An aerated concrete block prepared using tailings sand and a method of preparing the same

Abstract

The application relates to the technical field of building materials, and discloses aerated concrete blocks prepared from tailing sand and a preparation method thereof, which are prepared from iron tailing sand, steel slag powder, desulfurization gypsum, ordinary Portland cement, quicklime, a composite gas-releasing agent composed of aluminum powder paste and hydrogen peroxide, a composite foam stabilizer composed of modified tea saponin and polyether silicone oil, hydroxypropyl methyl cellulose, metakaolin and polycarboxylate superplasticizer, and are prepared from iron tailing sand as a core siliceous raw material, in cooperation with industrial solid wastes such as steel slag powder and desulfurization gypsum, in combination with calcareous raw materials and a composite gas-releasing and foam-stabilizing system through raw material pretreatment, accurate stirring and pouring, cutting and shaping and segmented gradient autoclave curing. The alkali-sulfate synergy excitation improves the activity of the tailing sand, optimizes the pore structure, realizes high utilization of solid wastes, and synergistically improves the product strength, thermal insulation and impermeability, is low in cost, free of secondary pollution, and is suitable for various building walls and in line with the green building material development policy.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, and more specifically, to an aerated concrete block prepared using tailings sand and its preparation method. Background Technology

[0002] Autoclaved aerated concrete (AAC) blocks are widely used in building infill walls and insulation walls due to their advantages such as being lightweight, having good thermal insulation properties, and providing sound insulation. With the advancement of policies promoting the resource utilization of industrial solid waste, tailings sand, as a byproduct of mining, is gradually becoming a potential siliceous raw material for AAC blocks due to its high silica and aluminum content.

[0003] However, in existing technologies, tailings sand suffers from low activity and incomplete hydration, resulting in its dosage in aerated concrete typically being only 40%–50%, limiting solid waste utilization. Furthermore, relying solely on cement or quicklime for activation easily leads to problems such as uncontrolled slurry setting rate and poor bubble stability, making it difficult to balance product strength and insulation. Either the lightweighting results in insufficient strength (compressive strength < 3.5 MPa), or the strength meets the standard but the bulk density is too high (> 650 kg / m³). 3 However, it also has drawbacks such as poor impermeability (water absorption rate > 45%). In addition, traditional autoclaving processes mostly adopt constant temperature and pressure modes, with curing time as long as 12 to 15 hours, resulting in high energy consumption, low production efficiency, and the direct disposal of cutting waste, causing secondary pollution.

[0004] Therefore, developing a high-performance, low-energy-consumption, and environmentally friendly aerated concrete block with high tailings sand content and its preparation method is of great practical significance. Summary of the Invention

[0005] In view of this, the present invention proposes an aerated concrete block prepared using tailings sand and its preparation method, aiming to solve the problems of insufficient activity of tailings sand, high cement content, low solid waste utilization rate, and high autoclaving energy consumption in the current technology.

[0006] This invention proposes an aerated concrete block prepared using tailings sand, comprising the following components in parts by weight: The ingredients are: 60-80 parts iron tailings sand, 20-30 parts steel slag powder, 8-12 parts desulfurized gypsum, 15-25 parts ordinary silicate cement, 10-15 parts quicklime, 0.8-1.5 parts composite foaming agent, 0.3-0.8 parts composite foam stabilizer, 0.2-0.5 parts hydroxypropyl methylcellulose, 5-10 parts metakaolin, and 0.5-1.2 parts polycarboxylate superplasticizer.

[0007] Furthermore, the composite gas-generating agent is prepared by mixing aluminum powder paste and hydrogen peroxide in a mass ratio of 1:3 to 5.

[0008] Furthermore, the composite foam stabilizer is prepared by compounding modified tea saponin and polyether silicone oil in a mass ratio of 2:1 to 1.5.

[0009] A method for preparing aerated concrete blocks using tailings sand includes the following steps: (1) Raw material pretreatment: Iron tailings sand, steel slag powder and desulfurized gypsum are crushed and dried respectively, and quicklime is crushed and passed through an 80-mesh sieve to obtain solid pretreated raw materials for later use; (2) Stirring and pouring: Mix all the pretreated solid raw materials and stir dry. Add polycarboxylate superplasticizer and water and stir wet. Then add composite gas generator and composite foam stabilizer, continue stirring, and quickly pour into the mold. Let it stand at room temperature for initial setting to obtain the pre-set green body. (3) Cutting and shaping: After the initial solidification of the billet is demolded, it is cut to the set size by a wire cutting machine. The cutting waste is mixed into the new material for recycling to obtain the shaped billet; (4) Segmented gradient autoclaving: The shaped blank is cured in four stages in sequence. The four stages of curing include the first stage of preheating, the second stage of pressurization, the third stage of constant temperature, and the fourth stage of depressurization. After curing, the finished aerated concrete blocks are obtained.

[0010] Furthermore, the drying temperature in step (1) is 105~110℃.

