Modified asphalt, asphalt mixture and preparation method and application thereof

Abstract

The application provides modified asphalt, asphalt mixture and a preparation method and application thereof, raw materials of the modified asphalt include the following components in mass fraction: 70-98 parts of base asphalt, 5-20 parts of desulfurized rubber and 2-15 parts of North American rock asphalt. The modified asphalt has good storage stability, high-temperature anti-rutting property, anti-fatigue property, low-temperature anti-cracking property and anti-aging property, that is, the modified asphalt has excellent comprehensive performance, and solves the problem that it is difficult to obtain modified asphalt with excellent comprehensive performance in the prior art.

Description

Technical Field

[0001] This invention relates to modified asphalt, asphalt mixtures, their preparation methods and applications. Background Technology

[0002] Traffic channelization, increased axle load, and external environmental factors are among the main causes of early-stage asphalt pavement distress, placing higher demands on the performance and durability of asphalt mixtures. To improve pavement quality and extend the service life of asphalt roads, one improvement method is to incorporate modifiers into the asphalt. Currently, the most widely used modifier is polymer modifiers, represented by SBS. These modifiers have good compatibility with the base asphalt, significant modification effects, and relatively mature preparation methods, thus they are widely used in high-grade asphalt pavements. However, they also suffer from problems such as poor stability, easy segregation, and high cost.

[0003] Natural rock asphalt has good compatibility with base asphalt. Proper use can significantly improve the high-temperature stability, water loss resistance, and aging resistance of asphalt mixtures, reduce the temperature sensitivity of the mixture, and thus improve the durability of the pavement structure. However, rock asphalt can increase the softening point, decrease the penetration and ductility of base asphalt, and adversely affect low-temperature performance.

[0004] Waste rubber-modified asphalt is a common type of modified asphalt, but waste rubber powder has poor compatibility with asphalt, often contains a large number of rubber particles, and suffers from many drawbacks such as high viscosity, low fluidity, poor high-temperature storage stability, and easy segregation, limiting its application and development. Compared with ordinary rubber powder, desulfurized rubber has significantly improved compatibility with asphalt, improving the viscosity and low-temperature performance of rubber-modified asphalt. However, desulfurized rubber-modified asphalt also has many problems, such as reduced resistance to deformation, poor aging resistance, and insufficient high-temperature performance, and its performance needs further improvement.

[0005] To develop a modified base asphalt with excellent high and low temperature performance, researchers added different modifiers to improve its properties. Patent application CN201810564891.1 (publication date 2018.11.02) discloses a composite modified desulfurized rubber asphalt and its preparation method. The composite modified desulfurized rubber asphalt includes 70# base asphalt, desulfurized rubber powder, and a polyphosphate composite modifier. Furthermore, this invention further enhances the reaction depth of the desulfurized rubber through a two-stage development process, resulting in a composite modified desulfurized rubber asphalt with good high and low temperature performance and low viscosity, which is beneficial for the recycling of waste rubber. However, this composite modified desulfurized rubber asphalt and its preparation method also have some problems. For example, the long high-temperature shear time of the desulfurized rubber in this preparation method can lead to the volatilization of lightweight components in the asphalt and easy thermal oxidative aging of the asphalt.

[0006] Albanian rock asphalt-rubber powder composite modified asphalt was prepared by using Albanian rock asphalt and rubber powder as composite modifiers. This improved the low-temperature performance, anti-aging performance and high-temperature rutting resistance of the base asphalt. However, the rubber-modified asphalt is prone to problems such as poor compatibility with the base asphalt, easy segregation, high viscosity, and inconvenience in production and construction (Wang Yao. Study on the performance of Albanian rock asphalt / rubber powder composite modified asphalt and its mixture [D]. Chang'an University, 2021).

[0007] As can be seen from the above, existing modified asphalt improves one aspect of rubber's performance but reduces other aspects of asphalt's performance, making it difficult to obtain modified asphalt with excellent overall performance. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to overcome the difficulty in obtaining modified asphalt with excellent comprehensive performance in the prior art, and provides modified asphalt, asphalt mixture, preparation method and application of the same, wherein the modified asphalt has good storage stability, high temperature rutting resistance, fatigue resistance, low temperature crack resistance and aging resistance, that is, the modified asphalt has excellent comprehensive performance.

[0009] This invention provides a modified asphalt, the raw materials of which include the following components in parts by weight: 70-98 parts of base asphalt, 5-20 parts of desulfurized rubber and 2-15 parts of North American rock asphalt.

