A method for testing the chloride ion concentration inside an ice body of chloride salt solution

Abstract

The present invention relates to a method for testing the chloride ion concentration within a chloride salt solution ice body. The method first draws a working curve: a chloride salt solution of a certain concentration is prepared, injected into an elastic material mold, and placed in a single-sided heat-conducting insulation container to be cooled in a cooling box to form an ice body; the ice body is evenly divided into several sections along the depth direction, and the polarization resistance of the solution after each ice block melts in the depth direction is tested. The chloride ion concentration in the solution after the ice block melts is tested, and a curve is drawn showing the relationship between the chloride ion concentration corresponding to the ice block and the corresponding position depth of each ice block in the entire ice body. A curve is then established showing the relationship between polarization resistance and chloride ion concentration. When testing the concentration of a chloride salt solution ice body, the polarization resistance of the chloride salt solution ice body after melting is first measured, and the concentration value of the chloride salt solution ice body is obtained based on the established curve showing the relationship between polarization resistance and chloride ion concentration. The present invention achieves rapid and convenient testing of the concentration of a chloride salt solution ice body.

Description

Technical Field

[0001] The present invention relates to the field of materials science, and in particular to a method for testing the chloride ion concentration inside an ice body of a chloride salt solution. Background Art

[0002] To mitigate the phenomenon of snow and ice forming on concrete pavements in winter, the pavement must be sprayed with a chloride-salt deicing solution or de-icing fluid. These chloride salts enter the concrete's internal pores, exacerbating freeze-thaw damage during freeze-thaw cycles. Numerous theories exist regarding freeze-thaw damage to concrete, including the hydrostatic pressure theory, the osmotic pressure theory, the critical water saturation theory, and the salt crystallization theory. In 1944, AR Collins applied the frozen soil expansion theory to concrete and proposed the water segregation and stratification theory. This theory states that when water in the pores of concrete is exposed to temperatures below freezing, it freezes layer by layer from the outside to the inside, forming layers on the concrete surface. The expansion stress generated by this freezing causes the concrete to degrade layer by layer, resulting in delamination. If the water contains salt, the changes in the internal salt concentration and resulting freezing pressure during the layer-by-layer freezing process warrant further study. Measuring the internal salt concentration of frozen salt solutions has important scientific and practical value for studying the freezing pressure of solutions within concrete and further explaining the principles of freeze-thaw damage to concrete.

[0003] Current methods for measuring Cl- concentration in solutions are based on the water-soluble chloride ion content analysis method, total chloride ion content analysis method, and rapid chloride ion content determination method specified in the Ministry of Transport standard JTJ270-98, "Testing Procedures for Concrete in Water Transport Engineering." The water-soluble chloride ion content analysis method and the total chloride ion content analysis method primarily utilize the experimental setup for the AgNO3 titration method, while the rapid chloride ion determination method uses an electrode and a calomel electrode placed in the liquid phase, and the electrode potential is measured to estimate the chloride ion concentration. These methods require the use of large amounts of AgNO3 solution, which is highly toxic and requires sample and hazardous waste disposal, potentially causing environmental pollution. Summary of the Invention

[0004] The present invention aims to provide a method for testing the chloride ion concentration inside a chloride salt solution ice body, so as to achieve a fast and convenient test of the concentration of the chloride salt solution ice body.

[0005] To achieve the above object, the technical solution provided by the present invention is:

[0006] A method for testing the chloride ion concentration inside an ice body of a chloride salt solution comprises the following steps:

[0007] (1) Drawing the working curve:

[0008] Step 1: Prepare a chloride solution of a certain concentration and inject it into the elastic material mold;

[0009] Step 2: Place the elastic material mold filled with chloride salt solution in a heat-insulating container with single-sided heat transfer;

[0010] Step 3: Place the single-sided heat-conducting insulation container in a cooling box, add a reference solution into the cooling box, place a temperature sensor into the reference solution, and set the cooling target temperature of the cooling box to be lower than the freezing point of the chloride salt solution;

[0011] Step 4: Start cooling box refrigeration;

[0012] Step 5: When the temperature measured by the temperature sensor in the reference solution remains unchanged and is consistent with the cooling target temperature of the cooling box, the cooling operation of the cooling box is stopped. At this time, the chloride salt solution has become an ice body.

