Durability Characteristics and Microstructural Properties of Concrete Reinforced With Coconut Fibre

Abstract

The increasing demand for sustainable construction materials has encouraged research into natural fibres as alternatives to conventional reinforcement materials in concrete. Coconut fibre, an agricultural waste material with favourable physical and mechanical properties, has considerable potential for improving the sustainability and durability of concrete. This study investigated the durability characteristics and microstructural properties of concrete reinforced with different coconut fibre contents, with emphasis on water absorption, water permeability, sulphate resistance, acid resistance, freeze–thaw resistance, and microstructural development. Concrete specimens containing 0%, 0.5%, 1.0%, and 1.5% coconut fibre were produced and tested at specified curing and exposure periods. The coconut fibre was characterised based on its physical and mechanical properties, while the aggregates were assessed for suitability for concrete production. Durability assessments included water absorption, water permeability, sulphate resistance, acid resistance, and freeze–thaw tests. Microstructural investigations were conducted using Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS), and X-Ray Diffraction (XRD) to evaluate morphology, fibre–matrix interaction, elemental composition, and crystalline phases. The results showed that the coconut fibre had a length of approximately 15–30 cm, diameter of 0.1–0.5 mm, density of 1.15–1.46 g/cm³, tensile strength of 100–250 MPa, aspect ratio of approximately 400:1, and Young’s modulus of 7.50 GPa. The 0.5% fibre mixture recorded the lowest water absorption at 28 days (4.6%), compared with 6.1% for the control mixture