Liquid moisture transport in combined ceramic brick and natural hydraulic lime mortar samples: Does the hygric interface resistance dominate the moisture transport?

Calle, Klaas; Kock, Tim De; Cnudde, Veerle; Bossche, Nathan Van Den

doi:10.1177/1744259119857762

Cited by 21 publications

(20 citation statements)

References 22 publications

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“…In February 2018, this journal published the article "Interface influence on moisture transport in buildings" [1], wherein an enquiry into the impact of material interfaces on moisture absorption in building materials is documented. This article continues previous research of this group on this topic [2][3][4][5][6], which was originally initiated with the seminal paper of de Freitas et al in 1996. In all of these studies, the interface impacts are characterised with maximum moisture flows over the interface, contrary to the much more widely employed characterisation with interface resistances though [7][8][9][10][11][12][13][14]. The investigation in [1] targets three types of material interfaces: 'air space' (two brick samples separated by an air space), 'perfect contact' (two brick samples in direct contact) and 'hydraulic contact' (bonded brick-mortar samples).…”

Section: Introductionmentioning

confidence: 60%

A critique on characterising interface resistances with maximum moisture flows

Janssen

2020

Construction and Building Materials

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In February 2018, this journal published the article "Interface influence on moisture transport in buildings". This critique firstly establishes that the reported 'hydric resistance' values overestimate the impacts of the material interfaces for the brick-mortar 'hydraulic contact' samples. It is shown that the actual flows after crossing the brick-mortar interface are 2 to 5 times higher than indicated by the article's 'hydric resistance' values. This critique secondly demonstrates that the article's main idea of characterising material interfaces with a maximal post-interface-flow is not dependable nor generalisable. This flow is not necessarily constant in time, and may depend on the interface's actual location, the surrounding materials' properties and the imposed boundary conditions, hence defying all generalisation. The conclusion of this critique is therefore that the processing methods and results of the disputed article are not reliable.

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Section: Introductionmentioning

confidence: 60%

A critique on characterising interface resistances with maximum moisture flows

Janssen

2020

Construction and Building Materials

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“…where h = height of air layer (m), d a = vapour diffusion coefficient for still air (s), P c = Capillary Pressure (Pa), P v = Vapour Pressure (Pa) Laboratory tests have measured the interface resistance between 1.0E08 and 1.0E12 m/s (Calle et al, 2019;Derluyn et al, 2011;Qiu et al, 2003). These values changed depending on the combination of materials, whether the mortar was dry or wet cured and whether the joints were oriented vertically or horizontally.…”

Section: Mortar -Unit Interface Resistancementioning

confidence: 99%

“…The interface resistance can be modelled in several ways. It can be modelled with as an explicit infinitesimal layer analogous to contact resistances in heat transfer (Calle et al, 2019; Derluyn et al, 2011; Janssen et al, 2012; Qiu et al, 2003); or as an air layer between materials as in equation (1) (Brocken, 1998).…”

Section: Literature Reviewmentioning

confidence: 99%

A methodology for hygrothermal modelling of imperfect masonry interfaces

Gutland

Bucking

Quintero

2021

Journal of Building Physics

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Hygrothermal models are important tools for assessing the risk of moisture-related decay mechanisms which can compromise structural integrity, loss of architectural features and material. There are several sources of uncertainty when modelling masonry, related to material properties, boundary conditions, quality of construction and two-dimensional interactions between mortar and unit. This paper examines the uncertainty at the mortar-unit interface with imperfections such as hairline cracks or imperfect contact conditions. These imperfections will alter the rate of liquid transport into and out of the wall and impede the liquid transport between mortar and masonry unit. This means that the effective liquid transport of the wall system will be different then if only properties of the bulk material were modelled. A detailed methodology for modelling this interface as a fracture is presented including definition of material properties for the fracture. The modelling methodology considers the combined effect of both the interface resistance across the mortar-unit interface and increase liquid transport in parallel to the interface, and is generalisable to various combinations of materials, geometries and fracture apertures. Two-dimensional DELPHIN models of a clay brick/cement-mortar masonry wall were created to simulate this interaction. The models were exposed to different boundary conditions to simulate wetting, drying and natural cyclic weather conditions. The results of these simulations were compared to a baseline model where the fracture model was not included. The presence of fractures increased the rate of absorption in the wetting phase and an increased rate of desorption in the drying phase. Under cyclic conditions, the result was higher peak moisture contents after rain events compared to baseline and lower moisture contents after long periods of drying. This demonstrated that detailed modelling of imperfections at the mortar-unit interface can have a definitive influence on results and conclusions from hygrothermal simulations.

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“…The fine particles form smaller pores near the interface, and this reduces liquid flow. Laboratory testing has measured the interface resistance between 1.0E08 and 1.0E12 m/s (Calle, De Kock, Cnudde, and Van den Bossche, 2019;Derluyn, Janssen, and Carmeliet, 2011;Qiu, Haghighat, and Kumaran, 2003). Simulations have demonstrated the effect that the interface resistance have on moisture uptake (Vereecken and Roels, 2013;Zhou, Desmarais, Vontobel, Carmeliet, and Derome, 2018).…”

Section: Masonry Interfacementioning

confidence: 99%

Detailed Modelling of the Masonry Unit-Mortar Interface Using Hygrothermal Simulation

Gutland¹,

Bucking²,

Quintero³

2020

XV International Conference on Durability of Building Materials and Components. eBook of Proceedings

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Hygrothermal models are important tool for assessing the risk of moisture-related decay mechanisms in historic masonry structures. However, there are significant uncertainties in the process related to material properties, boundary conditions and quality of construction that effect confidence in the model's predictions compared to measured values. This paper examines one potential source of uncertainty; the imperfect nature of mortar joints in masonry walls, exemplified by such things as open joints, hairline cracks and imperfect bonds at the interface between mortar and unit. These are rarely considered in hygrothermal modelling in detail, where perfect interfaces are typically inferred. The premise is that at this interface, liquid transport behaviour is more similar to that of a fracture than that of a bundle of capillaries. These fractures of varying heights (or aperture) can affect transport into and out of the plane of the wall (perpendicular plane) and impede the liquid transport between mortar and the masonry unit (in-plane). This could lead to the "effective" moisture transport being different than what would be predicted using measured bulk material properties. A more detailed method for modelling this interface, borrowing techniques from the field of geohydrology is presented which demonstrates the effect that detailed modelling of the mortar joint has on moisture transport in masonry. A brick wall with cement mortar is studied. A twodimensional hygrothermal model was created to demonstrate the effect of increased liquid conductivity into the wall cause by fractures.

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Liquid moisture transport in combined ceramic brick and natural hydraulic lime mortar samples: Does the hygric interface resistance dominate the moisture transport?

Cited by 21 publications

References 22 publications

A critique on characterising interface resistances with maximum moisture flows

A critique on characterising interface resistances with maximum moisture flows

A methodology for hygrothermal modelling of imperfect masonry interfaces

Detailed Modelling of the Masonry Unit-Mortar Interface Using Hygrothermal Simulation

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