Plant fiber modified and reinforced phosphogypsum-based mine filling material and preparation method thereof

Abstract

The invention relates to the technical field of mine filling materials, in particular to a plant fiber modified and reinforced ardealite-based mine filling material and a preparation method thereof, reselection tailings, flotation tailings and ardealite are used as main raw materials for preparing the filling material, the comprehensive utilization rate of phosphorite byproducts is increased, and the utilization rate of the phosphorite byproducts is increased. And the mechanical property and durability of the filling material are improved by adding plant fibers. The plant fibers and the ardealite have good compatibility and synergistic effect, so that the compressive strength, the tensile strength and the toughness of the filling body can be effectively improved. The filling material disclosed by the invention has better environmental friendliness, can utilize the ardealite solid waste, can consume the crop waste, reduces the pollution of the crop waste to the environment, can effectively reduce the mine filling cost, and has remarkable economic and social benefits.

Description

Technical Field

[0001] The present invention belongs to the field of mine filling materials, and particularly relates to a plant fiber modified and enhanced phosphogypsum-based mine filling material and a preparation method thereof. Background Art

[0002] Phosphorus ore is an important non-metallic strategic mineral resource. The scope of use of phosphorus ore is very wide, covering multiple fields such as agriculture, chemical industry, and construction, and is of great significance to economic development. However, continuous mining of phosphorus ore will inevitably generate a large number of mined-out areas, which will surely threaten the safe production of mines. In order to effectively solve this problem, filling technology has been widely applied. Therefore, higher requirements are put forward for the mechanical properties, durability, and environmental friendliness of filling materials.

[0003] A large amount of tailing waste will be generated during the process of phosphorus ore mining, such as flotation tailings and gravity separation tailings, and some phosphorus ore products will also be derived, such as phosphoric acid. For every 1t of phosphoric acid produced, 4.5t - 6t of phosphogypsum will be generated. The large stockpiling of a large amount of phosphogypsum, flotation tailings, and gravity separation tailings not only occupies a large amount of land resources, but also impurities such as P and F in phosphogypsum are likely to cause environmental pollution with the washing of rainwater. In addition, cement-based filling materials have a relatively high cost, and the tailing cemented filling body has certain disadvantages in mechanical properties, and has disadvantages such as high brittleness and poor crack resistance, resulting in poor performance of the tailing cemented filling body in terms of compressive strength and tensile strength. Plant fibers can improve the mechanical properties, crack resistance, etc. of the filling body through adsorption, bridging and other effects.

[0004] The prior art provides some technical ideas for utilizing tailing waste, phosphogypsum or improving the mechanical properties of tailing cemented filling bodies. For example, the Chinese invention patent with the patent publication number CN114133199A discloses a hemihydrate phosphogypsum-based geopolymer cemented phosphorus tailing filling material and a method for using it in mine filling. Using by-product hemihydrate phosphogypsum in the phosphorus chemical industry as the main raw material and mixing auxiliary materials as the cementitious material, and using phosphorus tailings and mine waste rock as the aggregate, a mixed filling material with high early strength, good bleeding resistance, good fluidity, and good water resistance is prepared. Another example is that Zhang Chunlei et al. carried out experimental research on the static mechanical properties of tailing cemented filling bodies containing hybrid fibers, and explored the effects of the hybridization of steel fibers (SF) and polypropylene fibers (PF) on the static mechanical properties and failure modes of tailing cemented filling bodies.

[0005] However, in the prior art, the comprehensive utilization rate of gravity separation tailings, flotation tailings, and phosphogypsum is not high, the cost is relatively high, and the crack resistance is poor, and further research work needs to be carried out. Summary of the Invention

[0006] Aiming at the problem of low comprehensive utilization rate of reselected tailings, flotation tailings, and phosphogypsum in the prior art, the present invention provides a plant fiber-modified and enhanced phosphogypsum-based mine filling material and a preparation method thereof. Using reselected tailings, flotation tailings, and phosphogypsum as the main raw materials for preparing the filling material, it improves the comprehensive utilization rate of phosphate ore by-products, and also improves the mechanical properties of the filling material by adding plant fibers.

[0007] The present invention provides a plant fiber-modified and enhanced phosphogypsum-based mine filling material, which includes coarse aggregate, fine aggregate, composite gel material, modification material, reinforcement material, and water; the coarse aggregate and the fine aggregate together form the filling aggregate; the fine aggregate uses flotation tailings; the coarse aggregate uses reselected tailings; the composite gel material uses a mixture composed of cement, phosphogypsum, and slag, which is used to improve the strength and durability of the filling material; the modification material uses quicklime, which is used to improve the gelling performance of phosphogypsum; the reinforcement material uses plant fibers.

[0008] In the prior art, there are technical solutions for preparing filling materials from components such as filling aggregate, gel material, modification material, and reinforcement material. However, the technical solution of using the three main by-products, namely reselected tailings, flotation tailings, and phosphogypsum, as the main raw materials for preparing filling materials during the phosphate ore development process is first proposed by the present invention. Preparing the new filling material can consume reselected tailings, flotation tailings, and phosphogypsum at the same time, which not only solves the stacking problem and improves the underground mining environment, but also simplifies the procurement control of raw materials and is more conducive to industrial implementation.

[0009] Furthermore, in order to better implement the present invention, the reinforcement material uses plant fibers treated with alkali.

[0010] Furthermore, in order to better implement the present invention, the plant fibers use any one of corn straw fibers, rice straw fibers, and jute fibers.

[0011] Furthermore, in order to better implement the present invention, the length of the plant fibers is 3 mm to 15 mm.

