Modelling of pitting corrosion in a reinforced concrete element

Chloride-induced corrosion of steel reinforcement is a significant problem in
modern concrete infrastructure, which can cause loss of reinforcing bar cross-section,
significant reduction of bond between reinforcing steel and concrete, concrete cover failure and eventually structural collapse. Therefore, the understanding of how the chloride-induced corrosion affects surrounding concrete can significantly contribute to early identification and
prediction of damage caused by corrosion to reinforced concrete structures. The current paper presents a new numerical (three-dimensional non-linear finite element) approach for the modelling of chloride-induced pits developing on a reinforcing bar surface. In this approach, the expansion of corrosion products is formulated using the thermal analogy method. The contact between concrete and steel bar is modelled using the Coulomb friction model. The nonuniform distribution of corrosion products on a reinforcing bar surface is achieved with an
analytical surface function postulated in a cylindrical coordinate system. The developed finite element model of a concrete block with an embedded steel bar was used for the analysis of the effect of the number and position of pits and the sensitivity of the bar pull-out force to the level of pitting corrosion and the number of pits. It was found that both the corrosion level and the pit number increased the pull-out force. The maximum value of the pull-out force depended on the confinement of the corroding bar and was highly affected by concrete cracking. The increase in the number of pits led to an earlier cracking of the concrete block. The mode of
cracking depended on the position of the pit on the bar circumference.