Loss of Ductility and Strength of Reinforcing Steel due to Pitting Corrosion

Trabajo presentado en el 8th International Conference on Fracture Mechanics of Concrete and Concrete Structures (FraMCoS-8), celebrado en Toledo (España), del 10 al 14 de marzo de 2013Any number of studies have been conducted in the past to analyse mechanical behaviour of corroded reinforcement steel bars. The general procedure adopted in most studies is threefold: In a first step, rebars are subjected to an accelerated corrosion procedure. Then the corrosion degree, which expresses the material loss of the specimen due to corrosion, is determined. Finally, the rebars are subjected to tensile testing and the obtained mechanical properties are related to the corrosion degree. However, further research is certainly needed on the consequences of localized corrosion phenomena. In presence of chloride anions able to break the passive layer, corrosion pits may be generated on the steel reinforcement. In this case, loss of mechanical properties will depend primarily on localized corrosion related aspects, like geometry and distribution of the pits, rather than on general material loss of the bars. This calls for an explicit geometrical characterization of pitting corrosion and analysis of its consequences on mechanical performance. In the present work, a numerical analysis on the tensile behaviour of B500B rebars, affected by a elliptically shaped corrosion pit, has been carried out. In a parametrical study, the principal mechanical properties characterizing strength and ductility of the bars have been determined as a function of the pit dimensions. Beside the maximum pit depth, the slenderness of the pits (length to depth ratio) has been found to affect considerably the mechanical properties of the rebars. The ductility of the bars is particularly sensitive to changes in pit geometry