PSI - Issue 31

Petr Konečný et al. / Procedia Structural Integrity 31 (2021) 147 – 153

152

6

Petr Kone č ný et al. / Structural Integrity Procedia 00 (2019) 000–000

5. Summary and conclusions This contribution investigates the concrete diffusion coefficient with respect to chloride ingress, focusing on measurements obtained by two methods - indirect laboratory measurements of electrical resistivity and direct chloride profile-based evaluation from samples exposed to in situ conditions. The diffusion coefficients from indirect electrical resistivity are systematically higher in all cases than those based on chloride profiles. The estimates based on electrical resistivity exhibit unrealistically small variability (coefficient of variation of 0.004). In stark contrast, in-situ measurements result in significant variability (coefficient of variation ranging from 0.15 up to 0.66) which is much higher than indicative values provided in the literature. It is judged that the systematically lower diffusion coefficients obtained from chloride profiles could be attributed to the fact that the requirement on constant surface concentration in these tests was not fulfilled; detailed analysis of the effect of varying chloride concentration on diffusion coefficient is within the scope of further research. The obtained results suggest that: • The estimate of diffusion coefficient from chloride profiles obtained from in-situ placed samples is deemed to be associated with large uncertainty in the case of short exposure times (say up to one year). • The cores should be drilled from the structure and laboratory chloride penetration tests should be performed for the very young bridges in order to compute D c . Future research directions include: • Model uncertainty evaluation for the chloride field exposure of young concrete (with age less than t lim ). • Preparation of the lab-based chloride profiles as a reference to field exposure if possible. • Study in order to specify t lim with respect to a chloride profile analysis. Acknowledgements This contribution is a part of the research project GACR 18-07949S. Results of the project GACR 20-01781S provided background information for the contribution. References AASHTO T358, 2013. Standard Method of Test for Surface Resistivity Indication of Concrete’s Ability to Resist Chloride Ion Penetration, 2017. https://doi.org/10.1520/C1202-12.2 ASTM C1202, 2012. Standard Test Method for Electrical Indication of Concrete’s Ability to Resist Chloride Ion Penetration. American Society for Testing and Materials. 1–8. https://doi.org/10.1520/C1202-12.2 ASTM C1543, 1996. Standard Test Method for Determining The Penetration of Chloride Ion into Concrete by Ponding. Astm. Birge, R.T., 1932. The calculation of errors by the method of least squares. Physical Review 40, 207–227. https://doi.org/10.1103/PhysRev.40.207 Chen, M.C., Yang, C., Fang, W., Xie, L., 2019. A full-range analysis of anchorage failure for reinforced concrete beams in chloride environment. Engineering Failure Analysis. https://doi.org/10.1016/j.engfailanal.2019.06.091 Collepardi, M., Marcalis, A., Turriziani, R., 1972. Penetration of Chloride Ions into Cement Pastes and Concretes. Journal of the American Ceramic Society 55, 534–535. https://doi.org/10.1111/j.1151-2916.1972.tb13424.x ČSN EN-14629, 2008. Products and systems for the protection and repair of concrete structures. Test methods. Determination of chloride content in hardened concrete. ČNI, Praha. DuraCrete, 2000. General Guidelines for Durability Design and Redesign. The European Union-Brite Euram III, Project No. BE95-1347, Probabilistic Performance -based Durability Design of Concrete Structures. Faber, M.H., Sorensen, J.D., 2002. Indicators for inspection and maintenance planning of concrete structures. Structural Safety. https://doi.org/10.1016/S0167-4730(02)00033-4 Faber, M.H., Straub, D., Maes, M.A., 2006. A computational framework for risk assessment of RC structures using indicators. Computer-Aided Civil and Infrastructure Engineering. https://doi.org/10.1111/j.1467-8667.2006.00429.x François, R., Arliguie, G., 1999. Effect of microcracking and cracking on the development of corrosion in reinforced concrete members. Magazine of Concrete Research. https://doi.org/10.1680/macr.1999.51.2.143 Ghosh, P., 2011. Computation of Diffusion Coefficients and Prediction of Corrosion Initiation in Concrete Structures. Holický, M., Retief, J. V., Sýkora, M., 2016. Assessment of model uncertainties for structural resistance. Probabilistic Engineering Mechanics 45,