Effect of tailings fineness on flow, strength, ultrasonic and microstructure characteristics of cemented paste backfill

Mill tailings generated from the processing plant have been increasingly used in cemented paste backfill (CPB); however, the effect of their fineness (<20 mu m) on the performance of CPB is still not well understood. In this study, artificial silicon tailings with various fineness, e.g., 33.9%, 44.16%, 54.42%, 64.48% and 74.94% were first prepared. Then, the effect of tailings fineness on the fluidity, unconfined compressive strength (UCS), ultrasonic pulse velocity (UPV) and microstructural properties of CPB were evaluated. The result shows that, the increased tailings fineness decreases the fluidity of fresh CPB by lowering the water film thickness (WFT). The UCS and UPV of CPB decrease significantly as tailings fineness increases up to 54.42%. With a further increase of tailings fineness, the UCS and UPV remain constant or slightly increases. It is also found that the total porosity increases with higher tailings fineness, whereas the critical pore diameter decreases. Additionally, the UCS of CPB increases linearly with a higher pore refinement index. As a result, it will contribute to the efficient utilization of tailings waste and rational design of CPB structures. (C) 2020 Elsevier Ltd. All rights reserved.