Cement-based high-early-strength grouting material, preparation method, application and grouting method thereof

Abstract

The application belongs to the technical field of building materials, and relates to a cement-based high-early-strength grouting material, a preparation method, application and grouting method thereof. The cement-based high-early-strength grouting material is composed of the following components in parts by weight: composite early-strength cement material 590-720 parts, superfine mineral admixture 200-280 parts, composite early-strength agent 21-34.5 parts, slurry stabilizer 29-50 parts, composite water reducing agent 5.5-10.5 parts and water 740-820 parts. The grouting material has the characteristics of good particle size distribution, high early strength, good flow and diffusion performance and strong slurry stability. The matched grouting method is used for reinforcing the compact granite alteration zone, which is beneficial to improving the mechanical properties, self-stability, tunnel excavation safety and efficiency of the stratum, reducing the occurrence of disasters such as surrounding rock instability and collapse, water and mud inrush and TBM being trapped, and realizing safe and efficient construction of the tunnel.

Description

Technical Field

[0001] This invention belongs to the field of building materials technology, specifically relating to a cement-based high early strength grouting material and its preparation method, application and grouting method. Background Technology

[0002] As the focus of underground engineering construction gradually shifts to the geologically complex western and southern regions, major infrastructure projects such as transportation and water conservancy often need to traverse towering mountains. These areas have complex geological structures and significant geostress environments, posing significant challenges to engineering construction. Taking complex geological tunnel engineering as an example, this region is characterized by "three highs" (high geothermal activity, high geostress, and high seismic intensity) and "four actives" (active neotectonic movements, active geothermal water environment, active exogenic geological conditions, and active shallow slope alteration processes). Against the backdrop of plate collision, deep faults provide channels for fluid transport, high geothermal activity provides energy, and active geothermal water acts as a chemical solvent, leading to the formation of granite alteration zones in ancient granites under long-term, intense chemical-physical coupling. This stratum has extremely low strength, is easily softened by water, and has poor self-stability, frequently causing disasters such as surrounding rock instability and collapse, water and mud inrushes, and TBM jamming during construction, which has become a recognized problem in the field of tunnel engineering.

[0003] To address such complex geological formations, advanced curtain grouting technology is commonly used for pre-reinforcement and improvement. In grouting within the alteration zone of dense granite, traditional grouting materials primarily consist of ordinary Portland cement and ultrafine cement. However, ordinary Portland cement suffers from poor injectability, insufficient grout stability, and long setting time; while ultrafine cement, despite its finer particle size and improved adaptability to alteration zones, still exhibits drawbacks such as low early strength and insufficient flow and diffusion properties, making it difficult to ensure ideal grouting reinforcement results. Summary of the Invention

[0004] The purpose of this invention is to provide a cement-based high early strength grouting material and grouting method suitable for dense granite alteration zones, thereby overcoming the shortcomings of existing technologies. This grouting material has the characteristics of superior particle size distribution, high early strength, good flow and diffusion performance, and strong grout stability. When used in conjunction with a matching grouting construction process to reinforce dense granite alteration zone strata, it is beneficial to significantly improve the mechanical properties and self-stabilizing ability of the strata, improve the safety and efficiency of tunnel excavation, reduce the occurrence of disasters such as surrounding rock instability and collapse, water and mud inrush, and TBM entrapment, and achieve safe and efficient tunnel construction.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows: In a first aspect, the present invention provides a cement-based high early strength grouting material, which is composed of the following components in parts by weight: The composition includes 590-720 parts of composite early-strength cementitious material, 200-280 parts of ultrafine mineral admixture, 21-34.5 parts of composite early-strength agent, 29-50 parts of paste stabilizer, 5.5-10.5 parts of composite water-reducing agent, and 740-820 parts of water. Composite early-strength cement material is composed of silicate cement clinker, gypsum, sulfoaluminate cement and high-alumina cement; The ultrafine mineral admixture is composed of silica fume, ultrafine fly ash, and slag powder; The composite early strength agent is composed of sodium sulfate, calcium chloride, lithium carbonate, triethanolamine, and water glass; The slurry stabilizer is composed of nano-SiO2, carbon nanotubes, nano-alumina, modified hydroxyethyl methyl cellulose ether, and bentonite; The composite water-reducing agent is composed of polycarboxylate-based water-reducing agent, naphthalene-based water-reducing agent and melamine-based water-reducing agent.

[0006] The silicate cement clinker in this invention provides a stable long-term strength foundation and forms the core framework of the slurry structure. Its hydration products synergistically with other components to ensure that the material's later strength does not decline. Gypsum, as a key setting regulator, reacts with sulfoaluminate / high-alumina cement to form ettringite, which is the main source of early strength. It also effectively controls setting time, prevents rapid cement setting, and ensures sufficient time for grouting. Sulfoaluminate cement is the core early-strength component of the system, with a rapid hydration rate, quickly generating early strength and reaching a relatively high strength within hours. Its hydration produces ettringite, which causes micro-expansion, compensating for slurry shrinkage and enhancing adhesion to fracture walls. High-alumina cement provides rapid setting and early strength development, reacts strongly with gypsum, and is an important component for early ettringite formation and strength enhancement. Although its coexistence with silicate systems can easily lead to later strength decline and cracking risks, the material in this invention is mainly for the pre-reinforcement and improvement of strata in advanced curtain grouting, where excavation of the working face occurs a few days after grouting, therefore the requirements for later strength are not high. The extremely fine particles of silica fume effectively fill the nanoscale pores between cement particles, significantly improving the density and impermeability of the grout. Furthermore, its high pozzolanic activity reacts with cement hydration products, significantly enhancing later-stage strength and durability. The microsphere effect of ultrafine fly ash provides physical lubrication, significantly improving grout fluidity and injectability without increasing water consumption. It also continuously optimizes the pore structure through secondary hydration, contributing to later-stage strength growth and reducing heat of hydration. The potential hydraulic properties of slag powder enable the formation of a large amount of low-alkalinity CSH gel in the later stages, significantly improving final strength and chemical stability. It also improves grout particle size distribution, increases density, inhibits alkali-aggregate reaction, and enhances durability. Therefore, this invention uses silicate cement clinker, gypsum, sulfoaluminate cement, high-alumina cement, silica fume, ultrafine fly ash, and slag powder as the cementitious matrix materials. Experimental results show that the grouting material obtained using the above combination exhibits good workability and mechanical properties.

