A low-temperature resistant rubber asphalt mixture and its preparation method

Abstract

This invention relates to the field of asphalt mixture technology and discloses a low-temperature resistant rubber asphalt mixture and its preparation method. The rubber asphalt mixture prepared by this invention comprises the following raw materials in parts by weight: 50-70 parts of base asphalt, 18-25 parts of waste tire rubber powder, 15-25 parts of coarse aggregate, 8-15 parts of fine aggregate, 4-8 parts of cold-resistant modifier, 3-6 parts of diatomaceous earth, and 0.5-1.5 parts of aromatic oil; wherein, the cold-resistant modifier can synergistically work with the waste tire rubber powder to improve the crack resistance and compressive strength of the asphalt matrix at low temperatures, thereby improving its low-temperature resistance.

Description

Technical Field

[0001] This invention relates to the field of asphalt mixture technology, specifically to a low-temperature resistant rubber asphalt mixture and its preparation method. Background Technology

[0002] In regions with severe cold, high altitudes, and large temperature differences, asphalt pavements commonly face the serious problem of low-temperature cracking. Under low-temperature conditions, conventional asphalt mixtures experience a sharp decrease in flexibility due to binder embrittlement and accumulated shrinkage stress, making them highly susceptible to thermal shrinkage cracks. These cracks not only damage the smoothness and integrity of the pavement but also provide channels for moisture and corrosive media to penetrate, accelerating base course damage and pavement structural performance degradation, significantly shortening road service life and increasing maintenance costs.

[0003] To improve the low-temperature performance of asphalt mixtures, the industry has mainly adopted technical approaches such as polymer modification (e.g., SBS, SBR), the use of rubberized asphalt, and the addition of various crack-resistant additives. Among these, rubberized asphalt, by introducing waste tire rubber powder, has shown outstanding performance in improving elasticity, fatigue resistance, and high-temperature properties. However, its low-temperature performance improvement often encounters bottlenecks: the compatibility of rubber powder particles with asphalt, dispersion stability, and rigidity at ultra-low temperatures remain insufficient. Traditional low-molecular-weight cold-resistant plasticizers, while reducing the brittle point, often come at the cost of sacrificing the material's high-temperature performance and long-term durability. Therefore, there is an urgent need for a rubberized asphalt mixture that simultaneously possesses low-temperature flexibility, crack resistance, and compressive strength. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a low-temperature resistant rubber asphalt mixture and its preparation method.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] A low-temperature resistant rubber asphalt mixture comprises the following raw materials in parts by weight: 50-70 parts base asphalt, 18-25 parts waste tire rubber powder, 15-25 parts coarse aggregate, 8-15 parts fine aggregate, 4-8 parts cold-resistant modifier, 3-6 parts diatomaceous earth, and 0.5-1.5 parts aromatic oil.

[0007] The waste tire rubber powder is made from waste automobile tire tread rubber that has been pulverized at low temperature and then ground to 80-200 mesh.

[0008] The coarse aggregate has a particle size of 6-15 mm, and the fine aggregate has a particle size of <2 mm.

[0009] The cold-resistant modifier has a core-shell structure, wherein carbon nanotubes are the core and polysiloxane is the shell;

[0010] Specifically, the cold-resistant modifier is prepared by the following steps:

[0011] Step A1: Under nitrogen atmosphere, 1,6-hexamethylene diisocyanate, sodium hydroxide and toluene are mixed and stirred at 45°C until homogeneous. Then the temperature is raised to 70°C and 3-aminopropyltriethoxysilane is added and stirred under reflux for 10-15 hours. Toluene is removed by rotary evaporation and dried under vacuum to obtain the intermediate product.

[0012] Furthermore, in step A1, the molar ratio of 1,6-hexamethylene diisocyanate and 3-aminopropyltriethoxysilane is 1:1;

[0013] Furthermore, in step A1, the mass of sodium hydroxide is 0.8 wt% to 1.2 wt% of the mass of 1,6-hexamethylene diisocyanate;

[0014] Step A2: Under nitrogen conditions, the intermediate product and dibutyltin dilaurate are stirred evenly in DMF, then polytetrahydrofuran diol is added, and the temperature is raised to 40°C and stirred for 2-3 hours. DMF is removed by vacuum distillation, and the product is dried under vacuum to obtain the functional monomer.

