A method for mild activation of coal cinder and a cementitious material containing the coal cinder

Abstract

The application provides a coal cinder mild activation method and a cementing material containing the coal cinder, and belongs to the cross technical field of solid waste resource utilization and mine filling material. The coal cinder mild activation method comprises the following steps: S1, drying the coal cinder and measuring the water content, so as to ensure that the water content is less than or equal to 1%; S2, mixing the coal cinder and calcium oxide and then grinding, adding water to the obtained mixed powder and continuously stirring, and heating to 80-90 DEG C and keeping for 50-90 min to obtain a solid-liquid mixture; S3, naturally cooling the solid-liquid mixture, filtering and drying the precipitate to obtain the activated coal cinder. The application further provides the cementing material containing the coal cinder, and the mass percentage of each component is as follows: coal cinder 60%-70%, fly ash 0-10%, slag 0-20%, calcium oxide 8-20%, cement clinker 5-20%, calcium chloride 2% and HPMC 0.2%. The application cooperatively utilizes three kinds of industrial solid wastes, i.e. coal cinder, slag and fly ash, and the prepared coal cinder-based cementing material can replace the high-cost cement in the mine filling material.

Description

Technical Field

[0001] This invention relates to the interdisciplinary technical field of solid waste resource utilization and mine backfill materials, and in particular to a method for the mild activation of coal slag and a cementitious material containing the coal slag. Background Technology

[0002] Coal ash is the residue produced after burning coal in power plants, boiler industries, and other coal-fired factories. China produces hundreds of millions of tons of coal ash annually. Due to limited utilization channels, large quantities of coal ash are stockpiled, not only occupying land and generating ash pollution, but also releasing sulfur-containing gases that pollute the atmosphere and harm the environment. Therefore, its resource utilization is crucial for solving environmental problems.

[0003] With the continuous development of backfilling technology, backfilling mining has been widely used in industrial waste disposal and goaf remediation due to its significant advantages of safety, environmental protection, economy, and efficiency. It aims to curb the hazards of goafs and industrial waste at the source, achieving the goal of "treating two harms with one waste." Coal slag, as an industrial waste residue, mainly contains a certain amount of cementing active substances such as SiO2 and Al2O3, exhibiting certain cementing properties. Using coal slag to make cementitious materials to replace cement in backfilling mining can reduce carbon dioxide emissions from cement production, protecting the ecological environment, while also improving resource recycling rates and reducing backfilling costs. Summary of the Invention

[0004] This invention overcomes the shortcomings of existing technologies by proposing a mild activation method for coal slag and a cementitious material containing the coal slag, thus solving problems such as incomplete activation and low utilization rate of coal slag in existing technologies. The resulting coal slag-based cementitious material has excellent properties such as high coal slag content, good cementing performance, and low production cost, and can be applied in the field of mine backfilling.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] This invention provides a method for the gentle activation of coal slag, comprising the following steps:

[0007] S1. After drying the coal slag, measure its moisture content to ensure that its moisture content is ≤1%;

[0008] Preferably, the drying temperature is 105±5℃ and the drying time is 2-4 hours.

[0009] S2. Mix and grind the coal slag and calcium oxide, add water to the resulting mixed powder and stir continuously, while heating to 80-90℃ and keeping it at that temperature for 50-90 minutes to obtain a solid-liquid mixture.

[0010] Preferably, the mass ratio of coal slag to calcium oxide is (60-70):(8-20).

[0011] Preferably, the mass ratio of the mixed powder to water is 1:(5-10).

[0012] S3. Allow the solid-liquid mixture to cool naturally, filter it, and then dry the precipitate to obtain activated coal slag.

[0013] Secondly, the present invention also provides a cementitious material containing the activated coal slag. The components and their mass percentages of the cementitious material are as follows: 60%-70% coal slag, 0-10% fly ash, 0-20% slag, 8-20% calcium oxide, 5-20% cement clinker, 2% calcium chloride, and 0.2% HPMC.

[0014] Preferably, the cement clinker is silicate cement with a strength grade of 42.5. Replacing it with silicate cement of 32.5 or 52.5 has the same effect, serving as an auxiliary activating material. The tricalcium silicate in the cement reacts with water to form CSH gel, which connects to the active sites on the surface of the coal slag particles, activating the activity of the coal slag and driving its hydration reaction. The coal slag-based cementitious material, after hydration, can form a hard solidified body, enabling the cementitious material to meet the requirements for setting and hardening.

