SBS dry modified asphalt mixture and preparation method thereof

Abstract

The present application relates to the field of road engineering, and specifically discloses a dry SBS modified asphalt mixture and a preparation method thereof, wherein the asphalt mixture is prepared by mixing raw materials including base asphalt, modifier and aggregate, wherein the modifier includes the following raw materials: SBS powder, solubilizer, stabilizer, rubber powder and modified nano-silica, wherein the modified nano-silica is prepared by PAMAM, 2,4-fluoro-3-hydroxybenzoic acid and carbodiimide hydrochloride and thioctic acid modified nano-silica; and its preparation method includes the following steps: uniformly mixing SBS powder, solubilizer, stabilizer, cross-linking agent, cross-linking accelerator, rubber powder and modified nano-silica to obtain the modifier; mixing the modifier with the aggregate, adding the heated base asphalt and mixing. The present application has the characteristics of solving the problems of segregation and reduction of product performance of modified asphalt during transportation and storage, and realizing the characteristics of SBS dry modified asphalt to improve the high and low temperature performance of asphalt mixture.

Description

Technical Field

[0001] The present application relates to the technical field of road engineering materials, and more specifically, to a dry SBS modified asphalt mixture and a preparation method thereof. Background Art

[0002] With the rapid development of expressways, the traffic volume is increasing, the vehicles are getting larger, and the number of heavy-loaded and overloaded vehicles is increasing. People have higher and higher requirements for the use of roads, and ordinary asphalt is difficult to meet the construction and use requirements. Polymer modified asphalt has been widely used because it can improve and improve the performance of road surfaces. Among them, SBS modified asphalt has become the main variety of polymer modified asphalt because it can significantly improve high temperature rutting resistance, low temperature cracking resistance, and enhance anti-aging and fatigue performance. It has been more and more widely used in actual projects.

[0003] However, at present, SBS modified asphalt is mainly modified by wet method, that is, SBS modifier is premixed with base asphalt in the factory to obtain finished modified asphalt, and then transported to the site for mixing with aggregates before use. This process requires SBS modified asphalt to go through the process of factory storage, transportation, and on-site storage before it can finally enter the mixing plant for mixing and use. SBS modified asphalt is a thermodynamically unstable system formed by using a high molecular polymer SBS modifier as a dispersed phase and uniformly dispersed in a certain particle size in the asphalt continuous phase by physical methods. Due to the differences in density, polarity, solubility parameters and other physical properties between SBS modifier and asphalt, this composite system is very prone to separation of SBS phase and asphalt phase, resulting in the segregation phenomenon that SBS gathers on the upper part and asphalt sinks on the lower part. This instability is not conducive to the large-scale production of SBS modified asphalt in factories, especially during storage and long-distance transportation. It can be seen that the existing wet-process modified asphalt mixture is prone to segregation and has high requirements for transportation and preservation. Even adding stabilizers cannot completely solve the segregation problem, which affects the quality of subsequent projects. The wet-process SBS modified asphalt technology faces difficult to overcome problems.

[0004] In recent years, new dry modification methods have received more and more attention. Dry modification is a process in which the asphalt mixture is directly mixed together during production and the modification is completed after the material is discharged. However, dry modification is currently mainly used in the field of physical modification, and the most widely used SBS modification has not been involved. Considering the advantages of SBS modified asphalt, how to use SBS dry modified asphalt to avoid the segregation and product performance degradation caused by thermodynamic instability during transportation and storage of modified asphalt is of great significance to the asphalt mixture preparation process. Summary of the invention

[0005] In order to solve the problem of segregation and reduced product performance of modified asphalt due to thermodynamic instability during transportation and storage, SBS dry-process modified asphalt is realized to improve the performance of asphalt mixture. The present application provides an SBS dry-process modified asphalt mixture and a preparation method thereof.

[0006] In a first aspect, the present application provides an SBS dry modified asphalt mixture, which adopts the following technical solution: an SBS dry modified asphalt mixture is prepared by mixing raw materials including base asphalt, a modifier and aggregate, wherein the modifier includes the following raw materials in parts by weight:

[0007] 20-30 parts of SBS powder, 4-8 parts of solubilizer, 3-5 parts of stabilizer, 8-12 parts of rubber powder and 12-15 parts of modified nano silicon dioxide, wherein the modified nano silicon dioxide is prepared from PAMAM, 2,4-fluoro-3-hydroxybenzoic acid and carbodiimide hydrochloride and lipoic acid modified nano silicon dioxide.

[0008] By adopting the above technical scheme, the SBS dry modified asphalt mixture in the present application is directly prepared by mixing base asphalt, modifier and aggregate, the modifier is mainly SBS powder, and the SBS can improve its dispersion and uniformity in the base asphalt after grinding, thereby improving the performance of the asphalt, and the addition of solubilizer can change the chemical composition ratio of the base asphalt, promote SBS to swell more fully, thereby improving the compatibility of SBS and asphalt, but the addition of solubilizer will reduce the high temperature performance of SBS modified asphalt.

