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Eingeladener Vortrag
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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.
Application of laser induced breakdown spectroscopy for the detection of hydrophobic coatings
(2001)
Laser-induced Breakdown Spectroscopy for determination of CI-, S-content in building materials
(2003)
Determination of Chloride Content in Concrete Structures with Laser-Induced Breakdown Spectroscopy
(2003)
Application of laser induced breakdown spectroscopy for the detection of hydrophobic coatings
(2001)
Determination of chloride content in concrete structures with laser-induced breakdown spectroscopy
(2005)
An important criterion for the evaluation of reinforced concrete structures is the measurement of the chloride content. This will normally be done by time consuming standard chemical methods. We propose the application of a spectroscopic technique, the laser-induced breakdown spectroscopy (LIBS), which provides the advantages of a fast measurement, the potential for on-site application and the possibility to investigate a wide range of different measuring points. The surface can be scanned, or depth profiles are available from cores. Measurements can be performed directly on the sample surface and the results are available in near real time. We present LIBS results measured on concrete cores as well as on grinded and pressed material in comparison with the results of standard chemical methods. The optimum LIBS set-up and the experimental conditions to detect and measure chlorine in building materials are reported. The limits of detection were determined and calibration curves were measured.
Ermittlung des Chloridgehaltes von Betonproben mit Laser-Induzierter Breakdown Spektroskopie (LIBS)
(2004)
Quantitative determination of sulfur content in concrete with laser-induced breakdown spectroscopy
(2005)
Laser-induced breakdown spectroscopy has been employed for the investigation of the sulfur content of concrete. Sulfur compounds are a natural but minor component in building materials. The ingress of sulfates or sulfuric acid constitutes a major risk of chemical aggression for concrete. There is a need for a fast method, which can be used on-site and is able to investigate a wide range of different measuring points, so that damages can be characterized.
For quantitative determination the sulfur spectral line at 921.3 nm is used. The optimum ambient atmosphere has been determined by comparison of measurements accomplished under air, argon and helium atmosphere.
Reference samples have been produced and calibration curves have been determined, the results of LIBS measurements are compared with results from chemical analysis. Defining a limit for the intensity ratio of a calcium and a oxygen spectral line can reduce the influence of the heterogeneity of the material, so that only spectra with a high amount of cementitious material are evaluated. Depth profiles and spatial resolved sulfur distributions are presented measured on concrete cores originating from a highly sulfate contaminated clarifier.