Cold asphalt mixture adapting to low-temperature environment and preparation method thereof

Abstract

The invention relates to the technical field of asphalt mixtures, and particularly discloses a cold asphalt mixture adapting to a low-temperature environment and a preparation method of the cold asphalt mixture. The cold asphalt mixture adapting to the low-temperature environment is prepared from the following raw materials in parts by weight: 5 to 8 parts of modified emulsified asphalt, 0.3 to 0.6 part of composite fiber, 4 to 6 parts of filler, 0.2 to 0.4 part of antifreeze agent, 0.5 to 2 parts of polyolefin elastomer and the balance of aggregate. When the modified emulsified asphalt is prepared, the nano filler is modified, so that the compatibility of the nano filler and an asphalt matrix is improved, and the low-temperature crack resistance of the cooled asphalt mixture is further improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of asphalt mixture, more particularly, it relates to a cold asphalt mixture suitable for low-temperature environment and a preparation method thereof. BACKGROUND

[0002] As the core material of road construction, the performance of asphalt mixture directly determines the service life and driving safety of the road. Traditional hot-mix asphalt mixture needs to be mixed and constructed at a high temperature of 150-180℃, which has problems such as high energy consumption, large carbon emissions, high-temperature exhaust pollution, etc. In addition, in the winter low-temperature environment (usually below 5℃) or emergency repair scene, it is easy to cause paving difficulty and insufficient compaction due to rapid temperature loss, resulting in early damage. Cold asphalt mixture gradually becomes the preferred material for special scenes such as cold region road construction, winter repair and tunnel paving, etc. due to its advantages such as normal temperature mixing, low energy consumption and flexible construction, which meets the energy saving and emission reduction requirements of green road construction.

[0003] However, the existing cold asphalt mixture has weak anti-freezing and thawing performance when applied in low-temperature environment (especially in the range of-10℃ to 5℃). Ice crystals are easily formed inside the mixture in low-temperature environment. After repeated freeze-thaw cycles, the structure compactness is damaged, the strength is greatly attenuated, and the service life of the road surface is shortened.

[0004] At present, most of the cold asphalt mixtures are prepared by adding fibers to asphalt. For example, the patent application file with publication number CN106431088A discloses a preparation method of a fiber cold patch asphalt mixture, which has a composition by mass percentage of 0.1%-0.5% of fiber, 3%-8% of cold patch asphalt, 3%-5% of filler, and the rest of aggregate. The fiber is polyester fiber or lignin fiber. The cold patch asphalt is composed of asphalt, diluent and clay mineral material in a mass ratio of 65-80:13-25:3-9. The clay mineral material includes any one or mixture of several of bentonite, kaolin, attapulgite and diatomite. At the same time, the asphalt is heated to 100-150℃, the clay mineral material is first added and stirred to completely dissolve in the asphalt, then the temperature is reduced to 60-100℃, the diluent is added and stirred uniformly to obtain the cold patch asphalt. In this scheme, the hydrophilic clay mineral material has poor compatibility with the hydrophobic asphalt in the preparation process of the cold patch asphalt, and is easy to form agglomerates and has weak interfacial adhesion. Not only will it induce microcracks and damage the asphalt colloid structure to weaken its low-temperature toughness by forming stress concentration points at low temperature, but also will accelerate the interface failure and crack propagation by synergistic effect with factors such as diluent volatilization and freeze-thaw cycle, ultimately resulting in insufficient low-temperature crack resistance of the mixture. SUMMARY

[0005] In order to improve the low-temperature crack resistance of the cold asphalt mixture, the present application provides a cold asphalt mixture suitable for low-temperature environment and a preparation method thereof.

[0006] In a first aspect, the application provides a cold asphalt mixture suitable for low-temperature environment, which adopts the following technical solution: The cold asphalt mixture suitable for low-temperature environment comprises the following raw materials by weight: 5-8 parts of modified emulsified asphalt, 0.3-0.6 parts of composite fiber, 4-6 parts of filler, 0.2-0.4 parts of anti-freezing agent, 0.5-2 parts of polyolefin elastomer, and the rest is aggregate. The preparation method of the modified emulsified asphalt comprises the following steps: After 50-65 parts of base asphalt by weight is heated, 10-20 parts of waste tire rubber powder emulsion by weight is added, and after stirring uniformly, 0.5-3 parts of SBS by weight and 0.5-2 parts of modified nano filler by weight are added, and after ultrasonic dispersion and shearing treatment, a modified asphalt premix is obtained. The modified asphalt premix is added with 0.5-2 parts of emulsifier by weight, 1-5 parts of diluent by weight and 25-45 parts of water by weight, and after stirring uniformly, emulsified asphalt is obtained, and finally 0.1-1 parts of anti-peeling agent by weight is added and stirred uniformly to obtain modified emulsified asphalt.

[0007] By adopting the above technical solution, the compatibility with the base asphalt is improved by modifying the nano filler in the modified emulsified asphalt, and the waste tire rubber powder emulsion and SBS form a synergistic toughening effect, effectively improving the low-temperature plasticity and mechanical properties of the asphalt matrix, and the anti-peeling agent strengthens the adhesion stability of the asphalt and the aggregate, and the reinforcing and crack inhibiting effect of the composite fiber on the mixture structure improves the low-temperature crack resistance of the cold asphalt mixture.

[0008] Preferably, the modified nano filler is obtained by grafting polyethylene glycol on the nano filler after plasma treatment.

[0009] By adopting the above technical solution, the surface of the nano filler is activated by plasma treatment, so that active functional groups such as hydroxyl and carboxyl are generated, the chemical inertness of the filler surface is broken and the reaction sites are increased, laying a foundation for subsequent grafting reaction; then the active functional groups are used for grafting reaction with polyethylene glycol, so that the polyethylene glycol molecules are firmly combined on the surface of the filler to form a functional modified layer. The dispersibility of the nano filler in the asphalt matrix is improved, the agglomeration phenomenon of the nano particles due to the large specific surface area is effectively inhibited, and the reinforcing effect is fully played; at the same time, the flexibility of polyethylene glycol can optimize the interfacial bonding force between the filler and the asphalt matrix, improve the compatibility between them, form a synergistic effect with SBS, waste tire rubber powder emulsion and other components, further enhance the low-temperature plasticity and mechanical properties of the modified asphalt, and improve the low-temperature crack resistance of the cold asphalt mixture.

