A fissure grouting material, a preparation method and application thereof

Abstract

This invention discloses a fissure grouting material, its preparation method, and its application, belonging to the technical field of radiation protection engineering materials. By mass, its raw materials include: 45-60 parts barite sand, 25-35 parts sulfoaluminate cement, 8-20 parts borax, 2-5 parts boron carbide powder, 1-5 parts nano-gadolinium oxide, 5-15 parts lithium slag powder, 3-8 parts barium sulfate whiskers, 3-8 parts polymer emulsion, 0.5-1.5 parts water-reducing agent, 0.1-0.5 parts stabilizer, and 18-25 parts water. This invention provides high-density gamma-ray shielding through barite sand, achieves all-round neutron protection through a quaternary composite neutron absorption system, enhances the material's toughness and shielding effect through barium sulfate whiskers, and ensures high fluidity and interfacial bonding strength of the grout through the polymer emulsion. This material is particularly suitable for sealing and shielding fissures in the surrounding rock of radioactive tunnels, possessing advantages such as excellent shielding effectiveness, good construction performance, high volume stability, and long-term durability.

Description

Technical Field

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

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] In major projects such as geological repositories for high-level radioactive waste and tunnels traversing high-radiation rock strata, rock fissures constitute prominent weak points in the radiation shielding system, allowing gamma photons and neutrons to continuously escape along these paths, creating a long-term risk of radiation leakage.

[0004] Current methods for sealing fissures primarily rely on traditional cement-based grouting materials. However, their inherent low density and lack of neutron-absorbing components result in poor overall shielding effectiveness against gamma rays and neutrons. Furthermore, shrinkage during the material's hardening process can easily lead to interfacial voids and microcracks, and insufficient grout stability can also create new leakage pathways. While specialized shielding materials such as lead and boron offer excellent performance, their cost and manufacturing limitations make them unsuitable for fissure repair applications. Therefore, there is an urgent need to develop a multifunctional grouting material that can achieve high-flow injection, high-density shielding, efficient neutron capture, and volumetric stability to fundamentally block radiation leakage paths. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a fissure grouting material, its preparation method, and its application. This invention provides a fissure grouting material for radioactive shielding of tunnel surrounding rock, which has excellent shielding performance, good construction performance, and strong stability, thus overcoming the shortcomings of existing technologies.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] In a first aspect, the present invention provides a fissure grouting material, comprising, by weight parts: 45-60 parts barite sand, 25-35 parts sulfoaluminate cement, 8-20 parts borax, 2-5 parts boron carbide powder, 1-5 parts nano gadolinium oxide, 5-15 parts lithium slag powder, 3-8 parts barium sulfate whiskers, 3-8 parts polymer emulsion, 0.5-1.5 parts water-reducing agent, 0.1-0.5 parts stabilizer, and 18-25 parts water.

[0008] Through the compounding and synergistic effects of the above components, this invention simultaneously solves three major challenges: radiation shielding, volume stability, and construction grouting. Functionally, it forms a composite radiation protection system of "high-density aggregate shielding against gamma rays + multi-component synergistic slowing and neutron absorption," achieving efficient shielding against mixed gamma-neutron radiation fields. Structurally, the micro-expansion of sulfoaluminate cement and the toughening and crack-resistant effects of polymer emulsion and barium sulfate whiskers jointly overcome material shrinkage, ensuring that the grout itself is dense and crack-free and firmly bonded to the surrounding rock, achieving long-term sealing. In terms of process, with the regulation of high-efficiency water-reducing agents and stabilizers, the high-density, high-solids-content composite grout can still maintain excellent fluidity, uniformity, and stability, meeting the requirements for economical and efficient grouting of deep, fine cracks.

[0009] This material system fundamentally improves upon the shortcomings of traditional grouting materials, such as weak shielding performance, easy shrinkage and cracking, and poor workability, providing an innovative solution for sealing fissures in radioactive rock masses.

[0010] In some embodiments of the present invention, the barite sand has a particle size of 200-400 mesh and a barium sulfate content of not less than 90%.

[0011] In this invention, the core function of barite sand is gamma-ray shielding, which provides high density (overall material density > 2.8 g / cm³). 3 The grouting material efficiently attenuates gamma photons through the photoelectric effect and Compton scattering. Its fineness of 200-400 mesh (approximately 38-75 micrometers) ensures good flowability and injectability, allowing it to penetrate deep into micro-cracks; a barium sulfate content of no less than 90% ensures a sufficiently high effective density, thus providing a stable and efficient shielding matrix for attenuating gamma rays.

[0012] Sulfoaluminate cement provides early strength, hydrates rapidly, and its hydration characteristics can produce moderate micro-expansion in the early stage, effectively compensating for the hardening shrinkage of the paste, thereby avoiding shrinkage cracks and ensuring tight bonding with the fractured rock wall; at the same time, its hydration products contain a large amount of crystal water, which can help slow down fast neutrons and enhance the neutron shielding ability of the material.

[0013] In some embodiments of the present invention, the aspect ratio of the barium sulfate whiskers is 10:1-20:1, and the diameter is 1-5 μm.

[0014] Barium sulfate whiskers possess reinforcing and toughening properties. The whisker structure is fully dispersed within the matrix, forming a dense three-dimensional network that improves the material's toughness, crack resistance, and overall strength, while also enhancing gamma-ray shielding. Furthermore, barium sulfate whiskers of this size do not significantly adversely affect the slurry's flowability and pourability, thus achieving an optimal balance between workability and final mechanical and shielding performance.

[0015] In this invention, polymer emulsion, water-reducing agent and stabilizer are functional additives that impart different properties to the crack grouting material.

