Refractory Technology
Addition of grog in fireclay brick during its manufacture is advantageous, because it results in

Less shrinkage in heating, decreased apparent porosity & increased specific gravity
All of these
Less addition of water to get a workable plasticity & lesser time required for drying the raw refractories and hence increased rate of production
High strength & thermal spalling resistance

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Refractory Technology
Carbon refractories

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

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