Steel slag sand and fine grain tailing composite filling mortar as well as preparation method and use method of steel slag sand and fine grain tailing composite filling mortar
By combining steel slag sand with fine-grained tailings, and using magnetic volcanic ash cementing materials and ultrafine particle capture agents to form large aggregates, the problems of low tailings utilization, high backfilling cost and uneven strength in cemented backfilling are solved, achieving a high-strength and low-cost backfilling effect.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- 樊鲁倩
- Filing Date
- 2026-03-03
- Publication Date
- 2026-05-12
AI Technical Summary
In existing cemented backfilling technologies, the utilization rate of tailings is low, the backfilling cost is high, the treatment of fine-grained tailings is difficult, the strength of the backfill body is uneven, and the amount of cementing material used is large, resulting in high backfilling costs.
A composite of steel slag sand and fine-grained tailings is used, and magnetic volcanic ash cementing material and ultrafine particle capture agent are used to form large agglomerates through magnetic aggregation and cross-linking, which reduces the amount of cementing material used and improves the strength and uniformity of the filling body.
It significantly improves the strength of the backfill, reduces the amount of cementing material, reduces backfilling costs, improves tailings utilization, and solves the problem of uneven strength of the backfill.
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Abstract
Description
Technical Field
[0001] This invention belongs to the technical field of tailings cemented backfill materials, and more specifically, relates to a composite backfill mortar for fine-grained steel slag sand tailings and its preparation and application methods. Background Technology
[0002] The industrial society's demand for mineral resources is increasing daily. While mining brings mineral resources, it also creates numerous goaf areas and tailings ponds on the surface, posing significant safety hazards to enterprises and society: goaf subsidence and tailings pond collapse. Mine backfilling is an effective means of controlling mining subsidence, and scholars both domestically and internationally have conducted extensive research on it, proposing many effective methods.
[0003] Backfilling mining methods and technologies are receiving increasing attention and are constantly being improved. On the one hand, through a deeper understanding of the physical and mechanical properties of backfilling materials and backfill bodies, research and development are underway for new backfilling materials that are widely available, low in cost, easy to prepare and transport, and have higher strength. On the other hand, by exploring the mechanical action mechanism of backfill bodies under mining geological conditions and combining it with the requirements of mining operations, new backfilling processes and methods are being studied.
[0004] Cemented backfilling is further divided into graded backfilling and full tailings backfilling. Graded tailings sand backfilling involves first classifying and desliming the tailings sand, using coarse-grained particles as aggregate, and then using cement as a binder. This allows the backfill slurry to dewater rapidly upon entering the stope, significantly improving the strength of the backfill. Therefore, graded tailings sand backfilling is the most widely used method in mine backfilling processes both domestically and internationally. Full tailings sand cemented backfilling uses ungraded, undeslimed, full-size tailings sand as backfill aggregate, mixed with a certain proportion of binder and water, and then filled into the underground goaf. As a new and efficient backfilling method, full tailings sand cemented backfilling can maximize the utilization of tailings resources and reduce environmental pollution and resource waste.
[0005] Although cemented backfilling has advantages such as simple backfilling system process, low backfill slurry concentration, and convenient slurry preparation and transportation, it also has at least one of the following problems:
[0006] 1) Low tailings utilization rate and difficulty in treating fine-grained tailings. When using coarse tailings as aggregate, the entire tailings need to be classified to remove the fine-grained portion. This portion of tailings has a very small particle size, is difficult to solidify, has low solidification strength, and is difficult to build dams, which further increases the difficulty of tailings treatment, increases the construction cost of tailings dams, and aggravates environmental pollution. 2) For some ores with complex occurrence conditions and low grade, further fine grinding is required to improve the recovery rate, so that the average particle size of the ore body is less than 0.03 mm, and -800 mesh is greater than 50%, +200 mesh is less than 10%, and +400 mesh is less than 30%. These ultrafine tailings have slow settling speed, are difficult to thicken, have poor permeability, are difficult to dewater, have high tailings pore pressure, and low consolidation strength.
[0007] 3) High backfilling costs. In backfilling mining, backfilling costs remain high, accounting for approximately 20% of the total mining cost, and sometimes even as high as 40%. Of this, the cost of cementing materials accounts for nearly 75% of the total backfilling cost. Due to their extremely fine particle size, graded ultrafine tailings, ultrafine whole tailings, and tailings mud, when they become colloids, they carry excessive amounts of colloidal water, leading to low cementing strength and difficulty in cementation. This necessitates increasing the amount of cementing materials used, further increasing backfilling costs and keeping them persistently high.
[0008] The strength and cost of cemented backfill are mainly determined by factors such as the properties of the tailings themselves, the concentration of the backfill slurry, and the selection of cementing materials, especially the particle size of the tailings in the tailings slurry and the bulk density after backfilling. Therefore, it is very important to conduct in-depth research on novel, low-cost, high-early-strength, and high-strength cementing systems. Adding fine sand to fine-grained tailings can significantly improve the strength of the backfill while reducing the amount of cementing material used. However, the difference in gravity settling velocity between coarse and fine particles such as fine sand (particle size ≥ 0.1 mm) and fine-grained tailings (particle size < 0.03 mm) can lead to uneven strength distribution in the consolidated body. Summary of the Invention
[0009] The main objective of this invention is to provide a composite backfill mortar made from fine-grained tailings and steel slag sand. By using fine-grained tailings as the main raw material, adding steel slag sand as fine aggregate, and employing magnetic pozzolanic cementitious material, the magnetic agglomeration and magnetic effect of the magnetic pozzolanic cementitious material and the micro-fine weak magnetic particles in the tailings can be utilized to drive other particles to approach the steel slag sand and form agglomerates. This avoids uneven distribution of the solidified body strength caused by the different gravity settling velocities of fine sand and fine-grained tailings. Therefore, it can significantly improve the strength of the backfill while reducing the amount of cementing material and backfilling cost.
[0010] The present invention also provides a preparation method and a method of using the above-mentioned steel slag sand fine-grained tailings composite backfill mortar, the overall preparation process and construction process of which are relatively simple; Furthermore, by applying an external magnetic field to further magnetize the mortar during the mortar preparation process or during the filling construction process, it is beneficial to further improve the compressive strength of the resulting mortar filling body.
