SBS / waste tire rubber powder composite asphalt modified additive and preparation method thereof

Abstract

The invention relates to the field of asphalt mixtures, and provides an SBS / waste tire rubber powder composite asphalt modified additive and a preparation method thereof. The modified additive comprises the following components in parts by weight: 50-80 parts of a reactive coupling agent with a core-shell structure, 10-30 parts of a cross-linking agent and 5-20 parts of organic modified montmorillonite. A reaction type composite additive composed of a reaction type coupling agent with a core-shell structure, a cross-linking agent and organic modified montmorillonite is designed and is realized by virtue of the synergistic effect of the three components: a controllable devulcanization-re-cross-linking agent firstly breaks a waste tire rubber powder over-dense sulfur cross-linked network so as to activate the reaction activity of the waste tire rubber powder over-dense sulfur cross-linked network; the reactive coupling agent with the core-shell structure forms chemical bonds with SBS and activated rubber powder through a core layer, the reactive coupling agent with the core-shell structure forms covalent bonds with asphalt and aggregate through a shell layer, and the organic modified montmorillonite is uniformly dispersed on each interface and reinforces the interface through physical entanglement and hydrogen bonds, so that a three-dimensional network of'chemical combination + physical reinforcement 'is finally constructed, and the binding force among the components is fundamentally improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of asphalt mixture, in particular to an SBS / waste tire rubber powder composite asphalt modifier and a preparation method thereof. BACKGROUND

[0002] SBS / waste tire rubber powder composite modified asphalt is widely used in road engineering due to its high elasticity of SBS and low temperature flexibility of waste tire rubber powder, but the core bottleneck is the weak bonding force between SBS, waste tire rubber powder, asphalt matrix and aggregate, which easily causes phase separation, water damage and strength decay.

[0003] The prior art relies on physical blending or simple additive compounding to improve performance, such as Chinese patent CN118496684A discloses "a high-viscosity high-elasticity modified asphalt and a preparation method thereof", which attempts to improve the viscoelastic properties of asphalt by adding SBS, waste tire rubber powder, compatibilizer, modified nano activator and crosslinking stabilizer in steps. However, this scheme has obvious limitations: first, the functions of compatibilizer and coupling agent are single, which can only initially improve the compatibility of two components, and cannot simultaneously realize the chemical bonding of SBS-rubber powder, asphalt-aggregate at multiple interfaces, and the components are still mainly physically combined; second, the dense sulfur crosslinking network of waste tire rubber powder is not effectively regulated, and the rubber powder remains "inert", with few reaction sites with SBS and asphalt, making it difficult to form a stable connection; third, the nano activator lacks synergistic design with other components, which easily agglomerates in asphalt, cannot fully play the role of interface reinforcement, and there is no clear functional linkage between the additives, making it difficult to build a stable network structure throughout multiple components. These defects result in limited improvement of the bonding force of composite asphalt mixture, which cannot meet the long-term service requirements of high-anti-rutting and high-durability road surfaces. SUMMARY

[0004] In view of the above deficiencies in the prior art, the core purpose of the present application is to solve the technical problem of weak bonding force between SBS, waste tire rubber powder, asphalt matrix and aggregate; specifically by designing a reactive composite additive composed of core-shell structure reactive coupling agent, crosslinking agent and organically modified montmorillonite, and through the synergistic effect of the three, the following is achieved: controllable sulfur breaking-re-crosslinking agent first breaks the over-dense sulfur crosslinking network of waste tire rubber powder to activate its reactivity, the core-shell structure reactive coupling agent then forms chemical bonds with SBS and activated rubber powder through the core layer, and forms covalent bonds with asphalt and aggregate through the shell layer, and the organically modified montmorillonite is uniformly dispersed at the interfaces and reinforces the interfaces through physical entanglement and hydrogen bonding, finally building a three-dimensional network of "chemical bonding + physical reinforcement", which fundamentally improves the bonding force between components.

[0005] The present application is realized by the following technical solutions: The first object of the present application is to provide a SBS / waste tire rubber powder composite asphalt modifying additive, which comprises, in parts by mass, a core-shell structure reactive coupling agent: 50-80 parts, a crosslinking agent: 10-30 parts, and an organic modified montmorillonite: 5-20 parts; The core layer material of the core-shell structure reactive coupling agent is maleic anhydride grafted polyethylene, and the shell layer material is bis-[3- (triethoxysilane) propyl] -disulfide. The crosslinking agent is composed of an organic zinc complex and an accelerator, and the mass ratio of the organic zinc complex to the accelerator is 1: (0.5-2).