[0015] Preferably, the main chemical components of the coal slag are active substances such as SiO2, Al2O3, and CaO, with a median particle size D50 of 21.24 μm and a specific surface area of ​​729.94 m² / kg.

[0016] Preferably, the calcium chloride has the molecular formula CaCl2, a solid content of not less than 96%, and appears as a white porous floc or granules. It is highly soluble in water and can improve the hydration reaction rate of cementitious materials and enhance the early strength of the materials.

[0017] Preferably, the hydroxypropyl methylcellulose (HPMC) has the following molecular formula. This material is an odorless, tasteless, and non-toxic white powder with advantages such as strong adhesion and easy solubility in water. It can improve the bonding strength of cementitious materials and enhance the adhesion to tailings.

[0018]

[0019] This invention modifies the particle size of coal slag through mechanical grinding, disrupting the dense, inert layer on the surface of the coal slag and activating its reactivity. Furthermore, it proposes using an alkaline solution at 80-90℃ to gently activate the coal slag, corroding the dense, difficult-to-hydrate layer on the surface of the coal slag, further activating the cementitious activity of the coal slag and improving the bonding performance of coal slag-based cementitious materials. This enables the utilization of large amounts of coal slag, solving the problem of insufficient utilization due to low coal slag content and low cementitious activity in cementitious materials. This invention uses three solid wastes—coal slag, mineral slag, and fly ash—to prepare cementitious materials for use in mines, replacing high-cost cement for backfilling mining, reducing environmental pollution from coal slag while also lowering mine backfilling costs.

[0020] Thirdly, the present invention provides a method for preparing the gelling material, comprising the following steps:

[0021] S1. Place the coal slag in an oven at 105±5℃ and dry it for 2-4 hours. Measure its moisture content and ensure that its moisture content is ≤1%.

[0022] S2. Weigh out coal slag and calcium oxide according to the proportion, mix them and grind them in a ball mill. Then add 5-10 kg of water to the resulting powder and stir continuously. At the same time, heat to 80-90℃ and keep warm for 50-90 minutes to obtain a solid-liquid mixture.

[0023] S3. Allow the solid-liquid mixture to cool naturally to 28-30℃, filter it, and then dry the precipitate to obtain the precursor powder of the cementitious material.

[0024] S4. Weigh out the precursor powder, cement, fly ash, slag, calcium chloride and HPMC according to the proportions, mix them and continue grinding them with a grinder to obtain the finished coal slag-based cementitious material.

[0025] Preferably, the grinding time is 5-6 minutes.

[0026] S5. Prepare a paste sample with a water-cement ratio of 0.5. Weigh out the solid powder of the coal slag-based cementitious material and water, stir it with a mixer, and after the solid and liquid are fully mixed, put it into a mold and use a vibration table to remove air bubbles in the filling body.

[0027] S6. After curing the prepared paste sample horizontally in the curing chamber for 24 hours, demold it and place it in a curing chamber at 20℃±1℃ and 95% relative humidity for 7d±2h or 28d±2h.

[0028] High-temperature steam curing is typically required to achieve high strength in the preparation of coal slag-based cementitious materials. For example, Chinese patent CN202010270687.6 requires curing at 40℃, while Chinese patent CN201810035936.6 describes plastic sealing curing at 40℃-60℃ or steam curing at 60℃-95℃. However, high-temperature curing of cementitious materials has poor applicability and limited practicality. This invention utilizes a mild alkaline solution to gently activate the coal slag, enabling it to achieve high strength through normal curing, thus overcoming the drawback of requiring high-temperature curing for coal slag cementitious materials.

[0029] The present invention also provides the application of the cementitious material in mine backfilling.

[0030] The advantages of this invention are:

[0031] 1. A method for activating coal slag is provided, which processes coal slag to obtain a matrix with high activation activity. First, the particle size and surface morphology of the coal slag are changed by mechanical grinding to increase new active surfaces. Second, the coal slag is gently activated using an alkaline solution at 80-90℃, which corrodes the dense silica film on the surface of the coal slag, providing more active sites for the hydration reaction. The active potential of the treated coal slag is fully explored, and its hydration reaction capacity is greatly enhanced, meeting the requirements for the preparation of filling binders in mines.

