A mine grouting material and a preparation method thereof

Abstract

The application discloses a mine grouting material and a preparation method thereof, and belongs to the technical field of mine materials. The mine grouting material comprises solid mixed powder and water glass solution, and the solid mixed powder comprises red mud, fly ash, granulated blast furnace slag powder and modified metakaolin-based core material. The modified metakaolin-based core material is prepared into an amorphous composite precursor by mechanical force chemical ball milling of metakaolin, silica fume, anhydrous gypsum and calcium hydroxide. The amorphous precursor is cooperated with the red mud through structural design, and in a low modulus cement-free alkali-activated four-component system, rapid solidification, high early strength and low temperature reactivity are simultaneously realized, and the flash setting phenomenon does not occur, so that the problems of easy flash setting and insufficient low-temperature activity of a low modulus alkali-activated system in the prior art are solved. The solidified body has a 1-day compressive strength of 25-30 MPa, a 3-day compressive strength of 40-45 MPa, and an initial setting time in a range of 5-20 minutes.

Description

Technical Field

[0001] This invention belongs to the field of mining materials technology, specifically relating to a mining grouting material and its preparation method. Background Technology

[0002] Mining grouting materials are indispensable functional materials in coal mine tunnel engineering, mainly used for coal mine wall seepage control, fractured rock mass reinforcement, tunnel surrounding rock support, and prevention of water inrush and sand collapse. With the increasing depth of coal mining, coal seam occurrence conditions are becoming increasingly complex. The mining process faces challenges such as high ground stress, high ground temperature, and high karst water pressure, placing more stringent requirements on the comprehensive performance of mining grouting materials. Ideal mining grouting materials not only need excellent mechanical strength and bonding properties to ensure the long-term stability of the rock mass, but also need to meet the differentiated construction needs under complex mining conditions in terms of permeability, setting time control, and durability.

[0003] Inorganic grouting reinforcement materials have been widely used in underground coal mine grouting reinforcement due to their advantages such as low cost, wide availability, and inherent flame retardancy. These materials are typically based on cement-based or cement-water glass two-liquid systems, with the addition of industrial solid wastes such as fly ash and slag to improve grout properties, and the rapid setting effect of water glass to effectively control gel time. However, traditional inorganic grouting materials consistently face a core contradiction in engineering applications: there is a mutually restrictive relationship between the three key indicators of mechanical strength, permeability, and setting rate, making it difficult to achieve a synergistic improvement in overall performance through simple component proportioning.

[0004] With the promotion of green mining concepts and the development of solid waste resource utilization technologies, alkali-activated geopolymer grouting materials, primarily made from industrial solid waste, have gradually become a research hotspot. These materials completely eliminate the need for cement, using fly ash, slag, and other siliceous aluminous solid wastes as precursors and alkaline solutions such as water glass as activators. Through alkali-activated reactions, they generate zeolite-like cementitious products, offering significant advantages such as low carbon footprint, environmental friendliness, and low cost. Red mud is a major solid waste discharged from the alumina industry, with huge annual emissions and low comprehensive utilization rates. Rich in iron oxide, alumina, silica, and residual alkali, it possesses natural potential as a precursor for alkali-activated geopolymers. Introducing red mud into mining grouting material systems not only allows the active siliceous aluminous components in red mud to participate in the geopolymerization reaction and contribute to its intensity, but also utilizes the residual alkali in red mud to create an auxiliary activation effect on the alkali-activated system, while providing a feasible path for the large-scale resource utilization of red mud.

[0005] For example, Chinese patent document CN117776640A discloses an early-strength alkali-activated grouting material and its preparation method (hereinafter referred to as "Prior Art 1"). This material uses granulated blast furnace slag, metakaolin, and fly ash as cementing components, and a water glass solution with a modulus of 1.2 to 1.6 as an alkali activator. Through optimization of the ternary system ratio and control of the activator modulus, a grouting material with excellent early strength is obtained, and its 24-hour compressive strength can exceed 20 MPa. However, the alkali activator modulus used in this scheme to ensure ultra-high early strength is as low as 1.2 to 1.6, which belongs to a strongly alkaline activation environment. Within this modulus range, when the system does not take effective alkali release control measures, the grout reacts extremely violently at room temperature, and the setting rate is difficult to control effectively. Instantaneous flash setting is very likely to occur during the mixing, pumping, and grouting process at the construction site, which may lead to pipe blockage accidents in severe cases, resulting in material waste and construction delays. Furthermore, the scheme does not address the resource utilization of red mud, a major industrial solid waste, and fails to fully leverage the cost advantages and environmental benefits of the comprehensive solid waste system. Moreover, although the scheme attempts to add multi-walled carbon nanotubes, it explicitly states that "the doping effect of multi-walled carbon nanotubes is not significant," indicating that the path of directly introducing nanofunctional components to improve the microstructure in this system is not smooth.

[0006] For example, Chinese patent document CN118145948A discloses a grouting material based on solid waste for mining and its preparation method (hereinafter referred to as "Prior Art 2"). This material uses rice husk ash, fly ash, and slag as cementing components and introduces river sand as aggregate. It is prepared by alkali activation to produce a grouting material with good fluidity and high early strength. However, the setting time of this method is relatively long and cannot be actively controlled as needed. In the face of emergency situations where mines need to quickly seal off water inflows, it cannot achieve timely and effective water stoppage.

[0007] The limitations of the aforementioned existing technologies reflect the common technical dilemmas faced by the field of soda ash activated geopolymer grouting materials: on the one hand, as shown in prior art 1, the use of a low-modulus, strongly alkaline activation environment to pursue high early strength often leads to uncontrolled reaction processes and flash setting; on the other hand, as shown in prior art 2, the rapid setting and early strength characteristics of the material are often sacrificed in order to obtain stable construction operation time. Furthermore, existing alkali-activated geopolymer systems have not effectively solved the problem of maintaining activity under low-temperature conditions, have not yet achieved the effective utilization of red mud in all-solid waste alkali-activated grouting materials, and face the challenges of difficult dispersion control and poor cost-effectiveness of nanomaterials. Summary of the Invention

[0008] The purpose of this invention is to provide a grouting material for mining and its preparation method, which can effectively solve the problems existing in the prior art, such as easy flash solidification of low modulus alkali-activated systems, low utilization rate of red mud resources, insufficient precision in setting time control, and poor low-temperature activity.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0010] A grouting material for mining includes a solid mixed powder and a water glass solution. The solid mixed powder comprises red mud, fly ash, granulated blast furnace slag powder, and modified metakaolin-based core material. Red mud accounts for 5%–15% of the total mass of the solid mixed powder, fly ash for 10%–25%, granulated blast furnace slag powder for 55%–70%, and the modified metakaolin-based core material for 3%–7%. The modulus of the water glass solution is 1.3–1.8, and the solid-liquid mass ratio of the solid mixed powder to the water glass solution is 1.2–1.6. The modified metakaolin-based core material is made by mixing metakaolin and silica fume at a mass ratio of 3:1–5:1, adding 8%–12% anhydrous gypsum and 5%–10% calcium hydroxide (by mass of the total metakaolin and silica fume), and ball milling to a Blaine surface area of ​​not less than 650 m². 2 / kg of amorphous composite precursor obtained.

[0011] Specifically, the red mud meets the following conditions: moisture content is less than 5%, fineness is such that the residue on an 80μm square hole sieve does not exceed 15%, pH value is 10-13, iron oxide content is 25%-45%, aluminum oxide content is 15%-25%, and silicon oxide content is 10%-20%.

