A device for testing the steady-state migration coefficient of chloride ions and a method for detecting the steady-state migration coefficient of chloride ions

Abstract

The application belongs to the technical field of chemical detection, and particularly relates to a testing device for chloride ion steady-state migration coefficient and a detection method for chloride ion steady-state migration coefficient. The testing device provided by the application can test cement paste slices, the cement paste slices do not contain coarse aggregate, interface transition zones, and large macroscopic cracks and bubbles, and the chloride ion steady-state migration coefficient measured by taking the cement paste slices as the testing object eliminates the influence of the macroscopic scale of concrete. Before the electro-migration test of the paste slices by using the testing device, the paste slices are soaked in a sodium hydroxide solution for adsorption saturation, so as to reduce the precipitation of alkali in the subsequent test process and avoid the influence of the solid chloride effect in the non-steady-state stage on the chloride ion migration process; the testing device provided by the application can detect the steady-state migration rate of chloride ions in the cement small test piece, so as to eliminate the influence of the macroscopic scale of concrete and the solid chloride effect.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of chemical detection, and particularly relates to a device for testing a steady-state chloride ion migration coefficient and a method for detecting the steady-state chloride ion migration coefficient. BACKGROUND

[0002] Concrete structures are an important part of modern infrastructure, and concrete is a widely used base material. The durability of concrete is crucial to ensuring the safety and service life of the facilities. The durability of concrete is mainly affected by factors such as chloride salt erosion, sulfate erosion, freeze-thaw cycles, carbonation, alkali-aggregate reaction, and stress failure. Among these factors, the corrosion of steel bars caused by chloride salt erosion is an important and increasingly prominent problem worldwide. Therefore, understanding the mechanism and factors leading to chloride salt erosion is crucial for developing effective corrosion prevention strategies and improving the durability of concrete structures.

[0003] For the study of the mechanism of chloride salt erosion, how to quickly and accurately test the chloride ion migration coefficient is of great significance to the study of the transport mechanism of chloride ions in concrete. The commonly used test methods for the chloride ion transport coefficient of concrete are mostly obtained through non-steady-state diffusion tests. The non-steady-state diffusion test simulates the real exposure under complete immersion conditions, forcing the chloride ions to penetrate unidirectionally, and the test sample is coated with epoxy resin on all surfaces except one. Chloride ions penetrate into the sample by diffusion and are partially bound by the cement paste, which is called the cement paste's solid chloride effect. Therefore, the apparent diffusion coefficient obtained by the non-steady-state diffusion test of chloride ions is the result of the simultaneous action of diffusion and binding of chloride ions, which limits the understanding of the transport mechanism of chloride ions. At the same time, the non-steady-state diffusion test requires a long immersion time, which is very time-consuming and labor-intensive. In addition, the non-steady-state migration test of concrete is mostly for large test specimens, and the apparent migration coefficient obtained by the test cannot reflect the changes in the local transport capacity of concrete, which means that the diffusion coefficient measured by the RCM method mentioned in the Standard Test Method for Long-Term Performance and Durability Performance of Ordinary Concrete GB / T 50082-2006 is related to the pore, crack, pore solution composition, and solid chloride, and it is difficult to establish the relationship between the microstructure of concrete and the transport capacity. SUMMARY

[0004] Therefore, the application provides a device for testing a steady-state chloride ion migration coefficient and a method for detecting the steady-state chloride ion migration coefficient. The test device provided by the application can accurately detect the steady-state chloride ion migration coefficient of a small cement test specimen, can explore the chloride ion transport capacity of the microstructure of concrete, and is beneficial to the study of the mechanism of chloride salt erosion of concrete structures.

[0005] In order to solve the above technical problems, the application provides a device for testing the steady-state migration coefficient of chloride ions, comprising an anode pool 2, an anode 1 arranged at either end of the anode pool 2;

[0006] Further comprising a cathode pool 5, a cathode 6 arranged at either end of the cathode pool 5;

[0007] The other end of the anode pool 2 and the other end of the cathode pool 5 are connected through a connecting structure; the connecting structure is provided with a sample chamber 7 to be tested.

[0008] Preferably, the anode pool 2 is provided with an anode liquid injection port 3 at one end close to the connecting structure; the cathode pool 5 is provided with a cathode liquid injection port 4 at one end close to the connecting structure.

