Geotechnical performance of chitosan-amended soil: a sustainable approach to strength, durability, and microstructural characterisation

Abstract

The development of sustainable materials has gained considerable attention as an alternative to conventional chemical stabilisers in ground improvement applications. This study presents a systematic investigation into the performance of three soils amended with chitosan. Atterberg’s limit and compaction characteristics were evaluated for both untreated and amended soil. The amended soil was optimised by varying doses at 0.5%, 1.0%, and 1.5% by dry weight of soil. The OMC was subsequently varied to further refine the soil-biopolymer mix design. UCS tests were conducted by varying the curing period up to 180 d to encompass long-term effects. California bearing ratio was conducted on specimens and confirmed an increase in load-bearing capacity. Durability performance was evaluated by subjecting amended soil to 9 alternate drying–wetting cycles, which demonstrated comparable resistance to moisture-induced degradation as compared to 5% cement-treated soil. X-ray diffraction and field emission scanning electron microscopy analysis provided mechanistic insight into the physicochemical interaction in amended soil. A machine learning model based on Extreme Gradient Boosting was applied to experimental UCS data obtained through this study. The model achieved high predictive accuracy (R2 = 0.93, RMSE = 19.37, and MAE = 17.12), demonstrating strong agreement with experimental results. The results collectively establish chitosan as a promising material with significant implications for sustainable construction and ground improvement engineering.