Natural radioactivity of barite concrete shields containing commonly used supplementary materials

The recycling of hazardous materials within new composites has a sustainable importance as it contributes on the reduction of high radionuclide concentrations. In this study, the effect of cementitious materials i.e. viscosity modifier, silica fume and fly ash on the 226Ra, 232Th and 40K activity levels of barite concrete shields was researched by using different mixing compositions in terms of binder content, w/b ratio and the amount of supplementary cementitious materials. In comparison to cement, silica fume and fly ash used in the production of concrete shields were found to have significantly higher activity levels of 40K, as well as 226Ra, 232Th and 40K, respectively. The 226Ra, 232Th and 40K activity levels of concrete shields range between 2.2 and 20.7 Bq kg−1; 2.6 and 7.0 Bq kg−1; 51.5 and 89.3 Bq kg−1, respectively. These activity values were found similar or less than those of building materials in the world. These satisfactory results are mostly caused by the barite source which has lower radioactivity levels. The concrete mixture details used in the study caused significant variation in the natural radioactivity of barite concrete shields. The introduction of silica fume which has high 40K activity levels and fly ash with high 226Ra, 232Th and 40K activity levels compared to cement and barite aggregate, significantly increased the radiological hazard parameters, although all results were found to be below the limits recommended by international reports. In conclusion, 226Ra activity levels of the concrete shields were significantly increased (up to 8.4 times) by the variation of mix design parameters used in comparison with concrete mixtures that have the least 226Ra activity level. The 232Th and 40K activity levels were as well increased in relatively less amounts (1.7 and 0.73 times higher, respectively).