A self-healing modified asphalt, asphalt mixture and method for preparing the same

Abstract

The present application relates to the technical field of asphalt modification, and particularly relates to a self-healing modified asphalt, asphalt mixture and a preparation method thereof. The self-healing modified asphalt comprises the following raw materials: base asphalt, organic modified montmorillonite and bagasse fiber. The added weight of the organic modified montmorillonite accounts for 0.5-5% of the weight of the base asphalt. The particle size of the organic modified montmorillonite is 0.5-30 microns, and the organic modified montmorillonite has a layered structure. The added weight of the bagasse fiber accounts for 0.1-5% of the weight of the base asphalt. The organic modified montmorillonite-bagasse fiber modified asphalt has low viscosity, small softening point and high penetration. The modified asphalt performs well in the crack repair process. The addition of the organic modified montmorillonite and the bagasse fiber significantly improves the self-healing performance of the modified asphalt. The self-healing performance of the organic modified montmorillonite-bagasse fiber modified asphalt is significantly better than that of rubber asphalt.

Description

Technical Field

[0001] This invention relates to the field of asphalt modification technology, and in particular to a self-healing modified asphalt, asphalt mixture, and its preparation method. Background Technology

[0002] With the rapid development of modern transportation infrastructure, asphalt pavement, as the main form of road surface, has seen its performance improvement and service life extension become a research focus. However, traditional base asphalt has certain limitations in terms of high-temperature stability, fatigue resistance, and self-healing ability. Under complex service environments such as frequent extreme weather and increased heavy traffic, it commonly suffers from high-temperature rutting, fatigue cracking, and other defects, leading to increased life-cycle maintenance costs and carbon emissions.

[0003] To overcome this technical challenge, modified asphalt material systems have undergone continuous innovation and development. Patent CN118324447 A discloses a modified steel slag asphalt mixture and its preparation method. The modified steel slag asphalt mixture comprises the following raw materials in parts by weight: 100 parts steel slag aggregate, 6-8 parts steel slag modifier, 4-6 parts asphalt, and 4-12 parts mineral powder; wherein, the steel slag content in the steel slag aggregate is 75wt%-100wt%; the steel slag aggregate forms the skeleton of the modified steel slag asphalt mixture, and a layer of steel slag modifier is bonded and coated on the surface of the steel slag aggregate. This steel slag modifier bonds with the asphalt to form a cross-linked spatial network structure; the mineral powder adheres to the asphalt. Patent CN120098458 A relates to a composite modifier for modified asphalt by grafting rubber powder with nanomaterials. In the modified asphalt, the rubber powder is modified by amylation and the nanomaterials are modified by carboxylation. By grafting the rubber powder and nanomaterials, the advantages of the rubber powder and nanomaterials can be fully utilized, and the high temperature, low temperature and water stability properties of asphalt and asphalt mixtures can be significantly improved.

[0004] During the service life of a road, asphalt pavement is subject to the combined effects of environmental factors and traffic loads, making it prone to the initiation of micro-cracks. These defects, through propagation and connection, will form macro-cracks, ultimately leading to structural damage to the pavement. The self-healing ability of asphalt materials is the capacity to autonomously repair internal micro-cracks or surface damage without direct external intervention, relying on their inherent properties or external stimuli, thus improving the mechanical strength of the asphalt material after self-healing. Existing modified asphalt can improve high-temperature performance and fatigue cracking resistance, but its self-healing performance varies significantly depending on the type and dosage of modifiers. As asphalt materials age, self-healing performance is significantly weakened, and the self-healing process is highly dependent on temperature and time. Overall, the self-healing performance of existing modified asphalt is relatively poor. Summary of the Invention

[0005] The purpose of this invention is to solve the problem of poor self-healing performance of existing modified asphalt, and to provide a self-healing modified asphalt, asphalt mixture and its preparation method.

[0006] In a first aspect, the present invention provides a self-healing modified bitumen comprising the following raw materials: base bitumen, organically modified montmorillonite, and bagasse fiber;

[0007] The organic modified montmorillonite is added at a weight of 0.5-5% of the base asphalt, the particle size of the organic modified montmorillonite is 0.5-30 μm, and the organic modified montmorillonite has a layered structure.

[0008] The weight of the bagasse fiber added accounts for 0.1% to 5% of the weight of the matrix asphalt.

[0009] In the technical solution of this invention, the modified asphalt includes base asphalt, organically modified montmorillonite, and bagasse fiber. The base asphalt is modified by the combined action of organically modified montmorillonite and bagasse fiber. The organically modified montmorillonite has a layered structure with a particle size of 0.5–30 μm and is added at a weight of 0.1–5%. Multiple experiments by the inventors have revealed that the addition of organically modified montmorillonite significantly enhances the self-healing ability of asphalt, effectively improving the repair efficiency of asphalt for microcracks, especially exhibiting superior stability and anti-aging properties under high-temperature conditions. Simultaneously, the addition of bagasse fiber, at a weight of 0.1–5%, increases the viscosity of the asphalt and improves its adsorption properties, significantly enhancing the asphalt's resistance to rutting, low-temperature cracking, aging, and fatigue. Research results confirm that the asphalt modified with organically modified montmorillonite-bagasse fiber has lower viscosity, a smaller softening point, and higher penetration, exhibiting excellent performance in crack repair.

[0010] By incorporating organically modified montmorillonite and bagasse fiber into the matrix asphalt, a composite modified asphalt is prepared. Through the synergistic integration of the unique performance advantages of organically modified montmorillonite and bagasse fiber, the synergistic effect of the two forms a multi-dimensional performance enhancement system, achieving the dual goals of improving the functionality of asphalt materials and green and low-carbon transformation.

[0011] Preferably, the added weight of the organically modified montmorillonite accounts for 1 to 4% of the weight of the base asphalt, and the added weight of the bagasse fiber accounts for 1 to 4% of the weight of the base asphalt.

[0012] More preferably, the organically modified montmorillonite accounts for 1-2% of the weight of the base asphalt, and the bagasse fiber accounts for 1-2% of the weight of the base asphalt. Specifically, the organically modified montmorillonite accounts for 1% of the weight of the base asphalt, and the bagasse fiber accounts for 2% of the weight of the base asphalt.

