Cemented filling material with large mixing amount of fly ash and high shear bearing capacity and preparation method of cemented filling material

Abstract

The invention provides a cemented filling material with a large mixing amount of fly ash and high shear bearing capacity and a preparation method of the cemented filling material, and relates to the technical field of mine filling. The cemented filling material comprises the following raw materials in percentage by mass: 70-80% of a solid material and 20-30% of water, wherein the total mass of the raw materials is 100%; the solid material comprises the following components in parts by weight: 55-70 parts of fly ash, 2-5 parts of cement, 5-15 parts of slag, 2-5 parts of carbide slag, 21-35 parts of tailings, 0.1-1 part of a fiber material and 1-3 parts of a composite activator. The cementing filling material breaks through three aspects of improving the activity of the fly ash through synergistic excitation modification, optimizing the structure through aggregate particle gradient grading design and reducing performance fluctuation through intelligent process control, so that efficient activation excitation of the volcanic ash activity of the fly ash can be realized, the mixing amount of the fly ash is increased, and the cost of the filling material is reduced; the problem that an existing filling material is low in anti-shearing bearing capacity is solved.

Description

Technical Field

[0001] This application relates to the field of mine backfilling technology, and in particular to a cemented backfilling material with high shear bearing capacity and a method for preparing it, containing a large amount of fly ash. Background Technology

[0002] Cemented tailings backfilling involves mixing tailings with a certain amount of cementitious material (such as cement) to form a backfill slurry. After solidification and hardening, it forms a backfill body with a certain strength to provide a mining platform, support the surrounding rock, and control ground pressure activity. As an important supporting structure for the goaf, the shear strength of the backfill body is one of the key indicators for evaluating its performance. If the shear strength of the backfill body is insufficient, it is prone to fracture, slippage, and other damage under shear force, leading to the loss of effective support for the goaf and subsequently causing serious safety accidents such as surrounding rock collapse and surface subsidence.

[0003] Traditional cemented backfill materials use cement as the main binder and fine tailings as aggregate. Cement-cemented fine tailings often suffer from problems such as prolonged setting time of the backfill slurry and slow strength development of the backfill body. In addition, cement costs account for too high a proportion in cemented tailings backfilling, typically reaching 50%-80% of the total cost of mine backfilling. Cement production consumes large amounts of resources such as limestone and coal, and emits large amounts of greenhouse gases and pollutants such as carbon dioxide and sulfur dioxide, putting significant pressure on the environment.

[0004] Fly ash is a solid waste generated during the high-temperature combustion process in coal-fired power plants and other enterprises. It mainly consists of unburned coal powder particles and fly ash, with a particle size typically between 1-100 μm. In mine backfilling, fly ash can be used as a cementing material, reducing the amount of cement and other cementing materials used while improving the strength and stability of the backfill. Simultaneously, it can be used as aggregate, improving the fluidity of the backfill slurry and reducing bleeding and segregation. Fly ash is widely available and inexpensive. Using fly ash as a backfill material can significantly reduce backfilling costs, minimize the land occupation and environmental pollution caused by fly ash accumulation, and achieve the resource utilization of solid waste, aligning with the concept of green development.

[0005] Fly ash is a "potentially cementitious active material," requiring activators to activate its pozzolanic activity. However, the effect of activating fly ash activity through a single method is limited, resulting in a restriction on the amount of fly ash in the filling material. At high dosages, the slow pozzolanic reaction leads to insufficient strength, making it difficult to meet the shear strength requirements of underground filling bodies. In addition, fly ash particles are mainly fine powder, and at high dosages, the particle size distribution range of the material is further narrowed, easily forming a "fine particle suspended structure" with a porosity of 25%-30%, reducing the shear strength of the filling body. The shear bearing capacity of the filling body is generally low, making it prone to shear failure in high-stress mining areas, leading to accidents such as roadway deformation and roof collapse.

[0006] Therefore, there is an urgent need to provide a cemented filling material to solve the above problems. Summary of the Invention

[0007] The purpose of this application is to provide a high-shear-capacity cemented filling material with a large amount of fly ash and its preparation method, so as to solve the above problems.

[0008] To achieve the above objectives, the first aspect of this application provides a high-shear-capacity cemented filling material with a large amount of fly ash, the raw materials of which include solid materials; The solid material, by weight, includes: 55-70 parts fly ash, 2-5 parts cement, 5-15 parts slag, 2-5 parts calcium carbide slag, 21-35 parts tailings, 0.1-1 parts fiber materials, and 1-3 parts composite activator.

[0009] Optionally, the high-volume fly ash cementitious backfill material with high shear capacity meets at least one of the following conditions: (1) The specific surface area of ​​the fly ash is 350-450 m². 2 / kg; (2) The fly ash includes Class I fly ash and / or Class II fly ash; (3) The loss on ignition of the fly ash is ≤5%.

[0010] Optionally, the high-volume fly ash cementitious backfill material with high shear capacity meets at least one of the following conditions: (1) The slag includes S95 grade granulated blast furnace slag; (2) The specific surface area of ​​the slag is 400-500 m². 2 / kg; (3) The mass content of Ca(OH)2 in the carbide slag is ≥80%; (4) The fineness of the carbide slag is 80-120 mesh.

[0011] Optionally, the tailings include coarse tailings and fine tailings; the coarse tailings have a particle size of 0.5-2.0 mm, and the fine tailings have a particle size of 0.075-0.5 mm.

[0012] Optionally, the high-volume fly ash cementitious backfill material with high shear capacity meets at least one of the following conditions: (1) The mud content of the coarse tailings is ≤3%; (2) The mud content of the fine tailings is ≤5%; (3) The mass ratio of the coarse tailings to the fine tailings is 1.5-2.5:1.

