Purple sand light weight ceramic block for sealing underground coal mine and preparation method thereof

Abstract

The application discloses a kind of purple sand light weight ceramic blocks for sealing in underground coal mine and a preparation method thereof, and belongs to the technical field of rapid sealing support in underground coal mine.The block is a two-phase structure of honeycomb-skeleton filling particles, the honeycomb skeleton is composed of Portland cement, purple sand clinker, zeolite, bentonite, fiber and graphene, and the skeleton is filled with graphite polystyrene foaming particles.Discrete mixing, moulding, high-speed precision cutting and curing are used to obtain the block during preparation.The application uses low-cost purple sand clinker, natural zeolite and bentonite to replace 3A, 5A and macroporous molecular sieve, the purple sand clinker adsorbs free sodium, magnesium and calcium ions, the zeolite removes sulfates and chlorides and adsorbs harmful gases such as ammonia nitrogen, and the bentonite absorbs water to expand, improving crack resistance and high humidity stability.

Description

Technical Field

[0001] This invention relates to the field of rapid sealing and support technology in underground coal mines, specifically to a lightweight purple clay ceramic block for underground sealing in coal mines and its preparation method. Background Technology

[0002] Temporary and permanent sealing operations in coal mines are crucial for mine ventilation control and goaf isolation, directly impacting mine safety and normal face succession. Currently, temporary sealing operations in coal mines primarily utilize brick and stone masonry walls, mainly "37" and "50" brick walls. After construction, cement mortar is applied to the wall surface for sealing. The main materials used are bricks, cement, and sand.

[0003] The traditional process has the following shortcomings: 1. Long construction period: The masonry and plastering processes are complicated and cannot meet the rapid sealing requirements in scenarios such as working face retreat and emergency rescue; 2. Poor deformation resistance: As a rigid support structure, it is easily cracked and collapsed under deep mining and severe mine pressure conditions, losing its sealing and support functions; 3. High transportation and construction costs: Large material consumption, high self-weight, large amount of underground auxiliary transportation, and high investment of manpower and time.

[0004] While the industry has conducted research on related technological improvements to address the aforementioned issues, core challenges remain at the material mechanism level. Research has found that the key factor restricting the long-term stability of existing silicate-based building block materials lies in the control of free CaO (calcium oxide) and free MgO (magnesium oxide) in the system. The specific reasons why free CaO and free MgO lead to reduced strength are as follows:

[0005] Volume expansion generates internal stress. Free CaO and free MgO undergo a slow hydration reaction upon contact with water, producing Ca(OH)₂ and Mg(OH)₂. Ca(OH)₂ increases in volume by approximately 90%, and Mg(OH)₂ by approximately 120%. This significant late-stage volume expansion generates irreversible tensile stress within the block, which in turn cracks the hardened cementitious structure, leading to material crumbling, a sharp decrease in strength, and even collapse.

[0006] It disrupts the cementitious structure. Calcium silicate hydrate (CSH), a product of cement hydration, is the main source of material strength. The large amount of free calcium and magnesium ions present in the system interferes with the normal hydration process, resulting in a less dense cementitious structure, a significant increase in porosity, and a weakened interfacial transition zone between aggregates and paste. Ultimately, this manifests as a significant decrease in compressive and flexural strength.

[0007] Poor stability leads to subsequent strength reduction. Silicate products, after several weeks or months of service in the high-humidity environment of underground coal mines, crack due to continuous delayed expansion, resulting in severe strength reduction. This defect is fatal for underground blocks that must maintain airtightness for extended periods.

[0008] To address the stability issues and strength reduction problems caused by free calcium and magnesium, current technological approaches tend to involve adding functional molecular sieves (such as 3A and 5A molecular sieves) to adsorb free ions. This is indeed one of the theoretically best ways to improve material performance. However, the high cost of molecular sieve materials prevents their widespread use in industrial fields such as underground coal mine sealing projects.

[0009] This invention addresses the problems of slow construction, easy damage to rigidity, and high transportation and construction costs of existing downhole temporary sealing technologies, and proposes a brand-new solution. Summary of the Invention

[0010] This invention provides a method for producing lightweight masonry blocks for underground coal mines. The blocks utilize purple clay clinker to replace 3A and 5A molecular sieves, adsorbing sodium, magnesium, and calcium ions released from silicates; natural zeolite to replace macroporous molecular sieves, removing free sulfates and chlorides; bentonite absorbs water and expands, improving crack resistance and material stability under high humidity conditions in coal mines; and zeolite adsorbs ammonia nitrogen / harmful gases, reduces bulk density, provides thermal and sound insulation, and improves material performance. The precast two-phase masonry block has a cuboid structure and employs a honeycomb skeleton-filled particle two-phase structure. The honeycomb skeleton is composed of silicate cement, purple clay clinker, zeolite, bentonite, fiber, and graphene. The skeleton is filled with graphite polystyrene foam particles. The purple clay clinker + green zeolite + sodium-based bentonite composite system replaces the high-cost molecular sieves, quantitatively controlling the calcium-magnesium balance to achieve lightweight, high-strength, crack-resistant, and rapid construction. This invention adopts an inorganic cementing system + purple clay ceramic particle composite technology route. Through precise ingredient batching, discrete mixing, molding, high-speed cutting and standardized packaging, it produces lightweight blocks that are lightweight, high-strength, anti-static, fireproof and have rigid-flexible conversion characteristics. The whole process is automated, modular, efficient and stable, and suitable for large-scale application in underground coal mine sealing projects.

[0011] A lightweight purple clay ceramic block for sealing underground coal mines, wherein the raw material composition of the lightweight purple clay ceramic block, based on 100 parts by weight of silicate cement, is as follows:

[0012] Basic cementitious materials and aggregates, by weight:

[0013] 90 to 110 parts of silicate cement, wherein the mass fraction of free calcium oxide in the silicate cement is <1.5% and the mass fraction of magnesium oxide is <5%;

[0014] The proportions are: 45 to 65 parts of Zisha clinker and 35 to 55 parts of zeolite, with a total proportion of 100 parts of Zisha clinker and zeolite.

[0015] 25 to 35 parts bentonite;

[0016] 30 to 40 parts of graphite polystyrene foam granules;

[0017] Graphene 4 to 8 parts;

[0018] 5 to 9 parts fiber;

[0019] Admixtures are calculated by weight based on 100 parts of silicate cement.

