Modeling the effect of sulphate on strength development of paste backfill and binder mixture optimization

The increasing use of paste backfill in underground mining makes it necessary to quantify the effect of sulphate on the strength development and economical performance of paste backfill. Therefore, the main objective of this study was to develop a methodological approach and a mathematical model to analyze and predict the strength development and cost of underground paste backfill containing different amounts of sulphate. This study demonstrates that the paste backfill can be defined as a “mixture system”. We were able to show that a material model based on quadratic functions can be a suitable basis for the prediction of both the mechanical [uniaxial compressible strength (UCS)] and economic (binder cost) properties of paste backfill. The developed models allowed us to obtain valuable results about the relationship between the sulphate quantity and the mechanical performance of the backfill and the prediction of its strength at different curing times. This study has demonstrated that the sulphate significantly influences paste backfill strength. This influence is related to its concentration, the curing time and the amount and chemical composition of the cement.