[0012] Specifically, the fly ash meets the following conditions: calcium oxide content is less than 18%, the residue on a 45μm square hole sieve is 8% to 12%, the loss on ignition is less than 5%, the water requirement ratio is not more than 95%, and the 28-day activity index is not less than 70%.

[0013] Preferably, the granulated blast furnace slag powder has a specific surface area of ​​400–500 m². 2 / kg, vitreous content not less than 90%, 7-day activity index not less than 65%, 28-day activity index not less than 85%.

[0014] Preferably, the calcium hydroxide is industrial-grade calcium hydroxide with a purity of not less than 90% and an average particle size D. 50 The thickness is 5–15 μm, and the BET specific surface area is not less than 10 m². 2 / g.

[0015] Specifically, the conditions for the ball milling process are as follows: the milling medium is zirconia balls, the ball-to-material mass ratio is 10:1 to 20:1, the filling rate is 30% to 45%, the rotation speed is 300 to 450 r / min, and the milling time is 60 to 90 min.

[0016] Furthermore, the modulus of the water glass solution is adjusted to the target value by adding sodium hydroxide solution, and the Baume degree of the water glass solution is 38-42°Bé.

[0017] Furthermore, the aforementioned mining grouting materials also include phosphate-based retarder accounting for 0.3% to 0.8% of the total mass of the solid mixed powder, or sulfate-based accelerator accounting for 0.5% to 1.0% of the total mass of the solid mixed powder.

[0018] The present invention also provides a method for preparing the above-mentioned mining grouting material, comprising the following steps:

[0019] (1) Preparation of solid mixed powder: Red mud, fly ash, granulated blast furnace slag powder and the prepared modified metakaolin-based core material are mixed evenly, wherein red mud accounts for 5% to 15% of the total mass of solid mixed powder, fly ash accounts for 10% to 25%, granulated blast furnace slag powder accounts for 55% to 70%, and modified metakaolin-based core material accounts for 3% to 7%;

[0020] (2) Prepare a water glass solution and adjust its modulus to 1.3 to 1.8;

[0021] (3) Mix the solid mixed powder with water glass solution at a solid-liquid mass ratio of 1.2 to 1.6 to obtain the grouting slurry.

[0022] Further, in step (3), the water glass solution is added to the stirring container and high-speed stirring is started. Then, the solid mixed powder is slowly added. The stirring speed is 800-1200 r / min, the feeding time is controlled at 90-150 seconds, and stirring is continued for 120-180 seconds after the feeding is completed.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) This invention improves rapid solidification, high early strength, and excellent impermeability by constructing a quaternary inorganic cementing system based on red mud, fly ash, slag, and modified metakaolin. Red mud, rich in active silica-alumina components and residual alkali, can participate in geological polymerization reactions and exert an auxiliary activating effect under alkali activation, promoting the dissociation of glass in slag and the formation of C-(A)-SH gel. The pozzolanic activity of fly ash undergoes a secondary hydration reaction under alkali activation. Granulated blast furnace slag powder contributes significantly to early strength due to its potential hydraulic properties. The highly active filling effect and nucleation of the modified metakaolin-based core material further densify and harden the microstructure of the slurry. The synergistic effect of these four components enables the consolidated body to achieve a compressive strength of 25–30 MPa after 1 day and 40–45 MPa after 3 days, while reducing the permeability coefficient to 1.0 × 10⁻⁶. -7 ~5.0×10 -6This invention achieves high early strength mechanical properties while ensuring excellent impermeability, meeting the requirements for rapid repair and reinforcement of fractured rock masses. Compared to existing technologies 1, which use alkali activators with modulus of 1.2 to 1.6 but fail to kinetically regulate alkali release, resulting in uncontrollable setting and flash solidification, and existing technologies 2, which have a long setting time of 85 to 131 minutes and cannot be controlled as needed, this invention achieves rapid solidification without flash solidification under low modulus strong alkali activation conditions through the structural design of an amorphous composite precursor and the introduction of red mud, while simultaneously optimizing high early strength.

[0025] (2) This invention pre-synthesizes amorphous composite precursors of metakaolin, silica fume, and calcium hydroxide in the solid phase, avoiding the process difficulties of directly dispersing independent nanoparticles in liquid slurry from the material design source. During ball milling, calcium hydroxide undergoes lattice distortion and amorphization transformation, significantly reducing its crystallinity. The dissolution rate of calcium ions and hydroxide ions is significantly slower than that of free calcium hydroxide, thus providing the slurry with sufficient normal working time and avoiding the flash coagulation problem commonly encountered when directly mixing alkaline materials under low modulus and strong alkaline conditions. In addition, existing technologies usually adopt conventional approaches such as reducing alkalinity or adding retarders to solve the problem of excessively rapid coagulation of alkali-activated materials. For example, existing technology 1 selects a stronger alkaline environment with a modulus of 1.2 to 1.6 to pursue early strength but does not perform kinetic control on alkali release, while existing technology 2 sacrifices rapid coagulation characteristics. This invention takes a novel approach, using the co-milling solid-phase reaction of anhydrous gypsum and calcium hydroxide during the solid-phase ball milling stage to encapsulate calcium hydroxide in an amorphous aluminosilicate network. This kinetically delays the instantaneous release of alkaline components, effectively preventing flash condensation even under strong alkaline activation conditions with moduli as low as 1.3 to 1.8, thus solving the problem of easy flash condensation in low-modulus systems.

[0026] (3) This invention employs a dual-parameter synergistic control of water glass modulus and solid-liquid ratio to regulate setting time. In this system, a decrease in water glass modulus increases alkalinity, thereby accelerating setting, while a decrease in solid-liquid ratio increases liquid content, also shortening setting time. Both parameters maintain consistency in their control direction. Under normal operating conditions (18–25°C), by jointly adjusting the two parameters, the initial setting time can be controlled within the range of 5–20 minutes, meeting the stringent requirements for ultra-short gelation time in emergency situations such as rapid sealing of gushing water. Furthermore, in scenarios requiring extended operating time, phosphate-based retarders can be used to directionally expand the control window to adapt to more complex conditions; in scenarios requiring further accelerated setting, such as low-temperature environments, sulfate-based accelerators can be used. This precise, wide-range, and scenario-adaptable control capability overcomes the shortcomings of existing technology 1, which is prone to flash setting due to the lack of an alkali release control mechanism in the 1.2–1.6 modulus range, and the limitations of existing technology 2, which has a long and unadjustable setting time.

[0027] (4) This invention achieves flexible adaptation to different construction temperatures and setting time requirements by adding phosphate-based retarders or sulfate-based accelerators. When the ambient temperature is above 30℃, adding 0.3% to 0.8% of the total mass of solid powder as a retarder can maintain the initial setting time at a level that is operable normally; when the ambient temperature is below 5℃, adding 0.5% to 1.0% of the total mass of solid powder as an accelerator can accelerate setting and improve the early strength development rate. The amount of retarder is approximately linearly positively correlated with the extension of setting time, and the increase in permeability coefficient is controllable when the amount of accelerator is in the range of 0.5% to 0.8%, ensuring the stability of construction quality under extreme temperature conditions.

[0028] (5) In this invention, the modified metakaolin-based core material can still maintain good reactivity under low temperature conditions. The amorphous composite precursor formed by ball milling has a high chemical potential energy, and its activation energy barrier for dissolution and initial hydration is relatively low, so that the system can still maintain a basic hydration reaction rate at low temperature of 2-5℃, without the near-dormant state of traditional alkali-activated slag systems at low temperatures. At the same time, the auxiliary activation effect of residual alkali in red mud can provide additional alkaline driving force at low temperatures. This intrinsic low-temperature activity advantage allows the initial setting time to be controlled within 20-28 minutes and the final setting time within 35-48 minutes at low temperature of 2-5℃ after combining with sulfate-based quick-setting agents, providing reliable material support for grouting projects under low-temperature construction conditions.

