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Chloride Binding and Its Effects on Characteristics of Cement-Based Materials
Published in Shi Caijun, Yuan Qiang, He Fuqiang, Hu Xiang, Transport and Interactions of Chlorides in Cement-Based Materials, 2019
Shi Caijun, Yuan Qiang, He Fuqiang, Hu Xiang
Nuclear magnetic resonance (NMR) 1H relaxometry is a non-destructive technique to investigate the content and distribution of proton (H) within samples. 1H NMR has been shown to be a powerful tool for the characterization of pore size distribution and porosity of cement pastes at the nanoscale owing to the proportional correlation between the 1H relaxation rate of water in pore spaces and the pore surface to volume ratio (Gajewicz et al. 2016). In geotechnical engineering, 1H NMR has been applied in detecting pore distribution and adsorbed water content. Tian et al. (Tian and Wei 2014; Tian et al. 2014) developed a method to distinguish the free and adsorbed water of clay based on the different freezing points and resistances to suction between adsorbed and free water by 1H NMR. Compared to clay or other soil materials, cement-based materials have a denser structure and lower total porosity, which makes it more difficult to separate the free and adsorbed water.
Automatic thermograms segmentation, preliminary insight into spilling drop test
Published in Quantitative InfraRed Thermography Journal, 2023
J. Melada, P. Arosio, M. Gargano, N. Ludwig
When performing broadband 1H-NMR relaxometry measurements, the longitudinal nuclear relaxation time T1 and the transverse nuclear relaxation time T2, two parameters related to the relaxation process of the hydrogen nuclear magnetisation, were measured. These parameters depend on the interaction between the hydrogen nuclei and the surrounding environment (i.e. other magnetic moments and all the other factors that interact with the spins of the hydrogen nuclei, like chemical functional groups, electron density, etc.). It must be noted that in the samples used for these measurements most hydrogen nuclei are water protons, therefore the obtained NMR signal reflects the information coming from the different water molecules inside the samples. In particular, NMR applied to saturated porous media measures the hydrogen nuclei concentration in the materials, which are imputed to fluids filling pore volumes [20]. Relaxation times of fluids confined in porous media are also strictly related to the geometry of the pores structure: the relaxation rate of water in porous media is increased in proportion to the surface-to-volume ratio (S/V) of the pore space [21]. Consequently, the 1H-NMR measurements assuming a spherical shape of the pores can provide information on porosity and pore size distribution of the porous materials.