[0011] Furthermore, in step (2), the solid-liquid ratio of the solid raw material and water is 1:0.4~0.6, wherein the water is warm water at 50~60℃; the stirring parameters for the dry material are: rotation speed 600~800r / min, time 2~3min; the stirring parameters for the wet material are: rotation speed 600~800r / min, time 5~10min.

[0012] Furthermore, in step (2), the stirring parameters after adding the composite foaming agent and the composite foam stabilizer are: rotation speed 600~800r / min, time 3~4min, temperature 50~60℃; the initial setting time is 40~60min.

[0013] Furthermore, the cutting waste material mentioned in step (3) is crushed and then mixed into the new material at a dosage of 5% to 15% for recycling, and it needs to be dried and pretreated simultaneously with the new material.

[0014] Furthermore, the preheating parameters in step (4) are: temperature 40~60℃, time 1~2h, heating rate 1~5℃ / min; the pressure increase is to increase the temperature and pressure to 1.2~1.5MPa at a rate of 3~5℃ / min, taking 1.5~2.5h; the constant temperature parameters are: pressure 1.2~1.5MPa, temperature 180~200℃, holding for 6~8h; the depressurization parameters are: to decrease to normal pressure at a rate of 0.1~0.2MPa / min, taking 0.5~1h.

[0015] This invention also protects the application of the above-mentioned aerated concrete blocks, specifically applicable to infill walls of civil buildings, thermal insulation walls of industrial plants, non-load-bearing walls of prefabricated buildings, and energy-saving renovation projects of existing buildings.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: In this invention, the tailings sand content exceeds the upper limit of 40%-50% in existing technologies, reaching 60%-70%. Combined with the synergistic addition of steel slag powder and desulfurized gypsum, the total utilization rate of solid waste is as high as 70%-80%, which greatly reduces the risks of land occupation and environmental pollution caused by tailings stockpiling. It fully complies with the national dual-carbon goals and the policy guidance of comprehensive utilization of industrial solid waste, and can achieve 100% recycling of cutting waste and re-mixing and recycling, solving the problem of secondary pollution caused by waste disposal in traditional processes, and forming a closed-loop utilization system of raw materials-production-waste recycling.

[0017] This invention utilizes the alkalinity of steel slag powder and the sulfate properties of desulfurized gypsum to form a low-cost activation system without additional activators. This avoids the corrosion and increased costs associated with the need for high-alkali activators in existing technologies, resulting in superior technical and economic efficiency.

[0018] This invention shortens the total curing time and reduces steam consumption by segmented control of preheating, pressurization, constant temperature and depressurization. It solves the pain points of long curing time and high energy consumption in traditional autoclaving processes, significantly improving production efficiency. Combined with precise static temperature control, it avoids problems such as premature coagulation of slurry and bubble rupture, thereby improving product qualification rate and reducing production losses.

[0019] This invention replaces large quantities of expensive cement and quartz sand with low-cost tailings sand. The steel slag powder and desulfurized gypsum in the composite activator are both industrial by-products, resulting in significantly lower raw material procurement costs than traditional formulas. At the same time, it reduces carbon emissions from cement usage, and all waste materials are recycled during the production process. Compared with the limitations of existing technologies that utilize solid waste but generate new pollution, this invention truly achieves a win-win situation for environmental protection and economic benefits, meets green building material production standards, and has higher market acceptance.

[0020] This invention promotes the full participation of SiO2 and Al2O3 in the hydration reaction of tailings sand through the synergistic effect of steel slag powder and desulfurized gypsum, generating more CSH gel and ettringite, thus solving the bottleneck of low strength caused by insufficient tailings sand activity and the need for high cement content in the prior art.

[0021] The technical solution in this invention differs from the traditional one-size-fits-all temperature and pressure control of autoclaving. The gradient process precisely regulates the formation process of hydration products, and with the help of foam stabilizers, it achieves uniform, fine, and low-connectivity pores, providing core support for product performance improvement. The technology is highly replicable and easy to promote in the industry. Detailed Implementation

[0022] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention. It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the present invention.

[0023] Furthermore, regarding the numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included within this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0024] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0025] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0026] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0027] This invention proposes an aerated concrete block prepared using tailings sand, comprising the following components in parts by weight: The ingredients are: 60-80 parts iron tailings sand, 20-30 parts steel slag powder, 8-12 parts desulfurized gypsum, 15-25 parts ordinary silicate cement, 10-15 parts quicklime, 0.8-1.5 parts composite foaming agent, 0.3-0.8 parts composite foam stabilizer, 0.2-0.5 parts hydroxypropyl methylcellulose, 5-10 parts metakaolin, and 0.5-1.2 parts polycarboxylate superplasticizer.

[0028] In this invention, the aerated concrete block is further preferably composed of the following components in parts by weight: 60-70 parts iron tailings sand, 20-27 parts steel slag powder, 8-10 parts desulfurized gypsum, 15-22 parts ordinary silicate cement, 10-12 parts quicklime, 0.8-1.2 parts composite foaming agent, 0.3-0.6 parts composite foam stabilizer, 0.2-0.4 parts hydroxypropyl methylcellulose, 5-8 parts metakaolin, and 0.5-1.0 parts polycarboxylate superplasticizer.

