Effect of SCB specimen size on mode I fracture parameters of asphalt concrete at low and intermediate temperatures

This research investigates the impact of specimen size on the fracture properties of asphalt concrete. Fracture experiments were conducted on semi -circular bend (SCB) specimens with three different radii of 75 mm, 43 mm, and 32 mm at low and intermediate temperatures (-30 degrees C, -20 degrees C, and 10 degrees C) under pure mode I loading. The findings indicate that an increase in specimen size leads to an improvement in fracture toughness (KC), work of fracture (Wf), and fracture energy (Gf). However, this effect becomes less significant as temperature rises. Additionally, the crack resistance index (CRI) demonstrates that the brittleness of asphalt concrete increases with decreasing temperature and increasing specimen size. Due to the nonlinear behavior of fracture at 10 degrees C, equivalent fracture toughness (K*C) was also calculated. Accordingly, the values of K*C at 10 degrees C were higher than those of KC. In the next step, the modified maximum tangential stress (MMTS) criterion is used to calculate the value of the fracture zone size (rc), which is influenced by both the specimen size and temperature. Finally, a correlation is established between specimen radius and mode I apparent fracture toughness at various temperatures using the experimental results and MMTS criterion. These results provide valuable insights into the behavior of asphalt concrete under different conditions, which can be used to properly design and maintain asphalt pavements.