[0013] Step 6: Immediately remove the ice formed by the chloride solution, measure the depth of the ice, and then evenly divide the ice into several sections along the depth direction;

[0014] Step 7: Melt the cut ice segments and test the polarization resistance of the solution formed after each segment of ice melts in the depth direction;

[0015] Step 8: Test the chloride ion concentration in the solution formed after each section of ice melts;

[0016] Step 9: Using the median depth of each ice segment in the overall ice mass as the horizontal axis and the chloride ion concentration in the solution formed after each ice segment melts as the vertical axis, draw a curve showing the relationship between the chloride ion concentration of each ice segment and the depth of each ice segment in the overall ice mass.

[0017] Step 10: Based on the corresponding relationship between chloride ion concentration and depth in the relationship curve obtained in step 9, and according to the polarization resistance of the solution formed after the melting of each section of ice in the depth direction measured in step 7, a relationship curve between polarization resistance and chloride ion concentration is established, with the chloride ion concentration of the solution formed after the melting of each section of ice as the abscissa and the polarization resistance as the ordinate;

[0018] (2) Test the concentration of ice in a chloride salt solution:

[0019] Melt the ice body of the chloride salt solution to be tested, measure the polarization resistance of the solution formed after the ice body of the chloride salt solution to be tested melts, and obtain the concentration value of the chloride salt solution ice body according to the relationship curve between the polarization resistance and the chloride ion concentration established in step (1).

[0020] To optimize the above technical solutions, specific measures taken also include:

[0021] Furthermore, the elastic modulus of the elastic material mold is ≥0.8 GPa; the height of the elastic material mold is 10 cm-1 m, and the diameter is 5 cm-10 cm.

[0022] Furthermore, the one-side heat-conducting heat-insulating container refers to a container with insulated walls and bottom and an open top. Furthermore, the one-side heat-conducting heat-insulating container is made of an insulation board with a thermal conductivity coefficient λ≤0.045W / m·K.

[0023] Furthermore, the reference solution is water; the negative value of the refrigeration target temperature refers to a temperature lower than the freezing point of the prepared chloride salt solution.

[0024] In step 6, the ice body is evenly divided into no less than 4 sections along the depth direction.

[0025] In step 7, an electrochemical three-electrode system is used to test the polarization resistance of the solution after the ice cubes melt in each section in the depth direction.

[0026] In step 8, the chloride ion concentration in the solution after each section of ice cubes melted is tested by titration.

[0027] In step 10, if the chloride salt solution ice body to be tested is large, the chloride salt solution ice body to be tested is cut into segments along the depth direction and then melted. The polarization resistance of the solution formed after the melting of each segmented ice block is measured, and then the chloride ion concentration value inside each segmented ice block is obtained based on the relationship curve between polarization resistance and chloride ion concentration.

[0028] As a preferred solution, the calculation formula for chloride ion concentration is:

[0029]

[0030] Where: a represents Cl - Mass concentration, expressed in %; C (AgNO3) Indicates the molar concentration of the titrant AgNO3 solution in g / mol; V (AgNO3) Indicates the volume of AgNO3 solution in ml; M(Cl) indicates Cl - The molar mass of the ice cube is expressed in g / mol; m0 represents the mass of the solution after the ice cube melts; where:

[0031]

[0032] λ represents the volume ratio of the solution after the ice cube melts that needs to be diluted during the titration test; V0 represents the volume of the solution before dilution, in ml; V 水 It indicates the volume of water added during dilution, in ml; V1 indicates the volume of the solution after dilution, in ml.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] The present invention provides a method for testing the mass concentration of chloride ions in an ice body of a chloride salt solution after freezing. The method comprises the following steps: the frozen chloride salt solution ice body is evenly divided into ice cubes along a depth direction; the polarization resistance of each ice cube segment is then tested using an electrochemical three-electrode system; each ice cube segment is melted and titrated to determine the mass concentration of the chloride salt solution. The obtained chloride ion concentration value of each ice cube segment can be used to analyze the relationship between the distribution of the mass concentration of chloride ions in the ice body of the chloride salt solution with depth after freezing, and the relationship between the chloride salt concentration at the same depth and the polarization resistance of the ice segment.

[0035] After establishing the relationship curve between polarization resistance and chloride ion concentration, this method can quickly and conveniently test the ice concentration of chloride salt solution.

