A toughened waterborne epoxy modified emulsified asphalt and a preparation method thereof

Abstract

The application provides a toughened water-based epoxy modified emulsified asphalt and a preparation method thereof, and the toughened water-based epoxy modified emulsified asphalt comprises base asphalt, a stabilizer, an emulsifier, styrene-butadiene latex and a water-based epoxy resin modifier; wherein the stabilizer comprises polyvinyl alcohol and anhydrous calcium chloride, and the emulsifier comprises a quaternary ammonium salt surfactant and cocamidopropyl betaine. The preparation process is simple, the prepared toughened water-based epoxy modified emulsified asphalt emulsion is stable, has excellent mechanical properties and storage stability, and the high and low temperature adaptability, the bonding performance and the long-term serviceability of the modified emulsified asphalt are improved.

Description

Technical Field

[0001] This invention relates to the field of emulsified asphalt technology, and more particularly to a toughened waterborne epoxy-modified emulsified asphalt and its preparation method. Background Technology

[0002] Emulsified asphalt can be mixed with aggregates or sprayed at lower temperatures, and has the advantages of low energy consumption, low environmental pollution and easy operation. It is widely used in road tack coats, fog seals, slurry seals and surface treatments, and is especially suitable for engineering scenarios with high requirements for construction temperature and environmental protection.

[0003] However, ordinary emulsified asphalt has poor performance and cannot meet the requirements for road use. In order to improve its durability, deformation resistance and temperature adaptability, it is often modified with polymers. Styrene-butadiene latex (SBR latex) has certain advantages in road construction in cold regions due to its excellent low-temperature flexibility and crack resistance, but its high-temperature performance improvement is limited, and the traditional "emulsification followed by modification" process is prone to uneven dispersion of modifiers, poor emulsion stability, and affects construction performance and long-term durability of materials.

[0004] In recent years, waterborne epoxy resins (WERs) have been gradually introduced into emulsified asphalt systems to enhance the mechanical strength, aging resistance, and interfacial adhesion of emulsion evaporation residues. Their water-based properties can also effectively reduce volatile organic compound emissions, aligning with the trend towards green and environmentally friendly development. However, their hydrophobicity and poor compatibility with waterborne emulsion systems make it difficult to form a continuous and dense cross-linked network using conventional addition methods, leading to easy phase separation and significant performance fluctuations in the emulsion.

[0005] In summary, while existing SBS, SBR, or waterborne epoxy-modified emulsified asphalts improve certain properties, they often suffer a decline in other performance indicators. They are unable to simultaneously achieve low-temperature flexibility, high-temperature stability, and storage stability, and thus cannot meet the current demand for multi-performance integrated emulsified asphalt materials in road engineering.

[0006] Traditional processes are constrained by the conflict between the WER curing reaction and the asphalt emulsification conditions: asphalt emulsification requires a high-temperature, high-shear environment, while WER undergoes irreversible pre-curing under these conditions, leading to system failure. Therefore, modified WER emulsified asphalt cannot be prepared simultaneously. Meanwhile, SBR latex exhibits poor stability at high temperatures, and the compatibility issues between SBR and the asphalt phase make simultaneous processing extremely difficult. Traditional single emulsifiers cannot simultaneously meet the emulsification requirements of multi-component systems, and stabilizers have limited effectiveness, failing to maintain system stability under harsh conditions and placing extremely high demands on equipment. Therefore, only a stepwise process under mild conditions can be employed: first preparing the matrix emulsified asphalt, then adding the modifier and stirring at low speed.

[0007] However, in this method, the dispersion effect of the modifier is limited. SBR latex can only adhere to the surface of the already formed asphalt emulsion particles and cannot penetrate into the interior to form a uniform dispersion. The modification effect is limited to the surface layer. When WER is added subsequently, since SBR has already occupied part of the asphalt surface, WER is difficult to fully contact with the asphalt. The two modifiers compete for adsorption at the interface and lack effective interaction, which easily leads to phase separation and fails to achieve a synergistic modification effect. As a result, the mechanical properties, high and low temperature adaptability, and long-term service performance of the modified emulsified asphalt are poor. At the same time, the stepwise addition causes modifiers with different densities and viscosities to easily settle and stratify during storage, resulting in poor system stability. Moreover, the process control is complicated, requiring precise control of the time, temperature, and stirring intensity of each step. It is difficult to ensure consistency between batches, resulting in high production costs and unstable quality control. Summary of the Invention

[0008] In view of this, the present invention proposes a toughened waterborne epoxy modified emulsified asphalt and its preparation method. The preparation process is simple, and the toughened waterborne epoxy modified emulsified asphalt emulsion obtained is stable, has excellent mechanical properties and storage stability, and synergistically improves the high and low temperature adaptability, adhesion performance and long-term service performance of the modified emulsified asphalt.