[0007] To improve the early mechanical properties of the material, enabling the grouting solid to possess the highest possible strength within hours to days after grouting, thus better supporting tunnel excavation, this invention employs a composite method of sodium sulfate, calcium chloride, lithium carbonate, triethanolamine, and water glass to enhance the early mechanical properties of the material. Sodium sulfate rapidly reacts with calcium hydroxide produced during cement hydration to generate gypsum and sodium hydroxide. The newly generated gypsum is more reactive and reacts quickly with the aluminum phase to form more ettringite, providing early strength. Furthermore, the generated sodium hydroxide stimulates the early activity of slag, ultrafine fly ash, and silica fume, collectively promoting the early formation of the grout structure. Calcium chloride accelerates the hydration reaction of calcium silicate, rapidly forming an early framework structure and providing extremely high early strength. Lithium carbonate has a significant effect on accelerating the setting and early strength of sulfoaluminate cement and high-alumina cement, accelerating the formation rate of ettringite. Triethanolamine primarily accelerates the hydration reaction of tricalcium aluminate through catalysis, altering its hydration process, and promotes the formation of the early AFm / AFt phase by competing with gypsum, thereby significantly improving early strength. Upon contact with water, water glass rapidly reacts with calcium ions precipitated during cement hydration to form calcium silicate gel, resulting in rapid setting and hardening. The aforementioned early-strength agents constitute a multi-layered, multi-target synergistic early-strength system. Water glass provides the basis for instantaneous solidification, calcium chloride and triethanolamine strongly drive the hydration of silicate and aluminate phases, while sodium sulfate and lithium carbonate primarily promote and optimize the rapid and abundant formation of ettringite. Experimental results show that the grouting material obtained using the above combination exhibits good early mechanical properties.

[0008] To improve the particle size distribution and slurry stability of the material system, this invention incorporates nano-SiO2, carbon nanotubes, nano-alumina, modified hydroxyethyl methyl cellulose ether, and bentonite. The nano-sized SiO2 particles can fill the spaces between micron-sized cement particles, achieving the densest packing. This not only increases matrix density but also reduces free water in the slurry, thereby enhancing slurry stability. Furthermore, at low dosages, by optimizing the particle size distribution, nano-SiO2 can reduce pore channels without significantly increasing slurry viscosity. This facilitates better permeation of the slurry under pressure through extremely fine fissures. Carbon nanotubes intertwine within the slurry to form a three-dimensional nanofiber network, physically binding cement particles and providing excellent steric hindrance, effectively preventing the sedimentation and segregation of solid particles and improving slurry uniformity and stability. This nano-network structure remains intact during pumped grouting, facilitating uniform and continuous "plunger flow" slurry penetration into fissures and preventing blockage of seepage channels due to component separation. The synergistic effect of nano-alumina and nano-SiO2 further fills finer nanoscale pores, which not only improves stability but also reduces the risk of the slurry being diluted or dispersed by formation water. Furthermore, its surface properties help regulate the rheology of the slurry; at certain dosages, it can increase the cohesion of the slurry, allowing it to better adhere to the fracture surface during infiltration and improving the effective plugging rate. Modified hydroxyethyl methyl cellulose ether (HEMC) prevents bleeding and segregation through physical association via thickening and adsorption network formation, and forms an interfacial film on the surface of cement particles to resist water erosion, thus endowing the material with underwater anti-dispersion properties. HEMC imparts good thixotropic properties to the slurry, meaning that the slurry thins during pumping shearing to facilitate infiltration and regains its viscosity after settling in the formation to prevent loss. This helps to achieve "easy infiltration and easy stabilization" in altered zones. Upon contact with water, bentonite absorbs water and expands in volume between layers, effectively adsorbing and fixing moisture. Through physical occupancy and water-locking, it reduces seepage channels and enhances the suspension stability of the grout. The dispersed flaky particles impart high thixotropy and yield stress to the grout, ensuring that solid particles are effectively suspended when the grout permeates through narrow fissures, preventing deposition and blockage of the seepage path due to changes in flow velocity. Experimental results show that the grouting material obtained using the above combination exhibits superior particle size distribution and grout stability.

[0009] Polycarboxylate-based, naphthalene-based, and melamine-based water-reducing agents are used synergistically to improve the flow and diffusion properties of the material. The comb-like molecular structure of polycarboxylate-based water-reducing agents, through steric hindrance, prevents cement particles from approaching each other for extended periods, thus imparting high fluidity and penetration diffusion capacity to the grout with low water consumption, allowing it to penetrate into finer fissures. Furthermore, polycarboxylate-based water-reducing agents achieve low viscosity and high dispersion, maintaining good fluidity under high pressure, which is crucial for long-distance penetration in dense fissure networks. Naphthalene-based water-reducing agents primarily disperse cement particles through electrostatic repulsion, effectively reducing water consumption and providing high initial fluidity, making the grout easy to pump and inject. However, its dispersion effect decays rapidly, making it unsuitable for long-term, long-distance penetration grouting when used alone. Melamine-based water-reducing agents, with electrostatic repulsion as the main mechanism, provide similar high initial fluidity to naphthalene-based water-reducing agents, but with slightly lower air entrainment, resulting in a denser grout. Polycarboxylate superplasticizers serve as the main component, providing durable and efficient flowability retention. Naphthalene-based and melamine-based superplasticizers optimize the initial rheological properties of the slurry through faster initial adsorption and dispersion rates, and may fine-tune the action mode of polycarboxylate molecules through competitive adsorption. This combination of fast and slow adsorption achieves complementary advantages, aiming to optimize the flow and diffusion properties of the slurry throughout the entire process from initial mixing and pumping to infiltration into the formation. Experimental results show that the grouting material obtained by using the above-mentioned combination of technologies exhibits superior flow and diffusion performance.

