A self-healing grouting material, its preparation method and application

Abstract

This invention provides a self-healing grouting material, its preparation method, and its application. By weight, the raw materials of the self-healing grouting material include the following components: 100 parts of cementitious material; 40-80 parts of water; 5-40 parts of polypropylene fiber-diatomite composite microbial carrier; 0-40 parts of mineral admixtures; and 0-5 parts of chemical additives. The polypropylene fiber-diatomite composite microbial carrier comprises a polypropylene fiber core layer and a diatomite gel shell layer. The diatomite gel shell layer is a gel network structure with embedded porous diatomite particles loaded with microorganisms. This invention solves the problem of insufficient timeliness of water-blocking performance in rock strata grouting in existing technologies, achieving long-term, adaptive sealing of seepage channels in rock strata fissures, and effectively enhancing the durable water-blocking capacity and overall stability of modified rock strata.

Description

Technical Field

[0001] This invention relates to the field of rock grouting reinforcement technology, and in particular to a grouting material with self-healing function, its preparation method and application. Background Technology

[0002] In coal mining and underground engineering construction, grouting is often required for the aquifer, overburden fracture zone, and surrounding rock fracture zone to improve the overall impermeability, shear strength, and bearing capacity of the rock strata, prevent confined water inrush accidents and sudden increases in water volume, and protect groundwater resources. Existing projects widely use ordinary Portland cement, ultrafine cement, and some chemical grouting materials as grouting materials. The resulting stone-like mass can reduce rock permeability for a certain period. However, under long-term mining stress, changes in confining pressure, and repeated water pressure, the grouted stone-like mass is prone to micro-cracks, fissure propagation, and interface debonding, leading to a gradual increase in permeability and a decrease in water-blocking performance. Ordinary cement-based grouting materials, after curing, lack the ability to spontaneously redeposit and seal seepage channels in micro-cracks that develop later. Once new seepage channels form inside the stone-like mass or at the stone-like mass-original rock interface, re-grouting or other remedial measures are required, resulting in high construction costs and difficulty in ensuring safety. Therefore, there is an urgent need for a rock grouting material that combines mechanical reinforcement and self-healing functions and can adapt to complex stress-hydraulic-chemical environments in deep formations, in order to solve the problem of insufficient timeliness of water-blocking performance in existing rock grouting technologies. Summary of the Invention

[0003] The purpose of this invention is to provide a grouting material with self-healing function, its preparation method and application, so as to solve the problems existing in the prior art, realize long-term and adaptive sealing of seepage channels in rock strata, and improve the long-term water resistance and stability of modified rock strata.

[0004] To achieve the above objectives, the present invention provides the following solution: One technical solution of this invention provides a grouting material with self-healing function, comprising the following components by weight: 100 parts of cementitious material; 40-80 parts of water; 5-40 parts of polypropylene fiber-diatomite composite microbial carrier; 0-40 parts of mineral admixture; and 0-5 parts of chemical additives. The polypropylene fiber-diatomite composite microbial carrier comprises a polypropylene fiber core layer and a diatomite gel shell layer. The diatomite gel shell layer covers the surface of the polypropylene fiber core layer and is a gel network structure with embedded porous diatomite particles loaded with microorganisms. The PP fiber (polypropylene fiber) improves the crack resistance and tensile strength of the stone, limiting the crack width and propagation rate.

[0005] Furthermore, the diatomaceous earth gel shell is a gel network structure formed by cross-linking sodium alginate. The diatomaceous earth-gel shell includes a cross-linked gel with sodium alginate as the matrix, which is cross-linked with calcium ions to form a Ca-calcium alginate gel network. The porous diatomaceous earth particles and microorganisms are uniformly dispersed and fixed in the gel network. The porous diatomaceous earth, as a microbial carrier, reduces the direct damage to microorganisms caused by the high alkalinity and high ionic strength of cement pore fluid. By fixing diatomaceous earth and microorganisms on the surface of PP fibers through the sodium alginate-calcium ion gel shell, the composite carrier forms a spatial network structure inside the stone body, making it easier to accumulate and deploy near potential fracture development areas. Thus, when fracture seepage occurs, it can preferentially generate a self-healing effect in critical areas.

[0006] Furthermore, the porous diatomaceous earth particles have a particle size of 0.1–0.5 mm, corresponding to 40–140 mesh. When the particle size is too small (less than 0.1 mm), the effective pore volume within a single particle is limited and close to the size of cement particles, making it easily clogged by hydration products, thus weakening the survival and subsequent release capacity of microorganisms. When the particle size is too large (greater than 0.5 mm), the size of a single particle is significantly larger than cement particles and the expected crack width, increasing the transition zone around the particle interface, making it prone to becoming a stress concentration source, and easily causing segregation and blockage in the slurry. Experiments show that when diatomaceous earth with a particle size of 0.1–0.5 mm is used as a fine aggregate carrier, it neither significantly increases slurry viscosity and reduces fluidity like excessively fine powder, nor causes segregation and blockage like large-diameter aggregates. While maintaining an initial fluidity of 245 mm and a 30-minute fluidity of 230 mm, the bleeding rate is controlled at 2.2%. Furthermore, the compressive strength of the material remained relatively stable at 32–35 MPa after incorporating diatomaceous earth particles of different sizes. The 28-day splitting tensile strength of the group with particles of 0.1–0.5 mm increased from 3.0 MPa to 3.6 MPa, an increase of approximately 20%; while the increase was only about 6.7% for the group with particles <0.1 mm and about 13.3% for the group with particles of 0.5–1.0 mm. When the diatomaceous earth particles are in the 0.1–0.5 mm range, they can more effectively form a micro-skeletal structure with PP fibers and cementitious matrix, significantly improving the crack and tensile strength of the aggregate without sacrificing compressive strength.

[0007] Furthermore, in the polypropylene fiber-diatomite composite microbial carrier, the mass ratio of polypropylene fiber to porous diatomite is 1:1 to 1:10, and the length of the polypropylene fiber is 6 to 12 mm and the diameter is 10 to 40 μm.