[0006] It should be noted that the core-shell structure reactive coupling agent adopts a "core-shell" bifunctional structure to specifically solve the combination pain points among multiple components: the core layer (maleic anhydride grafted polyethylene) melts at high temperature (170-180℃), and the maleic anhydride groups on the surface can react with the double bonds in the SBS molecular chain and the active groups (free radicals, amine groups) exposed after the broken bonds of the waste tire rubber powder to form stable C-O-C chemical bonds, thereby "stitching" SBS and the rubber powder into one body; the shell layer (bis-[3- (triethoxysilane) propyl] -disulfide) is hydrolyzed into silanol (-Si-OH) under the action of trace moisture, which on the one hand forms a hydrogen bond with the asphaltene in asphalt, and on the other hand reacts with the hydroxyl groups (-OH) on the surface of the aggregate to form a firm Si-O-covalent bond. This "double-headed bolt" type action realizes "full chemical bonding" from SBS, waste tire rubber powder to asphalt and aggregate, and completely breaks the limitations of traditional physical combination.

[0007] The crosslinking agent is composed of an organic zinc complex and an accelerator, and the mass ratio of the organic zinc complex to the accelerator is 1: (0.5-2).

[0008] The organic modified montmorillonite as a nanoscale interface reinforcing agent, the organic modified montmorillonite (NIE) solves the interface reinforcing problem through "biparental characteristics + nanometer effect": on the one hand, the organic modifier (such as quaternary ammonium salt) of the organic modified montmorillonite can form good compatibility with the polymer of SBS and activated rubber powder, and the inorganic core (layered silicate) can have hydrophobic-hydrophobic interaction with the aromatic component in the asphalt, and this "biparental" characteristic enables it to be uniformly dispersed in all interface regions of SBS-rubber powder, rubber powder-asphalt, asphalt-aggregate, like a "rivet" to strengthen the structural strength of the interface region through physical adsorption, molecular entanglement and hydrogen bonding; on the other hand, the nanometer sheet of the NIE has a large specific surface area, which can act as a nucleation point to guide SBS to form a more uniform and fine network structure, and at the same time, a physical barrier layer is formed at the interface, when the mixture is stressed, the nanometer sheet can hinder the generation and expansion of microcracks, avoid the failure of the weak interface due to stress concentration, and further synergistically improve the overall bonding force of each component.

[0009] The core-shell structure reactive coupling agent, controllable sulfur breaking-re-crosslinking agent and organic modified montmorillonite closely synergize to jointly improve the bonding force of each component of the asphalt mixture. Among them, the controllable sulfur breaking-re-crosslinking agent first breaks the dense sulfur crosslinking network in the waste tire rubber powder through the organic zinc complex, releases the rubber molecular chain segments with active groups, provides sufficient reaction sites for the core-shell structure reactive coupling agent, enables the maleic anhydride groups in the core layer of the core-shell structure reactive coupling agent to be efficiently combined with the double bonds of the SBS molecular chain and the active groups of the activated rubber powder, and the accelerator in the controllable sulfur breaking-re-crosslinking agent also guides the formation of sulfur bridge crosslinking points, which are interwoven with the chemical bonds formed by the core-shell structure reactive coupling agent, to strengthen the connection between SBS and rubber powder. And the double chemical network formed by the core-shell structure reactive coupling agent and the controllable sulfur breaking-re-crosslinking agent can clearly define the interface boundaries of each component, provide elastic support, and avoid the agglomeration of the organic modified montmorillonite, so that the organic modified montmorillonite is uniformly dispersed in all interfaces of SBS-rubber powder, asphalt-aggregate, etc. The organic modified montmorillonite further fills the microcracks in the interface through physical entanglement and hydrogen bonding, blocks the expansion of microcracks, reversely protects the crosslinking structure formed by the former two, and finally realizes the synergistic effect of "active activation-chemical connection-interface reinforcement", so that the components are more stably combined.

[0010] Further, the organic zinc complex is zinc diethyldithiocarbamate, and the accelerator is 2-mercaptobenzothiazole.

[0011] Further, the organic modified montmorillonite is sodium-based montmorillonite modified by cetyltrimethylammonium bromide.

[0012] Further, the average thickness of the core layer of the core-shell structure reactive coupling agent is 50-500 μm, and the average thickness of the shell layer is 0.5-10 μm.

