Modified water-permeable recycled concrete as well as preparation method and application thereof

Abstract

The invention discloses modified water-permeable recycled concrete and a preparation method and application thereof, and belongs to the technical field of recycled concrete.The interface bonding force of fluorinated graphene is improved by depositing silicon dioxide on the surface of fluorinated graphene, then the surface of bentonite is coated with the fluorinated graphene through hydrogen bond self-assembly, and after treatment is conducted through a silane coupling agent, the modified water-permeable recycled concrete is prepared. Polymerizing a polyvinyl alcohol-vinyl acetate copolymer on the surface of the bentonite-loaded fluorinated graphene / SiO2 powder; the polyvinyl alcohol-vinyl acetate copolymer can form a tight connection structure with soil through hydrogen bonds and cation exchange effects, and is adsorbed on the surfaces of soil particles to form a net-shaped structure with certain elasticity and toughness, so that a permanent protection layer is formed; the bentonite-loaded fluorinated graphene SiO2 is used as a carrier, so that the anti-ultraviolet and anti-aging capabilities of the copolymer can be improved, and the bentonite has ion exchange performance and can promote the interaction between the polyvinyl alcohol-vinyl acetate copolymer and soil particles.

Description

Technical Field

[0001] The present invention belongs to the technical field of recycled concrete, and specifically relates to a modified permeable recycled concrete and a preparation method and application thereof. Background Art

[0002] With the development of the economy and society and the progress of urban construction, the surface of modern cities has gradually been covered by reinforced concrete buildings and impermeable pavements. The impermeable pavements will hinder the infiltration of rainwater in rainy weather, making it impossible for rainwater to replenish groundwater well. Coupled with excessive extraction of groundwater, urban pavements are prone to sinking; and rainwater is discharged through drainage ditches. When there is heavy rain or rainstorm, rainwater will gather on the road surface, and a large amount of it will be concentrated in motor vehicle and bicycle lanes, causing large-scale water accumulation on the road surface; and the existing concrete pavement is generally dense in structure and has loud tire noise. When a vehicle is driving at high speed, the tire will press air into the space between the tire and the road surface when rolling in. After the tire rolls over, the air will rapidly expand and make noise. This noise is particularly obvious on rainy days, affecting the lives and work of residents. In addition, with the progress of municipal construction, a large amount of waste concrete is generated every day. At present, due to the difficulty in handling waste concrete, poor viscosity, easy cracks in paved roads, inability to match the various raw materials in new concrete, and mixed sources, its treatment is mainly open-air stacking or landfill, causing secondary pollution. If these waste concretes can be recycled and used for road paving without reducing performance, it will not only save costs and reduce the cost of construction waste removal and treatment, but also reduce pollution to the environment.

[0003] In the prior art, recycled coarse aggregate is often used to fill concrete. However, the hardened cement mortar remaining on the surface of the recycled coarse aggregate has a high porosity and a large water absorption rate. During the hydration process of the concrete, the moisture in the cement in contact with the phase-change gravel will be absorbed into the phase-change gravel, resulting in a reduction in the actual bound water amount of the cement and an inability to achieve complete hydration. This not only affects the mechanical strength of the final concrete, but also leads to poor interfacial bonding between the hardened cement slurry and the aggregate, poor performance in the interface transition zone, and easy separation when subjected to stress, even causing the concrete to break and collapse.

[0004] Chinese patent publication number CN107352868B discloses a permeable cement concrete and its construction method, using isocyanate-modified phenolic resin as a binder. The addition of short fibers improves the coarse aggregate interface of the cementitious material while ensuring the permeability of the concrete, increasing the bonding force between the coarse aggregates and improving the strength of the concrete. However, the isocyanate-modified phenolic resin used as a binder in this solution is prone to chain segment degradation under ultraviolet light or high temperature, resulting in brittle network structure. Summary of the Invention

[0005] The purpose of the present invention is to provide a modified permeable recycled concrete and its preparation method and application. By using bentonite-loaded fluorinated graphene / SiO2 powder as a carrier and polymerizing polyvinyl alcohol-vinyl acetate copolymer on the surface as a modified binder, the high stability of the fluorine groups in the bentonite-loaded fluorinated graphene / SiO2 powder can prevent the polyvinyl alcohol-vinyl acetate copolymer from aging and failure under ultraviolet irradiation.

