Solidification of river sediment by mayenite and biochar composite stabilizers: Strength development, microstructural evolution, and leaching behavior

Résumé fourni par la source

The resource utilization of urban river sediments is often hindered by their high-water content, poor mechanical properties, and potential environmental risks. In this study, a composite stabilization system based on mayenite (CA) and coconut-shell biochar (BC) was developed to simultaneously improve the engineering performance and environmental safety of contaminated sediments. The effects of initial water content, CA dosage, CA particle size, BC dosage, and BC particle size were systematically investigated using unconfined compressive strength (UCS) tests. The optimal conditions were 70% initial water content, 40% CA (250 mesh), and 20% BC (200 mesh), achieving a maximum UCS of 2.31 ± 0.11 MPa. Microstructural analyses revealed distinct functional roles of the two stabilizers. CA primarily provided mechanical stabilization by forming cementitious hydration products that bound sediment particles into a dense, continuous matrix, whereas BC mainly enhanced environmental stabilization through pore refinement and adsorption-assisted contaminant retention. As a result, the CA–BC composite significantly reduced the leaching of heavy metals, chemical oxygen demand, total nitrogen, and total phosphorus compared to CA stabilization alone. This study demonstrates that CA and BC play complementary roles in sediment stabilization, with CA dominating mechanical reinforcement and BC enhancing environmental stability, providing an effective strategy for the sustainable reuse of dredged sediments in geotechnical engineering.

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