Corrosion Of Steel Rebar Research Articles

Chloride corrosion of steel rebars in mortars with fly ash admixtures

This paper presents the results of an experimental investigation of the corrosion of steel rebars in different types of mortars immersed in 3·5% sodium chloride solution. The corrosion rate of the steel bars was determined in relation to the curing time and to the addition of Greek fly ash at 15 wt% and 30 wt%. The corrosion activity was evaluated by measuring: (a) the gravimetric weight loss of the reinforcing steel bars; (b) their corrosion rate using the linear polarization resistance technique; and (c) the total and free chloride content of the various mortars used, by a selective chloride electrode. Additionally some X-ray diffraction measurements were made in order to identify the complex substances formed. The results indicate that the addition of Greek fly ash, at both percentages, improves the corrosion behaviour of the reinforcing steel bars by lowering the free chloride content. Also, the 28 days of curing time increases the corrosion resistance of the specimens, especially those without additive. In all cases the 28-days cured specimens show a lower content of total and free chloride and a reduced corrosion rate with respect to the 1- and 7-days cured specimens.

The Use of Harmonic Analysis to Monitor Steel Rebar Corrosion in Concrete

The Use of Harmonic Analysis to Monitor Steel Rebar Corrosion in Concrete

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The aim of this study is to examine the performance of four different sets of reinforcing steel rebars, S220, S400, S500s Tempcore and S500s Vanadus, exposed to the Greek atmosphere, before their installation into the concrete. The performance against atmospheric corrosion of the aforementioned steel rebars was evaluated by means of microscopy techniques and corrosion rate measurements. In particular, we studied the influence of corrosion products of a set of reinforcement steels on the bond strength between concrete and steel bars, during the hydration process of cement. Furthermore, microscopy techniques and visual observation were used to identify the rust strains and the corrosion product morphology of steel reinforcements before their installation into the concrete. The experimental results shown that the steel type, which exhibits the higher resistance, as far as atmospheric corrosion concerns, was S220 reinforcing steel. In contrary, S500s Tempcore has the least corrosion resistance. The bond strength between concrete and the steel rebars was found to decrease with increasing weathering from 45 to 122 days, due to the morphology and to the thickness of the rust layers formed on steel surface, as observed by the ESEM.