Hygric properties of hydrophobized building materials

Abstract

Moisture loads due to wind-driven rain can lead to accelerated decay of exposed building facades. Hydrophobic impregnation reduces water absorption of facade materials and is thus presumed to decrease moisture related damages. Hydrophobic impregnation however also lowers the drying speed of the exposed facade, leaving mainly water vapour transfer to take place. This study examines the open porosity and capillary absorption coefficient of impregnated brick samples as well as the effect of hydrophobic impregnation on the vapour permeability of brick and mortar samples. The open porosity was measured with vacuum saturation test, the absorption coefficient was determined by water uptake tests, both done after one month of curing of the impregnated brick samples. The vapour permeability was `derived from cup tests and from drying tests. The resulting open porosity from brick samples indicates that the changes in the overall pore structure are minimal after impregnation. In addition, the absorption coefficient of brick was found to be fairly close to zero, even with low concentrations of active ingredient, and regardless the percentage of silane/siloxane. Our findings support the claim that the hydrophobic impregnation does not influence significantly the water vapour permeability of brick and mortar.

Hygrothermal assessment of four insulation systems for interior retrofitting of solid masonry walls through calibrated numerical simulations

“…The exterior surface of the wall models was kept as bare brick, except for PUR-CM+H, Phenolic+H, and AAC+H which were simulated as hydrophobised. This was achieved by lowering the water uptake coefficient, Aw, by a factor 1000 for the outermost 10 mm of the existing masonry wall, similar to what was experimentally determined in [45]. The initial conditions (temperature and RH) measured in the 7 sensor locations were applied to the simulation models as shown in Figure 2.…”

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

“…Additionally, it can be of interest in the design of future test setups for material characterisation or, for instance, in studies on moisture and salt transport in building materials, as kaolin clay is also used in this context (a.o. [22,23]).…”