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

Department of Building Materials, Technische Universität Dortmund, August-Schmidt-Str. 8, 44227 Dortmund, Germany
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Buildings 2020, 10(1), 18; https://doi.org/10.3390/buildings10010018
Received: 29 November 2019 / Revised: 2 January 2020 / Accepted: 13 January 2020 / Published: 20 January 2020
(This article belongs to the Special Issue Life Cycle Prediction and Maintenance of Buildings)
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. View Full-Text
Keywords: conservation; natural stone; long-term weathered; water repellents; durability; single-sided NMR conservation; natural stone; long-term weathered; water repellents; durability; single-sided NMR
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MDPI and ACS Style

Orlowsky, J.; Braun, F.; Groh, M. The Influence of 30 Years Outdoor Weathering on the Durability of Hydrophobic Agents Applied on Obernkirchener Sandstones. Buildings 2020, 10, 18.

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