[0012] Furthermore, in order to better implement the present invention, the plant fibers account for 0.1% to 0.5% of the total mass of the filling aggregate.

[0013] Furthermore, in order to better implement the present invention, the mass ratio of cement, phosphogypsum, and slag in the composite gel material is 7:2:1.

[0014] Furthermore, in order to better implement the present invention, 1 m 3The filling material includes 750 kg to 975 kg of coarse aggregate, 500 kg to 650 kg of fine aggregate, 250 kg to 500 kg of composite gel material, 1 kg to 2 kg of modification material, 1.25 kg to 8.25 kg of reinforcing material, and 500 kg to 625 kg of water.

[0015] Further, in order to better implement the present invention, the particle size range of the gravity separation tailings is 0.1 mm to 4.75 mm; the particle size range of the flotation tailings is 0.01 mm to 0.1 mm.

[0016] The present invention also provides a preparation method of a plant fiber modified and reinforced phosphogypsum-based mine filling material for preparing the above-mentioned filling material. In the preparation method, gravity separation tailings are used as the coarse aggregate, flotation tailings are used as the fine aggregate, a mixture composed of cement, phosphogypsum, and slag is used as the composite gel material, quicklime is used as the modification material, and plant fiber is used as the reinforcing material; after obtaining the raw materials, the coarse aggregate, fine aggregate, composite gel material, and modification material are first mixed and stirred, then the reinforcing material and water are added and stirred evenly to obtain a mixture slurry; then the mixture slurry is poured into a mold and cured to form.

[0017] Further, in order to better implement the present invention, when obtaining the raw materials, corn straw or rice straw or jute is prepared into sections according to the designed length, soaked in 1 mol / L sodium hydroxide solution for 24 hours, and then washed with clear water until the pH value is neutral to obtain the alkali-treated plant fiber as the reinforcing material.

[0018] The beneficial effects of the present invention are mainly as follows.

[0019] (1) A plant fiber modified and reinforced phosphogypsum-based mine filling material provided by the present invention uses gravity separation tailings, flotation tailings, and phosphogypsum as the main raw materials for preparing the filling material, relieves the pressure of tailing storage, and improves the comprehensive utilization rate of phosphate ore by-products.

[0020] (2) A plant fiber modified and reinforced phosphogypsum-based mine filling material provided by the present invention improves the strength of the filling material by adding plant fiber, which can not only enhance the tensile strength and compressive strength of the filling material, but also provides a new utilization way for waste crop straws.

[0021] (3) A plant fiber modified and reinforced phosphogypsum-based mine filling material provided by the present invention greatly reduces the cost of mine filling work.

[0022] (4) A plant fiber modified and reinforced phosphogypsum-based mine filling material provided by the present invention uses the alkali-treated plant fiber as the reinforcing material, hydrolyzes the polysaccharides in the natural plant fiber, and reduces the influence on the cement hydration reaction after mixing.

[0023] (5) The plant fiber modified and enhanced phosphogypsum-based mine filling material provided by the present invention uses quicklime as a modification material. After mixing, it can neutralize the acidic substances in phosphogypsum, provide an alkaline environment, which is beneficial to the formation of insoluble precipitates of soluble phosphorus, fluorine and other impurities in phosphogypsum, and reduce their migration risks.

[0024] (6) The plant fiber modified and enhanced phosphogypsum-based mine filling material provided by the present invention does not need to use external additives such as water reducers, pumping agents and retarders. In addition to saving the procurement cost of external additives, it can also reduce the quality control problems caused by the compatibility risks of external additives and the requirements for controlling the dosage of external additives.

[0025] (7) The plant fiber modified and enhanced phosphogypsum-based mine filling material provided by the present invention is an optimized scheme determined by comprehensively considering multiple dimensions such as the setting time, mechanical properties, durability and economy of the filling material for the raw materials of each component and the content of each component.

[0026] (8) The preparation method of the plant fiber modified and enhanced phosphogypsum-based mine filling material provided by the present invention is simple in operation, has low requirements for production equipment and production sites, and low quality control difficulty, and is very suitable for wide promotion and implementation. Description of the Drawings

[0027] Figure 1 It is a schematic diagram of the preparation method of the plant fiber modified and enhanced phosphogypsum-based filling material.

[0028] Figure 2 It is the SEM micrograph of the surfaces of three kinds of plant fibers; among them, Figure 2 (a) is the SEM micrograph of the surface of corn straw fiber, Figure 2 (b) is the SEM micrograph of the surface of rice straw fiber, Figure 2 (c) is the SEM micrograph of the surface of jute fiber.

[0029] Figure 3 It is the XRD image of the filling material specimens added with corn straw fiber, rice straw fiber, jute fiber and the filling material specimens as the control group cured for 28 days.

[0030] Figure 4 It is the compressive strength of the filling material specimens added with corn straw fibers of different lengths.

[0031] Figure 5 It is the compressive strength of the filling material specimens added with rice straw fibers of different lengths.

[0032] Figure 6 It is the compressive strength of the filling material specimens added with jute fibers of different lengths.

[0033] Figure 7 The compressive strength of the filling material specimens when adding corn straw fibers with different dosages.

[0034] Figure 8 The compressive strength of the filling material specimens when adding rice straw fibers with different dosages.

[0035] Figure 9 The compressive strength of the filling material specimens when adding jute fibers with different dosages.

[0036] Figure 10 The tensile strength of the filling material specimens when adding corn straw fibers with different lengths.

[0037] Figure 11 The tensile strength of the filling material specimens when adding rice straw fibers with different lengths.

[0038] Figure 12 The tensile strength of the filling material specimens when adding jute fibers with different lengths.