[0009] The technical solution of this invention is implemented as follows: In a first aspect, the present invention provides a toughened waterborne epoxy-modified emulsified asphalt, comprising a base asphalt, a stabilizer, an emulsifier, a styrene-butadiene latex, and a waterborne epoxy resin modifier. The stabilizer includes polyvinyl alcohol and anhydrous calcium chloride, and the emulsifier includes quaternary ammonium salt surfactant and cocamidopropyl betaine.

[0010] Based on the above technical solution, the quaternary ammonium salt surfactant further comprises hexadecyl / octadecyl mixed trimethylammonium chloride, with the chemical formula R–N. + (CH3)3Cl - , where R is a C16-C18 mixed-chain alkyl group.

[0011] Based on the above technical solution, further, by weight, it includes: 0.5-0.8 parts cocamidopropyl betaine and 145-160 parts base bitumen.

[0012] Based on the above technical solution, further comprising, by weight: 0.1 parts polyvinyl alcohol, 0.1 parts anhydrous calcium chloride, 2-3 parts quaternary ammonium salt surfactant, 6-9 parts styrene-butadiene latex and 20-24 parts waterborne epoxy resin modifier; The waterborne epoxy resin modifier comprises waterborne epoxy resin component A and curing agent component B, with a mass ratio of waterborne epoxy resin component A to curing agent component B of 1:1.

[0013] Based on the above technical solution, it further includes water, with a weight of 100 parts.

[0014] Based on the above technical solutions, the base asphalt further includes No. 70 base asphalt.

[0015] Based on the above technical solution, the molecular weight of the polyvinyl alcohol is further specified as 1000-3000.

[0016] Secondly, the present invention also provides a method for preparing the toughened waterborne epoxy-modified emulsified asphalt, comprising the following steps: Step S1: Heat water, add polyvinyl alcohol, stir, and obtain soap solution; Step S2: Add styrene-butadiene latex to the soap solution and stir until evenly dispersed; Step S3: Add anhydrous calcium chloride, quaternary ammonium salt surfactant, and cocamidopropyl betaine in sequence, stir, and adjust the pH. Step S4: Pour the base asphalt into the asphalt tank and heat it; Step S5: Preheat the colloid mill and soap solution tank, pour the soap solution into the soap solution tank, and let the soap solution and matrix asphalt flow into the colloid mill for grinding, and collect the emulsion; Step S6: Add waterborne epoxy resin modifier to the emulsion and stir to obtain the toughened waterborne epoxy modified emulsified asphalt.

[0017] SBR latex is added to a prepared soap solution, circulated, and stirred until homogeneous. The mixture is then fed into a colloid mill with heated asphalt through controlled flow to produce modified emulsified asphalt. Under mechanical force, the SBR and asphalt undergo thorough collision and fusion, resulting in emulsified asphalt with better modification and stabilization effects. However, if a single emulsifier or stabilizer is used, the modified emulsified asphalt becomes a dual-composite thermodynamically unstable system. Besides possessing the same properties as emulsified asphalt, the addition of SBR latex introduces instability factors. Therefore, the storage stability of modified emulsified asphalt is worse than that of emulsified asphalt, it is prone to water separation and stratification, and has a limited shelf life.

[0018] The compound emulsifier and stabilizer system described in this invention effectively solves the defects of traditional processes: the mixed-chain long-term quaternary ammonium salts (C16-C18) in the compound emulsifier can adapt to different polar components, providing stable adsorption sites for SBR during asphalt emulsification. Meanwhile, the pH buffering properties and amphiphilic structure of the zwitterionic surfactant cocamidopropyl betaine ensure the stability of SBR latex under high temperature and high shear conditions, achieving uniform dispersion of SBR into the asphalt during simultaneous emulsification and modification. The strong emulsifying ability of the cationic quaternary ammonium salt surfactant combined with the pH buffering performance of the zwitterionic surfactant cocamidopropyl betaine allows it to act as an anion or cation under different pH conditions, helping to stabilize the system. The inner cationic layer densely adsorbs the oil phase, while the outer zwitterionic layer dynamically regulates interfacial tension and inhibits aggregation. Especially when modifiers are added, it can maintain interfacial stability, forming a more stable interfacial film. The complementary HLB values ​​cover different polar components, ensuring uniform dispersion of SBR latex in the soap solution without demulsification, thereby producing stable SBR-modified emulsified asphalt.