[0010] In some other embodiments, the weight ratio of silicate cement clinker, gypsum, sulfoaluminate cement and high-alumina cement in the composite early-strength cement material is (480-560):(25-35):(60-80):(30-40). The weight ratio of silica fume, ultrafine fly ash and slag powder in the ultrafine mineral admixture is (40-60):(90-120):(70-100). The weight ratio of sodium sulfate, calcium chloride, lithium carbonate, triethanolamine and water glass in the composite early strength agent is (8-14):(10-15):(0.15-0.25):(0.1-0.2):(3-5). The weight ratio of nano-SiO2, carbon nanotubes, nano-alumina, modified hydroxyethyl methyl cellulose ether, and bentonite in the slurry stabilizer is (2-3):(0.3-0.5):(7-11):(0.4-0.6):(20-30). The weight ratio of polycarboxylate superplasticizer, naphthalene superplasticizer and melamine superplasticizer in the composite water-reducing agent is (0.8-1.2):(3-5):(2-4).

[0011] In some implementations, the average particle size of the silicate cement clinker is not higher than 8 μm.

[0012] Sulfoaluminate cement and high-alumina cement have a specific surface area ≥900m². 2 / kg, preferably 1000m 2 / kg; The alumina content in high-alumina cement is not less than 60%.

[0013] In some embodiments, the specific surface area of ​​silica fume is ≥15000 m² / kg, and the SiO2 content is ≥85%.

[0014] The specific surface area of ​​ultrafine fly ash and slag powder is ≥800m². 2 / kg; Sodium sulfate, calcium chloride, and lithium carbonate are of analytical grade.

[0015] In some implementations, the content of triethanolamine as an active ingredient is ≥99%.

[0016] The water glass has a modulus of 3.0-3.4, preferably 3.1, and a Baumé degree of 38.

[0017] In some embodiments, the specific surface areas of nano-SiO2, carbon nanotubes, and nano-alumina are each not less than 250 m². 2 / g, 100m 2 / g and 30m 2 / g.

[0018] The average particle sizes of nano-SiO2, carbon nanotubes, and nano-alumina are no higher than 20 nm, 30 nm, and 50 nm, respectively. The modified hydroxyethyl methyl cellulose ether is a hydroxyethyl methyl cellulose ether modified with aldehydes, with a viscosity of 150,000 and an effective substance content of ≥99%. Specifically, the preparation method of modified hydroxyethyl methyl cellulose ether is as follows: hydroxyethyl methyl cellulose ether is dispersed in a mixed solvent of ethanol and water; aldehydes are added and the pH is adjusted to 2-4, and the reaction is carried out at 50-70℃ for 2-4 h; after neutralization with alkali, the ether is washed, dried and pulverized to obtain modified hydroxyethyl methyl cellulose ether.

[0019] Aldehydes are formaldehyde solutions with a mass percentage of 30-40 wt%.

[0020] The bentonite is sodium-based bentonite with a specific surface area ≥800 m². 2 / kg, expansion ratio 20-30 times.

[0021] In some embodiments, the water reduction rate of the polycarboxylate superplasticizer is not less than 40%, and the content of the active ingredient is ≥96%.

[0022] The water reduction rate of naphthalene-based water-reducing agents shall not be less than 20%, and the solid content shall be ≥99%. The water reduction rate of melamine-based water-reducing agents shall not be less than 20%, and the content of effective ingredients shall be ≥99%.

[0023] In a second aspect, the present invention provides a method for preparing the cement-based high early strength grouting material described in the first aspect, comprising the following steps: (1) Pre-dry mix nano-SiO2, nano-alumina and part of ultrafine fly ash and stir evenly to obtain micro-nano powder; mix carbon nanotubes, part of polycarboxylate superplasticizer and part of water, stir with a glass rod or prepare a suspension in an ultrasonic cleaner; (2) Add silicate cement clinker, gypsum, sulfoaluminate cement, high alumina cement, silica fume, the remaining ultrafine fly ash, slag powder, sodium sulfate, calcium chloride, lithium carbonate, modified hydroxyethyl methyl cellulose ether, bentonite, and the micro-nano powder in step (1) into a mixer and mix evenly to obtain a mixed dry powder. (3) Add water glass, triethanolamine, the remaining polycarboxylate superplasticizer, naphthalene superplasticizer, melamine superplasticizer and the suspension in step (1) to the remaining water and stir evenly to obtain a mixed liquid; (4) Mix the liquid mixture in step (3) with the dry powder mixture in step (2) and stir evenly to obtain a cement-based high early strength grouting material suitable for the alteration zone of dense granite.

[0024] Thirdly, the present invention provides the application of the cement-based high early strength grouting material described in the first aspect in grouting of the alteration zone of dense granite.

[0025] Fourthly, the present invention provides a grouting method for cement-based high early strength grouting materials, comprising the following steps: (1) The cement-based high early strength grouting material described in the first aspect is injected into the formation using a low-pressure, slow-seepage method; (2) After the grouting pressure stabilizes and begins to rise slowly, the grouting pressure is gradually increased to allow the grout to penetrate further into the finer fissures of the formation. (3) When the grouting pressure reaches 70%–80% of the design final pressure, maintain the pressure and continue grouting; (4) After the grouting pressure reaches the design final pressure, maintain grouting for a period of time. When the grouting speed is lower than one-quarter of the initial grouting speed and the final grouting volume does not exceed 6L / min, stop grouting.

