Influence of lead, zinc, iron (III) and chromium (III) oxides on the setting time and strength development of Portland cement

摘要

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_2O_3, PbO, and Fe_2O_3. The amount of these metal oxides in the formulations was selected according to the composition of inorganic wastes from thermal processes: 0-30 percent dry wt. for Fe_2O_3, 0-15 percent dry wt. for ZnO, and 0-2.5 percent dry wt. for PbO and Cr_2O_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. F_2O_3 does not affect the ST and UCS at short sample ages; however, at long sample ages, it decreases the UCS of the product.