A method for composite modified asphalt using waste polystyrene and cement

Abstract

The invention belongs to the field of building materials technology. For the problem that the building insulation material of the present stage polystyrene board is difficult to recycle after being discarded, the present invention discloses a method for composite modified asphalt using waste polystyrene and cement, comprising the following steps: waste polystyrene is cleaned, crushed into polystyrene particles for standby use after drying, then the matrix asphalt is stirred while heating, polystyrene particles and cement are mixed when being heated to 160-180 DEG C, stirring evenly, then placed in a 120-160 DEG C oven and cultivated at a constant temperature for 0.5-3h, then placed in a high-speed shearing machine and stirred at 200-400r / min for 3-10min, finally placed in a 120-160 DEG C oven and cultivated at a constant temperature for 15-60min, to obtain modified asphalt; the dosage of the waste polystyrene is 0.1-6%, and the dosage of the cement is 0.1-4%. The composite modifier composed of polystyrene / cement of the present invention can improve the high and low temperature performance of asphalt as a whole, realizes the recycling of waste polystyrene, reduces project cost, and realizes the sustainable development of civil engineering materials.

Description

Technical Field

[0001] The invention belongs to the technical field of building materials, and in particular relates to a method for compositely modifying asphalt by utilizing waste polystyrene and cement. Background Art

[0002] Asphalt pavement is increasingly used in modern transportation due to its advantages in driving comfort, construction time, and post-maintenance. However, due to factors such as the rapid growth of modern road traffic and the significant increase in truck axle loads, some typical asphalt pavement problems, such as rutting and cracking, are also receiving increasing attention. Research on asphalt modification has broad application prospects.

[0003] Polystyrene insulation materials are commonly used in construction. Depending on the molding process, they can be divided into two types: EPS (expanded polystyrene) and XPS (extruded polystyrene). These materials are difficult to degrade naturally, and direct combustion produces toxic gases. Therefore, the harmless and resourceful utilization of polystyrene in construction solid waste is a very difficult problem. Summary of the Invention

[0004] The purpose of the present invention is to overcome the shortcomings of the existing technology and provide a method for using waste polystyrene and cement to compositely modify asphalt. By making a composite modifier from polystyrene and cement recovered from construction solid waste, the composite modifier is used to modify asphalt. This can not only improve the high and low temperature performance and road performance of asphalt, but also realize the recycling of waste polystyrene foam, which is a very difficult to handle construction waste, and achieve efficient utilization of solid waste resources.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] An asphalt composite modifier includes 0.1-6% (mass percentage) of waste polystyrene and 0.1-4% (mass percentage) of cement. Preferably, the modifier includes 3.5-4.5% of waste polystyrene and 2-3% of cement.

[0007] A modified asphalt comprises, by mass percentage, 88-99.8% base asphalt, 0.1-4% cement, and 0.1-8% polystyrene. Preferably, by mass percentage, the modified asphalt comprises, by mass percentage, 93-94% base asphalt, 2-3% cement, and 3.5-4.5% polystyrene.

[0008] A method for composite modified asphalt using waste polystyrene and cement comprises the following steps:

[0009] Waste polystyrene is cleaned, dried, and crushed into polystyrene pellets for later use. The base asphalt is then heated and stirred to ensure uniform distribution in all directions. When heated to 160-180°C, the polystyrene pellets and cement are added and stirred thoroughly. The asphalt is then placed in an oven at 120-160°C for 0.5-3 hours to allow the polystyrene to fully swell in the asphalt. As the amount of polystyrene added increases, the stirring time increases accordingly, depending on the state of the modified asphalt. The asphalt is then placed in a high-speed shearing machine and stirred at 200-400 rpm for 3-10 minutes to fully expand, dissolve, and evenly distribute the polystyrene polymers, eliminating any bubbles on the asphalt surface. Finally, the asphalt is placed in an oven at 120-160°C for 15-60 minutes to obtain the modified asphalt.

[0010] The content of the waste polystyrene is 0.1-6%, and the content of the cement is 0.1-4%. Preferably, the content of the waste polystyrene is 3.5-4.5%, and the content of the cement is 2-3%. More preferably, the content of the waste polystyrene is 4%, and the content of the cement is 2.5%.

