Preparation method of diatomite compound modified asphalt

Abstract

The invention discloses a preparation method of diatomite compound modified asphalt, and belongs to the technical field of nano materials. According to the method, the modified asphalt material with excellent performance is prepared by compounding and modifying the diatomite and the asphalt. The preparation method comprises the following steps: firstly, pretreating diatomite to obtain nanoscale diatomite particles; then, mixing the nano diatomite with asphalt, and preparing the modified asphalt through a specific compounding process. According to the method, a novel compounding technology is adopted, and uniform dispersion and tight combination of diatomite and asphalt are achieved. The prepared modified asphalt has excellent high temperature resistance, aging resistance and crack resistance, and is suitable for the fields of road construction and the like. Meanwhile, the method is simple in process and low in cost, and has good economic benefits and environmental protection benefits.

Description

Technical Field

[0001] The present invention belongs to the technical field of nanomaterials, and in particular relates to a method for preparing diatomite-compounded modified asphalt. Background Art

[0002] Asphalt, a key road construction material, is widely used in the paving of roads, airport runways, and other infrastructure due to its excellent adhesion, water resistance, and durability. However, traditional asphalt materials have significant performance drawbacks in practical applications. For example, at high temperatures, asphalt softens easily, leading to rutting on the road surface; at low temperatures, asphalt becomes brittle and prone to cracking. Furthermore, asphalt is susceptible to aging over time due to factors such as ultraviolet rays, oxygen, and moisture, further reducing the service life and safety of the road surface. Therefore, the research and development of modified asphalt has become a key technical direction for improving road performance.

[0003] Currently, common methods for asphalt modification include polymer modification, rubber modification, and fiber modification. Polymer modification is widely used because it significantly improves asphalt's elasticity and temperature resistance. For example, SBS (styrene-butadiene-styrene) modified asphalt, by adding SBS copolymers, effectively enhances its high-temperature stability and low-temperature crack resistance. However, polymer-modified asphalt faces several challenges in production and application, such as poor compatibility between the polymer and asphalt, prone to segregation, and high production costs, which limit its adoption in small and medium-sized projects.

[0004] Rubber-modified asphalt is another common modification technology, typically prepared by adding rubber powder from scrap tires to asphalt. This method not only improves the elasticity and fatigue resistance of asphalt but also enables resource recycling. However, the preparation process for rubber-modified asphalt is complex, and the dispersion of rubber particles in asphalt is poor, which can easily lead to uneven modification. In addition, fiber modification technology can enhance the tensile strength of asphalt by adding materials such as glass fiber or polyester fiber, but the high cost and processing difficulty of fiber materials also limit its scope of application.

[0005] In recent years, with the advancement of nanotechnology, nanomaterials have shown great potential in asphalt modification due to their unique physical and chemical properties. Nanomaterials, with their high specific surface area and excellent interfacial effects, can improve the mechanical properties and durability of asphalt at the microscopic level. For example, nanosilica is often used in asphalt modification due to its excellent chemical stability and reinforcing properties. Carbon nanotubes are another widely studied modification material. Their high strength and high thermal conductivity can enhance asphalt's crack resistance and high-temperature resistance. However, the preparation and dispersion of carbon nanotubes require extremely high technical requirements, and their production costs far exceed those of traditional modification materials, limiting their practical application. Additionally, materials such as nanoclay and nanozinc oxide have also been explored for asphalt modification, but they generally suffer from poor dispersibility and unstable modification results. Diatomaceous earth, a naturally occurring nanoporous material with a high specific surface area, excellent adsorption properties, and chemical stability, has recently garnered increasing attention in the asphalt modification field. Diatomaceous earth's porous structure can adsorb light components in asphalt, improving the asphalt's viscosity-temperature characteristics and thus enhancing its high-temperature stability. However, simple diatomite-modified asphalt performs poorly in terms of low-temperature crack resistance, and the dispersion of diatomite particles in asphalt has not been effectively resolved, which affects the stability of the modification effect. Furthermore, existing technologies have little research on diatomite pretreatment and compounding technologies, with most methods remaining at the level of simple mixing and failing to fully realize the potential of diatomite as a nanomaterial. While the cost of diatomite-modified asphalt is lower than that of nanosilica or carbon nanotubes, its performance improvement is limited, making it difficult to meet the comprehensive performance requirements of asphalt materials for modern high-grade roads.

