Soil consistency and interparticle characteristics of xanthan gum biopolymer–containing soils with pore-fluid variation

Biopolymer–soil technology is currently recognized as an environmentally friendly soil improvement method for geotechnical engineering practices. However, concerns exist regarding biopolymer fine-soil applications because the performance of biopolymers is based on an electrical interaction with clay or a pore fluid. Thus, the effect of water content and pore-fluid chemistry on biopolymer behavior in soil must first be clarified in terms of biopolymer applications. In this study, the liquid limits of xanthan gum biopolymer–treated clay–sand mixtures (clayey silt, kaolinite, montmorillonite, and sand) were obtained using three chemically distinct pore fluids (deionized water, 2 mol/L NaCl brine, and kerosene). Xanthan gum has contrary effects to the soil consistency, where the liquid limit can decrease via xanthan gum–induced particle aggregation or increase due to xanthan gum hydrogel formation. The clay-mineral type governed the xanthan gum behavior in the deionized water, while the pore-fluid chemistry governed the xanthan gum behavior in the brine and the kerosene.