[0010] This invention, by adding North American rock asphalt and desulfurized rubber to base asphalt and controlling the ratio of North American rock asphalt, desulfurized rubber and base asphalt, provides modified asphalt with good storage stability, high-temperature rutting resistance, fatigue resistance, low-temperature crack resistance and aging resistance, that is, excellent comprehensive performance.

[0011] In this invention, the ash content of the North American rock bitumen is preferably ≤1.0%.

[0012] In this invention, the asphalt content of the North American rock asphalt is preferably ≥90%. By controlling the asphalt content and ash content of the North American rock asphalt, the modified asphalt can have better high-temperature rutting resistance.

[0013] In this invention, the softening point of the North American rock bitumen can be conventional in the art, preferably 160-185℃.

[0014] In this invention, the water content of the North American rock bitumen can be conventional in the art, preferably <0.5%.

[0015] In this invention, the North American rock bitumen refers to UINTAITE North American hard bitumen produced in the Uintah Basin in eastern Judea, northern United States.

[0016] In this invention, the particle size of the desulfurized rubber can be conventional in the art, preferably 40 mesh.

[0017] In this invention, the sol content of the desulfurized rubber is preferably >50%.

[0018] In this invention, the Mooney viscosity of the desulfurized rubber is preferably <40.

[0019] In this invention, the base asphalt can be a conventional base asphalt in the art, preferably PG64-22 asphalt. In PG64-22, 64 represents the high-temperature grade for which the asphalt is applicable, meaning that the asphalt can withstand road surface temperatures of at least 64°C; 22 represents the low-temperature grade for which the asphalt is applicable, meaning that the asphalt can withstand road surface temperatures dropping to below -22°C.

[0020] In this invention, the kinematic viscosity of the base asphalt at 135°C is preferably ≤3 Pa·s.

[0021] In this invention, the flash point of the base asphalt is preferably ≥260℃.

[0022] In a preferred embodiment of the present invention, the raw material of the modified asphalt includes the following components in parts by weight: 72-87 parts of base asphalt, 8-18 parts of desulfurized rubber, and 2-10 parts of North American rock asphalt.

[0023] In a preferred embodiment of the present invention, the modified asphalt raw materials comprise 72 parts by mass of the base asphalt, 10 parts by mass of the North American rock asphalt, and 18 parts by mass of the desulfurized rubber. By combining 10 parts of North American rock asphalt and 18 parts of desulfurized rubber, the modified base asphalt grade is improved from PG64-22 to exceed the performance of PG76-22, exhibiting good storage stability, high and low temperature performance, and anti-aging properties. It is estimated that the modified asphalt prepared by combining 10 parts of natural rock asphalt and 18 parts of desulfurized rubber is 5%-20% cheaper than commercially available SBS modified asphalt, with lower production costs, enabling its widespread application in road engineering.

[0024] In another preferred embodiment of the present invention, the raw materials of the modified asphalt contain 77 parts by mass of the base asphalt, 10 parts by mass of the North American rock asphalt, and 13 parts by mass of the desulfurized rubber.

[0025] In another preferred embodiment of the present invention, the raw materials of the modified asphalt include 82 parts by mass of the base asphalt, 10 parts by mass of the North American rock asphalt, and 8 parts by mass of the desulfurized rubber.

[0026] The present invention also provides a method for preparing modified asphalt, which includes the following steps: at 175-185°C, 70-98 parts of North American rock asphalt, 5-20 parts of desulfurized rubber and 2-15 parts of base asphalt are sheared and mixed to obtain the modified asphalt.

[0027] In this invention, the shear mixing time is related to the scale of the mixture, preferably 20-60 minutes, for example 30 minutes.

[0028] In this invention, the shear mixing rate can be a conventional rate in the art, preferably 10,000-18,000 rpm, for example 12,000 rpm.

[0029] In this invention, the stirring temperature for shear mixing is preferably 170-185°C, for example, 180°C.

[0030] In this invention, the order of shear mixing can be conventional in the art, preferably by first mixing the base asphalt with the desulfurized rubber, swelling it, and then adding the North American rock asphalt.

[0031] The swelling time is preferably 0.5-12 hours, for example, 1 hour.

[0032] In this invention, the shearing and mixing is preferably carried out in a reaction vessel.

[0033] The present invention also provides a modified asphalt, which is prepared by the above-described modified asphalt preparation method.

