Ceramsite-Gypsum Solid Waste System Rock-Like Similar Material and Its Preparation Method and Application

Abstract

The present invention relates to the technical field of rock-like materials, and discloses a ceramsite-gypsum solid waste system rock-like similar material, its preparation method and application. The ceramsite-gypsum solid waste system rock-like similar material is prepared from desulfurized gypsum, water-absorbing ceramsite, retarder and water; the mass ratio of desulfurized gypsum, water-absorbing ceramsite and retarder is 200-400:5-50:0.5-0.9; the mass ratio of water to desulfurized gypsum is 0.43-0.47:1. The water-absorbing ceramsite is obtained by soaking ceramsite in water. By limiting the mass ratio of water to desulfurized gypsum and the mass ratio of desulfurized gypsum to water-absorbing ceramsite, the present invention obtains a low-strength and high-brittle material that can simulate a material with a strength not exceeding 3 MPa and a brittleness index of 0.15-0.23, and exhibits brittle failure characteristics, meeting the requirements for low-strength and high-brittle similar materials, and effectively solving the problems that the hard rock similar model test materials prepared by the prior art have relatively high strength and relatively low brittleness index.

Description

Technical Field

[0001] The present invention belongs to the technical field of rock-like materials, and particularly relates to a ceramsite-gypsum solid waste system rock-like similar material, a preparation method thereof, and an application thereof. Background Art

[0002] In the related research of coal mining, it is often necessary to carry out dynamic simulation tests on the rock failure process. In the tests, similar materials need to be made into similar models, and then the deformation and failure conditions of the similar models under external actions are observed, etc., and the deformation and failure conditions of the rocks can be deduced according to the similarity criteria, providing a scientific basis for the design of coal mining projects.

[0003] Most of the currently disclosed rock-like materials use quartz sand and cement as aggregates and binders, which have a long curing period and high raw material costs. Due to the high bonding strength of the hydration products, the uniaxial compressive strength of the prepared rock-like similar materials is as high as dozens of MPa or more, showing obvious limitations for simulating rock-like similar materials with low-strength and high-brittle performance requirements.

[0004] The prior art discloses a similar material for extrusion 3D printing of tunnel lining models. Referring to Chinese Patent CN118084433A, the density of the similar material is 21.4 g / cm 3 ~23.2 g / cm 3 、the compressive strength is 473.4 kPa~1804.6 kPa, the elastic modulus is 371.8 MPa~1332.9 MPa, and the tensile strength is 45.1 kPa~128.4 kPa. This technology selects traditional quartz sand and cement as aggregates and binders, requires curing under specific conditions, has a long preparation period, high production costs, and the prepared similar materials have high strength and cannot meet the requirements of low-strength and high-brittle performance. Chinese Patent CN109679291A discloses a transparent hard rock similar model test material and a preparation method thereof, which are prepared by using 25 parts of epoxy resin, 25 parts of modified curing agent, and 0~5 parts of saturated alcohol rosin solution, and the compressive strength is between 10~100 MPa. The raw materials used in this technology, epoxy resin and curing agent, are both chemical reagents, with relatively high raw material costs, and it also cannot meet the conditions of low-strength and high-brittleness. Chinese Patent CN105967562A discloses a hard rock similar model test material and a preparation method thereof, which uses fine river sand, barite powder, silicone rubber, rosin, and alcohol as raw materials, and through different mass ratios, obtains a similar model test material with the stress-strain characteristics of hard rock; the uniaxial compressive strength of this material is relatively low, the uniaxial compressive strength range is 1.2 MPa~1.6 MPa, and the brittleness index is relatively low, and it also cannot meet the requirements of low-strength and high-brittleness. Summary of the Invention

[0005] To solve the above technical problems, the present invention provides a ceramsite - gypsum solid waste - based rock - like similar material, its preparation method and application.

[0006] To achieve the above object, the technical solution of the present invention is as follows.

[0007] A ceramsite - gypsum solid waste - based rock - like similar material is prepared from desulfurized gypsum, water - absorbing ceramsite, retarder and water;

[0008] The mass ratio of the desulfurized gypsum, the water - absorbing ceramsite and the retarder is 200 - 400:5 - 50:0.5 - 0.9;

[0009] The mass ratio of the water to the desulfurized gypsum is 0.43 - 0.47:1; the water - absorbing ceramsite is obtained by soaking ceramsite in water.

