Submarine tunnel concrete chloride ion impermeability testing device and testing method

Abstract

The invention discloses a device and a method for testing impermeability of chloride ions in subsea tunnel concrete, belongs to the technical field of building industries, establishes the relationship among the total amount of a sodium chloride solution, the penetration depth of the chloride ions, the permeability coefficient of the chloride ions and the resistivity, and innovatively provides a method for detecting the permeability coefficient of the chloride ions based on the resistivity. And a precise determination model for determining the concrete chloride ion diffusion depth and the chloride ion diffusion coefficient through the resistivity is constructed. The detection device designed by the invention comprises a test piece forming mold, a test piece placement platform, a pressurization permeation module, a resistivity test module, a central control system and a computer output system, and can be suitable for evaluating the chloride ion impermeability of concrete structures serving in environments with different seawater depths and different seawater concentrations. The total amount of the sodium chloride solution, the chloride ion penetration depth and the chloride ion penetration resistance coefficient in the subsea tunnel concrete can be accurately measured, and the device has the advantages of being easy and convenient to operate and high in intelligent degree.

Description

Technical Field

[0001] The present invention relates to the technical field of the construction industry, and more specifically to a device and method for testing the chloride ion impermeability of concrete for a submarine tunnel. Background Art

[0002] Currently, under the policy of building a maritime power, the basic engineering construction in China has gradually developed to the deep sea. The deep-sea basic engineering construction provides convenient conditions for the development of marine resources, transportation, etc., such as submarine tunnels. However, the abundant chloride ions in the marine environment cause serious durability erosion to the reinforced concrete structure. Chloride ion erosion will lead to the reduction of the bond between the steel bar and the concrete, steel bar corrosion and other damages, which is a great potential safety hazard during the entire service life of the reinforced concrete structure. Therefore, it is of great significance to propose a method for evaluating the impermeability performance of concrete and control indexes in the marine environment. The methods proposed at home and abroad for testing the chloride ion permeability of concrete include: the electric flux method, the RCM method based on the penetration depth, and the Permit method, but there are the following problems:

[0003] ① Before the test by the electric flux method, the concrete specimens need to be saturated with water, which cannot accurately and quantitatively explain the anti-ion permeability of the concrete. Moreover, the conductive area is too large, and as the voltage increases, the temperature of the specimens and the solution will rise, which will affect the chloride ion transmission speed, resulting in a significant improvement in the measured anti-ion permeability of the concrete with mineral admixtures added.

[0004] ② The basic assumption of the RCM method directly regards the pore solution flow inside the concrete as the water solution flow, ignoring the convective diffusion effect of the water solution. For low-strength concrete, when the capillary action on the adsorption of chloride ions is ignored, the theoretical chloride ion penetration depth will be less than the measured chloride ion penetration depth. For high-strength concrete, if the influence of the diffusion effect is ignored, the theoretical chloride ion penetration depth will be too large.

[0005] ③ The Permit method has a slightly poor test effect on concrete with high density, and this method only has a high test accuracy within the depth range of 15 mm on the surface layer of the concrete, and cannot evaluate the anti-chloride ion penetration performance inside the concrete. During the test, there are subjective differences in the definition of the steady state stage, and different rates of change of the conductivity will be obtained due to the differences in data analysis, and then different chloride ion migration coefficients will be calculated.

[0006] The invention patent with the publication number CN116359110A discloses a curing box that can simulate the chloride salt erosion environment of concrete. However, this device cannot study the chloride ion erosion performance under different water pressure environments. The invention patent with the publication number CN118549262A provides a device for studying the durability deterioration evolution law of a submarine tunnel that can be pressurized. However, this device cannot achieve non-destructive detection of the chloride ion penetration depth and chloride ion concentration distribution inside the concrete specimen. The invention patent with the publication number CN118888040A provides a real-time detection method for testing the change of the pH value inside concrete. However, this test method needs to use a physical structure for testing and cannot adjust the water pressure. Therefore, it is impossible to directly analyze the test of the chloride ion permeability resistance of concrete under different water pressures.

[0007] Currently, the evaluation of the chloride ion permeability resistance of concrete mostly uses a single index of chloride ion diffusion coefficient, and the above methods all have the problem that they cannot analyze the chloride ion permeability resistance of concrete when different water pressures are applied to the specimens. Therefore, it is of great significance to develop a convenient, efficient and high-precision test method and device for the chloride ion permeability resistance of concrete and propose a more comprehensive index for the chloride ion permeability resistance of concrete for the evaluation of the chloride ion permeability resistance of concrete in the marine environment. Summary of the Invention

[0008] The present invention aims to solve at least one of the above technical problems in the prior art to a certain extent.

[0009] To this end, an object of the present invention is to provide a test device for the chloride ion impermeability of submarine tunnel concrete, including a resistivity test module to be tested, a pressure penetration module, a central control system, a computer output system, a specimen forming mold, a specimen to be tested, and a specimen placement platform;

[0010] Wherein, the computer output system is electrically connected to the resistivity test module to be tested and the pressure penetration module respectively;

[0011] The central control system is electrically connected to the resistivity test module to be tested and the pressure penetration module respectively;

[0012] The specimen forming mold is fixed on the specimen placement platform, the specimen to be tested is cast and formed in the specimen forming mold, and the specimen to be tested is electrically connected to the resistivity test module and the pressure penetration module respectively;

[0013] The pressure penetration module includes a hemispherical pressure nozzle, a liquid conduit, a flowmeter, a pressure tank, a gas conduit, and an air compressor. The hemispherical pressure nozzle is disposed within the specimen forming mold and is connected to one end of the liquid conduit. The other end of the liquid conduit is connected to the water outlet hole on the pressure tank. The air outlet hole on the air compressor is connected to the air inlet hole on the pressure tank through the gas conduit. The flowmeter is fixed on the liquid conduit.

[0014] The computer output system is electrically connected to the flowmeter, and the central control system is electrically connected to the air compressor.

[0015] The resistivity testing module includes a potentiostat, a junction box, wires, tungsten-copper rod electrodes, screw insulating sleeves, and a bottom plate with a hollow bottom.

[0016] A number of screw insulating sleeves are provided. The number of tungsten-copper rod electrodes is twice that of the screw insulating sleeves, and a tungsten-copper rod electrode is screwed at both the bottom end and the top end of the screw insulating sleeve.

[0017] The tungsten-copper rod electrode at the bottom end of the screw insulating sleeve is inserted into the bottom plate with a hollow bottom, and the bottom plate with a hollow bottom is placed within the specimen forming mold.

[0018] A wire is led out from each of the tungsten-copper rod electrodes at the bottom end of the screw insulating sleeves and connected to one end of the junction box. The other end of the junction box leads out a wire and is connected to the negative electrode of the potentiostat.

[0019] The tungsten-copper rod electrodes at the top end of the screw insulating sleeves are inserted into the hemispherical pressure nozzle, and the tungsten-copper rod electrodes at the top end of the screw insulating sleeves are welded to each other. A wire is led out from the welding point and connected to the positive electrode of the potentiostat.

[0020] The computer output system is electrically connected to the potentiostat, and the central control system is electrically connected to the potentiostat.

[0021] Further, the hemispherical pressure nozzle is a prefabricated component. The frame part of the hemispherical head is composed of a conduit joint, a stainless steel perforated plane, and a stainless steel perforated hemispherical surface. The perforation range of the stainless steel perforated plane is within the range where the conduit joint is welded to the stainless steel perforated plane for the entry of water flow. The perforation range of the stainless steel perforated hemispherical surface is the entire hemispherical cross-section to ensure uniform pressurized penetration of water flow. The conduit joint is connected to the liquid conduit.

[0022] A flowmeter is installed on the liquid conduit. The accuracy of the flowmeter is 0.1 ml, which can accurately measure the volume of sodium chloride solution flowing through the inside of the liquid conduit, and thus obtain the total amount of sodium chloride solution invading the specimen to be tested. The two sides of the liquid conduit are respectively connected to the hemispherical pressure nozzle and the pressure tank.

[0023] The pressure tank consists of a cover and a tank body. A sealing strip is arranged inside the cover. The cover and the tank body are connected by first to tenth tight bolts to ensure the sealing during the pressurization process. The pressure tank is used to contain sodium chloride solution and control the water pressure. A pressure gauge, a pressure relief valve and an air inlet are arranged above the cover. A first handle and a second handle are arranged on both sides of the cover. A pressure water outlet valve is arranged on one side of the tank body. A first pulley, a second pulley, a third pulley and a fourth pulley are arranged below the tank body to facilitate the movement of the pressure tank filled with sodium chloride solution during the test.

