Coal gangue coarse aggregate performance evaluation and echelon utilization method

Abstract

The invention relates to the technical field of building materials, in particular to a coal gangue coarse aggregate performance evaluation and echelon utilization method, which is characterized in that coal gangue coarse aggregate is divided into a plurality of particle size intervals and density groups mainly through particle size and density differences, and then physical performance tests such as crushing indexes, apparent density and water absorption are carried out. And based on a test result, performing score assignment and summarization on the coal gangue subjected to echelon utilization according to a scoring standard so as to realize reasonable evaluation on the coal gangue. According to the method, echelon treatment is carried out through the physical characteristics of the aggregate, high-quality classification of different granularities and densities is achieved, light substances in the aggregate are effectively removed, and a new thought and technical support are provided for high-quality utilization of the coal gangue.

Description

Technical Field

[0001] The present invention relates to the technical field of building materials, and specifically to a method for evaluating the performance of coal gangue coarse aggregate and its hierarchical utilization. Background Art

[0002] Coal gangue (CG) is the main industrial solid waste generated during coal mining and washing processes. Its accumulation is huge and the utilization rate is low. Currently, the main treatment method of coal gangue is still stacking and landfill. However, this method not only occupies a large amount of land resources, but also causes a series of environmental problems, such as heavy metal ions seeping into groundwater, spontaneous combustion releasing toxic gases (such as SO2, CO, etc.) and dust pollution. Therefore, how to efficiently and environmentally resourcefully utilize coal gangue has become a current research hotspot.

[0003] In recent years, researchers have found that using coal gangue as concrete coarse aggregate can effectively consume a large amount of coal gangue and reduce the environmental burden. However, untreated coal gangue aggregate has defects such as low activity and insufficient strength, which limits its dosage in concrete. For this reason, researchers have proposed a variety of modification technologies to improve the performance of coal gangue aggregate, mainly including thermal activation, surface coating, microbial mineralization and water glass modification, etc. Although these technologies can improve the performance of coal gangue aggregate to a certain extent, there are still problems such as high energy consumption, complex process and long treatment cycle, which are difficult to meet the requirements of large-scale industrial applications.

[0004] Aggregate hierarchical utilization, as a low-cost and high-benefit resource utilization technology, can classify aggregates according to their physical properties and achieve reasonable configuration and efficient utilization of aggregates through a scientific scoring system. This method can not only give full play to the performance advantages of different grades of aggregates, but also significantly reduce resource waste and environmental load.

[0005] Therefore, developing a resource treatment method for coal gangue coarse aggregate based on hierarchical utilization, through classification treatment and reasonable configuration, to improve the application performance of coal gangue aggregate in fields such as concrete, can not only achieve the high-value utilization of industrial solid waste, but also provide a new technical path for the large-scale resource utilization of coal gangue, which has important environmental and economic significance. Summary of the Invention

[0006] To solve the deficiencies of the existing technology, the present invention provides a method for evaluating the performance of coal gangue coarse aggregate and its hierarchical utilization, aiming to solve the problems of high pollution, complex process and high cost existing in the modification treatment of coal gangue in the existing technology. Through the hierarchical utilization technology, the present invention not only reduces the production cost, simplifies the treatment process, but also reduces the pollution of industrial waste to the environment and promotes the development of circular economy, with significant economic and ecological benefits.

[0007] Specifically, the present invention provides a method for evaluating the performance of coal gangue coarse aggregate, comprising the following steps:

[0008] S1. Crushing and screening the coal gangue to obtain particle size of 4.75mm-9.5mm.

