Pore-Structure-Based Determination of Unsaturated Hygric Properties of Porous Materials
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A reliable and practical method of hygric property characterisation is a major determinant in properly analysing hygric performance of built constructions. The current empirical approach, however, yields data that are still incomplete, not fully representative, and not entirely reliable. In this study, hygric properties are therefore determined directly from pore structure information by applying stationary unsaturated pore-scale physics to model moisture storage and transport. The pore space is captured by visualisation techniques and further extracted into a discrete network of variably shaped pore bodies interconnected by pore throats. In this network, corner and surface adsorption and capillary condensation are simulated to define the moisture storage. Air entrapment is furthermore considered to determine the capillary moisture content. The resulting spatial moisture distribution in the pore network allows moisture to flow, in wet elements in the liquid phase and in dry elements in the vapour phase. The adsorbed corner and surface films moreover enable additional liquid flow. These various simultaneous flows aggregately define the transport property. A comparison to measured data validates the presented hygric property model.
KeywordsHygric properties Moisture retention curve Moisture permeability curve Pore-network model Unsaturated flow Porous materials
The authors gratefully thank Professor Jeff Gostick for making his code open source, and Dr. Steven Claes and Dr. Chi Feng for their PNMs and measured data of the sintered-glass filter, respectively. Muhammad Islahuddin thanks Dr. Evy Vereecken for fruitful discussions.
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