Pavement surface and base layer simultaneous reclamation with cement-emulsified asphalt: mix design, effectiveness, and mechanisms

To address the limited co-recycling of asphalt surface and base layers and the lack of interfacial mechanism studies, this research proposes a composite cold recycling technology using cement-emulsified asphalt (CA) mortar. The method enables synchronous regeneration of reclaimed asphalt pavement (RAP) and reclaimed base material (RBP), with improved mechanical performance through optimized material proportions. A multiscale experimental design refined the RAP/RBP ratio, cement content, and emulsified asphalt dosage. Mechanical tests, pull-off strength, Dynamic Shear Rheometry (DSR), and scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS) were conducted to evaluate performance and interfacial bonding. The optimal formulation (1.5% cement, 5% emulsified asphalt) achieved 0.85 MPa tensile strength and 9.8% void ratio. A 7–10 µm interfacial fusion depth and a 12.5% increase in dynamic shear modulus confirmed strong adhesion and fatigue resistance at the RAP interface. In contrast, the RBP interface exhibited irregular cement morphology and weaker bonding, indicating a need for further enhancement.