Experimental investigations on bond strength between coconut fibre and concrete

Effect of fibre embedment lengths, diameters, pretreatment conditions and concrete mix design ratios on the bond strength between single coconut fibre and concrete is investigated. Fibres are prepared and categorised manually. Fibre diameters are measured by a stereomicroscope. Fibre and concrete properties are also determined experimentally. The simplified equations are proposed for estimating the fibre tensile stress, elastic modulus and toughness. Single fibre pull-out tests are carried out to determine load–slippage curves with the help of an Instron tensile machine having load cell. Bond strength and energy required for fibre pullout are calculated from the experimental data. The results show that fibres have the maximum bond strength with concrete when (i) embedment length is 30 mm, (ii) fibres are thick, (iii) treated with boiling water, and (iv) concrete mix design ratio is 1:3:3. Similar effects are observed for energy required for fibre pullout. With the obtained knowledge, empirical equations are also developed to determine the bond strength and energy required for fibre pullout.