Preparation method of composite solidified coal gangue material for ground hardening of mine roadway

Abstract

The present application relates to coal mine solid waste resource utilization technical field, disclose a kind of preparation method of composite solidified coal gangue material in mine roadway ground hardening, comprising: the primary coal gangue is sorted into multistage aggregate and powder, and the powder is activated and coated modification by calcination;Modified coal gangue powder, aggregate and multi-component curing agent are uniformly mixed, and the moisture content of mixed material is controlled;After in-situ paving and high-frequency vibration, it is covered and maintained;The present application improves the activity of high-dosage coal gangue through thermal excitation and chemical excitation synergistic mechanism, constructs interface anchoring layer on the surface of powder and induces directional nucleation of hydration product, and the dry shrinkage stress of hardening body is offset by the digestion and expansion of curing component, to enhance the mechanical properties and corrosion resistance durability of roadway ground hardening layer.

Description

Technical Field

[0001] This invention relates to a method for preparing composite solidified coal gangue material for hardening the surface of mine roadways, belonging to the field of coal mine solid waste resource utilization technology. Background Technology

[0002] In the coal mining and washing process, coal gangue, as the largest solid waste in terms of emissions, has become an industry standard for the resource utilization of coal gangue in the construction of green mines. Converting coal gangue into hardening materials for mine roadways can not only absorb large-scale accumulated solid waste but also reduce investment in roadway infrastructure construction. However, mine roadways are located deep underground in complex conditions, and must withstand long-term high humidity, water immersion, acid and alkali corrosion, and frequent crushing by heavy-duty transport equipment. Existing technologies mostly use basic physical filling methods or low-level alkaline activation methods to utilize coal gangue. This technological paradigm has obvious inherent limitations: to maintain the basic mechanical strength, it often requires sacrificing the material's long-term impermeability and structural stability as a hidden cost. Under typical high-stress and strong corrosive pressure conditions, traditional hardened surfaces are prone to structural deterioration, leading to increased maintenance frequency and safety risks with increasing service life. Carbon neutralization of large-scale industrial solid waste... From the perspective of comprehensive and harmless disposal, traditional utilization of coal gangue is mostly limited to low-level blending. Due to its nature as a multiphase aluminosilicate mineral with extremely low thermodynamic activity, it is generally believed in the industry that it cannot serve as the main cementitious structure, especially at high blending levels, such as above 80%. Under extreme working conditions, how to achieve a decoupled balance between low cement clinker consumption, high solid waste disposal, and long-term heavy-duty durability is an international technical bottleneck restricting the green transformation and development of coal mines. Existing technologies often overlook the physicochemical evolution of coal gangue under the erosion of complex underground chemical media, such as acidic mine water and harmful gases. Therefore, developing a multi-scenario universal composite solidified coal gangue cementitious network framework that can adapt to various extreme or high-value engineering scenarios, not only limited to roadway surface hardening, but also covering mine shotcrete support with high cohesion requirements and industrial imitation stone products with high density requirements, and possessing micro-level synergistic stimulation and macro-level environmental friendliness, is the key to realizing a closed loop in the entire industrial chain of bulk solid waste.

[0003] To address the aforementioned challenges, a linear improvement approach that simply increases the amount of silicate cement would not only result in significant economic costs and carbon footprint pressure due to the high consumption of cement clinker, but would also induce significant hydration heat runaway within the hardened body, generating numerous shrinkage microcracks. These cracks, acting as preferential penetration channels for corrosive ions, would accelerate the disintegration of the material's internal structure. Furthermore, simple mechanical crushing processes are insufficient to destroy the chemical passivation layer on the surface of coal gangue particles, failing to overcome the kinetic barriers to particle activation, resulting in consistently low interfacial bond strength between the aggregate and the cementitious matrix. Specifically, existing technologies suffer from the following shortcomings: 1. Incomplete activation of the surface activity of coal gangue aggregate, resulting in it only playing an inert filling role within the hardened body, unable to form a dense network structure with strong chemical bonds; 2. A single function of the curing system, making it difficult to balance the early strength enhancement of the hardened material with the long-term chemical protection requirements under extreme acid, alkali, and high humidity environments; 3. Low compatibility between the preparation process and the continuous pumping and casting requirements of confined underground spaces, leading to engineering defects such as bleeding, segregation, or uneven curing of the hardened layer.

