Utilization of limestone powder and water-reducing admixture in cemented paste backfill of coarse copper mine tailings

• Increasing finer LP up to 10 wt% improves workability of coarse tailings CPB.
• Coupled effects of LP and WRA are outstanding beneficial to workability of CPB.
• The complex incorporation of LP and WRA benefits mechanical performance of CPB.
• The UCS of CPB becomes larger when the pores of CPB samples becomes finer.

The purpose of this study is to assess the coupled effects of limestone powder (LP) and water-reducing admixture (WRA) dosages (by dry total mass) on the properties of cemented paste backfill (CPB) of coarse copper mine tailings. The mineralogical analysis and pore structure of the hardened samples are investigated by X-ray diffraction (XRD) and mercury intrusion porosimeter (MIP). Increasing LP dosages up to 10 wt% is beneficial to the workability of CPB mixtures, thereafter, the slump of CPB mixtures tends to decrease. The complex incorporation of LP and WRA remarkably improves the workability of CPB mixtures and increases the unconfined compressive strength (UCS) and the long-term stability of CPB samples by reducing W/B ratio without decreasing the slump value. The pores of CPB samples tend to become finer with increasing curing times and the incorporation of LP and WRA at the same slump value of CPB mixtures.