[0006] The purpose of the present invention can be achieved through the following technical solutions: A method for preparing modified permeable recycled concrete comprises the following steps: Step 1: Through the sol-gel method, tetraethyl silicate is hydrolyzed using alkaline catalysis to in situ generate nano-SiO2 particles on the surface of fluorinated graphene, and then the fluorinated graphene / SiO2 is loaded on bentonite using hydrogen bond self-assembly to obtain bentonite-loaded fluorinated graphene / SiO2 powder.

[0007] Step 2: After loading fluorinated graphene / SiO2 on bentonite and modifying it with γ-aminopropyltriethoxysilane, polyvinyl alcohol-vinyl acetate copolymer is polymerized on the surface to obtain a modified binder.

[0008] Step 3: Mixing polycarboxylate water reducer and deionized water in a mass ratio of 2.9-3.2:90-110 to obtain a water reducer dilution solution; stirring and mixing silicate cement of model P.O42.5, Class F Grade I fly ash, recycled concrete aggregate, modified binder and water reducer dilution solution to obtain a modified permeable recycled concrete.

[0009] Furthermore, in step three, the usage ratio of silicate cement, fly ash, recycled concrete aggregate, modified binder and water reducer dilution is 260-270kg:30-40kg:1100-1200kg:30-40kg:150-160kg.

[0010] Furthermore, the specific preparation steps of bentonite-loaded fluorinated graphene / SiO2 powder in step 1 are as follows: The fluorinated graphene and ethanol solution are added to a reactor, stirred at 20-25°C and 500-600 r / min for 20-30 minutes, and then 30-40% ammonia water is added to adjust the pH value to 9-10, and then tetraethyl silicate is added, and the stirring reaction is continued for 20-24 hours, so that the tetraethyl silicate is hydrolyzed in an alkaline environment to form nano-SiO2 particles and loaded on the surface of the fluorinated graphene to obtain a graphene oxide suspension; the graphene oxide suspension, bentonite and N,N-dimethylformamide are added to a reactor, stirred at 20-25°C and 500-600 r / min for 1-2 hours, filtered, and the filter cake is washed with deionized water and anhydrous ethanol for 2-3 times respectively, and vacuum dried at 60-80°C for 1-2 hours to obtain bentonite-loaded fluorinated graphene / SiO2 powder.

[0011] Furthermore, the usage ratio of fluorinated graphene, ethanol solution, ammonia water and tetraethyl silicate is 50-60 g: 800-900 mL: 12-14 mL: 70-80 mL.

[0012] Furthermore, the usage ratio of graphene oxide suspension, bentonite and N,N-dimethylformamide is 40-50 mL: 80-90 g: 1-2 L.

[0013] Furthermore, the specific preparation steps of the modified binder in step 2 are as follows: Modified bentonite-loaded fluorinated graphene / SiO2 powder and deionized water are added to a reactor, stirred at 20-25°C and 500-600r / min for 40-60min, then polyvinyl alcohol is added, heated to 90-100°C, stirred until the material is completely dissolved, then cooled to 40-45°C, octylphenol polyoxyethylene ether as an emulsifier is added, and the stirring reaction is continued for 30-40min, then vinyl acetate and potassium persulfate as an initiator are added, heated to 65-70°C, kept warm for 1-2h, cooled to 45-50°C, sodium bicarbonate is added to adjust the pH value to 6-7, and then dibutyl phthalate as a plasticizer is added, and stirring is continued for 40-60min. The mixture is naturally cooled and discharged to obtain a modified binder.

[0014] Furthermore, the usage ratio of modified bentonite-loaded fluorinated graphene / SiO2 powder, deionized water, polyvinyl alcohol, octylphenol polyoxyethylene ether, vinyl acetate, potassium persulfate and dibutyl phthalate is 30-40 g: 1-2 L: 50-60 mL: 1-2 g: 20-30 mL: 1-2 g: 1-2 g.

