Investigation of Stability and Underlying Mechanism of Unstable Subgrades Loess Modified by Carbide Slag in Road Construction Projection

The repurposing of carbide slag (CS) coupled with the advancement of eco-friendly engineering methodologies promises a novel approach to addressing the technical challenges inherent in loess refinement. This inquiry delves into the feasibility of employing CS as an economically viable and ecologically sustainable remedy to amplify the engineering attributes of loess within the context of optimal preservation. In this investigation, assorted quantities of CS, spanning from 1% to 6%, were infused into the loess. The efficacy of CS as an additive was ascertained through a comprehensive array of tests administered across varied curing durations (0, 5, 10, 20, and 30 days), concentrating on its influence over the soil’s mechanical attributes. The study conducted various tests such as dual hydrometer, Attberg limit, specific gravity, compaction, unconfined compressive strength (UCS), consolidation, physico-chemical properties (pH, conductivity), and chemical analysis (sodium percentage and sodium adsorption rate). The study demonstrated that the incorporation of CS into loess resulted in an increase in hydraulic conductivity, UCS, and optimum water content while reducing maximum dry density, plasticity, and compressibility. Specifically, the application of 6% CS resulted in a significant 6.7-fold increase in UCS from 226.8 (kPa) to 1508.8 (kPa) over a 30-day curing period. It was also observed that the addition of CS and curing period resulted in a decrease in soil pH from 8.5 to 7.5 and an increase in electrical conductivity (EC) from 250 to 490 μs/cm. When the CS concentration was increased to 6%, the amount of Na+ ions, the total soluble salts, and the percentage of Na in the loess decreased. The phenomenon can be ascribed to the replacement of Ca2+ for Na+, leading to a more slender, diffuse double layer and heightened stability. The application of calcium silicate in loess subgrades enhances their stability and potency, concurrently providing an ecologically sound waste management resolution. Consequently, it emerges as a profoundly viable choice for ameliorating loess within the realm of the construction sector.

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