A dry powder asphalt mixture and its preparation method

Abstract

The present application relates to the technical field of asphalt mixtures, and specifically discloses a high-performance dry-powdered asphalt mixture and a preparation method thereof. A preparation method for a high-performance dry-powdered asphalt mixture comprises the following steps: 1) mixing polyacrylonitrile, metal oxide, and solvent, and stirring the mixture to obtain a precursor solution A; 2) dissolving cyclodextrin in anhydrous ethanol to obtain a base solution; then adding calcium chloride, polylauryl methacrylate, polycaprolactone, and a surfactant, and mixing the mixture to obtain a precursor solution B; 3) performing conjugate electrospinning on the precursor solution A and the precursor solution B to obtain fractal fibers; 4) immersing the fractal fibers in an impregnation solution to obtain a composite fiber material; 5) dry-mixing the aggregate, fly ash, and composite fiber material, then adding asphalt and continuing to mix, and then adding mineral powder and mixing to obtain the mixture. The high-performance dry-powdered asphalt mixture prepared by the present application has the advantages of high stability and crack resistance.

Description

Technical Field

[0001] The present application relates to the technical field of asphalt mixtures, and more specifically, to a dry powder asphalt mixture and a preparation method thereof. Background Art

[0002] Asphalt mixtures are widely used as the top layer material for road structures due to their excellent road performance. However, in complex environmental conditions, such as those in seasonally frozen areas, the top layer is directly affected by freeze-thaw cycles, resulting in performance degradation and cracking. This negatively impacts road safety and pavement life, while also increasing road operation and maintenance costs.

[0003] To improve the current service status of pavement, adding fibers to asphalt mixtures has been proven to be an effective way to increase pavement durability and extend its service life, meeting the service requirements of pavement materials under complex environmental conditions to a certain extent. Asphalt mixtures are typical multiphase composite materials, and the material system is complex, multi-level, and variable. In particular, after the addition of fibers, in addition to the asphalt mortar / aggregate interface, a large number of new asphalt mortar / fiber interfaces are formed within the system, which not only changes the performance of the asphalt mortar, but also affects the bonding state of the asphalt mortar / aggregate interface, ultimately forming multiple asphalt mortar / fiber / aggregate interfaces. This multiple and complex interface behavior greatly affects the mechanical response of the asphalt mixture, and thus affects the pavement's crack resistance, durability, and service life.

[0004] The main types of fibers currently used both domestically and internationally include plant fibers, polymer fibers, mineral fibers, and inorganic fibers. For example, the addition of basalt fibers can increase the viscosity of asphalt mortar, inhibit asphalt flow, and enhance its mechanical properties. The addition of polyacrylonitrile fibers significantly improves the rutting resistance of asphalt mixtures, but polyacrylonitrile fibers have high construction temperature requirements. Glass fibers can improve asphalt mixtures' crack resistance and high-temperature performance, but they are brittle and difficult to produce and apply.

[0005] To address this, technicians have developed composite fiber processes. For example, patent application publication number CN106431088A discloses a method for preparing fiber cold-patch asphalt mixtures. The addition of polyester fibers, lignin fibers, and other materials to the asphalt mixture improves the road performance of the asphalt mixture to a certain extent, including Marshall stability, high-temperature stability, low-temperature crack resistance, and water stability. Another example is patent application publication number CN103739239A, which discloses a composite fiber material for asphalt mixtures. The material is formed by mixing three different types of fiber materials, lignin fiber, basalt fiber, and sepiolite fiber, in a certain proportion. This composite fiber material can extend the improvement effect of single fiber materials on the road performance of asphalt mixtures to the composite fiber material, and can comprehensively improve the various road performance characteristics of the road asphalt surface layer.

[0006] For the composite fibers in the above documents, although the corresponding performance can be improved to a certain extent through the complementary effect of different fibers, with the introduction of multiple fibers, the mechanical properties of each fiber, such as fracture strength, elastic modulus and other indicators, vary greatly, which will introduce more types of asphalt mortar / fiber interfaces into the system, affecting the mechanical response of the fiber asphalt mixture, and thus affecting the comprehensive performance of the pavement, such as anti-cracking. Summary of the Invention

[0007] In order to further improve the comprehensive performance of fiber-doped asphalt mixture, the present application provides a dry powder mixed asphalt mixture and a preparation method thereof.

