A diatomite asphalt mixture modifier, its preparation method and application

Abstract

The application belongs to the technical field of modified asphalt, and discloses a diatomite asphalt mixture modifier, a preparation method and application thereof. The preparation method comprises the following steps: calcining and activating diatomite and grinding to obtain activated diatomite powder; taking part of the activated diatomite powder and modifying by alkali liquor to obtain modified diatomite; and compounding the remaining activated diatomite powder, the modified diatomite and lignin fiber according to a mass ratio of 1:(0.5-1.5):(0.1-0.5) to obtain the modifier. The application also provides the modifier prepared by the method, a modified asphalt mixture containing the modifier and a preparation method thereof. The three-step method of "calcination activation-alkali liquor modification-fiber compounding" synergistically acts to fundamentally solve the technical problem of poor compatibility between diatomite and asphalt, and the prepared modified asphalt mixture has obvious improvement in high-temperature anti-rutting, low-temperature anti-cracking and anti-aging road performances, and has excellent comprehensive performance.

Description

Technical Field

[0001] This invention relates to the field of modified asphalt technology, and in particular to a diatomaceous earth asphalt mixture modifier, its preparation method, and its application. Background Technology

[0002] Under the long-term effects of vehicle loads and environmental factors, asphalt pavements are highly susceptible to aging, leading to pavement diseases such as rutting, cracking, and water damage. Adding modifiers to the base asphalt to improve the durability and service life of asphalt pavements has become an industry consensus.

[0003] Currently, polymeric organic modifiers are the most widely used in engineering applications. These mainly include thermoplastic elastomers, represented by styrene-butadiene-styrene block copolymers (SBS), and recycled elastomer materials such as waste tire rubber powder (CR). While these polymeric modifiers can improve the high and low temperature performance of asphalt, they still have certain limitations. On the one hand, thermoplastic elastomers and the small-molecule asphalt matrix are thermodynamically incompatible; differences in density and polarity cause the modified asphalt to easily undergo phase separation during high-temperature storage. On the other hand, waste rubber powder exists mainly in a swollen state in asphalt, which easily leads to a sharp increase in asphalt viscosity, high construction temperatures, and the release of large amounts of volatile organic compounds and hydrogen sulfide gas during production, posing a serious threat to the health of construction workers and the ecological environment.

[0004] As a low-cost silicate mineral, diatomaceous earth possesses unique structural characteristics such as abundant pores, large specific surface area, and strong adsorption. Its microporous structure interacts with lightweight components in asphalt, thereby improving asphalt performance and demonstrating good engineering application potential. However, unmodified diatomaceous earth is rich in silanol groups (Si-OH), exhibiting strong hydrophilicity, while asphalt is a hydrophobic organic material, resulting in extremely poor interfacial compatibility. Direct blending leads to uneven dispersion and agglomeration of diatomaceous earth in asphalt, forming a weak interface with the asphalt matrix. This not only fails to leverage the advantages of its porous structure but may also degrade the performance of the asphalt mixture. Summary of the Invention

[0005] In view of this, the present invention proposes a diatomaceous earth asphalt mixture modifier, its preparation method, and its application scheme. This scheme solves the interfacial compatibility problem between diatomaceous earth and asphalt through a specific three-step process of "activation-modification-compounding," and constructs a composite modification system with synergistic effects, thereby significantly improving the overall road performance of asphalt mixtures.

[0006] The technical solution of the present invention is achieved in the following ways: In a first aspect, the present invention provides a method for preparing a diatomaceous earth asphalt mixture modifier, comprising the following steps: S1. Calcining and grinding diatomaceous earth to obtain activated diatomaceous earth powder; S2. Take a portion of the activated diatomaceous earth powder obtained in step S1, immerse it in an alkaline solution for modification treatment, filter it, wash it, and dry it to obtain modified diatomaceous earth. S3. Take another portion of the activated diatomaceous earth powder obtained in step S1 and mix it with the modified diatomaceous earth and lignin fiber obtained in step S2. Stir and mix well to obtain the diatomaceous earth asphalt mixture modifier.

[0007] Based on the above technical solutions, preferably, in step S3, the mass ratio of the activated diatomaceous earth powder, modified diatomaceous earth and lignin fiber is 1:0.5~1.5:0.1~0.5.

[0008] More preferably, in step S1, the calcination temperature is 350℃~450℃; the calcination time is 90min~210min.

