Grouting material based on coal gangue and preparation method thereof

Abstract

The invention discloses a grouting material based on coal gangue and a preparation method of the grouting material. The preparation method comprises the following steps: pretreating the coal gangue; uniformly stirring the pretreated coal gangue, cement and a novel magnesium expanding agent to obtain a first dry mixture; adding a polycarboxylic acid high-performance water reducing agent and cellulose nanocrystals into the first dry mixture, and uniformly stirring to obtain a second dry mixture; adding latex powder and a coupling agent into the second dry mixed material, and uniformly stirring to obtain a third dry mixed material; adding polyacrylonitrile fibers into the third dry blend, and uniformly stirring at a low speed to obtain a fourth dry blend; and mixing and stirring the fourth dry mixture and water to obtain the grouting material based on coal gangue. The pretreated coal gangue is used as the raw material, and the overall performance of the grouting material can be improved.

Description

Technical Field

[0001] This application relates to a grouting material, specifically to a grouting material based on coal gangue and its preparation method. Background Art

[0002] In current engineering construction, grouting materials are widely used in fields such as foundation reinforcement, tunnel lining, waterproofing and leakage stoppage. However, traditional grouting materials have problems such as insufficient strength, poor durability, and low environmental friendliness. These problems are particularly prominent when applied to complex geological conditions or occasions with high environmental protection requirements. As a solid waste, the large accumulation of coal gangue not only occupies land resources but may also cause environmental pollution. How to effectively utilize coal gangue to prepare high-performance grouting materials, which not only solves the problem of solid waste treatment but also meets the high-strength and high-durability requirements in engineering applications, has become a research hotspot. However, existing coal-gangue-based grouting materials often face problems such as insufficient activation, uneven component dispersion, and unreasonable additive ratio during the preparation process, resulting in the performance of the final product not reaching the ideal state. Therefore, this application aims to provide an efficient and environmentally friendly coal-gangue-based grouting material and its preparation method through a series of innovative pretreatment steps and reasonable formulation design to overcome the above technical problems and improve the overall performance of the grouting material. Summary of the Invention

[0003] Aiming at the deficiencies in the prior art, the main purpose of this application is to provide a coal-gangue-based grouting material and its preparation method, aiming to overcome the above technical problems and improve the overall performance of the grouting material.

[0004] To achieve the above objectives, this application provides the following technical solutions:

[0005] A coal-gangue-based grouting material, by mass, the grouting material includes: pretreated coal gangue: 50 - 70 parts; cement: 20 - 30 parts; novel magnesium-based expansive agent: 2 - 5 parts; polycarboxylate-based high-performance water reducer: 0.1 - 1 part; cellulose nanocrystals: 0.5 - 2 parts; latex powder: 5 - 10 parts; coupling agent: 0.5 - 1 part; polyacrylonitrile fiber: 0.5 - 1.5 parts; nano-silica: 3 - 5 parts; graphene: 0.05 - 0.2 part.

[0006] The present application also provides a preparation method of a grouting material based on coal gangue, and the method includes: pre-treating the coal gangue; uniformly stirring the pre-treated coal gangue, cement, and a novel magnesia-based expansive agent to obtain a first dry mixture; adding a polycarboxylate-based high-performance water reducer and cellulose nanocrystals to the first dry mixture, and uniformly stirring to obtain a second dry mixture; adding latex powder and a coupling agent to the second dry mixture, and uniformly stirring to obtain a third dry mixture; adding polyacrylonitrile fibers to the third dry mixture, and slowly stirring uniformly to obtain a fourth dry mixture; mixing and stirring the fourth dry mixture and water to obtain a grouting material based on coal gangue.

[0007] Optionally, the pre-treating the coal gangue includes: cleaning and drying the coal gangue; crushing the dried coal gangue; removing carbon from the crushed coal gangue; purifying the coal gangue after carbon removal; activating the purified coal gangue; performing high-pressure homogenization treatment on the activated coal gangue; ball-milling and drying the coal gangue after high-pressure homogenization treatment.

