Synergistic densification treatment technology of phosphogypsum and aluminum ash

Phosphogypsum and aluminum ash are typical bulk industrial solid wastes produced by phosphorus chemical and aluminum electrolysis industries respectively, both of which are characterized by large yield, low utilization rate and high environmental risk. In this article, high-density blocks were synthesized for the first time by densification treatment with phosphogypsum and aluminum ash. The mechanical and waterproof properties of the blocks formed after densification treatment under different ratios, densification pressures and curing time were also investigated. The experimental results indicate that the blocks treated by densification demonstrate a remarkable comprehensive performance under the optimal conditions of a ratio between phosphogypsum and aluminum ash of 1:9, densification pressure of 300 MPa and curing time of 5 d. Under such conditions, the compressive and flexural strength of the blocks are 58 MPa and 1.7 MPa respectively, with water absorption rate of about 5.3% and softening coefficient of 0.99. The leachable efficiency of toxic and harmful elements in the block materials is low, meeting the requirements for environmental protection, and thus densification treatment can be used for the harmless treatment of solid waste. The method provides a feasible research idea for simulating the change of underground minerals under the action of surface pressure and exploring the harmless and resourceful treatment of bulk solid waste. The technology is expected to be applied in the field of high-density filling and building materials prepared from solid waste.