Abstract: The management of dredging sediments and plastic waste is of increasing environmental, societal, and economic importance. To address this, we produced lightweight aggregates composed of 70% sediment based mineral filler and 30% thermoplastic waste containing polypropylene, polyethylene, and polystyrene. When tested, the aggregates satisfied the requirements of the European Standard EN 13055-1 for lightweight aggregates and exhibited good mechanical properties and low water absorption compared to natural aggregates. Based on these results, the formulated lightweight aggregates were found to be suitable for use as a partial replacement for up to 30% of the natural sand in mortar formulations