[0008] Optionally, carbon is removed from the crushed coal gangue by oxidation treatment.

[0009] Optionally, the coal gangue after carbon removal is purified by pickling and ultrasonic vibration.

[0010] Optionally, nanoparticles are introduced for high-pressure homogenization treatment of the activated coal gangue.

[0011] Optionally, low-temperature plasma is introduced for ball-milling the coal gangue after high-pressure homogenization treatment.

[0012] Optionally, nano-silica is added during the preparation of the second dry mixture.

[0013] Optionally, graphene is added during the preparation of the third dry mixture.

[0014] The present application can achieve the following beneficial effects: The present application provides an innovative grouting material based on coal gangue and its preparation method. Through a series of efficient pre-treatment steps and reasonable formulation design, it can not only effectively remove impurities in coal gangue and improve its activity and dispersibility, but also significantly enhance the mechanical properties, durability, and environmental protection characteristics of the grouting material, thus overcoming the problems existing in traditional grouting materials such as insufficient activation, uneven component dispersion, and unreasonable additive ratio, providing an efficient and environmentally friendly solution, and greatly improving the overall performance of the grouting material. Description of the Drawings

[0015] Figure 1 is a schematic flowchart of a preparation method of a grouting material based on coal gangue provided by an embodiment of the present application;

[0016] Figure 2 It is a schematic flow diagram of the pretreatment of coal gangue provided by another embodiment of the present application. Specific Embodiments

[0017] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present application.

[0018] It should be noted that all directional indications (such as up, down, left, right, front, back...) in the embodiments of the present application are only used to explain the relative positional relationship and movement conditions between components in a specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indications will also change accordingly.

[0019] In the present application, unless otherwise clearly defined and limited, the terms "connection", "fixation", etc. should be understood in a broad sense. For example, "fixation" can be a fixed connection, a detachable connection, or integrated; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two components or the interaction relationship between two components, unless otherwise clearly limited. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0020] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present application, the descriptions of "first", "second", etc. are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one such feature. In addition, the meaning of "and / or" appearing throughout the text includes three parallel solutions. Taking "A and / or B" as an example, it includes solution A, solution B, or a solution that satisfies both A and B at the same time. In addition, the technical solutions between various embodiments can be combined with each other, but it must be based on the ability of those of ordinary skill in the art to implement. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present application.

[0021] In an exemplary embodiment, the present application provides a grouting material based on coal gangue. By mass, the grouting material includes: pretreated coal gangue: 50 - 70 parts; cement: 20 - 30 parts; novel magnesia-based expansive agent: 2 - 5 parts; polycarboxylate-based superplasticizer: 0.1 - 1 part; cellulose nanocrystals: 0.5 - 2 parts; latex powder: 5 - 10 parts; coupling agent: 0.5 - 1 part; polyacrylonitrile fiber: 0.5 - 1.5 parts; nano-silica: 3 - 5 parts; graphene: 0.05 - 0.2 parts. Preferably, the material includes: pretreated coal gangue: 55 - 65 parts; cement: 22 - 28 parts; novel magnesia-based expansive agent: 2 - 4 parts; polycarboxylate-based superplasticizer: 0.3 - 0.7 part; cellulose nanocrystals: 1 - 2 parts; latex powder: 7 - 9 parts; coupling agent: 0.5 - 1 part; polyacrylonitrile fiber: 0.8 - 1.2 parts; nano-silica: 3 - 5 parts; graphene: 0.05 - 0.15 parts. More preferably, the material includes: pretreated coal gangue: 60 parts; cement 25 parts; novel magnesia-based expansive agent: 3 parts; polycarboxylate-based superplasticizer: 0.5 part; cellulose nanocrystals: 1.5 parts; latex powder: 8 parts; coupling agent: 0.8 part; polyacrylonitrile fiber: 1 part; nano-silica: 4 parts; graphene: 0.1 part.

