Performance of coir fibre-reinforced concrete incorporating crushed coconut shells as a partial replacement for coarse aggregates

Resumo

The increasing demand for sustainable construction materials has intensified the exploration of agricultural waste as viable alternatives to conventional concrete constituents. This study investigates the durability performance of coir fibre-reinforced concrete incorporating crushed coconut shell aggregates (CCSA) as partial replacements for conventional coarse aggregates. An experimental research design was adopted in which concrete mixes with varying proportions of CCSA and coir fibres were prepared and evaluated. Durability performance was assessed through water absorption, density, crack resistance, and non-destructive testing methods, including Schmidt Hammer rebound and Ultrasonic Pulse Velocity (UPV) tests, to evaluate surface hardness, internal integrity, and resistance to micro-cracking. The results show that increasing CCSA content reduces workability and density due to its high water absorption and lower specific gravity compared to conventional aggregates, while improving sustainability through reduced reliance on natural stone. However, the incorporation of coir fibres enhances cohesion, reduces segregation, and improves crack resistance through fibre-bridging mechanisms that limit micro-crack propagation. The combined use of UPV and Schmidt Hammer tests indicated variations in internal integrity and surface hardness across the tested mixes. The reported findings suggest that moderate CCSA replacement levels of 10–20%, combined with controlled coir fibre content, offer a potential balance between crack resistance and durability performance. However, thermal exposure reduced flexural strength across the tested mixes, while saline exposure revealed variations in surface hardness and compressive strength with coir fibre content. The findings demonstrate that the performance of concrete incorporating crushed coconut shells and coir fibres depends on the proportions used and the environmental exposure conditions. It is recommended that CCSA replacement levels not exceeding 20%, combined with coir fibre contents of approximately 0.2–0.3%, be considered for further evaluation through long-term durability testing under relevant environmental exposure conditions before wider structural application. This study contributes to the understanding of the potential use of agricultural waste in concrete production, supporting resource efficiency and sustainable construction practices, particularly in regions with abundant coconut waste resources. It is recommended that crushed coconut shell aggregate replacement levels not exceed 20%, combined with coir fibre contents of approximately 0.2–0.3%, and that these mixes undergo long-term durability testing under relevant environmental exposure conditions before being considered for wider structural application.