Characteristic Behavior of Hydration of Magnesium Oxide

Abstract

A refractory brick is made of heat-resistance material which is mainly magnesium oxide (MgO). The used refractory material can be used for reclamation. But the magnesium oxide which is the main component in refractory blocks tends to be hydrated, resulting in magnesium hydroxide (Mg(OH2)). The hydration from MgO to Mg(OH2) is associated with volume expansion. In the study, a new equipment is developed to accelerate the hydration process and measure volume expansion and expansion pressure. X-ray Diffraction (XRD) and scanning electron microscope (SEM) was adopted to investigate further the hydration process. In this study, disk-shaped refractory materials were used to measure the volume expansion under a given confining stress condition such as 60 kPa, 263 kPa, and 5.94 MPa. And the expansion pressure was also measured under no volume expansion condition. The results show that the volume expansion reaches 380% for 60 kPa and 263 kPa confining stress condition, and 255% for 5.94 MPa confining stress condition. The expansion pressure can reach over 6.5 MPa. The results of this study are applicable to various engineering applications of refractory materials.