Cold asphalt mixture suitable for low temperature environment and method for preparing the same

Abstract

The application relates to the technical field of asphalt mixtures, and particularly discloses a cold asphalt mixture suitable for low-temperature environments and a preparation method thereof. The cold asphalt mixture suitable for low-temperature environments comprises the following raw materials in parts by weight: 5-8 parts of modified emulsified asphalt, 0.3-0.6 parts of composite fibers, 4-6 parts of fillers, 0.2-0.4 parts of an anti-freezing agent, 0.5-2 parts of a polyolefin elastomer, and the rest is aggregate. In the preparation of the modified emulsified asphalt, the nano filler is modified to improve the compatibility between the nano filler and the asphalt matrix, and thus the low-temperature crack resistance of the prepared cold asphalt mixture is 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:

[0007] 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.

[0008] The preparation method of the modified emulsified asphalt comprises the following steps:

[0009] After 50-65 parts by weight of base asphalt is heated, 10-20 parts by weight of waste tire rubber powder emulsion is added, and after uniform stirring, 0.5-3 parts by weight of SBS and 0.5-2 parts by weight of modified nano filler are added, and after ultrasonic dispersion and shearing treatment, a modified asphalt premix is obtained.

[0010] The modified asphalt premix is added to 0.5-2 parts by weight of emulsifier, 1-5 parts by weight of diluent and 25-45 parts by weight of water, and after uniform stirring, emulsified asphalt is obtained, and finally 0.1-1 parts by weight of anti-peeling agent is added and stirred uniformly to obtain modified emulsified asphalt.

[0011] 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 in combination with the reinforcing and crack inhibiting effect of the composite fiber on the mixture structure, the low-temperature crack resistance of the cold asphalt mixture is improved.

[0012] Preferably, the modified nano filler is obtained by grafting polyethylene glycol on the nano filler after plasma treatment.

[0013] 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 groups 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 the 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 components such as SBS and waste tire rubber powder emulsion, 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.

[0014] Preferably, the nanofiller is one or more of montmorillonite and graphene.

[0015] Preferably, the nanofiller is a mixture of montmorillonite and graphene with a mass ratio of 1: (2-5).

[0016] 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 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 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 and improve the freeze-thaw splitting strength ratio.

[0017] 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; grafting polyethylene glycol on the surface of the nanocomposite to obtain the modified nanofiller.

[0018] 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 characteristics of covalent bonds, avoiding problems such as separation of filler interfaces and interlayer peeling in long-term use; at the same time, the synergistic effect of the two is more significant, and the two-dimensional sheet-layer covalent network constructed by chemical combination can efficiently transfer stress, 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 strengthen the interface bonding between the filler and the asphalt matrix, further improving the low-temperature ductility of the modified emulsified asphalt.

[0019] 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).

[0020] 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.

[0021] Preferably, the composite fiber is a mixture of polyester fiber and lignin fiber with a mass ratio of (5-7):(3-5).

[0022] 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.

[0023] Preferably, the filler is a mixture of cement and limestone with a mass ratio of (4-6):(1-2).

[0024] 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.

[0025] 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).

[0026] By adopting the technical scheme, the basalt macadam forms a rigid framework with high strength and low-temperature resistance, providing support for the mixture against shrinkage deformation in a low-temperature environment; the manufactured sand fills the gaps between the macadam, improves the density to reduce the damage of pore ice crystals in the freeze-thaw cycle, and increases the contact area with the modified emulsified asphalt to strengthen the interface bonding; the old pavement milling material uses the morphological characteristics of the recycled aggregate to assist the framework filling, and the old asphalt can improve the low-temperature bonding continuity in cooperation with the modified emulsified asphalt. The three work together to not only ensure the low-temperature crack resistance and freeze-thaw stability through the cooperation of basalt and manufactured sand, but also realize resource recycling through old material recycling, and the gradation is continuous and controllable, taking into account the workability of cold-mixing construction and long-term structural durability.

[0027] In a second aspect, the application provides a preparation method of cold asphalt mixture suitable for low-temperature environment, adopting the following technical scheme:

[0028] A preparation method of cold asphalt mixture suitable for low-temperature environment, comprising the following steps:

[0029] After the aggregate and the composite fiber are stirred at room temperature, the modified emulsified asphalt is added, and after uniform stirring, the filler, the anti-freezing agent and the polyolefin elastomer are added, and after uniform stirring, the cold asphalt mixture is obtained after cooling to room temperature.

