The Influence of 30 Years Outdoor Weathering on the Durability of Hydrophobic Agents Applied on Obernkirchener Sandstones

The durability of eleven different water repellents applied on one sandstone type was studied after a long-term weathering at seven different locations in Germany. By measuring colour changes, it could be shown that the formation of black crusts, the deposition of particles and biogenic growth cause...

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Bibliographic Details
Published in:Buildings (Basel) 2020-01, Vol.10 (1), p.18
Main Authors: Orlowsky, Jeanette, Braun, Franziska, Groh, Melanie
Format: Article
Language:English
Subjects:
Absorption
Archives & records
Capillary pressure
Capillary water
Color
conservation
Crusts
Durability
Humidity
Hydrophobicity
Influence
long-term weathered
Low pressure
Mathematical analysis
natural stone
NMR
Nuclear magnetic resonance
Pipes
Precipitation
Repellents
Sandstone
single-sided nmr
Standard deviation
Stone
Velocity
Water absorption
Water depth
water repellents
Water uptake
Weathering
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Summary:The durability of eleven different water repellents applied on one sandstone type was studied after a long-term weathering at seven different locations in Germany. By measuring colour changes, it could be shown that the formation of black crusts, the deposition of particles and biogenic growth caused a gradual darkening as well as significant changes in total colour over time. Additionally, the water absorption behaviour was investigated with two different methods: applying a low pressure using the pipe method and capillary water absorption measurements from a wet underlay. Afterwards, the test results were analysed with four different evaluation methods: calculation of the protection degree from pipe method and capillary water absorption, determination of the velocity of water uptake during capillary water absorption and calculation of the damaged depth of the stone surface using single-sided NMR technique. The growing damaged depth leads to an increase of the water uptake velocity and to a decrease of the protection degree of the applied hydrophobing agents. Three protective agents based on isobutyltrimethoxysilane showed already after two years of outdoor weathering a clear loss of performance, which significantly increased after 30 years of exposure.
ISSN:2075-5309
2075-5309
DOI:10.3390/buildings10010018