Shear strength of crosslinked xanthan gum biopolymer treated sand-clay mixture

Cr3+-crosslinked xanthan gum (CrXG) has emerged as a promising solution for enhancing moisture resilience, wet strength, and durability in biopolymer-soil treatment (BPST) applications. However, its shear strength behavior across diverse soil compositions remains insufficiently explored. This study investigates the shear strength characteristics of CrXG-soil composites, spanning from poorly graded sand to clayey silty sand using direct shear tests (DST) under varying moisture states (initially wet, dried, and re-submerged). The results show that CrXG treatment achieves optimal performance in pure sand at low confinement, with an increase in cohesion and a decrease in internal friction angle. Adding clay particles accelerates the crosslinking process, with CrXG-soil composite with 15% clay content (CSM15) demonstrating consistent shear strength improvements across all confining stresses due to agglomeration effects of the CrXG-clay matrix. XG-treated composites exhibit significant strength gains when dried but suffer severe strength losses upon re-submersion due to swelling. In contrast, CrXG-treated CSM15 retains shear strength across moisture states, demonstrating superior environmental resilience. These findings highlight the potential of CrXG-treated CSM15 for sustainable geotechnical applications, including slope stabilization and erosion control.