Method for detecting reaction calcium of low-carbon cementing material for aerated concrete

Abstract

The invention discloses a method for detecting reaction calcium of a low-carbon cementing material for aerated concrete. The method solves the technical problem that calcium participating in a digestion reaction cannot be accurately described or evaluated in the prior art. The method comprises the working procedures of sample pretreatment, test solution preparation and titration measurement, and is used for measuring the calcium participating in the digestion reaction, such as f-CaO, C2S, C4A3S and C4AF, so that the content of the calcium participating in the reaction can be evaluated. The detection result of the invention has good stability, reproducibility and accuracy. And in the aspect of detection speed, the method has the characteristics of high analysis speed, short detection period and high analysis efficiency, and in the aspect of detection flow, the method is simple to operate, easy to learn and understand, has no too high requirements on test and analysis personnel, and has better popularization and application prospects.

Description

Technical Field

[0001] The invention relates to the technical field of raw material detection for preparing aerated concrete, and in particular to a method for detecting calcium reacted by a low-carbon cementitious material for aerated concrete. Background Art

[0002] As a raw material for preparing aerated concrete, low-carbon cementitious materials have mineral compositions including f-CaO (free calcium oxide), C2S (dicalcium silicate), C4A3S (calcium sulfoaluminate), C4AF (tetracalcium aluminoferrate) and CaSO4 (calcium sulfate). Digestion time and digestion temperature are important parameters for preparing aerated concrete, and digestion time and digestion temperature are mainly determined by the large amount of heat released by f-CaO (free calcium oxide) during the reaction, which is conducive to the hydrothermal synthesis reaction of calcium silicon. At the same time, other calcium salts also have certain hydration reactions, release heat and promote the reaction. Therefore, the content of calcium involved in the reaction cannot be fully evaluated from the f-CaO content alone. Therefore, it is necessary to introduce a concept of calcium reaction of low-carbon cementitious materials for aerated concrete and provide a detection method. Summary of the invention

[0003] The object of the present invention is to provide a method for detecting calcium in reaction of low-carbon cementitious materials for aerated concrete, which can more accurately detect the content of calcium in the low-carbon cementitious materials participating in the digestion reaction.

[0004] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0005] A method for detecting calcium reaction of low-carbon cementitious material for aerated concrete comprises the following steps:

[0006] S1. Sample pretreatment: Grind and sieve the low-carbon gelling material and store it in a sealed container;

[0007] S2. Preparation of test solution: weigh the ground and sieved low-carbon gelling material and place it in a dry conical flask, add carbon dioxide-free water and shake the conical flask to disperse the low-carbon gelling material, then add sucrose solution to react and shake, then let it stand for 20 to 25 minutes, filter out the liquid in the conical flask, wash the wall of the conical flask with carbon dioxide-free water 5 to 6 times to obtain a washing liquid, collect the filtered liquid and the washing liquid and mix them to obtain a test solution;

[0008] S3. Titration calculation: After the test solution is cooled to room temperature, add 6 to 7 drops of phenolphthalein indicator solution, and then titrate the test solution with hydrochloric acid standard titration solution until the test solution changes from red to colorless and does not return to color within 30 seconds. Finally, calculate the mass fraction of reaction calcium in the low-carbon cementitious material based on the titration operation.

[0009] Furthermore, the S1 comprises: S11, passing the low-carbon cementitious material through a 150-micron square hole sieve to obtain a first undersize material and a first oversize material; S12, grinding the first oversize material and passing it through a 150-micron square hole sieve again to obtain a second undersize material; S13, fully mixing the first undersize material and the second undersize material and sealing them for storage.

[0010] Furthermore, in S2, 100 ml of carbon dioxide-free water is added to each gram of low-carbon gelling material for dispersion, and 100 ml of sucrose solution is added to each gram of low-carbon gelling material for reaction.

[0011] Furthermore, in S2, after adding the sucrose solution, the conical flask is covered with a stopper, and then shaken every 5 minutes. After each shaking, the stopper is removed, and the stopper and the wall of the conical flask are rinsed with water without carbon dioxide.

[0012] Furthermore, in S2, the concentration of the sucrose solution is 300 g / L, and the preparation is as follows: 300 g of sucrose is dissolved in carbon dioxide-free water, diluted to 1000 ml with carbon dioxide-free water, 1 ml of phenolphthalein indicator solution is added, neutralized with sodium hydroxide solution to a slightly reddish color, and sealed for storage.