[0009] Therefore, the present application also adds modified nano-silica obtained by modifying nano-silica with PAMAM, 4-fluoro-3-hydroxybenzoic acid and lipoic acid. PAMAM, as a macromolecular polymer network structure, can improve the high temperature resistance of asphalt mixture, and the addition of nano-silica improves the high temperature, low temperature and fatigue resistance of asphalt mixture. 4-fluoro-3-hydroxybenzoic acid introduces hydroxyl groups, carboxyl groups and fluorine elements into the benzene ring structure, and the hydroxyl groups containing fluorine atoms and lipoic acid molecules form covalent bonds through interaction, connecting to form longer chain polymers, and forming polylipoic acid through the polymerization of hydroxyl groups and lipoic acid. The carboxyl groups on the polylipoic acid molecular chain react with the amino groups on the PAMAM molecular chain to form amide bonds, thereby realizing the introduction of PAMAM molecules into the polylipoic acid molecular chain to form larger three-dimensional network structure molecules, further improving the high temperature, low temperature, crack resistance and fatigue resistance of asphalt mixture. Labor performance, the introduction of benzene ring structure improves the high temperature rutting resistance of asphalt mixture, and the benzene ring structure has a higher affinity for aromatic hydrocarbons, which improves lipophilicity. The introduction of benzene ring structure can enhance the interaction between SBS and asphalt, so that SBS is dispersed in the matrix asphalt in the form of a spatial network, thereby greatly improving the asphalt performance. The introduction of polylipoic acid can improve the viscosity function of SBS modified asphalt, which helps to improve the performance of asphalt. Moreover, sulfur induces chemical changes between SBS and asphalt to form a stable network structure, which plays a role in rapid cross-linking of SBS and asphalt, thereby realizing the application of SBS dry modified asphalt. When preparing asphalt mixture, the SBS-containing modifier, asphalt and aggregate are directly put into the mixing plant for use, achieving the effect of mixing and modification, eliminating the traditional SBS wet modification production link, and avoiding the problems of segregation and performance index attenuation during storage and transportation.

[0010] Optionally, the modified nano-silicon dioxide is prepared by the following method:

[0011] Dissolve carbodiimide hydrochloride and lipoic acid in a dichloromethane solution, stir for 20-30 minutes, then drop 2,4-fluoro-3-hydroxybenzoic acid, stir for 1-2 hours, then add PAMAM, heat to 50-65°C, then add platinum catalyst and phosphoric acid, react at 50-65°C for 1-2 hours, cool, add nano-silica, soak for 30-40 minutes, filter, and dry to obtain modified nano-silica.

[0012] By adopting the above technical scheme, carbodiimide hydrochloride is used as a coagulant and dehydrating agent to promote the formation reaction of esters and amides. Under the condition of carbodiimide hydrochloride, the hydroxyl group in 2,4-fluoro-3-hydroxybenzoic acid reacts and polymerizes with thioctic acid to form polythioic acid. A benzene ring, an ester group, a fluorine group and a carboxylic acid group are introduced into the polythioic acid molecular chain. Then, under the conditions of a catalyst and a phosphoric acid catalyst and temperature, the carboxylic acid group reacts with the amino group in PAMAM to form an amide, thereby realizing the grafting and polymerization reactions of PAMAM, 2,4-fluoro-3-hydroxybenzoic acid and thioctic acid, forming a macromolecular network polymer containing fluorine, an ester group, a benzene ring and an amide group, thereby significantly improving the comprehensive performance of asphalt and improving the interaction between SBS and asphalt.

[0013] Optionally, during the preparation of modified nano-silicon dioxide, the raw materials are added according to the following weight parts:

[0014] 3-5 parts of carbodiimide hydrochloride, 20-30 parts of thioctic acid, 15-22 parts of dichloromethane, 8-12 parts of 2,4-fluoro-3-hydroxybenzoic acid, 5-8 parts of PAMAM, 0.05-0.15 parts of platinum catalyst, 0.05-0.15 parts of phosphoric acid, and 10-18 parts of nano silicon dioxide.

[0015] Optionally, the stabilizer is polyisobutylene and triallyl isocyanurate in a mass ratio of 1:(0.5-0.8).

[0016] By adopting the above technical scheme, polyisobutylene as a stabilizer can promote the dispersion of SBS and matrix asphalt, increase the compatibility between the two, and help improve the high-temperature rutting resistance and low-temperature cracking resistance of modified asphalt. Triallyl isocyanurate is used as a cross-linking agent for SBS and asphalt. The active group -NCO in triallyl isocyanurate can undergo addition reaction with the carbon-carbon double bond in SBS to form a -SS- free bond, replacing the original C=C double bond, thereby realizing the cross-linking and modification of SBS, and the active group -NCO reacts with the functional group in asphalt to form a stable chemical bond, thereby realizing rapid cross-linking of SBS and asphalt, improving the performance of asphalt mixture and realizing modification by stirring.