[0022] Figure 1 FIG. is a schematic flow chart of a preparation method of a grouting material based on coal gangue provided by an exemplary embodiment of the present application, as Figure 1 described, the preparation method includes the following steps:

[0023] S1: Pretreat the coal gangue, as Figure 2 shown, specifically including the following steps:

[0024] S11: Wash the coal gangue to remove impurities, place the washed coal gangue in an infrared radiation device (infrared radiation can specifically heat the moisture in the coal gangue without overheating the fixed part in the coal gangue, which helps to avoid damage to the internal structure of the coal gangue or causing compositional changes, making the coal gangue more easily dispersed and more evenly distributed during subsequent mixing, thus contributing to improving the consistency and stability of the grouting material), heat and dry it at a temperature of 80°C - 150°C, and synchronously apply ultrasonic vibration during the infrared radiation process to promote the faster migration of the moisture inside the coal gangue to the surface and evaporation;

[0025] S12: First, place the dried coal gangue in a jaw crusher for preliminary crushing to break large pieces of coal gangue into smaller particles. Subsequently, use a counter - impact crusher for further crushing to reduce the particle size of the coal gangue. While crushing, screen the coal gangue to timely remove particles that have reached the required particle size and prevent over - crushing (over - pulverization will lead to unnecessary energy consumption increase and dust problems).

[0026] S13: Remove carbon from the crushed coal gangue.

[0027] In this step, removing carbon from the crushed coal gangue includes the following steps:

[0028] First, prepare an aqueous solution containing hydrogen peroxide (H2O2) and an appropriate catalyst (such as copper sulfate CuSO4 or iron ions Fe 3+ ). The choice of catalyst is based on its ability to promote the decomposition of H2O2 to produce free radicals with stronger oxidation ability.

[0029] Second, disperse the crushed coal gangue in the above oxidation solution and place it in a special microwave reactor. Set the microwave power and treatment time so that the coal gangue rapidly heats up under the action of the microwave field. At the same time, H2O2 rapidly decomposes under the action of the catalyst to generate strongly oxidizing hydroxyl radicals (·OH). These free radicals can efficiently attack and oxidize the carbon impurities in the coal gangue, converting them into carbon dioxide gas and discharging it. The local heating effect of the microwave can ensure that the oxidation process is more uniform and efficient. Compared with traditional heating methods, it can achieve better carbon removal effect at a lower temperature.

[0030] Finally, after completing the microwave - assisted oxidation treatment, transfer the coal gangue to an ultrasonic cleaning tank filled with deionized water and start the ultrasonic device. High - frequency vibration helps to peel off the possibly remaining oxidation products and unreacted chemicals, and promotes the dispersion of fine particles to prevent agglomeration.

[0031] This application conducts wet oxidation treatment on crushed coal gangue through microwave assistance, which can achieve efficient carbon removal at a relatively low temperature and requires a lower temperature compared to traditional high-temperature sintering. Therefore, energy consumption can be reduced. Additionally, by using an aqueous solution containing hydrogen peroxide (H2O2) and an appropriate amount of catalyst, and placing the crushed coal gangue in a microwave reactor, the coal gangue is rapidly heated under the action of the microwave field. Meanwhile, H2O2 rapidly decomposes under the action of the catalyst to generate strongly oxidizing hydroxyl radicals (·OH). These radicals can efficiently attack and oxidize the carbon impurities in the coal gangue, converting them into carbon dioxide gas and discharging it. Compared with high-temperature sintering, this method can achieve better carbon removal effect at a lower temperature (microwave can specifically heat the moisture and other polar molecules in the coal gangue without overheating the coal gangue itself. This selective heating can lead to the generation of local high-temperature regions inside the coal gangue, which is conducive to accelerating the chemical reaction rate, especially for reactions that require a relatively high temperature, such as the decomposition of H2O2 to generate hydroxyl radicals (·OH). In contrast, high-temperature sintering uniformly heats the entire system and is difficult to achieve the same local high-temperature effect. Additionally, under the action of the microwave field, the decomposition rate of H2O2 increases significantly, and with the help of a catalyst (such as copper sulfate CuSO4 or iron ions Fe 3+ ), strongly oxidizing hydroxyl radicals (·OH) can be generated more efficiently. These radicals have strong oxidation ability and can quickly attack and oxidize the carbon impurities in the coal gangue, converting them into carbon dioxide gas and discharging it. During the traditional high-temperature sintering process, although some carbon can be removed, its efficiency and thoroughness are far inferior to the oxidation treatment assisted by microwave). Since the oxidation treatment can effectively remove the carbon impurities in the coal gangue, the surface of the coal gangue particles becomes cleaner, which is beneficial to subsequent activation treatment and the compatibility and synergistic effect with other additives, thus contributing to the formation of a more uniform and stable grouting material system.

