Method for recycling and reusing urban construction waste to prepare building materials

Abstract

The application relates to the field of building materials, in particular to a method for preparing building materials from recycled urban construction waste, wherein amorphous silicon dioxide, an ionic liquid, sodium hydroxide and water are mixed and heated to 60-80 DEG C, insoluble substances are removed after stirring and reaction, the pH is adjusted to 9-10 to obtain an active silicon solution, recycled aggregates are impregnated with the active silicon solution, and then added to a sodium metaaluminate solution for stirring and reaction, and the solid is collected and dried, the prepared recycled building materials are used for preparing concrete with extremely high mechanical strength, the performance of the recycled aggregates can be essentially improved, waste is turned into treasure, and the method has positive significance for developing urban construction waste recycling.

Description

Technical Field

[0001] This invention relates to the field of building materials, specifically to a method for preparing building materials by recycling and reusing urban construction waste. Background Technology

[0002] my country's annual construction waste production exceeds 3 billion tons, with waste concrete accounting for over 70%. Crushing and screening waste concrete to prepare recycled coarse aggregate is the main approach to resource utilization. However, the surface of recycled aggregate is covered with 30-50% old hardened cement mortar, resulting in an interfacial bond strength with the cement paste that is only 40-60% of that of natural aggregate, severely limiting its application in concrete. Currently, chemical modification of recycled aggregate often involves dissolving the old mortar with strong acids such as sulfuric acid. While this can reduce water absorption and improve the interfacial bond with the cement paste, this method only removes the old mortar without generating a reinforcing phase, and its own strength loss rate is high. Vacuum impregnation treatment with nano-silica or nano-calcium carbonate solutions can strengthen recycled aggregate, but nanoparticles are prone to agglomeration and have difficulty penetrating internal micropores, and the improvement in the interfacial bond performance between recycled aggregate and cement paste is relatively small. Summary of the Invention

[0003] Purpose of the invention: In view of the above-mentioned technical problems, the present invention proposes a method for recycling and reusing urban construction waste to prepare building materials.

[0004] The technical solution adopted is as follows: A method for recycling and reusing urban construction waste to prepare building materials is as follows: Urban construction waste treated with silane coupling agent is immersed in a leaching solution, ultrasonically treated, and the solids are collected to obtain recycled aggregate. Amorphous silica, ionic liquid, sodium hydroxide and water are mixed and heated to 60-80℃. After stirring and reacting, the insoluble matter is removed by filtration, and the pH is adjusted to 9-10 to obtain an active silica solution. After impregnating the recovered aggregate with an active silica solution, it is then added to a sodium aluminate solution and stirred to react. The solid is then collected and dried.

[0005] Furthermore, the urban construction waste is concrete discarded at urban building demolition sites that has been mechanically crushed, washed and graded, then screened into two particle sizes: 5-16mm and 16-31.5mm, and then mixed and compounded in a 1:1 mass ratio.

[0006] Furthermore, the dissolution solution comprises tartaric acid, disodium ethylenediaminetetraacetate, and a penetrant, and the pH is adjusted to 11-12 with sodium hydroxide.

[0007] The molecular structure of silane coupling agents (such as KH-550, KH-560, and KH-570) contains both inorganic and organic groups. This bifunctional structure enables them to form "molecular bridges" between the dissolved chelated calcium ions and the pores inside the construction waste. This chemical bonding retains the chelated calcium ions in the pores inside the construction waste, reducing their entry into the leaching solution. This lays the foundation for subsequent heterogeneous nucleation of hydrated calcium silicate gel, achieving a closed loop of "repairing its own defects with the calcium and aluminum resources of the aggregate itself".

[0008] Tartaric acid is a hydroxycarboxylic acid chelating agent. Although its chelating ability for calcium ions is weaker than that of disodium ethylenediaminetetraacetate (EDTA), it has a retarding effect. This retarding effect is significant in reducing the thermal stress caused by the heat of hydration within the recycled aggregate, preventing calcium ion loss due to cracks, prolonging the reaction time between disodium ethylenediaminetetraacetate and calcium ions, and improving dissolution efficiency. Furthermore, the hydroxyl groups of tartaric acid can form weak complexes with calcium ions, assisting the chelating effect of disodium ethylenediaminetetraacetate. Disodium ethylenediaminetetraacetate is a multidentate chelating agent; its amino and carboxyl groups can form stable chelates with calcium ions. This chelating effect is highly selective. Under alkaline conditions, disodium ethylenediaminetetraacetate preferentially binds to calcium ions without significantly complexing magnesium or aluminum ions. This selectivity stems from the high matching degree between the ionic radius of calcium ions and the chelating cavity of disodium ethylenediaminetetraacetate, while other ions have larger differences in radius or charge density, making it difficult to form stable chelates.

