High-elasticity asphalt self-healing capsule and preparation method thereof

Abstract

The invention discloses a high-elasticity asphalt self-healing capsule and a preparation method thereof. The high-elasticity asphalt self-healing capsule is composed of a calcium alginate / elastomer composite capsule wall and a high-viscosity regenerant capsule core, the mass ratio of the sodium alginate to the elastomer in the composite capsule wall is 10: (0.5-2), and the mass ratio of the high-viscosity regenerant to the sodium alginate is (0.1-0.33): 1; the elastomer is one of rubber powder, nitrile rubber, thermoplastic polyurethane and a styrene-butadiene-styrene block copolymer; the high-viscosity regenerant is one of aromatic oil, high-aromatic mineral oil and heavy petroleum fraction, and the kinematic viscosity at 25 DEG C is 80-130 mPas; through the asphalt self-healing capsule with the characteristic of high elasticity, the elastic property of the asphalt pavement is improved, the strain adaptation interval is widened, frost heaving deformation is effectively buffered, load fatigue stress is resisted, temperature shrinkage deformation is adapted, base layer reflection stress is relieved, and the occurrence rate of various cracking diseases is reduced from the source.

Description

Technical Field

[0001] This invention belongs to the field of road engineering materials technology, specifically relating to an asphalt self-healing capsule and its preparation method. Background Technology

[0002] Asphalt pavement, with its core advantages such as high smoothness, excellent driving comfort, and ease of construction, has been widely used in highway and urban road construction. However, during its entire service life, it is susceptible to cracking due to multiple cracking factors, and existing technologies are unable to solve this problem at its root.

[0003] Asphalt pavement cracking occurs in various scenarios: In winter, low temperatures cause internal moisture to freeze and expand, inducing frost heave cracking; in summer, high temperatures and heavy loads cause the viscoelastic properties of asphalt to deteriorate, and long-term exposure to vehicle cyclic loads can lead to accumulated stress in wheel tracks, resulting in fatigue cracks; in spring and autumn, fluctuating diurnal temperatures cause asphalt to oxidize and age due to prolonged exposure, increasing its brittleness and causing transverse or longitudinal shrinkage cracks due to temperature contraction; furthermore, if the pavement base layer cracks due to settlement or drying shrinkage, the cracks can reflect upwards to the asphalt surface layer, forming base layer reflective cracks. The core issue of this type of cracking is the lack of elasticity in the pavement, making it difficult to effectively buffer deformation impacts and resist stress accumulation, leading to the easy initiation and rapid propagation of cracks.

[0004] Currently, the mainstream repair methods are still mainly manual crack filling and sealing, which have limitations such as the need for temporary traffic interruption, high construction costs, and poor repair timeliness. Although some self-healing asphalt technologies have introduced capsule-type rejuvenators, most existing capsules only focus on the single crack repair function and lack the ability to systematically improve the elasticity of the pavement. They cannot reduce the generation of cracks from the source and generally suffer from problems such as insufficient self-healing long-term effect, complex preparation process, and poor economic efficiency, making it difficult to meet the needs of large-scale application in highway engineering. Summary of the Invention

[0005] Traditional asphalt self-healing capsules only focus on crack repair and lack the function of improving pavement elasticity. In addition, they have weak resistance to frost heave in low-temperature environments and cannot assist in breaking ice layers. Furthermore, the synergy between the release of rejuvenator and the enhancement of elasticity is insufficient, making it difficult to meet the needs of asphalt pavements in various scenarios during winter.

[0006] To address the aforementioned problems, this invention provides a high-elasticity asphalt self-healing capsule that simultaneously achieves two technical objectives. Firstly, by using the highly elastic asphalt self-healing capsule, it enhances the elastic performance of asphalt pavement, broadens the strain adaptation range, effectively buffers frost heave deformation, resists load fatigue stress, adapts to temperature shrinkage deformation, and alleviates base layer reflective stress, thereby fundamentally reducing the incidence of various cracking defects. Secondly, it synergistically strengthens the long-term functionality of the self-healing capsule while possessing the advantages of simple preparation process and controllable cost, thus systematically solving the core cracking pain point of asphalt pavement throughout its entire service life.

[0007] To achieve the above objectives, the following technical solution is adopted: A high-elasticity asphalt self-healing capsule is composed of a calcium alginate / elastomer composite capsule wall and a high-viscosity regenerator core. The mass ratio of sodium alginate to elastomer in the composite capsule wall is 10:(0.5-2), and the mass ratio of the high-viscosity regenerator to sodium alginate is (0.1-0.33):1. The kinematic viscosity of the high-viscosity regenerator at 25°C is 80-130 mPa. s.

[0008] According to the above scheme, the elastomer is one of rubber powder, nitrile rubber, thermoplastic polyurethane, and styrene-butadiene-styrene block copolymer.

[0009] According to the above scheme, the high-viscosity regenerator is one of aromatic oil, high-aromatic mineral oil, or heavy petroleum fraction.

[0010] This invention also provides a method for preparing the above-mentioned high-elasticity asphalt self-healing capsule, comprising the following steps: (1) Add the elastomer to the sodium alginate solution and stir to form a basic suspension; (2) Add high-viscosity aromatic oil and emulsifier to the basic suspension, and prepare an emulsion by shearing; (3) The emulsion was then dropped into a calcium chloride solution to solidify and form wet capsules. Finally, the capsules were dried in an oven to obtain the finished capsules.

[0011] According to the above scheme, the emulsifier mentioned in step (2) is Tween 80, and the amount added is 0.5-1 wt% of the mass of the basic suspension.

[0012] According to the above scheme, the shearing rate in step (2) is 4000-5000 r / min and the shearing time is 40-60 min.

[0013] According to the above scheme, the concentration of calcium chloride solution in step (3) is 5.0 to 10 wt%.

[0014] According to the above scheme, the curing reaction temperature in step (3) is 25℃ and the reaction time is 30min.

[0015] According to the above scheme, the drying process in step (3) includes drying at 50°C for more than 5 hours.

[0016] The present invention also provides an asphalt concrete pavement, wherein the above-mentioned high-elasticity asphalt self-healing capsules are added, and the amount added accounts for 0.3-0.5 wt% of the mass of the asphalt concrete and 8-9 wt% of the mass of the asphalt.

