Effective calcium content rapid self-detection method based on conductivity test

Abstract

The invention provides an effective calcium content rapid self-detection method based on a conductivity test, and relates to the technical field of road engineering detection. The rapid self-detection method for the effective calcium content comprises the following steps: preparing an ammonium chloride solution and a lime stabilizing material; putting the lime stabilizing material into a beaker, and adding water to prepare a mixed solution; assembling and calibrating a conductivity meter, and erecting an electrode and a burette; carrying out a titration experiment by using an ammonium chloride solution, and detecting the conductivity of the solution by using a conductivity meter; recording the corresponding relation between the ammonium chloride solution titer and conductivity, drawing a curve image, and searching the ammonium chloride solution titer at a reaction end point; and calculating the effective calcium content in the lime stabilizing material according to the reaction endpoint titration amount. The effective calcium content in the lime stabilizing material is accurately detected through the conductivity change rule, the experiment steps are simplified, a standard curve does not need to be drawn, the detection time is shortened, and the detection and construction efficiency is improved.

Description

Technical Field

[0001] The invention relates to the technical field of road engineering detection, and in particular to a rapid self-detection method for effective calcium content based on conductivity testing. Background Art

[0002] Lime stabilized materials are widely used in roads and can effectively improve the road's bearing capacity, stability and durability. However, in its actual application, the effective calcium content in lime stabilized materials is the key to construction. Too low or too high effective calcium content will lead to substandard road strength, stability and compaction. Therefore, how to quickly and accurately detect the effective calcium content in lime stabilized materials is an important link in the field of construction quality control.

[0003] Currently, commonly used methods for detecting the effective calcium content in lime-stabilized materials include EDTA titration and direct-reading calcium analyzer methods, but the existing methods have the following problems: (1) The existing methods all require multiple experiments to draw a standard curve before the detection work begins, and determine the effective calcium content in the lime-stabilized material based on the standard curve and the test results of the test sample. In the entire detection process, there are also steps such as repeated extraction and transfer of the upper clear liquid. The detection steps are complicated and take a lot of time. (2) The existing methods require the use of a variety of chemical reagents during the detection process, including strong alkaline solutions such as sodium hydroxide, which poses a huge safety risk. (3) The traditional EDTA titration method, in which the test results are judged by the human eye through color changes, has a large human error. (4) Due to the increase in the number of uses and the influence of the chemical composition in the detection solution, the electrodes used in the traditional direct-reading calcium analyzer are inevitably worn during the detection process, affecting the accuracy of the test results and requiring regular maintenance or replacement. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention provides a rapid self-detection method for effective calcium content based on conductivity testing. By using the examples of the present invention, the problems that the traditional effective calcium content detection method needs to draw a standard curve, the detection steps are complicated, the detection process needs to use dangerous chemical reagents, and the detection results are greatly affected by equipment and manual processing can be solved. The effective calcium content is determined by directly detecting the conductivity change law of a mixed solution containing lime stabilizing materials, the experimental steps are simplified, and the detection efficiency and the accuracy of the detection results are improved.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solutions:

[0006] A rapid self-detection method for effective calcium content based on conductivity testing, the detection method comprising the following steps:

[0007] S1, prepare an ammonium chloride solution with a mass fraction of a, and use slaked lime, plain soil and water to prepare a lime-stabilized material with a mass of M to achieve an optimal moisture content;

[0008] S2. Put the lime-stabilized material into a beaker and add a certain amount of water to prepare a mixed solution;

[0009] S3, assembling and calibrating a conductivity meter, setting up electrodes and a burette above the mixed solution, and injecting a sufficient amount of ammonium chloride solution into the burette as a titrant;

[0010] S4, continuously adding ammonium chloride solution to the above-mentioned mixed solution, and using a conductivity meter to detect the conductivity of the solution during the titration process;

[0011] S5, record the corresponding relationship between the titration amount of the ammonium chloride solution and the conductivity of the solution, draw a conductivity-titration curve image, record the inflection point of the curve as the reaction end point, and record the titration amount of the ammonium chloride solution at the reaction end point;

[0012] S6. Calculate the effective calcium content in the lime-stabilized material according to the titration of the ammonium chloride solution at the reaction end point;

[0013] Preferably, the calculation method of effective calcium content is:

[0014]

[0015] In the formula, x 检测 is the effective calcium content in the lime-stabilized material obtained by testing; m 检测钙 is the effective calcium mass detected; m 土 is the mass of the base soil in the lime-stabilized material; Mr 氯化铵 is the relative molecular mass of ammonium chloride; Mr 氢氧化钙 is the relative molecular mass of calcium hydroxide; h is the titration of ammonium chloride solution at the reaction end point; a is the mass fraction of ammonium chloride solution.

