A method for characterizing the activity of light-burned magnesia and a method for preparing magnesite cement

Abstract

The present invention proposes a method for characterizing the activity of light-burned magnesium oxide, comprising the following steps: calculating the active magnesium oxide content in the light-burned magnesium oxide; calculating the mass of the light-burned magnesium oxide based on the active magnesium oxide content; detecting the reaction time of the light-burned magnesium oxide with a weak acid; and obtaining a characterization result of the activity of the light-burned magnesium oxide based on the active magnesium oxide content and the reaction time. The present invention comprehensively considers the effective content of active magnesium oxide in the light-burned magnesium oxide and its reaction rate, characterizing both the amount of magnesium oxide that can participate in the hydration reaction and the speed of the magnesium oxide hydration reaction, thereby more comprehensively reflecting the activity characteristics of the light-burned magnesium oxide. The method of the present invention has a fast detection time and high accuracy, and is suitable for production; based on the characterization method of the present invention, the content of magnesium oxide participating in the hydration reaction can be accurately controlled, thereby achieving quality control of the light-burned magnesium oxide used in the preparation of magnesia cement and quality control of magnesia cement.

Description

Technical Field

[0001] The invention relates to a characterization method, in particular to a characterization method for the activity of light-burned magnesia, and also to a method for preparing magnesite cement. Background Art

[0002] Light-burned magnesia is the primary raw material for new, green magnesia cement. Its activity is crucial for its performance and forming properties. Its activity characterizes its ability to participate in chemical or physicochemical processes. It is an essential property of magnesia, primarily influenced by lattice distortion, structural relaxation, and defects.

[0003] Researchers have used parameters such as grain size, lattice distortion, and specific surface area to characterize the activity of magnesium oxide. However, studies have found that the particle size and surface morphology of magnesium oxide powder will affect the above parameters, making them unable to reflect the activity well. In addition, the test method has high requirements on equipment, and its operability in actual production is not high.

[0004] Current studies have confirmed a good correlation between active magnesium oxide content and the activity of light-burned magnesium oxide. Using active magnesium oxide content to characterize the activity of light-burned magnesium oxide is currently the most commonly used method. There are two physical and chemical methods for determining active magnesium oxide content: nitrogen adsorption and iodine adsorption for the former, and hydration, weak acid reaction, and chloride ion determination for the latter. Physical methods primarily measure the adsorption capacity of magnesium oxide and are less able to accurately reflect chemical activity. Chemical methods can provide a relatively accurate estimate of the active magnesium oxide content, but during the production of magnesia cement, it was found that magnesia cement prepared by controlling the active magnesium oxide content often exhibited significant differences in molding ability and compressive strength, and sometimes even failed to mold. Therefore, using active magnesium oxide content as an indicator to characterize the activity of light-burned magnesium oxide in the preparation of magnesia cement is inaccurate.

[0005] Other researchers have used the reaction rate of light-burned magnesia with weak acids to characterize its activity. For example, the standards "Magnesium Oxide Expansion Agent for Concrete" (CBMF 19-2017) and "Technical Specification for Magnesium Oxide for Hydraulic Concrete" (DL / T5296-2013) use phenolphthalein as an indicator to measure the reaction time of light-burned magnesia with citric acid to assess its activity. However, when using the methods in these standards to control the use of light-burned magnesia to prepare magnesite cement, problems such as excessive heat generation and rapid coagulation arise. Expanding the reaction time range often results in excessive strength fluctuations in the prepared magnesite cement, making it difficult to control its properties.

[0006] Researchers believe that the content of active magnesium oxide in light-burned magnesium oxide, the hydration reaction rate and other factors have a combined impact on the performance of magnesia cement. This is also the fundamental reason why there is no universal indicator to measure the activity of light-burned magnesium oxide.