[0013] The second object of the present application is to provide a preparation method of the SBS / waste tire rubber powder composite asphalt modification additive, which comprises the following steps: At normal temperature, the core-shell structure reactive coupling agent, the crosslinking agent and the organic modified montmorillonite are dry mixed to obtain the SBS / waste tire rubber powder composite asphalt modification additive.

[0014] Further, the preparation method of the core-shell structure reactive coupling agent comprises the following steps: The core layer material maleic anhydride grafted polyethylene is heated to 120-150 DEG C to melt, the shell layer material bis-[3- (triethoxysilyl) propyl]-disulfide is atomized and sprayed on the surface of the molten core layer under the action of shearing, and after coating, cooling and granulation, the core-shell structure reactive coupling agent is obtained.

[0015] Further, the preparation method of the organic modified montmorillonite comprises the following steps: The sodium-based montmorillonite is dispersed in water to form a slurry, heated to 60-80 DEG C, and then a quaternary ammonium salt intercalation agent is added to carry out ion exchange reaction, and after reaction, filtration, washing, drying and grinding, the organic modified montmorillonite is obtained.

[0016] The third object of the present application is to provide an application of the SBS / waste tire rubber powder composite asphalt modification additive, which is used for preparing SBS / waste tire rubber powder composite asphalt mixture.

[0017] Further, the mass of the modification additive is 0.5-3% of the total mass of the SBS / waste tire rubber powder composite asphalt mixture.

[0018] Further, the SBS / waste tire rubber powder composite asphalt mixture is used for paving high-anti-rutting pavement, high-elasticity low-noise pavement or high-durability bridge deck pavement.

[0019] The technical scheme of the embodiment of the present application has at least the following advantages and beneficial effects: (1) The multi-component combination is fundamentally improved, and the core defects of the traditional system are solved: through the "full-chemical bonding" of the core-shell structure reactive coupling agent, the "sulfur bridge network construction" of the crosslinking agent and the "interface physical reinforcement" of the organic modified montmorillonite, a "chemical+physical" dual combination mechanism is formed, the problem of weak combination between SBS, waste tire rubber powder, asphalt matrix and aggregate is completely improved, and phenomena such as phase separation, water damage and strength attenuation easily occurring in traditional physical blending are avoided.

[0020] (2) Realize efficient activation and high-value utilization of waste tire rubber powder: the organic zinc complex in the crosslinking agent can selectively break the waste tire rubber powder over sulfur crosslinking network, activate its reactivity, retain the elastic characteristics of the rubber powder, and enable it to form stable chemical bonds with SBS and asphalt, promoting the recycling of waste tires, and at the same time giving the composite system excellent elastic recovery ability and permanent deformation resistance.

[0021] (3) Precise matching of component functions and strong synergy, building a stable three-dimensional network: the core-shell structure reactive coupling agent solves the problem of chemical connection at multiple interfaces, the crosslinking agent focuses on the activation of rubber powder and the chemical crosslinking of SBS-rubber powder, and the organic modified montmorillonite reinforces the interface microstructure. The three work in time sequence and complement each other in function. The crosslinking agent provides reaction sites for the coupling agent, the chemical network formed by the coupling agent and the crosslinking agent provides a dispersion carrier for the montmorillonite, and the montmorillonite protects the chemical network in reverse. Finally, a homogeneous and stable three-dimensional composite network is formed.

[0022] (4) Simple preparation and application process, easy to industrialize: the modified additives can be prepared by dry mixing at room temperature without the need for complex equipment. The preparation process of the core-shell structure coupling agent and the organic modified montmorillonite is mature (such as melt spraying coating, ion exchange modification), and the operation difficulty is low. When applied, only 0.5-3% of the modified additives need to be added to the mixture, which is suitable for existing asphalt mixing equipment and does not require large-scale modification of the production line.

[0023] (5) Wide application scenarios, suitable for various high-performance pavement needs: the composite asphalt mixture prepared by the modified additives has high rut resistance, high elasticity, low noise, high durability, etc., and can be flexibly used for high rut resistance pavement, high elasticity low noise pavement and high durability bridge pavement, meeting the differentiated needs of different engineering scenarios for pavement performance.

