Evaluation of mechanical behaviours of construction and demolition waste based on constant radial stiffness triaxial test

Construction and Demolition Waste (CDW) constitutes a major global waste stream, and its integration into infrastructure presents a critical pathway toward achieving net-zero emissions in the construction sector. Recycled concrete aggregate (RCA) and recycled glass (RG), two prominent CDW materials, are increasingly utilised in pavement applications as substitutes for natural aggregates. This study investigates the mechanical performance of RG–RCA blends under cyclic loading using the Constant Radial Stiffness Triaxial (CRST) test, which more accurately simulates field-representative boundary conditions than conventional Repeated Load Triaxial (RLT) tests. Blends with varying RG contents (30–50 %) and moisture contents (5–11 %) were compacted to 98 % of maximum dry density and then subjected to 50,000 load cycles. Results show that RG content and moisture level significantly influence compaction, with optimum dry density achieved at 30 % RG. Particle breakage was more severe at low moisture and low fines content. CRST testing captured principal stress rotation and residual stress development, with an average stress path slope of 2.73:1, closer to in situ conditions than the fixed 3:1 in RLT tests. Plastic strain increased with both moisture and RG content, peaking at 50 % RG and 11 % moisture. An empirical model linking axial plastic strain to saturation and fines content showed high accuracy (R 2 = 0.98). Resilient modulus is more affected by moisture than RG content and increases with cyclic loading due to densification. However, its variation does not consistently reflect plastic strain trends, indicating it should be used alongside plastic strain for reliable performance evaluation of RG–RCA mixtures. These results support the controlled use of CDW in unbound layers for sustainable pavement design.