PSI - Issue 43

Petr Miarka et al. / Procedia Structural Integrity 43 (2023) 124–129 Author name / Structural Integrity Procedia 00 (2022) 000 – 000

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interconnection of the pores (internal and on the surface) can lead in practical applications to the increased chloride ingress to the concrete material, which can eventually lead to the corrosion of the steel reinforcement. The observed location of the crack in the material’s internal structure is in the location with relatively low stress conditions unlike it suggests the general expectation, i.e., the location around the initial notch. Although, the crack was localized, there is no direct evidence of cyclic damage. Such a crack can be present in the microstructure before start of the cyclic tests. Nonetheless, in long-term exposure to cyclic load a specimen failure can occur in this location. As it these observed pores can act as a stress concentrator from which the fatigue crack can initiate Ríos et. al (2019) . To justify this statement, a comprehensive numerical analysis is necessary, which would take into account the random distribution of material properties, as well as the pore and aggregate distribution or a series of μCT scans at different condition should be made to detect cyclic damage. However, this is the topic that deserves special attention on its own. Conclusion This experimental study has focused on the analysis of the fatigue damage in the high-performance concrete. This damage, i.e. a crack, was localised by the  CT tomography, which allowed the analysis of the internal damage and material’s structure. The analyzed specimen was exposed to the total number of 2  10 6 load cycles, which is considered as a fatigue limit for concrete materials used in the building industry. The  CT analysis allowed for the observation of the internal damage, high material heterogeneity, porosity and which can be the location of the crack initiation due to exposure to cyclic loads. Furthermore, this crack connects the internal pores with the pores present on the sample’s surface , which can be in the practical application a path where the chlorides or other aggressive elements can penetrate to the concrete material resulting into reinforcement corrosion. Acknowledgements The financial support from the project 21-08772S provided by Czech Science Foundation is gratefully appreciated. The 2 nd , 3 rd and 4 th author would like to acknowledge the financial support from the mobility project No. 8J22AT008. References ACI PRC-215-92: Considerations for Design of Concrete Structures Subjected to Fatigue Loading, 1997. The International Federation for Structural Concrete (fib – Fédération internationale du béton) CEB-FIB Model Code 2010 - First complete draft, Bulletin, 55, 2010. European Committee for Standardization Eurocode 2: Design of concrete structures — Part 1 – 1: General rules and rules for buildings Belgium, Brussels, 2004. Lee, M.K., Barr, B.I.G. 2004. An overview of the fatigue behaviour of plain and fibre reinforced concrete. Cement and Concrete Composites 26 299-305 Loeffler, C.M., Qiu, Y., Martin, B., Heard, W., Williams, B., Nie, X. 2018. Detection and segmentation of mechanical damage in concrete with X-Ray microtomography. Materials Characterization 142, 515 – 522. Miarka, P., Seitl, S., Bílek, V., Cifuentés, H., 2022. Assessment of fatigue resistance of concrete: S- N curves to the Paris’ law curves . Construction and Building Materials 341, 1-18. Nawy, E.G. 2001. Fundamentals of High-Performance Concrete, Wiley. Ríos, J.D., Leiva, C., Ariza, M., Seitl, S., Cifuentes, H., 2019. Analysis of the tensile fracture properties of ultra-high-strength fiber reinforced concrete with different types of steel fibers by X-ray tomography. Materials & Design, 107582. Seitl, S., Miarka, P., Klusák, J., Domski, J., Katzer, J., Šimonová, H., Keršner, Z. , 2018 Change of a crack propagation rate in fine-grained cement-based composites due to partial replacement of aggregate by ceramic waste Key Engineering Materials, 2018, 761 KEM, pp. 111 – 115. Seitl, S., Miarka, P., Šimonová, H., Frantík, P., Keršner, Z. , Domski, J., Katzer, J., 2019. Change of fatigue and mechanical fracture properties of a cement composite due to partial replacement of aggregate by red ceramic waste. Periodica Polytechnica Civil Engineering, (1), 152 – 159. Šimonová, H., Kucharczyková, B., Bílek, V., Malíková, L., Miarka, P., Lipowczan, M., 2021. Mechanical Fracture and Fatigue Characteristics of Fine-Grained Composite Based on Sodium Hydroxide-Activated Slag Cured under High Relative Humidity. Applied Sciences – Basel 11(1), 1-20. Snoeck, D., Dewanckele, J., Cnudde, V., De Belie, N., 2016. X-ray computed microtomography to study autogenous healing of cementitious materials promoted by superabsorbent polymers. Cement and Concrete Composites 65, 83-93.