Aggregate gradation as a key parameter in optimizing asphalt mixtures for wireless energy transmission

Abstract

The increasing adoption of electric vehicles and the goal of reducing carbon emissions have steadily heightened interest in wireless power transfer (WPT) technologies within transportation infrastructure. This study aims to optimize the dielectric properties of asphalt pavement materials to improve WPT efficiency. Accordingly, four different asphalt mixtures are designed with maximum aggregate sizes of 12 mm, 19 mm, 25 mm, and 38 mm, and five specimens are produced for each mixture under laboratory conditions. The prepared specimens are placed between two coils with a 6 cm separation, and measurements are carried out in the 100-110 kHz range using a Vector Network Analyzer (VNA). The measurement results are compared with reference data in air, and the electromagnetic wave transmission performance of the asphalt samples is evaluated. The analysis findings showed that among the four mixtures, the mixture identified as M4-which has smaller aggregate sizes and a relatively high bitumen content-achieved the highest transmission efficiency (96.6 %). This superior performance stems from the mixture's dielectric properties being closer to those of air and from the decreased void ratio within the material, which together minimize electromagnetic losses. In addition, the consistent outcomes obtained for samples prepared from different mixtures validate methodological repeatability. The results indicate that selecting an appropriate asphalt composition can significantly enhance the efficiency of roadway-based wireless charging systems and offer a sustainable improvement proposal for electric vehicle infrastructure.