<p>In this study, sedimentation tests were proposed as a complementary test to the swell index (SI), which is one of the performance-based test methods determining the barrier performance of bentonites. Initially, SI tests were conducted to find the critical CaCl₂ concentration at which the SI in deionized water and in the CaCl₂ solution was the same. The critical CaCl₂ concentration was found at 1.5–3.0 mM. Following SI tests the sedimentation tests were performed. In flocculation-type of sedimentation, tests were completed within 24&#xa0;h. Thus, the target was to achieve flocculation sedimentation for all bentonites to finish the tests quickly. Then, the performance evaluation was conducted to correlate SI and final sediment volume (FSV) with the liquid limit and hydraulic conductivity of bentonites. The coefficient of determination (R²) obtained for FSV was always greater than the R² obtained for SI. In the case of DIW, for example, the R² between FSV and liquid limit was 0.79 whereas the R² between SI and liquid limit was 0.36. Similarly, R² was 0.93 and 0.17 when FSV and SI were correlated with hydraulic conductivity, respectively. For CaCl₂ concentrations of 1.5 and 3.0 mM, the R² gradually decreased for both test methods.</p>