[0026] In some other embodiments, in step (1), the grouting pressure of the low-pressure slow seepage method is 0-2MPa, and the grouting speed is 10-30L / min; In step (2), when the grouting pressure is stable at 2MPa, the grouting pressure is gradually increased by 0.5-1.0MPa per level. In step (3), the final pressure is designed to be 5-6 MPa, and the grouting time is 10-30 min.

[0027] The beneficial effects of this invention are: (1) This invention significantly shortens the setting time of the grout by combining silicate cement clinker, sulfoaluminate cement, and high-alumina cement, and introduces ultrafine solid waste mineral admixtures to optimize particle size distribution and enhance mechanical properties. With the help of co-utilization of solid waste and precise control of admixtures, this grouting material is superior to traditional materials in terms of flowability, particle plasticity, and early strength, demonstrating significant comprehensive performance advantages. Specifically, the grouting material prepared by this invention has a flowability ≥292mm, an initial viscosity ≤23.4mPa·s, a bleeding rate ≤3.8%, an initial setting time ≥1.8h ≥3h, an undisturbed slurry absorption rate ≥6%, a compressive strength ≥1.5MPa ≥12h, a compressive strength ≥3MPa ≥1d, a compressive strength ≥5MPa ≥3d, and a compressive strength ≥8MPa ≥7d.

[0028] (2) The grouting material and supporting process can achieve efficient penetration of the grout into the stratum and effectively fill the pores without relying on ultra-high pressure fracturing. The material can form high early strength within hours to days, significantly improving the mechanical properties and self-stabilizing ability of the stratum, which helps to enhance the safety and construction efficiency during tunnel excavation, reduce engineering risks such as surrounding rock instability, water and mud inrush, and TBM jamming, and ensure safe and efficient tunnel construction.

[0029] (3) By introducing industrial solid waste as part of the raw materials, this invention not only realizes the high added value utilization of solid waste resources, but also improves the economic efficiency of grouting materials, which helps to promote the large-scale disposal and green circular application of bulk industrial solid waste. Detailed Implementation

[0030] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The properties of some of the raw materials used are as follows: The average particle size of silicate cement clinker is no higher than 8μm.

[0031] Sulfoaluminate cement and high-alumina cement have a specific surface area ≥900m². 2 / kg, preferably 1000m 2 / kg.

[0032] The alumina content in high-alumina cement is not less than 60%.

[0033] The specific surface area of ​​silica fume is ≥15000 m² / kg, and the SiO2 content is ≥85%.

[0034] The specific surface area of ​​ultrafine fly ash and slag powder is ≥800m². 2 / kg.

[0035] Sodium sulfate, calcium chloride, and lithium carbonate are of analytical grade.

[0036] The content of triethanolamine active ingredient is ≥99%.

[0037] The water glass has a modulus of 3.0-3.4, preferably 3.1, and a Baumé degree of 38.

[0038] The specific surface areas of nano-SiO2, carbon nanotubes, and nano-alumina are each not less than 250 m². 2 / g, 100m 2 / g and 30m 2 / g, the average particle sizes of nano-SiO2, carbon nanotubes and nano-alumina are no higher than 20nm, 30nm and 50nm respectively.

[0039] The modified hydroxyethyl methyl cellulose ether is a hydroxyethyl methyl cellulose ether modified with aldehydes, with a viscosity of 150,000 and an effective substance content of ≥99%.

[0040] This invention does not impose any particular limitation on the preparation method of modified hydroxyethyl methyl cellulose ether. A preferred method is as follows: 100 parts by weight of hydroxyethyl methyl cellulose ether is dispersed in a mixed solvent of ethanol and water. 3-8 parts by weight of an aldehyde are added under stirring. The pH is adjusted to 2-4 using an acid catalyst, and the reaction is carried out at 50-70°C for 2-4 hours. After the reaction is complete, the mixture is neutralized with alkali, and the product is obtained after washing, drying, and pulverizing. The aldehyde is preferably a 30-40 wt% formaldehyde solution.

[0041] The bentonite is sodium-based bentonite with a specific surface area ≥800 m². 2 / kg, expansion ratio 20-30 times.

[0042] The water reduction rate of polycarboxylate superplasticizer is not less than 40%, and the content of effective ingredients is ≥96%.

[0043] Naphthalene-based water-reducing agents are yellowish-brown powders with a water reduction rate of not less than 20% and a solid content of ≥99%.

[0044] Melamine-based water-reducing agents have a water reduction rate of not less than 20% and an effective ingredient content of ≥99%.

[0045] To address the problems of existing grouting materials, such as long setting time, high shrinkage rate, and insufficient impermeability and durability, and the difficulties in controlling the quality of gravel and the poor grouting effect of traditional gravel backfilling and cement grouting processes, which can easily lead to a series of disasters such as segment displacement, misalignment, damage, and water leakage, this invention proposes a cement-based high-early-strength grouting material and construction process suitable for the alteration zone of dense granite.

[0046] To enable those skilled in the art to better understand the technical solution, the technical solution will be described in detail below with reference to specific embodiments and comparative examples. It should be noted that the specific embodiments are explanations of the present invention rather than limitations.

[0047] In the following examples, the modified hydroxyethyl methyl cellulose ether was prepared as follows: 100 parts by weight of hydroxyethyl methyl cellulose ether were weighed and placed in a reactor. A mixed solvent consisting of 250 parts by weight of anhydrous ethanol and 150 parts by weight of deionized water was added. Stirring was started, and the mixture was allowed to fully disperse and swell at 300 rpm for 30 minutes. While stirring continuously, 5 parts by weight of formaldehyde solution (concentration 37 wt%) was slowly added dropwise to the system. After the addition was complete, the pH of the reaction system was adjusted to 2.5 with dilute hydrochloric acid. The temperature of the reaction system was raised to 60°C and maintained at this temperature for 3 hours. After the reaction was completed, the system was cooled to room temperature. The pH of the reaction system was neutralized to 7.0 with 10 wt% sodium hydroxide solution. The obtained product was filtered, and the filter cake was washed three times with 300 parts by weight of 70% ethanol aqueous solution to remove residual reaction reagents and byproducts. The washed filter cake was dried in a vacuum drying oven at 80°C for 6 hours until constant weight was achieved. Finally, the dried block product was pulverized using a pulverizer and passed through a 100-mesh sieve to obtain a white powdery modified hydroxyethyl methyl cellulose ether product.

