Coal gangue activation treatment method and calcined coal gangue prepared thereby and application thereof

Abstract

The application relates to the field of building materials, and particularly discloses a coal gangue activation treatment method, calcined coal gangue prepared by the method and application, the treatment method comprises the following steps: pretreatment: crushing and screening coal gangue to obtain coal gangue particles; pretreatment: treating the coal gangue particles in a eutectic solvent, and performing ultrasonic auxiliary treatment for 2-3 hours, and obtaining pretreated coal gangue after washing, the eutectic solvent comprises HBA components and HBD components, the HBA components are selected from a mixture of choline chloride and an amide compound, and the HBD components are selected from a mixture of a carboxylic acid compound and a polyhydric alcohol mixture; calcination: calcining the pretreated coal gangue at 400-450 DEG C to obtain calcined coal gangue, and the application further discloses the calcined coal gangue prepared by the method, and the application has the characteristics of realizing coal gangue activation treatment at a lower energy consumption.

Description

Technical Field

[0001] This application relates to the field of building materials, and more specifically, to a method for activating coal gangue, the resulting calcined coal gangue, and its applications. Background Technology

[0002] As one of the most important structural materials, concrete's performance significantly impacts building structures. The main technical approaches to improving concrete durability are the use of chemical and mineral admixtures. Mineral admixtures participate in hydration, act as cementing materials, improve the microstructure of interfaces, and block internal pores in concrete, thereby enhancing its durability. Currently, the main mineral admixtures used include slag, fly ash, and silica fume.

[0003] Coal gangue, a solid waste generated during coal mining and washing, not only occupies land but also pollutes the environment when it is piled up in large quantities. Currently, the resource utilization of coal gangue has become a hot topic in the coal industry. However, due to the large amount of inorganic minerals and organic matter contained in coal gangue, its activity is low, making it difficult to utilize directly. Therefore, processing and activating coal gangue holds promise for replacing traditional mineral admixtures, solving the problem of coal gangue resource utilization, improving various properties of concrete, especially durability, and realizing the recycling of solid waste from the coal industry in construction engineering.

[0004] Currently, the activation methods for coal gangue mainly include physical activation and chemical activation. Physical activation mainly involves changing the pore structure and specific surface area of ​​coal gangue through high-temperature calcination, ball milling, etc., to improve its activity. Chemical activation involves adding chemical reagents such as acids or alkalis to treat coal gangue to promote increased activity. However, physical methods for calcining coal gangue involve high calcination temperatures and high energy consumption, while chemical activation methods require high-concentration acid and alkali treatments that place high demands on equipment and have low activation efficiency. These factors restrict the large-scale industrial application of coal gangue activation. Summary of the Invention

[0005] To address the high energy consumption of existing methods while simultaneously achieving coal gangue activation treatment, this application provides a coal gangue activation treatment method, the resulting calcined coal gangue, and its applications.

[0006] In a first aspect, this application provides a method for activating coal gangue, employing the following technical solution:

[0007] A method for activating coal gangue includes the following steps:

[0008] Pre-processing: The coal gangue is crushed and screened to obtain coal gangue particles;

[0009] Pretreatment: Coal gangue particles are treated in a eutectic solvent and ultrasonically assisted for 2-3 hours. After washing with water, pretreated coal gangue is obtained. The eutectic solvent includes HBA and HBD components. The HBA component is a mixture of choline chloride and amide compounds, and the HBD component is a mixture of carboxylic acid compounds and polyols.

[0010] Calcination: Pretreated coal gangue is calcined at 400-450℃ to obtain calcined coal gangue.

[0011] By adopting the above technical solution, coal gangue is mainly composed of aggregated minerals with high stability and complete crystal forms, such as quartz and kaolinite. These minerals are difficult to react with other substances at room temperature. When coal gangue is activated by high-temperature calcination, the kinetic energy of each micro-particle in the coal gangue increases at high temperature, which causes the bridge bonds between silicon-oxygen tetrahedra and aluminum-oxygen trigonometric bodies to break. This destroys the thermodynamically stable glass phase structure formed by the orderly arrangement of molecules, resulting in a large amount of active alumina and silicon oxide in the calcined coal gangue, thus achieving activation.

