Strength and hydration products of cemented paste backfill from sulphide-rich tailings using reactive MgO-activated slag as a binder

•Cemented paste backfill (CPB) is among the best available waste management techniques.•MgO content in MgO-GGBS significantly influences the strength development of CPB.•A optimum content of reactive MgO in MgO-GGBS is proposed as 7.5 wt%.•The secondary expansive gypsum is not detected in all the CPB.•Sulphides in CPB using MgO-GGBS as a binder will be stable. This paper investigated the potential of using reactive MgO-activated ground granulated blastfurnace slag (MgO-GGBS) as a binder in cemented paste backfill (CPB) from sulphide-rich tailings. The effects of reactive MgO content of MgO-GGBS on the unconfined compressive strength (UCS) of CPB were investigated. The test results showed that the CPB achieved target strength (≧1.0 MPa) at 28 d and the UCS at 360 d showed an increasing trend when MgO-GGBS dosage was 14 wt% and reactive MgO content of MgO-GGBS was 2.5–7.5 wt%. Thermodynamic calculations and analyses of potential reactions including acid and sulphate attack have been performed. The hydration products were identified by X-ray diffraction (XRD) and thermogravimetry analysis (TG/DTG). Finally, the hydration mechanism of CPB was discussed based on the thermodynamic and experimental results. The conclusion is that MgO-GGBS will be a promising binder for tailings with sulphide.