[0019] The low molecular weight polyvinyl alcohol (PVA) in the compound stabilizer (molecular weight 1000-3000) can quickly penetrate and form a stable protective film at the SBR-asphalt interface, preventing SBR latex aggregation. At the same time, anhydrous CaCl2 regulates ionic strength and complexes with polar groups, providing long-term stability. The SBR-modified emulsified asphalt formed by this compound system has better interfacial stability and more active sites. When WER is added subsequently, WER can form a synergistic network with the pre-dispersed uniform SBR latex, avoiding competitive adsorption and achieving a true composite modification effect. Meanwhile, the multiple stabilization mechanisms of the system ensure storage stability and batch consistency.

[0020] The low molecular weight PVA in the compound stabilizer provides rapid steric stability, while anhydrous CaCl2 regulates ionic strength and complexes with polar groups. The dual mechanism works synergistically to improve the fluidity and stability of the emulsion, which can significantly reduce the viscosity increase caused by the simultaneous emulsification and modification of SBR latex and prevent separation during storage.

[0021] Compared to a single system, the combination of emulsifiers and stabilizers significantly improves emulsification efficiency, enhances the system's anti-coagulation ability, and gives the modified emulsified asphalt better storage stability. It also synergistically improves the high and low temperature adaptability, adhesion performance, and long-term service performance of the modified emulsified asphalt.

[0022] Based on the above technical solution, further, in step S1, the heating temperature is 75~80℃, the stirring rate is 300 rpm, and the stirring time is 5 min.

[0023] Based on the above technical solution, further, in step S2, the stirring method includes: first stirring at a rate of 500 rpm for 5 minutes, and then stirring at a rate of 1000 rpm for 3 minutes until the mixture is evenly dispersed.

[0024] Based on the above technical solution, further, in step S3, the stirring rate is 300 rpm and the stirring time is 5 min.

[0025] Based on the above technical solution, further, step S3 also includes adjusting the pH to 1.4-1.6 after stirring and letting it stand for 2 minutes.

[0026] Based on the above technical solution, further, in step S4, the heating temperature is 140~145℃.

[0027] Based on the above technical solution, further, step S4 also includes self-circulation at a flow rate of 180 L / min after heating.

[0028] Based on the above technical solutions, further, in step S5, the preheating is heating to 80°C, and the grinding rate is 9000~10000 rpm.

[0029] Based on the above technical solution, further, step S5 also includes pouring soap solution into the soap solution tank and then circulating it at a flow rate of 120L / min. The outlet of the colloid mill is adjusted to the waste liquid outlet. The soap solution tank is opened first, and after the soap solution flows out of the waste liquid pipe, the asphalt tank is quickly opened so that the soap solution and the matrix asphalt flow into the colloid mill for grinding.

[0030] Based on the above technical solution, further, in step S6, the stirring rate is 500 rpm and the stirring time is 10 min.

[0031] Compared with the prior art, the present invention has the following beneficial effects: Based on a process of simultaneous emulsification and modification, a novel toughened waterborne epoxy-modified emulsified asphalt and its preparation method are proposed. By compounding cationic surfactants and amphoteric surfactants, specifically cocamidopropyl betaine, as emulsifiers, along with organic and inorganic stabilizers, a stable SBR-modified emulsified asphalt is first prepared. This asphalt is then better compatible with the waterborne epoxy resin modifier, forming a more stable three-dimensional network structure, thus providing a more stable toughened waterborne epoxy-modified emulsified asphalt. Compared to composite modified emulsified asphalt prepared by emulsification followed by modification, this preparation process is simpler, significantly reduces the particle size distribution of the emulsified asphalt, and yields a stable toughened waterborne epoxy-modified emulsified asphalt emulsion with excellent mechanical properties and storage stability. It also synergistically improves the high and low temperature adaptability, adhesion performance, and long-term service performance of the modified emulsified asphalt. Attached Figure Description

[0032] Figure 1 The results are from the boiling water test of Example 1, Comparative Example 1, Comparative Example 7 and Comparative Example 8. Detailed Implementation

