Rheology of ultrafine tailings cemented paste backfill: The effect of the aqueous solution pH and superplasticiser dosage

pH is an important factor affecting the rheology of fresh ultrafine tailings cemented paste backfill (UTCPB). In this study, the effect of solution pH on the packing density of fresh UTCPB containing polycarboxylate superplasticizer (PCE) was investigated experimentally. The effect of PCE dosage on the dynamic rheology and thixotropy of the UTCPB at both pH 2 and 7 of the aqueous solution was investigated. A relationship model between water film thickness (WFT) and dynamic rheological parameters of UTCPB was constructed. In addition, the improved model for predicting rheological parameters considering flocs was developed. The results show that the packing density and WFT of the ultrafine tailings cemented paste are significantly influenced by the pH of the mixture and the PCE dosage. The packing density and WFT at pH 2 were greater than those at pH 7. For aqueous solution pH 2, the critical micelle concentration (CMC) was approximately 0.05% and the thixotropic index decreased with increasing PCE dosage. For aqueous solution pH 7, the CMC is between approximately 0 and 0.05%. The relationship between WFT and the rheological parameters of UTCPB is exponential. The proposed rheological parameter prediction model has high accuracy and applicability. The results of this study could provide guidance for the design and application of UTCPB in mines.