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.