[0029] (6) This invention adopts a red mud-fly ash-slag-modified metakaolin-based quaternary inorganic cementitious system without the addition of nano-functional particles. The total content of red mud, fly ash and slag in the solid powder can reach more than 90%. All three are industrial solid wastes, widely available and inexpensive. In particular, red mud is a major solid waste in the alumina industry. Introducing it into the grouting material system for mining not only realizes the resource utilization of waste, but also has significant environmental and social benefits. The modified metakaolin-based core material uses metakaolin and silica fume as raw materials and only requires a simple ball milling mixing process to prepare. The addition amount is only 3% to 7% of the total mass of solid powder. No chemical pretreatment or surface modification process is required. The overall material cost is reduced by about 2.5 to 3.0 times compared with the nano-material modification scheme. While ensuring excellent comprehensive performance, it improves the economic feasibility of large-scale engineering applications.

[0030] (7) After the grouting slurry of the present invention is mixed in step 3, thanks to the delaying effect of the amorphous precursor formed by solid-phase ball milling on the release of alkaline components and the reasonable proportion of active components in red mud, the viscosity of the slurry is controlled in the range of 150 to 350 mPa·s. In this viscosity range, the slurry has good pumpability and penetration diffusion ability, and can effectively enter the micro-fractures of the rock mass. At the same time, the delayed release mechanism allows the slurry to maintain a stable and sufficient working time in the temperature range of 15 to 25°C. No instantaneous flash solidification phenomenon occurs under strong alkaline activation conditions with a modulus of 1.3 to 1.8. This overcomes the common technical problems of traditional low-modulus water glass alkaline activation systems, provides sufficient working window for mixing, pumping and grouting operations at the construction site, and reduces the risk of pipe blockage and material waste caused by accidental flash solidification.

[0031] (8) This invention introduces red mud as one of the components of solid mixed powder. The active components such as iron oxide (25%~45%), alumina (15%~25%) and silicon oxide (10%~20%) in red mud participate in the alkali-activated geological polymerization reaction. At the same time, the residual alkali in red mud (containing 2%~8% Na2O) can play an auxiliary activating role in the early stage of contact with water glass solution, accelerating the dissociation of the slag glass structure and the dissolution of active silicon aluminum components. This complements the alkali release delay mechanism of the modified metakaolin-based core material. The former provides the activation driving force in the early stage of the reaction, while the latter avoids flash solidification caused by excessive alkali release through kinetic regulation. The two work together to achieve the technical effect of "fast solidification without flash solidification". Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0033] Example 1

[0034] This embodiment provides a grouting material for mining, based on a quaternary inorganic cementing system of red mud-fly ash-slag-modified metakaolin. It utilizes low-modulus water glass as an alkaline activator to achieve rapid setting, hardening, and high early strength in the cementing material. The entire technical solution includes the following core steps: preparation of solid mixed powder, preparation of water glass solution, mixing of grouting slurry, and grouting construction. The technical details of each step are described in detail below.

[0035] Step 1: Preparation of solid mixed powder

[0036] Prepare the solid powder components. The solid powder consists of four parts: red mud, fly ash, granulated blast furnace slag powder, and modified metakaolin-based core material. Among them, red mud accounts for 5% to 15% of the total mass of the solid powder, fly ash accounts for 10% to 25% of the total mass of the solid powder, granulated blast furnace slag powder accounts for 55% to 70% of the total mass of the solid powder, and the modified metakaolin-based core material is added at 3% to 7% of the total mass of the solid powder.

[0037] In this embodiment, the amount of red mud is set to 10% of the total mass of solid powder, the amount of fly ash is set to 20% of the total mass of solid powder, the amount of granulated blast furnace slag powder is set to 65% of the total mass of solid powder, and the amount of modified metakaolin-based core material is set to 5% of the total mass of solid powder.

[0038] Regarding the technical specifications of the red mud, the red mud selected in this embodiment meets the following parameter requirements: water content of 3%, fineness controlled so that the residue on an 80μm square-hole sieve does not exceed 15%, pH value of approximately 11.5, iron oxide content of approximately 35%, alumina content of approximately 20%, silica content of approximately 15%, and residual alkali content (calculated as Na2O) of approximately 5%. The auxiliary activating effect of residual alkali in the red mud and the main activating effect of water glass solution together constitute the alkali activation driving force. The active alumina and silica components in the red mud participate in the geological polymerization reaction to generate iron-containing C-(A)-SH gel and NASH gel, which fill the pores inside the hardened slurry, improving the structural density and mechanical strength.

[0039] Regarding the technical specifications of fly ash, the fly ash selected in this embodiment meets the following parameter requirements: calcium oxide content is less than 18%, fineness is controlled within the range of 8% to 12% residue on a 45μm square-hole sieve, loss on ignition is less than 5%, water requirement ratio does not exceed 95%, and 28-day activity index is not less than 70%. The pozzolanic activity of fly ash is a core element for its use as a key component in grouting materials—under alkaline conditions, the active silica-alumina oxides in fly ash undergo a secondary hydration reaction with calcium hydroxide in the hydration products, generating CSH gel and CAH gel, which fill the pores inside the hardened grout, improving structural density and mechanical strength.

[0040] Regarding the technical specifications of granulated blast furnace slag powder, the granulated blast furnace slag powder selected in this embodiment meets the following parameter requirements: specific surface area of ​​400 m². 2 / kg to 500m 2Within the range of / kg, the vitreous content is not less than 90%, the activity index is not less than 65% after 7 days and not less than 85% after 28 days, and the fluidity ratio is not less than 95%. The main chemical components of granulated blast furnace slag powder include calcium oxide, silicon dioxide, aluminum oxide, and magnesium oxide, and its potential hydraulic properties are activated under the action of alkaline activators. Unlike the slow pozzolanic reaction of fly ash, the hydration reaction of slag starts up relatively quickly under the action of activators, and can provide a considerable contribution to mechanical strength in the early stage of grouting.

[0041] The preparation method for modified metakaolin-based core materials is as follows:

[0042] Metakaolin and silica fume are mixed in a mass ratio of 3:1 to 5:1, meaning metakaolin comprises 60% to 80% of the mixture and silica fume comprises 20% to 40%. Anhydrous gypsum is then added to the mixture at a mass ratio of 8% to 12% of the total mass of the metakaolin and silica fume, followed by calcium hydroxide at a mass ratio of 5% to 10% of the total mass of the metakaolin and silica fume. The calcium hydroxide used is industrial grade, with a purity of not less than 90% and an average particle size D. 50 The BET specific surface area is controlled within the range of 5μm to 15μm and is not less than 10m². 2 / g. The above mixture was placed in a ball mill for ball milling. The ball milling media were zirconia balls, the ball-to-material mass ratio was 10:1 to 20:1, the filling rate was controlled within the range of 30% to 45%, the ball milling time was controlled within the range of 60 minutes to 90 minutes, the ball milling speed was controlled within the range of 300 r / min to 450 r / min, and the output fineness was controlled to have a residue of less than 5% on an 80μm square hole sieve and a Blaine specific surface area of ​​not less than 650m². 2 / kg, which confirms that sufficient amorphization has been achieved, resulting in modified metakaolin-based core material.

