Factors affecting the reactivity of the CaO-SiO2-Al2O3-Fe2O3 mixture

This work deals with the factors affecting the reactivity of the CaO-SiO2-Al2O3-Fe2O3 mixture. Especially, the effect of the mixture's fineness and the effect of various additives are studied. Two groups of samples were studied. The first one consisted of limestone and clay mixtures having the same chemical composition but different granulometry (residue at 90 mum: 6-27%). Both separately ground and interground mixtures were examined. A special procedure was applied in order to determine the individual fineness of clay and limestone in interground mixtures. The second one included one reference CaO-SiO2-Al2O3-Fe2O3 mixture and a series of modified mixtures, prepared by mixing the reference sample with 1% w/w of various chemical grade oxides. In this way the effect of added cations can be studied. The effect on the reactivity was evaluated on the basis of the unreacted lime content in samples sintered at temperature between 1200 degreesC and 145 degreesC. In addition x-ray diffraction and differential scanning calorimetry were used in order to study the products and the reactions during the sintering. It is concluded that the fineness of limestone strongly affects the sintering process and especially the formation of calcium silicates and the liquid phase, while the clay's fineness has no significant effect. Besides, it is found that the certain added ions have a remarkable effect on the reactivity of the CaO-SiO2-Al2O3-Fe2O3 system, at high temperature, which is directly related to the electronic configuration of these ions. It is generally concluded that the use of selected additions is a more efficient way to control the reactivity of the CaO-SiO2-Al2O3-Fe2O3 mixture.