[0016] The polymer emulsion is either a styrene-acrylic emulsion or an acrylic emulsion, used to improve the workability of the fissure grouting material. Both emulsions possess excellent film-forming properties, adhesion, and flexibility, effectively improving the wettability and flowability of the grout, preventing particle sedimentation and segregation, enhancing the bond strength with the rock fissure surface, and improving the toughness, crack resistance, and durability of the hardened material. This achieves a synergistic improvement in workability and durability, ensuring that the grout maintains structural integrity and sealing performance under long-term radiation conditions, and preventing the formation of new leakage channels due to cracking or peeling.

[0017] The water-reducing agent is a polycarboxylate-based water-reducing agent used to improve workability. This agent achieves high water reduction at extremely low dosages and significantly improves slurry fluidity at low water-cement ratios, allowing it to penetrate micro-cracks. The low water-cement ratio directly increases the final density and strength of the slurry and effectively prevents high-density aggregate segregation and slurry bleeding, ensuring that the material has a uniform and stable high-density microstructure after hardening, which is beneficial for achieving reliable and durable radiation shielding.

[0018] In some embodiments of the present invention, the stabilizer is hydroxypropyl methylcellulose ether (HPMC). HPMC is a highly efficient water-soluble polymer that can significantly improve the viscosity and water retention of the slurry, thereby effectively preventing the sedimentation and segregation of high-density aggregates such as barite sand during pouring and settling, ensuring a uniform slurry composition. This stability is a prerequisite for obtaining a hardened body with a uniform high-density microstructure, directly guaranteeing the reliability of radiation shielding performance. Simultaneously, HPMC has good compatibility with water-reducing agents and polymer emulsions, and can work synergistically to maintain the stability of the slurry while ensuring its fluidity. This is crucial for achieving successful pouring and long-term performance of the material in deep, fine cracks.

[0019] In this invention, the composite neutron absorber is composed of borax, boron carbide powder, nano-gadolinium oxide, and lithium slag powder. These four components form a multi-level synergistic protection system of "moderation-primary absorption-deep purification-stabilization." This system synergistically moderates fast neutrons through the crystal water of borax and lithium, efficiently captures thermal neutrons using boron-10 (derived from borax and boron carbide), and performs deep purification using ultra-high cross-section nano-gadolinium oxide. Simultaneously, lithium slag powder, as an active material, improves the microstructure of the slurry, ensuring the integration of protective efficacy and long-term material stability. This economically and efficiently solves the fundamental problem of insufficient protection against mixed γ-neutron radiation fields by traditional materials.

[0020] In some embodiments of the present invention, the boron carbide powder has a particle size of 800-1200 mesh and a purity of not less than 95%. Borax (Na2B4O7·10H2O) has neutron shielding function, and boron (B) element has a high thermal neutron absorption cross section, which can effectively capture thermal neutrons; the crystal water in borax further assists in slowing down fast neutrons. Boron carbide powder can enhance neutron absorption. As a highly efficient neutron absorber, boron carbide has a higher thermal neutron absorption cross section, enhancing the shielding effect.

[0021] In some embodiments of the present invention, the nano-gadolinium oxide has a particle size of 30-50 nm and a purity of not less than 99%. It is used to achieve nanoscale shielding. The nano-gadolinium oxide has an extremely high neutron absorption cross section (49000 barn) and is uniformly dispersed in the crack grouting material by forming a core-shell structure with polymers such as emulsions.

[0022] In some embodiments of the present invention, the lithium slag powder has a particle size of 400-600 mesh and a Li2O content of not less than 2.5%. It is used to enhance activity; lithium-containing compounds can promote cement hydration and improve early strength, while lithium also has a neutron moderating effect.

[0023] In some embodiments of the present invention, the raw materials of the fissure grouting material, by weight, include: 45-60 parts barite sand, 25-35 parts sulfoaluminate cement, 8-18 parts borax, 2-5 parts boron carbide powder, 1-4 parts nano-gadolinium oxide, 5-12 parts lithium slag powder, 3-8 parts barium sulfate whiskers, 3-8 parts polymer emulsion, 0.5-1.5 parts water-reducing agent, 0.1-0.5 parts stabilizer, and 18-25 parts water. The fissure grouting material obtained by this formulation exhibits superior performance.

[0024] In some embodiments of the present invention, the raw materials of the fissure grouting material, by weight, include: 45-60 parts barite sand, 25-35 parts sulfoaluminate cement, 8-15 parts borax, 2-5 parts boron carbide powder, 1-3 parts nano-gadolinium oxide, 5-10 parts lithium slag powder, 3-8 parts barium sulfate whiskers, 3-8 parts polymer emulsion, 0.5-1.5 parts water-reducing agent, 0.1-0.5 parts stabilizer, and 18-25 parts water. The fissure grouting material obtained by this formulation exhibits superior performance.

[0025] In some embodiments of the present invention, the raw materials of the fracture grouting material, by weight, include: 50-55 parts barite sand, 28-30 parts sulfoaluminate cement, 12-15 parts borax, 3-4 parts boron carbide powder, 2 parts nano-gadolinium oxide, 8 parts lithium slag powder, 5-7 parts barium sulfate whiskers, 6-8 parts polymer emulsion, 0.8-1.0 parts water-reducing agent, 0.2-0.3 parts stabilizer, and 22-23 parts water. The fracture grouting material obtained by this formulation has superior performance.

[0026] In some embodiments of the present invention, the density of the fissure grouting material is 2.8-3.2 g / cm³. 3 The fluidity is 260-300 mm. The fracture grouting material provided by this invention, through the synergistic design of its components, achieves efficient, durable, and workable radial sealing of rock fractures.

[0027] A second aspect of the present invention provides a method for preparing the fracture grouting material described in the first aspect, comprising: Dry the barite powder and lithium slag powder, and sieve them for later use; Nano-gadolinium oxide was mixed with a portion of the polymer emulsion, and then the remaining polymer emulsion was added and mixed to form a composite emulsion. Weigh out barite sand, sulfoaluminate cement, and lithium slag powder according to the proportions, and perform the first dry mixing; add borax and boron carbide powder, and perform the second dry mixing; add barium sulfate whiskers, and perform the third dry mixing to obtain the dry mixture. Add the water-reducing agent to water and stir to dissolve it, add the stabilizer and continue stirring, and finally add the composite emulsion to form a mixture; The mixture is added to the dry mix in several batches and stirred to obtain the crack grouting material.

