PSI - Issue 62

Edoardo Proverbio et al. / Procedia Structural Integrity 62 (2024) 285–298 Author name / Structural Integrity Procedia 00 (2019) 000–000

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instead of 0.80 R m ) would be advisable in performing FIP tests. However, since FIP and DIBt tests relate only to hydrogen embrittlement mechanisms, tests more selective to a mechanism of active path dissolution should be identified.

Fig. 5. Cracks propagation in cold drawn prestressing steel wire after failure following FIP (left) and DIBt (right) test condition (Proverbio & Longo, 2004)

Still, the FIP test (due to its shorter duration) appears to be suited to quality control of steel grade and for comparison of different grades of the same steel when hydrogen embrittlement is suspected to be the cause of environmental cracking, even if due to its aggressiveness. Notwithstanding, the FIP test could lead to a risk of rejecting steel that otherwise would perform satisfactorily as wll as based on the 2,000 h duration limit criterium of the DIBt test it cloud be a risk of approving steel that should be rejected (M Elices et al., 2008). These aspect therefore still need an adeuqate in-depth analysis.

5. Conclusions

Even so the small number of cases, compared to the problems related to general corrosion, brittle fracture of prestressing steel still remains a relevant issue for prestressed concrete structures. Indeed, brittle behaviour is frequently not easy to predict. On the other hand, general corrosion and wide pitting do not lead to significant alarm when properly identified and controlled, furthermore, their effect on the mechanical behaviour of the structure and propagation during time can be easily modelled. Atomic hydrogen is the main responsible for the brittle behaviour of the prestressing steel, hydrogen embrittlement (HE) and hydrogen-induced stress corrosion cracking (HISCC) as well as hydrogen-assisted cracking (HAC) are the main mechanisms involving hydrogen interaction with the metal crystal lattice, in such a case small acute defects, pitting or crevice corrosion could be sites for crack initiation. HE can occur also before steel element utilization due to improper storage or after installation before grouting operation and it is not necessarily related to