Densification behavior of warm stone mastic asphalt with construction and demolition waste aggregate under repeated compressive loading

Construction and demolition waste (CDW) aggregate is generally characterized by lower mechanical strength compared to conventional natural aggregates. Surprisingly, research has shown that asphalt mixtures incorporating CDW aggregates exhibit improved stability, resilient modulus, and resistance to rutting. This study examines the underlying mechanisms responsible for this behavior by evaluating the post-compaction behavior of the mixtures under repetitive loading using Densification Index (Di) and Consolidation Index (Ki). The two unique indices provide a novel approach for linking material-level responses to macro-scale mechanical performance. The results show that the mixtures demonstrate significant densification and consolidation under cyclic loading, with Di increasing from 1.10 to 1.40 and Ki increasing from 4.1 to 8.4. In addition, replacing 30 % of the natural aggregate with CDW aggregates resulted in a Stability of 10.6 kN, a resilient modulus of 2099 MPa when tested at 25°C, a creep stiffness modulus of 22.34 MPa, and a Tensile strength ratio (TSR) of 82 %. However, at 40 % and 50 % CDW aggregate replacement, decreased moisture resistance was observed, with TSR values of 73 % and 64 %, respectively. Mediation statistical analysis confirmed that densification has a significant influence on dynamic stiffness. This research provides a foundation for the performance-based design of recycled asphalt pavements, targeting both structural longevity and environmental benefits.