Hygric resistance in multilayer building materials – a prevision new methodology

CONSTRUCT-LFC, Faculty of Engineering (FEUP), University of Porto, Rua Dr. Roberto Frias, s/n, 4200-465 Porto, Portugal.

Abstract

This work presents the results of an experimental campaign in order to determine the hygric resistance in multilayered building components, with different interface types. The results show a slowing of the wetting process due to the interfaces hygric resistance. The samples with hydraulic contact interface (cement mortar) present lower absorption rate than the samples with lime mortar. The influence of air space between layers was also demonstrated, i.e., the air space interfaces increase the coefficients of capillary significantly, as the distances from the contact with water increase.

The hygric resistance was calculated by three different methods: gravimetric and gamma-ray methods, and the new methodology proposed, an automatic calculation method without human opinion/criteria. The “knee point” was detected, numerically, in water absorption curves and the moisture-dependent interface resistance was quantified and validated for transient conditions. The methodology proposed to detect the “knee point” can be also used in the future for different multilayer materials with an interface, in order to obtain more correct hygric resistance values to be used in future numerical simulations.