[0036] The present invention establishes a relationship curve between the chloride ion concentration corresponding to each ice segment and the corresponding position depth of each ice segment in the entire ice body based on the polarization resistance of the solution after each ice segment melts in the depth direction. This allows for rapid determination of the ice body concentration of the chloride salt solution, reduces the use of AgNO3, and improves work efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 3. This is a schematic diagram of a test process for measuring how the mass concentration of chloride ions inside an ice body of a NaCl solution changes with depth after the solution freezes in an embodiment of the present invention.

[0038] Figure 2 8 is a graph showing the change in mass concentration of chloride ions in the ice body of NaCl solution with depth in an embodiment of the present invention.

[0039] Figure 3 1 is a curve showing the relationship between polarization resistance and chloride ion mass concentration after melting of ice cubes cut from an ice body of NaCl solution in an embodiment of the present invention. DETAILED DESCRIPTION

[0040] The above contents of the present invention are further described in detail below in the form of embodiments, but this should not be understood as the scope of the above subject matter of the present invention being limited to the following embodiments. All technologies implemented based on the above contents of the present invention fall within the scope of the present invention.

[0041] The experimental methods used in the following examples are conventional methods unless otherwise specified, and the reagents, methods and equipment used are conventional reagents, methods and equipment in the art unless otherwise specified.

[0042] A method for testing the chloride ion concentration inside an ice body of chloride salt solution, such as Figure 1 The test process diagram is shown in FIG, which includes the following steps:

[0043] (1) Drawing the working curve:

[0044] Step 1: Prepare a chloride solution with a mass concentration of 2% NaCl and inject it into the elastic material mold;

[0045] Step 2: Place the elastic material mold in a heat-insulating container with single-sided heat transfer;

[0046] Step 3: Place the single-sided heat-conducting insulation container in a cooling box, add a reference solution into the cooling box, place a temperature sensor into the reference solution, and set the cooling target temperature of the cooling box to a negative value;

[0047] Step 4: Start cooling box refrigeration;

[0048] Step 5: When the temperature of the reference solution remains constant and is consistent with the target temperature of the cooling box, the cooling operation of the cooling box is stopped. At this time, the chloride salt solution has become an ice body.

[0049] Step 6: After taking out the heat preservation container, immediately remove the elastic material mold on the surface of the ice body, take out the ice body, measure the height (i.e., depth) of the ice body to be 10 cm, and evenly divide the ice body into 11 ice blocks along the depth direction;

[0050] Step 7: Melt the cut ice cubes and test the polarization resistance of each ice cube using an electrochemical three-electrode system;

[0051] Step 8: According to the water-soluble chloride ion test method of the specification "Testing Procedures for Concrete in Water Transport Engineering" JTJ270-97, test the chloride ion concentration in the solution after each section of ice is melted.

[0052] Step 9: Using the median depth of each ice segment in the entire ice mass as the horizontal axis and the chloride ion concentration in the solution after each ice segment melts as the vertical axis, draw a curve showing the relationship between the chloride ion concentration of each ice segment and the depth of each ice segment in the entire ice mass.

[0053] Step 10: Using the chloride ion concentration in the solution after each ice cube melts as the horizontal axis and the polarization resistance as the vertical axis, establish a curve showing the relationship between polarization resistance and chloride ion concentration;

[0054] The elastic modulus of the elastic material mold is ≥0.8GPa.

[0055] The thermal insulation container with single-sided heat transfer refers to a container with insulated walls and bottom and an open top; the thermal insulation container with single-sided heat transfer can be made of an insulation board with a thermal conductivity coefficient of λ≤0.045W / m·K.

[0056] The reference solution is water.

[0057] A negative refrigeration target temperature refers to a temperature below the freezing point of the prepared chlorine salt solution.

[0058] The chloride ion concentration in the solution after each section of ice melted was tested by titration. In order to save the amount of AgNO3 solution, the solution after the ice melted should be diluted before the experiment so that the mass concentration of the diluted solution is less than 3%. Then, 10-20 ml of the diluted chloride salt solution was taken for titration.