[0004] Therefore, how to ensure the physical and mechanical properties and long-term service stability of roadway surfaces under extreme underground working conditions while maintaining a high coal gangue content through multi-level activity regulation of coal gangue and synergistic solidification of multiple functional components has become a key technical issue that urgently needs to be addressed in this field. Summary of the Invention

[0005] To address the problems mentioned in the background art, the technical solution of the present invention is as follows: A method for preparing composite solidified coal gangue material for hardening the surface of mine roadways, comprising the following steps:

[0006] Step S101: The raw coal gangue is crushed and screened to form coarse aggregate with a particle size of 10 mm to 25 mm, fine aggregate with a particle size of 2 mm to 10 mm, and coal gangue powder with a particle size of no more than 0.075 mm. The coal gangue powder is calcined and activated at 700℃ to 800℃ for 1.5 h to 2.5 h. After cooling, silane coupling agent and sodium stearate are added for ball milling and coating to prepare modified coal gangue powder.

[0007] Step S102: Mix 35 to 45 parts of silicate cement clinker, 5 to 8 parts of desulfurized gypsum, 20 to 30 parts of slag powder, 10 to 15 parts of fly ash, 3 to 6 parts of silica fume, 2 to 5 parts of quicklime, 1 to 3 parts of early-strength water-reducing agent, 0.5 to 1.5 parts of retarding synergist, and 1 to 2 parts of corrosion inhibitor according to the mass ratio to prepare a composite curing agent;

[0008] Step S103: Coarse aggregate, fine aggregate, modified coal gangue powder and composite curing agent are put into a forced mixer for dry mixing and wet mixing by spraying mixing water to prepare composite cured coal gangue mixture; by controlling the amount of mixing water added, the mass moisture content of composite cured coal gangue mixture is maintained in the range of 9% to 11%.

[0009] Step S104: The composite solidified coal gangue mixture is laid on the ground to be hardened in the mine roadway, with a paving thickness of 150mm to 250mm. The composite solidified coal gangue mixture is vibrated using a high-frequency vibration device.

[0010] Step S105: Cover the surface of the hardened body with a waterproof isolation film. The waterproof isolation film blocks the migration of internal moisture of the composite solidified coal gangue mixture to the external environment, and utilizes the volume expansion generated by the slaking of quicklime in the composite curing agent to offset the drying shrinkage during the hydration process of the hardened body.

[0011] Preferably, in the modified coal gangue powder, the total mass ratio of silane coupling agent and sodium stearate is 0.5% to 1.5%; in step S103, the mass ratio of coarse aggregate, fine aggregate, modified coal gangue powder and composite curing agent is: 40 to 50 parts of coarse aggregate, 25 to 35 parts of fine aggregate, 8 to 12 parts of modified coal gangue powder and 6 to 10 parts of composite curing agent.

[0012] Preferably, in step S101, the ball milling coating is carried out at a stirring speed of 800 r / min to 1200 r / min, so that the silane coupling agent and sodium stearate form a hydrophobic layer on the surface of the coal gangue powder.

[0013] Preferably, in step S102, the early-strength water-reducing agent is a polycarboxylate-based high-efficiency water-reducing agent; the retarding synergist is a compound of citric acid and sodium gluconate in a mass ratio of 1:1; and the corrosion inhibitor is a compound of calcium nitrite and benzotriazole in a mass ratio of 2:1.

[0014] Preferably, step S103 includes the following sub-steps: step S1031, coarse aggregate and fine aggregate are added to a forced mixer and mixed for 1 to 2 minutes; step S1032, modified coal gangue powder and composite curing agent are added to the forced mixer and mixed for 2 to 3 minutes; step S1033, mixing water is added in two batches and the mixture is discharged after wet mixing for 4 to 6 minutes.

[0015] Preferably, in step S104, the vibration stops when the surface of the composite solidified coal gangue mixture shows a slurry and no bubbles emerge, and the duration of single-point vibration is 40s to 70s.