[0028] This method is simple and highly controllable, and can stably prepare grouting materials with high fluidity, excellent stability, high radiation shielding effectiveness and micro-expansion characteristics, which can meet the needs of grouting construction and long-term protection of deep and fine cracks.

[0029] In some embodiments of the present invention, barite powder is dried to constant weight at 105±5℃ and passed through a 200-400 mesh sieve for later use; lithium slag powder is dried to constant weight at 80±5℃ and passed through a 400-600 mesh sieve for later use.

[0030] In some embodiments of the present invention, nano-gadolinium oxide is mixed with 1 / 3 of the formulation amount of polymer emulsion and ultrasonically dispersed, and then the remaining polymer emulsion is added for further ultrasonic treatment to form a composite emulsion.

[0031] In some embodiments of the present invention, gadolinium nanoparticles are mixed with 1 / 3 of the formulated amount of polymer emulsion and ultrasonically dispersed for 10-15 minutes at an ultrasonic power of 800-1000 W. Subsequently, the remaining polymer emulsion is added and ultrasonic treatment continues to be performed, so that the gadolinium nanoparticles are uniformly coated in the polymer emulsion, forming a core-shell composite emulsion (wherein the total weight ratio of gadolinium nanoparticles to the polymer emulsion is 1:2-1:3). This stepwise ultrasonic process of adding the emulsion utilizes the initial high concentration and strong shear force to thoroughly break up the agglomeration of nanoparticles, and then maintains system stability through subsequent gradient dilution. This greatly improves the density and uniformity of the core-shell coating, effectively preventing the agglomeration of nanoparticles and ensuring their uniform dispersion and interfacial enhancement in the slurry.

[0032] In some embodiments of the present invention, the first dry mixing speed is 60-80 r / min and the time is 3-4 minutes; the second dry mixing speed is 80-100 r / min and the time is 2-3 minutes; the third dry mixing speed is 100-120 r / min and the time is 1-2 minutes.

[0033] A stepwise dry-mixing process is employed, utilizing gradient-strengthened mechanical forces to achieve precise dispersion and encapsulation of materials at each stage. First, a relatively long dry-mixing time (3-4 minutes) is performed at a lower rotation speed (60-80 r / min) to ensure initial uniform mixing of the high-density, large-particle-size barite sand with matrix materials such as cement and lithium slag powder, preventing dust generation and separation. A second dry-mixing is then performed at a higher rotation speed (80-100 r / min) to fully embed fine powdered functional fillers such as borax and boron carbide into the matrix gaps, achieving micro-dispersion. Finally, barium sulfate whiskers are mixed in briefly (1-2 minutes) at the highest rotation speed (100-120 r / min). While avoiding excessive whisker breakage, high-intensity shear force is used to rapidly and uniformly distribute them throughout the dry mix, forming precursors for a three-dimensional network framework. This process scientifically matches the physical properties (particle size, density, morphology) of different components, ensuring the uniformity of multiphase and multi-scale materials to the greatest extent from the source, laying a decisive foundation for obtaining a highly uniform slurry after subsequent wet mixing.

[0034] In some embodiments of the present invention, the water-reducing agent is added to 60% of the formulated water and stirred for 2 minutes; the stabilizer is added and stirred for 1 minute; the core-shell structured composite emulsion is added and stirred for 2 minutes; the remaining water is added and stirred until a mixture is formed. This gradient liquid preparation process ensures the dissolution and dispersion of the additives (especially preventing the HPMC stabilizer from clumping) by utilizing a relatively high concentration in the early stage, while ensuring that the final mixture contains the complete amount of formulated water through subsequent water dilution.

[0035] A gradient liquid preparation process is employed, which maximizes the functionality of each liquid phase component and ensures homogeneous and stable solution by strictly controlling the hydration and dissolution sequence of additives. First, the water-reducing agent is preferentially dissolved in 60% water, allowing its molecular chains to fully extend and preventing subsequent interference from other components in its dissolution and dispersion, thus ensuring its full water-reducing efficiency. A stabilizer is then added, which better disperses and hydrates in the homogeneous water-reducing agent solution, forming a uniform thickening network and providing a stable medium environment for the subsequent introduction of a high-solids-content composite emulsion. Finally, the pre-dispersed composite emulsion is added, preventing premature demulsification due to high-concentration electrolytes or shear forces, ensuring the dispersion of nano-gadolinium oxide and the film-forming properties of the polymer. Finally, dilution with water ensures that the final mixture contains the complete amount of formulated water. This gradient liquid preparation process optimizes the thermodynamics and kinetics of dissolution, hydration, and dispersion of each component, resulting in a homogeneous and stable mixture, providing a crucial guarantee for subsequent uniform mixing with dry mixes to obtain high-performance slurries.

[0036] In some embodiments of the present invention, 50% of the mixed liquid is added to the dry mixture and stirred at 60 r / min for 2 minutes to initially wet the powder; the remaining 50% of the mixed liquid is added and stirred at 80-100 r / min for 2 minutes to make the slurry uniform; the slurry is stirred at 120-150 r / min for 3-5 minutes until a slurry with uniform color, good fluidity, and no lumps is formed, thus obtaining the crack grouting material.

[0037] By adopting a graded wet mixing process and employing a strategy of step-by-step liquid addition and gradient acceleration, the core problems of clumping, uneven wetting, aggregate settling, and insufficient component dispersion that are prone to occur during the mixing process of high-density, multi-component composite dry mixes are systematically solved.