[0013] Preferably, the base asphalt is at least one of 70# or 90#.

[0014] Preferably, the performance requirements of the base asphalt are: penetration 60~80mm, softening point ≥46℃, and ductility ≥100cm.

[0015] Preferably, the bagasse fiber has a fiber length of ≤6mm and an ash content of 13~23%.

[0016] More preferably, the oil absorption rate of the bagasse fiber is 5 to 9.

[0017] Preferably, the organically modified montmorillonite has a moisture content of ≤5% at 105℃ and a bulk density of 0.25~0.45g / cm³. 3 .

[0018] Preferably, the organically modified montmorillonite has a layered structure with an interlayer spacing greater than 1.1 nm. The interlayer spacing is calculated using the Bragg equation based on the position of the first diffraction peak in the XRD pattern of the organically modified montmorillonite. The interlayer spacing was calculated. When organically modified montmorillonite has a large interlayer spacing, it is conducive to the formation of intercalation structures through nano-exfoliation, which can improve the self-healing properties of modified asphalt.

[0019] A second aspect of the present invention provides a method for preparing self-healing modified asphalt, comprising the following steps:

[0020] S1. First, heat the base asphalt to 120-160°C, so that the asphalt is in a molten and flowing state;

[0021] S2. Add the organic modified montmorillonite mentioned above to a self-healing modified asphalt, stir to form a uniform dispersion system, and perform high-speed shearing at 150-170℃;

[0022] S3. Add the bagasse fiber to the self-healing modified asphalt, and continue stirring until a uniform mixture is achieved. Perform low-speed shearing at 140-160°C to obtain the modified asphalt.

[0023] In the above technical solution, organic modified montmorillonite-bagasse fiber modified asphalt is prepared by melt blending.

[0024] Preferably, the high-speed shearing process in step S2 is as follows: shearing at a shearing rate of 4500–5500 r / min for 40–50 min. During the preparation process, due to the small particle size of the organically modified montmorillonite material, it is prone to agglomeration, leading to uneven dispersion in the asphalt. The shearing rate and shearing time are key factors affecting the modified material. After numerous experiments, the inventors determined the high-speed shearing process to be: shearing at a shearing rate of 4500–5500 r / min for 40–50 min.

[0025] Preferably, the low-speed shearing process in step S3 is as follows: shearing at a shearing rate of 200-400 r / min for 25-40 min.

[0026] The present invention also provides the application of the above-mentioned self-healing modified asphalt in road engineering.

[0027] The present invention also provides an asphalt mixture, the asphalt mixture comprising the following components in parts by weight:

[0028] The mixture comprises 10-30 parts coarse aggregate, 60-150 parts fine aggregate, 120-300 parts filler, and 10-20 parts modified asphalt, wherein the modified asphalt is a self-healing modified asphalt as described above or prepared according to the preparation method of the self-healing modified asphalt described above.

[0029] Preferably, the asphalt mixture further includes 1 to 5 parts of anti-stripping agent.

[0030] Preferably, the asphalt mixture is of type AC-13 or AC-16.

[0031] Preferably, when the asphalt mixture is of type AC-13, the gradation ratio of the coarse aggregate and the fine aggregate is as follows: 100% by mass passing through a 16mm square-hole sieve, 96-99.5% by mass passing through a 13.2mm square-hole sieve, 65-72% by mass passing through a 9.5mm square-hole sieve, 35-40% by mass passing through a 4.75mm square-hole sieve, 25-28% by mass passing through a 2.36mm square-hole sieve, 16-20% by mass passing through a 1.18mm square-hole sieve, 11-14% by mass passing through a 0.6mm square-hole sieve, 8.5-10% by mass passing through a 0.3mm square-hole sieve, 6.5-7.5% by mass passing through a 0.15mm square-hole sieve, and 4.5-6% by mass passing through a 0.075mm square-hole sieve.

[0032] Preferably, the asphalt mixture is prepared by the following method:

[0033] The coarse aggregate and the fine aggregate are mixed and dry-mixed for 40-80 seconds; then the modified asphalt is added and wet-mixed for 1-2 minutes; finally, the filler is added and stirred for 40-120 seconds to obtain an asphalt mixture.

[0034] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0035] 1. This invention provides a self-healing modified asphalt. The organically modified montmorillonite-bagasse fiber modified asphalt has lower viscosity, lower softening point and higher penetration. The modified asphalt performs excellently in crack repair. The addition of organically modified montmorillonite and bagasse fiber significantly improves the self-healing performance of the modified asphalt. The self-healing performance of the organically modified montmorillonite-bagasse fiber modified asphalt is significantly better than that of rubber asphalt.

[0036] 2. The modified asphalt provided by this invention incorporates organic modified montmorillonite-bagasse fiber to improve the asphalt's rutting resistance factor, increase the critical temperature, reduce temperature sensitivity, increase elastic recovery ability, and improve the modified asphalt's high-temperature deformation resistance. It also exhibits good anti-aging properties and effectively improves the adhesion of the modified asphalt.

[0037] 3. The modified asphalt mixture of this invention innovatively combines agricultural waste bagasse fiber with organically modified montmorillonite material. In terms of sustainable development, it not only realizes the high-value utilization of solid waste resources and improves the service performance of modified asphalt pavement, but also reduces carbon emissions throughout the entire life cycle. It not only provides a new technical solution for improving the durability of asphalt pavement, but also has important theoretical value and practical significance in the dimensions of waste resource utilization, nanomaterial engineering application and low-carbon road construction, and strongly supports the green transformation of transportation infrastructure. Attached Figure Description

[0038] Figure 1 The curve of the anti-rutting factor as a function of temperature in test example 4;

[0039] Figure 2 The curve showing the phase angle versus temperature in Test Example 4;

[0040] Figure 3 MSCR test results under different stresses: (a) 0.1 kPa; (b) 3.2 kPa;

[0041] Figure 4 This is a graph showing the relationship between shear stress and shear strain.