[0020] The mixture comprises 5-7 parts silica fume, 1.5-2.5 parts calcium aluminate-based accelerator, wherein the calcium aluminate-based accelerator is composed of: 5%-10% SiO2, 40%-50% Al2O3, with the balance being CaO; 2-4 parts calcium formate, wherein the calcium formate is composed of: 90%-98% Ca(HCOO)2, with the balance being unavoidable impurities; and 1-2 parts reinforcing agent, wherein the reinforcing agent is a polypropylene fiber reinforcing agent or a mineral powder reinforcing agent, wherein the polypropylene fiber reinforcing agent is composed of: 95%-99% polypropylene; and the mineral powder reinforcing agent is composed of: 25%-35% SiO2, 10%-25% Al2O3, 10%-25% CaO ... 15%–25%, with the remainder being CaO, MgO, and unavoidable impurities; 2–4 parts of organosilicon composite water-repellent agent, the composition of which by mass percentage is: 30%–40% organosilicon component, 10%–20% surfactant, and the remainder being carrier; 2–5 parts of polycarboxylate superplasticizer, the composition of which by mass percentage is: 40%–50% polycarboxylate groups, 5%–10% other additives, and the remainder being water; 1.5–3 parts of early-strength agent, the early-strength agent being a calcium chloride-sodium sulfate composite early-strength agent, the composition of which by mass percentage is: 40%–50% CaCl2, 30%–40% Na2SO4, and the remainder being additives; 1–2 parts of lithium-based sealing and curing agent, 1–3 parts of redispersible latex powder, 1–3 parts of xanthan gum powder, and 2–5 parts of fumed silica.

[0021] Furthermore, based on 100 parts of silicate cement, the raw materials also include 0.1 to 1 part of hydroxypropyl methylcellulose ether, 0.1 to 1 part of starch ether, and 15 to 20 parts of fly ash by weight. The composition of the fly ash by mass percentage is: 40% to 50% SiO2, 20% to 30% Al2O3, with the balance being Fe2O3 and other unavoidable impurities.

[0022] Furthermore, the purple clay clinker is made by naturally weathering purple clay ore for 6 months, then drying it, and finally firing it in a kiln at 700℃~850℃ for 6 hours. After firing, it is crushed and sieved to obtain clinker particles with a fineness of over 400 mesh. Its chemical composition by mass percentage is as follows: SiO2 60.0%~62.0%, Al2O3 19.5%~20.5%, Fe2O3 7.0%~8.5%, CaO 0.5%~0.8%, Na2O 0.05%~0.10%, K2O 1.0%~1.5%, MgO 1.2%~1.6%, TiO2 1.0%~1.2%, and loss on ignition 5.8%~6.5%.

[0023] The zeolite is green zeolite with an ammonia absorption value >150mg / g;

[0024] The fibers include wood fibers and silica fibers. Based on 100 parts of silicate cement, the wood fibers are 0.5 to 1 part and the silica fibers are 5 to 7 parts. The wood fibers have a length of 3 mm to 5 mm and a diameter of 20 μm to 50 μm. The silica fibers have a length of 6 mm to 10 mm and a diameter of 10 μm to 30 μm.

[0025] The graphite polystyrene foam particles have a particle size of 0.1 mm to 0.3 mm, and their composition by mass percentage is: 80% to 90% polystyrene and 10% to 20% graphite; the graphene has a thickness of 0.5 nm to 1.5 nm, a sheet diameter of 1 μm to 5 μm, and a graphene purity of 95% to 99%.

[0026] The rigid-to-flexible transformation of the purple clay lightweight ceramic block exhibits good reversibility. The test method is as follows: a pressure testing machine is used to apply pressure to the block. When the pressure reaches 0.4MPa to 0.5MPa, the honeycomb skeleton breaks, and the block as a whole becomes flexible, with a deformation of 3mm to 5mm. After the pressure is removed, the block can maintain its flexible state for 2h to 4h, and then gradually returns to its initial rigid state. After repeating the test 5 to 8 times, the block can still maintain good rigid-to-flexible transformation performance without obvious damage or strength reduction.

[0027] The purple clay lightweight ceramic blocks also possess the following properties:

[0028] Compressive strength: After 28 days of curing, the compressive strength is 0.3 MPa to 0.4 MPa;

[0029] Antistatic surface resistance: 1×10 6 Ω~1×10 9 Ω meets downhole anti-static requirements; fire resistance rating:

[0030] It meets the Class A non-combustible standard, with a fire resistance rating of ≥2 hours;

[0031] Adsorption performance: Zeolite ammonia adsorption value 150mg / g~180mg / g, purple clay clinker ammonia adsorption value 80 mg / g~100mg / g;

[0032] Flexible conversion starting pressure: 1MPa~3MPa, deformation during conversion: 3mm~5mm;

[0033] Impermeability: Permeability coefficient ≤ 1×10 -7 cm / s;

[0034] Dimensional stability: In a humid underground environment with humidity of 80% to 90% and temperature of 10℃ to 30℃, after 30 days of storage, the dimensional change rate is ≤0.1%.

[0035] A method for using lightweight purple clay ceramic blocks for sealing underground coal mines includes the following steps:

[0036] S1. Discrete mixing: Using discrete mixing technology, all raw materials are first mixed evenly, then water is added and stirred at 800r / min to 1200r / min for 15min to 25min to obtain a uniformly mixed slurry; the mass ratio of water added to raw materials is (0.35 to 0.45):1.

[0037] S2. Material Discharge: The uniformly mixed slurry is injected into the mold box at a constant rate of 0.5 to 1.5 m³ / h until the box is full, and the surface is kept flat; to prevent material stratification and segregation, and to ensure the uniformity of the internal structure of the blocks;

[0038] S3. Pressing, Molding, and Demolding: Apply constant pressure to the full box of slurry, ranging from 15MPa to 25MPa, for 3 to 8 minutes to expel air, improve the density of the green body, and form a stable green body with a honeycomb-like continuous phase skeleton; then let it stand for 8 to 12 hours at room temperature (20℃ to 25℃) and humidity (50% to 70%) until the green body strength reaches 3 to 5MPa, then demold to obtain the green body; after demolding, an initial curing process is required, with an initial curing environment of 20℃ to 25℃ and humidity (60% to 80%) for 24 to 48 hours to ensure stable green body strength and avoid cracking and deformation after demolding;

[0039] S4. High-speed precision cutting: When the blank strength is 0.3MPa~0.5MPa, the cutting speed is 1m / min~3m / min and the cutting blade speed is 3000r / min~5000r / min for precise vertical and horizontal bidirectional cutting, and the cutting error is controlled within ±0.5mm;

[0040] S5. Stacking, Curing and Packaging: Qualified blocks are automatically stacked for subsequent curing. Curing conditions are as follows: curing period of 28 days, ambient temperature of 18℃~22℃, humidity of 70%~80%. After 28 days of curing, the compressive strength and flexural strength of the blocks are ≥0.5MPa and ≥0.5MPa, respectively. Standardized waterproof packaging is used, with 2 to 4 blocks per package, packaged in waterproof woven bags with heat-sealing technology to facilitate storage, transportation and underground loading and unloading.

[0041] An application of lightweight purple clay ceramic blocks for sealing underground coal mines is disclosed, which are used in underground sealing isolation bodies. The isolation bodies are constructed by splicing the lightweight blocks. There is an adhesive layer between adjacent prefabricated two-phase blocks, and an airtight layer formed by spraying a coating layer is provided at the junction of the isolation body and the rock mass and / or on the surface of the isolation body.