[0007] Therefore, it is urgent to develop a characterization method for the activity of light-burned magnesia suitable for the preparation of magnesite cement. Summary of the Invention

[0008] The present invention proposes a method for characterizing the activity of light-burned magnesia. The method adopts two parameters, namely, the active magnesia content and the reaction rate of light-burned magnesia, to collaboratively characterize the activity of light-burned magnesia. This method solves the problem that the activity of light-burned magnesia used in preparing magnesite cement cannot be accurately characterized and the quality of magnesia cannot be accurately determined.

[0009] The technical solution of the present invention is achieved as follows:

[0010] According to a first aspect of an embodiment of the present invention, a method for characterizing the activity of light-burned magnesium oxide is provided.

[0011] In one embodiment, a method for characterizing the activity of light-burned magnesium oxide comprises the following steps:

[0012] Step S1, calculating the active magnesium oxide content in light-burned magnesium oxide;

[0013] Step S2, calculating the mass of light-burned magnesium oxide based on the active magnesium oxide content;

[0014] Step S3, detecting the reaction time of light-burned magnesium oxide and weak acid;

[0015] Step S4, obtaining a characterization result of the activity of the light-burned magnesium oxide based on the active magnesium oxide content and the reaction time of the light-burned magnesium oxide with the weak acid: when the active magnesium oxide content and the reaction time are within the characterization range, when the active magnesium oxide content and the reaction time are within the characterization range, the activity of the light-burned magnesium oxide is inversely proportional to the reaction time at the same active magnesium oxide content; when the reaction time is the same, the activity of the light-burned magnesium oxide is inversely proportional to the active magnesium oxide content.

[0016] Optionally, in step S1, the step of calculating the active magnesium oxide content in the light-burned magnesium oxide comprises:

[0017] Weigh w1 of light-burned magnesium oxide and place it in a container. After adding distilled water, the container is in a non-completely closed state and allowed to stand for 12 hours or more at an ambient temperature of 25±2°C and a relative humidity of 70±5%. Dry to constant weight. Cool to room temperature and weigh w2. According to the formula Get the active magnesium oxide content.

[0018] Optionally, repeat the above operation 3-5 times and take the average value to obtain the active magnesium oxide content. average value.

[0019] Optionally, in the step of drying to constant weight, the drying temperature is 105±5°C for pre-drying for 6 hours, and then the temperature is raised to 150±5°C.

[0020] Optionally, the container is in a non-completely closed state, for example, the container lid is closed with a gap left. The reason is that during the hydration reaction, the CO2 in the air will undergo secondary reactions and have a certain impact on the hydration reaction. The present invention needs to ensure the CO2 content in the air; if the lid is too open, the water will be consumed too quickly, which will affect the ion concentration in the water.

[0021] Optionally, the mass w1 of the light-burned magnesia before standing and hydrating and the mass w2 of the light-burned magnesia after standing and hydrating are both accurate to 0.0001 g.

[0022] Optionally, in step S2, the step of calculating the mass of light-burned magnesium oxide based on the active magnesium oxide content includes:

[0023] The mass of light burned magnesium oxide is It is the average value of active magnesium oxide content.

[0024] Optionally, the step of detecting the reaction time of the light-burned magnesium oxide and the weak acid comprises:

[0025] Step S31, weighing light-burned magnesium oxide, citric acid and deionized water;

[0026] Step S32, adding citric acid and deionized water into a container and heating and stirring, and adding 2-3 drops of phenolphthalein indicator after the citric acid is completely dissolved;

[0027] Step S33, adding light-burned magnesium oxide to the solution obtained in step S32, stirring and immediately starting timing;

[0028] Step S34, observing the color change of the solution in step S33 and recording the color change time;

[0029] Step S35, repeat steps S32-S34 to obtain the average color change time

[0030] Optionally, step S31 further includes placing the light-burned magnesium oxide, citric acid and deionized water at room temperature of 25±2° C. for 24 hours to make the raw materials the same as room temperature.

[0031] Optionally, in step S31, based on the active magnesium oxide content in step S1, the mass ratio of citric acid: light-burned magnesium oxide: deionized water is Weighing, where It is the average value of active magnesium oxide content.

[0032] Optionally, in step S32, the stirring speed is 700 rpm and the heating temperature is 40±0.5°C.