[0013] Optionally, the fibrous material includes one or more of steel fibers, basalt fibers, and polypropylene fibers.

[0014] Optionally, the high-volume fly ash cementitious backfill material with high shear capacity meets at least one of the following conditions: (1) The steel fiber has a length of 10-15 mm and a diameter of 0.3-0.5 mm; (2) The basalt fibers are 6-12 mm in length and 10-20 μm in diameter; (3) The polypropylene fiber has a length of 8-10 mm and a diameter of 20-30 μm.

[0015] Optionally, the raw materials of the composite activator, based on a total mass of 100%, include: Water glass 40-50%, sodium sulfate 15-25%, nano SiO2 5-10%, sodium aluminate 3-8%, balance water.

[0016] A second aspect of this application provides a method for preparing the high-shear-capacity cemented backfill material with a large amount of fly ash, comprising: The raw materials of the cementitious filling material are mixed to obtain a slurry; The slurry is cured to obtain the cemented filling material.

[0017] Optionally, the preparation method of the high-shear-capacity cemented backfill material with high fly ash content satisfies at least one of the following conditions: (1) The mixture includes: Fly ash, cement, slag, and carbide slag are mixed in a first mixing process to obtain a first mixture. The first mixture and tailings are then mixed a second time to obtain a second mixture; The second mixture and the fibrous material are then mixed a third time to obtain a third mixture; The third mixture, the composite activator, and water are then mixed in a fourth mixture. (2) The water content in the slurry is 20-30% by mass.

[0018] Compared with the prior art, the beneficial effects of this application include: The high-shear-capacity cemented backfill material with high fly ash content provided in this application achieves breakthroughs in three aspects: synergistic activation modification to enhance fly ash activity, aggregate particle gradient gradation design to optimize structure, and intelligent process control to reduce performance fluctuations. This enables efficient activation of fly ash pozzolanic activity, increases fly ash content, reduces backfill material costs, and solves the problem of low shear-capacity in current backfill materials.

[0019] The method for preparing high-shear-capacity cemented backfill material with high fly ash content provided in this application is simple to operate and the raw materials are readily available. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation on the scope of this application.

[0021] Figure 1 The images show the raw materials, cementitious filling material, and cementitious filling slurry of the high-shear-capacity cemented filling material with high fly ash content provided in Example 1. Figure 2 SEM image of a cemented backfill material with high shear capacity and high fly ash content; Figure 3 This is a test diagram for tensile strength. Detailed Implementation

[0022] First, the solution provided in this application will be explained in more detail as follows: The first aspect of this application provides a cementitious backfill material with high shear bearing capacity and large amount of fly ash, the raw materials of which include solid materials; The solid material, by weight, includes: 55-70 parts fly ash, 2-5 parts cement, 5-15 parts slag, 2-5 parts calcium carbide slag, 21-35 parts tailings, 0.1-1 parts fiber materials, and 1-3 parts composite activator.

[0023] Optionally, the solid materials, by weight, can be any value between 55, 60, 65, 70, or 55-70 parts for fly ash; any value between 2, 3, 4, 5, or 2-5 parts for cement; any value between 5, 10, 15, or 5-15 parts for slag; any value between 2, 3, 4, 5, or 2-5 parts for carbide slag; any value between 2, 3, 4, 5, or 2-5 parts for tailings; any value between 21, 25, 30, 35, or 21-35 parts for fibrous materials; any value between 0.1, 0.5, 1, or 0.1-1 parts for composite activator; and any value between 1, 2, 3, or 1-3 parts for composite activator.

[0024] It is important to note that the high-shear-capacity cemented backfill material with high fly ash content of this invention, through the synergistic effect of slag (providing active SiO2 and Al2O3), carbide slag (providing an alkaline environment of Ca(OH)2), and composite activator (high alkaline environment + sulfate + nanocrystal nuclei), forms a "solid waste-chemical" dual-activation system. This effectively disrupts the glassy structure on the surface of fly ash, promotes the dissolution of active SiO2 and Al2O3, and reacts with Ca... 2+The reaction generates more CSH gel and ettringite, significantly improving the hydration degree and cementitious activity of fly ash, and greatly increasing the fly ash content in cemented backfill materials. By incorporating fibers into the backfill material to form a three-dimensional network structure, when the backfill material is subjected to shear force, the fibers bear part of the stress through interfacial bonding force, preventing crack initiation and propagation, and significantly improving the shear strength and toughness of the backfill material. Different types of fibers can be selected according to engineering requirements; steel fiber reinforcement provides the best effect, while polypropylene fiber has the lowest cost.

[0025] In some embodiments, the high-volume fly ash high-shear-capacity cementitious filling material satisfies at least one of the following conditions: (1) The specific surface area of ​​the fly ash is 350-450 m². 2 / kg; Optionally, the specific surface area of ​​fly ash can be 350 m². 2 / kg, 400 m 2 / kg, 450 m 2 / kg or 350-450m 2 Any value between / kg; (2) The fly ash includes Class I fly ash and / or Class II fly ash; (3) The loss on ignition of the fly ash is ≤5%.

[0026] Optionally, the loss on ignition of fly ash can be any value of 1%, 2%, 3%, 4%, 5% or ≤5%.

[0027] It is important to note that fly ash, as the main raw material, participates in the hydration reaction through pozzolanic activity, generating cementitious products that improve the mechanical properties of the filling material, and also plays a filling role, increasing the density of the filling material; therefore, it is recommended to use Grade I or II fly ash with a specific surface area of ​​350-450 m². 2 When within the range of / kg, it can be guaranteed to have good potential volcanic ash activity.