[0042] Figure 5 For each asphalt yield strain diagram;

[0043] Figure 6 Self-healing curves of organically modified montmorillonite-bagasse fiber modified bitumen with different added weights: (a) M1Z1; (b) M1Z2; (c) M1Z3; (d) M2Z1; (e) M2Z2; (f) M2Z3; (g) M3Z1; (h) M3Z2; (i) M3Z3;

[0044] Figure 7 Self-healing properties of organically modified montmorillonite-bagasse fiber modified asphalt with different added weights;

[0045] Figure 8 A graph showing the trend of self-healing under different types and degrees of aging of asphalt;

[0046] Figure 9 Charts showing the yield strain of different asphalt materials;

[0047] Figure 10 A spatial plot of the GR constants for different asphalts;

[0048] Figure 11 represents the GR constant for different asphalts;

[0049] Figure 12 The graph shows the pull-out test results for different asphalt materials. Detailed Implementation

[0050] The present invention will now be described in further detail with reference to specific embodiments. However, this should not be construed as limiting the scope of the present invention to the following embodiments; all technologies implemented based on the content of the present invention fall within the scope of the present invention.

[0051] Example 1

[0052] This embodiment provides a self-healing modified asphalt, comprising the following raw materials: base asphalt, organically modified montmorillonite, and bagasse fiber; the added weight of organically modified montmorillonite accounts for 0.5-5% of the weight of the base asphalt, and the particle size of the organically modified montmorillonite is 0.5-30 μm; the organically modified montmorillonite has a layered structure; the added weight of bagasse fiber accounts for 0.1-5% of the weight of the base asphalt, the fiber length of the bagasse fiber is ≤6 mm, and the ash content is 13-23%. The preparation method of the modified asphalt includes the following steps:

[0053] S1. First, heat 800g of base asphalt to 135℃, and make the asphalt melt and flow under constant temperature conditions; the base asphalt is Donghai 70# base asphalt, and the organic modified montmorillonite is a layered silicate clay mineral.

[0054] S2. Add the designed weight of organic modified montmorillonite. During continuous mechanical stirring, add the organic modified montmorillonite gradually in batches. Stir with a glass rod for 5 minutes until a uniform dispersion system is formed. Visually confirm that there are no agglomerated particles.

[0055] The mixture was then heated to 140°C and the high-speed shearing device was started. Under the condition of removing the external heat source, high-speed shearing was carried out at 150-170°C and the mixture was continuously stirred for a certain period of time to prepare asphalt with added weight of organic modified montmorillonite.

[0056] S3. While maintaining the asphalt's fluidity, add the designed weight of bagasse fiber in batches. Continue heating to maintain the asphalt's fluidity while stirring until the fiber and asphalt are evenly mixed. Perform low-speed shearing at 150℃±5℃ to obtain the modified asphalt. Before adding, the bagasse fiber is dried in an oven at 60℃. During stirring, the stirring rod should be extended to the bottom of the container as much as possible to ensure the fiber is evenly dispersed in the asphalt, thus maximizing the fiber reinforcement effect and preventing asphalt aging. The low-speed shearing process is 300 r / min + 30 min.

[0057] For the aforementioned raw materials, organically modified montmorillonite is a layered structure prepared using intercalation, sol-gel, and in-situ polymerization methods. This layered structure consists of two layers of silicon-oxygen tetrahedra sandwiching a layer of aluminum-oxygen octahedra, forming a "sandwich" structure. This layered structure is a key structural feature for its use as a nanofiller or reinforcing material. Exchangeable cations exist between the layers. Organically modified montmorillonite can be homemade or commercially available; commercially available nano-montmorillonite is also available. Bagasse fiber is a natural plant fiber extracted from the residue (bagasse) after sugarcane processing. It possesses environmentally friendly, renewable, and biodegradable properties.

[0058] The performance requirements for the base asphalt are: penetration 60~80mm, softening point ≥46℃, and ductility ≥100cm; the organic modified montmorillonite has a moisture content ≤5% at 105℃ and a bulk density of 0.25~0.45g / cm³. 3 The interlayer spacing is greater than 1.1 nm; the fiber length of bagasse fiber is ≤6 mm, the oil absorption rate is 5~9, and the ash content is 13~23%.

[0059] Test Example 1

[0060] This test case investigated the effects of different types of organically modified montmorillonite on the properties of modified asphalt. Three types of organically modified montmorillonite—DK4, HFGEL-170, and WSG-PN06—were used. DK4 is a dual-long-chain alkylammonium modified montmorillonite, HFGEL-170 is an organoammonium modified organomontmorillonite, and WSG-PN06 is a biodegradable plastic modified montmorillonite. The montmorillonite content in all three types was >96%. The particle size was 845 mesh for DK4, 1270 mesh for HFGEL-170, and 800 mesh for WSG-PN06. At 105℃, the moisture content was ≤5%, and the bulk density was 0.25-0.45 g / cm³ for all three types. 3SEM analysis was performed on three types of organically modified montmorillonite. DK4 organically modified montmorillonite showed no edge curling and had relatively little adhering material. HFGEL and WSG organically modified montmorillonite showed obvious edge curling and more surface adhering material, especially WSG. This may be due to incomplete reaction between the organic modifier and the organically modified montmorillonite, potentially affecting the intercalation mixing between asphalt and organically modified montmorillonite. XRD analysis was performed on the three types of organically modified montmorillonite. Based on the position of the first diffraction peak, the interlayer spacing could be calculated using the Bragg equation. The interlayer spacings of DK4, HFGEL, and WSG were calculated and are shown in Table 1.

[0061] Table 1 Calculation results of interlayer spacing

[0062]

[0063] The interlayer spacing of different organically modified montmorillonite varies. WSG has the smallest interlayer spacing, only 1.03 nm, indicating that asphalt components have difficulty diffusing into the interlayers of the organically modified montmorillonite, making it difficult to form an interlayer structure. In contrast, DK4 and HFGEL have interlayer spacings that are 21.36% and 26.21% higher than WSG, respectively, indicating larger interlayer spacings that facilitate nano-exfoliation and the formation of intercalation structures, thus improving the performance of organically modified montmorillonite-modified asphalt. Based on the SEM and XRD test results, the use of WSG-type organically modified montmorillonite will not be considered in subsequent tests.

