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The majority of the built infrastructure is made of concrete, which is a multiphase system made of cement, aggregates, water and pores (every year nearly 4 billion tons of cement are produced which is largest mass flow generated by mankind). 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 ett-ringite formation. For the standard procedure in civil engineering cores are taken, cut in slices, grinded and the obtained homogenized powder is solved in acid and investigated by standard procedures. BAM has developed the LIBS technique for the 2D evaluation of the chemical composition of concrete [1-5]. The technique is established for automated laborato-ry 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. LIBS is a surface technique. 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 measure-ment 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 and the possibility of automated measurements which save a lot of man-power and time. As an example the investigation of ingress profiles for standard diffusion and migration tests in civil engi-neering takes hours in comparison to just a few minutes using LIBS. At the same time a 2D-evaluation provides information about hot spots of elemental concentration which may not be found by standard methods.
The state of the art of LIBS technique for applications in civil engineering will be presented, including typical results of 2D investigation of concrete in laboratory. The performance is also demonstrated by examples for on-site applications using a mobile LIBS system. The road map to standardization is presented as well.
In den letzten 15 Jahren hat im deutschen Autobahnnetz die Anzahl von Schäden an Betonfahrbahnen, die vor 2005 er-richtet wurden zugenommen. Dies führt oft zu einer Vermin-derung der Lebensdauer von 30 auf 10 bis 15 Jahre. Trotz umfassender Untersuchungen wurde die Ursache bis jetzt nicht eindeutig geklärt, jedoch scheint die Alkali-Kieselsäure-Reaktion (AKR) hierbei eine Rolle zu spielen. Vor diesem Hintergrund wurden AKR-Performance-Tests entwickelt, die jedoch die mechanischen Einwirkungen aus Klima und Ver-kehr nicht berücksichtigen. Aus diesem Grund wurde eine AKR-Forschergruppe von der Deutschen Forschungsgemein-schaft ins Leben gerufen, welche sich experimentell und auf Simulationsebene mit diesem Thema befasst. Inhalt dieses Beitrages sind ausgewählte Ergebnisse des an der BAM bear-beiteten experimentellen Projektteils, welche in eine auf die Auswirkung einer mechanischen Degradation fokussierte Promotionsarbeit einfließen.