Coal gangue micro-powder filling material as well as preparation method and application thereof

Abstract

The invention relates to a coal gangue filling material in the prior art as well as a preparation method and application thereof, and belongs to the technical field of filling materials. Comprising the following raw materials in parts by weight: 600-700 parts of coal gangue micro powder; 100 to 140 parts of fly ash; 140 to 180 parts of cement; 8 to 12 parts of gypsum; 28 to 32 parts of an exciting agent; and 4-6 parts of a water reducing agent. According to the invention, a large amount of industrial wastes such as coal gangue and fly ash are utilized, environmental pollution caused by the wastes is reduced, the wastes are converted into functional materials for filling, high-valued utilization of the industrial wastes is realized, active SiO2 and Al2O3 are released and more C-S-H gel and ettringite are generated by utilizing the composite activity excitation effect of the excitant, and the utilization rate of the C-S-H gel and ettringite is increased. And the compactness and the early strength of the system are improved.

Description

Technical Field

[0001] This invention belongs to the field of filling material technology, and particularly relates to a coal gangue micro powder filling material, its preparation method and application. Background Technology

[0002] Coal gangue is a solid waste generated during coal mining and washing. It is a dark gray rock with a low carbon content and harder than coal, which is associated with coal seams during coal formation. Its emissions are enormous, typically accounting for 10% to 25% of coal production, and even higher under certain complex geological conditions. Coal gangue has a complex composition, and the residual carbon and combustible organic matter it contains may spontaneously combust under certain conditions, especially in high-sulfur gangue, releasing large amounts of SO2, CO, CO2, and NO. x In addition, toxic and harmful gases (such as H2S) and soot cause serious air pollution and the greenhouse effect.

[0003] Existing technologies may not fully utilize industrial wastes such as coal gangue and fly ash, or the utilization rate may be low. As a result, these wastes are still mainly dumped in the open or landfilled, which not only occupies a lot of land, but also poses environmental pollution and safety hazards such as spontaneous combustion and release of toxic gases, and the treatment cost is high.

[0004] Existing coal gangue filling materials suffer from problems such as low strength, poor fluidity, and unreasonable setting time, making it difficult to meet the requirements for material strength and workability in projects such as mine goaf filling and roadway support. Furthermore, the materials have poor synergy, failing to effectively solve the compatibility problem between cementitious materials and industrial waste, or lacking the synergistic effect of additives such as high-efficiency activators and water-reducing agents, resulting in insufficient hydration reaction, loose structure, and affecting overall performance.

[0005] The information disclosed in this background section is intended only to enhance the understanding of the overall background of the invention and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0006] To address the technical problems of high processing costs, environmental issues, and safety hazards associated with coal gangue in existing technologies, this paper provides a coal gangue micro powder filling material, its preparation method, and its application.

[0007] The first aspect of this invention provides a coal gangue micro powder filling material comprising the following raw materials in parts by weight: 675 parts of coal gangue powder: 120 parts fly ash; 160 parts cement; 10 parts plaster; 30 parts of activator; 5 parts water-reducing agent.

[0008] In some embodiments, the coal gangue powder has a particle size of <300 mesh, a SiO2 content of 40%-50%, and an Al2O3 content of 15%-25%.

[0009] In some embodiments, the gypsum contains ≥90% CaSO4•2H2O.

[0010] In some embodiments, the activator is a sodium hydroxide and sodium sulfate complex, wherein the mass ratio of sodium hydroxide to sodium sulfate is 2:1. The activator belongs to the category of alkaline activators used in alkaline-activated cementitious material systems.

[0011] In some embodiments, the water-reducing agent is a polycarboxylate-based high-performance water-reducing agent with a water reduction rate ≥25%, chloride ion content ≤0.1%, and sodium sulfate content ≤5%.

[0012] In some embodiments, water is also included, and the water-to-binder ratio of the water bath activator is 0.4-0.5.