[0009] High-temperature calcination of diatomaceous earth removes organic impurities from its pores, re-exposing numerous blocked nanopores and significantly increasing the specific surface area, resulting in a diatomaceous earth matrix with a rich porous structure and high adsorption activity. When used for asphalt modification, this matrix exhibits high-temperature adsorption of the matrix asphalt and low-temperature release of lightweight components, helping to prevent oil bleeding on pavements and improve low-temperature crack resistance. Furthermore, grinding the calcined diatomaceous earth further increases its specific surface area while making its particle size distribution more uniform, ultimately yielding diatomaceous earth powder with a fully activated pore structure.

[0010] More preferably, in step S2, the alkaline solution is a sodium hydroxide solution or potassium hydroxide solution with a concentration of 1 mol / L to 1.5 mol / L, and the modification treatment time is 30 min to 60 min.

[0011] Activated diatomaceous earth is surface-treated with an alkaline solution. Under alkaline conditions, some Si-O-Si bonds on the surface of the activated diatomaceous earth break, forming more silanol groups (Si-OH) and active sites, which enhances the interfacial bonding strength with the polar components of asphalt, thereby improving the system stability of asphalt mixtures at different temperatures.

[0012] Activated diatomaceous earth, modified diatomaceous earth, and lignin fiber achieve synergistic effects through functional complementarity. Activated diatomaceous earth, acting as a porous carrier, reversibly adsorbs asphalt components to regulate asphalt properties. Modified diatomaceous earth, through surface Si-OH formation, bridges the gap between activated diatomaceous earth and asphalt, improving their interfacial compatibility and dispersion stability. Lignin fiber forms a three-dimensional network within the asphalt system, enhancing low-temperature crack resistance while further preventing the agglomeration and sedimentation of diatomaceous earth particles. The synergistic effect of these three components improves the high and low temperature performance and stability of asphalt mixtures.

[0013] Secondly, the present invention provides a diatomaceous earth asphalt mixture modifier prepared by the above preparation method.

[0014] Thirdly, the present invention provides the application of the above-mentioned diatomaceous earth asphalt mixture modifier in road engineering. A modified asphalt mixture, the components of which include the above-mentioned diatomaceous earth asphalt mixture modifier.

[0015] Based on the above technical solutions, preferably, the modified asphalt mixture, by mass parts, comprises: Base asphalt: 5-10 parts; steel slag aggregate: 70-100 parts; nano zinc oxide: 0.1-1 parts; mineral powder: 1-5 parts; additives: 0.2-1 parts; the diatomaceous earth asphalt mixture modifier: 5-15 parts.

[0016] More preferably, the base asphalt is 70# base asphalt.

[0017] More preferably, the additive is a mixture of equal masses of epoxy resin and polyetheramine. During heating, the two gradually form a cross-linked structure, activating the Si-OH groups and active sites on the diatomaceous earth surface, which in turn generate strong hydrogen bond adhesion with the additive. This improves the high-temperature stability of the asphalt mixture while facilitating the compounding of diatomaceous earth with other components. Simultaneously, the free ether bonds in the polyetheramine enhance the flexibility of the cross-linked network, synergistically improving the low-temperature crack resistance of the asphalt mixture.

[0018] Fourthly, the present invention provides a method for preparing the above-mentioned modified asphalt mixture, comprising the following steps: T1. After crushing and drying the steel slag, add mineral powder and nano zinc oxide and stir evenly. Keep it at a constant temperature of 100°C to obtain the first mixture. T2. Mix the diatomaceous earth asphalt mixture modifier and additives evenly, add them to the base asphalt and stir evenly to obtain a second mixture; T3. After heating the second mixture obtained in step T2 to 155℃~160℃, add the first mixture obtained in step T1, stir and mix evenly to obtain the modified asphalt mixture.

[0019] This invention preferably uses steel slag as the filler aggregate. Steel slag has a rough surface and high compressive strength, which can enhance the skeletal structure strength and rutting resistance of asphalt mixtures; at the same time, it can reduce the preparation cost of this invention and realize the recycling of waste steel slag resources.

[0020] Based on the above technical solutions, preferably, the drying process is carried out at a temperature of 145℃~155℃ for 30min~60min.