[0011] To achieve the above objectives, the technical solution provided by this invention is as follows: The first aspect of this invention provides a composite backfill mortar made from fine-grained steel slag sand tailings. The mortar raw materials include fine-grained tailings, steel slag sand, magnetic pozzolanic cementitious material, a degreasing agent, and an ultrafine particle trapping agent, wherein: At least 90% of the tailings particles in the fine tailings pass through a 200-mesh sieve, and their D50 is ≤20 micrometers. The particle size range of the steel slag sand is 0.1~1mm; The magnetic volcanic ash cementitious material comprises volcanic ash components, an activator, and magnetic powder particles. Based on the completely dry tailings in fine-grained tailings, the mass ratio of the magnetic volcanic ash cementitious material to the completely dry tailings is 1:4~12, and the remanent magnetic induction intensity of the magnetic powder particles is 0.15~2.5mT, accounting for 5~10% of the total mass of the magnetic volcanic ash cementitious material. The deflocculating agent includes a high-valent metal cationic inorganic flocculant; The ultrafine particle trapping agent includes polyacrylamide (PAM).
[0012] To address the problems of low filling strength, high cost, low tailings utilization rate, and complex treatment in existing cemented backfill bodies in mines, this application provides a composite backfill mortar made of steel slag sand and fine-grained tailings. This composite backfill mortar uses fine-grained tailings as the main raw material and steel slag sand as the fine aggregate. By combining fine-grained tailings and steel slag sand, the strength of the backfill body can be significantly improved while reducing the amount of cementing materials and backfill costs.
[0013] However, it should be noted that the filling slurry formed after mixing cementitious materials, fine tailings, and relatively coarse sand is prone to segregation, resulting in uneven strength distribution of the solidified body. Based on this, this application employs magnetic pozzolanic cementitious materials. The magnetic powder particles in the magnetic pozzolanic cementitious materials, along with the micro- and weakly magnetic particles in the fine tailings, can carry other particles towards the magnetic steel slag sand through magnetic aggregation and magnetic effects. Furthermore, under the cross-linking effect of an ultrafine particle trapping agent, it will form a large agglomerate with steel slag sand as its core. Because the de-gelling agent in the agglomerates and the magnetic pozzolanic cementitious material release high-valence metal cations during hydrolysis, the absolute value of the Zeta potential of the fine tailings flocs is reduced, resulting in de-gelling. This converts the colloidal water they carry into free water, thereby reducing the gaps between particles. The large agglomerates with steel slag sand as the core will undergo overall gravity settling. After settling, the particles are densely packed. In addition, the magnetic pozzolanic cementitious material in the steel slag sand-fine mud tailings slurry after settling will generate a large amount of colloid, which cements the steel slag sand tailings into a filling whole. Therefore, it can effectively improve the overall strength of the solidified body and the uniformity of its strength distribution, and solve the technical problems existing in tailings filling in the prior art, especially the technical problems existing in the filling of fine-particle iron tailings.
[0014] It should also be noted that the ultrafine particle capture agent in this application is polyacrylamide, which not only helps to polymerize and agglomerate the components to form large agglomerates, but also effectively captures ultrafine particles in fine tailings and volcanic ash cementitious materials, while also effectively ensuring the fluidity of the resulting mortar.
[0015] In addition, this application uses fine-grained tailings directly as the main raw material, which has a high utilization rate of tailings and does not require complex overflow classification and other processing of tailings.
[0016] According to any of the technical solutions described in the first aspect of the present invention, the magnetic powder particles are magnetized steel slag micro powder or magnetic concentrate powder or a combination thereof, and their specific surface area is 300 m². 2 / kg≤S≤700m 2 / kg, preferably 400m 2 / kg≤S≤500m 2 / kg. The magnetic concentrate powder is obtained by magnetizing concentrate powder, and the magnetization process parameters are: external magnetic field strength ≥0.1T.
[0017] According to any of the technical solutions described in the first aspect of the present invention, the fine-grained tailings are whole tailings or overflow-classified tailings obtained by grinding and magnetic separation of pyrite or magnetite. The fine-grained tailings are used after being prepared into tailings slurry. The tailings concentration of the fine-grained tailings slurry is ≥45%, and the slump is ≥180cm; more preferably, the tailings slurry concentration is ≥50%, and the slump is ≥200cm.
[0018] According to any of the technical solutions described in the first aspect of the present invention, the steel slag sand is hot slag produced by converter steelmaking, drum air-cooled slag or hot pouring slag, and the mass ratio of steel slag sand to dry tailings is 1:3~12, based on the absolutely dry tailings in fine tailings.
[0019] Furthermore, the preferred particle size range of the steel slag sand is 0.2~0.5mm, and the preferred mass ratio of steel slag sand to oven-dried tailings is 1:4~10.
[0020] Furthermore, the preferred mass ratio of the magnetic volcanic ash cementitious material to the oven-dry tailings is 1:5 to 8.
[0021] According to any of the technical solutions described in the first aspect of the present invention, the degreasing agent is an iron salt, an aluminum salt or a combination thereof, more preferably a polyferric chloride or a polyaluminum chloride or a composite thereof in any mass ratio, and its mass ratio with the oven-dried tailings is 1:500~3000, more preferably 1:1000~2000. The ultrafine particle capture agent can be any one of anionic PAM, cationic PAM, or nonionic PAM, and its mass ratio with the oven-dried tailings is 1:10000~1000000, more preferably 1:10000~100000.
[0022] According to any of the technical solutions described in the first aspect of the present invention, the volcanic ash component is natural volcanic ash or artificial volcanic ash, preferably artificial volcanic ash, wherein the artificial volcanic ash is at least one of water-quenched blast furnace slag powder, fly ash, and slag powder, and its specific surface area is ≥400 m². 2 / kg, further preferably ≥500m 2 / kg.
[0023] Furthermore, the proportion of glass phase in the artificial volcanic ash powder is ≥90%, preferably ≥95%, and the calcium oxide content in the artificial volcanic ash powder is ≥30%, preferably ≥40%.