[0008] In a first aspect, the present application provides a method for preparing a dry powder asphalt mixture, which adopts the following technical solution:

[0009] A method for preparing a dry powder asphalt mixture comprises the following steps:

[0010] 1) Mixing polyacrylonitrile, metal oxide, and solvent and stirring until uniformly mixed to prepare precursor solution A;

[0011] 2) Dissolve cyclodextrin in anhydrous ethanol to prepare a base solution; then add calcium chloride, polylauryl methacrylate, polycaprolactone, and a surfactant and mix well; then introduce excess carbon dioxide, allow to stand, and degas to prepare precursor solution B;

[0012] 3) Precursor liquid A and precursor liquid B are respectively delivered into syringes, and conjugate electrospinning is performed under the action of a high voltage electric field, and fractal fibers are obtained after winding;

[0013] 4) Tetrabutylammonium hydroxide solution, L-hydroxyproline and α-cellulose are uniformly mixed to prepare an impregnation solution, the fractal fibers are immersed in the impregnation solution, and then washed with deionized water, dried and cut to obtain a composite fiber material;

[0014] 5) Take 900-950 parts of aggregate, 60-70 parts of fly ash, and 4-5.5 parts of composite fiber material and dry mix them. Then add 60-70 parts of asphalt and continue mixing. Then add 30-50 parts of mineral powder and mix evenly.

[0015] Preferably, in step 1), the mass percentage of polyacrylonitrile in the precursor solution A is 15-18.5%;

[0016] And / or, in step 1), the mass percentage of the metal oxide in the precursor solution A is 0.15-0.3%;

[0017] And / or, in step 1), the solvent is one of N,N-dimethylformamide, dimethyl sulfoxide, sulfolane, and dimethylacetamide.

[0018] Preferably, the preparation method of the metal oxide comprises the following steps:

[0019] S1: Mix polysaccharide, urea, attapulgite and deionized water, then add ferric chloride and manganese chloride, control the pH value to 3-3.5, perform ultrasonic dispersion and let it stand to obtain a slurry;

[0020] S2: Slurry is slowly added dropwise to sodium hydroxide solution, aged for 2-3 hours, filtered out and transferred to an ice bath for cooling, centrifuged, washed with deionized water, dried and ground to obtain the product.

[0021] Preferably, the polysaccharide is one or more of carrageenan, sodium alginate, chitosan, and guar gum.

[0022] Preferably, the average particle size of the attapulgite is 20-150 μm.

[0023] Preferably, the molar ratio of Fe:Mn in the slurry is (2-2.5):1.

[0024] Preferably, in step 2), the mass percentage of cyclodextrin in the precursor solution B is 15-18.5%;

[0025] And / or, in step 2), the mass ratio of calcium chloride, polylauryl methacrylate, polycaprolactone, and surfactant is (0.5-0.75):(1-1.5):(2-3):(0.01-0.03);

[0026] And / or, in step 2), the surfactant is one of dodecyltrimethylammonium chloride, hexadecyltrimethylammonium chloride, and octadecyltrimethylammonium chloride.

[0027] Preferably, in step 3), the flow rate ratio of precursor solution A to precursor solution B is 1:(0.35-0.5).

[0028] Preferably, in step 4), the average length of the composite fiber material is 6 mm;

[0029] And / or, in step 4), the mass ratio of tetrabutylammonium hydroxide solution, L-hydroxyproline and α-cellulose is 1:(0.05-0.1):(0.1-0.15);

[0030] And / or, in step 4), the immersion time is 5-10 minutes.

[0031] In a second aspect, the present application provides a dry powder asphalt mixture prepared using the above-mentioned preparation method.

[0032] In summary, this application has the following beneficial effects:

[0033] 1. The present application first dry-mixes the aggregate, fly ash and composite fiber material, then adds asphalt for mixing, and finally adds mineral powder. On the one hand, this mixing method can reduce the entanglement and agglomeration between the fibers, making the composite fiber material more evenly dispersed. On the other hand, it can enhance the bonding force between the components of the mixture, increase the internal friction, and greatly improve the high-temperature stability and low-temperature crack resistance of the mixture.

[0034] 2. The fractal fibers made by two-component electrospinning are used in this application. After being impregnated, they are cut into composite fiber materials of appropriate size. Compared with traditional basalt fibers, polyester fibers or cellulose fibers, the composite fiber materials of this application have better interfacial bonding with the mixture matrix. Moreover, the composite fiber materials overlap with each other to form a bridge fiber network, which makes the asphalt mixture have higher strength and stiffness. In addition, the fiber surface of the composite fiber material forms a fractal structure with a large specific surface area, which can absorb more asphalt. Therefore, the asphalt addition amount in the asphalt mixture of this application is slightly higher, which also makes the bonding force between the fiber and the mixture greater, and the dynamic stability of the system is increased, which improves the high temperature stability and anti-cracking performance to a certain extent.