[0009] Gangue particles in three particle size ranges: 9.5mm-16mm and 16mm-26.5mm;

[0010] S2. Determine the density of the coal gangue particles in the three particle size ranges, and screen the coal gangue particles in each particle size range into three groups according to the density range:

[0011] Low density group: density range is 2000kg / m 3 Up to 2350kg / m 3 ;

[0012] Medium density group: density range is 2350kg / m 3 Up to 2500kg / m 3 ;

[0013] High density group: density greater than 2500kg / m 3 ;

[0014] S3. The water absorption rate, crushing index and apparent density of the low-density group, medium-density group and high-density group of coal gangue particles in the three particle size ranges screened in S2 are tested respectively, and the corresponding data are recorded;

[0015] S4. The water absorption rate, crushing index and apparent density data of each group of gangue particles measured in S3 are scored according to the scoring standard, and the scoring standard is as follows:

[0016] The water absorption of gangue particles is scored according to the standard BS EN 1992-3:2006 “Eurocode 2: Design of concrete structures - Part 3: Structures for the storage and containment of liquids”;

[0017] The crushing index of coal gangue particles is scored according to the document "Study on Random Characteristics and Grading Method of Recycled Coarse Aggregate";

[0018] The apparent density of gangue particles is assigned according to the standard BS EN 206:2013+A1:2016 "Concrete - Specification, performance, production and consistency";

[0019] S5. Summarize the water absorption rate, crushing index and apparent density scoring results of each group of gangue particles in S4, and calculate the total score of each group of gangue particles.

[0020] In some specific embodiments of the present invention, the specific operations in step S1 include: crushing the coal gangue and screening to obtain coal gangue particles with a particle size range of 4.75 mm - 26.5 mm; cleaning the obtained coal gangue particles to remove the coal ash on the surface and drying to remove the moisture; then screening the coal gangue again by particle size, and obtaining coal gangue particles in three particle size ranges of 4.75 mm - 9.5 mm, 9.5 mm - 16 mm, and 16 mm - 26.5 mm after screening.

[0021] In some specific embodiments of the present invention, the specific operations in step S2 include: preparing a suspension, placing the coal gangue particles of three particle sizes into a suspension container filled with the suspension respectively, starting the stirring device in the suspension container, operating at a preset rotation speed, so that the coal gangue is suspended at different heights according to its density difference, and then salvaging according to the density, and screening the coal gangue particles in each particle size range into three groups according to the density range:

[0022] Low-density group: the density range is 2000 kg / m 3 to 2350 kg / m 3 ;

[0023] Medium-density group: the density range is 2350 kg / m 3 to 2500 kg / m 3 ;

[0024] High-density group: the density is greater than 2500 kg / m 3 。

[0025] In some specific embodiments of the present invention, the suspension is a zinc chloride solution, and dilute hydrochloric acid is added to the zinc chloride solution.

[0026] In some specific embodiments of the present invention, the specific gravity of the suspension is 1.45 g / cm 3 , when the particle size ranges of the coal gangue particles are 4.75 - 9.5 mm, 9.5 - 16 mm, and 16 - 26.5 mm respectively, the preset rotation speeds are 1000 / rpm, 1240 / rpm, and 1400 / rpm respectively.

[0027] In some specific embodiments of the present invention, it further includes cleaning and drying the coal gangue particles after density screening to remove the residual suspension on the surface of the coal gangue particles.

[0028] In some specific embodiments of the present invention, the score assigned to the water absorption rate of the coal gangue particles is 1 - 4; the score assigned to the crushing index of the coal gangue particles is 1 - 5; the score assigned to the apparent density of the coal gangue particles is 1 - 5.

[0029] In some specific embodiments of the present invention, for the low-density group, medium-density group, and high-density group in the same particle size range, when the apparent density scores of the coal gangue particles are the same, according to the principle that the better the aggregate performance with the greater density, re-scoring is performed with 0.3 as the base; when the water absorption scores of the coal gangue particles are the same, according to the principle that the better the aggregate performance with the smaller water absorption, re-scoring is performed with 0.3 as the base; when the crushing index scores of the coal gangue particles are the same, according to the principle that the better the aggregate performance with the smaller crushing index, re-scoring is performed with 0.3 as the base.

[0030] In some specific embodiments of the present invention, coal gangue particles with different scores are used as coarse aggregates to prepare concrete specimens; mechanical property tests are carried out on the concrete specimens, and according to the test results, the correlation between the scores of coal gangue particles with different scores and the mechanical properties of the concrete is analyzed to verify the matching of the scores and the mechanical properties.

[0031] In some specific embodiments of the present invention, the mechanical property experiments include compressive strength tests and splitting tensile strength tests.

