Composite fiber modified asphalt mixture and preparation method thereof

Abstract

The invention relates to the technical field of road engineering materials, and particularly discloses a composite fiber modified asphalt mixture and a preparation method thereof. The composite fiber modified asphalt mixture comprises the following raw materials: asphalt, composite fibers, aggregate and mineral powder, wherein the composite fibers comprise aramid fibers and alkali-treated bamboo fibers. According to the composite fiber modified asphalt mixture provided by the invention, the aramid fibers and the alkali-treated bamboo fibers are synergistically compounded, so that the high-temperature stability, the low-temperature crack resistance, the water damage resistance and other properties of the asphalt mixture are comprehensively improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of road engineering materials, and particularly relates to a composite fiber modified asphalt mixture and a preparation method thereof. BACKGROUND

[0002] As an important material for road construction, the performance of asphalt mixture directly affects the service life and driving safety of the road. The stability of traditional asphalt mixture is low in a high-temperature environment, and rutting is easily formed after repeated rolling of heavy vehicles. In a low-temperature condition, the low-temperature crack resistance of traditional asphalt mixture is poor and stress concentration is easily caused, resulting in low-temperature cracking of the road surface. These structural defects not only accelerate the aging of asphalt mixture, but also bury the hidden danger of driving safety.

[0003] To improve the performance of asphalt mixture, fiber reinforcement technology has gradually become a research hotspot. As a "microscopic reinforcing bar", fiber can improve the performance of the mixture through multiple mechanisms. Its three-dimensional network structure can increase the proportion of structural asphalt, strengthen the interfacial adhesion between asphalt and aggregate, and significantly improve the crack resistance and fatigue resistance of the mixture by bridging cracks and absorbing stress. However, in the prior art, single fiber is often used to modify asphalt mixture, which is one-sided in improving effect. Even if the fiber is compounded, it is only at the level of simple physical mixing, and lacks functional synergy design. At the same time, there is a lack of systematic adaptation research on the fiber content and aggregate gradation. Too much coarse aggregate often leads to uneven distribution of fiber, or too much fine aggregate causes fiber aggregation and blockage, ultimately leading to the problem that high and low temperature resistance, economy and durability are difficult to achieve. SUMMARY

[0004] To overcome the above problems, the present application provides a composite fiber modified asphalt mixture, which realizes the comprehensive improvement of the high-temperature stability, low-temperature crack resistance and water damage resistance of the asphalt mixture through the synergistic compounding of aramid fiber and bamboo fiber.

[0005] In addition, the present application also provides a preparation method of the above-mentioned composite fiber modified asphalt mixture.

[0006] In addition, the present application also provides the application of the above-mentioned composite fiber modified asphalt mixture in road construction.

[0007] To achieve the above-mentioned application purposes, the present application adopts the following technical solutions: In a first aspect, the present application provides a composite fiber modified asphalt mixture, which comprises the following raw materials: asphalt, composite fiber, aggregate and mineral powder; wherein the composite fiber comprises aramid fiber and alkali-treated bamboo fiber; in the composite fiber modified asphalt mixture, the mass percentage content of the composite fiber is 0.1%-0.3%.

[0008] The aramid fiber can bridge aggregate particles, disperse traffic load stress, cooperatively bear stress with aggregate to form a three-dimensional skeleton network, and fundamentally enhance the mechanical support structure of the asphalt mixture; and the bamboo fiber can adsorb asphalt through a multi-stage pore structure, reduce the proportion of free asphalt, increase the content of structural asphalt, and optimize the distribution state of asphalt. The composite fiber modified asphalt mixture provided by the application cooperatively constructs a "adsorption-enhancement" dual-action system by using aramid fiber and alkali-treated bamboo fiber, and improves the high-temperature stability, low-temperature crack resistance and water damage resistance of the asphalt mixture.

[0009] The preferred content of the composite fiber can form a complete three-dimensional network structure in the mixture, which can ensure good reinforcing effect and avoid the problem of fiber agglomeration caused by excessive fiber, and greatly reduce the material cost.

[0010] Optionally, in the composite fiber modified asphalt mixture, the mass percentage content of the aramid fiber is 0.03%-0.09%.

[0011] Optionally, in the composite fiber modified asphalt mixture, the mass percentage content of the alkali-treated bamboo fiber is 0.21%-0.27%.