[0012] In this application, coal gangue is first crushed and screened, and then treated in a eutectic solvent under ultrasonic assistance. The amide compounds in the HBA component act as hydrogen bond acceptors. The nitrogen atoms in the amide molecules and the oxygen atoms on the carbonyl groups have lone pairs of electrons. These lone pairs of electrons form coordinate bonds and hydrogen bonds with metal ions such as silicon and aluminum in the coal gangue, changing the structure and charge distribution of silicates, thereby increasing the activity of coal gangue. The HBD component uses carboxylic acids and polyols. Carboxylic acids react with carbonates in coal gangue to generate soluble metal carboxylate salts, which helps to release metal ions. The hydroxyl groups in the polyol are highly polar and interact with the polar regions on the surface of coal gangue, weakening the original chemical bonds and making it easier for metal ions to dissolve, thus activating the coal gangue. The addition of choline chloride forms a more stable eutectic system with other components. The addition of eutectic solvent alters the internal chemical structure and charge distribution of coal gangue. Furthermore, the chemical reaction between the eutectic solvent and coal gangue helps to disrupt the original solid crystal structure of coal gangue, lowers the reaction temperature and activation energy, and improves the reactivity of coal gangue. This allows coal gangue to achieve a good activation effect when calcined at a lower temperature, thus reducing energy consumption.

[0013] When eutectic solvent treatment is combined with ultrasonic treatment, the ultrasonic treatment will promote the activation effect of the eutectic solvent on coal gangue, and will also destroy the mineral crystal structure in coal gangue, promote the transformation of mineral components and improve their activity. Then, the subsequent calcination treatment will further reduce the calcination temperature, so that the coal gangue can be calcined at a lower temperature, which can achieve the activation of coal gangue, and the activation effect is even better.

[0014] Optionally, in the calcination step, pretreated coal gangue and calcium fluoride are added together before calcination, and the mass of calcium fluoride added is 0.05-0.1 wt% of the pretreated coal gangue.

[0015] By adopting the above technical solution, the addition of calcium fluoride can lower the melting point during calcination, which helps to better decompose the mineral components in coal gangue, promotes the transformation of the structure in coal gangue, and further reduces the calcination temperature while improving the activation effect on coal gangue.

[0016] Optionally, in the pretreatment step, the eutectic solvent is dissolved in 4-6 times the volume of water to obtain the eutectic solvent solution for use, and the amount of eutectic solvent added is 8-10 wt% of the coal gangue particles.

[0017] By adopting the above technical solution, the use of eutectic solvent diluted with water can achieve better activation and structural modification of coal gangue, which is beneficial to the final improvement of coal gangue activity.

[0018] Optionally, in the pretreatment step, the amide compound may be one or more of formamide and acetamide;

[0019] The carboxylic acid mixture is a mixture obtained by mixing glycolic acid with one of citric acid, malic acid, or levulinic acid in a mass ratio of 1:(0.5-0.8).

[0020] The polyol is selected from one or more of ethylene glycol, glycerol, and xylitol.

[0021] By adopting the above technical solution, the carboxylic acid mixture includes at least glycolic acid. Glycolic acid contains both hydroxyl groups and carboxylic acids. Its chemical reaction with the coal gangue particles helps to destroy the original crystal structure of the coal gangue, increase disorder, and improve the activity of the coal gangue. Moreover, the addition of carboxylic acid helps to transform the crystal structure of the coal gangue, so that the coal gangue can achieve a better activation effect when calcined at a lower temperature.

[0022] Optionally, the mass ratio of choline chloride, amide compounds, carboxylic acid mixtures and polyols is 1:(1.2-1.5):(1.2-1.5):(0.6-0.8).

[0023] By adopting the above technical solution and controlling the proportion of raw materials added to the eutectic solvent, a stable eutectic solvent system is obtained, and a better activation effect is achieved by reducing the calcination temperature.