[0013] A second aspect of the present invention provides a method for preparing a coal gangue micro powder filling material, comprising the following steps: The dry-mixed material is obtained by uniformly mixing coal gangue powder, fly ash, cement, and gypsum. Add water to the activator to dissolve it and you get solution A; During the stirring of solution A, a water-reducing agent is added to solution A and stirred evenly to obtain solution B; The solution B is added to the dry mixture, and after post-processing, the coal gangue micro powder filling material is obtained.

[0014] In some embodiments, the method for preparing the coal gangue powder includes: After large pieces of coal gangue are crushed, a grinding aid is added and the mixture is ground for 30-40 minutes. The mixture is then sieved to obtain coal gangue powder with a particle size of less than 300 mesh. The grinding aid is selected from one or more of ethylene glycol, glycerol, and polymeric polyols; The grinding aid is 0.05%-0.5% of the coal gangue mass; preferably, the grinding aid is 0.1%-0.3% of the coal gangue mass.

[0015] In some embodiments, the post-processing includes stirring at a speed of 200-300 r / min for a duration of 5-8 min.

[0016] The third aspect of this invention provides an application of the above-mentioned coal gangue micro powder filling material and / or the coal gangue micro powder filling material prepared by the above preparation method in building environmental protection filling materials or mine void filling and roadway support.

[0017] The technical effects achieved by adopting the technical solution of the present invention are as follows: (1) This invention makes extensive use of industrial wastes such as coal gangue and fly ash, reducing the pollution of these wastes to the environment and converting them into functional materials that can be used for filling, realizing the high-value utilization of industrial solid waste. At the same time, it reduces the demand for natural aggregates, reduces the open-air dumping and landfilling of waste, reduces environmental pollution (such as avoiding the release of toxic gases from spontaneous combustion) and land occupation, realizes the high-value utilization of industrial solid waste, fits the national circular economy and green development concept, and has significant environmental benefits.

[0018] (2) This invention utilizes the combined active activation effect of the activator to disrupt the stable structure of silicon-oxygen bonds (Si-O) and aluminum-oxygen bonds (Al-O) in coal gangue powder and fly ash, releasing active SiO2 and Al2O3. These active components react with Ca(OH)2 produced by cement hydration in an alkaline environment to generate more CSH gel and ettringite. CSH gel is the main source of material strength, which can fill micropores and improve the density of the structure; ettringite can enhance the early strength of the system. Together, they improve the overall strength of the material (7d compressive strength ≥7MPa, 28d ≥15MPa).

[0019] (3) This invention also utilizes the dispersing and densifying effects of water-reducing agents: water-reducing agent molecules adsorb onto the surface of cement, coal gangue powder, and other particles, generating electrostatic repulsion between the particles and effectively dispersing agglomerated particles. This allows cement particles to come into more complete contact with water, resulting in a more complete hydration reaction and a more uniform distribution of the hydration products. At the same time, the dispersing effect reduces the water requirement and lowers the water-cement ratio, resulting in a lower porosity after the material hardens, a more uniform distribution of the hydration products, further improving the density and strength of the material, and solving the structural looseness problem that may exist in the prior art.

[0020] (4) When activators and water-reducing agents are used together, they effectively exert a synergistic effect. The activator promotes the reaction of active ingredients to generate more strength substances, while the water-reducing agent ensures that these substances can fill the structure evenly and reduce defects. Moreover, the dispersing effect of the water-reducing agent allows the activator to contact the raw materials more evenly, improves the activation efficiency, further promotes the hydration reaction and the utilization of active ingredients, and ultimately enables the material to achieve high strength. Detailed Implementation

[0021] The technical solution of the present invention is illustrated below with reference to specific embodiments. It should be understood that the one or more steps mentioned in the present invention do not preclude the existence of other methods and steps before or after the combined steps, or that other methods and steps may be inserted between these explicitly mentioned steps. It should also be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. Unless otherwise stated, the numbering of each method step is only for the purpose of identifying each method step, and not for limiting the order of each method or limiting the scope of the present invention. Changes or adjustments to their relative relationships, without substantial changes to the technical content, can also be considered as within the scope of the present invention.

[0022] The raw materials and instruments used in the examples are not subject to any specific restrictions on their source; they can be purchased from the market or prepared according to conventional methods known to those skilled in the art.

