Laser induced breakdown spectroscopy a new tool for the chemical investigation of concrete infrastructure

Speaker:
Wilsch, Gerd; BAM Bundesanstalt fur Materialforschung und -prufung; Germany

Authors:
Gottlieb, C.; Federal Institute for Materials Research and Testing (BAM); Germany
Günther, T.; Federal Institute for Materials Research and Testing (BAM); Germany
Millar, S.; Federal Institute for Materials Research and Testing (BAM); Germany
Sankat, N.; Federal Institute for Materials Research and Testing (BAM); Germany
Wiggenhauser, H.; Federal Institute for Materials Research and Testing (BAM); Germany
Wilsch, G.; Federal Institute for Materials Research and Testing (BAM); Germany

ID: ECNDT-0446-2018
Session: Civil Infrastructure 1
Room: J1
Date: 2018-06-11
Time: 13:50 - 14:10

Concrete is often used in combination with steel as reinforced concrete. Environmental influences, especially the ingress of harmful ions in combination with the ingress of water, trigger different damage processes which reduce the designed lifetime of a structure. The ingress of chlorides from de-icing salt or sea water leads to corrosion of the reinforcement. Also the carbonation of the concrete may trigger the corrosion of the reinforcement. The ingress of alkalis from de-icing salts may cause the expansion of the amorphous silica aggregates (alkali-silica reaction) through formation of a swelling gel of calcium silicate hydrate if water is present. The ingress of sulfates may cause spalling of the concrete surface due to ettringite formation.
BAM has developed the LIBS technique for automated laboratory use with high numbers of samples to investigate transport processes of harmful species (Cl-, CO2, SO42- and alkalis) in concrete. Information about ingress depth and the quantitative values are important to estimate the remaining lifetime of the infrastructure. To get information about the ingress depth, a core has to be taken and cut in the middle. The measurements are carried out at the cross section. The main advantages of LIBS are the direct measurement on the surface of the concrete, fast analysis (sample rate 100 Hz) with a spatial resolution of up to 100 µm, the consideration of the heterogeneity of the concrete. The possibility of automated measurements saves a lot of manpower and time. At the same time a 2D-evaluation provides information about hot spots of elemental concentration which may not be found by standard methods.
Typical results of 2D investigation of concrete in laboratory will be presented. The performance is also demonstrated by examples for onsite applications using a mobile LIBS system. The road map to standardization is presented as well.