The formation in high-alumina castables of low-melting eutectic compounds in the Al2O3.SiO2.CaO system, has claimed a gradual reduction of the CaO content of such refractories in order to optimize their performance at high temperature. After the development of low (LC) and ultra-low (ULC) cement castables and the attempt to substitute cement by other hydraulic binders as r-Al2O3, a novel class of refractory castable without hydraulic binders (zero-cement) is presented in this work. Such castables showed suitable mechanical strength after demoulding, yielding an accurate control of its particle size distribution and additivation. In this paper, high-alumina ULC and zero-cement castables are compared. The advantages of zero-cement castables are the absence of cure, their high mechanical strength after firing between 300 and 1400oC and the lack of eutectic compounds in the Al2O3.SiO2.CaO system.
castables; refractories; zero-cement