[0008] Furthermore, in the polypropylene fiber-diatomite composite microbial carrier, the mass ratio of sodium alginate to porous diatomite is 1:5 to 1:20.

[0009] Furthermore, the microorganisms include at least one of Bacillus subtilis, Bacillus pasteurellii, Bacillus spheroides, alkali-resistant mutants of Bacillus subtilis, alkali-resistant mutants of Bacillus pasteurellii, and alkali-resistant mutants of Bacillus spheroides, and the bacterial count loaded in the porous diatomaceous earth particles is 10 based on the dry weight of the bacterial cells. 7 ~10 10 CFU / g. The above-mentioned strains are all spore-forming bacteria of the genus *Bacillus*. They can survive for a long time in spore form under highly alkaline environments (pH 12-13) and wet-dry cycles in cement-based pore liquids. Their survival rate after 28 days of immersion in cement pore liquid remains above 40%. Experiments have shown that the above-mentioned preferred strains have strong urea hydrolysis and calcium carbonate-induced deposition capabilities. In engineering applications, the chemical composition of aquifer water has a certain degree of uncertainty. To improve the adaptability of the material of this invention under different water quality conditions, a synergistic effect of microbial communities can be formed by combining two or three strains. Under the same total loading conditions, the permeability coefficient reduction of the dual- or triple-strain system is about 15%-30% higher than that of the single-strain system, and the self-healing stability is better. Furthermore, when the loading is below 10... 7 At CFU / g, approximately 10 6 Under the CFU / g condition, after the same damage and repair period (28 days), the specimen permeability coefficient only decreased from 5.0 × 10⁻⁶. -7 m·s -1 Reduced to approximately 3.5 × 10 -7 m·s -1 The reduction was less than 30%; when the load was controlled at 10 7 ~10 10 CFU / g, especially at 10 8 ~10 9 When the CFU / g range is reached, the permeability coefficient of the specimen is 5.2 × 10⁻⁶. -7 m·s -1 Reduced to 6.0×10 -8 m·s -1 This reduces the load by approximately one order of magnitude; when the load exceeds 10 10 At CFU / g, as the loading increased, the permeability did not decrease significantly further. Instead, early gas secretion and localized micro-expansion occurred in some formulations.

[0010] Furthermore, the grouting material has a flowability of not less than 180 mm within 30 minutes and a bleeding rate of not more than 3%.

[0011] Furthermore, the polypropylene fiber accounts for 0.05% to 1.0% of the volume fraction in the grouting material. Under the same mass fraction conditions, the volume fraction of the fiber varies considerably. Those skilled in the art commonly use volume fraction to limit the fiber content in order to directly control the spatial distribution and effect of the fiber within the material. When the volume fraction of polypropylene fiber varies within the range of 0.05% to 1.0%, the compressive strength does not show a significant decrease, while the splitting tensile strength is increased by approximately 10% to 25% compared to the control group without fiber.

[0012] Furthermore, the cementitious material includes ordinary Portland cement and ultrafine cement, wherein the ordinary Portland cement accounts for 30-80% of the cementitious material by mass, and the ultrafine cement accounts for 20-70% of the cementitious material by mass. By adjusting the mass percentages of the two materials to vary within the ranges of 30-80% and 20-70%, a balance can be achieved between groutability, early and mid-term strength, impermeability and density, and suitability for self-healing microenvironment, rather than being arbitrarily set or a universal design.

[0013] Furthermore, the mineral admixture is one or a combination of fly ash, slag powder, and silica fume, with a dosage of 5-30% of the cementitious material mass. Limiting the mineral admixture to one or a combination of fly ash, slag powder, and silica fume, and controlling its dosage within the range of 5-30% of the cementitious material mass, comprehensively considers the fluidity of the grouting material, hydration heat control, degree of impermeability densification, and the alkalinity and Ca required for microbial self-healing. 2+ The optimization results obtained after supplying the conditions are as follows: When the dosage is less than 5%, it is difficult to make a significant contribution to the anti-permeability and self-healing performance; when the dosage is more than 30%, the early strength and system alkalinity are adversely affected, and the improvement of self-healing effect is limited or even reduced.

[0014] Furthermore, the chemical admixture includes one or more of the following: water-reducing agent, retarder, anti-segregation agent, expanding agent, and defoamer, with an admixture dosage of 0.1% to 5.0% of the mass of the cementitious material, in order to regulate the fluidity, water retention, and setting time of the slurry.

[0015] Furthermore, the preparation process of the polypropylene fiber-diatomite composite microbial carrier includes: S1, PP fiber pretreatment: After pretreatment, the polypropylene fiber is dried for later use; S2, Diatomaceous earth pretreatment and microbial loading: After pretreatment of porous diatomaceous earth, it is mixed with microbial suspension, and then the mixture is impregnated under vacuum, allowed to stand, separated and dried to obtain bacteria-loaded diatomaceous earth. The solid-liquid ratio of the porous diatomaceous earth to the microbial suspension is 1g:3-10mL. Once the solid-liquid ratio is significantly less than 1:3 or greater than 1:10, the bacterial loading and subsequent CaCO3 deposition effect will be significantly worse.

[0016] S3, Preparation of PP fiber-diatomite composite microbial carrier: The bacterial-loaded diatomite is added to a sodium alginate solution with a mass fraction of 0.5-1% to obtain a gel precursor solution; dried and prepared polypropylene fibers are added to the gel precursor solution and mixed, then transferred to a crosslinking agent solution for immersion, followed by washing and drying to obtain the polypropylene fiber-diatomite composite microbial carrier. Further, step S1 specifically includes: sequentially cleaning the PP fibers with organic solvents, rinsing with deionized water, and treating them with alkali to remove surface oil and improve surface roughness, followed by drying and sterilization for later use; Further, step S2 specifically includes: sieving, washing, drying and sterilizing porous diatomaceous earth to obtain diatomaceous earth particles with a particle size range of 0.1 to 0.5 mm; adding the diatomaceous earth particles to a high-concentration self-healing microbial suspension at a solid-liquid ratio of 1:(3 to 10), immersing them under vacuum conditions of -0.08 to -0.09 MPa for 10 to 30 minutes, restoring them to normal pressure and allowing them to stand for 1 to 4 hours, separating them and drying them at low temperature to obtain bacteria-loaded diatomaceous earth particles.