[0017] To address the shortcomings of traditional asphalt self-healing capsules in various scenarios (freezing heave, high-temperature heavy load, thermal shrinkage, base layer reflection), such as insufficient capsule wall elasticity, poor long-term release of rejuvenator, difficulty in adapting to various types of crack repair, and weak auxiliary effect on pavement crack resistance, this invention uses "calcium alginate / elastomer (rubber powder, nitrile rubber, SBS granules)" as the composite capsule wall and a high-viscosity rejuvenator as the core. By precisely controlling the distribution ratio of each component of the multi-elastomer, long-term controlled release of the rejuvenator and crack-oriented response release are achieved in multiple scenarios. This improves the self-healing performance and crack resistance of asphalt pavements in ordinary roads, expressways, coastal roads, and saline-alkali roads, extending the service life of the pavement. Specifically, the calcium alginate / elastomer composite capsule wall has high elasticity, and the elastomer is uniformly dispersed in the calcium alginate capsule wall matrix, which can enhance the elasticity of the capsule wall itself and its compatibility with asphalt mixtures, thereby improving the overall elasticity of the asphalt pavement. The high-viscosity rejuvenator in the capsule core exhibits excellent compatibility with asphalt. At 25°C, its viscosity is well-suited to the asphalt matrix, allowing for smooth release through the capsule wall pores. This effectively softens aged asphalt and restores its bonding properties. Simultaneously, it synergizes with the elasticity-enhancing function of the capsule wall, repairing cracks and strengthening the pavement's resistance to frost heave. The average particle size of the finished capsule is well-suited to the internal space of the asphalt mixture, ensuring stable dispersion and resistance to breakage. After blending, it significantly improves the elasticity of asphalt pavements.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention employs a composite capsule design of "calcium alginate / elastomer," which significantly improves the overall elasticity of asphalt pavement. When roads freeze in winter, the highly elastic pavement can reduce ice adhesion and residue through mechanical interaction with the ice layer under vehicle loads, solving the problems of traditional pavement reliance on de-icing salt and mechanical ice removal, which are difficult, prone to accidents, and pollute the environment. On the other hand, the enhanced pavement elasticity can not only effectively resist permanent deformation under long-term vehicle loads, reduce rutting, depressions, and other defects, extend the service life of the pavement, and reduce later maintenance costs, but also broaden the capsule's own strain range, better adapting to the dynamic changes in pavement frost heave deformation and vehicle loads.

[0019] When road surfaces develop cracks due to winter frost heave or long-term aging, the high-viscosity regenerator in the core can respond promptly to stress release at the cracks. It can not only repair cracks and restore the integrity of the road structure, but also block the penetration channels of water and impurities, preventing further aggravation of frost heave damage. At the same time, the composite capsule wall, relying on the synergistic effect of multiple elastomers, optimizes the stress-controlled release performance of the capsule, which can prevent the regenerator from being released in large quantities at one time in non-cracked scenarios, ensuring long-term repair effect.

[0020] Furthermore, the high-viscosity recycling agent used in the core exhibits superior high-temperature rutting resistance compared to ordinary asphalt recycling agents. The synergistic effect of calcium alginate and multi-elastomers further enhances the high-temperature stability of the core wall material; the core wall structure maintains over 98% integrity at an asphalt mixture mixing temperature of 180℃, preventing premature release of the recycling agent. Both the composite core wall material and the core material meet environmental protection requirements for road engineering, with no toxic reagents added during the preparation process. This significantly improves the elasticity, self-healing efficiency, and rutting resistance of asphalt materials under complex environments such as low-temperature freeze-thaw cycles and high-temperature heavy loads, while also prioritizing environmental friendliness and further extending the overall service life of the pavement. Detailed Implementation

[0021] The following embodiments further illustrate the technical solution of the present invention, but are not intended to limit the scope of protection of the present invention.

[0022] A specific embodiment provides a highly elastic calcium alginate asphalt self-healing capsule, which is obtained through the following steps: (1) Preparation of basic suspension: Weigh a certain amount of sodium alginate and elastomer particles, and add the elastomer particles to the sodium alginate solution at a mass ratio of 10:1; first use a stirring device to stir until the elastomer is evenly dispersed to obtain a homogeneous basic suspension.

[0023] (2) Emulsion preparation: Add high-viscosity regenerator aromatic oil (3 / 7 of the mass of sodium alginate) and Tween 80 (0.5%-1wt% of the mass of the basic suspension) to the above basic suspension; insert the shear head of the shearing machine into the mixing system, set the fixed shearing parameters, and shear for 40-60 minutes to form a uniform emulsion, ensuring that the aromatic oil is dispersed in the form of tiny droplets and that there is no stratification after standing.

[0024] (3) Capsule solidification and molding: Prepare a calcium chloride solution with a mass fraction of 5.0–10 wt% and place it in a container; use a dropper to draw up the emulsion, controlling the dropping height and rate, and drop the emulsion into the calcium chloride solution; Ca 2+ A cross-linking reaction occurs with sodium alginate, encapsulating aromatic oil droplets to form a composite wet capsule. After the addition is complete, the capsule is left to stand for a period of time to ensure that it is completely solidified and formed.

[0025] (4) Capsule drying treatment: Separate the solidified wet capsules from the calcium chloride solution and remove the residual solution on the surface; spread the wet capsules flat on the oven tray (the thickness is controlled within the range that does not affect the drying efficiency), set the oven temperature to 50℃, and continue drying for 5 hours; after drying, take them out and cool them to room temperature to obtain high elastic calcium alginate asphalt self-healing capsules.

[0026] The sodium alginate, rubber powder, nitrile rubber, thermoplastic polyurethane, and styrene-butadiene-styrene block copolymer used in the specific implementation method were obtained commercially and were chemically pure.

[0027] High-viscosity aromatic oil: Industrial grade, kinematic viscosity at 25℃ 80~120mm² / s, density (20℃) 0.92~0.96g / cm³ 3 It has a compatibility of ≥95% with 70# base asphalt.

[0028] High aromatic mineral oil: Industrial grade, model T-1000, kinematic viscosity at 25°C 90~130mm 2 / s, density (20℃) 0.93~0.97g / cm³ 3 It has a compatibility of ≥94% with 70# / 90# base asphalt.

[0029] Heavy petroleum fraction: industrial grade, distillation range 360–520℃, kinematic viscosity at 25℃ 100–130 mmHg 2 / s, density (20℃) 0.94~0.98g / cm³ 3 It has a compatibility of ≥93% with 70# base asphalt.

