Magnesium potassium phosphate cement prepared by the byproduct of magnesium oxide after producing Li_2CO_3 from salt lakes

摘要

Developing new types of chemically bonded phosphate ceramic materials that are environment-friendly, inexpensive and energy-efficient, has become a central theme today. Therefore, in this study, magnesium potassium phosphate cement (MKPC) was prepared from boron-containing magnesium oxide (B-MgO), a byproduct of the production of Li_2CO_3 from salt lakes. The properties of B-MgO calcined at various temperatures were investigated by XRD, SEM, LSPA and SNAA. The MKPC specimens were prepared at various calcination temperatures (from 800 °C to 1400 °C) of B-MgO and with various molar ratios of B-MgO to KH_2PO_4 or KDP (M/P) ranging from 3 to 6. Compression tests were conducted at various curing ages from 3 h to 28 d. The hydration products and microstructure of the specimens were analyzed by XRD and SEM, respectively. The experimental results demonstrated that the properties of B-MgO, such as the specific surface area, the deformation ratio and the total pore volume decreased with increasing calcination temperature. In addition, the early compressive strength of MKPC specimens decreased with increasing calcination temperature of B-MgO, and the long-term compressive strengths of MPC mortar remained constant with increasing calcination temperature of B-MgO. These results also indicated that cement with a high M/P ratio could have a high early strength. The MKPC specimens prepared by B-MgO calcined at 1000 °C and a M/P ratio of 6 exhibited a compressive strength of 35.6 MPa at 3 h, which met the mechanical property requirement of quick-repair materials.