Short-Term Changes in Soil Aggregate Stability in Biopolymer-Amended, Coarse-Grained Soil

This project aims to quantify how soil aggregate stability changes over time in biopolymer-amended, coarse-grained soil. Biopolymers, which are naturally occurring polymers that are found in living organisms, have been identified as possible materials to use for ground improvement. However, commonly used biopolymers such as xanthan gum and guar gum can be broken down and used by microorganisms in soil. Consequently, prior experiments have not explicitly considered how soil properties change due to biopolymer amendment degradation. To study biopolymer persistence in soil, unamended and biopolymer-amended (1.0% w/w xanthan gum and guar gum) coarse-grained soil samples were incubated in a greenhouse for 0, 5, 15, 30, 60, and 100 days. Following the greenhouse maturation time, soluble polysaccharide content and aggregate stability were measured for all soil samples. Soluble polysaccharide content decreased over time for both the guar gum and xanthan gum amended soils, indicating biopolymer degradation. However, after an initial decrease, aggregate stability increased rapidly for the biopolymer-amended soils, reaching 80%-90% by day 100. These results suggest that biopolymer effects on soil properties persist even as components of the biopolymer degrade within the soil.