A polyphosphoric acid-low density polyethylene composite modified asphalt and asphalt pavement material

Abstract

The present application belongs to the technical field of asphalt pavement materials, and particularly relates to a polyphosphoric acid-low density polyethylene composite modified asphalt and an asphalt pavement material. The polyphosphoric acid-low density polyethylene composite modified asphalt is made of base asphalt, a polyethylene modifier and polyphosphoric acid. The polyethylene modifier is a kind of high polymer material, and has good elasticity and toughness, and can enhance the ability of the asphalt to resist permanent deformation, the elastic recovery ability and the fatigue resistance at high temperature. The polyphosphoric acid can chemically react with some components in the asphalt to form chemical bonds, thereby enhancing the interaction force between the asphalt molecules, improving the overall strength of the asphalt, and improving the compatibility between the polyethylene modifier and the asphalt, so that the polyethylene modifier is more uniformly distributed in the asphalt, and the ability of the asphalt to resist permanent deformation, the elastic recovery ability and the fatigue resistance at high temperature are further enhanced.

Description

Technical Field

[0001] This invention belongs to the technical field of asphalt pavement materials, specifically a polyphosphate-low-density polyethylene composite modified asphalt and asphalt pavement materials. Background Technology

[0002] The invention and application of plastics is one of the important hallmarks of modern industrial civilization, giving rise to countless products that have driven social progress and significantly improved the quality of human life. From medical devices to electronic equipment, from food packaging to building materials, plastics, with their lightweight, durability, and low cost, have penetrated into all aspects of human life. However, due to their difficulty in natural degradation, they have caused many adverse effects on the Earth's ecological environment. Currently, many researchers are actively exploring innovative ways to convert waste plastics into asphalt modifiers and have successfully applied them in road construction.

[0003] Commonly used plastics for modifying asphalt include polyethylene (PE), polypropylene (PP), polystyrene (PS), polyvinyl chloride (PVC), polyurethane (PU), and polyester (PET). PE, as one of the most widely used plastic modifiers, is a linear high-molecular-weight long-chain aliphatic hydrocarbon formed by the addition polymerization of ethylene monomers. It is mainly divided into high-density polyethylene (HDPE) and low-density polyethylene (LDPE). The characteristic of polyethylene (PE) molecules is that they consist of long chains of carbon atoms, with two hydrogen atoms attached to each carbon atom. The addition of polyethylene can bring high hardness to asphalt and greatly reduce its deformation under traffic loads.

[0004] However, due to the non-polar nature of polyethylene, it is almost immiscible with asphalt, thus its applications are largely limited to the production of geomembranes. Furthermore, the low compatibility between polyethylene and asphalt can lead to phase separation in modified materials stored at high temperatures and without continuous stirring. In addition, while polyethylene significantly improves the high-temperature properties of asphalt, it negatively impacts its low-temperature properties. Summary of the Invention

[0005] To address the above problems, this invention provides a polyphosphoric acid-low-density polyethylene composite modified asphalt and asphalt pavement material, which solves the problems of poor compatibility between polyethylene and asphalt and the adverse effects of polyethylene on the low-temperature performance of asphalt when using polyethylene-modified asphalt.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A polyphosphoric acid-low-density polyethylene composite modified asphalt is prepared by a method comprising the following steps: heating a base asphalt to melt, then adding a polyethylene modifier, and mixing to obtain polyethylene modified asphalt; then heating and mixing the polyethylene modified asphalt and polyphosphoric acid to obtain polyphosphoric acid-low-density polyethylene composite modified asphalt; wherein the polyethylene modifier is low-density polyethylene or amino-modified low-density polyethylene; wherein the amino-modified low-density polyethylene is prepared by clicking reaction of chlorinated low-density polyethylene grafted with azide groups and then reacting it with a mixture of alkynyl aniline compounds.

[0008] Preferably, the preparation method of the chlorinated low-density polyethylene is as follows: low-density polyethylene and chlorine are subjected to a chlorination reaction in a solvent under the action of a catalyst to prepare chlorinated low-density polyethylene; the melting point of the low-density polyethylene is 112~115℃, and the chlorine content of the chlorinated low-density polyethylene is 24~36%.

[0009] Preferably, the chlorinated low-density polyethylene has a chlorine content of 24-26%.

[0010] Preferably, the method for grafting the azido group is as follows: chlorinated low-density polyethylene, sodium azide, and tetraethylammonium bromide are mixed and reacted in a solvent at 55-60°C for 5-7 hours to obtain azido-grafted low-density polyethylene; the mass ratio of the chlorinated low-density polyethylene, sodium azide, and tetraethylammonium bromide is 1:1.5-1.7:0.3-0.5.

[0011] Preferably, the click reaction with the acetylinyl aniline compound is carried out as follows: Azide-grafted low-density polyethylene, the acetylinyl aniline compound, cuprous bromide, and pentamethyldiethylenetriamine are mixed and reacted in a solvent to obtain amino-modified low-density polyethylene; the mass ratio of the acetylinyl-grafted low-density polyethylene to the acetylinyl aniline compound is 1:1.5~1.8, and the molar ratio of the acetylinyl aniline compound, cuprous bromide, and pentamethyldiethylenetriamine is 1:0.3~0.5:0.3~0.5.

[0012] Preferably, the acetylinyl aniline compound is 4-acetylinyl aniline or 2-acetylinyl aniline.

[0013] Preferably, the mass ratio of the base asphalt, polyethylene modifier, and polyphosphoric acid is 94~96:4~5:0.6~1.2.

[0014] Preferably, the temperature for heating and mixing polyethylene modified asphalt and polyphosphoric acid is 180~185℃, and the time is 30~60min.

[0015] Preferably, the base asphalt is Grade 70 A road petroleum asphalt.

[0016] An asphalt pavement material is composed of polyphosphate-low-density polyethylene composite modified asphalt and mineral aggregates as described above.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0018] The polyphosphoric acid-low-density polyethylene composite modified asphalt of this invention is made from base asphalt, polyethylene modifier, and polyphosphoric acid. The polyethylene modifier, as a polymer material, possesses good elasticity and toughness, enhancing the asphalt's resistance to permanent deformation, elastic recovery, and fatigue resistance at high temperatures. Polyphosphoric acid can chemically react with certain components in the asphalt, forming chemical bonds that strengthen the intermolecular forces of the asphalt molecules, improving its overall strength. It also improves the compatibility between the polyethylene modifier and the asphalt, allowing the polyethylene modifier to be more evenly distributed in the asphalt, thereby further enhancing the asphalt's resistance to permanent deformation, elastic recovery, and fatigue resistance at high temperatures. Furthermore, this invention utilizes a click reaction between azide-grafted low-density polyethylene and acetylenic aniline compounds to introduce amino and triazole groups into the polyethylene molecular chain. During the preparation of the modified asphalt, polyphosphoric acid can undergo a chemical cross-linking reaction with the amino groups, improving the compatibility between the asphalt and polyethylene. Simultaneously, the introduction of 4-acetylenic aniline into the amino groups improves the planarity and regularity of the cross-linked structure, effectively enhancing the asphalt's elastic deformation capacity and water stability. Furthermore, the network structure formed by the reaction of amino-modified low-density polyethylene, active groups in asphalt, and polyphosphoric acid is beneficial to improving the flexibility and low-temperature crack resistance of asphalt. At the same time, the amino groups in amino-modified low-density polyethylene or the phosphoramide groups formed by the reaction with phosphoric acid can improve the compatibility between modified asphalt and inorganic solid fillers, improve the asphalt's ability to encapsulate and disperse minerals, and thus improve the overall performance of asphalt mixtures. Attached Figure Description