[0032] 2. This invention enables the large-scale utilization of coal slag in mine backfill cementitious materials. Activation treatment to fully activate the coal slag is a prerequisite for its large-scale utilization. Further mixing with solid wastes such as slag and fly ash ensures both the early and later strength of the cementitious material, with the coal slag content reaching over 60%. This solves the problem of low coal slag content and low activity in cementitious material production, requiring steam curing and limiting its widespread use.

[0033] 3. This invention synergistically utilizes three industrial solid wastes: coal slag, mineral slag, and fly ash. The prepared coal slag-based cementitious material can replace high-cost cement in mine backfill materials. This not only reduces greenhouse gas emissions and natural resource consumption during cement production but also allows for the large-scale disposal of these solid wastes, mitigating the problems associated with stockpiling, thus demonstrating significant economic and environmental benefits. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 This is a flowchart of the preparation process of the present invention.

[0036] Figure 2 The images shown are scanning electron microscope (SEM) images of the activated coal slag prepared in Example 1 of this invention. (a) is a diagram of the coal slag under mild activation, and (b) is a microscopic image of the original coal slag particles.

[0037] Figure 3 Scanning electron microscope image of surface erosion in activated coal slag.

[0038] Figure 4 This is a schematic diagram illustrating the corrosion principle of a dense silicon oxide film on the surface of coal slag. Detailed Implementation

[0039] To make the technical problems, technical solutions and advantages of the present invention clearer, a detailed description will be given below in conjunction with the accompanying drawings and specific embodiments.

[0040] Example 1

[0041] A coal slag cementitious material includes coal slag and calcium oxide, wherein the amount of coal slag added accounts for 80% of the mass fraction of the coal slag cementitious material, and the amount of calcium oxide added accounts for 20% of the mass fraction of the cementitious material.

[0042] Example 2

[0043] A coal slag cementitious material includes coal slag, calcium oxide and cement clinker, wherein the amount of coal slag added accounts for 70% of the mass fraction of the cementitious material, the amount of calcium oxide added accounts for 10% of the mass fraction of the cementitious material, and the amount of cement clinker added accounts for 20% of the mass fraction of the cementitious material.

[0044] Example 3

[0045] A coal slag cementitious material, wherein the raw materials for preparation include coal slag, calcium oxide and slag, wherein the amount of coal slag added accounts for 70% of the mass fraction of the cementitious material, the amount of calcium oxide added accounts for 10% of the mass fraction of the cementitious material, and the amount of slag added accounts for 20% of the mass fraction of the cementitious material.

[0046] Example 4

[0047] A coal slag cementitious material, wherein the raw materials for preparation in this example include coal slag, calcium oxide, cement clinker and slag, wherein the amount of coal slag added accounts for 70% of the mass fraction of the cementitious material, the amount of calcium oxide added accounts for 10% of the mass fraction of the cementitious material, the amount of cement clinker added accounts for 10% of the mass fraction of the cementitious material, and the amount of slag added accounts for 10% of the mass fraction of the cementitious material.

[0048] Example 5

[0049] A coal slag cementitious material, wherein the raw materials for preparation include coal slag, calcium oxide, cement clinker, slag and calcium chloride, wherein the amount of coal slag added accounts for 70% of the mass fraction of the cementitious material, the amount of calcium oxide added accounts for 8% of the mass fraction of the cementitious material, the amount of cement clinker added accounts for 5% of the mass fraction of the cementitious material, the amount of slag added accounts for 15% of the mass fraction of the cementitious material, and the amount of calcium chloride added accounts for 2% of the mass fraction of the cementitious material.

[0050] Example 6

[0051] A coal slag cementitious material, in this example, includes coal slag, calcium oxide, cement clinker, slag, fly ash, and calcium chloride as raw materials. The amount of coal slag added accounts for 65% of the mass fraction of the cementitious material, the amount of calcium oxide added accounts for 8% of the mass fraction of the cementitious material, the amount of cement clinker added accounts for 5% of the mass fraction of the cementitious material, the amount of slag added accounts for 15% of the mass fraction of the cementitious material, the amount of fly ash added accounts for 5% of the mass fraction of the cementitious material, and the amount of calcium chloride added accounts for 2% of the mass fraction of the cementitious material.

