Search

Calcium sulfoaluminate (CSA) cement is a sulfate-based binder whose high-performance hydraulic behavior depends on the rapid formation of ettringite, when grinded clinker is hydrated in presence of gypsum. Ettringite is a calcium aluminum sulfate mineral characterized by high water content, estimated as 32 water molecules per formula unit. Three examples of utilization of near-infrared (NIR) spectroscopy are here shown. First of all, information on water distribution in pure ettringite was deduced and compared with infrared analyses. Then its thermal behavior has been followed up to 400 °C, allowing to improve the knowledge about water loss and thermal decomposition of this hydrated phase. Finally, the obtained results have been employed in order to follow hydration of CSA cement sample, demonstrating thus that NIR spectroscopy, being highly sensitive to water amount and distribution, can be an extremely useful tool for hydration studies. [ABSTRACT FROM AUTHOR]

Calcium sulphoaluminate (CSA) cement is considered the third series cement besides ordinary Portland 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 characterization 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 characterization of CSA cement and its main minerals. In order to identify which mineral phase is responsible for the different bands, Raman spectra have been acquired from synthesized yeelimite and belite phases (whose purity degree was checked by X-ray diffraction) and from calcium sulphate 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 diffraction, proved useful to follow the hydration process of CSA cement up to 28 days. [ABSTRACT FROM AUTHOR]