[0039] Figure 13 The tensile strength of the filling material specimens when adding corn straw fibers with different dosages.

[0040] Figure 14 The tensile strength of the filling material specimens when adding rice straw fibers with different dosages.

[0041] Figure 15 The tensile strength of the filling material specimens when adding jute fibers with different dosages. Specific implementation manners

[0042] The following further elaborates on the above content of the present invention in detail in combination with the specific implementation manners of the embodiments. However, this should not be construed as limiting the scope of the above subject matter of the present invention to the following examples. Without departing from the above technical idea of the present invention, various substitutions or changes made according to common general technical knowledge and customary means in the art should be included within the scope of the present invention.

[0043] Example 1:

[0044] Phosphogypsum has relatively fine particles, low permeability, and is easy to form a slurry when mixed with water. These characteristics make it not suitable for use as a filling aggregate. However, phosphogypsum has certain cementitious properties. After being treated, it can be combined with cement and used as a gel material in the filling material.

[0045] Both reselected tailings and flotation tailings have good particle size distributions and gradations, and have a certain strength themselves. They can be used as filling aggregates and are used to prepare tailings filling bodies with cementitious materials such as cement to fill mined-out areas. However, in the prior art, due to disadvantages such as high brittleness and poor crack resistance of the tailings cemented filling body, the performance of the tailings cemented filling body is poor in terms of compressive strength and tensile strength.

[0046] Plant fibers are obtained from crop straws. Straws are composed of phloem, xylem, and pith. The phloem has high toughness, large plasticity, and the phloem fibers of straws are long, and the bonding force between the fibers is good. Straws exhibit anisotropic mechanical properties. These physical and chemical properties of crops make them a promising choice as a reinforcing material for tailings filling bodies, which can better solve problems such as high brittleness and poor crack resistance of tailings cemented filling bodies.

[0047] Based on the above analysis, this embodiment provides a plant fiber-modified and enhanced phosphogypsum-based mine filling material, which includes coarse aggregate, fine aggregate, composite gel material, modification material, reinforcing material, and water. The coarse aggregate and the fine aggregate together form the filling aggregate. The specific raw materials of each component are as follows: the coarse aggregate uses reselected tailings; the fine aggregate uses flotation tailings; the composite gel material uses a mixture composed of cement, phosphogypsum, and slag, which is used to improve the strength and durability of the filling material; the modification material uses quicklime, which is used to improve the gelling performance of phosphogypsum; the reinforcing material uses plant fibers.

[0048] Reselected tailings are waste products generated after separating useful minerals by gravity separation method during phosphate ore beneficiation, and are in granular form. Solid particles with a particle size range of 0.1 mm to 4.75 mm are screened out from the reselected tailings and used as the skeleton of the filling material.

[0049] Flotation tailings are waste products generated after separating useful minerals by flotation method during phosphate ore beneficiation. Solid particles with a particle size range of 0.01 mm to 0.1 mm are screened out from the flotation tailings. The fine aggregate in this particle size range can be filled into the skeleton formed by the coarse aggregate and used as the main body of the filling material.

[0050] Phosphogypsum is a by-product generated during the production of phosphoric acid, mainly from the production of wet-process phosphoric acid. Slag is a by-product generated in metallurgy and mining engineering, mainly from metal smelting and ore processing. Finer slag powders usually have better reactivity and cementing properties, which can improve the strength and durability of the filling material. Usually, phosphogypsum with a micron-sized particle size, slag powder with a micron-sized particle size, and 42.5-grade Portland cement are purchased and mixed to form the composite cementitious material described in this embodiment. Further, phosphogypsum with a particle size range between 1 μm and 100 μm is screened out as the raw material for mixing the composite cementitious material.

[0051] Quicklime is usually obtained by calcining natural rocks mainly composed of calcium carbonate, and its main component is calcium oxide. The calcium hydroxide formed after quicklime reacts with water has cementitious properties, which can improve the bonding force and strength of the mixture and enhance the structural stability of the mixture. The process of quicklime reacting with water to form calcium hydroxide releases heat, and it will also react with other substances in the mixture. For example, it reacts with some heavy metal ions such as Pb 2 + and Cd 2 + to form hydroxide precipitates, reducing their environmental risks. By controlling the dosage of quicklime, ensuring that quicklime is fully mixed with phosphogypsum, and reducing the addition amount of traditional gel materials such as cement by stimulating the self-cementitious properties of phosphogypsum, the filling cost can be reduced while controlling the pH value within a reasonable range. Thus, through the modification of quicklime, the mechanical properties, environmental compatibility, and economy of phosphogypsum-based filling materials are significantly optimized, which is an important technical path for realizing green filling in mines.

[0052] This embodiment also provides a preparation method of a plant fiber-modified and reinforced phosphogypsum-based mine filling material for preparing the above-mentioned filling material. As Figure 1 shown, in the preparation method, the gravity separation tailings, flotation tailings, cement, phosphogypsum, slag, quicklime, plant fiber, and water are weighed respectively as required. First, the gravity separation tailings, flotation tailings, cement, phosphogypsum, slag, and quicklime are fully stirred, and then the plant fiber and water are added and mixed evenly to obtain a mixed slurry; then the mixed slurry is poured into a mold and cured to form a filling material.

[0053] Example 2:

[0054] This embodiment is optimized on the basis of Example 1.

