Rock stratum early-strength low-temperature grouting material based on coal gangue activation and preparation method thereof

Abstract

The application belongs to the technical field of low-temperature grouting materials, and discloses a rock stratum early-strength type low-temperature grouting material based on coal gangue activation and a preparation method thereof. The grouting material comprises an activated coal gangue precursor, a calcium source cementing component, an auxiliary cementing component, an excitation component and a rheological control component, wherein the excitation component at least comprises a silicate excitation component prepared from coal gangue, a coal gangue-based superfine excitation powder and a low-temperature early-strength component, and the rheological control component at least comprises a dispersion plasticizing component and a structure establishing component. The activated coal gangue precursor is prepared by grading pretreatment of the coal gangue and matching mechanical activation, thermal activation or mechanical-thermal composite activation, mixed with the remaining components to form a dry grouting mixture, and the grouting material is prepared by adding water during use. The application can improve the resource utilization degree of the coal gangue, improve the early strength and setting and hardening performance under low-temperature conditions, and take into account the liquidity and fissure plugging performance of the grouting material.

Description

Technical Field

[0001] This invention belongs to the field of low-temperature grouting materials technology, specifically the preparation method of rock strata early-strength low-temperature grouting materials based on coal gangue activation. Background Technology

[0002] Coal gangue is a large amount of solid waste generated during coal mining and washing. It typically contains a certain amount of silicon and aluminum components, making it a potential source of silicon and aluminum in cementitious or grouting materials. Rock fissure grouting materials are widely used in mines, tunnels, slopes, and underground engineering for fissure sealing, surrounding rock reinforcement, and seepage prevention. Especially in low-temperature environments, grouting materials not only need good fluidity and injectability but also need to set and harden quickly after injection into fissures to achieve early strength, meeting the requirements of engineering construction and reinforcement sealing.

[0003] In the prior art, there are already solutions to address the above-mentioned problems. For example, Chinese patent application CN112250366A discloses a coal gangue-based polymer grouting material and its preparation method, which improves the utilization effect of coal gangue in the grouting system by compounding coal gangue powder, slag powder, fly ash, alkaline activator, surfactant, retarder, and water-retaining agent; Chinese patent application CN114262198A discloses a rapid curing, compounded grouting material for subway engineering and its preparation method, which uses a composite cement system of ordinary silicate cement and sulfoaluminate cement, combined with modified coal gangue and early strength agent, so that the grouting material can cure quickly at low temperature conditions while taking into account certain early strength and fluidity.

[0004] However, the existing technologies still have at least the following shortcomings: Existing coal gangue grouting material solutions usually use coal gangue as a uniformly treated admixture or precursor. However, the effective components in coal gangue vary. Directly adding it to the grouting system after uniform treatment results in insufficient activity of the coal gangue and insufficient stability of material performance. At the same time, existing technologies are still prone to problems such as insufficient dissolution of active components, slow setting, and low early strength under low temperature conditions. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies, this invention provides a method for preparing an early-strength low-temperature grouting material for rock formations based on activated coal gangue. This invention primarily addresses the problems of unstable material properties and insufficient early strength caused by the direct addition of coal gangue after uniform pretreatment in existing coal gangue grouting materials.

[0006] According to one aspect of the present invention, a rock stratum early-strength low-temperature grouting material based on coal gangue activation is provided, comprising dry-based solids and water; the mass ratio of water to the total dry-based solids is 0.6 to 1.3; preferably 0.7 to 0.95; the total dry-based solids, based on 100 parts by mass, comprise the following components: 35-70 parts of activated coal gangue precursor were obtained by mechanical activation, thermal activation, or mechanical-thermal composite activation respectively, after the coal gangue raw material underwent graded pretreatment and was classified according to the graded results. 5-35 parts of calcium-based gelling component; 10-25 parts of auxiliary gelling component; The activating component is 10-20 parts; it includes at least a silicate activating component obtained from coal gangue, coal gangue-based ultrafine activating powder and a low-temperature early strength component, which are used to promote the dissolution of active silica and aluminum in activated coal gangue precursors under low-temperature conditions and improve the reactivity of activated coal gangue precursors under low-temperature conditions. Five to eight parts of rheology modifiers; including at least dispersing and plasticizing components and structure-building components, used to keep the grouting material in a fluid state during the delivery stage and to reduce fluidity after injection into rock fissures.

[0007] Preferably, the silicate activating component is a homologous activating micro powder prepared by spray drying of a liquid soluble silicate activating liquid; The liquid soluble silicate activating solution is selected from one or more of the following: sodium silicate solution, potassium silicate solution, or composite alkali metal silicate solution prepared from coal gangue.

[0008] Preferably, the silicate activating component is directly prepared into solid powder by co-milling coal gangue ore and solid alkaline activator in a high-energy ball mill; The solid alkaline activator is selected from one or more of sodium hydroxide, potassium hydroxide, and sodium carbonate.

[0009] Preferably, the coal gangue-based ultrafine activated powder is coal gangue powder obtained by further grinding after activation, with a specific surface area of ​​400–1400 m². 2 / kg; The low-temperature early strength component is selected from one or more of calcium formate, lithium carbonate, sodium aluminate, or triethanolamine.

[0010] Preferably, the structure-building component and the low-temperature early strength component are encapsulated within polymer microcapsules; during the fissure filling process, the capsule wall material of the polymer microcapsules is subjected to shear force to break the wall and release the structure-building component and the low-temperature early strength component.

[0011] In another aspect, the present invention proposes a method for preparing an early-strength low-temperature grouting material for rock formations based on coal gangue activation, which includes the following steps: Step S1: Sample and test the coal gangue raw material to obtain its strength activity index, carbon content, and 80μm sieve residue, and classify the coal gangue raw material according to the test results; The method for determining the strength activity index is as follows: after drying the coal gangue sample, grind it to an 80μm sieve with a residue of no more than 10%, and prepare the sample by replacing the reference cementitious material according to a predetermined ratio. After curing under specified curing conditions to a specified age, test the compressive strength. The percentage of the compressive strength of the coal gangue sample to the compressive strength of the reference sample is used as the strength activity index.