[0024] The pressure outlet valve controls the pressure inside the pressure tank when discharging water by adjusting the knob of the pressure outlet valve. When the air pressure in the tank reaches the set target pressure, the sodium chloride solution can be automatically released to ensure the stability of the water pressure during the pressurized penetration process. The pressure outlet valve is provided with a pressure valve knob and a water outlet hole;

[0025] The air compressor is used to inject air into the pressure tank for pressurization. A pressure gauge is arranged on the top of the air compressor, which can transmit the electrical signal of the pressure value to the central control system, so that the central control system can control the opening and closing of the air compressor during the pressurization process.

[0026] The liquid conduit connects the water outlet provided on the pressure tank with the hemispherical pressurized nozzle pre-buried inside the test piece, and the gas conduit connects the air outlet provided on the air compressor with the air inlet provided on the pressure tank.

[0027] Furthermore, the wires include a first wire, a second wire, a third wire, a fourth wire, a fifth wire, a sixth wire, and a seventh wire.

[0028] The tungsten copper rod electrode includes a first tungsten copper rod electrode, a second tungsten copper rod electrode, a third tungsten copper rod electrode, a fourth tungsten copper rod electrode, and a fifth tungsten copper rod electrode preset in a hemispherical pressure nozzle, and also includes a separate sixth tungsten copper rod electrode, a seventh tungsten copper rod electrode, an eighth tungsten copper rod electrode, a ninth tungsten copper rod electrode, and a tenth tungsten copper rod electrode.

[0029] The screw insulating sleeve comprises a first screw insulating sleeve, a second screw insulating sleeve, a third screw insulating sleeve, a fourth screw insulating sleeve and a fifth screw insulating sleeve. The first tungsten copper rod electrode and the sixth tungsten copper rod electrode are connected by screwing their ends into the first screw insulating sleeve, the second tungsten copper rod electrode and the seventh tungsten copper rod electrode are connected by screwing their ends into the second screw insulating sleeve, the third tungsten copper rod electrode and the eighth tungsten copper rod electrode are connected by screwing their ends into the third screw insulating sleeve, the fourth tungsten copper rod electrode and the ninth tungsten copper rod electrode are connected by screwing their ends into the first screw insulating sleeve, the fifth tungsten copper rod electrode and the tenth tungsten copper rod electrode are connected by screwing their ends into the third screw insulating sleeve; two tungsten copper rod electrodes in the same screw insulating sleeve do not contact each other.

[0030] Since the five electrodes are connected to the five tungsten copper rod electrodes below with insulating sleeves made of PCV material, they are pre-buried inside the specimen and are in an open circuit state before the sodium chloride solution penetrates. The electrodes are non-conductive. As the sodium chloride solution invades, a path is formed. The tungsten copper rod and the infiltrated concrete part form a parallel resistor to measure the change of the internal resistivity of the concrete during the penetration of the sodium chloride solution.

[0031] After the connection is completed, the second wire, the third wire, the fourth wire, the fifth wire and the sixth wire are respectively led out from the lower ends of the sixth tungsten copper rod electrode, the seventh tungsten copper rod electrode, the eighth tungsten copper rod electrode, the ninth tungsten copper rod electrode and the tenth tungsten copper rod electrode, and the junction box is used to connect the second wire, the third wire, the fourth wire, the fifth wire and the sixth wire to the seventh wire.

[0032] The ends of the sixth tungsten copper rod electrode, the seventh tungsten copper rod electrode, the eighth tungsten copper rod electrode, the ninth tungsten copper rod electrode and the tenth tungsten copper rod electrode are respectively inserted into the corresponding slots of the bottom plate of the PCV material with a hollow bottom, and a pentahedron can be formed after the insertion is completed. The angle between the side faces is 45°. The size of the bottom plate of the PCV material is consistent with the size of the mold used to prepare the test piece, which can ensure that the pentahedron does not deform after the electrode is installed and the concrete is poured and vibrated to obtain the test piece after the embedded electrode and pouring concrete.

[0033] The welding points of the first tungsten copper rod electrode, the second tungsten copper rod electrode, the third tungsten copper rod electrode, the fourth tungsten copper rod electrode and the fifth tungsten copper rod electrode are connected to the first wire, the first wire is connected to the positive pole of the constant potential (constant current) measuring instrument, and the seventh wire is connected to the negative pole of the constant potential (constant current) measuring instrument.

[0034] The first tungsten copper rod electrode, the second tungsten copper rod electrode, the third tungsten copper rod electrode, the fourth tungsten copper rod electrode and the fifth tungsten copper rod electrode are preset in the hollow hemisphere composed of the stainless steel perforated plane and the stainless steel perforated hemisphere. The angles between the first tungsten copper rod electrode to the fourth tungsten copper rod electrode are welded at 45°, and the fifth tungsten copper rod electrode at the center is welded at the center of the surrounding 4 electrodes. The five welded tungsten copper rod electrodes are connected at the center of the upper half plane of the hemisphere and extend through the center of the outer surface of the lower hemisphere of the hemispherical indenter.

[0035] The specimen forming mold is a rectangular parallelepiped with a size of 300mm×300mm×1mm. It is used to place electrodes and hemispherical pressure nozzles and cast concrete specimens to be tested. A groove is provided at the bottom to fix the vertically arranged tenth tungsten copper rod electrode.

[0036] Further, during testing, the specimen to be tested is placed on the specimen placement platform. A spirit level is set on the upper platform surface of the specimen placement platform, and knobs are provided on the legs of the specimen placement platform to adjust the height around the platform to ensure that the specimen remains horizontal during testing. Specifically, the knobs include a first knob, a second knob, a third knob, and a fourth knob.

[0037] In the solution of the present invention, the resistivity test module is provided with a screw insulating sleeve made of PCV material, a tungsten copper bar electrode, a bottom-hollowed PCV material bottom plate, forming a pentahedron, a potentiostat (galvanostat) and wires, for testing the resistivity of specimens under different chloride ion penetration depths, and establishing standard curves of "resistivity - chloride ion penetration depth", "resistivity - chloride ion permeability coefficient" and "resistivity - total amount of infiltrated sodium chloride solution" based on the resistivity.

[0038] In the present invention, the pressurized penetration module realizes injecting sodium chloride solution into the interior of the specimen under different water pressures. The pressure tank is used to hold sodium chloride solutions with different concentrations and provide a sealed environment to control the water pressure when infiltrating into the specimen. The pressurized penetration module is also equipped with an air compressor to adapt to pressurize the pressure tank, thereby realizing the test of the penetration performance of sodium chloride solution under any water pressure.

[0039] In the present invention, the central control system is used to control the opening and closing of the paths of the pressurized penetration module and the resistivity test module.

[0040] In the present invention, the computer output system is used to analyze the measured data. The computer output system is built-in with analysis software, which is respectively connected to the potentiostat (galvanostat) and the flowmeter, and can receive data of "concrete resistivity - time" from the potentiostat (galvanostat) and "total amount of infiltrated sodium chloride solution - time" from the flowmeter. Further, a standard curve of "concrete resistivity - total amount of infiltrated sodium chloride solution" is established based on the time parameter.

[0041] The specimen forming mold is used to form the specimen to be tested, and at the same time can fix the pentahedron assembled with the electrodes to prevent the deformation of the electrode arrangement during the concrete vibration forming process. The upper part of the mold is slightly higher than the upper plane of the installed hemispherical nozzle, which can ensure the close fit between the embedded hemispherical nozzle and the concrete;

[0042] The specimen placement platform is used to place the specimen to be tested during the test. Knobs are provided on the legs of the specimen placement platform to adjust the height of the specimen placement platform. A spirit level is provided on the upper part of the platform to level the platform during the adjustment process to ensure that the specimen remains horizontal during the loading process.

[0043] The present invention also provides a method for testing the chloride ion impermeability of submarine tunnel concrete, including the following steps:

[0044] (1) Concrete is injected into the specimen forming mold, and the specimen forming mold is removed after the concrete solidifies and forms. Then, the relationship between the total amount of sodium chloride solution infiltrated into the concrete and the resistivity is established using the submarine tunnel concrete chloride ion impermeability test device, and a standard curve of "total amount of sodium chloride solution-concrete resistivity" is obtained to achieve automatic determination of the total amount of chloride ions intruding into the concrete under different water pressures;

[0045] (2) The chloride ion impermeability test device for submarine tunnel concrete was used to obtain the chloride ion diffusion depth and chloride ion concentration distribution. The chloride ion concentration distribution curve inside the concrete under different water pressures was established according to Fick's second law and the chloride ion diffusion coefficient was calculated.

