Investigation on performance improvement of dredged sediment with high water content stabilized with alkali-activated materials

Purpose: This research presents experimental investigation into the performance improvement of dredged sediment (DS) stabilization with ternary alkali-activated materials (AAMs) based on fly ash (FA), ground granulated blast-furnace slag (GGBS), and desulfurization gypsum (DG) for use as embankment fill materials. Methods: The performance of stabilized DS was assessed through a series of pH, electrical conductivity (EC), and unconfined compressive strength (UCS) tests. Microstructure characterization was also conducted to reveal the performance improvement mechanism of stabilized DS. Results: The pH value of the stabilized DS exhibited a significant increase, reaching its peak at a DG content of 8%. This increase was attributed to the consumption of free water and the priority reaction of C-(A)-S–H. Subsequently, the pH value gradually decreased, primarily due to the consumption of OH⁻ through Ca(OH)₂ precipitation. Concurrently, the EC value steadily increased due to the rising Ca²⁺ concentration. Additionally, the UCS of the stabilized DS exhibited a noteworthy increase at a DG content of 8% and then showed a tendency to increase or decrease slightly with varying DG content, in line with the changes in pH value. Conclusions: The performance improvement of the stabilized DS was attributable to the cementation provided gels (i.e., geopolymer gel and C-(A)-S–H gel), along with the pore-filling of ettringite (AFt) in the alkaline environment. Conversely, the performance of stabilized DS deteriorated due to the presence of microcracks resulting from excessive AFt expansion.