[0009] Preferably, the sample chamber 7 to be tested is a cylinder, the diameter of the cylinder is 25-30 mm, and the height of the cylinder is 6-10 mm.

[0010] 4The application further provides a method for detecting the steady-state migration coefficient of chloride ions by using the device described in the above technical solution, comprising the following steps:

[0011] Mixing cement and water to form a cement stone;

[0012] Coating a waterproof material on the side of the cement stone to obtain a cement stone with a waterproof side;

[0013] Soaking the cement stone with a waterproof side in a sodium hydroxide solution to obtain a saturated cement stone;

[0014] Placing the saturated cement stone in the sample chamber 7 to be tested to perform the electric migration of chloride ions; filling the anode pool 2 with a sodium hydroxide solution and filling the cathode pool 5 with a mixed solution of sodium hydroxide and sodium chloride; the volume of the sodium hydroxide solution in the anode pool 2 remains unchanged during the electric migration of chloride ions, and the concentration of the mixed solution of sodium hydroxide and sodium chloride in the cathode pool 5 is not less than 90% of the initial concentration;

[0015] According to formula 1 and formula 2, the steady-state migration coefficient of chloride ions is calculated:

[0016]

[0017] Wherein, J is the flux of chloride ions through the sample at steady state, with the unit of mol / (m 2 ·s);

[0018] ΔC2 is the increased chloride ion concentration in the anode pool within the period of Δt at steady state, with the unit of mol / m 3 ;

[0019] V2 is the solution volume of the anode pool, with the unit of m 3 ;

[0020] Δt is the length of a time period used for calculation after steady state, in s;

[0021] A is the cross-sectional area of the sample, in m 2 ;

[0022] D is the steady-state migration coefficient of the sample, in m 2 / s;

[0023] R is the gas constant, R = 8.314 J / (mol·K);

[0024] T is the temperature, in K;

[0025] l is the thickness of the sample, in m;

[0026] C1 is the concentration of chloride ions in the cathode tank, in mol / m 3 ;

[0027] F is the Faraday constant, F = 96500 C / mol;

[0028] ΔE is the potential difference across the sample, in V.

[0029] Preferably, the mass ratio of water to cement is 0.3-0.5:1.

[0030] Preferably, the forming further comprises curing the formed product, the curing environment temperature is 17-23℃, the relative humidity of the curing environment is ≥90%, and the curing time is 28 days.

[0031] Preferably, the waterproof material comprises epoxy resin or silicone; and the coating thickness is 1-2 mm.

[0032] The molar concentration of the sodium hydroxide solution used for soaking is 0.28-0.32 mol / L; and the soaking time is 46-50 h.

[0033] Preferably, the molar concentration of the sodium hydroxide solution in the anode tank 2 is 0.28-0.32 mol / L.

[0034] Preferably, the molar concentration of sodium hydroxide in the mixed solution of sodium hydroxide and sodium chloride in the cathode tank 5 is 0.28-0.32 mol / L, and the molar concentration of sodium chloride is 0.48-0.52 mol / L.

[0035] Preferably, the electric current of the electric migration of chloride ions is 5-10 mA.

[0036] The application provides a testing device for chloride ion steady-state migration coefficient, comprising an anode pool 2, an anode 1 arranged at any end of the anode pool, a cathode pool 5, and a cathode 6 arranged at any end of the cathode pool 5, wherein the other end of the anode pool 2 and the other end of the cathode pool 5 are connected through a connecting structure, and a sample chamber 7 to be tested is arranged in the connecting structure. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 The structural schematic diagram of the testing device for chloride ion steady-state migration coefficient used for the embodiment 1 is shown, wherein 1 is an anode, 2 is an anode pool, 3 is an anode liquid injection port, 4 is a cathode liquid injection port, 5 is a cathode pool, 6 is a cathode, and 7 is a sample chamber to be tested.

[0038] Figure 2 The actual picture of the cement stone with waterproof side surface prepared in the embodiment 1 is shown.

[0039] Figure 3 The structural schematic diagram of the cement stone after adsorption saturation and installation of a rubber ring in the embodiment 1 is shown, wherein 8 is the adsorption saturated cement stone, 9 is a resin layer, and 10 is a rubber ring.

