Prediction of the spacing between thermal contraction cracks in asphalt pavements

Abstract

This article presents a simplified approach for the prediction of the spacing between thermal cracks in asphalt pavements based on a finite element formulation of linear elastic fracture mechanics applied to an idealized layered system in which the properties of the frozen layers are temperature dependent. The numerical model was valid for the case of a homogeneous semi-infinite medium and used to investigate the influence of various factors such as depth of frost front, modulus of deformation of frozen base material and of asphalt, and critical energy release rate for crack propagation on crack spacing. Moisture content in the base and subbase plays an important role by providing bonding between grains when frozen. Once cracks can propagate through bonded and brittle base material, calculated crack spacing is found between 25 and 90 m. The model gives support to a new hypothesis of low-temperature cracking which considers that a weaker asphalt strip, which is micro-cracked and bonded with ice wedges, associated with a gradual increase in the moisture content in the base and subbase can account for the field observations that the time where cracks are noticed does not necessarily correspond to the time of year when the pavement is at its lowest temperature.