Natural silica___________________?

Natural silica___________________?

A. Mainly contains quartz
B. Is not stable at high temperature
C. Transforms to other allotropic forms i.e. Tridymite and Cristobalite involving very high
volume changes
D. All A., B. and C.

Carbon refractories_____________________?

Carbon refractories_____________________?

A. Do not burn/oxidise, when exposed to air on heating
B. Are not attacked by slags, as they are not wetted by melts
C. Do not resist temperature fluctuations
D. Have extremely low thermal & electrical conductivities