[0015] Furthermore, modified bentonite-loaded fluorinated graphene / SiO2 powder is prepared by the following steps: γ-Aminopropyltriethoxysilane and deionized water are added to a reactor, and sodium hydroxide and acetic acid solution are added to adjust the pH value to 6.5-7. The mixture is stirred at 20-25°C and 500-600 r / min for 40-60 minutes. After the stirring reaction is completed, the mixture is allowed to stand for 1-2 hours. The bentonite-loaded fluorinated graphene / SiO2 powder and an ethanol solution with a mass fraction of 50-60% are mixed and added to the reactor. The mixture is stirred at 20-25°C and 500-600 r / min for 1-2 hours, filtered, and the filter cake is washed with deionized water and anhydrous ethanol for 2-3 times, respectively, and vacuum dried at 60-80°C for 1-2 hours to obtain modified bentonite-loaded fluorinated graphene / SiO2 powder.

[0016] Furthermore, the usage ratio of γ-aminopropyltriethoxysilane, deionized water, bentonite-loaded fluorinated graphene / SiO2 powder and ethanol solution is 50-60 g: 800-900 mL: 30-40 g: 100-120 mL.

[0017] The present invention also provides an application of the modified permeable recycled concrete in cement concrete.

[0018] Beneficial effects of the present invention: 1. The modified permeable recycled concrete prepared by the present invention has good density and compressive strength, high porosity and good permeability, and is not prone to cracks due to aging of the binder under long-term ultraviolet irradiation.

[0019] 2. The present invention deposits silicon dioxide on the surface of fluorinated graphene to improve the interfacial bonding force of fluorinated graphene, and then coats it on the surface of bentonite through hydrogen bond self-assembly to obtain bentonite-loaded fluorinated graphene / SiO2 powder. After being treated with a silane coupling agent, polyvinyl alcohol-vinyl acetate copolymer is polymerized on the surface of the bentonite-loaded fluorinated graphene / SiO2 powder; the hydrophilic groups on the polymer chain of the polyvinyl alcohol-vinyl acetate copolymer can form a tight connection structure with the soil through hydrogen bonds and cation exchange, while the hydrophobic CC long chains on the main chain penetrate, diffuse, and entangle, and are adsorbed on the surface of the soil particles to form a network structure with certain elasticity and toughness, effectively reducing the moisture content and density of the soil and forming a permanent protective layer. Using bentonite-loaded fluorinated graphene / SiO2 as a carrier can improve the anti-ultraviolet and anti-aging capabilities of the copolymer, and the ion exchange performance of bentonite can promote the interaction between the copolymer and soil particles.

[0020] 3. Fluorinated graphene / SiO2 coats bentonite through hydrogen bond self-assembly. SiO2 is deposited on the surface of fluorinated graphene, which can change the surface state of fluorinated graphene and effectively avoid the stacking of fluorinated graphene sheets, which is beneficial to the coating of fluorinated graphene on the surface of bentonite. The coating of fluorinated graphene can further improve the overall strength of bentonite. As a carrier of copolymer, it is beneficial to the interaction between copolymer and soil particles, and can also increase the specific surface area and porosity of bentonite, and increase the permeability to water. DETAILED DESCRIPTION

[0021] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0022] Example 1: A method for preparing modified permeable recycled concrete, comprising the following steps: S1: Add 50g of fluorinated graphene and 800mL of ethanol solution into a reactor, stir at 20℃ and 500r / min for 20min, then add 12mL of 30% ammonia water to adjust the pH to 9, then add 70mL of tetraethyl silicate, and continue stirring and reacting for 20h, so that tetraethyl silicate is hydrolyzed in an alkaline environment to form nano-SiO2 particles and loaded on the surface of fluorinated graphene to obtain graphene oxide suspension; add 40mL of graphene oxide suspension, 80g of bentonite and 1L of N,N-dimethylformamide into a reactor, stir at 20℃ and 500r / min for 1h, filter, wash the filter cake with deionized water and anhydrous ethanol twice respectively, and dry it in vacuum at 60℃ for 1h to obtain bentonite-loaded fluorinated graphene / SiO2 powder.

[0023] Through the sol-gel method, tetraethyl silicate is hydrolyzed by alkaline catalysis to in situ generate nano-SiO2 particles on the surface of fluorinated graphene.

[0024] The structure of fluorinated graphene / SiO2 is nano-SiO2 particles loaded on fluorinated graphene sheets. By loading nano-SiO2 particles on the surface of fluorinated graphene, the surface state of fluorinated graphene is changed, which can effectively avoid the stacking of fluorinated graphene sheets, improve the dispersibility and interface compatibility of fluorinated graphene in resin, and the -F and -OH groups on the fluorinated graphene nanosheets and the -OH and -COOH groups on the bentonite are abundant, so the fluorinated graphene / SiO2 is loaded on the bentonite through hydrogen bond self-assembly.

