Refractory Technology
Silica refractories

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

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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
Less shrinkage in heating, decreased apparent porosity & increased specific gravity
High strength & thermal spalling resistance

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