The volume of open, connected pores as a percentage of total volume, measured by weighing a sample dry, then saturated with boiling water and suspended in water, as in ASTM C20. Dense fireclay brick runs about 12 to 18 percent, good fired high-alumina and magnesia brick lower, and insulating brick far higher. Low open porosity limits slag, metal and gas penetration, but can make heat-up and thermal shock harder.
Apparent porosity on that lot is 22 percent, way over spec, slag's going to soak right into it.
Also heard as
- AP
- open porosity
- porosity
Related terms
Bulk density
Mass of a refractory divided by its total volume including pores, a quick check on quality and compaction.
Slag attack
Chemical dissolution and penetration of a refractory by molten slag, the main wear mode in metal processing.
CCS
Cold crushing strength: the room-temperature compressive strength of a refractory, in MPa or psi.