[0038] First, a 50% mixture is initially applied at low speed to gently and evenly wet the powder surface, forming a paste with basic cohesive properties. This effectively prevents powder agglomeration and instantaneous settling of heavy aggregates caused by a single addition of liquid. Then, the remaining mixture is added and the rotation speed is increased to further optimize the liquid-to-solid ratio in the pre-homogenized system, achieving overall fluidization and macroscopic homogeneity of the slurry. Finally, high-speed shear stirring is performed, using strong mechanical force to thoroughly break down any potential micro-aggregates, ensuring high dispersion of functional phases such as nanoparticles and whiskers, and effectively eliminating entrained air. This ultimately yields a high-quality slurry with uniform structure, excellent flowability, and no sedimentation or segregation.

[0039] In some embodiments of the present invention, the performance of the obtained crack grouting material is further tested and adjusted; The performance testing and adjustment includes: testing the slurry density and fluidity; the density should reach 2.8-3.2 g / cm³. 3The fluidity should reach 260-300 mm; adjust the water volume according to the test results, and the adjustment range should not exceed ±5% of the formula volume.

[0040] A third aspect of the present invention provides an application of the fissure grouting material described in the first aspect in the shielding of tunnel surrounding rock for video surveillance.

[0041] The beneficial effects of this invention are as follows: This invention provides a fracture grouting material that exhibits excellent comprehensive performance. Functionally, it utilizes high-density barite sand (4.3-4.5 g / cm³). 3 In synergy with barium sulfate whiskers, the density of the slurry after solidification reaches 2.8-3.2 g / cm³. 3 The linear attenuation coefficient for gamma rays reaches 0.185-0.205 m. -1 This material achieves highly efficient shielding against gamma rays (with a linear attenuation coefficient 89%-109% higher than ordinary cement slurry). It innovatively employs a quaternary neutron absorption composite system of borax, boron carbide, nano-gadolinium oxide, and lithium slag powder, constructing a three-tiered protection mechanism of "slowing down, primary absorption, and deep purification." This results in a thermal neutron absorption cross-section of 1250-1950 barn, 3-5 times higher than ordinary cement slurry, perfectly adapting to mixed gamma / neutron radiation fields. In terms of engineering performance, the material combines high fluidity (flowability 260-300 mm) with excellent stability (0% bleeding rate), allowing it to penetrate 0.2 mm micro-cracks. Its initial setting time of 45-90 minutes ensures sufficient construction time while rapidly building early strength. It also possesses high early strength (7-day compressive strength 26-32 MPa), micro-expansion (28-day shrinkage rate only 0.015%-0.025%), and strong crack resistance, ensuring tight adhesion and long-term sealing with the surrounding rock. In addition, the materials mainly use natural minerals and industrial solid waste (such as lithium slag powder), which are low in cost, environmentally friendly, chemically stable, and highly durable.

[0042] This invention also provides a method for preparing a fracture grouting material. Through precise process design, the material's performance is ensured to be stable and efficient. A "three-stage gradient dry mixing" method is employed to uniformly disperse components of different densities and particle sizes step by step. A "gradient liquid preparation" method optimizes the dissolution and dispersion sequence of the water-reducing agent, stabilizer, and composite emulsion, ensuring the effectiveness of each liquid phase functional component. Finally, a "staged wet mixing" method (step-by-step liquid addition and gradient acceleration) completely solves the problem of easy agglomeration and segregation in high-density composite grouts, resulting in a highly homogeneous grout. Core processes, such as ultrasonic dispersion to form a core-shell structure, effectively prevent the agglomeration of nano-gadolinium oxide, fully utilizing its function. The entire set of process parameters is precisely controllable, significantly improving the uniformity, stability, and reproducibility of product performance, laying a solid foundation for the large-scale reliable preparation of materials in engineering fields. Attached Figure Description

[0043] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0044] Figure 1 This is a flowchart of a method for preparing a fissure grouting material according to the present invention. Detailed Implementation

[0045] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0046] This invention provides a fissure grouting material, its preparation method, and its application, which improves the shielding, stability, and workability of fissure grouting materials and solves the problem of radioactive leakage in tunnel surrounding rock.

[0047] In the following examples, all raw materials or reagents used are commercially available.

[0048] Example 1 This embodiment provides a fissure grouting material for radioactive shielding of tunnel surrounding rock, the formula of which is: 50 parts barite sand (300 mesh), 30 parts sulfoaluminate cement, 5 parts barium sulfate whiskers, 25 parts composite neutron absorber (of which, 12 parts borax, 3 parts boron carbide, 2 parts nano gadolinium oxide, and 8 parts lithium slag powder), 6 parts styrene-acrylic emulsion, 0.8 parts polycarboxylate superplasticizer, 0.2 parts HPMC, and 22 parts water.

[0049] Please refer to the preparation process. Figure 1 The specific preparation steps are as follows: Step 1: Raw material pretreatment Barite powder is dried at 105℃ to constant weight and then passed through a 200-400 mesh sieve for later use.

[0050] The lithium slag powder is dried at 80℃ to constant weight and then passed through a 400-600 mesh sieve for later use.

[0051] Step 2: Preparation of core-shell composite emulsion Nano-gadolinium oxide was mixed with 1 / 3 of the formulation amount of styrene-acrylic emulsion and ultrasonically dispersed for 12 minutes at an ultrasonic power of 900 W. Then the remaining styrene-acrylic emulsion was added and ultrasonic treatment was continued to make the nano-gadolinium oxide uniformly coated in the styrene-acrylic emulsion to form a core-shell structured composite emulsion (the total weight ratio of nano-gadolinium oxide to styrene-acrylic emulsion was 1:2.5).

[0052] Step 3: Dry mixing in stages First dry mixing: Weigh out barite sand, sulfoaluminate cement and lithium slag powder according to the proportion, put them into the mixer and dry mix at 70 r / min for 3 minutes.

