Waterborne polyurethane dispersion modified emulsified asphalt micro-surfacing and method of making

Abstract

The application discloses a kind of water-based polyurethane dispersion modified emulsified asphalt micro-surfacing and its preparation method, preparation steps include: fine aggregate after oil-stone separation of recycled asphalt is screened and impurity is removed, preheating is dried to moisture content≤3%, silane coupling agent surface activation, and recycled fine aggregate is obtained;Emulsified asphalt is heated, and bubble is removed by keeping warm, polyurethane dispersion is added, and pre-dispersion is carried out by primary shear, secondary shear is refined, so that the dispersity of polyurethane dispersion is≥98.5%, and then by gradient cooling, calcium chloride, polyvinyl alcohol and sodium carboxymethyl cellulose are added, stirring, defoaming, and modified binder is obtained;Recycled fine aggregate, modified binder and filler are mixed and mixed, water is added to adjust consistency, paving, curing, and water-based polyurethane dispersion modified emulsified asphalt micro-surfacing is obtained.The micro-surfacing of the application has excellent wear resistance, crack resistance, corrosion resistance, and zero VOC emission, with the advantages of resource recycling and performance, suitable for multiple scene applications.

Description

Technical Field

[0001] This invention belongs to the field of road engineering materials technology, specifically relating to a waterborne polyurethane dispersion-modified emulsified asphalt micro-surfacing method and its preparation method. Background Technology

[0002] Microsurfacing, as a thin-layer asphalt pavement maintenance technology, is widely used in road maintenance due to its advantages such as convenient construction and significant maintenance effects. However, with the continuous increase in traffic load and increasingly complex environmental conditions, the performance of traditional microsurfacing materials is no longer sufficient to meet the needs of modern road use, especially in terms of durability, low-temperature performance, and resistance to fuel corrosion. At the same time, with the surge in asphalt pavement milling waste, how to efficiently utilize this waste has become an urgent problem for the industry. Currently, microsurfacing technology mainly uses modified emulsified asphalt as a binder, but traditional modifiers such as SBS have disadvantages such as high construction energy consumption and limited modification effects. CN104176985B discloses a waterborne polyurethane emulsified asphalt concrete, in which the waterborne polyurethane emulsion is mixed with emulsified asphalt and then used in asphalt concrete, exhibiting certain mechanical properties and stability. However, this technology cannot meet the special requirements of microsurfacing and does not solve the problem of the application of recycled materials. In the application of recycled materials, CN118184223A proposes a cold-recycled asphalt mixture that achieves the recycling of old asphalt pavement materials by adding modified emulsified asphalt and composite modifiers. CN107777923B proposes a durable seal coat for road or bridge pavement, using grafted ultra-high molecular weight polyethylene-waterborne polyurethane combined with emulsified asphalt to improve the material's impact resistance and adhesion. CN111849179A introduces a micro-surfacing emulsified asphalt suitable for low-temperature nighttime construction, which improves low-temperature construction performance by adding warm mix agents and modified latex. However, these technologies still need improvement in terms of micro-surfacing abrasion resistance, low-temperature crack resistance, and fuel corrosion resistance.

[0003] The existing technologies generally have the following defects: (1) Performance limitations: traditional micro-surfacing has poor wear resistance (1h wet wheel wear loss ≥680g / m²), weak low-temperature crack resistance (easily cracks at -10℃), and insufficient resistance to fuel corrosion (diesel immersion mass loss ≥12.7%), making it difficult to meet the needs of heavy-duty traffic. (2) Resource utilization issues: fine aggregates after traditional mechanical asphalt-aggregate separation are prone to defects such as poor bonding and rapid performance degradation when applied to micro-surfacing due to surface aging, strong adsorption, and insufficient activity. The resource utilization rate is less than 30%, resulting in a large amount of asphalt pavement milling waste not being effectively utilized. (3) Existing waterborne polyurethane modification technologies are mostly aimed at concrete or ordinary asphalt mixtures, lacking modification schemes for the special needs of micro-surfacing, resulting in unsatisfactory application effects of recycled materials. Therefore, it is of great significance to break through the bottleneck of recycled asphalt-aggregate separation application and simultaneously improve the wear resistance, crack resistance, and corrosion resistance of micro-surfacing. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to address the shortcomings of the prior art by providing a waterborne polyurethane dispersion-modified emulsified asphalt microsurfacing with excellent wear resistance, crack resistance, corrosion resistance and environmental friendliness, as well as its preparation method.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0006] A method for preparing an aqueous polyurethane dispersion-modified emulsified asphalt microsurfacing agent includes the following steps:

[0007] (1) The fine aggregate after separation of recycled asphalt and asphalt is screened to remove impurities, preheated and dried to a moisture content of ≤3%, and surface activated with silane coupling agent to obtain recycled fine aggregate;

[0008] (2) Heating the emulsified asphalt, heat preservation and defoaming, adding polyurethane dispersion, performing first-level shear pre-dispersion and second-level shear refinement to make the dispersion degree of polyurethane dispersion ≥98.5%, then avoiding demulsification of polyurethane dispersion by gradient cooling, adding calcium chloride, polyvinyl alcohol and sodium carboxymethyl cellulose, stirring, defoaming, to obtain modified binder;

[0009] (3) Mix the recycled fine aggregate, modified binder and filler, add water to adjust the consistency, spread and cure to obtain water-based polyurethane dispersion modified emulsified asphalt micro-surfacing.