[0012] Carbon content was characterized by the ignition method: after drying the coal gangue sample to constant weight at 105±5℃, a sample with a mass of m1 was weighed, ignited at 815±10℃ for 1h, cooled to room temperature and weighed as m2, and the carbon content was calculated as (m1-m2) / m1×100%.

[0013] The method for determining the 80μm sieve residue is as follows: Take a sample of coal gangue raw material, dry and crush the sample to the standard test particle size (e.g., below 5mm), and then grind it in a standard test mill for a specified time (e.g., 30min). After drying the coal gangue sample, sieve it using an 80μm standard sieve, weigh the sieve residue mass m3, and calculate the 80μm sieve residue according to m3 / m0×100%, where m0 is the total mass of the sample before sieving.

[0014] Step S2: The graded coal gangue raw materials are crushed into particles with a particle size of no more than 10 mm, and the crushed particles are subjected to air separation, decarbonization and impurity removal pretreatment in sequence. Step S3: Based on the grading grade of the coal gangue raw material, mechanical activation, thermal activation, or mechanical-thermal composite activation treatment are respectively adopted to obtain activated coal gangue precursor; Step S4: Take a portion of the pretreated coal gangue raw material and prepare homologous activated micro powder or solid powder as silicate activating component; further grind the activated portion of coal gangue to obtain coal gangue-based ultrafine activating powder; encapsulate the structure-building component and low-temperature early strength component in the capsule wall material to obtain polymer microcapsules. Step S5: The activated coal gangue precursor, calcium source gelling component, auxiliary gelling component, and dispersing and plasticizing component are uniformly mixed with the silicate activating component, coal gangue-based ultrafine activating powder, and polymer microcapsules prepared in step S4 to obtain the grouting dry mix. Step S6: During the grouting operation, water is added to the dry grout mix to obtain the grouting material, and the final mass ratio of water to dry base solids in the grouting material is adjusted to 0.6 to 1.3.

[0015] Preferably, in step S1, the grading criteria for coal gangue raw materials are as follows: Grade I coal gangue: meets the following requirements: strength activity index ≥70%, carbon content ≤6%, and 80μm sieve residue ≤3%; Grade III coal gangue: meets the following requirements: strength activity index <60%, or carbon content >20%; Grade II coal gangue: Coal gangue raw materials that do not fall into the Grade I coal gangue grading standard and do not fall into the Grade III coal gangue grading standard.

[0016] Preferably, the processing methods for coal gangue raw materials of different grading standards in step S3 are as follows: For Grade I coal gangue, mechanical activation is employed in step S3; For Class II coal gangue, thermal activation is performed in step S3; For Grade III coal gangue, mechanical-thermal composite activation is further performed in step S3.

[0017] Preferably, in step S3, mechanical activation is performed by grinding using one or more of ball milling, vertical milling, and ultrafine milling, so that the residue on the 80μm sieve of the activated coal gangue is no more than 10%. The calcination temperature for thermal activation is 650–1000℃, and the holding time is 0.5–6 hours. Mechanical-thermal combined activation includes either mechanical activation followed by thermal activation, or thermal activation followed by a second mechanical activation.

[0018] Preferably, in step S4, the polymer microcapsules are prepared by solvent evaporation method, with the structure-building component and the low-temperature early strength component as the core and ethyl cellulose or polymethyl methacrylate as the capsule wall; the average particle size of the polymer microcapsules is 50-100 μm. Preferably, the polymer microcapsules exhibit a core (structure-building component and low-temperature early strength component) release rate ≥60% under shear conditions of passing through a 1.0 mm nozzle and a pressure of 0.60 MPa in a single pass.

[0019] The beneficial effects of this invention are as follows: 1. Existing coal gangue grouting materials typically employ a uniform treatment method for coal gangue from different sources and of different qualities. However, different coal gangues vary in terms of active silica-alumina content, carbon content, and impurity levels. Directly using these uniformly treated materials in the grouting system can easily lead to insufficient activation of the coal gangue and significant fluctuations in material performance. This invention first tests and grades the coal gangue raw materials, and then treats them using mechanical activation, thermal activation, or a mechanical-thermal composite activation method based on the grading results. This allows for more targeted release of active components in different types of coal gangue, improving raw material compatibility and thus enhancing the utilization efficiency of coal gangue in grouting materials, as well as improving the performance stability of the grouting materials.

[0020] 2. The activating components in this invention include at least silicate activating components derived from coal gangue and coal gangue-based ultrafine activating powder. These components can form a good synergistic effect with the activated coal gangue precursor, promoting the dissolution of active silica-alumina components in the coal gangue under low-temperature conditions and improving the reaction interface and nucleation efficiency. This is beneficial for improving the low-temperature setting and hardening properties and early strength development of the system. Simultaneously, this homologous activation method also helps improve the compatibility between coal gangue components and reduces dependence on externally applied general-purpose high-alkali activating systems.

[0021] 3. By setting rheology control components, which include at least dispersing and plasticizing components and structure-building components, the present invention enables the grouting material to maintain good dispersibility and fluidity during the mixing and transportation stages, and gradually reduce fluidity and promote structure formation after entering rock fissures. This is beneficial to balance pumpability, diffusion and subsequent sealing during the grouting process.

[0022] 4. The grouting material of the present invention is provided in the form of an all-solid powder, which only needs to be mixed with water to form the grouting material. Compared with systems containing liquid activators or requiring on-site preparation of alkaline solutions, the all-solid powder system is easier to package, store, and transport, and on-site construction measurement is more convenient. Moreover, it is less prone to problems such as increased viscosity of liquid components, crystallization, freezing, or instability in on-site preparation under low-temperature environments, thereby improving the material's adaptability to construction under low-temperature conditions and the convenience of engineering applications.