[0010] The present invention controls the mass ratio of desulfurized gypsum and water - absorbing ceramsite, as well as the mass ratio of water to desulfurized gypsum, to regulate the mechanical properties of the ceramsite - gypsum solid waste - based rock - like similar material, and obtains the properties of a low - strength and high - brittleness material. Then, the setting time of desulfurized gypsum is regulated by the addition amount of the retarder to prevent the setting time of desulfurized gypsum from being too long or too short. The ceramsite - gypsum solid waste - based rock - like similar material in the present invention can meet the requirements of a low - strength and high - brittleness material, and its simulated strength does not exceed 3 MPa, and the brittleness index is 0.15 - 0.23.

[0011] In another preferred embodiment, the retarder is a plant - protein retarder. The retarder can ensure the setting time of desulfurized gypsum. Gypsum - type retarders are mainly divided into organic acid salts, phosphates and proteins. Organic acid salts mainly include citric acid, citrate, tartaric acid and tartrate salts, with significant setting - retardation effects, but large dosages and large strength losses for gypsum materials. Phosphates mainly include pyrophosphates, sodium tripolyphosphate, sodium polyphosphate, etc., with large dosages, poor setting - retardation effects and significant reduction of gypsum strength. Protein - type retarders have the advantages of small dosages, significant setting - retardation effects and less influence on gypsum strength. Therefore, plant - protein coagulants have the advantages of small dosages, good setting - retardation effects, low cost and environmental protection.

[0012] In another preferred embodiment, the particle size of the ceramsite is 0.8 cm - 1.4 cm, and the particle size of the desulfurized gypsum is 10 μm - 25 μm. At this particle - size range, the ceramsite can be evenly dispersed in the desulfurized gypsum and the retarder, ensuring the low - strength and high - brittleness characteristics of the mechanical properties of the ceramsite - gypsum solid waste - based rock - like similar material. Therefore, ceramsite with a particle - size within a certain range needs to be selected to form a uniform network structure. If the particle size of the ceramsite is too small, the strength of the material will increase significantly; if the particle size is too large, it is not conducive to forming.

[0013] In another preferred embodiment, the soaking time is 1 h - 2 h.

[0014] The second object of the present invention is to protect a preparation method of the ceramsite - gypsum solid waste system rock - like similar material, which specifically includes the following steps:

[0015] Mix and stir desulfurized gypsum, retarder and water according to a mass ratio, add water - absorbing ceramsite and continue to stir to obtain a mixed slurry;

[0016] Inject the mixed slurry into a mold, vibrate it until solid to obtain a specimen;

[0017] Cure the specimen at 23°C to 27°C for 24h to 48h, then demold and dry it to a constant weight to obtain the ceramsite - gypsum solid waste system rock - like similar material.

[0018] In another preferred embodiment, the rotation speed of the mixing and stirring is 60r / min to 150r / min, and the time is 3min to 5min. The stirring rate will affect the stirring efficiency and the curing time of desulfurized gypsum. The time for desulfurized gypsum to solidify when encountering water is within a certain range. If it is too fast, a certain amount of heat will be generated during the stirring process, accelerating the curing. If it is too slow, the stirring will be insufficient and local curing will occur.

[0019] In another preferred embodiment, the drying temperature is 30 to 40°C, and the time is 12h to 40h. At this temperature, the material is uniformly dried and cured at a constant temperature, ensuring that the moisture inside the material is slowly and evenly removed, preventing the sample from cracking due to too high temperature or uneven drying.

[0020] In another preferred embodiment, the standard for vibrating until solid is that there are no bubbles on the surface of the mixed slurry.

[0021] The third object of the present invention is to protect the application of the ceramsite - gypsum solid waste system rock - like similar material in rock mass simulation experiments.

[0022] In another preferred embodiment, the ceramsite - gypsum solid waste system rock - like similar material is used to simulate a low - strength and high - brittleness rock mass simulation material with a uniaxial compressive strength not exceeding 3MPa.

[0023] Compared with the prior art, the beneficial effects of the present invention are:

[0024] (1) By controlling the addition amounts of desulfurized gypsum and ceramsite, a low-strength and high-brittle material is obtained. The setting time of desulfurized gypsum is regulated by the addition amount of the retarder to prevent the setting time of desulfurized gypsum from being too long or too short. By controlling the mass ratio of water to desulfurized gypsum, the setting time can be effectively controlled, and the mechanical properties of the ceramsite-gypsum solid waste system rock-like similar material prepared can be controlled. The ceramsite-gypsum solid waste system rock-like similar material in the present invention can simulate a low-strength and high-brittle material with a strength not exceeding 3 MPa and a brittleness index of 0.15 - 0.23, and exhibits brittle failure characteristics, meeting the requirements for low-strength and high-brittle similar materials.