[0030] Example 1 1. Preparation of the basic suspension: Weigh 7.6g of sodium alginate and 0.76g of rubber powder at a mass ratio of 10:1, add them together to 291.6mL of deionized water, and place them in a 500mL beaker. First, stir with a glass rod for 10min to initially disperse the raw materials and avoid agglomeration of rubber powder. Then, place the beaker on a magnetic stirrer, set the speed to 200rpm, and stir continuously for 15min until there are no obvious particles in the solution, thus obtaining the basic suspension.

[0031] 2. Emulsion Preparation: Two components were added to the above-mentioned basic suspension: one was Tween 80 emulsifier, accounting for 0.5% of the mass of the basic suspension (the total mass of the basic suspension is about 300g, so about 1.5g of Tween 80 was added); the other was high-viscosity aromatic oil in a mass ratio of 3:7 with sodium alginate (7.6g of sodium alginate, so about 17.73g of aromatic oil was added). The shear head of the high-speed shearing machine was inserted into the solution, ensuring that the shear head was submerged 2-3cm below the liquid surface. The rotation speed was set to 4000r / min, and shearing was continued for 40min. During the shearing process, the state of the solution was observed regularly to avoid generating too many bubbles. After shearing, a uniform white emulsion was obtained. After standing for 30min, there was no stratification. At this time, the aromatic oil was dispersed in the form of 1-5μm microdroplets.

[0032] 3. For capsule solidification and molding, prepare 300 mL of a 5% (w / w) calcium chloride solution: Weigh 15 g of calcium chloride and add it to 285 mL of deionized water. Stir until completely dissolved and place in a 5 L beaker. Turn on the magnetic stirrer and set the speed to 200 rpm to maintain a stable flow of the calcium chloride solution. Use a dropper with a specification of 20 drops / mL to draw up the emulsion, controlling the vertical distance (dropping height) between the dropper and the surface of the calcium chloride solution to be 18 cm, and the dropping rate to be 40 drops / min. Slowly add the emulsion to the calcium chloride solution; the emulsion droplets should contact the Ca... 2+ A cross-linking reaction then occurs rapidly, forming spherical wet capsules with a diameter of 2-3 mm. After the addition is complete, continue stirring at 200 rpm for 10 minutes to ensure that the capsules are completely solidified and the capsule wall structure is stable.

[0033] 4. Capsule post-processing: Turn off the magnetic stirrer, filter out the wet capsules, and wash the capsules repeatedly with deionized water 3 times, using 500mL of water each time, until the final wash filtrate is collected; spread the washed capsules evenly on a porcelain plate, controlling the spreading thickness to ≤3mm, and place them in a forced-air drying oven at 50℃ for 5 hours; after drying, remove them and cool to room temperature to obtain high-elasticity calcium alginate self-healing capsules with an average particle size of 2.2mm and an elastic recovery rate of ≥85% (recovery rate within 10 minutes after 50% compression at 25℃).

[0034] 5. Capsule performance testing; Oil content testing: Using acetone extraction, the oil content of the capsule was measured to be 48.2%, indicating good encapsulation effect of aromatic oil; High temperature stability testing: Using TGA thermogravimetric analysis, the mass fraction of the high-elastic self-healing capsule remained at 98.5667% at 60℃, proving its good high temperature stability; Physical property testing: The capsule compression performance was tested by a universal testing machine, and the yield displacement exceeded 60%, which is significantly higher than that of pure seaweed calcium capsules.

[0035] Example 2 1. Weigh 7.6g of sodium alginate and 0.76g of nitrile rubber (industrial grade, acrylonitrile content 30%, pulverized to 60-100 mesh fine particles to avoid lumps and agglomeration) at a mass ratio of 10:1, and add them together to 291.6mL of deionized water in a 500mL beaker. First, stir with a glass rod for 15min (nitrile rubber has slightly poor hydrophilicity, so extend the initial stirring time) to break up the particle agglomerates. Then, place the beaker on a magnetic stirrer and set the speed to 250rpm (slightly increase the speed to enhance the dispersion effect). Continue stirring for 20min, scraping the adhering particles on the beaker wall with a glass rod every 5min until the solution is homogeneous and viscous with no obvious solid particles, thus obtaining the basic suspension.

[0036] 2. Two components were added to the above-mentioned basic suspension: one was Tween 80 emulsifier, accounting for 0.5% of the mass of the basic suspension (the total mass of the basic suspension was about 300g, so about 1.5g of Tween 80 was added); the other was high-viscosity aromatic oil with a mass ratio of 3:7 to sodium alginate (7.6g of sodium alginate, so about 17.73g of aromatic oil was added); the shear head of the high-speed shearing machine was inserted into the solution, ensuring that the shear head was submerged 2-3cm below the liquid surface and avoiding the cup wall, and the rotation speed was set to 4500r / min (the interface between nitrile rubber and the oil phase is strong, so slightly increasing the rotation speed ensures the uniformity of the emulsion droplets), and shearing was continued for 40min; during the shearing process, the process was paused for 30s every 10min to release air bubbles to avoid air bubbles affecting the core encapsulation; after shearing, a milky white homogeneous emulsion was obtained, which remained standing for 30min without stratification or floating oil, at which point the aromatic oil was dispersed in the form of 1-4μm microdroplets (the interfacial stabilizing effect of nitrile rubber made the droplet size slightly smaller than that in Example 1).

[0037] 3. Prepare 300 mL of a 5% (w / w) calcium chloride solution: Weigh 15 g of calcium chloride and add it to 285 mL of deionized water. Stir until completely dissolved and place in a 5 L beaker. Turn on the magnetic stirrer and set the speed to 200 rpm to maintain a stable laminar flow of the calcium chloride solution. Use a dropper with a specification of 20 drops / mL to draw up the emulsion, controlling the vertical distance between the dropper and the surface of the calcium chloride solution to be 18 cm, and the dropping rate to be 40 drops / min. Slowly add the emulsion to the calcium chloride solution. The emulsion droplets should contact the Ca... 2+ After rapid cross-linking, the nitrile rubber enhances the initial moldability of the capsule wall, forming spherical wet capsules with a diameter of 2.1 to 2.8 mm (with a more concentrated particle size distribution). After the droplet addition is completed, continue stirring at 200 rpm for 15 minutes (extending the curing time to ensure that the nitrile rubber and calcium alginate are fully combined), making the capsule wall structure dense and stable.