[0035] 3. In the fractal fiber preparation process of the present application, a certain amount of metal oxide is added to the precursor liquid A to enhance the toughness of the fractal fiber. Precursor liquid B uses polycaprolactone as a substrate and adds components such as cyclodextrin and polylauryl methacrylate to enhance the interfacial bonding force of the fractal fiber. In addition, the flow rate ratio of precursor liquid A to precursor liquid B is adjusted to make the fractal structure on the fiber surface more uniform, and after impregnation treatment, the micromechanical state between the fiber and the mixture matrix is improved, the interfacial shear strength is enhanced, and the anti-cracking performance and road performance of the mixture are further enhanced. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1It is a load-displacement test data chart of the composite fiber materials of Examples 1-3 of the present application and the polyacrylonitrile fiber of the control group.

[0037] Figure 2 This is an SEM image of the composite fiber material of Example 3 of the present application. DETAILED DESCRIPTION

[0038] The present application is further described in detail below with reference to the embodiments.

[0039] Unless otherwise specified, the raw materials used in the examples and comparative examples of the present application are all commercially available.

[0040] This application has undergone a large number of experiments and screenings to examine the performance differences between traditional fiber materials and composite fiber materials, and to optimize the preparation method of composite fiber materials. Without making major adjustments to components such as asphalt and aggregate, it further improves the anti-cracking performance and road performance of asphalt mixtures.

[0041] The present application provides a method for preparing a dry powder asphalt mixture, comprising the following steps:

[0042] 1) Mixing polyacrylonitrile, metal oxide, and solvent and stirring until uniformly mixed to prepare precursor solution A;

[0043] 2) Dissolve cyclodextrin in anhydrous ethanol to prepare a base solution; then add calcium chloride, polylauryl methacrylate, polycaprolactone, and a surfactant and mix well; then introduce excess carbon dioxide, allow to stand, and degas to prepare precursor solution B;

[0044] 3) Precursor liquid A and precursor liquid B are respectively delivered into syringes, and conjugate electrospinning is performed under the action of a high voltage electric field, and fractal fibers are obtained after winding;

[0045] 4) Tetrabutylammonium hydroxide solution, L-hydroxyproline and α-cellulose are uniformly mixed to prepare an impregnation solution, the fractal fibers are immersed in the impregnation solution, and then washed with deionized water, dried and cut to obtain a composite fiber material;

[0046] 5) Take 900-950 parts of aggregate, 60-70 parts of fly ash, and 4-5.5 parts of composite fiber material and dry mix them. Then add 60-70 parts of asphalt and continue mixing. Then add 30-50 parts of mineral powder and mix evenly.

[0047] Preferably, the aggregate includes coarse aggregate and fine aggregate, the coarse aggregate is basalt, and the fine aggregate is limestone. The specific gradation composition of the aggregate is shown in Table 1.

[0048] Table 1 Aggregate gradation composition of this application

[0049]

[0050] Preferably, the mineral powder of the present application is limestone mineral powder with a water content of 0.4% and a relative density of 2.705 g / cm -3 .

[0051] Preferably, the composition of the fly ash of the present application is as shown in Table 2.

[0052] Table 2 Composition of fly ash in this application

[0053]

[0054] Preferably, the asphalt of the present application is SBS modified asphalt, with a needle penetration (0.1 mm) of 72 at 25°C, a PI of 0.5, and a softening point of 86°C.

[0055] Preferably, in step 1), the mass percentage of polyacrylonitrile in the precursor solution A is 15-18.5%;

[0056] And / or, in step 1), the mass percentage of the metal oxide in the precursor solution A is 0.15-0.3%;

[0057] And / or, in step 1), the solvent is one of N,N-dimethylformamide, dimethyl sulfoxide, sulfolane, and dimethylacetamide.

[0058] In some specific embodiments, in step 1), the mass percentage of polyacrylonitrile in the precursor solution A may be 15-15.5%, 15.5-16%, 16-16.5%, 16.5-17%, 17-17.5%, 17.5-18%, or 18-18.5%; more preferably, the mass percentage of polyacrylonitrile in the precursor solution A may be 15%, 15.5%, 16%, 16.2%, 16.5%, 16.8%, 17%, 17.5%, 18%, or 18.5%, and under normal circumstances, better experimental results can be obtained when the mass percentage of polyacrylonitrile in the precursor solution A is 16.5%.

