Issue 50

Ch. Apostolopoulos et alii, Frattura ed Integrità Strutturale, 50 (2019) 548-559; DOI: 10.3221/IGF-ESIS.50.46 555 Additionally, specimens of 12mm nominal diameter record higher performance under LCF testing, than the corresponding specimens of 16mm nominal diameter. This annotation is closely associated with the lower corrosion damage (e.g. mass loss rate or/ and pitting severity) recorded. Combining the results of the tensile and the LCF tests, a correlation with real structures can take place. Analytically, it is a fact, that during strong earthquakes, yielding structures are subjected to increased number of cycles into the inelastic range and the accumulated damage may significantly affect their overall performance. However, little attention has been devoted by the research community on the combined effect of corrosion and LCF on steel reinforcement, since each one of these fac- tors affects the rebar durability and performance and shortens the life expectancy of structures [19-24]. It is known though, that besides external overt damage, more internal and subcutaneous phenomena are realized. At those areas, plethora of MnS and FeS compounds (potential sites of corrosion initiation or for the formation of corrosion paths) can be detected. Synergy of both internal and external corrosion factor, may result in premature and unexpected failure of the material [25]. In an effort to further investigate the degradation phenomena, which are related to the internal downgrading of the material, several SEM and EDX analyses took place. Prior to tensile testing, the cross sections of reference rebars were examined under scanning electron microscope, after having been polished to surface roughness of Ra < 0.8 μm. Figs.7 and 8 illustrate the SEM and EDX analyses in reference B400C, Φ16 steel, without tension. The area depicted is about 1300μm from the outer surface within the martensitic zone. Figure 7 : SEM analysis in reference B400C, Φ16 steel, without tension. 0 1 2 3 4 5 6 7 8 keV 0.0 0.5 1.0 1.5 2.0 2.5 cps/eV Fe Fe Mn Mn S 1.00 * Acquisition 8980 Figure 8 : EDX analysis in reference B400C, Φ16 steel, without tension.