[0052] Example 7

[0053] A cinder cementitious material, in this example, includes cinder, calcium oxide, cement clinker, slag, fly ash, calcium chloride, and HPMC as raw materials. The cinder content accounts for 65% of the mass fraction of the cementitious material, the calcium oxide content accounts for 8% of the mass fraction, the cement clinker content accounts for 5% of the mass fraction, the slag content accounts for 15% of the mass fraction, the fly ash content accounts for 5% of the mass fraction, the calcium chloride content accounts for 2% of the mass fraction, and the HPMC content accounts for 0.2% of the mass fraction.

[0054] The mine backfill materials in Examples 1-7 of this invention are prepared by the following method, and the preparation process is as follows: Figure 1 As shown, the specific steps include:

[0055] S1. Place the coal slag in an oven at 105±5℃ and dry it for 3 hours. Measure its moisture content and ensure that its moisture content is less than or equal to 1%.

[0056] S2. Weigh out the coal slag and calcium oxide according to the proportion, mix them and grind them in a ball mill for 30 minutes. Then add 8 kg of water to the resulting powder and stir continuously. At the same time, heat the solid-liquid mixture to 85°C and maintain the temperature for 60 minutes.

[0057] S3. Allow the solid-liquid mixture to cool naturally to 28-30℃, filter, and then dry the precipitate to obtain the precursor powder of the cementitious material.

[0058] S4. Weigh out the precursor powder, cement, fly ash, slag, calcium chloride and HPMC according to the proportions, mix them and continue grinding for 5-6 minutes to obtain the finished coal slag-based cementitious material.

[0059] S5. Prepare a paste sample with a water-cement ratio of 0.5. Weigh out the solid powder of the coal slag-based cementitious material and water, stir it with a mixer, and after the solid and liquid are fully mixed, put it into a mold and use a vibration table to remove air bubbles in the filling body.

[0060] S6. After curing the prepared paste sample horizontally in the curing chamber for 24 hours, demold it and place it in a curing chamber at 20℃±1℃ and 95% relative humidity for curing periods of 7d±2h and 28d±2h.

[0061] In the above embodiments, the mixture in step S4 varies depending on the raw materials. For example, in Example 1, the raw materials are only coal slag and calcium oxide, and in step S4, only the precursor powder is ground to obtain the finished coal slag-based cementitious material. The other steps are consistent in all embodiments.

[0062] Example 8

[0063] A cinder cementitious material is provided. As a comparative example, the cinder used in this example is unactivated virgin cinder. The raw materials used in this preparation include virgin cinder, calcium oxide, cement clinker, slag, fly ash, calcium chloride, and HPMC. The cinder content accounts for 65% of the mass fraction of the cementitious material, the calcium oxide content accounts for 8%, the cement clinker content accounts for 5%, the slag content accounts for 15%, the fly ash content accounts for 5%, the calcium chloride content accounts for 2%, and the HPMC content accounts for 0.2%.

[0064] The preparation process of Example 8 includes the following steps:

[0065] S1. Place the coal slag in an oven at 105±5℃ and dry it for 3 hours. Measure its moisture content and ensure that its moisture content is less than or equal to 1%.

[0066] S2. Weigh out coal slag, calcium oxide, cement, fly ash, slag, calcium chloride and HPMC according to the proportions, mix them and continue grinding for 5-6 minutes using a grinder to obtain the finished coal slag-based cementitious material.

[0067] S5. Prepare a paste sample with a water-cement ratio of 0.5. Weigh out the solid powder of the coal slag-based cementitious material and water, stir it with a mixer, and after the solid and liquid are fully mixed, put it into a mold and use a vibration table to remove air bubbles in the filling body.

[0068] S6. After curing the prepared paste sample horizontally in the curing chamber for 24 hours, demold it and place it in a curing chamber at 20℃±1℃ and 95% relative humidity for curing periods of 7d±2h and 28d±2h.

[0069] The strength, fluidity, and microstructure of the prepared coal slag-based cementitious material were tested. The process and data are as follows:

[0070] (1) Detection of microscopic properties of activated coal slag

[0071] High-resolution field emission scanning electron microscopy was used to observe the microstructure of activated coal slag treated with a mildly activated alkaline solution. Since the samples in this study were non-conductive, they needed to be sputter-coated with gold before high-resolution microstructure observation.

