Foamed asphalt mixture as well as preparation method and application thereof

Abstract

The invention discloses a foamed asphalt mixture as well as a preparation method and application thereof, and relates to the technical field of asphalt preparation. The foamed asphalt mixture prepared by the preparation method disclosed by the invention is prepared from modified asphalt, pure water, aggregate, cement, modified zeolite, pentaerythritol tetra-3-mercaptopropionate and a nucleophilic reagent. The modified asphalt is obtained by mixing modified SBS and matrix asphalt; the modified SBS is obtained by reacting chlorosulfonated SBS with [(4-aminophenyl) (hydroxyl) methyl] diethyl phosphonate, brominating and reacting with dimethyl sulfide; the modified zeolite is obtained by reacting pretreated zeolite with carbon dioxide, grafting 2, 2, 6, 6-tetramethylpiperidine-4-yl 4-aminobenzoate, and then reacting with methacrylic anhydride. The foamed asphalt mixture prepared by the preparation method disclosed by the invention has good flame retardance, ageing resistance and mechanical properties.

Description

Technical Field

[0001] The present invention relates to the technical field of asphalt preparation, in particular to a foamed asphalt mixture and a preparation method and application thereof. Background Art

[0002] Asphalt mixture is a road construction material made by mixing mineral aggregates such as crushed stone, sand, and mineral powder with asphalt mixture in a specific proportion. It is widely used in road construction. Foamed asphalt is a special asphalt material. By spraying a small amount of water into the hot asphalt at high temperature, the asphalt rapidly expands and forms a large foam structure. This foam structure significantly increases the contact area between the asphalt and the aggregate, thereby improving the bonding properties of the mixture. Foamed asphalt mixtures have a wide range of applications, especially in cold recycling technology, base stabilization, and road repair.

[0003] However, despite its numerous advantages, foamed asphalt mixtures also have some drawbacks. First, the mechanical properties of foamed asphalt mixtures are relatively weak. Especially under high temperature conditions, the foam structure easily collapses, resulting in a decrease in the overall strength of the mixture. Second, foamed asphalt mixtures have poor flame retardancy. In the event of a fire, the asphalt easily burns and releases harmful gases, increasing safety risks. Furthermore, foamed asphalt mixtures lack ideal aging resistance. Long-term exposure to high temperatures and ultraviolet light can cause material aging and performance degradation, shortening the lifespan of the road.

[0004] Through continuous technological innovation and process improvement, its mechanical properties, flame retardant properties and anti-aging properties can be further improved, making it more suitable for various complex road engineering environments. Summary of the Invention

[0005] The purpose of the present invention is to provide a foamed asphalt mixture and a preparation method and application thereof, so as to solve the problems existing in the prior art.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions: A foamed asphalt mixture, comprising modified asphalt, pure water, aggregate, cement, modified zeolite, a nucleophilic reagent, and pentaerythritol tetrakis-3-mercaptopropionate; As an optimization, the modified asphalt is obtained by mixing modified SBS and base asphalt.

[0007] As an optimization, the modified SBS is obtained by reacting chlorosulfonated SBS with diethyl [(4-aminophenyl)(hydroxy)methyl]phosphonate, followed by bromination and reaction with dimethyl sulfide.

[0008] As an optimization, the modified zeolite is obtained by reacting a pretreated zeolite with carbon dioxide, grafting 2,2,6,6-tetramethylpiperidin-4-yl 4-aminobenzoate, and then reacting with methacrylic anhydride.

[0009] A method for preparing a foamed asphalt mixture comprises the following steps: (1) SBS is modified by chlorosulfonation to obtain chlorosulfonated SBS; chlorosulfonated SBS and diethyl [(4-aminophenyl)(hydroxy)methyl]phosphonate are reacted to obtain pre-modified SBS; (2) reacting pre-modified SBS with dibromotriphenylphosphine to obtain brominated SBS; reacting brominated SBS with silver tetrafluoroborate and dimethyl sulfide to obtain modified SBS; (3) natural zeolite is treated with sodium hydroxide and reacted with aniline methyl trimethoxysilane to obtain pretreated zeolite; the pretreated zeolite, phenylsilane, and tetrabutylammonium acetate are reacted in a carbon dioxide atmosphere to obtain formyl zeolite; (4) reacting formyl zeolite and 2,2,6,6-tetramethylpiperidin-4-yl 4-aminobenzoate to obtain pre-modified zeolite; reacting the pre-modified zeolite and methacrylic anhydride to obtain modified zeolite; (5) Modified SBS and base asphalt are mixed to obtain modified asphalt; the following components are weighed: modified asphalt, pure water, aggregate, cement, modified zeolite, pentaerythritol tetrakis-3-mercaptopropionate, and nucleophilic reagent; the modified asphalt, modified zeolite, and pure water are mixed to obtain foamed asphalt; the foamed asphalt, aggregate, cement, nucleophilic reagent, and pentaerythritol tetrakis-3-mercaptopropionate are mixed to obtain a mixture.

