THE EFFECT OF NaF AND SnO2 ON THE CHARACTERISTICS OF PORTLAND CEMENT CLINKER AND CEMENT

In this paper it is investigated the effect of NaF and/or SnO2 on the characteristics of Portland cement clinker obtained by sintering of industrial raw meal containing 0.5% NaF, 0.5%SnO2 and 0.5% NaF+0.5% SnO2 (gravimetric percentages). The effect of the presence of NaF and/or SnO2 employed as mineralizers as compared with the raw mix without mineralizers was carried out by analyses of the free lime, by XRD analysis and optical microscopy. The combined use of NaF and SnO2 modifies the kinetics of free CaO binding process, meaning faster compared with the use of each individual, allowing lower clinker sintering temperature up to 100 degrees C. The quality of the obtained clinkers was good, being typical alite Portland clinkers. The CEM I type cements obtained by grinding clinkers with gypsum up to a fineness of approx. 3500 cm(2)/g complied in terms of their physical and mechanical properties with requirements of SR EN 197-1:2002. The presence of NaF and/or SnO2 determined an increase in the compressive strength at both short (2 and 7 day) and long (more than 28 days) terms.