[0024] (6) Both environmental benefits and engineering economy: On the one hand, the large-scale application of waste tire rubber powder reduces solid waste pollution and meets the green development concept. On the other hand, the additive has a low addition ratio, controllable preparation cost, and can extend the service life of the pavement and reduce the maintenance cost in the later period, taking into account the environmental and engineering economic value. DETAILED DESCRIPTION

[0025] Example 1 (1) Preparation of raw materials Core-shell structure reactive coupling agent raw materials: maleic anhydride grafted polyethylene (grafting rate 1.2%, melt index 8 g / 10 min), bis-[3- (triethoxysilyl) propyl] -disulfide (purity ≥98%, CAS No. 56706-10-6).

[0026] Crosslinking agent raw materials: zinc diethyl dithiocarbamate (purity ≥99%), 2-mercaptobenzothiazole (purity ≥98%).

[0027] Raw materials for preparing organic modified montmorillonite: sodium-based montmorillonite (cation exchange capacity 100 mmol / 100 g), hexadecyl trimethyl ammonium bromide (purity ≥ 99%).

[0028] Application raw materials: No. 90 base asphalt (penetration 82.4 x 0.1 mm, softening point 45℃), SBS modifier (linear, styrene content 30%), waste tire rubber powder (particle size 80 mesh, purity ≥ 99%), basalt coarse aggregate (crushing value 12%), limestone fine aggregate (angularity 35s), limestone powder (specific surface area 450 m² / kg).

[0029] (2) Preparation of each component of the modified additive Preparation of the core-shell structure reactive coupling agent: add maleic anhydride grafted polyethylene into the reaction kettle, heat to 135℃ to melt, open the shearing device (rotational speed 7000 r / min), uniformly spray bis-[3- (triethoxysilane) propyl] -disulfide on the surface of the molten core layer through a high-pressure atomizing nozzle (pressure 0.3 MPa), continue to coat for 15 min, then cool to 60℃ for cooling and shaping, and granulate by a granulator (particle size 2 mm) to obtain a core-shell structure reactive coupling agent with an average core layer thickness of 200 μm and an average shell layer thickness of 5 μm.

[0030] Preparation of the organic modified montmorillonite: disperse 100 g of sodium-based montmorillonite in 2000 mL of deionized water, stir to form a slurry with a mass concentration of 5%, heat to 70℃, slowly add 50 g of hexadecyl trimethyl ammonium bromide, and perform ion exchange reaction for 2 h under constant temperature stirring. After the reaction is completed, wash the product with deionized water until there is no bromide ion (test with silver nitrate solution without precipitation), vacuum dry at 80℃ for 4 h, crush to 200 mesh by a grinding machine, and obtain hexadecyl trimethyl ammonium bromide modified sodium-based montmorillonite.

[0031] Preparation of the crosslinking agent: take 10 parts of zinc diethyl dithiocarbamate and 10 parts of 2-mercaptobenzothiazole according to a mass ratio of 1:1, put them into a high-speed mixer and stir for 5 min, and then uniformly mix to obtain the crosslinking agent.

[0032] (3) Preparation of the SBS / waste tire rubber powder composite asphalt modified additive At room temperature, take 65 parts of the core-shell structure reactive coupling agent prepared above, 20 parts of the crosslinking agent, and 15 parts of the organic modified montmorillonite, add them into a double-cone mixer, and dry mix at a rotational speed of 30 r / min for 15 min to obtain a uniform SBS / waste tire rubber powder composite asphalt modified additive.

[0033] (4) Application of the modified additive and preparation of the composite asphalt mixture Preparation of composite asphalt: No. 90 base asphalt was heated to 160°C, 17% waste tire rubber powder and 2.5% SBS modifier were added, after stirring and soaking for 20 min, 1.5% of the above-mentioned modified additive was added, accounting for the total mass of the composite asphalt mixture, the temperature was raised to 175°C, and sheared for 30 min with a high-speed shearing machine (rotating speed 7500 r / min), and then developed at 175°C for 40 min to obtain the composite modified asphalt.

[0034] Mixing of composite asphalt mixture: The aggregate was weighed according to the ARAC-13 grading (coarse aggregate 65%, fine aggregate 25%, mineral powder 10%), heated to 180°C, and the above-mentioned composite modified asphalt (oil stone ratio 5.7%) was added, mixed in a forced mixer for 90 s to obtain the SBS / waste tire rubber powder composite asphalt mixture.

