Cracks are always present in reinforced concrete structures. In the presented research, influence of mechanical cracks on chloride ingress is studied. A compact reinforced concrete specimen was designed, mimicking the cracking behaviour of beam elements. Cracks of different widths were induced by means of mechanical loading. These cracked specimens were then subjected to weekly cycles of wetting and drying with NaCl solution. After the exposure, the specimens were cut, and chloride distributions were determined using Laser Induced Breakdown Spectroscopy (LIBS), an innovative technique which enables simultaneous determination of different elements with high spatial resolution and minimal specimen preparation. By combining element distributions of different elements, it is possible to discriminate between coarse aggregate particles, and the mortar matrix. It was found that the wider the crack is, the higher the ingress of chloride ions. This was, however, different for two tested concrete mixes. Due to highly inhomogeneous chloride distribution around the cracks, use of fine-scale experimental techniques for chloride mapping is advised, based on the presented study.

Während das Instandsetzungsprinzip W bei carbonatisierungsinduzierter Korrosion seit vielen Jahren als Standardverfahren etabliert ist, wird seine Anwendbarkeit bei chloridinduzierter Korrosion (W‐Cl) in der Fachwelt bis heute kontrovers diskutiert. Zwar ergeben sich aus seiner Anwendung gegenüber anderen Instandsetzungsverfahren auf den ersten Blick u. U. deutliche wirtschaftliche Vorteile, allerdings besteht bei diesem Verfahren ein deutlich höheres Risiko, dass das Instandsetzungsziel nicht erreicht wird.Im vorliegenden Beitrag werden die technischen Grundlagen des Instandsetzungsprinzips W‐Cl sowie der aktuelle Kenntnisstand – sowohl für den gerissenen als auch für den ungerissenen Beton – dargestellt und baurechtliche Konsequenzen, die sich aus dem erhöhten Ausführungsrisiko ergeben, diskutiert. Korrosionsmonitoring als Element zum Nachweis des Instandsetzungserfolgs bei Anwendung des Prinzips W‐Cl wird vorgestellt. Anhand von Anwendungsbeispielen werden sowohl die Risiken, die mit dem Verfahren verbunden sind, als auch das Potenzial bei erfolgreicher Anwendung veranschaulicht.

Die Laser induzierte Breakdown Spektroskopie (LIBS) bietet für die Analyse heterogener, mineralischer Baustoffe, wie z. B. Beton, deutliche Vorteile gegenüber konventionellen Methoden. Sie ermöglicht neben der Quantifizierung von Elementgehalten und ‐verteilungen im Baustoff auch die Differenzierung von Elementkonzentrationen innerhalb einzelner Phasen im Baustoff. So können beispielsweise die für die Alkali‐Kieselsäure‐Reaktion (AKR) interessanten Natriumkonzentrationen bestimmt und hinsichtlich ihrer Verteilung aufgelöst werden. Es lassen sich Natriumgehalte, welche sich in der Gesteinskörung befinden, separat von denen der Betonmatrix bestimmen. Der vorliegende Artikel befasst sich mit den Vor‐ und Nachteilen von LIBS als alternative Methode für die chemische Analyse von Baustoffen. Anhand von Beispielen aus der Praxis wird der derzeitige Stand der Technik dargestellt und ein Vergleich mit etablierten Messmethoden vorgenommen. Laser Induced Breakdown Spectroscopy (LIBS) in civil engineering – innovative analysis of building materials Compared to conventional methods the Laser Induced Breakdown Spectroscopy (LIBS) provides significant advantages for analysis of heterogeneous, mineral building materials as e.g. concrete. Besides providing the possibility to quantify element concentrations and distributions in building materials, this technique enables also to differentiate concentrations within different phases of the material. It is possible to determine sodium concentrations and distribution directly, which e.g. is important when regarding Alkali‐Silica‐Reaction (ASR). Sodium contents provided by the aggregates can be distinguished from those provided by the concrete matrix. The present article is concerned with the advantages and disadvantages of LIBS as alternative method for chemical analysis of building materials. On the basis of samples from practice the current state of the art is shown and different measurement techniques will be compared.

Although the complex changes at the steel-concrete interface due to cathodic polarisation are widely acknowledged to have a beneficial influence concerning the cathodic protection (CP) of steel in concrete, some questions concerning the repassivation of carbon steel in consequence of cathodic polarisation are still not satisfactorily clarified. In the recent literature, some indications are presented that repassivation occurs after a certain time of polarisation. Therefore, the investigations discussed in this paper aim to clarify, to what extent the re-passivation of carbon steel due to cathodic polarisation occurs, and if the ennoblement of OCP is a sufficient indication for repassivation. In a first step, the corrosion state of five nominal equal test specimens was determined by electrochemical impedance spectroscopy (EIS). After determining the initial corrosion state by evaluating the charge transfer resistance and the polarisation resistance, respectively, the specimens were polarised cathodically. Impedance data were recorded before, during and after polarisation. The impedance data were evaluated by equivalent circuit fitting with special attention to charge transfer resistances and the impact of diffusion on the corrosion and polarisation behaviour. The results indicate that the reduction of oxides and oxygen diffusion during cathodic polarisation has strong impact on the systems behaviour and that repassivation effects occur after switching off the polarisation current and during depolarisation, respectively.

A wide range of parameters was investigated by numerical calculations concerning their impact on DC stray current corrosion of reinforced concrete (RC) structures. A simplified model geometry was used to extract the relevant parameters and their interaction in terms of stray current‐affected structures. This study mainly focuses on RC structures that are fitted with cathodic protection installations. The findings reveal a complex interaction between the investigated parameters. The possible relevance of further parameters, which is not the subject of this study, was emphasised.