[0032] S14: Chemically purify the coal gangue after carbon removal;

[0033] In this step, chemically purifying the coal gangue after carbon removal specifically includes the following steps:

[0034] First, put the coal gangue after carbon removal into a reaction vessel containing dilute hydrochloric acid (HCl) or dilute sulfuric acid (H2SO4) solution. The solution concentration is controlled between 0.5 M and 1 M, and the soaking time is 2 to 4 hours. This step is mainly used to dissolve and remove carbonate and other acid-soluble impurities on the surface and in the pores of the coal gangue.

[0035] Second, after the preliminary acid washing is completed, immediately transfer the coal gangue to an ultrasonic cleaning tank and add an appropriate amount of deionized water. Start the ultrasonic equipment and use high-frequency vibration to further peel off the residues attached to the surface and in the tiny pores inside the coal gangue.

[0036] Next, put the ultrasonically cleaned coal gangue into a container containing a solution of sodium hydroxide (NaOH) or sodium carbonate (Na2CO3). The solution concentration is controlled between 0.1 M and 0.5 M, and the treatment time is 1 to 2 hours. The alkaline treatment helps to neutralize any residual acidic substances and can react with the silicon-aluminum components in the coal gangue to form a surface structure that is beneficial for subsequent activation treatment.

[0037] Finally, repeat the operation in the second step and ultrasonically clean the alkaline-treated coal gangue with deionized water to ensure that all chemical residues are completely removed.

[0038] S15: Microwave-assisted activation of the purified coal gangue;

[0039] In this step, first evenly disperse the purified coal gangue in the reactor, and then add an appropriate amount of chemical activator (such as an alkaline solution or an acidic solution) into the reactor to help open up some structures of the coal gangue, increase its surface area and porosity, and create conditions for subsequent microwave activation. Then, perform multi-band microwave pulse treatment on the coal gangue, which specifically includes the following steps:

[0040] First, apply microwave pulses at a lower frequency (such as 915 MHz). The microwaves at this frequency can penetrate deep into the internal structure of the coal gangue, heat and activate the internal mineral components.

[0041] Then switch to microwave pulses at a higher frequency (such as 2.45 GHz). This frequency is more suitable for rapid surface heating, helps to remove surface-adsorbed impurities and further expand the pore structure.

[0042] After the microwave treatment is completed, quickly remove the reactor from the microwave environment and let it cool naturally or use a gentle method to accelerate the cooling process to avoid damage to the internal structure of the coal gangue caused by sudden cooling.

[0043] In this application, microwave-assisted purification of the purified coal gangue can effectively open up some structures of the coal gangue, increase its surface area and porosity, help to enhance the chemical reaction activity between the coal gangue and cement and other additives, and thus improve the overall performance of the grouting material. In addition, due to its more open and porous structure, the coal gangue after microwave-assisted activation can better combine with other components to form a more solid and stable structural system, which will directly lead to a significant improvement in the mechanical properties such as the compressive strength and flexural strength of the grouting material. More importantly, the coal gangue after microwave-assisted activation can form a three-dimensional network structure, which can effectively prevent moisture, oxygen and other corrosive media from invading the interior of the grouting material, delay the aging process of the grouting material, and thus enhance the long-term durability and corrosion resistance of the grouting material.