[0040] Figure 4 The point line graph of the chloride ion concentration in the anode pool changing with time during the chloride ion electromigration process in the embodiment 1 is shown. DETAILED DESCRIPTION

[0041] The application provides a testing device for chloride ion steady-state migration coefficient, comprising an anode pool 2, an anode 1 arranged at any end of the anode pool.

[0042] In the application, the testing device for chloride ion steady-state migration coefficient further comprises a cathode pool 5 and a cathode 6 arranged at any end of the cathode pool 5.

[0043] In the present application, the other end of the anode pool 2 and the other end of the cathode pool 5 are connected by a connecting structure; a sample chamber 7 to be tested is arranged in the connecting structure. The present application has no special requirements for the connecting structure, as long as there is enough space to arrange the sample chamber 7 to be tested. As an embodiment of the present application, the connecting structure is a flange connection. As an embodiment of the present application, the sample chamber 7 to be tested is a cylinder, the diameter of which is preferably 25-30 mm, more preferably 28 mm; the height of the cylinder is preferably 6-10 mm, more preferably 8 mm. In the present application, the sample chamber 7 to be tested is in communication with the anode pool 2 and the cathode pool 5.

[0044] As an embodiment of the present application, the anode pool 2 is provided with an anode liquid injection port 3 near one end of the connecting structure; the cathode pool 5 is provided with a cathode liquid injection port 4 near one end of the connecting structure. The present application preferably injects an anode electrolyte solution into the anode pool 2 through the anode liquid injection port 3; the present application preferably injects a cathode electrolyte solution into the cathode pool 5 through the cathode liquid injection port 4.

[0045] Figure 1 The structural schematic diagram of the testing device for the steady-state migration coefficient of chloride ions used in Example 1, wherein 1 is an anode, 2 is an anode pool, 3 is an anode liquid injection port, 4 is a cathode liquid injection port, 5 is a cathode pool, 6 is a cathode, and 7 is a sample chamber to be tested.

[0046] The present application also provides a detection method for the steady-state migration coefficient of chloride ions using the above-mentioned testing device, which comprises the following steps:

[0047] After mixing the cement and water, a cement stone is formed;

[0048] A waterproof material is coated on the side surface of the cement stone to obtain a cement stone with a waterproof side surface;

[0049] The cement stone with a waterproof side surface is soaked in a sodium hydroxide solution to obtain a saturated cement stone;

[0050] The saturated cement stone is placed in the sample chamber 7 to be tested for electric migration of chloride ions; the anode pool 2 is filled with a sodium hydroxide solution, and the cathode pool 5 is filled with a mixed solution of sodium hydroxide and sodium chloride; the volume of the sodium hydroxide solution in the anode pool 2 remains unchanged during the electric migration of chloride ions, and the concentration of the mixed solution of sodium hydroxide and sodium chloride in the cathode pool 5 is not less than 90% of the initial concentration;

[0051] The steady-state migration coefficient of chloride ions is calculated according to Formula 1 and Formula 2:

[0052]

[0053] wherein J is the flux of chloride ions through the sample at steady state, with the unit of mol / (m2 ·s);

[0054] ΔC2 is the increased chloride ion concentration in the anode tank during the period of Δt in the steady state, in units of mol / m 3 In the present application, when the chloride ion concentration in the anode tank is in a state of linear rapid growth, it is called steady state. In the present application, after reaching steady state, the period of Δt contains at least five linear points, that is, the determination coefficient R 2 is greater than 0.9, it is considered that the five points can be approximately regarded as on a straight line, and ΔC2 / Δt is equal to the slope of the least square fitting line;

[0055] V2 is the solution volume of the anode tank, in units of m 3 ;

[0056] Δt is the length of a time period used for calculation after the steady state, in units of s;

[0057] A is the cross-sectional area of the sample, in units of m 2 ;

[0058] D is the steady-state migration coefficient of the sample, in units of m 2 / s;

[0059] R is the gas constant, taken as R = 8.314 J / (mol·K);

[0060] T is the temperature, in units of K;

[0061] l is the thickness of the sample, in units of m;

[0062] C1 is the chloride ion concentration in the cathode tank, in units of mol / m 3 ;

[0063] F is the Faraday constant, taken as F = 96500 C / mol;

[0064] ΔE is the potential difference between the two ends of the sample, in units of V.

