Prediction of Thermal Reflection Cracking in West Texas (18-3)

An economical means of rehabilitating deteriorated pavement is through the use of an overlay. The performance of overlay systems has, however, been far from satisfactory as the performance of any one system has varied widely among different installation sites. This study presents a rational approach for the prediction of overlay life and gives recommendations which are expected to extend the life of overlays. The predictions are made using linear elastic and viscoelastic stress analysis and viscoelastic fracture mechanics. Initially, a prediction scheme for viscoelastic thermal stresses in the overlay and old asphalt surface is used to predict thermal stresses more accurately than any previous attempt. These stresses are then applied to the crack surface to study the effects of material properties on crack development. The stress intensity factors necessary for this analysis are calculated using the finite element technique with the crack tip elements developed by Pian. Predictions of service life are made using the empirical relationship developed by Paris. The results show that there are three states of crack growth in an overlay each of which require different layered arrangements of material properties to lower the stress intensity factor and thus retard crack growth. The influence of viscoelasticity and elasticity properties on reduction of crack growth are presented with the service lives for typical asphaltic concretes. Computer codes are developed for each calculation step and are fully documented. The analysis performed using these codes represents an initial step in a rational design process to produce overlays resistant to environmental reflection cracking.