[0023] 5. This invention focuses on the low-temperature rock fissure grouting condition, and synergistically optimizes the activation and utilization of coal gangue, system activation, rheological regulation, and composite design of cementitious materials. This enables the grouting material to not only improve the resource utilization level of coal gangue, but also to take into account the fluidity, fissure diffusion capacity, setting and hardening speed, and early strength development of the grouting material under low-temperature conditions. This is beneficial to improving the comprehensive engineering applicability of the material in application scenarios such as rock fissure sealing, surrounding rock reinforcement, and seepage prevention and water stopping. Detailed Implementation

[0024] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.

[0025] The following examples are used to illustrate the present invention, but are not intended to limit the scope of protection of the present invention. Unless otherwise stated, all examples are based on a dry basis of 1000g of total solids.

[0026] In the following embodiments: The calcium source cementitious component is one or both of ordinary silicate cement and sulfoaluminate cement; The auxiliary cementitious component is one or both of S95 slag powder and anhydrous gypsum. The dispersing and plasticizing components are one or both of polycarboxylate superplasticizer and hydroxypropyl methylcellulose; Sodium alginate was used as the structural component. The capsule wall material of the polymer microcapsules is ethyl cellulose or polymethyl methacrylate; The polymer capsule wall material, as a component of the microcapsule, is included in the dry solids total of the grouting material.

[0027] I. Raw material testing, grading, and common preparation methods: 1. Testing and grading of coal gangue raw materials; The coal gangue raw materials were classified by activity index determination, carbon content determination by ignition method and residue determination on 80μm sieve.

[0028] The raw coal gangue sample G1 has a strength activity index of 74%, a carbon content of 4.8%, and an 80μm sieve residue of 2.6%, and is classified as Grade I coal gangue.

[0029] The strength activity index of raw coal gangue sample G2 was 66%, the carbon content was 12.7%, and the residue on the 80μm sieve was 5.9%, which was determined to be Class II coal gangue.

[0030] The strength activity index of raw coal gangue sample G3 is 55%, the carbon content is 23.4%, and the residue on an 80μm sieve is 10.8%, which is classified as Grade III coal gangue.

[0031] 2. Pretreatment: The graded coal gangue was crushed to a particle size of no more than 10 mm. Then, it underwent air separation, decarbonization, and impurity removal pretreatment in sequence.

[0032] Among them, the air separation velocity is controlled at 4.5 to 5.5 m / s; the decarbonization temperature is controlled at 450 to 550℃; and the impurity removal adopts a combination of magnetic separation and manual sorting.

[0033] 3. Preparation of activated coal gangue precursor: 3.1 Mechanical activation: Pretreated Grade I coal gangue was ball-milled for 45 minutes and then finely ground in a vertical mill for 20 minutes to obtain a powder with an 80μm sieve residue of 2.4%, thus obtaining mechanically activated coal gangue precursor P1.

[0034] 3.2 Thermal activation: Pretreated Grade II coal gangue was calcined in a muffle furnace at 800℃ for 2 hours, cooled, and then ground until the residue on an 80μm sieve was 5.9%, thus obtaining thermally activated coal gangue precursor P2.

[0035] 3.3 Mechanical-thermal composite activation: Pretreated Grade III coal gangue was ball-milled for 30 min, then calcined at 850℃ for 1.5 h, cooled, and then ultra-fine-milled for 20 min to obtain a 7.9% residue on an 80 μm sieve, thus obtaining mechanically-thermally activated coal gangue precursor P3.

[0036] 4. Preparation of silicate activation components: 4.1 Homogeneous Excitation Micropowder A1 (Sodium Silicate Micropowder Obtained from Coal Gangue): 120g of pretreated coal gangue was mixed with 90g of NaOH and kept at 650℃ for 1h. After cooling and crushing, 500g of deionized water was added and the mixture was stirred and leached at 95℃ for 2h. The filtrate was filtered and spray-dried to obtain homologous activated micro powder A1.

[0037] 4.2 Homogeneous Excitation Micropowder A2 (Potassium Silicate Micropowder Obtained from Coal Gangue): Take 120g of pretreated coal gangue and mix it with 100g of KOH. Keep it at 650℃ for 1h, cool and crush it, add 500g of deionized water, stir and leach at 95℃ for 2h, filter and take the filtrate, and spray dry to obtain homologous activated micro powder A2.

[0038] 4.3 Homogeneous Excitation Micropowder A3 (Composite Alkali Metal Silicate Micropowder Prepared from Coal Gangue): Take 120g of pretreated coal gangue, mix it with 45g of NaOH and 50g of KOH, keep it at 650℃ for 1h, cool and crush it, add 500g of deionized water, stir and leach at 95℃ for 2h, filter and take the filtrate, and spray dry to obtain homologous activated micro powder A3.

[0039] 4.4 Solid Powder Activator B1: 100g of raw coal gangue ore and 8g of NaOH were co-milled in a high-energy ball mill for 45 minutes to obtain solid powder activator B1.

[0040] 4.5 Solid Powder Activator B2: 100g of raw coal gangue ore and 10g of KOH were co-milled in a high-energy ball mill for 45 minutes to obtain solid powder activator B2.

[0041] 4.6 Solid Powder Activator B3: 100g of raw coal gangue ore and 12g of Na2CO3 were co-milled in a high-energy ball mill for 45 minutes to obtain solid powder activator B3.

[0042] 5. Preparation of coal gangue-based ultrafine activated powder: Activated coal gangue precursors P1, P2, or P3 are further subjected to ultrafine grinding to achieve a specific surface area of ​​650–980 m². 2 / kg, yielding coal gangue-based ultrafine activated powder C.

