Hydration of calcium aluminates and calcium sulfoaluminate studied by Raman spectroscopy

Raman spectroscopy has been used to follow the hydration of the main calcium aluminate phases present in calcium aluminate cement (CAC) and calcium sulfoaluminate cement (CSA) clinkers, i.e. C3A, CA, C12A7, CA2, C4AF and C4A3S¯. We investigate the reaction products induced by hydration on these six compounds. Spectra of anhydrous pure samples and pastes hydrated for 48 h were recorded. In order to contrast the Raman analysis results, the samples were also characterized by XRD and FTIR techniques. Hydration of calcium aluminates led to the formation of C3AH6, C2AH8 and aluminum hydroxide, and hydration of ferrite phases led to hydrogarnet phases. Meanwhile the hydration of C4A3S¯ led to the formation of ettringite and AFm phases. The Raman spectra analysis developed gives the details of the vibration of the different functional groups present in the calcium aluminate hydrated samples and our results show the potential of Raman spectroscopy in the study of the aluminate hydration on the cement chemistry. The product identity was confirmed by XRD and infrared spectroscopy.