A rapid detection method for calcium oxide and magnesium oxide content in cement for roads, bridges and tunnels

Abstract

The present invention provides a method for quickly detecting the content of calcium oxide and magnesium oxide in cement for roads, bridges and tunnels, and relates to the technical field of calcium oxide and magnesium oxide content detection. The detection method comprises the following steps: adding a digestion solution and an appropriate amount of pure water to cement to prepare a suspension, adding an appropriate amount of cobalt chloride to the suspension until it turns pink, placing a filter bag in the suspension, adding an appropriate amount of strong acidic cation exchange resin to the filter bag until the pink disappears, removing the filter bag containing the strong acidic cation exchange resin and placing it in an aluminum sulfate solution for treatment, filtering the aluminum sulfate solution and drying and weighing the precipitate produced in the solution, performing EDTA titration on the original suspension, and calculating the calcium oxide and magnesium oxide content. The present invention overcomes the shortcomings of the prior art. By separating calcium ions and magnesium ions and performing detection, the content of calcium oxide and magnesium oxide can be detected in only one test, while effectively improving the detection speed, accuracy and operational safety.

Description

Technical Field

[0001] The present invention relates to the technical field of calcium oxide and magnesium oxide content detection, and in particular to a method for quickly detecting the calcium oxide and magnesium oxide content in cement for roads, bridges and tunnels. Background Art

[0002] Cement for roads, bridges, and tunnels is a material commonly used in road, bridge, and tunnel construction. It hardens in air or water, firmly bonding materials like sand and stone together to form a strong concrete structure, such as bridge load-bearing structures, road pavements, and tunnel linings. The production of cement for roads, bridges, and tunnels must comply with relevant national standards. Cement stability and strength are particularly important. Cement stability reflects the uniformity of volume changes during the setting and hardening process, while cement strength reflects the ability of the hardened cement mortar specimen to withstand external forces. The calcium oxide and magnesium oxide content in cement determine these two characteristics. An appropriate calcium oxide content is crucial for achieving high strength in cement. However, excessive calcium oxide content can affect cement stability, while insufficient calcium oxide content can reduce strength. An appropriate amount of magnesium oxide can improve cement's volume stability, fire resistance, durability, and sulfate resistance. However, excessive magnesium oxide content in cement can reduce the quality of the building and even cause accidents. Therefore, the detection of calcium oxide and magnesium oxide content in cement is of great significance.

[0003] The current method for detecting the content of magnesium oxide and calcium oxide in cement is to detect by the method provided in the national standard GB / T176-2008 for cement chemical analysis, wherein the detection of calcium oxide content requires the method of high-temperature alkali fusion to treat the sample, which requires high-temperature calcination. There is a certain risk during the test process. In addition, the alkaline reagent added during the high-temperature calcination process will affect the result. In the detection of magnesium oxide content, the cement sample is treated with a hydrofluoric acid-perchloric acid system and then tested. The hydrofluoric acid introduced during the treatment process may cause certain damage to the instrument. The detection method of calcium oxide and magnesium oxide content in a kind of silicate cement provided by Publication No. CN108279274A is to detect calcium oxide and magnesium oxide content by ion chromatograph. However, the retention time of magnesium ion and calcium ion in ion chromatogram is relatively close. If the chromatographic conditions are not ideal, it may be difficult to achieve effective separation of the two. This will cause peak overlap or tailing, thereby affecting the accuracy of quantitative analysis. Summary of the Invention

[0004] In view of the shortcomings of the existing technology, the present invention provides a method for rapid detection of calcium oxide and magnesium oxide content in cement for roads, bridges and tunnels. By separating calcium ions and magnesium ions and conducting detection, the content of calcium oxide and magnesium oxide in cement can be detected in one test while effectively improving detection accuracy and operational safety.