[0025] (2) In the preparation process of the present invention, the mass ratio of water to desulfurized gypsum is controlled mainly because if the water-gypsum ratio content is too high, the water is not easily removed, the setting time is too long, the fluidity of the slurry is too large, and the ceramsite is likely to float on the surface of the slurry due to its porous structure, affecting the dispersion of the ceramsite in the slurry. If the water-gypsum ratio content is too low, the curing rate of the slurry accelerates, the fluidity is low, the slurry is difficult to be stirred evenly, and the internal bubbles are not easily discharged, which will also seriously affect the uniformity of the structure of the similar material. Description of the Drawings

[0026] Figure 1 It is the stress-strain curve diagram of the ceramsite-gypsum solid waste system rock-like similar material with different ceramsite contents in the present invention; among them, a is the stress-strain curve diagram of T6; b is the stress-strain curve diagram of T5; c is the stress-strain curve diagram of T4; d is the stress-strain curve diagram of T3; e is the stress-strain curve diagram of T2; f is the stress-strain curve diagram of T1.

[0027] Figure 2 It is the stress-strain curve of the cubic specimen in Example 2 of the present invention and the sample diagram after uniaxial compressive strength test; a is the stress-strain curve diagram, and the inset a1 in it is the sample photo after uniaxial compressive strength test; b is the internal cross-sectional view.

[0028] Figure 3 It is the SEM diagram of the cubic specimen in Example 2 of the present invention. Detailed Embodiments

[0029] Next, the technical solutions in the present invention will be clearly and completely described in combination with the specific embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0030] In the methods described in the embodiments of the present invention, unless otherwise specified, they are all conventional methods. The materials, reagents, etc. used, unless otherwise specified, can all be obtained from commercial channels.

[0031] The experimental raw materials used in the following examples are:

[0032] (1) Ceramic aggregate: The performance index D50 is a particle size of 0.8 cm to 1.4 cm, purchased from Jincai Building Materials Sales Co., Ltd. In the present invention, the ceramic aggregate is used as an aggregate in a rock-like material.

[0033] (2) Desulfurization gypsum: 600 mesh, from Henan Wuhu Environmental Protection Technology Co., Ltd., is an industrial by-product produced by limestone desulfurization of flue gas after coal combustion, and serves as a binder.

[0034] (3) Retarders: One of the main drawbacks of desulfurized gypsum in cementitious materials is its short setting time. This is not conducive to the production and application of desulfurized gypsum as a cementitious material. Therefore, retarders are added to the application of desulfurized gypsum to adjust the hydration rate and setting time. Gypsum retarders are mainly divided into organic acids and soluble salts, alkaline phosphates and macromolecular protein compounds. The present invention uses a protein retarder, the mechanism of which is that protein and its hydrate are adsorbed on the surface of dihydrate gypsum particles to prevent germ formation, or form protective colloids to hinder the hydration of hemihydrate gypsum. It is a white powder produced by Beijing Kelly Tianwei Chemical.

[0035] 1. Equipment and instruments used:

[0036] (1) Electronic analytical balance: weighing accuracy is 0.1 mg, maximum range is 200 g, used for weighing raw materials and retarders.

[0037] (2) Planetary cement slurry mixer: used to mix raw materials with water to make them uniform. In the embodiment of the present invention, the gypsum slurry was stirred for 1 minute, and then stirred for another 1 minute after adding ceramsite.

[0038] (3) Standard Favica apparatus: This instrument is manufactured according to ISO9597-1989 and is used to determine the setting time of gypsum slurry.

[0039] (4) Steel ruler: This experiment is used to determine the fluidity of gypsum slurry.

[0040] (5) Electric constant temperature air drying oven: used to dry samples and utensils. In the embodiment of the present invention, the operating temperature is 20°C, the drying time is 24h, and the maximum operating temperature is 25°C.

[0041] (6) Electronic universal testing machine: Model WDW-50, used to perform uniaxial compression tests and mechanical property tests on samples. The testing machine controls loading by controlling the displacement size, and the loading speed is 0.6 mm / min. This ensures that the obtained stress-strain curve is complete and reliable, while avoiding damage to the testing machine caused by sudden destruction of the specimen.

[0042] (7) X-ray diffractometer: Model XRD-6000, with a scanning range of 10° to 80° (2θ), used for analyzing the phase composition of the test specimens.

[0043] (8) Scanning electron microscope: Model S-3000N, used for high-resolution microscopic morphology analysis of the sample surface, with a magnification between 500 and 30,000 times.

[0044] (9) Molds: All molds used in this experiment are made of ABS plastic. The molds used are divided into two types. One is cylindrical, with dimensions of Φ50mm × 100mm; the other is cubic, with dimensions of 100mm × 100mm × 100mm. To facilitate demolding, lubricating oil needs to be evenly applied inside the molds before filling.