[0043] In the above preparation process, metakaolin is an amorphous silica-alumina oxide obtained by calcining kaolin at a temperature range of 650℃ to 850℃ to remove structural water. It has a large specific surface area and high activity. Silica fume meets the following conditions: SiO2 content ≥93%, amorphous SiO2 content accounts for no less than 85% of the total SiO2, sieve residue on a 45μm square hole sieve ≤3%, activity index (28 days) ≥90%, and water requirement ratio ≤110%. The addition of silica fume can increase the silica content of the system, providing sufficient silicon source for the subsequent alkali-activated reaction. The sulfate ions dissolved by anhydrous gypsum in an alkaline environment can react with the aluminate components in the metakaolin hydration products to form ettringite (AFt), playing a micro-expansion filling effect. Under the high-energy mechanical force of ball milling, calcium hydroxide, metakaolin, and silica fume undergo a solid-phase reaction, resulting in lattice distortion and amorphization on the particle surface. The crystallinity of calcium hydroxide is significantly reduced, transforming into a chemically inhibited amorphous calcium aluminosilicate composite precursor. In the initial stage of contact with water glass solution, the dissolution rate of calcium ions and hydroxide ions in this precursor is significantly slower than that of free calcium hydroxide, thus giving the slurry sufficient normal working time and effectively overcoming the flash coagulation problem commonly encountered when conventional alkaline materials are directly mixed under strongly alkaline activation conditions with modulus as low as 1.3 to 1.8.

[0044] The modified metakaolin-based core material prepared above was added to a gravity-free twin-shaft paddle mixer in a preset ratio along with red mud, fly ash, and granulated blast furnace slag powder. The revolution speed of the mixer was set to 35 r / min to 45 r / min, the rotation speed was set to 2.8 times to 3.2 times the revolution speed, and the mixing time was set to 8 minutes to 12 minutes to ensure that the red mud was fully dispersed during the mixing process and that the four solid powder components were uniformly dispersed, thus obtaining a solid mixed powder.

[0045] Step 2: Prepare water glass solution

[0046] In this embodiment, the industrial water glass stock solution was selected with a modulus (i.e., the molar ratio of silica to sodium oxide) in the range of 1.6 to 1.8 and a concentration in the range of 35°Bé to 45°Bé. The industrial water glass was diluted with water at a predetermined mass ratio to obtain a water glass solution with a target modulus of 1.6.

[0047] The specific preparation process is as follows: First, use a Baumé hydrometer to measure the Baumé value of the industrial water glass stock solution, and calculate the dilution water consumption according to the target Baumé. If the initial modulus of the industrial water glass stock solution is slightly higher than the target value of 1.6, the modulus can be adjusted to the target range by adding sodium hydroxide solution. The addition amount of sodium hydroxide is determined by iterative calculation according to the target modulus, the mass of sodium oxide and silicon dioxide in the water glass stock solution, based on the alkali equivalent balance relationship, or by using the modulus blending calculation formula commonly used in the field. When necessary, fine-tuning is carried out through small-scale blending tests to ensure that the modulus accurately reaches the target value. In actual operation, sodium hydroxide is prepared into an aqueous solution with a concentration of 10% to 15%, and slowly added to the water glass solution under stirring conditions. The stirring time is not less than 15 minutes to ensure that sodium hydroxide is completely dissolved and evenly distributed in the solution.

[0048] The dilution water consumption is calculated according to the target concentration. If it is necessary to adjust the Baumé of the water glass solution from the stock solution Baumé to the target Baumé within the range of 38°Bé to 42°Bé, the following empirical formula can be used to estimate the water addition amount:

[0049] Water addition amount = mass of water glass stock solution × (stock solution Baumé / target Baumé - 1);

[0050] After mixing the calculated water addition amount with the water glass stock solution, use a Baumé hydrometer to measure the solution concentration. If the measured value is within ±0.5°Bé of the target range, it is considered qualified. If the deviation is large, fine-tuning is required. The prepared water glass solution should be left standing for defoaming treatment for not less than 30 minutes to eliminate the bubbles introduced during the stirring process, and a water glass solution with a modulus of 1.6 and a Baumé of 40°Bé is obtained.

[0051] Step 3: Mix the grouting slurry

[0052] Fully mix the solid mixed powder prepared in Step 1 and the water glass solution prepared in Step 2 according to the preset solid-liquid mass ratio. The solid-liquid mass ratio in this embodiment is set to 1.4, that is, every 1.4 mass units of solid mixed powder are mixed with 1.0 mass unit of water glass solution.

[0053] The specific operation process is as follows: Pre-add the water glass solution to the stirring container, start the high-speed stirring equipment, and control the stirring speed within the range of 800 r / min to 1200 r / min. While starting the stirring, slowly add the solid mixed powder in batches, and control the feeding time within the range of 90 seconds to 150 seconds. After the feeding is completed, continue to stir at the same speed for 120 seconds to 180 seconds to make the solid powder and the water glass solution fully mixed evenly, and obtain a uniform grouting slurry.

[0054] During high-speed stirring, the slurry temperature will rise. In this embodiment, the slurry temperature is controlled within the range of 15°C to 25°C using a cooling water jacket. If the slurry temperature exceeds 25°C, the stirring speed must be reduced or stirring must be stopped for cooling to prevent the water glass solution from accelerating gelation due to excessive temperature. Benefiting from the delaying effect of the amorphous composite precursor formed by ball milling on alkali release and the synergistic effect of the active components in red mud, the slurry formulated in this invention has a stable and sufficient workable time under strongly alkaline activation conditions with a modulus as low as 1.6, and no instantaneous flash coagulation phenomenon was observed.

[0055] After mixing, allow the slurry to stand for 60 to 120 seconds to defoam. The purpose of this standing defoaming is to allow air bubbles trapped in the slurry due to high-speed mixing to rise and be expelled naturally, thus preventing air bubbles from remaining in the slurry during the grouting process and affecting the density and mechanical properties of the stone.

[0056] The key performance indicators of the obtained grout are as follows: the grout viscosity is controlled within the range of 150 mPa·s to 350 mPa·s (measured using a rotational viscometer at a speed of 6 r / min), and the grout density is controlled within 1.90 g / cm³. 3 Up to 2.00 g / cm 3 Within the specified viscosity range, the above viscosity range ensures good pumpability of the slurry, while the density data is consistent with the formulation design of a solid-liquid ratio of 1.4.

[0057] This embodiment employs a dual-parameter approach of controlling setting time using both water glass modulus and solid-liquid ratio. In this system, a decrease in water glass modulus increases alkalinity, thus accelerating setting; a decrease in solid-liquid ratio increases liquid content, also accelerating setting. Both parameters work in the same direction to control setting time. Using a modulus of 1.6 and a solid-liquid ratio of 1.4 as a baseline, the observed trends are as follows: for every 0.1 unit decrease in water glass modulus, the initial setting time of the slurry is shortened by approximately 2 to 4 minutes; for every 0.1 unit decrease in solid-liquid ratio, the initial setting time is shortened by approximately 1 to 3 minutes. Conversely, increasing the modulus or solid-liquid ratio correspondingly prolongs the setting time. The difference between the final setting time and the initial setting time is controlled within the range of 10 to 20 minutes.

[0058] Taking the baseline parameters of this embodiment (modulus 1.6, solid-liquid ratio 1.4) as an example, the measured initial setting time is 8 to 15 minutes, and the final setting time is 18 to 30 minutes. If an initial setting time of 5 to 8 minutes is required to be achieved quickly within the modulus range of 1.3 to 1.8, the water glass modulus can be reduced to 1.3, and the solid-liquid ratio can be adjusted to 1.2. If the initial setting time needs to be extended to 15 to 20 minutes, the water glass modulus can be increased to 1.8, and the solid-liquid ratio can be adjusted to 1.6.