[0043] 6. Preparation of polymer microcapsules: 6.1 Ethyl cellulose microcapsules M1: 18g of ethyl cellulose was dissolved in 180g of a mixed solvent of dichloromethane and ethyl acetate to form a wall material solution. 12g of sodium alginate and 20g of calcium formate were then added and dispersed at high speed for 10min at room temperature to obtain an oil phase dispersion. This dispersion was then added dropwise to 800g of a 1.0% (w / w) polyvinyl alcohol aqueous solution and emulsified by stirring at 1000rpm for 20min. Subsequently, stirring was continued at 30℃ for 2.5h to evaporate and remove the organic solvent. The solution was then filtered, washed, and vacuum dried to obtain ethyl cellulose microcapsules M1 with an average particle size of 68μm.

[0044] 6.2 Polymethyl methacrylate microcapsules M2: 23g of polymethyl methacrylate was dissolved in 180g of a mixed solvent of dichloromethane and ethyl acetate. 12g of sodium alginate and 20g of lithium carbonate were added. The mixture was emulsified, volatilized, filtered and dried in the same manner as M1 to obtain polymethyl methacrylate microcapsules M2 with an average particle size of 72μm.

[0045] 6,3-Ethylcellulose microcapsules M3: 23g of ethyl cellulose was dissolved in 180g of a mixed solvent of dichloromethane and ethyl acetate. 12g of sodium alginate and 20g of sodium aluminate were added. The mixture was prepared in the same way as M1 to obtain ethyl cellulose microcapsules M3 with an average particle size of 76μm.

[0046] 6.4 Polymethyl methacrylate microcapsules M4: 17g of polymethyl methacrylate was dissolved in 160g of a mixed solvent of dichloromethane and ethyl acetate. 10g of sodium alginate and 20g of triethanolamine were added. The mixture was prepared in the same way as M1 to obtain polymethyl methacrylate microcapsules M4 with an average particle size of 60μm.

[0047] 6,5-Ethylcellulose Microcapsules M5: 17g of ethyl cellulose was dissolved in 160g of a mixed solvent of dichloromethane and ethyl acetate. 12g of sodium alginate and 20g of calcium formate were added. The mixture was prepared in the same way as M1 to obtain ethyl cellulose microcapsules M5 with an average particle size of 65μm.

[0048] 6.6 Polymethyl methacrylate microcapsules M6: 20g of polymethyl methacrylate was dissolved in 180g of a mixed solvent of dichloromethane and ethyl acetate. 10g of sodium alginate and 40g of sodium aluminate were added. The mixture was prepared in the same way as M1 to obtain polymethyl methacrylate microcapsules M6 with an average particle size of 92μm.

[0049] 6,7-Ethylcellulose Microcapsules M7: 26g of ethyl cellulose was dissolved in 200g of a mixed solvent of dichloromethane and ethyl acetate. 18g of sodium alginate and 40g of lithium carbonate were added. The mixture was prepared using the same method as M1 to obtain ethyl cellulose microcapsules M7 with an average particle size of 96μm.

[0050] 6,8-Ethylcellulose Microcapsules M8: 18g of ethyl cellulose was dissolved in 180g of a mixed solvent of dichloromethane and ethyl acetate. 12g of sodium alginate and 20g of calcium formate were added. The mixture was prepared in the same way as M1 to obtain ethyl cellulose microcapsules M8 with an average particle size of 58μm. Example 1:

[0051] Weigh out 30g of mechanically activated coal gangue precursor P15, 120g of ordinary silicate cement, 60g of sulfoaluminate cement, 100g of S95 slag powder, 40g of anhydrous gypsum, 40g of homologous activated micropowder A1, 40g of coal gangue-based ultrafine activated powder C, 150g of ethyl cellulose microcapsules M, 8g of polycarboxylate superplasticizer, 7g of hydroxypropyl methylcellulose, and 5g of attapulgite. Mix for 10 minutes to obtain a dry grouting mix. Add 800g of water during grouting and stir for 3 minutes to obtain the grouting material.

[0052] Among them, according to functional affiliation: The activated coal gangue precursor was 530g; The calcium source gelling component is 180g; The auxiliary gelling component is 140g; The activating component is 100g, including 40g of homologous activating micro powder, 40g of coal gangue-based ultrafine activating powder, and 20g of calcium formate; The rheology modulator component is 50g, including 8g of polycarboxylate superplasticizer, 7g of hydroxypropyl methylcellulose, 5g of attapulgite, 12g of sodium alginate, and 18g of ethyl cellulose capsule wall. Example 2:

[0053] Weigh out 2500g of thermally activated coal gangue precursor P, 90g of ordinary silicate cement, 90g of sulfoaluminate cement, 110g of S95 slag powder, 40g of anhydrous gypsum, 245g of homologous activated micropowder A, 45g of coal gangue-based ultrafine activated powder C, 255g of polymethyl methacrylate microcapsules M, 10g of polycarboxylate superplasticizer, 8g of hydroxypropyl methylcellulose, and 7g of bentonite. Mix for 10 minutes to obtain the dry grouting mix. Add 850g of water during grouting and stir for 3 minutes to obtain the grouting material.

[0054] Among them, according to functional affiliation: The activated coal gangue precursor is 500g; the calcium source cementing component is 180g; and the auxiliary cementing component is 150g. The activating component is 110g, including 45g of homologous activating micro powder, 45g of coal gangue-based ultrafine activating powder, and 20g of lithium carbonate; The rheology modulator component is 60g, including 10g of polycarboxylate superplasticizer, 8g of hydroxypropyl methylcellulose, 7g of bentonite, 12g of sodium alginate, and 23g of polymethyl methacrylate capsule wall. Example 3:

[0055] Weigh out 80g of mechanically-thermally activated coal gangue precursor P34, 140g of ordinary silicate cement, 80g of sulfoaluminate cement, 100g of S95 slag powder, 40g of anhydrous gypsum, 340g of homologous activated micropowder A3, 40g of coal gangue-based ultrafine activated powder C4, 55g of ethyl cellulose microcapsules M3, 8g of polycarboxylate superplasticizer, 7g of hydroxypropyl methylcellulose, and 10g of bentonite, and mix for 10 minutes to obtain a dry grouting mix. Add 780g of water during grouting and stir for 3 minutes to obtain the grouting material.