[0010] In the above-mentioned method for preparing waterborne polyurethane dispersion modified emulsified asphalt micro-surfacing, preferably, in step (1), the surface activation of the silane coupling agent is achieved by spraying a silane coupling agent aqueous solution with a mass percentage concentration of 0.4% to 0.6% onto the surface of the dried fine aggregate and stirring to activate it. The amount of the silane coupling agent aqueous solution is 0.1% to 0.4% of the mass of the fine aggregate after separation of recycled asphalt and asphalt.

[0011] In the above-mentioned method for preparing micro-surfacing modified emulsified asphalt using waterborne polyurethane dispersion, preferably, in step (2), the amount of polyurethane dispersion is 5% to 25% of the mass of emulsified asphalt; the ratio of the solid content of the polyurethane dispersion to the solid content of the emulsified asphalt is 12% to 18%; the calcium chloride accounts for 0.08% to 0.25% of the mass of the modified binder; the polyvinyl alcohol accounts for 0.15% to 0.6% of the mass of the modified binder; and the sodium carboxymethyl cellulose accounts for 0.03% to 0.1% of the mass of the modified binder.

[0012] In the above-mentioned method for preparing waterborne polyurethane dispersion modified emulsified asphalt microsurfacing, preferably, in step (3), the mass ratio of the recycled fine aggregate, modified binder and filler is 210-250:112-124:10-15; the consistency is 2.2cm-3.2cm as tested by the funnel method.

[0013] In the above-mentioned method for preparing waterborne polyurethane dispersion modified emulsified asphalt micro-surfacing, preferably, in step (1), the sieving and impurity removal involves passing the fine aggregate after separation of oilstone and stone through a double-layer sieve to remove dust and oversized particles. The double-layer sieve is a 0.15mm and 5mm double-layer sieve, or a 0.3mm and 5mm double-layer sieve. The preheating and drying temperature is 50℃~60℃, and the preheating and drying time is 10min~15min. The stirring and activation speed is 280rpm~320rpm, and the stirring and activation time is 4min~6min.

[0014] In the above-mentioned method for preparing waterborne polyurethane dispersion modified emulsified asphalt microsurfacing, preferably, in step (2), the amount of polyurethane dispersion is 12% to 24% of the mass of emulsified asphalt, the mass ratio of calcium chloride, polyvinyl alcohol, and sodium carboxymethyl cellulose is 1:2.9 to 3.1:0.45 to 0.55, the storage temperature of the modified binder is 40℃ to 50℃, the storage stability is ≥15 months, and the segregation rate is ≤1.5%.

[0015] In the above-mentioned method for preparing waterborne polyurethane dispersion modified emulsified asphalt microsurfacing, preferably, in step (3), the filler is PO42.5 cement and / or has a specific surface area ≥320m². 2 / kg of mineral powder.

[0016] In the above-mentioned method for preparing waterborne polyurethane dispersion modified emulsified asphalt micro-surfacing, preferably, in step (1), the fine aggregate particle size after separation of the recycled asphalt and asphalt is 0-5 mm, the sand equivalent is ≥60%, and the Los Angeles abrasion is ≤30%; the silane coupling agent is γ-glycidoxypropyltrimethoxysilane or γ-methacryloyloxypropyltrimethoxysilane.

[0017] In the above-mentioned method for preparing waterborne polyurethane dispersion modified emulsified asphalt microsurfacing, preferably, in step (2), the emulsified asphalt is a cationic matrix asphalt, with 70# road petroleum asphalt as the matrix, a solid content of 52% to 65%, a softening point of 70℃, an evaporation residue softening point ≥68℃, a ductility of ≥35cm at 5℃, and a slow demulsification rate; the polyurethane dispersion is a cationic polyester type BY-1040 or a nonionic polyether type YC-F205, wherein the cationic polyester type BY-1040 has a solid content of 43% to 48%, a particle size of 70nm to 90nm, and an elongation ≥500%; and the nonionic polyether type YC-F205 has a solid content of 43% to 45%, a particle size of 50nm to 80nm, and an elongation ≥550%.

[0018] In the above-mentioned method for preparing waterborne polyurethane dispersion modified emulsified asphalt microsurfacing, preferably, in step (2), the rotation speed of the first-stage shear is 3500 rpm to 4500 rpm and the time is 4 min to 6 min, and the rotation speed of the second-stage shear is 5500 rpm to 6500 rpm and the time is 6 min to 9 min.

[0019] In the above-mentioned method for preparing waterborne polyurethane dispersion modified emulsified asphalt microsurfacing, preferably, in step (2), the heating temperature is 62℃~70℃, the holding time is 10min~15min; the primary shear temperature is 60℃~67℃, the secondary shear temperature is 55℃~62℃; the gradient cooling rate is 1.0℃ / min~4.0℃ / min; the target temperature of the gradient cooling is 48℃~55℃; the stirring speed is 600rpm~900rpm, and the time is 4min~6min; the defoaming is static defoaming, and the static time is 2min~3min.

