A coarse aggregate, a method for producing the same, a mixed aggregate, a filling slurry, and a filling body

Abstract

The application provides a kind of coarse aggregate and its preparation method, mixed aggregate, filling slurry and filling body, belongs to the technical field of mine filling.The raw materials of the coarse aggregate include superfine tailings 80-90wt%, quicklime 5-12wt%, fly ash 0-8wt%, based on the total mass of the raw materials of the coarse aggregate being 100%.The coarse aggregate absorbs a large amount of superfine tailings, while realizing the resource utilization of superfine tailings filling, solving the problems of low utilization rate of superfine tailings filling, insufficient capacity of tailings pond and discharge pollution, and has significant environmental benefits.In addition, using the coarse aggregate to optimize the grading of superfine tailings can not only improve the fluidity of the filling slurry but also improve the strength of the filling body.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of mine filling, and particularly relates to a coarse aggregate, a preparation method thereof, a mixed aggregate, a filling slurry and a filling body. BACKGROUND

[0002] Ultra-fine tailings generally refer to a type of tailings with an average particle size of less than 30 μm, a fine particle content of more than 50% below 20 μm, a particle content of less than 10% above 74 μm, and a particle content of not more than 30% above 37 μm, which are difficult to handle during the mining process. A large amount of ultra-fine tailings are discharged into tailings storage for stacking, which not only occupies land resources, but also pollutes the surrounding environment, and there is a risk of tailings dam collapse. With the increasing environmental awareness, how to economically, safely and environmentally dispose of ultra-fine particle tailings is a difficult problem that needs to be solved urgently at present.

[0003] The ultra-fine tailings cemented filling method is to mix the ultra-fine tailings as aggregate with a certain amount of cementing material and water to form a filling slurry, which is backfilled into the mined-out area, and the filling body formed by hardening of the filling slurry provides an operating platform for underground mining and realizes ground pressure control, which is an effective way to dispose of large quantities of tailings, is conducive to reducing the land occupation of tailings ponds and reducing safety risks, and has significant environmental and economic benefits. For example, patent application file CN113087480A discloses an application type cemented filling material containing ultra-fine tailings and a preparation method and application thereof. The raw materials of the cemented filling material include cementing material, aggregate and water. The cementing material includes the following components by weight fraction: steel slag 10-30 parts, mineral powder 30-60 parts, gypsum 0-30 parts, and desulfurization ash 5-20 parts. The aggregate includes ultra-fine tailings. The mass ratio of the cementing material to the aggregate is 1:4-7. The slurry concentration of the cemented filling material is 50-65%. SUMMARY

[0004] The present application is based on the discovery and recognition of the inventors on the following facts and problems: due to the small particle size and large specific surface area of ultra-fine tailings, the flowability of the prepared filling slurry and the compressive strength of the filling body after hardening and shaping of the filling slurry are not ideal, in order to ensure that the filling slurry has good flow performance at a higher concentration, so as to ensure that the filling slurry can smoothly reach the underground goaf, at the same time, in order to ensure that the filling body also has excellent compressive strength, so as to ensure the safety of the goaf and prevent the occurrence of underground collapse accidents, related technologies such as patent application files CN111217543A and CN112430022A have made corresponding exploration on the cementing material in the filling slurry, which improves the cementing ability of the ultra-fine tailings, and further improves the performance of the filling slurry and the filling body. But the improvement of the performance of the filling slurry and the filling body is still limited, and it is necessary to further improve the performance of the filling slurry and the filling body from other aspects. At present, there is no related technology to prepare ultra-fine tailings into coarse aggregate and then apply it to mine filling, therefore, it is necessary to propose a coarse aggregate and its preparation method, mixed aggregate, filling slurry and filling body.

[0005] The present application aims to at least solve one of the technical problems in the related art. To this end, embodiments of the present application propose a coarse aggregate and its preparation method, mixed aggregate, filling slurry and filling body.

[0006] The present application provides a coarse aggregate, wherein the raw materials of the coarse aggregate include 80-90wt% of ultra-fine tailings, 5-12wt% of quicklime and 0-8wt% of fly ash, based on the total mass of the raw materials of the coarse aggregate being 100%.

