PSI - Issue 67

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ScienceDirect

Procedia Structural Integrity 67 (2025) 17–22 Structural Integrity Procedia 00 (2024) 000–000 Structural Integrity Procedia 00 (2024) 000–000

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International Symposium on Nanotechnology in Construction Materials NICOM8 Nanomechanical testing of gamma-irradiated building composites Jiˇr´ı Neˇmecˇek 1a , Jan Procha´zka b , Martin Keppert c , Patricie Halodova´ b , Jitka Neˇmecˇkova´ a , Jiˇr´ı Neˇmecˇek 2a, ∗ a Czech Technical University in Prague, Faculty of Civil Engineering, Department of Mechanics, Tha´kurova 7, 166 29, Prague 6, Czech Republic b Research Centre Rˇezˇ, Hlavn´ı 130 Rˇezˇ, Husinec 250 68, Czech Republic c Czech Technical University in Prague, Faculty of Civil Engineering, Department of Materials Engineering and Chemistry, Tha´kurova 7, 166 29, Prague 6, Czech Republic Abstract Nuclear power plants worldwide are aging and will soon reach the end of their designated lifetimes. Consequently, extending their safe operation to 80 years has become the focus of extensive research. The e ff ects of irradiation on concrete are multiscale but have primarily been studied using macroscopic samples, where a decrease in mechanical properties has been reported. This study focuses on the micro-scale e ff ects of gamma irradiation on cement paste exposed to a wide range of relative humidities (0%–100%). Nanoindentation was employed as the main tool to quantify micro-mechanical parameters, such as Young’s modulus and hardness. A significant increase in Young’s modulus ( ∼ 25%) was found at relative humidities below 11%, attributed to the combined e ff ects of water radiolysis and drying. In contrast, a decrease in Young’s modulus ( ∼ 26%) was observed in samples irradiated in water. Samples irradiated at medium humidities (33%–76%) showed negligible damage due to the irradiation. © 2024 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http: // creativecommons.org / licenses / by-nc-nd / 4.0 / ) Peer-review under responsibility of NICOM8 Chairpersons. Keywords: Nanoindentation; Gamma irradiation; C-S-H gel; Cement paste; Relative humidity International Symposium on Nanotechnology in Construction Materials NICOM8 Nanomechanical testing of gamma-irradiated building composites Jiˇr´ı Neˇmecˇek 1a , Jan Procha´zka b , Martin Keppert c , Patricie Halodova´ b , Jitka Neˇmecˇkova´ a , Jiˇr´ı Neˇmecˇek 2a, ∗ a Czech Technical University in Prague, Faculty of Civil Engineering, Department of Mechanics, Tha´kurova 7, 166 29, Prague 6, Czech Republic b Research Centre Rˇezˇ, Hlavn´ı 130 Rˇezˇ, Husinec 250 68, Czech Republic c Czech Technical University in Prague, Faculty of Civil Engineering, Department of Materials Engineering and Chemistry, Tha´kurova 7, 166 29, Prague 6, Czech Republic Abstract Nuclear power plants worldwide are aging and will soon reach the end of their designated lifetimes. Consequently, extending their safe operation to 80 years has become the focus of extensive research. The e ff ects of irradiation on concrete are multiscale but have primarily been studied using macroscopic samples, where a decrease in mechanical properties has been reported. This study focuses on the micro-scale e ff ects of gamma irradiation on cement paste exposed to a wide range of relative humidities (0%–100%). Nanoindentation was employed as the main tool to quantify micro-mechanical parameters, such as Young’s modulus and hardness. A significant increase in Young’s modulus ( ∼ 25%) was found at relative humidities below 11%, attributed to the combined e ff ects of water radiolysis and drying. In contrast, a decrease in Young’s modulus ( ∼ 26%) was observed in samples irradiated in water. Samples irradiated at medium humidities (33%–76%) showed negligible damage due to the irradiation. © 2024 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http: // creativecommons.org / licenses / by-nc-nd / 4.0 / ) Peer-review under responsibility of NICOM8 Chairpersons. Keywords: Nanoindentation; Gamma irradiation; C-S-H gel; Cement paste; Relative humidity © 2024 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of NICOM8 Chairpersons

1. Introduction 1. Introduction

Concrete, as one of the most widely used man-made materials in the world, is also employed in nuclear power plants (NPPs) for biological shielding, reactor vessel foundations, and in containers for radioactive waste storage. Long-term degradation due to radiation and thermal strains has been widely reported by many authors and summarized by Rosseel et al. (2016) and Field et al. (2015) resulting in a reduction in macroscopic mechanical properties, such as compressive and tensile strengths, and elasticity modulus. This degradation ultimately leads to the deterioration of reinforced concrete members in NPP (Park et al. (2016)). Concrete, as one of the most widely used man-made materials in the world, is also employed in nuclear power plants (NPPs) for biological shielding, reactor vessel foundations, and in containers for radioactive waste storage. Long-term degradation due to radiation and thermal strains has been widely reported by many authors and summarized by Rosseel et al. (2016) and Field et al. (2015) resulting in a reduction in macroscopic mechanical properties, such as compressive and tensile strengths, and elasticity modulus. This degradation ultimately leads to the deterioration of reinforced concrete members in NPP (Park et al. (2016)).

2452-3216 © 2024 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of NICOM8 Chairpersons 10.1016/j.prostr.2025.06.003 2210-7843 © 2024 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http: // creativecommons.org / licenses / by-nc-nd / 4.0 / ) Peer-review under responsibility of NICOM8 Chairpersons. 1 Postdoctoral researcher at Czech Technical University in Prague, Orcid: 0000-0002-5635-695X. 2 Professor at Czech Technical University in Prague, Orcid: 0000-0002-3565-8182. ∗ Corresponding author. Tel.: + 420 224 354 309. E-mail address: jiri.nemecek@fsv.cvut.cz 2210-7843 © 2024 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http: // creativecommons.org / licenses / by-nc-nd / 4.0 / ) Peer-review under responsibility of NICOM8 Chairpersons. 1 Postdoctoral researcher at Czech Technical University in Prague, Orcid: 0000-0002-5635-695X. 2 Professor at Czech Technical University in Prague, Orcid: 0000-0002-3565-8182. ∗ Corresponding author. Tel.: + 420 224 354 309. E-mail address: jiri.nemecek@fsv.cvut.cz