## 4 Conclusions  
The novel solid waste-based backfill material developed in this study can treat and utilize desulfurization ash in large quantities. The effect of different HCDA, PCE, and SS additions on the rheological properties of DSPB was investigated. The conclusions to be drawn are listed below. (1) The setting time of DSPB slurry increased with decreasing HCDA content, increasing PCE dosing prolonged the setting time, and increasing SS content shortened it, but regardless of the changing influencing factors, the DSPB samples demonstrated suitable setting characteristics to meet the construction requirements. (2) The initial yield stress and plastic viscosity decreased by up to 88% and 34.9% with decreasing HCDA doping. At high HCDA dosing, the rheological parameters of the slurry decreased with time, attributed to the disruption of the flocculated structure of the slurry. With the decrease in HCDA dosage, the rheological parameters decreased and then increased, which was related to the increased release of reactive Si and Al due to the increase in slag dosage. When the PCE dosage increased, the \"card house\" structure led to an increase and then a decrease in the initial yield stress and plastic viscosity of the DSPB, and a high dosage of PCE improved the rheological properties by dispersing the particles. PCE showed an increase in yield stress with time at low dosage. The opposite was true at high dosage, and there was no obvious pattern to the change in plastic viscosity with time. SS significantly reduced the yield stress initially, but increased it with increasing dosage due to the C-S-H gel generated. Meanwhile, SS reduced the initial plastic viscosity, but at high dosage it resulted in a slight increase due to the viscosity of the sodium silicate solution itself. The role of SS on time-dependent rheology is reflected in that it could accelerate the hydration reaction and gel generation and reduce the rheological parameters; the high dosage of SS could further reduce the plastic viscosity, which may be related to the plasticizing effect of silicate oligomers. Figure 13: T\({}_{2}\) distribution of DSPB slurries with different SS dosages. Different reaction times: (**a**) 15 min; (**b**) 30 min; (**c**) 45 min; (**d**) 60 min. (3) The proportion of HCDA and GBFS affected the fluidity of DSPB. The initial fluidity was the largest in 85% HCDA, and with the reduction in the proportion of HCDA, the fluidity was significantly improved. The increase in PCE doping significantly improved the fluidity and reduced the loss. Activator SS doping on the slurry flow complex and a moderate amount of silicate oligomer plasticization reduced the initial fluidity. Excessive addition due to its own viscosity was higher, and the hydration reaction and C-S-H gel generation were promoted, so the fluidity was reduced. The findings in this study indicate the huge potential of using novel DSPB material for mine backfilling. The current study was carried out mainly in a laboratory, as well as in the field for preliminary practical checks. The study mainly investigated the rheological properties of DSPB and lacked the assessment of durability properties such as wet and dry cycling and carbonation resistance, as well as environmental safety assessment such as heavy metal ion leaching capability. In the future, the engineering practice of using DSPB in combination with mine waste rock and tailing to prepare full tailing backfill paste is needed to expand its application and enhance its utilization. Writing--original draft, project administration, supervision, W.L. ; methodology, investigation, J.C.; writing--review and editing, funding acquisition, data curation, W.M. All authors have read and agreed to the published version of the manuscript. This research was funded by the Provincial Special Project for the Construction of National Sustainable Development Agenda Innovation Demonstration Zone in Chenzhou City (2023 sfq50). Not applicable. Data availability Statement: Data will be made available on request.