[0045] (10) Agate mortar, respectively used for preparing a small amount of powdered samples when performing X-ray diffraction and infrared spectroscopy analysis.

[0046] Example 1

[0047] A ceramsite - gypsum solid waste system rock-like similar material is prepared from desulfurized gypsum, water-absorbing ceramsite, retarder and water;

[0048] The mass ratio of desulfurized gypsum, water-absorbing ceramsite and retarder is 300:10:0.8; the mass ratio of water to desulfurized gypsum is 0.45:1.

[0049] The water-absorbing ceramsite is obtained by soaking ceramsite with a particle size of 1.1 cm in water for 1 h.

[0050] The retarder is a plant protein retarder, and the particle size of desulfurized gypsum is 12 μm.

[0051] The preparation method of the above-mentioned ceramsite - gypsum solid waste system rock-like similar material includes the following steps:

[0052] S1. Add desulfurized gypsum, retarder and water to a blender, stir at 100 r / min for 5 min until evenly mixed, then add water-absorbing ceramsite and continue to stir for 5 min. Stop stirring after observing that the gypsum slurry evenly coats the outer surface of the ceramsite to obtain a mixed slurry.

[0053] S2. Pour the mixed slurry into a pre-prepared cylindrical mold, vibrate for 5 min until there are no bubbles on the surface of the mixed slurry to obtain a specimen.

[0054] S3. After curing the specimen at 23°C for 24 h, dry it at 40°C for 24 h until constant weight to obtain the ceramsite - gypsum solid waste system rock-like similar material.

[0055] Example 2

[0056] A ceramsite - gypsum solid waste system rock - like similar material is prepared from desulfurized gypsum, water - absorbing ceramsite, retarder and water;

[0057] The mass ratio of desulfurized gypsum, water - absorbing ceramsite and retarder is 200:15:0.6; the mass ratio of water to desulfurized gypsum is 0.43:1.

[0058] The water - absorbing ceramsite is obtained by soaking ceramsite with a particle size of 0.8 cm in water for 1 h.

[0059] The retarder is a plant - protein retarder, and the particle size of the desulfurized gypsum is 10 μm.

[0060] The preparation method of the above - mentioned ceramsite - gypsum solid waste system rock - like similar material specifically includes the following steps:

[0061] S1. Add desulfurized gypsum, retarder and water into a mixer and stir at 80 r / min for 3 min until evenly mixed, then add water - absorbing ceramsite and continue to stir for 3 min. Stop stirring after observing that the gypsum slurry evenly wraps the outer surface of the ceramsite to obtain a mixed slurry.

[0062] S2. Pour the mixed slurry into a pre - prepared cylindrical mold and vibrate it for 5 min until there are no bubbles on the surface of the mixed slurry to obtain a specimen.

[0063] S3. Cure the specimen at 23 °C for 24 h, and then dry it at 30 °C for 12 h until constant weight to obtain the ceramsite - gypsum solid waste system rock - like similar material.

[0064] Example 3

[0065] A ceramsite - gypsum solid waste system rock - like similar material is prepared from desulfurized gypsum, water - absorbing ceramsite, retarder and water;

[0066] The mass ratio of desulfurized gypsum, water - absorbing ceramsite and retarder is 300:25:0.7; the mass ratio of water to desulfurized gypsum is 0.46:1.

[0067] The water - absorbing ceramsite is obtained by soaking ceramsite with a particle size of 1.0 cm in water for 2 h.

[0068] The retarder is a plant - protein retarder, and the particle size of the desulfurized gypsum is 25 μm.

[0069] The preparation method of the above - mentioned ceramsite - gypsum solid waste system rock - like similar material specifically includes the following steps:

[0070] S1. Add desulfurized gypsum, retarder and water into a mixer and stir at 100 r / min for 4 min until evenly mixed, then add water - absorbing ceramsite and continue to stir for 4 min. Stop stirring after observing that the gypsum slurry evenly wraps the outer surface of the ceramsite to obtain a mixed slurry.

[0071] S2. Pour the prepared mixed slurry into a pre-prepared cylindrical mold, and vibrate it for 8 minutes until there are no bubbles on the surface of the mixed slurry to obtain a specimen.

[0072] S3. After curing the specimen at 27 °C for 36 h, dry it at 35 °C for 20 h until it reaches a constant weight to obtain the ceramsite - gypsum solid waste system rock - like similar material.

[0073] Example 4

[0074] A ceramsite - gypsum solid waste system rock - like similar material is prepared from desulfurized gypsum, water - absorbing ceramsite, retarder and water;

[0075] The mass ratio of desulfurized gypsum, water - absorbing ceramsite and retarder is 400:35:0.8; the mass ratio of water to desulfurized gypsum is 0.44:1.

