The effect of foreign ions on the reactivity of the CaO-SiO2-Al2O3-Fe2O3 system Part II:: Cations

The subject of this paper is the effect of foreign cations on the reactivity of the CaO-SiO2-Al2O3-Fe2O3 system. One reference mixture and eighteen modified mixtures, prepared by mixing the reference sample with 1% w/w of chemical grade MnO2, CuO, V2O5, PbO, CdO, ZrO2, Li2O, MoO3, Co2O3, NiO, WO3, ZnO, Nb2O5, CrO3, Ta2O5, TiO2, BaO2 and H3BO3 were studied. The effect on the reactivity is evaluated on the basis of the free lime content in samples sintered at 1200 and 1450 degreesC. At 1200 degreesC, the reactivity of the mixture is greatly increased in the presence of Cu and Li oxides. Based on their effect at 1450 degreesC, the added elements can be divided into three groups. W, Ta, Cu, Ti and Mo show the most positive effect, decreasing the free CaO (fCaO) content by 30-60%, compared with the pure sample. Cr and B cause an increase of fCaO content, while the rest of the elements exhibit a marginal positive effect. According to their volatility at 1450 degreesC, the added compounds can be subdivided into three groups of low (Ti4-, Cu2+, Mo6+, W+6, V5+, Zn2+, Zr4+), moderate (Cr6+, Co3+, Ni2+, Mn4+) and high volatility (Cd2+, Pb2+). All burned samples, analyzed by means of X-ray diffraction, have a final mineralogical composition, which corresponds to the structure of a typical clinker. (C) 2002 Elsevier Science Ltd. All rights reserved.