Life cycle assessment of magnesium phosphate cement production

Magnesium phosphate cement (MPC) is gaining attention in the field of rapid repair and coatings due to its superior qualities, yet little research has been done on the carbon footprint of MPC preparation. It's necessary to investigate its environmental implications for the sustainable development and application of MPC. This study develops a life cycle inventory of the production of MgO with three different production processes and the production of two phosphates and applies the inventory to conduct a life cycle assessment from cradle to gate for four scenarios of MPC production: Scenario 1 (S1) - dry route MgO and potassium dihydrogen phosphate (PDP) as raw materials; Scenario 2 (S2) - wet route MgO and PDP as raw materials; Scenario 3 (S3) - salt lake MgO and PDP as raw materials; Scenario 4 (S4) - dry route MgO and ammonium dihydrogen phosphate (ADP) as raw materials. Moreover, the sensitivity analysis and cost analysis of MPC are carried out. In order to comprehensively evaluate the low carbon properties of MPC, the carbon emissions of MPC and the commonly used rapid repair materials and coatings are compared. Results indicate S2 shows the highest global warming, which is 3.97%, 74.55, and 1.41% higher than S1, S3, and S4, respectively. The environmental impact of MPC mainly comes from the production stage of MgO and phosphate (52% - 67%). In three MgO production routes, S3 shows the best environmental performance. In two phosphates, S4 has a smaller impact on most impact categories. Sensitivity analysis also indicates that MgO and phosphate have a greater impact on the production of MPC. In addition, the cost of S2 is 2.91%, 0.37%, and 15.40% higher than that of S1, S3, S4, respectively, and S4 shows the best economic benefit. Furthermore, MPC has great advantages in rapid repair and coating, and can reduce carbon emissions by 12% - 97% compared to other rapid repair materials and coatings.