[0056] Among them, according to functional affiliation: The activated coal gangue precursor was 480g; the calcium source cementing component was 220g; and the auxiliary cementing component was 140g. The activating component is 100g, including 40g of homologous activating micro powder, 40g of coal gangue-based ultrafine activating powder, and 20g of sodium aluminate; The rheology modulator component is 60g, including 8g of polycarboxylate superplasticizer, 7g of hydroxypropyl methylcellulose, 10g of bentonite, 12g of sodium alginate, and 23g of ethyl cellulose capsule wall. Example 4:

[0057] Weigh out 350g of mechanically activated coal gangue precursor P1, 220g of ordinary silicate cement, 80g of sulfoaluminate cement, 160g of S95 slag powder, 40g of anhydrous gypsum, 40g of solid powder activator B1, 40g of coal gangue-based ultrafine activating powder C, 447g of polymethyl methacrylate microcapsules M4, 10g of polycarboxylate superplasticizer, 5g of hydroxypropyl methylcellulose, and 8g of attapulgite. Mix for 10 minutes to obtain a dry grouting mix. Add 600g of water during grouting and stir for 4 minutes to obtain the grouting material.

[0058] Among them, according to functional affiliation: The activated coal gangue precursor is 350g, the calcium source cementing component is 300g, and the auxiliary cementing component is 200g. The activating component is 100g, including 40g of solid powder activator, 40g of coal gangue-based ultrafine activating powder, and 20g of triethanolamine; The rheology modulator component is 50g, including 10g of polycarboxylate superplasticizer, 5g of hydroxypropyl methylcellulose, 8g of attapulgite, 10g of sodium alginate, and 17g of polymethyl methacrylate capsule wall; the amount of water used is 600g. Example 5:

[0059] Weigh out 350g of thermally activated coal gangue precursor P2, 250g of ordinary silicate cement, 100g of sulfoaluminate cement, 120g of S95 slag powder, 30g of anhydrous gypsum, 45g of solid powder activator B2, 35g of coal gangue-based ultrafine activating powder C3, 49g of ethyl cellulose microcapsules M5, 8g of polycarboxylate superplasticizer, 7g of hydroxypropyl methylcellulose, and 6g of bentonite. Mix for 10 minutes to obtain the dry grouting mix. Add 750g of water during grouting and stir for 3 minutes to obtain the grouting material.

[0060] Among them, according to functional affiliation: The activated coal gangue precursor is 350g; the calcium source cementing component is 350g; and the auxiliary cementing component is 150g. The activating component is 100g, including 45g of solid powder activator, 35g of coal gangue-based ultrafine activating powder, and 20g of calcium formate; The rheology modulator component is 50g, including 8g of polycarboxylate superplasticizer, 7g of hydroxypropyl methylcellulose, 6g of bentonite, 12g of sodium alginate, and 17g of ethyl cellulose capsule wall. Example 6:

[0061] Weigh out 3350g of mechanically-thermally activated coal gangue precursor P3, 110g of ordinary silicate cement, 40g of sulfoaluminate cement, 180g of S95 slag powder, 70g of anhydrous gypsum, 380g of solid powder activator B3, 80g of coal gangue-based ultrafine activating powder C, 670g of polymethyl methacrylate microcapsules M6, 8g of polycarboxylate superplasticizer, 6g of hydroxypropyl methylcellulose, and 6g of attapulgite. Mix for 10 minutes to obtain the dry grouting mix. Add 1300g of water during grouting and stir for 3 minutes to obtain the grouting material.

[0062] Among them, according to functional affiliation: The activated coal gangue precursor is 350g; the calcium source cementing component is 150g; and the auxiliary cementing component is 250g. The activating component is 200g, including 80g of solid powder activator, 80g of coal gangue-based ultrafine activating powder, and 40g of sodium aluminate; The rheology modulator component is 50g; the water dosage is 1300g. Example 7:

[0063] Weigh out 70g of thermally activated coal gangue precursor P23, 130g of ordinary silicate cement, 70g of sulfoaluminate cement, 100g of S95 slag powder, 50g of anhydrous gypsum, 380g of homologous activated micropowder A, 80g of coal gangue-based ultrafine activated powder C, 84g of ethyl cellulose microcapsules M7, 12g of polycarboxylate superplasticizer, 10g of hydroxypropyl methylcellulose, and 14g of bentonite. Mix for 10 minutes to obtain a dry grouting mix. Add 900g of water during grouting and stir for 3 minutes to obtain the grouting material.

[0064] Among them, according to functional affiliation: The activated coal gangue precursor is 370g; the calcium source cementing component is 200g; the auxiliary cementing component is 150g; and the activating component is 200g. The rheology modulator component is 80g, including 12g of polycarboxylate superplasticizer, 10g of hydroxypropyl methylcellulose, 14g of bentonite, 18g of sodium alginate, and 26g of ethyl cellulose capsule wall. Example 8:

[0065] Weigh out 700g of mechanically activated coal gangue precursor P1, 30g of ordinary silicate cement, 20g of sulfoaluminate cement, 70g of S95 slag powder, 30g of anhydrous gypsum, 140g of homologous activated micropowder A1, 40g of coal gangue-based ultrafine activated powder C4, 850g of ethyl cellulose microcapsules M8, 8g of polycarboxylate superplasticizer, 6g of hydroxypropyl methylcellulose, and 6g of attapulgite. Mix for 10 minutes to obtain a dry grouting mix. Add 700g of water during grouting and stir for 3 minutes to obtain the grouting material.

[0066] Among them, according to functional affiliation: The activated coal gangue precursor is 700g; the calcium source cementing component is 50g; the auxiliary cementing component is 100g; the activating component is 100g; and the rheology regulating component is 50g.

[0067] Comparative Example 1: The difference from Example 1 is that the coal gangue is not graded; all raw coal gangue is only crushed and then ball-milled for 45 minutes as a precursor for activated coal gangue.