[0065] The cement and water are mixed to obtain a cement stone. In the present application, the cement is preferably Portland cement; the Portland cement is preferably ONODA PⅡ52.5 cement. In the present application, the mass ratio of water to cement is preferably 0.3-0.5:1, more preferably 0.35-0.4:1. In the present application, the mixing preferably comprises slow stirring and fast stirring in sequence. In the present application, the slow stirring and fast stirring are performed in an NJ-160A cement paste stirrer; the revolution speed of the stirrer blade during slow stirring is preferably 62±5 r / min, and the rotation speed of the stirrer blade during slow stirring is preferably 140±5 r / min; the time for slow stirring is preferably 1.8-2.2 min, more preferably 2 min. In the present application, the revolution speed of the stirrer blade during fast stirring is preferably 125±10 r / min, and the rotation speed of the stirrer blade during fast stirring is preferably 285±10 r / min; the time for fast stirring is preferably 1.8-2.2 min, more preferably 2 min.

[0066] In the present application, the molding preferably comprises placing the cement paste obtained by mixing cement and water in a mold, vibrating and standing. In the present application, the mold is preferably a PVC pipe, and the diameter of the PVC pipe is preferably consistent with the diameter of the sample chamber 7 to be measured. In the present application, the standing time is preferably 22-26 h, more preferably 24 h.

[0067] In the present application, the molding preferably further comprises cutting the product after molding and demolding; and curing the product after demolding. In the present application, the height of the product after cutting is preferably consistent with the height of the sample chamber 7 to be measured. In the present application, the environmental temperature for curing is preferably 17-23℃, more preferably 20℃; the relative humidity of the curing environment is preferably ≥90%, and the curing time is preferably 28 days. In the present application, the cement stone after cutting is preferably cylindrical, more preferably round.

[0068] After obtaining the cement stone, the present application coats a waterproof material on the side of the cement stone to obtain a cement stone with a waterproof side. In the present application, the coating preferably further comprises polishing the cement stone after curing before coating. The present application does not have special requirements for polishing, and conventional methods in the art can be used. Polishing in the present application can reduce the roughness of the side of the cement stone, which is beneficial for subsequent coating. In the present application, the waterproof coating material preferably comprises epoxy resin or silicone, more preferably epoxy resin. In the present application, the thickness of the coating is preferably 1-2 mm, more preferably 1.3-1.8 mm.

[0069] The present application coats the side of the cement stone with waterproof material, and forms a waterproof layer on the side of the cement stone to avoid leakage of the anode electrolyte solution in the anode pool 2 and the cathode electrolyte solution in the cathode pool 5 from the side of the sample to be tested.

[0070] In the present application, the coating preferably further comprises curing the product after coating. In the present application, the curing temperature is preferably room temperature; and the curing time is preferably 1-3 days, more preferably 2 days.

[0071] After obtaining the side waterproofed cement stone, the present application immerses the side waterproofed cement stone in a sodium hydroxide solution to obtain a cement stone saturated with adsorption. In the present application, the molar concentration of the sodium hydroxide solution used for immersion is preferably 0.28-0.32 mol / L, more preferably 0.3 mol / L; and the immersion time is preferably 46-50 h, more preferably 48 h. In the present application, the immersion is preferably carried out under vacuum conditions, and the vacuum degree of the vacuum conditions is preferably 1-5 kPa, more preferably 4-5 kPa. The present application does not have special limitations on the amount of the sodium hydroxide solution used, as long as it can be immersed.

[0072] The present application saturates the side waterproofed cement stone with sodium hydroxide solution by immersion, and reduces the precipitation of alkali in the pore solution of the cement stone in the subsequent test process, so that the influence of convection can be ignored.

[0073] The present application preferably wipes off the moisture on the surface of the product after immersion.

[0074] After obtaining the cement stone saturated with adsorption, the present application places the cement stone saturated with adsorption in the sample chamber 7 to perform electro-migration of chloride ions. In the present application, the electro-migration of chloride ions preferably further comprises leak testing of the test device for the steady-state migration coefficient of chloride ions before the electro-migration of chloride ions. In the present application, the leak testing preferably comprises injecting a sodium hydroxide solution with a molar concentration of 0.3 mol / L into the anode pool 2 and the cathode pool 5 respectively, and then standing for 20-24 h.