[0020] In the above-mentioned method for preparing waterborne polyurethane dispersion modified emulsified asphalt microsurfacing, preferably, in step (3), the mixing speed is 600 rpm to 1200 rpm and the mixing time is 2 min to 3 min.

[0021] In the preferred embodiment of the above-mentioned method for preparing waterborne polyurethane dispersion modified emulsified asphalt microsurfacing, the paving thickness is 4mm to 10mm and the paving speed is 1.8m / min to 3.5m / min; wherein, the paving thickness for highways is 5mm to 8mm, and the paving thickness for airport runways is 8mm to 10mm and is paved in two stages, each stage being 4mm to 5mm.

[0022] In the above-mentioned method for preparing waterborne polyurethane dispersion modified emulsified asphalt microsurfacing, preferably, the curing is performed at room temperature for 35 min to 70 min, and the opening time to traffic is ≤1.2 hours when the ambient temperature is ≥15℃; the curing time is extended to 80 min to 100 min in cold plateau areas with an ambient temperature of -15℃ to 5℃ and an altitude of ≥3000m.

[0023] As a general technical concept, the present invention also provides a waterborne polyurethane dispersion modified emulsified asphalt microsurfacing prepared by the preparation method described above.

[0024] Preferably, in the above-mentioned waterborne polyurethane dispersion-modified emulsified asphalt microsurfacing, the 1-hour wet wheel abrasion loss of the waterborne polyurethane dispersion-modified emulsified asphalt microsurfacing is ≤440g / m. 2 The splitting tensile strength at -10℃ is ≥1.6MPa, the mass loss after immersion in diesel for 24 hours is ≤4.8%, and the interfacial pull-out strength is ≥1.7MPa.

[0025] Preferably, when the above-mentioned waterborne polyurethane dispersion modified emulsified asphalt micro-surfacing is applied to an extreme low temperature environment of -20℃ to -30℃, nonionic polyether type YC-F205 is used. The waterborne polyurethane dispersion modified emulsified asphalt micro-surfacing has a splitting tensile strength ≥1.8MPa at -20℃ and a strength loss ≤8% after 20 freeze-thaw cycles.

[0026] Compared with the prior art, the advantages of the present invention are as follows:

[0027] (1) The present invention discloses a method for preparing waterborne polyurethane dispersion modified emulsified asphalt micro-surfacing. This method involves sieving, preheating, and activating the recycled asphalt aggregate with a silane coupling agent to obtain recycled fine aggregate; multi-stage shear blending of PUD with emulsified asphalt, combined with a "calcium chloride + polyvinyl alcohol + CMC" composite stabilizer to prepare a modified binder; and mixing and paving the recycled fine aggregate, modified binder, and filler. When PUD is mixed with emulsified asphalt, it is uniformly dispersed through two-stage shear, resulting in a polyurethane dispersion degree ≥98.5%. This forms an "interface-strengthened-interpenetrating network" composite structure with the pretreated recycled fine aggregate, ensuring that the wet wheel wear loss after 1 hour of micro-surfacing is ≤440 g / m². 2 The splitting tensile strength at -10℃ is ≥1.6MPa, and the mass loss after diesel immersion is ≤4.8%. Overall performance is improved by 32%–65% compared to traditional micro-surfacing of natural aggregates, and by 50%–225% compared to micro-surfacing of mechanically recycled aggregates. This invention is compatible with existing equipment, has zero VOC emissions, and reduces total lifecycle costs by 45%.

[0028] (2) In the preparation method of the present invention, PUD does not participate in the emulsification process, but is only used as an independent modifier and physically blended and dispersed in emulsified asphalt (dosage 5% to 25%), avoiding chemical consumption of PUD in the emulsification stage and maximizing its elastic network construction ability. The fine aggregate after separation of recycled asphalt and asphalt is surface-treated by a silane coupling agent. The amino group of the silane coupling agent reacts with the hydroxyl group on the surface of the fine aggregate to form a chemical bond, and the other end is compatible with the ester group of PUD, constructing a molecular-level interface transition zone to improve the adhesion between the fine aggregate and the asphalt. The composite stabilizer composed of inorganic salt calcium chloride, water-soluble high molecular weight polyvinyl alcohol and sodium carboxymethyl cellulose, through the synergistic effect of "inorganic ion regulation + high molecular weight film formation + cellulose ether dispersion", significantly improves the colloidal stability of PUD-modified emulsified asphalt, the interfacial adhesion with recycled aggregate and the construction performance. It is an indispensable key auxiliary material of the present invention, providing an important guarantee for the efficient utilization of recycled aggregate and micro-surfacing in heavy-duty scenarios.

[0029] (3) The preparation method of the present invention establishes the compatibility relationship of the ternary material “PUD-emulsified asphalt-recycled fine aggregate”. By controlling the ratio of PUD solid content to emulsified asphalt solid content (preferably 12% to 18%), the coating rate of recycled aggregate is ensured to be ≥95%, which effectively solves the problem of uneven coating of traditional recycled materials.

