A method for producing lightweight building blocks from construction waste

Abstract

The application belongs to the technical field of building materials, and specifically discloses a method for preparing light-weight building blocks from construction waste. The method comprises the following steps: (1) grinding the construction waste, dispersing it in water, and stirring for 15-20 min to obtain a mixed solution one, which is ready for use; (2) mixing cement, waste mine powder, a thickening agent, a dispersing agent, water and a solidifying agent, and stirring for 6-9 min to obtain a mixed solution two, which is ready for use; (3) mixing the mixed solution one and the mixed solution two, adding a chemical foaming agent, stirring for 45-50 s, and pouring into a standard brick mold to obtain a building block semi-finished product; and (4) curing the building block semi-finished product to obtain a building block. The method ensures the strength and fluidity of the building block through the cooperation of various components, the bubbles in the mixture are uniform through molding, and the final product has the characteristics of light weight, heat preservation, waste utilization and high strength.

Description

Technical Field

[0001] This application relates to the technical field of building materials, and in particular to a method for preparing lightweight blocks from construction waste. Background Technology

[0002] Construction waste refers to solid waste generated during the construction, expansion, demolition, or renovation of buildings, mainly including waste concrete, waste bricks and tiles, waste mortar, and waste soil.

[0003] The resource utilization of construction waste has become a research hotspot. Currently, the main ways to recycle construction waste in the field of building materials include: using it as recycled aggregate to prepare concrete or blocks, using it as roadbed filler, and producing recycled bricks. Among these, using construction waste to prepare lightweight blocks is an important direction for realizing its high added value.

[0004] In the prior art, masonry blocks are artificial block-shaped building materials used for building walls. Their external dimensions are usually larger than ordinary clay bricks. They can be made from concrete, industrial waste or local materials, and have advantages such as saving arable land, utilizing waste, and high construction efficiency.

[0005] Blocks are made by mixing waste bricks, concrete blocks, cement and other cementing materials and then casting or pressing them. However, because waste bricks have high water absorption and low strength, when they are used as recycled aggregate in blocks, the strength of recycled concrete made from old clay brick coarse aggregate is lower than that of ordinary concrete. Furthermore, the strength of recycled concrete decreases as the waste brick replacement rate increases, making it impractical for practical applications. Summary of the Invention

[0006] To address the issue of low strength in recycled concrete made from coarse aggregate from old clay bricks, this application provides a method for preparing lightweight blocks from construction waste.

[0007] This application provides a method for preparing lightweight blocks from construction waste, employing the following technical solution: A method for preparing lightweight blocks from construction waste includes the following steps: (1) Grind the construction waste, disperse it in water, stir for 15-20 minutes to obtain a mixture, and set aside; (2) Mix cement, waste mineral powder, thickener, dispersant, water and curing agent, stir for 6-9 minutes to obtain mixture two, and set aside; (3) Mix liquid one and liquid two, add aluminum powder as a chemical foaming agent, stir for 45-50s, and pour into a standard brick mold to obtain a semi-finished block product; (4) Curing the semi-finished blocks to obtain blocks.

[0008] By employing the above technical solutions, grinding construction waste ensures the uniformity and surface smoothness of the blocks, avoiding stress concentration caused by large particles or affecting the foaming effect. Dispersing the construction waste in water allows it to be uniformly suspended, forming a homogeneous mixture, laying the foundation for subsequent mixing with the cementitious slurry.

[0009] Cement is the primary cementitious material, providing early strength and bonding force. Waste mineral powder, as an auxiliary cementitious material, undergoes secondary hydration under the activation of cement hydration products, improving later strength and density, while also utilizing waste materials. Thickeners increase the viscosity of the paste, retain water, and prevent excessive evaporation of moisture after block molding, while also helping to suspend aggregates and air bubbles, preventing segregation. Dispersants reduce the water-cement ratio while maintaining fluidity, thereby increasing strength. This ensures that various powders and admixtures are fully dissolved and dispersed in water, forming a uniform and stable cementitious paste (i.e., mixture two).

[0010] Mix liquid one and liquid two together, and combine the pretreated aggregate with the cementitious slurry so that the aggregate particles are coated with cementitious material to form a uniform mixture.

