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.