Method for compositely modifying asphalt by using waste polystyrene and cement

Abstract

The invention belongs to the technical field of building materials, and discloses a method for compositely modifying asphalt by using waste polystyrene and cement in order to solve the problem that at the present stage, polystyrene boards serving as building thermal insulation materials are difficult to recycle after being discarded. Comprising the following steps: cleaning and drying waste polystyrene, crushing the waste polystyrene into polystyrene particles for later use, heating and stirring matrix asphalt, adding the polystyrene particles and cement when the matrix asphalt is heated to 160-180 DEG C, uniformly stirring, putting into a drying oven at 120-160 DEG C, culturing for 0.5-3 hours at a constant temperature, putting into a high-speed shearing machine, stirring for 3-10 minutes at a speed of 200-400 r / min, and cooling to room temperature. And finally, putting the mixture into a drying oven at 120-160 DEG C, and carrying out constant-temperature cultivation for 15-60 minutes to obtain the modified asphalt. The doping amount of the waste polystyrene is 0.1-6%, and the doping amount of the cement is 0.1-4%. The composite modifier composed of polystyrene / cement can integrally improve the high and low temperature performance of asphalt, recycle of waste polystyrene is achieved, the construction cost is reduced, and sustainable development of civil engineering materials is achieved.

Description

Technical Field

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

[0002] Asphalt pavement is increasingly used in modern traffic pavement due to its advantages in driving comfort, construction period and post-maintenance. However, due to the rapid growth of modern road traffic volume and the greatly increased axle load of trucks, some typical diseases of asphalt pavement are also receiving increasing attention, such as rutting and cracking. The research on asphalt modification has broad application prospects.

[0003] Polystyrene board insulation materials are often used in buildings. According to different molding processes, they can be divided into two types: EPS (expanded polystyrene) and XPS (extruded polystyrene). These materials are difficult to degrade in nature, and direct combustion will produce toxic gases. Therefore, how to make harmless and resource-based use 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 deficiencies of the existing technology and provide a method for composite modified asphalt using waste polystyrene and cement. The polystyrene and cement recovered from construction solid waste are made into a composite modifier for modifying asphalt, which can not only improve the high and low temperature performance and road performance of asphalt, but also realize the recycling of waste polystyrene foam, a very difficult to handle construction waste, and realize the efficient utilization of solid waste resources.

[0005] To achieve the above object, the present invention adopts the following technical solutions: An asphalt composite modifier includes 0.1-6% (mass percentage) of waste polystyrene and 0.1-4% (mass percentage) of cement. Preferably, it includes 3.5-4.5% of waste polystyrene and 2-3% of cement.

[0006] A modified asphalt comprises, by mass percentage, 88-99.8% of base asphalt, 0.1-4% of cement and 0.1-8% of polystyrene. Preferably, by mass percentage, the modified asphalt comprises, by mass percentage, 93-94% of base asphalt, 2-3% of cement and 3.5-4.5% of polystyrene.

[0007] A method for composite modified asphalt using waste polystyrene and cement comprises the following steps: The waste polystyrene is cleaned, dried and crushed into polystyrene particles for use. Then the matrix asphalt is heated and stirred to make the asphalt evenly distributed in all directions. When it is heated to 160-180℃, polystyrene particles and cement are added and stirred evenly. Then, it is placed in a 120-160℃ oven for constant temperature incubation for 0.5-3h to allow the polystyrene to fully swell in the asphalt. As the amount of polystyrene added increases, the corresponding stirring time is appropriately increased according to the state of the modified asphalt. Then it is placed in a high-speed shearing machine and stirred at 200-400r / min for 3-10min to fully stretch, dissolve, and evenly distribute the polystyrene polymer, and eliminate bubbles on the surface of the asphalt. Finally, it is placed in a 120-160℃ oven for constant temperature incubation for 15-60min to obtain modified asphalt.

[0008] 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%.

[0009] Preferably, the waste polystyrene is derived from expanded polystyrene EPS or extruded polystyrene XPS. Both materials are essentially polystyrene, and the difference lies in the molding method. In order to fully integrate the waste polystyrene with asphalt, the waste polystyrene is washed, dusted, impurities removed, dried, and then crushed into particles with a crusher, and some impurities are picked out to obtain polystyrene particles.

[0010] Preferably, the mixing method after adding the 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.

[0011] 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.