[0046] (3) According to the data obtained in step (1) and step (2), the standard curves of "chloride ion diffusion depth-concrete resistivity" and "chloride ion diffusion coefficient-concrete resistivity" are established to realize the permeability coefficient and chloride ion diffusion depth measurement based on resistivity, form a concrete impermeability index with dual control of "chloride ion diffusion coefficient" and "total amount of sodium chloride solution", and form an evaluation index based on resistivity.

[0047] Furthermore, in step (1), the electrodes embedded inside the test piece in the dry state are in an open circuit state. With the intrusion of the sodium chloride solution, the two tungsten copper rod electrodes on each screw insulation sleeve form a path through the sodium chloride solution. With the increase in the total amount of intrusion of the sodium chloride solution, the resistivity inside the concrete continues to decrease, and a standard curve of "total amount of sodium chloride solution-concrete resistivity" is established based on the time parameter. In the above operation, the standard curve of "total amount of sodium chloride solution-concrete resistivity" under different water pressures and different seawater concentrations only needs to be tested once, and can be directly called to perform concrete chloride ion impermeability test later.

[0048] Furthermore, there are five screw insulating sleeves, and after the sodium chloride solution penetrates, five connected tungsten copper rod electrodes are formed. The resistance of the pre-embedded tungsten copper rod electrodes inside the test piece and the internal resistance of the concrete meet the following conditions: the five tungsten copper rod electrodes are connected in parallel, and the total resistance of the parallel tungsten copper rod electrodes and the internal resistance of the concrete are connected in series. The calculation formula is shown in Formula 1:

[0049]

[0050] Where: R E is the total resistance of the five resistors in parallel, R1 is the resistance of a single tungsten copper rod electrode, R C is the resistance value inside the concrete, R T is the total resistance of the electrodes and the internal resistance of the concrete after parallel connection, U is the overall voltage inside the test piece measured by the constant potential (constant current) measuring instrument, V, I is the current of the complete path inside the test piece measured by the constant potential (constant current) measuring instrument, A.

[0051] The above formula 1 is obtained by the following method:

[0052] Let the resistance of each electrode rod be R1, and the resistance of the concrete be R C , and the equivalent circuit of the internally embedded electrode is as follows Figure 10 as shown. Among them, the electrode rods are in parallel, and the resistance value after parallel connection can be calculated by formula 1. The total resistance of the 5 tungsten-copper rod electrodes after parallel connection is as shown in formula 2. The electrodes after parallel connection are connected in series with the concrete resistance. The total resistance of the series-connected device can be calculated according to formula 3. The potentiostat (galvanostat) can directly obtain the voltage and resistance inside the specimen and calculate the total resistivity R T of the specimen, as shown in formula 4. By combining formula 3 and formula 4, the resistivity inside the concrete after penetration (such as 8 h) under different water pressures can be obtained, as shown in formula 5.

[0053]

[0054]

[0055] In the formula: R E is the total resistance of the five resistances after parallel connection, R1 is the resistance of a single tungsten-copper rod electrode, R C is the resistance value inside the concrete, R T is the total resistance of the electrodes after parallel connection and the resistance inside the concrete, and U and I are the overall voltage and current of the specimen measured by the potentiostat (galvanostat), respectively.

[0056] Taking the addition of a 3% concentration sodium chloride solution to the pressure tank as an example, the pressure tank is sealed by tightening bolts, the knob of the pressure outlet valve is adjusted to set the corresponding water pressure during water outlet, a liquid conduit is used to connect the hemispherical pressure nozzle embedded in the specimen and the pressure tank, a gas conduit is used to connect the pressure tank and the air compressor, and the flowmeter set on the liquid conduit is connected to the computer output system to output in real time the variation curve of the total amount of infiltrated sodium chloride solution with time.

[0057] The expected air pressure value of the air compressor is set on the central control system. In order to avoid the influence of electrode polarization on the chloride ion transport inside the concrete, the resistivity acquisition frequency is set to 1 min / time in the central control system, and the test time is set to 8 h. After the setting is completed, click the "Start" button in the "Central Control System" to start the test.

[0058] Since the concentration of the sodium chloride solution is constant, let the concentration of the sodium chloride solution used for the test be ρ, g / L, and let the volume of the sodium chloride solution infiltrated into the concrete measured by the flowmeter at the end of the test be V. At this time, the total amount Q NaCl of the sodium chloride infiltrated into the concrete can be calculated by formula 6.

[0059] QNaCl = ρV Equation 6

[0060] After the test starts, the central control system controls the potentiostat (galvanostat) in real time to continuously obtain the "concrete resistivity - time" curve, and the flowmeter outputs the "total amount of intruded sodium chloride solution - time" curve in real time. By comparing the time parameters of the two curves, the "total amount of intruded sodium chloride solution - concrete resistivity" standard curve can be obtained. After continuously obtaining the "total amount of intruded sodium chloride solution - concrete resistivity" standard curves under different water pressures and different chloride ion concentrations, a standard curve library can be established and directly called later to realize the test of the total amount of intruded sodium chloride solution inside the submarine tunnel concrete based on resistivity under different water pressures and different chloride ion concentrations.

[0061] Furthermore, in step (1), obtaining the "solution concentration - phase difference" standard curve includes the following steps:

[0062] 1) Connect the tungsten - copper rod electrodes and form a pentahedron with the bottom - hollowed PCV - material bottom plate, ensuring that the five electrode rods intersect at the center of the upper surface of the specimen to be tested, and four of them pass through the four corners of the lower surface of the specimen to be tested respectively, and the other electrode passes through the center of the lower surface of the specimen to be tested; during the test process, the circuit is evenly distributed to ensure the stability of the measured resistivity inside the concrete.

[0063] 2) Place the constructed pentahedron of electrode rods in the specimen - forming mold and stir the concrete to be tested according to the method in "Standard for Test Methods of Physical and Mechanical Properties of Concrete" (GB / T50081 - 2019). After stirring is completed, load it into the specimen - forming mold with electrodes placed and vibrate it to compact. Form and cure until the age of 28 days, take out the specimen to be tested and dry it, and use epoxy resin to seal the upper surface of the specimen to be tested to ensure the sealing during the intrusion process of the sodium chloride solution. After sealing, it is ready for use.

[0064] 3) Connect the test device to start the test. To avoid the phenomenon of electrode heating due to too high voltage, set the test voltage to 20V. After the test is completed, obtain the "concrete resistivity - time" and "total amount of intruded sodium chloride solution - time" curves, and establish the "total amount of sodium chloride solution - concrete resistivity" standard curve based on the analysis of time.

[0065] The "total amount of sodium chloride solution - concrete resistivity" standard curves under different water pressures and different seawater concentrations in the above operations only need to be tested once, and can be used for the automatic determination of the total amount of intruded chloride ions inside the concrete under different water pressures in subsequent tests.

[0066] Further, in step (2), testing the chloride ion penetration depth, establishing the chloride ion concentration distribution curve inside the concrete under different water pressures and calculating the chloride ion diffusion coefficient includes the following steps:

[0067] 1) Transfer the tested specimens to the press, split them along the central interface in the height direction, and immediately conduct the test on the intrusion depth of the sodium chloride solution. The depth test shall be completed within 2 minutes;

[0068] 2) After the depth test, use the core sampling and chloride ion titration method to test the chloride ion concentration on the cross-section where the electrode is located at the center of the lower surface of the specimen to be tested. Set the powder sampling interval to 3 mm, 5 mm, 10 mm, 15 mm, 20 mm, 25 mm... and sample at intervals of 5 mm until the sampling of the entire cross-section where the tungsten copper bar electrode is located is completed. After measuring the chloride ion concentration, analyze it using Fick's second law, and use Fick's second law to characterize the chloride ion concentration on this cross-section and calculate the chloride ion diffusion coefficient. The specific analysis formula is shown in Equation II;

[0069]

[0070] In the formula: C0 is the chloride ion concentration in the initial state of the concrete, C s is the concentration of the sodium chloride solution at the pressure spray head, that is, the concentration of the sodium chloride solution filled in the pressure tank. erf is the error function, and D is the diffusion coefficient (m 2 / s).

[0071] Fick's second law is mainly used to characterize the diffusion flux, that is, the diffusion mass flow through a unit interface area perpendicular to the diffusion direction per unit time, which can be represented by J. The expression of Fick's second law is shown in Equation 7.

[0072]

[0073] In the formula: J(x,t) is the diffusion flux corresponding to the position of the diffusion depth x at time t; D is the diffusion coefficient (m 2 / s); C(x,t) is the chloride ion concentration (%) at the diffusion depth of x at time t.

