The aim of this study is to develop an inverse method for identifying the hygric properties of hygroscopic building materials from a dynamic testing coupled with numerical modeling. To validate the accuracy of the identified parameters, a hygroscopic characterization campaign is carried out beforehand using standard methods. The study considers both abiotic material (cellular concrete) and biotic material (hemp concrete). The sorption isotherm is measured according to EN NF 12571 standard gravimetric method, including primary desorption curves. These isotherms are modeled using the Van GenHuchten and Huang models. The water vapour permeability is measured according to standard steady-state method EN NF 12572 and the moisture buffer value (MBV) according to the NORDTEST project. The developed inverse method makes it possible to identify sorption isotherms and vapor permeability by adjusting the modeled MBV kinetics to experimental data. This method is based on a combination of the internal heat and mass transfer code, TMC (short for "Transfert de masse et de chaleur" in French), and nonlinear least-squares optimization using the MATLAB solver, lsqcurvefit. Mass gain/loss during MBV test is simulated with TMC, and hygric parameters are identified by minimizing the difference between simulated and experimental kinetics. The robustness of the inverse method, TMCId, is assessed. Results are satisfactory for both cellular concrete and hemp-concrete, with and without hysteresis. • An inverse method is developed to identify hygric parameters of building materials • It allows identifying sorption curves with hysteresis or not, and vapour permeability • The experimental data corresponds to kinetics of mass of MBV test • The method is efficient for both abiotic and biotic materials • Its robustness is assessed considering initial values and measurement noise
Khaled et al. (Wed,) studied this question.