[0034] The present invention also provides an asphalt mixture comprising the above-mentioned modified asphalt and filler.

[0035] In this invention, the modified asphalt accounts for 5%-7.5% of the mass percentage of the asphalt mixture.

[0036] In this invention, the filler can be a conventional filler used for asphalt mixtures in the art, such as coarse aggregate, fine aggregate, mineral filler, etc.

[0037] The present invention also provides the application of the above-mentioned modified asphalt in asphalt pavement.

[0038] Based on common knowledge in the field, the above-mentioned preferred conditions can be combined arbitrarily to obtain various preferred embodiments of the present invention.

[0039] The reagents and raw materials used in this invention are all commercially available.

[0040] The positive and progressive effects of this invention are as follows:

[0041] This invention uses North American rock asphalt and desulfurized rubber to composite modify the base asphalt. The resulting modified asphalt exhibits superior overall performance compared to SBS-modified asphalt, possessing excellent low-temperature crack resistance, fatigue resistance, high-temperature rutting resistance, storage stability, and aging resistance. It solves the problems of poor low-temperature crack resistance and easy segregation during storage caused by single rock asphalt modification, and overcomes the issues of insufficient high-temperature performance and high viscosity caused by single rubber powder modification. Attached Figure Description

[0042] Figure 1 The flowcharts for the preparation and testing of modified asphalt in each embodiment are shown.

[0043] Figure 2 These are characterization diagrams of the high-temperature rutting performance of the modified asphalt in Examples 1-3 and Comparative Example 1;

[0044] Figure 3 The high-temperature rutting performance characterization diagrams are for the modified asphalt in Comparative Examples 1-3.

[0045] Figure 4 The high-temperature rutting performance characterization diagrams are for the modified asphalts in Examples 4-6.

[0046] Figure 5 The high-temperature rutting performance characterization diagrams are for the modified asphalt in Examples 7-9.

[0047] Figure 6 The fatigue characterization diagrams are for the modified asphalt in Comparative Examples 1-3.

[0048] Figure 7 These are fatigue characterization diagrams of the modified asphalt in Examples 4-6 and Comparative Example 2;

[0049] Figure 8 Principal plots of the complex modulus of the modified asphalt in Examples 1, 2 and Comparative Examples 1-3;

[0050] Figure 9 The main phase angle (frequency) curves of the modified asphalt in Examples 1, 2 and Comparative Examples 1-3 are shown.

[0051] Figure 10 The low-temperature performance characterization diagrams are for the modified asphalt in Examples 1-3 and Comparative Example 1.

[0052] Figure 11 The graphs show the short-term anti-aging properties of the modified asphalt in Examples 1-3 and Comparative Examples 1-3.

[0053] Figure 12 These are characterization diagrams of the long-term anti-aging properties of the modified asphalt in Examples 1-3 and Comparative Examples 1-3;

[0054] Figure 13The images show the anti-aging properties of the modified asphalt in Example 1 and Comparative Example 1, characterized by Fourier transform infrared spectroscopy. Detailed Implementation

[0055] The present invention is further illustrated below by way of embodiments, but the invention is not limited to the scope of the embodiments described herein. Experimental methods in the following embodiments that do not specify specific conditions were performed according to conventional methods and conditions, or as selected according to the product instructions.

[0056] Figure 1 The following are flowcharts illustrating the preparation and testing of modified asphalt in each embodiment. Figure 1 The present invention will be described in further detail below.

[0057] In the following embodiments and comparative examples:

[0058] The base asphalt was PG64-22 base asphalt purchased from an asphalt manufacturing plant in Tennessee, USA.

[0059] North American rock bitumen has a softening point of 160-185℃, bitumen content >90%, ash content ≤1.0%, and water content <0.5%.

[0060] Iranian rock bitumen has a softening point of 170-200℃, a bitumen content of 82-85%, an ash content of 15-18%, and a water content of <1%.

[0061] The softening point of the Budun rock asphalt is ≥80℃, the asphalt content is 22-30%, the ash content is 73-80%, and the water content is <1%.

[0062] All of the above natural rock asphalt is commercially available.

[0063] The desulfurized rubber granules were provided by Shanghai Jiao Tong University.

[0064] As a reference group for modified asphalt, SBS modified asphalt was purchased from a Tennessee asphalt manufacturing plant in the United States, specifically PG76-22. In the following tables and figures, SBS refers to PG76-22 grade SBS modified asphalt purchased from the Tennessee asphalt manufacturing plant in the United States.

