A polymer emulsifier for cold-mixing and cold-paving emulsified asphalt concrete and a preparation method thereof

Abstract

The present application relates to the technical field of road material, and specifically provides a polymer emulsifier for cold mixing and cold paving emulsified asphalt concrete, the polymer emulsifier is a ternary polymer produced by polymerization of acrylamide AM, N-vinyl pyrrolidone NVP and N-vinyl imidazole NVI, and the molecular weight is 3000-10000; wherein the molar ratio of the three monomers AM, NVP and NVI is 5-2:3:2-5. The ternary polymer emulsifier can be used for high-viscosity and high-solid-content emulsified asphalt, so that the emulsified asphalt still has good storage stability under the condition of high solid content, can broaden the application range of the emulsified asphalt, and solve the technical problems that the modified emulsified asphalt prepared by the prior art is difficult to consider high solid content, high viscosity and good storage stability, and is difficult to be used as a surface layer.

Description

Technical Field

[0001] This invention relates to the field of road materials technology, specifically to a polymer emulsifier for cold-mixed and cold-laid emulsified asphalt concrete and its preparation method. Background Technology

[0002] Asphalt is a viscous or semi-solid petroleum product widely used in road construction, waterproofing materials, and other fields. Emulsified asphalt is a liquid asphalt product made by mixing asphalt particles with water and adding an appropriate amount of emulsifier through mechanical stirring. It is easy to construct and environmentally friendly. Essentially, emulsified asphalt is a mixture obtained by stably dispersing asphalt particles in water containing an emulsifier. Cold-mix emulsified asphalt concrete refers to a mixture made by mixing emulsified asphalt with aggregates (such as crushed stone, sand, etc.) and, if necessary, fillers (such as mineral powder) in a certain proportion under normal temperature conditions. The advantage of cold-mix emulsified asphalt concrete is that it achieves good workability without the need for heating.

[0003] Using cold-mix emulsified asphalt concrete instead of hot-mix asphalt concrete can significantly reduce carbon emissions, improve the environmental friendliness of the construction process, and reduce the impact of weather factors. However, due to the low viscosity and low solids content of the undiluted asphalt used to prepare emulsified asphalt, it is usually only used as a functional layer material in applications such as prime coats, tack coats, and slurry seals, and is difficult to use as a surface layer in cold-mix cold-lay asphalt concrete. Therefore, the low viscosity and low solids content of current emulsified asphalt are the main problems limiting the application range of cold-mix emulsified asphalt concrete. Summary of the Invention

[0004] (a) Technical problems to be solved

[0005] In view of the above-mentioned shortcomings and deficiencies of the prior art, the present invention provides a polymer emulsifier for cold-mixed and cold-laid emulsified asphalt concrete. Using the polymer emulsifier, high-viscosity and high-solids-content emulsified asphalt can be prepared, and the emulsified asphalt can be further prepared into cold-mixed emulsified asphalt concrete, thus solving the technical problem that the currently prepared cold-mixed emulsified asphalt concrete is generally difficult to use as a surface layer due to the low viscosity and low solids content of the emulsified asphalt.

[0006] (II) Technical Solution

[0007] In a first aspect, the present invention provides a polymer emulsifier for cold-mixed and cold-laid emulsified asphalt concrete, wherein the polymer emulsifier is a ternary polymer formed by the polymerization of acrylamide (AM), N-vinylpyrrolidone (NVP), and N-vinylimidazolium (NVI), and its molecular weight is 3000-10000; wherein the molar ratio of the three monomers AM, NVP, and NVI is 5-2:3:2-5; preferably, the molar ratio of the three monomers AM, NVP, and NVI is 5:3:2.

[0008] Secondly, the present invention provides a method for preparing a polymer emulsifier for cold-mixed and cold-laid emulsified asphalt concrete, comprising the following steps:

[0009] S1. Disperse acrylamide monomer AM, N-vinylpyrrolidone monomer NVP and N-vinylimidazolium monomer NVI in water to obtain a mixed solution;

[0010] S2. Treat the mixed solution to remove or reduce dissolved oxygen in the mixed solution;

[0011] S3. Under inert gas protection, add a water-soluble initiator to the mixed solution, control the reaction temperature at ≤53℃ to carry out the polymerization reaction, and keep stirring continuously during the polymerization process;

[0012] S4. After the reaction is complete, acetone is added to the reaction system to precipitate the precipitate. The precipitate is washed and dried in a vacuum drying oven to obtain AM-VP-VI ternary polymer emulsifier.