[0030] By adopting the technical scheme, the adding order of the preparation method follows the logic of framework pre-dispersion-bonding coating-function enhancement, the aggregate and the composite fiber are first stirred at room temperature, the fiber can be uniformly attached to the surface of the aggregate by means of the mechanical dispersion of the aggregate, avoiding fiber clumping, laying a foundation for the subsequent formation of a three-dimensional reinforcing network; then the modified emulsified asphalt is added, which can uniformly coat the surfaces of the fiber and the aggregate on the premise that they have been fully mixed, strengthening the interface bonding; finally, the filler, the anti-freezing agent and the polyolefin elastomer are added, which can fill the void structure of the asphalt-aggregate-fiber matrix formed in the early stage, and make the functional additives uniformly dispersed in the asphalt system, ensuring that the dense effect of the filler, the freezing point adjustment effect of the anti-freezing agent and the low-temperature toughness improvement effect of the polyolefin elastomer are efficiently exerted. This preparation method not only ensures the uniformity of the dispersion of each component, but also promotes the multi-dimensional action of framework support, fiber reinforcement, asphalt bonding and functional additives, ultimately improving the low-temperature performance and structural stability of the mixture.

[0031] In summary, the application has the following beneficial effects:

[0032] 1. The modification of the nano filler in the application can improve its compatibility with asphalt; at the same time, the waste tire rubber powder emulsion in the modified emulsified asphalt forms a synergistic toughening effect with SBS, which cooperates with the reinforcing effect of the modified nano filler to effectively improve the low-temperature plasticity and mechanical properties of the asphalt matrix.

[0033] 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.

[0034] 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.

[0035] 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

[0036] The present application will be further described in detail below with reference to the embodiments.

[0037] Unless otherwise specified, the raw materials used in the preparation examples, embodiments, and comparative examples of this application are all commercially available.

[0038] Preparation Examples 1-13: Modified Emulsified Asphalt

[0039] Preparation Example 1

[0040] This preparation example discloses a method for preparing modified emulsified asphalt, specifically including the following steps:

[0041] (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.

[0042] 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℃).

[0043] Modified nanofiller: 10 g of 2000 mesh graphene (layer number ≤5) was added to 2 L of a mixed solvent of ethanol and water (volume ratio 3:1), and dispersed for 30 min under 500 W ultrasonic (pulse mode: work for 2 s and stop for 1 s) to obtain a suspension; 1 g of γ-aminopropyl triethoxysilane and 1 g of octadecyl triethoxysilane were mixed at a ratio of 1:1, added to 300 mL of ethanol, and then diluted hydrochloric acid was added to adjust the pH to 4, and stirred at 800 rpm for 15 min at room temperature to obtain a silane solution; the silane solution was added to the suspension at a rate of 1 drop / s, the temperature was raised to 65°C, and magnetic stirring was carried out at 800 rpm for 4 h, after the reaction was completed, the mixture was centrifuged at 8000 rpm for 10 min, the solid was collected, washed with ethanol and deionized water alternately until the supernatant pH was 7, and freeze-dried at -50°C for 12 h to obtain modified graphene with an average particle size of 1.5 μm;

[0044] (2) The modified asphalt premix was cooled to 70°C, 0.5 g of emulsifier, 2 g of diluent, 25 g of deionized water and 0.1 g of polyamide anti-stripping agent were added, and stirred at 300 rpm for 15 min to obtain modified emulsified asphalt;

[0045] The emulsifier is a mixture of sorbitan monooleate (Span-80, HLB=4.3) and polyoxyethylene sorbitan monolaurate (Tween-20, HLB=16.7) at a ratio of 2:1;

[0046] The diluent is a mixture of biodiesel (fatty acid methyl ester) and vegetable oil (low erucic rapeseed oil CAS: 120962-03-0) at a ratio of 6:4.