[0055] First of all, plant straw contains a large amount of substances such as cellulose, hemicellulose, and lignin, becoming an important source of plant fiber. Cellulose and hemicellulose are polysaccharides, and the hydrolysis of polysaccharides into monosaccharides may inhibit the hydration of cement. Therefore, it is necessary to pretreat the plant straw with alkali and use the alkali-treated plant fiber as the reinforcing material in the filling material. The SEM micrographs of the surfaces of three plant fibers are as Figure 2 shown; among them, Figure 2 (a) is the SEM micrograph of the surface of corn straw fiber, Figure 2 (b) is the SEM micrograph of the surface of rice straw fiber, Figure 2 (c) is the SEM micrograph of the surface of jute fiber.

[0056] Further, this embodiment provides a method for alkali-treating plant straw. First, the plant straw is immersed in a 1 mol / L sodium hydroxide solution for 24 h, and then washed with clean water until neutral, that is, the pH value is about 7. In the actual processing process, usually, the pH value detection result between 6.5 and 8 can be considered qualified for washing. After alkali treatment, the plant straw is cut into sections of the designed length and then reserved for use.

[0057] Secondly, in order to study the influence of factors such as adding plant fibers, adding different types of plant fibers, adding plant fibers of different lengths, and adding plant fibers with different dosages on the performance of the filling material, multiple groups of tests are designed according to the idea that "the selection and quality of coarse aggregate, fine aggregate, composite gel material, modified material and water are the same, and only the specific selection of the reinforcing material, the length of the fiber section, and the dosage of plant fiber are not completely the same". Each group of tests is prepared according to the preparation of 1 m 3 The filling material specimens are weighed with the raw materials of each component to prepare specimens of the same size and then the performance is tested.

[0058] Specifically, in each group of tests, there are 960 kg of coarse aggregate, 640 kg of fine aggregate, 280 kg of cement, 80 kg of phosphogypsum, 40 kg of slag, 2 kg of quicklime, and 500 kg of water. The coarse aggregate uses reselected tailings with a particle size range of 0.1 mm to 4.75 mm, and the fine aggregate uses flotation tailings with a particle size range of 0.01 mm to 0.1 mm. The cement used to form the composite gel material is 42.5-grade Portland cement. The preparation method of all filling material specimens is as follows: Step S1, respectively obtain reselected tailings, flotation tailings, cement, phosphogypsum, slag, and quicklime according to the design values and pour them into the slurry mixer and stir for 4 minutes; Step S2, pour the plant fibers into the slurry mixer in small amounts and multiple times and add water to stir evenly; Step S3, pour the mixed slurry into the mold for casting; Step S4, repeat Step S1, Step S2, and Step S3 until the required quantity and different types of filling material specimens are obtained. The cast specimens are placed in a standard curing room and cured for 28 days under the conditions of a temperature of 20 ± 2 °C and a relative humidity of 95%, and the tensile strength and compressive strength are tested.

[0059] For the filling material specimens without adding fibers, the compressive strengths measured after curing for 7 d, 14 d, and 28 d are 2.21 Mpa, 2.49 Mpa, and 2.93 Mpa respectively, and the tensile strength measured after curing for 28 d is 1.01 Mpa.

[0060] In the first group of test groups, corn straw fiber is used as the reinforcing material, and the dosage is 0.1% of the total filling aggregate. The fiber section lengths are designed as 3 mm, 6 mm, 9 mm, 12 mm, and 15 mm respectively, and multiple configurations of the reinforcing material are carried out. The test numbers are recorded as No.1(A), No.1(B), No.1(C), No.1(D), and No.1(E) in sequence.

[0061] The test results of the tensile strength and compressive strength of each specimen in the first group of test groups are shown in Table 1:

[0062] Table 1 Test results of the tensile strength and compressive strength of each specimen in the first group of test groups

[0063]

[0064]

[0065] The filling material specimens obtained for test numbers No.1(A), No.1(B), No.1(C), No.1(D), and No.1(E) were respectively tested. For the filling material specimen of test number No.1(A), the compressive strengths measured after curing for 7d, 14d, and 28d were 1.66 Mpa, 1.83 Mpa, and 2.06 Mpa respectively, and the tensile strength measured after curing for 28d was 0.94 Mpa. For the filling material specimen of test number No.1(B), the compressive strengths measured after curing for 7d, 14d, and 28d were 1.73 Mpa, 2.06 Mpa, and 2.17 Mpa respectively, and the tensile strength measured after curing for 28d was 0.99 Mpa. For the filling material specimen of test number No.1(C), the compressive strengths measured after curing for 7d, 14d, and 28d were 2.04 Mpa, 2.42 Mpa, and 2.60 Mpa respectively, and the tensile strength measured after curing for 28d was 1.03 Mpa. For the filling material specimen of test number No.1(D), the compressive strengths measured after curing for 7d, 14d, and 28d were 2.44 Mpa, 2.66 Mpa, and 3.12 Mpa respectively, and the tensile strength measured after curing for 28d was 1.11 Mpa. For the filling material specimen of test number No.1(E), the compressive strengths measured after curing for 7d, 14d, and 28d were 1.88 Mpa, 2.13 Mpa, and 2.39 Mpa respectively, and the tensile strength measured after curing for 28d was 1.07 Mpa.

[0066] From Table 1 combined with Figure 4 、 Figure 10 it can be seen that when other component parameters are the same, corn straw fiber is selected for addition, the content of plant fiber is the same, and only the length of the fiber segments is different, the difference in the length of corn straw fiber has a greater impact on the compressive strength of the filling material and a smaller impact on the tensile strength of the filling material. Further comparison shows that the filling material with 12 mm corn straw fiber added has better compressive strength and tensile strength.

[0067] The second group of test groups uses corn straw fiber as the reinforcing material. The fiber segment length is 12 mm, and the dosages are designed as 0.2%, 0.3%, 0.4%, and 0.5% respectively, and various configurations of reinforcing materials are carried out. The test numbers are sequentially recorded as No.2(A), No.2(B), No.2(C), and No.2(D).