[0012] Preferably, the polystyrene particles are heated to a molten state and then mixed into the matrix asphalt.

[0013] Preferably, the method for composite-modifying asphalt using waste polystyrene and cement comprises the following steps: The waste polystyrene is cleaned, dried and crushed into polystyrene particles for standby use, and then the base asphalt is heated and stirred, and when it is heated to 160-180°C, the molten polystyrene particles and cement are added. After adding, it is first stirred manually 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 15-40min, and then placed in a 120-160°C oven for constant temperature incubation for 0.5-3h, and then placed in a high-speed shearing machine for stirring at 200-400r / min for 3-10min, and finally placed in a 120-160°C oven for constant temperature incubation for 15-60min to obtain modified asphalt.

[0014] The beneficial effects of the present invention are: (1) The present invention uses waste polystyrene and cement composite modifier to modify asphalt. Cement and polystyrene are mutually bonded and together with asphalt form a three-phase continuous network structure blending system, 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, the content of polar components increases, and the interaction between asphalt molecules gradually increases, causing the asphalt to harden and the anti-deformation ability to increase. When the modifier dosage is moderate, polystyrene and asphalt can be well compatible, polystyrene can swell 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 a large number of crystal centers, thereby changing the distribution of paraffin in asphalt, so that the proportion of each component of asphalt reaches the best, and 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.

[0015] (2) Cement particles have a porous structure and a rough surface, forming a relatively dense overall structure with asphalt, allowing the asphalt to form more structural asphalt, thereby significantly improving the high-temperature performance of modified asphalt.

[0016] (3) The use of polystyrene and cement to modify asphalt and recycle polystyrene-related materials not only has a low treatment cost compared to other treatment methods, but can also be used efficiently and on a large scale in road projects, reducing the occupation of land resources and ecological environmental damage caused by the stacking of waste polystyrene, and achieving sustainable development of the civil engineering industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The crushed extruded polystyrene XPS particles of the present invention; Figure 2The crushed expanded polystyrene EPS particles of the present invention; Figure 3 The microscopic distribution of the modified asphalt under the fluorescence microscope of the present invention; Figure 4 Comparison of the needle penetration test results of the modified asphalts prepared in Examples 1-8 of the present invention and Comparative Example 1; Figure 5 Comparison of softening point test results of modified asphalts prepared in Examples 1-8 of the present invention and Comparative Example 1; Figure 6 Comparison of ductility test results of modified asphalts prepared in Examples 1-8 of the present invention and Comparative Example 1; Figure 7 The needle penetration test results of the modified asphalts prepared in Example 2, Example 6 and Comparative Examples 2-5 of the present invention are compared; Figure 8 The softening point test results of the modified asphalts prepared in Example 2, Example 6 and Comparative Examples 2-5 of the present invention are compared; Fig. 9 The ductility test results of the modified asphalt prepared in Example 2, Example 6 and Comparative Examples 2-5 of the present invention are compared; Fig.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; Fig.11 The creep rate test results of the modified asphalts prepared in Example 2, Example 6 and Comparative Examples 2-5 of the present invention are compared; Fig.12 The test results of dynamic stability DS of modified asphalt mixtures prepared in Example 2, Example 6 and Comparative Examples 1-5 of the present invention are compared; Fig.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 B Comparison of test results; Fig.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

[0018] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0019] Unless otherwise specified, the reagents involved in the embodiments of the present invention are all commercially available products and can be purchased through commercial channels.

[0020] The present invention utilizes waste polystyrene and cement composite modified asphalt, wherein the waste polystyrene can be derived from expanded polystyrene EPS or extruded polystyrene XPS, which are crushed into particles for use. Figure 1 , 2 The microscopic distribution of the modified asphalt under a fluorescence microscope is shown in Figure 3 . Example 1

[0021] The raw materials are taken according to the following mass percentages: 2% expanded polystyrene EPS, 2.5% cement, and 95.5% 70# base asphalt.

