Performance Evaluation and Self-Healing Properties of Asphalt Mixtures Containing RAP Materials and Rice Bran Oil Capsules

Environmental and financial concerns have motivated road authorities to limit the utilization of natural resources in road construction, particularly the resources that cannot be renewed. To fulfill such requirements, pavement researchers have successfully utilized reclaimed asphalt pavement (RAP) materials as an attractive alternative to their natural counterparts. In practice, rejuvenators are often used to amend the properties of the RAP binder. The addition of the rejuvenator in the mixtures containing RAP materials could completely change the behavior of the mixtures. Such changes in the mechanical responses of the asphalt mixtures are essential aspects of pavements’ lifetime performance and should be considered during the asphalt mix design. Although the self-healing performance of asphalt mixtures prepared by virgin materials is well researched, a few research studies have been carried out to investigate the healing properties of asphalt mixtures prepared by RAP materials. This paper examines the influence of the addition of rice bran oil (RBO) capsules on the self-healing performance and mechanical properties of the asphalt mixtures containing various amounts of RAP: 20% and 40% and control mix containing no RAP material. In general, it was found that the addition of the capsules into the mixtures with RAP materials decreased the resilient modulus and flow number (FN) values. As a consequence of the fact that some part of the rejuvenator inside capsules is released into the mixture during mixing and compaction; moreover, the skeleton structure of capsules is weaker than aggregates, which allows the reduction in the maximum density. Further, the addition of capsules into the asphalt mixture without RAP has increased the fracture energy since the inclusion of capsules would increase the bond between asphalt binder and aggregates. In contrast, encapsulated mixtures containing RAP materials had lower fracture energy values compared with their corresponding mixtures without capsule addition. Furthermore, the results revealed that the addition of RBO capsules to the mixtures with RAP materials increased the healing performance of mixtures due to the fact that the reduced viscosity of aged asphalt binder had increased following the gradual release of the rejuvenator; therefore, the microcracks were closed and prevented further damages.