[0015] Furthermore, in step A2, the molar ratio of the intermediate product to polytetrahydrofuran diol is 1:1;

[0016] Furthermore, in step A2, the mass of dibutyltin dilaurate is 0.06wt%-0.09wt% of the mass of polytetrahydrofuran diol;

[0017] Step A3: Disperse carbon nanotubes evenly in a mixture of ethanol and water using ultrasonication, adjust the pH of the solution to 10, then add dimethyldiethoxysilane and tetraethyl orthosilicate and stir evenly. Heat to 45°C and react for 1 hour, then add the functional monomer and stir for 40-60 minutes. Finally, add trifluoropropanetrimethoxysilane and stir for 1-2 hours. Filter, wash, and dry to obtain the cold-resistant modifier.

[0018] Furthermore, in step A3, the ratio of carbon nanotubes, mixed solution, dimethyldiethoxysilane, tetraethyl orthosilicate, functional monomer, and trifluoropropanetrimethoxysilane is 5g:60mL:1-2g:0.5-1g:0.2-0.6g:0.1-0.3g;

[0019] Furthermore, the volume ratio of ethanol to water in the mixture in step A3 is 2:1.

[0020] A method for preparing a low-temperature resistant rubber asphalt mixture includes the following steps:

[0021] Weigh the raw materials according to the weight proportions, heat and stir the aromatic oil at 100-120℃, then add the base asphalt, and shear and stir at 4000-6000 rpm / min for 10-15 min. Then add the waste tire rubber powder, diatomaceous earth and cold-resistant modifier, and shear and stir at 1000-2000 rpm / min for 35 min. Then add the coarse aggregate and fine aggregate, and shear and stir at 500 rpm / min for 1-2 h to obtain the low-temperature resistant rubber asphalt mixture.

[0022] The beneficial effects of this invention are:

[0023] The rubber asphalt mixture prepared by this invention is made by mixing base asphalt, waste tire rubber powder coarse aggregate and fine aggregate as main raw materials, and adding diatomaceous earth, cold-resistant modifier and aromatic oil as additives. Among them, the cold-resistant modifier can work synergistically with waste tire rubber powder to improve the crack resistance and compressive strength of the asphalt matrix at low temperature, thereby improving its low temperature resistance.

[0024] The cold-resistant modifier in this invention uses carbon nanotubes as the core layer and polysiloxane as the shell structure. The functional monomers of the polysiloxane contain urea bonds, polyether structures, and terminal hydroxyl groups, and trifluoropropanetrimethoxysilane is also introduced. The introduction of the cold-resistant modifier improves the overall performance of the matrix at low temperatures. The carbon nanotubes in the core layer, after being dispersed in asphalt, form a three-dimensional network structure at the micro-nano scale. At low temperatures, this network acts like a "steel mesh," effectively transferring and dispersing locally concentrated thermal stress, preventing cracking caused by stress concentration. Simultaneously, it acts as a "bridging" mechanism when microcracks initiate, inhibiting further crack opening and propagation, consuming fracture energy, and thus enabling the matrix to maintain excellent crack resistance at low temperatures. The polysiloxane shell maintains extremely high flexibility and elasticity at low temperatures, wrapping around the carbon nanotube core, essentially coating the rigid carbon nanotubes with an "elastic body," making the entire modifier particle a flexible reinforcing unit in the asphalt, fundamentally improving the performance of the matrix. The composite material exhibits excellent deformation capacity at low temperatures. Urea bonds act as strong hydrogen bond donors and acceptors, forming a reversible dynamic hydrogen bond network between the modifier and the polar components of asphalt, as well as between modifier molecules. Under low-temperature stress, these dynamic hydrogen bonds can undergo "breakage-reorganization," effectively dissipating energy and indirectly improving the compressive strength of the matrix. The shell layer is also grafted with flexible, oleophilic polyether segments, which are well compatible with the lightweight components in the asphalt, acting as an internal plasticizer to further reduce the low-temperature brittleness of the matrix. This also allows for more uniform and stable dispersion of the modifier within the matrix. Furthermore, the hydroxyl groups at the ends of the modifier can form strong chemical bonds or strong hydrogen bonds with the aggregate surface, greatly enhancing the interfacial adhesion between asphalt and aggregate and preventing delamination at the interface during low-temperature shrinkage. Finally, the introduction of highly hydrophobic -CF3 groups reduces the adsorption of moisture by the asphalt mixture, protecting the asphalt-aggregate interface and preventing moisture erosion of the interface under low-temperature freeze-thaw cycles, indirectly improving long-term durability and interfacial integrity at low temperatures. Detailed Implementation