[0009] Penetrants can enhance penetration and promote calcium ion contact, enabling the mixed solution of disodium EDTA and tartaric acid to penetrate deeply into the pores and capillaries inside the recycled aggregate. The internal structure of recycled aggregate is complex, and penetrants can transport disodium EDTA and tartaric acid to these areas, where they react with calcium ions that are normally difficult to access, thereby increasing the dissolution rate of calcium ions.

[0010] Furthermore, the mass ratio of tartaric acid, disodium ethylenediaminetetraacetate, and penetrant is 80-100:3-6:1-2.

[0011] Furthermore, the ionic liquid is a hydroxyl-functionalized ionic liquid.

[0012] Furthermore, the hydroxyl-functionalized ionic liquid is obtained by reacting N-methylimidazolium with chlorinated fatty alcohols.

[0013] Furthermore, the chlorinated fatty alcohol is any one or any combination of two or more of 2-chloroethanol, 3-chloropropanol, 4-chlorobutanol, 5-chloropentanol, and 6-chlorohexanol.

[0014] Furthermore, the mass ratio of the amorphous silica, ionic liquid, and sodium hydroxide is 20-40:3-6:60-80.

[0015] Furthermore, vacuum-pressure impregnation is used when impregnating recycled aggregates with active silica solution.

[0016] Furthermore, the vacuum-pressure impregnation cycle is greater than or equal to 3 times.

[0017] The beneficial effects of this invention are: This invention provides a method for recycling and reusing urban construction waste to prepare building materials. This invention selectively dissolves calcium ions in old cement mortar through weak acid complexation without damaging the aggregate itself, laying the foundation for subsequent heterogeneous nucleation of hydrated calcium silicate gel, and realizing a closed loop of "using the aggregate's own calcium and aluminum resources to repair its own defects".

[0018] Ionic liquids weaken the Si-O bond energy by interacting with the σ antibonding orbitals of silicate ions through the π electrons of the imidazole ring, thus shifting the hydrolysis equilibrium of silicate ions towards the formation of [SiO(OH)3]. - The [SiO(OH)3] moves in the direction of [SiO(OH)3] and is coated with it through hydrogen bonding. - The surface prevents them from colliding and self-aggregating. After penetrating into the pores of the recycled aggregate through impregnation, [SiO(OH)3]... - It reacts with chelated calcium ions to form hydrated calcium silicate gel, which reinforces the recycled aggregate. Sodium aluminate impregnation can further react with [SiO(OH)3]. - Copolymerization produces sodium aluminum silicate hydrate gel, thereby improving the strength of recycled aggregates through dual-gel self-assembly.

[0019] The recycled building materials prepared by this invention produce concrete with extremely high mechanical strength, achieving a fundamental improvement in the performance of recycled aggregates. Moreover, it turns waste into treasure, which is of positive significance for the development of urban construction waste recycling and reuse. Detailed Implementation

[0020] Unless otherwise specified in the examples, the conditions were performed under standard conditions or as recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products. Techniques not mentioned in this invention refer to existing technologies. Unless otherwise specified, the following examples and comparative examples are parallel experiments, using the same processing steps and parameters.

