PSI - Issue 17

S. Tsouli et al. / Procedia Structural Integrity 17 (2019) 268–275 S. Tsouli, Lekatou A.G., C. Nikolaidis, S. Kleftakis / Structural Integrity Procedia 00 (2019) 000 – 000

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Table 1 shows a decrease in i corr and an increase in E corr with FA increasing up to 20 wt.% FA. Similarly, Fig, 1 shows a shift of the forward polarization curves to lower currents. In compatibility with previous efforts on 304L immersed in mildly acidic and strongly alkaline electrolytes (Lekatou et al. (2019)), this behavior may be attributed to the increase in the pozzolanic activity with FA content increasing. As mentioned in Introduction, C-S-H can protect the steel more efficiently than Ca(OH) 2 . However, the trend of corrosion resistance increasing with FA addition is reversed at 25 wt.% FA, in terms of i corr , passive current values, hysteresis loop surface area and E a/c tr -E corr values can be explained by the agglomeration of the very fine FA particles. Consequently, the contact area between FA and Ca(OH) 2 particles is limited and the pozzolanic reaction is less effective. The Ca-rich agglomerates of FA can bind more water making the steel surface more conductive, accounting for the relatively high passive current values . 3.2 Salt spray and tensile testing Figure 2a-d illustrates the macrostructural state of 316L reinforced concrete cubes containing 20 wt.% FA (2a-b) and 25 wt.% FA (2c-d) after salt spraying for 4 m. Visual inspection reveals a good state of the surfaces. Figure 3 presents stress-strain curves of 316L rebars embedded in concrete containing FA (0 - 25 wt.%) before and after 2 m of salt spraying. Salt spraying for 2 m did not affect significantly the tensile properties of the 316L rebars. The only noticeable change is a slight decrease in elongation after 2 m, which, however is statistically significant only in the case of 0 and 25 wt.% FA. Figure 4 compares the tensile testing performances of 316L and 304L rebars embedded in concrete with FA (0 - 25 wt.%) before and after 2 m of salt spraying. Not any significant differences in the tensile performances of the two steels are observed either, besides somewhat increased elongations for 304L.

Fig. 2. 316L reinforced concrete after 4 m of salt spraying: (a) & (b) 20 wt.% FA; (c) & (d) 25 wt.% FA containing.

Fig. 3. Stress-strain curves of 316L rebars embedded in concrete with different FA contents before (0 m) and after salt spraying (2 m).