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- LIBS (13)
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- Chloride (5)
- Chlorine (4)
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Am Deutschen Dom wurden Mikrowellenabsorptionsmessungen, Radar und Infarot- Thermographie als moderne zerstörungsfreie Prüfverfahren der Feuchtemessung in Mauerwerk erprobt. Ergänzende numerische Simulationsrechnungen des gekoppelten Wärme- und Feuchtetransports sollen bei der Auswahl von Trockenlegungskonzepten helfen.
Zusammenfassung
Die Laser Induced Breakdown Spectroscopy (LIBS) ist eine analytische Methode mit der die Elementverteilung auf der Oberfläche von Proben orts- und tiefenaufgelöst ermittelt werden kann. Ein intensiver, infraroter Laserstrahl wird auf die Oberfläche fokussiert. Durch die hohe Energiedichte werden einige Mikrogramm Material verdampft und ein Plasma gebildet. Bei der Ausdehnung und Abkühlung des Plasmas wird die charakteristische Fluoreszenz der verdampften Elemente abgestrahlt und mit spektroskopischen Mitteln analysiert. Die Empfindlichkeit der Methode liegt im ppm-Bereich, die typische Messgenauigkeit beträgt einige Prozent. Die Ergebnisse liegen quasi on-line vor, es ist keine Probenpräparation notwendig und die Apparatur ist vor Ort einsetzbar.
Im Artikel werden Anwendungen der LIBS zur Untersuchung von Baustoffen beschrieben. Die Ergebnisse der Ermittlung der Salzverteilung in Baustoffen, der Untersuchung der Betonzusammensetzung und dem Nachweis von hydrophobierten Schichten auf unterschiedlichen Baustoffen werden vorgestellt.
Determination of chloride content in concrete structures with laser-induced breakdown spectroscopy
(2003)
The Chloride content is an important factor which influences the durability of concrete structures. The standard methods are mostly intricate, time consuming and require a chemical laboratory. This article describes the application of a spectroscopic method, the laser-induced breakdown spectroscopy (LIBS), for the determination of Chloride contents in concrete and mortar specimens. LIBS can be used on-site, needs no sample preparation and is able to investigate rapidly a large number of different measuring points. The LIBS set-up and the experimental conditions to detect Chlorides are reported. Calibration curves are presented and the limit of detection (LOD) is determined. Results measured on different concrete cores are presented and compared with the results of standard chemical methods.
The high amount of building waste material requires innovative strategies for high-order re-use of the material. With Laser Induced Breakdown Spectroscopy (LIBS) both the elemental composition of building materials and trace elements can be determined with a real-time measurement, even on-site and in a harsh industrial environment. We present the experimental data on heavy metal detection in the ppm concentration range, as well as calibration curves. Further on we demonstrate the characterization of cement and concrete concerning the main components by means of Rankin diagrams. We suggest an implementation of LIBS in the processing of building waste materials to allow a high-order re-use.
The moisture condition of solid brick and sandstone walls of historic buildings may be examined and monitored non-destructively and effectively by means of a novel combination of test methods which provide useful information on planning and monitoring rehabilitation and maintenance measures.
Results are presented of an interdisciplinary research project of BAM on the moisture balance in the main cornice area of the Berlin Zeughaus. The main part of the investigations was carried out in 1994 and 1995. The quality of the prognosticated drying out process has been verified annually by means of measurements up to 2002. The depth-resolved local moisture determinations were accomplished with a microwave method developed by BAM. The moisture profiles revealed excessive moisture in the building element and reflected the slow drying process. Additionally, endoscopic examinations and chemical and physical analyses of miniature samples were carried out as well to help interpret the results. Hygrothermal data could be calculated from the quasi non-destructive tests and the parameters determined by the laboratory tests. Based on the 1995 measured moisture profile in the building element, the predicted simulation calculation indicated that a relatively long drying out process must be anticipated. Therefore the planned waterproofing sealing can at the earliest be applied to the surface of the building element in 2005. The good correlation of predicted and measured moisture profiles of the past years demonstrates the high quality of the new combination of test methods.