Shear Behavior of the Recycled Concrete Aggregate–Geogrid Interface Under Various Particle Size Distributions: Experiment Investigation and Prediction

Geosynthetic materials provide effective reinforcement for recycled concrete aggregate (RCA), offering a promising approach to green and low-carbon transportation development. This study investigates the interfacial shear behavior of RCA–geogrid systems under varying particle sizes (G1, G2, G3, G4), normal stresses (50, 100, 150 kPa), and shear rates (0.5, 1.0, 2.0, 4.0 mm/min). Prediction models for interfacial shear strength and deformation are proposed. Results indicate that the interface exhibits shear softening across different particle size distributions and normal stresses. RCA with well-graded particle size distributions (G1, G2, G3) showed higher peak shear strength and friction angle, along with smaller vertical displacements, compared to poorly graded RCA (G4). While shear rate had little influence on peak shear strength, it significantly affected vertical displacement. Furthermore, predictive formulas for interface shear strength and deformation were developed considering the curvature coefficient. Since shear strength is critical in determining RCA’s capacity to resist shear forces, these findings highlight its importance for ensuring structural integrity and enhancing its application in sustainable construction.