[0065] Example 1

[0066] 72 parts by mass of base asphalt were heated to 160°C and then poured into a reactor. 18 parts by mass of desulfurized rubber were added to the reactor. The reactor was heated to 180°C and allowed to swell for 1 hour. Then 10 parts by mass of North American rock asphalt were added and the mixture was high-speed sheared and mixed at 12,000 rpm for 0.5 hours to obtain modified asphalt.

[0067] Example 2

[0068] 77 parts by mass of base asphalt were heated to 160°C and then poured into a reactor. 13 parts by mass of desulfurized rubber were added to the reactor. The reactor was heated to 180°C and allowed to swell for 1 hour. Then 10 parts by mass of North American rock asphalt were added and the mixture was high-speed sheared and mixed at 12,000 rpm for 0.5 hours to obtain modified asphalt.

[0069] Example 3

[0070] 82 parts by mass of base asphalt were heated to 160°C and then injected into a reactor. 8 parts by mass of desulfurized rubber were added to the reactor. The reactor was heated to 180°C and allowed to swell for 1 hour. Then 10 parts by mass of North American rock asphalt were added, and the mixture was high-speed sheared and mixed at 12,000 rpm for 0.5 hours to obtain modified asphalt.

[0071] Example 4

[0072] 77 parts by mass of base asphalt were heated to 160°C and then poured into a reactor. 18 parts by mass of desulfurized rubber were added to the reactor. The reactor was heated to 180°C and allowed to swell for 1 hour. Then 5 parts by mass of North American rock asphalt were added and the mixture was high-speed sheared and mixed at 12,000 rpm for 0.5 hours to obtain modified asphalt.

[0073] Example 5

[0074] 82 parts by mass of base asphalt were heated to 160°C and then poured into a reactor. 13 parts by mass of desulfurized rubber were added to the reactor. The reactor was heated to 180°C and allowed to swell for 1 hour. Then 5 parts by mass of North American rock asphalt were added and the mixture was high-speed sheared and mixed at 12,000 rpm for 0.5 hours to obtain modified asphalt.

[0075] Example 6

[0076] 87 parts by mass of base asphalt were heated to 160°C and then poured into a reactor. 8 parts by mass of desulfurized rubber were added to the reactor. The reactor was heated to 180°C and allowed to swell for 1 hour. Then 5 parts by mass of North American rock asphalt were added, and the mixture was high-speed sheared and mixed at 12,000 rpm for 0.5 hours to obtain modified asphalt.

[0077] Example 7

[0078] 80 parts by mass of base asphalt were heated to 160°C and then poured into a reactor. 18 parts by mass of desulfurized rubber were added to the reactor. The reactor was heated to 180°C and allowed to swell for 1 hour. Then 2 parts by mass of North American rock asphalt were added and the mixture was high-speed sheared at 12,000 rpm for 0.5 hours to obtain modified asphalt.

[0079] Example 8

[0080] 85 parts by mass of base asphalt were heated to 160°C and then poured into a reactor. 13 parts by mass of desulfurized rubber were added to the reactor. The reactor was heated to 180°C and allowed to swell for 1 hour. Then 2 parts by mass of North American rock asphalt were added and the mixture was high-speed sheared at 12,000 rpm for 0.5 hours to obtain modified asphalt.

[0081] Example 9

[0082] 90 parts by mass of base asphalt were heated to 160°C and then poured into a reactor. 8 parts by mass of desulfurized rubber were added to the reactor. The reactor was heated to 180°C and allowed to swell for 1 hour. Then 2 parts by mass of North American rock asphalt were added, and the mixture was high-speed sheared and mixed at 12,000 rpm for 0.5 hours to obtain modified asphalt.

[0083] Comparative Example 1

[0084] 90 parts by weight of base asphalt were heated to 160°C and then injected into a reactor. The reactor was heated to 180°C, and 10 parts by weight of North American rock asphalt were added. The mixture was then subjected to high-speed shear mixing at 12,000 rpm for 0.5 hours to obtain modified asphalt.

[0085] Comparative Example 2

[0086] 95 parts by weight of base asphalt were heated to 160°C and then injected into a reactor. The reactor was heated to 180°C, and 5 parts by weight of North American rock asphalt were added. The mixture was then subjected to high-speed shear mixing at 12,000 rpm for 0.5 hours to obtain modified asphalt.

