Abstract:

Cemented paste backfill is commonly used as a secondary support in mined-out stopes in modern cut-and-fill and long-hole sublevel stoping mining operations. It has proven to be a highly efficient technique that allows to maximize ore recovery while reusing up to 50% of the waste rock (tailings) as a backfill material. This process reduces the environmental footprint of the tailings stored on surface and associated hazards.

To reach strength requirements, paste backfill must incorporate a cementitious binder. The cost of the binder itself can account for up to 80% of the total backfilling operation cost. Therefore, reducing binder content in paste backfill can generate substantial savings while also reducing related CO₂ emissions from purchased consumables. The strength loss associated with binder reduction can be compensated by using paste backfill admixtures, which allows to increase the solid content of paste while maintaining a similar workability. Such technologies can have an impact on reducing the cement consumption related to the mining industry globally and therefore their use support reducing emissions associated with cement production.

In this study, cemented paste backfill mixes from three (3) different Canadian mines have been studied in the laboratory to validate the potential binder reduction through the use of paste backfill admixtures. In all three cases, the use of carefully selected admixture allowed to increase the solid content of the paste mix in the range of 3 to 4.5% depending on the mix while maintaining workability. The potential reduction in the binder content to get similar strength as the reference paste mix while maintaining similar workability was estimated in the laboratory and ranged from 14 to 26%. This potential reduction in the binder content could result in reducing the CO₂eq per kg of paste by 4 to 26% depending on the mix design considered. These results illustrate that admixture technologies can have powerful effect on paste mix design with significant potential for binder reduction while maintaining strength and workability requirements. While the focus of this study was binder reduction with associated economical and environmental benefits, the potential rheological improvements obtained by using paste backfill admixtures could allow for other benefits in the cemented paste backfill, such as reduced operating pressure or increased paste throughput.

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Sara Arcila Gut

Biography