The present work examines the synthesis of tricalcium aluminate (for use as a synthetic slag) from the non-saline dross produced in the manufacture of metallic aluminum in holding furnaces. Three types of input drosses were used with Al2O3 contents ranging from 58 to 82 wt %. Calcium aluminates were formed via the mechanical activation (reactive milling) of different mixtures of dross and calcium carbonate, sintering at 1300 °C. The variables affecting the process, especially the milling time and the Al2O3/CaO molar ratio, were studied. The final products were examined via X-Ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy. The reactive milling time used was 5 h in a ball mill, for a ball/dross mass ratio of 6.5. For a molar relationship of 1:3 (Al2O3/CaO), sintered products with calcium aluminate contents of over 90% were obtained, in which tricalcium aluminate (C3A) was the majority compound (87%), followed by C12A7 (5%).