An Investigation into the Potential Use of Calcium Carbonate Nanoparticles in Mine Backfill

This study is part of large and ongoing investigation into the potential use of calcium carbonate nanoparticles (NCaCO3) to improve the mechanical and physical properties of mine backfill. The investigation was conducted in two phases. In phase I, gold tailings were used to prepare backfill sample using Portland cement (PC) as the binding agent under various NCaCO3 and superplasticizer (SP) dosages. In phase II, fine silica sand was used to minimize the reactive nature of tailings, which can adversely affect uniaxial compressive strength (UCS). Samples in this phase were prepared under various NCaCO3 dosages using slag:PC weight ratios of 80:20 as the binding agent. Select samples from phase II were subjected to Mercury Intrusion Porosimetry (MIP) to compare microstructural properties before and after addition of NCaCO3. Phase I results showed that the UCS of samples containing NCaCO3 was low, even when SP was used to improve particle dispersion. Phase II samples exhibited up to 9.5% higher UCS after 28 days of curing at a NCaCO3 dosage of 6% by weight of binder. MIP results showed that samples containing NCaCO3 were less porous than the corresponding controlled silica sand backfill samples, which in turn influenced the UCS results.