Microwave crack healing on conventional and modified asphalt mixtures with different additives: an experimental approach

Self-healing asphalt by increasing bitumen temperature using microwave radiation is an effective technique for crack-healing on asphalt mixtures. Normally, these types of asphalt mixtures contain metal additives that promote microwave heating. However, results from the literature suggest that crack-heling would be possible without additives. If this is possible, existing asphalt pavements could be healed by microwave heating. The objective of this research is to evaluate the crack-healing capabilities of conventional asphalt mixtures without metal additives. With this purpose, the authors studied and compared the crack-healing capabilities of conventional asphalt mixtures without metal additives with modified mixtures containing steel fibre, metal shavings, and Silicon Carbide, the last being a novel ceramic material for the crack-healing of asphalt mixtures by microwaves. The authors conducted three-point bending tests on semi-circular asphalt samples to calculate the flexural strength of asphalt. Results of the research showed that the effect of additives that promote microwave heating on the crack-healing of mixtures was a small reduction of the average healing ratio. Additionally, it was found that the effect of additives that promote microwave heating on the surface temperature of samples was either a small increase or small decrease, similar to the effect observed in the healing of mixtures. X-Ray computed tomography results showed that the virgin aggregates used contained metals, which explains the heating and good crack-healing of the reference mixtures. Overall, results of crack-healing tests indicate that asphalt mixtures with aggregates that naturally heat with microwave radiation could be crack-healed without the addition of additives to promote microwave heating.