3 Results and Discussion are displayed in Figure on the left. The complete set of raw data of the calorimetric experiments is provided in the Supporting Information (Figure ). The addition of the sodium salts decreases the early heat compared to the reference sample of C 3 A that was hydrated solely in pure water. Although other authors have reported sodium sulfate as the least effective of various alkali sulfates in reducing the dissolution rate of C 3 A, our findings show a significant decrease in early heat in the presence of Na 2 SO 4 . The heat of hydration after 3 h is reduced from 893.6 J g -1 (reference) to 596.1 J g -1 with NaNO 3 , 578.9 J g -1 with NaCl and 323.2 J g -1 with Na 2 SO 4 . NaNO 3 and NaCl modified the hydration kinetics to a comparable extent. The presence of Na 2 SO 4 has the most significant effect on the hydration rate of the C 3 A suspension. by almost 65 %. To summarize, the sodium salts reducing the heat after 3 h in the following order: