| Summary: | The main objective of this study was to analyze the influence that the addition of finely ground hydrated lime has on chloride-induced reinforcement corrosion in eco-efficient concrete made with 50% cement replacement by fly ash. Six tests were carried out: mercury intrusion porosimetry, chloride migration, accelerated chloride penetration, electrical resistivity, and corrosion rate. The results show that the addition of 10–20% of lime to fly ash concrete did not affect its resistance to chloride penetration. However, the cementitious matrix density is increased by the pozzolanic reaction between the fly ash and added lime. As a result, the porosity and the electrical resistivity improved (of the order of 10% and 40%, respectively), giving rise to a lower corrosion rate (i<sub>CORR</sub>) of the rebars and, therefore, an increase in durability. In fact, after subjecting specimens to wetting–drying cycles in a 0.5 M sodium chloride solution for 630 days, corrosion is considered negligible in fly ash concrete with 10% or 20% lime (i<sub>CORR</sub> less than 0.2 µA/cm<sup>2</sup>), while in fly ash concrete without lime, corrosion was low (i<sub>CORR</sub> of the order of 0.3 µA/cm<sup>2</sup>) and in the reference concrete made with Portland cement, only the corrosion was high (i<sub>CORR</sub> between 2 and 3 µA/cm<sup>2</sup>).
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