[0012] Optionally, the mass ratio of the aramid fiber to the alkali-treated bamboo fiber is 1: (3-9).

[0013] The preferred mass ratio of the aramid fiber to the alkali-treated bamboo fiber in the application realizes the complementary effect of the functions of the two types of fibers, so that the mixture has good high-temperature stability and low-temperature crack resistance, the failure strain is increased by more than 35%, and the dynamic stability is still maintained at an ideal level, realizing the synergistic optimization of the performance of the asphalt mixture. In addition, the mass ratio range can be flexibly adjusted according to different engineering requirements such as climate conditions and traffic load.

[0014] Optionally, the length of the aramid fiber is 5-6mm.

[0015] In a preferred embodiment of the application, the properties of the aramid fiber are shown in Table 1 below.

[0016] Table 1 Optionally, the length of the alkali-treated bamboo fiber is 5-6mm.

[0017] In a preferred embodiment of the application, the properties of the alkali-treated bamboo fiber are shown in Table 2 below.

[0018] Table 2 Optionally, the preparation method of the alkali-treated bamboo fiber comprises the following steps: Bamboo fiber was immersed in a 4%-6% NaOH solution at a mass ratio of 1:20 and stirred for 30-40 minutes in a water bath at 60℃±5℃. Then, it was rinsed with deionized water until the pH of the filtrate was close to neutral and dried until the moisture content was ≤2% to obtain alkali-treated bamboo fiber.

[0019] This invention effectively removes lignin and hemicellulose from the surface of bamboo fibers by alkali treatment, thereby increasing the specific surface area of ​​the fibers and providing more contact sites for asphalt adsorption. It also exposes a large number of active hydroxyl groups, which can form strong hydrogen bonds with the polar components in the asphalt and synergistically enhance the interfacial bonding strength with the covalent bond network formed with aramid fibers.

[0020] Optionally, the asphalt includes base asphalt and / or modified asphalt.

[0021] Optionally, the aggregate includes at least one of basalt, limestone, or diabase.

[0022] Optionally, the mineral powder includes limestone mineral powder.

[0023] Optionally, the base asphalt includes 70# asphalt and / or 90# asphalt, and the modified asphalt includes SBS modified asphalt and / or rubber modified asphalt.

[0024] Optionally, the asphalt-aggregate ratio of the composite fiber modified asphalt mixture is 6.2%-6.7%.

[0025] Optionally, the composite fiber modified asphalt mixture has an SMA-13 ​​gradation, with a 4.75mm sieve passing rate of 20%-34%, a 2.36mm sieve passing rate of 15%-26%, and a 0.075mm sieve passing rate of 8%-12%. Preferably, the 4.75mm sieve passing rate is 26%-34%, the 2.36mm sieve passing rate is 20%-25%, and the 0.075mm sieve passing rate is 9%-11%. The preferred 4.75mm sieve passing rate can control the coarse / fine aggregate ratio, avoiding problems such as decreased rutting resistance and uneven fiber dispersion caused by an overly loose skeleton or excessive fine aggregate. The preferred 2.36mm sieve passing rate can balance the skeleton gap and density, ensuring sufficient asphalt coating and ample fiber dispersion space. The preferred 0.075mm sieve passing rate can control the aggregate-asphalt binder thickness, ensuring the formation of a continuous asphalt film.

[0026] Based on the SMA-13 ​​gradation, this application precisely controls the aggregate skeleton structure by controlling the passing rate of key sieve holes, matching the composite fiber content and the asphalt-aggregate ratio, and achieving targeted adaptation to engineering scenarios.

[0027] As a further aspect of the present invention: when asphalt mixtures are applied in heavy-duty traffic areas or high-temperature scenarios such as ports and logistics parks, the passing rate of the 4.75mm sieve is adjusted to 28%±0.5%, the passing rate of the 2.36mm sieve is 21.6%±0.5%, and the passing rate of the 0.075mm sieve is 10.9%±0.5% (coarse skeleton type). The mass ratio of aramid fiber to alkali-treated bamboo fiber is 1:(3-4), and the asphalt-aggregate ratio is 6.2%-6.3%. At this time, the coarse skeleton aggregate provides the main load-bearing structure, the aramid fiber is embedded in the aggregate gaps to form reinforcing ribs, and the low asphalt-aggregate ratio inhibits asphalt flow deformation. The three work together to make the dynamic stability of the mixture reach 6200 times / mm, which can effectively resist rutting deformation under high-temperature conditions. Preferably, the 4.75mm sieve has a pass rate of 28%, the 2.36mm sieve has a pass rate of 21.6%, the 0.075mm sieve has a pass rate of 10.9%, the mass ratio of aramid fiber to bamboo fiber is 1:3, and the asphalt mixture has an asphalt-aggregate ratio of 6.2%.