[0013] According to a preferred embodiment of the present invention, in S1, the molar ratio of the three monomers AM, NVP, and NVI is 5-2:3:2-5; preferably, the molar ratio of the three monomers AM, NVP, and NVI is 5:3:2. Wherein, when AM is at the upper limit of the ratio, NVI is at the lower limit of the ratio; conversely, when AM is at the lower limit of the ratio, NVI is at the upper limit of the ratio.

[0014] In the AM-VP-VI ternary polymer, monomer AM has good water solubility; increasing its proportion improves the hydrophilicity of the polymer chain, its solubility or dispersibility in water, and increases its water absorption capacity and viscosity. Monomer NVP has even higher hydrophilicity; increasing its proportion significantly enhances the polymer's water solubility and compatibility with polar substances. NVP can improve the copolymer's film-forming ability and has some biodegradability potential. NVI carries a cationic charge and exhibits some hydrophilicity in water, but due to its cyclic structure, it also imparts some hydrophobic properties to the polymer. NVI can introduce a positive charge; increasing its proportion can enhance the interaction between the copolymer and negatively charged surfaces, and may also increase the material's antibacterial properties. By changing the proportion of the three monomers, the hydrophilicity / hydrophobicity of the copolymer can be controlled. An appropriate NVI ratio can yield a polymer with certain hydrophobicity while maintaining good water dispersibility.

[0015] The AM-VP-VI ternary polymer cationic emulsifier provided by this invention has a molecular weight of 3000-10000. On the one hand, its long-chain structure intertwines with asphalt molecules, anchoring them within asphalt particles. On the other hand, by introducing hydrophilic groups such as amide groups, imidazole five-membered heterocycles, and pyrrolidone groups into the molecular structure, the interaction between these molecules and water can be enhanced, and the interfacial tension between asphalt and water can be reduced through steric hindrance, thereby improving the storage stability of the emulsified asphalt system.

[0016] According to a preferred embodiment of the present invention, in S1, the total molar concentration of the three monomers in the mixed solution is 1.2-1.8 mol / L, preferably 1.5 mol / L.

[0017] According to a preferred embodiment of the present invention, in S2, nitrogen gas is introduced into the mixed solution to remove or reduce dissolved oxygen in the mixed solution; specifically, nitrogen is continuously introduced into the mixed solution for 30-50 minutes.

[0018] According to a preferred embodiment of the present invention, in S3, the water-soluble initiator is azobisisobutylamidine hydrochloride, which has good water solubility and can efficiently initiate polymerization reactions in aqueous solutions. Highly efficient initiation: Compared with general azo initiators, AAPH has higher initiation efficiency, capable of generating polymers with relatively high molecular weight and good water solubility, and with fewer residual substances. Mild decomposition conditions: AAPH decomposes at relatively low temperatures, producing polymers with high linearity and high molecular weight; suitable for polymerization reactions under low-temperature conditions. After decomposition, AAPH releases two cationic groups and nitrogen gas, does not contain toxic cyano groups, and the decomposition products are non-toxic, making it safer and more environmentally friendly. Under light conditions, especially under ultraviolet irradiation, AAPH can efficiently initiate polymerization reactions.

[0019] According to a preferred embodiment of the present invention, in step S3, azobisisobutylamidine hydrochloride is added as a low-concentration solution at a uniform flow rate during the polymerization reaction, with the reaction temperature controlled at 50°C. Preferably, the concentration of the azobisisobutylamidine hydrochloride solution is 0.05-0.06 mol / L, and the total amount of azobisisobutylamidine hydrochloride is 1 / 6-1 / 8 of the total molar ratio of the reactants. In step S3, the stirring speed during polymerization is 180 rpm-220 rpm, and the reaction time is 7.5-8.5 h. Azobisisobutylamidine hydrochloride can also be replaced with an equimolar amount of azodicyanovalerate (ACVA), ammonium persulfate (APS), or potassium persulfate (KPS). ACVA, APS, and KPS have good water solubility and can be used to replace azobisisobutylamidine hydrochloride. Azobisisobutyronitrile (AIBN) or azobisisovalerate (AIVN) have poor water solubility and contain toxic cyano groups, making them unsafe and environmentally unfriendly.

[0020] According to a preferred embodiment of the present invention, in step S4, after the reaction is completed, 1.5-3 times the volume of acetone is added to the reaction system, stirred, allowed to stand, and the precipitate is separated. The precipitate is washed with ethanol 2-3 times and dried in a vacuum drying oven at 50°C for 24 hours to obtain the AM-VP-VI ternary polymer emulsifier.

