Comportamento a corrosione di armature in acciaio e acciaio zincato in una malta ad attivazione alcalina a base di metacaolino dopo carbonatazione accelerata

The work presents the corrosion behavior of bare and galvanized steel rebars embedded in metakaolin alkali-activated mortar and traditional cement-based mortar belonging to the same mechanical strength class (R3 class with Rc ≥ 25 MPa, according to UNI EN 1504-3). Tests were conducted evaluating both the corrosion potential and the polarization resistance throughout the first month of curing and during the subsequent weekly wet/dry cycles in tap water after exposure to a chamber with 3% of CO2. During the first month, the high alkalinity of alkali-activated mortar delays the achievement of the passive state in particular for galvanized steel rebars, even though, after that period, they reach the same polarization resistance of those embedded in the cement-based mortar. During accelerated carbonation, the neutralization of alkalinity in alkali-activated mortar occurs more quickly than in cement-based mortar. During exposure to wet/dry cycles in tap water, both bare and galvanized steel rebars show comparable polarization resistance values in both studied mortars.