Preparation method of prefabricated autoclaved aerated concrete slab made of solid-waste-based sulfur-aluminum-iron cementing material

Abstract

The invention discloses a preparation method of a prefabricated autoclaved aerated concrete slab made of a solid-waste-based sulfur-aluminum-iron binding material. The preparation method comprises the following steps: preparing dry substances of the material; carrying out solid waste pretreatment by a mechanical ball milling method; adding ardealite, aluminum ash, coal gangue, fly ash, steel slag and carbide slag at the moment; calcining and directionally mineralizing after pretreatment; secondarily grinding the intermediate material; adding the secondarily ground intermediate material, cement, aluminum powder and water, and foaming; after the slurry is thickened, multi-frequency vibration is carried out in the pouring process; after pouring is completed, multi-temperature curing is conducted; after curing is completed, the highly-doped solid waste-based functional prefabricated autoclaved aerated concrete slab product is obtained. According to the autoclaved aerated concrete slab, dependence on natural resources is effectively reduced, meanwhile, carbon dioxide emission in the production process is reduced, and meanwhile, the compressive strength and the breaking strength of the autoclaved aerated concrete slab are improved; the service life of the material is prolonged; the preparation process is simplified, and the production difficulty and cost are reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of building materials, and in particular to a method for preparing a sulphur-aluminium-iron based cementitious material from solid waste and its application, specifically a method for preparing a sulphur-aluminium-iron cementitious material from industrial solid waste and using the material to produce prefabricated autoclaved aerated concrete panels. Background Art

[0002] Autoclaved aerated concrete (AAC) panels, as a new building material, offer advantages such as light weight, excellent thermal insulation, and strong workability, making them widely used in construction projects. However, traditional AAC panels still have some shortcomings in practical applications, limiting their application and development. Existing AAC panels are primarily made from raw materials such as cement, lime, sand, gypsum, and aluminum powder, and are manufactured through a series of process steps including mixing, pouring, pre-curing, cutting, and steam curing.

[0003] However, existing technical solutions have several disadvantages and shortcomings: Resource consumption and environmental pollution: The main raw materials used in the production of existing autoclaved aerated concrete panels are cement, lime, and sand. The production and transportation of these raw materials not only consumes a large amount of natural resources but also generates significant amounts of carbon dioxide emissions, causing serious environmental pollution. Furthermore, lime production produces a large amount of dust, further exacerbating environmental pollution. High energy consumption: The production of autoclaved aerated concrete panels requires a steam curing process, which consumes a large amount of energy to heat and maintain the high-pressure environment. This high energy consumption not only increases production costs but also places a significant strain on energy resources, failing to meet current energy conservation and emission reduction requirements. Inadequate mechanical properties: Due to their porous structure, traditional autoclaved aerated concrete panels, while offering good thermal insulation properties, suffer from poor mechanical properties, particularly in terms of compressive and flexural strength. This limits their application in load-bearing structures and reduces their market competitiveness. Poor durability: Existing autoclaved aerated concrete panels are susceptible to environmental factors such as humidity and temperature fluctuations over long-term use, leading to degradation of material properties and insufficient durability. Especially in humid environments, autoclaved aerated concrete panels easily absorb water, causing the panels to lose strength and expand in volume, shortening their service life. The production process is complex: Traditional autoclaved aerated concrete panels require multiple steps, including mixing, pouring, pre-curing, cutting, and steam curing. Each step requires strict control of process parameters, and even the slightest mistake can lead to product quality issues. Furthermore, the production process requires a large amount of water, which not only increases production costs but also wastes water resources. Summary of the Invention

[0004] In response to the problems of resource consumption and environmental pollution, insufficient mechanical properties, poor durability and complex preparation process in the existing technology, the present invention provides a method for preparing a prefabricated autoclaved aerated concrete board made of solid waste-based sulfur-aluminum-iron cementitious materials.