[0048] Example 1 (1) A cement-based high early strength grouting material suitable for the alteration zone of dense granite, in parts by weight, silicate cement clinker: gypsum: sulfoaluminate cement: high alumina cement: silica fume: ultrafine fly ash: slag powder: sodium sulfate: calcium chloride: lithium carbonate: triethanolamine: water glass: nano SiO2: carbon nanotubes: nano alumina: modified hydroxyethyl methyl cellulose ether: bentonite: polycarboxylate superplasticizer: naphthalene superplasticizer: melamine superplasticizer: water = 480: 30: 80: 35: 40: 105:100: 11: 15: 0.15: 0.15: 3: 2: 0.4: 11: 0.5: 25: 0.8: 5: 4: 740.

[0049] (2) A method for preparing cement-based high early strength grouting material suitable for the alteration zone of dense granite, comprising the following steps: Nano-SiO2, nano-alumina and 30% ultrafine fly ash are pre-dry mixed and stirred evenly to obtain micro-nano powder; carbon nanotubes, 50% polycarboxylate superplasticizer and 25% water are mixed and stirred with a glass rod or prepared in an ultrasonic cleaner to obtain a suspension.

[0050] Silicate cement clinker, gypsum, sulfoaluminate cement, high-alumina cement, silica fume, the remaining 70% of ultrafine fly ash, slag powder, sodium sulfate, calcium chloride, lithium carbonate, modified hydroxyethyl methyl cellulose ether, bentonite, and micro / nano powders are all poured into a mixer and stirred evenly to obtain a mixed dry powder.

[0051] Add water glass, triethanolamine, the remaining 50% of polycarboxylate superplasticizer, naphthalene superplasticizer, melamine superplasticizer, and suspension to the remaining 75% of water and stir until homogeneous to obtain a mixed liquid.

[0052] The mixed liquid and mixed dry powder are mixed and stirred evenly to obtain a cement-based high early strength grouting material suitable for the alteration zone of dense granite.

[0053] (3) A grouting method for cement-based high early strength grouting materials applicable to the alteration zone of dense granite, comprising the following steps: Step 1: Prepare a high-pressure grouting pump and ensure it is working properly; connect the grouting pipeline, and after drilling, use high-pressure air to clean the debris inside the hole. After cleaning the grouting hole, install the hole opening pipe and grout stop device.

[0054] Step 2: Prepare cement-based high early strength grouting material suitable for the alteration zone of dense granite.

[0055] Step 3: Clean and connect the grout outlet and the borehole pipe of the grouting pipeline. Start grouting using a low-pressure slow seepage method. The grouting pressure is 0-2MPa and the grouting speed is 10-30L / min. Inject the cement-based high early strength grouting material suitable for the alteration zone of dense granite into the formation through the grouting pipe.

[0056] Step 4: After the grouting pressure stabilizes at 2MPa and begins to rise slowly, gradually increase the pumping pressure (0.5-1.0MPa per stage). The grout will penetrate into smaller cracks under pressure. When the pressure rises to 70%-80% of the design final pressure, continue grouting for a period of time while maintaining the pressure.

[0057] Step 5: Gradually increase the grouting pressure to the designed final pressure of 5-6 MPa, and maintain grouting for 10-30 minutes. When the grouting speed is less than one-quarter of the initial grouting speed, stop grouting in that hole. The grouting flow rate at the end of grouting should not exceed 6 L / min.

[0058] Step 6: When all grouting holes have met the single-hole grouting conditions and there is no leakage, stop grouting for the entire section.

[0059] Example 2 A cement-based high-early-strength grouting material suitable for the alteration zone of dense granite, comprising, by weight, silicate cement clinker: gypsum: sulfoaluminate cement: high-alumina cement: silica fume: ultrafine fly ash: slag powder: sodium sulfate: calcium chloride: lithium carbonate: triethanolamine: water glass: nano-SiO2: carbon nanotubes: nano-alumina: modified hydroxyethyl methyl cellulose ether: bentonite: polycarboxylate superplasticizer: naphthalene superplasticizer: melamine superplasticizer: water = 560: 30: 60: 30: 40: 90: 85: 8: 12.5: 0.25: 0.1: 5: 2.5: 0.4: 9: 0.4: 30: 1.2: 3: 2: 780.

[0060] The preparation method and grouting method of the grouting material are the same as those in Example 1.

[0061] Example 3 A cement-based high-early-strength grouting material suitable for the alteration zone of dense granite, comprising, by weight, silicate cement clinker: gypsum: sulfoaluminate cement: high-alumina cement: silica fume: ultrafine fly ash: slag powder: sodium sulfate: calcium chloride: lithium carbonate: triethanolamine: water glass: nano-SiO2: carbon nanotubes: nano-alumina: modified hydroxyethyl methyl cellulose ether: bentonite: polycarboxylate superplasticizer: naphthalene superplasticizer: melamine superplasticizer: water = 520: 25: 70: 40: 50: 120: 70: 14: 12.5: 0.15: 0.2: 3: 3: 0.3: 9: 0.5: 30: 1.0: 3: 2: 820.

[0062] The preparation method and grouting method of the grouting material are the same as those in Example 1.

