LAUSR

Abstract 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 °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 °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 °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.