Characterization of pore structures of hydrated cements and natural shales by ¹²⁹Xe NMR spectroscopy

Abstract ¹²⁹Xe NMR of adsorbed xenon gas is a sensitive tool for the characterization of porous materials. Here we exploit, for the first time, ¹²⁹Xe NMR to investigate the nanoscale porous structures in hydrated white cements and natural shale. Signals of xenon in mesopores and larger voids are well resolved in the spectra of the cement samples, and the exchange rate between these sites was determined to be 100−300 s⁻¹ at room temperature. The spectra imply that the mesopore size is the smallest and the exchange rate is the highest in the sample with the lowest initial water/cement ratio. The heat of adsorption of xenon in the cements is similar to that in silica gels, about 12 kJ/mol. The shale spectra include a very broad signal, covering a range of about 600 ppm, implying that the adsorbed xenon interacts with the paramagnetic impurities present in the samples