[0030] (4) The preparation method of the present invention uses γ-glycidoxypropyltrimethoxysilane (KH-560) or γ-methacryloxypropyltrimethoxysilane (KH-570) to activate the fine aggregate after separation of recycled asphalt and asphalt, both of which can achieve good technical results. Among them, the epoxy group of KH-560 can react with the hydroxyl group on the surface of fine aggregate and form a chemical bond with the amino group of PUD. At an addition amount of 0.1% to 0.4%, the interfacial pull-out strength can reach 1.7 MPa or above. KH-570 is more suitable for use in combination with modifiers containing double bonds. At a treatment temperature of 50°C, the interfacial porosity can be controlled below 1.2%.

[0031] (5) The preparation method of the present invention is compatible with existing slurry seal equipment, requires no additional modification, and reduces construction costs and resource consumption; it adopts "all-water system + recycled aggregate" to achieve zero VOC emissions and resource utilization of milling waste (utilization rate ≥90%), which is in line with the "dual carbon" and circular economy policies and is suitable for multiple application scenarios.

[0032] (6) The microsurfacing of emulsified asphalt modified by the waterborne polyurethane dispersion of the present invention has a wet wheel wear loss of ≤440g / m² in 1 hour. 2It has a splitting strength of ≥1.6MPa at -10℃, ≥1.8MPa in extreme low temperature scenarios (-20℃), and a mass loss of ≤4.8% after diesel immersion. It is suitable for various scenarios such as highways, airport runways (deformation rate ≤2.8% under 80-ton load, dynamic stability ≥8000 times / mm at 60℃, and service life ≥9 years) and high-altitude and cold regions (construction energy consumption is reduced by 85% compared to SBS modified micro-surface treatment), and has the advantages of resource recycling and performance. Detailed Implementation

[0033] The present invention will be further described below in conjunction with the specification and specific preferred embodiments, but this does not limit the scope of protection of the present invention.

[0034] Example 1

[0035] The present invention discloses a method for preparing waterborne polyurethane dispersion-modified emulsified asphalt microsurfacing, with highways at room temperature as the application scenario, comprising the following steps:

[0036] (1) The fine aggregate after separation of recycled asphalt and asphalt is screened through a double-layer sieve of 0.15mm and 5mm to remove impurities, dust and oversized particles, and put into a drying drum to preheat and dry at 55℃ for 12min until the moisture content is ≤2.5%. A 0.5% silane coupling agent KH-550 aqueous solution is sprayed on the surface of the dried fine aggregate and stirred at 300rpm for 5min to activate it, thus obtaining recycled fine aggregate;

[0037] (2) Add emulsified asphalt to the feed tank of the colloid mill, heat it to 65°C, keep it at the temperature for 12 minutes to remove bubbles, add PUD, perform primary shear pre-dispersion for 5 minutes at 4000 rpm and 65°C, and then perform secondary shear refinement for 7 minutes at 6000 rpm and 60°C to make the PUD dispersion ≥98.5%. Gradual cooling is performed at a rate of 3.0°C / min to 52°C. Gradual cooling can avoid PUD demulsification. Add calcium chloride, polyvinyl alcohol and CMC, stir at 750 rpm for 5 minutes, let stand for 2 minutes to remove bubbles, and obtain modified binder (storage temperature 40-50°C).

[0038] (3) Add recycled fine aggregate, modified binder and filler into the mixing bin of slurry sealer in proportion, mix and stir, add water to adjust the consistency to 2.8cm (funnel test), mix at 900rpm for 2.5min (to ensure uniform coating of recycled aggregate), spread and cure to obtain PUD modified emulsified asphalt micro-surfacing.

[0039] The paving process utilizes existing slurry seal pavers with a paving thickness of 6mm, a paving speed of 1.8m / min to 3.5m / min, an ambient temperature of 28℃, and a curing period of 45 minutes before traffic can resume.

[0040] In this embodiment, the raw material formula (based on 100 kg of emulsified asphalt) is as follows:

[0041] Emulsified asphalt: cationic type (70# base asphalt, solid content 62%, softening point 70℃) 100kg;

[0042] PUD: Polyurethane dispersion, specifically cationic polyester type BY-1040 (solid content 45%, particle size 80nm, elongation 520%) 16kg;

[0043] Recycled asphalt-aggregate separation fine aggregate: 0-5mm (sand equivalent 62%, Los Angeles abrasion 28%) 220kg;

[0044] 0.44 kg of 0.5% silane coupling agent KH-550 aqueous solution (the dosage is 0.2% of the mass of fine aggregate after separation of recycled asphalt and asphalt) is obtained by mixing pure silane coupling agent KH-550 with deionized water at a mass ratio of 0.5:99.5 and stirring evenly.

[0045] Filler: 11 kg of PO42.5 cement and mineral powder mixed at a mass ratio of 1:1;

[0046] Stabilizers: 0.18 kg calcium chloride, 0.54 kg polyvinyl alcohol, 0.09 kg CMC.