[0024] According to any of the technical solutions described in the first aspect of the present invention, the activator comprises an alkaline activator and a sulfate activator, and the mass of the alkaline activator and the sulfate activator accounts for 5-25% and 10-25% of the total mass of the magnetic pozzolanic cementitious material, respectively.
[0025] Furthermore, the alkaline activator includes at least one of quicklime powder, hydrated lime powder, lightly calcined magnesia powder, rapid-hardening sulfoaluminate cement, aluminate cement, and high-grade general-purpose silicate cement, preferably at least one of quicklime powder, hydrated lime powder, rapid-hardening sulfoaluminate cement, and high-grade general-purpose silicate cement, wherein the grade of the high-grade general-purpose silicate cement is preferably ≥42.5 MPa, and the specific surface area of the magnetic pozzolanic cementitious material is ≥400 m². 2 / kg.
[0026] Furthermore, the sulfate activator includes at least one of anhydrous calcium sulfate, calcium sulfate dihydrate, calcium sulfate hemihydrate, sodium sulfate, potassium sulfate, and alum, preferably at least one of calcium sulfate, calcium sulfate dihydrate, calcium sulfate hemihydrate, and potassium sulfate.
[0027] The second aspect of the present invention provides a method for preparing composite backfill mortar of steel slag sand fine-grained tailings as described in the first aspect, comprising: mixing the raw materials of the composite backfill mortar of steel slag sand fine-grained tailings and stirring evenly to obtain a sample of composite backfill mortar of steel slag sand fine-grained tailings.
[0028] Furthermore, the process of mixing the raw materials of the steel slag sand fine-grained tailings composite backfill mortar and stirring them evenly to obtain a sample of the steel slag sand fine-grained tailings composite backfill mortar specifically includes: 1) Prepare corresponding aqueous solutions of the breaker and the ultrafine particle capture agent, wherein the mass concentration of the breaker solution is 1% and the mass concentration of the ultrafine particle capture agent solution is 1 / 1000. 2) According to the metering ratio of each raw material in the steel slag sand fine-grained tailings composite backfill mortar, the weighed magnetic volcanic ash cementitious material, steel slag sand, breaker solution, and ultrafine particle capture agent solution are added to the fine mud tailings (slurry) in sequence. Then, the mixture is stirred with a mixer. Preferably, the rotation speed of the mixer blades is not less than 60 rpm, and the stirring time is 2 to 5 minutes, more preferably 2 to 3 minutes. Then, the mixture is poured into a mold to form a sample of steel slag sand fine-grained tailings composite backfill mortar.
[0029] The obtained steel slag sand fine-grained tailings composite backfill mortar samples were cured at 20℃ and 90% relative humidity. After one day of curing, the samples were demolded and cured for 3, 7, and 28 days. The strength of the mortar samples at each age was tested. The unconfined compressive strength of the samples was ≥1MPa at 3 days, ≥1.8MPa at 7 days, and ≥3MPa at 28 days. After curing the steel slag sand fine-grained tailings composite backfill mortar samples in 10 atm water vapor for 3 days, their unconfined compressive strength was ≥3.5MPa.
[0030] According to any of the technical solutions described in the second aspect of the present invention, the method further includes: immediately placing the mixed steel slag sand fine-grained tailings composite backfill mortar sample in an external magnetic field in a fluid state for magnetization treatment, so as to enhance the magnetism of weak magnetic particles and magnetic particles in the mortar, wherein the strength of the external magnetic field is not less than 0.1T, and the magnetization time is 0.5 to 5 seconds, preferably 1 to 2 seconds.
[0031] The magnetized steel slag sand fine-grained tailings composite backfill mortar samples were cast into molds and then cured at 20℃ and 90% relative humidity. After one day of curing, the samples were demolded and cured for 3, 7, and 28 days. The strength of the mortar samples at each age was tested. The unconfined compressive strength of the samples was ≥1.5MPa at 3 days, ≥2.5MPa at 7 days, and ≥3.5MPa at 28 days. After the magnetized steel slag sand fine-grained tailings composite backfill mortar samples were cured in 10 atm water vapor for 3 days, their unconfined compressive strength was ≥3.9MPa.
[0032] In other words, by placing the freshly mixed fluid steel slag sand fine-grained tailings composite backfill mortar sample in an external magnetic field for magnetization treatment, it is beneficial to further improve the compressive strength of the sample.
[0033] The third aspect of the present invention also provides a method for using the steel slag sand fine-grained tailings composite backfill mortar as described in the first aspect, comprising: filling the prepared steel slag sand fine-grained tailings composite backfill mortar into the underground space to be backfilled.
[0034] According to any of the technical solutions described in the third aspect of the present invention, the method further includes: during the process of filling the prepared steel slag sand fine-grained tailings composite backfill mortar into the underground space to be backfilled, applying an external magnetic field to the backfill mortar, wherein the strength of the external magnetic field is not less than 0.1T and the magnetization time is 0.5 to 5 seconds.
[0035] The fourth aspect of the present invention also provides a mine backfill body, which is obtained by filling with the steel slag sand fine tailings composite backfill mortar described in the first aspect.
[0036] Compared with the prior art, the technical solution provided by this invention has the following advantages: (1) This invention uses magnetic volcanic ash cementitious material, that is, introduces magnetic powder particles, so as to cleverly utilize the magnetism of steel slag sand, magnetic powder particles and tailings fine particles, so that the fine tailings will agglomerate under the action of magnetic field force. Therefore, on the one hand, it can effectively prevent the segregation of filling slurry and uneven distribution of solidified body strength caused by the different gravity settling speed of fine tailings and steel slag sand. Thus, it can make full use of the fine aggregate effect of steel slag sand. On the other hand, the agglomerates formed will overcome the repulsive force of the agglomerates and undergo gravity settling, so that excess water in the tailings slurry will be discharged from the tailings particles. The fine tailings will be closely close to each other, thus reducing the volume of the mortar solidified body and increasing its density, laying the foundation for improving the mechanical properties of solidified tailings.
