Mechanical and hydraulic improvement of highly organic soil using Xanthan Gum: A strength–microstructure approach

Highly organic soils are often challenging for geotechnical applications due to their low strength, high compressibility, and increased permeability. This study investigates the efficacy of xanthan gum (XG) biopolymer as an ecofriendly alternative to traditional, carbon-intensive soil stabilizers. A comprehensive series of laboratory experiments was conducted to assess the effects of XG on the compaction behavior, unconfined compressive strength (UCS), elastic modulus (E₅₀), and permeability of organic soils. XG dosages ranged from 0% to 5% (by dry weight of soil), with aging periods extending up to 60 days. The test results demonstrate that 1% XG significantly improves the mechanical properties of the soil, achieving a sixfold increase in UCS and E₅₀ greater than 20,000 kPa within 28 days of aging. Additionally, permeability was reduced by 3–5 orders of magnitude, meeting the stringent requirements for hydraulic barrier applications. Scanning electron microscopy (SEM) identified the formation of a bridging gel matrix and associated pore-clogging as the key microstructural mechanisms responsible for the significant gains in strength and the drastic reduction in permeability. Based on the analysis of strength, stiffness, and permeability, 1% XG was identified as the optimal dosage. These findings highlight the significant potential of XG as a sustainable, cost-effective solution for stabilizing highly organic soils, offering substantial performance enhancement while maintaining environmental benefits. XG presents a viable alternative to conventional stabilizers in geotechnical applications, particularly in projects requiring environmentally conscious and efficient material solutions.