[0024] Optionally, clay rock-type coal gangue can be used in the pretreatment step.

[0025] By adopting the above technical solution, clay rock coal gangue is selected, which has higher pozzolanic activity. Pozzolanic activity refers to the reaction of active components in volcanic ash with water at high temperature to generate hydraulic products such as calcium silicate and calcium aluminosilicate. These products have higher strength and stability. Using clay rock coal gangue with higher pozzolanic activity in concrete will better improve the strength and durability of concrete.

[0026] Optionally, the particle size of the coal gangue particles in the pretreatment step is 50μm-1mm.

[0027] By adopting the above technical solution, the coal gangue is processed into the above-mentioned particle size range in the pretreatment step, which is more conducive to the subsequent activation operation.

[0028] Optionally, in the calcination step, the pretreated coal gangue is mixed and stirred with sodium thiosulfate before calcination, and the amount of sodium thiosulfate added is 3-5 wt% of the pretreated coal gangue.

[0029] By adopting the above technical solution, silicon and aluminum in coal gangue exist in a stable form. The addition of sodium thiosulfate can interact with the hydroxyl or oxygen atoms on its surface, changing its surface properties and helping to increase the activity of alumina and silicon oxide, thereby increasing the content of active alumina and silicon oxide. Moreover, the addition of sodium thiosulfate plays a catalytic role in the activation process of coal gangue, accelerating the reaction of coal gangue with other activators and improving the activation efficiency. Furthermore, sodium thiosulfate can also react with the organic components in coal gangue, destroying the stable chemical structure, thereby destroying the stable crystal structure in coal gangue and helping to improve the activity of coal gangue.

[0030] Secondly, this application provides a calcined coal gangue, employing the following technical solution:

[0031] A type of calcined coal gangue is prepared by the above method.

[0032] By adopting the above technical solution and through the chemical-physical activation method of coal gangue in this application, the activity of coal gangue can be significantly improved under lower calcination temperature conditions.

[0033] Thirdly, this application provides an application of calcined coal gangue, employing the following technical solution:

[0034] The application of calcined coal gangue in concrete, as described above.

[0035] By adopting the above technical solution, the calcined coal gangue prepared in this application has higher activity, which allows the calcined coal gangue to react with alkaline materials such as lime to generate a hydraulic substance, which can be used as an admixture for concrete to improve the strength, wear resistance, impermeability and durability of concrete, thereby improving the overall performance of concrete.

[0036] In summary, this application has the following beneficial effects:

[0037] 1. The addition of eutectic solvent in this application alters the internal chemical structure and charge distribution of coal gangue. Furthermore, the chemical reaction between eutectic solvents helps to break down the original solid crystal structure of coal gangue, reduce the reaction temperature and activation energy, and improve the reactivity of coal gangue. This allows coal gangue to achieve a good activation effect when calcined at a lower temperature, thus reducing energy consumption.

[0038] 2. When treating with eutectic solvents, ultrasonic treatment is combined with ultrasonic treatment. Ultrasonic treatment will promote the activation effect of the eutectic solvent on coal gangue, and will also destroy the mineral crystal structure in coal gangue, promote the transformation of mineral components and improve their activity. Then, the subsequent calcination treatment will further reduce the calcination temperature, so that the coal gangue can be calcined at a lower temperature, thus achieving the activation of coal gangue.

[0039] 3. The addition of calcium fluoride in this application can lower the melting point during calcination, which helps the mineral components in coal gangue to melt and decompose better, promotes the transformation of the structure in coal gangue, and further reduces the calcination temperature while improving the activation effect on coal gangue; 4. The carboxylic acid mixture in the eutectic solvent of this application includes at least glycolic acid. Glycolic acid contains both hydroxyl and carboxylic acid. Its chemical reaction with the coal gangue particles helps to destroy the original crystal structure of coal gangue, increase disorder, and improve the activity of coal gangue. Moreover, more importantly, the addition of carboxylic acid may also affect the melting behavior of coal gangue, which helps the mineral components in coal gangue to melt and decompose better, and helps the transformation of the crystal structure of coal gangue, so that coal gangue can achieve a better activation effect when calcined at a lower temperature. Detailed Implementation

[0040] The present application will be further described in detail below with reference to the embodiments. It should be noted that: unless otherwise specified, the conditions in the following embodiments are carried out according to conventional conditions or the conditions recommended by the manufacturer. Unless otherwise specified, the raw materials used in the following embodiments can be obtained from commercially available sources.