[0047] Performance tests were conducted according to the relevant specifications in Table 1, and the results are as follows:

[0048] 1-hour wet wheel wear loss: 412 g / m 2 ;

[0049] Low-temperature splitting strength (-10℃): 1.72 MPa;

[0050] Interfacial pull-out strength: 1.8 MPa;

[0051] Mass loss after 24 hours of diesel immersion: 4.5%;

[0052] Separation rate after 6 months of storage: 1.3%;

[0053] Recycled aggregate coating rate: 96%.

[0054] The performance test items involved in the above embodiments and comparative examples of the present invention are carried out in accordance with the specifications in Table 1 below.

[0055] Table 1 - Performance Testing Reference Specifications for Micro-surfaces Prepared in Embodiments and Comparative Examples of the Invention

[0056]

[0057] Example 2

[0058] The present invention discloses a method for preparing waterborne polyurethane dispersion-modified emulsified asphalt microsurfacing, with the application scenario being an extreme low temperature environment of -20℃. The steps are basically the same as those in Example 1, with the only difference being:

[0059] In step (1), after the fine aggregate is screened to remove impurities, it is dried at 60℃ for 15 minutes until the moisture content is ≤1.8% to ensure that the surface is dry;

[0060] In step (2), the primary shear temperature is 62℃, the secondary shear temperature is 58℃, and the time is 8min;

[0061] In step (3), the ambient temperature during paving is -15℃, the recycled mixture does not require additional preheating, and the curing time is 70 minutes.

[0062] In this embodiment, the raw material formula (based on 100 kg of emulsified asphalt) is as follows:

[0063] Emulsified asphalt: cationic type (70# base asphalt, solid content 60%, softening point 68℃) 100kg;

[0064] PUD: Nonionic polyether type YC-F205 (solid content 43%, particle size 70nm, elongation 560%) 14kg;

[0065] Recycled asphalt-aggregate separation fine aggregate: 0-5mm (sand equivalent 60%, Los Angeles abrasion 29%) 230kg;

[0066] 0.46 kg of 0.5% silane coupling agent KH-550 aqueous solution (the dosage is 0.2% of the mass of fine aggregate after separation of recycled asphalt and asphalt stone).

[0067] Filler: 13.8 kg of PO42.5 cement;

[0068] Stabilizers: 0.20 kg calcium chloride, 0.60 kg polyvinyl alcohol, 0.10 kg CMC.

[0069] Performance tests were conducted according to the relevant specifications in Table 1, and the results are as follows:

[0070] Low-temperature splitting strength (-20℃): 1.9 MPa;

[0071] Dynamic stability at 60℃: 7800 cycles / mm;

[0072] Freeze-thaw cycle resistance (-20℃~25℃, 20 cycles): Strength loss ≤7%;

[0073] Interfacial pull-out strength: 1.7 MPa.

[0074] Example 3

[0075] The present invention discloses a method for preparing waterborne polyurethane dispersion-modified emulsified asphalt microsurfacing, with the application scenario of heavy-load airport runway. The steps are basically the same as those in Example 1, with the only difference being:

[0076] In step (1), the fine aggregate after separation of recycled asphalt and asphalt is screened by a 0.3-5mm double-layer sieve, dried at 58℃ for 13min, and activated by two sprays with a 0.5% aqueous solution of silane coupling agent KH-550, with each spray amount being 0.15% of the mass of the fine aggregate after separation of recycled asphalt and asphalt.

[0077] In step (3), the paving is done in two stages, each with a thickness of 5 mm and an interval of 15 minutes. After each paving, a light roller (3 tons) is used to compact the surface three times to ensure full compaction.

[0078] In this embodiment, the raw material formula (based on 100 kg of emulsified asphalt) is as follows:

[0079] Emulsified asphalt: cationic type (70# base asphalt, solid content 65%, softening point 72℃) 100kg;

[0080] PUD: Cationic polyester type BY-1040 (solid content 48%, particle size 90nm, elongation 530%) 20kg;

[0081] Recycled asphalt-aggregate separation fine aggregate: 0-5mm (sand equivalent 65%, Los Angeles abrasion 25%) 240kg;

[0082] 0.72 kg of 0.5% silane coupling agent KH-550 aqueous solution (the dosage is 0.3% of the mass of fine aggregate after separation of recycled asphalt and asphalt stone);

[0083] Filler: 14.4 kg of PO42.5 cement;

[0084] Stabilizers: 0.25 kg calcium chloride, 0.75 kg polyvinyl alcohol, 0.12 kg CMC.

[0085] Performance tests were conducted according to the relevant specifications in Table 1, and the results are as follows:

[0086] Load test: Simulating an 80-ton aircraft takeoff and landing load, the deformation rate under the 80-ton load is ≤2.8%;

[0087] Mass loss after 24 hours of diesel immersion: 3.9%;

[0088] Estimated service life: 9-11 years;

[0089] Recycling rate of resources: 92%.

[0090] Example 4

[0091] The present invention discloses a method for preparing waterborne polyurethane dispersion-modified emulsified asphalt microsurfacing, with the application scenario being a high-altitude, cold region at an altitude of 3500m and an air temperature of -10℃ to 10℃. The steps are basically the same as in Example 1, with the only difference being:

[0092] In step (1), after the fine aggregate is screened to remove impurities, it is dried at 60℃ for 15 minutes until the moisture content is ≤2% to avoid freezing at low temperature;

[0093] In step (2), when adding stabilizer for stabilization treatment, the temperature of the modified binder is controlled at 50°C to avoid excessively high viscosity;

[0094] In step (3), the ambient temperature is 5℃ and the curing time is 90min.