[0038] 4. Turn off the magnetic stirrer, filter out the wet capsules, and wash them repeatedly with deionized water 3 times. Spread the washed capsules evenly on a ceramic plate, controlling the thickness of the spread to ≤3mm (to avoid deformation caused by stacking), and place them in a forced-air drying oven. Set the temperature to 50℃ and dry for 5 hours. After drying, remove the capsules and allow them to cool naturally to room temperature to obtain high-elasticity calcium alginate self-healing capsules. The average particle size of the finished product is 2.3mm, and the elastic recovery rate is ≥90% (after being compressed by 50% at 25℃ and released, the recovery rate within 10 minutes is higher than that of Example 1 due to the superior elasticity of nitrile rubber).

[0039] 5. Capsule performance testing; Oil content testing: Using acetone extraction, the oil content of the capsule was measured to be 43.7%, indicating good encapsulation effect of aromatic oil; High temperature stability testing: Using TGA thermogravimetric analysis, the mass fraction of the high-elastic self-healing capsule remained at 96.3395% at 60℃, proving its good high temperature stability; Physical performance testing: The capsule compression performance was tested by a universal testing machine, and the yield displacement exceeded 60%, which is significantly higher than that of pure seaweed calcium capsules.

[0040] Example 3 1. Weigh 7.6g of sodium alginate and 0.76g of SBS granules (industrial grade, styrene content 35%, pulverized to 60-100 mesh to avoid lumps and agglomeration) at a mass ratio of 10:1. Add them together to 291.6mL of deionized water and place them in a 500mL beaker. First, stir with a glass rod for 15min (SBS granules have slightly lower surface polarity, so extending the initial stirring time ensures uniform particle dispersion and avoids agglomeration) to break up the particle agglomerates. Then, place the beaker on a magnetic stirrer, set the speed to 250rpm, and stir continuously for 20min. During this period, use a glass rod to scrape the adhering particles on the beaker wall every 5min until the solution is homogeneous and viscous with no obvious solid particles, thus obtaining the basic suspension.

[0041] 2. Add two components to the above-mentioned basic suspension: one is Tween 80 emulsifier accounting for 0.5% of the mass of the basic suspension (the total mass of the basic suspension is about 300g, so about 1.5g of Tween 80 is added); the other is high-viscosity aromatic oil with a mass ratio of 3:7 to sodium alginate (sodium alginate is 7.6g, so about 17.73g of aromatic oil is added); insert the shear head of the high-speed shearing machine into the solution, ensuring that the shear head is submerged 2-3cm below the liquid surface and avoids the cup wall, set the rotation speed to 4500r / min (the block structure of SBS can enhance the compatibility of the oil phase interface and ensure the uniformity of the emulsion droplets), and continue shearing for 40min; during the shearing process, pause for 30s every 10min to release air bubbles to avoid air bubbles affecting the core encapsulation; after shearing, a milky white homogeneous emulsion is obtained, which shows no stratification or floating oil after standing for 30min, at which point the aromatic oil is dispersed in the form of 1-3μm microdroplets (the interface regulation effect of SBS makes the droplet size more uniform).

[0042] 3. Prepare 300 mL of a 5% calcium chloride solution: Weigh 15 g of calcium chloride and add it to 285 mL of deionized water. Stir until completely dissolved and place in a 5 L beaker. Turn on the magnetic stirrer and set the speed to 200 rpm to maintain a stable laminar flow of the calcium chloride solution. Use a dropper with a specification of 20 drops / mL to draw up the emulsion, controlling the vertical distance between the dropper and the surface of the calcium chloride solution to be 18 cm, and the dropping rate to be 40 drops / min. Slowly add the emulsion to the calcium chloride solution. The emulsion droplets should contact the Ca... 2+ After rapid cross-linking, SBS enhances the uniformity of capsule wall formation, resulting in spherical wet capsules with a diameter of 2.0-2.7 mm (the particle size distribution is more uniform than in Example 2). After the addition is completed, continue stirring at 200 rpm for 15 min (to ensure that the cross-linked structure of SBS and calcium alginate is fully cured), making the capsule wall structure dense and stable.

[0043] 4. Turn off the magnetic stirrer, filter out the wet capsules, and wash them repeatedly with deionized water 3 times. Spread the washed capsules evenly on a ceramic plate, controlling the thickness of the spread to ≤3mm (to avoid deformation caused by stacking), and place them in a forced-air drying oven. Set the temperature to 50℃ and dry for 5 hours. After drying, remove the capsules and allow them to cool naturally to room temperature to obtain high-elasticity calcium alginate self-healing capsules. The average particle size of the finished product is 2.2mm, and the elastic recovery rate is ≥92% (after being compressed by 50% at 25℃, the recovery rate within 10 minutes is improved by more than 2% compared to Example 2, thanks to the excellent elastic recovery performance of SBS).

[0044] 5. Capsule performance testing; Oil content testing: Using acetone extraction, the oil content of the capsule was measured to be 44.1%, indicating good encapsulation effect of aromatic oil; High temperature stability testing: Using TGA thermogravimetric analysis, the mass fraction of the high-elastic self-healing capsule remained at 97.1% at 60℃, proving that it has better high temperature stability than Example 2; Physical property testing: The capsule compression performance was tested by a universal testing machine, and the yield displacement exceeded 65%, which is significantly higher than that of pure calcium alginate capsules and capsules of Example 2, demonstrating the enhancing effect of SBS on capsule wall toughness.

[0045] Example 4 1. Weigh 7.6g of sodium alginate and 0.76g of EVA granules (industrial grade, vinyl acetate content 20%, pulverized to 60-100 mesh to avoid lumps and agglomeration) at a mass ratio of 10:1. Add them together to 291.6mL of deionized water and place in a 500mL beaker. First, stir with a glass rod for 12min (EVA has moderate hydrophilicity to ensure initial dispersion of particles) to break up the particle agglomerates. Then, place the beaker on a magnetic stirrer, set the speed to 230rpm, and stir continuously for 18min. During this period, use a glass rod to scrape the particles adhering to the beaker wall every 5min until the solution is homogeneous and viscous with no obvious solid particles, thus obtaining the basic suspension.