[0041] The method provided in this application involves crushing and screening coal gangue to obtain the aggregate. The degree of crushing in this step is adjusted according to the intended use of the coal gangue. The calcined and activated coal gangue can be used as an admixture, coarse aggregate, or fine aggregate in concrete. When used as coarse aggregate, the calcined coal gangue is processed to have a size greater than 5mm, while when used as fine aggregate, the crushed and screened coal gangue has a size less than 5mm, thus improving the performance of concrete.

[0042] Example 1

[0043] A method for activating coal gangue includes the following steps:

[0044] S1. Pretreatment: Using 1kg of coal gangue as the treatment standard, the clay rock coal gangue is crushed and screened to obtain coal gangue particles with a particle size of 50μm-1mm.

[0045] S2. Pretreatment: Dissolve 9 wt% of the coal gangue particles from step S1 in a eutectic solvent in 5 times the volume of water to obtain a eutectic solvent solution. Then, immerse the coal gangue particles obtained after pretreatment in step S1 in the eutectic solvent solution and treat them with ultrasonic assistance for 2.5 hours. The ultrasonic treatment frequency is 25 kHz and the ultrasonic power is 30 W. After washing with water, the pretreated coal gangue is obtained.

[0046] The eutectic solvent is a liquid composed of HBA and HBD components heated and stirred at 90°C. The HBA component is a mixture of choline chloride and amide compounds, and the HBD component is a mixture of carboxylic acid mixture and polyol. The mass ratio of choline chloride, amide compounds, carboxylic acid mixture and polyol is 1:1.3:1.3:0.7. The amide compound is formamide, the carboxylic acid mixture is a mixture of glycolic acid and citric acid at a mass ratio of 1:0.6, and the polyol is ethylene glycol.

[0047] S3. Calcination: The pretreated coal gangue is calcined at 430℃ for 1 hour to obtain calcined coal gangue.

[0048] Example 2

[0049] A method for activating coal gangue includes the following steps:

[0050] S1. Pretreatment: Using 1kg of coal gangue as the treatment standard, the clay rock coal gangue is crushed and screened to obtain coal gangue particles with a particle size of 50μm-1mm.

[0051] S2. Pretreatment: Dissolve 8 wt% of the coal gangue particles from step S1 in a eutectic solvent in 4 times the volume of water to obtain a eutectic solvent solution. Then, immerse the coal gangue particles obtained after pretreatment in step S1 in the eutectic solvent solution and treat them with ultrasonic assistance for 2 hours. The ultrasonic treatment frequency is 22 kHz and the ultrasonic power is 28 W. After washing with water, the pretreated coal gangue is obtained.

[0052] The eutectic solvent is a liquid composed of HBA and HBD components heated and stirred at 90°C. The HBA component is a mixture of choline chloride and amide compounds, and the HBD component is a mixture of carboxylic acid mixture and polyol. The mass ratio of choline chloride, amide compounds, carboxylic acid mixture and polyol is 1:1.2:1.2:0.6. The amide compound is acetamide, the carboxylic acid mixture is a mixture of glycolic acid and levulinic acid at a mass ratio of 1:0.5, and the polyol is glycerol.

[0053] S3. Calcination: The pretreated coal gangue is calcined at 400℃ for 40 minutes to obtain calcined coal gangue.

[0054] Example 3

[0055] A method for activating coal gangue includes the following steps:

[0056] S1. Pretreatment: Using 1kg of coal gangue as the treatment standard, the clay rock coal gangue is crushed and screened to obtain coal gangue particles with a particle size of 50μm-1mm.