[0037] (2) The present invention further utilizes the cross-linking effect of ultrafine particle trapping agent (PAM), which can capture ultrafine tailings (particle size <1μm) in fine tailings by the branches of ultrafine particle trapping agent, and further form large agglomerates of highly dispersed ultrafine tailings; while the high-valence metal cations in the de-colloiding agent and cementing material can further reduce the absolute value of the Zeta potential of fine tailings micelles, resulting in de-colloiding effect, and the colloidal water between fine tailings particles is converted into free water, so that fine tailings can come together and contact each other, thus further reducing the amount of cementing material used in cementing unit tailings.
[0038] (3) The addition of steel slag sand to the mortar increases the density and fluidity of the mortar per unit volume. The active aggregate effect of steel slag sand strengthens the fine particle packing structure of the filling body. At the same time, the Ca(OH)2 released from the steel slag sand continues to participate in the secondary pozzolanic reaction, which makes the strength of the mortar continuously increase.
[0039] (4) In the process of preparing or filling the filling mortar, the present invention magnetizes the filling material by applying an external magnetic field, which is beneficial to further improve the mechanical properties of the resulting filling material. Detailed Implementation
[0040] To further understand the present invention, specific embodiments are now described in detail. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of this disclosure. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of this disclosure for ease of explanation. However, it will be apparent that one or more embodiments may be practiced without these specific details.
[0041] Furthermore, all terms used herein (including technical and scientific terms) shall have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein shall be interpreted in a manner consistent with the context of this specification, and not in an idealized or overly rigid manner. The terms “comprising,” “including,” etc., as used herein, indicate the presence of the stated features, steps, operations, and / or components, but do not preclude the presence or addition of one or more other features, steps, operations, or components.
[0042] Furthermore, it should be understood that all numerical ranges defined herein include both all range values and all specific values within that range. Due to space limitations, only some values are listed as examples in the following embodiments, and do not constitute any limitation on the scope of protection of this application. For example, the mass of magnetic powder particles accounts for 5-10% of the total mass of the magnetic pozzolanic cementitious material, which can be 5-7%, 7.5-9%, 8-10%, or 5-10% of the total mass of the magnetic pozzolanic cementitious material, or it can be 5%, 6%, 7.5%, 8%, 9%, or 10% of the total mass of the magnetic pozzolanic cementitious material. Moreover, the specific material selection for components such as steel slag sand, pozzolanic components, and activators is not limited to the specific embodiments below.
[0043] Example 1 The steel slag sand fine-grained tailings composite backfill mortar of this embodiment is composed of five raw materials: 1) steel slag sand, 2) magnetic volcanic ash cementitious material, 3) fine-grained tailings, 4) breaker, and 5) ultrafine particle capture agent PAM. Among them, based on the oven-dry tailings in the fine-grained tailings, the mass ratio of steel slag sand to oven-dry tailings is 1:4; the mass ratio of magnetic volcanic ash cementitious material to oven-dry tailings is 1:5; the mass ratio of breaker to oven-dry tailings is 1:1000; and the mass ratio of ultrafine particle capture agent PAM to oven-dry tailings is 1:10000.
[0044] Furthermore, in this embodiment, the steel slag sand is hot slag produced by converter steelmaking, and its particle size ranges from 0.2 to 0.5 mm. The composition of the magnetic volcanic ash cementitious material is as follows: alkaline activator accounts for 5% by mass, sulfate activator accounts for 10% by mass, artificial volcanic ash accounts for 80% by mass, and magnetic powder accounts for 5% by mass; the specific surface area of the magnetic volcanic ash cementitious material is 500 m². 2 / kg.
[0045] The magnetic powder particles are magnetized steel slag micro powder with a specific surface area S of 600 m². 2 / kg, with a residual magnetic induction intensity of 0.15mT, this magnetized steel slag powder is obtained by magnetizing steel slag powder under a magnetic field of 1.0T; the alkaline activator is quicklime powder, the sulfate activator is anhydrous calcium sulfate; the artificial volcanic ash is water-quenched blast furnace slag powder, labeled S105.
[0046] The fine tailings are the fine tailings from the grinding and magnetic separation of magnetite at Maanshan Iron and Steel Group's Baixiangshan Mine. 90% of the fine tailings pass through a 200m sieve, with a D50 of 13 micrometers. The tailings slurry has a tailings mass concentration of 50% and a slump of 200cm.
[0047] The decolloiding agent is polyferric chloride; the ultrafine particle capture agent PAM is anionic PAM.
[0048] The preparation process of the steel slag sand fine-grained tailings composite backfill mortar in this embodiment is as follows: (1) First, the breaker and the ultrafine particle capture agent PAM are prepared into corresponding solutions, wherein the mass concentration of the breaker solution is 1% and the mass concentration of the PAM solution is 1 / 1000. (2) Then, according to the metering ratio of each raw material in the composite backfill mortar of steel slag sand fine tailings in this embodiment, the weighed magnetic volcanic ash cementitious material, steel slag sand, breaker solution and PAM solution are added to the fine mud tailings (slurry) in sequence. Then, the mixture is stirred with a mixer. The stirring speed of the mixer blade is 60 rpm and the stirring time is 2 minutes to obtain the steel slag sand fine tailings composite backfill mortar sample.
[0049] Samples of composite backfill mortar made from steel slag sand and fine-grained tailings were injected into standard mortar molds and cured at 20°C and 90% relative humidity. After one day of curing, the samples were demolded and cured for 3, 7, and 28 days. The unconfined compressive strength of the cured mortar samples at each age was then tested. The unconfined compressive strength of the cured mortar samples was found to be 1.8 MPa at 3 days, 2.5 MPa at 7 days, and 4 MPa at 28 days. After curing in 10 atm water vapor for 3 days, the unconfined compressive strength of the cured mortar samples was 5 MPa.
[0050] Example 2 The steel slag sand fine-grained tailings composite backfill mortar of this embodiment has the same material composition and mass ratio as in Embodiment 1.
