TY - JOUR A1 - Kruschwitz, Sabine T1 - NDT for microstructure and moisture investigation of porous building material JF - The e-journal of nondestructive testing & ultrasonics N2 - Non-destructive testing methods are mostly applied and established for the detection of embedded mounting parts or structural defects in building elements. The assessment of the concrete microstructure or microstructural changes like chemical alterations or the formation of microcracks, e.g. due to material aging, freeze-thaw cycles, alkali-silica reaction and ettringite, is not in the focus of ndt research though. Concrete moisture and enhanced salt contents, which usually trigger all chemical microstructural changes, are other material properties, lacking reliable ways of measuring. But, the assessment of such material properties, on the long term also in a depth resolved manner, is definitely important, when the sustainability of our concrete infrastructure buildings shall be evaluated. New consideration like the potential use of ndt, in particular the combination of different methods and alternate ways of data analysis are subject of research currently undertaken at BAM. These approaches involve for example working towards (i) a deeper understanding of how to measure moisture distributions reliably and follow transport phenomena, (ii) the use of stray phenomena in radar and ultrasound to locate material inhomogeneities or (iii) the application of LIBS for the delineation of diffusion and migration processes but also (iv) the use of new tools for data analysis like data fusion. First results are presented and new ideas discussed. T2 - NDT-CE 2015 - International symposium non-destructive testing in civil engineering CY - Berlin, Germany DA - 15.09.2015 KW - Screed KW - Moisture KW - Non-destructive testing KW - Radar KW - Microstructure KW - Monitoring KW - Concrete deterioration KW - Cracking PY - 2015 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-347593 UR - http://www.ndt.net/?id=18354 SN - 1435-4934 VL - 20 IS - 11 SP - 1 EP - 5 PB - NDT.net CY - Kirchwald AN - OPUS4-34759 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kruschwitz, Sabine A1 - Feldmann, Rüdiger T1 - Comparison of non-destructive moisture measurement methods on cement and calcium sulphate based screed samples JF - The e-journal of nondestructive testing & ultrasonics N2 - Measuring the moisture content of floor screeds is usually done with minor destructive testing methods like Darr drying or the Calcium Carbid (CM) method. These require small samples, deliver only punctual information and still have proven not to be very reliable. Hence, a study has been made using the standard destructive tests as well as a suite of non-destructive testing methods working out their use for moisture determination. In this study five partners from research institutes and industry worked together and intensively researched different technologies. The main focus was put on the varying sensitivity of the measuring techniques in different moisture ranges. Especially for low moisture contents ( or ‘critical’ moisture contents when the screed is dry enough to be covered with the final floor finish), several commercial devices including the most commonly used CM-method failed to determine the correct moisture content for cementitious samples. Hence the need for more accurate, if possible non-destructive methods is high, taking also into account that the chemistry (and physical properties) of screeds may vary strongly depending on their origin and purpose. T2 - NDT-CE 2015 - International symposium non-destructive testing in civil engineering CY - Berlin, Germany DA - 15.09.2015 KW - Screed KW - Moisture KW - Non-destructive testing KW - Radar KW - Capacitive methods KW - Resistivity KW - Multi-sensor KW - Electrics KW - Monitoring PY - 2015 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-347602 UR - http://www.ndt.net/?id=18368 SN - 1435-4934 VL - 20 IS - 11 SP - 1 EP - 4 PB - NDT.net CY - Kirchwald AN - OPUS4-34760 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kruschwitz, Sabine A1 - Munsch, Sarah Mandy A1 - Strangfeld, Christoph A1 - Wöstmann, Jens A1 - Borchardt, Kerstin T1 - Eignung zerstörungsfreier Messtechnik für die Bestimmung der Belegreife von Estrichen JF - Bautechnik N2 - Die Bestimmung der Belegreife von Estrichen erfolgt im Bauwesen meist unter Verwendung von zerstörenden Verfahren, die Probenentnahmen erfordern und nur punktuelle Daten liefern. Bei anhydritgebundenen Estrichen gelten 0,5 M% und bei zementgebundenen ca. 3,5 M% und höher als belegreifer Feuchtegehalt. Die Belegreife wird als Feuchtegehalt in Masseprozent (M%) bezogen auf die Trockenmasse des Baustoffes angegeben. Zur zerstörungsfreien Feuchtemessung existieren verschiedene einfach zu bedienende