Although asphalt concrete overlay systems represent a rapid and economical
alternative for the repair of deteriorated pavements, reflective cracking continues to be major
cause of premature deterioration of these systems. A better understanding of the complex mechanisms
behind reflective cracking in asphalt overlays must first be obtained before significant
advances in reflective crack prevention and mechanics-based overlay design can be fully realized.
Traditional modeling approaches have not provided a direct means for the study of crack initiation
and propagation in pavements. The cohesive zone fracture modeling approach provides a rational
means for modeling cracking in structural systems consisting of quasi-brittle materials, as a finite
length scale associated with the fracturing process is considered. A bi-linear cohesive zone model
(Song et al., 2006) was used in the simulation of cracking in three field pavement sections studied
in a recent NSF GOALI project. Detailed field performance data, especially crack maps from
visual surveys were obtained and compared to the numerical simulation results. The temperature
boundary conditions were generated using the Enhanced Integrated Climatic Model developed by
Dempsey et al. (1990) based upon air temperatures obtained from National Weather Service databases.
Viscoelastic bulk and cohesive fracture material properties for these pavement sections
were obtained by laboratory testing of specimens fabricated from 150-mm field cores, in accordance
with a new, efficient testing suite (Wagoner et al., 2006). A series of numerical simulations
were performed using finite element models, which provided new insights towards the mechanisms
of cracking in asphalt concrete overlays under thermal and mechanical loads. A series of
finite element analyses were performed with hypothetical overlay configurations in an effort to
demonstrate the concept of a “simulation-guided” interlayer/overlay design process, which allows
the direct consideration of initiating and propagating cracks in one or more overlay layers.