Determination of total chloride content in cement pastes with laser-induced breakdown spectroscopy (LIBS)

Abstract The presented work discusses the accuracy of Laser Induced Breakdown Spectroscopy (LIBS) in determining the total chloride content in cement pastes. LIBS as an emission spectroscopy method is used to detect simultaneously several elements present in cement-based materials. By scanning surfaces the variability in the spatial distribution of elements can be visualised. However, for a quantification of the results, studies are necessary to characterise possible influences due to the wide variation of the chemical compositions in which cement can occur. It is shown how the calibration can be done, how the calibration samples were produced, and which statistical parameters are necessary to describe the precision of the regression. The performance of LIBS is estimated by detecting chloride in validation samples. Therefore, 55 samples and 7 sets with changing mix compositions were produced. The presented study deals with possible influences of different mix compositions, including different cations of chloride, varying w/c-ratios and the partial replacement of Portland cement with blast furnace slag (50% BFS) and limestone (30% LS). Comparing the LIBS results with potentiometric titration, an accuracy of ±0.05 wt%/total has been determined.