[0017] Further, step S3 specifically includes: preparing a sodium alginate aqueous solution with a mass fraction of 0.5-1%; adding bacterial-loaded diatomaceous earth to the sodium alginate solution to form a uniformly dispersed diatomaceous earth-microorganism gel precursor solution; adding the pretreated PP fibers obtained in step S1 to the gel precursor solution to uniformly coat the surface of the PP fibers with a sodium alginate gel layer containing diatomaceous earth and microorganisms; then transferring the coated PP fibers to a 0.05-0.25 mol / L CaCl2 solution for immersion in for 1-20 minutes for fixation, so that sodium alginate crosslinks with calcium ions to form a diatomaceous earth-microorganism gel shell layer coating the surface of the PP fibers; then washing and drying to obtain a PP fiber-diatomaceous earth composite microbial carrier.

[0018] Further, in step S3, the mass ratio of sodium alginate to bacterial-loaded diatomaceous earth is 1:5 to 1:20, the mass ratio of polypropylene fiber to bacterial-loaded diatomaceous earth is 1:1 to 1:10, and the CaCl2 solution soaking temperature is 5 to 30°C. Within this range: the shell can form a continuous coating, providing sufficient protection for the bacterial-loaded diatomaceous earth, while the gel interior still retains interconnected pores (facilitating the exchange of nutrients and Ca). 2+ diffusion).

[0019] Further, the alkali treatment in S1 is as follows: PP fibers are immersed in a 1-10 wt% NaOH solution and reacted at 40-80°C for 10-60 min, then rinsed with deionized water until neutral and dried.

[0020] Furthermore, the bacterial concentration of the self-healing microbial suspension in S2 is 10. 8 ~10 9The concentration of bacteria-laden diatomaceous earth particles is controlled within 1–10 wt%, and the final moisture content is controlled within this range.

[0021] In addition, the present invention also provides a method for preparing a grouting material with self-healing function as described above, comprising the following steps: The cementitious material, water, polypropylene fiber-diatomite composite microbial carrier, mineral admixtures and chemical additives are mixed and stirred in a preset ratio to obtain a grouting material with self-healing function.

[0022] Furthermore, the specific preparation method of the grouting material includes: PP fiber-diatomite composite microbial carrier accounting for 5-30% of the total mass of cementitious material; the mixing process first involves dry mixing of cementitious material and mineral admixture for 30-120 seconds, then adding water and chemical additives and wet mixing for 60-300 seconds, and finally adding composite microbial carrier and stirring at low speed for 60-180 seconds to reduce shear damage to microorganisms.

[0023] A third aspect of the present invention provides an application of a self-healing grouting material as described above in rock grouting modification. When this material is injected into aquifers in the roof or floor of a coal seam, water-conducting fracture zones in overlying strata, or layered rock masses, the solidified grouting stone body, under stress-hydraulic-chemical coupling, achieves long-term self-healing of fracture seepage and continuous water blocking of confined aquifers through the synergistic effect of PP fiber crack control and microbial-induced CaCO3 precipitation in the diatomaceous earth carrier.

[0024] The present invention discloses the following technical effects: This invention provides a self-healing grouting material, its preparation method, and its application. The grouting material of this invention achieves long-term, adaptive sealing of seepage channels in rock fissures through a synergistic mechanism of "fiber-controlled cracking, porous carrier enrichment, and microbial-induced deposition," thereby improving the long-term water-blocking and stability of modified rock strata. The polypropylene fiber-diatomite composite microbial carrier in the grouting material comprises a polypropylene fiber core layer and a diatomite gel shell layer. The diatomite gel shell layer coats the surface of the polypropylene fiber core layer and is a gel network structure containing several porous diatomite particles loaded with microorganisms. In this invention, PP fibers can improve the crack resistance and tensile strength of the stone body, limiting the crack width and propagation rate; in addition, microorganisms induce CaCO3 deposition around the cracks and fibers, providing secondary filling and sealing of newly formed micro-cracks and seepage channels. Porous diatomaceous earth, acting as a microbial carrier, mitigates the direct damage to microorganisms caused by the high alkalinity and high ionic strength of cement pore fluid. A sodium alginate-calcium ion gel shell immobilizes the diatomaceous earth and microorganisms on the surface of PP fibers, allowing the composite carrier to form a spatial network structure within the stone body. This facilitates enrichment and deployment near potential fracture development areas, enabling preferential self-repair at critical locations when fracture seepage occurs. This invention utilizes microbial-induced carbonate deposition to generate new mineral fillers in situ within fractures and pores. These fillers synergistically construct a denser microstructure with existing hydration products. Under stress-hydraulic-chemical coupling, microorganisms can continuously participate in the adaptive regulation of seepage channels for a certain period, maintaining a low permeability level in the modified rock layer after initial grouting and solidification. This is beneficial for improving the long-term water-blocking effect of modified aquifers or overburden fracture zones. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a schematic diagram of the cross-sectional structure of the PP fiber-diatomite composite microbial carrier of the present invention; Figure 2 This is a schematic diagram of the longitudinal structure of the PP fiber-diatomite composite microbial carrier of the present invention, which enables self-repair at cracks. Figure 3 This is an image of an undried sample of the PP fiber-diatomite composite microbial carrier from Example 1 of the present invention. Figure 4 This is a product image of the dried PP fiber-diatomite composite microbial carrier of Example 1 of the present invention.