[0035] Example 2 This example is based on the disclosure of Example 1, with the following modifications: Preparation of SBS / waste tire rubber powder composite asphalt modification additive: At room temperature, 75 parts of the above-prepared core-shell structure reactive coupling agent, 15 parts of crosslinking agent and 10 parts of organic modified montmorillonite were weighed and added into a double-cone mixer, and dry mixed at a speed of 30 r / min for 15 min to obtain a uniform SBS / waste tire rubber powder composite asphalt modification additive.

[0036] Example 3 This example is based on the disclosure of Example 1, with the following modifications: Preparation of SBS / waste tire rubber powder composite asphalt modification additive At room temperature, 80 parts of the above-prepared core-shell structure reactive coupling agent, 15 parts of crosslinking agent and 5 parts of organic modified montmorillonite were weighed and added into a double-cone mixer, and dry mixed at a speed of 30 r / min for 15 min to obtain a uniform SBS / waste tire rubber powder composite asphalt modification additive.

[0037] Comparative Example 1 This comparative example is based on the disclosure of Example 1, with the following modifications: The SBS / waste tire rubber powder composite asphalt modification additive does not contain a core-shell structure reactive coupling agent.

[0038] Comparative Example 2 This comparative example is based on the disclosure of Example 1, with the following modifications: The SBS / waste tire rubber powder composite asphalt modification additive does not contain a crosslinking agent.

[0039] Comparative Example 3 This comparative example is based on the disclosure of Example 1, with the following modifications: The SBS / waste tire rubber powder composite asphalt modification additive does not contain organic modified montmorillonite.

[0040] The composite modified bitumen obtained from Examples 1 to 3 and Comparative Examples 1 to 3 was subjected to performance determination, and the results are shown in Table 1, and the performance determination method of the composite modified bitumen is as follows: High temperature performance: According to the “Standard Test Methods of Bitumen and Bituminous Mixture for Highway Engineering” (JTGE20-2011), Brookfield rotational viscosity test (T0625) was carried out, and the viscosity at 135℃ was taken as the evaluation index.

[0041] Low temperature performance: According to the JTGE20-2011, BBR test (T0627) was carried out, and the creep stiffness S was taken as the evaluation index.

[0042] Elastic recovery performance: According to the JTGE20-2011, elastic recovery test (T0662) was carried out, and the elastic recovery rate at 25℃ was tested.

[0043] Storage stability: According to the JTGE20-2011, segregation test (T0661) was carried out, and the softening point difference between the upper and lower sections was determined after the sample was placed in an oven at 163℃ for 48 hours.

[0044] Table 1 Performance of the composite modified bitumen of Examples 1 to 3 and Comparative Examples 1 to 3

[0045] As can be seen from Table 1, the data in Table 1 intuitively reflects the differences in the core performance of the composite modified bitumen in different groups, and fully verifies the key improvement effect of the synergistic effect of the three components in the composite additive on the performance of the bitumen. From the 135℃ viscosity related to construction and workability, the viscosity of Examples 1 to 3 is in the range of 2.1 to 2.5 Pa・s, which belongs to the appropriate viscosity range for road construction, while the viscosity of Comparative Example 1 without core-shell structure reactive coupling agent (CRC) is as high as 3.8 Pa・s, and the excessively high viscosity will increase the difficulty of bitumen mixing and paving, indicating that the introduction of CRC can effectively control the fluidity of the bitumen system; the viscosity of Comparative Example 2 without controllable sulfur-breaking-re-crosslinking agent (CRV) is only 1.9 Pa・s, and the excessively low viscosity may cause the bitumen to soften easily at high temperature service, further demonstrating the stabilizing effect of the crosslinking network constructed by CRV on the viscosity.

[0046] From the low temperature crack resistance index of the creep stiffness S at -18℃, the stiffness value of Examples 1 to 3 is 185 to 211 MPa, which is significantly lower than that of Comparative Example 1 (283 MPa) and Comparative Example 2 (242 MPa), and the lower the creep stiffness, the better the flexibility of the bitumen at low temperature, and the stronger the crack resistance, because after the CRC “stitches” the SBS and the rubber powder and the CRV optimizes the sulfur bridge network, the bitumen system is not easy to break due to stress concentration at low temperature; when CRC or CRV is absent, the internal binding force of the system is weak, the low temperature stiffness is greatly increased, and the crack resistance performance is deteriorated.

