Standard and sample preparation for the micro XRF quantification of chlorides in hardened cement pastes

One of the principal reasons for premature deterioration in reinforced concrete is chloride-induced corrosion. In materials such as stone, or earthen materials, salt crystallization plays a significant damaging role, and chloride distribution is an important factor. The reliable quantification of chlorides can therefore provide fundamental insights into their behaviour in such materials, particularly in concrete. One of the most widely used techniques for chloride quantification in concrete includes a destructive sample preparation for either titration (powder dissolved in nitric acid) or XRF (powder fused into pellets). However, in order to obtain a quantitative mapping of chlorides, a more effective approach with a higher spatial resolution is essential. We present here a new method with a (semi) non-destructive approach, whose limits of quantification are suitable for fundamental studies of the behaviour of chlorides in concrete. This work also emphasizes the standard and sample preparation, an aspect often overlooked by other authors. The achieved levels of trueness are comparable to those indicated by the international standard organization procedure for cement chemical analysis with XRF.