[0028] In some embodiments, the cement includes 42.5 grade ordinary Portland cement, which can provide early hydration kinetics for the filler material, work synergistically with other cementing materials to improve the early strength of the filler material, and significantly reduce the cost of the filler material.

[0029] In some embodiments, the high-volume fly ash high-shear-capacity cementitious filling material satisfies at least one of the following conditions: (1) The slag includes S95 grade granulated blast furnace slag; (2) The specific surface area of ​​the slag is 400-500 m². 2 / kg; Optionally, the specific surface area of ​​the slag can be 400 m².2 / kg, 450 m 2 / kg, 500 m 2 / kg or 400-500m 2 Any value between / kg; (3) The mass content of Ca(OH)2 in the carbide slag is ≥80%; Optionally, the mass content of Ca(OH)2 in the carbide slag can be any value of 80%, 85%, 90%, 95% or ≥80%; (4) The fineness of the carbide slag is 80-120 mesh.

[0030] Optionally, the fineness of the carbide slag can be 80 mesh, 90 mesh, 100 mesh, 110 mesh, 120 mesh or any value between 80 and 120 mesh.

[0031] It should be noted that slag and carbide slag serve as auxiliary cementing materials and activating components. Slag provides active SiO2 and Al2O3, while carbide slag provides an alkaline environment of Ca(OH)2. The two complement fly ash and jointly promote the hydration reaction.

[0032] In some embodiments, the tailings include coarse tailings and fine tailings; the coarse tailings have a particle size of 0.5-2.0 mm, and the fine tailings have a particle size of 0.075-0.5 mm.

[0033] Optionally, the particle size of coarse tailings can be any value between 0.5mm, 1mm, 1.5mm, 2mm or 0.5-2mm, and the particle size of fine tailings can be any value between 0.075mm, 0.1mm, 0.2mm, 0.3mm, 0.4mm, 0.5mm or 0.075-0.5mm.

[0034] It should be noted that, as aggregate, coarse tailings (0.5-2.0mm) form the skeleton structure, while fine tailings (0.075-0.5mm) fill the gaps between coarse tailings. The aggregate particle size distribution is optimized by a mass ratio of 1.5-2.5:1 to improve the density of the filling material.

[0035] In some embodiments, the high-volume fly ash high-shear-capacity cementitious filling material satisfies at least one of the following conditions: (1) The mud content of the coarse tailings is ≤3%; Optionally, the mud content of the coarse tailings can be any value of 1%, 2%, 3% or ≤3%; (2) The mud content of the fine tailings is ≤5%; Optionally, the mud content of the fine tailings can be any value of 1%, 2%, 3%, 4%, 5% or ≤5%; (3) The mass ratio of the coarse tailings to the fine tailings is 1.5-2.5:1.

[0036] Optionally, the mass ratio of coarse tailings to fine tailings can be 1.5:1, 2:1, 2.5:1, or any value between 1.5 and 2.5:1.

[0037] It is important to note that by rationally designing the ratio of coarse tailings (0.5-2.0mm) to fine tailings (0.075-0.5mm) (1.5-2.5:1), the coarse particles form a skeleton structure, the fine particles fill the gaps between the coarse particles, and cementing materials such as fly ash fill the gaps between the fine particles, achieving a "coarse-fine-micro" tiered dense stacking, reducing the porosity of the filling material, improving structural integrity, and enhancing the shear bearing capacity of the filling material.

[0038] In some embodiments, the fibrous material includes one or more of steel fibers, basalt fibers, and polypropylene fibers.

[0039] It is important to note that fibrous materials prevent crack propagation through bridging, thereby improving the shear resistance and toughness of the filling material. Steel fibers, basalt fibers, or polypropylene fibers can be selected, with their length and diameter optimized to ensure dispersion and reinforcement.

[0040] In some embodiments, the high-volume fly ash high-shear-capacity cementitious filling material satisfies at least one of the following conditions: (1) The steel fiber has a length of 10-15 mm and a diameter of 0.3-0.5 mm; Optionally, the length of the steel fiber can be any value between 10mm, 11mm, 12mm, 13mm, 14mm, 15mm or 10-15mm, and the diameter can be any value between 0.3mm, 0.4mm, 0.5mm or 0.3-0.5mm. (2) The basalt fibers are 6-12 mm in length and 10-20 μm in diameter; Optionally, the length of the basalt fiber can be any value between 6mm, 7mm, 8mm, 9mm, 10mm, 11mm, 12mm or 6-12mm, and the diameter can be any value between 10μm, 15μm, 20μm or 10-20μm. (3) The polypropylene fiber has a length of 8-10 mm and a diameter of 20-30 μm.

[0041] Optionally, the length of the polypropylene fiber can be any value between 8mm, 9mm, 10mm or 8-10mm, and the diameter can be any value between 20μm, 25μm, 30μm or 20-30μm.

[0042] In some embodiments, the raw materials of the composite activator, based on a total mass of 100%, include: Water glass 40-50%, sodium sulfate 15-25%, nano SiO2 5-10%, sodium aluminate 3-8%, balance water.

[0043] Optionally, the raw materials of the composite activator, based on a total mass of 100%, may be: water glass (40%, 45%, 50%, or any value between 40-50%), sodium sulfate (15%, 20%, 25%, or any value between 15-25%), nano-SiO2 (5%, 6%, 7%, 8%, 9%, 10%, or any value between 5-10%), and sodium aluminate (3%, 4%, 5%, 6%, 7%, 8%, or any value between 3-8%).