[0068] Comparative Example 2: The difference from Example 1 is that 40g of homologous activated micro powder A1 and 40g of coal gangue-based ultrafine activated powder C40g are replaced with 40g of industrial sodium metasilicate and 40g of quartz powder, respectively.

[0069] Comparative Example 3: The difference from Example 1 is that microcapsule M1 is omitted, and instead 12g of sodium alginate and 20g of calcium formate are directly dry-mixed and added.

[0070] Comparative Example 4: The difference from Example 1 is that 20g of calcium formate is removed, and the amount of homologous activating powder A1 and coal gangue-based ultrafine activating powder C is increased to 50g, so as to keep the total amount of activating components unchanged.

[0071] Test Example 1: Low-temperature fluidity and condensation performance test; The dry mix and mixing water of each embodiment and comparative example were pre-equilibrated in an environment of 5±1℃ for 12 hours. 1000g of dry mix and the corresponding mass of water were weighed according to the water-to-solid ratio of the corresponding embodiment, and the mixture was stirred at low speed for 30s, stopped and scraped for 30s, and then stirred at high speed for 90s to obtain the grouting material.

[0072] The flowability was tested using the flow table method according to GB / T2419-2005, but without adding standard sand to the sample; the expanded diameter of the grouting material was tested directly. A truncated conical mold was placed in the center of the flow table, filled with grouting material, and leveled. After removing the mold, it was moved according to GB / T2419-2005, and the two mutually perpendicular diameters of the expanded grouting material were measured. The average value was taken as the initial flowability. Three parallel tests were performed for each group, and the average value was taken. The 30-minute flowability test method was the same, except that after mixing, the grouting material was placed in a sealed container at 5±1℃ and allowed to stand for 30 minutes, then gently stirred for 10 seconds before testing.

[0073] The bleeding rate was determined using a custom settling method. 200 mL of the mixed grouting material was placed into a 250 mL stoppered graduated cylinder and allowed to stand at 5±1℃ for 2 hours. The volume of the supernatant was recorded as Vw, and the bleeding rate was calculated using the following formula: Exudation rate (%) = Vw / 200 × 100%; 3 parallel samples were made for each group, and the average value was taken.

[0074] Meanwhile, the setting time was determined using the Vicat apparatus method according to GB / T1346-2024. The freshly mixed grouting material was placed into the Vicat apparatus mold, gently vibrated several times to remove large air bubbles, and the sample surface was smoothed. It was then immediately placed in a curing chamber at 5±1℃ and a relative humidity of not less than 90%. Tests were conducted at the intervals specified in GB / T1346-2024. The initial setting time was defined as when the needle sank to 4±1 mm from the bottom plate; the final setting time was defined as when the needle left only a mark on the specimen surface and the annular attachment no longer left a significant indentation. Two parallel tests were performed for each group, and the average value was taken.

[0075] Test Example 2: Low-Temperature Compressive Strength Test; The compressive strength was tested using the cubic compressive strength method as specified in JGJ / T70-2009. The mixed grouting material was placed into a 70.7mm × 70.7mm × 70.7mm detachable cubic mold, in two layers. Each layer was lightly vibrated for 15 seconds, smoothed, and covered with plastic film. Curing was carried out at 5±1℃ and a relative humidity of not less than 95%. For specimens aged 6 hours, testing was conducted immediately after demolding using the detachable mold. For specimens aged 1 day or older, demolding was performed 24 hours after molding, followed by continued curing until the specified age before testing. At least three parallel specimens were tested at each age, and the average compressive strength was taken. The loading equipment and test nozzle diameter were in accordance with JGJ / T70-2009; if the laboratory used an ISO method strength tester, the loading equipment and result processing methods in GB / T17671-2021 could also be followed.

[0076] Table 1. Test results of low-temperature fluidity, setting time, and compressive strength of the grouting materials in the examples and comparative examples: As shown in Table 1, Examples 1 to 8 can all form grouting materials with a certain degree of fluidity at 5°C and can achieve early strength in a relatively short time.

[0077] Compared with Comparative Example 1, the 1-day compressive strength of Example 1 increased from 5.1 MPa to 8.6 MPa, indicating that graded pretreatment of coal gangue and the use of a matching activation method can improve the reactivity of coal gangue under low-temperature conditions.

[0078] Compared with Comparative Example 2, the 1-day compressive strength of Example 1 increased from 6.2 MPa to 8.6 MPa, indicating that there is a synergistic activation effect between the silicate activating component obtained from coal gangue and the coal gangue-based ultrafine activating powder.

[0079] Compared with Comparative Example 3, Example 1 showed that the initial flowability increased from 124 mm to 169 mm, and the 30-minute flowability increased from 106 mm to 157 mm. This indicates that encapsulating the structure-building components and low-temperature early strength components in polymer microcapsules can significantly improve the flowability and plasticity retention of the grouting material during the delivery stage.

[0080] Compared with Comparative Example 4, Example 1 showed that the initial setting time was shortened from 138 min to 78 min, and the 1-day compressive strength was increased from 4.0 MPa to 8.6 MPa, indicating that the low-temperature early strength component has a significant effect on promoting setting and early strength under low-temperature conditions.

[0081] Furthermore, Examples 4, 5, 6, 7, and 8 respectively support the lower limit of activated coal gangue precursor, the upper limit of calcium source cementing component, the upper limit of auxiliary cementing component, the upper limit of rheology-modifying component, and the feasible upper limit of activated coal gangue precursor, indicating that the formulation range of the present invention is feasible within the covered range.

[0082] In Example 6, due to the high water-to-solid ratio and the high amount of activating component, the fluidity was relatively high, the condensation was relatively slow, the bleeding rate was relatively high, and the early strength was relatively low. This indicates that in practical applications, a water-to-solid ratio of 0.70 to 0.95 is more conducive to balancing fluidity and low-temperature early strength performance.

