Stress-Strain Behavior of FRP-Confined Recycled Aggregate Concrete

A large amount of research has been conducted on recycled aggregate concrete (RAC) due to its social, environmental, and economic significance. However, the in situ application of RAC has so far been mainly limited to nonstructural purposes, as the performance of RAC, in both the short and long term, is inferior to its normal concrete counterpart. Existing research has shown that the performance of concrete in compression members can be significantly enhanced through external confinement using steel tubes and fiber-reinforced polymer (FRP) tubes/wraps. Some recent research has examined the behavior of steel tubes filled with RAC, but the research on the behavior of RAC confined with FRP has been rather limited. Research is therefore needed to better understand the stress-strain behavior of and develop a reliable stress-strain model for FRP-confined RAC to facilitate the design of members with FRP-confined RAC. This paper presents the results of the first systematic experimental study on the axial compressive behavior of FRP-confined RAC in which 18 FRP-confined RAC cylinders were tested. The effects of the replacement ratio of coarse aggregate (ratio between the mass of recycled coarse aggregate to the total mass of coarse aggregate) and degree of FRP confinement are investigated. Both the axial and lateral strain responses of the specimens are examined in detail. The test results show that specimens with a replacement ratio of 20% behave similarly to that of normal concrete, but specimens with a replacement ratio of 100% exhibit a lower strength and a different stress-strain response. The applicability of two existing stress-strain models for FRP-confined normal concrete to FRP-confined RAC is also examined.