[0033] Optionally, in step S33, the stirring speed is 700 rpm and the heating temperature is 40±0.5°C.

[0034] According to a second aspect of an embodiment of the present invention, a method for characterizing the activity of light-burned magnesia for preparing magnesite cement is provided.

[0035] According to a third aspect of an embodiment of the present invention, a method for preparing magnesite cement is provided.

[0036] In one embodiment, the setting time and / or calorific value of magnesite cement prepared from light-burned magnesia is controlled based on the above characterization method.

[0037] Optionally, the characterization range of the activity of the light-burned magnesia used to prepare magnesite cement is: the active magnesia content is 45% to 75%; when the reaction time is less than 10 minutes, the activity of the light-burned magnesia is too high; when the reaction time is 10 to 45 minutes, the activity of the light-burned magnesia is high; when the reaction time exceeds 45 minutes, the activity of the light-burned magnesia is low.

[0038] The beneficial effects of the present invention are:

[0039] 1. The present invention comprehensively considers the effective content of active magnesium oxide in light-burned magnesium oxide and its reaction rate. The active magnesium oxide content index determines the condition control of the reaction rate test, characterizing both the amount of magnesium oxide that can participate in the hydration reaction and the speed of the magnesium oxide hydration reaction, thereby more comprehensively reflecting the activity characteristics of light-burned magnesium oxide.

[0040] 2. The present invention comprehensively considers the effective content of active magnesium oxide in light-burned magnesium oxide and its reaction rate, and relatively completely characterizes the activity of light-burned magnesium oxide, including the content of substances that can participate in the reaction in the light-burned magnesium oxide, the reaction rate, and the heat generation rate during the indirect reaction process, so that the quality of the light-burned magnesium oxide can be accurately grasped; the above-mentioned substance content, reaction rate and heat generation will have an important or even decisive impact on the quality of magnesite cement, the processable volume of magnesite cement workpieces, etc. Therefore, based on the characterization method of the present invention, the content of magnesium oxide participating in the hydration reaction can be accurately controlled, the setting time and calorific value of magnesite cement can be more accurately controlled, and the quality control of light-burned magnesium oxide for preparing magnesite cement can be achieved.

[0041] 3. Existing methods for characterizing the activity of light-burned magnesia are inaccurate, often resulting in significant differences in the quality of magnesite cement obtained under the same parameter conditions. However, the method of the present invention can accurately determine the activity and more precisely control the quality of magnesite cement. In addition, the reaction time detection cycle of light-burned magnesia currently suitable for magnesite cement preparation takes several hours or even days, which is a lengthy process for engineering applications. However, this method can be completed in a few minutes to 1 hour, greatly shortening the detection time. Therefore, the method and indicators for characterizing the activity of light-burned magnesia proposed in the present invention not only ensure the integrity of the activity characterization, but also have a fast detection time and high accuracy, which is conducive to application in production. DETAILED DESCRIPTION

[0042] To facilitate understanding of the features and effects of the present invention by persons having ordinary skill in the art, the following provides a general description and definition of terms and expressions used in this specification and claims. Unless otherwise indicated, all technical and scientific terms used herein have the ordinary meanings as understood by those skilled in the art in connection with the present invention. In the event of any conflict, the definitions in this specification shall prevail.

[0043] As used herein, the terms "comprise," "include," "have," "contain," or any similar terms are open-ended transitional phrases that are intended to encompass non-exclusive inclusions. For example, a composition or article containing multiple elements is not limited to the elements listed herein, but may also include other elements not expressly listed but generally inherent to the composition or article. In addition, unless expressly stated to the contrary, the term "or" refers to an inclusive "or" rather than an exclusive "or." For example, any of the following situations satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist), A is false (or does not exist) and B is true (or exists), and both A and B are true (or exist). In addition, as used herein, the terms "comprise," "include," "have," and "contain" should be interpreted as specifically disclosing and encompassing closed or semi-closed transitional phrases such as "consisting of" and "consisting essentially of."

