Abstract: Semi-dry sintering desulfurization ash is a bulk solid waste generated by the steel industry,characterized by low utilization rate and high environmental pollution potential.River channel silt,on the other hand,exhibits high water content and significant pollutant loads,making it unsuitable for direct engineering application.To synergistically address the disposal challenges of these two types of solid wastes and achieve the concept of "treating waste with waste",this study developed a composite curing agent for river channel silt solidification using desulfurization ash as the main raw material,supplemented by cement clinker,fly ash,red mud,ground granulated blast furnace slag,and silica fume.The physicochemical properties of the desulfurization ash were characterized by XRF,XRD,and SEM.Ten formulations with different desulfurization ash contents (15%~60%) were designed,and the solidified silt was tested for unconfined compressive strength,California bearing ratio (CBR),free swell ratio,water content,pH value,and heavy metal content.The solidification mechanism was elucidated through microstructural analysis.The results show that the optimal desulfurization ash content is 15%,yielding a 28-day unconfined compressive strength of 1.44 MPa,CBR of 29.78%,free swell ratio of 2.45%,and water content of 19.6%,all meeting the re quirements for subgrade backfill.The strength decreases with increasing desulfurization ash content.After solidification,the contents of heavy metals such as Mn,Zn,Pb,and Cr are significantly reduced,far below the national standard limits.Microstructural analysis reveals that the alkaline components in the desulfurization ash activate the hydration reactions of the cemen titious materials,generating C-S-H and C-A-S-H gels,which fill pores,bind particles,and immobilize heavy metal ions through chemical complexation.The developed curing agent provides a feasible pathway for the resource utilization of desulfu rization ash and dredged silt,and the solidified soil exhibits both environmental safety and engineering applicability.

Key words: semi-dry sintering desulfurization ash,solidified silt,composite curing agent,unconfined compressive strength,heavy metal immobilization