ABSTRACT
Cracking occurs in many different forms in asphalt concrete pavements. Thermal, fatigue, and reflective cracking are all common. Thermal cracking is generally considered a Mode I type crack, or a pure opening crack. Research in asphalt pavements has indicated that fracture mechanics is a plausible tool in characterizing and analyzing Mode I crack initiation and propagation. However, with the introduction of a wheel load, Mode I is not found isolated in the field. With a wheel load, a combination of Mode I and Mode II cracking usually occurs. Mode II cracking is a shearing crack, or a sliding crack, and often occurs as a wheel passes over an overlay with an existing joint. The joint below the overlay can deflect, causing a vertical sliding of the overlay. The combination of Mode I and Mode II cracking is called Mixed-Mode cracking (Anderson, 2005).