[0047] Preparation Example 2

[0048] The present preparation example discloses a preparation method of modified emulsified asphalt, which specifically comprises the following steps:

[0049] (1) 60 g of 90# base asphalt was heated to 170°C, 15 g of waste tire rubber powder emulsion was added, stirred at 800 rpm for 15 min, 2 g of SBS and 1 g of modified nanofiller were added, and treated for 20 min under 500 W ultrasonic and 5000 rpm shearing to obtain a modified asphalt premix;

[0050] The waste tire rubber powder emulsion is obtained by mixing 80 mesh 100 g of waste tire devulcanized rubber powder with 100 g of deionized water, adding 2 g of sodium dodecyl benzene sulfonate and 2 g of Tween-80, and treating for 30 min under 15000 rpm shearing, and then dispersing for 15 min under 500 W ultrasonic (work for 3 s and stop for 1 s, water bath cooling to control the temperature ≤60°C);

[0051] Modified nanofiller: 10 g of 2000 mesh graphene (layer number ≤5) was added to 2 L of a mixed solvent of ethanol and water (volume ratio 3:1), and dispersed for 30 min under 500 W ultrasonic (pulse mode: work for 2 s and stop for 1 s) to obtain a suspension; 1 g of γ-aminopropyl triethoxysilane and 1 g of octadecyl triethoxysilane were mixed at a ratio of 1:1, added to 300 mL of ethanol, and then 1 g of octadecyl triethoxysilane was added dropwise to adjust the pH to 4, and stirred at 800 rpm for 15 min at room temperature to obtain a silane solution; the silane solution was added dropwise into the suspension at a rate of 1 drop / s, the temperature was raised to 65°C, and magnetic stirring was carried out at 800 rpm for 4 h, after the reaction was completed, the mixture was centrifuged at 8000 rpm for 10 min, the solid was collected, washed with ethanol and deionized water alternately until the supernatant pH was 7, and freeze-dried at -50°C for 12 h to obtain modified graphene with an average particle size of 1.5 μm;

[0052] (2) The modified asphalt premix was cooled to 70°C, 1.5 g of emulsifier, 3.5 g of diluent, 35 g of deionized water and 0.5 g of polyamide anti-stripping agent were added, and stirred at 300 rpm for 15 min to obtain modified emulsified asphalt;

[0053] The emulsifier is a mixture of sorbitan monooleate (Span-80, HLB=4.3) and polyoxyethylene sorbitan monolaurate (Tween-20, HLB=16.7) at a ratio of 2:1;

[0054] The diluent is a mixture of biodiesel (fatty acid methyl ester) and vegetable oil (low erucic rapeseed oil CAS:120962-03-0) at a ratio of 6.5:3.5.

[0055] Preparation Example 3

[0056] The present preparation example discloses a preparation method of modified emulsified asphalt, which specifically comprises the following steps:

[0057] (1) 65 g of 90# base asphalt was heated to 170°C, 20 g of waste tire rubber powder emulsion was added, stirred at 800 rpm for 15 min, 3 g of SBS and 2 g of modified nanofiller were added, and treated for 20 min under 500 W ultrasonic and 5000 rpm shearing to obtain a modified asphalt premix;

[0058] The waste tire rubber powder emulsion is obtained by mixing 80 mesh 100 g of waste tire devulcanized rubber powder with 100 g of deionized water, adding 2 g of sodium dodecyl benzene sulfonate and 2 g of Tween-80, and treating for 30 min under 15000 rpm shearing, and then dispersing for 15 min under 500 W ultrasonic (work for 3 s and stop for 1 s, water bath cooling to control the temperature ≤60°C);

[0059] Modified nanofiller: 10 g of 2000 mesh graphene (layer number ≤5) was added into 2 L of mixed solvent of ethanol and water (volume ratio 3:1), and dispersed for 30 min under 500 W ultrasonic (pulse mode: work for 2 s and stop for 1 s) to obtain a suspension; 1 g of γ-aminopropyl triethoxysilane and 1 g of octadecyl triethoxysilane were mixed at a ratio of 1:1, then 300 mL of ethanol was added, and dilute hydrochloric acid was added dropwise to adjust the pH to 4, and stirred at 800 rpm for 15 min at room temperature to obtain a silane solution; the silane solution was added dropwise into the suspension at a rate of 1 drop / s, and the temperature was raised to 65°C and stirred at 800 rpm for 4 h; after the reaction was completed, the mixture was centrifuged at 8000 rpm for 10 min, the solid was collected, washed with ethanol and deionized water alternately until the supernatant pH was 7, and freeze-dried at -50°C for 12 h to obtain modified graphene with an average particle size of 1.5 μm;

[0060] (2) The modified asphalt premix was cooled to 70°C, 2 g of emulsifier, 5 g of diluent and 45 g of deionized water were added, and stirred at 300 rpm for 10 min to obtain an emulsified asphalt; finally, 1 g of polyamide anti-stripping agent was added, and stirred for 5 min to obtain a modified emulsified asphalt;

[0061] The emulsifier is a mixture of sorbitan monooleate (Span-80, HLB=4.3) and polyoxyethylene sorbitan monolaurate (Tween-20, HLB=16.7) at a ratio of 2:1;

[0062] The diluent is a mixture of biodiesel (fatty acid methyl ester) and vegetable oil (low erucic rapeseed oil CAS: 120962-03-0) at a ratio of 7:3.

