Anti-bleeding high-rheological coal gangue grouting filling material and preparation method and application thereof

Abstract

This invention discloses a coal gangue grouting and filling material with high rheological resistance and resistant to bleeding, its preparation method, and its application, relating to the field of mine filling material technology. The grouting and filling material, by mass percentage, comprises: 70%~75% coal gangue, 0.55%~2.3% composite rheology modifier, and the balance being water; wherein the composite rheology modifier includes an air-entraining agent and a dispersant, with a mass ratio of (90~99):(1~10); the air-entraining agent is a surface-active foaming material, and the dispersant is a phosphate additive. In its preparation, coal gangue is first mixed with water and stirred to obtain an initial slurry; then the air-entraining agent and dispersant are mixed to prepare the composite rheology modifier; finally, the composite rheology modifier is added to the initial slurry and stirred until homogeneous to obtain the grouting and filling material. This grouting and filling material uses coal gangue as the main raw material, has a simple preparation process, and possesses excellent fluidity, stability, and pumpability.

Description

Technical Field

[0001] This invention belongs to the technical field of mine backfill materials, specifically relating to a coal gangue grouting backfill material resistant to bleeding and high rheology, its preparation method, and its application. Background Technology

[0002] With the rapid development of the coal industry, the output of coal gangue, as a major associated waste, has been increasing year by year, and its resource utilization has become an important issue for the sustainable development of the coal industry. Using coal gangue as a grouting and backfilling material in mine goaf areas can not only solve the problems of land occupation and environmental pollution caused by coal gangue storage, but also meet the backfilling needs for safe mine production, thus having significant economic and environmental benefits.

[0003] Currently, the application of coal gangue in grouting and filling has a certain technological foundation. Chinese invention patent CN112897964A discloses a waste coal mine filler based on coal gangue, which improves the strength and corrosion resistance of the filler by adding components such as cement, sand, and fly ash. Chinese invention patent CN114542171A proposes an improved method for grouting and filling materials for overburden isolation, using only coal gangue powder as the main material, and improving fluidity and reducing sedimentation rate by adding suspending additives. Furthermore, regarding the improvement of the rheological properties of grouting and filling materials, Chinese invention patent CN108358496B discloses a rheology modifier for red mud and fly ash grouting and filling materials, which significantly improves the material's fluidity through the compounding of components such as naphthalene-based water-reducing agents and air-entraining agents.

[0004] However, existing technologies for grouting and backfilling of coal gangue still have many technical shortcomings. First, coal gangue contains a large amount of clay minerals such as kaolin and montmorillonite, which easily form colloidal structures in water, significantly increasing the viscosity of the system and affecting the pumpability of the grout. Second, the uneven particle size distribution after coal gangue crushing exacerbates the internal mechanical imbalance of the grout, easily leading to segregation and stratification, resulting in unstable backfilling quality. Third, the admixtures used in existing technologies, such as fly ash, slag, and silica fume, have limited effectiveness in counteracting mud disturbance, especially when the mud activity of the coal gangue is high. Furthermore, mud particles in the grout easily undergo complex reactions with the hydration products of cementitious materials, causing low early strength and loose structure, and increasing the risk of pipe blockage, seriously affecting the efficiency and quality of backfilling construction. Summary of the Invention

[0005] To overcome the technical problems of poor fluidity, easy segregation and bleeding, and poor pumping performance of existing coal gangue grouting and filling materials due to high clay content, this invention provides a coal gangue grouting and filling material with high rheological properties and bleeding resistance, as well as its preparation method and application. Through the synergistic effect of composite air-entraining agent and phosphate additives, the grout structure is optimized and the rheological properties are improved, significantly improving the filling construction efficiency and safety.

[0006] To achieve the above objectives, the present invention employs the following technical solution: In a first aspect, the present invention provides a coal gangue grouting and filling material with high rheology resistance and water seepage resistance, comprising the following components by mass percentage: 70%~75% coal gangue, 0.55%~2.3% composite rheology modifier, and the balance being water; The composite rheology modifier includes an air-entraining agent and a dispersant, wherein the mass ratio of the air-entraining agent to the dispersant is (90~99):(1~10).

[0007] A further improvement of the present invention is that the air-entraining agent is a surface-active foaming material, and the dispersant is a phosphate additive; wherein the phosphate additive is selected from at least one of sodium tripolyphosphate, aluminum phosphate, and sodium phosphate.

[0008] A further improvement of the present invention is that the dispersant is sodium tripolyphosphate, and the sodium tripolyphosphate accounts for 0.05~0.15% of the total mass of the coal gangue grouting filling material.

[0009] A further improvement of the present invention is that the surface-active foaming material is a rosin-based air-entraining agent.

[0010] A further improvement of the present invention is that the rosin-based air-entraining agent is maleic rosin.

[0011] A further improvement of the present invention is that the rosin is a water-soluble saponified product generated by the saponification reaction of sodium hydroxide, wherein the mass ratio of rosin, sodium hydroxide and water is (60~65):(10~15):(20~30).

