Abstract: We conducted indoor experimental research to evaluate the unconfined compressive strength, splitting strength, resilient modulus, and dry-wet and freeze-thaw durability of phosphogypsum-activated cement-lime solidified red mud for road applications. The aim was to investigate the feasibility of using this solidified red mud as a road base material. The experimental results demonstrate that the best road base performance is achieved when the curing agent mixing ratio is m_cement:m_lime:m_{phosphogypsum}=8:2:2. The 7-day unconfined compressive strength reaches 4.18 MPa, meeting the strength requirements of road base. The splitting strength and resilient modulus at 28-day age are 0.256 MPa and 1 020 MPa, respectively. After five cycles of dry-wet and freeze-thaw, the mass change rate is less than 2%, and the strength loss index (BDR) exceeds 80%. Microscopic analysis using a mercury intrusion test reveals that the AFt (ettringite) generated from the reaction of phosphogypsum could enhance the strength of red mud by filling pores (0.1~1 μm) in the solidified red mud. However, excessive AFt causes volumetric expansion and gives rise to micro-crack pores (1~10 μm), resulting in deteriorated strength performance. In conclusion, the performance test results indicate that the solidified red mud prepared with a ratio of m_{red mud}:m_cement:m_lime:m_{phosphogypsum}=100:8:2:2 can be effectively used as a substitute for traditional pavement base materials. This discovery provides a broader avenue for the comprehensive utilization of red mud.

Key words: red mud, road engineering, road base, unconfined compressive strength, road performance