[0029] In this invention, the composite gas-generating agent is preferably prepared by mixing aluminum powder paste and hydrogen peroxide in a mass ratio of 1:3 to 5, and more preferably by mixing aluminum powder paste and hydrogen peroxide in a mass ratio of 1:4 to 5.

[0030] In this invention, the composite foam stabilizer is preferably composed of modified tea saponin and polyether silicone oil in a mass ratio of 2:1 to 1.5, and more preferably composed of modified tea saponin and polyether silicone oil in a mass ratio of 2:1.2 to 1.5.

[0031] This invention adds iron tailings sand to the aerated concrete blocks. The iron tailings sand can provide SiO2 and Al2O3, providing the core material basis for the hydration reaction, filling the pores of the slurry, and improving the density of the structure. It forms an alkali-sulfate dual-activation system with steel slag powder and desulfurized gypsum, which overcomes the bottleneck of insufficient activity and allows SiO2 and Al2O3 to fully participate in hydration to generate CSH gel and ettringite.

[0032] This invention adds steel slag powder to the aerated concrete blocks. The steel slag powder provides an alkaline environment, activates the tailings sand, and can destroy the inert SiO2 film on the surface of the iron tailings sand, activating its potential activity. It contains free CaO, participates in the hydration reaction to form gel, improves strength, and can also inhibit shrinkage cracks caused by excessive heat of hydration. In synergy with desulfurized gypsum, the alkalinity and sulfate concentration are matched to promote the orderly growth of ettringite. If the dosage is too low, the alkalinity will be insufficient and the activity will not be fully activated; if it is too high, it will lead to excessive heat of hydration and easily cause cracks.

[0033] The present invention adds desulfurized gypsum to the aerated concrete blocks, the desulfurized gypsum providing SO4. 2-It reacts with hydration products to form ettringite, which can improve strength and volume stability, slow down the initial setting speed of slurry, and is suitable for mixing and casting processes. It can also digest the desulfurization by-products of coal-fired power plants, reduce environmental pressure, and form a double-excitation closed loop with steel slag powder to increase the amount and stability of ettringite formation. If the dosage is too low, the amount of ettringite formation will be insufficient, and if it is too high, it will easily lead to efflorescence.

[0034] This invention adds ordinary silicate cement to the aerated concrete blocks. The ordinary silicate cement can hydrate to generate CSH gel and Ca(OH)2, providing initial strength for the initial setting stage of the block, improving slurry adhesion, enhancing molding performance, and synergistically providing sufficient Ca to the dual-activation system with quicklime. 2+ This ensures the hydration reaction continues, relies on a dual-excitation system to achieve strength enhancement, and significantly reduces raw material costs.

[0035] The present invention adds quicklime to the aerated concrete blocks. The digestion reaction of the quicklime can release a large amount of Ca(OH)2, which provides raw materials for the formation of gel and ettringite. The digestion reaction is exothermic, which maintains the slurry temperature, promotes the synergistic effect of gas generation and hydration, and can also help steel slag powder to increase the alkalinity of the system, enhance the activation of tailings sand activity, and ensure that the digestion reaction rate matches the slurry flowability.

[0036] The present invention adds a composite gas-generating agent to the aerated concrete block. The composite gas-generating agent includes aluminum powder paste and hydrogen peroxide. The hydrogen peroxide decomposes rapidly to generate initial bubbles, and the aluminum powder paste reacts slowly to replenish the bubbles, forming a rapid start-up and continuous replenishment gas-generating mode, and controlling the porosity of the slurry, thus providing a structural basis for thermal insulation.

[0037] This invention does not impose any specific limitation on the concentration of hydrogen peroxide; any concentration known to those skilled in the art can be used.

[0038] The present invention adds a composite foam stabilizer to the aerated concrete block. The composite foam stabilizer includes modified tea saponin and polyether silicone oil. The modified tea saponin is adsorbed on the surface of the bubbles to form a high-strength liquid film, and the polyether silicone oil reduces the interfacial tension, inhibits bubble coalescence and rupture, ensures that the bubbles are small and impermeable, and optimizes the pore structure.

[0039] The present invention adds hydroxypropyl methylcellulose to the aerated concrete blocks. The hydroxypropyl methylcellulose can improve the water retention of the slurry, prevent bleeding and stratification, ensure the uniformity of the slurry in the initial setting stage, increase the viscosity of the slurry, improve the pouring fluidity, avoid slurry leakage from the mold, and also improve the bonding strength of the green body and reduce damage during the cutting process.

[0040] The present invention adds metakaolin to the aerated concrete block. The metakaolin contains highly active Al2O3, which accelerates the hydration reaction, promotes the densification of CSH gel, fills the micropores, and synergistically forms a dense structure with ettringite, thereby improving compressive strength and reducing pore connectivity, thus improving impermeability.