[0012] Secondly, the present invention also provides a method for preparing the above-mentioned coal gangue grouting and backfilling material resistant to bleeding and high rheology, comprising the following steps: Step 1: Mix coal gangue with water and stir to obtain the initial slurry; Step 2: Mix the air-entraining agent and the dispersant according to the specified ratio to prepare a composite rheology modifier; Step 3: Add the composite rheology modifier obtained in Step 2 to the initial slurry obtained in Step 1, stir evenly, and obtain the coal gangue grouting and filling material with high rheology and resistance to bleeding.

[0013] A further improvement of the present invention is that the preparation method of the composite rheology modifier in step 2 is as follows: first, sodium hydroxide is dissolved in water, then mixed and stirred with maleic rosin heated to a liquid state, and after cooling, a paste is obtained. The paste is diluted with water to prepare an air-entraining agent solution. Finally, a dispersant is added to the air-entraining agent solution and mixed evenly to obtain the composite rheology modifier.

[0014] A further improvement of the present invention is that the stirring temperature in step 3 is 10~35℃ and the stirring time is 5~15min.

[0015] Thirdly, the present invention also provides the application of the above-mentioned anti-bleeding and high-rheology coal gangue grouting and filling material in the grouting and filling project of the goaf in the mine.

[0016] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a coal gangue grouting and filling material with high rheological resistance and resistance to bleeding. By limiting the coal gangue content to 70%~75%, it achieves high-value utilization of solid waste while providing skeletal support for the grout. The addition of a composite rheology modifier at 0.55%~2.3% can fully exert its modifying effect while avoiding excessive introduction that would affect strength. The air-entraining agent and dispersant work synergistically at a mass ratio of 90~99:1~10: the air-entraining agent introduces a micron-sized bubble network during stirring, reducing direct contact and friction between particles and lowering apparent viscosity; the dispersant dissociates to generate negative charges, which synergistically work with the bubbles to make the coal gangue particles strongly negatively charged, generating strong electrostatic repulsion, effectively destroying the flocculated structure formed by clay minerals and releasing the trapped free water. Test data shows that the initial spread of this material can reach 930~996mm, an improvement of approximately 41%~51% compared to materials without composite rheology modifiers; the bleeding rate after 2 hours of standing is 0%, completely solving the problem of conventional materials having a bleeding rate as high as 4.2%~18.8%; at the same time, the slump retention rate after 2 hours exceeds 90%, and the pressure loss in the pumping straight pipe is only 4.8~5.1 MPa / km. The core fluidity and anti-bleeding indicators represent a significant breakthrough, meeting the engineering application requirements for high rheological and high-stability materials in grouting and filling of mining goaf areas.

[0017] This invention also provides a method for preparing a high-rheology coal gangue grouting material resistant to bleeding. First, coal gangue is mixed with water to obtain an initial slurry, ensuring the coal gangue particles are fully wetted and dispersed in the water, creating a uniform dispersion environment for subsequent modification. Then, an air-entraining agent and a dispersant are pre-mixed in a specific ratio to prepare a composite rheology modifier, avoiding the uneven distribution or incomplete local reactions that might result from separate additions. Finally, the composite rheology modifier is added to the initial slurry and stirred evenly. This post-addition method allows the composite rheology modifier to precisely act on the particle surface after the slurry is formed. The entire method is simple and easy to operate, requiring no complex equipment or stringent parameter control. Test data shows that this method can stably and efficiently prepare high-performance materials with an expansion of 930-996 mm and no bleeding upon standing. The process steps are simplified, parameters are controllable, and the proportion of coal gangue in the raw materials is as high as 70%-75%, resulting in high solid waste utilization and significant cost advantages. It is more suitable for large-scale industrial production in mine backfilling projects and has good industrialization prospects. Attached Figure Description

[0018] The accompanying drawings described herein are for illustrative purposes only and are not intended to limit the scope of the invention in any way. Furthermore, the shapes and proportions of the components in the drawings are merely illustrative to aid in understanding the invention and do not specifically limit the shapes and proportions of the components of the invention.

[0019] Figure 1 The apparent viscosity of the grouting filling material obtained in Examples 1-3 of this invention varies with shear rate. Figure 2 The curves showing the variation of shear stress with shear rate for the grouting filling materials obtained in Examples 1-3 of this invention are shown. Figure 3 The apparent viscosity of the slurry obtained in Comparative Examples 1-3 of this invention varies with shear rate. Figure 4 The curves showing the change of shear stress with shear rate for the slurries obtained in Comparative Examples 1-3 of this invention are shown. Detailed Implementation

[0020] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0021] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0022] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0023] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0024] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0025] This invention provides a coal gangue grouting and filling material with high rheological resistance and water seepage resistance, comprising the following components by mass percentage: 70%~75% coal gangue, 0.55%~2.3% composite rheology modifier, and the balance being water; wherein the composite rheology modifier includes an air-entraining agent and a dispersant, and the mass ratio of the air-entraining agent to the dispersant is (90~99):(1~10).