[0046] 2. Add two components to the above-mentioned basic suspension: one is Tween 80 emulsifier, accounting for 0.5% of the mass of the basic suspension (the total mass of the basic suspension is about 300g, so about 1.5g of Tween 80 is added); the other is high aromatic mineral oil (model T-1000, sodium alginate 7.6g, so about 17.73g of high aromatic mineral oil is added) in a 3:7 mass ratio with sodium alginate. Insert the shear head of the high-speed shearing machine into the solution, ensuring that the shear head is submerged 2-3cm below the liquid surface and avoids the cup wall. Set the rotation speed to 4200r / min (EVA has excellent interfacial compatibility, ensuring uniform dispersion of emulsion droplets), and continue shearing for 40min. During the shearing process, pause for 30s every 10min to release air bubbles to avoid affecting the core encapsulation. After shearing, a milky white homogeneous emulsion is obtained. After standing for 30min, there is no stratification or floating oil. At this point, the high aromatic mineral oil is dispersed in the form of 1-4μm microdroplets (EVA). The interface stabilizing effect ensures uniform distribution of emulsion droplets.

[0047] 3. Prepare 300 mL of a 5% calcium chloride solution: Weigh 15 g of calcium chloride and add it to 285 mL of deionized water. Stir until completely dissolved and place in a 5 L beaker. Turn on the magnetic stirrer and set the speed to 200 rpm to maintain a stable laminar flow of the calcium chloride solution. Use a dropper with a specification of 20 drops / mL to draw up the emulsion, controlling the vertical distance between the dropper and the surface of the calcium chloride solution to be 18 cm, and the dropping rate to be 40 drops / min. Slowly add the emulsion to the calcium chloride solution. The emulsion droplets should contact the Ca... 2+ After rapid cross-linking, EVA enhances the stability of the capsule wall formation, resulting in spherical wet capsules with a diameter of 2.0–2.9 mm. After the addition is complete, continue stirring at 200 rpm for 12 minutes (to ensure that EVA and calcium alginate are fully cross-linked and cured), making the capsule wall structure dense and stable.

[0048] 4. Turn off the magnetic stirrer, filter out the wet capsules, and wash them repeatedly with deionized water 3 times. Spread the washed capsules evenly on a ceramic plate, controlling the thickness of the spread to ≤3mm (to avoid deformation caused by stacking), and place them in a forced-air drying oven. Set the temperature to 50℃ and dry for 5 hours. After drying, remove the capsules and allow them to cool naturally to room temperature to obtain high-elasticity calcium alginate self-healing capsules. The average particle size of the finished product is 2.4mm, and the elastic recovery rate is ≥88% (after being compressed by 50% at 25℃, the recovery rate within 10 minutes is improved by more than 3% compared to Example 1, thanks to the excellent flexibility of EVA).

[0049] 5. Capsule performance testing; Oil content testing: Using acetone extraction, the oil content of the capsule was measured to be 46.5%, indicating that the high aromatic mineral oil encapsulation effect is good; High temperature stability testing: Using TGA thermogravimetric analysis, the mass fraction of the high-elastic self-healing capsule was found to remain at 98.2% at 60℃, proving that its high temperature stability is better than that of Example 2; Physical performance testing: The capsule compression performance was tested by a universal testing machine, and the yield displacement exceeded 62%, which is significantly higher than that of pure calcium alginate capsules, reflecting the enhancing effect of EVA on the flexibility of the capsule wall.

[0050] Example 5 1. Weigh 7.6g of sodium alginate and 0.76g of natural rubber (NR) granules (industrial grade, Mooney viscosity ML (1+4) 60-80 at 100℃, pulverized to 60-100 mesh to avoid lumps and agglomeration) at a mass ratio of 10:1. Add them together to 291.6mL of deionized water and place in a 500mL beaker. First, stir with a glass rod for 18min (natural rubber has poor hydrophilicity, so extend the initial stirring time to ensure dispersion) to break up the granule agglomerates. Then, place the beaker on a magnetic stirrer, set the speed to 260rpm, and stir continuously for 22min. During this period, use a glass rod to scrape the adhering granules on the beaker wall every 5min until the solution is homogeneous and viscous with no obvious solid particles, thus obtaining the basic suspension.

[0051] 2. Add two components to the above-mentioned basic suspension: one is 0.5% of the emulsifier Tween 80 (the total mass of the basic suspension is about 300g, so about 1.5g of Tween 80 is added); the other is a heavy petroleum fraction with a mass ratio of 3:7 to sodium alginate (boiling range 360-520℃, sodium alginate 7.6g, so about 17.73g of heavy petroleum fraction is added). Insert the shear head of the high-speed shearing machine into the solution, ensuring that the shear head is submerged 2-3cm below the liquid surface and avoids the cup wall. Set the rotation speed to 4600r / min (the elastic properties of natural rubber require a higher shearing speed to ensure droplet refinement), and continue shearing for 40min. During the shearing process, pause for 30s every 10min to release air bubbles to avoid affecting the core encapsulation. After shearing, a milky white homogeneous emulsion is obtained. After standing for 30min, there is no stratification or floating oil. At this point, the heavy petroleum fraction is in the form of 1-5μm... Dispersion in the form of tiny droplets (the elastic network effect of natural rubber enhances the stability of the droplets).

[0052] 3. Prepare 300 mL of a 5% calcium chloride solution: Weigh 15 g of calcium chloride and add it to 285 mL of deionized water. Stir until completely dissolved and place in a 5 L beaker. Turn on the magnetic stirrer and set the speed to 200 rpm to maintain a stable laminar flow of the calcium chloride solution. Use a dropper with a specification of 20 drops / mL to draw up the emulsion, controlling the vertical distance between the dropper and the surface of the calcium chloride solution to be 18 cm, and the dropping rate to be 40 drops / min. Slowly add the emulsion to the calcium chloride solution. The emulsion droplets should contact the Ca... 2+ After rapid cross-linking, the natural rubber enhances the elasticity and moldability of the capsule wall, forming spherical wet capsules with a diameter of 2.1 to 3.0 mm (with excellent particle roundness). After the addition is completed, continue stirring at 200 rpm for 18 minutes (to ensure that the cross-linked structure of natural rubber and calcium alginate is dense), so as to stabilize the capsule wall structure.

