Technical Note: Considerations to Avoid Corrosion Rate Estimate Error of the Reinforcing Steel if Based Only on Concrete’s Electrical Resistivity

In recent years, the use of electrical resistivity (ρ) of concrete as a design parameter has intensified, ranging from its use as a durability index in laboratories for the characterization of cement-based materials, as well as in inspection of existing structures, to diagnose the pathological problems they present. It has also been used as a durability index to accept or reject a concrete mixture during the construction of concrete infrastructure that it should comply as a durable concrete mixture. ρ of concrete has also been used as an indirect measure of the corrosion rate (i_corr) of the embedded steel in concrete to determine not only the time of corrosion initiation but also the propagation time of corrosion of reinforcing or prestressing steel. This allows indirect measurements of i_corr from ρ measurements on the concrete surface without the need to connect the reinforcing or prestressing steel to the measuring equipment. The present investigation presents some results from the literature that corroborate this direct correlation between ρ of concrete and i_corr of the embedded steel for some exposure conditions, and some considerations are discussed to avoid possible measurement interpretation errors if this correlation is used in real structures.