[0063] Preparation Example 4

[0064] This preparation example is basically the same as Preparation Example 2, except that the modified nanofiller: 5 g of dried 2000 mesh sodium-based montmorillonite (vacuum dried at 105°C for 2 h) was added into 0.3 L of mixed solvent of ethanol and deionized water (volume ratio 3:1), and dispersed for 25 min under 400 W ultrasonic to obtain a montmorillonite suspension; 0.4 g of γ-aminopropyl triethoxysilane (KH-550) and 0.2 g of sodium dodecyl benzene sulfonate were mixed at a ratio of 2:1, 40 mL of ethanol was added, dilute hydrochloric acid was added dropwise to adjust the pH to 4, and stirred at 800 rpm for 20 min at room temperature to obtain a modified solution; the modified solution was added dropwise into the montmorillonite suspension at a rate of 1 drop / s, the temperature was raised to 65°C and 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, washed with ethanol and deionized water alternately (until the supernatant pH was 7), and freeze-dried at -50°C for 12 h to obtain modified montmorillonite with an average particle size of 1.5 μm.

[0065] Preparation Example 5

[0066] This preparation example is basically the same as Preparation Example 2, except that the modified nanofiller: 2 g of modified graphene in Preparation Example 2 is mixed with 1 g of modified montmorillonite in Preparation Example 4, 0.1 L of a mixed solvent of ethanol and deionized water (volume ratio 3:1) is added, 0.09 g of toluene diisocyanate (TDI) is added, and 500 W ultrasonic (pulse mode) dispersion is performed for 20 min, followed by magnetic stirring at 60°C and 800 rpm for 2 h; after centrifugation, washing, and freeze-drying, the modified nanofiller is obtained.

[0067] Preparation Example 6

[0068] This preparation example is basically the same as Preparation Example 2, except that the modified nanofiller: 3.5 g of modified graphene in Preparation Example 2 is mixed with 1 g of modified montmorillonite in Preparation Example 4, 0.1 L of a mixed solvent of ethanol and deionized water (volume ratio 3:1) is added, 0.09 g of toluene diisocyanate (TDI) is added, and 500 W ultrasonic (pulse mode) dispersion is performed for 20 min, followed by magnetic stirring at 60°C and 800 rpm for 2 h; after centrifugation, washing, and freeze-drying, the modified nanofiller is obtained.

[0069] Preparation Example 7

[0070] This preparation example is basically the same as Preparation Example 2, except that the modified nanofiller: 5 g of modified graphene in Preparation Example 2 is mixed with 1 g of modified montmorillonite in Preparation Example 4, 0.1 L of a mixed solvent of ethanol and deionized water (volume ratio 3:1) is added, 0.09 g of toluene diisocyanate (TDI) is added, and 500 W ultrasonic (pulse mode) dispersion is performed for 20 min, followed by magnetic stirring at 60°C and 800 rpm for 2 h; after centrifugation, washing, and freeze-drying, the modified nanofiller is obtained.

[0071] Preparation Example 8

[0072] The preparation example is basically the same as preparation example 6, except that the modified nanofiller surface is grafted with polyethylene glycol obtained in preparation example 6, specifically: 2 g of the modified nanofiller obtained in preparation example 6 is added to 100 mL of a mixed solvent of deionized water and ethanol (volume ratio 1:1), and dispersed by 300 W ultrasonic for 20 min to form a suspension; 1 g of carboxyl-terminated polyethylene glycol with a molecular weight of 2000 is dissolved in 50 mL of the above mixed solvent, and then 0.3 g of 1-ethyl-(3-dimethylaminopropyl) carbodiimide and 0.2 g of N-hydroxysuccinimide are added, and stirred at room temperature for 15 min to obtain a mixed solution; the mixed solution is added dropwise into the suspension at a rate of 1 drop / s, the pH of the system is adjusted to 6.5, the temperature is raised to 50°C, and magnetic stirring is carried out at 500 rpm for 6 h, after the reaction is completed, centrifugation is carried out at 8000 rpm for 10 min, the solid is collected, and washed with deionized water and ethanol alternately until the pH of the supernatant is 7, and then freeze-dried at -50°C for 12 h to obtain a modified nanofiller with an average particle size of 1.5 μm.

