Refractory Technology
Natural silica

Mainly contains quartz
All of these
Is not stable at high temperature
Transforms to other allotropic forms i.e tridymite and cristoballite involving very high volume changes

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

All of these
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
Less shrinkage in heating, decreased apparent porosity & increased specific gravity

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