[0044] S16: Perform high-pressure homogenization treatment on the activated coal gangue;

[0045] In this step, first, the activated coal gangue is dispersed in a suitable liquid medium (such as water) to form a suspension with a certain concentration. Second, an appropriate amount of nanoparticles (such as nano-silica, nano-aluminum oxide, etc.) is added to the suspension. These nanoparticles can physically adsorb or chemically bond with the surface of the coal gangue particles under high-pressure conditions, helping to fill the tiny defects inside and on the surface of the coal gangue, thereby enhancing its structural stability and reactivity. Finally, the coal gangue suspension containing nanoparticles is placed in a high-pressure pulsed device (such as a high-pressure homogenizer), and a series of high-intensity pressure pulses (several hundred megapascals or higher) are applied to the suspension to further refine the coal gangue particles and achieve a highly uniform distribution. By introducing nanoparticles in this application, not only can the tiny defects inside the coal gangue be filled, but it also helps to improve its compatibility and synergistic effect with other additives, thus facilitating the preparation of higher-quality grouting materials.

[0046] S17: Ball mill and dry the coal gangue after high-pressure homogenization treatment;

[0047] In this step, first, the coal gangue after high-pressure homogenization treatment is loaded into a dynamic ball mill tank, and a low-temperature plasma generator (such as a radio-frequency plasma source or a microwave plasma source) is set inside or outside the ball mill tank to generate low-temperature plasma. Start the low-temperature plasma generator, and continuously introduce low-temperature plasma into the ball mill tank during the ball milling process.

[0048] It should be noted that compared with the conventional ball milling process, the introduction of low-temperature plasma can more effectively break the aggregation between coal gangue particles, promote the effective refinement of particles, and also increase the specific surface area of the coal gangue, thereby enhancing its activity. In addition, through plasma treatment, the impurities and oxide layers on the surface of the coal gangue particles can be removed, making the surface of the coal gangue particles cleaner. Due to the fact that the coal gangue particles after plasma ball milling are clean and activated on the surface, they show better dispersibility when mixed with other materials, thus helping to form a more uniform and stable grouting material system, and further improving the performance of the final product.

[0049] Furthermore, the ball-milled coal gangue is evenly spread in a microwave drying device for drying. During the drying process, the coal gangue needs to be kept in a slightly stirred or turned state, which helps to promote the uniform distribution of heat and moisture and avoid local overheating or uneven drying. It should be noted that during the drying process, the present application adopts a staged drying strategy, that is, the microwave drying equipment is first set to a higher power to quickly remove most of the free water in the coal gangue, and then switched to a lower power to finely remove bound water and other residual moisture. By adopting a staged drying strategy, the drying speed can be guaranteed and the physical and chemical properties of the coal gangue can be protected from damage.

[0050] S2: adding the pretreated coal gangue, cement and novel magnesium expansion agent into a high-speed shear mixer and stirring them fully to obtain a first dry mix;

[0051] In this step, the three components of coal gangue, cement and new magnesium expansion agent constitute the basic skeleton structure of the grouting material. Through the strong stirring of the high-speed shear mixer, these components can achieve a good dispersion effect, laying the foundation for the subsequent addition of additives.

[0052] S3: adding a polycarboxylic acid-based high-performance water reducer and cellulose nanocrystals to the first dry blend, and stirring evenly to obtain a second dry blend;

[0053] In this step, the water reducer is mainly used to reduce the amount of water while maintaining fluidity and improving the working performance of the grouting material. Cellulose nanocrystals can enhance the mechanical strength and toughness of the grouting material. Adding these two ingredients at this stage and fully mixing them with the first dry mix helps them to be evenly dispersed in the system.

[0054] S4: adding latex powder and coupling agent to the second dry blend, and stirring to obtain a third dry blend;

[0055] In this step, the latex powder can improve the cohesiveness and durability of the grouting material, while the coupling agent is used to enhance the compatibility between the different components. Adding these two components at this stage and stirring them can better combine them with the second dry mix.

