Masonry brick–cement mortar interface resistance to water transport determined with neutron radiography and numerical modeling

Abstract

Masonry is one of the most common building envelope systems in the world, providing an excellent water protection solution against rain. Water transport in masonry walls composed of bricks and mortar joints can be strongly affected by the nature of the interface between brick and mortar. In this study, two-dimensional water uptake experiments and numerical simulations are performed to study the effect of interface resistance on moisture transport in masonry samples with horizontal and vertical interfaces. Neutron radiography is used to document the time- and space-resolved moisture content distribution in different masonry samples. In the simulation of moisture transport, an interface resistance models the imperfect contact between brick and mortar. A good agreement between measured and simulated moisture content distribution is observed for different masonry samples. Moisture transport in masonry could be strongly affected by the interface resistance, when interface is in proximity to moisture source. The orientation, horizontal or vertical, of the interface between brick and mortar does not have an influence on the value of the interface resistance. However, the interface resistance depends on the capillary pressure at the interface. In the range of capillary moisture transport, a lower capillary pressure at the interface will lead to a larger interface resistance.

Does kaolin clay really create a perfect hydraulic interface contact between materials?

“…These values might seem large, but are much smaller than the (few) RIF-values for actual brick-mortar interfaces presented in the literature[19,28,29]. For instance, Derluyn et al[19] inferred a hydraulic interface resistance of 1.25 x 10 10 m/s between a brick (with Acap = 0.116 kg/(m 2 s 0.5 )) and a wet cured mortar (Acap = 0.015 kg/(m 2 s 0.5 )) and of 2.5 x 10 10 m/s between the same brick and a dry cured mortar (Acap = 0.010 kg/(m 2 s 0.5 )).…”

“…As mentioned in Section 2.4, in the current study, the estimated interface resistance is assumed to be a constant; and this while some studies state the interface resistance to be possibly dependent on capillary pressure or moisture content [9,27,28,29 ]. A further study on this dependency, based on for instance moisture profile measurements, is required.…”

On the potential of clustering approaches for hygrothermal material properties based on three degradation risks in solid masonry constructions

“…can be represented quite accurate by an individual volume of continuous 1-D historic brickwork for real climate conditions (Vereecken and Roels, 2013). There may be discrepancies on this assumption where the impact of the interface resistance becomes significant (Gutland et al, 2021;Zhou et al, 2020aZhou et al, , 2020b but is not the intention of this paper to make absolute statements about individual cases. The studied historical wall assemblies comprised a single leaf masonry with a plaster finish on the inner surface.…”

A methodology for hygrothermal modelling of imperfect masonry interfaces

“…Simulations have also demonstrated the effect that the interface resistance has on moisture absorption when exposed to realistic wind-driven rain and rising damp conditions (Vereecken and Roels, 2013; Zhou et al, 2018). A different laboratory test performed by Zhou et al (2020) designed to measure water uptake while considered interface resistances found a noticeably quicker advance in the wetting front adjacent to an interface with a visible crack. The authors noted a need for an absorption model for masonry with cracks at the interface.…”