[0021] The present invention has the following advantages over the prior art: (1) Through the synergistic modification process of "high temperature calcination activation - alkaline chemical modification - fiber physical compounding", the nanopores of diatomite are re-exposed, and the specific surface area is significantly increased; the technical problems of easy particle agglomeration of diatomite and poor compatibility with asphalt are solved, and diatomite is endowed with the regulatory role of high temperature adsorption matrix asphalt and low temperature release of lightweight components.

[0022] (2) Alkali treatment enhances the reactivity of the activated diatomite surface, further strengthening its compatibility and interfacial bonding strength with the asphalt system. In the subsequent asphalt mixture preparation process, the strong hydrogen bonding between the additives and Si-OH can adhere well to the diatomite surface, which is beneficial for the diatomite to be compounded with other components.

[0023] (3) Activated diatomaceous earth, modified diatomaceous earth and lignin fiber are compounded. While lignin cellulose improves the low-temperature crack resistance of asphalt mixture, it can also work synergistically with activated diatomaceous earth and modified diatomaceous earth to prevent the agglomeration and sedimentation of diatomaceous earth particles, thereby effectively improving the road performance of asphalt mixture. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 The graph shows the difference in softening point between the modifier and the base asphalt prepared in the control group, Examples 1-5, and Comparative Examples 1-8 of this invention. Figure 2 The following are test samples of modified asphalt mixtures prepared with different modifiers according to the present invention: a is the modified asphalt mixture prepared in Example 6, b is the modified asphalt mixture prepared in Comparative Example 9, and c is the modified asphalt mixture prepared in Comparative Example 10. Detailed Implementation

[0026] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0027] The sources of some of the raw materials in the following examples are as follows: diatomaceous earth was purchased from Xilong Scientific Co., Ltd.; lignin fiber was purchased from Hefei Kinu Biotechnology Co., Ltd.; 70# matrix asphalt and mineral powder were provided by Guangxi Jiaoke New Material Technology Co., Ltd.; and steel slag was provided by China Baowu Steel Group Co., Ltd.

[0028] Example 1: This embodiment provides a diatomaceous earth asphalt mixture modifier, which is prepared through the following steps: S1. Calcine 100g of diatomaceous earth at 400℃ for 120min, grind it until it passes through a 200-mesh sieve, and obtain activated diatomaceous earth powder.

[0029] S2. Take 31.25g of the activated diatomaceous earth powder and immerse it completely in 50mL of 1mol / L sodium hydroxide solution for 60min for modification treatment. After immersion, filter it and then wash it alternately with deionized water and ethanol until the washing solution is neutral. Then dry it in an oven at 60℃ for 480min and grind it to pass through a 400-mesh sieve to obtain modified diatomaceous earth.

[0030] S3. Take another portion of the activated diatomaceous earth powder (62.5g), mix it with the modified diatomaceous earth (31.25g) and lignin fiber (6.25g) obtained in step S2 at a mass ratio of 1:0.5:0.1 to obtain the diatomaceous earth asphalt mixture modifier.

[0031] Example 2: This embodiment provides a diatomaceous earth asphalt mixture modifier, which is prepared through the following steps: S1. Calcine 100g of diatomaceous earth at 350℃ for 90min, grind it until it passes through a 200-mesh sieve, and obtain activated diatomaceous earth powder.

[0032] S2. Take 43.5g of the activated diatomaceous earth powder and immerse it completely in 70mL of 1mol / L sodium hydroxide solution for 30min for modification treatment. After immersion, filter it and then wash it alternately with deionized water and ethanol until the washing solution is neutral. Then dry it in an oven at 60℃ for 480min and grind it to pass through a 400-mesh sieve to obtain modified diatomaceous earth.

[0033] S3. Take another portion of the activated diatomaceous earth powder 43.5g and mix it with the modified diatomaceous earth 43.5g and lignin fiber 13g obtained in step S2 at a mass ratio of 1:1:0.3 to obtain the diatomaceous earth asphalt mixture modifier.

[0034] Example 3: This embodiment provides a diatomaceous earth asphalt mixture modifier, which is prepared through the following steps: S1. Calcine 100g of diatomaceous earth at 450℃ for 210min, grind it until it passes through a 200-mesh sieve, and obtain activated diatomaceous earth powder.

[0035] S2. Take 50g of the activated diatomaceous earth powder and immerse it completely in 70mL of 1.5mol / L potassium hydroxide solution for 60min for modification treatment. After immersion, filter it and then wash it alternately with deionized water and ethanol until the washing solution is neutral. Then dry it in an oven at 60℃ for 480min and grind it to pass through a 400-mesh sieve to obtain modified diatomaceous earth.

