Low-carbon remediation of contaminated marine mud sediment for efficient in-situ recycling and application

The improper disposal of marine bottom soft sediment poses significant risks to both ecological systems and human health. Due to its complex composition and contamination, sustainable remediation and reuse remain a major challenge. In tandem, the land limitation in some regions does not offer easy waste treatment, which in some cases hinders local governments in their waste management strategies. To overcome these challenges, this study proposes low-carbon treatments for contaminated marine mud, aimed at promoting efficient in-situ recycling and application as backfilling materials. The optimal treatments and long-term stability of the mud were attained by using aluminosilicate raw materials. Specifically, Unconfined Compressive Strengths (UCS) of up to 7.75, 4.24, 8.69, and 3.15 MPa were achieved respectively in mixtures containing 25% OPC, fly ash, slag, and 5% river sand. These mixtures not only improved the strength but also significantly immobilized the heavy metals efficiently, producing engineered-fill materials that meet both Chinese (GB36600-2018) and U.S. (EPA 540/2-86/001) standards, stipulated for health and environmental safety. Furthermore, the XRD analysis reveals a primary phase dominated by SiO₂ and secondary phases of Ca(CO₃), Mn_1.7Fe_1.3O₄ and a complex silicate mineral phase. Each phase contributes to distinct structural, chemical and mechanical development of the solidified mud, which was influenced by the supplemented raw minerals, as confirmed by the morphological analysis. The proposed treatment formulations not only facilitate large-scale recycling of contaminated marine mud into valuable construction materials, but also advance environmental protection, enhance resource efficiency, and support the goals of carbon reduction and neutrality. (Figure presented.)