Study on Pretreatment of Phosphogypsum and Preparation of Non Burning Building Materials

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 activation, and the compressive strength, and microstructure of the non-sintering 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 showed that, when 100 g phosphogypsum was added with 200 mL activator, after 24 hours of excitation under room temperature, the main crystalline phase CaSO4·2H2O of phosphogypsum have smaller grains and lower crystallinity. Microstructure analysis showed that the particles of tabular phosphogypsum were powdered, and the original plate-like crystal form became smaller plates. Thus, its gelation activity was improved. When the content of phosphogypsum was 80%, the compressive strength of non-burning building materials after maintenance for 7 days, 28 days and after immersion in water for 24h were 15.13 MPa, 16.4 MPa and 11.8 MPa, respectively. The micro morphology showed that the particle size gradient was appropriate and the density was very high, which was very beneficial to improve the strength of the material.