[0023] In some embodiments, the method for preparing a coal gangue micro powder backfill material provided by the present invention includes the following steps: (1) Raw material pretreatment Large pieces of coal gangue are coarsely crushed using equipment such as jaw crushers to initially reduce their particle size; The coal gangue is then further crushed using equipment such as a cone crusher to reduce its particle size to a suitable range. Preferably, the coal gangue particle size is further reduced to below 4.75 mm to facilitate subsequent grinding. The crushed coal gangue is fed into a ball mill for grinding. The grinding time is controlled at 30-40 minutes. Grinding aids can be added appropriately during the grinding process to improve grinding efficiency and reduce energy consumption. After grinding, the coal gangue is sieved using 270-mesh and 300-mesh standard sieves to obtain coal gangue powder with a particle size of less than 300 mesh for later use. The SiO2 content of this coal gangue powder is in the range of 40%-50%, and the Al2O3 content is in the range of 15%-25%.

[0024] The fly ash is sieved to remove large particles and ensures that its fineness meets the GB / T1596-2017 standard, Class F, Grade II or above, with a sieve residue of ≤30% on a 45μm square hole sieve and a water requirement ratio of ≤105%.

[0025] In some implementations, polyols are preferred grinding aids, such as ethylene glycol, glycerol, and polymeric polyols. Ethylene glycol reduces friction between cement particles, making grinding smoother, and also has an antifreeze effect, which is beneficial for winter construction. Glycerol increases material flowability, reduces particle agglomeration, and improves grinding efficiency and quality. Polymeric polyols are mixtures of polyols and esters, appearing as brown, viscous liquids. They enhance both the early and later strength of cement and can be combined with alkanolamines for synergistic effects. They can replace alcohols such as ethylene glycol, diethylene glycol, and glycerol. When processing coal gangue powder, polyol grinding aids can optimize its particle morphology and improve dispersibility.

[0026] Generally, in raw material systems primarily composed of coal gangue powder, the addition amount of grinding aids is between 0.05% and 0.5% by weight. This is because grinding aids, as surface-active substances, can effectively reduce surface energy and promote grinding even in small amounts. If the dosage is too low, it cannot adequately disperse particles and reduce agglomeration, making it difficult to significantly improve grinding efficiency; while excessive dosage not only increases costs but may also affect the normal hydration reaction of cement and other cementitious materials, adversely impacting the later strength and other properties of the material.

[0027] Preferably, when the grinding aid dosage is between 0.1% and 0.3%, the grinding effect on coal gangue powder and the overall performance improvement in this dry-mixed shotcrete material are optimal. Within this range, grinding aid components such as alkanolamines (e.g., triethanolamine) and polyols can be fully adsorbed on the surface of coal gangue particles, effectively reducing van der Waals forces between particles, reducing agglomeration, and making the coal gangue powder easier to refine during grinding, and able to be evenly dispersed in other raw materials (e.g., cement, fly ash). At the same time, this dosage range will not interfere with the cement hydration process, and can also synergistically enhance the comprehensive performance of the material with other additives (e.g., water-reducing agents, activators), such as improving the fluidity, strength development, and adhesion to the substrate of the shotcrete material. For example, when using a grinding aid composed of polymeric polyol and triethanolamine, adding it at a dosage of 0.2% can shorten the grinding time of coal gangue powder by 15%-20%, and the prepared dry-mixed sprayed slurry material has good workability during spraying construction, and the compressive strength after hardening is increased by 10%-15% compared with that without the grinding aid.

[0028] (2) Material mixing The weighed coal gangue powder, fly ash, cement, and gypsum are added to a forced mixer in sequence. Dry mixing is performed first, with the mixing speed controlled at 100-150 r / min and the mixing time at 3-5 min, so that the components are fully mixed and uniform, and the dry-mixed material is obtained.

[0029] The cement is 42.5 grade ordinary Portland cement, conforming to GB175-2023 standard, with initial setting ≥45min and final setting ≤600min; the gypsum is building gypsum with CaSO4•2H2O content ≥90%.

