Parameters of pavement structure.

Self-healing microcapsules in the asphalt pavement must be kept intact under vehicle load to ensure there is enough rejuvenator in capsules when cracks appear in asphalt pavement. In this paper, the crack resistance of self-healing microcapsules in asphalt pavement was evaluated. Firstly, an expanding multi-scale analysis was conducted based on proposed mesoscopic mechanical models with the aim to determine the mechanical parameters for the following contracting multi-scale analysis. Secondly, the periodic boundary condition was introduced for the contracting multi-scale analysis and the stress field of the capsule wall was obtained. Finally, the effects of the design parameters of the microcapsule on its crack resistance in asphalt pavement were investigated. The results showed that the incorporation of microcapsules has almost no effect on the elastic constants of the asphalt mixture. The core could be simplified as an approximately incompressible solid with the elastic constants determined by the proposed mesoscopic mechanical model. With the increase of the modulus of the capsule wall, the mean maximum tensile stress of the capsule wall increased from 0.372 MPa to 0.465 MPa, while with the decrease of the relative radius of the capsule core, the mean maximum tensile stress of the capsule wall increased from 0.349 MPa to 0.461 MPa. The change in the mean maximum tensile stress of the capsule wall caused by the change of capsule diameter was within 5%. The relative radius of the capsule core and the elastic modulus of capsule wall were two key parameters in capsule design. Besides, the microcapsules with the wall made of resin would not crack under the vehicle load before microcracks occurred in asphalt pavement.

沥青路面中的自修复微胶囊（self-healing microcapsules）需在车辆荷载作用下保持完整，以确保当沥青路面出现裂缝时，微胶囊内能够留存足够的再生剂（rejuvenator）。本文针对沥青路面内自修复微胶囊的抗裂性能展开了评价。首先，基于提出的细观力学模型（mesoscopic mechanical models）开展扩展多尺度分析，以确定后续收缩多尺度分析所需的力学参数；其次，引入周期性边界条件（periodic boundary condition）进行收缩多尺度分析，得到了胶囊壁的应力场（stress field）；最后，探究了微胶囊设计参数对其在沥青路面中抗裂性能的影响。研究结果显示，掺入微胶囊对沥青混合料（asphalt mixture）的弹性常数（elastic constants）几乎无影响。微胶囊芯材可简化为近似不可压缩固体（incompressible solid），其弹性常数由所提出的细观力学模型确定。随着胶囊壁模量（modulus）的提升，胶囊壁的平均最大拉应力（tensile stress）从0.372 MPa增至0.465 MPa；而随着胶囊芯材相对半径的减小，胶囊壁的平均最大拉应力从0.349 MPa增至0.461 MPa。胶囊直径变化对胶囊壁平均最大拉应力的影响幅度控制在5%以内。胶囊芯材相对半径与胶囊壁弹性模量是微胶囊设计的两项核心参数。此外，采用树脂制备壁材的微胶囊，在沥青路面出现微裂缝之前，不会在车辆荷载作用下发生开裂。