Coal gangue regenerated light and fine aggregate, green lightweight concrete and preparation process

Abstract

The invention discloses a coal gangue regenerated light and fine aggregate, green lightweight concrete and a preparation process, and belongs to the technical field of building materials, the method comprises the following steps: reacting polyethylene glycol methacrylate and maleic anhydride in the presence of an initiator to obtain a modified liquid, pre-mixing rice hull ash and oxidized short carbon fibers, and adding an initiator to obtain a mixture; the preparation method comprises the following steps: mixing rice hull ash with carbon fiber, spraying a modification liquid to obtain modified rice hull ash-carbon fiber composite powder, mixing coal gangue powder, fly ash, the composite powder, a nano material and the like, granulating, carrying out segmented roasting to obtain coal gangue regenerated light and fine aggregate, and finally, mixing the aggregate with cement, fly ash and the like, and curing to obtain the green lightweight concrete. Through hydrophobic coating of the modified liquid, filling of the nano material and a solid waste synergistic mechanism, the technical problems of hydrophilicity of the rice hull ash, contradiction between light weight and high strength of a traditional lightweight aggregate and extensive utilization of solid wastes are solved, so that the lightweight and fine aggregate has the characteristics of light weight and high strength, the strength of the prepared concrete reaches the standard, the apparent density is low, and the application range is wide. And the requirements of ultra-low energy consumption buildings are met.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of building materials, and particularly relates to a coal gangue regenerated light fine aggregate and green lightweight concrete and a preparation process. BACKGROUND

[0002] Coal gangue is a main solid waste generated in the process of coal mining and washing and processing, is a black gray rock with low carbon content and higher hardness than coal, and is associated with coal seams in the process of coal formation. Traditional utilization approaches of the coal gangue are concentrated in the fields of mine backfilling of goaf, roadbed laying, land reclamation and power generation, and problems such as extensive utilization mode and low product added value exist, it is difficult to fully develop the material potential, and a large amount of coal gangue that is not efficiently utilized is long-term stacked, which can easily cause land occupation and environmental pollution.

[0003] In the field of building materials, light aggregate is the core component for preparing lightweight concrete. Traditional light aggregate has defects such as narrow strength adaptation range, high apparent density, incomplete particle size distribution and lack of internal curing function, and is difficult to meet the preparation requirements of lightweight concrete of different strength grades. In addition, the energy consumption in the production process is high, which does not meet the industrial policy of developing ultra-low energy consumption buildings. Therefore, it is a key problem to be solved in the industry to develop a regenerated light fine aggregate and a matching green lightweight concrete which have the characteristics of lightweight, high strength, complete gradation and low carbon environmental protection, and can realize high-value utilization of coal gangue.

[0004] A kind of lightweight coal gangue functional aggregate and its preparation method and application are disclosed in Chinese patent CN117125918B. By compounding coal gangue powder, fly ash, rice husk ash as a pore-forming agent and MnO2, through mixing, granulation, and staged roasting processes, a green, lightweight, high water absorption and high strength functional aggregate is prepared.

[0005] However, the rice husk ash in the above-mentioned scheme is mainly composed of amorphous silicon dioxide, and the surface is rich in silicon hydroxyl groups, which has high water absorption. This leads to uneven water absorption during granulation, reduces the structural strength of the green balls prepared by disc granulation, and easily causes disintegration during drying and rotary kiln processes, which affects the yield of the coal gangue aggregate. SUMMARY

[0006] The purpose of the present application is to provide a coal gangue regenerated light fine aggregate and green lightweight concrete and a preparation process. By means of hydrophobic coating of a modification liquid, nano material filling and solid waste synergistic mechanism, the problems of hydrophilicity of rice husk ash, contradiction between lightweight and high strength of traditional light aggregate, and extensive utilization of solid waste are solved. The light fine aggregate has the characteristics of lightweight and high strength, the prepared concrete meets the strength standard and has low apparent density, and meets the demand of ultra-low energy consumption buildings.

[0007] The purpose of the present application can be achieved by the following technical solutions:

[0008] The coal gangue regenerated light fine aggregate is prepared by disc granulation and sintering of powder materials, and the powder materials comprise the following components in parts by mass:

[0009] The coal gangue powder 425-850 parts, fly ash 75-150 parts, modified rice husk ash-carbon fiber composite powder 40-100 parts, nano metakaolin 10-12.5 parts, and ultra-fine aluminum hydroxide 5-7 parts.