[0051] The preparation method of the steel slag sand fine-grained tailings composite backfill mortar in this embodiment differs from that in Embodiment 1 in that: after mixing and stirring the raw materials for 3 minutes to obtain a steel slag sand fine-grained tailings composite backfill mortar sample, the mortar sample is injected into a plastic standard mortar mold, and then the mortar sample is placed in an external magnetic field with an external magnetic field strength of 0.15T for 1 second, which enhances the magnetism of the weak magnetic particles and magnetic particles in the mortar, i.e., magnetizes them. Then, it is placed under the conditions of 20℃ and 90% relative humidity for curing. After curing for one day, it is demolded and cured under the above conditions for 3 days, 7 days, and 28 days. The unconfined compressive strength of the mortar sample at each age is tested. The unconfined compressive strength of the sample at 3 days is 2.2MPa, at 7 days is 3.2MPa, at 28 days is 4.5MPa, and after curing in 10 atm water vapor for 3 days, the unconfined compressive strength is 5.8MPa.
[0052] Example 3 The raw material composition of the steel slag sand fine-grained tailings composite backfill mortar in this embodiment is detailed in Table 1.
[0053] Furthermore, in this embodiment, the steel slag sand is the drum air-cooled slag produced by converter steelmaking, which has been stored for more than 1 year and has a particle size range of 0.2~0.5mm; The material composition of the magnetic volcanic ash cementitious material is as follows: alkaline activator accounts for 10% by mass, sulfate activator accounts for 10% by mass, artificial volcanic ash accounts for 70% by mass, and magnetic powder accounts for 10% by mass. The magnetic powder particles are Fe3O4 concentrate powder with a specific surface area S of 500 m². 2 / kg, with a residual magnetic induction intensity of 2.5mT, the magnetic powder particles are obtained by magnetizing Fe3O4 concentrate powder under a magnetic field of 1.0T; The alkaline activator is a composite of quicklime powder and hydrated lime powder, with a mass ratio of 2:1. The specific surface area of the magnetic pozzolanic cementitious material is 450 m². 2 / kg; the sulfate activator is calcium sulfate dihydrate; The artificial volcanic ash is composed of water-quenched blast furnace slag powder and fly ash, with a composite ratio of 5:1, and is designated as S105. The fine tailings in this embodiment are the overflow classification tailings after grinding and magnetic separation of magnetite from Maanshan Iron and Steel Baixiangshan Mine. 90% of the fine tailings pass through a 200m sieve, and its D50 is 13 microns. The tailings concentration of the fine tailings slurry is 50%, and the slump is 200cm. In this embodiment, the desiccant is polyaluminum chloride, and the ultrafine particle capture agent PAM is anionic PAM.
[0054] Table 1. Composition of steel slag sand fine-grained tailings composite backfill mortar in Examples 1-6
[0055] The preparation process of the steel slag sand fine-grained tailings composite backfill mortar in this embodiment is as follows: (1) First, the breaker and the ultrafine particle capture agent PAM are prepared into corresponding solutions, wherein the solution concentration of the breaker is 1% and the solution concentration of the ultrafine particle capture agent PAM is 1 / 1000. (2) Then, according to the metering ratio of each raw material in the composite backfill mortar of steel slag sand fine tailings in this embodiment, the weighed magnetic volcanic ash cementitious material, steel slag sand, inorganic setting agent solution and PAM solution are added to the fine mud tailings (slurry) in sequence. Then, the mixture is stirred with a mixer. The stirring speed of the mixer blade is 60 rpm and the stirring time is 2 minutes to obtain a sample of composite backfill mortar of steel slag sand fine tailings.
[0056] The mortar sample was injected into a standard mortar mold and cured at 20℃ and 90% relative humidity. After one day of curing, it was demolded and cured for 3, 7, and 28 days under the same conditions. The strength of the cured mortar sample at each age was tested. The unconfined compressive strength of the cured mortar sample was 1.2 MPa at 3 days, 2.1 MPa at 7 days, and 3.1 MPa at 28 days. After curing in 10 atm water vapor for 3 days, the unconfined compressive strength of the cured mortar sample was 3.5 MPa.
[0057] The construction process of the steel slag sand fine-grained tailings composite backfill mortar in this embodiment is as follows: The prepared mortar is flowed by gravity through a regular backfilling pipeline and finally filled into the underground space to be backfilled. The magnetic pozzolanic cementitious material in the mortar and the fine magnetic particles in the tailings are driven into the steel slag sand by magnetic aggregation and magnetic action. With the cross-linking effect of PAM, it will become a large agglomerate. When the high-valence metal cations released by the de-gelling agent and the magnetic pozzolanic cementitious material in the agglomerate reduce the Zeta potential of the ultrafine tailings flocs, the de-gelling effect occurs, and the colloidal water it carries is converted into free water. The gap between particles is reduced, and the large agglomerate with steel slag sand as the core will undergo overall gravity settling. After settling, the particles are densely packed. In addition, the magnetic pozzolanic cementitious material in the steel slag sand-fine mud tailings mortar after settling will produce a large amount of colloid, which binds the steel slag sand tailings into a whole backfill. After 28 days, the core was intact, and its unconfined compressive strength was 3.0 MPa.
[0058] Example 4 The raw material composition of the steel slag sand fine-grained tailings composite backfill mortar in this embodiment is detailed in Table 1.
[0059] Furthermore, in this embodiment, the steel slag sand is hot slag produced by converter steelmaking, and the hot slag has been stored for more than 1 year, with a particle size range of 0.1~0.6mm.
[0060] The material composition of the magnetic volcanic ash cementitious material is as follows: alkaline activator accounts for 7.5% by mass, sulfate activator accounts for 12.5% by mass, artificial volcanic ash accounts for 75% by mass, and magnetic powder accounts for 5% by mass. The magnetic powder particles are Fe3O4 concentrate powder with a specific surface area S of 500 m². 2 / kg; the residual magnetic induction intensity is 2.5mT. This magnetized concentrate powder is obtained by magnetizing Fe3O4 concentrate powder under a magnetic field of 1.0T.
[0061] The alkaline activator is 52.5PO cement, and the specific surface area of the magnetic pozzolanic cementitious material is 550 m². 2 / kg; The sulfate activator is calcium sulfate hemihydrate; The artificial volcanic ash is composed of water-quenched blast furnace slag powder and boiler slag, with a composite ratio of 4:1, and is designated as S115. The fine tailings are the fine tailings from the grinding and magnetic separation of magnetite at Maanshan Iron and Steel Baixiangshan Mine. 90% of the fine tailings pass through a 200m sieve, with a D50 of 13 micrometers. The tailings slurry has a tailings concentration of 50% and a slump of 200cm. The degreasing agent is polyferric chloride; The ultrafine particle capture agent PAM is cationic PAM.
