The microstructural change of C-S-H at elevated temperature in Portland cement/GGBFS blended system

This investigation focuses on the change of C-S-H gels in Portland cement (PC) paste and PC/ground granulated blast-furnace slag (GGBFS) blended paste at elevated temperature up to 800 degrees C. Spark-like phase, which might be spurrite, can be found in the inner product of C3S in PC paste when the temperature is higher than 600 degrees C. The gels in PC paste show an obvious change in composition in comparison with the gels in GGBFS blended paste at elevated temperature. After 600 degrees C, the continuous decomposition and shrinkage of C-S-H gels results in the increase of small pores (10-40 nm) in both pastes. The nitrogen adsorption results show that some gels, which should be C-A-S-H in GGBFS blended paste, are quite stable at high temperature. The results of this study provide a comprehensive understanding of the different behavior between gels in PC paste and GGBFS blended paste at high temperature.