Natural radioactivity and human exposure by raw materials and end product from cement industry used as building materials

During the manufacturing process in the cement industry, raw materials of different levels of natural radioactivity are utilized. In this study we present the radiological impact of cements as a building material and the different raw materials used in their manufacture. A total of 218 samples of raw materials and their end product cements were collected from the cement industry of Macedonia (The Former Yugoslav Republic) during the period 2005–2007. The specific activities, evaluated by gamma spectrometry analysis, showed the highest mean specific activity in fly ash (226Ra, 107 ± 45 Bq kg−1; 232Th, 109 ± 30 Bq kg−1; 40K, 685 ± 171 Bq kg−1), which is used as a raw material. However, the final cement product usually has relatively lower activity compared with the activity of the raw material and the mean specific activity of the final cement products were lower (226Ra, 42 ± 10 Bq kg−1; 232Th, 28 ± 6 Bq kg−1; 40K, 264 ± 50 Bq kg−1). The radium equivalent activity and the hazard index were calculated for each sample to assess the radiation hazard. The mean annual effective dose originating from the cements was found to be 111 ± 22 μSv y−1, which is below the recommended EC limit of 300 μSv y−1.