Enhancing mechanical properties and freeze-thaw durability of xanthan-stabilized kaolinite clay with randomly distributed animal-based fibers

Due to the limited load-bearing capacity of kaolinite soil, stabilizing it with chemical stabilizers has gained considerable attention. However, these stabilizers often pose environmental concerns. As a result, there has been growing interest in using natural and eco-friendly materials to improve soil properties. This laboratory study presents a novel composite approach for soil treatment, combining sheep wool fibers (SWF) and xanthan gum (XG) biopolymer. Kaolinite soil was mixed with varying concentrations of XG (0.5%, 1%, and 2%), with curing times of 1, 7, 14, and 28 days, and different proportions of SWF (0.3%, 0.6%, and 0.9%). Tests conducted included compaction, unconfined compressive strength (UCS), indirect tensile strength (ITS), California bearing ratio (CBR), freeze-thaw (F-T) cycles, scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS). The optimal XG content was initially determined to be 1% through UCS testing. Subsequently, the effects of this optimal XG concentration combined with varying SWF ratios were investigated. The UCS and ITS results indicated significant improvements, with the compressive and tensile strengths of the XG-SWF-treated soil being 582% and 354% higher, respectively, than those of the control samples. The addition of SWF increased the ductility of the samples, resulting in greater failure strain. The optimal fiber content was found to be 0.6%; beyond this concentration, fiber twisting and aggregation reduced the structural integrity of the specimens. The combined application of XG and SWF enhanced the CBR value by 177%. F-T cycle tests also demonstrated that XG-SWF-treated samples experienced less strength loss compared to the control group. SEM and EDS analyses further validated the mechanical testing results from a micromechanical perspective. Overall, the findings suggest that XG- and SWF-enhanced soil can serve as an excellent subgrade material for infrastructure applications, such as foundations, roads, and railways, based on its improved mechanical performance.