Sustainable development solidification of dredged silt by fluorogypsum with the flocculation and activation of shell powder.

The improper disposal of dredged silt may lead to land occupation, ecological contamination, reduced river flood discharge capacity, and navigation channel obstruction. Based on its inherent characteristics, a dual-functional composite solidifier used for simultaneous flocculation and solidification was developed. Its flocculation efficacy was evaluated by specific resistance to filtration (SRF), capillary suction time (CST), unconfined compressive strength (UCS) testing coupled with moisture transformation analysis etc. Results demonstrate that 3% of shell powder addition is optimal through Ca2+-mediated charge neutralization, electrical double layer compression and alkaline-stimulated gelation. Fluorogypsum facilitates the formation of AFt crystal for pore-filling, while the hydration of shell powder provides alkaline Ca(OH)2 to drive pozzolanic reactions to form C-S(A)-H gels which play a role in cementation and densification. The UCS of solidified soil reaches 2.52 MPa at the synergistic effect of the comprehensive waste utilization which displays superior sustainability and cost-effectiveness over conventional cement-based approaches. The solidified soil exhibits friendliness towards green plants. This disposal method achieves the recycling and resource recovery of three types of solid waste.