[0033] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0034] In the following specific embodiments, the molecular weight of polyvinyl alcohol is 1000-3000, and it is a white powdery solid purchased from Zhengzhou Yufan Biotechnology Co., Ltd. The quaternary ammonium salt surfactant is a mixed-chain quaternary ammonium salt surfactant, consisting of a hexadecyl / octadecyl trimethylammonium chloride, with the chemical formula R–N. + (CH3)3Cl - R is a C16-C18 mixed-chain alkyl group, purchased from Hongyuan Chemical and Honghan Detergent Company. Quaternary ammonium salts of C16 and C18 carbon chains were dissolved in anhydrous ethanol at a ratio of (1~1.5):1 to prepare homogeneous solutions of 0.1-0.5 mol / L. A homogeneous mixed precursor system was constructed using the good solubility of both in ethanol. Subsequently, the two solutions were combined at room temperature and simultaneously subjected to ultrasonic treatment at 100-300 W power for 10-20 minutes. The cavitation effect and mechanical vibration of the ultrasound promoted molecular diffusion, driving the spontaneous orderly arrangement of molecules and the formation of a stable assembly structure. After removing the solvent by rotary evaporation (40-60℃, pressure <50kPa), a uniformly dispersed mixture was finally obtained. Cocamidopropyl betaine was purchased from Shandong Tenghui Daily Chemical Co., Ltd. Anhydrous calcium chloride is in the form of spiky spherical anhydrous calcium chloride granules, purchased from Gongyi Jiezhiyuan Water Treatment Materials Co., Ltd. The base asphalt is No. 70 base asphalt; Styrene-butadiene latex was purchased from Shandong Fushun New Material Technology Co., Ltd. The water-based epoxy resin modifier was purchased from Dongguan Guangtong Chemical Products Co., Ltd.

[0035] Example 1 This embodiment provides a toughened waterborne epoxy-modified emulsified asphalt and its preparation method. The toughened waterborne epoxy-modified emulsified asphalt comprises the following components in parts by weight: 100 parts deionized water, 0.1 parts polyvinyl alcohol, 8 parts styrene-butadiene latex, 0.1 parts anhydrous calcium chloride, 2.5 parts quaternary ammonium salt surfactant, 0.6 parts cocamidopropyl betaine, 150 parts 70# base asphalt, and 22 parts waterborne epoxy resin modifier (including 11 parts waterborne epoxy resin component A and 11 parts curing agent component B).

[0036] Its preparation method includes the following steps: Step S1: Heat 1000kg of deionized water to 78℃, slowly add 1kg of polyvinyl alcohol, and stir at low speed of 300 rpm for 5 minutes to obtain soap solution; Step S2: Add 80 kg of styrene-butadiene latex (SBR) to the soap solution, stir at 500 rpm for 5 min and then at 1000 rpm for 3 min until evenly dispersed; Step S3: Add 1 kg of anhydrous calcium chloride, 25 kg of quaternary ammonium salt surfactant, and 6 kg of cocamidopropyl betaine in sequence. Continue stirring at a low speed of 300 rpm for 5 min, then adjust the pH to 1.4–1.6 with hydrochloric acid and let stand for 2 min. Step S4: Pour 1500 kg of 70# base asphalt into an asphalt tank, heat it to 143°C, and circulate it at a flow rate of 180 L / min. Step S5: Preheat the colloid mill and soap solution tank to 80 ℃, pour the soap solution obtained in step S1 into the soap solution tank, and circulate it at a flow rate of 120L / min. Step S6: Adjust the outlet of the colloid mill to the waste liquid outlet. First, open the soap liquid tank. After the soap liquid flows out of the waste liquid pipe, quickly open the asphalt tank to let it flow into the colloid mill with the speed increased to 9500 rpm for grinding. After removing the initial soap liquid waste, adjust the outlet of the colloid mill to the product outlet and collect the emulsion. Step S7: Add 110 kg of waterborne epoxy resin component A and 110 kg of curing agent component B to the obtained emulsion, and stir at 500 rpm for 10 min to obtain toughened waterborne epoxy modified emulsified asphalt.

[0037] Example 2 This embodiment provides a toughened waterborne epoxy-modified emulsified asphalt and its preparation method. The toughened waterborne epoxy-modified emulsified asphalt comprises the following components in parts by weight: 100 parts deionized water, 0.1 parts polyvinyl alcohol, 6 parts styrene-butadiene latex, 0.1 parts anhydrous calcium chloride, 2 parts quaternary ammonium salt surfactant, 0.5 parts cocamidopropyl betaine, 145 parts 70# base asphalt, and 20 parts waterborne epoxy resin modifier (including 10 parts waterborne epoxy resin component A and 10 parts curing agent component B). The preparation method includes the following steps: Step S1: Heat 1000kg of deionized water to 75℃, slowly add 1kg of polyvinyl alcohol, and stir at low speed of 300 rpm for 5 minutes to obtain soap solution; Step S2: Add 60 kg of styrene-butadiene latex (SBR latex) to the soap solution, stir at 500 rpm for 5 min and then at 1000 rpm for 3 min until evenly dispersed; Step S3: Add 1 kg of anhydrous calcium chloride, 20 kg of quaternary ammonium salt surfactant, and 5 kg of cocamidopropyl betaine in sequence. Continue stirring at a low speed of 300 rpm for 5 min, then adjust the pH to 1.4–1.6 with hydrochloric acid and let stand for 2 min. Step S4: Pour 1450 kg of 70# base asphalt into the asphalt tank, heat it to 140℃, and circulate it at a flow rate of 180 L / min. Step S5: Preheat the colloid mill and soap solution tank to 80 ℃, pour the soap solution obtained in step S1 into the soap solution tank, and circulate it at a flow rate of 120L / min. Step S6: Adjust the outlet of the colloid mill to the waste liquid outlet, first open the soap liquid tank, and after the soap liquid flows out of the waste liquid pipe, quickly open the asphalt tank to let it flow into the colloid mill with the speed increased to 9000 rpm for grinding. After removing the initial soap liquid waste, adjust the outlet of the colloid mill to the product outlet and collect the emulsion. Step S7: Add 100 kg of waterborne epoxy resin component A and 100 kg of curing agent component B to the obtained emulsion, and stir at 500 rpm for 10 min to obtain toughened waterborne epoxy modified emulsified asphalt.