[0010] As an optimization, the preparation method of the pre-modified SBS in step (1) is as follows: weigh SBS, chloroform, chlorosulfonic acid, and thionyl chloride in a mass ratio of 1:(20-30):(1-2):(0.7-0.9); add the SBS and chloroform to chlorosulfonic acid at 5°C, heat to 45-55°C, stir for 60-70 minutes, add thionyl chloride, continue stirring for 60-70 minutes, cool to room temperature, precipitate with 0°C pure water, filter, wash with 0°C pure water, and vacuum dry to obtain chlorosulfonated SBS; chlorosulfonated SBS, diethyl [(4-aminophenyl)(hydroxy)methyl]phosphonate, and N,N-dimethylformamide are mixed in a mass ratio of 1:(0.2-0.3):(20-30), heated to 40-50°C, and reacted for 2-3 hours. A 10wt% aqueous sodium carbonate solution is used to adjust the pH to 9-10, and the mixture is precipitated with pure water, filtered, washed, and vacuum-dried to obtain pre-modified SBS; the SBS is a styrene-butadiene-styrene block copolymer, model LG501.

[0011] As an optimization, the preparation method of the modified SBS in step (2) is as follows: pre-modified SBS, tetrahydrofuran, pyridine and dibromotriphenylphosphine are mixed in a mass ratio of 1:(20-30):(10-12):(0.5-0.6) at 0-4°C and stirred for 1-1.5h, heated to room temperature and reacted for 2-3h. After the reaction, brominated SBS is obtained by rotary evaporation under reduced pressure; brominated SBS, silver tetrafluoroborate and dichloroethane are mixed in a mass ratio of 1:(0.3-0.4):(20-30) and heated to 50-60°C and stirred for 10min, 0.2-0.3 times the mass of dimethyl sulfide of the brominated SBS is added and the mixture is heated to 85°C and refluxed for 25-30min. After the reaction is completed, the mixture is cooled to room temperature, precipitated with pure water, filtered, washed and vacuum dried to obtain the modified SBS.

[0012] As an optimization, the preparation method of the formyl zeolite in step (3) is as follows: natural zeolite and 20wt% sodium hydroxide solution are mixed in a mass ratio of 1:(8-10), stirred at 60°C for 6h, filtered, washed and dried to obtain porous zeolite; porous zeolite, aniline methyl trimethoxysilane and ethanol are mixed in a mass ratio of 1:(5-6):(80-100), ultrasonicated for 30min, stirred at room temperature for 4-5h, filtered, washed and dried to obtain pretreated zeolite; under a carbon dioxide atmosphere, pretreated zeolite, phenylsilane and tetrabutylammonium acetate are mixed in a mass ratio of 1:(5-6):(0.01-0.02), stirred and reacted at 0-2°C for 50-60min, heated to 20-25°C for reaction for 5-6h, and filtered, washed and dried after the reaction to obtain formyl zeolite; the natural zeolite has a particle size of 200 mesh and a water content of 7%.

[0013] As an optimization, the preparation method of the modified zeolite in step (4) is as follows: under nitrogen protection, formyl zeolite, chloroform, 2,2,6,6-tetramethylpiperidin-4-yl 4-aminobenzoate, and phosphorus pentachloride are mixed in a mass ratio of 1:(20-30):(1-1.2):(1.5-1.7) at 5°C for 50-60 minutes, heated to room temperature and stirred for 2-3 hours, then heated to 60-65°C and refluxed for 2-3 hours. After the reaction is completed, the mixture is cooled to room temperature, the pH is adjusted to 8-9 with 35wt% ammonia water, and the pre-modified zeolite is obtained by filtration, washing, and drying. The pre-modified zeolite, dimethylaminopyridine, triethylamine, dichloromethane, and methacrylic anhydride are mixed in a mass ratio of 1:(0.1-0.2):(2-3):(50-60):(1-2), stirred at room temperature for 10-12 hours, filtered, washed with saturated sodium carbonate solution, and dried to obtain the modified zeolite.

[0014] As an optimization, the preparation method of the foamed asphalt mixture in step (5) is as follows: modified SBS and base asphalt are weighed in a mass ratio of 1:(20-25), the base asphalt is heated to 175-180°C, and the modified SBS is added and sheared and stirred for 50-60 minutes to obtain modified asphalt; the following components are weighed, in parts by mass: 15-20 parts of modified asphalt, 2-3 parts of pure water, 70-90 parts of aggregate, 2-3 parts of cement, 2-3 parts of modified zeolite, 1-2 parts of pentaerythritol tetrakis-3-mercaptopropionate, and 0.1 part of nucleophilic reagent; the modified asphalt, modified zeolite, and pure water are mixed at 160-175°C to obtain foamed asphalt; the foamed asphalt, aggregate, cement, pentaerythritol tetrakis-3-mercaptopropionate, and nucleophilic reagent are mixed at 140-160°C to obtain the foamed asphalt mixture.

[0015] As an optimization, the matrix asphalt in step (5) is 70#A grade matrix asphalt; the aggregate is pumice with a water absorption rate of ≤1% and a mud content of ≤1%; the cement is P.O42.5 ordinary Portland cement; and the nucleophilic reagent is dimethylphenylphosphine.

