Feasibility of atomic and molecular laser induced breakdown spectroscopy (LIBS) to in-situ determination of chlorine in concrete : final report.

PDFTech Report00119410 BDV31-977-32ChlorineConcreteLasersSpectroscopyConcrete structuresFloridaFlorida. Dept. of TransportationOmenetto, NicoloJones, W. B.Smith, B. W.Guenther, T.Ewusi-Annan, E.University of FloridaFlorida. Dept. of TransportationUS Transportation CollectionLaser-induced breakdown spectroscopy (LIBS) has been studied as a fast method of detecting chlorine in concrete samples. Both single pulse (SP) and double pulse (DP) experiments have been tested. Several combinations of lasers (Neodymium-Yttrium Aluminum Garnet (Nd:YAG), XeCl, and ArF Excimer lasers with an Intensified Charge Coupled Device (ICCD) detector were used, namely (i) YAG single pulse ablation, (ii) YAG-YAG orthogonal double pulse ablation-excitation, (iii) XeCl-YAG orthogonal double pulse ablation-excitation,and (iv) ArF-YAG double pulse ablation-excitation. An ionic chlorine line at 479.454 nm was then selected, and results optimized in a He atmosphere. Moreover, we have investigatedin detail the use of CaCl emission band at 593.5 nm as an alternative detection scheme. The samples (mortar and cement) were provided by the Florida Department of Transportation State Materials Office (Gainesville)and the BAM Institute in Berlin (Germany). Using single-pulse LIBS, the ionic line limit of detection (LOD) was 0.04% Cl, and the molecular CaCl band LOD was 0.05%. Both results were obtained in a He environment. Contrary to expectations and to literature results, our double pulse experiments did not improve the detection limit.The results obtained in this report are discussed in terms of the following criteria: (i) achievement of the original goals of the project achieved; (ii) the analytical validity of the proposed approach and the benefits resulting from the implementation of the developed technique in a different laboratory; and (iii) the importance of \ue2\u20ac\u153in situ\ue2\u20ac? detection of Cl in concrete and of a mobile LIBS system for stand-off operation