[0044] Throughout this document, all features or conditions defined as numerical ranges or percentage ranges are for simplicity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered to encompass and specifically disclose all possible subranges and individual values ​​within those ranges, particularly integer values. For example, a description of a range "1 to 8" should be considered to specifically disclose all possible subranges such as 1 to 7, 2 to 8, 2 to 6, 3 to 6, 4 to 8, 3 to 8, and so forth, particularly those defined by all integer values, and should be considered to specifically disclose individual values ​​within those ranges such as 1, 2, 3, 4, 5, 6, 7, and 8. Unless otherwise indicated, the foregoing interpretation applies to all of the present disclosure, regardless of whether the ranges are comprehensive or not.

[0045] If a quantity or other value or parameter is expressed as a range, a preferred range, or a series of upper and lower limits, it should be understood that all ranges consisting of any upper limit or preferred value of the range and any lower limit or preferred value of the range have been specifically disclosed herein, regardless of whether these ranges are disclosed separately. In addition, when a numerical range is mentioned herein, unless otherwise specified, the range should include its endpoints and all integers and fractions within the range.

[0046] In this document, numerical values ​​should be understood to have the accuracy of the number of significant digits of the numerical value, provided that the purpose of the invention can be achieved. For example, the number 40.0 should be understood to cover the range from 39.50 to 40.49.

[0047] In this document, where Markush groups or optional terms are used to describe features or embodiments of the present invention, those skilled in the art will appreciate that any combination of all subgroups or individual elements within the Markush group or optional list can also be used to describe the present invention. For example, if X is described as "selected from the group consisting of X1, X2, and X3," this fully describes the claim that X is X1 and the claim that X is X1 and / or X2. Furthermore, where Markush groups or optional terms are used to describe features or embodiments of the present invention, those skilled in the art will appreciate that any combination of all subgroups or individual elements within the Markush group or optional list can also be used to describe the present invention. Accordingly, for example, if X is described as "selected from the group consisting of X1, X2, and X3," and Y is described as "selected from the group consisting of Y1, Y2, and Y3," this fully describes the claim that X is X1, X2, or X3, and Y is Y1, Y2, or Y3.

[0048] The following detailed description is merely illustrative in nature and is not intended to limit the present invention and its uses. In addition, this document is not bound by any theory described in the foregoing prior art or summary of the invention or in the following detailed description or examples.

[0049] Example 1

[0050] Step S1, weigh light-burned magnesium oxide w1 = 2.0000g, place it in a weighing bottle, add 20ml of distilled water, cover the container with a lid and leave a gap, and let it stand for hydration reaction for ≥12h, with the ambient temperature controlled at 25±2℃ and relative humidity at 70±5%; after hydration, place it in an oven at 105±5℃ for pre-drying for 6h, then heat it to 150±5℃ and dry it to constant weight; cool the sample to room temperature in a drying dish, and weigh the mass after hydration reaction w2; according to the formula Calculate the active magnesium oxide content; repeat 3 times and take the average value as the active magnesium oxide content

[0051] Step S2, placing light-burned magnesium oxide, citric acid and deionized water in a room at room temperature of 25±2°C for 24 hours to make the raw materials reach the same temperature as room temperature;

[0052] Step S3, according to the mass ratio of citric acid: light-burned magnesium oxide: Calculate the masses of citric acid, light-burned magnesium oxide, and deionized water;

[0053] Step S4, weighing deionized water in a beaker, adding the weighed citric acid to the deionized water, and weighing the light-burned magnesium oxide using weighing paper, with the mass of the citric acid, light-burned magnesium oxide, and deionized water all being accurate to 0.0001 g;

[0054] Step S5, placing the beaker containing deionized water and citric acid on a magnetic stirrer at a speed of 700 rpm and a heating temperature of 40±0.5°C, and adding 2-3 drops of phenolphthalein indicator after the citric acid is completely dissolved and the solution temperature stabilizes;

[0055] Step S6, adding the weighed light-burned magnesium oxide to the solution of step S4, immediately starting the timer, and continuously stirring with a magnetic stirrer at a stirring speed of 700 rpm and a temperature of 40±0.5°C;

[0056] Step S7, continuously observing the solution of step S6, and when the color changes, immediately stop timing and record the color change time t;

[0057] Step S8, repeat the above steps S3-S7 3 times and take the average color change time

[0058] Step S9, thus and As a parameter for evaluating the activity of light-burned magnesia, it is used to control the activity index of light-burned magnesia used in the preparation of magnesite cement.