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

[0006] A method for rapidly detecting the content of calcium oxide and magnesium oxide in cement for roads, bridges and tunnels, the method comprising the following steps:

[0007] S1、To the Add 100 grams of cement sample to the container ml of digestion solution and stir thoroughly. After the reaction is complete, add d ml of pure water to prepare a suspension sample; , ;

[0008] S2, add the above suspension sample g of cobalt chloride hexahydrate until the suspension turns pink;

[0009] S3. Take the filter bag and immerse the bag body into the pink suspension prepared in step S2 above, with the upper opening of the filter bag extending above the suspension liquid level;

[0010] S4. Add the strong acidic cation exchange resin into the filter bag in batches from the upper opening of the filter bag until the pink color in the suspension disappears;

[0011] S5. Take out the filter bag together with the strong acidic cation exchange resin therein, and wash the remaining suspension on its surface with clean water, and pour the solution obtained after washing back into the suspension;

[0012] S6, the cleaned filter bag together with the strong acidic cation exchange resin therein is placed in a container filled with aluminum sulfate, after stirring, the filter bag is taken out and its surface is washed with clean water, and the solution obtained after washing is poured back into the aluminum sulfate solution;

[0013] S7, filter the aluminum sulfate solution after standing, dry it and weigh the mass of the precipitate obtained by filtration m p1 gram;

[0014] S8. Perform EDTA titration test on the suspension in S5. Determine the amount of titrant consumed at the end of the titration based on the color change of the solution. ml;

[0015] S9, according to the quality of the precipitate in S7 Grams, and the amount of titrant consumed in S8 ml, calculate the content of calcium oxide and magnesium oxide in cement, and

[0016] The calculation formula for calcium oxide content is: ;

[0017] The calculation formula for magnesium oxide content is: ;

[0018] Where: is the calcium oxide content in cement; is the magnesium oxide content in cement, is the ratio of the molar masses of calcium oxide and calcium sulfate; is the ratio of the molar masses of magnesium oxide and EDTA-Na2; is the mass fraction of EDTA-Na2 solution.

[0019] Preferably, the digestion solution is dilute hydrochloric acid with a mass fraction of 10%.

[0020] Preferably, in step S1 .

[0021] Preferably, in step S2 .

[0022] Preferably, the method of adding the strongly acidic cation exchange resin in step S4 includes the following steps:

[0023] S4-1, add to the filter bag α ml of strong acidic cation exchange resin and stir;

[0024] in, , where [] is the rounding down symbol;

[0025] S4-2. Observe the color of the solution:

[0026] ①If the solution color does not change, add ml of strong acidic cation exchange resin and stirred, wherein: ;

[0027] ②If the color of the solution disappears, stop adding the strong acid cation exchange resin.

[0028] Preferably, the filter bag after cleaning in step S6 is placed in a container filled with aluminum sulfate and stirred for 30 seconds every 5 minutes, and the filter bag is taken out after a total treatment of 30 minutes.

[0029] Preferably, the method for the EDTA titration test in step S8 comprises the following steps:

[0030] S8-1. Insert a pH meter into the suspension in S5 and add appropriate amounts of triethanolamine solution and ammonia-ammonium chloride buffer solution until the pH value of the suspension reaches 10;

[0031] S8-2, adding chrome black T indicator to the suspension;

[0032] S8-3. Place the suspension under a burette and use the burette to add an appropriate amount of EDTA-Na2 to the solution;

[0033] S8-4. Observe the color change of the solution:

[0034] ① If the solution color does not change, repeat step S8-3;

[0035] ②If the solution turns blue, record the amount of titrant consumed. ml.

[0036] The present invention provides a method for rapidly detecting the content of calcium oxide and magnesium oxide in cement for roads, bridges and tunnels. Compared with the prior art, the method has the following advantages:

[0037] (1) Unlike the traditional technology for detecting the content of calcium oxide and magnesium oxide in cement, the present invention can detect the content of calcium oxide and magnesium oxide in cement with only one test. The present invention dissolves the calcium oxide and magnesium oxide in lime, separates the calcium ions and magnesium ions, and detects them. The calcium ions are detected by precipitation method, and the magnesium ions are detected by EDTA titration method. This avoids the cumbersome steps and operations in traditional technology, is simple to operate, and has no technical requirements for operators. It improves the detection speed of magnesium oxide and calcium oxide in cement while ensuring the detection accuracy.

