Investigation of the combination of microwave heating and calcium alginate capsule rejuvenation healing methods for cold mix asphalt considering the type of compaction effort

Abstract

Healing behavior of asphalt mixes can affect the pavement life and life cycle cost. Effects of encapsulated rejuvenators and microwave heating methods (as two approaches to improve self-healing behavior) on the cold mix asphalt (CMA) were studied separately and simultaneously at different compaction conditions (i.e., different types and levels of compaction). For this aim, capsules of calcium alginate (CAG) loaded with waste sunflower oil (WSO) and waste engine oil (WEO) were used as encapsulated rejuvenators and iron (Fe) powder was used as a heat conductive material to spread microwave heating into the samples. Moreover, the synergetic effect of powder-based heat-absorbing additives and encapsulated rejuvenators on the healing performance (HP) was also investigated. The chemical test results showed that the Fe powder is compatible with the bitumen emulsion. Pre- and post-healing semi-circular bending (SCB) fracture experiments were conducted before and after healing to check for the effect of the healing method and compaction effort on the HP of CMA. The results indicated higher effectiveness of the microwave heating rather than the encapsulated rejuvenators for facilitating the healing of cracked areas in asphalt mixes. Combining microwave heating and encapsulated rejuvenation methods was not successful in improving the HP, and the healing index was reduced 10 to 15% when both methods were combined. Compaction condition was more influential than the healing method, and the adverse impact of inadequate compaction could not be compensated with any healing methods. It was shown that the healing index can be improved by more than 10% when a proper compaction was applied to the specimens.