| As the period of comprehensive road maintenance arrives in China,the significance of road surface maintenance technology in the field of road traffic has become increasingly prominent.Although traditional maintenance techniques have partly addressed the problem of asphalt road cracking,they still have shortcomings,such as short service life,high maintenance costs,and environmental pollution.Asphalt selfhealing microcapsule technology can achieve self-healing during the early stages of micro-crack formation in asphalt pavement,thereby extending the pavement’s service life.The application of this technology can meet maintenance needs,reduce operating costs,improve transportation speed and safety,and promote the development of new pavement materials and long-life pavements,which has long-term significance for the sustainable development of the road traffic field.This article develops self-healing microcapsules suitable for asphalt pavements,prepares self-healing asphalt using microcapsules,and analyzes its properties to evaluate its self-healing ability.The main research content is as follows:Firstly,sunflower seed oil and urea-formaldehyde resin were used as core and shell materials,respectively,to prepare microcapsules.The mechanism of microcapsule formation was revealed by analyzing the reaction mechanism of urea-formaldehyde resin and the encapsulation process of self-healing microcapsules.The study discussed the effects of p H value,reaction temperature,and monomer ratio on urea-formaldehyde prepolymer.Additionally,the study analyzed the effects of surfactant concentration,coreshell ratio,emulsification rate,p H value,and endpoint reaction temperature on selfhealing microcapsules using single-factor analysis.The Box-Behnken response surface method was used to determine the optimal preparation process parameters,which were an emulsification rate of 1000 r/min,a core-shell ratio of 1.71,a surfactant concentration of 0.70 wt%,a p H value of 2.84,and a reaction temperature of 60°C.The microcapsules prepared under the optimal process were subjected to performance testing.The results showed that they had a regular spherical morphology,a D50 of about 51.41 μm,a core content of 81.47%,a thermal decomposition temperature of 230°C,and a hardness and Young’s modulus of 0.26 GPa and 2.5 GPa,respectively.The performance of self-healing asphalt containing microcapsules was investigated.The maximum content of microcapsules was determined based on the extension index.The blending and construction temperatures of the self-healing asphalt were analyzed by means of the viscosity-temperature curve.The high and low-temperature rheological properties of the self-healing asphalt containing microcapsules were studied using dynamic shear rheometer(DSR)and bending beam rheometer(BBR),respectively.The results showed that the self-healing asphalt containing microcapsules exhibited enhanced resistance to high-temperature deformation,but reduced stress relaxation and lowtemperature deformation capability.The microcapsules remained intact and uniformly dispersed in the asphalt as observed by optical microscope(OM)and X-ray computed tomography(XCT).Finally,temperature-frequency scan tests were conducted on the self-healing asphalt with microcapsules.The flow behavior index n was used to characterize its self-healing performance.The results showed that microcapsule rupture improved the asphalt’s flow behavior and reduced its temperature dependence for self-repair.The self-healing ability of the asphalt was tested with the extension self-repair test.The study also discussed the impact of microcapsule content and temperature on the self-healing effect.To simulate self-healing in intermittent and continuous traffic flow,two intermittent self-healing dynamic shear rheometer(DSR)tests were designed.The study analyzed the effect of microcapsule content on the self-healing of the asphalt.Based on the results of the two intermittent tests,the study recommends a microcapsule content of 0.5 wt% to 0.7 wt%for self-repair. |
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