Investigating the Influence of Raw and Treated Coconut Fibre Obtained from Agricultural Residue on the Strength and Durability Characteristics of High-Strength Concrete

Abstract

The use of coconut fibre (CF) from agricultural waste offers a sustainable solution to environmental challenges by reusing residues from the coconut industry. This approach respects the principles of sustainability and environmental preservation by minimising waste and encouraging the use of renewable resources in construction. A study was carried out to assess the effectiveness of untreated (UT) and treated CFs as reinforcement in high-strength concrete (HSC), targeting an average strength of 60 MPa. The study evaluated the mechanical and durability characteristics of HSC reinforced with raw and processed coconut fibres (CFR-HSC). The CFs underwent physical treatment by boiling and chemical treatment using a 1% sodium hydroxide (NaOH) solution. Different fibre contents were examined, and analyses including scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) were carried out on untreated and treated fibres. The results showed that additional fibre content reduced the workability of the concrete, its fresh density, and its air void content, but that the treated fibres had better workability than the UT fibres. While compressive strength was not significantly improved with CFR-HSC compared to the HSC control mix after 28 days of curing, tensile and flexural strengths were improved with fibre content. Notably, the NaOH-treated (NT) CF showed the greatest increase in tensile strength, while the boiling-treated (BT) CF showed the greatest improvement in flexural strength. An increase in fibre content resulted in a reduction in crack width, and CFR-HSC showed an increase in water absorption but better resistance to sulfuric acid, with NT CF producing the most promising results.