[0064] Two types of organically modified montmorillonite (DK4 and HFGEL) were selected to prepare modified asphalt using the method in Example 1. Donghai 70# base asphalt was used to prepare modified asphalt with different organically modified montmorillonite addition weights (1%, 2%, 3%, 4%). The addition weight of bagasse fiber accounted for 2% of the weight of the base asphalt. The three major indicators of the asphalt were tested for the original sample and after short-term aging to analyze the influence of organically modified montmorillonite material on the asphalt performance. The results are shown in Table 2. The short-term aging condition was aging at 163℃ for 5 hours.

[0065] Table 2 Test data of three major indicators for the original samples and short-term aging of two types of modified asphalt.

[0066]

[0067] The data in the table show that organically modified montmorillonite has a significant impact on asphalt properties, manifested as a decrease in ductility and an increase in softening point. The effect on ductility is more pronounced, but the effect on penetration is inconsistent. This is because the addition of organically modified montmorillonite disperses in the asphalt, forming intercalation and exfoliation structures that hinder asphalt movement, thus lowering the softening point of the modified asphalt. The formed intercalation structures act as heat-resistant barriers, hindering heat transfer and limiting the high-temperature movement of asphalt molecules, delaying the asphalt softening process and leading to an increase in the softening point. The two organically modified montmorillonite materials have different effects on asphalt properties. DK4 shows a more significant improvement in the three major indicators and anti-aging properties of asphalt. At the same added weight, the increase in softening point and the decrease in ductility of DK4-modified asphalt are both greater than those of HFGEL, indicating that DK4 has a better effect on improving asphalt properties. Table 3 shows a comparison of the softening point increases of the two modified asphalts before and after aging. It can be observed that the softening point increase of DK4 modified asphalt under different addition weights is less than that of HFGEL modified asphalt, indicating that DK4 organic modified montmorillonite has a better effect on improving the anti-aging performance of asphalt than HFGEL.

[0068] Table 3. Softening point increment of two modified asphalts

[0069]

[0070] Test Example 2

[0071] This test example investigated the effects of different fibers on the properties of modified asphalt. Bagasse fiber and flocculent lignin fiber were used. The bagasse fiber raw material was provided by Guangxi Jiaoke Group Co., Ltd. The bagasse fiber had a fiber length of 3.18 mm, an oil absorption rate of 6.2 times, and an ash content of 16.4%. The lignin fiber had a fiber length of 6 mm, an oil absorption rate of 7.66 times, and an ash content of 18%. Modified asphalt was prepared using the method described in Example 1, using Donghai 70# base asphalt. Modified asphalt with different fiber addition weights (2%, 3%, and 4%) was prepared. The organic modified montmorillonite used was DK4, with an addition weight accounting for 2% of the base asphalt weight. Three major performance indicators were tested on the modified asphalt with various addition weights of bagasse fiber and lignin fiber. The results are shown in Table 4.

[0072] Table 4. Test results of the three major indicators

[0073]

[0074] After being dispersed in asphalt, fibers form a three-dimensional network framework, which combines with asphalt molecules to form a stable cross-linked structure. This cross-linked structure significantly improves the elastic modulus of asphalt and restricts the slippage of molecular chains. The fiber network can maintain its structural integrity at high temperatures, effectively resisting the flow deformation of asphalt, leading to an increase in softening point and a decrease in penetration. Because the cross-linked network structure formed by fibers directly inhibits the stretching orientation and cooperative movement of molecular chains, and the fibers may adsorb lightweight components, causing the asphalt colloid to harden, the ductility of fiber-modified asphalt is significantly reduced. The two fiber materials have different effects on the properties of asphalt, with lignin fiber having a more significant impact on softening point and average penetration. When the fiber addition weight is 2%, the ductility change trends of the two modified asphalts are basically the same, but lignin fiber increases the softening point to 62.9℃, which is higher than that of bagasse fiber (57.6℃). Moreover, with the increase of the addition weight, the increase in softening point of lignin fiber is more significant, and the penetration of lignin fiber asphalt is lower than that of bagasse fiber asphalt at the same addition weight. This is mainly because lignin fibers have a dense structure that effectively hinders the free movement of asphalt molecular chains. Their surface is rich in polar groups such as hydroxyl groups, enabling them to form stronger physical adsorption and chemical bonds with the resins and asphaltenes in asphalt. Bagasse fibers, on the other hand, are shorter and less flexible, easily agglomerating, and have fewer polar groups, resulting in weaker interfacial bonding with asphalt, relying primarily on physical filling. After short-term aging, the decrease in lignin fiber is more significant, possibly because the fiber molecular chains break more severely during aging, leading to a greater decrease in softening point and penetration than bagasse fibers. Consequently, the modified asphalt exhibits lower anti-aging properties, making bagasse fibers superior to lignin fibers in terms of anti-aging performance.

[0075] SEM analysis of bagasse fiber and lignin fiber revealed that bagasse fiber exhibits a typical columnar dispersion morphology with a distinct surface texture, while lignin fiber presents a wide, thin, sheet-like structure. The fibers are long and slender and prone to entanglement. This morphological characteristic not only affects their dispersion in the asphalt matrix but may also lead to impurity inclusions. Furthermore, bagasse fiber possesses a unique honeycomb-like cavity structure, formed by interconnected thin-walled cells creating a three-dimensional network that effectively accommodates the asphalt matrix material. In contrast, lignin fiber has a smooth surface and lacks internal cavities. The crystallinity index of lignin fiber is higher than that of bagasse fiber. Bagasse fiber is also softer, making it easier for asphalt to adsorb, thus improving the adhesion between asphalt and fiber.

[0076] Test Example 3

[0077] This test example uses the method of Example 1 to test the effect of three different high-speed shear processes in step S2 on the dispersibility of organically modified montmorillonite. The three processes are 3000rpm+30min, 5000rpm+45min and 7000rpm+45min, respectively, for the preparation of modified asphalt. During the preparation process, the weight of bagasse fiber added accounts for 2% of the weight of the matrix asphalt. The penetration, ductility and softening point of the asphalt are used as the three major indicators for evaluation. The test results are shown in Table 5.