[0030] (3) Preparation of activation solution Add the composite activator (sodium hydroxide and sodium sulfate mixed in a mass ratio of 2:1) to water prepared with a water-cement ratio of 0.4-0.5, stir to dissolve, and prepare the activating solution (solution A).

[0031] (4) Preparation of water-reducing agent solution During the stirring process, the water-reducing agent is slowly added to the activation solution, and stirring is continued until the water-reducing agent is fully dissolved to obtain a water-reducing agent solution (solution B).

[0032] The preferred water-reducing agent is a high-performance polycarboxylate-based water-reducing agent with a water reduction rate of ≥25%, chloride ion content ≤0.1%, and sodium sulfate content ≤5%.

[0033] (5) Filling grout Slowly add the well-mixed water-reducing agent solution (solution B) to the dry-mixed material, and simultaneously start the mixer. Adjust the mixing speed to 200-300 r / min and the mixing time to 5-8 min to ensure that the material and solution are fully mixed to form a uniform filling slurry, i.e., coal gangue micro powder filling material.

[0034] Example 1 The weighed 675 parts of coal gangue powder, 120 parts of fly ash, 160 parts of cement, and 10 parts of gypsum were added to a forced mixer in sequence. Dry mixing was carried out first, with the mixing speed controlled at 100 r / min and the mixing time at 5 min, so that the components were fully mixed and uniform, and the dry-mixed material was obtained for later use.

[0035] Dissolve 30 parts of activator in water and add it to water prepared at a water-to-gel ratio of 0.4. Stir to dissolve and prepare activating solution (solution A). The activator consists of 20 kg of sodium hydroxide and 10 kg of sodium sulfate.

[0036] During the stirring process, 5 parts of polycarboxylate-based high-performance water-reducing agent were slowly added to the activation solution, and stirring was continued until the water-reducing agent was fully dissolved, resulting in a water-reducing agent solution (solution B). The above-mentioned uniformly mixed water-reducing agent solution (solution B) was slowly added to the dry-mixed material, and the mixer was started at the same time. The stirring speed was adjusted to 200 r / min, and the stirring time was 8 min, so that the material and solution were fully mixed to form a uniform filling slurry.

[0037] Premixing the activator and water-reducing agent before adding them to the dry-mixed material can improve the synergistic efficiency of the activator and water-reducing agent, ensuring the fluidity and stability of the slurry. Specifically, the activator (a complex of sodium hydroxide and sodium sulfate) needs an alkaline environment to function, while polycarboxylate-based water-reducing agents can disperse particles more stably under alkaline conditions. Premixing the activator and water-reducing agent allows the water-reducing agent molecules to fully dissolve and form a homogeneous system with the activator. This ensures that when subsequently added to the dry-mixed material, both can simultaneously contact the particles such as coal gangue powder and cement. The activator promotes the release of active ingredients (SiO2, Al2O3), while the water-reducing agent immediately disperses the particles, avoiding local agglomeration that hinders the reaction, thereby improving the activation efficiency and the uniformity of hydration products. The core function of the water-reducing agent is to disperse particles through electrostatic repulsion, reducing water demand. If the activator is added before the water-reducing agent, the excessively high local concentration of the activator may cause premature hydration and agglomeration of cement particles, reducing the dispersion effect of the water-reducing agent. Premixing allows the water-reducing agent to "encapsulate" the activator ions in advance, reducing their instantaneous impact on the cement and ensuring that the slurry spread meets the design requirement of 200-250mm, facilitating pipeline transportation. In addition, premixing the liquid components (activator solution and water-reducing agent) into a single solution B before adding the dry mix reduces the number of steps required for adding materials, reduces the problem of uneven mixing caused by errors in the order of adding materials, and ensures the overall stability of the slurry performance.

[0038] Performance testing The standard curing conditions for coal gangue micro powder backfill material are as follows: (1) Temperature requirements The curing environment temperature should be maintained at 20±2℃. Excessive temperature fluctuations will affect the cement hydration rate: too high a temperature will cause the early strength to increase too quickly but the later strength to be insufficient; too low a temperature will slow down the hydration reaction and delay the strength development.

