1374174 - Measurements of Asphalt Concrete’s Aggregate Dielectric Constant Using Ground Penetrating Radar

Over the past three decades, ground penetrating radar (GPR) has been implemented for various applications in civil engineering infrastructure, including predicting in-situ density of asphalt concrete (AC) pavements. To overcome the limitations of predicting asphalt concrete density using statistical regressions, the electromagnetic mixing theory may be used. The mixing theory relates the bulk dielectric constant of the AC mix to its components’ dielectric constants and their corresponding volumetric proportions. Volumetric proportions of AC components could be determined from the job mix formula. The dielectric constants of binder and air components are known to be approximately 3 and 1, respectively. However, cores are usually obtained to back-calculate the aggregates’ dielectric constant, which depends on aggregate minerology. In this study, an aggregate dielectric constant database is being generated. Laboratory testing of common aggregate types in Illinois (e.g., Limestone, Dolomite, Granite, and Traprock) have been conducted to determine their dielectric constant. This allows predicting AC density nondestructively without taking cores. This approach was implemented on an AC pavement section at Bourbonnais, IL. Al-Qadi Cao Abufares (ACA) density model was applied on the collected raw GPR data to determine AC density. The results were compared to actual core densities taken for quality control purposes.