[0087] Comparative Example 3

[0088] 98 parts by weight of base asphalt were heated to 160°C and then injected into a reactor. The reactor was heated to 180°C, and 2 parts by weight of North American rock asphalt were added. The mixture was then subjected to high-speed shear mixing at 12,000 rpm for 0.5 hours to obtain modified asphalt.

[0089] Comparative Example 4

[0090] 98 parts by weight of base asphalt were heated to 160°C and then injected into a reactor. The reactor was heated to 180°C, and 2 parts by weight of Iranian rock asphalt were added. The mixture was then subjected to high-speed shear mixing at 12,000 rpm for 0.5 hours to obtain modified asphalt.

[0091] Comparative Example 5

[0092] 95 parts by weight of base asphalt were heated to 160°C and then injected into a reactor. The reactor was heated to 180°C, and 5 parts by weight of Iranian rock asphalt were added. The mixture was then subjected to high-speed shear mixing at 12,000 rpm for 0.5 hours to obtain modified asphalt.

[0093] Comparative Example 6

[0094] 90 parts by weight of base asphalt were heated to 160°C and then injected into a reactor. The reactor was heated to 180°C, and 10 parts by weight of Iranian rock asphalt were added. The mixture was then subjected to high-speed shear mixing at 12,000 rpm for 0.5 hours to obtain modified asphalt.

[0095] Comparative Example 7

[0096] 98 parts by mass of base asphalt were heated to 160°C and then injected into a reactor. The reactor was heated to 180°C, and 2 parts by mass of Buton rock asphalt were added. The mixture was then subjected to high-speed shear mixing at 12,000 rpm for 0.5 hours to obtain modified asphalt.

[0097] Comparative Example 8

[0098] 95 parts by weight of base asphalt were heated to 160°C and then injected into a reactor. The reactor was heated to 180°C, and 5 parts by weight of Buton rock asphalt were added. The mixture was then subjected to high-speed shear mixing at 12,000 rpm for 0.5 hours to obtain modified asphalt.

[0099] Comparative Example 9

[0100] 90 parts by mass of base asphalt were heated to 160°C and then injected into a reactor. The reactor was heated to 180°C, and 10 parts by mass of Buton rock asphalt were added. The mixture was then subjected to high-speed shear mixing at 12,000 rpm for 0.5 hours to obtain modified asphalt.

[0101] Effect Example

[0102] According to the American Society for Testing and Materials (ASTM D7173-20) standard, the cigar tube test is used to evaluate the storage stability of modified bitumen.

[0103] This invention uses dynamic shear rheology testing (DSR test) to evaluate the low-temperature cracking, medium-temperature fatigue and high-temperature rutting resistance of modified asphalt.

[0104] The complex modulus and phase angle of modified asphalt were tested according to the National Highway and Transportation Association (AASHTOT 315 and T313-10) to characterize the low-temperature ductility and viscoelasticity of the modified asphalt.

[0105] The Bending Beam Creep Test (BBR) is conducted according to the American Association of Highway and Transportation (AASHTO) standard (T313) to characterize the creep stiffness coefficient (S) and creep rate (m) of modified asphalt. In the PG classification, these two indicators—the creep stiffness coefficient (S) and creep rate (m)—are commonly used to evaluate the low-temperature performance of asphalt. A smaller S value and a larger m value indicate better crack resistance. The low-temperature grade of asphalt is determined by simultaneously satisfying the conditions of S ≤ 300 MPa and m ≥ 0.3.

[0106] The anti-aging properties of modified asphalt are evaluated in two ways: 1) dynamic shear rheological tests are used to determine the changes in rutting factor of asphalt binder under different aging degrees; 2) Fourier transform infrared spectroscopy is used to calculate the changes in carbonyl area under different aging degrees.

[0107] 1. Stability Characterization

[0108] The storage stability of modified asphalt was evaluated using the cigar tube test.

[0109] In the experiment, approximately 50g of modified asphalt was introduced into an aluminum foil tube. The aluminum foil tube was then placed in an oven at 163±5℃ and left to stand for 48±1 hours. Immediately afterwards, the aluminum foil tube was placed in a refrigerator for at least 4 hours to allow it to solidify. Finally, the aluminum foil tube containing asphalt was removed, cut into three parts, and the asphalt from the upper and lower parts was extracted to prepare specimens for subsequent dynamic shear rheological tests.

