Recycling hazardous steel slag after thermal treatment to produce a binder for cemented paste backfill

Steel slag is a solid waste during steel production, which poses substantial environmental impacts. The present work explored the feasibility of preparing an eco-friendly binder for cemented paste backfill (CPB) using steel slag after being thermal treated. Steel slag was calcined at 600, 800 and 1000 degrees C. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) were performed to study the structure modification on steel slag after thermal treatment. Steel slag calcined at 1000 degrees C (SS100) showed the highest pozzolanic reactivity due to the formation of dicalcium silicate (C2S). SS1000 was then used to prepare binders for CPB supplemented by metakaolin (MK) and silica fume (SF). The results showed that samples with 15 wt% MK and 5 wt% SF addition (P3) demonstrated the optimal performances. After curing for 28 days, the CPB samples (CPB3) using P3 as a binder showed the highest compressive strength (2.88 MPa) at a binder/tailings ratio of 1/4, reaching around 88.7% of that of the CPB samples made using ordinary Portland cement (OPC). Leaching tests showed that all the toxic metals were stabilized in CPB3, which posed no environmental risk. (C) 2021 Published by Elsevier B.V.