Quintero Olaya, S, Zhang, C, Yang, Y, Moturi, SA & Williams, D 2026, 'Fibre reinforcement to improve tensile strength and desiccation behaviour of 
red mud at reduced moisture contents for tailings storage facility closure', in AB Fourie, G Boggs, J Heyes & M Tibbett (eds), Mine Closure 2026: Proceedings of the 19th International Conference on Mine Closure, Australian Centre for Geomechanics, Perth, pp. 1-16, https://doi.org/10.36487/ACG_repo/2615_135
(https://papers.acg.uwa.edu.au/p/2615_135_Quintero_Olaya/)
Abstract: Red mud (bauxite residue) tailings is caustic, clayey silt-sized material characterised by high water retention, slow consolidation and low strength development during discharge into tailings storage facilities (TSFs), resulting in ongoing operational challenges and increased closure complexity. As red mud TSFs progress towards closure and rehabilitation, these characteristics can translate into elevated porewater pressures, limited strength gain and long-term instability risks, including groundwater levels remaining close to the surface.
This study investigates the use of polypropylene (PP) and high-density polyethylene (HDPE) fibre reinforcement to improve the mechanical behaviour of red mud at reduced moisture contents (MCs) relevant to closure and rehabilitation phases. These fibre types are known to exhibit long-term chemical stability in highly alkaline red mud environments. Three fibre types were incorporated into red mud over a range of MCs, with testing focused on conditions close to the optimum moisture content (OMC). Unconfined compressive strength (UCS) and Brazilian tensile strength (BTS) tests were undertaken to quantify strength enhancement attributable to fibre inclusion, with particular attention given to tensile behaviour and crack development during desiccation.
The fibre reinforcement approach was evaluated using shrinkage–moisture relationships and tensile strength testing, providing a mechanistic assessment of crack resistance and strength retention under desiccation conditions. The results indicate that fibre reinforcement contributes to increased tensile and compressive strength by around 2 times the unreinforced red mud and promotes improved post-cracking behaviour as the MC decreases.
Fibre addition was observed to enhance air entry development and to limit crack propagation during desiccation, resulting in a more stable material fabric at lower moisture contents. These findings suggest that fibre reinforcement may provide a viable pathway to improve red mud strength and desiccation performance with a void ratio decrease by up to 6% at liquid limit (LL), thereby reducing closure stage stability risks and supporting more robust rehabilitation outcomes for red mud TSFs.