Abstract
The present study investigates the effect of β-hemihydrate gypsum (HG) dosages on the mechanical and microstructural performance of cemented paste backfill (CPB) produced from sulphide-rich mine tailings using NaOH-activated slag (NAS) as the major binder. X-ray diffraction (XRD), scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP) analyses were carried out to elucidate the mineralogical composition and microstructure of NAS-HG-CPB samples. The results illustrate that the main hydration products of NAS-HG-CPB from sulphide-rich tailings are crystalline (CaSO4•2H2O and ettringite (AFt), 3CaO•Al2O3•3CaSO4•32H2O) and amorphous. The results also show that the 28 d unconfined compressive strength (UCS) of CPB with 30 wt. % HG replacing NAS increased by 52% compared to the UCS of CPB containing no HG, and both have stable long-stage (180 d) UCS (i.e., no strength loss). Excess HG addition (≧50 wt. %) reduced the early-stage (≦28 d) UCS of NAS-HG-CPB and led to unstable long-stage (180 d) UCS by the formation of secondary gypsum. The use of 30 wt. % HG replacing NAS in NAS-HG-CPB accelerates the hydration process of ground granulated blast furnace slag (GGBS) in the alkaline solution by forming ettringite (AFt), leading to the denser microstructure and improved mechanical performance in comparison with CPB containing no HG. The NAS-HG binder with low dosages of HG (≦30 wt. %) will be a promising binder for stabilising sulphide and non-sulphide tailings and CPB production.
Highlights
Sulphide-rich tailings are produced during the beneficiation or the treatment of sulphide ores and concentrates
Weak secondary gypsum (CaSO42H2O) peak in the X-ray diffraction (XRD). This could imply that the main hydration products of NaOH-activated slag (NAS)-hemihydrate gypsum (HG)-cemented paste backfill (CPB) are crystalline butproducts, no strength loss is noticed
The results show that the 180 d unconfined compressive strength (UCS) of NAS-HG-CPB h
Summary
Sulphide-rich tailings are produced during the beneficiation or the treatment of sulphide ores and concentrates. While non-ferrous mine tailings are used in backfill operations, the high sulphide content may influence CPB’s durability, especially when ordinary Portland cement (OPC) is used as the binder. Sulphates (SO4 2− ) and acidity resulting from the oxidation of sulphide minerals (i.e., pyrite) in the presence of water and air may cause potential durability problems (i.e., strength loss) in CPB. There are no studies on the effect of β-hemihydrate gypsum (HG) dosages on the properties of CPB from sulphide-rich mine tailings using NaOH-activated slag (NAS). In order to increase the early-stage strength of CPB using NAS as binders and effectively recycle waste gypsum to solve the environmental problem, the effect of βhemihydrate gypsum dosages on the mechanical performance and microstructure of CPB using NaOH-activated slag as binders is investigated in the current study. A series of X-ray diffraction (XRD), scanning electron microscope (SEM) and mercury intrusion porosimetry (MIP) analyses was carried out to elucidate the mineralogical composition and microstructure of CPB samples associated with mechanical performance
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
