Compressive strength of soils amended with a bacterial succinoglycan: effects of soluble salts and organic matter

Abstract

The ability to stabilize soils in a cost effective and efficient manner has utility in both civil and military applications. This study examines the ability of a bacterial succinoglycan to bind and strengthen the silt fractions of three geochemically different surface soils. Small-scale specimen preparation and uniaxial compression test methods were developed to observe effects of biopolymer concentration and silt surface condition on specimen stress–strain response. Results indicate that the biopolymer was effective at strengthening all three natural silts and when applied at concentrations of 1–15 mg·mL−1, the increase in strength was linear. Silt surface condition was then modified by sequential removal of soluble salts and organic matter. For two of the silts, the removal of salts and organic matter had significant and cumulative negative effects on specimen compressive strength, deformation at peak stress, time to failure, and absorbed strain energy at failure. For a silt characterized by a high cation exchange capacity, high pH, and low aggregate percentage, the removal of organic matter did not reduce compressive strength beyond the level associated with the removal of soluble salts. Results from this study indicate that surface modification can significantly affect the compressive strength of silt materials and identified aggregate content as a principal determinant.