[0074] When integrating both sides of Equation 6 from the initial time 0 to time t, the amount of chloride ions invading the concrete through the position where the diffusion depth is x per unit area within time t can be obtained, as shown in Equation 8.

[0075]

[0076] Since the chloride ion concentration at the hemispherical pressure spray head is constant, assuming that the concrete is a semi-infinite body with respect to the exposed interface and the chloride ion concentration at an infinite distance from the exposed interface is the initial concentration, the analytical solution of the expression of Fick's second law can be obtained as shown in Equation 9.

[0077]

[0078] Where: C0 is the chloride ion concentration in the concrete in the initial state, C s is the sodium chloride solution concentration at the pressure spray head, that is, the sodium chloride solution concentration filled in the pressure tank, and erf is the error function.

[0079] When the chloride ion concentrations at different concentrations inside the concrete are measured, the chloride ion diffusion coefficients at different pressures can be obtained by regression analysis according to Equation 9.

[0080] Further, in step S3, establishing the standard curves of "chloride ion diffusion depth - concrete resistivity" and "chloride ion diffusion coefficient - concrete resistivity" includes the following steps:

[0081] 1) According to the chloride ion diffusion depth and the final internal resistance R of the concrete at the end of the test c Establish the standard curve of "chloride ion diffusion depth - concrete resistivity";

[0082] 2) According to the chloride ion diffusion coefficient and the final internal resistance R of the concrete at the end of the test c Establish the standard curve of "chloride ion diffusion coefficient - concrete resistivity";

[0083] The standard curves of "chloride ion diffusion depth - concrete resistivity" and "chloride ion diffusion coefficient - concrete resistivity" under different water pressures and different seawater concentrations only need to be tested once, and can be directly called later for the chloride ion impermeability test of different concretes.

[0084] The present invention provides a test method and device for characterizing the chloride ion penetration resistance of submarine tunnel concrete. Its basic principle is to evaluate the chloride ion penetration resistance of concrete based on resistivity. This method can effectively test the chloride ion penetration depth and chloride ion penetration coefficient of concrete under different water pressures in a non-destructive state, and proposes a dual-parameter control index for the chloride ion penetration resistance of concrete, namely "chloride ion penetration coefficient + total amount of chloride ion intrusion". Description of the Drawings

[0085] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained according to the provided drawings without creative efforts.

[0086] Figure 1 It is a schematic structural diagram of a test device for the chloride ion impermeability of submarine tunnel concrete provided by the present invention;

[0087] Figure 2Schematic diagram of the specimen forming die structure of the chloride ion impermeability test device for submarine tunnel concrete provided by the present invention;

[0088] Figure 3 Schematic diagram of the specimen placement platform structure for placing specimens in the chloride ion impermeability test device for submarine tunnel concrete provided by the present invention;

[0089] Figure 4 Schematic diagram of the hemispherical pressure nozzle structure provided by the present invention;

[0090] Figure 5 Schematic diagram of the pressure tank structure for controlling the water pressure during the test provided by the present invention;

[0091] Figure 6 Schematic diagram of the arranged tungsten-copper rod electrodes after installation provided by the present invention;

[0092] Figure 7 Schematic diagram of the installed tungsten-copper rod electrodes and test mold provided by the present invention;

[0093] Figure 8 Schematic diagram of the pressure water outlet valve provided by the present invention;

[0094] Figure 9 Schematic diagram of the flow chart of the chloride ion impermeability test method for submarine tunnel concrete provided by the present invention;

[0095] Figure 10 Internal equivalent circuit diagram of the specimen to be tested with embedded electrodes;

[0096] Figure 11 Relationship diagram between chloride ion diffusion coefficient and internal resistivity of concrete;

[0097] In the attached drawings, the list of structures represented by each reference numeral is as follows: 1 - computer output system, 2 - potentiostat, 3 - central control system, 4 - junction box, 5 - wire, 6 - tungsten copper rod electrode, 7 - hemispherical pressure nozzle, 8 - screw insulating sleeve, 9 - bottom - hollowed base plate, 10 - specimen to be tested, 11 - specimen placement platform, 12 - level gauge, 13 - knob, 14 - liquid conduit, 15 - flowmeter, 16 - pressure tank, 17 - lid, 18 - tank body, 19 - pressure water outlet valve, 20 - pressure gauge, 21 - pressure relief valve, 22 - air inlet hole, 23 - gas conduit, 24 - handle, 25 - bolt, 26 - pulley, 27 - air outlet hole, 28 - air compressor, 29 - pressure gauge, 30 - conduit joint, 31 - stainless - steel perforated plane, 32 - stainless - steel perforated hemispherical surface, 33 - specimen forming die, 34 - groove, 35 - pressure valve knob, 36 - water outlet hole; 501 - first wire, 502 - second wire, 503 - third wire, 504 - third wire, 505 - fifth wire, 506 - sixth wire, 507 - seventh wire; 601 - first tungsten copper rod electrode, 602 - second tungsten copper rod electrode, 603 - third tungsten copper rod electrode, 604 - fourth tungsten copper rod electrode, 605 - fifth tungsten copper rod electrode, 606 - sixth tungsten copper rod electrode, 607 - seventh tungsten copper rod electrode, 608 - eighth tungsten copper rod electrode, 609 - ninth tungsten copper rod electrode, 6010 - tenth tungsten copper rod electrode; 801 - first screw insulating sleeve, 802 - second screw insulating sleeve, 803 - third screw insulating sleeve, 804 - fourth screw insulating sleeve, 805 - fifth screw insulating sleeve; 1301 - first knob, 1302 - second knob, 1303 - third knob, 1304 - fourth knob; 2401 - first handle, 2402 - second handle; 2501 - first bolt, 2502 - second bolt, 2503 - third bolt, 2504 - fourth bolt, 2505 - fifth bolt, 2506 - sixth bolt, 2507 - seventh bolt, 2508 - eighth bolt, 2509 - ninth bolt, 25010 - tenth bolt; 2601 - first pulley, 2602 - second pulley, 2603 - third pulley, 2604 - fourth pulley. Detailed implementation manners

[0098] The embodiments of the present invention will be described in detail below. The examples of the embodiments are shown in the attached drawings, where the same or similar reference numerals represent the same or similar elements or elements with the same or similar functions from beginning to end. The embodiments described below by referring to the attached drawings are exemplary and are intended to explain the present invention, and should not be construed as a limitation to the present invention.

[0099] In the description of the present invention, it should be understood that the orientation or positional relationships indicated by the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. are based on the orientation or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation on the present invention.

[0100] In addition, the terms "first" and "second" are only used for descriptive purposes, and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, the meaning of "a plurality" is two or more, unless otherwise specifically defined.

[0101] In the present invention, unless otherwise clearly specified and defined, the terms such as "mounted", "connected", "connected to", "fixed", etc. should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or integrated; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0102] In the present invention, unless otherwise clearly specified and defined, the first feature being "above" or "below" the second feature may include the direct contact between the first and second features, or may include the situation where the first and second features are not in direct contact but in contact through other features therebetween. Moreover, the first feature being "above", "over" and "on" the second feature includes that the first feature is directly above and obliquely above the second feature, or merely indicates that the horizontal height of the first feature is higher than that of the second feature. The first feature being "under", "beneath" and "under" the second feature includes that the first feature is directly below and obliquely below the second feature, or merely indicates that the horizontal height of the first feature is lower than that of the second feature.

