Zerstörungsfreie Bestimmung der Auslaugung von Beton mittels einseitiger Wasserstoff‐Kernspinresonanz

Holthausen, Robert Schulte; Raupach, Michael; Merkel, Melanie; Breit, Wolfgang

doi:10.1002/bate.202000003

Cited by 1 publication

(4 citation statements)

References 23 publications

(41 reference statements)

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“…Thus, a detected decay curve always consists of several individual exponential functions, which can be assigned to the different types of pores present in the samples. The separation of the individual signals takes place either through a multi-exponential fit or inverse Laplace transformation [4,19]. Further information on the detected number of relaxation components and the method of curve fitting used for the available sample material follows in Section 3.…”

Section: Nmr Measurementsmentioning

confidence: 99%

“…Then, the sample was wrapped in a one-layer vapour-tight polyethylene film and placed with the weathered side downwards on the NMR device (Figure 3, right). The glass plate prevented direct contact between the film and the sample surface, which separated the barely distinguishable NMR signals from the plastic film and material and allowed for the sample surface to be detected more accurately [4].…”

Section: Nmr Measurementsmentioning

confidence: 99%

“…Overall, this showed once more that this NMR measuring method is well suited for determining the porosity of different natural stone types [24]. In order to obtain further information from the measured exponential relaxation curves about the existing porosity, as well as different pore sizes in individual depths of the samples, a curve fitting was performed by means of a multi-exponential fit [4]. Based on the two types of pores present in the investigated sample material listed in Section 2, which were detected using mercury porosimetry, two relaxation components were assumed, and thus, a bi-exponential fit was used for the evaluation.…”

Section: Commentioning

confidence: 99%

“…Analysis of the pore structure of mineral building materials is conventionally carried out using mercury porosimetry and additional microscopic transillumination of thin sections [1,2]. Furthermore, investigations using the NMR technique produced successful porosity analyses of concrete samples [3,4]. The study presented in this paper was intended to evaluate the extent to which nuclear magnetic resonance spectroscopy could be used as a non-destructive measuring method to evaluate the depth-dependent detection of the porosity distribution and changes in weathered natural stones.…”

Section: Introductionmentioning

confidence: 99%

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Analysing the Porosity Distribution in Stone Surfaces by Means of Unilateral NMR after Long-Term Outdoor Weathering

Groh

Orlowsky

Holthausen³

2022

Materials

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Porosity changes in the near-surface area of sandstones due to long-term weathering can produce deterioration. Therefore, porosity analyses on weathered sandstones are significant for detecting possible influences on the pore structure. Classical methods for determining the porosity and pore size distribution in sandstones can only investigate the entire sample volume. In contrast, in this publication, the porosity was analysed in 0.2 mm steps over a depth of 5 mm by means of single-sided NMR measurements on water-saturated sandstones under vacuum. Evaluations of Obernkirchener and Schleeriether Sandstones that were weathered outdoors in Germany for over 30 years are presented. The results showed that the water content in Vol.-% strongly correlated with the normalised NMR signal. The unweathered sandstones showed a uniform distribution of micro and capillary pores throughout the stone depth. As a result of 30 years of outdoor weathering, changes in the pore structure occurred at the sandstone surface due to weathering down to depths of about 0.6 mm. The porosity of the Schleeriether Sandstone samples, mainly the microporosity, clearly increased in this region. Due to the dominance of capillary pores in the Obernkirchener Sandstone, the changes were not as pronounced, but a shift towards smaller pores in the surface area was observable.

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Section: Nmr Measurementsmentioning

confidence: 99%

Section: Nmr Measurementsmentioning

confidence: 99%