Aging effect on combined mode fracture resistance of bitumen

Crack growth behaviour of aged and unaged 30/40 asphalt binder at subzero temperature was studied both experimentally and theoretically using a test sample called inclined notched bend beam specimen. A series of fracture tests were conducted on this specimen at two subzero temperatures and different combinations of modes I and II. The fracture toughness of tested asphalt binder was significantly dependent on the aging condition such that the load-carrying capacity of aged bitumen was up to 60% less than the corresponding fracture resistance of unaged bitumen. Moreover, the effective fracture resistance value of tested binder was reduced by increasing the contribution of mode II and also decreasing the test temperature. The obtained experimental results for both binder types were also evaluated theoretically using a stress base crack growth theory.