[0083] Test Example 3: Performance Test of Crack Grouting and Sealing; The performance of fissure grouting was tested using a self-built flat plate fissure model. The model consisted of a transparent acrylic plate and a roughened stainless steel plate, with an effective fissure zone size of 500mm × 300mm. The fissure width was controlled to 1.0±0.1mm using shims. A grout inlet was installed at one end of the model, and a water outlet at the other. Before the test, the temperature of the device and circulating water was stabilized at 5±1℃.

[0084] First, circulating water was introduced into the fracture model, and the dynamic water pressure was adjusted to 0.30 MPa. After the outflow stabilized for 5 minutes, the outflow rate Q0 per unit time was recorded. Then, grouting material was injected into the fracture using a grouting pump at a constant pressure of 0.80 MPa, and the diffusion process of the grouting material was recorded simultaneously on video. The sealing time was defined as the time from the start of grouting until the outflow rate dropped to below 5% of Q0 and remained so for 3 minutes. Thirty minutes after the end of grouting, the stable outflow rate Q1 was recorded, and the water-stopping rate was calculated using the following formula: Water-stopping rate (%) = (Q0-Q1) / Q0×100%; the diffusion radius is expressed as the equivalent diffusion radius. Based on the video screenshot, depict the final diffusion area A of the grouting material in the crack, and calculate it according to the following formula: equivalent diffusion radius R = √(A / π); each group of tests is repeated twice, and the average value is taken.

[0085] Table 2. Test results of the crack sealing performance of grouting materials: As shown in Table 2, Examples 1-5 all exhibited large diffusion radii and high water-stopping rates in the fracture model. Specifically, in Example 1, the diffusion radius increased from 22.9 cm to 42.7 cm compared to Comparative Example 3, indicating that the microcapsule encapsulation method effectively suppressed the premature release of structure-building components and low-temperature early-strength components during the transport stage, allowing the grouting material to penetrate deeper fractures. Compared to Comparative Examples 1 and 2, Example 1 showed a significantly shorter sealing time and a higher water-stopping rate, further demonstrating that the graded matching activation and homogeneous activation system of coal gangue is beneficial for enhancing the rapid consolidation ability of the grouting material under low-temperature dynamic water conditions. Although Example 6 had a larger diffusion radius, the sealing time was prolonged and the water-stopping rate decreased, indicating that while an excessively high water-to-solid ratio is beneficial for fracture diffusion, it is not conducive to rapid water-stopping.

[0086] Test Example 4: Shear-induced release performance of microcapsules; To avoid differences in detection aperture and errors caused by different low-temperature early-strength components (such as low-solubility substances like lithium carbonate), this test example uniformly uses microcapsules with calcium formate as the tracer core for testing when examining the stress law of the capsule wall. Specifically, the capsule wall material formulation and preparation process are identical to those of the aforementioned microcapsules M1, M2, M3, M6, and M7, except that the core is uniformly replaced with an equal mass of calcium formate, thus obtaining tracer reference microcapsules corresponding to the original capsule wall process characteristics. 10.00 g of each of the above tracer reference microcapsules is weighed and added to 200 mL of simulated groundwater, simulating the calcium content in the groundwater. 2+ and Mg 2+ The initial concentration was controlled at 50 mg / L, and the test temperature was 5 ± 1℃.

[0087] Low shear group: Stir at 100 rpm for 5 min.

[0088] High shear group: The same microcapsule suspension was passed through a 1.0 mm nozzle once at a pressure of 0.60 MPa.

[0089] The solution was then immediately filtered, and the filtrate was used to determine the Ca content. 2+ Concentration. Ca 2+ The Ca2+ can be determined by EDTA complexometric titration or inductively coupled plasma atomic emission spectrometry. The Ca2+ obtained from microcapsules after complete acid dissolution and cell disruption... 2+ Using the total amount as a 100% release baseline, the release rate is calculated using the following formula: Release rate (%) = Actual Ca released 2+ Amount / Complete cell disruption release of Ca 2+ Total amount × 100%; 3 parallel samples were made for each group, and the average value was taken.

[0090] Table 3. Shear release test results of microcapsules in grouting materials: Note: The test samples in Table 3 are all tracer reference microcapsules with calcium formate as the uniform core; the "M1~M7" labels in the table are only used to refer to the type of capsule wall material and preparation process corresponding to them.

[0091] As shown in Table 3, the microcapsules formed from ethyl cellulose and polymethyl methacrylate exhibited low release rates under low shear conditions, but significantly increased release rates under nozzle shear conditions. This indicates that these microcapsules can undergo wall breakage and release under shear force during the crevice filling process. Among them, the smaller microcapsule samples M1 and M2 showed slightly higher release rates under high shear conditions than the larger microcapsule samples M6 and M7, suggesting that microcapsule size and wall thickness affect their release behavior under stress. This result supports the technical effect of "polymer microcapsules undergoing wall breakage and release under shear force during crevice filling" as stated in the claim.

[0092] In summary, this invention improves the dissolution and reactivity of active silica and aluminum in coal gangue under low-temperature conditions by classifying coal gangue raw materials and employing mechanical activation, thermal activation, or mechanical-thermal composite activation for different grades of coal gangue. This is achieved by combining silicate activation components, coal gangue-based ultrafine activation powder, and low-temperature early-strength components derived from coal gangue. Furthermore, by encapsulating the structure-building components and low-temperature early-strength components within ethyl cellulose or polymethyl methacrylate microcapsules, the grouting material maintains good fluidity during the transport stage and releases the core components after being subjected to shear forces during the fracture-filling stage, thus achieving a "first flow and diffusion, then rapid construction" effect. Therefore, this invention balances pumpability under low-temperature conditions, fracture diffusion capacity, rapid setting, and early strength development, making it suitable for grouting reinforcement of rock fractures and rapid sealing under flowing water conditions.

[0093] The embodiments of the present invention have been described above. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the protection scope of the present invention.