[0056] S5: adding polyacrylonitrile fiber to the third dry blend, and stirring at a low speed to obtain a fourth dry blend;

[0057] In this step, polyacrylonitrile fibers can significantly improve the crack resistance and toughness of the grouting material. Since the fibers are prone to entanglement, low-speed stirring is required to avoid fiber breakage or agglomeration and ensure that they can be evenly distributed in the grouting material.

[0058] S6: Mixing and stirring the fourth dry mixed material and water to obtain a grouting material based on coal gangue.

[0059] In this step, the present application adopts a method of adding water in stages. First, about 70% of the total amount of water is added, and then the remaining water is gradually added until a suitable consistency and fluidity are achieved. It should be noted that by initially adding most of the water, a basic mixing system can be quickly formed, enabling the fourth dry mix to start preliminary fusion. This helps ensure that all solid components are fully wetted and begin to be preliminarily dispersed, laying a foundation for subsequent fine adjustment. If all the water is added at once, the fourth dry mix may become too thin, making it difficult for the components within the fourth dry mix to bind well with each other, thus affecting the formation and stability of the initial structure of the grouting material.

[0060] It should be noted that the reason for adding the above materials in batches in the present application is as follows:

[0061] 1) Different components have different physical and chemical properties. For example, basic skeleton materials such as cement and coal gangue have significant differences in particle size, density, and morphology from additives such as polycarboxylate-based high-performance water reducers and cellulose nanocrystals. If all components are added at once, it may cause some components to not be fully dispersed, affecting the uniformity and stability of the final grouting material.

[0062] 2) Additives such as polycarboxylate-based high-performance water reducers need to work under specific conditions to achieve the best performance. By first mixing the basic skeleton materials (such as pretreated coal gangue, cement, and new magnesium-based expansive agent) evenly to form the first dry mix, and then gradually adding other components (such as water reducers, cellulose nanocrystals, latex powder, coupling agent, and polyacrylonitrile fiber), a relatively stable and uniform basic environment can be provided for these additives, which helps them play their roles better.

[0063] 3) Polyacrylonitrile fibers are prone to entanglement, and adding them at low speed can avoid fiber breakage or agglomeration; while adding water in stages helps to quickly form a basic mixing system and gradually adjust to the ideal consistency and fluidity, ensuring the good working performance of the grouting material.

[0064] In summary, the present application adds each material in batches based on the understanding of the component characteristics and the need for precise control of the preparation process, aiming to achieve the best dispersion effect, promote chemical reactions, avoid adverse reactions, and facilitate process control, thereby being beneficial to improving the overall performance of the coal gangue-based grouting material.

[0065] In another exemplary embodiment, the present application also provides a method for preparing a coal gangue-based grouting material. Different from the previous embodiment, in this embodiment, nano-silica is added during the preparation of the second dry mix.

[0066] In this embodiment, nano-silica has extremely high activity and small particle size, and can form a uniformly dispersed microstructure during the preparation of the grouting material. It undergoes a secondary reaction with cement and other matrix materials, which can effectively reduce the micro-cracks and pores inside the grouting material, thereby increasing the density of the grouting material, and further improving the mechanical properties such as the compressive strength and flexural strength of the grouting material. In addition, nano-silica can also accelerate the hydration process of cement and promote the development of the early strength of the grouting material, thus effectively improving the construction efficiency and shortening the construction period.

[0067] This application compared the performance of the grouting material prepared by adding nano-silica with that of the previous embodiment, as shown in Table 1 specifically:

[0068] Table 1

[0069]

[0070] As can be seen from Table 1, compared with the case without adding nano-silica, the grouting material prepared after adding nano-silica has been greatly improved in various performance indicators.

[0071] In another exemplary embodiment, this application also provides a preparation method of a grouting material based on coal gangue. Different from the previous embodiment, graphene is added in the process of preparing the third dry mixture in this embodiment.