[0059] Step 4: Grouting Construction

[0060] The grout prepared in step 3 is injected into the rock mass to be reinforced or the leakage area using a grouting pump. Grouting pressure is a key process parameter determining the grouting effect; in this embodiment, the grouting pressure is controlled within the range of 0.5 MPa to 2.0 MPa. The specific grouting pressure setting needs to be determined comprehensively based on factors such as the degree of fracture development, permeability coefficient, and grouting depth of the rock mass to be reinforced. For dense rock masses with low fracture development, the grouting pressure should be appropriately increased to 1.5 MPa to 2.0 MPa; for fractured rock masses with high fracture development, the grouting pressure should be appropriately reduced to 0.5 MPa to 1.0 MPa to prevent excessive penetration or fracturing of the rock mass under high pressure.

[0061] After grouting is completed, the grout gradually undergoes a hydration-gel reaction under alkaline activation and temperature. The silica and alumina oxides in the grout undergo an alkaline-activated reaction under the combined action of sodium hydroxide and water glass. The active iron oxide, alumina, and silica components in the red mud, as well as the glassy components in the slag, rapidly dissociate under a low-modulus, strongly alkaline environment, generating cementitious products mainly composed of hydrated calcium silicate (CSH), hydrated calcium aluminosilicate (CASH), and iron-containing hydration products. The active components in the modified metakaolin-based core material begin to participate in the hydration process in the early stages of the reaction, providing early filling effects and nucleation sites. The active components in the red mud and fly ash continue to play a role in the later stages of the hydration reaction, generating more CSH and CASH gels through secondary hydration reactions, filling the micropores inside the hardened grout, and improving the overall density and mechanical strength.

[0062] The solidified body after the grout has set and hardened has the following performance indicators: 1-day compressive strength of 25 MPa to 30 MPa, 3-day compressive strength of 40 MPa to 45 MPa; bond strength of 2.0 MPa to 3.0 MPa; and permeability coefficient of 1.0 × 10⁻⁶. -7 cm / s to 5.0 × 10 -6 cm / s; volume shrinkage rate less than 1.5%.

[0063] The above performance indicators show that the mining grouting material provided in this embodiment meets or exceeds the existing technology in terms of early mechanical strength, permeability, and volume stability. In particular, the ultra-high early strength at 1 day and 3 days can meet the emergency engineering needs of rapid repair, reinforcement of fractured rock masses, and seepage control in coal mine tunnels. The effective control of volume shrinkage rate is due to the micro-expansion effect generated by the hydration of anhydrous gypsum to form ettringite, as well as the filling effect and densification compensation of the iron-containing microstructure in red mud.

[0064] Furthermore, when the ambient temperature deviates from the standard temperature range (18℃ to 25℃), this embodiment achieves adaptive adjustment of the setting time by adding admixtures. The specific adjustment scheme is as follows:

[0065] When the ambient temperature exceeds 30℃, add 0.3% to 0.8% of the total mass of solid powder as a phosphate-based retarder (such as sodium tripolyphosphate or sodium hexametaphosphate) to slow down the setting rate of the grout and prevent insufficient grouting time due to excessively rapid setting at high temperatures. The amount of retarder added is positively correlated with the ambient temperature; for every 5℃ increase in ambient temperature, the retarder dosage increases by 0.15% to 0.2%.

[0066] When the ambient temperature is below 5℃, add 0.5% to 1.0% of the total mass of solid powder with a sulfate-based accelerator (such as anhydrous aluminum sulfate or sodium sulfate) to accelerate the setting speed of the grout and prevent the grout from setting too slowly at low temperatures, which would lead to delayed gel strength development. The amount of accelerator added is negatively correlated with the ambient temperature; for every 5℃ decrease in ambient temperature, the amount of accelerator should be increased by 0.2% to 0.3%.

[0067] The admixture is added during the mixing of the grouting slurry in step 3, that is, at the initial stage of high-speed stirring, along with the solid mixed powder, to ensure that the admixture is evenly dispersed in the slurry.

[0068] To verify the effectiveness of the grouting material and preparation method in this embodiment, the following related experiments were conducted:

[0069] The tunnel is 580 meters deep, traversing mainly alternating layers of sandstone and mudstone. Some sections contain fissures ranging from 2mm to 8mm in width, with a seepage rate of approximately 3.5m³. 3 / h.

[0070] Grouting Scheme: The grouting slurry was prepared using the method described in this embodiment, with a solid-liquid ratio set at 1.4, a water glass modulus set at 1.6, and a grouting pressure set at 1.2 MPa. First, a cement-water glass dual-liquid grouting method was used to seal the cracks, injecting approximately 150 L of cement-based grouting slurry; subsequently, approximately 200 L of the modified metakaolin-based grouting slurry of this invention was injected. The injection interval between the two grouts was controlled within the range of 3 to 5 minutes. After grouting was completed, quality testing was conducted, and the results showed that the leakage rate was reduced to 0.2 m. 3 The water blocking rate is below 94%; the compressive strength of the specimens molded under the same laboratory conditions is 28 MPa after 1 day, 43 MPa after 3 days, and 2.5 MPa after 3 days. All performance indicators meet the design requirements.

[0071] Example 2

[0072] The differences from Example 1 are as follows:

[0073] In step 1, the proportions of the solid mixed powder are adjusted as follows: red mud 5%, fly ash 15%, granulated blast furnace slag powder 70%, modified metakaolin-based core material 5%, and the remaining 5% is supplemented by fly ash to make the total 100%, i.e., red mud 5%, fly ash 20%, slag 70%, and core material 5%. Reducing the proportion of red mud decreases the total amount of residual alkali and active iron oxide content in the system, which is beneficial for adjusting the system's coagulation characteristics towards a slightly slower pace.

[0074] In step 2, the modulus of the water glass solution is set to 1.8, and the concentration is 42°Bé. Increasing the modulus reduces the relative content of sodium oxide in the water glass solution, weakens the alkaline activation ability, and is beneficial for appropriately extending the setting time.

[0075] In step 3, the solid-liquid ratio is set to 1.6. Increasing the solid-liquid ratio means that the amount of water glass solution used is relatively reduced, the effective alkali content and the volume of the reaction medium in the system are reduced, the reaction rate is slowed down, and thus the solidification time is further extended, which is completely consistent with the control trend established in Example 1.

[0076] Based on the above parameter adjustments, the setting time test results of this embodiment are as follows: initial setting time 15 to 20 minutes, final setting time 28 to 38 minutes. This setting time range is suitable for scenarios requiring a slightly longer operating window in rapid repair operations. Meanwhile, the solidified body exhibits a 1-day compressive strength of 25 MPa to 28 MPa and a 3-day compressive strength of 38 MPa to 42 MPa, maintaining high early strength characteristics.

[0077] To verify the lower limit of the setting time control range, while maintaining the same proportions of 10% red mud, 20% fly ash, 65% slag, and 5% core materials, the water glass modulus was reduced to 1.3, and the solid-liquid ratio was reduced to 1.2. At this point, the initial setting time was shortened to 5-8 minutes, the final setting time to 15-22 minutes, the 1-day compressive strength of the solidified body was 28-32 MPa, and the 3-day compressive strength was 42-46 MPa. The slurry viscosity increased slightly but remained within the pumpable range, and the flowability met the requirements for grouting construction. No flash setting or rapid setting occurred. The experimental results show that, thanks to the alkali release delay mechanism of the amorphous composite precursor and the combined effect of red mud, even with a water glass modulus as low as 1.3, the system can still achieve ultra-fast solidification while maintaining good workability, breaking through the technical bottleneck of easy flash setting in traditional low-modulus alkali-activated systems.