[0036] S3. Take another portion of the activated diatomaceous earth powder (33.3g), mix it with the modified diatomaceous earth (50g) and lignin fiber (16.7g) obtained in step S2 at a mass ratio of 1:1.5:0.5 to obtain the diatomaceous earth asphalt mixture modifier.

[0037] Example 4: This embodiment provides a diatomaceous earth asphalt mixture modifier: Unlike Example 3, in step S3, 38.5g of the activated diatomaceous earth powder, 57.7g of the modified diatomaceous earth, and 3.8g of lignin fiber are mixed in a mass ratio of 1:1.5:0.1 to obtain the diatomaceous earth asphalt mixture modifier. The remaining steps are the same as in Example 3.

[0038] Example 5: This embodiment provides a diatomaceous earth asphalt mixture modifier: Unlike Example 3, in step S3, 50g of the activated diatomaceous earth powder, 25g of the modified diatomaceous earth, and 25g of lignin fiber are mixed in a mass ratio of 1:0.5:0.5 to obtain the diatomaceous earth asphalt mixture modifier. The remaining steps are the same as in Example 3.

[0039] Example 6: This embodiment provides a modified asphalt mixture. It should be noted that in this embodiment, 1 part is 100g, and its preparation method is as follows: T1. After crushing 85 parts of steel slag, dry it at 150℃ for 60 minutes. Then, add 2.5 parts of mineral powder and 0.5 parts of nano zinc oxide in sequence and stir evenly. Keep it at a constant temperature of 100℃ to obtain the first mixture.

[0040] T2. Heat 10 parts of the diatomaceous earth asphalt mixture modifier prepared by the method of Example 1 in a scaled-up manner to 150°C, add an equal mass of epoxy resin and polyetheramine mixture (0.5 parts in total) as an additive and stir until homogeneous. Then add it to 8 parts of base asphalt and stir until homogeneous to obtain the second mixture.

[0041] T3. After heating the second mixture to 160°C, add the first mixture obtained in step T1 and stir to mix evenly to obtain the modified asphalt mixture.

[0042] Example 7: This embodiment provides a modified asphalt mixture. It should be noted that in this embodiment, 1 part is 100g, and its preparation method is as follows: T1. After crushing 70 parts of steel slag, dry it at 145℃ for 30 minutes. Then add 1 part of mineral powder and 0.1 part of nano zinc oxide and stir evenly. Keep it at 100℃ to obtain the first mixture.

[0043] T2. Five parts of the diatomaceous earth asphalt mixture modifier prepared by the method of Example 2 were heated to 150°C, and an equal mass of epoxy resin and polyetheramine mixture (0.2 parts in total) was added as an additive and stirred until homogeneous. Then, it was added to five parts of base asphalt and stirred until homogeneous to obtain the second mixture.

[0044] T3. After heating the second mixture to 160°C, add the first mixture obtained in step T1 and stir to mix evenly to obtain the modified asphalt mixture.

[0045] Example 8: This embodiment provides a modified asphalt mixture. It should be noted that in this embodiment, 1 part is 100g, and its preparation method is as follows: T1. After crushing 100 parts of steel slag, dry it at 155℃ for 40 minutes. Then add 5 parts of mineral powder and 1 part of nano zinc oxide and stir evenly. Keep it at 100℃ to obtain the first mixture.

[0046] T2. Heat 15 parts of the diatomaceous earth asphalt mixture modifier prepared by the method of Example 3 in a scaled-up manner to 150°C, add an equal mass of epoxy resin and polyetheramine mixture (1 part in total) as an additive and stir until well mixed. Then add it to 10 parts of base asphalt and stir until well mixed to obtain the second mixture.

[0047] T3. After heating the second mixture to 160°C, add the first mixture obtained in step T1 and stir to mix evenly to obtain the modified asphalt mixture.

[0048] Comparative Example 1: Unlike Example 1, no modified diatomaceous earth was used. Instead, 62.5g of activated diatomaceous earth and 6.25g of lignin fiber were used to prepare the diatomaceous earth asphalt mixture modifier. The activated diatomaceous earth powder and lignin fiber were mixed at a mass ratio of 1:0.1 to obtain the diatomaceous earth asphalt mixture modifier. The remaining steps were the same as in Example 1.