[0005] The production of traditional autoclaved aerated concrete panels primarily relies on natural resources such as cement, lime, and sand, resulting in significant resource consumption and the generation of large amounts of carbon dioxide during the production process, causing environmental pollution. To address this issue, the present invention utilizes industrial solid waste, such as slag and fly ash, as primary raw materials, effectively reducing reliance on natural resources and lowering carbon dioxide emissions during the production process, thereby contributing to comprehensive resource utilization and environmental protection.

[0006] Traditional autoclaved aerated concrete panels, due to their porous structure, have good thermal insulation properties but poor mechanical properties, particularly low compressive and flexural strength, which limits their application in load-bearing structures. To address this issue, the present invention introduces a sulfide-aluminum-iron cementitious material with high strength and adhesion, thereby improving the compressive and flexural strengths of autoclaved aerated concrete panels and enhancing their mechanical properties, making their application in construction projects more extensive and reliable.

[0007] Existing autoclaved aerated concrete panels are susceptible to environmental factors during long-term use, leading to degradation of material properties and insufficient durability. In particular, in humid environments, they easily absorb water, resulting in decreased strength and volume expansion, which reduces their service life. The sulphur-aluminium-iron cementitious material employed in the present invention has excellent corrosion and moisture resistance, making the resulting autoclaved aerated concrete panels less susceptible to environmental factors during long-term use, significantly improving their durability and extending their service life.

[0008] The traditional production process of autoclaved aerated concrete panels requires multiple complex steps, each requiring strict control of process parameters, increasing production complexity and costs. This invention simplifies the production process by optimizing the formulation and process flow, reducing both complexity and costs. Furthermore, by reducing water use, the production process is more environmentally friendly and economical.

[0009] To achieve the above objectives, the present invention adopts the following technical solutions.

[0010] A method for preparing a prefabricated autoclaved aerated concrete board made of solid waste-based sulfur-aluminum-iron cementitious materials comprises the following steps: (1) Material dry matter content: phosphogypsum 6-10%, aluminum ash 12-23%, coal gangue 0-5%, fly ash 20-30%, steel slag 15-20%, calcium carbide slag 3-8%, cement 4-13%, lime 6-17%, aluminum powder 0.1-0.2%, water-to-material ratio 0.6; (2) Mechanical ball milling is used for solid waste pretreatment; at this time, phosphogypsum, aluminum ash, coal gangue, fly ash, steel slag, and calcium carbide slag are added.

[0011] Solid waste contains impurities and pollutants, and there are significant differences in morphology and activity between different solid wastes. Mechanical ball milling solid waste pretreatment technology is used to control pressure and temperature, and the solid waste is subjected to high levels of impact and friction in a short period of time, resulting in simple physical changes in the material (particle size becomes smaller) and triggering a series of chemical processes (crystal structure destruction and transformation), thereby producing highly active materials.

[0012] During grinding, steel balls of different sizes and other rigid materials (similar in size to the solid waste) are installed in the cylinder. During the grinding process, the solid waste material should occupy 30%±5% of the effective volume of the ball mill cylinder.

[0013] When the motor drives the ball mill cylinder to rotate through gears, the grinding material and solid waste are subjected to corresponding arc motion under the action of friction and centrifugal force. The solid waste is impacted and rubbed by the grinding material, thereby achieving large particle crushing and fine grinding. As the fineness increases, certain siliceous minerals in the solid waste except quartz will further participate in the hydrothermal synthesis reaction, thereby increasing the reaction rate.

[0014] (3) Calcination after pretreatment and directional mineralization; as a result of calcination, an intermediate material with anhydrous calcium sulfoaluminate, Fe-A1 substituted calcium sulfoaluminate, dicalcium silicate, iron phase and anhydrous calcium sulfate as the main mineral components is obtained.

[0015] (4) Secondary grinding of intermediate materials; the number of particles with a size below 85 μm in secondary grinding is controlled to be 5%; After secondary grinding, air bubble adjustment is performed during the concrete slab preparation process, and the uniformity of air bubble distribution is improved by controlling the slurry consistency and multi-frequency vibration.

