Characterisation of cement treated red mud for subbase and base construction

Red mud is an industrial waste produced when bauxite ore is processed to extract aluminium and is dumped into the tailing dam in slurry form and occupies large areas, with limited usage. Physical and geotechnical characterisation (stress-strain and volume-change analysis) were carried out upon red mud and cement treated red mud (3–9%) to examine its probable utilisation in road infrastructure. Different tests were carried out to assess the application of red mud as cement treated sub-base and base layers, namely, unconfined compressive strength (UCS), indirect tensile strength (ITS), split tensile strength (STS), resilient modulus (RM), durability, capillarity, linear shrinkage (LS) and fatigue, along with its failure patterns. Red mud was observed as fine-grained silt-size material with continuous cluster of irregularly shaped particles. With increase in cement content, particle irregularity decreased. Stress‒strain and volume change behaviours of red mud are similar to silt-sized fine-grained materials. The UCS/ITS/STS/RM/LS/fatigue life of cement treated red mud increases with increasing cement content and curing period, while capillarity rise decreases, similar to that of conventional soil. At lower cement contents, the failure pattern shows ductile behaviour while at higher cement contents, the material illustrated a brittle nature with failure cracks in a linear manner and zig-zag formation. Considering the strength obtained from different tests, 4.95% cement treated red mud can be employed for constructing a sub base layer while it did not satisfy the minimum criteria for application in cement treated base layer per the present study.