[0016] Preferably, in step S105, the duration of sealed curing is 3 to 5 days; after the sealed curing is completed, the waterproof isolation film is removed, and the plant is naturally cured for 28 days under the condition that the relative humidity is not lower than 85%.

[0017] Preferably, during the wet mixing process in step S103, a chemical passivation layer is prepared on the surface of the coarse and fine aggregates by means of the active sites adsorbed on the surface of the corrosion inhibitor, in order to block the penetration of acidic water in the mine roadway into the interior of the hardened body.

[0018] Preferably, the mass ratio of coal gangue in the composite solidified coal gangue mixture is not less than 80%; and the compressive strength of the hardened body at 28 days is not less than 35 MPa.

[0019] Preferably, the composite solidified coal gangue mixture prepared by the methods in steps S101 to S103 is used in mine shotcrete support or industrial imitation stone products.

[0020] Compared with the prior art, the beneficial effects of the present invention are:

[0021] 1. By calcining coal gangue powder within a specific temperature range, the kaolinite component, which was originally in a stable state, undergoes a dehydroxylation reaction and transforms into a metakaolinite phase with high pozzolanic activity. Based on this, a composite modifier composed of silane coupling agent, anhydrous sodium sulfate, and nano-silica is used. The heterogeneous nucleation sites provided by nanomaterials and the chemical activation effect of sulfate on the aluminosilicate structure induce the generation of a large amount of hydrated calcium silicate gel and ettringite crystals in the early stage of hydration. This synergistic coupling mechanism of thermal and chemical activation solves the contradiction of low surface activity and weak bonding force with cementing materials in high-content coal gangue at the microscopic level, ensuring that the hardened body can still form a high-strength cementing network even with a high proportion of solid waste.

[0022] 2. This invention employs a multi-grade coal gangue skeleton system composed of coarse aggregate, fine aggregate, and modified micro powder. By utilizing the stepwise filling effect of different particle sizes, the initial porosity of the hardened body is reduced. Combined with a corrosion inhibitor composed of calcium nitrite and benzotriazole in the composite curing agent, a dense chemical passivation film is constructed on the surface of the aggregate and the pore walls of the hardened body. This passivation layer exhibits a high physical barrier and electrochemical blocking effect against the high humidity and acid-alkali corrosive media commonly found in underground mines. It effectively alleviates the structural deterioration phenomena such as sanding, cracking, and peeling that are prone to occur in conventional curing materials under long-term heavy-load rolling and water immersion conditions, thus extending the service life of the roadway surface.

[0023] 3. By precisely controlling the moisture content of the mixture to 9% to 11% and combining it with the closed curing process after underground paving and compaction, this invention effectively regulates the rate of moisture migration during the curing process by forming a waterproof isolation boundary on the surface of the hardened body. This mechanism ensures that the cementitious system remains within the optimal hydration reaction window in the closed and high-humidity environment of the mine. Utilizing the dynamic balance between early-strength water-reducing agent and retarding synergist, while ensuring rapid early strength growth of the hardened body, the volume shrinkage during the material setting process is offset by compensating for the shrinkage effect. This process synergy tailored to the actual construction environment of the mine avoids the concentration of shrinkage stress caused by internal and external temperature differences or humidity fluctuations, reduces the risk of penetrating cracks in the roadway surface, and shortens the curing period from construction completion to the point where the roadway is passable.

[0024] 4. Significant low-carbon and environmentally friendly effects and synergistic effects of treating multiple solid wastes with waste: This invention breaks the traditional paradigm of cementitious materials relying on high-carbon cement clinker. The mass ratio of coal gangue in the mixture can be no less than 80%, and it synergistically absorbs multiple sources of industrial solid waste such as desulfurized gypsum, slag powder, fly ash, and silica fume, realizing a typical multi-solid waste complementary ecological catalysis. The hydrophobic layer on the surface of the modified powder works synergistically with the corrosion inhibitor composed of calcium nitrite and benzotriazole, which not only blocks the penetration of acidic water from the mine, but also implements a dual stabilization of the heavy metal elements that may remain inside the coal gangue through chemical passivation and physical lattice encapsulation at the microscopic level, eliminating the risk of secondary environmental pollution during the reuse of solid waste. The overall carbon footprint is reduced by more than 65% compared with pure cement-based materials of the same strength, demonstrating excellent ecological and environmental benefits. Attached Figure Description

[0025] Figure 1 This is a flowchart illustrating the preparation and step-by-step construction process of the mine roadway surface hardening material according to the present invention.