[0016] Preferably, the method for configuring the lime-stabilized material in step S1 comprises the following steps:

[0017] S1-1, take the soil and slaked lime for the construction site, and air-dry the soil and slaked lime;

[0018] S1-2, water and air-dried soil and slaked lime are used to prepare lime-stabilized materials with a mass of M to achieve the best moisture content. The formula for water, soil and slaked lime is:

[0019] M=m 土 +m 配置钙 +m 水

[0020]

[0021] Where M is the total mass of lime-stabilized material; m 土 is the mass of the base soil in the lime-stabilized material; m 配置钙 is the mass of slaked lime in the configured lime stabilization material; m 水 is the mass of water in the lime-stabilized material; ω is the optimum moisture content of the lime-stabilized material; x 配置 It is the effective calcium content of lime-stabilized materials.

[0022] Preferably, in step S3, a sufficient amount of ammonium chloride solution is injected into the burette, and the judgment formula is:

[0023]

[0024] Where, L is the minimum volume of ammonium chloride solution required; m 钙max is the maximum effective calcium mass in the lime stabilized material; ρ is the density of the ammonium chloride solution; a is the mass fraction of the ammonium chloride solution; Mr 氯化铵 is the relative molecular mass of ammonium chloride; Mr 氢氧化钙 is the relative molecular mass of calcium hydroxide; t is the volume of ammonium chloride solution titrated each time.

[0025] Preferably, the specific operation method in step S4 includes the following steps:

[0026] S4-1, control the burette to titrate the ammonium chloride solution into the beaker, titrating 2 mL of ammonium chloride solution each time;

[0027] S4-2, stir with a stirring rod and let stand for 30 seconds to allow ammonium chloride to fully react with calcium hydroxide in the mixed solution to generate calcium chloride, change the number and type of ions in the solution, and change the conductivity. Use a conductivity meter to detect the conductivity of the solution at this time;

[0028] S4-3, repeat steps S4-1 and S4-2. After each titration, stir the solution to allow ammonium chloride to fully react with calcium hydroxide in the mixed solution. When the calcium hydroxide reacts completely, titrate the ammonium chloride solution again. No chemical reaction occurs, only the number of ions in the solution changes, and the conductivity changes. The conductivity change rate before and after the complete reaction of calcium hydroxide is different. During this period, detect the solution conductivity until the ammonium chloride solution is consumed.

[0029] Preferably, the specific operation method of step S5 includes the following steps:

[0030] S5-1: According to step S4, the corresponding relationship between the titration amount of the ammonium chloride solution and the conductivity of the mixed solution is recorded, and a conductivity-titration curve image is drawn according to the corresponding relationship;

[0031] S5-2: According to the conductivity-titration curve image, find the inflection point of the curve, record it as the reaction endpoint, and determine the titration of the ammonium chloride solution corresponding to the reaction endpoint.

[0032] The present invention provides a rapid self-detection method for effective calcium content based on conductivity testing, which has the following advantages over the prior art:

[0033] (1) The present invention provides a rapid self-detection method for effective calcium content based on conductivity testing. Only one conductivity test is required in a container containing a mixture of lime-stabilized materials to accurately measure the effective calcium content in the lime-stabilized material. This overcomes the problem that the traditional detection steps are complicated and multiple experiments are required to draw a standard curve during detection. The experimental operation steps are simplified, the detection time is shortened, and the detection and construction efficiency is effectively improved.

[0034] (2) The present invention provides a rapid self-detection method for effective calcium content based on conductivity testing. It is not necessary to accurately measure the conductivity of a mixed solution containing a lime-stabilized material. It is only necessary to determine the conductivity change pattern to quantify the effective calcium content in the lime-stabilized material. This avoids inaccurate conductivity measurement due to electrode wear and the inaccurate effective calcium content detection results caused by it. This overcomes the problems of traditional detection methods that have human eye recognition errors or are affected by electrode wear, and improves the reliability of the detection results.

