Microencapsulated Sunflower Oil for Rejuvenation and Healing of Asphalt Mixtures

Abstract

Microencapsulation of rejuvenators was introduced as a new approach to increase the efficiency of rejuvenators toward improving the self-healing rate of asphalt pavement. This study had two primary objectives: (1) to examine the thermal stability of prepared microcapsules containing sunflower oil as core material, and (2) to evaluate the effect of the microcapsule in increasing the self-healing ability of asphalt mixtures. Results showed an acceptable thermal stability of double-walled polyurethane and urea-formaldehyde (PU/UF) microcapsules in the temperature range encountered during mix production. Furthermore, asphalt binder stiffness and m-value measurements demonstrated that microcapsules were successful in decreasing low-temperature stiffness and increasing the m-value of the binder blends. Healing of the cracks defined by reversal of the crack opening was validated in all mixtures through digital image analysis. The mixtures containing sunflower oil as a rejuvenator showed the best performance in self-healing efficiency. However, the healing efficiency of the mix with microcapsules was lower than the mixture with the rejuvenator. This is possibly because of the amount of rejuvenator released from the microcapsules, which was limited to the microcapsules around the crack and not all the rejuvenator available in the mix. The samples healed at room temperature showed higher healing efficiency, compared with the specimens in the oven. The difference in healing efficiency between the two healing conditions (room temperature versus oven temperature) was the largest at Day 1; however, the difference became less pronounced with the progression of healing.