Cracking Performance Evaluation of RAP Mixes

Cracking is one of the most common pavement distresses that affect the design life and durability of hot-mix asphalt pavements. The evaluation of cracking resistance is essential in pavement design. Several laboratory tests and performance indicators are used to evaluate cracking resistance. This study examines the sensitivity of various cracking tests and performance indicators to the change in mix composition and evaluates the variability and correlation between various cracking performance indicators. The cracking performance indicators used in this study are IDEAL-${\mathrm{CT}}_{\mathrm{Index}}$, cracking resistance index (CRI), ${\mathrm{N}}_{\mathrm{flex}}$, ${\mathrm{Weibull}}_{\mathrm{CRI}}$, fracture energy (${\mathrm{G}}_{\mathrm{f}}$), ${\mathrm{IDT}}_{\mathrm{Strength}}$, ${\mathrm{IDT}}_{\mathrm{Modulus}}$, and flexibility index (FI). The results showed that ${\mathrm{IDT}}_{\mathrm{Modulus}}$ and ${\mathrm{IDT}}_{\mathrm{Strength}}$ captured the change in binder content, binder grade, and RAP content. Other indices, including IDEAL-${\mathrm{CT}}_{\mathrm{Index}}$, ${\mathrm{Weibull}}_{\mathrm{CRI}}$, CRI, and ${\mathrm{N}}_{\mathrm{flex}}$, were sensitive to binder content and to only one RAP source. RAP source was found to have a significant effect on cracking performance in this study. The results also showed that high RAP content (up to 50%) provided performance comparable to that of the control mix depending on the RAP source. In addition, cracking performance could be improved by increasing the binder content in mixes with stiffer RAP materials. This indicates the importance of balanced mix design when incorporating RAP materials in asphalt mixes.