[0019] Figure 1 This is an external view of the low-density polyethylene in Embodiment 1 of the present invention;

[0020] Figure 2 The infrared spectrum of the asphalt in Comparative Example 1 of this invention is shown.

[0021] Figure 3 The infrared spectrum of the modified asphalt in Comparative Example 2 of this invention is shown.

[0022] Figure 4 The infrared spectrum of the modified asphalt in Example 1 of this invention;

[0023] Figure 5 This is a sample image from the low-temperature bending beam rheological test in this invention;

[0024] Figure 6This is a graph showing the relationship between the bulk density and the asphalt-aggregate ratio of the modified asphalt prepared with different asphalt-aggregate ratios using Example 3 in this invention.

[0025] Figure 7 This is a graph showing the relationship between the stability of asphalt mixtures prepared with different asphalt-aggregate ratios using the modified asphalt of Example 3 in this invention and the asphalt-aggregate ratio.

[0026] Figure 8 This is a graph showing the relationship between the porosity and the asphalt ratio of asphalt mixtures prepared with different asphalt-aggregate ratios using the modified asphalt of Example 3 in this invention.

[0027] Figure 9 This is a graph showing the relationship between the flow value and the asphalt-aggregate ratio of asphalt mixtures prepared with different asphalt-aggregate ratios using the modified asphalt of Example 3 in this invention.

[0028] Figure 10 This is a graph showing the relationship between the aggregate void ratio and the asphalt-aggregate ratio of asphalt mixtures prepared with different asphalt-aggregate ratios using the modified asphalt of Example 3 in this invention.

[0029] Figure 11 This is a graph showing the relationship between asphalt saturation and asphalt-aggregate ratio for asphalt mixtures prepared with different asphalt-aggregate ratios using the modified asphalt of Example 3 in this invention.

[0030] Figure 12 This is an image of the vehicle-mounted plate prepared for measuring dynamic stability in this invention.

[0031] Figure 13 This is an appearance diagram of the Marshall specimen prepared for the immersion Marshall test in this invention. Detailed Implementation

[0032] To enable those skilled in the art to better understand the technical solution, the present invention will be described in detail below with reference to embodiments. The description in this part is only exemplary and explanatory, and should not be used to limit the scope of protection of the present invention in any way.

[0033] Specific embodiments of the polyphosphoric acid-low-density polyethylene composite modified asphalt of the present invention are as follows:

[0034] Example 1

[0035] The polyphosphate-low-density polyethylene composite modified asphalt of this embodiment is prepared by a method including the following steps: heating the base asphalt to 160°C until it melts, then shearing it at a speed of 500 r / min, while simultaneously applying low-density polyethylene (appearance as shown in the image)... Figure 1(As shown) The low-density polyethylene (LDPE) was slowly added to the base asphalt and sheared for 30 minutes to allow it to fully swell in the base asphalt. Then, the temperature was raised to 180℃, and the mixture was sheared at 4000 r / min for 1 hour to obtain polyethylene-modified asphalt. The temperature was then maintained at 180℃, the shear rate was reduced to 500 r / min, and polyphosphoric acid was slowly added to the polyethylene-modified asphalt. The mixture was then stirred and sheared for another 30 minutes to obtain polyphosphoric acid-LDPE composite modified asphalt. The base asphalt was No. 70 Grade A road petroleum asphalt produced by Hunan Baoli Asphalt Co., Ltd.; the melting point of the LPE was 112℃, and the melt flow rate, tested according to standard GB / T 3682.1-2018, was 2.17 g / 10 min; the polyphosphoric acid was provided by Maclean's reagent, with an H3PO4 content of 105%; the mass ratio of base asphalt, LPE, and polyphosphoric acid was 95.4:4:0.6.

[0036] Example 2

[0037] The polyphosphoric acid-low-density polyethylene composite modified asphalt of this embodiment is prepared by a method including the following steps: heating the base asphalt to 160°C until it melts, then shearing it at a speed of 500 r / min while slowly adding low-density polyethylene to the base asphalt, stirring and shearing for 30 min to allow the low-density polyethylene to fully swell in the base asphalt; then raising the temperature to 180°C and shearing it at a speed of 4000 r / min for 1 h to obtain polyethylene modified asphalt; then maintaining the temperature at 180°C, reducing the shearing rate to 500 r / min, and slowly adding polyphosphoric acid to the polyethylene modified asphalt, continuing to stir and shear for 30 min to obtain polyphosphoric acid-low-density polyethylene composite modified asphalt. The base asphalt was Grade A 70 road petroleum asphalt produced by Hunan Baoli Asphalt Co., Ltd.; the low-density polyethylene had a melting point of 112℃ and a melt flow rate of 2.17g / 10min as tested according to standard GB / T 3682.1-2018; the polyphosphoric acid was provided by Maclean's reagent and had an H3PO4 content of 105%; the mass ratio of base asphalt, low-density polyethylene and polyphosphoric acid was 95.1:4:0.9.

[0038] Example 3

[0039] The polyphosphoric acid-low-density polyethylene composite modified asphalt of this embodiment is prepared by a method including the following steps: heating the base asphalt to 160°C until it melts, then shearing it at a speed of 500 r / min while slowly adding low-density polyethylene to the base asphalt, stirring and shearing for 30 min to allow the low-density polyethylene to fully swell in the base asphalt; then raising the temperature to 180°C and shearing it at a speed of 4000 r / min for 1 h to obtain polyethylene modified asphalt; then maintaining the temperature at 180°C, reducing the shearing rate to 500 r / min, and slowly adding polyphosphoric acid to the polyethylene modified asphalt, continuing to stir and shear for 30 min to obtain polyphosphoric acid-low-density polyethylene composite modified asphalt. The base asphalt was Grade A 70 road petroleum asphalt produced by Hunan Baoli Asphalt Co., Ltd.; the low-density polyethylene had a melting point of 112℃ and a melt flow rate of 2.17 g / 10 min as tested according to standard GB / T 3682.1-2018; the polyphosphoric acid was provided by Maclean's reagent and had an H3PO4 content of 105%; the mass ratio of base asphalt, low-density polyethylene and polyphosphoric acid was 94.8:4:1.2.

