Synthesis and Formation Process of a Typical Doped Solid-Solution Ye’elimite (Ca3.8Na0.2Al5.6Fe0.2Si0.2SO16): Experiments and Kinetic Analysis

Abstract

Ye’elimite is a dominant phase in calcium sulfoaluminate cement, which is a promising alternative type of cementitious binder. Ca3.8Na0.2Al5.6Fe0.2Si0.2SO16 (abbreviated as ss-C4A3$) is a kind of typical doped solid-solution ye’elimite. In this study, the formation process of ss-C4A3$ was investigated. Clinkers of ss-C4A3$ were sintered at various temperatures for different holding times. X-ray diffraction tests and Rietveld quantitative phase analysis were conducted to determine the phase compositions of the clinkers. Meanwhile, the formation process of ss-C4A3$ was analyzed by kinetic theory. The results show that solid reactions between intermediate phases (calcium aluminate phases) and anhydrite mainly resulted in the formation of ss-C4A3$. In the conditions of 1150–1250 °C, ss-C4A3$ tended to be formed and stable until 4 h. However, when the sintering temperature was 1300 °C, the ss-C4A3$ decreased to generate calcium aluminate phases after 2 h. Compared to other kinetic models, the three-dimensional diffusion model mostly conformed with the formation process of ss-C4A3$, and the fitting results obtained by the Jander model exhibited the highest correlation coefficients. The activation energy of ss-C4A3$ formation equaled 285.6 kJ/mol, which was smaller than that of stoichiometric ye’elimite.