A monolithic refractory of graded aggregate, fines and a binder, usually calcium aluminate cement, that sets hydraulically after mixing with a measured amount of water. It is placed by pouring with vibration, self-flowing, pumping or casting into molds for precast shapes. Classes run from conventional through low, ultra-low and no-cement types, plus lightweight insulating castables. Extra water makes placing easier and the lining weaker and more porous.
Castable says 5.5 to 6 percent water, I see anybody hosing it in the mixer and you're off the job.
Every litre of extra water you add to make a castable flow easier comes back as porosity and lost strength. Weigh the water, don't eyeball it.
Also heard as
- refractory concrete
Related terms
Low-cement castable
Dense castable with 1 to 2.5 percent lime from cement, using micro-fines and dispersants for strength and low porosity.
Calcium aluminate cement
Hydraulic cement that binds most refractory castables, sold in grades of roughly 40 to 80 percent alumina.
Ball-in-hand test
Quick field check of castable water content: squeeze a ball of mix, toss it, and see whether it holds.
Dry-out
Controlled first heat-up of a new monolithic lining to drive off water without cracking or spalling.