Sulfate-induced changes in rheological properties of fibre-reinforced cemented paste backfill

Cemented paste backfill (CPB), a soft concrete-like material, is extensively used in underground mines worldwide for ground support and/or mine waste disposal. One of the most important ingredients in CPB is cement but it is expensive and can amount to 75% of the cost of the CPB. Therefore, CPB reinforced with fibres has been proposed and introduced in backfill operations to reduce the overall cement usage and cost, as well as improve the mechanical performance of CPB. However, the rheological properties of fibre-reinforced CPB and the factors that affect them are not well understood. The objective of this study is to therefore evaluate the effect of sulfate, which is commonly found in CPB, on the yield stress and viscosity of fibre-reinforced CPB through a series of experiments. The results show that the yield stress decreases with an increase in the initial sulfate content, while the viscosity increases as the sulfate content is increased. The sulfate ions significantly affect the amount and type of cement hydration products that form in the backfill matrix as well as the zeta potential of the fibre-reinforced CPB. The presented findings will contribute to improve the design and optimisation of backfill transport systems.