10.4122/1.1000000907
Derluyn, Hannelore
Hannelore
Derluyn
hannelore.derluyn@bwk.kuleuven.be
Moonen, Peter
Peter
Moonen
peter.moonen@bwk.kuleuven.be
Carmeliet, Jan
Jan
Carmeliet
jan.carmeliet@bwk.kuleuven.be
Derluyn, Hannelore
Hannelore
Derluyn
hannelore.derluyn@bwk.kuleuven.be
Moisture transfer across the interface between brick and mortar joint
8th Symposium on Building Physics in the Nordic Countries
2008
2008
Moisture transport in masonry is an important research subject in building physics related to durability issues such as cracking due to restrained shrinkage, frost damage, staining due to salt efflorescence or algae growth, salt damage due to crystallization; and is of particular interest for the renovation and construction industry.
Moisture transfer in masonry, being a multi-layered material, is not as straightforward as in homogeneous porous material. A first aspect is the dependence of moisture transport properties of mortars on the curing conditions. A second aspect is the contact between brick and mortar joint. Perfect hydraulic contact, meaning a continuity of the capillary pressure at the interface, can only be assured artificially by applying a kaolin layer between brick and mortar. Real contact between brick and joint mortar seems to be an imperfect contact, resulting in a resistance for moisture transport.
The main issue in the modelling of moisture transfer in masonry is how to cover the behaviour at the interface between brick and mortar joint. In literature, several authors introduce in their model an additional resistance in order to cover the influence of the interface on the moisture transport (Qui et al. 2002; Holm et al. 1996; de Freitas et al. 1996). In this paper, three modelling approaches are presented to describe liquid water transport in masonry, with special attention to the transport across the interface.
Experiments are performed on masonry samples consisting of brick-mortar joint-brick. Moisture uptake perpendicular and parallel to the mortar joint is measured using X-ray analysis. A first modelling approach is to consider the interface as a thin layer of mortar, where the thickness is determined from experiments. This thin layer has adapted properties, taking into account a reduced permeability and the presence of compaction voids. A second modelling approach is to add a resistance between the brick and the mortar joint. A third modelling approach is based on the partition of unity technique. The interface is assumed to be an imperfect contact where a damage parameter describes the discontinuity in capillary pressure. Both transfer directions (perpendicular and parallel to the mortar joint) are simulated and a comparison between the three modeling approaches is made.