[0053] Second dry mixing: Add borax and boron carbide powder, and continue dry mixing at 90 r / min for 2 minutes.

[0054] Third dry mixing: Add barium sulfate whiskers and dry mix at 110 r / min for 1.5 minutes until uniformly mixed to obtain a dry mixture.

[0055] Step 4: Gradient solution preparation First-gradient solution preparation: Add the polycarboxylate superplasticizer to 60% of the formula amount of water and stir for 2 minutes until completely dissolved.

[0056] Second-gradient solution preparation: Add HPMC and stir for 1 minute until evenly dispersed.

[0057] Third gradient liquid preparation: Add the core-shell structured composite emulsion obtained in step two and stir for 2 minutes to form a uniform first mixture.

[0058] Fourth gradient preparation: Add the remaining 40% of the formula amount of water, and continue stirring for 1-2 minutes until a uniform second mixture is formed.

[0059] Step 5: Graded Wet Mixing First wet mixing: Pour 50% of the second mixture obtained in step four into the dry mixture obtained in step three, and stir at a low speed of 60 r / min for 2 minutes to allow the powder to be initially moistened.

[0060] Second wet mixing: Add the remaining 50% of the second mixture and stir at a medium speed of 90 r / min for 2 minutes to make the slurry uniform.

[0061] Third wet mixing: Stir at 150 r / min for 4 minutes until a paste with uniform color, good fluidity, and no lumps is formed.

[0062] Example 2 This embodiment provides a fissure grouting material for radioactive shielding of tunnel surrounding rock, the formula of which is: 55 parts barite sand (400 mesh), 28 parts sulfoaluminate cement, 7 parts barium sulfate whiskers, 29 parts composite neutron absorber (of which, 15 parts borax, 4 parts boron carbide, 2 parts nano gadolinium oxide, and 8 parts lithium slag powder), 8 parts acrylic emulsion, 1.0 part polycarboxylate superplasticizer, 0.3 parts HPMC, and 23 parts water.

[0063] The preparation method is the same as in Example 1.

[0064] Example 3 This embodiment provides a fissure grouting material for radioactive shielding of tunnel surrounding rock. The difference from Embodiment 1 is that the amount of borax is increased from 12 parts to 18 parts. The remaining components and preparation method are the same as in Embodiment 1.

[0065] Example 4 This embodiment provides a fissure grouting material for radioactive shielding of tunnel surrounding rock. The difference from Embodiment 1 is that the proportions of borax, boron carbide, nano-gadolinium oxide, and lithium slag powder are the same as in Embodiment 1, only the batches of raw materials differ. The remaining components and preparation methods are the same as in Embodiment 1.

[0066] Example 5 This embodiment provides a fracture grouting material for radioactive shielding of tunnel surrounding rock, which differs from Embodiment 1 in that the amount of nano-gadolinium oxide is increased from 2 parts to 4 parts. The remaining components and preparation method are the same as in Embodiment 1.

[0067] Example 6 This embodiment provides a fissure grouting material for radioactive shielding of tunnel surrounding rock. The difference from Embodiment 1 is that the lithium slag powder is increased from 8 parts to 12 parts. The remaining components and preparation method are the same as in Embodiment 1.

[0068] The performance of the crack grouting material obtained in the example was tested using the following method: (1) Density: The apparent density was determined in accordance with the test method in the "Standard for Test Methods of Basic Performance of Building Mortar" (JGJ / T 70-2009).

[0069] (2) Flowability: The flowability was determined by the “truncated cone flowability method” specified in Appendix A of the “Technical Specification for Application of Cement-based Grouting Materials” (GB / T 50448-2015).

[0070] (3) Initial setting time: The initial setting time was determined in accordance with the "Test Methods for Standard Consistency Water Requirement, Setting Time and Soundness of Cement" (GB / T1346-2011).

[0071] (4) 7d compressive strength: The specimens were molded, cured and compressive strength was determined in accordance with the provisions of the "Test Method for Strength of Cement Mortar (ISO Method)" (GB / T 17671-2021).

[0072] (5) 28d shrinkage rate: Refer to the shrinkage test method in the "Standard for Test Methods of Basic Performance of Building Mortar" (JGJ / T 70-2009) to measure the length change rate of the specimen under standard curing conditions.

[0073] (6) Linear attenuation coefficient: The narrow beam gamma-ray transmission method was used for determination. Cs-137 was used as the standard radiation source. The intensity of gamma rays passing through solidified specimens of different thicknesses was measured using a NaI(Tl) scintillation detector or a high-purity germanium (HPGe) detector. The gamma rays were calculated based on the formula of exponential attenuation law of the radiation.

[0074] (7) Thermal neutron absorption cross section: The neutron transmission method was used for measurement. An Am-Be neutron source was used to obtain a thermal neutron beam through paraffin slowing. The thermal neutron count rate before and after the neutron beam passed through a solidified specimen of a specified thickness was measured using a He-3 proportional counter tube. The thermal neutron absorption cross section (barn) was calculated by combining the material density and composition.

[0075] (8) Minimum injectable crack: An empirical test was conducted using a parallel plate adjustable crack simulation device. Two flat, transparent high-strength glass or acrylic plates were fixed in parallel, and the gap between the two plates was adjusted using precision shims (adjustment accuracy was 0.05 mm). Under a constant grouting pressure of 0.2 MPa, it was observed whether the grout could continuously and smoothly fill and penetrate the gap without any aggregate gapping or blockage. The minimum gap width that could be successfully penetrated was recorded as the minimum injectable crack.

[0076] The test results are shown in Table 1.