[0038] Example 3 This embodiment provides a toughened waterborne epoxy-modified emulsified asphalt and its preparation method. The toughened waterborne epoxy-modified emulsified asphalt comprises the following components in parts by weight: 100 parts deionized water, 0.1 parts polyvinyl alcohol, 9 parts styrene-butadiene latex, 0.1 parts anhydrous calcium chloride, 3 parts quaternary ammonium salt surfactant, 0.8 parts cocamidopropyl betaine, 160 parts 70# base asphalt, and 24 parts waterborne epoxy resin modifier (including 12 parts waterborne epoxy resin component A and 12 parts curing agent component B).

[0039] The preparation method includes the following steps: Step S1: Heat 1000kg of deionized water to 80℃, slowly add 1kg of polyvinyl alcohol, and stir at low speed of 300 rpm for 5 minutes to obtain soap solution; Step S2: Add 90 kg of styrene-butadiene latex (SBR latex) to the soap solution, stir at 500 rpm for 5 min and then at 1000 rpm for 3 min until evenly dispersed; Step S3: Add 1 kg of anhydrous calcium chloride, 30 kg of quaternary ammonium salt surfactant, and 8 kg of cocamidopropyl betaine in sequence. Continue stirring at a low speed of 300 rpm for 5 min, then adjust the pH to 1.4–1.6 with hydrochloric acid and let stand for 2 min. Step S4: Pour 1600 kg of 70# base asphalt into the asphalt tank, heat it to 145℃, and circulate it at a flow rate of 180 L / min. Step S5: Preheat the colloid mill and soap solution tank to 80°C, pour the soap solution obtained in step S1 into the soap solution tank, and circulate it at a flow rate of 120L / min. Step S6: Adjust the outlet of the colloid mill to the waste liquid outlet, first open the soap liquid tank, and after the soap liquid flows out of the waste liquid pipe, quickly open the asphalt tank to let it flow into the colloid mill with the speed increased to 10,000 rpm for grinding. After removing the initial soap liquid waste, adjust the outlet of the colloid mill to the product outlet and collect the emulsion. Step S7: Add 120 kg of waterborne epoxy resin component A and 120 kg of curing agent component B to the obtained emulsion, and stir at 500 rpm for 10 min to obtain toughened waterborne epoxy modified emulsified asphalt.

[0040] Comparative Example 1 The difference between this comparative example and Example 1 is that: Step S2 is excluded. Step S7: Add 80 kg of styrene-butadiene latex (SBR latex) to the obtained emulsion, stir at 500 rpm for 5 min, add 110 kg of waterborne epoxy resin component A and 110 kg of curing agent component B respectively, and stir at 500 rpm for 10 min respectively to obtain toughened waterborne epoxy modified emulsified asphalt.

[0041] Comparative Example 2 The difference between this comparative example and Example 1 is that it does not contain polyvinyl alcohol.

[0042] Comparative Example 3 The difference between this comparative example and Example 1 is that it does not contain anhydrous calcium chloride.

[0043] Comparative Example 4 The difference between this comparative example and Example 1 is that it does not contain cocamidopropyl betaine.

[0044] Comparative Example 5 The difference between this comparative example and Example 1 is that it does not contain quaternary ammonium salt surfactants.

[0045] Comparative Example 6 The difference between this comparative example and Example 1 is that this comparative example uses a method of first emulsifying and then modifying to prepare WER / SBR modified emulsified asphalt, including the following steps: Step S1: Heat 1000 kg of deionized water to 78°C, slowly add 1 kg of polyvinyl alcohol (PVA), and manually stir evenly for 5 min; then, add 1 kg of anhydrous CaCl2 and 25 kg of quaternary ammonium salt surfactant in sequence, and manually stir evenly for 15 min to mix them thoroughly. Adjust the pH to 1.4~1.6 and let it stand for 2 min to obtain soap solution.