[0040] Example 4

[0041] The polyphosphoric acid-low-density polyethylene (LDPE) composite modified asphalt of this embodiment is prepared by a method including the following steps: The base asphalt is heated to 160°C until melted, then sheared at 500 r / min while amino-modified LDPE is slowly added to the base asphalt. The mixture is stirred and sheared for 30 min to allow the amino-modified LDPE to fully swell in the base asphalt. Then, the temperature is raised to 180°C, and the mixture is sheared at 4000 r / min for 1 h to obtain polyethylene-modified asphalt. The temperature is then maintained at 180°C, the shear rate is reduced to 500 r / min, and polyphosphoric acid is slowly added to the polyethylene-modified asphalt. The mixture is stirred and sheared for another 30 min to obtain the polyphosphoric acid-LDPE composite modified asphalt. The base asphalt is Grade 70 A road petroleum asphalt produced by Hunan Baoli Asphalt Co., Ltd.; the polyphosphoric acid is provided by Maclean's reagent, with an H3PO4 content of 105%; the mass ratio of base asphalt, amino-modified LDPE, and polyphosphoric acid is 94.8:4:1.2; the preparation method of amino-modified LDPE is as follows:

[0042] (1) Low-density polyethylene (LDPE) with a mass ratio of 1:20 (LDPE has a melting point of 112℃ and a melt flow rate of 2.17 g / 10 min as measured by standard GB / T 3682.1-2018) and carbon tetrachloride solvent are added to the reactor. Then, azobisisobutyronitrile (azobisisobutyronitrile is 1% of the mass of LDPE) is added as a catalyst. The mixture is heated to 68℃ and stirred until the LDPE is fully dissolved. Chlorine gas is then continuously introduced into the liquid phase material in the reactor. The mass of chlorine gas introduced per minute is 0.8 times the mass of LDPE. The chlorine gas escaping from the liquid phase material during the reaction is released through the reactor outlet. After collection, the chlorine gas dissolved in the liquid phase material is reused. The chlorine gas reacts with the low-density polyethylene. After 5 minutes of reaction, the chlorine gas is stopped, and the liquid in the reactor is cooled to room temperature. Then, the reaction liquid is deacidified and desolventized with dry air to obtain a crude product. The crude product is then washed with a 10% sodium thiosulfate solution, followed by washing with a 5% sodium hydroxide solution and deionized water. After drying, white granular chlorinated low-density polyethylene is obtained. The chlorine content of the chlorinated low-density polyethylene is 24.76%.

[0043] (2) Chlorinated low-density polyethylene and anhydrous tetrahydrofuran in a mass ratio of 1:15 were added to a stirred tank and stirred until the chlorinated low-density polyethylene was fully dissolved. Then, sodium azide and tetraethylammonium bromide (the mass ratio of chlorinated low-density polyethylene, sodium azide and tetraethylammonium bromide was 1:1.5:0.3) were added to the stirred tank. The material in the stirred tank was heated to 55°C and stirred for 5 hours. The tetrahydrofuran was removed by vacuum distillation to obtain a crude product. The crude product was then washed with a large amount of deionized water and ethanol in sequence and dried to obtain azide-grafted low-density polyethylene.

[0044] (3) Dissolve azido-grafted low-density polyethylene in tetrahydrofuran to obtain an azido-grafted low-density polyethylene solution with a mass fraction of 4%. Then, dry nitrogen gas is introduced into the azido-grafted low-density polyethylene solution, and 4-ethynylaniline, cuprous bromide and pentamethyldiethylenetriamine are added to the azido-grafted low-density polyethylene solution (the mass ratio of azido-grafted low-density polyethylene and 4-ethynylaniline is 1:1.5, and the molar ratio of 4-ethynylaniline, cuprous bromide and pentamethyldiethylenetriamine is 1:0.3:0.3). Stir the reaction for 8 hours, distill under reduced pressure to obtain crude product, and then wash the crude product with a large amount of deionized water and methanol in sequence. After drying, amino-modified low-density polyethylene is obtained.

[0045] Example 5

[0046] The polyphosphoric acid-low-density polyethylene (LDPE) composite modified asphalt of this embodiment is prepared by a method including the following steps: The base asphalt is heated to 160°C until melted, then sheared at 500 r / min while amino-modified LDPE is slowly added to the base asphalt. The mixture is stirred and sheared for 30 min to allow the amino-modified LDPE to fully swell in the base asphalt. Then, the temperature is raised to 180°C, and the mixture is sheared at 4000 r / min for 1 h to obtain polyethylene-modified asphalt. The temperature is then maintained at 180°C, the shear rate is reduced to 500 r / min, and polyphosphoric acid is slowly added to the polyethylene-modified asphalt. The mixture is stirred and sheared for another 30 min to obtain the polyphosphoric acid-LDPE composite modified asphalt. The base asphalt is Grade 70 A road petroleum asphalt produced by Hunan Baoli Asphalt Co., Ltd.; the polyphosphoric acid is provided by Maclean's reagent, with an H3PO4 content of 105%; the mass ratio of base asphalt, amino-modified LDPE, and polyphosphoric acid is 94.8:4:1.2; the preparation method of amino-modified LDPE is as follows:

[0047] (1) Low-density polyethylene (LDPE) with a mass ratio of 1:20 (LDPE has a melting point of 112℃ and a melt flow rate of 2.17 g / 10 min as tested according to standard GB / T 3682.1-2018) and carbon tetrachloride solvent are added to the reactor. Then, azobisisobutyronitrile (azobisisobutyronitrile is 1% of the mass of LDPE) is added as a catalyst. The mixture is heated to 68℃ and stirred until the LDPE is fully dissolved. Chlorine gas is then continuously introduced into the liquid phase material in the reactor. The mass of chlorine gas introduced per min is 1.1 times the mass of LDPE. The chlorine gas escaping from the liquid phase material during the reaction is released through the reactor outlet. After collection, the chlorine gas dissolved in the liquid phase material is reused. The chlorine gas reacts with the low-density polyethylene. After 8 minutes of reaction, the chlorine gas is stopped, and the liquid in the reactor is cooled to room temperature. Then, the reaction liquid is deacidified and desolventized with dry air to obtain a crude product. The crude product is then washed with a 10% sodium thiosulfate solution, followed by washing with a 5% sodium hydroxide solution and deionized water. After drying, white granular chlorinated low-density polyethylene is obtained. The chlorine content of the chlorinated low-density polyethylene is 35.79%.