[0021] Example 1: A method for recycling and reusing urban construction waste to produce building materials: Waste concrete from urban building demolition sites is mechanically crushed, washed, and graded, then screened into two particle sizes: 5-16mm and 16-31.5mm. These are then mixed in a 1:1 mass ratio to obtain urban construction waste. KH-550 is dissolved in an ethanol-water mixture (ethanol:water volume ratio 4:1) to prepare a 10% mass fraction solution. The pH of the solution is adjusted to 1 with acetic acid, and after stirring for 15 minutes, the urban construction waste is added to the solution at a solid-liquid mass ratio of 1:10 to ensure the particles remain intact. The aggregate was fully submerged, stirred with a stirrer for 1 hour, and then allowed to stand for 24 hours. The solid was then filtered out and dried. The solid was then added to the dissolution solution at a solid-liquid mass ratio of 1:10. The dissolution solution was prepared by mixing DL-tartaric acid, disodium ethylenediaminetetraacetate, penetrant JFC, and water at a mass ratio of 80:4.5:1.5:1000 to obtain a homogeneous solution. The pH was then adjusted to 11-12 with 1M sodium hydroxide solution. After ultrasonic vibration treatment at 45℃ for 2 hours, the aggregate was filtered, the solid was collected, and washed with cold water to obtain the recovered aggregate. The recovered aggregate was placed in a dark place for later use. Amorphous silica, 1-hydroxyethyl-3-methylimidazolium chloride, sodium hydroxide, and water were mixed in a mass ratio of 30:5:70:350 and heated to 70°C. After stirring for 2 hours, the mixture was filtered to remove insoluble matter. The pH was then adjusted to 9.5 with hydrochloric acid to obtain an activated silica solution. The aggregate was recovered by impregnating it with the activated silica solution at room temperature using a vacuum-pressure impregnation method. The vacuum-pressure impregnation cycle was repeated 3 times. The vacuum stage had a vacuum degree of -0.08 MPa for 15 minutes, and the pressure stage had a vacuum degree of 0.3 MPa for 15 minutes. The solid was then collected and added to a 10% sodium aluminate solution at a solid-liquid mass ratio of 1:10. The mixture was stirred for 2 hours. Finally, the mixture was filtered, and the collected solid was dried.

[0022] Example 2: A method for recycling and reusing urban construction waste to produce building materials: Waste concrete from urban demolition sites is mechanically crushed, washed, and graded, then screened into two particle sizes: 5-16mm and 16-31.5mm. These are then mixed in a 1:1 mass ratio to obtain urban construction waste. KH-550 is dissolved in an ethanol-water mixture (ethanol:water volume ratio 4:1) to prepare a 10% mass fraction solution. The pH of the solution is adjusted to 1 with acetic acid, and after stirring for 15 minutes, the urban construction waste is added to the solution, with a solid-liquid mass ratio of 1:10, ensuring particle size distribution. Completely submerge the aggregate, stir with a stirrer for 1 hour, and then let it stand for 24 hours. Filter out the solid and dry it. Then add it to the dissolution solution at a solid-liquid mass ratio of 1:10. The dissolution solution is a homogeneous solution obtained by mixing DL-tartaric acid, disodium ethylenediaminetetraacetate, penetrant JFC and water at a mass ratio of 100:6:2:1000. Then adjust the pH to 11-12 with 1M sodium hydroxide solution, ultrasonically vibrate at 45℃ for 2 hours, filter, collect the solid and rinse with cold water to obtain the recovered aggregate. Place the recovered aggregate in a dark place for later use. Amorphous silica, 1-hydroxyethyl-3-methylimidazolium chloride, sodium hydroxide, and water were mixed in a mass ratio of 40:6:80:350 and heated to 80°C. After stirring for 2 hours, the mixture was filtered to remove insoluble matter. The pH was then adjusted to 9.5 with hydrochloric acid to obtain an activated silica solution. The aggregate was recovered by impregnating it with the activated silica solution at room temperature using a vacuum-pressure impregnation method. The vacuum-pressure impregnation cycle was repeated 3 times. The vacuum stage had a vacuum degree of -0.08 MPa and a time of 15 minutes, while the pressure stage had a vacuum degree of 0.3 MPa and a time of 15 minutes. The solid was then collected and added to a 10% sodium aluminate solution at a solid-liquid mass ratio of 1:10. The mixture was stirred for 2 hours. Finally, the mixture was filtered, and the collected solid was dried.

