A new temperature correction methodology for FWD deflections on full-depth asphalt pavements

Falling weight deflectometer (FWD) deflections are key indicators of flexible pavement structural capacity, but are strongly influenced by test temperature. This study proposes a new method to correct temperature effects in FWD measurements for full-depth asphalt pavements. Finite element simulations were conducted to quantify pavement responses over a wide temperature range, from very low to very high. Temperature correction factors were formulated using a unified Sigmoid function that incorporates effective pavement temperature, asphalt layer thickness, and subgrade stiffness. Results show that temperature affects not only the central deflection but also deflections farther from the load, highlighting the need to correct the entire deflection basin. A new evaluation metric, the temperature correction difference index (TCDI), is introduced to evaluate the accuracy of correction strategies. Among temperature definitions, quarter-depth and layer-interface temperatures yield more accurate corrections than conventional mid-depth or average temperatures, especially for thick pavements. The framework also integrates machine learning to estimate temperature profiles from readily available inputs (surface temperature, air temperature, and time of day). Field validation demonstrates improved accuracy relative to conventional methods and supports practical implementation by transportation agencies.