[0042] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0043] 1. This invention utilizes low-cost purple clay clinker, natural zeolite, and bentonite in a synergistic formulation to replace expensive 3A and 5A molecular sieves. Its porous structure adsorbs free sodium, magnesium, and calcium ions from the silicate system, effectively controlling the calcium and magnesium ion content in the material, inhibiting volume expansion, and significantly improving the long-term volume stability and durability of the blocks in the high-humidity environment of coal mines (dimensional change rate ≤0.1%, service life ≥5 years). Simultaneously, natural zeolite replaces macroporous molecular sieves to remove harmful ions such as free sulfates and chlorides from the system; and bentonite is introduced, utilizing its water-swelling properties to enhance the material's crack resistance and volume stability under high-humidity conditions in underground coal mines. The porous structure of zeolite can also effectively adsorb ammonia nitrogen and harmful gases underground, reduce the material's bulk density, and provide thermal and sound insulation functions, thereby comprehensively improving the material's service performance. The micro-dense purple clay, combined with the organosilicon water-repellent agent, reduces the permeability coefficient of the blocks to as low as 1×10⁻⁶. -7 The density of the blocks is 1 cm / s, which significantly reduces the interconnected pores, blocks gas leakage and water penetration, and ensures the airtightness and impermeability of the sealed wall. The interlocking reinforcement structure of fiber-graphene-purple clay particles, combined with polypropylene fiber reinforcement, results in a 28-day compressive strength of ≥15MPa and a flexural strength of ≥2.5MPa. It has high load-bearing capacity and excellent crack resistance, and can resist deformation and microcrack propagation caused by underground mining pressure.

[0044] 2. This invention uses cement with low free calcium and magnesium content, controlling the following in the cement: free CaO < 1.5%; MgO < 5% (national standard limit); it utilizes purple clay, zeolite, and bentonite to inhibit expansion, with purple clay diluting free calcium and magnesium, and zeolite adsorbing Ca. 2+ Mg 2+To reduce late-stage hydration expansion, bentonite adsorption and ion exchange stabilize the system and reduce expansion stress. These three materials can replace expensive molecular sieves to achieve high strength, crack resistance, and other special functions, completing most of the hydration process earlier and avoiding concentrated expansion later. In silicate systems, free calcium oxide and free magnesium oxide undergo significant volume expansion during late-stage hydration upon contact with water, triggering internal tensile stress that leads to block cracking and structural loosening. Simultaneously, they interfere with the formation of cement hydration products, resulting in reduced compressive strength and decreased long-term stability.

[0045] 3. The lightweight blocks prepared by this invention have a honeycomb skeleton structure. The two-phase structure composed of the honeycomb skeleton and graphite polystyrene foam particles gives the blocks reversible rigid-flexible transformation characteristics: under a ground pressure of 1-3 MPa, the skeleton breaks but the whole block does not fall apart, absorbing energy through flexible deformation; after pressure relief, it can automatically restore rigidity and can be reused, solving the problem that traditional rigid sealed walls are easily crushed and fail. This prefabricated two-phase block has a cuboid structure and adopts a honeycomb skeleton-filled particle two-phase structure: the honeycomb skeleton is composed of silicate cement, purple clay clinker, zeolite, bentonite, fiber and graphene composite, and the skeleton is filled with graphite polystyrene foam particles, which can meet the requirements of underground sealed support. It also has the characteristics of light weight, high strength, strong deformation resistance, non-combustible, heat insulation and anti-static properties, and is suitable for rapid sealing and temporary isolation operations in coal mines.

[0046] 4. The lightweight blocks prepared using this invention form an insulating body with strong resistance to deformation, non-combustible, heat insulation, and antistatic properties. It achieves a fire rating of Class A, a fire resistance limit of ≥2 hours, and an antistatic resistance of 10 Ω·cm. 6 ~10 9 It contains Ω and also possesses the strong adsorption capacity of zeolite for ammonia nitrogen and harmful gases, fully meeting the stringent safety requirements for fire prevention, explosion prevention, and airtight emergency rescue in coal mines. Simultaneously, it allows for rapid construction, requiring less manpower and time. Traditionally, a 4m x 5m, 40cm thick wall requires 48 man-hours, while the lightweight blocks prepared by this invention require only 6 man-hours. The blocks are bonded using a thin layer of silicate mortar, with a bonding thickness of less than 3mm. This structural feature provides excellent sealing, significantly reducing construction labor and time costs.

[0047] 5. The aforementioned blocks and the resulting underground isolation structure have a continuous phase consisting of a robust honeycomb framework structure primarily composed of inorganic composite materials made of silicate cement. The honeycomb interior is filled with graphite polystyrene foam particles, which possess excellent energy absorption and electrical conductivity. A small amount of graphene is incorporated into the inorganic composite material, further enhancing its antistatic properties. When subjected to significant external forces, such as underground dynamic pressure, the silicate honeycomb wall material will fracture first. However, due to the fibrous tension within the framework and the internal bonding of the flexible and resilient graphite polystyrene foam particles, the overall structure will not break or collapse, maintaining its integrity. The stressed portions exhibit flexibility and elasticity after crushing, preventing the wall from losing its support and sealing function. The material exhibits both crushability and post-crushing flexibility; this flexibility and elasticity absorb energy, partially absorbing the energy of underground rockburst. Attached Figure Description

[0048] Figure 1 This is a comparative diagram of the mesopore size distribution of purple clay in Example 1 of the present invention. Detailed Implementation

[0049] This disclosure, and its various embodiments, will now be described more fully below. However, this disclosure may be implemented in many different ways and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be exhaustive and complete, and will fully convey the scope of this disclosure to those skilled in the art.

[0050] In this embodiment, the zeolite used is green zeolite produced and purified by Chaoyang, with an ammonia absorption value >150mg / g, and the bentonite used is sodium bentonite.

[0051] The terminology used herein is for the purpose of describing specific implementations only. Unless the context clearly specifies otherwise, "a," "an," "the," and "at least one" are not limited in quantity and may cover both singular and plural forms; "or" means "and / or" and includes any and all combinations of the items listed herein. All terms (including technical and scientific terms) are interpreted in the manner commonly understood by those skilled in the art and are not intended to be idealized or overly formalized; "comprising" and "including" do not exclude other related properties, quantities, steps, components, etc.

[0052] In view of the shortcomings of existing technologies such as slow construction of downhole isolation bodies, easy fracturing and collapse, and high labor and time costs, this disclosure provides a temporary sealing wall material, as well as its prefabricated products and usage methods.

[0053] This sealed wall material uses silicate cement, fly ash, graphite polystyrene foam particles, graphene, inorganic fiber materials, and various functional materials as its main raw materials. It is non-toxic, odorless, non-volatile, non-radioactive, and water-insoluble, making it a green and environmentally friendly material. It also possesses lightweight, high strength, anti-static, non-flammable, and heat-insulating properties. Its preparation method involves uniformly coating graphite polystyrene foam particles with inorganic composite materials, followed by pressing, bonding, and curing.

