Issue 50

A.G. Lekatou et alii, Frattura ed Integrità Strutturale, 50 (2019) 423-437; DOI: 10.3221/IGF-ESIS.50.36 435 Cyclic potentiodynamic polarization of 304L stainless steel rebars in an acid rain simulating solution containing Ca(OH) 2 and different fly ash (FA) quantities at alkaline pHs, reveals true passivity and non-occurrence of localized corrosion. The relative trends of the voltammograms corresponding to the different FA contents are very similar to those observed in the low pH electrolyte. Similarly to the case of the low pH electrolyte, the trend of corrosion resistance increasing with FA addition was reversed at 25 wt.% FA. A clear superiority of the corrosion performance of 304L in the high pH electrolyte over that in the low pH electrolyte has been exhibited. The feasibility of replacing 316L stainless steels in critical applications, such as the restoration of ancient monuments, provided that FA is included in the concrete mixture as a corrosion inhibitor, even at low contents (10 or 15 wt.%), has been manifested. Microstructural examination of 304 L corroded in the acidic electrolyte revealed that a main reason for the positive effect of the FA addition is the formation of films -products of Ca(OH) 2 -fly ash-acid rain chemical interaction. However, high FA amounts (in this case 25 wt.% FA), promote localised corrosion. Not any visual indications of corrosion have been observed in concrete cubes reinforced with 304L rebar during salt spraying for 4 m. Partial replacement of cement by fly ash did not significantly affect the tensile properties of the 304L rebar before or after salt spraying except a slight decrease in the elastic modulus with FA increasing within statistical error though. 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