Solid waste cementitious material cemented tailings sand filling body and preparation method and application thereof

Abstract

The present application relates to the technical field of industrial solid waste resource utilization, and discloses a solid waste cementing material cemented tailing sand filling body and a preparation method and application thereof, the filling body is formed by filling material slurry through standing hydration curing solidification forming, the filling material comprises: 600-850 parts of tailing sand, 80-180 parts of solid waste cementing material, 120-220 parts of mixing water and 2-8 parts of functional additive; the solid waste cementing material is compounded by the following mass fractions of industrial solid waste components: 40-60 parts of slag, 20-35 parts of fly ash, 10-20 parts of steel slag and 3-8 parts of activator; the functional additive is compounded by a pumping agent, a retarder and an expansive agent in a mass ratio of 2-4:1-2:1. The present application realizes the collaborative consumption of tailing sand and industrial solid waste, is low-carbon and environmentally friendly, and has remarkable ecological benefits. The filling body has excellent working performance, mechanical properties and durability, and can stably adapt to harsh working conditions such as underground mine humidity and complex ground pressure.

Description

Technical Field

[0001] This invention relates to the field of industrial solid waste resource utilization technology, and more specifically, to a solid waste cementitious material gelled end mineral sand backfill body, its preparation method and application. Background Technology

[0002] Mining processes generate large quantities of tailings. The accumulation of these tailings not only occupies valuable land resources but also easily triggers geological disasters such as landslides and mudslides. Furthermore, harmful components in the tailings may seep into groundwater, causing ecological damage. Meanwhile, industries such as steel and power generate large amounts of industrial solid waste, including slag, fly ash, and steel slag. This type of solid waste also faces challenges such as difficult storage, high disposal costs, and low resource utilization rates, placing enormous pressure on the ecological environment.

[0003] Currently, in mine goaf backfilling and roadway support projects, ordinary Portland cement is commonly used as the cementing material, with tailings sand as aggregate to prepare the backfill. However, the production process of ordinary Portland cement is energy-intensive, generates large amounts of carbon emissions, and is costly, resulting in a high overall cost for backfilling projects. Furthermore, ordinary Portland cement has poor compatibility with tailings sand, easily leading to problems such as insufficient strength, poor integrity, and shrinkage cracking in the backfill, affecting the stability and safety of the backfilling project.

[0004] To address the aforementioned issues, existing technologies have introduced solutions that partially utilize industrial solid waste to replace cement in the preparation of cementitious materials. However, these solutions suffer from several drawbacks: First, the amount of solid waste is too low, failing to fully achieve the goal of solid waste disposal. Second, complex modification treatments of the solid waste are required (such as high-temperature calcination and chemical activator modification), increasing the complexity and cost of the preparation process, and the modification process may generate secondary pollution. Third, the solid waste components are not properly matched, failing to fully leverage the synergistic hydration and cementitious effects between different solid wastes, resulting in cementitious materials with low strength and poor stability, making it difficult to meet the actual needs of mine backfilling projects. Fourth, the fluidity and pumpability of the backfill slurry are difficult to control, easily leading to problems such as pump blockage and slurry stratification, and its adaptability to large-scale construction in mines is insufficient. Fifth, the long-term stability and resistance to environmental erosion of the backfill body are poor, making it difficult to adapt to complex working conditions such as dampness and alternating acid and alkali environments underground.

[0005] Based on this, a solid waste cementitious material tailings backfill body and its preparation method are provided, which do not require complex modification processes, have high solid waste content, low cost, excellent performance, and are suitable for large-scale construction in mines. This enables efficient and coordinated disposal of mine tailings and industrial solid waste, and has become a key technical problem that urgently needs to be solved in the field of mine backfilling and solid waste resource utilization. Summary of the Invention

[0006] In view of this, the present invention proposes a solid waste cementitious material with cementitious end mineral sand backfill body, its preparation method and application, aiming to solve at least one of the current background technical problems.

