Investigating particle breakage and compressibility characteristics of unbound aggregate materials recycled from building demolition wastes

The use of recycled building demolition wastes (BDWs) as unbound aggregate materials (UAMs) is one of the resource-conserving, economical, and eco-friendly alternatives for pavement base/subbase construction. The mesoscale strength and crushing properties of individual coarse aggregate particles significantly affect macroscopic strength and deformation behavior of such recycled UAMs. In this paper, the crushing strength and compressive deformation of recycled BDW aggregates of different sizes and constituents were systematically studied from single particle crush tests and oedometer tests, respectively. The test results demonstrate that the single-particle crushing strength exhibited significant size effect and the peak crushing stress values decreased with increasing particle size for the same constituent type of recycled BDW particles. The stress-strain relationship obtained from oedometer tests was well described by the hyperbolic function. Under the same vertical stress level, the vertical strain and the yield stress values of the oedometer specimens increased and decreased gradually with increasing particle size, respectively. Finally, the relative breakage index B _r was used to quantify particle breakage for each particle size range under different vertical stress levels. The ultimate crushing state of each particle size range was obtained from the limit of each predictive equation of the relative breakage index B _r.