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] Example 1: The cold-resistant modifier was prepared by the following steps:

[0027] Step A1: Under nitrogen atmosphere, 0.1 mol of 1,6-hexamethylene diisocyanate, sodium hydroxide, and 100 mL of toluene were mixed and stirred thoroughly at 45°C. The mixture was then heated to 70°C, and 0.1 mol of 3-aminopropyltriethoxysilane was added and stirred under reflux for 10 h. Toluene was removed by rotary evaporation, and the mixture was dried under vacuum to obtain the intermediate product. The mass of sodium hydroxide was 0.8 wt% of the mass of 1,6-hexamethylene diisocyanate.

[0028] Step A2: Under nitrogen atmosphere, mix 0.1 mol of the intermediate product and dibutyltin dilaurate in 150 mL of DMF until homogeneous, then add 0.1 mol of polytetrahydrofuran diol (HO[CH2CH2CH2CH2O]). n H, and n=3), and heated to 40℃ and stirred for 2h, DMF was removed by vacuum distillation, and the product was dried under vacuum to obtain the functional monomer, with the mass of dibutyltin dilaurate being 0.06wt% of the mass of polytetrahydrofuran diol;

[0029] Step A3: Disperse 5g of carbon nanotubes evenly in a mixture of 40mL ethanol and 20mL water by ultrasonication, adjust the pH of the solution to 10, then add 1g of dimethyldiethoxysilane and 1g of tetraethyl orthosilicate and stir evenly. Heat to 45℃ and react for 1h, then add 0.2g of functional monomer and stir for 40min. Finally, add 0.1g of trifluoropropanetrimethoxysilane and stir for 1h. Filter, wash and dry to obtain the cold-resistant modifier.

[0030] Example 2: The cold-resistant modifier was prepared by the following steps:

[0031] Step A1: Under nitrogen atmosphere, 0.1 mol of 1,6-hexamethylene diisocyanate, sodium hydroxide, and 100 mL of toluene were mixed and stirred thoroughly at 45°C. The mixture was then heated to 70°C, and 0.1 mol of 3-aminopropyltriethoxysilane was added and stirred under reflux for 12 h. Toluene was removed by rotary evaporation, and the mixture was dried under vacuum to obtain the intermediate product. The mass of sodium hydroxide was 1.0 wt% of the mass of 1,6-hexamethylene diisocyanate.

[0032] Step A2: Under nitrogen atmosphere, mix 0.1 mol of the intermediate product and dibutyltin dilaurate in 150 mL of DMF until homogeneous, then add 0.1 mol of polytetrahydrofuran diol (HO[CH2CH2CH2CH2O]). n H, and n=3), and heated to 40℃ and stirred for 2.5h, DMF was removed by vacuum distillation, and the product was dried under vacuum to obtain the functional monomer, with the mass of dibutyltin dilaurate being 0.075wt% of the mass of polytetrahydrofuran diol;

[0033] Step A3: Disperse 5g of carbon nanotubes evenly in a mixture of 40mL ethanol and 20mL water using ultrasonication. Adjust the pH of the solution to 10, then add 1.5g of dimethyldiethoxysilane and 0.8g of tetraethyl orthosilicate and stir until homogeneous. Heat the mixture to 45℃ and react for 1 hour. Then add 0.4g of functional monomer and stir for 50 minutes. Finally, add 0.2g of trifluoropropanetrimethoxysilane and stir for 1.5 hours. Filter, wash, and dry to obtain the cold-resistant modifier.