[0007] This invention proposes a solid waste cementitious material backfill material, wherein the backfill material is formed by static hydration curing and solidification of a backfill slurry, and the backfill material comprises the following components in parts by weight: Tailings sand 600-850 parts, solid waste cementitious material 80-180 parts, mixing water 120-220 parts, functional admixture 2-8 parts; The solid waste cementitious material is compounded from the following industrial solid waste components in parts by weight: 40-60 parts slag, 20-35 parts fly ash, 10-20 parts steel slag, and 3-8 parts activator. The functional admixture is a mixture of pumping agent, retarder, and expanding agent in a mass ratio of 2-4:1-2:1.

[0008] Preferably, the tailings sand includes coarse particles, medium particles, and fine particles, wherein the coarse particles have a particle size of 1-5 mm, the medium particles have a particle size of 0.25-1 mm, and the fine particles have a particle size of 0.075-0.25 mm. The mass ratio of the coarse, medium and fine tailings sand is 15-25:30-40:35-45.

[0009] Preferably, the glass content of the granulated blast furnace slag is ≥85%; The fly ash is Grade I or Grade II fly ash, with a loss on ignition ≤8% and a water requirement ratio ≤105%. The steel slag undergoes aging treatment, resulting in a free calcium oxide content of ≤3%.

[0010] Preferably, the activator is a mixture of gypsum and carbide slag or quicklime, with a mass ratio of 2-4:1; the gypsum is at least one of desulfurized gypsum, phosphogypsum, or fluorogypsum.

[0011] Preferably, the pumping agent is a polycarboxylate-based high-efficiency pumping agent with a solid content of 40%-50%; The retarder is sodium gluconate or sodium citrate, and the retarding time is 2-6 hours; The expanding agent is an ettringite-type expanding agent with an expansion rate of 0.02%-0.05%.

[0012] The present invention also provides a method for preparing the solid waste cementitious material gelling end mineral sand backfill body described in the above technical solution, comprising the following steps: (1) The original tailings sand from the mine is fed into a multi-stage screening device for grading and screening. It is then graded and reorganized according to three particle sizes: coarse, medium, and fine. Oversized impurities and large rock masses are removed. Afterward, a combined process of water washing to remove mud and negative pressure vacuum dewatering is used for purification to obtain graded homogenized pretreated tailings sand. (2) Take slag and steel slag separately for low-temperature constant temperature drying and segmented gradient grinding, and take fly ash and activator components for air separation to remove impurities and fineness homogenization treatment, and store them for later use; (3) Mix the industrial solid waste components after pretreatment in step (2) according to the ratio, and use a two-stage stirring method of low-speed premixing and high-speed activation mixing. At the same time, introduce normal pressure dry air to perform gas phase homogenization and conditioning to complete the micro-activation of the solid waste particle surface and obtain homogenized and activated solid waste cementitious material. (4) The pretreated tailings sand obtained in step (1) and the solid waste cementitious material obtained in step (3) are first dry-forced premixed, and then mixing water and compound functional additives are added in steps. After stirring, a homogeneous filling slurry is obtained. (5) The homogeneous filling slurry is pumped to the underground goaf or underground vacant area through a wear-resistant closed pumping pipeline. After hydration and hardening, solid waste cemented tailings sand filling body is obtained.

[0013] Preferably, in step (2), the temperature of the low-temperature constant temperature drying is 60-80℃, and the time is 2-4h; The segmented gradient grinding process specifically involves: first grinding with a ball mill to achieve a specific surface area ≥ 350m². 2 / kg, then finely ground using a vertical roller mill until the specific surface area is ≥500m². 2 / kg.

[0014] Preferably, in step (4), the dry forced premixing time is 3-5 min and the mixing speed is 60-80 r / min; The specific method of adding the mixing water and compound functional additives in stages is as follows: first, add 60%-70% of the total water volume of the mixing water and stir for 1-2 minutes, then add the remaining mixing water and all functional additives and stir for 3-5 minutes.

