PSI - Issue 67

Jiří Němeček et al. / Procedia Structural Integrity 67 (2025) 17 – 22 J. Neˇmecˇek et al. / Structural Integrity Procedia 00 (2024) 000–000

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Fig. 1. (a) Typical force-displacement curves of the main phases. (b) Example of statistical deconvolution performed on an irradiated 4% RH sample.

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Fig. 2. Typical frequency plots of E for irradiated and control samples stored at (a) 11% RH; (b) 33% RH; (c) 100% RH.

The separation into groups was performed using the statistical deconvolution method described in Constantinides et al. (2007). An example of the separation for the sample irradiated at 4% RH is shown in Fig. 1b, where the peak of the main hydrates is dominant, while the unreacted clinker is less frequent. The results for the main hydrate phases are summarized in Fig. 3 for E and H . For simplification, samples were divided into three categories according to the RH level. The first category con sisted of samples at very low RH (4% and 11%). In this case, a significant increase in both E + 25% and H up to + 35% were observed in irradiated samples compared to the control pair, see Fig. 3 and Table 1. This can likely be explained by the loss of water from the C–S–H gel interlayer space, caused by a combination of drying and water radiolysis Baral et al. (2022); Neˇmecˇek et al. (2019); Suwanmaneechot et al. (2020). Similar findings were reported by Baral et al. (2022), who observed a 15%–25% increase in the nanoindentation Young’s modulus for C–S–H pel lets gamma irradiated up to a total dose of 189 MGy at 11% RH, where interlayer water removal was confirmed by thermogravimetric analysis and decrease of basal spacing by X-ray di ff raction (XRD). The second category consisted of samples stored at medium RH levels (33%, 43%, and 76%). In this category, the relative changes in E between irradiated and control samples were relatively small compared to the first category, see Table 1. A slight increase in E was observed in the irradiated samples, ranging from 2% to 7%. However, the H did not follow this trend, decreasing from 43% RH onwards, with minimal di ff erences observed between the samples. Additionally, the changes in E across these RH levels were not significant, suggesting that both the irradiated and control samples were not a ff ected by hydration or carbonation. In terms of RH, the samples are comparable to those