Bio-cementitious stabilization of problematic soils using xanthan gum, calcium carbide residue, and bamboo fibers

Expansive clay soil has a low load-bearing capacity, so chemical stabilizers are commonly used to improve its strength. However, many stabilizers raise environmental concerns. To reduce reliance on conventional chemicals, researchers are exploring sustainable alternatives. This study investigates a novel method for stabilizing clay using a combination of the biopolymer xanthan gum (XG), calcium carbide residue (CCR), and bamboo fibers (BF). Clay samples were prepared with varying XG contents (1 %, 1.5 %, and 2 %), cured for 1, 7, 14, 28, and 56 days, stabilized with CCR (1.5 %, 3 %, and 4.5 %), and reinforced with BF (0.1 %, 0.3 %, and 0.5 %). The samples were tested for compaction, unconfined compressive strength (UCS), indirect tensile strength (ITS), freeze–thaw (F-T) resistance, ultrasonic pulse velocity (UPV), and microstructure using X-ray diffraction (XRD) and scanning electron microscopy (SEM). UCS results identified 1.5 % XG as the optimal content. Combining this with CCR, 2 % CCR produced the highest compressive strength while reducing the need for chemical stabilizers. Adding BF further enhanced soil performance, with the best results at 0.3 % fiber content; higher amounts caused clumping and reduced stability. Overall, the XG-CCR-BF combination increased compressive and tensile strengths by 1376 % and 919.4 %, respectively, improved ductility, raised UPV by 49 %, and enhanced resistance to F–T damage. Micromechanical analyses confirmed that strength gains were due to hydrogel and cementitious gel formation. These findings suggest that XG-CCR-BF-stabilized clay is a sustainable, high-performance material suitable for applications such as adobe bricks, road bases, and subgrades.