[0059] In some specific embodiments, in step 1), the mass percentage of metal oxide in the precursor solution A can be 0.15-0.17%, 0.17-0.2%, 0.2-0.23%, 0.23-0.25%, or 0.25-0.3%. More preferably, the mass percentage of metal oxide in the precursor solution A can be 0.15%, 0.17%, 0.19%, 0.2%, 0.23%, 0.25%, 0.28%, or 0.3%. Under normal circumstances, when the mass percentage of metal oxide in the precursor solution A is 0.2%, better experimental results can be obtained.

[0060] Preferably, the preparation method of the metal oxide comprises the following steps:

[0061] S1: Mix polysaccharide, urea, attapulgite and deionized water, then add ferric chloride and manganese chloride, control the pH value to 3-3.5, perform ultrasonic dispersion and let it stand to obtain a slurry;

[0062] S2: Slurry is slowly added dropwise to sodium hydroxide solution, aged for 2-3 hours, filtered out and transferred to an ice bath for cooling, centrifuged, washed with deionized water, dried and ground to obtain the product.

[0063] Preferably, the polysaccharide is one or more of carrageenan, sodium alginate, chitosan, and guar gum. More preferably, the polysaccharide is composed of carrageenan and sodium alginate in a mass ratio of 1:2.5.

[0064] Preferably, the average particle size of the attapulgite is 20-150 μm. More preferably, when the average particle size of the attapulgite is 50-100 μm, better experimental results can be obtained.

[0065] Preferably, the molar ratio of Fe:Mn in the slurry is (2-2.5): 1. Generally, when the molar ratio of Fe:Mn in the slurry is 2:1, the experimental effect is better.

[0066] Preferably, in step 2), the mass percentage of cyclodextrin in the precursor solution B is 15-18.5%;

[0067] In some specific embodiments, the mass percentage of cyclodextrin in precursor solution B can be 15-15.5%, 15.5-16%, 16-16.5%, 16.5-17%, 17-17.5%, 17.5-18%, or 18-18.5%. More preferably, the mass percentage of cyclodextrin in precursor solution B can be 15%, 15.5%, 16%, 16.5%, 17%, 17.5%, 18%, or 18.5%. Under normal circumstances, when the mass percentage of cyclodextrin in precursor solution B is 18%, better experimental results can be obtained.

[0068] And / or, in step 2), the mass ratio of calcium chloride, polylauryl methacrylate, polycaprolactone, and surfactant is (0.5-0.75):(1-1.5):(2-3):(0.01-0.03);

[0069] In some specific embodiments, in step 2), the mass ratio of calcium chloride, polylauryl methacrylate, polycaprolactone, and surfactant can be 0.5:1:2:0.01, 0.6:1:2:0.01, 0.65:1:2:0.01, 0.7:1:2:0.01, 0.75:1:2:0.01, 0.5:1.2:2:0.01, 0.5:1.5:2:0.01, 0.5:1:2.5:0.01, 0.5:1:3:0.01, 0.6:1.2:2:0.0 1. 0.6:1.5:2:0.01, 0.65:1.5:2:0.01, 0.7:1.5:2:0.01, 0.75:1.5:2:0.01, 0.7:1:2:0.02, 0.75:1:2:0.03, 0.75:1:2.5:0.01, 0.75:1:3:0.01; More preferably, under normal circumstances, when the mass ratio of calcium chloride, polylauryl methacrylate, polycaprolactone, and surfactant is 0.6:1.5:3:0.015, the experimental effect is better.

[0070] And / or, in step 2), the surfactant is one of dodecyltrimethylammonium chloride, hexadecyltrimethylammonium chloride, and octadecyltrimethylammonium chloride.

[0071] Preferably, in step 3), the flow rate ratio of precursor solution A to precursor solution B is 1:(0.35-0.5).

[0072] In some specific embodiments, the flow rate ratio of precursor liquid A and precursor liquid B can be 1:(0.35-0.38), 1:(0.38-0.4), 1:(0.4-0.45), 1:(0.45-0.5), and more preferably, the flow rate ratio of precursor liquid A and precursor liquid B can be 1:0.35, 1:0.38, 1:0.4, 1:0.43, 1:0.45, 1:0.5, and, after screening, under normal circumstances, a better experimental effect can be obtained when the flow rate ratio of precursor liquid A and precursor liquid B is 1:0.38.

