Study on the high‐temperature behavior and rehydration characteristics of hardened cement paste

The high‐temperature behavior and rehydration characteristics of the hardened cement paste and their mechanisms have been studied in this paper. X‐ray diffraction and thermogravimetry are used to establish the effect of elevated temperatures on the mineralogical changes that occurred in the hardened cement paste. The change of microstructure was characterized by scanning electron microscopy. The results showed that with the temperature increased, the compressive strength of hardened cement paste first increased and then decreased. According to micromeasurements, at 400°C, the porosity and average pore diameter of hardened cement paste increased slightly, while at 800°C, the porosity and average pore diameter of hardened cement paste increased sharply. When hardened cement paste was cured after exposing to 400°C, its pore structure and phase composition had no change, while when hardened cement paste was cured after exposing to 800°C, there are new hydration products, and its pore structure may be finer, but it cannot fully recover to the original state. Copyright © 2014 John Wiley & Sons, Ltd.