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Coal fly ash (CFA) samples used in building construction were assessed for natural radioactivity by gamma-ray spectrometry analysis. Activity concentrations in the original CFA sample were 101, 55.5 and 493 Bq kg−1 for 226Ra, 232Th and 40K, respectively. They were compared with the activity concentrations measured in five fineness ranges (from < 45 to > 200 µm). Then, the finer the CFA is, the higher the activity concentrations. Radioactive hazard was assessed for 765 samples collected for 10 years. The annual effective dose was 0.95 mSv y−1 for the fly ash and lower than 1 mSv y−1 for all the scenarios considered for a building material. Therefore, CFA may be used to manufacture building materials safely. [ABSTRACT FROM AUTHOR]

The natural radioactivity in coal fly ash and natural pozzolan Portland cement samples produced in Spain was measured by gamma spectrometry. Activity concentrations of 226Ra, 232Th and 40K ranged from 15.7 to 88.3 Bq kg−1, from 12.8 to 81.0 Bq kg−1 and from 37.0 to 678.0 Bq kg−1, respectively. The radiological hazards samples owing to the mentioned natural radioactivity were inferred from determinations of the activity concentration index, I, absorbed dose rate, Dext, and annual effective dose, Ep, which falls within 0.20 mSv to 0.87 mSv (coal-cement) and 0.18 mSv to 0.50 mSv (pozzolan-cement) (≤ 1 mSv, threshold criterion). Therefore, these cements are proper to be used for building purposes as result of their radiological assessment. [ABSTRACT FROM AUTHOR]