Research Of Magnesium Phosphate Cement Modified By Fly Ash And Repair Performance

Magnesium phosphate cement (MPC) is a new type of cement material, which sets and hardens through acid base reactions. It has many advantages such as rapid harden, high early strength and volume stability, with good prospects for the rapid repair of cement concrete pavement. Current research is focused on its hydration mechanisms and hydration products, but less research has been done on performance and technology on construction site. This paper has been studied the basic components of magnesium phosphate cement for construction performance. The bond strength and volume stability have been improved and the color of magnesium phosphate cement has been adjusted by adding fly ash. The mechanical properties and dimensional stability of magnesium phosphate cement paste and mortar under different content of fly ash have been studied comparatively. The hydration product microstructure of magnesium phosphate cement has been analyzed by SEM. Compared to ordinary Portland concrete and sulpho aluminate cement, the repair effects of magnesium phosphate concrete by adding different content fly ash under pre-aggregate aggregate construction and dumping construction have been analyzed. The repairing construction method of magnesium phosphate cement has been determined for different types of damage.The thesis obtained the following conclusions: The construction performance of magnesium phosphate cement is related to specific surface area of magnesium oxide, P/M, retarder content and water-cement ratio. The fluidity of magnesium phosphate cement and the bond strength to Portland cement have been improved by adding fly ash. Adding fly ash can also reduce the maximum expansion value of magnesium phosphate cement and improve the volume stability, meanwhile reducing costs, adjusting the color of cement. Compared with ordinary Portland cement and sulpho aluminate cement, the strength and the bond strength of the magnesium phosphate cement mixed with fly ash develops faster and gets stronger. Besides, magnesium phosphate cement mixed with fly ash only needs a simple treatment to patch repair parts, and normal operation after 2h. Magnesium phosphate concrete with dumping process aggregate works better performance and higher strength than the pre-construction process.