[0026] Specifically, the air-entraining agent is a surface-active foaming material, and the dispersant is a phosphate additive; wherein the phosphate additive is selected from at least one of sodium tripolyphosphate, aluminum phosphate, and sodium phosphate.

[0027] Preferably, the dispersant is sodium tripolyphosphate, and the sodium tripolyphosphate accounts for 0.05~0.15% of the total mass of the coal gangue grouting filling material.

[0028] Preferably, the surface-active foaming material is a rosin-based air-entraining agent, specifically maleic rosin. Using maleic rosin as an air-entraining agent, the rosin soap produced by its reaction with alkali exhibits excellent foaming performance and bubble stability, capable of forming a uniform and dense bubble network.

[0029] The rosin is a water-soluble saponified product generated by the saponification reaction of sodium hydroxide, wherein the mass ratio of rosin, sodium hydroxide and water is (60~65):(10~15):(20~30).

[0030] This invention also provides a method for preparing a coal gangue grouting and backfilling material resistant to bleeding and high rheology, comprising the following steps: Step 1: Mix coal gangue with water and stir to obtain the initial slurry; Step 2: Mix the air-entraining agent and the dispersant according to the specified ratio to prepare a composite rheology modifier; Specifically, sodium hydroxide is first dissolved in water, then mixed and stirred with rosin heated to a liquid state, and after cooling, a paste is obtained. This paste is then diluted with water to prepare an air-entraining agent solution. Finally, a dispersant is added to the air-entraining agent solution and mixed evenly to obtain a composite rheology modifier.

[0031] Step 3: Add the composite rheology modifier obtained in Step 2 to the initial slurry obtained in Step 1, and stir at 10~35℃ for 5~15 minutes to obtain the coal gangue grouting and filling material with high rheology and resistance to bleeding.

[0032] The present invention also provides an application of a coal gangue grouting and filling material with high rheological resistance to bleeding in the grouting and filling project of mining goaf.

[0033] The anti-bleeding and high-rheology coal gangue grouting filling material proposed in this invention mainly achieves modification and flowability improvement of high-mud coal gangue through the following four synergistic mechanisms: (1) Air-entraining agent microstructure construction mechanism. The air-entraining agent introduces micron-sized bubbles during the stirring process, forming a uniformly dispersed bubble network structure in the slurry, reducing the direct contact and friction between particles inside the slurry, reducing the apparent viscosity; increasing the particle migration space, improving the lubricity of the flow interface; buffering the disturbance of mud particles, preventing the slurry structure from being destroyed. This mechanism enables the slurry to obtain foam-like structural support, thereby maintaining good rheological properties during transportation. (2) Phosphate reaction gel mechanism. Phosphate additives (such as aluminum phosphate and sodium phosphate) form phosphate gels or composite hydrates with calcium ions and aluminum ions in the alkaline cement environment, improving the bonding strength between particles, building a stable skeleton; reducing the interference of mud particles on the cement hydration reaction; enhancing early strength, and improving the stability of the slurry structure. This gel acts as a "bridge" in the microstructure, enhancing the consistency and anti-segregation performance of the slurry. (3) Slurry interference inhibition mechanism. Through the synergistic effect of microbubble dispersion and gel enhancement, a composite regulatory structure is formed inside the slurry, and the slurry is separated by the bubble and gel structure; the factors that interfere with hydration due to slurry water absorption are adsorbed by the stabilizer or diluted by the composite reaction; fine particle agglomeration is blocked and dispersed by bubbles, and is stabilized by gel adsorption. (4) Electrostatic repulsion mechanism. The clay minerals in coal gangue are rich in Ca 2+ Mg 2+ Fe 3+High-valence metal ions, negatively charged bubbles generated by the air-entraining agent, and the negative charge dissociated from sodium tripolyphosphate give the particle surface a negative charge. This charge strongly adsorbs the positively charged coal gangue particles, increasing the negative charge on the particle surface. This generates strong electrostatic repulsion between particles and between bubbles and particles, thereby disrupting the flocculation structure between particles and releasing the trapped free water. In terms of performance, this material exhibits a 20% increase in spread, an 18% increase in slump, and significantly improved pumpability. It shows no bleeding after 24 hours of standing and enhanced resistance to stratification and segregation. Its mechanical properties meet engineering requirements, and its compressive strength is unaffected. Furthermore, the formulation can be flexibly adjusted according to the type of coal gangue, resulting in low preparation cost and an environmentally friendly formulation that meets the needs of green mine construction. It has broad application value in the resource utilization of coal gangue.

[0034] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0035] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" represents weight percentage, "parts" represents parts by weight, and "ratio" represents weight proportion.

