Evaluation of Cracking Performance Indices from Disk-Shaped Compact Tension Testing

Performance-engineered mix designs and performance-based specifications for asphalt mixtures rely on not only establishing performance properties but relevance and representation of field performance of asphalt mixtures. This paper presents a comparative evaluation of various performance indices from fracture tests with respect to asphalt mix properties and field reflective cracking performance of asphalt overlays. Fracture energy (Gf) is currently the primary index used when evaluating the disk-shaped compact tension (DCT) test results. However, Gf does not directly take into consideration the behavior of the post peak region of the load-displacement curve, which may indicate the mixture’s ability to resist crack propagation and provide insight into fracture processes (e.g., crack growth velocity). It is possible to have two DCT specimens with similar Gf values but significantly different load-displacement responses. This study evaluates Gf in addition to three other indices that consider the full load-displacement behavior: fracture strain tolerance (FST), rate-dependent cracking index (RDCI) and a newly proposed DCTIndex. A total of 5 asphalt mixtures and corresponding reflective cracking performance of these mixtures from 4 full-scale pavement test sections (asphalt overlay on Portland cement concrete) are used to compare field performance and equivalent Gf, FST, RDCI and DCTIndex values for the various overlay sections. Results from this study provide insight into the applicability of the various indices from DCT testing in performance-engineered mix design approaches.