Structural condition assessment of asphalt pavement semi-Rigid bases using FWD deflection basin parameters

Abstract

Assessing structural conditions of semi-rigid bases in asphalt pavements is essential for effective base treatment in reconstruction and expansion (R&E) projects. Although various falling weight deflectometer (FWD) parameters have been developed for this purpose, field-validated parameters are still missing. This study identifies the appropriate FWD deflection basin parameter (DBP) through sensitivity analysis, correlation examination, and on-site milling and inspection. Findings indicate D20-D60 as the most suitable DBP, with 23 µm and 40 µm thresholds for warning and severe conditions, respectively. The correlation between D20-D60 and cracking rate suggests that high cracking rates suggest base weakness, whereas low rates may not guarantee structural integrity due to maintenance masking effects. On-site milling further confirmed this finding, demonstrating the alignment between D20-D60 assessments and field observations. The outcome of this study is anticipated to provide a practical DBP for evaluating semi-rigid base conditions and to inform base treatment strategies in R&E projects.