[0027] Reference numerals: 1. PP fiber core layer; 2. Diatomaceous earth gel shell layer surrounding the PP fiber core layer; 3. Porous diatomaceous earth particles dispersed in the gel shell layer; 4. Self-healing microorganisms loaded in the pores and gel network of diatomaceous earth; 5. Cement-based cementitious material matrix encapsulating the composite microbial carrier; 6. Cracks in rock mass or grouting stone mass; 7. Mineral deposits such as CaCO3 induced by microorganisms; 8. Direction of groundwater seepage within the cracks. Detailed Implementation

[0028] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0029] It should be understood that the terminology used herein is merely for describing particular embodiments and is not intended to limit the invention. Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of the invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail. Various modifications and variations to the specific embodiments described herein are possible without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will be apparent to those skilled in the art. This specification and embodiments are exemplary only. The terms “comprising,” “including,” “having,” “containing,” etc., as used herein, are open-ended terms meaning that they include, but are not limited to, these terms.

[0030] In the following embodiments of the present invention, the sources of the bacterial strains involved are as follows: *Sporosarcina pasteurii* was purchased from BNCC (accession number BNCC337394), and *Bacillus subtilis* was purchased from the China General Microbiological Culture Collection Center (CGMCC) (accession number CGMCC 1.1087). Other microorganisms capable of inducing CaCO3 precipitation (at least one of *Bacillus subtilis*, *Sporosarcina pasteurii*, *Bacillus spheroides*, alkali-resistant mutant of *Bacillus subtilis*, alkali-resistant mutant of *Sporosarcina pasteurii*, and alkali-resistant mutant of *Bacillus spheroides*) can be used in the technical solution of the present invention.

[0031] In this embodiment of the invention, the raw materials are sourced from: 1) Ordinary Portland cement: P.O42.5 or P.O52.5 ordinary Portland cement is selected. It is a commercially available product produced by local cement production enterprises that meets the GB175 standard. Those skilled in the art can select ordinary Portland cement with equivalent performance to replace it according to the needs of the project.

[0032] 2) Ultrafine cement: Ultrafine silicate cement with an average particle size of not more than 10μm and a specific surface area of ​​not less than 800m² / kg is selected. It is a commercially available ultrafine cement product that meets the requirements of enterprise standards or industry standards. Other ultrafine cements with similar particle size and activity characteristics can also be used as substitutes.

[0033] 3) Fly ash: Grade II or Grade I fly ash that meets the requirements of GB / T1596 is selected and is a commercially available product that is a by-product of coal-fired power plants.

[0034] 4) Slag powder: Select S95 or S105 grade granulated blast furnace slag powder that meets the requirements of GB / T18046. It is a commercially available slag powder product.

[0035] 5) Silica fume: Select silica fume or silica powder that meets the requirements of GB / T27690. It is a commercially available product that is a by-product of industrial ferrosilicon smelting and has been collected, screened and dried.

[0036] 6) Porous diatomaceous earth: Industrial-grade diatomaceous earth filter material or filler is selected. It is a commercially available diatomaceous earth product that has been calcined or not. The original particle size is obtained by sieving to obtain porous diatomaceous earth particles with a particle size range of 0.1 to 0.5 mm as described in this invention.

[0037] 7) Polypropylene fiber (PP fiber): Commercially available engineering-grade chopped polypropylene fiber is selected. It is a monofilament or mesh monofilament synthetic fiber with a length of 6-12 mm, a diameter of 10-40 μm, a tensile strength of not less than 300 MPa, and an elastic modulus of not less than 3 GPa. Those skilled in the art can select PP fiber with equivalent performance as a substitute as needed.

[0038] 8) Sodium alginate: Select analytical grade or food grade sodium alginate, which is a commercially available powder product. After dissolving, it is used to prepare microbial embedding gels. Calcium chloride (CaCl2): Analytical grade or chemically pure calcium chloride is selected. It is a commercially available product and is used for cross-linking sodium alginate.

[0039] 9) Chemical admixtures: including high-efficiency water-reducing agents, retarders, anti-segregation agents, expansion agents, etc., all of which are commercially available concrete admixture products, such as polycarboxylate-based high-efficiency water-reducing agents and hydroxycarboxylate-based retarders, which meet the requirements of relevant national or industry standards.

[0040] 10) Alkaline treatment agents and cleaning solvents: such as sodium hydroxide solution, anhydrous ethanol and deionized water are all commercially available chemical reagents. Among them, sodium hydroxide and anhydrous ethanol are preferably of analytical grade, and deionized water is obtained from the laboratory water treatment system.

[0041] Comparative Example 1 The difference between this comparative example and Example 1 is that: only ordinary Portland cement is used as the cementitious material, without the addition of ultrafine cement; only fly ash is added to the mineral admixtures, without the addition of slag powder and silica fume; and the source and specifications of the remaining raw materials are the same as in Example 1.

[0042] Comparative Example 2 The difference between this comparative example and Example 1 is that porous diatomaceous earth and sodium alginate were not used; only commercially available PP short-cut fibers were used for reinforcement. The sources of other raw materials such as cement, mineral admixtures, and additives are the same as in Example 1.

[0043] Comparative Example 3 The difference between this comparative example and Example 1 is that this is a grouting material containing microorganisms and diatomaceous earth carrier but without PP fiber, while the other raw materials such as cement, mineral admixtures, and additives are from the same sources as in Example 1.

[0044] Comparative Example 4 The difference between this comparative example and Example 2 is that: no PP fiber, no diatomaceous earth microbial carrier, and no self-healing bacteria are added to the formula. The ratio of ordinary silicate cement to ultrafine cement, fly ash content, water-cement ratio, and the types and amounts of water-reducing agent and retarder are the same as in Example 2.

[0045] Comparative Example 5 The difference between this comparative example and Example 2 is that the same volume fraction of PP fiber as in Example 2 is incorporated into the formulation, but porous diatomaceous earth and sodium alginate are not used, no composite microbial carrier is prepared, and no microorganisms are introduced; the remaining cementitious material system, water-cement ratio, fly ash content, and the types and amounts of water-reducing agent and retarder are the same as in Example 2.