[0010] Preferably, the nano filler is one or more of montmorillonite and graphene.

[0011] Preferably, the nanofiller is a mixture of montmorillonite and graphene with a mass ratio of 1:(2-5).

[0012] By adopting the above technical solution, the two-dimensional carbon sheet layer of graphene has super-high mechanical strength and toughness, can inhibit the propagation of low-temperature micro-cracks through the bridging effect, and can efficiently transfer stress; the layered silicate structure of montmorillonite can accommodate asphalt molecules through intercalation, improve the stability of the system, and delay the erosion of oxygen and ultraviolet light on the asphalt by virtue of the interlayer barrier effect. After mixing, the flexibility of graphene and the rigidity of montmorillonite form a rigid-flexible multi-scale structure, which not only alleviates the problem of easy agglomeration of graphene, but also makes up for the deficiency of the mechanical properties of montmorillonite. It can not only improve the low-temperature crack resistance of cold asphalt mixture, but also improve the bending failure strain at extremely low temperature by synergistically inhibiting crack initiation and propagation; it can also enhance the anti-aging and anti-freezing and thawing ability, and the barrier property of montmorillonite and the thermal conductivity of graphene synergistically resist environmental erosion to improve the freeze-thaw splitting strength ratio.

[0013] Preferably, the preparation method of the modified nanofiller is: modifying graphene by oxygen plasma treatment to obtain carboxylated graphene, modifying montmorillonite by ammonia plasma treatment to obtain aminated montmorillonite; carrying out amidation reaction on the carboxylated graphene and the aminated montmorillonite to obtain a nanocomposite; and grafting polyethylene glycol on the surface of the nanocomposite to obtain the modified nanofiller.

[0014] By adopting the above technical solution, the chemical combination between graphene and montmorillonite not only greatly improves the structural stability of the modified nanofiller, but also resists freeze-thaw cycles by virtue of the high bond energy of the covalent bond, avoiding problems such as separation of the filler interface and interlayer peeling in long-term use; at the same time, the synergistic effect of the two is more significant, the two-dimensional sheet-layer covalent network constructed by chemical combination can achieve efficient stress transfer, the crack bridging effect of graphene and the intercalation enhancement effect of montmorillonite are deeply synergized, and the stress buffer of the polyethylene glycol flexible segment improves the material toughness and crack resistance; in addition, the functional groups introduced by plasma modification and the subsequent PEG grafting effectively inhibit the agglomeration tendency of nanoparticles, and at the same time, the interface adhesion between the filler and the asphalt matrix is strengthened, further improving the low-temperature ductility of the modified emulsified asphalt.

[0015] Preferably, the modified nanofiller is obtained by compounding the nanofiller with oxidized polyethylene wax after plasma treatment, and then grafting polyethylene glycol; the mass ratio of the nanofiller to the oxidized polyethylene wax is (85-95):(5-15).

[0016] By adopting the technical scheme, the oxidized polyethylene wax is stably combined with the nano filler through chemical bonding to form a rigid skeleton-flexible segment composite structure; the rigidity of the nano filler and the flexible segment of the wax cooperate to disperse low-temperature stress and block crack propagation through the rigid skeleton, and to relieve shrinkage strain and improve low-temperature flexibility through the flexible segment, and meanwhile, the wax molecules can avoid agglomeration of the nano particles and are compatible with the subsequently grafted polyethylene glycol, so that the dispersibility of the nano filler in the emulsified asphalt and the asphalt compatibility are balanced, and the low-temperature anti-cracking performance of the cold asphalt mixture is enhanced.

[0017] Preferably, the composite fiber is a mixture of polyester fiber and lignin fiber with a mass ratio of (5-7):(3-5).

[0018] By adopting the technical scheme, the polyester fiber constructs a rigid support skeleton with high strength to resist tensile stress generated by low-temperature shrinkage, and the lignin fiber buffers local stress concentration with good flexibility, and the two cooperate to form a three-dimensional network structure to effectively inhibit crack initiation and propagation; compared with a single fiber, the compound system can significantly improve the low-temperature anti-cracking performance of the mixture, and at the same time, enhance the interface bonding stability, and through the synergistic effect of the fiber and the asphalt, the low-temperature flexibility and structural integrity are taken into account.

[0019] Preferably, the filler is a mixture of cement and limestone with a mass ratio of (4-6):(1-2).

[0020] By adopting the technical scheme, the cement as an active component can have a hydration reaction with the water released by the demulsification of the emulsified asphalt, and the generated hydration calcium silicate and other gel products not only fill the interstitial gaps of the aggregate, but also enhance the interface bonding force between the asphalt and the aggregate to form a transition zone combining rigidity and flexibility; the limestone as an inert filling component optimizes the aggregate gradation by virtue of the fine particle size to improve the compactness of the mixture and reduce the pore stress concentration during low-temperature shrinkage. Under the synergistic effect of the two, the hydration product of the cement provides low-temperature early strength support, and the filling effect of the limestone reduces the internal porosity of the structure, and together they build a dense and strongly bonded stable structure to uniformly transmit stress at low temperature. Compared with single cement or single limestone, the compound system can not only improve the compressive strength, but also retain the low-temperature flexibility through the dense structure and interface reinforcement, and adapt to the strength and flexibility balance requirements in low-temperature environment.

[0021] Preferably, the aggregate is a mixture of basalt macadam, machine-made sand and old road milling material with a mass ratio of (40-60):(15-30):(20-35).