[0034] Example 3: The cold-resistant modifier was prepared by the following steps:

[0035] Step A1: Under nitrogen atmosphere, 0.1 mol of 1,6-hexamethylene diisocyanate, sodium hydroxide, and 100 mL of toluene were mixed and stirred thoroughly at 45°C. The mixture was then heated to 70°C, and 0.1 mol of 3-aminopropyltriethoxysilane was added and stirred under reflux for 15 h. Toluene was removed by rotary evaporation, and the mixture was dried under vacuum to obtain the intermediate product. The mass of sodium hydroxide was 1.2 wt% of the mass of 1,6-hexamethylene diisocyanate.

[0036] Step A2: Under nitrogen atmosphere, mix 0.1 mol of the intermediate product and dibutyltin dilaurate in 150 mL of DMF until homogeneous, then add 0.1 mol of polytetrahydrofuran diol (HO[CH2CH2CH2CH2O]). n H, and n=3), and heated to 40℃ and stirred for 3h, DMF was removed by vacuum distillation, and the product was dried under vacuum to obtain the functional monomer, with the mass of dibutyltin dilaurate being 0.09wt% of the mass of polytetrahydrofuran diol;

[0037] Step A3: Disperse 5g of carbon nanotubes evenly in a mixture of 40mL ethanol and 20mL water using ultrasonication. Adjust the pH of the solution to 10, then add 2g of dimethyldiethoxysilane and 0.5g of tetraethyl orthosilicate and stir until homogeneous. Heat the mixture to 45℃ and react for 1 hour. Then add 0.6g of functional monomer and stir for 60 minutes. Finally, add 0.3g of trifluoropropanetrimethoxysilane and stir for 2 hours. Filter, wash, and dry to obtain the cold-resistant modifier.

[0038] Example 4: A method for preparing a low-temperature resistant rubber asphalt mixture includes the following steps:

[0039] 50 parts of base asphalt, 18 parts of waste tire rubber powder, 15 parts of coarse aggregate, 8 parts of fine aggregate, 4 parts of the cold-resistant modifier prepared in Example 1, 3 parts of diatomaceous earth, and 0.5 parts of aromatic oil.

[0040] Weigh the raw materials according to the weight parts, heat and stir the aromatic oil at 100°C, then add the base asphalt, and shear and stir at 4000 rpm / min for 10 min. Then add the waste tire rubber powder, diatomaceous earth and the cold-resistant modifier prepared in Example 1, and shear and stir at 1000 rpm / min for 35 min. Then add the coarse aggregate and fine aggregate, and shear and stir at 500 rpm / min for 1 h to obtain the low-temperature resistant rubber asphalt mixture.

[0041] Example 5: A method for preparing a low-temperature resistant rubber asphalt mixture includes the following steps:

[0042] 60 parts of base asphalt, 22 parts of waste tire rubber powder, 20 parts of coarse aggregate, 12 parts of fine aggregate, 6 parts of the cold-resistant modifier prepared in Example 2, 4.5 parts of diatomaceous earth, and 1 part of aromatic oil.

[0043] Weigh the raw materials according to the weight parts, heat and stir the aromatic oil at 110°C, then add the base asphalt, and shear and stir at 5000 rpm / min for 12 min. Then add the waste tire rubber powder, diatomaceous earth and the cold-resistant modifier prepared in Example 2, and shear and stir at 1500 rpm / min for 35 min. Then add the coarse aggregate and fine aggregate, and shear and stir at 500 rpm / min for 1.5 h to obtain the low-temperature resistant rubber asphalt mixture.

