Abstract: Phosphogypsum has poor cementitious activity, which hinders its large consumption in the field of building materials. By studying the phase and microstructure of phosphogypsum pretreated by alkali excitation, and the compressive strength, phase and microstructure of the non-burning building materials prepared with the high content phosphogypsum, the process parameters of preparing high content and high compressive strength non-burning building materials with phosphogypsum were obtained. The result shows that, when 100 g phosphogypsum is added with 100 mL activator, after 24 h of excitation under room temperature, the main crystalline phase CaSO₄·2H₂O of phosphogypsum has smaller grains and lower crystallinity. Microstructure analysis shows that the size of calcium sulfate particles increases and the amount of fine particles decreases significantly after pretreatment. Thus, its gelation activity is improved. When the content of phosphogypsum is 80% (mass fraction), compared with the untreated phosphogypsum, the compressive strength of the prepared non-burning building materials after maintening for 7 d, 28 d and immersion in water are significantly improved, which are 13.79 MPa, 18.22 MPa and 11.44 MPa, respectively. Its micromorphology shows that there is no obvious boundary between the calcium sulfate particles, they are almost integrated with high density, which is very beneficial to the strength of the materials.

Key words: phosphogypsum, pretreatment, alkali excitation, compressive strength, non-burning building material