New Insights into the Effect of Calcium Formate on the Hydration Process of Tricalcium Silicate

In this research, the impact of calcium formate (CF) on the hydration process of tricalcium silicate (C3S, the most abundant component in portland cement) was investigated by setting time test, compressive strength test, isothermal calorimetry, X-ray diffraction (XRD), thermogravimetric analysis (TGA), and scanning electron microscopy energy-dispersive spectroscopy (SEM-EDS). The incorporation of CF led to a decrease in setting times and enhanced early strength of the C3S specimen. Furthermore, the heat release of the C3S sample was increased by the addition of CF. Results from XRD and TGA indicated that the hastening of solidification and the rapid development of initial strength in C3S pastes by CF was not due to its promotion of C3S hydration level. On the contrary, CF impeded the initial hydration process of C3S. However, the study of the hydration level of C3S revealed that the incorporation of CF led to a noticeably greater water-to-silica ratio (H/S) in the calcium silicate hydrate (C─ S─ H) phase, primarily as a result of water molecules infiltrating the C─ S─ H. This elevated H/S ratio in C─ S─ H contributed to a rise in the volume of water utilized throughout the hydration process of C3S for each unit, which stands as the principal factor behind the hastened setting and the initial strength increase observed in C3S paste due to the presence of CF.