[0068] The test results of the tensile strength and compressive strength of each specimen in the second group of test groups are shown in Table 2:

[0069] Table 2 Test results of the tensile strength and compressive strength of each specimen in the second group of test groups

[0070]

[0071] The filling material specimens obtained from test numbers No.1(D), No.2(A), No.2(B), No.2(C), and No.2(D) are respectively tested. For the filling material specimen of test number No.2(A), the compressive strengths measured after curing for 7 d, 14 d, and 28 d are 4.03 Mpa, 5.19 Mpa, and 7.16 Mpa respectively, and the tensile strength measured after curing for 28 d is 1.14 Mpa. For the filling material specimen of test number No.2(B), the compressive strengths measured after curing for 7 d, 14 d, and 28 d are 4.06 Mpa, 4.81 Mpa, and 6.89 Mpa respectively, and the tensile strength measured after curing for 28 d is 1.17 Mpa. For the filling material specimen of test number No.2(C), the compressive strengths measured after curing for 7 d, 14 d, and 28 d are 3.71 Mpa, 4.36 Mpa, and 6.52 Mpa respectively, and the tensile strength measured after curing for 28 d is 1.20 Mpa. For the filling material specimen of test number No.2(D), the compressive strengths measured after curing for 7 d, 14 d, and 28 d are 3.65 Mpa, 4.54 Mpa, and 5.89 Mpa respectively, and the tensile strength measured after curing for 28 d is 0.98 Mpa.

[0072] Combined with Table 1 and Table 2 Figure 7 , Figure 13 it can be seen that when other component parameters are the same, corn straw fiber is selected for addition, the fiber segment length is the same, and only the dosage of plant fiber is different, the difference in the dosage of corn straw fiber has a greater impact on the compressive strength of the filling material and a smaller impact on the tensile strength of the filling material.

[0073] The third group of test groups uses rice straw fiber as the reinforcing material, and the dosage is 0.1% of the total filling aggregate. The fiber segment lengths are designed as 3 mm, 6 mm, 9 mm, 12 mm, and 15 mm respectively, and various configurations of reinforcing materials are carried out. The test numbers are sequentially recorded as No.3(A), No.3(B), No.3(C), No.3(D), and No.3(E).

[0074] Comparative findings show that when the content of plant fiber is controlled at 0.2%, the filling material has relatively high compressive strength, and when the content of plant fiber is controlled at 0.4%, the filling material has relatively high tensile strength.

[0075] The test results of the tensile strength and compressive strength of each specimen in the third test group are shown in Table 3:

[0076] Table 3 Test Results of Tensile Strength and Compressive Strength of Each Specimen in the Third Test Group

[0077]

[0078] The filling material specimens obtained from test numbers No.3(A), No.3(B), No.3(C), No.3(D), and No.3(E) were respectively tested. For the filling material specimen of test number No.3(A), the compressive strengths measured at 7d, 14d, and 28d of curing were 2.75 Mpa, 3.09 Mpa, and 3.70 Mpa respectively, and the tensile strength measured at 28d of curing was 1.10 Mpa. For the filling material specimen of test number No.3(B), the compressive strengths measured at 7d, 14d, and 28d of curing were 2.27 Mpa, 2.70 Mpa, and 3.33 Mpa respectively, and the tensile strength measured at 28d of curing was 1.00 Mpa. For the filling material specimen of test number No.3(C), the compressive strengths measured at 7d, 14d, and 28d of curing were 2.35 Mpa, 2.78 Mpa, and 3.16 Mpa respectively, and the tensile strength measured at 28d of curing was 0.97 Mpa. For the filling material specimen of test number No.3(D), the compressive strengths measured at 7d, 14d, and 28d of curing were 2.22 Mpa, 2.60 Mpa, and 2.93 Mpa respectively, and the tensile strength measured at 28d of curing was 0.89 Mpa. For the filling material specimen of test number No.3(E), the compressive strengths measured at 7d, 14d, and 28d of curing were 2.01 Mpa, 2.40 Mpa, and 2.64 Mpa respectively, and the tensile strength measured at 28d of curing was 0.82 Mpa.

[0079] From Table 3 combined with Figure 5 、 Figure 11 it can be seen that when other component parameters are the same, rice straw fiber is selected for addition, the content of plant fiber is the same, and only the length of the fiber segments is different, the difference in the length of rice straw fiber has a greater impact on the compressive strength of the filling material and a smaller impact on the tensile strength of the filling material. Further comparison reveals that the filling material with 3mm rice straw fiber added has relatively better compressive strength and tensile strength.

[0080] The fourth test group uses rice straw fiber as the reinforcing material. The fiber segment length is 12 mm, and the dosages are designed as 0.2%, 0.3%, 0.4%, and 0.5% respectively, and various configurations of reinforcing materials are carried out. The test numbers are sequentially recorded as No.4(A), No.4(B), No.4(C), and No.4(D).