[0063] Example 4 A cement-based high-early-strength grouting material suitable for the alteration zone of dense granite, comprising, by weight, silicate cement clinker: gypsum: sulfoaluminate cement: high-alumina cement: silica fume: ultrafine fly ash: slag powder: sodium sulfate: calcium chloride: lithium carbonate: triethanolamine: water glass: nano-SiO2: carbon nanotubes: nano-alumina: modified hydroxyethyl methyl cellulose ether: bentonite: polycarboxylate superplasticizer: naphthalene superplasticizer: melamine superplasticizer: water = 480: 25: 70: 40: 60: 120: 100: 11: 10: 0.2: 0.2: 5: 2.5: 0.5: 7: 0.6: 20: 0.8: 4: 4: 820.

[0064] The preparation method and grouting method of the grouting material are the same as those in Example 1.

[0065] Example 5 A cement-based high-early-strength grouting material suitable for the alteration zone of dense granite, comprising, by weight, silicate cement clinker: gypsum: sulfoaluminate cement: high-alumina cement: silica fume: ultrafine fly ash: slag powder: sodium sulfate: calcium chloride: lithium carbonate: triethanolamine: water glass: nano-SiO2: carbon nanotubes: nano-alumina: modified hydroxyethyl methyl cellulose ether: bentonite: polycarboxylate superplasticizer: naphthalene superplasticizer: melamine superplasticizer: water = 520: 35: 80: 35: 60: 90: 85: 14: 10: 0.2: 0.1: 4: 2: 0.5: 7: 0.6: 20: 1.0: 5: 3: 780.

[0066] The preparation method and grouting method of the grouting material are the same as those in Example 1.

[0067] Example 6 A cement-based high-early-strength grouting material suitable for the alteration zone of dense granite, comprising, by weight, silicate cement clinker: gypsum: sulfoaluminate cement: high-alumina cement: silica fume: ultrafine fly ash: slag powder: sodium sulfate: calcium chloride: lithium carbonate: triethanolamine: water glass: nano-SiO2: carbon nanotubes: nano-alumina: modified hydroxyethyl methyl cellulose ether: bentonite: polycarboxylate superplasticizer: naphthalene superplasticizer: melamine superplasticizer: water = 560: 35: 60: 30: 50: 105: 70: 8: 15: 0.25: 0.15: 4: 3: 0.3: 11: 0.4: 25: 1.2: 4: 3: 740.

[0068] The preparation method and grouting method of the grouting material are the same as those in Example 1.

[0069] Comparative Example 1 The difference from Example 6 is that sulfoaluminate cement and high-alumina cement were not added, while the other materials and steps were the same as in Example 6.

[0070] Comparative Example 2 The difference from Example 6 is that silica fume, ultrafine fly ash and slag powder were not added, while the other materials and steps were the same as in Example 6.

[0071] Comparative Example 3 The difference from Example 6 is that sodium sulfate, calcium chloride, lithium carbonate, triethanolamine and water glass were not added, while the other materials and steps were the same as in Example 6.

[0072] Comparative Example 4 The difference from Example 6 is that nano-SiO2, carbon nanotubes and nano-alumina were not added, while the other materials and steps were the same as in Example 6.

[0073] Comparative Example 5 The difference from Example 6 is that modified hydroxyethyl methyl cellulose ether and bentonite were not added, while the other materials and steps were the same as in Example 6.

[0074] Comparative Example 6 The difference from Example 6 is that no polycarboxylate superplasticizer, naphthalene superplasticizer, or melamine superplasticizer was added; all other materials and steps were the same as in Example 6.

[0075] Comparative Example 7 The difference from Example 6 is that no nano-alumina was added, but the other materials and steps are the same as in Example 6.

[0076] Comparative Example 8 The difference from Example 6 is that lithium carbonate was not added, but the other materials and steps are the same as in Example 6.

[0077] Comparative Example 9 The difference from Example 6 is that no polycarboxylate superplasticizer was added, while the other materials and steps are the same as in Example 6.

[0078] Comparative Example 10 The difference from Example 6 is that the grouting method used is high-pressure grouting, while the other materials and steps are the same as in Example 6. The specific operation steps are as follows: Step 1: Prepare a high-pressure grouting pump and ensure it is working properly; connect the grouting pipeline, and after drilling, use high-pressure air to clean the debris inside the hole. After cleaning the grouting hole, install the hole opening pipe and grout stop device.

[0079] Step 2: Prepare cement-based high early strength grouting material suitable for the alteration zone of dense granite.

[0080] Step 3: Clean and connect the grout outlet and the borehole pipe of the grouting pipeline. Start grouting with a high and fixed grouting pressure of 4MPa and a grouting speed of <10L / min. Inject the cement-based high early strength grouting material suitable for the alteration zone of dense granite into the formation through the grouting pipe.

[0081] Step 4: Gradually increase the grouting pressure to the designed final pressure of 5-6 MPa, then stop grouting in that hole.

[0082] Step 5: When all grouting holes have met the single-hole grouting conditions and there is no leakage, stop grouting for the entire section.

[0083] Comparative Example 11 The difference from Example 6 is that no modified hydroxyethyl methyl cellulose ether was added; all other materials and steps were the same as in Example 6.

[0084] Comparative Example 12 The difference from Example 6 is that high-alumina cement was not added, but the other materials and steps are the same as in Example 6.

[0085] The performance testing method is as follows: 1. The flowability test was conducted according to the method in GB / T 8077-2012 "Test Method for Homogeneity of Concrete Admixtures", using a metal truncated cone mold with an upper and lower diameter of 36mm and 60mm respectively and a height of 60mm.

[0086] 2. Initial viscosity values ​​were tested according to the rheometer's product manual and the methods in GB / T 43876-2024 "Method for Determination of Viscosity of Cement Paste". The testing instrument used was an AMETEK Brookfield RST-SST soft solid rheometer, and the test procedures and processes were controlled by the accompanying Rheo3000 software.

[0087] 3. The bleeding rate test shall be conducted in accordance with the principle of the volumetric method of the bleeding rate test in GB / T 50080-2016 "Standard for Test Method of Performance of Ordinary Concrete Mixtures", and a 100mL graduated cylinder shall be used for the test.