[0048] (2) Chlorinated low-density polyethylene and anhydrous tetrahydrofuran in a mass ratio of 1:15 were added to a stirred tank and stirred until the chlorinated low-density polyethylene was fully dissolved. Then, sodium azide and tetraethylammonium bromide (the mass ratio of chlorinated low-density polyethylene, sodium azide and tetraethylammonium bromide was 1:1.5:0.3) were added to the stirred tank. The material in the stirred tank was heated to 55°C and stirred for 5 hours. The tetrahydrofuran was removed by vacuum distillation to obtain a crude product. The crude product was then washed with a large amount of deionized water and ethanol in sequence and dried to obtain azide-grafted low-density polyethylene.

[0049] (3) Dissolve azido-grafted low-density polyethylene in tetrahydrofuran to obtain an azido-grafted low-density polyethylene solution with a mass fraction of 4%. Then, dry nitrogen gas is introduced into the azido-grafted low-density polyethylene solution, and 4-ethynylaniline, cuprous bromide and pentamethyldiethylenetriamine are added to the azido-grafted low-density polyethylene solution (the mass ratio of azido-grafted low-density polyethylene and 4-ethynylaniline is 1:1.5, and the molar ratio of 4-ethynylaniline, cuprous bromide and pentamethyldiethylenetriamine is 1:0.3:0.3). Stir the reaction for 8 hours, distill under reduced pressure to obtain crude product, and then wash the crude product with a large amount of deionized water and methanol in sequence. After drying, amino-modified low-density polyethylene is obtained.

[0050] Example 6

[0051] The polyphosphoric acid-low-density polyethylene (LDPE) composite modified asphalt of this embodiment is prepared by a method including the following steps: The base asphalt is heated to 160°C until melted, then sheared at 500 r / min while amino-modified LDPE is slowly added to the base asphalt. The mixture is stirred and sheared for 30 min to allow the amino-modified LDPE to fully swell in the base asphalt. Then, the temperature is raised to 180°C, and the mixture is sheared at 4000 r / min for 1 h to obtain polyethylene-modified asphalt. The temperature is then maintained at 180°C, the shear rate is reduced to 500 r / min, and polyphosphoric acid is slowly added to the polyethylene-modified asphalt. The mixture is stirred and sheared for another 30 min to obtain the polyphosphoric acid-LDPE composite modified asphalt. The base asphalt is Grade 70 A road petroleum asphalt produced by Hunan Baoli Asphalt Co., Ltd.; the polyphosphoric acid is provided by Maclean's reagent, with an H3PO4 content of 105%; the mass ratio of base asphalt, amino-modified LDPE, and polyphosphoric acid is 94.8:4:1.2; the preparation method of amino-modified LDPE is as follows:

[0052] (1) Low-density polyethylene (LDPE) with a mass ratio of 1:20 (LDPE has a melting point of 112℃ and a melt flow rate of 2.17 g / 10 min as tested according to standard GB / T 3682.1-2018) and carbon tetrachloride solvent are added to the reactor. Then, azobisisobutyronitrile (azobisisobutyronitrile has a mass of 1% of the mass of LDPE) is added as a catalyst. The mixture is heated to 68℃ and stirred until the LDPE is fully dissolved. Chlorine gas is then continuously introduced into the liquid phase material in the reactor. The mass of chlorine gas introduced per min is 0.8 times the mass of LDPE. The chlorine gas escaping from the liquid phase material during the reaction is released through the reactor outlet. After collection, the chlorine gas dissolved in the liquid phase material is reused. The chlorine gas reacts with the low-density polyethylene. After 5 minutes of reaction, the chlorine gas is stopped, and the liquid in the reactor is cooled to room temperature. Then, the reaction liquid is deacidified and desolventized with dry air to obtain a crude product. The crude product is then washed with a 10% sodium thiosulfate solution, followed by washing with a 5% sodium hydroxide solution and deionized water. After drying, white granular chlorinated low-density polyethylene is obtained. The chlorine content of the chlorinated low-density polyethylene is 24.76%.

[0053] (2) Chlorinated low-density polyethylene and anhydrous tetrahydrofuran in a mass ratio of 1:15 were added to a stirred tank and stirred until the chlorinated low-density polyethylene was fully dissolved. Then, sodium azide and tetraethylammonium bromide (the mass ratio of chlorinated low-density polyethylene, sodium azide and tetraethylammonium bromide was 1:1.5:0.3) were added to the stirred tank. The material in the stirred tank was heated to 55°C and stirred for 5 hours. The tetrahydrofuran was removed by vacuum distillation to obtain a crude product. The crude product was then washed with a large amount of deionized water and ethanol in sequence and dried to obtain azide-grafted low-density polyethylene.

[0054] (3) Dissolve azido-grafted low-density polyethylene in tetrahydrofuran to obtain an azido-grafted low-density polyethylene solution with a mass fraction of 4%. Then, dry nitrogen gas is introduced into the azido-grafted low-density polyethylene solution, and 2-ethynylaniline, cuprous bromide and pentamethyldiethylenetriamine are added to the azido-grafted low-density polyethylene solution (the mass ratio of azido-grafted low-density polyethylene and 2-ethynylaniline is 1:1.5, and the molar ratio of 2-ethynylaniline, cuprous bromide and pentamethyldiethylenetriamine is 1:0.3:0.3). Stir the reaction for 8 hours, distill under reduced pressure to obtain crude product, and then wash the crude product with a large amount of deionized water and methanol in sequence. After drying, amino-modified low-density polyethylene is obtained.

[0055] Comparative Example 1

[0056] The asphalt used in this comparative example is the base asphalt from Example 1.

[0057] Comparative Example 2

[0058] The modified asphalt in this comparative example was prepared by a method comprising the following steps: heating the base asphalt to 160°C until melted, then shearing it at a speed of 500 r / min while slowly adding low-density polyethylene to the base asphalt, stirring and shearing for 30 min to allow the low-density polyethylene to fully swell in the base asphalt; then raising the temperature to 180°C and shearing it at a speed of 4000 r / min for 1 h to obtain the modified asphalt. The base asphalt was No. 70 Grade A road petroleum asphalt produced by Hunan Baoli Asphalt Co., Ltd.; the melting point of the low-density polyethylene was 112°C, and the melt flow rate tested according to standard GB / T 3682.1-2018 was 2.17 g / 10 min; the mass ratio of base asphalt to low-density polyethylene was 98:2.