[0078] To verify the upper limit of the setting time control range, while keeping the above proportions unchanged, the water glass modulus was increased to 1.8, and the solid-liquid ratio was increased to 1.6. At this point, the setting time was extended to 15-20 minutes for initial setting and 28-38 minutes for final setting. This setting time range is suitable for rapid repair operations requiring slightly longer operation times.

[0079] The systematic experimental data of this embodiment show that, by synergistically controlling the water glass modulus and the solid-liquid ratio, the setting time of the grouting material can be adjusted within the range of 5 to 20 minutes. Within the above-mentioned control range, the key performance indicators of the grout, such as viscosity, compressive strength, and permeability coefficient, are all kept within the acceptable range for engineering purposes, and flash setting does not occur.

[0080] Example 3

[0081] This embodiment provides a mining grouting material and its preparation method optimized for high-temperature construction environments, as detailed below:

[0082] In step 1, the proportions of the solid mixed powder are the same as in Example 1, namely 10% red mud, 20% fly ash, 65% slag, and 5% modified metakaolin-based core material. Based on this, in step 3, during the mixing of the grouting slurry, an additional 0.6% by weight of sodium tripolyphosphate is added as a retarder.

[0083] The process of adding the retarder is as follows: Sodium tripolyphosphate is pre-ground until it passes entirely through an 80μm square-hole sieve to ensure that its fineness is basically consistent with that of the solid mixed powder. Sodium tripolyphosphate and the solid mixed powder are pre-mixed in a mixer for 5 to 8 minutes to allow the retarder to be uniformly adsorbed onto the surface of each solid particle. Then, the pre-mixed powder is mixed and stirred with a water glass solution to obtain the grouting slurry with the added retarder.

[0084] This embodiment was tested under ambient temperatures ranging from 32°C to 38°C. The test results showed that the reference grout without retarder (parameters same as in Example 1, modulus 1.6, solid-liquid ratio 1.4) had an initial setting time of 5 to 7 minutes and a final setting time of 12 to 18 minutes at 32°C, indicating excessively rapid setting and an extremely short working window. However, with the addition of 0.6% sodium tripolyphosphate retarder, under the same ambient temperature, the initial setting time increased to 12 to 18 minutes, and the final setting time increased to 25 to 35 minutes, significantly increasing the working window and meeting the time requirements for normal grouting construction in high-temperature environments.

[0085] Meanwhile, this embodiment compared and tested the effect of different retarder dosages on setting time. When the retarder dosage was 0.3%, the initial setting time at 32℃ was 8 to 11 minutes, and the final setting time was 18 to 25 minutes. When the retarder dosage increased to 0.8%, the initial setting time at 32℃ increased to 18 to 25 minutes, and the final setting time increased to 32 to 42 minutes. The experimental data showed that the retarder dosage and the extension of setting time had an approximately linear positive correlation, which facilitates the adjustment of setting time according to ambient temperature during construction.

[0086] It should be noted that the addition of retarder has a certain impact on the final mechanical properties and permeability of the solidified slurry. When the retarder dosage is in the range of 0.3% to 0.6%, the decrease in 3-day compressive strength is controlled within 5%, and the permeability coefficient remains at 10. -6 The speed is on the order of cm / s. When the retarder dosage exceeds 0.8%, the 3-day compressive strength decreases by more than 10%, and the permeability coefficient may increase by an order of magnitude. In this case, it is necessary to compensate for the loss of mechanical and impermeability properties by appropriately increasing the amount of modified metakaolin-based core material (from 5% to 6%). Experimental results show that by adjusting the retarder dosage and the amount of core material added, the variation in 3-day compressive strength and permeability coefficient can be controlled within an acceptable range for engineering purposes while maintaining the target setting time.

[0087] Example 4

[0088] This embodiment provides a mining grouting material and its preparation method optimized for low-temperature construction environments, as detailed below:

[0089] In step 1, the proportions of the solid mixed powder are the same as in Example 1, namely 10% red mud, 20% fly ash, 65% slag, and 5% modified metakaolin-based core material. Based on this, anhydrous aluminum sulfate, at 0.8% of the total mass of the solid powder, is added as a quick-setting agent during the mixing of the grouting slurry in step 3.

[0090] The process of adding the accelerator is as follows: Anhydrous aluminum sulfate is pre-ground and passed through a 100μm square-hole sieve to ensure no agglomeration. The anhydrous aluminum sulfate and solid powder are mixed in a mixer for 6 to 10 minutes to ensure uniform dispersion. The pre-mixed powder is then mixed and stirred with a water glass solution to obtain the grouting slurry with the added accelerator. Because anhydrous aluminum sulfate dissolves rapidly in an alkaline environment and reacts with water glass to form aluminum silicate colloid, the accelerator should be added 1 to 2 minutes before grouting to avoid premature reaction in the mixing container, which could affect the slurry's performance.

[0091] This embodiment was tested under ambient temperatures ranging from 2°C to 5°C. The test results showed that the reference slurry without added accelerator (parameters same as in Example 1, modulus 1.6, solid-liquid ratio 1.4) had an initial setting time of 35 to 45 minutes and a final setting time of 55 to 70 minutes at 3°C. The setting rate was slower than at room temperature, and the 1-day compressive strength of the solidified body was only 10 to 15 MPa, indicating a significant lag in early strength development. However, after adding 0.8% anhydrous aluminum sulfate accelerator, under the same ambient temperature, the initial setting time was shortened to 20 to 28 minutes, and the final setting time was shortened to 35 to 48 minutes. Early strength was improved, and the 1-day compressive strength reached 18 to 22 MPa.

[0092] Furthermore, this embodiment compared and tested the effect of different accelerator dosages on setting time. When the accelerator dosage was 0.5%, the initial setting time at 3°C ​​was 28 to 35 minutes, and the final setting time was 45 to 55 minutes. When the accelerator dosage increased to 1.0%, the initial setting time at 3°C ​​decreased to 12 to 18 minutes, and the final setting time decreased to 22 to 30 minutes. However, when the accelerator dosage exceeded 1.0%, the grout exhibited rapid setting, the viscosity increased sharply during stirring, the grouting performance deteriorated significantly, and the 3-day compressive strength of the solidified body dropped below 30 MPa. Therefore, this embodiment determined the upper limit of the accelerator dosage to be 1.0%, and the optimal dosage range to be 0.5% to 0.8%.

[0093] This embodiment further verifies the effect of accelerators on the permeability of slurry. At an ambient temperature of 3°C, the slurry with 0.8% anhydrous aluminum sulfate accelerator exhibited a permeability coefficient of 3.0 × 10⁻⁶ after setting and hardening. -6 cm / s to 8.0×10 -6 The permeability coefficient is cm / s, slightly higher than that of the reference grout, but still meets the permeability performance requirements for coal mine grouting and seepage prevention projects. When the dosage of the quick-setting agent is controlled within the range of 0.5% to 0.8%, the increase in the permeability coefficient can be controlled within the acceptable range for the project.

[0094] Example 5

[0095] This embodiment provides a grouting construction scheme using a dual-liquid alternating injection method, which is suitable for grouting reinforcement projects under complex geological conditions.

