Performance and Mechanism of an Alkali-Activated Multifunctional Curing Agent for Silt Solidification

In light of its curing and green environmental protection effects, the application of an alkali-activated multifunctional curing agent was undertaken for the remediation of silt in coastal areas. In this paper, the curing effect and curing mechanism of cement–phosphogypsum–fly ash–lime as a multifunctional silt curing agent under the action of an alkaline activator were investigated. The effects of alkaline activator dosing and the relative dosing of a multifunctional curing agent on the mechanical and water stability properties of specimens were comparatively analyzed by carrying out unconfined compressive strength and water stability tests. Furthermore, microanalysis was conducted using scanning electron microscopy and energy spectrum analysis (SEM + EDS), X-ray diffraction (XRD), and thermogravimetric analysis (TG) tests. The objective of these analyses was to reveal the curing mechanism of a multifunctional curing agent. The experimental findings indicate that the addition of an alkaline activator enhances the strength of solidified silt, though it exerts minimal influence on the enhancement of water stability. It is recommended that the mass fraction of NaOH in multifunctional curing agent systems be set at 2%, while the mass fraction of phosphogypsum is advised to be 60%. Under this mixing ratio, the hydration products are able to more effectively act as binding agents for soil particles, thereby filling the internal pores and creating a more compact internal structure in the solidified silt. This, in turn, enhances the compressive strength and water stability of the material. The research results can provide a theoretical basis for the application of industrial solid waste in the treatment of silt and for other practical projects.