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The paper presents the damage model of German Research Unit 537 which was used as a working hypothesis for the development of a user-friendly design model. Excerpts from the laboratory experiments and numerical calculations processed in project A of the research unit are presented here. The excerpts include the quantification of self-corrosion, geometrical effects in the macrocell corrosion, development of corroding steel surface and pit depth as well as the quantification of the resistivity of the concrete and the corrosion of steel in cracked concrete.
Dieses Merkblatt beschreibt die Anwendung elektrochemischer Potentialmessungen (häufig auch als Potentialfeldmessung bezeichnet) zur Detektion von Bewehrungsstahlkorrosion an Stahlbetonbauwerken. Mit Hilfe dieses Verfahrens können Bereiche korrodierender Bewehrung zerstörungsfrei lokalisiert werden. In der Regel kommt diese Messmethode bei der Detektion chloridinduzierter Korrosion zum Einsatz. In Abgrenzung hierzu sollte die Abschätzung der Gefahr einer karbonatisierungsinduzierten Korrosion durch Bestimmung der Karbonatisierungstiefe und der Betondeckung erfolgen.
Electrochemical half-cell potential measurements for the detection of reinforcement corrosion
(2014)
This specification describes the application of electrochemical half‐cell potential measurements (frequently also called potential mapping) for the detection of reinforcement corrosion in reinforced concrete structures. Areas of corroding reinforcement steel can be located in a nondestructive manner by means of this procedure. Half‐cell potential measurements are used in order to detect chloride‐induced corrosion. However, it is not recommended in order to assess the risk of carbonation‐induced corrosion. For this purpose the determination of the carbonation depth and the concrete cover appear to be more appropriate.
The content of this specification exclusively refers to the application of mobile, local variable reference electrodes, which are only placed on the concrete surface while measuring. The technique distinguishes itself thereby from the range of corrosion monitoring systems with stationary installed reference electrodes and sensor systems, respectively, whereby it is possible to continuously track measurements within the area of the installed electrodes. However, these methods are not dealt with in this specification.
Corrosion monitoring of reinforced concrete structures:The DGZfP specification B12 Collaboration
(2023)
Corrosion monitoring of reinforced or prestressed concrete structures has becomeincreasingly important in recent years. Areas of application include componentsthat are no longer accessible after completion or where potential fieldmeasurements cannot be carried out due to existing coatings. Corrosion monitoringcan also be used to monitor the progress of corrosion in corroding systems, e.g. to prove the success of repair measures according to repair principle 8 in accordancewith EN 1504‐9 or repair method 8.3 in accordance with the DIBt repair guideline.It also could be used to prove the functionality of cathodic corrosion protectionsystems in accordance with ISO 12696. Despite the increasing importance ofcorrosion monitoring, no guidelines orrecommendations existed until 2018. Thisgap was closed by the English version of specification B12,“Corrosion Monitoringof Reinforced and Prestressed Concrete Structures,”of the German Society for Non‐Destructive Testing, which was published in 2021. This article introducesspecification B12 by explaining the basicmeasurement principles and illustratingthe potential of corrosion monitoring in new and existing buildings.
The subcommittee “Corrosion Detection in Reinforced Concrete” is a technical committee within the scope of the German Society for Non-Destructive Testing (DGZfP). The international working group consists of engineers and scientists from Germany, Austria and Switzerland who work at research institutes or engineering firms and aims for the practical implementation of non-destructive testing in civil engineering (NDT-CE) methods to assess the corrosion condition of reinforced concrete (RC) structures. Therefore, the group works on technical specifications that explain the necessary theoretical background of the presented techniques but mainly provide helpful instructions for the application on-site and in the laboratory.
Based on the corrosion process of steel in concrete the specifications focus on selected topics where the field engineer is getting into contact with the phenomenon. Therefore, specification B 12 highlights corrosion monitoring in reinforced and prestressed concrete structures and presents different approaches to monitor the initiation and propagation phase of corrosion and shows case studies of where these techniques were applied successfully.
Specification B 03 deals with the potential-mapping technique. In addition to this specification, practical training courses and certification in this method have been developed and are offered by the working group members and are organized by the DGZfP.
Both specifications, B 03 as well as B 12, are available in English. In the case of specification B 03, the current version is still in the translation process and will be available soon.
Currently, the group is working on a new specification for measuring the electrical resistivity of cementitious materials, for example, to evaluate the suitability of mortars for cathodic protection applications and to validate the influence of the concrete resistivity with regard to corrosion processes of steel in concrete.
Given the increasing impact of corrosion damages on infrastructural structures, the working group would like to introduce the use of the mentioned specifications to an interested international audience and thus offer the possibility to reliably detect corrosion damages at an early stage to prevent significant damages or high repair costs on RC structures.
Die Potentialmessung kann zum Auffinden korrosionsaktiver Bereiche neben Stahlbetonbauwerken auch bei Spannbetonbauwerken angewandt werden, die mit Spannstählen im direkten Verbund hergestellt werden. Bei Vorspannsystemen mit metallischen Hüllrohren im nachträglichen Verbund ist eine Aussage über den Korrosionszustand des Hüllrohrs, nicht aber des Spannstahls möglich. Messungen an Spannbetonbauteilen erfordern grundsätzlich die besonderen Kenntnisse eines Spezialisten.
Korrosionsmonitoring von Stahl- oder Spannbetonbauwerken hat in den vergangenen Jahren als Ergänzung zur herkömmlichen Bauwerksuntersuchung deutlich an Relevanz gewonnen. Einsatzgebiete sind z. B. Bauteile, die nach Fertigstellung nicht mehr zugänglich sind oder an denen aufgrund vorhandener Beschichtungen keine Potentialfeldmessungen durchgeführt werden können. Weiterhin kann Korrosionsmonitoring auch für die Überwachung des Korrosionsfortschritts an korrodierenden Systemen z. B. zum Nachweis des Instandsetzungserfolgs bei Anwendung des Prinzips W-Cl gemäß Instandsetzungsrichtlinie des DAfStb oder zum Funktionsnachweis bei KKS-Installationen nach DIN EN ISO 12696 eingesetzt werden. Trotz zunehmender Bedeutung Existieren für das Korrosionsmonitoring bis dato keine Richtlinien oder Handlungsempfehlungen. Diese Lücke soll das Merkblatt B12 „Korrosionsmonitoring von Stahl- und Spannbetonbauwerken“ der Deutschen Gesellschaft für
zerstörungsfreie Prüfung DGZfP füllen, das im Frühjahr 2018
veröffentlicht wurde. In diesem Beitrag werden das Merkblatt B12 vorgestellt, die grundlegenden Messprinzipien erläutert und anhand von Anwendungsbeispielen das Potenzial von Korrosionsmonitoring bei Neubau- und Bestandsobjekten illustriert.
This specification describes how corrosion monitoring is used to check the condition of reinforced and prestressed concrete members. In this specification, the term "corrosion monitoring" covers all methods in which it is possible to continuously track corrosion-relevant variables in the area of stationary, built-in sensors. This specification does not cover other possible methods, such as potential field measurements, involving the use of mobile, portable sensors that are placed temporarily on the membersurface to take measurements.