[0073] Preparation example 9

[0074] The preparation example is basically the same as preparation example 2, except that the modified nanofiller:

[0075] S1, 10 g of graphene is ultrasonically treated in 1 L of N-methylpyrrolidone at 1000 W for 2 h and vacuum dried at 70°C, and then treated under the conditions of a vacuum degree of 20 Pa, an oxygen flow rate of 25 sccm, and a radio frequency power of 100 W for 12 min to obtain carboxylated graphene; 35 g of sodium-based montmorillonite is treated under the conditions of a vacuum degree of 20 Pa, an ammonia flow rate of 30 sccm, and a radio frequency power of 80 W for 18 min to obtain aminated montmorillonite; the above carboxylated graphene, aminated montmorillonite, 4 g of 1-ethyl-(3-dimethylaminopropyl) carbodiimide, and 3 g of N-hydroxysuccinimide are added to anhydrous N,N-dimethylformamide, and stirred at 75°C for 10 h under nitrogen protection to obtain a nanocomposite;

[0076] S2, 10 g of the nanocomposite is added to 120 mL of deionized water and ultrasonically treated at 300 W for 30 min, and then 4 g of hydroxyl-terminated polyethylene glycol with a molecular weight of 2000 and 0.5 g of a condensing agent dicyclohexyl carbodiimide are added, and after stirring at 40°C under nitrogen protection for 6 h, the product is obtained by filtration, and then washed with anhydrous ethanol and acetone in sequence, dispersed in 120 mL of deionized water, and then 0.2 g of concentrated sulfuric acid is added, and after stirring at 85°C for 7 h, washed with deionized water until neutral, freeze-dried and ground to obtain a modified nanofiller with an average particle size of 50 nm.

[0077] Preparation example 10

[0078] The preparation example is basically the same as preparation example 9, except that the modified nanofiller:

[0079] S1, 10 g graphene was treated by ultrasonic in 1 L N-methylpyrrolidone for 2 h at 1000 W and dried in vacuum at 70 °C, then the carboxylated graphene was obtained by treating at 20 Pa vacuum, 25 sccm oxygen flow and 100 W radio frequency power for 12 min; 35 g sodium montmorillonite was treated by 20 Pa vacuum, 30 sccm ammonia flow and 80 W radio frequency power for 18 min to obtain the aminated montmorillonite; the carboxylated graphene, the aminated montmorillonite, 4 g 1-ethyl-(3-dimethylaminopropyl) carbodiimide and 3 g N-hydroxysuccinimide were added into anhydrous N, N-dimethylformamide, and heated to 75 °C under nitrogen protection to stir for 10 h to obtain the nanocomposite;

[0080] S2, 17 g nanocomposite was added into 150 mL anhydrous N, N-dimethylformamide, and dispersed by ultrasonic at 300 W for 30 min, then 3 g paste-like polyethylene oxide wax (model: QH7415) was added, and heated to 80 °C under nitrogen protection to stir for 3 h to obtain the wax-nanocomposite;

[0081] S3, 10 g wax-nanocomposite was added into 120 mL deionized water, and dispersed by ultrasonic at 300 W for 30 min, then 4 g hydroxyl-terminated polyethylene glycol with a molecular weight of 2000 and 0.5 g condensing agent dicyclohexyl carbodiimide were added, and stirred at 40 °C under nitrogen protection for 6 h to obtain the product after filtration, which was washed with anhydrous ethanol and acetone in sequence, then dispersed in 120 mL deionized water, 0.2 g concentrated sulfuric acid was added, and stirred at 85 °C for 7 h, then washed with deionized water until neutral, and obtained the modified nanofiller with an average particle size of 50 nm after freeze-drying and grinding.