[0038] (2) The present invention utilizes a strong acid cation exchange resin material to achieve the effect of separating calcium ions and magnesium ions, thereby detecting the contents of calcium ions and magnesium ions separately. In addition, the strong acid cation exchange resin can be recycled. After the test, the strong acid cation exchange resin can be restored to its regeneration capacity and participate in the recycling of the next test through steps such as backwashing with clean water, injection of a strong acid regeneration agent, slow flushing, and fast flushing, which is beneficial to sustainable development.

[0039] (3) This invention avoids the high-temperature alkali melting step used in conventional techniques to treat cement, ensuring the safety of the test operation and being more energy-efficient. Furthermore, this method avoids the use of hydrofluoric acid in conventional testing techniques, ensuring that the test equipment is not damaged. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is a flow chart of the method for quickly detecting the content of magnesium oxide and calcium oxide in cement for roads, bridges and tunnels according to the present invention;

[0041] Figure 2 This is a schematic diagram of the placement of the filter bag and container in Example 1 of the present invention;

[0042] In the figure: 1. filter bag; 2. beaker; 3. suspension. DETAILED DESCRIPTION

[0043] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention are clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0044] Example 1:

[0045] 1. Instruments and reagents

[0046] Laboratory electronic precision balance; burette; beaker; flask; glass funnel; filter paper; glass rod; filter bag; stainless steel measuring spoon (1 / 2 teaspoon); cobalt chloride hexahydrate (analytical grade); aluminum sulfate 18-hydrate (analytical grade); 10% dilute hydrochloric acid (analytical grade); ammonia water (concentration 25-28%); ammonium chloride (analytical grade); EDTA-Na2·2H2O (analytical grade); triethanolamine (analytical grade); strongly acidic cation exchange resin; ultrapure water used in the laboratory; the sample used was ordinary Portland cement sample P.O42.5 (produced by Zhucheng Yangchun Cement Co., Ltd.).

[0047] 2. Preparation of aluminum sulfate solution, EDTA-Na2 and ammonia-ammonium chloride buffer:

[0048] Place 400 g of aluminum sulfate 18hydrate in a conical flask, add 645.9 g of purified water, and shake to dissolve it completely to prepare a 20% aluminum sulfate solution.

[0049] Take 40 g of EDTA-Na2·2H2O in a conical flask, add 325.6 g of purified water and shake to dissolve it completely to prepare a 10% EDTA-Na2 solution;

[0050] Take 5.4 grams of ammonium chloride in a conical flask, add 800 grams of water into the flask and shake to dissolve it completely. Insert a pH meter into the flask and gradually add ammonia water until the pH of the solution reaches 11.0 to prepare an ammonia-ammonium chloride buffer solution.

[0051] 3. Detection of calcium oxide and magnesium oxide in cement:

[0052] S1. Add 200 ml of 10% dilute hydrochloric acid to a beaker containing 20 g of cement sample and stir. After the reaction is complete, add 300 ml of purified water to prepare a suspension.

[0053] S2. Add 9.71 g of cobalt chloride hexahydrate to the suspension and stir until the solution turns a distinct pink color;

[0054] S3. Reference Figure 2 Place the filter bag into the suspension, making sure the bag is in full contact with the suspension;

[0055] S4, adding an appropriate amount of strong acid cation exchange resin to the filter bag in batches until the pink color in the suspension disappears, comprising the following steps:

[0056] Add 310 ml of strong acid cation exchange resin to the filter bag and stir; if the solution color does not change, add another 5 ml of strong acid cation exchange resin and stir;

[0057] S5. Remove the filter bag and clean the remaining suspension on its surface with clean water, and pour the solution obtained after cleaning back into the suspension;

[0058] S6. Place the filter bag containing the strongly acidic cation exchange resin into a 500 ml beaker filled with 20% aluminum sulfate by mass, stir for 30 seconds every 5 minutes, remove the filter bag after 30 minutes, and rinse its surface with clean water, then pour the rinsed solution back into the aluminum sulfate solution;