[0017] Optionally, the stabilizer also includes a styrene-maleic anhydride copolymer obtained by polymerizing styrene monomer, maleic anhydride monomer and versatate vinyl ester monomer under the action of an initiator and then sulfonating, and the added mass ratio of the styrene-maleic anhydride copolymer to triallyl isocyanurate is 1:(0.8-1.2).

[0018] By adopting the above technical scheme, styrene-maleic anhydride copolymer can be used as a catalyst to accelerate the cross-linking reaction between polylipoic acid and rubber powder and asphalt, so that the modifier and the base asphalt can be quickly cross-linked after mixing, and the purpose of SBS dry-process modified asphalt can be achieved. In addition, maleic anhydride is reactive and can undergo cross-linking reaction with olefin bonds and active functional groups in SBS and asphalt, which is helpful for SBS modified asphalt. At the same time, it can also form a stable three-dimensional network structure, thereby enhancing the comprehensive properties of the modified asphalt, such as high temperature stability and low temperature crack resistance.

[0019] Optionally, the styrene-maleic anhydride copolymer is prepared by the following method:

[0020] Styrene monomer, maleic anhydride monomer and versatate vinyl carbonate monomer are mixed, N, N-dimethylformamide solvent and initiator are added, the temperature is raised to 45-55°C, stirred, and then the temperature is further raised to 80-85°C, reacted for 3-4 hours, cooled, filtered to obtain a filter cake, the filter cake is dissolved in dichloromethane, and then the temperature is raised to 45-55°C, fuming sulfuric acid is added dropwise, reacted for 1.5-2.5 hours, the pH is adjusted to neutral, and dried to obtain a styrene-maleic anhydride copolymer.

[0021] By adopting the above technical scheme, styrene monomer, maleic anhydride monomer and tert-butyl vinyl carbonate monomer are polymerized to obtain a blended polymer. The double bonds in tert-butyl vinyl carbonate have good reactivity and can be copolymerized with styrene and maleic anhydride to improve the molecular chain and molecular structure of the copolymer, further improve the high and low temperature resistance of SBS modified asphalt, and the steric hindrance formed by its end group and the non-polarity of the alkyl group are conducive to improving the compatibility of SBS with hydrocarbon asphalt, and can also reduce the surface tension of SBS, thereby improving the compatibility of SBS with matrix asphalt. Then, the blended polymer is introduced with sulfonic acid groups through sulfonation. The introduction of sulfonic acid groups improves the catalytic activity of styrene-maleic anhydride copolymer in the modifier system, further promotes the rapid crosslinking of SBS and matrix asphalt, which is conducive to the rapid melting and dispersion of SBS and rapid crosslinking with matrix asphalt after SBS and matrix asphalt are added to the mixing plant, thereby realizing the dry modification of the two.

[0022] Optionally, when preparing styrene-maleic anhydride copolymer, the added mass ratio of styrene, maleic anhydride and versatate is 1: (0.4-0.6): (0.3-0.5), the added mass ratio of N,N-dimethylformamide solvent is 70-80wt% of the styrene monomer, the added amount of initiator is 3-5wt% of the styrene monomer, the added amount of dichloromethane is 6-8 times the mass of the filter cake, the mass concentration of oleum is 15-25%, and the added amount of oleum is 8-10wt% of the added amount of the filter cake.

[0023] Optionally, the solubilizing agent is an alcohol solubilizing agent; the matrix asphalt is one or both of rock asphalt and petroleum asphalt.

[0024] Optionally, the alcohol solubilizer is one or more of ethanol, isopropanol, and glycerol.

[0025] By adopting the above technical solution, the alcohol compound can form hydrogen bonds with the SBS modifier and asphalt, improve the interaction between the two, and thus improve the comprehensive performance of the SBS dry-process modified asphalt.

[0026] Optionally, the added mass ratio of base asphalt, modifier and aggregate is (4-6):(1-1.5):100.

[0027] In a second aspect, the present application provides a method for preparing an SBS dry modified asphalt mixture, which adopts the following technical solution:

[0028] A method for preparing a SBS dry modified asphalt mixture comprises the following steps:

[0029] The SBS powder, the solubilizer, the stabilizer, the crosslinking agent, the crosslinking accelerator, the rubber powder and the modified nano-silicon dioxide are uniformly mixed to obtain a modifier;

[0030] The aggregate is heated to 220-240°C, the base asphalt is heated to 150-170°C, and then the modifier is mixed with the aggregate, and then the heated base asphalt is added and mixed for 10-15 minutes to obtain the SBS dry modified asphalt mixture.

[0031] By adopting the above technical scheme, in the preparation method of the above asphalt mixture, the modifier, aggregate and base asphalt are directly put into the mixing plant for heating and then mixed and stirred to realize SBS dry-process modified asphalt, achieving the effect of modification during mixing. Compared with the traditional SBS wet-process modified asphalt that goes through the swelling stage, grinding stage and development stage, the present application does not need to go through hot storage to allow the modified asphalt to develop, nor does it need to go through the transportation process, thereby solving the problem of segregation and reduced product performance caused by thermodynamic instability during transportation and storage of traditional SBS wet-process modified asphalt.

