Toward the sustainable stabilization of dredged sediment using biopolymers: a mechanical performance study

• Biopolymers provide an eco-friendly alternative for dredged sediment stabilization. • Compressive strength and consistency of DS enhanced by biopolymer treatment. • Biopolymer increased cohesion in all cases, while effects on friction angle varied with the biopolymer type. • SEM/EDS analyses revealed distinct bonding mechanisms, demonstrating that strength gain depends on both polymer content and microstructural interactions. Each year, over one billion cubic meters of sediments are dredged from ports and inland water bodies to maintain navigability and ensure infrastructure safety, creating significant landfill and environmental challenges. Dredged sediments are typically characterized by high moisture content, low bearing capacity, and limited shear strength. Their sustainable reuse requires effective stabilization and remediation strategies. Recent advancements in soil stabilization have increasingly focused on sustainable bio-binders, particularly biopolymers, due to their eco-friendly properties. This study evaluates the effectiveness of four biopolymers, namely calcium alginate (AL), chitosan (CH), xanthan gum (XA), and guar gum (GG) as sustainable bio-binders for improving dredged sediments from the Port of Koper, Slovenia. Mechanical testing demonstrated that 1 wt% XA, AL, and CH increased unconfined compressive strength by 40%, 29%, and 10%, respectively. Direct shear tests revealed that AL and XA increased cohesion by 52% and 104%, respectively, while reducing the friction angle by 4°. In contrast, CH and GG enhanced both cohesion (by 81% and 37%, respectively) and the friction angle (by 1° in each case). Consolidation characteristics were also improved, with reduced settlement under normal load. Microstructural analysis identified the formation of biopolymer matrices including fibrous networks, gel films, and particle clusters that explain the mechanical improvements. The findings confirm that biopolymer stabilization is a viable technique to convert dredged marine sediments into engineered materials, minimizing landfill disposal, and supporting the transition to more sustainable construction practices.