[0054] The continuous phase of the material is a robust honeycomb skeleton composed mainly of inorganic composite materials made of silicate cement. The honeycomb is filled with graphite polystyrene foam particles with energy absorption and conductivity. The graphene and inorganic nanoscale active materials in the inorganic composite material can significantly improve the antistatic and airtight properties. The principle is as follows: the reaction with calcium hydroxide forms silicate gel, which reduces the directional arrangement of calcium hydroxide at the cement paste aggregate interface, improves the pore structure of hardened cement, promotes the hydration reaction of C3S (tricalcium silicate) and C2S (dicalcium silicate) in cement, and fills the pores of concrete. The generated hydrated calcium silicate further refines the capillary pores and makes them disconnected. The unreacted residue can fill the pores between cement particles and at the paste-aggregate interface, optimize the material structure and improve airtightness.

[0055] When not subjected to external impact or crushing, the material structure is stable and has high strength; when subjected to greater external forces such as underground dynamic pressure, the honeycomb wall in the stressed part breaks first, but with the help of the fiber traction in the skeleton and the flexible and resilient graphite polystyrene foam particles, the material as a whole will not break or collapse, and can maintain its shape integrity. The stressed part exhibits flexible elasticity, ensuring the wall's support and sealing functions.

[0056] The following example is a prefabricated block made based on the above-mentioned materials.

[0057] The zeolite used in this embodiment is green zeolite produced in Beipiao, Chaoyang, Liaoning Province: ammonia absorption value >150mg / g, mass percentage range: SiO2 65%~75%, Al2O3 10%~15%, Fe2O3 2%~5%, CaO 2%~4%, MgO 1%~3%.

[0058] A lightweight purple clay ceramic block for sealing underground coal mines, wherein the raw material composition of the lightweight purple clay ceramic block, based on 100 parts by weight of silicate cement, is as follows:

[0059] Basic cementitious materials and aggregates, by weight:

[0060] 90 to 110 parts of silicate cement, wherein the mass fraction of free calcium oxide in the silicate cement is <1.5% and the mass fraction of magnesium oxide is <5%;

[0061] The proportions are: 45 to 65 parts of Zisha clinker and 35 to 55 parts of zeolite, with a total proportion of 100 parts of Zisha clinker and zeolite.

[0062] 25 to 35 parts bentonite;

[0063] 30 to 40 parts of graphite polystyrene foam granules;

[0064] Graphene 4 to 8 parts;

[0065] 5 to 9 parts fiber;

[0066] Admixtures are calculated by weight based on 100 parts of silicate cement.

[0067] The mixture comprises 5-7 parts silica fume, 1.5-2.5 parts calcium aluminate-based accelerator, wherein the calcium aluminate-based accelerator is composed of: 5%-10% SiO2, 40%-50% Al2O3, with the balance being CaO; 2-4 parts calcium formate, wherein the calcium formate is composed of: 90%-98% Ca(HCOO)2, with the balance being unavoidable impurities; and 1-2 parts reinforcing agent, wherein the reinforcing agent is a polypropylene fiber reinforcing agent or a mineral powder reinforcing agent, wherein the polypropylene fiber reinforcing agent is composed of: 95%-99% polypropylene; and the mineral powder reinforcing agent is composed of: 25%-35% SiO2, 10%-25% Al2O3, 10%-25% CaO ... 15%–25%, with the remainder being CaO, MgO, and unavoidable impurities; 2–4 parts of organosilicon composite water-repellent agent, the composition of which by mass percentage is: 30%–40% organosilicon component, 10%–20% surfactant, and the remainder being carrier; 2–5 parts of polycarboxylate superplasticizer, the composition of which by mass percentage is: 40%–50% polycarboxylate groups, 5%–10% other additives, and the remainder being water; 1.5–3 parts of early-strength agent, the early-strength agent being a calcium chloride-sodium sulfate composite early-strength agent, the composition of which by mass percentage is: 40%–50% CaCl2, 30%–40% Na2SO4, and the remainder being additives; 1–2 parts of lithium-based sealing and curing agent, 1–3 parts of redispersible latex powder, 1–3 parts of xanthan gum powder, and 2–5 parts of fumed silica.

[0068] The role of lithium-based sealing and curing agents is to accelerate curing, improve early strength, and shorten demolding and curing time; reduce the alkalinity of cement hydration products, inhibit the later expansion of free CaO / MgO, and improve volume stability; densify the surface, reduce water absorption, and improve impermeability and weathering resistance.

[0069] The role of redispersible latex powder is to improve flexibility, crack resistance, and bonding strength, and prevent brittle fracture of the honeycomb skeleton; improve the slurry encapsulation and enhance the interfacial bonding between the inorganic phase and graphite polystyrene particles; improve impact resistance and water resistance, and reduce drying shrinkage cracking.

[0070] The function of xanthan gum powder is to thicken and retain water, preventing slurry from bleeding, separating, and segregating; to improve the fluidity of the slurry and the uniformity of the molding, ensuring the stability of the honeycomb structure; and to improve the thixotropy of the slurry, facilitating molding and reducing defects.

[0071] The role of fumed silica is to fill micro-aggregates, refine pores, and improve density and strength; thicken and thixotropicate to prevent the sedimentation of powders such as graphene and purple clay clinker; improve impermeability, wear resistance, and water resistance, and enhance the stability of the system.

[0072] Furthermore, based on 100 parts of silicate cement, the raw materials also include 0.1 to 1 part of hydroxypropyl methylcellulose ether, 0.1 to 1 part of starch ether, and 15 to 20 parts of fly ash by weight. The composition of the fly ash by mass percentage is: 40% to 50% SiO2, 20% to 30% Al2O3, with the balance being Fe2O3 and other unavoidable impurities.

[0073] Furthermore, the purple clay clinker is made by naturally weathering purple clay ore for 6 months, then drying it, and finally firing it in a kiln at 700℃~850℃ for 6 hours. After firing, it is crushed and sieved to obtain clinker particles with a fineness of over 400 mesh. Its chemical composition by mass percentage is as follows: SiO2 60.0%~62.0%, Al2O3 19.5%~20.5%, Fe2O3 7.0%~8.5%, CaO 0.5%~0.8%, Na2O 0.05%~0.10%, K2O 1.0%~1.5%, MgO 1.2%~1.6%, TiO2 1.0%~1.2%, and loss on ignition 5.8%~6.5%.

[0074] The zeolite is green zeolite with an ammonia absorption value >150mg / g;

[0075] The fibers include wood fibers and silica fibers. Based on 100 parts of silicate cement, the wood fibers are 0.5 to 1 part and the silica fibers are 5 to 7 parts. The wood fibers have a length of 3 mm to 5 mm and a diameter of 20 μm to 50 μm. The silica fibers have a length of 6 mm to 10 mm and a diameter of 10 μm to 30 μm.

[0076] The graphite polystyrene foam particles have a particle size of 0.1 mm to 0.3 mm, and their composition by mass percentage is: 80% to 90% polystyrene and 10% to 20% graphite; the graphene has a thickness of 0.5 nm to 1.5 nm, a sheet diameter of 1 μm to 5 μm, and a graphene purity of 95% to 99%.

[0077] The rigid-to-flexible transformation of the purple clay lightweight ceramic block exhibits good reversibility. The test method is as follows: a pressure testing machine is used to apply pressure to the block. When the pressure reaches 0.4MPa to 0.55MPa, the honeycomb skeleton breaks, and the block as a whole becomes flexible, with a deformation of 3mm to 5mm. After the pressure is removed, the block can maintain its flexible state for 2h to 4h, and then gradually returns to its initial rigid state. After repeating the test 5 to 8 times, the block can still maintain good rigid-to-flexible transformation performance without obvious damage or strength reduction.

