Heating potential of aggregates in asphalt mixtures exposed to microwaves radiation

Abstract Recent studies have shown that microwave energy can repair micro-cracks in asphalt mixtures by heating them. This process may be described as assisted self-healing. Several studies have tested different types of asphalt mixtures with various metallic additions in order to increase the susceptibility to microwaves and consequently the effectiveness of the healing process. Usually, aggregates account for more than 90% in weight of the asphalt mixture, playing an important role in heating efficacy. This is due to the different energy-heating ramps for each type of aggregate giving rise to different temperatures and energy-repair rates. The studies carried out on this subject are scarce and in no case clarify the influence of the aggregate type in terms of microwave susceptibility of asphalt mixtures. Focusing efforts on this issue would promote a change in the manufacturer's design or repair of asphalt pavements, since it would extend the service life and will greatly reduce the economic and polluting effects, such as the release of greenhouse gases into the atmosphere and the volume of waste from the maintenance of roads. In this study, by means of different laboratory tests, detailed petrographic, mineralogical, and chemical analyses have been carried out on 10 different aggregates frequently used for pavements construction. Additionally, a procedure has been developed to measure the aggregates heating potential under microwave radiation. Based on the results of the study a classification for aggregates, according to their heating potential under microwaves, is proposed. This classification should be taken into account in order to optimise the asphalt mixture formula and to estimate the energy to be applied to asphalt mixtures for effective assisted self-healing.