[0041] The present invention adds a polycarboxylate superplasticizer to the aerated concrete blocks. The polycarboxylate superplasticizer can reduce the water-cement ratio, reduce water consumption, increase the density of hydration products, improve slurry fluidity, reduce mixing energy consumption, adapt to precise casting process, and promote the dispersion of raw materials to avoid local agglomeration.

[0042] This invention does not impose any specific limitations on the type of polycarboxylate superplasticizer; any type well-known to those skilled in the art can be used.

[0043] A method for preparing aerated concrete blocks using tailings sand includes the following steps: (1) Raw material pretreatment: Iron tailings sand, steel slag powder and desulfurized gypsum are crushed and dried respectively, and quicklime is crushed and passed through an 80-mesh sieve to obtain solid pretreated raw materials for later use; (2) Stirring and pouring: Mix all the pretreated solid raw materials and stir dry. Add polycarboxylate superplasticizer and water and stir wet. Then add composite gas generator and composite foam stabilizer, continue stirring, and quickly pour into the mold. Let it stand at room temperature for initial setting to obtain the pre-set green body. (3) Cutting and shaping: After the initial solidification of the billet is demolded, it is cut to the set size by a wire cutting machine. The cutting waste is mixed into the new material for recycling to obtain the shaped billet; (4) Segmented gradient autoclaving: The shaped blank is cured in four stages in sequence. The four stages of curing include the first stage of preheating, the second stage of pressurization, the third stage of constant temperature, and the fourth stage of depressurization. After curing, the finished aerated concrete blocks are obtained.

[0044] In this invention, the drying temperature in step (1) is preferably 105~110℃, and more preferably 106~110℃.

[0045] In this invention, the solid-liquid ratio of the solid raw material and water in step (2) is preferably 1:0.4~0.6, more preferably 1:0.4~0.5, wherein the water is preferably warm water at 50~60℃, more preferably warm water at 50~58℃; the stirring parameters for the dry material are preferably: rotation speed 600~800r / min, time 2~3min, more preferably rotation speed 650~800r / min, time 2~2.5min; the stirring parameters for the wet material are preferably: rotation speed 600~800r / min, time 5~10min, more preferably rotation speed 650~800r / min, time 5~8min.

[0046] In this invention, the stirring parameters after adding the composite foaming agent and composite foam stabilizer in step (2) are preferably: rotation speed 600~800 r / min, time 2~4 min, temperature 50~60℃, and more preferably 650~800 r / min, time 3~4 min, temperature 50~58℃; the initial setting time is preferably 40~60 min, and more preferably 50~60 min.

[0047] In this invention, the cutting waste material described in step (3) is preferably added to the new material at a dosage of 5% to 15% for recycling, and it needs to be dried and pretreated simultaneously with the new material. More preferably, it is added to the new material at a dosage of 8% to 15% for recycling.

[0048] In this invention, the preheating parameters in step (4) are preferably: temperature 40~60℃, time 1~2h, and heating rate 1~5℃ / min, more preferably 45~60℃, time 1~1.5h, and heating rate 1.5~5℃ / min; the pressure increase is preferably at a rate of 3~5℃ / min to 1.2~1.5MPa, taking 1.5~2.5h, more preferably at a rate of 3.5~5℃ / min to 1.3~1.5MPa. a. The time taken is 1.5~2 hours; the preferred constant temperature parameters are: pressure 1.2~1.5MPa, temperature 180~200℃, and holding time 6~8 hours, more preferably pressure 1.3~1.5MPa, temperature 185~200℃, and holding time 6~7 hours; the preferred depressurization parameters are: depressurization at a rate of 0.1~0.2MPa / min to atmospheric pressure, taking 0.5~1 hours, more preferably depressurization at a rate of 0.15~0.2MPa / min to atmospheric pressure, taking 0.6~1 hours.

[0049] This invention also protects the application of the above-mentioned aerated concrete blocks, specifically applicable to infill walls of civil buildings, thermal insulation walls of industrial plants, non-load-bearing walls of prefabricated buildings, and energy-saving renovation projects of existing buildings.

[0050] In this invention, unless otherwise specified, all raw materials required for preparation are commercially available products well known to those skilled in the art.

