Effect of Temperature on the Fracture Characteristics of Hot Mix Asphalt Mixtures Using the Semi-Circular Bend (SCB) Test

This study investigates the temperature-dependent fracture behavior of hot mix asphalt using the Semi-Circular Bend (SCB) test and nonlinear fracture mechanics principles. SCB specimens prepared from gyratory-compacted mixtures were notched at three depths and tested at four different temperatures (23 °C, 0 °C, -11 °C, and -22 °C). The Two-Parameter Model (TPM), the compliance approach, and the J-integral method were employed to determine nonlinear fracture parameters, including fracture toughness, effective crack length, elastic modulus, and critical crack tip opening displacement (CTODc). Load CMOD curves were analyzed to determine elastic modulus from initial compliance values, while nonlinear fracture toughness was calculated based on equivalent crack length at peak load. Results showed that temperature is the most dominant variable influencing fracture behavior, explaining more than 75% of the observed variation. As the temperature decreased, the elastic modulus and fracture toughness significantly increased, indicating stiff and brittle behavior, whereas higher temperatures led to increased CTODc and more ductile fracture characteristics. The findings demonstrate that nonlinear fracture mechanics and TPM provide reliable and physically meaningful fracture characterization for asphalt mixtures. The outcomes highlight the importance of temperature in pavement fracture performance and confirm that nonlinear fracture approaches are useful tools for performance-based asphalt pavement design, particularly in cold climate regions susceptible to thermal cracking.