[0076] The water - absorbing ceramsite is obtained by soaking ceramsite with a particle size of 1.4 cm in water for 2 h.

[0077] The retarder is a plant - protein retarder, and the particle size of the desulfurized gypsum is 25 μm.

[0078] The preparation method of the above - mentioned ceramsite - gypsum solid waste system rock - like similar material specifically includes the following steps:

[0079] S1. Add desulfurized gypsum, retarder and water to a mixer and stir at 120 r / min for 5 minutes until evenly mixed, then add water - absorbing ceramsite and continue to stir for 5 minutes. Stop stirring after observing that the gypsum paste evenly wraps the outer surface of the ceramsite to obtain a mixed slurry.

[0080] S2. Pour the mixed slurry into a pre - prepared cylindrical mold, and vibrate it for 10 minutes until there are no bubbles on the surface of the mixed slurry to obtain a specimen.

[0081] S3. After curing the specimen at room temperature for 48 h, dry it at 40 °C for 40 h until it reaches a constant weight to obtain the ceramsite - gypsum solid waste system rock - like similar material.

[0082] Example 5

[0083] A ceramsite - gypsum solid waste system rock - like similar material is prepared from desulfurized gypsum, water - absorbing ceramsite, retarder and water;

[0084] The mass ratio of desulfurized gypsum, water - absorbing ceramsite and retarder is 400:50:0.9; the mass ratio of water to desulfurized gypsum is 0.44:1.

[0085] The water - absorbing ceramsite is obtained by soaking ceramsite with a particle size of 1.4 cm in water for 2 h.

[0086] The retarder is a plant protein retarder, and the particle size of the desulfurized gypsum is 25 μm.

[0087] The preparation method of the above-mentioned ceramsite-gypsum solid waste system rock-like similar material specifically includes the following steps:

[0088] S1. Add desulfurized gypsum, retarder and water to a mixer and stir at 150 r / min for 5 min until evenly mixed, then add absorbent ceramsite and continue to stir for 5 min. Stop stirring after observing that the desulfurized gypsum slurry evenly wraps the outer surface of the ceramsite to obtain a mixed slurry.

[0089] S2. Pour the mixed slurry into a pre-prepared cylindrical mold and vibrate it for 10 min until there are no bubbles on the surface to obtain a specimen.

[0090] S3. Cure the specimen at 25 °C for 48 h, then bake it at 40 °C for 40 h until constant weight to obtain the ceramsite-gypsum solid waste system rock-like similar material.

[0091] The uniaxial compressive strengths of the ceramsite-desulfurized gypsum solid waste system rock-like similar materials prepared in Examples 1 to 5 are all between 2.42 MPa and 2.70 MPa.

[0092] In order to further illustrate the effect of the ceramsite-desulfurized gypsum solid waste system rock-like similar material, the following experiments were conducted. In the following experiments, the mass ratio of water to desulfurized gypsum is uniformly referred to as the water-gypsum ratio.

[0093] 1. Influence of ceramsite addition amount on the performance of the ceramsite-desulfurized gypsum solid waste system rock-like similar material

[0094] Under the condition of fixing the water-gypsum ratio at 0.45:1, adjust the content of ceramsite to determine the influence of the aggregate content on its performance. The experimental formula is designed as shown in Table 1. Since the maximum ceramsite content that the selected molding mold can accommodate is limited, the ceramsite mass of 90% of the maximum capacity of the mold, that is, 50 g, is regarded as the ceramsite content of 90% in the similar material system of this experiment, and so on. Six groups of different ceramsite content formulas numbered T1, T2, T3, T4, T5, and T6 are designed for experimental research.

[0095] Table 1 Actual specimen formula

[0096] Number Desulfurized gypsum / g Ceramsite / g Water / g Retarder / g Ceramsite content / % T1 300 50 135 0.75 90 T2 300 38.9 135 0.75 70 T3 300 27.7 135 0.75 50 T4 300 16.7 135 0.75 30 T5 300 5.6 135 0.75 10 T6 300 0 135 0.75 0

[0097] 2. Influence of water-gypsum ratio on the ceramsite-gypsum solid waste system rock-like similar material

[0098] The water-plaster ratio of the ceramsite-gypsum solid waste system's rock-like similar material is determined through experiments. With the bone glue ratio of desulfurized gypsum to ceramsite and the dosage of retarder fixed, the ratio of water to desulfurized gypsum, i.e., the water-plaster ratio, is determined, and the setting time is controlled within 24 hours or even shorter. The optimal water-plaster ratio of the ceramsite-gypsum solid waste system's rock-like similar material is determined by the slurry fluidity and setting time. The specific specimen proportions are shown in Table 2. The mass of ceramsite is fixed at 90% of the maximum capacity of the mold, i.e., 50 g, and 5 groups of different water-plaster ratios are designed, numbered S1, S2, S3, S4, and S5. The mass ratio of desulfurized gypsum to ceramsite is 4:1, and the addition amount of retarder is 1 g.