[0013] Furthermore, in S2 and S3, the concentration of the phenolphthalein indicator solution is 10 g / L, and the configuration is as follows: 1 g of phenolphthalein is dissolved in 100 ml of anhydrous ethanol.

[0014] Furthermore, in S3, the concentration of the hydrochloric acid standard titration solution is 1 mol / L, and the configuration is as follows: 83 mL of hydrochloric acid is diluted to 1000 mL with water, and the density of the hydrochloric acid is 1.18 g / cm 3 ~1.19g / cm 3 , the mass fraction is 36% to 38%.

[0015] Furthermore, in S3, the calculation formula for the mass fraction of the reaction calcium is as follows:

[0016]

[0017] In the formula, ω 反应钙 is the mass fraction of reaction calcium, %; T CaO is the titration degree of hydrochloric acid standard titration solution on calcium oxide, mg / mL; V1 is the volume of hydrochloric acid standard titration solution consumed during titration, mL; m1 is the mass of low-carbon gelling material weighed in S2, g;

[0018] The calculation formula of the titration degree of hydrochloric acid standard titration solution to calcium oxide is as follows:

[0019] T CaO =c HCl ×28.04;

[0020] In the formula, c HCl is the concentration of standard hydrochloric acid titration solution, mol / L; 28.04 is the molar mass of 1 / 2CaO, g / mol.

[0021] Furthermore, the chemical reaction principle of the detection is as follows:

[0022] In the S2, water without carbon dioxide is added for multiple times: first, free calcium oxide in the low-carbon cementitious material is reacted with water to generate calcium hydroxide: CaO+H2O→Ca(OH)2; second, calcium salt in the low-carbon cementitious material is reacted to generate calcium hydroxide, the calcium salt includes C2S, C4A3S, C4AF, and the calcium salt takes C2S as an example, and the specific chemical formula of C2S is 2CaO·SiO2: 2(2CaO·SiO2)+4H2O→3CaO·2SiO2·3H2O+Ca(OH)2;

[0023] In S2, the sucrose solution is added to react with the free calcium oxide and the generated calcium hydroxide to generate sucrose calcium: C 12 H 22 O 11 +CaO+2H2O→C 12 H 12 O 11 ·CaO·2H2O,C 12 H 22 O 11 +Ca(OH)2+H2O→C 12 H 12 O 11 ·CaO·2H2O;

[0024] In S3, the generated calcium sucrose reacts with the titrated hydrochloric acid standard titration solution to generate calcium chloride:

[0025] C 12 H 12 O 11 ·CaO·2H2O+2HCl→CaCl2+2C 12 H 22 O 11 +2H2O.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1. The present invention grinds and sieves the low-carbon gelling material to optimize the particle size of the material, make the particle size uniform, and eliminate the error caused by the particle size to the test result as much as possible.

[0028] 2. The present invention uses water without carbon dioxide, which can prevent free calcium oxide from reacting with carbon dioxide to form calcium carbonate and thus affect the test results.

[0029] 3. The present invention adds sucrose solution for reaction and shakes, and the shaking promotes the unreacted calcium hydroxide and free calcium oxide on the bottle wall to fully react with the sucrose; and after shaking, the bottle wall and bottle stopper of the conical flask are washed with carbon dioxide-free water to wash away the attached substances, thereby promoting the attached calcium hydroxide and free calcium oxide to fully react with the sucrose.

[0030] 4. The present invention separates solids and liquids by filtering, which has two effects: first, the solid contains calcium salts that cannot be hydrolyzed, that is, calcium salts that cannot undergo hydration reaction, which prevents hydrochloric acid from reacting with such calcium salts to generate Ca 2 + , and excessive consumption of hydrochloric acid will affect the judgment of the titration end point; secondly, the test solution during titration contains only liquid, which is conducive to the observation of the titration end point.

[0031] 5. The detection results of the method provided by the present invention have good stability, reproducibility and accuracy. In terms of detection speed, it has the characteristics of fast analysis speed, short detection cycle and high analysis efficiency. In terms of detection process, it is simple to operate, easy to learn and understand, and has no high requirements for test analysts, and has good prospects for promotion and application. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present invention. The terms "first", "second", etc. in the present invention are used to distinguish different objects, rather than to describe a specific order.

