Damage detection in cementitious materials with optimized absolute electrical resistance tomography

Electrical resistance tomography (ERT) serves as a non-invasive, non-destructive, non-radioactive imaging technique. It has potential applications in industrial and biological imaging. This paper presents an optimized inverse algorithm, named Newton’s Constrained Reconstruction Method (NCRM), to detect damage in cementitious materials. Several constraints were utilized in the proposed algorithm to optimize initial parameters. The range and spatial distribution of conductivities within the sample were chosen as two main constraints. Two sets of numerical and a set of experimental voltage data were used to reconstruct conductivity distribution images based on this algorithm. To evaluate the quality of reconstructed images, two image quality evaluation indicators, correlation coefficient and position error were used. Results show that the proposed algorithm NCRM has the ability to enhance the reconstructed image quality with fewer artifacts and has better positioning accuracy.

Subdomain integration method of electrical resistance tomography for multiple flaws detection in cementitious materials

Electrical Resistance Tomography (ERT) has been widely used for detecting cementitious materials with one type of flaw. To extend the ERT for multi-flaws detection in a larger concrete plate, this paper develops a subdomain integration method. The adjacent driver pattern and absolute imaging scheme of ERT are adopted to reconstruct the inner electrical conductivity field of a concrete specimen which contains three different inclusions, namely, a copper bar, a piece of plexiglass, and a drop of saline solution. The feasibility of subdomain integration method for multiple flaws detection in cementitious materials is analyzed by theoretical analyses of the equipotential line density and the image quality evaluation indicator. The concrete specimen is divided into four, nine, and 16 subdomains for detection. The image reconstruction results obtained by the subdomain detection method are compared with each other, and with the results of a global detection method. Results indicate that the effective area of subdomain largely relies on the density of equipotential lines, as well as the measurement errors. Subdomain integration method is effective in detecting a relatively large cementitious component with multi-flaws.