[0015] The present invention also provides an application of the solid waste cementitious material gelled end mineral sand backfill body described in the above technical solution, specifically in the application of filling of mining goaf, roadway support, backfilling of rock and soil foundation pits or solid waste disposal in underground engineering.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) This invention uses mine tailings sand as aggregate and synergistically utilizes bulk industrial solid wastes such as slag, fly ash, and steel slag to construct a cementing system, which greatly reduces the dependence on natural sand and gravel and ordinary silicate cement. The entire process does not require high-temperature calcination, which significantly reduces production energy consumption and carbon emissions, effectively solves the problems of tailings storage land occupation, geological disasters and water and soil pollution, and meets the requirements of green mine construction and dual-carbon strategy, with significant ecological benefits.

[0017] (2) This invention achieves a slump of 24-26cm in the filling slurry through precise gradation of tailings sand, synergistic hydration of multiple solid wastes and compounding of functional additives. It has good fluidity, strong pumpability, and is not prone to stratification and segregation or pumping blockage. It has rapid early strength development and stable later strength. It has good volume stability and effectively inhibits cracking. It can adapt to harsh working conditions such as underground moisture, acid and alkali alternation, and complex ground pressure. It has a long service life and high engineering safety.

[0018] (3) The present invention adopts low temperature drying, segmented gradient grinding, two-stage stirring and gas phase conditioning and activation process, without the need for complex high temperature modification or strong chemical activation, with less equipment investment, short process route and short production cycle, and significantly reduced overall energy consumption; solid waste raw materials are widely available and inexpensive, replacing high-priced cement and greatly reducing raw material costs; construction is compatible with conventional pumping equipment, without the need for additional large equipment, effectively reducing the comprehensive cost of mine backfilling projects, with outstanding economic benefits, and suitable for large-scale promotion and application. Detailed Implementation

[0019] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention. It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the present invention.

[0020] Furthermore, regarding the numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included within this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0021] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0022] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0023] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0024] This invention provides a solid waste cementitious material backfill body, wherein the backfill body is formed by static hydration curing and solidification of a backfill slurry, and the backfill material comprises the following components in parts by weight: Tailings sand 600-850 parts, solid waste cementitious material 80-180 parts, mixing water 120-220 parts, functional admixture 2-8 parts; The solid waste cementitious material is compounded from the following industrial solid waste components in parts by weight: 40-60 parts slag, 20-35 parts fly ash, 10-20 parts steel slag, and 3-8 parts activator. The functional admixture is a mixture of pumping agent, retarder, and expanding agent in a mass ratio of 2-4:1-2:1.

[0025] In this invention, the tailings sand includes coarse particles, medium particles, and fine particles of tailings sand. The coarse particles have a particle size of 1-5 mm, the medium particles have a particle size of 0.25-1 mm, and the fine particles have a particle size of 0.075-0.25 mm. The mass ratio of the coarse, medium and fine tailings sand is 15-25:30-40:35-45.

[0026] In this invention, tailings sand is used as the core aggregate of the backfill. After multi-stage screening and gradation reorganization, it forms a continuous and dense particle skeleton, which can replace natural sand and gravel aggregates and reduce resource consumption. The well-graded tailings sand particles are tightly interlocked, which can significantly improve the density, compressive strength and volume stability of the backfill, reduce shrinkage cracking, and meet the core requirements of aggregate gradation and strength for underground backfill.

[0027] In this invention, the glass content of the granulated blast furnace slag is ≥85%; The fly ash is Grade I or Grade II fly ash, with a loss on ignition ≤8% and a water requirement ratio ≤105%. The steel slag undergoes aging treatment, resulting in a free calcium oxide content of ≤3%.

[0028] The granulated blast furnace slag in this invention has a high glass content and strong activity. After hydration, it can generate a large amount of hydrated calcium silicate and hydrated calcium aluminate gel, which is the core of the cementitious material's strength. The Class I / II fly ash particles are fine and have stable activity, which can exert the micro-aggregate filling effect and pozzolanic activity, improve the later strength of the cementitious material, and reduce the heat of hydration. The aged steel slag has a low free calcium oxide content and good volume stability, which can supplement the calcium source and optimize the mineral composition of the cementitious system. The three are synergistically compounded to maximize the hydration and cementation potential of industrial solid waste and reduce cement dependence.

