Enhancement of mechanical strength in lightweight EPS geopolymer composites using coconut fiber

Abstract This study examines the effect of coconut fiber (CF) on the mechanical properties of a sustainable building material known as lightweight ambient-cured geopolymer composites (CFLWGC). Coconut fibers, with mean diameter 0.4 mm and lengths of 2, 4, and 6 cm, were incorporated into the composite at varying contents (0.5%, 1%, 1.5%, and 2% by binder mass) to study their effect on CFLWGC. The resulting CFLWGC was thoroughly charaffigcterized for its physical and mechanical attributes, including density, workability, compressive strength, and splitting tensile strength. Results showed that incorporating coconut fibers significantly improved mechanical properties with optimal compressive strength of 11.265 MPa (30% increase) and highest split tensile strength of 1.464 MPa (35% improvement) at 4 cm fiber length and 1% content. However, excessive fiber volume or length reduced compressive strength to 7.821 MPa (25% decrease) and split tensile strength to 0.548 MPa (62.5% reduction). Longer fiber lengths (6 cm) and higher fiber contents generally decreased tensile strength, indicating that while moderate fiber addition enhances performance, excessive fiber volume or length negatively impacts the composites’ mechanical properties.