Dynamic effects in porous building materials
01.02.2019 – 31.01.2021
Funding agency: Austrian Science Fund (FWF), Erwin Schrödinger Fellowship
Grant recipient: Michele Bianchi Janetti
Host institution: KU Leuven (BE), Building Physics and Sustainable Design section
Abstract
Moisture is often the critical factor when judging built structures’ durability and sustainability as well as building occupants’ health and comfort, for which the accurate understanding and reliable assessment of moisture transfer in building materials are crucial.
Although the use of numerical models for prediction of the moisture risk is well-established, fundamental kinetics of moisture storage and transfer in porous building materials are not fully understood yet. Available numerical models based on the continuum approach generally assume the moisture transfer potential (capillary pressure) to be independent of the (de)saturation rate (speed of local saturation changes over time). Several experimental findings reveal though that this assumption might be inaccurate in some cases. In particular, it has been noted that sufficiently high (de)saturation rates may significantly influence moisture transfer processes. This phenomenon is addressed in the literature as “dynamic effects”.
This project attempts at explaining potential causes of dynamic effects as well as at quantifying their influence on the imbibition and dying processes in different building materials. Numerical pore scale algorithms are developed and applied to investigate the (dynamic) moisture transfer and storage behaviour of porous materials. In addition, an experimental campaign is carried out on exemplary materials (calcium silicate, ceramic brick and aerated concrete). The obtained numerical and experimental results allow one to gain better insight on the causes of dynamic effects as well as on their impact on moisture transfer in building materials.
Left: Phase-field simulation of moisture distribution in an exemplary pore structure. The red and blue colours denote the wetting and non-wetting fluid respectively; Right: Exemplary moisture retention curves for a steady state and transient imbibition process. The deviation between the steady state and transient curve is due to dynamic effects.
Publications
Bianchi Janetti M, Janssen H. (2020). Impact of the drying rate on the moisture retention curve of porous building materials. Construction and Building Materials 258:1-9. https://doi.org/10.1016/j.conbuildmat.2020.119451.
Bianchi Janetti M, Janssen H. (2020). Pore scale modelling of moisture transfer in building materials with the phase field method. E3S Web of Conferences, 172. https://doi.org/10.1051/e3sconf/202017204004
Bianchi Janetti M, Janssen H. (2019). Characterization of the diffusivity through water-uptake tests, MATEC Web of Conferences, 282. https://doi.org/10.1051/matecconf/201928202040