[0049] Comparative Example 2: Unlike Example 1, lignin fibers were not used; instead, 62.5g of activated diatomaceous earth and 31.25g of modified diatomaceous earth were used to prepare the diatomaceous earth asphalt mixture modifier. The activated diatomaceous earth powder and modified diatomaceous earth were mixed at a mass ratio of 1:0.5 to obtain the diatomaceous earth asphalt mixture modifier. The remaining steps were the same as in Example 1.

[0050] Comparative Examples 3-4: Unlike Example 1, in step S1, the calcination temperatures are 300°C and 500°C, respectively, while the remaining steps are the same as in Example 1.

[0051] As can be seen from the comparison between Example 1 and Comparative Examples 3-4, the calcination temperature range described in this invention can effectively remove organic impurities from the pores of diatomaceous earth while avoiding excessive sintering. This preserves and expands its natural porous structure, increases the specific surface area and adsorption capacity, allowing the modifier to adsorb more asphalt at high temperatures and release asphalt at low temperatures, thus improving the high-temperature rutting resistance and low-temperature crack resistance of the road surface. If the temperature is below 350℃, the removal of organic impurities is incomplete, the pores are severely blocked, the increase in specific surface area is limited, and the modification effect is not significant. If the temperature is above 450℃, diatomaceous earth may sinter or the pores may collapse, the specific surface area will decrease, the adsorption and release functions will be lost, and the stability of the asphalt mixture will be reduced.

[0052] Comparative Examples 5-6: Unlike Example 1, in step S1, the calcination time is 60 min and 240 min respectively, while the remaining steps are the same as in Example 1.

[0053] As can be seen from the comparison between Example 1 and Comparative Examples 5-6, the calcination time range described in this invention can ensure that the diatomaceous earth is fully activated, allowing the pore structure to be fully exposed, achieving the ideal specific surface area and adsorption performance, while avoiding energy waste and structural damage caused by prolonged calcination. If the calcination time is less than 90 minutes, the activation is insufficient, impurities remain, and the improvement of the pore structure is limited; if it is greater than 210 minutes, the diatomaceous earth may experience over-sintering, pore collapse, a decrease in specific surface area, and a weakening of adsorption capacity, ultimately affecting the high-temperature rutting resistance and low-temperature crack resistance of the asphalt mixture.

[0054] Comparative Example 7: Unlike Example 1, in step S3, the activated diatomaceous earth powder, modified diatomaceous earth, and lignin fiber are mixed evenly at a mass ratio of 1:0.3:0.05 to obtain the modifier. The remaining steps are the same as in Example 1.

[0055] Comparative Example 8: Unlike Example 1, in step S3, the activated diatomaceous earth powder, modified diatomaceous earth, and lignin fiber are mixed evenly at a mass ratio of 1:1.8:0.7 to obtain the modifier. The remaining steps are the same as in Example 1.

[0056] As can be seen from the comparison between Example 1 and Comparative Examples 7-8, insufficient modified diatomaceous earth results in inadequate bridging effect on activated diatomaceous earth, leading to limited improvement in its compatibility with asphalt; insufficient lignin fibers make it difficult for the fiber network to form effectively; excessive modified diatomaceous earth may over-encapsulate activated diatomaceous earth, hindering the "adsorption-release" function of its porous structure and affecting the high-temperature stability of asphalt and asphalt mixtures. Excessive lignin fibers significantly increase the viscosity of the mixture, leading to poor workability and potentially introducing new performance weaknesses due to fiber agglomeration.

[0057] Comparative Example 9: Unlike Example 6, 10 parts (1 part is 100g) of the modifier were prepared using the preparation method of Comparative Example 1, and the remaining steps were the same as in Example 6.

[0058] Comparative Example 10: Unlike Example 6, 10 parts (1 part is 100g) of the modifier were prepared using the preparation method of Comparative Example 2, and the remaining steps were the same as in Example 6.

[0059] The specific surface area and oil absorption value of the diatomaceous earth asphalt mixture modifiers prepared in Examples 1-5 and Comparative Examples 1-8 of this invention were tested, and the testing process and results are as follows.

[0060] 1. Specific Surface Area (BET) Test Specific surface area was used to evaluate the improvement of the pore structure of diatomaceous earth by high-temperature calcination activation and alkali modification. A larger specific surface area indicates more abundant pores and a stronger ability to adsorb bitumen.