[0028] As a further aspect of the present invention: when asphalt mixtures are applied to general road scenarios such as highways and urban arterial roads, the passing rate of the 4.75mm sieve is adjusted to 30%±0.5%, the passing rate of the 2.36mm sieve is 24.39%±0.5%, and the passing rate of the 0.075mm sieve is 9.63%±0.5% (balanced type). The mass ratio of aramid fiber to alkali-treated bamboo fiber is 1:(4.5-5.5), and the asphalt-aggregate ratio is 6.3%-6.5%. At this time, the gaps in the median gradation skeleton accommodate the asphalt-fiber composite, the bamboo fiber fills the microcracks and absorbs stress, the aramid fiber inhibits crack propagation, and the medium asphalt-aggregate ratio optimizes the interface coating, thus achieving a good balance between rutting resistance (dynamic stability 5800 times / mm) and crack resistance (breaking strain 2600με). Preferably, the 4.75mm sieve has a pass rate of 30%, the 2.36mm sieve has a pass rate of 24.39%, the 0.075mm sieve has a pass rate of 9.63%, the mass ratio of aramid fiber to bamboo fiber is 1:5, and the asphalt mixture has an asphalt-aggregate ratio of 6.3%.

[0029] As a further aspect of this invention: when asphalt mixtures are applied to crack-resistant freeze-thaw regions, the passing rate of the 4.75mm sieve is adjusted to 32%±0.5%, the passing rate of the 2.36mm sieve is 20.5%±0.5%, and the passing rate of the 0.075mm sieve is 9.4%±0.5% (fine type). The mass ratio of aramid fiber to alkali-treated bamboo fiber is 1:(7-8), and the asphalt-aggregate ratio is 6.5%-6.6%. At this time, the fine gradation reduces the water penetration path, the bamboo fiber thickens the asphalt film through capillary adsorption, and the high asphalt-aggregate ratio compensates for low-temperature hardening. Together, they increase the flexural tensile strength of the mixture to 2800kPa, which can effectively alleviate low-temperature shrinkage stress and prevent temperature cracks in the pavement. It is particularly suitable for application in cold northern regions. Preferably, the 4.75mm sieve has a pass rate of 32%, the 2.36mm sieve has a pass rate of 20.5%, the 0.075mm sieve has a pass rate of 9.4%, the mass ratio of aramid fiber to bamboo fiber is 1:7, and the asphalt mixture has an asphalt-aggregate ratio of 6.5%.

[0030] As a further aspect of this invention: when asphalt mixtures are applied to rainy, high-asphalt-content, and anti-bleeding scenarios, the passing rate of the 4.75mm sieve is adjusted to 34%±0.5%, the passing rate of the 2.36mm sieve is 23.2%±0.5%, and the passing rate of the 0.075mm sieve is 9.4%±0.5% (fine type). The mass ratio of aramid fiber to alkali-treated bamboo fiber is 1:(8-9), and the asphalt-aggregate ratio is 6.6%-6.7%. At this time, the high fine aggregate content forms a mineral oil-locking network, the nanopores of bamboo fiber adsorb free asphalt, and the high asphalt-aggregate ratio is completely anchored, thereby increasing the water damage resistance (TSR value) of the mixture to over 90%, effectively preventing pavement damage caused by water damage, and preventing bleeding problems caused by excessive asphalt. The leakage loss is ≤0.08%, making it particularly suitable for hot and humid rainy areas. Preferably, the 4.75mm sieve has a pass rate of 34%, the 2.36mm sieve has a pass rate of 23.2%, the 0.075mm sieve has a pass rate of 9.4%, the mass ratio of aramid fiber to bamboo fiber is 1:9, and the asphalt mixture has an asphalt-aggregate ratio of 6.7%.

