Recycled use of dredged sludge for river bank slope protection: Role of water adsorbents

The increasing volume of dredged sludge (DS) poses considerable challenges in geotechnical engineering. This study proposes a stabilization strategy to utilize DS as a riverbank slope protection material through the combined application of industrial waste-based binders and water adsorbents (WAs). The key lies in elucidating the synergistic role of WAs, which, while not directly participates in chemical reactions, effectively adsorbs free pore water. This dewatering process mitigates the “dilution effect” on reactive ions, thereby enhancing conditions for hydration and pozzolanic reactions. The optimal industrial waste-based binder, designated as CFG, was formulated with calcium carbide residue (CCR), fly ash (FA), and ground granulated blast-furnace slag (GGBS) at a ratio of 0.65:0.11:0.24. The synergistic binder was further optimized with a CFG: superabsorbent polymer (SAP): carboxymethyl cellulose (CMC): bentonite ratio of 10:0.1:2:6. Laboratory tests demonstrated that the stabilized DS exhibited continuous strength development and satisfactory durability under wet–dry cycles. Mineralogical and microstructural analyses confirmed that the dewatering effect facilitated the formation of denser and more compact cementitious gels, thereby improving both strength and structural integrity. Field application in riverbank slope protection further validated the practical feasibility of this approach, achieving substantial strength gains and ensuring environmental safety. This study offers a sustainable and effective method for the beneficial reuse of DS in geotechnical engineering applications.