[0099] Table 2 Specimen Formulation

[0100]

[0101]

[0102] Mechanical Property Test: Demold the specimens after they are completely dry, sand the two ends smoothly, measure the final height, and conduct a uniaxial compression test.

[0103] 3. Test Methods

[0104] 1) Uniaxial Compression Test

[0105] The uniaxial compression test is a common rock mechanics test method used to determine the compressive strength and deformation properties of rocks when subjected to pressure perpendicular to their surfaces. The uniaxial compression test is one of the important methods for evaluating the compressive strength and deformation properties of rocks and is widely used in fields such as geological engineering, geotechnical engineering, and mining engineering.

[0106] According to GB / T 23561.8 - 2024, the calculation formulas for stress, strain, and elastic modulus are as follows:

[0107]

[0108] Where: σ is the stress, MPa; p is the load corresponding to the strain, kN; F is the initial bearing area of the specimen, cm 2 .

[0109]

[0110] Where: ε is the strain; ΔL is the deformation of the specimen, mm; L is the original length of the specimen, mm.

[0111]

[0112] Where: E t is the elastic modulus, MPa; σ a is the stress at the starting point of the straight line segment in the stress-strain curve, MPa; σb is the stress at the end point of the straight line segment in the stress-strain curve, MPa; ε a is the strain value at the starting point of the straight line segment in the stress-strain curve; ε b is the strain value at the end point of the straight line segment in the stress-strain curve.

[0113] 2) X-ray diffraction analysis

[0114] X-ray diffraction analysis is a technique used to determine the microstructural parameters of crystalline and certain amorphous materials. The method is based on the principle that different substances have their own unique crystal structures. When a material is irradiated with X-rays of a certain intensity, the crystal planes will reflect secondary fluorescent X-rays according to Bragg's law. Qualitative and quantitative analysis can be performed by analyzing the diffraction angle and the integrated intensity of the spectrum. This analysis method is one of the most commonly used characterization test techniques in scientific research, and data processing usually requires the use of professional software such as Jade and HighScore.

[0115] 3) Scanning electron microscope, abbreviated as SEM

[0116] Scanning electron microscopy uses an electron beam as a light source, scans the surface of a solid sample with a very finely focused electron beam in a raster scanning manner, and obtains surface morphology information of the sample by detecting secondary electrons. The advantages of scanning electron microscopy include multi-angle observation of samples, direct analysis of surface structure, good three-dimensional images, and micro-area analysis. This experiment aims to use scanning electron microscopy to analyze the morphology of each phase, the connection relationship of the interface, etc.

[0117] 4. Parameter evaluation index

[0118] 1) Brittleness index

[0119] The rock brittleness index is an evaluation index that describes the brittleness of rocks. It is usually determined by experiments or observations of the failure mode and crack extension of rocks under stress. The higher the value of the brittleness index, the easier it is for the rock to fail in a brittle manner, that is, it is more likely to crack and break after being subjected to a certain stress. In the fields of engineering and geology, understanding the brittleness index of rocks is very important for design and construction. For projects that require drilling, excavation or blasting in rocks. In addition, in geological exploration and mineral exploration, the brittleness index is also one of the important indicators for evaluating rock quality and stability. The brittleness index is an important factor in evaluating the fracturability of shale and predicting collapse, rock bursts and earthquakes. At the same time, brittleness not only has a significant impact on the machinability, drillability and excavability of rocks, but is also closely related to the sustainable mining and safe construction of coal mines. Understanding the brittleness index of rocks can help engineers choose appropriate processes and equipment to reduce the occurrence of accidents.

[0120] This embodiment is for quantitatively evaluating the brittleness of materials. The brittleness index is defined by the full stress parameters of the ceramsite - gypsum solid waste system - like rock similar materials, and the calculation formula is as follows:

[0121]

[0122] In the formula: BI zhou is the brittleness index, k ac is the slope of the straight line connecting the peak and the residual point; σ p is the peak stress; σ r is the residual strength. When BI zhou ≤1.0, there is a strong rockburst tendency; when BI zhou >1.0, there is no rockburst tendency.

