Morphological controls on flow conductivity and viscosity of bentonite-polymer composite

In this study, we investigate the morphological organization of polymers in bentonite polymer composites (BPCs) used in geosynthetic clay liners (GCLs) and controls on hydraulic conductivity and viscosity. A limited understanding of the relationship between the microstructure of BPCs and their macroscopic engineering behavior motivates this study. Polymer resides in the inter-granular pores of the bentonite based on synchrotron based small angle X-ray scattering (SAXS) measurements, scanning electron microscopy (SEM) imaging, and pore size analyses. On wetting, the polymer swells to produce a swollen hydrogel residing in the intergranular pores. Enhanced tortuosity arising from hydrogel formation reduces the hydraulic conductivity of BPCs. Higher viscosity of BPC slurry is attributed to the higher shear resistance emerging from swelling of the polymer fraction on wetting. These findings link the morphological features of BPCs to observed hydraulic conductivity and viscosity of these materials.