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

摘要

The formation kinetics of tricalcium aluminate (C_3A) and calcium sulfate yielding calcium sulfoaluminate (C_4A_3$) and the decomposition kinetics of calcium sulfoaluminate were investigated by sintering a mixture of synthetic C_3A and gypsum. The quantitative analysis of the phase composition was performed by X-ray powder diffraction analysis using the Rietveld method. The results showed that the formation reaction SCa^Oe-trCaS04 -> CaAO^ (SO_4) + 6CaO was the primary reaction < 1350°C with/and activation energy of 231 ± 42 kJ/mol; while the decomposition reaction 2Ca_4Al_6O_(12)(SO_4) + 10CaO -> 6Ca_3Al_2O_6 + 2SO_2 ↑ + O_2 ↑ primarily occurred beyond 1350 °C with an activation energy of 792 ± 64kJ/mol. The optimal formation region for C_4A_3$ was from 1150 °C to 1350 °C and from 6 h to 1 h, which could provide useful information on the formation of C_4A_3$ containing clinkers. The Jander diffusion model was feasible for the formation and decqmposition of calcium sulfoaluminate. Ca~(2+) and SO_4~(2-) were the diffusive species in both the formation and decomposition reactions.