[0039] (2) Humidity requirements Relative humidity must be ≥95%. High humidity prevents moisture evaporation from the test block surface, avoids cracking due to dryness, and ensures complete cement hydration. Common moisture retention methods include: Place in a standard curing chamber (with automatic temperature and humidity control); Immerse it in still water at 20±2℃ (the water level should be at least 50mm above the top surface of the test block).

[0040] Test Results After 7 days, the compressive strength can reach more than 7MPa, and after 28 days, the compressive strength can reach more than 15MPa, which can meet the strength requirements for filling in underground engineering such as mines, effectively support the surrounding rock, and prevent the surrounding rock from deforming and collapsing.

[0041] Flowability: Due to the addition of water-reducing agent, the filling slurry has good flowability and an expansion of 200-250mm, which can be smoothly transported in the pipeline and can fill all corners well during the filling process, ensuring the compactness of the filling.

[0042] Setting time: The initial setting time of the material can be controlled within 1-2 hours, and the final setting time within 3-4 hours. This not only meets the time requirements for mixing and conveying during construction, but also allows for rapid setting and hardening after filling, thus improving construction efficiency.

[0043] Through the synergistic effect of gypsum and activators, gypsum provides sulfate ions to regulate the activation efficiency of activators (such as alkaline substances, aluminates, etc.) on cementitious materials (such as slag, fly ash, etc.). Activators promote the dissolution of active ingredients, while gypsum inhibits early rapid setting caused by excessive hydration. At the same time, both promote the formation and stabilization of hydration products (such as ettringite, CSH gel), ultimately improving material strength and workability.

[0044] Example 2 The weighed 675 parts of coal gangue powder, 120 parts of fly ash, 160 parts of cement, and 10 parts of gypsum were added to a forced mixer in sequence. Dry mixing was carried out first, with the mixing speed controlled at 150 r / min and the mixing time at 3 min, so that the components were fully mixed and uniform, and the dry-mixed material was obtained for later use.

[0045] Dissolve 30 parts of activator in water and add it to water prepared at a water-to-gel ratio of 0.5. Stir to dissolve and prepare activating solution (solution A). The activator consists of 20 kg of sodium hydroxide and 10 kg of sodium sulfate.

[0046] During the stirring process, 5 parts of polycarboxylate-based high-performance water-reducing agent were slowly added to the activation solution, and stirring was continued until the water-reducing agent was fully dissolved, resulting in a water-reducing agent solution (solution B). The above-mentioned uniformly mixed water-reducing agent solution (solution B) was slowly added to the dry-mixed material, and the mixer was started at the same time. The stirring speed was adjusted to 300 r / min, and the stirring time was 5 min, so that the material and solution were fully mixed to form a uniform filling slurry.

[0047] Tests showed that the performance of the filling slurry prepared in this embodiment was consistent with that in Example 1.

[0048] Example 3 The weighed 675 parts of coal gangue powder, 120 parts of fly ash, 160 parts of cement, and 10 parts of gypsum were added to a forced mixer in sequence. Dry mixing was carried out first, with the mixing speed controlled at 130 r / min and the mixing time at 3-5 min, so that the components were fully mixed and uniform, and the dry-mixed material was obtained for later use.

[0049] Dissolve 30 parts of activator in water and add it to water prepared at a water-to-binder ratio of 0.45. Stir to dissolve and prepare activating solution (solution A). The activator consists of 20 kg of sodium hydroxide and 10 kg of sodium sulfate.

[0050] During the stirring process, 5 parts of polycarboxylate-based high-performance water-reducing agent were slowly added to the activation solution, and stirring was continued until the water-reducing agent was fully dissolved, resulting in a water-reducing agent solution (solution B). The above-mentioned uniformly mixed water-reducing agent solution (solution B) was slowly added to the dry-mixed material, and the mixer was started at the same time. The stirring speed was adjusted to 250 r / min, and the stirring time was 6 min, so that the material and solution were fully mixed to form a uniform filling slurry.

[0051] Tests showed that the performance of the filling slurry prepared in this embodiment was consistent with that in Example 1.

