Potash waste process rheology: initial testing of performance of binders and other additives to proposed waste slurries

Synopsis As part of a project to study the feasibility of reducing discharges from a potash mine by stowing tailings materials underground, a series of beaker tests was carried out to examine the efficiency of a number of binders appl ied to different ratios of centrifuge and filter cakes. It was envisaged th at the tailings could be treated with a binder to produce a solid material within 24 h of placement underground. In total, 73 combinations were produc ed and compared. Strength development tests were performed on two mixes wit h three binder combinations over a period of 14 days in the SChEME laborato ries at the University of Nottingham, England. Viscosity measurement tests and subsequent rheology modification tests were also carried out to establi sh the pumping characteristics of various mixes. Stowage of the 100% filter cake slurry was accorded precedence on environme ntal grounds, but its pseudoplastic nature was found to present serious pum ping difficulties. It was concluded that neither the use of binders to stab ilize the placed slurry nor that of chemical admixtures to modify the slurr y viscosity would be feasible economically. As a consequence, it is now pro posed to use coarse salt notation tailings in the centrifuge cake to alter the slurry viscosity and to add binders to part of the slurry only, employi ng this material for the construction of underground retaining weirs.