Laboratory Determination of Hydraulic Conductivity and Diffusion Coefficient of Bentonite-Enhanced Sand Mixtures

Bentonite-enhanced sand (BES) mixtures are usually used in contaminant barrier systems in solid and radioactive waste disposal sites. In these types of barriers permeability is the most important property and the contaminant migration by molecular diffusion must be low. In this study the hydraulic conductivity and pure diffusion tests were performed on compacted BES mixtures with 10, 20, 30 and 40% bentonite contents. Experimental results illustrated that with increasing bentonite content, the hydraulic conductivity of BES mixtures decreased substantially and chloride effective diffusion coefficient decreased. Except for BES mixture with 10% bentonite content, the hydraulic conductivities of remaining BES mixtures meet the minimum recommended standard for hydraulic conductivity of contaminant barrier systems. The pure diffusion tests on BES mixtures resulted in the chloride effective diffusion coefficients ranging from 3.1×10-10 m2/s to 1.7×10-10 m2/s for 10% to 40% bentonite contents, respectively

Keywords:

Bentonite-enhanced sand (BES) mixtures , contaminant barrier , hydraulic conductivity , diffusion Coefficient