[0016] The present invention also provides an application of the foamed asphalt mixture prepared according to the method for preparing the foamed asphalt mixture in road construction.

[0017] Compared with the prior art, the beneficial effects achieved by the present invention are: The foamed asphalt mixture prepared by the present invention comprises modified asphalt, pure water, aggregate, cement, modified zeolite, pentaerythritol tetrakis-3-mercaptopropionate, and a nucleophilic reagent; the modified asphalt is obtained by mixing modified SBS and base asphalt; the modified SBS is obtained by reacting chlorosulfonated SBS with diethyl [(4-aminophenyl)(hydroxy)methyl]phosphonate, followed by bromination and then reacting with dimethyl sulfide; the modified zeolite is obtained by reacting pretreated zeolite with carbon dioxide, grafting 2,2,6,6-tetramethylpiperidin-4-yl 4-aminobenzoate, and then reacting with methacrylic anhydride.

[0018] First, SBS is chlorosulfonated to impart sulfonyl chloride groups to the benzene rings on the styrene structures at both ends. [(4-aminophenyl)(hydroxy)methyl]phosphonic acid diethyl ester is grafted onto the ester through the reaction of sulfonyl chloride and amino groups. The hydroxyl groups on the [(4-aminophenyl)(hydroxy)methyl]phosphonic acid diethyl ester are then converted to bromine through the action of dibromotriphenylphosphine. This hydroxyl group then undergoes a nucleophilic substitution reaction with dimethyl sulfide to form a sulfonium salt. The introduction of sulfur and phosphorus elements can provide the material with excellent flame retardant properties. Furthermore, the SBS containing cations in the main chain can enhance the adhesion between SBS and asphalt, thereby reducing the adhesion between asphalt and enhancing the fluidity of asphalt. Secondly, after the natural zeolite is treated with alkali, the pore structure can be unblocked and the water content can be increased. As a foaming agent for foamed asphalt, aniline methyl trimethoxysilane introduces an aniline methyl structure on the surface of the natural zeolite. Under the action of carbon dioxide, a formyl group is generated, which then reacts with 2,2,6,6-tetramethylpiperidin-4-yl 4-aminobenzoate to generate a benzamidine structure while also introducing a hindered amine structure with antioxidant properties. Benzamidine has good ultraviolet absorption properties due to the presence of its conjugated structure. The hindered amine structure and the benzamidine structure can give the material good anti-aging properties. It then reacts with methacrylic anhydride to introduce double bonds on the surface of the zeolite. Finally, the modified asphalt, pure water and zeolite are mixed and foamed to obtain foamed asphalt, and the foamed asphalt, aggregate, cement, pentaerythritol tetrakis-3-mercaptopropionate and nucleophilic reagent are mixed to obtain a foamed asphalt mixture. Under the action of the nucleophilic reagent, the thiol groups on pentaerythritol tetrakis-3-mercaptopropionate form a cross-linked network between zeolite and SBS and between SBS through the thiol-ene reaction, which can further improve the mechanical properties of the mixture. DETAILED DESCRIPTION

[0019] 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.

[0020] The matrix asphalt described in the following examples and comparative examples is Donghai brand Jinling Petrochemical 70#A grade matrix asphalt; the aggregate is pumice with a water absorption rate of ≤1% and a mud content of ≤1%; the cement is P.O42.5 ordinary Portland cement; the nucleophilic reagent is dimethylphenylphosphine; the SBS is a styrene-butadiene-styrene block copolymer, model LG501, purchased from LG Chemical in South Korea; the natural zeolite has a particle size of 200 mesh and a water content of 7%.