[0059] Comparative Example 3

[0060] The modified asphalt in this comparative example was prepared by a method comprising the following steps: heating the base asphalt to 160°C until melted, then shearing it at a speed of 500 r / min while slowly adding low-density polyethylene to the base asphalt, stirring and shearing for 30 min to allow the low-density polyethylene to fully swell in the base asphalt; then raising the temperature to 180°C and shearing it at a speed of 4000 r / min for 1 h to obtain the modified asphalt. The base asphalt was No. 70 Grade A road petroleum asphalt produced by Hunan Baoli Asphalt Co., Ltd.; the melting point of the low-density polyethylene was 112°C, and the melt flow rate tested according to standard GB / T 3682.1-2018 was 2.17 g / 10 min; the mass ratio of base asphalt to low-density polyethylene was 96:4.

[0061] Comparative Example 4

[0062] The modified asphalt in this comparative example was prepared by a method comprising the following steps: heating the base asphalt to 160°C until melted, then shearing it at a speed of 500 r / min while slowly adding low-density polyethylene to the base asphalt, stirring and shearing for 30 min to allow the low-density polyethylene to fully swell in the base asphalt; then raising the temperature to 180°C and shearing it at a speed of 4000 r / min for 1 h to obtain the modified asphalt. The base asphalt was No. 70 Grade A road petroleum asphalt produced by Hunan Baoli Asphalt Co., Ltd.; the melting point of the low-density polyethylene was 112°C, and the melt flow rate tested according to standard GB / T 3682.1-2018 was 2.17 g / 10 min; the mass ratio of base asphalt to low-density polyethylene was 94:6.

[0063] Experimental Example 1

[0064] In this experimental example, infrared spectroscopy analysis was used to characterize the structure of the asphalt or modified asphalt in Example 3 and Comparative Examples 1-2. The results are as follows: Figure 2-4As shown. By Figure 2-4 It can be seen that the base asphalt is at 2919cm -1 and 2851cm -1 There are two distinct strong absorption peaks at 1680–1450 cm⁻¹, which are attributed to the CH vibrations between cycloalkanes and alkanes. -1 The peaks generated within this range are mainly characteristic peaks produced by the C=C skeletal vibrations of the conjugated double bond of the benzene ring, with the peak at 1602 cm⁻¹ being particularly prominent. -1 The nearby characteristic peak is the stretching vibration of aromatic C=C, at 1457 cm⁻¹. - The absorption peak at 1376 cm⁻¹ is a result of the in-plane bending vibration of the methylene-CH₂- group. -1 The absorption peak at 1000–500 cm⁻¹ is a result of the CH bending vibration in -CH₃. -1 The range mainly consists of smaller absorption peaks generated by the irregularity of the CH plane on the benzene ring.

[0065] Compared with the base asphalt, the modified asphalt in Comparative Example 2 did not show significant changes in its infrared spectrum, but at 723 cm⁻¹... -1 The enhanced characteristic peaks in the vicinity compared to the base asphalt are due to the in-plane rocking vibrations of CH2 in the low-density polyethylene. Compared to the base asphalt, the modified asphalt in Comparative Example 2 did not exhibit new characteristic peaks in its infrared spectrum, indicating no chemical change. Therefore, the low-density polyethylene and asphalt primarily coexist physically.

[0066] Comparing the modified asphalt of Example 1 with the base asphalt, at 1010 cm... -1 The appearance of new characteristic peaks is related to the stretching vibrations of POC or P=O bonds. This is because polyphosphoric acid contains phosphate groups, which react with components in asphalt when added to it, forming new phosphate-derived compounds. It is also possible that, under the influence of polyphosphoric acid, the polar portions of asphalt molecules form more complex cross-linked networks.

[0067] Experiment Example 2

[0068] This experimental example tests the stability of the modified asphalt from Examples 1-6 and Comparative Example 3 using a segregation test. The segregation test was conducted according to T0661-2011 of the standard JTG E20-2011. The obtained asphalt sample was divided into three equal parts, and the top and bottom thirds were removed. The top and bottom asphalt samples were heated to prepare the final samples. A dynamic shear rheometer (DSR) was used to perform a temperature scan test on the top and bottom of the asphalt samples. The stress was 12%, the loading frequency was 10 rad / s, and the test temperature was 64℃. The rutting factor of the modified asphalt was obtained, and then the segregation rate R of the modified asphalt was calculated. S R SA smaller absolute value indicates better thermal storage stability of the asphalt. The rutting factor is defined as the ratio of the complex modulus to the sine of the phase angle (G). * / sinδ), segregation rate R S The calculation method is as follows:

[0069]

[0070] Wherein, the lower part represents the rutting factor of the bottom third of the sample, and the upper part represents the rutting factor of the top third of the sample.

[0071] The segregation rate test results of the modified asphalt in Examples 1-6 and Comparative Example 3 are shown in Table 1.

[0072] Table 1. Calculation results of segregation rate test of modified asphalt

[0073]

[0074] Table 1 shows that the modified asphalt in Comparative Example 3 exhibited the highest segregation rate, indicating poor compatibility between low-density polyethylene and the asphalt matrix. Examples 1-3 show that the segregation rate of the modified asphalt decreased significantly with increasing polyphosphoric acid content after the addition of polyphosphoric acid. Examples 3-6 show that the segregation rate of the modified asphalt further decreased when amino-modified low-density polyethylene was used. This is because polyphosphoric acid can bond with the amino groups in amino-modified low-density polyethylene, improving the compatibility between the asphalt and polyethylene molecular chains. However, the segregation rate of the modified asphalt increased with increasing chlorine content in chlorinated low-density polyethylene, indicating excessive cross-linking of the modified low-density polyethylene, leading to poor compatibility with asphalt. Furthermore, when 2-ethynylaniline was used to introduce the amino group, the close proximity of the amino group to the triazole group resulted in significant steric hindrance, hindering the reaction with polyphosphoric acid. Even after the reaction to generate phosphate ester groups, the cross-linked structure exhibited poor planarity and irregularity, leading to poor compatibility with asphalt and consequently increasing the segregation rate.

[0075] Experimental Example 3

[0076] This experimental example tests the deformation recovery capacity and low-temperature crack resistance of asphalt or modified asphalt from Examples 1-6 and Comparative Examples 1-4 using multi-stress creep recovery tests and low-temperature bending beam rheological tests. The multi-stress creep recovery test method is as follows: A rotating thin-film oven test (RTFOT) was used. Short-term aged asphalt samples were prepared according to the requirements of AASTO TP70-90. The short-term aged asphalt samples were used, set to stress recovery mode, using a 25mm plate, and the test temperature was 64℃. During the test, the stress was set to 3.2kPa. The experimental phase included a series of repeated loading-unloading cycles, totaling 10 cycles, each lasting 10 seconds (1 second loading time and 9 seconds unloading time). The creep recovery rate R of the asphalt was obtained after the experiment. The low-temperature bending beam rheological test was conducted according to T0627-2011 in JTG E20-2011. A bending beam rheometer was used to test the asphalt samples. The prepared samples are shown below. Figure 5 As shown, the test temperature was -18℃, and the creep rate was calculated after the experiment. The creep recovery rate and creep rate of the asphalt or modified asphalt in Examples 1-6 and Comparative Examples 1-4 are shown in Table 2.

