Assessment of binder test methods for detecting cracking susceptibility in asphalt mixtures

Abstract

Asphalt binders are crucial in roadway construction, significantly influencing the performance and durability of asphalt mixtures. Even with identical mix designs, the performance of these mixtures can vary depending on the Performance Grade (PG) of the binder used. This study aims to identify and evaluate test methods for assessing binder quality, specifically in terms of cracking resistance. Twenty binder samples, representing four PGs (PG 64–22, PG 64–28, PG 70–22, and PG 76–22), were selected for failure and rheological testing. These binders were incorporated into asphalt mixtures, which were then evaluated for cracking resistance using the IDEAL cracking test (IDEAL-CT).

The findings revealed significant correlations among ΔTc, R-value, poker chip stiffness, phase angle, and Glover–Rowe parameters. Specifically, the phase angle at 25 °C and 10 rad/s and the G-R parameter at 35 °C and 10 rad/s showed strong correlations with the CT_index (R² = 0.82 and 0.88, respectively), while poker chip stiffness also demonstrated a notable correlation (R² = 0.61). Although using the G-R parameter to derive VECD damage curves improved the correlation between N_f and CT_index (R² = 0.46), it was less effective than other parameters. Therefore, the phase angle at 25 °C and 10 rad/s is recommended as it can be easily obtained through standard PG grading tests. Additionally, the comparison of the phase angle with the IDEAL-CT test parameters indicated that the ductility of asphalt mixtures is closely linked to the binder’s phase angle. The strong correlations between asphaltenes and phase angle emphasizes the essence of phase angle in mixture cracking and failure mechanisms.