[0029] In this invention, the activator is a mixture of gypsum and carbide slag or quicklime, with a mass ratio of 2-4:1; the gypsum is at least one of desulfurized gypsum, phosphogypsum, or fluorogypsum.

[0030] This invention uses activators to activate the potential activity of slag, fly ash, and steel slag: gypsum provides sulfate ions to promote the formation of ettringite and improve the early strength and impermeability of the backfill; carbide slag / quicklime provides an alkaline environment to accelerate the hydration reaction of solid waste particles and enhance the bonding force of the cementing system. The combination of the two can precisely control the hydration rate and adapt to the strength development requirements of the low temperature and humid environment underground.

[0031] In this invention, the pumping agent is a polycarboxylate-based high-efficiency pumping agent with a solid content of 40%-50%; The retarder is sodium gluconate or sodium citrate, and the retarding time is 2-6 hours; The expanding agent is an ettringite-type expanding agent with an expansion rate of 0.02%-0.05%.

[0032] The polycarboxylate-based pumping agent in this invention can significantly improve the fluidity of the filling slurry, reduce the water-cement ratio, enhance pumpability, and avoid blockage during long-distance pumping; the sodium gluconate / sodium citrate retarder can extend the slurry setting time, adapting to the rhythm of long-distance downhole transportation and layered pouring construction; the ettringite-type expansive agent can compensate for the hydration shrinkage of the filling body, inhibit cracking, and improve volume stability. The three work together to achieve dual optimization of the slurry's construction performance and the filling body's durability.

[0033] The present invention also provides a method for preparing the solid waste cementitious material gelling end mineral sand backfill body described in the above technical solution, comprising the following steps: (1) The original tailings sand from the mine is fed into a multi-stage screening device for grading and screening. It is then graded and reorganized according to three particle sizes: coarse, medium, and fine. Oversized impurities and large rock masses are removed. Afterward, a combined process of water washing to remove mud and negative pressure vacuum dewatering is used for purification to obtain graded homogenized pretreated tailings sand. (2) Take slag and steel slag separately for low-temperature constant temperature drying and segmented gradient grinding, and take fly ash and activator components for air separation to remove impurities and fineness homogenization treatment, and store them for later use; (3) Mix the industrial solid waste components after pretreatment in step (2) according to the ratio, and use a two-stage stirring method of low-speed premixing and high-speed activation mixing. At the same time, introduce normal pressure dry air to perform gas phase homogenization and conditioning to complete the micro-activation of the solid waste particle surface and obtain homogenized and activated solid waste cementitious material. (4) The pretreated tailings sand obtained in step (1) and the solid waste cementitious material obtained in step (3) are first dry-forced premixed, and then mixing water and compound functional additives are added in steps. After stirring, a homogeneous filling slurry is obtained. (5) The homogeneous filling slurry is pumped to the underground goaf or underground vacant area through a wear-resistant closed pumping pipeline. After hydration and hardening, solid waste cemented tailings sand filling body is obtained.

[0034] In this invention, in step (2), the temperature of the low-temperature constant temperature drying is 60-80℃ and the time is 2-4h; The segmented gradient grinding process specifically involves: first grinding with a ball mill to achieve a specific surface area ≥ 350m². 2 / kg, then finely ground using a vertical roller mill until the specific surface area is ≥500m². 2 / kg.

[0035] Low-temperature constant-temperature drying can remove surface moisture from slag and steel slag, preventing damp clumping and ensuring grinding uniformity; segmented gradient grinding can refine particles step by step, increase specific surface area, fully expose active sites of solid waste, enhance hydration reaction activity, and lay the foundation for high strength and high stability of cementitious materials.

[0036] In this invention, in step (4), the dry forced premixing time is 3-5 min and the stirring speed is 60-80 r / min; The specific method of adding the mixing water and compound functional additives in stages is as follows: first, add 60%-70% of the total water volume of the mixing water and stir for 1-2 minutes, then add the remaining mixing water and all functional additives and stir for 3-5 minutes.