[0044] It is important to note that multiple components synergistically stimulate the activity of fly ash: water glass provides an alkaline environment, disrupting the glassy structure of fly ash; sodium sulfate promotes the formation of ettringite; nano-SiO2 acts as a crystal nucleus to accelerate the hydration reaction; and sodium aluminate increases the aluminum content of the hydration products, enhancing structural stability.

[0045] Synergistic effect among components in the composite activator: In the composite activator, water glass is a soluble alkali metal silicate material, the main component of which is sodium silicate (Na2O•nSiO2). Water glass first undergoes a hydrolysis reaction in aqueous solution, rapidly increasing the pH value of the system and creating a strongly alkaline environment, promoting the dissolution and ionization of sodium sulfate; the silicate ions (SiO3-) produced by the hydrolysis of water glass... 2- It can react with sodium sulfate to form ettringite (AFt), which interweaves with it to form a more stable skeleton structure, thereby improving the strength and structural stability of the filling.

[0046] Nano-SiO2 has a large specific surface area and extremely high pozzolanic activity. The alkaline environment provided by water glass can promote the reaction between silanol groups (Si-OH) on the surface of nano-SiO2 and calcium hydroxide (Ca(OH)2), accelerating the formation of calcium silicate hydrate (CSH) gel. At the same time, nano-SiO2 can also fill the pores of CSH gel generated by the hydrolysis of water glass and reaction products such as AFt generated by the reaction of sodium sulfate, making the gel structure more compact.

[0047] Sodium aluminate hydrolysis can produce aluminum hydroxide (Al(OH)3) colloid and sodium ions (Na+). + ), and SiO3 produced by the hydrolysis of water glass 2- These factors work together to form products such as hydrated calcium aluminum silicate, increasing the strength of the filling material. Furthermore, the alkaline environment provided by water glass promotes the hydrolysis of sodium aluminate, generating more Al(OH)3 colloids. The Na+ produced by the hydrolysis of sodium aluminate... + Na ionized with sodium sulfate+ The combined effect can accelerate the hydration of cement particles; the hydrolysis products of sodium aluminate and the SO4 released from the dissociation of sodium sulfate 2- The reaction generates AFt and hydrated calcium aluminate (CAH), optimizing the structure of the hydration products; the Al(OH)3 colloid generated by the hydrolysis of sodium aluminate can interact with the active sites on the surface of nano-SiO2 to form a more stable gel network structure and improve the strength of the filling.

[0048] Synergistic effect of composite activator with other components in solid material: Composite activators play a crucial role in activating the potential activity of fly ash and mineral powder. The alkaline environment generated by the hydrolysis of water glass can disrupt the glassy network structure in fly ash and slag, promoting the dissolution of active components such as SiO2 and Al2O3, which then react with Ca(OH)2 and SO4 dissociated from sodium sulfate in the system. 2- The reaction generates CSH gel and AFt; the high activity and small size effect of nano-SiO2 can synergistically react with the active components in fly ash and slag to generate more CSH gel; the Al(OH)3 colloid produced by the hydrolysis of sodium aluminate can also form products such as hydrated calcium aluminate with cementing properties with fly ash and slag, thereby improving the strength of the filling body.

[0049] Cement hydration is crucial for providing early strength, and composite activators can effectively promote the cement hydration process. Sodium sulfate ionizes to produce Na... + It can be adsorbed on the surface of cement particles, reducing their surface energy and accelerating the hydrolysis reaction of tricalcium silicate (C3S) and dicalcium silicate (C2S) in cement clinker, enabling cement to generate CSH gel and Ca(OH)2 more quickly and improving the early strength of the filling body; the alkaline environment generated by the hydrolysis of water glass can also promote the hydration reaction of cement.

[0050] The main component of calcium carbide slag is Ca(OH)2, which has a certain alkalinity. The composite activator works synergistically with the calcium carbide slag to effectively utilize the calcium source within it. SiO3 is produced by the hydrolysis of water glass. 2- It can react with Ca in carbide slag 2+ The sodium sulfate combines to form a gelling CSH gel. SO42- ions from the ionization of sodium sulfate... 2- With Ca 2+ The reaction generates AFt, which further enhances the strength of the filling material. At the same time, the alkaline components in the composite activator complement the alkalinity of the carbide slag, maintaining the alkaline environment of the system and promoting the activation of raw materials such as fly ash and slag.

[0051] Tailings provide the basic skeletal structure for the backfill, while the composite activator works synergistically with the tailings to enhance the adhesion between the tailings and other cementing components. The composite activator stimulates the formation of hydration products such as CSH gel and AFt in cementing materials like fly ash and slag, which tightly encapsulate tailings particles, forming effective bonding bridges between them and creating a tight, integrated bond between the tailings and the cementing materials. The small size effect of nano-SiO2 allows it to fill the tiny pores between the tailings and the cementing materials, further enhancing the interfacial bonding strength.

[0052] Fiber-based materials primarily enhance their toughness and crack resistance through their inherent physical properties. Composite activators promote the hydration reaction of cementitious materials, generating more CSH gel products that better encapsulate the fibers, strengthening the interfacial bond between the fibers and the cementitious material. Simultaneously, the fibers provide more attachment sites for the growth of hydration products, resulting in a more uniform distribution of these products around the fibers, optimizing the material's microstructure, and thus improving both strength and toughness.

[0053] It is also important to note the synergistic effect of the various raw materials in the cementitious filling material: This system uses fly ash as the base and cement, slag, carbide slag, tailings, fiber materials, and composite activators as auxiliary materials. It reduces costs and optimizes strength development through a combination of main and auxiliary materials.

