Efficient stabilization of dredged sediment by combining nano-modification and low-carbon supersulfated cement

Abstract

Supersulfated cement (SSC) is considered an environmentally friendly alternative to ordinary Portland cement (OPC), while its stabilization efficiency on dredged sediment (DS) is still unclear. Three types of SSC were prepared by combining ground granulated blast-furnace slag, alkali-activator NaOH, and a sulfate waste source, yielding SSCE (from electrolytic manganese residue), SSCP (from phosphogypsum), and SSCD (from desulfurization gypsum). To further enhance the stabilization efficiency of SSC on DS, nano-SiO 2 (NS) and nano-Al 2 O 3 (NA) were incorporated individually and as a composite blend. Mechanical properties and microstructural analyses were conducted to evaluate the stabilization efficiency and elucidate the underlying mechanisms. The leaching toxicity of SSCE-stabilized DS was investigated via leaching tests. The results showed that both alkali-activation and nano-modification can significantly improve the strength development of SSC-stabilized DS. At least 15% NaOH was required for SSC to achieve the same stabilization efficiency as OPC. The optimum NA-modified SSCD-stabilized DS demonstrated superior strength compared to OPC-stabilized DS. Composite NS/NA-modification was more efficient than using NS or NA individually. For DS stabilized with SSCE, SSCP, and SSCD, the optimal NS-to-NA mass ratios were 7:3, 3:7, and 3:7, respectively. Notably, the nano-modified SSCE-stabilized DS showed no environmental risks. Incorporating NS and NA into SSC-stabilized DS respectively promoted the formation of C-S-H gel and ettringite. A micro-mechanism model was developed to explain the strength evolution of nano-modified SSC-stabilized DS. This study provides a theoretical basis for the application of SSC in DS stabilization, and facilitates the collaborative resource utilization of industrial solid wastes and DS.

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