[0036] Example 1 This embodiment provides a coal gangue grouting and filling material with high rheological resistance and resistance to bleeding. By weight percentage, it comprises the following components: 70% coal gangue, 2% composite rheology modifier, and 28% water. The coal gangue particle size is no greater than 3 mm; the composite rheology modifier by weight percentage comprises 95% air-entraining agent and 5% dispersant; the air-entraining agent by weight percentage comprises 62.5% maleic rosin, 12.5% ​​sodium hydroxide, and 25% water; the dispersant is sodium tripolyphosphate.

[0037] The preparation method of the above-mentioned coal gangue grouting and backfilling material is as follows: Step 1: Weigh 70% coal gangue and 28% water by mass percentage, add them to a mixer and mix evenly to obtain the initial slurry, then let it stand for later use. Step 2: Weigh out 62.5% maleic rosin, 12.5% ​​sodium hydroxide, and 25% water by mass percentage. First, mix the sodium hydroxide and water evenly. Then, heat the maleic rosin to 80°C to make it liquid. Slowly pour the sodium hydroxide aqueous solution into the molten maleic rosin in portions while stirring. After the reaction is complete, a paste-like saponification product is formed. Dilute the paste-like saponification product with water to prepare an air-entraining agent solution with a mass fraction of 10% using the saponification reaction product as the solute. Let it stand for later use. Step 3: Add the weighed sodium tripolyphosphate to the air-entraining agent solution prepared in Step 2, mix well, and obtain the composite rheology modifier; Step 4: Weigh 2% of the composite rheology modifier prepared in Step 3 by mass percentage and add it to the initial slurry obtained in Step 1. Stir at 25°C for 10 minutes until uniform, and the grouting and filling material of the coal gangue with high rheology and resistance to bleeding is obtained.

[0038] Example 2 This embodiment provides a coal gangue grouting and filling material with high rheological resistance and resistance to bleeding. By mass percentage, it comprises the following components: 72% coal gangue, 2% composite rheology modifier, and 26% water. The coal gangue particle size is no greater than 3 mm; the composite rheology modifier by mass percentage comprises 95% air-entraining agent and 5% dispersant; the air-entraining agent by mass percentage comprises 62.5% maleic rosin, 12.5% ​​sodium hydroxide, and 25% water; the dispersant is sodium tripolyphosphate.

[0039] The preparation method of the above-mentioned coal gangue grouting and backfilling material is as follows: Step 1: Weigh 72% coal gangue and 26% water by mass percentage, add them to a mixer and mix evenly to obtain the initial slurry, then let it stand for later use. Step 2: Weigh out 62.5% maleic rosin, 12.5% ​​sodium hydroxide, and 25% water by mass percentage. First, mix the sodium hydroxide and water evenly. Then, heat the maleic rosin to 80°C to make it liquid. Slowly pour the sodium hydroxide aqueous solution into the molten maleic rosin in portions while stirring. After the reaction is complete, a paste-like saponification product is formed. Dilute the paste-like saponification product with water to prepare an air-entraining agent solution with a mass fraction of 10% using the saponification reaction product as the solute. Let it stand for later use. Step 3: Add the weighed sodium tripolyphosphate to the air-entraining agent solution prepared in Step 2, mix well, and obtain the composite rheology modifier; Step 4: Add all the composite rheology modifier prepared in Step 3 to the initial slurry obtained in Step 1, stir at 25°C for 10 minutes until uniform, and obtain the water-resistant and high-rheology coal gangue grouting filling material. The water content of the filling material is 26%.

[0040] Example 3 This embodiment provides a coal gangue grouting and filling material with high rheological resistance and resistance to bleeding. By mass percentage, it comprises the following components: 74% coal gangue, 2% composite rheology modifier, and 24% water. The coal gangue particle size is no greater than 3 mm; the composite rheology modifier by mass percentage comprises 95% air-entraining agent and 5% dispersant; the air-entraining agent by mass percentage comprises 62.5% maleic rosin, 12.5% ​​sodium hydroxide, and 25% water; the dispersant is sodium tripolyphosphate.

[0041] The preparation method of the above-mentioned coal gangue grouting and backfilling material is as follows: Step 1: Weigh 74% coal gangue and 24% water by mass percentage, add them to a mixer and mix evenly to obtain the initial slurry, then let it stand for later use. Step 2: Weigh out 62.5% maleic rosin, 12.5% ​​sodium hydroxide, and 25% water by mass percentage. First, mix the sodium hydroxide and water evenly. Then, heat the maleic rosin to 80°C to make it liquid. Slowly pour the sodium hydroxide aqueous solution into the molten maleic rosin in portions while stirring. After the reaction is complete, a paste-like saponification product is formed. Dilute the paste-like saponification product with water to prepare an air-entraining agent solution with a mass fraction of 10% using the saponification reaction product as the solute. Let it stand for later use. Step 3: Add the weighed sodium tripolyphosphate to the air-entraining agent solution prepared in Step 2, mix well, and obtain the composite rheology modifier; Step 4: Weigh 2% of the composite rheology modifier prepared in Step 3 by mass percentage and add it to the initial slurry obtained in Step 1. Stir at 25°C for 10 minutes until uniform, and the water-resistant, high-rheology coal gangue grouting filling material is obtained. The water content of the filling material is 26%.

