微胶囊沥青自愈合行为与微观机理

Self-healing behavior and microscopic mechanism of microencapsulated asphalt

为探究微胶囊沥青自愈合行为及其影响因素,采用原位聚合法制备微胶囊,以宏观试验与微观试验相结合的方法,从微胶囊的应力控释、毛细作用与扩散行为三方面揭示其自愈合行为的微观机理;进行了微胶囊沥青的拉拔-愈合-拉拔试验,采用自愈率(试件愈合后拉拔强度与初始拉拔强度之比)作为评价指标,考察了微胶囊掺量和愈合时间对微胶囊沥青自愈率的影响规律;进行了微胶囊沥青的动态剪切试验,对比疲劳试验前后微胶囊沥青的微观形态,考察微胶囊的应力控释特性;借助荧光显微镜,可视化了芯材在微裂缝中的横、纵向毛细作用与在沥青中的扩散过程;借助显微图像软件中的实时录像功能,观测微胶囊沥青微裂缝的愈合过程;采用红外光谱测试微胶囊芯材和拉拔-愈合-拉拔试验前后微胶囊沥青的官能团,考察芯材在沥青中的释放行为。分析结果表明:微胶囊掺量从0提升至8%时,自愈率从16.70%提高至48.92%,表明微胶囊沥青的自愈率随着微胶囊掺量的增加而逐渐增大,当微胶囊掺量为4%时,愈合120 min的自愈率是愈合10 min的1.85倍,表明微胶囊沥青的自愈率随着沥青愈合时间的延长而逐渐增大,这说明提高荷载休息期和微胶囊掺量对增强微胶囊沥青自愈合性能具有积极作用;微胶囊沥青的微观自愈合机理为,微裂缝尖端应力刺破微胶囊的囊壁而释放囊芯愈合剂,芯材在毛细管作用力的驱动下流动、扩散,并与附近的沥青接触、浸湿,从而达到修复沥青微裂缝的目的。

In order to explore the self-healing behavior of microencapsulated asphalt and its influencing factors,microcapsules were prepared by in-situ polymerization,and the micro-mechanism of self-healing behavior of microcapsules was revealed from three aspects:stress-controlled release,capillary action,and diffusion behavior by combining macro-test and micro-test.The pull-heal-pull test of microencapsulated asphalt was carried out,the self-healing rate(the ratio of pulling strength after healing to initial pulling strength) was used as the evaluation index,and the effect rules of microcapsule content and healing time on the self-healing rate were investigated.The dynamic shear rheological test of microencapsulated asphalt was carried out,and the stress-controlled release characteristics of microencapsulated asphalt were investigated by comparing the microstructures of microencapsulated asphalt before and after the fatigue test.The horizontal and vertical capillary action of core material in micro-cracks and the diffusion process of core material in microencapsulated asphalt were visualized by the fluorescence microscope.The healing process of micro-cracks in microencapsulated asphalt was observed by the real-time video recording function in microscopic image software.The release behavior of core material in microencapsulated asphalt was investigated by testing the functional groups of microcapsule core material and microencapsulated asphalt before and after the pull-heal-pull test based on infrared spectrum.Analysis results show that the self-healing rate increases from 16.70% to 48.92% when the microcapsule dosage increases from 0 to 8%,indicating that the self-healing rate of microencapsulated asphalt increases gradually with the increase of microcapsule dosage.When the microcapsule dosage is 4%,the self-healing rate in 120 min is 1.85 times that in 10 min,indicating that the self-healing rate of microencapsulated asphalt increases gradually with the extension of asphalt healing time.Obviously,increasing the load rest period and microcapsule dosage has a positive effect on enhancing the self-healing performance of microencapsulated asphalt.The microscopic self-healing mechanism of microencapsulated asphalt is that the microcapsule shell is punctured under the stress at the tip of the microcrack,then the core healing agent is released,so that the core material flows and diffuses under the drive of capillary force,contacts with nearby asphalt and is soaked,so as to achieve the purpose of repairing asphalt microcracks.2 tabs,12 figs,36 refs.