[0062] The preparation process of the steel slag sand fine-grained tailings composite backfill mortar in this embodiment is as follows: (1) First, the breaker and the ultrafine particle capture agent PAM are prepared into corresponding solutions, wherein the solution concentration of the breaker is 1% and the solution concentration of PAM is 1 / 1000; (2) Then, according to the metering ratio of each raw material in the composite backfill mortar of steel slag sand fine-grained tailings, the measured magnetic volcanic ash cementitious material, steel slag sand, breaker solution, and ultrafine particle capture agent PAM solution are added to the fine mud tailings (slurry) in sequence. Then, the mixture is stirred with a mixer. The stirring speed of the mixer blade is 60 rpm and the stirring time is 2 minutes to obtain a sample of steel slag sand fine-grained tailings composite backfill mortar.
[0063] The mortar was poured into a standard mortar mold and cured at 20℃ and 90% relative humidity. After one day of curing, the mold was removed, and the mortar was cured for 3, 7, and 28 days under the same conditions. The strength of the cured mortar samples at each age was then tested. The unconfined compressive strength of the cured mortar samples was 1.5 MPa at 3 days, 2.5 MPa at 7 days, and 3.5 MPa at 28 days. After curing in 10 atm water vapor for 3 days, the unconfined compressive strength of the cured mortar samples was 4.2 MPa.
[0064] The construction process of the steel slag sand fine-grained tailings composite backfill mortar in this embodiment is as follows: The prepared mortar is first flowed through a section of non-magnetic pipe made of austenitic stainless steel or wear-resistant PVC. A magnetic field with a strength of 0.15T is applied to the pipe to enhance the magnetism of the weakly magnetic tailings fine particles, steel slag powder, and concentrate powder in the mortar. Then, it flows through a regular backfilling pipe and is finally filled into the underground space to be backfilled. The magnetic pozzolanic cementitious material in the mortar and the fine magnetic particles in the tailings rely on magnetic aggregation and magnetic effects to drive other particles toward the steel slag sand. In addition, PAM (Polymerized Atomium) further enhances the magnetism of the ultrafine tailings particles. Cross-linking leads to the formation of a large agglomerate. When the high-valence metal cations released from the de-colloiding agent and magnetic pozzolanic cementitious material in the agglomerate reduce the Zeta potential of the fine tailings flocs, a de-colloiding effect is produced, causing the colloidal water it carries to be converted into free water. The gaps between particles are reduced, and the large agglomerate with steel slag sand as the core will undergo overall gravity settling. After settling, the particles are densely packed. In addition, the magnetic pozzolanic cementitious material in the steel slag sand-fine tailings slurry after settling will produce a large amount of colloid, which cements the steel slag sand tailings into a filling whole. After 28 days, the core sample was intact, and the unconfined compressive strength of the core sample was 4.1 MPa.
[0065] Example 5 The raw material composition of the steel slag sand fine-grained tailings composite backfill mortar in this embodiment is detailed in Table 1.
[0066] Furthermore, in this embodiment, the steel slag sand is hot slag produced by converter steelmaking, which has been stored for more than one year and has a particle size range of 0.1~0.5mm.
[0067] The material composition of the magnetic volcanic ash cementitious material is as follows: alkaline activator accounts for 7.5% by mass, sulfate activator accounts for 10% by mass, artificial volcanic ash accounts for 75% by mass, and magnetic powder accounts for 7.5% by mass. The magnetic powder particles are steel slag micro-powder, which is obtained through magnetization treatment. The residual magnetic induction intensity is 0.7 mT, and the specific surface area S is 500 m². 2 / kg; The alkaline activator is composed of 52.5PO cement and quicklime in a 2:1 ratio. The magnetic pozzolanic cementitious material has a specific surface area of 550 m². 2 / kg; The sulfate activator is composed of calcium sulfate hemihydrate and anhydrous gypsum in a ratio of 1:4. The artificial volcanic ash is water-quenched blast furnace slag powder, designated as S105. The fine tailings are the fine tailings from the grinding and magnetic separation of magnetite (containing pyrite) from Longqiao Mine in Lujiang County, Anhui Province. 90% of the fine tailings pass through a 200m sieve, with a D50 of 11 micrometers. The tailings slurry has a tailings concentration of 48% and a slump of 180cm. The degreasing agent is polyferric chloride; The ultrafine particle capture agent PAM is non-ionic PAM.
[0068] The steel slag sand fine-grained tailings composite backfill mortar of this embodiment is prepared in the same way as in Example 3. The unconfined compressive strength of the sample is 1.5 MPa after 3 days, 2.5 MPa after 7 days, and 3.5 MPa after 28 days. After curing in 10 atm water vapor for 3 days, the unconfined compressive strength is 4.1 MPa.
[0069] Example 6 The raw material composition of the steel slag sand fine-grained tailings composite backfill mortar in this embodiment is detailed in Table 1.
[0070] Furthermore, in this embodiment, the steel slag sand is hot slag produced by converter steelmaking, which has been stored for more than one year and has a particle size range of 0.1~0.5mm.
[0071] The alkaline activator accounts for 7.5% by mass, the sulfate activator accounts for 10%, the artificial volcanic ash accounts for 75%, and the magnetic powder accounts for 7.5%. The magnetic powder particles are steel slag micro-powder, which is obtained through magnetization treatment. The residual magnetic induction intensity is 0.7 mT, and the specific surface area S is 500 m². 2 / kg; The alkaline activator is composed of 52.5PO cement and quicklime in a 1:1 ratio. The magnetic pozzolanic cementitious material has a specific surface area of 450 m². 2 / kg; The sulfate activator is composed of potassium sulfate and anhydrous gypsum in a ratio of 1:4. The artificial volcanic ash is water-quenched blast furnace slag powder, designated as S95. The fine tailings are the fine tailings from the grinding and magnetic separation of pyrite at Maanshan Iron and Steel Luohe Mine. 90% of the fine tailings pass through a 200-mesh sieve, with a D50 of 19μm. The tailings slurry has a tailings concentration of 55% and a slump of 200cm. The degreasing agent is polyferric chloride; The ultrafine particle capture agent PAM is anionic PAM.