[0046] Example 1 A self-healing grouting material suitable for reinforcing excavated rock formations on confined aquifers is designed as follows: 1. Based on a total mass of 100 parts of cementitious material, the mass ratio of each component of the grouting material in this embodiment is as follows: Table 1 Material Proportions for Example 1 2. Preparation of composite carriers and materials (1) Pretreatment of PP fibers Short PP fibers with a length of 9 mm and a diameter of approximately 20 μm were selected. The PP fibers were ultrasonically cleaned in anhydrous ethanol for 10 min, the ethanol was discarded, and the fibers were rinsed twice with deionized water. The fibers were then immersed in a 5 wt% NaOH solution and treated at 60 °C for 30 min. The fibers were rinsed with deionized water until the pH of the effluent was approximately 7, and then dried in a 60 °C oven for 4 h. After drying, the fibers were sterilized by autoclaving at 121 °C and 0.1 MPa for 30 min and then cooled for later use.

[0047] (2) Diatomaceous earth pretreatment and microbial loading Industrial diatomaceous earth was selected and sieved through a standard sieve of 35–150 mesh, with a particle size of 0.1–0.5 mm being collected. The diatomaceous earth was repeatedly washed with deionized water until the supernatant was clear, and then dried at 105℃ for 12 hours. It was then autoclaved at 121℃ and 0.1 MPa for 30 minutes. The sterilized diatomaceous earth was added to a suspension of *Bacillus pasteurellii* at a solid-liquid ratio of 1:5 (g:mL), resulting in a bacterial concentration of approximately 10⁸ CFU / mL. The container containing the diatomaceous earth and bacterial suspension was placed in a vacuum drying oven, and a vacuum was drawn to -0.08 MPa and maintained for 20 minutes before returning to normal pressure. The mixture was then allowed to stand at room temperature with slight shaking for 2 hours to allow the bacteria to fully enter and adsorb into the pores of the diatomaceous earth. The solid and liquid were separated by filtration, and the diatomaceous earth was dried in a 30℃ constant temperature oven until the moisture content was less than 5 wt%, yielding bacteria-loaded diatomaceous earth particles. In step (2), the preparation process of *Bacillus pasteurellii* suspension includes: 1) Seed culture preparation: Select 1-3 single colonies of each cultured strain and inoculate them into 50-200 mL of liquid nutrient broth medium. Incubate at 30℃ and 170 r / min for 24 h with shaking to allow the cells to grow to the logarithmic growth phase or stationary phase, thus obtaining the seed culture; 2) Scale-up culture: Inoculate the seed culture at a volume ratio of 1-5% into sterilized and cooled main culture medium. Incubate at 30℃ and 170 r / min with shaking for 12-36 h. The culture is terminated when the turbidity OD600 of the culture medium reaches 0.8-1.5. 3) Centrifugation and washing: Centrifuge the cultured bacterial solution at 5000 r / min, discard the supernatant, and add an equal volume of sterile physiological saline; repeat centrifugation and resuspension 1-2 times to remove excess culture medium components and obtain washed bacterial sludge; 4) Preparation of bacterial suspension: Add the bacterial sludge to the pre-prepared sterile physiological saline and disperse evenly to obtain a bacterial suspension with a concentration of about 108 CFU / mL.

[0048] (3) Preparation of PP fiber-diatomite composite microbial carrier A 1.0% sodium alginate aqueous solution was prepared. The bacteria-carrying diatomaceous earth was added to the sodium alginate solution at a dry basis ratio of 1:10, and stirred until homogeneous to form a diatomaceous earth-microbial gel precursor solution. Pretreated PP fibers were added to the precursor solution and mechanically stirred for 5 minutes to uniformly coat the fiber surface with a sodium alginate gel layer containing bacteria-carrying diatomaceous earth. The coated fibers were then transferred to a 0.2 mol / L CaCl2 solution and immersed for 10 minutes to allow sodium alginate to crosslink with calcium ions, forming a calcium ion-calcium alginate gel shell. After removal, the fibers were quickly rinsed once with sterile water and dried at 30°C for 12 hours to obtain a PP fiber-diatomaceous earth composite microbial carrier. The mass ratio of PP fiber to bacteria-carrying porous diatomaceous earth was 1:3, and the mass ratio of sodium alginate to bacteria-carrying porous diatomaceous earth was 1:10. Based on a total mass of 100 parts of cementitious material, the PP fiber content is converted to 0.20 parts, corresponding to a volume fraction of PP and carrier in the grouting material of approximately 0.10%.

[0049] 3. Preparation of grouting materials Ordinary silicate cement, ultrafine cement, and slag powder were added to a mixer in a specific ratio and dry-mixed for 60 seconds. A water-reducing agent was dissolved in the mixing water and added to the mixer while stirring, and wet-mixed for 120 seconds to obtain a uniform cement slurry. The prepared PP fiber-diatomite composite microbial carrier was added to the slurry and stirred at low speed for 120 seconds to ensure uniform dispersion, thus obtaining the self-healing grouting material of this embodiment. The porous diatomite particles in the obtained grouting material have a particle size of 0.1–0.5 mm; according to the flowability test method for cement-based grouting materials, the flowability within 30 minutes is approximately 230 mm, and the bleeding rate is approximately 2.2%. Figure 1 This is a schematic diagram of the cross-sectional structure of the PP fiber-diatomite composite microbial carrier of the present invention. Figure 2 This is a schematic diagram of the longitudinal structure of the PP fiber-diatomite composite microbial carrier of the present invention, which enables self-repair at cracks. Figure 3 This is a photograph of the PP fiber-diatomite composite microbial carrier prepared according to the process in Example 1 in its undried state. Figure 4 This is a picture of the finished PP fiber-diatomite composite microbial carrier prepared and dried according to the process in Example 1.