[0081] The test results of the tensile strength and compressive strength of each specimen in the fourth test group are shown in Table 4:

[0082] Table 4 Test results of the tensile strength and compressive strength of each specimen in the fourth test group

[0083]

[0084] The filling material specimens obtained from test numbers No.3(D), No.4(A), No.4(B), No.4(C), and No.4(D) are respectively tested. For the filling material specimen of test number No.4(A), the compressive strengths measured after curing for 7 days, 14 days, and 28 days are 3.52 Mpa, 4.49 Mpa, and 4.93 Mpa respectively, and the tensile strength measured after curing for 28 days is 1.13 Mpa. For the filling material specimen of test number No.4(B), the compressive strengths measured after curing for 7 days, 14 days, and 28 days are 3.38 Mpa, 4.07 Mpa, and 4.85 Mpa respectively, and the tensile strength measured after curing for 28 days is 1.12 Mpa. For the filling material specimen of test number No.4(C), the compressive strengths measured after curing for 7 days, 14 days, and 28 days are 3.23 Mpa, 3.58 Mpa, and 4.71 Mpa respectively, and the tensile strength measured after curing for 28 days is 0.94 Mpa. For the filling material specimen of test number No.4(D), the compressive strengths measured after curing for 7 days, 14 days, and 28 days are 3.38 Mpa, 3.86 Mpa, and 4.56 Mpa respectively, and the tensile strength measured after curing for 28 days is 0.85 Mpa.

[0085] Combined with Table 3 and Table 4 Figure 8 、 Figure 14 It can be seen that when other component parameters are the same, rice straw fiber is selected and added, the fiber segment length is the same, and only the dosage of plant fiber is different, the difference in the dosage of rice straw fiber has a certain impact on the compressive strength and tensile strength of the filling material. Further comparison shows that when the dosage of plant fiber is controlled within 0.2% - 0.5%, the difference in the compressive strength of the filling material is not significant and is better than that of the filling material with a dosage of 0.1%, while when the dosage of plant fiber is controlled within 0.1% - 0.3%, the tensile strength of the filling material is better than that of the filling material with a dosage greater than 0.3%.

[0086] The fifth test group uses jute fiber as the reinforcing material, and the dosage is 0.1% of the total filling aggregate. The fiber segment lengths are designed as 3mm, 6mm, 9mm, 12mm, and 15mm respectively, and various configurations of reinforcing materials are carried out. The test numbers are sequentially recorded as No.5(A), No.5(B), No.5(C), No.5(D), and No.5(E).

[0087] The test results of the tensile strength and compressive strength of each specimen in the fifth test group are shown in Table 5:

[0088] Table 5 Test results of the tensile strength and compressive strength of each specimen in the fifth test group

[0089]

[0090] The filling material specimens obtained from the test numbers No.5(A), No.5(B), No.5(C), No.5(D), and No.5(E) are respectively tested. For the filling material specimen of test number No.5(A), the compressive strengths measured after curing for 7d, 14d, and 28d are 1.95Mpa, 2.12Mpa, and 2.51Mpa respectively, and the tensile strength measured after curing for 28d is 0.86Mpa. For the filling material specimen of test number No.5(B), the compressive strengths measured after curing for 7d, 14d, and 28d are 1.81Mpa, 1.94Mpa, and 2.20Mpa respectively, and the tensile strength measured after curing for 28d is 0.849Mpa. For the filling material specimen of test number No.5(C), the compressive strengths measured after curing for 7d, 14d, and 28d are 1.82Mpa, 2.36Mpa, and 2.47Mpa respectively, and the tensile strength measured after curing for 28d is 0.87Mpa. For the filling material specimen of test number No.5(D), the compressive strengths measured after curing for 7d, 14d, and 28d are 2.17Mpa, 2.39Mpa, and 3.58Mpa respectively, and the tensile strength measured after curing for 28d is 0.99Mpa. For the filling material specimen of test number No.5(E), the compressive strengths measured after curing for 7d, 14d, and 28d are 1.93Mpa, 2.01Mpa, and 2.14Mpa respectively, and the tensile strength measured after curing for 28d is 0.95Mpa.

[0091] From Table 5 combined with Figure 6 、 Figure 12 it can be seen that when other component parameters are the same, jute fiber is selected for addition, the dosage of plant fiber is the same, and only the length of the fiber segment is different, the difference in the length of jute fiber has a certain impact on the compressive strength and tensile strength of the filling material. Further comparison shows that adding 12mm jute fiber has better compressive strength and tensile strength than adding jute fibers of other lengths.

[0092] The sixth test group uses jute fiber as the reinforcing material. The fiber segment lengths are all 12 mm, and the dosages are designed to be 0.2%, 0.3%, 0.4%, and 0.5% respectively, and various configurations of reinforcing materials are carried out. The test numbers are sequentially recorded as No.6(A), No.6(B), No.6(C), and No.6(D).

[0093] The test results of the tensile strength and compressive strength of each specimen in the sixth test group are shown in Table 4:

[0094] Table 6 Test results of the tensile strength and compressive strength of each specimen in the sixth test group

[0095]

[0096] The filling material specimens obtained from test numbers No.5(D), No.6(A), No.6(B), No.6(C), and No.6(D) are respectively tested. For the filling material specimen of test number No.6(A), the compressive strengths measured after curing for 7 days, 14 days, and 28 days are 3.22 Mpa, 3.80 Mpa, and 4.54 Mpa respectively, and the tensile strength measured after curing for 28 days is 1.10 Mpa. For the filling material specimen of test number No.6(B), the compressive strengths measured after curing for 7 days, 14 days, and 28 days are 2.36 Mpa, 2.93 Mpa, and 3.44 Mpa respectively, and the tensile strength measured after curing for 28 days is 1.07 Mpa. For the filling material specimen of test number No.6(C), the compressive strengths measured after curing for 7 days, 14 days, and 28 days are 2.04 Mpa, 2.33 Mpa, and 2.89 Mpa respectively, and the tensile strength measured after curing for 28 days is 1.03 Mpa. For the filling material specimen of test number No.6(D), the compressive strengths measured after curing for 7 days, 14 days, and 28 days are 3.76 Mpa, 5.03 Mpa, and 6.10 Mpa respectively, and the tensile strength measured after curing for 28 days is 1.16 Mpa.