[0051] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0052] Example 1 Raw materials: 60 parts iron tailings sand, 20 parts steel slag powder, 8 parts desulfurized gypsum, 15 parts ordinary silicate cement, 10 parts quicklime, 0.8 parts composite foaming agent (aluminum powder paste: hydrogen peroxide = 1:4), 0.3 parts composite foam stabilizer (modified tea saponin: polyether silicone oil = 2:1.2), 0.2 parts hydroxypropyl methylcellulose, 5 parts metakaolin, 0.5 parts polycarboxylate superplasticizer; Preparation method: (1) Raw material pretreatment: Iron tailings sand, steel slag powder and desulfurized gypsum were crushed and dried at 106℃; quicklime was crushed and passed through an 80-mesh sieve to obtain solid pretreated raw materials for later use. (2) Stirring and casting: Mix all the pretreated solid raw materials and dry stir at 650 r / min for 2.5 min. Add polycarboxylate superplasticizer and 50°C warm water and wet stir at 650 r / min for 8 min. The solid-liquid ratio of solid raw materials to water is 1:0.4. Then add composite gas-generating agent and composite foam stabilizer and continue stirring at 650 r / min and 50°C for 3 min. Quickly pour into the mold and let it stand at room temperature for 50 min to initially set to obtain the pre-set green body. (3) Cutting and shaping: After the initial solidification of the billet is demolded, it is cut to the set size by a wire cutting machine. The cutting waste is added to the new material at a rate of 8% for recycling and needs to be dried and pretreated at the same time as the new material to obtain the shaped billet. (4) Segmented gradient autoclaving: The shaped green body is cured in four stages in sequence. The four stages of curing include the first stage of preheating, the second stage of pressurization, the third stage of constant temperature, and the fourth stage of depressurization. The preheating parameters are 45℃ temperature, 1.5h time, and heating rate of 1.5℃ / min; the pressurization is to increase the temperature and pressure to 1.3MPa at a rate of 3.5℃ / min and take 2h; the constant temperature parameters are 1.3MPa pressure and 185℃ temperature and hold for 6h; the depressurization parameters are to reduce the pressure to normal pressure at a rate of 0.15MPa / min and take 0.6h. After curing, the finished aerated concrete blocks are obtained.

[0053] Example 2 Raw materials: 65 parts iron tailings sand, 24 parts steel slag powder, 9 parts desulfurized gypsum, 18 parts ordinary silicate cement, 11 parts quicklime, 1 part composite foaming agent (aluminum powder paste: hydrogen peroxide = 1:4.5), 0.5 parts composite foam stabilizer (modified tea saponin: polyether silicone oil = 2:1.3), 0.3 parts hydroxypropyl methylcellulose, 6 parts metakaolin, 0.8 parts polycarboxylate superplasticizer; Preparation method: (1) Raw material pretreatment: Iron tailings sand, steel slag powder and desulfurized gypsum were crushed and dried at 108℃; quicklime was crushed and passed through an 80-mesh sieve to obtain solid pretreated raw materials for later use. (2) Stirring and casting: Mix all the pretreated solid raw materials and dry stir at 700 r / min for 2.5 min. Add polycarboxylate superplasticizer and 55℃ warm water and wet stir at 700 r / min for 6 min. The solid-liquid ratio of solid raw materials to water is 1:0.45. Then add composite gas-generating agent and composite foam stabilizer and continue stirring at 700 r / min and 55℃ for 3.5 min. Quickly pour into the mold and let it stand at room temperature for 55 min to initially set to obtain the pre-set green body. (3) Cutting and shaping: After the initial solidification of the billet is demolded, it is cut to the set size by a wire cutting machine. The cutting waste is added to the new material at a rate of 10% for recycling and needs to be dried and pretreated at the same time as the new material to obtain the shaped billet. (4) Segmented gradient autoclaving: The shaped green body is subjected to four stages of curing in sequence. The four stages of curing include the first stage of preheating, the second stage of pressurization, the third stage of constant temperature, and the fourth stage of depressurization. The preheating parameters are 50℃ temperature, 1.2h time, and heating rate of 3℃ / min; the pressurization is to increase the temperature and pressure to 1.4MPa at a rate of 4℃ / min, which takes 1.8h; the constant temperature parameters are 1.4MPa pressure and 190℃ temperature, which is maintained for 6.5h; the depressurization parameters are to reduce the pressure to normal pressure at a rate of 0.18MPa / min, which takes 0.8h. After curing, the finished aerated concrete blocks are obtained.

[0054] Example 3 Raw materials: 70 parts iron tailings sand, 27 parts steel slag powder, 10 parts desulfurized gypsum, 22 parts ordinary silicate cement, 12 parts quicklime, 1.2 parts composite foaming agent (aluminum powder paste: hydrogen peroxide = 1:5), 0.6 parts composite foam stabilizer (modified tea saponin: polyether silicone oil = 2:1.5), 0.4 parts hydroxypropyl methylcellulose, 8 parts metakaolin, 1.0 part polycarboxylate superplasticizer; Preparation method: (1) Raw material pretreatment: Iron tailings sand, steel slag powder and desulfurized gypsum were crushed and dried at 110℃; quicklime was crushed and passed through an 80-mesh sieve to obtain solid pretreated raw materials for later use. (2) Stirring and casting: Mix all the pretreated solid raw materials and stir dry at 800 r / min for 2 min. Add polycarboxylate superplasticizer and 58℃ warm water and stir wet at 800 r / min for 5 min. The solid-liquid ratio of solid raw materials to water is 1:0.5. Then add composite gas-generating agent and composite foam stabilizer and continue stirring at 800 r / min and 58℃ for 3 min. Quickly pour into the mold and let it stand at room temperature for 60 min to initially set to obtain the pre-set green body. (3) Cutting and shaping: After the initial solidification of the billet is demolded, it is cut to the set size by a wire cutting machine. The cutting waste is added to the new material at a rate of 15% for recycling and needs to be dried and pretreated at the same time as the new material to obtain the shaped billet. (4) Segmented gradient autoclaving: The shaped green body is subjected to four stages of curing in sequence. The four stages of curing include the first stage of preheating, the second stage of pressurization, the third stage of constant temperature, and the fourth stage of depressurization. The preheating parameters are 60℃ temperature, 1h time, and 5℃ / min heating rate; the pressurization is to increase the temperature and pressure to 1.5MPa at a rate of 5℃ / min, which takes 1.5h; the constant temperature parameters are 1.5MPa pressure and 200℃ temperature, which is kept at 7h; the depressurization parameters are to reduce the pressure to normal pressure at a rate of 0.2MPa / min, which takes 1h. After curing, the finished aerated concrete blocks are obtained.