[0032] In summary, this application has the following beneficial effects:

[0033] 1. The asphalt mixture provided by the present application is to directly put the modifier, aggregate and base asphalt into a mixing plant, heat them and mix them, so as to realize SBS dry modified asphalt, and achieve the effect of modification during mixing. Compared with the traditional SBS wet modified asphalt which goes through the swelling stage, grinding stage and development stage, the present application does not need to go through the hot storage to make the modified asphalt develop, nor does it need to go through the transportation process, thus solving the problem of segregation and reduced product performance caused by thermodynamic instability during transportation and storage of traditional SBS wet modified asphalt;

[0034] 2. The present application also adds modified nano-silica obtained by PAMAM, 4-fluoro-3-hydroxybenzoic acid and lipoic acid modified nano-silica. 4-fluoro-3-hydroxybenzoic acid is polymerized with lipoic acid through hydroxyl groups to form polylipoic acid, and PAMAM molecules are introduced into the polylipoic acid molecular chain to form larger three-dimensional network structure molecules, which further improve the high temperature, low temperature, crack resistance and fatigue resistance of the asphalt mixture. The introduction of the benzene ring structure improves the high temperature rutting resistance of the asphalt mixture and enhances the interaction between SBS and asphalt, so that SBS is dispersed in the matrix asphalt in the form of a spatial network, thereby greatly improving the asphalt performance. In addition, the introduction of polylipoic acid induces chemical changes between SBS and asphalt to form a stable network structure, which plays a role in rapid cross-linking of SBS and asphalt, thereby realizing the application of SBS dry modified asphalt;

[0035] 3. In the present application, styrene monomer, maleic anhydride monomer and tert-butyl vinyl carbonate monomer are polymerized to obtain a polymer blend. The double bonds in tert-butyl vinyl carbonate have good reactivity and can be copolymerized with styrene and maleic anhydride to improve the molecular chain and molecular structure of the copolymer, further improve the high and low temperature resistance of SBS modified asphalt, and the steric hindrance formed by its end groups and the non-polarity of the alkyl group are conducive to improving the compatibility of SBS with hydrocarbon asphalt, and can also reduce the surface tension of SBS, thereby improving the compatibility of SBS with matrix asphalt. Then, the polymer blend is sulfonated to introduce sulfonic acid groups. The introduction of sulfonic acid groups improves the catalytic activity of styrene-maleic anhydride copolymer in the modifier system, further promotes the rapid crosslinking of SBS and matrix asphalt, which is conducive to the rapid melting and dispersion of SBS and rapid crosslinking with matrix asphalt after SBS and matrix asphalt are added to the mixing plant, thereby realizing the dry modification of the two. DETAILED DESCRIPTION

[0036] The present application is further described in detail below in conjunction with the examples. It is particularly noted that if no specific conditions are specified in the following examples, the experiments are carried out according to conventional conditions or the conditions recommended by the manufacturer. Unless otherwise specified, the raw materials used in the following examples can be obtained from common commercial sources.

[0037] The rubber powder in the following examples is waste tire rubber powder with a particle size of 80-100 mesh;

[0038] SBS powder is SBS powder with a particle size of 800-1000 mesh obtained by grinding and screening. SBS is SBS model 792E produced by Jinan Shanhai Chemical Technology Co., Ltd.

[0039] The cross-linking agent is a sulfur cross-linking agent;

[0040] The cross-linking accelerator is sodium dibutyl dithiocarbamate;

[0041] The matrix asphalt is selected from one or both of rock asphalt and petroleum asphalt, and the petroleum asphalt is A-70 road petroleum asphalt; the aggregate is selected from coarse aggregate, fine aggregate and mineral powder in a mass ratio of 100:(30-40):(10-15), the coarse aggregate is selected from crushed stone A and crushed stone B in a mass ratio of 1:(0.6-0.8), the particle size of crushed stone A is 5-10mm, and the particle size of crushed stone B is 10-18mm; the fine aggregate is machine-made sand with a particle size of 3-5mm, and the mineral powder is S95 grade mineral powder.

[0042] The following preparation examples 1-3 are preparation examples of modified nano-silicon dioxide:

[0043] Preparation Example 1

[0044] A method for preparing modified nano-silicon dioxide comprises the following steps:

[0045] 4 kg of carbodiimide hydrochloride and 25 kg of lipoic acid were dissolved in 20 kg of dichloromethane solution, stirred for 25 min, then 10 kg of 2,4-fluoro-3-hydroxybenzoic acid was added dropwise, stirred for 1.5 h, then 6 kg of PAMAM was added, the temperature was raised to 60 ° C, then 0.1 kg of platinum catalyst and 0.1 kg of phosphoric acid were added, reacted at 60 ° C for 1.5 h, cooled, 15 kg of nano-silica was added, soaked for 35 min, filtered, and dried to obtain modified nano-silica.

