Interpretation of ion exchange in soil-bentonite mixtures
Interpretation of ion exchange in soil-bentonite mixtures
This study investigated the Ca2+-Na+ exchange within soil-bentonite (SB) mixtures, commonly employed in the construction of vertical cut-off walls, with a primary focus on the Ca2+ sorption and Na+ desorption processes. Batch tests were conducted using sodium bentonite, decomposed granite soil, and SB (7.5% mass fraction of bentonite), in CaCl2 solutions with concentrations ranging from 0.5 to 50 mmol/L. The results revealed a significant impact of the water- absorbing swell of bentonite on the volume of the bulk solution, which interfered the calculation of Ca2+ sorption. Notably, Na+ desorption ceased when the bulk Ca2+ concentration exceeded 4 mmol/L, simplifying the development of Ca2+-Na+ exchange into Ca2+ sorption process. The sorption isotherms of SB, Soil, and bentonite are proportional to their respective bentonite mass fractions. By incorporating parameters related to volume change and sorption isotherms, an average concentration of montmorillonite interlayer space (Cin) was proposed. Correlations were founded between Cin and the hydraulic conductivity of SB, offering insights into permeability changes based on batch test results.
R. Yu; Atsushi Takai; Tomohiro Kato; Takeshi Katsumi
18th European Conference on Soil Mechanics and Geotechnical Engineering (ECSMGE2024)
D - Current and new construction methods
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