Geotechnical behavior of high-plastic clays treated with biopolymer: macro–micro-study

The quantification of long-term performance of mechanically/chemically treated problematic soils is still under discussion. Likewise, exploring the availability and use of eco-friendly and sustainable stabilizing admixtures is a parallel area of contemporary research. This paper presents the laboratory results of a highly plastic soil strengthened with xanthan gum (XG) biopolymer to determine its suitability as a suitable subgrade for pavements. The XG content varied from 0 to 5 percent, and the specimens were tested at different aging periods (0‒60 days). The unconfined compressive strength (UCS) of soil strengthened with 1.5% XG content showed a considerable enhancement in strength by 314 percent, strength improvement ratio (SRI) increased by 8.3 times, and energy absorption capacity (E_v) by 1.4 times, resulting in a hard-quality subgrade for pavement construction. The compression (C_c) and rebound (C_s) indices were greatly reduced by 78 percent, as well as the swell potential parameters (percent swell (S_w) and swell pressure (S_p)) were decreased by 85 percent on average. The hydraulic conductivity of treated soil as well as the moisture-mass losses in freeze–thaw durability test was also found to be greatly enhanced with increased XG content. Aging time also plays a pivotal role in enhancing the strength and anti-deformation characteristics of stabilized soil up to 60 days. SEM coupled with EDX analysis proved the aggregation of soil particles by hydro-gelling effect of biopolymer, which helps in the improvement of strength and durability. Therefore, XG biopolymer has a promising potential as an alternative admixture for treating widespread fat subgrade soils.