Mine backfill as part of tailings management

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Tailings management have become a crucial part of the mine operation in several areas: operational excellence, safety, profitability, mine closure and last but not least, sustainability.

Mine backfill has become an increasingly important operation in modern mining, not only as a proven method for improving ore recovery in underground mines but also as a strategic approach to tailings disposal and sustainable mine closure. The number of mine backfill operations is growing worldwide due to cost-effective solutions and the continuous advancement of industry expertise. Backfill accounts for approximately 20% of total mining costs, making it one of the largest single operational expenses. Among these costs, the binder represents the most significant share, contributing around 60% to 70% of total backfill expenses. Market trends indicate a continuous rise in the cost of OPC (Ordinary Portland Cement) in recent years. At the same time, the global push for reducing carbon footprints has accelerated the transition toward more environmentally friendly binders.

Clinker, a key component of OPC, is already at its production limit and is expected to become increasingly expensive over time. Supplementary cementitious materials (SCMs) appear has one of the most interesting solutions, both from a cost perspective and a sustainability aspect. SCMs are however also affected by similar trends: fly ash (FA), a byproduct of coal-fired power plants, is expected to decline significantly in volumes, while ground granulated blast furnace slag (GGBFS), a byproduct of steel manufacturing, do not present significant volumes to be a viable option for high volume clinker replacement (Figure 1).

In light of these developments, a more sustainable and long-term solution lies in the use of activated clays in combination with limestone as alternative raw materials for binders, with the flagship of those binders being the Limestone Calcined Clay Cement, so called LC³ binder. Evaluating market trends, Master Builders Solutions put significant efforts to understand the potential of those new systems for mine backfill applications and underground backfill disposal, looking at opportunities to improve and make them more cost effective (Figure 2). Our research provided significant breakthroughs in development of technologies suitable for this promising application – for more details see reference [2].

Master Builders Solutions recently developed a new and innovative admixture technology for low clinker and CO₂ reduced binders, namely Intelligent Cluster System (ICS). The finely tuned chemical structures of the diverse polymer clusters optimize both workability retention and cement hydration by adapting the release mechanism of polymers to the characteristics of the cement matrix. The unique mechanism of action of ICS technology thus ensures excellent flowability and rheology even at high temperatures, allowing easy pumping and placing of cemented paste backfill.

Master Builders Solutions game-changing technology pushes the limits of low-clinker mixtures by enabling the easy usage of high volumes of clinker substitutes while safeguarding high backfill quality. For backfill, the ICS technology is available under the MasterRoc MFxxx-LC³ range.

Comparing performance of the backfill mixes using LC³ binders with traditional cements, the high specific surface and different mineralogy of calcined clays make the cemented paste backfill more stiff and less fluid, requiring effective admixtures making these backfill mixes transportable (Figure 3). Master Builders Solutions has been intensively working on these issues and our current R&D work showed the feasibility and readiness of both admixture and binder technology for cemented paste backfill applications – see reference [3].

LC³ binders, and more generally binders containing activated clays, used in combination with the MasterRoc MF-LC³ range, based on ICS technology, will significantly contribute to improving performances of mine backfill mixes and improving ESG ratings for the entire mining operation. Reducing cost, carbon footprint and amount of tailings disposed underground, with innovative and sustainable binders, directly targets the social responsibility of mining industry, for which innovative admixtures are facilitators towards net zero goals.

Master Builders Solutions is a leading global manufacturer of concrete admixtures, as well as other solutions for concrete construction, focussed on delivering its vision: Inspiring people to build better. Master Builders Solutions provides value-added technology and market-leading R&D capabilities to improve the performance of construction materials and to enable the reduction of CO₂ emissions in the production of concrete. Founded in 1909, Master Builders Solutions has ca. 1700 employees operating 37 production sites globally, supporting their customers in mastering their building challenges of today – for a decarbonised future.

1. K. Scrivener, F. Martirena, S. Bishnoi, S. Maity, Calcined clay limestone cements (LC3), Cem. Concr. Res. 114 (2018) 49–56. 
2. S. Dhers, R. Guggenberger, D. Freimut, S. Fataei, P. Schwesig, Z. Martic, Impact of Admixtures on Environmental Footprint, Rheological and Mechanical Properties of LC3 Cemented Paste Backfill Systems, Minerals (2023), 13, 1552. https://doi.org/10.3390/min13121552 
3. S. Dhers, D. Freimut, Z. Martic, R. Salter, Admixture impact on rheological properties of a calcined clay binder for cemented paste backfill, Paste (2024) – AB Fourie & D Reid (eds), https://doi.org/10.36487/ACG_repo/2455_09