Kenji Reichling

Visualisation of the Electrical Resistivity Distribution of Reinforced Concrete

The electrical resistivity of concrete is a characteristic property correlating with different durability related parameters, e.g. the degree of water saturation, the corrosion rate of the reinforcement or the chloride diffusion coefficient. On structures the resistivity can be determined non-destructively by using a Wenner setup. The analysis is based on the assumption of a homogeneous semi-infinite concrete element. Based on the heterogeneous structure of reinforced concrete (e.g. reinforcement bars, moisture differences) the electrical field is deformed which may lead to misinterpretations.

Tomographische Widerstandsmessungen an Stahlbetonbauteilen

Due to the requirements regarding the maintenance of structures the demand for non-destructive methods increase steadily. The electrical resistivity of concrete is a parameter which can be correlated with different durability aspects of reinforced concrete structures (e.g. porosity, saturation degree, diffusion coefficients, corrosion rate). But the typical methods for determining non-destructively the resistivity on concrete structures are not reliable in cases of heterogeneous resistivity distributions (e.g. reinforcement bars, saturation gradients). Within this paper a geophysical method is presented to determine resistivity tomograms. To study the application on concrete structures measurements are carried out on reinforced concrete specimens. An electrode setup according to Wenner is compared with the dipol dipol setup in order to identify heterogeneities in reinforced concrete.

Was verrät uns der elektrische Widerstand über den Beton

The electrical resistivity of concrete is frequently used as a measure to assess the durability of reinforced concrete structures. This paper correlates the resistivity and the saturation of concrete samples using on Archie ́s law in order to characterise their pore structure. The results are compared with a previously used empirical model. The correlation of the results with the pore structure of the concrete is discussed to illustrate the potential of the presented approach.

Determination of electrochemical potential gradients without reinforcement connection in reinforced concrete structures

Different non destructive diagnostic tools are available to assess the condition of a reinforced concrete structure. Potential mapping is an approved method to locate areas with a high risk of chloride induced corrosion. A novel approach has been developed to locate critical areas without a reinforcement connection by using a set of external electrodes. The results are converted and displayed as a vector, comparable with a compass, that the critical areas can be located directly. The methodology is explained and measuring results are compared with the conventional method. (A)

BETOSCAN – Ein mobiles Roboter Messsystem für die Diagnose von bewehrten Betonböden / BETOSCAN – An Instrumented Mobile Robot System for the Diagnosis of Reinforced Concrete Floors

A huge number of reinforced concrete floors, e.g. of parking garages or bridge decks are exposed to de-icing salts and thereby subject to a high risk of chloride induced reinforcement corrosion. To be able to properly maintain such concrete floors the whole concrete surface needs to be assessed regarding the following key parameters: concrete cover, carbonation depth, chloride profile, cracks, spalls, hollow areas, condition of the reinforcement, etc. As optimal basis for such an assessment several measurements have to be carried out over the whole concrete surface including mapping of electrochemical potentials and the parameters as mentioned above. For large structures with areas of often some thousand m the costs for a full evaluation are usually not accepted by the clients resulting in reduced diagnosis works and design decisions for protection and repairs far on the safe side due to limited data. To overcome this problem a research and development project has been initiated with several partners from research and industry to develop a robotic system which is able to drive over large concrete surfaces and take all relevant data automatically in one step. Furthermore the data collected from the measuring systems can be evaluated together resulting in different synergetic effects: Evaluations on the optimal repair method can be carried out automatically for single points and certain areas enabling the engineers to separate the whole concrete surface into areas subject to different measures from doing nothing over e.g. applying protective coatings up to traditional repair by removing the concrete cover. Furthermore detailed maps are available for design and execution of repair works including cracks and locally damaged concrete. Actually a prototype of the system is under development. This paper focuses on the possible fields of applications for the BETOSCAN system.