Moisture localisation in unsaturated materials using nuclear magnetic resonance experiments, X-ray computed tomography and pore network modeling

Abstract

Due to the detrimental effects of moisture in the built environment, there is continuous interest in non-destructive experimental techniques that localize and/or quantify moisture in materials. To this aim, nuclear magnetic resonance (NMR) experiments, X-ray computed tomography (XCT) and pore network modelling (PNM) are heavily researched. Since these techniques are all based on different physical principles and assumptions, comparing their results is not only necessary, but can provide valuable insights as well. Since most research, centered around these three approaches, solely focuses on water-saturated materials, in this study, these approaches are used to determine the size distributions of the water islands in unsaturated materials. By comparing the results of all three methods, it can be concluded that NMR mainly focuses on the biggest water islands/columns (i.e. large pore corners and filled pores) while the other techniques are capable of representing all water islands. PNM and XCT imaging provide similar results with the exception that PNM slightly overestimates both size as well as quantity of the water islands trapped in pore corners. Nevertheless, due to PNM being by far the fastest approach, it remains a valuable first estimation of the distribution of moisture in unsaturated materials.