Abstract
Alongside well-researched themes such as water and moisture, the service life and function of masonry veneers are often compromised by precipitation combined with poor design considerations, execution, and selection of materials. Little research has been carried out on the subject of the impact of mortar consistency on masonry’s resistance to driving rain. Water-repellent (WR) impregnation is typically considered a quick fix when problems occur. Wall-panels of 1 m2 built with different flow table values for the mortar have been tested in a driving rain chamber, where both time-lapse videos and the measuring of penetrated water are used to evaluate performance. Subsequently, the panels were impregnated with the most common types of WR products and re-tested. The analysis shows that changing the mortar mix from dry to wet can decrease the penetration of driving rain by a factor of ten. The test results presented in this article show that mortar with low water content gives a porous interfacial transition zone (ITZ), thereby increasing the rate of water penetration. The tested WRs are found to be ineffective in increasing masonry’s resistance to high pressure driving rain. The results, combined with what is already known about WR treatments on masonry, call for careful consideration before applying such treatment. This proves especially true in countries with much driving rain followed by frequent freeze-thaw cycles.
Highlights
Climate changes are assumed to result in a warmer and wetter climate in Norway [1,2], leading to an increased risk of defects and the early decay of buildings
Using wet masonry mortar has been shown to be effective in achieving good bonding between mortar and brick, strongly reducing water permeability and improving the resistance to driving rain
Based on the driving rain test and the thin section analysis, we find it reasonable to assume that the interfacial transition zone (ITZ) between mortar and brick masonry does have air voids that cannot be protected from moisture ingress by applying WR impregnation
Summary
Climate changes are assumed to result in a warmer and wetter climate in Norway [1,2], leading to an increased risk of defects and the early decay of buildings. Warmer and moister conditions will lead to new challenges for the performance of masonry within the Norwegian context [3], related to increased amounts of rain This proves especially true in combination with the increased challenge posed by more frequent freeze-thaw conditions in new regions of the country, in particular the densely populated areas around the capital Oslo. The increased risk of defects and early decay in buildings inflicted by the new physical conditions caused by climate change are clearly not limited to Norway. This country, experiences some challenges that are exemplary, in that they push the consequences of the changes to a conceptual and physical endpoint. With its geographical and Buildings 2017, 7, 70; doi:10.3390/buildings7030070 www.mdpi.com/journal/buildings
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