[0025] S2: Add 50g of γ-aminopropyltriethoxysilane and 800mL of deionized water into the reactor, add sodium hydroxide and acetic acid solution to adjust the pH value to 6.5, stir at 20℃ and 500r / min for 40min, let it stand for 1h after the stirring reaction, mix 30g of bentonite-loaded fluorinated graphene / SiO2 powder with 100mL of 50% ethanol solution by mass and add it into the reactor, stir at 20℃ and 500r / min for 1h, filter, wash the filter cake with deionized water and anhydrous ethanol twice respectively, and dry it in vacuum at 60℃ for 1h to obtain modified bentonite-loaded fluorinated graphene / SiO2 powder.

[0026] By treating with γ-aminopropyltriethoxysilane, silanol bonds are generated by hydrolysis and combined with hydroxyl groups on the surface of bentonite-loaded fluorinated graphene / SiO2 powder, so that the bentonite-loaded fluorinated graphene / SiO2 powder has amino groups.

[0027] S3: Add 30g of modified bentonite loaded fluorinated graphene / SiO2 powder and 1L of deionized water into the reactor, stir at 20℃ and 500r / min for 40min, then add 50mL of polyvinyl alcohol, heat to 90℃, stir until the material is completely dissolved, then cool to 40℃, add 1g of octylphenol polyoxyethylene ether as an emulsifier, continue stirring and react for 30min, then add 20mL of vinyl acetate and 1g of potassium persulfate as an initiator, heat to 65℃, keep warm for 1h, cool to 45℃, add sodium bicarbonate to adjust the pH to 6, then add 1g of plasticizer dibutyl phthalate, continue stirring for 40min, cool naturally, and discharge to obtain a modified binder.

[0028] After copolymerization modification of vinyl acetate, a polyvinyl alcohol-vinyl acetate copolymer with strong water resistance is obtained. The polymer contains a large number of carboxyl and hydroxyl groups, which can combine with the amino groups on the surface of modified bentonite-loaded fluorinated graphene / SiO2 powder, so that the high molecular polymer can be fixed on the surface of modified bentonite-loaded fluorinated graphene / SiO2.

[0029] S4: 2.9 kg of polycarboxylate water reducer and 90 kg of deionized water are mixed to obtain a water reducer dilution solution; 260 kg of Portland cement with model P.O42.5, 30 kg of Class F Grade I fly ash, 1100 kg of recycled concrete aggregate, 30 kg of modified binder and 150 kg of the water reducer dilution solution are stirred and mixed to obtain a modified permeable recycled concrete.

[0030] Example 2: A method for preparing modified permeable recycled concrete, comprising the following steps: S1: 55 g of fluorinated graphene and 850 mL of ethanol solution were added to a reactor, stirred at 22.5 ° C and 550 r / min for 25 min, then 13 mL of 35% ammonia water was added to adjust the pH to 9.5, and then 75 mL of tetraethyl silicate was added. The stirring reaction continued for 22 h, so that the tetraethyl silicate was hydrolyzed in an alkaline environment to form nano-SiO2 particles and loaded on the surface of the fluorinated graphene to obtain a graphene oxide suspension; 45 mL of graphene oxide suspension, 85 g of bentonite and 1.5 L of N, N-dimethylformamide were added to a reactor, stirred at 22.5 ° C and 550 r / min for 1.5 h, filtered, and the filter cake was washed twice with deionized water and anhydrous ethanol respectively, and vacuum dried at 70 ° C for 1.5 h to obtain bentonite-loaded fluorinated graphene / SiO2 powder.

[0031] S2: Add 55g of γ-aminopropyltriethoxysilane and 850mL of deionized water into the reactor, add sodium hydroxide and acetic acid solution to adjust the pH value to 6.75, stir at 22.5℃ and 550r / min for 50min, let it stand for 1.5h after the stirring reaction, mix 35g of bentonite-loaded fluorinated graphene / SiO2 powder and 110mL of 55% ethanol solution into the reactor, stir at 22.5℃ and 550r / min for 1.5h, filter, wash the filter cake twice with deionized water and anhydrous ethanol respectively, and dry it in vacuum at 70℃ for 1.5h to obtain modified bentonite-loaded fluorinated graphene / SiO2 powder.

