Influence of blending proportion on mechanical and microstructural properties of cement-stabilized full-depth reclamation base

• The effects of blending proportion, cement content, and curing on FDR performance are studied. • The 60:40, 70:30, and 80:20 blends with 4% cement meet IRC standards, while the 70:30 blend with 5% cement achieves the highest UCS. • SEM and XRD confirm a denser matrix with C–S–H, calcite, and alite. • A 25–35% reduction in UCS is observed under soaked conditions. • Optimal gradation and binder dosage are recommended for sustainable FDR bases. This study investigates the influence of various blending proportions (coarse: fine), varying cement dosages, and curing durations on the mechanical behavior of cement stabilized full depth reclaimed (FDR) pavement materials to be used as a base layer. The FDR process promotes sustainability by recycling in-place pavement layers, reducing dependence on virgin aggregates, and minimizing environmental impacts. Laboratory investigations are carried out on five blending proportions (80:20, 70:30, 60:40, 50:50, and 40:60) stabilized with 3%, 4%, and 5% cement contents by dry weight. Specimens are tested at curing ages of 7, 14, and 28 days to evaluate strength development. The testing program includes unconfined compressive strength (UCS), flexural strength (FS), and indirect tensile strength (ITS), in addition to ultrasonic pulse velocity (UPV) for non-destructive evaluation. Microstructural performance is examined through scanning electron microscopy (SEM) and X-ray diffraction (XRD). Results showed that cement stabilization distinctly improved strength with the 70:30 coarse-to-fine blend at 5% cement, achieving the highest UCS (10.25 MPa), FS (1.17 MPa), and ITS (0.67 MPa) after 28 days. UPV values increase consistently with higher cement and coarse aggregate contents, ranging from 1920 m/s to 2891 m/s. SEM and XRD confirmed the formation of calcium silicate hydrate (C-S-H) gel, calcite, alite, and muscovite, which enhanced particle interlock and reduced porosity. The findings highlight that optimizing aggregate gradation and binder dosage can produce durable, resource-efficient base layers, and that UPV offers a practical tool for in-field quality assessment.