Development of a composite specimen interface cracking (CSIC) test for top-down cracking

Pavement top-down cracking performance not only depends on pavement layer material characteristics, but also on layer interface conditions. Interface conditions involve both the shear resistance along the interface and the cracking resistance across the interface provided by the interface bonding agents. Regarding hot-mix asphalt (HMA), currently available tests are mainly focused on pavement layer material properties. When thick polymer modified asphalt emulsion (PMAE) was applied at the interface between an open-graded friction course (OGFC) and a dense graded structural layer, a bonded interface was formed by the migration of PMAE up into the OGFC air voids. Shear strength tests, which can well characterize the adhesive film effect of interface bonding agents, cannot fully capture the effect of bonded interface on pavement cracking performance. To simulate the crack initiation and propagation process and evaluate the effect of bonded interface conditions on top-down cracking performance, a composite specimen interface cracking (CSIC) test was developed. The developed system involves repeated tensile loading and monitoring of the rate of damage development (reduction in stiffness) on composite specimens specifically designed for this purpose. Number of loading cycles to failure and damage rate results from the proposed test on three different interface conditions clearly indicate that this test method can be used to optimize bonding agents and application rates for enhanced cracking performance. This method may also provide a suitable specification test for evaluation of interface conditions on reflective cracking performance. Copyright by ASTM Int'l (all rights reserved).