Recycling dredged mud slurry using vacuum-solidification combined method with sustainable alkali-activated binder

Dredged sediments with high water content is difficult to be treated and beneficially reused because of their poor engineering characteristics. To treat those slurry, this paper introduces a novel mechanical-chemical combined method, i.e., vacuum-solidification (VS) combined method, and investigates its performance in dewatering and strength improvement. Corresponding model tests using vacuum-only preloading method and binder-only solidification method, respectively, were conducted. Ground granulated blast-furnace slag, an industrial by-product, activated by hydrated lime, magnesium oxide or carbide slag was used as the binder in the proposed method. The mass of discharged water due to vacuum consolidation was measured during the model test. Soil samples were taken after vacuum preloading for unconfined compression test, permeability test, X-ray diffraction, scanning electron microscopy and mercury intrusion porosimetry to analyze the strength development, hydraulic and microstructural properties of the treated soil. The results indicate that the VS combined method exhibits a remarkable enhancement in both volume reduction efficiency and the strength improvement effectiveness. The type and content of activators have an obvious influence on the performance of the combined method. This study preliminarily revealed the mechanism and effect of using the VS combined method with alkali-activated GGBS as binder to treat high water content dredged mud.