[0047] The recovery rates of Examples 1-3 reached 85.1-92.2% in the 25℃ elastic recovery rate reflecting the elastic recovery ability of asphalt, among which Example 1 showed the best performance of 92.2%, while Comparative Example 1 (without CRC) was only 65.5% and Comparative Example 2 (without CRV) was only 74.7%, with a significant gap, which indicated that the chemical bonding of CRC and the sulfur bridge crosslinking of CRV together endowed the asphalt with excellent elastic recovery ability and effectively resisted the permanent deformation caused by vehicle load; the lack of any key component would greatly reduce the elastic recovery rate and could not meet the demand of high-elasticity pavement.

[0048] In the 48h softening point difference index best reflecting the storage stability of asphalt, the softening point differences of Examples 1-3 were only 1.8-2.3℃, far lower than the high-quality standard of “not more than 3℃” in the industry specification, while the softening point difference of Comparative Example 1 (without CRC) reached 8.4℃, far exceeding the standard, which indicated that CRC solved the compatibility problem of SBS and rubber powder and avoided phase separation during storage; even Comparative Example 3 without organic modified montmorillonite (NIE) had a softening point difference of 4.6℃, higher than that of Examples, further proving that the nano-interface reinforcing effect of NIE could assist the stable system and reduce the risk of delamination. Overall, the composite modified asphalts of Examples 1-3 all showed excellent performance in construction workability, low-temperature crack resistance, elastic recovery ability and storage stability, and were significantly better than Comparative Examples lacking any key component, highlighting the technical value of the synergistic effect of the three components.

[0049] The composite asphalt mixtures obtained from Examples 1-3 and Comparative Examples 1-3 were subjected to performance determination, and the results are shown in Table 2. The performance determination method of the composite asphalt mixture is as follows: High-temperature anti-rutting ability: referring to JTGE20-2011, a rutting test (T0719) was performed, and the dynamic stability (DS) at 60℃ was taken as the evaluation index.

[0050] Low-temperature anti-cracking performance: referring to JTGE20-2011, a low-temperature beam bending test (T0715) was performed, and the failure strain (με) at -10℃ was taken as the evaluation index.

[0051] Water stability: referring to JTGE20-2011, a freeze-thaw splitting test (T0729) was performed, and the freeze-thaw splitting strength ratio was taken as the evaluation index.

[0052] Fatigue resistance: referring to AASHTOT321 standard, a four-point beam bending fatigue test was performed at 15℃, 10Hz frequency and 400 micro-strain, and the fatigue life (cycle number) was taken as the evaluation index.

[0053] Table 2 Performance of composite asphalt mixtures of Examples 1-3 and Comparative Examples 1-3

[0054] From Table 2, the data in Table 2 focuses on the road performance of the composite asphalt mixture, clearly showing that the composite additive of the application comprehensively improves the high-temperature rut resistance, low-temperature crack resistance, water stability and fatigue resistance of the mixture, and through comparison with the comparative examples, the irreplaceability of each key component is clear. In the dynamic stability index for measuring high-temperature rut resistance, the dynamic stability of Examples 1-3 is 7214-8562 times / mm, among which Example 1 performs best with 8562 times / mm, while the dynamic stability of Comparative Example 1 without CRC is only 4513 times / mm, and the dynamic stability of Comparative Example 2 without CRV is only 5828 times / mm, both of which are much lower than the examples, because the "chemical bridge" formed by CRC and the sulfur bridge network formed by CRV together strengthen the combination of SBS, rubber powder and asphalt, so that the mixture can resist the permanent deformation caused by vehicle load at high temperature; the absence of any component makes the three-dimensional network structure of the system incomplete, and the rut resistance performance decreases significantly.

[0055] From the low-temperature failure strain reflecting the low-temperature crack resistance performance, the strain values of Examples 1-3 are 2959-3257 με, and the greater the strain, the greater the deformation that the mixture can withstand at low temperature without cracking, while the strain of Comparative Example 1 (without CRC) is only 2147 με, and the strain of Comparative Example 2 (without CRV) is only 2651 με, which is obviously brittle at low temperature, because the composite additive makes the combination of each component in the mixture tight and has a certain flexibility, which can buffer stress and avoid crack generation when shrinking at low temperature; the absence of key components will lead to increased rigidity of the system and weakened crack resistance.