[0072] In this embodiment, graphene has extremely high strength and rigidity. By adding graphene, the compressive strength, tensile strength and elastic modulus of the grouting material can be greatly improved. Graphene can form a three-dimensional network structure in the matrix, effectively transfer the load and prevent crack propagation, thereby enhancing the overall mechanical properties of the grouting material. In addition, due to the chemical stability and physical barrier effect of graphene, it can effectively prevent moisture, oxygen and other corrosive media from invading the inside of the grouting material, thereby delaying the aging process of the grouting material and enhancing the long-term durability and corrosion resistance of the grouting material.

[0073] This application compared the performance of the grouting material prepared by adding graphene with that of the previous embodiment, as shown in Table 2 specifically:

[0074] Table 2

[0075]

[0076]

[0077] As can be seen from Table 2, compared with the previous embodiment, in this embodiment, the grouting material prepared after adding graphene shows higher compressive strength, flexural strength, lower porosity and water absorption, and better early strength development.

[0078] In this embodiment, during the preparation of the third dry-mixed material, a shape memory polymer (such as polyurethane, polycaprolactone) is further added (which needs to be added after the latex powder and the coupling agent). The role of the coupling agent is to enhance the compatibility and adhesion between different components, and the presence of the shape memory polymer can help the coupling agent disperse better in the entire mixing system, and form a more compact interfacial bond during the curing process, which helps to improve the consistency and stability of the overall structure of the grouting material. By introducing the shape memory polymer, it can form an "intelligent" network structure inside the grouting material. When the grouting material has tiny cracks, through appropriate external stimuli (such as temperature changes), the shape memory polymer can return to its original form, thereby closing the cracks and preventing further expansion, thus improving the durability and service life of the grouting material.

[0079] Based on the above embodiment, the present application further adds microcapsules containing a repair agent during the preparation of the fourth dry-mixed material. When microcracks appear inside the grouting material, the microcapsules rupture and release the repair agent. These repair agents can fill the cracks in the grouting material and undergo chemical reactions to form a solidified substance to close the cracks, thereby preventing the cracks from further expanding, and thus extending the service life of the grouting material. By instantly repairing minor damages, the intrusion paths of moisture, oxygen, and other corrosive media can be significantly reduced, thereby slowing down the aging process of the grouting material and improving its long-term durability and corrosion resistance.

[0080] The present application compares the properties of the coal gangue after the above pretreatment, the coal gangue without any pretreatment, and the coal gangue after grinding treatment. The specific comparison results are shown in Table 3 as follows:

[0081] Table 3

[0082]

[0083] As can be seen from Table 1, the coal gangue pretreated in the present application has finer particles and a cleaner surface, so it has the best dispersibility and the highest reaction activity index, which is beneficial to accelerating the curing process of the grouting material.

[0084] Furthermore, the present application compares the properties of the grouting materials prepared from the coal gangue after the above pretreatment, the coal gangue without any pretreatment, and the coal gangue after grinding treatment. The specific comparison results are shown in Table 4 as follows:

[0085] Table 4

[0086]

[0087] As can be seen from Table 2, compared with the gangue without any pretreatment and the gangue after grinding treatment, the properties of the grouting material prepared from the pretreated gangue in this application are the best, which

[0088] demonstrates the superiority of the pretreatment method described in this application in improving the properties of the grouting material.

[0089] Based on the above embodiments, after obtaining the grouting material in this application, the grouting material is also subjected to vacuum degassing treatment to remove air bubbles in the grouting material, thereby improving the density and strength of the grouting material.