[0011] Preferably, the waste polystyrene is derived from expanded polystyrene (EPS) or extruded polystyrene (XPS). Both materials are essentially polystyrene, differing in the molding method. To fully integrate the waste polystyrene with the asphalt, the waste polystyrene is washed, dusted, dried, and then crushed into granules using a grinder. Impurities are then removed to obtain polystyrene granules.

[0012] Preferably, the mixing method after adding the polystyrene particles and cement is: first manually stirring for 2-8 minutes, then stirring with a high-speed shearing machine at a speed of 200-400 r / min for 8-20 minutes, and then stirring at a speed of 500-700 r / min for 15-40 minutes.

[0013] The particle sizes of the polystyrene particles and cement are as small as possible, and the particle sizes of the polystyrene particles and cement are 0.1-3000 μm, preferably 0.1-500 μm.

[0014] Preferably, the polystyrene particles are heated to a molten state and then incorporated into the matrix asphalt.

[0015] Preferably, the method for composite-modifying asphalt using waste polystyrene and cement comprises the following steps:

[0016] The waste polystyrene is cleaned, dried and crushed into polystyrene particles for later use. The matrix asphalt is then heated while stirring. When heated to 160-180°C, the molten polystyrene particles and cement are added. After addition, the mixture is manually stirred for 2-8 minutes, and then stirred with a high-speed shearing machine at a speed of 200-400r / min for 8-20 minutes, and then stirred at a speed of 500-700r / min for 15-40 minutes. After that, the mixture is placed in a 120-160°C oven for constant temperature incubation for 0.5-3 hours, and then placed in a high-speed shearing machine for stirring at 200-400r / min for 3-10 minutes. Finally, the mixture is placed in a 120-160°C oven for constant temperature incubation for 15-60 minutes to obtain modified asphalt.

[0017] The beneficial effects of the present invention are:

[0018] (1) The present invention uses waste polystyrene and cement composite modifier to modify asphalt. The cement and polystyrene adhere to each other and form a three-phase continuous network structure blend system with asphalt, which is more stable, thereby improving the high-temperature performance of the modified asphalt. In the process of polystyrene swelling in the matrix asphalt, it absorbs the light components in the asphalt to form a continuous spatial network structure. As the small molecular components in the asphalt decrease and the content of polar components increases, the interaction between the asphalt molecules gradually increases, causing the asphalt to harden and its deformation resistance to increase. When the modifier dosage is moderate, polystyrene and asphalt can be well compatible, polystyrene expands well, can swell well in asphalt, can improve the ductility of asphalt, that is, can improve the low-temperature performance of asphalt. The adsorption of polystyrene on wax can form numerous crystallization centers, thereby changing the distribution of paraffin in asphalt and optimizing the ratio of each component of asphalt. The wax content directly affects the ductility and adhesion of the asphalt system, so polystyrene-modified asphalt can improve the ductility of asphalt, thereby improving the low-temperature performance of asphalt. Polystyrene / cement composite modification can improve the high and low temperature performance of asphalt as a whole, and its modification mechanism is mainly physical modification.

[0019] (2) Cement particles have a porous structure and a rough surface, forming a denser overall structure with asphalt, which enables the asphalt to form more structural asphalt, thereby significantly improving the high-temperature performance of the modified asphalt.

[0020] (3) The polystyrene and cement composite modified asphalt is used to recycle polystyrene-related materials. Compared with other treatment methods, it not only has low treatment costs, but can also be used efficiently on a large scale in road projects, reducing the land resources occupied by waste polystyrene stacking and the damage to the ecological environment, thus achieving sustainable development of the civil engineering industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Crushed extruded polystyrene XPS particles of the present invention;

[0022] Figure 2 The crushed expanded polystyrene EPS particles of the present invention;

[0023] Figure 3 The microscopic distribution of the modified asphalt under the fluorescence microscope of the present invention is shown;

[0024] Figure 4 Comparison of the needle penetration test results of the modified asphalt prepared in Examples 1-8 of the present invention and Comparative Example 1;

[0025] Figure 5 Comparison of softening point test results of modified asphalt prepared in Examples 1-8 of the present invention and Comparative Example 1;

[0026] Figure 6 Comparison of ductility test results of modified asphalt prepared in Examples 1-8 of the present invention and Comparative Example 1;

[0027] Figure 7 Comparison of the needle penetration test results of the modified asphalt prepared in Example 2, Example 6 and Comparative Examples 2-5 of the present invention;

