Compression Behavior of Concrete Columns Strengthened by a Hybrid BFRP/HDPE Tube Coupled with a Crumb Rubber Concrete Cladding Layer

A previous study proved that the confinement of fiber-reinforced polymer (FRP) effectively improves the load capacity and ductility of concrete columns. High-density polyethylene (HDPE) material, which exhibits excellent erosion resistance and high ductility, possesses enormous potential for strengthening structural columns. Based on the discussion, the combination of these two materials as hybrid confinement is investigated in this study. As an energy-dissipating material with excellent ductility, rubber concrete is employed in the hybrid strengthening method as an anti-collision layer. A novel composite system that comprises external FRP-HDPE confinement and an infilled rubber concrete layer is proposed in this study. An experimental test investigates its compressive strength, and three variables are considered, including the diameter of the HDPE tube, the layers of FRP sheets, and the addition of rubber particles in rubber concrete. The test results show that the ultimate compressive strength of specimens is improved with an increase in the diameter of the HDPE tube and layers of the FRP sheet, while the higher addition of rubber particles can reduce the compressive strength. However, these three variables have a positive effect on the deformation capacity of the specimens. A theoretical model is proposed for predicting the ultimate axial stress of specimens, which can provide a reference for designing this hybrid reinforcement.