[0032] S3: Add 35g of modified bentonite-loaded fluorinated graphene / SiO2 powder and 1.5L of deionized water into the reactor, stir at 22.5℃ and 550r / min for 50min, then add 55mL of polyvinyl alcohol, heat to 95℃, stir until the material is completely dissolved, then cool to 42.5℃, add 1.5g of octylphenol polyoxyethylene ether as an emulsifier, continue stirring and react for 35min, then add 25mL of vinyl acetate and 1.5g of potassium persulfate as an initiator, heat to 67.5℃, keep warm for 1.5h, cool to 47.5℃, add sodium bicarbonate to adjust the pH to 6.5, then add 1.5g of plasticizer dibutyl phthalate, continue stirring for 50min, cool naturally, and discharge to obtain a modified binder.

[0033] S4: 3.05 kg of polycarboxylate water reducer and 100 kg of deionized water are mixed to obtain a water reducer dilution solution; 265 kg of Portland cement with model P.O42.5, 35 kg of Class F Grade I fly ash, 1150 kg of recycled concrete aggregate, 35 kg of modified binder and 155 kg of the water reducer dilution solution are stirred and mixed to obtain a modified permeable recycled concrete.

[0034] Example 3: A method for preparing modified permeable recycled concrete, comprising the following steps: S1: 60 g of fluorinated graphene and 900 mL of ethanol solution were added to a reactor, stirred at 25°C and 600 r / min for 30 min, then 14 mL of 40% ammonia water was added to adjust the pH to 10, and then 80 mL of tetraethyl silicate was added. The stirring reaction continued for 24 h, so that the tetraethyl silicate was hydrolyzed in an alkaline environment to form nano-SiO2 particles and loaded on the surface of the fluorinated graphene to obtain a graphene oxide suspension; 50 mL of graphene oxide suspension, 90 g of bentonite and 2 L of N,N-dimethylformamide were added to a reactor, stirred at 25°C and 600 r / min for 2 h, filtered, and the filter cake was washed with deionized water and anhydrous ethanol three times respectively, and vacuum dried at 80°C for 2 h to obtain bentonite-loaded fluorinated graphene / SiO2 powder.

[0035] S2: Add 60g of γ-aminopropyltriethoxysilane and 900mL of deionized water into the reactor, add sodium hydroxide and acetic acid solution to adjust the pH value to 7, stir at 25℃ and 600r / min for 60min, let it stand for 2h after the stirring reaction, mix 40g of bentonite-loaded fluorinated graphene / SiO2 powder and 120mL of 60% ethanol solution into the reactor, stir at 25℃ and 600r / min for 2h, filter, wash the filter cake with deionized water and anhydrous ethanol three times respectively, and dry it in vacuum at 80℃ for 2h to obtain modified bentonite-loaded fluorinated graphene / SiO2 powder.

[0036] S3: Add 40g of modified bentonite loaded fluorinated graphene / SiO2 powder and 2L of deionized water into the reactor, stir at 25℃ and 600r / min for 60min, then add 60mL of polyvinyl alcohol, heat to 100℃, stir until the material is completely dissolved, then cool to 45℃, add 2g of octylphenol polyoxyethylene ether as an emulsifier, continue stirring and react for 40min, then add 30mL of vinyl acetate and 2g of potassium persulfate as an initiator, heat to 70℃, keep warm for 2h, cool to 50℃, add sodium bicarbonate to adjust the pH to 7, then add 2g of plasticizer dibutyl phthalate, continue stirring for 60min, cool naturally, and discharge to obtain a modified binder.

[0037] S4: 3.2 kg of polycarboxylate water reducer and 110 kg of deionized water are mixed to obtain a water reducer dilution solution; 270 kg of Portland cement of model P.O42.5, 40 kg of Class F Grade I fly ash, 1200 kg of recycled concrete aggregate, 40 kg of modified binder and 160 kg of the water reducer dilution solution are stirred and mixed to obtain a modified permeable recycled concrete.

[0038] Comparative Example 1: Based on Example 3, the fluorinated graphene in step S1 was replaced with graphene oxide, and the other steps remained unchanged to prepare a modified permeable recycled concrete.