[0021] Example 1, a method for preparing a foamed asphalt mixture, the method for preparing the foamed asphalt mixture comprising the following preparation steps: (1) SBS, chloroform, chlorosulfonic acid, and thionyl chloride were weighed in a mass ratio of 1:20:1:0.7; SBS and chloroform were mixed and added to chlorosulfonic acid at 5°C, heated to 55°C, stirred for 70 minutes, thionyl chloride was added, and stirring was continued for 70 minutes. The mixture was cooled to room temperature, precipitated with pure water at 0°C, filtered, washed with pure water at 0°C, and dried in vacuum to obtain chlorosulfonated SBS; chlorosulfonated SBS, diethyl [(4-aminophenyl)(hydroxy)methyl]phosphonate, and N,N-dimethylformamide were mixed in a mass ratio of 1:0.2:20, heated to 50°C, and reacted for 3 hours. The pH was adjusted to 9 using a 10 wt% aqueous sodium carbonate solution, precipitated with pure water, filtered, washed, and dried in vacuum to obtain pre-modified SBS; (2) At 0°C, pre-modified SBS, tetrahydrofuran, pyridine, and dibromotriphenylphosphine were mixed in a mass ratio of 1:20:10:0.5 and stirred for 1.5 hours, then heated to room temperature for reaction for 3 hours. After the reaction, brominated SBS was obtained by rotary evaporation under reduced pressure. Brominated SBS, silver tetrafluoroborate, and dichloroethane were mixed in a mass ratio of 1:0.3:20 and heated to 60°C for stirring for 10 minutes. Dimethyl sulfide (0.2 times the mass of brominated SBS) was added and heated to 85°C for reflux reaction for 30 minutes. After the reaction, the mixture was cooled to room temperature, precipitated with pure water, filtered, washed, and vacuum dried to obtain modified SBS. (3) Natural zeolite and 20 wt% sodium hydroxide solution were mixed in a mass ratio of 1:8, stirred at 60 ° C for 6 h, filtered, washed and dried to obtain porous zeolite; porous zeolite, aniline methyl trimethoxysilane and ethanol were mixed in a mass ratio of 1:5:80, ultrasonicated for 30 min, stirred at room temperature for 5 h, filtered, washed and dried to obtain pretreated zeolite; pretreated zeolite, phenylsilane and tetrabutylammonium acetate were mixed in a mass ratio of 1:5:0.01 in a carbon dioxide atmosphere, stirred at 0 ° C for 60 min, heated to 25 ° C for 6 h, filtered, washed and dried to obtain formyl zeolite; (4) Under nitrogen protection, formyl zeolite, chloroform, 2,2,6,6-tetramethylpiperidin-4-yl 4-aminobenzoate, and phosphorus pentachloride were mixed at a mass ratio of 1:20:1:1.5 at 5°C for 60 minutes, heated to room temperature and stirred for 2 hours, then heated to 65°C and refluxed for 3 hours. After the reaction was completed, the mixture was cooled to room temperature, and the pH was adjusted to 9 with 35 wt% ammonia water. The mixture was filtered, washed, and dried to obtain a pre-modified zeolite. The pre-modified zeolite, dimethylaminopyridine, triethylamine, dichloromethane, and methacrylic anhydride were mixed at a mass ratio of 1:0.1:2:50:1, stirred at room temperature for 12 hours, filtered, washed with saturated sodium carbonate solution, and dried to obtain a modified zeolite. (5) Modified SBS and base asphalt were weighed in a mass ratio of 1:20. After heating the base asphalt to 180°C, the modified SBS was added and sheared and stirred for 60 minutes to obtain modified asphalt. The following components were weighed, in parts by mass: 15 parts of modified asphalt, 2 parts of pure water, 70 parts of aggregate, 2 parts of cement, 2 parts of modified zeolite, 1 part of pentaerythritol tetrakis-3-mercaptopropionate, and 0.1 parts of nucleophilic reagent. The modified asphalt, modified zeolite, and pure water were mixed at 175°C to obtain foamed asphalt. The foamed asphalt, aggregate, cement, pentaerythritol tetrakis-3-mercaptopropionate, and nucleophilic reagent were mixed at 160°C to obtain a mixture.

[0022] Example 2, a method for preparing a foamed asphalt mixture, the method for preparing the foamed asphalt mixture comprising the following preparation steps: (1) SBS, chloroform, chlorosulfonic acid, and thionyl chloride were weighed in a mass ratio of 1:25:1.5:0.8; SBS and chloroform were mixed and added to chlorosulfonic acid at 5°C, heated to 50°C, stirred for 65 minutes, thionyl chloride was added, and stirring was continued for 65 minutes. The mixture was cooled to room temperature, precipitated with pure water at 0°C, filtered, washed with pure water at 0°C, and dried in vacuum to obtain chlorosulfonated SBS; chlorosulfonated SBS, diethyl [(4-aminophenyl)(hydroxy)methyl]phosphonate, and N,N-dimethylformamide were mixed in a mass ratio of 1:0.25:25, heated to 45°C, and reacted for 2.5 hours. The pH was adjusted to 9 using a 10 wt% aqueous sodium carbonate solution, precipitated with pure water, filtered, washed, and dried in vacuum to obtain pre-modified SBS; (2) At 3°C, pre-modified SBS, tetrahydrofuran, pyridine, and dibromotriphenylphosphine were mixed in a mass ratio of 1:25:11:0.55 and stirred for 1.3 hours, then heated to room temperature for reaction for 2.5 hours. After the reaction, brominated SBS was obtained by rotary evaporation under reduced pressure. Brominated SBS, silver tetrafluoroborate, and dichloroethane were mixed in a mass ratio of 1:0.35:25 and heated to 55°C for stirring for 10 minutes. Dimethyl sulfide (0.25 times the mass of brominated SBS) was added and heated to 85°C for reflux reaction for 27 minutes. After the reaction, the mixture was cooled to room temperature, precipitated with pure water, filtered, washed, and vacuum dried to obtain modified SBS. (3) Natural zeolite and 20 wt% sodium hydroxide solution were mixed in a mass ratio of 1:9, stirred at 60 ° C for 6 h, filtered, washed and dried to obtain porous zeolite; porous zeolite, aniline methyl trimethoxysilane and ethanol were mixed in a mass ratio of 1:5.5:90, ultrasonicated for 30 min, stirred at room temperature for 4.5 h, filtered, washed and dried to obtain pretreated zeolite; pretreated zeolite, phenylsilane and tetrabutylammonium acetate were mixed in a mass ratio of 1:5.5:0.01 in a carbon dioxide atmosphere, stirred at 1 ° C for 55 min, heated to 23 ° C for 5.5 h, filtered, washed and dried to obtain formyl zeolite; (4) Under nitrogen protection, formyl zeolite, chloroform, 2,2,6,6-tetramethylpiperidin-4-yl 4-aminobenzoate, and phosphorus pentachloride were mixed at a mass ratio of 1:25:1.1:1.6 at 5°C for 55 minutes, heated to room temperature and stirred for 2.5 hours, then heated to 63°C and refluxed for 2.5 hours. After the reaction was completed, the mixture was cooled to room temperature, and the pH was adjusted to 9 with 35 wt% ammonia water. The mixture was filtered, washed, and dried to obtain a pre-modified zeolite. The pre-modified zeolite, dimethylaminopyridine, triethylamine, dichloromethane, and methacrylic anhydride were mixed at a mass ratio of 1:0.15:2.5:55:1.2, stirred at room temperature for 11 hours, filtered, washed with saturated sodium carbonate solution, and dried to obtain a modified zeolite. (5) Modified SBS and base asphalt were weighed in a mass ratio of 1:23. After heating the base asphalt to 176°C, the modified SBS was added and sheared and stirred for 55 minutes to obtain modified asphalt. The following components were weighed, in parts by mass: 17 parts of modified asphalt, 2.5 parts of pure water, 80 parts of aggregate, 2.5 parts of cement, 2.5 parts of modified zeolite, 1.2 parts of pentaerythritol tetrakis-3-mercaptopropionate, and 0.1 parts of nucleophilic reagent. The modified asphalt, modified zeolite, and pure water were mixed at 165°C to obtain foamed asphalt. The foamed asphalt, aggregate, cement, pentaerythritol tetrakis-3-mercaptopropionate, and nucleophilic reagent were mixed at 150°C to obtain a mixture.

