Value-added utilization of phosphogypsum industrial by-products in producing green Ultra-High performance Concrete: Detailed reaction kinetics and microstructure evolution mechanism

This paper presents an effective method for producing green ultra-high-performance concrete containing phosphogypsum aggregates to meet the demand for a sustainable environment. More exactly, the low field nuclear magnetic technology (LF-NMR), nanoindentation, and Backscattering images (BSEM) are used to clarify the hydration process and microstructure evolution of phosphogypsum-based ultra-high performance concrete (PG-UHPC). The results indicate that the mechanical performance of PG-UHPC decreases slightly as phosphogypsum aggregate content increases, but it is still capable of meeting the requirements of applications. Moreover, the introduction of phosphogypsum aggregate in UHPC accelerates water migration and directly affects its hydration degree. Lastly, a reasonable sulfur content can limit the degradation of interfacial transition zone and reduce the risk of matrix cracking in PG-UHPC. To conclude, advanced composite building materials with low environmental burden are prepared as a reference for the development of green ultra-high-performance concrete.