[0021] Thirdly, the present invention provides an emulsified asphalt comprising 70-75% modified base asphalt, 0.5-1.2% of the AM-VP-VI ternary polymer emulsifier as described in claim 8, 0.1-0.5% of a solid nanopowder stabilizer, 0.1-1% of additives, and the balance being water; the additives include a pH adjuster, which adjusts the pH of the emulsified asphalt to 2-3; the solid nanopowder stabilizer is nano-sized anhydrous calcium chloride powder; and the modified base asphalt is SBS and SBR co-modified base asphalt.

[0022] The base asphalt is 70# base asphalt, which can be one of SK-90, Zhonghai-90, and Jingbo-90. Preferably, in addition to the pH adjuster, the additives may also include other additives, such as thickeners, antioxidants, rust inhibitors, and corrosion inhibitors, which can be added as needed. The pH adjuster maintains the emulsified asphalt at a low pH, such as pH 2-3, and the pH adjuster is hydrochloric acid. Preferably, the base asphalt is road petroleum asphalt.

[0023] SBS (styrene-butadiene-styrene block copolymer) and SBR (styrene-butadiene rubber) co-modified base asphalt are used to improve the properties of base asphalt. The SBS and SBR co-modified base asphalt can be modified using existing techniques. For example, the base asphalt can be melted under heating conditions, and then pre-weighed SBS and SBR can be dispersed in the base asphalt. The mixture can then be treated using a shear mill (e.g., at 10,000-12,000 rpm) for 5-10 minutes. Experiments show that SBS accounts for 3-6% of the mass of the base asphalt, and SBR accounts for 2-4%; when the SBS content is 5% and the SBR powder content is 4%, the prepared modified base asphalt achieves good overall performance.

[0024] SBS forms a flexible network structure, allowing asphalt to maintain a certain degree of flexibility at low temperatures and preventing it from flowing at high temperatures. SBR increases the viscosity and cohesive strength of the asphalt, improving its resistance to deformation. SBS provides better high and low temperature performance, while SBR helps enhance the durability and adhesion of asphalt. SBS imparts good low-temperature ductility and high-temperature stability to asphalt, reduces temperature sensitivity, improves the durability of the pavement under extreme weather conditions, increases the elasticity and resilience of the asphalt, and reduces the risk of cracking caused by repeated vehicle loads. The addition of SBR enhances the adhesion of asphalt to aggregates and improves waterproofing performance, reducing the possibility of water damage. An appropriate ratio of SBS and SBR can give modified asphalt good fluidity and pumpability, facilitating construction.

[0025] Preferably, the nano-sized anhydrous calcium chloride powder has a particle size of 1-100 nm, more preferably 20-50 nm; preferably, the nano-sized anhydrous calcium chloride powder is pre-modified with hexadecyltrimethoxysilane (CTMS) (impregnation modification) to improve its dispersibility in water. Solid nanoparticles spontaneously adsorb at the oil-water interface, forming a protective film that prevents droplet aggregation, thereby achieving long-term stability of the emulsion. Unlike emulsified asphalt stabilized with surfactants, this protective film is more stable than films formed by traditional surfactants because nano-inorganic powders are not easily desorbed from the interface (irreversible adsorption of solid particles). Emulsified asphalt exhibits high thermodynamic stability, remaining stable even under extreme conditions (such as high temperature and high salt concentration).

[0026] The AM-VP-VI ternary polymer emulsifier prepared in this invention serves two purposes: firstly, it emulsifies and disperses asphalt; secondly, it modifies the emulsified asphalt, improving the adhesion between the emulsified asphalt and aggregates, increasing the viscosity of the emulsified asphalt, making it easier to handle during construction, and helping to prevent segregation, thus producing high-viscosity emulsified asphalt. This ternary polymer, together with nano-sized anhydrous calcium chloride, acts as a dispersant, helping to uniformly disperse the various components in the emulsified asphalt and improving the stability of the emulsion. This ternary polymer can also introduce special functional groups, thereby enhancing the elasticity, toughness, and other mechanical properties of asphalt, improving its anti-aging properties, and extending its service life. By adjusting the proportion of each monomer in the AM-VP-VI ternary polymer, the hydrophilicity and hydrophobicity of the polymer can be controlled, thus affecting the storage stability and workability of the emulsified asphalt.