[0007] The coarse aggregate of the present application embodiment has the following advantages and technical effects:

[0008] (1) The raw materials of the coarse aggregate of the present application embodiment contain 80-90wt% of ultra-fine tailings, which is conducive to the large-scale absorption of ultra-fine tailings, realizes the resource utilization of ultra-fine tailings, solves the problems of low utilization rate of ultra-fine tailings, insufficient capacity of tailings pond and discharge pollution, and has significant environmental benefits;

[0009] (2) The raw materials of the coarse aggregate of the present application embodiment contain 5-12wt% of quicklime, which generates calcium hydroxide when it meets water, and can be used as an alkaline activator to react with SiO2, Al2O3 and other active ingredients in ultra-fine tailings and fly ash to generate a series of hydration products such as hydrated calcium silicate and hydrated calcium aluminate, which act as cementing materials to produce good cementing effect on ultra-fine tailings, facilitate the agglomeration and granulation of ultra-fine tailings, form raw material particles, and finally generate the coarse aggregate of the present application embodiment through sintering;

[0010] (3) The raw material of the coarse aggregate of the embodiment contains 0-8wt% fly ash, the fly ash itself has certain activity and adhesion, can increase the forming of the granular material and improve the strength of the granular material, reduce the amount of the first cementitious material, and reduce the cost of the granular material; meanwhile, the fly ash has particle morphology effect and micro-fine aggregate effect, improves the water retention of the granular material, improves the compactness of the granular material, and reduces the occurrence of dry shrinkage cracks in the curing process of the granular material;

[0011] (4) The coarse aggregate of the embodiment is subsequently replaced by a part of the ultra-fine tailings to prepare the filling material slurry, due to the effect of reasonable gradation, the obtained filling material slurry has better liquidity compared with the filling material slurry prepared by using the ultra-fine tailings as the aggregate, so that the filling material slurry can smoothly reach the underground goaf, and the compressive strength of the filling body is also greatly increased, so that the stability of the goaf is ensured, and the occurrence of underground collapse accidents and the surface subsidence are avoided.

[0012] (5) The coarse aggregate of the embodiment can significantly improve the strength of the filling body, compared with the filling body prepared by using the ultra-fine tailings as the aggregate in the related art, even if the amount of the cementitious material is reduced, the filling body of the embodiment can meet the strength requirement of the mine filling, so that when the coarse aggregate of the embodiment is subsequently replaced by a part of the ultra-fine tailings to prepare the filling material slurry, compared with the filling material slurry prepared by using the ultra-fine tailings as the aggregate, the amount of the cementitious material required is less, and the cost of the cementitious material for the mine filling can be greatly reduced.

[0013] In some embodiments, the raw material of the coarse aggregate includes 85-90wt% ultra-fine tailings, 5-10wt% quicklime, and 0-5wt% fly ash, based on 100% of the total mass of the raw material of the coarse aggregate.

[0014] In some embodiments, the raw material of the coarse aggregate includes 85wt% ultra-fine tailings, 10wt% quicklime, and 5wt% fly ash, based on 100% of the total mass of the raw material of the coarse aggregate.

[0015] In some embodiments, the particle size of the coarse aggregate is 5-10mm.

[0016] The embodiment of the present application also provides a preparation method of the coarse aggregate, including the following steps:

[0017] (1) mixing various raw materials of the coarse aggregate according to a specified proportion to obtain a mixture;

[0018] (2) adding water to the mixture and granulating to obtain green balls;

[0019] (3) calcining the green balls, and obtaining the coarse aggregate after cooling.

[0020] The preparation method of the coarse aggregate of the embodiment of the present application has the advantages and technical effects that:

[0021] The preparation method of the embodiment of the present application is simple to operate and convenient for large-scale industrialization promotion.

[0022] In some embodiments, in step (2), the amount of water added is 5-25wt% of the mass of the mixture.

[0023] In some embodiments, in step (2), the particle size of the green balls is 5-10mm.

[0024] In some embodiments, in step (3), the calcination temperature is 800-1000℃, and the calcination time is 20-60 minutes.

[0025] In some embodiments, in step (3), the green balls are first air-dried and then oven-dried before calcination.

[0026] The embodiment of the present application also provides a mixed aggregate, which comprises the coarse aggregate of the embodiment of the present application and ultra-fine tailings.