[0006] In summary, although the existing asphalt modification technology has improved the performance of asphalt to a certain extent, it still faces the following problems: Uneven dispersion of modifiers: Whether it is polymers, nanomaterials or diatomaceous earth, it is difficult to ensure the uniformity of dispersion in asphalt, resulting in unstable modification effect. Limited modification effect: While existing technologies improve the high-temperature performance of asphalt, they often sacrifice low-temperature crack resistance, or are insufficient in improving anti-aging performance. High production costs: The high cost of nanomaterials and polymer modifiers limits the promotion and application of modified asphalt, while low-cost modification methods such as diatomaceous earth modification can hardly meet high performance requirements. Process complexity: Some modification technologies require complex pretreatment or processing equipment, which increases production difficulty and energy consumption. Summary of the Invention

[0007] 1. Problems to be solved

[0008] To address the aforementioned problems of the existing technologies, the present invention focuses on resolving the following issues: In existing technologies, it is difficult to ensure uniform dispersion of modifiers (such as polymers, nanomaterials, or diatomaceous earth) in asphalt, resulting in unstable modification effects and impacting long-term performance. This invention improves the dispersibility of diatomaceous earth particles in asphalt by optimizing the diatomaceous rock pretreatment process and novel compounding techniques, ensuring uniform and stable modification. Existing modification technologies often sacrifice low-temperature crack resistance or inadequate aging resistance when improving high-temperature performance, making comprehensive optimization difficult. This invention leverages the synergistic effects of diatomaceous rock with other modifiers to achieve comprehensive improvements in high-temperature stability, low-temperature crack resistance, and aging resistance. The high cost of nanomaterials and polymer modifiers limits their widespread application, while low-cost methods such as diatomaceous earth modification fail to meet high-performance requirements. This invention uses natural diatomaceous rock as the primary material and combines a simplified process to reduce costs while ensuring high performance, making it suitable for large-scale application. The preparation and use of some modifiers can cause pollution, making them incompatible with green building requirements. This invention utilizes natural diatomaceous rock and a low-energy process, offering excellent environmental performance and meeting the demand for green materials in modern engineering. Existing technologies often require complex pretreatment or equipment, increasing production complexity and energy consumption. The present invention optimizes the process, simplifies the steps, reduces energy consumption and equipment requirements, and enhances the feasibility of industrial production. Existing modified asphalt performs poorly in extreme environments (such as high and low temperatures, and freeze-thaw cycles), making it difficult to meet the requirements of high-grade roads. The modified asphalt prepared by the present invention exhibits excellent stability under harsh conditions and is suitable for complex environments. Existing modified asphalt is susceptible to aging and performance degradation due to ultraviolet light, oxygen, and moisture. The present invention uses diatomite as a composite modification to enhance aging resistance, extend service life, and reduce maintenance costs. Existing technologies have limited effectiveness in improving the adhesion between asphalt and aggregate, especially in wet conditions or acid rain, resulting in flaking. The present invention uses diatomite as a modification to enhance bond strength and improve resistance to water damage. Some modified asphalts have poor fluidity, which affects construction quality. The modified asphalt prepared by the present invention has excellent fluidity, facilitates construction, and ensures road surface quality. Existing technologies are difficult to control and standardize. The present invention optimizes the process and control measures to ensure quality stability and batch consistency, making it suitable for large-scale production. In summary, the present invention solves the above problems through diatomite compounding modification technology, and provides a high-performance, economical, practical, green and environmentally friendly modified asphalt preparation method.

[0009] 2. Technical solution

[0010] To solve the above problems, the present invention adopts the following technical solutions.

[0011] A method for preparing diatomite-modified asphalt comprises the following steps: (1) diatomite pretreatment: diatomite is pickled with 5-10% hydrochloric acid by mass, and then activated at 400-500°C for 1-2h to obtain a specific surface area ≥300 (2) Preparation of bio-based composite modifier: castor oil-based polyurethane prepolymer and natural rubber are mixed in a mass ratio of 3:1-5:1, nano-cerium dioxide is added as a catalyst, and pre-reacted at 120-140 ° C for 30-60 min to obtain a bio-based composite modifier; (3) staged mixing: the matrix asphalt is heated to 150-160 ° C, the activated diatomaceous earth of step (1) and the bio-based composite modifier of step (2) are added in sequence, and high-speed shearing is carried out at 5000-8000 rpm for 30-45 min to obtain a mixed system; (4) synergistic enhancement: manganese slag powder is added to the mixed system, the temperature is controlled at 80-90 ° C, and low-speed stirring is carried out for 2-3 h to obtain a synergistic system; (5) thermal cross-linking and curing: the synergistic system is degassed and cured at 140-150 ° C under vacuum conditions.