[0077] Table 1. Performance of the fracture grouting materials obtained in Examples 1 to 6 Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 <![CDATA[Density (g / cm 3 )]]> 2.98 3.05 3.02 2.95 3 2.96 Flowability (mm) 280 270 272 278 273 277 Initial setting time (min) 48 55 50 47 49 48 7-day compressive strength (MPa) 30.2 28.8 28.3 29.1 28.5 29.5 28-day shrinkage rate (%) 0.018 0.019 0.02 0.022 0.019 0.017 <![CDATA[Linear attenuation coefficient (m -1 )]]> 0.201 0.208 0.198 0.192 0.205 0.195 Thermal neutron absorption cross section (barn) 1950 1880 2100 1850 2350 2050 Minimum injectable crack (mm) 0.2 0.2 0.2 0.2 0.2 0.2 Testing revealed that the fracture grouting material obtained in Example 1 exhibited the best overall performance, with a grout density of 2.98 g / cm³. 3 The fluidity was 280 mm, and the initial setting time was 48 min. The 7-day compressive strength of the cured body was 30.2 MPa, and the 28-day shrinkage rate was 0.018%. The linear attenuation coefficient for Cs-137 γ-rays was 0.201 m. -1 The thermal neutron absorption cross section is 1950 barn, and the minimum injectable fracture is 0.2 mm.

[0078] The grout density of the fracture grouting material obtained in Example 2 was 3.05 g / cm³. 3 The fluidity is 270 mm, and the initial setting time is 55 min. The 7-day compressive strength is 28.8 MPa, and the gamma-ray attenuation coefficient is 0.208 m. -1 The thermal neutron absorption cross section is 1880 barn, and the minimum injectable fracture is 0.2 mm.

[0079] A comparison of Example 3 and Example 1 shows that the thermal neutron absorption cross section increased from 1950 barn to 2100 barn (an increase of 7.7%), and the density increased from 2.98 g / cm³.3 Slightly increased to 3.02 g / cm³ 3 It is evident that increasing the amount of borax can further enhance the neutron absorption effect, but the rate of increase slows down. The optimal range for borax dosage is 8-15 parts to avoid waste of raw materials.

[0080] A comparison of Example 4 and Example 1 shows that the deviation is small; for example, the thermal neutron absorption cross section is 1850 barn, decreasing by only 5.1%. This demonstrates that the present invention eliminates the influence of raw material batch fluctuations on the performance of the fracture grouting material, and the fracture grouting material provided by the present invention exhibits good stability.

[0081] Compared to Example 1, Example 5 showed an increase in the thermal neutron absorption cross section from 1950 barn to 2350 barn (a 20.5% increase), and an increase in density from 2.98 g / cm³. 3 Slightly increased to 3.00 g / cm³ 3 It is evident that increasing the amount of nano-gadolinium oxide can significantly improve neutron shielding effectiveness. However, a core-shell structure process must be matched to avoid agglomeration. A dosage of 1-3 parts nano-gadolinium oxide balances effectiveness and economy.

[0082] Compared with Example 1, Example 6 showed that the 7-day compressive strength decreased from 30.2 MPa to 29.5 MPa (a decrease of 1.0%), the 28-day shrinkage rate decreased from 0.018% to 0.017%, and the thermal neutron absorption cross-section increased from 1950 barn to 2050 barn. It is evident that increasing the amount of lithium slag powder has limited effect on performance improvement and increases slurry viscosity; a dosage of 5-10 parts lithium slag powder represents the balance point between performance and workability.

[0083] Comparative Example 1 This comparative example provides a crack grouting material, which is a sulfoaluminate cement paste with a water-cement ratio of 0.5.

[0084] Comparative Example 2 This comparative example provides a crack grouting material. The difference from Example 1 is that the borax is reduced from 12 parts to 5 parts, while the remaining components and preparation method are the same as in Example 1.

[0085] Comparative Example 3 This comparative example provides a crack grouting material, which differs from Example 1 in that the boron carbide is reduced from 3 parts to 1 part, while the remaining components and preparation method are the same as in Example 1.

[0086] Comparative Example 4 This comparative example provides a crack grouting material, which differs from Example 1 in that nano-gadolinium oxide is completely removed (reduced from 2 parts to 0 parts), while the remaining components and preparation method are the same as in Example 1.

[0087] Comparative Example 5 This comparative example provides a fracture grouting material. The difference from Example 1 is that the lithium slag powder is reduced from 8 parts to 3 parts, while the remaining components and preparation method are the same as in Example 1.

[0088] Comparative Example 6 This comparative example provides a crack grouting material. The difference from Example 1 is that the "three-step dry mixing" is eliminated. The barite sand, cement, lithium slag powder, borax, boron carbide, and barium sulfate whiskers are mixed at one time (stirred at 80 r / min for 5 minutes). The remaining components and preparation methods are the same as in Example 1.

[0089] Comparative Example 7 This comparative example provides a fracture grouting material. The difference from Example 1 is that the "three-gradient liquid preparation" is eliminated. Instead, the water-reducing agent, stabilizer, and core-shell structure composite emulsion are added to the water at one time (stirring for 5 minutes). The remaining components and preparation methods are the same as in Example 1.

[0090] Comparative Example 8 This comparative example provides a crack grouting material. The difference from Example 1 is that the "three-stage wet mixing" is cancelled, and all the mixture is added to the dry mix at one time (stirred at 120 r / min for 5 minutes). The remaining components and preparation methods are the same as in Example 1.

[0091] The performance of the crack grouting material obtained in the comparative example was tested using the same testing method as in the embodiment. The test results are shown in Table 2.