[0027] The mixed aggregate of the embodiment of the present application has the advantages and technical effects that:

[0028] The mixed aggregate of the embodiment of the present application contains both the coarse aggregate of the embodiment of the present application and ultra-fine tailings, and through the reasonable grading of the two, the mixed aggregate is more conducive to improving the fluidity of the filling slurry and the compressive strength of the filling body than the aggregate that uses only ultra-fine tailings.

[0029] In some embodiments, the mass ratio of the coarse aggregate to the ultra-fine tailings is 1:9-4:6.

[0030] The embodiment of the present application also provides a filling slurry, which comprises the mixed aggregate of the embodiment of the present application, cementitious material and water.

[0031] The filling slurry of the embodiment of the present application has the advantages and technical effects that:

[0032] (1) The filling slurry of the embodiment of the present application uses the mixed aggregate of the embodiment of the present application as the aggregate, and has better fluidity than the filling slurry that uses only ultra-fine tailings as the aggregate, and the compressive strength of the filling body obtained after the filling slurry of the embodiment of the present application is hardened and shaped is also better.

[0033] (2) The filling slurry of the embodiment of the present application optimizes the grading of the ultra-fine tailings by using the coarse aggregate of the embodiment of the present application, and can obviously reduce the amount of cementitious material compared with the filling slurry that uses only ultra-fine tailings as the aggregate, thereby reducing the cost of mine filling cementitious material.

[0034] The present application also provides a filling body formed by hardening and shaping the filling slurry.

[0035] The filling body of the present application has the advantages and technical effects of:

[0036] Compared with the filling body formed by the filling slurry using ultra-fine tailings as aggregate, the filling body of the present application has higher compressive strength, greatly improving the safety of mine filling. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 is a flowchart of the preparation method of the coarse aggregate of the present application;

[0038] Figure 2 is a flowchart of the preparation method of the filling slurry of the present application. DETAILED DESCRIPTION

[0039] The embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to explain the present application, and cannot be understood as a limitation of the present application.

[0040] The present application provides a coarse aggregate, wherein the raw materials of the coarse aggregate include 80-90wt% of ultra-fine tailings, 5-12wt% of quicklime and 0-8wt% of fly ash, based on the total mass of the raw materials of the coarse aggregate being 100%.

[0041] The raw materials of the coarse aggregate of the present application include ultra-fine tailings, quicklime and fly ash. In the subsequent preparation process of the coarse aggregate, the quicklime first reacts with water to generate calcium hydroxide, and the calcium hydroxide is used as an alkaline activator to activate the activity of the fly ash in the calcination process. At the same time, the active components such as SiO2 and Al2O3 in the fly ash and the ultra-fine tailings are dissolved and react with calcium ions to generate a series of hydration products such as hydrated calcium silicate and hydrated calcium aluminate. These hydration products can act as cementitious materials to produce good cementation effect on the ultra-fine tailings, facilitate the agglomeration and granulation of the ultra-fine tailings to form raw material particles, and finally sinter to generate the coarse aggregate of the present application. The coarse aggregate of the present application can not only be used for filling in the mined-out area or open pit of a mine, but also can be stacked on the surface of the falling area of the natural caving mining method as a cover layer, or discharged to the waste rock yard, so as to solve the problems of insufficient tailings reservoir capacity and tailings discharge difficulty caused by the difficulty in approval of the tailings reservoir.

[0042] The coarse aggregate of the embodiment of the present application is mainly used for accommodating ultra-fine tailings and improving the performance of filling slurry and filling body. The ultra-fine tailings are obtained from mines and used for mines, and thus the specific type of the ultra-fine tailings is not particularly limited, for example, the ultra-fine tailings can be gold mine ultra-fine tailings, silver mine ultra-fine tailings, copper mine ultra-fine tailings, iron mine ultra-fine tailings, etc. Meanwhile, the composition of the ultra-fine tailings is not particularly limited, but it can be understood that if the content of SiO2 in the ultra-fine tailings is 40-70 wt%, and the content of Al2O3 is 5-20 wt%, it is more beneficial to form coarse aggregate with relatively high compressive strength.

