Chemical Compatibility andEngineering Performance of aHigh-Plasticity Indian Bentonite Under Salt, Acid and Synthetic Municipal Leachate Exposure
DOI:
https://doi.org/10.7492/2tspre29Keywords:
Bentonite, chemical compatibility, landfill liner, synthetic leachate, swelling, consolidation, compressibilityAbstract
Bentonite-based barriers are widely adopted in engineered waste containment systems due to their low hydraulic conductivity and self-sealing capacity; however,
their long-term performance is vulnerable to chemically aggressive environments. This study examines the chemical degradation mechanisms governing the hydromechanical behavior of high-swelling sodium bentonite exposed to monovalent (NaCl), divalent (CaCl₂), and synthetic landfill leachate solutions. Comprehensive
laboratory testing was conducted to evaluate changes in hydration behavior, consistency limits, compaction response, swelling potential, compressibility,
consolidation characteristics, mechanical strength, and settlement behavior under increasing ionic concentration.Baseline characterization confirmed the suitability
of the bentonite for barrier applications, with a liquid limit of 380%, free swell index of 150%, and hydraulic conductivity of approximately 5 × 10⁻¹¹ m/s. Chemical
exposure produced marked degradation trends. NaCl solutions caused progressive diffuse double layer compression, reducing swell by nearly 40% and increasing
dry density by up to 8% as concentration increased from 0.1 M to 1.0 M. In contrast, CaCl₂ exposure resulted in severe fabric alteration through divalent cation
exchange, leading to swelling suppression exceeding 80%, a reduction in unconfined compressive strength of more than 60%, and an increase in compression
index from 0.50 to 0.80. Pre-consolidation pressure decreased by up to 30%, indicating heightened susceptibility to permanent deformation. The synthetic leachate
produced intermediate responses due to mixed ionic and organic interactions. These findings demonstrate that divalent cation contamination poses a critical risk to
bentonite liner integrity and highlight the necessity of chemical compatibility assessment in geotechnical barrier design for waste containment facilities.