[0022] By adopting the above technical solution, basalt crushed stone, with its high strength and low-temperature resistance, forms a rigid skeleton, providing support against shrinkage deformation in low-temperature environments for the mixture. Manufactured sand, through continuous gradation, fills the gaps between the crushed stone, increasing density to reduce pore ice crystal damage during freeze-thaw cycles and increasing the contact area with modified emulsified asphalt to strengthen interfacial bonding. Milled aggregate from old road surfaces utilizes its recycled aggregate morphology to assist in skeleton filling, while old asphalt can synergistically improve low-temperature bonding continuity with modified emulsified asphalt. The combined effect of these three elements ensures low-temperature crack resistance and freeze-thaw stability through the combination of basalt and manufactured sand, achieves resource recycling through the recycling of old materials, and provides continuous and controllable gradation, balancing workability for cold-mix construction with long-term structural durability.

[0023] Secondly, this application provides a method for preparing cold asphalt mixtures adapted to low-temperature environments, employing the following technical solution: A method for preparing cold asphalt mixture adapted to low-temperature environments includes the following steps: After mixing aggregates and composite fibers at room temperature, modified emulsified asphalt is added. After mixing evenly, fillers, antifreeze agents, and polyolefin elastomers are added. After mixing evenly, the mixture is cooled to room temperature to obtain cold asphalt mixture.

[0024] By adopting the above technical solution, the addition sequence of the above preparation method follows the logic of skeleton pre-dispersion - bonding coating - functional reinforcement. First, the aggregate and composite fiber are stirred at room temperature. The mechanical dispersion of the aggregate allows the fiber to be uniformly attached to the aggregate surface, avoiding fiber agglomeration and laying the foundation for the subsequent formation of a three-dimensional reinforcement network. Then, modified emulsified asphalt is added. With the fiber and aggregate already fully mixed, the asphalt can more uniformly coat the surfaces of the two, strengthening the interfacial bonding. Finally, fillers, antifreeze agents, and polyolefin elastomers are added. The void structure of the asphalt-aggregate-fiber matrix formed in the previous stage can be used to achieve fine particle filling. At the same time, the functional additives are uniformly dispersed in the asphalt system, ensuring that the compaction effect of the filler, the freezing point regulation effect of the antifreeze agent, and the low-temperature toughness improvement effect of the polyolefin elastomer are effectively exerted. This preparation method not only ensures the uniform dispersion of each component, but also promotes the multi-dimensional effect of skeleton support, fiber reinforcement, asphalt bonding, and functional additives, ultimately improving the low-temperature performance and structural stability of the mixture.

[0025] In summary, this application has the following beneficial effects: 1. This application modifies the nanofiller to improve its compatibility with asphalt; at the same time, the waste tire rubber powder emulsion incorporated into the modified emulsified asphalt forms a synergistic toughening effect with SBS, which, together with the reinforcing effect of the modified nanofiller, effectively improves the low-temperature plasticity and mechanical properties of the asphalt matrix.

[0026] 2. The nanofiller in this application is obtained by grafting polyethylene glycol onto the nanofiller after plasma treatment. This improves the dispersion stability of the nanofiller in the asphalt matrix, effectively inhibits the agglomeration of nanoparticles due to their large specific surface area, and fully exerts their reinforcing effect. At the same time, the flexibility of polyethylene glycol can optimize the interfacial bonding force between the filler and the asphalt matrix, further improving the low-temperature crack resistance of the asphalt mixture.

[0027] 3. The nanofiller used in this application is a mixture of graphene and montmorillonite, and the two are chemically bonded together to improve the structural stability of the modified nanofiller, and the synergistic enhancement effect is more significant, which further improves the low-temperature crack resistance of asphalt mixture.

[0028] 4. This application introduces oxidized polyethylene wax into the modified nanofiller. The oxidized polyethylene wax is chemically bonded to the nanofiller and stably combined. The rigidity of the nanofiller and the flexible segments of the wax work synergistically. The rigid skeleton can disperse low-temperature stress and prevent crack propagation, while the flexible segments can alleviate shrinkage strain and improve low-temperature flexibility. At the same time, the wax molecules can prevent the agglomeration of nanoparticles and are compatible with the subsequently grafted polyethylene glycol. This balances the dispersibility of the nanofiller in emulsified asphalt and the compatibility of asphalt, thereby enhancing the low-temperature crack resistance of cold asphalt mixtures. Detailed Implementation

[0029] The present application will be further described in detail below with reference to the embodiments.

[0030] Unless otherwise specified, the raw materials used in the preparation examples, embodiments, and comparative examples of this application are all commercially available.

[0031] Preparation Examples 1-13: Modified Emulsified Asphalt Preparation Example 1 This preparation example discloses a method for preparing modified emulsified asphalt, specifically including the following steps: (1) Take 50g of 90# base asphalt and heat it to 170℃. Add 20g of waste tire rubber powder emulsion and stir at 800rpm for 15min. Add 0.5g of SBS and 0.5g of modified nanofiller. Turn on 500W ultrasound and 5000rpm shearing and process for 20min to obtain modified asphalt premix. Among them, waste tire rubber powder emulsion is obtained by mixing 100g of 80-mesh waste tire desulfurized rubber powder with 100g of deionized water, adding 2g of sodium dodecylbenzenesulfonate and 2g of Tween-80, treating it under shear at 15000rpm for 30min, and then ultrasonically dispersing it at 500W for 15min (working for 3s and stopping for 1s, with water bath cooling to control the temperature ≤60℃). Modified nanofiller: 10g of 2000-mesh graphene (≤5 layers) was added to 2L of a mixed solvent of ethanol and water (volume ratio 3:1) and dispersed under 500W ultrasonic (pulse mode: 2s on, 1s off) for 30min to obtain a suspension; 1g of γ-aminopropyltriethoxysilane and 1g of octadecyltriethoxysilane were mixed at a ratio of 1:1, 300mL of ethanol was added, and then dilute hydrochloric acid was added dropwise to adjust the pH to 4. The mixture was stirred at 800rpm for 15min at room temperature to obtain a silane solution; the silane solution was added dropwise to the suspension at a rate of 1 drop / s, the temperature was raised to 65℃ and magnetically stirred at 800rpm for 4h. After the reaction was completed, the mixture was centrifuged at 8000rpm for 10min, the solid was collected, and the supernatant was washed alternately with ethanol and deionized water until the pH of the supernatant was 7. The mixture was freeze-dried at -50℃ for 12h to obtain modified graphene with an average particle size of 1.5μm; (2) Cool the above modified asphalt premix to 70°C, add 0.5g emulsifier, 2g diluent, 25g deionized water and 0.1g polyamide anti-stripping agent, stir at 300rpm for 15min to obtain modified emulsified asphalt; The emulsifier is a mixture of sorbitan monooleate (Span-80, HLB=4.3) and polyoxyethylene dehydrated sorbitan monolaurate (Tween-20, HLB=16.7) in a ratio of 2:1. The diluent is a mixture of biodiesel (fatty acid methyl ester) and vegetable oil (low erucic acid rapeseed oil CAS: 120962-03-0) in a ratio of 6:4.