[0043] In some embodiments, the raw materials of the coarse aggregate include 85-90 wt% of ultra-fine tailings, 5-10 wt% of quicklime, and 0-5 wt% of fly ash, based on the total mass of the raw materials of the coarse aggregate being 100%. When the content of the ultra-fine tailings is too low, it is not conducive to large-scale accommodation and utilization of waste ultra-fine tailings. When the content of the ultra-fine tailings is too high, the corresponding contents of the quicklime and / or the fly ash are too low, which is not conducive to the subsequent generation of sufficient hydration products, and thus is not conducive to the formation of the coarse aggregate by cementing the ultra-fine tailings. Preferably, in some embodiments, the raw materials of the coarse aggregate include 85 wt% of ultra-fine tailings, 10 wt% of quicklime, and 5 wt% of fly ash, based on the total mass of the raw materials of the coarse aggregate being 100%.

[0044] In some embodiments, the particle size of the coarse aggregate is 5-10 mm. The coarse aggregate with the particle size in the range is more conducive to reasonable grading with the ultra-fine tailings, and improving the performance of the filling slurry and the filling body.

[0045] The embodiment of the present application also provides a preparation method of the coarse aggregate, as shown in Figure 1 The preparation method includes the following steps:

[0046] (1) mixing various raw materials of the coarse aggregate according to a specified ratio to obtain a mixture;

[0047] (2) adding water to the mixture and granulating to obtain green balls;

[0048] (3) calcining the green balls, and obtaining the coarse aggregate after cooling.

[0049] The preparation method of the embodiment of the present application first obtains a mixture through step (1), then preforms green balls through step (2), and finally obtains the coarse aggregate of the embodiment of the present application through calcination treatment reaction of step (3). In step (2), quicklime in the raw material reacts with water to generate calcium hydroxide, providing an alkaline environment and a large amount of calcium ions; fly ash and ultra-fine tailings generate a series of hydration products such as hydrated calcium silicate and hydrated calcium aluminate silicate through pozzolanic reaction with calcium ions in the alkaline environment, which has a good consolidation and agglomeration effect on the ultra-fine tailings, granulates the ultra-fine tailings, makes the green ball forming better, and finally sintering generates the coarse aggregate of the embodiment of the present application. The preparation method of the embodiment of the present application is simple to operate and convenient for large-scale industrialization.

[0050] In step (1) of the preparation method of the embodiment of the present application, the mass fraction of the dry raw material is used for batching, so the various raw materials can be dried in advance in step (1), preferably at 90-100℃; or the water content of the various raw materials is tested in step (1), and the batching is calculated based on the mass fraction of the dry raw material, and then compared with the foregoing method, the water amount is correspondingly reduced when water is added in step (2).

[0051] In some embodiments, the water amount added in step (2) is 5-25wt% of the mass of the mixture, which is more conducive to the forming of the green ball. This water amount refers to the corresponding water amount when the dry raw material is used for batching in step (1).

[0052] In some embodiments, the particle size of the green ball in step (2) is 5-10mm. This is convenient for subsequent preparation of coarse aggregate with a particle size of 5-10mm.

[0053] In some embodiments, the green ball is first air-dried and then dried in step (3) before calcination. The pre-air-drying is to avoid the breakage of the green ball, and the drying is conducive to improving the equipment productivity of the subsequent calcination process and improving the calcination quality. Preferably, the green ball is air-dried for 1-2 hours and then dried at 80-110℃ for 3-6 hours.

[0054] In some embodiments, the calcination temperature in step (3) is 800-1000℃, and the calcination time is 20-60 minutes. The mine filling body is different from concrete, and the requirement for compressive strength is relatively low. The 28d compressive strength of the one-step filling of most mines is required to be not less than 2MPa, and the 28d compressive strength of the two-step filling is required to be not less than 1MPa, so that the calcination temperature in this step can be in the range of 800-1000℃ to obtain qualified coarse aggregate, without the need to increase the calcination temperature, which is conducive to cost reduction and efficiency improvement.

[0055] The embodiment of the present application also provides a mixed aggregate comprising the coarse aggregate of the embodiment of the present application and ultra-fine tailings.

[0056] The mixed aggregate of the embodiment of the present application contains both the coarse aggregate of the embodiment of the present application and the ultra-fine tailings, and through reasonable grading of the two, the mixed aggregate is more conducive to improving the fluidity of the filling slurry and the compressive strength of the filling body relative to the aggregate using all ultra-fine tailings.

