Micromechanical characterization of γ-irradiated cement paste exposed to different relative humidity conditions

In this study, well-hydrated cement paste samples made from Portland cement CEM I-42.5R were gamma irradiated with a 200 TBq 60Co source, resulting in a total absorbed dose of 13.82MGy. During irradiation, the samples were stored under specific relative humidity (RH) conditions of 11 %, 33 %, 76 %, 96 %, and water. Grid nanoindentation was performed on polished sample surfaces to assess the nanoindentation Young’s modulus of both irradiated and non-irradiated control samples. An increase in Young’s modulus by 9.3 % was observed for irradiated samples at low RH (11 %). Samples stored at medium RHs (33 %, 76 %) showed negligible differences in micromechanical properties. However, a significant decrease in Young’s modulus, approximately 15 %, was measured for samples stored at high RHs (96 %, water).