A comparative study on the mechanical properties and durability of ordinary concrete and red mud-based concrete

This study investigates the effects of different red mud (RM) dosage levels on the mechanical properties and durability of concrete. Six mixtures, designated as 0#, 3#, 4#, 5#, 6#, and 7#, are prepared. Their workability, mechanical properties, impermeability, freeze-thaw resistance, sulfate resistance and microstructural characteristics are evaluated. The results show that compressive strength initially increases and then decreases with increasing RM dosage. Among the investigated mixtures, the 3#-5# mixtures exhibit comparatively favorable compressive-strength performance. In contrast, flexural strength decreases with increasing RM dosage, whereas ultimate deflection increases. These results suggest that low-RM mixtures may have potential for pavement-related applications, although further verification is required for structural applications governed by flexural capacity. The 3# mixture exhibits lower water-penetration indicators than the ordinary-concrete control and shows the highest retained compressive strength and the lowest strength loss among the RM-containing mixtures after freeze-thaw cycling. XRD and SEM observations qualitatively reveal changes in hydration products and microstructural morphology following RM incorporation. Overall, the 3# mixture exhibits the best balance between mechanical performance and durability among the investigated mixtures. The results provide experimental evidence for further evaluation and optimization of RM-containing concrete for potential engineering applications.