[0046] Preparation Example 2

[0047] A method for preparing modified nano-silicon dioxide comprises the following steps:

[0048] 3kg of carbodiimide hydrochloride and 20kg of lipoic acid are dissolved in 15-22kg of dichloromethane solution, stirred for 20min, then 8kg of 2,4-fluoro-3-hydroxybenzoic acid is added dropwise, stirred for 1h, then 5kg of PAMAM is added, the temperature is raised to 50°C, then 0.05kg of platinum catalyst and 0.05kg of phosphoric acid are added, reacted at 50°C for 2h, cooled, 10kg of nano-silica is added, soaked for 30min, filtered, and dried to obtain modified nano-silica.

[0049] Preparation Example 3

[0050] A method for preparing modified nano silicon dioxide comprises the following steps:

[0051] 5 kg of carbodiimide hydrochloride and 30 kg of lipoic acid were dissolved in 22 kg of dichloromethane solution, stirred for 30 min, then 12 kg of 2,4-fluoro-3-hydroxybenzoic acid was dropped, stirred for 2 h, then 8 kg of PAMAM was added, the temperature was raised to 65 ° C, then 0.15 kg of platinum catalyst and 0.15 kg of phosphoric acid were added, reacted at 65 ° C for 1 h, cooled, 18 kg of nano-silica was added, soaked for 40 min, filtered, and dried to obtain modified nano-silica.

[0052] Comparative Preparation Example 1

[0053] A method for preparing modified nano-silicon dioxide is carried out according to the method in Preparation Example 1, except that PAMAM is not added to the raw materials.

[0054] Comparative Preparation Example 2

[0055] A method for preparing modified nano-silica is carried out according to the method in Preparation Example 1, except that 2,4-fluoro-3-hydroxybenzoic acid is replaced by p-hydroxybenzoic acid in equal amounts.

[0056] Comparative Preparation Example 3

[0057] A method for preparing modified nano-silicon dioxide is carried out according to the method in Preparation Example 1, except that thioctic acid is not added to the raw materials.

[0058] Example 1

[0059] A method for preparing a SBS dry modified asphalt mixture comprises the following steps:

[0060] S1, 25kg SBS powder, 6kg solubilizer, 4kg stabilizer, 0.4kg crosslinking agent, 0.2kg crosslinking accelerator, 10kg rubber powder and 13kg modified nano-silicon dioxide prepared in Preparation Example 1 were mixed uniformly to obtain a modifier;

[0061] S2. Based on 1000 kg of aggregate, heat the aggregate to 230° C., heat the base asphalt to 160° C., then mix the modifier obtained in step S1 with the aggregate, then add the heated base asphalt, mix for 12 minutes, and obtain an SBS dry modified asphalt mixture.

[0062] Among them, in step S1, the stabilizer is polyisobutylene and triallyl isocyanurate in a mass ratio of 1:0.6; the solubilizer is an alcohol solubilizer, specifically propylene glycol; the crosslinker is a sulfur crosslinker; the crosslinking accelerator is sodium dibutyl dithiocarbamate;

[0063] In step S2, the mass ratio of base asphalt, modifier and aggregate is 5:1.2:100, and the base asphalt is A-70 road petroleum asphalt; the aggregate is coarse aggregate, fine aggregate and mineral powder in a mass ratio of 100:35:12, the coarse aggregate is crushed stone A and crushed stone B in a mass ratio of 1:0.7, the particle size of crushed stone A is 5-10mm, and the particle size of crushed stone B is 10-18mm; the fine aggregate is machine-made sand with a particle size of 3-5mm, and the mineral powder is S95 grade mineral powder.

[0064] Example 2

[0065] A method for preparing a SBS dry modified asphalt mixture comprises the following steps:

[0066] S1, 20kg SBS powder, 4kg solubilizer, 3kg stabilizer, 0.3kg crosslinking agent, 0.1kg crosslinking accelerator, 8kg rubber powder and 12kg modified nano-silicon dioxide prepared in Preparation Example 2 were mixed uniformly to obtain a modifier;

[0067] S2. Based on 1000 kg of aggregate, heat the aggregate to 220° C., heat the base asphalt to 150° C., then mix the modifier obtained in step S1 with the aggregate, then add the heated base asphalt, mix for 10 minutes, and obtain an SBS dry modified asphalt mixture.

[0068] Among them, in step S1, the stabilizer is polyisobutylene and triallyl isocyanurate in a mass ratio of 1:0.5; the solubilizer is an alcohol solubilizer, specifically propylene glycol; the crosslinker is a sulfur crosslinker; the crosslinking accelerator is sodium dibutyl dithiocarbamate;

[0069] In step S2, the mass ratio of base asphalt, modifier and aggregate is 4:1:100, and the base asphalt is A-70 road petroleum asphalt; the aggregate is coarse aggregate, fine aggregate and mineral powder in a mass ratio of 100:30:10, the coarse aggregate is crushed stone A and crushed stone B in a mass ratio of 1:0.6, the particle size of crushed stone A is 5-10mm, and the particle size of crushed stone B is 10-18mm; the fine aggregate is machine-made sand with a particle size of 3-5mm, and the mineral powder is S95 grade mineral powder.