[0077] Table 2 Creep recovery rate and creep rate of modified asphalt

[0078]

[0079] Creep recovery rate reflects the recovery ability of asphalt after deformation under stress. Generally, a higher creep recovery rate indicates a higher proportion of elastic recovery and stronger recoverable deformation capacity. Table 2 shows that the creep recovery rate of the base asphalt is zero, indicating that the base asphalt mainly exhibits plastic strain with a very low proportion of elastic recovery. Only the modified asphalts in Examples 4-6 maintain a creep recovery rate above 50%, demonstrating that they can still maintain good elastic deformation characteristics under this load level. Examples 1-3 and Comparative Examples 2-4 show that the creep recovery rate of the modified asphalt increases with the increase of low-density polyethylene and polyphosphate incorporation. This result indicates that the addition of low-density polyethylene and polyphosphate can significantly improve the creep recovery performance of modified asphalt, thereby effectively improving its mechanical response in practical applications. As shown in Examples 3-6, the creep recovery rate of modified asphalt increases after using amino-modified low-density polyethylene. This indicates that the cross-linked network structure formed by the reaction of polyphosphoric acid, asphalt, and amino-modified low-density polyethylene is beneficial to improving the elastic deformation capacity of asphalt. Furthermore, excessively high cross-linking density will lead to a decrease in elastic deformation capacity. Moreover, the introduction of amino groups using 4-ethynylaniline is beneficial to improving the planarity and regularity of the cross-linked structure, thereby effectively improving the elastic deformation capacity of asphalt.

[0080] Creep rate reflects the stress relaxation ability of asphalt under sustained load. A higher creep rate indicates that the asphalt can better relieve stress and exhibits better low-temperature crack resistance. Comparative Examples 1-4 show that, compared with base asphalt, the creep rate of modified asphalt decreases with increasing low-density polyethylene (LDPE) content. This indicates that the addition of LPE negatively impacts the modified asphalt's resistance to permanent deformation and stress relaxation, thus negatively affecting its low-temperature crack resistance. Examples 1-3 show that the creep rate of modified asphalt decreases to some extent with increasing polyphosphoric acid (PPA) content. This may be because PPA has a relatively small molecular weight, which alters the original colloidal structure of the asphalt, reducing its flexibility. Examples 3-6 show that the creep rate of modified asphalt increases after using amino-modified LPE, and the creep rate of the modified asphalt in Example 4 exceeds that of the base asphalt. This indicates that the network structure formed by the reaction of amino-modified LPE, the active groups in the asphalt, and PPA is beneficial for improving the flexibility and low-temperature crack resistance of asphalt.

[0081] Experiment Example 4

[0082] This experimental example is used to determine the optimal asphalt-aggregate ratio when preparing AC-13C asphalt mixtures from the asphalt of Comparative Example 1 or the modified asphalt of Examples 3-6 and Comparative Example 2. Taking the modified asphalt of Example 3 as an example, the method for determining the optimal asphalt-aggregate ratio is as follows: Based on the design requirements of JTG F40-2004, the Marshall design method was used to design the aggregate gradation, and the aggregate gradation design is shown in Table 3; then, using basalt as aggregate and limestone as mineral powder, AC-13C asphalt mixture was prepared. The performance parameters of coarse aggregate are shown in Table 4, the performance parameters of fine aggregate are shown in Table 5, and the performance parameters of mineral powder are shown in Table 6; when preparing AC-13C asphalt mixture, five asphalt-aggregate ratios of 4.5%, 5.0%, 5.5%, 6.0%, and 6.5% were selected for testing. According to the test method T0702 in JTG E20-2011, 25 standard Marshall specimens were prepared for the five asphalt-aggregate ratios (five parallel samples in each group), and the volume parameters and key indicators such as mechanical properties of each group of specimens were systematically measured. The Marshall test results of AC-13C asphalt mixtures prepared using the modified asphalt of Example 3 with different asphalt-aggregate ratios are shown in Table 7. Based on the experimental results in Table 7, the corresponding relationships between the bulk density, stability, void ratio, flow value, aggregate void ratio, asphalt saturation, and asphalt-aggregate ratio of the asphalt mixtures are plotted, as follows: Figure 6-11 As shown.

[0083] Table 3 Mineral Gradation Design Table

[0084]

[0085] Table 4 Performance parameters of coarse aggregate

[0086]

[0087] Table 5 Performance parameters of fine aggregates

[0088]

[0089] Table 6. Performance parameters of mineral materials

[0090]

[0091] Table 7. Marshall test results of AC-13C asphalt mixtures prepared with different asphalt-aggregate ratios.

[0092]

[0093] According to Table 7 and Figure 6-11 Based on the results, the corresponding asphalt-aggregate ratios for each key control index were extracted: peak bulk density a1 = 6.1%, peak stability a2 = 6.1%, median target porosity a3 = 5.72%, and median asphalt saturation a4 = 5.29%. The optimal asphalt-aggregate ratio OAC1 was determined using the arithmetic mean method, calculated as follows:

[0094] OAC1=(a1+a2+a3+a4) / 4=5.8%.

[0095] Then, by considering the acceptable ranges of various indicators (except VMA and bulk density), the range OAC that the oil-aggregate ratio together satisfies is determined. min =5.43% and OAC max =5.7%, the optimal oil-stone ratio OAC2 was calculated using the interval median method (rounded to one decimal place), and the calculation method is as follows:

[0096] OAC2=(OAC min +OAC max ) / 2=5.6%.

[0097] The optimal oil-aggregate ratio (OAC) was finally determined using the comprehensive balance method, and the calculation method is as follows:

[0098] OAC = (OAC1 + OAC2) / 2 = 5.7%.

[0099] Based on the above calculations, the optimal asphalt-aggregate ratio for the modified asphalt in Example 3 is 5.7%. Similarly, calculations show that the optimal asphalt-aggregate ratio for the modified asphalt in Comparative Example 3 is 5.4%, the optimal asphalt-aggregate ratio for the base asphalt in Example 4 is 4.8%, the optimal asphalt-aggregate ratio for the modified asphalt in Example 5 is 5.5, the optimal asphalt-aggregate ratio for the modified asphalt in Example 5 is 5.6, and the optimal asphalt-aggregate ratio for the modified asphalt in Example 6 is 5.5.