[0073] Preferably, in step 4), the average length of the composite fiber material is 6 mm;

[0074] And / or, in step 4), the mass ratio of tetrabutylammonium hydroxide solution, L-hydroxyproline and α-cellulose is 1:(0.05-0.1):(0.1-0.15);

[0075] In some specific embodiments, the mass ratio of tetrabutylammonium hydroxide solution, L-hydroxyproline and α-cellulose can be 1:0.05:0.1, 1:0.06:0.1, 1:0.07:0.1, 1:0.08:0.1, 1:0.09:0.1, 1:0.05:0.12, 1:0.05:0.15, 1:0.06:0.12, 1:0.06:0.15, 1:0.07:0.12, 1:0.07:0.15, 1:0.08:0.12, 1:0.08:0.15, 1:0.09:0.12, and 1:0.09:0.15. Under normal circumstances, when the mass ratio of tetrabutylammonium hydroxide solution, L-hydroxyproline and α-cellulose is 1:0.075:0.15, better experimental results can be obtained.

[0076] And / or, in step 4), the immersion time is 5-10 minutes. Example 1

[0077] The method for preparing the dry powder asphalt mixture of this embodiment includes the following steps:

[0078] 1) Dried polyacrylonitrile powder (relative molecular weight 5×10 4 ) is dissolved in N,N-dimethylformamide solvent, heated to fully dissolve, and then the metal oxide is added and mixed and stirred. The precursor solution A is prepared by mixing evenly. The mass fraction of polyacrylonitrile in the precursor solution A is controlled to be 16.5%, and the mass fraction of the metal oxide in the precursor solution A is controlled to be 0.2%;

[0079] The preparation method of the metal oxide comprises the following steps:

[0080] S1: 35 g of polysaccharide, 5 g of urea, 20 g of attapulgite, and 150 mL of deionized water were mixed uniformly, and then 2 g of ferric chloride hexahydrate and 0.732 g of manganese chloride tetrahydrate were added. The pH value was controlled to be 3-3.5. After ultrasonic dispersion, the mixture was allowed to stand to obtain a slurry. The molar ratio of Fe:Mn in the slurry was 2:1.

[0081] S2: The slurry was slowly added dropwise to 100 mL of 3 M sodium hydroxide solution, aged for 3 h, filtered, transferred to an ice bath for cooling, centrifuged, washed three times with deionized water, dried, and ground;

[0082] 2) β-cyclodextrin was dissolved in anhydrous ethanol to prepare a base solution; calcium chloride, polylauryl methacrylate, polycaprolactone, and a surfactant were then added and mixed uniformly, with the mass ratio of calcium chloride, polylauryl methacrylate, polycaprolactone, and surfactant controlled to be 0.6:1.5:3:0.015. Excess carbon dioxide was then introduced, and the mixture was allowed to stand and degas to prepare precursor solution B. The mass percentage of cyclodextrin in precursor solution B was controlled to be 18%;

[0083] 3) Precursor A and precursor B were delivered to syringes 1 and 2, respectively. The flow rates of syringes 1 and 2 were controlled to achieve a flow rate ratio of 1:0.38. Syringe 1 was negatively charged and syringe 2 was positively charged. Under the action of a high-voltage electric field, precursors A and B were stretched into fibers. Under the action of electrostatics, they aggregated and formed a cone, and fibers were formed by stretching and twisting. Fractal fibers were obtained after winding and collection. The voltage of syringe 1 was 18 kV, and the voltage of syringe 2 was 15 kV. The total flow rate of precursors A and B was 3.5 mL / min, and the winding speed was 0.16 mm / s.

[0084] 4) A 40% by mass tetrabutylammonium hydroxide solution, L-hydroxyproline, and α-cellulose were mixed in a mass ratio of 1:0.075:0.15 to prepare an impregnation solution. The fractal fibers were immersed in the impregnation solution for 10 minutes, washed with deionized water, dried, and cut to obtain a composite fiber material with an average length of 6 mm and a diameter of 15 μm.

[0085] 5) Take 9 kg of aggregate, 0.6 kg of fly ash, and 0.04 kg of composite fiber material and put them into an automatic mixer for dry mixing for 90 seconds. Then add 0.6 kg of molten asphalt and mix thoroughly for 90 seconds. Then add 0.5 kg of mineral powder and continue mixing for 90 seconds to obtain a dry powder mixed asphalt mixture.

