Permanent deformation behaviour of pavement base and subbase containing recycle concrete aggregate, coarse and fine crumb rubber

Pavement layers must be sufficiently strong to carry all traffic loads and resist the accumulation of permanent deformations such as rutting and avoid premature failures including top-down cracking during their service lives. In recent years, the utilization of recycled construction and demolition (C&D) materials in civil and transportation infrastructure construction has been considered as a significant solution to replace conventional and natural aggregates, therefore to achieve the goal of building low-carbon footprint constructed facilities. Unfortunately, limited data have yet reported on the permanent deformation behaviour of the recycled materials in pavement, especially the effect of crumb rubber and rubber size with C&D aggregates on the permanent deformation behaviour in base and subbase layers. This paper provides unique laboratory information and testing results in this regard. In this study, two different groups of crumb rubber particles with sizes ranged from 400 to 600 µm (fine) and 15-20 mm (coarse) were separately added to 20 mm recycled concrete aggregate (RCA) and 20 mm crushed rock (CR) at 0.5, 1 and 2% by weight of the aggregates to study the effects of crumb rubber and rubber size on permanent deformation behaviour of RCA and CR aggregates. In particular, the permanent deformation behaviour of the RCA/CR with crumb rubber was investigated through the repeated load triaxial tests. It was observed that the CR samples should be avoided for use in base and subbase courses.