Strength and Microstructure Properties of Cemented Paste Backfill; Effect of Class-C Fly Ash

In this study, the effect of Class-C Fly ash (FA) as partial replacement (5-15% by weight) to sulphide tailings on the strength and microstructure properties of cemented paste backfill (CPB) was examined. Within this scope, CPB samples of control were prepared at 8.5 wt.% binder dosage while the other samples containing FA were prepared at 7.5 wt.% binder dosage. These samples were subjected to uniaxial compressive strength (UCS) and porosity (MIP) tests. Findings revealed that all CPB samples containing FA produced notably higher (1.18-3.16 fold) UCSs than control samples. All CPB samples ensured the stability criterion for backfill material (UCS≥1.0MPa), whilst, only the CPB samples containing 15 wt.% FA exceeded the roof (ground) support criterion (UCS≥5.0MPa). When the developments of porosity (MIP) were investigated, the partial replacement of sulphide tailings with FA enhanced the microstructure properties of CPB samples. These results suggest that the utilization of Class-C Fly ash (FA) as partial replacement to sulphide tailings is highly beneficial for the improvement of the strength, durability and microstructure properties of CPB