[0057] S2. Pretreatment: Dissolve 10wt% of the coal gangue particles from step S1 in a eutectic solvent in 6 times the volume of water to obtain a eutectic solvent solution. Then, immerse the coal gangue particles obtained after pretreatment in step S1 in the eutectic solvent solution and treat them with ultrasonic assistance for 3 hours. The ultrasonic treatment frequency is 26KHz and the ultrasonic power is 32W. After washing with water, the pretreated coal gangue is obtained.

[0058] The eutectic solvent is a liquid composed of HBA and HBD components heated and stirred at 90°C. The HBA component is a mixture of choline chloride and amide compounds, and the HBD component is a mixture of carboxylic acid mixture and polyol. The mass ratio of choline chloride, amide compounds, carboxylic acid mixture and polyol is 1:1.5:1.5:0.8. The amide compound is formamide, the carboxylic acid mixture is a mixture of glycolic acid and malic acid in a mass ratio of 1:0.8, and the polyol is xylitol.

[0059] S3. Calcination: The pretreated coal gangue is calcined at 450℃ for 80 minutes to obtain calcined coal gangue.

[0060] Example 4

[0061] A method for activating coal gangue is carried out according to the method in Example 1, except that in step S3 calcination, pretreated coal gangue and calcium fluoride are added together before calcination, and the mass of calcium fluoride added is 0.08 wt% of the pretreated coal gangue.

[0062] Example 5

[0063] A method for activating coal gangue is carried out according to the method in Example 1, except that in step S3 calcination, pretreated coal gangue and calcium fluoride are added together before calcination, and the mass of calcium fluoride added is 0.05 wt% of the pretreated coal gangue.

[0064] Example 6

[0065] A method for activating coal gangue is carried out according to the method in Example 1, except that in step S3 calcination, pretreated coal gangue and calcium fluoride are added together before calcination, and the mass of calcium fluoride added is 0.1 wt% of the pretreated coal gangue.

[0066] Example 7

[0067] A method for activating coal gangue, which is carried out according to the method in Example 1, except that the pretreated coal gangue is mixed and stirred with sodium thiosulfate before calcination, and the amount of sodium thiosulfate added is 4 wt% of the pretreated coal gangue.

[0068] Example 8

[0069] A method for activating coal gangue, which is carried out according to the method in Example 1, except that the pretreated coal gangue is mixed and stirred with sodium thiosulfate before calcination, and the amount of sodium thiosulfate added is 3 wt% of the pretreated coal gangue.

[0070] Example 9

[0071] A method for activating coal gangue, which is carried out according to the method in Example 1, except that the pretreated coal gangue is mixed and stirred with sodium thiosulfate before calcination, and the amount of sodium thiosulfate added is 5 wt% of the pretreated coal gangue.

[0072] Comparative Example 1

[0073] A method for activating coal gangue is carried out according to the method in Example 1, except that step S2 pretreatment is not performed.

[0074] Comparative Example 2

[0075] A method for activating coal gangue is carried out according to the method in Example 1, except that the pretreatment in step S2 is not performed, and the calcination temperature in step S3 is 650°C and the calcination time is 2 hours.

[0076] Comparative Example 3

[0077] A method for activating coal gangue, performed according to the method in Example 1, except that in step S2 pretreatment step, formamide is selected as the HBA component and ethylene glycol is selected as the HBD component, and the mass ratio of formamide to ethylene glycol is 1.3:0.7.

[0078] Comparative Example 4

[0079] A method for activating coal gangue is carried out according to the method in Example 1, except that in the pretreatment step S2, ethylene glycol is used as the HBD component, no carboxylic acid mixture is added, and the mass ratio of choline chloride, formamide and ethylene glycol is 1:1.3:0.7.

[0080] Comparative Example 5

[0081] A method for activating coal gangue is carried out according to the method in Example 1, except that in the pretreatment step S2, the HBA component is formamide, no choline chloride is added, and the mass ratio of formamide, carboxylic acid mixture and polyol is 1.3:1.3:0.7.

