PSI - Issue 64

Hernán Xargay et al. / Procedia Structural Integrity 64 (2024) 1790–1797 Hernán Xargay / Structural Integrity Procedia 00 (2019) 000 – 000

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4. Conclusions OPC normal-strength mortar samples thermally treated in the range of 20 °C to 600 °C have been investigated in this work. Three-point bending tests were performed and both loading response and AE were monitored during those tests. In the following, some concluding remarks are pointed out:  Flexural strength progressively decreases as maximum temperature exposure increases.  The transition from a continuum to a discontinuum state in the material, characterized by the development of discrete macro-crack openings, is accompanied by a change in AE energy rate and distribution.  The correlation between AE signal characteristics and cracking modes provides valuable insights into fracture mechanisms and can be helpful in the analysis of structural pathologies.  As thermal damage advances, cracking modes tend to change from tensile to shear or mixed mode.  The increase of dispersion in AE results with the increase of temperature highlights the importance of considering thermal damage when analyzing AE data. In practical applications involving real structures with significant thermal damage, the detectability of AE should be taken into account. Under such circumstances, the AE generated during loading may exhibit lower amplitude and energy due to material weakening. Additionally, the waves may experience greater attenuation owing to increased discontinuities. Finally, these laboratory scale experimental results confirm the potential capabilities of AE technique in the frame of Structural Health Monitoring for detecting active cracking processes in adequately instrumented structural elements. Future research works will be aimed at extending this procedure to other cement based composites and different stress state conditions to collect information in order to calibrate the AE measurements with fracture mechanics parameters. Acknowledgements The authors gratefully acknowledge the financial support of the proje ct “ Bio-based Energy-efficient materials and Structures for Tomorrow ” (BEST) . This project has received funding from Horizon Europe - Research and innovation programme under the grant agreement 101086440. References Aggelis, D.G. (2011). Classification of cracking mode in concrete by acoustic emission parameters. Mechanics Research Communications, 38, 153 – 157. Alam, S. Y. & Loukili A. (2017). Transition from energy dissipation to crack openings during continuum – discontinuum fracture of concrete. International Journal of Fracture, 206, 49-66. Arioz, O. (2007). Effects of elevated temperatures on properties of concrete, Fire Safety Journal, 42(8), 516-522. Culfik, M.S. & Ozturan, T. (2002). Effect of elevated temperatures on the residual mechanical properties of high-performance mortar. Cement and Concrete Research, 32, 809-816. Ma, Q., Guo, R., Zhao, Z., Lin, Z. & He, K. (2015). Mechanical properties of concrete at high temperature - A review. Construction and Building Materials, 93, 371-383. Naus, D.J. (2010). A compilation of elevated temperature concrete material property data and information for use in assessments of nuclear power plant reinforced concrete structures (NUREG/CR-7031). US Nuclear Regulatory Commission, Washington. Nielsen, C.V. & Bicanic, N. (2003). Residual fracture energy of high-performance and normal concrete subject to high temperatures. Materials and Structures, 36, 515-521. Ohno, K. & Ohtsu, M. (2010). Crack classification in concrete based on acoustic emission. Construction and Building Materials, 24, 2339-2346. Ohno, K., Uji, K., Ueno, A. & Ohtsu, M. (2014). Fracture process zone in notched concrete beam under three-point bending by acoustic emission. Construction and Building Materials, 67, 139-145. RILEM Technical Committee 212-ACD (2010). Test method for classification of active cracks in concrete structures by acoustic emission. Materials and Structures, 43, 1187-1189. Ripani, M., Xargay, H., Iriarte, I., Bernardo, K., Caggiano, A. & Folino, P. (2020). Thermal action on normal and high strength cement mortars. Applied sciences, 10, 6455. Saliba, J., Loukili, A., Regoin, J.P., Grégorie, D., Verdon, L. & Pijaudier-Cabot, G. (2015). Experimental analysis of crack evolution in concrete by the acoustic emission technique. Frattura e Integritá Strutturale, 34, 300-308. Xargay, H., Folino, P., Sambataro, L. & Etse, G. (2018). Temperature effects on failure behavior of self-compacting high strength plain and fiber reinforced concrete. Construction and Building Materials, 165, 723-734.