Application of Fourier transform infrared spectroscopy in cement Alkali quantification

Abstract

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 [C3A(ss)] is used for Alkali quantification. Regression analysis of a plot correlating FTIR absorption band area ratio (750/923 cm−1) to equivalent Alkali Na2O e (Na2O e = % Na2O + 0.658 × % K2O) 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 $$ A_{{750\,{\text{cm}}^{ - 1} }} $$ to $$ A_{{923\,{\text{cm}}^{ - 1} }} $$ band area ratio and the magnitude of the disorder coefficient (C d).