Non-Fickian diffusion in biosourced materials: Prediction of the delay between relative humidity and moisture content

Abstract

This work focuses on non-Fickian diffusion in biosourced building materials. To study these memory effects in this kind of materials, an original and automatic device was conceived and built. It allows a series of samples to be submitted, simultaneously, to a perturbation of RH at its front face and to record the evolution of sample mass and of RH at its back face. When analyzed using a classical heat and mass transfer model, the experimental data depicts a delay between RH and moisture content, the RH evolution being too fast. To address this problem, a new formulation able to model those types of behaviors using memory functions was used. To test the predictive potential of the new formulation, these memory functions were not identified but taken from a previous work, where they were determined experimentally using minute samples. A full set of experiments performed with Low Density Fiberboard (LDF) and Medium Density Fiberboard (MDF) was simulated using this new formulation feed by the experimental memory functions. The good agreement found between simulated and experimental results proves the predictive potential of the new macroscopic formulation.