[0037] In this invention, dry forced premixing can initially mix tailings sand and cementitious materials, reducing segregation during subsequent water addition and mixing; step-by-step water addition and multiple mixing can avoid local agglomeration and uneven dispersion of admixtures, ensuring the fluidity, uniformity and stability of the slurry, and adapting to pumping construction requirements.

[0038] The present invention also provides an application of the solid waste cementitious material gelled end mineral sand backfill body described in the above technical solution, specifically in the application of filling of mining goaf, roadway support, backfilling of rock and soil foundation pits or solid waste disposal in underground engineering.

[0039] Example 1 The filling material is prepared according to the following mass percentages: 600 parts tailings sand, 80 parts solid waste cementitious material, 120 parts mixing water, and 2 parts functional admixture. The solid waste cementitious material consists of 40 parts slag, 20 parts fly ash, 10 parts steel slag, and 3 parts activator. The functional admixture is a compound of 2 parts polycarboxylate-based high-efficiency pumping agent with a solid content of 45%, 1 part sodium gluconate retarder, and 1 part ettringite-type expanding agent in a specific ratio. The granulated blast furnace slag used has a glass content of no less than 85%, the fly ash is Grade II with a loss on ignition controlled below 8%, the steel slag has a free calcium oxide content ≤3% after aging treatment, and the activator is prepared by mixing desulfurized gypsum and quicklime in a mass ratio of 2:1. The specific preparation steps are as follows: (1) Tailings sand pretreatment: The raw tailings sand discharged from the mine is sent to a multi-stage vibrating screen device. After three-stage grading and screening, it is re-graded and reorganized according to the preset coarse, medium and fine ratio. Among them, 15 parts are coarse particles of 1-5mm, 30 parts are medium particles of 0.25-1mm, and 35 parts are fine particles of 0.075-0.25mm. Stones, impurities and other oversized materials are removed at the same time. Then the reorganized tailings sand is sent to a water washing equipment to remove mud. Then the moisture content is controlled to below 1.5% by negative pressure vacuum dewatering process to obtain pretreated tailings sand with uniform gradation and high cleanliness. (2) Pretreatment of industrial solid waste: Take corresponding proportions of slag and steel slag, place them in a low-temperature constant temperature drying equipment, and dry them continuously at 70℃ for 3 hours to completely remove surface adsorbed moisture; after drying, send them to a ball mill for grinding until the specific surface area reaches 380m². 2 / kg, then transferred to a vertical roller mill for fine grinding, so that the final specific surface area is not less than 520m². 2 / kg; At the same time, fly ash and activator are subjected to air separation and fineness homogenization treatment to ensure that the powder particles are uniform and free of agglomerated impurities, and are ready for use; (3) Preparation of solid waste cementitious material: The pretreated slag, steel slag, fly ash and activator are put into the mixing equipment according to the ratio. First, the mixture is premixed at a low speed of 30 r / min for 2 minutes, and then the speed is increased to 120 r / min for high-speed activation and mixing for 3 minutes. During the entire mixing process, normal pressure dry air is continuously introduced to carry out gas phase homogenization and conditioning, fully activate the active sites on the surface of solid waste particles, and prepare homogenized and activated solid waste cementitious material. (4) Preparation of filling slurry: The pretreated tailings sand and activated cementitious material are added to a forced mixer and dry forced premixed at a speed of 70 r / min for 4 minutes to make the aggregate and cementitious powder initially uniformly mixed; then 70% of the total water volume of the mixing water is added and stirred for 1.5 minutes, then the remaining mixing water and all the compound functional additives are added and stirred for another 4 minutes to ensure that the components are fully integrated and form a homogeneous filling slurry with good fluidity and uniform stability. (5) Pumping and curing molding: The prepared filling slurry is transported to the designated goaf area in the mine through wear-resistant closed pumping pipelines and left to stand naturally for hydration and curing for 28 days at room temperature. After it is fully hydrated and hardened, a stable solid waste cementitious material gel tailings ore filling body is obtained.