[0026] Figure 2 This is a logic diagram of the mechanism for the synergy of multi-dimensional process elements and the realization of hardened body performance in this invention.

[0027] The objectives, features, and advantages of this invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0028] The technical solutions of the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application are within the scope of protection of this application.

[0029] A method for preparing a composite solidified coal gangue material for hardening the surface of a mine roadway includes the following steps:

[0030] Step S101: The raw coal gangue is crushed and screened to form coarse aggregate with a particle size of 10 mm to 25 mm, fine aggregate with a particle size of 2 mm to 10 mm, and coal gangue powder with a particle size of no more than 0.075 mm. The coal gangue powder is calcined and activated at 700℃ to 800℃ for 1.5 h to 2.5 h. After cooling, silane coupling agent and sodium stearate are added for ball milling and coating to prepare modified coal gangue powder.

[0031] Step S102: Mix 35 to 45 parts of silicate cement clinker, 5 to 8 parts of desulfurized gypsum, 20 to 30 parts of slag powder, 10 to 15 parts of fly ash, 3 to 6 parts of silica fume, 2 to 5 parts of quicklime, 1 to 3 parts of early-strength water-reducing agent, 0.5 to 1.5 parts of retarding synergist, and 1 to 2 parts of corrosion inhibitor according to the mass ratio to prepare a composite curing agent;

[0032] Step S103: Coarse aggregate, fine aggregate, modified coal gangue powder and composite curing agent are put into a forced mixer for dry mixing and wet mixing by spraying mixing water to prepare composite cured coal gangue mixture; by controlling the amount of mixing water added, the mass moisture content of composite cured coal gangue mixture is maintained in the range of 9% to 11%.

[0033] Step S104: The composite solidified coal gangue mixture is laid on the ground to be hardened in the mine roadway, with a paving thickness of 150mm to 250mm. The composite solidified coal gangue mixture is vibrated using a high-frequency vibration device.

[0034] Step S105: Cover the surface of the hardened body with a waterproof isolation film. The waterproof isolation film blocks the migration of internal moisture of the composite solidified coal gangue mixture to the external environment, and utilizes the volume expansion generated by the slaking of quicklime in the composite curing agent to offset the drying shrinkage during the hydration process of the hardened body.

[0035] Preferably, in the modified coal gangue powder, the total mass ratio of silane coupling agent and sodium stearate is 0.5% to 1.5%; in step S103, the mass ratio of coarse aggregate, fine aggregate, modified coal gangue powder and composite curing agent is: 40 to 50 parts of coarse aggregate, 25 to 35 parts of fine aggregate, 8 to 12 parts of modified coal gangue powder and 6 to 10 parts of composite curing agent.

[0036] Preferably, in step S101, the ball milling coating is carried out at a stirring speed of 800 r / min to 1200 r / min, so that the silane coupling agent and sodium stearate form a hydrophobic layer on the surface of the coal gangue powder.

[0037] Preferably, in step S102, the early-strength water-reducing agent is a polycarboxylate-based high-efficiency water-reducing agent; the retarding synergist is a compound of citric acid and sodium gluconate in a mass ratio of 1:1; and the corrosion inhibitor is a compound of calcium nitrite and benzotriazole in a mass ratio of 2:1.

[0038] Preferably, step S103 includes the following sub-steps: step S1031, coarse aggregate and fine aggregate are added to a forced mixer and mixed for 1 to 2 minutes; step S1032, modified coal gangue powder and composite curing agent are added to the forced mixer and mixed for 2 to 3 minutes; step S1033, mixing water is added in two batches and the mixture is discharged after wet mixing for 4 to 6 minutes.

[0039] Preferably, in step S104, the vibration stops when the surface of the composite solidified coal gangue mixture shows a slurry and no bubbles emerge, and the duration of single-point vibration is 40s to 70s.

[0040] Preferably, in step S105, the duration of sealed curing is 3 to 5 days; after the sealed curing is completed, the waterproof isolation film is removed, and the plant is naturally cured for 28 days under the condition that the relative humidity is not lower than 85%.