[0070] Example 3

[0071] A method for preparing a SBS dry modified asphalt mixture comprises the following steps:

[0072] S1, 30kg SBS powder, 8kg solubilizer, 5kg stabilizer, 0.5kg crosslinking agent, 0.3kg crosslinking accelerator, 12kg rubber powder and 15kg modified nano-silicon dioxide prepared in Preparation Example 3 were mixed uniformly to obtain a modifier;

[0073] S2. Based on 1000 kg of aggregate, heat the aggregate to 240° C., heat the base asphalt to 170° C., then mix the modifier obtained in step S1 with the aggregate, then add the heated base asphalt, mix for 15 minutes, and obtain an SBS dry modified asphalt mixture.

[0074] Among them, in step S1, the stabilizer is polyisobutylene and triallyl isocyanurate in a mass ratio of 1:0.8; the solubilizer is an alcohol solubilizer, specifically propylene glycol; the crosslinker is a sulfur crosslinker; the crosslinking accelerator is sodium dibutyl dithiocarbamate;

[0075] In step S2, the mass ratio of base asphalt, modifier and aggregate is 6:1.5:100, and the base asphalt is A-70 road petroleum asphalt; the aggregate is coarse aggregate, fine aggregate and mineral powder in a mass ratio of 100:40:15, the coarse aggregate is crushed stone A and crushed stone B in a mass ratio of 1:0.8, the particle size of crushed stone A is 5-10mm, and the particle size of crushed stone B is 10-18mm; the fine aggregate is machine-made sand with a particle size of 3-5mm, and the mineral powder is S95 grade mineral powder.

[0076] Example 4

[0077] A method for preparing an SBS dry modified asphalt mixture is carried out according to the method in Example 1, except that in step S1, styrene-maleic anhydride copolymer is added together with the SBS powder, the added mass ratio of the styrene-maleic anhydride copolymer to triallyl isocyanurate is 1:1, and the styrene-maleic anhydride copolymer is prepared by the following method:

[0078] Based on 10 kg of styrene monomer, styrene monomer, maleic anhydride monomer and versatate vinyl ester monomer are mixed in a mass ratio of 1:0.5:0.4, N,N-dimethylformamide solvent and initiator-benzoyl peroxide BPO are added, the temperature is raised to 50°C, stirred, and then continued to be raised to 80°C, reacted for 3.5 hours, cooled, filtered to obtain a filter cake, the filter cake is dissolved in dichloromethane, and then the temperature is raised to 50°C, fuming sulfuric acid with a mass concentration of 20% is added dropwise, reacted for 2 hours, the pH is adjusted to neutral, and dried to obtain a styrene-maleic anhydride copolymer.

[0079] The added mass ratio of N,N-dimethylformamide solvent is 75wt% of the styrene monomer, the added amount of initiator is 4wt% of the styrene monomer, the added amount of dichloromethane is 7 times the mass of the filter cake, and the added amount of fuming sulfuric acid is 9wt% of the added amount of the filter cake.

[0080] Example 5

[0081] A method for preparing an SBS dry modified asphalt mixture is carried out according to the method in Example 1, except that in step S1, styrene-maleic anhydride copolymer is added together with the SBS powder, the added mass ratio of the styrene-maleic anhydride copolymer to triallyl isocyanurate is 1:0.8, and the styrene-maleic anhydride copolymer is prepared by the following method:

[0082] Based on 10 kg of styrene monomer, styrene monomer, maleic anhydride monomer and versatate vinyl ester monomer are mixed in a mass ratio of 1:0.4:0.3, N,N-dimethylformamide solvent and initiator-benzoyl peroxide BPO are added, the temperature is raised to 45°C, stirred, and then continued to be raised to 80°C, reacted for 4 hours, cooled, and filtered to obtain a filter cake, the filter cake is dissolved in dichloromethane, and then the temperature is raised to 45°C, fuming sulfuric acid with a mass concentration of 15% is added dropwise, the reaction is carried out for 1.5 hours, the pH is adjusted to neutral, and dried to obtain a styrene-maleic anhydride copolymer.

[0083] The added mass ratio of N,N-dimethylformamide solvent is 70wt% of the styrene monomer, the added amount of initiator is 3wt% of the styrene monomer, the added amount of dichloromethane is 6 times the mass of the filter cake, and the added amount of fuming sulfuric acid is 8wt% of the added amount of the filter cake.

