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.
Highlights
As the production process of calcium sulfoaluminate (CSA) cement produces fewerCO2 emissions and consumes less energy compared to Portland cement, CSA cement is treated as a type of alternative and low-carbon binder [1,2]
Based on the Rietveld quantitative phase analysis for clinkers sintered at various temperatures for different holding times, the formation process of ss-C4 A3 $ was investigated through the lens of kinetic theory
The formation process of ss-C4 A3 $ mainly resulted from solid reactions between the intermediate phases and anhydrite, which did not involve the formation of st-C4 A3 $
Summary
As the production process of calcium sulfoaluminate (CSA) cement produces fewerCO2 emissions and consumes less energy compared to Portland cement, CSA cement is treated as a type of alternative and low-carbon binder [1,2]. Ye’elimite is a dominant phase in CSA cement and generally accounts for over 50 wt.% in CSA clinkers [6,7]. Sintering conditions of CSA clinkers are determined by the forming conditions of ye’elimite; the main hydration products of CSA cement result from the reactions between ye’elimite and gypsum [8,9,10,11,12]. Certain types of doping ions (such as iron ions and sodium ions et al.) enter into the lattices of ye’elimite in the manufacturing process of CSA clinkers, which leads to the formation of doped/solid-solution ye’elimite [16,17,18]. When solid waste is utilized as raw materials, various types of solid-solution ye’elimite tend to be formed more [19]. A series of recent studies focused on different types of doped ye’elimite, including strontium-bearing ye’elimite, barium-bearing ye’elimite, and iron-bearing ye’elimite
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