[0010] Further, the modified rice husk ash-carbon fiber composite powder is prepared by spraying a modification liquid during the mixing and stirring of rice husk ash and short carbon fibers.

[0011] Further, the modified rice husk ash-carbon fiber composite powder is prepared by the following specific steps:

[0012] The rice husk ash and the short carbon fibers treated by nitric acid oxidation are added to a stirring kettle, stirred for 5 min at 25-30 DEG C, sodium dodecyl sulfonate is added, stirred for 2-3 min at 40-60 r / min, the composite powder is transferred to a high-efficiency mixer, the modification liquid is sprayed on the flowing powder during the stirring, after the spraying is completed, the stirring is continued for 3-5 min at 40-45 DEG C and 40-60 r / min, and the modified rice husk ash-carbon fiber composite powder is obtained.

[0013] Further, the length of the short carbon fibers is 1-3 mm.

[0014] Further, the usage ratio of the rice husk ash, the short carbon fibers, the sodium dodecyl sulfonate and the modification liquid is 600-800 g: 100 g: 5-10 g: 70-100 mL.

[0015] Further, the modification liquid is prepared by the following specific steps:

[0016] Polyethylene glycol methacrylate, maleic anhydride and toluene are added to a reaction kettle, ultrasonic dispersion is carried out for 18 min at 28 DEG C and 650 r / min, dibenzoyl peroxide is added to the kettle, and reaction is carried out for 2.25 h at 80-95 DEG C, after the reaction is completed, the reaction product is transferred to petroleum ether for precipitation, filtration is carried out, the precipitate is collected and dried to constant weight, the dried product is dissolved in 20 times mass of an ethanol aqueous solution, and the modification liquid is obtained.

[0017] Further, the mass fraction of the ethanol aqueous solution is 75%.

[0018] Further, the usage ratio of the polyethylene glycol methacrylate, the maleic anhydride, the toluene and the dibenzoyl peroxide is 140-160 g: 2.25-3.75 g: 170-200 mL: 0.35-0.5 g.

[0019] Further, the temperature at which the initiator dibenzoyl peroxide functions is 80-95 DEG C.

[0020] The application discloses a preparation process of green lightweight concrete.

[0021] The coal gangue regenerated light fine aggregate, cement and fly ash with a particle size of less than 75 microns are put into a concrete mixer, and stirred at 100-150 r / min for 2-3 min, then water and a water reducing agent are added, and the stirring is continuously carried out at 200-250 r / min for 3-4 min, then deionized water is slowly added into the mixer in 2-3 batches, the stirring is carried out at 200-250 r / min for 1-2 min, the mixture is poured into a mold, and is left to stand for 24 h, then the concrete is demolded and cured for 28 d, so as to obtain the green lightweight concrete.

[0022] Further, the amount ratio of the coal gangue regenerated light fine aggregate, cement, fly ash and water reducing agent is 4.5-5.5 kg: 1-1.75 kg: 175-525 g: 10-25 g.

[0023] The application has the following beneficial effects:

[0024] 1. In the application, the coal gangue regenerated light fine aggregate uses modified rice husk ash-carbon fiber composite powder as a pore-forming agent material, which can reduce the water absorption of the rice husk ash, and the adhered short carbon fibers can play a role in skeleton support, improve the structural strength of the rice husk ash, help the disc granulation to maintain a high porosity, improve the compressive strength of the coal gangue regenerated light fine aggregate, and make the coal gangue regenerated light fine aggregate maintain a high porosity, so as to meet the use requirements of the green lightweight concrete.

[0025] 2. In the preparation process of the modified rice husk ash-carbon fiber composite powder, a modified liquid is used for hydrophobic modification and adhesion.

[0026] The carboxyl groups in the modified liquid form hydrogen bonds with the silicon hydroxyl groups of the rice husk ash and the hydroxyl groups of the oxidized carbon fibers, the polyethylene glycol hydrophobic chains form a coating layer, the introduction of maleic anhydride increases the polar sites of the molecular chains of the modified liquid, the interaction between the modified liquid and the powder surface is more sufficient, the polyethylene glycol hydrophobic chains can be uniformly and closely spread on the surface of the rice husk ash, the hydrophilic sites of the rice husk ash are closed, and the adhesion or looseness of the raw material balls caused by uneven water absorption during granulation is avoided.