[0053] 4. Turn off the magnetic stirrer, filter out the wet capsules, and wash them repeatedly with deionized water 3 times. Spread the washed capsules evenly on a porcelain plate, controlling the thickness of the spread to ≤3mm (avoid stacking to prevent deformation), and place them in a forced-air drying oven. Set the temperature to 50℃ and dry for 5 hours. After drying, remove the capsules and allow them to cool naturally to room temperature to obtain high-elasticity calcium alginate self-healing capsules. The average particle size of the finished product is 2.5mm, and the elastic recovery rate is ≥93% (after being compressed by 50% at 25℃ and released, the recovery rate within 10 minutes is higher than that of Example 3 due to the excellent elasticity of natural rubber).

[0054] 5. Capsule performance testing; Oil content testing: Using acetone extraction, the oil content of the capsule was measured to be 45.8%, indicating that the heavy petroleum fraction was well encapsulated; High-temperature stability testing: Using TGA thermogravimetric analysis, the mass fraction of the high-elastic self-healing capsule remained at 97.5% at 60℃, proving its excellent high-temperature stability; Physical property testing: The capsule compression performance was tested using a universal testing machine, and the yield displacement exceeded 68%, which was significantly higher than that of pure calcium alginate capsules and capsules from other examples, highlighting the synergistic enhancement effect of natural rubber on the elasticity and toughness of the capsule wall.

[0055] Comparative Example 1 (Preparation of capsules without elastomer and with common light oil as regenerator) 1. Preparation of capsule wall solution: Weigh 8.4g of sodium alginate and add it to 291.6mL of deionized water (without adding elastomer). Place it in a 500mL beaker. Stir with a glass rod for 10min, then place it on a magnetic stirrer and stir at 200rpm for 30min until the solution is homogeneous and transparent to obtain pure sodium alginate solution.

[0056] 2. Preparation of emulsion: Add Tween 80 (0.5% of the total mass of the solution, about 1.5g) and ordinary light oil - sunflower seed oil (mass ratio of sodium alginate to sodium alginate 3:7, about 19.6g) to pure sodium alginate solution; adjust the speed of the high-speed shearing machine to 4500r / min and shear continuously for 40min to obtain a white emulsion, which does not separate into layers after standing for 30min.

[0057] 3. Capsule curing and post-treatment: The curing, molding, washing, and drying steps are completely consistent with those in Example 1: 5% calcium chloride solution is added, stirred at 200 rpm for 30 min, vacuum filtered, washed three times with deionized water, and dried in a 50℃ oven for 5 h to obtain capsules without rubber powder and with light oil as the regenerator.

[0058] 4. Capsule performance testing; Oil content testing: As in Example 1, the oil content was measured to be 49.1% using acetone extraction, indicating a acceptable encapsulation effect of light oil; High-temperature stability testing: After being placed in a 60℃ oven for 24 hours, the mass retention rate was only 92.3%, indicating significant leakage of regenerant and poor high-temperature stability; Physical property testing: After being compressed by 50% at 25℃, the elastic recovery rate within 10 minutes was only 35%, showing no obvious elasticity; Comparative Example 2 (Preparation of capsules with excess elastomer and aromatic oil as regenerator) 1. Preparation of capsule wall solution: Weigh 7.6g of sodium alginate and 2.28g of rubber powder (parameters same as in Example 1) at a mass ratio of 10:3 (excess elastomer, 3 times that of Example 1), add them together to 291.6mL of deionized water, and place them in a 500mL beaker; stir with a glass rod for 15min, then place on a magnetic stirrer and stir at 250rpm for 40min. A large number of undispersed rubber powder agglomerates still exist in the solution, making it difficult to form a homogeneous system.

[0059] 2. Emulsion preparation: Add Tween 80 (about 1.5 g) and high-viscosity aromatic oil (same as in Example 1, about 17.73 g) to the above system; shear at 4500 r / min for 40 min. Due to the agglomeration of rubber powder, the emulsion is not uniform and local stratification occurs. The particle size distribution of aromatic oil droplets is disordered (2-10 μm).

[0060] 3. Capsule curing and post-processing: The curing, washing and drying steps are the same as in Example 1. Finally, capsules with uneven particle size (1.8-3.5 mm) and rough surface are obtained. Some capsules are damaged due to the presence of agglomerates.

[0061] 4. Capsule performance testing; Oil content testing: The oil content was 41.5% as determined by acetone extraction, indicating poor encapsulation effect and easy residue of regenerator in the gaps between aggregates; High temperature stability testing: The mass retention rate was 93.7% at 60℃, indicating that excessive elastomers damaged the compactness of the capsule wall and increased the risk of regenerator leakage; Physical property testing: After compression of 50% at 25℃, the elastic recovery rate was 62%, which was higher than that of Comparative Example 1, but the uneven mechanical properties of the capsule wall caused by agglomeration made it prone to breakage during compression.

[0062] Comparative Example 3 (Preparation of capsules with insufficient elastomer and aromatic oil as regenerator) 1. Preparation of capsule wall solution: Weigh 7.6g of sodium alginate and 0.15g of rubber powder (parameters same as in Example 1) at a mass ratio of 10:0.2 (the elastomer content is insufficient, only 1 / 5 of that in Example 1), and add them together to 291.6mL of deionized water. Place the mixture in a 500mL beaker. After stirring according to the steps in Example 1, a uniform and transparent basic suspension is obtained (low elastomer content, no obvious dispersion difference).

[0063] 2. Preparation of emulsion: Add Tween 80 (about 1.5 g) and high viscosity aromatic oil (same as in Example 1, about 17.73 g); shear at 4000 r / min for 40 min to obtain a homogeneous emulsion with aromatic oil droplet size of 1-6 μm.

[0064] 3. Capsule solidification and post-processing: The steps are the same as in Example 1. Finally, capsules with an average particle size of 2.1 mm and a smooth surface are obtained, and their appearance is not much different from that of pure sodium alginate capsules.

[0065] 4. Capsule performance testing; Oil content testing: The oil content was 48.7% as determined by acetone extraction, indicating good encapsulation effect; High temperature stability testing: The mass retention rate was 97.2% at 60℃, which is better than Comparative Examples 1 and 2, but close to Example 1; Physical performance testing: After compression by 50% at 25℃, the elastic recovery rate was only 45% within 10 minutes, indicating a weak elasticity improvement effect, which cannot meet the crack resistance requirements, and the performance difference from pure sodium alginate capsules is not significant.

