Assessment of binder aggregate behavior of bituminous mixes using log-periodic feedlines based microstrip filter

This paper presents a comprehensive study on the characterization of bituminous mixes using microwave-based measurements. We investigated the electromagnetic properties of different samples, such as bituminous concrete (BC) and open-grade friction course (OGFC), using a novel two-port ring filter with log-periodic feedlines (operating from 0.35 - 0.65 GHz) designed on the RT/Duroid 5880 substrate. The specimens were evaluated based on average attenuation and group delay measurements, revealing distinct electromagnetic behaviors. The specimens’ calculated and measured flow rates were correlated to these factors (with an error of 0.05). This shows that the filter can accurately measure the flow rates needed to study how the binder and aggregate interact in bituminous mixes. Findings show that OGFC and BC samples are very different in how they respond to electromagnetic fields and how they flow. This shows how sensitive and valuable microwave techniques are for studying bitumen and building roads.