Effects of magnetite incorporation in a chemically bonded phosphate ceramic

In this study, coarse magnetite (>63 μm) is introduced as a reactive component in wollastonite-based chemically bonded phosphate ceramics (WPC). It is found that WPC with coarse magnetite results in the formation of new stable microstructural phases such as iron phosphate cementitious matrix. The new ceramics (M-WCP) exhibit much lower shrinkage than WPC even after heating at elevated temperatures —eight times less shrinkage at 200 °C. Stiffness increases sharply from the 11.4 GPa of WPC to 23.4 GPa by adding coarse magnetite filler (M-WPC). The stiffness of WPC is reduced by more than 50% by heating above 100 °C, while M-WPC preserves more than 70% of its stiffness when heated up to 700 °C. Compressive strength increases from the 52 MPa of WPC, up to 80 MPa (M-WPC) by introducing coarse magnetite as reactive component. The new iron phosphate cementitious material —with attractive microstructural and mechanical properties besides high dimensional and thermal stability— can be recommended for many applications in construction, waste stabilization, and storage systems for radioactive materials.