A Sustainable Composite Cementitious Material Manufactured by Phosphogypsum Waste

The phosphogypsum is a by-product of the phosphate fertilizer industry. It has accumulated over several decades, and not only takes up a large amount of land, but also poses a significant risk to the environment and resource waste. In order to promote the use of phosphogypsum, its hydration hardening characteristics are studied using a scanning electron microscope, X-ray diffractometer and mercury intrusion porosimeter. When the amount of phosphogypsum is increased, a decreasing trend in the reaction degree, non-evaporable water and portlandite is observed. Among them, the reaction degree and non-evaporable water, flexural strength and compressive strength reached their maximum when the content of phosphogypsum was 10%, which were as follows: 22.34 %, 21.13 %, 9.02 MPa and 49.8 MPa, respectively. Meanwhile, phosphogypsum can participate in the secondary hydration reaction in the system and act as a microaggregate. The addition of no more than 30% phosphogypsum can enhance mechanical characteristics, reduce porosity, refine pore size distributions and densify the microstructure. The findings of this study may aid in the production of phosphogypsum-based composite cementitious materials with superior performance, thereby promoting phosphogypsum recycling and protecting the environment.