Characterization and Prediction of Size‐Independent Fracture Properties of SBS‐Modified Asphalt Concrete Using a Boundary Effect Model

ABSTRACT To characterize the quasi‐brittle fracture behavior of highly heterogeneous asphalt concrete structures, it is essential to identify fracture parameters that are independent of specimen size and the crack‐tip damage zone. This study develops a boundary effect model for determining size‐independent fracture parameters—tensile strength, fracture toughness, and fracture energy—of Styrene‐Butadiene‐Styrene (SBS)‐modified asphalt concretes. These parameters are directly derived from peak loads obtained in small notched three‐point bending tests at −10 , 0 , and 23 , with notch depths of 7 and 10 . The mean, upper, and lower limits of the fracture parameters are determined through normal distribution analysis, avoiding curve fitting. Structural fracture curves are constructed to evaluate the fracture behavior. Furthermore, the peak load predictions and theoretical minimum size meeting linear elastic fracture mechanics are quantified. The effects of discrete coefficients, discrete numbers, and average grain sizes are also analyzed to reflect the material's heterogeneity. Summary Improved BEM enables precise prediction of fracture parameters from peak load directly. Size‐independent fracture parameters are validated under varying notch depths and temperatures. Normal distribution avoids fitting errors, enhancing the reliability of fracture assessment. Quasi‐brittle behavior clarified via discrete metrics reflecting asphalt heterogeneity