The invention concerns an additive-containing ground calcined alumina used as constituent of a refractory material precursor characterized in that it comprises an organofunctional silane, the organic function being typically an epoxy function, an alkyl function, an alcohol function or a diol function. Preferably said organofunctional silane is an oxyranyl-alkyl-silane, of chemical formula C.sub.9H.sub.20O.sub.5Si. Said additive-containing alumina can be obtained by adding said organofunctional silane during grinding to take advantage of its anti-caking properties, the intimate and homogeneous mixture being obtained as a result of grinding. It may also result from a post-grinding mixing.