Kinetics of calcium sulfoaluminate formation from tricalcium aluminate, calcium sulfate and calcium oxide

The formation kinetics of tricalcium aluminate (C(3)A) and calcium sulfate yielding calcium sulfoaluminate (C(4)A(3)$) and the decomposition kinetics of calcium sulfoaluminate were investigated by sintering a mixture of synthetic C(3)A and gypsum. The quantitative analysis of the phase composition was performed by X-ray powder diffraction analysis using the Rietveld method. The results showed that the formation reaction 3Ca(3)Al(2)O(6)+ CaSO4 -> Ca4Al6O12 (SO4) + 6CaO was the primary reaction <1350 degrees C with and activation energy of 231 +/- 42 kl/mol; while the decomposition reaction 2Ca(4)Al(6)O(12)(SO4) + 10CaO -> 6Ca(3)Al(2)O(6) + 2SO(2) up arrow + O-2 up arrow primarily occurred beyond 1350 C with an activation energy of 792 641Wmol. The optimal formation region for C(4)A(3)$ was from 1150 degrees C to 1350 degrees C and from 6 h to 1 h, which could provide useful information on the formation of C(4)A(3)$ containing clinkers. The Jander diffusion model was feasible for the formation and decomposition of calcium sulfoaluminate. Ca2(+) and SO42- were the diffusive species in both the formation and decomposition reactions. (C) 2013 Elsevier Ltd. All rights reserved.