[0012] Preferably, the specific surface area of the diatomaceous earth in step (1) is 19-65 Its main component is amorphous silicon dioxide, with a solid content of 85%-94%. For diatomite, raw materials are selected from Cretaceous diatomite deposits, with diatom shell integrity of ≥80%. The particle size distribution is: D50 is controlled within 5-15μm, of which particles <2μm account for ≤10%, and particles >30μm account for ≤5%. Impurities: aluminum oxide ≤4.5%, iron oxide ≤1.2%, and loss on ignition ≤8%.

[0013] Preferably, the mass ratio between diatomaceous earth and hydrochloric acid in step (1) is 1:(3-8).

[0014] Preferably, the preparation method of castor oil-based polyurethane prepolymer in step (2) is as follows: castor oil (CAS No.: 8001-79-4, acid value ≤ 2.0 mgKOH / g, peroxide value ≤ 10 mmol / kg, density: 0.945-0.965 (25℃), viscosity: 650-800 (20℃), refractive index: 1.473-1.477 (20℃)) dehydrated under vacuum conditions at 100-120℃ for 2-4h, controlling the moisture content ≤0.05wt%, according to castor oil and diphenylmethane diisocyanate (CAS No.: 101-68-8, density: 1.19 ) molar ratio of 1: (1.8-2.6) is added, followed by adding 0.1-0.5% of the mass of castor oil stannous octoate (CAS No.: 301-10-0), reacting at 70-90 ° C for 30-60 min under nitrogen protection, then adding 1,4-butanediol (CAS No.: 110-63-4), according to the molar ratio of 1,4-butanediol to diphenylmethane diisocyanate of 0.2: 1-0.5: 1, continuing to react at 80-100 ° C for 1-2 h, degassing at 120-140 ° C, vacuum degree ≤-0.095 MPa for 30-45 min to obtain a castor oil-based polyurethane prepolymer; the CAS number of natural rubber in step (2) is 9006-04-6, and the density is 1.05 .

[0015] Preferably, the particle size of the nano-cerium dioxide in step (2) is 20-50 nm; the added mass of the nano-cerium dioxide in step (2) is 0.5-1.5% of the castor oil-based polyurethane prepolymer.

[0016] Preferably, the CAS number of the matrix asphalt in step (3) is 8052-42-4, which complies with the JTGF40-2004 standard; the final mass percentage of the activated diatomaceous earth in step (3) is 5-15%; and the final mass percentage of the bio-based composite modifier in step (3) is 3-8%.

[0017] Preferably, the final mass percentage of manganese slag powder in the mixed system in step (4) is 5-10%; wherein the particle size of the manganese slag powder is ≤10 μm. Manganese slag powder is an industrial by-product, and its main components (by mass percentage) are: silicon dioxide: CAS7631-86-9 (accounting for 48.09%), aluminum oxide: CAS1344-28-1 (11.36%), and calcium oxide: CAS1305-78-8 (19.55%).

[0018] Preferably, the rotation speed of the low-speed stirring in step (4) is 100-300 rpm.

[0019] Preferably, the curing time in step (5) is 2-4 hours, and the curing temperature is 60-80°C.

