Calcined fireclay or crushed fired brick used as coarse aggregate in fireclay bricks, mortars and castables, and by potters in clay bodies. Because it has already shrunk during its first firing, grog stabilizes dimensions, reduces drying and firing cracks and opens the structure for better thermal shock resistance. Recycled spent brick is often crushed back into grog.
Add more grog to the patch mix, it's cracking all over as it dries.
Also heard as
- chamotte
- calcined fireclay
Related terms
Fireclay
Alumina-silica clay refractory, the classic firebrick, graded from low duty to super duty.
Fines
Smallest particle fraction of a refractory mix, which fills the gaps between coarse grains and forms the bond.
Refractory mortar
Fine refractory mix used to lay and bond firebrick, either heat-setting, air-setting or phosphate-bonded.
PLC
Permanent linear change: the lasting shrinkage or growth of a refractory after heating and cooling.