[0078] Table 5. Test data of the three major indicators for each process

[0079]

[0080] The data in the table show that different shearing processes affect the properties of modified asphalt, with a much stronger impact on ductility than on penetration and softening point. As shearing time and rate increase (from process 1 to process 3), shear strength increases, penetration decreases, and softening point rises. Considering both processing efficiency and material dispersion, the high-speed shearing process in step S2 is 5000 rpm for 45 minutes.

[0081] Test Example 4

[0082] In this test example, different modified asphalts were prepared using the modified asphalt preparation method in Example 1. The weights of DK4 organic modified montmorillonite added were 1%, 2%, and 3%, respectively, and the weights of bagasse fiber added were 1%, 2%, and 3%, respectively. The high-speed shearing process in step S2 was 5000 rpm + 45 min. The modified asphalt samples are shown in Table 6. The high-temperature performance, fatigue performance, self-healing performance, anti-aging performance, and adhesion performance of different modified asphalts were tested.

[0083] Table 6. Added weight of modified asphalt samples

[0084]

[0085] (1) High temperature performance

[0086] Temperature scanning was performed on different modified asphalts. The tests were conducted according to the AASHTO T315 standard. The high-temperature performance of asphalt was evaluated using the rutting factor (G* / sinδ), phase angle (δ), critical temperature (THS), and temperature sensitivity.

[0087] like Figure 1As shown, with the increase of the added weight of organically modified montmorillonite and bagasse fiber, the rutting resistance factor generally shows a trend of first increasing and then decreasing. When the added weight of organically modified montmorillonite is 1% and 3%, the trend shows a trend of first increasing and then decreasing with the increase of the added weight of bagasse fiber. When the added weight of organically modified montmorillonite is 2%, the trend shows a trend of first decreasing and then increasing. Among them, the rutting factors of M1Z1 and M2Z3 are the lowest and highest values ​​for each added weight, which are 2.69 kPa and 3.97 kPa, respectively. The effect of added bagasse fiber weight is consistent with that of added organic modified montmorillonite, indicating that both organic modified montmorillonite and bagasse fiber modifiers can effectively improve the high-temperature rutting resistance of asphalt. However, the effect is affected by the added weight; both excessively high and low addition weights are detrimental to the rutting resistance of modified asphalt. The main reason is that if the addition weight is too low, the organic modified montmorillonite and bagasse fiber cannot form an effective network structure, leading to a decrease in the rutting resistance factor of the asphalt. If the addition weight is too high, the modified materials are difficult to disperse, resulting in agglomeration and ultimately stress concentration, further reducing the rutting resistance factor of the asphalt. Organic modified montmorillonite, with its layered structure, forms a three-dimensional network structure in asphalt, restricting the flow of asphalt molecules and enhancing intermolecular forces, thus increasing viscosity. Furthermore, the strong interlayer forces of organic modified montmorillonite allow it to interact strongly with polar molecules in the asphalt, increasing the cohesive force of the asphalt and making it more difficult for the asphalt to deform at high temperatures, thereby improving the rutting resistance factor. Bagasse fiber further improves rheological properties and enhances resistance to deformation by providing toughness and strength, dispersing stress and absorbing lightweight components.

[0088] As temperature rises, the phase angle of organically modified montmorillonite-bagasse fiber modified asphalt gradually increases, such as... Figure 2 As shown, the phase angle of the organically modified montmorillonite-bagasse fiber modified asphalt is lower than that of the base asphalt, proving that it can still maintain excellent elastic recovery performance under high temperature conditions, effectively improving the deformation resistance of the organically modified montmorillonite-bagasse fiber asphalt at high temperatures.

[0089] The critical temperatures of organically modified montmorillonite-bagasse fiber-modified asphalt were all higher than those of the base asphalt, as shown in Table 7. Organically modified montmorillonite and bagasse fiber effectively increased the critical temperature of asphalt. Specifically, M1Z1 modified asphalt increased by 2.32℃ compared to the base asphalt, while M3Z2 increased by 5.69℃. This indicates that the addition of modifiers effectively improved the high-temperature performance of asphalt, but this was significantly affected by the weight of the modifier added. The critical temperatures of organically modified montmorillonite-bagasse fiber-modified asphalt, regardless of the added weight, were all lower than those of rubber asphalt, but the difference was small; the critical temperature of M3Z2 was only 2.03℃ lower than that of rubber asphalt.

[0090] Table 7 Critical Temperatures of Different Asphalts

[0091]

[0092] The deformation recovery characteristics and resistance to permanent deformation of organically modified montmorillonite composite bagasse fiber modified asphalt were tested using MSCR (multi-stress creep recovery) according to AASHTO T350-14 standard. Results under different stresses are shown below. Figure 3 As shown, compared with basic asphalt materials, composite modified asphalt exhibits superior delayed deformation characteristics, mainly due to the interfacial bonding effect between organically modified montmorillonite and bagasse fiber. Among them, M1Z3 type composite modified asphalt exhibits the best rutting resistance, primarily because the addition of fibers adsorbs lighter components in the asphalt, thereby increasing the proportion of elastic components. The fibers form a perfect spatial network in the asphalt, improving the asphalt binder's resistance to high-temperature deformation. Simultaneously, the organically modified montmorillonite forms a delamination structure in the asphalt, which hinders the flow and deformation of asphalt molecules at high temperatures. Rubber-modified asphalt, due to its stable internal network structure, suppresses its deformation under external forces, resulting in a strain much smaller than other asphalts.

[0093] (2) Fatigue performance analysis

[0094] Linear amplitude scanning (LAS) testing of asphalt can simulate the repeated action of traffic loads on asphalt, accelerate the fatigue damage process, obtain DC curves, and analyze the material damage characteristics through DC curve analysis to evaluate the fatigue performance of asphalt binder under repeated loading. The LAS test is based on the AASHTO TP101 technical standard. With the gradual increase of shear strain, the shear stress changes of modified asphalt and base asphalt show similar trends, both first rising to a peak and then decreasing. However, the shear stress of rubber asphalt continuously increases within the strain range of 0% to 30%. This indicates that during the strain increase process, both base asphalt and modified asphalt exhibit fatigue damage, while rubber asphalt does not show fatigue damage at 30% strain. This suggests that the fatigue resistance of rubber asphalt is far superior to that of base asphalt and organically modified montmorillonite-bagasse fiber modified asphalt. Figure 4 and Figure 5 As shown.