[0078] The purple clay lightweight ceramic blocks also possess the following properties:

[0079] Compressive strength: After 28 days of curing, the compressive strength is 0.3 MPa to 0.4 MPa;

[0080] Antistatic surface resistance: 1×10 6 Ω~1×10 9 Ω meets downhole anti-static requirements; fire resistance rating:

[0081] It meets the Class A non-combustible standard, with a fire resistance rating of ≥2 hours;

[0082] Adsorption performance: Zeolite ammonia adsorption value 150mg / g~180mg / g, purple clay clinker ammonia adsorption value 80 mg / g~100mg / g;

[0083] Flexible conversion starting pressure: 1MPa~3MPa, deformation during conversion: 3mm~5mm;

[0084] Impermeability: Permeability coefficient ≤ 1×10 -7 cm / s;

[0085] Dimensional stability: In a humid underground environment with humidity of 80% to 90% and temperature of 10℃ to 30℃, after 30 days, the dimensional change rate is ≤0.1%.

[0086] A method for using lightweight purple clay ceramic blocks for sealing underground coal mines includes the following steps:

[0087] S1. Discrete mixing: Using discrete mixing technology, all raw materials are first mixed evenly, then water is added and stirred at 800r / min to 1200r / min for 15min to 25min to obtain a uniformly mixed slurry; the mass ratio of water added to raw materials is (0.35 to 0.45):1.

[0088] S2. Material Discharge: The uniformly mixed slurry is injected into the mold box at a constant rate of 0.5 to 1.5 m³ / h until the box is full, and the surface is kept flat; to prevent material stratification and segregation, and to ensure the uniformity of the internal structure of the blocks;

[0089] S3. Pressing, Molding, and Demolding: Apply constant pressure to the full box of slurry, ranging from 15MPa to 25MPa, for 3 to 8 minutes to expel air, improve the density of the green body, and form a stable green body with a honeycomb-like continuous phase skeleton; then let it stand for 8 to 12 hours at room temperature (20℃ to 25℃) and humidity (50% to 70%) until the green body strength reaches 3 to 5MPa, then demold to obtain the green body; after demolding, an initial curing process is required, with an initial curing environment of 20℃ to 25℃ and humidity (60% to 80%) for 24 to 48 hours to ensure stable green body strength and avoid cracking and deformation after demolding;

[0090] S4. High-speed precision cutting: The blank is fed into the cutting station by an automated gripping mechanism, and the high-speed cutting system performs precise cutting in both vertical and horizontal directions; when the blank strength is 0.3MPa~0.5MPa, the cutting speed is 1m / min~3m / min and the cutting blade speed is 3000r / min~5000r / min, and the cutting error is controlled within ±0.5mm.

[0091] S5. Stacking, Curing, and Packaging: Qualified blocks are automatically stacked for subsequent curing. Curing conditions are as follows: curing period of 28 days, ambient temperature of 18℃~22℃, humidity of 70%~80%. After 28 days of curing, the compressive strength of the blocks is ≥15MPa, and the flexural strength is ≥2.5MPa. Standardized waterproof packaging is used, with 2~4 blocks per package, packaged in waterproof laminated woven bags. The bag opening is sealed using a heat-sealing process for easy storage, transportation, and underground loading and unloading. The packaging is labeled with product name, specifications, production date, strength grade, and other information.

[0092] Example 1

[0093] 1. Raw materials

[0094] Zisha (purple clay) clinker: Sourced from Zisha mine in Kazuo County, Chaoyang City, Liaoning Province. After natural weathering for 6 months, it was dried and fired in a kiln at 780℃ for 6 hours. After crushing and sieving, it obtained 400-mesh fine particles. Chemical composition (mass percentage): SiO2 61.40%, Al2O3 20.16%, Fe2O3 7.74%, CaO 0.64%, Na2O 0.07%, K2O 1.31%, MgO 1.46%, TiO2 1.10%, loss on ignition 6.12%.

[0095] Green zeolite: The type is clinoptilolite, produced in Beipiao, Liaoning Province, with a particle size of 300 mesh and an ammonia absorption value of 165 mg / g; chemical composition (mass percentage): SiO2 70%, Al2O3 12%, Fe2O3 3.5%, CaO 3%, MgO 2%. Portland cement: P·O42.5 grade ordinary Portland cement, produced in Zibo, Shandong Province, with a strength grade of 42.5 MPa.

[0096] Graphite polystyrene foam granules: particle size 0.2mm, mass percentage: polystyrene 85%, graphite 15%, origin: Langfang, Hebei.

[0097] Graphene: 1.0 nm thick, 3 μm in diameter, 98% pure, produced in Wuxi, Jiangsu Province.

[0098] Fibers: wood fiber (4mm in length, 35μm in diameter, 98% purity) and silica fiber (8mm in length, 20μm in diameter, 99% purity), produced in Xinxiang, Henan.

[0099] Admixtures: calcium aluminate-based coagulant (Al2O3 45%, CaO 35%, SiO2 8%), polycarboxylate-based high-efficiency water-reducing agent (polycarboxylate groups 45%, additives 8%, water 47%), organosilicon composite water-repellent agent (organosilicon components 35%, surfactants 15%, carrier 50%), calcium chloride-sodium sulfate composite early strength agent (CaCl2 45%, Na2SO4 35%, additives 20%), polypropylene fiber reinforcing agent (polypropylene content 97%), all industrial grade, produced in Suzhou, Jiangsu Province.

[0100] Other raw materials: bentonite (200 mesh, from Chifeng, Inner Mongolia), silica fume (92% purity, from Anshan, Liaoning), lithium-based sealing and curing agent (industrial grade, from Guangzhou, Guangdong), redispersible latex powder (industrial grade, from Shanghai), xanthan gum powder (industrial grade, from Qingdao, Shandong), fumed silica (industrial grade, from Hangzhou, Zhejiang).

[0101] 2. Proportioning

[0102] Basic cementitious materials and aggregates (parts by weight): 100 parts silicate cement, 55 parts purple clay clinker, 45 parts green zeolite, 30 parts bentonite, 35 parts graphite polystyrene foamed particles, 6 parts graphene, and 7 parts fiber (including 0.8 parts wood fiber and 6.2 parts silica fiber).

[0103] The admixtures, based on 100 parts of silicate cement, are as follows (by weight): 6 parts silica fume, 2 parts calcium aluminate-based accelerator, 3 parts calcium formate, 1.5 parts polypropylene fiber reinforcing agent, 3 parts organosilicon composite water-repellent agent, 3.5 parts polycarboxylate-based high-efficiency water-reducing agent, 2.2 parts calcium chloride-sodium sulfate composite early-strength agent, 1.5 parts lithium-based sealing and curing agent, 2 parts redispersible latex powder, 2 parts xanthan gum powder, and 3.5 parts fumed silica.