[0046] Step S2: At the same time, weigh 1500 kg of base asphalt, heat it to 143°C, and circulate it at a flow rate of 180 L / min. Step S3: Preheat the colloid mill to 80°C, pour the soap solution at 80°C into the colloid mill, start the colloid mill, and after 20 seconds, slowly pour the preheated matrix asphalt into the colloid mill. After it is completely poured in, circulate and grind for 1 minute to prepare dark brown ordinary emulsified asphalt (EA-1). Step S4: First, use a mixer to mix 80kg of SBR latex with EA-1 at room temperature for 5 minutes at a speed of 500rpm to obtain SBR modified emulsified asphalt (EA-2). Step S5: Add 110 kg of epoxy resin component A and 110 kg of curing agent component B to EA-2 in sequence, and stir at 500 rpm for 10 min to obtain WER / SBR modified emulsified asphalt.

[0047] Comparative Example 7 The difference between this comparative example and Example 1 is that it does not include steps S2 and S7, that is, it does not contain SBR latex and waterborne epoxy resin modifier.

[0048] Comparative Example 8 The difference between this comparative example and Example 1 is that it does not include step S2, i.e., it does not contain SBR latex.

[0049] Performance testing 1. According to the "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" (JTG E20-2011) and relevant AASHTO specifications, particle size analysis was performed on the samples of Examples 1-3 and Comparative Examples 1-6. Temperature scanning, multiple stress creep recovery test, linear amplitude scanning test, and bending beam rheometer test were conducted on their evaporation residues. The test results are shown in Tables 1-4 below.

[0050] Table 1 Particle size analysis data

[0051] As can be seen from the comparison between Example 1 and Comparative Example 1 in Table 1, through process improvement, the average particle size Dv(50) of toughened waterborne epoxy modified emulsified asphalt decreased from 2.77 mm to 2.24 mm, a reduction of 23.66%; and the maximum particle size Dv(90) decreased from 10 mm to 6.63 mm, a reduction of 50.83%. The overall average particle size and maximum particle size showed a trend of Example 1 > Example 3 > Example 2 > Comparative Example 4 > Comparative Example 5 > Comparative Example 3 > Comparative Example 2 > Comparative Example 1 > Comparative Example 6, indicating that process optimization brought about a more significant reduction in droplet size and narrowing of distribution; smaller Dv(50) and lower Dv(90) mean a significant reduction in large particle groups, which is beneficial to suppressing the aggregation of emulsified asphalt particles caused by gravity sedimentation; During storage, if droplets tend to settle (or float) under the influence of gravity, their velocity can be approximately described by Stokes' law:

[0052] in and The densities are those of asphalt droplets and the continuous aqueous phase, respectively. Where is the droplet radius, For continuous phase viscosity, This is the acceleration due to gravity.

[0053] The process by which emulsified asphalt particles aggregate due to molecular thermal motion is called flocculation (recoverable). After flocculation, the asphalt particles agglomerate into large-diameter asphalt particles (non-recoverable), which then settle under gravity. Therefore, to ensure the stability of emulsified asphalt, it is necessary to prevent flocculation, agglomeration, and sedimentation. The significant reduction in particle size resulting from process improvements indicates that the introduction of compound stabilizers and emulsifiers significantly improves the dispersion efficiency and interfacial stability of the system. On the one hand, it alters the viscosity and interfacial tension characteristics of the continuous phase; on the other hand, it may further improve the interfacial film strength through cross-linking, more fully dispersing the asphalt into droplets during shear dispersion and forming a more uniform and stable interfacial film, reducing the tendency for particle aggregation and growth.

[0054] This is because the mixed-chain-length (C16-C18) quaternary ammonium salt surfactant in the compound emulsifier of this invention can adapt to different polar components, providing stable adsorption sites for SBR latex during asphalt emulsification. Meanwhile, the pH buffering properties and amphiphilic structure of the zwitterionic surfactant cocamidopropyl betaine LP-CAB-35 ensure the stability of SBR latex under high temperature and high shear conditions, achieving uniform dispersion of SBR latex into the asphalt during simultaneous emulsification and modification. The low-molecular-weight PVA (molecular weight 1000-3000) in the compound stabilizer can quickly penetrate and form a stable protective film at the SBR-asphalt interface, preventing SBR latex aggregation. Simultaneously, the spiky anhydrous CaCl2 regulates ionic strength and complexes with polar groups, providing long-term stability. The SBR-modified emulsified asphalt formed by this compound system exhibits better interfacial stability and more active sites. When WER is subsequently added, it forms a synergistic network with the pre-dispersed SBR latex, avoiding competitive adsorption and achieving a true composite modification effect. Furthermore, the system's multiple stabilization mechanisms ensure storage stability and batch consistency.

