HEALING IN ASPHALT CONCRETE PAVEMENTS: IS IT REAL?

Abstract

Microcrack healing of asphalt concrete during rest periods is among the many variables influencing the lab-to-field fatigue shift factor. Experimental approaches to evaluating this mechanism, both in the laboratory and in the field are presented. Three techniques introduced in this paper include the nonlinear viscoelastic correspondence principle, the impact-resonance test method for the laboratory characterization, and the stress-wave testing method for in situ characterization of asphalt concrete pavements. When analyzing the change in stress-strain behavior of asphalt concrete during rest periods, one must consider both the relaxation and healing of microcracks. A nonlinear viscoelastic correspondence principle based on the pseudo-strain concept was successfully applied to both controlled-stress and controlled-strain uniaxial testing under varying test conditions. The principle enabled determination of the healing potential of asphaltic mixtures. The impact-resonance test method appeared to be an excellent means of evaluating the change in elastic properties of asphalt concrete resulting from damage growth or healing. Finally, 24-hr stress-wave testing of a pavement section demonstrated a decrease in the elastic modulus as temperature increased, and an increase in the elastic modulus after the rest period, possibly due to microcrack healing in asphalt concrete layers.