[0016] (5) Add the secondary ground intermediate material, cement, aluminum powder and water for foaming; slurry foaming process: by adding cement and lime to react with water to produce calcium hydroxide, the slurry pH ≥ 12, the temperature ≥ 30 ° C, and aluminum powder as the foaming agent of the concrete slab. At this stage, aluminum powder is added to the slurry, and the oxide film on its surface is quickly removed. It reacts with water to displace the hydrogen in the water, releasing gas to form bubbles.

[0017] (6) After the slurry thickens, multi-frequency vibration is performed during the pouring process; Slurry thickening process: Phosphogypsum and aluminum ash can be used as sources of the sulfur-aluminum-iron system, while fly ash and waste slag can be used as sources of silicon raw materials. The optimal mixing ratio is selected based on the gas generation rate of aluminum powder. During the slurry preparation process, when fly ash, steel slag, and calcium carbide slag are mixed at a ratio of 4:3:1, accounting for 40% by weight, and the concentration of the multi-solid waste slurry is controlled at 55% ± 2%, the best thickening effect and slurry expansion effect are achieved. The slurry thickening rate is consistent with the foaming rate.

[0018] During the pouring process, the solid waste mixed slurry undergoes multi-frequency vibration to ensure uniform distribution of bubbles within the concrete slab. At the start of pouring, the added aluminum powder rapidly releases gas, generating a large number of bubbles and promoting rapid expansion of the slurry. Lateral vibration then occurs, causing the bubbles to diffuse laterally. When the slurry expands to the edge of the mold, the lateral movement ceases, gas generation slows and gradually stabilizes, and longitudinal vibration is applied, causing the bubbles to rise slowly and evenly upward. When a sufficient number of bubbles appear on the slurry surface, vibration ceases, and the bubbles are evenly distributed throughout the slurry. This method of operation ensures thorough mixing and reaction of the slurry, further improving the distribution and quality of the pores within the blank and ensuring internal structural stability.

[0019] (7) After pouring, multi-temperature curing is performed; a high-pressure reactor is used for high-temperature and high-pressure curing. High-temperature steam transfers heat from the surface to the curing plate through heat conduction. The curing process is divided into five stages: pre-curing, heating, constant temperature, cooling, and heat preservation. The temperature changes evenly throughout the process, and the curing of the highly doped solid waste-based functional prefabricated autoclaved aerated concrete board is promoted under the condition of gradually increasing temperature gradient, thereby avoiding defects such as cracking, strength reduction, and yield reduction caused by excessive temperature differences between the inside and outside of the specimen.

[0020] (8) After the curing is completed, a highly doped solid waste-based functional prefabricated autoclaved aerated concrete board product is obtained.

[0021] Furthermore, the specific process of mechanical ball milling in step (2) is as follows: during the grinding process, the solid waste material should account for 30%±5% of the effective volume of the ball mill cylinder, the ball milling speed is 15 r / min~40 r / min, and the ball milling time is 1 h±20 min.

[0022] Furthermore, the raw materials in step (3) were dried at 110 °C until a constant weight was reached, the raw materials were mixed in a pre-designed ratio, homogenized by grinding, and then calcined in a resistance holding furnace. The samples were calcined at heating rates of 6.5, 5, and 2.5 °C / min for 120, 60, and 40 min, respectively, and maintained at a temperature of 1200 °C for 30 min, and then quickly air-cooled to room temperature.

[0023] Furthermore, the secondary grinding time in step (4) is 30 min and the rotation speed is 48 r / min.

[0024] Furthermore, the slurry concentration is controlled at 55%±2%; the specific operation of the multi-frequency vibration is as follows: in the first stage, starting from mold injection, the aluminum powder quickly releases gas and promotes the rapid expansion of the slurry, generating a large number of bubbles. With the lateral vibration, the bubbles diffuse laterally to both sides. When the slurry expands to the edge of the mold, the lateral movement stops; in the second stage, the gas generation of the aluminum powder slows down and gradually stabilizes, accompanied by longitudinal vibration, and the bubbles rise slowly and evenly; in the third stage, when a certain number of bubbles appear on the surface of the slurry, the vibration stops and the bubbles are evenly arranged in the slurry.

