Corrosion behavior of steel bar and corrosive cracking of concrete induced by magnesium-sulfate-chloride ions

Abstract

The evolution of steel bar and corrosive-crack propagation of reinforced concrete in three different solutions including MgSO4, Mg2+-SO42--Cl, and seawater were examined using electrochemical impedance spectroscopy. Results showed that seawater had the most serious corrosion effect on steel bar in concrete. MgSO4 combined with chloride ions could accelerate the damage process of passive film, whereas Mg(OH)2 and gypsum particles could be produced and deposited on the steel-bar surface to block the diffusion of sulfate and chloride ions into the passive film. The crack propagation of concrete in single chloride environment increased with time linearly, but the existence of MgSO4in chloride solution could change the crack-propagation behavior of reinforced concrete from linear to nonlinear. The existence of Ca(OH)2 in MgSO4and MgSO4-NaCl solutions could not delay the initial corrosion time but reduce the corrosion rate of steel bar by 60%-85%.