[0104] Optional raw materials, based on 100 parts of silicate cement, include: 0.5 parts of hydroxypropyl methylcellulose ether, 0.5 parts of starch ether, and 18 parts of fly ash.

[0105] Water addition: The water-to-powder ratio is 0.4:1 (total powder mass is 302.5 parts, water addition is 121 parts).

[0106] 3. Preparation process

[0107] Discrete mixing: A planetary discrete mixer (model SJH-50, power 5.5kW) is used. First, silicate cement, purple clay clinker, green zeolite, bentonite, fiber, graphene, all admixtures and optional raw materials are put into the mixer and stirred at low speed for 5 minutes (500r / min). After mixing evenly, the preset amount of water is slowly added, the speed is adjusted to 1000r / min, and stirring is continued for 20 minutes to obtain a slurry that is evenly mixed, free of lumps and has good fluidity.

[0108] Material feeding: An automatic feeding machine (model BL-800, power 2.2kW) is used to uniformly inject the mixed slurry into a rectangular mold (300mm×300mm×150mm) at a speed of 1.0m³ / h. The material is fed into the mold until it is full. The surface is then leveled with a scraper to ensure a smooth surface and prevent material stratification and segregation.

[0109] Compression molding: A hydraulic press (model YAW-3000, pressure range 0-3000kN) is used to apply a constant pressure of 20MPa to the full tank of slurry, hold the pressure for 5 minutes, remove excess air from the slurry, make the slurry dense, and form a blank with a honeycomb skeleton structure.

[0110] Standing and demolding: Place the pressed blank along with the mold in a constant temperature and humidity environment of room temperature (22℃) and humidity of 60% for 10 hours. After the blank strength reaches 4MPa, demold it using a manual demolding device to obtain the blank.

[0111] Initial curing: Place the demolded green body into a constant temperature and humidity curing chamber (model SHBY-40B), set the temperature to 20℃ and the humidity to 70%, and cure for 36 hours to ensure the strength of the green body is stable and to avoid cracking and deformation.

[0112] High-speed precision cutting: A CNC high-speed cutting machine (model QG-600, power 7.5kW) is used to feed the initially cured blank (strength 0.5MPa) into the cutting station. The cutting speed is set to 2m / min and the cutting blade speed is 4000r / min. Vertical and horizontal bidirectional cutting is performed to ensure that the size of the cut block is 300mm×300mm×150mm and the cutting error is ≤±0.5mm.

[0113] Final curing: Place the cut and qualified blocks into a curing room, set the temperature to 20±2℃ and the humidity to 75%, and cure naturally for 28 days to obtain finished precast blocks.

[0114] 4. Characterization and Testing (Key Performance Data)

[0115] The test methods all refer to the corresponding national standards, and the specific test data are as follows:

[0116] Porosity: 42% (Test method: GB / T 1966-2005);

[0117] Average pore size: 80 nm (Test method: GB / T 1966-2005);

[0118] Specific surface area: 18.5 m² 2 / g (Test method: GB / T 19587-2004);

[0119] Ammonia absorption capacity: zeolite ammonia absorption value 165mg / g, purple clay clinker ammonia absorption value 90mg / g (test method: GB / T17669.3-1999).

[0120] Compressive strength: 18MPa (cured for 28 days, test method: GB / T 4111-2013);

[0121] Flexural strength: 2.8 MPa (cured for 28 days, test method: GB / T 4111-2013);

[0122] Antistatic surface resistance: 5×10 7 Ω (Test method: GB / T 1410-2006);

[0123] Fire rating: Class A non-combustible, fire resistance limit 2.2h (test method: GB / T 8624-2012);

[0124] Permeability coefficient: 8×10 -8 cm / s (Test method: GB / T 50082-2009);

[0125] Flexible conversion initial pressure: 3MPa, deformation during conversion: 4mm (test method: GB / T 50081-2019).

[0126] Dimensional change rate: 0.08% (placed in a humid underground environment for 30 days, test method: GB / T 4111-2013);

[0127] The block prepared in this embodiment exhibits a honeycomb skeleton fragmentation rate of over 93.5% when subjected to a pressure of 1 MPa or higher, specifically 1.2 MPa, resulting in a block with predominantly flexible physical properties. The raw materials, proportions, and preparation process are consistent with those in Example 1. Characterization tests show that after applying 1.2 MPa pressure, the skeleton fragmentation rate is 94.2%, and the overall deformation of the block reaches 5 mm. The block demonstrates stable flexibility and can effectively resist downhole dynamic pressure impacts.

[0128] The block prepared in this embodiment, when subjected to a pressure of 0.5 MPa, exhibits localized fragmentation of its honeycomb-like skeleton, causing the area near the pressure-bearing surface of the precast block to become flexible and tightly bonded to the surrounding area, resulting in a good sealing effect. As the pressure continues to increase, when the pressure reaches 1 MPa, the 300 mm side cube block completely transforms into a flexible material. The raw materials, proportions, and preparation process are consistent with those in Example 1. Tests show that at 0.5 MPa, the localized fragmentation area accounts for approximately 35%, improving the sealing performance by 20%; at 1.0 MPa, it becomes completely flexible with a deformation of 4.8 mm, achieving the optimal sealing effect.

[0129] When the building blocks prepared in this embodiment are subjected to high temperatures (≥600℃), the mixture of graphene and graphitic polystyrene foam particles filling the pores of the honeycomb skeleton structure will melt and shrink. At this time, the main structure of the building blocks is a honeycomb silicate material-based structure, which has excellent antistatic properties, is lightweight and flame-retardant; it also has good thermal insulation capabilities, with a thermal insulation coefficient ≤0.040W / (m·K). Tests show that after high-temperature melting and shrinkage, the surface resistivity of the building blocks drops to 1×10⁻⁶. 7 Ω, the fire resistance rating remains Class A non-combustible, and the fire resistance limit is increased to 2.5h, which can effectively prevent the spread of fire when it starts in a coal mine.

[0130] On average, there are 5 to 7 (specifically 6) graphite polystyrene foam particles in each pore of the honeycomb skeleton. The raw materials, proportions, and preparation process are the same as in Example 1, except that the filling density of the graphite polystyrene foam particles is adjusted. This filling amount makes the flexible transformation of the block more uniform, reduces the deformation fluctuation range to ±0.2mm, and at the same time ensures the lightweight characteristics of the block, maintaining a weight of about 9.0kg.

[0131] Figure 1 This is a comparative diagram of the mesopore size distribution of Zisha clay. The diagram shows that the pores of Zisha clay can replace 3A and 5A molecular sieves; zeolite can replace macroporous molecular sieves; Zisha clay controls the balance of calcium and magnesium, while zeolite controls the balance of free salts; thus ensuring the material's long-term strength.

[0132] Example 2

[0133] Based on Example 1, the raw materials, proportions, preparation process, and characterization tests were all consistent with Example 1, except that the amount of graphene added was increased to 130% of the total graphene content. After filling, the surface resistivity of the block decreased to 3 × 10⁻⁶. 7 Ω significantly improves conductivity, making it suitable for scenarios with higher requirements for anti-static properties in underground wells.