[0020] The preparation method of diatomite composite modified asphalt achieves a comprehensive improvement in asphalt performance through the synergistic effect of multiple components. Its core mechanism can be analyzed from the following perspectives: Diatomite pretreatment mechanism: Acid washing and activation: 5-10% hydrochloric acid treatment can effectively remove metal oxide impurities in diatomite and expose more silanol active sites. After acid washing, high-temperature activation at 400-500℃ removes bound water, increasing the specific surface area of diatomite from 19-65 Increase to ≥300 , forming a multi-level pore structure. Interface enhancement mechanism: The activated nano-diatomaceous earth combines with asphalt through the dual effects of physical adsorption and chemical bonding: Physical adsorption: The porous structure of diatomaceous earth (pore size 2-50nm) can adsorb saturated and aromatic components in asphalt to reduce the free volume; Chemical bonding: Silicon hydroxyl groups form hydrogen bonds with polar components in asphalt (such as colloids), and react with the -NCO groups of polyurethane prepolymers to form Si-OC bonds. Mechanism of action of bio-based composite modifiers: Toughening mechanism of castor oil-based polyurethanes: The long-chain fatty acids in castor oil (ricinoleic acid content ≥85%) give polyurethanes excellent flexibility. The -NCO / -OH molar ratio in the prepolymer is controlled at 1.8-2.6 to form a moderately cross-linked network structure, and its storage modulus (G') can reach 10 3 Pa level, effectively improving the elastic recovery properties of asphalt. Natural rubber / polyurethane synergistic effect: an interpenetrating network structure is formed through dynamic vulcanization technology: the polyurethane phase provides a rigid skeleton (Tg≈-35℃); the rubber phase (Tg≈-70℃) dissipates stress through segment movement; the two work together to maintain the loss factor tanδ of the composite modifier at 0.4-0.6 in the range of -40℃ to 60℃. Manganese slag powder reinforcement mechanism: micro-nano composite reinforcement: manganese slag powder with a particle size of ≤10μm forms a micron-nano secondary reinforcement system with diatomaceous earth: nano diatomaceous earth (5-15wt%) fills the asphalt continuous phase, and micron manganese slag powder (5-10wt%) constructs the skeleton structure. This graded filling increases the complex modulus G* of the composite asphalt by 40-60%. Interface chemical reaction: The MnO2 component (content 2-5%) is partially converted into Mn during the shear process. 3+ catalyzes the oxidative crosslinking of asphalt components, forming a denser network structure. The impact of process parameters on performance: High-speed shear dynamics: Shear forces generated at 5000-8000 rpm reduce the diatomite / modifier dispersion size from the micron level to 200-500 nm. Calculations show that when the shear time is ≥30 minutes, the dispersed phase particle size conforms to a Weibull distribution (shape parameter k = 2.1-2.5). Thermal crosslinking and curing optimization: Vacuum degassing at 140-150°C reduces the system viscosity to bubble diameters ≤50 μm. Subsequent curing at 60-80°C enhances the crosslink density, ensuring stable viscoelastic properties within the temperature range of -20°C to 80°C. Through multi-scale structural control and interface engineering, this technology achieves a fatigue life of 11,000 cycles (ASTM D7460), a more than 300% improvement over traditional SBS-modified asphalt. This performance improvement is primarily due to the synergistic effect of the ternary system of diatomite, biomodifier, and manganese slag powder.

[0021] 3. Beneficial effects

[0022] Compared with the existing technology, the beneficial effects of the present invention are as follows: Comprehensive performance improvement: The present invention significantly improves the comprehensive performance of modified asphalt through the synergistic effect of diatomaceous earth pretreatment and bio-based composite modifier. Specifically, it is manifested in the enhancement of high-temperature stability, low-temperature crack resistance and aging resistance. For example, the softening point of the modified asphalt is increased to 56-64°C, the ductility reaches 85-110cm, and the fatigue life is extended to 8800-11000 times, which can meet the high standards required for high-grade road construction. Uniform dispersion of modifier: By adopting high-speed shearing and synergistic enhancement processes, the present invention effectively solves the problem of uneven dispersion of traditional modifiers in asphalt, ensures the stability and consistency of the modification effect, and thus improves the overall quality of the asphalt. Low cost: The present invention uses natural diatomaceous earth and industrial by-product manganese slag powder as the main raw materials, and combines it with an optimized preparation process to significantly reduce production costs. This low-cost advantage makes it suitable for large-scale industrial production and promotion and application. Green and environmentally friendly: By using bio-based materials and low-energy consumption processes, the present invention reduces environmental pollution during the production process, meets the standards of green building and sustainable development, and demonstrates good environmental benefits. Simple process: This invention optimizes diatomite pretreatment and modifier compounding techniques, reducing equipment complexity and energy consumption requirements, making the production process simpler and more efficient, and facilitating implementation in industrial scenarios. Excellent construction performance: The modified asphalt exhibits excellent fluidity, strong adhesion, and high resistance to water damage, adapting to the demands of road construction in complex environments and further enhancing its practical value.

[0023] In summary, the present invention overcomes the limitations of existing technologies such as unstable performance, high cost, and insufficient environmental protection through technological innovation and material optimization, and achieves a comprehensive improvement in the performance of modified asphalt. It also has both economic benefits and environmental advantages and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a physical picture of the diatomite compounded modified asphalt prepared in Example 1.

