Application of the capacitance and X-ray measurement techniques for monitoring the structure of concrete beams

Maciej Niedostatkiewicz1, Krzysztof Grudzie?2, Zbigniew Chaniecki2, Andrzej Romanowski2, Jakub Betiuk2

1Gdansk University of Technology, Department of Fundamentals of Building and Material Engineering, Gdansk, Poland, mniedost@kis.p.lodz.pl

2Technical University of Lodz, Computer Engineering Department, Lodz, Poland, kgrudzi@kis.p.lodz.pl

ABSTRACT

The knowledge of the structure concrete beams is essential from the building constructions safety point of view. The undesirable decrease of the load capacity of the reinforced concrete elements may cause to arise local non-continuities (i.e. soft imperfections). Moreover, in these structural elements the local material over-stiffening (i.e. hard imperfections) may occur, as well. First type is characterized with the lower concentration of the pattern element. It should be noted, that another inclusions can be found in case of the reinforced concrete elements, like: parts of wood and parts of PVC pipe to transfer electric wires, water or heating fluid. The second type of irregularity concerns the steel bars, which may cause the structure distortion of the concrete. Moreover, they may contribute to make concentration of the stresses at concrete element in case of its improper location. The necessity of scale estimation and location description of the irregularity is very important not while manufacturing the reinforced concrete element but frequently after this process during buildings exploitation. It is then of the great importance to apply a non-invasive diagnostics method which allows precise resolvement of the characteristics irregularity parameters. This method must be safe for human health. Moreover, it must be simple for application and relatively cheap. Additionally, it must provide the possibility to apply it to the normal, real-life-scale elements.

The measurement techniques, which meet the conditions mentioned above, are X-ray radiography or the Electrical Capacitance Tomography (ECT). The presented novel approach consists in application of the ECT for inspection of the structure of the solid body, containing inclusions of different density of the components. For interpretation of measurement results, in case of ECT just capacitance unprocessed measurement data are analyzed, and in case of X-ray basic radiography images are used. Capacitance measurements are acquired with use of two planes of parallel arrays, 8 electrode each, 16 electrode sensor. Experiments are conducted using concrete bars with various, artificially introduced, inclusions and either ECT electrodes mounted aside, or X-ray scanned. Results revealed interesting conclusions, especially in case of capacitance measurements, indicated the range of possible ECT use for such applications, proving the general feasibility of both techniques use.

Keywords capacitance raw data analysis, sensor, concrete beams, imperfections, X-ray radiography