[0031] Secondly, the present invention provides a method for preparing the above-mentioned composite fiber modified asphalt mixture, comprising the following steps: S1. Preheat the asphalt, aggregates, and mineral powder separately; S2. Mix the preheated aggregate with alkali-treated bamboo fiber, then add aramid fiber and continue stirring. Add the preheated asphalt and continue stirring. Finally, add mineral powder and stir to obtain the composite fiber modified asphalt mixture.

[0032] The optimized material mixing sequence not only reduces fiber damage rate but also ensures uniform fiber dispersion. Bamboo fiber is added first, which can pre-form a stable asphalt transition layer on the aggregate surface; then aramid fiber is added, which can orderly construct a three-dimensional reinforcing network at the bamboo fiber-asphalt interface, avoiding fiber damage and ensuring good spatial distribution; finally, asphalt is added to ensure that the fiber is uniformly distributed in the asphalt phase.

[0033] Thirdly, the present invention provides the application of the above-mentioned composite fiber modified asphalt mixture in road construction.

[0034] In summary, the composite fiber-modified asphalt mixture and its preparation method provided by the present invention have the following beneficial effects: This invention achieves a comprehensive improvement in the high-temperature stability, low-temperature crack resistance, and water damage resistance of asphalt mixtures through the synergistic blending of aramid fibers and alkali-treated bamboo fibers. The aramid fibers provide high-strength support and enhance rutting resistance, while the bamboo fibers improve asphalt adsorption, thereby enhancing crack resistance and water stability. Furthermore, the fiber ratio can be flexibly adjusted according to engineering requirements, achieving good results in heavy-load, rainy, or cold regions, making it particularly suitable for the construction of high-grade highways and heavy-load roads. Attached Figure Description

[0035] Figure 1 This is an appearance diagram of aramid fiber in one embodiment of the present invention; Figure 2 This is an appearance diagram of alkali-treated bamboo fiber in one embodiment of the present invention; Figure 3 This is a SEM view of aramid fiber according to one embodiment of the present invention; Figure 4 This is a SEM test image of alkali-treated bamboo fiber according to one embodiment of the present invention. Detailed Implementation

[0036] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0037] Before further describing specific embodiments of the present invention, it should be understood that the scope of protection of the present invention is not limited to the specific embodiments described below; it should also be understood that the terminology used in the embodiments of the present invention is for describing specific embodiments and not for limiting the scope of protection of the present invention.

[0038] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise stated in the invention, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0039] It is worth noting that the mineral powder used in this invention is limestone mineral powder.

[0040] The aramid fibers used in this invention have the physical properties shown in Table 1.

[0041] The alkali-treated bamboo fiber used in this invention has the physical properties shown in Table 2 and is prepared by the following method: bamboo fiber is cut into short fibers with a length of 3-5 mm, and the bamboo fiber is immersed in a 5% NaOH solution at a mass ratio of 1:20. The solution is stirred continuously for 35 min under a 60℃ water bath to remove lignin and hemicellulose from the surface of the bamboo fiber. The solution is then rinsed with deionized water until the pH of the filtrate is 7, and then dried in an 80℃ oven until the moisture content is ≤2% to obtain alkali-treated bamboo fiber.

[0042] The remaining raw materials are all commercially available products, so their sources are not specifically limited.

[0043] Example 1 This embodiment provides a composite fiber-modified asphalt mixture, and the preparation method specifically includes the following steps: (1) According to the gradation table of composite fiber modified asphalt mixture in Table 3, weigh the aggregate (with a 4.75mm sieve passing rate of 28%) and mineral powder respectively, and preheat them in an oven at 175℃ for 4.5h; at the same time, place the asphalt in the oven for heating, adjust to an appropriate temperature and heat for 3.5h to avoid asphalt aging. Weigh the alkali-treated bamboo fiber and aramid fiber according to the mass percentage of the asphalt mixture. The alkali-treated bamboo fiber content is 0.225% of the total mass of the asphalt mixture, and the aramid fiber content is 0.075% of the total mass of the asphalt mixture (i.e., the mass ratio of alkali-treated bamboo fiber to aramid fiber is 3:1). SBS modified asphalt is selected; the aggregate is limestone, and the gradation is SMA-13.

