Stress-strain behavior of FRP-confined concrete containing recycled concrete lumps

A novel method to recycle concrete is to crush demolition concrete into large pieces and then to directly mix the resulting recycled concrete lumps (RCLs) with fresh concrete to produce a new kind of recycled concrete referred to as compound concrete. This method avoids the complexity of recycling concrete into aggregates and enables the achievement of a higher recycling ratio and a lower recycling cost. However, due to the large sizes of RCLs and the weak interfaces between fresh concrete and RCLs, compound concrete is much more heterogeneous than normal concrete. A new technique has recently been explored to improve the properties of such compound concrete, in which the compound concrete is provided with a substantial amount of confinement from an external fiber-reinforced polymer (FRP) confining tube. This paper presents the results of an experimental program of axial compression tests on compound concrete-filled FRP tubular columns in which the FRP tubes were prefabricated using the wet lay-up method with fibers only in the hoop direction. The tubes had a negligible axial stiffness, which allows the stress-strain behavior of FRP-confined compound concrete to be clearly revealed. The test results show that, when a significant level of FRP confinement is provided, the behavior of FRP-confined compound concrete is similar to that of FRP-confined normal concrete with a strength equal to that of the fresh concrete. An existing stress-strain model previously developed for FRP-confined normal concrete is evaluated in the paper using the test results of FRP-confined compound concrete. (C) 2020 Elsevier Ltd. All rights reserved.

Automated summary

A novel method for recycling concrete involves crushing demolition concrete into large pieces and mixing them directly with fresh concrete to produce compound concrete. This approach avoids the complexity of recycling concrete into aggregates, but the resulting compound concrete is more heterogeneous than normal concrete. A new technique involving external fiber-reinforced polymer (FRP) confinement has been explored to improve the properties of compound concrete, with promising results from experimental tests on FRP-confined compound concrete-filled columns.