[0054] The "dual effect" of fly ash serves two purposes: firstly, as an inert filler, it fills the gaps between material particles, optimizes material gradation, and reduces overall porosity; secondly, through "secondary hydration," it generates additional CSH gel, compensating for later strength loss, reducing cement usage, and lowering costs. The CSH gel and Ca(OH)2 generated during cement hydration are the main sources of early strength, rapidly improving the initial stability of the backfill. The active components in slag react with the Ca(OH)2 provided by cement and carbide slag, generating more CSH gel and CAH gel, significantly improving the mid-to-late-stage strength of the backfill. The main component of carbide slag is Ca(OH)2, which provides an alkaline environment for the activation of fly ash and slag, promoting secondary hydration reactions; secondly, it replaces part of the cement, utilizing the characteristics of industrial solid waste to reduce raw material costs, while supplementing the calcium content in the system to ensure sufficient hydration reactions.

[0055] Tailings particles, acting as inert aggregates, are uniformly dispersed in the cementitious system, forming the basic structural framework of the backfill and bearing external loads. The particle size distribution of tailings complements that of fine particles such as fly ash and slag, filling the tiny voids between backfill materials, further reducing the porosity of the backfill, increasing overall density, and indirectly improving strength.

[0056] The fiber-like materials are uniformly dispersed inside the material, which can prevent crack propagation through "bridging effect", reduce the generation of macro cracks, and improve crack resistance. The fiber surface forms a good bond with CSH gel, which enhances the interfacial bonding force between the fiber and the matrix and further optimizes the overall mechanical properties.

[0057] The composite activator can break the inert SiO2 and Al2O3 glassy structure on the surface of fly ash and slag, accelerating their secondary hydration reaction with Ca(OH)2 and shortening the early strength development cycle. The composite activator can promote more uniform generation and distribution of hydration products, reduce the precipitation of coarse crystals (such as Ca(OH)2), and form a denser CSH gel network structure, further improving the strength of the filling material. A second aspect of this application provides a method for preparing the high-shear-capacity cemented filling material with a large amount of fly ash, comprising: The raw materials of the cementitious filling material are mixed to obtain a slurry; In some embodiments, the solid material is pretreated, the pretreatment including drying and passing through an 80-mesh sieve to remove impurities; In some embodiments, a PLC control system is used for intelligent batching; The slurry is cured to obtain the cemented filling material.

[0058] Optionally, the temperature for maintenance can be 18-22℃, and the humidity ≥90%.

[0059] Optionally, the preparation method of the high-shear-capacity cemented backfill material with high fly ash content satisfies at least one of the following conditions: (1) The mixture includes: Fly ash, cement, slag, and carbide slag are mixed in a first mixing process to obtain a first mixture. In some embodiments, the first mixing time is 1-2 minutes and the rotation speed is 100-150 r / min; The first mixture and tailings are then mixed a second time to obtain a second mixture; In some embodiments, the second mixing time is 1-2 minutes and the rotation speed is 150-200 r / min; The second mixture and the fibrous material are then mixed a third time to obtain a third mixture; In some embodiments, the third mixing time is 30-60 seconds; The third mixture, the composite activator, and water are then mixed in a fourth mixture.

[0060] In some embodiments, the rotational speed of the fourth mixing is controlled to be 200-300 r / min, and the flowability is 180-220 mm; (2) The water content in the slurry is 20-30% by mass.

[0061] Optionally, the water content in the slurry can be any value between 20%, 25%, 30%, or 20-30%.

[0062] The implementation schemes of this application will be described in detail below with reference to specific embodiments. However, those skilled in the art will understand that the following embodiments are only for illustrating this application and should not be regarded as limiting the scope of this application. Unless otherwise specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments used without specified manufacturers are all conventional products that can be purchased commercially.

[0063] Example 1 The first aspect of this embodiment provides a high-shear-bearing capacity cemented filling material with a large amount of fly ash, comprising 30 parts by weight of water and 70 parts by weight of solid material; The solid material consists of the following raw materials in parts by weight: fly ash (Grade II fly ash, specific surface area of ​​450 m²). 2 / kg, loss on ignition ≤5%) 55 parts, 42.5 grade ordinary Portland cement 5 parts, slag (S95 grade granulated blast furnace slag, specific surface area 480m²) 2 / kg, 7d activity index 75%, 28d activity index 102%) 10 parts, carbide slag 3 parts, coarse tailings (particle size 0.5-2.0mm, mud content ≤3%) 15 parts, fine tailings (particle size 0.075-0.5mm, mud content ≤5%) 10 parts, steel fiber (length 12mm, diameter 0.4mm), composite activator 1 part; The composite activator, by total mass of 100%, includes: 40% water glass, 25% sodium sulfate, 25% nano-SiO, 5% sodium aluminate, and 25% water.

[0064] The second aspect of this embodiment provides a method for preparing a cemented backfill material with high shear capacity and large fly ash content, as detailed below: (1) Mix the composite activator with water to prepare an activator solution; (2) Dry mix fly ash, cement, slag, and carbide slag for 1 minute (100 r / min); (3) Add coarse tailings and fine tailings, and dry mix for 1 minute (150 r / min). (4) Add steel fibers and dry mix for 30 seconds; (5) Add activator to obtain solid material (cemented filling material), then add water and wet mix for 4 min (200 r / min), control the fluidity to 200 mm, and obtain cemented filling slurry; (6) After the cemented filling grout is formed, it is cured at 20℃ and 95% humidity for 3 days, 7 days and 28 days.

[0065] Among them, the raw materials for high-shear-bearing-capacity cemented backfill materials with high fly ash content, as well as the physical samples of the prepared cemented backfill materials and cemented backfill slurries, are as follows: Figure 1 As shown.