[0055] Comparative Example 1 Raw materials: 60 parts iron tailings sand, 15 parts steel slag powder, 8 parts desulfurized gypsum, 15 parts ordinary silicate cement, 10 parts quicklime, 0.8 parts composite foaming agent (aluminum powder paste: hydrogen peroxide = 1:4), 0.3 parts composite foam stabilizer (modified tea saponin: polyether silicone oil = 2:1.2), 0.2 parts hydroxypropyl methylcellulose, 5 parts metakaolin, 0.5 parts polycarboxylate superplasticizer; Preparation method: (1) Raw material pretreatment: Iron tailings sand, steel slag powder and desulfurized gypsum were crushed and dried at 106℃; quicklime was crushed and passed through an 80-mesh sieve to obtain solid pretreated raw materials for later use. (2) Stirring and casting: Mix all the pretreated solid raw materials and dry stir at 650 r / min for 2.5 min. Add polycarboxylate superplasticizer and 50°C warm water and wet stir at 650 r / min for 8 min. The solid-liquid ratio of solid raw materials to water is 1:0.4. Then add composite gas-generating agent and composite foam stabilizer and continue stirring at 650 r / min and 50°C for 3 min. Quickly pour into the mold and let it stand at room temperature for 50 min to initially set to obtain the pre-set green body. (3) Cutting and shaping: After the initial solidification of the billet is demolded, it is cut to the set size by a wire cutting machine. The cutting waste is added to the new material at a rate of 8% for recycling and needs to be dried and pretreated at the same time as the new material to obtain the shaped billet. (4) Segmented gradient autoclaving: The shaped green body is subjected to four stages of curing in sequence. The four stages of curing include the first stage of preheating, the second stage of pressurization, the third stage of constant temperature, and the fourth stage of depressurization. The preheating parameters are 45℃ temperature, 1.5h time, and heating rate of 1.5℃ / min; the pressurization is to increase the temperature and pressure to 1.3MPa at a rate of 3.5℃ / min, which takes 2h; the constant temperature parameters are 1.3MPa pressure and 185℃ temperature, which is maintained for 6h; the depressurization parameters are to reduce the pressure to normal pressure at a rate of 0.15MPa / min, which takes 0.6h. After curing, the finished aerated concrete blocks are obtained.

[0056] Comparative Example 2 Desulfurized gypsum was not used in the raw materials; the other raw materials were the same as in Example 1. The preparation method is the same as in Example 1.

[0057] Comparative Example 3 Raw materials: 60 parts iron tailings sand, 20 parts steel slag powder, 8 parts desulfurized gypsum, 15 parts ordinary silicate cement, 10 parts quicklime, 0.8 parts composite foaming agent (aluminum powder paste: hydrogen peroxide = 1:4), 0.3 parts composite foam stabilizer (modified tea saponin: polyether silicone oil = 2:1.2), 0.2 parts hydroxypropyl methylcellulose, 5 parts metakaolin, 0.5 parts polycarboxylate superplasticizer; Preparation method: (1) Raw material pretreatment: Iron tailings sand, steel slag powder and desulfurized gypsum were crushed and dried at 106℃; quicklime was crushed and passed through an 80-mesh sieve to obtain solid pretreated raw materials for later use. (2) Stirring and casting: Mix all the pretreated solid raw materials and dry stir at 650 r / min for 2.5 min. Add polycarboxylate superplasticizer and 50°C warm water and wet stir at 650 r / min for 8 min. The solid-liquid ratio of solid raw materials to water is 1:0.4. Then add composite gas-generating agent and composite foam stabilizer and continue stirring at 650 r / min and 50°C for 3 min. Quickly pour into the mold and let it stand at room temperature for 50 min to initially set to obtain the pre-set green body. (3) Cutting and shaping: After the initial solidification of the billet is demolded, it is cut to the set size by a wire cutting machine. The cutting waste is added to the new material at a rate of 8% for recycling and needs to be dried and pretreated at the same time as the new material to obtain the shaped billet. (4) Constant temperature autoclaving: directly pressurize and heat to 1.3MPa and 190℃, keep at constant temperature for 15h, and the finished aerated concrete blocks are obtained after curing.