[0095] In this embodiment, the raw material formula (based on 100 kg of emulsified asphalt) is as follows:

[0096] Emulsified asphalt: cationic type (70# base asphalt, solid content 63%, softening point 71℃) 100kg;

[0097] PUD: Nonionic polyether type YC-F205 (solid content 45%, particle size 80nm, elongation 555%) 22kg;

[0098] Recycled asphalt-aggregate separation fine aggregate: 0-5mm (sand equivalent 61%, Los Angeles abrasion 27%) 235kg; 0.47kg of 0.5% silane coupling agent KH-550 aqueous solution (dosage is 0.2% of the mass of the fine aggregate after recycling asphalt-aggregate separation);

[0099] Filler: 11.75 kg of PO42.5 cement;

[0100] Stabilizers: 0.22 kg calcium chloride, 0.66 kg polyvinyl alcohol, 0.11 kg CMC.

[0101] Performance tests were conducted according to the relevant specifications in Table 1, and the results are as follows:

[0102] 1-hour wet wheel wear loss: 430g / m 2 ;

[0103] Low-temperature splitting strength (-15℃): 1.8 MPa;

[0104] Traffic opening hours: 1.5 hours.

[0105] Comparative Example 1

[0106] This comparative example aims to verify the core role of the PUD independent modification module. The design concept is to replace the PUD modifier with the traditional SBR latex modifier, while the remaining modules (recycled aggregate pretreatment, gradient shear process, and ternary composite stabilizer system) are consistent with those in Example 1.

[0107] Specifically, the modifier used was SBR latex instead of cationic polyester PUD (BY-1040) in Example 1. The types, parameters and dosages of emulsified asphalt, recycled aggregate, KH-550 pretreatment reagent, filler and composite stabilizer remained unchanged. The recycled aggregate still underwent a three-stage pretreatment process of "sieving-55℃ preheating-300rpm stirring activation". The modified binder was prepared using the same two-stage shear parameters. The construction process was completely consistent with Example 1 (6mm paving, 28℃ curing for 45min).

[0108] Among them, SBR latex has a solid content of 50%, and the amount used is 14.4 kg. The effective ingredient mass is 14.4 kg × 50% = 7.2 kg (which is consistent with the effective ingredient mass of PUD in Example 1).

[0109] Performance tests were conducted according to the relevant specifications in Table 1. The results show that the wet wheel wear loss of this comparative example reached 720 g / m in 1 hour. 2 Compared to 412 g / m³ in Example 1 2 The yield increased by 74.7%; the splitting tensile strength at -10℃ was only 1.1 MPa, a decrease of 36.0% compared to Example 1; the mass loss after 24 hours of diesel immersion was 10.2%, an increase of 126.7% compared to Example 1. These results indicate that traditional SBR latex cannot replace the elastic network construction capability of PUD. The PUD independent modification module is the core for improving the wear resistance, crack resistance, and corrosion resistance of micro-surfaced materials, and its directional optimization effect on asphalt modification is irreplaceable.

[0110] Comparative Example 2

[0111] This comparative example is used to verify the necessity of the recycled aggregate pretreatment module. It retains the PUD modifier, gradient preparation process and composite stabilizer system, but omits the preheating and silane activation treatment of the recycled aggregate.

[0112] Specifically, the recycled asphalt-aggregate was only screened and impurities removed using 0.15mm and 5mm double-layer sieves, without preheating and drying, and had a natural moisture content of about 8%. It was also not activated by spraying silane coupling agent KH-550 aqueous solution. The PUD used was the same BY-1040 (16kg) as in Example 1. The modified binder was still prepared using the "two-stage shear + ternary stabilizer" process, and the construction parameters were the same as in Example 1.

[0113] Performance tests were conducted according to the relevant specifications in Table 1. The results showed that the interfacial pull-out strength of this comparative example was only 0.7 MPa, a decrease of 61.11% compared to 1.8 MPa in Example 1; the recycled aggregate coating rate was only 65%, a decrease of 32.29% compared to 96% in Example 1; and the segregation rate after 6 months of storage reached 4.8%, an increase of 269.2% compared to 1.3% in Example 1. These results confirm that the problems of surface aging and insufficient activity of recycled aggregates can only be solved through pretreatment of "preheating and dehydration + silane coupling agent molecular bridging". The absence of this module will directly destroy the interfacial bonding between the aggregate and the binder, resulting in a significant decrease in system stability and structural strength.

[0114] Comparative Example 3

[0115] This comparative example focuses on verifying the role of the gradient preparation process module. The design retains the PUD modifier and recycled aggregate pretreatment module, but replaces the "two-stage gradient shearing process" of this invention with the traditional single-stage shearing, and replaces the "ternary composite stabilizer" with a single polyvinyl alcohol stabilizer. The remaining parameters are consistent with those in Example 1.

