base plate, to the right of the fixed support on the same side. A return spring is located between the spring baffle and the fixed support on the same side.

Description

Technical Field

[0001] This disclosure relates to the field of reinforced concrete durability testing technology, specifically to a test apparatus and its application for the migration of chloride ions in concrete under tensile load. This disclosure can be used to experiment with and detect the migration of chloride ions in concrete under long-term tensile load. Background Technology

[0002] Reinforced concrete structures in the highly saline northwest and eastern coastal areas of my country are susceptible to chloride ion corrosion. Chloride ions penetrate the concrete cover through diffusion, convection, and electromigration, causing the passivation film on the reinforcing steel to fail, further leading to electrochemical corrosion and accelerating steel corrosion. Steel corrosion gradually causes cracking of the protective layer and a decrease in the load-bearing capacity of the structure, resulting in structural failure before its design service life and causing significant safety problems and economic losses.

[0003] Chloride ion penetration of concrete is typically slow and is the result of the combined effects of load and environment. Different experimental designs lead to discrepancies between experimental results and actual conditions. Load action is often a simplified term for long-term load action, accompanied by time-dependent effects such as creep; however, rapid chloride ion penetration tests after preloading do not fully capture these time-dependent effects. Bending loads are easy to apply in experiments and can simulate both compression and tension, but the stress along the erosion path is linearly distributed, violating the single-variable principle and thus suitable only for simplified simulation of thin-layer components. Concrete is often used as a compression member, therefore, erosion tests under tension are less frequently conducted.

[0004] The experimental methods and apparatus must consider, and even demonstrate, the similarity of materials, loads, and environments. Experimental research needs to optimize experimental methods and apparatus to obtain an accurate description of the ion erosion process by factors such as different materials, holding times, load types, and load levels. Currently, the chloride ion erosion test apparatus under axial tension (application publication number CN116026693A) applies loads to concrete specimens using a universal testing machine. This load is an axial tension cyclic load, which is difficult to meet the requirements for long-term bearing, and the local immersion of the specimen side in the solution may cause the eroding solution to diffuse to other locations.

[0005] In the existing technology, the statistical data of other load type experimental devices are as follows: Figure 12 As shown, the data parameters reflected in terms of bearing time, load type, load level and erosion mode are clearly visible. The existing experimental devices cannot meet the experimental requirements of long-term axial tensile loads, and cannot well simulate or reflect the real situation through experimental results. Naturally, they also cannot meet the needs of the increasingly demanding design and construction of concrete structures.

[0006] Continuously improving concrete durability testing methods is an inevitable process. To meet the needs of durability issues in practical reinforced concrete engineering, 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 concrete cylinder pipe (PCCP) as an example, the direct and indirect losses caused by insufficient durability of PCCP in North America and North Africa have exceeded expectations.

[0007] Due to water pressure, the protective layer of PCCPs is under constant tension. In-depth research into the migration patterns of chloride ions in the protective layer of PCCPs in high-salinity areas under operating loads is of great significance for the durability design and evaluation of PCCPs.

[0008] Currently, there are no technical solutions on the market to address the aforementioned technical problems. Summary of the Invention

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

[0010] To achieve the above-mentioned technical objectives, the technical solution disclosed herein is implemented as follows:

[0011] The first objective of this disclosure is to provide a test device for measuring the migration law of chloride ions under tensile load in concrete, which includes a base plate, a fixed support on each of the left and right sides of the top of the base plate, and N transparent boxes and N+1 tensioning components between the two fixed supports. Each transparent box contains a prism-shaped concrete specimen of a corresponding size.

[0012] A resistance strain gauge is installed on the top of the prismatic concrete specimen, and the prismatic concrete specimen is connected to the strain measuring instrument through the resistance strain gauge.

[0013] A hydraulic hollow jack is also installed on the left side of the top of the base 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. The hydraulic hollow jack is also connected to a hydraulic loading pump.

[0014] A spring baffle is provided on the right side of the top of the base plate. The spring baffle is located on the right side of the fixed support on the same side. A return spring is provided between the spring baffle and the fixed support on the same side.

[0015] Hydraulic hollow jacks, prismatic concrete test blocks, and spring baffles are arranged in a row along the top of the base plate, and each pair is detachably connected by a traction assembly. The left and right side walls and fixed supports of the transparent box are respectively passed through by adjacent traction assemblies. The left and right side walls and fixed supports of the transparent box are respectively provided with openings for the traction assemblies to pass through. The return spring is sleeved on the traction assembly connected to the spring baffle.