[0027] The introduced short carbon fibers form a spatial network structure in the composite powder, provide skeleton support for the raw material balls, reduce the deformation and breakage of the raw material balls in the process of granulation stirring and transportation, and further improve the wear resistance and breakage resistance of the raw material balls.

[0028] Therefore, the polyethylene glycol methacrylate in the modified liquid is modified by maleic anhydride grafting, which helps to increase the viscosity of the polymer, improve the binding force of the rice husk ash and the chopped carbon fiber, and reduce the water absorption of the rice husk ash. The water absorption of the powder material such as fly ash is balanced, the fiber reinforcement of the chopped carbon fiber is combined, which helps to improve the structural strength of the green ball of the disc granulation, and improve the yield of the finished product of the coal gangue regenerated light fine aggregate.

[0029] 3. In the raw material of the coal gangue regenerated light fine aggregate, the addition of nano-metakaolin and ultra-fine aluminum hydroxide plays a key role in the whole process.

[0030] During granulation, the particle size is filled with gaps, dispersion is strengthened, agglomeration of composite powder is avoided, and material uniformity is improved to ensure uniformity of green ball size; during calcination, nano-metakaolin reacts to form stable calcium-aluminum silicate substances, filling the gaps between the aggregates, and forming a dense inorganic film on the surface of the rice husk ash, physically isolating water from the contact of the rice husk ash silicon hydroxyl, and ultra-fine aluminum hydroxide decomposes into Al2O3 to form a protective layer to inhibit oxidation of carbon fiber, and optimize the density of the aggregate, and synergistically improve the structural integrity and mechanical strength of the aggregate; during the preparation of concrete, the pozzolanic activity of nano-metakaolin can react with the cement hydration products to generate additional C-S-H gel, strengthening the concrete interfacial transition zone, and the micro-aggregate effect of ultra-fine aluminum hydroxide can refine the pores, together improving the compressive strength of the concrete, while reducing the bleeding and segregation of the concrete mixture. DETAILED DESCRIPTION

[0031] The technical solutions in the embodiments of the present application will be clearly and completely described below in combination with the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0032] Embodiment 1: A coal gangue regenerated light fine aggregate and green light concrete and preparation process

[0033] S1: 150g of polyethylene glycol methacrylate, 3g of maleic anhydride and 187mL of toluene are added to a reaction kettle, ultrasonic dispersion is carried out at a temperature of 28℃ and a rotation speed of 650r / min for 18min, then 0.4g of initiator diphenylboric acid is added to the kettle, and the reaction is carried out at 80-95℃ for 2.25h. After the reaction is completed, the reaction product is transferred to petroleum ether for precipitation, filtration, collection of the precipitate and drying to constant weight. The dried product is dissolved in 20 times the mass of 75% ethanol aqueous solution to obtain a modified liquid.

[0034] The initiator benzoyl peroxide can stably decompose at 80-95℃ to generate free radicals. The free radicals initiate an addition reaction between the active hydrogen on the polyethylene glycol methacrylate chain and the double bond of maleic anhydride, introducing an anhydride active group (-CO-O-CO-) onto the polyethylene glycol methacrylate molecular chain. The anhydride group hydrolyzes to form a carboxyl group.

[0035] S2: Take 700g of rice husk ash and 100g of short-cut carbon fibers with a length of 1-3mm and treated with 30% nitric acid by mass, add them to a mixing tank, and dry mix for 5 minutes at a temperature of 28℃. Add 7.5g of sodium dodecyl sulfonate dispersant to the composite powder and premix for 3 minutes at a speed of 500r / min. Transfer the mixed composite powder to a high-efficiency mixer. During the mixing process, spray 85mL of the modification liquid evenly onto the flowing powder in the form of atomization. Nitrogen gas is introduced during the spraying process to protect the carbon fibers from oxidation. After the spraying is completed, continue stirring for 25-30 minutes at a temperature of 40-45℃ and a speed of 800-1000r / min to obtain the modified rice husk ash-carbon fiber composite powder.

[0036] The carboxyl groups (-COOH) in the modified liquid can be directionally adsorbed with the silanol groups (-Si-OH) on the surface of rice husk ash and the hydroxyl groups (-OH) introduced on the surface of carbon fiber after oxidation through hydrogen bonding, thereby anchoring the modified liquid on the surface of the composite powder. At the same time, the hydrophobic segments of polyethylene glycol in the modified liquid spread on the powder surface to form a continuous coating layer, sealing the hydrophilic sites on the surface of rice husk ash. High-speed stirring ensures that each powder particle is uniformly coated through mechanical shearing force, avoiding subsequent granulation defects caused by insufficient local coating. Furthermore, the introduction of carbon fiber constructs a porous and high-strength structure.