[0097] From Table 6 combined with Figure 9 、 Figure 15 It can be seen that when other component parameters are the same, jute fiber is selected for addition, the fiber segment lengths are the same, and only the dosage of plant fiber is different, the difference in the dosage of jute fiber has a greater impact on the compressive strength of the filling material and a smaller impact on the tensile strength of the filling material. Further comparison shows that when the dosage of jute fiber is controlled at 0.5%, it has better compressive strength and tensile strength than other dosages.

[0098] In addition, for the specimens with corn straw fiber added, the filling material specimens with test number No. 2(A) were used; for the specimens with rice straw fiber added, the filling material specimens with test number No. 4(A) were used; for the specimens with jute fiber added, the filling material specimens with test number No. 6(D) were used; no plant fiber was added to the control group specimens. The above four types of filling material specimens were cured for 28 days and then subjected to XRD tests. The intensity of the diffraction peaks of different hydration products can reflect the influence degree of different plant fibers on the hydration reaction of cement, and thus show the promotion effect of different plant fibers on the compressive strength of the filling body. As Figure 3 shown, CS corresponds to corn straw fiber, RS corresponds to rice straw fiber, and JF corresponds to jute fiber.

[0099] It can be seen from Figure 3 that: from the diffraction peaks of the XRD test results, it can be known that hydration products such as ettringite (Aft), calcium hydroxide (CH), and calcium silicate hydrate (C-S-H) were formed during the hydration process of the filling material, providing strength for the specimens. It can also be seen that although no new diffraction peaks were generated after adding natural fibers, the intensity of the diffraction peaks corresponding to the hydration products changed, indicating that the addition of natural fibers made the hydration reaction proceed more thoroughly. The formation of hydration products enhanced the bond between the natural fibers and the filling body matrix, thereby improving the mechanical strength of the specimens. The diffraction peaks corresponding to the hydration products of different natural fibers added were different: the diffraction peak of the corn straw fiber CS added was the strongest, followed by the rice straw fiber RS and the jute fiber JF. This indicates that the adhesion between the corn straw fiber and the specimen matrix may be stronger than that of the other two fibers, and the promotion effect of the corn straw fiber on the compressive strength of the filling material is the most significant. These findings are consistent with the following compressive strength test results.

[0100] Through the above six groups of tests, the effect of fiber length on strength can be analyzed. When the natural fiber is short, the contact area between the natural fiber and the sample matrix is limited, and defects are prone to occur around the fiber, resulting in weak bonding strength between the natural fiber and the matrix; when the natural fiber reaches the critical length, the entire fiber surface and both ends are in full contact with the matrix, which increases the bonding strength between the natural fiber and the matrix, resulting in improved compressive strength. In addition, it can be seen that the sensitivity of the sample to fiber length varies depending on the fiber type. According to the compressive strength results, the sensitivity of the sample to natural fibers is from high to low: RS>CS>JF. This may be related to the chemical composition of the three natural fibers. The different natural fiber compositions lead to differences in the performance of different types of fibers. In addition, the shape of each fiber also has a certain influence. CS is blocky, RS is tubular, and JF is filamentous. When the tubular RS is mixed with the slurry, it has a large contact area and is well bonded to the slurry, maximizing the hydration reaction of the slurry. However, after the fiber length exceeds the critical length, the slurry cannot fill the interior of the RS, thereby reducing the bonding strength. The block structure of CS has a large contact area, and it increases with the increase of fiber length. The bonding strength is the best at the critical length, which can maximize the compressive strength. On the contrary, the contact area between the filamentous JF and the slurry is limited, and its addition amount is low, which provides less bonding effect on the sample than the inhibitory effect, resulting in weaker bonding effect, reduced compressive strength and lower than the control group.

[0101] Through the above six groups of tests, the influence of fiber content on the performance can be analyzed. The distribution of natural fibers with different contents in the specimen matrix, combined with the compressive strength results, shows that natural fibers play a bridging role in the matrix. When the content of natural fibers increases, the bearing area of the effective stress also increases, thereby enhancing the bonding degree between the fibers and the matrix, inhibiting crack propagation, improving the anti-shedding property of the specimen, and thus increasing the compressive strength. In addition, natural fibers are foreign substances for the filling material, and alkalized natural fibers still have a certain inhibitory effect on the hydration reaction. When the fiber content increases to the critical threshold, this inhibitory effect gradually strengthens, which will also reduce the bonding strength between the fibers and the matrix and weaken the bridging effect of natural fibers. However, before the optimal fiber content level, the bridging effect of the fibers is still stronger than the inhibitory effect, resulting in an increase in compressive strength when the fiber content increases. When the fiber content exceeds the critical content, excessive fibers will appear in phenomena such as lapping and overlapping, thereby reducing the contact area between the fibers and the matrix, easily generating defects and reducing the bonding strength between the fibers and the matrix, which will also weaken the bridging effect and lead to a decrease in compressive strength as the fiber content increases. In addition, for different fibers, the improvement effect of the same fiber content on the compressive strength of the specimen is different, which may be related to the different surface morphologies and appearances of different fibers. For example, when the JF content is 0.5 wt%, the compressive strength is the largest, indicating that at this content, the strongest bonding effect and the most effective bridging effect are provided within the specimen.