[0082] Preparation Example 11

[0083] The preparation example is basically the same as Preparation Example 10, except that in S2, 18 g nanocomposite was added into 150 mL anhydrous N, N-dimethylformamide, and dispersed by ultrasonic at 300 W for 30 min, then 2 g paste-like polyethylene oxide wax (model: QH7415) was added, and heated to 80 °C under nitrogen protection to stir for 3 h to obtain the wax-nanocomposite.

[0084] Preparation Example 12

[0085] The preparation example is basically the same as Preparation Example 10, except that in S2, 19 g nanocomposite was added into 150 mL anhydrous N, N-dimethylformamide, and dispersed by ultrasonic at 300 W for 30 min, then 1 g paste-like polyethylene oxide wax (model: QH7415) was added, and heated to 80 °C under nitrogen protection to stir for 3 h to obtain the wax-nanocomposite.

[0086] Preparation Example 13

[0087] The present preparation example discloses a preparation method of modified emulsified asphalt, specifically comprising the following steps:

[0088] (1) Take 50 g of 90# base asphalt and heat it to 170°C, add 20 g of waste tire rubber powder emulsion, stir at 800 rpm for 15 min, add 0.5 g of SBS and 0.5 g of 2000 mesh graphene (layer number ≤5), turn on 500W ultrasonic and 5000 rpm shear, process for 20 min to obtain a modified asphalt premix;

[0089] The waste tire rubber powder emulsion is obtained by mixing 80 mesh 100 g of devulcanized rubber powder from waste tires with 100 g of deionized water, adding 2 g of sodium dodecyl benzene sulfonate and 2 g of Tween-80, processing under 15000 rpm shear for 30 min, and then dispersing under 500W ultrasonic for 15 min (working for 3 s and stopping for 1 s, water bath cooling to control the temperature ≤60°C).

[0090] (2) Cool the above modified asphalt premix to 70°C, add 0.5 g of emulsifier, 2 g of diluent, 25 g of deionized water and 0.1 g of polyamide anti-stripping agent, stir at 300 rpm for 15 min to obtain modified emulsified asphalt;

[0091] The emulsifier is obtained by mixing sorbitan monooleate (Span-80, HLB=4.3) and polyoxyethylene sorbitan monolaurate (Tween-20, HLB=16.7) at a ratio of 2:1.

[0092] The diluent is obtained by mixing biodiesel (fatty acid methyl ester) and vegetable oil (low erucic rapeseed oil CAS: 120962-03-0) at a ratio of 6:4.

[0093] The present preparation example is a laboratory small test preparation method of modified emulsified asphalt. In actual production, the component usage can be scaled up according to the formulation and usage of cold asphalt mixture in the examples, and the required scale of modified emulsified asphalt can be prepared according to the raw material proportion of the present preparation example.

[0094] Example 1

[0095] The embodiment provides a cold asphalt mixture suitable for a low-temperature environment, which comprises 5 kg of modified emulsified asphalt, 0.3 kg of composite fibers (0.15 kg of polyester fibers and 0.15 kg of lignin fibers), 4 kg of fillers (3.2 kg of cement and 0.8 kg of limestone), 0.2 kg of an anti-freezing agent (polyethylene glycol with a molecular weight of 200), 0.5 kg of a polyolefin elastomer (ethylene-octene copolymer) and 90 kg of aggregates (40 kg of basalt macadam, 30 kg of machine-made sand and 20 kg of old road milling materials), wherein the modified emulsified asphalt is obtained by using the preparation example 1.

[0096] In the raw materials, the basalt macadam has a continuous gradation of 5-20 mm, a crushing value of ≤12% and a content of needle and flaky particles of ≤8%; the machine-made sand has a particle size of 0.075-6 mm, wherein the content of particles with a particle size of 0.075-5 mm accounts for ≥30%, and the content of stone powder is ≤3%; the old road milling materials have a particle size of 0-20 mm, and are activated by 5 g of waste rubber oil and 5 g of furfural extract oil after preheating at 65 ℃; the cement is P.O42.5 grade ordinary portland cement, and has a fineness passing rate of ≥85% through a 0.08 mm square hole screen; the limestone has a particle size of <0.075 mm and a specific surface area of ≥300 m 2 / kg; the polyester fibers have a length of 6-12 mm, the lignin fibers have a length of 3-6 mm, and the fiber diameter is ≤30 μm.

