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

The radionuclide activities of Ra-226, Th-232 and K-40 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 Bqkg(-1), 9.78-26.3 Bqkg(-1) and 156.5-489.4 Bqkg(-1) for Ra-226, Th-232 and K-40, respectively. The radiological parameters in cement samples were calculated as follows: mean radium equivalent activity Ra-eq = 67.87 Bqkg(-1), gamma index I = 0.256, alpha index I = 0.067, the absorbed gamma dose rate D = 60.76 nGyh(-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 Bqkg(-1) for Ra-226, 13.1-20.5 Bqkg(-1) for Th-232 and 250.4-494.4 Bqkg(-1) for K-40. The calculated radiological parameters of cements were lower than calculated radiological parameters of cement composites.