Experimental research on magnesium phosphate cements containing alumina

The main concern of the present work is to understand the effects of the addition of alumina on the properties of magnesium phosphate cement with respect to changes in temperature, mechanical properties, porosity and microstructure of hydration products. Experimental results demonstrated that the presence of alumina could reduce the intensity of exothermic reactions, as well as prolonged the setting time. Also, a significant increase in compressive strength was observed during all hardening stages after the substitution of magnesia by alumina. However, the effectiveness of alumina was limited by its solubility. Successive addition of alumina caused a cumulative increase in water requirement as indicated by a gradual loss in workability. Furthermore, the addition of alumina led to a reduction in porosity, and left a finely porous structure. Finally, the hydration products were examined through the techniques of thermogravimetric (DTA-TG), Scanning Electronic Microscopic-Energy Dispersive Spectrometer (SEM-EDs) and mercury intrusion porosimetry (MIP). These experimental results provided detailed information to improve basic understanding of magnesium phosphate cement blended with alumina and the structures of hydration products.