[0033] Example

[0034] As a preferred embodiment of the present invention, a method for detecting calcium reaction of a low-carbon cementitious material for aerated concrete disclosed in this embodiment is characterized in that it comprises the following steps:

[0035] S1. Pass the low-carbon cementitious material through a 150-micron square hole sieve to obtain a first undersize and a first oversize; grind the first oversize and make it pass through a 150-micron square hole sieve to obtain a second undersize; fully mix the first undersize and the second undersize, and seal and store them in a clean, dry sample bottle;

[0036] S2. Weigh 0.5000 g of the ground and sieved low-carbon gelling material, accurate to 0.0001 g, and place it in a 250 ml clean and dry conical flask. Add 50 ml of carbon dioxide-free water and shake the conical flask to disperse the low-carbon gelling material. Then add 50 ml of sucrose solution to react, cover the conical flask with a stopper and shake it. Let it stand for 20 minutes. During this period, shake it every 5 minutes. Remove the stopper and rinse the stopper and the bottle wall with water without carbon dioxide. Filter the liquid in the conical flask with a quick filter paper, wash the bottle wall of the conical flask with water without carbon dioxide for 5 to 6 times to obtain a washing liquid. Collect the filtered liquid and the washing liquid and mix them in a 400 ml beaker to obtain a test solution.

[0037] S3. After the test solution is cooled to room temperature, add 6 to 7 drops of phenolphthalein indicator solution, and then titrate the test solution with hydrochloric acid standard titration solution until the test solution changes from red to colorless and does not return to color within 30 seconds. Finally, calculate the mass fraction of reactive calcium in the low-carbon cementitious material based on the titration operation. The calculation formula for the mass fraction of reactive calcium is as follows:

[0038]

[0039] In the formula, ω 反应钙 is the mass fraction of reaction calcium, %; T CaO is the titration degree of hydrochloric acid standard titration solution on calcium oxide, mg / mL; V1 is the volume of hydrochloric acid standard titration solution consumed during titration, mL; m1 is the mass of low-carbon gelling material weighed in S2, g;

[0040] The calculation formula of the titration degree of hydrochloric acid standard titration solution to calcium oxide is as follows:

[0041] T CaO =c HCl ×28.04;

[0042] In the formula, c HCl is the concentration of standard hydrochloric acid titration solution, mol / L; 28.04 is the molar mass of 1 / 2CaO, g / mol.

[0043] In this embodiment, the concentration of the sucrose solution is 300 g / L, and the preparation is as follows: 300 g of sucrose is dissolved in carbon dioxide-free water, diluted to 1000 ml with carbon dioxide-free water, 1 ml of phenolphthalein indicator solution is added, neutralized with sodium hydroxide solution to a slightly reddish color, and sealed for storage;

[0044] The concentration of phenolphthalein indicator solution is 10 g / L and is prepared as follows: dissolve 1 g of phenolphthalein in 100 ml of anhydrous ethanol;

[0045] The concentration of the hydrochloric acid standard titration solution is 1 mol / L, and the configuration is as follows: 83 mL of hydrochloric acid is diluted to 1000 mL with water. The density of the hydrochloric acid is 1.18 g / cm3 ~1.19g / cm 3 , the mass fraction is 36% to 38%.

[0046] Among them, the concentration of the hydrochloric acid standard titration solution needs to be calibrated, that is, the concentration of the hydrochloric acid standard titration solution in S3 is the concentration of the hydrochloric acid standard titration solution after calibration, and the operation is as follows:

[0047] Weigh 0.8 g (m2) of sodium carbonate (NaCO3, standard reagent) that has been dried at 130°C for 2 h, accurate to 0.0001 g, place in a 250 ml dry conical flask, add 100 ml of water to dissolve it, add 2 to 3 drops of methyl red indicator solution, and then calibrate with standard hydrochloric acid until the solution slowly titrates to red. Heat the solution to boil and simmer for 2 minutes, cover with a stopper or watch glass, cool to room temperature, and continue titrating until a stable red color (V2) appears.

[0048] The calculation formula for the concentration of the hydrochloric acid standard titration solution after calibration is as follows:

[0049]

[0050] In the formula, c HCl is the concentration of the hydrochloric acid standard titration solution after calibration, mol / L; m2 is the mass of the sodium carbonate weighed, g; V2 is the volume of the hydrochloric acid standard titration solution consumed during calibration, mL; 53.0 is the molar mass of 1 / 2Na2CO3, g / mol.