[0082] Comparative Example 6

[0083] A method for activating coal gangue is carried out according to the method in Example 1, except that in the pretreatment step S2, the eutectic solvent is directly replaced by an equal amount of citric acid.

[0084] Comparative Example 7

[0085] A method for activating coal gangue is carried out according to the method in Example 1, except that in the pretreatment step S2, the eutectic solvent is directly replaced by an equal amount of citric acid.

[0086] Performance testing

[0087] The pozzolanic activity of the coal gangue prepared in the above embodiments and comparative examples was tested to characterize the activity-enhancing effect of the coal gangue. Specifically, the calcium hydroxide consumption method was used. This method is based on the fact that claystone-type coal gangue, after high-temperature calcination, produces amorphous silica and alumina. Amorphous silica and alumina can react with calcium hydroxide to form hydrated silicates, aluminates, etc., and the reaction process consumes calcium hydroxide. The specific detection method is as follows:

[0088] The coal gangue and calcium oxide prepared in the examples and comparative examples were mixed at a mass ratio of 8:2. 10g of the sample was accurately weighed, added to 500mL of water, stirred thoroughly, and then sealed in a test tube with a rubber stopper. The mixture was cured at room temperature. 1g of the hydrated sample after 28 days of curing was taken, dried at 60℃, and ground to a specific surface area of ​​400m². 2 / kg, sealed and stored. The remaining calcium hydroxide in the coal gangue-calcium hydroxide-water system was determined by the glycerol-anhydrous ethanol method. The difference between the amount of calcium hydroxide in the initial sample and the remaining amount is the amount of calcium hydroxide reacted. The level of reaction reflects the activity of coal gangue. The percentage of calcium hydroxide reaction to the initial calcium hydroxide mass is the activity of coal gangue. The statistical results are shown in Table 1 below.

[0089] Table 1:

[0090]

[0091] Referring to the test results in Table 1 above, it can be seen that the coal gangue prepared in this application has excellent pozzolanic activity. Referring to the test results of Examples 1 and 4-6, it can be seen that when calcium fluoride and pretreated coal gangue are co-calcined, the activity of the prepared coal gangue is significantly improved at the same calcination temperature. Referring to the test results of Examples 1 and 7-9, it can be seen that the addition of sodium thiosulfate can further improve the activity of the coal gangue. Referring to the test results of Example 1 and Comparative Example 1, when the coal gangue is calcined directly at 430℃ without pretreatment, its activity is low. Combined with the test results of Comparative Example 2, it can be seen that after step S2 treatment, the activity of this application is close to or even better than that of current high-temperature calcination at 650℃. The method provided in this application can achieve activation of coal gangue at a lower calcination temperature, with effects similar to or even better than existing high-temperature calcination methods, greatly reducing energy consumption.

[0092] Referring to the test results of Examples 1 and Comparative Examples 3-5, it can be seen that in Comparative Example 3, the activity effect on coal gangue was significantly reduced when choline chloride and carboxylic acid compounds were not added to the eutectic solvent. In Comparative Example 4, the effect was also significantly reduced when carboxylic acid compounds were not added. In Comparative Example 5, choline chloride was not added, and its effect was improved compared to Comparative Examples 3 and 4, but it was significantly lower than that of Comparative Example 1. This is mainly because the addition of choline chloride helps to form a stable eutectic system, thereby exerting its effect. Referring to the test results of Comparative Examples 6 and 7, the activity effect on coal gangue was still poor when the eutectic solvent was not treated and the treatment was carried out at a lower temperature and with weak acid.

