ANALYSIS OF CRACK RESISTANCE OF ASPHALT CONCRETE OVERLAYS--A FRACTURE MECHANICS APPROACH

Abstract

Cracking is one of the major distress modes that cause premature failure of asphalt concrete pavements. Formation of cracks in asphalt concrete pavements can be the result of the following: applied traffic loads, temperature-induced thermal stresses, freeze-thaw damage due to water infiltration, aging effects, and so forth. A conceptual framework to characterize (and quantify, if possible) the crack resistance of asphalt concrete pavement systems based on a fracture mechanics theory is presented. A cohesive crack model, which is similar to the Dugdale-Barenblatt type of models proposed for ductile yielding of metals, was used to simulate the progressive crack formation and propagation in asphalt concrete. A parametric study was conducted to study the effects of temperature, fiber reinforcement, and overlay thickness on the crack resistance of asphalt concrete overlays. It was found that a thicker overlay has a much higher temperature crack resistance, which is in agreement with general field observations. Furthermore, although it was found that at lower service temperature the overlay has a much higher temperature resistance, this improvement is not enough to compensate for a much larger temperature differential and contraction displacement caused by the service temperature drop. Fiber reinforcement was found to slightly increase the crack resistance of the asphalt concrete overlays. It was further observed that the temperature crack resistance is proportional to the increase of the tensile strength.