<p>Efficient waste management is critical for environmental sustainability, yet the road sector continues to generate substantial waste during maintenance. This study addresses this challenge by exploring the transformative potential of Reclaimed Asphalt Pavement (RAP) aggregates, not merely as a waste filler, but as a functional modifier in cementitious composites. While previous research often limits RAP replacement to 60%, this investigation uniquely evaluates a full spectrum of substitution levels from 0% to 100% (at 20% increments) to bridge the gap between flowability, strength, and long-term durability. Our comprehensive experimental analysis reveals a complex interplay between the aged bitumen coating and the cement matrix, affecting interfacial bonding and energy absorption. Results demonstrate that RAP incorporation up to 40% achieves an optimal balance, maintaining structural integrity while improving key durability properties. Crucially, beyond this threshold, the study highlights a significant shift toward enhanced ductility and fracture energy, despite a reduction in compressive strength. These findings suggest a novel pathway for developing resilient semi-rigid or hybrid pavement systems that integrate the flexibility of asphalt with the structural rigidity of concrete. By providing a detailed mechanistic understanding of RAP’s multifaceted impact, including its effect on drying shrinkage and ultrasonic pulse velocity, this research offers a strategic framework for advancing resource efficiency and sustainable construction practices in urban and low-volume road infrastructures.</p>