[0058] Performance testing: (1) The dry density (kg / m³) 3 The test involves randomly selecting three blocks from the finished product, cutting a cubic specimen from the center along its length, with three specimens per group. The specimens are dried in an oven at 105±5℃ until constant weight (the difference between two weighings ≤0.5%), cooled to room temperature, and then weighed. The dry density ρ0 = dried mass of the specimen (kg) / volume of the specimen (m³). 3 The testing was conducted in accordance with Clause 6.3 of GB / T 11968-2020 "Autoclaved Aerated Concrete Blocks".

[0059] (2) The compressive strength (MPa) test involves randomly selecting 3 blocks from the finished product, cutting a cubic specimen from the center along the length direction, with 3 specimens per group. After drying to constant weight, the specimens are weighed and then uniformly loaded at a rate of 0.2~0.3 MPa / s until the specimen fails. The maximum failure load F is recorded. The compressive strength f = F (N) / the area of ​​the specimen under pressure (mm²) 2 The testing was conducted in accordance with Clause 6.4 of GB / T 11968-2020 "Autoclaved Aerated Concrete Blocks".

[0060] (3) The thermal conductivity (W / (m・K)) is tested using the protective hot plate method, and the test is based on Article 5 of GB / T 10294-2008 "Steady-state thermal resistance and related properties of thermal insulation materials - protective hot plate method".

[0061] (4) In the water absorption rate (%) test, a 100mm×100mm×100mm test block dried to constant weight is weighed and the dry mass m0 is measured. The test block is completely immersed in clean water at 20±5℃, with the water level 20mm above the top surface of the test block. After soaking for 24 hours, the test block is taken out, the surface moisture is wiped dry with a wet towel, and the saturated mass m1 is weighed immediately. The water absorption rate W=[m1-m0) / m0]×100%. The test is based on Article 6.5 of GB / T11968-2020 Autoclaved Aerated Concrete Blocks.

[0062] (5) The average diameter of the pores (mm) was detected by microscopic imaging method, and the detection was based on GB / T 29906-2013 "Materials for Molded Polystyrene Board Thin Plastering Exterior Wall Insulation System" (Pore Structure Auxiliary Test Method).

[0063] (6) The pore connectivity rate (%) was detected by indirect method combined with microscopic analysis, and the detection was based on JGJ / T70-2009 "Standard for Test Methods of Basic Performance of Building Mortar".

[0064] The performance of the finished products prepared in Examples 1-3 and Comparative Examples 1-3 was tested, and the results are shown in Table 1 below. Table 1. Performance test results of the finished products prepared in Examples 1-3 and Comparative Examples 1-3 Performance Comparison: The ternary solid waste system of iron tailings sand, steel slag powder, and desulfurized gypsum, combined with the composite gas-generating and foam-stabilizing agent and the segmented gradient autoclaving process of this invention can achieve a synergistic effect of high solid waste content, compressive strength, and thermal conductivity, breaking through the bottlenecks of traditional technologies. The aerated concrete blocks in Examples 1-3 prepared using the raw materials and preparation methods described in this invention have a dry density of 530~570 kg / m³. 3 The aerated concrete blocks have a compressive strength of 5.2~6.3 MPa and a thermal conductivity of 0.09~0.11 W / (m·K). They exhibit good lightweight, compressive strength, and thermal insulation properties, and require only 10.1h~10.5h of curing time during preparation. Comparative Examples 1-3 were compared using a single variable. In Comparative Example 1, insufficient steel slag powder content led to insufficient alkalinity, resulting in a lower compressive strength of only 3.9 MPa, while increasing thermal conductivity and water absorption by 0.14 W / (m·K) and 51%, respectively. The product's strength and thermal insulation properties deteriorated simultaneously. In Comparative Example 2, desulfurized gypsum was omitted, resulting in a compressive strength of only 4.2 MPa and a thermal conductivity of 0.13 W / (m·K). The lack of sulfate activation led to insufficient ettringite formation, decreased structural density, insufficient pore liquid film stability, and bubble coalescence, resulting in a pore diameter of 1. 3mm, connectivity rate 25%, water absorption rate deteriorated; in Comparative Example 3, gradient autoclaving was cancelled and replaced with direct pressurization and heating, requiring 15h curing, without preheating and slow pressurization stage, the green body was subjected to thermal shock and microcracks were generated, hydration products formed disorderedly, although the pores were not excessively large (1.1mm), the connectivity rate was 20%, resulting in a decrease in strength and thermal insulation, with a compressive strength of only 4.6MPa and a thermal conductivity of 0.12W / (m・K); and in Examples 1-3, the total amount of solid waste including iron tailings sand, steel slag powder, and desulfurized gypsum was 88~107 parts, the amount of iron tailings sand was 60~70 parts, the iron tailings sand admixture was 65.4%~68.2%, the solid main materials were iron tailings sand, steel slag powder, desulfurized gypsum, ordinary Portland cement, quicklime, metakaolin, with a total amount of 119.8~149 parts, and the solid waste utilization rate was 71.8~74.6%.

