Mass diffusivity determination of various building materials based on inverse analysis of relative humidity evolution at the back face of a sample

Abstract

In this study, we use a novel method to determine the mass diffusion coefficients of hygroscopic materials. The experiment involves subjecting one face of the sample to relative humidity (RH) variations over time and measuring the RH at the back face. The imposed RH and temperature are measured during the experiment, and they are used as boundary conditions in a comprehensive computational code to address heat and mass transfer in porous media. This new method is utilized to characterize the following building materials: autoclave aerated concrete, plaster, poplar wood, pine wood, medium-density fiberboard and low-density fiberboard. This paper provides the details regarding the determination of the sorption isotherms of the selected materials that are required for the determination of mass diffusivity. The obtained electrical tortuosity values are compared with geometrical tortuosity values determined via microtomography and three-dimensional image processing. The agreement between the two tortuosity values is applicable only for porous media with narrow pore size distribution.