Effect of Gypsum Addition on the Mechanical and Microstructural Performance of Sulphide-Rich Cemented Paste Backfill

The present study investigates the effect of β-hemihydrate gypsum (HG) dosages on mechanical and microstructural performance cemented paste backfill (CPB) produced from sulphide-rich mine tailings using NaOH-activated slag (NAS) as major binder. X-ray diffraction (XRD), scanning electron microscopy (SEM) mercury intrusion porosimetry (MIP) analyses were carried out to elucidate mineralogical composition microstructure NAS-HG-CPB samples. results illustrate that main hydration products are crystalline (CaSO4•2H2O ettringite (AFt), 3CaO•Al2O3•3CaSO4•32H2O) amorphous. also show 28 d unconfined compressive strength (UCS) CPB with 30 wt. % HG replacing NAS increased by 52% compared UCS containing no HG, both have stable long-stage (180 d) (i.e., loss). Excess addition (≧50 %) reduced early-stage (≦28 led unstable formation secondary gypsum. use in accelerates process ground granulated blast furnace (GGBS) alkaline solution forming leading denser improved comparison HG. NAS-HG binder low (≦30 will be a promising for stabilising sulphide non-sulphide production.