[0055] Table 2. Fatigue life prediction under different strains, times

[0056] Table 3. Results of multi-stress creep recovery experiments at 52 degrees Celsius

[0057] As shown in Tables 2 and 3, under different strain levels, the fatigue lives of Examples 1-3 are all higher than those of Comparative Examples 1-6, indicating better fatigue performance. At 52 degrees Celsius, the average recovery rate of evaporation residue in Examples 1-3 is significantly higher than that in Comparative Examples 1-6, while the unrecoverable creep compliance is reduced, indicating that Examples 1-3 have stronger elastic recovery ability and resistance to permanent deformation. This is because Examples 1-3 adopt a simultaneous emulsification and modification process and introduce a waterborne epoxy-SBR composite modification system. During the emulsification process, the waterborne epoxy and SBR latex form a dense and continuous elastic network structure. This network improves the elastic recovery ability of asphalt residue, with an R value significantly higher than other groups, while inhibiting plastic flow at high temperatures and significantly reducing the Jnr value. The polymer network structure formed by waterborne epoxy and SBR maintains good stress dispersion ability and delays crack initiation and propagation under different stress levels, and Examples 1-3 exhibit high fatigue lives under different stress levels.

[0058] Comparative Examples 2-5 also employed a simultaneous emulsification and modification process, but without the use of compounded emulsifiers or stabilizers. The dispersion stability of the waterborne epoxy and SBR during emulsification was insufficient, leading to agglomeration or phase separation of some modified components during the emulsification or curing stages. This resulted in an incomplete network structure and limited elastic phase continuity, leading to a lower R-value and a correspondingly higher Jnr value compared to the examples. Simultaneously, stress concentration was more pronounced, resulting in a relatively lower fatigue life.

[0059] Comparative Examples 1 and 6 employed a pre-emulsification followed by modification process, with the modifier added only after emulsification was complete. The waterborne epoxy-SBR modifier exhibited poor compatibility with the asphalt matrix, resulting in uneven distribution of the elastic phase, a significant decrease in recovery capacity, and a greater likelihood of irreversible deformation under high stress, leading to the lowest fatigue life.

[0060] Table 4. Results of Bending Beam Rheometer (BBR) Tests

[0061] In the BBR test, the larger the stiffness modulus S, the greater the possibility of brittle fracture of the specimen; the larger the value of m, the better the stress relaxation performance of the specimen and the stronger its low-temperature crack resistance.

[0062] As shown in Table 4, Examples 1-3 employed a simultaneous emulsification and modification process and introduced a waterborne epoxy-SBR composite modification system. During emulsification, the epoxy underwent partial cross-linking, and the SBR provided an elastic network, enabling the asphalt matrix to form a continuous elastic-viscosity network structure. This structure effectively released stress at low temperatures, thus exhibiting a lower S value and a higher m value, indicating good flexibility and stress relaxation ability, and the best resistance to low-temperature cracking. Comparative Examples 2-5, although also employing a simultaneous emulsification and modification process, did not use a compound emulsifier or stabilizer, resulting in partial agglomeration or uneven dispersion of epoxy and SBR during emulsification, insufficient network continuity, relatively high stiffness at low temperatures, limited stress relaxation ability, and lower low-temperature performance than Examples 1-3. Comparative Examples 1 and 6 employed a pre-emulsification and post-modification process, with the modifier added only after emulsification was completed. This resulted in uneven distribution of the modifier, discontinuous network structure, and significant hardening of the material at low temperatures, exhibiting the highest S value and the lowest m value, indicating poor flexibility, weak stress relaxation ability, and the worst low-temperature crack resistance.

[0063] The reason for this is that the compound emulsifier and stabilizer have optimized the process of emulsification and modification at the same time. The two modifiers work synergistically to form a more stable three-dimensional cross-linked network structure between SBR latex and waterborne epoxy resin in emulsified asphalt, which synergistically improves the mechanical properties, high and low temperature adaptability, adhesion performance and long-term service performance of modified emulsified asphalt.

[0064] 2. According to the "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" (JTG E20-2011) T 0624-2011, the samples of Example 1, Comparative Example 1, Comparative Example 7 and Comparative Example 8 were subjected to viscosity and toughness tests. The test results are shown in Table 5 below.

[0065] Table 5 Results of Viscosity and Toughness Tests

[0066] As shown in Table 5, after simultaneous emulsification and modification, the toughness of the evaporation residue of the emulsified asphalt in Example 1 is higher than that of the comparative examples 1, 7, and 8 prepared using the conventional process, and Example 1 exhibits relatively high toughness. This indicates that after simultaneous emulsification and modification, compared to base emulsified asphalt, WER-modified emulsified asphalt, or composite modified emulsified asphalt prepared by emulsification followed by modification, the material still possesses greater resilience after the yielding stage, and its toughness is enhanced.