[0027] Thickeners include polyvinyl alcohol (PVA), polyacrylamide (PAM), and cellulose derivatives such as hydroxypropyl methylcellulose (HPMC). PVA has good water solubility and film-forming properties, which can enhance the mechanical stability and adhesion of emulsified asphalt. PAM is used to increase the viscosity of emulsified asphalt, improving its shear resistance and storage stability. Cellulose derivatives can increase the viscosity of the emulsion and improve its stability. In addition, antioxidants such as phenolic compounds can prevent the emulsified asphalt from deteriorating due to oxidation during storage. Rust inhibitors such as sodium nitrite can prevent the inner walls of metal containers from rusting, thus protecting the emulsified asphalt from contamination. Preservatives include sodium benzoate, potassium sorbate, or isothiazolinone compounds, which prevent the growth of microorganisms and the resulting spoilage, separation, or performance degradation of the emulsified asphalt.

[0028] Furthermore, the preparation method of the emulsified asphalt can be carried out with reference to the following steps:

[0029] (1) The nano-sized anhydrous calcium chloride powder modified with hexadecyltrimethoxysilane (CTMS) and AM-VP-VI ternary polymer emulsifier were dispersed in water, the pH value was adjusted to 2-3 with hydrochloric acid, and the mixture was preheated to 60-70℃ to obtain an aqueous dispersion.

[0030] (2) Heat the modified base asphalt to about 120-150℃ (e.g., 135℃) until it reaches a fluid state and ensures good fluidity; while continuously stirring the aqueous dispersion (500-1000 rpm), slowly pour the molten modified base asphalt into the aqueous dispersion; gradually increase the stirring speed during the pouring of the modified base asphalt.

[0031] (3) At a temperature of 80-90℃, use a colloid mill at a speed of 3000-5000rpm for 30-60 minutes until the mixture becomes uniform and free of obvious particles. Finally, adjust the pH value as needed and add other additives (if any), stir evenly to obtain the emulsified asphalt.

[0032] Fourthly, the present invention also provides a cold-mixed, cold-laid emulsified asphalt concrete, which, by mass percentage, comprises: 3-6% of the above-mentioned emulsified asphalt, 90-94% aggregate, and 0-3% filler. The aggregate consists of crushed stone and sand of a certain gradation; the filler is mineral powder (such as S95 mineral powder), which is selectively added as needed.

[0033] (III) Beneficial Effects

[0034] The AM-VP-VI ternary polymer prepared in this invention can be used to prepare emulsified asphalt with good storage stability, high viscosity, and high solids content. The solids content of the prepared emulsified asphalt is 70%-75% (existing emulsified asphalt generally does not exceed 70%, otherwise its stability is very poor), with a 5-day storage stability of <3%, and an average particle size of <3μm. Its adhesion to coarse aggregates is comparable to that of hot-mix asphalt concrete, and its asphalt softening point is ≥85℃, with a dynamic viscosity at 60℃ ≥23000 Pa·s. The ternary polymer emulsifier of this invention comprehensively improves the high viscosity, high solids content, and high storage stability of emulsified asphalt.

[0035] By preparing emulsified asphalt with high viscosity and high solids content, and further using the mixture of emulsified asphalt with aggregates and fillers, a cold-mixed and cold-laid emulsified asphalt concrete is obtained, which gives the cold-mixed and cold-laid emulsified asphalt concrete a wider range of applications.

[0036] This invention solves the problems of low viscosity and low solid content of emulsified asphalt in the prior art, which usually can only be used as a functional layer material in applications such as prime coat, tack coat, and slurry seal, but is difficult to use as a cold-mixed cold-laid asphalt concrete surface layer. Attached Figure Description

[0037] Figure 1 The infrared spectrum of the AM-VP-VI ternary polymer prepared in Example 1 is shown.

[0038] Figure 2 The image shows the 1H NMR spectrum of the AM-VP-VI ternary polymer prepared in Example 1.

[0039] Figure 3 The images show the TG-DSC analysis results of the AM-VP-VI ternary polymers prepared in Examples 1-4.

[0040] Figure 4 The results of the bromophenol blue test are for the AM-VP-VI ternary polymer prepared in Example 1. Detailed Implementation

[0041] To better explain and facilitate understanding of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0042] Example 1

[0043] This embodiment provides an AM-VP-VI ternary polymer emulsifier, prepared by the following method:

[0044] (1) Weigh 2.6655g acrylamide, 2.50065g N-vinylpyrrolidone and 1.41165g N-vinylimidazolium and dissolve them in 50mL of deionized water to obtain a mixed solution with a total concentration of 1.5mol / L. Then, purge with nitrogen gas for 30min to remove dissolved oxygen from the mixed solution.

