Enhancing mechanical performance of green fiber cement composites: Role of eco-friendly alkyl ketene dimer on surfaces of hemp fibers

Fiber composites reinforced natural fibers have attracted more attention in sustainable building materials due to the high Young's modulus, availability, and biodegradability. However, poor interfacial bonding of the fiber-reinforced cement composites attributed to the intrinsically swelling-shrinkage behavior of the hydrophilic natural fibers, seriously limits the strength development of the composite. Here, an eco-friendly and low-cost surface treatment agent, alkyl ketene dimer (AKD), is innovatively introduced for reinforcing the combined effect of hemp fiber (HF)/cement matrix. The experimental approach includes the chemical modification of hemp fibers, followed by the direct preparation of fiber cement composites. Fourier transformation infrared spectroscopy (FTIR) and water absorption test analyses confirmed that the modified HF surface was successfully grafted with AKD, leading to superior hydrophobic characterization and reduced swelling-shrinking behavior. Adding the modified HF to the cement composites effectively enhanced their mechanical properties and toughness capacity by strengthening the interfacial bond of modified HF/Mortar. The modified fiber-reinforced mortar has the highest increment (28 % in compressive strength and 24 % in flexural strength, respectively) from 7 d to 28 d among all investigated mortars. Furthermore, the micro-observation of fractured mortar composites supports the strengthened interface of the modified fibers/cement matrix. The study provides a feasible and practical approach to improving the comprehensive strength properties of hemp fiber-reinforced cement composites. It benefits the practical industrial-scale application of biomaterials in low-cost housing, thus enhancing sustainability.