[0066] SEM images of high-shear-capacity cemented backfill materials with high fly ash content, such as... Figure 2 As shown.

[0067] Example 2 The difference from Example 1 is that the solid material is composed of the following raw materials in parts by weight: 60 parts fly ash, 5 parts cement, 10 parts slag, 2 parts carbide slag, 15 parts coarse tailings, 6 parts fine tailings, 0.5 parts basalt fiber (9 mm in length and 15 μm in diameter), and 1.5 parts composite activator.

[0068] The composite activator, by total mass of 100%, includes: 45% water glass, 20% sodium sulfate, 8% nano-SiO2, 7% sodium aluminate, and 25% water.

[0069] Example 3 The difference from Example 1 is that the solid material is composed of the following raw materials in parts by weight: 65 parts fly ash, 2 parts cement, 8 parts slag, 2 parts carbide slag, 15 parts coarse tailings, 6 parts fine tailings, 0.1 parts polypropylene fiber (8 mm in length and 25 μm in diameter), and 1.9 parts composite activator.

[0070] The composite activator, by total mass of 100%, includes: 50% water glass, 15% sodium sulfate, 10% nano-SiO2, 3% sodium aluminate, and 22% water.

[0071] Example 4 The difference from Example 1 is that the solid material is composed of the following raw materials in parts by weight: 68 parts fly ash, 2 parts cement, 5 parts slag, 2 parts carbide slag, 15 parts coarse tailings, 6 parts fine tailings, 0.5 parts steel fiber (12 mm in length and 0.4 mm in diameter), and 1.5 parts composite activator.

[0072] The composite activator, by total mass of 100%, includes: 55% water glass, 10% sodium sulfate, 12% nano-SiO2, 3% sodium aluminate, and 20% water.

[0073] Comparative Example 1 The difference from Example 1 is that the solid material is composed of the following raw materials in parts by weight: 50 parts fly ash, 20 parts cement, 15 parts coarse tailings, and 15 parts fine tailings. That is, no slag, carbide slag, fiber materials, or composite activators are added to the solid material.

[0074] Comparative Example 2 The difference from Example 1 is that the composite activator does not contain nano-SiO2.

[0075] Comparative Example 3 The difference from Example 1 is that sodium aluminate is not added to the composite activator.

[0076] Comparative Example 4 The difference from Example 1 is that sodium sulfate is not added to the composite activator.

[0077] Comparative Example 5 The difference from Example 1 is that no water glass is added to the composite activator.

[0078] Comparative Example 6 The difference from Example 1 is that the solid material does not contain cement.

[0079] Comparative Example 7 The difference from Example 1 is that the solid material does not contain tailings.

[0080] Comparative Example 8 The difference from Example 1 is that the solid material is composed of the following raw materials in parts by weight: 78 parts fly ash, 1.5 parts cement, 4 parts slag, 1 part carbide slag, 10 parts coarse tailings, 5 parts fine tailings, 0.05 parts steel fiber, and 0.45 parts composite activator.

[0081] The cemented filling materials prepared in the above examples and comparative examples were tested for tensile strength and compressive strength after curing for 3 days, 7 days, and 28 days, respectively. The tensile strength test results are shown in Table 1. The tensile strength test results are as follows: Figure 3 As shown in Table 2, the test results of the compressive strength are as follows.

[0082] Table 1 Tensile Strength (MPa)

[0083] Table 2 Compressive Strength (MPa)

[0084] analyze: From the above tests, we can see that: (1) A horizontal comparison of the test results of Examples 1, 2, 3 and 4 shows that, compared with basalt fiber and polypropylene fiber, the tensile strength and compressive strength of the filling material are significantly improved after the addition of steel fiber. The core mechanism is to achieve efficient stress transfer through "high strength bearing + strong interface bonding". The steel fiber itself has extremely high tensile strength and its elastic modulus is much higher than the other two types of fiber. It can efficiently bear the tensile stress generated inside the filling material like a "skeleton" and effectively suppress the generation and expansion of microcracks. In addition, steel fibers are mostly irregular structures such as end hook type and wave type, which can form a firm mechanical bond with the filling slurry. The "anchoring effect" can prevent the fiber from debonding from the matrix and ensure the continuous and effective transfer of stress.

[0085] (2) A comparison of the test results of Comparative Example 1 with those of Examples 1, 2, 3, and 4 shows that when fiber materials, slag, carbide slag, and composite activators are not added to the filling material, the tensile strength and compressive strength of the filling body are significantly reduced, especially the tensile strength. The tensile strength of Comparative Example 1 after 28 days of curing is reduced by 77.90%, 73.30%, 70.65%, and 75.72% respectively compared with Examples 1, 2, 3, and 4. This is mainly attributed to the loss of the synergistic effect of each raw material in activation, structural optimization, and stress transfer. Slag, as an auxiliary cementing material, can provide active SiO2 and Al2O3, which react with Ca(OH)2 in the system to generate CSH gel and CAH gel to supplement the strength in the middle and later stages. After its absence, the total amount of cementing products is reduced, and the internal... The density of the cementitious skeleton decreases; fibrous materials can form a three-dimensional network structure within the filling material, preventing crack propagation by bridging cracks and dispersing shear stress. Without these materials, the filling material is prone to macroscopic cracks under tension and rapid microcrack aggregation under compression, resulting in a loss of crack resistance and structural integrity. Calcium carbide slag provides a high content of Ca(OH)2, creating a strongly alkaline environment for the activation of fly ash and slag, promoting the dissolution of active components, and supplementing calcium sources to ensure CSH gel formation. Without this material, the system's pH value decreases, calcium sources are insufficient, and hydration reactions are incomplete. Without the composite activator, the activity of fly ash and slag is difficult to activate, hydration efficiency decreases significantly, and the amount and distribution of cementitious products are low and uneven, ultimately leading to increased porosity within the filling material, weakened aggregate particle bonding, and a significant reduction in tensile and compressive strength. Due to the high cement content in Comparative Example 1, there is a certain alkaline activation effect on fly ash, allowing the filling material to still maintain a certain compressive strength.