[0028] Figure 8 Comparison of softening point test results of modified asphalt prepared in Example 2, Example 6 and Comparative Examples 2-5 of the present invention;

[0029] Figure 9 Comparison of ductility test results of modified asphalt prepared in Example 2, Example 6 and Comparative Examples 2-5 of the present invention;

[0030] Figure 10 Comparison of stiffness modulus test results of modified asphalts prepared in Example 2, Example 6, and Comparative Examples 2-5 of the present invention;

[0031] Figure 11 Comparison of creep rate test results of modified asphalt prepared in Example 2, Example 6 and Comparative Examples 2-5 of the present invention;

[0032] Figure 12 Comparison of the test results of dynamic stability DS of the modified asphalt mixtures prepared in Example 2, Example 6 and Comparative Examples 1-5 of the present invention;

[0033] Figure 13 The flexural tensile strain of the modified asphalt mixtures prepared in Example 2, Example 6 and Comparative Examples 1-5 of the present invention is Ɛ B Comparison of test results;

[0034] Figure 14 The test results of the water immersion residual stability ratio (%) of the modified asphalt mixtures prepared in Example 2, Example 6 and Comparative Examples 1-5 of the present invention are compared. DETAILED DESCRIPTION

[0035] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0036] Unless otherwise specified, all reagents involved in the embodiments of the present invention are commercially available products and can be purchased through commercial channels.

[0037] The present invention utilizes waste polystyrene and cement composite modified asphalt, the waste polystyrene can be derived from expanded polystyrene EPS or extruded polystyrene XPS, which are crushed into particles and then used. Figure 1 、 2 The microscopic distribution of the modified asphalt under a fluorescence microscope is shown in Figure 3 . Example 1

[0038] The raw materials are taken according to the following mass percentages: 2% expanded polystyrene EPS, 2.5% cement, and 95.5% 70# matrix asphalt.

[0039] A method for composite modified asphalt using waste polystyrene and cement includes the following steps: washing and removing impurities from the waste polystyrene, drying it, and then crushing it into polystyrene granules for later use. The base asphalt is then heated and stirred to ensure uniform distribution in all directions. The polystyrene granules (heated until molten) and cement are then added to the base asphalt when heated to 170°C. After addition, the mixture is manually stirred for 3 minutes. The mixture is then stirred using a high-speed shear at 300 rpm for 10 minutes and then at 600 rpm for 20 minutes. The mixture is then placed in a 140°C oven and incubated at this constant temperature for 1 hour to allow the polystyrene to fully swell in the asphalt. As the amount of polystyrene added increases, the stirring time is appropriately increased based on the state of the modified asphalt. The mixture is then stirred in the high-speed shear at 300 rpm for 5 minutes to fully expand, dissolve, and evenly distribute the polystyrene molecules, eliminating surface bubbles. Finally, the mixture is placed in a 140°C oven and incubated at this constant temperature for 30 minutes to obtain the modified asphalt. Example 2

[0040] The raw materials are taken according to the following mass percentages: 4% expanded polystyrene EPS, 2.5% cement, and 93.5% 70# matrix asphalt.

[0041] A method for composite modified asphalt using waste polystyrene and cement includes the following steps: washing and removing impurities from the waste polystyrene, drying it, and then crushing it into polystyrene granules for later use. The base asphalt is then heated and stirred to ensure uniform distribution in all directions. The polystyrene granules (heated until molten) and cement are then added to the base asphalt when heated to 170°C. After addition, the mixture is manually stirred for 3 minutes. The mixture is then stirred using a high-speed shear at 300 rpm for 10 minutes and then at 600 rpm for 20 minutes. The mixture is then placed in a 140°C oven and incubated at this constant temperature for 1 hour to allow the polystyrene to fully swell in the asphalt. As the amount of polystyrene added increases, the stirring time is appropriately increased based on the state of the modified asphalt. The mixture is then stirred in the high-speed shear at 300 rpm for 5 minutes to fully expand, dissolve, and evenly distribute the polystyrene molecules, eliminating surface bubbles. Finally, the mixture is placed in a 140°C oven and incubated at this constant temperature for 30 minutes to obtain the modified asphalt. Example 3

[0042] The raw materials are taken according to the following mass percentages: 6% expanded polystyrene EPS, 2.5% cement, and 91.5% 70# matrix asphalt.

