Non-destructive detection of the efficiency of long-term weathered hydrophobic natural stones using single-sided NMR

Braun, Franziska; Orlowsky, Jeanette

doi:10.1016/j.culher.2019.07.005

Cited by 11 publications

(16 citation statements)

References 15 publications

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“…These high standard deviations suggest that the hydrophobic agents, based on silane, penetrate uneven into the pore system of the sandstones. Furthermore, these materials showed no clear line between hydrophilic and hydrophobic zone [13]. The other materials, especially based on siloxane, showed after wetting the surface a clear boundary between dry (hydrophobic) and wet (hydrophilic).…”

Section: Stone Typementioning

confidence: 87%

“…Table 2 provides an overview of the chemical composition and active ingredient content of the used products as well as characteristic values of OKS treated with these agents. The penetration depth of the hydrophobic agents was measured with a calliper on the triangle-shaped slices, which were moistened for this purpose [1, 2,13]. The measurement was carried out on the cut side.…”

Section: Stone Typementioning

confidence: 99%

“…The NMR MOUSE ® PM 25 (Mobile Universal Surface Explorer, registered trademark of RWTH Aachen University, Aachen, Germany) allows the non-destructive detection of moisture distribution inside porous materials via nuclear magnetic resonance. The measurement technique is described amongst others in [13,24,25].…”

Section: Moisture Distribution Inside the Stone-degradation Depthmentioning

confidence: 99%

“…The amplitude (signal of proton density) depends on the amount of water in the porous stone. Based on 51 measurements, a correlation between amplitude and amount of absorbed water was determined for untreated and treated OKS [13]. A threshold for the amplitude was defined: if the amplitude is ≤0.05 the water content is ≤0.1 kg/m² and the protection degree is ≥95%.…”

Section: Moisture Distribution Inside the Stone-degradation Depthmentioning

confidence: 99%

“…The influence of the composition of the agents, leading among other things to various penetration depths, is determined with three different test methods. Based on the work done in [13], a damaged depth inside the weathered stone is calculated for the first time. The term damaged depth describes the extent of damage in the uppermost area of the natural stone surface.…”

Section: Introductionmentioning

confidence: 99%

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

2020

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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.

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Section: Stone Typementioning

confidence: 87%

Section: Stone Typementioning

confidence: 99%

Section: Moisture Distribution Inside the Stone-degradation Depthmentioning

confidence: 99%

Section: Moisture Distribution Inside the Stone-degradation Depthmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

2020

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Development of a Single-Sided Magnetic Resonance Surface Scanner: Towards Non-Destructive Quantification of Moisture in Slaked Lime Plaster for Maintenance and Remediation of Heritage Architecture

Nakashima

2023

J Nondestruct Eval

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Single-sided time-domain proton magnetic resonance (MR) surface scanners are useful for non-destructive measurements of moisture. A mobile single-sided MR sensor unit employing two concentric ring magnets was constructed for the in situ quantification of moisture in slaked lime plaster used in the outer walls and roofs of heritage architecture. This sensor unit allows for non-destructive measurements of water proton relaxation 1.5 to 13.5 mm beneath the surfaces of walls and roofs. The following laboratory experiments on water-saturated porous slaked lime plaster samples were performed. (i) The porosity (water volume fraction) was measured in approximately eight minutes with a root mean square error of 1.9 vol%. (ii) The fundamental MR-related property (i.e. proton surface relaxivity) needed for the estimation of the pore size distribution was also measured successfully. (iii) The pore volume expansion due to frost damage was successfully detected as a significant change in the transverse relaxation time distribution. These results demonstrate that the portable MR surface scanner is a promising non-destructive testing tool for the maintenance and remediation of heritage architecture made of plaster.

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About the effectiveness of a hydrophobic surface treatment of Baumberger Sandstones

Orlowsky

Groh

Braun³

2022

Environ Earth Sci

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The Baumberger Sandstone, a sandy limestone, is used since the Middle Ages as a building material not only in the surrounding Münster region of North Rhine-Westphalia (Germany), where it is quarried since to date. To prevent the ingress of water and reduce weathering processes conservation methods, mostly in form of organosilicon compounds, were used. This study deals with the performance of applied hydrophobing agents on Baumberger Sandstone samples and their influence on the weathering processes during long-term exposure. The samples were exposed at several locations in Germany to different climatic conditions for up to 24 years. Afterwards, investigations concerning the water absorption behaviour and the degree of superficial damages were carried out. With an evaluation method on basis of NMR measurements, a very low and uneven distributed effective hydrophobic zone could be detected. This caused an ingress of water in the uppermost part and a progressive weathering of investigated natural stones. Thus the hydrophobic surface treatment did not lead to a significant decrease of weathering or damaging processes. Based on these results a hydrophobic surface treatment of Baumberger Sandstone seems not to be suitable.

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Non-destructive detection of the efficiency of long-term weathered hydrophobic natural stones using single-sided NMR

Cited by 11 publications

References 15 publications

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

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

Development of a Single-Sided Magnetic Resonance Surface Scanner: Towards Non-Destructive Quantification of Moisture in Slaked Lime Plaster for Maintenance and Remediation of Heritage Architecture

About the effectiveness of a hydrophobic surface treatment of Baumberger Sandstones

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