Valorization of rice husk-derived cellulose microfibers as sustainable reinforcement in fiber-cement composites through mechanical and microstructural analysis

Fiber-cement composites are used in lightweight construction due to their favorable balance of mechanical and physical properties. This study investigates the influence of rice husk-derived cellulose microfibers on the performance of fiber-cement boards. Specimens were prepared with varying fiber concentrations (0.0, 3.0, 6.0, 9.0 and 12.0% wt.) and air-cured for 28 days. Characterization included X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), 3-point bending testing to determine the Modulus of Rupture (MOR) and Modulus of Elasticity (MOE), and physical measurements of dry bulk density and water absorption. Data were validated using one-way ANOVA at a 95% confidence level. Results showed that 9.0%wt. of cellulose as the optimal dosage, enhancing the MOR by 202.1% and increasing the MOE by 59.0% compared to the control. Microstructural analysis revealed that the hydrophilic nature of the microfibers facilitates internal curing and secondary hydration, promoting calcium silicate hydrate gel formation. This mechanism densifies the matrix and improves fiber anchoring, as suggested by SEM observations. Physically, the inclusion of cellulose reduces bulk density, favoring the development of lightweight materials, despite an increase in water absorption caused by inherent fiber porosity. The valorization of agro-industrial waste like rice husk optimizes the mechanical integrity of fiber-cement composites and offers a promising and potential sustainable alternative for the lightweight building systems in the construction sector.