[0043] A method for composite modified asphalt using waste polystyrene and cement includes the following steps: washing and removing impurities from the waste polystyrene, drying it, and then crushing it into polystyrene granules for later use. The base asphalt is then heated and stirred to ensure uniform distribution in all directions. When heated to 160-180°C, the polystyrene granules (heated until molten) and cement are added. After addition, the mixture is manually stirred for 3 minutes. A high-speed shear is then used to stir the mixture at 300 rpm for 10 minutes, then at 600 rpm for 20 minutes. The mixture is then placed in a 140°C oven and incubated at this constant temperature for 1 hour to allow the polystyrene to fully swell in the asphalt. As the amount of polystyrene added increases, the stirring time is appropriately increased based on the state of the modified asphalt. The mixture is then placed in a high-speed shear and stirred at 300 rpm for 5 minutes to fully expand, dissolve, and evenly distribute the polystyrene molecules, eliminating surface bubbles. Finally, the mixture is placed in a 140°C oven and incubated at this constant temperature for 30 minutes to obtain the modified asphalt. Example 4

[0044] The raw materials are taken according to the following mass percentages: 8% expanded polystyrene EPS, 2.5% cement, and 89.5% 70# matrix asphalt.

[0045] A method for composite modified asphalt using waste polystyrene and cement includes the following steps: washing and removing impurities from the waste polystyrene, drying it, and then crushing it into polystyrene granules for later use. The base asphalt is then heated and stirred to ensure uniform distribution in all directions. When heated to 160-180°C, the polystyrene granules (heated until molten) and cement are added. After addition, the mixture is manually stirred for 3 minutes. A high-speed shear is then used to stir the mixture at 300 rpm for 10 minutes, then at 600 rpm for 20 minutes. The mixture is then placed in a 140°C oven and incubated at this constant temperature for 1 hour to allow the polystyrene to fully swell in the asphalt. As the amount of polystyrene added increases, the stirring time is appropriately increased based on the state of the modified asphalt. The mixture is then placed in a high-speed shear and stirred at 300 rpm for 5 minutes to fully expand, dissolve, and evenly distribute the polystyrene molecules, eliminating surface bubbles. Finally, the mixture is placed in a 140°C oven and incubated at this constant temperature for 30 minutes to obtain the modified asphalt. Example 5

[0046] The raw materials are taken according to the following mass percentages: 2% extruded polystyrene XPS, 2.5% cement, and 95.5% 70# matrix asphalt.

[0047] A method for composite modified asphalt using waste polystyrene and cement includes the following steps: washing and removing impurities from the waste polystyrene, drying it, and then crushing it into polystyrene granules for later use. The base asphalt is then heated and stirred to ensure uniform distribution in all directions. The polystyrene granules (heated until molten) and cement are then added to the base asphalt when heated to 170°C. After addition, the mixture is manually stirred for 3 minutes. The mixture is then stirred using a high-speed shear at 300 rpm for 10 minutes and then at 600 rpm for 20 minutes. The mixture is then placed in a 140°C oven and incubated at this constant temperature for 1 hour to allow the polystyrene to fully swell in the asphalt. As the amount of polystyrene added increases, the stirring time is appropriately increased based on the state of the modified asphalt. The mixture is then stirred in the high-speed shear at 300 rpm for 5 minutes to fully expand, dissolve, and evenly distribute the polystyrene molecules, eliminating surface bubbles. Finally, the mixture is placed in a 140°C oven and incubated at this constant temperature for 30 minutes to obtain the modified asphalt. Example 6

[0048] The raw materials are taken according to the following mass percentages: 4% extruded polystyrene XPS, 2.5% cement, and 93.5% 70# matrix asphalt.