[0134] Example 3

[0135] Compared to Example 1, the difference lies in the fiber ratio: 0.8 parts wood fiber and 6.2 parts silica fiber (i.e., 0.5 to 1 part by weight of wood fiber and 5 to 7 parts by weight of silica fiber) are adjusted to provide tension and support when the honeycomb skeleton collapses, increasing overall toughness. The raw materials, other ratios, and preparation process are consistent with Example 1. Characterization tests show that the adjusted block's flexural strength increased to 3.0 MPa, with no significant scattering after skeleton collapse, and significantly enhanced toughness.

[0136] Example 4

[0137] Compared to Example 1, the difference lies in the following: the precast blocks are cubes with a side length of 300mm, a standard weight of 9.0kg, and the volume of one block is equivalent to that of 37 red bricks (standard red brick dimensions are 240mm×115mm×53mm), and the weight is equivalent to that of 3.5 red bricks (a single red brick weighs approximately 2.57kg). With simple auxiliary tools, workers can pick them up with one hand. The raw materials, proportions, preparation process, and core performance are all consistent with Example 1, only the mold size is adjusted to 300mm×300mm×300mm. These blocks are lightweight yet large in volume, significantly reducing the time spent on handling and laying, making them suitable for emergency construction scenarios.

[0138] Example 5

[0139] Compared to Example 1, the difference lies in the precast blocks: the precast blocks are cuboids with a standard size of 600mm × 300mm × 300mm. The raw materials, proportions, preparation process, and core performance are consistent with Example 1, only the mold size is adjusted. For example, under the same construction conditions (building a 10m² wall with a thickness of 300mm), using red machine-made bricks requires 4000 bricks, and hollow bricks require 513 bricks, while the blocks in this example only require 180 bricks. In terms of labor time, red machine-made bricks require 12 people working two full shifts (8 hours each), and hollow bricks require 6 people working one full shift, while the blocks in this example only require 5 people working 4.5 hours, significantly saving manpower and transportation vehicles, and improving construction efficiency.

[0140] Example 6

[0141] Compared with Example 1, the difference lies in the particle size of the graphite polystyrene foam particles in the precast blocks, which ranges from 0.1 mm to 0.3 mm and has a normal distribution with a mean of 0.22 mm (of which particles with a diameter of 0.20-0.24 mm account for 60%). The raw materials, other proportions, and preparation process are consistent with Example 1. Characterization tests show that when the honeycomb skeleton collapses, the graphite polystyrene foam particles with these parameters stabilize the flexible deformation of the blocks at 3.8-4.2 mm, meeting the design requirements. Simultaneously, the weight of the blocks is reduced to 8.8 kg, demonstrating a good overall weight reduction effect and facilitating handling.

[0142] Example 7

[0143] Compared with Example 1, the difference lies in that the raw materials also include hydroxypropyl methylcellulose ether and starch ether. Using the addition amounts of other components in Example 1 as a reference, 0.6 parts by weight of both hydroxypropyl methylcellulose ether and starch ether were added, based on 100 parts of silicate cement. The raw materials, remaining proportions, and preparation process are consistent with Example 1. After addition, the slurry fluidity increased by 15%, the block forming qualification rate increased to 99%, the dimensional error was further reduced to ±0.3 mm, and the construction performance was significantly optimized.

[0144] Example 8

[0145] Compared to Example 1, the difference lies in the addition of 7 parts by weight of fly ash to the blocks. Based on 100 parts of silicate cement, this increases the workability of the material, promoting the encapsulation of silicate materials onto graphene and graphite polystyrene foam particles, thus improving the quality of the honeycomb structure formation. The raw materials, remaining proportions, and preparation process are consistent with Example 1. After addition, the uniformity of the honeycomb skeleton pores increases by 25%, the porosity stabilizes at 41-43%, the compressive strength of the blocks increases to 18.5 MPa, and the structural stability is better.

[0146] Example 9

[0147] The isolation structure is constructed by splicing together multiple precast blocks as described in any of the preceding embodiments; wherein, an adhesive layer is provided between adjacent precast blocks, the adhesive layer using an organosilicon adhesive with a thickness of 2-3 mm; both the interface between the isolation structure and the rock mass and the surface of the isolation structure have a sprayed airtight layer, the airtight layer using a polyurethane airtight coating with a spray thickness of 0.5-1 mm; the isolation structure is 300 mm thick in a single-layer construction state. After splicing, the impermeability coefficient of this isolation structure is ≤5×10⁻⁶. -8 cm / s, overall compressive strength ≥16MPa, suitable for various enclosed scenarios in coal mines, convenient to construct and with excellent sealing effect.

[0148] Example 1 of this invention details the source, composition, proportion, and complete preparation process parameters of all raw materials, and provides test data and methods for 13 key properties, including porosity, compressive strength, and ammonia absorption value. Examples 2-8, based on this, made single-variable adjustments to key parameters such as graphene dosage, fiber ratio, block size, and type of additives, fully verifying the feasibility and adjustability of the technical solution, and supporting the scope of protection claimed in the claims.

[0149] Example 1 demonstrates that the blocks can transform from rigid to flexible under a pressure of 1.0-1.2 MPa; Example 3 demonstrates that the blocks retain their toughness after collapse; Examples 4 and 6 demonstrate the product's lightweight characteristics; Example 2 demonstrates the blocks' antistatic properties; the high-temperature test in Example 1 verifies the blocks' fire-resistant and heat-insulating properties; Example 9 further verifies the excellent impermeability and ease of construction after being constructed into an isolation structure. All performance data are supported by test methods and standards. Examples 5 and 9 also demonstrate the advantages of the blocks in improving construction efficiency and forming an integral, sealed structure, indicating that the specification fully explains the industrial application scenarios of the invention.

