Electrochemical Tests for the Determination of the Critical Chloride Threshold of Steel in Concrete with Blended Cements

摘要

The service life of reinforced concrete (RC) structures exposed to marine environments or the action of de-icing salts is limited by the corrosion of steel bars. To predict the service life of a RC structure, and especially the initiation time, a reliable estimation of the critical chloride threshold is required. This parameter is strongly influenced by many factors related to the environment and the concrete. This paper presents the results of chloride penetration tests carried out on concrete specimens made with different types of binder, with bars in free corrosion conditions, in order to detect the critical corrosion threshold. During the exposure period of two and a half years, the corrosion behaviour of bars was monitored through measurements of corrosion potential and corrosion rate. Afterwards, potentiostatic polarization tests, during which the potential was increased by step +50 mV per hour and the circulating current was monitored, were carried out on selected specimens. Results of the tests allowed the investigation of the relationship between the potential at which corrosion occurred, during ponding or potentiostatic polarization tests, and the critical chloride content. Considering a range of potential of-100/+100 mV vs SCE, some effect of pozzolanic additions in leading to higher values of the chloride threshold could be observed in this work.