[0088] 4. Initial setting time test: The test was conducted according to the method in GB / T 1346-2011 "Standard Water Requirement, Setting Time and Soundness Test Methods for Cement". The testing instrument used was the new national standard Vicat apparatus, and the initial setting time of the freshly mixed grout was tested using an initial setting needle. Flexural-compressive ratio: The compressive strength and flexural strength of the material were tested according to the method in GB / T 17671-2021 "Test Method for Strength of Cement Mortar (ISO Method)". The flexural-compressive ratio was calculated by dividing the flexural strength by the compressive strength.

[0089] 5. The undisturbed formation grouting rate test includes on-site undisturbed formation sampling and grouting test. The undisturbed formation grouting rate (volume ratio) of the grouting material is calculated by analyzing parameters such as the mass of the formation samples before and after the grouting test and the density of the grouting material.

[0090] 6. The compressive strength test shall be conducted in accordance with the method in GB / T 17671-2021 "Test Method for Strength of Cement Mortar (ISO Method)".

[0091] The working performance of each embodiment and comparative example was tested, including fluidity, initial viscosity, bleeding rate, initial setting time, and undisturbed formation slurry absorption rate. The results are shown in Table 1. The mechanical properties of each embodiment and comparative example were tested, including 12-hour compressive strength, 1-day compressive strength, 3-day compressive strength, and 7-day compressive strength. The results are shown in Table 2.

[0092] Table 1. Test results of the workability of a cement-based high early strength grouting material suitable for the alteration zone of dense granite.

[0093] Table 2. Mechanical property test results of a cement-based high early strength grouting material suitable for the alteration zone of dense granite.

[0094] As can be seen from Tables 1 and 2, all embodiments exhibit excellent overall performance balance: suitable flowability, initial viscosity and setting time, low bleeding rate, high undisturbed formation slurry absorption rate, and good early mechanical properties, with Embodiment 6 showing the best overall performance. Specifically, the grouting materials of Embodiments 1-6 all meet the following core performance indicators: flowability ≥ 280 mm, initial viscosity ≤ 25 mPa·s, bleeding rate ≤ 4%, initial setting time ≥ 1.5 h (3 h ≥ 1.5 h), undisturbed formation slurry absorption rate ≥ 6%, 12 h compressive strength ≥ 2 MPa, 1 day compressive strength ≥ 4 MPa, 3 day compressive strength ≥ 7 MPa, and 7 day compressive strength ≥ 10 MPa.

[0095] Comparative Example 1 data shows that the addition of sulfoaluminate cement and high-alumina cement significantly reduced the material's fluidity, bleeding rate, and initial setting time, significantly improved its early mechanical properties, and reduced the slurry absorption rate of the undisturbed formation. Comparative Example 2 data shows that the addition of silica fume, ultrafine fly ash, and slag powder significantly reduced the material's fluidity and bleeding rate, slightly increased the initial setting time, reduced the slurry absorption rate of the undisturbed formation, and significantly enhanced its early mechanical properties. Comparative Example 3 data shows that the addition of sodium sulfate, calcium chloride, lithium carbonate, triethanolamine, and water glass significantly shortened the material's initial setting time and greatly improved its performance. The data from Comparative Example 4 show that the addition of nano-SiO2, carbon nanotubes, and nano-alumina promotes a reduction in the material's bleeding rate and an enhancement in its mechanical properties. Simultaneously, due to gradation optimization, the undisturbed slurry absorption rate slightly increases. Comparative Example 5 shows that the addition of modified hydroxyethyl methyl cellulose ether and bentonite significantly reduces the material's bleeding rate and slightly decreases its mechanical properties. Comparative Example 6 shows that the addition of polycarboxylate-based, naphthalene-based, and melamine-based water-reducing agents significantly improves the material's flow properties and undisturbed slurry absorption rate, while significantly reducing the material's initial viscosity. Comparative Example 7 shows that the absence of nano-alumina leads to an increase in the material's bleeding rate, while slightly reducing the undisturbed slurry absorption rate and mechanical properties. Comparative Example 8 shows that the absence of lithium carbonate significantly increases the material's initial setting time and bleeding rate, and significantly reduces its early compressive strength. Comparative Example 9 shows that the absence of polycarboxylate-based water-reducing agents significantly reduces the material's flowability, significantly increases its initial viscosity, and reduces the undisturbed slurry absorption rate. Comparative Example 10 shows that using the traditional high-pressure grouting method, the undisturbed grout absorption rate of the material in the original formation is significantly reduced, indicating that the high-pressure grouting method has poor applicability to dense formations. Simultaneously, the compressive strength of the material is slightly reduced under high-pressure grouting. Comparative Example 11 shows that the absence of modified hydroxyethyl methyl cellulose ether significantly increases the material's bleeding rate, while slightly improving its mechanical properties. Comparative Example 12 shows that the absence of high-alumina cement increases the material's fluidity, bleeding rate, and initial setting time, significantly reducing its early mechanical properties, while slightly increasing the grout absorption rate in the original formation.