[0116] Specifically, the modified binder was prepared using a single-stage shearing process with a rotation speed of 6000 rpm and a shearing time of 12 min, without performing a gradient operation of "first-stage pre-dispersion-second-stage refinement"; only 0.5% polyvinyl alcohol was selected as the stabilizer; other conditions were the same as in Example 1.

[0117] Performance tests were conducted according to the relevant specifications in Table 1. The results showed that the PUD dispersion of this comparative example was only 82%, a decrease of 16.75% compared to 98.5% in Example 1; the segregation rate after 6 months of storage reached 7.5%, an increase of 476.9% compared to Example 1; and the wet wheel abrasion loss after 1 hour was 580 g / m. 2 The yield increased by 40.8% compared to Example 1. This result indicates that single-stage shearing cannot achieve uniform dispersion of PUD, and a single stabilizer lacks the synergistic effect of "ion regulation-steric hindrance-interface enhancement". The gradient preparation process module is the key to ensuring the stability and performance uniformity of the modified system.

[0118] Comparative Example 4

[0119] This comparative example serves as a benchmark for traditional regenerative microsurfacing technologies. The innovative modules of this invention were completely removed during the design phase, and conventional industry technical solutions were adopted.

[0120] Specifically, SBR latex was used as the modifier instead of PUD; the recycled asphalt oilstone-separated fine aggregate was only screened to remove impurities, without preheating or activation with silane coupling agents; the modified binder adopted a single-stage shearing process (6000 rpm, shearing time 12 min), and only calcium chloride was added as the stabilizer (calcium chloride mass ratio of emulsified asphalt was 0.3%); a single PO42.5 cement was used as the filler, with the same dosage as in Example 1; the mixing time during construction was 3 min, the paving thickness was 6 mm, and the curing time was 60 min.

[0121] Performance tests were conducted according to the relevant specifications in Table 1. The results showed that the core performance of this comparative example was comprehensively degraded: the wet wheel wear loss reached 850 g / m in 1 hour. 2 Compared to Example 1, the yield increased by 106.3%; the low-temperature splitting tensile strength at -10℃ was only 0.8 MPa, a decrease of 53.49% compared to Example 1; the interfacial pull-out strength was 0.6 MPa, a decrease of 66.67% compared to Example 1; and the total life-cycle cost reached 180 yuan / m. 2 Compared to 95 yuan / m² in Example 1 2 The increase was 89.5%. This result fully demonstrates that the innovative modules of "PUD modification - aggregate activation - two-stage gradient shear - ternary composite stabilizer - scenario adaptation" in this invention have formed a synergistic effect, and their overall value is far higher than that of a single technology improvement. They are the core guarantee for realizing the high-value utilization of recycled aggregates and the breakthrough in micro-surface treatment performance.

[0122] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention, or modify them into equivalent embodiments, without departing from the spirit and technical essence of the invention. Therefore, any simple modifications, equivalent substitutions, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention, without departing from the content of the present invention, shall still fall within the scope of protection of the present invention.

Claims

1. A process for the preparation of a waterborne polyurethane dispersion modified emulsified asphalt microsurfacing characterized in that, The method comprises the following steps: (1) screening and removing impurities from the fine aggregate after separating the reclaimed asphalt oil stone, preheating and drying to a water content of less than or equal to 3%, and surface activating with a silane coupling agent to obtain a reclaimed fine aggregate; The particle size of the fine aggregate after separating the reclaimed asphalt oil stone is 0-5 mm; (2) heating and insulating the emulsified asphalt to remove bubbles, adding a polyurethane dispersion, pre-dispersing by primary shearing, refining by secondary shearing, making the dispersion degree of the polyurethane dispersion greater than or equal to 98.5%, avoiding the breakage of the polyurethane dispersion by gradient temperature reduction, adding calcium chloride, polyvinyl alcohol and sodium carboxymethyl cellulose, stirring, defoaming, and obtaining a modified binder; The amount of the polyurethane dispersion is 5%-25% of the mass of the emulsified asphalt; (3) mixing and mixing the reclaimed fine aggregate, the modified binder and the filler, adding water to adjust the consistency, paving, curing, and obtaining a water-based polyurethane dispersion modified emulsified asphalt micro-surfacing; In step (1), the surface activation with the silane coupling agent is spraying a 0.4%-0.6% mass percentage silane coupling agent aqueous solution on the surface of the dried fine aggregate and stirring to activate, and the amount of the silane coupling agent aqueous solution is 0.1%-0.4% of the mass of the fine aggregate after separating the reclaimed asphalt oil stone; In step (2), the ratio of the solid content of the polyurethane dispersion to the solid content of the emulsified asphalt is 12%-18%; the amount of the calcium chloride is 0.08%-0.25% of the mass of the modified binder, the amount of the polyvinyl alcohol is 0.15%-0.6% of the mass of the modified binder, and the amount of the sodium carboxymethyl cellulose is 0.03%-0.1% of the mass of the modified binder; In step (3), the mass ratio of the reclaimed fine aggregate, the modified binder and the filler is 210-250:112-124:10-15; the consistency is 2.2 cm-3.2 cm by funnel test.