[0052] Comparative Example 1 The same method as in Example 1 was used, except that the activating solution (solution A) was added to the dry-mixed material first, and then the water-reducing agent was added to the dry-mixed material. Otherwise, it was the same as in Example 1.

[0053] Results: Agglomeration occurred, making it difficult to form a uniform filling slurry. Segregation or bleeding occurred during the curing process, making it impossible to guarantee the expansion standard and affecting pipeline transportation and filling density.

[0054] This is because adding an activator first creates an alkaline environment that can cause cement particles to hydrate and agglomerate rapidly. Subsequent addition of a water-reducing agent then struggles to fully disperse these agglomerated particles, reducing dispersion efficiency. Even with longer mixing times, the cement hydration reaction can proceed prematurely and excessively, affecting setting time (the document requires initial setting of 1-2 hours and final setting of 3-4 hours), thus reducing construction efficiency.

[0055] Comparative Example 2 The same method as in Example 1 was used, except that the water-reducing agent was added to the dry-mixed material first, and then the activating solution (solution A) was added to the dry-mixed material. Otherwise, it was the same as in Example 1.

[0056] Results: Uneven local moisture distribution, unstable slurry fluidity, segregation or bleeding occurred.

[0057] This is because water-reducing agent molecules preferentially adsorb onto the surface of cement particles, hindering the contact between the activator and coal gangue powder and fly ash, thus weakening the release efficiency of the active ingredients. Even with a longer mixing time, the cement hydration reaction will proceed prematurely and excessively, affecting the setting time (the document requires initial setting of 1-2 hours and final setting of 3-4 hours), and reducing construction efficiency.

[0058] Comparative Example 3 The same method as in Example 1 was used, except that no activator and water-reducing agent were added; otherwise, it was the same as in Example 1.

[0059] Results: The prepared filling grout had poor fluidity and an expansion of only 120 mm. After curing using the same method as in Example 1, the filling material had a loose structure, a 7-day strength of 5 MPa, and a 28-day compressive strength of less than 11 MPa.

[0060] This invention has significant advantages in environmental protection and resource utilization. It makes extensive use of industrial waste such as coal gangue powder and fly ash, transforming them into functional filling materials. This reduces the open-air dumping and landfilling of waste, lowers environmental pollution (such as avoiding the release of toxic gases from spontaneous combustion), and reduces land occupation. It realizes the high-value utilization of industrial solid waste, which is in line with the national circular economy and green development concept, and has significant environmental benefits.

[0061] Superior mechanical properties and structural stability are achieved through the action of a composite activator (sodium hydroxide and sodium sulfate in a 2:1 ratio), which disrupts the stable structure of silicon-oxygen bonds (Si-O) and aluminum-oxygen bonds (Al-O) in coal gangue powder and fly ash, releasing active SiO2 and Al2O3. These react with Ca(OH)2 produced during cement hydration to generate more CSH gel (enhancing structural density) and ettringite (strengthening early strength), significantly improving material strength (7-day compressive strength ≥7MPa, 28-day ≥15MPa). The use of a polycarboxylate-based high-performance water-reducing agent (water reduction rate ≥25%) disperses particles, reduces water demand and porosity, resulting in a more uniform distribution of hydration products, further improving material density and strength, and solving the structural looseness problem that may exist in existing technologies.

[0062] The working performance material is better suited to construction needs. It has good fluidity (expansion of 200-250mm), can be smoothly transported through pipelines, and can fully fill the corners of mine goaf or roadways to ensure filling density.

[0063] The setting time is controllable (initial setting 1-2 hours, final setting 3-4 hours), which not only meets the time requirements for construction operations such as mixing and conveying, but also enables rapid setting and hardening, improving construction efficiency and overcoming problems such as poor fluidity and unreasonable setting time that may exist in existing technologies.

[0064] The technical advantages of additive synergistic effect: The activator and water-reducing agent work synergistically: the activator promotes the reaction of active ingredients to generate strong substances, and the water-reducing agent ensures that these substances fill the structure uniformly; at the same time, the dispersing effect of the water-reducing agent improves the uniformity of contact between the activator and the raw materials, and improves the activation efficiency, which solves the problem of single action and poor synergy of additives that may exist in the existing technology.