[0086] (3) Comparison of the test results of Comparative Examples 2, 3, 4, and 5 with those of Example 1 shows that the absence of any raw material in the composite activator leads to varying degrees of reduction in the tensile and compressive strength of the filling material. The tensile strength of Comparative Examples 2, 3, 4, and 5 after 28 days of curing decreased by 47.94%, 45.69%, 44.19%, and 46.82%, respectively, and the compressive strength after 28 days of curing decreased by 30.86%, 29.94%, 30.25%, and 34.88%, respectively. This is mainly because the core function of water glass is to hydrolyze in the system to generate a strongly alkaline environment, destroying the dense glassy structure on the surface of fly ash, providing the necessary conditions for the dissolution of active SiO2 and Al2O3. At the same time, the SiO3 produced by its hydrolysis 2- Can be used with Ca 2+ The CSH gel is formed. Without it, the system becomes insufficiently alkaline, the fly ash vitreous structure is difficult to break down, the hydration reaction is slow and incomplete, the amount of gel products generated is significantly reduced, the porosity of the filling increases, the tensile strength decreases due to the lack of gel bonding and crack resistance, and the compressive strength decreases due to insufficient structural density.

[0087] Sodium sulfate ionizes into SO4 in the system. 2- It can be used with Ca 2+ AlO2 - The reaction produces ettringite, which is distributed in a needle-like, interwoven pattern. This ettringite fills the tiny pores inside the infill, increasing the structural density. Simultaneously, the presence of sodium sulfate accelerates the hydration of cement particles, promoting early strength development. Without sodium sulfate, ettringite formation is hindered, pores cannot be effectively filled, structural integrity decreases, and early hydration kinetics are insufficient. This results in lower tensile strength of the infill due to the lack of ettringite bridging and crack resistance, and reduced compressive strength in later stages due to higher porosity and insufficient structural support.

[0088] Nano-SiO2 possesses an ultra-large specific surface area and high pozzolanic activity. On one hand, it can act as a "nucleus" to adsorb hydration products, accelerating gel formation and uniform distribution, and shortening the hydration reaction cycle. On the other hand, its tiny particle size can fill the fine pores between CSH gel and ettringite, further densifying the structure. When missing, the formation rate of hydration products slows down and their distribution becomes uneven, easily forming "weak areas." When the filler is subjected to tension, cracks are prone to occur and propagate in these weak areas, leading to a decrease in tensile and compressive strength.

[0089] Sodium aluminate hydrolyzes to produce Al(OH)3 colloid and Na⁺. The Al(OH)3 colloid can react with SiO₃. 2- Ca 2+ The reaction generates CAH gel, while simultaneously replenishing Al in the system. 3+ Promotes the formation of ettringite; Na +It can also adsorb onto the surface of cement particles, reducing surface energy and accelerating cement hydration. When missing, CAH gel formation decreases, the amount of ettringite produced is insufficient, and structural stability decreases, making it prone to cracking during tensile testing due to insufficient gel toughness.

[0090] (4) A comparison of the test results of Comparative Example 6 and Example 1 shows that the tensile and compressive strengths of the filling body are significantly reduced after cement is missing in the cemented filling material, especially the early strength (3d and 7d strength). Compared with Example 1, the tensile strength of Comparative Example 6 after 28 days of curing is reduced by 50.19% and the compressive strength is reduced by 38.07%. This is because cement is the core source of early hydration power of the system and plays an irreplaceable supporting role in the formation of the overall cemented structure. When cement comes into contact with water, it will quickly undergo a hydration reaction to generate CSH gel and Ca(OH)2. CSH gel is the main carrier of early cemented strength and can quickly bond fly ash, tailings and other particles to form the initial structure; Ca(OH)2 provides an initial alkaline environment for the activation of fly ash and slag, and promotes the further dissolution of the glassy structure of fly ash by the composite activator. Without cement, the early hydration reaction of the system slows down, the amount of CSH gel generated decreases sharply, and an effective cement skeleton cannot be formed in the early stage. At the same time, the initial supply of Ca(OH)2 is insufficient, which will delay the activation efficiency of the composite activator on fly ash activity. Even if carbide slag is added later to supplement alkalinity, it cannot make up for the strength loss caused by the early hydration lag.