[0086] The polysaccharide is composed of carrageenan and sodium alginate in a mass ratio of 1:2.5. The average particle size of the attapulgite is 50 μm. Example 2

[0087] The method for preparing the dry powder asphalt mixture of this embodiment includes the following steps:

[0088] 1) Dried polyacrylonitrile powder (relative molecular weight 5×10 4 ) is dissolved in N,N-dimethylformamide solvent, heated to fully dissolve, and then the metal oxide is added and mixed and stirred. The precursor solution A is prepared by mixing evenly. The mass fraction of polyacrylonitrile in the precursor solution A is controlled to be 16.5%, and the mass fraction of the metal oxide in the precursor solution A is controlled to be 0.2%;

[0089] The preparation method of the metal oxide comprises the following steps:

[0090] S1: 35 g of polysaccharide, 5 g of urea, 20 g of attapulgite, and 150 mL of deionized water were mixed uniformly, and then 2 g of ferric chloride hexahydrate and 0.732 g of manganese chloride tetrahydrate were added. The pH value was controlled to be 3-3.5. After ultrasonic dispersion, the mixture was allowed to stand to obtain a slurry. The molar ratio of Fe:Mn in the slurry was 2:1.

[0091] S2: The slurry was slowly added dropwise to 100 mL of 3 M sodium hydroxide solution, aged for 3 h, filtered, transferred to an ice bath for cooling, centrifuged, washed three times with deionized water, dried, and ground;

[0092] 2) β-cyclodextrin was dissolved in anhydrous ethanol to prepare a base solution; calcium chloride, polylauryl methacrylate, polycaprolactone, and a surfactant were then added and mixed uniformly, with the mass ratio of calcium chloride, polylauryl methacrylate, polycaprolactone, and surfactant controlled to be 0.6:1.5:3:0.015. Excess carbon dioxide was then introduced, and the mixture was allowed to stand and degas to prepare precursor solution B. The mass percentage of cyclodextrin in precursor solution B was controlled to be 18%;

[0093] 3) Precursor A and precursor B were delivered to syringes 1 and 2, respectively. The flow rates of syringes 1 and 2 were controlled to achieve a flow rate ratio of 1:0.38. Syringe 1 was negatively charged and syringe 2 was positively charged. Under the action of a high-voltage electric field, precursors A and B were stretched into fibers. Under the action of electrostatics, they aggregated and formed a cone, and fibers were formed by stretching and twisting. Fractal fibers were obtained after winding and collection. The voltage of syringe 1 was 18 kV, and the voltage of syringe 2 was 15 kV. The total flow rate of precursors A and B was 3.5 mL / min, and the winding speed was 0.16 mm / s.

[0094] 4) A 40% by mass tetrabutylammonium hydroxide solution, L-hydroxyproline, and α-cellulose were mixed in a mass ratio of 1:0.075:0.15 to prepare an impregnation solution. The fractal fibers were immersed in the impregnation solution for 10 minutes, washed with deionized water, dried, and cut to obtain a composite fiber material with an average length of 6 mm and a diameter of 15 μm.

[0095] 5) Take 9.5 kg of aggregate, 0.7 kg of fly ash, and 0.055 kg of composite fiber material and put them into an automatic mixer for dry mixing for 90 seconds. Then add 0.7 kg of molten asphalt and mix thoroughly for 90 seconds. Then add 0.5 kg of mineral powder and continue mixing for 90 seconds to obtain a dry powder mixed asphalt mixture.

[0096] The polysaccharide is composed of carrageenan and sodium alginate in a mass ratio of 1:2.5. The average particle size of the attapulgite is 100 μm. Example 3

[0097] The method for preparing the dry powder asphalt mixture of this embodiment includes the following steps:

[0098] 1) Dried polyacrylonitrile powder (relative molecular weight 5×10 4) is dissolved in N,N-dimethylformamide solvent, heated to fully dissolve, and then the metal oxide is added and mixed and stirred. The precursor solution A is prepared by mixing evenly. The mass fraction of polyacrylonitrile in the precursor solution A is controlled to be 16.5%, and the mass fraction of the metal oxide in the precursor solution A is controlled to be 0.2%;

[0099] The preparation method of the metal oxide comprises the following steps:

[0100] S1: 35 g of polysaccharide, 5 g of urea, 20 g of attapulgite, and 150 mL of deionized water were mixed uniformly, and then 2 g of ferric chloride hexahydrate and 0.732 g of manganese chloride tetrahydrate were added. The pH value was controlled to be 3-3.5. After ultrasonic dispersion, the mixture was allowed to stand to obtain a slurry. The molar ratio of Fe:Mn in the slurry was 2:1.