2. The method of claim 1, wherein the aqueous polyurethane dispersion modified emulsified asphalt microsurfacing is prepared by the steps of: In step (1), the screening and removing impurities is removing dust and super-particle size particles from the fine aggregate after separating the oil stone by a double-layer screen, the double-layer screen is a 0.15 mm and 5 mm double-layer screen, or a 0.3 mm and 5 mm double-layer screen; the preheating and drying temperature is 50-60°C, and the preheating and drying time is 10-15 min; the stirring and activation speed is 280-320 rpm, and the stirring and activation time is 4-6 min; In step (2), the amount of the polyurethane dispersion is 12%-24% of the mass of the emulsified asphalt, and the mass ratio of the calcium chloride, the polyvinyl alcohol and the sodium carboxymethyl cellulose is 1:2.9-3.1:0.45-0.55; the storage temperature of the modified binder is 40-50°C, the storage stability is greater than or equal to 15 months, and the segregation rate is less than or equal to 1.5%; In step (3), the filler is a P042.5 cement and / or a mineral powder having a specific surface area > 320 m 2 / kg.

3. The method of claim 1, wherein the waterborne polyurethane dispersion modified emulsified asphalt microsurfacing is prepared by the steps of: In step (1), the sand equivalent of the fine aggregate after separating the reclaimed asphalt oil stone is greater than or equal to 60%, and the Los Angeles abrasion is less than or equal to 30%; the silane coupling agent is γ-glycidoxypropyltrimethoxysilane or γ-methacryloyloxypropyltrimethoxysilane. In step (2), the emulsified asphalt is cationic base asphalt, with 70# road petroleum asphalt as the base, solid content of 52% to 65%, softening point of 70℃, evaporation residue softening point ≥ 68℃, 5℃ ductility ≥ 35 cm, and demulsification speed of slow cracking; the polyurethane dispersion is cationic polyester BY-1040 or non-ionic polyether YC-F205, the solid content of the cationic polyester BY-1040 is 43% to 48%, the particle size is 70 nm to 90 nm, and the elongation is ≥ 500%; the solid content of the non-ionic polyether YC-F205 is 43% to 45%, the particle size is 50 nm to 80 nm, and the elongation is ≥ 550%.

4. The method of claim 1, wherein the waterborne polyurethane dispersion modified emulsified asphalt microsurfacing is prepared by the steps of: In step (2), the rotation speed of the primary shearing is 3500 rpm to 4500 rpm, and the time is 4 min to 6 min; the rotation speed of the secondary shearing is 5500 rpm to 6500 rpm, and the time is 6 min to 9 min.

5. Process for the preparation of a waterborne polyurethane dispersion modified emulsified bitumen micro-surfacing according to any one of claims 1 to 4, characterized in that, In step (2), the heating temperature is 62℃ to 70℃, and the holding time is 10 min to 15 min; the primary shearing temperature is 60℃ to 67℃, and the secondary shearing temperature is 55℃ to 62℃; the gradient cooling rate is 1.0℃ / min to 4.0℃ / min; the target temperature of the gradient cooling is 48℃ to 55℃, the stirring rotation speed is 600 rpm to 900 rpm, and the time is 4 min to 6 min; the defoaming is static defoaming, and the static time is 2 min to 3 min.

6. Process for the preparation of a waterborne polyurethane dispersion modified emulsified bitumen micro-surfacing according to any one of claims 1 to 4, characterized in that, In step (3), the rotation speed of the mixing is 600 rpm to 1200 rpm, and the mixing time is 2 min to 3 min. The paving thickness is 4 mm to 10 mm, and the paving speed is 1.8 m / min to 3.5 m / min; wherein, the paving thickness of the highway is 5 mm to 8 mm, and the paving thickness of the airport runway is 8 mm to 10 mm and is paved in two times, each time 4 mm to 5 mm; The curing is normal temperature curing for 35 min to 70 min, the traffic opening time is ≤ 1.2 hours when the environmental temperature is ≥ 15℃, the curing time is extended to 80 min to 100 min when the environmental temperature is -15℃ to 5℃ and the altitude is ≥ 3000 m.

7. The water-based polyurethane dispersion modified emulsified asphalt micro-surfacing prepared by the preparation method of any one of claims 1 to 6.

8. The aqueous polyurethane dispersion modified emulsified asphalt microsurfacing of claim 7, wherein, The 1h wet wheel abrasion loss of the waterborne polyurethane dispersion modified emulsified asphalt micro-surfacing is ≤440g / m 2 , the low temperature splitting tensile strength at -10℃ is ≥1.6MPa, the mass loss after diesel immersion for 24h is ≤4.8%, and the interfacial drawing strength is ≥1.7MPa.

9. The aqueous polyurethane dispersion modified emulsified asphalt microsurfacing of claim 7, wherein, When applied in an extremely low temperature environment of -20℃ to -30℃, the non-ionic polyether YC-F205 is used, the water-based polyurethane dispersion modified emulsified asphalt micro-surfacing has a low temperature splitting tensile strength ≥ 1.8 MPa at -20℃, and the strength loss is ≤ 8% after 20 times of freeze-thaw cycles.

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