A comparative study of steel reinforced concrete and flax fibre reinforced polymer tube confined coconut fibre reinforced concrete beams

This paper experimentally investigates the flexural behaviour of circular steel rebar-coconut fibre reinforced concrete and flax fibre reinforced polymer tube-confined coconut fibre reinforced concrete composite beams. Conventional steel reinforced concrete beam and flax fibre reinforced polymer tube-confined plain concrete were considered as reference. A total of 18 beams were tested under 4-point bending. For flax fibre reinforced polymer-confined concrete specimens, two different tube thicknesses were used, i.e. 2-layers and 4-layers fabric. The effect of coconut fibre inclusion on the flexural behaviour of steel rebar-coconut fibre reinforced concrete and flax fibre reinforced polymer tube confined coconut fibre reinforced concrete beams were evaluated. In addition, the performance of flax fibre reinforced polymer tube-confined plain concrete and flax fibre reinforced polymer tube-confined coconut fibre reinforced concrete composite beams were compared with steel reinforced concrete and steel rebar-coconut fibre reinforced concrete beams. The test results indicate that coir inclusion slightly increased the load-carrying capacity but significantly enhanced the energy absorption of the steel rebar-coconut fibre reinforced concrete beam, compared to the steel reinforced concrete beam. For both flax fibre reinforced polymer-confined plain concrete and coconut fibre reinforced concrete, an increase in tube thickness provides a larger ultimate load, deflection and ductility of the beams. In comparison with the brittle failure of flax fibre reinforced polymer tube-confined plain concrete, coconut fibre inclusion modified the failure modes of flax fibre reinforced polymer tube-confined coconut fibre reinforced concrete to be ductile. The comparative study showed that 4-layer flax fibre reinforced polymer plain concrete and flax fibre reinforced polymer tube-confined coconut fibre reinforced concrete beams experienced lower deflection, higher ultimate load and higher energy absorption than the steel reinforced concrete beam.