A fractional factorial design (2 4 - 1 ) of experiments was carried out to study the influence of metal oxides on cement properties: unconfined compressive strength (UCS), setting time (ST), bulk density (BD) and noncombined water (NCW). Four metal oxides, usually contained in inorganic wastes from thermal processes, were studied: ZnO, Cr 2 O 3 , PbO, and Fe 2 O 3 . The amount of these metal oxides in the formulations was selected according to the composition of inorganic wastes from thermal processes: 0-30% dry wt. for Fe 2 O 3 , 0-15% dry wt. for ZnO, and 0-2.5% dry wt. for PbO and Cr 2 O 3 . The analysis of the experimental results shows that ZnO retards strongly the ST with respect to that of the cement; it also decreases the UCS of the final product at short ages, but its effect decreases with the sample age. Fe 2 O 3 does not affect the ST and UCS at short sample ages; however, at long sample ages, it decreases the UCS of the product.