[0100] Experimental Example 5

[0101] This experimental example evaluates the high-temperature stability of asphalt mixtures prepared from the asphalt of Comparative Example 1 or the modified asphalt of Examples 3-6 and Comparative Example 2 through rutting tests. The experimental method is as follows: Based on the optimal asphalt-aggregate ratio determined in Experimental Example 4, asphalt or modified asphalt was prepared into AC-13C asphalt mixtures according to the optimal asphalt-aggregate ratio. Vehicle plates with dimensions of 300mm × 300mm × 50mm were prepared according to the test method T0703 in specification JTG E20-2011. Figure 12 As shown, the specimens were placed at room temperature for 48 hours, and then kept at a constant temperature of 60℃ for 6 hours in a rutting apparatus. At the start of the test, a vertical load of 780N (equivalent wheel pressure 0.7MPa) was applied, simulating the cyclic shear stress of heavy traffic at a frequency of 42 times / min. Rolling displacement curves were collected in real time, and deformation data from 45 to 60 minutes were extracted according to specifications to calculate dynamic stability and quantitatively characterize the mixture's resistance to rutting deformation. The calculation method for dynamic stability is as follows:

[0102]

[0103] Where: DS is the dynamic stability, times / mm; N is the rolling frequency, 42 times / min; d1 is the deformation at t1, mm; d2 is the deformation at t2, mm; C1 is the testing machine coefficient, taken as 1.0; C2 is the specimen coefficient, taken as 1.0.

[0104] The high-temperature stability test results of the asphalt mixtures prepared from the asphalt of Comparative Example 1 or the modified asphalt of Examples 3-6 and Comparative Example 2 are shown in Table 8.

[0105] Table 8. High-temperature stability test results of asphalt mixtures

[0106]

[0107] Table 8 shows that the dynamic stability of the asphalt mixture in Comparative Example 1 was 1533 cycles / mm, while that of the modified asphalt mixture in Comparative Example 3 was 4773 cycles / mm, representing an improvement of 211.4% compared to the base asphalt, more than double. Furthermore, the deformation at 45 min and 60 min was also reduced, indicating that the addition of low-density polyethylene significantly improves the high-temperature stability of the asphalt mixture. The dynamic stability of the composite modified asphalt mixture in Example 3 was 6364 cycles / mm, an improvement of 33.3% compared to the modified asphalt mixture in Comparative Example 3. Its deformation at 45 min and 60 min was further reduced, indicating that the polyphosphoric acid / low-density polyethylene composite further improved the high-temperature stability of the mixture. Examples 3-6 show that after using amino-modified low-density polyethylene, the dynamic stability of the asphalt mixture further increased, and the deformation further decreased. This indicates that the chemical cross-linking of polyphosphoric acid, amino-modified low-density polyethylene, and the active groups in the asphalt effectively resists deformation caused by external loads, improving the thermal stability of the asphalt mixture. Meanwhile, due to the excessive chlorine content of chlorinated low-density polyethylene or the excessive crosslinking density when 2-ethynylaniline is used to introduce amino groups, the system becomes brittle, which in turn reduces the deformation resistance of asphalt mixtures.

[0108] Experimental Example 6

[0109] This experimental example evaluates the low-temperature crack resistance of asphalt mixtures prepared from the asphalt of Comparative Example 1 or the modified asphalt of Examples 3-6 and Comparative Example 2 through a low-temperature bending beam test. The experimental method is as follows: Based on the optimal asphalt-aggregate ratio determined in Experiment 4, asphalt or modified asphalt was prepared into AC-13C asphalt mixtures according to the optimal asphalt-aggregate ratio. Then, according to the test procedure of JTG E20-2011 T 0715, a standard small beam specimen (250mm×30mm×35mm) was used to carry out a low-temperature bending beam test. The specimens were cured in a constant temperature chamber at -10℃±0.5℃ for 4 hours to ensure uniform temperature. A three-point bending load was applied at a rate of 50mm / min using an MTS universal testing machine. The load-displacement curve was recorded in real time by the data acquisition system, and the bending tensile strength R was obtained after data processing. B Maximum bending tensile strain ε B Then calculate the bending stiffness modulus S. B The results of the low-temperature crack resistance test of the asphalt prepared by Comparative Example 1 or the modified asphalt prepared by Examples 3-6 and Comparative Example 2 are shown in Table 9.

[0110] Table 9. Results of Low-Temperature Crack Resistance Tests on Asphalt Mixtures

[0111]

[0112] Table 9 shows that, compared with base asphalt, modified asphalt exhibits superior load-bearing capacity and resistance to deformation at low temperatures. (Flexural stiffness modulus S) B The flexural stiffness modulus is an important indicator of the mechanical properties of asphalt mixtures under low-temperature conditions. A higher modulus indicates that the mixture is more rigid and has strong resistance to deformation, but it has lower toughness and is prone to cracking at low temperatures. It can be seen that the flexural stiffness modulus of the modified asphalt mixture in Comparative Example 3 and the composite modified asphalt mixture in Example 3 are both lower than that of the base asphalt. However, the flexural stiffness modulus of the composite modified asphalt mixture in Example 3 is higher than that of the modified asphalt mixture in Comparative Example 3. After using amino-modified low-density polyethylene, the flexural stiffness modulus of the asphalt mixture increases. However, the flexural stiffness modulus of the asphalt mixture in Example 4 is close to that of the base asphalt, indicating that its network cross-linking structure is not too dense. This allows the asphalt mixture to have both high strength and good toughness. However, with the increase of chlorine content in chlorinated low-density polyethylene and the introduction of amino groups using 2-ethynylaniline, the network cross-linking structure becomes too dense, resulting in lower system toughness and poorer low-temperature crack resistance.

[0113] Experimental Example 7

[0114] This experiment evaluates the water stability of asphalt mixtures prepared from the asphalt of Comparative Example 1 or the modified asphalt of Examples 3-6 and Comparative Example 2 through the immersion Marshall test and freeze-thaw splitting test. The experimental method is as follows: Based on the optimal asphalt-aggregate ratio determined in Experiment 4, asphalt or modified asphalt was prepared into AC-13C asphalt mixtures according to the optimal asphalt-aggregate ratio. Then, the asphalt mixtures were subjected to the immersion Marshall test according to the test method T 0709 in specification JTG E20-2011. The Marshall specimens were divided into control samples and immersion samples for comparative analysis: the stability MS of the control sample was measured after being kept in a constant temperature water bath at 60℃ for 30 min; the stability MS1 of the immersion sample was measured after being kept in a water bath environment at the same temperature for 48 h, and then the residual stability MS0 was calculated; MS0 is equal to the ratio of MS1 to MS. The Marshall specimens prepared during the test are shown in the figure. Figure 13 As shown; the freeze-thaw splitting tensile test was conducted according to the test procedure T 0729 in standard JTG E20-2011. The calculation method for the freeze-thaw splitting tensile strength ratio of asphalt mixture is as follows:

[0115]

[0116]

[0117]

[0118] In the formula: R T1 R T2 P represents the splitting tensile strength of the two groups of specimens, in MPa; T1P T2 The maximum test load for the two sets of specimens is N; , is the average splitting tensile strength of the two groups of specimens, MPa; h1 and h2 are the test heights of the two groups of specimens, mm; TSR is the freeze-thaw splitting tensile strength ratio, %.