[0101] S2: The slurry was slowly added dropwise to 100 mL of 3 M sodium hydroxide solution, aged for 3 h, filtered, transferred to an ice bath for cooling, centrifuged, washed three times with deionized water, dried, and ground;

[0102] 2) β-cyclodextrin was dissolved in anhydrous ethanol to prepare a base solution; calcium chloride, polylauryl methacrylate, polycaprolactone, and a surfactant were then added and mixed uniformly, with the mass ratio of calcium chloride, polylauryl methacrylate, polycaprolactone, and surfactant controlled to be 0.6:1.5:3:0.015. Excess carbon dioxide was then introduced, and the mixture was allowed to stand and degas to prepare precursor solution B. The mass percentage of cyclodextrin in precursor solution B was controlled to be 18%;

[0103] 3) Precursor A and precursor B were delivered to syringes 1 and 2, respectively. The flow rates of syringes 1 and 2 were controlled to achieve a flow rate ratio of 1:0.38. Syringe 1 was negatively charged and syringe 2 was positively charged. Under the action of a high-voltage electric field, precursors A and B were stretched into fibers. Under the action of electrostatics, they aggregated and formed a cone, and fibers were formed by stretching and twisting. Fractal fibers were obtained after winding and collection. The voltage of syringe 1 was 18 kV, and the voltage of syringe 2 was 15 kV. The total flow rate of precursors A and B was 3.5 mL / min, and the winding speed was 0.16 mm / s.

[0104] 4) A 40% by mass tetrabutylammonium hydroxide solution, L-hydroxyproline, and α-cellulose were mixed in a mass ratio of 1:0.075:0.15 to prepare an impregnation solution. The fractal fibers were immersed in the impregnation solution for 10 minutes, washed with deionized water, dried, and cut to obtain a composite fiber material with an average length of 6 mm and a diameter of 15 μm.

[0105] 5) Take 9 kg of aggregate, 0.65 kg of fly ash, and 0.05 kg of composite fiber material and put them into an automatic mixer for dry mixing for 90 seconds. Then add 0.65 kg of molten asphalt and mix thoroughly for 90 seconds. Then add 0.35 kg of mineral powder and continue mixing for 90 seconds to obtain a dry powder mixed asphalt mixture.

[0106] The polysaccharide is composed of carrageenan and sodium alginate in a mass ratio of 1:2.5. The average particle size of the attapulgite is 50 μm.

[0107] control group

[0108] The preparation method of the dry powder asphalt mixture of the control group includes the following steps:

[0109] Take 9kg of aggregate, 0.6kg of fly ash, and 0.04kg of polyacrylonitrile fiber (average length 6mm, diameter about 15μm) and put them into an automatic mixer for dry mixing for 90s, then add 0.6kg of molten asphalt and mix thoroughly for 90s, then add 0.5kg of mineral powder and continue mixing for 90s to obtain dry powder mixed asphalt mixture.

[0110] Performance testing

[0111] 1. The dry powder asphalt mixtures of Examples 1-3 and the control group were subjected to Marshall stability tests. The test results are shown in Table 3.

[0112] Table 3 Marshall test results of dry powder asphalt mixtures of Examples 1-3 and the control group

[0113]

[0114] As can be seen from Table 3, the composite fiber material of the present application has higher stability and better crack resistance than conventional polyacrylonitrile fiber.

[0115] 2. Take the dry powder mix asphalt mixtures of Examples 1-3 and the control group, and according to the requirements of the "Test Procedure for Asphalt and Asphalt Mixtures in Highway Engineering" (JTG E20-2011), use a wheel roller to roll the mixture into plate-shaped specimens. After the plate specimens are cooled at room temperature for 12 hours, they are processed into prismatic specimens with a length of 250 mm, a width of 30 mm, and a height of 35 mm using a fully automatic cutting machine. Three specimens are prepared for each group of mixtures.

[0116] The prepared specimens were placed in a constant temperature water bath at -10°C and kept warm until the temperature of the specimens was consistent with that of the constant temperature water bath and the temperature readings were stable. After the insulation was completed, a multifunctional fully automatic asphalt pressure tester was used to load the span of the prism at a loading rate of 50 mm / min. The parameters of the specimens after loading were recorded, and the mid-span height and width were measured respectively. The anti-cracking properties such as flexural strain and bending stiffness modulus were calculated according to the requirements of the specification. The specific results are shown in Table 4.