[0023] Example 3: A method for recycling and reusing urban construction waste to produce building materials: Waste concrete from urban demolition sites is mechanically crushed, washed, and graded, then screened into two particle sizes: 5-16mm and 16-31.5mm. These are then mixed in a 1:1 mass ratio to obtain urban construction waste. KH-550 is dissolved in an ethanol-water mixture (ethanol:water volume ratio 4:1) to prepare a 10% mass fraction solution. The pH of the solution is adjusted to 1 with acetic acid, and after stirring for 15 minutes, the urban construction waste is added to the solution, with a solid-liquid mass ratio of 1:10, ensuring the particle size distribution is optimal. The particles were completely submerged and stirred with a stirrer for 1 hour, then allowed to stand and soak for 24 hours. The solid was then filtered out and dried, and added to the dissolution solution at a solid-liquid mass ratio of 1:10. The dissolution solution was prepared by mixing DL-tartaric acid, disodium ethylenediaminetetraacetate, penetrant JFC, and water at a mass ratio of 80:3:1:1000 to obtain a homogeneous solution. The pH was then adjusted to 11-12 with 1M sodium hydroxide solution, and the mixture was ultrasonically vibrated at 45℃ for 2 hours. After filtration, the solid was collected and rinsed with cold water to obtain the recovered aggregate. The recovered aggregate was placed in a dark place for later use. Amorphous silica, 1-hydroxyethyl-3-methylimidazolium chloride, sodium hydroxide, and water were mixed in a mass ratio of 20:3:60:350 and heated to 60°C. After stirring for 2 hours, the mixture was filtered to remove insoluble matter. The pH was then adjusted to 9.5 with hydrochloric acid to obtain an activated silica solution. The aggregate was recovered by impregnating it with the activated silica solution at room temperature using a vacuum-pressure impregnation method. The vacuum-pressure impregnation cycle was repeated 3 times. The vacuum stage had a vacuum degree of -0.08 MPa and a time of 15 minutes, while the pressure stage had a vacuum degree of 0.3 MPa and a time of 15 minutes. The solid was then collected and added to a 10% sodium aluminate solution at a solid-liquid mass ratio of 1:10. The mixture was stirred for 2 hours, and the solid was collected and dried.

[0024] Example 4: A method for recycling and reusing urban construction waste to produce building materials: Waste concrete from urban demolition sites is mechanically crushed, washed, and graded, then screened into two particle sizes: 5-16mm and 16-31.5mm. These are then mixed in a 1:1 mass ratio to obtain urban construction waste. KH-550 is dissolved in an ethanol-water mixture (ethanol:water volume ratio 4:1) to prepare a 10% mass fraction solution. The pH of the solution is adjusted to 1 with acetic acid, and after stirring for 15 minutes, the urban construction waste is added to the solution, with a solid-liquid mass ratio of 1:10, ensuring particle size distribution. Completely submerge the aggregate, stir with a stirrer for 1 hour, and then let it stand for 24 hours. Filter out the solid and dry it. Then add it to the dissolution solution at a solid-liquid mass ratio of 1:10. The dissolution solution is a homogeneous solution obtained by mixing DL-tartaric acid, disodium ethylenediaminetetraacetate, penetrant JFC and water at a mass ratio of 100:3:2:1000. Then adjust the pH to 11-12 with 1M sodium hydroxide solution, ultrasonically vibrate at 45℃ for 2 hours, filter, collect the solid and rinse with cold water to obtain the recovered aggregate. Place the recovered aggregate in a dark place for later use. Amorphous silica, 1-hydroxyethyl-3-methylimidazolium chloride, sodium hydroxide, and water were mixed in a mass ratio of 20:6:60:350 and heated to 80°C. After stirring for 2 hours, the mixture was filtered to remove insoluble matter. The pH was then adjusted to 9.5 with hydrochloric acid to obtain an activated silica solution. The aggregate was recovered by impregnating it with the activated silica solution at room temperature using a vacuum-pressure impregnation method. The vacuum-pressure impregnation cycle was repeated 3 times. The vacuum stage had a vacuum degree of -0.08 MPa and a time of 15 minutes, while the pressure stage had a vacuum degree of 0.3 MPa and a time of 15 minutes. The solid was then collected and added to a 10% sodium aluminate solution at a solid-liquid mass ratio of 1:10. The mixture was stirred for 2 hours. Finally, the mixture was filtered, and the collected solid was dried.