[0096] In steps 1 to 3, a modified metakaolin-based grouting slurry was prepared according to the parameters of Example 1, with a solid-liquid ratio of 1.4 and a water glass modulus of 1.6. Simultaneously, a common silicate cement-based grouting slurry was prepared as the second component slurry using conventional methods, with a water-cement ratio controlled within the range of 0.6 to 0.8 and a cement slurry density controlled at 1.65 g / cm³. 3 Up to 1.80 g / cm 3 Within the range.

[0097] The specific operation process of alternating dual-liquid injection is as follows: First, inject modified metakaolin-based grout, with an injection volume of 35% to 45% of the total grouting volume. Then, inject ordinary cement-based grout, with an injection volume of 55% to 65% of the total grouting volume. The injection interval between the two grouts should be controlled within the range of 2 to 5 minutes. Too short an injection interval may cause the two grouts to mix and react prematurely in the grouting pipeline, resulting in pipeline blockage; too long an injection interval may cause the first-injected grout to initially solidify in the cracks, reducing the penetration and diffusion effect of the subsequently injected grout.

[0098] The grouting pressure control scheme is as follows: During the stage of injecting modified metakaolin-based grout, the grouting pressure is controlled within the range of 0.8MPa to 1.2MPa, utilizing the good permeability of the grout to fill small cracks and micropores; during the stage of injecting ordinary cement-based grout, the grouting pressure is increased to 1.5MPa to 2.0MPa, utilizing the higher strength characteristics of the cement-based grout to seal and reinforce larger cracks.

[0099] In this embodiment, the modified metakaolin-based grout has low viscosity and good permeability, enabling it to preferentially penetrate into fine cracks and form a dense internal reinforcement layer. The subsequently injected ordinary cement-based grout fills the space outside the already formed internal reinforcement layer, forming an external load-bearing layer. This process utilizes the window of 2-5 minutes during which the modified grout is still in a good flow state (initial setting time is 8-15 minutes), allowing the subsequent cement grout to effectively diffuse and form a tightly bonded interface. The core value of this alternating two-liquid injection method lies in using the excellent permeability of the modified grout to ensure sufficient filling of fine cracks, while simultaneously reducing overall material costs through the large-volume filling of the cement grout. The resulting gradient composite structure achieves dual optimization of performance and cost.

[0100] To verify the effect of alternating two-liquid injection on the overall properties of the solidified body, the following comparative experiment was designed:

[0101] Four groups of specimens were prepared and grouted using pure modified metakaolin-based grout, pure cement-based grout, a mixture of modified metakaolin-based and cement-based grout (i.e., the two grouts were pre-mixed in a mixing container and then injected in one go), and an alternating two-component injection method. The 3-day compressive strength and bond strength of each group of specimens were measured under the same curing conditions. Test results show that the 3-day compressive strength of the pure modified metakaolin-based grout specimen is 43.0 MPa, and the bond strength is 2.5 MPa; the 3-day compressive strength of the pure cement-based grout specimen is 18.0 MPa, and the bond strength is 1.2 MPa; the 3-day compressive strength of the mixed grout specimen injected in one go is 35.5 MPa, and the bond strength is 2.1 MPa, with its strength falling between the two pure grouts. This indicates that while the two grouts are chemically compatible, their physical homogeneity prevents them from fully realizing their optimal structures. The 3-day compressive strength of the specimen injected with alternating two grouts is 45.0 MPa, and the bond strength is 2.8 MPa. Experimental data demonstrate that the alternating two-grout injection method can fully utilize the advantages of both grouts while avoiding mutual dilution and structural interference caused by premature mixing. By constructing a gradient composite structure with a dense internal structure and a high external structure, it maintains a strength no lower than that of the pure modified grout while reducing overall material costs. Its comprehensive benefits are superior to the injection methods using pure modified grout or premixed grout.

[0102] Comparative Example 1

[0103] This comparative example provides a mining grouting material without added red mud as a comparison to verify the effect of red mud on improving the overall performance of the grouting material.

[0104] The solid powder in Comparative Example 1 consisted of fly ash, granulated blast furnace slag powder, and modified metakaolin-based core material. Fly ash accounted for 25% of the total mass of the solid powder, granulated blast furnace slag powder accounted for 70%, and modified metakaolin-based core material accounted for 5%. The relative ratio of fly ash to slag in this formulation was basically consistent with that in Example 1 (20:65), and no red mud was added. Other step parameters were consistent with those in Example 1, namely, the water glass modulus was 1.6 and the solid-liquid ratio was 1.4.

[0105] The test results of Comparative Example 1 showed that the slurry viscosity was basically the same as that of Example 1; the 1-day compressive strength was 18 MPa to 22 MPa, lower than the 25 MPa to 30 MPa of Example 1; the 3-day compressive strength was 30 MPa to 35 MPa, lower than the 40 MPa to 45 MPa of Example 1; and the permeability coefficient was 3.0 × 10⁻⁶. -6 cm / s to 1.0×10 -5 cm / s, higher than 1.0 × 10⁻⁶ in Example 1. -7 cm / s to 5.0 × 10 -6 cm / s; Regarding setting time, the initial setting time was 8 to 15 minutes, and the final setting time was 18 to 30 minutes, which was not significantly different from Example 1.

[0106] The comparative data above show that the addition of red mud has a significant positive impact on the mechanical strength and permeability of the grouting material. The active iron oxide, alumina, and silica components abundant in red mud participate in the alkali-activated geological polymerization reaction, generating iron-containing hydrated aluminosilicate gel, which enhances the density and mechanical properties of the hardened grout. At the same time, the auxiliary activating effect of residual alkali in red mud accelerates the dissociation of the slag glass structure and promotes the formation of early hydration products, thereby achieving a significant increase in early strength and a decrease in the permeability coefficient.

[0107] Comparative Example 2

[0108] This comparative example provides a mining grouting material with setting time controlled by a single parameter, as a comparison to verify the superiority of the dual-parameter control mechanism.

[0109] The solid powder composition of Comparative Example 2 was the same as that of Example 1, namely 10% red mud, 20% fly ash, 65% slag, and 5% modified metakaolin-based core material. The water glass modulus was set to 1.6, the solid-liquid ratio was fixed at 1.4, and the solid-liquid ratio was not adjusted. The setting time was controlled only by the water glass modulus.

[0110] Four condensation time control schemes were designed for the experiment: Group A reduced the water glass modulus from 1.6 to 1.3; Group B reduced the water glass modulus from 1.6 to 1.2; Group C increased the water glass modulus from 1.6 to 1.8; and Group D increased the water glass modulus from 1.6 to 2.0. The setting time test results for each group are as follows: Group A: initial setting time was 6 to 10 minutes, final setting time was 15 to 22 minutes, and 3-day compressive strength was 38 MPa to 44 MPa; Group B: initial setting time was 4 to 6 minutes, final setting time was 10 to 16 minutes, but the viscosity of the slurry in Group B increased significantly, and the flowability decreased. The 3-day compressive strength was 35 MPa to 40 MPa; Group C: initial setting time was 12 to 16 minutes, final setting time was 22 to 32 minutes, and 3-day compressive strength was 36 MPa to 42 MPa; Group D: initial setting time was 20 to 28 minutes, final setting time was 35 to 48 minutes, and the 3-day compressive strength of the solidified body in Group D decreased to 30 MPa to 36 MPa.

[0111] Comparative analysis shows that relying solely on the water glass modulus as a single parameter for control has significant limitations: while a low modulus can further shorten the setting time, it increases the slurry viscosity, leading to poor pourability and a risk of flash setting; while a high modulus can prolong the setting time, it results in a significant loss of mechanical strength. Particularly in group D, despite containing 5% of the core material, the 3-day strength (30-36 MPa) was significantly lower than that of Example 1 due to the modulus deviating severely from the optimal range, demonstrating the importance of synergistic matching between the modulus and the system proportions. Comparative data from Example 1 and Comparative Example 2 show that the dual-parameter synergistic control mechanism of water glass modulus and solid-liquid ratio offers higher control precision, a wider control range, and a more balanced control effect, enabling control of setting time while maintaining good slurry workability and high early-strength mechanical strength.