[0025] Furthermore, multi-temperature curing is divided into five stages: pre-curing, heating, constant temperature, cooling, and heat preservation.

[0026] Furthermore, in the pre-curing stage, the sample was placed in a pre-curing chamber for pre-curing at 60°C for 45 min; in the heating stage, the sample was sent to a high-pressure reactor for steam curing at a temperature of 0.5°C / min. -1 The temperature rises slowly at a certain speed; constant temperature stage: the temperature in the high-pressure reactor reaches and stabilizes at 195℃±3℃, the pressure is controlled at 1.20MPa±0.05MPa, and the constant temperature is maintained for 1 hour; cooling stage: after the constant temperature process is completed, the temperature is reduced at a rate of 1℃ / min, maintaining a specific gradient to prevent cracking and other problems caused by rapid temperature drop; insulation stage: when the temperature drops to 45℃, insulation is carried out for 50 minutes to promote the initial hydration of the concrete slab. The hydrated calcium silicate produced provides the basis for the strength of the concrete slab.

[0027] Beneficial effects 1. The present invention mainly uses industrial solid waste such as aluminum ash, fly ash, steel slag, coal gangue, etc. as raw materials, which not only reduces dependence on natural resources and saves resources, but also effectively utilizes industrial waste and reduces waste accumulation and environmental pollution.

[0028] 2. The present invention utilizes a sulfoaluminum-iron cementitious material, which exhibits high strength and adhesion, thereby enhancing the compressive and flexural strengths of the autoclaved aerated concrete slab. Furthermore, the material exhibits excellent corrosion and moisture resistance, making the resulting concrete slab less susceptible to environmental influences during long-term use and significantly improving its durability.

[0029] 3. The present invention simplifies the preparation process by optimizing the formula and process flow, reduces production difficulty and cost, and improves the environmental friendliness and economic efficiency of the production process by reducing the use of water resources.

[0030] 4. This invention uses mechanical ball milling to pre-treat solid waste. By controlling pressure and temperature, the solid waste is subjected to high levels of impact and friction in a short period of time, thereby reducing the particle size and increasing its activity. Furthermore, by precisely controlling process parameters such as slurry consistency and multi-frequency vibration, the uniformity of bubble distribution within the concrete slab and the stability of its pore structure are ensured.

[0031] 5. The present invention adopts a multi-temperature curing process, including five stages: pre-curing, heating, constant temperature, cooling and insulation. By precisely controlling the temperature and time of each stage, the problems of cracking and strength reduction caused by temperature differences are avoided, and the stability and durability of the material are improved.

[0032] 6. By optimizing the process and material ratio, the highly doped solid waste-based functional prefabricated autoclaved aerated concrete board prepared by the present invention exhibits excellent multifunctional properties such as sound insulation, fire resistance, heat insulation, and lightweight, meeting national standard requirements and providing more options for construction projects. DETAILED DESCRIPTION

[0033] The present invention will be further described below with reference to the examples, but the present invention is not limited by the following examples.

[0034] Example 1 1. Solid waste raw materials are bulk solid waste from large industrial parks. Among them, aluminum ash, fly ash, steel slag, and coal gangue are the main silicon-aluminum-iron-based raw materials, industrial by-product gypsum is used as a calcium sulfate-based raw material, and carbide slag is used as a calcium-based correction raw material. These materials are intermediate raw materials for sulfur-aluminum-iron-based cementitious materials.

[0035] 2. Material dry matter content: phosphogypsum 6-10%, aluminum ash 12-23%, coal gangue 0-5%, fly ash 20-30%, steel slag 15-20%, carbide slag 3-8%, cement 4-13%, lime 6-17%, aluminum powder 0.1-0.2%, water-to-material ratio 0.6.

[0036] 3. Experiments were conducted with the proportion of solid waste materials set at 70%, 80%, and 90%.

