Effects of impressed current density on corrosion induced cracking of concrete cover

Abstract

Accelerated corrosion by means of impressed current technique is widely adopted to investigate durability problems of reinforced concrete structures caused by reinforcement corrosion. In this paper, the influence of the impressed current density level between 50 and 300 μA/cm2 on the corrosion induced cracking of concrete cover was experimentally studied. X-ray diffraction (XRD) method was used to determine the compositions and expansion coefficient of corrosion products under different current density levels. Smart aggregate (SA) and digital image correlation (DIC) techniques were applied to monitor the inner and outer surface cracking of reinforced concrete specimens, respectively, which will further determine the corresponding critical corrosion degrees. The experimental results indicate that the expansion coefficient of steel corrosion products decreased as the impressed current density increased, resulting in the increase of corrosion degree at inner and outer surface cracking of concrete cover. In addition, the existing numerical approaches based on three-stage model or two-stage model were conducted to predict the critical corrosion degree at different current density level. The comparison of simulation results with test results shows that the corrosion products filling into the pores happened together with the corrosion layer accumulating, which means the two-stage model outperformed three-stage model to describe the cracking process of concrete cover in the accelerated corrosion test.