[0065] In summary, this invention uses iron tailings sand as the core siliceous raw material, in conjunction with industrial solid waste such as steel slag powder and desulfurized gypsum, and combines it with calcareous raw materials and a composite gas-generating and foam-stabilizing system. The process involves raw material pretreatment, precise mixing and casting, cutting and shaping, and segmented gradient autoclaving. By synergistic activation of alkali and sulfate to enhance the activity of the tailings sand and optimize its pore structure, this invention achieves high utilization of solid waste. The product exhibits synergistic improvements in strength, thermal insulation, and impermeability, is low-cost, and produces no secondary pollution. It is suitable for various building walls and aligns with green building materials development policies.

[0066] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the present invention. The scope of protection of the present invention is determined by the appended claims.

[0067] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. An aerated concrete block prepared using tailings sand, characterized in that, The components include the following parts by mass: The ingredients are: 60-80 parts iron tailings sand, 20-30 parts steel slag powder, 8-12 parts desulfurized gypsum, 15-25 parts ordinary silicate cement, 10-15 parts quicklime, 0.8-1.5 parts composite foaming agent, 0.3-0.8 parts composite foam stabilizer, 0.2-0.5 parts hydroxypropyl methylcellulose, 5-10 parts metakaolin, and 0.5-1.2 parts polycarboxylate superplasticizer.

2. An aerated concrete block prepared using tailings sand according to claim 1, characterized in that, The composite gas-generating agent is prepared by mixing aluminum powder paste and hydrogen peroxide in a mass ratio of 1:3~5.

3. An aerated concrete block prepared using tailings sand according to claim 1, characterized in that, The composite foam stabilizer is prepared by compounding modified tea saponin and polyether silicone oil in a mass ratio of 2:1 to 1.

5.

4. A method for preparing aerated concrete blocks using tailings sand as described in any one of claims 1 to 3, characterized in that, Includes the following steps: (1) Raw material pretreatment: Iron tailings sand, steel slag powder and desulfurized gypsum are crushed and dried respectively, and quicklime is crushed and passed through an 80-mesh sieve to obtain solid pretreated raw materials for later use; (2) Stirring and pouring: Mix all the pretreated solid raw materials and stir dry. Add polycarboxylate superplasticizer and water and stir wet. Then add composite gas generator and composite foam stabilizer, continue stirring, and quickly pour into the mold. Let it stand at room temperature for initial setting to obtain the pre-set green body. (3) Cutting and shaping: After the initial solidification of the billet is demolded, it is cut to the set size by a wire cutting machine. The cutting waste is mixed into the new material for recycling to obtain the shaped billet; (4) Segmented gradient autoclaving: The shaped blank is cured in four stages in sequence. The four stages of curing include the first stage of preheating, the second stage of pressurization, the third stage of constant temperature, and the fourth stage of depressurization. After curing, the finished aerated concrete blocks are obtained.

5. The method for preparing aerated concrete blocks using tailings sand according to claim 4, characterized in that, The drying temperature in step (1) is 105~110℃.

6. The method for preparing aerated concrete blocks using tailings sand according to claim 4, characterized in that, In step (2), the solid-liquid ratio of the solid raw material and water is 1:0.4~0.6, wherein the water is warm water at 50~60℃; the stirring parameters for the dry material are: rotation speed 600~800r / min, time 2~3min; the stirring parameters for the wet material are: rotation speed 600~800r / min, time 5~10min.

7. The method for preparing aerated concrete blocks using tailings sand according to claim 4, characterized in that, The stirring parameters after adding the composite foaming agent and composite foam stabilizer in step (2) are: rotation speed 600~800r / min, time 3~4min, temperature 50~60℃; the initial setting time is 40~60min.

8. The method for preparing aerated concrete blocks using tailings sand according to claim 4, characterized in that, The cutting waste material described in step (3) is crushed and then mixed into the new material at a rate of 5% to 15% for recycling. It also needs to be dried and pretreated simultaneously with the new material.

9. A method for preparing aerated concrete blocks using tailings sand according to claim 4, characterized in that, The preheating parameters in step (4) are: temperature 40~60℃, time 1~2h, heating rate 1~5℃ / min; the pressure increase is to increase the temperature and pressure to 1.2~1.5MPa at a rate of 3~5℃ / min, taking 1.5~2.5h; the constant temperature parameters are: pressure 1.2~1.5MPa, temperature 180~200℃, holding for 6~8h; the depressurization parameters are: to decrease to atmospheric pressure at a rate of 0.1~0.2MPa / min, taking 0.5~1h.

10. An application of the aerated concrete block as described in any one of claims 1 to 3, characterized in that, The aerated concrete blocks are specifically used for infill walls in civil buildings, thermal insulation walls in industrial plants, non-load-bearing walls in prefabricated buildings, and energy-saving renovation projects for existing buildings.

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