Impact of particle shape on breakage of recycled construction and demolition aggregates

Abstract

Granular recycled Construction and Demolition (C&D) materials used in pavement structures and embankments experience static and dynamic loading during their service life. As a result, particle crushing causing serious issues such as settlements may occur. Particle breakage depends on different factors such as particle mineralogy, loading condition, particle size, and particle shape. A new insight into the importance and effects of particle shape on the degree of crushing is presented. In this study, breakage of individual C&D particles with different mineralogy and microstructure was studied. The fracture characteristics were found to be highly dependent on the particle shape factor. The particle behaviour at different scales from a single particle to particle assembly is presented and discussed. Discrete Element Method (DEM) was also used to clarify evolution of cracks through the particles. DEM assisted in measuring breakage energy more accurately by partitioning and tracking the energy dissipation especially through the creation of new surfaces during fragmentation. Precise three-dimensional particle shapes were generated by a large number of bonded spherical sub-particles and used to model single particle crushing and particle assembly crushing. The results demonstrated that brittle C&D granular materials with higher degree of sphericity and lower flakiness index would show higher resistance to breakage.