[0103] Embodiment 1

[0104] A test device for the chloride ion impermeability of submarine tunnel concrete, comprising a resistivity test module to be tested, a pressure penetration module, a central control system 3, a computer output system 1, a specimen forming mold 33, a specimen to be tested 10, and a specimen placement platform 11;

[0105] Among them, the computer output system 1 is electrically connected to the resistivity test module to be tested and the pressure penetration module respectively;

[0106] The central control system 3 is electrically connected to the resistivity test module to be tested and the pressure penetration module respectively;

[0107] The specimen forming mold 33 is fixed on the specimen placement platform 11, and the specimen to be tested 10 is cast and formed in the specimen forming mold 33. The specimen to be tested 10 is electrically connected to the resistivity test module and the pressure penetration module respectively;

[0108] The pressure penetration module includes a hemispherical pressure nozzle 7, a liquid conduit 14, a flow meter 15, a pressure tank 16, a gas conduit 23 and an air compressor 28. The hemispherical pressure nozzle 7 is arranged in the specimen forming mold 33 and is connected to one end of the liquid conduit 14. The other end of the liquid conduit 14 is connected to the water outlet hole 36 on the pressure tank 16; The air outlet hole 27 on the air compressor 28 is connected to the air inlet hole 22 on the pressure tank 16 through the gas conduit 23; The flow meter 15 is fixed on the liquid conduit 14;

[0109] The computer output system 1 is electrically connected to the flow meter 15, and the central control system 3 is electrically connected to the air compressor 28;

[0110] The resistivity test module includes a potentiostat 2, a junction box 4, a wire 5, a tungsten-copper rod electrode 6, a screw insulating sleeve 8 and a bottom plate 9 with a hollow bottom;

[0111] A number of screw insulating sleeves 8 are provided. The number of tungsten-copper rod electrodes 6 is twice that of the screw insulating sleeves, and a tungsten-copper rod electrode 6 is screwed at both the bottom end and the top end of the screw insulating sleeve 8;

[0112] The tungsten-copper rod electrode 6 at the bottom end of the screw insulating sleeve 8 is inserted into the bottom plate 9 with a hollow bottom, and the bottom plate 9 with a hollow bottom is placed in the specimen forming mold 33;

[0113] A wire 5 is led out from each tungsten-copper rod electrode 6 at the bottom end of the screw insulating sleeve 8 and connected to one end of the junction box 4. The other end of the junction box 4 leads out a wire 5 and is connected to the negative electrode of the potentiostat 2;

[0114] The tungsten-copper rod electrode 6 at the top end of the screw insulating sleeve 8 is inserted into the hemispherical pressure nozzle 7, and the tungsten-copper rod electrodes 6 at the top end of the screw insulating sleeve 8 are welded to each other, and a wire 5 is led out from the welding point and connected to the positive electrode of the potentiostat 2;

[0115] The computer output system 1 is electrically connected to the potentiostat 2, and the central control system 3 is electrically connected to the potentiostat 2.

[0116] In some embodiments, the hemispherical pressure nozzle 7 is a prefabricated component. The frame part of the hemispherical pressure head consists of a conduit joint 30, a stainless steel perforated flat surface 31, and a stainless steel perforated hemispherical surface 32. The perforation range of the stainless steel perforated flat surface 31 is within the range where the conduit joint 30 is welded to the stainless steel perforated flat surface 31, for the entry of water flow. The perforation range of the stainless steel perforated hemispherical surface 32 is the entire hemispherical cross-section, to ensure the uniform pressurized infiltration of water flow.

[0117] In some embodiments, a flow meter 15 is installed on the liquid conduit 14. The accuracy of the flow meter is 0.1 ml, which can accurately measure the volume of sodium chloride solution flowing through the inside of the liquid conduit 14, and thus obtain the total amount of sodium chloride solution invading the inside of the specimen 10 to be tested. The two sides of the liquid conduit 14 are respectively connected to the hemispherical pressure nozzle 7 and the pressure tank 16.

[0118] In some embodiments, the pressure tank 16 consists of a lid 17 and a tank body 18. A sealing strip is provided inside the lid 17. The lid 17 and the tank body are connected by the first to tenth tight bolts 2501 to 2510, so as to ensure the sealing performance during the pressurization process. The pressure tank 16 is used to hold the sodium chloride solution and control the water pressure. An air pressure gauge 20, a pressure relief valve 21, and an air inlet hole 22 are provided above the lid 17. First handle 2401 and second handle 2402 are provided on both sides of the lid 17. A pressure water outlet valve 19 is provided on one side of the tank body 18. A pressure valve knob 35 and a water outlet hole 36 are provided on the pressure water outlet valve 19. First pulley 2601, second pulley 2602, third pulley 2603, and fourth pulley 2604 are provided below the tank body 18, facilitating the movement of the pressure tank filled with sodium chloride solution during the test.

[0119] In some embodiments, the pressure water outlet valve 19 controls the pressure inside the pressure tank 16 when discharging water by adjusting the rotation of the pressure water outlet valve 35. When the air pressure in the tank reaches the set target air pressure, the sodium chloride solution can be automatically released to ensure the stability of the water pressure during the pressurized infiltration process.

[0120] In some embodiments, the air compressor 28 is used to inject air into the pressure tank 16 for pressurization. A pressure gauge 29 is provided on the upper part of the air compressor 28, which can transmit the electrical signal of the pressure value to the central control system 3 for the central control system 3 to control the opening and closing of the air compressor 28 during the pressurization process.

[0121] In some other embodiments, the liquid conduit 14 connects the water outlet hole 34 provided on the pressure tank 16 and the hemispherical pressure nozzle 7 embedded inside the specimen, and the gas conduit 23 connects the air outlet hole 27 provided on the air compressor 28 and the air inlet hole 22 provided on the pressure tank 16.

[0122] In some embodiments, the wire 5 includes a first wire 501, a second wire 502, a third wire 503, a fourth wire 504, a fifth wire 505, a sixth wire 506, and a seventh wire 507.

[0123] The tungsten copper rod electrode 6 includes a first tungsten copper rod electrode 601, a second tungsten copper rod electrode 602, a third tungsten copper rod electrode 603, a fourth tungsten copper rod electrode 604, and a fifth tungsten copper rod electrode 605 pre - arranged in the hemispherical pressure nozzle 7, and also includes separate sixth tungsten copper rod electrode 606, seventh tungsten copper rod electrode 607, eighth tungsten copper rod electrode 608, ninth tungsten copper rod electrode 609, and tenth tungsten copper rod electrode 6010.

[0124] The screw insulating sleeve 8 includes a first screw insulating sleeve 801, a second screw insulating sleeve 802, a third screw insulating sleeve 803, a fourth screw insulating sleeve 804, and a fifth screw insulating sleeve 805. The first tungsten copper rod electrode 601 and the sixth tungsten copper rod electrode 606 are connected by screwing their ends into the first screw insulating sleeve 801. The second tungsten copper rod electrode 606 and the seventh tungsten copper rod electrode 607 are connected by screwing their ends into the second screw insulating sleeve 808. The third tungsten copper rod electrode 603 and the eighth tungsten copper rod electrode 608 are connected by screwing their ends into the third screw insulating sleeve 803. The fourth tungsten copper rod electrode 604 and the ninth tungsten copper rod electrode 609 are connected by screwing their ends into the fourth screw insulating sleeve 804. The fifth tungsten copper rod electrode 605 and the tenth tungsten copper rod electrode 6010 are connected by screwing their ends into the fifth screw insulating sleeve 805; the two tungsten copper rod electrodes in the same screw insulating sleeve do not come into contact.

[0125] Since the 5 electrodes are connected to the 5 tungsten copper rod electrodes below by insulating sleeve rods made of PCV material, after being embedded inside the specimen, it is in an open - circuit state before the sodium chloride solution seeps in, and the electrodes do not conduct electricity. As the sodium chloride solution invades, a circuit is formed, and the tungsten copper rods and the wetted part of the concrete form a parallel resistance for measuring the change in the internal resistivity of the concrete during the process of sodium chloride solution penetration.

[0126] After connection, the second wire 502, the third wire 503, the fourth wire 504, the fifth wire 505, and the sixth wire 506 are respectively led out from the lower ends of the sixth tungsten copper rod electrode 606, the seventh tungsten copper rod electrode 607, the eighth tungsten copper rod electrode 608, the ninth tungsten copper rod electrode 609, and the tenth tungsten copper rod electrode 6010. The junction box 4 is used to connect the second wire 502, the third wire 503, the fourth wire 504, the fifth wire 505, and the sixth wire 506 to the seventh wire 507.

[0127] The ends of the sixth tungsten copper rod electrode 606, the seventh tungsten copper rod electrode 607, the eighth tungsten copper rod electrode 608, the ninth tungsten copper rod electrode 609, and the tenth tungsten copper rod electrode are respectively inserted into the corresponding slots of the bottom plate 9 of PCV material with a hollow bottom, and a pentahedron can be formed after the insertion is completed. The angle between the side surfaces is 45°. The size of the bottom plate 9 of PCV material is consistent with the size of the mold used to prepare the test piece, which can ensure that the pentahedron will not be deformed after the electrode is installed and the concrete is poured and vibrated to obtain the test piece 10 after the electrode is embedded and the concrete is poured.

[0128] The welding points of the first tungsten copper rod electrode 601, the second tungsten copper rod electrode 602, the third tungsten copper rod electrode 603, the fourth tungsten copper rod electrode 604 and the fifth tungsten copper rod electrode 605 are connected to the first wire 501, the first wire 501 is connected to the positive pole of the constant potential (constant current) measuring instrument 2, and the seventh wire 607 is connected to the negative pole of the constant potential (constant current) measuring instrument 2.

