Abstract: In order to confirm the possibility of solidification of arsenic-containing tailings by blast furnace slag-steel slag based cementitious materials （metallurgical slag cementitious material， abbreviation is MSC）， taking the lead-zinc mine tailings of a concentrator in Guangxi that contain 0.11% arsenic and the leaching concentrations of arsenic is 0.66 mg/L as the research object to prepare paste filling materials. The effects of the formulation of the cementitious material on the fluidity of the paste filling materials， the compressive strength of the solidified body， the leaching concentrations of arsenic and the pH of the leachate were investigated. Experimental results show that， if the mixed ratio of the backfilling materials of cementing agent to tailings is 1∶4， and subsequently the backfilling materials has a solid content of 86% in weight， and the dosage ratio of blast furnace slag， steel slag， desulfurization gypsum， and calcium hydroxide is 51%， 25.5%， 8.5%， and 15%， the fluidity of the filling slurry is 300 mm， and meet the requirements of paste filling and self-flow conveying. The average compressive strength of the solidified body is 20.19 MPa after 28 days curing at 40 ℃， and meet the requirements of cemented backfilling for compressive strength of filling body. The leaching concentrations of arsenic is lower than testing limit that is 0.004 mg/L. The addition of calcium hydroxide makes MSC more effective to immobilize arsenic. It is mainly reflected in the reaction of calcium hydroxide with arsenic ions to form Ca-As-O salt with low solubility， and is encapsulated by cementitious material hydration product C-S（A）-H gel. Furthermore， the addition of calcium hydroxide increases the pH of the leachate and the concentrations of Ca₂₊ in the leachate， and Ca₂₊ react with AsO₄^3-， AsO₃^3-， in formation of Ca-As insoluble precipitates to reduce the arsenic leaching concentrations.

Key words: Blast furnace slag, Steel slag, Solidification, Arsenic, Cemented backfilling