[0041] Preferably, during the wet mixing process in step S103, a chemical passivation layer is prepared on the surface of the coarse and fine aggregates by means of the active sites adsorbed on the surface of the corrosion inhibitor, in order to block the penetration of acidic water in the mine roadway into the interior of the hardened body.

[0042] Preferably, the mass ratio of coal gangue in the composite solidified coal gangue mixture is not less than 80%; and the compressive strength of the hardened body at 28 days is not less than 35 MPa.

[0043] Preferably, the composite solidified coal gangue mixture prepared by the methods in steps S101 to S103 is used in mine shotcrete support or industrial imitation stone products.

[0044] Example 1: This example combines Figures 1 to 2 This document describes a method for preparing a composite solidified coal gangue material for hardening the surface of mine roadways, as follows: Figure 1As shown, in step S101, raw coal gangue is crushed and screened into multi-sized aggregates and micro powders. The micro powders are then calcined and activated at 700℃ to 800℃ for 1.5h to 2.5h. After cooling, silane coupling agent and sodium stearate are added for ball milling and coating to prepare modified coal gangue micro powders. Subsequently, in step S102, silicate cement clinker, desulfurized gypsum, slag micro powder, fly ash, silica fume, quicklime, early-strength water-reducing agent, retarder, and corrosion inhibitor are thoroughly mixed in predetermined mass proportions to prepare a composite curing agent. After proceeding to step S103, coarse and fine aggregates, modified micro powders, and composite curing agent are added. The mixer performs dry mixing and wet mixing by spraying mixing water. By precisely controlling the amount of mixing water added, the moisture content of the mixture is maintained in the range of 9% to 11%, thus preparing the composite solidified coal gangue mixture. Then, in step S104, the mixture is laid on the ground to be hardened and its spreading thickness is controlled to be 150mm to 250mm. It is then compacted by high-frequency vibration equipment. Finally, in step S105, a waterproof isolation film is covered on the surface of the hardened body to prevent the internal moisture from migrating to the external environment. The volume expansion generated by the slaking of quicklime in the composite curing agent is used to offset the drying shrinkage of the hardened body during the hydration process.

[0045] like Figure 2 As shown, the process elements and mechanism of this composite solidified coal gangue material in hardening the mine roadway surface present a multi-dimensional synergistic logical structure. In terms of raw material activation and modification, the construction of the interface anchoring layer is promoted through the sorting of multi-grade aggregates and micro powders of coal gangue, calcination activation at 700℃ to 800℃, and ball milling coating of silane coupling agent and sodium stearate. In terms of multi-component solidification, the system integrates silicate cement clinker and desulfurized gypsum, slag micro powder, fly ash and silica fume, as well as calcium nitrite and benzo[a]trimethylammonium bicarbonate. The synergistic effect of nitrile inhibitors; in terms of mixing process control, emphasis is placed on dry and wet mixing in a forced mixer, with the moisture content controlled at 9% to 11% and the mixing water added in two stages; in terms of construction and maintenance mechanisms, high-frequency vibration is used until the slurry is precipitated and there are no air bubbles, waterproof isolation film is used for sealed maintenance, and the expansion force generated by quicklime slaking is used to offset the drying shrinkage stress, ultimately achieving the high-performance application of coal gangue materials in mine roadway surface hardening projects.