[0022] A method for composite modified asphalt using waste polystyrene and cement comprises the following steps: cleaning and removing impurities from waste polystyrene, drying and crushing the waste polystyrene into polystyrene particles for standby use, then heating and stirring the matrix asphalt to make the asphalt evenly distributed in all directions, adding polystyrene particles (adding after heating to melting) and cement when heated to 170°C, stirring manually for 3 minutes after adding, then stirring at a speed of 300r / min for 10 minutes with a high-speed shearing machine, and then stirring at a speed of 600r / min for 20 minutes, and then placing in a 140°C oven for constant temperature cultivation for 1 hour, so that the polystyrene is fully swollen in the asphalt. As the amount of polystyrene added increases, the corresponding stirring time is appropriately increased according to the state of the modified asphalt. Then, placing in a high-speed shearing machine and stirring at 300r / min for 5 minutes, the polystyrene polymer is fully stretched, dissolved, and evenly distributed, and the bubbles on the surface of the asphalt are eliminated, and finally, placing in a 140°C oven for constant temperature cultivation for 30 minutes to obtain the modified asphalt. Example 2

[0023] The raw materials are taken according to the following mass percentages: 4% expanded polystyrene EPS, 2.5% cement, and 93.5% 70# base asphalt.

[0024] A method for composite modified asphalt using waste polystyrene and cement comprises the following steps: cleaning and removing impurities from waste polystyrene, drying and crushing the waste polystyrene into polystyrene particles for standby use, then heating and stirring the matrix asphalt to make the asphalt evenly distributed in all directions, adding polystyrene particles (adding after heating to melting) and cement when heated to 170°C, stirring manually for 3 minutes after adding, then stirring at a speed of 300r / min for 10 minutes with a high-speed shearing machine, and then stirring at a speed of 600r / min for 20 minutes, and then placing in a 140°C oven for constant temperature cultivation for 1 hour, so that the polystyrene is fully swollen in the asphalt. As the amount of polystyrene added increases, the corresponding stirring time is appropriately increased according to the state of the modified asphalt. Then, placing in a high-speed shearing machine and stirring at 300r / min for 5 minutes, the polystyrene polymer is fully stretched, dissolved, and evenly distributed, and the bubbles on the surface of the asphalt are eliminated, and finally, placing in a 140°C oven for constant temperature cultivation for 30 minutes to obtain the modified asphalt. Example 3

[0025] The raw materials are taken according to the following mass percentages: 6% expanded polystyrene EPS, 2.5% cement, and 91.5% 70# base asphalt.

[0026] A method for composite modified asphalt using waste polystyrene and cement comprises the following steps: cleaning and removing impurities from waste polystyrene, drying and crushing the waste polystyrene into polystyrene particles for standby use, then heating and stirring the matrix asphalt to make the asphalt evenly distributed in all directions, adding polystyrene particles (heated to melt and then added) and cement when heated to 160-180°C, stirring manually for 3 minutes after adding, then stirring at 300r / min for 10 minutes with a high-speed shearing machine, then stirring at 600r / min for 20 minutes, and then placing in a 140°C oven for constant temperature cultivation for 1 hour, so that the polystyrene is fully swollen in the asphalt. As the amount of polystyrene added increases, the corresponding stirring time is appropriately increased according to the state of the modified asphalt. Then, placing in a high-speed shearing machine and stirring at 300r / min for 5 minutes, the polystyrene polymer is fully stretched, dissolved, and evenly distributed, and the bubbles on the surface of the asphalt are eliminated, and finally, placing in a 140°C oven for constant temperature cultivation for 30 minutes to obtain the modified asphalt. Example 4

[0027] The raw materials are taken according to the following mass percentages: 8% expanded polystyrene EPS, 2.5% cement, and 89.5% 70# base asphalt.

[0028] A method for composite modified asphalt using waste polystyrene and cement comprises the following steps: cleaning and removing impurities from waste polystyrene, drying and crushing the waste polystyrene into polystyrene particles for standby use, then heating and stirring the matrix asphalt to make the asphalt evenly distributed in all directions, adding polystyrene particles (heated to melt and then added) and cement when heated to 160-180°C, stirring manually for 3 minutes after adding, then stirring at 300r / min for 10 minutes with a high-speed shearing machine, then stirring at 600r / min for 20 minutes, and then placing in a 140°C oven for constant temperature cultivation for 1 hour, so that the polystyrene is fully swollen in the asphalt. As the amount of polystyrene added increases, the corresponding stirring time is appropriately increased according to the state of the modified asphalt. Then, placing in a high-speed shearing machine and stirring at 300r / min for 5 minutes, the polystyrene polymer is fully stretched, dissolved, and evenly distributed, and the bubbles on the surface of the asphalt are eliminated, and finally, placing in a 140°C oven for constant temperature cultivation for 30 minutes to obtain the modified asphalt. Example 5

[0029] The raw materials are taken according to the following mass percentages: 2% extruded polystyrene XPS, 2.5% cement, and 95.5% 70# base asphalt.

