This is a non-destructive test is used in the determination of the adequacy of the concrete cover by determining the corrosion risk of embedded steel. The corrosion risk significantly depends on the different harmful materials and their accession into the concrete. The higher the concrete porosity is, the easier for these corrosive materials to get near to the embedded steel, consequently the durability of the structure becomes limited in time. The apparent porosity measurements of concrete can be carried out by analyzing the conductivity in a function of moisture content, or it’s opposite: the electrical resistivity.
The test will be carried out using a two-point and a four-point Wenner probe resistivity meter. These meters use a probe with four terminals set up in a linear array with a distance “a” between the probes. The two outer probes are for the introduction of the current, whereas the two center electrodes are the voltage measurement points. When the probe touches the concrete surface, the electronic control unit circulates the test current and measures the potential between the inner points. The electronic contact is made of foam pads, which are to be saturated with Potassium Chloride preliminarily for electrical conductivity.