Sustainable soil improvement using marine-derived biopolymers: strength and durability perspectives

This study provides a comprehensive evaluation of marine biopolymers for sustainable soil stabilization. It offers critical insights for countries with abundant ocean resources to support the selection of suitable biopolymer for soil enhancement. The experimental program covers a wide range of mechanical and microstructural evaluations to support a broad understanding of biopolymer-treated soil behaviour. A range of marine biopolymers was tested with a specific focus on chitosan due to its distinct structure and bonding capability. The study focused on engineered kaolinite-sand mixtures, selected for their ability to represent complex and variable soil conditions commonly encountered in the field. Experimental variables such as biopolymer content, curing time, and soil composition were systematically controlled. Mechanical properties were assessed using UCS, and static and dynamic triaxial tests to determine shear strength and resilient modulus. Durability was assessed through five cycles of wetting and drying to replicate long-term environmental exposure. Results showed that biopolymer content and soil type significantly influenced strength development and water resistance. Chitosan achieved up to a tenfold increase in UCS, with substantial strength retention and low mass loss under cyclic conditions. Microstructural analysis using scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR) provided insights into the chemical bonding and physical interactions at the soil–biopolymer interface. A mechanical model was proposed to explain these interactions. Overall, the study demonstrates the potential of marine biopolymers as effective, ecofriendly alternatives to traditional chemical stabilizers, offering a sustainable solution for geotechnical engineering applications.