[0110] The upper layer, lower layer, and average value are the rutting factors of the upper part, lower part, and upper and lower average of the aluminum foil tube. The separation system is calculated by the following formula:

[0111] Separation coefficient = (the larger of the rutting factors of the upper and lower parts of the aluminum foil tube - the average of the rutting factors of the upper and lower parts of the aluminum foil tube) / the average of the rutting factors of the upper and lower parts of the aluminum foil tube.

[0112] The stability test results of the base asphalt, the modified asphalt prepared in Examples 1-3 and Comparative Example 1, and the SBS modified asphalt are shown in Table 1.

[0113] As shown in Table 1, the base asphalt exhibits a relatively small separation coefficient, while the SBS-modified asphalt exhibits the smallest separation coefficient. The separation coefficients of Examples 1-3 of this invention do not exceed 11%, with Example 1 reducing the separation coefficient to 2.70%, approaching that of the SBS-modified asphalt, demonstrating excellent storage stability. In contrast, the technical solution in Comparative Example 1 increases the separation coefficient of the modified asphalt, reducing its storage stability. Therefore, adding desulfurized rubber can effectively improve the storage stability of modified asphalt.

[0114] Table 1

[0115]

[0116] 2. High-temperature rutting resistance characterization

[0117] The high-temperature rutting resistance of modified asphalt was evaluated using the dynamic shear rheology test (DSR test).

[0118] The rutting factor was used to evaluate the high-temperature rutting resistance of modified asphalt. A higher rutting factor value indicates better high-temperature rutting resistance. The high-temperature rutting resistance factor values ​​of the modified asphalts prepared in Examples 1-3 and Comparative Examples 1-9 are shown in Table 2 and... Figure 2-5 As shown in the image.

[0119] Table 2

[0120]

[0121]

[0122] Rock bitumen is mainly used to improve the high-temperature rutting resistance of modified asphalt; a high rutting factor indicates a good modification effect. This invention uses North American rock bitumen to prepare modified asphalt and evaluates its performance.

[0123] From Table 2 and Figure 2-5 It can be seen that the rutting factor of the modified asphalt in Examples 1-3 is significantly higher than that of the SBS modified asphalt, the modified asphalt in Comparative Examples 1-9, and the base asphalt. This indicates that the modified asphalt provided by the present invention possesses excellent high-temperature rutting resistance. (Comparison) Figure 3 , Figure 4 and Figure 5 It can be seen that North American rock bitumen has the best modification effect, Iranian rock bitumen has a moderate modification effect, and Buton rock bitumen has the worst modification effect.

[0124] Figure 2 The results show that the rutting factor of the modified asphalt in Examples 1-3 is higher than that of SBS modified asphalt and base asphalt, and Examples 1 and 2 can further improve the high-temperature rutting properties of the modified asphalt.

[0125] Figure 3 The results show that while adding North American rock asphalt alone to the base asphalt in Comparative Examples 1-3 increases the rutting factor of the base asphalt, thereby improving its high-temperature rutting resistance, only the modified asphalt in Comparative Example 1 has a slightly higher rutting factor than the SBS-modified asphalt. The modified asphalts in Comparative Examples 2 and 3 still have lower rutting factors than the SBS-modified asphalt. This indicates that adding North American rock asphalt alone has a limited effect on improving the rutting resistance of base asphalt.

[0126] Figure 4 The results show that the modified asphalt in Comparative Examples 4-5, due to the addition of Iranian rock asphalt to the base asphalt, improved the rutting resistance of the base asphalt. However, only the modified asphalt in Comparative Example 6 had a slightly higher rutting factor than the SBS modified asphalt at low temperatures. At high temperatures, the rutting factor of the modified asphalt in Comparative Example 6 was lower than that of the SBS modified asphalt, while the rutting factors of the modified asphalt in Comparative Examples 2 and 3 were still much lower than those of the SBS modified asphalt. This indicates that adding North American rock asphalt alone has a limited effect on improving the rutting resistance of the base asphalt.

[0127] Figure 5The results show that although Buton rock asphalt was added to the modified asphalt in Comparative Examples 7-8, its improvement on the rutting resistance of the base asphalt was limited. The modified asphalt in Comparative Examples 1-9 was slightly better than the base asphalt, but much worse than the SBS modified asphalt.