[0016] Preferably, N>=1.

[0017] Preferably, N is determined according to actual needs, and preferably, N=2. That is, there are a total of 2 transparent boxes and 3 tensioning components between the two fixed supports. When N=2, the hydraulic hollow jack is connected to the leftmost prismatic concrete specimen, the two adjacent prismatic concrete specimens are connected to each other, and the spring baffle is connected to the rightmost prismatic concrete specimen through a corresponding tensioning component.

[0018] Preferably, the bottom of the transparent box is provided with rolling casters, and the transparent box moves back and forth on the top of the base plate by rolling casters.

[0019] Preferably, the traction assembly includes a universal bearing, with a tie rod at each of the left and right ends of the universal bearing. One end of the tie rod is detachably connected to the universal bearing, and the other end of the tie rod is detachably connected to a hydraulic hollow jack, a prismatic concrete test block, or a spring baffle. The other end of the tie rod passes through an opening in the transparent box or fixed support.

[0020] Preferably, the top of the prismatic concrete specimen is sealed with polyurea sealant.

[0021] Preferably, the openings in the transparent box are sealed.

[0022] Preferably, the prismatic concrete specimen is provided with anchors symmetrically at both ends. The anchors include steel plates, each of the four corners of the steel plate is provided with a small anchor hole and the center is provided with a large anchor hole. Each small anchor hole is provided with a small anchor rod, which extends from the corresponding small anchor hole into the interior of the prismatic concrete specimen.

[0023] Each large anchor hole is equipped with a large internal thread rod, which extends from the large anchor hole into the interior of the prismatic concrete specimen.

[0024] The axial center lines of both the small anchor rod and the large internal thread rod are parallel to the axial center line of the prismatic concrete specimen.

[0025] The tie rod has external threads and is threaded to a larger internal thread rod, thus connecting the tie rod to the prismatic concrete specimen. Specifically, the smaller anchor rod and the larger internal thread rod are parallel to the long sides of the front, back, top, and bottom surfaces of the prismatic concrete specimen.

[0026] Preferably, a sealing nut is provided at the opening of the transparent box, and the other end of the tie rod passes through the sealing nut into the transparent box and is connected to the prismatic concrete test block. The transparent box is sealed at its opening by the sealing nut, thereby preventing the corrosive solution from leaking out of the transparent box through the opening.

[0027] Preferably, the sealing nut includes a threaded outer nut and an inner nut, with the outer nut fitted onto the inner nut. An oil seal is also provided inside the sealing nut, and the corresponding pull rod passes through the outer nut, the inner nut, and the oil seal together.

[0028] The second objective of this disclosure is to provide an application of the experimental apparatus for studying the migration behavior of chloride ions under tensile loads in concrete, comprising the following steps:

[0029] S1: Prepare several prismatic concrete test blocks of uniform size;

[0030] S2: Select M prism-shaped concrete specimens from all the prism-shaped concrete specimens as limit test specimens;

[0031] S3: Place the ultimate test specimens on a universal testing machine and slowly stretch them until failure. Record the failure load values ​​respectively. Then take the average value of all failure load values ​​and define it as the axial tensile ultimate load of the prism-shaped concrete specimen.

[0032] S4: Set the erosion test period T and specify the load P. Select N additional prismatic concrete specimens from the remaining prismatic concrete specimens as erosion test pieces, place them in transparent boxes, and complete the assembly of the test device.

[0033] S5: Operate the hydraulic loading pump to keep all corrosion test pieces, tensioning components, hydraulic hollow jacks, pressure sensors and return springs in an axially aligned state;

[0034] S6: Pour NaCl etching solution into all transparent boxes respectively, so that each of the etching test pieces is immersed in NaCl etching solution;

[0035] S7: Operate the hydraulic loading pump, and by checking the load display, load each corrosion test piece to the specified load P. In addition, continuously test and record the strain data of each corrosion test piece using a strain measuring instrument.

[0036] S8: Periodically check to ensure that the concentration of NaCl erosion solution in each transparent box remains constant before and after, and that the load display reading remains at the specified load P.

[0037] S9: After the immersion time of each corrosion test piece reaches the corrosion test cycle T, close the test device, take out each corrosion test piece, and extract several core samples from the corrosion location of each corrosion test piece.

[0038] S10: Cut each core sample into slices, record the depth of the erosion test specimen corresponding to each slice, then grind the slices into powder, use the titration method to test the chloride ion concentration of slices at different depths, and plot the relationship curve between chloride ion penetration concentration and penetration depth.