[0056] In the TSR index for evaluating water stability, the TSR of Examples 1-3 is 88.2%-92.1%, which meets the requirement of "TSR not less than 85%" for high durability pavement, while the TSR of Comparative Example 1 (without CRC) is only 78.8%, and the TSR of Comparative Example 3 (without NIE) is only 86.4%, both of which are lower than the examples, because the Si-O covalent bond formed by the shell layer of CRC and the aggregate, and the "rivet" effect of NIE at the interface can effectively block the intrusion of water and reduce water damage; the absence of CRC or NIE makes the interface bonding between asphalt and aggregate easy to be damaged by water, and the water stability decreases.

[0057] In the fatigue life index of anti-fatigue performance, the fatigue life of examples 1-3 is 982-1251 thousand times, and the fatigue life of comparative examples 1 (without CRC) and 2 (without CRV) is only 552 thousand times and 851 thousand times respectively, and the difference is large, because the "physical-chemical" three-dimensional network constructed by the three components can disperse stress and delay the expansion of micro-cracks under repeated load; the network structure is defective if any component is missing, and fatigue damage will quickly accumulate, resulting in a shortened life. In summary, the composite asphalt mixture of examples 1-3 is superior to comparative examples in various road performances, and example 1 realizes balanced and excellent high-temperature, low-temperature, water stability and anti-fatigue performance by virtue of the optimal component ratio, fully proving the technical effectiveness of the composite additive.

Claims

1. A modified asphalt additive based on SBS / waste tire rubber powder, characterized in that, The modified additives, by weight, include: 50-80 parts of a core-shell reactive coupling agent, 10-30 parts of a crosslinking agent, and 5-20 parts of an organically modified montmorillonite. The core material of the core-shell structure reactive coupling agent is maleic anhydride-grafted polyethylene, and the shell material is bis-[3-(triethoxysilyl)propyl]-disulfide. The crosslinking agent is composed of an organozinc complex and an accelerator, and the mass ratio of the organozinc complex to the accelerator is 1:(0.5-2).

2. The SBS / waste tire rubber powder composite asphalt modifier additive according to claim 1, characterized in that, The organic zinc complex is zinc diethyldithiocarbamate, and the accelerator is 2-mercaptobenzothiazole.

3. The SBS / waste tire rubber powder composite asphalt modifier according to claim 1, characterized in that, The organically modified montmorillonite is sodium-based montmorillonite modified with hexadecyltrimethylammonium bromide.

4. The SBS / waste tire rubber powder composite asphalt modifier additive according to claim 1, characterized in that, The core-shell structure reactive coupling agent has an average core layer thickness of 50–500 μm and an average shell layer thickness of 0.5–10 μm.

5. A method for preparing the SBS / waste tire rubber powder composite asphalt modifier according to any one of claims 1 to 4, characterized in that, The method includes: At room temperature, the core-shell structure reactive coupling agent, the crosslinking agent, and the organic modified montmorillonite are dry-mixed to obtain the SBS / waste tire rubber powder composite asphalt modifier.

6. The preparation method of the SBS / waste tire rubber powder composite asphalt modifier according to claim 5, characterized in that, The preparation method of the core-shell structured reactive coupling agent includes: The core material, maleic anhydride-grafted polyethylene, is heated to 120-150°C to melt. Under shearing action, the shell material, bis-[3-(triethoxysilyl)propyl]-disulfide, is atomized and sprayed onto the surface of the molten core layer. After coating, cooling, and granulation, the core-shell structure reactive coupling agent is obtained.

7. The preparation method of the SBS / waste tire rubber powder composite asphalt modifier according to claim 5, characterized in that, The preparation method of the organically modified montmorillonite includes: Sodium-based montmorillonite was dispersed in water to form a slurry, heated to 60-80°C, and then a quaternary ammonium salt intercalating agent was added to carry out an ion exchange reaction. After the reaction was completed, the slurry was filtered, washed, dried, and ground to obtain the organically modified montmorillonite.

8. The application of the SBS / waste tire rubber powder composite asphalt modifier according to any one of claims 1 to 4, characterized in that, The modified additive is used to prepare SBS / waste tire rubber powder composite asphalt mixture.

9. The application of the SBS / waste tire rubber powder composite asphalt modifier according to claim 8, characterized in that, The mass of the modified additive is 0.5 to 3% of the total mass of the SBS / waste tire rubber powder composite asphalt mixture.

10. The application of the SBS / waste tire rubber powder composite asphalt modifier according to claim 8, characterized in that, The SBS / waste tire rubber powder composite asphalt mixture is used to pave high rutting resistance pavement, high elasticity and low noise pavement, or high durability bridge deck pavement layer.

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