Effect of bond on compressive behaviour of flax fibre reinforced polymer tube–confined coir fibre reinforced concrete

Abstract

This study investigated the effect of flax fibre reinforced polymer and concrete bond on the compressive behaviour of flax fibre reinforced polymer–confined plain concrete and coir fibre reinforced concrete. Three types of bond were considered, i.e. concrete confined by (1) flax fibre reinforced polymer tube, (2) flax fibre reinforced polymer tube with internal flax fibre reinforced polymer rings and (3) flax fibre reinforced polymer wrapping. They were termed as naturally, mechanically and adhesively bonded, respectively. A total of 18 flax fibre reinforced polymer–confined plain concrete and coir fibre reinforced concrete cylinders were tested under axial compression. The test results indicated that all the three flax fibre reinforced polymer confinements increased the ultimate compressive strength and ductility of the concrete significantly compared to the unconfined concrete. It was found that the type of flax fibre reinforced polymer and concrete bond has a significant effect on the ultimate strength and axial strain of the confined cylinders. The composite cylinder with naturally bonded offered the largest ultimate strength and axial strain. In all cases of flax fibre reinforced polymer–confined coir fibre reinforced concrete, the coir fibre inclusion reduced the numbers and widths of the cracks in the concrete. Additionally, existing confinement stress and strain models were used to predict the experimental results of the confined plain concrete and coir fibre reinforced concrete cylinders.