[0093] Application examples

[0094] The coal gangue prepared in the embodiments and comparative examples of this application was used as an admixture in concrete. Specifically, 100 kg of coal gangue, 200 kg of cement, 90 kg of water, 30 kg of fly ash and 5 kg of water-reducing agent were mixed for 15 min, then 450 kg of coarse aggregate and 550 kg of fine aggregate were added and mixed for 25 min to obtain the test concrete. The coal gangue was calcined coal gangue prepared in the embodiments and comparative examples of this application. The fine aggregate was calcined coal gangue (prepared in the embodiments and comparative examples of this application) and sand in a mass ratio of 1:0.3. The sand was fine sand with a coefficient modulus of 1.8-2.0. The coarse aggregate was crushed stone, and the crushed stone was 5-15 mm continuously graded crushed stone. The fly ash was Class F Grade I fly ash. The water-reducing agent was polycarboxylate water-reducing agent (can be purchased from Jinan Hongtai Chemical Co., Ltd., model 0007). The cement was ordinary Portland cement of PO42.5. The concrete prepared from calcined coal gangue using the embodiments and comparative examples of this application was tested for 28-day compressive strength (MPa) in accordance with GB / T50081-2016 "Standard for Test Methods of Mechanical Properties of Ordinary Concrete". The test results are shown in Table 2 below.

[0095] Comparative Application Examples

[0096] The method described in the application example was followed, except that the coal gangue admixture was replaced with an equal amount of fly ash, and sand was used as the fine aggregate. Control concrete was prepared according to the method described in the application example, and the 28-day compressive strength (MPa) of the control concrete was tested according to GB / T50081-2016 "Standard for Test Methods of Mechanical Properties of Ordinary Concrete". The test results are shown in Table 2 below.

[0097] Table 2:

[0098]

[0099] Referring to the test results in Table 1 above, and in conjunction with the test results of the comparative application examples, it can be seen that when the calcined coal gangue prepared by the processing method in this application is applied to concrete, it helps to improve the strength of the concrete.

[0100] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A method for activating coal gangue, characterized in that, Includes the following steps: Pre-processing: The coal gangue is crushed and screened to obtain coal gangue particles; Pretreatment: Coal gangue particles are treated in a eutectic solvent and ultrasonically assisted. After washing with water, pretreated coal gangue is obtained. The eutectic solvent includes HBA and HBD components. The HBA component is a mixture of choline chloride and amide compounds, and the HBD component is a mixture of carboxylic acid compounds and polyols. Calcination: Pretreated coal gangue is calcined at 400-450℃ to obtain calcined coal gangue; The carboxylic acid mixture is a mixture obtained by mixing glycolic acid with one of citric acid, malic acid, or levulinic acid in a mass ratio of 1:(0.5-0.8).

2. The method for activating coal gangue according to claim 1, characterized in that: In the calcination step, pretreated coal gangue and calcium fluoride are added together and then calcined, and the mass of calcium fluoride added is 0.05-0.1 wt% of the pretreated coal gangue.

3. The method for activating coal gangue according to claim 1, characterized in that: In the pretreatment step, the eutectic solvent is dissolved in 4-6 times the volume of water to obtain the eutectic solvent solution for use, and the amount of eutectic solvent added is 8-10 wt% of the coal gangue particles.

4. The method for activating coal gangue according to claim 1, characterized in that: In the pretreatment step, the amide compound is selected from one or more of formamide and acetamide; the polyol is selected from one or more of ethylene glycol, glycerol and xylitol.

5. The method for activating coal gangue according to claim 1, characterized in that: The mass ratio of choline chloride, amide compounds, carboxylic acid mixtures and polyols is 1:(1.2-1.5):(1.2-1.5):(0.6-0.8).

6. The method for activating coal gangue according to claim 1, characterized in that: The coal gangue used in the pretreatment step is clay rock coal gangue.

7. The method for activating coal gangue according to claim 1, characterized in that: The particle size of the coal gangue particles in the pretreatment step is 50μm-1mm.

8. The method for activating coal gangue according to claim 1, characterized in that: In the calcination step, the pretreated coal gangue is mixed and stirred with sodium thiosulfate before calcination. The amount of sodium thiosulfate added is 3-5 wt% of the pretreated coal gangue.

9. Calcined coal gangue prepared by the method described in any one of claims 1-8.

10. The application of calcined coal gangue in concrete as described in claim 9.

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