Modes I and II stress intensity factors of semi-circular bend specimen computed for two-phase aggregate/mastic asphalt mixtures

The cracking behavior of asphalt mixtures in the shape of angled edge crack semi-circular bend (SCB) specimens created by the generation and packing algorithm was investigated numerically. Using extensive two-dimensional finite element analyses, the effects of crack length and crack inclination angle, elastic modulus of aggregates and mastic parts, Poisson's ratios of aggregates and mastic parts, shape of aggregates, distribution pattern for the aggregates inside the asphalt mastic, crack tip location, and air void distribution on geometry factors (Y-I and Y-II) were investigated. It was shown that the crack tip location has a significant effect on the magnitude and sign of geometry factors but the shape of aggregates had no sound influence on both modes I and II stress intensity factors. Geometry factors obtained from heterogeneous modeling (i.e. two-phase aggregate/mastic asphalt mixture) when the crack tip is located inside the aggregates were greater than those obtained from homogeneous model. On the other hand, if the crack tip is located inside the mastic part, the geometry factors will be smaller than the homogeneous SCB model. The crack growth path was predicted using the maximum tensile stress criterion. It was shown that the aggregates could change the crack growth path locally; however, the general direction of crack growth in heterogeneous and homogeneous modeling is the same.