Reintroducing the poker chip direct tension test for asphalt concrete mixtures

Abstract

Mode I fracture in flexible pavements occurs due to the inability of asphalt concrete (AC) mixtures to resist tensile stresses. At binder scale, microcracks nucleate and gradually coalesce into macrocracks at mixture scale. Various laboratory test procedures have been developed to simulate cracking mechanism. This study reintroduces the AC poker chip test to evaluate cracking mechanisms in three AC mixes with varying Recycled Asphalt Pavement (RAP) content and compares the energy dissipated curves with two additional test methods: Indirect Tensile Test (IDT) and Illinois Flexibility Index Test (I-FIT). The results indicate that the AC poker chip test is a useful test geometry, as it allows for total energy dissipation into crack initiation and propagation. Specimens with higher aspect ratios were better suited for testing due to more uniform stress distributions. Finally, a unified energy-based characterization revealed that high RAP mixtures require greater energy for crack initiation but exhibit brittle crack propagation behavior.