[0032] The present invention also provides a method for hierarchical utilization of coal gangue coarse aggregates. The performance of coal gangue coarse aggregates is evaluated according to the coal gangue coarse aggregate performance evaluation method described in any one of the above, the total performance scores of coal gangue coarse aggregates in each density group of each particle size range are obtained, and hierarchical classification and utilization of coal gangue in each density group of each particle size range are carried out according to the total score results.

[0033] The present invention also provides the application of the coal gangue particles screened by the coal gangue coarse aggregate performance evaluation method described in any one of the above in mine backfilling projects, building projects, bridge projects, highway projects or tunnel projects.

[0034] The present invention has the following remarkable advantages and effects compared with the prior art:

[0035] 1. Low equipment cost and convenient operation

[0036] The equipment adopted by the present invention has a simple structure, low cost, and a simple operation process. There is no need for complex treatment processes, which significantly improves production efficiency and is suitable for large-scale industrial applications.

[0037] 2. Hierarchical utilization and high resource utilization rate

[0038] Through the hierarchical utilization technology, reasonable hierarchical utilization can be carried out according to different characteristics such as the strength and particle size of coal gangue, which significantly improves the utilization rate of coal gangue coarse aggregates and reduces resource waste.

[0039] 3. Simple process, energy saving and environmental protection

[0040] The entire preparation process is simple and easy, reducing manpower and time costs; at the same time, the process has low energy consumption, meets the requirements of energy conservation and environmental protection, and has significant economic and environmental benefits.

[0041] 4. High-value utilization of waste, environmentally friendly

[0042] Using coal gangue as the main raw material for modification and treatment has achieved high-value utilization of industrial waste, reduced dependence on natural resources, reduced the pressure of waste on the environment, and promoted the development of a circular economy.

[0043] 5. Promote sustainable development

[0044] The present invention not only solves the problems of high pollution and high cost of traditional coal gangue treatment technology, but also provides a new way for the resource utilization of industrial waste, and has important social, economic and ecological value. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0046] Figure 1 The present invention provides a flow chart of a method for evaluating the performance of gangue coarse aggregate and its cascade utilization. DETAILED DESCRIPTION

[0047] In conjunction with specific embodiments, the present invention will be further described. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope limited by the application.

[0048] Example 1: Performance evaluation of gangue coarse aggregate

[0049] The gangue was crushed in a jaw crusher, and after preliminary screening, the gangue particles with a particle size of 4.75-26.5 mm were obtained. After outdoor air drying, the gangue was finally screened to obtain gangue particles with different particle sizes of 4.75-9.5 mm, 9.5-16 mm, and 16-26.5 mm. The mass of each particle size was weighed and stored for later use. An appropriate amount of zinc chloride particles was placed in an aqueous solution and dissolved using a magnetic stirrer to prepare 1.45 g / cm 3Zinc chloride solution; in addition, a small amount of dilute hydrochloric acid is added to prevent hydrolysis of the zinc chloride solution. Place the mixer on the round barrel, and then place the prepared zinc chloride solution and coal gangue particles in different particle size ranges into the barrel. On this basis, fix the height of the mixing paddle of the mixer (1-2 cm higher than the top surface of the aggregate), the height of the solution, and the height of the aggregate; take the mixer speed as the independent variable. Since the suspension speeds of different particle sizes are different, therefore, when the particle size ranges of the coal gangue are 4.75-9.5 mm, 9.5-16 mm, and 16-26.5 mm respectively, control the mixer speeds to be 1000 / rpm, 1240 / rpm, and 1400 / rpm respectively. Fix the fishing depth to be 7 cm and 14 cm below the liquid level until the coal gangue at the previous liquid level is fished out, and then fish at the next height to obtain coal gangue particles in the low-density group (density range: 2000 kg / m 3 to 2350 kg / m 3 ), the medium-density group (density range: 2350 kg / m 3 to 2500 kg / m 3 ), and the high-density group (density greater than 2500 kg / m 3 ). Finally, wash the surface of the coal gangue particles in the low-density group, medium-density group, and high-density group with hot water (zinc chloride has a high solubility in hot water), and place the waste liquid in the waste liquid barrel for retention.