[0025] Example 5: A method for recycling and reusing urban construction waste to produce building materials: Waste concrete from urban demolition sites is mechanically crushed, washed, and graded, then screened into two particle sizes: 5-16mm and 16-31.5mm. These are then mixed in a 1:1 mass ratio to obtain urban construction waste. KH-550 is dissolved in an ethanol-water mixture (ethanol:water volume ratio 4:1) to prepare a 10% mass fraction solution. The pH of the solution is adjusted to 1 with acetic acid, and after stirring for 15 minutes, the urban construction waste is added to the solution, with a solid-liquid mass ratio of 1:10, ensuring the particle size distribution is optimal. The particles were completely submerged and stirred with a stirrer for 1 hour, then allowed to stand and soak for 24 hours. The solid was then filtered out and dried, and added to the dissolution solution at a solid-liquid mass ratio of 1:10. The dissolution solution was prepared by mixing DL-tartaric acid, disodium ethylenediaminetetraacetate, penetrant JFC, and water at a mass ratio of 80:6:1:1000 to obtain a homogeneous solution. The pH was then adjusted to 11-12 with 1M sodium hydroxide solution, and the mixture was ultrasonically vibrated at 45℃ for 2 hours. After filtration, the solid was collected and rinsed with cold water to obtain the recovered aggregate. The recovered aggregate was placed in a dark place for later use. Amorphous silica, 1-hydroxyethyl-3-methylimidazolium chloride, sodium hydroxide, and water were mixed in a mass ratio of 40:3:80:350 and heated to 60°C. After stirring for 2 hours, the mixture was filtered to remove insoluble matter. The pH was then adjusted to 9.5 with hydrochloric acid to obtain an activated silica solution. The aggregate was recovered by impregnating it with the activated silica solution at room temperature using a vacuum-pressure impregnation method. The vacuum-pressure impregnation cycle was repeated 3 times. The vacuum stage had a vacuum degree of -0.08 MPa and a time of 15 minutes, while the pressure stage had a vacuum degree of 0.3 MPa and a time of 15 minutes. The solid was then collected and added to a 10% sodium aluminate solution at a solid-liquid mass ratio of 1:10. The mixture was stirred for 2 hours. Finally, the mixture was filtered, and the collected solid was dried.

[0026] Comparative Example 1: The process is essentially the same as in Example 1, except that the urban construction waste was not treated with the silane coupling agent KH-550.

[0027] A method for recycling and reusing urban construction waste to produce building materials: The waste concrete from urban building demolition sites is mechanically crushed, washed, and graded, then screened into two particle sizes: 5-16mm and 16-31.5mm. These two sizes are then mixed in a 1:1 mass ratio to obtain urban construction waste. The urban construction waste is added to a leachate solution with a solid-liquid mass ratio of 1:10. The leachate solution is a homogeneous solution obtained by mixing DL-tartaric acid, disodium ethylenediaminetetraacetate, penetrant JFC, and water in a mass ratio of 80:4.5:1.5:1000. The pH is then adjusted to 11-12 with 1M sodium hydroxide solution, and the mixture is ultrasonically vibrated at 45℃ for 2 hours. After filtration, the solid is collected and washed with cold water to obtain recycled aggregate. The recycled aggregate is then placed in a dark place for later use. Amorphous silica, 1-hydroxyethyl-3-methylimidazolium chloride, sodium hydroxide, and water were mixed in a mass ratio of 30:5:70:350 and heated to 70°C. After stirring for 2 hours, the mixture was filtered to remove insoluble matter. The pH was then adjusted to 9.5 with hydrochloric acid to obtain an activated silica solution. The aggregate was recovered by impregnating it with the activated silica solution at room temperature using a vacuum-pressure impregnation method. The vacuum-pressure impregnation cycle was repeated 3 times. The vacuum stage had a vacuum degree of -0.08 MPa for 15 minutes, and the pressure stage had a vacuum degree of 0.3 MPa for 15 minutes. The solid was then collected and added to a 10% sodium aluminate solution at a solid-liquid mass ratio of 1:10. The mixture was stirred for 2 hours. Finally, the mixture was filtered, and the collected solid was dried.

[0028] Comparative Example 2: It is basically the same as Example 1, except that the urban construction waste was not treated with leachate.