[0050] 4. Strength and Permeability Comparison Test (1) Experimental design The grouting material of this embodiment was poured into a standard mold (50mm×50mm×50mm) and cured for 28 days. Comparative materials were set up: Comparative Example 1 was an ordinary cement-based grouting material without PP fiber or microbial carrier; Comparative Example 2 was a grouting material with PP fiber but without microorganisms or diatomaceous earth carrier; and Comparative Example 3 was a grouting material with microorganisms and diatomaceous earth carrier but without PP fiber. All other conditions were the same.

[0051] (2) Unconfined compressive strength test Table 2 shows that, under the same curing conditions, the 28-day compressive strength of the material in this embodiment is 34.2 MPa, which is about 5.2% higher than that of Comparative Example 1 (without fiber and microbial carrier) and slightly lower than that of Comparative Example 2 (with only PP fiber), but remains at a similar level. However, the strength of Comparative Example 3 (containing only microorganisms and diatomaceous earth carrier but without PP fiber) is significantly lower than that of ordinary cement-based grouting material. This indicates that using only diatomaceous earth carrier weakens the strength of cement-based materials. However, after introducing the diatomaceous earth-PP fiber composite carrier, the compressive strength of the material still meets the requirements of engineering applications, and no significant strength degradation occurs. The purpose of using a composite carrier in this invention is to introduce a self-healing carrier while ensuring strength, as referenced in subsequent permeability self-healing tests.

[0052] Table 2 Compressive strength of different materials at 28 days (3) Permeability self-healing test Φ50mm×100mm stone specimens were subjected to uniaxial compression loading to 60% of their peak strength at 28 days of age. After unloading, internal microcracks were formed. The specimens were then placed in a permeation apparatus, and the permeability coefficient was tested under a confining pressure of 1.0 MPa and an osmotic pressure difference of 0.5 MPa. Subsequently, the specimens were immersed in simulated mine water containing calcium ions and nutrients for 28 days, and the permeability coefficient was measured again. The composition and preparation process of the simulated mine water included: each 1L of solution contained: 3.0g CaCl2·2H2O, 1.5g NaHCO3, 15.0g urea, 1.5g NH4Cl, 2.0g yeast extract, and 3.0g NaCl, with the remainder being deionized water. The pH was adjusted to 8.5±0.2 using NaOH or HCl. After preparation, the solution was sterilized at 121℃ for 20 minutes and cooled to room temperature. The solution temperature was maintained at 20±2℃ during the curing process.

[0053] As shown in Table 3, the permeability coefficients of Comparative Examples 1 and 2 increased significantly after damage, and remained at approximately 10 after 28 days of self-healing. -7 m·s -1 The magnitude indicates that traditional cement-based grouting materials and materials containing only PP fibers are insufficient for effective self-repair of internal microcracks. Comparative Example 3 showed the highest permeability coefficient after damage, which decreased by approximately 70.7% after 28 days of self-repair. In this embodiment, the material, after undergoing the same loading and curing process, showed a permeability coefficient of 5.2 × 10⁻⁶. -7 m·s -1 Reduced to 6.0×10 -8 m·s -1The PP fiber-diatomite composite microbial carrier of the present invention reduces the concentration by about one order of magnitude, which is significantly better than the comparative material. This indicates that the present invention can induce carbonate deposition under fracture seepage conditions and produce a continuous sealing effect on the seepage channel.

[0054] Table 3 Self-healing permeability of different materials Example 1 of this invention uses a single self-healing strain without adding any additional retarder. By comparing with Comparative Examples 1 to 3 in Tables 2 and 3, it is demonstrated that the basic configuration of the PP fiber-diatomite composite microbial carrier significantly improves the crack resistance and self-healing ability of the stone body under standard curing and single loading-repair conditions.

[0055] Example 2 A self-healing grouting material suitable for modifying high-mineralization aquifers in coal seam roofs and under conditions of strong mining stress is designed as follows: 1. Based on a total mass of 100 parts of cementitious material, the mass ratio of each component of the grouting material in this embodiment is as follows: Table 4 Material Proportions for Example 2 2. Preparation of composite carriers and materials (1) Microbial compound loading A mixed bacterial suspension was prepared by mixing Bacillus subtilis and Bacillus pasteurellium at a 1:1 volume ratio, with a bacterial concentration of 10. 8 ~10 9 CFU / mL; the remaining steps of diatomaceous earth sieving, washing, drying and sterilization are the same as in Example 1; diatomaceous earth is added to the mixed bacterial suspension at a solid-liquid ratio of 1:6, vacuum degree -0.09MPa, soaked for 30 min, and separated after standing at normal pressure for 4 h; dried at 30℃ until the water content is <3wt% to obtain mixed bacterial-loaded diatomaceous earth.

[0056] (2) Preparation of PP fiber-diatomite composite microbial carrier A 1.0% sodium alginate solution was used, with a sodium alginate to mixed bacterial carrier diatomaceous earth mass ratio of 1:15. PP fibers, 12 mm in length and approximately 30 μm in diameter, were treated with 8% wt NaOH solution at 70°C for 45 min. The adhesive coating and CaCl2 curing steps were the same as in Example 1, except the CaCl2 concentration was adjusted to 0.3 mol / L and the soaking time was 15 min. The mixture was dried at 30°C for 24 h to obtain a composite microbial carrier with higher density. The PP to carrier (porous diatomaceous earth) mass ratio was 1:3. Based on a total cementitious material mass of 100 parts, the polypropylene fiber content in this example was converted to 0.20 parts, corresponding to a volume fraction of 0.10% in the grouting material.

[0057] (3) Preparation of grouting materials Similar to Example 1, except that a retarder was added during the wet mixing stage to ensure sufficient working time for the slurry under long-distance transportation conditions. Comparative materials were set up: Comparative Example 4 did not contain PP fiber, diatomaceous earth microbial carrier, or introduce any self-healing bacteria; the ratio of ordinary silicate cement to ultrafine cement, fly ash content, water-cement ratio, and the types and amounts of water-reducing agent and retarder were the same as in Example 2. Comparative Example 5 incorporated the same volume fraction of PP fiber as in Example 2, but did not use porous diatomaceous earth and sodium alginate, did not prepare a composite microbial carrier, and did not introduce microorganisms; the remaining cementitious material system, water-cement ratio, fly ash content, and the types and amounts of water-reducing agent and retarder were the same as in Example 2.