[0023] Example 3, a method for preparing a foamed asphalt mixture, the method for preparing the foamed asphalt mixture comprising the following preparation steps: (1) SBS, chloroform, chlorosulfonic acid, and thionyl chloride were weighed in a mass ratio of 1:30:2:0.9; SBS and chloroform were mixed and added to chlorosulfonic acid at 5°C, heated to 45°C, stirred for 70 min, thionyl chloride was added, and continued to stir for 60 min, cooled to room temperature, precipitated with pure water at 0°C, filtered, washed with pure water at 0°C, and vacuum dried to obtain chlorosulfonated SBS; chlorosulfonated SBS, diethyl [(4-aminophenyl)(hydroxy)methyl]phosphonate, and N,N-dimethylformamide were mixed in a mass ratio of 1:0.3:30, heated to 40°C, and reacted for 2 h. The pH was adjusted to 9 using a 10 wt% aqueous sodium carbonate solution, precipitated with pure water, filtered, washed, and vacuum dried to obtain pre-modified SBS; (2) At 4°C, pre-modified SBS, tetrahydrofuran, pyridine, and dibromotriphenylphosphine were mixed and stirred in a mass ratio of 1:30:12:0.6 for 1 hour, and the mixture was heated to room temperature for 2 hours. After the reaction, brominated SBS was obtained by rotary evaporation under reduced pressure. Brominated SBS, silver tetrafluoroborate, and dichloroethane were mixed in a mass ratio of 1:0.4:30 and heated to 50°C for 10 minutes. Dimethyl sulfide (0.3 times the mass of brominated SBS) was added and the mixture was heated to 85°C for reflux reaction for 25 minutes. After the reaction, the mixture was cooled to room temperature, precipitated with pure water, filtered, washed, and vacuum dried to obtain modified SBS. (3) Natural zeolite and 20 wt% sodium hydroxide solution were mixed in a mass ratio of 1:10, stirred at 60 ° C for 6 h, filtered, washed and dried to obtain porous zeolite; porous zeolite, aniline methyl trimethoxysilane and ethanol were mixed in a mass ratio of 1:6:100, ultrasonicated for 30 min, stirred at room temperature for 4 h, filtered, washed and dried to obtain pretreated zeolite; pretreated zeolite, phenylsilane and tetrabutylammonium acetate were mixed in a mass ratio of 1:6:0.02 under a carbon dioxide atmosphere, stirred at 2 ° C for 50 min, heated to 20 ° C for 5 h, filtered, washed and dried to obtain formyl zeolite; (4) Under nitrogen protection, formyl zeolite, chloroform, 2,2,6,6-tetramethylpiperidin-4-yl 4-aminobenzoate, and phosphorus pentachloride were mixed at a mass ratio of 1:30:1.2:1.7 at 5°C for 50 minutes, heated to room temperature and stirred for 2 hours, then heated to 60°C and refluxed for 2 hours. After the reaction was completed, the mixture was cooled to room temperature, and the pH was adjusted to 8 with 35 wt% ammonia water. The mixture was filtered, washed, and dried to obtain a pre-modified zeolite. The pre-modified zeolite, dimethylaminopyridine, triethylamine, dichloromethane, and methacrylic anhydride were mixed at a mass ratio of 1:0.2:3:60:2, stirred at room temperature for 10 hours, filtered, washed with saturated sodium carbonate solution, and dried to obtain a modified zeolite. (5) Modified SBS and base asphalt were weighed in a mass ratio of 1:25. After heating the base asphalt to 175°C, the modified SBS was added and sheared and stirred for 50 minutes to obtain modified asphalt. The following components were weighed, in parts by mass: 20 parts of modified asphalt, 3 parts of pure water, 90 parts of aggregate, 3 parts of cement, 3 parts of modified zeolite, 2 parts of pentaerythritol tetrakis-3-mercaptopropionate, and 0.1 parts of nucleophilic reagent. The modified asphalt, modified zeolite, and pure water were mixed at 160°C to obtain foamed asphalt. The foamed asphalt, aggregate, cement, pentaerythritol tetrakis-3-mercaptopropionate, and nucleophilic reagent were mixed at 140°C to obtain a mixture.