[0090] Based on the above embodiments, this application also introduces an interfacial modification technology into the grouting material. Specifically, before mixing the pretreated gangue with cement, a layer of nano-silica or graphene oxide is coated on the surface of the gangue. Nano-silica and graphene oxide have extremely high specific surface areas, which can provide more contact points to physically and chemically interact with the cement matrix, helping to form a more compact interfacial bond, thereby enhancing the bonding force between the gangue and the cement matrix. In addition, the introduction of nano-silica and graphene oxide helps to reduce the agglomeration phenomenon between gangue particles, enabling them to be more evenly distributed in the cement matrix. Good dispersibility not only helps to improve the uniformity of the grouting material but also avoids stress concentration points caused by local aggregation, thereby improving the mechanical properties of the grouting material.

[0091] It should be noted that the cement used in this application is low-carbon cement (such as alkali-activated cementitious materials). By using low-carbon cement, the carbon emissions during the preparation of the grouting material can be reduced. In addition, the gel structure formed by low-carbon cement is denser than that of ordinary Portland cement. This more compact microstructure can effectively reduce the porosity and permeability, thereby improving the overall durability of the grouting material. At the same time, low-carbon cement can also reduce the intrusion paths of water and other corrosive substances, further enhancing the corrosion resistance of the grouting material.

[0092] The above are only the preferred embodiments of this application, and do not limit the patent scope of this application. Any equivalent structural or equivalent process transformation made using the content of the specification and drawings of this application, or directly or indirectly applied in other related technical fields, shall be equally included in the patent protection scope of this application.

Claims

1. A grouting material based on coal gangue, characterized in that: In parts by mass, the grouting material comprises: Pretreated coal gangue: 50-70 parts; Cement: 20-30 parts; New magnesium expansion agent: 2-5 parts; Polycarboxylic acid high performance water reducing agent: 0.1 to 1 part; Cellulose nanocrystals: 0.5-2 parts; Latex powder: 5-10 parts; Coupling agent: 0.5-1 part; Polyacrylonitrile fiber: 0.5-1.5 parts; Nano silicon dioxide: 3-5 parts; Graphene: 0.05-0.2 parts.

2. A method for preparing a grouting material based on coal gangue, characterized in that: The method comprises: Pre-treatment of coal gangue; The pretreated coal gangue, cement and new magnesium expansion agent are uniformly stirred to obtain a first dry mixture; Adding a polycarboxylic acid-based high-performance water reducing agent and cellulose nanocrystals to the first dry blend, and stirring evenly to obtain a second dry blend; Adding latex powder and coupling agent to the second dry blend, and stirring evenly to obtain a third dry blend; Adding polyacrylonitrile fiber to the third dry blend, and stirring at a low speed to obtain a fourth dry blend; The fourth dry mix and water are mixed and stirred to obtain a gangue-based grouting material.

3. The method for preparing a grouting material based on coal gangue according to claim 2, characterized in that: The pretreatment of the coal gangue comprises: Clean and dry the coal gangue; Crushing the dried coal gangue; Decarbonize the crushed coal gangue; Purify the coal gangue after carbon removal; Activate the purified coal gangue; The activated coal gangue is subjected to high pressure homogenization treatment; The coal gangue after high pressure homogenization treatment is ball milled and dried.

4. The method for preparing a grouting material based on coal gangue according to claim 3, characterized in that: The crushed coal gangue is decarbonized through oxidation treatment.

5. The method for preparing a grouting material based on coal gangue according to claim 3, characterized in that: The coal gangue after decarbonization is purified by acid washing and ultrasonic vibration.

6. The method for preparing a grouting material based on coal gangue according to claim 3, characterized in that: The purified coal gangue is activated with the assistance of microwaves.

7. The method for preparing a grouting material based on coal gangue according to claim 3, characterized in that: The activated coal gangue is homogenized under high pressure by introducing nanoparticles.

8. The method for preparing a grouting material based on coal gangue according to claim 3, characterized in that: The coal gangue after high pressure homogenization treatment is ball milled by introducing low temperature plasma.

9. The method for preparing a grouting material based on coal gangue according to claim 2, characterized in that: Nano silicon dioxide is added during the preparation of the second dry blend.

10. The method for preparing a grouting material based on coal gangue according to claim 2, characterized in that: Graphene is added during the preparation of the third dry blend.

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