Abstract
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.
Fillers are used for a variety of reasons: cost reduction, improved processing, density and porosity control, improved mechanical properties, dimensional stability and thermal stability [13]. The different properties of fillers are influenced by the particle size, shape and surface chemistry. In this field of research, the term reactive filler is commonly used to describe materials that are not completely inert and do more than ensure cost reduction.
•Introducing Coarse magnetite (>63 μm) in WPC results in the formation of stable chemical phases.•The new ceramics exhibit much lower shrinkage than WPC even after heating at elevated temperatures.•Compressive strength increases by 50% by introducing coarse magnetite as reactive component.•The new iron phosphate cementitious material exhibits high dimensional and thermal stability.