[0032] Preparation Example 2 This preparation example discloses a method for preparing modified emulsified asphalt, specifically including the following steps: (1) Take 60g of 90# base asphalt and heat it to 170℃. Add 15g of waste tire rubber powder emulsion and stir at 800rpm for 15min. Add 2g of SBS and 1g of modified nanofiller. Turn on 500W ultrasound and 5000rpm shearing and process for 20min to obtain modified asphalt premix. Among them, waste tire rubber powder emulsion is obtained by mixing 100g of 80-mesh waste tire desulfurized rubber powder with 100g of deionized water, adding 2g of sodium dodecylbenzenesulfonate and 2g of Tween-80, treating it under shear at 15000rpm for 30min, and then ultrasonically dispersing it at 500W for 15min (working for 3s and stopping for 1s, with water bath cooling to control the temperature ≤60℃). Modified nanofiller: 10g of 2000-mesh graphene (≤5 layers) was added to 2L of a mixed solvent of ethanol and water (volume ratio 3:1) and dispersed under 500W ultrasonic (pulse mode: 2s on, 1s off) for 30min to obtain a suspension; 1g of γ-aminopropyltriethoxysilane and 1g of octadecyltriethoxysilane were mixed at a ratio of 1:1, 300mL of ethanol was added, and then dilute hydrochloric acid was added dropwise to adjust the pH to 4. The mixture was stirred at 800rpm for 15min at room temperature to obtain a silane solution; the silane solution was added dropwise to the suspension at a rate of 1 drop / s, the temperature was raised to 65℃ and magnetically stirred at 800rpm for 4h. After the reaction was completed, the mixture was centrifuged at 8000rpm for 10min, the solid was collected, and the supernatant was washed alternately with ethanol and deionized water until the pH of the supernatant was 7. The mixture was freeze-dried at -50℃ for 12h to obtain modified graphene with an average particle size of 1.5μm; (2) Cool the above modified asphalt premix to 70°C, add 1.5g emulsifier, 3.5g diluent, 35g deionized water and 0.5g polyamide anti-stripping agent, stir at 300rpm for 15min to obtain modified emulsified asphalt; The emulsifier is a mixture of sorbitan monooleate (Span-80, HLB=4.3) and polyoxyethylene dehydrated sorbitan monolaurate (Tween-20, HLB=16.7) in a ratio of 2:1. The diluent was prepared by mixing biodiesel (fatty acid methyl ester) and vegetable oil (low erucic acid rapeseed oil CAS: 120962-03-0) in a ratio of 6.5:3.5.

[0033] Preparation Example 3 This preparation example discloses a method for preparing modified emulsified asphalt, specifically including the following steps: (1) Take 65g of 90# base asphalt and heat it to 170℃. Add 20g of waste tire rubber powder emulsion and stir at 800rpm for 15min. Add 3g of SBS and 2g of modified nanofiller. Turn on 500W ultrasound and 5000rpm shearing and process for 20min to obtain modified asphalt premix. Among them, waste tire rubber powder emulsion is obtained by mixing 100g of 80-mesh waste tire desulfurized rubber powder with 100g of deionized water, adding 2g of sodium dodecylbenzenesulfonate and 2g of Tween-80, treating it under shear at 15000rpm for 30min, and then ultrasonically dispersing it at 500W for 15min (working for 3s and stopping for 1s, with water bath cooling to control the temperature ≤60℃). Modified nanofiller: 10g of 2000-mesh graphene (≤5 layers) was added to 2L of a mixed solvent of ethanol and water (volume ratio 3:1) and dispersed under 500W ultrasonic (pulse mode: 2s on, 1s off) for 30min to obtain a suspension; 1g of γ-aminopropyltriethoxysilane and 1g of octadecyltriethoxysilane were mixed at a ratio of 1:1, 300mL of ethanol was added, and then dilute hydrochloric acid was added dropwise to adjust the pH to 4. The mixture was stirred at 800rpm for 15min at room temperature to obtain a silane solution; the silane solution was added dropwise to the suspension at a rate of 1 drop / s, the temperature was raised to 65℃ and magnetically stirred at 800rpm for 4h. After the reaction was completed, the mixture was centrifuged at 8000rpm for 10min, the solid was collected, and the supernatant was washed alternately with ethanol and deionized water until the pH of the supernatant was 7. The mixture was freeze-dried at -50℃ for 12h to obtain modified graphene with an average particle size of 1.5μm; (2) Cool the above modified asphalt premix to 70°C, add 2g emulsifier, 5g diluent and 45g deionized water, stir at 300rpm for 10min to obtain emulsified asphalt; finally add 1g polyamide anti-stripping agent, stir for 5min to obtain modified emulsified asphalt. The emulsifier is a mixture of sorbitan monooleate (Span-80, HLB=4.3) and polyoxyethylene dehydrated sorbitan monolaurate (Tween-20, HLB=16.7) in a ratio of 2:1. The diluent is a mixture of biodiesel (fatty acid methyl ester) and vegetable oil (low erucic acid rapeseed oil CAS: 120962-03-0) in a ratio of 7:3.

