Assessment of Natural Radioactivity Levels of Cements and Cement Composites in the Slovak Republic

The radionuclide activities of 226 Ra, 232 Th and 40 K and radiological parameters (radium equivalent activity, gamma and alpha indices, the absorbed gamma dose rate and external and internal hazard indices) of cements and cement composites commonly used in the Slovak Republic have been studied in this paper. The cement samples of 8 types of cements from Slovak cement plants and five types of composites made from cement type CEM I were analyzed in the experiment. The radionuclide activities in the cements ranged from 8.58–19.1 Bq·kg −1 , 9.78–26.3 Bq·kg −1 and 156.5–489.4 Bq·kg −1 for 226 Ra, 232 Th and 40 K, respectively. The radiological parameters in cement samples were calculated as follows: mean radium equivalent activity Ra eq = 67.87 Bq·kg −1 , gamma index I γ = 0.256, alpha index I α = 0.067, the absorbed gamma dose rate D = 60.76 nGy·h −1 , external hazard index H ex = 0.182 and internal hazard index H in was 0.218. The radionuclide activity in composites ranged from 6.84–10.8 Bq·kg −1 for 226 Ra, 13.1–20.5 Bq·kg −1 for 232 Th and 250.4–494.4 Bq·kg −1 for 40 K. The calculated radiological parameters of cements were lower than calculated radiological parameters of cement composites.