Characterization of Coconut and Oil Palm Natural Fibers with Optimized Mixing Methods for Cement Composites

Abstract Natural fibers such as coconut and oil palm offer sustainable reinforcement for cement composites, but their variability in properties and compatibility with cement matrices present challenges. Both fibers exhibit variations and inconsistent characteristics, necessitating tailored mixing protocols to ensure consistent fiber dispersion in cement mixtures. The mixing method largely governs the dispersion of fibers within a matrix, which influences both the fresh and hardened properties of fiber-reinforced materials. Hence, this study attempts to evaluate the impact of five different mixing methods on cement composites reinforced with coconut and oil palm fibers, formulating 15 mix designs and characterizing the fibers for replication accuracy. The effects of mixing methods on water absorption, flowability, setting time, compressive, and flexural strength were assessed, along with fiber–matrix interactions in hardened samples. It was observed that the premix II produced the best flowability, improving it by approximately 3.7% for coconut and 3.0% for oil palm composites, while also reducing water absorption by 87% and 85%, respectively, without affecting setting time. For mechanical performance, coconut composites achieved the highest compressive (37.1%) and flexural (19.3%) strengths with the postmix method. In contrast, oil palm composites reached the highest compressive strength (19.2%) with comixing, and the highest flexural strength (9.1%) with premix III methods. However, some mixing methods produced more consistent performance while not achieving the highest mechanical or fresh properties because the fiber dispersion in the mix was more uniform. In conclusion, coconut and oil palm fibers are abundant, underutilized tropical agricultural wastes with demonstrated mechanical potential. They are cost-effective, sustainable, and applicable in non-load-bearing construction materials; hence, this study investigates appropriate mixing methods to optimize both fresh and hardened properties for broader construction applications.