[0050] For the coal gangue particles in the low-density group, medium-density group, and high-density group with three particle size ranges after screening, respectively conduct tests on the mass (G1) before water absorption, the mass (G2) after drying, the mass (G3) before crushing, the mass (G4) after crushing, the mass (G5) in the apparent density test, the volume (V1) before putting into the container, and the volume (V2) after putting into the container, and then calculate the water absorption rate (Q1), crushing index (Q2), and apparent density (Q3) according to the following formulas.

[0051]

[0052] Score the water absorption rate, crushing index, and apparent density data of each group of coal gangue particles measured in S3 according to the scoring criteria. The scoring criteria are as follows:

[0053] Score the water absorption rate of the coal gangue particles according to the standard BS EN 1992-3:2006 "Eurocode 2: Design of concrete structures - Part 3: Liquid storage and containment structures", and the score is 1-5.

[0054] Score the crushing index of the coal gangue particles according to the literature "Research on the random characteristics and grading methods of recycled coarse aggregates", and the score is 1-5.

[0055] The apparent density of coal gangue particles is scored according to the standard BS EN 206:2013+A1:2016 "Concrete - Specification, performance, production and conformity", and the score is 1 - 4.

[0056] For the low - density group, medium - density group and high - density group in the same particle size range, when the apparent density scores of coal gangue particles are the same, according to the principle that the better the aggregate performance with the greater density, a re - score is made with 0.3 as the base; when the water absorption scores of coal gangue particles are the same, according to the principle that the better the aggregate performance with the smaller water absorption, a re - score is made with 0.3 as the base; when the crushing index scores of coal gangue particles are the same, according to the principle that the better the aggregate performance with the smaller crushing index, a re - score is made with 0.3 as the base.

[0057] According to the above evaluation steps, the hierarchical utilization and evaluation results of coal gangue coarse aggregate in this embodiment are as follows (the scoring results of the low - density group, medium - density group and high - density group in different particle size ranges):

[0058] (1) The density of low - density (4.75 - 9.5 mm) coal gangue particles is 2.194 g / cm 3 , the score is 1, the water absorption rate is 3.06%, the score is 4.6, the crushing index is 28.77, the score is 3.3, and the total score is 8.9.

[0059] (2) The density of medium - density (4.75 - 9.5 mm) coal gangue particles is 2.373 g / cm 3 , the score is 1.3, the water absorption rate is 3.59%, the score is 4, the crushing index is 30.61, the score is 3, and the total score is 8.3.

[0060] (3) The density of high - density (4.75 - 9.5 mm) coal gangue particles is 2.534 g / cm 3 , the score is 3.6, the water absorption rate is 3.30%, the score is 4.3, the crushing index is 25.55, the score is 3.6, and the total score is 11.5.

[0061] (4) The density of low - density (9.5 - 16 mm) coal gangue particles is 2.235 g / cm 3 , the score is 1, the water absorption rate is 2.47%, the score is 5, the crushing index is 19.29, the score is 3, and the total score is 9.

[0062] (5) The density of medium - density (9.5 - 16 mm) coal gangue particles is 2.429 g / cm 3 , the score is 1.3, the water absorption rate is 2.40%, the score is 5.3, the crushing index is 18.60, the score is 4.3, and the total score is 10.9.

[0063] (6) The density of high-density (9.5 - 16 mm) coal gangue particles is 2.524 g / cm 3 , with a score of 3.6, water absorption rate of 2.38%, score of 5.6, crushing index of 15.52, score of 5.6, and a total score of 14.8.

[0064] (7) The density of low-density (16 - 26.5 mm) coal gangue particles is 2.334 g / cm 3 , with a score of 1, water absorption rate of 1.88%, score of 5.6, crushing index of 12.77, score of 5, and a total score of 11.6.

[0065] (8) The density of medium-density (16 - 26.5 mm) coal gangue particles is 2.420 g / cm 3 , with a score of 1.3, water absorption rate of 2.04%, score of 5, crushing index of 11.02, score of 5.3, and a total score of 11.6.