[0044] (2) Asphalt mixture was prepared by mechanical mixing at 180℃. First, the aggregate and bamboo fiber were mixed for 90s to ensure that the fiber and aggregate were fully dispersed. Then, aramid fiber was added and mixed for 90s. Then, asphalt was added and mixed for 90s to ensure that the asphalt and aggregate were fully in contact. Finally, mineral powder was added and mixed for 90 seconds to enhance the asphalt’s ability to coat the fiber. The composite fiber modified asphalt mixture was obtained and named ABF-1.

[0045] Example 2 This embodiment provides a composite fiber modified asphalt mixture, which differs from Embodiment 1 only in that: the 4.75mm sieve passing rate is 30%, the alkali-treated bamboo fiber content is 0.25% of the total mass of the asphalt mixture, and the aramid fiber content is 0.05% of the total mass of the asphalt mixture (i.e., the mass ratio of alkali-treated bamboo fiber to aramid fiber is 5:1). Everything else is the same as in Embodiment 1.

[0046] The resulting composite fiber-modified asphalt mixture was named ABF-2.

[0047] Example 3 This embodiment provides a composite fiber modified asphalt mixture, which differs from Embodiment 1 only in that: the 4.75mm sieve passing rate is 32%, the alkali-treated bamboo fiber content is 0.2625% of the total mass of the asphalt mixture, and the aramid fiber content is 0.0375% of the total mass of the asphalt mixture (i.e., the mass ratio of alkali-treated bamboo fiber to aramid fiber is 7:1). Everything else is the same as in Embodiment 1.

[0048] The resulting composite fiber-modified asphalt mixture was named ABF-3.

[0049] Example 4 This embodiment provides a composite fiber modified asphalt mixture, which differs from Embodiment 1 only in that: the 4.75mm sieve passing rate is 34%, the alkali-treated bamboo fiber content is 0.27% of the total mass of the asphalt mixture, and the aramid fiber content is 0.03% of the total mass of the asphalt mixture (i.e., the mass ratio of alkali-treated bamboo fiber to aramid fiber is 9:1). Everything else is the same as in Embodiment 1.

[0050] The resulting composite fiber-modified asphalt mixture was named ABF-4.

[0051] Comparative Example 1 The asphalt mixture provided in this comparative example differs from that in Example 4 only in that the alkali-treated bamboo fiber is replaced with lignin fiber, the lignin fiber content is 0.27% of the total mass of the asphalt mixture, and the aramid fiber content is 0.03% of the total mass of the asphalt mixture (i.e., the mass ratio of lignin fiber to aramid fiber is 9:1). All other aspects are the same as in Example 4.

[0052] The resulting asphalt mixture was named ACF.

[0053] Comparative Example 2 The asphalt mixture provided in this comparative example differs from that in Example 4 only in that it does not contain aramid fiber, but only alkali-treated bamboo fiber, with a dosage of 0.3% of the total mass of the asphalt mixture. All other aspects are the same as in Example 4.

[0054] The resulting asphalt mixture was named BF.

[0055] The composite fiber modified asphalt mixtures provided in Examples 1-4 have an SMA-13 ​​gradation, as shown in Table 3. The amount of composite fiber is shown in Table 4, and the asphalt-aggregate ratio is shown in Table 5 (the asphalt-aggregate ratio refers to the percentage of the mass ratio of asphalt to aggregate in the asphalt mixture; aggregate includes aggregates and mineral powder).

[0056] Table 3. SMA-13 ​​Gradation of Composite Fiber Modified Asphalt Mixtures in Examples 1-4 Table 4. Fiber Composite Ratio Corresponding to Different 4.75mm Sieve Aperture Passage Rates in Examples 1-4 Table 5. Asphalt-aggregate ratio of composite fiber modified asphalt mixtures in Examples 1-4 Composite fiber modified asphalt mixtures were prepared using untreated bamboo fiber and alkali-treated bamboo fiber, respectively. The asphalt mixtures were dissolved using a dry-mixing method, the fibers were separated, and their distribution was quantitatively analyzed. The agglomeration rate of the fibers under real-world conditions was calculated, serving as the basis for evaluating the uniformity of fiber dispersion in the asphalt mixture. Asphalt mixture specimens from Examples 1-4 were taken out and immersed in the organic solvent trichloroethylene. The asphalt dissolution process was accelerated by stirring. After dissolution, the specimens were divided into four equal parts. The fibers were then sieved out. The separated fibers were dried to constant weight in a constant-temperature oven and weighed using a precision balance. The mass data of the fibers was recorded. The difference in the total weight of the four equal parts of fibers was used to evaluate the uniformity of dispersion of different fibers in the asphalt mixture, as shown in formula (1). The agglomeration rate calculation results are shown in Table 6.