[0039] S11: Based on the relationship curves drawn in S10, the relevant chloride ion migration patterns are finally summarized.

[0040] Preferably, M is determined according to actual needs, and preferably, M=3. M=3 means that 3 prism-shaped concrete specimens are selected as limit test specimens to calculate the axial tensile limit load of the prism-shaped concrete specimens by the average value method.

[0041] Preferably, the concentration of the NaCl etching solution is determined according to actual needs, and is preferably 1%-5%.

[0042] Preferably, each transparent chamber is prepared with a NaCl etching solution of the same or different concentrations. That is, the NaCl etching solution concentrations in different transparent chambers can be different or the same, thereby meeting the needs of chloride ion testing at different concentrations.

[0043] Preferably, the specified load P is less than the axial tensile ultimate load. In practice, the specified load P applied to each corrosion test specimen should be less than the axial tensile ultimate load it can withstand.

[0044] Preferably, the erosion test cycle T is determined according to actual needs, and preferably, T>=60 days.

[0045] Preferably, the eroded location of the erosion test specimen used for sampling is the unsealed eroded surface of a prismatic concrete specimen.

[0046] Compared with the prior art, the beneficial effects of this disclosure are: (A). This disclosure has an independent loading device and load display, which can carry out experiments without relying on 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 the investigation of different influencing factors at the same time, and can meet the needs of long-term load and immersion.

[0047] (B) Compared with existing preloaded re-soaking techniques, this disclosure achieves chloride erosion while the concrete test block is under load, which is closer to actual engineering.

[0048] (C) Compared to the technique of partial immersion during loading, this disclosure immerses the entire test block in the solution, which is closer to the requirements of one-dimensional erosion.

[0049] (D) Compared with the prior art, this disclosure is simple to operate and does not require much maintenance during long-term loading. Attached Figure Description

[0050] To more clearly illustrate the technical solutions in the embodiments of this disclosure or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0051] Figure 1 This is a schematic diagram illustrating the application of the experimental apparatus described in this disclosure.

[0052] Figure 2 This is a perspective view of a partial structure of the test apparatus described in this disclosure (excluding the prismatic concrete specimen, pressure sensor, hydraulic loading pump, and strain gauge).

[0053] Figure 3 These are front view, top view, left view, and right view of a partial structure of the test apparatus described in this disclosure (excluding the prismatic concrete specimen, pressure sensor, hydraulic loading pump, and strain gauge).

[0054] Figure 4 This is a schematic diagram of the fit between the base plate and the fixed support described in this disclosure.

[0055] Figure 5 This is a structural schematic diagram of the prismatic concrete test block (including anchorage) described in this disclosure.

[0056] Figure 6 This is a perspective view of the prism-shaped concrete specimen (including anchorage), polyurea sealing material, tie rod, and resistance strain gauge assembly described in this disclosure.

[0057] Figure 7 yes Figure 6 Other perspective views and three-dimensional cross-sectional views of the combination.

[0058] Figure 8 This is a schematic diagram showing the prismatic concrete specimen described in this disclosure before and after being placed into the transparent box.

[0059] Figure 9 This is a partial illustration of the transparent box, prismatic concrete test block, and tension assembly (tension rod, universal bearing) described in this disclosure.

[0060] Figure 10 This is a schematic diagram of the sealing nut described in this disclosure.

[0061] Figure 11 This is a schematic diagram of extracting a core sample from an erosion test specimen in S9 as described in this disclosure.

[0062] Figure 12It is a statistical data set of the current test device's duration of load, load type, load level, and erosion mode in the existing technology.

[0063] In the diagram: 1. Base plate; 101. Channel steel; 2. Fixed support; 3. Universal bearing; 4. Prismatic concrete specimen; 401. Small anchor bolt; 402. Perforated stainless steel plate; 403. Large internal threaded rod; 404. Unsealed corroded surface; 405. Polyurea sealant; 5. Tie rod; 6. Hydraulic hollow jack; 7. Pressure sensor; 8. Load indicator; 9. Hydraulic loading pump; 10. Rolling pulley; 11. Transparent box; 12. Resistance strain gauge; 13. Strain gauge; 14. Corrosion solution; 15. Sealing nut; 1501. Outer nut; 1502. Inner nut; 1503. Oil seal; 16. Return spring; 17. Spring baffle; 18. Core sample. Detailed Implementation

[0064] The technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this disclosure, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this disclosure are within the scope of protection of this disclosure.

