Improving Collapsible Soil Stability with Aluminum Oxide Nanoparticles: A Mechanical Perspective

Collapsible soils require improvement due to settlement caused by saturation. The environmental issues associated with traditional stabilizers and nanomaterials’ unique properties have made using these materials suitable for soil improvement. The research review shows that the effect of nano-aluminum on the characteristics of collapsible soils has yet to be evaluated. Nano-aluminum, with very small dimensions and a high specific surface, has high reactivity and ion exchange capacity. This study performed tests, such as standard Proctor compaction, Atterberg limit, unconfined compressive strength, indirect tensile strength, ultrasonic pulse velocity (UPV), and scanning electron microscopy (SEM), on stabilized collapsible soil with different nano-aluminum oxide contents at various curing times. The results showed that increasing the nano-aluminum oxide content increased the liquid limit and plastic limit of the collapsible soil. The plastic limit increased by 43% when adding 1.5% nano-aluminum oxide. The optimum nano-aluminum oxide content for stabilizing loess soil was 0.6%. The UPV of loess soil also increased with an increase in nano-aluminum oxide content up to the optimum content. The UPV of loess soil with the optimum nano-aluminum oxide content (0.6%) increased by 2.45 times after 28 days of curing. Also, the results of UPV tests can be used to predict the mechanical properties of collapsible soil stabilized with nano-aluminum oxide. SEM images showed that the unstabilized sample has voids in the coarse-grained texture. In contrast, the sample stabilized with nano-aluminum oxide showed reduced voids and the formation of strong bonds between soil particles.