[0029] A method for recycling and reusing urban construction waste to produce building materials: The waste concrete from urban building demolition sites is mechanically crushed, washed, and graded, then screened into two particle sizes: 5-16mm and 16-31.5mm. These two sizes are then mixed and compounded in a 1:1 mass ratio to obtain urban construction waste. KH-550 is dissolved in an ethanol-water mixture (ethanol:water volume ratio 4:1) to prepare a 10% mass fraction solution. The pH of the solution is adjusted to 1 with acetic acid, and after stirring for 15 minutes, the urban construction waste is added to the solution at a solid-liquid mass ratio of 1:10 to ensure that the particles are completely submerged. The mixture is stirred for 1 hour and then allowed to stand for 24 hours. The solid is then filtered out and dried to obtain recycled aggregate. Amorphous silica, 1-hydroxyethyl-3-methylimidazolium chloride, sodium hydroxide, and water were mixed in a mass ratio of 30:5:70:350 and heated to 70°C. After stirring for 2 hours, the mixture was filtered to remove insoluble matter. The pH was then adjusted to 9.5 with hydrochloric acid to obtain an activated silica solution. The aggregate was recovered by impregnating it with the activated silica solution at room temperature using a vacuum-pressure impregnation method. The vacuum-pressure impregnation cycle was repeated 3 times. The vacuum stage had a vacuum degree of -0.08 MPa for 15 minutes, and the pressure stage had a vacuum degree of 0.3 MPa for 15 minutes. The solid was then collected and added to a 10% sodium aluminate solution at a solid-liquid mass ratio of 1:10. The mixture was stirred for 2 hours. Finally, the mixture was filtered, and the collected solid was dried.

[0030] Comparative Example 3: It is basically the same as Example 1, except that 1-hydroxyethyl-3-methylimidazolium chloride is not added.

[0031] A method for recycling and reusing urban construction waste to produce building materials: Waste concrete from urban building demolition sites is mechanically crushed, washed, and graded, then screened into two particle sizes: 5-16mm and 16-31.5mm. These are then mixed in a 1:1 mass ratio to obtain urban construction waste. KH-550 is dissolved in an ethanol-water mixture (ethanol:water volume ratio 4:1) to prepare a 10% mass fraction solution. The pH of the solution is adjusted to 1 with acetic acid, and after stirring for 15 minutes, the urban construction waste is added to the solution at a solid-liquid mass ratio of 1:10 to ensure the particles remain intact. The aggregate was fully submerged, stirred with a stirrer for 1 hour, and then allowed to stand for 24 hours. The solid was then filtered out and dried. The solid was then added to the dissolution solution at a solid-liquid mass ratio of 1:10. The dissolution solution was prepared by mixing DL-tartaric acid, disodium ethylenediaminetetraacetate, penetrant JFC, and water at a mass ratio of 80:4.5:1.5:1000 to obtain a homogeneous solution. The pH was then adjusted to 11-12 with 1M sodium hydroxide solution. After ultrasonic vibration treatment at 45℃ for 2 hours, the aggregate was filtered, the solid was collected, and washed with cold water to obtain the recovered aggregate. The recovered aggregate was placed in a dark place for later use. Amorphous silica, sodium hydroxide, and water in a mass ratio of 30:70:350 were mixed and heated to 70°C. After stirring for 2 hours, the mixture was filtered to remove insoluble matter. The pH was then adjusted to 9.5 with hydrochloric acid to obtain an activated silica solution. The aggregate was recovered by impregnating it with the activated silica solution at room temperature using a vacuum-pressure impregnation method. The vacuum-pressure impregnation cycle was repeated 3 times. The vacuum stage had a vacuum degree of -0.08 MPa and a time of 15 minutes, while the pressure stage had a vacuum degree of 0.3 MPa and a time of 15 minutes. The solid was then collected and added to a 10% sodium aluminate solution at a solid-liquid mass ratio of 1:10. The mixture was stirred for 2 hours. Finally, the mixture was filtered, and the collected solid was dried.

[0032] Comparative Example 4: It is basically the same as Example 1, except that it is not treated with sodium aluminate solution.

