Characteristics and sustainable use of fine-grained sediment in the Three Gorges Reservoir, China

Reservoir siltation poses a global threat to sustainable water resource management. The Three Gorges Reservoir (TGR), one of the largest hydropower projects globally, faces significant challenges from fine-grained sediment accumulation (<0.031 mm). This study systematically examines the physicochemical properties, siltation dynamics, and resource recovery potential of TGR sediments through integrated analyses, including X-ray diffraction, particle size distribution, and chemical characterization. The mud fraction was identified as rich in quartz and layered silicate clay minerals with alkali-activation activity, whereas the sand fraction primarily comprised quartz and anorthite, functioning as an inert filler. Novel eco-brick formulations utilizing dredged sediment were developed, including mud-sand composites with unconfined compressive strength (UCS) up to 12.8 MPa and cement-stabilized variants exceeding 50 MPa. These formulations reduce CO₂ emissions by 74.2–85.1 % compared to conventional fired clay bricks, which is attributed to the elimination of energy-intensive calcination and partial cement replacement. Particle packing optimization via the Modified Andreasen & Andersen model demonstrated that a 1:3 mud-to-sand ratio maximized packing density and mechanical performance. A sustainable utilization pathway was proposed, including the production of ecological aggregates and eco-bricks, which simultaneously provides a reservoir sedimentation adaptive strategy and delivers low-carbon construction materials compatible with circular economy principles.