[0030] A method for composite modified asphalt using waste polystyrene and cement comprises the following steps: cleaning and removing impurities from waste polystyrene, drying and crushing the waste polystyrene into polystyrene particles for standby use, then heating and stirring the matrix asphalt to make the asphalt evenly distributed in all directions, adding polystyrene particles (adding after heating to melting) and cement when heated to 170°C, stirring manually for 3 minutes after adding, then stirring at a speed of 300r / min for 10 minutes with a high-speed shearing machine, and then stirring at a speed of 600r / min for 20 minutes, and then placing in a 140°C oven for constant temperature cultivation for 1 hour, so that the polystyrene is fully swollen in the asphalt. As the amount of polystyrene added increases, the corresponding stirring time is appropriately increased according to the state of the modified asphalt. Then, placing in a high-speed shearing machine and stirring at 300r / min for 5 minutes, the polystyrene polymer is fully stretched, dissolved, and evenly distributed, and the bubbles on the surface of the asphalt are eliminated, and finally, placing in a 140°C oven for constant temperature cultivation for 30 minutes to obtain the modified asphalt. Example 6

[0031] The raw materials are taken according to the following mass percentages: 4% extruded polystyrene XPS, 2.5% cement, and 93.5% 70# base asphalt.

[0032] A method for composite modified asphalt using waste polystyrene and cement comprises the following steps: cleaning and removing impurities from waste polystyrene, drying and crushing the waste polystyrene into polystyrene particles for standby use, then heating and stirring the matrix asphalt to make the asphalt evenly distributed in all directions, adding polystyrene particles (adding after heating to melting) and cement when heated to 170°C, stirring manually for 3 minutes after adding, then stirring at a speed of 300r / min for 10 minutes with a high-speed shearing machine, and then stirring at a speed of 600r / min for 20 minutes, and then placing in a 140°C oven for constant temperature cultivation for 1 hour, so that the polystyrene is fully swollen in the asphalt. As the amount of polystyrene added increases, the corresponding stirring time is appropriately increased according to the state of the modified asphalt. Then, placing in a high-speed shearing machine and stirring at 300r / min for 5 minutes, the polystyrene polymer is fully stretched, dissolved, and evenly distributed, and the bubbles on the surface of the asphalt are eliminated, and finally, placing in a 140°C oven for constant temperature cultivation for 30 minutes to obtain the modified asphalt. Example 7

[0033] The raw materials are taken according to the following mass percentages: 6% extruded polystyrene XPS, 2.5% cement, and 91.5% 70# base asphalt.

[0034] A method for composite modified asphalt using waste polystyrene and cement comprises the following steps: cleaning and removing impurities from waste polystyrene, drying and crushing the waste polystyrene into polystyrene particles for standby use, then heating and stirring the matrix asphalt to make the asphalt evenly distributed in all directions, adding polystyrene particles (heated to melt and then added) and cement when heated to 160-180°C, stirring manually for 3 minutes after adding, then stirring at 300r / min for 10 minutes with a high-speed shearing machine, then stirring at 600r / min for 20 minutes, and then placing in a 140°C oven for constant temperature cultivation for 1 hour, so that the polystyrene is fully swollen in the asphalt. As the amount of polystyrene added increases, the corresponding stirring time is appropriately increased according to the state of the modified asphalt. Then, placing in a high-speed shearing machine and stirring at 300r / min for 5 minutes, the polystyrene polymer is fully stretched, dissolved, and evenly distributed, and the bubbles on the surface of the asphalt are eliminated, and finally, placing in a 140°C oven for constant temperature cultivation for 30 minutes to obtain the modified asphalt. Example 8

[0035] The raw materials are taken according to the following mass percentages: 8% extruded polystyrene XPS, 2.5% cement, and 89.5% 70# base asphalt.