[0024] Comparative Example 1: The preparation method of the foamed asphalt mixture of Comparative Example 1 differs from that of Example 2 in that the method does not contain steps (1) to (2), and step (5) is modified as follows: SBS and base asphalt are weighed in a mass ratio of 1:23, the base asphalt is heated to 176°C, and then SBS is added and sheared and stirred for 55 minutes to obtain modified asphalt; the following components are weighed, in parts by mass: 17 parts of modified asphalt, 2.5 parts of pure water, 80 parts of aggregate, 2.5 parts of cement, 2.5 parts of modified zeolite, 1.2 parts of pentaerythritol tetrakis-3-mercaptopropionate, and 0.1 part of nucleophilic reagent; the modified asphalt, modified zeolite, and pure water are mixed at 165°C to obtain foamed asphalt; and the foamed asphalt, aggregate, cement, pentaerythritol tetrakis-3-mercaptopropionate, and nucleophilic reagent are mixed at 150°C to obtain a mixture.

[0025] Comparative Example 2: The preparation method of the foamed asphalt mixture of Comparative Example 2 differs from that of Example 2 in that steps (3) to (4) are not included, and step (5) is modified as follows: modified SBS and base asphalt are weighed in a mass ratio of 1:23, the base asphalt is heated to 176°C, and then the modified SBS is added and sheared and stirred for 55 minutes to obtain modified asphalt; the following components are weighed, in parts by mass: 17 parts of modified asphalt, 2.5 parts of pure water, 80 parts of aggregate, 2.5 parts of cement, 2.5 parts of natural zeolite, 1.2 parts of pentaerythritol tetrakis-3-mercaptopropionate, and 0.1 part of nucleophilic reagent; the modified asphalt, natural zeolite, and pure water are mixed at 165°C to obtain foamed asphalt; and the foamed asphalt, aggregate, cement, pentaerythritol tetrakis-3-mercaptopropionate, and nucleophilic reagent are mixed at 150°C to obtain a mixture.

[0026] Comparative Example 3: The preparation method of the foamed asphalt mixture of Comparative Example 3 differs from that of Example 2 in that step (5) is modified as follows: modified SBS and base asphalt are mixed in a mass ratio of 1:23, the base asphalt is heated to 176°C, and then the modified SBS is added and sheared and stirred for 55 minutes to obtain modified asphalt; the following components are weighed, in parts by mass: 17 parts of modified asphalt, 2.5 parts of pure water, 80 parts of aggregate, 2.5 parts of cement, and 2.5 parts of modified zeolite; the modified asphalt, modified zeolite, and pure water are mixed at 165°C to obtain foamed asphalt; and the foamed asphalt, aggregate, and cement are mixed at 150°C to obtain a mixture.

[0027] Test Example 1, flame retardant performance test: Test method: The oxygen index of the mixtures prepared in the examples and comparative examples was measured using a JF-3 instrument in accordance with the standard NB / SH / T 0815-2010. The results are shown in Table 1: From the comparison of the experimental data of Examples 1 to 3 and Comparative Examples 1 to 3 in Table 1, it can be found that the foamed asphalt mixture prepared by the present invention has good flame retardant properties.

[0028] By comparison, the oxygen index of Examples 1 to 3 is greater than the limiting oxygen index of Comparative Example 1, indicating that the SBS is chlorosulfonated to impart sulfonyl chloride groups to the benzene rings on the styrene structures at both ends. Diethyl [(4-aminophenyl)(hydroxy)methyl]phosphonate is grafted onto the sulfonyl chloride through the reaction between the sulfonyl chloride and the amino group. The hydroxyl group on the diethyl [(4-aminophenyl)(hydroxy)methyl]phosphonate is then converted to bromine through the action of dibromotriphenylphosphine, and then a nucleophilic substitution reaction occurs with dimethyl sulfide to form a sulfonium salt. The introduction of sulfur and phosphorus elements can provide the material with good flame retardant properties.