[0057] The mixed aggregate of the embodiment of the present application, through reasonable grading of the coarse aggregate and the ultra-fine tailings, is more conducive to improving the fluidity of the filling slurry and the compressive strength of the filling body relative to the aggregate using all ultra-fine tailings in the related art.

[0058] In some embodiments, the mass ratio of the coarse aggregate to the ultra-fine tailings is 1:9-4:6, preferably 3:7, which is more conducive to reasonable grading of the aggregate, thereby improving the performance of the filling slurry and the filling body. When the proportion of the coarse aggregate is too low, the skeleton effect of the coarse aggregate in the filling body is weak, which is not conducive to the growth of the strength of the filling body; when the proportion of the coarse aggregate is too high, the overall packing density of the mixed aggregate is reduced, which is also not conducive to the development of the strength, and a high proportion of the coarse aggregate will undoubtedly increase the filling cost.

[0059] The embodiment of the present application also provides a filling slurry, which comprises the mixed aggregate of the embodiment of the present application, cementitious material and water.

[0060] The filling slurry of the embodiment of the present application, wherein the aggregate is the mixed aggregate of the embodiment of the present application, has better fluidity relative to the filling slurry using all ultra-fine tailings as the aggregate, and the compressive strength of the filling body obtained after the filling slurry of the embodiment of the present application is hardened and shaped is also better; in addition, the filling slurry of the embodiment of the present application optimizes the grading of the ultra-fine tailings by using the coarse aggregate of the embodiment of the present application, and relative to the filling slurry using all ultra-fine tailings as the aggregate, the amount of cementitious material can be obviously reduced, thereby reducing the cost of the cementitious material for mine filling.

[0061] The filling slurry of the embodiment of the present application does not have special limitations on the specific type of cementitious material, which may be at least one of Portland cement, ordinary Portland cement, slag Portland cement, pozzolanic Portland cement, fly ash Portland cement, composite Portland cement and cementitious powder, or any suitable cementitious material for the filling body disclosed in the related art.

[0062] In some embodiments, the mass ratio of the cementitious material to the mixed aggregate is 1:(5-10), that is, the sand-cement ratio in the filling slurry is 1:(5-10). When the sand-cement ratio is too high, it is not conducive to the large-scale absorption of ultra-fine tailings, and the cost of the cementitious material will increase. When the sand-cement ratio is too low, it is not conducive to improving the compressive strength of the filling body.

[0063] In some embodiments, the mass concentration of the filling slurry is 65-75%. When the mass concentration of the filling slurry is too low, it is not conducive to the large amount of consumption of ultra-fine tailings and the improvement of the strength of the filling body. When the mass concentration of the filling slurry is too high, it is not conducive to the improvement of the fluidity of the filling slurry. It should be noted that the mass concentration of the filling slurry in the embodiments of the present application can be adjusted according to the mass ratio of the coarse aggregate and the ultra-fine tailings. When the mass ratio of the coarse aggregate and the ultra-fine tailings is low, the mass concentration of the filling slurry can be appropriately reduced, and vice versa. The slurry concentration of the cemented filling material in the related art CN113087480A is only 50-65%, compared with CN113087480A, the mass concentration of the filling slurry in the embodiments of the present application is higher, which is more conducive to the large amount of consumption of ultra-fine tailings, and in addition, the filling slurry in the embodiments of the present application can still have good fluidity at a higher mass concentration.

[0064] In some embodiments, according to the requirements of the mine, the cement-sand ratio is preferably 1:6, and the mass concentration of the filling slurry is preferably 70%. The cement-sand ratio and the mass concentration are conducive to improving the fluidity of the filling slurry, while also ensuring that the filling body has good compressive strength.

[0065] The embodiments of the present application also provide a filling body obtained by hardening and shaping the filling slurry of the embodiments of the present application.

[0066] The filling body of the embodiments of the present application has higher compressive strength than the filling body formed by the filling slurry using ultra-fine tailings as aggregate, which greatly improves the safety of mine filling.

[0067] The present application will be described in detail below with reference to the embodiments and the accompanying drawings.

[0068] Embodiment 1

[0069] A kind of coarse aggregate, with the total mass of the raw material of coarse aggregate being 100%, the raw material of coarse aggregate includes gold mine ultra-fine tailings 85wt%, quicklime 10wt%, fly ash 5wt%, and the particle size of coarse aggregate is 5-10mm.

