White paper: Portland-limestone cements in paste backfill – performance limits and hidden environmental costs

Authors: Salvoldi, B; Kraft, T Download Paper Open access courtesy of:

DOI https://doi.org/10.36487/ACG_repo/2655_07

Cite As:
Salvoldi, B & Kraft, T 2026, 'White paper: Portland-limestone cements in paste backfill – performance limits and hidden environmental costs', in AB Fourie, M Horta, M Oliveira & S Wilson (eds), Paste 2026: Proceedings of the 28th International Conference on Paste, Thickened and Filtered Tailings, Australian Centre for Geomechanics, Perth, pp. 1-18, https://doi.org/10.36487/ACG_repo/2655_07



Abstract:
Portland-limestone cements (PLC) are increasingly promoted as a sustainable option in cement production, where partial clinker replacement reduces CO₂ emissions. While effective in concrete, this assumption has been transferred uncritically to cemented paste backfill (CPB). In CPB systems, which are dominated by ultrafine tailings and a relatively small binder fraction, the mechanisms that make limestone beneficial in concrete are largely absent. Instead, limestone additions can negatively impact water demand and strength development. This paper re-assesses the role of PLC in CPB by reviewing underlying mechanisms, published performance data, and environmental implications. Evidence indicates that limestone substitution often leads to reduced mechanical strength, higher binder requirements, and increased susceptibility to chemical deterioration, ultimately undermining sustainability claims. The paper argues that use of PLC in CPB represents misplaced sustainability and highlights alternative binders, particularly through the use of locally available supplementary cementitious materials, that offer more credible economic and environmental benefits for mine backfilling.

Keywords: Portland-limestone cement, limestone, cemented paste backfill, backfill, ultra-fine tailings, sustainability, supplementary cementitious materials

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