[0044] Example 6: A method for preparing a low-temperature resistant rubber asphalt mixture includes the following steps:

[0045] 70 parts of base asphalt, 25 parts of waste tire rubber powder, 25 parts of coarse aggregate, 15 parts of fine aggregate, 8 parts of the cold-resistant modifier prepared in Example 3, 6 parts of diatomaceous earth, and 1.5 parts of aromatic oil.

[0046] Weigh the raw materials according to the weight parts, heat and stir the aromatic oil at 120°C, then add the base asphalt, and shear and stir at 6000 rpm / min for 15 min. Then add the waste tire rubber powder, diatomaceous earth and the cold-resistant modifier prepared in Example 3, and shear and stir at 2000 rpm / min for 35 min. Then add the coarse aggregate and fine aggregate, and shear and stir at 500 rpm / min for 2 h to obtain the low-temperature resistant rubber asphalt mixture.

[0047] Comparative Example 1: This comparative example is a rubber asphalt mixture. The difference between this example and Example 6 is that the cold-resistant modifier prepared in Example 3 was not added. All other aspects are the same.

[0048] Comparative Example 2: This comparative example is a rubber asphalt mixture. The difference between this example and Example 6 is that carbon nanotubes are used instead of the cold-resistant modifier prepared in Example 3. All other aspects are the same.

[0049] Comparative Example 3: This comparative example is a rubber asphalt mixture. The difference between this example and Example 6 is that polysiloxane-coated carbon nanotubes are used instead of the cold-resistant modifier prepared in Example 3. All other aspects are the same.

[0050] The above-mentioned polysiloxane-coated carbon nanotubes are prepared by the following steps: 5g of carbon nanotubes are ultrasonically dispersed evenly in a mixture of 40mL ethanol and 20mL water, the pH of the solution is adjusted to 10, then 2.5g of dimethyldiethoxysilane and 1.5g of tetraethyl orthosilicate are added and stirred evenly, and the mixture is heated to 45℃ and reacted for 2h. After filtration, washing and drying, polysiloxane-coated carbon nanotubes are obtained.

[0051] The performance of the rubber asphalt mixtures prepared in Examples 4-6 and Comparative Examples 1-3 was tested:

[0052] (1) The freeze-thaw cycle test was conducted using the following temperature cycle: soaking in a 20℃ water bath for 30 min, then bagging, adding 10 ml of clean water and placing in a -18℃ environment for 16 h, then heating in a 60℃ water bath for 24 h, and then performing three cycles.

[0053] (2) Bending and tensile strain test: The small beam test was conducted at a test temperature of -10℃ and a loading rate of 50mm / min. The specimen was a prism with a length of 250mm, a width of 30mm, and a height of 35mm, which was cut after being formed by roller rolling.

[0054] (3) Conduct uniaxial compression tests (prepare specimens with a diameter of 100 mm and a height of 100 mm) in accordance with standard JTGE20-2011 "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" to test compressive strength and splitting tensile strength (-10℃).

[0055] The test results are shown in Table 1:

[0056]

[0057] As can be seen from Table 1, after low-temperature performance testing, the rubber asphalt mixture prepared by this invention exhibits a freeze-thaw splitting strength ratio in the range of (90-93)%, a flexural strain in the range of (2789-2933) με, a compressive strength in the range of (5.6-6.1) MPa, and a splitting tensile strength in the range of (3.46-3.75) MPa. This demonstrates that the rubber asphalt mixture still possesses excellent crack resistance, compressive strength, and other properties at low temperatures.

[0058] The above content is merely an example and illustration of the concept of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the scope defined by the inventive concept, they should all fall within the protection scope of the present invention.