[0059] The calculation formula for chloride ion concentration is:

[0060]

[0061] Where: a represents Cl - Mass concentration, expressed in %; C (AgNO3) Indicates the molar concentration of the titrant AgNO3 solution in g / mol; V (AgNO3) Indicates the volume of AgNO3 solution in ml; M(Cl) indicates Cl - The molar mass of the ice cube is expressed in g / mol; m0 represents the mass of the solution after the ice cube melts; where:

[0062]

[0063] λ represents the volume ratio of the solution after the ice cube melts that needs to be diluted during the titration test; V0 represents the volume of the solution before dilution, in ml; V 水 It indicates the volume of water added during dilution, in ml; V1 indicates the volume of the solution after dilution, in ml.

[0064] Test results:

[0065] The original data records used in drawing the working curve in step (1) are shown in Table 1. The relationship curve between the chloride ion concentration corresponding to each ice segment and the corresponding position depth of each ice segment in the entire ice body is shown in Table 1. Figure 2 The relationship curve between polarization resistance and chloride ion concentration is established by taking the chloride ion concentration in the solution after each ice cube melts as the horizontal axis and the polarization resistance as the vertical axis. Figure 3 .

[0066] Table 1 Original data used to draw the working curve

[0067]

[0068] from Figure 2 The curve pattern shows that the salt concentration is higher on the surface of the ice, the concentration in the ice increases with depth, and the concentration is highest at the bottom.

[0069] from Figure 3 The curve law shows that there is a significant correlation between the polarization resistance of the solution and the chloride ion concentration, and the correlation coefficient is as high as 0.996.

[0070] By configuring chloride solutions of different concentrations, the relationship curves between polarization resistance and chloride ion concentration can be established to improve accuracy.

[0071] (2) Test the concentration of ice in a chloride salt solution:

[0072] Melt the ice body of the chloride salt solution to be tested, measure the polarization resistance of the solution formed after the ice body of the chloride salt solution to be tested melts, and obtain the concentration value of the chloride salt solution ice body according to the relationship curve between the polarization resistance and the chloride ion concentration established in step (1).

[0073] For example, the polarization resistance of the solution formed after the chloride solution ice melts is 87RP / Ω·cm 2 ,from Figure 3 The relationship curve between polarization resistance and chloride ion concentration shows that the concentration of the chloride salt solution ice body is 1.4%.

[0074] Since the chloride ion concentration inside the chloride salt ice changes with depth after freezing, if the chloride salt solution to be tested is large, follow the steps below:

[0075] a) When the chloride solution ice body to be tested is taken out from the freezing ground, mark its depth direction;

[0076] b) cutting the chloride solution ice body to be tested into sections along the depth direction;

[0077] c) melting each segment of the chloride salt solution ice body to be tested, and measuring the polarization resistance of the solution formed after the segment of ice is melted;

[0078] d) Obtain the chloride ion concentration value inside each segment of the ice cube based on the relationship curve between polarization resistance and chloride ion concentration.

[0079] If the chloride salt ice block itself is relatively small, the chloride ion concentration corresponding to the polarization resistance of the solution formed after its direct melting can correspond to the chloride ion concentration value in the middle of the chloride salt ice block. The mass concentration of the chloride salt solution in the present invention is generally 0.1-20%. In this embodiment, the commonly used 2% NaCl is used. Other chloride salt concentrations, such as 3% NaCl and 5% NaCl, can also be used for experiments. After the chloride salt ice block freezes, the chloride ion concentration inside it varies with depth. Experiments have shown that the resistance values corresponding to the corresponding concentration values in the relationship curve between polarization resistance and chloride ion concentration are equivalent.