[0042] Test and Result Analysis of Examples 1-3: 1) Liquidity test The initial slump and spread of the grouting filling materials obtained in Examples 1-3 were tested using a slump cone, as well as the slump and spread after mixing for different times. The test results are shown in Table 1.

[0043] Table 1. Slump and spread of the grouting filling materials obtained in Examples 1-3

[0044] As shown in Table 1, the grouting materials prepared in Examples 1-3 all exhibit excellent fluidity. With the increase in the coal gangue mass fraction from 70% to 74%, the initial slump slightly decreased from 292 mm to 285 mm, and the initial spread decreased from 996 mm to 930 mm, but both were still far higher than the requirements of conventional grouting materials. With the mixing time extended to 2 hours, the decrease in slump and spread for each proportion of materials was very small. The 70% group, after 2 hours of mixing, still achieved a slump of 280 mm and a spread of 900 mm, demonstrating good fluidity retention. This indicates that the present invention, through the synergistic effect of the composite rheology modifier, can effectively suppress the viscosity increase and fluidity decay caused by clay particles, allowing the slurry to maintain a stable flow state for a longer period, meeting the requirements for material fluidity and workability in mine grouting construction.

[0045] 2) Drainage rate test The water bleeding rate of the grouting filling materials obtained in Examples 1-3 was tested using a graduated cylinder after standing for different times. The test results are shown in Table 2.

[0046] Table 2. Water bleeding rate of grouting materials obtained in Examples 1-3

[0047] As shown in Table 2, no water bleeding occurred in the grouting materials prepared in Examples 1-3 after standing for 1 hour and 2 hours. This indicates that the addition of the composite rheology modifier effectively suppressed the segregation of the grout, and the material has excellent stability, ensuring the uniformity and long-term stability of the filling.

[0048] 3) Pumping performance test The filling material prepared in Example 3 was used to conduct a loop tube experiment. The slump and spread before and after the loop tube were tested using a slump cone, and the flow velocity data under different pressures in the loop tube were measured. The test results are shown in Tables 3 and 4.

[0049] Table 3. Slump and spread of the grouting filling material prepared in Example 3 during and after pumping.

[0050] Table 4. Loop test pressure data of the grouting filling material prepared in Example 3

[0051] Table 3 shows that the slump is 255 mm and the spread is 590 mm when pumped uniformly. After pumping, the slump is 256 mm and the spread is 550 mm. The fluidity remains basically unchanged before and after pumping, indicating that the material has excellent pumping stability and no significant risk of pipe blockage. Table 4 shows that the straight pipe pressure loss is stable in the range of 4.8~5.1 MPa / km at different flow rates, and the pressure loss is small, indicating that the material has good rheological properties and is suitable for long-distance pipeline transportation.

[0052] 4) Rheological property testing The rheological parameters of the grouting materials obtained in Examples 1-3, including apparent viscosity and shear stress, were tested using an MCR-72 rheometer. The test results are as follows: Figure 1 and Figure 2 As shown.

[0053] Figure 1 The curve shows the apparent viscosity as a function of shear rate. Figure 1 It can be seen that all three grouting materials with different mass fractions exhibit shear-thinning rheological properties, meaning that the apparent viscosity gradually decreases with increasing shear rate. This characteristic is beneficial for pumping the grout during pipeline transportation; the viscosity reduction at high shear rates can decrease pumping resistance, while the viscosity recovery at low shear rates can maintain grout stability. Among them, the higher the mass fraction of coal gangue, the greater the apparent viscosity of the grout, but all materials maintain good shear-thinning behavior.

[0054] Figure 2 The curve shows the variation of shear stress with shear rate. Figure 2 It can be seen that the shear stress of the three different mass fractions of grouting materials increases with the increase of shear rate, and the curves exhibit nonlinear characteristics, indicating that the materials have yield stress. The existence of yield stress enables the grout to maintain structural stability in a static state, preventing particle sedimentation and bleeding; while under shear action, it can flow, which is beneficial for pumping construction. This characteristic further verifies the advantage of the material of the present invention in possessing both good fluidity and stability.

[0055] As demonstrated in Examples 1-3, this invention successfully solves the technical problem of poor fluidity and easy bleeding in high-mud coal gangue slurry through the synergistic effect of the air-entraining agent and phosphate dispersant in the composite rheology modifier. In Example 3, when the coal gangue mass fraction reached 74%, the initial slump was 270 mm and the spread was 750 mm. After standing for 2 hours, the slump remained at 255 mm. Furthermore, no bleeding occurred in any of the examples after standing for 2 hours. Loop pipe experiments showed virtually no loss of fluidity before and after pumping, with a straight pipe pressure loss of only 4.8~5.1 MPa / km. Rheological tests indicated that the slurry exhibited shear thinning characteristics and yield stress. This material, using coal gangue as the main raw material, has a simple preparation process and combines excellent fluidity, stability, and pumping performance, providing a reliable technical solution for the resource utilization of high-mud coal gangue.