[0045] (2) The mixed solution was heated to 50℃. Under a nitrogen atmosphere, 0.052 mol / L azobisisobutylamidine hydrochloride initiator (aqueous solution) was added to the mixed solution at a rate of 30 mL / h. The reaction temperature was controlled at 48-50℃, the stirring speed was 190 rpm, and the reaction was carried out for 8 h. Finally, acetone with a volume of 2 times that of the reaction system was added. After stirring, the precipitate was separated, washed once with water, washed once with ethanol, and dried in a vacuum drying oven at 50℃ for 24 h to obtain AM-VP-VI ternary polymer emulsifier; wherein the molar ratio of the three monomers AM, NVP, and NVI was 5:3:2.

[0046] Example 2

[0047] This embodiment provides an AM-VP-VI ternary polymer emulsifier, prepared by the following method:

[0048] (1) Weigh 2.8432g acrylamide, 3.3342g N-vinylpyrrolidone and 2.8233g N-vinylimidazol and dissolve them in 50mL of deionized water, and then pass nitrogen gas through the solution for 35min to remove dissolved oxygen.

[0049] (2) The mixed solution was heated to 52℃. Under a nitrogen atmosphere, 0.050 mol / L azobisisobutylamidine hydrochloride initiator (aqueous solution) was added to the mixed solution at a rate of 36.25 mL / h. The reaction temperature was controlled at 50-52℃, the stirring speed was 200 rpm, and the reaction was carried out for 8 h. Finally, acetone with a volume of 2 times that of the reaction system was added. After stirring, the precipitate was formed, separated, washed twice with ethanol, and dried in a vacuum drying oven at 50℃ for 24 h to obtain AM-VP-VI ternary polymer emulsifier; wherein the molar ratio of the three monomers AM, NVP, and NVI was 4:3:3.

[0050] Example 3

[0051] This embodiment provides an AM-VP-VI ternary polymer emulsifier, prepared by the following method:

[0052] (1) Weigh 2.1324g acrylamide, 3.3342g N-vinylpyrrolidone and 1.8822g N-vinylimidazol and dissolve them in 50mL of deionized water, and then pass nitrogen gas through the solution for 30min to remove dissolved oxygen.

[0053] (2) The mixed solution was heated to 49℃. Under a nitrogen atmosphere, 0.042 mol / L azobiscyanopentanoic acid (ACVA) (aqueous solution) was added to the mixed solution at a rate of 31.25 mL / h. The reaction temperature was controlled at 48-49℃, the stirring speed was 220 rpm, and the reaction was carried out for 8 h. Finally, acetone with a volume of 2 times that of the reaction system was added. After stirring, the precipitate was formed, separated, washed twice with ethanol, and dried in a vacuum drying oven at 50℃ for 24 h to obtain AM-VP-VI ternary polymer emulsifier; wherein the molar ratio of the three monomers AM, NVP, and NVI was 3:3:2.

[0054] Example 4

[0055] This embodiment provides an AM-VP-VI ternary polymer emulsifier, prepared according to Example 1, except that the masses of the three polymer monomers acrylamide, N-vinylpyrrolidone, and N-vinylimidazolium in Example 1 are adjusted to: 1.4216 g acrylamide, 3.3342 g N-vinylpyrrolidone, and 4.7055 g N-vinylimidazolium, respectively. The remaining steps are the same as in Example 1. In the AM-VP-VI ternary polymer emulsifier prepared in this embodiment, the molar ratio of AM, NVP, and NVI monomers is 2:3:5.

[0056] like Figure 1 The image shows the infrared spectrum of the AM-VP-VI ternary polymer prepared in Example 1. The range is 3500-3100 cm⁻¹. -1 The corresponding double peaks for primary amides, with 3340 cm⁻¹ -1 For NH asymmetric stretching, 3194cm -1 Symmetrical stretching of NH. 3000-2900cm -1 This corresponds to the CH vibration in the polymer backbone. At 1657 cm⁻¹ -1 Stretching of (-CONH2)C=O can be observed at 1665cm. -1 The stretching vibrations of the carbonyl group (C=O) in the lactam ring of N-vinylpyrrolidone are nearly overlapping, and the characteristic peaks show a generally decreasing trend with decreasing acrylamide monomer content. Meanwhile, at 1417 cm⁻¹... -1 CN stretching corresponding to acrylamide. With increasing N-vinylimidazolium monomer content, at 905 cm... -1 The characteristic intra-ring bending and ring stretching bands of imidazole showed a gradual increase in infrared peaks at 1230 cm⁻¹. -1 The imidazole ring is CN stretched, 1110 and 1084 cm. -1 The stretching vibration of the CH group in the imidazole ring can be observed.

