Cold-bond agglomeration of gold mill tailings for backfill using gypsum betahemihydrate and cement as low cost binders

Abstract

Several types of binder have been studied at Laurentian University using the Cold-Bond Tailings Agglomeration (CBTA) process of fine mill tailings. Most of these binders have been alkaline (lime, blast furnace slag cement, Portland cement, etc.). However, the application of non-alkaline and more economical binders should be examined. Investigation of the cold-bonding ability of gypsum (beta-hemihydrate form), which is the most common and economical form of gypsum, was the main objective of this study. A drum pelletizer was used in the agglomeration process to investigate the influence of varying the moisture content of the pellets, binder dosages, pellet size, and curing period on the strength of the agglomerates. The investigation of the properties of gypsum as a binder for cold-bond agglomeration of fine gold mill tailings showed that the wet strength of the green pellets is strongly influenced by the moisture content. In general, green pellets achieved sufficient wet strength to withstand breakage during transportation. Also, an increase in pellet size resulted in an increase in the strength of pellets. The cured pellets developed higher strength with addition of gypsum to cement than using Portland cement alone as the binder. Therefore, as a lowcost binder, gypsum (beta-hemihydrate) can be utilized economically in the agglomeration process of fine gold mill tailings. Since flue gas desulphurisation gypsum (FGD) products are now available in the market, it is viable to use it as a low cost binder for the CBTA process.