[0061] Referring to GB / T 19587 "Determination of Specific Surface Area of ​​Solid Substances by Gas Adsorption BET Method": The samples of diatomaceous earth asphalt mixture modifiers prepared in Examples 1-5 and Comparative Examples 1-8, and unmodified diatomaceous earth (control sample), were vacuum dried to constant weight at 105℃; the nitrogen adsorption-desorption isotherms of the samples were determined using the nitrogen adsorption method at liquid nitrogen temperature (-196℃); the specific surface area (m²) of the samples was calculated using the BET model. 2 / g).

[0062] 2. Oil absorption value test The oil absorption value is used to evaluate the modifier's adsorption capacity for asphalt. A higher oil absorption value indicates a stronger ability to adsorb asphalt and prevent bleeding at high temperatures, indirectly reflecting its rutting resistance.

[0063] Referring to GB / T 5211.15 "General Test Methods for Pigments and Extenders - Part 15: Determination of Oil Absorption": Weigh 5g of the diatomaceous earth asphalt mixture modifier samples prepared in Examples 1-5 and Comparative Examples 1-8, and 5g of unmodified diatomaceous earth (control sample), respectively. Place them on a glass plate. Use dioctyl phthalate (DOP, density 0.986g / mL) as the test oil, adding it drop by drop while continuously grinding and mixing with a spatula. When the sample just clumps together, with no excess free oil and no surface reflection, record the volume of oil consumed (mL). Calculate the oil absorption value (g / 100g) using the following formula: Oil absorption value = (volume of oil consumed × oil density) / sample mass × 100.

[0064] 3. Segregation softening point difference test The compatibility between diatomaceous earth asphalt mixture modifiers and base asphalt was evaluated using the difference in segregation softening points. The smaller the difference in segregation softening points, the stronger the interaction between the surface diatomaceous earth asphalt mixture modifier and the asphalt, and the better its dispersion stability in the asphalt.

[0065] Referring to Section T 0661 of JTG 3410-2025 "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering": Take 3g of samples of diatomaceous earth asphalt mixture modifiers prepared in Examples 1-5 and Comparative Examples 1-8, and 3g of unmodified diatomaceous earth (control sample), respectively. Mix each sample with 50g of hot-melt base asphalt for 30 minutes. After mixing, slowly pour the samples into an open aluminum tube and let them stand in a 163℃ oven for 48 hours. Then, remove the segregated samples from the oven and freeze them vertically in a refrigerator for 6 hours. Finally, divide the segregated samples into three equal sections and test the softening point of the upper and lower sections. Calculate the difference in softening point (℃) using the following formula: Difference in softening point = Softening point of the lower part of the sample - Softening point of the upper part of the sample.

[0066] The specific surface area, oil absorption value, and softening point difference between the diatomaceous earth asphalt mixture modifier prepared in this invention and the base asphalt are as follows: Figure 1 As shown in Table 1.

[0067] As shown in Table 1, although Comparative Example 1 showed improved performance compared to the unmodified diatomaceous earth (control sample), it was still significantly lower than the specific surface area and oil absorption value of the modifiers in Examples 1-5. This indicates that alkali modification is a key step in further improving the pore structure and adsorption capacity of diatomaceous earth. The absence of this step will lead to a significant decrease in the specific surface area and oil absorption value of the modifier, thus affecting its modification effect on asphalt mixtures. Comparative Example 2, having only removed lignin fibers while retaining the high-temperature calcination activation and alkali modification steps, had a specific surface area and oil absorption value that were essentially equivalent to those of Example 1. This indicates that the addition or absence of lignin fibers has little impact on the specific surface area and oil absorption value of the modifier itself. This is because lignin fibers are non-porous fiber materials, primarily contributing to crack resistance and reinforcement rather than adsorption.

[0068] Depend on Figure 1 It can be seen that, although the softening point difference of the asphalt prepared using Comparative Example 1 is improved compared to that of the asphalt without modified diatomaceous earth (control sample), it is still significantly lower than that of the asphalt prepared in Examples 1-5. This indicates that alkali modification treatment is a key step in further improving the interfacial bonding strength between diatomaceous earth and the polar components of asphalt. The absence of this step will lead to a significant decrease in the compatibility between the modifier and the asphalt, thereby affecting its modification effect on the asphalt mixture. Comparative Example 2, due to the removal of lignin fibers, shows a significant difference in the softening point difference of the asphalt prepared compared to Examples 1-5. This indicates that the addition or absence of lignin fibers affects the stability of the asphalt system. This is because lignin fibers form a three-dimensional network in the asphalt system, which, while playing a role in low-temperature crack resistance and reinforcement, further prevents the agglomeration and sedimentation of diatomaceous earth particles.