[0065] like Figure 1-12 As shown, in order to facilitate understanding of the above technical solutions of this disclosure, the following will provide a detailed description of the above technical solutions of this disclosure through specific usage methods.

[0066] The first objective of this disclosure is to provide a test device for the migration law of chloride ions under tensile load in concrete, which includes a base plate 1, a fixed support 2 on each of the left and right sides of the top of the base plate 1, and N transparent boxes 11 and N+1 tensioning components between the two fixed supports 2. Each transparent box 11 contains a prism-shaped concrete specimen 4 of a size adapted to it.

[0067] The top of the prismatic concrete specimen 4 is equipped with a resistance strain gauge 12, and the prismatic concrete specimen 4 is connected to the strain measuring instrument 13 through the resistance strain gauge 12.

[0068] A hydraulic hollow jack 6 is provided on the left side of the top of the base 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. A hydraulic loading pump 9 is also connected to the hydraulic hollow jack 6.

[0069] A spring baffle 17 is provided on the right side of the top of the base 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.

[0070] Hydraulic hollow jacks 6, prismatic concrete test blocks 4, and spring baffles 17 are arranged in a row along the top of the base plate 1, and each pair is detachably connected by a traction assembly; the left and right side walls and fixed supports 2 of the transparent box 11 are respectively passed through by adjacent traction assemblies, and the left and right side walls and fixed supports 2 of the transparent box 11 are respectively provided with openings for the traction assemblies to pass through, and the return spring 16 is sleeved on the traction assembly connected to the spring baffles 17.

[0071] In one embodiment, N>=1.

[0072] In one embodiment, N is determined according to actual needs, preferably N=2. That is, between the two fixed supports 2, there are a total of 2 transparent boxes 11 and 3 traction components. When N=2, the hydraulic hollow jack 6 is connected to the leftmost prismatic concrete test block 4, the two adjacent prismatic concrete test blocks 4 are connected to each other, and the spring baffle 17 is connected to the rightmost prismatic concrete test block 4, respectively, through a corresponding traction component.

[0073] In one embodiment, the bottom of the transparent box 11 is provided with a rolling pulley 10, and the transparent box 11 moves back and forth on the top of the base plate 1 by means of the rolling pulley 10.

[0074] In one embodiment, the traction assembly includes a universal bearing 3, with a pull rod 5 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 a hydraulic hollow jack 6, a prismatic concrete test block 4, or a spring baffle 17. The other end of the pull rod 5 passes through an opening made in the transparent box 11 or the fixed support 2.

[0075] In one embodiment, the top of the prismatic concrete specimen 4 is sealed with polyurea sealant 405;

[0076] In one embodiment, the opening of the transparent box 11 is sealed.

[0077] In one embodiment, anchors are symmetrically provided at both ends of the prismatic concrete specimen 4. The anchors include steel plates 402. Each of the four corners of the steel plate 402 is provided with a small anchor hole and a large anchor hole is provided in the middle. Each small anchor hole is provided with a small anchor rod 401. The small anchor rod 401 extends from the corresponding small anchor hole into the interior of the prismatic concrete specimen 4.

[0078] Each large anchor hole is equipped with a large internal thread rod 403, which extends from the large anchor hole into the interior of the prismatic concrete specimen 4.

[0079] The axial center lines of both the small anchor rod 401 and the large internal thread rod 403 are parallel to the axial center line of the prismatic concrete specimen 4.

[0080] Tie rod 5 has external threads and is threaded to a large internal thread rod 403, thereby connecting tie rod 5 to prism-shaped concrete specimen 4. That is, small anchor rod 401 and large internal thread rod 403 are parallel to the long sides of the front, back, top and bottom sides of prism-shaped concrete specimen 4.

[0081] 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 is sealed at its opening by the sealing nut 15, thereby preventing the corrosive solution from leaking out of the transparent box 11 through the opening.

[0082] In one embodiment, the sealing nut 15 includes an outer nut 1501 and an inner nut 1502 connected by threads. 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 together.

[0083] In one embodiment, two channel steels 101 can be welded to the bottom of the base plate 1 to improve bending stiffness.

[0084] In one embodiment, the base plate 1 can be treated for corrosion protection by boiling and painting.

[0085] In one embodiment, six leveling screws can be installed at the four corners of the base plate 1 to ensure that the device is placed flat on the ground.

[0086] In one embodiment, the base plate 1 can be provided with multiple rows of corresponding connecting holes for the fixed supports 2 at both the left and right ends. The fixed supports 2 are also provided with corresponding connecting holes, which facilitates the adjustment of the position of the fixed supports 2 and can accommodate more prismatic concrete test blocks 4 of different sizes.

