Rosales, C, Courcelles, B & Demers, I 2026, 'Hydrogeological behaviour of stabilised paste and filtered tailings cover systems under extreme climate conditions', 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. 1-11, https://doi.org/10.36487/ACG_repo/2655_05 (https://papers.acg.uwa.edu.au/p/2655_05_Rosales/) Abstract: Tailings cover systems represent a promising strategy for mine site reclamation, particularly in areas with limited access to natural resources, as they help to control acid mine drainage (AMD) generation. However, their long-term durability can be compromised under extreme climatic conditions. Processes such as cracking and pore size redistribution often indicate internal structural changes that reduce the hydraulic performance of the cover. Cyclic events, including prolonged droughts and freezing temperatures, are among the main climatic stressors that accelerate such degradation. The initial solid content strongly influences the structural stability and hydrogeological response of cover systems. Lower solid content increases the susceptibility to internal changes. For instance, paste tailings tend to develop wide cracks shortly after deposition due to rapid water loss by evaporation and drainage. In contrast, filtered tailings more commonly exhibit finer fissures associated with settlement, low density or inadequate compaction procedures, effects that are amplified under cyclic extreme climatic conditions. To overcome these limitations, this study investigates slag–cement stabilised tailings as an alternative cover system. Column tests were conducted under controlled laboratory conditions to simulate extreme climatic cycles and evaluate the hydrogeological behaviour of stabilised paste and filtered tailings. Results show that the slag–cement stabilisation effectively limited structural variations after curing. Furthermore, stabilised paste tailings exhibited superior performance in maintaining a high degree of saturation, suggesting enhanced resilience to cyclic climatic stresses. Keywords: paste, filtered, tailings, stabilisation, cover system, freezing-thawing, wetting–drying