PSI - Issue 39

Jesús Toribio et al. / Procedia Structural Integrity 39 (2022) 488–493 Author name / Procedia Structural Integrity 00 (2021) 000–000

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1. Introduction Environmentally assisted cracking is a problem of major general concern in civil and structural engineering, either in the form of localized anodic dissolution (or pure stress corrosion cracking) or as hydrogen embrittlement. In addition, long-term material degradation can occur (Nykyforchyn et al., 2009) due to the simultaneous action of applied stresses and aggressive environment . It is seen that Cl – ions can induce the fracture of the passive film that would be formed at a pH of 12.5, as discussed by Hredil and Toribio (2014), Tang et al. (2012) and Li and Sagüés (2002), so that the pH inside the pit would decrease (Hredil and Toribio, 2014), thereby enhancing a hydrogen embrittlement mechanism, a really dangerous phenomenon in prestressed concrete structures, e.g., motorway viaducts where accidents have been reported by Vehovar et al. (1998) due to the degrading action of hydrogen on the prestressing steel wire. Previous research does exist on hydrogen embrittlement of high-strength cold-drawn pearlitic steel for prestressing wires using notched specimens (Toribio, 1992; 1993; 1996) and cracked ones (Toribio and Lancha, 1993; 1998; Toribio and Ovejero, 1999; 2001; 2007; Toribio et al., 2004). However, in the scientific literature there is a scarcity of data on hydrogen embrittlement of smooth wires of pearlitic steel, mainly due to the big scatter of experimental results, although some classical references do exist (Cherry and Price, 1980), as well as recent ones (Hredil et al., 2015; Hredil and Toribio, 2016). In this research framework, the present paper studies the crack paths and the hydrogen embrittlement behaviour of initially-smooth samples of cold drawn pearlitic steel wires (commercial prestressing steel wires). 2. Experimental procedure Mechanical properties of the commercial prestressing steel wires (cold drawn pearlitic steel) used are as follows: Young’s modulus E= 208 GPa, yield strength σ Y = 1.49 GPa and ultimate tensile strength (UTS) σ R = 1.83 GPa. An evaluation was made of the fracture behaviour exhibited by initially-smooth samples of cold drawn pearlitic steel wires ( commercial prestressing steel wires ) subjected to constant extension rate tensile (CERT) tests in aggressive environment promoted by a corrosion cell with a three electrode assembly: (i) metallic sample or working electrode, (ii) reference electrode ( saturated calomel electrode ) and (iii) counter-electrode (platinum electrode), as shown in Fig. 1.

Fig. 1. Testing device.