[en] The metallurgical concepts with regard to the structures and properties of calcium aluminate melts have been based upon analogies within ternary CaO-Al₂O₃-SiO₂ systems. In this work the results of surface tension, density and viscosity of some calcium aluminate slags, in the temperature range of 1500 to 1600 degree centigrade are presented and the results are discussed based upon recent structural characterisation results of crystalline aluminates. The compositional range investigated was from 45 to 53 weight-% alumina. The results indicate a reduction in density as the molar ratio CaO-Al₂O₃ decreases. Surface tension falls on increasing either the molar ratio CaO-Al₂O₃ or temperature. Conversely, viscosity increases with increasing molar ratio CaO-Al₂O₃ and decreasing temperature. The compositional dependence of both surface tension and viscosity data may be associated with the presence of some aluminium ions in octahedral co-ordination, and a concept of surface behaviour is proposed which involves surface activity of aluminate anions containing aluminium ions in a reduced valence state, such as Al''2+. (Author) 21 refs