Abstract Quantitative relations between the corrosion rate of reinforcements (i corr) and the degree of pore saturation (PS) and resistivity ( ϱ) of mortars without Cl − and with 2% Cl − were obtained. The mortar specimens were cured in a water fog chamber before the final exposure at 50°C and 50% relative humidity (RH). The electrolyte supply was found to determined the mortar resistivity which varies over a wide range (5 × 10 3−5 × 10 7 ωcm) and this in turn influences the i corr of the reinforcements. There is a critical practical PS value (PS cp) that results in a mortar resistivity of 10 5 ωcm, below which i corr values are too small to pose any durability problems. Below the PS cp value, the resistivity of the mortar prevents active state corrosion of reinforcements as effectively as passivating layers of steel in mortars without Cl −.