[0096] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. The application of a cement-based high early strength grouting material in grouting of altered zones of dense granite, characterized in that, The cement-based high early strength grouting material is composed of the following components in parts by weight: The composition includes 590-720 parts of composite early-strength cementitious material, 200-280 parts of ultrafine mineral admixture, 21-34.5 parts of composite early-strength agent, 29-50 parts of paste stabilizer, 5.5-10.5 parts of composite water-reducing agent, and 740-820 parts of water. The composite early-strength cement material is composed of silicate cement clinker, gypsum, sulfoaluminate cement and high-alumina cement; The ultrafine mineral admixture is composed of silica fume, ultrafine fly ash and slag powder; The composite early strength agent is composed of sodium sulfate, calcium chloride, lithium carbonate, triethanolamine and water glass; The slurry stabilizer is composed of nano-SiO2, carbon nanotubes, nano-alumina, modified hydroxyethyl methyl cellulose ether, and bentonite. The composite water-reducing agent is composed of polycarboxylate-based water-reducing agent, naphthalene-based water-reducing agent and melamine-based water-reducing agent; the weight ratio of silicate cement clinker, gypsum, sulfoaluminate cement and high-alumina cement in the composite early-strength cement material is (480-560):(25-35):(60-80):(30-40); The weight ratio of silica fume, ultrafine fly ash and slag powder in the ultrafine mineral admixture is (40-60):(90-120):(70-100). The weight ratio of sodium sulfate, calcium chloride, lithium carbonate, triethanolamine and water glass in the composite early strength agent is (8-14):(10-15):(0.15-0.25):(0.1-0.2):(3-5). The weight ratio of nano-SiO2, carbon nanotubes, nano-alumina, modified hydroxyethyl methyl cellulose ether, and bentonite in the slurry stabilizer is (2-3):(0.3-0.5):(7-11):(0.4-0.6):(20-30). The weight ratio of polycarboxylate superplasticizer, naphthalene superplasticizer, and melamine superplasticizer in the composite water-reducing agent is (0.8-1.2):(3-5):(2-4). The grouting material has the following properties: flowability ≥ 292 mm, initial viscosity ≤ 23.4 mPa·s, bleeding rate ≤ 3.8%, initial setting time ≥ 1.8 h (3 h ≥ 1.8 h), grout absorption rate in undisturbed formation ≥ 6%, compressive strength ≥ 1.5 MPa (12 h ≥ 1.5 MPa), compressive strength ≥ 3 MPa (1 day ≥ 3 MPa), compressive strength ≥ 5 MPa (3 days ≥ 5 MPa), and compressive strength ≥ 8 MPa (7 days ≥ 8 MPa).

2. The application as described in claim 1, characterized in that, The average particle size of the silicate cement clinker is not higher than 8 μm; The specific surface area of ​​the sulfoaluminate cement and high-alumina cement is ≥900 m². 2 / kg; The alumina content in high-alumina cement is not less than 60%.

3. The application as described in claim 1, characterized in that, The specific surface area of ​​silica fume is ≥15000 m² / kg, and the SiO2 content is ≥85%. The specific surface area of ​​the ultrafine fly ash and slag powder is ≥800m². 2 / kg; The sodium sulfate, calcium chloride, and lithium carbonate are of analytical grade. The content of the effective substance in the triethanolamine is ≥99%; The water glass has a modulus of 3.0-3.4 and a Baume degree of 35-40.

4. The application as described in claim 1, characterized in that, The specific surface areas of the nano-SiO2, carbon nanotubes, and nano-alumina are each not less than 250 m². 2 / g, 100 m 2 / g and 30 m 2 / g; The average particle sizes of nano-SiO2, carbon nanotubes, and nano-alumina are no higher than 20 nm, 30 nm, and 50 nm, respectively. The modified hydroxyethyl methyl cellulose ether is an aldehyde-modified hydroxyethyl methyl cellulose ether with a viscosity ≥150,000 and an effective substance content ≥99%. The bentonite is sodium-based bentonite with a specific surface area ≥800 m². 2 / kg, expansion ratio 20-30 times.

5. The application as described in claim 1, characterized in that, The water reduction rate of the polycarboxylate superplasticizer is not less than 40%, and the content of effective ingredients is ≥96%; The water reduction rate of the naphthalene-based water-reducing agent is not less than 20%, and the solid content is ≥99%. The water reduction rate of the melamine-based water-reducing agent is not less than 20%, and the content of effective ingredients is ≥99%.

6. A method for preparing a cement-based high early strength grouting material according to any one of claims 1-5, characterized in that, Includes the following steps: (1) Pre-dry mix nano-SiO2, nano-alumina and part of ultrafine fly ash and stir evenly to obtain micro-nano powder; mix carbon nanotubes, part of polycarboxylate superplasticizer and part of water, stir with a glass rod or prepare a suspension in an ultrasonic cleaner; (2) Add silicate cement clinker, gypsum, sulfoaluminate cement, high alumina cement, silica fume, the remaining ultrafine fly ash, slag powder, sodium sulfate, calcium chloride, lithium carbonate, modified hydroxyethyl methyl cellulose ether, bentonite, and the micro-nano powder in step (1) into a mixer and mix evenly to obtain a mixed dry powder. (3) Add water glass, triethanolamine, the remaining polycarboxylate superplasticizer, naphthalene superplasticizer, melamine superplasticizer and the suspension in step (1) to the remaining water and stir evenly to obtain a mixed liquid; (4) Mix the liquid mixture in step (3) with the dry powder mixture in step (2) and stir evenly to obtain a cement-based high early strength grouting material suitable for the alteration zone of dense granite.

7. A grouting method for a cement-based high early strength grouting material, characterized in that, Includes the following steps: (1) The cement-based high early strength grouting material described in any one of claims 1-5 is injected into the formation of a dense granite alteration zone using a low-pressure slow-seepage method; (2) After the grouting pressure stabilizes and begins to rise slowly, the grouting pressure is gradually increased; (3) When the grouting pressure reaches 70%–80% of the design final pressure, maintain the pressure and continue grouting; (4) After the grouting pressure reaches the design final pressure, maintain grouting for a period of time. When the grouting speed is lower than one-quarter of the initial grouting speed and the final grouting volume does not exceed 6L / min, stop grouting.

8. The grouting method for the cement-based high early strength grouting material as described in claim 7, characterized in that, In step (1), the grouting pressure of the low-pressure slow seepage method is 0.1-2 MPa, and the grouting speed is 10-30 L / min; In step (2), when the grouting pressure stabilizes at 2 MPa, the grouting pressure is gradually increased by 0.5-1.0 MPa per level. In step (3), the final pressure is designed to be 5-6 MPa, and the grouting time is 10-30 min.

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