Mechanical properties of lightweight gypsum composites comprised of seagrass Posidonia oceanica and pine (Pinus sylvestris) wood fibers

Abstract Considering the current environmental awareness and the increasing interest in advanced and sustainable materials, the use of natural fibers has become a common practice owing to their appealing characteristics. This study assesses the mechanical properties with respect to bending and compression, impact bending resistance as well as the hardness of gypsum plaster composed with the Mediterranean seagrass (Posidonia oceanica) and pine wood (Pinus sylvestris) fibers. The addition of fibers from 1 to 6 wt% led to a reduction of density from 5% to 30%, respectively. In terms of mechanical properties, composites containing up to 2% wood fiber develop enhanced flexural and compression strength by 28% and 4% respectively; however, a further addition worsened these properties. Composites comprised of seagrass yielded a decrease in strength; yet, the fracture energy absorbed by the material before it completely lost its load-bearing capacity increased. Correspondingly, the impact resistance of the seagrass composites was 57% higher than that of unreinforced plaster. Surface hardness tests indicated that the smaller wood fibers are more effective in transferring the load on a small scale and therefore can improve localized strength compared to larger seagrass fibers. The addition of seagrass and wood fibers presents a sustainable and ecological way to improve the major properties of gypsum products.