[0059] Existing methods for characterizing the quality of light-burned magnesia include active MgO content and reaction time. This application tested both of these methods. As shown in Table 1, Example 1 employs the characterization method of the present invention, organically combining active MgO content and reaction time. Comparative Example 1 uses a prior art characterization method that only considers active MgO content, while Comparative Example 2 uses a prior art characterization method that only considers reaction time. This comparison of the three methods intuitively demonstrates the characterization method of the present invention.

[0060] Table 1

[0061]

[0062]

[0063] As shown in Table 1, in Comparative Example 1, the active MgO contents of products 1# and 2# are similar, but the performance of the cement test blocks prepared therefrom differs greatly. In the two groups of products 3# and 4#, and 5# and 6#, the active MgO contents are similar, but the performance of the cement test blocks prepared therefrom does not differ much. Therefore, the correspondence between the active MgO content and the performance of the prepared cement test blocks is unstable.

[0064] In Comparative Example 2, although the reaction times of products 1# and 2# differ greatly, the performance of the prepared cement test blocks also differ greatly, and the difference between the two can be distinguished. However, in the two groups of products 3# and 4#, and 5# and 6#, although the reaction times differ greatly, the performance of the prepared cement test blocks does not differ much, and cannot be effectively distinguished. Therefore, there is no corresponding relationship between the reaction time indicator and the performance of the prepared cement test blocks.

[0065] After multiple tests, the activity characterization range for light-burned magnesia used in magnesite cement preparation is: an active MgO content of 45% to 75% and a reaction time of 10 to 45 minutes. In the examples, products 5# and 6#, while having similar active MgO contents, produced cement blocks with the shorter reaction time exhibited superior performance. Therefore, after determining the active MgO content of the product, adjusting the reaction time can effectively influence the performance of the resulting cement blocks.

[0066] Regarding the molar ratio of active MgO to water in Table 1, water is one of the main raw materials for making magnesite cement. Too much water increases defects in magnesite cement and reduces strength. Too little water leads to uneven mixing of the raw materials and incomplete hydration, resulting in poor quality and low strength of the produced cement. The active MgO content determines the amount of water required for cement production. Therefore, characterizing the activity of light-burned magnesia solely by active MgO content or reaction time is inaccurate and cannot accurately determine the quality of cement produced from light-burned magnesia.

[0067] The present invention combines the active magnesium oxide content and the reaction time, which is not a simple combination of the two, but an organic combination, which is mainly reflected in the following aspects: 1. The mass of the light-burned magnesium oxide used to detect the reaction time is different. The mass of the light-burned magnesium oxide used to detect the reaction time in the existing method is fixed. In the present invention, the mass of the light-burned magnesium oxide is calculated based on the active magnesium oxide content, and is different each time the material is received; 2. The test temperature used to detect the reaction time is different. The reaction temperature used to detect the reaction time in the existing method is controlled at 30°C, while the present invention requires it to be higher than 30°C. After multiple tests, 40°C is more suitable, which can effectively shorten the detection time and effectively distinguish the activity differences among the light-burned magnesium oxides.