Claims

1. A low-temperature resistant rubber asphalt mixture, characterized in that, The raw materials include the following parts by weight: 50-70 parts base asphalt, 18-25 parts waste tire rubber powder, 15-25 parts coarse aggregate, 8-15 parts fine aggregate, 4-8 parts cold-resistant modifier, 3-6 parts diatomaceous earth, and 0.5-1.5 parts aromatic oil. The waste tire rubber powder is made from waste automobile tire tread rubber that has been pulverized at low temperature and then ground to 80-200 mesh. The coarse aggregate has a particle size of 6-15 mm, and the fine aggregate has a particle size of <2 mm. The cold-resistant modifier has a core-shell structure, wherein carbon nanotubes form the core and polysiloxane forms the shell; the polysiloxane is made from dimethyldiethoxysilane, tetraethyl orthosilicate, functional monomers, and trifluoropropanetrimethoxysilane; the functional monomers are prepared by reacting intermediate products with polytetrahydrofurandiol, wherein the intermediate products are prepared by reacting 1,6-hexamethylene diisocyanate with 3-aminopropyltriethoxysilane; The cold-resistant modifier is prepared by the following steps: Step A1: Under nitrogen atmosphere, 1,6-hexamethylene diisocyanate, sodium hydroxide and toluene are mixed and stirred at 45°C until homogeneous. Then the temperature is raised to 70°C and 3-aminopropyltriethoxysilane is added and stirred under reflux for 10-15 hours. Toluene is removed by rotary evaporation and dried under vacuum to obtain the intermediate product. Step A2: Under nitrogen conditions, the intermediate product and dibutyltin dilaurate are stirred evenly in DMF, then polytetrahydrofuran diol is added, and the temperature is raised to 40°C and stirred for 2-3 hours. DMF is removed by vacuum distillation, and the product is dried under vacuum to obtain the functional monomer. Step A3: Disperse carbon nanotubes evenly in a mixture of ethanol and water using ultrasonication, adjust the pH of the solution to 10, then add dimethyldiethoxysilane and tetraethyl orthosilicate and stir evenly. Heat to 45°C and react for 1 hour, then add the functional monomer and stir for 40-60 minutes. Finally, add trifluoropropanetrimethoxysilane and stir for 1-2 hours. Filter, wash, and dry to obtain the cold-resistant modifier.

2. The low-temperature resistant rubber asphalt mixture according to claim 1, characterized in that, In step A1, the molar ratio of 1,6-hexamethylene diisocyanate and 3-aminopropyltriethoxysilane is 1:

1.

3. The low-temperature resistant rubber asphalt mixture according to claim 1, characterized in that, In step A1, the mass of sodium hydroxide is 0.8wt%-1.2wt% of the mass of 1,6-hexamethylene diisocyanate.

4. The low-temperature resistant rubber asphalt mixture according to claim 1, characterized in that, In step A2, the molar ratio of the intermediate product to polytetrahydrofuran diol is 1:

1.

5. The low-temperature resistant rubber asphalt mixture according to claim 1, characterized in that, In step A2, the mass of dibutyltin dilaurate is 0.06wt%-0.09wt% of the mass of polytetrahydrofurandiol.

6. The low-temperature resistant rubber asphalt mixture according to claim 1, characterized in that, In step A3, the ratio of carbon nanotubes, mixed solution, dimethyldiethoxysilane, tetraethyl orthosilicate, functional monomer, and trifluoropropanetrimethoxysilane is 5g:60mL:1-2g:0.5-1g:0.2-0.6g:0.1-0.3g.

7. The low-temperature resistant rubber asphalt mixture according to claim 1, characterized in that, The volume ratio of ethanol to water in the mixture in step A3 is 2:

1.

8. A method for preparing the low-temperature resistant rubber asphalt mixture according to any one of claims 1-7, characterized in that, The process includes the following steps: Weigh the raw materials according to the weight proportions, heat and stir the aromatic oil at 100-120℃, add the base asphalt, and shear and stir at a speed of 4000-6000 rpm / min for 10-15 min, then add waste tire rubber powder, diatomaceous earth and cold-resistant modifier, and shear and stir at a speed of 1000-2000 rpm / min for 35 min, then add coarse aggregate and fine aggregate, and shear and stir at a speed of 500 rpm / min for 1-2 h to obtain the low-temperature resistant rubber asphalt mixture.

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