[0069] Table 1. Specific surface area and oil absorption value tests of the modifiers prepared in Examples 1-5 and Comparative Examples 1-8 of this invention.

[0070] To verify the modification effect of the diatomaceous earth asphalt mixture modifier provided in Examples 1-3 and Comparative Examples 1-2 on asphalt mixtures, this invention tested the effects of the modified asphalt mixtures prepared in Examples 6-8 and Comparative Examples 9-10 on structural strength, anti-aging properties, and crack resistance. Asphalt mixtures without the diatomaceous earth asphalt mixture modifier (referred to as the control group) were used as a comparison for further explanation. The specific testing methods are as follows: Structural strength test (Marshall stability test): Referring to method T0709 in the "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" (JTG 3410-2025), the asphalt mixture is molded into Marshall specimens, and its stability (unit: kN) and flow value (unit: mm) are determined.

[0071] Anti-aging performance test (accelerated aging test of asphalt mixture): The asphalt mixture was subjected to a short-term aging test (165℃, 120min) according to method T0734 in JTG 3410-2025. After aging, its residual stability (%) was measured to evaluate its anti-aging ability.

[0072] Crack resistance test (low temperature beam bending test): According to method T0715 in JTG 3410-2025, a three-point bending test was carried out at -10℃ to determine the maximum bending tensile strain (με) and bending stiffness modulus (MPa) to evaluate the low temperature crack resistance.

[0073] The performance data of the modified asphalt mixtures prepared in Examples 6-8 and Comparative Examples 9-10 above, as well as the asphalt mixture without diatomaceous earth asphalt mixture modifier (referred to as the control group), are shown in Table 2.

[0074] Table 2 Performance Tests of Modified Asphalt Mixtures Prepared Using the Modifier of the Present Invention

[0075] As shown in Table 2, the modified asphalt mixtures prepared in Examples 6-8 of this invention are significantly superior to the control group and comparative examples 9-10 in terms of structural strength, anti-aging performance, and low-temperature crack resistance. Specifically, the Marshall stability (11.8kN~12.5kN) of Examples 6-8 is 44%~52% higher than that of the control group (8.2kN) and 20%~28% higher than that of Comparative Example 9 (9.8kN); the residual stability ratio (91.6%~92.3%) is 13.8%~14.6% higher than that of the control group (78.5%) and 8.4%~9.1% higher than that of Comparative Example 9 (83.2%); and the maximum flexural tensile strain (2580με~2650με) is 39.5%~43.2% higher than that of the control group (1850με) and 21.7%~25.0% higher than that of Comparative Example 9 (2120με).

[0076] Compared with Example 6 ( Figure 2 Compared to example a), the present invention has a comparative example 10 ( Figure 2 The modified asphalt mixture in c) showed certain differences in performance (without lignin fibers), compared to Comparative Example 9 ( Figure 2In example b), the Marshall stability of the modified asphalt mixture (11.2 kN) was slightly lower than that of Example 6 (12.5 kN), but still significantly higher than that of Comparative Example 10 (9.8 kN) and the control group (8.2 kN), indicating that alkali modification and activation treatment are the main factors for improving structural strength, while lignin fibers have a certain reinforcing effect but are not the decisive factor. The residual stability ratio (88.5%) of the modified asphalt mixture of Comparative Example 10 was lower than that of Example 6 (92.3%), but still better than that of Comparative Example 9 (83.2%), indicating that the lack of lignin fibers reduced the structural stability during the aging process. The maximum flexural strain (2280 με) of the modified asphalt mixture of Comparative Example 10 was significantly lower than that of Example 6 (2650 με), while the flexural stiffness modulus (3350 MPa) was higher than that of Example 6 (2980 MPa), indicating that the lack of lignin fibers seriously affected the low-temperature crack resistance, verifying the key role of lignin fibers in improving the low-temperature flexibility of asphalt mixtures.

