Abstract
The effect of gamma-ray irradiation on cement mortar properties is investigated in this study in order to understand the mechanism behind the strength and stiffness reduction, which may be significant according to the available researches. 60Co irradiation facility with the generating dose rate of 0.1–10 Gy/s and the total activity of 4.4·1015 Bq (120 kCi) was used to perform the irradiation, so that the total observed dose of the irradiated samples reached the values ranging from 12.0 to 15.0 MGy. An identical set of control samples was placed in the same laboratory conditions away from gamma radiation. The results of nanoindentation, X-ray diffraction analysis and mercury intrusion porosimetry of the irradiated and the control samples are shown and explained in detail in this study. The nanoindentation creep compliance and the nanoindentation elastic modulus of the irradiated and the control samples do not show any significant difference. The mineral composition obtained using the X-ray diffraction analysis of the irradiated and the control samples is also similar. The pore structure rearrangement and microcrack occurrence, which were evidenced by the mercury intrusion porosimetry and scanning electron microscopy, led to the porosity increase and may be attributed to the significant decrease of compressive strength.
Highlights
Concrete structures and elements, such as biological shields of nuclear power plants, irradiation facility walls and casks for radioactive waste storage, may be exposed to long-term ionizing radiation (Vaitová et al 2018; Khmurovska et al 2019a)
It was considered that the indents with the elastic modulus lower than 40 GPa may belong to the C–S–H gel phase; see Fig. 8a, where the indentation elastic moduli of all the indents are shown
All the indents were checked by scanning electronic microscopy (SEM), since it is known that the C–S–H gel phase has dark gray color in SEM-BSE images
Summary
Concrete structures and elements, such as biological shields of nuclear power plants, irradiation facility walls and casks for radioactive waste storage, may be exposed to long-term ionizing radiation (Vaitová et al 2018; Khmurovska et al 2019a). The data scatter of the control and the irradiation samples are very similar, it can be concluded that the effect of gamma-ray irradiation on cement paste creep is insignificant even at nano-level.
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