Electrochemical polarization and impedance of reinforced concrete and hybrid fiber-reinforced concrete under cracked matrix conditions

Highlights: • Corrosion products form matrix cracks that are resisted by fiber reinforcement. • Corrosion-induced cracks result in greater anodic current response. • Stern-Geary coefficient for active corrosion determined to be B = 28.1 mV. • Lower ohmic matrix and charge transfer resistances for greater cover cracking and rebar pitting. • Lower exponent α of CPE in EIS equivalent circuit for greater steel pitting. In this paper, we investigate the influence of cementitious matrix cracking on the electrochemical polarization and impedance behaviors of corroding reinforced concrete and crack-resistant reinforced hybrid fiber-reinforced concrete (HyFRC). Samples were exposed to a chloride environment for 2.5 years while in either a continuous tensile stress state or in a nonloaded condition, and were periodically monitored for Tafel polarization responses. Electrochemical impedance spectroscopy (EIS) was additionally performed at the conclusion of the test program. Greater severity of corrosion-induced matrix splitting cracks along the length of embedded steel reinforcing bars and subsequent formation of anodic surfaces were found to affect several electrochemical parameters, including increase of the corrosion current and decrease of the ohmic resistance of concrete. Cathodic and anodic Tafel coefficients and Stern-Geary coefficients for passive and active samples are also reported, highlighted by a Stern-Geary coefficient of B = 28.1 mV for active corrosion.