[0097] The embodiment also provides a preparation method of the cold asphalt mixture suitable for a low-temperature environment, and the method comprises the following steps:

[0098] According to the above proportioning, the basalt macadam, the machine-made sand and the old road milling materials are dried to a water content of ≤2%, the old road milling materials are activated by 5 g of waste rubber oil and 5 g of furfural extract oil after preheating at 65 ℃, and then are mixed with the basalt macadam, stirred at 300 rpm for 5 min, and then the machine-made sand is added and stirred at 300 rpm for 5 min, and then screening is performed to ensure that the gradation meets the AC-16C gradation, a silane coupling agent (0.1 kg of γ-glycidyl ether oxypropyl trimethoxysilane is diluted with 1 L of an ethanol-water mixture with a volume ratio of 3:1, and diluted hydrochloric acid is added dropwise to adjust the pH to 4, and stirring is performed at room temperature to obtain) is sprayed by using a mist nozzle, and the aggregates are obtained by stirring at 300 rpm for 10 min.

[0099] The aggregates obtained above are stirred with the composite fibers at room temperature and at 300 rpm for 8 min, the modified emulsified asphalt is added and stirred at room temperature and at 200 rpm for 10 min, the fillers, the anti-freezing agent and the polyolefin elastomer are sequentially added, and stirring is performed at 350 rpm for 6 min, and the discharge temperature is controlled to be 30 ℃.

[0100] Example 2

[0101] This example is substantially the same as Example 1, except that this example provides a cold asphalt mixture adapted to a low temperature environment, which includes 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 anti-freezing agent (polyethylene glycol having a molecular weight of 200), 1.3 kg of polyolefin elastomer (ethylene-octene copolymer), and 86.5 kg of aggregate (43.25 kg of basaltic rock, 21.625 kg of machine-made sand, and 21.625 kg of old pavement milling material), wherein the modified emulsified asphalt is obtained by using Preparation Example 1.

[0102] Example 3

[0103] This example is substantially the same as Example 1, except that this example provides a cold asphalt mixture adapted to a low temperature environment, which includes 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 anti-freezing agent (polyethylene glycol having a molecular weight of 200), 1.3 kg of polyolefin elastomer (ethylene-octene copolymer), and 86.5 kg of aggregate (43.25 kg of basaltic rock, 21.625 kg of machine-made sand, and 21.625 kg of old pavement milling material), wherein the modified emulsified asphalt is obtained by using Preparation Example 1.

[0104] Example 4

[0105] This example is substantially the same as Example 2, except that the modified emulsified asphalt of this example is obtained by using Preparation Example 2.

[0106] Example 5

[0107] This example is substantially the same as Example 2, except that the modified emulsified asphalt of this example is obtained by using Preparation Example 3.

[0108] Example 6

[0109] This example is substantially the same as Example 2, except that the modified emulsified asphalt of this example is obtained by using Preparation Example 4.

[0110] Example 7

[0111] This example is substantially the same as Example 2, except that the modified emulsified asphalt of this example is obtained by using Preparation Example 5.

[0112] Example 8

[0113] This example is substantially the same as Example 2, except that the modified emulsified asphalt of this example is obtained by using Preparation Example 6.

[0114] Example 9

[0115] This example is substantially the same as Example 2, except that the modified emulsified asphalt of this example is obtained using the product of Preparation Example 7.

[0116] Example 10

[0117] This example is substantially the same as Example 2, except that the modified emulsified asphalt of this example is obtained using the product of Preparation Example 8.

[0118] Example 11

[0119] This example is substantially the same as Example 2, except that the modified emulsified asphalt of this example is obtained using the product of Preparation Example 9.

[0120] Example 12

[0121] This example is substantially the same as Example 2, except that the modified emulsified asphalt of this example is obtained using the product of Preparation Example 10.

[0122] Example 13

[0123] This example is substantially the same as Example 2, except that the modified emulsified asphalt of this example is obtained using the product of Preparation Example 11.

[0124] Example 14

[0125] This example is substantially the same as Example 2, except that the modified emulsified asphalt of this example is obtained using the product of Preparation Example 12.

[0126] Comparative Example 1

[0127] This comparative example is substantially the same as Example 1, except that the modified emulsified asphalt of this comparative example is obtained using the product of Preparation Example 13.

[0128] Test standards:

[0129] Low temperature ductility test: The modified emulsified asphalt obtained in Preparation Examples 1-13 was tested according to the standard GB / T4508, and the test results are recorded in Table 1.

