Development and propagation of surface-initiated longitudinal wheel path cracks in flexible highway pavements

The primary distress mode of over 90% of high-type bituminous pavements scheduled for rehabilitation in Florida is longitudinal wheel path cracking. This situation creates an immediate need for a clear definition of the growth mechanisms of this costly mode of failure. These cracks initiate at the surface of thick and thin asphalt concrete layers and propagate downwards in an opening mode, as evidenced by observations of trench sections and cores taken from field sites. Literature review has shown that several researchers have presented observations and/or hypotheses that attempt to explain the surface cracking phenomenon, but a complete identification for the crack propagation mechanism that considers factors found in the field does not exist.; Parametric study analyses performed were focused on predicting near-surface crack tip stresses and determining which factors result in tensile crack growth downwards from the surface of the pavement. The finite element analysis program ABAQUS was used along with other analytical models to compute stress intensity factors at the crack tip and to determine the propensity of effects such as pavement structure, crack length, load spectra (load magnitude and wander in wheel path), tire-pavement interface stresses, and temperature- or aged-induced stiffness gradients. Stress analyses were performed using actual measured radial truck tire-pavement interface stresses obtained from a tire research company in Ohio. Thermal analyses were conducted using temperatures measured by National Oceanic and Atmospheric Agency (NOAA) daily for several years in various north-central Florida locations. Furthermore, a sensitivity analysis of finite element model types indicated that modified 2D pavement models are suitable for representing 3D pavement bending.; The physical presence of a crack or discontinuity must be considered in pavement design in order to properly account for surface crack growth in asphalt concrete pavements. The load spectra, such as tire-pavement interface stresses produced under radial truck tires and load wander in the wheel path, in combination with stiffness gradients caused by seasonal temperatures and aging, will apparently result in tensile failure that is the primary mechanism of surface-initiated longitudinal crack propagation in the wheel paths.