The concept of self-healing asphalt mixtures by bitumen temperature increase has been used by researchers to create an asphalt mixture with crack-healing properties by microwave or induction heating. Metals, normally steel wool fibers (SWF), are added to asphalt mixtures prepared with virgin materials to absorb and conduct thermal energy. Metal shavings, a waste material from the metal industry, could be used to replace SWF. In addition, reclaimed asphalt pavement (RAP) could be added to these mixtures to make a more sustainable road material. This research aimed to evaluate the effect of adding metal shavings and RAP on the properties of asphalt mixtures with crack-healing capabilities by microwave heating. The research indicates that metal shavings have an irregular shape with widths larger than typical SWF used with asphalt self-healing purposes. The general effect of adding metal shavings was an improvement in the crack-healing of asphalt mixtures, while adding RAP to mixtures with metal shavings reduced the healing. The average surface temperature of the asphalt samples after microwave heating was higher than temperatures obtained by induction heating, indicating that shavings are more efficient when mixtures are heated by microwave radiation. CT scan analysis showed that shavings uniformly distribute in the mixture, and the addition of metal shavings increases the air voids. Overall, it is concluded that asphalt mixtures with RAP and waste metal shavings have the potential of being crack-healed by microwave heating.

Microwave heating of asphalt mixtures containing metal fibers is a promising technology for asphalt pavement rehabilitation. The main characteristic of these types of mixtures is that they have the ability to self-heal their cracks when external microwave heating is applied. Prior to this study, the assessment of crack-healing has only been conducted in mixtures prepared with virgin aggregate materials. This paper, however, presents results of research in which the effect of adding reclaimed asphalt pavement (RAP) and metallic fibers was studied. The volumetric properties of the mixtures indicated that the air voids content increased with the fiber content. The indirect tensile stiffness modulus of the mixtures increased with the addition of RAP. Clusters of fibers were found in the mixtures by means of CT-Scan analysis. The general effect of RAP addition was a decrease in the healing of the mixtures, and the effect of fibers was an increase in the healing. Overall, it is concluded that asphalt mixtures with RAP and metal fibers have the potential for crack-healing via microwave heating.