Study on hydration mechanism of Ternesite-Ye’elimite binary system: Fid-Bau Portal

Study on hydration mechanism of Ternesite-Ye’elimite binary system

Wu, Yufeng / Li, Pengcheng / Huang, Xiaofei / Li, Weifeng / Sun, Jinfeng / Ma, Suhua

Abstract Calcium sulfoaluminate (CSA) cement attracts attention for its low carbon emissions, but the reaction mechanism of ternesite (C5S2$) and ye’elimite (C4A3$) remains unclear. In this work, the hydration process of C5S2$, C4A3$, and the C5S2$-C4A3$ (TY) binary system were studied. The cumulative heat release of the TY binary system depends on the content of C4A3$, the highest cumulative heat in the system is TY-F about 250 J/g. The pore solution analysis reveals that C5S2$ dissolves slowly in contact with water, releasing Ca²⁺, SO4 ^2- and OH^- at the initial hydration. The C5S2$ is activated by C4A3$, the degree of C5S2$ in TY system is approximately 40%. In the hydration of the TY binary system, the dissolution of C5S2$ produces gypsum at an early age, while the other hydration products (strätlingite, C-S-H) are slowly form after 28d of hydration. The presence of C5S2$ reduces the crystallinity of monosulfate(AFm) and aluminum hydroxide(AH3), resulting in an amorphous content of up to 40–50% in the TY system after 90 days of hydration. Based on the experimental data, when the mass ratio of C4A3$/C5S2$ is lower than 1, C2ASH8 was detected by XRD, the content of C2ASH8 was 17.50% in the TY-A system after 90 d of hydration.

Highlights • The hydration process of the C5S2$-C4A3$ system was studied. • The hydration degree of C5S2$ in the system could reach over 40%. • The presence of C5S2$ affects the crystallinity of AFm and AH3. • The C4A3$/C5S2$ (≤1) favors the stabilization of the AFt and the formation of strätlingite.