Quantitative Analysis of Chloride Ion Diffusion in Cementitious Materials Using Al27 NMR Spectroscopy

Abstract

AbstractNuclear magnetic resonance (NMR) spectroscopy was employed to evaluate the effects of chloride ion diffusion on the chemical environment of hydrated cement paste and concrete. Al27 magic angle spinning NMR spectra were obtained at different depths from the surface (surface, 3 mm, and 6 mm) exposed to chloride ion solution after 1 month. Deconvolution of Al27 NMR spectra obtained from different depths of concrete exposed to salt solution revealed a clear trend in chloride penetration. Most importantly, the intensities and areas under peaks corresponding to Friedel’s salt (8.5 ppm) and ettringite (13.3 ppm), which reflect the extent of chemical binding of chloride by cement hydrates, dropped with increasing depth. These trends demonstrate the ability of Al27 NMR spectroscopy to track chloride ion diffusion into the concrete. Fourier-transform infrared spectroscopy spectroscopy and wet chemistry methods were employed in order to verify the findings of NMR spectroscopy.