[0034] Preparation Example 4 This preparation example is basically the same as Preparation Example 2, except that: Modified nanofiller: 5g of dried 2000-mesh sodium montmorillonite (vacuum dried at 105℃ for 2h) was added to a mixed solvent of 0.3L ethanol and deionized water (volume ratio 3:1), and ultrasonically dispersed at 400W for 25min to obtain a montmorillonite suspension; 0.4g of γ-aminopropyltriethoxysilane (KH-550) and 0.2g of sodium dodecylbenzenesulfonate were mixed at a ratio of 2:1, 40mL of ethanol was added, and dilute salt was added dropwise. The pH was adjusted to 4 with acid, and the mixture was stirred at 800 rpm for 20 min at room temperature to obtain a modified solution. The modified solution was added dropwise to the montmorillonite suspension at a rate of 1 drop / s, and the temperature was raised to 65℃ and magnetically stirred at 800 rpm for 5 h. After the reaction was completed, the mixture was centrifuged at 10000 rpm for 10 min, the solid was collected, and the solid was washed alternately with ethanol and deionized water (until the pH of the supernatant was 7). The solid was then freeze-dried at -50℃ for 12 h to obtain modified montmorillonite with an average particle size of 1.5 μm.

[0035] Preparation Example 5 This preparation example is basically the same as Preparation Example 2, except that: Modified nanofiller: 2g of modified graphene from Preparation Example 2 and 1g of modified montmorillonite from Preparation Example 4 were mixed, 0.1L of a mixed solvent of ethanol and deionized water (volume ratio 3:1) was added, 0.09g of toluene diisocyanate (TDI) was added, and the mixture was dispersed by ultrasonication (pulse mode) at 500W for 20min, followed by magnetic stirring at 60℃ and 800rpm for 2h; after centrifugation, washing, and freeze-drying, the modified nanofiller was obtained.

[0036] Preparation Example 6 This preparation example is basically the same as Preparation Example 2, except that: Modified nanofiller: 3.5g of modified graphene from Preparation Example 2 and 1g of modified montmorillonite from Preparation Example 4 were mixed, 0.1L of a mixed solvent of ethanol and deionized water (volume ratio 3:1) was added, 0.09g of toluene diisocyanate (TDI) was added, and the mixture was dispersed by ultrasonication (pulse mode) at 500W for 20min, followed by magnetic stirring at 60℃ and 800rpm for 2h; after centrifugation, washing, and freeze-drying, the modified nanofiller was obtained.

[0037] Preparation Example 7 This preparation example is basically the same as Preparation Example 2, except that: Modified nanofiller: 5g of modified graphene from Preparation Example 2 and 1g of modified montmorillonite from Preparation Example 4 were mixed, 0.1L of a mixed solvent of ethanol and deionized water (volume ratio 3:1) was added, 0.09g of toluene diisocyanate (TDI) was added, and the mixture was dispersed by ultrasonication (pulse mode) at 500W for 20min, followed by magnetic stirring at 60℃ and 800rpm for 2h; after centrifugation, washing, and freeze-drying, the modified nanofiller was obtained.

[0038] Preparation Example 8 This preparation example is basically the same as Preparation Example 6, except that: in Preparation Example 6, polyethylene glycol is grafted onto the surface of the modified nanofiller. Specifically, 2g of the modified nanofiller obtained in Preparation Example 6 is added to 100mL of a mixed solvent of deionized water and ethanol (volume ratio 1:1), and ultrasonically dispersed at 300W for 20min to form a suspension; 1g of carboxyl-terminated polyethylene glycol with a molecular weight of 2000 is added to 50mL of the above mixed solvent to dissolve it, and then 0.3g of 1-ethyl-(3-dimethylaminopropyl) (2) carbodiimide and 0.2 g N-hydroxysuccinimide were stirred at room temperature for 15 min to obtain a mixture. The mixture was added dropwise to the suspension at a rate of 1 drop / s, the pH of the system was adjusted to 6.5, the temperature was raised to 50℃ and magnetically stirred at 500 rpm for 6 h. After the reaction was completed, the mixture was centrifuged at 8000 rpm for 10 min, the solid was collected, and the solid was washed alternately with deionized water and ethanol until the pH of the supernatant was 7. The solid was then freeze-dried at -50℃ for 12 h to obtain modified nanofiller with an average particle size of 1.5 μm.

[0039] Preparation Example 9 This preparation example is basically the same as Preparation Example 2, except that: the modified nanofiller is: S1, 10g of graphene was sonicated in 1L of N-methylpyrrolidone at 1000W for 2h and vacuum dried at 70℃. Then, it was treated for 12min under vacuum of 20Pa, oxygen flow rate of 25sccm, and radio frequency power of 100W to obtain carboxylated graphene. 35g of sodium montmorillonite was treated for 18min under vacuum of 20Pa, ammonia flow rate of 30sccm, and radio frequency power of 80W to obtain aminated montmorillonite. The above carboxylated graphene, aminated montmorillonite, 4g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide and 3g of N-hydroxysuccinimide were added to anhydrous N,N-dimethylformamide and heated to 75℃ under nitrogen protection and stirred for 10h to obtain a nanocomposite. S2, 10g of the nanocomposite was added to 120mL of deionized water and sonicated at 300W for 30min. Then, 4g of hydroxyl-terminated polyethylene glycol with a molecular weight of 2000 and 0.5g of condensing agent dicyclohexylcarbodiimide were added. The mixture was stirred and reacted at 40℃ under nitrogen protection for 6h. After filtration, the product was obtained. The product was washed successively with anhydrous ethanol and acetone, dispersed in 120mL of deionized water, and 0.2g of concentrated sulfuric acid was added. The mixture was stirred and reacted at 85℃ for 7h. After washing with deionized water until neutral, the product was freeze-dried and ground to obtain modified nanofiller with an average particle size of 50nm.

