Modelling of the hygrothermal properties of hemp concrete using a methodology combining X-ray tomography and FEM numerical simulation.

Bio-aggregate concretes, exemplified by hemp concrete, have attracted increasing attention in sustainable construction due to their low thermal conductivity, excellent moisture-buffering capacity, and reduced environmental impact. However, accurately modelling their hygrothermal properties remains challenging. In this study, a finite-element framework is developed based on the realistic 3D heterogeneous microstructure of hemp concrete obtained by X-ray micro-computed tomography (XCT) to determine the equivalent thermal conductivity and water vapor permeability. Specifically, XCT is used to reconstruct the material geometry, and image segmentation is employed to extract key structure parameters, including phase volume fractions and aggregate orientation. The hygrothermal properties of the binder matrix and hemp aggregates are identified through a combination of laboratory measurements and homogenization techniques. Hygrothermal governing equations are then solved on the heterogeneous finite-element model in COMSOL to derive the transverse and longitudinal equivalent thermal conductivity and water vapor permeability, and the results are compared with analytical homogenization predictions. The findings highlight the importance of accounting for microstructural features, particularly aggregate orientation and pore morphology, when predicting the hygrothermal performance of hemp concrete