[0080] The above description is only a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Any simple modification, equivalent replacement and improvement made by any technician familiar with the profession to the above embodiment without departing from the scope of the technical solution of the present invention and based on the technical essence of the present invention shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for measuring the chloride ion concentration inside an ice body of a chloride salt solution, characterized by: The following steps are involved: (1) Drawing the working curve: Step 1: Prepare a chloride solution of a certain concentration and inject it into the elastic material mold; Step 2: Place the elastic material mold filled with chloride salt solution in a heat-insulating container with single-sided heat transfer; Step 3: Place the single-sided heat-conducting insulation container in a cooling box, add a reference solution into the cooling box, place a temperature sensor into the reference solution, and set the cooling target temperature of the cooling box to be lower than the freezing point of the chloride salt solution; Step 4: Start cooling box refrigeration; Step 5: When the temperature measured by the temperature sensor in the reference solution remains unchanged and is consistent with the cooling target temperature of the cooling box, the cooling operation of the cooling box is stopped. At this time, the chloride salt solution has become an ice body. Step 6: Immediately remove the ice formed by the chloride solution, measure the depth of the ice, and then evenly divide the ice into several sections along the depth direction; Step 7: Melt the cut ice segments and test the polarization resistance of the solution formed after each segment of ice melts in the depth direction; Step 8: Test the chloride ion concentration in the solution formed after each section of ice melts; Step 9: Using the median depth of each ice segment in the overall ice mass as the horizontal axis and the chloride ion concentration in the solution formed after each ice segment melts as the vertical axis, draw a curve showing the relationship between the chloride ion concentration of each ice segment and the depth of each ice segment in the overall ice mass. Step 10: Based on the corresponding relationship between chloride ion concentration and depth in the relationship curve obtained in step 9, and according to the polarization resistance of the solution formed after the melting of each section of ice in the depth direction measured in step 7, a relationship curve between polarization resistance and chloride ion concentration is established, with the chloride ion concentration of the solution formed after the melting of each section of ice as the abscissa and the polarization resistance as the ordinate; (2) Test the concentration of the ice body in the chloride salt solution to be tested: Melt the ice body of the chloride salt solution to be tested, measure the polarization resistance of the solution formed after the chloride salt solution ice body to be tested is melted, and obtain the concentration value of chloride ions in the chloride salt solution ice body according to the relationship curve between polarization resistance and chloride ion concentration established in step (1).

2. The method for testing the chloride ion concentration inside an ice body of chloride salt solution according to claim 1, characterized in that: The elastic modulus of the elastic material mold is ≥0.8 GPa; the height of the elastic material mold is 10 cm-1 m, and the diameter is 5 cm-10 cm.

3. The method for testing the chloride ion concentration inside an ice body of chloride salt solution according to claim 1, characterized in that: The one-side heat-conducting heat-insulating container refers to a container with insulated walls and bottom and an open top.

4. The method for testing the chloride ion concentration inside an ice body of chloride salt solution according to claim 3, characterized in that: The single-sided heat-conducting insulation container is made of an insulation board with a thermal conductivity coefficient λ ≤ 0.045 W / m·K.

5. The method for testing the chloride ion concentration inside an ice body of chloride salt solution according to claim 1, characterized in that: The reference solution is water; the negative refrigeration target temperature refers to a temperature lower than the freezing point of the prepared chloride salt solution.

6. The method for testing the chloride ion concentration inside an ice body of chloride salt solution according to claim 1, characterized in that: In step 6, the ice body is evenly divided into no less than 4 sections along the depth direction.

7. The method for testing the chloride ion concentration inside an ice body of chloride salt solution according to claim 1, characterized in that: In step 7, an electrochemical three-electrode system is used to test the polarization resistance of the solution after the ice cubes melt in each section in the depth direction.

8. The method for testing the chloride ion concentration inside an ice body of chloride salt solution according to claim 1, characterized in that: In step 8, the chloride ion concentration in the solution after each section of ice cubes melted is tested by titration.

9. The method for testing the chloride ion concentration inside an ice body of chloride salt solution according to claim 1, characterized in that: In step 2, the chloride solution ice to be tested is segmented along the depth direction and then melted. The polarization resistance of the solution formed after the melting of each segmented ice block is measured, and then the chloride ion concentration value inside each segmented ice block is obtained based on the relationship curve between polarization resistance and chloride ion concentration.

10. The method for testing the chloride ion concentration inside an ice body of chloride salt solution according to claim 9, characterized in that: The calculation formula for chloride ion concentration is: in: a Cl - Mass concentration, expressed in %; C (AgNO3) Indicates the molar concentration of the titrant AgNO3 solution in mol / ml; V (AgNO3) Indicates the volume of AgNO3 solution in ml; M (Cl) represents Cl - The molar mass of a substance is expressed in g / mol; m 0 represents the mass of the solution after the ice cube melts; where: λ represents the volume ratio of the solution after the ice cube melts that needs to be diluted during the titration test; V 0 represents the volume of the solution before dilution, in ml; V 水 Indicates the volume of water added during dilution, in ml; V 1 represents the volume of the diluted solution in ml.

Images