[0051] The concentration of the methyl red indicator solution is 2 g / L, and the preparation is as follows: 0.2 g of methyl red is dissolved in 100 mL of anhydrous ethanol.

[0052] Method Validation:

[0053] 1. To determine that the standing time in S2 is 20 minutes, the following experiment is carried out:

[0054] Take three kinds of low-carbon cementitious material samples, take several portions of each sample, each portion is 0.5000g, put them into heat-insulating containers, add 50ml of carbon dioxide-free water, quickly cover the lid, read and record the temperature every 2 minutes, the experimental results are shown in Table 1 below:

[0055] Table 1

[0056]

[0057] Note: The temperature of the sample at a certain time in Table 1 is the average value of multiple tests.

[0058] According to Table 1, the temperature starts to drop after about 20 minutes, so the standing time is determined to be 20 to 25 minutes.

[0059] 2. To determine the number of washing times after filtration, the following experiment was conducted:

[0060] Take three kinds of low-carbon gelling material samples, take several portions of each sample, 0.5000g each, put them in a 250ml clean, dry conical flask, quickly add 50ml of carbon dioxide-free water, shake the conical flask to disperse the sample, add 50ml of sucrose solution, cover the bottle stopper, shake, let it stand for 20-25min, shake it every 5min during this period, remove the bottle stopper, and rinse the bottle stopper and bottle wall with water without carbon dioxide. After standing, filter with fast filter paper, wash each sample for different times, drip phenolphthalein indicator solution on the filter paper, observe the color, and record it. The test results are shown in Table 2 below:

[0061] Table 2

[0062]

[0063] Note: The color of the sample in the table at a certain number of washings is the darkest color among multiple tests.

[0064] According to Table 2, when the number of washes is 4, there is basically no C on the filter paper. 12 H 12 O 11 ·CaO·2H2O, add phenolphthalein indicator solution and it is colorless, and the number of washing times after filtration is determined to be 5 to 6 times.

[0065] 3. Precision experiment

[0066] Three low-carbon cementitious material samples were selected, and the reaction calcium content was measured according to the detection method of the present invention, and the relative standard deviation was calculated. The experimental results are shown in Table 3 below:

[0067] Table 3

[0068]

[0069] 4. Recovery rate experiment

[0070] A low-carbon cementitious material sample was selected, and different amounts of CaO (standard pure) were added respectively. The reaction calcium content was determined according to the detection method of the present invention. Each group of samples was analyzed in parallel 5 times, and the average value was taken to calculate the recovery rate. The experimental results are shown in Table 4 below:

[0071] Table 4

[0072]

[0073] The results of the precision experiment and the recovery rate experiment show that the analysis result of the detection method of the present invention has a small deviation, and the precision and accuracy can meet the detection requirements.

[0074] Finally, it should be noted that the above embodiments are only preferred embodiments of the present invention to illustrate the technical solutions of the present invention, rather than limiting them, and certainly not limiting the patent scope of the present invention. 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 recorded in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. These modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention. In other words, any changes or modifications made to the main design concept and spirit of the present invention that have no substantive significance, and the technical problems they solve are still consistent with the present invention, should be included in the protection scope of the present invention. In addition, the direct or indirect application of the technical solutions of the present invention in other related technical fields is also included in the patent protection scope of the present invention.

Claims

1. A method for detecting calcium reaction of low-carbon cementitious material for aerated concrete, characterized in that: The following steps are involved: S1. Sample pretreatment: Grind and sieve the low-carbon gelling material and store it in a sealed container; S2. Preparation of test solution: weigh the ground and sieved low-carbon gelling material and place it in a dry conical flask, add carbon dioxide-free water and shake the conical flask to disperse the low-carbon gelling material, then add sucrose solution to react and shake, then let it stand for 20 to 25 minutes, filter out the liquid in the conical flask, wash the wall of the conical flask with carbon dioxide-free water 5 to 6 times to obtain a washing liquid, collect the filtered liquid and the washing liquid and mix them to obtain a test solution; S3. Titration calculation: After the test solution is cooled to room temperature, add 6 to 7 drops of phenolphthalein indicator solution, and then titrate the test solution with hydrochloric acid standard titration solution until the test solution changes from red to colorless and does not return to color within 30 seconds. Finally, calculate the mass fraction of reaction calcium in the low-carbon cementitious material based on the titration operation.