[0029] Test Example 2, Splitting Strength Test: Test Method: The splitting strength of the mixtures prepared in the Examples and Comparative Examples was tested according to the splitting test method for asphalt mixtures in JTG-E20-2011 at a temperature of -10°C and a loading rate of 1 mm / min. The results are shown in Table 2. Anti-aging performance test: Test method: The mixture was subjected to thermal oxidation aging test according to the standard JTG / E20 T0734, with a temperature of 140°C, a heating time of 4 hours, and a loose density of 20 kg / m 2 The mixture is stirred once every hour; the mixture after thermal oxidation aging is placed in a UV aging box for UV aging test; the UV radiation intensity is 40mW / cm 2 The UV wavelength was 365nm, the temperature was 60℃, and the aging time was 10 days. The mixture was stirred once every 12 hours. The splitting strength retention rate before and after aging was tested and calculated according to the splitting strength test method. The results are shown in Table 2: From the comparison of the experimental data of Examples 1 to 3 and Comparative Examples 1 to 3 in Table 2, it can be found that the foamed asphalt mixture prepared by the present invention has good mechanical properties and anti-aging properties.

[0030] The splitting strengths of Examples 1 to 3 are greater than those of Comparative Examples 2 to 3, and the splitting strength retention rates of Examples 1 to 3 are greater than those of Comparative Example 2. This indicates that after the natural zeolite is treated with alkali, aniline methyl trimethoxysilane introduces an aniline methyl structure on the surface of the natural zeolite, generates a formyl group under the action of carbon dioxide, and then reacts with 2,2,6,6-tetramethylpiperidin-4-yl 4-aminobenzoate to generate a benzamidine structure while also introducing a hindered amine structure with antioxidant properties. Benzamidine has good ultraviolet absorption due to its conjugated structure. The hindered amine structure and the benzamidine structure can give the material good anti-aging properties; it then reacts with methacrylic anhydride to introduce double bonds on the surface of zeolite; the modified asphalt, pure water and zeolite are mixed and foamed to obtain foamed asphalt; the foamed asphalt, aggregate, cement, pentaerythritol tetrakis-3-mercaptopropionate and a nucleophilic reagent are mixed to obtain a foamed asphalt mixture; under the action of the nucleophilic reagent, the thiol groups on pentaerythritol tetrakis-3-mercaptopropionate form a cross-linked network between zeolite and SBS, and between SBS and SBS through a thiol-ene reaction, which can further improve the mechanical properties of the mixture.

[0031] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims, not the foregoing description, and all variations within the meaning and range of equivalents of the claims are intended to be encompassed therein. Any reference in a claim should not be construed as limiting the claim to which it relates.

Claims

1. A foamed asphalt mixture, characterized in that: The foamed asphalt mixture comprises modified asphalt, pure water, aggregate, cement, modified zeolite, nucleophilic reagent, and pentaerythritol tetrakis-3-mercaptopropionate; The modified asphalt is obtained by mixing modified SBS and base asphalt; the modified SBS is obtained by reacting chlorosulfonated SBS with diethyl [(4-aminophenyl)(hydroxy)methyl]phosphonate, followed by bromination and then reacting with dimethyl sulfide; The modified zeolite is obtained by reacting pretreated zeolite with carbon dioxide, grafting 2,2,6,6-tetramethylpiperidin-4-yl 4-aminobenzoate, and then reacting with methacrylic anhydride.

2. A method for preparing a foamed asphalt mixture, characterized in that: The method comprises the following preparation steps: (1) SBS is modified by chlorosulfonation to obtain chlorosulfonated SBS; chlorosulfonated SBS and diethyl [(4-aminophenyl)(hydroxy)methyl]phosphonate are reacted to obtain pre-modified SBS; (2) reacting pre-modified SBS with dibromotriphenylphosphine to obtain brominated SBS; reacting brominated SBS with silver tetrafluoroborate and dimethyl sulfide to obtain modified SBS; (3) natural zeolite is treated with sodium hydroxide and reacted with aniline methyl trimethoxysilane to obtain pretreated zeolite; the pretreated zeolite, phenylsilane, and tetrabutylammonium acetate are reacted in a carbon dioxide atmosphere to obtain formyl zeolite; (4) reacting formyl zeolite and 2,2,6,6-tetramethylpiperidin-4-yl 4-aminobenzoate to obtain pre-modified zeolite; reacting the pre-modified zeolite and methacrylic anhydride to obtain modified zeolite; (5) Modified SBS and base asphalt are mixed to obtain modified asphalt; the following components are weighed: modified asphalt, pure water, aggregate, cement, modified zeolite, pentaerythritol tetrakis-3-mercaptopropionate, and nucleophilic reagent; the modified asphalt, modified zeolite, and pure water are mixed to obtain foamed asphalt; the foamed asphalt, aggregate, cement, nucleophilic reagent, and pentaerythritol tetrakis-3-mercaptopropionate are mixed to obtain a mixture.