[0040] Example 2 Preparation of filling material: By weight, it includes 750 parts tailings sand, 130 parts solid waste cementitious material, 170 parts mixing water, and 5 parts functional additives. The solid waste cementitious material consists of 50 parts slag, 28 parts fly ash, 15 parts steel slag, and 5 parts activator. The functional additives are a compound of 3 parts polycarboxylate-based high-efficiency pumping agent with a solid content of 50%, 1.5 parts sodium citrate retarder, and 1 part ettringite-type expanding agent in a specific ratio. The granulated blast furnace slag used has a glass content of no less than 85%, the fly ash is Grade I with a loss on ignition controlled below 6%, and the steel slag, after aging, has a free calcium oxide content ≤2.5%. The activator is prepared by mixing phosphogypsum and carbide slag in a 3:1 weight ratio. The specific preparation steps are as follows: (1) Tailings sand pretreatment: The original tailings sand from the mine is sent to a multi-stage screening device. After three-stage grading and screening, the gradation and reorganization are completed according to the preset particle size ratio. 1-5mm coarse particles account for 20 parts, 0.25-1mm medium particles account for 35 parts, and 0.075-0.25mm fine particles account for 40 parts. Large rock masses, debris and other unqualified materials are removed at the same time. Then, the mud impurities in the tailings sand are thoroughly removed by water washing process. After negative pressure vacuum dewatering treatment, the moisture content is stably controlled below 1.2% to obtain gradation homogeneous, clean and dry pretreated tailings sand. (2) Pretreatment of industrial solid waste: Take corresponding proportions of slag and steel slag, put them into a low-temperature drying equipment, and dry them at a constant temperature of 65°C for 4 hours to avoid moisture and clumping that would affect the grinding effect; after drying, the material is first ground in a ball mill until the specific surface area reaches 400m². 2 / kg, then finely ground using a vertical roller mill to achieve a specific surface area of ​​not less than 550m². 2 / kg; At the same time, the fly ash and activator are subjected to air separation to remove impurities and fineness homogenization to ensure the activity and uniformity of the powder, and are ready for use; (3) Preparation of solid waste cementitious material: All pretreated industrial solid waste components are mixed according to the ratio. First, they are premixed at a low speed of 25 r / min for 3 minutes, and then activated and mixed at a high speed of 130 r / min for 2 minutes. During the stirring process, normal pressure dry air is continuously introduced for conditioning treatment to fully stimulate the potential hydration activity of solid waste and obtain homogenized activated solid waste cementitious material. (4) Preparation of filling slurry: The pretreated tailings sand and activated cementitious material are put into a forced mixer and dry premixed at a speed of 65r / min for 5 minutes to achieve the initial uniform mixing of aggregate and cementitious powder; then 65% of the total water volume of mixing water is added and stirred for 2 minutes, then the remaining mixing water and all compound functional additives are added and stirred for 3.5 minutes to fully disperse and blend the components of the slurry to form a uniform, stable, and pumpable filling slurry; (5) Pumping and curing molding: The slurry is transported to the underground goaf through a wear-resistant and sealed pumping pipeline. It is hydrated and cured for 28 days under normal temperature conditions. After it is completely cured and molded, a high-strength and high-stability solid waste cementitious material gelling end mineral sand filling body is obtained.

[0041] Performance testing The following tests were performed on Examples 1 and 2: (1) Slump test of filling slurry: The test index is the fluidity of the slurry, and the standard is "Standard for Test Method of Performance of Ordinary Concrete Mixture" (GB / T 50080-2016). During the test, the prepared homogeneous filling slurry is loaded into the standard slump cylinder at one time, compacted in layers, and the surface is smoothed. The slump cylinder is lifted vertically at a uniform speed. After the slurry slumps and stabilizes, the vertical distance from the top of the cylinder to the highest point of the slurry is measured. Each group is tested 3 times and the average value is taken.