[0037] Table 1 Proportion of solid waste materials Note: Unit (%) 4. There are impurities and pollutants in the solid waste, and there are significant differences in morphology and activity between different solid wastes. The current mechanical ball milling solid waste pretreatment technology is adopted, with aluminum ash at 18 r / min, maintained for 20 min, fly ash, steel slag, and stone slag at 36 r / min, maintained for 90 min, and coal gangue at 32 r / min, maintained for 60 min.

[0038] 5. During grinding, install grinding steel balls of different sizes and other rigid materials (similar in size to the solid waste) in the cylinder. During the grinding process, the solid waste material should account for 30%±5% of the effective volume of the ball mill cylinder.

[0039] 6. The material after primary grinding is calcined at 1150~1250℃ and directionally mineralized to obtain an intermediate material with anhydrous calcium sulfoaluminate, Fe-A1 soluble calcium sulfoaluminate, dicalcium silicate, iron phase and anhydrous calcium sulfate as the main mineral components.

[0040] 7. Grind the intermediate material for the second time at 48 r / min for 30 min, and control the number of particles below 85 μm to be 5%.

[0041] 8. After pretreatment, bubble adjustment is performed during the preparation of the concrete slab, and the uniformity of bubble distribution is improved by controlling the slurry consistency and multi-frequency vibration.

[0042] 9. Slurry foaming process: Calcium hydroxide is produced by adding cement and lime to react with water. The slurry pH is ≥12 and the temperature is ≥30°C. Aluminum powder is used as a foaming agent for the concrete slab. At this stage, aluminum powder is added to the slurry. The oxide film on its surface is quickly removed and it reacts with water to displace the hydrogen in the water, releasing gas to form bubbles.

[0043] 10. Slurry thickening process: During the slurry preparation process, when fly ash, steel slag, and calcium carbide slag are mixed in a ratio of 4:3:1, accounting for 40% by weight, and the concentration of the multi-solid waste slurry is controlled at 55% ± 2%, the best thickening effect and slurry expansion effect are achieved. The slurry thickening speed is consistent with the foaming speed.

[0044] 11. The solid waste mixed slurry undergoes multi-frequency vibration during the pouring process to ensure uniform distribution of bubbles in the concrete slab. At the beginning of pouring, the added aluminum powder rapidly releases gas, generating a large number of bubbles, which promotes rapid expansion of the slurry. Lateral vibration is then applied, causing the bubbles to diffuse laterally. When the slurry expands to the edge of the mold, the lateral movement ceases, gas generation slows and gradually stabilizes, and longitudinal vibration is applied, causing the bubbles to rise slowly and evenly upward. When a sufficient number of bubbles appear on the slurry surface, vibration ceases, and the bubbles are evenly distributed throughout the slurry.

[0045] 12. After pouring, place the sample in a curing chamber for multi-temperature curing. The curing process is divided into five stages: pre-curing, heating, constant temperature, cooling, and heat preservation.

[0046] 13. Pre-curing stage: Place the sample in the pre-curing chamber for pre-curing and keep it at a temperature of about 60°C for about 45 minutes.

[0047] 14. Heating stage: send it into the high-pressure reactor for steam curing, and the temperature rises slowly at a rate of 0.5℃ / min.

[0048] 15. Constant temperature stage: The temperature in the autoclave reaches and stabilizes at 195℃±3℃, the pressure is controlled at 1.20MPa±0.05MPa, and the constant temperature is maintained for 1 hour.

[0049] 16. Cooling stage: After the constant temperature process is completed, the temperature is reduced at a rate of 1°C / min to maintain a specific gradient to prevent cracking and other problems caused by rapid temperature drop.

[0050] 17. Insulation stage: When the temperature drops to 45℃, keep it warm for 50 minutes to promote the initial hydration of the concrete slab. The hydrated calcium silicate produced provides the basis for the strength of the concrete slab. 18. Turn off the instrument and remove the concrete slab sample about 40 minutes later.

[0051] 19. Through raw material pretreatment, bubble coordinated control, and multi-temperature stage curing steps, a highly doped solid waste-based functional prefabricated autoclaved aerated concrete board product is obtained.