[0102] Combined with the conclusions obtained from the six groups of tests in this embodiment:

[0103] (1) When the length of natural fibers increases from 3 mm to 15 mm, both CS (with a length of 12 mm) and RS (with lengths of 3 mm, 6 mm, and 9 mm) can improve the compressive strength of the specimen, and this effect strengthens over time; when the content of natural fibers increases from 0.1 wt% to 0.5 wt%, the compressive strength of the specimens with CS and RS added first increases and then decreases, the compressive strength of the specimens with JF added first increases, then decreases, and finally increases again; when the CS content is 0.2 wt% (with a length of 12 mm), the improvement effect of the compressive strength is the best, and it is 144.4% higher than the control group on the 28th day respectively;

[0104] (2) When the length of natural fibers increases from 3 mm to 15 mm, both CS (with lengths of 9 mm, 12 mm, and 15 mm) and RS (with a length of 3 mm) can improve the tensile strength of the specimen, among which the improvement effect of CS is the best; as the fiber content increases from 0.1 wt% to 0.5 wt%, the tensile strength of the specimens with CS and RS added first increases and then decreases, the tensile strength of the specimens with JF added first increases and then decreases, and then increases again; when the CS length is 12 mm and the content is 0.4 wt%, the tensile strength is increased by 18.8% compared with the control group.

[0105] Other parts of this embodiment are the same as those of Embodiment 1, so they will not be described again.

[0106] Embodiment 3:

[0107] Based on Embodiments 1 and 2, a 1m 3 filling material is prepared, and 750 kg to 975 kg of gravity separation tailings are weighed as coarse aggregate, 500 kg to 650 kg of flotation tailings are weighed as fine aggregate, 250 kg to 500 kg of composite gel material, 1 kg to 2 kg of quicklime as a modification material, 1.25 kg to 8.25 kg of reinforcing material, and 500 kg to 625 kg of water. The mass ratio of cement, phosphogypsum, and slag in the composite gel material is 7:2:1.

[0108] In another specific embodiment, the reinforcing material is selected from any one of plant fibers such as corn straw fiber, rice straw fiber, and jute fiber; the length of the plant fiber segments is controlled within 3 mm to 15 mm, and the plant fiber is controlled to account for 0.1% to 0.5% of the total mass of the coarse aggregate and the fine aggregate.

[0109] In another specific embodiment, the particle size range of the gravity separation tailings is from 0.1 mm to 4.75 mm; the particle size range of the flotation tailings is from 0.01 mm to 0.1 mm.

[0110] Other parts of this embodiment are the same as those of Embodiments 1 and 2, so they will not be described again.

[0111] The above are only the preferred embodiments of the present invention, and do not impose any form of limitation on the present invention. Any simple modification or equivalent change made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A plant fiber modified and reinforced phosphogypsum-based mine filling material, characterized in that, It includes coarse aggregate, fine aggregate, composite gel material, modification material, reinforcing material and water; the coarse aggregate and the fine aggregate together form the filling aggregate; the coarse aggregate uses gravity separation tailings; the fine aggregate uses flotation tailings; the composite gel material uses a mixture composed of cement, phosphogypsum and slag, which is used to improve the strength and durability of the filling material; the modification material uses quicklime, which is used to improve the gelling property of phosphogypsum; the reinforcing material uses plant fiber.

2. The plant fiber modified and reinforced phosphogypsum-based mine filling material according to claim 1, wherein The reinforcing material uses plant fiber treated with alkali.

3. A plant fiber modified and reinforced phosphogypsum-based mine filling material according to claim 1, characterized in that, The plant fiber uses any one of corn straw fiber, rice straw fiber and jute fiber.

4. A plant fiber-modified enhanced phosphogypsum-based mine filling material according to claim 1, characterized in that, The length of the plant fiber is 3mm to 15mm.

5. A plant fiber modified and reinforced phosphogypsum-based mine filling material according to claim 1, characterized in that, The plant fiber accounts for 0.1% to 0.5% of the total mass of the filling aggregate.

6. The plant fiber modified and enhanced phosphogypsum-based mine filling material according to claim 1, wherein In the composite gel material, the mass ratio of cement, phosphogypsum and slag is 7:2:

1.

7. A plant fiber modified and reinforced phosphogypsum-based mine filling material according to claim 1, characterized in that, 1 m³ of filling material includes 750 kg to 975 kg of coarse aggregate, 500 kg to 650 kg of fine aggregate, 250 kg to 500 kg of composite gel material, 1 kg to 2 kg of modification material, 1.25 kg to 8.25 kg of reinforcing material and 500 kg to 625 kg of water.

8. A plant fiber modified and reinforced phosphogypsum-based mine filling material according to claim 1, characterized in that, The particle size range of the gravity separation tailings is 0.1 mm to 4.75 mm; the particle size range of the flotation tailings is 0.01 mm to 0.1 mm.

9. A preparation method of a plant fiber modified and strengthened phosphogypsum-based mine filling material, characterized in that, It is used for preparing a plant fiber modified and enhanced phosphogypsum-based mine filling material as described in claim 1; In the preparation method, after obtaining the raw materials, first mix and stir the coarse aggregate, fine aggregate, composite gel material and modification material, then add the reinforcing material and water and stir evenly to obtain a mixture slurry; then pour the mixture slurry into a mold and cure it into shape; When obtaining the raw materials, use gravity separation tailings as the coarse aggregate, use flotation tailings as the fine aggregate, use a mixture composed of cement, phosphogypsum and slag as the composite gel material, use quicklime as the modification material, and use plant fiber as the reinforcing material.

10. The preparation method of a plant fiber modified and reinforced phosphogypsum-based mine filling material according to claim 9, characterized in that, When obtaining the raw materials, cut corn straw or rice straw or jute into sections according to the designed length, soak them in 1 mol / L sodium hydroxide solution for 24 hours, and then wash them with clean water until the pH value is neutral to obtain plant fiber treated with alkali as the reinforcing material.

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