Aging behavior of nanomodified dredged sand: Case study from Anzali Lagoon

Dredging in lagoon environments yields large volumes of sand-rich sediments that are commonly stockpiled or discarded due to their loose structure, organic residues, and low initial strength. Developing efficient reuse strategies for these materials is essential for reducing disposal impacts and promoting sustainable land management around sensitive wetland systems. This study examines the mechanical and microstructural behavior of dredged sand from the Anzali Lagoon (northern Iran) stabilized with nano-clay (NC), nano-silica (NS), and nano-alumina (NA). Direct shear tests were performed at relative densities of 30, 50, and 70%, immediately after preparation and after 90 days of aging, supported by Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), and sensitivity assessment using the Cosine Amplitude Method (CAM). Increasing nanoparticle content up to 1% enhanced shear strength, whereas higher dosages caused agglomeration-related reduction. At 70% relative density and 1% dosage, aging raised cohesion by ∼48%, 56%, and 50% for NC, NS, and NA, respectively, while friction angle increased by 4%, 5%, and 3.8%. SEM revealed pore refinement and denser packing, and XRD indicated no new crystalline phases, confirming physical strengthening. Among the additives, NS showed the highest efficiency.