[0128] 3. Characterization of fatigue resistance

[0129] The fatigue factor is used to evaluate the fatigue resistance of modified asphalt. Generally, the lower the fatigue factor value, the better the fatigue resistance of the modified asphalt. The fatigue factors of the modified asphalts prepared in the above examples and comparative examples are shown in Table 2 and... Figure 6-7 As shown. The fatigue factor values ​​of the modified asphalt prepared in Examples 1-9 are significantly lower than those of the modified asphalt prepared in Comparative Examples 1-9. Furthermore, the fatigue factor values ​​of the modified asphalt prepared in Examples 1 and 4-7 of this invention are even lower than those of SBS modified asphalt. This indicates that the modified asphalt provided by this invention can significantly reduce the fatigue factor and improve the fatigue resistance of the modified asphalt. That is, when desulfurized rubber and natural rock asphalt are within a preferred ratio range, the combination of desulfurized rubber and natural rock asphalt can even achieve fatigue resistance superior to SBS modified asphalt. In contrast, the fatigue factors of the modified asphalt provided in Comparative Examples 1-9 are generally higher than those of the base asphalt, and are all significantly higher than those of SBS modified asphalt, indicating that adding natural rock asphalt alone reduces the fatigue resistance of the base asphalt.

[0130] Figure 6 The results show that among Comparative Examples 1-3, the modified asphalt in Comparative Example 2 has the lowest fatigue factor. Compared with the fatigue factor of the base asphalt, the fatigue factor of the modified asphalt in Comparative Examples 1-3 with the addition of North American rock asphalt alone has not changed or has increased. This indicates that the addition of North American rock asphalt alone does not improve the anti-aging performance of the base asphalt, but may instead lead to a decrease in its fatigue resistance.

[0131] Figure 7 The results show that the fatigue factor of the modified asphalt prepared in Examples 4-6 is significantly higher than that of the base asphalt, and even higher than that of the modified asphalt prepared in SBS modified asphalt and Comparative Example 2. This indicates that the simultaneous addition of appropriate proportions of North American rock asphalt and desulfurized rubber can enable the modified asphalt to have better fatigue resistance than SBS modified asphalt.

[0132] 4. Low-temperature performance characterization

[0133] The low-temperature ductility of modified asphalt is evaluated using the complex modulus. A higher complex modulus value indicates better low-temperature ductility of the modified rubber.

[0134] The complex modulus versus frequency master curves of the modified asphalt in Examples 1, 2 and Comparative Examples 1-3 are shown below. Figure 8As shown, the complex modulus of the base asphalt is generally the lowest. In the low-frequency region, the complex modulus of the modified asphalt in Comparative Examples 1-3 is slightly higher than that of the base asphalt, indicating that the addition of rock asphalt can effectively improve the complex modulus of the modified asphalt. The complex modulus of the modified asphalt in Examples 1 and 2 is higher than that of Comparative Examples 1-3 and SBS modified asphalt, indicating that the modified asphalt provided by this invention significantly improves low-temperature ductility.

[0135] The phase angle and frequency master curve of modified asphalt are shown below. Figure 9 As shown, the temperature and frequency conditions are consistent with the complex modulus master curve; the lower the phase angle value, the lower the viscosity of the modified asphalt. The base asphalt exhibits the highest phase angle across all frequencies, while the added natural rock asphalt generally has a lower phase angle, indicating a reduction in the viscosity of the modified asphalt. Examples 1 and 2 are particularly effective in reducing the viscosity of the modified asphalt. Especially in the low-frequency region, the phase angle of the modified asphalt prepared in Example 1 is close to that of SBS modified asphalt; while the phase angle of the modified asphalt prepared in Example 2 is generally lower than that of SBS modified asphalt, indicating that the modified asphalt prepared in Example 2 has lower viscosity.

[0136] The creep stiffness coefficient S and creep rate m of modified asphalt are shown in Table 3 and Figure 10 As shown, the modified asphalt in Examples 1-3 of this invention can effectively reduce the creep stiffness coefficient S and increase the creep rate m, thereby improving the low-temperature performance of the modified asphalt. Example 1 can improve the low-temperature performance of the modified asphalt to near the technical specifications of SBS modified asphalt. However, Comparative Example 1 has a higher creep stiffness coefficient S and a lower creep rate m, thus reducing the low-temperature performance of the modified asphalt.