[0087] In one embodiment, the universal bearing 3 can adopt a socket design, and is detachably connected to the tie rod 5 via a pin. Ample space can be maintained at the socket joint to ensure it remains horizontal under stress during testing.

[0088] In one embodiment, the pressure sensor 7 is preferably a spoke-type load cell. The pressure sensor 7 is preferably 105mm in diameter, 37mm in height, has a measuring range of 5t, and is subjected to force through a central threaded hole. The load magnitude is displayed using a load indicator 8.

[0089] In one embodiment, the return spring 16, being confined between the fixed support 2 on the right side and the spring baffle 17, provides return elasticity. During implementation, it is important to ensure that the return spring 16 has sufficient stiffness to guarantee that even after the prismatic concrete specimen 4 reaches its axial tensile limit load, it can still restore the experimental device after removal of the prismatic concrete specimen 4, and that the compression range during loading does not exceed the jacking range of the hydraulic hollow jack 6. This is a matter of common knowledge.

[0090] In one embodiment, the strain gauge 13 is preferably an intelligent static strain gauge with a built-in microcontroller for management, button operation, and dual-window display. Preferably, the strain gauge 13 supports arbitrary bridge configuration at each measuring point, electronic switch switching of measuring points, simultaneous display of force and strain, high-reliability silicone keyboard operation, AC / DC power supply, convenient full-setup functions, and various measurement functions such as fixed-point and scanning. It also supports standalone, USB-connected, and multi-unit networked measurements.

[0091] In one embodiment, the dimensions of the base plate 1 are preferably 1500×200×40mm, and the material is preferably steel.

[0092] In one embodiment, the prism-shaped concrete specimen 4 is preferably a specimen cast with a given concrete mix proportion. Anchors are placed at both ends of the specimen during casting, such as... Figure 5 As shown. The anchorage is preferably made of stainless steel. The small anchor rod 401 is 80mm long and is fixed to the perforated stainless steel plate 402. The large internally threaded rod can be 90mm long and can be fixed to the middle of the perforated stainless steel plate 402. The anchorage is used to ensure more uniform stress distribution when the prismatic concrete specimen 4 is stretched.

[0093] In one embodiment, the pull rod 5 is preferably a stainless steel straight rod with a diameter of 20mm, which can be used to connect the prism concrete test block 4, the universal bearing 3, the spring baffle 17 and the pressure sensor 7, and can pass through the opening of the fixed support 2 and the transparent box 11.

[0094] In one embodiment, the hydraulic hollow jack 6 is preferably 223mm in outer diameter, 117mm in inner diameter, and 223mm in height. It can be connected to the pressure sensor 7 via the pull rod 5, and the hydraulic hollow jack 6 can be manually pressurized using the hydraulic loading pump 9.

[0095] In one embodiment, the transparent box 11 can be made of polypropylene (plastic material) with a thickness of 5mm. The connection position with the pull rod 5 can be sealed by a sealing nut 15. Multiple rolling pulleys 10 are provided 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 horizontal.

[0096] In one embodiment, the rolling pulley 10 and the sealing nut 15 are preferably made of non-metallic materials.

[0097] In one embodiment, the structure of the sealing nut 15 can be as follows: Figure 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 leakage of corrosive solution and 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 airtightness of the connection between the transparent box 11 and the pull rod 5.

[0098] In one embodiment, the helical spring 16 is constrained between the fixed support 2 and the spring baffle 17; it has sufficient stiffness to ensure that the test block can return to its original shape after unloading even if it reaches the ultimate tensile strength, and the compression range during loading does not exceed the jacking range of the hydraulic hollow jack 6.

[0099] The second objective of this disclosure is to provide an application of the experimental apparatus for studying the migration behavior of chloride ions under tensile loads in concrete, comprising the following steps:

[0100] S1: Prepare several prismatic concrete test blocks of the same specifications;

[0101] S2: Select M prism-shaped concrete specimens 4 from all the prism-shaped concrete specimens 4 as limit test specimens;

[0102] S3: Place the ultimate test specimens on a universal testing machine and slowly stretch them until failure. Record the failure load values ​​respectively. Then take the average value of all failure load values ​​and define it as the axial tensile ultimate load of the prismatic concrete specimen 4.

[0103] S4: Set the erosion test period T and specify the load P. Select N additional prismatic concrete test blocks 4 from the remaining prismatic concrete test blocks 4 as erosion test specimens, place them in the transparent box 11 respectively, and complete the assembly of the test device.

