To improve the flowability and hydration resistance of MgO fines, microsilica
is also used as binder, individually or along with hydratable alumina.
However, its presence significantly decreases the castables’ hot strength
due to liquid formation. Calcium aluminate (CA) cement is sometimes used
as well, although its addition also leads to formation of low-melting phases
at high temperatures and thus decreases hot strength and slag corrosion
resistance.