[0049] A method for composite modified asphalt using waste polystyrene and cement includes the following steps: washing and removing impurities from the waste polystyrene, drying it, and then crushing it into polystyrene granules for later use. The base asphalt is then heated and stirred to ensure uniform distribution in all directions. The polystyrene granules (heated until molten) and cement are then added to the base asphalt when heated to 170°C. After addition, the mixture is manually stirred for 3 minutes. The mixture is then stirred using a high-speed shear at 300 rpm for 10 minutes and then at 600 rpm for 20 minutes. The mixture is then placed in a 140°C oven and incubated at this constant temperature for 1 hour to allow the polystyrene to fully swell in the asphalt. As the amount of polystyrene added increases, the stirring time is appropriately increased based on the state of the modified asphalt. The mixture is then stirred in the high-speed shear at 300 rpm for 5 minutes to fully expand, dissolve, and evenly distribute the polystyrene molecules, eliminating surface bubbles. Finally, the mixture is placed in a 140°C oven and incubated at this constant temperature for 30 minutes to obtain the modified asphalt. Example 7

[0050] The raw materials are taken according to the following mass percentages: 6% extruded polystyrene XPS, 2.5% cement, and 91.5% 70# matrix asphalt.

[0051] A method for composite modified asphalt using waste polystyrene and cement includes the following steps: washing and removing impurities from the waste polystyrene, drying it, and then crushing it into polystyrene granules for later use. The base asphalt is then heated and stirred to ensure uniform distribution in all directions. When heated to 160-180°C, the polystyrene granules (heated until molten) and cement are added. After addition, the mixture is manually stirred for 3 minutes. A high-speed shear is then used to stir the mixture at 300 rpm for 10 minutes, then at 600 rpm for 20 minutes. The mixture is then placed in a 140°C oven and incubated at this constant temperature for 1 hour to allow the polystyrene to fully swell in the asphalt. As the amount of polystyrene added increases, the stirring time is appropriately increased based on the state of the modified asphalt. The mixture is then placed in a high-speed shear and stirred at 300 rpm for 5 minutes to fully expand, dissolve, and evenly distribute the polystyrene molecules, eliminating surface bubbles. Finally, the mixture is placed in a 140°C oven and incubated at this constant temperature for 30 minutes to obtain the modified asphalt. Example 8

[0052] The raw materials are taken according to the following mass percentages: 8% extruded polystyrene XPS, 2.5% cement, and 89.5% 70# matrix asphalt.

[0053] A method for composite modified asphalt using waste polystyrene and cement includes the following steps: washing and removing impurities from the waste polystyrene, drying it, and then crushing it into polystyrene granules for later use. The base asphalt is then heated and stirred to ensure uniform distribution in all directions. When heated to 160-180°C, the polystyrene granules (heated until molten) and cement are added. After addition, the mixture is manually stirred for 3 minutes. A high-speed shear is then used to stir the mixture at 300 rpm for 10 minutes, then at 600 rpm for 20 minutes. The mixture is then placed in a 140°C oven and incubated at this constant temperature for 1 hour to allow the polystyrene to fully swell in the asphalt. As the amount of polystyrene added increases, the stirring time is appropriately increased based on the state of the modified asphalt. The mixture is then placed in a high-speed shear and stirred at 300 rpm for 5 minutes to fully expand, dissolve, and evenly distribute the polystyrene molecules, eliminating surface bubbles. Finally, the mixture is placed in a 140°C oven and incubated at this constant temperature for 30 minutes to obtain the modified asphalt.

[0054] Comparative Example 1

[0055] In this comparative example, the asphalt was not modified and 100% 70# base asphalt was directly used.

[0056] Comparative Example 2

[0057] The raw materials are taken according to the following mass percentages: 2.5% cement and 97.5% 70# matrix asphalt.

[0058] A method for modifying asphalt using cement comprises the following steps: heating and stirring a base asphalt to uniformly distribute the asphalt in all directions; adding cement when heated to 160-180°C; manually stirring for 3 minutes; stirring at 300 r / min for 10 minutes and then at 600 r / min for 20 minutes using a high-speed shear; and then incubating in a 140°C oven at a constant temperature for 1 hour to fully disperse the cement in the asphalt. The asphalt is then stirred in a high-speed shear at 300 r / min for 5 minutes to fully expand and evenly distribute the cement particles and eliminate air bubbles on the asphalt surface; and finally incubating in a 140°C oven at a constant temperature for 30 minutes to obtain the modified asphalt.

[0059] Comparative Example 3

[0060] The raw materials are taken according to the following mass percentages: 4% expanded polystyrene EPS and 96% 70# matrix asphalt.