[0104] S5: Operate the hydraulic loading pump 9 to keep all corrosion test pieces, traction components, hydraulic hollow jacks 6, pressure sensors 7 and return springs 16 in an axially aligned state;

[0105] S6: Pour NaCl etching solution into all transparent boxes 11 respectively, so that each etching test piece is immersed in NaCl etching solution;

[0106] S7: Operate the hydraulic loading pump 9, and load each corrosion test piece to the specified load P by viewing the load display 8. In addition, continuously test and record the strain data of each corrosion test piece by the strain measuring instrument 13.

[0107] S8: Periodically check to ensure that the concentration of NaCl erosion solution in each transparent box 11 remains constant before and after, and that the reading of the load display 8 remains at the specified load P.

[0108] S9: After the immersion time of each corrosion test piece reaches the corrosion test cycle T, the test device is turned off, each corrosion test piece is taken out, and several core samples are extracted from the corrosion location of each corrosion test piece.

[0109] S10: Cut each core sample 18 into slices, record the depth of the erosion test specimen corresponding to each slice, then grind the slices into powder, use the titration method to test the chloride ion concentration of slices at different depths, and plot the relationship curve between chloride ion penetration concentration and penetration depth.

[0110] S11: Based on the relationship curves drawn in S10, the relevant chloride ion migration patterns are finally summarized.

[0111] In one embodiment, M is determined according to actual needs, preferably M=3. M=3 means that three prism-shaped concrete specimens 4 are selected as ultimate test specimens to calculate the axial tensile ultimate load of the prism-shaped concrete specimens 4 by the average value method.

[0112] In one embodiment, the concentration of the NaCl etching solution is determined according to actual needs, and is preferably 1%-5%.

[0113] In one embodiment, each transparent chamber 11 is filled with NaCl etching solutions of the same or different concentrations. That is, the concentrations of the NaCl etching solutions in different transparent chambers 11 can be different or the same, thereby meeting the needs of chloride ion testing at different concentrations.

[0114] In one embodiment, the specified load P is less than the axial tensile ultimate load. During implementation, the specified load P applied to each corrosion test specimen should be less than its axial tensile ultimate load capacity.

[0115] In one embodiment, the erosion test period T is determined according to actual needs, preferably T>=60 days.

[0116] In one embodiment, the eroded location of the erosion test specimen used for sampling is preferably the unsealed eroded surface 404 of the prismatic concrete test block 4.

[0117] To more fully illustrate the implementation process of the method portion of this disclosure, the following implementation examples can be referred to:

[0118] (Step 1) As described above, pour a batch of prismatic concrete test blocks 4 with anchors.

[0119] (Step 2) Randomly select 3 test blocks as ultimate test specimens and conduct ultimate axial tensile tests to determine the ultimate tensile strength of the prismatic concrete test block 4.

[0120] (Step 3) Place the selected ultimate test specimens on a universal testing machine and slowly stretch them until failure. Record the failure load value for each specimen. Then, take the average value of all failure load values ​​and define it as the axial tensile ultimate load of the prismatic concrete specimen 4. The meaning of axial tensile ultimate load: the ultimate tensile strength of the prismatic concrete specimen 4.

[0121] (Step 4) Set the erosion test period T and the specified load P. From the remaining prismatic concrete specimens 4, select two more prismatic concrete specimens 4 as erosion test pieces, and place them in two transparent boxes 11 respectively. Complete the assembly of the entire test apparatus. Ensure the secure connection of the erosion test pieces, resistance strain gauges 12, and strain gauges 13. The specified load P is set to 60% of the axial tensile ultimate load. The erosion test period T is the predetermined erosion test duration.

[0122] (Step 5) Check that all corrosion test pieces, traction components, hydraulic hollow jacks 6, pressure sensors 7, and return springs 16 are axially aligned. If not, apply appropriate load by operating the hydraulic loading pump 9 to achieve axial alignment for all corrosion test pieces, traction components, hydraulic hollow jacks 6, pressure sensors 7, and return springs 16.

[0123] (Step 6) Add 5% NaCl solution to the transparent box 11, so that each corrosion test piece is immersed in the NaCl corrosion solution.

[0124] (Step 7) Operate the hydraulic loading pump 9, and by checking the load display 8, load each corrosion test piece to the specified load P. Continuously test and record the strain data of each corrosion test piece using the strain gauge 13. The strain data is transmitted through the resistance strain gauge 12.

