Correlations Between Localized Pitting Corrosion and Deflection in Reinforced Concrete Beams Subjected to Accelerated Corrosion

Abstract

Corrosion is one of the main deterioration phenomena in reinforced concrete structures. This paper investigates the correlations between localized pitting corrosion and measured performance indicators in reinforced concrete beams subjected to sustained relative deflection and accelerated corrosion through impressed current. Strain measurements from distributed optical fibre sensors were used to calculate the deflection, crack distribution and crack widths over time and thus to quantify changes in performance indicators with corrosion. Once the accelerated corrosion test was concluded, the steel reinforcement bars in the region affected by corrosion were carefully extracted and 3D laser scanning was carried out for the assessment of the reinforcement corrosion. More specifically, laser scanning results were used to identify the localized pitting regions in the vicinity of transversal cracks and consequently the total amount of steel corroded in the same. By assuming the following three hypotheses: (i) an effective pit length at the cracks, (ii) at the beginning of the corrosion process all the applied current and consequently all the corrosion was localized at the pits, (iii) any variation observed in the deflection is attributed to corrosion, therefore proportionality between deflections and loss of steel exists. The total corroded volume of steel was calculated and later compared to the 3D scanning. The results revealed that the volume loss in the pits calculated using Faraday’s law and the proposed method was in very good agreement to the direct volume measured by means of the 3D scanning. Consequently, a direct relation between corrosion and deflection could be established.