Improving damping properties of cement mortar using oxidized and methyl methacrylate-grafted coconut fibers

As sustainable materials gain attention, coconut fiber has been increasingly utilized for damping modifications in composites. However, existing methods mainly emphasized enhancing interfacial Coulomb friction, overlooking interfacial viscoelasticity, which limited the efficiency of damping improvement. This study aimed to modify the surface of raw coconut fiber (RCF) to enhance their interfacial viscoelasticity in cement-matrixed materials. The modification process used cerium ammonium nitrate solution to oxidize coconut fibers (CANCF), and further grafted methyl methacrylate (MMA) onto the fiber surface (MMACF). Characterization techniques were employed to assess the effects of modifications on the surface morphology and physicochemical properties of the fibers. Experiments also evaluated the fibers’ impacts on the mechanical and dynamic properties of cement mortar. The results indicated that the cerium ammonium nitrate disrupted hexagonal rings in cellulose molecular chains, which therefore promoted fiber surface viscoelasticity and facilitated grafting MMA. Meanwhile, modification treatments weakened the air-entraining capacity of coconut fibers, mitigating the loss in compressive strength. Compared to cement mortar with RCF, CANCF and MMACF enhanced compressive strength by up to 48.9 % and 43.7 %, respectively. Dynamic tests revealed that CANCF increased the elastic stiffness of cement mortar, while did not significantly improve its energy dissipation capacity. Grafting MMA compensated for this deficiency, increasing the loss tangent of cement mortar by up to 32.2 % at 0.5 vol% dosage compared to incorporating RCF. Overall, the modification measures can offer promising prospects for applying coconut fibers in cement-matrixed materials.