[0084] Example 6

[0085] A method for preparing an SBS dry modified asphalt mixture is carried out according to the method in Example 1, except that in step S1, styrene-maleic anhydride copolymer is added together with the SBS powder, the mass ratio of the styrene-maleic anhydride copolymer to triallyl isocyanurate is 1:1.2, and the styrene-maleic anhydride copolymer is prepared by the following method:

[0086] Based on 10 kg of styrene monomer, styrene monomer, maleic anhydride monomer and versatate vinyl ester monomer are mixed in a mass ratio of 1:0.6:0.5, N,N-dimethylformamide solvent and initiator-benzoyl peroxide BPO are added, the temperature is raised to 55°C, stirred, and then continued to be raised to 85°C, reacted for 3 hours, cooled, and filtered to obtain a filter cake, the filter cake is dissolved in dichloromethane, and then the temperature is raised to 55°C, fuming sulfuric acid with a mass concentration of 25% is added dropwise, the reaction is carried out for 2.5 hours, the pH is adjusted to neutral, and dried to obtain a styrene-maleic anhydride copolymer.

[0087] The added mass ratio of N,N-dimethylformamide solvent is 80wt% of the styrene monomer, the added amount of initiator is 5wt% of the styrene monomer, the added amount of dichloromethane is 8 times the mass of the filter cake, and the added amount of fuming sulfuric acid is 10wt% of the added amount of the filter cake.

[0088] Example 7

[0089] A method for preparing an SBS dry modified asphalt mixture is carried out according to the method in Example 4, except that when preparing the styrene-maleic anhydride copolymer, versatate vinyl carbonate is not added to the raw material, and is replaced by styrene monomer and maleic anhydride monomer in a mass ratio of 1:0.5.

[0090] Example 8

[0091] A method for preparing an SBS dry modified asphalt mixture is carried out according to the method in Example 4, except that when preparing the styrene-maleic anhydride copolymer, no subsequent sulfonation operation is performed after filtering to obtain the filter cake, and the preparation is directly added as the styrene-maleic anhydride copolymer.

[0092] Comparative Example 1

[0093] A method for preparing an SBS dry modified asphalt mixture is carried out according to the method in Example 1, except that in step S1, an equal amount of modified nano silicon dioxide is replaced by nano silicon dioxide.

[0094] Comparative Examples 2-3

[0095] A method for preparing an SBS dry modified asphalt mixture is carried out according to the method in Example 1, except that the modified nano silicon dioxide in step S1 is the modified nano silicon dioxide prepared in Comparative Example 1 and Comparative Example 2, respectively.

[0096] Comparative Example 4

[0097] A method for preparing an SBS dry modified asphalt mixture is carried out according to the method in Example 1, except that the modified nano-silicon dioxide in step S1 is the modified nano-silicon dioxide prepared in Comparative Example 3, and the amount of cross-linking agent added is 0.6 kg.

[0098] Performance Testing

[0099] The asphalt mixtures prepared in the above examples and comparative examples were subjected to low temperature bending test failure strain (-10°C), rutting dynamic stability (60°C, 0.7MPa) and freeze-thaw splitting residual strength ratio tests according to "JTG E20-2011 Highway Engineering Asphalt and Asphalt Mixture Test Specifications". The test results are shown in Table 1 below:

[0100] Table 1:

[0101]

[0102] Referring to the test results in Table 1 above, it can be seen that the SBS dry modified asphalt mixture prepared in this application has excellent high temperature rutting resistance, low temperature crack resistance and other properties. Combining the test results of Example 1 and Examples 4-6, it can be seen that when a styrene-maleic anhydride copolymer with styrene, maleic anhydride and tert-carbonate as monomers is added to the stabilizer and sulfonated, the high and low temperature resistance of the final asphalt mixture is significantly improved. Referring to the results of Example 1, Example 4 and Example 7, it can be seen that when tert-carbonate is not added to the polymerization monomer when preparing styrene-maleic anhydride copolymer, its high and low temperature performance is significantly reduced. Combining the test results of Example 8, it can be seen that when preparing styrene-maleic anhydride copolymer, when sulfonation is not performed after polymerization, its high and low temperature performance is also reduced, but it is better than Example 7. The addition of tert-carbonate monomers can not only improve the molecular chain network structure, but also the steric hindrance effect helps to improve the compatibility of SBS with the matrix asphalt and improve the comprehensive performance of the modified asphalt.

[0103] Referring to the test results of Example 1 and Comparative Example 1, it can be seen that when the modified nano-silica is replaced by nano-silica in equal amounts, the comprehensive performance of the SBS dry-modified asphalt mixture is poor. Referring to the test results of Example 1 and Comparative Examples 2 and 3, when PAMAM is not added to the modified nano-silica in Comparative Example 2, the high and low temperature performance is significantly reduced. When 2,4-fluoro-3-hydroxybenzoic acid is replaced by p-hydroxybenzoic acid in equal amounts when the nano-silica is modified in Comparative Example 3, that is, when there is no fluorine functional group in the final system, its high and low temperature performance is also significantly reduced. The introduction of fluorine element can significantly improve the high and low temperature performance of SBS dry-modified asphalt and improve the comprehensive performance of the pavement. Referring to the test results of Comparative Example 4, polylipoic acid is not introduced into the modified nano-silica in Comparative Example 4, and when the amount of sulfonic acid cross-linking agent is increased in the modifier system, the high and low temperature performance of the final asphalt mixture is lower than that of Example 1.