[0011] Adding aluminum powder (a chemical foaming agent) and a curing agent allows the hydrogen gas generated by the aluminum powder to form tiny bubbles in the slurry, causing the blocks to expand in volume and decrease in density, thus achieving lightweight construction. Rapid mixing for 45-50 seconds ensures uniform dispersion of the aluminum powder while preventing excessive mixing time that could lead to bubble bursting or premature escape. The curing agent accelerates cement hydration, ensuring that the early strength development of the blocks keeps pace with the foaming and expansion process, preventing formwork collapse.

[0012] Curing accelerates hydration, improves early strength, and shortens the production cycle. It also enhances the volume stability and durability of the blocks. During curing, the bubbles generated by the aluminum powder are gradually fixed by the hardened slurry, forming a stable porous structure. The entire process ensures interfacial bonding through aggregate pretreatment, guarantees strength and fluidity through slurry design, achieves lightweight through chemical foaming, and ensures uniform bubble formation through rapid mixing and timely molding. The final product is lightweight, insulating, and utilizes waste materials.

[0013] Preferably, the curing steps include the following: placing the semi-finished blocks in a constant temperature curing chamber at a temperature of 50-70℃ for 12-14 hours under constant temperature and pressure.

[0014] By adopting the above technical solution, during the curing process, the siliceous and calcareous materials in the slurry react to form tobermorite crystals, which have high crystallinity and good stability, resulting in blocks with strength far exceeding that of naturally cured products of the same density. A curing process of 50-70℃ for 12-14 hours maximizes the activity of construction waste and mineral powder, producing high-strength, low-shrinkage, and highly durable high-quality blocks. Under high-pressure steam conditions, the internal structure of the material becomes more dense and uniform, effectively eliminating the risk of later shrinkage and cracking, and greatly improving the product's weathering and impermeability.

[0015] Preferably, the construction waste is composed of recycled construction waste, gypsum, and basalt fiber, and the recycled construction waste includes waste bricks, broken concrete, old bricks and tiles, and old stone.

[0016] By adopting the above technical solutions, recycled construction waste, mainly including waste bricks, broken concrete, old bricks and tiles, and old stone, serves as the main aggregate for lightweight blocks, providing a volumetric framework and structural support, thus realizing the resource-based recycling of construction solid waste. Gypsum-assisted cementitious components can reduce the difficulty of block molding, improve slurry fluidity, and enhance the fire resistance and frost resistance of the blocks. It also works synergistically with subsequent cement and waste mineral powder to enhance overall bonding strength. Basalt fiber reinforcing components can improve the crack resistance and toughness of the blocks, reduce cracks caused by shrinkage during curing, and improve the mechanical stability and service life of the blocks.

[0017] Preferably, the pretreatment of the recycled construction waste includes the following: The recycled construction waste is crushed to a particle size ≤2mm, dispersed in hydrochloric acid solution, stirred for 20-25min, washed with water, then dispersed in sodium hydroxide solution, soaked for 10-15min, washed with water, and calcined at 700-710℃ for 2-3h to obtain a mixture; The mixture is mixed with carbon nanotubes, polyvinyl alcohol and composite glass fiber are added, stirred for 2-3 hours, and dried to obtain recycled construction waste.

[0018] By employing the above technical solution, hydrochloric acid can dissolve the limestone adhering to the surface of waste particles, etch away the loose layer, and clean the pores. Treatment with sodium hydroxide solution provides alkali activation, etching the micropores on the aggregate surface, allowing it to participate in the hydration reaction more quickly and form stronger chemical bonds when subsequently mixed with cement paste. Calcination removes residual water of crystallization and causes a phase transformation of the mineral phases within the waste, generating a highly active amorphous aluminosilicate glass. Simultaneously, organic impurities are burned off, the pore structure is refined, and the specific surface area is increased.

[0019] The calcined mixture is then combined with carbon nanotubes, polyvinyl alcohol (PVA), and composite glass fibers. The carbon nanotubes, acting as a nanoscale reinforcing material, aim to fill microcracks on the aggregate surface and form nanoscale bridging between the macro-aggregate and cement paste, significantly improving the density and strength of the interfacial transition zone. Carbon nanotubes also significantly enhance the fracture toughness and crack resistance of the blocks. PVA, dissolved in water to form a viscous liquid, anchors the carbon nanotubes, preventing them from detaching or agglomerating during subsequent mixing. Furthermore, it firmly adheres the composite glass fibers to the surface of the recycled aggregate. The film-forming properties of PVA create an organic film on the aggregate surface. The composite glass fibers, adhered to the aggregate surface or mixed within the aggregate by PVA, form a three-dimensional network support within the blocks, improving crack resistance and toughness.

