Application of Fourier transform infrared spectroscopy in cement Alkali quantification

Alkali in cement is responsible for the Alkali–silica-reaction phenomenon that manifests itself in the form of premature cracking in concrete structures such as bridge decks and concrete pavements. X-ray fluorescence spectroscopy (XRF) is commonly used for cement Alkali quantification but a simpler and faster analytical procedure based on Fourier transform infrared spectroscopy (FTIR) has been expanded for this purpose. An analytical absorption band at 750 cm −1 in the FTIR spectra of cement samples belonging to Alkali solid solution of tricalcium aluminate [C 3 A(ss)] is used for Alkali quantification. Regression analysis of a plot correlating FTIR absorption band area ratio (750/923 cm −1 ) to equivalent Alkali Na 2 O e (Na 2 O e = % Na 2 O + 0.658 × % K 2 O) measured by XRF shows a linear correlation coefficient, R 2 , of 0.97. High Alkali cement samples show a higher microstructural disorder coefficient, C d , which is a reactivity criterion introduced by Bachiorrini and co-authors (Proceedings of the seventh international conference on concrete alkali-aggregate reactions‚ 1986 ) for ASR-susceptible aggregates. Results of this research indicate applicability of FTIR technique to quantitatively predict cement vulnerability to ASR through the A 750 cm − 1 to A 923 cm − 1 band area ratio and the magnitude of the disorder coefficient ( C d ).