[0025] Figure 2 This is a scanning electron microscope image of the diatomite-modified asphalt prepared in Example 1.

[0026] Figure 3 This is a physical picture of the activated diatomaceous earth prepared in Example 1.

[0027] Figure 4 is a scanning electron microscope image of the activated diatomaceous earth prepared in Example 1.

[0028] Figure 5 This is a transmission electron micrograph of the bio-based composite modifier prepared in Example 1. DETAILED DESCRIPTION

[0029] The present invention is described in detail below through specific examples. However, the use and purpose of these exemplary embodiments are merely illustrative of the present invention and are not intended to limit the actual scope of protection of the present invention in any form, nor are they intended to limit the scope of protection of the present invention to these examples. For parameter ranges not mentioned, intermediate values are selected. In addition, for mass percentages or weight percentages not explicitly stated or mentioned, they generally refer to the final concentration after addition.

[0030] Example 1

[0031] The preparation method of diatomite composite modified asphalt is as follows: Step (1) Diatomite pretreatment: Take 100g of diatomite and pickle it with 400g of 8% by mass hydrochloric acid. After pickling, activate it at a high temperature of 450°C for 1.5h to obtain activated diatomite. Step (2) Preparation of bio-based composite modifier: Preparation of castor oil-based polyurethane prepolymer: Take 200g of castor oil and dehydrate it under vacuum at 110°C for 3h. Add 130g of diphenylmethane diisocyanate (MDI) and 0.6g of stannous octoate, and react at 80°C under nitrogen protection for 45min. Add 1,4-butanediol 15g and react at 90°C for 1.5h. Degas at 130°C and vacuum degree of -0.095MPa for 40min to obtain castor oil-based polyurethane prepolymer. Preparation of bio-based composite modifier: Mix 150g of castor oil-based polyurethane prepolymer with 37.5g of natural rubber. Add 1.125g of nano-cerium dioxide and pre-react at 130°C for 45 minutes to obtain a bio-based composite modifier. Step (3) Mixing in stages: Heat 1000g of matrix asphalt to 155°C. Add 100g of activated diatomaceous earth and 50g of bio-based composite modifier in sequence. Shear at 6500rpm for 40 minutes to obtain a mixed system. Step (4) Synergistic enhancement: Add 75g of manganese slag powder to the mixed system. Control the temperature to 85°C and stir at 200rpm for 2.5h to obtain a synergistic system. Step (5) Thermal cross-linking and curing: Degassing treatment at 145°C under vacuum conditions. Curing at 70°C for 3h. The prepared product is as follows Figure 1 As shown in the scanning electron microscope image Figure 2 In addition, the physical image and scanning electron microscope image of activated diatomite are shown as follows: Figure 3 and Figure 4 At the same time, the transmission electron microscopy image of the bio-based composite modifier is shown in Figure 5 shown.

[0032] Example 2

[0033] Diatomaceous earth pretreatment: hydrochloric acid concentration 5%, high temperature activation temperature 400°C, activation time 1 hour. Other steps are the same as in Example 1.

[0034] Example 3

[0035] Bio-based composite modifier: castor oil-based polyurethane prepolymer and natural rubber in a mass ratio of 3:1 (i.e., 150g:50g). Other steps are the same as in Example 1.

[0036] Example 4

[0037] Mixing in stages: high-speed shearing speed 5000 rpm, time 30 min. Other steps are the same as in Example 1.

[0038] Example 5

[0039] Synergistic enhancement: The mass of manganese slag powder is 50 g, and the stirring speed is 100 rpm. Other steps are the same as those in Example 1.

[0040] Example 6

[0041] Thermal cross-linking curing: curing temperature 60° C., time 2 h. Other steps are the same as in Example 1.

[0042] Example 7

[0043] Diatomaceous earth pretreatment: hydrochloric acid concentration 10%, high temperature activation temperature 500°C, activation time 2 hours. Other steps are the same as in Example 1.

[0044] Example 8

[0045] Bio-based composite modifier: castor oil-based polyurethane prepolymer and natural rubber mass ratio of 5:1 (i.e. 150g:30g). Other steps are the same as Example 1.

[0046] Example 9

[0047] Mixing in stages: high-speed shearing speed 8000 rpm, time 45 min. Other steps are the same as in Example 1.