[0036] A method for composite modified asphalt using waste polystyrene and cement comprises the following steps: cleaning and removing impurities from waste polystyrene, drying and crushing the waste polystyrene into polystyrene particles for standby use, then heating and stirring the matrix asphalt to make the asphalt evenly distributed in all directions, adding polystyrene particles (heated to melt and then added) and cement when heated to 160-180°C, stirring manually for 3 minutes after adding, then stirring at 300r / min for 10 minutes with a high-speed shearing machine, then stirring at 600r / min for 20 minutes, and then placing in a 140°C oven for constant temperature cultivation for 1 hour, so that the polystyrene is fully swollen in the asphalt. As the amount of polystyrene added increases, the corresponding stirring time is appropriately increased according to the state of the modified asphalt. Then, placing in a high-speed shearing machine and stirring at 300r / min for 5 minutes, the polystyrene polymer is fully stretched, dissolved, and evenly distributed, and the bubbles on the surface of the asphalt are eliminated, and finally, placing in a 140°C oven for constant temperature cultivation for 30 minutes to obtain the modified asphalt.

[0037] Comparative Example 1 In this comparative example, the asphalt is not modified, and 100% 70# base asphalt is directly used.

[0038] Comparative Example 2 The raw materials are taken according to the following mass percentages: 2.5% cement and 97.5% 70# base asphalt.

[0039] A method for modifying asphalt using cement comprises the following steps: heating and stirring the base asphalt to make the asphalt evenly distributed in all directions, adding cement when heated to 160-180°C, manually stirring for 3 minutes after the addition, stirring at 300r / min for 10 minutes with a high-speed shearing machine, stirring at 600r / min for 20 minutes, and then placing in a 140°C oven for constant temperature incubation for 1 hour to make the cement fully dispersed in the asphalt. Then placing in a high-speed shearing machine for stirring at 300r / min for 5 minutes to make the cement particles fully stretched and evenly distributed, and eliminate the bubbles on the surface of the asphalt, and finally placing in a 140°C oven for constant temperature incubation for 30 minutes to obtain the modified asphalt.

[0040] Comparative Example 3 The raw materials are taken according to the following mass percentages: 4% expanded polystyrene EPS and 96% 70# base asphalt.

[0041] A method for modifying asphalt using waste polystyrene comprises the following steps: cleaning and removing impurities from waste polystyrene, drying and crushing the waste polystyrene into polystyrene particles for standby use, then heating and stirring the matrix asphalt to make the asphalt evenly distributed in all directions, adding polystyrene particles (adding after heating to melting) when heated to 160-180°C, manually stirring for 3 minutes after adding, then stirring at a speed of 300r / min for 10 minutes with a high-speed shearing machine, then stirring at a speed of 600r / min for 20 minutes, and then placing in a 140°C oven for constant temperature cultivation for 1 hour, so that the polystyrene is fully swollen in the asphalt. As the amount of polystyrene added increases, the corresponding stirring time is appropriately increased according to the state of the modified asphalt. Then, placing in a high-speed shearing machine and stirring at 300r / min for 5 minutes, the polystyrene polymer is fully stretched, dissolved, and evenly distributed, and the bubbles on the surface of the asphalt are eliminated, and finally, placing in a 140°C oven for constant temperature cultivation for 30 minutes to obtain the modified asphalt.

[0042] Comparative Example 4 The raw materials are taken according to the following mass percentages: 4% of extruded polystyrene XPS and 96% of 70# base asphalt.

[0043] A method for modifying asphalt using waste polystyrene comprises the following steps: cleaning and removing impurities from waste polystyrene, drying and crushing the waste polystyrene into polystyrene particles for standby use, then heating and stirring the matrix asphalt to make the asphalt evenly distributed in all directions, adding polystyrene particles (adding after heating to melting) when heated to 160-180°C, manually stirring for 3 minutes after adding, then stirring at a speed of 300r / min for 10 minutes with a high-speed shearing machine, then stirring at a speed of 600r / min for 20 minutes, and then placing in a 140°C oven for constant temperature cultivation for 1 hour, so that the polystyrene is fully swollen in the asphalt. As the amount of polystyrene added increases, the corresponding stirring time is appropriately increased according to the state of the modified asphalt. Then, placing in a high-speed shearing machine and stirring at 300r / min for 5 minutes, the polystyrene polymer is fully stretched, dissolved, and evenly distributed, and the bubbles on the surface of the asphalt are eliminated, and finally, placing in a 140°C oven for constant temperature cultivation for 30 minutes to obtain the modified asphalt.

[0044] Comparative Example 5 The raw materials were taken according to the following mass percentages: 4% SBS modifier and 96% 70# base asphalt.

