Water Transport in Brick, Stone and Concrete

Hall, Christopher; Hoff, W D

doi:10.4324/9780203301708

Cited by 274 publications

(376 citation statements)

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“…It has been shown (e.g. Hall & Hoff 2002) that the van Genuchten equation describes the capillary potential of brick, stone and concrete materials just as for soils, although data are sparse. The van Genuchten equation describes the dependence of the capillary potential J on water content q and can be written as Q = (q − q r )/(q s − q r ) = [1 + (aJ) n ] −n , where a and n are material parameters.…”

Section: Unsaturated-flow Modelmentioning

confidence: 99%

“…We note that this is equivalent to a 300 mm slab with evaporation from both faces (N = 2). (Although we model a uniform slab with no mortar joints, earlier work (Hall & Hoff 2002) shows that an averaged composite sorptivity can adequately describe the flow through two dissimilar materials in hydraulic contact, so this method is also applicable to composite masonry structures). We use a sorptivity S = 1.0 mm min −1/2 , typical of building limestones and sandstones (Hall & Hoff 2002); and an effective porosity q w = 0.2, typical of the capillary moisture content of such stones.…”

Section: Benchmark Problem With Seasonal Variation In Evaporationmentioning

confidence: 99%

“…(Although we model a uniform slab with no mortar joints, earlier work (Hall & Hoff 2002) shows that an averaged composite sorptivity can adequately describe the flow through two dissimilar materials in hydraulic contact, so this method is also applicable to composite masonry structures). We use a sorptivity S = 1.0 mm min −1/2 , typical of building limestones and sandstones (Hall & Hoff 2002); and an effective porosity q w = 0.2, typical of the capillary moisture content of such stones. Taking the evaporation rate e = 0.001 mm min −1 (a constant value approximately equal to the UK PE averaged over one calendar year), we find that the steady-state height of rise h ss = 865 mm and the steady flow rate through the wall is about 1.25 L d −1 per metre length of wall.…”

Section: Benchmark Problem With Seasonal Variation In Evaporationmentioning

confidence: 99%

“…In an SF model (e.g. Hall & Hoff 2002), the height of rise h(t) is well defined as the position of the boundary of demarcation between wetted and dry zones. Evaporation occurs from the wetted vertical surface (here, N = 1 for a wall subject to evaporation from one face and N = 2 for two-sided evaporation).…”

Section: Sharp-front Modelmentioning

confidence: 99%

“…q r is a residual water content (taken here as equal to the initial water content q i = 0.01); q s is the maximum water content (taken here as the effective volume fraction porosity of the material q w = 0.2). In these UF simulations, we have used J(q) data for a British fired-clay brick (Gummerson et al 1980), fitted to the van Genuchten equation (Hall & Hoff 2002). The data were obtained by a standard pressure membrane procedure.…”

Section: Unsaturated-flow Modelmentioning

confidence: 99%

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Moisture dynamics in walls: response to micro-environment and climate change

et al. 2010

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A coupled sharp-front (SF) liquid transport and evaporation model is used to describe the capillary rise of moisture in monoliths and masonry structures. This provides a basis for the quantitative engineering analysis of moisture dynamics in such structures, with particular application to the conservation of historic buildings and monuments. We show how such a system responds to seasonal variations in the potential evaporation (PE) of the immediate environment, using meteorological data from southern England and Athens, Greece. Results from the SF analytical model are compared with those from finite-element unsaturated-flow simulations. We examine the magnitude and variation of the total flow through a structure as a primary factor in long-term damage caused by leaching, salt crystallization and chemical degradation. We find wide seasonal variation in the height of moisture rise, and this, together with the large estimated water flows, provides a new explanation of the observed position of salt-crystallization damage. The analysis also allows us to estimate the effects of future climate change on the capillary moisture dynamics of monoliths and masonry structures. For example, for southern England, predicted increases in PE for the period 2070-2100 suggest substantial increases in water flux, from which we expect increased damage rates.

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Section: Unsaturated-flow Modelmentioning

confidence: 99%

Section: Benchmark Problem With Seasonal Variation In Evaporationmentioning

confidence: 99%

Section: Benchmark Problem With Seasonal Variation In Evaporationmentioning

confidence: 99%

Section: Sharp-front Modelmentioning

confidence: 99%

Section: Unsaturated-flow Modelmentioning

confidence: 99%

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Moisture dynamics in walls: response to micro-environment and climate change

et al. 2010

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Effects of microstructure on water imbibition in sandstones using X‐ray computed tomography and neutron radiography

et al. 2017

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Capillary imbibition in variably saturated porous media is important in defining displacement processes and transport in the vadose zone and in low‐permeability barriers and reservoirs. Nonintrusive imaging in real time offers the potential to examine critical impacts of heterogeneity and surface properties on imbibition dynamics. Neutron radiography is applied as a powerful imaging tool to observe temporal changes in the spatial distribution of water in porous materials. We analyze water imbibition in both homogeneous and heterogeneous low‐permeability sandstones. Dynamic observations of the advance of the imbibition front with time are compared with characterizations of microstructure (via high‐resolution X‐ray computed tomography (CT)), pore size distribution (Mercury Intrusion Porosimetry), and permeability of the contrasting samples. We use an automated method to detect the progress of wetting front with time and link this to square‐root‐of‐time progress. These data are used to estimate the effect of microstructure on water sorptivity from a modified Lucas‐Washburn equation. Moreover, a model is established to calculate the maximum capillary diameter by modifying the Hagen‐Poiseuille and Young‐Laplace equations based on fractal theory. Comparing the calculated maximum capillary diameter with the maximum pore diameter (from high‐resolution CT) shows congruence between the two independent methods for the homogeneous silty sandstone but less effectively for the heterogeneous sandstone. Finally, we use these data to link observed response with the physical characteristics of the contrasting media—homogeneous versus heterogeneous—and to demonstrate the sensitivity of sorptivity expressly to tortuosity rather than porosity in low‐permeability sandstones.

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Mass Transfer

2012

Building Physics – Heat, Air and Moisture

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Water Transport in Brick, Stone and Concrete

Cited by 274 publications

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Moisture dynamics in walls: response to micro-environment and climate change

Moisture dynamics in walls: response to micro-environment and climate change

Effects of microstructure on water imbibition in sandstones using X‐ray computed tomography and neutron radiography

Mass Transfer

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