[0052] Comparative Example 1 The difference from Example 1 is that the solid waste is not pretreated and is directly ground. The other steps are the same to obtain a concrete slab.

[0053] Comparative Example 2 The difference from Example 1 is that multi-frequency vibration is not used. Other steps are the same to obtain a concrete slab.

[0054] Comparative Example 3 The difference from Example 1 is that the concrete slab is directly cured without multi-stage curing. The temperature is maintained at 195° C. and a pressure of 1.20 MPa for 1 hour, and then cooled to room temperature. The other steps are the same to obtain a concrete slab.

[0055] The basic properties of the samples were measured, and the mass loss, dry density, compressive strength, drying shrinkage, frost resistance and thermal conductivity were compared and analyzed with GB / T15762-2020, and the fire resistance integrity was compared and analyzed with GB / T 9978.1-2008.

[0056] When the solid waste content is 80%, it shows excellent performance indicators and meets the standard requirements. The highly mixed multi-source solid waste-based highly doped functional prefabricated autoclaved aerated concrete board has excellent multifunctionality.

[0057] Table 2 Performance Analysis Note: Unit (dry density - kg / m 3 , compressive strength-MPa, drying shrinkage-mm / m, thermal conductivity-w / m·k, fire resistance integrity-min) Analysis shows that the high-dosage functional prefabricated autoclaved aerated concrete panels based on multi-source solid waste exhibit good functional performance in terms of sound insulation, fire resistance, heat insulation, and lightweight.

[0058] The widespread use of industrial solid waste in autoclaved aerated concrete panels can conserve non-renewable resources and reduce energy consumption. It also allows for more efficient waste disposal, mitigating environmental risks to the land. Therefore, the development of prefabricated autoclaved aerated concrete panels using solid waste-based sulfur-aluminum-iron cementitious materials has great potential for reducing environmental impact and offers significant economic benefits.

[0059] 1. Raw Material Selection and Proportioning: This invention utilizes bulk industrial solid waste as its primary raw materials, such as aluminum ash, fly ash, steel slag, and coal gangue, combined with industrial by-products such as gypsum and carbide slag. Through rational proportioning and usage, a sulfur-aluminum-iron based cementitious material is produced. This material not only effectively utilizes industrial solid waste, reducing reliance on natural resources, but also enhances its performance through precise optimization of the proportions.

[0060] 2. Solid Waste Pretreatment Technology: This invention uses mechanical ball milling to pretreat solid waste. By controlling pressure and temperature, the solid waste is subjected to high levels of impact and friction within a short period of time, thereby reducing the particle size and increasing its activity. This pretreatment technology not only effectively removes impurities and pollutants from the solid waste but also enhances the chemical reactivity of the material.

[0061] 3. Bubble Control and Slurry Preparation: During the preparation process, the uniformity of bubble distribution is improved by controlling the slurry's consistency and using multi-frequency vibration. Aluminum silver powder is used as a foaming agent to control the slurry's foaming and thickening processes. Precisely controlling the foaming and thickening rates ensures uniform expansion of the slurry and stable bubble distribution, thereby improving the pore structure and internal quality of the concrete slab.

[0062] 4. Multi-temperature curing process: The present invention adopts a multi-temperature curing process, including five stages: pre-curing, heating, constant temperature, cooling and insulation. By precisely controlling the temperature and time of each stage, it avoids cracking and strength reduction caused by temperature differences, and improves the stability and durability of the material.

[0063] 5. Multifunctionality and Performance Optimization: Through raw material pretreatment, bubble control, and multi-temperature curing, highly doped solid waste-based functional prefabricated autoclaved aerated concrete panels are produced. These panels exhibit excellent fire resistance, thermal insulation, and lightweight properties, meeting national standards. This versatility opens up the potential for a wide range of material applications.

[0064] The foregoing is merely an embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application should all be included within the scope of the claims of the present application.

