Abstract
The sintering and the structure of clinkers, modified by the introduction of different ionic forms of sulfur and phosphorus into the raw mix, were examined. One reference synthetic mixture and 25 modified mixtures were prepared by mixing the reference sample with 0.5, 1.0, 1.5, 2.0 and 2.5%w/w of chemical grade CaSO4, CaS, Ca3(PO4)2, CaHPO4 and Ca(H2PO4)2. Free lime content in all samples was measured. The sintering reactions in samples were recorded by means of differential thermal analysis. The texture of the clinkers was examined using a scanning electron microscope and EDX. It is concluded that, despite of their relatively low doping concentration in the raw mix, P and S affect considerably its reactivity and the texture of the clinker. The various ionic forms of the same element (SO4 2-, S2- for S, PO4 3-, HPO4 2- and H2PO4 - for P) exhibit a different and unequivocal effect on the reactivity of the synthetic raw mix and on the texture of the corresponding clinkers. S (in both forms) and P (added as HPO4 2-) are mainly dissolved in the melt and they have a positive effect on the burnability of the raw mix. P (added as PO4 3- or H2PO4-) is preferentially accumulated in belite. In this case further stabilization of β-C2S occurs and the binding of the free lime is hindered.
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Kolovos, K.G., Tsivilis, S. & Kakali, G. Study of clinker dopped with P and S compounds. Journal of Thermal Analysis and Calorimetry 77, 759–766 (2004). https://doi.org/10.1023/B:JTAN.0000041655.82776.09
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DOI: https://doi.org/10.1023/B:JTAN.0000041655.82776.09