Non-Destructive Evaluation of Strength and Porosity of Bituminous Mixes Using Log- Periodic Feedlines-Based Ring Filter

This study examines the quality and structural integrity of bituminous mixes in road construction. An innovative and non-destructive evaluation (NDE) approach is employed, specifically utilizing a log-periodic feedlines (LPFs) based ring filter. This study investigates the correlation between the existence of voids, attenuation, and group delay in various bituminous mix samples through the utilization of microwave imaging. The results show that for non-porous samples with 3.24% average porosity and 16.978 kN average load, the slope change for attenuation (
$\alpha $
) is 56.9%, while group delay (
$\tau _{g}$
) is 43.94%. Porosity changes significantly, with a 50% shift in slope
$\alpha $
and a 58% change in
$\tau _{g}$
, respectively, demonstrating that the areas with higher group delay and attenuation suggest the existence of voids. The relationships between group delay and attenuation with load and porosity are indicated by
$R^{2}$
values of 0.82 and 0.79 for load and 0.85 and 0.79 for porosity, respectively (for porous samples) and 0.83 and 0.8 for load and 0.82 and 0.86 for porosity, respectively (for non-porous samples). This provides valuable knowledge regarding potential deficiencies in road construction materials. The research presented in this study contributes to the importance of electromagnetic (EM) wave-based testing methods by establishing a correlation between these variations and the quality of bituminous mixes.