[0091] (5) A comparison of the test results of Comparative Example 7 and Example 1 shows that the compressive strength and tensile strength of the filling body also decreased after the tailings were missing from the cemented filling material, but the decrease was less than that of the missing cement. Compared with Example 1, the tensile strength of Comparative Example 7 decreased by 37.45% and the compressive strength decreased by 27.88% after 28 days of curing. Coarse and fine tailings, as core aggregates, jointly undertake the roles of "skeleton support" and "gradation optimization". Their absence will directly destroy the structural integrity of the filling body, resulting in a significant decrease in tensile and compressive strength. From the perspective of structural support, coarse tailings are the "rigid skeleton core" of the filling body, with high particle hardness and strong resistance to deformation; fine tailings, on the other hand, act as "gap filler", filling the gaps between coarse tailings particles and reducing the large pores formed by the coarse particles. After the coarse tailings are missing, the filling body loses the rigid skeleton support, and the overall structure is in a "soft cemented state". Under pressure, it is prone to compression collapse due to the lack of a deformation-resistant aggregate skeleton. From the perspective of gradation and density, the coarse tailings and fine tailings are designed with a mass ratio of 1.5-2.5:1, which can achieve a "coarse-fine" particle gradient gradation. Combined with fine powder cementitious materials such as fly ash, a dense structure of "coarse particle skeleton - fine particle filling - cementitious material bonding" is formed, and the porosity can be controlled at a low level. When fine tailings are missing, the gaps between coarse tailings particles cannot be filled, resulting in a large number of interconnected large pores. The cementitious material cannot completely encapsulate the coarse tailings particles, leading to weakened interfacial bonding between the aggregate and the cementitious product. Under tension, cracks are easily generated at the interface, resulting in a decrease in tensile strength. If both coarse and fine tailings are missing, the system relies only on fine particles such as fly ash and slag, which easily forms a "fine-particle suspended structure" with dense and unevenly distributed internal pores. Under compression, stress concentrates at the pores, causing local structural damage and rapid propagation, resulting in a sharp drop in compressive strength. At the same time, the loose fine-particle structure lacks the bridging effect of aggregates, and cracks easily propagate rapidly along the pores under tension, further exacerbating the reduction in tensile strength.

[0092] (6) Comparison of the test results of Comparative Example 8 and Example 1 shows that when the proportion of cementitious filling material is not within the set dosage range, the tensile strength and compressive strength of the filling body are reduced. Compared with Example 1, the tensile strength of Comparative Example 8 after 28 days of curing is reduced by 35.96% and the compressive strength is reduced by 30.97%. This is because the set proportion of each raw material (such as 55-70 parts of fly ash, 2-5 parts of cement, 5-15 parts of slag, 2-5 parts of carbide slag, 21-35 parts of tailings, 0.1-1 parts of fiber materials, and 1-3 parts of composite activator) is designed based on the principle of "active synergy, dense structure, and balanced stress transmission". Deviation of the proportion will destroy the functional synergy of each component, resulting in a decrease in tensile strength and compressive strength.

[0093] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

[0094] Furthermore, those skilled in the art will understand that although some embodiments herein include certain features included in other embodiments but not others, combinations of features from different embodiments are intended to be within the scope of this application and form different embodiments. For example, any of the claimed embodiments can be used in any combination. The information disclosed in this background section is intended only to enhance the understanding of the general background of this application and should not be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

Claims

1. A high-shear-capacity cementitious filling material with a large amount of fly ash, characterized in that, Its raw materials include solid materials; The solid material, by weight, includes: 55-70 parts fly ash, 2-5 parts cement, 5-15 parts slag, 2-5 parts calcium carbide slag, 21-35 parts tailings, 0.1-1 parts fiber materials, and 1-3 parts composite activator.

2. The high shear capacity cemented filling material with high fly ash content according to claim 1, characterized in that, At least one of the following conditions must be met: (1) The specific surface area of ​​the fly ash is 350-450 m². 2 / kg; (2) The fly ash includes Class I fly ash and / or Class II fly ash; (3) The loss on ignition of the fly ash is ≤5%.

3. The high shear capacity cemented filling material with high fly ash content according to claim 1, characterized in that, At least one of the following conditions must be met: (1) The slag includes S95 grade granulated blast furnace slag; (2) The specific surface area of ​​the slag is 400-500 m². 2 / kg; (3) The mass content of Ca(OH)2 in the carbide slag is ≥80%; (4) The fineness of the carbide slag is 80-120 mesh.

4. The high shear capacity cemented filling material with high fly ash content according to claim 1, characterized in that, The tailings include coarse tailings and fine tailings; the coarse tailings have a particle size of 0.5-2.0 mm, and the fine tailings have a particle size of 0.075-0.5 mm.

5. The high shear capacity cemented filling material with high fly ash content according to claim 4, characterized in that, At least one of the following conditions must be met: (1) The mud content of the coarse tailings is ≤3%; (2) The mud content of the fine tailings is ≤5%; (3) The mass ratio of the coarse tailings to the fine tailings is 1.5-2.5:

1.

6. The high shear capacity cemented filling material with high fly ash content according to claim 1, characterized in that, The fibrous materials include one or more of steel fibers, basalt fibers, and polypropylene fibers.

7. The high shear capacity cemented filling material with high fly ash content according to claim 6, characterized in that, At least one of the following conditions must be met: (1) The steel fiber has a length of 10-15 mm and a diameter of 0.3-0.5 mm; (2) The basalt fibers are 6-12 mm in length and 10-20 μm in diameter; (3) The polypropylene fiber has a length of 8-10 mm and a diameter of 20-30 μm.

8. The high-shear-capacity cemented backfill material with high fly ash content according to any one of claims 1-7, characterized in that, The raw materials of the composite activator, based on a total mass of 100%, include: Water glass 40-50%, sodium sulfate 15-25%, nano SiO2 5-10%, sodium aluminate 3-8%, balance water.

9. A method for preparing a high-shear-capacity cemented backfill material with a large amount of fly ash as described in any one of claims 1-8, characterized in that, include: Solid materials and water are mixed to obtain a slurry; The slurry is cured to obtain the cemented filling material.

10. The preparation method of the high shear capacity cemented filling material with high fly ash content according to claim 9, characterized in that, At least one of the following conditions must be met: (1) The mixture includes: Fly ash, cement, slag, and carbide slag are mixed in a first mixing process to obtain a first mixture. The first mixture and tailings are then mixed a second time to obtain a second mixture; The second mixture and the fibrous material are then mixed a third time to obtain a third mixture; The third mixture, the composite activator, and water are then mixed in a fourth mixture. (2) The water content in the slurry is 20-30% by mass.

Images