Application of FTIR for Quantification of Alkali in Cement

Alkali-silica reaction (ASR) in cement is a major contributor to failure of cement structures around the world, causing increased repair costs and possible rebuild expenses. Alkali levels are indicative of the potential for ASR and are therefore measured and quantified. A linear correlation relating cement alkali concentration measured by X-ray fluorescence spectroscopy (XRF) and peak ratio measured by Fourier transform infrared spectroscopy (FTIR) is developed. Regression analysis of plots correlating alkali content measured by FTIR absorption band (750 cm-1/923 cm-1) ratio versus equivalent alkali (Na2O)e (%Na2O + 0.658 % K2O) quantified by XRF show linear correlation coefficient, R2, of 0.97. Results of this investigation are discussed in terms of microstructural disorder coefficient Cd which is a reactivity criterion for ASR-susceptible aggregates proposed by Bachiorrini [31]. XRF is a popular technique for alkali quantification but FTIR is faster, safer, and less expensive technique compared to XRF. Portable instrumentation is available for both techniques but FTIR systems are less expensive