[0059] S7, filtering the aluminum sulfate solution after standing, drying and weighing the filtered precipitate to a mass of 30.05 g;

[0060] S8, performing an EDTA titration test on the suspension in S5, and determining, based on the change in solution color, that the titrant consumption at the end of the titration is 61 ml, comprising the following steps:

[0061] S8-1. Insert a pH indicator into the suspension in S5 and add 5 ml of triethanolamine solution and an appropriate amount of ammonia-ammonium chloride buffer solution until the pH value of the solution is 10;

[0062] S8-2, add 2 drops of chrome black T indicator to the suspension in S5;

[0063] S8-3. Place the suspension in S5 under the burette and add 1 mL of 10% EDTA-Na2 dropwise to the solution. If the solution does not change color, repeat S8-2 and S8-3 until the solution turns blue. Record the amount of titrant consumed: 61 mL.

[0064] S9, water According to the following formula, the content of calcium oxide in cement is calculated to be 61.6%:

[0065]

[0066] The content of calcium oxide in cement is calculated to be 61.6%, where: ω 1 is the calcium oxide content in cement; m p1 It is the mass that produces calcium sulfate precipitation; K 1 is the ratio of the molar masses of calcium oxide and calcium sulfate;

[0067] The content of magnesium oxide in cement is calculated as 3.64% according to the following formula:

[0068]

[0069] Where, ω 2 is the magnesium oxide content in cement; ω 3 is the mass fraction of EDTA-Na2 solution; l is the titrant consumption; K 2 is the ratio of the molar masses of magnesium oxide and EDTA-Na2.

[0070] Example 2:

[0071] Calcium oxide and magnesium oxide content detection and verification:

[0072] (1) Take 14g calcium oxide and 0.8g magnesium oxide in a beaker and stir them evenly to prepare the sample to be tested;

[0073] (2) Add 200 ml of 10% dilute hydrochloric acid to the beaker containing the sample to be tested and stir. After the reaction is complete, add 300 ml of purified water to prepare the test solution;

[0074] (3) Add 9.71 g of cobalt chloride hexahydrate to the test solution and stir until the solution turns distinctly pink;

[0075] (4) Place the filter bag in the pink test solution, ensuring that the bag is in full contact with the test solution;

[0076] (5) Add 310 mL of strong acidic cation exchange resin to the filter bag until the pink color disappears in the test solution;

[0077] (6) Take out the filter bag and clean the solution remaining on its surface with clean water, and pour the solution obtained after cleaning back into the original solution;

[0078] (7) Place the filter bag containing the strong acidic cation exchange resin into a 500 ml beaker filled with 20% aluminum sulfate by mass, stir for 30 seconds every 5 minutes, remove the filter bag after 30 minutes and wash its surface with clean water, and pour the washed solution back into the aluminum sulfate solution;

[0079] (8) Filter the aluminum sulfate solution after standing, dry it, and weigh the precipitate obtained by filtration, which is 32.47 g;

[0080] (9) Perform an EDTA titration test on the original solution in step (6). Based on the change in solution color, determine that the titrant consumption at the end of the titration is 64 ml:

[0081] Insert a pH indicator into the original solution in step (5) and add 5 ml of triethanolamine solution and an appropriate amount of ammonia-ammonium chloride buffer solution until the solution pH is 10;

[0082] Add 2 drops of chrome black T indicator to the original solution in S5;

[0083] Place the original solution under the burette and add 1 mL of 10% EDTA-Na2 to the solution. If the solution does not change color, repeat the above steps until it turns blue. Record the amount of titrant consumed as 64 mL.

[0084] (10) Based on the mass of the precipitate obtained, which is 32.47 g, and the amount of titrant consumed, which is 64 ml, the mass of calcium oxide is calculated to be 13.37 g; the mass of magnesium oxide is calculated to be 0.76 g.

[0085] The calcium oxide and magnesium oxide results calculated overall above have small errors and high accuracy.

[0086] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. 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 various embodiments of the present invention.

