Behavior and analytical modeling of natural flax fibre-reinforced polymer tube confined plain concrete and coir fibre-reinforced concrete

As reinforcement flax fibre has the potential to replace glass fibre in fibre-reinforced polymer, composite and coir fibre can be used in concrete. To achieve sustainable construction, this study presents an experimental investigation of a flax fibre-reinforced polymer tube as concrete confinement. Results of 24 flax fibre-reinforced polymer tube-confined plain concrete and coir fibre-reinforced concrete cylinders under axial compression are presented. Test results show that both flax fibre-reinforced polymer tube-confined plain concrete and fibre-reinforced concrete offer high axial compressive strength and ductility. A total of 23 existing design- and analysis-oriented models were considered to predict the ultimate axial compressive strength and strain of flax fibre-reinforced polymer tube-confined plain concrete and fibre-reinforced concrete. It was found that a few existing design- and analysis-oriented models predicted the ultimate strengths of all the flax fibre-reinforced polymer tube-confined plain concrete and fibre-reinforced concrete cylinders accurately. However, no strain models considered match the ultimate strains of these specimens. Two new equations are proposed to evaluate the ultimate axial strain of flax fibre-reinforced polymer tube-confined plain concrete and fibre-reinforced concrete.