Transforming dredged sediment into reactive clay: Critical review of calcination, reactivity, and sustainable valorization as supplementary cementitious material

Dredged sediment (DS) is generated worldwide in large volumes through routine port and waterway maintenance, yet its disposal presents environmental and economic challenges. Recently, calcined dredged sediment (CDS) has emerged as a supplementary cementitious material (SCM), offering a viable alternative to traditional SCMs, such as fly ash and slag cement. This review synthesizes current knowledge on the physical, chemical, and mineralogical characteristics of raw DS and pretreatment strategies aimed at dewatering, organic matter removal, and contaminant stabilization. The effects of calcination on the production of reactive amorphous aluminosilicates are also discussed. Emphasis is placed on physicochemical changes revealed by experimental analysis and molecular dynamics simulations, which clarify the dehydroxylation and amorphization pathways of clay minerals, such as kaolinite, illite, and montmorillonite. Reactivity assessments based on the strength activity index and isothermal calorimetry confirm that CDS can meet the ASTM requirements for Class N pozzolans under optimized calcination conditions. Research studies on its application in mortar, concrete, and geopolymer mixtures demonstrate promising performance. Finally, challenges with regard to feedstock variability, heavy metal management, process scalability, and standardization are discussed, alongside perspectives for the future integration of CDS into sustainable and circular cementitious systems.