[0020] The resulting recycled construction waste surface exhibits both nanoscale carbon nanotubes (filling microcracks) and millimeter-scale glass fibers (for macroscopic crack resistance), forming a perfect reinforcing gradient. Polyvinyl alcohol, as a flexible transition layer, alleviates stress concentration between rigid inorganic aggregates and cement stone, improving interfacial toughness and giving the recycled construction waste good mechanical properties and durability.

[0021] Preferably, the preparation of the composite glass fiber includes the following steps: grinding glass fibers to a length ≤2mm, then dispersing them in a citric acid solution, soaking for 3-5 minutes, washing with water, then dispersing them in deionized water, adding nano-diatomaceous earth and polyacrylate, stirring at a temperature of 60-65℃ for 30-35 minutes, and drying to obtain the composite glass fiber.

[0022] By employing the above technical solution, citric acid solution etches glass fibers, creating uniform micro-pits and etching grooves on the smooth glass fiber surface, which greatly increases the specific surface area and surface roughness of the fibers.

[0023] Diatomaceous earth particles themselves have a rough morphology and a huge specific surface area. During the mixing process, nano-sized diatomaceous earth particles are adsorbed into the pits etched by citric acid solution, forming a rough surface. Polyacrylate emulsion particles fuse to form a continuous organic film, firmly adhering the nano-diatomaceous earth to the fiber surface, forming a composite coating layer. This improves the flexibility and compatibility of glass fibers, preventing brittle fracture. This organic film can physically isolate high-concentration alkaline ions in cement pore liquid, preventing the alkali solution from directly eroding the silica skeleton of glass fibers, fundamentally solving the durability problem of glass fibers in cement. At the same time, it enhances the high-temperature resistance and crack resistance of composite fibers, subsequently improving the reinforcement, toughening, and alkali resistance of blocks.

[0024] Preferably, the waste mineral powder is composed of slag micro powder and sepiolite fiber.

[0025] By adopting the above technical solution, slag powder undergoes a secondary hydration reaction with cement hydration product Ca(OH)2 under autoclaving and high-temperature conditions, generating more hydrated calcium-silica-alumina gel and strengthening the matrix structure. Sepiolite fibers possess excellent high-temperature resistance, adsorption, and mechanical properties, adsorbing onto the surface of the slag powder and acting as micro-reinforcing steel to prevent crack propagation. Furthermore, its fiber network significantly improves the yield stress and thixotropy of the slurry, helping to stabilize bubbles generated by aluminum powder and preventing bubble coalescence and floating.

[0026] The combination of slag micron powder and sepiolite fiber works synergistically. The sepiolite fiber fills the gaps between slag particles, forming a denser packing structure, reducing porosity and increasing strength. During autoclaving, the Ca²⁺ released from the hydrolysis of slag reacts with the nano-SiO₂ on the surface of the sepiolite fiber to generate hydrated calcium silicate. This chemically bonds the fiber to the slag matrix, rather than through simple physical embedding, significantly enhancing interfacial adhesion and thus improving the toughness and crack resistance of the blocks.

[0027] Preferably, the sepiolite fiber is obtained by pretreatment with a silane coupling agent and nano-silica.

[0028] By employing the above technical solution, the silane coupling agent is first hydrolyzed to generate silanol, which then undergoes a dehydration condensation reaction with the hydroxyl groups on the sepiolite surface to form stable covalent bonds. The silane coupling agent is then attached to the sepiolite surface through a grafting reaction, and some coupling agent molecules can enter the nanopores inside the sepiolite, altering its crystal lattice structure. The silane coupling agent exists on the surface of sepiolite nanofibers through both physical coating and chemical bonding. After silane modification, the aggregation behavior of the sepiolite nanofibers is reduced, and the thermal stability of the sepiolite is improved.

[0029] The surface of nano-silica is also rich in hydroxyl groups, which can continue to react with the organic functional groups at the ends of silane coupling agents, or connect to the sepiolite surface through silane molecules as bridges. Utilizing the high specific surface area and high activity of nano-silica, the micropores on the surface of sepiolite fibers are filled, refining the fiber surface structure and simultaneously enhancing the rigidity and wear resistance of the modified layer. It works synergistically with the sepiolite fibers to provide reinforcement, further improving the stability of subsequent coating layers, resulting in sepiolite fibers with comprehensive properties.