[0046] Example 2: Multi-scenario Adaptive Application and Collaborative Verification of High-Performance Composite Curing Coal Gangue Materials. This example aims to verify the adaptive broad-spectrum applicability and rheological control capability of the core technology matrix of modified coal gangue micropowder-multi-component composite curing agent in multiple engineering scenarios. Modified coal gangue micropowder and composite curing agent were prepared separately according to strict steps, wherein the total mass ratio of silane coupling agent and sodium stearate in modified coal gangue micropowder was 1.0%. Subsequently, aggregate, modified coal gangue micropowder and composite curing agent were put into forced-air... The mixture was dry-mixed in a mixer and wet-mixed with sprayed mixing water, controlling the total mass ratio of coal gangue in the mixture to be 82%, and maintaining the mass moisture content within the range of 9.5%~10.5%, thus obtaining the core composite solidified coal gangue mixture. To fully protect and verify the technical performance of this material under different extreme service conditions, the same batch of general-purpose mixture was parallelly diverted to the following two typical extended application scenarios for engineering verification: Verification direction A: Application in mine wet shotcrete support conditions, adjusting the coarse aggregate particle size in the mixture... The thickness is controlled within 10mm to 15mm. The mixture is then fed into a wet shotcrete machine, and continuously and evenly sprayed onto the surface of the surrounding rock wall to be supported in the mine using a high-pressure air source. The shotcrete thickness is controlled at 150mm. Due to the enormous high-frequency impact kinetic energy generated by the multi-stage aggregates inside the mixture during high-pressure spraying, a dense laitance quickly and adaptively precipitates on the surface of the shotcrete layer without any air bubbles emerging, forming a microscopic chemical passivation layer on the rock wall surface. Subsequently, a waterproof, insulating, and curing membrane is sprayed onto the outer surface of the shotcrete layer. To counteract stress buildup during the coagulation process of the shotcrete support layer, a closed-loop curing system was implemented for 4 days, followed by natural curing downhole for 28 days. The bond strength between the shotcrete support layer and the surrounding rock reached 2.4 MPa, and the compressive strength at 28 days reached 38.5 MPa. After 180 days of continuous service under alternating erosion from high-humidity water and acidic corrosive media downhole, the overall structure of the support layer remained intact, with no peeling, cracking, or sandblasting deterioration. This perfectly demonstrated the safe service of high-concentration solid waste in continuous shotcrete support scenarios downhole.

[0047] Verification Direction B: Production of high-value bulk solid waste-based industrial imitation stone products. The prepared core composite solidified coal gangue mixture is directly poured into a 600mm×600mm×50mm standard steel mold for building imitation stone. The mold is then locked onto a high-frequency vibration pressing table, and a composite vibration device is activated for heavy-duty compaction. Vibration continues for 60 seconds until a uniform slurry appears on the upper surface of the mold without any air bubbles. After compaction, a waterproof isolation film is immediately covered on the exposed upper surface of the mold and pressurized to seal it, completely preventing internal moisture from migrating to the external environment. After continuous curing in a sealed state for 4 days, the mold is demolded and placed in an environment with a relative humidity of 90%. The material is naturally cured in a curing room for 28 days. Finally, the hardened surface is mechanically micro-ground and polished to produce high-performance bulk solid waste-based imitation stone slabs. The surface of this imitation stone product is extremely dense, and its texture and physical feel are comparable to natural granite. Its 28-day compressive strength is as high as 42.1 MPa, and its water absorption rate is extremely low, less than 1.2%. Thanks to the hydrophobic layer and passivation barrier constructed on the surface of the micro powder by silane coupling agent and sodium stearate, this imitation stone exhibits excellent resistance to freeze-thaw cycles, heavy-load crushing, and staining and erosion. All technical indicators fully meet or partially exceed the technical standards of high-grade architectural decoration and heavy-duty paving imitation stone slabs for mining.

[0048] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention.

[0049] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a composite solidified coal gangue material for hardening the surface of a mine roadway, characterized in that, Includes the following steps: Step S101: The raw coal gangue is crushed and screened to form coarse aggregate with a particle size of 10 mm to 25 mm, fine aggregate with a particle size of 2 mm to 10 mm, and coal gangue powder with a particle size of no more than 0.075 mm. The coal gangue powder is calcined and activated at 700℃ to 800℃ for 1.5 h to 2.5 h. After cooling, silane coupling agent and sodium stearate are added for ball milling and coating to prepare modified coal gangue powder. Step S102: Mix 35 to 45 parts of silicate cement clinker, 5 to 8 parts of desulfurized gypsum, 20 to 30 parts of slag powder, 10 to 15 parts of fly ash, 3 to 6 parts of silica fume, 2 to 5 parts of quicklime, 1 to 3 parts of early-strength water-reducing agent, 0.5 to 1.5 parts of retarding synergist, and 1 to 2 parts of corrosion inhibitor according to the mass ratio to prepare a composite curing agent; Step S103: Coarse aggregate, fine aggregate, modified coal gangue powder and composite curing agent are put into a forced mixer for dry mixing and wet mixing by spraying mixing water to prepare composite cured coal gangue mixture; by controlling the amount of mixing water added, the mass moisture content of composite cured coal gangue mixture is maintained in the range of 9% to 11%. Step S104: The composite solidified coal gangue mixture is laid on the ground to be hardened in the mine roadway, with a paving thickness of 150mm to 250mm. The composite solidified coal gangue mixture is vibrated using a high-frequency vibration device. Step S105: Cover the surface of the hardened body with a waterproof isolation film. The waterproof isolation film blocks the migration of internal moisture of the composite solidified coal gangue mixture to the external environment, and utilizes the volume expansion generated by the slaking of quicklime in the composite curing agent to offset the drying shrinkage during the hydration process of the hardened body.