[0048] Example 10

[0049] Synergistic enhancement: Manganese slag powder mass 100g, stirring speed 300rpm. Other steps are the same as Example 1.

[0050] Comparative Example 1

[0051] The diatomite pretreatment step was omitted, and 100 g of unactivated diatomite was used directly. Other steps were the same as in Example 1.

[0052] Comparative Example 2

[0053] No nano-cerium dioxide was added during the preparation of the bio-based composite modifier. Other steps were the same as in Example 1.

[0054] Comparative Example 3

[0055] No activated diatomaceous earth was added during the staged mixing. The other steps were the same as in Example 1.

[0056] Comparative Example 4

[0057] No manganese slag powder was added during the synergistic enhancement. Other steps were the same as those in Example 1.

[0058] Comparative Example 5

[0059] No vacuum degassing treatment was performed during the thermal crosslinking curing. Other steps were the same as those in Example 1.

[0060] Comparative Example 6

[0061] Only 150 g of castor oil-based polyurethane prepolymer was used in the bio-based composite modifier, and no natural rubber was added. Other steps were the same as in Example 1.

[0062] Comparative Example 7

[0063] The high shear speed was reduced to 3000 rpm and the mixing time was shortened to 15 minutes. The other steps were the same as those in Example 1.

[0064] Comparative Example 8

[0065] During the synergistic enhancement, the stirring temperature was increased to 100° C. and the stirring speed was increased to 500 rpm. Other steps were the same as in Example 1.

[0066] Product performance testing

[0067] Physical Property Tests: Penetration Test (ASTM D5) evaluates asphalt hardness. The penetration depth of a standard needle into asphalt within 5 seconds at 25°C is measured (unit: 0.1 mm). Softening Point Test (ASTM D36) evaluates asphalt heat resistance. The ball and ring method is used to measure the temperature at which asphalt softens. The softening point temperature is measured (unit: °C). Ductility Test (ASTM D113) evaluates asphalt ductility. The asphalt specimen is stretched to the breaking length at 5°C. The ductility is measured (unit: cm).

[0068] High-temperature stability testing: The dynamic shear rheology (DSR) test (ASTM D7175) evaluates asphalt's rutting resistance at high temperatures. The complex modulus (G*) and phase angle (δ) of asphalt are measured at high temperatures (e.g., 60°C). The metric is G* / sinδ (unit: kPa), which is used to determine the high-temperature performance grade (PG). The DSR test after aging in a rotating thin film oven (RTFO) (ASTM D2872) evaluates asphalt's short-term aging performance. After aging at 163°C for 85 minutes, the DSR test is performed. The metric is G* / sinδ after aging.

[0069] Low-temperature crack resistance testing: The bending beam rheometer (BBR) test (ASTM D6648) evaluates asphalt's crack resistance at low temperatures. It measures asphalt stiffness and creep rate at low temperatures (e.g., -12°C). The following indicators are used: stiffness (S) and creep rate (m). The pressure aging vessel (PAV) post-aging BBR test (ASTM D6521) evaluates asphalt's long-term aging performance. After aging for 20 hours at 100°C and 2.1 MPa, the BBR test is performed. The following indicators are used: S and m after aging.

[0070] Viscoelastic Performance Testing: Dynamic Mechanical Analysis (DMA) evaluates the viscoelastic behavior of asphalt (ASTM D7175 (DSR)), measuring the storage modulus (G') and loss modulus (G'') at different temperatures and frequencies. The performance indicators include G', G'', and tan δ. Fatigue Testing (ASTM D7460) evaluates the fatigue resistance of asphalt through tensile fatigue testing, with the performance indicator being fatigue life (Nf).

[0071] Table 1 Test results

[0072]

[0073]

[0074] As shown in Table 1, Examples 1-10: Features: The complete preparation method (diatomite pretreatment, preparation of a bio-based composite modifier, staged mixing, synergistic reinforcement, and thermal crosslinking curing) was followed, with some variations in parameters (such as hydrochloric acid concentration, activation temperature, shear speed, and manganese slag powder content). Properties: Low penetration (46-55), high softening point (56-64°C), high ductility (85-110 cm), high G* / sinδ (4.5-5.4 kPa), low stiffness (S) (180-225 MPa), high creep rate (m) (0.31-0.39), and long fatigue life (Nf) (8,800-11,000 cycles).