[0070] The preparation method of the above-mentioned coarse aggregate, as shown in Figure 1 includes the following steps:

[0071] (1) the gold mine ultra-fine tailings, quicklime, fly ash are placed in a drying oven and dried at 90℃, wherein the chemical composition of the gold mine ultra-fine tailings is shown in Table 1, and the particle size distribution of the gold mine ultra-fine tailings is shown in Table 2;

[0072] (2) the dried raw materials are mixed and homogenized according to the mass fraction of gold mine ultra-fine tailings 85wt%, quicklime 10wt%, and fly ash 5wt%, to obtain a mixture;

[0073] (3) Spraying 10wt% of water into the mixture, and using a disc granulator to prepare the mixed material into green balls with a particle size of about 10mm;

[0074] (4) Placing the prepared green balls in a drying oven at 100°C for 3 hours;

[0075] (5) Placing the dried green balls into a rotary kiln and calcining at 850°C for 35 minutes, and after natural cooling, obtaining granular aggregate, i.e. coarse aggregate, with a particle size of 5-10mm.

[0076] A mixed aggregate, comprising the above coarse aggregate and gold mine ultra-fine tailings, and the mass ratio of the coarse aggregate to the gold mine ultra-fine tailings is 3:7, wherein the chemical composition of the gold mine ultra-fine tailings is shown in Table 1, and the particle size distribution of the gold mine ultra-fine tailings is shown in Table 2.

[0077] A preparation method of the above mixed aggregate, as shown in Figure 2 , comprising the following steps: weighing 396g of the above coarse aggregate and 924g of gold mine ultra-fine tailings to mix and homogenize, and preparing a mixed aggregate.

[0078] A filling slurry, comprising the above mixed aggregate, P.O 42.5 cement (cementitious material) and water, with a sand-cement ratio of 1:6 and a mass concentration of 70wt%.

[0079] A preparation method of the above filling slurry, as shown in Figure 2 , comprising the following steps: mixing and homogenizing the above mixed aggregate, 220g of P.O 42.5 cement and 660g of water to prepare a filling slurry.

[0080] A filling body, obtained after hardening and shaping of the above filling slurry.

[0081] Example 2

[0082] A coarse aggregate, wherein the raw materials of the coarse aggregate include gold mine ultra-fine tailings 90wt%, quicklime 7wt%, fly ash 3wt%, and the particle size of the coarse aggregate is 5-10mm, with the total mass of the raw materials of the coarse aggregate being 100%. Other conditions are the same as those in Example 1.

[0083] Example 3

[0084] A coarse aggregate, wherein the raw materials of the coarse aggregate include gold mine ultra-fine tailings 80wt%, quicklime 12wt%, fly ash 8wt%, and the particle size of the coarse aggregate is 5-10mm, with the total mass of the raw materials of the coarse aggregate being 100%. Other conditions are the same as those in Example 1.

[0085] Example 4

[0086] A coarse aggregate, based on the total mass of the raw materials of the coarse aggregate as 100%, the raw materials of the coarse aggregate include 88wt% gold mine ultrafine tailings, 12wt% quicklime, 0wt% fly ash, and the particle size of the coarse aggregate is 5-10mm.

[0087] Comparative Example 1

[0088] A filling slurry comprises ultrafine gold ore tailings, PO 42.5 cement (cementing material) and water, with a cement-to-sand ratio of 1:6 and a mass concentration of 70 wt%. The chemical composition of the ultrafine gold ore tailings is shown in Table 1, and the particle size distribution of the ultrafine gold ore tailings is shown in Table 2.

[0089] The above-described method for preparing filling slurry includes the following steps: mixing and homogenizing 1320g of gold ore ultrafine tailings, 220g of P.O42.5 cement and 660g of water to prepare filling slurry.

[0090] A filling material is obtained by hardening and molding the filling slurry described above.

[0091] Filling performance test: The spread and slump of the filling slurry of Examples 1-4 and Comparative Example 1 were measured, and then cast into test blocks. The compressive strength was measured after curing for 7 days and 28 days. The specific test results are shown in Table 3.