2. The method for preparing a composite solidified coal gangue material for hardening the surface of a mine roadway according to claim 1, characterized in that, In the modified coal gangue powder, the total mass ratio of silane coupling agent and sodium stearate is 0.5% to 1.5%; in step S103, the mass ratio of coarse aggregate, fine aggregate, modified coal gangue powder and composite curing agent is: 40 to 50 parts of coarse aggregate, 25 to 35 parts of fine aggregate, 8 to 12 parts of modified coal gangue powder and 6 to 10 parts of composite curing agent.

3. The method for preparing a composite solidified coal gangue material for hardening the surface of a mine roadway according to claim 1, characterized in that, In step S101, the ball milling coating is carried out at a stirring speed of 800 r / min to 1200 r / min, so that the silane coupling agent and sodium stearate form a hydrophobic layer on the surface of the coal gangue powder.

4. The preparation method of the composite solidified coal gangue material for hardening the surface of mine roadways according to claim 1, characterized in that, In step S102, the early-strength water-reducing agent is a polycarboxylate-based high-efficiency water-reducing agent; the retarding synergist is a compound of citric acid and sodium gluconate in a mass ratio of 1:1; and the corrosion inhibitor is a compound of calcium nitrite and benzotriazole in a mass ratio of 2:

1.

5. The method for preparing a composite solidified coal gangue material for hardening the surface of a mine roadway according to claim 1, characterized in that, Step S103 includes the following sub-steps: Step S1031, coarse aggregate and fine aggregate are put into a forced mixer and mixed for 1 min to 2 min; Step S1032, modified coal gangue powder and composite curing agent are added to the forced mixer and mixed for 2 min to 3 min; Step S1033, mixing water is added in two batches and the mixture is discharged after wet mixing for 4 min to 6 min.

6. The method for preparing a composite solidified coal gangue material for hardening the surface of a mine roadway according to claim 1, characterized in that, In step S104, vibration is stopped when slurry appears on the surface of the composite solidified coal gangue mixture and no bubbles emerge. The duration of single-point vibration is 40s to 70s.

7. The method for preparing a composite solidified coal gangue material for hardening the surface of a mine roadway according to claim 1, characterized in that, In step S105, the duration of sealed curing is 3 to 5 days; after the sealed curing is completed, the waterproof isolation film is removed, and the plant is naturally cured for 28 days under the condition that the relative humidity of the environment is not lower than 85%.

8. The method for preparing a composite solidified coal gangue material for hardening the surface of a mine roadway according to claim 4, characterized in that, In the wet mixing process of step S103, a chemical passivation layer is prepared on the surface of coarse and fine aggregates by adsorbing corrosion inhibitors onto the active sites on the surface of the coarse and fine aggregates, in order to block acidic water in the mine roadway from penetrating into the hardened body.

9. The method for preparing a composite solidified coal gangue material for hardening the surface of a mine roadway according to claim 1, characterized in that, The mass ratio of coal gangue in the composite solidified coal gangue mixture shall not be less than 80%; and the compressive strength of the hardened body at 28 days shall not be less than 35 MPa.

10. The method for preparing a composite solidified coal gangue material for hardening the surface of a mine roadway according to claim 1, characterized in that, Application of the composite solidified coal gangue mixture prepared by the methods in steps S101 to S103 in mine shotcrete support or industrial imitation stone products.

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