Estudo sobre a influência de barras de aço na medição da resistividade elétrica superficial do concreto

Abstract

The development of non-destructive tests for characterization and determination of concrete quality has an important role on diagnostic engineering in civil construction. One of the important characteristics of concrete to determine its durability is the surface electrical resistivity of the concrete, since this characteristic is directly related to the possibility of attacks of aggressive agents to the concrete. It was verified that the methods used to determine the surface electrical resistivity of the concrete use electric current for the determination of this parameter, and are used in reinforced concrete structures, therefore, they present steel bars. For this reason, this study was carried out with the objective of analyzing the influence of steel bars on the measurements of surface electrical resistivity of concrete. Twelve specimens were cast, eight with steel bars (four bars) and four without steel bars (reference). Half of the specimens were cast with CP-V-ARI cement and the other half with CP-IV-32-RS cement. Measurements were made in various configurations (device positions) on the plates. It was identified that the samples produced with CP-IV-32-RS presented higher electrical resistivity values than the specimens produced with CP-V-ARI probably due to the presence of pozzolana that reduces the permeability of the concrete and consequently increases the surface electrical resistivity. It was also identified that the configurations in the specimens with bars that have measurements closer to the reference ones (without bars) are those perpendicular to the bars with the apparatus in the center of the bars. It was verified that the more bars near the end electrodes of the device used (Resipod-Proceq), the greater the impact of these bars, that is, more current will pass through the bars and less current will pass through the concrete, consequently, the smaller the difference of potential measured in the central electrodes and lower the superficial electrical resistivity.