[0040] Preparation Example 10 This preparation example is basically the same as Preparation Example 9, except that: the modified nanofiller is: S1, 10g of graphene was sonicated in 1L of N-methylpyrrolidone at 1000W for 2h and vacuum dried at 70℃. Then, it was treated for 12min under vacuum of 20Pa, oxygen flow rate of 25sccm, and radio frequency power of 100W to obtain carboxylated graphene. 35g of sodium montmorillonite was treated for 18min under vacuum of 20Pa, ammonia flow rate of 30sccm, and radio frequency power of 80W to obtain aminated montmorillonite. The above carboxylated graphene, aminated montmorillonite, 4g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide and 3g of N-hydroxysuccinimide were added to anhydrous N,N-dimethylformamide and heated to 75℃ under nitrogen protection and stirred for 10h to obtain a nanocomposite. S2, 17g of the nanocomposite was added to 150mL of anhydrous N,N-dimethylformamide and ultrasonically dispersed at 300W for 30min. Then, 3g of paste-like oxidized polyethylene wax (model: QH7415) was added, and the mixture was heated to 80℃ under nitrogen protection and stirred for 3h to obtain the wax-nanocomposite. S3. 10g of wax-nanocomposite was added to 120mL of deionized water and sonicated at 300W for 30min. Then, 4g of hydroxyl-terminated polyethylene glycol with a molecular weight of 2000 and 0.5g of condensing agent dicyclohexylcarbodiimide were added. The mixture was stirred and reacted at 40℃ under nitrogen protection for 6h. After filtration, the product was obtained. The product was washed successively with anhydrous ethanol and acetone, dispersed in 120mL of deionized water, and 0.2g of concentrated sulfuric acid was added. The mixture was stirred and reacted at 85℃ for 7h. After washing with deionized water until neutral, the product was freeze-dried and ground to obtain modified nanofiller with an average particle size of 50nm.

[0041] Preparation Example 11 This preparation example is basically the same as Preparation Example 10, except that: in S2, 18g of the nanocomposite was added to 150mL of anhydrous N,N-dimethylformamide and ultrasonically dispersed at 300W for 30min. Then, 2g of paste-like oxidized polyethylene wax (model: QH7415) was added, and the mixture was heated to 80℃ under nitrogen protection and stirred for 3h to obtain the wax-nanocomposite.

[0042] Preparation Example 12 This preparation example is basically the same as Preparation Example 10, except that: in S2, 19g of the nanocomposite was added to 150mL of anhydrous N,N-dimethylformamide and ultrasonically dispersed at 300W for 30min. Then, 1g of paste-like oxidized polyethylene wax (model: QH7415) was added, and the mixture was heated to 80℃ under nitrogen protection and stirred for 3h to obtain the wax-nanocomposite.

[0043] Preparation Example 13 This preparation example discloses a method for preparing modified emulsified asphalt, specifically including the following steps: (1) Take 50g of 90# base asphalt and heat it to 170℃. Add 20g of waste tire rubber powder emulsion and stir at 800rpm for 15min. Add 0.5g of SBS and 0.5g of 2000 mesh graphene (layers ≤ 5). Turn on 500W ultrasound and 5000rpm shearing and treat for 20min to obtain modified asphalt premix. Among them, waste tire rubber powder emulsion is obtained by mixing 100g of 80-mesh waste tire desulfurized rubber powder with 100g of deionized water, adding 2g of sodium dodecylbenzenesulfonate and 2g of Tween-80, treating it under shear at 15000rpm for 30min, and then ultrasonically dispersing it at 500W for 15min (working for 3s and stopping for 1s, with water bath cooling to control the temperature ≤60℃). (2) Cool the above modified asphalt premix to 70°C, add 0.5g emulsifier, 2g diluent, 25g deionized water and 0.1g polyamide anti-stripping agent, stir at 300rpm for 15min to obtain modified emulsified asphalt; The emulsifier is a mixture of sorbitan monooleate (Span-80, HLB=4.3) and polyoxyethylene dehydrated sorbitan monolaurate (Tween-20, HLB=16.7) in a ratio of 2:1. The diluent is a mixture of biodiesel (fatty acid methyl ester) and vegetable oil (low erucic acid rapeseed oil CAS: 120962-03-0) in a ratio of 6:4.

[0044] This preparation example is a laboratory-scale preparation method for modified emulsified asphalt. In actual production, the dosage of each component can be simultaneously scaled up according to the formulation of cold asphalt mixture in the example and the raw material ratio of this preparation example to prepare the required scale of modified emulsified asphalt.

[0045] Example 1 This embodiment provides a cold asphalt mixture adapted to low-temperature environments, comprising 5 kg of modified emulsified asphalt, 0.3 kg of composite fibers (0.15 kg of polyester fiber and 0.15 kg of lignin fiber), 4 kg of filler (3.2 kg of cement and 0.8 kg of limestone), 0.2 kg of antifreeze (polyethylene glycol with a molecular weight of 200), 0.5 kg of polyolefin elastomer (ethylene-octene copolymer), and 90 kg of aggregate (40 kg of basalt crushed stone, 30 kg of manufactured sand, and 20 kg of old road milling material), wherein the modified emulsified asphalt is obtained using Preparation Example 1.

[0046] Among the raw materials, the basalt crushed stone has a continuous gradation of 5-20mm particle size, a crushing value ≤12%, and a needle-like / flaky particle content ≤8%; the manufactured sand has a particle size of 0.075-6mm, of which the content of particles with a particle size of 0.075-5mm accounts for ≥30%, and the stone powder content is ≤3%; the old road milling material has a particle size controlled at 0-20mm, and after preheating at 65℃, it is activated by 5g of waste rubber oil and 5g of furfural extract oil; the cement is P.O42.5 grade ordinary Portland cement, with a fineness passing through a 0.08mm square hole sieve with a pass rate ≥85%; the limestone has a particle size <0.075mm and a specific surface area ≥300m². 2 / kg; polyester fiber length is 6-12mm, lignin fiber length is 3-6mm, and fiber diameter is ≤30μm.