[0030] Preferably, the sepiolite fiber is prepared as follows: sepiolite fibers are cut to a length ≤30μm, then dispersed in anhydrous ethanol, washed for 10-12 min, dried, then dispersed in an aqueous solution of silane coupling agent, nano-silica is added, stirred for 1-2 h, and dried to obtain sepiolite fibers.

[0031] By adopting the above technical solution, the natural fibers of sepiolite are relatively short. Excessively long fibers are prone to agglomeration, while excessively short fibers lose their reinforcing effect. ≤10μm fibers fall into the category of short-cut fibers. The aim is to ensure uniform dispersion within the cement matrix while maintaining a certain aspect ratio to bridge cracks. One end of the silane coupling agent (e.g., methoxy / ethoxy) condenses with the hydroxyl groups on the sepiolite surface after hydrolysis, while the other end (e.g., amino, epoxy, etc.) interacts with the cement matrix or polymer, improving the interfacial bond between the fiber and cement.

[0032] Nano-silica was added during silane treatment. The nano-SiO2 surface is rich in hydroxyl groups, which can also react with silane, thus being firmly anchored to the sepiolite surface. The surface roughness of the nano-modified sepiolite fibers is greatly increased, providing stronger mechanical interlocking force when in contact with the cement matrix. At the same time, the nano-SiO2 can chemically react with cement hydration products to achieve chemical bonding.

[0033] The modified sepiolite fiber will play a good role in reinforcing, toughening and interface optimization in the blocks, thereby improving the overall performance of the blocks.

[0034] Preferably, the curing agent is a slag-based composite curing agent.

[0035] By adopting the above technical solution, the active activating component in the slag-based composite curing agent can quickly activate the hydration activity of cement and slag powder, promote the condensation of water glass and the cross-linking of organic components, shorten the initial setting time of the slurry, ensure that the pores of aluminum powder are quickly fixed after foaming, avoid pore merging, collapse and floating, ensure uniform pores and stable structure inside the block, and enhance the overall mechanical strength, toughness and long-term stability of the block.

[0036] Secondly, this application provides the application of lightweight blocks prepared by the method described above for preparing lightweight blocks from construction waste in the preparation of roadbed materials.

[0037] In summary, this application has the following beneficial effects: 1. In this application, the entire process ensures interfacial bonding through aggregate pretreatment, guarantees strength and fluidity through cementitious slurry design, achieves lightweight through chemical foaming, ensures uniform bubble formation through rapid mixing and timely molding, and provides curing. The final product has the characteristics of being lightweight, heat-insulating, and utilizing waste.

[0038] 2. In this application, curing can accelerate hydration, improve early strength, shorten the production cycle, and improve the volume stability and durability of the blocks. During the curing process, the bubbles generated by the aluminum powder are gradually fixed by the hardened slurry, forming a stable porous structure.

[0039] 3. In this application, the grinding of construction waste ensures the uniformity and surface flatness of the blocks, avoiding stress concentration or affecting the foaming effect caused by large particles; waste mineral powder, as an auxiliary cementitious material, undergoes secondary hydration under the activation of cement hydration products, improving the later strength and density, while making use of waste. Detailed Implementation

[0040] The present application will be further described in detail below with reference to the embodiments.

[0041] The raw materials used in the examples and comparative examples are all commercially available.

[0042] Preparation Example 1 Pre-treatment of recycled construction waste includes the following: 10 kg of recycled construction waste was crushed to a particle size ≤ 2 mm, dispersed in 30 L of 2% hydrochloric acid solution, stirred for 25 min, washed with water, then dispersed in 30 L of 4% sodium hydroxide solution, soaked for 15 min, washed with water, and calcined at 710 °C for 3 h to obtain a mixture. The mixture was mixed with 1 kg of carbon nanotubes, 0.9 kg of polyvinyl alcohol and 4 kg of composite glass fiber were added, stirred for 3 hours and dried to obtain recycled construction waste.

[0043] The preparation of composite glass fiber includes the following steps: grinding 5 kg of glass fiber to a length ≤ 2 mm, then dispersing it in 10 L of 5% citric acid solution, soaking for 5 min, washing with water, then dispersing it in 25 L of deionized water, adding 1.5 kg of nano diatomaceous earth and 1 kg of polyacrylate (purchased from Weifang Ruiguang Chemical Co., Ltd.), stirring at 65℃ for 35 min, and drying to obtain composite glass fiber.