Claims

1. A method for preparing a prefabricated autoclaved aerated concrete board made of solid waste-based sulfur-aluminum-iron cementitious materials, characterized in that: The following steps are involved: (1) Material dry matter content: 6-10% phosphogypsum, 12-23% aluminum ash, 0-5% coal gangue, 20-30% fly ash, 15-20% steel slag, 3-8% calcium carbide slag, 4-13% cement, 6-17% lime, 0.1-0.2% aluminum powder, water-to-material ratio 0.6; (2) Pre-treatment of solid waste by mechanical ball milling; at this time, phosphogypsum, aluminum ash, coal gangue, fly ash, steel slag, and calcium carbide slag are added; (3) Calcination after pretreatment and directional mineralization; (4) Secondary grinding of intermediate materials; the number of particles with a secondary grinding size below 85 μm is controlled to be 5%; (5) Adding the secondary ground intermediate material, cement, aluminum powder and water to foam; (6) After the slurry thickens, multi-frequency vibration is performed during the pouring process; (7) Multi-temperature curing after pouring; (8) After solidification is completed, a highly doped solid waste-based functional prefabricated autoclaved aerated concrete board product is obtained.

2. The method for preparing a prefabricated autoclaved aerated concrete board made of solid waste-based sulfur-aluminum-iron cementitious materials according to claim 1, characterized in that: The specific process of mechanical ball milling in step (2) is as follows: during the grinding process, the solid waste material should account for 30%±5% of the effective volume of the ball mill cylinder, the ball milling speed is 15 r / min~40 r / min, and the ball milling time is 1 h±20 min.

3. The method for preparing a prefabricated autoclaved aerated concrete board made of solid waste-based sulfur-aluminum-iron cementitious materials according to claim 1, characterized in that: The raw materials in step (3) were dried at 110°C until a constant weight was reached, the raw materials were mixed in a pre-designed ratio, homogenized by grinding, and then calcined in a resistance holding furnace. The samples were calcined at heating rates of 6.5, 5, and 2.5°C / min for 120, 60, and 40 min, respectively, and maintained at a temperature of 1200°C for 30 min, and then rapidly air-cooled to room temperature.

4. The method for preparing a prefabricated autoclaved aerated concrete board made of solid waste-based sulfur-aluminum-iron cementitious materials according to claim 1, characterized in that: The secondary grinding time in step (4) is 30 min, and the rotation speed is 48 r / min.

5. The method for preparing a solid waste-based sulfur-aluminum-iron cementitious material prefabricated autoclaved aerated concrete board according to claim 1, characterized in that: The slurry concentration is controlled at 55%±2%; the specific operation of multi-frequency vibration is as follows: in the first stage, starting from mold injection, aluminum powder quickly releases gas and promotes the rapid expansion of the slurry, generating a large number of bubbles, followed by lateral vibration, and the bubbles diffuse laterally to both sides. When the slurry expands to the edge of the mold, the lateral movement stops; in the second stage, the gas release rate of aluminum powder slows down and tends to be stable, accompanied by longitudinal vibration, and the bubbles float upward slowly and evenly; In the third stage, when a certain number of bubbles appear on the surface of the slurry, the vibration stops and the bubbles are evenly arranged in the slurry.

6. The method for preparing a prefabricated autoclaved aerated concrete board made of solid waste-based sulfur-aluminum-iron cementitious materials according to claim 1, characterized in that: Multi-temperature curing consists of five stages: pre-curing, heating, constant temperature, cooling, and insulation.

7. The method for preparing a prefabricated autoclaved aerated concrete board made of solid waste-based sulfur-aluminum-iron cementitious materials according to claim 6, characterized in that: Pre-curing stage: place the sample in the pre-curing chamber for pre-curing and keep it at 60℃ for 45min; heating stage: send it into the high-pressure reactor for steam curing, and the temperature rises slowly at a rate of 0.5℃ / min; constant temperature stage: the temperature in the high-pressure reactor reaches and stabilizes at 195℃±3℃, the pressure is controlled at 1.20 MPa±0.05MPa, and the constant temperature is maintained for 1h; cooling stage: after the constant temperature process is completed, the temperature is reduced at a rate of 1℃ / min; insulation stage: when the temperature drops to 45℃, keep it warm for 50min.

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