[0033] A method for recycling and reusing urban construction waste to produce building materials: Waste concrete from urban building demolition sites is mechanically crushed, washed, and graded, then screened into two particle sizes: 5-16mm and 16-31.5mm. These are then mixed in a 1:1 mass ratio to obtain urban construction waste. KH-550 is dissolved in an ethanol-water mixture (ethanol:water volume ratio 4:1) to prepare a 10% mass fraction solution. The pH of the solution is adjusted to 1 with acetic acid, and after stirring for 15 minutes, the urban construction waste is added to the solution at a solid-liquid mass ratio of 1:10 to ensure the particles remain intact. The aggregate was fully submerged, stirred with a stirrer for 1 hour, and then allowed to stand for 24 hours. The solid was then filtered out and dried. The solid was then added to the dissolution solution at a solid-liquid mass ratio of 1:10. The dissolution solution was prepared by mixing DL-tartaric acid, disodium ethylenediaminetetraacetate, penetrant JFC, and water at a mass ratio of 80:4.5:1.5:1000 to obtain a homogeneous solution. The pH was then adjusted to 11-12 with 1M sodium hydroxide solution. After ultrasonic vibration treatment at 45℃ for 2 hours, the aggregate was filtered, the solid was collected, and washed with cold water to obtain the recovered aggregate. The recovered aggregate was placed in a dark place for later use. Amorphous silica, 1-hydroxyethyl-3-methylimidazolium chloride, sodium hydroxide, and water were mixed in a mass ratio of 30:5:70:350 and heated to 70°C. After stirring for 2 hours, the mixture was filtered to remove insoluble matter. The pH was then adjusted to 9.5 with hydrochloric acid to obtain an activated silica solution. The aggregate was recovered by impregnating it with the activated silica solution at room temperature using a vacuum-pressure impregnation method. The vacuum-pressure impregnation cycle was repeated 3 times. The vacuum stage had a vacuum degree of -0.08 MPa and a time of 15 min, while the pressure stage had a vacuum degree of 0.3 MPa and a time of 15 min. The solid was then collected and dried.

[0034] Comparative Example 5: It is basically the same as Example 1, except that commercially available nano silica sol (Xuancheng Jingrui New Materials) is used for treatment.

[0035] A method for recycling and reusing urban construction waste to produce building materials: Waste concrete from urban building demolition sites is mechanically crushed, washed, and graded, then screened into two particle sizes: 5-16mm and 16-31.5mm. These are then mixed in a 1:1 mass ratio to obtain urban construction waste. KH-550 is dissolved in an ethanol-water mixture (ethanol:water volume ratio 4:1) to prepare a 10% mass fraction solution. The pH of the solution is adjusted to 1 with acetic acid, and after stirring for 15 minutes, the urban construction waste is added to the solution at a solid-liquid mass ratio of 1:10 to ensure the particles remain intact. The aggregate was fully submerged, stirred for 1 hour, and then allowed to stand for 24 hours. The solid was then filtered out and dried. The solid was then added to a dissolution solution at a solid-liquid mass ratio of 1:10. The dissolution solution was a homogeneous solution obtained by mixing DL-tartaric acid, disodium ethylenediaminetetraacetate, penetrant JFC, and water at a mass ratio of 80:4.5:1.5:1000. The pH was adjusted to 11-12 with 1M sodium hydroxide solution, and the mixture was ultrasonically vibrated at 45℃ for 2 hours. After filtration, the solid was collected and rinsed with cold water to obtain recovered aggregate. The recovered aggregate was then stored in a dark place for later use. A vacuum-pressure impregnation method was used. Commercially available nano-silica sol was used to impregnate the recovered aggregate at room temperature. The vacuum-pressure impregnation cycle was 3 times. The vacuum stage had a vacuum degree of -0.08 MPa for 15 minutes, and the pressure stage had a vacuum degree of 0.3 MPa for 15 minutes. The solid was then collected and dried.

[0036] Performance testing Concrete was prepared from the samples prepared in Examples 1-5 and Comparative Examples 1-5 of the present invention according to the following formula: 350 kg of silicate cement, 70 kg of Class II amorphous silica, 825 kg of sample, 720 kg of river sand, 7.5 kg of polycarboxylate superplasticizer, and 189 kg of water.

[0037] The compressive strength of the concrete prepared above was tested in accordance with GB / T50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete". The test results are shown in Table 1.

