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Soil stabilisation through materials such as lime or cement have considerable environmental penalty due to high embodied energy of the cementitious material. Biogeotechnology allows cement formation with dramatically reduced carbon footprint and promises a sustainable soil improvement method. In the current study, investigations were performed to evaluate the effect of biopolymer Xanthan gum and Microbially Induced Calcite Precipitation (MICP) on cementation of sands as well as sand-clay mixtures individually as well as in combination. The unconfined compressive strength tests and micrographic analysis through scanning electron microscope and energy dispersive X-ray spectroscopy results revealed that synergistic effect of biopolymer and MICP resulted in superior performance. Water absorption test indicated that the Xanthan gum was susceptible to water attack and incorporation of MICP helped in addressing the concern. Therefore, the present study was successful in overcoming the individual limitations of biopolymer and MICP as a sustainable soil stabilisation technology.

To achieve the sustainability goals, Australia must dramatically reduce use of cement for stabilisation of soil used in road bases. Bio-based binders for soil stabilization are potential alternatives. Biocementation through Microbially Induced Calcite Precipitation (MICP) is well researched. Some research on biopolymeric stabilization is also available. This paper explores the synergistic effect of combined biopolymer and biocement for the stabilization of sandy soil and road bases. The soil has been stabilised using both biopolymer xanthan gum and MICP. The synergy between biopolymer and MICP has been evaluated by giving a few samples a combined treatment. The performance has been evaluated by compressive strength tests, micrographic analysis and water absorption. Although biopolymer treatment improved the compressive strength it degraded significantly in presence of water. Relatively high water absorption of xanthan gum could be mitigated by MICP. The study demonstrates that MICP surface coating is a sustainable solution to overcome this limitation of biopolymer. Likewise, the addition of biopolymers reduces the release of ammonia from MICP. The present study unravels the potential of a composite bio-treatment for stabilisation of road bases.

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