[0129] In some embodiments, the first tungsten copper rod electrode 601, the second tungsten copper rod electrode 602, the third tungsten copper rod electrode 603, the fourth tungsten copper rod electrode 604 and the fifth tungsten copper rod electrode 605 are preset in the hollow hemisphere composed of the stainless steel perforated plane 31 and the stainless steel perforated hemispherical surface 32, and the angle between the first tungsten copper rod electrode 601 to the fourth tungsten copper rod electrode 604 is 45° welded, and the fifth tungsten copper rod electrode 605 at the center is welded at the center position of the surrounding 4 electrodes. The five welded tungsten copper rod electrodes 605 are connected at the center of the upper half plane 27 of the hemisphere and extend through the center of the outer surface of the lower hemispherical surface 32 of the hemispherical indenter.

[0130] In some embodiments, the specimen forming mold 33 is a rectangular parallelepiped with dimensions of 300mm×300mm×150mm, and is used to place the electrode 6 and the hemispherical pressure nozzle 7 and cast to form a concrete specimen 10 to be tested. A groove 34 is provided at the bottom thereof to fix the vertically arranged tenth tungsten copper rod electrode 6010.

[0131] In some embodiments, during testing, the test piece 10 is placed on a test piece placement platform 11, a level 12 is provided on the platform surface of the test piece placement platform 11, and knobs 13 are provided on the legs of the test piece placement platform 11 to adjust the height of the platform around to ensure that the test piece remains level during testing. Specifically, the knobs 13 include a first knob 1301, a second knob 1302, a third knob 1303, and a fourth knob 1304.

[0132] Example 2

[0133] A test method for characterizing the chloride ion penetration resistance of submarine tunnel concrete comprises the following steps:

[0134] (1) Use the device of Example 1 to establish the relationship between the total amount of sodium chloride solution infiltrated into the concrete and the resistivity, obtain the "total amount of sodium chloride solution - concrete resistivity" standard curve, and realize the automatic determination of the total amount of chloride ions infiltrated into the concrete under different water pressures;

[0135] (2) Obtain the chloride ion diffusion depth and chloride ion concentration distribution, and establish the chloride ion concentration distribution curve inside the concrete under different water pressures and calculate the chloride ion diffusion coefficient according to Fick's second law;

[0136] (3) Establish the "chloride ion diffusion coefficient - concrete resistivity" standard curve, realize the determination of the permeability coefficient based on the resistivity, propose the concrete impermeability index with double control of "chloride ion diffusion coefficient" and "total amount of sodium chloride solution", and propose the evaluation index based on the resistivity.

[0137] In step (1), the resistivity of wet concrete is close to 100 Ω·m. For concrete with a saturated surface dry state, its resistivity is generally about 1×10 4 Ω·m. For completely dry concrete, its resistivity reaches 10 9 Ω·m. Generally, for cement-based materials in the service stage, it is considered that their resistivity is 100 - 10 5 Ω·m. Therefore, when the conductivity of the concrete is almost completely insulated in the completely dry state, its conductivity completely depends on the presence or absence of electrolyte solution inside.

[0138] The first tungsten-copper rod electrode to the fourth tungsten-copper rod electrode are respectively connected to the sixth tungsten-copper rod electrode to the tenth tungsten-copper rod electrode by screw insulating sleeves made of PCV material. The sixth tungsten-copper rod electrode to the ninth tungsten-copper rod electrode and the bottom PCV material base plate with a hollowed-out bottom form a pentahedron, as shown in the appendix Figure 6 shown. The included angle between the upper four planes is 45°. The fifth tungsten-copper rod electrode is connected to the tenth tungsten-copper rod electrode, and the tenth tungsten-copper rod electrode is installed in the central groove of the mold. The installed state is as shown in the appendix Figure 7 shown. Therefore, inside the specimen to be tested after drying, each electrode is in an open circuit state. When the sodium chloride solution continuously infiltrates, the conductivity near the screw insulating sleeve made of PCV material increases, and each electrode forms a circuit, and then the measurement of the concrete resistivity can be realized.

[0139] After the circuit of each electrode is formed, since the material of the tungsten-copper rod electrode is uniform, the resistance value of each electrode is constant and known. Let the resistance of each tungsten-copper rod electrode used in the test be R1, and the resistance of the concrete be R C , at this time, the five installed tungsten-copper rod electrodes are in parallel, and the total resistance of the parallel electrodes and the resistance inside the concrete are in series. The equivalent circuit inside the specimen with embedded electrodes is as follows Figure 10 shown. The total resistance value of the five parallel tungsten-copper rod electrodes can be obtained from

[0140] Formula 1 can be transformed into Formula 2.

[0141]

[0142] Since the parallel electrodes are connected in series with the concrete resistor, the total resistance of the series device can be calculated according to Formula 3. The constant potential (constant current) measuring instrument can directly obtain the voltage and resistance inside the prepared test piece, and the total resistivity R of the test piece can be calculated by Formula 4. T By combining equations 3 and 4, we can obtain the internal resistivity of concrete after 8 hours of penetration under different water pressures (the final test time can be adjusted according to the strength grade of the specimen), as shown in equation 5.

[0143]

[0144] Where: R E is the total resistance of the five resistors in parallel, R1 is the resistance of a single tungsten copper rod electrode, R C is the resistance value inside the concrete, R T is the total resistance of the electrodes and the internal resistance of the concrete after parallel connection, U is the overall voltage inside the test piece measured by the constant potential (constant current) measuring instrument, V, I is the current of the complete path inside the test piece measured by the constant potential (constant current) measuring instrument, A.

[0145] Add 3% sodium chloride solution into the pressure tank, seal the pressure tank by tightening bolts, adjust the knob of the pressure water outlet valve, set the corresponding water pressure when the water is discharged, connect the hemispherical pressurized nozzle embedded in the test piece and the pressure tank with a liquid conduit, connect the pressure tank and the air compressor with a gas conduit, and connect the flow meter set on the liquid conduit to the computer output system to output the change curve of the total amount of intruded sodium chloride solution over time in real time.

[0146] Set the expected air pressure value of the air compressor on the central control system. In order to avoid the electrode polarization phenomenon affecting the chloride ion transmission inside the concrete, set the resistivity acquisition frequency to 1min / time in the central control system (the resistivity acquisition frequency can be adjusted according to the total test time), and set the test time to 8h. After the settings are completed, click the "Start" button in the "Central Control System" to start the test.

[0147] Since the concentration of sodium chloride solution is constant, let the concentration of sodium chloride solution used for the test be ρ, g / L, let the volume of sodium chloride solution intruding into the concrete measured by the flowmeter when the test is completed be V, and the total amount of sodium chloride intruding into the concrete at this time is Q NaCl It can be calculated by formula 6.

[0148]

[0149] After the test starts, the central control system controls the potentiostat (galvanostat) in real time to continuously obtain the "resistivity - time" curve, and the flowmeter outputs the "volume of sodium chloride solution invaded - time" curve in real time. By comparing the time parameters of the two curves, the "total volume of sodium chloride solution invaded - concrete resistivity" standard curve can be obtained. After that, this standard curve can be directly called to realize the test of the total volume of sodium chloride solution invaded in the concrete structure of the submarine tunnel based on resistivity.

[0150] In step S2, to obtain the chloride ion diffusion depth and chloride ion concentration distribution, and establish the chloride ion concentration distribution curve inside the concrete under different water pressures and calculate the chloride ion diffusion coefficient according to Fick's second law, it can be completed according to the following steps;

[0151] After the test is completed, split the specimen from the central position, and immediately measure the invasion depth of the sodium chloride solution. The depth measurement needs to be completed within 2 minutes. After the depth measurement is completed, use the method of drilling powder sampling and chloride ion titration to measure the chloride ion concentration on the cross - section where the tenth electrode is located. The powder sampling intervals are 3mm, 5mm, 10mm, 15mm, 20mm, 25mm..., and sampling is carried out at intervals of 5mm until the sampling of the entire cross - section where the tenth tungsten - copper rod electrode is located is completed. Use Fick's second law to characterize the chloride ion concentration on this cross - section and calculate the chloride ion diffusion coefficient.

[0152] Fick's second law is mainly used to characterize the diffusion flux, that is, the diffusion mass flow rate through a unit interface area perpendicular to the diffusion direction per unit time, which can be represented by J. The expression of Fick's second law is shown in Equation 7.

[0153]

[0154] In the formula: J(x,t) is the diffusion flux corresponding to the position of diffusion depth x at time t; D is the diffusion coefficient (m 2 / s); C(x,t) is the chloride ion concentration (%) at the diffusion depth of x at time t.