[0072] (2) Flowability measurement

[0073] The flowability test of cement paste was conducted using a truncated conical mold. Cement paste was poured into the mold (the small circle at the top of the mold had a diameter of 36 mm, the large circle at the bottom had a diameter of 60 mm, and the height was 60 mm). After filling, the mold was pressed down to ensure it was completely filled, leveled, and then lifted vertically, slowly, and steadily. When the paste stopped flowing and no longer expanded, the diameters of the two conical molds in opposite directions were measured, and the average value was taken as the flowability.

[0074] (2) Compressive strength test

[0075] The slurry was poured into 40×40×40mm molds, placed horizontally in a curing chamber, and cured for 24 hours before demolding. The molds were then placed at 20℃±1℃ and 95% relative humidity for further curing. After curing periods (7d±2h, 28d±2h), the compressive strength of the specimens was measured using a YAW-600 rock pressure tester to verify their mechanical properties.

[0076] The test results are shown below:

[0077] (1) Mild activation effect of coal slag

[0078] This invention provides a method for composite activation of coal slag. The microstructure of the activated coal slag in Example 1 was observed using a high-resolution field emission scanning electron microscope, and the activation effect of alkaline high-temperature solution on the coal slag was analyzed. Figure 2 (a) is a diagram of the mild activation process of coal slag in an alkaline solution, including mixing and grinding coal slag and calcium oxide, placing it in a beaker, adding water, heating and activating it on a magnetic stirrer, with the rotor rotating continuously in the beaker, causing the coal slag particles to move continuously, so that the coal slag is heated evenly and activated completely. Figure 2 (b) is a microscopic image of unactivated undisturbed coal slag. The surface of the coal slag particles is smooth and there are very few corrosion spots.

[0079] Figure 3The image shows a microscopic scanning electron microscope (SEM) image of the activated coal slag particles. It can be seen that after mechanical grinding and gentle activation with an alkaline solution, firstly, the surface morphology of the coal slag particles is disrupted by mechanical grinding, increasing the number of new active surfaces. Secondly, there is significant erosion on the surface of the coal slag particles. The calcium oxide dissolves, making the aqueous solution alkaline, and the heating of the solution creates a strong erosion system for the coal slag, corroding the dense silica film on the surface and increasing the content of active aluminum and silicon, thus providing more reaction sites for chemical reactions.

[0080] Figure 4 This diagram illustrates the corrosion principle of a dense silica film on the surface of coal slag. As shown, the silica film on the surface of the coal slag particles is corroded by alkaline ions (OH-). - and Ca 2+ Corrosion damages and creates gaps, leading to [Si(OH)3] formation. - [Al(OH)4] - The release of large amounts of active silicon and aluminum ions enhances the cementing activity of the coal slag. The incorporation of calcium oxide provides calcium ions, which are raw materials for the hydration reaction. The introduction of calcium ions helps generate the hydration product CSH gel phase, increasing the polymerization degree of the cementitious material and giving the coal slag-based cementitious material higher early compressive strength.

[0081] (2) Performance of coal slag-based cementitious materials

[0082] Table 1. Performance of Cementitious Materials

[0083]

[0084] Table 1 shows that in Example 1, the addition of 20% CaO by mass to the coal slag for gentle alkaline solution activation resulted in good activation. Without the addition of other auxiliary activators, the specimen cast from pure activated coal slag showed a spread of 7.2 cm and a 28-day uniaxial compressive strength of 6.16 MPa. This indicates that the coal slag was successfully activated and possesses good cementitious activity.

[0085] The activation effects of other activation materials, cement clinker and slag, on mildly activated coal slag were tested, as in Examples 2, 3, and 4. In all examples, the coal slag was mildly activated by incorporating 10% CaO by mass. In Example 2, 20% cement was incorporated to activate the coal slag; the poured sample showed a spread of 7.7 cm and a 28-day uniaxial compressive strength of 10.87 MPa, demonstrating a significant improvement in activation. In Example 3, 20% slag was used to assist in activation of the coal slag; the activation effect was worse than with cement clinker, but the flowability was improved. The 28-day uniaxial compressive strength was 8.06 MPa, and the spread was 7.9 cm. In Example 4, 10% cement clinker and 10% slag were incorporated to perform composite activation of the coal slag; the poured sample showed a spread of 7.8 cm and a 28-day uniaxial compressive strength of 11 MPa. This indicates that the composite activation effect of cement clinker and slag is superior to that of activation with only clinker or slag.

