Authors: Tarr, K; Bedard, I; Kim, H

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Tarr, K, Bedard, I & Kim, H 2015, 'Acti-Gel® 208 as an additive for paste and hydraulic backfill', in R Jewell & AB Fourie (eds), Proceedings of the 18th International Seminar on Paste and Thickened Tailings, Australian Centre for Geomechanics, Perth, pp. 391-405.

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Paste technology has progressed to a widely accepted, cost-effective backfill method, and is also used extensively in surface tailings disposal. The non-segregating nature of paste makes it a very attractive option for backfilling, and its stacking behaviour due to its low water content significantly reduces the risks associated with surface tailings dam failure. While the capital and operating costs for the preparation and transportation of paste are higher than that of hydraulic fill, there are significant benefits with respect to transportation, such as reduced pipe wear and reduced risk of pipe plugging, not to mention the benefits associated with greatly reducing the water handling issues underground. From an environmental standpoint, the benefits of paste versus hydraulic fill include the ability to place more of the fine tailings fraction underground, thereby reducing the need for surface tailings storage. Another environmental benefit is the reduced risk of downstream contamination in the case of a tailings dam failure, due to the fact that disposing of the tailings in a paste form means virtually no need for liquid containment, and therefore no means for the tailings to travel downstream. Portland cement is typically used to solidify backfill, whether paste or hydraulic. This represents a major cost in mining operations due to production and haulage costs of ordinary Portland cement. In addition, the manufacturing of cement raises environmental considerations because it produces a considerable amount of CO2 emissions. Therefore, the search for additives which allow for a reduction in the required cement content in backfill has been ongoing for decades. Acti-Gel®208 is a highly purified magnesium aluminosilicate that acts as a high performance anti-settling agent and rheology modifier used in a wide variety of water-based industrial applications. Studies have shown that as an additive in paste backfill, it results in improved strength and flow properties, such as friction loss and segregation. This paper presents the results of a study conducted by Active Minerals International LLC for a South African gold mine operation in 2013, as well as the results of a study conducted by the CanmetMINING Sudbury Laboratory for Vale Canada Ltd. in Sudbury, Ontario, Canada, in 2014. The feasibility of ActiGel®208 as a cost-effective additive for underground paste and hydraulic backfill applications was investigated through the preparation of samples to compare the strength and flowability characteristics of standard mixes to those containing different dosages of Acti-Gel®208. It was found that at a low dosage of 0.03 wt%, Acti-Gel®208 delivered enhanced performance in unconfined compressive strength tests as well as in the pilot-scale flow tests. A significant reduction in binder content could be realised with addition of Acti-Gel®208 at the gold mine operation in South Africa, as well as at the Coleman and Creighton Operations in Sudbury, Ontario, Canada. The economic benefits of such a binder reduction with respect to the Canadian operations are also discussed in this paper.

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