Compressive Behavior of CFRP-Confined Recycled Aggregate Concrete in Different-Sized Circular Sections

Structural applications of recycled aggregate concrete (RAC) have been rare in practice owing to its inferior strength and durability compared with natural aggregate concrete (NAC). Among the various methods attempted to facilitate the wider structural applications of RAC, the newly proposed method of fiber reinforced polymer (FRP) jacketing is particularly attractive due to the dual benefits of confinement and corrosion insulation. The few relevant studies on FRP-confined RAC have all been conducted on relatively small-scale specimens with no attention being paid to the possible size effect. This paper presents a series of axial compression tests on carbon FRP (CFRP)-confined RAC/NAC cylinders at three different scales with diameters ranging from 150 to 300mm. In particular, some different-sized specimens were designed to have the same FRP confinement stiffness to allow for the first-ever examination of the possible size effect in FRP-confined RAC. The test results indicate that no appreciable size effect appears to exist in FRP-confined RAC or in FRP-confined NAC in the size range considered. The test results also show that FRP confinement effectiveness is marginally affected by the use of recycled aggregate. The compressive behavior of the two types of concrete can be almost equally well predicted by using stress-strain models originally proposed for FRP-confined NAC.