[0095] With increasing bagasse fiber content, the yield strength of asphalt initially increases and then decreases. However, increasing the content of organically modified montmorillonite leads to a continuous increase in the yield strength of the asphalt. When the bagasse fiber content is 1%, the yield strains of modified asphalt with 1%, 2%, and 3% organically modified montmorillonite content are 8.25%, 8.41%, and 10.52%, respectively. Low addition weights of organically modified montmorillonite have a negative impact on the yield strain of the modified asphalt. However, with increasing addition weight, the yield strain continuously increases, indicating that in the low addition weight stage, the organically modified montmorillonite layers are not fully exfoliated, easily forming structural defects. High addition weights achieve effective intercalation and exfoliation, and the rigid support and barrier effect of the organically modified montmorillonite nanoparticles, in conjunction with the fiber network, jointly improve the material's yield strength. When the organically modified montmorillonite content is 1%, the yield strains of modified asphalt with 1%, 2%, and 3% bagasse fiber content are 8.25%, 10.21%, and 8.20%, respectively, all lower than that of the base asphalt. Low addition weight of bagasse fiber results in poor interaction with pitch, leading to a decrease in yield strain. As the addition weight increases, the fiber forms a network structure, improving the yield strength. However, when the addition weight is too high, fiber agglomeration and stress concentration cause the yield strain to decrease.

[0096] (3) Self-healing performance analysis

[0097] To evaluate the self-healing ability of asphalt materials, the self-healing performance of asphalt and its adhesive was studied using DSR and other equipment. The DSR test temperature was 20℃, with a strain loading of 5%, parallel plates with a diameter of 8 mm, a plate spacing of 2 mm, an interval time of 1800 s, and a damage degree of 35%. The results are as follows: Figure 6 , Figure 7 As shown, where The initial dynamic shear modulus of the asphalt before healing. The final dynamic modulus of asphalt before healing. The slope of the complex modulus decay over loading time is used to characterize the self-healing properties of asphalt.

[0098] As shown in the figure, when the weight of bagasse fiber added is 1%, the self-healing performance first increases and then decreases with the increase of the weight of organically modified montmorillonite. When the weight of bagasse fiber added is 2% and 3%, the self-healing performance continuously decreases with the increase of the weight of organically modified montmorillonite. This indicates that there is an optimal weight for both organically modified montmorillonite and bagasse fiber. Among them, the modified asphalt in groups M1Z2 and M2Z1 has better self-healing performance than other weights, indicating that the self-healing performance is optimal when the total weight of organically modified montmorillonite and bagasse fiber added is 3%. The self-healing performance of modified asphalt is affected by the synergistic effect of the weight of organically modified montmorillonite and bagasse fiber added, which is 1% and 2% respectively. This is mainly because the modifiers are more uniformly dispersed in the asphalt with the increase of the weight of organically modified montmorillonite and bagasse fiber added. Organically modified montmorillonite constructs a stable composite system within asphalt through intercalation or exfoliation. This microstructure effectively inhibits the migration and dissociation of asphalt molecular chains under alternating loads, strengthening the interactions between components. Bagasse fibers exist in a disordered, dispersed form within the asphalt matrix, forming an interwoven network structure in three-dimensional space. This not only achieves synergistic deformation with the asphalt but also delays microcrack initiation and plastic rheological processes through physical barrier effects. The adhesion between the fiber and asphalt interface effectively dissipates stress concentration. Under external forces, the elastic deformation of the fibers exhibits energy storage characteristics. After unloading, the release of elastic potential energy drives the material system to return to its initial state. This dynamic response mechanism significantly enhances the self-healing performance of the asphalt composite material. With continued increases in added weight, organically modified montmorillonite and bagasse fibers agglomerate in the asphalt, resulting in more asphalt coating on the fiber surface. Furthermore, higher added weights lead to fiber clumping, reducing self-healing performance. Since M1Z2 has the highest self-healing performance, this addition weight was used in the subsequent analysis of factors affecting self-healing and anti-aging performance tests for organic modified montmorillonite-bagasse fiber modified asphalt.

[0099] Unaged modified asphalt exhibits better self-healing properties than base asphalt, with organically modified montmorillonite-bagasse fiber modified asphalt showing superior self-healing properties compared to rubber asphalt. For example... Figure 8As shown, the self-healing properties of rubber asphalt and organically modified montmorillonite-bagasse fiber-modified asphalt with the optimal addition weight were improved by 112.59% and 132.73%, respectively, compared to the base asphalt. The intercalation / exfoliation composite system constructed by organically modified montmorillonite in the asphalt matrix can effectively inhibit the migration and breakage of molecular chains under fatigue loads, strengthen intermolecular interactions, and at the macroscopic level, this is reflected in the improved self-healing ability of the material. The incorporation of organically modified montmorillonite also enhances the stiffness of the asphalt system and promotes the rapid repair of microscopic defects. Bagasse fiber-modified asphalt endows the material with excellent viscoelastic response and self-healing properties through a three-dimensional network formation mechanism. When organically modified montmorillonite and bagasse fiber work synergistically, the interface coupling between the two constructs a denser multi-level structure, which not only significantly improves the fatigue resistance and durability of the composite system, but also achieves a synergistic enhancement of self-healing efficiency. Under short-term aging conditions, the self-healing coefficients of base asphalt, M1Z2 asphalt, and rubber asphalt decreased by 4.64, 10.87, and 10.88 respectively compared to the unaged state. Long-term aging further reduced the self-healing coefficients by 2.05, 6.91, and 6.73. This phenomenon indicates that as the aging process deepens, the content of lightweight components in asphalt gradually decreases, causing the asphalt to gradually transform from a sol-gel type to a gel type. However, organically modified montmorillonite and bagasse fiber exhibited good anti-aging properties, effectively mitigating the negative impact of aging on asphalt fluidity. Under any aging condition, the self-healing performance of asphalt ranked as follows: M1Z2 > rubber asphalt > base asphalt.