[0056] Example 4 This embodiment provides a coal gangue grouting and filling material with high rheological resistance and resistance to bleeding. By mass percentage, it comprises the following components: 70% coal gangue, 0.6% composite rheology modifier, and 29.4% water. The coal gangue particle size is no greater than 3 mm; the composite rheology modifier by mass percentage comprises 90% air-entraining agent and 10% dispersant; the air-entraining agent by mass percentage comprises 60% maleic rosin, 15% sodium hydroxide, and 25% water; the dispersant is sodium tripolyphosphate.

[0057] The preparation method of the above-mentioned coal gangue grouting and backfilling material is as follows: Step 1: Weigh 70% coal gangue and 29.4% water by mass percentage, add them to a mixer and mix evenly to obtain the initial slurry, then let it stand for later use. Step 2: Weigh out 60% rosin, 15% sodium hydroxide, and 25% water by mass percentage. First, mix the sodium hydroxide and water evenly. Then, heat the rosin to 80°C to make it liquid. Slowly pour the sodium hydroxide aqueous solution into the molten rosin in portions while stirring. After the reaction is complete, a paste-like saponification product is formed. Dilute the paste-like saponification product with water to prepare an air-entraining agent solution with a mass fraction of 10% using the saponification reaction product as the solute. Let it stand for later use. Step 3: Add the weighed sodium tripolyphosphate to the air-entraining agent solution prepared in Step 2, mix well, and obtain the composite rheology modifier; Step 4: Weigh 0.6% of the composite rheology modifier prepared in Step 3 by mass percentage, add it to the initial slurry obtained in Step 1, and stir at 20°C for 12 minutes until uniform, thus obtaining the coal gangue grouting and filling material with high rheology and resistance to bleeding.

[0058] The initial slump and spread of the filling material were tested using a slump cone, as well as the slump and spread after mixing for different times. The test results are shown in Table 5.

[0059] Table 5. Slump and spread of the grouting filling material obtained in Example 4

[0060] As shown in Table 5, the initial slump of the grouting material prepared in Example 4 was 289 mm and the spread was 978 mm, indicating excellent fluidity. After stirring for 2 hours, the slump was still 276 mm and the spread was 834 mm, indicating good fluidity retention. This shows that the composite rheology modifier can still effectively improve the fluidity of the slurry and suppress mud interference at a low dosage of 0.6%.

[0061] The bleeding rate of the grouting filling material obtained in Example 4 was tested using a graduated cylinder after standing for different times. The test results are shown in Table 6.

[0062] Table 6. Water bleeding rate of the grouting filling material obtained in Example 4

[0063] As shown in Table 6, the grouting filling material prepared in Example 4 showed no bleeding after standing for 1 hour and 2 hours, indicating excellent grout stability. This demonstrates that the composite rheology modifier at this ratio is sufficient to construct a stable grout skeleton and effectively prevent segregation.

[0064] Example 5 This embodiment provides a coal gangue grouting and filling material with high rheological resistance and resistance to bleeding. By weight percentage, it comprises the following components: 70% coal gangue, 1.2% composite rheology modifier, and 28.8% water. The coal gangue particle size is no greater than 3 mm; the composite rheology modifier by weight percentage comprises 98% air-entraining agent and 2% dispersant; the air-entraining agent by weight percentage comprises 65% maleic rosin, 10% sodium hydroxide, and 25% water; the dispersant is sodium tripolyphosphate.

[0065] The preparation method of the above-mentioned coal gangue grouting and backfilling material is as follows: Step 1: Weigh 70% coal gangue and 28.8% water by mass percentage, add them to a mixer and mix evenly to obtain the initial slurry, then let it stand for later use. Step 2: Weigh out 65% rosin, 10% sodium hydroxide, and 25% water by mass percentage. First, mix the sodium hydroxide and water evenly. Then, heat the rosin to 80°C to make it liquid. Slowly pour the sodium hydroxide aqueous solution into the molten rosin in portions while stirring. After the reaction is complete, a paste-like saponification product is formed. Dilute the paste-like saponification product with water to prepare a 10% (by mass) air-entraining agent solution with the saponification reaction product as the solute. Let it stand for later use. Step 3: Add the weighed sodium tripolyphosphate to the air-entraining agent solution prepared in Step 2, mix well, and obtain the composite rheology modifier; Step 4: Weigh 1.2% of the composite rheology modifier prepared in Step 3 by mass percentage, add it to the initial slurry obtained in Step 1, and stir at 30°C for 8 minutes until uniform, thus obtaining the coal gangue grouting and filling material with high rheology and resistance to bleeding.

[0066] The initial slump and spread of the filling material were tested using a slump cone, as well as the slump and spread after mixing for different times. The test results are shown in Table 7.