[0061] A method for modifying asphalt using waste polystyrene comprises the following steps: washing and removing impurities from the waste polystyrene, drying it, and then crushing it into polystyrene granules for later use. The base asphalt is then heated and stirred to ensure uniform distribution in all directions. The polystyrene granules are then added (heated until molten) when heated to 160-180°C. After addition, the mixture is manually stirred for 3 minutes. The mixture is then stirred using a high-speed shear at 300 rpm for 10 minutes, then at 600 rpm for 20 minutes. The mixture is then placed in a 140°C oven and incubated at this constant temperature for 1 hour to allow the polystyrene to fully swell in the asphalt. As the amount of polystyrene added increases, the stirring time is appropriately increased based on the state of the modified asphalt. The mixture is then stirred in a high-speed shear at 300 rpm for 5 minutes to fully expand, dissolve, and evenly distribute the polystyrene molecules, eliminating any bubbles on the asphalt surface. Finally, the mixture is placed in a 140°C oven and incubated at this constant temperature for 30 minutes to obtain the modified asphalt.

[0062] Comparative Example 4

[0063] The raw materials are taken according to the following mass percentages: 4% extruded polystyrene XPS and 96% 70# matrix asphalt.

[0064] A method for modifying asphalt using waste polystyrene comprises the following steps: washing and removing impurities from the waste polystyrene, drying it, and then crushing it into polystyrene granules for later use. The base asphalt is then heated and stirred to ensure uniform distribution in all directions. The polystyrene granules are then added (heated until molten) when heated to 160-180°C. After addition, the mixture is manually stirred for 3 minutes. The mixture is then stirred using a high-speed shear at 300 rpm for 10 minutes, then at 600 rpm for 20 minutes. The mixture is then placed in a 140°C oven and incubated at this constant temperature for 1 hour to allow the polystyrene to fully swell in the asphalt. As the amount of polystyrene added increases, the stirring time is appropriately increased based on the state of the modified asphalt. The mixture is then stirred in a high-speed shear at 300 rpm for 5 minutes to fully expand, dissolve, and evenly distribute the polystyrene molecules, eliminating any bubbles on the asphalt surface. Finally, the mixture is placed in a 140°C oven and incubated at this constant temperature for 30 minutes to obtain the modified asphalt.

[0065] Comparative Example 5

[0066] The raw materials are taken according to the following mass percentages: 4% SBS modifier and 96% 70# base asphalt.

[0067] A method for modifying asphalt using SBS comprises the following steps: heating and stirring a base asphalt to uniformly distribute the asphalt in all directions; adding an SBS modifier when heated to 160-180°C; manually stirring for 3 minutes; stirring at 300 r / min for 10 minutes and then at 600 r / min for 20 minutes using a high-speed shear; and then incubating in a 140°C oven at a constant temperature for 1 hour to allow the SBS to fully swell in the asphalt. The asphalt is then stirred in a high-speed shear at 300 r / min for 5 minutes to fully expand, dissolve, and evenly distribute the SBS polymer, and to eliminate bubbles on the asphalt surface. Finally, the asphalt is incubated in a 140°C oven at a constant temperature for 30 minutes to obtain the modified asphalt.

[0068] The raw material ratios of Examples 1-8 and Comparative Examples 1-5 are summarized in Table 1 below:

[0069] Table 1 Raw materials and their corresponding weight fractions (wt%) of Examples 1-8 and Comparative Examples 1-5

[0070]

[0071] 1. Basic performance test of asphalt

[0072] 1. Overall results of performance testing

[0073] The modified asphalts produced in Examples 1-8 were tested for penetration, softening point, ductility, and low-temperature flexural beam rheology (the low-temperature flexural beam rheology tests were conducted primarily on Examples 2 and 6 and Comparative Examples 1-5) to test the improved asphalt properties achieved by utilizing waste polystyrene and cement. Comparative Examples 1-5 served as a control group. The test results are shown in Table 2 below. Table 2 shows that the properties of the modified asphalts produced in the present invention meet regulatory requirements.

[0074] Table 2 Performance test results of modified asphalt prepared in Examples 1-8 and Comparative Examples 1-5

[0075]

[0076] 2. Analyze the impact of changes in waste polystyrene and cement content on asphalt performance

[0077] The penetration, softening point and ductility test results of Examples 1-8 and Comparative Example 1 are plotted as Figure 4-6 , analyze the effects of changes in waste polystyrene and cement content on asphalt performance.