[0112] Comparative Example 3

[0113] This comparative example provides a grouting material for mining using nano-silica and carbon nanotubes as modified materials, serving as a comparison to verify the advantages of the present invention in terms of economy and practicality of using red mud and modified metakaolin-based core materials.

[0114] The solid powder in Comparative Example 3 consisted of red mud, fly ash, granulated blast furnace slag powder, and nano-modified materials. The total mass of red mud, fly ash, and slag was 100%, with red mud accounting for 10%, fly ash for 20%, and slag for 70%. The amount of nano-silica added was 1.5% of the total mass of red mud, fly ash, and slag, and the amount of carbon nanotubes added was 0.3% of the total mass of red mud, fly ash, and slag. Before incorporation, the nano-silica and carbon nanotubes underwent surface modification treatment to improve their dispersibility. The specific treatment method was as follows: the nano-silica and carbon nanotubes were ultrasonically dispersed in anhydrous ethanol for 30 to 45 minutes at a dispersion power of 300 W to 400 W and a dispersion frequency of 20 kHz to 40 kHz. Then, a dispersant (polycarboxylate superplasticizer) was added, and ultrasonic dispersion continued for 15 to 20 minutes. Finally, the materials were dried at 80°C to 100°C to obtain the surface-modified nanomaterials. The other steps and parameters remain the same as in Example 1.

[0115] The test results of Comparative Example 3 showed that: during the preparation of the nano-modified slurry, the ultrasonic dispersion treatment was time-consuming (approximately 45 to 60 minutes), and the equipment energy consumption was high; the addition of nano-silica and carbon nanotubes led to an increase in slurry viscosity; the 1-day compressive strength of the solidified body was 24 MPa to 28 MPa, which was basically the same as the 25 MPa to 30 MPa of Example 1; the 3-day compressive strength was 38 MPa to 43 MPa, which was similar to the 40 MPa to 45 MPa of Example 1; and the permeability coefficient was 2.0 × 10⁻⁶. -6 cm / s to 8.0×10 -6 cm / s, similar to Example 1. However, from an economic perspective, the market price of nano-silica is about 30 to 50 times that of fly ash, and the market price of carbon nanotubes is more than 1,000 times that of slag. Even with a small addition amount (about 1.8% in total), its material cost reaches more than 30% of the total cost of solid powder. At the same time, its dispersion treatment increases process time and equipment energy consumption.

[0116] From the perspective of technical stability, the dispersion effect of nanomaterials in Comparative Example 3 is affected by multiple factors such as ultrasonic dispersion power, time, and temperature. In actual operation, the batch-to-batch variation in dispersion uniformity is relatively large. The stability coefficient of the mechanical properties of the solidified body (the ratio of the maximum to the minimum compressive strength of the same batch of specimens after 3 days) is approximately 1.15 to 1.25, slightly higher than the 1.05 to 1.12 of Example 1. In contrast, this invention uses red mud and modified metakaolin-based core materials. The red mud only requires simple drying and sieving pretreatment, and the core materials only require ball milling and mixing treatment. No surface modification or special dispersion treatment of nanomaterials is required, resulting in better batch-to-batch performance stability. Furthermore, the proportion of industrial solid waste in all solid powder components is high, and the material cost is low.

[0117] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. All modifications made based on the design principles of the present invention, and modifications made without creative effort, shall fall within the scope of protection of the present invention.

Claims

1. A grouting material for mining, characterized in that, The mixture comprises a solid mixed powder and a water glass solution. The solid mixed powder includes red mud, fly ash, granulated blast furnace slag powder, and modified metakaolin-based core material. Red mud accounts for 5%–15% of the total mass of the solid mixed powder, fly ash for 10%–25%, granulated blast furnace slag powder for 55%–70%, and modified metakaolin-based core material for 3%–7%. The modulus of the water glass solution is 1.3–1.8, and the solid-liquid mass ratio of the solid mixed powder to the water glass solution is 1.2–1.

6. The modified metakaolin-based core material is made by mixing metakaolin and silica fume at a mass ratio of 3:1–5:1, adding 8%–12% anhydrous gypsum and 5%–10% calcium hydroxide (by mass of the total metakaolin and silica fume), and ball milling to a Blaine surface area of ​​not less than 650 m². 2 / kg of amorphous composite precursor obtained.

2. The grouting material for mining according to claim 1, characterized in that, The red mud meets the following conditions: moisture content is less than 5%, fineness is such that the residue on an 80μm square hole sieve does not exceed 15%, pH value is 10-13, iron oxide content is 25%-45%, aluminum oxide content is 15%-25%, and silicon oxide content is 10%-20%.

3. The grouting material for mining according to claim 2, characterized in that, The fly ash meets the following conditions: calcium oxide content is less than 18%, residue on a 45μm square hole sieve is 8% to 12%, loss on ignition is less than 5%, water requirement ratio is not more than 95%, and 28-day activity index is not less than 70%.

4. The grouting material for mining according to claim 3, characterized in that, The specific surface area of ​​the granulated blast furnace slag powder is 400–500 m². 2 / kg, vitreous content not less than 90%, 7-day activity index not less than 65%, 28-day activity index not less than 85%.

5. The grouting material for mining according to claim 4, characterized in that, The calcium hydroxide is industrial grade calcium hydroxide with a purity of not less than 90% and an average particle size D. 50 The thickness is 5–15 μm, and the BET specific surface area is not less than 10 m². 2 / g.

6. The grouting material for mining according to claim 5, characterized in that, The conditions for ball milling are as follows: the milling medium is zirconia balls, the ball-to-material mass ratio is 10:1 to 20:1, the filling rate is 30% to 45%, the rotation speed is 300 to 450 r / min, and the milling time is 60 to 90 min.

7. The grouting material for mining according to claim 6, characterized in that, The modulus of the water glass solution is adjusted to the target value by adding sodium hydroxide solution, and the Baumé degree of the water glass solution is 38-42°Bé.

8. The mining grouting material according to any one of claims 1 to 7, characterized in that, It also includes phosphate-based retarder accounting for 0.3% to 0.8% of the total mass of the solid mixed powder, or sulfate-based accelerator accounting for 0.5% to 1.0% of the total mass of the solid mixed powder.

9. A method for preparing the mining grouting material according to any one of claims 1 to 8, characterized in that, Includes the following steps: (1) Preparation of solid mixed powder: Red mud, fly ash, granulated blast furnace slag powder and the prepared modified metakaolin-based core material are mixed evenly, wherein red mud accounts for 5% to 15% of the total mass of solid mixed powder, fly ash accounts for 10% to 25%, granulated blast furnace slag powder accounts for 55% to 70%, and modified metakaolin-based core material accounts for 3% to 7%; (2) Prepare a water glass solution and adjust its modulus to 1.3 to 1.8; (3) Mix the solid mixed powder with water glass solution at a solid-liquid mass ratio of 1.2 to 1.6 to obtain the grouting slurry.

10. The method according to claim 9, characterized in that, In step (3), the water glass solution is added to the stirring container and high-speed stirring is started. Then, the solid mixed powder is slowly added. The stirring speed is 800-1200 r / min, and the feeding time is controlled at 90-150 seconds. After the feeding is completed, stirring is continued for 120-180 seconds.