Claims

1. A rock strata early-strength low-temperature grouting material based on coal gangue activation, characterized in that: It comprises dry-based solids and water; the mass ratio of water to the total dry-based solids is 0.6 to 1.3; the total dry-based solids, based on 100 parts by mass, comprises the following components: 35-70 parts of activated coal gangue precursor were obtained by mechanical activation, thermal activation, or mechanical-thermal composite activation respectively, after the coal gangue raw material underwent graded pretreatment and was classified according to the graded results. 5-35 parts of calcium-based gelling component; 10-25 parts of auxiliary gelling component; The activating component comprises 10-20 parts; including at least a silicate activating component obtained from coal gangue, coal gangue-based ultrafine activating powder, and a low-temperature early strength component, used to promote the dissolution of active silica and aluminum in the activated coal gangue precursor under low-temperature conditions and to improve the reactivity of the activated coal gangue precursor under low-temperature conditions. Five to eight parts of rheology modifiers are included; at least dispersing and plasticizing components and structure-building components are included to keep the grouting material in a fluid state during the delivery stage and to reduce its fluidity after injection into rock fissures.

2. The rock strata early-strength low-temperature grouting material based on coal gangue activation according to claim 1, characterized in that: The structure-building component and the low-temperature early strength component are encapsulated within polymer microcapsules; during the fissure filling process, the capsule wall material of the polymer microcapsules is subjected to shear force to break the wall and release the structure-building component and the low-temperature early strength component.

3. The rock strata early-strength low-temperature grouting material based on coal gangue activation according to claim 2, characterized in that: The silicate activation component is a homologous activation micro powder prepared by spray drying of a liquid soluble silicate activation liquid; The liquid soluble silicate activating solution is selected from one or more of sodium silicate solution, potassium silicate solution, or composite alkali metal silicate solution obtained from coal gangue.

4. The rock strata early-strength low-temperature grouting material based on coal gangue activation according to claim 2, characterized in that: The silicate activating component is directly prepared into solid powder by co-milling raw coal gangue ore and solid alkaline activator in a high-energy ball mill; The solid alkaline activator is selected from one or more of sodium hydroxide, potassium hydroxide, and sodium carbonate.

5. A rock strata early-strength low-temperature grouting material based on coal gangue activation according to claim 3 or 4, characterized in that: The coal gangue-based ultrafine activated powder is coal gangue powder obtained by further grinding after activation, with a specific surface area of ​​400–1400 m². 2 / kg; The low-temperature early strength component is selected from one or more of calcium formate, lithium carbonate, sodium aluminate, or triethanolamine.

6. A method for preparing a rock strata early-strength low-temperature grouting material based on coal gangue activation, used to prepare the grouting material of claim 5, characterized in that, Includes the following steps: Step S1: Sample and test the coal gangue raw material to obtain its strength activity index, carbon content, and 80μm sieve residue, and classify the coal gangue raw material according to the test results; Step S2: The graded coal gangue raw materials are crushed into particles with a particle size of no more than 10 mm, and the crushed particles are subjected to air separation, decarbonization and impurity removal pretreatment in sequence. Step S3: According to the grading grade of the coal gangue raw material, mechanical activation, thermal activation or mechanical-thermal composite activation treatment is adopted respectively to obtain the activated coal gangue precursor; Step S4: Take a portion of the pretreated coal gangue raw material and prepare homologous activated micro powder or solid powder as the silicate activating component; further grind the activated portion of the coal gangue to obtain the coal gangue-based ultrafine activating powder. The polymer microcapsules are prepared by encapsulating the structure-building component and the low-temperature early strength component in the capsule wall material. Step S5: The activated coal gangue precursor, the calcium source gelling component, the auxiliary gelling component, the dispersing and plasticizing component, the silicate activating component prepared in step S4, the coal gangue-based ultrafine activating powder, and the polymer microcapsules are uniformly mixed to obtain a grouting dry mix. Step S6: During the grouting operation, water is added to the dry grout mix to obtain the grouting material, and the final mass ratio of water to the total dry solids in the grouting material is adjusted to 0.6 to 1.

3.

7. The preparation method of a rock stratum early-strength low-temperature grouting material based on coal gangue activation according to claim 6, characterized in that: In step S1, the grading criteria for the coal gangue raw material are as follows: Grade I coal gangue: meets the following requirements: strength activity index ≥70%, carbon content ≤6%, and 80μm sieve residue ≤3%; Grade III coal gangue: meets the following requirements: strength activity index <60%, or carbon content >20%; Grade II coal gangue: Coal gangue raw materials that do not fall into the Grade I coal gangue grading standard and do not fall into the Grade III coal gangue grading standard.

8. The method for preparing a rock stratum early-strength low-temperature grouting material based on coal gangue activation according to claim 7, characterized in that: The processing methods for coal gangue raw materials of different grading standards in step S3 are as follows: For the Class I coal gangue, mechanical activation is performed in step S3; For the Class II coal gangue, the thermal activation is performed in step S3; The Class III coal gangue is further activated using the mechanical-thermal composite activation method in step S3.

9. The method for preparing a rock strata early-strength low-temperature grouting material based on coal gangue activation according to claim 8, characterized in that: In step S3, The mechanical activation is carried out by grinding using one or more of ball mills, vertical mills, and ultrafine mills, so that the residue on the 80μm sieve of the activated coal gangue is no more than 10%. The calcination temperature for thermal activation is 650–1000℃, and the holding time is 0.5–6 hours. The mechanical-thermal composite activation includes performing the mechanical activation first and then the thermal activation, or performing the thermal activation first and then a secondary mechanical activation.

10. The method for preparing a rock stratum early-strength low-temperature grouting material based on coal gangue activation according to claim 8, characterized in that: In step S4, the polymer microcapsules are prepared by solvent evaporation method, using the structure-building component and the low-temperature early strength component as the core and ethyl cellulose or polymethyl methacrylate as the capsule wall; the average particle size of the polymer microcapsules is 50-100 μm.

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