[0075] Comparative Examples 1-8: Characteristics: Omission or modification of key steps (e.g., non-activated diatomaceous earth, absence of nano-cerium dioxide, and absence of manganese slag powder) resulted in decreased performance. Properties: High penetration (56-63), low softening point (52-58°C), low ductility (60-80 cm), low G* / sinδ (2.5-4.0 kPa), high stiffness (S) (220-270 MPa), low creep rate (m) (0.22-0.32), and short fatigue life (Nf) (4000-7500 cycles).

[0076] The above content is a further detailed description of the present invention in conjunction with specific implementation methods. It cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, they can make several simple deductions or substitutions without departing from the concept of the present invention, which should be regarded as falling within the scope of protection determined by the claims submitted for the present invention.

Claims

1. A method for preparing diatomite-modified asphalt, characterized by: The following steps are involved: (1) Diatomite pretreatment: After the diatomite is pickled with 5-10% hydrochloric acid by mass, it is activated at 400-500℃ for 1-2h to obtain a specific surface area of ≥300 (2) Preparation of bio-based composite modifier: castor oil-based polyurethane prepolymer and natural rubber are mixed in a mass ratio of 3:1-5:1, nano-cerium dioxide is added as a catalyst, and pre-reacted at 120-140 ° C for 30-60 min to obtain a bio-based composite modifier; (3) staged mixing: the matrix asphalt is heated to 150-160 ° C, the activated diatomaceous earth of step (1) and the bio-based composite modifier of step (2) are added in sequence, and high-speed shearing is carried out at 5000-8000 rpm for 30-45 min to obtain a mixed system; (4) synergistic enhancement: manganese slag powder is added to the mixed system, the temperature is controlled at 80-90 ° C, and low-speed stirring is carried out for 2-3 h to obtain a synergistic system; (5) thermal cross-linking and curing: the synergistic system is degassed and cured at 140-150 ° C under vacuum conditions.

2. The method for preparing diatomite composite modified asphalt according to claim 1, characterized in that: The specific surface area of diatomaceous earth in step (1) is 19-65 Its main component is amorphous silicon dioxide, with a solid content of 85%-94%.

3. The method for preparing diatomite-modified asphalt according to claim 1, characterized in that: The mass ratio between diatomaceous earth and hydrochloric acid in step (1) is 1:(3-8).

4. The method for preparing diatomite-modified asphalt according to claim 1, characterized in that: The preparation method of the castor oil-based polyurethane prepolymer in step (2) is as follows: dehydrate castor oil under vacuum conditions at 100-120°C for 2-4h, control the moisture content to be ≤0.05wt%, add castor oil and diphenylmethane diisocyanate at a molar ratio of 1: (1.8-2.6), then add stannous octoate at a mass ratio of 0.1-0.5% of castor oil, react at 70-90°C for 30-60min under nitrogen protection, then add 1,4-butanediol, add 1,4-butanediol and diphenylmethane diisocyanate at a molar ratio of 0.2:1-0.5:1, continue to react at 80-100°C for 1-2h, degas at 120-140°C and vacuum degree ≤-0.095MPa for 30-45min to obtain a castor oil-based polyurethane prepolymer; the CAS number of the natural rubber in step (2) is 9006-04-6, and the density is 1.05 .

5. The method for preparing diatomaceous earth composite modified asphalt according to claim 1, characterized in that: The particle size of the nano-cerium dioxide in step (2) is 20-50 nm; the added mass of the nano-cerium dioxide in step (2) is 0.5-1.5% of the castor oil-based polyurethane prepolymer.

6. The method for preparing diatomite-modified asphalt according to claim 1, characterized in that: The CAS number of the matrix asphalt in step (3) is 8052-42-4; the final mass percentage of the activated diatomaceous earth in step (3) is 5-15%; and the final mass percentage of the bio-based composite modifier in step (3) is 3-8%.

7. The method for preparing diatomite-modified asphalt according to claim 1, characterized in that: The final mass percentage of the manganese slag powder in the mixed system in step (4) is 5-10%; wherein the particle size of the manganese slag powder is ≤10 μm.

8. The method for preparing diatomite-compounded modified asphalt according to claim 1, characterized in that: The rotation speed of the low-speed stirring in step (4) is 100-300 rpm.

9. The method for preparing diatomite-modified asphalt according to claim 1, characterized in that: The curing time in step (5) is 2-4 hours, and the curing temperature is 60-80°C.

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