Shear strength development in dredged sediment stabilized by ternary geopolymer governed by gelation and crystallization

This study introduces a novel ternary geopolymer binder based on ground granulated blast furnace slag (GGBS), fly ash (FA), and desulfurization gypsum (DG) for stabilizing dredged sediment (DS). The primary motivation is to transform DS into a viable construction fill material by achieving the required strength standards for large-scale utilization. The research methodology integrates consolidated-undrained triaxial shear tests for mechanical evaluation and microstructural characterization for mechanism analysis. Results reveal that strength development is governed by synergistic gelation-crystallization. Key findings include: (1) Increasing DG content improves deviatoric stress–strain behavior through AFt crystallization, although 4% DG slightly compromises early strength. Confining pressure enhances peak strength by promoting densification. (2) Higher initial water content shifts failure to hardening, increasing ductility by 40-60% but reducing peak strength by 18-34% due to particle lubrication, partially compensated by confining pressure. (3) AFt formation substantially improves deformability, raising failure strain by 84–115% and secant modulus by up to 190% per 4% DG increment. (4) Microstructural analysis confirms that geopolymer and C-A-S-H gels establish the primary binding network, while AFt crystals refine pores. This binder system shows significant potential for treating high-water-content DS and provides a basis for optimizing strength-ductility performance.