Geotechnical investigation of reclaimed asphalt pavement and xanthan gum treated silty sand

This thesis conducts a comprehensive investigation into the impact of recycled waste construction material and an eco-friendly biopolymer on the stabilization of local soil. The laboratory-based experimental program focused on silty sand (SM) soil treated with 10% reclaimed asphalt pavement (RAP) and Xanthan gum (XG) concentrations (0%, 0.5%, 1%, and 3% by total dry weight) across curing periods of 0, 7, 28, and 56 days. Results indicate distinct effects on soil properties: RAP reduced liquid limit, plastic limit, and optimum water content (OMC) while increasing maximum dry density (MDD). Conversely, XG elevated these parameters and decreased MDD. In 7-day cured specimens, the inclusion of 10% reclaimed asphalt pavement (RAP) significantly enhanced compressive strength. The initial strength of 2983 kPa for the clean soil rose to 3464.9 kPa with the addition of RAP. Incremental changes were observed at rates of 0.5%, 1%, and 3% XG, resulting in compressive strengths of 4754.9 kPa, 6189.6 kPa, and 7999.1 kPa, respectively. Curing effects on strength were partially positive, peaking at 28 days. The biopolymer positively influenced shear strength but exhibited a paradoxical outcome in consolidation and California bearing capacity tests, increasing consolidation while decreasing bearing capacity. In summary, this study highlights the multifaceted effects of XG on soil behaviour, emphasizing the need for a nuanced exploration of the intricate interplay between XG and water in soil systems.