[0067] Table 7 Slump and spread of the grouting filling material obtained in Example 5

[0068] The bleeding rate of the grouting filling material obtained in Example 5 was tested using a graduated cylinder for different standing times. The test results are shown in Table 8.

[0069] Table 8. Water bleeding rate of the grouting filling material obtained in Example 5

[0070] A comparison of Examples 1, 4, and 5 shows that the fluidity of the grouting material gradually increases as the content of the composite rheology modifier increases from 0.6% to 1.2% and then to 2%. The initial slump increases from 289 mm to 290 mm and then to 292 mm, and the initial spread increases from 978 mm to 984 mm and then to 996 mm. The spread retention rate after stirring for 2 hours also increases accordingly, reaching 85.3%, 88.4%, and 90.4%, respectively. This indicates that the higher the content of the composite rheology modifier, the more significant the improvement in slurry fluidity and the stronger the fluidity retention ability. However, no bleeding occurred after standing for 2 hours at all three dosages, indicating that a low dosage of 0.6% is sufficient to construct a stable slurry skeleton. In practical applications, an appropriate dosage can be selected according to the fluidity requirements, balancing performance and cost.

[0071] Comparative Example 1 This comparative example provides a coal gangue grouting filling material, which, by mass percentage, comprises the following components: 70% coal gangue and 30% water. The particle size of the coal gangue is no greater than 3 mm.

[0072] The preparation method of the above-mentioned coal gangue grouting and backfilling material is as follows: Weigh out 70% coal gangue and 30% water by weight percentage, add them to a mixer and mix well to obtain a slurry.

[0073] Comparative Example 2 This comparative example provides a coal gangue grouting filling material, which, by mass percentage, comprises the following components: 72% coal gangue and 28% water. The particle size of the coal gangue is no greater than 3 mm.

[0074] The preparation method of the above-mentioned coal gangue grouting and backfilling material is as follows: Weigh out 72% coal gangue and 28% water by mass percentage, add them to a mixer and mix evenly to obtain a slurry.

[0075] Comparative Example 3 This comparative example provides a coal gangue grouting filling material, which, by mass percentage, comprises the following components: 74% coal gangue and 26% water. The particle size of the coal gangue is no greater than 3 mm.

[0076] The preparation method of the above-mentioned coal gangue grouting and backfilling material is as follows: Weigh out 74% coal gangue and 26% water by mass percentage, add them to a mixer and mix evenly to obtain a slurry.

[0077] Comparative analysis of tests and results for Examples 1-3: 1) Liquidity test The initial slump and spread of the slurries obtained in Comparative Examples 1-3 were tested using a slump cone, as well as the slump and spread after stirring for different times. The test results are shown in Table 9.

[0078] Table 9 Slump and spread of the slurries obtained in Comparative Examples 1-3

[0079] As shown in Table 9, Comparative Example 3 (74% coal gangue) without the addition of composite rheology modifier had an initial slump of 265 mm, but an initial spread of only 66 mm, far lower than the 750 mm of Example 3. This indicates extremely poor slurry fluidity, and the spread further decreased to 44 mm after standing for 2 hours, resulting in severe loss of fluidity. This is mainly due to the formation of flocculated structures by the clay particles in the coal gangue, leading to high slurry viscosity and difficulty in flow.

[0080] 2) Drainage rate test The bleeding rate of the slurries obtained from Comparative Examples 1-3 after standing for different times was tested using a graduated cylinder. The test results are shown in Table 10.

[0081] Table 10. Bleeding rate of slurries obtained in Comparative Examples 1-3

[0082] Table 10 shows that Comparative Examples 1-3 all exhibited varying degrees of water bleeding, with the bleeding being more severe at lower coal gangue mass fractions. Comparative Example 1 (70%) showed a water bleeding rate as high as 18.8% after 2 hours of standing, while Comparative Example 3 (74%) also reached 4.2%. Compared to Examples 1-3, which showed no water bleeding after 2 hours of standing, this indicates that the slurry stability was poor and prone to stratification and segregation without the addition of the composite rheology modifier.

[0083] 3) Pumping performance test The slurry prepared in Comparative Example 3 was used to conduct a loop test. The slump and spread before and after the loop were tested using a slump cone, and the flow rate data under different pressures in the loop were measured. The test results are shown in Tables 11 and 12.

[0084] Table 11 Slump and spread of the slurry prepared in Comparative Example 3 during and after pumping.

[0085] Table 12 Pressure data of the slurry prepared in Comparative Example 3 for loop test

[0086] Table 11 shows that in Comparative Example 3, the slump was 220 mm and the spread was 300 mm when pumped uniformly, but the slump was 200 mm and the spread was 290 mm after pumping, indicating significantly lower fluidity than Example 3 (slump greater than 255 mm before and after pumping). Table 12 shows that the straight pipe pressure loss was as high as 8.978-12.645 MPa / km, much higher than the 4.8-5.1 MPa / km of Example 3, indicating that the slurry without the addition of composite rheology modifier had high pumping resistance and was prone to pipe blockage.

