Abstract: Iron-tailing sand, as an industrial waste, would take a significant amount of land for the disposal, along with the local environmental pollution at the disposal site. Therefore, if the iron tailing sand could be used as highway subgrade fill material, it would reduce the disposal area if the strength of the iron tailing sand could be improved the lime to meet the strength and compaction requirements of the subgrade fill material for the expressway construction. The maximum dry density and the other basic physical and mechanical indices of the modified iron tailing sand were tested. Throughout the comparative study, it was found that the strength of the modified iron tailing sand was much stronger than that of the natural tailing sand. The seven-day unconfined compressive strength of the modified specimen after 5 and 10 dry and wet cycles was tested, and compared with the natural tailing sand samples, it was found that the strength of the iron tailing sand would change to different degrees with the increase cycles. When the lime soil ratio reaches 12%, the strength curve maintains a stable trend after several cycles, which indicating that the sample durability also meets the requirements of the subgrade material for the highway construction.

Key words: iron tailing sand, lime improved soils, subgrade fill material, mechanical properties