[0038] As can be seen from Examples 1-5 in Table 1 above, the concrete prepared using the recycled building materials of the present invention has extremely high mechanical strength.

[0039] The comparison between Example 1 and Comparative Example 1 shows that the mechanical strength of concrete prepared from urban construction waste treated with silane coupling agent KH-550 can be effectively improved. The reason may be that the silane coupling agent can reduce the loss of chelated calcium ions into the leaching solution, increase the amount of subsequent hydrated calcium silicate gel and sodium aluminum silicate hydrate gel, and improve the strengthening effect.

[0040] The comparison between Example 1 and Comparative Example 2 shows that the urban construction waste was not treated with leaching solution, and the old cement mortar on the surface and inside of the urban construction waste did not change, resulting in low mechanical strength of the prepared concrete.

[0041] A comparison of Example 1 and Comparative Example 3 shows that the ionic liquid weakens the Si-O bond energy through the interaction of the π electrons of the imidazole ring with the σ antibonding orbitals of the silicate ion, thus pushing the hydrolysis equilibrium of the silicate ion towards the formation of [SiO(OH)3]. - The direction of movement is [SiO(OH)3]. - CSH formed by chelating calcium ions has a high degree of polymerization and a dense structure, while CSH formed by silicate ions and chelated calcium ions has low strength, weak interlayer bonding, and poor reinforcing effect.

[0042] A comparison of Example 1 and Comparative Example 4 shows that sodium aluminate impregnation can further react with [SiO(OH)3]. - Copolymerization produces sodium aluminum silicate hydrate gel, thereby improving the strength of recycled aggregates through double gel self-assembly. Therefore, sodium aluminate impregnation can enhance the mechanical strength of concrete prepared from recycled building materials.

[0043] A comparison of Example 1 and Comparative Example 5 shows that the recycled building material prepared by the present invention has better performance than the recycled building material obtained by nano-silica sol treatment.

[0044] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for recycling and reusing urban construction waste to prepare building materials, characterized in that, Specifically as follows: Urban construction waste treated with silane coupling agent is immersed in a leaching solution, ultrasonically treated, and the solids are collected to obtain recycled aggregate. Amorphous silica, ionic liquid, sodium hydroxide and water are mixed and heated to 60-80℃. After stirring and reacting, the insoluble matter is removed by filtration, and the pH is adjusted to 9-10 to obtain an active silica solution. After impregnating the recovered aggregate with an active silica solution, it is then added to a sodium aluminate solution and stirred to react. The solid is then collected and dried. The dissolution solution includes tartaric acid, disodium ethylenediaminetetraacetate and a penetrant, and the pH is adjusted to 11-12 with sodium hydroxide. The ionic liquid is a hydroxyl-functionalized ionic liquid; The hydroxyl-functionalized ionic liquid is obtained by reacting N-methylimidazolium with chlorinated fatty alcohols.

2. The method for recycling and reusing urban construction waste to prepare building materials as described in claim 1, characterized in that, The urban construction waste is concrete discarded at urban building demolition sites that has been mechanically crushed, washed and graded, then screened into two particle sizes: 5-16mm and 16-31.5mm, and then mixed and compounded in a 1:1 mass ratio.

3. The method for recycling and reusing urban construction waste to prepare building materials as described in claim 1, characterized in that, The mass ratio of tartaric acid, disodium ethylenediaminetetraacetate, and penetrant is 80-100:3-6:1-2.

4. The method for recycling and reusing urban construction waste to prepare building materials as described in claim 1, characterized in that, The chlorinated fatty alcohol is any one or any combination of two or more of 2-chloroethanol, 3-chloropropanol, 4-chlorobutanol, 5-chloropentanol, and 6-chlorohexanol.

5. The method for recycling and reusing urban construction waste to prepare building materials as described in claim 1, characterized in that, The mass ratio of the amorphous silica, ionic liquid, and sodium hydroxide is 20-40:3-6:60-80.

6. The method for recycling and reusing urban construction waste to prepare building materials as described in claim 1, characterized in that, Vacuum-pressure impregnation is used when recovering aggregates by impregnating them with active silica solution.

7. The method for recycling and reusing urban construction waste to prepare building materials as described in claim 5, characterized in that, The vacuum-pressure impregnation cycle is greater than or equal to 3 times.

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