Fracture resistance of HMA mixtures under mixed mode I/III loading at different subzero temperatures

In the present work, fracture resistance of two types of hot mix asphalt (HMA) mixtures (i.e. the first one contained a normal binder, and the second one contained the same binder but modified by crumb rubber of recycled tyres) was successfully characterized using an asymmetric disc bend specimens. The experiments were performed under different loadings of pure mode I, pure mode II and two mixed mode I/III at three subzero temperatures. The HMA mixture contained crumb rubber was found to more resist against the fracture than that contained the normal binder. The results also showed that by decreasing the temperature, fracture resistance of the HMA mixtures first increased and then reduced. In addition, as the proportion of mode III at the crack tip (from pure mode I to pure mode III) increased, the HMA resistance against the crack growth reduced. Meanwhile, for the pure mode I loading, the crack growth path was along the initial crack; while, by adding the mode III to the mode I at the crack tip, the crack growth path twisted correspondingly further.