Experimental investigation of corrosion-induced cracking, spalling and delamination of bridge decks

Corrosion of the steel rebar is one of the major deterioration mechanisms of reinforced concrete structures. The build-up of corrosion products around the reinforcing steel induces tensile stresses in the surrounding concrete, leading to cracking of the concrete cover when its tensile resistance is exceeded. Corrosion-induced failure mechanisms of the concrete cover that have been observed in the field are longitudinal cracking (parallel to the direction of reinforcement), spalling and delamination. Previous research efforts have lead to the development of analytical and finite element models to simulate the damage induced in the concrete cover by the growth of corrosion products. These models have distinguished different failure mechanisms in reinforced concrete bridge decks by developing relationships between the cover-to-rebar diameter ratio c/d and spacing-to-rebar diameter ratio s/d. Although corrosion-induced cracking is a widespread problem in concrete infrastructure suffering from reinforcing steel corrosion, there is not much experimental or field data available to verify these models. The objective of this research is to validate those relationships experimentally through accelerated corrosion laboratory tests. Nine reinforced concrete specimens with different geometrical dimensions and reinforcing steel arrangements were tested. These specimens have been designed to obtain different corrosion-induced failure patterns as estimated by previous finite element modelling. Corrosion of the reinforcing steel was induced by means of a potentiostat PGSTAT100 with a corrosion current density varying between 150 to 200 muA/cm2 and held constant for a period that varied between two to three weeks. A comparison and analysis of the obtained results were done against results obtained from a finite element model. Due to differences observed in the comparison, a modification was applied on the previous numerical equations in order to better present the different modes of corrosion-induced failure of reinforced concrete bridge decks.