Recycled fishing net fibers from the mediterranean sea as a resource in gypsum-based composites: characterization and environmental assessment

The growing accumulation of abandoned, lost, or otherwise discarded fishing gear is a critical environmental problem because of its persistence, slow degradation, and contribution to marine pollution. The construction sector consumes large amounts of non-renewable resources annually, and fibers from fishing nets can be used to manufacture construction materials that help reduce pressure on natural raw material consumption. However, the addition of this type of secondary material is limited to 2 wt%, and its performance in construction composites as a substitute for the original raw materials at higher proportions is unknown. This research has demonstrated, through physical-mechanical and environmental characterization, that replacing gypsum with recycled polyamide fibers can reach up to 45.0% by volume in composites suitable for construction. Bending tests on prefabricated plates (40 × 30 × 1.5 cm) showed a significant strength improvement (+25.8%) at a 15.0% volume replacement of gypsum with recycled fibers. Conversely, a progressive reduction in mechanical strength was observed in standard RILEM prismatic specimens (4 × 4 × 16 cm). This progressive incorporation of fibers increased impact resistance and reduced capillary water absorption, reaching 0.464 kg/m 2 ·s 1 / 2 in the composite with 45.0% fiber replacement by volume. Additionally, the progressive decrease in density and thermal conductivity observed led to an improvement in thermal resistance in real construction systems of up to 29.8%. Finally, the multi-scenario life-cycle analysis of the composites produced showed that using recycled fibers in gypsum composites improves environmental performance, even with longer supply chains. These results demonstrate the viability of fibers from abandoned fishing nets for the manufacture of gypsum-based prefabricated products produced under circular economy criteria with a high percentage of revaluation and recovery of discarded materials.