[0035] (3) The present invention provides a rapid self-detection method for effective calcium content based on conductivity testing, which uses only one chemical reagent, ammonium chloride solution, to complete the effective calcium content detection work, thereby overcoming the problem that traditional detection methods require the use of multiple chemical reagents including sodium hydroxide strong alkaline solution, which brings great safety risks, reduces the safety risks of the detection work, and reduces the harm to operators during the detection process. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a flow chart of a rapid self-detection method for effective calcium content based on conductivity testing of the present invention;

[0037] Figure 2 The conductivity-titration curve of the lime-stabilized material with an effective calcium content of 3% in Example 1 of the present invention;

[0038] Figure 3 The conductivity-titration curve of the lime-stabilized material with an effective calcium content of 6% in Example 2 of the present invention; DETAILED DESCRIPTION

[0039] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention is clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0040] Embodiment 1:

[0041] A rapid self-test method for effective calcium content based on conductivity testing, such as Figure 1 , including the following steps:

[0042] S1: Prepare a 10% ammonium chloride solution, and use slaked lime, plain soil and water to prepare a lime-stabilized material with a mass of 100g to achieve an optimal moisture content;

[0043] S1-1: Take 200g of anhydrous ammonium chloride solid and 1800g of water, and prepare 2000g of ammonium chloride solution with a mass fraction of 10%;

[0044] S1-2: Take the raw soil and slaked lime from the construction site and air-dry them;

[0045] S1-3: Take a certain amount of water, air-dried soil and slaked lime to prepare a lime-stabilized material with a mass of 100g and an effective calcium content of 3% to achieve the optimal moisture content.

[0046] The method for quantitatively eliminating lime, soil and water is as follows:

[0047] M=m 土 +m 配置钙 +m 水 =100

[0048]

[0049] m 水 =ω*(m 土 +m 配置钙 )=0.1405*(85.13+2.55)≈12.32

[0050] Where M is the total mass of lime-stabilized material; m 土 is the mass of the base soil in the lime-stabilized material; m 配置钙 is the mass of slaked lime in the configured lime stabilization material; m 水 is the mass of water in the lime-stabilized material; ω is the optimum moisture content of the lime-stabilized material; x 配置 It is the effective calcium content of lime-stabilized material.

[0051] The qualities of slaked lime, plain soil and water used are shown in Table 1;

[0052] Table 1

[0053]

[0054] S2: Place the lime-stabilized material into a beaker and add 400 mL of water to prepare a mixed solution;

[0055] S2-1: Take 100g of lime-stabilized material with an effective calcium content of 3% and put it into a beaker, and add 400mL of water to the beaker to form a mixed solution, stir the mixed solution with a stirring rod, and let it stand for 10 minutes.

[0056] S3: Assemble and calibrate the conductivity meter, set up electrodes and a burette above the mixed solution, and inject a sufficient amount of ammonium chloride solution into the burette as a titrant;

[0057] S3-1: Select an electrode with a cell constant of 10, connect the electrode to the conductivity meter, and calibrate the conductivity meter using a conductivity standard solution;

[0058] S3-2: Insert the electrode into the mixed solution to detect the conductivity of the mixed solution, set up a burette above the beaker, and inject a sufficient amount of 10% ammonium chloride solution into the burette.

[0059] The injection of sufficient ammonium chloride solution, considering the complete reaction of calcium hydroxide in slaked lime, in this embodiment, a lime stabilized material with an effective calcium content of 3% is configured. At different construction sites, the minimum required ammonium chloride solution should be calculated according to the highest effective calcium content, and after ensuring that the calcium hydroxide in the lime stabilized material with the highest effective calcium content has completely reacted, at least 10 titrations are still performed to draw a complete conductivity-titration curve image. The calculation formula for the minimum required ammonium chloride solution in this embodiment is as follows:

[0060]

[0061] Because 100mL>55.28mL, more than 10 titrations can still be performed after the calcium hydroxide reaction is complete, so 100mL of ammonium chloride solution is injected into the burette.