[0057] Equation (1): DI = σ / μ In the formula: σ- is the standard deviation of fiber distribution, reflecting the degree of dispersion of fiber distribution (%); μ - represents the average fiber distribution (%); DI represents the agglomeration rate of fibers in asphalt mixtures. The smaller this value, the more uniform the fiber distribution.

[0058] Table 6. Fiber aggregation rate of composite fiber modified asphalt mixtures in Examples 1-4 As shown in Table 6, the agglomeration rate of the alkali-treated group was lower than that of the untreated group. This indicates that alkali treatment removes lignin and hemicellulose from the surface of bamboo fiber, reduces the adhesion between fibers, makes the dispersion more uniform, and at the same time, it hydroxylates the fiber surface, enhances the electrostatic repulsion effect, and reduces fiber entanglement.

[0059] The asphalt mixtures prepared in Examples 1-4 and Comparative Examples 1-3 were tested for high-temperature performance, low-temperature performance and water stability in accordance with the test procedures of the "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" (JTG E20-2011). The test results of each performance are shown in Table 7.

[0060] Table 7 Road Performance of Composite Fiber Modified Asphalt Mixtures As shown in Table 7, the composite fiber modified asphalt mixture provided by the present invention can improve low-temperature crack resistance and water stability while maintaining high-temperature performance, thus solving the problem that traditional fiber modification technology cannot take multiple properties into account.

[0061] 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 or 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 composite fiber-modified asphalt mixture, characterized in that, The raw materials include asphalt, composite fibers, aggregates and mineral powder; wherein the composite fibers include aramid fibers and alkali-treated bamboo fibers; in the composite fiber modified asphalt mixture, the mass percentage content of the composite fibers is 0.1%-0.3%.

2. The composite fiber-modified asphalt mixture as described in claim 1, characterized in that, In composite fiber modified asphalt mixtures, the aramid fiber has a mass percentage content of 0.03%-0.09%; and / or, In the composite fiber modified asphalt mixture, the alkali-treated bamboo fiber has a mass percentage content of 0.21%-0.27%; and / or, The mass ratio of the aramid fiber to the alkali-treated bamboo fiber is 1:(3-9).

3. The composite fiber-modified asphalt mixture as described in claim 1, characterized in that, The aramid fiber has a length of 5-6 mm.

4. The composite fiber-modified asphalt mixture as described in claim 1, characterized in that, The length of the alkali-treated bamboo fiber is 5-6 mm.

5. The composite fiber-modified asphalt mixture as described in claim 1, characterized in that, The method for preparing alkali-treated bamboo fiber includes the following steps: Bamboo fiber was immersed in a 4%-6% NaOH solution at a mass ratio of 1:20 and stirred for 30-40 minutes in a water bath at 60℃±5℃. Then, it was rinsed with deionized water until the pH of the filtrate was close to neutral and dried until the moisture content was ≤2% to obtain alkali-treated bamboo fiber.

6. The composite fiber-modified asphalt mixture as described in claim 5, characterized in that, The asphalt includes base asphalt and / or modified asphalt; The aggregate includes at least one of basalt, limestone or diabase; The mineral powder includes limestone mineral powder.

7. The composite fiber-modified asphalt mixture as described in claim 6, characterized in that, The base asphalt includes 70# asphalt and / or 90# asphalt, and the modified asphalt includes SBS modified asphalt and / or rubber modified asphalt.

8. The composite fiber-modified asphalt mixture as described in claim 1, characterized in that, The asphalt-aggregate ratio of the composite fiber modified asphalt mixture is 6.2%-6.7%.

9. The method for preparing composite fiber modified asphalt mixture according to any one of claims 1-8, characterized in that, Includes the following steps: S1. Preheat the asphalt, aggregates, and mineral powder separately; S2. Mix the preheated aggregate with alkali-treated bamboo fiber, then add aramid fiber and continue stirring. Add the preheated asphalt and continue stirring. Finally, add mineral powder and stir to obtain the composite fiber modified asphalt mixture.

10. The application of the composite fiber modified asphalt mixture according to any one of claims 1-8 or the composite fiber modified asphalt mixture prepared by the preparation method according to claim 9 in road construction.

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