[0042] (2) Setting time test of filling slurry: The test indicators are initial setting time and final setting time. The standards are "Standard for Test Method of Performance of Ordinary Concrete Mixture" (GB / T 50080-2016) and "Specification for Test of Performance of Mine Filling Body" (YS / T5212-2019). The slurry is poured into a standard mold and placed in an environment of 20±2℃ and relative humidity ≥95% for curing. The penetration resistance meter is used for timed testing. The time corresponding to the penetration resistance reaching 3.5MPa is the initial setting time and 28MPa is the final setting time is recorded. Two parallel tests are conducted and the average value is taken.

[0043] (3) Compressive strength test of filling body: The test index is 7d and 28d compressive strength. The standard is "Test method for strength of cement mortar (ISO method)" (GB / T 17671-2021) and "Specification for performance test of mine filling body" (YS / T 5212-2019). The slurry is injected into a 100mm×100mm×100mm cube mold, vibrated and compacted, cured at room temperature for 24 hours and demolded. It is then transferred to a standard curing room for curing until the corresponding age. The universal testing machine is used to load and test at a rate of 0.5MPa / s. The average value of 3 samples in each age group is taken.

[0044] (4) 28-day drying shrinkage test of filling body: The test index is the drying shrinkage rate. The standard is "Test Method for Strength of Cement Mortar (ISO Method)" (GB / T 17671-2021) and "Test Specification for Performance of Mine Filling Body" (YS / T 5212-2019). The slurry is injected into a 100mm×100mm×515mm prism mold, cured for 24 hours, demolded and measured the initial length. After curing in an environment of 20±2℃ and 50%±5% relative humidity for 28 days, the length is measured again and the shrinkage rate is calculated. The average value of 3 samples in each group is taken.

[0045] (5) Test of impermeability grade of filling body: The test index is the impermeability grade, and the standard is "Test Method for Strength of Cement Mortar (ISO Method)" (GB / T 17671-2021) and "Test Specification for Performance of Mine Filling Body" (YS / T 5212-2019). The slurry is injected into the frustum impermeability test mold and cured for 28 days. Then it is installed in the permeameter and pressurized step by step from 0.2MPa. Each step is kept at constant pressure for 8 hours. The grade is determined by the maximum water pressure at which there is no water seepage at the end face after 8 hours.

[0046] (6) Solid waste comprehensive utilization rate test: The test index is the solid waste comprehensive utilization rate, which is calculated according to the proportion of the total mass of tailings sand, slag, fly ash and steel slag in the filling material to the total mass of the filling material, and is used to evaluate the level of solid waste resource utilization.

[0047] The test results are shown in Table 1: Table 1 Test Results As shown in Table 1, the solid waste cementitious material prepared by this invention exhibits excellent comprehensive performance of tailings sand backfill, meeting the engineering requirements for backfilling in mining goaf areas. The backfill slurry slump reaches 24-26 cm, exhibiting good fluidity and pumpability. The setting time is controlled within the range of 3.5-7.5 hours, demonstrating excellent construction adaptability. The 7-day compressive strength of the backfill is no less than 4.2 MPa, and the 28-day compressive strength reaches 8.5-10.2 MPa, exhibiting rapid early strength development and stable later strength, meeting the mechanical properties required for underground support. The 28-day drying shrinkage rate is only 0.06%-0.08%, demonstrating good volume stability and effectively inhibiting cracking. The impermeability grade reaches P6-P8, exhibiting excellent durability and adaptability to humid and complex underground working conditions. The comprehensive utilization rate of solid waste reaches 82%-85%, achieving large-scale synergistic disposal of tailings sand and industrial solid waste, combining engineering practicality, economic efficiency, and green environmental benefits.

[0048] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A solid waste cementitious material gelling end mineral sand backfill body, characterized in that, The filling material is formed by static hydration curing and solidification of filling slurry, and the filling material comprises the following components in parts by weight: Tailings sand 600-850 parts, solid waste cementitious material 80-180 parts, mixing water 120-220 parts, functional admixture 2-8 parts; The solid waste cementitious material is compounded from the following industrial solid waste components in parts by weight: 40-60 parts slag, 20-35 parts fly ash, 10-20 parts steel slag, and 3-8 parts activator. The functional admixture is a mixture of pumping agent, retarder, and expanding agent in a mass ratio of 2-4:1-2:

1.

