Durability and Cracking Resistance Evaluation of Recycled Asphalt Concrete Pavement with High RAP Content

To address the critical issues of low-temperature cracking and insufficient fatigue durability in high-content Recycled Asphalt Pavement (RAP) mixtures caused by aging-induced embrittlement, this study aims to establish a cross-scale cracking resistance evaluation system ranging from binder rheological properties to mixture failure behavior. This research selected various RAP contents (15%–60%) and rejuvenator dosages (0%–12%) to quantify the fatigue damage evolution of rejuvenated binders using Linear Amplitude Sweep (LAS) tests combined with the Viscoelastic Continuum Damage (VECD) model. Furthermore, Semi-Circular Bend (SCB) tests were employed under two loading modes—low-temperature (−12°C) monotonic loading and intermediate-temperature (20°C) cyclic loading—to evaluate the low-temperature fracture toughness and fatigue life of the mixtures, respectively. Experimental results indicate that the hardening of aged asphalt in RAP significantly impairs the stress relaxation capacity of the material, leading to a decay in cracking resistance. LAS tests confirmed that the rejuvenator effectively softens the binder and retards micro-crack propagation; specifically, a 12% dosage increased the fatigue life of the aged binder by approximately 56%. At the mixture level, low-temperature SCB tests revealed a “dosage threshold” effect for high RAP content: for mixtures with 60% RAP, low dosages of rejuvenator showed limited improvement, whereas a 12% dosage was required to significantly elevate the fracture energy (Gf) from 5.57 to 6.49 J/m2, realizing a transition from brittle to ductile behavior. Cyclic SCB tests further demonstrated that 60% RAP caused a precipitous drop in fatigue life by 74% compared to the virgin mixture (down to 1896 cycles), while the addition of 12% rejuvenator restored the life to 5967 cycles, significantly reversing the risk of fatigue cracking. This study quantifies the non-linear gain laws of rejuvenator dosage on cracking resistance and confirms that adopting a high-dosage rejuvenator strategy (>9%) is a key technical pathway to ensure the long-term cracking durability of high-RAP pavement.