The use of Raman spectroscopy as a versatile characterization tool for calcium sulphoaluminate cements: a compositional and hydration study

Calcium sulphoaluminate (CSA) cement is considered the third series cement besides ordinary Port- land cement (OPC) and calcium aluminate (CA) cement. It is produced from gypsum, bauxite and limestone at 1,300 °C and consists of yeelimite, belite and anhydrite as main mineral phases. In the last years, many attempts have been made in applying Raman spectroscopy for the char- acterization of cement, clinker minerals and supplementary cementing materials (SCMs), revealing that this technique is a valuable tool for the identification of different phases in cements. In this work micro-Raman spectroscopy has been used, together with X-ray diffraction, for the character- ization of CSA cement and its main minerals. In order to identify which mineral phase is responsible for the differ- ent bands, Raman spectra have been acquired from syn- thesized yeelimite and belite phases (whose purity degree was checked by X-ray diffraction) and from calcium sul- phate di-hydrate and anhydrous (gypsum and anhydrite, respectively). On these bases, Raman spectra collected on CSA clinker and cement have been successfully assigned. Moreover, Raman spectroscopy, together with X-ray dif- fraction, proved useful to follow the hydration process of CSA cement up to 28 da