[0087] 4) Rheological property testing The rheological parameters of the slurries obtained in Comparative Examples 1-3, including apparent viscosity and shear stress, were tested using an MCR-72 rheometer. The test results are as follows: Figure 3 and Figure 4 As shown.

[0088] Figure 3 The curve shows the apparent viscosity as a function of shear rate. Figure 3 It can be seen that although the slurries in Comparative Examples 1-3 exhibit a certain shear thinning trend, their apparent viscosity is generally high, and the viscosity decreases only slightly with increasing shear rate. Compared with the examples, the viscosity of the slurry without the addition of composite rheology modifier is significantly higher, indicating that the flocculated structure formed by the mud particles has not been effectively destroyed, and free water is trapped in the flocculated structure, resulting in poor slurry fluidity.

[0089] Figure 4 The curve shows the variation of shear stress with shear rate. Figure 4 It can be seen that although the slurries in Comparative Examples 1-3 also exhibited non-Newtonian fluid characteristics, their overall shear stress was higher, and their yield stress was significantly greater than that of the examples. The higher yield stress means that the slurry requires a greater external force to initiate flow, which is consistent with the higher pressure loss in the loop test, further illustrating that the slurry without the addition of composite rheology modifier has poor pumpability and is more difficult to construct.

[0090] The test results of Comparative Examples 1-3 show that the coal gangue grouting material without the addition of composite rheology modifier has the following problems: poor fluidity, with an initial spread of only 66 mm; poor stability, with a bleeding rate as high as 4.2%~18.8% after 2 hours of standing; poor pumpability, with a straight pipe pressure loss of 8.978~12.645 MPa / km, making it prone to pipe blockage; and poor rheological properties, with high apparent viscosity and yield stress. These problems severely restrict the practical application of coal gangue grouting material in mining engineering, further highlighting the technical advantages of this invention in improving slurry properties through composite rheology modifier.

[0091] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A coal gangue grouting and filling material resistant to bleeding and high rheology, characterized in that, By mass percentage, it comprises the following components: 70%~75% coal gangue, 0.55%~2.3% composite rheology modifier, and the balance being water; The composite rheology modifier includes an air-entraining agent and a dispersant, wherein the mass ratio of the air-entraining agent to the dispersant is (90~99):(1~10).

2. The coal gangue grouting and filling material resistant to bleeding and high rheology according to claim 1, characterized in that, The air-entraining agent is a surface-active foaming material, and the dispersant is a phosphate additive; wherein the phosphate additive is selected from at least one of sodium tripolyphosphate, aluminum phosphate, and sodium phosphate.

3. The coal gangue grouting and filling material resistant to bleeding and high rheology according to claim 2, characterized in that, The dispersant is sodium tripolyphosphate, which accounts for 0.05-0.15% of the total mass of the coal gangue grouting filling material.

4. The coal gangue grouting and filling material resistant to bleeding and high rheology according to claim 2, characterized in that, The surface-active foaming material is a rosin-based air-entraining agent.

5. The coal gangue grouting and filling material resistant to bleeding and high rheology according to claim 4, characterized in that, The rosin-based air-entraining agent is Malaysian rosin.

6. The coal gangue grouting and filling material resistant to bleeding and high rheology according to claim 5, characterized in that, The rosin is a water-soluble saponified product generated by the saponification reaction of sodium hydroxide, wherein the mass ratio of rosin, sodium hydroxide and water is (60~65):(10~15):(20~30).

7. A method for preparing a coal gangue grouting and backfilling material resistant to bleeding and high rheology as described in any one of claims 1 to 6, characterized in that, Includes the following steps: Step 1: Mix coal gangue with water and stir to obtain the initial slurry; Step 2: Mix the air-entraining agent and the dispersant according to the specified ratio to prepare a composite rheology modifier; Step 3: Add the composite rheology modifier obtained in Step 2 to the initial slurry obtained in Step 1, stir evenly, and obtain the coal gangue grouting and filling material with high rheology and resistance to bleeding.

8. The preparation method of a coal gangue grouting and filling material resistant to bleeding and high rheology according to claim 7, characterized in that, The preparation method of the composite rheology modifier in step 2 is as follows: first, dissolve sodium hydroxide in water, then mix and stir with maleic rosin heated to liquid state, cool to obtain a paste, dilute with water to prepare an air-entraining agent solution; finally, add dispersant to the air-entraining agent solution, mix evenly to obtain the composite rheology modifier.

9. The preparation method of a coal gangue grouting and filling material resistant to bleeding and high rheology according to claim 7, characterized in that, The stirring temperature in step 3 is 10~35℃, and the stirring time is 5~15min.

10. The application of a coal gangue grouting and filling material with high rheological resistance as described in any one of claims 1 to 6 in grouting and filling projects in mining goaf areas.

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