## 1 Introduction  
Aggregates constitute approximately 70% of the volume of a concrete mixture; that is why large amounts of crushed rock, gravel, and sand are being extracted, processed, and transported around the world, generating environmental and economic costs. The use of recycled concrete aggregate (RA) for the production of concrete began at the end of World War II. Debris obtained by the demolition of concrete pavements, roads, and building foundations and structures were satisfactorily reused around the world [1]. It is estimated that more than 10,000 tons of public, private, and industrial construction and demolition waste are generated daily in Mexico [2]. The interest in investigating and using RA to produce new concrete is because concrete is a material that is demanded at the population growth rate and because the use of RA is an alternative to natural aggregates and has potential for exploitation for the great amounts of construction and demolition debris that are generated worldwide annually.  
On the other hand, due to the necessity to ensure the durability of reinforced concrete structures--mainly against steel corrosion as it is one of the most frequent diseases--a tendency of incorporating more advanced concepts of durability is observed on the basis of the regulation design. There are many proposals based on the modeling of the attack mechanism for service life prediction [3; 4]. However, despite the evident importance of taking real properties into account when estimating the durability to prevent significant mistakes in the results, only some of them are based on concrete \"performance\" and they are called indicators of durability [5; 6]. One of the durability indicators is the electrical resistivity of concrete (\(\rho\)), inverse of conductivity, and it is a volumetric measurement of the electrolytic resistance (Re) of the material, which through [PERSON]'s law is expressed as the ratio of voltage to applied current (Re = V/I). It was initially developed in geophysics [7], extensively researched in concrete with different types of cement [8], and is a property that reflects the ability of the porous medium of transporting electrical charge in a finite or semi-infinite volume. The corrosion process of the reinforcement steel is schematized in Figure 1[9], where the surface of the corroded steel works as a combination electrode that is composed of anodes and cathodes electrically connected through the same steel, upon which a couple of anodic and cathodic reactions occur.  
The pore solution of concrete works as an aqueous medium, that is, an electrolyte through which ions transport electric charge. Thus, \(\rho\) emerges as a key parameter in the corrosion process because it reflects the ability of the ions dissolved in the aqueous phase contained in the concrete pores to transport electric charge.  
Some research on recycled aggregate concrete (RAC) show that the use of RA increases the porosity of the new concrete [10; 11; 12], which it is linked to \(\rho\) because it represents the paths for ionic conductivity [13; 14; 15]. It is evident, and some investigations have confirmed [16; 17], that \(\rho\) is inversely proportional to the corrosion current density of the reinforcement steel (\(\mathbf{i}_{\text{corr}}\)) making it a fundamental parameter in the electrochemical corrosion process of steel embedded in concrete. In order to determine the influence that the use of RA (coarse and fine) on the electrical resistivity of concrete and in the corrosion current density of reinforcement steel, these durability parameters were evaluated using electrochemical techniques varying the percentage of recycled fine aggregates (RFA) and recycled coarse aggregates (RCA) contained in the concrete.