Four different imported silica bricks were investigated. The results of this investigation were as follows: The tridymite contents of two silica bricks were more than that of the conventional brick, which is the reason we had previously adopted them in hot stoves, and there was no quartz remaining in those bricks. However, tridymite contents of the other two silica bricks were less than in the conventional brick, and a little quartz remained. Three silica bricks had expansion and increased apparent porosity after the compressive creep test at 1823K. These bricks transformed remarkably to cristobalite from tridymite, and it is presumed that strain and porosity were increased by vacancies that occurred in the structure by this phase transformation. Sample A was improved by the addition of CaO. It was possible to control the phase transformation to cristobalite in Sample A and the expansion of the sample after creep was decreased.
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