PSI - Issue 13

Myroslava Hredil / Procedia Structural Integrity 13 (2018) 1657–1662 Author name / Structural Integrity Procedia 00 (2018) 000–000

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partitions in the near-surface concrete layer and weaken the bond strength resulting in a worsening of the composite integrity. Therefore adhesion disturbance in RC during impressed current application is possible not only due to ions redistribution in concrete matrix but also as a result hydrogen evolution. Hydrogen bubbles were observed visually during cathodic polarization on the lateral surface of the specimen and at the upper top face of it in the place of steel–concrete contact designating two ways for hydrogen to leave the specimen. Therefore hydrogen moves from the steel–concrete interface upwards along the reinforcement, and also through the whole concrete cover. It is not clear whether its movement is equilibrium or it accompanies with appearance of stresses and, respectively, defects in concrete matrix. This aspect is important since it could indicate not only bond disturbance at the steel–concrete interface, but also hydrogen assisted cracking of concrete. Conclusions  The electrochemical approach is used for accelerated RC structures degradation: anode polarization for corrosion simulation of the reinforcement, and cathodic impressed current for its hydrogen charging.  Intensive dissolution of the reinforcement embedded in concrete under anode electrochemical conditions leads to RC specimens cracking which could accompany by their extensive filling with corrosion products. In this case concrete cover cracking is delayed, because spreading of corrosion products suppresses potential rise of their expanding pressure. However essential outflow of corrosion products from the interface concrete– reinforcement could weaken bond strength.  Prolonged application of cathodic impressed current causes bond strength degradation in reinforced concrete. The reasons of the bond weakening could be not only electrochemical processes in concrete such as ions migration but also hydrogen evolution at the steel–concrete interface. Special attention should be paid to possible impact of stresses produced in concrete by hydrogen moving outwards from the interface through concrete matrix, which allows supposition of hydrogen induced cracking in concrete. References Song H.-V., Saraswathy. V., 2007. Corrosion monitoring of reinforced concrete structures – a review. Int. J. Electrochem. Sci. 2, 1–28. Ma, Y., G., Zhongzhao Wang, L., Zhang, J., 2017. Experimental investigation of corrosion effect on bond behavior between reinforcing bar and concrete. Construction and Building Materials 152, 240–249. Toribio, J., Ovejero, E., 2007. Hydrogen assisted cracking in progressively drawn pearlitic steel. Corrosion Science 49, 3539–3556. Toribio, J., Lorenzo, M., Vergara D., 2016. Hydrogen embrittlement susceptibility of prestressing steel wires: the role of the cold-drawing conditions. Procedia Structural Integrity 2, 626–631. Mikryukov, V.R., Syomin, A.P., Konovalov S.V., Ivanov, Yu.F., Gromov, V.E., 2006. Structure and hot-rolled reinforcement rods properties evolution in the process of long service life. Materials Science and Engineering A 430, 125–131. Page, C.L., Al Khalaf, M.N., Ritchie, A.G.B, 1978. Steel/mortar interface: mechanical characteristics and electrocapillarity. Cement and Concrete Research 8, 481–490. Hredil, М.І., Toribio, J., 2014. Corrosion resistance of prestressing steel wires. Materials science 3, 665–670. Hredil, M.I., 2013. Express method for the evaluation of the effect of corrosion of reinforcement on the integrity of reinforced concrete. Materials Science 3, 94–397. Wong, H.S., Zhao, Y.X., Karimi, A.R., Buenfeld N.R., Jin, W.L., 2010. On the penetration of corrosion products from reinforcing steel into concrete due to chloride-induced corrosion. Corrosion Science 52:7, 2469–2480. Rasheeduzzafar, Ali, M.G., Al-Sulaimani, G.J., 1993. Degradation of bond between reinforcing steel and concrete due to cathodic protection current, ACI Mater. J. 90 (1), 8– 15. Chang, J.J., 2002. A study of the bond degradation of rebar due to cathodic protection current. Cement and Concrete Research 32, 657–663. Sagoe-Crentsil, K.K., Glasser, F.P., 1993. ‘Green corrosion products’, iron solubility and the role of chloride in the corrosion of steel at high pH. Cem. Concr. Res. 23, 785–791.