Ordinary Portland cement was mixed with deuterium oxide with a heavy water/cement ratio of 0.6 to monitor the in situ hydration, while acquiring diffraction patterns every 2.5 min. Two different experiments were carried out under different heating conditions. In one case, the temperature was uniformly raised from room temperature to 98 °C at a heating rate of 20 °C/h. In the second case, the heating was performed from 32 °C to 100 °C at a slower rate: 12 °C/h. The disappearance and appearance of relevant anhydrous and hydrated phases were monitored and quantified by fitting isolated diffraction peaks to Gaussians. Ca3SiO5 dissolved completely during the experiment and Ca2SiO4 only partially disappeared. Ca(OD)2 precipitated and its growth rate exhibited a sigmoidal shape. Ettringite and hillebrandite formed but then dissolved before the end of the experiments. At the end only Ca(OD)2 and some Ca2SiO4 remained as crystalline phases.

Peer reviewed