Claims

1. A lightweight purple clay ceramic block for sealing underground coal mines, characterized in that, The raw material composition of the purple clay lightweight ceramic blocks, by weight, with silicate cement as a base of 100 parts, is as follows: Basic cementitious materials and aggregates, by weight: 90 to 110 parts of silicate cement, wherein the mass fraction of free calcium oxide in the silicate cement is <1.5% and the mass fraction of magnesium oxide is <5%; The proportions are: 45 to 65 parts of Zisha clinker and 35 to 55 parts of zeolite, with a total proportion of 100 parts of Zisha clinker and zeolite. 25 to 35 parts bentonite; 30 to 40 parts of graphite polystyrene foam granules; Graphene 4 to 8 parts; 5 to 9 parts fiber; Admixtures are calculated by weight based on 100 parts of silicate cement. The mixture comprises 5-7 parts silica fume, 1.5-2.5 parts calcium aluminate-based accelerator, wherein the calcium aluminate-based accelerator is composed of: 5%-10% SiO2, 40%-50% Al2O3, and the balance being CaO; 2-4 parts calcium formate, wherein the calcium formate is composed of: 90%-98% Ca(HCOO)2, and the balance being unavoidable impurities; and 1-2 parts reinforcing agent, wherein the reinforcing agent is a polypropylene fiber reinforcing agent or a mineral powder reinforcing agent, wherein the polypropylene fiber reinforcing agent is composed of: 95%-99% polypropylene; and the mineral powder reinforcing agent is composed of: 25%-35% SiO2, 10%-25% Al2O3, 10%-25% CaO ... 15%–25%, with the remainder being CaO, MgO, and unavoidable impurities; 2–4 parts of organosilicon composite water-repellent agent, the composition of which by mass percentage is: 30%–40% organosilicon component, 10%–20% surfactant, and the remainder being carrier; 2–5 parts of polycarboxylate superplasticizer, the composition of which by mass percentage is: 40%–50% polycarboxylate groups, 5%–10% other additives, and the remainder being water; 1.5–3 parts of early-strength agent, the early-strength agent being a calcium chloride-sodium sulfate composite early-strength agent, the composition of which by mass percentage is: 40%–50% CaCl2, 30%–40% Na2SO4, and the remainder being additives; 1–2 parts of lithium-based sealing and curing agent, 1–3 parts of redispersible latex powder, 1–3 parts of xanthan gum powder, and 2–5 parts of fumed silica. The purple clay clinker is made by naturally weathering purple clay ore for 6 months, then drying it, and then firing it in a kiln at 700℃~850℃ for 6 hours. After firing, it is crushed and sieved to obtain clinker particles with a fineness of over 400 mesh. Its chemical composition by mass percentage is as follows: SiO2 60.0%~62.0%, Al2O3 19.5%~20.5%, Fe2O3 7.0%~8.5%, CaO 0.5%~0.8%, Na2O 0.05%~0.10%, K2O 1.0%~1.5%, MgO 1.2%~1.6%, TiO2 1.0%~1.2%, and loss on ignition 5.8%~6.5%.

2. The lightweight purple clay ceramic block for sealing underground coal mines according to claim 1, characterized in that, Based on 100 parts of silicate cement, the raw materials also include 0.1 to 1 part of hydroxypropyl methylcellulose ether, 0.1 to 1 part of starch ether, and 15 to 20 parts of fly ash by weight. The composition of the fly ash by mass percentage is: 40% to 50% SiO2, 20% to 30% Al2O3, with the balance being Fe2O3 and other unavoidable impurities.

3. The lightweight purple clay ceramic block for sealing underground coal mines according to claim 1, characterized in that, The zeolite is green zeolite with an ammonia absorption value >150mg / g; The fibers include wood fibers and silica fibers. Based on 100 parts of silicate cement, the wood fibers are 0.5 to 1 part and the silica fibers are 5 to 7 parts. The wood fibers have a length of 3 mm to 5 mm and a diameter of 20 μm to 50 μm. The silica fibers have a length of 6 mm to 10 mm and a diameter of 10 μm to 30 μm. The graphite polystyrene foam particles have a particle size of 0.1 mm to 0.3 mm, and their composition by mass percentage is: 80% to 90% polystyrene and 10% to 20% graphite; the graphene has a thickness of 0.5 nm to 1.5 nm, a sheet diameter of 1 μm to 5 μm, and a graphene purity of 95% to 99%.

4. The lightweight purple clay ceramic block for sealing underground coal mines according to claim 1, characterized in that, The rigid-to-flexible transformation of the purple clay lightweight ceramic block exhibits good reversibility. The test method is as follows: a pressure testing machine is used to apply pressure to the block. When the pressure reaches 0.4MPa to 0.5MPa, the honeycomb skeleton breaks, and the block as a whole becomes flexible, with a deformation of 3mm to 5mm. After the pressure is removed, the block can maintain its flexible state for 2h to 4h, and then gradually returns to its initial rigid state. After repeating the test 5 to 8 times, the block can still maintain good rigid-to-flexible transformation performance without obvious damage or strength reduction. The purple clay lightweight ceramic blocks also possess the following properties: Compressive strength: After 28 days of curing, the compressive strength is 0.3 MPa to 0.4 MPa; Antistatic surface resistance: 1 x 10 6 Ω ~ 1 x 10 9 Ω meet the requirements of downhole antistatic; Fire resistance rating: It meets the Class A non-combustible standard, with a fire resistance rating of ≥2 hours; Adsorption performance: Zeolite ammonia adsorption value 150mg / g~180mg / g, purple clay clinker ammonia adsorption value 80 mg / g~100mg / g; Flexible conversion starting pressure: 1MPa~3MPa, deformation during conversion: 3mm~5mm; Impermeability: Permeability coefficient ≤ 1×10 -7 cm / s; Dimensional stability: In a humid underground environment with humidity of 80% to 90% and temperature of 10℃ to 30℃, after 30 days, the dimensional change rate is ≤0.1%.

5. A method for constructing lightweight purple clay ceramic blocks for underground sealing in coal mines according to any one of claims 1-4, characterized in that... Includes the following steps: S1. Discrete mixing: Using discrete mixing technology, all raw materials are first mixed evenly, then water is added and stirred at 800r / min~1200r / min for 15min~25min to obtain a uniformly mixed slurry; the mass ratio of water to raw materials is (0.35~0.45):1; S2. Material Discharge: The uniformly mixed slurry is injected into the mold box at a constant rate of 0.5m³ / h to 1.5m³ / h until the box is full, while keeping the surface flat; to prevent material stratification and segregation, and to ensure the uniformity of the internal structure of the blocks; S3. Pressing, Molding, and Demolding: Apply constant pressure to the full box of slurry, ranging from 15MPa to 25MPa, for 3 to 8 minutes to expel air, improve the density of the green body, and form a stable green body with a honeycomb-like continuous phase skeleton; then let it stand for 8 to 12 hours at room temperature (20℃ to 25℃) and humidity (50% to 70%) until the green body strength reaches 3 to 5MPa, then demold to obtain the green body; after demolding, an initial curing process is required, with an initial curing environment of 20℃ to 25℃ and humidity (60% to 80%) for 24 to 48 hours to ensure stable green body strength and avoid cracking and deformation after demolding; S4. High-speed precision cutting: When the blank strength is 0.3MPa~0.5MPa, the cutting speed is 1m / min~3m / min and the cutting blade speed is 3000r / min~5000r / min for precise vertical and horizontal bidirectional cutting, and the cutting error is controlled within ±0.5mm; S5. Stacking, Curing and Packaging: Qualified blocks are automatically stacked for subsequent curing. Curing conditions are as follows: curing period of 28 days, ambient temperature of 18℃~22℃, humidity of 70%~80%. After 28 days of curing, the compressive strength and flexural strength of the blocks are ≥0.5MPa and ≥0.5MPa, respectively. Standardized waterproof packaging is used, with 2 to 4 blocks per package, packaged in waterproof woven bags with heat-sealing technology to facilitate storage, transportation and underground loading and unloading.

6. The application of the lightweight purple clay ceramic block for underground sealing in coal mines as described in any one of claims 1-4, characterized in that, An isolation body for use in well sealing is provided, wherein the isolation body is constructed by splicing lightweight blocks; wherein an adhesive layer is provided between adjacent prefabricated two-phase blocks, and an airtight layer is provided at the junction of the isolation body and the rock mass and / or on the surface of the isolation body, formed by a sprayed coating layer.

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