Volume 37, Issue 6 (November 2009)
Evaluating Parameters for Characterization of Cracking in Asphalt Concrete
This study evaluates parameters derived from laboratory tests to characterize crack initiation and propagation within the semi-circular asphalt concrete samples in the laboratory. Asphalt samples are compacted using a Superpave gyratory compactor, and then sliced and notched using a laboratory saw. The notch acts to facilitate crack initiation. Notched samples are subjected to a strain controlled compressive load in three point bending. Crack opening displacements (CODs) and loads are recorded in real time using four linear variable displacement transducers. Ultimate load, COD at ultimate load, cracking potential, fracture load, crack velocity, and slope of the crack propagation curve are determined from laboratory test results and evaluated for their suitability in characterizing crack initiation and crack propagation. In essence, these parameters are evaluated through examining the effects of notch tip location, moisture condition, and void ratio on crack initiation and propagation. It is shown that crack initiation can be best characterized by the ultimate load. Crack velocity and slope of the crack propagation curve show promise in characterizing crack propagation in the notched asphalt samples.