[0075] In the present application, the anode tank 2 is filled with sodium hydroxide solution; the volume of the sodium hydroxide solution in the anode tank 2 is preferably 60-70 mL, more preferably 63-66 mL; the molar concentration of the sodium hydroxide solution in the anode tank 2 is preferably 0.28-0.32 mol / L, more preferably 0.3 mol / L. In the present application, the volume of the sodium hydroxide solution in the anode tank 2 is preferably 5-10 mL less than the volume of the anode tank 2. In the present application, the cathode tank 5 is filled with a mixed solution of sodium hydroxide and sodium chloride; the molar concentration of sodium hydroxide in the mixed solution of sodium hydroxide and sodium chloride in the cathode tank 5 is preferably 0.28-0.32 mol / L, more preferably 0.3 mol / L; the molar concentration of sodium chloride in the mixed solution of sodium hydroxide and sodium chloride in the cathode tank 5 is preferably 0.48-0.52 mol / L, more preferably 0.5 mol / L.

[0076] In the present application, the cement stone saturated with adsorption is installed in a rubber ring slightly smaller than its diameter, and then installed in the sample chamber 7 to be tested.

[0077] In the present application, the volume of the sodium hydroxide solution in the anode tank 2 remains unchanged during the electro-migration of chloride ions, and the concentration of the mixed solution of sodium hydroxide and sodium chloride in the cathode tank 5 is not less than 90% of the initial concentration. In the present application, the concentration of chloride ions in the anode tank 2 is preferably detected every 2-4 days, and the detection is stopped when the concentration of chloride ions in the anode tank stably increases. In the present application, the test solution is taken through the anode liquid inlet 3 for detection. In the present application, 5 mL of test solution is preferably taken for testing when the concentration of chloride ions in the solution in the anode tank 2 is low, and 1 mL of test solution is preferably taken for testing when the concentration of chloride ions is high. In the present application, after each time the solution is taken, an equal amount of 0.3 mol / L sodium hydroxide solution is preferably added to maintain the volume of the solution in the anode tank unchanged, and the measurement results need to be corrected subsequently. In the present application, an automatic titrator and 0.1 mol / L silver nitrate solution are preferably used to titrate the concentration of chloride ions in the solution taken from the anode tank 2.

[0078] In the present application, the electrolyte solution in the cathode tank is preferably replaced every 4 days to maintain the concentration of the electrolyte solution in the cathode tank 5 stable during the test period, which is not less than 90% of the initial concentration.

[0079] The present application preferably tests the connection of the direct current power source to move the chloride ions from the cathode pool 5 to the anode pool 2 through the cement stone saturated by adsorption. In the present application, the current of the electromigration of the chloride ions is preferably 5-10 mA, and more preferably 6-8 mA; in the present application, the voltage of the electromigration is preferably 2-5 V, and more preferably 2.67-3 V. The present application preferably uses a multimeter to periodically measure the voltage and current values at both ends of the sample. The present application starts to test the micro-migration method by power on, and the solution of the anode pool is taken every 2 days to test the chloride ion concentration. Through the test, it is found that before the chloride binding capacity of the cement stone (the cement stone will chemically combine with the chloride ions and physically adsorb part of the migrated chloride ions) is consumed, the chloride ions migrated from the cathode pool under the action of the electric field cannot all reach the anode pool through the test piece, and the chloride ion concentration in the anode pool shows a non-linear slow growth trend, which is called non-steady state. The chloride ion concentration in the anode pool starts to show a linear rapid growth state after the fifth day of the test, which is called steady state.

[0080] Under the action of the applied electric field, the diffusion effect and the influence of other ions in the pore solution can be ignored compared with the electromigration term; under the action of the constant electric field, the electric field along the potential change of the sample to be tested is linearly attenuated.

[0081] The chloride ion steady-state migration coefficient is calculated according to formula 1 and formula 2:

[0082]

[0083] Under the conditions of ignoring the diffusion effect and the influence of other ions in the pore solution, ignoring the convection effect, keeping the chloride ion concentration of the electrolyte solution in the cathode pool unchanged, and applying a constant electric field, the present application calculates the chloride ion steady-state migration coefficient by using the simplified formula of the Nernst-Planck equation, which simplifies the calculation process and improves the accuracy of the test results.