[0155] When integrating both sides of Equation 7 from time 0 to time t, the amount of chloride ions invading the concrete through the position of diffusion depth x per unit area within time t can be obtained, as shown in Equation 8.

[0156]

[0157] Since the chloride ion concentration is constant at the hemispherical pressure nozzle, assuming that the concrete is a semi - infinite body with respect to the exposed interface and the chloride ion concentration at an infinite distance from the exposed interface is the initial concentration, the analytical solution of the expression of Fick's second law can be obtained as shown in Equation 9.

[0158]

[0159] where: C0 is the chloride ion concentration in the concrete under the initial state, C s is the concentration of sodium chloride solution at the pressure spray nozzle, that is, the concentration of sodium chloride solution filled in the pressure tank, and erf is the error function.

[0160] When the chloride ion concentrations at different concentrations inside the concrete are measured, the chloride ion diffusion coefficients at different pressures can be obtained by regression analysis using Equation 9.

[0161] In step S3, the standard curves of "chloride ion diffusion depth - concrete resistivity" and "chloride ion diffusion coefficient - concrete resistivity" can be obtained according to the following method:

[0162] Combined with the chloride ion diffusion depth and the final internal resistance R of the concrete at the end of the test respectively c and the chloride ion diffusion coefficient and the final internal resistance of the concrete at the end of the test, the standard curves of "chloride ion diffusion depth - concrete resistivity" and "chloride ion diffusion coefficient - concrete resistivity" are established respectively. Subsequently, a standard curve library can be established based on the established standard curves of "chloride ion diffusion depth - concrete resistivity" and "chloride ion diffusion coefficient - concrete resistivity" under different water pressures and different seawater concentrations to realize the non-destructive evaluation of the chloride ion impermeability of the submarine tunnel concrete.

[0163] Example 3 conducts further tests according to the method of Example 2

[0164] Place the dried test piece on the test piece placement platform, connect the first wire to the positive pole of the potentiostat (galvanostat), use the junction box to connect the second wire to the sixth wire to the seventh wire, connect the seventh wire to the negative pole of the potentiostat (galvanostat), connect the output port of the potentiostat (galvanostat) to the computer output system to export the change of the internal resistivity of the test piece with time, connect the input port of the potentiostat (galvanostat) to the central control system to facilitate setting the resistivity acquisition frequency using the central control system. In order to avoid the influence of overheating of the electrode on the test result due to too high voltage, set the test voltage to 20V, and set the resistivity acquisition frequency to 1 min / time in the central control system (the acquisition frequency of the resistivity can be adjusted according to the total test time), set the test time to 8h (which can be appropriately adjusted according to the strength grade of the test piece to be tested), and standby after installation;

[0165] Check the airtightness inside the pressure tank, check the integrity of the sealing strip in the pressure tank lid. After confirming good airtightness, add a 3% concentration sodium chloride solution (the concentration of the sodium chloride solution can be adjusted according to test requirements) into the tank body of the pressure tank. Connect the pressure tank lid and the tank body with the first to the tenth tight bolts. Adjust the water pressure of the pressure outlet valve. When testing the concrete impermeability performance at a water pressure of 0.6 MPa, adjust the pressure valve knob to 0.6 MPa. Connect one end of the liquid conduit equipped with a flowmeter to the water outlet hole of the pressure outlet valve and the other end to the water inlet hole of the hemispherical pressurized nozzle, and connect the output end of the flowmeter to the computer output system to measure the total amount of sodium chloride intrusion during the test of the concrete impermeability performance of the undersea tunnel;

[0166] Connect one end of a gas conduit to the air outlet hole of the air compressor and the other end to the air inlet hole of the pressure tank. Use the central control system to set the constant air pressure of the air compressor to 0.6 MPa. A pressure gauge is set on the upper part of the air compressor to provide real-time feedback on the output air pressure of the air compressor to ensure the stability of the simulated water pressure;

[0167] Close the pressure relief valve of the pressure tank. Click the "Start" button on the central control system, and the test system starts to run. When the internal air pressure of the pressure tank stabilizes to 0.6 MPa, the sodium chloride solution continuously penetrates into the concrete through the hemispherical pressurized nozzle until the test ends and the equipment stops automatically;

[0168] During this process, since the equivalent circuit shows that the resistance between the internally embedded tungsten-copper rod electrodes and the internal resistance of the concrete satisfies the parallel connection of 5 tungsten-copper rod electrodes, and the total resistance of the parallel tungsten-copper rod electrodes is in series with the internal resistance of the concrete.

[0169] Combined with the chloride ion diffusion depth and the final internal resistance R of the concrete at the end of the test respectively c And the chloride ion diffusion coefficient and the final internal resistance of the concrete at the end of the test respectively establish the "chloride ion diffusion depth - concrete resistivity" and "chloride ion diffusion coefficient - concrete resistivity" standard curves.

[0170] Through the test results of concrete with different strength grades under different water pressures, a standard curve library is established. Subsequently, when evaluating the chloride ion permeability resistance of a certain strength grade of concrete under a certain water pressure and a certain chloride ion concentration, it can be directly tested by the method of embedding electrodes. Based on the resistivity, the chloride ion permeability coefficient, chloride ion diffusion depth, and total amount of chloride ions can be directly obtained, which has higher accuracy than only using a single index of chloride ion permeability coefficient.

[0171] Example 4

[0172] Prepare the corresponding concrete using the concrete mix ratio for the partial subsea tunnel, and analyze the relationship between the chloride ion diffusion coefficient and the internal resistivity of the concrete at the end of the test according to the method of Example 2. The results are as Figure 11 shown. The results show that there is a good correlation between the internal resistivity of the concrete and the chloride ion diffusion coefficient. Therefore, this method can provide a new method for non-destructively evaluating the internal chloride ion permeability coefficient of the concrete.

[0173] In the description of this specification, the description referring to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples", etc. means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine the different embodiments or examples described in this specification.

[0174] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. A test device for the chloride ion impermeability of submarine tunnel concrete, characterized in that It includes a resistivity test module to be tested, a pressure penetration module, a central control system, a computer output system, a specimen forming mold, a specimen to be tested, and a specimen placement platform; Among them, the computer output system is electrically connected to the resistivity test module to be tested and the pressure penetration module respectively; The central control system is electrically connected to the resistivity test module to be tested and the pressure penetration module respectively; The specimen forming mold is fixed on the specimen placement platform, the specimen to be tested is cast and formed in the specimen forming mold, and the specimen to be tested is electrically connected to the resistivity test module and the pressure penetration module respectively; The pressure penetration module includes a hemispherical pressure nozzle, a liquid conduit, a flow meter, a pressure tank, a gas conduit, and an air compressor. The hemispherical pressure nozzle is arranged in the specimen forming mold and is connected to one end of the liquid conduit. The other end of the liquid conduit is connected to the water outlet hole on the pressure tank; the air outlet hole on the air compressor is connected to the air inlet hole on the pressure tank through the gas conduit; the flow meter is fixed on the liquid conduit; The computer output system is electrically connected to the flow meter, and the central control system is electrically connected to the air compressor; The resistivity test module includes a potentiostat, a junction box, wires, tungsten-copper rod electrodes, screw insulating sleeves, and a bottom plate with a hollow bottom; There are several screw insulating sleeves, the number of tungsten-copper rod electrodes is twice that of the screw insulating sleeves, and a tungsten-copper rod electrode is screwed at both the bottom end and the top end of the screw insulating sleeve; The tungsten-copper rod electrode at the bottom end of the screw insulating sleeve is inserted into the bottom plate with a hollow bottom, and the bottom plate with a hollow bottom is placed in the specimen forming mold; A wire is led out from each tungsten-copper rod electrode at the bottom end of the screw insulating sleeve and connected to one end of the junction box, and a wire is led out from the other end of the junction box and connected to the negative pole of the potentiostat; The tungsten-copper rod electrodes at the top ends of the screw insulating sleeves are inserted into the hemispherical pressure nozzle, and the tungsten-copper rod electrodes at the top ends of the screw insulating sleeves are welded to each other, and a wire is led out from the welding point and connected to the positive pole of the potentiostat; The computer output system is electrically connected to the potentiostat, and the central control system is electrically connected to the potentiostat.

2. The testing device for chloride ion impermeability of submarine tunnel concrete according to claim 1, characterized in that, The pressure tank is composed of a lid and a tank body. A sealing strip is arranged inside the lid, and the lid and the tank body are connected by bolts; a pressure gauge, a pressure relief valve, and an air inlet hole are arranged above the lid, handles are arranged on both sides of the lid, a pressure water outlet valve is arranged on one side of the tank body, and pulleys are arranged below the tank body to facilitate the movement of the pressure tank filled with sodium chloride solution during the test; A pressure gauge is arranged on the air compressor, the pressure gauge is electrically connected to the central control system, and the central control system controls the switch of the air compressor by an electrical signal.