[0065] This invention utilizes solid waste resources by processing coal gangue into functional materials that can be used for backfilling, thereby achieving high-value utilization of industrial solid waste and aligning with the national concepts of circular economy and green development.

[0066] The technical solution provided by this invention can be applied to the field of building material preparation: it involves the optimization of cementitious material system and admixture compounding technology, and the development of new environmentally friendly filling materials through the synergistic effect of materials such as coal gangue powder and fly ash with cement and gypsum.

[0067] The technical solution provided by this invention can also be applied to the field of mining engineering technology: the material is suitable for engineering scenarios such as filling of goaf and roadway support in mines, and can effectively support the surrounding rock and prevent deformation and collapse. It can effectively solve the problems of surface subsidence and surrounding rock stability caused by mining, ensure safe and efficient mining, and solve the problem of limited applicable scenarios of existing technologies.

[0068] The foregoing description of specific exemplary embodiments of the present invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made in accordance with the foregoing teachings. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize the invention. Various exemplary embodiments and various alternatives and modifications are possible. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A coal gangue micro powder filling material, characterized in that, The ingredients include the following parts by weight: 600-700 parts of coal gangue powder; 100-140 parts fly ash; 140-180 parts cement; 8-12 parts plaster; Activator 28-32 parts; 4-6 parts of water-reducing agent.

2. The coal gangue micro powder filling material according to claim 1, characterized in that, The ingredients include the following parts by weight: 675 parts of coal gangue powder; 120 parts fly ash; 160 parts cement; 10 parts plaster; 30 parts of stimulant; 5 parts water-reducing agent.

3. The coal gangue micro powder filling material according to claim 1, characterized in that, The coal gangue powder has a particle size of <300 mesh, a SiO2 content of 40%-50%, and an Al2O3 content of 15%-25%. And / or, the content of CaSO4•2H2O in the gypsum is ≥90%.

4. The coal gangue micro powder filling material according to claim 1, characterized in that, The activator is a complex of sodium hydroxide and sodium sulfate, wherein the mass ratio of sodium hydroxide to sodium sulfate is 2:

1.

5. The coal gangue micro powder filling material according to claim 1, characterized in that, The water-reducing agent is a polycarboxylate-based high-performance water-reducing agent with a water reduction rate of ≥25%, a chloride ion content of ≤0.1%, and a sodium sulfate content of ≤5%.

6. The coal gangue micro powder filling material according to claim 1, characterized in that, It also includes water, and the water-to-binder ratio of the water bath activator is 0.4-0.

5.

7. A method for preparing a coal gangue micro powder filling material, characterized in that, Includes the following steps: The dry-mixed material is obtained by uniformly mixing coal gangue powder, fly ash, cement, and gypsum. Add water to the activator to dissolve it and you get solution A; During the stirring of solution A, a water-reducing agent is added to solution A and stirred evenly to obtain solution B; The solution B is added to the dry mixture, and after post-processing, the coal gangue micro powder filling material is obtained.

8. The preparation method according to claim 7, characterized in that, The method for preparing the coal gangue powder includes: After large pieces of coal gangue are crushed, a grinding aid is added and the mixture is ground for 30-40 minutes. The mixture is then sieved to obtain coal gangue powder with a particle size of less than 300 mesh. The grinding aid is selected from one or more of ethylene glycol, glycerol, and polymeric polyols; The grinding aid is 0.05%-0.5% of the coal gangue mass; preferably, the grinding aid is 0.1%-0.3% of the coal gangue mass.

9. The preparation method according to claim 7, characterized in that, The post-processing includes stirring, with a stirring speed of 200-300 r / min and a stirring time of 5-8 min.

10. The application of the coal gangue micro powder filling material according to any one of claims 1-6 and / or the coal gangue micro powder filling material prepared by the preparation method according to any one of claims 7-9 in building environmental protection filling materials or mine goaf filling and roadway support.