Study On Properties Modification Of Magnesium Phosphate Cement

Magnesium Phosphate Cement?MPC?is a new type phosphoric acid-based binder,which can be rapidly cured at room temperature.It is prepared by a neutralization reaction and belongs to a chemically bonded phosphate ceramic?CBPC?.Therefore,it has some special features of cement and ceramics.Because of its advantages of room temperature curing,fast hardening speed,high early strength,and protection against steel bars and steel plates,it can be used in repair materials,curing hazardous waste,and metal protective coatings.The shortcomings of early hydration speed and high cost limit the large-scale application of MPC.Besides,MPC has high-temperature resistance,but there is little research in the field of high-temperature resistance and the high-temperature resistance is not ideal.In this paper,the corresponding measures to change the hydration performance and cost of MPC,as well as the high-temperature resistance of MPC coatings.The inorganic hydrated iron salt FeCl₃·6H₂O with a melting point of 37?was incorporated into MPC.During the hydration process,FeCl₃·6H₂O underwent a phase transition and absorbed part of the hydration heat,which relieved the continuous increase in system temperature,delayed the hydration heat release rate and effectively prolonged the setting time and improved the workability of MPC.When FeCl₃·6H₂O content was 1.0%,the hydration performance,compressive strength and water resistance of MPC have been significantly improved.In this work,gold tailing was incorporated into MPC to reduce the economic cost of MPC.and it was incorporated into MPC through two different pathways.The effect of gold tailings on MPC properties was studied.It was found that gold tailings were incorporated into MPC as a reactive substance,which could reduce the economic cost of MPC,realize the recycling of gold tailings,and improve the late-stage compressive strength of MPC.The compressive strength was improved by a factor of 114.94%when an additional 10%M was replaced by GT;when the displacement of GT was 30%,it yielded a compressive strength approaching the basic group.The MPC coating had cracks and holes after high temperatures,and the high-temperature resistance was poor,but after 1440h of salt spray,the interface between the coating and the substrate was still intact,which indicates that the coating had excellent corrosion resistance.The addition of functional filler talc powder and mica powder,zirconia or gold tailings improved the high-temperature resistance of MPC coatings.They were able to effectively suppress the volume effect of MPC during heating,or to reduce the difference in coefficient of thermal expansion between the coating and the steel.However,their influence on the corrosion resistance of the coating was different,and the mechanism was not yet clear,which needs to be further research.In this paper,the investigations on the improvement of hydration performance,cost issues and improvement of high temperature resistance are beneficial to the practical application of MPC,especially the modification of high temperature resistance.In particular,the investigation on the high temperature and corrosion resistance of MPC coatings has provided new ideas for expanding the application of MPC in the field of high temperature and corrosion resistance.