[0044] Preparation Example 2 The difference from Preparation Example 1 is that carbon nanotubes are not added during the pretreatment of recycled construction waste.

[0045] Preparation Example 3 The difference from Preparation Example 1 is that polyvinyl alcohol is not added during the pretreatment of recycled construction waste.

[0046] Preparation Example 4 The difference from Preparation Example 1 is that no composite glass fiber is added during the pretreatment of recycled construction waste.

[0047] Preparation Example 5 The difference from Preparation Example 1 is that no nano-diatomite is added in the preparation of the composite glass fiber.

[0048] Preparation Example 6 The difference from Preparation Example 1 is that no polyacrylate is added in the preparation of the composite glass fiber.

[0049] Preparation Example 7 The sepiolite fiber was prepared as follows: 8 kg of sepiolite fiber was cut to a length ≤30 μm, then dispersed in 29 L of anhydrous ethanol, washed for 12 min, dried, and then dispersed in 25 L of 0.3% silane coupling agent KH550 aqueous solution. 1 kg of nano silica was added, stirred for 2 h, and dried to obtain sepiolite fiber.

[0050] Preparation Example 8 The difference from Preparation Example 7 is that no aqueous solution of silane coupling agent is added in the preparation of sepiolite fibers.

[0051] Preparation Example 9 The difference from Preparation Example 7 is that no nano-silica is added in the preparation of sepiolite fibers.

[0052] Example 1 A method for preparing lightweight blocks from construction waste, comprising the following steps: (1) Grind 25kg of construction waste to a particle size of less than 5mm, disperse it in 10L of water, stir for 18min to obtain a mixture, and set aside; (2) Mix 5 kg of cement, 8 kg of waste mineral powder, 0.02 kg of thickener hydroxypropyl methylcellulose, 0.03 kg of dispersant lignin sulfonate (purchased from Jinan Jiayang Chemical Co., Ltd.), 20 L of water and 0.5 kg of curing agent, stir for 7 min to obtain mixture II, and set aside; (3) Mix liquid one and liquid two, add 0.5 kg of chemical foaming agent aluminum powder, stir for 48 s, and pour into a standard brick mold to obtain a semi-finished block; (4) Curing the semi-finished blocks to obtain blocks.

[0053] The curing steps include the following: placing the semi-finished blocks in a constant temperature curing chamber at 60℃ for 12 hours.

[0054] The construction waste consists of recycled construction waste, 6 kg of gypsum, and 5 kg of basalt fiber. The recycled construction waste includes waste bricks, broken concrete, old bricks and tiles, and old stone.

[0055] The waste mineral powder consists of 5 kg of slag powder and sepiolite fiber.

[0056] The curing agent is a slag-based composite curing agent, specifically microsilica powder.

[0057] The pre-treated recycled construction waste was prepared using Preparation Example 1, and the sepiolite fiber was prepared using Preparation Example 7.

[0058] Example 2: A method for preparing lightweight blocks from construction waste, which differs from Example 1 in that no gypsum is added to the construction waste.

[0059] Example 3: A method for preparing lightweight blocks from construction waste, which differs from Example 1 in that basalt fibers are not added to the construction waste.

[0060] Example 4: A method for preparing lightweight blocks from construction waste, which differs from Example 1 in that the pretreatment of the recycled construction waste is carried out in Preparation Example 2.

[0061] Example 5: A method for preparing lightweight blocks from construction waste, which differs from Example 1 in that the pretreatment of the recycled construction waste adopts the method described in Example 3.

[0062] Example 6: A method for preparing lightweight blocks from construction waste, which differs from Example 1 in that the pretreatment of the recycled construction waste adopts the method described in Example 4.

[0063] Example 7: A method for preparing lightweight blocks from construction waste, which differs from Example 1 in that the pretreatment of the recycled construction waste is carried out using Preparation Example 5.

[0064] Example 8: A method for preparing lightweight blocks from construction waste, which differs from Example 1 in that the pretreatment of the recycled construction waste is carried out using Preparation Example 6.

[0065] Example 9: A method for preparing lightweight blocks from construction waste, which differs from Example 1 in that the waste mineral powder is not mixed with sepiolite fiber.

[0066] Example 10: A method for preparing lightweight blocks from construction waste, which differs from Example 1 in that the sepiolite fibers are prepared using Example 8.