[0039] Comparative Example 2: Based on Example 3, without going through step S2, the modified bentonite-loaded fluorinated graphene / SiO2 powder in step S3 is replaced by the bentonite-loaded fluorinated graphene / SiO2 powder in step S1, and the other steps remain unchanged to prepare modified permeable recycled concrete.

[0040] Comparative Example 3: Based on Example 3, tetraethyl silicate in step S2 is discarded so that it cannot be hydrolyzed in an alkaline environment to form nano-SiO2 particles and loaded on the surface of fluorinated graphene. The other steps remain unchanged to prepare modified permeable recycled concrete.

[0041] The modified permeable recycled concrete obtained in Examples 1 to 3 and Comparative Examples 1 to 3 was cast in a mold (100 mm × 100 mm × 100 mm) and demoulded after 24 hours. The concrete samples were then transferred to a curing room for standard curing for 28 days before testing. The UV aging test was carried out in a UV aging box with an UV intensity of 210 W / m 2 , the aging temperature is 60℃ and the aging time is 6 days.

[0042] Table 1 Performance test table of modified permeable recycled concrete before aging , Table 2 Performance test table of modified permeable recycled concrete after aging , As can be seen from Tables 1 and 2, the modified permeable recycled concrete obtained in Examples 1 to 3 has significantly better compressive strength, flexural strength, relative density, porosity and water permeability than the comparative example, and after the UV aging test, the performance degradation of the embodiment is less than that of the comparative example, indicating that the modified permeable recycled concrete prepared by the present invention has good density and compressive strength, high porosity and good water permeability, and is not prone to cracks due to aging of the binder under long-term ultraviolet irradiation.

[0043] In Comparative Example 1, fluorinated graphene is replaced with graphene oxide, and fluorinated graphene is coated on the surface of bentonite as a filler for recycled concrete. The high stability of the CF bond can improve the anti-aging performance of the polyvinyl alcohol-vinyl acetate copolymer polymerized on the surface. The polyvinyl alcohol-vinyl acetate copolymer can interact with soil particles, which helps to avoid aging of the copolymer.

[0044] In Comparative Example 2, the modified bentonite-loaded fluorinated graphene / SiO2 powder is replaced with the bentonite-loaded fluorinated graphene / SiO2 powder in step S1, and is treated with γ-aminopropyltriethoxysilane to hydrolyze and generate silanol bonds that combine with the hydroxyl groups on the surface of the bentonite-loaded fluorinated graphene / SiO2 powder, so that the bentonite-loaded fluorinated graphene / SiO2 powder is provided with amino groups. The amino groups can combine with the polyvinyl alcohol-vinyl acetate copolymer, and the polymer contains a large number of carboxyl and hydroxyl groups, which can combine with the amino groups on the surface of the modified bentonite-loaded fluorinated graphene / SiO2 powder, so that the high molecular polymer can be fixed on the surface of the modified bentonite-loaded fluorinated graphene / SiO2.

[0045] In Comparative Example 3, tetraethyl silicate is omitted, and the structure of fluorinated graphene / SiO2 is that nano-SiO2 particles are loaded on fluorinated graphene sheets. By loading nano-SiO2 particles on the surface of fluorinated graphene, the surface state of fluorinated graphene is changed, which can effectively avoid stacking between fluorinated graphene sheets and improve the dispersibility and interface compatibility of fluorinated graphene in the resin.

[0046] While the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations can be made to the embodiments without departing from the principles and spirit of the invention.

Claims

1. A method for preparing modified permeable recycled concrete, characterized in that: The steps include: Step 1: Using a sol-gel method, tetraethyl silicate is hydrolyzed using alkaline catalysis to in-situ generate nano-SiO2 particles on the surface of fluorinated graphene. The fluorinated graphene / SiO2 is then loaded onto bentonite using hydrogen bond self-assembly to obtain bentonite-loaded fluorinated graphene / SiO2 powder. Step 2: loading fluorinated graphene / SiO2 onto bentonite and modifying it with γ-aminopropyltriethoxysilane, and polymerizing polyvinyl alcohol-vinyl acetate copolymer on the surface to obtain a modified binder; Step 3: Mixing a polycarboxylate water reducer and deionized water in a mass ratio of 2.9-3.2:90-110 to obtain a water reducer dilution solution; stirring and mixing silicate cement, fly ash, recycled concrete aggregate, a modified binder and the water reducer dilution solution to obtain a modified permeable recycled concrete.

