Steel Slag Binder And Its Application In The Cemented Tailings Backfill

Cemented tailings backfill(CTB)has been widely applied since mining activities have shifted into deeper areas as well as sticker environmental protection policies.The finer tailings markedly increases the cost of backfilling binder material.The slag from iron production has been widespread used and has a higher price than Portland cement,while the steel slag from steel production has not yet been used sufficiently.In order to reduce the cost of backfilling,in the present work,a steel slag binder was developed with low cost and high performance for mine backfilling.Additionally,the rheological properties of the backfilling mixtures were also inspected.The findings can contribute to the efficiency and low-cost cemented backfilling as well as to the large scale high-value utilization of steel slag.The following works were presented.Firstly,in order to improve the low hydraulic properties of steel slag,the blast furnace slag and gypsum were added for activation.From proportion test,a steel slag binder(SFG)made of 35%steel slag,20%fluorgypsum,and 45%blast furnace slag was obtained,which has higher mechanical performance than Portland cement(PCI)in cemented tailings backfill.The hydration products were inspected through XRD,TG/DTG,and SEM analysis.After that,a coupled activation mechanism was introduced for the excellent hydration properties of the SFG.The activation mechanism consumes the expansive f-CaO and f-MgO,solving the volume instability of the SFG,which was approved by long term volume and strength monitoring.Secondly,an application of the utilization of SSB in Fujian Makeng Iron Mine was introduced,where the mechanical and rheological properties of the SSB-CTB were validated in engineering conditions of variant binder contents,solid mass concentrations,and aggregates.The results showed that the SSB can meet the variant strength requirements for the mining method of open-stope with subsequent filling.The influence of the aforementioned variation on the rheological properties of the SSB-CTB were studied and pressure drop of the CTB in pipeline transport was predicted,which the SSB-CTB can meet the flowability requirements.Additionally,the unit cost as well as the annual consumption of the SFG was only 57.4%and 53.3%of the PCI respectively,which showed great economic benefits.Finally,challenges of backfilling mixtures pipeline transportation was analyzed in deep and cold areas.The time-dependent evolution of the yield stress and viscosity of the CTB was experimentally examined.Effects of mix components(binder content,slag proportion,initial sulphate content,and salinity)and temperature on the rheological properties on the CTB were discussed.The findings can contribute to theoretical foundation for mine backfilling in deep and cold areas.