Claims

1. A method for rapid detection of calcium oxide and magnesium oxide content in cement for roads, bridges and tunnels, characterized in that: The detection method comprises the following steps: S1、To the Add 100 grams of cement sample to the container ml of digestion solution and stir thoroughly. After the reaction is complete, add d ml of pure water to prepare a suspension sample; , ; S2, add the above suspension sample g of cobalt chloride hexahydrate until the suspension turns pink; S3. Take the filter bag and immerse the bag body into the pink suspension prepared in step S2 above, with the upper opening of the filter bag extending above the suspension liquid level; S4. Add the strong acidic cation exchange resin into the filter bag in batches from the upper opening of the filter bag until the pink color in the suspension disappears; S5. Take out the filter bag together with the strong acidic cation exchange resin therein, and wash the remaining suspension on its surface with clean water, and pour the solution obtained after washing back into the suspension; S6, the cleaned filter bag together with the strong acidic cation exchange resin therein is placed in a container filled with aluminum sulfate, after stirring, the filter bag is taken out and its surface is washed with clean water, and the solution obtained after washing is poured back into the aluminum sulfate solution; S7, filter the aluminum sulfate solution after standing, dry it and weigh the mass of the precipitate obtained by filtration m p1 gram; S8. Perform EDTA titration test on the suspension in S5. Determine the amount of titrant consumed at the end of the titration based on the color change of the solution. ml; S9, according to the quality of the precipitate in S7 Grams, and the amount of titrant consumed in S8 ml, calculate the content of calcium oxide and magnesium oxide in cement, and The calculation formula for calcium oxide content is: ; The calculation formula for magnesium oxide content is: ; Where: is the calcium oxide content in cement; is the magnesium oxide content in cement, is the ratio of the molar masses of calcium oxide and calcium sulfate; is the ratio of the molar masses of magnesium oxide and EDTA-Na2; is the mass fraction of EDTA-Na2 solution.

2. The method for rapid detection of calcium oxide and magnesium oxide content in cement for roads, bridges and tunnels according to claim 1, characterized in that: The digestion solution is dilute hydrochloric acid with a mass fraction of 10%.

3. The method for rapid detection of calcium oxide and magnesium oxide content in cement for roads, bridges and tunnels according to claim 1, characterized in that: In step S1 .

4. The method for rapid detection of calcium oxide and magnesium oxide content in cement for roads, bridges and tunnels according to claim 1, characterized in that: In step S2 .

5. The method for rapid detection of calcium oxide and magnesium oxide content in cement for roads, bridges and tunnels according to claim 1, characterized in that: The method of adding the strongly acidic cation exchange resin in step S4 comprises the following steps: S4-1, add to the filter bag α ml of strong acidic cation exchange resin and stir; in, , where [] is the rounding down symbol; S4-2. Observe the color of the solution: ①If the solution color does not change, add ml of strong acidic cation exchange resin and stirred, wherein: ; ②If the color of the solution disappears, stop adding the strong acid cation exchange resin.

6. The method for rapid detection of calcium oxide and magnesium oxide content in cement for roads, bridges and tunnels according to claim 1, characterized in that: The cleaned filter bag in step S6 is placed in a container filled with aluminum sulfate and stirred for 30 seconds every 5 minutes, and the filter bag is taken out after a total treatment of 30 minutes.

7. The method for rapid detection of calcium oxide and magnesium oxide content in cement for roads, bridges and tunnels according to claim 1, characterized in that: The method for the EDTA titration test in step S8 comprises the following steps: S8-1. Insert a pH meter into the suspension in S5 and add appropriate amounts of triethanolamine solution and ammonia-ammonium chloride buffer solution until the pH value of the suspension reaches 10; S8-2, adding chrome black T indicator to the suspension; S8-3. Place the suspension under a burette and use the burette to add an appropriate amount of EDTA-Na2 to the solution; S8-4. Observe the color change of the solution: ① If the solution color does not change, repeat step S8-3; ②If the solution turns blue, record the amount of titrant consumed. ml.

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