3. The method for preparing a foamed asphalt mixture according to claim 2, wherein: The preparation method of the pre-modified SBS in step (1) is as follows: weigh SBS, chloroform, chlorosulfonic acid, and thionyl chloride in a mass ratio of 1:(20-30):(1-2):(0.7-0.9); add the SBS and chloroform to chlorosulfonic acid at 5°C, heat to 45-55°C, stir for 60-70 minutes, add thionyl chloride, continue stirring for 60-70 minutes, cool to room temperature, precipitate with 0°C pure water, filter, wash with 0°C pure water, and vacuum dry to obtain chlorosulfonated SBS Chlorosulfonated SBS, diethyl [(4-aminophenyl)(hydroxy)methyl]phosphonate, and N,N-dimethylformamide were mixed in a mass ratio of 1:(0.2-0.3):(20-30), heated to 40-50°C, and reacted for 2-3 hours. A 10 wt% aqueous sodium carbonate solution was used to adjust the pH to 9-10. The mixture was precipitated with pure water, filtered, washed, and vacuum-dried to obtain pre-modified SBS. The SBS was a styrene-butadiene-styrene block copolymer, model LG501.

4. The method for preparing a foamed asphalt mixture according to claim 2, wherein: The preparation method of the modified SBS in step (2) is as follows: pre-modified SBS, tetrahydrofuran, pyridine, and dibromotriphenylphosphine are mixed in a mass ratio of 1:(20-30):(10-12):(0.5-0.6) at 0-4°C and stirred for 1-1.5h, heated to room temperature and reacted for 2-3h, and after the reaction, SBS bromide is obtained by rotary evaporation under reduced pressure; SBS bromide, silver tetrafluoroborate, and dichloroethane are mixed in a mass ratio of 1:(0.3-0.4):(20-30) and heated to 50-60°C and stirred for 10min, 0.2-0.3 times the mass of dimethyl sulfide of the brominated SBS is added, the temperature is raised to 85°C and refluxed for 25-30min, the reaction is cooled to room temperature after the reaction is completed, and the modified SBS is obtained by precipitation with pure water, filtration, washing, and vacuum drying.

5. The method for preparing a foamed asphalt mixture according to claim 2, wherein: The preparation method of the formyl zeolite in step (3) is as follows: natural zeolite and 20wt% sodium hydroxide solution are mixed in a mass ratio of 1:(8-10), stirred at 60°C for 6h, filtered, washed and dried to obtain porous zeolite; porous zeolite, aniline methyl trimethoxysilane and ethanol are mixed in a mass ratio of 1:(5-6):(80-100), ultrasonicated for 30min, stirred at room temperature for 4-5h, filtered, washed and dried to obtain pretreated zeolite; under a carbon dioxide atmosphere, pretreated zeolite, phenylsilane and tetrabutylammonium acetate are mixed in a mass ratio of 1:(5-6):(0.01-0.02), stirred and reacted at 0-2°C for 50-60min, heated to 20-25°C for reaction for 5-6h, and filtered, washed and dried after the reaction to obtain formyl zeolite; the natural zeolite has a particle size of 200 mesh and a water content of 7%.

6. The method for preparing a foamed asphalt mixture according to claim 2, wherein: The preparation method of the modified zeolite in step (4) is as follows: under nitrogen protection, formyl zeolite, chloroform, 2,2,6,6-tetramethylpiperidin-4-yl 4-aminobenzoate, and phosphorus pentachloride are mixed in a mass ratio of 1:(20-30):(1-1.2):(1.5-1.7) at 5°C for 50-60 minutes, heated to room temperature and stirred for 2-3 hours, then heated to 60-65°C and refluxed for 2-3 hours. After the reaction is completed, the mixture is cooled to room temperature, the pH is adjusted to 8-9 with 35wt% ammonia water, and the pre-modified zeolite is obtained by filtering, washing, and drying. The pre-modified zeolite, dimethylaminopyridine, triethylamine, dichloromethane, and methacrylic anhydride are mixed in a mass ratio of 1:(0.1-0.2):(2-3):(50-60):(1-2), stirred at room temperature for 10-12 hours, filtered, washed with saturated sodium carbonate solution, and dried to obtain the modified zeolite.

7. The method for preparing a foamed asphalt mixture according to claim 2, wherein: The preparation method of the foamed asphalt mixture in step (5) is as follows: modified SBS and base asphalt are weighed in a mass ratio of 1:(20-25), the base asphalt is heated to 175-180° C., and the modified SBS is added and sheared and stirred for 50-60 minutes to obtain modified asphalt; The following components are weighed in parts by mass: 15-20 parts of modified asphalt, 2-3 parts of pure water, 70-90 parts of aggregate, 2-3 parts of cement, 2-3 parts of modified zeolite, 1-2 parts of pentaerythritol tetrakis-3-mercaptopropionate, and 0.1 part of a nucleophile; the modified asphalt, modified zeolite, and pure water are mixed at 160-175° C. to obtain foamed asphalt; the foamed asphalt, aggregate, cement, pentaerythritol tetrakis-3-mercaptopropionate, and nucleophile are mixed at 140-160° C. to obtain a foamed asphalt mixture.

8. The method for preparing a foamed asphalt mixture according to claim 2, wherein: In step (5), the matrix asphalt is 70#A grade matrix asphalt; the aggregate is pumice with a water absorption rate of ≤1% and a mud content of ≤1%; the cement is P.O42.5 ordinary Portland cement; and the nucleophilic reagent is dimethylphenylphosphine.

9. Use of the foamed asphalt mixture prepared by the method for preparing the foamed asphalt mixture according to any one of claims 2 to 8 in road construction.

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