[0067] 3. According to the "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" (JTG E20-2011) T 0654-2011, the samples of Example 1, Comparative Example 1, Comparative Example 7, and Comparative Example 8 were subjected to the boiling water method test. The test results are shown in Table 6 and... Figure 1 As shown.

[0068] Table 6 Adhesion Grade

[0069] Referring to the test specifications for the adhesion between emulsified asphalt and coarse aggregate, and using the adhesion grade evaluation standard for ordinary asphalt, it was found that Example 1 with improved process had the highest adhesion grade and the smallest aggregate spalling area, which was better than Comparative Example 1 (emulsified first and then modified), Comparative Example 7 (without modifier), and Comparative Example 8 (WER modified). This indicates that the process of simultaneous emulsification and modification makes the two modifiers more evenly dispersed in the emulsified asphalt, forming a stable network structure. Compared with Comparative Example 8, SBR latex, as an elastomer, can better absorb and disperse stress, suppress brittle spalling caused by WER curing, and exert a stronger bonding effect in the adhesion process with coarse aggregate.

[0070] In summary, the present invention provides a toughened waterborne epoxy-modified emulsified asphalt and its preparation method. The preparation process is simple, and the toughened waterborne epoxy-modified emulsified asphalt emulsion obtained is stable, possesses excellent mechanical properties and storage stability, and synergistically improves the high and low temperature adaptability, adhesion performance and long-term service performance of the modified emulsified asphalt.

[0071] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing toughened waterborne epoxy-modified emulsified asphalt, characterized in that, The toughened waterborne epoxy-modified emulsified asphalt includes a base asphalt, a stabilizer, an emulsifier, a styrene-butadiene latex, and a waterborne epoxy resin modifier. The stabilizer includes polyvinyl alcohol and anhydrous calcium chloride, and the emulsifier includes quaternary ammonium salt surfactant and cocamidopropyl betaine. The toughened waterborne epoxy-modified emulsified asphalt comprises, by weight: 0.5-0.8 parts cocamidopropyl betaine, 145-160 parts base asphalt, 0.1 parts polyvinyl alcohol, 0.1 parts anhydrous calcium chloride, 2-3 parts quaternary ammonium salt surfactant, 6-9 parts styrene-butadiene latex, and 20-24 parts waterborne epoxy resin modifier; The waterborne epoxy resin modifier includes waterborne epoxy resin component A and curing agent component B, with a mass ratio of waterborne epoxy resin component A to curing agent component B of 1:

1. The preparation method of the toughened waterborne epoxy-modified emulsified asphalt includes the following steps: Step S1: Heat water, add polyvinyl alcohol, stir, and obtain soap solution; Step S2: Add styrene-butadiene latex to the soap solution and stir until evenly dispersed; Step S3: Add anhydrous calcium chloride, quaternary ammonium salt surfactant, and cocamidopropyl betaine in sequence, stir, and adjust the pH. Step S4: Pour the base asphalt into the asphalt tank and heat it; Step S5: Preheat the colloid mill and soap solution tank, pour the soap solution into the soap solution tank, and let the soap solution and matrix asphalt flow into the colloid mill for grinding, and collect the emulsion; Step S6: Add waterborne epoxy resin modifier to the emulsion and stir to obtain the toughened waterborne epoxy modified emulsified asphalt.

2. The method for preparing toughened waterborne epoxy-modified emulsified asphalt as described in claim 1, characterized in that, In step S1, the heating temperature is 75~80℃, the stirring speed is 300 rpm, and the stirring time is 5 min.

3. The method for preparing toughened waterborne epoxy-modified emulsified asphalt as described in claim 1, characterized in that, In step S2, the stirring method includes: first stirring at a speed of 500 rpm for 5 minutes, and then stirring at a speed of 1000 rpm for 3 minutes until the mixture is evenly dispersed.

4. The method for preparing toughened waterborne epoxy-modified emulsified asphalt as described in claim 1, characterized in that, In step S3, the stirring rate is 300 rpm, the stirring time is 5 min, and the pH is adjusted to 1.4-1.

6.

5. The method for preparing toughened waterborne epoxy-modified emulsified asphalt as described in claim 1, characterized in that, In step S4, the heating temperature is 140~145℃.

6. The method for preparing toughened waterborne epoxy-modified emulsified asphalt as described in claim 1, characterized in that, In step S5, the preheating is heating to 80°C, and the grinding rate is 9000~10000 rpm.

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