The benefits of incorporating chemical admixtures into mine paste fill designs are numerous and cost effective, especially when incorporating metrics such as energy- and cement consumption, reduced dewatering costs, reduced downtime and pipe blockages as well as reduced plant maintenance costs into the equation. The addition of admixtures is a tool to optimize the backfill product in order to have a direct feedback on the backfill quality and numerous operating cost centres. Using admixtures provides the paste fill engineer with a tool to adjust and modify many variables of the paste mix. The following variables can be modified in order to obtain a cost performing backfill paste: enhanced rheological behaviour (better thixotropic profile, improved slump, better pumpeability), reduced water content, reduced cement content or change of cement type, increased solid content, improved compressive strength and improved cure time. An adjustment to any of the mix design variables can result in significant improvements of the paste cost-performance and reduction in overall operational expenses. Test results have proven that the addition of a single admixture at relatively low dosage of 1% to 3% by weight of cement can have powerful effects in modifying the parameters listed above. A prerequisite for good results is a good understanding about the mineralogy and granulometry of the ore host and therefore the source of the tailing material which leads to a customized adjustment of the used admixture in any given paste backfill operation. This paper outlines results from different mine backfill pastes and how to come up with the right admixture choice.
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