[0084] In order to further illustrate the present application, the technical solutions provided by the present application are described in detail below in conjunction with the embodiments, but they should not be understood as limiting the scope of protection of the present application.

[0085] Example 1

[0086] The water and the Onoda PⅡ 52.5 cement are placed in the NJ-160A cement paste mixer in a mass ratio of 0.35:1, and slow stirring for 2 min and fast stirring for 2 min are sequentially performed to obtain the cement paste; during the slow stirring process, the stirring blade revolution speed is 62±5 r / min, and the rotation speed is 140±5 r / min; during the fast stirring process, the stirring blade revolution speed is 125±10 r / min, and the rotation speed is 285±10 r / min.

[0087] The neat cement paste was placed in a PVC tube with a diameter of 28 mm and a height of 40 mm, and after being vibrated and left to stand for 24 h, the sample was cut into a height of 8 mm, and after being demolded, it was placed in an environment with a temperature of 20℃ and a relative humidity of ≥90% for 28 days;

[0088] After polishing the sample after curing, a 2mm-thick layer of epoxy resin was applied to the side, and it was cured at room temperature for 2 days to obtain a side-waterproof cement stone;

[0089] The side-waterproof cement stone was immersed in a 0.3 mol / L sodium hydroxide solution under a vacuum of 5 kPa for 48 h to obtain a saturated adsorption cement stone;

[0090] After injecting a 0.3 mol / L sodium hydroxide solution into the anode tank 2 and the cathode tank 5 and leaving it to stand for 24 h, the sample was tested for leakage; after the sample passed the leakage test, the saturated adsorption cement stone was installed in a rubber ring slightly smaller than its diameter and fixed in the sample chamber 7 using screws; 66 mL of a 0.3 mol / L sodium hydroxide solution was filled into the anode tank 2 through the anode liquid inlet 3; 66 mL of a mixed solution of sodium hydroxide with a 0.3 mol / L concentration and sodium chloride with a 0.5 mol / L concentration was filled into the cathode tank 5 through the cathode liquid inlet 4; the anode 1 (graphite electrode) and the cathode 6 (graphite electrode) were connected to a direct current power supply; the chloride ion electro-migration was carried out under the conditions of a voltage of 2.67 V, a current of 7 mA, and a temperature of 25℃; every 3 days, the anode solution (1 mL each time) was taken out through the anode liquid inlet 3, and the chloride ion concentration in the anode tank was detected by using an automatic titrator and a 0.1 mol / L silver nitrate solution to titrate the anode solution; after each time the solution was taken out, an equal amount of 0.3 mol / L sodium hydroxide solution was added to the anode tank 2 to maintain the volume of the anode tank solution; the cathode solution was replaced every 4 days to maintain the stability of the electrolyte solution concentration in the cathode tank 5;

[0091] According to the detection results and formulas 1 and 2, the chloride ion steady-state migration coefficient was calculated to be 2.00×10 -12 m 2 / s.

[0092] Figure 2 A physical diagram of the side-waterproof cement stone prepared in Example 1.

[0093] Figure 3 A structure diagram of the saturated adsorption cement stone in Example 1 after installing a rubber ring, wherein 8 is the saturated adsorption cement stone, 9 is the resin layer, and 10 is the rubber ring.

[0094] The detection results during the chloride ion electro-migration detection process are listed in Table 1.

[0095] Table 1 Chloride ion concentration in the anode tank at different times during the chloride ion transference of Example 1

[0096] Detection time (days) Chloride molar concentration (mol / L) 5 0.0175 7 0.0285 10 0.0635 13 0.0788 15 0.1248

[0097] A plot of the chloride ion concentration in the anode tank versus time is shown in Figure 1. Figure 4

[0098] According to Table 1 and Figure 4 The slope of the steady state stage is 10.11 mol / (m 3 ·d) which is equivalent to 1.2 x 10 - 4 mol / (m 3 ·s) and the value of J calculated from equation 1 is 1.3 x 10 -5 mol / (m 2 ·s) and the value of D calculated from equation 2 is 2.00 x 10 -12 m 2 / s.