[0078] Depend on Figure 4As can be seen, with increasing EPS or XPS content, the penetration of modified asphalt shows a trend of first decreasing, then increasing, and then decreasing again. Relative to the base asphalt, XPS penetration decreased by 37.2%, 21.6%, 33.3%, and 49.9% at 2%, 4%, 6%, and 8% respectively, while EPS penetration decreased by 46.3%, 41.4%, 48.9%, and 54.6% at 2%, 4%, 6%, and 8% respectively. XPS-modified asphalt generally has a greater penetration than EPS-modified asphalt.

[0079] Depend on Figure 5 As can be seen, the softening point of modified asphalt increases with increasing EPS or XPS content. When XPS content is 2%, 4%, 6%, and 8%, the softening point increases by 10.2%, 12.6%, 15.1%, and 16.5%, respectively, compared to the base asphalt. When EPS content is 2%, 4%, 6%, and 8%, the softening point increases by 5%, 6%, 7.2%, and 8.2%, respectively, compared to the base asphalt. XPS-modified asphalt generally has a better softening point than EPS-modified asphalt.

[0080] Depend on Figure 6 It can be seen that in terms of ductility, when the XPS content is 2% and 4%, the ductility of asphalt increases by 3.7% and 23.3% respectively; when the EPS content is 2% and 4%, the ductility of asphalt increases by 1.9% and 12.6% respectively. When the content is too large, when the XPS content is 6% and 8%, the ductility of asphalt decreases by 6% and 35.8% respectively; when the EPS content is 6% and 8%, the ductility of asphalt decreases by 11.6% and 51.2% respectively. The ductility of XPS modified asphalt is generally better than that of EPS modified asphalt. From the comparison, it can be concluded that the overall performance of modified asphalt is improved compared to the base asphalt, and the modification effect is best when the polystyrene content is 4%.

[0081] 3. Comparison of the effects of optimal dosage of composite modifier and single modifier on asphalt performance

[0082] The test results of needle penetration, softening point, ductility, stiffness modulus and creep rate of Example 2, Example 6 and Comparative Examples 2-5 are plotted as follows: Figure 7-11 , the effects of the optimal dosage of the composite modifier of the present invention (Example 2, Example 6) and the single modifier (Comparative Examples 2-5) on the asphalt performance were compared and analyzed.

[0083] from Figure 7 The comparison shows that in terms of needle penetration, compared with Examples 2 and 6, Comparative Examples 2-5 have an upward trend, indicating that the needle penetration of asphalt modified with the composite modifier is lower than that of asphalt modified with a single modifier, and the effect of composite modification is better.

[0084] Depend on Figure 8 It can be seen that in terms of softening point, compared with Examples 2 and 6, the softening point of Comparative Examples 2-5 has a downward trend, indicating that the composite modification effect is better and is close to the effect of SBS single modified asphalt (Comparative Example 5).

[0085] Depend on Figure 9 It can be seen that in terms of ductility, compared with Examples 2 and 6, Comparative Examples 2-5 have a downward trend, indicating that the asphalt modified with the composite modifier has better low-temperature performance.

[0086] Depend on Figure 10 It can be seen that in terms of stiffness modulus, compared with Examples 2 and 6, Comparative Examples 2-5 have an upward trend, indicating that the stiffness modulus of asphalt modified with the composite modifier is smaller, and has an effect close to that of SBS single modification.

[0087] Depend on Figure 11 It can be seen that, in terms of creep rate, compared with Examples 2 and 6, Comparative Examples 2-5 have an upward trend.

[0088] A comparative analysis of Examples 2 and 6 and Comparative Examples 2-5 demonstrates that composite modifiers can improve the overall high- and low-temperature performance of asphalt. Extruded polystyrene (XPS) is superior to expanded polystyrene (EPS) in modifying asphalt. This is because XPS has a higher density than EPS. When XPS and EPS are added to asphalt at equal dosages, XPS is smaller, more dispersed, and swells more fully, resulting in a better asphalt modification effect. The modified asphalt mortar composed of XPS and cement achieves a modification effect approaching that of SBS-modified asphalt, demonstrating a significant asphalt modification effect.