3. The testing device for chloride ion impermeability of submarine tunnel concrete according to claim 2, characterized in that, The wires include a first wire, a second wire, a third wire, a fourth wire, a fifth wire, a sixth wire, and a seventh wire; The tungsten copper rod electrode includes a first tungsten copper rod electrode, a second tungsten copper rod electrode, a third tungsten copper rod electrode, a fourth tungsten copper rod electrode, and a fifth tungsten copper rod electrode preset in a hemispherical pressure nozzle, and also includes a sixth tungsten copper rod electrode, a seventh tungsten copper rod electrode, an eighth tungsten copper rod electrode, a ninth tungsten copper rod electrode, and a tenth tungsten copper rod electrode; the tops of the first tungsten copper rod electrode, the second tungsten copper rod electrode, the third tungsten copper rod electrode, the fourth tungsten copper rod electrode, and the fifth tungsten copper rod electrode intersect at the center of the hemispherical pressure nozzle; a first wire is welded at the intersection, and the first wire is connected to the positive electrode of the constant potential measuring instrument; The screw insulation sleeve comprises a first screw insulation sleeve, a second screw insulation sleeve, a third screw insulation sleeve, a fourth screw insulation sleeve and a fifth screw insulation sleeve; The first tungsten copper rod electrode and the sixth tungsten copper rod electrode are connected by screwing their ends into the first screw insulation sleeve, the second tungsten copper rod electrode and the seventh tungsten copper rod electrode are connected by screwing their ends into the second screw insulation sleeve, the third tungsten copper rod electrode and the eighth tungsten copper rod electrode are connected by screwing their ends into the third screw insulation sleeve, the fourth tungsten copper rod electrode and the ninth tungsten copper rod electrode are connected by screwing their ends into the fourth screw insulation sleeve, and the fifth tungsten copper rod electrode and the tenth tungsten copper rod electrode are connected by screwing their ends into the fifth screw insulation sleeve; the two tungsten copper rod electrodes in the same screw insulation sleeve do not contact; After the connection is completed, the second wire, the third wire, the fourth wire, the fifth wire and the sixth wire are respectively connected to the lower ends of the sixth tungsten copper rod electrode, the seventh tungsten copper rod electrode, the eighth tungsten copper rod electrode, the ninth tungsten copper rod electrode and the tenth tungsten copper rod electrode; the junction box connects the second wire, the third wire, the fourth wire, the fifth wire and the sixth wire to the seventh wire, and the seventh wire is connected to the negative pole of the constant potential meter.

4. A test method for the chloride ion impermeability of submarine tunnel concrete, characterized in that, The device according to claim 1 comprises the following steps: (1) Concrete is injected into the specimen forming mold, and the specimen forming mold is removed after the concrete solidifies and forms. Then, the relationship between the total amount of sodium chloride solution infiltrated into the concrete and the resistivity is established using the submarine tunnel concrete chloride ion impermeability test device, and the standard curve of "total amount of sodium chloride solution-concrete resistivity" is obtained to realize the automatic determination of the total amount of chloride ions intruding into the concrete under different water pressures; (2) The chloride ion impermeability test device for submarine tunnel concrete was used to obtain the chloride ion diffusion depth and chloride ion concentration distribution. The chloride ion concentration distribution curve inside the concrete under different water pressures was established according to Fick's second law and the chloride ion diffusion coefficient was calculated. (3) Based on the data obtained in step (1) and step (2), standard curves of "chloride ion diffusion depth-concrete resistivity" and "chloride ion diffusion coefficient-concrete resistivity" are established to achieve the permeability coefficient and chloride ion diffusion depth measurement based on resistivity, form a concrete impermeability index with dual control of "chloride ion diffusion coefficient" and "total amount of sodium chloride solution", and form an evaluation index based on resistivity.

5. The testing method for chloride ion impermeability of submarine tunnel concrete according to claim 4, characterized in that, In step (1), the electrodes embedded inside the test piece in the dry state are in an open circuit state. As the sodium chloride solution invades, the two tungsten copper rod electrodes on each screw insulation sleeve form a path through the sodium chloride solution. As the total amount of sodium chloride solution intrusion increases, the resistivity inside the concrete continues to decrease. A standard curve of "total amount of sodium chloride solution-concrete resistivity" is established based on the time parameter.

6. The method for testing the chloride ion impermeability of concrete in a submarine tunnel according to claim 5, characterized in that There are 5 screw insulation sleeves. After the sodium chloride solution penetrates, 5 connected tungsten copper rod electrodes are formed. The resistance of the embedded tungsten copper rod electrodes inside the test piece and the internal resistance of the concrete meet the following conditions: 5 tungsten copper rod electrodes are connected in parallel, and the total resistance of the parallel tungsten copper rod electrodes and the internal resistance of the concrete are connected in series. The calculation formula is shown in Formula I: Where: R E is the total resistance of five resistors in parallel, R1 is the resistance of a single tungsten-copper bar electrode, R C is the resistance value inside the concrete, R T is the total resistance of the electrode and the resistance inside the concrete in parallel, U is the overall voltage inside the test piece measured by a potentiostat (galvanostat), V, and I is the current of the complete path inside the test piece measured by a potentiostat (galvanostat), A.

7. The method for testing the chloride ion impermeability of concrete for a subsea tunnel according to claim 6, wherein, In step (1), obtaining the "solution concentration-phase difference" standard curve includes the following steps: 1) Connect the tungsten copper rod electrodes and form a pentahedron with the bottom of the PCV material hollowed out, ensuring that the five electrode rods intersect at the center of the upper surface of the test piece, and four of the electrodes pass through the four corners of the lower surface of the test piece respectively, and the other electrode passes through the center of the lower surface of the test piece; 2) Place the constructed electrode rod pentahedron in the specimen forming mold, stir the concrete to be tested according to the method of the "Standard for Test Methods of Physical and Mechanical Properties of Concrete", put it into the specimen forming mold after the electrode is placed and vibrate it, form and cure it to 28 days, take out the specimen to be tested and dry it, seal the upper surface of the specimen to be tested with epoxy resin to ensure the sealing during the intrusion of sodium chloride solution, and set it aside after sealing; 3) Connect the test device and start the test. After the test is completed, obtain the "concrete resistivity-time" and "total amount of sodium chloride solution intrusion-time" curves, and establish the "total amount of sodium chloride solution-concrete resistivity" standard curve based on time analysis.

8. A method for testing the chloride ion impermeability of concrete in a subsea tunnel according to claim 4, characterized in that, Testing the chloride ion penetration depth in step (2), establishing the chloride ion concentration distribution curve inside the concrete under different water pressures and calculating the chloride ion diffusion coefficient include the following steps: 1) Transfer the tested specimen to the press, split it at the center interface along the height direction, and immediately conduct a sodium chloride solution penetration depth test. The depth test must be completed within 2 minutes; 2) After the depth test is completed, the chloride ion concentration test is performed on the cross section where the electrode is located at the center of the lower surface of the bed to be tested by drilling sampling and chloride ion titration method. The powder sampling interval is set to 3mm, 5mm, 10mm, 15mm, 20mm, 25mm..., and the sampling of the cross section where the entire tungsten copper rod electrode is located is completed at an interval of 5mm. After the chloride ion concentration is measured, Fick's second law is used for analysis. The specific analysis formula is shown in Formula II; Where: C0 is the chloride ion concentration in the concrete under the initial state, C s is the sodium chloride solution concentration at the pressure nozzle, which is the sodium chloride solution concentration filled in the pressure tank, erf is the error function, and D is the diffusion coefficient (m 2 / s).

9. A method for testing the chloride ion impermeability of concrete in a subsea tunnel according to claim 4, characterized in that, In step S3, the standard curves of "chloride ion diffusion depth-concrete resistivity" and "chloride ion diffusion coefficient-concrete resistivity" are established, including the following steps: 1) Based on the chloride ion diffusion depth and the final internal resistance R of the concrete at the end of the test c Establish a "chloride ion diffusion depth - concrete resistivity" standard curve; 2) Based on the chloride ion diffusion coefficient and the final internal resistance R of the concrete at the end of the test c Establish a "chloride ion diffusion coefficient - concrete resistivity" standard curve; The standard curves of "chloride ion diffusion depth-concrete resistivity" and "chloride ion diffusion coefficient-concrete resistivity" under different water pressures and seawater concentrations only need to be tested once, and can be directly called to perform chloride ion impermeability tests on different concretes later.

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