[0068] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for characterizing the activity of light-burned magnesia for preparing magnesite cement, characterized in that: The activity of light-burned magnesium oxide was characterized using the following steps: Step S1, calculating the active magnesium oxide content in light-burned magnesium oxide; Step S2, calculating the mass of light-burned magnesium oxide based on the active magnesium oxide content; Step S3, detecting the reaction time of light-burned magnesium oxide and weak acid; Step S4, obtaining the characterization result of the activity of the light-burned magnesia according to the active magnesia content and the reaction time. The characterization range of the activity of the light-burned magnesia used to prepare magnesia cement is: the active magnesia content is 45% to 75%; when the reaction time is less than 10 minutes, the activity of the light-burned magnesia is too high; when the reaction time is 10 to 45 minutes, the activity of the light-burned magnesia is high; when the reaction time exceeds 45 minutes, the activity of the light-burned magnesia is low.

2. The method for characterizing the activity of light-burned magnesia for preparing magnesite cement according to claim 1, wherein: In step S1, the step of calculating the active magnesium oxide content in the light-burned magnesium oxide comprises: Weigh w1 of light-burned magnesium oxide, place it in a container, add distilled water, and place the container in a non-completely closed state. Let it stand for hydration for ≥12h. The ambient temperature is 25±2℃ and the relative humidity is 70±5%. Dry it to constant weight at 105±5℃. Pre-dry it for 6h, then heat it to 150±5℃. After cooling to room temperature, weigh w2 and calculate the weight according to the formula: Get the active magnesium oxide content.

3. The method for characterizing the activity of light-burned magnesia for preparing magnesite cement according to claim 2, wherein: The mass w1 of light-burned magnesium oxide before standing and hydrating and the mass w2 of light-burned magnesium oxide after standing and hydrating are both accurate to 0.0001 g.

4. The method for characterizing the activity of light-burned magnesia for preparing magnesite cement according to claim 1, wherein: In step S2, the step of calculating the mass of light-burned magnesium oxide based on the active magnesium oxide content includes: The mass of light burned magnesium oxide is It is the average value of active magnesium oxide content.

5. The method for characterizing the activity of light-burned magnesia for preparing magnesite cement according to claim 1, wherein: In step S3, the step of detecting the reaction time of light-burned magnesium oxide and weak acid includes: Step S31, weighing light-burned magnesium oxide, citric acid and deionized water; Step S32, adding citric acid and deionized water into a container and heating and stirring, and adding 2-3 drops of phenolphthalein indicator after the citric acid is completely dissolved; Step S33, adding light-burned magnesium oxide to the solution obtained in step S32, stirring and immediately starting timing; Step S34, observing the color change of the solution in step S33 and recording the color change time; Step S35, repeat steps S32-S34 to obtain the average color change time 6. The method for characterizing the activity of light-burned magnesia for preparing magnesite cement according to claim 5, wherein: Step S31 further includes placing light-burned magnesium oxide, citric acid and deionized water at room temperature of 25±2° C. for 24 hours to make the raw materials the same as room temperature.

7. The method for characterizing the activity of light-burned magnesia for preparing magnesite cement according to claim 5, wherein: In step S31, the mass ratio of citric acid: light-burned magnesium oxide: deionized water is It is the average value of active magnesium oxide content.

8. The method for characterizing the activity of light-burned magnesia for preparing magnesite cement according to claim 7, wherein: The masses of the citric acid, light-burned magnesium oxide, and deionized water are all accurate to 0.0001 g.

9. The method for characterizing the activity of light-burned magnesia for preparing magnesite cement according to claim 5, wherein: In step S32, the stirring speed is 700 rpm and the heating temperature is 40±0.5°C.

10. The method for characterizing the activity of light-burned magnesia for preparing magnesite cement according to claim 5, wherein: In step S33, the stirring speed is 700 rpm and the heating temperature is 40±0.5°C.

11. The method for characterizing the activity of light-burned magnesia for preparing magnesite cement according to claim 1, wherein: In step S4, the step of obtaining the characterization result of the activity of the light-burned magnesium oxide according to the active magnesium oxide content and the reaction time includes: when the active magnesium oxide content and the reaction time are within the characterization range, at the same active magnesium oxide content, the activity of the light-burned magnesium oxide is inversely proportional to the reaction time; at the same reaction time, the activity of the light-burned magnesium oxide is inversely proportional to the active magnesium oxide content.