[0037] S3: Add 6.4 kg of coal gangue powder and 1.1 kg of fly ash (passed through a 75 μm sieve) to a mixing vessel and dry-mix at 28℃ and 400 r / min for 5 min. Then add 0.7 kg of modified rice husk ash-carbon fiber composite powder, 113 g of nano-kaolin, and 60 g of ultrafine aluminum hydroxide. Dry-mix at 550 r / min for 18 min. Pass the mixture through a 100-mesh standard sieve and then uniformly feed it into a 500 mm diameter disc granulator. Set the rotation speed to 55 r / min and the inclination angle to 45°. 45 mL of the granulator is then added. Water is sprayed in via atomization. When the raw material pellets reach a particle size of ≤4.75mm, water spraying is stopped and the raw material pellets are removed. The dried raw material pellets are then transferred to a muffle furnace and subjected to a segmented heating and roasting process. The temperature is increased from room temperature to 400℃ at a rate of 5℃ / min, held for 75min, and then increased to 1180℃ at the same rate while introducing a small amount of nitrogen gas. The temperature is held for 40min, and the material is allowed to cool naturally to room temperature. The cooled aggregate is then removed and sieved through a standard sieve to collect particles with a particle size range of 0.15-5mm, ultimately yielding recycled coal gangue lightweight aggregate.

[0038] S4: Add 5kg of recycled coal gangue lightweight aggregate, 1.4kg of cement, and 350g of fly ash passing through a 75μm standard sieve to a concrete mixer. Dry mix for 3 minutes at 125r / min. Then add 450g of water and 17.5g of water-reducing agent. Wet mix for 3.5 minutes at 230r / min. Slowly add 225g of deionized water in 2-3 batches to the mixer. Maintain a mixing speed of 230r / min for 1.5 minutes until the mixture is a uniform slurry. Pour into a mold, let stand for 24 hours, demold, and cure the concrete for 28 days in a standard curing room with a temperature of 18-22℃ and a relative humidity of ≥90% to obtain a green lightweight concrete.

[0039] Examples 2-4: A coal gangue recycled lightweight fine aggregate and green lightweight concrete and its preparation process. The difference from Example 1 is that the amount of material added in step S1 is different, while the other steps and parameters remain the same. The specific amount of material added is shown in Table 1 below.

[0040] Table 1. Comparison of Material Usage in Step S1

[0041]

[0042] Examples 5-6: A recycled lightweight fine aggregate from coal gangue and green lightweight concrete and its preparation process. The difference from Example 1 is that the amount of material added in step S2 is different, while the other steps and parameters remain the same. The specific amount of material added is shown in Table 2 below.

[0043] Table 2. Comparison of material usage in step S2

[0044]

[0045] Examples 7-8: A recycled lightweight fine aggregate from coal gangue and green lightweight concrete and its preparation process. The difference from Example 1 is that the granulation parameters in step S3 are different, while the remaining steps and parameters remain the same. The specific parameter values ​​are shown in Table 3 below.

[0046] Table 3. Comparison of granulation parameters in step S3

[0047]

[0048] In this invention, polyethylene glycol methacrylate, with a weight-average relative molecular mass of approximately 300, was purchased from Guangdong Shengke Biochemical Technology Co., Ltd.; maleic anhydride, benzoyl peroxide, and sodium dodecyl sulfonate were purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; rice husk ash was purchased from Shanghai Hongjun Horticultural Supplies Co., Ltd.; coal gangue powder was purchased from Lingshou County Quanda Mineral Products Processing Plant; fly ash was purchased from Wuhan Jiye Chemical Co., Ltd.; nano-metakaolin was purchased from Lingshou County Ruikai Products Co., Ltd.; and ultrafine aluminum hydroxide was purchased from Jinan Yeqing Biotechnology Co., Ltd.

[0049] Comparative Example 1: Based on Example 1, step S1 was removed and the modifying liquid was not sprayed in step S2, while the remaining material dosages and process parameters remained unchanged, resulting in a coal gangue recycled lightweight fine aggregate and green lightweight concrete.

