Refractory Technology
Spalling resistance of a refractory can not be increased by

Making it denser
Decreasing its thermal co-efficient of expansion
Using a coarser grog during its manufacture
Increasing its porosity

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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
High strength & thermal spalling resistance
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

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