[0062] S4: continuously adding the ammonium chloride solution dropwise to the above-mentioned mixed solution, and using a conductivity meter to detect the conductivity of the solution during the titration process;

[0063] S4-1: Control the burette to titrate the ammonium chloride solution into the beaker, titrating 2 mL of ammonium chloride solution each time;

[0064] S4-2: Stir with a stirring rod and let stand for 30 seconds to allow ammonium chloride to fully react with calcium hydroxide in the mixed solution to generate calcium chloride, change the number and type of ions in the solution, and increase the conductivity. Use a conductivity meter to detect the conductivity of the solution at this time;

[0065] S4-3: Repeat steps S4-1 and S4-2. After each titration, stir the solution to allow ammonium chloride to fully react with calcium hydroxide in the mixed solution. When the calcium hydroxide reacts completely, titrate the ammonium chloride solution again. No chemical reaction occurs, which increases the number of ions in the solution and increases the conductivity. The conductivity increase rates before and after the complete reaction of calcium hydroxide are different. During this period, detect the solution conductivity until the ammonium chloride solution is consumed.

[0066] S5: Record the corresponding relationship between the titration amount of the ammonium chloride solution and the conductivity of the solution, draw a conductivity-titration curve image according to the corresponding relationship, record the inflection point of the curve as the reaction end point, and record the titration amount of the ammonium chloride solution at the reaction end point;

[0067] S5-1: According to step S4, as the titration amount of the ammonium chloride solution increases, the conductivity of the mixed solution continues to rise, and the corresponding relationship between the titration amount of the ammonium chloride solution and the conductivity of the mixed solution is recorded, as shown in Table 2;

[0068] Table 2

[0069]

[0070]

[0071] According to the above correspondence, a conductivity-titration curve is drawn, such as Figure 2 As shown;

[0072] S5-2: Based on Figure 2 The curve image has an inflection point at the point where the titration amount is 38 ml. This point is recorded as the reaction end point, that is, the calcium hydroxide in the mixed solution reacts completely, and thereafter the ammonium chloride solution is titrated without chemical reaction. Moreover, the conductivity growth rates of the mixed solution before and after the calcium hydroxide reaction are different. Therefore, an inflection point appears in the conductivity-titration curve image. The titration amount of the ammonium chloride solution at the reaction end point is determined and recorded based on the inflection point.

[0073] S6: Calculate the effective calcium content in the lime-stabilized material based on the titration amount of ammonium chloride solution h=38 ml at the reaction end point;

[0074] The calculation method of the effective calcium content is as follows:

[0075]

[0076] The effective calcium content of the lime-stabilized material is x=3.09%, and the detection is accurate.

[0077] Embodiment 2:

[0078] S1: Step S1 is the same as in Example 1, and a lime-stabilized material having a mass of 100 g and an effective calcium content of 6% and an optimal moisture content is prepared;

[0079] The qualities of slaked lime, plain soil and water used are shown in Table 3;

[0080] Table 3

[0081]

[0082] S2: Step S2 is the same as in Example 1.

[0083] S3: Step S3 is the same as in Example 1, wherein a sufficient amount of ammonium chloride solution is injected, and the calculation formula for the minimum amount of ammonium chloride solution required is as follows:

[0084]

[0085] Since 100mL>87.25mL, more than 10 titrations can still be performed after the calcium hydroxide reaction is complete, so 100mL of ammonium chloride solution is injected into the burette.

[0086] S4: Step S4 is the same as in Example 1.

[0087] S5: Step S5 is the same as in Example 1, and the corresponding relationship between the titration amount of the ammonium chloride solution and the conductivity of the mixed solution is shown in Table 4;

[0088] Table 4

[0089]

[0090]

[0091] According to the above correspondence, a conductivity-titration curve is drawn, such as Figure 3 As shown, according to Figure 3 The curve image has an inflection point when the titration amount is 70 ml, and this point is recorded as the reaction endpoint.

[0092] S6: Calculate the effective calcium content in the lime-stabilized material based on the titration amount of ammonium chloride solution h=70 ml at the reaction end point;

[0093] The calculation method of the effective calcium content is as follows:

[0094]

[0095] The effective calcium content of the lime-stabilized material is x=5.98%, and the detection is accurate.