12. A method for preparing magnesite cement, characterized in that: The setting time and / or calorific value of magnesite cement prepared by light-burned magnesia is controlled based on the following steps, including: Step S1, calculating the active magnesium oxide content in light-burned magnesium oxide; Step S2, calculating the mass of light-burned magnesium oxide based on the active magnesium oxide content; Step S3, detecting the reaction time of light-burned magnesium oxide and weak acid; Step S4, obtaining the characterization result of the activity of the light-burned magnesia according to the active magnesia content and the reaction time. The characterization range of the activity of the light-burned magnesia used to prepare magnesia cement is: the active magnesia content is 45% to 75%; when the reaction time is less than 10 minutes, the activity of the light-burned magnesia is too high; when the reaction time is 10 to 45 minutes, the activity of the light-burned magnesia is high; when the reaction time exceeds 45 minutes, the activity of the light-burned magnesia is low.

13. A method for preparing magnesite cement according to claim 12, characterized in that: In step S1, the step of calculating the active magnesium oxide content in the light-burned magnesium oxide comprises: Weigh w1 of light-burned magnesium oxide, place it in a container, add distilled water, and place the container in a non-completely closed state. Let it stand for hydration for ≥12h. The ambient temperature is 25±2℃ and the relative humidity is 70±5%. Dry it to constant weight at 105±5℃. Pre-dry it for 6h, then heat it to 150±5℃. After cooling to room temperature, weigh w2 and calculate the weight according to the formula: Get the active magnesium oxide content.

14. A method for preparing magnesite cement according to claim 13, characterized in that: The mass w1 of light-burned magnesium oxide before standing and hydrating and the mass w2 of light-burned magnesium oxide after standing and hydrating are both accurate to 0.0001 g.

15. A method for preparing magnesite cement according to claim 12, characterized in that: In step S2, the step of calculating the mass of light-burned magnesium oxide based on the active magnesium oxide content includes: The mass of light burned magnesium oxide is It is the average value of active magnesium oxide content.

16. A method for preparing magnesite cement according to claim 12, characterized in that: In step S3, the step of detecting the reaction time of light-burned magnesium oxide and weak acid includes: Step S31, weighing light-burned magnesium oxide, citric acid and deionized water; Step S32, adding citric acid and deionized water into a container and heating and stirring, and adding 2-3 drops of phenolphthalein indicator after the citric acid is completely dissolved; Step S33, adding light-burned magnesium oxide to the solution obtained in step S32, stirring and immediately starting timing; Step S34, observing the color change of the solution in step S33 and recording the color change time; Step S35, repeat steps S32-S34 to obtain the average color change time 17. A method for preparing magnesite cement according to claim 16, characterized in that: Step S31 further includes placing light-burned magnesium oxide, citric acid and deionized water at room temperature of 25±2° C. for 24 hours to make the raw materials the same as room temperature.

18. A method for preparing magnesite cement according to claim 16, characterized in that: In step S31, the mass ratio of citric acid: light-burned magnesium oxide: deionized water is It is the average value of active magnesium oxide content.

19. A method for preparing magnesite cement according to claim 18, characterized in that: The masses of the citric acid, light-burned magnesium oxide, and deionized water are all accurate to 0.0001 g.

20. The method for preparing magnesite cement according to claim 16, wherein: In step S32, the stirring speed is 700 rpm and the heating temperature is 40±0.5°C.

21. The method for preparing magnesite cement according to claim 16, wherein: In step S33, the stirring speed is 700 rpm and the heating temperature is 40±0.5°C.

22. A method for preparing magnesite cement according to claim 12, characterized in that: In step S4, the step of obtaining the characterization result of the activity of the light-burned magnesium oxide according to the active magnesium oxide content and the reaction time includes: when the active magnesium oxide content and the reaction time are within the characterization range, at the same active magnesium oxide content, the activity of the light-burned magnesium oxide is inversely proportional to the reaction time; at the same reaction time, the activity of the light-burned magnesium oxide is inversely proportional to the active magnesium oxide content.

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