[0050] Comparative Example 2: Based on Example 1, no short-cut carbon fibers were added in step S2 to obtain powder containing only modified rice husk ash. The amount of other materials and process parameters remained unchanged, and finally a coal gangue recycled lightweight fine aggregate and green lightweight concrete were obtained.

[0051] Comparative Example 3: Based on Example 1, nano-kaolin and ultrafine aluminum hydroxide were not added in step S3, while the dosage of other materials and process parameters remained unchanged, resulting in a coal gangue recycled lightweight aggregate and green lightweight concrete.

[0052] Performance tests were conducted on the recycled lightweight aggregates and green lightweight concrete prepared in Examples 1-8 and Comparative Examples 1-2. The 24-hour water absorption rate of the modified rice husk ash-carbon fiber composite powder was determined according to GB / T17431.1-2010. The modified rice husk ash-carbon fiber composite powder prepared in step S2 was dried, weighed, and then soaked in distilled water for 24 hours before being weighed again, characterizing the improvement effect of rice husk ash on hydrophilicity. The apparent density and compressive strength of the recycled lightweight aggregates were tested according to GB / T17431.1-2010, directly characterizing the lightweight and high-strength properties of the recycled lightweight aggregates. The apparent density and 28-day compressive strength of the green lightweight concrete were determined according to GB / T50081-2019, characterizing the lightweight and high-strength properties of the concrete, respectively.

[0053] Table 4 Performance Test Table

[0054]

[0055] As shown in Table 4, Examples 1-8 involve sequentially modifying rice husk ash with hydrophobic coating and constructing a short-cut carbon fiber skeleton. Furthermore, nano-kaolin and ultrafine aluminum hydroxide are introduced during aggregate preparation for reinforcement. This achieves improvements in the hydrophilicity of the modified rice husk ash-carbon fiber composite powder, synergistic effects of lightweight and high strength in recycled coal gangue aggregates, and comprehensive performance enhancements in green lightweight concrete that combine lightweight, high strength, and low shrinkage. With the key components of the modifying liquid adjusted within a reasonable range in step S1, the carboxyl content and hydrophobic chain density in the modifying liquid are matched to the number of silanol groups on the surface of the rice husk ash. The 24-hour water absorption rate of the composite powder remains low, ensuring uniform water absorption during granulation. In step S2, as the amount of rice husk ash increases, the amount of modifying liquid increases simultaneously. Combined with the stable spatial network of the short-cut carbon fibers, the apparent density of the aggregate does not increase significantly, and the compressive strength is optimized. In step S3, the reasonable control of granulation parameters ensures uniform particle size of the raw material pellets and regular pore structure of the aggregate after calcination, further improving the compactness of the concrete interface transition zone.

[0056] In Comparative Example 1, since no modifying liquid was prepared or sprayed, only unmodified rice husk ash-carbon fiber composite powder was used. The silanol groups on the surface of the rice husk ash were completely exposed, causing the water absorption rate of the composite powder to rise sharply to over 15% in 24 hours. Uneven water absorption during granulation caused the aggregate balls to stick together or become loose. After calcination, the aggregate cracked and had irregular pores, resulting in an increase in apparent density and a decrease in compressive strength. In the subsequent concrete preparation, the water absorption of the aggregate caused an imbalance in the water-cement ratio, an increase in apparent density and insufficient compressive strength, which could not meet the requirements of ultra-low energy consumption buildings for lightweight and high-strength concrete.

[0057] Comparative Example 2, due to the absence of chopped carbon fibers in step S2 and the preparation of only modified rice husk ash powder, lacked the spatial network skeleton support of chopped carbon fibers. As a result, the raw material pellets exhibited weak deformation resistance after granulation, and the aggregates could not form a porous-high-strength structure after calcination, leading to a decrease in compressive strength. In concrete preparation, the aggregates had insufficient mechanical bearing capacity, and the 28-day compressive strength decreased. Furthermore, due to the lack of carbon fiber-assisted dispersion, the internal pore distribution of the concrete was uneven, with performance falling between that of Example 1 and Comparative Example 1. This verifies the necessity of chopped carbon fibers for supporting the aggregate skeleton and improving concrete strength.

