Sand mix interlayer retarding reflective cracking in asphalt concrete overlay

This study evaluated the performance effectivenss of sand mix interlayer in controlling reflective cracking in asphalt concrete (AC) overlaid existing jointed concrete pavement (JCP) using a three-dimentional finite element (FE) model. A cohesive zone model was incorporated into the FE model to characterize the fracture behavior of the AC overlay under transient vehicular loading. A limit state load approach was used to determine the resistance of the AC overlay to reflective cracking in terms of normalized axle load of an overload equivalent to an 80-kN single-axle load. The study concluded that the sand mix interlayer enhanced the fracture resistance of the AC overlay due to its relatively high fracture energy. A macro-crack level of reflective cracking was initiated in the wearing course in the AC overlay earlier than in the leveling binder, so-called crack jumping. The softer the sand mix, the tougher it may be, but it may cause shear rutting in the AC overlay. As the bearing capacity of the JCP becomes lower, more fractured area was developed in the AC overlay and the performance effectiveness of the sand mix interlayer was better.