The drying of refractory castables has been investigated numerous times over the past thirty years but little has been reported on the drying rate effect on steam spalling.  Due to the fact that explosive spalling still occurs from time to time manufacturer’s still recommend very conservative drying schedules.

The effect of this is that very long drying times are recommended for refractory castables. 

Crowley and Johnson [1972] carried out laboratory tests on a number of dense and insulating castables at two different heating rates (930C/hr and 460C/hr).  This work found that there is little need to have long heating times or hold periods but caution is required for thick and very low permeability materials.  It was found that refractories cured at temperatures less than 200C are more susceptible to explosive spalling.  It was also concluded that insulation materials can be heated faster than dense refractories.