[0092] Table 1 Chemical composition of ultrafine tailings from gold mines

[0093] Ingredients SiO2 Al2O3 CaO K2O Na2O MgO MnO Fe TiO2 S Others Content / % 66.89 14.72 1.57 6.06 1.22 0.54 0.1 1.86 0.13 0.31 6.6

[0094] Table 2. Particle size distribution of ultrafine tailings from gold mines

[0095] Particle size / pm <5 <10 <20 <38 <45 <74 <100 <200 Content / % 34.72 56.42 78.20 92.03 94.08 98.12 99.27 100

[0096] Table 3. Test results of filling performance of filling slurry and filling body in Examples 1-4 and Comparative Example 1.

[0097]

[0098] By comparing Examples 1-4 and Comparative Example 1, it can be seen that the addition of coarse aggregate greatly improves the slump, spread, and compressive strength at 7d and 28d of the filling slurry.

[0099] The coarse aggregates in Examples 1-4 can not only be used to prepare filling slurry for filling goaf areas in mines, but also for backfilling open pits, or piled on top of caving areas in natural caving mining as a cover layer, or discharged to waste rock dumps to solve the problems of insufficient tailings pond capacity and difficulty in tailings discharge caused by the difficulty in approving tailings ponds.

[0100] In this disclosure, the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" mean that a particular feature, structure, material, or characteristic is included in at least one embodiment or example of the present disclosure. The illustrative appearances of the above-mentioned terms in various places in the specification are not necessarily referred to the same embodiment or example. Moreover, the particular features, structures, materials, or characteristics can be combined in any suitable manner in one or more embodiments or examples. Furthermore, the terminology "comprising" is used in the disclosure as comprising but not limited to, that is, it is open-ended and does not exclude the presence of additional features, structures, materials, or characteristics.

[0101] Although the embodiments of the present disclosure have been shown and described above, it is understood that the above-described embodiments are exemplary, and are not to be interpreted as limiting the present disclosure, and the ordinary skilled in the art can make changes, modifications, replacements, and variations to the above-described embodiments within the scope of the present disclosure.

Claims

1. A coarse aggregate, characterized in that, The raw material of the coarse aggregate comprises 80-90 wt% of ultra-fine tailings, 5-12 wt% of quicklime and 3-8 wt% of fly ash, based on the total mass of the raw material of the coarse aggregate being 100%. The preparation method of the coarse aggregate comprises the following steps: (1) mixing various raw materials of the coarse aggregate according to a specified ratio to obtain a mixture; (2) adding water to the mixture and granulating to obtain green balls; (3) calcining the green balls and obtaining the coarse aggregate after cooling.

2. The coarse aggregate according to claim 1, characterized in that, The raw material of the coarse aggregate comprises 85-90 wt% of ultra-fine tailings, 5-10 wt% of quicklime and 3-5 wt% of fly ash, based on the total mass of the raw material of the coarse aggregate being 100%.

3. The coarse aggregate according to claim 2, characterized in that, The raw material of the coarse aggregate comprises 85 wt% of ultra-fine tailings, 10 wt% of quicklime and 5 wt% of fly ash, based on the total mass of the raw material of the coarse aggregate being 100%.

4. The coarse aggregate according to any one of claims 1 to 3, characterized in that, The particle size of the coarse aggregate is 5-10 mm.

5. The coarse aggregate of claim 1, wherein, In step (2), the amount of water added is 5-25 wt% of the mass of the mixture.

6. The coarse aggregate of claim 1, wherein, In step (2), the particle size of the green balls is 5-10 mm.

7. The coarse aggregate of claim 1, wherein In step (3), the calcination temperature is 800-1000 ℃ and the calcination time is 20-60 minutes.

8. The coarse aggregate of claim 1, wherein, In step (3), the green balls are first air-dried and then oven-dried before calcination.

9. A mixed aggregate, characterized in that, The coarse aggregate according to any one of claims 1-8 and the ultra-fine tailings.

10. The mixed aggregate of claim 9, wherein, The mass ratio of the coarse aggregate to the ultra-fine tailings is 1:9-4:

6.

11. A fill material slurry, characterized by, The mixed aggregate, the cementitious material and the water according to claim 9 or 10.

12. A prosthesis, characterized by Obtained after the hardening of the filling slurry according to claim 11.

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