ABSTRACT
Compound concrete, which refers to fresh concrete partly replaced with coarsely crushed demolition concrete (recycled concrete lumps or RCLs hereafter), is a simpler recycling process than the reuse of recycled concrete aggregates. The inherent weakness of the interface between RCLs and fresh concrete can be suppressed when a substantial amount of confinement can be provided as that in concrete-filled steel tubular (CFST) columns. The local buckling of CFST columns can be further delayed or suppressed when fibre-reinforced polymer (FRP) is used to jacket the steel tubes. The potential use of the composite column is as piers in rebuilt bridges. The paper presents and interprets the results of an experimental study on the mechanical behavior of CFST piers with compound or normal concrete subjected to combined axial compression and cyclic lateral loading. Four large-scale piers were tested, including a reinforced-concrete (RC) pier, a CFST pier, two GFRP-jacketed CFST piers with or without RCLs, to investigate the influence of parameters such as confinement types and concrete types. The test results indicate that the seismic behavior of the GFRP-jacketed CFST pier with compound concrete is comparable to that of fresh concrete; the use of GFRP jackets is effective in delaying the local buckling failure at the end of a cantilevered pier; the ductility and lateral load-carrying capacity of the RC pier can be significantly enhanced due to confinement.