2. The method for preparing a modified permeable recycled concrete according to claim 1, characterized in that: The usage ratio of the silicate cement, fly ash, recycled concrete aggregate, modified binder and water reducer dilution in step 3 is 260-270kg: 30-40kg: 1100-1200kg: 30-40kg: 150-160kg.

3. The method for preparing a modified permeable recycled concrete according to claim 1, characterized in that: The specific preparation steps of the bentonite-loaded fluorinated graphene / SiO2 powder in step 1 are as follows: The fluorinated graphene and ethanol solution are added to a reactor, stirred at 20-25°C and 500-600 r / min for 20-30 minutes, and then 30-40wt% ammonia water is added to adjust the pH value to 9-10, and then tetraethyl silicate is added, and the stirring reaction is continued for 20-24 hours to obtain a graphene oxide suspension; the graphene oxide suspension, bentonite and N,N-dimethylformamide are added to a reactor, stirred at 20-25°C and 500-600 r / min for 1-2 hours, filtered, washed, and vacuum dried to obtain bentonite-loaded fluorinated graphene / SiO2 powder.

4. The method for preparing a modified permeable recycled concrete according to claim 3, characterized in that: The usage ratio of the fluorinated graphene, the ethanol solution, the ammonia water and the tetraethyl silicate is 50-60 g: 800-900 mL: 12-14 mL: 70-80 mL.

5. The method for preparing a modified permeable recycled concrete according to claim 3, characterized in that: The usage ratio of the graphene oxide suspension, bentonite and N,N-dimethylformamide is 40-50 mL: 80-90 g: 1-2 L.

6. The method for preparing modified permeable recycled concrete according to claim 4, characterized in that: The specific preparation steps of the modified binder in step 2 are as follows: Add modified bentonite-loaded fluorinated graphene / SiO2 powder and deionized water into a reactor, stir at 20-25°C and 500-600r / min for 40-60min, then add polyvinyl alcohol, heat to 90-100°C, stir until the material is completely dissolved, then cool to 40-45°C, add octylphenol polyoxyethylene ether, continue stirring and react for 30-40min, then add vinyl acetate and potassium persulfate, heat to 65-70°C, keep warm for 1-2h, cool to 45-50°C, add sodium bicarbonate to adjust the pH value to 6-7, then add dibutyl phthalate, continue stirring for 40-60min, cool naturally, and discharge to obtain a modified binder.

7. The method for preparing modified permeable recycled concrete according to claim 6, characterized in that: The usage ratio of the modified bentonite-loaded fluorinated graphene / SiO2 powder, deionized water, polyvinyl alcohol, octylphenol polyoxyethylene ether, vinyl acetate, potassium persulfate and dibutyl phthalate is 30-40 g: 1-2 L: 50-60 mL: 1-2 g: 20-30 mL: 1-2 g: 1-2 g.

8. The method for preparing modified permeable recycled concrete according to claim 6, characterized in that: The modified bentonite-loaded fluorinated graphene / SiO2 powder is prepared by the following steps: γ-aminopropyltriethoxysilane and deionized water were added to a reactor, sodium hydroxide and acetic acid solution were added to adjust the pH value to 6.5-7, and the mixture was stirred at 20-25° C. and 500-600 r / min for 40-60 min. After the stirring reaction was completed, the mixture was allowed to stand for 1-2 h. Bentonite-loaded fluorinated graphene / SiO2 powder and 50-60 wt% ethanol solution were mixed and added to the reactor. The mixture was stirred at 20-25° C. and 500-600 r / min for 1-2 h. The mixture was filtered, washed, and vacuum-dried to obtain modified bentonite-loaded fluorinated graphene / SiO2 powder. The usage ratio of the γ-aminopropyltriethoxysilane, deionized water, bentonite-loaded fluorinated graphene / SiO2 powder and ethanol solution is 50-60 g: 800-900 mL: 30-40 g: 100-120 mL.

9. A modified permeable recycled concrete, characterized in that: Prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the modified permeable recycled concrete according to claim 9 in cement concrete.