A functional structure for state functions of moisture transfer in heritage building elements

Abstract The good knowledge of the moisture transfer in materials used in the construction of architectonic cultural heritage is a key issue to define conservation and restoration actions. In recent years, numerical models are used in this field to improve the hygrothermal characterization of these materials. However, the structure of state functions involved in the modelization is not standardised, and they present a highly empirical parametrization. For this reason, the main objective of this work is to review the structure of the state functions corresponding to moisture transport (moisture content, liquid and vapour water permeabilities) and to suggest more compact functional structures that allow reducing the number of parameters. Two conventional tests used to characterize the hygrothermal behaviour of heritage elements, (i) water absorption by capillary test (EN 15801) and (ii) water vapour permeability test (EN 15803) have been simulated to check the capacity and quality of the moisture transfer simulation with the new functions. These numerical exercises were carried out using a moisture transport module implemented in COMSOL Multiphysics. The material selected was the limestone used in the construction of the Cathedral of Santa Maria and San Julian (Cuenca, Spain). The satisfactory results obtained demonstrate the utility of the functions proposed to model the hydraulic conductivity and diffusion resistance factor. A significant reduction in the number of material parameters is achieved without compromising the simulation capacity.