Refractory Technology
Silica refractories

All of these
Crack when subjected to sudden change of temperature
Have lower thermal conductivity than fireclay bricks
Can not be used in the dome of hot blast stoves

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

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

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