Potential and challenges of in situ ATR-FTIR spectroscopy in the analysis of cement hydration: Combined evaluation with in-situ and ex-situ XRD

The core of this study is the detailed investigation of early age cement hydration by ATR-FTIR spectroscopy. Spectra were obtained in situ on a CEM I 52.5R during the first 24 h of hydration. The data is discussed in conjunction with the quantitative phase contents obtained by in situ and ex situ X-ray diffraction. Cement pastes with water-to-cement ratios of 0.3, 0.37, and 0.45 are compared with regard to suitability for the method and the influence of water content on reaction kinetics. In addition, different data evaluation methods are compared with respect to outcome and effort. Whereas the determination of characteristic integral areas proves to be sufficient for qualitative tracking of water consumption and the formation of hydration products like C-S-H and ettringite (AFt), detailed peak fitting provides additional information on the variation of overlaying peaks during raw material consumption and product formation and reveals structural changes within individual phases. • Development of a peak-fitting procedure for ATR data of cement hydration. • Detection of Si-OH bond formation at the interface of clinker phases and water. • Structural evolution of C-S-H in the context of overall progression of hydration. • Early-age determination of the formation and structural stability of AFt. • Reasonability of hydration kinetics proven by calorimetric data.