The present work reflects the results obtained on the study of the concrete leaching in beams and slabs in real structures. Leaching is a phenomenon that promotes the migration of ions from the solution of the pores to the outer side of the structural elements, lowering the pH value of the pore solution and accelerating the corrosion rate of the bars. The objective of this study is to demonstrate how this phenomenon has a remarkable impact on the durability of structures. The investigations were carried out in existing buildings after 5 years of exposure. To evaluate the deterioration rate of the buildings, techniques of polarization resistance, electrical resistivity of concrete and corrosion potentials were applied. Calculation of the remaining section of the reinforced was perform from the direct measurement of the section loss on the steel bars. The research concludes by demonstrating the negative effect of leaching on the durability of the structures