Dieter Schaurich

LIBS for non-destructive testing of element distributions on surfaces

Abstract A laser-based technique for the quasi non-destructive evaluation of surfaces of building materials is presented. Laser-induced breakdown spectroscopy (LIBS) is an analytical tool to determine the chemical composition of laser evaporated material. After the material has been vaporized by the high energy laser pulse the elements emit their specific fluorescence. This radiation is used to identify the elements in the evaporated material by spectroscopic methods. The mass of the evaporated material is of the order of micrograms; this means LIBS is a quasi non-destructive method for building applications. The main advantages of LIBS are the direct measurement without any preparation and the possibility to measure on site and to obtain on-line results. LIBS is a well-known technique which has been successfully applied in the areas of material testing, medicine and industrial process control. This article reports on the progress of LIBS applications for building materials by the use of some examples: identification and analysis of the main components of concrete; determination of salt concentrations in building materials; and measuring the relative element composition to a depth of up to 10 mm with high geometrical resolution.

Imaging laser analysis of building materials - practical examples

The Laser induced Breakdown Spectroscopy (LIBS) is supplement and extension of standard chemical methods and SEM‐ or Micro‐RFA‐applications for the evaluation of building materials. As a laboratory method LIBS is used to gain color coded images representing composition, distribution of characteristic ions and/or ingress characteristic of damaging substances. To create a depth profile of element concentration a core has to be taken and split along the core axis. LIBS was proven to be able to detect all important elements in concrete, e. g. Chlorine, Sodium or Sulfur, which are responsible for certain degradation mechanisms and also light elements like lithium or hydrogen. Practical examples are given and a mobile system for on‐site measurements is presented.