2. The solid waste cementitious material gelling end mineral sand backfill body according to claim 1, characterized in that, The tailings sand includes coarse, medium and fine particles. The coarse particles have a particle size of 1-5 mm, the medium particles have a particle size of 0.25-1 mm, and the fine particles have a particle size of 0.075-0.25 mm. The mass ratio of the coarse, medium and fine tailings sand is 15-25:30-40:35-45.

3. The solid waste cementitious material gelling end mineral sand backfill body according to claim 1, characterized in that, The granulated blast furnace slag has a glass content of ≥85%; The fly ash is Grade I or Grade II fly ash, with a loss on ignition ≤8% and a water requirement ratio ≤105%. The steel slag undergoes aging treatment, resulting in a free calcium oxide content of ≤3%.

4. The solid waste cementitious material gelling end mineral sand backfill body according to claim 1, characterized in that, The activator is a mixture of gypsum and carbide slag or quicklime, with a mass ratio of 2-4:1; the gypsum is at least one of desulfurized gypsum, phosphogypsum, or fluorogypsum.

5. The solid waste cementitious material gelling end mineral sand backfill body according to claim 1, characterized in that, The pumping agent is a polycarboxylate-based high-efficiency pumping agent with a solid content of 40%-50%. The retarder is sodium gluconate or sodium citrate, and the retarding time is 2-6 hours; The expanding agent is an ettringite-type expanding agent with an expansion rate of 0.02%-0.05%.

6. A method for preparing a solid waste cementitious material gelled end mineral sand backfill body according to any one of claims 1-5, characterized in that, Includes the following steps: (1) The original tailings sand from the mine is fed into a multi-stage screening device for grading and screening. It is then graded and reorganized according to three particle sizes: coarse, medium, and fine. Oversized impurities and large rock masses are removed. Afterward, a combined process of water washing to remove mud and negative pressure vacuum dewatering is used for purification to obtain graded homogenized pretreated tailings sand. (2) Take slag and steel slag separately for low-temperature constant temperature drying and segmented gradient grinding, and take fly ash and activator components for air separation to remove impurities and fineness homogenization treatment, and store them for later use; (3) Mix the industrial solid waste components after pretreatment in step (2) according to the ratio, and use a two-stage stirring method of low-speed premixing and high-speed activation mixing. At the same time, introduce normal pressure dry air to perform gas phase homogenization and conditioning to complete the micro-activation of the solid waste particle surface and obtain homogenized and activated solid waste cementitious material. (4) The pretreated tailings sand obtained in step (1) and the solid waste cementitious material obtained in step (3) are first dry-forced premixed, and then mixing water and compound functional additives are added in steps. After stirring, a homogeneous filling slurry is obtained. (5) The homogeneous filling slurry is pumped to the underground goaf or underground vacant area through a wear-resistant closed pumping pipeline. After hydration and hardening, solid waste cemented tailings sand filling body is obtained.

7. The method for preparing solid waste cementitious material gelled end mineral sand backfill body according to claim 6, characterized in that, In step (2), the temperature of the low-temperature constant temperature drying is 60-80℃, and the time is 2-4h; The segmented gradient grinding process specifically involves: first grinding with a ball mill to achieve a specific surface area ≥ 350m². 2 / kg, then finely ground using a vertical roller mill until the specific surface area is ≥500m². 2 / kg.

8. The method for preparing solid waste cementitious material gelled end mineral sand backfill body according to claim 6, characterized in that, In step (4), the dry forced premixing time is 3-5 min, and the mixing speed is 60-80 r / min; The specific method of adding the mixing water and compound functional additives in stages is as follows: first, add 60%-70% of the total water volume of the mixing water and stir for 1-2 minutes, then add the remaining mixing water and all functional additives and stir for 3-5 minutes.

9. The application of a solid waste cementitious material with cementitious end-filled mineral sand backfill body according to any one of claims 1-5, characterized in that, The specific applications are in filling goaf areas in mines, roadway support, backfilling of rock and soil foundation pits, or disposal of solid waste in underground engineering.

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