Handgeräte, die u. a. auf elektrischen, elektromagnetischen und kapazitiven Methoden beruhen. In dieser Arbeit wurden ein kapazitives (Kugelsonde), ein elektromagnetisches (Mikrowellensensoren) und ein elektrisches Messverfahren (Vierelektroden-Sonde) untersucht. Mit Ausnahme der Vierelektroden-Sonde weisen die Handgeräte keine ausreichende Sensitivität in Bereichen niedriger Feuchtegehalte unterhalb von 1 M% auf und scheinen somit nicht für anhydritgebundene Estriche geeignet zu sein. Für zementgebundene Estriche lassen sich hingegen mit allen getesteten Geräten Änderungen in dem Bereich der Belegreife erfassen. In dieser Arbeit wird zusätzlich die Wasserabgabe in g/m²/Tag als Bezugsgröße herangezogen. Die Wasserabgabe stellt ein geeigneteres Maß für die Schadensträchtigkeit dar und ermöglicht direkte Vergleiche unabhängig von der verwendeten Estrichart. Für alle getesteten Estriche konnte eine Wasserabgabe von ca. 8-10 g/m²/Tag als Belegreifegrenzwert bestimmt werden. N2 - The determination of the readiness for covering of screeds in the construction industry is usually carried out by using destructive methods, which require sampling and only provide punctual data. As non-destructive testing methods, various hand tools exist, which are based on electrical and capacitive methods and are easy to handle. In this study, a capacitive spherical probe, a 4-Electrode probe in Wenner configuration and microwave probes were tested. With the exception of the 4-Electrode probe, the hand instruments do not have sufficient sensitivity in ranges of low humidity below 1 M%, and therefore do not appear to be suitable for anhydrite-bound screeds with a readiness of covering at 0.5 M%. On the other hand, for cement-bound screeds, it is possible to record changes in the range of the readiness of covering. The readiness of covering is usually stated and determined in reference to the relative moisture content. For the purpose of really assessing the risk of damage, we suggest to rather use the “water loss” in g/m²/day. Our results show in direct comparisons that value of approximately 8-10 g/m²/day is a reliable indicator for the readiness for covering of all tested screed types. KW - Estrich KW - Feuchte KW - Zerstörungsfreie Prüfung KW - Calcium-Carbid-Methode KW - Mikrowellensensoren KW - Vierelektroden-Sonde KW - Kapazitive Kugelsonde KW - Screed KW - Moisture KW - Readiness for covering KW - Non-destructive testing KW - Calcium carbide method KW - Microwave KW - 4-electrode probe KW - Capacitive spherical probe PY - 2017 DO - https://doi.org/10.1002/bate.201700051 SN - 1437-0999 N1 - Geburtsname von Munsch, Sarah Mandy: Nagel, S. M. - Birth name of Munsch, Sarah Mandy: Nagel, S. M. VL - 95 IS - 4 SP - 265 EP - 274 PB - Ernst & Sohn AN - OPUS4-43169 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Strangfeld, Christoph A1 - Kruschwitz, Sabine T1 - Determination of readiness for laying based on material moisture, corresponding relative humidity, and water release JF - Materials Testing N2 - The moisture content of the subfloor has to be determined before installation to avoid damages of the floor covering. Only if the readiness for layering is reached, an installation without damages can be expected in all cases. In general, three different approaches exist to measure the residual water content: determination of the moisture content, determination of the water release, or determination of the corresponding relative humidity. All three approaches are tested in laboratory at eight different screed types including two different samples thicknesses in each case. The moisture content and the water release are measured by sample weighing, the corresponding relative humidity is measured by embedded sensors. All three approaches are compared and correlated to each other. The evaluations show only weak correlation and, in several cases, contradicting results. Samples are considered as being ready for layering and not-being ready for layering at the same time, depending on the chosen approach. Due to these contradicting results, a general threshold for the risk of damage cannot be derived based on these measurements. Furthermore, the experiment demonstrates that the measurement of corresponding relative humidity is independent of the considered screed type or screed composition. This makes the humidity measurement to very promising approach for the installation of material moisture monitoring systems in the future. KW - Material moisture KW - Readiness for laying KW - Screed KW - Corresponding relative humidity KW - Partially saturated pores PY - 2020 DO - https://doi.org/10.3139/120.111581 VL - 62 IS - 10 SP - 1033 EP - 1040 PB - Carl Hanser Verlag GmbH & Co. KG CY - München AN - OPUS4-51405 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -