Thermal stability of limestone calcined clay cement (LC³) at moderate temperatures 100-400?C

The mechanical properties, phase evolution, microstructure development and (re)hydration properties of limestone calcined clay cement (LC3) paste and mortar were investigated to understand their thermal stability under moderate temperatures (100-400 degrees C). The residual compressive strengths of LC3 and Portland cement (PC) mortars kept constant or slightly increased from ambient to 300 degrees C, and sharply dropped at 400 degrees C. At 100 degrees C, monocarboaluminate (Mc) and ettringite (AFt) converted into hemicarboaluminate (Hc) and monosulfate (Ms), and caused partial dehydroxylation of C-(A)-S-H. As the temperature increased, at 200-300 degrees C, due to the decomposition of large fraction of hydration products, macroscopic cracks and microstructure damage occurred. At 400 degrees C, the mean chain length (MCL) of C-(A)-S-H gel decreased, accompanied by the shift of Si and Alcoordination number and the formation of active sites. Under water saturation conditions, the microstructure showed self-repairing performance.