[0130] Marshall stability test: Marshall experiments were performed according to the method of T0709 in the standard JTGE20-2011 "Standard Test Methods for Bituminous Paving Mixtures", and 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.

[0131] Freeze-thaw splitting test: the freeze-thaw splitting of the asphalt mixtures obtained from each example and the comparative example was tested according to the method of T0729 in JTGE20-2011 "Standard Test Methods of Bitumen and Bituminous Mixtures for Highway Engineering", and the test results are recorded in Table 2.

[0132] Table 1 Performance test data of modified emulsified asphalt in Preparation Examples 1-13

[0133]

[0134] Table 2 Performance test data of cold asphalt mixtures suitable for low-temperature environment in Examples 1-14 and Comparative Example 1

[0135]

[0136] Referring to Tables 1 and 2, in combination with Examples 1 and 2, it can be seen that, by modifying the nano filler, the compatibility of the nano filler with the asphalt is improved, the low-temperature ductility of the obtained modified emulsified asphalt is improved, and the mechanical strength and low-temperature crack resistance of the prepared asphalt mixture are improved.

[0137] Referring to Tables 1 and 2, in combination with Examples 2, 6 and 7, it can be seen that, by using a mixture of graphene and montmorillonite, the flexibility of graphene and the rigidity of montmorillonite form a multi-scale structure of rigidity and flexibility, which not only alleviates the problem of easy agglomeration of graphene, but also makes up for the insufficient mechanical properties of montmorillonite. The low-temperature crack resistance of the cold asphalt mixture is improved, the crack initiation and propagation are inhibited, the bending failure strain under extreme low temperature is improved, and the mechanical strength of the prepared asphalt mixture is improved.

[0138] Referring to Tables 1 and 2, in combination with Examples 8 and 10, it can be seen that, by modifying the surface of the nano filler to graft polyethylene glycol, the flexibility of polyethylene glycol can optimize the interfacial bonding force between the filler and the asphalt matrix, improve the compatibility of the two, improve the low-temperature ductility of the obtained modified emulsified asphalt, and further improve the mechanical strength and low-temperature crack resistance of the prepared asphalt mixture.

[0139] Referring to Tables 1 and 2, in combination with Examples 10 and 11, it can be seen that, by grafting polyethylene glycol after plasma treatment of the nano filler, compared with grafting polyethylene glycol after modification by a silane coupling agent, the plasma treatment activates the surface of the nano filler to produce active functional groups such as hydroxyl and carboxyl groups, breaks the chemical inertness of the filler surface and increases the reaction sites, laying a foundation for subsequent grafting reaction; then, the active functional groups react with polyethylene glycol to make the polyethylene glycol molecules firmly bond to the surface of the filler, forming a functional modified layer, and further improving the interfacial bonding force between the nano filler and the asphalt matrix.

[0140] Referring to Tables 1 and 2, in combination with Examples 11 and 12, it can be seen that the present application can further improve the low-temperature ductility of the modified emulsified asphalt by introducing an appropriate amount of oxidized polyethylene wax in the plasma treatment and surface grafting of the nano filler with polyethylene glycol, the rigidity of the nano filler cooperates with the flexible segment of the wax, which can not only disperse low-temperature stress and block crack propagation through the rigid skeleton, but also relieve shrinkage strain and improve low-temperature flexibility through the flexible segment, and at the same time, the wax molecules can avoid nano particle agglomeration and are compatible with the subsequently grafted polyethylene glycol, balancing the dispersibility of the nano filler in the emulsified asphalt and the asphalt compatibility, and enhancing the low-temperature anti-cracking performance of the cold asphalt mixture.

[0141] The specific embodiments are only an explanation of the present application, which is not a limitation of the present application, and those skilled in the art can make modifications to the embodiments without creative contribution after reading the specification, but as long as it is within the scope of the claims of the present application, it is protected by the patent law.

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 shear 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. The modified nanofiller is obtained by plasma treatment followed by grafting polyethylene glycol onto the nanofiller; The nanofiller is a mixture of montmorillonite and graphene in a mass ratio of 1:(2-5).

2. The cold asphalt mixture adapted to low-temperature environments according to claim 1, 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.

3. The cold asphalt mixture adapted to low-temperature environments according to claim 1, 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).

4. 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).

5. 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).

6. 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).

7. The method for preparing cold asphalt mixture adapted to low-temperature environments according to any one of claims 1-6, 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.

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