Effect of temperature on the water content of C-A-S-H in plain Portland and blended cements

This study aims to investigate the change with temperature of the water content of the C-(A)-S-H of plain cement (PC) and Limestone Calcined Clay Cement (LC3). The water content was determined by various methods: thermogravimetric analysis (TGA), H-1-nuclear magnetic resonance (H-1 NMR), scanning electron microscopy in energy X-ray spectroscopy mode (SEM-EDS) and grey level in backscattered electron imaging (SEM-BSE). The comparison between TGA on dried pastes and (HNMR)-H-1 on undried pastes indicates that about 75% of gel water is exchanged during the hydration stoppage. Moreover, the amount of gel water in the inner C-S-H determined by SEM-EDS is close to overall gel water content, indicating little difference in gel water between inner and outer product. SEM-BSE is not as accurate as the other methods. Overall, the water content decreases with temperature and it is very similar between PC and (LC3) despite the significant difference of Ca/Si ratio and Al content.