Comparative assessment of natural radionuclide content of cement brands used within Nigeria and some countries in the world

The gamma spectrometric analysis of different brands of cement used as building and construction material in Nigeria has been carried out in this study. Samples of 12 brands of gray Ordinary Portland Cement (OPC) and 5 brands of white cement of six samples each were collected and analyzed for their radiological content using gamma spectrometry method. The average value of Ra-226, Th-232, and K-40 for OPC is 30.2 +/- 10.4 Bq kg(-1), 24.6 +/- 7.1 Bq kg(-1), and 251.3 +/- 27.6 Bq kg(-1) respectively and the average value for the white cement is 41.9 +/- 16.7 Bq kg(-1), 30.1 +/- 9.4 Bq kg(-1) and 340.2 +/- 37.7 Bq kg(-1) respectively. The total average content of Ra-226, Th-232, and K-40 for all the cement brand samples are 36.1 +/- 13.6 Bq kg(-1), 27.4 +/- 83 Bq kg(-1), and 295.8 +/- 32.7 Bq kg(-1) respectively. These values obtained are lower when compared to the world average values (Ra-226-50 Bq kg(-1),Th-232-50 Bq kg(-1) and K-40-500 Bq kg(-1)) for building materials. The estimated radium equivalent activities (Ra-eq), representative index (I gamma), average absorbed gamma-dose rate (D), the annual effective dose rate (AEDE), annual gonadal dose equivalent (AGDE) external and internal hazard indices and the Excess life cancer risk (ELCR) were lower than the recommended safe limit and are comparable with results from similar studies conducted in other countries. The evaluated mean gonadal dose equivalents of three cement brand samples were found to be higher than the world average for building material while others are less than the world average. A comparison of the average activity values obtained in Nigeria cement and other countries of the world show that those countries with history of high radionuclide solid minerals have activity concentration far above that of Nigerian cement, while these values agreed with those obtained in other countries. (C) 2013 Elsevier B.V. All rights reserved.