Environmental Engineering Reference
In-Depth Information
4
Plaster at
Plaster at
Plaster and whitewash
Plaster at
“adobe”
Figure 11.12. Water uptake coefficient of the adobe brick and bitumen plaster
Figure 11.13. Micro-drop on the bitumen plaster at 4% by weight bitumen content
Futhermore, a micro-drop on the bitumen surface has a hemispheric shape and a
contact angle greater than 90° (see Figure 11.19). Coating the minerals, the bitumen
decreases their superficial tension and changes the wetting characteristics; the
highest superficial water tension in comparison to the bitumen film leads to a
hemispherical drop on the surface; i.e. the surface becomes hydrophobic [MER 00].
It is clear that the water vapor permeability properties of the bitumen plaster
allow the adobe brick and earthen architecture to “breathe”. Below 5% bitumen
content the plaster is still sufficiently open to water vapor diffusion. The water vapor
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