[0092] Table 2. Performance of the fracture grouting materials obtained from Comparative Examples 1 to 8 <![CDATA[Density (g / cm 3 )]]> Flowability (mm) 7-day compressive strength (MPa) 28-day shrinkage rate (%) <![CDATA[γ-ray attenuation coefficient (m -1 )]]> Thermal neutron absorption cross section (barn) Minimum injectable crack (mm) Comparative Example 1 2.18 280 22.3 0.15 0.098 350 0.5 Comparative Example 2 2.85 275 27.6 0.025 0.162 1100 0.2 Comparative Example 3 2.88 270 26.9 0.026 0.168 1400 0.2 Comparative Example 4 2.90 276 27.3 0.024 0.175 1200 0.2 Comparative Example 5 2.92 274 25.8 0.028 0.188 1650 0.2 Comparative Example 6 2.82 255 24.7 0.035 0.178 1700 0.3 Comparative Example 7 2.86 248 25.2 0.032 0.181 1750 0.3 Comparative Example 8 2.80 242 23.9 0.040 0.176 1680 0.4 Compared to Example 1, the thermal neutron absorption cross section of the fracture grouting material obtained in Comparative Example 2 decreased from 1950 barn to 1100 barn (a decrease of 43.6%), and the gamma-ray attenuation coefficient decreased from 0.201 m. -1 Reduced to 0.162 m -1 It is evident that borax is a core component of neutron "moderation-absorption," and its dosage directly determines the neutron shielding effectiveness. Borax is irreplaceable in composite neutron absorbers.

[0093] Compared to Example 1, the thermal neutron absorption cross-section of the fracture grouting material obtained in Comparative Example 3 decreased from 1950 barn to 1400 barn (a decrease of 28.2%), and the 7-day compressive strength decreased from 30.2 MPa to 26.9 MPa. This demonstrates that boron carbide is a highly efficient thermal neutron absorber, while also contributing to improved material strength. This further proves the rationality of the 2-5 parts boron carbide dosage range; insufficient dosage leads to a dual decrease in both shielding and mechanical properties.

[0094] Compared to Example 1, the thermal neutron absorption cross section of the fracture grouting material obtained in Comparative Example 4 decreased from 1950 barn to 1200 barn (a decrease of 38.5%), and the gamma-ray attenuation coefficient decreased from 0.201 m. -1 Reduced to 0.175 m -1 It is evident that nano-gadolinium oxide (30-50 nm) possesses both deep neutron purification and gamma-ray-assisted shielding functions, making it a "key supplementary component" of composite neutron absorbers, thus demonstrating the necessity of its dosage of 1-3 parts.

[0095] Compared with Example 1, the 7-day compressive strength of the fracture grouting material obtained in Comparative Example 5 decreased from 30.2 MPa to 25.8 MPa (a decrease of 14.6%), while the 28-day shrinkage rate increased from 0.018% to 0.028% (an increase of 55.6%). This demonstrates that lithium slag powder (industrial solid waste) possesses a triple effect of "hydration promotion - neutron moderation - volume stabilization." Insufficient dosage leads to a decrease in mechanical properties and volume stability, proving the rationality of its dosage of 5-10 parts.

[0096] Compared to Example 1, the density of the crack grouting material obtained in Comparative Example 6 was 2.98 g / cm³. 3 Reduced to 2.82 g / cm³ 3 (A decrease of 5.4%), the fluidity decreased from 280 mm to 255 mm (a decrease of 8.9%), and the minimum injectable crack increased from 0.2 mm to 0.3 mm. It can be seen that step-by-step dry mixing can avoid the separation of high-density aggregate (barite sand) and lightweight fiber (barium sulfate whiskers), ensuring the uniformity of component dispersion, proving that this process is the key to adapting to micro-cracks.

[0097] Compared to Example 1, the flowability of the crack grouting material obtained in Comparative Example 7 decreased from 280 mm to 248 mm (a decrease of 11.4%), the initial setting time was abnormally extended from 48 min to 55 min, and slight bleeding occurred in the grout (bleed rate 0.5%). This undesigned delay in initial setting time and bleeding phenomenon indicate that one-time liquid preparation leads to uneven dispersion and even local agglomeration of the water-reducing agent and stabilizer. The agglomerates abnormally encapsulate cement particles, thus interfering with the normal early hydration process. Therefore, gradient liquid preparation can effectively avoid additive agglomeration and emulsion demulsification, proving that this process plays a decisive role in ensuring workability and hydration controllability.

[0098] Although the ideal initial setting time range for the grouting material of this invention is 45-90 min, and both Example 2 (55 min) and Comparative Example 7 (55 min) fall within this range, their causes and properties are completely different. Example 2's setting time was due to the increased amount of polymer emulsion and barium sulfate whiskers; the polymer material naturally delayed cement hydration, which is a controlled state within the formulation design, and both fluidity and strength remained excellent. Comparative Example 7, however, represents an "abnormal extension." The formulation of Comparative Example 7 is exactly the same as that of Example 1. Under the same formulation, simply changing the "gradient liquid preparation" to "one-time liquid preparation" extended the initial setting time from 48 min to 55 min. This extension is negative. Because of the one-time water mixing, the water-reducing agent and stabilizer (HPMC) did not achieve sufficient gradient dissolution, resulting in localized agglomeration. Simultaneously, the high-concentration electrolyte environment caused partial demulsification of the core-shell composite emulsion. These agglomerates and the demulsified polymer abnormally and unevenly coated the surface of the cement particles, acting like a poor "isolation film," artificially blocking the normal rapid hydration process of sulfoaluminate cement in its early stages. This "abnormal stagnation" is not only reflected in the longer initial setting time, but also more directly in the collapse of macroscopic properties. It directly leads to a significant decrease in slurry fluidity (from 280 mm to 248 mm) and the appearance of 0.5% bleeding.

[0099] Compared with Example 1, the 7-day compressive strength of the fracture grouting material obtained in Comparative Example 8 decreased from 30.2 MPa to 23.9 MPa (a decrease of 20.9%), the 28-day shrinkage rate increased from 0.018% to 0.040% (an increase of 122%), and the minimum injectable fracture increased from 0.2 mm to 0.4 mm. It is evident that staged wet mixing can avoid "agglomeration" of dry-mixed materials, ensuring grout homogeneity. Simplifying the process leads to a significant decrease in mechanical properties, volume stability, and injectability.