[0123] 2) Impact energy index

[0124] The impact tendency of rock strata refers to its property of accumulating deformation energy and causing impact damage, which is used to judge the rockburst tendency of rocks. The energy impact index A proposed by Gong Fengqiang et al. is introduced CF , and this index is defined by the full stress - strain curve of the rock, and the calculation formula is as follows:

[0125]

[0126] In the formula: A CF is the impact energy index, A1 is the area before the peak, and A2 is the area after the peak. When A CF >3.0, the similar material has strong rockburst property; when 2.0<A CF ≤3.0, the similar material has medium rockburst property; when 1.0≤A CF ≤2.0, the similar material has weak rockburst property; when A CF <1.0, the similar material has no rockburst property.

[0127] 3) Determination of water - gypsum ratio

[0128] The setting time and fluidity of specimens S1, S2, S3, S4, and S5 are measured respectively, and the results are shown in Table 3.

[0129] Table 3 Experimental data table

[0130]

[0131] As shown in Table 3, it can be seen from the fluidity data that the addition amount of water has a great influence on it. As the water-plaster ratio decreases, the decrease in the fluidity of the slurry is relatively large. S1 is too thin and it is not easy to adhere to the blades during stirring. S5 is too thick, resulting in the machine stalling and requiring manual mixing. Moreover, when measuring the fluidity, the specimen does not collapse. When grouting, if the desulfurized gypsum slurry is too thick, it cannot be fully mixed with the ceramsite evenly. If it is too thin, the ceramsite will float during vibration, which also affects the uniformity of the specimen and thus its strength. The water-plaster ratios of S2, S3, and S4 can be well mixed with the ceramsite evenly and are also relatively easy to mix during stirring. Therefore, the water-plaster ratio suitable for the curing and forming of this similar material is determined to be 0.43 - 0.47.

[0132] The water-plaster ratio determines the curing time of the desulfurized gypsum and the mechanical properties of the sample. If the content of the water-plaster ratio is too high, the water is not easy to remove, the curing time is too long, the fluidity of the slurry is too large, and the ceramsite is likely to float on the surface of the slurry due to its porous structure, affecting the dispersion of the ceramsite in the slurry. If the content of the water-plaster ratio is too low, the curing rate of the slurry accelerates, the fluidity is low, the slurry is difficult to stir evenly, and the internal bubbles are not easy to discharge, which will also seriously affect the uniformity of the structure of the similar material. The uniform dispersion of the aggregate in the slurry, the water content inside the system, and the pore content will all affect the mechanical properties of the similar material, and the resulting changes in mechanical properties are randomly fluctuating and irregular. Therefore, in this invention, experiments are carried out on the water-plaster ratio of the ceramsite-desulfurized gypsum similar material system to determine the water-plaster ratio suitable for the curing and forming of this similar material.

[0133] 4) Influence of aggregate content on properties

[0134] Uniaxial compression tests were carried out on cylindrical specimens with different ceramsite contents, and the stress-strain curves obtained are as Figure 1 shown, and the data are shown in Table 4.

[0135] Table 4 Experimental data table

[0136]

[0137] The impact energy index shows an increasing trend with the increase of the aggregate content. T2 and T4 have strong rockburst properties; T1 belongs to medium rockburst properties; T3 and T6 have weak rockburst properties; T5 has no rockburst property, which is relatively abnormal. The brittleness index < 1, and the specimen has a rockburst tendency. Analyzing the stress-strain curve Figure 1 , it can be seen that the curve drops rapidly after reaching the peak strength, showing brittle failure characteristics, and it can be preliminarily judged as a brittle material. Moreover, the brittle failure characteristics of the two groups of T2 and T4 are more obvious, and the curve drops steeply when loaded to the peak strength. From the data, as the ceramsite addition amount increases, its peak strength shows a gradually decreasing trend, and the optimal ceramsite content suitable for the forming of this similar material is determined to be 30% - 70%.

[0138] The present invention conducts experiments on the influence of the ceramsite content in the ceramsite-desulfurized gypsum similar material system on the mechanical properties, and determines the optimal ceramsite content of 30% - 70% suitable for the preparation and molding of this similar material. The stress-strain curve of the prepared cubic T2 specimen and the photos of the samples after uniaxial compressive strength testing are as Figure 2 shown. It can be seen that the uniaxial compressive strength is 1.9 MPa, and the stress-strain curve drops rapidly after reaching the peak strength, showing brittle failure characteristics. It can be preliminarily judged as a brittle material, and the strength meets the specified range. In the scanning electron microscope, a large number of prismatic or irregularly shaped crystals, namely calcium sulfate dihydrate, can be seen, which are the products of the hydration of hemihydrate gypsum and the crystallization of calcium sulfate dihydrate when it meets water. The micrograph of the cubic T2 specimen in Example 2 is as Figure 3 shown. The loose and porous microstructure is ceramsite, which can store a certain amount of water when mixed with water and gypsum, and continuously supply water for the hydration reaction in the later stage of the reaction, enabling the complete hydration of hemihydrate gypsum and its complete conversion into structurally hard calcium sulfate dihydrate. It can be observed from the cross-section that the combination of gypsum and ceramsite is weak, and the contact interface is clear. The presence of porous ceramsite is judged to be at the junction of the two substances. At the same time, a small number of gypsum pits are observed, indicating that when the specimen is subjected to external stress, the material fractures mainly in the form of the fracture of the porous structure of ceramsite, and partially fractures along the contact surface, mainly due to the weak combination between the two substances.