[0045] A method for modifying asphalt using SBS comprises the following steps: heating and stirring the base asphalt to make the asphalt evenly distributed in all directions, adding the SBS modifier when heated to 160-180°C, manually stirring for 3 minutes after the addition, stirring at 300r / min for 10 minutes with a high-speed shearing machine, stirring at 600r / min for 20 minutes, and then placing in a 140°C oven for constant temperature cultivation for 1 hour to allow the SBS to fully swell in the asphalt. Then placing in a high-speed shearing machine for stirring at 300r / min for 5 minutes to allow the SBS polymer to fully stretch, dissolve, and evenly distribute, and eliminate bubbles on the surface of the asphalt, and finally placing in a 140°C oven for constant temperature cultivation for 30 minutes to obtain the modified asphalt.

[0046] The raw material ratios of the above Examples 1-8 and Comparative Examples 1-5 are summarized in Table 1 below: Table 1 Raw materials and their corresponding weight fractions (wt%) of Examples 1-8 and Comparative Examples 1-5 1. Basic performance test of asphalt

[0047] 1. Overall results of performance testing The modified asphalts prepared in Examples 1-8 were subjected to tests of penetration, softening point, ductility and low-temperature bending beam rheology (wherein the low-temperature bending beam rheology test was mainly conducted on Examples 2, 6 and Comparative Examples 1-5) to test the improvement effect of the present invention on the performance of asphalt using waste polystyrene and cement, and Comparative Examples 1-5 were used as the control group. The test results are shown in Table 2 below. It can be seen from Table 2 that the performance of the modified asphalt prepared in the present invention meets the specification requirements.

[0048] Table 2 Performance test results of modified asphalt obtained from Examples 1-8 and Comparative Examples 1-5

[0049] 2. Analysis of the impact of changes in waste polystyrene and cement content on asphalt performance 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.

[0050] Depend on Figure 4It can be seen that in terms of needle penetration, with the increase of EPS or XPS content, the needle penetration index of modified asphalt shows a trend of first decreasing, then increasing, and then decreasing. Compared with the base asphalt, the XPS content decreased by 37.2%, 21.6%, 33.3%, and 49.9% when it was 2%, 4%, 6%, and 8%, respectively, and the EPS content decreased by 46.3%, 41.4%, 48.9%, and 54.6% when it was 2%, 4%, 6%, and 8%, respectively. The needle penetration of XPS modified asphalt is generally greater than that of EPS modified asphalt.

[0051] Depend on Figure 5 It can be seen that in terms of softening point, with the increase of EPS or XPS content, the softening point of modified asphalt shows an upward trend. When the XPS content is 2%, 4%, 6%, and 8%, the softening point is increased by 10.2%, 12.6%, 15.1%, and 16.5% respectively compared with the base asphalt. When the EPS content is 2%, 4%, 6%, and 8%, the softening point is increased by 5%, 6%, 7.2%, and 8.2% respectively compared with the base asphalt. The softening point of XPS modified asphalt is generally better than that of EPS modified asphalt.

[0052] 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, and 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, and 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 with that of base asphalt, and the modification effect is best when the polystyrene content is 4%.

[0053] 3. Comparison of the effects of optimal dosage of composite modifier and single modifier on asphalt performance The test results of the 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.

[0054] 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 by the composite modifier is lower than that of asphalt modified by a single modifier, and the effect of composite modification is better.

[0055] Depend on Figure 8It 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 can be close to the effect of SBS single modified asphalt (Comparative Example 5).

[0056] Depend on Fig. 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 by the composite modifier has better low-temperature performance.

[0057] Depend on Fig.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 by the composite modifier is smaller and has an effect close to that of SBS single modification.

[0058] Depend on Fig.11 It can be seen that, in terms of creep rate, relative to Examples 2 and 6, Comparative Examples 2-5 have an upward trend.

[0059] Through the comparative analysis of the above Examples 2 and 6 and Comparative Examples 2-5, it can be concluded that the composite modifier can improve the high and low temperature performance of asphalt as a whole. The modification effect of extruded polystyrene XPS on asphalt is better than that of expanded polystyrene EPS. This is because the density of XPS is greater than that of EPS. After the same amount of XPS and EPS are added to asphalt, XPS has a smaller volume in asphalt, is more dispersed in asphalt, and swells more fully, which has a better modification effect on asphalt. The modification effect of XPS and cement composite modified asphalt mortar can reach a level close to that of SBS modified asphalt, and the modification effect on asphalt is obvious.