[0100] The embodiments and comparative examples of this invention jointly demonstrate that the formulation system of "45-60 parts barite sand + 25-35 parts sulfoaluminate cement + 16-33 parts composite neutron absorber (8-15 parts borax, 2-5 parts boron carbide, 1-3 parts nano gadolinium oxide, 5-10 parts lithium slag powder) + 3-8 parts barium sulfate whiskers" and the process system of "stepwise dry mixing + gradient liquid preparation + graded wet mixing" are the only necessary combination to achieve "high shielding efficiency - high construction adaptability - high volume stability". Any missing component / deviation in dosage or simplification of process will lead to a significant decrease in performance.

[0101] This invention, through innovative raw material composition and preparation process, especially the triple neutron absorption system and core-shell structure pretreatment technology, is significantly superior to traditional solutions in terms of radiation shielding performance, construction applicability and long-term stability. It specifically solves the technical problem of radioactive shielding of tunnel surrounding rock fissures, forming a clear distinction and technological advancement from existing technologies.

[0102] The above description is merely a preferred embodiment of the present invention and is not intended to limit the 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. A fracture grouting material, characterized in that, By weight, the raw materials include: 45-60 parts barite sand, 25-35 parts sulfoaluminate cement, 8-20 parts borax, 2-5 parts boron carbide powder, 1-5 parts nano gadolinium oxide, 5-15 parts lithium slag powder, 3-8 parts barium sulfate whiskers, 3-8 parts polymer emulsion, 0.5-1.5 parts water-reducing agent, 0.1-0.5 parts stabilizer, and 18-25 parts water.

2. The fracture grouting material as described in claim 1, characterized in that, The barite sand has a particle size of 200-400 mesh and a barium sulfate content of not less than 90%. Preferably, the barium sulfate whiskers have an aspect ratio of 10:1-20:1 and a diameter of 1-5 μm; Preferably, the polymer emulsion is a styrene-acrylic emulsion or an acrylic emulsion; Preferably, the water-reducing agent is a polycarboxylate-based water-reducing agent; Preferably, the stabilizer is hydroxypropyl methylcellulose ether; Preferably, the boron carbide powder has a particle size of 800-1200 mesh; Preferably, the gadolinium nanoparticles have a particle size of 30-50 nm; Preferably, the lithium slag powder has a particle size of 400-600 mesh and a Li2O content of not less than 2.5%.

3. The fracture grouting material as described in claim 2, characterized in that, By weight, the raw materials include: 45-60 parts barite sand, 25-35 parts sulfoaluminate cement, 8-18 parts borax, 2-5 parts boron carbide powder, 1-4 parts nano gadolinium oxide, 5-12 parts lithium slag powder, 3-8 parts barium sulfate whiskers, 3-8 parts polymer emulsion, 0.5-1.5 parts water-reducing agent, 0.1-0.5 parts stabilizer, and 18-25 parts water; Preferably, the raw materials of the crack grouting material, by weight, include: 45-60 parts barite sand, 25-35 parts sulfoaluminate cement, 8-15 parts borax, 2-5 parts boron carbide powder, 1-3 parts nano gadolinium oxide, 5-10 parts lithium slag powder, 3-8 parts barium sulfate whiskers, 3-8 parts polymer emulsion, 0.5-1.5 parts water-reducing agent, 0.1-0.5 parts stabilizer, and 18-25 parts water.

4. The fracture grouting material as described in claim 1, characterized in that, The raw materials of the fissure grouting material, by weight, include: 50-55 parts barite sand, 28-30 parts sulfoaluminate cement, 12-15 parts borax, 3-4 parts boron carbide powder, 2 parts nano gadolinium oxide, 8 parts lithium slag powder, 5-7 parts barium sulfate whiskers, 6-8 parts polymer emulsion, 0.8-1.0 parts water-reducing agent, 0.2-0.3 parts stabilizer, and 22-23 parts water.

5. The crack grouting material according to any one of claims 1-4, characterized in that, The density of the fissure grouting material is 2.8-3.2 g / cm³. 3 The fluidity is 260-300 mm.

6. A method for preparing the fracture grouting material according to claim 1, characterized in that, include: Dry the barite powder and lithium slag powder, and sieve them for later use; Nano-gadolinium oxide was mixed with a portion of the polymer emulsion, and then the remaining polymer emulsion was added and mixed to form a composite emulsion. Weigh out barite sand, sulfoaluminate cement, and lithium slag powder according to the proportions, and perform the first dry mixing; add borax and boron carbide powder, and perform the second dry mixing; add barium sulfate whiskers, and perform the third dry mixing to obtain the dry mixture. Add the water-reducing agent to water and stir to dissolve it, add the stabilizer and continue stirring, and finally add the composite emulsion to form a mixture; The mixture is added to the dry mix in several batches and stirred to obtain the crack grouting material.

7. The preparation method according to claim 6, characterized in that, The first dry mixing speed is 60-80 r / min, and the time is 3-4 minutes; the second dry mixing speed is 80-100 r / min, and the time is 2-3 minutes; the third dry mixing speed is 100-120 r / min, and the time is 1-2 minutes.

8. The preparation method according to claim 6, characterized in that, Add the water-reducing agent to 60% of the formula amount of water and stir for 2 minutes; add the stabilizer and stir for 1 minute; add the core-shell structured composite emulsion and stir for 2 minutes; add the remaining water and stir well to form a mixture.

9. The preparation method according to claim 6, characterized in that, Add 50% of the mixture to the dry mix and stir at 60 r / min for 2 minutes; add the remaining 50% of the mixture and stir at 80-100 r / min for 2 minutes; then stir at 120-150 r / min for 3-5 minutes to obtain the crack grouting material.

10. The application of the fissure grouting material according to claim 1 in radioactive shielding of tunnel surrounding rock.

Images