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In order to explore the effect of the foaming agent type on the properties of foamed mixture lightweight soil mixed with bauxite tailings (FMLSB), low-density (437.5 kg/m3 and 670 kg/m3) and high-density (902.5 kg/m3 and 1170 kg/m3) FMLSB were prepared using protein-based and synthetic-based foaming agents (AF and SF, respectively). The foam stability, micro characteristics, compressive strength, fluidity, and volume of water absorption of the FMLSB were investigated. The results showed that the foam made from AF had better strength and stability compared to SF. The internal pore sizes of both AF- and SF-FMLSB at low density were large, but at high density the internal pore sizes and area porosity of AF-FMLSB were smaller than those of SF-FMLSB. In terms of compressive strength, the compressive strength of AF-FMLSB was improved by 17.5% to 43.2% compared to SF-FMLSB. At low density, the fluidity of AF- and SF-FMLSB is similar, while at high density the fluidity of AF-FMLSB is much higher than that of SF-FMLSB. In addition, the stable volume of water absorption of SF-FMLSB is smaller than that of AF-FMLSB at low density, and the corresponding water resistance is better, but the situation is reversed at high density.

In order to make better use of the BTs slurry with high water content stored in tailings ponds by wet method, foamed mixture lightweight soil (FMLSB) at four wet density were prepared using dry BTs and BTs slurry with different water contents. Their wet density, fluidity, unconfined compressive strength and water absorption were tested through indoor test, and the experimental results were analyzed by microstructure analysis. The results show that the performance of FMLSB improves as the wet density and water content of BTs slurry increase. FMLSB prepared by BTs slurry with 60% water content is poorly fluidity. That means at lower wet density due to the connected internal pores, its strength is significantly reduced and water absorption is significantly increased compared to the dry BTs group. However, with the increase of wet density, the above adverse effects of FMLSB caused by BTs slurry with low water content will decrease; and with the increase in water content of BTs slurry, its internal pore structure is significantly improved, the same as its unconfined compressive strength. When the water content is 100%, its performance is no different from that of dry BTs group. With the increase of wet density, the C-S-H produced by hydration reaction of FMLSB increases, forming a dense skeleton structure together with BTs particles and the unconfined compressive strength increases exponentially. The research results can provide a scientific basis for the direct utilization of high water content BTs slurry in tailings pond.