[0057] like Figure 2The image shows the 1H NMR spectrum of the AM-VP-VI ternary polymer prepared in Example 1. The AM-VP-VI ternary polymer was dissolved in D₂O. 1 The H-NMR spectrum revealed that δ = 4.790 ppm represents the chemical shift of the solvent heavy water; the chemical shifts of hydrogen in the main chain methyl (-CH3-) and methylene (-CH2-) groups are mainly concentrated between 1.24 and 1.85 ppm; δ = 2.36 ppm represents the chemical shift of acrylamide -CH-; and δ = 2.20 ppm (2H), 1.97 ppm (2H), and 3.26 ppm (2H) represent the chemical shifts of hydrogen on the methylene group of the pyrrolidone ring. Furthermore, in the ternary polymer... 1 In the 1H-NMR spectrum, the characteristic peaks of 6.7–8.0 ppm are attributed to hydrogen atoms on the imidazole ring of N-vinylimidazolium. Combined with infrared spectroscopy, it was confirmed that a cationic ternary polymer emulsifier was successfully synthesized from acrylamide, N-vinylimidazolium, and N-vinylpyrrolidone via an aqueous solution method.

[0058] like Figure 3 The image shows the TG-DSC analysis results of the AM-VP-VI ternary polymers prepared in Examples 1-4. The thermal decomposition process of polymers synthesized with different monomer ratios can be roughly divided into three stages. In the first stage (140℃-320℃), due to the residual solvent in the polymer, the mass loss is mainly due to the evaporation of adsorbed water and the volatilization of free water, with a mass loss of approximately 10%-15%. In the second stage (320℃-450℃), the functional groups such as amides and imidazole five-membered heterocycles in the copolymer undergo thermal decomposition, causing the grafted chemical groups to separate from the polymer backbone. In the third stage (450℃-800℃), further degradation of the polymer is considered due to the decomposition of the C-C bonds in the polymer backbone and the incompletely decomposed pyrrolidone rings in the side chains.

[0059] like Figure 4 The image shows the bromophenol blue assay of the AM-VP-VI ternary polymer prepared in Example 1. 10 ml of the prepared bromophenol blue solution was placed in a test tube, and 2 ml of a 1.0% (w / w) cationic surfactant aqueous solution was added. After shaking the tube, the bromophenol blue solution changed from red to blue-purple. This is because the bromophenol blue reagent complexes with a cationic substance, causing the color to change from red to blue-purple, thus indicating that the AM-VP-VI ternary polymer is a cationic emulsifier.

[0060] Comparative Example 1

[0061] This comparative example is based on Example 1, but with increased amounts of N-vinylpyrrolidone and N-vinylimidazole, but without adding the monomer acrylamide. Specifically, 3.750 g of N-vinylpyrrolidone and 2.1175 g of N-vinylimidazole are weighed and dissolved in 50 mL of deionized water, and a cationic binary polymer is prepared according to the method of Example 1, wherein the molar ratio of N-vinylpyrrolidone to N-vinylimidazole is 3:2.

[0062] Comparative Example 2

[0063] This comparative example is based on Example 1, but with increased amounts of acrylamide and N-vinylimidazole, but without the addition of the monomer N-vinylpyrrolidone. Specifically, 3.998 g of acrylamide and 2.1175 g of N-vinylimidazole were weighed and dissolved in 50 mL of deionized water, and a cationic binary polymer was prepared according to the method of Example 1, wherein the molar ratio of acrylamide to N-vinylimidazole was 5:2.

[0064] Example 5

[0065] In this embodiment, the AM-VP-VI ternary polymer emulsifier prepared in Example 1 was used to formulate modified emulsified asphalt. The composition and preparation method of the modified emulsified asphalt are as follows:

[0066] (1) Preparation of modified matrix asphalt

[0067] The 70# base asphalt (brand name Zhonghai-90) was melted under heating conditions, and SBS and SBR were dispersed in the base asphalt. The modified base asphalt was then processed at 12,000 rpm for 5 minutes using a shear mill to obtain the modified base asphalt. SBS accounted for 4% of the original base asphalt mass, and SBR accounted for 3% of the original base asphalt mass.