[0047] This embodiment also provides a method for preparing the above-mentioned cold asphalt mixture adapted to low-temperature environments, comprising the following steps: According to the above proportions, basalt crushed stone, manufactured sand, and old road milling material are dried to a moisture content of ≤2%. After preheating the old road milling material at 65℃, it is activated with 5g of waste rubber oil and 5g of furfural extract oil, and then mixed with basalt crushed stone. The mixture is stirred at 300rpm for 5min, then manufactured sand is added, and the mixture is stirred at 300rpm for 5min. After sieving to ensure that it meets the AC-16C gradation, a silane coupling agent (0.1kg of γ-glycidyl etheroxypropyltrimethoxysilane diluted with 1L of ethanol-water mixture at a volume ratio of 3:1, and the pH is adjusted to 4 by adding dilute hydrochloric acid, and stirred at room temperature) is sprayed using a mist nozzle and stirred at 300rpm for 10min to obtain aggregate. After mixing the aggregate and composite fiber obtained above at 300 rpm for 8 minutes at room temperature, add modified emulsified asphalt and mix at 200 rpm for 10 minutes at room temperature. Then add filler, antifreeze and polyolefin elastomer in sequence and mix at 350 rpm for 6 minutes. Control the discharge temperature to 30℃.

[0048] Example 2 This embodiment is basically the same as Embodiment 1, except that this embodiment provides a cold asphalt mixture adapted to low-temperature environments, comprising 6.5 kg of modified emulsified asphalt, 0.45 kg of composite fiber (0.27 kg of polyester fiber and 0.18 kg of lignin fiber), 5 kg of filler (3.85 kg of cement and 1.15 kg of limestone), 0.25 kg of antifreeze (polyethylene glycol with a molecular weight of 200), 1.3 kg of polyolefin elastomer (ethylene-octene copolymer), and 86.5 kg of aggregate (43.25 kg of basalt crushed stone, 21.625 kg of manufactured sand, and 21.625 kg of old road milling material), wherein the modified emulsified asphalt is obtained using Preparation Example 1.

[0049] Example 3 This embodiment is basically the same as Embodiment 1, except that this embodiment provides a cold asphalt mixture adapted to low-temperature environments, comprising 8 kg of modified emulsified asphalt, 0.6 kg of composite fibers (0.42 kg of polyester fiber and 0.18 kg of lignin fiber), 6 kg of filler (4.5 kg of cement and 1.5 kg of limestone), 0.4 kg of antifreeze (polyethylene glycol with a molecular weight of 200), 2 kg of polyolefin elastomer (ethylene-octene copolymer) and 83 kg of aggregate (49.8 kg of basalt crushed stone, 12.45 kg of manufactured sand and 29.05 kg of old road milling material), wherein the modified emulsified asphalt is obtained using Preparation Example 1.

[0050] Example 4 This embodiment is basically the same as Example 2, except that the modified emulsified asphalt in this embodiment is the one obtained in Preparation Example 2.

[0051] Example 5 This embodiment is basically the same as Example 2, except that the modified emulsified asphalt in this embodiment is the one obtained in Preparation Example 3.

[0052] Example 6 This embodiment is basically the same as Example 2, except that the modified emulsified asphalt in this embodiment is the one obtained in Preparation Example 4.

[0053] Example 7 This embodiment is basically the same as Example 2, except that the modified emulsified asphalt in this embodiment is the one obtained in Preparation Example 5.

[0054] Example 8 This embodiment is basically the same as Example 2, except that the modified emulsified asphalt in this embodiment is the one obtained in Preparation Example 6.

[0055] Example 9 This embodiment is basically the same as Embodiment 2, except that the modified emulsified asphalt in this embodiment is the one obtained in Preparation Example 7.

[0056] Example 10 This embodiment is basically the same as Example 2, except that the modified emulsified asphalt in this embodiment is the one obtained in Preparation Example 8.

[0057] Example 11 This embodiment is basically the same as Embodiment 2, except that the modified emulsified asphalt in this embodiment is the one obtained in Preparation Example 9.

[0058] Example 12 This embodiment is basically the same as Embodiment 2, except that the modified emulsified asphalt in this embodiment is the one obtained in Preparation Example 10.

[0059] Example 13 This embodiment is basically the same as Embodiment 2, except that the modified emulsified asphalt in this embodiment is the one obtained in Preparation Example 11.

[0060] Example 14 This embodiment is basically the same as Embodiment 2, except that the modified emulsified asphalt in this embodiment is the one obtained in Preparation Example 12.

[0061] Comparative Example 1 This comparative example is basically the same as Example 1, except that the modified emulsified asphalt in this comparative example is the one obtained in Preparation Example 13.

[0062] Testing standards: Low-temperature ductility test: The modified emulsified asphalt obtained in Preparation Examples 1-13 was tested according to GB / T4508 standard, and the test results are recorded in Table 1.

[0063] Marshall stability test: The Marshall test was conducted according to the method in T0709 of JTGE20-2011 "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering". The molding stability of the asphalt mixtures obtained in each example and comparative example was tested, and the test results are recorded in Table 2.

[0064] Frost cracking and splitting test: Frost cracking and splitting test was conducted according to the method in T0729 of JTGE20-2011 "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering". The frost cracking and splitting ratio of the asphalt mixtures obtained in each example and comparative example were tested, and the test results are recorded in Table 2.

[0065] Table 1. Performance test data of modified emulsified asphalt in Preparation Examples 1-13

[0066] Table 2 Performance test data of cold asphalt mixtures adapted to low-temperature environments in Examples 1-14 and Comparative Example 1

[0067] Referring to Tables 1 and 2, and in conjunction with Example 1 and Comparative Example 1, it can be seen that this application improves the compatibility between nanofillers and asphalt by modifying the nanofillers, thereby improving the low-temperature ductility of the resulting modified emulsified asphalt, and thus improving the mechanical strength and low-temperature crack resistance of the asphalt mixture.

