Fracture Mechanisms in Asphalt Concrete

Micromechanical processes that lead to fracture of asphalt concrete are characterized through four-point bending tests of asphalt concrete beams, and through a series of experiments which model a fundamental, previously undocumented crack arrest and toughening mechanism observed in asphalt concrete. These latter tests are performed on idealized bitumen and aluminium specimens. The results show that failure of asphalt concrete occurs primarily through the growth and coalescence of voids within the bitumen at high temperatures, and primarily through brittle fracture either within the bitumen or along the interfaces between the bitumen and the reinforcing rocks at lower temperatures. The results also show that the toughness of asphalt concrete is enhanced by the ability of reinforcing rocks to stop the growth of cracks by deflecting their paths.