[0066] Comparative Example 4 (Preparation of capsules containing rubber powder and low-viscosity light oil as the regenerator) 1. Preparation of capsule wall solution: According to the formula and steps in Example 1, 7.6g of sodium alginate and 0.76g of rubber powder were weighed to prepare a homogeneous basic suspension.

[0067] 2. Emulsion preparation: Add Tween 80 (approximately 1.5g) and low-viscosity light oil (viscosity 15-25mPa at 25℃) to the base suspension. s, with a mass ratio of sodium alginate of 3:7, approximately 17.73 g); sheared at 4000 r / min for 40 min to obtain a white emulsion. After standing for 30 min, no stratification occurred, but the droplet size was relatively small (0.5–3 μm).

[0068] 3. Capsule curing and post-processing: The steps are the same as in Example 1, and finally capsules with an average particle size of 2.0 mm are obtained. The appearance is not significantly different from that in Example 1.

[0069] 4. Capsule performance testing; Oil content testing: The oil content was measured to be 50.3% by acetone extraction. Low-viscosity oil is easily encapsulated, but its adsorption is poor; High-temperature stability testing: After being placed in a 60℃ oven for 24 hours, the mass retention rate was only 89.6%. Low-viscosity regenerator easily penetrated the capsule wall, resulting in serious leakage; Physical performance testing: After being compressed by 50% at 25℃, the elastic recovery rate was 83%, which is close to that of Example 1. However, due to the easy leakage of the regenerator, the self-healing long-term effect is poor in practical applications. After 3 freeze-thaw cycles, the self-healing efficiency dropped to 30% (Example 1 still maintained more than 65%).

[0070] The specific implementation also provides application examples, including the construction and performance characterization of asphalt pavement modified with rubber powder and high-elasticity self-healing capsules.

[0071] I. Application of Raw Materials and Scheme Design Core materials: Example 1 group used rubber powder modified high elastic self-healing capsules prepared in Example 1 (average particle size of finished product 2.2mm, elastic recovery rate ≥60%, oil content 48.2%); Comparative Example 1 group used non-elastomer + light oil capsules prepared in Comparative Example 1 (elastic recovery rate 35%, oil content 49.1%); Comparative Example 4 group used elastic capsule wall + light oil capsules prepared in Comparative Example 4; and blank group (no capsules added).

[0072] Asphalt mixture formula: AC-13 type asphalt mixture is used, with 5.0% of 70# base asphalt and aggregate gradation conforming to JTG F40-2004 standard; the capsule dosage is 0.4% of the total mass of the mixture, accounting for 8.4% of the asphalt mass.

[0073] Construction plan: All three mixtures were prepared according to conventional asphalt pavement construction technology (mixing temperature 160~165℃, paving temperature ≥150℃, compaction temperature ≥140℃); the capsules were added in the later stage of mixing (30s before discharge) to avoid damage to the capsules due to prolonged exposure to high temperature; the test paving sections were all standard sections with a length of 20m, a width of 3m, and a thickness of 4cm, and the compaction degree was controlled above 96%.

[0074] II. Performance Testing and Characterization (Corresponding to Technical Effect Verification) (I) Characterization of the overall elasticity improvement effect of asphalt pavement Test methods: According to JTG E20-2011 "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering", the dynamic resilient modulus (a core indicator characterizing elasticity) of three sets of pavement core samples (100 mm in diameter and 150 mm in height) was tested at 25℃ (normal temperature) and -10℃ (low temperature) using a dynamic modulus tester. Simultaneously, the fracture toughness (reflecting elastic deformation capacity) of the core samples was tested using a bending test. The test results are shown in Table 1.

[0075] Table 1

[0076] Conclusion: The pavement with elastomer capsules (Comparative Example 4 and Example 1) has better elastic properties than the blank group and Comparative Example 1. However, the improvement of Example 1 is the most significant. Its room temperature rebound modulus is 28.75% higher than that of the blank group, and it reaches 9860 MPa at low temperature. This proves that the synergistic effect of rubber powder elastomer and high viscosity aromatic oil can maximize the enhancement of pavement elastic deformation capacity and provide a core foundation for resisting load and frost heave.

[0077] (II) Characterization of anti-frost heave effect in winter Test method: The freeze-thaw cycle test was used to simulate the harsh winter environment. According to the T0729-2011 standard, three sets of pavement core samples were placed in -20℃ for 12 hours and thawed in water at 20℃ for 12 hours as one freeze-thaw cycle. After 0, 5, 10 and 15 cycles, the splitting strength retention rate (characterizing the resistance to frost heave damage) and the frost heave crack propagation rate (the crack width change was monitored by digital image correlation method) of the core samples were tested. At the same time, on-site observations were carried out in winter on the test road section to record the time of frost heave crack formation and the maximum crack width.

[0078] 1. The splitting strength retention rate is shown in Table 2.

[0079] Table 2

[0080] 3. Frost heave crack propagation rate (after 15 cycles): 0.032 mm / cycle for the control group, 0.028 mm / cycle for comparative example 1, 0.020 mm / cycle for comparative example 4, and 0.011 mm / cycle for example 1. Conclusion: The introduction of elastomers can significantly improve the frost heave resistance of pavements. The first example group still maintained a 79% splitting strength retention rate after 15 freeze-thaw cycles and had the lowest crack propagation rate. The core reason is the synergistic compatibility between high-viscosity aromatic oil and rubber powder elastomer: high-viscosity oil can fill the pores of the capsule wall for a long time and reduce water penetration during freeze-thaw, while rubber powder enhances the elastic buffer of the capsule wall. Under the dual action, the frost heave resistance and durability are far superior to Comparative Example 4 (low-viscosity oil + elastomer) and Comparative Example 1 (low-viscosity oil + no elastomer).

[0081] (III) Ice fragmentation and de-icing effect test: 1. Indoor simulation: A uniform ice layer with a thickness of 5 mm was prepared on the surface of three sets of road core samples (frozen at -10℃ for 24 hours). The MTS loading system was used to simulate vehicle load (single axle pressure 0.7 MPa, corresponding to the tire pressure of a fully loaded truck, loading frequency 1 Hz, 10 cycles) to monitor the ice layer cracking time, number of cracks and the proportion of detached area. 2. Field observation: During the low-temperature period of winter (average temperature -5~2℃), continuous observation was conducted on the test road section for 30 days. The thickness of the ice layer on the road surface, the ice layer fragmentation after vehicle compaction, and the de-icing efficiency (the percentage of the area where the ice layer naturally falls off without manual / mechanical intervention) were recorded. The test results are shown in Table 3.