[0100] (4) Anti-aging performance analysis

[0101] M1Z2 modified asphalt exhibits better anti-aging properties than base asphalt, and aging has a weaker effect on its yield strain. For example... Figure 9 As shown, the yield strain of base asphalt aged for short and long periods increased by 21.8% and 31.0% respectively compared to the unaged state, indicating that aging leads to hardening and reduced elasticity of the base asphalt. However, the organically modified montmorillonite and bagasse fiber in M1Z2 modified asphalt effectively inhibited the effect of aging on yield strain. This is mainly because the organically modified montmorillonite forms intercalation or exfoliation structures in the asphalt, effectively suppressing the impact of aging. This demonstrates that the anti-aging performance of M1Z2 modified asphalt is superior to that of base asphalt, and the effect of aging on its yield strain is weaker.

[0102] As aging progresses, the risk of cracking in various asphalt materials increases. However, organically modified montmorillonite and bagasse fiber can significantly reduce the impact of aging on cracking risk. Figure 10 and Figure 11As shown, after different degrees of aging, the GR index of both organic modified montmorillonite-bagasse fiber modified asphalt and base asphalt increased to varying degrees, but the increase was different for different asphalts. The GR constants of the base asphalt and M1Z2 after PAV aging were 14.07 and 3.57 kPa, respectively, which were 11.41 and 3.04 kPa higher than those in the unaged state, indicating that M1Z2 asphalt has good anti-aging properties.

[0103] (5) Adhesion performance analysis

[0104] The adhesion properties of asphalt are an important factor affecting the service performance of asphalt pavements. A fully automated pull-out adhesion tester was used to test the adhesion properties of asphalt with different modifier addition weights. Figure 12 As shown, the addition of organically modified montmorillonite and bagasse fiber both improve the adhesion properties of asphalt, and the improvement increases with the increase of the added weight. When the added weight of organically modified montmorillonite and bagasse fiber modified asphalt is 4%, the pull-out strengths are 2.065 and 2.521 MPa, respectively, which are 43.47% and 75.14% higher than those of the base asphalt. This indicates that high added weights of organically modified montmorillonite and bagasse fiber can significantly improve the adhesion of asphalt. This is mainly because the montmorillonite flakes form intercalation or exfoliation structures in the asphalt, increasing the viscosity of the asphalt. The surface of bagasse fiber has natural grooves and microporous structures, which form a physical anchoring effect with the asphalt, increasing the contact area and improving the mechanical interlocking force. At the same time, bagasse fiber adsorbs saturated and aromatic components in the asphalt, promoting the enrichment of resins and asphaltenes and improving the viscosity of the asphalt.

[0105] Example 2

[0106] This embodiment provides an asphalt mixture, which comprises the following components in parts by weight:

[0107] 10-30 parts coarse aggregate, 60-150 parts fine aggregate, 120-300 parts filler, and 10-20 parts modified asphalt.

[0108] In this embodiment, the coarse aggregate is diabase with a gradation of 13.2mm, 9.5mm and 4.75mm, the fine aggregate is mainly limestone, the filler is finely ground limestone ore powder, and the asphalt mixture is AC-13 or AC-16 type.

[0109] Asphalt mixtures are prepared by the following methods:

[0110] Mix coarse and fine aggregates and dry mix for 50-60 seconds; then add modified asphalt and wet mix for 1-2 minutes; finally add filler and mix for 60-80 seconds to obtain asphalt mixture.

[0111] Test Example 5

[0112] This test example is used to test asphalt mixtures with different gradations. The asphalt mixture was prepared using the method in Example 2. The asphalt mixture was of type AC-13, and the aggregate gradation is shown in Table 8. The aggregate was a mixture of coarse and fine aggregates.

[0113] Table 8. Gradation Design of AC-13 Asphalt Mixture

[0114]

[0115] Three groups of asphalt content were set for the asphalt mixture, and two specimens were made for each group. The bulk relative density (γf), stability (MS), flow value (FL), void ratio (VV), aggregate void ratio (VMA), and effective asphalt saturation (VFA) were measured using the Marshall stability test. The test results are shown in Table 9.

[0116] Table 9. Mix design results for three gradations

[0117]

[0118] Based on the data in the table, and considering the test results and actual construction applications, the optimal gradation is gradation one.

[0119] Test Example 6

[0120] This test case was used to test asphalt mixtures with different oil-to-aggregate ratios. The asphalt mixture was prepared using the method in Example 2. This test case used the response surface methodology (RSM) to explore the correlation between multiple independent variables and a single response variable. The weight of organically modified montmorillonite, the weight of bagasse fiber, and the oil-aggregate ratio were selected as influencing factors. The response model was established with bagasse fiber weights of 1%, 2%, and 3% (proportion of the mass of the base asphalt), organically modified montmorillonite weights of 1%, 2%, and 3%, and oil-aggregate ratios of 4%, 5%, and 6%. Gradation type 1 was used. The weights of each modifier added are shown in Table 10.

[0121] Table 10 Response Surface Experimental Design Scheme

[0122]

[0123] The void ratio (VV), aggregate void ratio (VAM), effective asphalt saturation (VFA), and stability (MS) of the above 15 design mix proportions were tested. The test results are shown in Table 11.

[0124] Table 11 Results of Mix Proportion Tests Using Response Surface Methodology

[0125]

[0126] Using the above data, a central composite design method was employed to establish a predictive model for the interaction of four response values ​​(VV, VMA, VFA, and MS) between three influencing factors—the weight of organically modified montmorillonite, the weight of bagasse fiber, and the asphalt-aggregate ratio—in asphalt mixtures. 2 All indicators exceeded 0.9, and the statistical significance test P values ​​were all below the critical value of 0.05. The error distributions of each performance parameter met the normality assumption, and a significant linear correlation was observed between the measured data and the predicted values. The weight of organically modified montmorillonite and the asphalt-aggregate ratio had significant effects on VV, VFA, and MS, while the weight of bagasse fiber had significant effects on VV and VMA. Through comprehensive analysis of the indicators, the optimized asphalt-aggregate ratio was determined to be 4.68%.