[0125] (Step 8) Periodically check to ensure that the concentration of the NaCl erosion solution in each transparent chamber 11 remains constant before and after, and that the reading on the load indicator 8 remains at the specified load P. Note: If the load decreases during the immersion process, promptly press the loading pump to replenish the pressure and ensure it remains at the specified load P; if the NaCl solution concentration changes during immersion, it should be addressed immediately.

[0126] (Step 9) When the erosion reaches the erosion test cycle T, shut down the test device, remove each erosion test piece, and extract several core samples 18 from the eroded location of each erosion test piece. A water drill can be used to drill core samples 18 from the eroded surface of each erosion test piece.

[0127] (Step 10) Cut each core sample 18 into slices, record the depth of the erosion test specimen corresponding to each slice, then grind the slices into powder, use titration to test the chloride ion concentration of slices at different depths, and plot the relationship curve between chloride ion penetration concentration and penetration depth.

[0128] (Step 11) Based on the relationship curve drawn by S10, the relevant chloride ion migration rules are finally summarized.

[0129] During implementation, multiple experimental devices can be used to conduct different tests on the same batch of test blocks. These tests can include a blank control group, different NaCl solution concentrations, different load sizes, different load times, and different concrete mix proportions. Plotting the relationship between chloride ion penetration concentration and penetration depth allows for comparison of the differences in this curve under different material proportions, soaking times, and load sizes, enabling the selection of more suitable concrete materials and exploring the chloride ion migration patterns under different loads and load times. Summarizing the chloride ion migration patterns can be based on the unsteady-state diffusion law, combined with the relationship between plastic damage in concrete under load, thereby concluding a precise and reliable general law of chloride ion migration in concrete under actual loading conditions.

[0130] In summary, through the unique design of this disclosure, compared with the prior art, the beneficial effects of this disclosure are as follows: (A) This disclosure has an independent loading device and load display, which can be used to conduct experiments without relying on existing universal loading equipment in the laboratory. The device occupies a small area and can accommodate multiple sets of the same equipment to conduct investigations of different influencing factors simultaneously, meeting the requirements for long-term load holding and immersion. (B) Compared with existing pre-loading and re-immersion techniques, this disclosure achieves chloride erosion while the concrete specimen is under load, which is closer to actual engineering. (C) Compared with the technique of partial immersion during loading, this disclosure immerses the specimen completely in the solution, which is closer to the requirements of one-dimensional erosion. (D) Compared with the prior art, this disclosure is simple to operate and requires little maintenance during long-term loading.

[0131] The above description is merely a preferred embodiment of this disclosure and is not intended to limit this disclosure. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this disclosure should be included within the protection scope of this disclosure.

Claims

1. A test device for concrete chloride ion migration law under tensile load, characterized in that, The utility model provides a kind of concrete prism test piece erosion test device, including bottom plate (1), the left and right sides of the top of bottom plate (1) are equipped with one fixed support (2) respectively, two fixed support (2) between being equipped with N transparent box (11) and N+1 pull assembly, each transparent box (11) respectively place one size and its compatible prism concrete test piece (4), N>=1, the top of prism concrete test piece (4) is equipped with resistance strain gauge (12), and prism concrete test piece (4) is connected with strain measuring instrument (13) by resistance strain gauge (12), the left side of the top of bottom plate (1) is additionally equipped with hydraulic hollow jack (6), and hydraulic hollow jack (6) is located in the left side of the fixed support (2) of same side, and the left end of hydraulic hollow jack (6) is connected with pressure sensor (7), and pressure sensor (7) is connected with load display (8), and hydraulic hollow jack (6) is additionally connected with hydraulic loading pump (9), and the right side of the top of bottom plate (1) is additionally equipped with spring baffle (17), and spring baffle (17) is located in the right side of the fixed support (2) of same side, and reset spring (16) is arranged between spring baffle (17) and the fixed support (2) of same side, and hydraulic hollow jack (6), each prism concrete test piece (4), spring baffle (17) are sequentially arranged in a line along the top of bottom plate (1), and are respectively detachably connected by one pull assembly between each other, and the left and right side walls of transparent box (11) and fixed support (2) are respectively penetrated by adjacent pull assembly, and the left and right side walls of transparent box (11) and fixed support (2) are respectively provided with opening for pull assembly to penetrate, reset spring (16) is sleeved on the pull assembly connected with spring baffle (17), NaCl erosion solution is poured into all transparent box (11) respectively, each erosion test piece is immersed in NaCl erosion solution, and the left and right ends of prism concrete test piece (4) are symmetrically provided with anchor, and the anchor includes steel plate (402), the four corners of steel plate (402) are symmetrically provided with one small anchor hole, and the middle part is provided with one big anchor hole, each small anchor hole is provided with one small anchor rod (401) correspondingly, and small anchor rod (401) extends from corresponding small anchor hole to the inside of prism concrete test piece (4).