[0117] Table 4 Test results of crack resistance of dry powder asphalt mixtures of Examples 1-3 and the control group

[0118]

[0119] 3. The above-mentioned asphalt and mineral powder were mixed evenly at a powder-to-binder ratio of 1:1 as the matrix material. The uncut composite fiber materials of Examples 1-3 and the polyacrylonitrile fiber of the control group were taken, the fibers were straightened, one end was buried in the matrix material, and then a tensile load was applied along the axial direction of the fiber to gradually pull the fiber out. The tensile load-displacement relationship was recorded using a micromechanical experimental platform. The test parameters were: fiber length 15 cm, tensile speed 3 mm / min, temperature 25 ° C, and burial depth 6 mm. The test results are as follows: Figure 1 As shown, it can be seen that the fractal fiber of the present application has higher peak load and stability than traditional polyacrylonitrile fiber, which helps to improve the anti-cracking performance and road performance of the mixture.

[0120] The composite fiber material of Example 3 was tested by scanning electron microscope. The test results are as follows: Figure 2 As shown, it can be seen that the surface of the composite fiber material of the present application has a fractal structure, which is beneficial to improving the anti-cracking performance of the mixture.

[0121] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A method for preparing a dry powder asphalt mixture, characterized in that: The steps include: 1) Polyacrylonitrile, a metal oxide, and a solvent are mixed and stirred to obtain a precursor solution A; the mass percentage of polyacrylonitrile in the precursor solution A is 15-18.5%; the mass percentage of the metal oxide in the precursor solution A is 0.15-0.3%. The preparation method of the metal oxide comprises the following steps: S1: uniformly mixing a polysaccharide, urea, attapulgite, and deionized water, then adding ferric chloride and manganese chloride, controlling the pH value to 3-3.5, ultrasonically dispersing, and allowing to stand to obtain a slurry; S2: slowly adding the slurry dropwise to a sodium hydroxide solution, aging for 2-3 hours, filtering, transferring to an ice bath for cooling, centrifuging, washing with deionized water, drying, and grinding to obtain the slurry; 2) Dissolve cyclodextrin in anhydrous ethanol to prepare a base solution; then add calcium chloride, polylauryl methacrylate, polycaprolactone, and a surfactant in a mass ratio of (0.5-0.75):(1-1.5):(2-3):(0.01-0.03) and mix evenly; then introduce excess carbon dioxide, allow to stand, and degas to prepare precursor solution B; the mass percentage of cyclodextrin in precursor solution B is 15-18.5%; 3) Precursor liquid A and precursor liquid B are respectively delivered into syringes, and conjugate electrospinning is performed under the action of a high voltage electric field, and fractal fibers are obtained after winding; 4) Tetrabutylammonium hydroxide solution, L-hydroxyproline, and α-cellulose were uniformly mixed to prepare an impregnation solution, and the fractal fibers were immersed in the impregnation solution, and then washed with deionized water, dried, and cut to prepare a composite fiber material; the average length of the composite fiber material was 6 mm; 5) Take 900-950 parts of aggregate, 60-70 parts of fly ash, and 4-5.5 parts of composite fiber material and dry mix them. Then add 50-60 parts of asphalt and continue mixing. Then add 30-50 parts of mineral powder and mix evenly.

2. The method for preparing a dry powder asphalt mixture according to claim 1, characterized in that: In the step 1), the solvent is one of N,N-dimethylformamide, dimethyl sulfoxide, sulfolane, and dimethylacetamide.

3. The method for preparing a dry powder asphalt mixture according to claim 1, characterized in that: The polysaccharide is one or more of carrageenan, sodium alginate, chitosan and guar gum.

4. The method for preparing a dry powder asphalt mixture according to claim 1, wherein: The average particle size of the attapulgite is 20-150 μm.

5. The method for preparing a dry powder asphalt mixture according to claim 1, characterized in that: The molar ratio of Fe:Mn in the slurry is (2-2.5):

1.

6. The method for preparing a dry powder asphalt mixture according to claim 1, characterized in that: In the step 2), the surfactant is one of dodecyltrimethylammonium chloride, hexadecyltrimethylammonium chloride, and octadecyltrimethylammonium chloride.

7. The method for preparing a dry powder asphalt mixture according to claim 1, characterized in that: In step 3), the flow rate ratio of precursor solution A to precursor solution B is 1:(0.35-0.5).

8. The method for preparing a dry powder asphalt mixture according to claim 1, characterized in that: In the step 4), the mass ratio of tetrabutylammonium hydroxide solution, L-hydroxyproline and α-cellulose is 1:(0.05-0.1):(0.1-0.15); And / or, in step 4), the immersion time is 5-10 minutes.

9. A dry powder asphalt mixture prepared by the preparation method according to any one of claims 1 to 8.

Images