2. The method for detecting the reaction calcium of low-carbon cementitious material for aerated concrete according to claim 1, characterized in that: The S1 comprises: S11, passing the low-carbon cementitious material through a 150-micron square hole sieve to obtain a first undersize and a first oversize; S12, grinding the first oversize and passing it through a 150-micron square hole sieve to obtain a second undersize; S13, fully mixing the first undersize and the second undersize, and sealing and storing them.

3. The method for detecting the reaction calcium of low-carbon cementitious material for aerated concrete according to claim 1, characterized in that: In S2, 100 ml of carbon dioxide-free water is added to each gram of low-carbon gelling material for dispersion, and 100 ml of sucrose solution is added to each gram of low-carbon gelling material for reaction.

4. The method for detecting the reaction calcium of low-carbon cementitious material for aerated concrete according to claim 1, characterized in that: In S2, after adding the sucrose solution, the conical flask is covered with a stopper, and then shaken every 5 minutes. After each shaking, the stopper is removed, and the stopper and the wall of the conical flask are rinsed with water without carbon dioxide.

5. The method for detecting the reaction calcium of low-carbon cementitious material for aerated concrete according to claim 1, characterized in that: In the S2, the concentration of the sucrose solution is 300 g / L, and the preparation is as follows: 300 g of sucrose is dissolved in carbon dioxide-free water, diluted to 1000 ml with carbon dioxide-free water, 1 ml of phenolphthalein indicator solution is added, neutralized with sodium hydroxide solution to a slightly reddish color, and sealed for storage.

6. The method for detecting the reaction calcium of low-carbon cementitious material for aerated concrete according to claim 5, characterized in that: In S2 and S3, the concentration of the phenolphthalein indicator solution is 10 g / L, and the preparation is as follows: 1 g of phenolphthalein is dissolved in 100 ml of anhydrous ethanol.

7. The method for detecting the reaction calcium of low-carbon cementitious material for aerated concrete according to claim 1, characterized in that: In S3, the concentration of the hydrochloric acid standard titration solution is 1 mol / L, and the configuration is as follows: 83 mL of hydrochloric acid is diluted to 1000 mL with water. The density of the hydrochloric acid is 1.18 g / cm 3 ~1.19g / cm 3 , the mass fraction is 36% to 38%.

8. The method for detecting the reaction calcium of low-carbon cementitious material for aerated concrete according to claim 1, characterized in that: In S3, the calculation formula for the mass fraction of the reaction calcium is as follows: In the formula, ω 反应钙 is the mass fraction of reaction calcium, %; T CaO is the titration degree of hydrochloric acid standard titration solution on calcium oxide, mg / mL; V1 is the volume of hydrochloric acid standard titration solution consumed during titration, mL; m1 is the mass of low-carbon gelling material weighed in S2, g; The calculation formula of the titration degree of hydrochloric acid standard titration solution to calcium oxide is as follows: T CaO =c HCl ×28.04; In the formula, c HCl is the concentration of standard hydrochloric acid titration solution, mol / L; 28.04 is the molar mass of 1 / 2CaO, g / mol.

9. The method for detecting the reaction calcium of low-carbon cementitious material for aerated concrete according to claim 1, characterized in that: The chemical reaction principle of the detection is as follows: In the S2, water without carbon dioxide is added for many times: first, free calcium oxide in the low-carbon cementitious material is reacted with water to generate calcium hydroxide: CaO+H2O→Ca(OH)2; second, calcium salt in the low-carbon cementitious material is reacted to generate calcium hydroxide, wherein calcium salt is taken as an example of C2S, and the specific chemical formula of C2S is 2CaO·SiO2: 2(2CaO·SiO2)+4H2O→3CaO·2SiO2·3H2O+Ca(OH)2; In S2, the sucrose solution is added to react with the free calcium oxide and the generated calcium hydroxide to generate sucrose calcium: C 12 H 22 O 11 +CaO+2H2O→C 12 H 12 O 11 ·CaO·2H2O,C 12 H 22 O 11 +Ca(OH)2+H2O→C 12 H 12 O 11 ·CaO·2H2O; In S3, the generated calcium sucrose reacts with the titrated hydrochloric acid standard titration solution to generate calcium chloride: C 12 H 12 O 11 ·CaO·2H2O+2HCl→CaCl2+2C 12 H 22 O 11 +2H2O.

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