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- 2018 (2) (entfernen)
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- LIBS (2)
- CF-LIBS (1)
- Cement (1)
- Concrete (1)
- MC-LIBS (1)
- Mobile-LIBS (1)
- On-site analysis (1)
Organisationseinheit der BAM
- 8.2 Zerstörungsfreie Prüfmethoden für das Bauwesen (2) (entfernen)
Two calibration-free LIBS techniques are used for the quantitative analysis of synthetic cement samples: the CF-LIBS based on the Boltzmann plot method and the Monte Carlo (MC) LIBS based on the iterative spectrum fitting. In CF-LIBS, the inverse problem is solved, i.e. the elemental concentrations are determined by the reconstruction of plasma parameters from spectra. The MC-LIBS technique solves the direct problem by finding the highest correlation between the model-generated and experimental spectrum. The accuracy of both calibration-free LIBS methods suffers from factors such as inaccurately determined instrumental function, the deviation of experimental plasma from the mathematical model used, not taking into account the collection geometry and from the uncertainty of spectroscopic data. Therefore, the both calibration-free LIBS approaches are applied to synthetic spectra which perfectly suit the mathematical model of the method. This test yields the accuracy of both the approaches for the ideal case. In addition, the accuracy of both methods is investigated for non-isothermal plasma, because real laser-induced plasma often has high gradients in temperature. Both methods assume an isothermal plasma.
Quantitative on-site analysis of harmful elements in building structures with a mobile LIBS-System
(2018)
Environmental influences and damage processes drastically reduce the durability of concrete and reinforced concrete structures. Much of this damage can be traced back to the penetration of harmful elements into the concrete. These elements cause damage processes such as the chlorine-induced corrosion, the alkali-silica reaction or the carbonization. For the maintenance the knowledge of the element concentration and the penetration depth of these harmful elements is essential. Based on this data, a maintenance concept can be developed and an estimation of the remaining service life-time can be carried out.
Typically, chemical analyzes are used to determine harmful elements in concrete, which are costly and time consuming. As an alternative method LIBS is used. On-site measurements were carried out with a mobile LIBS-System to determine harmful elements in a parking garage. A scanner is used to obtain a two-dimensional element mapping. For the quantitative analysis, a calibration of the system is carried out with 15 reference samples based on cement with NaCl with a concentration range of chlorine of 0.05 to 2.5 wt.%. To determine the penetration profile of the harmful element chlorine, concrete cores were drilled, split and analyzed directly on-site.