Performance evaluation of cement grouted bituminous mixes containing reclaimed asphalt pavement material: Role of RAP binder aging and binder-grout adhesion

Reuse of reclaimed asphalt pavement (RAP) material in cement grouted bituminous mixes (CGBM) offers environmental and economic benefits. Yet, limited studies have examined the performance behaviour of CGBM-RAP mixes, particularly using hot mix asphalt. This study investigates the influence of chemical characteristics of aged RAP binder and cement grout on the performance of CGBM containing RAP material. Blended RAP binders were evaluated using physical tests and FTIR (Fourier transform infrared spectroscopy)-based aging indices. Cohesion and binder–grout adhesion were quantified via surface free energy measurements. Performance characteristics, including rutting, moisture susceptibility, abrasion, fuel, and fatigue resistance, were assessed for CGBM containing 0, 20, 35, and 50 % RAP material. Results indicated that increasing RAP content raised binder stiffness and aging indices, which improved rutting, fatigue, and moisture resistance of CGBM-RAP mixes. However, this behaviour of increased stiffness was accompanied by a reduction in cohesion (within the binder) and interfacial adhesion between binder and cement grout, leading to increased abrasion loss. A strong correlation was observed between aging indices, binder physical properties, and performance parameters of CGBM containing RAP material. Despite reduced adhesion, all mixes exhibited high fuel resistance (retained strength > 90 %). The findings confirm that RAP binder aging plays a critical role in governing the interfacial adhesion and CGBM performance, influencing both beneficial and adverse effects depending on the performance parameter considered.