[0099] The detailed calculation process is as follows:

[0100] The determination coefficient R 2 = 0.94 is calculated using the least square method, which is equal to the slope of the fitting line, i.e.:

[0101]

[0102] V2 = 66 mL = 6.6 x 10 -7 m 3

[0103] A = πr 2 = π x 28 2 ≈ 615.75 mm 2 ≈ 6.2 x 10 -4 m 2

[0104]

[0105]

[0106] Although the above examples have made a detailed description of the present application, it is only a part of the embodiments of the present application, but not all the embodiments, and people can also obtain other embodiments according to the present embodiments without creativity, which all belong to the protection scope of the present application.​

Claims

1. A method for detecting the steady-state migration coefficient of chloride ions, comprising the following steps: Cement and water are mixed and shaped to obtain cement stone. The process after molding also includes: curing the molded product, wherein the curing environment temperature is 17~23℃, the relative humidity of the curing environment is ≥90%, and the curing time is 28 days; A waterproof material is applied to the side of the cement stone to obtain a cement stone with waterproof sides. The waterproof cement stone is immersed in a sodium hydroxide solution to obtain saturated cement stone; the molar concentration of the sodium hydroxide solution used for immersion is 0.28~0.32 mol / L; the immersion time is 46~50 h. The adsorbed saturated cement stone was placed in the sample chamber (7) for chloride ion electromigration; the anode cell (2) was filled with sodium hydroxide solution, and the cathode cell (5) was filled with a mixed solution of sodium hydroxide and sodium chloride; the chloride ion concentration in the anode cell (2) was detected every 2 to 4 days until the chloride ion concentration in the anode cell steadily increased and the detection was stopped; during the chloride ion electromigration process, the volume of sodium hydroxide solution in the anode cell (2) remained unchanged, the concentration of the mixed solution of sodium hydroxide and sodium chloride in the cathode cell (5) was not less than 90% of the initial concentration, and the molar concentration of sodium chloride in the mixed solution of sodium hydroxide and sodium chloride in the cathode cell (5) was 0.48 to 0.52 mol / L; the voltage of the electromigration was 2 to 5 V; Calculate the chloride ion steady-state migration coefficient using formulas 1 and 2: Formula 1, Formula 2: Where J is the flux of chloride ions through the sample at steady state, in mol / (m²). 2 ·s); ΔC2 represents the increase in chloride ion concentration in the anode pool during the steady-state time interval Δt, expressed in mol / m³. 3 ; V2 is the solution volume in the anode tank, in cubic meters (m³). 3 ; Δt is the length of a time interval used for calculation after steady state, in seconds; A is the cross-sectional area of ​​the sample, in m². 2 ; D is the steady-state mobility coefficient of the sample, in m. 2 / s; R is the gas constant, taken as R = 8.314 J / (mol·K); T represents temperature, and the unit is K. l represents the thickness of the sample, in meters (m). C1 is the chloride ion concentration in the cathode cell, in mol / m³. 3 ; F is the Faraday constant, taken as F = 96500 C / mol; ΔE is the potential difference across the sample, in V; The method for detecting the steady-state migration coefficient of chloride ions utilizes a testing device including an anode cell (2) and an anode (1) located at either end of the anode cell. It also includes a cathode cell (5) and a cathode (6) disposed at either end of the cathode cell (5). The other end of the anode pool (2) and the other end of the cathode pool (5) are connected by a connecting structure; a sample chamber (7) is provided in the connecting structure; the sample chamber (7) is a cylinder with a diameter of 25~30mm and a height of 6~10mm.

2. The detection method according to claim 1, characterized in that, The anode pool (2) is provided with an anode injection port (3) near the end of the connecting structure; the cathode pool (5) is provided with a cathode injection port (4) near the end of the connecting structure.

3. The detection method according to claim 1, characterized in that, The mass ratio of water to cement is 0.3~0.5:

1.

4. The detection method according to claim 1, characterized in that, The waterproof material includes epoxy resin or silicone; the coating thickness is 1~2mm.

5. The detection method according to claim 1, characterized in that, The molar concentration of sodium hydroxide solution in the anode pool (2) is 0.28~0.32 mol / L.

6. The detection method according to claim 1, characterized in that, The molar concentration of sodium hydroxide in the mixed solution of sodium hydroxide and sodium chloride in the cathode cell (5) is 0.28~0.32 mol / L.

7. The detection method according to claim 1, 5, or 6, characterized in that, The current for the electromigration of chloride ions is 5~10mA.

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