[0127] Test Example 7

[0128] This test example uses the method of Example 2 to prepare asphalt mixtures. The gradation is gradation one, which includes 16.5 parts coarse aggregate, 98 parts fine aggregate, 186 parts filler, and 14 parts modified asphalt. The modified asphalt contains 1% DK4 organic modified montmorillonite and 2% bagasse fiber. The asphalt-aggregate ratio is 4.68%. Asphalt mixtures with 1% organic modified montmorillonite and 2% bagasse fiber modified asphalt are used as comparisons. Splitting crack tests, small beam bending tests, and carbon emission evaluations are conducted on different asphalt mixtures.

[0129] (1) Splitting test

[0130] Indirect tensile tests of asphalt mixtures were conducted in accordance with the relevant provisions of the "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" (JTG E20-2011 T 0716). The results of the splitting test are shown in Table 12.

[0131] Table 12 Splitting Test Data

[0132]

[0133] Organically modified montmorillonite and bagasse fiber can effectively improve the splitting properties of asphalt mixtures, and the improvement is more significant with increasing addition weight and blending. Organically modified montmorillonite and bagasse fiber can effectively improve the deformation degree of the main splitting failure zone of the mixture, with bagasse fiber showing a more significant improvement effect.

[0134] (2) Beam bending test

[0135] The test environment for the small beam bending test was -10℃, the loading rate was maintained at 50mm / min, and the test device was equipped with a three-point bending support with a span of 200mm. The laser positioning system was used to ensure that the indenter and the center of the specimen were accurately aligned. After the test, the failure tensile strength, maximum tensile strain and bending stiffness modulus were calculated. The results of the small test are shown in Table 13.

[0136] Table 13 Beam bending test data

[0137]

[0138] Small beam bending tests revealed that organically modified montmorillonite and bagasse fiber can significantly increase the maximum flexural strain of asphalt mixtures. On the one hand, organically modified montmorillonite and bagasse fiber prolong the deformation time of the main flexural failure zone, and on the other hand, they also improve the deformation degree of the main flexural failure zone of the mixture.

[0139] (3) Carbon emission assessment

[0140] One of the advantages of organically modified montmorillonite-bagasse fiber modified bitumen is its green attributes. On the one hand, organically modified montmorillonite is a processed material of inorganic minerals, while bagasse fiber is a product based on waste bagasse. Therefore, conducting relevant carbon emission assessments is beneficial for quantitatively analyzing its green effectiveness.

[0141] This test case uses the Life Cycle Analysis (LCA) method to calculate carbon emissions during the construction and maintenance periods of a proposed asphalt pavement structure. The construction period primarily considers carbon emissions from materials and construction, while the maintenance period primarily considers carbon emissions from typical maintenance technologies. A comprehensive analysis of carbon emissions during both the construction and maintenance periods shows that rubber-modified asphalt pavement has slightly better life cycle carbon emissions than base asphalt pavement, reducing emissions by only 3.36% compared to base asphalt pavement. Organically modified montmorillonite-bagasse fiber-modified asphalt pavement significantly reduces carbon emissions, decreasing them by 12.23% compared to base asphalt pavement. This indicates that organically modified montmorillonite-bagasse fiber-modified asphalt pavement has a significant emission reduction advantage throughout its life cycle.

[0142] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A self-healing modified asphalt, characterized in that, The raw materials include: base bitumen, organically modified montmorillonite, and bagasse fiber; The organic modified montmorillonite is added at 1% of the weight of the base asphalt, the particle size of the organic modified montmorillonite is 0.5-30 μm, the organic modified montmorillonite has a layered structure, and the interlayer spacing of the organic modified montmorillonite is greater than 1.1 nm. The bagasse fiber is added at a weight of 2% of the base asphalt.

2. The self-healing modified asphalt according to claim 1, characterized in that, The base asphalt is at least one of 70# or 90#.

3. The self-healing modified asphalt of claim 1, wherein, The bagasse fiber has a fiber length of ≤6mm and an ash content of 13~23%.

4. A process for the preparation of a self-healing modified bitumen according to any one of claims 1 to 3, characterized in that, Includes the following steps: S1. First, heat the base asphalt to 120-160℃, so that the asphalt is in a molten and flowing state; S2. Add the organically modified montmorillonite, stir to form a uniformly dispersed system, and perform high-speed shearing at 150-170℃; S3. Add the bagasse fiber and continue stirring until a uniform mixture is achieved. Perform low-speed shearing at 140-160°C to obtain modified asphalt.

5. The method of claim 4, wherein the self-healing modified asphalt is prepared by the steps of: The high-speed shearing process in step S2 is as follows: shearing at a shearing rate of 4500-5500 r / min for 40-50 min; the low-speed shearing process in step S3 is as follows: shearing at a shearing rate of 200-400 r / min for 25-40 min.

6. An asphalt mixture characterized in that, The asphalt mixture comprises the following components in parts by weight: The mixture comprises 10-30 parts coarse aggregate, 60-150 parts fine aggregate, 120-300 parts filler, and 10-20 parts modified asphalt, wherein the modified asphalt is a self-healing modified asphalt as described in any one of claims 1-3 or a self-healing modified asphalt prepared by a method according to claim 4 or 5.

7. An asphalt mixture according to claim 6, characterized in that, The asphalt mixture is AC Type 13 or AC Type 16; when the asphalt mixture is AC In type 13, the gradation ratio of the coarse aggregate and the fine aggregate is as follows: 100% by mass passing through a 16mm square-hole sieve, 96-99.5% by mass passing through a 13.2mm square-hole sieve, 65-72% by mass passing through a 9.5mm square-hole sieve, 35-40% by mass passing through a 4.75mm square-hole sieve, 25-28% by mass passing through a 2.36mm square-hole sieve, 16-20% by mass passing through a 1.18mm square-hole sieve, 11-14% by mass passing through a 0.6mm square-hole sieve, 8.5-10% by mass passing through a 0.3mm square-hole sieve, 6.5-7.5% by mass passing through a 0.15mm square-hole sieve, and 4.5-6% by mass passing through a 0.075mm square-hole sieve.

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