[0137] Table 3

[0138]

[0139] 5. Anti-aging properties

[0140] Figure 11 and Figure 12 This shows the rutting factor ratio of modified asphalt under short-term and long-term aging. Short-term aging (RTFOT), or rotating thin-film oven aging test, simulates the aging process of asphalt and aggregate mixing. The specific operation of the RTFOT aging test follows the "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" (JTG E20-2011). Long-term aging, or pressure aging chamber method (PAV), simulates the aging of asphalt after 10 years of use on roads. The test method is found in the American Association of Highway and Transportation Standards (AASHTOPP1). Rutting factor ratio = rutting factor value after aging / rutting factor value before aging. A higher rutting factor ratio indicates poorer aging resistance.

[0141] Depend on Figure 11 and Figure 12 It can be seen that under long-term aging, the rutting factor ratios of Comparative Examples 1-3 all increased compared to SBS modified asphalt, while the rutting resistance factor ratios of Examples 1-3 all decreased compared to SBS modified asphalt, indicating that the modified asphalt provided by the present invention has stronger anti-aging ability. Under short-term aging, the rutting factor ratios of the modified asphalts in Comparative Examples 1 and 2 all increased compared to SBS modified asphalt, while the rutting factor ratio of the modified asphalt in Comparative Example 3 was basically equivalent to that of SBS modified asphalt; while the rutting factor ratios of the modified asphalts in Examples 1 and 2 decreased compared to SBS modified asphalt under short-term aging, indicating that the modified asphalt provided by the present invention also exhibited high anti-aging performance under short-term aging.

[0142] Based on the results of the carbonyl area change experiment using Fourier transform infrared spectroscopy, as follows: Figure 13 As shown. For unaged modified bitumen, rock bitumen will slightly increase the carbonyl index.

[0143] The carbonyl index CI = the wavelength of the carbonyl bond (C=O) is at 1700 cm⁻¹. -1 The area on the left and right sides / the reference area, where the reference area is the wavelength of the carbonyl bond (C=O) at wavenumber = 2920cm. -1 wavenumber = 2851cm -1 wavenumber = 1455cm -1 wavenumber = 1375cm -1 The larger the carbonyl index (CI), the greater the degree of aging of the asphalt. For modified asphalt after long-term aging, Example 1 shows better anti-aging performance.

[0144] In summary, the modified asphalt provided by this invention has better overall performance than SBS modified asphalt, exhibiting good storage stability, high-temperature rutting resistance, low-temperature crack resistance, fatigue resistance, and aging resistance, thus achieving the desired composite performance.

Claims

1. A modified asphalt, characterized in that, Its raw materials include the following components in parts by weight: 72 parts by weight of base asphalt, 10 parts by weight of North American rock asphalt, and 18 parts by weight of desulfurized rubber; the base asphalt is PG64-22 asphalt.

2. The modified asphalt according to claim 1, characterized in that, The ash content of the North American rock bitumen is ≤1.0%; And / or, the bituminous content of the North American rock bitumen is ≥90%; And / or, the softening point of the North American rock bitumen is 160-185°C; And / or, the water content of the North American rock bitumen is <0.5%.

3. The modified asphalt according to claim 1, characterized in that, The sol content of the desulfurized rubber is >50%; And / or, the Mooney viscosity of the desulfurized rubber is <40; And / or, the particle size of the desulfurized rubber is 40 mesh.

4. A method for preparing modified asphalt, characterized in that, It includes the following steps: The modified asphalt is obtained by shearing and mixing the raw materials of any one of claims 1-3 at 175-185°C.

5. The method for preparing modified asphalt according to claim 4, characterized in that, The shearing and mixing time is 20-60 minutes; And / or, the rate of shear mixing is 10,000-18,000 rpm; And / or, the stirring temperature for the shear mixing is 170-185°C; And / or, the shear mixing is carried out in a reaction vessel; And / or, the shear mixing involves first mixing the base bitumen with the desulfurized rubber, swelling it, and then adding the North American rock bitumen.

6. The method for preparing modified asphalt according to claim 5, characterized in that, The shearing and mixing time is 30 minutes; And / or, the rate of shear mixing is 12,000 rpm; And / or, the stirring temperature for the shear mixing is 180°C.

7. The method for preparing modified asphalt according to claim 5, characterized in that, The swelling time is 0.5-12 hours.

8. The method for preparing modified asphalt according to claim 7, characterized in that, The swelling time is 1 hour.

9. An asphalt mixture, characterized in that, It includes the modified bitumen and filler as described in any one of claims 1-3.

10. The application of the modified asphalt as described in any one of claims 1-3 in asphalt pavement.

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