[0067] Example 11 A method for preparing lightweight blocks from construction waste, which differs from Example 1 in that the sepiolite fiber is prepared using Example 9.

[0068] Comparative Example 1 A method for preparing lightweight blocks from construction waste, which differs from Example 1 in that no waste mineral powder is added.

[0069] The performance testing experiment was conducted on a method for preparing lightweight blocks from construction waste obtained in Examples 1-11 and Comparative Example 1. Compressive strength test: The blocks are tested in accordance with GB11968 "Autoclaved Aerated Concrete Blocks" to determine the compressive strength of the blocks.

[0070] Freeze-thaw resistance test: The durability of the blocks under freeze-thaw cycle conditions was tested according to GB / T 11969-2020 "Test Method for Performance of Autoclaved Aerated Concrete". The results were determined by the mass loss and strength loss after freezing. The test results are shown in Table 1.

[0071] Table 1 Test data for the examples and comparative examples

[0072] As shown in Table 1, the lightweight blocks prepared from construction waste in Example 1 of this application exhibit good mechanical properties and durability. Specifically, the 7-day compressive strength of Example 1 is 4.1 MPa, and the 28-day compressive strength is 4.5 MPa. In the frost resistance test, the mass loss rate is 0.8%, and the strength loss rate is 3%. Therefore, the lightweight blocks prepared from construction waste in this application possess good mechanical properties. The entire preparation process ensures interfacial bonding through aggregate pretreatment, guarantees strength and fluidity through cementitious slurry design, achieves lightweighting through chemical foaming, and ensures uniform bubble formation through rapid mixing and timely molding. After curing, the final product possesses characteristics such as lightweight, heat insulation, durability, and high strength.

[0073] In Examples 2-3, no gypsum or basalt fiber was added to the construction waste, respectively. Table 1 shows that the 7-day / 28-day compressive strength, frost resistance mass loss rate, and strength loss rate of Examples 2-3 were significantly worse than those of Examples 1-2. This indicates that gypsum-assisted cementitious components can reduce the difficulty of block molding, improve slurry fluidity, and enhance the fire resistance and frost resistance of the blocks. It also works synergistically with subsequent cement and waste mineral powder to strengthen the overall bonding force. The basalt fiber reinforcing component can improve the crack resistance and toughness of the blocks, reduce cracks caused by shrinkage during curing, and improve the mechanical stability and service life of the blocks.

[0074] In Examples 4-6, carbon nanotubes, polyvinyl alcohol (PVA), and composite glass fiber were not added to the pretreatment of recycled construction waste, respectively. Table 1 shows that the mass loss rate and strength loss rate in the 7-day / 28-day compressive strength and frost resistance tests of Examples 4-6 were significantly worse than those of Examples 1-2. This indicates that carbon nanotubes, as nanoscale reinforcing materials, aim to fill microcracks on the aggregate surface and form a nanoscale bridge between the macro-aggregate and cement paste, significantly improving the density and strength of the interface transition zone. Carbon nanotubes significantly improve the fracture toughness and crack resistance of the blocks. The film-forming properties of PVA form an organic film on the aggregate surface, increasing the strength of the blocks. Composite glass fiber is adhered to the aggregate surface or mixed between aggregates by PVA, forming a three-dimensional network support in the blocks, improving crack resistance and toughness.

[0075] In the preparation of composite glass fibers in Examples 7-8, neither nano-diatomite nor polyacrylate was added. As shown in Table 1, the test results for 7-day / 28-day compressive strength, frost resistance, mass loss rate, and strength loss rate in Examples 7-8 were significantly worse than those in Examples 1-2. This indicates that the polyacrylate emulsion particles fuse to form a continuous organic film, firmly adhering the nano-diatomite to the fiber surface, forming a composite coating layer. This solves the durability problem of glass fibers in cement, improves the high-temperature resistance and crack resistance of the composite fibers, and subsequently enhances the reinforcement, toughening, and alkali resistance of the blocks.

[0076] In Example 9, no sepiolite fiber was added to the waste mineral powder. As can be seen from Table 1, the test results of 7-day / 28-day compressive strength, frost resistance, mass loss rate, and strength loss rate of Example 9 were significantly worse than those of Examples 1-2. This indicates that sepiolite fiber has excellent high temperature resistance, adsorption, and mechanical properties. It is adsorbed on the surface of slag powder and acts as a micro-reinforcing steel, preventing crack propagation and improving the overall performance of slag powder.

