The Influence of Intermittent Localized Corrosion on the Mechanical Propertiesof Steel Rebars

Steel rebars are conventionally used in combination with concrete in buildings and civil engineering structures. A main degradation issue of these composite systems is the localized corrosion of the steel rebars. This fact promotes a scaling of the concrete surface and an aggressive localized attack of the rebars, until a cross-section reduction and detrimental static consequences. In this concern, steel rebars were immersed in a 3.5 % weight NaCl solution. A set of rebars were subjected to continuous immersion in the solution, whereas another set to a cyclic exposure consisting of immersion and drying at 25oC, 50oC and 100oC. The cyclic exposure and the temperature influenced the corrosion speed. A different extent of localized deterioration was detected. Some surface corrosion features barely affected the tensile properties of the rebar. Only at a later corrosion stage, the morphological features of the degradation contributed to a lowering of the mechanical properties, especially the tensile strength. The load-extension response of reinforcement during the tension tests did not directly correlate with the rust grade and the visual degradation aspect. An increase in the temperature and the water evaporation enhanced the presence of pits until 50oC. Corrosion pits were also seen, if the exposition to the solution was done in an intermittent rapid and cyclic mode, along the corroded bars. The corrosion features tend to affect the stress-strain response in tension of the rebars.