Evaluation of Cracking Resistance Performance of Modified Asphalt Mixes Using Simple Performance Tests and Binder Double Edge Notch Test

Cracking is a major distress mechanism that compromises the long-term durability of flexible pavements, particularly under oxidative aging. This study evaluates whether the unnotched semi-circular bending (SCB) test can serve as a practical surrogate companion to the indirect tensile asphalt cracking test (IDEAL-CT) for performance-based cracking assessment of modified asphalt mixtures. Seven plant-produced mixtures containing polymer-modified bitumen, crumb rubber-modified bitumen, and plastomer-modified binders were tested under short- and long-term aging conditions. Among SCB-derived parameters, the cracking resistance index (CRI), defined as the ratio of failure energy to peak load, showed the strongest relationship with IDEAL-CT CT index (R2 = 0.90 for STA and 0.80 for LTA). Binder-level validation was performed using the double-edge notched tension (DENT) test; the resulting crack tip opening displacement (CTOD) aligned with mixture-level indices (R2 > 0.83), supporting consistent ranking across binder types. Acceptance-oriented thresholds for the CT Index, CRI, and CTOD were calibrated for this material system and aging protocol, and surrogate classifications were found to reproduce IDEAL-CT decisions across the evaluated cases. The results support the use of unnotched SCB (using CRI) and DENT CTOD as practical screening surrogates, in conjunction with IDEAL-CT, for quality control and quality assurance applications in modified asphalt mixtures.