Preparation and Characterization of Magnetite-Based Iron Phosphate Cement

Iron phosphate cement (IPC) was prepared through the reaction between magnetite and phosphoric acid. The influences of magnetite-to-phosphoric acid (M/PA) mass ratio on the hydration temperature, setting behavior, compressive strength, hydration product, and microstructure of IPC pastes were investigated. Results showed that an increase in the M/PA ratio can slow down the setting reaction and lower the peak hydration temperature. The compressive strengths of IPC pastes at different ages first increased and then decreased with the M/PA increasing from 2.3 to 5.5. The M/PA of 2.6 generates the highest compressive strengths for IPC pastes specimens at different ages, which were 21, 27, 30, and 33 MPa at 1, 3, 7, and 28 days, respectively. Furthermore, multiple characterizations including X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDS) revealed that the amorphous iron phosphate phase was mainly formed as the binder phase and the transformation of Fe (II) into Fe (III) occurred during the formation of IPC hydration products.