[0058] In Comparative Example 3, since nano-kaolin and ultrafine aluminum hydroxide were not added in step S3, the gaps between the coal gangue powder and fly ash particles could not be effectively filled, exacerbating the agglomeration problem of the composite powder, resulting in insufficient density of the raw material pellets, increased aggregate porosity after calcination, and decreased compressive strength. In concrete preparation, the lack of additional CSH gel generated by the activity of nano-kaolin volcanic ash and the micro-aggregate effect of ultrafine aluminum hydroxide resulted in a weak interfacial transition zone, decreased 28-day compressive strength, and insufficient pore refinement. This further verified the key role of nanomaterial filling reinforcement in improving aggregate density and concrete structural stability.

[0059] It should be noted that, in this document, terms such as “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0060] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention.

Claims

1. A type of recycled lightweight aggregate from coal gangue, prepared by disc granulation and sintering of powder materials, characterized in that, The powder material comprises the following components by mass: 425-850 parts of coal gangue powder, 75-150 parts of fly ash, 40-100 parts of modified rice husk ash-carbon fiber composite powder, 10-12.5 parts of nano-kaolin, and 5-7 parts of ultrafine aluminum hydroxide. The modified rice husk ash-carbon fiber composite powder is prepared by spraying a modification liquid onto rice husk ash and chopped carbon fiber during the mixing and stirring process.

2. The recycled lightweight aggregate from coal gangue according to claim 1, characterized in that, The modified rice husk ash-carbon fiber composite powder is prepared through the following specific steps: Rice husk ash and chopped carbon fibers treated with nitric acid oxidation were added to a mixing tank and stirred at 25-30℃ for 5 minutes. Sodium dodecyl sulfonate was then added and stirred at 40-60 r / min for 2-3 minutes. The composite powder was then transferred to a high-efficiency mixer. During the stirring process, a modifying liquid was sprayed onto the flowing powder. After the spraying was completed, the mixture was stirred at 40-45℃ and 40-60 r / min for another 3-5 minutes to obtain the modified rice husk ash-carbon fiber composite powder.

3. The recycled lightweight aggregate from coal gangue according to claim 2, characterized in that, The length of the chopped carbon fiber is 1-3 mm.

4. The recycled lightweight aggregate from coal gangue according to claim 2, characterized in that, The ratio of rice husk ash, chopped carbon fiber, sodium dodecyl sulfonate, and modifying liquid is 600-800g:100g:5-10g:70-100mL.

5. A recycled lightweight aggregate from coal gangue according to claim 2, characterized in that, The modified liquid is prepared through the following specific steps: Polyethylene glycol methacrylate, maleic anhydride, and toluene were added to a reaction vessel and ultrasonically dispersed at 28°C and 650 r / min for 18 min. Then, benzoyl peroxide was added to the vessel and the reaction was carried out at 80-95°C for 2.25 h. After the reaction was completed, the reaction product was transferred to petroleum ether to precipitate. The product was filtered, collected, and dried to constant weight. The dried product was dissolved in 20 times its mass of ethanol aqueous solution to obtain the modified solution.

6. The recycled lightweight aggregate from coal gangue according to claim 5, characterized in that, The ratio of polyethylene glycol methacrylate, maleic anhydride, toluene, and benzoyl peroxide is 140-160g: 2.25-3.75g: 170-200mL: 0.35-0.5g.

7. A recycled lightweight aggregate from coal gangue according to claim 5, characterized in that, The ethanol-water solution has a mass fraction of 75%.

8. A process for preparing green lightweight concrete, characterized in that, Preparation includes the following steps: Coal gangue recycled lightweight fine aggregate, cement, and fly ash passing through a 75μm standard sieve are put into a concrete mixer and mixed at 100-150 r / min for 2-3 minutes. Then water and water-reducing agent are added, and the mixture is continuously mixed at 200-250 r / min for 3-4 minutes. Deionized water is then slowly added to the mixer in 2-3 batches, and the mixture is stirred at 200-250 r / min for 1-2 minutes. The mixture is poured into a mold, left to stand for 24 hours, demolded, and cured for 28 days to obtain a green lightweight concrete. The recycled lightweight aggregate of coal gangue is the recycled lightweight aggregate of coal gangue as described in any one of claims 1-7.

9. The preparation process of green lightweight concrete according to claim 8, characterized in that, The ratio of the amount of recycled coal gangue lightweight aggregate, cement, fly ash and water-reducing agent is 4.5-5.5 kg: 1-1.75 kg: 175-525 g: 10-25 g.

10. A green lightweight concrete, characterized in that, It is prepared by the preparation process described in any one of claims 8-9.

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