[0119] The results of the immersion Marshall test of the asphalt prepared by Comparative Example 1 or the modified asphalt prepared by Examples 3-6 and Comparative Example 2 are shown in Table 10, and the results of the freeze-thaw splitting test are shown in Table 11.

[0120] Table 10 Results of the Marshall Immersion Test

[0121]

[0122] Table 11 Results of freeze-thaw splitting test

[0123]

[0124] Table 10 shows that the stability of the Marshall specimens decreased to varying degrees after immersion in water. This phenomenon indicates that water erosion weakens the asphalt-aggregate interface bonding performance, leading to a decrease in the overall mechanical strength of the mixture, i.e., the asphalt mixture suffered some water damage. Comparative analysis shows that the base asphalt mixture in Comparative Example 1 had the lowest residual stability, at only 82.95%. The modified asphalt mixture in Comparative Example 3 had a residual stability of 90.61%, an increase of 8.02% compared to the base asphalt mixture, indicating that the addition of low-density polyethylene improved its resistance to water damage. The modified asphalt mixture in Example 3 had a further improved residual stability of 92.32%, indicating that the synergistic effect of polyphosphoric acid and low-density polyethylene can further improve the water stability of the asphalt mixture. Meanwhile, after using amino-modified low-density polyethylene, the stability of asphalt mixture is further improved due to the formation of cross-linking system. However, when the chlorine content of chlorinated low-density polyethylene is too high, it will introduce amino groups with high hydrophilicity, which will reduce the hydrophilicity of the system. At the same time, when 2-ethynylaniline is used to introduce amino groups, the cross-linking structure formed by it has poor planarity and irregular structure, which makes it easy for water to penetrate, thereby reducing the ability to resist water damage.

[0125] Table 11 shows that the splitting tensile strength of the standard Marshall specimens decreased after freeze-thaw cycles, indicating that the asphalt mixtures suffered varying degrees of water damage. The freeze-thaw splitting tensile strength ratio of the base asphalt mixture in Comparative Example 1 was 81.01%, while that of the modified asphalt mixture in Comparative Example 3 was 89.59%, representing an 8.58% increase compared to the base asphalt. This indicates that the addition of low-density polyethylene improved the water damage resistance of the asphalt mixture. The tensile strength ratio of the composite modified asphalt mixture in Example 3 was 91.52%, a further 1.93% increase compared to the modified asphalt mixture in Comparative Example 3. This demonstrates that the water damage resistance of the asphalt mixture was further improved after the polyphosphate / low-density polyethylene composite was applied. Furthermore, the use of amino-modified low-density polyethylene further increased the splitting tensile strength and enhanced the water damage resistance of the asphalt mixture, consistent with the results of the immersion Marshall test.

[0126] It should be noted that, in this document, the terms "comprising," "including," and any other variations are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Specific examples have been used in this document to illustrate the principles and implementation methods of the present invention. These examples are merely for the purpose of helping to understand the method and core ideas of the present invention. The above descriptions are only preferred embodiments of the present invention. It should be pointed out that, due to the limitations of written expression and the objective existence of infinite specific structures, those skilled in the art can make several improvements, modifications, or variations without departing from the principles of the present invention, and can also combine the above technical features in an appropriate manner. These improvements, modifications, variations, or combinations, or the direct application of the concept and technical solution of the present invention to other situations without modification, should all be considered within the scope of protection of the present invention.

Claims

1. A polyphosphoric acid-low-density polyethylene composite modified asphalt, characterized in that, The method comprises the following steps: heating the base asphalt to melt, then adding a polyethylene modifier and mixing to obtain polyethylene modified asphalt; then heating and mixing the polyethylene modified asphalt and polyphosphoric acid to obtain polyphosphoric acid-low-density polyethylene composite modified asphalt; wherein the polyethylene modifier is amino-modified low-density polyethylene; wherein the amino-modified low-density polyethylene is obtained by click reaction of chlorinated low-density polyethylene grafted with azide groups and then reacting it with a mixture of alkynyl aniline compounds, wherein the chlorine content of the chlorinated low-density polyethylene is 24-26%; wherein the alkynyl aniline compound is 4-ethynyl aniline, and the mass ratio of the base asphalt, polyethylene modifier and polyphosphoric acid is 94-96:4-5:0.6-1.

2.

2. The polyphosphoric acid-low-density polyethylene composite modified asphalt according to claim 1, characterized in that, The preparation method of the chlorinated low-density polyethylene is as follows: low-density polyethylene and chlorine are chlorinated in a solvent under the action of a catalyst to obtain chlorinated low-density polyethylene; the melting point of low-density polyethylene is 112~115℃.

3. The polyphosphoric acid-low-density polyethylene composite modified asphalt according to claim 1, characterized in that, The method for grafting the azido group is as follows: chlorinated low-density polyethylene, sodium azide, and tetraethylammonium bromide are mixed and reacted in a solvent at 55-60°C for 5-7 hours to obtain azido-grafted low-density polyethylene; the mass ratio of the chlorinated low-density polyethylene, sodium azide, and tetraethylammonium bromide is 1:1.5-1.7:0.3-0.

5.

4. The polyphosphoric acid-low-density polyethylene composite modified asphalt according to claim 3, characterized in that, The method for the click reaction with alkynyl aniline compounds is as follows: Azide-grafted low-density polyethylene, alkynyl aniline compounds, cuprous bromide, and pentamethyldiethylenetriamine are mixed and reacted in a solvent to obtain amino-modified low-density polyethylene; the mass ratio of the azide-grafted low-density polyethylene to the alkynyl aniline compounds is 1:1.5~1.8, and the molar ratio of the alkynyl aniline compounds, cuprous bromide, and pentamethyldiethylenetriamine is 1:0.3~0.5:0.3~0.

5.

5. The polyphosphoric acid-low-density polyethylene composite modified asphalt according to any one of claims 1-4, characterized in that, The polyethylene-modified asphalt and polyphosphoric acid are heated and mixed at a temperature of 180~185℃ for 30~60 minutes.

6. The polyphosphoric acid-low-density polyethylene composite modified asphalt according to any one of claims 1-4, characterized in that, The base asphalt is No. 70 Grade A road petroleum asphalt.

7. An asphalt pavement material, characterized in that, It is composed of polyphosphoric acid-low-density polyethylene composite modified asphalt and mineral aggregate as described in any one of claims 1-6.

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