Compressibility and Permeability of Carbide Sludge–Ground Granulated Blast Furnace Slag-Treated Clay Slurry

Abstract

Dredged clay slurry is usually regarded as a waste material due to its high water content, high compressibility, and low strength. Treating dredged clay slurry with carbide sludge (CS)–activated ground granulated blastfurnace slag (GGBS) can efficiently improve its strength. However, the compressibility and permeability behavior of CS-GGBS–treated slurry have not been investigated. In this study, a marine clay slurry with water content of 100% was treated with 60 kg/m3 of CS-GGBS, and the compressibility and permeability were evaluated. The untreated clay was also investigated as a reference. The results showed that although the treated slurries had a significantly higher initial void ratio (∼2.5) than that of the untreated clay (0.96), they yielded similar vertical strains, that is, around 25%–31%, in an oedometer test. The compression curve of the treated slurries consisted of two distinct phases, which can be elucidated by the evolution of the soil-cementation structure. At the pre-yield state, the cemented structure of CS-GGBS–treated slurry sustained the external stress, leading to insignificant strain. When the vertical stress exceeded the yield stress, the soil-cementation structure largely collapsed, and considerable strain occurred due to its high void ratio. In this stage, the compression index (Cc) of the treated slurry was three times higher than that of the untreated clay. Additionally, the treated slurry had a coefficient of consolidation (cv) 30–100 times greater than that of the untreated clay, which was attributed to its high permeability. During the oedometer test, the permeability of the treated slurry decreased sharply upon initial compression of the specimens, and then decreased at a lower rate as the void ratio decreased, presenting a bilinear correlation between permeability and the void ratio.