Experimental investigations on coconut-fibre rope tensile strength and pullout from coconut fibre reinforced concrete

The utilisation of coconut-fibre ropes as vertical reinforcement in mortar-free interlocking structures is under consideration for use in cost-effective earthquake-resistant housing. The walls are intended to be constructed with novel interlocking blocks, and coconut fibre reinforced concrete (CFRC) is used as a construction material (presented in a separate study). The rope anchorage is achieved by embedding it in the foundation and top tie-beams. The bond between the rope and the CFRC plays an important role, and the rope tensile strength is also significant in the overall stability of the proposed structure. The rope tension generated due to earthquake loading should be less than both the pullout force and the rope tensile load to avoid the structure collapse. As a pilot study, the scope of the current work is limited to the axial pullout behaviour and tensile capacity of the rope. Therefore, the bond strength between the rope and CFRC, and the energy required to pull out ropes from CFRC are investigated experimentally using rope pullout tests. The factors considered include rope embedment length, rope diameter, pre-treatment condition, concrete mix design ratio, fibre content and knot in the material matrix. The tensile strength and elongation of coconut-fibre ropes were determined considering the parameters of rope diameter and pre-treatment. To increase the pullout energy, bond strength and tensile strength of the rope, the boiling treatment was found to be beneficial compared to chemical treatment. The pullout energy increases with an increase in embedment length, rope diameter, cement and fibre content in the matrix. With the knowledge obtained, empirical equations are proposed to determine the pullout energy, bond strength and tensile strength of the rope.

► The rope tensile strength and rope pullout from concrete is investigated experimentally.
► Load–slippage curves are obtained from the rope pullout tests.
► The stress–strain curves of the coconut-fibre ropes are obtained.
► Empirical equations are proposed for tensile and bond strength.
► The increased tensile and bond strength is achieved with boiling treatment.