2. The test apparatus for concrete chloride ion migration rule under tensile load according to claim 1, characterized in that, N=2, that is, between two fixed supports (2), a total of 2 transparent boxes (11) and 3 pull assemblies are provided.

3. The test apparatus for concrete chloride ion migration rule under tensile load according to claim 1, characterized in that, The bottom of transparent box (11) is provided with rolling pulley (10), and the transparent box (11) reciprocates on the top of bottom plate (1) through rolling pulley (10).

4. The test apparatus for concrete chloride ion migration rule under tensile load according to claim 1, characterized in that, The pulling assembly comprises a universal bearing (3), and one pulling rod (5) is arranged at each left and right end of the universal bearing (3), one end of the pulling rod (5) is detachably connected with the universal bearing (3), the other end of the pulling rod (5) is detachably connected with the hydraulic hollow jack (6) or the prismatic concrete test block (4) or the spring baffle (17), and the other end of the pulling rod (5) penetrates through an opening of the transparent box (11) or a fixed support (2).

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

6. The test apparatus for concrete chloride ion migration rule under tensile load according to claim 4, characterized in that, Each large anchor hole position is provided with a large internal threaded rod (403) extending 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 pulling rod (5) is provided with external threads and is threadedly connected with the large internal threaded rod (403), so that the pulling rod (5) is connected with the prismatic concrete test block (4).

7. The test apparatus for concrete chloride ion migration rule under tensile load according to claim 4, characterized in that, The opening of the transparent box (11) is provided with a sealing nut (15), and the other end of the pulling rod (5) is connected with the prismatic concrete test block (4) after penetrating into the transparent box (11) through the sealing nut (15).

8. The test apparatus for concrete chloride ion migration rule under tensile load according to claim 7, characterized in that, The sealing nut (15) comprises a threaded outer nut (1501) and an inner nut (1502), the outer nut (1501) is sleeved on the inner nut (1502), and an oil seal (1503) is further arranged in the sealing nut (15), and the pulling rod (5) penetrates through the outer nut (1501), the inner nut (1502) and the oil seal (1503) correspondingly.

9. Use of the test apparatus for the concrete chloride ion migration law under tensile load according to any one of claims 1-8, characterized in that, The method comprises the following steps: S1: a plurality of prismatic concrete test blocks (4) with the same specification are prepared; S2: M prismatic concrete test blocks (4) are selected from all the prismatic concrete test blocks (4) as limit test pieces; S3: the limit test pieces are respectively placed on a universal testing machine, slowly stretched to failure, and the failure load values are respectively recorded, then the average value of all the failure load values is taken as the axial tensile ultimate load of the prismatic concrete test block (4); S4: an erosion test period T and a specified load P are set, N prismatic concrete test blocks (4) are selected from the remaining prismatic concrete test blocks (4) as erosion test pieces, and are respectively placed in the transparent box (11), and the complete assembly of the test device is completed; S5: the hydraulic loading pump (9) is operated, so that all the erosion test pieces, pulling assemblies, hydraulic hollow jacks (6), pressure sensors (7) and reset springs (16) are kept in axial consistency; S6: NaCl erosion solution is poured into all the transparent boxes (11), so that each erosion test piece is soaked in the NaCl erosion solution; S7: operating the hydraulic loading pump (9), loading each of the erosion test pieces to the specified load P by checking the load display (8), and continuously testing and recording the strain data of each of the erosion test pieces by the strain gauge (13); S8: periodically checking to ensure that the concentration of the NaCl erosion 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 of the erosion test pieces reaches the erosion test period T, turning off the test device, taking out each of the erosion test pieces, and extracting a plurality of core samples (18) from the eroded position of each of the erosion test pieces; S10: slicing each of the core samples (18), recording the depth of the inside of the erosion test piece corresponding to each slice, then grinding the slices into powders, testing the chloride ion concentration of the slices at different depths by titration, and drawing a relationship curve of the chloride ion concentration and the penetration depth; S11: according to the relationship curve drawn in S10, finally summarizing the relevant chloride ion migration law.

10. 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 configured with the NaCl erosion solution with the same or different concentration; the specified load P is less than the axial tensile ultimate load; and the erosion test period T is >=60 days.

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