[0089] 2. Asphalt mixture performance test

[0090] This part of the performance test is based on the design of AC-13 asphalt mixture. The gradation design method is as follows: referring to the upper and lower limits and median of the gradation, according to the principle of adjusting the gradation to S-type, the aggregate range is divided into four grades of 0-3mm, 3-5mm, 5-10mm, and 10-16mm for screening. By optimizing the gradation of the key sieve hole dosage and referring to the median of the gradation, the gradation design formula of AC-13 asphalt mixture is finally determined. The design gradation composition is shown in Table 3.

[0091] Table 3 Gradation composition of AC-13 asphalt mixture

[0092]

[0093] The optimal asphalt-to-stone ratio of the asphalt mixture made from different modified asphalts of the present invention was determined by the Marshall test, as shown in Table 4, so as to conduct relevant performance tests of the modified asphalt mixture.

[0094] Table 4 Optimal oil-stone ratio of different modified asphalt mixtures

[0095]

[0096] The modified asphalt prepared in Example 2, Example 6 and Comparative Examples 1-5 was used to prepare AC-13 type asphalt mixture according to the above gradation and asphalt-to-stone ratio. The asphalt mixture performance tests were then conducted, including high temperature rutting, low temperature beam bending and water immersion Marshall tests, to further verify the feasibility of using waste polystyrene and cement composite modified asphalt. Figure 12-14 .

[0097] Depend on Figure 12-14 As can be seen, in terms of high-temperature performance (dynamic stability), the XPS / cement composite modified asphalt mixture (Example 6) achieved the best performance, approaching the high-temperature performance of the SBS modified asphalt mixture (Comparative Example 5). In terms of low-temperature performance (flexural and tensile strain), the higher the low-temperature flexural and tensile strain value of the composite modified asphalt mixture, the stronger the low-temperature deformation capacity and the better low-temperature performance. In terms of water-temperature stability (residual stability after immersion in water), the composite modified asphalt's residual stability after immersion in water is close to that of the SBS modified asphalt mixture, indicating its better ability to resist spalling and prevent loosening and particle loss.

[0098] In summary, XPS / cement as a composite modifier for asphalt has better overall effects on asphalt mortar and asphalt mixture than a single modification, and can achieve effects close to those of SBS modified asphalt.

[0099] Finally, it should be noted that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or substitute equivalents for some of the technical features. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for composite modified asphalt using waste polystyrene and cement, characterized by: The following steps are involved: The waste polystyrene is cleaned, dried, and crushed into polystyrene particles for later use. The base asphalt is then heated while stirring. When heated to 160-180°C, the polystyrene particles and cement are added and stirred evenly. The asphalt is then placed in a 120-160°C oven for constant temperature incubation for 0.5-3 hours. The asphalt is then placed in a high-speed shearing machine and stirred at 200-400 r / min for 3-10 minutes. The asphalt is then placed in a 120-160°C oven for constant temperature incubation for 15-60 minutes to obtain the modified asphalt. The content of the waste polystyrene is 3.5-4.5%, and the content of the cement is 2-3%; The waste polystyrene is derived from extruded polystyrene XPS.

2. The method according to claim 1, wherein: The mixing method after adding polystyrene particles and cement is: first manually stir for 2-8 minutes, then use a high-speed shearing machine to stir at a speed of 200-400 r / min for 8-20 minutes, and then stir at a speed of 500-700 r / min for 15-40 minutes.

3. The method according to claim 1, wherein: The polystyrene particles are heated to a molten state and then mixed into the matrix asphalt.

4. The method according to claim 1, wherein: The following steps are involved: The waste polystyrene is cleaned, dried and crushed into polystyrene particles for later use. The matrix asphalt is then heated while stirring. When heated to 160-180°C, the molten polystyrene particles and cement are added. After addition, the mixture is manually stirred for 2-8 minutes, and then stirred with a high-speed shearing machine at a speed of 200-400r / min for 8-20 minutes, and then stirred at a speed of 500-700r / min for 15-40 minutes. After that, the mixture is placed in a 120-160°C oven for constant temperature incubation for 0.5-3 hours, and then placed in a high-speed shearing machine for stirring at 200-400r / min for 3-10 minutes. Finally, the mixture is placed in a 120-160°C oven for constant temperature incubation for 15-60 minutes to obtain modified asphalt.

5. A modified asphalt prepared according to any one of claims 1 to 4, characterized in that: In terms of mass percentage, it includes: matrix asphalt 93-94%, cement 2-3% and waste polystyrene 3.5-4.5%.

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