Assessment of Bentonite Compatibility with Salinity Using Centrifugation-Based Water Retention

A generalized centrifugation-based water retention (CWR) test has been developed to evaluate the chemical compatibility of geosynthetic clay liner bentonites with different inorganic aqueous solutions of various types and ionic strengths of two salts, NaCl and CaCl₂, and to serve as a surrogate for the standard swell index (SI) test. The intention of this study is to provide the industry and researchers with a powerful, robust, and accurate method that fulfills the same pre-screening role as the SI test but is more efficient, quantifiable, and reproducible. The steps to optimize the centrifugation-based test are reported and discussed, and the effects of various parameters (e.g., g level, centrifugal duration, ionic strength of inorganic salts, etc.) on the water retention characteristics of bentonite are analyzed and evaluated. In general, water retention of bentonites decreased with increasing salt loads and centrifugal forces. Centrifugal duration (30 min versus 60 min) had little to no effect on the measured CWR values. The CWR strongly correlated with SI for the same samples, enabling predictions of SI of Na-bentonite in weak to strong saline solutions.