[0082] Table 3

[0083] Explanation: In Example 1, under vehicle load, the highly elastic pavement can generate continuous "elastic impact vibration," which, combined with the low freezing point of the high-viscosity aromatic oil, can quickly break up the ice layer and promote its removal. In contrast, in Comparative Example 4, the low-viscosity light oil is prone to leakage, and the synergy between the oil and the elastomer is weak, so the ice layer easily re-adhedes after breaking up. Comparative Example 1 has no elastomer, so the pavement cannot recover quickly after deformation and cannot cause secondary damage to the ice layer. The de-icing effect of both is far inferior to that of Example 1.

[0084] Conclusion: The synergistic effect of the elastomer capsule wall and the high-viscosity regenerator is the key to achieving efficient de-icing. The high-viscosity oil can maintain compatibility with the road surface for a long time and avoid early leakage, while the elastomer provides sufficient elastic deformation capacity and accelerates ice layer fragmentation through elastic impact under load, achieving the dual effect of "anti-frost heave + de-icing".

[0085] (iv) Characterization of rutting resistance Test Method: According to JTG E20-2011 T0719 standard, the dynamic stability (DS, unit: cycles / mm) of three groups of asphalt mixture slabs (300mm×300mm×50mm) under a high temperature of 60℃ and a load of 0.7MPa was tested using a rutting tester. Higher dynamic stability indicates stronger resistance to rutting. Test Results: The dynamic stability of the blank group was 3120 cycles / mm, Comparative Example 1 was 3380 cycles / mm, Comparative Example 4 was 4280 cycles / mm, and Example 1 was 4650 cycles / mm (an improvement of 49.04% compared to the blank group and 8.65% compared to Comparative Example 4).

[0086] Conclusion: The pavement with elastomer capsules showed better rutting resistance than the non-elastomer group, with Example 1 showing the best performance. This was attributed to the synergistic stabilizing effect of high-viscosity aromatic oil and rubber powder elastomer: high-viscosity oil can enhance the high-temperature cohesiveness of asphalt mixtures, while rubber powder enhances the elastic stability of pavement structure. The synergistic effect of the two significantly alleviated rutting at high temperatures, far superior to the synergistic effect of Comparative Example 4 (low-viscosity oil + elastomer).

[0087] (V) Summary Example 1: Asphalt pavement modified with rubber powder and high-elasticity self-healing capsules achieves multiple technical advantages through the synergistic effect of the capsule wall rubber powder and calcium alginate: 1. Significantly improved overall elasticity: The dynamic rebound modulus at room temperature / low temperature and flexural toughness are increased by 28.75%, 16.00%, and 45.31% respectively compared to the control group, which is superior to other control groups. 2. Outstanding resistance to frost heave: After 15 freeze-thaw cycles, the splitting strength retention rate reaches 79%, and the crack propagation rate is only 34.38% of the control group, which is the best among the five groups. 3. Highly efficient ice layer breaking and de-icing effect: The indoor ice layer detachment area accounts for 72%, and the on-site de-icing efficiency is 85%, which are 2.57 times and 2.66 times that of the control group, respectively. The core reason is the synergistic effect of the elastomer and high viscosity oil. 4. Excellent rutting resistance: The dynamic stability reaches 4650 cycles / mm, which is 49.04% higher than the control group and superior to the four comparative groups with low viscosity oil combinations. In summary, this technology can comprehensively improve the winter freeze-thaw resistance, traffic safety, and high-temperature service stability of asphalt pavements, thereby extending the service life of the pavement.

Claims

1. A high-elasticity asphalt self-healing capsule, characterized in that... The capsule is composed of a calcium alginate / elastomer composite capsule wall and a high-viscosity regenerant core; the mass ratio of sodium alginate to elastomer in the composite capsule wall is 10:(0.5-2), and the mass ratio of the high-viscosity regenerant to sodium alginate is (0.1-0.33):1; the kinematic viscosity of the high-viscosity regenerant at 25°C is 80-130 mPa. s.

2. The high-elasticity asphalt self-healing capsule as described in claim 1, characterized in that... The elastomer is one of rubber powder, nitrile rubber, thermoplastic polyurethane, or styrene-butadiene-styrene block copolymer.

3. The high-elasticity asphalt self-healing capsule as described in claim 1, characterized in that... The high-viscosity regenerator is one of aromatic oil, high-aromatic mineral oil, or heavy petroleum fraction.

4. The preparation method of the high-elasticity asphalt self-healing capsule according to claim 1, characterized in that... Includes the following steps: (1) Add the elastomer to the sodium alginate solution and stir to form a basic suspension; (2) Add high-viscosity aromatic oil and emulsifier to the basic suspension, and prepare an emulsion by shearing; (3) The emulsion was then dropped into a calcium chloride solution to solidify and form wet capsules. Finally, the capsules were dried in an oven to obtain the finished capsules.

5. The preparation method of the high-elasticity asphalt self-healing capsule as described in claim 4, characterized in that... The emulsifier mentioned in step (2) is Tween 80, and the amount added is 0.5-1 wt% of the mass of the base suspension.

6. The preparation method of the high-elasticity asphalt self-healing capsule as described in claim 4, characterized in that... In step (2), the shearing rate is 4000-5000 r / min and the shearing time is 40-60 min.

7. The preparation method of the high-elasticity asphalt self-healing capsule as described in claim 4, characterized in that... The concentration of the calcium chloride solution in step (3) is 5.0 to 10 wt%.

8. The preparation method of the high-elasticity asphalt self-healing capsule as described in claim 4, characterized in that... In step (3), the curing reaction temperature is 25℃ and the reaction time is 30min.

9. The preparation method of the high-elasticity asphalt self-healing capsule as described in claim 4, characterized in that... The drying process in step (3) involves drying at 50°C for more than 5 hours.

10. An asphalt concrete pavement, characterized in that... The high-elastic asphalt self-healing capsule as described in claim 1 was added, with the addition amount accounting for 0.3-0.5 wt% of the mass of asphalt concrete and 8-9 wt% of the mass of asphalt.

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