Investigation of phosphogypsum-based cementitious materials: The effect of lime modification

Abstract

Phosphogypsum-based cementitious material (PBC) is acknowledged as a low-carbon green composite material. The addition of lime to modify PBC has been found to significantly enhance PBC utilization rate. This study investigates the effects of varying lime contents in PBC on mechanical properties, volume expansion, hydration products, micromorphology, and pore structure of modified Phosphogypsum (PS). The results demonstrate that lime effectively counteracts the retarding effect of water-soluble impurities in PS, thereby reducing setting time. Additionally, the 7 days and 28 days strength of PBC initially increases and then decreases with increasing lime content, with the 28 days compressive strength of B0 (0.5%) reaching 48 MPa. A 0.5% lime-modified PS proves beneficial in promoting PBC hydration, reducing pore size, densifying the microstructure, and enhancing mechanical properties. Moreover, the volume expansion results highlight the significant influence of the alkaline environment on both the generation and distribution of ettringite, consequently impacting PBC expansion.

Keywords

• Lime-modified phosphogypsum
• Setting time
• Mechanical properties
• Volume expansion
• Hydration products
• Microstructure