[0066] (9) The density of high-density (16 - 26.5 mm) coal gangue particles is 2.564 g / cm 3 , with a score of 4.6, water absorption rate of 1.99%, score of 5.3, crushing index of 10.45, score of 5.6, and a total score of 15.5.

[0067] Example 2: Utilization of coal gangue coarse aggregate and verification of the matching between score and mechanical properties

[0068] Combine the coal gangue with the highest scores in the three particle size ranges (all high-density groups) into coarse aggregate, and prepare concrete according to the ratio of cement: coal gangue powder: sand: coal gangue fine aggregate: gravel: coal gangue coarse aggregate: water = 361:19:501.6:125.4:888.3:380.7:152. Then, conduct compressive strength and splitting tensile strength tests respectively. The test results are as follows: the compressive strength is 36.95 MPa, and the splitting tensile strength is 1.88 MPa.

[0069] Combine the medium-density coal gangue in the three particle size ranges into coarse aggregate, and prepare concrete according to the ratio of cement: coal gangue powder: sand: coal gangue fine aggregate: gravel: coal gangue coarse aggregate: water = 361:19:501.6:125.4:888.3:380.7:152. Then, conduct compressive strength and splitting tensile strength tests respectively. The test results are as follows: the compressive strength is 32.90 MPa, and the splitting tensile strength is 1.88 MPa.

[0070] Combine the low-density coal gangue in three groups of particle size ranges into coarse aggregate, and prepare concrete according to the ratio of cement: coal gangue powder: sand: coal gangue fine aggregate: gravel: coal gangue coarse aggregate: water = 361:19:501.6:125.4:888.3:380.7:152. Then, conduct compressive strength and splitting tensile strength tests respectively. The test results are: the compressive strength is 30.63 MPa, and the splitting tensile strength is 2.19 MPa.

[0071] Combine the coal gangue with the lowest scores in three groups of particle size ranges (the medium-density group coal gangue particles used in the 16 - 26.5 mm particle size range) into coarse aggregate, and prepare concrete according to the ratio of cement: coal gangue powder: sand: coal gangue fine aggregate: gravel: coal gangue coarse aggregate: water = 361:19:501.6:125.4:888.3:380.7:152. Then, conduct compressive strength and splitting tensile strength tests respectively. The test results are: the compressive strength is 27.13 MPa, and the splitting tensile strength is 1.60 MPa.

[0072] Prepare ordinary concrete using natural gravel, and prepare concrete according to the ratio of cement: sand: gravel: water = 380:627:1269:152. Then, conduct compressive strength and splitting tensile strength tests respectively. The test results are: the compressive strength is 38.97 MPa, and the splitting tensile strength is 3.66 MPa.

[0073] The test results show that the physical indexes of the coal gangue with hierarchical utilization have an internal connection with the scores, and the concrete with the highest score, ordinary and the lowest score are compared, highlighting the effectiveness of the scores.

[0074] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for evaluating the performance of coal gangue coarse aggregate, characterized in that: The steps include: S1. Crushing and screening the coal gangue to obtain particle size of 4.75mm-9.5mm. Gangue particles in three particle size ranges: 9.5mm-16mm and 16mm-26.5mm; S2. Determine the density of the coal gangue particles in the three particle size ranges, and screen the coal gangue particles in each particle size range into three groups according to the density range: Low density group: density range is 2000kg / m 3 Up to 2350kg / m 3 ; Medium density group: density range is 2350kg / m 3 Up to 2500kg / m 3 ; High density group: density greater than 2500kg / m 3 ; S3. The water absorption rate, crushing index and apparent density of the low-density group, medium-density group and high-density group of coal gangue particles in the three particle size ranges screened in S2 are tested respectively, and the corresponding data are recorded; S4. The water absorption rate, crushing index and apparent density data of each group of gangue particles measured in S3 are scored according to the scoring standard, and the scoring standard is as follows: The water absorption of gangue particles is scored according to the standard BS EN 1992-3:2006 “Eurocode 2: Design of concrete structures - Part 3: Structures for the storage and containment of liquids”; According to the literature "Study on Random Characteristics and Classification Method of Recycled Coarse Aggregate", the crushing index of coal gangue particles is scored; The apparent density of gangue particles is assigned according to the standard BS EN 206:2013+A1:2016 "Concrete - Specification, performance, production and consistency"; S5. Summarize the water absorption rate, crushing index and apparent density scoring results of each group of gangue particles in S4, calculate the total score of each group of gangue particles, and grade and utilize each group of gangue according to the total score results.