[0058] 3. Comparison of strength, permeability, and water resistance chemical properties (1) Compressive strength and water chemical resistance Grouting material specimens (50mm×50mm×50mm) were prepared and cured in water for 28 days. Then, they were eroded in simulated high-mineralization mine water for 28 days (Na+=370mg / L, K+=20mg / L, Ca2+=35mg / L, Mg2+=5mg / L, HCO3-=196mg / L, SO42-=528mg / L, Cl-=163mg / L, pH=8.5). The compressive strength before and after erosion was measured.

[0059] Table 5 Comparison of compressive strength before and after erosion by high-mineralization solution Example 2 further employs a mixed bacterial system based on Example 1, with the addition of a retarder. The aim is to make the material of this invention more adaptable to long-distance downhole grouting, complex surrounding rock temperature fields, and stress disturbances caused by repeated mining. On one hand, the mixed bacteria (e.g., Bacillus subtilis + Bacillus pasteurellus) can balance survival under different pH, salinity, and hydrochemical environments with CaCO3 deposition capacity, improving long-term self-healing stability. On the other hand, the addition of the retarder can prolong the grout setting time, improve pumpability and diffusivity during grouting, reduce the risk of early cracking, and provide more favorable construction conditions for the enrichment and deposition of microorganisms in fractures.

[0060] (2) Permeability and self-healing ability Perform three cycles of "load damage-permeability test-repair curing" on the slurry-aggregate body (refer to the current standards for permeability testing of rock or cement-based materials), and record the permeability coefficient after each cycle.

[0061] The comparative material maintained a permeability coefficient of 10 after multiple loading-repair cycles. -7 m·s -1The material exhibited no significant self-healing ability at the level of [magnitude missing]. In Example 2, after each loading damage, the material was repaired for 28 days with a high-mineralization solution containing nutrients, and its permeability coefficient increased from 10 [magnitude missing]. -7 m·s -1 The magnitude was reduced to 10 -8 m·s -1 The magnitude of the flow indicates a stable self-sealing ability of the seepage channels, proving that the composite microbial carrier of this invention can continue to work in complex hydrochemical environments.

[0062] Table 6. Evolution of permeability coefficient under multi-cycle loading-repair conditions Example 3 Under the same bacterial strain, bacterial suspension concentration, vacuum degree (-0.08 MPa), vacuum impregnation time (20 min), atmospheric pressure settling time (2 h), and drying conditions (30–40 °C) as in Example 2, only the solid-liquid ratio of porous diatomaceous earth to microbial suspension was changed, while all other conditions remained unchanged. This was to investigate the effect of the solid-liquid ratio on the bacterial carrying capacity of diatomaceous earth and its subsequent CaCO3 deposition ability. Specific groupings are as follows: Comparative Example 6: Solid-liquid ratio was 1g:1mL; Example 3-1: Solid-liquid ratio was 1g:3mL; Example 3-2: Solid-liquid ratio was 1g:6mL; Example 3-3: Solid-liquid ratio is 1g:10mL; Comparative Example 7: Solid-liquid ratio was 1g:15mL.

[0063] Porous diatomaceous earth (particle size 0.1–0.5 mm) from the same source and a mixed bacterial suspension (bacterial concentration approximately 1 × 10⁻⁶) were used. 8 (CFU / mL). After vacuum impregnation, standing, and low-temperature drying, the bacterial-loaded diatomaceous earth samples were subjected to the following tests: 1) Determination of initial loading (CFU / g) by plate count method; 2) Determination of bacterial survival rate after soaking in simulated cement pore liquid with pH≈12.5 prepared by Ca(OH)2–NaOH for 28 days. For each 1L of solution, add 2.0g of Ca(OH)2, 0.4-0.8g of NaOH, add about 900mL of deionized water, stir for 2h, and adjust the pH to 12.5±0.1 using 1mol / L NaOH solution and dilute hydrochloric acid. 3) The amount of CaCO3 deposited after 28 days of reaction in simulated mine water containing calcium ions and nutrients was determined.

[0064] Table 7 Comparison of the properties of diatomaceous earth under different solid-liquid ratios As shown in Table 7, when the solid-liquid ratio is 1g:1mL (Comparative Example 6), the viscosity of the mixed system is relatively high. Under vacuum impregnation conditions, the bacterial suspension cannot fully penetrate the internal pores of the diatomaceous earth, and the bacteria mainly adhere to the outer surface of the particles. The initial loading is only 3.0×10⁻⁶. 8 With a CFU / g concentration and a CaCO3 deposition rate of only 20 mg / g, the self-repair potential is limited. However, when the solid-liquid ratio is 1 g: 3–6 mL (Examples 3-1 and 3-2), the bacterial suspension exhibits good fluidity and a high bacterial concentration, enabling it to fully wet the pores under negative pressure, thus increasing the initial loading to 5.5–7.0 × 10⁻⁶. 8 The CFU / g, 28-day survival rate, and CaCO3 deposition all significantly increased, with the 1g:6mL group showing the best performance. When the solid-liquid ratio increased to 1g:10mL (Examples 3-3), although a high loading capacity and CaCO3 deposition were still achieved, the indicators were slightly lower than the 1g:6mL group due to further dilution of the bacterial suspension. When the solid-liquid ratio continued to increase to 1g:15mL (Comparative Example 7), the bacterial suspension became too dilute, reducing the number of bacteria in contact with the diatomaceous earth pore walls per unit time, and the initial loading capacity decreased to 4.0 × 10⁻⁶. 8 CFU / g, and the amount of CaCO3 deposition also decreased significantly.