[0077] In Examples 10-11, no aqueous solution of silane coupling agent or nano-silica was added during the preparation of sepiolite fibers. Table 1 shows that the mass loss rate and strength loss rate in the 7-day / 28-day compressive strength and freeze-thaw resistance tests of Examples 10-11 were significantly worse than those of Examples 1-2. This indicates that the silane coupling agent and nano-silica work synergistically. After silane modification, the agglomeration behavior of the sepiolite nanofibers is reduced, and the thermal stability of sepiolite is improved. The high specific surface area and high activity of nano-silica fill the micropores on the surface of the sepiolite fibers, enhancing the rigidity and wear resistance of the modified layer. It works synergistically with the sepiolite fibers to further improve the stability of the subsequent coating layer, resulting in sepiolite fibers with comprehensive properties.

[0078] Comparative Example 1 did not include waste mineral powder. As shown in Table 1, the test results for 7-day / 28-day compressive strength, frost resistance mass loss rate, and strength loss rate of Comparative Example 1 were significantly worse than those of Examples 1-2. This indicates that waste mineral powder, as an auxiliary cementitious material, undergoes secondary hydration under the activation of cement hydration products, improving later-stage strength and density, and subsequently altering the corresponding properties of the blocks.

[0079] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A method for preparing lightweight blocks from construction waste, characterized in that, Includes the following steps: (1) Grind the construction waste, disperse it in water, stir for 15-20 minutes to obtain a mixture, and set aside; (2) Mix cement, waste mineral powder, thickener, dispersant, water and curing agent, stir for 6-9 minutes to obtain mixture two, and set aside; (3) Mix liquid one and liquid two, add aluminum powder as a chemical foaming agent, stir for 45-50s, and pour into a standard brick mold to obtain a semi-finished block product; (4) Curing the semi-finished blocks to obtain blocks.

2. The method for preparing lightweight blocks from construction waste according to claim 1, characterized in that, The curing steps include the following: placing the semi-finished blocks in a constant temperature curing chamber at a temperature of 50-70℃ for 12-14 hours.

3. The method for preparing lightweight blocks from construction waste according to claim 1, characterized in that, The construction waste consists of recycled construction waste, gypsum, and basalt fiber. The recycled construction waste includes waste bricks, broken concrete, old bricks and tiles, and old stone.

4. A method for preparing lightweight blocks from construction waste according to claim 3, characterized in that, The pretreatment of recycled construction waste includes the following: The recycled construction waste is crushed to a particle size ≤2mm, dispersed in hydrochloric acid solution, stirred for 20-25min, washed with water, then dispersed in sodium hydroxide solution, soaked for 10-15min, washed with water, and calcined at 700-710℃ for 2-3h to obtain a mixture; The mixture is mixed with carbon nanotubes, polyvinyl alcohol and composite glass fiber are added, stirred for 2-3 hours, and dried to obtain recycled construction waste.

5. A method for preparing lightweight blocks from construction waste according to claim 4, characterized in that, The preparation of the composite glass fiber includes the following steps: grinding glass fibers to a length ≤2mm, then dispersing them in a citric acid solution, soaking for 3-5 minutes, washing with water, then dispersing them in deionized water, adding nano-diatomaceous earth and polyacrylate, stirring at a temperature of 60-65℃ for 30-35 minutes, and drying to obtain the composite glass fiber.

6. The method for preparing lightweight blocks from construction waste according to claim 1, characterized in that, The waste mineral powder is composed of slag powder and sepiolite fiber.

7. A method for preparing lightweight blocks from construction waste according to claim 1, characterized in that, The sepiolite fiber was obtained by pretreatment with silane coupling agent and nano-silica.

8. A method for preparing lightweight blocks from construction waste according to claim 7, characterized in that, The sepiolite fiber was prepared as follows: sepiolite fibers were cut to a length ≤30μm, then dispersed in anhydrous ethanol, washed for 10-12 min, dried, then dispersed in an aqueous solution of silane coupling agent, nano-silica was added, stirred for 1-2 h, and dried to obtain sepiolite fibers.

9. A method for preparing lightweight blocks from construction waste according to claim 1, characterized in that, The curing agent is a slag-based composite curing agent.

10. The use of lightweight blocks prepared by the method for preparing lightweight blocks from construction waste as described in any one of claims 1-9 in the preparation of roadbed materials.

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