[0068] Referring to Tables 1 and 2, and in conjunction with Examples 2, 6, and 7, it can be seen that the nanofiller of this application, by employing a mixture of graphene and montmorillonite, achieves a multi-scale structure that combines the flexibility of graphene with the rigidity of montmorillonite, thus alleviating the problem of graphene's tendency to agglomerate and compensating for the shortcomings of montmorillonite's mechanical properties. This improves the low-temperature crack resistance of cold asphalt mixtures by synergistically inhibiting crack initiation and propagation, thereby increasing the flexural failure strain at extreme low temperatures and enhancing the mechanical strength of the prepared asphalt mixture.

[0069] Referring to Tables 1 and 2, and in conjunction with Examples 8 and 10, it can be seen that this application modifies the surface of nanofillers by grafting polyethylene glycol. The flexibility of polyethylene glycol can optimize the interfacial bonding force between the filler and the asphalt matrix, improve their compatibility, and increase the low-temperature ductility of the resulting modified emulsified asphalt, thereby improving the mechanical strength and low-temperature crack resistance of the asphalt mixture.

[0070] Referring to Tables 1 and 2, and in conjunction with Examples 10 and 11, it can be seen that, compared to modifying with silane coupling agents before grafting polyethylene glycol, this application utilizes plasma treatment to treat the nanofiller before grafting polyethylene glycol. Plasma treatment activates the surface of the nanofiller, generating active functional groups such as hydroxyl and carboxyl groups, breaking the chemical inertness of the filler surface and increasing reaction sites, thus laying the foundation for subsequent grafting reactions. Subsequently, these active functional groups are used to perform a grafting reaction with polyethylene glycol, causing polyethylene glycol molecules to firmly bind to the filler surface, forming a functional modified layer, which further improves the interfacial bonding force between the nanofiller and the asphalt matrix.

[0071] Referring to Tables 1 and 2, and in conjunction with Examples 11 and 12, it can be seen that this application can further improve the low-temperature ductility of the modified emulsified asphalt by introducing an appropriate amount of oxidized polyethylene wax into the nanofiller after plasma treatment and surface grafting with polyethylene glycol. The rigidity of the nanofiller and the flexible segments of the wax work synergistically, which can both disperse low-temperature stress and prevent crack propagation through the rigid skeleton, and alleviate shrinkage strain and improve low-temperature flexibility through the flexible segments. At the same time, the wax molecules can prevent the agglomeration of nanoparticles and are compatible with the subsequently grafted polyethylene glycol, balancing the dispersibility of the nanofiller in the emulsified asphalt and the compatibility of the asphalt, thereby enhancing the low-temperature crack resistance of the cold asphalt mixture.

[0072] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A cold asphalt mixture adapted to low-temperature environments, characterized in that, The raw materials include the following parts by weight: 5-8 parts modified emulsified asphalt, 0.3-0.6 parts composite fiber, 4-6 parts filler, 0.2-0.4 parts antifreeze, 0.5-2 parts polyolefin elastomer, and the balance being aggregate; The method for preparing the modified emulsified asphalt includes the following steps: After heating 50-65 parts by weight of base asphalt, add 10-20 parts by weight of waste tire rubber powder emulsion, stir evenly, add 0.5-3 parts by weight of SBS and 0.5-2 parts by weight of modified nanofiller, and then perform ultrasonic dispersion and shearing treatment to obtain modified asphalt premix. Add 0.5-2 parts by weight of emulsifier, 1-5 parts by weight of diluent and 25-45 parts by weight of water to the modified asphalt premix, stir evenly to obtain emulsified asphalt, and finally add 0.1-1 parts by weight of anti-stripping agent and stir evenly to obtain modified emulsified asphalt.

2. The cold asphalt mixture adapted to low-temperature environments according to claim 1, characterized in that, The modified nanofiller is obtained by plasma treatment followed by grafting polyethylene glycol onto the nanofiller.

3. The cold asphalt mixture adapted to low-temperature environments according to claim 2, characterized in that, The nanofiller is one or more of montmorillonite and graphene.

4. The cold asphalt mixture adapted to low-temperature environments according to claim 3, characterized in that, The nanofiller is a mixture of montmorillonite and graphene in a mass ratio of 1:(2-5).

5. The cold asphalt mixture adapted to low-temperature environments according to claim 4, characterized in that, The modified nanofiller is prepared by: modifying graphene with oxygen plasma to obtain carboxylated graphene, modifying montmorillonite with ammonia plasma to obtain aminated montmorillonite; subjecting carboxylated graphene and aminated montmorillonite to amidation reaction to obtain nanocomposite; and grafting polyethylene glycol onto the surface of the nanocomposite to obtain modified nanofiller.

6. The cold asphalt mixture adapted to low-temperature environments according to claim 2, characterized in that, The modified nanofiller is obtained by plasma treatment of the nanofiller, compounding it with oxidized polyethylene wax, and then grafting polyethylene glycol; the mass ratio of the nanofiller to oxidized polyethylene wax is (85-95):(5-15).

7. The cold asphalt mixture adapted to low-temperature environments according to claim 1, characterized in that, The composite fiber is a mixture of polyester fiber and lignin fiber in a mass ratio of (5-7):(3-5).

8. The cold asphalt mixture adapted to low-temperature environments according to claim 1, characterized in that, The filler is a mixture of cement and limestone in a mass ratio of (4-6):(1-2).

9. The cold asphalt mixture adapted to low-temperature environments according to claim 1, characterized in that, The aggregate is a mixture of basalt crushed stone, manufactured sand and old road milling material in a mass ratio of (40-60):(15-30):(20-35).

10. The method for preparing cold asphalt mixture adapted to low-temperature environments according to any one of claims 1-9, characterized in that, Includes the following steps: After mixing aggregates and composite fibers at room temperature, modified emulsified asphalt is added. After mixing evenly, fillers, antifreeze agents, and polyolefin elastomers are added. After mixing evenly, the mixture is cooled to room temperature to obtain cold asphalt mixture.

Images