[0104] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make modifications to the present embodiment without any creative contribution as needed. However, as long as it is within the scope of the claims of the present application, it shall be protected by the patent law.

Claims

1. A SBS dry modified asphalt mixture, characterized in that: It is made by mixing raw materials including base asphalt, modifier and aggregate. Wherein, the modifier comprises the following raw materials in parts by weight: 20-30 parts of SBS powder, 4-8 parts of solubilizer, 3-5 parts of stabilizer, 0.3-0.5 parts of crosslinking agent, 0.1-0.3 parts of crosslinking accelerator, 8-12 parts of rubber powder and 12-15 parts of modified nano-silicon dioxide, wherein the modified nano-silicon dioxide is prepared from PAMAM, 2,4-fluoro-3-hydroxybenzoic acid and carbodiimide hydrochloride and thioctic acid modified nano-silicon dioxide; The stabilizer is selected from polyisobutylene and triallyl isocyanurate in a mass ratio of 1: (0.5-0.8), and the stabilizer also includes a styrene-maleic anhydride copolymer prepared by sulfonation after polymerization of styrene monomer, maleic anhydride monomer and versatate vinyl ester monomer under the action of an initiator, and the added mass ratio of styrene-maleic anhydride copolymer to triallyl isocyanurate is 1: (0.8-1.2).

2. The SBS dry modified asphalt mixture according to claim 1, characterized in that: The modified nano silicon dioxide is prepared by the following method: Dissolve carbodiimide hydrochloride and lipoic acid in a dichloromethane solution, stir for 20-30 minutes, then drop 2,4-fluoro-3-hydroxybenzoic acid, stir for 1-2 hours, then add PAMAM, heat to 50-65°C, then add platinum catalyst and phosphoric acid, react at 50-65°C for 1-2 hours, cool, add nano-silica, soak for 30-40 minutes, filter, and dry to obtain modified nano-silica.

3. The SBS dry modified asphalt mixture according to claim 2, characterized in that: During the preparation of modified nano-silicon dioxide, the raw materials are added according to the following weight parts: 3-5 parts of carbodiimide hydrochloride, 20-30 parts of thioctic acid, 15-22 parts of dichloromethane, 8-12 parts of 2,4-fluoro-3-hydroxybenzoic acid, 5-8 parts of PAMAM, 0.05-0.15 parts of platinum catalyst, 0.05-0.15 parts of phosphoric acid, and 10-18 parts of nano silicon dioxide.

4. The SBS dry modified asphalt mixture according to claim 1, characterized in that: The styrene-maleic anhydride copolymer is prepared by the following method: Styrene monomer, maleic anhydride monomer and versatate vinyl carbonate monomer are mixed, N, N-dimethylformamide solvent and initiator are added, the temperature is raised to 45-55°C, stirred, and then the temperature is further raised to 80-85°C, reacted for 3-4 hours, cooled, filtered to obtain a filter cake, the filter cake is dissolved in dichloromethane, and then the temperature is raised to 45-55°C, fuming sulfuric acid is added dropwise, reacted for 1.5-2.5 hours, the pH is adjusted to neutral, and dried to obtain a styrene-maleic anhydride copolymer.

5. The SBS dry modified asphalt mixture according to claim 4, characterized in that: When preparing styrene-maleic anhydride copolymer, the added mass ratio of styrene, maleic anhydride and tert-butyl vinyl carbonate is 1: (0.4-0.6): (0.3-0.5), the added mass ratio of N,N-dimethylformamide solvent is 70-80wt% of the styrene monomer, the added amount of initiator is 3-5wt% of the styrene monomer, the added amount of dichloromethane is 6-8 times the mass of the filter cake, the mass concentration of oleum is 15-25%, and the added amount of oleum is 8-10wt% of the added amount of the filter cake.

6. The SBS dry modified asphalt mixture according to claim 1, characterized in that: The solubilizer is an alcohol solubilizer; the crosslinker is a sulfur crosslinker; the crosslinking accelerator is sodium dibutyl dithiocarbamate; and the matrix asphalt is one or both of rock asphalt and petroleum asphalt.

7. The SBS dry modified asphalt mixture according to claim 1, characterized in that: The added mass ratio of base asphalt, modifier and aggregate is (4-6): (1-1.5):

100.

8. The method for preparing the SBS dry modified asphalt mixture according to any one of claims 1 to 7, characterized in that: The following steps are involved: The SBS powder, the solubilizer, the stabilizer, the crosslinking agent, the crosslinking accelerator, the rubber powder and the modified nano-silicon dioxide are uniformly mixed to obtain a modifier; The aggregate is heated to 220-240°C, the base asphalt is heated to 150-170°C, and then the modifier is mixed with the aggregate, and then the heated base asphalt is added and mixed for 10-15 minutes to obtain the SBS dry modified asphalt mixture.

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