[0072] The steel slag sand fine-grained tailings composite backfill mortar of this embodiment is prepared in the same way as in Example 2. The unconfined compressive strength of the sample is 2.5 MPa after 3 days, 3.5 MPa after 7 days, and 4.5 MPa after 28 days. After curing in 10 atm water vapor for 3 days, the unconfined compressive strength is 5.2 MPa.
[0073] Comparative Example 1 The tailings backfill mortar in this comparative example consists of fine-grained tailings from Baixiangshan Mine and a commercially available fine-grained tailings solidifier. The commercially available fine-grained tailings solidifier is composed of: 20% desulfurized gypsum, 10% 42.5PO cement, and 70% S95 mineral powder. The mass ratio of the solidifier to the oven-dried tailings is 1:5. The fine-grained tailings are the entire fine-grained tailings from the grinding and magnetic separation of magnetite from the Maanshan Iron and Steel Baixiangshan Mine. 90% of the fine-grained tailings pass through a 200m sieve, with a D50 of 13μm. The tailings concentration of the fine-grained tailings slurry is 50%, the slump is 200cm, and the specific surface area of the solidifier is 400m². 2 / kg.
[0074] Its preparation process is as follows: According to the measurement ratio of tailings backfill mortar, the tailings solidifying agent is added to the fine tailings (slurry), and then the mixture is stirred with a mixer. The stirring speed of the mixer blades is 60 revolutions per minute, and the stirring time is 2 minutes to obtain a fine-grained tailings backfill mortar sample.
[0075] The mortar was poured into a standard mortar mold and cured at 20℃ and 90% relative humidity. After one day of curing, the mold was removed, and the mortar was cured for 3, 7, and 28 days. The unconfined compressive strength of the cured mortar samples at each age was tested. The unconfined compressive strength of the cured mortar samples was 0.5 MPa at 3 days, 1.1 MPa at 7 days, and 2.1 MPa at 28 days. After curing in 10 atm water vapor for 3 days, the unconfined compressive strength of the cured mortar samples was 2.2 MPa.
[0076] Comparative Example 2 The tailings backfill mortar in this comparative example consists of fine-grained tailings from Zhongjiu Mine and a commercially available fine-grained tailings solidifier. The commercially available fine-grained tailings solidifier is composed of: 10% anhydrite, 10% 42.5PO cement, and 80% S95 mineral powder. The mass ratio of the solidifier to the oven-dried tailings is 1:4. The fine-grained tailings are the complete fine-grained tailings from the grinding and magnetic separation of magnetite from Maanshan Iron & Steel Zhongjiu Mine. 90% of the fine-grained tailings pass through a 200m sieve, with a D50 of 20μm. The tailings slurry has a tailings concentration of 55%, a slump of 180cm, and a specific surface area of 450m². 2 / kg.
[0077] Its preparation process is as follows: According to the measurement ratio of tailings backfill mortar, the tailings solidifying agent was added to the fine mud tailings (slurry), and then stirred with a mixer. The stirring speed of the mixer blades was 60 rpm, and the stirring time was 2 minutes to obtain a steel slag sand fine-grained tailings composite backfill mortar sample.
[0078] The mortar was poured into a standard mortar mold and cured at 20℃ and 90% relative humidity. After one day of curing, the mold was removed, and the mortar was cured for 3, 7, and 28 days under the same conditions. The strength of the cured mortar samples at each age was then tested. The unconfined compressive strength of the cured mortar samples was found to be 1.2 MPa at 3 days, 2.2 MPa at 7 days, and 2.9 MPa at 28 days. After curing in 10 atm water vapor for 3 days, the unconfined compressive strength of the cured mortar samples was 3.0 MPa.
[0079] Comparative Example 3 The tailings backfill mortar in this comparative example consists of fine-grained tailings from Zhongjiu Mine and a commercially available fine-grained tailings solidifier. The commercially available fine-grained tailings solidifier is composed of: 15% desulfurized gypsum, 15% 42.5PO cement, and 70% S95 mineral powder. The mass ratio of the solidifier to the oven-dried tailings is 1:6. The fine-grained tailings are overflow and classified fine-grained tailings from the grinding and magnetic separation of magnetite from Maanshan Iron & Steel Zhongjiu Mine. 90% of the fine-grained tailings pass through a 200m sieve, with a D50 of 20μm. The tailings slurry has a tailings concentration of 55%, a slump of 180cm, and a specific surface area of 420m². 2 / kg.
[0080] Its preparation process is as follows: According to the measurement ratio of tailings backfill mortar, the tailings solidifying agent was added to the fine mud tailings (slurry), and then stirred with a mixer. The stirring speed of the mixer blades was 60 rpm, and the stirring time was 2 minutes to obtain a steel slag sand fine-grained tailings composite backfill mortar sample.
[0081] The mortar was poured into a standard mortar mold and cured at 20℃ and 90% relative humidity. After curing for one day, the mold was removed, and the mortar was cured for 3, 7, and 28 days under the same conditions. The strength of the mortar samples at each age was then tested. The unconfined compressive strength of the samples was 0.4 MPa at 3 days, 0.9 MPa at 7 days, and 1.7 MPa at 28 days. After curing in 10 atm water vapor for 3 days, the unconfined compressive strength was 1.8 MPa.
[0082] Comparative Example 4 The steel slag sand fine-grained tailings composite backfill mortar of this comparative example is composed of five raw materials: 1) steel slag sand, 2) volcanic ash cementitious material, 3) fine-grained tailings, 4) breaker, and 5) ultrafine particle capture agent PAM. Unlike Example 1, the volcanic ash cementitious material of this comparative example does not contain magnetic particles. That is, the mass ratio of alkaline activator in the volcanic ash cementitious material is 5%, the mass ratio of sulfate activator is 10%, and the mass ratio of artificial volcanic ash is 85%.