[0077] The above results demonstrate that this invention achieves a synergistic effect between activated diatomaceous earth, modified diatomaceous earth, and lignin fiber through a three-step process involving high-temperature calcination activation, alkali surface modification, and lignin fiber compounding. Comparative Example 9, which lacks the alkali modification step, underwent high-temperature activation and fiber compounding, but due to the lack of organication of the diatomaceous earth surface and poor compatibility with the asphalt matrix, the improvement in various properties was significantly lower than in Examples 6-8. This further verifies that alkali modification is a crucial step in the preparation process of the modifier in this invention. Although lignin fiber has minimal impact on the specific surface area and oil absorption value of the modifier itself, it plays an irreplaceable role in crack resistance enhancement and stress dispersion in the mixture. Therefore, lignin fiber is a crucial and indispensable component for achieving the synergistic effect of the three components: activated diatomaceous earth, modified diatomaceous earth, and fiber.

[0078] The performance of the modified asphalt mixture of this invention is not achieved by a single component, but by the synergistic effect between the components. This invention combines a diatomaceous earth asphalt mixture modifier with base asphalt, nano-zinc oxide, steel slag, mineral powder, and additives to prepare the modified asphalt mixture. By activating the high specific surface area of ​​diatomaceous earth to achieve the functions of high-temperature adsorption and low-temperature release of asphalt, improving interfacial compatibility through diatomaceous earth modification, and enhancing crack resistance through lignin fiber, the three work synergistically. Combined with the anti-aging function of nano-zinc oxide and the reinforcing effect of steel slag, the resulting modified asphalt mixture exhibits significant improvements in structural strength (Marshall stability increased by 44%~52% compared to the control group), anti-aging performance (residual stability increased by 13.8%~14.6% compared to the control group), and low-temperature crack resistance (maximum flexural strain increased by 39.5%~43.2% compared to the control group). Comparative studies have verified that alkali modification is the key step in achieving these superior effects, effectively solving the technical problems of poor compatibility between modifiers and asphalt matrix and insufficient improvement in road performance in existing technologies, demonstrating promising engineering application prospects.

[0079] 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, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a diatomaceous earth asphalt mixture modifier, characterized in that, Includes the following steps: S1. Calcining and grinding diatomaceous earth to obtain activated diatomaceous earth powder; S2. Take a portion of the activated diatomaceous earth powder obtained in step S1, immerse it in an alkaline solution for modification treatment, filter it, wash it, and dry it to obtain modified diatomaceous earth. S3. Take another portion of the activated diatomaceous earth powder obtained in step S1 and mix it with the modified diatomaceous earth and lignin fiber obtained in step S2. Stir and mix well to obtain the diatomaceous earth asphalt mixture modifier. In step S3, the mass ratio of the activated diatomaceous earth powder, modified diatomaceous earth, and lignin fiber is 1:0.5~1.5:0.1~0.5; In step S1, the calcination temperature is 350℃~450℃; the calcination time is 90min~210min.

2. The preparation method according to claim 1, characterized in that, In step S2, the alkaline solution is a sodium hydroxide solution or potassium hydroxide solution with a concentration of 1 mol / L to 1.5 mol / L, and the modification treatment time is 30 min to 60 min.

3. A diatomaceous earth asphalt mixture modifier, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 2.

4. A modified asphalt mixture, characterized in that, Its components include the diatomaceous earth asphalt mixture modifier as described in claim 3.

5. The modified asphalt mixture as described in claim 4, characterized in that, By mass parts, the components include: Base asphalt: 5-10 parts; steel slag aggregate: 70-100 parts; nano zinc oxide: 0.1-1 parts; mineral powder: 1-5 parts; additives: 0.2-1 parts; the diatomaceous earth asphalt mixture modifier: 5-15 parts.

6. The modified asphalt mixture as described in claim 5, characterized in that, The additive is a mixture of equal masses of epoxy resin and polyetheramine.

7. A method for preparing modified asphalt mixture as described in any one of claims 5-6, characterized in that, Includes the following steps: T1. After crushing and drying the steel slag, mineral powder and nano zinc oxide are added and stirred evenly. The mixture is kept at a constant temperature of 100°C to obtain the first mixture. T2. Mix the diatomaceous earth asphalt mixture modifier and additives evenly, add them to the base asphalt and stir evenly to obtain a second mixture; T3. After heating the second mixture obtained in step T2 to 155℃~160℃, add the first mixture obtained in step T1, stir and mix evenly to obtain the modified asphalt mixture.

8. The method for preparing modified asphalt mixture as described in claim 7, characterized in that, The drying process involves treating the sample at a temperature of 145℃~155℃ for 30min~60min.

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