[0060] 2. Asphalt mixture performance test 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 range 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 gradation, the gradation design formula of AC-13 asphalt mixture is finally determined. The design gradation composition is shown in Table 3.

[0061] Table 3 Gradation composition of AC-13 asphalt mixture

[0062] The optimal asphalt-to-stone ratio of the asphalt mixture made of different modified asphalts of the present invention is determined by the Marshall experiment, as shown in Table 4, so as to carry out relevant performance tests of the modified asphalt mixture.

[0063] Table 4 Optimal asphalt-stone ratio of different modified asphalt mixtures

[0064] The modified asphalt prepared in Example 2, Example 6 and Comparative Examples 1-5 was made into AC-13 type asphalt mixture according to the above gradation and asphalt-to-stone ratio, and then the asphalt mixture performance test was carried out, 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. The results are shown in Figure 12-14 .

[0065] Depend on Figure 12-14 It can be seen that in terms of high temperature performance (dynamic stability), the XPS / cement composite modified asphalt mixture (Example 6) has the best effect, which is close to the high temperature performance of the SBS modified asphalt mixture (Comparative Example 5). In terms of low temperature (flexural tensile strain), the greater the low temperature flexural tensile strain value of the composite modified asphalt mixture, the stronger the low temperature deformation ability of the mixture and the better the low temperature performance. In terms of water temperature stability performance (residual stability after immersion in water), the residual stability of the composite modified asphalt after immersion in water is close to that of the SBS modified asphalt mixture, indicating that it has a better ability to resist peeling and prevent loose particles.

[0066] 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.

[0067] Finally, it should be noted that the above is only 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 can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for composite modified asphalt using waste polystyrene and cement, characterized in that: The following steps are involved: The waste polystyrene is washed, dried and crushed into polystyrene particles for standby use, and then the base asphalt is heated and stirred, and when it is heated to 160-180°C, the polystyrene particles and cement are added and stirred evenly, and then placed in a 120-160°C oven for constant temperature incubation for 0.5-3h, and then placed in a high-speed shearing machine for stirring at 200-400r / min for 3-10min, and finally placed in a 120-160°C oven for constant temperature incubation for 15-60min to obtain modified asphalt; The content of the waste polystyrene is 0.1-6%, and the content of the cement is 0.1-4%.

2. The method according to claim 1, characterized in that: The content of the waste polystyrene is 3.5-4.5%, and the content of the cement is 2-3%.

3. The method according to claim 1, characterized in that: The waste polystyrene comes from expanded polystyrene EPS or extruded polystyrene XPS.

4. The method according to claim 1, characterized in that: 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 200-400r / min for 8-20 minutes, and then stir at a speed of 500-700r / min for 15-40 minutes.

5. The method according to claim 1, characterized in that: The polystyrene particles are heated to a molten state and then mixed into the matrix asphalt.

6. The method according to any one of claims 1 to 5, characterized in that: The following steps are involved: The waste polystyrene is washed, dried and crushed into polystyrene particles for standby use, and then the base asphalt is heated and stirred, and when heated to 160-180°C, the molten polystyrene particles and cement are added, and after adding, they are first 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, and then placed in a 120-160°C oven for constant temperature cultivation for 0.5-3h, and then placed in a high-speed shearing machine for stirring at 200-400r / min for 3-10min, and finally placed in a 120-160°C oven for constant temperature cultivation for 15-60min to obtain modified asphalt; The content of the waste polystyrene is 3.5-4.5%, and the content of the cement is 2-3%.

7. An asphalt composite modifier, characterized in that: It includes waste polystyrene with a dosage of 0.1-6% and cement with a dosage of 0.1-4%.

8. The asphalt composite modifier according to claim 7, characterized in that: It includes 3.5-4.5% of waste polystyrene and 2-3% of cement.

9. A modified asphalt, characterized in that: In terms of mass percentage, it includes: base asphalt 88-99.8%, cement 0.1-4% and polystyrene 0.1-8%.

10. The modified asphalt according to claim 9, characterized in that: In terms of mass percentage, it includes: base asphalt 93-94%, cement 2-3% and polystyrene 3.5-4.5%.

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