[0083] The steel slag sand fine-grained tailings composite backfill mortar of this comparative example was prepared in the same way as in Example 1. The obtained steel slag sand fine-grained tailings composite backfill mortar sample was injected into a standard mortar mold and cured at 20°C and 90% relative humidity. After curing for one day, it was demolded and cured for 3 days, 7 days, and 28 days under the above conditions. The unconfined compressive strength of the cured mortar sample at each age was tested. The unconfined compressive strength of the cured mortar sample was 1.2 MPa at 3 days, 1.8 MPa at 7 days, and 2.5 MPa at 28 days. After curing in 10 atm water vapor for 3 days, the unconfined compressive strength of the cured mortar sample was 2.8 MPa.
[0084] Comparative Example 5 The steel slag sand fine-grained tailings composite backfill mortar of this comparative example is composed of five raw materials: 1) steel slag sand, 2) volcanic ash cementitious material, 3) fine-grained tailings, 4) breaker, and 5) ultrafine particle capture agent PAM. Unlike Example 1, the steel slag powder in the volcanic ash cementitious material of this comparative example is not subjected to additional magnetization treatment (its residual magnetic induction intensity is less than 0.15mT).
[0085] The steel slag sand fine-grained tailings composite backfill mortar of this comparative example was prepared in the same way as in Example 1. The obtained steel slag sand fine-grained tailings composite backfill mortar sample was injected into a standard mortar mold and cured at 20°C and 90% relative humidity. After curing for one day, it was demolded and cured for 3 days, 7 days, and 28 days under the above conditions. The unconfined compressive strength of the cured mortar sample at each age was tested. The unconfined compressive strength of the cured mortar sample was 1.0 MPa at 3 days, 1.6 MPa at 7 days, and 2.3 MPa at 28 days. After curing in 10 atm water vapor for 3 days, the unconfined compressive strength of the cured mortar sample was 2.55 MPa.
Claims
1. A composite backfill mortar made from fine-grained steel slag and sand tailings, characterized in that, The mortar raw materials include fine-grained tailings, steel slag sand, magnetic pozzolanic cementitious materials, demagnetizing agents, and ultrafine particle capture agents, among which: At least 90% of the tailings particles in the fine tailings can pass through a 200-mesh sieve, and their D50 ≤ 20 micrometers; The particle size range of the steel slag sand is 0.1~1mm; The magnetic volcanic ash cementitious material comprises volcanic ash components, an activator, and magnetic powder particles. Based on the completely dry tailings in fine-grained tailings, the mass ratio of the magnetic volcanic ash cementitious material to the completely dry tailings is 1:4~12, and the remanent magnetic induction intensity of the magnetic powder particles is 0.15~2.5mT, accounting for 5~10% of the total mass of the magnetic volcanic ash cementitious material. The deflocculating agent includes a high-valent metal cationic inorganic flocculant; The ultrafine particle trapping agent includes polyacrylamide.
2. The composite backfill mortar made from steel slag sand and fine-grained tailings according to claim 1, characterized in that, The magnetic powder particles are magnetized steel slag micro powder, magnetic concentrate powder, or a combination thereof, with a specific surface area of 300 m². 2 / kg≤S≤700m 2 / kg.
3. The composite backfill mortar made from fine-grained steel slag and tailings as described in claim 1, characterized in that, The volcanic ash composition is either natural volcanic ash or artificial volcanic ash, wherein the artificial volcanic ash is at least one of water-quenched blast furnace slag powder, fly ash, and slag powder, and its specific surface area is ≥400 m². 2 / kg; The activator comprises an alkaline activator and a sulfate activator, and the mass of the alkaline activator and the sulfate activator accounts for 5-25% and 10-25% of the total mass of the magnetic pozzolanic cementitious material, respectively.
4. The composite backfill mortar made from fine-grained steel slag and sand tailings according to claim 1, characterized in that, The fine-grained tailings are the full tailings or overflow classification tailings obtained by grinding and magnetic separation of pyrite or magnetite, with a tailings concentration of ≥45% and a slump of ≥180cm. The steel slag sand is made from hot slag produced by converter steelmaking, drum-cooled slag, or hot-pouring slag. Based on the absolutely dry tailings in fine-grained tailings, the mass ratio of steel slag sand to absolutely dry tailings is 1:3~12.
5. The steel slag sand fine-grained tailings composite backfill mortar according to any one of claims 1-4, characterized in that, The ultrafine particle capture agent is any one of anionic polyacrylamide, cationic polyacrylamide, or nonionic polyacrylamide, and its mass ratio with the oven-dried tailings is 1:10000~1000000. The degreasing agent is polyferric chloride or polyaluminum chloride or a compound thereof in any mass ratio, and its mass ratio with the oven-dried tailings is 1:500~3000.
6. The composite backfill mortar made from fine-grained steel slag and tailings as described in claim 5, characterized in that, The steel slag sand fine-grained tailings composite backfill mortar samples were cured at 20℃ and 90% relative humidity. The unconfined compressive strength was ≥1MPa after 3 days, ≥1.8MPa after 7 days, and ≥3MPa after 28 days. After the steel slag sand fine-grained tailings composite backfill mortar sample was cured in 10 atm water vapor for 3 days, its unconfined compressive strength was ≥3.5MPa.
7. A method for preparing a composite backfill mortar made from fine-grained steel slag sand tailings as described in any one of claims 1-6, characterized in that, include: The raw materials of the steel slag sand fine-grained tailings composite backfill mortar are mixed and stirred evenly to obtain a sample of the steel slag sand fine-grained tailings composite backfill mortar.
8. The preparation method according to claim 7, characterized in that, Also includes: The steel slag sand fine-grained tailings composite backfill mortar sample obtained by mixing was placed in an external magnetic field for magnetization treatment. The external magnetic field strength was not less than 0.1T and the magnetization time was 0.5~5 seconds.
9. A method of using the steel slag sand fine-grained tailings composite backfill mortar as described in any one of claims 1-6, characterized in that, include: The prepared steel slag sand fine-grained tailings composite backfill mortar is filled into the underground space to be backfilled.
10. The method of use according to claim 9, characterized in that, Also includes: During the process of filling the prepared steel slag sand fine-grained tailings composite backfill mortar into the underground space to be backfilled, an external magnetic field is applied to the backfill mortar. The strength of the external magnetic field is not less than 0.1T, and the magnetization time is 0.5~5 seconds.