Assessment of the natural radioactivity and radiological hazards in Turkish cement and its raw materials

The natural radioactivity due to presence of Ra-226, Th-232 and K-40 radionuclides in raw materials, intermediate products (clinker) and end products (22 different cement types) was measured using a gamma-ray spectrometry with HPGe detector. The specific radioactivity of Ra-226, Th-232 and K-40 in the analyzed cement samples ranged from 12.5 +/- 10.3 to 162.5 +/- 1.7 Bq kg(-1) with a mean of 40.5 +/- 26.7 Bq kg(-1), 6.7 +/- 0.3 to 124.9 +/- 2.5 Bq kg(-1) with a mean of 26.1 +/- 18.9 Bq kg(-1) and 64.4 +/- 2.3 to 679.3 +/- 18.2 Bq kg(-1) with a mean of 267.1 +/- 102.4 Bq kg(-1), respectively. The radium equivalent activity (Ra-eq), the gamma-index, the emanation coefficient, the Rn-222 mass exhalation rate and the indoor absorbed dose rate were estimated for the radiation hazard of the natural radioactivity in all samples. The calculated Ra-eq values of cement samples (37.2 +/- 8.7-331.1 +/- 15.5 Bq kg(-1) with a mean of 98.3 +/- 53.8) are lower than the limit of 370 Bq kg(-1) set for building materials. The Ra-eq values were compared with the corresponding values for cement of different countries. The mean indoor absorbed dose rate is slightly higher than the population-weighted average of 84 nGy h(-1). (C) 2007 Elsevier Ltd. All rights reserved.