Effect of flue gas desulfurization gypsum addition on critical chloride content for rebar corrosion in fly ash concrete

Abstract

The effect of flue gas desulfurization (FGD) gypsum addition on the critical chloride content (Ccrit) for rebar depassivation in fly ash concrete was studied. Open circuit potential and electrochemical impedance spectroscopy were employed for measurements of corrosion potential and corrosion current density, respectively. The results demonstrate that adding FGD gypsum decreases the Ccrit. Evolutions of corrosion potential and corrosion current density are found to obey a 3-parameter Weibull distribution. XRD analyses indicate that adding FGD gypsum facilitates the formation of ettringite phase, which increases the solid volume of hydrates. MIP results demonstrate that adding FGD gypsum decreases the critical pore diameter, which restrains the chloride transport. The improved chloride resistance can counterbalance the negative effect induced by the lower Ccrit, consequently postponing the corrosion initiation.