2. The method for evaluating the performance of coal gangue coarse aggregate according to claim 1, characterized in that: The specific operations of the step S1. include: crushing the coal gangue, screening to obtain coal gangue particles in the particle size range of 4.75mm-26.5mm; washing the obtained coal gangue particles to remove surface fly ash, and drying to remove moisture; then screening the coal gangue again to obtain coal gangue particles in three particle size ranges of 4.75mm-9.5mm, 9.5mm-16mm and 16mm-26.5mm.

3. The method for evaluating the performance of coal gangue coarse aggregate according to claim 1, characterized in that: The specific operation of step S2. includes: preparing a suspension, placing the three types of coal gangue particles of different particle sizes in a suspension container containing the suspension, starting a stirring device in the suspension container, and running the stirring device at a preset speed so that the coal gangue is suspended at different heights according to its density difference, and then fishing the coal gangue particles according to the density, and screening the coal gangue particles in each particle size range into three groups according to the density range: Low density group: density range is 2000kg / m 3 Up to 2350kg / m 3 ; Medium density group: density range is 2350kg / m 3 Up to 2500kg / m 3 ; High density group: density greater than 2500kg / m 3 .

4. The method for evaluating the performance of coal gangue coarse aggregate according to claim 3, characterized in that: The suspension is a zinc chloride solution, to which dilute hydrochloric acid is added; the suspension has a specific gravity of 1.45 g / cm 3 When the particle size ranges of the gangue particles are 4.75-9.5 mm, 9.5-16 mm and 16-26.5 mm, respectively, the preset rotation speeds are 1000 / rpm, 1240 / rpm and 1400 / rpm, respectively.

5. The method for evaluating the performance of coal gangue coarse aggregate according to claim 4, characterized in that: The method also includes washing and drying the coal gangue particles after density screening to remove the residual suspension on the surface of the coal gangue particles.

6. The method for evaluating the performance of coal gangue coarse aggregate according to claim 1, characterized in that: The score assigned to the water absorption rate of the gangue particles is 1-4; the score assigned to the crushing index of the gangue particles is 1-5; and the score assigned to the apparent density of the gangue particles is 1-5.

7. The method for evaluating the performance of coal gangue coarse aggregate according to claim 6, characterized in that: For the low-density group, medium-density group and high-density group in the same particle size range, when the apparent density scores of the gangue particles are the same, they are re-scored based on the principle that the larger the density, the better the aggregate performance; when the water absorption scores of the gangue particles are the same, they are re-scored based on the principle that the smaller the water absorption, the better the aggregate performance; when the crushing index scores of the gangue particles are the same, they are re-scored based on the principle that the smaller the crushing index, the better the aggregate performance.

8. The method for evaluating the performance of gangue coarse aggregate according to any one of claims 1 to 7, characterized in that: The method also includes a scoring verification step: using gangue particles with different scores as coarse aggregate to prepare concrete specimens; conducting mechanical property tests on the concrete specimens, and analyzing the correlation between the scores of gangue particles with different scores and the mechanical properties of concrete based on the test results to verify the matching of the scores and the mechanical properties.

9. A method for cascade utilization of gangue coarse aggregate, characterized in that: According to the performance evaluation method of coal gangue coarse aggregate according to any one of claims 1 to 8, the performance of coal gangue coarse aggregate is evaluated to obtain the total performance score of the coal gangue coarse aggregate of each density group in each particle size range, and the coal gangue of each density group in each particle size range is graded and utilized in a tiered manner according to the total score result.

10. Application of the coal gangue particles screened by the method for evaluating the performance of coal gangue coarse aggregate according to any one of claims 1 to 8 in mine backfill engineering, construction engineering, bridge engineering, highway engineering or tunnel engineering.

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