[0065] Example 4 Under the same bacterial strain, bacterial suspension concentration, solid-liquid ratio, vacuum degree, standing and drying conditions as in Example 2, only the mass ratio of sodium alginate to bacterial-loaded diatomaceous earth and the mass ratio of polypropylene fiber to bacterial-loaded diatomaceous earth in step S3 were changed to examine the differences in the composite carrier shell structure and self-healing effect.

[0066] 1) Under the conditions of a fixed PP:carrier (porous diatomaceous earth) mass ratio of 1:3 and a CaCl2 soaking temperature of 20℃, the sodium alginate:carrier mass ratio was changed as follows: Comparative Example 8: Sodium alginate:carrier = 1:3; Example 4-1: Sodium alginate:carrier = 1:5; Example 4-2: Sodium alginate:carrier = 1:10; Example 4-3: Sodium alginate:carrier = 1:20; Comparative Example 9: Sodium alginate:carrier = 1:30.

[0067] 2) Under the conditions of a fixed sodium alginate:carrier mass ratio of 1:10 and CaCl2 soaking temperature of 20℃, the mass ratio of PP fiber:carrier (porous diatomaceous earth) was changed: Example 4-4: PP:carrier = 1:3; Comparative Example 10: PP:carrier = 1:0.5; Comparative Example 11: PP:Carrier = 1:15 PP fiber-diatomite composite microbial carriers under different conditions were prepared using the aforementioned method. The amount of CaCO3 deposited after 28 days of reaction in simulated mine water containing calcium ions and nutrients was measured, as well as the permeability coefficient k_r after 28 days of single damage-repair maintenance.

[0068] Table 8. Effect of mass ratio on composite carrier and self-healing effect in step S3. When the sodium alginate:carrier mass ratio is between 1:5 and 1:20, the CaCO3 deposition is high, and the permeability coefficient k_r after repair is stable at the order of 10⁻⁸ m·s⁻¹. When the mass ratio is less than 1:5 (1:3), the CaCO3 deposition and k_r improvement are limited due to the excessively thick shell and limited mass transfer. When the mass ratio is greater than 1:20 (1:30), the bacteria are easily lost due to the discontinuous shell, and the self-repair effect is significantly reduced. When the PP:carrier mass ratio is between 1:1 and 1:10 (represented by 1:3 in the table), the composite carrier is evenly distributed along the fiber, and each fiber has a sufficient number of carriers. After self-repair, k_r can be maintained at the order of 10⁻⁸ m·s⁻¹. When the carrier is too small (1:0.5), there are insufficient effective bacterial spots on each fiber, and the permeability coefficient is reduced only slightly. When the carrier is too large (1:15), agglomeration is easy to form, the fluidity of the slurry becomes poor, and k_r is not further significantly reduced.

[0069] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A grouting material with self-healing function, characterized in that, By weight, the raw materials include the following components: 100 parts of cementitious material; 40-80 parts of water; 5-40 parts of polypropylene fiber-diatomite composite microbial carrier; 0-40 parts of mineral admixture; and 0-5 parts of chemical additives. The polypropylene fiber-diatomite composite microbial carrier comprises a polypropylene fiber core layer and a diatomite gel shell layer, wherein the diatomite gel shell layer is a gel network structure with embedded porous diatomite particles loaded with microorganisms.

2. The grouting material with self-healing function according to claim 1, characterized in that, The diatomaceous earth gel shell is a gel network structure formed by cross-linking sodium alginate.

3. The grouting material with self-healing function according to claim 1, characterized in that, The porous diatomaceous earth particles have a particle size of 0.1–0.5 mm.

4. The grouting material with self-healing function according to claim 1, characterized in that, In the polypropylene fiber-diatomite composite microbial carrier, the mass ratio of polypropylene fiber to porous diatomite is 1:1 to 1:10, and the length of the polypropylene fiber is 6 to 12 mm and the diameter is 10 to 40 μm.

5. The grouting material with self-healing function according to claim 2, characterized in that, In the polypropylene fiber-diatomite composite microbial carrier, the mass ratio of sodium alginate to porous diatomite is 1:5 to 1:

20.

6. The grouting material with self-healing function according to claim 1, characterized in that, The microorganisms include at least one of Bacillus subtilis, Bacillus pasteurellii, Bacillus spheroides, alkali-resistant mutants of Bacillus subtilis, Bacillus pasteurellii, and Bacillus spheroides, and the bacterial count loaded in the porous diatomaceous earth particles is 10 based on the dry weight of the bacteria. 7 ~10 10 CFU / g.

7. The grouting material with self-healing function according to claim 1, characterized in that, The cementitious material includes ordinary silicate cement and ultrafine cement, wherein the ordinary silicate cement accounts for 30-80% of the mass percentage of the cementitious material, and the ultrafine cement accounts for 20-70% of the mass percentage of the cementitious material.

8. The grouting material with self-healing function according to claim 1, characterized in that, The preparation process of the polypropylene fiber-diatomite composite microbial carrier includes: S1, After pretreatment of polypropylene fibers, they are dried for later use; S2, after pretreatment of porous diatomaceous earth, it is mixed with microbial suspension, and then the mixture is impregnated, allowed to stand, separated and dried under vacuum to obtain bacteria-carrying diatomaceous earth, wherein the solid-liquid ratio of the porous diatomaceous earth to the microbial suspension is 1g:3~10mL. S3, the bacterial-carrying diatomaceous earth is added to a sodium alginate solution with a mass fraction of 0.5-1% to obtain a gel precursor solution; dried and prepared polypropylene fibers are added to the gel precursor solution and mixed, then transferred to a crosslinking agent solution for soaking, and then washed and dried to obtain a polypropylene fiber-diatomaceous earth composite microbial carrier.

9. A method for preparing a grouting material with self-healing function as described in any one of claims 1 to 8, characterized in that, Includes the following steps: The cementitious material, water, polypropylene fiber-diatomite composite microbial carrier, mineral admixtures and chemical additives are mixed and stirred in a preset ratio to obtain a grouting material with self-healing function.

10. The application of the self-healing grouting material as described in any one of claims 1 to 8 in rock grouting modification.

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