Experimental Study on Phosphogypsum-Amended Red Mud as Road Base Material

Red mud is a byproduct of the aluminum oxide refining process that is an industrial waste residue. The storage of red mud can seriously contaminate the soil, water system, and atmosphere while also taking up a lot of valuable land resources. However, the use of stabilized/amended red mud technology in road engineering is relatively limited. Consequently, this research investigates how additives (cement, lime, and phosphogypsum) affect the strength of amended red mud as road base material. Additionally, it examines the effects of dry–wet and freeze–thaw cycles on the UCS, pH, dry density, and evolution of micropore structure in amended red mud with different phosphogypsum content. The findings reveal that, after five dry–wet and freeze–thaw cycles, the samples with 2% phosphogypsum content have a strong assurance rate of more than 85%. The percentage of micropores (0.01–0.1 μm) is reduced, although the percentage of small pores (0.1–1 μm) and medium pores (1–10 μm) is increased by dry–wet and freeze–thaw cycles. The cumulative mercury intake rises as the percentage increases, and the dry–wet cycle has a greater impact on the strength of amended red mud than the freeze–thaw cycle.