[0096] The above-mentioned Embodiment 1 and Embodiment 2 are only used to illustrate the technical solution of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, a person skilled in the art should understand that the technical solutions described in the aforementioned embodiments can still be modified, or some of the technical features thereof can be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A rapid self-detection method for effective calcium content based on conductivity test, characterized in that: The detection method comprises the following steps: S1, prepare an ammonium chloride solution with a mass fraction of a, and use slaked lime, plain soil and water to prepare a lime-stabilized material with a mass of M to achieve an optimal moisture content; S2. Put the lime-stabilized material into a beaker and add a certain amount of water to prepare a mixed solution; S3, assembling and calibrating a conductivity meter, setting up electrodes and a burette above the mixed solution, and injecting a sufficient amount of ammonium chloride solution into the burette as a titrant; S4, continuously adding ammonium chloride solution to the mixed solution, and using a conductivity meter to detect the conductivity of the solution during the titration process; S5, record the corresponding relationship between the titration amount of the ammonium chloride solution and the conductivity of the solution, draw a conductivity-titration curve image, record the inflection point of the curve as the reaction end point, and record the titration amount of the ammonium chloride solution at the reaction end point; S6. Calculate the effective calcium content in the lime-stabilized material according to the titration of the ammonium chloride solution at the reaction end point; The calculation method of the effective calcium content is: In the formula, x 检测 is the effective calcium content in the lime-stabilized material obtained by testing; m 检测钙 is the effective calcium mass detected; m 土 is the mass of the base soil in the lime-stabilized material; Mr 氯化铵 is the relative molecular mass of ammonium chloride; Mr 氢氧化钙 is the relative molecular mass of calcium hydroxide; h is the titration of ammonium chloride solution at the reaction end point; a is the mass fraction of ammonium chloride solution.

2. The method for rapid self-detection of effective calcium content based on conductivity test according to claim 1, characterized in that: The method for configuring the lime-stabilized material in step S1 comprises the following steps: S1-1, take the soil and slaked lime for the construction site, and air-dry the soil and slaked lime; S1-2, take water and the air-dried soil and slaked lime, and prepare lime-stabilized materials with a mass of M to achieve the best moisture content. The formula for taking water, soil and slaked lime is: M=m 土 +m 配置钙 +m 水 m 水 =ω*(m 土 +m 配置钙 ) Where M is the total mass of lime-stabilized material; m 土 is the mass of the base soil in the lime-stabilized material; m 配置钙 is the mass of slaked lime in the configured lime stabilization material; m 水 is the mass of water in the lime-stabilized material; ω is the optimum moisture content of the lime-stabilized material; x 配置 It is the effective calcium content of lime-stabilized materials.

3. The method for rapid self-detection of effective calcium content based on conductivity test according to claim 1, characterized in that: In step S3, a sufficient amount of ammonium chloride solution is injected into the burette, and the judgment formula is: Where, L is the minimum volume of ammonium chloride solution required; m 钙max is the maximum effective calcium mass in the lime stabilized material; ρ is the density of the ammonium chloride solution; a is the mass fraction of the ammonium chloride solution; Mr 氯化铵 is the relative molecular mass of ammonium chloride; Mr 氢氧化钙 is the relative molecular mass of calcium hydroxide; t is the volume of ammonium chloride solution titrated each time.

4. The method for rapid self-detection of effective calcium content based on conductivity test according to claim 1, characterized in that: The specific operation method in step S4 includes the following steps: S4-1, control the burette to titrate the ammonium chloride solution into the beaker, titrating 2 mL of ammonium chloride solution each time; S4-2, stir with a stirring rod and let stand for 30 seconds to allow ammonium chloride to fully react with calcium hydroxide in the mixed solution to generate calcium chloride, change the number and type of ions in the solution, and change the conductivity. Use a conductivity meter to detect the conductivity of the solution at this time; S4-3, repeat steps S4-1 and S4-2. After each titration, stir the solution to allow ammonium chloride to fully react with calcium hydroxide in the mixed solution. When the calcium hydroxide reacts completely, titrate the ammonium chloride solution again. No chemical reaction occurs, only the number of ions in the solution changes, and the conductivity changes. The conductivity change rate before and after the complete reaction of calcium hydroxide is different. During this period, detect the solution conductivity until the ammonium chloride solution is consumed.

5. The method for rapid self-detection of effective calcium content based on conductivity test according to claim 1, characterized in that: The specific operation method of step S5 comprises the following steps: S5-1: According to step S4, the corresponding relationship between the titration amount of the ammonium chloride solution and the conductivity of the mixed solution is recorded, and a conductivity-titration curve image is drawn according to the corresponding relationship; S5-2: According to the conductivity-titration curve image, find the inflection point of the curve, record it as the reaction endpoint, and determine the titration of the ammonium chloride solution corresponding to the reaction endpoint.

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