[0068] (2) Preparation of emulsified asphalt

[0069] Emulsified asphalt was prepared by weighing the following raw materials: 75% modified base asphalt, 1% AM-VP-VI ternary polymer emulsifier prepared in Example 1, 0.3% hexadecyltrimethoxysilane (CTMS) modified nano-anhydrous calcium chloride powder (particle size 20-50 nm), 0.1% hydrochloric acid (pH adjuster), 0.5% HPMC (thickener), 0.1% sodium benzoate (preservative), 0.2% butylated hydroxyanisole (BHA) (antioxidant), and the balance being deionized water.

[0070] Nanoscale anhydrous calcium chloride powder modified with hexadecyltrimethoxysilane (CTMS) and AM-VP-VI ternary polymer emulsifier were dispersed in water. The pH was adjusted to 2-3 with hydrochloric acid and preheated to 70°C to obtain an aqueous dispersion. Modified base asphalt was heated to approximately 135°C to a fluid state, ensuring good flowability. Molten modified base asphalt and thickener were slowly poured into the aqueous dispersion while continuously stirring (500 rpm). The stirring speed was gradually increased to 1000 rpm during the asphalt pouring process. Then, the mixture was sheared at 85°C and 4500 rpm for 45 minutes using a high-speed shear machine until it became homogeneous and free of obvious particles. Finally, the pH was adjusted to 2-3 as needed, and preservatives and antioxidants were added and stirred evenly to obtain emulsified asphalt.

[0071] Example 6

[0072] In this embodiment, the AM-VP-VI ternary polymer emulsifier prepared in Example 1 was used to formulate modified emulsified asphalt. The composition and preparation method of the modified emulsified asphalt are as follows:

[0073] (1) Preparation of modified matrix asphalt

[0074] The 70# base asphalt (brand name Zhonghai-90) was melted under heating conditions, and SBS and SBR were dispersed in the base asphalt. The modified base asphalt was then processed at 12,000 rpm for 5 minutes using a shear mill to obtain the modified base asphalt. SBS accounted for 5% of the original base asphalt mass, and SBR accounted for 4% of the original base asphalt mass.

[0075] (2) Preparation of emulsified asphalt

[0076] Emulsified asphalt was prepared according to the method in Example 5, consisting of 74% modified base asphalt, 1.2% AM-VP-VI ternary polymer emulsifier prepared in Example 2, 0.4% hexadecyltrimethoxysilane (CTMS) modified nano-anhydrous calcium chloride powder (particle size 20-50nm), 0.15% hydrochloric acid (pH adjuster), 0.1% sodium benzoate (preservative), 0.1% rust inhibitor, 0.15% butylated hydroxyanisole (BHA) (antioxidant), and the balance being deionized water.

[0077] Referring to the Technical Specification for Preventive Maintenance of Highway Asphalt Pavement (JTGT5142-01-2021), the properties of the above-mentioned modified emulsified asphalt were tested, and the test results are recorded in the table below:

[0078]

[0079] The modified emulsified asphalt prepared in Examples 5-6 has a solid content of 74-75%, and the storage stability (%) of this high-solid-content emulsified asphalt still fully meets the technical specifications. Currently, the highest solid content of existing emulsified asphalt is only 63%, and very rarely reaches 70%. The best 5-day storage stability of existing emulsified asphalt is ≤5%, while the modified emulsified asphalt prepared in Examples 5-6 achieves a 5-day storage stability of <3%. The average particle size of asphalt particles in existing emulsified asphalt is <5μm, while the average particle size of asphalt particles in the modified emulsified asphalt prepared in Examples 5-6 is <3μm. Furthermore, the softening point of the modified emulsified asphalt prepared in Examples 5-6 is ≥82℃, while the softening point of existing emulsified asphalt is generally ≥75℃. Therefore, the modified emulsified asphalt prepared in this invention has better high-temperature resistance and can adapt to high-temperature climatic environments.

[0080] Further test results showed that the modified emulsified asphalt prepared in Examples 5-6 had a dynamic viscosity of ≥23000 Pa·s at 60°C, while the existing emulsified asphalt had a dynamic viscosity of ≥20000 Pa·s at 60°C. Higher dynamic viscosity indicates stronger adhesion between the emulsified asphalt and aggregates, effectively improving the strength and durability of the final pavement and making it more suitable for use as an asphalt concrete surface layer. Furthermore, the high viscosity provides better storage stability, making it less prone to segregation or demulsification. Additionally, adhesion tests were conducted between the modified emulsified asphalt prepared in this example and coarse aggregate. The results showed that the adhesion performance of the emulsified asphalt to coarse aggregate was comparable to that of ordinary hot-mix asphalt to coarse aggregate.

