Analysis of Different Parameters in the Electrical Resistivity Test of Concrete

Abstract

Electrical resistivity is widely used to monitor the durability of concrete structures. However, the results obtained can be misinterpreted due to the effect of several parameters on the test. Therefore, the effect of six parameters on the electrical resistivity was investigated in this article. The studied parameters were (1) the thickness of the concrete cover; (2) the contact with the concrete mold; (3) the concrete aging; (4) the chloride presence; (5) the type of cure and exposure; and (6) the position of the equipment regarding the reinforcement direction. Tests were performed on aged non-reinforced concrete specimens (5 years old) and freshly casted specimens. The results showed that variation in the thickness of the reinforcement covers from 1.5 to 3.0 cm affects the electrical resistivity measurements, independently of the w/c ratio. The contact of the concreting mold with the specimen did not influence the values of electrical resistivity, independently of the w/c ratio. The effect of the chlorides incorporated into the mass of the concrete during casting is not significant on the electrical resistivity at 28 days. The electrical resistivity was 13.2% higher in specimens cured in a moist chamber, compared to curing in an uncontrolled external environment. The electrical resistivity was no longer influenced by the steel at a minimum parallel distance of 8.0 cm. Measurements performed perpendicular to the bar were not affected. These results are very important for a better interpretation of the results of this technique.