Investigation on the effect of geometrical and mechanical characterization of pavement layers on fatigue life of HMA overlay

Cracking of asphalt layers and pavements is one of the most common modes of failure in roads and highways, which can significantly increase the costof repair and rehabilitation. Since asphalt mixtures can behave as brittle materials at low temperature,brittle fracture and crack growth in pavements is usually observed at the surface of roads located in cold regions. Traffic loading (due to the weight of moving vehicles) and thermal stress (induced by daily or seasonal variations of field temperature), are two major parameters affecting nucleation and propagation of cracks inside the pavements. Reflective cracking is often observed in the overlays, and the growth of such cracks is an important problem in field. In this paper, a multi-layer asphalt pavement containing a reflective crack is analyzed and fatigue life, crack path and effective stress intensity factor are determined. Using extensive two-dimensional finite element analyses, the effect of modulus and thickness of overlay and existing asphalt layer on fatigue life of asphalt pavement were investigated. The results demonstrate that exceeding the thickness of overlay from a special amount causes abrupt increase in the fatigue life of asphalt pavement and also the HMA stiffness were the most influencing factors on the pavement fatigue life. Among the mechanical and geometrical properties of asphalt layers, overlay thinness has the most impact on the crack growth path. By increasing overlay thickness the crack grow path will have a smaller deviation from vertical direction.