[0081] When the AM-VP-VI ternary polymer emulsifier in Example 5 was replaced in equal amounts with the cationic binary polymer emulsifiers of Comparative Examples 1-2, the resulting modified emulsified asphalt, compared to the modified emulsified asphalt in Example 5, exhibited weaker adhesion to coarse aggregates, poorer mixing uniformity with both coarse and fine aggregates, and decreased storage stability, with a 5-day storage stability (%) of approximately 4.6-4.7%. This indicates that although Comparative Examples 1-2 also provide cationic macromolecular polymer emulsifiers, the binary polymer emulsifiers prepared in Comparative Examples 1-2 do not significantly improve the stability of high-solids-content modified emulsified asphalt as in the examples of this invention, and the adhesion of the modified emulsified asphalt also shows a decreasing trend. These trends are unfavorable for using emulsified asphalt in cold-mix cold-paved asphalt concrete surface layers.

[0082] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An emulsified asphalt, characterized in that, By weight percentage, it comprises: 70-75% modified base asphalt, 0.5-1.2% AM-VP-VI ternary polymer emulsifier, 0.1-0.5% solid nanopowder stabilizer, 0.1-1% additives, and the balance being water; the additives include a pH adjuster, which adjusts the pH of the emulsified asphalt to 2-3; the solid nanopowder stabilizer is hexadecyltrimethoxysilane-modified nano-sized anhydrous calcium chloride powder; the modified base asphalt is SBS and SBR co-modified base asphalt; The AM-VP-VI ternary polymer emulsifier is a ternary polymer formed by the polymerization of acrylamide AM, N-vinylpyrrolidone NVP, and N-vinylimidazolium NVI, with a molecular weight of 3000-10000; wherein the molar ratio of the three monomers AM, NVP, and NVI is 5-2:3:2-5.

2. The emulsified asphalt according to claim 1, characterized in that, Includes the following steps: S1. Disperse acrylamide monomer AM, N-vinylpyrrolidone monomer NVP and N-vinylimidazolium monomer NVI in water to obtain a mixed solution; S2. Treat the mixed solution to remove or reduce dissolved oxygen in the mixed solution; S3. Under inert gas protection, add a water-soluble initiator to the mixed solution, control the reaction temperature at ≤53℃ to carry out the polymerization reaction, and keep stirring continuously during the polymerization process; S4. After the reaction is complete, acetone is added to the reaction system to precipitate the precipitate. The precipitate is washed and dried in a vacuum drying oven to obtain AM-VP-VI ternary polymer emulsifier.

3. In the emulsified asphalt according to claim 2, in S1, the total molar concentration of the three monomers in the mixed solution is 1.2-1.8 mol / L.

4. In the emulsified asphalt according to claim 2, in step S2, nitrogen gas is introduced into the mixed solution to remove or reduce dissolved oxygen in the mixed solution; specifically, nitrogen is continuously introduced into the mixed solution for 30-50 minutes.

5. In the emulsified asphalt according to claim 2, in S3, the water-soluble initiator is azobisisobutylamidine hydrochloride; the azobisisobutylamidine hydrochloride is added in the form of a low-concentration solution, flowing at a uniform rate during the polymerization reaction, and the reaction temperature is controlled at 50°C.

6. In the emulsified asphalt according to claim 5, in S3, the concentration of azobisisobutylamidine hydrochloride solution is 0.05-0.06 mol / L, and the total amount of azobisisobutylamidine hydrochloride is 1 / 6-1 / 8 of the total molar ratio of the reacting monomers; in S3, the stirring speed during polymerization is 180 rpm-220 rpm; and the reaction time is 7.5-8.5 h.

7. In the emulsified asphalt according to claim 2, in step S4, after the reaction is completed, 1.5-3 times the volume of acetone is added to the reaction system, stirred, allowed to stand, the precipitate is separated, and the precipitate is washed with ethanol 2-3 times; then dried in a vacuum drying oven at 50°C for 24 hours to obtain the AM-VP-VI ternary polymer emulsifier.

8. A cold-mix, cold-lay emulsified asphalt concrete, characterized in that, By weight percentage, it comprises: 3-6% emulsified asphalt as described in any one of claims 1-7, 90-94% aggregate, and 0-3% filler.

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