2017 Volume 71 Issue 1 Pages 32-39
Cement manufacturers are replacing traditional raw materials and fuels with by-products and wastes. Alternative raw materials and secondary fuels contain minor elements which can influence burnability, clinker minerals and cement properties. Burnability affects the amount of free lime which also varies mineral composition and cement hydration. In order to optimize the utilization of alternative sources, this paper evaluated the effects of minor elements on clinker mineral and cement hydration under the conditions of uniform free lime effect and determined the limits of MgO, NiO, CuO, ZnO, TiO2, and P2O5.
Minor elements were differentiated into three groups based on similar effects on clinker minerals. Group Ⅰ, MgO and NiO, was distinguished by the presence of periclase and periclase-like crystal. Group Ⅱ, ZnO and CuO, was characterized by negligible changes to the silicate phase along with the formation of excess oxides which act as retarder on cement hydration at high additions. Group Ⅲ, TiO2 and P2O5 was defined by a decrease in C3S. The authors recommend the following limits for minor elements based on cement hydration and strength：MgO≤.2.00, for negligible effect, NiO≤1.95％ showed negligible effects, CuO≤0.48％ for negligible effects, ZnO≤0.97％ for beneficial strength gain, TiO2≤0.50％ showed negligible effects, P2O5≤0.91％ for negligible effects.
