A study of the parameters that affect the measurements of superficial electrical resistivity of concrete

Abstract

The electrical resistivity of concrete is an important property in the reinforcement corrosion kinetics, since this property and the oxygen access govern the process. Measurement of the electrical resistivity of concrete performed on the concrete surface using Wenner method (called the "superficial electrical resistivity of concrete" in Brazil) is nondestructive and can be rapidly performed in laboratory or in situ. However, this technique is not standardized in Brazil for concrete yet. There is a need to adapt test techniques and evaluation criteria established and used in other countries, with proper justification. Thus, this paper aims at quantifying and discussing some parameters that influence the measurements of superficial electrical resistivity as a contribution to the adoption of a test procedure in Brazil. Investigatins included the influence of the steel bar presence and the proximity to the edges of the concrete elements on measurements, as well as the evolution of the electrical resistivity with increasing hydration. Preliminary results show that it is necessary a minimum distance of 4 cm from the steel bar to avoid the interference of the reinforcement on the measurements; measurements made near the edges can provide more than 80% higher resistivity values; and that the electrical resistivity can increase more than 100% in 6 months due to the cement hydration process. © RILEM 2013.