[0139] In the process of deep coal mining, problems such as strata movement, collapse, and rock burst safety accidents are likely to occur. Through physical model simulation experiments in the laboratory, the present invention makes use of solid waste resources such as ceramsite and desulfurized gypsum to produce rock-like similar materials. Through uniaxial compression tests, various parameters under the influence of different factors are measured. From the results, it can be seen that as the content of ceramsite aggregate increases, the compressive strength decreases, and the impact energy index rises from 1.24 to 2.53; as the content of ceramsite aggregate increases, the brittle index ranges from 0.14 to 0.88, and the elastic modulus decreases from 0.88 GPa to 0.14 GPa. At the T2 ratio, that is, the ceramsite content is 70%, the water-plaster ratio is 0.45, the compressive strength is 2.70 MPa, the impact energy index is 7.7, the brittle index is 0.23, and the elastic modulus is 0.38 GPa. It shows high rock burst characteristics and brittle fracture failure forms.

[0140] The optimal water-plaster ratio in the present invention is 0.45, and the optimal ceramsite content is 70%. The rock-like similar material of the ceramsite-gypsum solid waste system obtained has a strength not exceeding 3 MPa and shows brittle failure characteristics, meeting the requirements for low-strength and high-brittle similar materials. This ratio conforms to the national standard GB / T23561.8 - 2024 for the determination method of the physical properties of coal and rocks.

[0141] Although the preferred embodiments of the present invention have been described, additional changes and modifications can be made to these embodiments by those skilled in the art once they learn of the basic inventive concept. Therefore, the appended claims are intended to be construed to include the preferred embodiments as well as all changes and modifications that fall within the scope of the present invention.

[0142] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention is also intended to include these changes and modifications.

Claims

1. A ceramsite-gypsum solid waste system rock-like similar material, characterized in that, The ceramsite - gypsum solid waste system rock - like similar material is prepared from desulfurized gypsum, water - absorbing ceramsite, retarder and water; The mass ratio of the desulfurized gypsum, the water - absorbing ceramsite and the retarder is 200 - 300:15 - 40:0.5 - 0.9; The mass ratio of the water to the desulfurized gypsum is 0.43 - 0.47:1; the water - absorbing ceramsite is obtained by soaking ceramsite in water; the retarder is a plant - protein retarder; the particle size of the ceramsite is 0.8 cm - 1.4 cm, and the particle size of the desulfurized gypsum is 10 μm - 25 μm; the soaking time is 1 h - 2 h.

2. A preparation method of a ceramsite-gypsum solid waste system rock-like similar material according to any one of claim 1, characterized in that, It includes the following steps: Mix and stir the desulfurized gypsum, retarder and water according to the mass ratio, add the water - absorbing ceramsite and continue to stir to obtain a mixed slurry; inject the mixed slurry into a mold and vibrate it solid to obtain a specimen; After curing the specimen at 23°C - 27°C for 24 h - 48 h, demold it and dry it to a constant weight to obtain the ceramsite - gypsum solid waste system rock - like similar material.

3. The preparation method of the ceramsite-gypsum solid waste system rock-like similar material according to claim 2, characterized in that, The rotation speed of the mixing and stirring is 60 r / min - 150 r / min, and the time is 3 min - 5 min; The time for adding the water - absorbing ceramsite and continuing to stir is 3 min - 5 min.

4. The preparation method of the ceramsite-gypsum solid waste system rock-like similar material according to claim 3, characterized in that, The temperature of the drying is 30°C - 40°C, and the time is 12 h - 40 h.

5. The preparation method of the ceramsite-gypsum solid waste system rock-like similar material according to claim 4, wherein, The standard of the vibrating solid is that there are no bubbles on the surface of the mixed slurry.

6. Application of the ceramsite - gypsum solid waste system rock - like similar material according to claim 1 in rock mass simulation experiments.

7. The application according to claim 6, characterized in that, The ceramsite - gypsum solid waste system rock - like similar material is used to simulate a rock mass simulation material with low strength and high brittleness whose uniaxial compressive strength does not exceed 3 MPa.

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