[0086] Calcium chloride (CaCl2) can significantly improve the early compressive strength of cementitious materials as an activator; fly ash can "deflocculate" and diffuse cementitious materials, improve workability, and increase casting density; HPMC increases the cohesive properties of cementitious materials and enhances their adhesion to tailings. Examples 5, 6, and 7 all involved mild activation with 8% CaO by mass. Example 5, under conditions of combined activation with cement clinker and slag, incorporated 2% calcium chloride by mass for activation, resulting in improved spread and 28-day uniaxial compressive strength. The spread was measured to be 8.2 cm, and the 28-day uniaxial compressive strength to be 10.87 MPa. Example 6, based on Example 5, added 5% fly ash, improving the flowability, workability, and uniaxial compressive strength of the slag-based cementitious material. The flowability was measured to be 9.1 cm, and the 28-day uniaxial compressive strength to be 14.98 MPa. Example 7, based on Example 6, added 0.2% HPMC, improving the bonding performance of the cementitious material and increasing its adhesion to tailings particles, but reducing its own flowability. The flowability was measured to be 8.4 cm, and the 28-day uniaxial compressive strength to be 15.21 MPa. In contrast, in Example 8, the activated coal slag used in Example 7 was replaced with unactivated coal slag without alkaline mild activation. All other proportions and dosages remained unchanged. The test spread was 8 cm, and the 28-day uniaxial compressive strength was 5.62 MPa, a decrease of 170.64% in uniaxial compressive strength. This demonstrates that alkaline mild activation can improve the cementing activity of coal slag and enhance the uniaxial compressive strength of the cementitious material sample.

[0087] The slag-based cementitious material obtained in Example 7 was used to prepare filling samples. The uniaxial compressive strength was 1.39 MPa at 3 days, 1.62 MPa at 7 days, and 2.66 MPa at 28 days.

[0088] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A cementitious material, characterized in that, It contains activated coal slag, and the components and their mass percentages of the cementitious material are as follows: coal slag 60%-70%, fly ash 0-10%, slag 0-20%, calcium oxide 8-20%, cement clinker 5-20%, calcium chloride 2%, and HPMC 0.2%; The method for preparing the activated coal slag includes the following steps: S1. After drying the coal slag, measure its moisture content to ensure that its moisture content is ≤1%; S2. Mix and grind the coal slag and calcium oxide, add water to the resulting mixed powder and stir continuously, while heating to 80-90℃ and keeping it at that temperature for 50-90 minutes to obtain a solid-liquid mixture. S3. Allow the solid-liquid mixture to cool naturally, filter it, and then dry the precipitate to obtain activated coal slag.

2. The cementitious material according to claim 1, characterized in that, In step S1, the drying temperature is 105±5℃ and the drying time is 2-4 hours.

3. The cementitious material according to claim 1, characterized in that, In step S2, the mass ratio of the mixed powder to water is 1:(5-10).

4. The cementitious material according to claim 1, characterized in that, The cement clinker is silicate cement with a strength grade of 42.5, 32.5 or 52.

5.

5. The method for preparing the cementitious material according to any one of claims 1 to 4, characterized in that, Includes the following steps: S1. Dry the coal slag in an oven at 105±5℃ for 2-4 hours to ensure that its moisture content is ≤1%; S2. Weigh out coal slag and calcium oxide according to the proportion, mix them and grind them in a ball mill. Then add 5-10 kg of water to the resulting powder and stir continuously. At the same time, heat to 80-90℃ and keep warm for 50-90 minutes to obtain a solid-liquid mixture. S3. Allow the solid-liquid mixture to cool naturally, filter it, and then dry the precipitate to obtain the precursor powder of the cementitious material. S4. Weigh out the precursor powder, cement clinker, fly ash, slag, calcium chloride and HPMC according to the proportions, mix them and continue grinding them with a grinder to obtain the finished coal slag-based cementitious material. S5. Prepare a paste sample with a water-cement ratio of 0.

5. Weigh out the solid powder of coal slag-based cementitious material and water, stir with a mixer, and after the solid and liquid are fully mixed, put it into a mold and use a vibrating table to remove air bubbles in the filling body. S6. After curing the prepared paste sample horizontally in the curing chamber for 24 hours, demold it and place it in a curing chamber at 20℃±1℃ and 95% relative humidity for 7d±2h or 28d±2h.

6. The application of the cementitious material according to any one of claims 1 to 4 in mine backfilling.

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